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Title:
APPARATUS AND METHOD FOR CONNECTING TWO SUBSTRATES FOR AN ELECTRIC COMPONENT
Document Type and Number:
WIPO Patent Application WO/2018/097995
Kind Code:
A1
Abstract:
An apparatus (1) for connecting two substrates (2, 3) for an electric component features a chamber (4) for inserting the substrates (2, 3), wherein a gas inlet (13) is arranged to direct a gas (14) in the chamber (4) in a targeted manner on the surface of at least one of the substrates (2, 3). The gas inlet (13) is particularly designed to control any warping of at least one of the substrates (2, 3), which may occur during a pre-conditioning phase due to inhomogeneous heat expansion of one of the substrates (2, 3) in the bonding level, different coefficients of thermal expansion of the two substrates (2, 3) or inhomogeneous temperature distribution. Thanks to the aimed direction of the gas (14) onto the surface of at least one of the substrates (2, 3), the warping of the substrates (2, 3) may be intensified or reduced, in particular any warping of the upper substrate (3) towards the lower substrate (2) can be avoided. This allows the prevention of any direct contact of the substrates (2, 3) during the pre-conditioning phase. During the pre-conditioning phase, one or several spacers (6) can be arranged between the substrates (2, 3), the spacers (6) being removed at the end of the pre-conditioning phase. In one set-up configuration, the apparatus (1) features a measuring device (for example, a device for optical distance determination such as a camera (18) arranged at the level of a gap between the substrates (2, 3)) to determine a distance (d) between the substrates (2, 3) and/or any warping of at least one of the substrates (2, 3). The apparatus may also feature a control circuit (21) to control and readjust the flow quantity and/or the temperature of the gas (14), thus controlling the warping of the substrates (2, 3), wherein the control circuit (21) shows the measuring result of the measuring device (18) as a control variable.

Inventors:
PORTMANN DR JÜRGEN (US)
STELTER MARK (US)
KONOPKA NIKLAAS (US)
LINDEN DR JENNIFER (US)
Application Number:
PCT/US2017/061738
Publication Date:
May 31, 2018
Filing Date:
November 15, 2017
Export Citation:
Click for automatic bibliography generation   Help
Assignee:
SNAPTRACK INC (US)
International Classes:
H01L21/67; B30B15/34; B32B37/06; H01L21/50; H03H9/10
Domestic Patent References:
WO2013121858A12013-08-22
Foreign References:
JP2013243333A2013-12-05
JP2002237678A2002-08-23
JP2000299330A2000-10-24
JP2008300394A2008-12-11
US20160005635A12016-01-07
JP2016054195A2016-04-14
JPH0887779A1996-04-02
JPS57102008A1982-06-24
Other References:
DRAGOI V: "From magic to technology: materials integration by wafer bonding", PROCEEDINGS OF SPIE, vol. 6123, 612314, 24 February 2006 (2006-02-24), XP040219581, DOI: 10.1117/12.646450
None
Attorney, Agent or Firm:
ROBERTS, Steven E. et al. (US)
Download PDF:
Claims:
Claims

1. Apparatus for connecting two substrates for an electric component,

featuring a chamber (4) for inserting the substrates (2, 3), wherein a gas inlet (13) is arranged to direct a gas (14) in the chamber (4) in a targeted manner onto the surface of at least one of the substrates (2, 3) .

2. Apparatus according to claim 1,

in which the gas inlet (13) is designed to prevent any direct contact of the substrates (2, 3) .

3. Apparatus according to one of the preceding claims,

in which the gas inlet (13) is designed to adjust the

temperature of at least one of the substrates (2, 3) .

4. Apparatus according to one of the preceding claims,

featuring an upper heating device (10) that is arranged above a carrier (9) for the substrates (2, 3), wherein the gas inlet (13) for directing the gas (14) in a targeted manner is designed to be in an area between the upper heating device (10) and the carrier ( 9 ) .

5. Apparatus according to claim 4,

in which the upper heating device (10) is integrated into a pressure device (11) that is designed to press the second

substrate (3) onto the first substrate (2) in a joining phase.

6. Apparatus according to one of the preceding claims,

featuring at least one further gas inlet to the directed and/or undirected inlet of a gas (14) into the chamber (4) .

7. Apparatus according to claim 6, in which the further gas inlet (16) is designed for the undirected inflow of a gas (14) into the chamber (4) .

8. Apparatus according to claim 6,

in which the further gas inlet to direct a gas (14) is

purposefully designed on the surface of at least one of the substrates (2, 3) .

9. Apparatus according to one of the preceding claims,

featuring a measuring device (18) to determine a distance (d) between the substrates (2, 3) .

10. Apparatus according to claim 9,

featuring a control circuit (21) to control the flow quantity and/or the temperature of the gas (14), wherein the control circuit (21) shows the measuring result of the measuring device (18) as a control variable.

11. Method for connecting two substrates for an electric component by an apparatus according to one of the preceding claims,

wherein the substrates (2, 3) are arranged in the chamber (4) and a gas (14) is directed onto the surface of at least one of the substrates (2, 3) .

12. Method according to claim 11,

wherein a spacer (6) is arranged between the substrates (2, 3) during a pre-conditioning phase, and wherein the gas (14) is allowed to flow in at least during the pre-conditioning phase.

13. Method according to one of the claims 11 or 12,

wherein the gas (14) prevents any direct contact of the

substrates (2, 3) during the pre-conditioning phase.

14. Method according to one of the claims 11 or 12, wherein a distance (d) between the substrates (2, 3) is measured, and the measured distance (d) value is used to adjust the flow quantity and/or the temperature of the gas (14) .

Description:
APPARATUS AND ME THOD FOR CONNECTING TWO SUBSTRATES FOR AN

ELECTRIC COMPONENT

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to German Patent Application No. 102016122486.3, filed November 22, 2016, which is expressly incorporated herein by reference in its entirety.

Description

This invention concerns an apparatus and a method for connecting two substrates for an electric component. This may especially also be an electromechanical component.

In order to reduce the height of the component as well as the lateral extension of electrical components, wafer bonding

technology is increasingly employed for individual component manufacturer and the production of modules. For this, two wafers or other substrates are connected with one another applying pressure and temperature. The substrates are inserted into a chamber for this process to take place, then are heated and subsequently joined. The connection may occur across the entire surface or alternatively across individual connection elements such as Cu carriers or polymer structures.

In order to have the joining of the substrates take place under the desired conditions, spacers are used to keep the substrates at a distance during a pre-conditioning phase, only bringing them into contact during a subsequent joining phase, when they are joined together under pressure. During the pre-conditioning phase, warping of the substrates may occur. Warping may, for example, correspond to a change in the distance between the substrates in certain areas of the substrates. This may, for instance, result in an early contact between the substrates, and the joining does not take place under the conditions planned. This may in particular lead to a weak and unreliable connection of the substrates.

One purpose of this invention is to offer an apparatus with improved properties for connecting two substrates.

According to a first aspect of the present invention, an

apparatus for connecting two substrates for an electric

component is specified. The components may, for example, be components for mobile radio communications. They may especially be RF components or modules such as filters or duplexers.

The apparatus has a chamber the substrates are inserted into. At least one gas inlet for directing a gas in a targeted manner onto the surface of at least one of the substrates is arranged in the chamber. The gas inlet especially features a nozzle that is aimed at the surface of a substrate.

Notably, the substrates in the chamber are arranged one above the other. For example, a first substrate is arranged on a carrier, and the second substrate arranged over the first substrate. The substrates may be arranged at a distance from one another during the pre-conditioning phase by means of one or several spacers. The spacers are then removed during the subsequent joining phase. In addition, the substrates may be fixed onto the carrier with a holding device. The spacers and/or the holding device are, for example, arranged only in one lateral edge area of the substrates.

During the pre-conditioning phase, there may be warping of at least one of the substrates especially in a central area. Such warping may occur due to mechanical and/or thermal influences. For example, warping may occur due to an inhomogeneous heat expansion of one of the substrates in the bonding level, different coefficients of thermal expansion for the two

substrates or due to an inhomogeneous temperature distribution. If there is, for example, a warping of the upper substrate in the direction of the lower substrate, there may be undesired contact of the substrates during the pre-conditioning phase.

The gas inlet is particularly designed to control any warping of at least one of the substrates. Due to the aimed direction of the gas onto the surface of at least one of the substrates, the warping of the substrates may be intensified or reduced. This means that in particular any warping of the upper substrates towards the lower substrate can be avoided. This allows the prevention of any direct contact of the substrates during the pre-conditioning phase. The available control variables are the gas flow quantity and the gas temperature.

For example, the gas inlet allows an accurate control of the temperature, especially of the temperature distribution of at least one of the substrates. In this way, the gas inserted may serve to provide a more homogeneous temperature distribution on the bond level. Alternatively, the gas may serve to achieve an inhomogeneous temperature distribution.

The apparatus may feature at least one heating device. For example, the apparatus features an upper heating device that is arranged above the substrates. The upper heating device is especially arranged above a carrier for the substrates. The upper heating device may be distanced from the substrates during the pre-conditioning phase. In particular, a gap may occur between the substrates and the heating device. In this case, the gas inlet may be designed to direct the gas precisely into an area between the upper heating device and the substrates and/or the carrier. Especially, one nozzle of the gas inlet points to an area between the upper heating device and the carrier.

The upper heating device may be integrated into a pressure device that is designed to press the substrates onto each other during a joining phase. In particular, the pressure device is lowered to the substrates after the pre-conditioning phase and presses the upper substrate onto the lower substrate.

The apparatus may feature one or several other gas inlets. The further gas inlet may be designed to allow a directed and/or undirected inflow of a gas.

For example, the apparatus features a gas inlet for an

undirected inflow of a gas into the chamber in addition to the gas inlet to direct the gas in a targeted manner onto the surface of the substrates. This may use the same gas or a different gas. For example, the gas inserted without direction serves as a process gas to set a desired atmosphere, to process an adhesive and/or to flush the chamber.

Alternatively, the additional gas inlet is designed to direct a gas in a targeted manner onto the surface of at least one of the substrates. In this way, the warping of the substrates may be monitored even more carefully.

In one set-up configuration, the apparatus features a measuring device to determine a distance between the substrates and/or any warping of at least one of the substrates. For example, the measuring device is designed for the optical determination of the distance. The measuring device may have a camera that is arranged at the level of a gap between the substrates and determines the distance between the substrates in a central area of the substrates, for example. This particularly allows one to determine any undesired contact of the substrates during the pre-conditioning phase.

The apparatus may also feature a control circuit to control the flow quantity and/or the temperature of the gas, wherein the control circuit shows the measuring result of the measuring device as a control variable. In this way, a desired value for the distance between the substrates can be set by readjusting the flow quantity and/or the gas temperature, for example, thus controlling the warping of the substrates.

According to a further aspect of this invention, a method for connecting two substrates for an electric component is

described, in which the apparatus described above is used. The substrates are arranged in the chamber and a gas is directed onto the surface of at least one of the substrates.

The gas is especially directed onto the substrates during a pre ¬ conditioning phase. This allows to control warping, e.g. a reduction of the distance between the substrates, and especially any direct contact of the substrates during the pre-conditioning phase can be prevented. During the pre-conditioning phase, one or several spacers can be arranged between the substrates.

In one set-up configuration, a distance between the substrates is measured during the application of the method. The distance is measured, for example, by means of the measuring device described above. The measured value for the distance may be used to readjust the flow quantity and/or the gas temperature.

Multiple aspects of an invention are described in the present disclosure. All properties that are disclosed with regard to the apparatus or the method are also accordingly disclosed with regard to the respective other aspect and even if the respective property is not explicitly mentioned within the context of the other aspect. Furthermore, the description of the objects given here is not limited to the individual specific set-up configurations.

Instead, the features of the individual set-up configurations can be arbitrarily combined as far as is technically meaningful.

In the following, the objects described here are explained in more detail on the basis of schematic example set-up configurations.

Shown are :

Figure 1 a cross-sectional view of a set-up configuration of a chamber and a method for connecting two substrates,

Figure 2 a cross-sectional view of another set-up

configuration of a chamber and a method for

connecting two substrates.

In the following Figures, the same reference characters

preferably refer to corresponding functional or structural parts of the various embodiments.

Figure 1 shows an apparatus 1 and a method for connecting two substrates 2, 3. The apparatus 1 features a chamber 4, especially a bonding chamber. The substrates 2, 3 are, for example, designed as wafers that are usually designed in a round form, or as others, e.g. rectangular or round substrates. The substrates 2, 3 have, for example, lateral dimensions of 15 cm to 30 cm each.

For example, the substrates 2, 3 that are connected with one another serve as housings for RF components or RF modules. The components may especially be produced in DSSP technology (die- sized SAW package technology) or eWLP technology (embedded wafer level ball grid array technology) . These technology offer a very high degree of miniaturization.

The substrates 2, 3 may feature the same material, e.g. Si, LiTaC>3, LiNb03 or S1O 2 . The substrates 2, 3 may also have different materials.

The substrates 2, 3 are arranged in the chamber 4 as a first step. The substrates 2, 3 are especially placed on a carrier 5. The first substrate 2 is placed onto the carrier 5, and the second substrate 3 arranged over the first substrate 2. The second substrate 3 is arranged at a distance from the first substrate 2 during a pre-conditioning phase by means of one or several spacers 6. The spacers 6 are removed at the end of the pre-conditioning phase.

The spacers 6 are only arranged on the lateral edge of the substrate 2, 3. Between the substrates is a cavity 7. For example, three spacers 6 are provided.

The substrates 2, 3 are mechanically fixed on the carrier 5 by means of a holding device 8. The holding device 8 is, for example, designed as a clamping device that presses the second substrate 3 in its edge area to the first substrate 2 and/or the spacer 6.

The substrates 2, 3 are, for example, connected to one another by adhesive bonding or polymer bonding. For adhesive bonding, an adhesive is, for example, applied to at least one of the

substrates 2, 3. The adhesive is, for example, a glue or a photoresist. The adhesive or the polymer may be applied without a structure, especially over the entire area, or in a structured manner. For example, the adhesive is applied to the lower

substrate 2. The substrate 2 may feature many insertion slots, wherein the adhesive is applied around each insertion slot. The substrates 2, 3 may alternatively also be connected to each other by eutectic bonding or direct bonding. For example, it may be a copper/tin-copper or a copper-copper bond. Other metals may also be used for the connection. For example, the metallic

structures to connect the substrates 2, 3 in a frame shape or as supporting elements.

During a preconditioning phase, the desired conditions for the connection of the substrates 2, 3 are adjusted. In particular, a desired temperature at the substrate 2, 3 location is set. For this purpose, the chamber 4 may have one or several heating devices 9, 10. For example, a lower heating device 9 is arranged below the first substrate 2. In particular, the lower heating device 9 is designed as a heating plate. The carrier 5 may be arranged on the lower heating device 9.

An upper heating device 10 may additionally be arranged in the chamber 4. The upper heating device 10 is, for example, placed above the second substrate 3. The upper heating device 10 may be integrated into a pressure device 11 that is held at a distance from the second substrate 3 during the pre-conditioning phase, then is moved closer to the second substrate 3 at the end of the pre-conditioning phase and presses the second substrate 3 to the first substrate 2 during the joining phase. The pressure device 11 is, for example, designed as a movable die.

During the pre-conditioning phase, warping 12 of the substrates 2, 3 may occur. Especially, the surface of at least one of the substrates 2, 3 is no longer level. For example, warping 12 may occur due to an inhomogeneous heat expansion of one of the

substrates 2, 3 on the bonding level, different thermal expansion coefficients for the two substrates 2, 3, or due to an

inhomogeneous temperature distribution. In addition, instances of warping 12 may also occur due to the influence of the holding device 8.

For example, warping 12 occurs in a central area of the second substrate 3 in one direction towards the top. Consequently, the distance d between the two substrates 2, 3 in one of the central areas of the substrates 2, 3 is greater than in an edge area of the substrates 2, 3.

There may also be warping of the second substrate 3 downwards, i.e. in the direction of the first substrate 2. The two

substrates 2, 3 may come into contact before this is desirable according to the process sequence. For adhesive bonds, this may lead to a modified degassing behavior and thus to bubbles in the connection. For other connections, premature contact of the substrates 2, 3 may lead to gases no longer reaching the entire surface of the substrates 2, 3. This may lead to a weak and unreliable connection of the substrates.

In order to prevent undesired warping 12, the chamber 4 has a gas inlet 13 for inserting a gas 14 in a directed manner onto the surface of at least one of the substrates 2, 3. The gas inlet 13 has, for instance, a nozzle 15 that points in the direction of the substrates 2, 3. Depending on the chamber 1, the substrate size, and type of substrate, there may be one or several such gas inlets 13.

The gas 14 is in particular directed in a targeted manner onto the surface of the second substrate 3. This may influence the heating of the second substrate 3 or both substrates 2, 3. For example, the gas 14 modifies the transfer of the heat generated by the upper heating device 10 on the second substrate 3. This may especially influence the heat transfer by convection. This allows an increase or a decrease of the warping 12. Through adjustment of the gas flow quantity and/or the gas temperature, the influence of the gas 14 on the second substrate can be adjusted in a targeted manner.

The gas 14 may feature one or several different gas components. The gas 14 may have other functions besides its function of influencing the warping, especially during pre-conditioning. For example, the gas 14 serves as a process gas to set a desired atmosphere, to process an adhesive and/or to flush the chamber 4. In particular, reducing gases are inserted into the chamber 4 for CuSn bonding connections, and nitrogen for adhesive

connections. The gas 14 may also simply serve to adjust the warping and be selected in such a way that it does not

negatively impact the pre-conditioning.

The chamber 4 may have an undirected gas inlet 16 in addition to the directed gas inlet 13. The undirected gas inlet 16 is, for example, arranged at the bottom of the chamber 4. Through the undirected gas inlet 16, a gas 17, especially a process gas, may be inserted into the chamber 4. The undirected gas inlet 16 does not serve to influence the warping of the substrates 2, 3. The gas 17 inserted through the undirected gas inlet 16 may be the same gas as the gas 14 inserted through the directed gas inlet 13. However, they may also be different gases.

After the pre-conditioning phase, the spacer 6 is removed and the pressure device 11 moved to the second substrate 3. The second substrate 3 is pressed to the first substrate 2 and the substrates 2, 3 are connected with one another. The gas inlet 13 can be turned off or remain turned on during this joining phase.

Figure 2 shows a further apparatus 1 for connecting two substrates 2, 3. In addition to the elements shown in Figure 1, the apparatus 1 features a control circuit 21 to control the flow quantity and/or the temperature of the gas 14. A measuring device 18 serves to measure a distance d between the substrates 2, 3 for this. The distance d in this case serves as a measure for the warping.

For example, the measuring device 18 features optical

monitoring, in particular, a camera that is arranged at the level of the gap between the two substrates 2, 3. The measuring device 18 is in particular placed at a point where the spacer 6 is not. This is not visible in detail in the cross-sectional view so as to maintain clear presentation. For example, a light source is arranged on a side opposite the camera.

The distance d between the substrates 2, 3 may serve as a control variable in the control circuit 21. The result of the distance measuring is input to circuit electronics 19 as an actual value x. In addition, a nominal value w is determined that compares the control electronics 19 with the actual value x and from that determines an actuating value y for an actuator 20. The actuator 20 is, for example, designed as a flow quantity controller and/or heater. Depending on the actuating value y, the flow quantity and/or the temperature of the gas 14 is modified until the actual value x of the distance d corresponds to the nominal value w.

This in particular allows the prevention of any contact of the substrates 2, 3 during the pre-conditioning phase. For example, the directed gas inlet 13 prevents warping of the upper substrate 3, or the upper substrate 3 is caused to slightly warp upwards.

The actuator 20 may additionally serve as a flow quantity control and/or heater for the gas 17 inserted via the undirected gas inlet 16.

As an alternative to the apparatus 1 with the control circuit 21 described above, a measuring device 18 to measure the distance d may also be provided without there being any adjustment. In this case, the measuring value serves, for instance, as a measure of the quality of the manufactured product.

List of reference signs

1 apparatus

2 first substrate

3 second substrate

4 chamber

5 carrier

6 spacer

7 cavity

8 holding device

9 lower heating device

10 upper heating device

11 pressure device

12 warping

13 gas inlet

14 gas

15 nozzle

16 undirected gas inlet

17 gas

18 measuring device

19 control electronics

20 actuator

21 control circuit d distance

x actual value

w nominal value y actuating value