JPH09134862A - Forming method of resist pattern - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a resist pattern from deteriorating in shape without varying it in dimensions through a small number of processes when an anti-reflection film is etched by a method wherein an antireflection film is applied onto a silicon substrate and converted into silyl by heating carried out under specific conditions. SOLUTION: An anti-reflection film 2 formed of novolak resin which contains light absorbing dye is applied onto a silicon substrate 1 and heated at a temperature of 200 deg.C in an atmosphere of hexamethyldisilazan for five minutes to be converted to silyl. Then, resist is applied onto a sililated antireflection film 3, exposed to light through a KrF excimer laser stepper, and developed for the formation of a resist pattern 4. Then, the antireflection film 3 is etched with CF4 gas using the resist pattern 4 as a mask. By this setup, a good resist pattern which is restrained from deteriorating in shape can be obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a resist pattern used as an etching mask, an ion implantation mask, etc. in a semiconductor or various device manufacturing process.

[0002]

2. Description of the Related Art In a conventional method of forming a resist pattern in a semiconductor manufacturing process, a resist layer is coated on a substrate and g-line (wavelength 436 nm) and i-line (wavelength 365n) are applied.
m) or KrF excimer laser (wavelength 248 nm)
Has been used, and a method of developing with an alkaline aqueous solution has been used. In such a conventional method, a phenomenon called so-called halation, which is a deterioration of the resist shape due to light reflected from the underlying substrate, is a serious problem.
There is also a problem called the standing wave effect in which the pattern dimension changes when the resist film thickness changes due to the step of the underlying substrate. These problems are caused by variations in transistor characteristics, disconnection, and
It causes problems such as short circuit.

As a method for solving such a problem, International Electron Device Meeting, Technical Digest (International Elec
tronDevice Meeting, Technical Digest), 1982
Year, pages 391-394, or a three-layer resist process, or under the resist as described in Solid State Technology (Japan Version), November 1993, pages 23-25. There is a method of using an antireflection film.

In the former three-layer resist process, the first resist is first coated on the substrate, and then spin coating is performed.
After coating on glass (SOG), baking is performed, and then a second resist is coated thereon, and ordinary exposure and development are performed. Then, the SOG is etched using the second resist pattern as a mask in plasma using a fluorine-based gas, and then the first resist is etched using SOG as a mask in plasma using oxygen gas. Here, the first resist plays a role of suppressing light reflected from the base substrate. However, this method requires two stages of etching under different conditions, the process is complicated, and there is a problem in the adhesion between the SOG and the resist.

Therefore, as one of means for solving these problems, Japanese Patent Laid-Open No. 2-304922 discloses a first two-layer resist process instead of applying SOG.
The method of silylating only the surface of the resist is disclosed. Although this method solves the problem of adhesion between the SOG and the resist, it requires etching separately for the silylated portion and the non-silylated portion in the first resist, which complicates the process. There is still the problem.

On the other hand, the method using the antireflection film has an advantage that the number of steps is smaller than that of the three-layer resist process while maintaining the antireflection effect. However, in this method, when etching the antireflection film, the selection ratio between the antireflection film and the resist is as small as about 1 under normal conditions, so that the resist shape deteriorates.
There is a problem.

As a means for solving this problem, Japanese Patent Application Laid-Open No. 64-52142 discloses a method of selectively silylating only the resist pattern surface on the antireflection film. According to this method, the selection ratio of the silylated resist pattern and the non-silylated antireflection film is about 20, and it is possible to prevent the shape deterioration of the resist pattern when etching the antireflection film. it can. However, since the volume of the resist pattern is expanded by silylating the resist pattern, another problem occurs that the pattern size varies.

[0008]

As described above, 3
Although problems such as halation can be solved by using a layer resist process or an antireflection film, even if these improved methods are used, the problem that the steps are complicated in the case of a three layer resist process, In this case, the problem that pattern dimension variation occurs remains.

The present invention has been made in order to solve the above-mentioned problems, and it is possible to prevent the resist shape from deteriorating at the time of etching the antireflection film without causing the resist dimensional variation in a small number of steps. An object of the present invention is to provide a pattern forming method.

[0010]

In order to achieve the above object, a method of forming a resist pattern according to the present invention includes a step of forming an organic antireflection film on a silicon substrate and a step of forming the entire antireflection film. Silylating step, forming a resist film on the antireflection film, irradiating the resist film with ultraviolet rays or deep ultraviolet rays, developing the resist film to form a resist pattern, and masking the resist pattern As a result, the antireflection film is etched in plasma containing an etching gas for the silicon oxide film.

In the present invention, the silylated layer is formed by incorporating silicon into the antireflection film by silylating the antireflection film. For example, when a novolac-based resin, which is a kind of antireflection film, is reacted with hexamethyldisilazane, the OH in the resin is changed as shown in Chemical Formula 1 below.
The H of the group is replaced with a silyl group, and a silylated layer having such a molecular structure is formed.

Embedded image

The etching resistance of the silylated layer has a characteristic similar to that of the resist and the silicon oxide film. For example, when etching is performed in oxygen gas plasma that etches a resist, the silylated layer is etched less than the resist, but is etched rather than the silicon oxide film. When etching is performed in a fluorine gas plasma that etches a silicon oxide film,
The silylated layer is not as etched as the silicon oxide film, but is etched more than the resist.

Therefore, when the antireflection film is etched using the resist pattern as a mask, if the etching is performed in plasma containing fluorine gas, the resist is hardly etched and only the antireflection film is etched. Since the selection ratio between the film and the resist is increased, the resist shape is not deteriorated. Furthermore, since the silylation of the antireflection film is performed before forming the resist film, the silylation does not deform the resist pattern.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to FIG. First, as shown in FIG. 1A, an antireflection film 2 made of, for example, a novolac resin film containing a light absorbing dye is applied on a silicon substrate 1, and then as shown in FIG. Hexamethyldisilazane was used to heat the antireflection film 2 at 200 ° C. for 5 minutes in the atmosphere to silylate the antireflection film 2. It should be noted that this condition is a condition under which the entire antireflection film 2 is silylated.

Then, after applying a resist on the anti-reflection film 3 which is entirely silylated, exposure and development are carried out by a KrF excimer laser stepper to form a resist pattern 4 as shown in FIG. 1 (c). Then, the antireflection film 3 is etched using the resist pattern 4 as a mask and an RIE etching device. At this time, CF ₄ gas (fluorine-based gas) is used as an etching gas, RF power is 100 W, and CF ₄ gas flow rate is 50.
The conditions are sccm, substrate temperature −50 ° C., and pressure 5 mTorr. Then, a pattern as shown in FIG. 1D is formed.

According to the resist pattern forming method of the present embodiment, when the antireflection film 3 is etched with CF ₄ gas while maintaining the antireflection effect, the silylated antireflection film 3 and the resist are removed. Since the selection ratio is large, it is possible to prevent the deterioration of the resist shape during etching. In fact, when the resist pattern obtained by the above method was observed with an electron microscope, a good pattern without deterioration of the resist shape was formed.

Since the silylation of the antireflection film 2 is performed before forming the resist film, the silylation does not cause the resist to expand, the resist pattern is not deformed, and the pattern size does not change.

Further, since the film to be formed is only two layers of the antireflection film and the resist film, and the entire antireflection film can be etched in a lump by silylating the entire antireflection film, so that the pattern formation is performed as compared with the conventional method. The number of steps required for can be reduced.

The technical scope of the present invention is not limited to the above embodiment, and various changes can be made without departing from the spirit of the present invention. For example, in the above-mentioned embodiment, the KrF excimer laser is used for the exposure, but the same effect can be obtained by performing the exposure using the g-line, i-line of a mercury lamp or the ArF excimer laser. In the above embodiment, the silylation temperature is set to 20.
Although it was set to 0 ° C, if the temperature is such that the silylation reaction proceeds,
The temperature may be any temperature not limited to 200 ° C., and the time may be arbitrary not limited to 5 minutes. However, it is necessary that these conditions are such that the entire antireflection film is silylated.

As the antireflection film, in addition to the novolac resin film containing the light absorbing dye, for example, a resist itself added with the light absorbing dye, or a light having a wavelength used for exposure without containing the dye is used. It is possible to use a resin or the like having a property of absorbing the. In the silylation step, a chlorosilane compound such as chlorotrimethylsilane may be used instead of the silazane compound such as hexamethyldisilazane, or a liquid phase silylation method may be used instead of the gas phase silylation method. The same effect can be obtained.

Further, CF ₄ was used as an etching gas for the antireflection film, but any gas may be used as long as it is used for etching the silicon oxide film, for example, CHF ₃ , or a mixture of CHF ₃ and CO. You may use gas etc.

[0022]

As described above in detail, according to the method of forming a resist pattern of the present invention, since the selectivity ratio between the silylated antireflection film and the resist is large, the antireflection film is etched. It is possible to prevent deterioration of the resist shape. Moreover, since the silylation of the antireflection film is performed before the resist is formed, the resist does not expand due to the silylation, and it is possible to prevent pattern deformation and dimensional variation, which is suitable for forming a fine resist pattern. Become. Further, the number of steps required for pattern formation can be reduced as compared with the conventional method.

[Brief description of the drawings]

FIG. 1 is a diagram showing a procedure of a method of forming a resist pattern according to an embodiment of the present invention.

[Explanation of symbols]

 1 Silicon Substrate 2 Antireflection Film 3 Silylated Antireflection Film 4 Resist Pattern

Claims (2)

[Claims] 1. A step of forming an organic antireflection film on a silicon substrate, a step of silylating the entire antireflection film, a step of forming a resist film on the antireflection film, and the resist. Irradiating the film with ultraviolet rays or deep ultraviolet rays, developing the resist film to form a resist pattern, and using the resist pattern as a mask to form the antireflection film in a plasma containing an etching gas for a silicon oxide film. A method of forming a resist pattern, which comprises a step of etching. 2. The method of forming a resist pattern according to claim 1, wherein a fluorine-based gas is used as the etching gas for the silicon oxide film.