Method for improving cutting morphology of silicon wafer
By shortening the steel wire reciprocating cycle and adjusting mortar liquid based on cutting depth, the method enhances silicon wafer surface flatness and reduces warping, addressing the limitations of existing slicing technologies.
Patent Information
- Application Number
- CN202411501048.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-10-25
- Publication Date
- 2024-12-20
AI Technical Summary
Current silicon wafer slicing methods, such as multi-wire mortar abrasive cutting, fail to adequately address the requirements for improved microscopic morphology, particularly in terms of surface flatness and warping, which are critical for advanced integrated circuits.
Shortening the single reciprocating motion cycle of the steel wire and adjusting the mortar liquid replacement based on the cutting depth of the crystal ingot to stabilize cutting ability, reduce line mark depth and spacing, and enhance surface flatness.
The method results in a more uniform and flat silicon wafer surface with reduced warping and thickness differences, improving the overall cutting morphology by stabilizing the cutting process and ensuring consistent heat dissipation across the ingot.
Smart Images
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Abstract
Description
Technical Field
[0001] The invention belongs to the technical field of lightly doped single crystal pulling methods, and in particular relates to a method for improving the cutting morphology of silicon slices. Background Art
[0002] Integrated circuits are developing rapidly in the direction of pursuing low cost and three-dimensionalization, and higher requirements are put forward for the quality, diameter, thickness and other indicators of single crystal silicon wafers. The current slicing process of semiconductor silicon wafers adopts multi-wire mortar abrasive cutting. The slicer is mainly composed of a processing chamber, a wire chamber, a mortar tank and other electrical control parts. A main roller shaft that can rotate at high speed is installed in the processing chamber. Multiple circles of steel wire are wrapped around the main roller shaft to form a wire net. The crystal ingot is fixed above the wire net with a clamp. During the processing process, the clamp carries the crystal ingot down and contacts with the high-speed rotating wire net to gradually slice it. The mortar is attached to the wire net for grinding. For slicing, NTC slicers are mainly used. Two wire wheels of new wire and old wire and multiple small wire wheels are installed in the wire chamber of the NTC slicer. During the cutting process, the steel wire reciprocates from the new / old wire. The mortar tank is filled with a mixed mortar of silicon carbide particles and cutting fluid. When the steel wire runs at high speed, the mortar uses the suspension of the cutting fluid to adhere to the wire net and contact the crystal ingot for grinding. When the processing table drives the clamped crystal ingot to feed downward, the crystal ingot can be cut. Figure 1 shown.
[0003] Currently, there are relevant parameter requirements for cut silicon wafers. In addition to the size of the warp value, downstream users pay more attention to the relative flatness of the microscopic morphology of the silicon wafer. Therefore, it is necessary to explore a method to improve the cutting morphology of silicon wafers. Summary of the invention
[0004] In view of this, the present invention provides a method for improving the morphology of silicon wafer cutting.
[0005] The technical solution adopted by the present invention to solve its technical problem is: A method for improving the cutting morphology of silicon wafers, characterized in that, during the process of cutting a crystal ingot, a single reciprocating motion cycle of a steel wire is shortened and a mortar liquid is replaced according to the cutting depth of the crystal ingot, so as to reduce the line mark depth, shorten the line mark spacing, enhance the surface flatness of the silicon wafer, and make the cutting morphology of the silicon wafer relatively flat.
[0006] Preferably, shortening a single reciprocating motion cycle of the steel wire means that the total processing time for cutting a crystal ingot remains unchanged, the speed of the crystal ingot moving downward remains unchanged, and the single reciprocating motion cycle of the steel wire is shortened.
[0007] Preferably, the shortening of the single reciprocating motion cycle of the steel wire is shortened to at least 0.45 times of the original single reciprocating motion cycle of the steel wire.
[0008] Preferably, the new mortar liquid is replaced each time with 1 / 4-1 / 3 of the total amount of the mortar liquid according to the cutting depth of the crystal ingot.
[0009] Preferably, the mortar liquid is replaced with new mortar liquid in an amount of 1 / 4-1 / 3 of the total amount each time according to the cutting depth of the crystal ingot, specifically, the mortar liquid is replaced 3 times according to the cutting depth of the crystal ingot.
[0010] Preferably, the period for replacing the slurry liquid three times according to the cutting depth of the ingot is: When the cutting depth of the ingot from top to bottom is from 0 to 30%-40%; When the cutting depth of the ingot from top to bottom is from 30%-40% to 45%-55%; When the cutting depth of the ingot from top to bottom is cut from 45%-55% to 70%-80%.
[0011] Compared with the prior art, the present invention has the following beneficial effects: The present invention provides a method for improving the cutting morphology of silicon wafers. During the process of cutting a crystal ingot, a single reciprocating motion cycle of a steel wire is shortened, and mortar liquid is replaced according to the cutting depth of the crystal ingot, so that the cutting ability of the steel wire is stabilized, the residence time of the steel wire on the surface of the silicon wafer is shortened, the depth of the line mark is reduced, and the spacing between the line marks is shortened, so that the thickness difference at various positions on the surface of the silicon wafer is reduced, the warping is smaller, the flatness of the silicon wafer surface is enhanced, and the cutting morphology of the silicon wafer is relatively flat. BRIEF DESCRIPTION OF THE DRAWINGS
[0012] Figure 1 Schematic diagram of a multi-wire cutting machine.
[0013] Figure 2 This is a single reciprocating motion cycle diagram of the steel wire in Example 1 and Comparative Example 1.
[0014] Figure 3 This is a graph showing the surface warpage of the silicon wafer in Example 1.
[0015] Figure 4 This is a silicon wafer morphology diagram of Example 1.
[0016] Figure 5 This is a graph showing the surface warpage of the silicon wafer of comparative example 1.
[0017] Figure 6 This is the silicon wafer morphology of comparative example 1.
[0018] Figure 7 This is the front view of the multi-wire cutting machine.
[0019] Figure 8 A top view of the flow control device.
[0020] Fig. 9 This is a curve diagram of the mortar flow control at the head of the crystal rod in Example 2.
[0021] Fig.10 This is a curve diagram of mortar flow control in the middle of the crystal rod in Example 2.
[0022] Fig.11 This is a curve diagram of the mortar flow control at the tail of the crystal rod in Example 2.
[0023] Fig.12 This is the mortar temperature curve diagram of Example 2.
[0024] Fig.13 This is a distribution diagram of the warp value of the silicon wafer after slicing in Example 2.
[0025] Fig.14 It is a front view of an existing multi-wire cutting machine.
[0026] Fig.15 It is a top view of an existing multi-wire cutting machine.
[0027] Fig.16 This is the mortar flow curve of comparative example 2.
[0028] Fig.17 This is the warp value distribution diagram of the silicon wafer after slicing in comparative example 2.
[0029] In the figure: a mortar main pipe 100, a crystal ingot head branch pipe 200, a crystal ingot middle branch pipe 300, and a crystal ingot tail branch pipe 400. DETAILED DESCRIPTION
[0030] The technical solutions and technical effects of the embodiments of the present invention are further described in detail below in conjunction with the accompanying drawings of the present invention.
[0031] A method for improving the cutting morphology of silicon wafers, characterized in that, during the process of cutting a crystal ingot, a single reciprocating motion cycle of a steel wire is shortened and a mortar liquid is replaced according to the cutting depth of the crystal ingot, so as to reduce the line mark depth, shorten the line mark spacing, enhance the surface flatness of the silicon wafer, and make the cutting morphology of the silicon wafer relatively flat.
[0032] Compared with the prior art, the present invention has the following beneficial effects: The present invention provides a method for improving the cutting morphology of silicon wafers. During the process of cutting a crystal ingot, a single reciprocating motion cycle of a steel wire is shortened, and mortar liquid is replaced according to the cutting depth of the crystal ingot, so that the cutting ability of the steel wire is stabilized, the residence time of the steel wire on the surface of the silicon wafer is shortened, the depth of the line mark is reduced, and the spacing between the line marks is shortened, so that the thickness difference at various positions on the surface of the silicon wafer is reduced, the warping is smaller, the flatness of the silicon wafer surface is enhanced, and the cutting morphology of the silicon wafer is relatively flat.
[0033] Furthermore, shortening a single reciprocating motion cycle of the steel wire means that the total processing time for cutting a crystal ingot remains unchanged, the speed of the crystal ingot moving downward remains unchanged, and the single reciprocating motion cycle of the steel wire is shortened.
[0034] Specifically, by shortening the single reciprocating motion cycle of the steel wire, the number of reciprocating cycles of the steel wire in the NTC machine increases, the time the steel wire stays at a certain position on the silicon wafer surface is shortened, the depth of the wire marks is low, and the spacing between the wire marks is small, and the surface of the silicon wafer is smoother.
[0035] Furthermore, the shortening of the single reciprocating motion cycle of the steel wire is shortened to at least 0.45 times of the original single reciprocating motion cycle of the steel wire. If it is less than 0.45 times, the wire breakage rate of the steel wire will increase.
[0036] Furthermore, according to the cutting depth of the crystal ingot, 1 / 4-1 / 3 of the total amount of the mortar liquid is replaced with new mortar liquid each time; specifically, according to the amount of new mortar liquid that needs to be replaced, a corresponding amount of old mortar liquid in the mortar tank is extracted and new mortar liquid is injected, and the composition of the new mortar liquid is the same as that of the original mortar liquid.
[0037] Furthermore, the mortar liquid is replaced with new mortar liquid of 1 / 4-1 / 3 of the total amount each time according to the cutting depth of the crystal ingot. Specifically, the mortar liquid is replaced 3 times according to the cutting depth of the crystal ingot to ensure the cutting ability of the steel wire at different positions.
[0038] Furthermore, the period of replacing the slurry liquid three times according to the cutting depth of the ingot is: When the cutting depth of the ingot from top to bottom is from 0 to 30%-40%; When the cutting depth of the ingot from top to bottom is from 30%-40% to 45%-55%; When the cutting depth of the ingot from top to bottom is cut from 45%-55% to 70%-80%.
[0039] Furthermore, during the multi-wire cutting process, different mortar flow rates are set according to the positions of the head, middle and tail of the ingot, and the mortar flow rates at the head, middle and tail of the ingot are adjusted respectively according to the cutting depth of the ingot, so as to accurately control the mortar flow rates in different cutting areas of the ingot, so that the warping values at different positions of the ingot are stable.
[0040] Specifically, in the multi-cutting process, different mortar flow rates are set according to the positions of the head, middle and tail of the ingot, and the mortar flow rates at the head, middle and tail of the ingot are adjusted respectively according to the cutting depth of the ingot, so as to accurately control the mortar flow rates in different cutting areas of the ingot, so that the heat dissipation capacity at different positions is the same during the ingot cutting process, the silicon wafers are heated equally, and no temperature difference is generated. Therefore, after the ingot is sliced, the warp distribution will not be higher at the head and lower at the tail, so that the warp distribution of the silicon wafers at the head, middle and tail of the ingot is uniform, and the morphology of each silicon wafer is relatively flat.
[0041] Furthermore, the head of the ingot refers to the position of 0-20% of the length of the ingot, the middle of the ingot refers to the position of 20%-80% of the length of the ingot, and the tail of the ingot refers to the position of 80%-100% of the length of the ingot.
[0042] Furthermore, the mortar flow rate control process at the head, middle and tail of the crystal ingot is as follows: as the cutting depth of the crystal ingot gradually increases, the mortar flow rate ratio gradually decreases.
[0043] Furthermore, the mortar flow control process at the head of the ingot is specifically as follows: When the cutting depth of the ingot from top to bottom is from 0 to 70%-78%, the mortar flow rate ratio is 100%-120% and remains stable; When the cutting depth of the ingot from top to bottom is from 70%-78% to 85%-92%, the mortar flow rate ratio decreases evenly from 100%-120% to 60%-80%; When the cutting depth of the ingot from top to bottom ranges from 85%-92% to 100%, the mortar flow rate ratio remains stable at 60%-80%.
[0044] Furthermore, the slurry flow control process in the middle of the ingot is specifically as follows: When the cutting depth of the ingot from top to bottom ranges from 0 to 15%-22%, the mortar flow rate ratio is stable at 130%-150%; When the cutting depth of the ingot from top to bottom is cut from 15%-22% to 25%-30%, the mortar flow rate ratio decreases evenly from 130%-150% to 100%-120%; When the cutting depth of the ingot from top to bottom is from 25%-30% to 80%-85%, the mortar flow rate is 100%-120% and remains stable; When the cutting depth of the ingot from top to bottom is cut from 80%-85% to 88%-92%, the mortar flow rate ratio decreases evenly from 100%-120% to 70%-90%; When the cutting depth of the ingot from top to bottom ranges from 88%-92% to 100%, the mortar flow rate ratio remains stable at 70%-90%.
[0045] Furthermore, the slurry flow control process at the tail of the ingot is specifically as follows: When the cutting depth of the ingot from top to bottom ranges from 0 to 45%-55%, the mortar flow rate ratio is stable at 110%-130%; When the cutting depth of the ingot from top to bottom increases from 45%-55% to 100%, the slurry flow rate decreases from 110%-130% to 50%-70%.
[0046] Furthermore, the mortar flow rate ratio=actual mortar flow rate / fixed mortar flow rate.
[0047] Furthermore, the fixed mortar flow rate is 140kg / min-170kg / min.
[0048] like Figure 7 , 8 As shown, further, the mortar flow control process of the head, middle and tail of the crystal ingot is controlled by a flow control device, and there are two flow control devices, which are respectively located on both sides of the crystal ingot, and the flow control device includes: a mortar main pipe 100, a crystal ingot head branch pipe 200, a crystal ingot middle branch pipe 300, and a crystal ingot tail branch pipe 400, and both ends of the crystal ingot head branch pipe 200, the crystal ingot middle branch pipe 300, and the crystal ingot tail branch pipe 400 are closed, the crystal ingot head branch pipe 200, the crystal ingot middle branch pipe 300, and the crystal ingot tail branch pipe 400 are located in the same straight line and parallel to the crystal ingot, and the crystal ingot head branch pipe 200, the crystal ingot middle branch pipe 300, and the crystal ingot tail branch pipe A plurality of spray holes are evenly arranged on one side of the branch pipe 400 facing the wire mesh, the axis of the mortar main pipe 100 is perpendicular to the axis of the ingot, the axis of the mortar main pipe 100 is perpendicular to the axes of the ingot head branch pipe 200, the ingot middle branch pipe 300, and the ingot tail branch pipe 400, the ingot head branch pipe 200, the ingot middle branch pipe 300, and the ingot tail branch pipe 400 are located in the same horizontal plane, and the axes of the ingot head branch pipe 200, the ingot middle branch pipe 300, and the ingot tail branch pipe 400 are parallel to the ingot, and the outlet of the mortar main pipe 100 is respectively connected with the middle of the ingot head branch pipe 200, the ingot middle branch pipe 300, and the ingot tail branch pipe 400.
[0049] The flow control device is installed on the multi-wire sawing machine. The ingot head branch pipe 200, the ingot middle branch pipe 300, and the ingot tail branch pipe 400 are all located above the wire mesh of the multi-wire sawing machine. The spray holes of the ingot head branch pipe 200, the ingot middle branch pipe 300, and the ingot tail branch pipe 400 are tilted to spray on the wire mesh of the multi-wire sawing machine to spray the mortar onto the wire mesh, and the heat from the silicon wafer cutting is taken away by the mortar liquid on the wire mesh.
[0050] Furthermore, solenoid valves and flow meters are respectively provided on the pipelines connecting the outlet of the mortar main pipe 100 with the middle parts of the ingot head branch pipe 200 , the ingot middle branch pipe 300 , and the ingot tail branch pipe 400 .
[0051] Furthermore, the solenoid valve and flow meter are electrically connected to the control module of the multi-wire saw, and the flow rates of the ingot head branch 200, the ingot middle branch 300, and the ingot tail branch 400 are controlled respectively by cutting the mortar flow rate ratio at different positions.
[0052] The use of the present invention is described by the following examples. Embodiment 1:
[0053] Take a 6-inch ingot and cut it using an NTC multi-wire saw to shorten the single reciprocating motion cycle of the steel wire to 30s. Figure 2 As shown in the figure (current cycle), the total amount of mortar in the mortar tank is 160L. When the ingot depth is 35%, 50%, and 75%, 40L of old mortar liquid is drawn out and replaced with 40L of new mortar liquid. The warpage of the cut silicon wafer surface is as follows Figure 3 As shown, the appearance is Figure 4 shown.
[0054] Comparative Example 1: Take a 6-inch ingot and cut it using an NTC multi-wire saw. The single reciprocating motion cycle of the steel wire is 65 seconds. Figure 2 As shown in the figure (original cycle), the total amount of mortar in the mortar tank is 160L. After processing one ingot, 85L of old mortar liquid is extracted and replaced with 85L of new mortar liquid. The warpage of the cut silicon wafer surface is as follows Figure 5 As shown, the appearance is Figure 6 shown.
[0055] Depend on Figures 3 to 6 It can be seen that the surface of the head, middle and tail silicon wafers processed in Comparative Example 1 is curved, and the surface warping of the silicon wafer processed in Example 1 is significantly improved, the overall trend is flattened, and the overall warping is reduced. Embodiment 2:
[0056] Take an 8-inch ingot and cut it using an NTC multi-wire saw. The multi-wire saw is equipped with a flow control device, such as Figure 7 , 8 As shown, the slurry flow control curves of the ingot head branch pipe 200, the ingot middle branch pipe 300, and the ingot tail branch pipe 400 are as follows: Figure 9-11 As shown, the fixed mortar flow rate is 140 kg / min, the mortar liquid is composed of cutting fluid and silicon carbide powder, and the temperature curve of the mortar liquid in the mortar main pipe 100 is as follows Fig.12 As shown, the single reciprocating motion cycle of the steel wire is shortened to 0.46 of the original. When the ingot depth is 35%, 50%, and 75%, 1 / 4 of the total amount of old mortar liquid in the mortar tank is drawn out and replaced with the corresponding amount of new mortar liquid. The results of cutting silicon wafers are shown in Fig.13 shown.
[0057] Comparative Example 2: Take an 8-inch ingot and cut it using an existing multi-wire saw. The multi-wire saw is not equipped with a flow control device, such as Fig.14 , 15 As shown, the mortar flow curve is as follows Fig.16 As shown, the rest is the same as in Example 2, and the result of cutting the silicon wafer is as follows Fig.17 shown.
[0058] Depend on Fig.13 , Fig.17 It can be seen that compared with comparative example 2, the overall warp value distribution of the silicon wafers cut in embodiment 2 is stable, and the warp value deviation of the head and tail silicon wafers is smaller than that of the middle silicon wafer.
[0059] What is disclosed above is only a preferred embodiment of the present invention, which certainly cannot be used to limit the scope of rights of the present invention. A person skilled in the art can understand that all or part of the processes of the above embodiments and equivalent changes made according to the claims of the present invention still fall within the scope of the invention.
Claims
1. A method for improving the cutting morphology of silicon wafers, characterized in that: During the process of cutting the crystal ingot, the single reciprocating motion cycle of the steel wire is shortened and the slurry is replaced according to the cutting depth of the crystal ingot to reduce the line mark depth, shorten the line mark spacing, enhance the flatness of the silicon wafer surface, and make the silicon wafer cutting morphology relatively flat.
2. The method for improving the cutting morphology of silicon wafers according to claim 1, characterized in that: The shortening of a single reciprocating motion cycle of the steel wire means that the total processing time for cutting a crystal ingot remains unchanged, the speed of the crystal ingot moving downward remains unchanged, and the single reciprocating motion cycle of the steel wire is shortened.
3. The method for improving the cutting morphology of silicon wafers according to claim 2, characterized in that: The shortening of the single reciprocating motion cycle of the steel wire is shortening to more than 0.45 times of the original single reciprocating motion cycle of the steel wire.
4. The method for improving the cutting morphology of silicon wafers according to any one of claims 1 to 3, characterized in that: The new mortar liquid is replaced with 1 / 4-1 / 3 of the total amount of the mortar liquid each time according to the cutting depth of the crystal ingot.
5. The method for improving the cutting morphology of silicon wafers according to claim 4, characterized in that: The method of replacing 1 / 4-1 / 3 of the total amount of the mortar liquid with new mortar liquid each time according to the cutting depth of the crystal ingot is specifically to replace the mortar liquid three times according to the cutting depth of the crystal ingot.
6. The method for improving the cutting morphology of silicon wafers according to claim 5, characterized in that: The period for replacing the slurry three times according to the cutting depth of the ingot is: When the cutting depth of the ingot from top to bottom is from 0 to 30%-40%; When the cutting depth of the ingot from top to bottom is from 30%-40% to 45%-55%; When the cutting depth of the ingot from top to bottom is cut from 45%-55% to 70%-80%.