JPH07230976A - Semiconductor substrate cleaning method, device, and system - Google Patents

Abstract

PURPOSE:To surely remove metal impurities from a semiconductor substrate without using harmful chemicals. CONSTITUTION:A semiconductor substrate 2 is housed in a chamber 1 as held by a vacuum chuck 3. An upper lid 5 is put on the chamber 1, and the inner atmosphere of the chamber 1 is replaced with an inert gas atmosphere. Pure water is applied onto the surface of the semiconductor substrate 2. Keeping the substrate 2 in this state, the surface of the substrate 2 is irradiated with ultraviolet rays. The surface of the semiconductor substrate 2 is rinsed with pure water and dried up.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a method for cleaning a semiconductor substrate,
The present invention relates to a cleaning device and a cleaning system, and more particularly, to a method for cleaning a semiconductor substrate, a cleaning device, and a cleaning system for removing metal impurities by irradiating the surface of the semiconductor substrate with ultraviolet light.

[0002]

2. Description of the Related Art As the degree of integration of semiconductor integrated circuits has increased, cleaning of semiconductor substrates has become very important.
Various methods have been proposed and put to practical use for cleaning semiconductor substrates up to now, and these methods should be roughly classified into wet cleaning using a chemical solution and dry cleaning using ultraviolet light or the like. You can

In the former wet cleaning, basically, the surface of the semiconductor substrate is cleaned by using a chemical solution such as hydrofluoric acid, hydrochloric acid, sulfuric acid, ammonia water, choline and hydrogen peroxide solution, and then ultrapure water is used. Rinsing has an advantage that not only organic impurities but also metal impurities can be completely removed. On the other hand, in the dry cleaning, the surface of the semiconductor substrate is irradiated with ultraviolet light in an atmosphere containing oxygen, and the irradiation of the ultraviolet light changes oxygen into highly reactive ozone, and this ozone removes organic impurities on the surface of the semiconductor substrate. It is decomposed and removed.

Recently, as a kind of wet cleaning, a method of irradiating with ultraviolet light while supplying a chemical solution to the surface of a semiconductor substrate is disclosed in, for example, Japanese Unexamined Patent Publication (Kokai) No. 3-50413 and Japanese Unexamined Patent Publication No. 4-15614. Proposed.

[0005]

However, the conventional wet cleaning method has a problem in that it uses a large amount of harmful chemical liquid and is therefore dangerous to handle and corrodes the equipment of the production line. Further, the drainage needs to be rendered harmless by a neutralization process or the like so that the problem of environmental pollution does not occur, which causes a problem of cost increase.

Further, as the degree of integration of semiconductor integrated circuits becomes higher, a higher-purity chemical solution is required, and as the diameter of a semiconductor substrate increases, the amount of chemical solution used for one cleaning tends to increase. Yes, all of these increased cleaning costs. Furthermore, in order to remove various metal impurities adhering to the surface of the semiconductor substrate by the wet cleaning method, it is necessary to sequentially use a plurality of types of chemicals, which results in a long cleaning time, and the cleaning of each chemical. There is also a problem that a large amount of pure water is required because a pure water rinse is performed between them.

On the other hand, the dry cleaning method has a problem that the metal impurities attached to the surface of the semiconductor substrate cannot be removed. Therefore, an object of the present invention is to provide a method for cleaning a semiconductor substrate that can reliably remove metal impurities without using a harmful chemical solution.
Still another object of the present invention is to provide a semiconductor substrate cleaning system capable of surely removing metal impurities and reusing pure water without using harmful chemicals. is there.

[0008]

In order to achieve this object, a method of cleaning a semiconductor substrate according to the invention comprises a step of horizontally supporting a semiconductor substrate by a supporting means, and pure water on the surface of the supported semiconductor substrate. To form a pure water thin film on the surface of the semiconductor substrate, irradiating the surface of the semiconductor substrate having the pure water thin film with ultraviolet light, and the semiconductor substrate irradiated with the ultraviolet light. And rinsing the rinsed semiconductor substrate with pure water, and drying the rinsed semiconductor substrate.

According to this method, the pure water thin film preferably has a thickness of about 2 mm to about 3 mm. It is preferable that the method further comprises the step of irradiating the surface of the supported semiconductor substrate with ultraviolet light in an oxygen-containing atmosphere before supplying the pure water to the surface of the semiconductor substrate.

It is preferable that the pure water is continuously supplied to the surface of the semiconductor substrate even during the irradiation of the ultraviolet light. It is desirable that the semiconductor substrate be rotated during the irradiation of the ultraviolet light. The step of irradiating the ultraviolet light is
It is preferable to include a step of creating the ultraviolet light by cutting a wavelength component of about 400 nm or more from the irradiation light from the light source.

Further, the semiconductor substrate cleaning apparatus according to the present invention comprises a supporting means for horizontally supporting the semiconductor substrate and pure water supplied to the surface of the supported semiconductor substrate to form a pure water thin film on the surface of the semiconductor substrate. For supplying ultraviolet light to the surface of the semiconductor substrate on which the pure water thin film is formed, and pure water on the surface of the semiconductor substrate irradiated with the ultraviolet light. A second pure water supply means for supplying water to rinse the surface of the semiconductor substrate and a drying means for drying the rinsed semiconductor substrate are provided.

In the semiconductor substrate cleaning apparatus having such a structure, the first and second pure water supply means are composed of the same pure water supply nozzle, and the ultraviolet light irradiation means is in the visible range. A light source that emits light having a wavelength up to the ultraviolet range, and a visible light cut that is disposed between the light source and the supporting means and blocks the visible light and irradiates only the ultraviolet light onto the surface of the semiconductor substrate. Preferably, the supporting means includes a filter, and the supporting means includes a rotatable shaft and a chuck that is fixed to the shaft and holds the semiconductor substrate, and the shaft is preferably rotated during the irradiation of the ultraviolet light.

Another semiconductor substrate cleaning apparatus according to the present invention is arranged so as to face a support means for horizontally supporting the semiconductor substrate and a surface of the semiconductor substrate supported by the support means so as to form a very small gap. And a pure water that is formed in the irradiation window and supplies pure water to the gap between the surface of the semiconductor substrate and the irradiation window to form a thin film of pure water on the surface of the semiconductor substrate. The water supply means and an ultraviolet light source for irradiating the surface of the semiconductor substrate on which the pure water thin film is formed with ultraviolet light through the irradiation window are provided.

In the semiconductor substrate cleaning apparatus having such a structure, the second irradiation window is arranged so as to face the back surface of the semiconductor substrate supported by the supporting means so as to form a very small gap. A thin film of pure water is provided on the back surface of the semiconductor substrate by forming pure water in the gap between the back surface of the semiconductor substrate and the second irradiation window. And a second ultraviolet light source for irradiating the back surface of the semiconductor substrate on which the pure water thin film is formed with ultraviolet light through the second irradiation window. Is preferred.

A semiconductor substrate cleaning system according to the present invention comprises a pure water producing unit, and pure water supplied from the pure water producing unit, applied on the surface of the semiconductor substrate in a thin film state, and the pure water is applied. The semiconductor substrate cleaning unit that irradiates the surface of the semiconductor substrate with ultraviolet light to clean the surface of the semiconductor substrate, and the pure water used in the semiconductor substrate cleaning unit is collected, and the pollution degree of the collected pure water is And a pure water recovery unit that circulates the pure water whose contamination degree is less than or equal to a predetermined value to the pure water production unit through a foreign matter removal filter. In the semiconductor substrate cleaning system having such a configuration, it is preferable that the pure water production unit injects into the pure water a reducing agent that reduces dissolved oxygen in the pure water when producing the pure water.

[0016]

According to the present invention, pure water is supplied to the surface of the semiconductor substrate after the semiconductor substrate is horizontally supported by the supporting means. The pure water is supplied so that a pure water thin film is formed on the surface of the semiconductor substrate. The surface of the semiconductor substrate on which the pure water thin film is formed is irradiated with ultraviolet light, and the semiconductor substrate irradiated with this ultraviolet light is rinsed with pure water. After this rinse, the semiconductor substrate is dried. When the surface of the semiconductor substrate is coated with pure water in a thin film and irradiated with ultraviolet light, metal impurities on the surface of the semiconductor substrate are removed.

Further, in the present invention, the support means horizontally supports the semiconductor substrate, and the pure water supply means supplies pure water to the gap between the surface of the semiconductor substrate and the irradiation window. This pure water is guided to the gap between the surface of the semiconductor substrate and the irradiation window, flows to the surface of the semiconductor substrate, and forms a thin film of pure water there. In this state, the ultraviolet light source irradiates the surface of the semiconductor substrate on which the pure water thin film is formed with ultraviolet light through the irradiation window.

Further, in the present invention, the pure water producing unit supplies the produced pure water to the semiconductor substrate cleaning unit. The semiconductor substrate cleaning unit applies pure water supplied from the pure water producing unit to the surface of the semiconductor substrate in a thin film form, and irradiates the surface of the semiconductor substrate coated with the pure water with ultraviolet light to emit the semiconductor substrate. Wash the surface of the. The pure water collecting unit collects the pure water used in the semiconductor substrate cleaning unit and measures the contamination degree of the collected pure water. The pure water whose degree of pollution is equal to or lower than a predetermined value is circulated to the pure water production unit through the foreign matter removal filter and reused.

[0019]

Embodiments of a semiconductor substrate cleaning method, cleaning apparatus and cleaning system according to the present invention will be described below with reference to FIGS. 1 and 2 show a first embodiment of a semiconductor substrate cleaning apparatus according to the present invention. In both drawings, a vacuum for vacuum-sucking a semiconductor substrate 2 is provided at the center of the bottom of a PTFE chamber 1. A chuck 3 is arranged, and this vacuum chuck 3 is attached to the tip of a shaft 4 which is inserted through the lower portion of the chamber 1. The shaft 4 is configured to be movable in the vertical direction and rotatable at high speed.

The upper lid 5 arranged above the chamber 1 has an ultraviolet light lamp chamber 6, and the ultraviolet light lamp chamber 6 has a low pressure mercury lamp 7 built therein. A bandpass filter 8 made of synthetic quartz, which functions as an ultraviolet light irradiation window, is attached to the lower surface of the ultraviolet light lamp chamber 6. As the bandpass filter 8, a visible light cut filter that transmits far ultraviolet light of the light emitted from the low-pressure mercury lamp 7 and cuts light on the long wavelength side is used. The upper lid 5 is connected to an upper lid opening / closing cylinder device 9 via a lamp holder 10, and the upper lid opening / closing cylinder device 9 drives the upper lid 5 to open / close with respect to the chamber 1.

As shown in FIG. 2, the chamber 1 includes a pure water discharge nozzle 11, a gas discharge nozzle 12, a shower nozzle 13, an exhaust duct 14, and a gate valve 1.
5, a drainage port 16, a liquid level sensor 17, an observation window 18, and the like are installed. The pure water discharge nozzle 11 and the gas discharge nozzle 12 are configured to be movable in the radial direction of the semiconductor substrate 2, the pure water discharge nozzle 11 discharges pure water over the entire surface of the semiconductor substrate 2, and the gas discharge nozzle 12 is Injecting an inert gas such as nitrogen gas or argon gas.

Next, the operation of this embodiment will be described. The semiconductor substrate 2 is suction-held by the vacuum chuck 3 so that its surface is horizontal. In this state, the upper lid 5 is covered by the opening / closing cylinder 9 on the chamber 1 to make the inside of the chamber 1 airtight. After this, the exhaust duct 1
4 exhausts the inside of the chamber 1, and the gas discharge nozzle 12 injects an inert gas into the chamber 1 to replace the chamber 1 with an inert gas atmosphere. At this time, the gas discharge nozzle 12 is reciprocated in the radial direction of the semiconductor substrate 2 in order to expedite the replacement with the inert gas atmosphere.

Thereafter, the pure water discharge nozzle 11 discharges pure water onto the surface of the semiconductor substrate 2 to form a thin film of pure water on the surface of the semiconductor substrate 2. At this time, the pure water discharge nozzle 11
Is reciprocated in the radial direction of the semiconductor substrate 2 to form a pure water thin film having a uniform thickness on the surface of the semiconductor substrate. After the pure water thin film is formed, the shaft 4 moves up to bring the semiconductor substrate 2 closer to the bandpass filter 8 by a predetermined amount. Then, the low-pressure mercury lamp 7 is turned on, and the surface of the semiconductor substrate 2 is irradiated with far-ultraviolet light through the bandpass filter 8. After irradiation with the far-ultraviolet light for a predetermined time, the semiconductor substrate 2 is lowered to a fixed position by the shaft 4, pure water is discharged again by the pure water discharge nozzle 11, and the semiconductor substrate 2 is rinsed.

Thereafter, the shaft 4 rotates at a high speed to rotate the cleaned semiconductor substrate 2 to remove pure water from the surface of the semiconductor substrate by a centrifugal force, and at the same time, the gas discharge nozzle 12 heats the heated nitrogen gas or the like. An inert gas is evenly sprayed onto the semiconductor substrate 2 to dry it.

As described above, when the semiconductor substrate 2 is coated with pure water in the form of a thin film and irradiated with ultraviolet light, the metal impurities can be washed and removed from the surface of the semiconductor substrate 2. The reason why the metal impurities can be removed in this manner is presumed to be that the metal adsorbed on the surface of the semiconductor substrate is desorbed in the liquid as a complex ion by a photochemical reaction by ultraviolet light.

Next, an experimental example of the semiconductor substrate cleaning method according to the present invention will be described below. The experiment was performed using the semiconductor substrate cleaning apparatus shown in FIGS. 1 and 2, and the experimental conditions are as follows. That is, the semiconductor substrate 2 is an n-type 2
Prepared and two p-type, each after cleaning with chemicals,
Forced contamination with iron (Fe), nickel (Ni), copper (Cu), and zinc (Zn). The chamber 1 is in a pure nitrogen atmosphere, and the thickness of the pure water thin film on the surface of the semiconductor substrate 2 is 2 mm around the semiconductor substrate surface and 3 mm at the surface center.
Met. The main emission spectrum of the low-pressure mercury lamp 7 is 18
4.9 nm and 253.7 nm, and the output of the low-pressure mercury lamp 7 was 32 mW / square cm at 184.9 nm and 8.0 mW / square cm at 253.7 nm.
The distance between the low-pressure mercury lamp 7 and the semiconductor substrate 2 is about 20 m
m, and the irradiation time of ultraviolet light was about 10 minutes. In addition, the semiconductor substrate is dried at 1900 rpm.
It was carried out by spraying nitrogen gas at about 60 ° C. onto the semiconductor substrate while rotating at.

As for the degree of contamination, the surface metal contamination concentration was measured at four points on the semiconductor substrate before and after cleaning, and the average value was calculated. The results of this experiment are shown in Table 1 below.

[Table 1] In Table 1, DL is less than or equal to the detection lower limit, and F
The detection limits for e, Ni, Cu, and Zn are 3, 1 ,.
A ^{8,0.9,0.5 (× 10 10 cm -2)} . As can be seen from Table 1, the metallic impurities can be effectively removed from the surface of the semiconductor substrate 2 by irradiating the semiconductor substrate 2 with pure water in a thin film state and irradiating with ultraviolet light. It is also effective to irradiate the surface of the semiconductor substrate with ultraviolet light in an oxygen-containing atmosphere before supplying pure water to the surface of the semiconductor substrate. Such cleaning
For example, it is particularly effective in removing copper (Cu) adsorbed in a hydrofluoric acid aqueous solution, and when silicon (Si) is oxidized by ultraviolet light and oxygen in the atmosphere, pure water after that is applied. The removal of copper (Cu) in the ultraviolet light irradiation treatment is significantly improved. Although an inert gas such as nitrogen is introduced into the chamber 1, the cleaning effect may be enhanced by introducing high-purity oxygen instead of high-purity nitrogen depending on the cleaning conditions.

FIG. 3 shows another modification of the present invention. A semiconductor substrate chuck 19 is attached to a shaft 4 which penetrates through a PTFE chamber 1. The semiconductor substrate chuck 19 has an outer periphery of the semiconductor substrate 2. The portion is gripped to hold the semiconductor substrate 2 horizontally. The pure water discharge nozzle 11 is
The semiconductor substrate 2 is arranged so that the pure water is discharged to almost the center of the semiconductor substrate 2 held by the semiconductor substrate chuck 19. A low-pressure mercury lamp 7 that emits an output of 80 mW / square cm at 254 nm is built in the ultraviolet light lamp chamber 6, and a visible light cut filter 8 is attached to the opening end of the ultraviolet light lamp chamber 6. The low-pressure mercury lamp 7 has a spectrum in the visible range of 400 nm to 700 nm in addition to the ultraviolet range. That is, 185 nm, 254 nm, 313 nm,
In addition to the ultraviolet spectrum of 365 nm, 405 nm,
It has a spectrum in the visible region of 436 nm, 546 nm, 578 nm ... The visible light cut filter 8 is 40
It blocks visible light of 0 nm to 700 nm and functions as a partition wall between the ultraviolet light lamp chamber 6 and the chamber 1.

Next, the operation of this modification will be described. After substituting the atmosphere in the chamber 1 with argon gas, the pure water discharge nozzle 11 discharges pure water with a flow rate of 0.2 l / min almost to the center of the semiconductor substrate 2 to form a pure water thin film on the entire surface of the semiconductor substrate. While coating, the low pressure mercury lamp 7 irradiates the surface of the semiconductor substrate with ultraviolet light. In order to uniformly irradiate the entire surface of the semiconductor substrate 2 with ultraviolet light, that is, to prevent uneven irradiation of ultraviolet light, the shaft 4 is irradiated during the irradiation of ultraviolet light.
Is about 10 r. p. Slow rotation at m.

The visible light cut filter 8 blocks visible light from the ultraviolet light and the visible light emitted from the low-pressure mercury lamp 7 and irradiates the semiconductor substrate 2 with only the ultraviolet light. As described above, when the semiconductor substrate 2 is irradiated with only ultraviolet light, copper (Cu), chromium (Cr), or iron (when the semiconductor substrate 2 is irradiated with both ultraviolet light and visible light). Fe)
It has been found through experiments that the removal rate of metals such as is significantly improved. FIG. 4 shows the experimental results when a full-wavelength transparent glass that transmits all wavelengths from the ultraviolet range to the visible range is installed in front of the mercury lamp and when the visible light cut filter 8 of FIG. 3 is installed. It is a thing. The horizontal axis shows the all-wavelength transmission glass and the visible light cut filter, and the vertical axis shows the metal removal rate. The removal rate represents the ratio of the amount of metal after the cleaning process to the amount of metal attached to the semiconductor substrate before the above cleaning process. It can be seen from FIG. 4 that copper (Cu), chromium (Cr), and iron (Fe) are significantly removed by using the visible light cut filter as compared with the full-wavelength transmission glass. In this way, the metal impurities are more effectively removed by cutting visible light and irradiating only ultraviolet light.
The structure is defined such that light from light sources other than the low-pressure mercury lamp 7 does not enter the chamber 1.

The pure water from the pure water discharge nozzle 11 is
Although a grade having a dissolved oxygen concentration of 50 ppb or less was used, it is possible to more efficiently remove metal impurities, especially copper, by discharging pure water in which oxygen is sufficiently dissolved by using a bubbler or the like. There was found. The rotation speed of the semiconductor substrate 2 during irradiation with ultraviolet light is about 10
Although the speed was low at rpm, the processing speed can be increased by increasing the speed. However, this increase in speed may cause the pure water applied to the semiconductor substrate to be scattered, and the scattered water may contaminate the semiconductor substrate. Therefore, it is desirable to take measures to prevent this.

In the modified example of FIG. 3, since ultraviolet light is irradiated while continuously supplying pure water to the surface of the semiconductor substrate, contaminants such as ions desorbed from the surface of the semiconductor substrate by irradiation with ultraviolet light are Since the pure water continuously supplied is immediately carried to the outside of the semiconductor substrate, it can be prevented from reattaching to the surface of the semiconductor substrate, and the effect of cleaning and removal is further enhanced.

FIG. 5 shows a second embodiment of the semiconductor substrate cleaning apparatus. The chamber 1 made of PTFE is provided on the side surface with a gate valve 20 for loading and unloading the semiconductor substrate 2 and an exhaust duct. 14 and 14 respectively. The semiconductor substrate chuck 19 supported by the shaft 4 holds the outer peripheral portion of the semiconductor substrate 2 and holds the semiconductor substrate 2 horizontally. Bandpass filters 8A and 8B and low-pressure mercury lamps 7A and 7B are arranged above and below the chuck 19, respectively. Further, a double nozzle 21 for discharging pure water and an inert gas is arranged between the bandpass filter 8A and the semiconductor substrate chuck 19, and similarly, the bandpass filter 8 is provided.
A double nozzle (not shown) is arranged between B and the semiconductor substrate chuck 19.

As shown in FIG. 6, the double nozzle 21 has an inner cylinder 21a arranged therein, and pure water flows through the inner cylinder 21a, so that the gap between the inner cylinder 21a and the outer wall 21b is not blocked. Active gas circulates. A discharge hole 21c for pure water and an inert gas is formed at the tip of the double nozzle 21.
Pure water and an inert gas are discharged from 1c.

Next, the operation of the second embodiment will be described.
The semiconductor substrate 2 is loaded into the chamber 1 through the gate valve 20 and held horizontally by the chuck 19. After that, the exhaust duct 14 exhausts the inside of the chamber 1, and the double nozzle 21 introduces nitrogen gas into the chamber 1 to replace oxygen in the chamber 1 with nitrogen. Then, the double nozzle 21 discharges pure water onto the surface of the semiconductor substrate 2 to form a thin film of pure water on the surface of the semiconductor substrate 2. Next, after the double nozzle 21 is retracted from above the front surface of the semiconductor substrate 2, the low pressure mercury lamps 7A and 7B are turned on to irradiate the front surface and the back surface of the semiconductor substrate 2 with ultraviolet light. When this irradiation is completed, the double nozzle 21 again discharges pure water to rinse the surface of the semiconductor substrate, and the shaft 4 moves to the semiconductor substrate 2 again.
Rotate at high speed to remove water. The double nozzle 2
No. 1 may discharge nitrogen simultaneously with the discharge of pure water. As a result, the pure water is in a spray state and is evenly applied to the semiconductor substrate. Also in this second embodiment, it is possible to irradiate ultraviolet light while continuously supplying pure water, and in this case as well, the shaft 4 is rotated during the irradiation of ultraviolet light in order to prevent uneven irradiation. Is desirable.

As described above, the second embodiment does not require the upper lid 5 as shown in FIG. 1 for loading and unloading the semiconductor substrate into the chamber 1, so that the cleaning apparatus of FIG. Suitable for large-scale washing. FIG. 7 shows a third embodiment, in which the carrier device 22 for the semiconductor substrate is the semiconductor substrate 2
Grip the outer peripheral edge of. Bandpass filters 8A and 8B face the front surface and the back surface of the semiconductor substrate 2, respectively, with a slight gap, for example, a gap of 2 mm. A discharge hole 23 for pure water and an inert gas is formed in the center of each of the bandpass filters 8A and 8B. Pure water and an inert gas supply pipe 24 is connected to these discharge holes 23.

Next, the operation of the third embodiment will be described. The supply pipe 24 sequentially supplies an inert gas and pure water to the discharge hole 2
3 to the gap between the front surface of the semiconductor substrate 2 and the bandpass filter 8A and the gap between the back surface of the semiconductor substrate 2 and the bandpass filter 8B. The introduced pure water is kept between the front surface of the semiconductor substrate 2 and the bandpass filter 8A and between the back surface of the semiconductor substrate 2 and the bandpass filter 8B by the surface tension. In this state, irradiation with ultraviolet light is performed, and after this irradiation is performed for a predetermined time, pure water for rinsing is introduced into the gap from the supply pipe 24 and the discharge hole 23. Note that ultraviolet light may be irradiated during the introduction of the pure water for the rinse. The semiconductor substrate may be dried by using centrifugal force or vacuum drying. Also in this third embodiment, it is possible to irradiate with ultraviolet light while continuously supplying pure water to the above-mentioned gap. Further, since the pure water is introduced through the discharge holes 23 formed in the bandpass filter 8, the pure water discharge nozzles 11 and 21 shown in FIGS. 1 and 5 are not necessary. There is an advantage that it can be remarkably close to.

In the above first, second and third embodiments,
I installed a bandpass filter, but of course,
Depending on the conditions, it may be possible to sufficiently remove the contaminants even if the bandpass filter is not attached.
Further, as the material of the chamber 1, PT which is chemically stable
Although the case of using FE has been described, it is preferable to use a quartz chamber when degassing is a problem. As the ultraviolet light source, instead of a mercury lamp, a light source such as a strobe that has a short irradiation time but a very high light intensity can be used. In this case, the processing time can be shortened.

FIG. 8 shows an embodiment of the semiconductor substrate cleaning system of the present invention.
The tank 25a, the ultraviolet light sterilization unit 25b, the reverse osmosis unit 25c, the vacuum degassing unit 25d, the polisher (ion exchange resin) 25e, and the ultrafiltration unit 25f are used to produce high-purity pure water. The pure water produced by the pure water producing unit 25 is supplied to the semiconductor substrate cleaning unit 26. The semiconductor substrate cleaning unit 26 is composed of semiconductor substrate cleaning devices 26a, 26b, 26c having the configurations shown in FIGS. 1, 3, 5, and 7. The pure water recovery unit 27 includes a plurality of resistivity measuring devices 27a, 27b, 27c and a particle removal filter 27.
d and a polisher 27e. The pure water collecting unit 27 collects the pure water used in the semiconductor substrate cleaning unit 26, and the specific resistance measuring devices 27a, 27
The specific resistance of the pure water collected by b and 27c is measured. If the specific resistance is, for example, 16 MΩcm or more, it is reusable and sent to the particle removal filter 27d. On the other hand,
If the specific resistance is, for example, less than 16 MΩcm, it is determined that the regeneration is not possible and is sent to the drainage treatment system 28.

The operation of this embodiment will be described. Pure water from the pure water production unit 25 is used as the semiconductor substrate cleaning unit 26.
The used pure water is collected in the pure water collecting unit 27. It should be noted that used pure water is generally mixed with particles, cations and anions, and its purity is lowered. The pure water recovery unit 27 uses the recovered pure water to measure specific resistances 27a, 27b, 2 and 2.
7c, if it has a relatively high purity, that is, if its specific resistance is, for example, 16 MΩcm or more, it is regenerated and is sent to the particle removal filter 27d, and if its specific resistance is less than 16 MΩcm, it is regenerated. As impossible,
Send to the waste liquid treatment system 28. Particle removal filter 27
d captures particles having a particle diameter of 0.1 μm or more from the used pure water, and then the used pure water is returned to the pure water producing unit 25 via the polisher 27e. Thus, the pure water is used as the pure water production unit 25 and the semiconductor substrate cleaning unit 2.
6 and the pure water recovery unit 27 are circulated and reused.

FIG. 9 is a graph showing the purity of the used pure water. As can be seen from this graph, in the conventional cleaning device using the chemical liquid, the pure water used for rinsing the chemical liquid is extremely contaminated. To be done. On the other hand, since the semiconductor substrate cleaning apparatus of the present invention uses pure water and ultraviolet light without using a chemical solution, the pollution of pure water is very small.

FIG. 10 is a graph showing the amount of pure water used by the semiconductor substrate cleaning system of FIG. 8 and the amount of pure water used by the conventional semiconductor substrate cleaning apparatus. As can be seen from this graph, the semiconductor substrate cleaning system of FIG.
Since the pure water in the semiconductor substrate cleaning apparatus is less contaminated and the pure water is recycled, the amount of pure water used is extremely smaller than that in the conventional semiconductor substrate cleaning apparatus.

FIG. 11 shows a modification of the embodiment of FIG. 8. In this modification, the reducing agent injection tank 25g, the polisher 25h, and the diluted hydrofluoric acid injection tank 25 are added to the configuration of FIG.
i and are added. This reducing agent injection tank 25g injects a reducing agent into the pure water from the vacuum degassing unit 25d as necessary to reduce dissolved oxygen in the pure water. The pure water in which this reducing agent is injected is sent to the polisher 25e via the polisher 25h.

Since the injection of the reducing agent reduces dissolved oxygen in pure water, when the semiconductor substrate cleaning unit 26 uses this pure water to clean the semiconductor substrate, a natural oxide film grows on the semiconductor substrate. Therefore, the injection of the reducing agent is effective when the low temperature epitaxial growth is performed after the cleaning process. As the reducing agent, a diluted aqueous solution of sulfurous acid (concentration: 1 g / l) can be used. Other reducing agents include oxalic acid, phosphorous acid, formic acid, aqueous ammonia, dilute aqueous solutions of methanol, formaldehyde, sodium sulfite, sodium bisulfite, etc. as long as the standard electrode potential in the aqueous solution is smaller than oxygen. Any one can be used. Moreover, the volume ratio of the reducing agent diluted aqueous solution and the pure water is preferably 1: 10000. The diluted hydrofluoric acid injection tank 25i injects the diluted hydrofluoric acid into the pure water from the polisher 25e, if necessary. The diluted hydrofluoric acid has a function of removing the natural oxide film on the surface of the semiconductor substrate.

FIG. 12 shows the relationship between the amount of reducing agent added and the concentration of dissolved oxygen in pure water. By injecting the reducing agent into pure water, the dissolved oxygen in pure water is reduced. I understand. FIG. 13 is a graph showing the relationship between the ultraviolet light irradiation time, the natural oxide film thickness, and the dissolved oxygen concentration. It can be seen that when the dissolved oxygen concentration of pure water is lowered, the natural oxide film does not grow.

FIG. 14 is a graph showing the relationship between the ultraviolet light irradiation time, the natural oxide film thickness, and the concentration of hydrofluoric acid in pure water. When hydrofluoric acid is injected into pure water, a reducing agent is injected. Similarly, it can be seen that the natural oxide film does not grow.

[0047]

As is apparent from the above description, according to the present invention, the surface of the semiconductor substrate on which the pure water thin film is formed is irradiated with ultraviolet light to wash and remove the metal impurities on the surface of the semiconductor substrate. Therefore, the cost of the cleaning process can be significantly reduced as compared with the conventional method using a chemical solution. Particularly, according to the invention described in claim 11, since the pure water is reused, the cost of the cleaning step can be further reduced.

[Brief description of drawings]

FIG. 1 is a front view showing a first embodiment of a semiconductor substrate cleaning method and a cleaning apparatus according to the present invention in a partial cross section.

FIG. 2 is a plan view showing a chamber of the semiconductor substrate cleaning apparatus of the first embodiment.

FIG. 3 is a vertical sectional view showing a modification of the first embodiment.

FIG. 4 is a graph showing metal removal rates when a visible light cut filter and a full-wavelength transmission glass are used, respectively.

FIG. 5 is a sectional view showing a second embodiment of the semiconductor substrate cleaning apparatus according to the present invention.

FIG. 6 is an enlarged vertical sectional view of the double nozzle of FIG.

FIG. 7 is a sectional view showing a third embodiment of the semiconductor substrate cleaning apparatus according to the present invention.

FIG. 8 is a block diagram showing an embodiment of a semiconductor substrate cleaning system according to the present invention.

FIG. 9 is a graph showing the relationship between the washing time of the semiconductor substrate and the pure water specific resistance.

FIG. 10 is a graph showing the relationship between the number of processed semiconductor substrates and the amount of pure water used.

FIG. 11 is a block diagram showing a modification of the embodiment of FIG.

FIG. 12 is a graph showing the relationship between the amount of reducing agent added and the concentration of dissolved oxygen in pure water.

FIG. 13 is a graph showing a relationship between an ultraviolet light irradiation time, a natural oxide film thickness, and a dissolved oxygen concentration.

FIG. 14 is a graph showing the relationship between ultraviolet light irradiation time, natural oxide film thickness, and hydrofluoric acid concentration in pure water.

[Explanation of symbols]

2 Semiconductor substrates 3, 19 Supporting means (chuck) 7 Ultraviolet light source (low-pressure mercury lamp) 8 Irradiation window (bandpass filter, visible light cut filter) 11, 21 Pure water supply means (pure water discharge nozzle) 25 Pure water production unit 26 Semiconductor Substrate Cleaning Unit 27 Pure Water Recovery Unit

Claims (12)

[Claims] 1. A step of horizontally supporting a semiconductor substrate by a supporting means, a step of supplying pure water to the surface of the supported semiconductor substrate to form a pure water thin film on the surface of the semiconductor substrate, Irradiating the surface of the semiconductor substrate on which the pure water thin film is formed with ultraviolet light, rinsing the semiconductor substrate irradiated with the ultraviolet light with pure water, and drying the rinsed semiconductor substrate A method of cleaning a semiconductor substrate, comprising: 2. The pure water thin film has a thickness of about 2 mm to about 3 mm.
The method for cleaning a semiconductor substrate according to claim 1, wherein: 3. The method further comprises the step of irradiating the surface of the supported semiconductor substrate with ultraviolet light in an oxygen-containing atmosphere before supplying the pure water to the surface of the semiconductor substrate. The method for cleaning a semiconductor substrate according to claim 1. 4. The method of cleaning a semiconductor substrate according to claim 1, wherein the pure water is continuously supplied to the surface of the semiconductor substrate even during the irradiation of the ultraviolet light. 5. The method of cleaning a semiconductor substrate according to claim 1, wherein the semiconductor substrate is rotated during the irradiation of the ultraviolet light. 6. The step of irradiating the ultraviolet light includes the step of creating the ultraviolet light by cutting a wavelength component of about 400 nm or more from the irradiation light from the light source. A method for cleaning a semiconductor substrate as described above. 7. Support means for horizontally supporting the semiconductor substrate,
First pure water supply means for supplying pure water to the surface of the supported semiconductor substrate to form a pure water thin film on the surface of the semiconductor substrate, and to the surface of the semiconductor substrate on which the pure water thin film is formed. Ultraviolet light irradiating means for irradiating ultraviolet light; second pure water supplying means for supplying pure water to the surface of the semiconductor substrate irradiated with the ultraviolet light to rinse the surface of the semiconductor substrate; And a drying means for drying the semiconductor substrate. 8. The first and second pure water supply means are composed of the same pure water supply nozzle, and the ultraviolet light irradiating means comprises:
A light source that emits light having a wavelength from the visible region to the ultraviolet region, and is disposed between the light source and the support means to block the light in the visible region and irradiate only the ultraviolet light onto the surface of the semiconductor substrate. A visible light cut filter; the supporting means includes a rotatable shaft; and a chuck fixed to the shaft and holding the semiconductor substrate, the shaft being rotated during irradiation of the ultraviolet light. The semiconductor substrate cleaning apparatus according to claim 7, which is characterized in that. 9. Support means for horizontally supporting the semiconductor substrate,
An irradiation window disposed so as to face the surface of the semiconductor substrate supported by the supporting means so as to form a minute gap, and a hole formed in the irradiation window between the surface of the semiconductor substrate and the irradiation window. Pure water supply means for supplying pure water to the gap to form a thin film of pure water on the surface of the semiconductor substrate, and ultraviolet light on the surface of the semiconductor substrate on which the pure water thin film is formed through the irradiation window. An apparatus for cleaning a semiconductor substrate, comprising: an ultraviolet light source for irradiation. 10. A second irradiation window, which is arranged to face the back surface of the semiconductor substrate supported by the supporting means so as to form a minute gap, and the second irradiation window. A second pure water supply means for supplying pure water to the gap between the back surface of the substrate and the second irradiation window to form a pure water thin film on the back surface of the semiconductor substrate, and the pure water thin film. The semiconductor substrate cleaning apparatus according to claim 9, further comprising: a second ultraviolet light source that irradiates ultraviolet light onto the back surface of the formed semiconductor substrate through the second irradiation window. 11. A pure water producing unit, and pure water supplied from the pure water producing unit is applied to the surface of a semiconductor substrate in a thin film form, and ultraviolet light is applied to the surface of the semiconductor substrate coated with the pure water. And a semiconductor substrate cleaning unit that cleans the surface of the semiconductor substrate by irradiating the surface of the semiconductor substrate and pure water used in the semiconductor substrate cleaning unit are collected, and the pollution degree of the collected pure water is measured. A cleaning system for a semiconductor substrate, comprising: a pure water recovery unit that circulates pure water having a predetermined value or less through the foreign matter removal filter to the pure water production unit. 12. The semiconductor substrate according to claim 11, wherein the pure water producing unit injects into the pure water a reducing agent that reduces dissolved oxygen in the pure water when producing the pure water. Cleaning system.