JPH10323779A - Method for cutting si substrate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method capable of conducting evaporating cutting or split cutting of a Si substrate. SOLUTION: A Si substrate 3 is cut by the local thermal shock generated by the processes namely; a process to have the Si substrate 3 heated by the irradiation of a laser beam 2-2, and a process to cut the heating. That is, the Si substrate 3 is cut by the process wherein the Si substrate 3 absorbs the laser beam 2-2 instantaneously and is heated rapidly, and the process that stops the irradiation of the laser beam 2-2 and sprays the gas to quickly cools the Si substrate 3. Furthermore, since the laser beam of about 9 μm wave length is most absorbed by the Si substrate 3, cutting is promoted by irradiating the Si substrate 3 with a CO2 laser beam chosen in a range of 9.1 μm-9.4 μm oscillation wave length.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for cutting a Si substrate, and more particularly to a method for cutting a Si substrate in a non-contact manner by using a CO ₂ laser beam.

[0002]

2. Description of the Related Art In recent years, the development of devices in which electronic circuits, optical circuits, and the like are mounted on a substrate made of a glass material, a magnetic material, a semiconductor material, a dielectric material, or the like has been actively performed. . Since several to thousands of these devices are formed in the substrate or on the front (or back) surface, in the final step, the substrate must be cut to separate each device. As a method of cutting and separating the substrate, a method of performing diamond blade dicing or scribing by irradiating a laser beam is used.

FIG. 8 shows an apparatus for cutting glass by irradiating a CO ₂ laser beam previously filed by the present applicant (Japanese Patent Application No. 5-63).
775).

In this apparatus, an assist gas G is blown from an assist gas introduction pipe 802 around a laser beam L irradiated from a CO ₂ laser (carbon dioxide laser) 801 and collected by a lens 806, and the laser beam L is applied to a base 803. By irradiating the upper glass substrate 804 and cutting the glass substrate 804 into two substrates A and B, the glass substrate 804
Are vacuum-adsorbed and fixed to the base 803 on the A side and the B side, respectively.

The groove 805 formed between the A side and the B side of the base 803 allows the laser beam L to penetrate the glass substrate 804, and the presence of the groove 805 allows the cutting state to be maintained. Can be.

[0006]

By the way, even if the glass substrate can be cut using the conventional cutting apparatus shown in FIG. 8, the Si substrate is cut by evaporation or splitting (a crack due to thermal stress is generated. The crack was developed by the trajectory of the CO ₂ laser beam and divided.

Accordingly, an object of the present invention is to solve the above-mentioned problems and to provide a cutting method capable of evaporating or cleaving a Si substrate.

[0008]

In order to achieve the above object, the present invention provides an Si substrate having an oscillation wavelength of 9.1 μm to 9.1 μm.
This is to cut the Si substrate by moving the Si substrate while irradiating a CO ₂ laser beam selected from a range of 4 μm.

Further, the present invention cuts a Si substrate by moving a CO ₂ laser beam while irradiating the Si substrate with a CO ₂ laser beam having an oscillation wavelength selected from a range of 9.1 μm to 9.4 μm. Is what you do.

In the present invention, in addition to the above structure, it is preferable to cut the Si substrate while blowing a gas such as N ₂ , O ₂ , Ar, or air along the irradiation direction of the CO ₂ laser beam.

In addition to the above-described structure, the present invention provides a method of mounting a Si substrate on a substrate holder having a groove or a slit through which a CO ₂ laser beam passes, and applying the CO ₂ laser beam to the Si holder.
Irradiation to the substrate is preferred.

In the present invention, in addition to the above structure, it is preferable that the Si substrate is cut by either evaporative cutting or split cutting.

In the present invention, in addition to the above structure, it is preferable to cut the Si substrate having the insulating film formed on the front surface, the back surface, or both surfaces.

According to the present invention, in addition to the above-described configuration, the oscillation wavelength is 9.
The CO ₂ laser beam in the range of 1 μm to 9.4 μm is preferably a CO ₂ laser beam selectively extracted by a grating.

According to the present invention, the step of irradiating the laser beam to the Si substrate and heating the same and the step of stopping the laser beam make it possible to reduce the
The i-substrate is locally cut by thermal shock. That is, the Si substrate is cut by the step of instantaneously absorbing the laser beam and rapidly heating the Si substrate, and the step of stopping the laser beam irradiation and rapidly blowing the gas to cool the Si substrate.

Here, the wavelength of the laser beam for absorbing the laser beam into the Si substrate was examined. FIG. 2 is a diagram showing the spectral transmittance characteristics of Si, in which the horizontal axis represents wavelength and the vertical axis represents transmittance. As a result, it was found that the laser beam having a wavelength of about 9 μm was most absorbed by the Si substrate. In order to realize a laser beam having such a wavelength, the oscillation wavelength of a CO ₂ laser oscillator may be effectively used.

FIG. 3 is a diagram showing the oscillation spectrum characteristics of the CO ₂ laser, wherein the horizontal axis indicates the wavelength and the vertical axis indicates the gain.

The CO ₂ laser oscillator, as shown in the figure,
Multi-mode oscillation is performed in a wide wavelength range of 9.1 μm to 11.3 μm. For this reason, a grating is provided in place of the rear side mirror of the optical resonator (the front side mirror and the rear side mirror) of the CO ₂ laser oscillator, and the reflection angle of the grating is adjusted. It has been found that a laser beam oscillating at one wavelength can be selectively extracted from a wavelength range where absorption is large, from 9.1 μm to 9.4 μm.

As can be seen particularly from FIG. 2, if an oscillation wavelength is selected from the wavelength band of 9.2 μm to 9.3 μm among the above-mentioned wavelength bands, a high laser beam output can be obtained and the cutting speed can be increased. .

Next, when evaporating and cutting the Si substrate,
In addition to applying thermal shock, it is necessary to prevent micro-cracks from occurring on the cut surface, to prevent the cut surface from being melted, and to prevent particles (particles) from adhering near the cut surface. is important. For that purpose, N ₂ , O ₂ ,
It is necessary to achieve rapid heating, rapid cooling and dry clean by spraying a gas such as Ar or air.

Also, when the Si substrate is cut by cleavage due to thermal stress, a rapid thermal expansion process of the laser beam irradiated surface of the Si substrate by rapid heating, gas blowing, and rapid cooling by laser beam movement ( It is important to instantaneously provide a rapid compression process due to temperature change).

For this purpose, a mechanism for blowing gas and moving the Si substrate to be cut or moving the laser beam is required. Furthermore, in order to realize ultra-local laser beam irradiation and rapid heating and cooling by stopping, it is important that a groove or slit through which a laser beam passes is formed in a substrate holder that holds a Si substrate. Note that S
SiO ₂ , SiO _{2 on} the front, back or both sides of the i-substrate
N, P to _{SiO 2, Ge, Ti, B} , Sb, Zn, N
If a material to which at least one kind of dopant such as a, Li, K or the like is added, or a material having a film formed of Si ₃ N ₄ or the like is used, the absorption of the laser beam into these films is promoted, so that more effect is obtained. The cutting can be performed in an appropriate manner.

[0023]

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings.

FIG. 1 is a conceptual diagram of a cutting apparatus to which the method for cutting a Si substrate according to the present invention is applied.

This cutting device uses a CO ₂ whose oscillation wavelength is variable.
A laser 1, an optical system 4 for condensing and guiding a laser beam 2-1 emitted from the CO ₂ laser 1 to a Si substrate 3 to be cut, a substrate holder 5 for holding the Si substrate 3, and an XYZ XYZ stage 6 moving in the direction
a nozzle 8 for supplying a quench gas 19 to the i-substrate 3,
A clean bench 9 covering the Si substrate 3 with the XYZ stage 6;

The CO ₂ laser 1 includes a CO ₂ laser tube 12 having a Brewster window 10 and an internal mirror 11, an external grating 13 disposed outside the Brewster window 10 of the CO ₂ laser tube 12, An angle adjusting unit 50 for adjusting the angle θ of the external grating unit 13 with respect to the center axis of the CO ₂ laser tube 12 is provided.

[0027] Inside the CO ₂ laser tube 12 mixed gas (CO _2, N _2, a gas mixture in a mixing ratio of 8:18:74 to the He) 14 is sealed, on either side of the CO ₂ laser tube 12 A pair of discharge electrodes 15-1 and 15-2 are provided. A high voltage is supplied between the electrodes 15-1 and 15-2 from a power supply (not shown). This power supply is CO
_2. A continuous oscillation drive circuit for continuously oscillating the laser 1 and a pulse oscillation drive circuit for pulse oscillation are built in, and any of the drive circuits can be driven.

The angle of the external grating section 13 can be adjusted by the angle adjusting section 50. The CO ₂ laser tube 12 can selectively oscillate the oscillation wavelength from the range of 9.1 μm to 9.4 μm by adjusting the angle θ by the external grating unit 13 and oscillate at a single wavelength. Then, the laser beam 2-1 oscillated by the single wavelength can be output through the internal mirror 11. The laser beam output from the internal mirror 11 is reflected by the total reflection mirror 16 of the optical system 4 and then reaches the condenser lens 17, where the laser beam 2-1 is condensed. The laser beam 2-2 condensed by the condenser lens 17 is focused on the surface of the Si substrate 3 and irradiated. Laser beam 2-2 is indicated by arrow 18-
N ₂ (or O ₂ , A
r, air) and the degree of cleanliness is increased. In addition, to promote rapid cooling to suppress micro cracks and to facilitate cutting and cutting,
The quenching gas (N ₂ ,
O ₂ , air, etc.) are blown in the direction of arrow 19. Si
The substrate 3 is fixedly installed on a substrate holder 5. The substrate holder 5 is fixed on an XYZ stage 6, where the Si substrate 3 is moved in the X, Y, and Z directions by rotation of a motor (not shown). Since the Si substrate 3 to be cut is provided in the clean bench 9, the excess atmosphere in the clean bench 9 is exhausted in the direction of arrow 20 by an exhaust device (not shown).

Next, a specific method of cutting the Si substrate will be described with reference to numerical values, but the method is not limited.

FIG. 4 is a view showing a state in which the cutting apparatus shown in FIG.
It is a schematic diagram which shows a mode when cutting a board | substrate.

A parallel laser beam (beam diameter: 12 mmφ, continuous oscillation output: 90 W) 2-1 having an oscillation wavelength of 9.3 μm is focused by the focusing lens 17. Focused laser beam 2-
2 is irradiated on the surface of a 0.5 mm thick Si substrate 3 and the CO ₂ laser device 1 is set so as to be focused. The diameter of the focal plane of the laser beam 2-2 is about 10
0 μm, and the output was 88 W. Arrow 18-
Gas supplied in the direction of 1, 18-2 has a pressure of 3 kg / cm
² N ₂ gas was used, and air at a pressure of 5 kg / cm ² was used as the quenching gas supplied in the directions of arrows 19-1 and 19-2. The XYZ substrate holder 5 to which the Si substrate 3 is fixed
As a result of irradiating the laser beam 2-2 onto the Si substrate 3 while moving the stage 6 in the X direction at a speed of 1 mm / sec, as shown in FIG.

Next, as a cleaving / cutting method, a flaw having a width of about 50 μm is previously formed on the edge of the Si substrate 3, and the flaw surface is used as a start position to irradiate the laser beam 2-2 while the Si substrate 3 is being cut. As a result of moving at a speed of 2 mm / sec,
It could be cut and cut. This cleaving and cutting is performed by the arrow 19
The quenching gas in the directions of -1, 19-2 is changed to the laser beam 2-
2 could be cut effectively by spraying it strongly immediately after irradiation on the Si substrate 3. Also, the higher the gas pressure of the quenching gas, the higher the cutting speed.

According to the method for cutting a Si substrate of the present invention, it is possible to cut various Si substrates.

FIG. 5 shows an insulating film (SiO 2) on the surface of the Si substrate 3.
₂ , B, P, Ge, Ti, Al, Na, L on SiO ₂
Addition of additives such as i, K, SiON, SiON
H etc.) FIG. When such an insulating film 21 is formed, the CO ₂ laser beam having a wavelength of 9.1 μm to 9.4 μm is more strongly absorbed by the insulating film 21, so that the cutting is further promoted.

FIG. 6 is a side view showing an Si substrate 3 having an insulating film 22 formed on the back surface.

Also in this case, the wavelength is from 9.1 μm to 9.4 μm.
Can be easily cut by irradiating a CO ₂ laser beam.

FIG. 7 is a side view showing a structure in which insulating films 21 and 22 are formed on the front and back surfaces of the Si substrate 3.

In this case, the wavelength is from 9.1 μm to 9.4 μm.
Cutting by the irradiation of the m ₂ CO ₂ laser beam is further promoted.

As described above, according to the present invention, (1) the Si substrate can be cut in a dry and clean atmosphere.

(2) No particles adhere to the surface of the cut Si substrate.

(3) Since it is not necessary to clean the cut Si substrate, there is no damage to electronic circuits and optical circuits on the Si substrate.

(4) The occurrence of microcracks can be suppressed,
The width of the cutting margin can be reduced.

(5) Conventionally, the cutting of the Si substrate was performed in an intermediate step, and thereafter, the bonding step, the packaging step, and the like were performed. However, according to the method of the present invention, the bonding and packaging steps were performed. This can be performed in a later final step, so that the process time can be reduced and quality control can be easily performed.

[0044]

In summary, according to the present invention, the following excellent effects are exhibited.

By moving the Si substrate or the CO ₂ laser beam while irradiating a CO ₂ laser beam having an oscillation wavelength selected from the range of 9.1 μm to 9.4 μm,
The Si substrate can be cut by evaporation or cut.

[Brief description of the drawings]

FIG. 1 is a diagram showing a conceptual diagram of a cutting apparatus to which a method for cutting a Si substrate according to the present invention is applied.

FIG. 2 is a diagram showing a spectral transmittance characteristic of Si.

FIG. 3 is a diagram showing an oscillation spectrum characteristic of a CO ₂ laser.

FIG. 4 is a schematic diagram showing a state when the Si substrate is cut by the cutting device shown in FIG. 1;

FIG. 5 is a side view showing an Si substrate on which an insulating film is formed.

FIG. 6 is a side view showing an insulating film formed on the back surface of a Si substrate.

FIG. 7 is a side view showing an insulating film formed on the front and back surfaces of a Si substrate.

FIG. 8 is a conceptual diagram showing an apparatus for cutting glass by irradiating a CO ₂ laser beam, which was previously filed by the present applicant.

[Explanation of symbols]

1 CO ₂ laser 2-2 laser beam 3 Si substrate 4 optics 5 substrate holder 6 XYZ stage 8 nozzle 9 clean bench 13 external grating unit

Claims (7)

[Claims] 1. An oscillation wavelength of 9.1 μm to 9.1 μm on a Si substrate.
By moving the Si substrate while irradiating a CO ₂ laser beam selected from a range of 4 μm,
A method for cutting a Si substrate, comprising cutting the substrate. 2. An oscillation wavelength of 9.1 μm to 9.1 μm on a Si substrate.
A method for cutting a Si substrate, comprising cutting the Si substrate by moving the CO ₂ laser beam while irradiating the CO ₂ laser beam selected from a range of 4 μm. 3. The method for cutting a Si substrate according to claim 1, wherein the Si substrate is cut while blowing a gas such as N ₂ , O ₂ , Ar, or air along the irradiation direction of the CO ₂ laser beam. . 4. The Si substrate is mounted on a substrate holder having a groove or a slit through which the CO ₂ laser beam passes, and the CO substrate is irradiated with the CO ₂ laser beam. The method for cutting a Si substrate according to any one of the above. 5. The method for cutting a Si substrate according to claim 1, wherein the Si substrate is cut by either evaporative cutting or split cutting. 6. The method for cutting a Si substrate according to claim 1, wherein the Si substrate having an insulating film formed on the front surface, the back surface, or both surfaces is cut. 7. The Si according to claim 1, wherein said CO ₂ laser beam having an oscillation wavelength in the range of 9.1 μm to 9.4 μm is a CO ₂ laser beam selectively extracted by a grating. Substrate cutting method.