Silicon wafer with laser mark and manufacturing method thereof

Abstract

In order to form uniform dot holes even when a deep laser mark of about 100 [mu] m is formed, this silicon wafer (1) has a crystal plane orientation (100), and has, on a surface having a surface roughness of 0.15-0.60 nm, an identification mark (5) comprising a plurality of dot holes (4) in which the lt of an opening (42) in the wafer surface (11) is less than the lt of the opening (42) in the wafer surface (11), and the lt of the dot holes (4) in the wafer surface (11) is less than the lt of the opening (42) in the wafer surface (11) is less than the lt of the dot holes (4) in the wafer surface (11). 100 gt; the length (L1) and lt in the direction; 110gt, 110gt; the ratio of the length (L2) in the direction is 1-1.10, and the lt of the opening (42); 100 gt; the length (L1) in the direction is 80 [mu] m to 110 [mu] m, the depth (D) of the cross section of the dot hole (4) is 80 [mu] m to 110 [mu] m, and the bottom surface (43) of the dot hole (4) is a plane of the (100) plane.

Description

Technical Field

[0001] The invention relates to a silicon wafer with a laser mark and a method for manufacturing the same. Background Art

[0002] On the outer periphery of the back side of a silicon wafer, for example, an identification mark formed by laser irradiation is sometimes engraved for wafer management or identification. The mark engraved by laser (hereinafter also referred to as a laser mark) is composed of characters or symbols formed by a collection of a plurality of dot holes (recesses), and is set to a size that can be recognized visually or by a camera.

[0003] As such a laser marking, the following is known: a mark composed of a dot hole formed into a shape suitable for removing residues of a photoresist or the like, having marking elements for forming a blind hole on a substrate, and a side wall having an upper side wall portion having an upper side wall angle and a lower side wall portion having a lower side wall angle; the upper side wall angle β is smaller than the lower side wall angle δ, and the depth D is about 12 μm or less (see Patent Document 1). Figure 2 ).

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: U.S. Patent Publication No. 2008 / 0135981 Summary of the invention

[0007] Problems to be solved by the invention

[0008] In the above-mentioned prior art, regarding the shape of the dot hole constituting the laser mark, since the etching anisotropy of silicon crystal is not mentioned, the above-mentioned angles β and δ are the same angles relative to all directions. Therefore, the shape of the upper part of the dot hole is made circular, but in order to achieve this, acid etching without crystal orientation dependence is required. However, in the method for forming a laser mark based on acid etching, when forming a deeper laser mark of about 100μm, there is a problem that the dot hole tends to become uneven due to the high etching speed.

[0009] An object of the present invention is to provide a silicon wafer with a laser mark which can form uniform dot holes even when a deep laser mark of about 100 μm is formed, and a method for producing the same.

[0010] Means used to solve problems

[0011] The present invention solves the above-mentioned problem by means of a silicon wafer with a laser mark: a silicon wafer with a crystal plane orientation of (100), a silicon wafer having an identification mark composed of a plurality of dot holes on a surface with a surface roughness of 0.15 to 0.60 nm, wherein the openings of the dot holes in the wafer surface are <100> The length of the direction <110> The ratio of the length of the opening to the direction is 1 to 1.10. <100> The length in the direction is 80 μm to 110 μm; the depth of the cross section of the aforementioned dot hole is 80 μm to 110 μm; and the bottom surface of the aforementioned dot hole is a (100) plane.

[0012] In the above invention, it is more preferred that the aforementioned dot hole <110> The angle formed by the side surface in the cross section in the direction and the above-mentioned wafer surface is 63 to 73 degrees.

[0013] In the above invention, it is more preferred that the aforementioned dot hole <100> The angle formed by the side surface in the cross section in the direction and the above-mentioned wafer surface is 56 to 70 degrees.

[0014] In the above invention, the protrusion height of the opening can be set to less than 25 nm from the surface of the wafer.

[0015] In the above invention, the protrusion height of the opening may be set to be 30 nm or more from the surface of the wafer.

[0016] In addition, the present invention also solves the above-mentioned problem through the following method for manufacturing a silicon wafer with a laser mark: after irradiating the wafer surface of a silicon wafer with a crystal plane orientation of (100) with a laser to form a blind hole with a depth of 80μm to 110μm, the silicon wafer is immersed in an aqueous potassium hydroxide solution with a concentration of more than 40wt%, and the wafer surface and the blind hole are etched to a thickness of 5 to 15μm, and then the wafer surface is ground.

[0017] In the above invention, when the laser is irradiated on the surface of the wafer, the laser can be irradiated with a first beam diameter and then with a second beam diameter smaller than the first beam diameter, or the laser can be irradiated with the second beam diameter and then with the first beam diameter.

[0018] In the above invention, when the laser beam is irradiated onto the surface of the wafer, the laser beam may be irradiated with a single beam diameter.

[0019] Effects of the Invention

[0020] According to the present invention, since the identification mark composed of a plurality of dot holes is formed by anisotropic etching of silicon crystal, a laser-marked silicon wafer having uniform dot holes can be obtained even when a deep laser mark of about 100 μm is formed. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is a front view showing an embodiment of a silicon wafer with a laser mark according to the present invention.

[0022] Figure 2 This is a flow chart showing one embodiment of a method for producing a silicon wafer with a laser mark according to the present invention.

[0023] Figure 3A Yes means Figure 2 A front view of a wafer and a cross-sectional view along line IIIA-IIIA showing an example of a laser irradiation process.

[0024] Figure 3B Yes means Figure 2 A front view of a wafer and a cross-sectional view along line IIIB-IIIB showing another example of the laser irradiation step.

[0025] Figure 4 It means it's over Figure 2 Front view of the wafer during the alkaline etching step.

[0026] Figure 5 It is along Figure 4 Cross-sectional view of the V-V line.

[0027] Figure 6 It is along Figure 4 Cross-sectional view of line VI-VI.

[0028] Figure 7 It means it's over Figure 2 A cross-sectional view of a wafer during the grinding step.

[0029] Figure 8 This is a diagram showing the crystal structure of a silicon single crystal.

[0030] Fig. 9 The following is the case when a dot hole is formed on a silicon wafer with a crystal plane orientation of (100) by anisotropic etching. <110> Direction cross-sectional view.

[0031] Fig.10 The following is the case when a dot hole is formed on a silicon wafer with a crystal plane orientation of (100) by anisotropic etching. <110> Direction cross-sectional view.

[0032] Fig.11 These are binary photographs of the dot holes of the examples and comparative examples observed in a front view. DETAILED DESCRIPTION

[0033] Figure 1 1 is a front view showing an embodiment of a silicon wafer with a laser mark according to the present invention. Figure 1In the silicon wafer 1 shown, a notch 2 consisting of a V-shaped notch is provided at a part of the outer periphery of the silicon wafer 1 in order to align the orientation of the silicon wafer 1 in the manufacturing process of semiconductor devices, etc. In addition, in the silicon wafer 1 shown in the figure, a laser mark engraving portion 3 is provided near the notch 2 in order to identify the individual wafer. The size of the laser mark engraving portion 3 in this example is not particularly limited, and is made into a size of about 2 mm×20 mm, or about 1.6 mm×16 mm, for example.

[0034] In the laser mark engraving part 3, as shown in an enlarged manner in the figure, a plurality of dot holes 4 are formed by irradiation of laser light, and as a plurality of sets of these dot holes 4, an identification mark composed of characters, bar codes, etc. is engraved. The characters, bar codes, etc. engraved in the laser mark engraving part 3 are read in various processes such as the manufacturing process of semiconductor devices, and are used to identify the quality of the silicon wafer 1. In this specification, a blind hole composed of a concave portion formed by one emission of laser light is referred to as a dot hole 4, a character, bar code, etc. composed of a plurality of dot holes 4 is referred to as an identification mark 5 (or a laser mark), and a silicon wafer 1 provided with a laser mark engraving part 3 is referred to as a silicon wafer with a laser mark related to the present invention.

[0035] Figure 2 The flowchart shows an embodiment of the method for manufacturing a silicon wafer with a laser mark according to the present invention. The method for manufacturing a silicon wafer with a laser mark according to the present embodiment includes: a slicing step (step S1) of cutting a disk-shaped wafer from a single crystal ingot; a flattening step (step S2) of making the thickness of the cut disk-shaped wafer uniform; a laser irradiation step (step S3) of irradiating a laser to the laser mark engraving portion 3 on the surface of the wafer with uniform thickness to form a prototype 41 of a plurality of dot holes 4; an alkali etching step (step S4) of etching the wafer surface including the laser mark engraving portion 3 having at least the prototype 41 of the dot hole 4 formed thereon using an alkali etchant to etch the prototype 41 of the dot hole 4 into the dot hole 4; and a grinding step (step S5) of grinding the etched wafer surface with a grinding liquid containing abrasive grains.

[0036] The slicing process of step S1 of this embodiment is a process of cutting a disk-shaped wafer by cutting the crystalline ingot with a wire saw in contact with the crystalline ingot while supplying a grinding fluid, or by cutting the crystalline ingot with a circumferential blade. The silicon wafer of this embodiment uses a silicon single crystal wafer with a crystal plane orientation of (100).

[0037] The flattening process of step S2 of the present embodiment is a process for improving the flatness of the wafer and making the thickness of the wafer close to the final thickness by grinding the surface of the wafer cut in the slicing process. When grinding is performed, for example, free abrasive grains in the range of #1000 to 1500 can be used for grinding. In addition, instead of grinding, a grinding process using a surface grinder or a double-sided surface grinder can be used to flatten the wafer with high precision to reduce the deviation and fluctuation of the thickness of the wafer. Grinding can be performed on both sides of the wafer or on only one side, but grinding both sides of the wafer is more preferred in terms of flatness.

[0038] In the laser irradiation process of step S3 of the present embodiment, the laser output from the laser source is intermittently irradiated to the laser marking engraving part 3 of the silicon wafer 1 multiple times to form a prototype 41 of a plurality of dot holes 4. The prototype 41 of the dot hole 4 formed here is a so-called blind hole having a bottom surface, a side surface and an opening. In addition, the prototype 41 of the dot hole 4 refers to the blind hole itself formed by irradiating the laser, and refers to the state before the alkali etching process of step S4 is implemented. These multiple dot holes 4 constitute a pattern of characters, graphics, symbols, etc., and ultimately become an identification mark 5. In addition, the identification mark 5 can be formed on either the surface or the back side of the silicon wafer 1, but it is more preferably the back side of the wafer with a surface roughness of 0.15 to 0.60 nm. In addition, the surface roughness described here refers to the root mean square roughness Rq when measuring a range of 10μm×10μm using an atomic force microscope (AFM).

[0039] The laser used in this process is not particularly limited, and infrared laser, CO2 laser, YLF laser, Nd:YAG laser, etc. can be used. Since the depth D of the dot hole 4 of the present embodiment is 80μm to 110μm, the depth of the prototype 41 of the dot hole 4 formed in the laser irradiation process is shallower than the processing allowance (5μm to 15μm) in the subsequent alkali etching process. For example, when the target value of the depth D of the final dot hole 4 is 100μm and the processing allowance in the subsequent alkali etching process is 5 to 15μm, the depth of the prototype 41 of the dot hole 4 formed in the laser irradiation process is 85 to 95μm. In addition, since the depth of the prototype 41 of the dot hole 4 formed by laser irradiation does not depend on the output of the laser but is related to the number of laser shots (or irradiation time), multiple shots are performed when the desired depth cannot be obtained by one shot.

[0040] Figure 3A Yes means Figure 2The front view (upper figure) and the cross-sectional view along line IIIA-IIIA (lower figure) of the silicon wafer 1 after the treatment of an example of the laser irradiation process in step S4 of FIG. In this example, the prototype 41 of the spot hole 4 is formed by laser beam with only a single beam diameter. The beam diameter of the laser in this example is not particularly limited, but due to the size of the opening 42 of the final spot hole 4 <100> The length of the direction is 80μm to 110μm, <100> The length of the direction <110> The ratio of the length in the direction is 1 to 1.10, so it is smaller than the processing allowance (5 μm to 15 μm) in the subsequent alkali etching process. <100> The target value of the length in the direction is 100 μm, and the length of the opening 42 is <110> When the target value of the length in the direction is 100 μm and the machining margin in the subsequent alkali etching step is 5 to 15 μm, the beam diameter of the laser light may be set to about 85 to 95 μm.

[0041] Figure 3B Yes means Figure 2 The front view (upper figure) and the cross-sectional view along the IIIB-IIIB line (lower figure) of the silicon wafer 1 after processing of another example of the laser irradiation process of step S4 of the present invention are shown. In this example, laser beams of different beam diameters are used to form the prototype 41 of the spot hole 4. For example, the laser beam is first irradiated with a first beam diameter having a relatively large beam diameter, and after the first prototype 411 of the spot hole 4 is formed, the laser beam is irradiated with a second beam diameter having a relatively small beam diameter to form the second prototype 412 of the spot hole 4. Alternatively, the laser beam may be first irradiated with a second beam diameter having a relatively small beam diameter, and after the second prototype 412 of the spot hole 4 is formed, the laser beam is irradiated with a first beam diameter having a relatively large beam diameter to form the first prototype 411 of the spot hole 4. In this way, by forming a side surface with a smaller inclination like the first prototype 411 in the prototype 41 of the spot hole 4, it is possible to suppress the elevation of the ridge height h of the opening 42 of the spot hole 4 when the grinding process is completed. This will be described later. In addition, the beam diameter of the laser beam can be controlled by the output and current value of the laser beam, and the beam diameter can be increased by increasing the output of the laser beam.

[0042] Back to Figure 2 The alkali etching process of step S4 of this embodiment is a process of immersing the silicon wafer 1 having the prototype 41 of the plurality of dot holes 4 formed thereon into a high concentration potassium hydroxide aqueous solution of 40wt% or more, and performing anisotropic etching on the wafer surface 11 and the prototype 41 of the dot holes 4. The etching processing allowance here is not particularly limited, and it is more preferably set to a thickness of about 5 to 15μm. By limiting the thickness of the etching processing allowance to this range, the shape of the opening 42 can be controlled to a predetermined shape.

[0043] The final point hole 4 of this embodiment is as follows Figure 4As shown, the opening 42 in the wafer surface 11 of the dot hole 4 <100> The length L1 of the direction is <110> The ratio of the length L2 in the direction is 1 to 1.10, and the length of the opening 42 is <100> The length L1 in the direction is 80 μm to 110 μm, the depth D of the cross section of the dot hole 4 is 80 μm to 110 μm, and the bottom surface 43 of the dot hole 4 is a (100) plane.

[0044] Figure 8 is a diagram showing the crystal structure of a silicon single crystal wafer with a crystal plane orientation of (100). Fig. 9 The following is a case where a blind hole is formed in a silicon wafer 1 with a crystal plane orientation of (100) and anisotropically etched. <110> Cross-sectional view of the direction, Fig.10 It is also along <100> Cross-sectional view in the direction. Figure 9-10 As shown in FIG. 1 , if a blind hole (hole 4) is formed in a silicon wafer 1 whose crystal plane orientation is (100), and anisotropic etching is performed using a high-concentration alkaline etchant, the bottom surface 43 of the blind hole (hole 4) becomes a (100) surface. <110> In the cross-sectional view of the direction, Fig. 9 As shown, the two side surfaces 44 of the bottom surface 43 become (111) surfaces or (122) surfaces, and the (311) surfaces are connected thereto. <100> In the cross-sectional view of the direction, Fig.10 As shown, the two side surfaces 45 of the bottom surface 43 are (110) surfaces or (120) surfaces.

[0045] In addition, if Fig. 9 As shown, along <110> In the cross section of the direction, when the side surface 44 presents the (111) plane, the angle α formed by the bottom surface 43 of the (100) plane and the side surface 44 of the (111) plane is 54 degrees, and when the side surface presents the (122) plane, the angle α formed by the bottom surface 43 of the (100) plane and the side surface 44 of the (122) plane is 70 degrees. In addition, the angle formed by the bottom surface 43 of the (100) plane and the side surface 44 of the (311) plane is 25 degrees. In addition, as Fig.10 As shown, along <100> In the cross section of the direction, when the side surface 45 presents a (110) surface, the angle β formed by the bottom surface 43 of the (100) surface and the side surface 45 of the (110) surface is 45 degrees, and when the side surface presents a (120) surface, the angle β formed by the bottom surface 43 of the (100) surface and the side surface 45 of the (120) surface is 64 degrees.

[0046] In this way, if a blind hole (point hole 4) is formed in a silicon wafer 1 whose crystal plane orientation is (100) and anisotropic etching is performed using a high-concentration alkaline etchant, a crystal plane with a relatively slow etching rate will appear, and a point hole 4 with a shape with smaller deviation can be obtained compared to acid etching.

[0047] Therefore, in the alkali etching process (step S4) of the present embodiment, etching is performed so that the dot hole 4 is formed along the Figure 9-10 However, the dot hole 4 of this embodiment does not need to be Figure 9-10 The dot hole 4 composed of complete crystal planes as shown may be formed by etching with an appropriate machining allowance so that a part of each of the crystal planes is revealed.

[0048] Figure 4 It means it's over Figure 2 A front view of a wafer in the alkali etching step of step S4, Figure 5 It is along Figure 4 The cross-sectional view of the V-V line, Figure 6 It is along Figure 4 A cross-sectional view of the line VI-VI. In addition, Figure 5 The crystal plane orientation of the silicon wafer 1 is (100) along <110> Cross-sectional view of the direction, Figure 6 Also along the same <100> In the final spot hole 4 of this embodiment, the opening 42 in the wafer surface 11 of the spot hole 4 is <100> The length L1 of the direction is <110> The ratio of the length L2 in the direction is 1 to 1.10. <100> The length L1 of the direction is <110> The ratio of the length L2 in the direction is greater than 1.10, that is, if L1 is too long, the (110) surface sandwiched by the (111) surface or the (311) surface in the opening 42 of the dot hole becomes narrower, so the change in film thickness becomes steep, stress is generated, and film peeling is likely to occur.

[0049] In the final dot hole 4 of this embodiment, Figure 5 The point hole 4 shown <110> The angle α formed by the side surface 44 and the wafer surface 11 (or the bottom surface 43) in the cross section in the direction is preferably 63 to 73 degrees. By setting the angle to be steep within the range that can be achieved by alkali etching, even if the surface with the identification mark 5 is ground and the spot hole becomes shallower during the equipment process, the shape of the opening 42 can be maintained, and the film peeling can be prevented while maintaining the visibility.

[0050] In addition, in the final dot hole 4 of this embodiment, Figure 6 The point hole 4 shown <100> The angle β formed by the side surface 45 and the wafer surface 11 (or the bottom surface 43) in the cross section in the direction is preferably 56 to 70 degrees. By setting the angle to be steep within the range that can be achieved by alkali etching, even if the surface with the identification mark 5 is ground and the spot hole becomes shallower during the equipment process, the shape of the opening 42 can be maintained, and the film peeling can be prevented while maintaining the visibility.

[0051] Back to Figure 2The grinding process of step S5 of this embodiment is a process of grinding both sides of the silicon wafer 1 after etching with a grinding liquid containing abrasive grains. Thus, the surface of the silicon wafer 1 is mirror-polished. As the grinding slurry, an alkaline slurry containing colloidal silicon oxide as a grinding abrasive grain can be used. Moreover, the grinding process can be carried out by embedding the silicon wafer 1 into a carrier, clamping the wafer with an upper platen and a lower platen to which a grinding cloth is attached, allowing a slurry such as colloidal silicon oxide to flow between the upper and lower plates and the wafer, rotating the upper and lower plates and the carrier in opposite directions, and performing a mirror-polishing process on both sides of the silicon wafer 1. Thus, the unevenness of the wafer surface can be reduced to obtain a wafer with a higher flatness.

[0052] In addition, after the grinding process, single-sided fine grinding is performed in which at least one side of the silicon wafer is finely ground on each single side. In this fine grinding, both single-sided grinding and double-sided grinding are included. In the case of grinding both sides, the surface of one side is ground and then the surface of the other side is ground. With this grinding, the roughness of the surface with the identification mark 5 becomes a specified range. In addition, when the identification mark 5 is set as the back side of the silicon wafer 1 and only the surface is finely ground, the surface becomes a surface with a lower roughness than the back side with the identification mark 5.

[0053] Figure 7 It means it's over Figure 2 A cross-sectional view of a silicon wafer 1 after the polishing step. In the silicon wafer 1 of the present embodiment, the protrusion height h of the opening 42 of the dot hole 4 in the wafer surface 11 is preferably less than 25 nm from the wafer surface 11. Figure 2 The laser irradiation of the laser irradiation process of step S3 causes the periphery of the opening 42 of the dot hole 4 to bulge in a ring shape. It is known that the bulge of the opening 42 is removed in the alkali etching process of step S4, but reappears in the polishing process of step S5.

[0054] For example, in a patent application previously filed by the applicant of the present application (Japanese Patent Gazette No. 2020-68231), the following report was made: Based on the speculation that insufficient abrasive grains act on the periphery of the spot hole during the grinding process, if a grinding slurry is supplied between the grinding pad and the silicon wafer to grind the surface of the silicon wafer, the abrasive grains contained in the grinding slurry fall into the spot hole and insufficient abrasive grains are present at the periphery of the spot hole. As a result, the amount of grinding at the periphery of the spot hole is reduced compared to the amount of grinding in other parts, and a raised portion is formed at the periphery of the spot hole.

[0055] Therefore, in the silicon wafer 1 of the present embodiment, in order to make the protrusion height h of the opening 42 of the dot hole 4 in the wafer surface 11 less than 25 nm from the wafer surface 11, it is preferred that the prototype 41 of the dot hole 4 be Figure 3BAs shown in FIG. 1 , a side surface with a small inclination like the first prototype 411 is formed so that there is no shortage of abrasive grains at the periphery of the spot hole 4. As a result, during the grinding process of step S5, the abrasive grains at the periphery of the spot hole 4 can stay at the first prototype 411, thereby eliminating the shortage of abrasive grains. As a result, the height h of the protrusion of the opening 42 in the wafer surface 11 of the spot hole 4 can be made less than 25 nm from the wafer surface 11, and the flatness of the laser marking portion 3 can be improved.

[0056] On the other hand, in the silicon wafer 1 of the present embodiment, the protrusion height h of the opening 42 of the dot hole 4 in the wafer surface 11 may be set to be 30 nm or more from the wafer surface 11. Figure 7 As shown in FIG. 1 , by leaving a ridge around the opening 42 of the dot hole 4, the etchant accumulated in the dot hole 4 can be prevented from flowing out. As a result, when the silicon wafer 1 is taken out from the etching tank, the etchant accumulated in the dot hole 4 can be prevented from unevenly etching the periphery of the dot hole 4. In addition, in order to make the ridge height h of the opening 42 in the wafer surface 11 of the dot hole 4 more than 30 nm from the wafer surface 11, for example, the prototype 41 of the dot hole 4 can be made as Figure 3A As shown in the figure, the side surface is made to be more inclined so that the abrasive grains are insufficient at the periphery of the dot hole 4.

[0057] As described above, according to the silicon wafer with laser marking of this embodiment, even if the identification mark 5 consisting of the dot hole 4 with a cross-sectional depth of 80μm to 110μm is formed on the silicon wafer 1 with a crystal plane orientation of (100), the dot hole 4 has a smaller deviation than that of acid etching.

[0058] In addition, according to the laser-marked silicon wafer of this embodiment, the opening 42 in the wafer surface 11 of the dot hole 4 is <100> The length L1 of the direction is <110> The ratio of the length L2 in the direction is set to 1 to 1.10, and the length of the opening 42 is set to <100> The length L1 in the direction is set to 80μm to 110μm, so the shape of the opening 42 of the spot hole 4 is a shape that depends on the crystal orientation but is smooth and continuous. As a result, stress concentration on the corner of the opening 42 is suppressed, and as a result, even if grinding or other processing is performed in the subsequent equipment process, the occurrence of film peeling is suppressed. In addition, since stress concentration is suppressed, even if heat treatment is performed in the subsequent equipment process, the occurrence of slip can be suppressed. Furthermore, since the spot hole 4 is relatively deep at 80μm to 110μm, even if grinding or other processing is performed in the subsequent equipment process, the recognition / identification can be ensured.

[0059] In addition, according to the manufacturing method of a silicon wafer with a laser mark of the present embodiment, when an identification mark 5 consisting of a dot hole 4 with a cross-sectional depth of 80 μm to 110 μm is formed on a silicon wafer 1 with a crystal plane orientation of (100), after irradiating the wafer surface 11 of the silicon wafer 1 with a crystal plane orientation of (100) with a laser to form a plurality of blind holes (prototypes 41 of the dot holes 4) with a depth of 80 μm to 110 μm, the silicon wafer 1 is immersed in an aqueous potassium hydroxide solution with a concentration of 40 wt % or more, the wafer surface 11 and the blind holes (prototypes 41 of the dot holes 4) are etched to a thickness of 5 to 15 μm, and then the wafer surface 11 is polished, so that the shape of the opening 42 of the dot hole 4 can be made to be a specific shape that is smoothly continuous although it depends on the shape of the crystal orientation.

[0060] In addition, according to the silicon wafer with laser marking of this embodiment, Figure 5 The point hole 4 shown <110> The angle α formed by the side surface 44 and the wafer surface 11 (or the bottom surface 43) in the cross section in the direction is 63 to 73 degrees. Figure 6 The point hole 4 shown <100> The angle β formed by the side surface 45 in the cross section of the direction and the chip surface 11 (or the bottom surface 43) is 56 to 70 degrees, and the cross-sectional shape of the dot hole 4 becomes a specific angle close to a right angle, so even if the laser mark engraving part 3 is ground or polished during the equipment process, good recognition / identification can be ensured.

[0061] [Example]

[0062] <<Example 1>>

[0063] After laser irradiation is performed on the outer periphery of a silicon wafer having a crystal plane orientation of (100) to form a prototype 41 of a dot hole 4, the silicon wafer is immersed in a potassium hydroxide aqueous solution having a concentration of 40 wt % or more, and the wafer surface 11 and the dot hole 4 are etched to a thickness of 10 μm to produce a prototype 41 having a depth D of 100.4 μm and a dot hole 4 ... <100> The length L1 in the direction is 95.8 μm. <100> The length L1 of the direction is <110> A laser-marked silicon wafer 1 having a dot hole 4 with a ratio (L1 / L2) of 1.04 in the length L2 direction. After forming a 1 μm thick nitride film on the silicon wafer 1, a rapid temperature rise heat treatment at 1000°C was performed, and the state of film peeling of the nitride film around the dot hole 4 was observed with an electron microscope. The results are shown in Table 1 together with the conditions. In addition, Fig.11 (A) shows a binary photograph of one dot hole 4 observed from the front view.

[0064] <<Example 2>>

[0065] In addition to making the depth D of the dot hole 4 87.9 μm, <100> The length L1 in the direction becomes 81.0 μm, so <100> The length L1 of the direction is <110> A silicon wafer 1 with a laser mark was prepared under the same conditions as in Example 1 except that the ratio of the length L2 in the direction (L1 / L2) was 1.05, and the state of film peeling was observed. The results are shown in Table 1 together with the conditions. Fig.11 (B) shows a binarized photograph of one dot hole 4 observed from the front view.

[0066] <<Comparative Example 1>>

[0067] In addition to making the depth D of the dot hole 4 89.2 μm, <100> The length L1 in the direction becomes 90.1 μm, so <100> The length L1 of the direction is <110> A silicon wafer 1 with a laser mark was prepared under the same conditions as in Example 1 except that the ratio of the length L2 in the direction (L1 / L2) was 1.23, and the state of film peeling was observed. The results are shown in Table 1 together with the conditions. Fig.11 (C) shows a binary photograph of one dot hole 4 observed from the front view.

[0068] [Table 1]

[0069]

[0070] <<Investigation>>

[0071] When the depth D of the dot hole 4 is set to 80 to 110 μm, if the opening 42 of the dot hole 4 <100> The length L1 of the direction is <110> When the ratio of the length L2 in the direction (L1 / L2) was 1 to 1.10 as in Examples 1 and 2, no film peeling was observed. On the other hand, when L1 / L2 exceeded 1.10 as in Comparative Example 1, film peeling was observed. This is presumably because Fig.11 As shown in the front view of (C), the opening 42 of the dot hole 4 of Comparative Example 1 has a large amount of processing allowance due to alkali etching, and is roughly quadrilateral. As a result, the (110) planes of the corners sandwiched by the (111) planes are narrow, so the change in film thickness becomes steep, generating stress and easily causing film peeling. Fig.11 (A) Example 1 and Fig.11 The opening 42 of the dot hole 4 of Example 2 shown in (B) is an octagon with rounded vertices, and the entire shape is close to a circle. As a result, the film thickness changes little, and the shape is less likely to cause stress concentration.

[0072] Description of Reference Numerals

[0073] 1…Silicon wafer

[0074] 11…Wafer surface

[0075] 2…Notch

[0076] 3…Laser marking department

[0077] 4…Point hole

[0078] 41…The prototype of the hole

[0079] 411…1st Prototype

[0080] 412…2nd prototype

[0081] 42…Opening

[0082] 43…Bottom

[0083] 44, 45…side

[0084] 5…Identification mark

[0085] L1… <100> Length of direction

[0086] L2… <110> Length of direction

[0087] α…along <110> The angle between the bottom and side surfaces in the cross section of the direction

[0088] β…along <100> The angle between the bottom and side surfaces in the cross section of the direction

[0089] h… Height of bulge at opening

Claims

1. A silicon wafer with a laser mark, which is a silicon wafer with a crystal plane orientation of (100), and has an identification mark consisting of a plurality of dot holes on a surface with a surface roughness of 0.15 to 0.60 nm, characterized in that: The opening of the wafer surface of the aforementioned dot hole <100> The length of the direction <110> The ratio of the length of the opening to the direction is 1 to 1.

10. <100> The length of the direction is 80μm to 110μm; The depth of the cross section of the aforementioned dot hole is 80 μm to 110 μm; The bottom surface of the aforementioned dot hole is a (100) plane.

2. The silicon wafer with laser marking according to claim 1, characterized in that: The aforementioned hole <110> The angle formed by the side surface in the cross section in the direction and the above-mentioned wafer surface is 63 to 73 degrees.

3. The silicon wafer with laser marking according to claim 1 or 2, characterized in that: The aforementioned hole <100> The angle formed by the side surface in the cross section in the direction and the above-mentioned wafer surface is 56 to 70 degrees.

4. The silicon wafer with laser marking according to claim 1 or 2, characterized in that: The protrusion height of the opening is less than 25 nm from the surface of the wafer.

5. The silicon wafer with laser marking according to claim 1 or 2, characterized in that: The protrusion height of the opening is greater than 30 nm from the wafer surface.

6. A method for manufacturing a silicon wafer with a laser mark, characterized in that: The surface of a silicon wafer with a crystal plane orientation of (100) is irradiated with laser light to form a plurality of blind holes with a depth of 80 μm to 110 μm. The silicon wafer is immersed in a potassium hydroxide aqueous solution having a concentration of 40 wt % or more, and the wafer surface and the blind hole are etched to a thickness of 5 to 15 μm. Then, the surface of the wafer is ground.

7. The method for manufacturing a silicon wafer with a laser mark according to claim 6, characterized in that: When the surface of the wafer is irradiated with laser light, After irradiating with laser light at a first beam diameter, irradiating with laser light at a second beam diameter smaller than the first beam diameter, or After irradiating with the laser beam at the second beam diameter, irradiating with the laser beam at the first beam diameter.

8. The method for manufacturing a silicon wafer with a laser mark according to claim 6, characterized in that: When the wafer surface is irradiated with laser light, the laser light is irradiated with a single beam diameter.

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