JP2007201196A - Wafer laminating device and wafer laminating method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a wafer laminating device and a wafer laminating method, wherein a normal-temperature laminating process of laminating wafers together at a normal temperature can be improved in throughput. <P>SOLUTION: The wafer laminating device is composed of a wafer introduction chamber 40 where the wafers Wa as laminating targets are introduced; a laminating chamber 60 in which the laminating surfaces of the wafers Wa and Wa are activated, and then the wafers Wa and Wa are laminated together at normal temperatures; a transfer chamber 50 in which a transfer means for transferring the wafers Wa and Wa that are not laminated together yet, and also transferring a laminate composed of two wafers Wa and Wa that have been laminated together already in the laminating chamber 60 is housed; and a degassing chamber 70 where an infrared lamp 75 is provided as a degassing means for removing a gas component adsorbed by the wafer Wa, before the wafer Wa introduced into the introduction chamber 40 is transferred to the laminating chamber 60, and the above chambers are formed of separate vacuum tanks. The wafers Wa and Wa as laminating targets are subjected to a degassing treatment in the degassing chamber 70 and then sent into the laminating chamber 60. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a wafer bonding apparatus and a wafer bonding method for bonding wafers, for example.

  Conventionally, MEMS (Micro Electro Mechanical System) has been known as a sensor element formed using micromachining technology. In recent years, sensor elements formed using micromachining technology and wafer level packaging technology have been researched and developed. ing.

  By the way, since the above-mentioned MEMS often forms a sensor substrate having a frame part and a movable part using a silicon wafer, an SOI wafer, or the like, by bonding a package substrate having the same size as the sensor substrate to the sensor substrate. When a sensor element is configured, a package substrate is formed using a silicon wafer, and the package substrate and the sensor substrate are bonded using a room temperature bonding method (for example, see Patent Document 1) in which silicon wafers are bonded to each other. It is possible to do.

  Here, in Patent Document 1, as a wafer bonding apparatus, as shown in FIG. 14, a wafer introduction chamber 40 into which a wafer Wa to be bonded is introduced and each bonding surface between the wafers Wa and Wa are activated. The wafer Wa, Wa and a laminated body of the two bonded wafers Wa, Wa are transported between the wafer introduction chamber 40 and the bonding chamber 60. There has been proposed one in which the transfer chamber 50 in which a robot or the like is housed is constituted by separate vacuum chambers. In the wafer bonding apparatus having the configuration shown in FIG. 14, a gate valve 91 is provided between the wafer introduction chamber 40 and the transfer chamber 50, and a gate valve 92 is provided between the transfer chamber 50 and the bonding chamber 60. It has been.

  In the room temperature bonding process of bonding the two wafers Wa and Wa at room temperature using the wafer bonding apparatus described above, the first vacuum for introducing the wafers Wa and Wa into the wafer introduction chamber 40 and evacuating the wafer introduction chamber 40. In the second evacuation step, in which the wafer Wa is transferred to the bonding chamber 60 via the transfer chamber 50 and then evacuated in the bonding chamber 60 until the desired degree of vacuum is reached. In this case, for example, an inert gas ion beam is irradiated onto the bonding surfaces of the two wafers Wa and Wa held by the two wafer holding members 65 and 66 from different beam irradiation devices (not shown) to thereby form the bonding surfaces. In the surface activation process to be activated, the push rod 67 is driven to push down the upper wafer holding member 66 in a direction approaching the lower wafer holding member 65 (direction of arrow E in FIG. 14). Both wafers Wa at room temperature, Wa both wafers Wa by matching the bonding surfaces of the bonding process for bonding the Wa, but it performed sequentially. In addition, although the said patent document 1 describes also irradiating an inert gas atom beam instead of an inert gas ion beam in the surface activation process which activates the joint surface of wafer Wa and Wa. In addition to a technique using an inert gas ion beam or an inert gas atom beam, a technique for activating a bonding surface by plasma irradiation is conventionally known.

In order to activate the bonding surfaces of the wafers Wa and Wa in the above-described bonding chamber 60, it is necessary to perform an activation process after setting the inside of the bonding chamber 60 to a high vacuum, and thus the wafer bonding having the configuration shown in FIG. In the apparatus, the wafer introduction chamber 40 and the bonding chamber 60 are divided into separate vacuum chambers, thereby improving throughput, yield, and bonding characteristics.
JP-A-10-92702

By the way, it is important to reduce impurities such as moisture in the bonding chamber 60 in order to obtain good bonding characteristics with high yield in the room temperature bonding process using the wafer bonding apparatus described above, depending on the bonding structure and bonding material. Although a vacuum degree of 1 × 10 ⁻⁴ Pa or less is required, even if the wafer introduction chamber 40 is used, the inside of the bonding chamber 60 is affected by the moisture adsorbed on the wafers Wa and Wa. Since it takes a long time to reach the desired degree of vacuum, further improvement in throughput is desired.

  The present invention has been made in view of the above reasons, and an object thereof is to provide a wafer bonding apparatus and a wafer bonding method capable of improving the throughput of a room temperature bonding process for bonding wafers at room temperature.

  In the invention of claim 1, the wafer introduction chamber into which the wafers to be bonded are introduced and the bonding chamber in which the wafers are bonded to each other at room temperature after the respective bonding surfaces of the wafers are activated by separate vacuum chambers. A multi-tank structure wafer bonding apparatus, comprising a degassing means for removing gas components adsorbed on the wafer before the wafer introduced into the wafer introduction chamber is transported to the bonding chamber. It is characterized by.

  According to the present invention, the degassing means for removing the gas component adsorbed on the wafer before the wafer introduced into the wafer introduction chamber is carried into the bonding chamber is provided. It is possible to reduce gas components such as moisture adsorbed on the substrate, shorten the time until the degree of vacuum in the bonding chamber reaches a desired degree of vacuum, and improve throughput. In addition, the ability to reduce gas components such as moisture adsorbed on the wafers transported into the bonding chamber enables a higher vacuum in the bonding chamber than in the past, and further increases the pressure in the airtight package such as the sensor element. Since a high vacuum can be achieved, it is possible to increase the sensitivity of the sensor element, in which it is desirable to set the inside of the hermetic package to a high vacuum in order to increase the sensitivity.

  According to a second aspect of the present invention, in the first aspect of the present invention, the degassing means comprises a heating device for heating the wafer.

  According to the present invention, gas components such as moisture adsorbed on the wafer can be effectively removed.

  According to a third aspect of the present invention, in the invention of the second aspect, the heating device is an irradiation heating device that heats the wafer by irradiating the wafer with infrared rays, electron beams, or laser light.

  According to the present invention, it is possible to improve the controllability of the heating rate and the cooling rate of the wafer, and it is possible to prevent the wafer from being damaged by thermal strain.

  According to a fourth aspect of the present invention, in the invention of the second or third aspect, the cooling means for lowering the temperature of the wafer raised by the heating before the wafer from which the gas component has been removed by the degassing means is transported to the bonding chamber. Is provided.

  According to the present invention, since the temperature difference between the two wafers to be bonded in the bonding chamber can be reduced, it is possible to prevent stress and wafer warpage caused by the temperature difference between the two wafers from occurring after bonding, The alignment accuracy of the two wafers can be increased.

  According to a fifth aspect of the present invention, in the first aspect of the invention, the degassing means includes a gas introducing means for introducing a gas for degassing into a vacuum tank for performing a degassing process, and a vacuum for evacuating the vacuum tank. It is characterized by comprising exhaust means.

  According to the present invention, gas components such as moisture adsorbed on the wafer can be removed without heating the wafer.

  According to a sixth aspect of the present invention, in the first to fifth aspects of the present invention, a conveyance path for the laminated body is set so as to take out the laminated body of wafers bonded in the bonding chamber from the wafer introduction chamber, and the degassing means is The laminated body is provided outside the conveyance path to the wafer introduction chamber.

  According to the present invention, the gas component adsorbed on the wafer before bonding transferred to the bonding chamber can be removed by the degassing means even during transfer of the laminated body after bonding (that is, degassing processing is performed). Therefore, the throughput can be improved as compared with the case where the degassing means is provided in the transport path of the laminated body into the wafer introduction chamber.

  According to the seventh aspect of the present invention, a wafer to be bonded is introduced into the wafer introduction chamber and then the wafer introduction chamber is evacuated, and the wafer is adsorbed on the wafer after the first evacuation step. A degassing step for removing the gas component, and a second vacuum evacuation for transferring the wafer from which the gas component has been removed in the degassing step into the bonding chamber and then evacuating the bonding chamber to a desired degree of vacuum or less. And a bonding step of bonding the wafers at room temperature after the activation process is performed on the bonding surface of the wafer after the second evacuation step.

  According to the present invention, since the degassing process for removing the gas component adsorbed on the wafer is provided between the first vacuum exhausting process and the second vacuum exhausting process, the wafer is brought into the bonding chamber. Gas components such as moisture adsorbed on the wafer before transfer can be reduced, and in the second evacuation process, the time until the inside of the bonding chamber reaches the desired degree of vacuum can be shortened. Throughput can be improved.

  In the first aspect of the invention, it becomes possible to reduce gas components such as moisture adsorbed on the wafer conveyed into the bonding chamber, and the time until the degree of vacuum in the bonding chamber reaches a desired degree of vacuum. This can be shortened and has the effect of improving the throughput.

  In invention of Claim 7, gas components, such as the water | moisture content adsorb | sucked to the wafer, before conveying a wafer into a joining chamber can be reduced, and it becomes until a joining chamber reaches | attains a desired vacuum degree in a 2nd vacuum exhaust process. Since the time can be shortened, the throughput of the wafer bonding apparatus can be improved.

  In this embodiment, a sensor element manufactured using a wafer bonding apparatus and a wafer bonding method according to the present invention will be described with reference to FIGS. 3 to 13, and then the wafer bonding apparatus and the wafer bonding method will be described.

  The sensor element exemplified in the present embodiment is an acceleration sensor, and is electrically connected to the sensor substrate 1 on which a sensing unit described later is formed and the sensing unit of the sensor substrate 1 as shown in FIGS. A through-hole wiring forming substrate (first package substrate) 2 having a through-hole wiring 24 to be connected and sealed to one surface side (upper surface side in FIG. 3C) of the sensor substrate 1; 1 is provided with a cover substrate (second package substrate) 3 sealed on the other surface side (the lower surface side in FIG. 3C). Here, the outer peripheral shapes of the sensor substrate 1, the through-hole wiring formation substrate 2, and the cover substrate 3 are rectangular, and the through-hole wiring formation substrate 2 and the cover substrate 3 are formed to have the same outer dimensions as the sensor substrate 1.

  The sensor substrate 1 described above processes an SOI wafer having an n-type silicon layer (active layer) 10c on an insulating layer (buried oxide film) 10b made of a silicon oxide film on a support substrate 10a made of a silicon substrate. The through-hole wiring forming substrate 2 is formed by processing the first silicon wafer, and the cover substrate 3 is formed by processing the second silicon wafer.

  6 to 8, the sensor substrate 1 includes a frame portion 11 having a frame shape (in the illustrated example, a rectangular frame shape), and a weight portion 12 disposed inside the frame portion 11 is on one surface side ( 3 (c) and 6 (b)), the frame portion 11 is swingably supported via four flexible strip-like bent portions 13. In FIG. In other words, the sensor substrate 1 is swingably supported by the frame portion 11 via the four flexure portions 13 in which the weight portion 12 disposed inside the frame-shaped frame portion 11 extends from the weight portion 12 in four directions. Has been. Here, the frame portion 11 is formed using the above-described SOI wafer support substrate 10a, insulating layer 10b, and silicon layer 10c. On the other hand, the bending part 13 is formed using the silicon layer 10c in the above-described SOI wafer, and is sufficiently thinner than the frame part 11.

  The weight part 12 is continuously integrated with each of the rectangular parallelepiped core part 12a supported by the frame part 11 via the four flexure parts 13 and the four corners of the core part 12a when viewed from the one surface side of the sensor substrate 1. And four accompanying portions 12b having a rectangular parallelepiped shape connected to each other. In other words, the weight portion 12 is formed integrally with the core portion 12a and the core portion 12a in which the other end portion of each bending portion 13 whose one end portion is connected to the inner side surface of the frame portion 11 is connected to the outer surface. It has four accompanying parts 12b arranged in the space between the part 12a and the frame part 11. That is, each appendage portion 12b is disposed in a space surrounded by the frame portion 11 and the core portion 12a and the two bent portions 13 and 13 extending in a direction orthogonal to each other when viewed from the one surface side of the sensor substrate 1. In addition, a slit 14 is formed between each of the accompanying portions 12b and the frame portion 11, and the interval between the adjacent accompanying portions 12b with the bending portion 13 interposed therebetween is longer than the width dimension of the bending portion 13. Yes. Here, the core portion 12a is formed using the above-described SOI wafer support substrate 10a, the insulating layer 10b, and the silicon layer 10c, and each accompanying portion 12b is formed using the SOI wafer support substrate 10a. It is. Thus, the surface of each associated portion 12b on the one surface side of the sensor substrate 1 is from the plane including the surface of the core portion 12a to the other surface side of the sensor substrate 1 (see FIG. 3C and FIG. 6B). (Lower surface side). Note that the above-described frame portion 11, weight portion 12, and each bending portion 13 of the sensor substrate 1 may be formed using a lithography technique and an etching technique.

  By the way, as shown in the lower right of each of FIGS. 6A and 6B, one direction along one side of the frame portion 11 in a plane parallel to the one surface of the sensor substrate 1 is the positive direction of the x-axis. If one direction along the side orthogonal to the one side is defined as the positive direction of the y-axis and one direction of the thickness direction of the sensor substrate 1 is defined as the positive direction of the z-axis, the weight portion 12 is extended in the x-axis direction. The pair of flexible portions 13 and 13 sandwiching the core portion 12a and the pair of flexible portions 13 and 13 extending in the y-axis direction and sandwiching the core portion 12a are supported by the frame portion 11. Will be. In the orthogonal coordinates defined by the three axes of the above-described x axis, y axis, and z axis, the center position of the weight portion 12 on the surface of the portion of the sensor substrate 1 formed by the silicon layer 10c is the origin.

  The bending portion 13 (the bending portion 13 on the right side of FIG. 6A) extended from the core portion 12a of the weight portion 12 in the positive direction of the x-axis is a pair of piezoresistors Rx2 and Rx4 in the vicinity of the core portion 12a. Is formed, and one piezoresistor Rz2 is formed in the vicinity of the frame portion 11. On the other hand, the bending portion 13 (the bending portion 13 on the left side of FIG. 6A) extended from the core portion 12a of the weight portion 12 in the negative direction of the x-axis is a pair of piezoresistors Rx1 in the vicinity of the core portion 12a. , Rx3 are formed, and one piezoresistor Rz3 is formed in the vicinity of the frame portion 11. Here, the four piezoresistors Rx1, Rx2, Rx3, and Rx4 formed in the vicinity of the core portion 12a are formed to detect acceleration in the x-axis direction, and the planar shape is an elongated rectangular shape. The wiring is formed so that the longitudinal direction coincides with the longitudinal direction of the bending portion 13 and wiring (diffuse layer wiring, metal wiring 17 formed on the sensor substrate 1 is formed so as to constitute the left bridge circuit Bx in FIG. Etc.). Note that the piezoresistors Rx1 to Rx4 are formed in a stress concentration region where stress is concentrated in the bent portion 13 when acceleration in the x-axis direction is applied.

  Further, the bending portion 13 (the upper bending portion 13 in FIG. 6A) extended from the core portion 12a of the weight portion 12 in the positive direction of the y-axis is a pair of piezoresistors Ry1, in the vicinity of the core portion 12a. Ry3 is formed, and one piezoresistor Rz1 is formed in the vicinity of the frame portion 11. On the other hand, the bending portion 13 (the lower bending portion 13 in FIG. 6A) extended from the core portion 12a of the weight portion 12 in the negative direction of the y-axis is a pair of piezoresistors Ry2 in the vicinity of the core portion 12a. , Ry4 are formed, and one piezoresistor Rz4 is formed at the end on the frame part 11 side. Here, the four piezoresistors Ry1, Ry2, Ry3, and Ry4 formed in the vicinity of the core portion 12a are formed to detect acceleration in the y-axis direction, and the planar shape is an elongated rectangular shape. The wiring (the diffusion layer wiring formed on the sensor substrate 1, the metal wiring 17 is formed so that the longitudinal direction coincides with the longitudinal direction of the bending portion 13 and constitutes the central bridge circuit By in FIG. Etc.). Note that the piezoresistors Ry1 to Ry4 are formed in a stress concentration region where stress is concentrated in the flexure 13 when acceleration in the y-axis direction is applied.

  Further, the four piezoresistors Rz1, Rz2, Rz3, and Rz4 formed in the vicinity of the frame portion 11 are formed for detecting acceleration in the z-axis direction, and constitute the right bridge circuit Bz in FIG. Thus, they are connected by wiring (a diffusion layer wiring formed on the sensor substrate 1, a metal wiring 17 or the like). However, the piezoresistors Rz1 and Rz4 formed in one set of the bent portions 13 and 13 of the two bent portions 13 and 13 are formed so that the longitudinal direction thereof coincides with the longitudinal direction of the bent portions 13 and 13. On the other hand, the piezoresistors Rz2 and Rz3 formed in the other set of flexures 13 and 13 are formed such that the longitudinal direction coincides with the width direction (short direction) of the flexures 13 and 13. Yes. 3-6, only the site | part of the metal wiring 17 in the sensor board | substrate 1 vicinity of the 1st joining metal layer 19 for connection is shown in figure, and illustration of a diffused layer wiring is abbreviate | omitted.

  The above-described sensor substrate 1 detects accelerations in the x-axis direction, the y-axis direction, and the z-axis direction that act on the sensor substrate 1 by detecting changes in the output voltages of the respective bridge circuits Bx to Bz. Can do. In the sensor substrate 1 described above, the weight portion 12 and each bending portion 13 constitute a movable portion, and each of the piezoresistors Rx1 to Rx4, Ry1 to Ry4, Rz1 to Rz4 is a sensing portion in the sensor substrate 1. Is configured.

  By the way, as shown in FIG. 9, the sensor substrate 1 includes two input terminals VDD and GND common to the above-described three bridge circuits Bx, By and Bz, two output terminals X1 and X2 of the bridge circuit Bx, Two output terminals Y1 and Y2 of the bridge circuit By and two output terminals Z1 and Z2 of the bridge circuit Bz are provided. These input terminals VDD and GND and output terminals X1, X2, Y1, Y2, and the like. Z1 and Z2 are provided as the first connection bonding metal layer 19 on the one surface side (that is, the through hole wiring forming substrate 2 side), and the through hole wiring 24 formed on the through hole wiring forming substrate 2 is provided. And are electrically connected. That is, eight connecting metal layers 19 for connection are formed on the sensor substrate 1, and eight through-hole wirings 24 are formed on the through-hole wiring forming substrate 2.

  In addition, a frame-shaped (rectangular frame-shaped) first sealing bonding metal layer 18 having a larger opening area than the frame portion 11 is formed on the frame portion 11 of the sensor substrate 1. The connection bonding metal layer 19 is disposed inside the first sealing bonding metal layer 18 in the frame portion 11. In the sensor substrate 1, an insulating film 16 made of a laminated film of a silicon oxide film and a silicon nitride film is formed on the silicon layer 10c on the one surface side, and a first connecting bonding metal layer 19 and The first sealing bonding metal layer 18 and the metal wiring 17 are formed on the insulating film 16.

  In addition, the first sealing bonding metal layer 18 and the first connecting bonding metal layer 19 have an adhesion improving Ti film interposed between the bonding Au film and the insulating film 16. In other words, the first sealing bonding metal layer 18 and the first connecting bonding metal layer 19 are a laminated film of a Ti film formed on the insulating film 16 and an Au film formed on the Ti film. It is comprised by.

  Each of the above-described piezoresistors Rx1 to Rx4, Ry1 to Ry4, Rz1 to Rz4, and each of the diffusion layer wirings is formed by doping a p-type impurity with an appropriate concentration in each formation site in the silicon layer 10c. The metal wiring 17 described above is formed by patterning a metal film (for example, an Al film, an Al alloy film, etc.) formed on the insulating film 16 by sputtering or vapor deposition using lithography technology and etching technology. The metal wiring 17 is electrically connected to the diffusion layer wiring through a contact hole provided in the insulating film 16. Further, the first connecting metal layer 19 for connection and the metal wiring 17 are connected to the metal wiring 17 in the first connecting metal layer 19 for connection, as shown in FIG. The substrate 2 is electrically connected so as to be positioned in a later-described displacement space forming recess 21 formed on the surface of the substrate 2 facing the sensor substrate 1.

  As shown in FIGS. 10 to 12, the through-hole wiring forming substrate 2 is formed on the surface on the sensor substrate 1 side (the lower surface side in FIG. 3C) with the weight portion 12 and each bending portion 13 of the sensor substrate 1. The above-mentioned displacement space forming recesses 21 that secure the displacement space of the movable portion that is configured are formed, and a plurality (eight in the present embodiment) penetrates in the thickness direction in the peripheral portion of the displacement space formation recesses 21. Through-holes 22 are formed, and an insulating film 23 made of a thermal insulating film (silicon oxide film) is formed across both surfaces in the thickness direction and the inner surface of the through-holes 22. A part of the insulating film 23 is interposed between the inner surface and the inner surface. In addition, although Cu is employ | adopted as a material of the through-hole wiring 24, not only Cu but Ni etc. may be employ | adopted, for example.

  In addition, the through-hole wiring forming substrate 2 has a plurality (eight in this embodiment, eight) electrically connected to the respective through-hole wirings 24 on the periphery of the displacement space forming concave portion 21 on the surface on the sensor substrate 1 side. ) Second connecting bonding metal layer 29 is formed. The through-hole wiring forming substrate 2 has a frame-shaped (rectangular frame-shaped) second sealing bonding metal layer 28 formed around the entire periphery of the surface on the sensor substrate 1 side. The eight second connecting bonding metal layers 29 have a rectangular shape whose outer peripheral shape is an elongated shape, and are disposed on the inner side of the second sealing bonding metal layer 28. Here, one end of the second connection bonding metal layer 29 is bonded to the through-hole wiring 24, and the other end side is outside the metal wiring 17 of the sensor substrate 1 and the sensor substrate 1. The first connecting bonding metal layer 19 is bonded and electrically connected.

  The second sealing bonding metal layer 28 and the second connecting bonding metal layer 29 have a Ti film for improving adhesion between the bonding Au film and the insulating film 23. In other words, the second sealing bonding metal layer 28 and the second connecting bonding metal layer 29 are a laminated film of a Ti film formed on the insulating film 23 and an Au film formed on the Ti film. It is comprised by.

  A plurality of external connection electrodes 25 electrically connected to the respective through-hole wirings 24 are formed on the surface of the through-hole wiring forming substrate 2 opposite to the sensor substrate 1 side. The outer peripheral shape of each external connection electrode 25 is rectangular.

  As shown in FIG. 13, the cover substrate 3 is formed with a recess 31 having a predetermined depth (for example, about 5 μm to 10 μm) that forms a displacement space of the weight portion 12 on the surface facing the sensor substrate 1. Here, the recess 31 is formed using a lithography technique and an etching technique. In the present embodiment, the concave portion 31 that forms the displacement space of the weight portion 12 is formed on the surface of the cover substrate 3 that faces the sensor substrate 1, but the core portion 12a and each associated portion 12b of the weight portion 12 are formed. The thickness of the portion formed using the support substrate 10a of the sensor substrate 1 is compared with the thickness of the portion formed using the support substrate 10a in the frame portion 11 in the thickness direction of the sensor substrate 1. If the weight 12 is made thinner by the allowable displacement amount, the weight portion in the direction intersecting the other surface is formed on the other surface side of the sensor substrate 1 without forming the recess 31 in the cover substrate 3. A gap that enables the displacement of 12 is formed between the weight portion 12 and the cover substrate 3.

  By the way, the sensor substrate 1 and the through-hole wiring formation substrate 2 in the above-described acceleration sensor are joined together with the first sealing bonding metal layer 18 and the second sealing bonding metal layer 28 and the first sealing metal. The connection bonding metal layer 19 and the second connection bonding metal layer 29 are bonded to each other, and the sensor substrate 1 and the cover substrate 3 are bonded to each other at the peripheral portions of the opposing surfaces. In addition, as shown in FIGS. 3A and 3B, the acceleration sensor described above includes a sensor wafer 10 in which a plurality of sensor substrates 1 are formed on the SOI wafer and a through-hole wiring formed in the first silicon wafer. A first package wafer 20 having a plurality of substrates 2 formed thereon and a second package wafer 30 having a plurality of cover substrates 3 formed on the above-described second silicon wafer, using a wafer bonding apparatus having a configuration shown in FIG. After the wafer level package structure 100 is formed by performing a room temperature bonding process for room temperature bonding at the wafer level, the wafer level package structure 100 is divided into individual acceleration sensors by a dividing process (dicing process) for dividing into individual acceleration sensors. FIG. 3C is a schematic cross-sectional view of a portion surrounded by a circle A in the wafer level package structure 100 shown in FIG. Therefore, the through-hole wiring forming substrate 2 and the cover substrate 3 have the same outer size as the sensor substrate 1, and a small chip size package can be realized and manufacture is facilitated. Here, in the above-described acceleration sensor, an airtight package is configured by the frame portion 11 of the sensor substrate 1, the through-hole wiring forming substrate 2 that is the first package substrate, and the cover substrate 3 that is the second package substrate. The movable part constituted by the weight part 12 and each bending part 13 can be displaced in the airtight package. In FIG. 1, the sensor substrate 1, the through-hole wiring forming substrate 2 that is the first package substrate, and the cover substrate 3 that is the second package substrate are the sensor wafer 10, the first package wafer 20, and the first package wafer, respectively. 2 is a part of the second package wafer 30.

  Hereinafter, the above-described wafer bonding apparatus will be described with reference to FIG. 1, but the above-described sensor wafer 10, first package wafer 20, second package wafer 30, and the like will be described as wafers Wa to be bonded.

  In the wafer bonding apparatus according to the present embodiment, the wafer introduction chamber 40 into which the wafer Wa to be bonded is introduced and the respective bonding surfaces of the wafers Wa and Wa are activated, and then the wafers Wa and Wa are bonded at room temperature. The wafers Wa and Wa before bonding are transported between the bonding chamber 60 to be performed, the wafer introduction chamber 40 and the bonding chamber 60, and between the wafer introduction chamber 40 and a degassing chamber 70 described later, and bonded in the bonding chamber 60. The transferred wafer 50 is introduced into the wafer introduction chamber 40 and a transfer chamber 50 in which a transfer means (not shown) for transferring the stacked wafers Wa and Wa between the bonding chamber 60 and the wafer introduction chamber 40 is stored. A degas chamber 70 provided with an infrared lamp 75 as a degas means for removing gas components adsorbed on the wafer Wa before the transferred wafer Wa is transferred into the bonding chamber 60 is constituted by a separate vacuum chamber. In In addition, a gate valve 91 is provided between the wafer introduction chamber 40 and the transfer chamber 50, and a gate valve 92 is provided between the transfer chamber 50 and the bonding chamber 60, and between the transfer chamber 50 and the degassing chamber 70. Is provided with a gate valve 93.

  The wafer introduction chamber 40 is provided to introduce the wafer Wa without opening the bonding chamber 60 to the atmosphere, and can be opened to the atmosphere and evacuated independently of the bonding chamber 60. That is, the wafer introduction chamber 40 is connected to a first evacuation system including an evacuation pump (not shown) and a gas pipe for introducing a gas for releasing air (eg, nitrogen gas). Since the wafer introduction chamber 40 is allowed even at a relatively low vacuum (for example, a degree of vacuum of about 10 Pa), a rotary pump or a dry pump is used as a vacuum exhaust pump used for evacuating the wafer introduction chamber 40. However, the present invention is not limited thereto, and other vacuum exhaust pumps may be used. The wafer introduction chamber 40 may be evacuated after introducing the wafer Wa by the first evacuation system so that the degree of vacuum is 10 Pa or less. It is desirable to evacuate to 0.1 Pa or less using a high vacuum pump such as a turbo molecular pump. Further, the gas for opening to the atmosphere is not limited to nitrogen gas, and other gases may be used.

  Incidentally, a wafer holder for preventing the wafer Wa from being damaged when the wafer Wa is transferred may be stored in the wafer introduction chamber 40, and the wafer holder holding the wafer Wa may be transferred by the transfer means. . In particular, when the wafer Wa is a wafer including a three-dimensional structure (sensor substrate 1) formed by a micromachining technique, such as the sensor wafer 10 described above, or a thinned wafer, It is preferable to use a wafer holder in order to prevent the wafer Wa from being damaged. In short, when the wafer Wa is a MEMS wafer such as the sensor wafer 10 or the package wafers 20 and 30 described above, it is preferable to use the wafer holder described above. In addition, as this wafer holder, you may make it convey by the said conveyance means combining the wafer holding members 65 and 66 which comprise the said joining mechanism.

  The transfer chamber 50 stores a robot or jig for transferring one or two wafers Wa as the transfer means, and is separate from other vacuum chambers (the wafer introduction chamber 40, the degas chamber 70, and the bonding chamber 60). Independent evacuation is possible. That is, the transfer chamber 50 is connected to a second vacuum exhaust system including a vacuum exhaust pump (not shown). In the present embodiment, the gate valve 91 is provided between the wafer introduction chamber 40 and the transfer chamber 50. However, the gate valve 91 is omitted to simplify and reduce the cost of the wafer bonding apparatus. Although the vacuum evacuation may be performed by the first evacuation system, when the gate valve 91 is provided, only the wafer introduction chamber 40 needs to be opened to the atmosphere when the wafer Wa is introduced, and thus the wafer Wa is removed from the wafer introduction chamber 40. There is an advantage that the time required for evacuation after being introduced into the inside is shortened.

  In the bonding chamber 60, a surface activation device (not shown) for activating the bonding surfaces of the two wafers Wa and Wa, and wafer holding members 65 and 66 for holding the two wafers Wa and Wa, respectively, are accommodated. The push rod 67 pushes down the other wafer holding member 66 located above the one wafer holding member 65 in the bonding chamber 60 in a direction approaching the one wafer holding member 65 (direction of arrow E in FIG. 1). And a third evacuation system including a evacuation pump for enabling evacuation independently of other vacuum chambers (wafer introduction chamber 40, transfer chamber 50, degassing chamber 70). It is connected. Here, as the surface activation device, an ion beam irradiation device for irradiating each of the wafers Wa and Wa with an ion beam, an atomic beam irradiation device for irradiating each of the wafers Wa and Wa with an atomic beam, or plasma on the wafers Wa and Wa. A plasma irradiation apparatus or the like that irradiates can be used, and may be appropriately selected depending on a device to be manufactured (acceleration sensor in the above example), required specifications, and the like. In the present embodiment, the two wafer holding members 65 and 66 and the push rod 67 constitute a bonding mechanism for bonding the two wafers Wa and Wa. Further, in the present embodiment, the wafers Wa and Wa are bonded to the wafer holding member 65 of the above-described bonding mechanism so that the wafers Wa and Wa can be bonded immediately after the bonding surfaces of the wafers Wa and Wa are activated. In the surface activation process for activating the bonding surfaces of the wafers Wa and Wa, the wafer holding used in the bonding process for bonding the wafers Wa and Wa is performed. A wafer holding member different from the members 65 and 66 is used, and after the surface activation process, the wafers Wa and Wa are held by the wafer holding members 65 and 66 used in the bonding process and the bonding process is performed. Good.

  The degas chamber 70 is provided for performing a degas process for removing gas components such as moisture adsorbed on the wafer Wa before bonding. The degas chamber 70 includes a vacuum exhaust pump (not shown). Is connected to the degassing chamber 70 without connecting the fourth evacuation system to the first evacuation system or the second evacuation system. The gas chamber 70 may be evacuated.

  In this embodiment, a gate valve 93 is provided between the degassing chamber 70 and the transfer chamber 50 in order to prevent the gas component desorbed from the wafer Wa from diffusing into the transfer chamber 50 or the bonding chamber 60. Although the fourth evacuation system for evacuating the inside of the degassing chamber 70 is connected to the degassing chamber 70, the gate valve 93 may be omitted for simplification and cost reduction of the wafer bonding apparatus. .

  By the way, in the wafer bonding apparatus of the present embodiment, the above-described infrared lamp 75 is provided as a degassing means, and the wafer Wa is heated and adsorbed to the wafer Wa by irradiating the wafer Wa with infrared rays from the infrared lamp 75. A gas component is removed (degassing is performed) by performing a degassing step of releasing (desorbing) a gas component such as moisture. Here, in the degassing step, the higher the heating temperature of the wafer Wa, the faster the degassing speed. In this embodiment, the heating temperature is set to a temperature of 100 to 200 ° C. in order to avoid thermal damage to the wafer Wa. Set within range. The heating temperature is not limited to the above temperature range, and may be set as appropriate according to device specifications, wafer bonding apparatus specifications, and the like.

  In the wafer bonding apparatus of the present embodiment, the infrared lamp 75 constitutes a heating apparatus that heats the wafer Wa. However, the heating apparatus is not limited to the infrared lamp 75, and other heating apparatuses such as a heater are used. In addition, by using a heating device that heats the wafer Wa as the degassing means, it is possible to effectively remove gas components such as moisture adsorbed on the wafer Wa. However, as the heating device, the wafer Wa is heated by irradiating the wafer Wa with infrared rays, like the infrared lamp 75, the wafer Wa is heated by irradiating the wafer Wa with an electron beam, or the wafer Wa is laser-treated. It is desirable to use an irradiation heating device that heats the wafer Wa by irradiating light, and by using the irradiation heating device as the heating device, the wafer Wa is adsorbed on the surface (including the bonding surface). The gas component (adsorbed gas molecules) such as moisture can be efficiently released, and the controllability of the heating rate and the cooling rate of the wafer Wa can be improved, and the wafer Wa is damaged by thermal strain. Can be prevented. Further, when the wafer Wa is held by the above-described wafer holder as described above, it is desirable to use an irradiation heating device in order to efficiently heat the surface of the wafer Wa.

  By the way, the wafer bonding apparatus of the present embodiment uses a heating device such as an infrared lamp 75 that heats the wafer Wa by irradiating the wafer Wa before bonding with infrared rays as the degassing means. When the wafer Wa that has been subjected to the degassing process is introduced into the bonding chamber 60 in a state where the temperature is higher than the normal temperature and the wafers Wa and Wa are bonded to each other, the temperature difference is caused by the temperature difference between the two wafers Wa and Wa. There are concerns that stress and warpage of the wafers Wa and Wa occur after bonding, and there is a concern that the alignment accuracy of the two wafers Wa and Wa at the time of bonding decreases.

  Therefore, in the wafer bonding apparatus according to the present embodiment, the cooling means 80 for lowering the temperature of the wafer Wa raised by the heating before the wafer Wa from which the gas component has been removed by the degassing means is transferred into the bonding chamber 60 is provided in the transfer chamber. 50 is provided. Here, the cooling means 80 is configured by a wafer stage maintained at a specified temperature equal to or lower than normal temperature, and by placing the wafer Wa on the wafer stage, the wafer Wa is transferred by heat conduction from the wafer Wa to the wafer stage. Is cooled. In the present embodiment, the cooling means 80 is provided in the transfer chamber 50, but the place where the cooling means 80 is provided is not limited to the transfer chamber 50 but may be in the wafer introduction chamber 40. In addition, another known cooling mechanism may be adopted for the configuration of the cooling means 80.

  Thus, in the wafer bonding apparatus according to the present embodiment, the temperature difference between the two wafers Wa and Wa to be bonded in the bonding chamber 60 can be reduced. Therefore, the stress caused by the temperature difference between the two wafers Wa and Wa, the wafer Wa, The warpage of Wa can be prevented from occurring after bonding, and the alignment accuracy of the two wafers Wa and Wa can be increased.

  In the wafer bonding apparatus of the present embodiment described above, a degassing unit is provided to remove the gas component adsorbed on the wafer Wa before the wafer Wa introduced into the wafer introduction chamber 40 is transferred into the bonding chamber 60. Therefore, it becomes possible to reduce gas components such as moisture adsorbed on the wafer Wa conveyed in the bonding chamber 60 until the degree of vacuum in the bonding chamber 60 reaches a desired degree of vacuum. Thus, the throughput can be improved without deteriorating the yield and junction characteristics. Further, in the wafer bonding apparatus of the present embodiment, the inside of the bonding chamber 60 can be made to have a higher vacuum than in the prior art by reducing gas components such as moisture adsorbed on the wafer Wa transferred into the bonding chamber 60. Therefore, it is possible to make the inside of the hermetic package such as the sensor element higher in vacuum, so that it is desirable to make the inside of the hermetic package high vacuum in order to increase sensitivity (for example, a gyro sensor). High sensitivity can be achieved.

  Further, in the wafer bonding apparatus according to the present embodiment, the wafer Wa formed of a stacked body of the wafers Wa and Wa bonded in the bonding chamber 60 is taken out from the wafer introduction chamber 40 so that the wafer Wa is transported. Is set, and the degassing means is provided outside the transfer path of the wafer Wa made of a laminated body into the wafer introduction chamber 40. Therefore, even during the transfer of the wafer Wa made of the laminated body after bonding, Since the gas component adsorbed on the wafer Wa before bonding transferred to 60 can be removed by the degassing means (that is, the degassing process can be performed), the degassing means is a wafer Wa made of a laminate. The throughput can be improved as compared with the case where it is provided in the transfer path to the wafer introduction chamber 40. In addition, the arrow shown with the broken line in FIG. 1 has shown the conveyance path | route of wafer Wa which consists of the conveyance path | route of wafer Wa and Wa before joining, or a laminated body.

  By the way, in the above-mentioned wafer bonding apparatus, although the case where the heating apparatus was used was illustrated as a degassing means, the structure of a degassing means is not restricted to a heating apparatus, Degassing chamber 70 which is a vacuum tank which performs a degassing process. And a fourth evacuation system which is a evacuation means for evacuating the degassing chamber 70, and the gas introduction and the evacuation are alternately performed a plurality of times. Degassing may be performed by repeating or by simultaneously introducing gas and evacuating and maintaining for a certain period of time. Gas components such as moisture adsorbed on the wafer Wa may be removed from the wafer Wa. It can be removed without heating. As the degassing gas introduced into the degassing chamber 70, for example, pure nitrogen gas that is relatively inexpensive and hardly contains impurities such as moisture may be used. However, the gas is not limited to pure nitrogen gas. An inert gas such as gas or argon gas, or another gas may be employed. Here, in order to perform degassing more effectively, it is effective to heat the gas for degassing when introduced into the degassing chamber 70, but in order to prevent thermal damage to the wafer Wa, What is necessary is just to set the heating temperature of the gas for degassing within the temperature range of about 60-100 degreeC, for example. In order to perform effective degassing, it is desirable to provide the degassing chamber 70 separately from the transfer chamber 50. However, the degassing chamber 70 is not provided, and the wafer introduction chamber 40 is degassed as, for example, the above-described irradiation. A heating device may be provided.

  Hereinafter, a wafer bonding method using the above-described wafer bonding apparatus will be described with reference to FIGS.

  First, the wafer introduction chamber 40 is opened to the atmosphere, and the wafer Wa to be bonded is introduced into the wafer introduction chamber 40. A first evacuation process is performed to evacuate the first evacuation system (S1). The predetermined degree of vacuum may be set to a degree of vacuum of about 10 Pa, for example, but is preferably set to 0.1 Pa or less, and when the predetermined degree of vacuum is set to a degree of vacuum of 0.1 Pa or less, For example, a rotary pump and a turbo molecular pump may be provided as the vacuum pump of the first vacuum pumping system.

  After the first evacuation step, the gate valve 91 between the wafer introduction chamber 40 and the transfer chamber 50 is opened, the wafer Wa is transferred into the transfer chamber 50 by the transfer means, and the gate valve 91 is closed. The gate valve 93 between the transfer chamber 50 and the degas chamber 70 is opened, the wafer Wa is transferred to the degas chamber 70 by the transfer means, the gate valve 93 is closed, and then the infrared lamp as the degas means described above. A degassing step of removing gas components adsorbed on the wafer Wa by irradiating the wafer Wa with infrared rays from 75 to heat the wafer Wa (S2). The degassing means is not limited to the infrared lamp 75, and other degassing means described above may be employed.

After the degassing step, the gate valve 93 is opened, the wafer Wa is placed on the wafer stage as the cooling means 80, the gate valve 93 is closed, the wafer Wa is cooled to room temperature, the gate valve 92 is opened, and the wafer Wa is removed. After the transfer into the bonding chamber 40, the gate valve 92 is closed, and then a second vacuum evacuation step is performed to evacuate the bonding chamber 60 to a desired degree of vacuum (S3). The desired degree of vacuum depends on the material of the wafer Wa, the device specifications, etc., but in this embodiment, a degree of vacuum of 1 × 10 ⁻⁴ Pa or less is desirable, and a degree of vacuum of 1 × 10 ⁻⁵ Pa or less. Is more desirable.

Then, after the second evacuation process, a surface activation process is performed in which an activation process is performed on the bonding surfaces of the wafers Wa and Wa held by the wafer holding members 65 and 66 in the bonding chamber 40 ( S4). In the surface activation step, the bonding surfaces of the wafers Wa and Wa are activated by irradiating the bonding surfaces of the wafers Wa and Wa with an ion beam, an atomic beam, or plasma, respectively. In the present embodiment, each bonding surface is irradiated with an argon ion beam in the surface activation process. However, in the surface activation process, not only the ion beam but also an atomic beam or plasma is used. The ion beam, the atomic beam, or the plasma may be selected as appropriate according to the material of the wafer Wa and Wa and the device specifications. Here, the gas used in the surface activation step is not limited to argon, but may be an inert gas such as nitrogen or helium. In the surface activation step, activation treatment other than ion beam irradiation, atomic beam irradiation, or plasma irradiation may be performed. In the wafer bonding method of this embodiment, the desired degree of vacuum is set to 1 × 10 ⁻⁴ Pa.

After the surface activation step, the inside of the joining chamber 60 is evacuated so that the degree of vacuum in the joining chamber 60 is equal to or lower than a specified degree of vacuum (for example, 1 × 10 ⁻⁴ Pa). A bonding step is performed in which the wafers Wa and Wa are brought into contact with each other and bonded together (S5). In the bonding step, the push rod 67 is pushed down in the direction of arrow E in FIG. 1 to bring the wafers Wa and Wa into contact with each other, and an appropriate load is applied as necessary to bond the wafers Wa and Wa together. Here, the load applied in the bonding process may be appropriately set depending on the materials of the wafers Wa and Wa, the specifications of the bonding performance, and the like.

  After the bonding process is completed, when the wafer Wa composed of a stack of two wafers Wa and Wa is transferred to the wafer introduction chamber 40, the gate valve 92 is opened and transferred into the transfer chamber 50, and then the gate valve 92 is opened. Then, the gate valve 91 is opened and transferred into the wafer introduction chamber 41 to close the gate valve 91. After the transfer to the wafer introduction chamber 40, the inside of the wafer introduction chamber 40 is returned to atmospheric pressure, What is necessary is just to take out from the introduction chamber 40.

  By the way, in manufacturing the wafer level package structure 100 described above, first, the sensor wafer 10 and the second package wafer 30 are first bonded at room temperature using the wafer bonding apparatus as two wafers Wa and Wa to be bonded. After that, the wafer bonding apparatus is used as two wafers Wa and Wa to be bonded to the first package wafer 20 and the wafer composed of the laminated body of the sensor wafer 10 and the second package wafer 30. Then, a second room temperature bonding process for room temperature bonding is performed. Here, each room-temperature bonding process includes all the processes from the first evacuation process to the bonding process.

  According to the wafer bonding method described above, a degassing step for removing a gas component adsorbed on the wafer Wa is provided between the first vacuum exhausting step and the second vacuum exhausting step. Gas components such as moisture adsorbed on the wafer Wa before the wafer Wa is transferred into the bonding chamber 60 can be reduced, and the time until the inside of the bonding chamber 60 reaches a desired degree of vacuum in the second evacuation step. Therefore, the throughput of the wafer bonding apparatus can be improved.

  A device manufactured using the above-described wafer bonding apparatus and wafer bonding method is not limited to a sensor element, and may be, for example, an integrated circuit element.

1 is a schematic configuration diagram of a wafer bonding apparatus in an embodiment. It is explanatory drawing of the wafer bonding method in the same as the above. The wafer level package structure same as the above is shown, (a) is a schematic plan view, (b) is a schematic side view, (c) is a principal part schematic sectional drawing. It is a schematic plan view of the acceleration sensor same as the above. The acceleration sensor same as the above is shown, (a) is an enlarged view of a main part of FIG. The sensor board | substrate in the same is shown, (a) is a schematic plan view, (b) is B-D 'schematic sectional drawing of (a). The sensor board | substrate in the same as the above is shown, (a) is D-D 'schematic sectional drawing of Fig.6 (a), (b) is C-C' schematic sectional drawing of Fig.6 (a). It is a schematic bottom view which shows the sensor board | substrate in the same as the above. It is a circuit diagram of the sensor board | substrate in the same as the above. The through-hole wiring formation board | substrate in the same as the above is shown, (a) is a schematic plan view, (b) is D-D 'schematic sectional drawing of (a). The through-hole wiring formation board | substrate in the same as the above is shown, and it is a principal part enlarged view of FIG.10 (b). It is a bottom view of the through-hole wiring formation board in the same as the above. The cover board | substrate in the same as the above is shown, (a) is a schematic plan view, (b) is D-D 'schematic sectional drawing of (a). It is a schematic block diagram of the wafer bonding apparatus which shows a prior art example.

Explanation of symbols

40 Wafer introduction chamber 50 Transfer chamber 60 Bonding chamber 65 Wafer holding member 66 Wafer holding member 67 Push rod 70 Degassing chamber 75 Infrared lamp 80 Cooling device 91 Gate valve 92 Gate valve 93 Gate valve Wa Wafer

Claims (7)

  A multi-tank structure in which a wafer introduction chamber into which wafers to be bonded are introduced and a bonding chamber in which wafers are bonded to each other at room temperature after activation of each bonding surface of the wafers are configured by separate vacuum chambers. A wafer bonding apparatus comprising a degassing means for removing a gas component adsorbed on a wafer before the wafer introduced into the wafer introduction chamber is transported to the bonding chamber. .   2. The wafer bonding apparatus according to claim 1, wherein the degassing means comprises a heating device for heating the wafer.   3. The wafer bonding apparatus according to claim 2, wherein the heating device is an irradiation heating device that heats the wafer by irradiating the wafer with infrared rays, electron beams, or laser light.   4. The cooling means for lowering the temperature of the wafer raised by the heating before the wafer from which the gas component has been removed by the degassing means is transferred into the bonding chamber. Wafer bonding equipment.   The degassing means comprises gas introducing means for introducing a gas for degassing into a vacuum chamber for performing degassing processing, and vacuum evacuating means for evacuating the vacuum chamber. Item 2. A wafer bonding apparatus according to Item 1.   The transport path of the stack is set so that the stack of wafers bonded in the bonding chamber is taken out from the wafer introduction chamber, and the degassing means is provided outside the transport path of the stack to the wafer introduction chamber. The wafer bonding apparatus according to claim 1, wherein:   A first evacuation step for evacuating the wafer introduction chamber after introducing a wafer to be bonded into the wafer introduction chamber, and a degassing for removing a gas component adsorbed on the wafer after the first evacuation step. A second vacuum evacuation step for transporting the wafer from which the gas component has been removed in the degassing step into the bonding chamber and then evacuating the bonding chamber to a desired degree of vacuum or less, and a second vacuum A wafer bonding method comprising: a bonding step of bonding wafers at room temperature after performing an activation process on a bonding surface of the wafer after the exhausting step.

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