JPH01223733A - Etching of titanium carbide film and titanium nitride film - Google Patents

Abstract

PURPOSE:To etch a titanium carbide film and a titanium nitride film stably at a fast etching rate and remove the films by performing plasma-dry-etching of the titanium carbide film and the titanium carbide film, to which hydrogen is doped, the titanium nitride film and the titanium nitride film, to which oxygen is doped, by using CF4 gas. CONSTITUTION:A substrate 5 on which a titanium carbide group film is laminated is exposed into plasma generated by applying a high-frequency field to CF4 gas introduced into a chamber 1 evacuated to a high vacuum once by employing a vacuum equipment and etched. Fluorine radicals are generated in plasma, and an outermost surface on which titanium carbide and titanium oxide mix is decomposed into TiF4, oxygen and hydrocarbon. A gaseous product containing titanium generated in the reaction process is sucked by a vacuum pump and removed. The titanium carbide group film after the outermost surface is gotten rid of is also etched similarly, and decomposed to a gaseous compound, thus accelerating etching. The same applies to the titanium nitride group film.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for etching titanium carbide-based films and titanium nitride-based films.

(Prior art) Titanium carbide films, hydrogen-doped titanium carbide films, titanium nitride films, and oxygen-doped titanium nitride films are chemically stable compounds and have electrical conductivity, and are used as surface coating agents for sheet glass. It has been widely used. In recent years, titanium carbide film has also been studied as a primary wall material for fusion reactors because it has strong resistance to hydrogen plasma and does not change in quality due to exposure to hydrogen plasma. In particular, hydrogen-doped titanium carbide films and oxygen-doped titanium nitride films have been used as transparent conductive and hydrogen plasma-resistant coating materials because of their significantly reduced temperature absorption, electrical conductivity, and hydrogen plasma resistance. battery,
Applications are also being considered in fields such as TPT and PDP. When applied to such fields, titanium carbide films and titanium nitride films tend to react with moisture adsorbed on the film surface and form a layer containing titanium oxide on the surface, but titanium oxide films are insulating. Therefore, forming an insulating layer at the interface between the transparent conductive film and the semiconductor becomes a problem. To remove the surface layer that has grown and deteriorated due to the growth of titanium oxide and expose the surface of the titanium carbide film and titanium nitride film, the film is etched with a mixed solution of hydrofluoric acid and nitric acid (fluoronitric acid) to allow the growth of titanium oxide. There is a known method to expose the surface that is not covered. However, when using hydrofluoric acid, there is a drawback that the surface of the glass substrate or quartz substrate on which no film is formed is eroded by the hydrofluoric acid. Furthermore, after etching in the liquid phase, new titanium oxide may grow on the surface while taking it out into the air and drying it, so it is necessary to wash it with pure water after etching and immediately dry it by blowing away the water droplets with dry nitrogen. There is.

(Problem to be Solved by the Invention 'XU) Since the conventional etching methods for titanium carbide films and titanium nitride films have the above-mentioned drawbacks, it is difficult to apply a hydrogen-resistant plasma coating to a transparent conductive substrate on a glass or quartz substrate. When it is desired to etch the surface layer of the titanium carbide film and titanium nitride film formed as As this progresses, the surface becomes rough and cloudy. Furthermore, when the film is formed as a hydrogen plasma-resistant protective film for a transparent conductive film, it is necessary to dry it in a short time and move on to the next process to prevent new titanium oxide from growing during the drying process after etching.

(Means for Solving the Problems) The present invention solves the above-mentioned problems and provides a titanium carbide film, a hydrogen-doped titanium carbide film, a titanium nitride film, and an oxygen-doped titanium nitride film. The present invention provides a method for etching titanium carbide films and titanium nitride films, which comprises performing plasma dry etching using CF4 gas.

In the present invention, a titanium carbide film refers to a titanium carbide film not doped with impurities or a titanium carbide film doped with hydrogen, and a titanium nitride film refers to a titanium nitride film not doped with impurities or a titanium carbide film doped with oxygen. A titanium nitride film.

In the present invention, a substrate on which a titanium carbide film or a titanium nitride film is laminated is etched by exposing it to a plasma of CF4 gas. conduct. More preferably, CF or gas to which oxygen is added at a rate of 10% or less is used.

(Function) In the method of etching a titanium carbide film of the present invention, a high-frequency electric field is applied to CF and gas introduced into a chamber evacuated to a high vacuum using a vacuum apparatus as shown in FIG. Etching is performed by exposing the substrate on which the titanium carbide film is laminated to the plasma generated by this process. Fluorine radicals are generated in the plasma and decompose the outermost surface containing a mixture of titanium carbide and titanium oxide into TiFn, oxygen, and hydrocarbons. In the reaction, oxygen only acts as a catalyst, and titanium oxide does not grow on the etched surface. Gaseous products containing titanium generated during this reaction process are removed by suction with a vacuum pump. After the outermost surface has been removed, the titanium carbide film is similarly etched and decomposed into gaseous compounds, and the etching progresses.

It is thought that the same effect applies to titanium nitride films.

(Example 1) A film 1', a titanium carbide film with a thickness of about 1200 nm and a titanium carbide film doped with hydrogen, are formed on soda lime glass by RF sputtering. The above two types of substrates are set in a plasma CVD vacuum chamber 1 as shown in Fig. 1, and after it is evacuated to a culmness of 2×IQ-'Lorr, 5% oxygen-added CF gas is introduced and the pressure is increased. I
The flow rate was adjusted to about torr. Next, a high-frequency voltage of 35 mw/cm" was applied between the electrodes to generate plasma in the chamber. The substrate was not heated. After 2 minutes, the plasma was stopped and the gas was introduced into the chamber. The residual gas was disposed of, and then the atmosphere was released and the substrate was taken out.The film thickness measurement result was about 100 0 for both cases, and there was no big difference.The back side of the substrate was not exposed to plasma. Therefore, there was no evidence of erosion, and there was no change compared to the unetched substrate.This shows that when etched under the above conditions, the titanium carbide film is etched at an etching rate of about 50 etchings per minute. .

(Example 2) A tin oxide transparent conductive film is formed on a soda lime glass substrate with a silica undercoat by atmospheric pressure CVD. Next, a hydrogen-doped titanium carbide film is formed on the surface of the tin oxide film of this substrate by RF sputtering in about 100 steps. This substrate exhibits a decrease in transmittance of only about 1% compared to a substrate on which only a tin oxide film is formed, and exhibits strong resistance to exposure to hydrogen plasma. When this substrate was stored in a room temperature atmosphere for about 10 days, it was confirmed by ESCA measurement that a layer containing about 50 layers of titanium carbide and titanium oxide had grown on the surface. This substrate was set in the vacuum chamber 1 of a plasma CVD apparatus, and after it was evacuated to a high vacuum, 100% CF and gas were introduced.
The pressure was adjusted to about r. 35m between the high frequency electrodes of the device
After applying a high frequency output of "w/cm" to generate plasma and etching for about 2 minutes, turn off the high frequency input and introduce the gas.After exhausting the residual gas, the chamber is opened to the atmosphere and the substrate is taken out. Ta. When this substrate was subjected to ESCA measurement and the surface composition was analyzed, it was found that a very thin titanium carbide film remained on the surface and a surface was obtained on which no titanium oxide had grown. Plasma CV on this substrate
When an amorphous solar cell was formed using the D method and its performance was tested, a conversion efficiency of about 9% was obtained. On the other hand, the conversion efficiency of the solar cell formed on the substrate-L which was not etched was 1% or less because the titanium oxide acted as an insulating layer.

(Effects of the Invention) The present invention is an excellent method for stably etching and removing titanium carbide films, hydrogen-doped titanium carbide films, titanium nitride films, and oxygen-doped titanium nitride films at a high etching rate. This is effective, especially in the case of a film formed on a glass or quartz substrate, without damaging the back surface of the substrate. In addition, the etching speed can be easily adjusted by changing the gas partial pressure and high frequency power during etching, and it is possible to remove thick films in a short time or to remove a small surface layer of the film at a slow rate. It is also possible to increase the speed. Furthermore, since it is a vacuum process, it is possible to transfer the etched surface to the next process without exposing it to the atmosphere and contaminating it, making it very useful in the semiconductor field, especially in solar cell manufacturing methods.

[Brief explanation of the drawing]

Claims (5)

[Claims] (1) A method for etching a titanium carbide film, which comprises plasma dry etching a titanium carbide film or a titanium carbide film doped with hydrogen using CF_4 gas. (2) A method for etching a titanium nitride film, which comprises plasma dry etching a titanium nitride film or a titanium nitride film doped with oxygen using CF_4 gas. (3) The etching method according to claim 1 or 2, characterized in that a gas obtained by adding oxygen to CF_4 gas is used. (4) In a method of manufacturing a solar cell by sequentially forming a transparent conductive film and amorphous silicon on a transparent insulating substrate, titanium carbide, titanium carbide containing hydrogen, titanium nitride, and titanium nitride containing oxygen are formed on the transparent conductive film. A protective film made of at least one of these is formed, and before forming amorphous silicon, the surface of the protective film is plasma dry etched using CF_4 gas, and then amorphous silicon is formed by a plasma CVD method. Characteristic solar cell manufacturing method. (5) The method for manufacturing a solar cell according to claim 4, characterized in that the protective film is plasma dry etched using a gas obtained by adding oxygen to CF_4 gas.