Wafer grinding and polishing method

Abstract

The invention provides a grinding and polishing processing method for a wafer, which belongs to the technical field of semiconductors and comprises the following steps: S1, carrying out primary grinding on the wafer by adopting an edge collapse process to obtain a semi-finished wafer; s2, carrying out secondary grinding on the semi-finished wafer by adopting an edge bulge process, and correcting the thickness deviation of the semi-finished wafer to obtain a wafer finished product; the sequence of the edge collapse process in the step S1 and the edge protrusion process in the step S2 is adjustable. According to the grinding and polishing processing method of the wafer, the existing single grinding is changed into two grinding, different processing effects of the two grinding methods are superposed, and one-way deviations caused by the single grinding are mutually counteracted, so that the processing effect of lower thickness deviation between the central area and the edge area of the wafer is realized, and the processing efficiency is improved. And the uniformity of the surface quality of the wafer is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of semiconductors, and more specifically, relates to a wafer grinding and polishing processing method. Background Art

[0002] The grinding and polishing of semiconductor wafers exists in multiple links of wafer substrate production and device production. The grinding and polishing process of wafers will change the thickness of each position of the wafer, which determines the thickness deviation of the wafer. In particular, as the size of wafers becomes larger and larger, the grinding and polishing removal amount at different positions of the wafer becomes more uneven due to the increase in the wafer area for grinding and polishing, which leads to a larger thickness deviation of large-sized wafers and increased processing difficulty. The unevenness of wafer thickness will have an adverse effect on device production, so the uniform thickness of large-sized wafers is an important indicator to measure the level of wafer processing. Summary of the invention

[0003] The object of the present invention is to provide a wafer grinding and polishing processing method, aiming to solve the problem that the grinding and polishing removal amount at different positions of the wafer is more uneven, resulting in large thickness deviation of the wafer.

[0004] To achieve the above object, the technical solution adopted by the present invention is: to provide a wafer grinding and polishing method, comprising the following steps: S1. Grind the wafer once using an edge collapse process to obtain a semi-finished wafer; S2, performing secondary grinding on the semi-finished wafer using an edge protrusion process, correcting the thickness deviation of the semi-finished wafer, and obtaining a finished wafer; The order of the edge collapse process in step S1 and the edge protrusion process in step S2 is adjustable.

[0005] As another embodiment of the present application, the thickness of the wafer to be ground is , the thickness of the wafer ground in step S1 , the thickness of the wafer ground in step S2 is , .

[0006] As another embodiment of the present application, before grinding in step S2, the thickness of the semi-finished wafer obtained in step S1 is measured to determine the thickness deviation of different positions of the semi-finished wafer. , ; Calculate the required correction thickness deviation value , , the thickness deviation of the finished wafer obtained after step S2 is completed .

[0007] As another embodiment of the present application, the grinding effect of the grinding liquid in the edge collapse process gradually decreases, and the grinding effect of the grinding liquid in the edge protrusion process gradually increases.

[0008] As another embodiment of the present application, the grinding liquid used in the edge collapse process contains polishing abrasive particles; the grinding liquid used in the edge protrusion process contains agglomerated abrasive particles, and the agglomerated abrasive particles are gradually dispersed under pressure to form polishing abrasive particles, and the grinding strength of the polishing abrasive particles is greater than that of the agglomerated abrasive particles.

[0009] As another embodiment of the present application, the polishing abrasive particles are single crystal or polycrystalline abrasive particles.

[0010] As another embodiment of the present application, both the edge collapse process and the edge protrusion process use a grinding and polishing machine. The grinding liquid in the grinding and polishing machine moves with the movement of the wafer, and the abrasive particles in the grinding liquid move from the edge area of ​​the wafer toward the center area of ​​the wafer.

[0011] As another embodiment of the present application, the grinding and polishing machine can be a single-sided grinding and polishing machine or a double-sided grinding and polishing machine.

[0012] As another embodiment of the present application, in the edge collapse process, changing the processing pressure can adjust the wear time of the polishing abrasive particles, and changing the processing speed can adjust the length of the moving path of the polishing abrasive particles; In the edge protrusion process, changing the processing pressure can adjust the dispersion time of the agglomerated abrasive particles, and changing the processing speed can adjust the length of the dispersion path of the agglomerated abrasive particles.

[0013] As another embodiment of the present application, in both the edge collapse process and the edge protrusion process, the width of the wafer edge collapse or protrusion can be changed by changing the particle size of the polishing abrasive particles in the polishing liquid.

[0014] The beneficial effect of the wafer grinding and polishing processing method provided by the present invention is that: compared with the prior art, the wafer grinding and polishing processing method of the present invention changes the existing single grinding into two grindings, and by superimposing the different processing effects of the two grinding methods, the unidirectional deviations brought by the single grinding process are offset each other, thereby achieving a processing effect of lower thickness deviation between the center area and the edge area of ​​the wafer, and improving the uniformity of the wafer surface quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0016] Figure 1A schematic diagram of the working principle of a double-sided grinding and polishing machine provided in an embodiment of the present invention; Figure 2 A schematic diagram of wafer arrangement of a double-sided grinding and polishing machine provided in an embodiment of the present invention; Figure 3 A schematic diagram of the working principle of a single-sided grinding and polishing machine provided in an embodiment of the present invention; Figure 4 A schematic diagram of wafer arrangement of a single-sided grinding and polishing machine provided in an embodiment of the present invention; Figure 5 A diagram showing the effect of a wafer after grinding using the edge collapse process provided by an embodiment of the present invention; Figure 6 A diagram showing the effect of a wafer after edge protrusion grinding provided by an embodiment of the present invention; Figure 7 A schematic diagram of a finished wafer provided in an embodiment of the present invention.

[0017] In the figure: 1. Rotating lower plate; 2. Rotating upper plate; 3. Polishing pad; 4. Wafer; 5. Rotating chassis; 6. Downward pressure rotating plate; 7. Adhesive layer; 8. Carrying plate; 9. Inner and outer gear rings; 10. Working area; 11. Planetary wheel tooling; 12. Center area; 13. Edge area. DETAILED DESCRIPTION

[0018] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0019] See also Figures 1 to 7 Now, the grinding and polishing method of the wafer 4 provided by the present invention is described. The grinding and polishing method of the wafer 4 comprises the following steps: S1, grinding the wafer 4 once by using an edge collapse process to obtain a semi-finished wafer 4; S2, performing secondary grinding on the semi-finished wafer 4 using an edge protrusion process, correcting the thickness deviation of the semi-finished wafer 4, and obtaining a finished wafer 4; The order of the edge collapse process in step S1 and the edge protrusion process in step S2 is adjustable.

[0020] Compared with the prior art, the grinding and polishing processing method of the wafer 4 provided by the present invention changes the existing single grinding into two grindings, and by superimposing the different processing effects of the two grinding methods, the unidirectional deviations brought by the single grinding process are offset each other, thereby achieving a processing effect of lower thickness deviation between the central area 12 and the edge area 13 of the wafer 4, and improving the uniformity of the surface quality of the wafer 4.

[0021] The existing single grinding can only improve the degree of edge collapse or edge bulge of the wafer 4, and reduce the thickness difference between the central area 12 and the edge area 13 of the wafer 4, but cannot fundamentally change the phenomenon of edge collapse or edge bulge, that is, the thickness difference between the central area 12 and the edge area 13 of the wafer 4 will gradually increase as the processing time of the wafer 4 increases. Grinding and polishing is essentially to grind off a certain thickness of the wafer 4, so the thickness that needs to be ground off is This determines that there will be an unavoidable thickness difference between the center area 12 and the edge area 13 of the wafer 4 after processing. .

[0022] It is now proposed to combine the edge collapse process and the edge protrusion process, and process the two steps in series so that the thickness of the edge collapse and the thickness of the edge protrusion offset each other, thereby reducing the thickness difference of the wafer 4 and further reducing the phenomenon of edge collapse or edge protrusion.

[0023] The formation principle of the edge collapse process is that under the action of the grinding liquid pressure, the polishing abrasive particles in the grinding liquid start to enter the gap between the wafer 4 and the polishing pad 3 from the edge of the wafer 4, and play a grinding role through the relative displacement during the processing. As the wafer 4 moves, the polishing abrasive particles move from the edge area 13 of the wafer 4 to the center area 12 of the wafer 4. During the movement, the polishing abrasive particles become blunt after being worn by the grinding of the edge of the wafer 4, and the grinding ability becomes worse, so the grinding thickness of the edge of the wafer 4 , Greater than the grinding thickness of the central area 12 of the wafer 4 , , thus forming an edge collapse morphology.

[0024] The principle of edge protrusion process is that under the action of pressure, the agglomerated abrasive particles in the grinding liquid start to enter the gap between wafer 4 and polishing pad 3 from the edge of wafer 4. Through relative displacement during processing, the agglomerated abrasive particles gradually disperse from large particles to small particles. At this time, the grinding effect is the weakest. As wafer 4 moves, the agglomerated abrasive particles move from the edge area 13 of wafer 4 to the center area 12 of wafer 4. During the movement, the agglomerated abrasive particles gradually disperse and become smaller until they are dispersed into polishing abrasive particles of a certain particle size. At this time, the grinding ability of the grinding liquid is the largest. Therefore, the grinding thickness of the center area 12 of wafer 4 is , Greater than the grinding thickness of the wafer 4 edge , , thus forming a raised edge morphology.

[0025] During the processing, the sequence of the edge collapse process and the edge protrusion process can be adjusted.

[0026] The thickness of the wafer 4 to be ground is , the thickness of the wafer 4 ground in step S1 , the thickness of the wafer 4 ground in step S2 is , . Set the required grinding thickness The process is divided into two steps, the edge collapse process and the edge protrusion process, which are processed in series. That is, the total thickness of the two steps is the total thickness of the wafer 4 that needs to be ground. and Can be the same or different.

[0027] Take the edge collapse process first and then the edge protrusion process as an example. In step S1, the edge collapse process is used to grind the wafer 4 to form a semi-finished wafer 4 with collapsed edges, and the grinding thickness of the central area 12 of the wafer 4 is less than the overall thickness to be ground. In step S2, the edge protrusion process is used to grind the wafer 4, and the edge protrusion process is used to grind the central area 12 with a stronger grinding force, so that the grinding thickness of the center of the wafer 4 in step S2 is greater than the grinding thickness of the edge area 13, thereby achieving the consistency of the grinding thickness of the central area 12 and the edge area 13.

[0028] Before grinding in step S2, the thickness of the semi-finished wafer 4 obtained in step S1 is measured to determine the thickness deviation of different positions of the semi-finished wafer 4. , ; Calculate the required correction thickness deviation value , , the thickness deviation of the finished wafer 4 obtained after step S2 is completed .

[0029] In the process, the grinding thickness of the wafer 4 is detected by taking the central area 12 as the measuring point. That is, in step S1, the grinding thickness of the central area 12 of the wafer 4 is , the thickness difference between the edge area 13 and the center area 12 is In step S2, the grinding thickness of the central area 12 of the wafer 4 is , the thickness difference between the edge area 13 and the center area 12 is According to the characteristics of the two processing technologies, and One is a positive number and the other is a negative number. The thickness deviation of the finished wafer 4 formed by the superposition of the two processes , The absolute value of That is, the thickness difference between the central area 12 and the edge area 13 of the wafer 4 after two grinding processes must be smaller than the thickness difference processed using the existing single grinding technology.

[0030] In order to smoothly implement the edge collapse process and the edge protrusion process, the grinding effect of the grinding liquid in the edge collapse process is gradually reduced, and the grinding effect of the grinding liquid in the edge protrusion process is gradually increased. There are abrasive particles in the grinding liquid, and the abrasive particles enter between the wafer 4 and the polishing pad 3. When the polishing pad 3 and the wafer 4 move relative to each other, the abrasive particles polish the surface of the wafer 4.

[0031] During the grinding process, the grinding effect can be adjusted and the edge collapse process and edge protrusion process can be switched only by changing the composition of the abrasive particles and utilizing the characteristics of abrasive particles with different components.

[0032] Specifically, the grinding liquid used in the edge collapse process contains polishing abrasive particles; the grinding liquid used in the edge protrusion process contains agglomerated abrasive particles, which gradually disperse under pressure to form polishing abrasive particles, and the grinding strength of the polishing abrasive particles is greater than that of the agglomerated abrasive particles.

[0033] In the edge collapse process, polishing abrasive particles are directly used in the grinding liquid, and the polishing abrasive particles are single crystal or polycrystalline abrasive particles. The abrasive particles are diamond powder particles or abrasive particles of other materials. Since the polishing abrasive particles have a large grinding ability during polishing, they will become blunt and the grinding ability will deteriorate due to wear during the grinding process. Therefore, as the polishing abrasive particles enter the center area 12 from the edge area 13, their grinding ability gradually decreases, and the grinding effect gradually decreases. The grinding thickness of the edge area 13 is greater than the grinding thickness of the center area 12.

[0034] Agglomerated abrasive is used in the grinding liquid in the edge protrusion process. Agglomerated abrasive is a combination of abrasive particles with a certain size, shape and strength formed by bonding a large number of small and irregular abrasive particles together with a ceramic binder or a resin binder. Agglomerated abrasive particles will disperse from large particles to small particles under the action of pressure until they become polishing abrasive particles.

[0035] During the processing, the agglomerated abrasive enters between the wafer 4 and the polishing pad 3 from the edge of the wafer 4. In the process of moving from the edge area 13 to the central area 12, the agglomerated abrasive is squeezed and dispersed in the process of moving until the agglomerated abrasive moves to the central area 12 and is decomposed into polishing abrasive. Since the agglomerated abrasive is bonded together when it is not dispersed, the grinding ability is poor. As the agglomerated abrasive is dispersed, the polishing abrasive inside is dispersed, and the polishing abrasive has a greater grinding ability. Therefore, in the process of moving the agglomerated abrasive, the grinding effect of the grinding fluid gradually increases.

[0036] In the edge protrusion process, since the grinding ability of the grinding liquid gradually increases, the grinding ability of the grinding liquid gradually increases and the grinding effect gradually increases as the agglomerated abrasive particles disperse during the process of the abrasive particles of the grinding liquid entering the central area 12 from the edge area 13. This makes the grinding thickness of the edge area 13 smaller than that of the central area 12.

[0037] In the edge collapse process, changing the processing pressure can adjust the wear time of the polishing abrasive particles, and changing the processing speed can adjust the length of the moving path of the polishing abrasive particles; in the edge protrusion process, changing the processing pressure can adjust the dispersion time of the agglomerated abrasive particles, and changing the processing speed can adjust the length of the dispersion path of the agglomerated abrasive particles. In both the edge collapse process and the edge protrusion process, the width of the edge collapse or protrusion of the wafer 4 can be changed by changing the particle size of the polishing abrasive particles in the grinding liquid. In both steps, the processing parameters can be adjusted to affect the width and thickness of the central area 12 and the edge area 13 of the wafer 4, thereby achieving the grinding thickness distribution of different position areas of the wafer 4.

[0038] The edge collapse process and the edge protrusion process both use a grinding and polishing machine. The grinding liquid in the grinding and polishing machine moves with the movement of the wafer 4, and the abrasive particles in the grinding liquid move from the edge area 13 of the wafer 4 toward the center area 12 of the wafer 4.

[0039] The grinding and polishing machine can be a single-sided grinding and polishing machine or a double-sided grinding and polishing machine.

[0040] When the grinding and polishing machine uses a double-sided grinding and polishing machine, since the two surfaces of the wafer 4 are processed at the same time, the rotation speed of the upper and lower disks can be adjusted respectively, resulting in different relative displacement speeds between the upper and lower surfaces of the wafer 4. The processing parameters are adjusted according to the upper and lower surfaces of the wafer 4 to achieve the grinding thickness distribution of different position areas of the wafer 4. Thus, different morphologies of the upper and lower surfaces are formed. Then the distribution of the total grinding thickness of the second grinding is matched, so that the morphologies of upper concave and lower flat, upper flat and lower concave, upper convex and lower flat, upper flat and lower convex, upper and lower convex, upper and lower concave, upper and lower flat, upper and lower concave, upper and lower flat, upper and lower concave, upper and lower concave, and upper convex and lower concave can be formed; or the width and thickness of the wafer center area 12 and the edge annular area are adjusted to achieve changes in different concave and convex curvatures, thereby realizing the processing of products with different morphologies. Figure 7 Four common wafer morphologies are listed in the figure: morphology a is a wafer morphology that is flat on both the top and the bottom, morphology b is a wafer morphology that is convex on the top and flat on the bottom, morphology c is a wafer morphology that is concave on the top and flat on the bottom, and morphology d is a wafer morphology that is concave on the top and convex on the bottom.

[0041] like Figure 1 and Figure 2As shown, the double-sided grinding and polishing machine has a rotating upper plate 2 and a rotating lower plate 1, and both the rotating upper plate 2 and the rotating lower plate 1 can rotate around their central axes. There is a planetary wheel fixture 11 between the rotating lower plate 1 and the rotating upper plate 2, and the planetary wheel fixture 11 has an installation position for limiting the wafer 4, and each planetary wheel fixture 11 has at least two installation positions for wafers 4. There are inner and outer gear rings 9 between the rotating lower plate 1 and the rotating upper plate 2, and an annular working area 10 is formed between the inner and outer gear rings 9. The planetary wheel fixture 11 is located in the working area 10, and the planetary wheel fixture 11 is meshed and connected with the inner and outer gear rings 9 at the same time. Multiple planetary wheel fixtures 11 can be installed in the working area 10 at the same time.

[0042] During grinding, polishing pads 3 are provided on both the rotating upper plate 2 and the rotating lower plate 1 , and the rotating upper plate 2 and the rotating lower plate 1 grind the upper and lower surfaces of the wafer 4 simultaneously with the aid of the polishing pads 3 installed thereon.

[0043] When the grinding and polishing machine uses a single-sided grinding and polishing machine, the single-sided grinding and polishing machine can process one surface before processing the other surface, so it is easier to achieve processing of different morphologies on the upper and lower surfaces than a double-sided grinding and polishing machine.

[0044] like Figure 3 and Figure 4 As shown, the single-side grinding and polishing machine includes a rotating chassis 5 and a downward pressure rotating disk 6, and the downward pressure rotating disk 6 is located above the rotating chassis 5 and faces the rotating chassis 5. A carrier plate 8 is installed at the bottom of the downward pressure rotating disk 6, and the wafer 4 is fixed to the bottom of the carrier plate 8 through an adhesive layer 7. The lower end surface of the wafer 4 is attached to the polishing pad 3 of the rotating chassis 5. The grinding liquid drips onto the polishing pad 3 on the rotating chassis 5 and enters between the wafer 4 and the polishing pad 3 from the gap between the two as the rotating chassis 5 rotates, so as to polish the lower surface of the wafer 4.

[0045] Optionally, there are multiple downward-pressing rotating disks 6 above the rotating chassis 5, and multiple wafers 4 are bonded to the bottoms of the multiple downward-pressing rotating disks 6. The multiple wafers 4 are polished under the joint action of the rotating chassis 5 and the downward-pressing rotating disks 6.

[0046] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for grinding and polishing a wafer, characterized in that: The following steps are involved: S1. Grind the wafer once using an edge collapse process to obtain a semi-finished wafer; S2, performing secondary grinding on the semi-finished wafer using an edge protrusion process, correcting the thickness deviation of the semi-finished wafer, and obtaining a finished wafer; The order of the edge collapse process in step S1 and the edge protrusion process in step S2 is adjustable.

2. The wafer grinding and polishing method according to claim 1, wherein: The thickness of the wafer to be ground is , the thickness of the wafer ground in step S1 , the thickness of the wafer ground in step S2 is , .

3. The wafer grinding and polishing method according to claim 2, wherein: Before grinding in step S2, the thickness of the semi-finished wafer obtained in step S1 is measured to determine the thickness deviation of different positions of the semi-finished wafer. , ; Calculate the required correction thickness deviation value , , the thickness deviation of the finished wafer obtained after step S2 is completed .

4. The wafer grinding and polishing method according to claim 1, wherein: The grinding effect of the grinding fluid in the edge collapse process gradually decreases, and the grinding effect of the grinding fluid in the edge protrusion process gradually increases.

5. The wafer grinding and polishing method according to claim 1, wherein: The grinding liquid used in the edge collapse process contains polishing abrasive particles; the grinding liquid used in the edge protrusion process contains agglomerated abrasive particles. Under the action of pressure, the agglomerated abrasive particles gradually disperse to form polishing abrasive particles, and the grinding strength of the polishing abrasive particles is greater than that of the agglomerated abrasive particles.

6. The wafer grinding and polishing method according to claim 5, characterized in that: The polishing abrasive grains are single crystal or polycrystalline abrasive grains.

7. The wafer grinding and polishing method according to claim 5, characterized in that: The edge collapse process and the edge protrusion process both use a grinding and polishing machine. The grinding liquid in the grinding and polishing machine moves with the movement of the wafer, and the abrasive particles in the grinding liquid move from the edge area of ​​the wafer to the center area of ​​the wafer.

8. The wafer grinding and polishing method according to claim 7, characterized in that: The grinding and polishing machine can be a single-sided grinding and polishing machine or a double-sided grinding and polishing machine.

9. The wafer grinding and polishing method according to claim 5, characterized in that: In the edge collapse process, changing the processing pressure can adjust the wear time of the polishing abrasive, and changing the processing speed can adjust the length of the moving path of the polishing abrasive. In the edge protrusion process, changing the processing pressure can adjust the dispersion time of the agglomerated abrasive particles, and changing the processing speed can adjust the length of the dispersion path of the agglomerated abrasive particles.

10. The wafer grinding and polishing method according to claim 9, characterized in that: In both the edge collapse process and the edge protrusion process, the width of the wafer edge collapse or protrusion can be changed by changing the particle size of the polishing abrasive particles in the grinding liquid.

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