Silicon wafer double-sided grinding processing method

Abstract

The invention discloses a silicon wafer double-sided grinding processing method. The method comprises the following steps: step 1, preparing grinding mortar; 2, an opposite grinding program is selected for opposite grinding of the upper grinding disc and the lower grinding disc; 3, after opposite grinding is completed, the disc type of a lower grinding disc is measured, the disc type range of the lower grinding disc is 60-120 microns, then the disc type numerical value of the lower grinding disc is selected as the rotation numerical value of a machining loose pulley piece, and when the disc type of the lower grinding disc is larger than or equal to the upper limit value of the disc type range, the rotation coefficient of the loose pulley piece is selected as a positive coefficient, and the range is 5-7 rpm; when the disc type is smaller than or equal to the lower limit value of the disc type range, the rotation coefficient of the loose pulley sheet is selected as a negative coefficient, and the range is-5 rpm to-7 rpm; and 4, equipment is started for normal grinding machining. The rotation value of the loose pulley sheet is corrected through disc type measurement, so that the disc type of the grinding disc is always kept in the optimal range, high-precision stable grinding is realized, meanwhile, the traditional disc repairing step is avoided, the processing time and the mortar consumption are saved, the grinding disc loss and the processing cost are reduced, and the method is suitable for large-scale silicon wafer production.

Description

Technical Field

[0001] This invention relates to the field of silicon wafer processing technology, and more specifically, to a method for double-sided grinding of silicon wafers to improve grinding accuracy and processing efficiency, applicable to the double-sided grinding process in semiconductor silicon wafer manufacturing. Background Technology

[0002] Silicon wafers are a crucial substrate material in integrated circuit manufacturing, with over 95% of semiconductor devices worldwide using them as their basic structure. The manufacturing process of silicon wafer substrates includes single crystal growth, rolling, slicing, grinding, etching, polishing, and cleaning. Among these, grinding, as the first step in silicon wafer thinning, plays a vital role in providing a solid foundation for subsequent silicon wafer processing by improving processing efficiency and ensuring stable surface quality such as wafer flatness.

[0003] The surface flatness of silicon wafers directly affects chip performance. From a systemic strategy perspective, silicon wafer flatness control needs to be implemented throughout the entire silicon wafer manufacturing process. The grinding process, in particular, is significantly influenced by the shape of the lower grinding wheel. Traditional grinding processes include wheel shape inspection, determining whether wheel repair is necessary based on the wheel shape, cleaning, and then grinding and processing. The wheel shape continuously changes during processing due to uneven wear at the center and edges of the larger wheel (lower grinding wheel). When the wheel shape exceeds a reasonable range, the TTV (Total Television Value) of the silicon wafer after grinding gradually deteriorates, reducing grinding accuracy and processing stability. Currently, wheel shape control is commonly achieved through wheel dressing, but each dressing has only a small impact on the wheel shape. Furthermore, the dressing time is long, reducing processing efficiency. The large amount of grinding slurry used also increases processing costs. Summary of the Invention

[0004] The purpose of this invention is to provide a method for double-sided grinding of silicon wafers. By clarifying the grinding slurry configuration ratio, optimizing the grinding step parameters, and establishing the correspondence between the disk shape value and the wheel plate rotation parameters, the goal of improving the grinding accuracy of silicon wafers, increasing processing efficiency and stability can be achieved.

[0005] To achieve the above-mentioned technical objectives, the present invention adopts the following technical solution: A method for double-sided grinding of silicon wafers includes the following steps: Step 1: Add water, grinding sand and suspending agent to the grinding mortar bucket in sequence to prepare the grinding mortar; Step 2: Select the grinding program to grind the upper and lower grinding discs together; Step 3: After grinding, measure the shape of the lower grinding disc with a micrometer. The disc shape range is 60μm-120μm. Then, select the rotation value of the grinding wheel blade based on the measured disc shape value. When the disc shape is greater than or equal to the upper limit of the disc shape range, select a positive coefficient for the grinding wheel blade rotation (a positive coefficient represents clockwise rotation), with a range of 5rpm to 7rpm; when the disc shape is less than or equal to the lower limit of the disc shape range, select a negative coefficient for the grinding wheel blade rotation (a negative coefficient represents counterclockwise rotation), with a range of -5rpm to -7rpm. Step 4: Select the processing program, load and unload the silicon wafers in sequence, and start the equipment for normal grinding processing.

[0006] In this invention, a suitable ratio of grinding slurry ensures that the grinding slurry has good dispersibility and fluidity. During subsequent processing, after flowing out from the upper plate, the grinding slurry can be evenly dispersed on the silicon wafer surface, simultaneously exerting mechanical grinding and lubrication effects, reducing scratches on the silicon wafer surface, and improving the grinding effect. Preferably, the water, grinding sand, and suspending agent in the grinding slurry are mixed in a mass-volume ratio of (90-100)L:30kg:(2.5-3)L.

[0007] In this invention, controlling the upper and lower grinding discs to perform a grinding operation can effectively improve the fit between the upper and lower grinding discs, reduce surface errors of the grinding discs, provide an accurate benchmark for subsequent disc shape measurement, and avoid uneven silicon wafer grinding caused by low grinding disc fit. Preferably, the grinding parameters of the upper and lower grinding discs are: grinding pressure of 1300-1500 kg, grinding slurry flow rate of 0.8-1.2 L / min, lower grinding disc rotation speed of 10-30 rpm, and grinding time of 6-10 min.

[0008] In this invention, the method for measuring the shape of the lower grinding disc using a micrometer is as follows: place the entire micrometer on the surface of the lower grinding disc, and after the readings of each micrometer pointer on the micrometer stabilize, select the maximum value of the reading of the middle micrometer and subtract the minimum value of the readings of the two outermost micrometers to obtain the disc shape value of the lower grinding disc at this time.

[0009] In this invention, the preferred diameter range of the lower grinding disk is 80μm-100μm. When the diameter of the lower grinding disk is greater than or equal to 100μm, the rotation coefficient of the polishing wheel is selected as a positive coefficient; when the diameter of the lower grinding disk is less than or equal to 80μm, the rotation coefficient of the polishing wheel is selected as a negative coefficient. This periodic dynamic adjustment method allows for adjustment and control of the disk shape during processing, improving grinding accuracy, saving grinding time and costs, and enhancing processing efficiency and stability, making it suitable for large-scale silicon wafer production.

[0010] In this invention, the key parameters set during the grinding process are: processing pressure of 1300-1500 kg, grinding slurry flow rate of 0.8-1.2 L / min, and lower grinding disc rotation speed of 10-30 rpm; and during the processing, the silicon wafer will rotate together with the wafer carrier between the upper and lower grinding discs, and with the uniformly dispersed grinding slurry, the silicon wafer can be precisely ground.

[0011] Compared with the prior art, the beneficial effects of the present invention are: This invention corrects the wheel's rotation value based on the measured disc shape, thus automatically mitigating the deterioration trend of the large disc during continuous processing. This ensures the disc shape remains within the optimal range, enabling high-precision and stable silicon wafer grinding. Furthermore, it avoids the step of using a dressing wheel and slurry to dress the disc during a rest period to maintain its shape, saving processing time and slurry usage, and reducing disc wear and processing costs. Attached Figure Description

[0012] Figure 1 This is a schematic diagram of the process of double-sided grinding of silicon wafers in an embodiment of the present invention.

[0013] Figure 2 This is a schematic diagram of the grinding disc shape under micrometer measurement in this invention. Detailed Implementation

[0014] To better understand the above-mentioned objectives, features, and advantages of the present invention, the present invention will be described in detail below with reference to the accompanying drawings and specific embodiments. The embodiments aim to illustrate in detail the complete operation process of silicon wafer grinding, ensuring that the parameters of each step are precisely controllable, thereby guaranteeing the quality of silicon wafer grinding.

[0015] like Figure 1 The diagram shown is a schematic flow chart of the double-sided grinding method for silicon wafers in an embodiment of the present invention. The double-sided grinding method for silicon wafers of the present invention includes the following steps: Step 1: Grinding mortar preparation.

[0016] Step 2: Grind the upper and lower grinding discs together.

[0017] Step 3: Measure the shape of the lower grinding disc and select the rotation parameters of the cruise wheel.

[0018] Step 4: Silicon wafer grinding process.

[0019] like Figure 2The diagram shows a schematic of the micrometer measurement of the lower grinding disc shape in this invention, illustrating the relative positional relationship between the micrometer and the lower grinding disc. During actual measurement, the entire micrometer is placed on the surface of the lower grinding disc. After the readings of each dial indicator on the micrometer stabilize, the maximum reading of the middle dial indicator minus the minimum reading of the two outermost dial indicators gives the disc shape value at that moment.

[0020] Example 1 Verification silicon wafer: 12-inch Czochralski lightly boron-doped silicon wafer, P-type, crystal orientation <100> The resistivity is 8-12 Ω·cm and the thickness is 880.0µm; the lower grinding disk has a diameter of 90μm.

[0021] Step 1: Grinding mortar preparation. First, add water, grinding sand and suspending agent to the grinding mortar bucket in sequence, and prepare the grinding mortar according to the mass-volume ratio of 90L:30kg:3L. The temperature of the mortar bucket should be 20℃ and it should be stirred continuously.

[0022] Step 2: Grinding of the upper and lower grinding discs. Select the grinding program to grind the upper and lower grinding discs together for 8 minutes, with a grinding pressure of 1400 kg, a grinding mortar flow rate of 0.8 L / min, and a lower grinding disc rotation speed of 10 rpm.

[0023] Step 3: Select a disc shape with a diameter of 90μm to start the experiment. At this time, select a wheel plate rotation speed of -6rpm (a negative value represents counterclockwise rotation).

[0024] Step 4: Silicon wafer grinding. The selected grinding program has the following settings: processing pressure 1400 kg, grinding slurry flow rate 0.8 L / min, lower grinding disc rotation speed 30 rpm, brush wheel revolution speed 15 rpm, and target grinding thickness 830 μm.

[0025] First, five wafers are evenly placed on a large tray. A quartz plate is placed in the center hole of wafer 1 to monitor the thickness. Then, four silicon wafers are placed in each wafer in a clockwise order for processing. The first wafer processed on each tray is used as the sample for testing. The thickness and TTV (Total Thickness Variation) are measured using an LPW (Light Point Width) meter.

[0026] After processing 100 trays, the diameter of the large tray was measured with a micrometer and found to be approximately 100 μm, representing an increase of about 10 μm. At this point, a wheel rotation speed of 6 rpm was selected (a positive value indicates clockwise rotation). Further silicon wafer grinding was then performed. The selected grinding program included a processing pressure of 1400 kg, a grinding slurry flow rate of 0.8 L / min, a lower grinding disc rotation speed of 30 rpm, a wheel revolution speed of 15 rpm, and a target grinding thickness of 830 μm. After processing 100 trays, the diameter of the large tray was measured with a micrometer and returned to 90 μm. The first wafer processed in each tray was used as a sample for testing, and the TTV (Total Transmission Value) was measured using an LPW (Liquidity Flow Measurement) instrument with a mean value of 0.69 and a standard deviation of 0.12. The total cost of grinding slurry for processing 200 trays was calculated as 2012 L of grinding slurry, with a total processing time of 66.7 hours.

[0027] Comparative Example 1 Verification silicon wafer: 12-inch Czochralski lightly boron-doped silicon wafer; P-type; crystal orientation <100> Resistivity 8-12 Ω·cm; Thickness 880.0 µm; Lower grinding disk diameter 90 µm; Step 1: Grinding mortar preparation. First, add water, grinding sand and suspending agent to the grinding mortar bucket in sequence, and prepare the grinding mortar according to the mass-volume ratio of 90L:30kg:3L. The temperature of the mortar bucket should be 20℃ and it should be stirred continuously.

[0028] Step 2: Grinding of the upper and lower grinding discs. Select the grinding program to grind the upper and lower grinding discs together for 8 minutes, with a grinding pressure of 1400 kg, a grinding mortar flow rate of 0.8 L / min, and a lower grinding disc rotation speed of 10 rpm.

[0029] Step 3: Select a disc shape with a diameter of 90μm to start the experiment. At this time, select a wheel plate rotation speed of -6rpm (a negative value represents counterclockwise rotation).

[0030] Step 4: Silicon wafer grinding. The selected grinding program has the following settings: processing pressure 1400 kg, grinding slurry flow rate 0.8 L / min, lower grinding disc rotation speed 30 rpm, brush wheel revolution speed 15 rpm, and target grinding thickness 830 μm.

[0031] First, five wafers were evenly placed on a large tray. A quartz plate was placed in the center hole of wafer 1 to monitor the thickness. Then, four silicon wafers were placed in each wafer in a clockwise order for processing. The first wafer processed in each tray was used as a sample for testing, and its thickness and TTV were measured using an LPW measuring instrument. After processing 200 trays, the tray diameter was measured to be approximately 110 μm using a micrometer. The first wafer processed in each tray was used as a sample for testing, and the TTV measured using an LPW measuring instrument had a mean value of 1.53 and a standard deviation of 0.45. The total cost of processing 200 trays of mortar was calculated as follows: 2012 L of grinding mortar was used, and the total processing time was 66.7 hours.

[0032] Comparative Example 2 Verification silicon wafer: 12-inch Czochralski lightly boron-doped silicon wafer; P-type; crystal orientation <100> Resistivity 8-12 Ω·cm; Thickness 880.0 µm; Lower grinding disk diameter 90 µm; Step 1: Grinding mortar preparation. First, add water, grinding sand and suspending agent to the grinding mortar bucket in sequence, and prepare the grinding mortar according to the mass-volume ratio of 90L:30kg:3L. The temperature of the mortar bucket should be 20℃ and it should be stirred continuously.

[0033] Step 2: Grinding of the upper and lower grinding discs. Select the grinding program to grind the upper and lower grinding discs together for 8 minutes, with a grinding pressure of 1400 kg, a grinding mortar flow rate of 0.8 L / min, and a lower grinding disc rotation speed of 10 rpm.

[0034] Step 3: Select a disc shape with a diameter of 90μm to start the experiment. At this time, select a wheel plate rotation speed of -6rpm (a negative value represents counterclockwise rotation).

[0035] Step 4: Silicon wafer grinding. The selected grinding program has a processing pressure of 1400 kg, a grinding slurry flow rate of 0.8 L / min, a lower grinding disc rotation speed of 30 rpm, a brush wheel revolution speed of 15 rpm, and a target grinding thickness of 830 μm. After processing 100 discs, remove the brush wheel and prepare for disc finishing.

[0036] Step 5: Grinding disc dressing. Place the four dressing wheels evenly on the large disc, select the dressing program to reduce the disc size to 90μm, rinse the large disc with a high-pressure water gun, and then replace the upper grinding wheel. The dressing program pressure is 1413kg, the dressing mortar flow rate is 1.2L / min, and the lower grinding disc rotation speed is 15rpm.

[0037] Step 6: Silicon wafer grinding. The selected grinding program has a processing pressure of 1400 kg, a grinding slurry flow rate of 0.8 L / min, a lower grinding disc rotation speed of 30 rpm, a roller wheel revolution speed of 15 rpm, and a target grinding thickness of 830 μm. After processing 100 discs, remove the roller wheel and prepare for disc finishing.

[0038] Step 7: Grinding disc dressing. Place the four dressing wheels evenly on the large disc, select the dressing program to reduce the disc size to 90μm, rinse the large disc with a high-pressure water gun, and then replace the upper grinding wheel. The dressing program settings are: large disc pressure 1413kg, dressing mortar flow rate 1.2L / min, and lower grinding disc rotation speed 15rpm.

[0039] During the grinding process, five silicon wafers are first evenly placed on a large disc. A quartz plate is placed in the center hole of wafer #1 to monitor the thickness. Then, four silicon wafers are placed in each wafer in a clockwise direction for processing. The first wafer processed in each disc is used as a sample for testing, and its thickness and total thickness volume (TTV) are measured using an LPW measuring instrument. After processing 200 discs, the disc diameter is measured to be 90 μm using a micrometer. The first wafer processed in each disc is used as a sample for testing, and the TTV measured using an LPW measuring instrument has a mean value of 1.05 and a standard deviation of 0.37. The total cost of processing 200 discs of mortar is calculated as follows: grinding sand consumption 2348 L, total processing time 75.0 h.

[0040] The verification conditions and results of the above Examples 1, 1 Comparative Examples, and 2 are compared in Table 1.

[0041] Table 1 The results of the various verification conditions show that Example 1, by adjusting the rotation coefficient of the cruise wheel plate to control the flatness of the lower grinding disc, improved the silicon wafer product parameter TTV compared with Comparative Example 1 (no adjustment was made to the large disc shape) and Comparative Example 2 (repairing the disc every 100 discs processed), and reduced the processing time by 11.1% and the mortar consumption cost by 14.3%.

Claims

1. A method for double-sided grinding of silicon wafers, characterized in that, Includes the following steps: Step 1: Add water, grinding sand and suspending agent to the grinding mortar bucket in sequence to prepare the grinding mortar; Step 2: Select the grinding program to grind the upper and lower grinding discs together; Step 3: After grinding, measure the shape of the lower grinding disc with a micrometer. The disc shape range is 60μm-120μm. Then, select the rotation value of the grinding wheel blade based on the measured disc shape value. When the disc shape is greater than or equal to the upper limit of the disc shape range, select a positive coefficient for the grinding wheel blade rotation, with a range of 5rpm to 7rpm; when the disc shape is less than or equal to the lower limit of the disc shape range, select a negative coefficient for the grinding wheel blade rotation, with a range of -5rpm to -7rpm. Step 4: Select the processing program, load and unload the silicon wafers in sequence, and start the equipment for normal grinding processing.

2. The method for double-sided grinding of silicon wafers according to claim 1, characterized in that, In step 1, the water, grinding sand and suspending agent in the grinding mortar are mixed in a mass-volume ratio of (90-100)L:30kg:(2.5-3)L.

3. The method for double-sided grinding of silicon wafers according to claim 1, characterized in that, In step 2, the grinding parameters for the upper and lower grinding discs are as follows: grinding pressure is 1300-1500 kg, grinding mortar flow rate is 0.8-1.2 L / min, lower grinding disc rotation speed is 10-30 rpm, and grinding time is 6-10 min.

4. The method for double-sided grinding of silicon wafers according to claim 1, characterized in that, In step 3, the method for measuring the shape of the lower grinding disc using a micrometer is as follows: Place the entire micrometer on the surface of the lower grinding disc, and after the readings of each micrometer pointer on the micrometer stabilize, select the maximum value of the reading of the middle micrometer and subtract the minimum value of the readings of the two outermost micrometers. This is the shape value of the lower grinding disc at this time.

5. The method for double-sided grinding of silicon wafers according to claim 1, characterized in that, In step 3, the size of the lower grinding disk ranges from 80μm to 100μm.

6. The method for double-sided grinding of silicon wafers according to any one of claims 1-5, characterized in that, In step 4, the key parameters are set during the grinding process: the processing pressure is 1300-1500 kg, the grinding slurry flow rate is 0.8-1.2 L / min, and the lower grinding disc rotation speed is 10-30 rpm.

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