(Technical background] In general, to transmit signals in optical communication systems, employed are optical components that connect to optical fibers, and these optical components are either integrated optical devices made of optical waveguide or active/passive components such as LD (laser diode), PD (photo diode), optical filter, lens, and so forth.

To transmit the optical signals effectively, the centers of the optical fibers and of the optical components must aligned accurately.

However, the techniques to connect the optical fibers and the optical components require not only accuracy but also expensive apparatuses to aid alignment and connection.

Such requirements are major obstacles to the low cost mass production of optical components.

For example, as shown in Fig. 1, a schematic diagram of the widely used method to connect optical fibers and optical waveguide devices, the optical device and the blocks to mount the input/output fibers are fabricated first.

The blocks have grooves of V, U, or other shapes, and the optical fibers are

mounted and fixed in the grooves.

Then, the side end surfaces, to be bonded to each other, of the waveguide device and the optical fibers are lapped and polished. The centers of the waveguide and the fibers are aligned accurately and connected with the aid of the alignment apparatus or alignment station.

In case the alignment station is used, the input optical fiber block on which one optical fiber is fixed is put first in contact with the input side of the optical waveguide device.

Next, the alignment station moves the input optical fiber block minutely to bring together the core centers of the input optical waveguide of the optical waveguide device and the input optical fiber until when the intensity of the light outputted through the input optical waveguide of the optical waveguide device from the input optical fiber reaches the maximum value.

Then, the output optical fiber block, on which one or more output optical fiber is mounted and fixed, is put in contact with the output side of the optical waveguide.

Next, the alignment station moves the output optical fiber block minutely to bring together the core centers of the output optical waveguide of the optical waveguide device and the output optical fiber until when the intensity of the light outputted through the one or more output optical fiber from the input optical fiber reaches the maximum value.

At this time, the connection of the input optical fiber and the input optical waveguide is fixed using epoxy, laser, adhesive, and so forth.

However, there is no reference point in this conventional connection method to match the axial center of the optical waveguide formed on the optical waveguide device and the axial center of the optical fiber mounted on the optical fiber block. Thus, the conventional method requires a special apparatus, and it takes a long time to fix the device and the blocks using epoxy just because the optimal connection status is determined only by the intensity of output light compared to the intensity of the input light through the optical fiber. Therefore, various expensive apparatuses are needed, or the method is not good enough for mass production.

Moreover, since optical waveguide devices and input/output optical fiber blocks are separately fabricated by so-called batch process and diced from different silicon wafers, a plurality of devices and blocks are fabricated at one time.

However, in case of the assembly process for connecting the optical waveguide device and input/output optical fiber blocks separately fabricated from different silicon substrates, it takes a long time to make one assembly, and many expensive alignment stations are also needed for assembly in mass, which work as big obstacles to reduce the cost of fabrication of the devices.

To get over such obstacle, structures to integrate optical fiber blocks to an optical waveguide device have been. One example of this structure is disclosed in Japanese Patent No. 2, 982, 861.

That is, an optical waveguide device and an optical fiber block are fabricated integrally using one substrate to connect the optical waveguide and the optical fiber core simply and quickly without expensive precision alignment station.

However, the optical device, on which an optical fiber block is integrated, needs a lot of mask processes and etch processes for fabrication, which make the whole fabrication process rather complicated.

Therefore, the method has a disadvantage that the price of the device is high due to the expensive unit fabrication cost.

[Detailed description of the invention] The present invention is to solve the above problems, and therefore the object of the present invention is to provide an inexpensive optical device proper for mass production and integration and a fabrication method for the same.

Another object of the present invention is to provide a simple fabrication method of an optical device.

To achieve the above objects, according to the present invention, an optical component to be connected to optical fibers, which is either integrated optical devices made of optical waveguide or active/passive components such as LD (laser diode), PD (photo diode), optical filter, lens, etc. , and input/output optical fiber blocks are fabricated on one substrate, the substrate is diced to each block, each block is lapped and polished, and all blocks are connected to each other. Then, the optical waveguide and optical fibers can be aligned simply and accurately without expensive alignment station.

That is, the optical device according to the present invention comprises: a first optical fiber block having one or more first optical fiber; a second optical fiber block which is formed on the same substrate as the first optical fiber block and has one or

more second optical fiber; and an optical device block which is formed on the same substrate as the first and second optical fiber blocks and used to be connected with the first and second optical fiber blocks; wherein the first and second optical fiber blocks are connected to two lateral faces of the optical device block which are designated to connected to the first and second optical fiber blocks; and areas and heights of the substrate connecting faces of the optical device block and the first and second optical fiber blocks to make upper and bottom faces of the optical device block are same in order for upper and bottom faces of the first and second optical fiber blocks parallel to each other.

Here, one or more connection guide of groove form can be formed on a part of upper faces of the optical device block and the first and second optical fiber blocks.

In addition, the optical device block is an optical waveguide device having one or more optical waveguide, and the first and second optical fiber blocks are connected to two lateral faces of the optical waveguide device to make the optical axes of the waveguide and those of the optical fibers correspond to each other. Connecting faces of the optical waveguide device block and the first and second optical fiber blocks are perpendicular to the upper face of the substrate and may not be perpendicular to the proceeding direction of the light passing through the optical waveguide device module and the first optical fiber or the optical waveguide device module and the second optical fiber.

The substrate can be made of any one of wafers for semiconductor fabrication process having a crystalline structure and being able to form grooves by etching method

such as dry, wet, or laser etching, substrates for optical materials being able to form grooves by dicing or laser processing, and substrates being able to form planar waveguide device or active optical devices including LD/PD and being able to form passive optical devices such as mirror, filter, or lens of 3-dimensional structure by micro-machining. Especially, the substrate can be made of any one of Si, GaAs, InP, Quartz, LiNb03, AIN, or plastic.

Moreover, the optical device block may include any one of planar optical device using Si02 or polymer material, LD, PD, or passive device having 3-dimensional structure fabricated by micro-machining such as filter, lens, or mirror.

A fabrication method of an optical device according to the present invention is for an optical device which a first and a second optical fiber blocks, each of which has one or more optical fiber, are connected to two lateral faces of an optical waveguide device having one or more optical waveguide, and it comprises the steps of : preparing a substrate having a first, second, and third areas; forming one or more optical waveguide in the second area of the substrate; dicing the substrate to separate the first, second, and third areas of the substrate to form a first sub-substrate having the first area, a second sub-substrate having the second area, and a third sub-substrate having the third area; arranging at least one optical fiber each on the first and third sub-substrates, respectively; lapping and polishing two lateral faces of the second sub-substrate and each one lateral face of the first and third sub-substrates; and aligning and connecting the first and third sub-substrates to two lateral faces of the second sub-substrate to make the lapped and polished lateral faces stand opposite to each other.

Here, it is preferable to form one or more groove by etching prescribed parts of the first and third sub-substrates to a prescribed depth, respectively, before the step of forming the optical waveguide or after the step of dicing the substrate. In addition, the groove, which is formed by etching prescribed parts of the first and third sub-substrates to a prescribed depth, may be formed on the surfaces of the first and third sub-substrates that are the same as or opposite to the surface of the second sub-substrate where the optical waveguide is formed.

Also, the substrate can be diced to make the dicing faces between the first, second, and third sub-substrates perpendicular to the upper face of the substrate and not perpendicular to the central axes of the optical waveguide in the step of dicing.

Another fabrication method according to the present invention comprises the steps of : preparing a substrate having a first, second, and third areas; forming a mask pattern on the first and third areas on the substrate; forming a lower clad layer on the entire surface of the substrate; forming one or more optical waveguide in the second area of the substrate by forming a core layer on the lower clad layer and patterning the core layer; forming an upper clad layer on the entire surface including the patterned core layer; dicing the substrate to separate the first, second, and third areas of the substrate to form a first sub-substrate having the first area, a second sub-substrate having the second area, and a third sub-substrate having the third area; exposing the mask pattern by removing the upper and lower clad layers formed on the first and third sub-substrates; forming one or more groove each of the first and third sub-substrates to a prescribed depth by etching using the mask pattern as mask and removing the mask pattern;

arranging optical fibers to correspond on the grooves, respectively; lapping and polishing two lateral faces of the second sub-substrate and each one lateral face of the first and third sub-substrates; and aligning and connecting the first and third sub- substrates to two lateral faces of the second sub-substrate to make the lapped and polished lateral faces stand opposite to each other.

Another fabrication method according to the present invention comprises the steps of : preparing a substrate having a first, second, and third areas; forming a first mask pattern on the first and third areas on the substrate; forming a lower clad layer on the entire surface of the substrate; forming one or more optical waveguide in the second area of the substrate by forming a core layer on the lower clad layer and patterning the core layer; forming an upper clad layer on the entire surface including the patterned core layer; forming a second mask pattern on the upper clad layer formed on the second area on the substrate; exposing the first mask pattern by removing the upper and lower clad layers formed on the first and third sub-substrates using the second mask pattern as mask; forming one or more groove each of the first and third sub-substrates to a prescribed depth by etching using the first mask pattern as mask and removing the first and second mask patterns; dicing the substrate to separate the first, second, and third areas of the substrate to form a first sub-substrate having the first area, a second sub- substrate having the second area, and a third sub-substrate having the third area; arranging optical fibers to correspond on the grooves, respectively; lapping and polishing two lateral faces of the second sub-substrate and each one lateral face of the first and third sub-substrates; and aligning and connecting the first and third sub-

substrates to two lateral faces of the second sub-substrate to make the lapped and polished lateral faces stand opposite to each other.

Another fabrication method according to the present invention comprises the steps of : preparing a substrate having a first, second, and third areas; forming a mask pattern on the first and third areas on the substrate; forming one or more groove each of the first and third sub-substrates to a prescribed depth by etching using the mask pattern as mask and removing the mask pattern; forming a lower clad layer on the entire surface of the substrate; forming one or more optical waveguide in the second area of the substrate by forming a core layer on the lower clad layer and patterning the core layer; forming an upper clad layer on the entire surface including the patterned core layer; exposing the substrate where the grooves are formed by removing the upper and lower clad layers formed on the first and third sub-substrates; dicing the substrate to separate the first, second, and third areas of the substrate to form a first sub-substrate having the first area, a second sub-substrate having the second area, and a third sub-substrate having the third area; arranging optical fibers to correspond on the grooves, respectively; lapping and polishing two lateral faces of the second sub-substrate and each one lateral face of the first and third sub-substrates; and aligning and connecting the first and third sub-substrates to two lateral faces of the second sub-substrate to make the lapped and polished lateral faces stand opposite to each other.

Another fabrication method according to the present invention comprises the steps of : preparing a substrate having a first, second, and third areas; forming a lower clad layer on the entire surface of the substrate; forming one or more optical waveguide

in the second area of the substrate by forming a core layer on the lower clad layer and patterning the core layer; forming an upper clad layer on the entire surface including the patterned core layer; exposing the substrate by etching the upper and lower clad layers on the first and third areas of the substrate using a mask where a prescribed pattern is formed and forming grooves by etching the exposed substrate; removing the upper and lower clad layers remained on the first and third areas of the substrate; dicing the substrate to separate the first, second, and third areas of the substrate to form a first sub- substrate having the first area, a second sub-substrate having the second area, and a third sub-substrate having the third area; arranging optical fibers to correspond on the grooves, respectively; lapping and polishing two lateral faces of the second sub-substrate and each one lateral face of the first and third sub-substrates; and aligning and connecting the first and third sub-substrates to two lateral faces of the second sub-substrate to make the lapped and polished lateral faces stand opposite to each other.

Here, the step of forming grooves in the first and third areas of the substrate may be constituted of the steps of : forming and patterning a mask layer on the upper clad layer; exposing the substrate by etching the upper and lower clad layers on the first and third areas of the substrate using the mask layer; and forming grooves by removing the mask layer and etching exposed substrate to a prescribed depth using the upper clad layer as mask, or it may be constituted of the steps of : preparing a mask where a prescribed pattern in formed; aligning the mask on the substrate; exposing the substrate by dry etching the upper and lower clad layers on the first and third area of the substrate using the mask; and forming grooves by removing the mask layer and etching exposed

substrate to a prescribed depth using the upper clad layer as mask.

Another fabrication method according to the present invention comprises the steps of : preparing a substrate having a first, second, and third areas; forming a mask pattern on one surface of the substrate, forming one or more groove each of the first and third areas of the substrate to a prescribed depth by etching using the mask pattern as mask, and removing the mask patterns; forming a lower clad layer on the entire surface of the opposite surface of the substrate to the surface where the grooves are formed ; forming one or more optical waveguide in the second area of the substrate by forming a core layer on the lower clad layer and patterning the core layer; forming an upper clad layer on the entire surface including the patterned core layer; dicing the substrate to separate the first, second, and third areas of the substrate to form a first sub-substrate having the first area, a second sub-substrate having the second area, and a third sub- substrate having the third area; removing the upper and lower clad layers formed on surfaces of the first and third sub-substrates; arranging optical fibers to correspond on the grooves of the first and third sub-substrates, respectively; lapping and polishing two lateral faces of the second sub-substrate and each one lateral face of the first and third sub-substrates; and aligning and connecting the first and third sub-substrates to two lateral faces of the second sub-substrate to make the lapped and polished lateral faces stand opposite to each other.

On the other hand, according to another aspect of the present invention, a first groove where an optical fiber is supposed to be arranged formed first, an optical waveguide is formed, and a second groove is formed by half cutting the connecting part

between the optical waveguide and the optical fiber block using dry or wet etching or dicing saw to make the fabrication process simple to solve the problem of cost elevation due to the complicated fabrication process of optical device where an optical fiber block is integrated.

That is, another fabrication method according to the present invention is to manufacture an optical device having an optical fiber block where an optical fiber is arranged, and the method comprises the steps of : preparing a substrate; forming one or more first groove by etching an area where the optical fiber is arranged on a surface of the substrate to a prescribed depth; forming one or more optical waveguide on the substrate to be placed in a line as corresponding first groove; forming a second groove by etching a boundary surface between the first groove and the optical waveguide to a prescribed depth; and arranging the optical fiber to the first groove and connecting the optical fiber to the optical waveguide.

Here, the step of forming the first groove may include the steps of : exposing an area of the substrate where the optical fiber is arranged by forming and patterning a mask layer on the substrate; forming a first groove by etching the exposed substrate to a prescribed depth using the mask layer as mask; and removing the mask layer.

In addition, the substrate can be made of any one of wafers for semiconductor fabrication process having a crystalline structure and being able to form grooves by etching method such as dry, wet, or laser etching, substrates for optical materials being able to form grooves by dicing or laser processing, and substrates being able to form planar waveguide device or active optical devices including LD/PD and being able to

form passive optical devices such as mirror, filter, or lens of 3-dimensional structure by micro-machining.

It is preferable that the first groove is etched to make the width of the upper part is wide and that of the lower part is narrow.

Moreover, the step of forming the optical waveguide may includes the steps of : forming a lower clad layer on the entire surface of the substrate; forming an optical waveguide in an area placed in a line as the first groove by forming and patterning a core layer on the lower clad layer; forming an upper clad layer on the entire surface including the optical waveguide; and exposing the substrate by removing the upper and lower clad layers of the area where the first groove is formed.

The second groove is formed by any one of dry etching, wet etching, dicing, laser processing, any combination of two or more of these, or micro-processing, and it is preferable that the lower surface of the second groove is placed lower than the lower surface of an optical fiber arranged on the first groove.

Another fabrication method according to the present invention comprises the steps of : preparing a substrate; forming a lower clad layer on the entire surface of the substrate; forming one or more optical waveguide on a prescribed area of the substrate by forming and patterning a core layer on the lower clad layer; forming an upper clad layer on the entire surface including the optical waveguide; exposing the substrate by etching the upper and lower clad layers in an area placed in a line with the waveguide using a mask where a prescribed pattern is formed and forming a first groove by first- etching the exposed substrate to a prescribed depth; forming a second groove by second-

etching a boundary surface between the first groove and the optical waveguide to a prescribed depth; and arranging the optical fiber to the first groove and connecting the optical fiber to the optical waveguide.

Here, the step of forming the first groove may include the steps of : forming and patterning a mask layer on the upper clad layer; exposing the substrate by etching an area of the upper and lower clad layers placed in a line with the optical waveguide; and removing the mask layer and forming a groove by etching the exposed substrate to a prescribed depth using the upper clad layer as mask, or it may include the steps of preparing a mask where a prescribed pattern is formed ; aligning the mask on the substrate; exposing the substrate by etching the upper and lower clad layers placed in a line with the optical waveguide using the mask; removing the mask layer and forming a first groove by etching the exposed substrate to a prescribed depth using the upper clad layer as mask; and removing the upper and lower clad layers remained on both sides of the first groove.

Another fabrication method according to the present invention comprises the steps of : preparing a substrate having a first area and a second area; forming a first mask pattern on the substrate; forming a lower clad layer on the entire surface of the substrate where the first mask pattern is formed; forming one or more optical waveguide on the second area by forming and patterning a core layer on the lower clad layer; forming an upper clad layer on the entire surface of the substrate where the optical waveguide is formed; forming a second mask pattern on the upper clad layer ; exposing the first mask pattern by etching the upper and lower clad layers of the second area using the second

mask pattern as mask; forming a first groove by etching the substrate of the second area to a prescribed depth using the first mask pattern as mask and removing the first mask pattern; forming a second groove by etching a boundary surface between the first groove and the optical waveguide to a prescribed depth; and arranging the optical fiber to the first groove and connecting the optical fiber to the optical waveguide.

[Bried description of the drawings] Fig. 1 shows a conventional method of connecting an optical waveguide device with input/output optical fiber blocks.

Figs. 2a through 2j are process perspective views showing a fabrication process of an optical device according to the first embodiment of the present invention.

Figs. 3a through 3j are process perspective views showing the fabrication process of the optical device according to the second embodiment of the present invention.

Figs. 4a through 4j are process perspective views showing the fabrication process of the optical device according to the third embodiment of the present invention.

Fig. 5 is a structural perspective view showing an optical device of the present invention having connection guides.

Figs. 6a through 6g are process perspective views showing the fabrication process of the optical device according to the fourth embodiment of the present invention.

Fig. 7 is a structural perspective view showing an optical device of the present invention in which a 18 optical waveguide device and input/output optical fiber blocks

are connected.

Figs. 8a through 8g are process perspective views showing the fabrication process of the optical device according to the fifth embodiment of the present invention.

Fig. 9 is a sectional view of an optical device in which the connection surface is slanted to prevent crosstalk.

Fig. 10 is a layout diagram showing a dicing method of a substrate according to the sixth embodiment of the present invention.

Figs. lla through llj are process perspective views showing the fabrication process of an optical device according to the seventh embodiment of the present invention.

Figs. 12a through 12j are process perspective views showing the fabrication method of an optical device according to the eighth embodiment of the present invention.

Figs. 13a through 13h are process perspective views showing the fabrication method of an optical device according to the ninth embodiment of the present invention.

Figs. 14a through 14h are process perspective views showing the fabrication method of an optical device according to the tenth embodiment of the present invention.

[Preferred embodiments] Now, preferred embodiments of the present invention will be described in detail with reference to accompanying drawings.

According to embodiments of the present invention, an optical component to be connected to optical fibers, which is either integrated optical devices made of optical

waveguide or active/passive components such as LD (laser diode), PD (photo diode), <BR> <BR> optical filter, lens, etc. , and input/output optical fiber blocks are fabricated on one substrate, the substrate is diced to each block, each block is lapped and polished, and all blocks are connected to each other. Then, the optical waveguide and optical fibers can be aligned simply and accurately without expensive alignment station. In the following embodiments, an optical waveguide device is mentioned as an example of an optical device connected to the optical fiber.

The First Embodiment Figs. 2a through 2j are process perspective views showing a fabrication method of an optical device according to the first embodiment of the present invention.

According to the first embodiment of the present invention, a mask layer to form grooves for mounting optical fibers is formed on a substrate, an optical waveguide is formed, the substrate is diced, and the grooves for mounting optical fibers are formed using the mask layer which is formed in advance.

First, as shown in Fig. 2a, a silicon substrate 11 having first and third areas on which optical fibers are supposed to be arranged and second area on which an optical waveguide is supposed to be formed is prepared. Mask layers 12 made of Si3N4, etc. are formed on upper and lower surfaces of prepared silicon substrate 11. Then, as shown in Fig. 2b, the mask layer 12 is patterned using conventional photolithography process to expose the second area of the substrate 11 on which the optical waveguide is supposed to be formed and the first and third areas of the substrate 11 on which the optical fibers are supposed to be arranged.

Next, as shown in Figs. 2c and 2d, a lower clad layer 13 and a core layer 14 are formed in order on the entire surface of the substrate 11.

Here, the lower clad layer 13 and the core layer 14 are made of Si02, and the thickness of each layer is a few to several tens uni.

Next, as shown in Fig. 2e, the core layer 14 is patterned and one or more optical waveguide 14a is formed on the substrate of the second area.

Here, the lower clad layer 13 has lower refractive index than that of the core layer to make the light reflect on boundary surface to make the light transmit well through the optical waveguide 14a, and the optical waveguide 14a has a role to transmit the light.' Next, as shown in Fig. 2f, an upper clad layer 15 is formed on the entire surface of the substrate including the optical waveguide 14a.

The upper clad layer 15 is also made of Si02 same as the lower clad layer 13, and the thickness thereof is about 20 um. It also has low refractive index to make the light reflect on boundary surface to make the light transmit well through the optical waveguide 14a.

Next, as shown in Fig. 2g, the substrate 11 is diced to separate the first, second, and third areas of the substrate 11, and the diced substrate 11 is separated to first sub- substrate 11 a having the first area, second sub-substrate 1 lb having the second area, and third sub-substrate lie having the third area.

Here, the first and third sub-substrates 11 a and lie become first and second optical fiber blocks, and the second sub-substrate llb becomes an optical waveguide

device through the following process.

Next, as shown in Fig. 2h, the upper clad layer 15 and the lower clad layer 13 formed on the first sub-substrate 11 a and the third sub-substrate lie are removed in order to expose the patterned mask layer 12.

At this time, the upper clad layer 15 and the lower clad layer 13 are removed by dry etching process using reaction gas such as CxFy group or CxCly group or wet etching process using HF solution, and so forth.

Next, as shown in Fig. 2i, the first sub-substrate 1 la and the third sub-substrate lie are etched to a prescribed depth using the mask layer 12 as mask to form one or more grooves, and the mask layer 12 is removed. Here, it is preferable that an etching process able to etch the patterned parts using the mask layer 12 in vertical direction such as dry etching, laser processing, etc. is used to prevent the lateral surfaces of the substrate other than the part to form the grooves from etching other than wet etching.

Here, the grooves are formed in V shape, U shape, or other shapes in which the optical fibers can be mounted, and now the first sub-substrate 11 a and the third sub- substrate 1 lc on which grooves are formed become the input optical fiber block and the output optical fiber block.

Next, though it is not shown in the drawings, the optical fibers are arranged and mounted to correspond on the grooves of the input/output optical fiber blocks.

Next, the side end surfaces, to be bonded each other, of the optical waveguide device and input/output optical fiber blocks are lapped and polished through the following process.

Finally, as shown in Fig. 2j, the input/output optical fiber blocks are aligned to put in contact with the optical waveguide device to make the lapped and polished side end surfaces be opposite to each other, and the connections are fixed using epoxy, etc. to complete the optical device.

At this time, for the connected optical waveguide device and the optical fiber blocks, the upper/lower surfaces of the optical waveguide device and the upper/lower surfaces of the input/output optical fiber blocks are parallel to each other, and the areas and heights of the substrate connection surfaces are equal.

As shown in the above, since the optical waveguide device and the optical fiber blocks are fabricated using the same substrate and separated according to the present invention, the optical axes of the optical waveguide and the optical fibers are matched simply without expensive conventional alignment station by aligning and connecting the optical waveguide device and the optical fiber blocks centering around one reference surface.

The second embodiment Figs. 3a through 3j are process perspective views showing the fabrication process of the optical device according to the second embodiment of the present invention.

According to the second embodiment, the optical waveguide is formed, the grooves for mounting the optical fibers are formed, and the substrate is diced to form each block.

First, as shown in Fig. 3a, a silicon substrate 21 having first and third areas on

which optical fibers are supposed to be arranged and second area on which an optical waveguide is supposed to be formed is prepared. Next, first mask layers 22 made of Si3N4, etc. are formed on upper and lower surfaces of prepared silicon substrate 21.

Then, as shown in Fig. 3b, the first mask layer 22 is patterned using conventional photolithography process to expose the second area of the substrate 21 on which the optical waveguide is supposed to be formed and the first and third areas of the substrate 21 on which the optical fibers are supposed to be arranged.

Next, as shown in Figs. 3c and 3d, a lower clad layer 23 and a core layer 24 are formed in order on the entire surface of the substrate 21.

Next, as shown in Fig. 3e, the core layer 24 is patterned and one or more optical waveguide 24a is formed on the substrate of the second area.

Next, as shown in Fig. 3f, an upper clad layer 25 is formed on the entire surface of the substrate including the optical waveguide 24a.

Next, as shown in Fig. 3g, the second mask layer 26 is formed on the upper clad layer 25 and patterned to remain the second mask layer 26 only on the upper clad layer 25 on the second area of the substrate 21.

Then, the upper clad layer 25 and the lower clad layer 23 formed on the first and the third areas of the substrate 21 are removed in order using the remaining second mask layer 26 pattern as mask to expose the first mask layer 22.

Next, as shown in Fig. 3h, the first and the third areas of the substrate are etched to a prescribed depth using the exposed first mask layer 22 as mask to form one or more grooves, and the first and second mask layers 22 and 26 are removed.

Next, as shown in Fig. 3i, the substrate 21 is diced to separate the first, second, and third areas of the substrate 21, and the diced substrate 21 is separated to first sub- substrate 21a having the first area, second sub-substrate 21b having the second area, and third sub-substrate 21c having the third area.

Here, the first and the third sub-substrates 21 a and 21 c become the input/output optical fiber blocks and the second sub-substrate 21b becomes the optical waveguide device.

Next, though it is not shown in the drawings, the optical fibers are arranged and mounted to correspond on the grooves of the input/output optical fiber blocks.

Next, the connecting surfaces, that is, side end surfaces, to be bonded each other, of the optical waveguide device and the input/output optical fiber blocks are lapped and polished through the following process.

Finally, as shown in Fig. 3j, the input/output optical fiber blocks are aligned to put in contact with the optical waveguide device to make the lapped and polished side end surfaces be opposite to each other, and the connections are fixed using epoxy, etc. to complete the optical device.

As described in the above, since the grooves of the optical fiber blocks are formed before dicing the substrate according to the second embodiment of the present invention, the process becomes simpler and more reliable.

The third embodiment Figs. 4a through 4j are process perspective views showing the fabrication process of the optical device according to the third embodiment of the present invention.

According to the third embodiment of the present invention, the grooves for mounting the optical fibers are formed, the optical waveguide is formed, and the substrate is diced to form. each block.

First, as shown in Fig. 4a, a silicon substrate 31 having first and third areas on which optical fibers are supposed to be arranged and second area on which an optical waveguide is supposed to be formed is prepared. Mask layers 32 made of Si3N4, etc. are formed on upper and lower surfaces of prepared silicon substrate 31. Then, as shown in Fig. 4b, the mask layer 32 is patterned using conventional photolithography process to expose the first and third areas of the substrate on which the optical fibers are supposed to be arranged.

Next, as shown in Fig. 4c, the first and the third areas of the substrate are etched to a prescribed depth using the mask layer 32 as mask to form one or more grooves, and the mask layer 32 is removed.

On the other hand, the grooves can be formed using a mask formed separately (shadow mask) other than the mask layer 32 is formed and patterned though the method shown in Fig. 4c is to use photolithography process which patterns the mask layer 32 and forms the grooves using the mask layer 32. However, it is preferable that the process enabling vertical direction etching such as dry etching, laser processing, etc. other than wet etching because the etching solution may permeate between the surface of the substrate and the mask to make it difficult to form minute pattern in the case that the mask formed separately and the wet etching process are used. If the mask formed separately is used other than the mask layer 32, the process becomes simple.

Next, as shown in Figs. 4d and 4e, a lower clad layer 33 and a core layer 34 are formed in order on the entire surface of the substrate 31 where the grooves are formed.

Next, as shown in Fig. 4f, the core layer 34 is patterned and one or more optical waveguide 34a is formed on the substrate of the second area.

Next, as shown in Fig. 4g, an upper clad layer 35 is formed on the entire surface of the substrate including the optical waveguide 34a.

Then, as shown in Fig. 4h, the upper clad layer 35 and the lower clad layer 33 formed on the first and the third areas of the substrate 31 are removed in order to expose the substrate 31.

Detailed description for Figs. 4i and 4j are omitted because it is same as Figs.

3i and 3j of the second embodiment.

The third embodiment of the present invention is same as the second embodiment in the point that the grooves are formed before dicing the substrate, but it is different from the second embodiment in the point that the grooves of the optical fiber blocks are formed before forming the optical waveguide.

Since the grooves of the optical fiber blocks are also formed before dicing the substrate according to the third embodiment of the present invention, the process becomes simpler and more reliable.

In addition, one or more connection guide parallel to the grooves where the optical fibers are supposed to be mounted can be formed by etching the first, second, and third areas of the substrate to a prescribed depth using the mask layer 32 or the shadow mask in the step of forming grooves in the first and the third areas of the

substrate as shown in Fig. 4c.

That is, the connection guides 41 are formed parallel to the optical waveguide 42 and the optical fibers 43 as shown in Fig. 5, and the central axes of the connection guides formed in the optical waveguide device 44 and those formed in the input/output optical fiber blocks correspond to each other.

Since the optical axes of the optical waveguide 42 and the optical fibers 43 become correspond automatically if the central axes of the connection guides 41 of the input/output optical fiber blocks 45 and 46 correspond to those of the optical waveguide device 44 when the optical waveguide 42 and the optical fibers 43 are connected, the connection between the optical waveguide and the optical fibers become simple.

The fourth embodiment Figs. 6a through 6g are process perspective views showing the fabrication process of the optical device according to the fourth embodiment of the present invention.

According to the fourth embodiment of the present invention, the grooves for mounting the optical fibers are formed using the upper clad layer used in the step of forming optical waveguide as mask other than the mask layer.

First, as shown in Fig. 6a, a lower clad layer 53 and a core layer 54 are formed in order on a silicon substrate 51 having first and third areas on which optical fibers are supposed to be arranged and second area on which an optical waveguide is supposed to be formed.

Next, as shown in Fig. 6b, the core layer 54 is patterned and one or more

optical waveguide 54a is formed on the substrate of the second area.

Next, as shown in Fig. 6c, an upper clad layer 55 is formed on the entire surface of the substrate including the optical waveguide 54a.

Next, as shown in Fig. 6d, a mask layer (not shown) is formed on the substrate where the upper clad layer 55 is formed and patterned using photolithography process to expose the upper clad layer 55 on the first and third areas on which optical fibers are arranged, the upper clad layer 55 and the lower clad layer 53 on the first and third areas of the substrate 51 are dry etched using the patterned mask layer as mask to expose the substrate 51, and the mask layer is removed. As shown in Fig. 63, the exposed substrate 51 is wet etched to a prescribed depth to form the grooves using the upper clad layer 55 as mask.

On the other hand, a mask formed in advance (shadow mask) can also be used other than the mask layer is formed and patterned using photolithography process in this step. Such mask can be aligned minutely using the align mark formed on the substrate or the optical waveguide as reference point.

Then, the upper and lower clad layers 55 and 53 remained on the first and the third areas of the substrate 51 are removed to expose the substrate 51.

Since Figs. 6f and 6g are same as Figs 3i and 3j of the second embodiment, detailed description will be omitted.

In addition, according to the fourth embodiment of the present invention, one or more connection guide parallel to the grooves where optical fibers are supposed to be mounted can also be formed as the third embodiment.

That is, the connection guide can be easily formed if the connection guide pattern can be formed together when the mask layer is pattered in the step of Fig. 6d or when the shadow mask is formed.

That is, the connection guides 41 are formed parallel to the optical waveguide 42 and the optical fibers 43 as shown in Fig. 5, and the central axes of the connection guides formed in the optical waveguide device 44 and those in the input/output optical fiber blocks 45 and 46 correspond to each other.

Fig. 7 shows the connection status of optical fibers and the 1x8 optical waveguide device fabricated according to the fabrication method of the present invention described above.

The fifth embodiment On the other hand, grooves for mounting optical fibers can be formed on the opposite surface of the substrate to the surface on which the optical waveguide is formed to make the fabrication process simpler.

Figs. 8a through 8g are process perspective views showing the fabrication process of the optical device according to the fifth embodiment of the present invention.

First, as shown in Fig. 8a, a silicon substrate 81 having first and third areas on which optical fibers are supposed to be arranged and second area on which an optical waveguide is supposed to be formed is prepared. Next, a mask layer 82 made of Si3N4, etc. is formed on one surface of prepared silicon substrate 81. Then, as shown in Fig. 8b, the mask layer 82 is patterned using conventional photolithography process to expose the first and third areas of the substrate 81 on which the optical fibers are supposed to be

arranged.

Next, as shown in Fig. 8c, the first and the third areas of the substrate are etched to a prescribed depth using the mask layer 82 as mask to form one or more grooves, and the mask layer 82 is removed (Fig. 8d).

At this time, a mask formed separately can also be used other than the mask layer 82 according to the needs.

Next, as shown in Fig. 8e, a lower clad layer 83 and a core layer 84 are formed in order on the opposite surface of the substrate 81 to the surface where the grooves are formed.

Next, as shown in Fig. 8f, the core layer 84 is patterned and one or more optical waveguide 84a is formed on the substrate 81 of the second area.

Next, as shown in Fig. 8g, an upper clad layer 85 is formed on the entire surface of the substrate including the optical waveguide 84a.

Next, as shown in Fig. 8h, the substrate 81 is diced to separate the first, second, and third areas of the substrate 81, and the diced substrate 81 is separated to first sub- substrate 8 la having the first area, second sub-substrate 81b having the second area, and third sub-substrate 81c having the third area.

Then, as shown in Fig. 8i, the upper and lower clad layers 85 and 83 of the first and the third sub-substrates 8 la and 81 c are removed using HF solution, and so forth.

Now, the first and the third sub-substrates 8 la and 81 c become the input/output optical fiber blocks and the second sub-substrate 81b becomes the optical waveguide device.

Next, the optical fibers are arranged and mounted to correspond on the grooves after turning the input/output optical fiber blocks upside down. Then, the side end surfaces, to be bonded to each other, of the optical waveguide device and input/output optical fiber blocks are lapped and polished through the following process. Finally, as shown in Fig. 8j, the input/output optical fiber blocks are aligned to put in contact with the optical waveguide device to make the lapped and polished side end surfaces be opposite to each other, and the connections are fixed using epoxy, etc. to complete the optical device.

At this time, for the connected optical waveguide device and the optical fiber blocks, the upper/lower surfaces of the optical waveguide device and the upper/lower surfaces of the input/output optical fiber blocks are parallel to each other, and the areas and heights of the substrate connection surfaces are equal. Therefore, optical fibers and the optical waveguide are easily aligned if only the center of the optical waveguide and those of the grooves for mounting the optical fibers, which are formed on different surfaces of the substrate, respectively, correspond.

Especially, fabrication process becomes simpler by forming the optical waveguide and the grooves for mounting the optical fibers on different surfaces of the substrate, respectively.

On the other hand, the optical waveguide are formed after forming the grooves for mounting the optical fibers on the opposite surface of the surface according to the fifth embodiment of the present invention, however, the order can be opposite.

The sixth embodiment

The sixth embodiment of the present invention is related to a method of making the cutting surfaces between the optical fiber blocks and the optical waveguide block slant.

When the optical fiber block and the optical waveguide block are connected to each other, return loss or crosstalk is caused by the a part of the light transmitting from one medium to the other, which is reflected on the boundary surface and transmitted to other waveguide or optical fiber, if the section of the optical fiber and that of the optical waveguide are connected to be perpendicular to the proceeding direction of the light.

Conventionally, the connection surfaces are polished and connected to make both surfaces have a slant to the perpendicular direction to the light proceeding direction to prevent such problems. Fig. 9 shows the sections of the connection surfaces using the above-described method. That is, as shown in Fig. 9, the connection surfaces of the optical fiber block and the optical waveguide block are polished and connected to have about 8 degree of inclination angle to the perpendicular direction to make the connection surface between the optical fiber and the optical waveguide not perpendicular to the light proceeding direction.

However, polishing process to make each block be slanted requires a pretty long time, and therefore, it makes the fabrication process inefficient.

Fig. 10 is a layout diagram showing a dicing method of a substrate according to the sixth embodiment of the present invention. Fig. 10 shows a method of dicing the substrate fabricated by the first embodiment of the present invention shown in Figs. 2a through f.

Here, let's set the direction of the central axes of the optical fiber and optical waveguide, that is, the light proceeding direction as x direction, the direction parallel to the surface of the substrate and perpendicular to x direction as y direction, and the direction perpendicular to the surface of the substrate as z direction.

According to the sixth embodiment of the present invention, as shown in Fig.

10, the substrate is diced in z direction to have a little inclination to the y direction. The angle between the diced section and y direction is preferably around 8 degree. Then, the lapping time can be reduced remarkably because only the optical fiber need to be substantially lapped to be parallel to the dicing section of the substrate after mounting the optical fiber to the groove.

It is preferable that the arrangement direction of each optical device and the arrangement of the grooves and waveguides in each optical device have an inclination corresponding to the dicing direction with regard that the wafer is diced with a slant because a plurality of optical devices are fabricated using one wafer in practical fabrication process. Therefore, it has to be considered when the mask to form each component is fabricated.

On the other hand, according to another aspect of the present invention, a method of forming an optical fiber block and an optical waveguide block are fabricated integrally. In addition, to solve the problem of the high cost due to complicated process when an integrated optical device is fabricated, an optical waveguide is formed after forming a first groove for arranging an optical fiber, and a second groove is formed by half cutting the connection part between the optical waveguide and the optical fiber

block using dry or wet etching, dicing saw, laser processing, and/or any combination of two or more of these, or micro-machining to make the process simple.

The seventh embodiment Figs. 11 a through 11 j are process perspective views showing the fabrication process of an optical device according to the seventh embodiment of the present invention.

As shown in Fig. 1 la, a mask layer 112 made of silicon nitride, etc. is formed on a silicon substrate 111. The mask layer 112 is patterned using conventional photolithography process to expose the substrate 111 on the area where an optical fiber is supposed to be arranged.

Then, as shown in Fig. l lc, the exposed substrate 111 is etched by wet etching process using the patterned mask layer 112 as mask to form a first groove 113, and the mask layer 112 is removed.

Here, The first groove 113 is formed to have a V shape where the width of the upper part is wide and that of the lower part is narrow.

As shown Figs. lid and live, a lower clad layer 114 and a core layer 115 are formed in order on the entire surface of the substrate 111 where the first groove is formed.

Here, the lower clad layer 114 and the core layer are made of Si02, and the thicknesses are around 20 um and 8 um, respectively.

Next, as shown in Fig. llf, the core layer 115 is patterned to form an optical waveguide 115 a placed in a line with the first groove 113.

A silica layer having low refractive index is deposited as the lower clad layer 114 to make the light total reflect in the optical waveguide 115a to pass through well, and the optical waveguide 115a is to pass the light.

Next, as shown in Fig. llg, an upper clad layer 116 is formed on the entire surface including the optical waveguide 115a.

The upper clad layer is also made of Si02 as the lower clad layer 114, and the thickness is around 20 (lm. Also, a silica layer having lower refractive index than the core layer is deposited to make the light total reflect in the optical waveguide 115a to pass through well.

Then, as shown in Fig. l lh, the upper clad layer 116 and the lower clad layer 114 on the area where the first groove 113 is formed are removed in order to expose the substrate 111.

At this time, the upper clad layer 116 and the lower clad layer 114 are removed by dry etching process using reaction gas such as CxFy group, CxCly group, etc. or by wet etching using HF, and so forth.

In this step, an optical fiber block where the optical waveguide 115a and an optical fiber are arranged is completed.

As shown in Fig. 1 li, the connection part between the optical waveguide 115a and the optical fiber block is half cut by dry or wet etching, dicing saw, laser processing, any combination of two or more of these, or micro-machining to form a second groove.

The reason why the second groove is formed is to align the center of the optical waveguide and that of the optical fiber smoothly.

Finally, as shown in Fig. llj, an optical fiber 110 is arranged on the first groove, and the optical fiber 110 is connected to the optical waveguide 115a to complete the optical device in which the optical fiber array block is integrated.

The eighth embodiment Figs. 12a through 12j are process perspective views showing the fabrication method of an optical device according to the eighth embodiment of the present invention.

The eighth embodiment of the present invention is different from the seventh embodiment of the present invention in that a mask is used to dry etch the substrate other than the mask layer.

The eighth embodiment of the present invention has an advantage that the process becomes simpler than the seventh embodiment because the groove is formed using a mask.

As shown in Fig. 12a, a mask 122 where a prescribed pattern is formed is prepared and aligned on a substrate 121.

Then, as shown in Fig. 12b, the substrate 121 of the area where an optical fiber is supposed to be arranged is dry etched using mask 122 to a prescribed depth to form a first groove 123, and the mask 122 is removed as shown in Fig. 12c.

Here, The first groove 123 is formed to have a V shape where the width of the upper part is wide and that of the lower part is narrow.

Descriptions about the following processes are omitted because they are equal to those of the seventh embodiment.

The ninth embodiment Figs. 13a through 13h are process perspective views showing the fabrication method of an optical device according to the ninth embodiment of the present invention.

The ninth embodiment of the present invention uses a mask as the eighth embodiment of the present invention, but it is different in that a groove is formed later.

According to the ninth embodiment of the present invention, grooves are formed together using one mask. Therefore, the fabrication process becomes simpler than those of the seventh and eighth embodiments.

As shown in Fig. 13a, a lower clad layer 134 and a core layer 135 are formed in order on the entire surface of a substrate 131, and an optical waveguide 135a is formed in a prescribed area by patterning the core layer 135.

Next, as shown in Fig. 13c, an upper clad layer 136 is formed on the entire surface including the optical waveguide 135a.

Then, as shown in Fig. 13d, a mask having a prescribed pattern is prepared and aligned on the substrate 131.

Next, as shown in Fig. 13e, the upper and lower clad layers 136 and 134 of an area in a line with the optical waveguide 135a are dry etched to expose the substrate 131 of an area where an optical fiber is supposed to be arranged, and the mask 132 is removed.

Next, as shown in Fig. 13f, the exposed substrate 131 is wet etched to a prescribed depth using the upper clad layer 136 as mask to fonn a first groove 133, and the remaining upper and lower clad layers 136 and 134 on both sides of the first groove

133 are removed.

Then, as shown in Fig. 13g, the connection part between the optical waveguide 135a and the optical fiber block is half cut by dry or wet etching, dicing saw, laser processing, any combination of two or more of these, or micro-machining to form a second groove.

Finally, as shown in Fig. 13h, an optical fiber 130 is arranged on the first groove, and the optical fiber 130 is connected to the optical waveguide 135a to complete the optical device in which the optical fiber array block is integrated.

The tenth embodiment Figs. 14a through 14h are process perspective views showing the fabrication method of an optical device according to the tenth embodiment of the present invention.

The tenth embodiment of the present invention forms the groove after forming the optical waveguide as the eighth embodiment of the present invention, but it is different in that a mask layer formed by photolithography process is used other than a mask.

As shown in Figs. 14a through 14c, the process of forming an optical waveguide 145a is same as that of the ninth embodiment.

However, the next step is, as shown in Fig. 14d, to form a mask layer 142 on an upper clad layer 146 and pattern it. Then, the upper and lower clad layers 146 and 144 of an area in a line with the optical waveguide 145a are etched to expose the substrate 141 of an area where an optical fiber is supposed to be arranged, and the mask layer 142 is removed.

Next, as shown in Fig. 14e, the exposed substrate 141 is etched to a prescribed depth using the upper clad layer 146 as mask to form a first groove, and the remaining upper and lower clad layers 146 and 144 on both sides of the first groove are removed.

Since the following process shown in Figs. 14f through 14h is same as that of the ninth embodiment, the description is omitted.

The eleventh embodiment According to the eleventh embodiment of the present invention, a mask layer to form a groove is formed, an optical waveguide is formed, and then a groove is formed as in the second embodiment. However, this embodiment can be used with a combination with the above-described second embodiment or another embodiments.

Therefore, it is not shown in the drawings.

First, a substrate including a first area where an optical waveguide is supposed to be formed and a second area where an optical fiber is supposed to be mounted is prepared. A first mask layer made of Si3N4, etc. is formed on the entire surface of the prepared substrate, and the first mask layer is patterned using photolithography process to expose the area where a first groove is supposed to be formed in the second area of the substrate.

Next, a lower clad layer and a core layer are formed in order on the entire surface of the substrate, and the core layer is patterned to form an optical waveguide in the first area of the substrate. Then, an upper clad layer is formed on the entire surface including the optical waveguide.

Next, a second mask layer is formed on the entire surface of the substrate and

patterned to expose the first mask layer by etching the upper and lower clad layers of the second area except the first area of the substrate.

Next, the substrate of the second area where an optical fiber is mounted is etched to a prescribed depth using the exposed first mask layer as mask to form one or more first groove, and the first and the second mask layers are removed.

Then, the connection part between the optical waveguide and the optical fiber block is half cut by dry or wet etching, dicing saw, laser processing, any combination of two or more of these, or micro-machining to form a second groove.

Finally, an optical fiber is arranged on the first groove, and the optical fiber is connected to the optical waveguide to complete the optical device in which the optical fiber array block is integrated.

On the other hand, the fabrication method of an optical device using a silicon substrate is described mainly in the above-described embodiments of the present invention. However, various wafers for semiconductor process having crystalline structure and enabling groove processing using various etching methods such as dry, wet, laser processing, etc. including GaAs, InP, etc. can be used. In addition, substrates for optical materials being able to form grooves by dicing or laser processing, and substrates being able to form planar waveguide device or active optical devices including LD/PD and being able to form passive optical devices such as mirror, filter, or lens of 3-dimensional structure by micro-machining can be also used. Moreover, the present invention can be applied to the A1N (Aluminum Nitride) or plastic substrate if dry etching method such as laser processing is user.

On the substrate, optical waveguides or active/passive devices can be formed directly. However, a planar optical device using Si02, polymer material, etc. can be formed, or a material which can be mounted on a compound semiconductor substrate such LD or PD, a passive device of 3-dimensional structure which can be fabricated by micro-machining such as filter, lens, mirror, etc. can be also formed on the substrate.

While the present invention has been described in detail with reference to the preferred embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the sprit and scope of the appended claims.

[Industrial Applicability] According to the present invention described above, the optical waveguide and the optical fiber can be connected accurately without expensive alignment station.

Therefore, the fabrication process time and cost can be reduced remarkably.

In addition, the fabrication method of the optical device according to the present invention is simple and good for mass production. Therefore, the reliability of the process is improved as well as the processing time and cost.