Wafer bonding equipment and wafer bonding systems for direct wafer bonding

Abstract

A wafer bonding device and a wafer bonding system are provided. The wafer bonding device comprises: a lower chuck for fixing a lower wafer at a peripheral portion of the lower chuck; an upper chuck for fixing an upper wafer; a bonding initiator for applying pressure to a central portion of the upper wafer until the central portion of the upper wafer touches a central portion of the lower wafer, thereby initiating a bonding process of the upper wafer and the lower wafer by deforming the upper wafer; and a bonding controller for controlling a bonding speed between the peripheral portion of the upper wafer and the peripheral portion of the lower wafer, so that the elastic deformation of the upper wafer is released before the peripheral portion of the upper wafer and the peripheral portion of the lower wafer are bonded.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims the priority of Korean Patent Application No. 10-2018-0094861 filed on August 14, 2018 in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference in its entirety. Technical Field

[0003] Exemplary embodiments of the inventive concept relate to a wafer bonding apparatus, a wafer bonding device for directly bonding a wafer using the wafer bonding apparatus, and a method of bonding a wafer in the wafer bonding device. Background Art

[0004] Chip / wafer stacking technology is widely used to increase chip density and performance of semiconductor packages.

[0005] Using chip / wafer stacking technology, a pair of silicon wafers are bonded to each other, usually by applying pressure. Through various semiconductor processes, tiny electronic circuits are formed on the wafers, and the pair of wafers are loaded onto the lower chuck and upper chuck of the wafer bonding equipment, respectively. Then, the upper chuck is forced to move down to the lower chuck.

[0006] In a conventional bonding apparatus, the upper wafer is fixed to the upper chuck under the action of vacuum by applying a fixing vacuum pressure to the peripheral portion of the upper wafer through the upper chuck. Then, a bonding pressure is applied to the central portion of the upper wafer through the upper chuck until the central portion of the upper wafer contacts the central portion of the lower wafer. Since the fixing vacuum pressure is released when the central portion of the upper wafer contacts the central portion of the lower wafer, bonding of the upper wafer and the lower wafer starts from the central portion thereof.

[0007] In this case, when the center portion of the upper wafer and the center portion of the lower wafer are forced to bond to each other by bonding pressure (hereinafter referred to as "center bonding"), the peripheral portion of the upper wafer and the peripheral portion of the lower wafer are naturally bonded to each other under the action of the gravity and restoring force of the wafers (hereinafter referred to as "peripheral bonding").

[0008] When the upper wafer and the lower wafer are peripherally bonded, since the central portion of the upper wafer is forcibly deformed when bonding with the lower wafer while the peripheral portion of the upper wafer is still fixed to the upper chuck, elastic energy is accumulated at the upper wafer and is maximized at the moment when the central bonding is initiated and the fixing vacuum pressure is released. When the peripheral portion of the upper wafer is separated from the upper chuck by releasing the fixing vacuum pressure, the upper wafer falls toward the lower wafer under the action of gravity with oscillation caused by the elastic energy.

[0009] In this case, the bonding time of performing the conventional bonding process may not be sufficient to restore the original shape of the upper wafer, and therefore, the deformed upper wafer is often bonded to the lower wafer. Then, the bonding of the deformed upper wafer to the lower wafer may cause misalignment between the upper wafer and the lower wafer. In addition, in the conventional bonding process, the bonding time is controlled by the elasticity of the upper wafer and the distance between the upper wafer and the lower wafer. Therefore, it may not be possible to accurately determine the bonding time that allows the upper wafer to return to its original shape. In addition, when the center portion of the lower wafer protrudes upward and the lower wafer is deformed into a convex shape in the process of controlling the bonding time between the upper wafer and the lower wafer, the air around the contact portion of the concave upper wafer and the convex lower wafer is squeezed out from between the center portion of the upper wafer and the center portion of the lower wafer toward its peripheral portion. Therefore, air vapor condenses on the surface of the peripheral portion of the upper wafer and the lower wafer, and causes bubble defects during the bonding process. Summary of the invention

[0010] According to an exemplary embodiment of the present invention, there is provided a wafer bonding device, which includes: a lower chuck, which is used to fix the lower wafer at the peripheral portion of the lower chuck; an upper chuck, which is used to fix the upper wafer; a bonding initiator, which is used to apply pressure to the central portion of the upper wafer until the central portion of the upper wafer touches the central portion of the lower wafer, thereby inducing a bonding process between the upper wafer and the lower wafer by deforming the upper wafer; and a bonding controller, which is used to control the bonding speed between the peripheral portion of the upper wafer and the peripheral portion of the lower wafer, so that the elastic deformation of the upper wafer is released before the peripheral portion of the upper wafer and the peripheral portion of the lower wafer are bonded.

[0011] According to an exemplary embodiment of the present invention, there is provided a wafer bonding system, the wafer bonding system comprising: a bonding buffer, the bonding buffer being used to fix an upper wafer to an upper chuck and a lower wafer to a lower chuck; and a bonding device, in which the upper chuck combined with the upper wafer and the lower chuck to be combined with the lower wafer are arranged so that the upper chuck and the lower chuck have a common central axis, and the upper wafer and the lower wafer are bonded into a bonded wafer, wherein the bonding device comprises: a bonding initiator, the bonding initiator being used to apply pressure to a central portion of the upper wafer until the central portion of the upper wafer touches a central portion of the lower wafer, thereby initiating a bonding process of the upper wafer and the lower wafer by deforming the upper wafer; and a bonding controller, the bonding controller being used to control a bonding speed between a peripheral portion of the upper wafer and a peripheral portion of the lower wafer, so that the elastic deformation of the upper wafer is released before the peripheral portion of the upper wafer and the peripheral portion of the lower wafer are bonded.

[0012] According to an exemplary embodiment of the present invention, a wafer bonding device is provided, which includes: a first chuck for setting a first wafer thereon; a second chuck for setting a second wafer thereon; a bonding initiator for moving a central portion of the second wafer to contact a central portion of the first wafer, wherein the second wafer is deformed when the second wafer moves to contact the central portion of the first wafer; and a bonding controller for moving the central portion of the second wafer back toward the second chuck before the peripheral portion of the second wafer is bonded to the peripheral portion of the first wafer. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] The above and other features of the present inventive concept will become more apparent by describing exemplary embodiments of the present inventive concept with reference to the accompanying drawings, in which:

[0014] Figure 1 is a structural view showing a wafer bonding apparatus according to an exemplary embodiment of the inventive concept;

[0015] Figure 2A It is shown Figure 1 A top view of a lower chuck of a wafer bonding apparatus shown in FIG.

[0016] Figure 2B It is along Figure 2A A cross-sectional view of the lower chuck cut along line II′ shown in FIG.

[0017] Figure 3 It is shown Figure 1 A cross-sectional view of an upper chuck of a wafer bonding apparatus shown in FIG.

[0018] Figure 4 is shown relative to Figure 1 A structural view of the arrangement of gas injectors for the upper wafer and the lower wafer of the wafer bonding device shown in FIG.

[0019] Figure 5 is a diagram showing an exemplary embodiment according to the concept of the present invention Figure 2B A cross-sectional view of a modified form of the lower chuck shown in;

[0020] Figure 6 is a diagram showing an exemplary embodiment according to the concept of the present invention Figure 3 A cross-sectional view of a modified form of the upper chuck shown in;

[0021] Figure 7 is a diagram showing an exemplary embodiment according to the concept of the present invention Figure 2B A cross-sectional view of another modified form of the lower chuck shown in;

[0022] Figure 8 is a diagram showing an exemplary embodiment according to the concept of the present invention Figure 3 A cross-sectional view of another modified form of the upper chuck shown in;

[0023] Fig. 9 is a structural view showing a wafer bonding system according to an exemplary embodiment of the inventive concept;

[0024] Fig. 10A and Fig. 10B It is shown in Fig. 9 A cross-sectional view of wafers bonded to each other in a wafer bonding system shown in FIG.

[0025] Fig.11A and Fig. 11B is a diagram showing an exemplary embodiment according to the concept of the present invention. Fig. 9 A cross-sectional view of a process step of securing a wafer to an upper chuck and a lower chuck in a wafer bonding system shown in FIG.

[0026] Fig.12 is an exemplary embodiment of the present invention. Fig. 9 A flow chart of a method for bonding wafers in a wafer bonding system shown in FIG.

[0027] Fig.13A , Fig. 13B , Fig. 13C and Fig.13D It is shown Fig.12 2 is a cross-sectional view showing the processing steps of a method of bonding wafers. DETAILED DESCRIPTION

[0028] Reference will now be made to exemplary embodiments of the inventive concept illustrated in the accompanying drawings, wherein like reference numerals may refer to like components.

[0029] Figure 1 is a structural view illustrating a wafer bonding apparatus according to an exemplary embodiment of the inventive concept.

[0030] Reference Figure 1 , a wafer bonding device 500 according to an exemplary embodiment of the inventive concept may include: a lower chuck 100 to which a lower wafer LW may be fixed at its peripheral portion; an upper chuck 200 to which an upper wafer UW may be fixed; and a bonding initiator 300 for applying pressure to a central portion of the upper wafer UW until the central portion of the upper wafer UW touches a central portion of the lower wafer LW, thereby initiating a bonding process of the upper wafer UW with the lower wafer LW accompanied by elastic deformation of the upper wafer UW. The wafer bonding device 500 may also include a bonding controller 400 for controlling a bonding speed between a peripheral portion of the upper wafer UW and a peripheral portion of the lower wafer LW, so that the elastic deformation of the upper wafer UW may be released before bonding between the peripheral portion of the upper wafer UW and the peripheral portion of the lower wafer LW.

[0031] The upper wafer UW and the lower wafer LW may include a processed silicon wafer having a plurality of integrated circuit (IC) devices and wirings that may be manufactured by a semiconductor process, or may include a bare silicon wafer. The upper wafer UW and the lower wafer LW may include not only a silicon wafer but also any other semiconductor substrate.

[0032] The lower chuck 100 may have a shape corresponding to the lower wafer LW, and may be deformed according to the deformation of the lower wafer LW. In the present exemplary embodiment, the lower wafer LW is fixed to the lower chuck 100 so that the lower wafer LW can be deformed into a convex curve. Therefore, the lower chuck 100 may include a circular flat plate having a flat area corresponding to the lower wafer LW, and the shape of the lower wafer LW may force the lower chuck 100 to have a convex shape.

[0033] Figure 2A It is shown Figure 1 FIG. 5 is a top view of a lower chuck of a wafer bonding apparatus 500, Figure 2B It is along Figure 2A FIG. 1 is a cross-sectional view of the lower chuck 100 cut along line II′.

[0034] Reference Figure 2A and Figure 2BThe lower chuck 100 may include: a lower body 110; a plurality of support pins 120, which protrude upward from the lower body 110 in a configuration in which the height of the support pins 120 gradually increases from the peripheral portion to the central portion of the lower body 110; and a lower chip holder 130, which penetrates the lower body 110 and fixes the lower chip LW to the support pins 120.

[0035] The lower body 110 may include an insulating material such as silicon carbide and may be formed in the shape of a wafer. Therefore, the lower body 110 may be provided with a linear portion F corresponding to a flat area of ​​the lower wafer LW, which may be used as an alignment reference when the lower wafer LW is aligned with the lower chuck 100.

[0036] For example, the lower body 110 may be divided into an inner portion and an outer portion by the step portion 112. The support pins 120 may be disposed on the inner portion of the lower body 110, and the outer portion of the lower body 110 may be provided as a spare area for additional use in a process of bonding the upper wafer UW and the lower wafer LW.

[0037] The step portion 112 may protrude from the upper surface of the lower body 110 by a predetermined height, and may be shaped like a ring extending along a circumferential line of the lower body 110 .

[0038] A plurality of support pins 120 may be arranged on the upper surface of the inner portion of the lower body 110 and may support the lower wafer LW. For example, the support pins 120 may be arranged on the inner portion of the lower body 110 such that the height of the support pins 120 may increase from the peripheral portion to the central portion of the lower body 110. Therefore, the support pins 120 close to the step portion 112 may have the smallest height, and the support pins 120 close to the central portion of the lower body 110 may have the largest height.

[0039] A plurality of lifting holes LH may be arranged at a central portion of the lower body 110 and an lifting guide 113 may be arranged around each lifting hole LH so that each lifting hole LH may be surrounded by the lifting guide 113. The lifter may pass through the lifting hole LH and may load the lower wafer LW onto the lower chuck 100.

[0040] In the present exemplary embodiment, four lifting holes LH and four lifting guides 113 may be arranged along a first circumferential line C1 having the same radius from the center of the lower body 110. However, more or less than four lifting holes LH and more or less than four lifting guides 113 may be provided for the lower body 110.

[0041] A plurality of first support pins 121 may be arranged on a first region of the lower body 110 defined by the first circumferential line C1 in a configuration in which the first support pins 121 may have the same height. Therefore, the center portion of the lower wafer LW may be fixed to the lower chuck 100 in a flat shape because the upper surfaces of the first support pins 121 may have the same horizontal height. Hereinafter, the center portion of the lower wafer LW having a flat shape may be referred to as a lower center portion LC. The center portion of the upper wafer UW may be referred to as an upper center portion UC.

[0042] A plurality of second support pins 122 may be arranged on a second region of the lower body 110 between the first circumferential line C1 and the step portion 112 in a configuration in which the height of the second support pins 122 may increase toward the center portion of the lower body 110. In other words, the support pins 122 close to the step portion 112 may have the smallest height, and the support pins 122 close to the elevating guide 113 may have the largest height. The second circumferential line C2 may be set around the second support pins 122. Figure 2A In the drawings, for example, reference numeral 114 may refer to a portion of the lower body 110 between the second circumferential line C2 and an edge of the lower body 110 .

[0043] Therefore, the lower wafer LW may be fixed to the lower chuck 100 in a curved shape because the lower wafer LW may be supported by the second supporting pins 122 having different heights. Hereinafter, the peripheral portion of the lower wafer LW having the curved shape may be referred to as a lower peripheral portion LP.

[0044] Therefore, the surface profile of the lower peripheral portion LP may vary according to the surface profile of the second support pins 122. In other words, the profile of the peripheral portion of the lower wafer LW may be determined by the height variation of the second support pins 122.

[0045] A lower gap line LVL may be disposed in the second region of the lower body 110 , and vacuum pressure for fixing the lower wafer LW to the lower chuck 100 may be applied to the lower wafer LW via the lower gap line LVL.

[0046] For example, the lower wafer holder 130 may include a vacuum chuck for sucking the lower wafer LW by vacuum pressure, and the vacuum pressure may be applied to the rear surface of the lower wafer LW through the lower gap line LVL.

[0047] The lower gap line LVL may be connected to a vacuum supply line 132 that may be connected to a single vacuum generator 134 , so that vacuum pressure generated from the vacuum generator 134 may be applied to the lower wafer LW via the vacuum supply line 132 and the lower gap line LVL.

[0048] Therefore, the lower wafer LW may be sucked by the vacuum pressure at the second region and may be fixed to the lower chuck 100 so that the lower wafer LW may be supported by the first support pins 121 and the second support pins 122. Therefore, the surface profile of the lower wafer LW may be deformed along the region defined by the upper surface of the support pins 120. For example, the surface of the lower wafer LW may be deformed into a convex curve CC1 protruding upward to the upper wafer UW (see Fig.13A ).

[0049] Although the present exemplary embodiment discloses that vacuum pressure is applied to the lower wafer LW around the lower center portion LC, vacuum pressure may be applied to different portions of the lower wafer LW as long as internal stress and strain of the lower wafer LW can be minimized. In addition, the structure of the lower wafer holder 130 may also vary depending on the connection positions of the lower gap line LVL and the vacuum supply line 132 and the vacuum portion of the lower wafer LW to which vacuum pressure may be applied.

[0050] Figure 3 It is shown Figure 1 FIG. 5 is a cross-sectional view of an upper chuck 200 of a wafer bonding apparatus 500 shown in FIG.

[0051] Reference Figure 3 , the upper chuck 200 may include an upper body 210 and an upper wafer holder 220. The penetration hole PH may be arranged at a central portion of the upper body 210, and the bonding initiator 300 may be disposed in the penetration hole PH. The upper wafer holder 220 may be arranged at a peripheral portion of the upper body 210.

[0052] The upper body 210 may also include an insulating material such as silicon carbide and may be formed in the shape of a wafer, just like the lower body 110. Therefore, the upper body 210 may be provided with a linear portion corresponding to a flat area of ​​the upper wafer UW, which may be used as an alignment reference when the upper wafer UW is aligned with the upper chuck 200.

[0053] For example, the central portion of the bonding initiator 300 may selectively penetrate the upper body 210, and bonding pressure may be applied to the central portion of the upper wafer UW by the bonding initiator 300. The upper wafer holder 220 may be disposed at a peripheral portion of the upper body 210, and the upper wafer UW may be fixed to the upper body 210 by the upper wafer holder 220.

[0054] The upper wafer holder 220 may include a vacuum chuck, similar to the lower wafer holder 130. Therefore, vacuum pressure may be applied to the rear surface of the upper wafer UW, and the rear surface of the upper wafer UW may be sucked upward toward the upper body 210 to fix the upper wafer UW to the upper body 210.

[0055] The vacuum pressure for fixing the upper wafer UW to the upper body 210 may be generated by the vacuum generator 134 of the lower chuck 100, or by an additional vacuum generator only for the upper wafer holder 220. An upper gap line may be provided in the upper body 210 so that the upper gap line may be connected to a vacuum supply line. In the present exemplary embodiment, the vacuum supply line may be arranged at one side of the upper body 210 and may be connected to the vacuum generator.

[0056] A plurality of lifting holes LH may be arranged around the penetration hole PH. The lifter may extend through the upper body 210 and may lift the upper wafer UW toward the upper body 210.

[0057] When the upper wafer UW is lifted close to the upper body 210 by the lifter, the upper wafer holder 220 may fix the upper wafer UW to the upper body 210 such that the upper wafer UW is fixed to the upper body 210 in a flat shape.

[0058] When the lower chuck 100 to which the lower wafer LW is fixed and the upper chuck 200 to which the upper wafer UW is fixed are aligned with each other with sufficient accuracy, the bonding initiator 300 can move downward through the penetration hole PH and can pressurize the central portion of the upper wafer UW. Therefore, the central portion of the upper wafer UW can be spaced apart from the upper body 210, while the peripheral portion of the upper wafer UW can still be fixed to the upper body 210 by the upper wafer holder 220. Therefore, the upper wafer UW is deformed so that the central portion of the upper wafer UW is deformed into a concave curve CC2 protruding toward the lower wafer LW (see Fig. 13B ). When the bonding initiator 300 presses the central portion of the upper wafer UW, the concave curve CC2 of the central portion of the upper wafer UW may contact the convex curve CC1 of the central portion of the lower wafer LW.

[0059] For example, the bond initiator 300 may include an elongated rod driven by an external power source such as an electric motor and hydraulic power.

[0060] The peripheral portion of the upper wafer UW may still be fixed to the upper body 210 by the upper wafer holder 220 until the moment when the lower wafer LW and the upper wafer UW may contact each other at the central portion of the convex curved portion of the lower wafer LW and the central portion of the concave curved portion of the upper wafer UW. Therefore, the peripheral portion of the upper wafer UW and the peripheral portion of the lower wafer LW may be spaced apart from each other so that the inter-wafer gap space IWS (see Fig. 13B) can be disposed between the peripheral portion of the upper wafer UW and the peripheral portion of the lower wafer LW. Since the upper wafer UW and the lower wafer LW can contact each other by virtue of their concavo-convex shapes, the size of the inter-wafer gap space IWS can be enlarged from the center portion to the peripheral portion of the upper wafer UW and the lower wafer LW. In addition, elastic deformation can be generated at both the upper wafer UW and the lower wafer LW.

[0061] At the moment when the central portion of the upper wafer UW and the central portion of the lower wafer LW contact each other, the vacuum pressure of the upper wafer holder 220 may be stopped. Therefore, the peripheral portion of the upper wafer UW may be separated from the peripheral portion of the upper body 210, and may fall toward the peripheral portion of the lower wafer LW accompanied by oscillation for releasing the elastic deformation of the upper wafer UW. Therefore, the peripheral portion of the upper wafer UW may be bonded to the peripheral portion of the lower wafer LW.

[0062] In this case, the bonding speed of the peripheral portion of the upper wafer UW and the peripheral portion of the lower wafer LW can be controlled by the bonding controller 400, so that the bonding time between the peripheral portion of the upper wafer UW and the peripheral portion of the lower wafer LW can be longer than the time for releasing the elastic deformation of the upper wafer UW. Therefore, after the peripheral portion of the upper wafer UW is fully restored to its original shape, the peripheral portion of the upper wafer UW can be bonded to the peripheral portion of the lower wafer LW. Therefore, during the bonding process, the alignment between the upper wafer UW and the lower wafer LW before the bonding process can be maintained. In other words, the bonding process between the upper wafer UW and the lower wafer LW can be performed with a sufficiently high alignment accuracy.

[0063] Since the peripheral portion of the upper wafer UW may fall toward the peripheral portion of the lower wafer LW, the bonding speed of the peripheral portion of the upper wafer UW may be controlled simply by changing the configuration of the inter-wafer gap space IWS.

[0064] In the present exemplary embodiment, the filling gas G may be filled into the inter-wafer gap space IWS to hinder the peripheral portion of the upper wafer UW from falling. In other words, the filling gas G in the inter-wafer gap space IWS may resist the falling of the peripheral portion of the upper wafer UW, thereby reducing the bonding speed of the peripheral portion of the upper wafer UW, and as a result, the bonding time for bonding the peripheral portion of the upper wafer UW to the peripheral portion of the lower wafer LW may be extended. Therefore, the bonding time may be sufficiently extended so that the elastic deformation of the upper wafer UW may be sufficiently released, and the peripheral portion of the upper wafer UW may be restored to its original shape simply by controlling the density of the filling gas G in the inter-wafer gap space IWS.

[0065] In the present exemplary embodiment, the bonding controller 400 may include a gas injector 410 for injecting a filling gas G directly into the inter-wafer gap space IWS.

[0066] For example, the gas injector 410 can be connected to a bonding chamber such as a bonding chamber ( Fig. 9 Therefore, the gas injector 410 can be moved downward from the top plate along the moving wiring to a position separated from the upper wafer UW and the lower wafer LW facing the inter-wafer gap space IWS. When the gas injection is completed, the gas injector 410 can be moved upward through the moving wiring.

[0067] Figure 4 4 is a structural view showing the arrangement of the gas injector 410 with respect to the upper wafer UW and the lower wafer LW.

[0068] Reference Figure 4 , the inter-wafer gap space IWS may be an open space exposed to its surrounding environment, and the gas injector 410 may be arranged around the upper wafer UW and the lower wafer LW. The gas injector 410 may be spaced apart from the upper wafer UW and the lower wafer LW so that the gas injector 410 may face the inter-wafer gap space IWS.

[0069] A plurality of gas injectors 410 may be arranged around the inter-wafer gap space IWS at the same intervals. For example, four gas injectors 410 may be arranged around the inter-wafer gap space IWS at four different angles of 0°, 90°, 180°, and 270°.

[0070] Therefore, the filling gas G can be efficiently injected into the gap space IWS between the wafers through the four gas injectors 410. In this way, the filling gas G can be filled in the gap space IWS between the wafers at a predetermined pressure. The filling gas G in the gap space IWS between the wafers can resist the falling of the peripheral portion of the upper wafer UW, thereby reducing the bonding speed of the peripheral portion of the upper wafer UW to the peripheral portion of the lower wafer LW.

[0071] For example, the filling gas G may be at a pressure of about 0.5 atm to about 1.5 atm in the gap space IWS between wafers. When the gap space IWS between wafers is in a vacuum state, the peripheral portion of the upper wafer UW may fall too fast, causing the peripheral portion of the upper wafer UW to bond to the peripheral portion of the lower wafer LW before the elastic deformation of the upper wafer UW is fully released. Therefore, during the bonding process, the alignment between the upper wafer UW and the lower wafer LW may be degraded. In contrast, when the internal pressure of the gap space IWS between wafers is too high, the bonding speed may be slow, thereby significantly reducing the overall efficiency of the bonding process.

[0072] Therefore, the internal pressure of the inter-wafer gap space IWS is controlled to reach a pressure close to atmospheric pressure to prevent excessive degradation of bonding efficiency, thereby fully releasing the elastic deformation of the upper wafer UW. For example, the inter-wafer gap space IWS may be at a pressure of about 0.5 atm to about 1.5 atm.

[0073] Since the filling gas G in the inter-wafer gap space IWS can be controlled only to sufficiently counteract the falling of the peripheral portion of the upper wafer UW, the internal pressure of the inter-wafer gap space IWS can be varied according to the surface characteristics and shape of the upper wafer UW.

[0074] Since the filling gas G may contact the upper wafer UW and the lower wafer LW in the inter-wafer gap space IWS, a chemical reaction between the filling gas G and the upper wafer UW and the lower wafer LW should be prevented. For this reason, the filling gas G may include gas such as argon (Ar), nitrogen (N 2 ) and helium (He) gas. In addition, oxygen (O 2 ) gas as the filling gas G, because through oxygen (O 2 )The chemical reaction between the gas and the silicon wafer can form an insulating layer on the upper wafer UW and the lower wafer LW.

[0075] Since the inter-wafer gap space IWS can be expanded from the center portion to the peripheral portion of the upper wafer UW and the lower wafer LW, the air between the contact surface of the upper wafer UW and the contact surface of the lower wafer LW can be squeezed out from the center portion toward the peripheral portion of the upper wafer UW and the lower wafer LW when the air adiabatically expands. Therefore, the vapor in the air may condense on the surfaces of the upper wafer UW and the lower wafer LW, thereby causing a bonding defect between the upper wafer UW and the lower wafer LW.

[0076] To this end, the filling gas G may include an inert gas having a negative Joule-Thomson coefficient. When the Joule-Thomson coefficient of the filling gas G is negative, the air is heated due to adiabatic collision, thereby preventing the condensation of vapor in the inter-wafer gap space IWS. When helium (He) gas having a negative Joule-Thomson coefficient is used as the filling gas G, the bonding speed of the upper wafer UW and the lower wafer LW is sufficiently reduced without generating vapor. Therefore, the upper wafer UW can be bonded to the lower wafer LW without any significant elastic deformation.

[0077] Figure 5 is a diagram showing an exemplary embodiment according to the concept of the present invention Figure 2B A cross-sectional view of a modified form of the lower chuck 100 is shown in FIG. Figure 6 is a diagram showing an exemplary embodiment according to the concept of the present invention Figure 3 A cross-sectional view of a modified form of the upper chuck 200 is shown in FIG. Figure 5 and Figure 6 In addition to the lower chuck 100 and the upper chuck 200 being provided with gas supply holes for supplying the filling gas G, the lower chuck 100 and the upper chuck 200 have the same Figure 2B and Figure 3 The lower chuck and the upper chuck shown in FIG. are substantially the same structure. Figure 5 and Figure 6 The same reference numerals in Figure 2A and Figure 3 , and any other detailed description of the same elements will be omitted.

[0078] Reference Figure 5 and Figure 6 , the lower gas supply holes LSH may be disposed at an edge of the lower body 110 , and the upper gas supply holes USH may be disposed at an edge of the upper body 210 .

[0079] In this case, the gas injector 410 may be arranged on the upper surface of the upper body 210 and on the rear surface of the lower body 110 so that the gas injector 410 may be inserted into the lower gas supply hole LSH and the upper gas supply hole USH, respectively. Therefore, the gas injector 410 may be assembled to the lower body 110 and the upper body 210 without any fasteners or fixing members.

[0080] The filling gas G may flow from the gas reservoir to the gas injector 410 through the flexible flow line, and may be injected into the inter-wafer gap space IWS through the lower gas supply holes LSH and the upper gas supply holes USH.

[0081] When the gas injector 410 is disposed around the upper wafer UW and the lower wafer LW and the filling gas G is directly injected into the inter-wafer gap space IWS, because the size of the inter-wafer gap space IWS may be relatively small, the injection efficiency of the filling space G may be relatively poor. In other words, the gas injector 410 may not be aligned with the inter-wafer gap space IWS.

[0082] However, when the gas injector 410 is connected to the lower gas supply holes LSH and the upper gas supply holes USH, the filling gas G may be supplied to the inter-wafer gap space IWS without any loss, and thus, the injection efficiency of the filling gas G may be sufficiently high.

[0083] Although the present exemplary embodiment discloses that the gas supply holes are provided in both the upper body 210 and the lower body 110 , the gas supply holes may be provided in only one of the upper body 210 and the lower body 110 .

[0084] Figure 7 is a diagram showing an exemplary embodiment according to the concept of the present invention Figure 2B FIG. 2 is a cross-sectional view of another modified form of the lower chuck 100 shown in FIG. Figure 8 is a diagram showing an exemplary embodiment according to the concept of the present invention Figure 3 A cross-sectional view of another modified form of the upper chuck 200 is shown in FIG. Figure 7 and Figure 8 In addition to the lower chuck 100 and the upper chuck 200 being respectively provided with a shielding wall and a shielding groove for separating the inter-wafer gap space IWS from its surrounding environment, the lower chuck 100 and the upper chuck 200 have the same Figure 5 and Figure 6 The lower chuck 100 and the upper chuck 200 shown in FIG. 1 have substantially the same structure. Figure 7 and Figure 8 The same reference numerals in Figure 2A and Figure 3 or Figure 5 and Figure 6 , and any other detailed description of the same elements will be omitted.

[0085] Reference Figure 7 and Figure 8 , the shielding wall 490 may be provided on an edge portion of the lower body 110 , and the shielding groove R may be provided on an edge portion of the upper body 210 corresponding to the shielding wall 490 .

[0086] When the alignment of the lower chuck 100 and the upper chuck 200 is completed, one of the lower chuck 100 and the upper chuck 200 may be moved toward the other so that the shielding wall 490 may be inserted into the shielding groove R. Therefore, the gap space IW between wafers may be closed and separated from its surroundings by the shielding wall 490. Therefore, the gap space IWS between wafers may be formed as a closed space by the shielding wall 490. The shielding groove R may have a depth d sufficient to accommodate the shielding wall 490 when the upper wafer UW and the lower wafer LW are in contact at their central portions.

[0087] In addition, the shielding wall 490 may be further provided with an opening, and the gas injector 410 may be connected to the opening. Therefore, the filling gas G may be supplied from the gas injector 410 into the closed inter-wafer gap space IWS through the opening.

[0088] For example, when the gas injector 410 is connected to the upper gas supply holes USH and the lower gas supply holes LSH, the filling gas G may be efficiently supplied into the closed inter-wafer gap space IWS, and the internal pressure of the inter-wafer gap space IWS may quickly reach a desired pressure.

[0089] In the wafer bonding apparatus according to an exemplary embodiment of the inventive concept, the filling gas G may be filled into the gap space IWS between the wafers to reach a predetermined internal pressure. Therefore, the falling of the peripheral portion of the upper wafer UW may be counteracted by the filling gas G, thereby reducing the falling speed of the upper wafer UW. Therefore, the bonding process between the peripheral portion of the upper wafer UW and the peripheral portion of the lower wafer LW may be performed after the elastic deformation of the upper wafer UW is fully released, thereby fully preventing the misalignment between the upper wafer UW and the lower wafer LW during the bonding process.

[0090] In addition, an inert gas having a negative Joule-Thomson coefficient may be used as the filling gas G. Therefore, during the bonding process performed between the upper wafer UW and the lower wafer LW, even if the size of the inter-wafer gap space IWS may be expanded from the central portion to the peripheral portion of the upper wafer UW and the lower wafer LW, condensation of vapor due to adiabatic expansion of air can be sufficiently prevented on the surfaces of the upper wafer UW and the lower wafer LW in the inter-wafer gap space IWS.

[0091] Therefore, misalignment of the upper wafer UW and the lower wafer LW and vapor condensation may be minimized during the bonding process.

[0092] Hereinafter, a wafer bonding system having a wafer bonding apparatus will be described in detail below.

[0093] Fig. 9 2 is a structural view showing a wafer bonding system according to an exemplary embodiment of the inventive concept. Fig. 9 In the embodiment, the bonding device 950 of the wafer bonding system 1000 may have the same Figures 1 to 8 The wafer bonding apparatus 500 described in detail has substantially the same structure. Figures 9 to 13D In the Figures 1 to 8 , and any other detailed description of the same elements may be omitted. In the following drawings, reference letter W may be used to represent, for example, a single wafer or a plurality of wafers.

[0094] Reference Fig. 9 The wafer bonding system 1000 according to an exemplary embodiment of the inventive concept may include a loading port 600 for loading and unloading a wafer W, a bonding unit 900 for bonding the wafer W, and a transfer unit 700 for transferring the wafer W between the loading port 600 and the bonding unit 900. Optionally, the wafer bonding system 1000 may further include a processing unit 800 for performing additional processing on the wafer W before mounting the wafer W to the bonding unit 900.

[0095] For example, the loading port 600 may be provided at one side of the transfer unit 700, and a wafer box including a plurality of wafers W may be provided on the loading port 600. Then, the transfer arm 720 may extract the wafers W from the wafer box one by one, and may transfer the wafers W to the bonding unit 900 and / or the processing unit 800.

[0096] The wafer W may include a first wafer W1 that may undergo a plurality of semiconductor manufacturing processes and a second wafer W2 that may not undergo any semiconductor manufacturing process.

[0097] Fig. 10A and Fig. 10B It is shown in Fig. 9 FIG. 4 is a cross-sectional view of wafers W bonded to each other in a wafer bonding system 1000 shown in FIG.

[0098] like Fig. 10A and Fig. 10B As shown, the first wafer W1 may include a first body 10, a plurality of conductive structures 20 that may be formed on the first body 10 by a plurality of semiconductor manufacturing processes, and a passivation layer 30 for covering the conductive structures 20. For example, the conductive structures 20 may include a plurality of integrated circuit (IC) devices and a plurality of wiring structures electrically connected to the IC devices.

[0099] In contrast, the second wafer W2 may include a bare wafer having only the second body 40. Optionally, before the second wafer W2 is supplied to the bonding unit 900, a surface protection layer 50 may be further formed on the second wafer W2 in the processing unit 800. Therefore, the bare wafer of the second wafer W2 may include the second body 40 and the surface protection layer 50.

[0100] Return to reference Fig. 9 The transfer chamber 710 may include a body formed in a box shape and having a closed transfer space TS. Therefore, the wafer W in the transfer chamber 710 may be fully protected from its surrounding environment and any contaminants. The transfer arm 720 may be fixed to the bottom of the transfer chamber 710 and may rotate in the transfer space TS.

[0101] Before the bonding process is performed in the bonding unit 900, an additional process may be selectively performed on the wafer W in the processing unit 800. For example, the processing unit 800 may include a cleaner 810 for cleaning the wafer W and a plasma processor 820 for processing the wafer W using plasma.

[0102] For example, before the second wafer W2 is supplied to the bonding unit 900, the surface protection layer 50 may be formed on the second body 40 of the second wafer W2 by plasma treatment in the plasma processor 820. In addition, the first wafer W1 and the second wafer W2 may be cleaned and rinsed in the cleaner 810 to remove surface contaminants from the first wafer W1 and the second wafer W2 before initiating the bonding process in the bonding unit 900.

[0103] A pair of wafers W may be supplied to the bonding unit 900 and may be formed into a bonded wafer BW (see Fig.13D ).

[0104] For example, the bonding unit 900 may include a bonding chamber 910, a base plate 920, a transfer track 930 located on the base plate 920, a bonding buffer 940, and a bonding device 950 fixed to the transfer track 930, wherein the bonding chamber 910 is connected to the transfer chamber 710 and has a bonding space BS connected to the transfer space TS.

[0105] For example, the bonding chamber 910 may be integrally provided with the transfer chamber 710 as an integrated physical structure, and various instruments for bonding the wafer W may be arranged in the bonding chamber 910. For example, the bonding space BS may be communicated with the transfer space TS. Therefore, the wafer W may be transferred from the loading port 600 to the bonding space BS by the transfer arm 720, and the bonded wafer BW may also be transferred to the loading port 600 via the transfer space TS by the transfer arm 720.

[0106] The bottom plate 920 may include a plate structure that may be disposed on the bottom portion and the top portion of the bonding chamber 910, and the transfer track 930 may be disposed on the bottom plate 920. The bottom plate 920 can absorb movement vibrations of the lower chuck 100 and the upper chuck 200. The transfer track 930 may include a pair of transfer lines located on the bottom plate 920.

[0107] The bonding buffer 940 may be arranged at a first end of the transfer track 930, and the bonding device 950 may be arranged at a second end of the transfer track 930 opposite to the first end. In the bonding buffer 940, one wafer W may be fixed to the upper chuck 200 and another wafer W may be fixed to the lower chuck 100, and the bonded wafer BW may be temporarily held in the bonding buffer 940 before being transferred back to the load port 600. In the bonding device 950, the upper wafer UW fixed to the upper chuck 200 and the lower wafer LW fixed to the lower chuck 100 may be bonded to each other, thereby forming a bonded wafer BW. The upper wafer UW and the lower wafer LW may be fixed to the upper chuck 200 and the lower chuck 100, respectively, according to the same fixing scheme and the same alignment requirements.

[0108] The bonding buffer 940 and the bonding apparatus 950 may be connected to each other through the transfer track 930 , and thus the upper chuck 200 with the upper wafer UW and the lower chuck 100 with the lower wafer LW may be transferred to the bonding apparatus 950 along the transfer track 930 .

[0109] A pair of wafers W may be transferred to the bonding buffer 940 by the transfer arm 720, and respectively, one of the wafers W may be fixed to the upper chuck 200 and the other of the wafers W may be fixed to the lower chuck 100. Therefore, the wafer W fixed to the upper chuck 200 may be formed as an upper wafer UW, and the wafer W fixed to the lower chuck 100 may be formed as a lower wafer LW. Therefore, the upper wafer UW and the lower wafer LW may include one of a first wafer W1 and a second wafer W2, respectively.

[0110] In the present exemplary embodiment, a first wafer W1 or a processed wafer may be provided as a lower wafer LW, and a second wafer W2 or a bare wafer may be provided as an upper wafer UW. However, a bare wafer may be provided as the lower wafer LW, and a processed wafer may be provided as the upper wafer UW. For example, because the upper wafer UW and the lower wafer LW may be fixed to the upper chuck 200 and the lower chuck 100, respectively, due to the same fixing scheme and the same alignment requirements, the upper wafer UW may be sufficiently stacked on the lower wafer LW as long as the upper chuck 200 and the lower chuck 100 are controlled to have the same center axis. In this case, the upper chuck 200 and the lower chuck 100 may be made symmetrical to each other in the vertical direction in the bonding device 950.

[0111] Fig.11A and Fig. 11B is a diagram showing an exemplary embodiment according to the concept of the present invention. Fig. 9 FIG. 1 is a cross-sectional view of a process step of fixing a wafer W to an upper chuck 200 and a lower chuck 100 in a wafer bonding system 1000 .

[0112] Reference Fig.11A The wafer W extracted from the load port 600 may be transferred to one of the lower wafer elevator LWL and the upper wafer elevator UWL by the transfer arm 720. The lower wafer elevator LWL may penetrate the lower chuck 100, and the upper wafer elevator UWL may penetrate the upper chuck 200.

[0113] When the wafer W is arranged on the lower wafer elevator LWL, the lower wafer elevator LWL may move downward through the elevator hole LH until the wafer W contacts the support pins 120. Then, the wafer W may be fixed to the support pins 120 (and also to the lower chuck 100) by the lower wafer holder 130, thereby forming the lower wafer LW. In this case, the support pins 120 may protrude from the surface of the lower chuck 100, and the wafer W may be deformed into a curved shape according to the surface profile of the support pins 120.

[0114] In the same manner, when the wafer W is arranged on the upper wafer elevator UWL, the upper wafer elevator UWL may move upward through the elevator hole LH until the wafer W contacts the upper chuck 200. Then, the wafer W may be fixed to the upper chuck 200 by the upper wafer holder 220, thereby forming the upper wafer UW.

[0115] When the upper chuck 200 bonded with the upper wafer UW and the lower chuck 100 bonded with the lower chuck LW are prepared in the bonding buffer 940, the upper chuck 200 and the lower chuck 100 may be transferred to the bonding apparatus 950 along the transfer track 930. Thereafter, the upper wafer UW and the lower wafer LW may be bonded to each other, thereby forming a bonded wafer BW.

[0116] The bonding device 950 may have Figures 1 to 8 The bonding apparatus 950 has the same structure as the wafer bonding apparatus 500 shown in FIG. 1 , and thus any detailed description of the bonding apparatus 950 may be omitted.

[0117] For example, a plurality of gas injectors 410 may be connected to the base plate 920 at the top portion of the bonding chamber 910 through a moving wiring. Therefore, the gas injectors 410 may move downward along the moving wiring from the top portion of the bonding chamber 910 in the bonding space BS. Therefore, the filling gas G may be injected into the gap space IWS between wafers.

[0118] In contrast, the gas injector 410 may be connected to the lower gas supply holes LSH and / or the upper gas supply holes USH, respectively. The filling gas G may be efficiently injected into the inter-wafer gap space IWS through the lower gas supply holes LSH and the upper gas supply holes USH.

[0119] A chemical reaction between the filling gas G and the upper and lower wafers UW and LW may be prevented in the inter-wafer gap space IWS. For example, the filling gas G may include gas such as argon (Ar), nitrogen (N 2 ) gas and helium (He) gas. In addition, oxygen (O 2 ) gas as the filling gas G, because through oxygen (O 2 )The chemical reaction between the gas and the silicon wafer can form an insulating layer on the upper wafer UW and the lower wafer LW.

[0120] In addition, an inert gas having a negative Joule-Thomson coefficient may be used as the filling gas G for preventing vapor condensation caused by adiabatic expansion of air in the inter-wafer gap space IWS, thereby preventing bubble defects on the surfaces of the upper and lower wafers UW and LW.

[0121] The shielding wall 490 may be further provided on the edge portions of the lower chuck 100 and the upper chuck 200 so that the inter-wafer gap space IWS may be surrounded and separated from its surroundings by the shielding wall 490. Therefore, the inter-wafer gap space IWS may be formed as a closed space by the shielding wall 490 and the filling gas G may be supplied to the closed space, thereby improving the injection efficiency of the filling gas G.

[0122] Therefore, in a bonding process for bonding the upper wafer UW and the lower wafer LW to each other, misalignment and vapor condensation may be minimized.

[0123] In the following, refer to Figures 12 to 13D A method of bonding the wafer W is described in detail.

[0124] Fig.12 is a diagram showing an exemplary embodiment according to the concept of the present invention. Fig. 9 Flowchart of a method for bonding wafers in a wafer bonding system shown in FIG. Fig.13A , Fig. 13B , Fig. 13C and Fig.13D It is shown Fig.12 2 is a cross-sectional view showing the processing steps of a method of bonding wafers.

[0125] Reference Fig.12 and Fig.13A , the lower chuck 100 bonded with the lower wafer LW and the upper chuck 200 bonded with the upper wafer UW may be transferred to the bonding chamber 910 , and the lower chuck 100 and the upper chuck 200 may be aligned with each other (step S100 ).

[0126] For example, the lower chuck 100 may be mounted on the bottom portion of the bonding apparatus 950, and the upper chuck 200 may be mounted on the top portion of the bonding apparatus 950. Then, the lower chuck 100 and the upper chuck 200 may be aligned with each other so that the lower chuck 100 and the upper chuck 200 may have the same central axis.

[0127] Since the upper wafer UW and the lower wafer LW can be fixed to the upper chuck 200 and the lower chuck 100 respectively according to the same fixing scheme and the same alignment requirements, when the upper chuck and the lower chuck are aligned with each other to have the same central axis, the upper wafer UW can be fully stacked on the lower wafer LW. In other words, the upper chuck 200 and the lower chuck 100 can be made symmetrical to each other in the vertical direction in the bonding apparatus 950.

[0128] In the present exemplary embodiment, the lower wafer LW may be supported by the support pins 120 having different heights, and thus, the surface profile of the lower wafer LW may be deformed into the convex curve CC1 according to the surface profile of the support pins 120 .

[0129] In this case, at least one of the upper chuck 200 and the lower chuck 100 can be moved upward or downward toward each other in the vertical direction to control the gap between the upper wafer UW and the lower wafer LW. Therefore, the gap between the upper wafer UW and the lower wafer LW can be controlled to a specified distance required by the direct silicon bonding process. In addition, the size of the inter-wafer gap space IWS can be determined by the width of the gap between the upper wafer UW and the lower wafer LW.

[0130] Reference Fig.12 and Fig. 13B , the central portion of the upper wafer UW may be pressurized until the central portion of the upper wafer UW contacts the central portion of the lower wafer LW while the peripheral portion of the upper wafer UW is still fixed to the upper chuck 200. In this case, the surface profile of the upper wafer UW may be deformed into a concave curve CC2 (step S200).

[0131] For example, the bonding initiator 300 , which may be fixed to the base plate 920 at the upper portion of the bonding apparatus 950 , may be moved downward through the penetration hole PH until the lower top end of the bonding initiator 300 is located below the upper chuck 200 .

[0132] Therefore, the upper wafer UW, which may be fixed to the upper chuck 200 in a flat shape, may be pushed downward by the bonding initiator 300 and separated from the upper chuck 200 at its center portion while the peripheral portion of the upper wafer UW is still fixed to the upper chuck 200. Therefore, the surface profile of the upper wafer UW may be deformed into the concave curve CC2 within the elastic deformation.

[0133] Since the surface profile of the lower wafer LW can be deformed into a convex curve CC1 protruding upward toward the upper wafer UW, the center portion of the upper wafer UW can first contact the center portion of the lower wafer LW, and a bonding process between the upper wafer UW and the lower wafer LW can be initiated at their center portions. In other words, a bonding process can be initiated at the center portions of the upper wafer UW and the lower wafer LW by the bonding initiator 300.

[0134] Reference Fig.12 and Fig. 13C , a filling gas G may be supplied into the inter-wafer gap space IWS between the peripheral portion of the upper wafer UW and the peripheral portion of the lower wafer LW (step S300 ).

[0135] At the moment when the central portion of the upper wafer UW contacts the central portion of the lower wafer LW, the bonding initiator 300 may be stopped, and the filling gas G may be supplied into the gap space IWS between the wafers. The filling gas G may be supplied into the gap space IWS between the wafers so that the internal pressure of the gap space IWS between the wafers may be close to the atmospheric pressure, for example, at a pressure of about 0.5 atm to about 1.5 atm.

[0136] For example, gases such as argon (Ar), nitrogen (N 2 Inert gases such as oxygen (O) and helium (He) are supplied into the inter-wafer gap space IWS to minimize chemical reactions with the upper wafer UW and the lower wafer LW. 2 ) gas as the filling gas G, because oxygen (O 2 ) chemically reacts with silicon (Si) to provide silicon dioxide (SiO 2 ) layer, and can prevent the upper wafer UW and the lower wafer LW from being affected by the surrounding environment of the gap space IWS between wafers.

[0137] For example, when an inert gas having a negative Joule-Thomson coefficient is used as the filling gas G, the temperature drop caused by the adiabatic expansion of air in the inter-wafer gap space IWS can be minimized, and as a result, in the inter-wafer gap space IWS, steam condensation (which can be referred to as a bubble defect) on the surfaces of the upper wafer UW and the lower wafer LW can be sufficiently prevented. Therefore, in the bonding process, the bubble defect can be sufficiently minimized.

[0138] In a modified exemplary embodiment of the present inventive concept, the filling gas G may be supplied into the gap space IWS between wafers through the upper supply hole USH penetrating the upper chuck 200 and the lower supply hole LSH penetrating the lower chuck 100, as shown in FIG. Figure 5 and Figure 6 In another modified exemplary embodiment of the present inventive concept, a shielding wall 490 may be disposed between the lower chuck 100 and the upper chuck 200 so that the inter-wafer gap space IWS may be closed and separated from its surroundings by the shielding wall 490. Therefore, the inter-wafer gap space IWS may be formed as a closed space and the filling gas G may be supplied into the closed inter-wafer gap space IWS, thereby improving the filling efficiency of the filling gas G.

[0139] Reference Fig.12 and Fig.13D , the peripheral portion of the upper wafer UW may be sufficiently restored to its original shape and may be bonded to the peripheral portion of the lower wafer LW, thereby forming a bonded wafer BW (step S400).

[0140] When the internal pressure of the inter-wafer gap space IWS reaches a desired pressure (eg, a pressure close to atmospheric pressure), the bonding initiator 300 may be moved back upward and the upper wafer holder 220 may be released.

[0141] Therefore, the peripheral portion of the upper wafer UW can be separated from the upper chuck 200 and fall toward the peripheral portion of the lower wafer LW. For example, the upper wafer UW may fall with fluctuations or oscillations of its peripheral portion due to elastic deformation. In this case, the falling of the peripheral portion of the upper wafer UW can be counteracted by the filling gas G in the gap space IWS between the wafers, so that the bonding time for bonding the peripheral portion of the upper wafer UW and the peripheral portion of the lower periphery LW can be extended to the extent that the elastic deformation of the upper wafer W can be fully released and the upper wafer UW can be restored to its original shape.

[0142] In other words, the bonding controller 400 can control the bonding time of the upper chip UW and the lower chip LW by using the filling gas G, so that the bonding of the peripheral portion of the upper chip UW and the peripheral portion of the lower chip LW can be triggered after the elastic deformation of the upper chip UW ends and the upper chip UW returns to its original shape.

[0143] Therefore, the bonding time of the upper wafer UW and the lower wafer LW may be increased to allow the upper wafer UW to recover to its original shape after deformation, and during the bonding process, misalignment between the upper wafer UW and the lower wafer LW may be substantially minimized.

[0144] When the upper wafer UW is not sufficiently bonded to the lower wafer LW, the bonding controller 400 may be stopped and the upper chuck 200 may be separated from the upper wafer UW. Thereafter, the upper chuck 200 may be moved upward, and the upper wafer UW and the lower wafer LW may remain on the lower chuck 100 as a bonded wafer BW. The bonded wafer BW may be removed from the lower chuck 100, and an additional process such as a heat treatment may be selectively performed on the bonded wafer BW.

[0145] Although the present exemplary embodiment discloses that the filling gas G can be supplied into the inter-wafer gap space IWS at the moment when the central portion of the upper wafer UW is bonded to the central portion of the lower wafer LW, the filling gas G can be supplied at other times according to the requirements of the bonding process and configuration of the wafer bonding system 1000.

[0146] For example, the filling gas G may be supplied into the inter-wafer gap space IWS before the central portion of the upper wafer UW and the central portion of the lower wafer LW are bonded. In this case, the filling gas G may be supplied after the gap distance between the upper wafer UW and the lower wafer LW is determined. Therefore, the internal pressure of the inter-wafer gap space IWS may be established before the upper wafer UW falls, thereby preventing the upper wafer UW from falling immediately when the peripheral portion of the upper wafer UW is separated from the upper chuck 200.

[0147] According to an exemplary embodiment of the present inventive concept, the filling gas G may be filled into the gap space IWS between the wafers to reach a predetermined internal pressure. Therefore, the falling of the peripheral portion of the upper wafer UW may be resisted by the filling gas G, thereby reducing the falling speed of the upper wafer UW. Therefore, the bonding process between the peripheral portion of the upper wafer UW and the peripheral portion of the lower wafer LW may be performed after the elastic deformation of the upper wafer UW is fully released (for example, after the upper wafer UW returns to its original state from the deformed state), thereby fully preventing misalignment between the upper wafer UW and the lower wafer LW during the bonding process.

[0148] In addition, an inert gas having a negative Joule-Thomson coefficient may be used as the filling gas G. Therefore, in the bonding process performed between the upper wafer UW and the lower wafer LW, although the size of the inter-wafer gap space IWS may be expanded from the central portion to the peripheral portion of the upper wafer UW and the lower wafer LW, condensation of vapor due to adiabatic expansion of air may be sufficiently prevented on the surfaces of the upper wafer UW and the lower wafer LW in the inter-wafer gap space IWS.

[0149] Therefore, during the bonding process, misalignment of the upper wafer UW and the lower wafer LW and vapor condensation may be minimized.

[0150] The exemplary embodiments of the present inventive concept described above provide a wafer bonding apparatus for directly bonding an upper wafer and a lower wafer, in which a gas injector for supplying a bonding control gas into a gap space between the upper wafer and the lower wafer is provided.

[0151] While the inventive concept has been described with reference to exemplary embodiments thereof, those skilled in the art will readily appreciate that many modifications are possible without departing from the scope of the inventive concept as defined by the appended claims.

Claims

1. A wafer bonding device, comprising: a lower chuck for fixing a lower wafer at a peripheral portion of the lower chuck; An upper chuck, the upper chuck being used to fix an upper wafer; a bonding initiator for applying pressure to a central portion of the upper wafer until the central portion of the upper wafer touches a central portion of the lower wafer, thereby initiating a bonding process of the upper wafer and the lower wafer by deforming the upper wafer; as well as a gas injector for controlling a bonding speed between the peripheral portion of the upper wafer and the peripheral portion of the lower wafer by injecting a filling gas into a gap between the peripheral portion of the lower wafer and the peripheral portion of the upper wafer to resist the falling of the peripheral portion of the upper wafer, so that the elastic deformation of the upper wafer is released before the peripheral portion of the upper wafer and the peripheral portion of the lower wafer are bonded, The lower chuck includes a lower body and a plurality of support pins, the plurality of support pins protrude upward from the lower body so that the protruding height of the support pins increases from the peripheral portion of the lower body to the central portion of the lower body, wherein the lower body is divided into an inner portion and an outer portion by a step portion, the step portion protruding from an upper surface of the lower body and shaped as a ring extending along a circumferential line of the lower body, and the inner portion includes the central portion and the peripheral portion of the lower body, and A lifting hole is arranged at the central portion of the lower body and a lifting guide is arranged around the lifting hole, a support pin among the plurality of support pins close to the step portion has a minimum height, and a support pin among the plurality of support pins close to the lifting guide has a maximum height.

2. The wafer bonding apparatus according to claim 1, wherein: The gap between the peripheral portion of the lower wafer and the peripheral portion of the upper wafer is under a pressure of 0.5 atm to 1.5 atm.

3. The wafer bonding apparatus according to claim 1, wherein: The filling gas includes argon, oxygen, nitrogen, helium or a combination thereof.

4. The wafer bonding apparatus according to claim 1, wherein: The filling gas includes an inert gas having a negative Joule-Thomson coefficient.

5. The wafer bonding apparatus according to claim 1, wherein: When the bonding process is initiated at the central portion of the lower wafer and the central portion of the upper wafer, the lower wafer is fixed to the lower chuck in an upwardly convex shape, and the upper wafer is deformed to have a downwardly concave shape, and the gap is expanded from the central portion of the upper wafer and the central portion of the lower wafer to the peripheral portion of the upper wafer and the peripheral portion of the lower wafer.

6. The wafer bonding apparatus according to claim 5, wherein: The lower chuck also includes a lower chip holder, which penetrates the lower body and fixes the lower chip to the supporting pin, and the upper chuck includes an upper body and an upper chip holder, the upper body has a hole for the bonding initiator to pass through, and the upper chip holder penetrates the upper body and fixes the peripheral portion of the upper chip to the upper body.

7. The wafer bonding apparatus according to claim 6, wherein: The gas injector is spaced apart from the upper chuck and the lower chuck to face the gap so that the filling gas is directly injected into the gap.

8. The wafer bonding apparatus according to claim 6, wherein: The gas injector is connected to the upper chuck and the lower chuck to inject the filling gas through the upper chuck or the lower chuck.

9. The wafer bonding apparatus according to claim 8, wherein: A supply hole is provided at a peripheral portion of the upper body and / or the peripheral portion of the lower body such that the gas injector is connected to the supply hole. 10 . The wafer bonding apparatus according to claim 6 , further comprising a shielding wall, wherein the shielding wall closes the gap to form a closed gap.

11. The wafer bonding apparatus according to claim 10, wherein: The shielding wall contacts a peripheral portion of a lower surface of the upper body and a peripheral portion of an upper surface of the lower body along a circumferential line of the upper body and the circumferential line of the lower body.

12. The wafer bonding apparatus according to claim 6, wherein: The upper wafer holder includes an upper vacuum line penetrating the upper body and an upper vacuum suction cup for applying vacuum pressure to the upper wafer to fix the upper wafer to the upper body, and the lower wafer holder includes a lower vacuum line penetrating the lower body and a lower vacuum suction cup for applying vacuum pressure to the lower wafer to fix the lower wafer to the lower body.

13. A wafer bonding system, comprising: a bonding buffer for securing the upper wafer to the upper chuck and the lower wafer to the lower chuck; as well as a bonding device in which the upper chuck bonded to the upper wafer and the lower chuck bonded to the lower wafer are arranged so that the upper chuck and the lower chuck have a common central axis, and the upper wafer and the lower wafer are bonded into a bonded wafer, Wherein, the bonding equipment comprises: a bonding initiator for applying pressure to a central portion of the upper wafer until the central portion of the upper wafer touches a central portion of the lower wafer, thereby initiating a bonding process of the upper wafer and the lower wafer by deforming the upper wafer; and a gas injector for controlling a bonding speed between the peripheral portion of the upper wafer and the peripheral portion of the lower wafer by injecting a filling gas into a gap between the peripheral portion of the lower wafer and the peripheral portion of the upper wafer to resist the falling of the peripheral portion of the upper wafer, so that the elastic deformation of the upper wafer is released before the peripheral portion of the upper wafer and the peripheral portion of the lower wafer are bonded, The lower chuck includes a lower body and a plurality of support pins, the plurality of support pins protrude upward from the lower body so that the protruding height of the support pins increases from the peripheral portion of the lower body to the central portion of the lower body, wherein the lower body is divided into an inner portion and an outer portion by a step portion, the step portion protruding from an upper surface of the lower body and shaped as a ring extending along a circumferential line of the lower body, and the inner portion includes the central portion and the peripheral portion of the lower body, and A lifting hole is arranged at the central portion of the lower body and a lifting guide is arranged around the lifting hole, a support pin among the plurality of support pins close to the step portion has a minimum height, and a support pin among the plurality of support pins close to the lifting guide has a maximum height.

14. The wafer bonding system according to claim 13, further comprising: a bonding chamber, the bonding chamber being used to enclose the bonding buffer and the bonding device in a bonding space; a conveying track for conveying the upper chuck and the lower chuck between the bonding buffer and the bonding device in the bonding space; as well as A base plate is located in the bonding space, and the conveying track is arranged on the base plate.

15. The wafer bonding system according to claim 13, wherein: The gas injector is spaced apart from the upper chuck and the lower chuck to face the gap so that the filling gas is directly injected into the gap.

16. The wafer bonding system of claim 15, wherein: The gas injector is connected to the upper chuck and / or the lower chuck so that the filling gas is injected through the upper chuck and / or the lower chuck. 17 . The wafer bonding system of claim 16 , further comprising a shielding wall, the shielding wall closing the gap to form a closed gap.

18. The wafer bonding system of claim 14, wherein: The bonding buffer includes an elevator disposed on the base plate and configured to move linearly so that the upper wafer is transferred to the upper chuck and the lower wafer is transferred to the lower chuck.

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