JPH07153728A - Silicon wafer surface treatment method by hot pure water cleaning - Google Patents

Abstract

PURPOSE:To provide a wafer surface treatment method of restraining the surface of a silicon wafer from charging with time, wherein the wafer can be less contaminated by particles and ammonia ions after it is cleaned with alkaline solution. CONSTITUTION:A silicon wafer is cleaned through an alkali cleaning method with a mixed solution composed of ammonia, hydrogen peroxide, and water to remove particles or the like in a silicon wafer surface processing method, wherein a silicon wafer is dipped into a mixed solution composed of ammonia, hydrogen peroxide, and water and then dipped into a hydrogen peroxide- containing hot pure water kept at a temperature of 80 deg.C or above again.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a silicon wafer by hot pure water cleaning capable of reducing particle contamination in a cleaning step of cleaning a silicon wafer which is a semiconductor substrate with a mixed solution of ammonia, hydrogen peroxide solution and water. The present invention relates to a surface treatment method for a wafer.

[0002]

2. Description of the Related Art Generally, in a manufacturing process of a silicon wafer (hereinafter referred to as a wafer) which is a semiconductor substrate, when a heat treatment is performed in a state where the surface of the wafer is contaminated with particles, a thermal oxide film caused by the particles is produced. Unevenness occurs and the yield rate of wafers is significantly reduced.

Therefore, conventionally, RCA cleaning (alkali cleaning) is performed by etching with a mixed solution of ammonia water, hydrogen peroxide solution and water to reduce particles adhering to the wafer, and then pure water is supplied. It was transferred to another rinse tank and rinsed for a predetermined time, and the wafer pulled up from the rinse tank was dried by a drying means such as a spinner.

[0004]

However, in the conventional wafer cleaning method described above, RC cleaning is performed in RCA cleaning.
Since the cleaning liquid A is contaminated with particles, when the wafer is pulled out from the cleaning liquid after cleaning, particles in the cleaning liquid reattach to the wafer.

Further, even when the overflow rinse is performed as the rinse treatment performed after the RCA cleaning, there is a problem that the particle removing ability is weak and the particles cannot be surely reduced.

Further, if only the overflow rinsing is performed after the RCA cleaning, ammonia ions, which are the components of the RCA cleaning solution, may remain on the surface of the silicon wafer, causing a change over time (TDH) on the wafer surface. There was a problem that the yield rate was reduced.

Therefore, an object of the present invention is to provide a surface treatment method for a silicon wafer, which can surely reduce particle contamination after RCA cleaning treatment, reduce ammonia ions, and suppress the occurrence of change over time. .

[0008]

A surface treatment method for a silicon wafer according to the present invention is a surface treatment method for a silicon wafer, which removes particles and the like of the silicon wafer by alkali cleaning with a mixed solution of ammonia, hydrogen peroxide solution and water. That is, the silicon wafer is dipped in a mixed solution of the ammonia, hydrogen peroxide solution and water and then dipped in warm pure water containing hydrogen peroxide solution at 80 ° C. or higher.

[0009]

Function: To perform the surface treatment of the wafer, the R of the wafer
After CA cleaning, a cleaning process with warm pure water is performed, and then a wafer rinsing process and a wafer drying process are performed. In addition, in the cleaning treatment with the warm pure water, 80
It is carried out by immersing the silicon wafer in warm pure water containing hydrogen peroxide solution at a temperature of not less than ° C.

According to such a wafer cleaning process with hot pure water, since hot water containing hydrogen peroxide water is used, the number of particles redeposited on the wafer after alkaline cleaning can be significantly reduced. Further, the remaining ammonia ions can be largely removed, so that the change with time of the dried wafer can be surely reduced. Further, since hydrogen peroxide water is mixed in the warm pure water, even if the warm pure water is heated to a high temperature, the surface of the wafer is not roughened, and the warm pure water can be used at a high temperature.
Further, it becomes possible to enhance the effect of removing particles.

[0011]

An embodiment of the present invention will be described below with reference to the drawings.

In the surface treatment of the wafer in this embodiment, after the RCA cleaning of the wafer, the cleaning treatment with hot pure water is performed, and then the rinsing treatment of the wafer and the drying treatment of the wafer are performed.

In the RCA cleaning process, alkali cleaning is performed by immersing the wafer in a mixed solution of ammonia, hydrogen peroxide and water.

Next, in the cleaning treatment with hot pure water, particles are washed by immersing the silicon wafer in warm pure water containing hydrogen peroxide solution at 80 ° C. or higher.

In the alkaline cleaning with the mixed solution of ammonia, hydrogen peroxide and water, the more times the cleaning is repeated,
The mixed solution is contaminated with particles and the wafer is re-contaminated when the wafer is pulled out of the mixed solution.However, in the cleaning process with warm pure water, particles are removed by warm pure water containing hydrogen peroxide solution, and reattachment of particles is reduced. , The particles on the surface of the wafer can be reduced.

It is considered that a dissolved oxide in warm pure water containing hydrogen peroxide forms a thick oxide film on the wafer surface, which makes it difficult for particles to reattach to the wafer surface.

The results of tests conducted by the present inventor are shown in FIGS.
Further, as shown in FIGS. 8 and 9, it can be seen that particles can be reliably reduced. 1 and 8 show the number of particles in the case where the rinse treatment and the drying treatment are performed after repeating the RCA cleaning treatment several times, and FIGS. 2 and 9 show the number of particles after repeating the RCA cleaning treatment several times. The numbers of particles in the case where the hot pure water cleaning process is performed, and then the rinse process and the drying process are performed are shown.

As can be clearly seen from these figures, the average number of particles was 1,100 in the conventional processing, but the average number of particles is about 69 in the processing method according to the present embodiment, and the number of particles is significantly increased. It was possible to reduce.

According to the cleaning treatment with warm pure water, 8
By performing the cleaning treatment with warm pure water containing a hydrogen peroxide solution at 0 ° C. or higher, it is possible to surely remove the ammonia ions remaining in the overflow rinse after the conventional alkali cleaning.

That is, as can be seen from the measurement results of ammonia ions shown in FIG. 3, even when the overflow rinse is performed after the alkali cleaning as in the conventional case, a small amount of the mixed liquid remains and the residual amount of ammonia ions is large. When the cleaning process is performed with warm pure water containing hydrogen peroxide, the amount of ammonia ions can be significantly reduced.

As a result, the occurrence of change over time (TDH) due to the residual ammonia ions could be greatly reduced. That is, as can be seen from FIG. 4 showing the conventional case, FIG. 5 showing the case of the present embodiment, and FIG. 10 comparing the both cases, cleaning treatment with warm pure water containing hydrogen peroxide solution at 80 ° C. or higher is performed after alkali cleaning. By performing the above, it is possible to reliably suppress the occurrence of change over time (TDH). In FIGS. 4 and 5, 1 indicates a wafer.

Further, as shown in FIG. 6, in a general cleaning process with hot pure water, the higher the temperature of the hot pure water is 80 ° C. or higher, the greater the effect of reducing particles, but the characteristics shown in FIG. As indicated by A, the surface roughness of the wafer surface increases. On the other hand, in this embodiment, as shown by the characteristic B in FIG. 7, by adding a small amount of hydrogen peroxide solution to the warm pure water, it is possible to eliminate the surface roughness of the wafer surface. Can be raised to a high temperature, and the reduction of particles can be further enhanced.

[0023]

As described above, according to the present invention,
After the alkali cleaning, by performing a cleaning treatment with warm pure water containing hydrogen peroxide solution, it is possible to significantly reduce the particles reattached to the wafer, and it is also possible to significantly remove the remaining ammonia ions. The change with time of the wafer can be surely reduced. Further, since hydrogen peroxide water is mixed in the hot pure water, even if the hot pure water is heated to a high temperature, the surface of the wafer is not roughened, and the temperature of the hot pure water can be increased to be used, and the effect of removing particles can be further improved. It became possible to raise.

[Brief description of drawings]

FIG. 1 is a diagram showing an amount of adhered particles in a conventional surface treatment method.

FIG. 2 is a diagram showing the amount of adhered particles in the hot pure water treatment of the example of the present invention.

FIG. 3 is a diagram showing a comparison of residual ammonia ion amounts by a conventional treatment method and a treatment method of the present embodiment.

FIG. 4 is a diagram of a wafer showing changes over time by a conventional processing method.

FIG. 5 is a diagram of a wafer showing a change with time according to the processing method of the present embodiment.

FIG. 6 is a diagram showing measurement results of temperature and particle amount in a hot pure water cleaning process.

FIG. 7 is a diagram showing a surface roughness of a wafer surface.

FIG. 8 is a diagram showing the number of particles in a conventional processing method.

FIG. 9 is a diagram showing the number of particles in the processing method of the present embodiment.

FIG. 10 is a diagram showing the presence or absence of change over time in the conventional processing method and in the present embodiment in comparison with the number of particles.

[Explanation of symbols]

 1 Silicon wafer

Claims (1)

[Claims] 1. A surface treatment method for a silicon wafer, which comprises removing particles and the like of a silicon wafer by alkali cleaning with a mixed solution of ammonia, hydrogen peroxide and water, wherein the ammonia is mixed with hydrogen peroxide and water. A method of surface treating a silicon wafer by washing with warm pure water, which comprises immersing the silicon wafer in a liquid and then immersing the silicon wafer in warm pure water containing hydrogen peroxide at 80 ° C. or higher.