KR19990055152A - Method of forming contact plug of semiconductor device - Google Patents

Abstract

The present invention is used as a contact plug using an ammonia / hydrogen peroxide mixed solution, an aqueous hydrofluoric acid solution injected with ozone and a mixed solution of hydrofluoric acid and hydrogen peroxide, which can control the etch selectivity of the doped amorphous silicon and silicon oxide film at 1: 1 By etching the silicon film, a planarized structure can be obtained, etching residues and silicon defects can be removed, and impurities, particles, etc. due to slurry generated during the CMP process can be prevented.

Description

Method of forming contact plug of semiconductor device

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a semiconductor device, and more particularly, to an etching and cleaning method using a silicon oxide film and an etching selectivity of silicon after forming a contact plug for forming a capacitor lower electrode in a capacitor of a DRAM.

In general, in forming a contact plug, an electrode thin film is embedded in a contact hole, and then an etch back process using a plasma dry etching method and a CMP method are performed to remove the electrode on the contact hole while leaving only the electrode thin film in the contact hole. There is a polishing method using a (chemical mechanical polishing) process.

A conventional method for forming a contact plug will be described with reference to FIGS. 1 to 3 as follows.

First, in FIG. 1, an isolation process is performed and conductive films 1 such as word lines and bit lines, silicon oxide films 2, and contact holes are formed, and then a doped amorphous silicon film 3 for contact plug is deposited to conduct. The figure which shows schematically sectional drawing of the state which contacted the film | membrane 1. As shown in FIG. In general, the silicon oxide film 2 used as an interlayer insulating film is made of a middle temperature oxide (MTO) film or the like by a chemical vapor deposition (CVD) method.

In order to form a contact plug in the structure as shown in FIG. 1, as shown in FIG. 2, the doped amorphous silicon film 3 is deposited and an etch back process is performed using a plasma dry etching method or a CMP process.

However, since the plasma dry etching method is difficult to control the etching degree and the etching selectivity of the doped amorphous silicon film and the silicon oxide film is large, the step A as shown in FIG. 2 occurs in the amorphous silicon film etching process. .

In addition, when using the CMP process, there is a problem in that the contact interface is not flattened (B) as shown in FIG. 3 due to the difference in the removal rate between the doped amorphous silicon film and the CVD silicon oxide film which is an interlayer insulating film. In addition, during the cleaning process performed after the etching process, the silicon oxide film used as the interlayer insulating film is etched by hydrofluoric acid, and the flattening problem is further exacerbated. Since impurities are problematic, a subsequent cleaning process is required. However, even if this separate cleaning process is performed, the problem of planarization still exists.

In order to solve the above problems, the present invention can easily achieve flattening by controlling the etching selectivity of the doped amorphous silicon and the silicon oxide film in a ratio of 1: 1 to suppress the step difference generated when the plug formed of the silicon film is formed. It is an object of the present invention to provide a method for forming a contact plug of a semiconductor device.

In addition, an object of the present invention is to provide a method for forming a contact plug of a semiconductor device capable of improving the reliability of the device by suppressing the generation of impurities and metal contaminants generated during the formation of the contact plug of the silicon film.

1 is a cross-sectional view of contact plug formation showing a cross section in which a doped silicon film is deposited in a contact hole;

Figure 2 is a cross-sectional view of forming a contact plug using a conventional plasma dry etching method.

Figure 3 is a cross-sectional view of forming a contact plug using a conventional CMP process.

Figure 4 is a cross-sectional view of forming a flattened contact plug according to the present invention.

FIG. 5 is a graph showing etching rates of silicon film and oxide film with respect to ammonia / hydrogen peroxide mixed solution. FIG.

6 is a graph showing the etching rate of an oxide film with respect to an aqueous solution mixed with hydrofluoric acid and hydrogen peroxide solution.

* Explanation of symbols for main parts of the drawings

1: conductive film 2: oxide film

3: silicon film

In order to achieve the above object, the present invention provides a method for forming a contact plug of a semiconductor, wherein the first conductive film is formed by coating a silicon oxide film on a first conductive film and forming a contact hole exposing a portion of the first conductive film. Depositing a silicon film connected to the upper portion of the entire structure; And etching the silicon film using the ammonia / hydrogen peroxide mixed solution.

The present invention provides a method for forming a contact plug of a semiconductor, wherein a silicon oxide film is connected to the first conductive film by forming a contact hole for coating a silicon oxide film on the first conductive film and exposing a partial region of the first conductive film. Depositing on top of the structure; And etching the silicon film using a hydrofluoric acid solution into which ozone is injected.

In addition, the present invention provides a method for forming a contact plug of a semiconductor, wherein a silicon oxide film is coated on a first conductive film, and a contact hole for exposing a partial region of the first conductive film is formed to be connected to the first conductive film. Depositing a film over the entire structure; And etching the silicon film by using a mixed solution of hydrofluoric acid and hydrogen peroxide solution.

Hereinafter, a first embodiment according to the present invention will be described in detail with reference to the accompanying drawings.

The contact plug forming method according to the first embodiment of the present invention uses an etching method using an ammonia / hydrogen peroxide solution when etching the doped amorphous silicon film 3 of FIG. 1.

1, the etching process is performed with an aqueous solution of 60 ° C. to 80 ° C. (hereinafter, a high concentration ammonia solution) in which ammonia, hydrogen peroxide and ultrapure water are mixed in a volume ratio of 2: 1: 5 to 3: 1: 5. Etch rates of the doped amorphous silicon film (hereinafter referred to as silicon film) 2 and silicon oxide film (hereinafter referred to as oxide film) 3 using the high concentration ammonia solution are as shown in FIG.

That is, when the oxide film 3 is exposed by etching the silicon film 2 deposited for the contact plug with a high concentration ammonia aqueous solution, the etching selectivity of the silicon film 2 and the oxide film 3 is 1: 1 to 2: Since the range is 1, the silicon film 2 can be etched while minimizing the loss of the interlayer insulating film. Thereafter, in order to remove the natural oxide film and the metallic impurities on the surface of the silicon film 2 due to the high concentration of ammonia solution, the hydrofluoric acid solution diluted with 100: 1 to 200: 1 (ultra pure water: hydrofluoric acid) was washed for 10 seconds. A flattened structure can be obtained as well.

The contact plug forming method according to the second embodiment of the present invention uses an etching method using a hydrofluoric acid solution (or ozone hydrofluoric acid) in which ozone gas is injected during etching of the silicon film 3 of FIG. 1.

1, the silicon film 3 is etched while controlling the injection of ozone gas into the hydrofluoric acid solution, and then the injection of the ozone gas is stopped and the cleaning process of the silicon film 3 is performed with the hydrofluoric acid solution. .

That is, after the completion of the process as shown in Fig. 2, 5-10 ppm ozone gas was continuously injected into the hydrofluoric acid solution of 100: 1 to 200: 1 (ultra pure water: hydrofluoric acid) at a uniform concentration to obtain the contact plug silicon film 2. After etching, the inflow of the ozone gas is stopped, and the cleaning process is performed only with an aqueous hydrofluoric acid solution to clean the natural oxide film and impurities on the silicon film 3 while minimizing the loss of the interlayer insulating film.

Subsequently, the contact plug forming method according to the third embodiment of the present invention uses an etching method using an aqueous solution (hereinafter referred to as hydrofluoric peroxide) in which hydrofluoric acid and hydrogen peroxide are mixed when etching the silicon film 3 of FIG. 1.

As shown in FIG. 6, when the ratio of hydrofluoric acid and hydrogen peroxide is mixed at 1:45 to 1:50, the etching selectivity of the silicon film 3 and the oxide film 2 is controlled to be 1: 1 or less. The amorphous silicon film 3 for contact plug is etched by treating the hydrofluoric acid fruit in this ratio in the state as shown in FIG. Even though the oxide film 2 is exposed in the subsequent etching process, since the etching selectivity is 1: 1 or less, the silicon film 3 is etched without bending the oxide film 2 and the silicon film 3. Thereafter, the natural oxide film on the silicon film 3 produced by the hydrofluoric acid aqueous solution of hydrofluoric acid can be washed with a hydrofluoric acid solution of 100: 1 (ultra pure water: hydrofluoric acid) to 200: 1 to form a flattened contact plug as shown in FIG. have.

As described above, in the plug forming method according to the present invention, the amorphous silicon and the interlayer insulating film deposited for the plug are controlled by adjusting the etching selectivity of the etching solution so that the etching selectivity between the silicon film and the oxide film is about 1: 1. The leveling with the silicon oxide film can be suppressed to obtain a flattened structure.

In addition, the present invention does not use the conventional dry etching process using the plasma during the silicon etching process, there is no inducement of silicon defect layer by the plasma, there is no influx of metallic impurities coming from the plasma etching equipment and suppress the generation of etching residues Can be.

Furthermore, it is possible to prevent the step difference between the interlayer insulating film and the amorphous silicon generated when using the CMP process and to prevent the generation of impurities and particles due to the slurry generated during the CMP process.

The present invention made as described above has the effect of simplifying the process of the semiconductor device and improving the reliability by performing the planarization process and the cleaning process only by the conductive layer etching process for the plug.

Claims (10)

In the method for forming a contact plug of a semiconductor, Depositing a silicon film on the entire structure by applying a silicon oxide film on the first conductive film and forming a contact hole exposing a portion of the first conductive film; And Etching the silicon film using the ammonia / hydrogen peroxide mixed solution. The method of claim 1, And cleaning the etched silicon film for 10 seconds with the hydrofluoric acid solution. The method of claim 1, The mixed solution is ammonia, hydrogen peroxide solution and ultrapure water, characterized in that the volume of 2: 1: 5 to 3: 1: 5. The method of claim 3, wherein The temperature of the mixed solution is 60 to 80 ℃ characterized in that the method. In the method for forming a contact plug of a semiconductor, Depositing a silicon film on the entire structure by applying a silicon oxide film on the first conductive film and forming a contact hole exposing a portion of the first conductive film; And Etching the silicon film using a hydrofluoric acid solution into which ozone is injected. The method of claim 5, Stopping the ozone injection after the silicon film is etched and cleaning the silicon film etched with hydrofluoric acid solution only. hurry, The hydrofluoric acid solution to which the ozone is injected is characterized in that 5 to 10ppm ozone gas is injected into a mixed solution of ultrapure water: hydrofluoric acid 100: 1 to 200: 1. The method of claim 5, The hydrofluoric acid solution to which the ozone is injected is characterized in that 5 to 10ppm ozone gas is injected into a mixed solution of ultrapure water: hydrofluoric acid 100: 1 to 200: 1. In the method for forming a contact plug of a semiconductor, Depositing a silicon film on the entire structure by applying a silicon oxide film on the first conductive film and forming a contact hole exposing a portion of the first conductive film; And Etching the silicon film using a mixed solution of hydrofluoric acid and hydrogen peroxide solution. The method of claim 8, And cleaning the etched silicon film with the hydrofluoric acid solution (ultra pure water: hydrofluoric acid) of 100: 1 to 200: 1. The method of claim 8, The ratio of hydrofluoric acid and hydrogen peroxide solution of the mixed solution is 1:45 to 1:50.