JPH11260786A - Cleaning method of semiconductor wafer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To simultaneously eliminate particles and metal impurities without needing a long time for cleaning, and exclude subsidiary generation of crystal defect of a wafer, by using aqueous solution containing NH4 Cl for cleaning. SOLUTION: Aqueous solution containing NH4 Cl is used for cleaning, and is adjusted in such a manner that ammonia water (NH4 OH concentration is about 28%) of semiconductor grade and chlorine solution (HCl concentration is about 30%) of semiconductor grade are made NH4 Cl, and 0.005 (weight/ volume)%-10 (weight/volume)% of NH4 Cl is measured and mixed in a specified amount of pure water. To the cleaning solution, H2 O2 may be added. In this case, the loadings are in the range of 0.005%-10% as the concentration (weight/ volume) of H2 O2 . By addition of H2 O2 , particles are easily eliminated. In this cleaning method, a brush scrubber may be used.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for cleaning a silicon wafer, which is capable of reducing contamination by particles and metal by a single cleaning in a RCA cleaning step of a silicon wafer used for a semiconductor substrate.

[0002]

2. Description of the Related Art Generally, in a process of manufacturing a silicon wafer serving as a semiconductor substrate, if heat treatment is performed in a state where the wafer surface is contaminated with particles or the like,
The unevenness of the thermal oxide film caused by the particles is generated, and the yield of the wafer is remarkably reduced. Also,
If metal impurities remain on the surface of the wafer, it will affect the electrical characteristics of the device, so it is required to remove metal impurities more and more as the density and density of devices increase. I have.

Therefore, conventionally, so-called RCA cleaning (alkaline cleaning) using SC1 and SC2 is performed to reduce the amount of particles and metal impurities adhering to the wafer, and thereafter, another rinse for supplying pure water is performed. The wafer is transferred to a tank and rinsed for a predetermined time, and the wafer lifted from the rinse tank is dried by a drying means such as a spinner.

[0004]

However, cleaning with an SC1 cleaning solution containing ammonia and hydrogen peroxide solution can remove particles but cannot remove metal impurities, and cleaning with an SC2 cleaning solution containing hydrogen peroxide solution and hydrochloric acid does not. Since metal impurities can be removed but particles cannot be removed, cleaning must be performed by a multi-tank type apparatus combining SC1 and SC2. Furthermore, S
Since it takes a long time to remove particles by C1, there is a problem that a crystal defect of a wafer called COP is generated as a secondary matter during cleaning by SC1. Therefore, an object of the present invention is to provide a cleaning method which can remove particles and metal impurities at the same time and does not generate COP.

[0005]

Means for Solving the Problems The present inventors have conducted various studies in order to solve the above-mentioned problems, and as a result, by using an aqueous solution containing NH ₄ Cl for cleaning, the cleaning can be performed without requiring a long time. It has been found that the object can be achieved by employing a cleaning method capable of simultaneously removing particles and metal impurities, and the present invention has been completed.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION In order to efficiently remove particles and metal impurities simultaneously, N contained in a cleaning liquid is required.
The concentration of H ₄ Cl is 0.005 (weight / volume)% to 10
(Weight / volume)%. 0.005 (weight /
If the concentration is less than 10% by volume, a sufficient effect cannot be obtained.
If the concentration exceeds 0 (weight / volume)%, post-processing for removing NH ₄ Cl remaining on the wafer takes time, which is not preferable. NH ₄ Cl used in the cleaning method of the present invention
The aqueous solution containing is prepared by using a semiconductor grade ammonia water (NH ₄ OH concentration around 28%) and a semiconductor grade hydrochloric acid solution (HCl concentration around 30%) as NH ₄ Cl and 0.005 (weight / volume)% to What is necessary is just to measure so that it may contain 10 (weight / volume)%, mix this with a predetermined amount of pure water, and carry out. Of course, it can be prepared from ammonium chloride, a semiconductor great. Of course, ammonium hydroxide or hydrogen chloride may be contained in excess. The aqueous solution containing an excess of ammonium hydroxide or hydrogen chloride can be prepared by adding aqueous ammonia or a dilute hydrochloric acid solution to an aqueous solution containing a predetermined amount of NH ₄ Cl so that ammonium hydroxide or hydrogen chloride is excessively contained. SC
The two cleaning solutions 1 and SC2 may be mixed and prepared so that the concentration ratio between ammonium hydroxide and hydrogen chloride is in the range of 1: 2 to 2: 1 (weight ratio). Further, when the SC1 and SC2 tanks are installed at the cleaning site, SC1 and SC2 can be supplied and mixed at a predetermined ratio from both tanks for cleaning.

[0007] H ₂ O ₂ may be further added to the cleaning solution according to the present invention. In this case, the amount of addition is determined by the concentration of H ₂ O ₂ (weight /
(% By volume) in the range of 0.005% to 10%.
The effect that particles can be easily removed by adding H ₂ O ₂ is exhibited. In the cleaning method according to the present invention, a brush scrubber may be used.
When a brush scrubber is used, the washing operation is usually performed while dropping pure water or the like, but the above-mentioned washing liquid may be used instead of pure water. Alternatively, the cleaning operation may be performed while simultaneously dropping pure water and the above cleaning liquid.

Hereinafter, the present invention will be described with reference to examples, but it is needless to say that the present invention is not limited to the examples.

[0009]

EXAMPLE A semiconductor-grade ammonia water and a semiconductor-grade hydrochloric acid solution are mixed with pure water, and N formed by reacting ammonia in the ammonia water with hydrochloric acid in the hydrochloric acid solution.
The washing solution prepared so that the final concentration of H ₄ Cl is 0.5 (weight / volume)% is dropped by 200 m in a usual manner.
The m silicon wafer was washed for 10 minutes.

[0010] As a control, 5 (weight / volume)
SC1 or 5% (w / v) with% NH ₄ OH
Of SC2 containing HCl alone was dropped for 10 minutes to clean a silicon wafer of the same size, and the remaining amount of particles and metal impurities on the wafer at that time was measured. The results are shown in Tables 1 and 2 together with the remaining amount of metal impurities. Particles were measured under a microscope with particles having a size of 0.2 μm or more remaining at five places having an area of 1 cm ² of a wafer arbitrarily selected by a cleaning method according to the present invention. The average remaining number per location is 10
Table 1 shows the number of particles remaining after SC1 or SC2 cleaning expressed as 0, and the amount of metal impurities was measured using a total reflection fluorescent X-ray apparatus.
Table 2 shows the amount of metal impurities in the cleaning by SC1 or SC2, where the amount of metal impurities by the cleaning method according to the present invention is expressed as 100.

[0011]

[Table 1]

[0012]

[Table 2]

As is clear from the results shown in Tables 1 and 2, a metal such as Al remains in the cleaning of only SC1, and a particle is significantly left in the cleaning of only SC2. In contrast, in the cleaning method according to the present invention, both can be removed simultaneously by one cleaning operation.

[0014]

When cleaning a silicon wafer used for a semiconductor substrate, the aqueous solution containing NH ₄ Cl according to the present invention is used as a cleaning liquid, whereby particles and metal impurities can be efficiently removed at the same time. . In addition, when an aqueous solution containing only NH ₄ Cl is used as the cleaning liquid, a single tank for storing the cleaning liquid is used to provide advantages in terms of equipment, maintenance and maintenance of the tank.
This has the effect of significantly reducing inspections.

Claims (5)

[Claims] 1. A semiconductor wafer cleaning method for cleaning a semiconductor wafer with an aqueous solution containing NH ₄ Cl. 2. The method according to claim 1, wherein the aqueous solution containing NH ₄ Cl is N 2
2. A mixture of an aqueous H ₄ OH solution and an aqueous HCl solution.
The method described in. 3. NH ₄ C in an aqueous solution containing NH ₄ Cl
3. The method according to claim 1, wherein the concentration of 1 ranges from 0.005 (weight / volume)% to 10 (weight / volume)%. 4. The concentration ratio between NH ₄ OH and HCl is 0.5
3. The method of claim 2, wherein 5. A mixed solution of NH ₄ OH and HCl is further mixed with H ₂ O.
_3. The method of claim ₂ , comprising: