Method for determining wafer polishing conditions, method for manufacturing wafer, and wafer single-side polishing system

Abstract

The invention provides a method for determining a polishing condition for polishing a single surface of a wafer by a polishing apparatus. The polishing device at least comprises a platform, a polishing pad arranged on the platform, and a polishing chuck arranged above the polishing pad. The grinding condition determination method comprises the following steps: setting a target range of a wafer grinding amount in-plane difference; on the basis of the correlation between the wafer polishing amount in-plane difference and the wafer polishing pressure in-plane difference, determining a prediction range of the wafer polishing pressure in-plane difference which is predicted to be capable of realizing the wafer polishing amount in-plane difference of the target range; and determining, on the basis of the correlation between the wafer polishing pressure in-plane difference and the pressing surface shape value of the polishing chuck, a pressing surface shape value range of the polishing chuck in which it is predicted that the wafer polishing pressure in-plane difference within the prediction range can be achieved.

Description

[0001] Cross-references of related applications This application claims the benefit of priority based on Japanese Patent Application No. 2022-107702, filed on July 4, 2022, the entire contents of which are hereby incorporated by reference as a special disclosure. Technical Field

[0002] The invention relates to a method for determining wafer grinding conditions, a method for manufacturing a wafer and a wafer single-side grinding system. Background Art

[0003] The device for grinding the surface of a wafer includes a single-side grinding device for grinding a single side of the wafer and a double-side grinding device for grinding both sides of the wafer. In the single-side grinding device, generally, the grinding target surface of the wafer held by the grinding chuck is pressed against the grinding pad attached to the platform while the grinding chuck and the platform are rotated respectively so that the grinding target surface of the wafer contacts the grinding pad. The grinding target surface of the wafer can be ground by supplying an abrasive between the grinding target surface and the grinding pad that are in contact in this way (for example, refer to Japanese Patent Publication No. 2007-274012 (the entire record of which is cited as a special disclosure)).

[0004] In a wafer grinding process (hereinafter also referred to as "wafer single-side grinding process") using a single-side grinding device, a grinding amount difference may occur in the surface of the wafer to be ground. For example, in Japanese Patent Publication No. 2007-274012, in order to suppress the warping of the outer periphery of the wafer after grinding due to the generation of the grinding amount difference in the surface, it is proposed to install an annular spacer between the wafer and the template holding the wafer (refer to claim 1, paragraph 0009, etc. of Japanese Patent Publication No. 2007-274012). However, since it is necessary to adjust the shape and configuration position of the spacer, it is not easy to control the grinding amount difference in the surface by the spacer. In addition, appropriately setting the grinding conditions can help control the grinding amount difference in the surface of the wafer single-side grinding, but in the past, in order to find such grinding conditions, a large number of attempts had to be repeated. Summary of the invention

[0005] An object of one embodiment of the present invention is to set appropriate polishing conditions and to easily control the in-plane polishing amount difference in a wafer single-side polishing step.

[0006] One embodiment of the present invention is as follows.

[0007] [1] A method for determining polishing conditions (hereinafter also referred to as "polishing condition determination method"), wherein a single side of a wafer is polished by a polishing apparatus. The grinding device at least comprises a platform, a grinding pad disposed on the platform, and a grinding chuck disposed above the grinding pad. The method for determining the above grinding conditions includes: Setting the target range of wafer grinding amount intra-plane difference; Determining a predicted range of wafer grinding pressure in-plane difference that is predicted to achieve the above-mentioned target range of wafer grinding amount in-plane difference based on a correlation between the wafer grinding amount in-plane difference and the wafer grinding pressure in-plane difference; and Based on the correlation between the wafer polishing pressure in-plane difference and the pressing surface shape value of the polishing chuck, a range of pressing surface shape values ​​of the polishing chuck that is predicted to be able to achieve the wafer polishing pressure in-plane difference within the above-predicted range is determined.

[0008] [2] The method for determining the polishing conditions according to [1], wherein the above-mentioned correlation between the in-plane difference of the wafer polishing amount and the in-plane difference of the wafer polishing pressure is a proportional relationship.

[0009] [3] The method for determining the polishing conditions according to [1] or [2], wherein the pressing surface of the polishing chuck is concave in shape with a central portion being recessed relative to the polishing pad side more than the peripheral portion, or is convex in shape with a central portion being protruding relative to the polishing pad side more than the peripheral portion, The determined pressing surface shape value range is the depression depth range of the concave shape or the protrusion height range of the convex shape.

[0010] [4] The method for determining the grinding conditions according to [3], wherein the above-mentioned correlation between the chip grinding pressure surface difference and the pressing surface shape value of the grinding chuck is a linear relationship between the chip grinding pressure surface difference and the above-mentioned recess depth or a linear relationship between the chip grinding pressure surface difference and the above-mentioned protrusion height.

[0011] [5] The method for determining grinding conditions according to [3] or [4] further includes determining the pressing surface shape of the grinding chuck by approximating the radial cross-sectional shape as a quadratic function.

[0012] [6] A method for determining grinding conditions according to any one of [3] to [5], wherein the depth range of the concave shape or the height range of the convex shape is determined based on one or both of the thickness and hardness of the grinding pad.

[0013] [7] The method for determining grinding conditions according to [6], further comprising: Determining the thickness of the polishing pad used in actual polishing; and When the determined thickness of the polishing pad is thinner than a predetermined reference thickness, the range of the recessed depth of the concave shape or the range of the protruding height of the convex shape is determined to be a narrower range.

[0014] [8] The method for determining grinding conditions according to [6] or [7], further comprising: Determine the hardness of the polishing pad used in actual polishing; and When the determined hardness of the polishing pad is harder than a predetermined reference hardness, the range of the recessed depth of the concave shape or the range of the protruding height of the convex shape is determined to be a narrower range.

[0015] [9] A method for manufacturing a wafer having a polished surface, comprising: Determining the grinding conditions by the method for determining grinding conditions described in any one of [1] to [8]; and A single side of the wafer is ground by a grinding device including a grinding chuck having a pressing surface having a shape within the determined pressing surface shape value range.

[0016]

[10] The manufacturing method according to [9], wherein the grinding chuck has a concave pressing surface with a recessed depth of 5 μm or more and 20 μm or less.

[0017]

[11] The manufacturing method according to [9] or

[10] , wherein the polishing device includes a polishing pad having a thickness of 0.864 mm ± 20% and a Young's modulus of 0.27 MPa ± 20%.

[0018]

[12] The manufacturing method according to any one of [9] to

[11] , wherein the wafer is a semiconductor wafer.

[0019]

[13] The manufacturing method according to

[12] , wherein the semiconductor wafer is a silicon wafer.

[0020]

[14] A wafer single-side grinding system comprising: A grinding device, comprising at least a platform, a grinding pad disposed on the platform, and a grinding chuck disposed above the grinding pad; and The polishing condition determination unit determines the polishing condition by the polishing condition determination method described in any one of [1] to [8].

[0021] According to one embodiment of the present invention, appropriate polishing conditions can be set to easily control the in-plane polishing amount difference in the wafer single-side polishing step. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is a partial schematic cross-sectional view of an example of a polishing device.

[0023] Figure 2 This is a schematic cross-sectional view of a grinding chuck (concave chuck) having a pressing surface having a concave shape in which the central portion is concave relative to the outer peripheral portion on the polishing pad side.

[0024] Figure 3This is a schematic cross-sectional view of a polishing chuck (convex chuck) having a pressing surface having a convex shape in which the central portion protrudes more than the outer peripheral portion toward the polishing pad side.

[0025] Figure 4 It is a graph showing the in-plane distribution of the wafer grinding amount (actually measured values) when a concave chuck is used and when a convex chuck is used.

[0026] Figure 5 This is a conceptual diagram of a two-dimensional axisymmetric model used when calculating the pressure applied to the polishing target surface of a wafer through simulation.

[0027] Figure 6 It is a graph showing the in-plane distribution (actual measurement results and simulation) of the pressure applied to the polishing target surface of the wafer when a concave chuck is used and when a convex chuck is used.

[0028] Figure 7 The circumferential average machining amount GBIR and p_max–p_min are shown.

[0029] Figure 8 The following is a result of calculating, by simulation, the pressure applied to the polishing target surface of the wafer when polishing chucks having various pressing surface shapes are used.

[0030] Fig. 9 The following is a result of calculating, by simulation, the pressure applied to the polishing target surface of the wafer when polishing chucks having various pressing surface shapes are used.

[0031] Fig.10 The results are shown in which the radial cross-sectional shape of the pressing surface of the grinding chuck was approximated by a quadratic function.

[0032] Fig.11 Graphs showing the dependence of the wafer polishing pressure in-plane difference on the polishing pad thickness and hardness. DETAILED DESCRIPTION

[0033] [Method for determining grinding conditions] One embodiment of the present invention relates to a method for determining polishing conditions for polishing one side of a wafer using a polishing apparatus.

[0034] The polishing device at least includes a platform, a polishing pad disposed on the platform, and a polishing chuck disposed above the polishing pad.

[0035] The above-mentioned grinding condition determination method includes: Setting the target range of wafer grinding amount intra-plane difference; Determining a predicted range of wafer grinding pressure in-plane difference that is predicted to achieve the above-mentioned target range of wafer grinding amount in-plane difference based on a correlation between the wafer grinding amount in-plane difference and the wafer grinding pressure in-plane difference; and Based on the correlation between the wafer polishing pressure in-plane difference and the pressing surface shape value of the polishing chuck, a range of pressing surface shape values ​​of the polishing chuck that is predicted to be able to achieve the wafer polishing pressure in-plane difference within the above-predicted range is determined.

[0036] As described in detail below, the inventors have newly discovered that the wafer grinding amount in-plane difference is correlated with the wafer grinding pressure in-plane difference, and the wafer grinding pressure in-plane difference is correlated with the pressing surface shape value of the grinding chuck. In the above-mentioned method for determining wafer grinding conditions, based on these correlations, it is possible to easily determine the grinding conditions predicted to achieve the desired wafer grinding amount in-plane difference.

[0037] The method for determining the above-mentioned wafer grinding conditions is described in more detail below. In the present invention and this specification, expressions such as "upper surface" and "lower surface" refer to "upper surface" and "lower surface" when the grinding device is in a state of grinding processing. Below, sometimes the description is based on the drawings, but the methods shown in the drawings are illustrative, and the present invention is not limited to the above methods.

[0038] <Grinding Object> The wafer to be polished may be, for example, a semiconductor wafer. The semiconductor wafer may be, for example, a silicon wafer such as a single crystal silicon wafer. For example, a silicon wafer can be produced by the following method. A single crystal silicon ingot is cut to obtain a block. A single crystal silicon ingot can be grown by known methods such as the CZ method (Czochralski method) and the FZ method (Floating Zone method). The obtained block is sliced ​​to form a wafer. Silicon wafers can be produced by subjecting the wafer to various processes. Examples of the above-mentioned processes include chamfering, flattening (polishing, grinding, lapping), and the like. The single-sided polishing process of the wafer in which the polishing conditions are determined by the above-mentioned polishing condition determination method is suitable, for example, as a polishing method in the final process of these wafer processes, i.e., the fine lapping process.

[0039] <Grinding device> (Structural example of polishing device) The above-mentioned polishing device is a wafer single-side polishing device, which at least includes a platform, a polishing pad arranged on the platform, and a polishing chuck arranged above the polishing pad. Figure 1 A partial schematic cross-sectional view showing an example of the above-mentioned polishing device.

[0040] Figure 1 The polishing device 1 shown has a platform 11 , a polishing pad 12 , a polishing chuck 14 , and a backing pad 13 . Figure 1The arrow in Schematically shows a state in which the upper portion of the grinding chuck 14 is pressurized.

[0041] The polishing device 1 rotates the platform 11 and the polishing chuck 14 respectively by a rotating mechanism (not shown) and makes the polishing target surface of the wafer W to be polished slide against the polishing pad 12 attached to the platform 11. The abrasive discharged from the abrasive supply mechanism (not shown) of the polishing device is supplied between the polishing target surface of the wafer W (the lower surface of the wafer W) and the polishing pad 12, and the polishing target surface of the wafer W is polished. As the abrasive, a polishing slurry generally used in CMP (chemical mechanical polishing) can be used.

[0042] The grinding chuck 14 may be a grinding chuck including a part of the lower surface 14a which is made of a rigid body, or a grinding chuck which is made of a rigid body as a whole. The rigid body may be, for example, ceramics. The lower surface 14a of the grinding chuck 14 is a pressing surface for pressing the wafer W via the back pad 13. In the grinding device 1, the back pad 13 is bonded to the pressing surface (lower surface) 14a of the grinding chuck 14. The back pad 13 can be bonded to the pressing surface 14a of the grinding chuck 14 by a known method such as using an adhesive. As the back pad 13, for example, a disc-shaped plate made of a material (such as foamed polyurethane, etc.) that shows adsorption due to the surface tension of water if it contains water can be used. As a result, the back pad 13 containing water can hold the wafer W (so-called water filling) during grinding.

[0043] (Shape of the pressing surface of the grinding chuck) exist Figure 1 In the polishing device 1 shown, the surface shape of the pressing surface 14a of the polishing chuck 14 is a plane. However, in the polishing device used in the single-side polishing process of the wafer in which the polishing conditions are determined by the above-mentioned polishing condition determination method, the pressing surface shape of the polishing chuck is not limited to a plane, and in one embodiment, it can be a concave shape in which the central part is recessed relative to the polishing pad side than the outer periphery; in another embodiment, it can be a convex shape in which the central part protrudes relative to the polishing pad side than the outer periphery. In addition, the pressing surface of the polishing chuck is usually circular when viewed from above. The description related to the shape in the present invention and this specification allows for errors that may usually occur. For example, in addition to a perfect circle, a circle also includes a shape that has a shape error from a circle within a range that may usually occur when manufacturing a polishing chuck. Hereinafter, a polishing chuck having a concave shape in which the central part is recessed relative to the polishing pad side than the outer periphery is referred to as a "concave chuck", and a polishing chuck having a convex shape in which the central part protrudes relative to the polishing pad side than the outer periphery is referred to as a "convex chuck".

[0044] Figure 22 is a schematic cross-sectional view of a grinding chuck (concave chuck) 24 having a pressing surface having a concave shape in which the central portion is concave relative to the polishing pad side than the outer peripheral portion. Figure 2 In the figure, the direction indicated by the arrow is the polishing pad side. This is important for the following Figure 3 The same is true for the concave shape. The “deepness of the concave” is the vertical distance between the center and the periphery of the pressing surface, for example Figure 2 The depth D is shown. The recess depth may be, for example, in the range of more than 0 μm and 50 μm or less, but is not limited to this range.

[0045] Figure 3 2 is a schematic cross-sectional view of a grinding chuck (convex chuck) 34 having a pressing surface having a convex shape in which the central portion protrudes relative to the polishing pad side more than the outer peripheral portion. Regarding the convex shape, the "protrusion height" is the vertical distance between the central portion and the outer peripheral portion of the pressing surface, for example Figure 3 The height H shown is shown. The protrusion height may be, for example, in the range of more than 0 μm and 30 μm or less, but is not limited to this range.

[0046] <Specific Example of Determination of Polishing Conditions> The present inventors have conducted the following measurements and simulations while conducting intensive studies in order to set appropriate polishing conditions and to easily control the in-plane polishing amount difference in the wafer single-side polishing step.

[0047] The wafer single-side grinding process of a silicon wafer with a diameter of 300 mm was carried out using a concave chuck and a convex chuck respectively. The concave chuck used was Figure 2 The concave chuck shown has a concave depth D of 10 μm and the convex chuck used is Figure 3 The protrusion height H shown is a convex chuck of 2 μm. As the polishing pad, a polishing pad with a thickness of 0.486 mm and a Young's modulus of 0.27 MPa was used.

[0048] Figure 4 This is a graph showing the in-plane distribution of the wafer grinding amount (relative value) when a concave chuck is used and when a convex chuck is used. The grinding amount can be calculated as the difference between the wafer thickness before grinding and the wafer thickness after grinding ("wafer thickness before grinding" - "wafer thickness after grinding"). Figure 4 In the figure, the wafer grinding amount is expressed as a relative value based on the target value of the wafer grinding amount. Figure 4 The graph shown in FIG. 1 shows that when a convex chuck is used, the grinding amount of the center portion is greater than that of the outer periphery. Figure 4 The graph shown shows that the difference in the amount of polishing within the wafer surface is smaller when a concave chuck is used than when a convex chuck is used.

[0049] The inventor used Figure 5 In the two-dimensional axisymmetric model of the conceptual diagram, in the single-side grinding process of the wafer using the above-mentioned concave chuck and the single-side grinding process of the wafer using the above-mentioned convex chuck, the pressure applied to the grinding object surface of the wafer is calculated by simulation for the state where the pressure P is applied to the grinding chuck. The simulation is performed when a grinding pad with a thickness of 0.486 mm and a Young's modulus of 0.27 MPa is used. The pressure simulation is performed by pressure calculation (finite element method) using ABAQUS (general nonlinear structural analysis software) manufactured by Dassault Systemes.

[0050] In addition, in the polishing device used in the wafer single-side polishing process described above, the pressure applied to the polishing target surface of the wafer was measured using a commercially available surface pressure sheet while the platform was fixed and the same pressure P as in the above simulation was applied to the polishing chuck. In the actual measurement, the data were averaged with the number of repeated measurements N=3, and the pressure distribution averaged in the circumferential direction was obtained.

[0051] Figure 6 Graphs showing the in-plane distribution of pressure applied to the polishing target surface of a wafer when a concave chuck is used and when a convex chuck is used (actual measurement results and simulations). Figure 6 In the figure, the pressure is expressed as a relative value based on the above pressure P. Figure 6 , it can be confirmed that the calculation results in the simulation roughly reproduce the measured results. Figure 4 as well as Figure 6 It can be confirmed that when a concave chuck having a small grinding amount difference within the wafer surface is used, the pressure difference within the wafer surface is also smaller than when a convex chuck is used.

[0052] Figure 7 The circumferential average machining amount GBIR and p_max–p_min are shown. The circumferential average machining amount GBIR on the vertical axis refers to the Figure 4 The difference between the maximum and minimum values ​​of the average grinding amount in the circumferential direction. The horizontal axis p_max–p_min refers to the Figure 6 The difference between the maximum and minimum values ​​of the pressure distribution obtained by simulation is shown. In order to ensure sufficient simulation accuracy and measurement accuracy, the data after removing 5 mm from the end of the wafer is used in the calculation. Figure 7 In the figure, the left mark shows the result when a concave chuck is used, and the right mark shows the result when a convex chuck is used. Figure 7 It can be confirmed that the more uniform the pressure distribution within the wafer surface, the more uniform the grinding amount within the wafer surface.

[0053] From the above results, it can be confirmed that there is a correlation between the in-plane difference of the wafer grinding amount and the in-plane difference of the wafer grinding pressure. Figure 7 The results shown also confirm that the correlation can be a proportional relationship. Figure 7 If the target range of the chip grinding amount in-plane difference is set to "circumferential average processing amount GBIR<30nm", it can be predicted that the chip grinding amount in-plane difference within this target range can be achieved by setting the chip grinding pressure in-plane difference to "p_max–p_min<1.5kPa".

[0054] In order to study the dependence of the pressure distribution applied to the polishing target surface of the wafer on the pressing surface shape of the grinding chuck, the inventors also conducted the following simulation on the single-side polishing process of the wafer. Figure 5 The two-dimensional axisymmetric model shown in the conceptual diagram was subjected to pressure calculation by the finite element method using ABAQUS (general nonlinear structural analysis software) manufactured by Dassault Systemes.

[0055] For the wafer single-side grinding process of silicon wafers with a diameter of 300 mm, use Figure 5 The two-dimensional axisymmetric model of the conceptual diagram is shown in FIG. , and the pressure applied to the polishing object surface of the wafer is calculated by simulation using polishing chucks with various pressing surface shapes and a polishing pad with a thickness of 0.486 mm and a Young's modulus of 0.27 MPa. Figure 8 The simulation results are shown.

[0056] The grinding chucks with various pressing surface shapes are as follows: The grinding chuck with a flat pressing surface (described later) Figure 8 "flat" in the middle) Figure 2 The concave chucks shown have a concave depth D of 10 μm, 20 μm, 30 μm, and 40 μm ( Figure 8 10μm, 20μm, 30μm, 40μm in the middle). Figure 3 The protrusion height H shown is 10μm, 20μm convex chuck ( Figure 8 10μm convex and 20μm convex in the middle).

[0057] Figure 8 as well as Fig. 9 The following is a result of calculating, by simulation, the pressure applied to the polishing target surface of the wafer when polishing chucks having various pressing surface shapes are used.

[0058] Figure 8This is the calculated pressure distribution. As the pressing surface shape of the grinding chuck changes from a concave shape to a convex shape, the pressure distribution changes in the same direction. In this way, it can be confirmed that the wafer grinding pressure in-plane difference (e.g., p_max–p_min) is related to the pressing surface shape value of the grinding chuck.

[0059] Fig. 9 It is based on Figure 8 The pressure distribution in the surface obtained in the above calculation p_max–p_min is plotted against the pressing surface shape value of the grinding chuck. The pressing surface shape value is the above-mentioned depression depth or protrusion height, which is 0μm in the case of a flat surface. Fig. 9 In the figure, the dotted line L1 is a straight line passing through the three points where the pressing surface shape value of the grinding chuck is -20μm (concave 20μm), the pressing surface shape value of the grinding chuck is -30μm (concave 30μm), and the pressing surface shape value of the grinding chuck is -40μm (concave 40μm). Fig. 9 In the figure, the dotted line L2 is a straight line passing through the three points where the pressing surface shape value of the grinding chuck is 0 μm (flat), the pressing surface shape value of the grinding chuck is 10 μm (convex 10 μm), and the pressing surface shape value of the grinding chuck is 20 μm (convex 20 μm). Fig. 9 , it can be confirmed that the in-plane difference of the wafer grinding pressure is related to the pressing surface shape value of the grinding chuck, and a linear relationship holds. Specifically, it can be considered that there is a linear relationship between the in-plane difference of the wafer grinding pressure and the depth of the concave shape of the concave chuck, and it can be considered that there is a linear relationship between the in-plane difference of the wafer grinding pressure and the protrusion height of the convex shape of the convex chuck. In more detail, it can be considered that when the pressing surface shape value of the grinding chuck is -13μm to -40μm, there is a linear relationship caused by Fig. 9 The linear relationship represented by the dotted line L1 in FIG. 1 is that when the pressing surface shape value of the grinding chuck is from –13 μm to 0 μm and from 0 μm to 20 μm, there is a linear relationship between the values ​​of Fig. 9 The dotted line L2 in the figure represents the linear relationship.

[0060] As previously noted, for example, based on Figure 7 , if the target range of the wafer grinding amount in-plane difference is set to "the circumferential average processing amount GBIR<30nm", it can be predicted that the wafer grinding amount in-plane difference within the target range can be achieved by setting the wafer grinding pressure in-plane difference to "p_max-p_min<1.5kPa". Fig. 9 The linear relationship represented by the dotted line L1 and the linear relationship represented by L2 can be predicted as "p_max-p_min<1.5kPa". The predicted range of the wafer grinding pressure in-plane difference can be predicted by using a concave shape with a depression depth of 4μm or more and 21μm or less ( Fig. 9 In the embodiment, the pressing surface shape value of the grinding chuck is a concave chuck with a range of -4μm to -21μm).

[0061] In addition, Fig. 9 In the figure, dashed line L1 and dashed line L2 are shown as straight lines passing through a plurality of marks. However, the above linear relationship is not limited to the above example. For example, a plurality of marks may be linearly approximated by a well-known fitting process such as the least square method to obtain a linear function, and the above prediction may be performed based on the linear relationship represented by the linear function.

[0062] In one embodiment, the pressing surface shape of the grinding chuck can be determined by approximating the radial cross-sectional shape to a quadratic function. The approximation based on the quadratic function can be performed, for example, as follows.

[0063] Regarding the pressing surface of the grinding chuck (circular when viewed from above), the outermost peripheral position is set to the position with a radius of r=167.5mm, and the vertical distance between the center of the pressing surface and the outermost peripheral position is set to the recessed depth of the concave shape for a concave chuck and the protrusion height of the convex shape for a convex chuck. In addition, the protrusion height is expressed as a positive (+) value and the recessed depth is expressed as a negative (–) value. If the pressing surface shape value (specifically, the protrusion height or the recessed depth) is determined, the pressing surface shapes of a plane, a protrusion height of 10μm, a protrusion height of 20μm, a recessed depth of 10μm, a recessed depth of 20μm, a recessed depth of 30μm, and a recessed depth of 40μm can be determined as follows: Use the following formula as a quadratic function: "y=a*r 2 +b", calculate the vertical distance from the center of the pressing surface in each part of the pressing surface as "y", and apply the calculated value to the two-dimensional axisymmetric model. In the above formula, b represents the relative height or relative depth. If the pressing surface shape value is set to C, a is calculated by a=C / (167.5) 2 Specifically, a and b in the above formula for calculating the shape of the pressing surface for calculating each pressing surface shape value are values ​​shown in the following Table 1. In Table 1, "E-07" and the like are index expressions as known in the art. Fig.10 The radial cross-sectional shape of the pressing surface of the grinding chuck produced by using a and b shown in Table 1 and the calculated value of y calculated by the above formula is plotted in the radial direction.

[0064] [Table 1] As described above, as a result of the inventor's in-depth research, it was newly discovered that the wafer grinding amount in-plane difference is related to the wafer grinding pressure in-plane difference, and the wafer grinding pressure in-plane difference is related to the pressing surface shape value of the grinding chuck. Based on these correlations, according to the following steps, it is possible to easily determine the grinding conditions predicted to achieve the desired wafer grinding amount in-plane difference.

[0065] First, the target range of the wafer grinding amount in-plane difference is set. The target range of the wafer grinding amount in-plane difference can be set according to the desired quality of the wafer manufactured by actual grinding. From the perspective of performing a single-side grinding process of a wafer with a smaller grinding amount in-plane difference, it is preferred to set the target range of the wafer grinding amount in-plane difference to be smaller. Actual grinding refers to the grinding actually performed to manufacture a product.

[0066] After setting the above target range, based on the correlation between the wafer grinding amount in-plane difference and the wafer grinding pressure in-plane difference, the predicted range of the wafer grinding pressure in-plane difference that is predicted to achieve the above target range of wafer grinding amount in-plane difference is determined.

[0067] Furthermore, based on the correlation between the wafer grinding pressure in-plane difference and the pressing surface shape value of the grinding chuck, a range of pressing surface shape values ​​of the grinding chuck that is predicted to be able to achieve the wafer grinding pressure in-plane difference within the above-mentioned predicted range is determined.

[0068] For example, in one embodiment, the thickness and hardness of the polishing pad are taken as specific values, and through the above-mentioned simulation, the correlation information (such as a graph, a relational expression, etc.) between the wafer grinding amount in-plane difference and the wafer grinding pressure in-plane difference and the correlation information (such as a graph, a relational expression, etc.) between the grinding pressure in-plane difference and the pressing surface shape value of the grinding chuck can be obtained. Then, based on the obtained correlation information, according to the above steps, the pressing surface shape value range of the grinding chuck that is predicted to achieve the desired wafer grinding amount in-plane difference can be determined.

[0069] In one embodiment, the pressing surface shape value range of the grinding chuck may be determined based on one of the thickness and hardness of the grinding pad. This will be described in more detail below.

[0070] Fig.11 Graphs showing the dependence of the wafer polishing pressure in-plane difference on the polishing pad thickness and hardness. Fig.11 The graph is created as follows.

[0071] The simulation described above was performed using a polishing pad having a thickness (hereinafter referred to as "reference thickness") of 0.486 mm and a Young's modulus (hereinafter referred to as "reference hardness") of 0.27 MPa. The simulation described above was performed by changing the thickness or hardness (specifically, Young's modulus) of the polishing pad. Specifically, the pressure distribution applied to the wafer was calculated when the thickness and Young's modulus of the polishing pad were assigned ±20% of the reference value (reference thickness, reference hardness). Fig.11 The upper limits of the depression depth and protrusion height are plotted at p_max–p_min=1.5 kPa.

[0072] like Fig.11 As shown in FIG. 1 , the thinner the polishing pad is and the harder the polishing pad is, the narrower the range of the pressing surface shape value (depression depth or protrusion height) of the polishing chuck that satisfies “p_max–p_min<1.5 kPa” becomes. Fig.11 In the example shown, the range of the pressing surface shape value of the grinding chuck that satisfies "p_max−p_min<1.5 kPa" is 5 μm or more and 20 μm or less in the concave shape.

[0073] From the above results, it can be confirmed that the thinner the thickness of the grinding pad is, the more narrow the range of the pressing surface shape value of the grinding chuck that is predicted to achieve the wafer grinding pressure surface difference of the predicted range is preferably set to. In addition, it can be confirmed that the harder the hardness of the grinding pad is, the more narrow the range of the pressing surface shape value of the grinding chuck that is predicted to achieve the wafer grinding pressure surface difference of the predicted range is preferably set to.

[0074] Therefore, for example, after determining the thickness of the grinding pad used in actual grinding, when the determined thickness of the grinding pad is thinner than a predetermined reference thickness, the range of the depression depth of the concave shape of the concave chuck or the range of the protrusion height of the convex shape of the convex chuck can be determined as a narrower range. For example, after determining the hardness of the grinding pad used in actual grinding, when the determined hardness of the grinding pad is harder than a predetermined reference hardness, the range of the depression depth of the concave shape of the concave chuck or the range of the protrusion height of the convex shape of the convex chuck can be determined as a narrower range. The above-mentioned reference thickness and reference hardness can be, for example, the thickness and hardness used in the simulation for obtaining the correlation information recorded above.

[0075] <Method for Manufacturing Wafer Having Polished Surface> One embodiment of the present invention relates to a method for manufacturing a chip having a grinding surface, the manufacturing method comprising: determining the grinding conditions by the above-mentioned grinding condition determination method; and grinding a single side of the chip by a grinding device including a grinding chuck having a pressing surface with a shape within a determined pressing surface shape value range.

[0076] In the above manufacturing method, in addition to grinding a single side of a wafer by a grinding device including a grinding chuck having a pressing surface with a shape within the pressing surface shape value range determined as described above, a known technique related to a manufacturing method of a wafer having a grinding surface can also be applied. The details of the wafer to be ground, the structure of the grinding device, the grinding process, etc. can be referred to the above description.

[0077] In one embodiment of the manufacturing method, based on the determination results described above, a grinding chuck having a concave pressing surface with a depression depth of 5 μm or more and 20 μm or less can be used. In addition, in one embodiment, based on the simulation results described above, as a grinding pad, a grinding pad having a thickness of 0.864 mm ± 20% and a Young's modulus of 0.27 MPa ± 20% can be used.

[0078] In addition, one embodiment of the present invention relates to a method for manufacturing a wafer having a polished surface, the method comprising polishing a single side of the wafer by a polishing device, the polishing device comprising: a polishing chuck having a concave pressing surface with a recessed depth of 5 μm or more and 20 μm or less; and a polishing pad having a thickness of 0.864 mm ± 20% and a Young's modulus of 0.27 MPa ± 20%. For details of the above-mentioned manufacturing method, please refer to the above description.

[0079] <Wafer Single-Side Grinding System> One embodiment of the present invention relates to a single-side polishing system for a wafer, comprising: a polishing device, which includes at least a platform, a polishing pad arranged on the platform, and a polishing chuck arranged above the polishing pad; and a polishing condition determination unit, which determines the polishing conditions by the above-mentioned polishing condition determination method.

[0080] In the above-mentioned grinding condition determination unit, for example, if the target range of the wafer grinding amount in-plane difference is input, then based on the correlation information (such as a graph, a relational expression, etc.) between the wafer grinding amount in-plane difference and the wafer grinding pressure in-plane difference obtained as described above and the correlation information (such as a graph, a relational expression, etc.) between the grinding pressure in-plane difference and the pressing surface shape value of the grinding chuck, it is possible to determine the pressing surface shape value range of the grinding chuck that is predicted to achieve the wafer grinding pressure in-plane difference within the predicted range. In addition, it is also possible to determine the pressing surface shape value range of the grinding chuck that is predicted to achieve the wafer grinding pressure in-plane difference within the predicted range based on one or both of the thickness and hardness of the grinding pad. Various calculations for determining the pressing surface shape value range of the grinding chuck can be performed using known calculation software.

[0081] In the above system, in the above grinding condition determination unit, the pressing surface shape value of the grinding chuck can be determined, and further, as described above, by approximating the radial cross-sectional shape to a quadratic function, the pressing surface shape of the grinding chuck can be determined. For example, a grinding chuck having the pressing surface shape determined in this way can be selected from a plurality of grinding chucks, and automatically or manually installed in a grinding device to implement a single-side grinding process of a wafer.

[0082] One embodiment of the present invention is useful in the technical field of semiconductor wafers such as silicon wafers.

Claims

1. A method for determining grinding conditions, grinding a single side of a wafer by a grinding device, The grinding device at least comprises a platform, a grinding pad disposed on the platform, and a grinding chuck disposed above the grinding pad, and is characterized in that: The method for determining the grinding conditions includes: Setting the target range of wafer grinding amount intra-plane difference; Determining a predicted range of wafer grinding pressure in-plane difference that is predicted to be able to achieve the target range of wafer grinding amount in-plane difference based on a correlation between the wafer grinding amount in-plane difference and the wafer grinding pressure in-plane difference; and Based on the correlation between the wafer polishing pressure in-plane difference and the pressing surface shape value of the polishing chuck, a range of pressing surface shape values ​​of the polishing chuck that is predicted to be able to achieve the wafer polishing pressure in-plane difference within the predicted range is determined.

2. The method for determining grinding conditions according to claim 1, characterized in that: The correlation between the in-plane difference of the wafer grinding amount and the in-plane difference of the wafer grinding pressure is a proportional relationship.

3. The method for determining grinding conditions according to claim 1, characterized in that: The pressing surface of the grinding chuck is concave in shape with the center portion being recessed relative to the grinding pad side compared to the outer periphery, or convex in shape with the center portion being protruding relative to the grinding pad side compared to the outer periphery. The determined pressing surface shape value range is a depression depth range of the concave shape or a protrusion height range of the convex shape.

4. The method for determining grinding conditions according to claim 3, characterized in that: The correlation between the wafer grinding pressure in-plane difference and the pressing surface shape value of the grinding chuck is a linear relationship between the wafer grinding pressure in-plane difference and the recess depth or a linear relationship between the wafer grinding pressure in-plane difference and the protrusion height.

5. The method for determining grinding conditions according to claim 3, characterized in that: The method for determining the grinding conditions further includes determining the pressing surface shape of the grinding chuck by approximating the radial cross-sectional shape to a quadratic function.

6. The method for determining grinding conditions according to claim 3, characterized in that: The method for determining the polishing conditions further determines a depression depth range of the concave shape or a protrusion height range of the convex shape based on one or both of a thickness and a hardness of the polishing pad.

7. The method for determining grinding conditions according to claim 6, characterized in that: The method for determining the grinding conditions also includes: Determining the thickness of the polishing pad used in actual polishing; and When the determined thickness of the polishing pad is thinner than a predetermined reference thickness, the recessed depth range of the concave shape or the protrusion height range of the convex shape is determined to be a narrower range.

8. The method for determining grinding conditions according to claim 6, characterized in that: The method for determining the grinding conditions also includes: Determine the hardness of the polishing pad used in actual polishing; and When the determined hardness of the polishing pad is harder than a predetermined reference hardness, the recess depth range of the concave shape or the protrusion height range of the convex shape is determined to be a narrower range.

9. A method for manufacturing a wafer having a polished surface, comprising: Determining the grinding conditions by the method for determining grinding conditions according to any one of claims 1 to 8; as well as A single side of the wafer is ground by a grinding device including a grinding chuck having a pressing surface having a shape within the determined pressing surface shape value range.

10. The manufacturing method according to claim 9, characterized in that: The grinding chuck has a concave pressing surface with a concave depth of 5 μm or more and 20 μm or less.

11. The manufacturing method according to claim 9, characterized in that: The grinding device includes a grinding pad having a thickness of 0.864 mm ± 20% and a Young's modulus of 0.27 MPa ± 20%.

12. The manufacturing method according to claim 9, characterized in that: The wafer is a semiconductor wafer.

13. The manufacturing method according to claim 12, characterized in that: The semiconductor wafer is a silicon wafer.

14. A wafer single-side grinding system, characterized in that: have: The grinding device at least comprises a platform, a grinding pad disposed on the platform, and a grinding chuck disposed above the grinding pad; as well as The polishing condition determination unit determines the polishing condition by the polishing condition determination method according to any one of claims 1 to 8.

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