Method for determining slicing conditions for semiconductor ingots and method for manufacturing semiconductor wafers

Abstract

To provide a new method for determining a slicing condition of a semiconductor ingot.SOLUTION: A slicing condition determination method for cutting a semiconductor ingot by a wire saw is performed by a wire saw 1 having a plurality of rollers 11, a wire 12, a slurry supply nozzle 13, a table 14 and a frame. The determination of a working condition includes determination of a cooling water temperature profile in a frame during slicing, and the determination of the cooling water temperature profile in the frame includes determination of a cooling water temperature profile of increasing flatness of a semiconductor wafer cut from the semiconductor ingot by slicing, on the basis of average shape data of a plurality of semiconductor wafers cut from the semiconductor ingot by slicing under a test working condition, and relation data of the cooling water temperature in the frame during the slicing under the test working condition.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a method for determining slicing processing conditions of a semiconductor ingot and a method for manufacturing a semiconductor wafer.

Background Art

[0002] A semiconductor wafer can be manufactured by cutting a semiconductor ingot (hereinafter, also simply referred to as "ingot") with a wire saw (slicing processing) (see Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Before slicing processing, the processing conditions of the wire saw device are set so that the ingot is sliced along the assumed cutting surface. On the other hand, the relative position variation (positional deviation) between the ingot and the wire of the wire saw that occurs during slicing processing causes unexpected warpage in the cut semiconductor wafer. Therefore, it is desirable to set the processing conditions of slicing processing to conditions that can suppress the above positional deviation in order to suppress the occurrence of unexpected warpage.

[0005] In view of the above, one aspect of the present invention aims to provide a new method for determining slicing processing conditions of a semiconductor ingot.

Means for Solving the Problems

[0006] Japanese Patent No. 3734018 (Patent Document 1) proposes supplying a temperature control medium to the workpiece during slicing so that the shape of warping during slicing can be predicted by simulation, and the temperature of the workpiece (specifically, the ingot) can be controlled based on the simulation results. In response to this, the inventors, while conducting research to provide a new method for determining the slicing conditions of semiconductor ingots, focused on the fact that in recent years, wire saws have been put into practical use that have a mechanism for circulating cooling water within a frame connected to multiple rollers around which wire is wound and an ingot support base. In such wire saws, changes in the shape of the frame due to temperature changes in the frame can cause a phenomenon in which the relative position of the ingot and the wire fluctuates (positional misalignment). This is because both the multiple rollers around which the wire is wound and the ingot support base are connected to the frame. As a result of further diligent research, the inventors have come to the following new method, which includes determining the cooling water temperature profile within the frame.

[0007] That is, one aspect of the present invention is as follows. [1] A method for determining processing conditions for slicing a semiconductor ingot using a wire saw (hereinafter also referred to as the "slicing processing condition determination method" or simply the "processing condition determination method"), The above slicing process is, Multiple rollers, The wire wrapped around the multiple rollers mentioned above, The frame connected to the above-mentioned multiple rollers, A semiconductor ingot support base connected to the above frame, This is done by a wire saw having The determination of the above processing conditions is This includes determining the cooling water temperature profile within the frame during the slicing process, The determination of the coolant temperature profile within the above frame is as follows: A method for determining processing conditions, comprising determining a cooling water temperature profile that enhances the flatness of semiconductor wafers cut from a semiconductor ingot by slicing, based on average shape data of multiple semiconductor wafers cut from a semiconductor ingot by slicing under test processing conditions. [2] The determination of the above processing conditions is Determination of the cooling water temperature profile in the above-mentioned multiple rollers during slicing, and Determination of the slurry temperature profile supplied to the wire during slicing. The method for determining processing conditions as described in [1], further comprising: [3] Determining the cooling water temperature profile in the above-mentioned rollers during slicing is: A method for determining processing conditions as described in [2], which includes determining a temperature profile that reduces the difference between the absolute value of the amount of warpage of the semiconductor wafer caused by the thermal expansion of the multiple rollers mentioned above and the absolute value of the amount of warpage of the semiconductor wafer caused by the thermal expansion of the semiconductor ingot to be sliced. [4] Determining the slurry temperature profile supplied to the wire during slicing is: A method for determining processing conditions as described in [2], which includes determining a temperature profile that reduces the difference between the absolute value of the amount of warpage of the semiconductor wafer caused by the thermal expansion of the multiple rollers mentioned above and the absolute value of the amount of warpage of the semiconductor wafer caused by the thermal expansion of the semiconductor ingot to be sliced. [5] Determining the cooling water temperature profile in the above-mentioned rollers during slicing is: This includes determining a temperature profile that reduces the difference between the absolute value of the warpage of the semiconductor wafer caused by the thermal expansion of the multiple rollers mentioned above and the absolute value of the warpage of the semiconductor wafer caused by the thermal expansion of the semiconductor ingot to be sliced, and Determining the slurry temperature profile supplied to the wire during slicing is: A method for determining processing conditions as described in [2], which includes determining a temperature profile that reduces the difference between the absolute value of the amount of warpage of the semiconductor wafer caused by the thermal expansion of the multiple rollers mentioned above and the absolute value of the amount of warpage of the semiconductor wafer caused by the thermal expansion of the semiconductor ingot to be sliced. The slicing process, in which the semiconductor ingot is cut by a wire saw, is determined by the processing condition determination method described in any of [6][1] to [5], and Cutting a semiconductor ingot using a wire saw under determined processing conditions to cut out semiconductor wafers from the semiconductor ingot. A method for manufacturing semiconductor wafers containing [the specified material]. [Effects of the Invention]

[0008] According to one aspect of the present invention, a novel method for determining slicing conditions for a semiconductor ingot can be provided. Furthermore, according to another aspect of the present invention, a method for manufacturing a semiconductor wafer can be provided in which slicing is performed under the slicing conditions determined by such method. [Brief explanation of the drawing]

[0009] [Figure 1] This is a schematic diagram (front view) showing an example of a wire saw. [Figure 2] (a) to (c) are schematic diagrams (side views) showing the operation of the wire saw during slicing. [Figure 3] (a) to (c) are schematic diagrams showing the cutting trajectory of an ingot during the slicing process. [Figure 4] The slurry supply temperature profile for test processing condition 1 is shown. [Figure 5] The frame cooling water temperature profile for test machining condition 1 is shown. [Figure 6] This shows the shape data of multiple wafers obtained by slicing under test processing condition 1 (the shape of wafers cut from each position on the ingot). [Figure 7] This shows the estimated amount of warping caused by the thermal expansion of the ingot. [Figure 8] Indicates the amount of warpage caused by the thermal expansion of the frame. [Figure 9] Shows the result of subtracting the amount of warpage shown in FIG. 7 and the amount of warpage shown in FIG. 8 from the shape data shown in FIG. 6.

Mode for Carrying Out the Invention

[0010] [Method for Determining Slicing Processing Conditions] One aspect of the present invention relates to a method for determining processing conditions for slicing a semiconductor ingot with a wire saw. The slicing process is performed by a wire saw having a plurality of rollers, a wire wound around the plurality of rollers, a frame connected to the plurality of rollers, and a semiconductor ingot support table connected to the frame. The determination of the processing conditions includes determining a cooling water temperature profile in the frame during the slicing process. The determination of the cooling water temperature profile in the frame includes determining a cooling water temperature profile that enhances the flatness of the semiconductor wafers cut out from the semiconductor ingot by slicing, based on the average shape data of a plurality of semiconductor wafers cut out from the semiconductor ingot by slicing under test processing conditions.

[0011] Hereinafter, the processing condition determination method will be described in more detail.

[0012] <Semiconductor Ingot> Examples of the semiconductor ingot used for the slicing process include various semiconductor ingots such as silicon ingots (preferably single crystal silicon ingots). For example, a single crystal silicon ingot can be produced by a known method, such as the CZ method (Czochralski method) or the FZ method (Floating Zone method). In the present invention and this specification, the semiconductor ingot used for the slicing process also includes a block cut to a predetermined length from an ingot produced by a known method.

[0013] <Slicing process> Slicing of semiconductor ingots is performed by cutting the semiconductor ingot with a wire saw. The slicing process will be described below with reference to the drawings. However, the present invention is not limited to the embodiments shown in the drawings.

[0014] Figure 1 is a schematic diagram (front view) showing an example of a wire saw. Figures 2(a) to 2(c) are schematic diagrams (side views) showing the operation of the wire saw during slicing. Figures 3(a) to 3(c) are schematic diagrams showing the cutting trajectory of an ingot during the slicing process. The wire saw 1 shown in Figure 1 has a wire 12 wound around two rollers 11. The wire 12 can travel in both directions between the two rollers 12, as indicated by the double-headed arrows in the figure. Although not shown in the figure, multiple wires 12 are wound around the two rollers 11 in the direction of the roller's length. A slurry supply nozzle 13 is positioned above each roller 11. The ingot (semiconductor ingot) 2 to be sliced ​​is held on the semiconductor ingot support base (hereinafter also referred to as the "table") 14 of the wire saw 1. As shown in Figure 2, the two rollers 11 and the table 14 are connected to the frame 15 of the wire saw. In the slicing process, the wire 12 is driven by rotating two rollers 11, and the ingot 2 is cut by lowering the table 14 and pressing it against the moving wire 12. During this slicing process, slurry is supplied to the wire 12 from the slurry supply nozzle 13. After ingot 2 is cut, the wire 12 is pulled out from the ingot by raising table 14. In this way, multiple cut semiconductor wafers are obtained.

[0015] In wire saw slicing, the temperature of the ingot and rollers rises due to frictional heat generated during the slicing process. This thermal expansion of the ingot and rollers due to the temperature rise causes displacement of the contact point between the wire and the ingot, resulting in misalignment and significant warping of the cut wafer, which degrades its flatness. The mechanism by which a wafer warps due to displacement during the slicing process will be explained below with reference to Figures 2(a)-(c) and 3(a)-(c). Figures 2(a) to 2(c) show the operation of the wire saw 1 shown in Figure 1 during slicing. In Figures 3(a) to 3(c), the side view of ingot 2 shows the position of wire 12 as a black circle and the cutting trajectory as a dashed line A. When slicing ingot 2, at the start of cutting (Figure 2(a)), the wire 12 enters ingot 2 at the position shown in Figure 3(a). In the middle of the cutting process (Figure 2(b)), the ingot 2 has shifted to the right in the figure, as indicated by the white arrow, and the roller 11 has shifted to the left in the figure, as indicated by the black arrow, relative to its position at the start of cutting (Figure 2(a)). At this time, the wire 12 has shifted to the left in the figure, relative to its position in Figure 3(a). At the end of the cutting process (Figure 2(c)), the ingot 2 has shifted to the left in the figure, as indicated by the white arrow, and the roller 11 has shifted to the right in the figure, as indicated by the black arrow, relative to its position in the middle of the cutting process (Figure 2(b)). At this time, the wire 12 has shifted to the right in the figure, relative to its position in Figure 3(b). As a result of the above, the cutting trajectory of the ingot curves from Figure 3(a) to Figure 3(c). When the cutting trajectory of the ingot is curved due to the displacement of the ingot and rollers, a large warp occurs in the wafer cut from the ingot, resulting in a deterioration of flatness. However, in a wire saw where the table and rollers are connected to a frame, the displacement of the table and rollers as described above can be suppressed by controlling the change in the shape of the frame by adjusting the temperature of the frame to which the table and rollers are connected. The temperature of the frame can be adjusted by the temperature of the cooling water inside the frame. Therefore, the above method for determining processing conditions determines the cooling water temperature profile inside the frame during the slicing process. Figure 2 shows a side view of the wire saw 1, which is shown as a front view in Figure 1. In this wire saw 1, the rear side wall of the frame 15 is connected to the table 14 and the roller 11, respectively. The frame 15 includes cooling water piping at least inside the rear side wall. A gap exists between the roller 11 and the front side wall of the frame 15.

[0016] The following explains how to determine the processing conditions for slicing, based on specific examples.

[0017] <Determination of processing conditions> Using a wire saw configured as shown in Figures 1 and 2, a 300 mm diameter semiconductor ingot was sliced ​​(slicing under test processing condition 1) with various processing parameters set as shown in Table 1, Figures 4 and 5. Except for not controlling the frame cooling water temperature, the same processing conditions as Test Processing Condition 1 were used as Test Processing Condition 2. A 300 mm diameter semiconductor ingot was sliced ​​(slicing under Test Processing Condition 1) while measuring the temperature of the semiconductor ingot. Known methods such as thermocouples and radiation thermometers can be used to measure the temperature of the semiconductor ingot. The temperature of the slurry discharged from the slurry nozzle to be supplied to the wire is referred to as the "slurry supply temperature," the temperature of the cooling water circulating in the cooling water piping within the frame is referred to as the "frame cooling water temperature," the temperature of the cooling water circulating in the cooling water piping within the rollers is referred to as the "roller cooling water temperature," the wire's travel speed is referred to as the "wire speed," and the tension applied to the wire during the slicing process is referred to as the "wire tension."

[0018] [Table 1]

[0019] Figure 6 shows some of the shape data (shape of wafers cut from each position of the ingot) of multiple wafers obtained by slicing under test processing condition 1, measured with a flatness measuring device manufactured by Kobelco Research Institute. One end of the ingot is designated as the TOP and the other as the BOTTOM, and each wafer is numbered 1st, 2nd, etc., from the TOP side towards the BOTTOM side. The shapes of multiple wafers obtained by slicing under test processing condition 2 were also measured using the same method as described above.

[0020] The amount of wafer warpage is thought to consist of the following three types of warpage. (1) Amount of warping due to thermal expansion of the ingot (2) Amount of warping caused by thermal expansion of the frame (more specifically, caused by the relative displacement between the table and rollers connected to the frame) (3) Amount of warping due to thermal expansion of the roller

[0021] The warping caused by thermal expansion of the ingot represents the change in the relative position between the ingot and the wire saw, assuming that the wire saw does not displace, due to the change in the ingot's dimensions caused by thermal expansion. When the length of the ingot is l, the temperature change is Δt, and the coefficient of thermal expansion is a constant α, the change in the ingot's dimensions due to thermal expansion, Δl, is calculated using the following formula (1).

[0022]

number

[0023] Therefore, "(1) the amount of warping due to thermal expansion of the ingot" can be estimated from the measured value of the ingot temperature. Figure 7 shows the results of estimating the amount of warping due to thermal expansion of the ingot from the measured value of the ingot temperature.

[0024] Because the thermal distribution of the ingot and the main roller is very small, the thermal expansion of the ingot and the main roller occurs symmetrically with respect to their respective centers. Since the centers of the ingot and the main roller are almost the same, it is thought that "(1) the amount of warping due to the thermal expansion of the ingot" and "(3) the amount of warping due to the thermal expansion of the roller" occur symmetrically on the left and right sides of Figure 2. On the other hand, "(2) the amount of warping due to the thermal expansion of the frame" displaces the entire main roller relative to the ingot, so it occurs in approximately the same direction and amount across all wafers. Therefore, by calculating the average shape of all wafers cut from a single ingot, "(1) the amount of warping due to the thermal expansion of the ingot" and "(3) the amount of warping due to the thermal expansion of the main roller" cancel each other out on the left and right sides of Figure 2, respectively, and "(2) the amount of warping due to the thermal expansion of the frame (more specifically, due to the relative displacement between the table connected to the frame and the roller)" can be calculated. Figure 8 shows "(2) Warpage due to thermal expansion of the frame," which is calculated as the average shape obtained by averaging the shapes of all wafers obtained by slicing under each test processing condition (test processing condition 1 or 2). From the results shown in Figure 8, it can be confirmed that the amount of warpage due to thermal expansion of the frame can be reduced by controlling the frame cooling water temperature. Therefore, for example, by comparing the average shape data obtained by slicing under different test processing conditions, the frame cooling water temperature profile of the test processing condition with less warpage in the average shape data can be determined as the frame cooling water temperature profile when actually slicing semiconductor ingots.

[0025] "(3) Warpage due to thermal expansion of the roller" can be calculated by subtracting the warpage amount in (1) and the warpage amount in (2) from the warpage amount of the wafer. Figure 9 shows the result of subtracting the warpage amount in (1) shown in Figure 7 and the warpage amount in (2) shown in Figure 8 from the shape data shown in Figure 6.

[0026] Figures 7 and 9 show that the amount of warping caused by (1) thermal expansion of the ingot and (3) thermal expansion of the roller tend to be in opposite directions. From these results, it can be seen that the amount of wafer warping can be reduced by appropriately setting the slurry supply temperature and roller cooling water temperature to reduce the difference between the absolute value of the amount of warping in (1) and the absolute value of the amount of warping in (3), and preferably, the amount of warping in (1) and the amount of warping in (3) can be canceled out by making the absolute values ​​of the amount of warping in (1) and the amount of warping in (3) the same. Furthermore, if the amount of warpage in (1) and the amount of warpage in (3) cancel each other out, the amount of warpage remaining in the wafer is the amount of warpage caused by the thermal expansion of the frame in (2). Also, even without completely canceling out the amount of warpage in (1) and the amount of warpage in (3), the amount of warpage caused by (1) and (3) can be reduced by reducing the difference between the absolute values ​​of the amount of warpage in (1) and the absolute values ​​of the amount of warpage in (3). Therefore, by controlling the frame cooling water temperature during the slicing process so as to reduce the amount of warpage caused by the thermal expansion of the frame in (2), it becomes possible to reduce the amount of wafer warpage and obtain a wafer with high flatness.

[0027] As described above, a method for determining processing conditions according to one aspect of the present invention includes determining a cooling water temperature profile that enhances the flatness of semiconductor wafers cut from a semiconductor ingot by slicing, based on the average shape data of a plurality of semiconductor wafers cut from a semiconductor ingot by slicing under test processing conditions.

[0028] Furthermore, a method for determining processing conditions according to one aspect of the present invention may include determining the cooling water temperature profile in the plurality of rollers during slicing, and determining the slurry temperature profile supplied to the wire during slicing.

[0029] Determining the cooling water temperature profile within the multiple rollers during the slicing process may involve determining a temperature profile that reduces the difference between the absolute value of the warpage of the semiconductor wafer due to the thermal expansion of the multiple rollers and the absolute value of the warpage of the semiconductor wafer due to the thermal expansion of the semiconductor ingot being sliced.

[0030] Determining the slurry temperature profile supplied to the wire during slicing may include determining a temperature profile that reduces the difference between the absolute value of the amount of warping of the semiconductor wafer due to the thermal expansion of the multiple rollers and the absolute value of the amount of warping of the semiconductor wafer due to the thermal expansion of the semiconductor ingot being sliced.

[0031] [Method for manufacturing semiconductor wafers] One aspect of the present invention relates to a method for manufacturing a semiconductor wafer, which includes determining processing conditions for slicing a semiconductor ingot using a wire saw by the above-described processing condition determination method, and performing slicing under the determined processing conditions to cut the semiconductor ingot with a wire saw and cut out a semiconductor wafer from the semiconductor ingot.

[0032] In the above manufacturing method, by performing slicing using processing conditions determined by the processing condition determination method according to one aspect of the present invention, it is possible to suppress the occurrence of warping in semiconductor wafers cut from semiconductor ingots and improve their flatness.

[0033] Details of the above manufacturing method can be provided through publicly known technologies related to the manufacture of semiconductor wafers. For example, semiconductor wafers that are shipped as products can be manufactured by applying various processing to semiconductor wafers cut from an ingot. Examples of such processing include chamfering, planarization (lapping, grinding, polishing), etching, and cleaning. In addition, semiconductor wafers that have undergone various processing may be subjected to one or more inspections before being shipped as products. Semiconductor wafers obtained by the above manufacturing method can be high-quality wafers with little or no warping and high flatness.

[0034] The present invention has been described above based on specific embodiments. However, the embodiments described are illustrative, and the present invention is not limited to the embodiments described. [Industrial applicability]

[0035] This invention is useful in the field of manufacturing various semiconductor wafers, such as silicon wafers.

Claims

1. A method for determining processing conditions for slicing a semiconductor ingot using a wire saw, The slicing process described above is Multiple rollers, The wires wound around the aforementioned multiple rollers, A frame connected to the aforementioned multiple rollers, A semiconductor ingot support base connected to the aforementioned frame, This is done by a wire saw having The determination of the aforementioned processing conditions is This includes determining the cooling water temperature profile within the frame during the slicing process and determining the cooling water temperature profile within the plurality of rollers during the slicing process. The determination of the cooling water temperature profile within the frame is as follows: This includes determining a cooling water temperature profile that enhances the flatness of semiconductor wafers cut from a semiconductor ingot by slicing, based on the average shape data of multiple semiconductor wafers cut from a semiconductor ingot by slicing under test processing conditions, and The determination of the cooling water temperature profile in the plurality of rollers during the slicing process is as follows: A method for determining processing conditions, including determining a temperature profile that reduces the difference between the absolute value of the amount of warping of a semiconductor wafer caused by the thermal expansion of the plurality of rollers and the absolute value of the amount of warping of a semiconductor wafer caused by the thermal expansion of the semiconductor ingot to be sliced.

2. A method for determining processing conditions for slicing a semiconductor ingot using a wire saw, The slicing process described above is Multiple rollers, The wires wound around the aforementioned multiple rollers, A frame connected to the aforementioned multiple rollers, A semiconductor ingot support base connected to the aforementioned frame, This is done by a wire saw having The determination of the aforementioned processing conditions is This includes determining the cooling water temperature profile within the frame during the slicing process and determining the slurry temperature profile supplied to the wire during the slicing process. The determination of the cooling water temperature profile within the frame is as follows: This includes determining a cooling water temperature profile that enhances the flatness of semiconductor wafers cut from a semiconductor ingot by slicing, based on the average shape data of multiple semiconductor wafers cut from a semiconductor ingot by slicing under test processing conditions, and The determination of the slurry temperature profile supplied to the wire during the slicing process is as follows: A method for determining processing conditions, including determining a temperature profile that reduces the difference between the absolute value of the amount of warping of a semiconductor wafer caused by the thermal expansion of the plurality of rollers and the absolute value of the amount of warping of a semiconductor wafer caused by the thermal expansion of the semiconductor ingot to be sliced.

3. The determination of the processing conditions is: The method further includes determining the cooling water temperature profile in the plurality of rollers during the slicing process, The determination of the cooling water temperature profile in the plurality of rollers during the slicing process is as follows: A method for determining processing conditions according to claim 2, comprising determining a temperature profile that reduces the difference between the absolute value of the amount of warpage of the semiconductor wafer caused by the thermal expansion of the plurality of rollers and the absolute value of the amount of warpage of the semiconductor wafer caused by the thermal expansion of the semiconductor ingot to be sliced.

4. The method for determining processing conditions described in any one of claims 1 to 3 to determine the slicing process in which a semiconductor ingot is cut by a wire saw, and Cutting a semiconductor ingot using a wire saw under determined processing conditions to cut out semiconductor wafers from the semiconductor ingot. A method for manufacturing semiconductor wafers containing [the specified material].

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