System for making ultraflat chips using warpage of recycled wafers

Abstract

The application provides a system for manufacturing an ultra-flat chip by using the warping degree of a recycled wafer, the recycled wafer has a first surface and a second surface arranged oppositely, and the system comprises a low-loss grinding unit, a low-loss polishing unit and an automatic thinning unit, wherein the low-loss grinding unit comprises a grinding pad and a grinding head, after the recycled wafer is subjected to low-loss grinding, a butterfly-shaped warping is formed on the second surface, the low-loss polishing unit comprises a polishing head and a polishing pad, the polishing head is used to drive the first surface of the recycled wafer to perform rotary contact with the polishing pad, and the first surface is polished to remove damage, and the automatic thinning unit comprises a thinning grinding machine group and a substrate, the thinning grinding machine group is used to perform thinning grinding on the first surface of the recycled wafer fixed on the substrate to remove the butterfly-shaped warping on the second surface. The application has simple and controllable process, and can realize the formation of the ultra-flat chip.

Description

Technical Field

[0001] This invention relates to the field of wafer polishing technology, and in particular to a system for fabricating ultraflat chips using the warpage of regenerated wafers. Background Technology

[0002] In the semiconductor industry, flatness is one of the decisive indicators for measuring the performance of a semiconductor wafer. Total thickness variation (TTV), as a measure of flatness, is an important parameter in the wafer planarization process. Chemical mechanical polishing (CMP) is currently the most widely used wafer planarization method. As the name suggests, this process mainly utilizes the mechanical principle of polishing, combined with chemical agents, to further smooth the uneven contours on the wafer surface caused by the crystal growth process, such as the back-side polishing required after front-side metallization in semiconductor manufacturing. It further applies pressure to the polishing wheel on the wafer to achieve planarization and meet the electrical requirements of the final product. Simply put, the purpose of chemical mechanical polishing is to smooth the surface of the completed integrated circuit to facilitate better growth yield of the next layer of metal interconnects.

[0003] Currently, the production of superflat wafers mainly involves slicing new wafer rods and then performing CMP processing. However, there is currently no market available for how to use regenerated wafers to produce superflat wafers. Summary of the Invention

[0004] This invention aims to address the gaps in existing technologies by providing a system for fabricating ultraflat chips using the warpage of regenerated wafers.

[0005] The present invention solves the technical problem by adopting the following technical solution: a system for fabricating ultraflat chips using the warpage of regenerated wafers, wherein the regenerated wafer has a first surface and a second surface disposed opposite to each other, and the system includes:

[0006] The low-loss polishing unit includes a polishing pad and a polishing head. The polishing head is used to drive the first surface of the regenerated wafer to rotate and contact the polishing pad and create a uniform roughness thereon. After the low-loss polishing, the regenerated wafer will form a butterfly-shaped warp that is recessed towards the second surface on the second surface.

[0007] The low-damage polishing unit includes a polishing head and a polishing pad. The polishing head is used to drive the first surface of the regenerated wafer with uniform roughness to make oscillating rotational contact with the polishing pad and polish the first surface to remove damage.

[0008] An automatic thinning unit includes a thinning and polishing machine and a substrate. The second surface of the regenerated wafer is fixed on the substrate after a medium is applied. The thinning and polishing machine is used to thin and polish the first surface of the regenerated wafer fixed on the substrate to remove the butterfly warp on the second surface.

[0009] In several embodiments, the low-loss polishing unit further includes:

[0010] One drive motor;

[0011] One driven shaft rotates with the drive motor;

[0012] A swing structure is connected to a driven shaft for transmission. The swing structure follows the movement of the driven shaft and makes a reciprocating swing motion in the horizontal direction.

[0013] The swing structure includes:

[0014] A connecting rod, one end of which is rotatably connected to the eccentric position of the driven shaft;

[0015] A connecting bracket is rotatably connected to the other end of the connecting rod;

[0016] An adapter is connected to the connecting frame and rotates with the polishing head;

[0017] The connecting frame swings back and forth with the connecting rod.

[0018] In several embodiments, the low-loss polishing unit uses a polishing slurry to perform low-loss polishing on the regenerated wafer. The polishing slurry is a slurry containing water, a suspending agent, and hard abrasive particles with a particle size of 900-1200 mesh, which cannot be embedded in the polishing pad.

[0019] In several embodiments, the medium is water-based wax or liquid wax.

[0020] In several embodiments, the substrate is an aluminum nitride substrate or a sapphire substrate.

[0021] In several embodiments, the system includes the following manufacturing steps:

[0022] S100, Low-loss polishing of the first surface: The regenerated wafer is placed into the low-loss polishing unit and polished with polishing slurry on the first surface of the regenerated wafer. The thickness removed by polishing is 2-3 μm, thereby creating a stress difference between the first surface and the second surface, which in turn forms a butterfly-shaped warp that is recessed towards the second surface on the second surface. The depth at the center of the butterfly-shaped warp is 8-12 μm.

[0023] S200, Low-loss polishing of the first surface: The regenerated wafer that has undergone low-loss grinding is placed into the low-loss polishing unit, and the polishing head performs low-loss polishing on the first surface of the regenerated wafer by reciprocating oscillation on the polishing pad. The polishing time is 35-45 minutes to remove the damage formed on the first surface after low-loss grinding.

[0024] S300, thinning and polishing of the first surface: a medium is applied to the second surface of the regenerated wafer after low-loss polishing, and then the regenerated wafer is fixed on the substrate. The second surface and the substrate are bonded together by the medium to keep the first surface in a horizontal state. Then, the first surface is polished and thinned by a thinning and polishing unit to eliminate butterfly warping and obtain an ultra-flat chip with a TTV < 5um.

[0025] In several embodiments, in step S300, the grinding and thinning process includes:

[0026] S301: The first surface is thinned and removed by a thinning and grinding unit, with a removal amount of 8-12um;

[0027] S302: Perform rough polishing and fine polishing processes on the first surface after thinning removal to remove grinding marks formed during the thinning removal process, as well as butterfly warping on the second surface.

[0028] The present invention has the following beneficial effects:

[0029] This invention utilizes regenerated wafers to fabricate ultra-flat chips, saving resources and reducing manufacturing costs. During the fabrication process, low-loss grinding and low-loss polishing eliminate the irregular bending inherent in the regenerated wafers. Homogeneous stress forms a fixed butterfly warp. Combining low-loss grinding, low-loss polishing, grinding thinning, intermediate polishing, and fine polishing, the butterfly warp can be eliminated, forming two ultra-flat surfaces, achieving the production of ultra-flat chips with a TTV < 5µm. Attached Figure Description

[0030] The accompanying drawings described herein are for illustrative purposes only and do not represent all possible implementations, nor should they be considered as limiting the scope of the invention.

[0031] Figure 1 The diagram schematically illustrates a system block diagram for fabricating an ultraflat chip using the warp of a regenerated wafer in one embodiment.

[0032] Figure 2 The structure of the low-loss grinding unit and the low-loss polishing unit in one embodiment is illustrated schematically;

[0033] Figure 3 Schematic illustration Figure 2 Top view of the low-to-medium loss polishing unit;

[0034] Figure 4 The structure of a regenerated wafer bonded to a substrate is illustrated schematically in one embodiment. Detailed Implementation

[0035] The embodiments of the present invention will be described in detail below. In order to make the objectives, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are some embodiments of the present invention, but not all embodiments.

[0036] Therefore, the detailed description of the embodiments of the present invention provided below is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0037] The terminology used herein is intended to explain the embodiments and is not intended to limit and / or restrict the invention.

[0038] like Figures 1-4 As shown, the present invention is used to fabricate an ultra-flat chip on a regenerated wafer 1. The fabrication system is mainly composed of a low-loss grinding unit, a low-loss polishing unit and an automatic thinning unit. First, the regenerated wafer 1 is ground and polished by the low-loss grinding unit and the low-loss polishing unit to form a relatively flat reference surface. Then, the automatic thinning unit is used to thin and perform rough polishing and fine polishing, thereby forming an ultra-flat chip structure.

[0039] Here, the regenerated wafer 1 is configured to have a first surface 101 and a second surface 102 that are disposed opposite to each other.

[0040] The low-loss polishing unit includes a polishing pad 11 and a polishing head 12. The polishing pad 11 is connected to a rotating platform. The polishing head 12 is used to drive the first surface 101 of the regenerated wafer 1 to rotate and contact the polishing pad 11 and create a uniform roughness on it. After low-loss polishing, the regenerated wafer 1 will form a butterfly-shaped warp that is recessed towards the second surface 102 on the second surface 102.

[0041] The low-loss grinding unit uses a grinding slurry to perform low-loss grinding on the regenerated wafer 1. The grinding slurry is a slurry containing water, a suspending agent and hard abrasive particles with a particle size of 900-1200 mesh. The hard abrasive particles cannot be embedded in the grinding pad 11. The suspending agent is water-based cutting oil, the hard abrasive particles are silicon carbide powder, and the grinding pad 11 is made of elastic PU material.

[0042] Furthermore, the low-damage polishing unit includes a polishing head 21 and a polishing pad 22. The polishing head 21 is used to drive the first surface 101 of the regenerated wafer 1 with uniform roughness to make oscillating rotational contact with the polishing pad 22. The polishing pad 22 is also connected to the rotating platform and polishes the first surface 101 to remove damage.

[0043] The low-damage polishing unit further includes: a drive motor; a driven shaft 23 that rotates with the drive motor; and a swing structure that is connected to the driven shaft 23, the swing structure following the movement of the driven shaft 23 and making a reciprocating swing motion in the horizontal direction; wherein the swing structure includes: a connecting rod 25, one end of which is rotatably connected to the eccentric position of the driven shaft 23; a connecting frame 26, which is rotatably connected to the other end of the connecting rod 25; and an adapter 27, which is connected to the connecting frame 26 and rotatably connected to the polishing head 21; the connecting frame 26 makes a reciprocating swing motion with the connecting rod 25.

[0044] The output end of the drive motor is arranged vertically upward and connected to the driven shaft 23 to drive it to rotate. A rod is eccentrically and vertically arranged on the upper end face of the driven shaft. Similarly, a rod is also arranged on the connecting frame 26. The two ends of the connecting rod 25 are fitted onto the two corresponding rods for rotational connection. The connecting piece 27 is connected to the lower outermost position of the connecting frame 26 and is rotatably connected to the polishing head 21. This can also be achieved by combining the rod with the bearing.

[0045] Furthermore, the automatic thinning unit includes a thinning and polishing machine and a substrate 202. The thinning and polishing machine can be a commercially available GRRIDER wafer back-side thinning and polishing machine. The second surface 102 of the regenerated wafer 1 is fixed on the substrate 202 after the coating medium 201 is applied. The thinning and polishing machine is used to thin and polish the first surface 101 of the regenerated wafer 1 fixed on the substrate 202 to remove the butterfly warp on the second surface 102.

[0046] The medium 201 is water wax or liquid wax, and the substrate 202 is an aluminum nitride substrate 202 or a sapphire substrate 202 with a flat end face.

[0047] The manufacturing process of this system is further explained below:

[0048] Step S100, low-loss polishing of the first surface 101: The regenerated wafer 1 is placed into the low-loss polishing unit, and the first surface 101 of the regenerated wafer 1 is polished with polishing slurry. The thickness removed by polishing is 2-3 μm, thereby generating a stress difference between the first surface 101 and the second surface 102, and then forming a butterfly-shaped warp that is recessed towards the second surface 102. The depth at the center of the butterfly-shaped warp is about 10 μm.

[0049] Step S200, low-loss polishing of the first surface 101: The regenerated wafer 1 that has undergone low-loss grinding is placed into the low-loss polishing unit, and the polishing head 21 performs low-loss polishing on the first surface 101 of the regenerated wafer 1 by reciprocating oscillation on the polishing pad 22. The polishing time is about 40 minutes to remove the damage formed on the first surface 101 after low-loss grinding.

[0050] Step S300, thinning and polishing of the first surface 101: The second surface 102 of the regenerated wafer 1, which has been polished with low loss, is coated with a dielectric 201, and then the regenerated wafer 1 is fixed on the substrate 202. The second surface 102 and the substrate 202 are bonded together by the dielectric 201 to keep the first surface 101 in a horizontal state. Then, the first surface 101 is polished and thinned by a thinning and polishing machine to eliminate the butterfly warp and obtain an ultra-flat chip with a TTV < 5um.

[0051] Step S300 mainly consists of steps S301 and S302. S301 includes thinning and removing the first surface 101 by using a thinning and polishing unit, with a removal amount of about 10 μm. S302 includes rough polishing and fine polishing processes on the first surface 101 after thinning and removal to remove the polishing marks formed during the thinning and removal process, as well as the butterfly warping of the second surface 102.

[0052] In summary, the present invention can stably control the thickness removed by grinding, the overall manufacturing process is simple and controllable, the removal effect is good, and an ultra-flat chip structure can be achieved.

[0053] The examples, embodiments, and particular forms of the invention illustrated have been shown and described in detail in the accompanying drawings and foregoing description, and should also be considered illustrative rather than restrictive. The description of a particular feature in one embodiment does not imply that those particular features must be limited to that one embodiment. Features of one embodiment can be used in combination with features of other embodiments, as will be understood by those skilled in the art, whether or not explicitly stated. Exemplary embodiments have been shown and described, and all variations and modifications fall within the spirit of the invention and are intended to be protected.

Claims

1. A system for fabricating ultraflat chips using the warpage of a reclaimed wafer, the reclaimed wafer having a first surface and a second surface disposed opposite to each other, characterized in that, The system includes: The low-loss polishing unit includes a polishing pad and a polishing head. The polishing head is used to drive the first surface of the regenerated wafer to rotate and contact the polishing pad and create a uniform roughness thereon. After the low-loss polishing, the regenerated wafer will form a butterfly-shaped warp on the second surface that is concave towards the first surface. The low-damage polishing unit includes a polishing head and a polishing pad. The polishing head is used to drive the first surface of the regenerated wafer with uniform roughness to make oscillating rotational contact with the polishing pad and polish the first surface to remove damage. An automatic thinning unit includes a thinning and polishing machine and a substrate. The second surface of the regenerated wafer is fixed on the substrate after a medium is applied. The thinning and polishing machine is used to thin and polish the first surface of the regenerated wafer fixed on the substrate to remove the butterfly warp on the second surface. The low-loss polishing unit also includes: One drive motor; One driven shaft rotates with the drive motor; A swing structure is connected to a driven shaft for transmission. The swing structure follows the movement of the driven shaft and makes a reciprocating swing motion in the horizontal direction. The swing structure includes: A connecting rod, one end of which is rotatably connected to the eccentric position of the driven shaft; A connecting bracket is rotatably connected to the other end of the connecting rod; An adapter is connected to the connecting frame and rotates with the polishing head; The connecting frame swings back and forth with the connecting rod.

2. The system for fabricating ultraflat chips using the warpage of regenerated wafers according to claim 1, characterized in that, The low-loss grinding unit uses a grinding slurry to perform low-loss grinding on the regenerated wafer. The grinding slurry is a slurry containing water, a suspending agent and hard abrasive particles with a particle size of 900-1200 mesh. The hard abrasive particles cannot be embedded in the grinding pad.

3. The system for fabricating ultraflat chips using the warpage of regenerated wafers according to claim 2, characterized in that, The medium is water-based wax or liquid wax.

4. The system for fabricating ultraflat chips using the warpage of regenerated wafers according to claim 3, characterized in that, The substrate is an aluminum nitride substrate or a sapphire substrate.

5. The system for fabricating ultraflat chips using the warpage of regenerated wafers according to claim 4, characterized in that, The system includes the following manufacturing steps: S100, Low-loss polishing of the first surface: The regenerated wafer is placed into the low-loss polishing unit and polished with polishing slurry on the first surface of the regenerated wafer. The thickness removed by polishing is 2-3 μm, thereby creating a stress difference between the first surface and the second surface, which in turn forms a butterfly-shaped warp that is recessed towards the second surface on the second surface. The depth at the center of the butterfly-shaped warp is 8-12 μm. S200, Low-loss polishing of the first surface: The regenerated wafer that has undergone low-loss grinding is placed into the low-loss polishing unit, and the polishing head performs low-loss polishing on the first surface of the regenerated wafer by reciprocating oscillation on the polishing pad. The polishing time is 35-45 minutes to remove the damage formed on the first surface after low-loss grinding. S300, thinning and polishing of the first surface: a medium is applied to the second surface of the regenerated wafer after low-loss polishing, and then the regenerated wafer is fixed on the substrate. The second surface and the substrate are bonded together by the medium to keep the first surface in a horizontal state. Then, the first surface is polished and thinned by a thinning and polishing unit to eliminate butterfly warping and obtain an ultra-flat chip with a TTV < 5um.

6. The system for fabricating ultraflat chips using the warpage of regenerated wafers according to claim 5, characterized in that, In step S300, the grinding and thinning process includes: S301: The first surface is thinned and removed by a thinning and grinding unit, with a removal amount of 8-12um; S302: Perform rough polishing and fine polishing processes on the first surface after thinning removal to remove grinding marks formed during the thinning removal process, as well as butterfly warping on the second surface.

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