Laser-marked silicon wafer and its manufacturing method

Abstract

To provide a silicon wafer with a laser mark, that becomes a uniform dot hole even in the case of forming a laser mark with a depth by 100 μm, and provide a manufacturing method of them.SOLUTION: Provided is a silicon wafer 1 of which a crystal plane orientation is (100), in which an identification mark 5 constructed by a plurality of dot holes 4 is provided onto a front surface having roughness of 0.15 to 0.60nm, a ratio of a length L1 of a <100> direction and a length L2 of a <110> direction of an open part 42 in a wafer front surface 11 of each dot hole 4 is 1 to 1.10, the length L1 of the <100> direction of the open part 42 is 80 μm to 110 μm, a depth D of a cross section of each dot hole 4 is 80 μm to 110 μm, and a bottom surface 43 of each dot hole 4 is a flat surface of the (100) surface.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a laser-marked silicon wafer and a method for manufacturing the same. [Background technology]

[0002] For the purpose of managing or identifying the wafer, an identification mark is sometimes printed by irradiating the backside or outer periphery of a silicon wafer with laser light. A mark printed with laser light (hereinafter also referred to as a laser mark) consists of letters or symbols made up of a group of multiple dot holes (recesses), and is large enough to be distinguished visually or by camera.

[0003] Known examples of this type of laser mark include a mark consisting of a dot hole shaped to be suitable for removing residues of photoresist and the like, each mark element forming a blind hole in a substrate, and a sidewall having an upper sidewall portion with an upper sidewall angle and a lower sidewall portion with a lower sidewall angle, where the upper sidewall angle β is smaller than the lower sidewall angle δ, and the depth D is approximately 12 μm or less (see FIG. 2 of Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] U.S. Publication No. 2008 / 0135981 Summary of the Invention [Problem to be solved by the invention]

[0005] In the above-mentioned conventional technology, the etching anisotropy of silicon crystal is not mentioned with regard to the shape of the dot holes that constitute the laser mark, so it is assumed that the angles β and δ are the same in all directions. Therefore, the shape of the top of the dot hole is circular, but to achieve this, acid etching that is independent of crystal orientation is required. However, when forming a deep laser mark of about 100 μm using acid etching, the etching speed is fast, which is a problem as it easily results in non-uniform dot holes.

[0006] The problem to be solved by the present invention is to provide a silicon wafer with laser marks, which result in uniform dot holes even when deep laser marks of about 100 μm are formed, and a method for manufacturing the same. [Means for solving the problem]

[0007] The present invention provides a silicon wafer having a crystal plane orientation of (100), a surface roughness of 0.15 to 0.60 nm, and an identification mark consisting of a plurality of dot holes, The opening of the dot hole on the wafer surface, <100> The length of the direction and <110> The ratio of the length in the direction of the opening is 1 to 1.10, <100> The length in the direction is 80 μm to 110 μm, The cross-sectional depth of the dot holes is 80 μm to 110 μm, The above problem is solved by providing a laser-marked silicon wafer in which the bottom surfaces of the dot holes are flat surfaces of the (100) plane.

[0008] In the above invention, the dot holes <110> It is more preferable that the angle formed between the side surface and the wafer surface in the cross section in the direction is 63 to 73 degrees.

[0009] In the above invention, the dot holes <100> It is more preferable that the angle formed between the side surface and the wafer surface in the cross section in the direction is 56 to 70 degrees.

[0010] In the above invention, the protrusion height of the opening of the dot hole on the wafer surface can be less than 25 nm from the wafer surface.

[0011] In the above invention, the protrusion height of the opening of the dot hole on the wafer surface may be 30 nm or more from the wafer surface.

[0012] In addition, the present invention provides a method for forming a blind hole having a depth of 80 μm to 110 μm by irradiating a laser beam onto the surface of a silicon wafer having a crystal plane orientation of (100), and then immersing the silicon wafer in an aqueous potassium hydroxide solution having a concentration of 40 wt % or more, and etching the wafer surface and the blind hole to a thickness of 5 to 15 μm; of an opening in the wafer surface; <100> The length of the direction and <110> The ratio of the length in the direction of the opening is 1 to 1.10, <100> A dot hole having a length in the direction of 80 μm to 110 μm and a bottom surface of the (100) plane is formed. The above-mentioned problems are also solved by a method for manufacturing a laser-marked silicon wafer, which then involves polishing the wafer surface.

[0013] In the above invention, when irradiating the wafer surface with laser light, the wafer surface can be irradiated with laser light at a first beam diameter and then with laser light at a second beam diameter smaller than the first beam diameter, or the wafer surface can be irradiated with laser light at the second beam diameter and then with laser light at the first beam diameter.

[0014] In the above invention, when the surface of the wafer is irradiated with laser light, the laser light may be irradiated with a single beam diameter. [Effects of the Invention]

[0015] According to the present invention, an identification mark consisting of multiple dot holes is formed by utilizing anisotropic etching of silicon crystal, so that even when forming deep laser marks of about 100 μm, it is possible to obtain a silicon wafer with laser marks in which the dot holes are uniform. [Brief explanation of the drawings]

[0016] [Figure 1]1 is a front view showing an embodiment of a laser-marked silicon wafer according to the present invention; [Figure 2] 1 is a flowchart showing an embodiment of a method for manufacturing a laser-marked silicon wafer according to the present invention. [Figure 3A] 3A and 3B are a front view and a cross-sectional view along line IIIA-IIIA of a wafer showing an example of the laser irradiation step in FIG. 2. [Figure 3B] 3B is a front view of a wafer and a cross-sectional view taken along line IIIB-IIIB, showing another example of the laser irradiation step of FIG. 2. [Figure 4] FIG. 3 is a front view showing the wafer after the alkaline etching step of FIG. 2 has been completed. [Figure 5] FIG. 5 is a cross-sectional view taken along line VV in FIG. [Figure 6] FIG. 6 is a cross-sectional view taken along line VI-VI in FIG. [Figure 7] FIG. 3 is a cross-sectional view showing the wafer after the polishing step of FIG. 2 has been completed. [Figure 8] 1 is a diagram showing the crystal structure of a silicon single crystal. [Figure 9] When dot holes are formed in a silicon wafer with a crystal plane orientation of (100) by anisotropic etching <110> FIG. [Figure 10] When dot holes are formed in a silicon wafer with a crystal plane orientation of (100) by anisotropic etching <100> FIG. [Figure 11] 1 is a binarized photograph of dot holes of an example and a comparative example observed from the front. DETAILED DESCRIPTION OF THE INVENTION

[0017] Fig. 1 is a front view showing one embodiment of a laser-marked silicon wafer according to the present invention. In the silicon wafer 1 shown in Fig. 1, a notch 2 consisting of a V-shaped notch is provided in part of the outer periphery of the silicon wafer 1 in order to align the orientation of the silicon wafer 1 during processes such as the manufacturing of semiconductor devices. The silicon wafer 1 shown in the figure also has a laser mark printed portion 3 provided near the notch 2 in order to identify individual wafers. The size of the laser mark printed portion 3 in this example is not particularly limited, but is, for example, about 2 mm x 20 mm or 1.6 mm x 16 mm.

[0018] As shown enlarged in the figure, the laser mark printing section 3 has a plurality of dot holes 4 formed by irradiation with laser light, and a collection of these dot holes 4 forms an identification mark consisting of characters, barcodes, etc. The characters, barcodes, etc. printed in the laser mark printing section 3 are read in each process, such as the semiconductor device manufacturing process, and are used to identify the quality, etc., of the silicon wafer 1. In this specification, a blind hole consisting of a recess formed by one shot of laser light is referred to as a dot hole 4, characters, barcodes, etc. composed of a plurality of dot holes 4 are referred to as an identification mark 5 (or laser mark), and a silicon wafer 1 provided with the laser mark printing section 3 is referred to as a laser-marked silicon wafer according to the present invention.

[0019] 2 is a flowchart showing one embodiment of a method for manufacturing a laser-marked silicon wafer according to the present invention. The method for manufacturing a laser-marked silicon wafer according to this embodiment includes the following steps: a slicing step (step S1) of cutting disk-shaped wafers from a single crystal ingot; a planarizing step (step S2) of uniforming the thickness of the cut disk-shaped wafers; a laser irradiation step (step S3) of irradiating laser mark printed areas 3 on the surfaces of the wafers with uniform thickness with laser light to form prototypes 41 of multiple dot holes 4; an alkaline etching step (step S4) of etching the wafer surface including at least the laser mark printed areas 3 on which the prototypes 41 of dot holes 4 have been formed, using an alkaline etchant to etch the prototypes 41 of dot holes 4 into dot holes 4; and a polishing step (step S5) of polishing the etched wafer surface with a polishing solution containing abrasive grains.

[0020] The slicing step in step S1 of this embodiment is a step of cutting out disk-shaped wafers by cutting the crystalline ingot with a wire saw while supplying a grinding fluid, or by cutting the crystalline ingot with a circular blade. Note that the silicon wafer used in this embodiment is a silicon single crystal wafer with a (100) crystal plane orientation.

[0021] The planarization step of step S2 in this embodiment is a step of lapping the surface of the wafer cut out in the slicing step to improve the flatness of the wafer and bring the thickness of the wafer closer to the final thickness. When lapping is performed, loose abrasive grains in the range of #1000 to 1500 can be used, for example. Alternatively, instead of lapping, a grinding step using a surface grinder or a double-sided simultaneous surface grinder may be used to flatten the wafer with high precision and reduce variations in wafer thickness and waviness. Lapping may be performed on both sides of the wafer or on only one side, but lapping on both sides of the wafer is more preferable in terms of flatness.

[0022] In the laser irradiation process of step S3 of this embodiment, laser light output from a laser light source is intermittently irradiated onto the laser mark printing area 3 of the silicon wafer 1 multiple times to form the prototypes 41 of multiple dot holes 4. The prototypes 41 of the dot holes 4 formed here are so-called blind holes, having a bottom surface, side surfaces, and an opening. The prototypes 41 of the dot holes 4 refer to the blind holes themselves formed by irradiating the laser light, and refer to the state prior to the alkaline etching process of step S4. These multiple dot holes 4 form a pattern such as letters, figures, or symbols, and ultimately become the identification mark 5. The identification mark 5 may be formed on either the front or back surface of the silicon wafer 1, but is preferably formed on the back surface of the wafer with a surface roughness of 0.15 to 0.60 nm. The surface roughness referred to here refers to the root-mean-square roughness Rq measured over a 10 μm × 10 μm area using an atomic force microscope (AFM).

[0023] The laser light used in this process is not particularly limited, and an infrared laser, CO2 laser, YLF laser, Nd:YAG laser, or the like can be used. In this embodiment, the depth D of the dot holes 4 is 80 μm to 110 μm, and therefore the depth of the original shapes 41 of the dot holes 4 formed in the laser irradiation process is shallower by the removal allowance (5 μm to 15 μm) in the subsequent alkaline etching process. For example, if the target value for the final depth D of the dot holes 4 is 100 μm and the removal allowance in the subsequent alkaline etching process is 5 to 15 μm, the depth of the original shapes 41 of the dot holes 4 formed in the laser irradiation process is 85 to 95 μm. The depth of the original shapes 41 of the dot holes 4 formed by laser irradiation does not depend on the output of the laser light but correlates with the number of shots (or irradiation time) of the laser light. Therefore, if the desired depth cannot be obtained with a single shot, multiple shots are performed.

[0024] FIG. 3A shows an example of the laser irradiation process in step S4 of FIG. 2, with a front view (upper view) of the processed silicon wafer 1 and a cross-sectional view (lower view) along line IIIA-IIIA. In this example, the original shape 41 of the dot hole 4 is formed using only laser light with a single beam diameter. The beam diameter of the laser light in this example is not particularly limited, but the opening 42 of the final dot hole 4 is <100> The length in the direction is 80 μm to 110 μm, <100> The length of the direction and <110> Since the ratio of the lengths in the directions is 1 to 1.10, the dimensions are smaller by the removal allowance (5 μm to 15 μm) in the subsequent alkaline etching process. <100> The target length in the direction is 100 μm, and the length of the opening 42 <110> When the target length in the direction is 100 μm and the removal amount in the subsequent alkaline etching step is 5 to 15 μm, the beam diameter of the laser light may be set to approximately 85 to 95 μm.

[0025] 3B is a front view (top view) and a cross-sectional view (bottom view) along line IIIB-IIIB of the silicon wafer 1 after processing, illustrating another example of the laser irradiation process in step S4 of FIG. 2. In this example, the prototypes 41 of the dot holes 4 are formed using laser beams of different beam diameters. For example, first, the laser beam is irradiated with a first beam diameter having a relatively large beam diameter to form the first prototypes 411 of the dot holes 4, and then the laser beam is irradiated with a second beam diameter having a relatively small beam diameter to form the second prototypes 412 of the dot holes 4. Alternatively, first, the laser beam is irradiated with a second beam diameter having a relatively small beam diameter to form the second prototypes 412 of the dot holes 4, and then the laser beam is irradiated with a first beam diameter having a relatively large beam diameter to form the first prototypes 411 of the dot holes 4. In this way, by forming side surfaces with a small inclination like the first original shape 411 on the original shape 41 of the dot hole 4, it is possible to prevent the protrusion height h of the opening 42 of the dot hole 4 from becoming too large when the polishing process is completed. This will be described later. The beam diameter of the laser light can be controlled by the output power and current value of the laser light, and the beam diameter can be increased by increasing the output power of the laser light.

[0026] Returning to Figure 2, the alkaline etching process of step S4 in this embodiment is a process in which the silicon wafer 1, on which the original shapes 41 of the multiple dot holes 4 have been formed, is immersed in a high-concentration aqueous potassium hydroxide solution with a concentration of 40 wt% or more, and the wafer surface 11 and the original shapes 41 of the dot holes 4 are anisotropically etched. The amount of etching removal here is not particularly limited, but a thickness of approximately 5 to 15 µm is more preferable. By limiting the thickness of the etching removal to this range, the shape of the openings 42 can be controlled to a predetermined shape.

[0027] The final dot hole 4 of this embodiment is, as shown in FIG. 4, the opening 42 of the dot hole 4 on the wafer surface 11. <100> Length L1 in the direction <110> The ratio of the length L2 in the direction of the opening 42 is 1 to 1.10. <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 flat (100) plane.

[0028] FIG. 8 shows the crystal structure of a silicon single crystal wafer with a crystal plane orientation of (100), and FIG. 9 shows the structure of a silicon wafer 1 with a crystal plane orientation of (100) in which a blind hole is formed and anisotropically etched. <110> The cross section along the direction, Fig. 10, is also <100> 9 and 10, when blind holes (dot holes 4) are formed in a silicon wafer 1 having a (100) crystal plane orientation and anisotropically etched using a high-concentration alkaline etchant, the bottom surfaces 43 of the blind holes (dot holes 4) become (100) planes. <110> In a cross-sectional view along the direction, as shown in FIG. 9, both side surfaces 44 of the bottom surface 43 are (111) or (122) planes, and the (311) planes are connected to these. <100> In a cross-sectional view along the direction, as shown in FIG. 10, both side surfaces 45 of the bottom surface 43 are (110) or (120) surfaces.

[0029] Also, as shown in Figure 9, <110> In a cross section along the direction, when the (111) plane appears on the side surface 44, 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 (122) plane appears on the side surface, 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. Note that the angle formed by the bottom surface 43 of the (100) plane and the side surface 44 of the (311) plane is 25 degrees. Also, as shown in FIG. 10, <100> In a cross section along the direction, when the (110) plane appears on the side surface 45, the angle β formed by the bottom surface 43 of the (100) plane and the side surface 45 of the (110) plane is 45 degrees, and when the (120) plane appears on the side surface, the angle β formed by the bottom surface 43 of the (100) plane and the side surface 45 of the (120) plane is 64 degrees.

[0030] In this way, when blind holes (dot holes 4) are formed in a silicon wafer 1 having a (100) crystal plane orientation and anisotropically etched using a high-concentration alkaline etchant, crystal planes with a relatively slow etching rate appear, and dot holes 4 with shapes that are less variable than those obtained by acid etching can be obtained.

[0031] Therefore, in the alkaline etching step (step S4) of this embodiment, etching is performed so that the dot holes 4 are aligned with the crystal planes shown in Figures 9 and 10. However, the dot holes 4 of this embodiment do not need to be dot holes 4 consisting of complete crystal planes as shown in Figures 9 and 10, and etching may be performed with an appropriate removal amount so that part of each of these crystal planes is exposed.

[0032] 4 is a front view showing the wafer after the alkaline etching process of step S4 in FIG. 2, FIG. 5 is a cross-sectional view taken along line VV in FIG. 4, and FIG. 6 is a cross-sectional view taken along line VI-VI in FIG. 4. Note that FIG. 5 shows the silicon wafer 1 having a crystal plane orientation of (100). <110> It is also a cross-sectional view along the direction, and Figure 6 is also <100> The final dot hole 4 of this embodiment is a cross-sectional view of the opening 42 on the wafer surface 11 of the dot hole 4. <100> Length L1 in the direction <110> The ratio of the length L2 in the direction is 1 to 1.10. <100> Length L1 in the direction <110> If the ratio of the length L1 to the length L2 in the direction is greater than 1.10, i.e., if L1 is too long, the (110) plane sandwiched between the (111) plane or the (311) plane at the opening 42 of the dot hole becomes narrow, causing abrupt changes in film thickness, which generates stress and makes the film more likely to peel off.

[0033] The final dot holes 4 of this embodiment are the dot holes 4 shown in FIG. <110> In a cross section taken along the direction, the angle α between the side surface 44 and the wafer surface 11 (or bottom surface 43) is preferably 63 to 73 degrees. By making the angle as steep as possible by alkaline etching, even if the surface with the identification mark 5 is ground in the device process to make the dot hole shallower, the shape of the opening 42 can be maintained, and film peeling can be prevented while maintaining visibility.

[0034] The final dot holes 4 of this embodiment are the dot holes 4 shown in FIG. <100> In a cross section taken along the direction, the angle β formed between the side surface 45 and the wafer surface 11 (or bottom surface 43) is preferably 56 to 70 degrees. By making the angle as steep as possible by alkaline etching, even if the surface with the identification mark 5 is ground in the device process to make the dot hole shallower, the shape of the opening 42 can be maintained, and film peeling can be prevented while maintaining visibility.

[0035] Returning to FIG. 2 , the polishing step of step S5 in this embodiment is a step of polishing both surfaces of the silicon wafer 1 after etching with a polishing liquid containing abrasive grains. This results in a mirror-polished surface of the silicon wafer 1. The polishing slurry may be an alkaline slurry containing colloidal silica as abrasive grains. This polishing step can be performed by fitting the silicon wafer 1 into a carrier, sandwiching the wafer between upper and lower surface plates with abrasive cloths attached, pouring a slurry such as colloidal silica between the upper and lower surface plates and the wafer, and rotating the upper and lower surface plates and the carrier in opposite directions to perform mirror polishing on both surfaces of the silicon wafer 1. This reduces the unevenness of the wafer surface, resulting in a wafer with high flatness.

[0036] After the polishing process, one-sided finish polishing is performed by finish-polishing at least one side of the silicon wafer. This finish polishing includes both polishing of only one side and polishing of both sides. When polishing both sides, one side is polished first, and then the other side is polished. This polishing brings the roughness of the side with the identification mark 5 within a predetermined range. If the identification mark 5 is on the back side of the wafer 1 and only the front side is finish-polished, the front side will have a lower roughness than the back side with the identification mark 5.

[0037] Fig. 7 is a cross-sectional view showing the silicon wafer 1 after the polishing step of Fig. 2 has been completed. In the silicon wafer 1 of this embodiment, the protrusion height h of the opening 42 of the dot hole 4 on the wafer surface 11 is preferably less than 25 nm from the wafer surface 11. The laser irradiation in the laser irradiation step of step S3 of Fig. 2 causes the peripheral edge of the opening 42 of the dot hole 4 to protrude in an annular shape. This protrusion of the opening 42 is removed in the alkaline etching step of step S4, but it has been found to reappear in the polishing step of step S5.

[0038] For example, in the applicant's earlier patent application (JP Patent Publication No. 2020-68231), it was reported that, based on the assumption that there was a shortage of abrasive grains acting on the periphery of the dot holes during the polishing process, when a polishing slurry was supplied between the polishing pad and the silicon wafer to polish the surface of the silicon wafer, the abrasive grains contained in the polishing slurry fell into the dot holes, causing a shortage of abrasive grains on the periphery of the dot holes, and as a result, the amount of polishing on the periphery of the dot holes was reduced compared to the amount of polishing on other parts, resulting in the formation of a raised portion on the periphery of the dot holes.

[0039] Therefore, in the silicon wafer 1 of this embodiment, in order to make the protrusion height h of the opening 42 of the dot hole 4 on the wafer surface 11 less than 25 nm above the wafer surface 11, it is preferable to form the original shape 41 of the dot hole 4 with a side surface with a small slope like the first original shape 411 as shown in FIG. 3B so as to prevent a shortage of abrasive grains at the periphery of the dot hole 4. This allows the abrasive grains at the periphery of the dot hole 4 to remain in the first original shape 411 during the polishing process of step S5, thereby eliminating a shortage of abrasive grains. This makes it possible to make the protrusion height h of the opening 42 of the dot hole 4 on the wafer surface 11 less than 25 nm above the wafer surface 11, thereby improving the flatness of the laser mark printed area 3.

[0040] In contrast, in the silicon wafer 1 of this embodiment, the protrusion height h of the opening 42 of the dot hole 4 on the wafer surface 11 may be 30 nm or more above the wafer surface 11. As shown in FIG. 7 , leaving a protrusion on the periphery of the opening 42 of the dot hole 4 can prevent the etchant accumulated in the dot hole 4 from flowing out. This can prevent the etchant accumulated in the dot hole 4 from etching the periphery of the dot hole 4 unevenly when the silicon wafer 1 is removed from the etching tank. Note that, in order to make the protrusion height h of the opening 42 of the dot hole 4 on the wafer surface 11 30 nm or more above the wafer surface 11, for example, the original shape 41 of the dot hole 4 may have a steeply inclined side as shown in FIG. 3A so that there is a shortage of abrasive grains at the periphery of the dot hole 4.

[0041] As described above, with the laser-marked silicon wafer of this embodiment, even when forming identification marks 5 consisting of dot holes 4 with cross-sectional depths of 80 μm to 110 μm on a silicon wafer 1 with a (100) crystal plane orientation, the dot holes 4 have less variation than those formed by acid etching.

[0042] In addition, according to the laser-marked silicon wafer of this embodiment, the openings 42 of the dot holes 4 on the wafer surface 11 are <100> Length L1 in the direction <110> The ratio of the length L2 in the direction of the opening 42 is 1 to 1.10. <100> Since the length L1 in the direction is set to 80 μm to 110 μm, the shape of the opening 42 of the dot hole 4 is smoothly continuous, although it depends on the crystal orientation. This suppresses stress concentration at the corners of the opening 42, and as a result, film peeling is suppressed even when processing such as grinding is performed in subsequent device processes. In addition, because stress concentration is suppressed, slippage can be suppressed even when heat treatment is performed in subsequent device processes. Furthermore, since the dot hole 4 is deep, at 80 μm to 110 μm, visibility and identifiability are ensured even when processing such as grinding is performed in subsequent device processes.

[0043] Furthermore, according to the method for manufacturing a laser-marked silicon wafer of this embodiment, when forming an identification mark 5 consisting of dot holes 4 with a cross-sectional depth of 80 μm to 110 μm on a silicon wafer 1 with a (100) crystal plane orientation, laser light is irradiated onto the wafer surface 11 of the silicon wafer 1 with a (100) crystal plane orientation to form a plurality of blind holes (original shapes 41 of the dot holes 4) with a depth of 80 μm to 110 μm, and then the silicon wafer 1 is immersed in a potassium hydroxide aqueous solution with a concentration of 40 wt % or more to etch the wafer surface 11 and the blind holes (original shapes 41 of the dot holes 4) to a thickness of 5 to 15 μm, and then the wafer surface 11 is polished.As a result, although the shape of the openings 42 of the dot holes 4 depends on the crystal orientation, it is possible to fabricate an identification mark 5 with a specific shape that is smoothly continuous.

[0044] Furthermore, according to the laser-marked silicon wafer of this embodiment, the dot holes 4 shown in FIG. <110> In the cross section in the direction, the angle α formed between the side surface 44 and the wafer surface 11 (or bottom surface 43) is 63 to 73 degrees, and the angle α of the dot hole 4 shown in FIG. <100> In the cross section in the direction, the angle β formed between the side surface 45 and the wafer surface 11 (or bottom surface 43) is 56 to 70 degrees, and the cross-sectional shape of the dot hole 4 is a specific angle that is close to a right angle, so good visibility and identifiability are ensured even if the laser mark printing portion 3 is ground or polished in a device process, etc. [Example]

[0045] Example 1 The outer periphery of a silicon wafer having a crystal plane orientation (100) is irradiated with laser light to form the original shape 41 of the dot hole 4, and then 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, thereby reducing the depth D to 100.4 μm, <100> The length L1 in the direction is 95.8 μm, <100> Length L1 in the direction <110> A laser-marked silicon wafer 1 was produced, having dot holes 4 with a ratio (L1 / L2) of the length L1 to the length L2 in the direction of 1.04. A 1 μm nitride film was formed on this silicon wafer 1, and then a rapid heating heat treatment was performed at 1000°C. The state of film peeling of the nitride film around the dot holes 4 was observed using an electron microscope. The results, along with the conditions, are shown in Table 1. A binarized photograph of one dot hole 4 observed from the front is shown in Figure 11(A).

[0046] Example 2 The depth D of the dot hole 4 is 87.9 μm. <100> The length L1 in the direction is 81.0 μm, <100> Length L1 in the direction <110> Laser-marked silicon wafers 1 were produced under the same conditions as in Example 1, except that the ratio (L1 / L2) of the length L1 to the length L2 in the direction was set to 1.05, and the state of film peeling was observed. The results, along with the conditions, are shown in Table 1. A binarized photograph of one dot hole 4 observed from the front is shown in Figure 11(B).

[0047] Comparative Example 1 The depth D of the dot hole 4 is 89.2 μm. <100> The length L1 in the direction is 90.1 μm, <100> Length L1 in the direction <110> Laser-marked silicon wafers 1 were produced under the same conditions as in Example 1, except that the ratio (L1 / L2) of the length L1 to the length L2 in the direction was set to 1.23, and the state of film peeling was observed. The results, along with the conditions, are shown in Table 1. A binarized photograph of one dot hole 4 observed from the front is shown in Figure 11(C).

[0048] [Table 1]

[0049] 《Consideration》 When the depth D of the dot hole 4 is set to 80 to 110 μm, the opening 42 of the dot hole 4, <100> Length L1 in the direction <110> When the ratio (L1 / L2) of the length L2 in the direction of the dot hole 4 to the length L1 in the direction of the dot hole 4 was 1 to 1.10, as in Examples 1 and 2, no film peeling was observed. In contrast, when L1 / L2 exceeded 1.10, as in Comparative Example 1, film peeling was observed. This is because, as shown in the front view photograph in FIG. 11(C), the opening 42 of the dot hole 4 in Comparative Example 1 was substantially rectangular due to the large amount of removal by alkaline etching. As a result, the (110) planes at the corners between the (111) planes were narrow, which presumably caused a steep change in film thickness, generating stress and making film peeling more likely. The opening 42 of the dot hole 4 in Example 1 shown in FIG. 11(A) and Example 2 shown in FIG. 11(B) was an octagon with circular vertices, resulting in a nearly circular shape overall. As a result, the change in film thickness was small and stress concentration was less likely to occur. [Explanation of symbols]

[0050] 1. Silicon wafer 11...wafer surface 2...notch 3...Laser mark printing area 4...Dot hole 41...Original dot hole 411...The first original form 412...Second original form 42...Opening 43...Bottom 44, 45...Side 5...Identification mark L1… <100> Direction Length L2… <110> Direction Length α… <110> The angle between the bottom and side of the cross section along the direction β… <100> The angle between the bottom and side of the cross section along the direction h... Height of opening

Claims

1. A silicon wafer having a crystal plane orientation of (100), a surface roughness of 0.15 to 0.60 nm, and an identification mark consisting of a plurality of dot holes on the surface, the ratio of the length of the opening of the dot hole in the <100> direction to the length in the <110> direction on the wafer surface is 1 to 1.10, and the length of the opening in the <100> direction is 80 μm to 110 μm; The cross-sectional depth of the dot holes is 80 μm to 110 μm, A laser-marked silicon wafer, wherein the bottom surface of the dot hole is a flat surface of the (100) plane.

2. 2. The laser-marked silicon wafer according to claim 1, wherein the angle formed between the side surface of the dot hole and the wafer surface in a cross section in the <110> direction is 63 to 73 degrees.

3. 3. The laser-marked silicon wafer according to claim 1, wherein the angle formed between the side surface of the dot hole and the wafer surface in a cross section in the <100> direction is 56 to 70 degrees.

4. 3. The laser-marked silicon wafer according to claim 1, wherein the opening has a protrusion height of less than 25 nm from the wafer surface.

5. 3. The laser-marked silicon wafer according to claim 1, wherein the opening has a protrusion height of 30 nm or more from the wafer surface.

6. A laser beam is irradiated onto the surface of a silicon wafer having a crystal plane orientation of (100) to form a plurality of blind holes having a depth of 80 μm to 110 μm, and then the silicon wafer is immersed in an aqueous potassium hydroxide solution having a concentration of 40 wt % or more, and the wafer surface and the blind holes are etched to a thickness of 5 to 15 μm, forming dot holes in which the ratio of the length of an opening in the wafer surface in the <100> direction to the length in the <110> direction is 1 to 1.10, the length of the opening in the <100> direction is 80 μm to 110 μm, and the bottom surface is a flat (100) plane; The method for manufacturing a laser-marked silicon wafer includes polishing the surface of the wafer.

7. When irradiating the surface of the wafer with laser light, After irradiating the laser beam with a first beam diameter, irradiating the laser beam with a second beam diameter smaller than the first beam diameter, or 7. The method for producing a laser-marked silicon wafer according to claim 6, wherein the laser beam is irradiated with the second beam diameter, and then the laser beam is irradiated with the first beam diameter.

8. 7. The method for producing a laser-marked silicon wafer according to claim 6, wherein when the wafer surface is irradiated with laser light, the laser light is irradiated with a single beam diameter.

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