A silicon wafer polishing method and a silicon wafer

Abstract

The application relates to a silicon wafer grinding method and a silicon wafer, and the grinding method comprises the following steps: S1, preparing a grinding liquid; S2, placing a silicon wafer to be ground between an upper grinding disc and a lower grinding disc of a grinding machine; S3, adding the grinding liquid into the grinding machine; S4, adjusting the grinding pressure, the rotating speed of the grinding machine, and the flow of the grinding liquid, starting the grinding machine to grind the silicon wafer, and obtaining a grinding preliminary product after the grinding is completed; and S5, carrying out post-treatment and quality detection on the grinding preliminary product, and selecting qualified silicon wafers. In step S1, the specific gravity of the grinding liquid is 1.20g / cc-1.28g / cc, and in step S4, the flow of the grinding liquid is 0.7L / min-2L / min. The flow of the grinding liquid and the specific gravity of the grinding liquid are simultaneously adjusted to appropriate ranges, the grinding effect is improved, qualified silicon wafers with a defect-free surface, good smoothness and a total thickness change of less than or equal to 1.5 microns before and after grinding are obtained.

Description

Technical Field

[0001] This invention belongs to the field of silicon wafer processing and manufacturing technology, specifically relating to a silicon wafer grinding method and a silicon wafer. Background Technology

[0002] Silicon wafers are the raw material for manufacturing semiconductor silicon devices, used to make high-power rectifiers, diodes, switching devices, high-power transistors, etc. Their subsequent products, such as integrated circuits and discrete semiconductor devices, are widely used in various fields. As an important semiconductor material, single-crystal silicon is widely used in photoelectric conversion and traditional semiconductor devices. Currently, more than 95% of semiconductor device companies worldwide use silicon wafers as the substrate functional material to produce semiconductor chips and devices.

[0003] The processing of silicon wafers requires a series of treatments on the silicon ingots obtained after growth, including cutting, outer diameter grinding, edge flattening or V-groove treatment, slicing, grinding, polishing and cleaning.

[0004] Grinding is a process of polishing the top and bottom surfaces of a silicon wafer to remove tool marks or lines, improve surface flatness, create a uniform surface damage layer, and minimize thickness variations between batches of wafers. This creates conditions for subsequent polishing and other processes to produce a damage-free wafer surface. Grinding is a crucial step in silicon wafer manufacturing, and its main purposes include: 1. Removing visible defects such as residual marks from the dicing process. 2. Eliminating residual processing stress from the slicing process. 3. Improving the surface uniformity, flatness, and edge smoothness of the finished product. 4. Improving the wafer's surface shape accuracy. 5. Reducing surface roughness. Therefore, grinding lays the foundation for ensuring the final silicon wafer meets all required testing standards, guaranteeing the overall quality and yield of the finished product.

[0005] With the rapid advancement of IC (integrated circuit) manufacturing technology, the geometric parameters of silicon wafers have an increasingly significant impact on the economic efficiency of the IC manufacturing process, leading to more stringent requirements for silicon wafer parameters. Current technology considers equipment to be the primary factor affecting silicon wafer quality; however, due to time and cost constraints, improvements to grinding equipment are time-consuming and costly, making it difficult to further enhance the grinding effect of silicon wafers in a short period.

[0006] Therefore, it is necessary to further optimize the grinding process and enhance the quality of silicon wafers. Summary of the Invention

[0007] (a) Technical problems to be solved

[0008] Current technology suggests that equipment is the main factor affecting silicon wafer quality. However, due to time and cost constraints, improving grinding equipment is time-consuming and costly, making it difficult to further improve the grinding effect of silicon wafers in a short period of time.

[0009] The researchers in this application believe that processes and equipment can also significantly impact the quality of finished silicon wafers. To further and rapidly optimize the surface quality of finished silicon wafers and save costs, the researchers in this application turned their attention to the grinding process. Through extensive research and practice, the researchers discovered that the flow rate of the grinding slurry and the specific gravity of the abrasive particles in the slurry have a significant impact on the planar grinding effect of the finished silicon wafers. The grinding effect can be improved by simultaneously controlling both the flow rate and the specific gravity of the grinding slurry, resulting in more high-quality silicon wafers.

[0010] (II) Technical Solution

[0011] To achieve the above objectives, in a first aspect, the present invention provides a silicon wafer polishing method, comprising the following steps:

[0012] S1: Prepare the grinding fluid;

[0013] S2: Place the silicon wafer to be ground between the upper and lower grinding discs of the grinder;

[0014] S3: Add the grinding fluid prepared in step S1 to the grinding machine;

[0015] S4: Adjust the grinding pressure, rotation speed, and flow rate of the grinding slurry of the grinding machine, start the grinding machine to grind the silicon wafer, and after grinding is completed, the initial grinding product is obtained;

[0016] S5: Perform post-processing and quality inspection on the initial polished product to select qualified silicon wafers;

[0017] In step S1, the specific gravity of the polishing slurry is 1.20 g / cc to 1.28 g / cc, and in step S4, the flow rate of the polishing slurry is 0.7 L / min to 2 L / min.

[0018] In this invention, the order of steps S1 and S2 can be arbitrarily changed without affecting the polishing effect of the silicon wafer. In step S1, the specific gravity of the polishing slurry refers to the ratio of the mass of the abrasive to the volume of the polishing slurry.

[0019] Before proceeding to step S2, the upper and lower grinding discs of the grinding machine can be repaired to keep the temperature of the grinding discs low and stable.

[0020] In step S2 above, the silicon wafer is specifically placed on the slot of the planetary gear. Driven by the sun gear and the gear ring, the planetary gear will rotate as a passive component and revolve around the center of the sun gear. Therefore, the silicon wafer placed on the planetary gear will rotate on its own axis and revolve around the sun gear at the same time.

[0021] In step S3 above, the prepared grinding slurry is placed in a grinding slurry tank, and the grinding slurry tank introduces the grinding slurry into the grinding machine.

[0022] In this invention, the flow rate and specific gravity of the polishing slurry directly affect the rotation speed of the silicon wafer and have a significant impact on the final polishing effect. In addition to the flow rate and specific gravity of the polishing slurry, factors such as the temperature of the polishing slurry, the rotation speed of the polishing machine, and the polishing pressure are comprehensively adjusted to optimize these conditions, resulting in an ideal silicon wafer.

[0023] Generally speaking, the faster the silicon wafer rotates during grinding, the better the grinding effect.

[0024] Through extensive research and experimentation, this invention has discovered that simultaneously adjusting the flow rate of the polishing slurry to 0.7L / min-2L / min and the specific gravity of the polishing slurry to 1.20g / cc-1.28g / cc can increase the rotation speed of the silicon wafer. Similarly, the specific gravity of the polishing slurry within the above range can also increase the rotation speed of the silicon wafer. Therefore, this invention improves the polishing effect and obtains high-quality silicon wafers with no chipping, notches, cracks, or scratches, good surface finish, and a total thickness change of ≤1.5μm before and after polishing.

[0025] When the specific gravity of the polishing slurry is less than 1.20 g / cc, for example, 1.15 g / cc, scratches will appear on the surface of the silicon wafer. This may be because the specific gravity of the polishing slurry is too low, resulting in uneven distribution of abrasive particles within the slurry, thus leading to uneven polishing of the silicon wafer and the formation of scratches. Conversely, when the specific gravity of the polishing slurry is greater than 1.28 g / cc, for example, 1.35 g / cc, the viscosity of the slurry will be too high due to the excessive abrasive content, thereby reducing the rotational speed of the silicon wafer. In addition, an excessively high specific gravity of the polishing slurry will also affect the uniformity of abrasive distribution, reducing the uniformity of abrasive distribution and causing abrasive sedimentation. Furthermore, the higher the specific gravity of the polishing slurry, the more abrasive is used, and the higher the corresponding cost. This invention controls the specific gravity of the polishing slurry within a small range, reducing production costs while ensuring good polishing results.

[0026] When the flow rate of the polishing slurry is less than 0.7 L / min, for example, 0.7 L / min, the rotation speed of the silicon wafer during polishing is also low due to the insufficient flow rate, resulting in poor polishing effect. Furthermore, a flow rate less than 0.7 L / min reduces the cooling effect on the upper and lower polishing discs, potentially causing deformation and further reducing the polishing effect. When the flow rate of the polishing slurry is greater than 2 L / min, for example, 5 L / min, the polishing effect is also poor, resulting in uneven silicon wafer thickness and a poor appearance. This is likely because the larger flow rate affects the pressure exerted on the silicon wafer by the upper and lower polishing discs, causing pressure changes and thus deteriorating the polishing effect.

[0027] In the silicon wafer polishing method described above, preferably, in step S1, the specific gravity of the polishing slurry is 1.25 g / cc-1.28 g / cc, and in step S4, the flow rate of the polishing slurry is 1.3 L / min-2 L / min.

[0028] In the silicon wafer polishing method described above, preferably, in step S1, the specific gravity of the polishing slurry is 1.27 g / cc, and in step S4, the flow rate of the polishing slurry is 2 L / min.

[0029] In the silicon wafer polishing method described above, preferably, in step S1, the polishing fluid includes deionized water, abrasive, and a suspending agent;

[0030] The abrasive is Al2O3 or B4C, with a purity greater than 99.9% and a particle size of 5-10 μm;

[0031] The suspending agent is a dispersant, surfactant, integrator, or thickener.

[0032] In this invention, the role of the suspending agent includes:

[0033] 1. Suspension Effect: After mixing abrasive and deionized water, stratification and abrasive grain sedimentation are likely to occur after a certain period of time. This phenomenon can be improved by adding a suspending agent. After adding a suspending agent, the abrasive is more evenly dispersed during the grinding process, and the system is stable, preventing the abrasive from settling over a long period. Specifically, rust inhibitors such as ECO#546 can be used. In addition to acting as a suspending agent, ECO#546 can also prevent the formation of rust on the iron upper and lower grinding discs, thus avoiding the impact of rust on silicon wafer performance.

[0034] 2. Cooling Effect: During the grinding process, the upper and lower grinding discs generate a large amount of heat. Thermal stress accumulates on the surface of the silicon wafer undergoing double-sided grinding, easily leading to cracks and edge chipping, thus affecting the quality of the finished silicon wafer. Therefore, cooling methods are indispensable during the grinding process. Suspension agents can effectively enhance the heat dissipation of the grinding slurry.

[0035] 3. Lubrication effect: During the grinding process, the suspending agent can form a dense protective layer on the surface of the silicon wafer and the abrasive, reducing the interaction force between the silicon wafer and the abrasive grains, thus achieving a lubrication effect.

[0036] In the silicon wafer grinding method described above, preferably, the volume ratio of the deionized water to the suspending agent is 16:1-25:1.

[0037] In the silicon wafer polishing method described above, preferably, in step S3, the temperature of the polishing fluid entering the polishing machine is 20℃-25℃, more preferably 20℃.

[0038] The upper and lower grinding discs are subject to thermal expansion and contraction, and are prone to deformation during the grinding process, affecting the final grinding effect. This invention maintains the temperature of the upper and lower grinding discs within a suitable range by controlling the temperature of the added grinding fluid; specifically, in actual operation, the temperature of the grinding fluid input to the grinding discs is controlled by controlling the temperature of the grinding fluid tank.

[0039] In the silicon wafer polishing method described above, preferably, in step S4, the polishing pressure of the polisher is adjusted to 6000-7000N, more preferably 6000N.

[0040] In the silicon wafer grinding method described above, preferably, in step S4, the grinding rotation speed of the grinder is adjusted to 40-50 r / min, more preferably 45 r / min.

[0041] In the silicon wafer grinding method described above, preferably, in step S5, the initial grinding product with no chipping, notches, cracks and scratches on the surface, and a total thickness change of ≤1.5μm before and after grinding, is a qualified silicon wafer.

[0042] Secondly, the present invention also provides a silicon wafer prepared by the above-mentioned silicon wafer grinding method. The silicon wafer has no chipping, no notches, no cracks or scratches on its surface, has good surface smoothness, and the total thickness change before and after grinding is ≤1.5μm. It has good quality and a high yield.

[0043] (III) Beneficial Effects

[0044] The beneficial effects of this invention are:

[0045] This invention employs a double-sided grinding process, where the silicon wafer undergoes both rotational motion and revolution around the sun gear during grinding. To a certain extent, the faster the silicon wafer's rotational speed during grinding, the better the grinding effect.

[0046] This invention achieves ideal silicon wafer polishing results by simultaneously adjusting the flow rate and the specific gravity of the abrasive in the polishing slurry to appropriate ranges. Specifically, this invention adjusts the flow rate of the polishing slurry to 0.7L / min-2L / min and the specific gravity to 1.20g / cc-1.28g / cc. Within these ranges, the flow rate and specific gravity of the polishing slurry both increase the rotational speed of the silicon wafer. Therefore, this invention improves the polishing effect, resulting in high-quality silicon wafers with no chipping, notches, cracks, or scratches, excellent surface finish, and a total thickness change of ≤1.5μm before and after polishing.

[0047] In addition, the silicon wafer grinding method of the present invention is simple, easy to operate, meets environmental protection requirements, and has low production costs. Detailed Implementation

[0048] To better explain and facilitate understanding of the present invention, the present invention will be described in detail below through specific embodiments.

[0049] Example 1

[0050] This embodiment provides a silicon wafer polishing method, including the following steps:

[0051] S1: Mix pure water, 99.99% pure Al2O3, and rust inhibitor ECO#546 evenly to prepare a grinding fluid with a specific gravity of 1.27 g / cc.

[0052] S2: Place the silicon wafer to be ground between the upper and lower grinding discs of the grinder.

[0053] S3: Add the grinding slurry prepared in step S1 to the grinder at a flow rate of 2L / min and a temperature of 20℃.

[0054] S4: Adjust the grinding pressure of the grinder to 6000N and the rotation speed (or revolution speed) to 45r / min. Start the grinder so that the silicon wafer moves in a relative planetary motion with the grinding disc to grind the silicon wafer and obtain the finished grinded silicon wafer.

[0055] Example 2

[0056] This embodiment provides a silicon wafer polishing method, which differs from Embodiment 1 in that the flow rate of the polishing slurry is 0.7 L / min.

[0057] Example 3

[0058] This embodiment provides a silicon wafer polishing method, which differs from Embodiment 1 in that the flow rate of the polishing slurry is 1.3 L / min.

[0059] Example 4

[0060] This embodiment provides a silicon wafer polishing method, which differs from Embodiment 1 in that the specific gravity of the polishing slurry is 1.20 g / cc.

[0061] Example 5

[0062] This embodiment provides a silicon wafer polishing method, which differs from Embodiment 1 in that the specific gravity of the polishing slurry is 1.25 g / cc.

[0063] Example 6

[0064] This embodiment provides a silicon wafer polishing method, which differs from Embodiment 1 in that the specific gravity of the polishing slurry is 1.28 g / cc.

[0065] Example 7

[0066] This embodiment provides a silicon wafer polishing method, which differs from Embodiment 1 in that the polishing pressure of the polishing machine is 6500N.

[0067] Example 8

[0068] This embodiment provides a silicon wafer polishing method, which differs from Embodiment 1 in that it uses B4C with a purity of 99.99% as the abrasive.

[0069] Comparative Example 1

[0070] The difference between this comparative example and Example 1 is that the flow rate of the grinding fluid is 0.5 L / min.

[0071] Comparative Example 2

[0072] The difference between this comparative example and Example 1 is that the flow rate of the grinding fluid is 5 L / min.

[0073] Comparative Example 3

[0074] The difference between this comparative example and Example 1 is that the flow rate of the grinding fluid is 10 L / min.

[0075] Comparative Example 4

[0076] The difference between this comparative example and Example 1 is that the specific gravity of the grinding slurry is 1.18 g / cc.

[0077] Comparative Example 5

[0078] The difference between this comparative example and Example 1 is that the specific gravity of the grinding slurry is 1.35 g / cc.

[0079] In each of the above embodiments and comparative examples, 15 sets of initial grinding products were obtained.

[0080] In the silicon wafer polishing process, key silicon wafer characteristic parameters that require attention include wafer flatness (TTV, the difference between the thickest and thinnest parts of the wafer, i.e., flatness, measured in μm), edge chipping, notches, cracks, and scratches. The initial polished products obtained in Examples 1-8 above are evaluated for quality, specifically including TTV and the appearance quality comprised of four defects: edge chipping, notches, cracks, and scratches.

[0081] Tables 1, 2, 3, and 4 show the TTV values ​​and average TTV values ​​of each initial grinding product in Examples 1-3, 4-6, 7-8, Comparative Examples 1-2, and 3-5, respectively.

[0082] Table 1. TTV values ​​and mean TTV values ​​of the initial grinding products from Examples 1-4.

[0083]

[0084] Table 2. TTV values ​​and mean TTV values ​​of the initial grinding products from Examples 5-8.

[0085]

[0086]

[0087] Table 3 shows the TTV values ​​and mean TTV values ​​of the initial grinding products from Comparative Examples 1-3.

[0088]

[0089]

[0090] Table 4 shows the TTV values ​​and mean TTV values ​​of the initial grinding products from Comparative Examples 4-5.

[0091]

[0092] The appearance of the initial polished products of Comparative Examples 1-5 is as follows: Most of the silicon wafers in Comparative Examples 1-5 have fine scratches on their surface.

[0093] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any other way. Any person skilled in the art can make changes or modifications to the above-disclosed technical content to create equivalent embodiments. However, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the protection scope of the present invention.

Claims

1. A method for grinding silicon wafers, characterized in that, Includes the following steps: S1: Prepare the grinding fluid; S2: Place the silicon wafer to be ground between the upper and lower grinding discs of the grinder; S3: Add the grinding fluid prepared in step S1 to the grinding machine; S4: Adjust the grinding pressure, rotation speed, and flow rate of the grinding slurry of the grinding machine, start the grinding machine to grind the silicon wafer, and after grinding is completed, the initial grinding product is obtained; The grinding speed of the grinder is 40-50 r / min; S5: Perform post-processing and quality inspection on the initial polished product to select qualified silicon wafers; the initial polished product with no chipping, no gaps, no cracks or scratches on the surface, and a total thickness change of ≤1.5μm before and after polishing is a qualified silicon wafer; In step S1, the specific gravity of the grinding slurry is 1.25 g / cc-1.28 g / cc; in step S4, the flow rate of the grinding slurry is 0.7 L / min-1.3 L / min. In step S1, the grinding fluid includes deionized water, abrasive, and a suspending agent; The abrasive is Al2O3 or B4C; The suspending agent is a dispersant, surfactant, integrator, or thickener.

2. The silicon wafer grinding method according to claim 1, characterized in that, In step S1, the specific gravity of the grinding slurry is 1.27 g / cc.

3. The silicon wafer grinding method according to claim 1, characterized in that, The volume ratio of the deionized water to the suspending agent is 16:1-25:

1.

4. The silicon wafer grinding method according to claim 1, characterized in that, In step S3, the temperature of the grinding fluid entering the grinding machine is 20℃-25℃.

5. The silicon wafer grinding method according to claim 1, characterized in that, In step S4, the grinding pressure of the grinder is adjusted to 6000-7000N.

6. A silicon wafer, characterized in that, It is prepared by any one of the silicon wafer grinding methods according to claims 1-5.

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