Silicon wafer surface grinding process

Abstract

The invention provides a silicon wafer surface grinding process which comprises slow descending pre-grinding and formal grinding, in the slow descending pre-grinding process, an upper grinding disc descends to be in contact with a lower grinding disc at a gradually-reduced descending speed, uneven points on a silicon wafer are ground, and in the formal grinding process, the whole silicon wafer is subjected to slow pressure grinding. The method has the beneficial effects that the instant impact pressure on the silicon wafer is reduced, fragments caused by concentrated stress are reduced, the crack rate of the silicon wafer is reduced, the surface parameter TTV of the silicon wafer is improved, and the grinding effect of the silicon wafer is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of silicon wafer processing, and in particular relates to a silicon wafer surface grinding process. Background Art

[0002] During the processing of silicon wafers, in order to ensure the polishing effect of silicon wafers, it is usually necessary to grind the silicon wafers with a grinder before polishing. The grinder includes an upper grinding disc and a lower grinding disc. The upper grinding disc and the lower grinding disc are coaxially arranged. The center gear ring and the outer gear ring jointly drive the planetary plate located between the upper grinding disc and the lower grinding disc to revolve and rotate, and grind the front and back sides of the silicon wafer placed in the planetary plate. A cylinder is connected to the upper grinding disc, which is used to drive the upper grinding disc close to the lower grinding disc to squeeze the silicon wafer. In the prior art, when the upper grinding disc and the lower grinding disc are in contact and squeezed, the instantaneous impact pressure can easily cause the silicon wafer to crack, and as the grinding pressure increases, the grinding fluid will damage the surface of the silicon wafer, affecting the grinding parameters of the silicon wafer surface. Summary of the invention

[0003] In order to solve the above technical problems, the present invention provides a silicon wafer surface grinding process, which effectively solves the technical problems of silicon wafer grinding cracks and grinding fluid causing damage to the silicon wafer surface, and overcomes the shortcomings of the prior art.

[0004] The technical solution adopted by the present invention is: a silicon wafer surface grinding process, comprising the following steps:

[0005] Slow-descent pre-grinding: the upper grinding disc descends at a gradually decreasing speed until it contacts the lower grinding disc, grinding the uneven spots on the silicon wafer;

[0006] Formal grinding, the entire silicon wafer is ground under slow pressure.

[0007] Further, the slow-down pre-grinding includes:

[0008] In the first slow-descent stage, the upper grinding disc descends to a first height at a first speed;

[0009] In the second slow descent stage, the upper grinding disc descends to a second height at a second descent speed;

[0010] In the third slow-down stage, the upper grinding disc is lowered at a third speed until it contacts the lower grinding disc;

[0011] In the pre-grinding stage, the uneven spots on the silicon wafer are ground with slow pressure.

[0012] Furthermore, the first descending speed is 8-15 mm / s, and the first height is 25-50 mm between the upper grinding disc and the lower grinding disc.

[0013] Furthermore, the second descending speed is 0.5-1 mm / s, and the second height is 1-5 mm between the upper grinding disc and the lower grinding disc.

[0014] Furthermore, the third descending speed is less than 0.5 mm / s.

[0015] Furthermore, the duration of the slow-down pre-grinding is less than or equal to 180 seconds.

[0016] Furthermore, the formal grinding includes preliminary grinding, rough grinding and fine grinding, and the grinding pressure and the flow rate of the grinding liquid are gradually increased.

[0017] Furthermore, during the initial grinding, the grinding pressure gradually increases to 400-600 kg, the grinding speed gradually increases to 34-36 rpm, and the flow rate of the grinding liquid gradually increases to 0.6-0.8 L / min.

[0018] Furthermore, during the coarse grinding, the grinding pressure is increased to 1500-1700 kg and remains unchanged, the grinding speed remains unchanged at 34-36 rpm, and the flow rate of the grinding liquid remains unchanged at 0.6-0.8 L / min.

[0019] Furthermore, during the fine grinding, the grinding pressure is kept constant at 1500-1700 kg, the grinding speed is kept constant at 34-36 rpm, and the flow rate of the grinding liquid is increased to 1.1-1.3 L / min and remains constant.

[0020] The advantages and positive effects of the present invention are: due to the adoption of the above technical solution, the instantaneous impact pressure on the silicon wafer is reduced, the fragments caused by concentrated stress are reduced, the crack rate of the silicon wafer is reduced, the surface parameter TTV of the silicon wafer is improved, and the grinding effect of the silicon wafer is improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 The present invention is a flow chart of a silicon wafer surface grinding process according to an embodiment of the present invention.

[0022] Figure 2 It is a formal grinding process curve diagram of a silicon wafer surface grinding process according to an embodiment of the present invention.

[0023] Figure 3 It is a comparison curve diagram of TTV of a silicon wafer surface grinding process according to an embodiment of the present invention and a grinding parameter of the prior art.

[0024] Figure 4 It is a block diagram comparing a silicon wafer surface grinding process according to an embodiment of the present invention with a grinding parameter TTV of the prior art. DETAILED DESCRIPTION

[0025] An embodiment of the present invention provides a silicon wafer surface grinding process, and the embodiment of the present invention is described below in conjunction with the accompanying drawings.

[0026] In the description of the embodiments of the present invention, it should be understood that the orientation or positional relationship indicated by the terms "top", "bottom", etc. is based on the orientation or positional relationship shown in the accompanying drawings, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention. In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "set" and "connect" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be directly connected, or indirectly connected through an intermediate medium, or it can be a connection between the two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood by specific circumstances.

[0027] like Figure 1 As shown, a silicon wafer surface grinding process according to an embodiment of the present invention includes two processes: slow-descent pre-grinding and formal grinding. During the slow-descent pre-grinding process, the upper grinding disc descends at a gradually decreasing descent speed until it contacts the lower grinding disc, and grinds along the uneven spots on the silicon wafer. The upper grinding disc slowly descends by gradually reducing the descent speed, thereby reducing the instantaneous impact pressure when contacting the lower grinding disc, thereby reducing the crack rate of the silicon wafer. By setting the slow-descent pre-grinding, the uneven spots on the silicon wafer are ground first to reduce the fragments caused by concentrated stress, and then the surface of the entire silicon wafer is formally ground to ensure the grinding effect of the entire silicon wafer.

[0028] Specifically, the slow-descent pre-grinding includes a first slow-descent stage, a second slow-descent stage, a third slow-descent stage and a pre-grinding stage. In the first slow-descent stage, the upper grinding disc descends to a first height at a first speed. In the second slow-descent stage, the upper grinding disc descends to a second height at a second descent speed. In the third slow-descent stage, the upper grinding disc descends to contact with the lower grinding disc at a third speed. In the pre-grinding stage, slow-pressure grinding is performed on uneven points on the silicon wafer.

[0029] Specifically, the first descending speed is 8-15 mm / s, and the first height is 25-50 mm from the upper grinding disc to the lower grinding disc. The second descending speed is 0.5-1 mm / s, and the second height is 1-5 mm from the upper grinding disc to the lower grinding disc. The third descending speed is less than 0.5 mm / s. The duration of the slow descending pre-grinding is less than or equal to 180 seconds.

[0030] Specifically, formal grinding includes preliminary grinding, rough grinding and fine grinding, and the grinding pressure and the flow rate of the grinding fluid gradually increase. As the grinding pressure gradually increases, the gap between the grinding disc and the silicon wafer gradually decreases, and the grinding fluid is not easy to flow, which can easily damage the surface of the silicon wafer. By increasing the flow rate of the grinding fluid, the grinding fluid can flow quickly and reduce damage to the silicon wafer.

[0031] Specifically, during the initial grinding, the grinding pressure gradually increases to 400-600 Kg, the grinding speed gradually increases to 34-36 rpm, and the flow rate of the grinding liquid gradually increases to 0.6-0.8 L / min.

[0032] Specifically, during the coarse grinding, the grinding pressure is increased to 1500-1700 kg and remains unchanged, the grinding speed remains unchanged at 34-36 rpm, and the flow rate of the grinding liquid remains unchanged at 0.6-0.8 L / min.

[0033] Specifically, during fine grinding, the grinding pressure is maintained at 1500-1700 kg, the grinding speed is maintained at 34-36 rpm, and the flow rate of the grinding liquid is increased to 1.1-1.3 L / min and remains unchanged.

[0034] Embodiment: A silicon wafer surface grinding process is used to grind an 8-inch silicon wafer, comprising the following steps:

[0035] S1: prepare silicon wafer;

[0036] Place the silicon wafer to be ground in the wafer soaking tank and soak it in deionized water to prevent oxidation of the silicon wafer surface.

[0037] S2: placing silicon wafer;

[0038] Take out the silicon wafer to be ground from the bubble tank and place it in the planetary plate of the grinder. After placing one plate of silicon wafers, check and confirm the placement of the silicon wafers to ensure that there is no wafer slippage or drilling. If there is such a problem, take out the wafers, re-place them, and confirm again until there is no abnormality mentioned above before starting the machine to avoid accidents such as wafer slippage and rollover during the grinding process. The silicon wafers in the planetary plate are placed with 8-inch silicon wafers, and the number of wafers placed per plate is required to be between 35 and 40, with a thickness of >650μm.

[0039] After placing the silicon wafers on the planetary sheet as required, apply a layer of grinding fluid evenly on the surface of the silicon wafers manually. Check whether there are impurities such as silicon wafers, silicon slag or quartz wafers on the surface of the upper grinding disc, and apply a layer of grinding fluid evenly on the surface of the upper grinding disc. Applying grinding fluid prevents the silicon wafer surface from directly rubbing against the grinding disc without grinding fluid at the beginning of grinding, causing damage to the silicon wafer. At the same time, applying a layer of grinding fluid on the silicon wafer also prevents the silicon wafer from being thrown out of the planetary sheet at the beginning of grinding.

[0040] In order to monitor the thickness of the silicon wafer during the grinding process, after the wafer is placed, a quartz wafer is placed at the center hole of any planetary wafer, and the thickness of the silicon wafer is monitored by detecting the thickness of the quartz wafer. The thickness of the quartz wafer is smaller than the thickness of the silicon wafer to be ground and greater than the target thickness of the grinding wafer.

[0041] S3: Slow-down pre-grinding

[0042] The first slow-down stage: the cylinder drives the upper grinding disc to descend at the first descending speed of 8 mm / s to a position 25 mm away from the lower grinding disc;

[0043] The second slow-down stage: the cylinder drives the upper grinding disc to descend to a position 1 mm away from the lower grinding disc at the second descending speed of 0.5 mm / s;

[0044] The third slow descent stage: the cylinder drives the upper grinding disc to descend at the third descent speed of 0.3 mm / s until it contacts the lower grinding disc. When contacting the silicon wafer, the buffer device on the cylinder can absorb the kinetic energy of the piston, allowing the cylinder to stop smoothly, further reducing impact and vibration.

[0045] Pre-grinding stage: The uneven spots on the silicon wafer are ground with slow pressure. The process parameters of the pre-grinding stage are set according to the following table:

[0046] step Time(s) Pressure(Kg) Speed ​​(rpm) Flow rate (L / min) 1 7 95 8 0.3 2 28 118 10 0.7 3 120 300 15 0.7

[0047] S4: Formal grinding

[0048] After the slow-down grinding is completed, formal grinding begins. During the formal grinding process, slow-pressure grinding is performed and the flow rate of the grinding liquid is gradually increased. The specific process curve is as follows: Figure 2 shown.

[0049] During the initial grinding, the grinding pressure gradually increased to 400Kg, the grinding speed gradually increased to 35rpm, the flow rate of the grinding liquid gradually increased to 0.7L / min, and the grinding liquid was prepared from grinding sand, water and grinding aid. The specific ratio was grinding sand: water: grinding aid = 1:3:0.1, and the particle size of the grinding sand was 7-8um.

[0050] During rough grinding, the grinding pressure increases to 1600Kg and remains unchanged, the grinding speed remains unchanged at 35rpm, and the flow rate of the grinding liquid remains unchanged at 0.7L / min. When the rough grinding is finished and the fine grinding stage is about to begin, the grinding pressure is slightly reduced to avoid excessive pressure, which will cause the silicon wafer to stick to the grinding disc for a long time and affect the grinding effect.

[0051] During fine grinding, the grinding pressure was kept constant at 1500 kg, the grinding speed was kept constant at 35 rpm, and the flow rate of the grinding liquid was increased to 1.2 L / min and remained constant.

[0052] During the formal grinding process, the grinding pressure, grinding speed and grinding fluid flow rate gradually increase. Compared with the existing grinding process in which the grinding pressure and grinding speed gradually increase and the grinding flow rate remains unchanged, the surface parameter TTV of the silicon wafer is improved, and the grinding effect of the silicon wafer is improved. Figure 3 and Figure 4 shown.

[0053] S5: Take the film

[0054] After the grinding machine is finished, the upper grinding disc rises under the drive of the cylinder. After confirming that the protective hooks of the upper grinding disc are all opened, the silicon wafer is placed in the wafer basket. Use a latex suction cup to suck the 1 / 2 radius of the silicon wafer, and handle it with care to avoid fragments. Remove the quartz wafer.

[0055] The advantages and positive effects of the present invention are:

[0056] 1. By setting up slow-down pre-grinding, the instantaneous impact pressure on the silicon wafer is reduced, the fragments caused by concentrated stress are reduced, and the crack rate of the silicon wafer is reduced.

[0057] 2. During the formal grinding process, the surface parameter TTV of the silicon wafer is improved by increasing the grinding pressure, grinding speed and grinding liquid flow rate, thereby improving the grinding effect of the silicon wafer.

[0058] The embodiments of the present invention are described in detail above, but the contents described are only preferred embodiments of the present invention and cannot be considered to limit the scope of implementation of the present invention. All equivalent changes and improvements made within the scope of the present invention should still fall within the scope of the patent coverage of the present invention.

Claims

1. A silicon wafer surface grinding process, characterized in that: The following steps are involved: Slow-down pre-grinding: the upper grinding disc descends at a gradually decreasing speed until it contacts the lower grinding disc, grinding the uneven spots on the silicon wafer; Formal grinding, the entire silicon wafer is ground under slow pressure.

2. A silicon wafer surface grinding process according to claim 1, characterized in that: The slow-down pre-grinding comprises: In the first slow-descent stage, the upper grinding disc descends to a first height at a first speed; In the second slow descent stage, the upper grinding disc descends to a second height at a second descent speed; In the third slow-down stage, the upper grinding disc is lowered at a third speed until it contacts the lower grinding disc; In the pre-grinding stage, uneven spots on the silicon wafer are ground with slow pressure.

3. A silicon wafer surface grinding process according to claim 2, characterized in that: The first descending speed is 8-15 mm / s, and the first height is 25-50 mm between the upper grinding disc and the lower grinding disc.

4. A silicon wafer surface grinding process according to claim 3, characterized in that: The second descending speed is 0.5-1 mm / s, and the second height is 1-5 mm between the upper grinding disc and the lower grinding disc.

5. A silicon wafer surface grinding process according to claim 4, characterized in that: The third descending speed is less than 0.5 mm / s.

6. A silicon wafer surface grinding process according to any one of claims 1 to 5, characterized in that: The duration of the slow-down pre-grinding is less than or equal to 180 seconds.

7. A silicon wafer surface grinding process according to any one of claims 1 to 5, characterized in that: The formal grinding includes preliminary grinding, rough grinding and fine grinding, and the grinding pressure and the flow rate of the grinding liquid are gradually increased.

8. A silicon wafer surface grinding process according to claim 7, characterized in that: During the initial grinding, the grinding pressure gradually increases to 400-600 kg, the grinding speed gradually increases to 34-36 rpm, and the flow rate of the grinding liquid gradually increases to 0.6-0.8 L / min.

9. A silicon wafer surface grinding process according to claim 8, characterized in that: During the rough grinding, the grinding pressure is increased to 1500-1700 kg and remains unchanged, the grinding speed remains unchanged at 34-36 rpm, and the flow rate of the grinding liquid remains unchanged at 0.6-0.8 L / min.

10. A silicon wafer surface grinding process according to claim 9, characterized in that: During the fine grinding, the grinding pressure is kept constant at 1500-1700 kg, the grinding speed is kept constant at 34-36 rpm, and the flow rate of the grinding liquid is increased to 1.1-1.3 L / min and remains constant.

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