JPH0774135A - Dry-cleaning method of substrate surface - Google Patents

Abstract

PURPOSE:To clean the surface of a substrate having adhering substances which are objects to be removed by a method wherein the short wavelength output pulse beam of a laser is applied to the substrate surface. CONSTITUTION:If the pulse beam of a KrF excimer laser outputted from a KrF excimer laser oscillator 10 is applied to the surface of a substrate A, adhering substances on the substrate A surface which are objects to be removed are decomposed by the integrated effect of laser photodecomposition by the KrF excimer laser, the vibration of the substrate surface caused by the laser abrasion or the impact of the laser pulse, etc., and removed from the substrate A surface and the substrate A surface is cleaned. With this constitution, the adhering substances on the substrate surface can be removed in the air. Further, the cleaning of the substrate surface which is free from exhaust of organic substances, noises and environmental pollution and excellent from the viewpoint of environmental protection can be achieved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dry surface of a semiconductor, a metal, a ceramic, a magnetic material, an optical element, or the like (hereinafter collectively referred to simply as "substrate surface").
The present invention relates to a cleaning method, and more particularly, to a dry cleaning method for a substrate surface for removing adherent substances such as organic stains and inorganic stains attached to the substrate surface from the substrate surface.

[0002]

2. Description of the Related Art Conventionally, as a cleaning method for removing adhered substances such as organic stains and inorganic stains adhered to a substrate surface from the substrate surface, a wet process such as ultrasonic cleaning using an organic solvent is used. The following cleaning methods are generally known.

The ultrasonic cleaning using an organic solvent is
The substrate is placed in a solution in which an organic solvent such as trichlorethylene or freon is dissolved, and the synergistic effect of the organic solvent dissolved in the solution and the ultrasonic waves propagating in the solution causes the surface of the substrate placed in the solution to move. It is for cleaning.

[0004]

However, in the conventional method for cleaning the surface of the substrate as described above, trichlorethylene, which has a harmful effect on the human body, or CFC, which destroys the ozone layer, is used as the organic solvent. Therefore, there is a problem in that the organic solvent may leak to the external environment to cause pollution and also cause a global environment destruction.

Further, in the factory where the above-mentioned conventional cleaning method is carried out, there is a problem that the health of workers at the site may be impaired by the ultrasonic waves and the emission of the vapor of the organic solvent. It was

Further, since it is necessary to replace the organic solvent and work to put the substrate in and out of the solution, the cleaning work becomes complicated and is not very efficient.

Furthermore, there are problems that the substrate that reacts with the organic solvent cannot be cleaned and that the size of the substrate that cannot be put into the ultrasonic cleaning device cannot be cleaned.

The present invention has been made in view of the above-mentioned various problems of the prior art, and its object is to clean the surface of the substrate without using an organic solvent or ultrasonic waves. A new method for dry cleaning of the substrate surface by a new dry process with excellent practicality, which replaces the cleaning method by a wet process such as ultrasonic cleaning using an organic solvent. To provide.

[0009]

In order to achieve the above object, a method for dry-cleaning a substrate surface according to the present invention is such that a substrate having an adhering substance as an object to be removed on the substrate has a short-wave pulse shape. Is irradiated with a laser having an output beam of 1 to remove the deposits attached to the surface of the substrate.

[0010]

[Function] Irradiates a substrate having a deposit such as an organic stain or an inorganic stain to be removed on the surface with a laser having a short-wavelength pulsed output beam (short-wavelength pulse laser) with an appropriate light intensity. Then, the adhered substances on the substrate surface are decomposed and removed from the substrate surface by the total action such as laser photolysis by the short wavelength pulsed laser, laser ablation, or vibration of the substrate surface due to the impact of the laser pulse. The substrate surface can be cleaned.

Therefore, the substrate surface can be cleaned by a dry process which does not use an organic solvent which may cause pollution or an ultrasonic wave which may adversely affect the human body.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a dry cleaning method for a substrate surface according to the present invention will be described in detail below with reference to the drawings.

FIG. 1 shows a schematic configuration of a dry cleaning system for carrying out the dry cleaning method according to the present invention.

In the dry cleaning system shown in FIG. 1, a KrF excimer laser in an excimer laser is adopted as a short wavelength pulse laser, and reference numeral 10 is a KrF excimer laser oscillator 10. Shows. The KrF excimer laser oscillator 10 outputs a pulsed output beam (pulse beam) having a wavelength of 248 nm and a pulse width of 20 ns.

Further, the dry cleaning system includes a beam homogenizer 12 for converting a pulse beam output from the KrF excimer laser oscillator 10 into a beam having a uniform light intensity distribution, and the beam homogenizer 12 An electric aperture 14 that can change the aperture 14a that controls the size and shape of the output pulse beam and a movable electric stage 16 are provided to reduce the pulse beam output from the aperture 14a of the electric aperture 14. Alternatively, a condensing lens 18 made of quartz glass for enlarging, a belt conveyor 20 on which a plurality of substrates A are placed and sequentially moved, and a speed controller 22 for adjusting the moving speed of the belt conveyor 22.
And a mirror 24 for reflecting the pulse beam output from the condenser lens 18 to the substrate A on the belt conveyor 20, and the states of various devices such as the KrF excimer laser oscillator 10 and the beam homogenizer 12 described above. And a power measuring device 26 for detecting and displaying.

The aperture 1 of the electric aperture 14
The size and the light intensity of the pulse beam with which the surface of the substrate A is irradiated are adjusted by the position of 4a and the condenser lens 18.

Then, the KrF excimer laser oscillator 1
0, the electric aperture 14, the electric stage 16, the speed controller 22, and the power measuring device 26
CPU 30a, ROM via the interface 28
It is connected to a control unit 30 including a RAM 30b and a RAM 30c.

The ROM 30b is determined by the frequency of the pulse beam of the KrF excimer laser output from the KrF excimer laser oscillator 10, the size and shape of the aperture 14a formed by the electric aperture 14, and the moving position of the electric stage 16. The position of the condensing lens 18 and the moving speed of the belt conveyor 20 adjusted by the speed controller 22 are suitable for the material of the substrate A and the component of the deposit that is the removal target attached to the surface of the substrate A. A predetermined program is stored so that the conditions can be set.

In the RAM 30c, the CPU 30a has R
It is used as a working area when executing the program stored in the OM 30b.

The dry cleaning system can be constructed in the atmosphere and need not be constructed not only in the solution but also in the vacuum.

In the above structure, the control unit 30 controls the frequency of the pulse beam of the KrF excimer laser output from the KrF excimer laser oscillator 10, the size and shape of the aperture 14a formed by the electric aperture 14, the electric stage. The position of the condenser lens 18 determined by the moving position of 16 and the moving speed of the belt conveyor 20 adjusted by the speed controller 22 are controlled, and the material of the substrate A and the object to be removed attached to the surface of the substrate A are controlled. Conditions suitable for the components of the deposit are set.

In this way, with the conditions set, the substrate A
When the surface of the substrate is irradiated with the pulse beam of the KrF excimer laser output from the KrF excimer laser oscillator 10, the adhered substance, which is the removal target on the surface of the substrate A, becomes KrF.
The laser light is decomposed by a comprehensive action such as laser photolysis by an excimer laser, laser ablation, or vibration of the substrate surface due to the impact of a laser pulse, so that it is removed from the surface of the substrate A, and the surface of the substrate A can be cleaned. it can.

The cleaning effect of the dry cleaning system as described above will be described in detail below.

FIG. 2 (a) is a micrograph showing a state in which an organic adhesive having a thickness of several microns is attached to the surface of the magnetic head slider (ferrite substrate). This Figure 2
When the surface of the magnetic head slider in the state of (a) is irradiated with 2500 pulses of a KrF excimer laser pulse beam at a light intensity of 60 mJ / cm ² by the dry cleaning system, it is shown in FIG. Thus, the organic adhesive on the surface of the magnetic head slider was completely removed.

As a result of surface analysis of the state of FIG. 2B using Auger electron spectroscopy, it was proved that the magnetic head slider surface was completely clean.

It is considered that the temperature rise of the ferrite substrate due to the irradiation of the pulsed beam having the light intensity of 60 mJ / cm ² is small, and the damage to the substrate due to the heat is small.

As shown in FIG. 2 (a), the state in which the organic adhesive having a thickness of several microns is attached means
Since the adhered matter is extremely thickly adhered and the adhered matter due to ordinary surface dirt is on the nanometer order, such nanometer order adhered matter is
Pulsed beam of F excimer laser 60 mJ / cm
It was confirmed that it can be removed by irradiating several pulses (within 10 pulses) with a light intensity of ² .

Further, by increasing the light intensity of the pulse beam of the KrF excimer laser, it was possible to reduce the number of pulses required for cleaning the deposit on the substrate surface.

Therefore, it is possible to clean the surface of the substrate with a minimum number of pulses by previously obtaining the threshold of the light intensity that damages the substrate, and when the threshold of the light intensity is high. If a high-power, high-frequency KrF excimer laser is used for the cleaning, the cleaning efficiency can be extremely improved.

FIG. 3 (a) is a micrograph showing a state in which fingerprints are attached to the surface of the glass substrate. This FIG. 3 (a)
On the glass substrate surface in the state of, the KrF excimer laser pulse
Focus the beam to a light intensity of 500 mJ / cm ² and
Upon pulse irradiation, fingerprints on the surface of the glass substrate were completely removed as shown in FIG.

By the way, according to the measurement result of EPMA (electron probe material analysis), the fingerprint contains not only organic components containing C and O, but also inorganic components such as K, Na, Cl and Ca. However, according to the dry cleaning method for the substrate surface of the present invention, even a stain containing a complicated component such as a fingerprint is irradiated with one pulse of a KrF excimer laser which is a short wavelength pulse laser. As a result, it could be completely removed from the substrate surface.

Incidentally, in addition to the deposits attached to the surface of the glass substrate, the deposits attached to the surface of the quartz glass substrate can be similarly removed. As described above, the method for dry-cleaning a substrate surface of the present invention can clean the surface of a glass substrate or the like, and thus can be used for surface cleaning of optical equipment.

Further, a KrF excimer laser is set to 500
When condensing light intensity up to mJ / cm ² and irradiating the surface of a metal such as Cu or SUS, dirt attached to the surface of the metal
It was clarified by the optical microscope and Auger electron spectroscopy that it could be cleaned with a few pulses.

Further, as shown in FIG. 4, in the area where the surface of Cu is painted with a felt pen, KrF excimer
Focus the laser to a light intensity of 500 mJ / cm ² and
With 0 pulse irradiation, the ink application by the felt pen was removed, and a clean metal surface could be obtained.

Similarly, as shown in FIG. 5, when a KrF excimer laser is focused to a light intensity of 500 mJ / cm ² in a region where the surface of SUS is painted with a felt pen and 20 pulses are applied, the felt is irradiated. -The ink application with the pen was removed, and a clean metal surface could be obtained.

Therefore, the dry surface of the substrate according to the present invention
The cleaning method can be used for cleaning the surface of a PCB (printed circuit board), outgassing the inner wall of the chamber of a vacuum device, or the like. Moreover, by selectively irradiating only the dirty portion of the substrate surface with the pulse laser, it is possible to completely clean only the dirty portion without affecting the unclean portion. Like

Further, it goes without saying that it can be also used for surface cleaning of semiconductor wafers and surface cleaning of electronic materials such as ceramics and superconducting materials.

In the dry cleaning method for the substrate surface according to the present invention using the KrF excimer laser, the influence of oxygen and carbon in the atmosphere on the substrate surface is extremely small. That is, for example, the migration distance of molecules in the atmosphere for 20 ns is estimated to be 0.1 micron or less, and during irradiation of the KrF excimer laser,
Decomposition products of contaminants (contamination) are explosively released from the substrate surface. Therefore, the probability of reaction between molecules in the atmosphere and the surface of the substrate is considered to be very low unless surface melting occurs.

Furthermore, in the above embodiment, the KrF excimer laser of the excimer laser was used as the short wavelength pulse laser, but the Xe is not limited to this.
In addition to excimer lasers such as Cl excimer laser (wavelength 308 nm) and ArF excimer laser (wavelength 193 nm), a solid-state laser or a semiconductor laser, which is a short wavelength pulsed output beam with a wavelength of 400 nm or less, is appropriately used. Of course, you can do that. The pulse width can also be set appropriately.

Furthermore, unlike the wet process using an organic solvent, a short wavelength pulse in the atmosphere
Since the adhered matter is removed by a dry process by laser irradiation, a real process during the cleaning process such as observation by a video CCD camera, measurement of surface reflectance by a laser probe, generation of sound waves by laser-induced surface vibration, etc. In-situ observation of thyme can be done.

[0041]

Since the present invention is constructed as described above, it has the following effects.

Since a substrate having an adhered substance as an object to be removed on its surface is irradiated with a laser having a short-wavelength pulsed output beam, the adhered substance adhered to the surface of the substrate is removed. Irradiating a substrate with a contaminant such as organic stains or inorganic stains to be removed on the surface with a pulsed output beam of short wavelength (short wavelength pulsed laser) with appropriate light intensity results in short Adhesives on the substrate surface are decomposed and removed from the substrate surface by the combined action of laser photolysis by wavelength pulsed laser, laser ablation, or vibration of the substrate surface due to the impact of laser pulse. Can be cleaned.

Therefore, according to the dry cleaning method for the substrate surface of the present invention, (1) the adhered substances on the substrate surface can be removed in the atmosphere. (2) Clean the pollution-free substrate surface, which is excellent in environmental protection without emission of organic substances and noise, by a dry process without using organic solvents that affect the human body and the environment such as trichloroethylene and freon. Can be achieved. (3) Since cleaning is performed by irradiating the substrate with a short-wavelength pulsed laser, high-speed cleaning can be realized, and since an organic solvent is not used, it is not necessary to perform waste liquid treatment, and cleaning work is simplified. It is suitable for large-scale processing. (4) It can be widely used for surface cleaning of semiconductors, metals, ceramics, magnetic materials, optical elements and the like. (5) Only the dirty portion of the substrate surface can be selected and irradiated with the short-wavelength pulse laser, which is efficient. The effect such as can be obtained.

[Brief description of drawings]

FIG. 1 is a schematic configuration explanatory view showing a dry cleaning system for carrying out a dry cleaning method for a substrate surface according to the present invention.

FIG. 2A is a micrograph showing a state in which an organic adhesive having a thickness of several microns is attached to the surface of a magnetic head slider. FIG. 2 (b), the indicated magnetic head slider surface in FIG. 2 (a), the pulse beam of KrF excimer laser at a light intensity of 60 mJ / cm ² 25
It is a microscope picture which shows the state after irradiating 00 pulses.

FIG. 3 (a) is a micrograph showing a state in which fingerprints are attached to the surface of a glass substrate. FIG. 3B is the same as FIG.
On the glass substrate surface shown in (a), KrF excimer
It is a microscope picture which shows the state after irradiating 1 pulse of the pulse beam of a laser with the light intensity of 500 mJ / cm ² .

[FIG. 4] A region after the surface of Cu is filled with a felt pen and condensed with a KrF excimer laser to a light intensity of 500 mJ / cm ² and 20 pulses are irradiated, and the above KrF excimer laser is irradiated. It is a micrograph which compares and shows the area | region which did not do.

FIG. 5: 500 mJ / cm ^{2 of} KrF excimer laser is applied to the area where the surface of SUS is painted with a felt pen.
The area after concentrating up to the light intensity of 20 pulses and irradiating 20 pulses,
3 is a micrograph showing a comparison between a region not irradiated with the KrF excimer laser.

[Explanation of symbols]

 10 KrF Excimer Laser Oscillator 12 Beam Homogenizer 14 Electric Aperture 14a Aperture 16 Electric Stage 18 Condensing Lens 20 Belt Conveyor 22 Speed Controller 24 Mirror 26 Power Measuring Instrument 28 Interface 30 Controller 30a CPU 30b ROM 30c RAM

[Procedure amendment]

[Submission date] April 28, 1994

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Claims (4)

[Claims] 1. A substrate having a deposit as an object to be removed on its surface is irradiated with a laser having a pulsed output beam of a short wavelength to remove the deposit on the surface of the substrate. A method for dry cleaning the surface of a substrate, characterized in that 2. The dry cleaning method for a substrate surface according to claim 1, wherein the wavelength of the laser having the pulsed output beam is 400 nm or less. 3. The substrate according to claim 1, wherein the laser having the pulsed output beam is selectively applied only to a region of the surface of the substrate where the deposit is attached. How to dry and clean the surface. 4. The dry cleaning method for a substrate surface according to claim 1, 2 or 3, wherein a laser having the pulsed output beam is irradiated in the atmosphere.