JPH1022255A - Cleaning method and cleaning equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To retard later adsorption of organic matter or growth of native oxide by stabilizing the surface of a silicon substrate after cleaning. SOLUTION: After the surface of a silicon substrate 15 is exposed to vapor containing hydrofluoric acid and etched, the silicon substrate 15 is held in a non-oxidative atmosphere and residual fluorine atoms F on the surface of the silicon substrate 15 are substituted by hydrogen atoms H. Since the surface of the silicon substrate 15 can be terminated completely with hydrogen H, it can be stabilized after cleaning.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for cleaning a surface of a silicon substrate.

[0002]

2. Description of the Related Art In the manufacturing process of a semiconductor device, various types of contamination are generated. Among the contamination, a substrate on which a silicon wafer, a polycrystalline silicon film, or an amorphous silicon film is formed as an uppermost layer (hereinafter referred to as a substrate). There is a trace amount of organic substances adsorbed on the surface of the silicon substrate) and a thin natural oxide film growing on the surface of the silicon substrate.

When these organic substances and natural oxide films are present on the surface of the silicon substrate, for example, TiSi ₂ or Co
When forming a silicide such as Si, even if a heat treatment for silicidation is performed after Ti or Co or the like is sputter-deposited on the surface of the silicon substrate, the Ti or Co or the like is uniformly diffused into the silicon substrate. Therefore, high-quality silicide cannot be formed.

Further, even if a gate oxide film is formed by thermally oxidizing the surface of a silicon substrate, a gate oxide film having excellent film quality cannot be formed. In addition, since the crystal structure on the surface of the silicon substrate is disordered, an epitaxial layer having an excellent crystal structure cannot be grown on the silicon substrate. Further, the contact resistance in the contact portion increases, and the diffusion of impurities is hindered.

Therefore, if an organic substance is adsorbed or a natural oxide film grows on the surface of the silicon substrate, it is difficult to manufacture a semiconductor device having excellent operation characteristics on the silicon substrate. These organic substances and natural oxide films are adsorbed and grow on the surface of the silicon substrate simply by leaving it in a dust-free atmosphere or storing it in a plastic container.

Therefore, as one method for removing organic substances and natural oxide films present on the surface of the silicon substrate, dry etching of the surface of the silicon substrate is performed by exposing the surface of the silicon substrate to a vapor containing hydrogen fluoride. Cleaning has been performed.

FIG. 5 shows a conventional example of a cleaning apparatus for that purpose. In this conventional cleaning apparatus, the chamber 1
1, a hydrogen fluoride gas supply pipe 12, a nitrogen supply pipe 13, and a steam supply pipe 14 are connected. Further, a rotary chuck 16 for the silicon substrate 15 is provided to penetrate the chamber 11, and an exhaust pipe 17 is also connected to the chamber 11.

In a conventional cleaning method using the cleaning apparatus shown in FIG. 5, a silicon substrate having a natural oxide film 18 grown on its surface or an organic substance 19 adsorbed thereon as shown in FIG. The hydrogen fluoride gas 15 and the water vapor are supplied into the chamber 11 from the hydrogen fluoride gas supply pipe 12 and the water vapor supply pipe 14 while the rotary 15 is rotated in a fixed state by the rotary chuck 16.

As a result, as shown in FIG. 4B, the natural oxide film 18 and the organic substance 19 are removed by dry etching with water vapor containing hydrogen fluoride gas. afterwards,
In order to prevent the chamber 11 from being corroded, the nitrogen supply pipe 1
3 supplies nitrogen into the chamber 11 and discharges water vapor containing hydrogen fluoride gas from the exhaust pipe 17 to the outside of the chamber 11.

[0010]

However, when the natural oxide film 18 and the organic substance 19 are dry-etched with water vapor containing hydrogen fluoride gas, as shown in FIG. At the same time, fluorine atoms remain. Therefore, if the silicon substrate 15 is thereafter left in the air as shown in FIG. 4C, the natural oxide film 18 may grow again in a very short time as shown in FIG. Organic matter 19 is adsorbed.

Therefore, in the conventional cleaning method shown in FIG. 4 and the conventional cleaning apparatus shown in FIG. 5, it is possible to obtain a silicon substrate 15 which can manufacture a semiconductor device having excellent operating characteristics. It was difficult.

As another method for removing an organic substance or a natural oxide film present on the surface of a silicon substrate,
Etching is also performed by immersing a silicon substrate in hydrofluoric acid. However, in this method, since rinsing with pure water is usually performed after etching, no fluorine atoms remain on the surface of the silicon substrate, and the above-described problem does not occur.

[0013]

A cleaning method according to the present invention comprises a step of exposing a surface of a silicon substrate to a vapor containing hydrogen fluoride to etch the surface, and a step of cleaning the silicon substrate after the etching by a non-oxidizing method. Hold in the atmosphere,
Replacing a fluorine atom remaining on the surface with a hydrogen atom.

In the cleaning method according to the present invention, the replacement may be performed by a hydrogen radical.

In the cleaning method according to the present invention, the hydrogen radicals may be generated by generating hydrogen plasma.

In the cleaning method according to the present invention, the hydrogen plasma may be generated by utilizing an ECR phenomenon.

A cleaning apparatus according to the present invention comprises a first processing chamber to which a steam containing hydrogen fluoride is supplied, and a load lock connected to the first processing chamber and capable of maintaining a non-oxidizing atmosphere. And a second processing chamber connected to the load lock chamber and supplied with hydrogen.

In the cleaning method according to the present invention, the silicon substrate whose surface has been etched with a vapor containing hydrogen fluoride is kept in a non-oxidizing atmosphere, and the fluorine atoms remaining on the surface are replaced with hydrogen atoms. As a result, the surface can be completely terminated with hydrogen. As a result, it is possible to stabilize the surface of the silicon substrate after cleaning, and suppress the subsequent adsorption of organic substances and the growth of a natural oxide film.

In the cleaning apparatus according to the present invention, a non-oxidizing atmosphere can be maintained between the first processing chamber supplied with the vapor containing hydrogen fluoride and the second processing chamber supplied with hydrogen. Since the load lock chamber is connected, the silicon substrate etched in the first processing chamber can be transferred to the second processing chamber for processing without being exposed to the atmosphere.

Therefore, the fluorine atoms remaining on the surface of the silicon substrate can be completely replaced with hydrogen atoms, and the surface of the etched silicon substrate can be completely terminated with hydrogen. As a result, it is possible to stabilize the surface of the silicon substrate after cleaning, and suppress the subsequent adsorption of organic substances and the growth of a natural oxide film.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of a cleaning method and a cleaning apparatus according to the present invention will be described below with reference to FIGS. FIG. 2 shows a cleaning apparatus of the present embodiment. In this cleaning apparatus, the chamber 11 and the like for performing dry etching with water vapor containing hydrogen fluoride gas have substantially the same configuration as the conventional cleaning apparatus shown in FIG.

However, in the cleaning apparatus of the present embodiment, the load lock chamber 21 is connected to the chamber 11,
A quartz chamber 22 for performing R hydrogen plasma processing is connected to the load lock chamber 21. Magnetron 23
Are connected to the quartz chamber 22, and a coil 26 is wound from the waveguide 24 to the quartz chamber 22. A high-frequency electrode 27 on which the silicon substrate 15 is mounted is provided in the quartz chamber 22.

In the cleaning method of the present embodiment using the cleaning apparatus shown in FIG. 2, the natural oxide film 18 growing or adsorbed on the silicon substrate 15 as shown in FIGS. And the organic matter 19 are removed by dry etching with water vapor containing hydrogen fluoride gas in the chamber 11, and until the inside of the chamber 11 is replaced with nitrogen, substantially the same as the conventional cleaning method shown in FIG. A similar process is performed.

However, in the cleaning method of the present embodiment, the silicon substrate 15 is then transferred from the chamber 11 to the load lock chamber 21. Then, after evacuating nitrogen in the load lock chamber 21 to evacuate the load lock chamber 21,
The silicon substrate 15 is quickly transferred to the quartz chamber 22 and subjected to hydrogen plasma processing under the following conditions.

Hydrogen flow rate 100 sccm Pressure 1.0 Pa Microwave output 850 W (2.45 GHz) Substrate bias 0 V Temperature 20 ° C.

As a result, as shown in FIG. 1C, the fluorine atoms remaining on the surface of the silicon substrate 15 are replaced by hydrogen radicals in the hydrogen plasma, and a complete hydrogen-terminated surface is obtained. Therefore, as shown in FIG. 1D, even if the silicon substrate 15 is left in the air thereafter, the growth of the natural oxide film 18 and the adsorption of the organic substance 19 are suppressed.

This is because the silicon substrate 15 after the dry etching is transported in a non-oxidizing atmosphere which is either a nitrogen atmosphere or a vacuum, and is subjected to a hydrogen plasma treatment. In order to make the atmosphere non-oxidizing, another inert gas may be supplied instead of supplying nitrogen from the nitrogen supply pipe 13.

FIG. 3 shows the result of analyzing the surface of the silicon substrate 15 after cleaning by x-ray photoelectron spectroscopy. The thickness of the natural oxide film, the amount of carbon contained in the organic substance, and the standing time after cleaning are shown. The relationship is shown. It is apparent from FIG. 3 that the regrowth of the native oxide film 18 and the re-adsorption of the organic substance 19 are suppressed in the present embodiment as compared with the conventional example. The amount of carbon was measured by irradiating the carbon with x-rays and analyzing the kinetic energy of photoelectrons emitted from its 1s orbit.

Further, in this embodiment, after the inside of the chamber 11 is replaced with nitrogen after the dry etching, the silicon substrate 15 is transferred to the load lock chamber 21, and the load lock chamber 21 is evacuated. Load lock chamber 21 and quartz chamber 22 using steam containing hydrogen hydride gas
Corrosion is prevented.

In the above embodiment, the hydrogen plasma is generated by using the ECR phenomenon.
There is no need to use the CR phenomenon. Further, the fluorine atoms on the surface of the silicon substrate 15 are replaced by the hydrogen radicals in the hydrogen plasma, but hydrogen radicals other than those in the hydrogen plasma may be used. Is also good.

[0031]

According to the cleaning method and the cleaning apparatus of the present invention, the surface of the silicon substrate after cleaning can be stabilized and the subsequent adsorption of organic substances and the growth of a natural oxide film can be suppressed. A silicon substrate from which an excellent semiconductor device can be manufactured can be obtained.

[Brief description of the drawings]

FIG. 1 is a side sectional view showing a cleaning method according to an embodiment of the present invention in the order of steps.

FIG. 2 is a side sectional view schematically showing a cleaning apparatus according to an embodiment of the present invention.

FIG. 3 is a graph showing the relationship between the standing time of a silicon substrate, the thickness of a natural oxide film, and the strength of C _1s .

FIG. 4 is a side sectional view showing a cleaning method according to a conventional example of the present invention in the order of steps.

FIG. 5 is a side sectional view schematically showing a cleaning apparatus as a conventional example of the present invention.

[Explanation of symbols]

Reference Signs List 11 chamber (first processing chamber) 12 hydrogen fluoride gas supply pipe 13 nitrogen supply pipe 14 water vapor supply pipe 15 silicon substrate 21 load lock chamber 22 quartz chamber (second processing chamber) 25 hydrogen supply pipe

Claims (5)

[Claims] A step of exposing the surface of the silicon substrate to a vapor containing hydrogen fluoride to etch the surface; and maintaining the silicon substrate after the etching in a non-oxidizing atmosphere and remaining on the surface. Replacing the existing fluorine atoms with hydrogen atoms. 2. The cleaning method according to claim 1, wherein the replacement is performed by a hydrogen radical. 3. The cleaning method according to claim 2, wherein the hydrogen radicals are generated by generating hydrogen plasma. 4. The cleaning method according to claim 3, wherein said hydrogen plasma is generated by utilizing an ECR phenomenon. 5. A method according to claim 1, further comprising the step of supplying a steam containing hydrogen fluoride.
A load lock chamber connected to the first processing chamber and capable of maintaining a non-oxidizing atmosphere state; and a second processing chamber connected to the load lock chamber and supplied with hydrogen. A cleaning device comprising: