Method for recycling composite wafer

Abstract

The invention provides a composite wafer recycling method, which relates to the technical field of semiconductors, and comprises the following steps: removing a first bonding wafer in a composite wafer with poor bonding and a bonding surface layer of a supporting wafer bonded with the first bonding wafer in stages; carrying out wafer brushing treatment on the bonding surface of the supporting wafer; polishing the bonding surface of the supporting wafer to enable the bonding surface to reach preset flatness; and carrying out secondary bonding again on the bonding surface of the polished support wafer. By physically stripping the surface layers of the bonding surfaces of the first bonding wafer and the supporting wafer and reprocessing the bonding surface of the Si supporting wafer, silicon wafer recovery and reproduction can be realized, the production cost can be greatly saved, the bonding quality of the composite wafer can be better controlled, and the overall output rate is improved.

Description

Technical Field

[0001] The present application relates to the field of semiconductor technology, and in particular to a method for recycling and reusing composite wafers. Background Art

[0002] With the advancement of wireless communication technology, 5G and future mobile communication technologies have increasing performance requirements for surface acoustic wave filters. Traditional surface acoustic wave (SAW) filters and bulk acoustic wave (BAW) filters have certain limitations in achieving high rectangularity, ultra-low in-band loss and ultra-large bandwidth. The emergence of bonded wafers has greatly promoted the development of filters. Bonded wafers can form structures with multiple sound velocity regions by bonding wafers of different materials or structures. They can be used to manufacture more complex SAW filter structures, thereby achieving steeper filter cutoff characteristics.

[0003] However, bonded wafers have higher requirements on raw material specifications. How to solve the high cost and low output problems of domestically produced bonded wafers is the biggest challenge currently faced by domestic bonded wafer manufacturers. Summary of the invention

[0004] The purpose of the embodiments of the present application is to provide a method for recycling and reusing composite wafers, which can control the bonding quality of wafers, improve output rate, and reduce production costs.

[0005] In one aspect of an embodiment of the present application, a method for recycling and reusing a composite wafer is provided, comprising removing in stages a first bonding wafer in a composite wafer with poor bonding and a bonding surface layer of a supporting wafer bonded to the first bonding wafer; Performing a wafer brushing process on the bonding surface of the support wafer; Polishing the bonding surface of the support wafer so that the bonding surface reaches a preset flatness; Secondary bonding is performed again on the bonding surface of the polished support wafer.

[0006] Optionally, the step of removing the bonding surface layer of the first bonding wafer and the supporting wafer bonded to the first bonding wafer in the composite wafer with poor bonding in stages includes: Placing the composite wafer on a stage, using a thinning machine grinding wheel to remove the first bonded wafer of a preset thickness in the first stage; The second stage completely removes the first bonding wafer and removes the bonding surface layer of the supporting wafer.

[0007] Optionally, the composite wafer is placed on a stage, and a thinning machine grinding wheel is used to remove the first bonded wafer of a preset thickness in the first stage. After that, the method further includes: The composite wafer after removing the first bonded wafer of a preset thickness in the first stage is subjected to heat treatment at a temperature of 250° C. to 350° C. and a time of 60 min to 120 min.

[0008] Optionally, the removal parameters of the first stage include: grinding wheel speed 1000rpm~2000rpm, carrier speed 200rpm~350rpm, removal rate 0.2um / s~0.3um / s.

[0009] Optionally, the removal parameters of the second stage include: grinding wheel speed 1200rpm~1700rpm, carrier speed 230rpm~300rpm, removal rate 0.1um / s~0.2um / s.

[0010] Optionally, the performing a brushing process on the bonding surface of the supporting wafer includes: Using a wafer brushing machine to perform a wafer brushing process on the bonding surface of the support wafer to remove residual particles on the surface of the bonding surface; The composite wafer is dried after being brushed.

[0011] Optionally, the rotation speed of the brush head of the sheet brush machine is 1000rpm~1500rpm, the translation speed of the brush head is 15mm / s~30mm / s, the moving path of the brush head is repeated 2 times~4 times, the spinner speed of the sheet brush machine is 400rpm~700rpm, the liquid medicine used by the sheet brush includes at least ammonia water and hydrogen peroxide, and the spraying of the liquid medicine is repeated 2 times~4 times.

[0012] Optionally, the spin-drying rotation speed is 100 rpm to 2500 rpm, and the spin-drying time is 25 s to 35 s.

[0013] Optionally, polishing the bonding surface of the support wafer so that the bonding surface reaches a preset flatness includes: Polishing the bonding surface of the support wafer by chemical mechanical polishing; Among them, the polishing liquid flow rate is 50ml / min~100ml / min, the fixed plate speed is 40rpm~100rpm, the polishing head speed is 40rpm~100rpm, the holding ring pressure is 3.0 psi~8.0psi, the wafer pressure is 3.0 psi~8.0psi, and the processing temperature is 20℃~40℃.

[0014] The method for recycling and reusing composite wafers provided in the embodiment of the present application includes removing the bonding surface layer of the first bonding wafer and the supporting wafer bonded to the first bonding wafer in the composite wafer with poor bonding in stages; performing a sheet brush treatment on the bonding surface of the supporting wafer; polishing the bonding surface of the supporting wafer to make the bonding surface reach a preset flatness; and re-bonding on the bonding surface of the polished supporting wafer. By physically peeling off the bonding surface layers of the first bonding wafer and the supporting wafer and reprocessing the bonding surface of the Si supporting wafer, silicon wafer recycling and reproduction can be achieved, which can greatly save production costs, better control the bonding quality of composite wafers, and improve overall output. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments of the present application will be briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without paying creative work.

[0016] Figure 1 is a flow chart of the method for recycling and reusing composite wafers provided in this embodiment; Figure 2 This is one of the schematic diagrams of the composite wafer structure with poor bonding provided in this embodiment; Figure 3 is a schematic diagram of the composite wafer structure after the first stage of thinning provided in this embodiment; Figure 4 is a schematic diagram of the composite wafer structure after the second stage of thinning provided in this embodiment; Figure 5 is a schematic diagram of the composite wafer structure after wafer brushing provided in this embodiment; Figure 6 is a schematic diagram of the structure of the composite wafer after polishing provided in this embodiment; Figure 7 This is one of the schematic diagrams of the composite wafer structure after secondary bonding provided in this embodiment; Figure 8 This is the second schematic diagram of the composite wafer structure with poor bonding provided in this embodiment; Fig. 9 This is the second schematic diagram of the composite wafer structure after secondary bonding provided in this embodiment.

[0017] Icon: 100 - support wafer; 101 - first bonding wafer; 102 - gap; 103 - bonding surface; 104 - bulge; 105 - second bonding wafer; F1 - first direction. DETAILED DESCRIPTION

[0018] The technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application.

[0019] In the description of this application, it should be noted that the terms "inside", "outside", etc. indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, or the orientation or positional relationship in which the product of the application is usually placed when in use, which is only for the convenience of describing this application and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on this application. In addition, the terms "first", "second", etc. are only used to distinguish the description, and cannot be understood as indicating or implying relative importance.

[0020] It should also be noted that, unless otherwise clearly specified and limited, the terms "disposed" and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a direct connection, or an indirect connection through an intermediate medium, or it can be the internal communication of two elements. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0021] Please refer to Figure 1 As shown, the embodiment of the present application provides a method for recycling and reusing a composite wafer, comprising: Step 200 : screening composite wafers with poor bonding, where the composite wafer includes a support wafer 100 and a first bonded wafer 101 bonded to the support wafer 100 .

[0022] The composite wafer is formed by bonding the support wafer 100 and the first bonding wafer 101, and the first bonding wafer 101 is bonded to the bonding surface of the support wafer 100. For example, in a LT ‌ (multifunctional crystal material)-Si (silicon) composite wafer, Si is used as the support wafer 100, and LT is used as the first bonding wafer 101 bonded to the Si support wafer 100.

[0023] The composite wafers with no cracks, no hidden cracks, no missing corners but poor bonding are selected, such as Figure 2 As shown, the support wafer 100 only forms pores on the bonding surface 103 with the first bonding wafer 101, and other positions are basically free of defects, so as to facilitate the subsequent bonding of a new first bonding wafer 101 on the support wafer 100 and ensure the quality of the composite wafer bonded twice. LT is used as the first bonding wafer 101, and its optional thickness is 1um to 15um.

[0024] Step 201 : removing the first bonded wafer 101 and the surface layer of the bonding surface 103 of the supporting wafer 100 bonded to the first bonded wafer 101 in the composite wafer with poor bonding in stages.

[0025] The composite wafer is placed on a stage, and the Si on the surface of the entire LT first bonding wafer 101 and the bonding surface 103 is removed by using a thinning machine grinding wheel.

[0026] In the first stage, the first bonded wafer 101 of a preset thickness is removed; for example, taking the LT first bonded wafer 101 with a thickness of 3 um in the first direction F1 as an example, the removal amount of the first bonded wafer 101 is 1 um to 3 um in thickness. Figure 3 As shown, a portion of the thickness of the first bonded wafer 101 can be removed, and a portion of the thickness of the first bonded wafer 101 can be retained on the supporting wafer 100 to thin the first bonded wafer 101; or the entire first bonded wafer 101 can be directly removed, depending on the thickness of the first bonded wafer 101.

[0027] The removal parameters of the first stage include: grinding wheel speed 1000rpm~2000rpm, carrier speed 200rpm~350rpm, and removal rate 0.2um / s~0.3um / s.

[0028] The composite wafer after the first bonding wafer 101 with a preset thickness is removed in the first stage is heat treated at a temperature of 250° C. to 350° C. for 60 min to 120 min.

[0029] Adding a heat baking process after the first-stage removal process helps release the internal stress of the composite wafer caused by differences in material properties, reduces the risk of support wafer 100 cracking caused by the second-stage thinning, and improves the success rate of the thinning process.

[0030] In the second stage, the first bonding wafer 101 is completely removed, and the surface layer of the bonding surface 103 of the supporting wafer 100 is removed, so that defects on the bonding surface 103 of the first bonding wafer 101 and the supporting wafer 100 can be removed, for example Figure 4 As shown, after the second stage process is completed, the gap 102 on the bonding surface 103 is cleaned, but defects such as bulges 104 may be left on the bonding surface 103, so the bonding surface 103 needs to be subsequently subjected to sheet brushing treatment.

[0031] The removal parameters of the second stage include: grinding wheel speed 1200rpm~1700rpm, carrier speed 230rpm~300rpm, and removal rate 0.1um / s~0.2um / s.

[0032] Step 202 : performing a wafer brushing process on the bonding surface 103 of the support wafer 100 .

[0033] like Figure 5As shown, in order to further process defects such as bulges 104 on the bonding surface 103 , a wafer brushing machine is used to perform a wafer brushing process on the bonding surface 103 of the support wafer 100 to remove residual particles on the surface of the bonding surface 103 .

[0034] The brush head of the sheet brush machine used in sheet brushing has a rotation speed of 1000rpm~1500rpm, a translation speed of 15mm / s~30mm / s, a moving path of the brush head repeated 2~4 times, a spinner disk of the sheet brush machine having a rotation speed of 400rpm~700rpm, and the liquid medicine used in the sheet brush includes at least ammonia water and hydrogen peroxide, and the spraying of the liquid medicine is repeated 2~4 times.

[0035] The composite wafer after the wafer brushing is dried. The drying process is a multi-stage rotary drying process, the drying speed is 100rpm to 2500rpm, and the drying time is 25s to 35s.

[0036] After the wafer is spun dry with a brush, the bonding surface 103 may be uneven, so it is necessary to polish the bonding surface 103. Specifically, step 203 is performed: polishing the bonding surface 103 of the support wafer 100 so that the bonding surface 103 reaches a preset flatness.

[0037] The bonding surface 103 of the support wafer 100 is polished by chemical mechanical polishing. Figure 6 shown.

[0038] Among them, the polishing liquid flow rate is 50ml / min to 100ml / min, and the polishing liquid can be optionally combined with composite abrasives and specific reagents to meet the needs of chemical mechanical polishing processing of silicon wafers and other supporting wafers 100. The fixed plate speed is 40rpm to 100rpm, the polishing head speed is 40rpm to 100rpm, the holding ring pressure is 3.0psi to 8.0psi, the wafer pressure is 3.0psi to 8.0psi, and the processing temperature is 20℃ to 40℃.

[0039] Step 204 : re-bonding is performed on the bonding surface 103 of the polished support wafer 100 .

[0040] For example Figure 7 As shown, the polished Si support wafer 100 is re-bonded with a new lithium tantalate wafer to form a new second bonded wafer 105. The surface of the bonded composite wafer is smooth without obvious defects such as bubbles, meeting the circulation and inspection standards.

[0041] In summary, the method for recycling and reusing composite wafers provided in the embodiment of the present application uses equipment and processes that are existing conditions for bonding production. Since the cost of raw materials accounts for a high proportion of the cost of the bonding process production, by physically peeling off the surface layer of the bonding surface 103 of the first bonding wafer 101 and the supporting wafer 100, and reprocessing the bonding surface 103 of the Si supporting wafer 100, silicon wafer recycling and reproduction can be achieved, which can greatly save production costs, better control the bonding quality of composite wafers, and improve overall output.

[0042] like Figure 8 and Fig. 9 The figures shown are schematic diagrams of a composite wafer with poor bonding and a composite wafer after recycling and reuse. By comparison, it can be seen that the bonding quality of the composite wafer after secondary bonding is better by adopting the composite wafer recycling and reuse method of the present application.

[0043] The above description is only an embodiment of the present application and is not intended to limit the protection scope of the present application. For those skilled in the art, the present application may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for recycling composite wafers, characterized in that: include: Removing the bonding surface layer of the first bonding wafer and the supporting wafer bonded to the first bonding wafer in the composite wafer with poor bonding in stages; Performing a wafer brushing process on the bonding surface of the support wafer; Polishing the bonding surface of the support wafer so that the bonding surface reaches a preset flatness; Secondary bonding is performed again on the bonding surface of the polished support wafer.

2. The method for recycling composite wafers according to claim 1, characterized in that: The step of removing the bonding surface layer of the first bonding wafer and the supporting wafer bonded to the first bonding wafer in the composite wafer with poor bonding in stages includes: Placing the composite wafer on a stage, using a thinning machine grinding wheel to remove the first bonded wafer of a preset thickness in the first stage; The second stage completely removes the first bonding wafer and removes the bonding surface layer of the supporting wafer.

3. The method for recycling composite wafers according to claim 2, characterized in that: The composite wafer is placed on a carrier, and a thinning machine grinding wheel is used to remove the first bonded wafer of a preset thickness in the first stage. After that, the method further includes: The composite wafer after the first bonded wafer of a preset thickness is removed in the first stage is subjected to heat treatment at a temperature of 250° C. to 350° C. for a time of 60 min to 120 min.

4. The method for recycling composite wafers according to claim 2 or 3, characterized in that: The removal parameters of the first stage include: grinding wheel speed 1000 rpm ~ 2000 rpm, stage speed 200 rpm ~ 350 rpm, and removal rate 0.2um / s ~ 0.3um / s.

5. The method for recycling composite wafers according to claim 2 or 3, characterized in that: The removal parameters of the second stage include: grinding wheel speed 1200 rpm ~ 1700 rpm, stage speed 230 rpm ~ 300 rpm, and removal rate 0.1um / s ~ 0.2um / s.

6. The method for recycling composite wafers according to claim 1, characterized in that: The step of performing a brushing process on the bonding surface of the supporting wafer comprises: Using a wafer brushing machine to perform a wafer brushing process on the bonding surface of the support wafer to remove residual particles on the surface of the bonding surface; The composite wafer is dried after being brushed.

7. The method for recycling composite wafers according to claim 6, characterized in that: The rotation speed of the brush head of the sheet brush machine is 1000rpm~1500rpm, the translation speed of the brush head is 15mm / s~30mm / s, the moving path of the brush head is repeated 2 times~4 times, the rotation speed of the spinner of the sheet brush machine is 400rpm~700rpm, the liquid medicine used by the sheet brush includes at least ammonia water and hydrogen peroxide, and the spraying of the liquid medicine is repeated 2 times~4 times.

8. The method for recycling composite wafers according to claim 6, characterized in that: The spin speed is 100rpm~2500rpm, and the spin time is 25s~35s.

9. The method for recycling composite wafers according to claim 1, characterized in that: The step of polishing the bonding surface of the supporting wafer so that the bonding surface reaches a preset flatness includes: Polishing the bonding surface of the support wafer by chemical mechanical polishing; Among them, the polishing liquid flow rate is 50 ml / min~100 ml / min, the fixed plate speed is 40rpm~100rpm, the polishing head speed is 40rpm~100rpm, the holding ring pressure is 3.0 psi~8.0psi, the wafer pressure is 3.0 psi~8.0psi, and the processing temperature is 20℃~40℃.

Images