JPH0458528A - Cleaning treatment method - Google Patents

Abstract

PURPOSE:To execute a cleaning treatment which can prevent the surface of a material to be treated such as a semiconductor wafer of the like from being oxidized spontaneously by a method wherein the material to be treated is irradiated with ultraviolet rays in a state that the material to be treated is immersed in water in which hydrogen has been dissolved. CONSTITUTION:Hydrogen 2 is dissolved in water from a water-supply port 1 via a gas-permeable film 4 in a hydrogen dissolution apparatus 3 on the upstream side of a cleaning treatment tank 5. A hydrogen-dissolving water supply port 6, an overflow mechanism 7, a drainage port 8, an ultraviolet light source 9 and a holding mechanism 10 of an object to be treated are fitted to at the cleaning treatment tank 5; and a single-wafer treatment is executed. A low- pressure mercury lamp is used as the ultraviolet light source 9 considering an irradiation wavelength or the like; light radiated from the low-pressure mercury lamp efficiently activates hydrogen in the water near the surface of the object to be treated; and a treatment by the activated hydrogen is executed efficiently. Thereby, it is possible to execute a cleaning treatment which can prevent the surface of the object to be treated such as a semiconductor wafer or the like from being oxidized spontaneously.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a cleaning treatment method, and particularly to a cleaning treatment method for semiconductor wafers using pure water or ultrapure water.

[Conventional technology]

In integrated circuit technology, with the progress of finer patterns and ultra-high integration, contamination from particles, organic substances, metals, etc., which had been a problem in the past, has become a problem, as well as natural oxidation of wafers as a source of contamination. ing.

In order to prevent natural oxide films on wafers, it is considered important to reduce dissolved oxygen in pure water or ultrapure water for cleaning.

It has been confirmed that natural oxidation of silicon can be prevented using ultrapure water, which has a dissolved oxygen concentration of several parts per billion (ppb), in which dissolved oxygen has been reduced to the limit using current technology. However, even in this case, it is recognized that a natural oxide film is formed if exposed to air for even a short time, and the wafer is exposed to inert gas such as nitrogen gas, water vapor, or solvent vapor. Countermeasures have been proposed to prevent exposure to air by keeping the product in a warm environment.

However, in these cases, the silicon surface is still active and may be oxidized (in the presence of small amounts of oxygen).

Furthermore, even with ultrapure water that has reduced dissolved oxygen to the limit using current technology, metals such as aluminum wired on wafers are more active than silicon, so it is necessary to prevent natural oxidation of these metals. is said to be insufficient.

[Problem to be solved by the invention]

As described above, in the conventional cleaning treatment method, the surface of the semiconductor wafer is in a state where it is susceptible to natural oxidation due to the inclusion of a very small amount of oxygen, that is, a state where it is susceptible to surface contamination.

Therefore, the present invention solves the above problems and cleans the object.
In particular, it is an object of the present invention to provide a cleaning treatment method that can control the surface of a semiconductor wafer or the like to prevent natural oxidation.

[Means to solve the problem]

In order to achieve the above object, the present invention provides a cleaning treatment method characterized by immersing a substance to be treated in pure water or ultrapure water in which hydrogen is dissolved and irradiating it with ultraviolet rays.

In the cleaning treatment method of the present invention, semiconductor wafers can be used as the substance to be treated, and hydrogen is preferably dissolved in pure water or ultrapure water through a gas permeable membrane.

The ultraviolet irradiation is performed using a low-pressure mercury lamp as a light source, and the protection tube of the lamp is at least partially submerged in water, and the surface opposite to the surface facing the substance to be treated has an elliptical shape with the lamp position as the focal point. It is preferable to use one provided with a reflecting mirror.

[For production]

By irradiating water in which hydrogen is dissolved with ultraviolet light,
Hydrogen in water absorbs light energy and becomes activated. The activated hydrogen causes the surface of the silicon of the semiconductor wafer to be terminated with hydrogen, making it less susceptible to oxidation. Furthermore, even if a small amount of dissolved oxygen remains, the presence of activated hydrogen creates a reducing atmosphere, which prevents metals such as aluminum on the wafer from being oxidized.

Here, the lifespan of activated hydrogen is estimated to be extremely short, less than a second, because the absorbed energy is transferred to surrounding water, etc., and the activated hydrogen is Contact is very important.

In the present invention, this problem was solved by irradiating a semiconductor wafer etc. with ultraviolet light while immersing it in water in which hydrogen was dissolved.

〔Example〕

EXAMPLES Hereinafter, the present invention will be specifically explained with reference to Examples, but the present invention is not limited thereto.

Example 1 FIG. 1 is a schematic sectional view showing an example of an embodiment of a processing apparatus used in the method of the present invention. Moreover, FIG. 2 is an enlarged schematic cross-sectional view of the ultraviolet light source of the apparatus used in this treatment method.

This processing apparatus has a hydrogen dissolving device 3 on the upstream side of the cleaning treatment tank 5. This hydrogen dissolving device 3 includes a gas permeable membrane 4
This is a device that dissolves hydrogen 2 into water from the water supply port 1 through the water supply port 1. With the normal method of blowing hydrogen gas into water, it is necessary to supply excess hydrogen, which generates surplus hydrogen that must be treated, but this device dissolves hydrogen through a membrane. Therefore, it is sufficient to supply only the amount dissolved in water, and no surplus hydrogen is generated and there is no danger. Furthermore, since the amount of hydrogen dissolved in water in the present invention is sufficient compared to the saturated concentration, the hydrogen in water does not volatilize during the treatment. Although hydrogen remaining in the waste water is not shown in this figure, it can be easily removed by blowing air in the presence of a catalyst, if necessary.

The cleaning treatment tank 5 has a hydrogen-dissolved water supply port 6, an overflow mechanism 7, a drain port 8, an ultraviolet light source 9, and a processing object holding mechanism 10, and performs foliar processing on wafers.

A low-pressure mercury lamp 14 is used as the ultraviolet light source 9 due to the simplicity of the device, the irradiation wavelength, etc., and at least a part of the lamp protection tube 12 is underwater, and the surface opposite to the surface facing the substance to be treated is An elliptical reflecting mirror 13 whose focal point is at the lamp position is provided. The light emitted from the low-pressure mercury lamp 14 is
The light is reflected by the elliptical reflecting mirror 13, and is vertically and intensively irradiated onto the water near the surface of the wafer 11, which is the object to be processed. That is, hydrogen in water near the surface of the object to be treated is efficiently activated, and treatment with activated hydrogen is efficiently performed.

〔Effect of the invention〕

As described above, according to the method of the present invention, natural oxidation of the surface of a material to be processed, such as a semiconductor wafer, is prevented.

[Brief explanation of drawings]

FIG. 1 is a schematic sectional view showing an example of an embodiment of a cleaning treatment apparatus used in the method of the present invention, and FIG. 2 is a schematic sectional view showing an example of an ultraviolet light source used in the cleaning treatment apparatus. I: Water supply port, 2: Hydrogen for dissolving, 3: Hydrogen dissolving device, 4:
Gas permeable membrane, 6: Hydrogen dissolved water supply port, mechanism, 8: Drain port, 9: Processed material holding mechanism, 11 12: Lamp protection tube, 1 14: Low pressure mercury lamp 5: Cleaning treatment tank, 7: Overflow Ultraviolet light source, 10: Object to be processed (wafer) 3: Elliptical reflector,

Claims (4)

[Claims] 1. A cleaning treatment method characterized by immersing a substance to be treated in pure water or ultrapure water in which hydrogen is dissolved and irradiating it with ultraviolet rays. 2. 2. The cleaning method according to claim 1, wherein the substance to be treated is a semiconductor wafer. 3. 3. The cleaning method according to claim 1, wherein hydrogen is dissolved in pure water or ultrapure water through a gas permeable membrane. 4. The light source for ultraviolet irradiation is a low-pressure mercury lamp, and at least a portion of the protective tube of the lamp is submerged in water, and an elliptical reflecting mirror whose focal point is at the lamp position is provided on the opposite side to the surface facing the substance to be treated. 4. The cleaning treatment method according to claim 1, 2 or 3, wherein: