JP2001308052A - Semiconductor substrate cleaning method - Google Patents

Abstract

(57) Abstract: Provided is a cleaning method for suppressing erosion of a metal film in cleaning a semiconductor substrate having a metal film. A semiconductor substrate having a metal film is prepared from (1) hydrogen peroxide solution, ozone water or electrolytic anode water, (2) an inorganic acid or alkali agent, (3) a complexing agent and / or a surfactant. The substrate surface is cleaned while preventing erosion of the metal film using a cleaning liquid.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for cleaning a semiconductor substrate having a metal film on the surface.

[0002]

2. Description of the Related Art In recent years, the demand for higher speed and higher performance in semiconductor devices has led to lower resistance of materials, and the use of metal materials has been increasing. Further, with the progress of multi-layer wiring and miniaturization of elements, more precise and precise processing is required, and the margin of processing dimensions is becoming smaller. As the degree of integration of the semiconductor device increases, it becomes essential to improve the yield by improving the cleanliness of the surface of the semiconductor device without organic matter, foreign matter and metal contamination. Therefore, a more precise cleaning method is required.

Conventionally, semiconductor device cleaning includes SPM (sulfuric acid-hydrogen peroxide) cleaning for removing organic substances or resist, APM (SC-1, ammonia-hydrogen peroxide) cleaning for removing foreign substances, and contaminant metal removal. HPM (S
A so-called RCA cleaning method comprising a combination of (C-2, hydrochloric acid-hydrogen peroxide) cleaning is used, and the cleaning effect has been improved by the ultra-purification of a chemical solution and the combined use of physical cleaning power such as megasonic. Also, a cleaning method using ozone water or functional water in place of hydrogen peroxide, and cleaning for the purpose of simultaneously removing foreign substances and contaminated metals by adding a chelating agent to the cleaning liquid during APM cleaning. Cleaning techniques have also been improved, including the development of methods.

However, these cleaning methods are particularly effective when the surface of the semiconductor substrate is bare silicon or a silicon oxide film, but are easily eroded by an oxidizing liquid such as a copper film, a tungsten film, a WSix (tungsten silicide) film, and a Ti film.
When a metal film such as a W (Titan) film is present, such a film is greatly eroded. Therefore, a reduction in processing accuracy and a change in the resistance value caused by the deterioration are seen, and it cannot be said that the cleaning method is appropriate. It was necessary to develop a new cleaning method.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems in the prior art, and to provide a cleaning method which does not corrode or erode metals on a semiconductor substrate, and provides a clean and highly processed surface. Is to provide.

[0006]

Means for Solving the Problems The present inventors have made intensive studies on cleaning a semiconductor substrate having a metal film, and have found that adding a complexing agent and / or a surfactant to acidic or alkaline hydrogen peroxide or the like. To prevent erosion of the metal film,
The inventors have found that a clean semiconductor surface can be obtained, and have reached the present invention.

That is, according to the present invention, a semiconductor substrate having a metal film is prepared by (1) aqueous hydrogen peroxide, ozone water or electrolytic anode water, (2) an inorganic acid or alkali agent, (3) a complexing agent and / or an interface. Using a cleaning solution consisting of an activator,
The present invention relates to a method for cleaning a semiconductor substrate, which comprises cleaning a substrate surface while preventing erosion of a metal film. Hereinafter, the present invention will be described in more detail.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The metal film of the present invention is tungsten, copper, aluminum, cobalt, titanium or tantalum, or a compound thereof with silicon, nitrogen or oxygen, and may be an alloy containing a plurality of these. Among them, it is particularly effective for a tungsten metal film having a corrosion area under an alkaline oxidizing solution.

In the cleaning liquid of the present invention, hydrogen peroxide, ozone water or electrolytic anode water is used. The inorganic acid used in the cleaning solution of the present invention is sulfuric acid, hydrochloric acid, nitric acid or hydrofluoric acid, and a combination of several kinds of these acids may be used.

The alkaline agent used in the cleaning solution of the present invention includes ammonia water, alkylammonium hydroxides (tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrapropylammonium hydroxide, tetrabutylammonium hydroxide, trimethylethylammonium hydroxide). , Choline, etc.), alkylamines (propylamine, butylamine, pentylamine, cyclohexylamine, diethylamine, N-methyl-n-butylamine, N-methylcyclohexylamine, ethylenediamine, 1,2-diaminopropane, 1,3-diamino Propane, 1,2-cyclohexanediamine, N-methyl-1,3-diaminopropane, N, N′-diethylethylenediamine, N,
N, N ′, N′-tetramethylethylenediamine, diethylenetriamine, 3,3′-diaminodipropylamine, N, N-diethylethylenediamine, or alkanolamines (ethanolamine, propanolamine, diethanolamine, 2-aminocyclo Hexanol, N-methylethanolamine, N-ethylethanolamine, N-ethyldiethanolamine, 2-
Diethylaminoethanol, 3-diethylamino-1-
Propanol, etc.), and combinations of these several types may be used. Of these, tetramethylammonium hydroxide “TMAH” has a large cleaning effect while suppressing metal erosion.

The complexing agent used in the cleaning solution of the present invention is a phosphoric acid compound or a phosphonic acid chelating agent. Specifically, methyl diphosphonic acid, aminotris (methylene phosphonic acid), ethylidene diphosphonic acid, 1-hydroxyethylidene-1,1-diphosphonic acid, 1-hydroxypropylidene-1,1-diphosphonic acid, 1- Hydroxybutylidene-1,1-diphosphonic acid, ethylaminobis (methylenephosphonic acid), 1,2-propylenediaminetetra (methylenephosphonic acid) “PDTP”, dodecylaminobis (methylenephosphonic acid), nitrotris (methylenephosphonic acid) ), Ethylenediaminebis (methylenephosphonic acid), ethylenediaminetetra (methylenephosphonic acid) "EDTP", hexenediaminetetra (methylenephosphonic acid), diethylenetriaminepenta (methylenephosphonic acid) "DTPP", cyclohexanediaminetetra (meth Lenphosphonic acid), and their ammonium salts, alkali metal salts, and alkaline earth metal salts. Among them, EDTP, PDTP and DTPP are preferred.

The surfactant used in the present invention may be a cationic, anionic, nonionic or zwitterionic surfactant, but is preferably an anionic surfactant containing a polycarboxylic acid as a main component. .

In the present invention, when a washing solution comprising (1) an aqueous solution of hydrogen peroxide, (2) an alkali agent, and (3) a complexing agent and / or a surfactant is used, hydrogen peroxide of 0.01 to 0.01% is used.
5% by weight, preferably 0.1-1% by weight, alkaline agent 0.1-5% by weight, preferably 0.3-3% by weight, complexing agent and / or surfactant 1 ppb-1% by weight, preferably Is 10 to 1000 ppm, with the balance being water. When the content of hydrogen peroxide is 0.01% by weight or less, the foreign matter removing effect is reduced, and when the content is 5% by weight or more, metal erosion increases. If the complexing agent is 1 ppb or less, metal erosion increases, and even if it is added at 1% by weight or more, a significant improvement in the effect cannot be expected. The washing temperature is 20 to 90C, preferably 40 to 60C. 2
If the temperature is lower than 0 ° C., the effect of removing foreign substances is reduced.

In the present invention, (1) hydrogen peroxide (2)
When a cleaning solution comprising a hydrochloric acid (3) complexing agent and / or a surfactant is used, 0.01 to 5% by weight of hydrogen peroxide, preferably 0.1 to 4% by weight, and 1 to 10% by weight of hydrochloric acid, preferably 3-5% by weight, 1 ppb-1% by weight of complexing agent and / or surfactant, preferably 10-1000 pp
m, the remainder is water. The washing temperature is from 20 to 90C, preferably from 50 to 70C.

In the present invention, (1) hydrogen peroxide (2)
When a cleaning solution comprising a sulfuric acid (3) complexing agent and / or a surfactant is used, 0.7 to 5% by weight (10%) of hydrogen peroxide is used.
0%), preferably 1-3% by weight, sulfuric acid 75-95
% By weight, preferably 87-90% by weight, complexing agent and / or
Or 1 ppb to 1% by weight of a surfactant, preferably 10
~ 1000 ppm, the balance being water. The washing temperature is 80
To 130 ° C, preferably 85 to 100 ° C.

[0016]

EXAMPLES Tungsten pieces were immersed in various chemical solutions to determine the etching rate.

Example 1 Ammonia water: hydrogen peroxide: ultrapure water = 1: 4: 20, 8
Washing was performed by adding 100 ppm of EDTP at 5 ° C.
Similarly, washing without adding a complexing agent was performed as Comparative Example 1.

Example 2 Ammonia water: hydrogen peroxide: ultra pure water = 1: 4: 20,7
Washing was performed by adding 100 ppm of DTPP at 0 ° C.
Similarly, washing without adding a complexing agent was performed as Comparative Example 2.

Example 3 Ammonia water: hydrogen peroxide: ultra pure water = 1: 4: 40,7
Washing was performed by adding 100 ppm of PDTP at 0 ° C.
Similarly, washing without adding a complexing agent was performed as Comparative Example 3.

[0020]

[Table 1]

Example 4 TMAH: hydrogen peroxide: ultrapure water = 1: 4: 20, 70
Washing was performed by adding 100 ppm of DTPP at ℃. Similarly, washing without adding a complexing agent was performed as Comparative Example 4.

Example 5 TMAH: hydrogen peroxide: ultrapure water = 1: 4: 40, 70
Washing was carried out by adding 100 ppm of PDTP at 100 ° C. Similarly, washing without adding a complexing agent was performed as Comparative Example 5.

Example 6 TMAH: hydrogen peroxide: ultrapure water = 1: 4: 20, 50
Washing was carried out by adding 100 ppm of PDTP at 100 ° C. Similarly, washing without adding a complexing agent was performed as Comparative Example 6.

[0024]

[Table 2]

Example 7 Sulfuric acid: hydrogen peroxide = 4: 1 at 120 ° C., DTPP100
Cleaning was performed by adding ppm. Similarly, washing without adding a complexing agent was performed as Comparative Example 7.

Example 8 Sulfuric acid: hydrogen peroxide = 4: 1 at 100 ° C., DTPP100
Cleaning was performed by adding ppm.

Example 9 Sulfuric acid: hydrogen peroxide = 4: 1, 100 ° C., Poise 520
Washing was performed by adding 100 ppm (manufactured by Kao, anionic surfactant). Similarly, washing without adding a surfactant was performed as Comparative Example 8.

EXAMPLE 10 Sulfuric acid: hydrogen peroxide = 4: 1, 90 ° C., DTPP 100p
pm was added for washing. Similarly, washing without adding a complexing agent was performed as Comparative Example 9.

[0029]

[Table 3]

Example 11 Hydrochloric acid: hydrogen peroxide: ultrapure water = 1: 1: 6, 85 ° C., DT
Washing was performed by adding 100 ppm of PP. Similarly, washing without adding a complexing agent was performed as Comparative Example 10.

[0031]

[Table 4]

Example 12 Alumina particles having an average particle diameter of 0.3 μm were attached to a tungsten piece at 1000 particles / cm ² , and were subjected to megasonic cleaning with the chemicals used in Examples 1 to 6. After washing, as observed by a scanning electron microscope and a particle counter, no alumina particles were detected. At this time, the etching rate of tungsten was determined according to Examples 1 to 6 shown in Tables 1 and 2.
Was equivalent to the value of

Example 13 A resist was applied on a tungsten piece.
Megasonic cleaning was performed with the chemical used in Step 9. After washing
As a result of observation by SEM, it was confirmed that the resist could be removed. At this time, the etching rate of tungsten was equal to the value in Table 3.

Example 14 A tungsten film contaminated with iron so as to have a concentration of 1.0 × 10 ¹³ atoms / cm ² was immersed and washed in the chemical solution used in Example 11. After washing, the amount of iron adhering to the tungsten surface was evaluated, and as a result, was 1.0 × 10 ⁹ atoms / cm ² or less.
It was confirmed that iron contamination was removed. At this time, the etching rate of tungsten was 5 nm / min.

[0035]

According to the present invention, when cleaning a semiconductor substrate having a metal film, the metal film can be precisely cleaned without greatly eroding the metal film.

Claims (6)

[Claims] 1. A semiconductor substrate having a metal film, comprising: (1) aqueous hydrogen peroxide, ozone water or electrolytic anodic water, (2) an inorganic acid or alkali agent, (3) a complexing agent and / or a surfactant, A method for cleaning a semiconductor substrate, comprising cleaning a substrate surface while preventing erosion of a metal film by using a cleaning solution comprising: 2. The cleaning method according to claim 1, wherein the metal film is made of tungsten, copper, aluminum, cobalt, titanium, or tantalum, a compound thereof with silicon, nitrogen, or oxygen, or an alloy containing a plurality of these. 3. The cleaning method according to claim 1, wherein the inorganic acid is sulfuric acid, hydrochloric acid, nitric acid or hydrofluoric acid. 4. The cleaning method according to claim 1, wherein the alkaline agent is aqueous ammonia, an alkyl ammonium hydroxide, an alkylamine or an alkanolamine. 5. The cleaning method according to claim 1, wherein the complexing agent is a phosphoric acid compound or a phosphonic acid compound, or a salt thereof. 6. The method according to claim 1, wherein the surfactant is cationic, anionic,
The cleaning method according to claim 1, wherein the cleaning method is a nonionic or zwitterionic surfactant.