KR19990005869A - Wafer cleaning method - Google Patents

Abstract

1. TECHNICAL FIELD OF THE INVENTION

The present invention relates to a wafer cleaning method.

2. Technical problem to be solved by the invention

In order to solve the problem that a large number of particles are generated and the etching uniformity is decreased when etching the wafer using a buffer etching solution to remove the native oxide layer in the contact hole.

3. Summary of the Solution of the Invention

Prior to the cleaning process using an etching buffer solution, a sub-piran cleaning process can be performed to suppress the generation of particles and to improve the etching uniformity.

Description

Wafer cleaning method

The present invention relates to a wafer cleaning method.

In the semiconductor manufacturing process, a cleaning process for removing the native oxide film inside the contact hole is required after forming the contact hole and before depositing an electrode such as polysilicon, tungsten silicide, titanium / titanium nitride, and tungsten.

A conventional method of cleaning a wafer using a buffered etch solution (BOE) and hydrofluoric acid (HF) is as follows. First, the wafer is dipped in HF or BOE solution to remove the native oxide film inside the contact hole. Afterwards, pure water (DIW) washing is performed to remove the remaining oxide film without being removed by HF or BOE solution. For pure water washing, pure water of 24 to 26 ° C is used, and a quick dump rinse (QDR) method and an overflow method are used. Even after pure water cleaning, the wafer is finally cleaned by an overflow method using pure water in order to remove the remaining oxide film. The wafer is then dried using a tumble dryer or a dryer using isopropyl alcohol.

In the wafer cleaning process, a BOE or HF solution is mainly used, and the electrode layer is deposited immediately after the wafer drying process by dipping the wafer into the solution. As such, when cleaning the wafer surface using only BOE or HF solution, the wafer surface is exposed to air containing organic pollutants, so that organic pollutants are adsorbed on the wafer surface and remain unremoved even after cleaning with BOE solution. do. This generates a lot of particles, reducing device deterioration and yield. In addition, the oxide film etched by the BOE solution has a problem that the etching uniformity is not good.

Accordingly, the present invention provides a method for cleaning a wafer of a semiconductor device capable of suppressing particle generation and improving etching uniformity by performing a PIRANHA cleaning process before performing a cleaning process using an etching buffer solution. There is a purpose.

Wafer cleaning method according to the present invention for achieving the above object is to perform a sub-ranch cleaning process to remove organic and inorganic substances on the surface of the wafer, and primary pure water to remove the organic and inorganic residues remaining on the wafer surface Performing a cleaning step, dipping the wafer into an etching solution to remove the oxide film, performing a second pure cleaning to remove the oxide film remaining on the wafer surface, and finally cleaning the wafer. And drying the wafer.

The accompanying drawings are graphs showing the degree of particle generation according to the number of measurements.

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

The cleaning method of the wafer according to the present invention is as follows. First, sub-ranch cleaning is performed to remove organic and inorganic substances from the wafer surface. Piranha rinsing is a process of dipping a wafer in a solution of sulfuric acid (H ₂ SO ₄ ) and hydrogen peroxide (H ₂ O ₂ ) at 4: 1 for 5 to 15 minutes and then removing the chemical solution from the wafer surface using pure water. Means. At this time, the temperature of the mixed solution is 110 ~ 130 ℃. Subsequently, the first pure washing is carried out to remove organic and inorganic substances which are not completely removed by the sub-piran washing. At this time, pure water washing is performed using pure water of 24 to 26 ° C and pure water of 60 to 80 ° C, using a QDR method and an overflow method. The wafer is then dipped in HF or BOE solution to remove the native oxide film inside the contact hole. After that, a second pure water washing is performed to remove the remaining oxide film without being removed by HF or BOE solution. For pure water cleaning, use pure water of 24 ~ 26 ℃ and use Quick Dump Rinse (QDR) method and overflow method. After performing the pure water cleaning, the wafer is finally cleaned by an overflow method using pure water in order to remove the remaining oxide film. The wafer is then dried using a tumble dryer or a dryer using isopropyl alcohol. As a result of sequentially performing the piranha process, the BOE cleaning process and the drying process, particle generation can be suppressed and etching uniformity can be improved.

The accompanying drawings are graphs showing the degree of particle generation according to the number of measurements. Before the wafer cleaning by BOE solution or HF solution is performed, the pyran may be removed before the electrode layer is deposited immediately after the wafer cleaning by BOE solution or HF solution. It can be seen that generation of particles was greatly suppressed when the lower cleaning step was performed. In addition, the following table shows the difference in the thickness of the etched oxide film when the wafer is cleaned with the BOE solution or the HF solution and the thickness of the etched oxide film when the pyranhaid process is performed before the wafer is cleaned with the BOE solution or the HF solution. Indicates. As can be seen from the table, it can be seen that the etching uniformity is improved in the case of the present invention that has undergone the Piran process.

Measuring point BOE cleaning (100: 1BOE 2 sec dipping) Piranha + BOE (100: 1 2 sec dipping) Oxide thickness before dipping (Å) Oxide thickness after dipping (Å) Etched Oxide Thickness Oxide thickness before dipping Oxide thickness after dipping Etched Oxide Thickness One 980 964 16 979 962.0 17 2 979 962 17 979 960 19 3 979 962 17 979 961 18 4 980 969 11 979 960 19 5 980 969 11 980 961 19 6 975 959 16 976 954 22 7 976 956 20 976 954 22 8 978 969 9 978 957 21 9 980 963 17 979 959 20 Average 978.6 963.7 14.9 978.3 958.7 19.7 Uniformity (%) 36.9 12.7

As described above, according to the present invention, by performing the sub-ranch cleaning process before the BOE cleaning process, particle generation due to the adsorption of organic contaminants present in the air on the wafer surface exposed in the semiconductor manufacturing process line is suppressed and the etching uniformity is improved.

There is an excellent effect of improving device characteristics and yield.

Claims (7)

Performing a sub-ranch cleaning process to remove organics and inorganics from the surface of the wafer, performing a first pure cleaning to remove organics and inorganics remaining on the surface of the wafer, and removing the oxide film to remove the oxide film. Dipping in an etching solution, performing a second pure cleaning to remove an oxide film remaining on the surface of the wafer, final cleaning of the wafer, and drying the wafer. Wafer cleaning method. The method of claim 1, wherein the sub-ranch cleaning process is performed in a mixed solution at 110 to 130 ° C. for 5 to 15 minutes. The wafer cleaning method according to claim 1, wherein the first pure water cleaning is performed by a quick dump rinse method using pure water at 24 to 26 ° C and an overflow cleaning method using pure water at 60 to 80 ° C. The method of claim 1, wherein the etching solution uses any one of hydrofluoric acid and a buffered etching solution. The wafer cleaning method according to claim 1, wherein the second pure water cleaning step is performed sequentially using a quick dump rinse method and an overflow cleaning method using pure water at 24 to 26 ° C. The wafer cleaning method according to claim 1, wherein the final cleaning is performed in an overflow method using pure water. The method of claim 1, wherein the wafer is dried using a tumble dryer or a dryer using isopropyl alcohol.