WAFER PRODUCTION PROCESS

Abstract

Manufacturing process for a wafer (W) produced by slice-cutting a monocrystalline ingot using a wire saw machine and grinding the wafer (W), the process comprising: a first resin application grinding step (S2); a second resin application grinding step (S3); and a third surface grinding step (S4), wherein The first resin application grinding step (S2) includes: a first coating layer formation step (S21) to apply a curing material to an entire second surface (W2) of the wafer (W) to form a flat first coating layer (RH1); a first surface grinding step (S22) to place the wafer (W) on a table (21) of a grinding machine such that the first coating layer (RH1) is in contact with a reference surface (211) of the table (21), and subsequent surface grinding of a first surface (W1) of the wafer (W) by the grinding machine; and a first coating layer removal step (S23) to remove the first coating layer (RH1) after the first surface grinding step (S22) from the second surface (W2) of the wafer (W); the second resin application grinding step (S3) includes: a second coating layer formation step (S31) to apply the curing material to the entire first surface (W1) of the wafer (W) to form a flat second coating layer (RH2); a second surface grinding step (S32) to place the wafer (W) onto the table (21) of the grinding machine, such that the second coating layer (RH2) is in contact with the reference surface (211) of the table (21), and subsequent surface grinding of the second surface (W2) of the wafer (W) by the grinding machine; and a second coating layer removal step (S33) to remove the second coating layer (RH2) after the second surface grinding step (S32) from the first surface (W1) of the wafer (W), and the third surface grinding step (S4) includes: Placing the wafer (W) on the table (21) such that a recently surface-ground surface is in contact with the reference surface (211) of the table (21) of the grinding machine, and subsequent surface grinding of a surface of the wafer (W) opposite the surface in contact with the reference surface (211) by the grinding machine.

Description

TECHNICAL FIELD

[0001] The present invention relates to a manufacturing method of a wafer. TECHNICAL BACKGROUND

[0002] To create a tiny structure through photolithography, it is necessary to planarize a wafer surface. In particular, it has recently been proposed to reduce so-called "nanotopography," which is a surface undulation with components having a wavelength λ in the range of 0.2 mm to 20 mm and a PV (peak-to-valley) value in the range of 0.1 µm to 0.2 µm, to improve wafer flatness (see, for example, JP H08 - 66850 A, JP 2015 - 8247 A).

[0003] A manufacturing method disclosed in JP H08 - 66 850 A comprises a resin application step of completely covering a first surface of a wafer produced by slicing an ingot, a step of grinding a second surface of the wafer while holding the first surface, and then a step of grinding the first surface of the wafer while holding the second surface.

[0004] In a manufacturing method disclosed in JP 2015-8247A, after a curable resin is applied to a second surface of a wafer and the curable resin is flattened and cured, a first surface of the wafer is ground while holding the flat surface of the curable resin, and then the curable resin is removed. It should be noted that this technique is sometimes referred to as "resin deposition grinding" hereinafter. Next, the second surface is ground while holding the first surface of the wafer that has undergone resin deposition grinding. Then, the resin deposition grinding and the surface grinding of the surface not ground by resin deposition grinding are repeated.

[0005] Meanwhile, in order to slice a monocrystalline ingot, it is proposed to use a fixed abrasive grain wire saw in which abrasive grains are fixed to an outer peripheral surface of the wire, instead of a loose abrasive grain process of supplying a cutting fluid containing abrasive grains, thereby reliably supplying the abrasive grains near the cylinder center of the monocrystalline ingot (see, for example, JP 2010 - 74 056 A).

[0006] DE 11 2014 000 276 T5 discloses a wafer processing method in which a reference surface is created by grinding a wafer surface and applying a hardenable material to the entire wafer surface, so that simultaneous planarization of both wafer surfaces is possible. SUMMARY OF THE INVENTION PROBLEM(S) TO BE SOLVED BY THE INVENTION

[0007] In the grinding step by applying the resin as disclosed in JP H08 - 66 850 A, since the resin is applied while the undulation and warpage of the wafer are present, the undulation remains due to the difference in the resin thickness, which causes a difference in the elastic deformation of the resin.

[0008] According to the disclosure of JP 2015-8247 A, the undulation is removed by repeating the sequence of resin deposition grinding and surface grinding. However, repeating the grinding of both wafer surfaces requires at least four grinding steps, resulting in low productivity.

[0009] The surface conditions of the wafer at the time of slicing were not considered a major problem because, even if the undulation remains on the wafer surface, the wafer is ground to remove the undulation after a flat reference surface is created by the resin applied to the wafer surface during the resin deposition step. However, it was found through an experiment by the present inventors that even after the resin deposition process, as disclosed in JP H08-66850 A, the nanotopography quality of the wafer surface remains insufficient after mirror polishing.

[0010] In addition, it was found that the use of the wire with fixed abrasive grain in the in-slicing step as in JP 2010 - 74 056 A causes a large process damage to the wafer and consequently a very large corrugation on the wafer surface after the in-slicing step, which leads to an additional deterioration of the nanotopography.

[0011] An object of the invention is to provide a wafer manufacturing method capable of manufacturing a wafer having excellent nanotopography characteristics without impairing productivity. MEANS FOR SOLVING THE PROBLEM(S)

[0012] As a result of dedicated studies to achieve the above object, the inventors have found that when a wafer surface is surface ground after being coated with a curing material, the productivity of the wafer can be improved and the nanotopography quality of the resulting wafer can be improved by, instead of surface grinding only once on one surface after the curing material is applied to an opposite surface, in addition to the initial surface grinding, performing a second surface grinding on the opposite surface after the curing material is applied to the one surface, and additionally performing a third surface grinding on the surface ground in the initial surface grinding, thereby achieving the invention.

[0013] Specifically, after a slicing step, a first surface of a wafer is surface ground, and a second surface thereof is coated with a curing material. After the curing material on the second surface is removed, the second surface is then surface ground, and the first surface is coated with the curing material. After the curing material on the first surface is removed, the first surface is further surface ground. Through the above process, the nanotopography quality can be improved without compromising productivity.

[0014] A first aspect of the invention is a manufacturing method for a wafer produced by slicing a monocrystalline ingot using a wire saw and grinding the wafer, the method comprising: a first resin deposition grinding step; a second resin deposition grinding step; and a third surface grinding step, wherein the first resin deposition grinding step comprises: a first coating layer forming step of applying a curing material to an entire second surface of the wafer to form a flat first coating layer; a first surface grinding step of placing the wafer on a table of a grinding machine such that the first coating layer is in contact with a reference surface of the table, and then surface grinding a first surface of the wafer by the grinding machine;and a first coating layer removal step for removing the first coating layer from the second surface of the wafer after the first surface grinding step. The second resin deposition grinding step comprises: a second coating layer formation step for applying the curing material to the entire first surface of the wafer to form a flat second coating layer; a second surface grinding step for placing the wafer on the table of the grinding machine so that the second coating layer is in contact with the reference surface of the table, and then surface grinding the second surface of the wafer by the grinding machine;and a second coating layer removing step for removing the second coating layer after the second surface grinding step from the first surface of the wafer, and wherein the third surface grinding step comprises: placing the wafer on the table so that a last surface-ground surface is in contact with the reference surface of the table of the grinding machine, and then surface grinding a surface of the wafer opposite the surface in contact with the reference surface by the grinding machine;

[0015] According to the above first aspect of the invention, a wafer having excellent nanotopography quality can be manufactured without impairing productivity.

[0016] A second aspect of the invention is a manufacturing method of a wafer based on the first aspect, wherein between the second resin deposition grinding step and the third surface grinding step: the first resin deposition grinding step is only additionally performed; or at least one repetition of the first resin deposition grinding step and the second resin deposition grinding step is additionally performed in this order; or at least one repetition of the first resin deposition grinding step and the second resin deposition grinding step is performed in this order and then the first resin deposition grinding step is performed.

[0017] According to the above second aspect of the invention, a wafer having further excellent nanotopography quality can be manufactured by performing the first resin deposition grinding step and the second resin deposition grinding step a plurality of times.

[0018] A third aspect of the invention is a wafer manufacturing method in which a grinding allowance in the first resin deposition grinding step is equal to or larger than a grinding allowance in the third surface grinding step.

[0019] According to the above third aspect of the invention, a wafer having excellent nanotopography quality can be manufactured by setting the grinding allowance in the first resin deposition grinding step equal to or larger than the grinding allowance in the third surface grinding step, even with a small grinding allowance in total.

[0020] A fourth aspect of the invention is a manufacturing method based on the first to third aspects, in which the wire saw machine slices the monocrystalline ingot using a wire with fixed abrasive grain.

[0021] According to the fourth aspect of the invention, even when a wafer having a large corrugation is used, which is obtained particularly by using a wire saw with fixed abrasive grain, the corrugation can be minimized by the manufacturing process, so that a wafer having excellent nanotopography quality can be manufactured.

[0022] A fifth aspect of the invention is an invention based on the first to fourth aspects, wherein a diameter of the wafer is 300 mm or more, and particularly 450 mm or more.

[0023] According to the above fifth aspect of the invention, a wafer having excellent nanotopography quality can be manufactured even when the diameter of the wafer is 300 mm or more, or particularly 450 mm or more, even with a small grinding allowance as a whole. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a flowchart showing an overall procedure of a wafer manufacturing method according to an exemplary embodiment of the invention. Fig. Figure 2 illustrates steps of the wafer manufacturing process. Fig. Figure 3 illustrates steps of the wafer manufacturing process according to the Fig. 2 steps shown. Fig. 4 illustrates the manufacturing process of the wafer according to Example 1 of the invention. Fig. Figure 5 illustrates steps of the wafer manufacturing process according to Comparisons 1 and 2 of the invention. Fig. Figure 6 illustrates steps of the wafer manufacturing process according to Comparison 2 according to the Fig. 5 steps shown. Fig. Figure 7 is a nanotopography map of Example 1 and Comparisons 1, 2 after a mirror polishing step. Fig. Figure 8 illustrates nanotopography measurements of Example 1 and Comparisons 1, 2. DESCRIPTION OF THE EMBODIMENT(S)

[0024] Exemplary embodiment(s) of the invention are described below with reference to the accompanying drawings.

[0025] As in Fig. 1, a wafer manufacturing method includes a slicing step S1 for slicing a monocrystalline ingot using a wire saw machine to manufacture a thin disc-shaped wafer, a first resin deposition grinding step S2, a second resin deposition grinding step S3, and a third surface grinding step S4.The first resin deposition grinding step S2 includes: a first coating layer forming step S21 of applying the curing material to an entire second surface of the wafer to form a flat first coating layer; a first surface grinding step S22 of placing the wafer on a table so that the first coating layer is in contact with a reference surface of the table of the grinding machine, and then surface grinding the first surface of the wafer with the grinding machine; and a first coating layer removing step S23 of removing the first coating layer from the second surface of the wafer after the first surface grinding step S22.The second resin deposition grinding step S3 includes: a second coating layer forming step S31 of applying the curing material to the entire first surface of the wafer to form a flat second coating layer; a second surface grinding step S32 of placing the wafer on the table so that the second coating layer is in contact with the reference surface of the table of the grinding machine, and then surface grinding the second surface of the wafer with the grinding machine; and a second coating layer removing step S33 of removing the second coating layer from the first surface of the wafer after the second surface grinding step S32.In the third surface grinding step S4, the wafer is placed on the table so that the surface subjected to surface grinding for the last time is in contact with the reference surface of the table of the grinding machine, and then the surface of the wafer opposite the surface in contact with the reference surface is surface ground by the grinding machine.

[0026] Note that a lapping step may be performed in a period between the slicing step S1 and the first resin deposition grinding step S2. Further, a step of chamfering an outer periphery of the wafer, which is not specifically described, may be performed in any period from a time point after the slicing step S1 to a time point after the third surface grinding step S4, and by any number of times (ie, once or more). For example, a first chamfering may be performed after the slicing step S1, and a second chamfering may be performed after the third surface grinding step S4 for a larger chamfering amount than the first chamfering.

[0027] Furthermore, in the wafer manufacturing method in the exemplary embodiment, both the first resin deposition grinding step S2 and the second resin deposition grinding step S3 are only required to be performed at least once. For example, between the second resin deposition grinding step S3 and the third surface grinding step S4, only the first resin deposition grinding step S2 may be additionally performed, the first resin deposition grinding step S2 and the second resin deposition grinding step S3 may be repeatedly performed at least once in this order, or after the first resin deposition grinding step S2 and the second resin deposition grinding step S3 are repeatedly performed at least once in this order, the first resin deposition grinding step S2 may be performed as the last step.It should be noted that in the third surface grinding step S4, the surface that was not subjected to surface grinding in the first resin application grinding step S2 or the second resin application grinding step S3, which are performed immediately before the third surface grinding step S4, is surface ground.

[0028] Satisfactory nanotopographic characteristics of the wafer surface can be achieved by dividing the resin deposition grinding step into multiple resin deposition grinding steps for the top and bottom surfaces of the wafer. Although it is difficult to completely remove the undulation component present on the wafer in a single resin deposition grinding step to improve the nanotopographic characteristics, it is specifically found that repeating the resin deposition grinding steps each time the resin deposition grinding step is repeated can improve the nanotopographic characteristics. As described above, repeating the resin deposition grinding steps can reduce the undulation on the wafer surface to improve the nanotopographic characteristics of the wafer surface.

[0029] Next, the wafer manufacturing process will be described with reference to Fig. 2 described in detail.

[0030] Fig. Figure 2(A) shows the states of a wafer W produced by slicing an ingot using the wire saw with fixed abrasive grain.

[0031] A plurality of wafers W can be produced from the ingot in a single slicing step using a known multi-wire sawing machine (not shown). The multi-wire sawing machine includes a guide roller provided with multiple grooves for guiding multiple wires, a roller for rotating the wires, and the multiple wires of ultra-thin steel wires wound around the guide roller and the roller. The roller rotates at high speed, and an object to be cut is pressed against the multiple wires exposed between the guide roller and the roller to cut the object into multiple pieces.

[0032] The multi-wire sawing machine is categorized into a fixed abrasive grain machine and a loose abrasive grain machine depending on the use of abrasive grains for slicing. The fixed abrasive grain machine uses steel wires to which diamond abrasive grains or the like are bonded by vapor deposition or the like. In the loose abrasive grain machine, the wires are used while applying a slurry containing a mixture of abrasive grains and oil solution. The fixed abrasive grain machine, in which the wires with the bonded abrasive grains themselves slice the object, requires a short slicing time and is excellent in terms of productivity. Furthermore, the slurry, which may contain chips as a result of slicing, is not used in the fixed abrasive grain machine and therefore does not need to be disposed of.Accordingly, the machine with fixed abrasive grain is environmentally friendly and economical.

[0033] Both machine types are usable in the exemplary embodiment. However, the fixed-grain wire saw is preferable in terms of environmental and economic benefits. It should be noted that using the fixed-grain wire saw causes significant machining damage to the wafer surface and results in large undulations being generated on the wafer surface after the slicing step, which may result in unfavorable nanotopography. However, using the method of the present invention, a wafer with excellent nanotopography characteristics (i.e., with a low nanotopography value) can be manufactured.

[0034] As in Fig. As shown in Fig. 2(A), cyclically occurring undulations W11, W12 are present on a first surface W1 and a second surface W2 of the wafer W after the slicing step by the wire saw with fixed abrasive grain and a lapping step.

[0035] Fig. 2(B) shows an example of a holding press device 10 used in the first coating layer forming step S21. First, a curing material R forming a coating layer is dropped onto a highly planarized plate 11 of the holding press device 10. While the first surface W1 of the wafer W is sucked and held on a holding surface 121 of a holder 12, the holding surface 121 is moved downward to press the second surface W2 of the wafer W against the curing material R. Thereafter, while the pressure applied to the holding surface 121 is released to eliminate elastic deformation of the undulations W11, W21 remaining on the wafer W, the curing material R is cured on the second surface W2 of the wafer W to form a first coating layer RH1.The surface of the first coating layer RH1 in contact with the plate 11 is highly planarized by the above step, thereby defining a reference surface RH11 for grinding the first surface W1 of the wafer W.

[0036] The curable material R can be applied to the wafer W, for example by: spin coating, wherein the curable material R is dropped onto the second surface W2 of the wafer W with the second surface W2 facing upwards and the wafer W is rotated to distribute the curable material R over the entire second surface W2; screen printing, in which a screen film is placed on the second surface W2, the curable material R is placed on the screen film and the curable material R is compressed using a squeegee; applying the curable material R to the entire second surface W2 by spraying by electrospray deposition or the like and then bringing the coated surface into contact with and pressing it against the highly planarized plate 11;and, in addition to the above processes, processes capable of highly planarizing a surface of the wafer W with the curing material R. The curing material R is preferably a thermosetting resin, a thermoreversible resin, a photosensitive resin, or the like in terms of peelability after processing. In particular, the photosensitive resin is also preferable in that no heat stress is applied. In the exemplary embodiment, a UV-curable resin is used as the curing material R. Specific examples of the material for the curing material R include a synthetic rubber and an adhesive (e.g., wax).

[0037] Fig. 2(C) shows an example of a surface grinder 20 used in the first surface grinding step S22. Initially, the reference surface RH11 of the first coating layer RH1 formed in the first coating layer forming step S21 is placed on a highly planarized reference surface 211 of a vacuum chuck 21 of the surface grinder 20, and is sucked and held by it. Subsequently, a grinding wheel 23 provided with a grindstone 22 on one side is placed on top of the wafer W placed on the reference surface 211. Then, while the grindstone 22 is kept in contact with the first surface W1 of the wafer W, the grinding wheel 23 and the vacuum chuck 21 are rotated to grind the first surface W1 of the wafer W.

[0038] Fig. Figure 3(D) shows the first coating layer removal step S23. The first coating layer RH1 is peeled off the wafer W, whose first surface W1 is surface ground in the first surface grinding step S22. The first coating layer RH1 can be chemically removed using a solvent.

[0039] At this time, the undulation W11 still remains on the surface-ground first surface W1 of the wafer W, although it has been slightly reduced by surface grinding. It is speculated that this is because the thickness of the first coating layer RH1 varies depending on parts of the wafer surface due to the size of the undulation W21, so any difference in the elastic deformation of the parts of the wafer caused by the pressure applied during surface grinding is expressed as the residual undulation W11.

[0040] Subsequently, the second coating layer forming step S31 for forming the second coating layer on the first surface W1 is carried out using the same machine as that in the Fig. 2(B), the second surface grinding step S32 for surface grinding the second surface W2 using the same machine as that shown in the first coating layer forming step S21 shown in Fig. 2(C) and the second coating layer removing step S33 for peeling the second coating layer from the first surface W1 as in the Fig. 3(D) is performed. In other words, the second resin application grinding step S3 is performed.

[0041] Fig. 3(E) shows an example of the third surface grinding step S4. The surface grinding machine is the same as the surface grinder 20 used in the first surface grinding step S22. For example, when the second resin deposition grinding step S3 is performed immediately before the third surface grinding step S4, the second surface W2 of the wafer W, which has undergone surface grinding in the second surface grinding step S32, is directly placed on the reference surface 211 of the vacuum chuck 21 and is sucked and held by it, and the first surface W1 of the wafer W is ground. Thus, the wafer W whose both surfaces are highly planarized, as shown in FIG. Fig. 3(F).

[0042] It should be noted that the first resin application grinding step S2 and / or the second resin application grinding step S3 may further be performed between the second resin application grinding step S3 and the third surface grinding step S4.

[0043] For example, when the third surface grinding step S4 is performed after the first resin deposition grinding step S2 and the second resin deposition grinding step S3 are repeated three times in this order, the grinding allowance in each grinding step is 15 to 30 µm in the initial first surface grinding step S22, 20 to 40 µm in the initial second surface grinding step S32, 5 to 10 µm in the secondary first surface grinding step S22, and 5 to 10 µm in the secondary and tertiary second surface grinding steps S32 and the tertiary first surface grinding step S22. Both surfaces of the wafer W that have undergone the third surface grinding step S4 and are therefore highly planarized exhibit improved nanotopography characteristics each time the grinding step is performed.The frequency of resin deposition grinding steps is three (two first resin deposition grinding steps S2 and one second resin deposition grinding step S3) or more and can be determined depending on the required nanotopography characteristics. Examples

[0044] Next, the example of the invention and comparisons are described in detail below. It should be noted that the wafers W used in Example 1 and Comparisons 1 and 2 are 300 mm diameter wafers W obtained by slicing a monocrystalline silicon ingot under the same conditions using a wire saw with fixed abrasive grain. Example 1

[0045] The states of the wafer in the respective steps of Example 1 of the invention are shown in Fig. 4. The processing steps of Example 1 are described with reference to Fig. 4 described.

[0046] As in Fig. As shown in Figure 4(B), a UV-curable resin was prepared according to the method described in Fig. 4(A), the first coating layer RH1 is applied and cured to the second surface W2 of the wafer W in the slicing step S1 shown in FIG. 4(A), thereby forming the first coating layer RH1 having the flat reference surface RH11 (first coating layer forming step S21). Note that the first coating layer RH1 formed on the second surface W2 may initially be formed on the first surface W1. When the first coating layer RH1 is formed on the first surface W1, the second surface W2 and the first surface W1 are interchanged in the following description.

[0047] Subsequently, with the reference surface RH11 of the first coating layer RH1 sucked and held by the vacuum chuck 21, the first surface W1 of the wafer W was surface ground by a first grinding allowance of 15 µm (to a plane indicated by a dashed line P1) (first surface grinding step S22). Then, as shown in Fig. 4(C), the first coating layer RH1 is peeled off (first coating layer removing step S23).

[0048] Next, as in Fig. 4(D), after the wafer W, which has undergone the first resin application grinding step S2, is turned over (first turning over step), a UV-curable resin is applied and cured on the first surface W1 of the wafer W to form the second coating layer RH2 having the flat reference surface RH21, as shown in Fig. 4(E) (second coating layer formation step S31). Then, with the reference surface RH21 sucked and held by the vacuum chuck 21, the second surface W2 of the wafer W was surface ground by a second grinding allowance of 20 µm (to a plane indicated by a dashed line P2) (second surface grinding step S32). Then, as shown in Fig. 4(F), the second coating layer RH2 is peeled off (second coating layer removing step S33).

[0049] Subsequently, after the wafer W which has undergone the second resin deposition grinding step S3 was turned over as shown in Fig. 4(G) (second turning step), when the second surface W2 is sucked and held by the vacuum chuck 21 after the second resin deposition grinding step S3, the first surface W1 of the wafer W is surface ground by a third grinding allowance of 5 µm (to a plane indicated by a dashed line P3) (third surface grinding step S4).

[0050] The entire process was thus completed to obtain the wafer W of Example 1, both surfaces of which were highly planarized, as shown in Fig. 4(H). Comparison 1

[0051] The states of the wafer in the respective steps of Comparison 1 are shown in Fig. 5. In Comparison 1, the steps in the first resin application grinding step S2, the second resin application grinding step S3, and the third surface grinding step S4 in Example 1 were performed except for the second coating layer forming step S31, the second coating layer removing step S33, and the third surface grinding step S4.

[0052] The Fig. 5(A) to 5(D) correspond to the Fig. 4(A) to 4(D) except that the second coating layer forming step S31 is not performed in the second resin application grinding step S3. According to the Fig. 5(A) to 5(D), when the first surface W1 having undergone the first surface grinding step S22 is sucked and held by the vacuum chuck 21, the second surface W2 of the wafer W has been surface ground to the plane indicated by the dashed line P2, as shown in Fig. 5(D) (second surface grinding step S32), whereby a wafer W of Comparison 1 is obtained as shown in Fig. 5(E). The grinding allowances in the first surface grinding step S22 and the second surface grinding step S32 were 20 µm each. Comparison 2

[0053] The states of the wafer in the respective steps of Comparison 2 are shown in Fig. 6. In Comparison 2, the steps in Comparison 1 were repeated two or more times.

[0054] At the beginning, the steps of Comparison 1 were carried out, which are described in the Fig. 5(A) to 5(E). It should be noted that the grinding allowances in the first surface grinding step S22 and the second surface grinding step S32 in Comparison 2 were each 15 µm. Next, after the wafer W was turned over, as shown in Fig. 6(F) (turning step), the second coating layer RH2 is formed on the second surface W2 of the wafer W with a UV-curable resin as shown in Fig. 6(G) (second coating layer formation step). Subsequently, with the reference surface RH21 of the second coating layer RH2 sucked and held by the vacuum chuck 21, the first surface W1 of the wafer W was surface ground by a third grinding allowance of 5 µm (to the plane indicated by the dashed line P3) (third surface grinding step). Then, as shown in Fig. 6(H), the second coating layer RH2 was peeled off (second coating layer removal step). Then, with the first surface W1 having undergone the third surface grinding being sucked and held by the vacuum chuck 21, the second surface W2 of the wafer W was surface ground by a grinding allowance of 5 µm (to the plane indicated by the dashed line P4) (fourth surface grinding step), thereby obtaining a wafer W of Comparison 2 as shown in Fig. 6(J). Evaluation test 1

[0055] It was examined how the surface textures of the wafer W in Example 1 and Comparisons 1, 2 affect the nanotopography on the wafer surface after subsequent mirror polishing.

[0056] Specifically, after the upper and lower surfaces of each of the wafers W obtained in Example 1 and Comparisons 1, 2 were roughly polished using a double-sided polishing machine, final polishing was applied to the surface of each of the wafers using a single-sided polishing machine to prepare wafers W whose surfaces were mirror-polished (conventional mirror polishing). Fig. Figure 7 is a nanotopography map showing height difference measurements in each of the mirror-polished wafer surfaces, measured using an optical interferometric flatness meter (Wafersight 2, manufactured by KLA Tencor Corporation), visualizing the nanotopography measurements in gradation after the measurements of the mirror-polished wafers were filtered to remove long-wavelength components. In the representation of the height difference in Fig. Figure 7 shows the height difference of the nanotopography. The darker color represents the lower height and the lighter color the higher height. The darkest part is located at -20 nm from the average height and the brightest part is located at +20 nm from the average height. Thus, the height difference from the lowest to the highest height is 40 nm. Note that the nanotopography was measured using three freely designated points on the outer periphery of the corrected wafer. Accordingly, the nanotopography map shows the height difference on the non-adhered wafer surface.

[0057] As in Fig. As shown in Figure 7, Example 1 exhibits a substantially uniform color density exhibiting a small height difference over the entire surface. It is speculated that the highly planarized surface with improved nanotopography characteristics can be obtained with small allowances due to the first resin deposition grinding step, in which the nanotopography characteristics of the wafer surface are improved although the warpage and undulation are not completely removed, the second resin deposition grinding step, in which the warpage and undulation of the wafer surface are sufficiently reduced, and the third surface grinding step, in which surface grinding is performed using the wafer surface whose warpage and undulation are sufficiently reduced as the reference surface.

[0058] In Comparison 1, the height difference shown by a gradation pattern is observable across the entire wafer. It is therefore clear that the height difference caused by the corrugation remains throughout the wafer surface.

[0059] From Comparison 2, which shows a substantially uniform color density, it can be seen that the height difference is small across the entire surface, as in Example 1. The highly planarized surface as in Example 1 can also be obtained in Comparison 2. In contrast to the three surface grinding steps in Example 1, Comparison 2, which requires four surface grinding steps, exhibits low productivity. Evaluation test 2

[0060] In the same way as in evaluation test 1, the effect of the surface textures of the wafers W on the nanotopography on the mirror-polished wafer surface was examined.

[0061] In this test, a plurality of wafers W were prepared under the same conditions as those in Example 1 and Comparisons 1, 2, and each of the plurality of wafers W was mirror-polished under the same conditions as those in Evaluation Test 1 (rough polishing using the double-sided polishing machine + finish polishing using the single-sided polishing machine) to prepare the wafers W whose surfaces were mirror-polished. Fig. Figure 8 is a diagram showing measurements of the nanotopography on each of the mirror-polished surfaces of the wafers W (window size 10 mm) measured using an optical interferometric flatness meter (Wafersight 2, manufactured by KLA Tencor Corporation).

[0062] As from Fig.As can be seen from Figure 8, the height difference is in a range of 9 to 11 nm in Example 1, 17 to 28 nm in Comparison 1 and 9 to 11 nm in Comparison 2. The wafers W in Example 1 and Comparison 2 each have a highly planarized surface whose total nanotopography is 11 nm or less. EXPLANATION OF REFERENCE SYMBOLS

[0063] W... wafer, W1... first surface, W2... second surface

Claims

[1] A manufacturing method for a wafer (W) produced by slicing a monocrystalline ingot using a wire saw machine and grinding the wafer (W), the method comprising: a first resin application grinding step (S2); a second resin application grinding step (S3); and a third surface grinding step (S4), wherein The first resin application grinding step (S2) includes: a first coating layer forming step (S21) for applying a curing material to an entire second surface (W2) of the wafer (W) to form a flat first coating layer (RH1); a first surface grinding step (S22) for placing the wafer (W) on a table (21) of a grinding machine such that the first coating layer (RH1) is in contact with a reference surface (211) of the table (21), and then surface grinding a first surface (W1) of the wafer (W) by the grinding machine; and a first coating layer removing step (S23) for removing the first coating layer (RH1) after the first surface grinding step (S22) from the second surface (W2) of the wafer (W); wherein the second resin application grinding step (S3) comprises: a second coating layer forming step (S31) for applying the curing material to the entire first surface (W1) of the wafer (W) to form a flat second coating layer (RH2); a second surface grinding step (S32) for placing the wafer (W) on the table (21) of the grinding machine so that the second coating layer (RH2) is in contact with the reference surface (211) of the table (21), and then surface grinding the second surface (W2) of the wafer (W) by the grinding machine; and a second coating layer removing step (S33) for removing the second coating layer (RH2) after the second surface grinding step (S32) from the first surface (W1) of the wafer (W), and wherein the third surface grinding step (S4) comprises: Placing the wafer (W) on the table (21) such that a last surface-ground surface is in contact with the reference surface (211) of the table (21) of the grinding machine, and then surface-grinding a surface of the wafer (W) opposite the surface in contact with the reference surface (211) by the grinding machine. [2] The method according to claim 1, wherein between the second resin application grinding step (S3) and the third surface grinding step (S4): only the first resin application grinding step (S2) is additionally carried out; or at least one repetition of the first resin application grinding step (S2) and the second resin application grinding step (S3) is additionally carried out in this order; or at least one repetition of the first resin application grinding step (S2) and the second resin application grinding step (S3) is carried out in this order and then the first resin application grinding step (S2) is carried out. [3] The method according to claim 1, wherein a grinding allowance in the first resin application grinding step (S2) is equal to or larger than a grinding allowance in the third surface grinding step (S4). [4] The method according to any one of claims 1 to 3, wherein the wire saw machine slices the monocrystalline ingot using a wire with fixed abrasive grain. [5] The method according to any one of claims 1 to 4, wherein a diameter of the wafer (W) is 300 mm or more.

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