JPH06252037A - Method of preventing contamination of wafer surface and method of forming resist pattern - Google Patents

Abstract

PURPOSE:To provide an excellent pattern to reduces the effects of a wafer and to form a highly reliable electrode wiring layer by forming a coating film on a wafer at first and then a carbon-containing coating film on the surface of the coating film and eliminating the coating film after the formation. CONSTITUTION:A silicon wafer 1 is prepared. A borophosphosilicate glass(BPSG) film 2 is deposited by an ordinary CVD method so that a 80mum thick film may be formed on the wafer 1. Then, a 5wt.% aqueous solution of a maleic anhydride and acrylic acid copolymer (mean molecular weight 10000) is applied by spin-coating so that a film of 20mum thickness may be formed, thereby forming a coating film 3 on the BPSG film 2. During this operation, the transfer of the wafer between the BPSG film deposition and the coating film formation is carried out in a nitrogen atmosphere so that the wafer is not exposed to the air. Then, the coating layer 3 is removed by cleaning the surface of the wafer for 30 secondes, thereby exposing the surface of the BPSG film 2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a semiconductor device, and more particularly to a method for preventing substrate surface contamination and a method for forming a resist pattern.

[0002]

2. Description of the Related Art In the manufacture of integrated circuits, a method of forming a fine pattern on a semiconductor substrate and etching the substrate by using this pattern as a mask is used. The pattern forming process usually has the following structure.
That is, first, a solution containing a resin and a photosensitizer is applied onto a substrate such as a semiconductor and dried to form a resist film (photosensitive resin film). Then, the resist film is subjected to an exposure treatment for selectively irradiating energy rays such as light,
After that, a resist pattern is formed on the substrate by a developing process. When forming this resist pattern,
Many resists use a phenolic resin that is excellent in sensitivity to exposure light and dry etching resistance.

At present, the degree of integration of integrated circuits is 2-3.
It is highly integrated at a speed of four times a year, but along with this, the pattern of circuit elements is becoming finer year by year, and moreover, it is necessary to strictly control the dimensional accuracy. Currently, as a resist for a phenol resin, for example, a positive resist composed of a novolak resin and a naphthoquinonediazide compound is often used, but recently, from the viewpoint of demand for high resolution and improvement in sensitivity, an acid catalytic reaction has been performed. Expectations for chemically amplified resists to be used are increasing. In the case of, for example, a positive type, this chemically amplified resist is mainly composed of a resin and a photo-acid generator. Among them, as the resin, the hydroxyl group of the phenol-based resin which was originally alkali-soluble is used as a suitable protective group (for example, What is blocked with an ester bond) to make it alkali-insoluble is used. When such a resist is exposed, the acid generated in the exposed portion attacks the ester bond in the subsequent baking step to cause the elimination reaction of the protective group, and as a result, the hydroxyl group of the base resin is changed. When exposed, the exposed part becomes alkali-soluble. Since this reaction proceeds in a chain using an acid as a catalyst, the sensitivity becomes extremely high. Further, this type of resist has a high light transmittance even in the deep ultraviolet region.

On the other hand, as described above, the chemically amplified resist has extremely high sensitivity, but on the other hand, it has a drawback that it is strongly influenced by the base in the patterning step. That is, a small amount of basic substance on the surface of the substrate to be processed, which is the base,
For example, in the presence of ammonia or the like, the acid generated by exposure is deactivated and loses its effectiveness as a catalyst, so that the bottom portion of the resist film becomes difficult to dissolve in the developing solution and the resist pattern is formed.
Shape deteriorates. In an extreme case, a poorly soluble layer will be formed at the interface between the resist film and the underlying layer. Also, in order to increase the dimensional conversion difference when etching the underlying substrate,
It becomes difficult to control the pattern size with high accuracy. In the current process using a chemically amplified resist, the actual situation is that no effective method for reducing the influence from the base has been found yet.

Further, the ammonia may adhere to the surface of a substrate to be processed in a process such as surface treatment or diffusion. If the atmosphere contains water, the ammonia reacts with the water and ammonia water (NH ₄ OH), which causes contamination or corrosion of the surface of the electrode wiring layer (aluminum layer or the like) already formed or formed thereafter. further,
Ammonia is decomposed at a high temperature and reacts with a semiconductor such as metal or silicon to form an amide, imide, or nitride film, which causes a problem that the resistance value of the electrode wiring or the contact resistance value increases. .

[0006]

As described above, in the process of the conventional technique using the chemically amplified resist, the shape of the resist pattern is deteriorated due to the influence from the base (in particular, the influence of the basic substance), and In this case, there is a problem that a poorly soluble layer is formed at the interface between the resist film and the base.

Further, for example, in the surface treatment or diffusion process, when the attached ammonia contains water in the atmosphere, it reacts with the water to become ammonia water, and the surface of the electrode wiring layer (aluminum layer etc.) It causes pollution and corrosion. Further, ammonia is decomposed at a high temperature and reacts with a semiconductor such as metal or silicon to form an amide, imide, or nitride film, and there is a problem that the resistance value of electrode wiring or the contact resistance value increases. It was

The present invention has been made in view of the above-mentioned circumstances, and it is possible to prevent the contamination of the substrate surface for reducing the influence from the base to obtain a good resist pattern and forming a highly reliable electrode wiring layer. An object of the present invention is to provide a method and a method for forming a resist pattern.

[0009]

Therefore, according to the present invention, after a layer to be treated is formed on a substrate, a coating film containing carbon as a component is formed on the surface of the layer to be treated, and then the substrate to be treated is formed. The feature is that the covering film is removed. As the coating film, for example, a water-soluble polymer film can be used, and particularly an acidic polymer film having a function of adsorbing a basic substance is more effective. Further, as the layer to be treated,
For example, various metal films, silicide films, oxide films, nitride films (S
Examples of the antireflection film include an iN film, a TiN film) and a sputter carbon.

Further, according to the present invention, first, a layer to be treated is formed on a substrate, then a coating film containing carbon as a component is formed on the surface of the layer to be treated, and then the coating film is removed. This exposes the surface of the layer to be processed, forms a resist film on the surface of the layer to be processed, and then exposes and develops the resist film. Here, in removing the coating film, a method such as removal with pure water and an aqueous solution or exposure to a plasma atmosphere containing oxygen can be used.

[0011]

[Function] As a result of earnest research by the present inventor, the resist pattern
It has been revealed that the main factor that deteriorates the shape of the substrate is the basic substance (especially ammonia) in the atmosphere adsorbed on the surface of the base.

In the method of preventing contamination of the surface of the substrate of the present invention, after the layer to be treated is formed on the substrate, a coating film containing carbon as a component is formed on the surface of the layer to be treated. The basic substance can be absorbed in the coating film, and the surface contamination due to the adsorption of the basic substance on the surface of the layer to be treated as described above can be prevented. Therefore,
It is possible to obtain a highly accurate and favorable resist pattern and to form highly reliable electrode wiring free from contamination, corrosion, and resistance value deterioration. In particular, if a water-soluble polymer film is used as the coating film, a relatively simple spin coating method can be used.
Furthermore, if an acidic polymer film having a function of adsorbing a basic substance is used as the coating film, it is more effective in preventing surface contamination.

Further, in the method of forming a resist pattern of the present invention, after first forming a layer to be processed on a substrate,
A coating film containing carbon as a component is formed on the surface of the layer to be processed, and then the surface of the layer to be processed is exposed by removing the coating film, and immediately thereafter the surface of the layer to be processed. Since the resist film is formed on, it is possible to make the coating film absorb the basic substance,
It is possible to prevent a basic substance in the atmosphere from being mixed between the layer to be processed and the resist film. Therefore, the shape of the resist pattern after exposing and developing the resist film becomes extremely good. Further, by using a method of treating with pure water and an aqueous solution, or exposing to a plasma atmosphere containing oxygen, it becomes possible to completely and quickly remove the coating layer.

[0014]

EXAMPLES Examples of the method for preventing substrate surface contamination and the method for forming a resist pattern according to the present invention will be described below.
A detailed description will be given with reference to the drawings. Embodiment 1 FIG. 1 is a process sectional view showing a method for preventing substrate surface contamination according to an embodiment of the present invention.

First, as shown in FIG. 1A, a silicon substrate 1 is prepared, and a boron phosphorus silicate glass (BPSG) film 2 is deposited on the substrate 1 by an ordinary CVD method so as to have a thickness of 80 μm. It was

Then, as shown in FIG. 1 (b), a 5 wt% aqueous solution of maleic anhydride and acrylic acid copolymer having a weight average molecular weight of 10,000 is spin-coated to a film thickness of 20 μm, and then applied onto the BPSG film 2. The coating film 3 was formed. At this time, the substrate was transported between the BPSG film deposition step and the coating film formation step in a nitrogen atmosphere so that the substrate surface did not come into contact with the outside air.

Next, this substrate is subjected to an ammonia concentration of 5 pp.
It was left for 3 days in the clean room of m. Thereafter, as shown in FIG. 1 (c), the substrate surface is washed with pure water for 30 seconds to remove the coating layer 3 made of the maleic anhydride and acrylic acid copolymer, and the BPSG film 2 is removed.
The surface was exposed.

After that, when the amount of adsorbed ammonia on the surface of the BPSG film 2 was examined, 20 ng of ammonia was detected per substrate. The amount of adsorbed ammonia was quantified by immersing the substrate in 100 ml of pure water for 30 minutes to extract impurities, and then analyzing the extract by ion chromatography. By the way, as a comparative example, BPS was left for 3 days in a clean room without forming the coating film 3 made of the maleic anhydride and acrylic acid copolymer.
About 700 ng of ammonia was detected from the G film surface. From these results, it was proved that the coating film 3 was extremely effective in preventing adsorption of ammonia. By using this substrate, it is possible to obtain a highly accurate and good resist pattern, and when forming an electrode wiring layer of aluminum, tungsten, etc., form a highly reliable electrode wiring without contamination, corrosion, or resistance value deterioration. It was confirmed that you can do it.

In this embodiment, the coating film 3 is removed by washing with pure water. However, other than this, the coating film 3 may be removed with a basic aqueous solution such as an aqueous solution of tetramethylammonium hydroxide. Is also possible. In addition,
Even if this aqueous solution remains, it does not affect the subsequent processes (particularly the resist process).

The layer to be processed on the silicon substrate may be a carbon film formed by a sputtering method. Also in this case, a coating film made of a maleic anhydride and an acrylic acid copolymer was formed in the same manner as in the above method, and the coating film was left standing in a clean room for 3 days. It was confirmed that the amount was reduced to 1/20 or less as compared with the case where the film was not formed. The carbon film used at this time is preferably used as an antireflection film when the resist film is subjected to pattern exposure. Example 2

The present embodiment is characterized in that the substrate is exposed to an oxygen plasma atmosphere and the coating film 3 is removed by plasma ashing. Other than that, it is the same as the first embodiment. Also in this example, as in the case of Example 1, the deposition of the BPSG film, the formation of the coating film, and the leaving experiment in the clean room were conducted. Also in this case BPSG
It was confirmed that the amount of adsorbed ammonia on the film surface was significantly reduced as compared with the case where the coating film was not formed. Example 3

2A to 2D are sectional views showing steps of a method of forming a resist pattern according to an embodiment of the present invention. Also, FIG.
FIG. 6 is a view showing a cross-sectional shape of a resist pattern formed by a conventional method. The same parts as those in FIG. 1 are designated by the same reference numerals and detailed description thereof will be omitted. The BPSG film 2 was deposited on the silicon substrate 1 in the same manner as in Example 1 (see FIG.
(A)), the formation of the coating film 3 (FIG. 2 (b)), and the standing experiment in a clean room were conducted. The substrate is placed in a resist processing apparatus having an ammonia concentration of 1 ppb or less, and the surface of the substrate is washed with pure water for 30 seconds to remove the coating film 3
Was removed to expose the surface of the BPSG film 2 (see FIG. 2).
(C)). Here, the coating film 3 may be removed by the oxygen plasma treatment shown in the second embodiment.

Immediately thereafter, the surface of the BPSG film 2 was primed for 20 seconds with a non-amine silane coupling agent.
After the treatment, a sulfonium salt-based photoacid generator and poly-p
A solution containing an ester compound of hydroxystyrene was spin-coated and baked on a hot plate at 100 ° C. for 2 minutes to form a resist 4 film having a thickness of 1.0 μm (FIG. 2).
(D)). Next, the resist film 4 was pattern-exposed through a mask using a reduction projection exposure apparatus using a KrF excimer laser having a wavelength of 248.4 nm as a light source.

Thereafter, the substrate was baked on a hot plate at 110 ° C. for 1 minute, and then the resist film 4 was applied to 2.
By developing with a 38 wt% tetramethylammonium hydroxide aqueous solution for 80 seconds, a resist pattern having a line width of 0.4 μm was formed (FIG. 2 (e)). It should be noted that, from the step of removing the coating film 3 to the step of developing, all were performed by continuous processing in the resist processing apparatus having an ammonium concentration of 1 ppb or less. As shown in FIG. 2E, according to this example, a fine resist pattern having a line width of 0.4 μm could be formed with a good contour.

Also, when a resist pattern is formed by the same method as above except that the coating film is removed by exposing the substrate to an oxygen plasma atmosphere, a fine resist pattern having a line width of 0.4 μm is formed. Was formed with a good contour.

On the other hand, in the case of the conventional method in which the resist pattern is formed without protecting the substrate surface with the coating film,
As shown in FIG. 3, deterioration of the shape at the bottom of the resist pattern (a poorly soluble layer at the interface with the base) was observed.
From this, it is clear that the resist pattern forming method of the present invention is extremely effective in reducing the influence from the base.

Although the maleic anhydride and acrylic acid copolymer film was used as the coating film in Examples 1 to 3 described above, polyvinyl alcohol, polyvinyl phenol,
A water-soluble polymer film such as polymaleic acid or butyl rubber may be used. Further, as a resist, the effect is particularly great for a chemically amplified resist. Furthermore, various modifications can be made without departing from the scope of the present invention.

[0028]

As described above in detail, the method of preventing contamination of the substrate surface and the method of forming the resist pattern according to the present invention has a good contour pattern when the resist which is easily influenced by the underlying substrate is patterned. -Can be formed.

[Brief description of drawings]

FIG. 1 is a process sectional view showing a method for preventing substrate surface contamination according to a first embodiment of the present invention.

FIG. 2 is a view showing a cross-sectional shape of a resist pattern formed by the method of the third embodiment of the present invention.

FIG. 3 is a view showing a cross-sectional shape of a resist pattern formed by a conventional method.

[Explanation of symbols]

 1 silicon substrate 2 BPSG film 3 coating film 4 resist film

Claims (9)

[Claims] 1. A coating film containing carbon as a component for absorbing a basic substance is formed on the surface of a layer to be processed on a substrate, and thereafter,
A method for preventing substrate surface contamination, comprising removing the coating film. 2. The method for preventing substrate surface contamination according to claim 1, wherein the coating film is a water-soluble polymer film. 3. The method for preventing substrate surface contamination according to claim 1, wherein the coating film is an acidic polymer film. 4. The processed layer is a metal film, a silicide film,
2. The method for preventing substrate surface contamination according to claim 1, wherein the method is an oxide film, a nitride film or a sputter carbon film. 5. A step of forming a coating film containing carbon as a component on the surface of the layer to be processed on the substrate, and a step of exposing the surface of the layer to be processed by removing the coating film. A method of forming a resist pattern, comprising: a step of forming a resist film on the surface of the layer to be processed; and a step of exposing and developing the resist film. 6. The method of forming a resist pattern according to claim 5, wherein the coating film is a water-soluble polymer film. 7. The method of forming a resist pattern according to claim 4, wherein the coating film is removed with pure water. 8. The method for forming a resist pattern according to claim 5, wherein the coating film is removed by exposing the substrate to a plasma atmosphere containing oxygen. 9. The processed layer is a metal film, a silicide film,
6. The method of forming a resist pattern according to claim 5, wherein the method is an oxide film, a nitride film and a sputter carbon film.