JP2002184724A - Silicon ingot cutting device, cutting method and silicon wafer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a silicon ingot cutting device and a cutting method which are capable of accurately cutting off a silicon ingot without producing any swarf. SOLUTION: A silicon ingot cutting device (25) which cuts off a silicon ingot (18) at right angles to its longer direction is equipped with an excimer laser (1) which continuously oscillates an excimer laser beam (11) and a condensing optical system (24) which condenses the excimer laser beam (11) and irradiates the surface of the silicon ingot (18) with the condensed excimer laser beam (11). That is, the silicon ingot cutting device (25) irradiates the surface of the silicon ingot (18) with the continuously oscillated excimer laser beam (11) to cut off the ingot (11) at right angles to its longitudinal direction.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cutting apparatus, a cutting method, and a silicon wafer produced by cutting a silicon ingot with high accuracy without cutting chips.

[0002]

2. Description of the Related Art Conventionally, there has been known an ingot cutting apparatus for cutting a silicon ingot to produce a silicon disk serving as a base of a silicon wafer. It is disclosed on page 33. FIG. 8 is a schematic configuration diagram of an ingot cutting device according to the related art, and the related art will be described below with reference to FIG. In FIG. 8, the silicon ingot cutting device 2
Reference numeral 5 includes a wire row including a plurality of wires 19 which are arranged in parallel at predetermined intervals and reciprocate. By pressing such a wire 19 against the silicon ingot 18 and reciprocating the wire 19 while supplying a polishing liquid (not shown), the silicon ingot 18 is cut into a silicon disk 21 having a predetermined thickness (for example, 1.4 mm). I do.

[0003] Thereafter, the cut silicon disk 21 is
Each process such as chamfering, lapping, and polishing is performed to manufacture a silicon wafer 35 having a thickness of about 750 μm. In the following description, the longitudinal direction of the cylindrical silicon ingot 18 is referred to as a vertical direction, and a plane that is perpendicular to the longitudinal direction and corresponds to the surface of the silicon disk 21 formed by cutting is referred to as a horizontal plane.

[0004]

However, the prior art has the following problems. That is, in the silicon ingot cutting device 25 using the wire 19, a cutting width about the thickness of the wire 19 is required, and the silicon ingot 18 corresponding to the cutting width is discarded as chips. According to the prior art, the thickness of the wire 19 is, for example, 1
In order to manufacture a silicon wafer 35 having a thickness of about 60 to 180 μm and a thickness of 750 μm, the silicon ingot 18 having a width of about 160 to 180 μm is discarded. Since the production of the silicon ingot 18 requires a large amount of electric power, there is a problem that energy is wasted by discarding chips.

In view of the above problem, as a cutting method that does not generate chips, there is known a technique in which a brittle material is cleaved using a laser beam emitted from a CO2 or YAG laser oscillator (see, for example, Japanese Patent Application Laid-Open No. H11-157572). For example, "The Japan Society of Precision Engineering", 199
February, 1992, pp. 196-199). This means that the brittle material is focused and irradiated with CO2 laser light or YAG laser light,
It is about to cut.

[0006] However, such a laser cutting,
It is difficult to apply to the manufacture of the silicon wafer 35. That is, the long-wavelength laser light oscillated from the CO2 laser or the YAG laser has a low absorptance to be absorbed by silicon, and penetrates from the surface of the silicon ingot 18 into the inside. Therefore, there is a problem that the cut surface becomes rough or the cut is not performed.

The present invention has been made in view of the above problems, and provides a silicon ingot cutting apparatus and a silicon ingot cutting method capable of cutting a silicon ingot with high accuracy without generating chips. It is an object.

[0008]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention relates to a silicon ingot cutting apparatus for forming a silicon disk by cutting a silicon ingot at predetermined intervals. An excimer laser device that oscillates laser light and a condensing optical system that condenses excimer laser light on the surface of the silicon ingot are provided.

According to this structure, the ultraviolet excimer laser light is absorbed by the surface of the silicon ingot at a high absorption rate. Therefore, since strong energy concentrates only on the surface of the silicon ingot, a local temperature rise causes thermal stress, which tends to cause breakage. Alternatively, since excimer laser light has high photon energy, silicon bonds are locally broken, cracks are formed from the silicon bonds, and cracks are likely to occur. This makes it possible to manufacture a silicon disk having a smooth cross section and an accurate width. Also, since no chips are produced, silicon is hardly wasted. Also,
The same applies to a silicon wafer obtained by processing a silicon disk obtained by this cutting device.

Further, in the present invention, the excimer laser light may be continuously oscillated, and the excimer laser light may be condensed and cut into a silicon ingot. According to such a configuration, since the excimer laser light continuously oscillates, the silicon ingot can be continuously irradiated with the excimer laser light. As a result, the fractured surface becomes smoother than in the case of irradiating the pulse laser beam, and a highly accurate silicon disk can be obtained.
The same applies to a silicon wafer obtained by processing a silicon disk obtained by this cutting device.

The surface of the silicon wafer according to the present invention is obtained by oxidizing the surface of the silicon wafer obtained by cutting the excimer laser beam using a plasma gas excited by microwaves. According to the excimer laser cleaving, a crystal such as a silicon ingot is easily cleaved particularly from a cleavage plane. From this, not only the (100) plane of silicon but also, for example, the (111) plane and the (11) plane
0) The silicon wafer can be cut with high accuracy so that the surface becomes the front surface. The (111) plane and the (110) plane can be oxidized evenly by the oxidation using the plasma gas. Therefore, (11
ICs can be manufactured on the 1) plane and the (110) plane, and further high-performance ICs and ICs with unprecedented characteristics can be manufactured.
There is a possibility that C can be obtained.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment according to the present invention will be described in detail with reference to the drawings. First, a first embodiment will be described. FIG. 1 shows a configuration diagram of a silicon ingot cutting device 25 according to the first embodiment. In FIG. 1, a silicon ingot cutting device 25 includes an excimer laser device 1 and a condenser lens 24 that collects the excimer laser light 11 oscillated from the excimer laser device 1. The silicon ingot 18 is mounted on a rotatable rotary stage 32. The condensed excimer laser light 11 is irradiated at a predetermined distance from, for example, the upper part of the silicon ingot 18. The excimer laser light 11 condensed by the rotation of the silicon ingot 18 irradiates the surface of the silicon ingot 18 in a circumferential shape.

The light absorptivity of silicon has a strong wavelength dependence, and ultraviolet light such as excimer laser light 11 is
And absorb about several hundred thousand times the infrared light oscillated from the CO2 laser device. Therefore, the excimer laser beam 11 applied to the surface of the silicon ingot 18 is intensively absorbed in a narrow range of a very shallow portion of the surface. As a result, on the surface of the silicon ingot 18, the temperature difference between the temperature of the part irradiated with the excimer laser light 11 and the temperature of the part not irradiated with the excimer laser light 11 becomes very large, and a huge thermal stress is generated. Thereby, the cleavage is suitably performed, and the silicon disk 21 can be easily obtained. Note that the mechanism of the cleaving is not limited to the mechanism caused by the thermal stress. That is, since the excimer laser beam 11 has a higher photon energy than the infrared wavelength laser beam, the silicon bond is easily broken by one photon or two photons. As a result, a minute crack is formed from the condensing portion of the excimer laser beam 11, and the cutting progresses at a stretch. The silicon disk 21 separated from the silicon ingot 18 by the cleavage is removed by, for example, an arm 22 having a suction mechanism at the tip. Then, a laser beam 11 is applied to a place lowered by a predetermined width by an optical system (not shown), and a new silicon disk 21 is separated by cutting.

The silicon ingot 18 is set, for example, such that the (100) plane of the crystal is a horizontal plane.
Therefore, when cutting is performed, the wafer is cut so that the (100) plane becomes the surface of the silicon wafer 35. At this time,
For example, if the silicon ingot 18 is installed so that the (110) plane of the crystal is a horizontal plane, the (110) plane
If the (111) plane is set so as to be a horizontal plane, the (111) plane becomes the surface of the silicon wafer 35, respectively.

At this time, instead of mounting the silicon ingot 18 on the rotary stage 32, the lower portion of the silicon ingot 18 may be irradiated with the excimer laser beam 11 so that the silicon ingot 18 is suspended from a rotating mechanism. Alternatively, as shown in FIG.
7 and scan mirror 36 scan in a horizontal plane,
Irradiation around the fixed silicon ingot 18 may be performed. Thereby, the silicon ingot 18 is cut, and the silicon disk 21 is generated.

FIG. 3 is a sectional view showing another example of the silicon ingot cutting device 25 according to the first embodiment. FIG.
, The silicon ingot 18 is mounted on a fixed base 31. The silicon ingot cutting device 25
A beam shaper 41 for shaping the excimer laser beam 11 emitted from the excimer laser device 1 into a circle, a ring prism 39 for shaping the circular excimer laser beam 11 into a ring, and the ring-shaped excimer laser beam 11 inside. A ring concave mirror 40 for reflecting and condensing light is provided. The excimer laser beam 11 traveling from the left in FIG. 3 is shaped into a circle by the beam shaper 41 and is reflected downward by the mirror 38. And the ring prism 3
9, the beam is shaped into a hollow ring-shaped beam, and the beam diameter can be expanded. Then, the light is reflected by the ring concave mirror 40 to the inner peripheral portion thereof and condensed on the surface of the silicon ingot 18. The optical system such as the ring prism 39 is adjusted so that the excimer laser beam 11 is irradiated on the surface of the silicon ingot 18 at the same height in the vertical direction.

Thus, the excimer laser beam 11 is simultaneously irradiated on the outer peripheral surface of the silicon ingot 18. As a result, since the outer peripheral surface of the silicon ingot 18 is instantaneously heated over the entire circumference at the same time, a large thermal stress is generated, and the silicon ingot 18 is instantaneously cut in the same horizontal plane. That is, according to the silicon ingot cutting device 25 as shown in FIG.
It is not necessary to rotate 8 and the silicon disk 21 can be generated by short-time irradiation.

As described above, according to the present embodiment, the excimer laser beam 11 oscillated from the excimer laser device 1 is condensed and irradiated on the surface of the silicon ingot 18, and the silicon ingot 18 is cut by cutting. I have. As a result, chips are hardly generated from the silicon ingot 18 at the time of cutting, so that not only silicon is wasted but also the silicon disk 21 on which chips are generated.
To the silicon wafer 35. Further, the excimer laser beam 11 may be focused on a small area, and the high output excimer laser device 1 is not required. According to the excimer laser cutting, not only the (100) plane of silicon but also, for example, the (111) plane or (1) plane
10) The surface can be cut smoothly with high precision.

Next, a second embodiment will be described. FIG.
FIG. 4 shows a configuration diagram of an excimer laser device according to a second embodiment. In FIG. 4, an excimer laser device 1 includes a gas circulating unit 4 for circulating a laser gas as a laser medium,
The apparatus includes a microwave generation unit 5 for generating a microwave 30 for exciting a laser gas, and a laser chamber 2 having an amplification unit (not shown in FIG. 4) for oscillating the excimer laser light 11 therein. The gas circulating unit 4 includes a wind tunnel 27 through which the laser gas circulates. In the wind tunnel 27,
A blower 14 for circulating the laser gas and sending it into the laser chamber 2 and a heat exchanger 3 for cooling the laser gas are connected. Further, a part of the wind tunnel 27 is formed of the bellows 10 to make the connection flexible.

The microwave generator 5 includes a microwave generator 12 for generating a microwave 30, a microwave waveguide 13 for transmitting the microwave 30 into the laser chamber 2, an isolator 15, and a tuner 16. Have. A microwave 30 is generated from the microwave generator 12 by electric power supplied from a power supply (not shown). As an example, the frequency of the microwave 30 is 2.45 GHz. The microwave 30 generated from the microwave generator 12 propagates in the microwave waveguide 13 and the T-shaped tube 17.
At, the microwave is divided into a microwave 30 traveling upward and a microwave 30 traveling downward. At this time, each power becomes パ ワ ー of the microwave 30 generated from the original microwave generator 12. Upper and lower microwaves 30,3
0 passes through the isolators 15 and 15 that prevent the microwave 30 from returning, and passes through the tuners 16 and 16 to achieve impedance matching.

FIG. 5 shows the inside of the laser chamber 2.
An amplification section 26 is provided inside the laser chamber 2, and the front and rear portions of the amplification section 26 are sealed by windows 7 and 9 through which the excimer laser light 11 passes. A front mirror 6 that partially reflects the excimer laser light 11 and a rear mirror 8 that totally reflects the excimer laser light 11 are provided before and after the windows 7 and 9 as resonators. A laser gas indicated by an arrow 29 flows through the amplifying unit 26 at a high speed in the left-right direction in FIG. Tuner 1
The upper and lower microwaves 30, 30 having passed through the laser chambers 6, 16 are linearly applied to the amplifying unit 26 in the laser chamber 2 from above and below in the vertical direction, and continuously excite the laser gas inside the laser chamber 2. Thus, the excimer laser beam 11 can be continuously oscillated in a direction perpendicular to the flow direction of the laser gas and the irradiation direction of the microwaves 30. At this time, the distance between the front mirror 6 and the rear mirror 8 (this is referred to as a resonator length) and the size of the region irradiated with the microwave 30 are set so that the oscillating excimer laser light 11 becomes a single mode. It is even better to decide Accordingly, since the excimer laser beam 11 oscillates in a single mode, the light collecting property of the excimer laser beam 11 is improved, and the surface of the silicon ingot 18 can be more intensively irradiated. Therefore, thermal stress increases and cracking suitably occurs.

As described above, according to the second embodiment, the cutting is performed by the excimer laser beam 11 oscillated from the excimer laser device 1 excited by the microwave 30. According to the excimer laser device 1 excited by the microwave 30, the excimer laser light 11 can be continuously oscillated. Therefore, for example, when the excimer laser device 1 according to the second embodiment is used for the silicon ingot cutting device 25 shown in FIGS.
1 is continuously irradiated on the outer peripheral surface of the silicon ingot 18. Therefore, compared with the case of irradiating the pulsed excimer laser light 11, the laser light 11 is more efficiently concentrated,
Thermal stress increases, and a smooth fractured surface can be obtained. In addition, by continuously irradiating, it is possible to accurately control the energy of the excimer laser beam 11 irradiating the silicon ingot 18, and it is possible to irradiate more than necessary energy and roughen the cut surface. Not even.

Next, means for oxidizing the surface of the silicon wafer 35 will be specifically described. Silicon wafer 3
5 is obtained by subjecting the silicon disk 21 obtained by cutting the silicon ingot 18 by the silicon ingot cutting device 25 to various processes such as chamfering, lapping, and polishing. In order to form an IC on the silicon wafer 35 thus obtained, its surface needs to be oxidized. 6 and 7 are explanatory views of the silicon oxidizing apparatus 28. FIG. 6 is a sectional view, and FIG.
FIG. 6 and 7, the silicon oxidizing apparatus 28 includes a hollow cylindrical oxidizing chamber 23 in which a silicon wafer 35 is placed. Microwave generator 3
The microwave 33 generated from 4 passes through the waveguide 47 and enters the inside of the oxidation chamber 23 downward in FIG. Then, it is irradiated downward by a radial line slot antenna 43 having a plurality of openings 43A provided on the lower surface of the disk.

Below the radial line slot antenna 43, a grid-like shower plate 42 for discharging a process gas 44 downward is arranged. The shower plate 42 is connected to the outside of the oxidation chamber 23 by a pipe 46, and introduces a process gas 44 into the oxidation chamber 23 from the pipe 46. Below the shower plate 42, a silicon wafer 35 is placed horizontally. As the process gas 44, for example, a mixed gas of krypton (Kr) and oxygen (O2) is preferable. The process gas 44 spouted downward from the shower plate 42 is turned into plasma by microwaves, and the oxidizing power is strengthened to become a plasma gas 45. This plasma gas 45 is blown onto the surface of the silicon wafer 35,
Oxidizes the surface uniformly. Oxidation by such a microwave 33 is characterized in that there is almost no direction dependency on the crystal plane of silicon. That is, conventionally, only (100) could be oxidized uniformly, but, for example, the (111) plane and (110) plane can be oxidized uniformly. Therefore, the silicon ingot 18 is manufactured in advance so that the (111) plane is a horizontal plane, and the silicon ingot 18 is cut by the excimer laser beam 11 so that the surface of the silicon wafer 35 becomes (11).
1) It becomes a plane. Even for such a (111) plane, uniform oxidation is possible.

For example, in order to improve the performance of CMOS and the like formed on the silicon wafer 35, such as miniaturization and low power consumption, the (100) plane, which has been the mainstream until now, is not used.
In some cases, it is better to use another surface as the surface of the silicon wafer 35. However, conventionally, it has been difficult to accurately cut a surface other than the (100) surface, and it has been difficult to uniformly oxidize a surface other than the (100) surface. However, according to the silicon ingot cutting device 25 of the present invention, surfaces other than the (100) plane can be cut smoothly with high precision, and according to the silicon oxidizing device 28 of the present invention, uniform oxidation is also possible. That is, the performance of the IC formed on the silicon wafer 35 can be further improved. In addition, it is possible to manufacture an IC having characteristics different from those in the past.

In the description of each of the above-described embodiments, the silicon ingot 18 is cut at a predetermined interval and the silicon disc 2 is cut.
Although only cutting in the case of manufacturing No. 1 has been described, the present invention is not limited to this. For example, the present invention can be applied to a case where a silicon ingot is divided into two equal parts or three equal parts in the longitudinal direction and cut into a bulk having a predetermined width.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a silicon ingot cutting device according to a first embodiment.

FIG. 2 is a configuration diagram showing another embodiment of a silicon ingot cutting device.

FIG. 3 is a configuration diagram showing another embodiment of a silicon ingot cutting device.

FIG. 4 is a configuration diagram of an excimer laser device according to a second embodiment.

FIG. 5 is an explanatory diagram of an amplification unit inside a laser chamber.

FIG. 6 is a sectional view of a silicon oxidation apparatus.

FIG. 7 is an AA view of FIG. 6;

FIG. 8 is a schematic configuration diagram of a silicon ingot cutting device according to a conventional technique.

[Explanation of symbols]

1: excimer laser device, 2: laser chamber, 3: heat exchanger, 4: gas circulation unit, 5: microwave generation unit, 6:
Front mirror, 7: window, 8: rear mirror,
9: window, 10: bellows, 11: excimer laser light, 12: microwave generator, 13: microwave waveguide, 14: blower, 15: isolator, 16: tuner, 17: T-tube, 18: silicon ingot, 19:
Wire, 24: condenser lens, 25: silicon ingot cutting device, 26: amplifier, 27: wind tunnel, 28: silicon oxidizer, 29: laser gas flow, 30: microwave, 3
1: fixed stage, 32: rotating stage, 33: microwave,
34: microwave generator, 35: silicon wafer, 3
6: scan mirror, 37: mirror, 38: mirror, 3
9: ring prism, 40: ring concave mirror, 41: beam shaper, 42: shower plate, 43: radial line slot antenna, 44: process gas, 45: plasma gas, 46: piping, 47: waveguide.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Narutoshi Sugawa 35-2-102 Kawauchi Moto Hasekura, Aoba Ward, Sendai City, Miyagi Prefecture (72) Inventor Toshikuni Shinohara 2-2-4 Odawara Miyagino Ward, Sendai City, Miyagi Prefecture 303 F term (reference) 3C069 AA01 BA08 BB01 CA04 EA05 4E068 AE00 CA01 DA10 DB11

Claims (7)

[Claims] A silicon ingot cutting device (25) for cutting a silicon ingot (18) perpendicularly to its longitudinal direction, comprising: an excimer laser device (1) for oscillating an ultraviolet excimer laser beam (11); A silicon ingot cutting device, comprising: a converging optical system (24) for converging and irradiating (11) on the surface of the silicon ingot (18). 2. The silicon ingot cutting device according to claim 1, wherein said excimer laser device is a continuous wave excimer laser device for continuously oscillating excimer laser light. Ingot cutting device. 3. A silicon ingot cutting method for cutting a silicon ingot (18) perpendicularly to the longitudinal direction, wherein the excimer laser beam (11) of ultraviolet light oscillated from the excimer laser device (1) is used for cutting the silicon ingot (18). A method for cutting a silicon ingot, comprising irradiating the surface with light and cutting the silicon ingot (18) by cutting. 4. The method for cutting a silicon ingot according to claim 3, wherein the excimer laser beam is continuously oscillated to irradiate the silicon ingot. 5. An excimer laser beam (11) oscillated from an excimer laser device (1) is condensed and irradiated on the surface of a silicon ingot (18), and the silicon ingot (18) is cut at predetermined intervals in a direction perpendicular to the longitudinal direction. Silicon wafer manufactured by the above. 6. The silicon wafer according to claim 5, wherein the surface is oxidized by using a plasma gas excited by the microwave. 7. The silicon wafer according to claim 5, wherein the excimer laser beam (11) is an excimer laser device (1).
A silicon wafer characterized by being an excimer laser beam (11) continuously oscillated from the substrate.