CROSS-REFERENCE TO RELATED APPLICATION(S)

[0001] This application claims priority to U.S. Provisional Patent Application No. 62/952,891 filed on December 23, 2019, the contents of which are incorporated herein by reference.

TECHNICAL FIELD

[0002] The following relates generally to systems and methods for monitoring conditions in semiconductor processing chambers, particularly using optical fibers having Fiber Bragg Grating (FBG) sensors.

BACKGROUND

[0003] In many semiconductor manufacturing steps, the manufacturing processes are temperature dependent. For example, in plasma etching, small variations in temperature can cause considerable changes in etching rates or critical dimension (“CD”) uniformity. Thus, the inability to precisely measure and control wafer temperature can lead to process yield loss. Additionally, accurate temperature measurement and control is becoming of increasing importance as features produced using such semiconductor manufacturing processes continue to decrease in size.

[0004] A common technique for measuring wafer temperature is phosphor thermometry, which is often carried out using contact phosphor-based temperature sensors. These sensors operate by remote, optical excitation of the phosphor and subsequent analysis of the re-emitted, temperature dependent optical signal. A single, point-based measurement can be implemented using, for example, a fiber optic delivery system with a single photodetector. Multiple single point measurements can be used to build a temperature profile across the wafer chuck and thus the water itself. However, the need for physical installation of such probes can result in space constraints, limiting the number of accessible measurement points on the chuck. Moreover, it can be burdensome to manage the multiple optical cables necessitated by using multiple probes in such a configuration. [0005] Other methods for monitoring wafer temperature include the use of thermocouples or resistance temperature detectors (“RTDs”). However, thermocouples and RTDs are electrical devices and thus are prone to electromagnetic interference. This electromagnetic interference can arise from ambient electromagnetic fields and/or radio frequency energy which is used in some processes to ignite or strike a plasma. Additionally, acquiring multiple single point temperature measurements with these devices can necessitate a plurality of cables, which can be difficult to manage.

[0006] The above issues have been addressed by implementing Fiber Bragg Grating (“FBG”) sensors, which are well suited for measuring temperature and stress. An FBG is an optical filtering device that reflects light of a specific wavelength and is present within the core of an optical fiber. The wavelength of light that is reflected depends on the spacing of a periodic variation or modulation of the refractive index that is present within the fiber core. This grating structure acts as a band-rejection optical filter which reflects light within a narrow wavelength range. Being a completely optical device, an FBG sensor is immune to electromagnetic interference. Moreover, FBG technology provides the ability to multiplex many FBG sensors in a single optical fiber.

[0007] FBGs have been incorporated in dummy, or test wafers and electrostatic chucks (“ESCs”) to measure the temperature of same. The FBG sensors enable 2D temperature mapping of test wafers and ESCs, and thus can be used to, e.g., analyze the impact of an ESC temperature gradient on process uniformity. However, strain induced elongation of the FBGs can be indistinguishable from temperature induced elongation, and it can be challenging to install the FBGs in such a way that strain induced signals do not interfere with temperature induced signals. Additionally, replacing a faulty or damaged optical fiber that is physically embedded within or glued to wafers or ESCs can require physically accessing the chamber, which can be time consuming and can compromise the sealed environment in the chamber.

[0008] An object of the following is to provide methods and systems for incorporating FBG sensors into semiconductor processing chambers that address one or more of the above drawbacks. SUMMARY

[0009] The following provides systems and methods for using FBG sensors to measure the temperature of many points on surfaces in semiconductor processing chambers with improved accuracy, while minimizing the number of connections/cables required. In one aspect, there is provided a method of reducing strain on and/or increasing thermal response speed of FBG sensors. The method comprises inserting the FBG array into a protective capillary and filling the capillary with a thermal exchange fluid. In another aspect, there is provided a system for accessing a protective capillary having a fiber optic cable therein, the system comprising a capillary connector including an expansion joint and an open end for connecting to a fiber optic connector. In yet another aspect, there is provided a system for relieving strain on FBG sensors using strain relieving blocks. The strain relieving blocks can each have a channel defined therein adapted to receive an FBG sensor, particularly such that a bend can be introduced into the portion of the fiber including the FBG sensor. The FBG sensors can also be sealed within the blocks and immersed in a thermal exchange fluid.

[0010] In one aspect, there is provided a method of reducing strain on an FBG array and/or accessing the FBG array, the FBG array being for measuring temperature of at least one surface, the method comprising: placing in contact with the at least one surface a capillary adapted to slidably receive the FBG array; and inserting the FBG array into the capillary.

[0011] In an implementation of the method, the capillary is placed in contact with the at least one surface by being physically embedded in an object having the at least one surface.

[0012] In another implementation of the method, the capillary is physically embedded in the object by being at least partially surrounded by an additive manufacturing material.

[0013] In yet another implementation of the method, the capillary is glued to the at least one surface.

[0014] In another aspect, there is provided a method of increasing thermal response speed of an FBG array for measuring temperature of at least one surface, the method comprising: providing near the at least one surface a sealable channel adapted to slidably receive the FBG array; at least partially filling the channel with a thermal exchange fluid; and inserting the FBG array into the channel. [0015] In an implementation of the method, the method further comprises hermetically sealing the channel.

[0016] In another implementation of the method, the channel is defined within a capillary, and the sealable channel is provided near the at least one surface by placing the capillary in contact with the at least one surface.

[0017] In yet another implementation of the method, the capillary is physically embedded in an object having the at least surface by being at least partially surrounded by an additive manufacturing material.

[0018] In yet another implementation of the method, the capillary is glued to the at least one surface.

[0019] In yet another implementation of the method, the channel is defined within an object having the at least surface.

[0020] In yet another aspect, there is provided a connection assembly for connecting an optical fiber feedthrough to an FBG array disposed in a capillary, the capillary being provided in a sealable enclosure, the feedthrough defining a sealable opening in the enclosure, the system comprising: the capillary having a first end adapted to releasably engage a fiber optic connector; and the fiber optic connector being attached to the optical fiber feedthrough.

[0021] In an implementation of the assembly, the first end of the capillary includes an expansion joint for absorbing thermal expansion and/or contraction of the capillary.

[0022] In another implementation of the assembly, the FBG array is for measuring temperature of an object in the sealable enclosure, and a second end of the capillary is connected to the object.

[0023] In yet another implementation of the assembly, the capillary is physically embedded in the object.

[0024] In yet another implementation of the assembly, the object is an electrostatic chuck, and the enclosure is a semiconductor processing chamber.

[0025] In yet another aspect, there is provided a system for increasing response speed of an FBG array disposed in a capillary, the capillary being provided in a sealable enclosure, the system comprising: the capillary having a first end attached to a fiber optic connector; the fiber optic connector being attached to an optical fiber feedthrough; a sealed volume defined in the capillary and fiber optic connector; and the sealed volume comprising a fluid for increasing a rate of heat transfer between an outer surface of the capillary and the FBG array.

[0026] In an implementation of the system, the first end of the capillary includes an expansion joint for absorbing thermal expansion and/or contraction of the capillary and/or fiber optic connector.

[0027] In another implementation of the system, the FBG array is for measuring temperature of an object in the sealable enclosure, and a second end of the capillary is connected to the object.

[0028] In yet another implementation of the system, the capillary is physically embedded in the object.

[0029] In yet another implementation of the system, the object is an electrostatic chuck, and the enclosure is a semiconductor processing chamber.

[0030] In yet another aspect, there is provided a system for relieving strain on an FBG array for measuring the temperature of a surface, the system comprising: at least one strain relieving block; and each strain relieving block having a channel defined therein adapted to receive the FBG array.

[0031] In an implementation of the system, each channel is sized such that a bend can be provided in an FBG sensor in the channel to relieve strain on the FBG sensor.

[0032] In another implementation of the system, the channel is sealable and adapted to receive and contain a fluid for increasing a rate of heat transfer between the block and the respective FBG sensor.

[0033] In yet another implementation of the system, the strain relieving blocks include a low mechanical loss material.

BRIEF DESCRIPTION OF THE DRAWINGS [0034] Embodiments will now be described with reference to the appended drawings wherein:

[0035] FIG. 1 is a schematic diagram of a conventional optical fiber including FBG sensors.

[0036] FIG. 2A is a schematic diagram of a remote configuration of a system for measuring temperature of a test wafer having FBG sensors therein, in a semiconductor processing chamber.

[0037] FIG. 2B is a top, cross-sectional view of the test wafer shown in FIG. 2A.

[0038] FIG. 2C is a front, cross-sectional view of the test wafer shown in FIGS. 2A and

2B.

[0039] FIG. 3A is a schematic diagram of a non-remote configuration of a system for measuring temperature of an ESC having FBG sensors therein, in a semiconductor processing chamber.

[0040] FIG. 3B is a front, cross-sectional view of the test wafer shown in FIG. 3A.

[0041] FIG. 3C is a front, cross-sectional view of the connection assembly shown in

FIG. 3A.

[0042] FIG. 3D is a front, cross-sectional view of the connection assembly shown in FIG. 3A, in an assembled state.

[0043] FIG. 4 is a front, cross-sectional view of another optical fiber connection assembly.

[0044] FIG. 5 is a perspective view of a strain relieving block.

[0045] FIG. 6 is a perspective view of another strain relieving block.

[0046] FIG. 7 is a perspective view of yet another strain relieving block.

[0047] FIG. 8A is a perspective view of a yet another strain relieving block.

[0048] FIG. 8B is a side view of the strain relieving block. [0049] FIG. 8C is a front view of the strain relieving block.

[0050] FIG. 8D is a cross-sectional view, taken along a line A-A drawn in FIG. 8C, of the strain relieving block.

[0051] FIG. 8E is a top view of a test wafer equipped with an optical fiber extending through strain relieving blocks attached to the wafer.

[0052] FIG. 9 is a top view of a test wafer having an FBG array attached thereto in a “finger” like configuration.

[0053] FIG. 10 is a top view of a test wafer having a plurality FBG arrays arranged thereon in parallel.

DETAILED DESCRIPTION

[0054] Provided herein are systems and methods for implementing FBG sensors in semiconductor chambers to measure the temperature of components therein. The use of FBGs to generate 2D temperature maps in test wafers, ESCs and other equipment in semiconductor processing chambers can enable more accurate temperature calibration, uniformity tuning and chamber matching.

[0055] It will be understood that, unless otherwise indicated, the term “optical fiber” as used hereinafter may refer to an optical fiber having FBG sensors, such as that discussed with respect to FIG. 1.

[0056] One or more of the terms “vertical”, “vertically”, “horizontal”, “horizontally”, “top”, “bottom”, “upwardly”, “downwardly”, “upper” and “lower” are used throughout this specification. It will be understood that these terms are not intended to be limiting. These terms are used for convenience and to aid in describing the features herein, for instance as illustrated in the accompanying drawings.

[0057] FIG. 1 is a schematic illustration of a portion of a conventional FBG optical fiber 1 including a waveguide 3 having a core 2 therein, the core 2 including three FBG sensors 4 arranged in series. Each sensor 4 can be configured to reflect a different wavelength, and the grating therein can deform in response to, inter alia, strain and temperature. [0058] The methods and systems described below are discussed in the context of a general semiconductor etching chamber. However, it can be appreciated that the methods and systems can be applied in other semiconductor processing chambers.

[0059] FIG. 2A is a schematic diagram of a remotely configured system 100 for remotely measuring the temperature of a test wafer 108 in a semiconductor processing chamber 102. The temperature of the wafer 108 can be measured using FBG sensors attached to the surface of the wafer 108, as described in greater detail with respect to FIGS. 2B and 2C.

The system 100 comprises a stand, or pedestal 104 extending upwardly into the processing chamber 102, the pedestal having an ESC 106 positioned thereon. The ESC 106 includes an edge ring 134 and can hold the test wafer 108 in place thereover, in the conventional manner. The system 100 further comprises an etchant gas assembly 115 outside the chamber 102, the gas assembly 115 being configured to feed the etchant gas through a cover, or lid 112 of the chamber 102 to a showerhead 114. The showerhead 114 can include a distribution assembly 110 for conveying etchant into the chamber.

[0060] The remotely configured system 100 comprises a window 118 in a sidewall of the chamber 102 through which light from an optical fiber 113 (shown in FIGS. 2B and 2C) and a light source (not shown) can pass. The light source can be included in an FBG interrogator 120. Suitable components including, but not limited to an I/O coupler 116 can be provided between an open fiber end 147 (FIG. 2B) and the FBG interrogator 120, to enable optical communication therebetween. The light source can emit broadband light, which can be directed into the optical fiber 113. The return signal from the optical fiber 113 comprises one or more narrow band profiles each corresponding to a respective FBG sensor 105.

[0061] It can be appreciated that the system 100 is simplified for clarity and ease of illustration. The system can further include different and/or additional elements such as, for example, volume phase grating, various lenses, and mirrors for transmitting light between the optical fiber 113 and the FBG interrogator 120.

[0062] FIG. 2B is a top, cross-sectional view of the test wafer 108, showing a wafer surface 109 having the optical fiber 113 embedded therein. The grooves shown in FIG. 2C are omitted from FIG. 2B for clarity. FIG. 2C is a cross-sectional front view of the test wafer 108 which includes a first, or bottom wafer 142 connected to a second, or top wafer 140.

The top and bottom wafers 140 and 142 can be connected to one another using an adhesive such as, e.g., Room-Temperature-Vulcanizing (“RTV”) silicone or an epoxy, direct optical contacting, diffusion bonding, or any other suitable wafer bonding technique. As shown in FIG. 2C, the optical fiber 113 can be embedded in the test wafer 108 by being positioned within a groove 144 defined in the surface 109 of the bottom wafer 142. The optical fiber 113 is arranged in a spiral pattern in this example embodiment; however, the optical fiber can be arranged in other patterns, such as those described further below.

[0063] The optical fiber 113 can sit in the groove 144 without being connected thereto, resulting in greater freedom to expand and contract as compared to being glued to the groove 144 at multiple points therealong. This, in turn, can help to prevent strain induced measurement errors and/or buckling of the optical fiber 113. Optionally, an end 145 (FIG.

2B) of the optical fiber 113 can be attached to the groove 144 by way of an adhesive such as, e.g., an epoxy. The optical fiber 113 can also be attached to the groove 144 using a superalloy such as, e.g., titanium aluminide (TiAI). By being attached at the end 145 only, the fiber can expand and contract longitudinally relative the end 145 (the point of attachment). The optical fiber 113 can alternatively be attached to the groove 144 at a different, single point along the length of the fiber 113. The groove 144 can also be filled with a suitable heat conducting fluid (e.g., the thermal exchange fluids discussed further below) if the fluid is suitably contained in the groove 144 by a sealing technique, such as that described above with respect to FIG. 2C. For particularly high temperature applications, molten salts or other suitable materials can be used as the heat conducting, or thermal exchange fluid provided adequate care is paid to the effect of their molten/solid transition effect on the performance and lifetime of the sensors 105.

[0064] Continuing with FIG. 2B, the optical fiber 113 includes a plurality of FBG sensors 105. The location of each FBG sensor 105 is indicated with the character “X”. The plurality of FBG sensors 105 distributed throughout the test wafer 108 can enable the generation of a 2D temperature map of the wafer 108 along the surface 109.

[0065] It can be appreciated that one or more optical fibers can be provided within respective grooves defined in a test wafer or an ESC. Such optical fibers can be pressed into the grooves and/or connected thereto at a single point (e.g., an end) along each optical fiber. It can also be appreciated that one or more grooves can be cut in other patterns, such as, e.g., a finger-like pattern. Advantages of a finger-like pattern are discussed in greater detail further below. The optical fibers can be coated in suitable jacketing such as, e.g., polyimide, acrylate, aluminum, copper, gold, Ormocer® or Ormocer®-T. [0066] FIG. 3A is a schematic diagram of a non-remotely configured system 200, implemented in the chamber 102, for monitoring the temperature of an ESC 206 having a wafer 208 thereon. The ESC 206 can have an optical fiber 213 (FIGS. 3B and 3C) embedded therein, the optical fiber 206 being contained within a protective capillary 244.

The protective capillary 244 can be made from materials including, but not limited to, metal (e.g., stainless steel), glass and polyimide/PEEK/PTFE. The protective capillary 244 can be embedded in the ESC 206 by additive manufacturing, e.g., by 3-D printing the ESC 206 around the capillary 244. It can be appreciated that the protective capillary 244 can be embedded in a similar manner into other components of semiconductor processing chambers.

[0067] The system 200 further includes a connection assembly 227 which is described in detail with respect to FIGS. 3C and 3D. The assembly 227 comprises a conventional optical fiber feedthrough 225 which can be connected to a suitable optical fiber connector 252 positioned in the chamber 102. The optical fiber connector 252 can be, e.g., an LC, FC, SC, or ST connector. The optical fiber connector 252 and feedthrough 225 can enable optical communication between the optical fiber 213 and the FBG interrogator 120 via a cable 202.

[0068] The connector 252 can include a male end 250 having a circumferential groove 254 defined therein. The assembly 227 further comprises a capillary connector 249 having a first, or female end 246 adapted to engage the male end 250. In particular, an O-ring 248 provided within the female end 246 can removably engage the groove 254 defined in the male end 250. It can be appreciated that the opposing ends of the capillary connector and optical fiber connector can include different connection mechanisms.

[0069] The assembly 227 can enable easy installation of the optical fiber 213 into the capillary, since the optical fiber 213 can be pushed into the stainless steel capillary 244. Additionally, should the optical fiber 213 and/or optical fiber connector 252 fail during operation, these components can easily be removed from the capillary 244 and capillary connector 249, and subsequently replaced.

[0070] Continuing with FIG. 3C, the capillary connector 249 also includes a bellows 260 at a second end thereof. The bellows 260 can be made from a metal such as, e.g., stainless steel. Although not shown, the bellows 260 can be corrugated to accommodate for thermal expansion and contraction of the capillary connector 249 and the capillary 244. The capillary 244, which is made from stainless steel in this example embodiment, can extend into an interior of the bellows 260. The capillary 244 and the bellows 260 can be connected together at a point 251 by, for example, laser welding. It can be appreciated that other expansion joints or mechanisms can be used instead of the bellows 260.

[0071] FIG. 3D illustrates the assembly 227 in an assembled state. The bellows 260 can accommodate for thermal expansion and contraction of the components in the assembly 227 in response to temperature fluctuations within the chamber 102. It can be appreciated that the connection assembly 227 can be implemented in semiconductor processing chambers having different configurations than that shown in FIG. 3A. More generally, the connection assembly 227 can be implemented in any system where it is desirable to measure conditions in a sealed or pressurized vessel using an FBG array provided in a capillary. It can also be appreciated that the bellows 260 can be omitted from the assembly 227 (i.e., no expansion joint included in the assembly 227) if absorption of such thermal expansion and contraction is not required.

[0072] FIG. 4 depicts an example embodiment of a different connector assembly 427. The connector assembly 427 comprises a vacuum feedthrough connector 430, a fiber optic connector 452, a metal capillary 444, and a bellows 460 provided between the fiber optic connector 452 and the metal capillary 444. An optical fiber 413 is provided within a hermetically sealed volume 453 which can be defined by an interior of the metal capillary 444, bellows 460, and fiber optic connector 452. The metal capillary 444 can be embedded in an ESC (not shown) as discussed above. The metal capillary 444 can be connected to the bellows 460 by way of, for example, laser welding at a point 451. The bellows 460 can also be connected to the fiber optic connector 452 by laser welding at a point 457. It can be appreciated that the fiber optic connector 452 shown is not necessarily the type that would be used and is provided for illustrative purposes. The fiber optic connector 452 can be, e.g., any of the fiber optic connectors listed above when describing FIG. 3C. Similar to the assembly 227, the hermetically sealed volume 453 can be filled with a thermal exchange media (e.g., those listed above). The bellows 460 can accommodate for thermal expansion and contraction of the assembly 427 components, which can be exacerbated by the presence of the thermal exchange media having a high coefficient of thermal expansion (relative to the components). It can be appreciated that a different expansion joint or mechanism can be used instead of bellows. It can also be appreciated that the bellows 460 can be omitted from the assembly 427 (i.e., no expansion joint included in the assembly 427) if absorption of such thermal expansion and contraction is not required. [0073] It can be appreciated that the protective capillary can be incorporated into an ESC in other ways, such as those discussed above with respect to the test wafer. For example, the protective capillary can be attached to the ESC using an adhesive such as, e.g., RTV or epoxy, or using a superalloy metal such as, e.g., TiAI. It can also be appreciated that a protective capillary such as that discussed with respect to FIGS. 3A-3C and 4 can be used when incorporating an optical fiber into or onto a test wafer, or other components of a semiconductor processing chamber (e.g., an edge ring, a showerhead, the chamber lid, etc.).

[0074] Strain on an optical fiber can also be reduced using strain relieving blocks, which can be made from a low mechanical loss material such as, e.g., a ceramic or metal.

Example embodiments of basic strain relieving blocks are depicted in FIGS. 5-7. FIG. 5 illustrates a strain relieving block having a channel 402 extending longitudinally therethrough, and an attachment surface 404 which can be connected to the surface of a test wafer using an adhesive, such as an epoxy or a superalloy. The channel 402 can be adapted to receive an optical fiber (not shown). The purpose of such channel 402 is discussed in greater detail with respect to FIGS. 8A-8D, which illustrate a more detailed strain relieving block. The strain relieving blocks shown in FIG. 6 and 7 are similar to that shown in FIG. 5, and thus similar features are described with the same reference numbers, but with the first character of each number replaced with “5” and “6” for FIGS. 6 and 7, respectively.

[0075] FIGS. 8A-8D illustrate another strain relieving block 700. Turning to FIG. 8D, the block 700 can have a central channel 706 extending longitudinally therethrough, between a first end channel 715a and a second end channel 715b. The first and second end channels 715a and 715b can optionally have diameters larger than that of the central channel 706. An optical fiber 713 can be provided within the channels 715a, 715b and 706. As shown, the diameter of the central channel 706 can be substantially larger than an outer diameter of the optical fiber 713 such that a bend 713a can be formed in the fiber 713, and more particularly in an FBG sensor 705 positioned within the central channel 706. The bend 713a can compensate for strain sensitivity of the FBG sensor 705 (i.e., can deform instead of the grating in the sensor 705), thereby minimizing or preventing strain induced error in temperature measurements. First and second openings 702a and 702b can be defined in an upper surface the block 700, and can each be positioned at opposite ends of the central channel 706. The first and second openings 702a and 702b can be adapted to introduce a sealant, such as glue, to create seals 708a and 708b between the end channels 715 and the central channel. The central channel 706 can be filled with a thermal exchange fluid, such as an inert gas, oil, silicone oil, molten salts, or other non-solid thermal exchange media.

The thermal exchange fluid can be introduced into the central channel 706 through a central opening 703 defined in the block. The U-bend 713b can float freely in the thermal exchange fluid, thereby substantially isolating the sensor 705 from strain. The thermal exchange fluid can increase the rate of heat transfer between the block material and the sensor 705, thereby improving response time.

[0076] It can be appreciated that features similar to those discussed with respect to FIGS. 8A-8D can be incorporated into the blocks shown in FIGS. 5-7, and vice versa. For example, the channels shown in FIG. 8D can be rectangular instead of cylindrical. The channels could also be open to the chamber environment, as shown in FIG. 7.

[0077] FIG. 8E is a test wafer 808 having a number of the strain relieving blocks 700 attached to a top surface 802 of the test wafer 808. The optical fiber 713 can be fed through the channels in each block 700 such that an FBG sensor 705 (not shown) can be positioned and sealed therein in the manner discussed above. A bottom surface 814 of the blocks 810 can be attached to the top surface 802 of the wafer 808 using, e.g., an adhesive or a superalloy metal. It can be appreciated that the strain relieving blocks 700 can be attached to other components of a semiconductor processing chamber (e.g., an ESC, edge ring, chamber wall, shower head, etc.).

[0078] It can be appreciated that the strain relieving blocks described above can be used to relieve strain on and/or increase measurement accuracy of an FBG array in other temperature sensing applications (i.e., outside of semiconductor processing).

[0079] FIG. 9 illustrates a test wafer 8 having an optical fiber 13 attached to a top surface 9 of the wafer 8. The optical fiber 13 is arranged in a “finger” type configuration to reduce the length of the fiber 13 that is curved (“curved length”). It is postulated that reducing the curved length of the fiber 13 can improve the quality of the return signals from FBG sensors 5 in the fiber 13, resulting in more accurate temperature measurements. This finger type configuration contrasts the spiral configuration in which the majority of the fiber containing the FBG array is curved (e.g., as shown in FIG. 2B). The location of each FBG sensor 5 is indicated with the character “X”. The plurality of FBG sensors 5 distributed across the surface 109 of the test wafer 108 can enable the generation of a two-dimensional (“2-D”) temperature map of the surface 109. It will be understood that such finger type configuration of the fiber can be implemented in one or more of the example embodiments discussed above.

[0080] FIG. 10 illustrates a test wafer 88 having a plurality of optical fibers 813 attached to a top surface 89 of the wafer 88. The fibers 13 are arranged in a “separate” finger configuration (i.e., fingers in parallel), to reduce the curvature of the fibers 13 while still distributing FBG sensors 805 across the surface of the wafer 808 to generate a 2-D temperature map thereof. It can be appreciated that the separate finger configuration can be implemented with less than four or more than four optical fibers.

[0081] For simplicity and clarity of illustration, where considered appropriate, reference numerals may be repeated among the figures to indicate corresponding or analogous elements. In addition, numerous specific details are set forth in order to provide a thorough understanding of the examples described herein. However, it will be understood by those of ordinary skill in the art that the examples described herein may be practiced without these specific details. In other instances, well-known methods, procedures and components have not been described in detail so as not to obscure the examples described herein. Also, the description is not to be considered as limiting the scope of the examples described herein.

[0082] It will be appreciated that the examples and corresponding diagrams used herein are for illustrative purposes only. Different configurations and terminology can be used without departing from the principles expressed herein. For instance, components and modules can be added, deleted, modified, or arranged with differing connections without departing from these principles.

[0083] The steps or operations in the flow charts and diagrams described herein are just for example. There may be many variations to these steps or operations without departing from the principles discussed above. For instance, the steps may be performed in a differing order, or steps may be added, deleted, or modified.

[0084] Although the above principles have been described with reference to certain specific examples, various modifications thereof will be apparent to those skilled in the art as outlined in the appended claims.