JP2003007655A - Dry surface cleaning apparatus using laser - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a dry surface cleaning apparatus for removing contaminants of the surface, utilizing a laser. SOLUTION: The cleaning apparatus comprises a laser 1 for generating a laser beam 2, a beam transfer control means 11 for splitting the laser beam 2 into a first and second laser beams 15, 16 to be propagated in mutually different directions, a frequency-modulating means 13 for modulating the second laser beam 16 to generate a short-wavelength laser beam 14, having wavelength shorter than the wavelength of the second laser beam 16 and a laser-focusing lens 22 for converging the first laser beam 15 on a laser focus 24 around the surface of a work 6, to generate a plasma impulse wave 25 around the focus 24.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dry surface cleaning apparatus using a laser, and more particularly, to an improved cleaning speed and efficiency without causing surface damage regardless of the kind of surface contaminants and the size of base material. The present invention relates to a dry type surface cleaning device using a laser capable of cleaning a substrate with a laser.

[0002]

In the semiconductor industry, submicrometer contaminants cause serious problems such as circuit failure and poor yield on semiconductor surfaces. For example, particles of 0.06 μm or less may cause a fatal device defect in the next-generation household dynamic random access memory and the microprocessor. So the contamination control for silicon wafers is
It has become a serious problem in manufacturing related fields. With the increasing density of chip devices, there is a need for a technique to effectively remove the smallest particles from the semiconductor surface. It becomes more difficult. Traditional cleaning techniques such as gas jets, scrubbing, supersonic and chemical fluxes cannot effectively remove small particles below the micrometer and can cause mechanical damage to the surface. However, the use of excessive amounts of water and compounds may cause environmental pollution.

Recently, the laser cleaning technique has been known to provide a new method to the environment friendly method which can effectively remove smaller particles as it is a dry process. However, particle removal is related to the laser absorption of the particle surface that produces different cleaning forces, so that the particle surface cleaning efficiency depends strongly on the laser wavelength and the physical properties of the particle. Become. This makes it difficult to remove all particles with different optical and thermal properties using specific wavelengths due to the different interaction between the laser and the particles. Further, since the laser spot is small, the cleaning speed is relatively slow.

In order to solve the problems of conventional laser cleaning methods, Vaught (US Pat. No. 5,025)
3,424) discloses a shock wave particle removal method and apparatus for removing particles from a wafer surface using laser-induced shock waves. A laser beam to remove particles is focused into the atmosphere by a focusing lens to ionize air particles around the laser focus and generate a laser-induced plasma shock wave. The laser-induced plasma shock wave generated at this time is used to clean the wafer surface.

However, a part of the laser beam generated together with the laser-induced plasma shock wave is directly irradiated on the wafer surface, which may damage the wafer surface.

In addition, the conventional laser-induced plasma shock wave described above is an inorganic dry particle (inorganic dry particle).
s) can be effectively removed, but organic contaminant particles and layers (organic contamin) remaining on the wafer surface
There is a drawback that ated particles and layers) cannot be removed effectively.

Further, since the conventional laser-induced plasma shock wave is generated in air, the strength of the shock wave generated is small, and elements such as oxygen existing in the air are ionized to cause oxidation such as oxidation on the wafer surface. May cause surface damage.

[0008]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and an object thereof is laser-induced plasma for removing inorganic surface contaminants from one laser. A first laser beam for generating a shock wave and a second laser beam for effectively removing organic surface contaminants may be generated together to effectively remove organic and inorganic surface contaminants on the wafer surface. It is to provide a dry type surface cleaning device capable of performing.

Another object of the present invention is to prevent the laser beam from irradiating the surface of the work object by changing the advancing direction of the laser beam which causes damage to the wafer surface, and thus the work object. Still another object of the present invention is to essentially prevent surface damage of the laser and to enable effective cleaning work by laser-induced shock waves. It is possible to prevent damage to the surface of the base material due to a chemical reaction and to effectively remove surface contaminants.

[0010]

To achieve the above objects, according to one aspect of the present invention, there is provided a dry surface cleaning apparatus for removing contaminants on the surface of a work piece, the method comprising a laser beam. Generating a laser beam, a beam transmission control means for dividing the laser beam into a first laser beam and a second laser beam so that the first and second laser beams travel in mutually different directions, and a second laser beam. Working with the frequency modulation means for modulating to generate a short wavelength laser beam having a wavelength shorter than that of the second laser beam, and for directly removing contaminants on the surface using the short wavelength laser beam; and the first laser beam. Focus on the laser focus around the surface of the object to generate a plasma shock wave around the laser focus, and use the plasma shock wave to clean the surface on the surface. Dry surface cleaning apparatus comprising a laser focusing lens to clean the substance.

[0011]

1 is a schematic view showing a dry type surface cleaning apparatus according to the present invention.

The laser beam 2 generated by one laser oscillating means 1 passes through two different paths, and a first laser beam 15 for generating a plasma shock wave 25 and a second laser beam 14 for generating a short wavelength laser beam 14. The laser beam 16 is divided and transmitted. The beam transfer control means 11 may use a switching mirror 12 that operates by an on-off method, a beam separator (not shown) that operates by a beam separation method, or the like.

In order to perform cleaning using a plasma shock wave, a Q-switching Nd: YAG laser beam 2 having a fundamental wavelength of about 1064 nm is continuously reflected by a switching mirror 12 and a reflecting mirror 3,
The first laser beam 15 is directed onto the surface of the work piece 6. When the focusing lens 22 is used to focus the first laser beam 15, a plasma shock wave 25 is generated around the laser focus 24 from the air-induced plasma generated by the laser spark in air. The plasma shock wave 25 can be used to remove surface contaminants 5 deposited on the surface of the work piece 6. The intensity of the first laser beam 15 at the laser focus 24 is preferably about 10 ¹² W / cm ² . When the gas particles in the air begin to separate due to the strong electric field induced by the focused laser beam, they are ionized and then rapidly heated to generate a plasma shock wave.

The intensity of the first laser beam 15 can be increased around the laser focus 4 by expanding the beam size of the first laser beam 15 using the beam expander 21. Further, the laser nozzle 23 can be used to inject additional gas along the traveling direction of the first laser beam 15, as shown in detail in FIG. A transparent wave guide is used as the surface damage prevention means 31, and the plasma shock wave 25 is used in the first laser beam 15, but by the beam not used,
It is possible to prevent the surface of the work 6 from being damaged.

In order to precisely remove the organic particles and layers remaining on the surface of the work 6, the switching mirror 12
Is turned off, and the second laser beam 16 having the fundamental wavelength is passed through the frequency harmonic generating means 13. The second laser beam 16 having the fundamental wavelength (1064 nm) is a half-wavelength (532 nm) laser beam by the frequency harmonic generating means 13 and a ⅓ wavelength (approximately 3).
55nm) laser beam or 1/4 wavelength (266n
m) short wavelength laser beam 14 such as a laser beam
And is irradiated with the short wavelength laser beam 14 directly onto the surface of the work 6 by using the reflection mirror 9, so that the surface of the work 6 such as an organic substance adheres to the surface. The pollutant 5 can be effectively removed. Further, the order of the cleaning method may be changed so that the short wavelength laser beam 14 is first used to remove the organic material, and then the plasma shock wave 25 is used to remove any other particles. Further, when the beam transfer control means 11 is replaced with a beam separator, the plasma shock wave 25 and the short wavelength laser beam 14
Can be used simultaneously for surface cleaning. Therefore, using only one laser, the versatile cleaning (m
ulti-purpose cleaning).

On the other hand, the work 6 is attached to the work attaching means 41. The work adhering means 41 includes a vacuum chuck 43 having a cavity that is close to the other surface of the work 6, that is, the back side, and a vacuum pump 51 that vacuums the cavity to attach the work 6. And a vacuum line 52 connecting the vacuum chuck 43 and the vacuum pump 51.

The system controller 71 controls the laser 1 via the laser control line 72, the beam transfer control means 11 via the beam transfer control line 73, and the gas supply unit via the gas supply control line 76. 61 to control the vacuum pump 51 via the vacuum pump control line 75.
To control. In the system controller 71, the work attachment means 41 is horizontal and / or via the work movement control line 74.
Alternatively, it is moved vertically or is controlled to be rotated with respect to the vertical axis of the work 6. When the work adhering means 41 is rotated, the surface contaminants 5 removed from the surface of the work 6 are scattered by the centrifugal force.

FIG. 2 is a schematic diagram showing the laser nozzle means 23 shown in FIG. 1 according to the present invention.

The first laser beam 15 is incident on the laser nozzle 23. The laser nozzle 23 focuses the first laser beam 15 on the laser focus 4, a focus lens 22 for protecting the focus lens 22, and a gas inlet 61 for introducing gas from the gas supplier 61. It has a mouth 27 and a nozzle end 28 for outputting gas. The gas is injected with the laser beam through the nozzle end 28. Desirably, the gas travels along the traveling direction of the first laser beam 15, so that the particles detached by the plasma shock wave 25 generated around the laser focus 24 can be effectively removed. Further, a protective glass 26 is used, and the focus lens 22 is generated by the plasma shock wave 25 generated around the laser focus 24.
To prevent the focus lens 22 from being contaminated by gas. Instead of general air,
When an inert gas such as Ar, He, Ne, N ₂ is injected through the gas inlet 27, plasma is generated around the laser focus 24 more easily and strongly,
More powerful shock waves can be generated. The use of an inert gas has the advantage of reducing surface damage such as surface oxidation of oxygen particles contained in the air itself due to plasma. The intensity of the plasma shock wave generated in the Ar atmosphere is approximately doubled as compared with the plasma shock wave generated in the general air composed of about 80% of fume and about 20% of oxygen.
This is because the plasma generated by the high density laser beam in the Ar atmosphere can be generated more easily than the plasma generated by the high density laser beam in the air atmosphere.

FIG. 3 is a schematic view showing the principle of surface damage generation by plasma shock waves.

The focus lens 22 is used to form a laser focus 24 for the first laser beam 15 in the atmosphere above the surface of the workpiece 6 to be cleaned. When the energy of the first laser beam 15 is equal to or higher than the threshold value around the laser focus 24, the air around the laser focus 24 is ionized, and a strong plasma is generated. Plasma shock wave 25 generated at this time
Are propagated in all directions, and the propagating shock wave 25 removes all contaminant particles on the surface of the work 6. But first
The total energy of the laser beam 15 is the plasma shock wave 2
The first laser beam 1 that is not used to generate
A part of 5 will be incident on the surface of the work 6 along its traveling path. The first laser beam 15 incident on the surface of the work 6 is converted into heat on the surface and causes surface damage 32 on the surface of the work 6. Particularly, the surface of a material sensitive to heat or light such as a semiconductor material, a porcelain material, an organic material, a thin film coating layer, etc. is seriously damaged.

FIG. 4 is a schematic view for explaining the basic principle of the surface damage prevention method according to the present invention.

When light travels from the transparent solid material 38 into the air 39, it can either be transmitted to the air 39 or be reflected by the air 39, depending on its incident angle θ. As shown in FIG. 4, when the incident angle θ of the incident light 35 is 90 degrees, most of the light is transmitted as refracted light 36 to the air 39. When the incident angle θ of the incident light is smaller than 90 degrees and larger than the total reflection critical angle θ _C , a part of the incident light 35 is reflected by the air 39 as the reflected light 37, and the remaining part of the incident light 35 has a constant refraction. Refracted light with angles 3
6 is transmitted to the air 39. However, the incident angle θ
Is smaller than the critical angle θ _C , the incident light 35 is totally reflected from the contact surface between the transparent solid substance 38 and the air 39 without leaking to the outside. Such a phenomenon is called total reflection of light, and the present invention can effectively change the traveling direction of the laser beam by utilizing such a property. Examples of the transparent solid substance 38 include glass, quartz, diamond, and sodium chloride crystal (NaCl crystal). 47
Degree, the critical angle for total internal reflection of diamond is about 66
It is degree.

FIG. 5 is a schematic view showing a first example of the surface damage preventing method according to the present invention.

A rod 33 of transparent solid material having a circular or polygonal cross section can be used as the surface damage preventing means 31 shown in FIG. A rod 33 is provided between the periphery of the laser focus 24 where the plasma shock wave 25 is generated and the surface of the work 6 which is irradiated with the laser beam. Laser focus 2
The first laser beam 15 passing through 4 is incident on one end of the rod 33. As shown in FIG. 5, when the incident angle θ between the first laser beam 15 and the side surface of the rod 33 is smaller than the total reflection critical angle θ _{C, the} light is transmitted through the end of the rod 33. The entire laser beam is guided into the rod 33 and then emitted to the outside through the other end of the rod 33. As a result, by providing a rod-shaped transparent solid substance that causes total reflection, the traveling direction of the laser beam irradiated onto the surface of the work 6 can be freely adjusted. Since the first laser beam 15 does not affect the surface of the work 6 at all, no surface damage by the first laser beam 15 will occur.

FIG. 6 is a schematic view showing a second example of the surface damage preventing method according to the present invention.

The prism 34 made of a transparent solid material is shown in FIG.
It can be used as the surface damage prevention means 31 shown in FIG. Laser focus 24 where plasma shock wave 25 is generated
The first laser beam 15 is incident through one surface of the prism 34 by providing the prism 34 between the periphery and the surface of the work 6 to which the laser beam is irradiated. As shown in FIG. 6, when the incident angle θ between the laser beam incident on the prism 34 and the reflecting surface of the prism 34 is smaller than the total reflection critical angle θ _{C, the} total incident light on the prism 34 is reduced. The laser beam is totally reflected, travels to another surface of the prism 34, and then is emitted. As a result, the prism 3 made of a transparent solid material that causes total internal reflection
By providing 4, the traveling direction of the laser beam irradiated onto the surface of the work 6 can be freely adjusted. The first laser beam 15 is applied to the surface of the work piece 6.
Has no effect on the first laser beam 15
Will not cause any surface damage.

As shown in FIGS. 5 and 6, the important point in the surface damage prevention method using total reflection is that the laser beam entering the transparent solid substance can cause total reflection inside the substance. This means that the positions and orientations of the substances 33 and 34 must be controlled so as to maintain the angle below the threshold value.

FIG. 7 shows a work moving means 40 according to the present invention.
FIG.

The work moving means 40 is a work attaching means 41 for firmly fixing the work 6 such as a wafer, and a rotation for rotating the work attaching means 41 for efficiently cleaning the surface of the work 6. Means 42, linear movement means 4
It is composed of 7. The work attachment means 41 includes a vacuum chuck 43 for securely holding the work 6 and the work 6.
And a vacuum pump 51 for bringing the cavity between the vacuum chuck 43 and the vacuum chuck 43 into a vacuum state.
It is composed of a rotary fitting 53 and a vacuum line 52 for connecting to each other.

The rotating means 42 is provided in the opposite direction to which the work 6 is fixed with the vacuum chuck 43 as a reference, and the bearing 44, the drive motor 46 and the power transmission member for supporting the work adhering means 41 so as to rotate. It consists of 45. The linear movement means 47 comprises a slide movement device for linearly moving the work 6.

The surface contaminants 5 removed from the surface of the work 6 by the plasma shock wave 25 or the short wavelength laser beam 14 are effectively separated to the outside by the rotational centrifugal force of the work 6 by the drive motor 46. Blower 81
Thus, the surface contaminant 5 is separated downward. The linear movement means 47 is linearly moved in the left-right direction or the vertical direction so that the entire surface of the work 6 is cleaned while the work 6 rotates.

As described above, since the surface contaminant 5 is cleaned by the small movement of the laser 1, the cleaning can be stably performed. Further, by rotating the work 6, high-speed cleaning and effective particle blowing of surface contaminants by centrifugal force can be performed. Since the work 6 is rotating, even if the work 6 is moved by ½ of the size of the work 6 in each direction, the work 6 can be entirely cleaned. Compared with the conventional two-dimensional bidirectional xy scanning method, which requires moving the work 6 by the size of the work 6 along each direction of the work 6, the scanning method according to the present invention is temporal and spatial. Is efficient.

In FIG. 1, the surface of the work 6 to be cleaned is kept horizontal. However, as shown in FIG. 6, the surface of the work piece 6 is, for example, 90 degrees with respect to the horizontal plane.
When the cleaning is performed with a tilt, the possibility that the surface contaminant 5 separated by the shock wave 25 is reattached to the surface due to gravity is reduced, and the surface contaminant is easily removed downward along the air flow of the blower 81. You can

Although the preferred embodiments of the present invention have been described above, those skilled in the art could make various modifications without departing from the scope of the claims of the present invention.

[0036]

As described above, according to the present invention, it is possible to generate two different laser beams by using one laser and use these alternately or simultaneously to perform two different cleanings. Therefore, the organic particles, which have been difficult to remove by the conventional plasma shock wave, can be easily removed. Moreover, one laser device can remove various contaminants.

The use of the surface damage preventive means such as the rod or the prism according to the present invention prevents the surface damage of the work which may be caused by a part of the laser beam irradiated directly on the surface of the work in the conventional plasma shock wave cleaning process. Can be prevented. Therefore, by using the surface damage preventing means according to the present invention, the surface damage of a sensitive work object such as a wafer can be essentially prevented, and the plasma shock wave dry cleaning can be effectively performed.

By using the beam expander and the laser nozzle according to the present invention, the cleaning efficiency of the conventional plasma shock wave cleaning method can be substantially improved.

By using the work moving means according to the present invention, a high speed cleaning can be carried out, the detached contaminating particles are prevented from recontaminating and, consequently, the surface particles are permanently removed. You can

The apparatus according to the present invention comprises a dry surface cleaning process for a substrate wafer during a semiconductor manufacturing process, LCD, T
It can be used for a surface cleaning process in a flat panel display manufacturing process such as FT, PDP, OLED, and ELD, and a surface cleaning process in a manufacturing process for microelectronic components, porcelain components, precision-machined lenses and the like.

[Brief description of drawings]

FIG. 1 is a schematic view showing a dry surface cleaning apparatus according to the present invention.

2 is a schematic diagram showing the laser nozzle means shown in FIG. 1 according to the present invention.

FIG. 3 is a schematic diagram for explaining the principle of surface damage generation by plasma shock waves.

FIG. 4 is a schematic diagram for explaining a basic principle of the surface damage prevention method according to the present invention.

FIG. 5 is a schematic view showing a first example of the surface damage prevention method according to the present invention.

FIG. 6 is a schematic view showing a second example of the surface damage preventing method according to the present invention.

FIG. 7 is a schematic view showing a work moving means according to the present invention.

[Explanation of symbols]

1 laser 2 laser beam 3 reflection mirror 5 surface pollutants 6 work 11 Beam transmission control means 12 switching mirrors 13 Frequency modulation means 14 Short wavelength laser beam 21 beam expander 22 Focus lens 23 Laser nozzle 24 laser focus 25 plasma shock wave 31 Surface damage prevention means 41 Work attachment means 43 Vacuum chuck

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Zhao Sheng ▲ HO ▼             Pun, 117, Sanga-dong, Yongin-si, Gyeonggi-do, Republic of Korea             Rim Apartment 103-901 F term (reference) 3B116 AA03 AB01 AB34 AB47 BB89                       BC01                 5F004 AA14 BB03 BB16 BB18 BC02                       DA21 DA22 DA23 DA25                 5F072 AB02 JJ04 JJ20 KK05 KK12                       KK15 KK30 MM08 QQ02 RR01                       RR03 RR05 SS06 YY08

Claims (17)

[Claims] 1. A dry surface cleaning apparatus for removing contaminants on the surface of a work, comprising a laser for generating a laser beam, the laser beam being divided into first and second laser beams, Beam transfer control means for causing the first and second laser beams to travel in different directions, and modulating the second laser beam to generate a short wavelength laser beam having a wavelength shorter than the wavelength of the second laser beam, Frequency modulation means for directly removing contaminants on the surface using the short wavelength laser beam, and focusing the first laser beam on the laser focus around the surface of the work piece to generate a plasma shock wave around the laser focus. A dry type including a laser focusing lens for cleaning surface contaminants on the surface using the plasma shock wave Surface cleaning apparatus. 2. The dry surface cleaning apparatus according to claim 1, further comprising a laser nozzle provided around the laser focus and injecting an ionized gas in a traveling direction of the laser beam. 3. The dry surface cleaning apparatus of claim 2, wherein the gas is selected from the group containing Ar, He, Ne and N ₂ . 4. The transparent waveguide according to claim 1, further comprising a transparent waveguide provided along a traveling path of the first laser beam to disperse a part of the first laser beam that is not used for generating the plasma shock wave. The dry surface cleaning device described. 5. The dry surface cleaning apparatus of claim 4, wherein the transparent waveguide is made of a transparent solid material selected from the group consisting of glass, quartz, diamond and sodium chloride crystals. 6. The dry surface cleaning apparatus according to claim 4, wherein the transparent waveguide has a prism shape for performing total reflection on the part of the first laser beam. 7. The dry surface cleaning apparatus according to claim 4, wherein the transparent waveguide has a rod shape for performing total reflection on the part of the first laser beam. 8. The dry surface cleaning apparatus according to claim 1, wherein the beam transfer control means is a beam splitter. 9. The dry surface cleaning apparatus according to claim 1, wherein the beam transmitting means is a switching mirror. 10. The frequency modulator is frequency modulation means for generating the short wavelength laser beam, and the wavelength of the short wavelength laser beam is approximately 100 nm to approximately 600 n.
The dry surface cleaning apparatus according to claim 1, wherein the dry surface cleaning apparatus is m. 11. The dry surface cleaning apparatus of claim 1, further comprising a beam expander that increases the size of the first laser beam to increase the power density of the first laser beam at the laser focus. 12. The dry method according to claim 1, wherein the laser beam has a pulse period of about 1 nanosecond to about 100 nanoseconds, a pulse energy of about 0.1 J to about 100 J, and a wavelength of about 500 nm to about 200 nm. Surface cleaning device. 13. The wavelength of the short wavelength laser beam is 1/2, 1/3 or 1 / the fundamental wavelength of the laser beam.
4. The dry surface cleaning device according to claim 1, which is 4. 14. The dry surface cleaning apparatus according to claim 13, wherein the fundamental wavelength of the laser beam is approximately 1064 nm generated by an Nd: YAG laser. 15. The dry surface cleaning apparatus according to claim 1, further comprising a work adhering unit for adhering the work, and a moving unit for rotating and moving the work. 16. The dry surface cleaning apparatus according to claim 1, wherein the surface of the work is inclined by a certain angle with respect to a horizontal plane. 17. The work chucking means includes a vacuum chuck having a cavity adjacent to another surface of the work chuck, a vacuum pump for vacuuming the cavity to stick the work chuck, and the vacuum chuck. The dry surface cleaning apparatus according to claim 15, further comprising a vacuum line connecting the vacuum pump.