JP3198878B2 - Surface treatment composition and substrate surface treatment method using the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface treatment composition and a method for treating a surface of a substrate using the composition. More specifically, the present invention relates to a method for treating a surface of a substrate which can prevent contamination of metal impurities from the surface treatment composition to the surface of the substrate, and stably achieve a very clean substrate surface, and a surface treatment composition used therefor.

[0002]

2. Description of the Related Art With the increasing integration of various devices typified by VLSIs and TFT liquid crystals, the demand for cleaning the substrate surface is becoming increasingly severe. There are various contaminants that hinder the cleaning, and among the contaminants, metal contamination in particular degrades the electrical characteristics of the device. In order to prevent such deterioration, it is necessary to reduce the concentration of metal impurities on the substrate surface on which the device is formed as much as possible. Therefore, the substrate surface is generally cleaned with a specific type of cleaning agent.

[0003] Conventionally, this type of cleaning agent includes ultrapure water,
An aqueous solution of an acid, an alkali, an oxidizing agent, a surfactant, or the like, electrolytic ionic water, a high-purity organic solvent, and the like are generally used.
In addition to excellent cleaning performance, the cleaning agent is required to have an extremely low impurity concentration in the cleaning agent in order to prevent metal contamination from the cleaning agent to the substrate. In order to satisfy such demands, purifying semiconductor chemicals has been promoted, and the concentration of metal impurities contained in the chemicals immediately after purification is as follows:
It has reached a level that is difficult to detect with current analytical techniques.

[0004] As described above, despite the fact that the impurities in the cleaning agent have reached a level that is difficult to detect, it is still difficult to achieve a high-purity surface due to the metal impurities removed from the substrate in the cleaning tank. However, it is inevitable to contaminate the cleaning agent. That is, the metal impurities once detached from the surface are mixed into the cleaning agent and contaminate the cleaning agent. Then, metal impurities are attached to the substrate from the contaminated cleaning agent (reverse contamination).

In the semiconductor cleaning process, [ammonia + hydrogen peroxide + water] cleaning (commonly called “SC-1 cleaning”) (RC
A Review, p.187-206, June (1970), etc.) are widely used. The main cleaning is usually performed at 40 to 90 ° C., and the cleaning composition is usually (30% by weight ammonia water):
(31% by weight aqueous hydrogen peroxide): (water) = 0.05 to 1:
Those having a capacity ratio of about 1: 5 are provided for use. But,
Although this cleaning method has high particle removal ability and organic matter removal ability, when a very small amount of metal such as Fe, Al, Zn, or Ni is present in the solution, it has a problem that it adheres to the substrate surface and causes reverse contamination. . For this reason, in the semiconductor cleaning step, usually, [ammonia + hydrogen peroxide + water] cleaning is followed by [hydrochloric acid + hydrogen peroxide + water] cleaning (so-called “SC-2”).
Cleaning with an acidic cleaning agent such as "cleaning") removes metal contamination on the substrate surface.

As described above, in order to efficiently and stably obtain a highly clean surface in the cleaning step, a technique for preventing such reverse contamination has been required. The problem of metal impurities in the solution adhering to the substrate surface and contaminating the substrate surface is not only a cleaning process, but also a substrate using a solution such as an alkali etching process for a silicon substrate or an etching process for a silicon oxide film using diluted hydrofluoric acid. This is a major problem in the entire surface treatment process. In the diluted hydrofluoric acid etching step, if there is a noble metal impurity such as Cu or Au in the liquid, it adheres to the silicon surface and significantly degrades the electrical characteristics of the device such as carrier lifetime. In addition, in the alkaline etching step, if there is a trace amount of metal impurities such as Fe and Al in the liquid, the impurities easily adhere to the substrate surface. Therefore, a technique for preventing such contamination has been strongly demanded.

In order to solve this problem, a method of adding a complexing agent such as a chelating agent to a surface treating agent to trap metal impurities in the liquid as a stable water-soluble complex and prevent the metal impurities from adhering to the substrate surface. Has been proposed. JP-A-50-158281
In Japanese Patent Application Laid-Open Publication No. H11-163, it is proposed that a complexing agent such as ammonium cyanide or ethylenediaminetetraacetic acid (EDTA) is added to an aqueous solution of tetraalkylammonium hydroxide to prevent metal impurities from adhering to the surface of the semiconductor substrate. In JP-A-3-219000, a chelating agent such as catechol and thyrone is used. In JP-A-5-275405, a complexing agent such as a phosphonic acid chelating agent or condensed phosphoric acid is used.
In JP-A-6-163495, a complexing agent such as a hydrazone derivative is added to an alkaline cleaning solution such as [ammonia + hydrogen peroxide + water] to prevent metal impurities from adhering to the substrate, thereby allowing particles and organic substances to be removed. Along with pollution
Techniques for achieving a substrate surface free of metal contamination have been proposed.

However, when these complexing agents are added, a specific metal (for example, Fe) has an effect of preventing adhesion or removing, but a metal other than Fe (which tends to contaminate the processing solution and the substrate). For example, Al) has a problem that the effect of the complexing agent is extremely small, and a sufficient effect cannot be obtained even if a large amount of complexing agent is added.

Japanese Patent Application Laid-Open No. 6-216098 discloses that in order to solve this problem, the substrate is washed with a [ammonia + hydrogen peroxide + water] cleaning solution to which a chelating agent such as a phosphonic acid chelating agent is added, It describes that rinsing is performed with a hydrofluoric acid aqueous solution of 1 ppm or more. This is because the addition of a phosphonic acid-based chelating agent does not sufficiently reduce Al contamination on the substrate surface, and is intended to remove Al by etching using a hydrofluoric acid aqueous solution of 1 ppm or more in a later step. . As described above, the conventional metal adhesion preventing method is not sufficiently effective, and when the substrate needs to be cleaned,
Metal contamination must be removed in a later step, which increases the number of steps and causes an increase in production cost.

[0010]

As described above, contamination of metal impurities from the surface treatment composition to the surface of the substrate is a serious problem, but the technique for preventing it is still insufficient. For this reason, various kinds of complexing agents have been added to prevent adhesion, but at present there is no sufficient improvement.

The present invention has been made to solve the above-mentioned problems, and can prevent contamination of metal impurities from the surface treatment composition to the substrate surface, and can stably achieve a very clean substrate surface. An object of the present invention is to provide a surface treatment method for a substrate and a surface treatment composition used for the method.

[0012]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to solve the above-mentioned problems, and as a result, it has been found that a specific complexing agent is added and contained as a metal adhesion inhibitor in a surface treatment composition. The present inventors have found that the effect of preventing metal impurities from adhering to the substrate from the processing solution is remarkably improved, and arrived at the present invention.

That is, the gist of the present invention is to provide a liquid composition for surface treatment of a semiconductor substrate containing a complexing agent composed of ethylenediaminediorthohydroxyphenylacetic acid [commonly known as EDDHA] as a metal adhesion inhibitor, and to use the same. A method for treating a surface of a semiconductor substrate.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.
In the present invention, the surface treatment liquid composition is a general term for a surface treatment liquid used for the purpose of cleaning, etching, polishing, forming a film, and the like of a substrate. In the present invention, the complexing agent used as the metal adhesion inhibitor is ethylenediaminediorthohydroxyphenylacetic acid.

In terms of the effect of preventing metal adhesion when the content is constant, ethylenediamine diorthohydroxyphenylacetic acid is excellent and is preferably used.

The amount of the complexing agent added as a metal adhesion inhibitor varies depending on the type and amount of metal impurities in the liquid to be prevented from adhesion and the level of cleanliness required on the surface of the substrate. However, as a total addition amount in the surface treatment composition, it is usually 10 ^{-7 to} 5% by weight, preferably 10
^{-6 to} 0.1% by weight. If the amount is too small, the effect of preventing metal adhesion is not sufficient, while if it is too large, no further effect is obtained, and there is a risk that the complexing agent, which is a metal adhesion inhibitor, adheres to the substrate surface. Is not preferable because it is expensive.

As the main component, an aqueous solution of water, an acid, an alkali, an oxidizing agent, a reducing agent, a surfactant, or the like, electrolytic ionic water, an organic solvent, or a mixed solution thereof is usually used. In particular, the present invention is preferably used in an alkaline aqueous solution or a diluted hydrofluoric acid solution used for cleaning or etching a semiconductor substrate, since metal impurities in the solution are extremely easily attached to the substrate surface.

In the present invention, an alkaline aqueous solution is a general term for aqueous solutions whose pH is higher than 7. Representative examples of the alkaline component include ammonia. Further, hydroxides of alkali metals or alkaline earth metals such as sodium hydroxide, potassium hydroxide and calcium hydroxide; alkaline salts such as sodium hydrogen carbonate and ammonium hydrogen carbonate; or tetramethylammonium hydroxide, trimethyl-2- A quaternary ammonium hydroxide such as hydroxyethylammonium hydroxide (choline) is also used. These alkalis may be added at least two times without any problem.
The surface treatment composition is used so that the total concentration in the whole solution is 0.01 to 30% by weight.

Further, an oxidizing agent such as hydrogen peroxide may be appropriately blended in such an alkaline aqueous solution.
In the semiconductor wafer cleaning step, when cleaning bare (silicon-free) silicon, an oxidizing agent is added, whereby etching and surface roughness of the wafer can be suppressed. When hydrogen peroxide is added to the alkaline aqueous solution of the present invention, it is usually used so that the concentration of hydrogen peroxide in the entire solution of the surface treatment composition is in the range of 0.01 to 30% by weight.

The present invention is also preferably used for a surface treatment composition containing so-called alkaline electrolytic ionic water as a main component, which is said to be obtained by electrolyzing water. In the present invention, the method of adding the complexing agent to the surface treatment composition is not particularly limited. Among the components that mainly constitute the surface treatment composition (for example, ammonia water, hydrogen peroxide water, and water in the case of the cleaning composition used for the SC-1 cleaning), any one component or a plurality of components is used. A complexing agent may be blended in advance and the remaining components may be mixed and used later, or the complexing agent may be blended and used after mixing mainly constituent components.

The liquid composition for surface treatment of the present invention is used for surface treatment such as cleaning, etching, polishing, film formation and the like of a substrate such as a semiconductor in which metal impurity contamination of the substrate becomes a problem. In particular, cleaning of semiconductor substrates that require a highly clean substrate surface,
The present invention is suitably used for etching. When the present invention is applied to alkali cleaning such as [ammonia + hydrogen peroxide + water] cleaning among semiconductor substrate cleaning, the problem of metal impurity adhesion to the substrate, which was a problem of the cleaning method, is improved. By this cleaning, a highly clean substrate surface free of metal contamination as well as particles and organic contamination is achieved, which is extremely preferable.

When the present invention is used for cleaning a substrate, a method of directly contacting a liquid with the substrate is used. Such cleaning methods include dip-type cleaning in which a cleaning tank is filled with a cleaning liquid and immersing the substrate, spray-type cleaning in which the liquid is sprayed on the substrate and cleaning, and spin-type cleaning in which the cleaning liquid is dropped on the substrate and rotated at high speed. And the like. The present invention can be used in any of the above cleaning methods, but preferably uses dip-type cleaning.
Regarding the washing time, the washing is performed for an appropriate time, but is preferably 10 seconds to 30 minutes, more preferably 30 seconds to 15 minutes. If the time is too short, the cleaning effect will not be sufficient, and if it is too long, the throughput will only be deteriorated, and the cleaning effect will not increase and is meaningless. The washing may be performed at room temperature, but may be performed with heating for the purpose of improving the washing effect. Also,
At the time of cleaning, a cleaning method using physical force may be used in combination. Examples of such a cleaning method using physical force include ultrasonic cleaning and mechanical cleaning using a cleaning brush.

[0023]

EXAMPLES Next, specific embodiments of the present invention will be described with reference to examples, but the present invention is not limited to the following examples unless it exceeds the gist thereof. Examples-1 to 2 and Comparative Examples-1 to 11 Ammonia water (30% by weight), hydrogen peroxide solution (31% by weight) and water were mixed in a volume ratio of 0.25: 1: 5, and the mixture was obtained. A predetermined amount of the complexing agent shown in Table 1 was added to the aqueous solvent as a metal adhesion inhibitor to prepare a composition for surface treatment.
The amount of the complexing agent added was shown in% by weight based on the aqueous solvent, and the name was shown by the above-mentioned common name. (Examples 1 and 2 and Comparative Examples 4 to 11) As Comparative Examples 1 to 3, ethylenediaminetetrakis (methylphosphonic acid), a complexing agent described in JP-A-5-275405, was added to the aqueous solvent. Commonly known as EDTPO]
A composition to which oxalic bis (salicylidenehydrazide) as a complexing agent described in JP-B-163495 was added and a composition to which no complexing agent was added were also prepared.

Al, F were added to the surface treatment solution thus prepared.
e was added as chlorides by 10 ppb each, and then a clean silicon wafer (p-type, CZ, plane orientation (100))
For 10 minutes. During the immersion, the temperature of the surface treatment liquid is
Warmed and maintained at 40-50 ° C. The silicon wafer after the immersion was overflow-rinsed with ultrapure water for 10 minutes, then dried by nitrogen blowing, and A
l, Fe was quantified. A adhered on silicon wafer
1 and Fe were recovered with a mixed solution of hydrofluoric acid 0.1% by weight and hydrogen peroxide 1% by weight, the amount of the metal was measured by a flameless atomic absorption method, and converted to a substrate surface concentration (atoms / cm ² ). .
The results are shown in Table 1.

[0025]

[Table 1]

[0026]

The surface treatment composition of the present invention contains a specific complexing agent as a metal adhesion inhibitor, thereby preventing contamination of metal impurities such as Al and Fe from the surface treatment composition onto the substrate surface. An extremely clean substrate surface can be stably achieved. In particular, when the present invention is applied to alkali cleaning of a semiconductor substrate typified by [ammonia + hydrogen peroxide + water] cleaning and the like, the problem of metal impurity attachment to the substrate, which was a problem of the cleaning method, is improved. Thereby, by the washing,
A highly clean substrate surface free of metal contamination as well as particles and organic contamination is achieved. For this reason, acid cleaning such as [hydrochloric acid + hydrogen peroxide + water] cleaning, which has been conventionally used after the cleaning, can be omitted, and the cleaning cost and the cost of a clean room such as exhaust equipment can be significantly reduced. To become
This is a great advantage for industrial production of semiconductor integrated circuits. In addition, when etching or cleaning a metal substrate or a substrate whose surface is formed with a metal, if a metal having a lower ionization tendency than the metal to be treated is present as an impurity in the liquid, the metal adheres electrochemically to the substrate surface. However, when the present invention is used, the metal impurities become a stable water-soluble metal complex, which can be prevented. Further, if the present invention is applied to an abrasive slurry for polishing a substrate, it is possible to prevent metal impurities present in a large amount in the abrasive slurry and being concentrated in the slurry as the substrate is polished from adhering to the substrate. it can.

──────────────────────────────────────────────────続 き Continued on the front page (58) Fields surveyed (Int. Cl. ⁷ , DB name) C11D 7/06 C11D 3/60 H01L 21/304 H01L 21/308 CA (STN) CAOLD (STN) REGISTRY (STN )

Claims (5)

(57) [Claims] 1. A liquid composition for treating a surface of a semiconductor substrate, comprising a complexing agent comprising ethylenediaminediorthohydroxyphenylacetic acid as a metal adhesion inhibitor. 2. The method according to claim 1 , wherein the surface treatment of the semiconductor substrate is performed on a semiconductor substrate.
2. The method according to claim 1, wherein the surface is etched, polished or cleaned.
Liquid composition for surface treatment. 3. A surface treatment liquid composition according to claim 1 or 2 as a main component an aqueous alkaline solution. 4. The liquid composition for surface treatment according to claim 3 , wherein the alkaline aqueous solution is an aqueous solution containing ammonia and hydrogen peroxide. 5. A method for treating a surface of a semiconductor substrate with claim 1 for surface treatment liquid composition according to any one of the four.