JPH07106224A - Pattern formation method - Google Patents

Abstract

(57) [Summary] [Structure] A chemical vapor deposition method using an organometallic material such as organosilane as a raw material is used to form a resist film on a substrate while changing the composition and growth conditions of the raw material. After irradiating with a patterned energy ray, development is performed to form a resist pattern. [Effect] By forming various sensitivity distributions, light absorption distributions, and refractive index distributions in the depth direction of the resist film, the effects of light absorption of the resist and reflection from the underlying substrate are reduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pattern forming method used for forming a fine pattern on various solid-state devices.

[0002]

2. Description of the Related Art In order to improve the degree of integration and operation speed of solid-state elements such as LSI, circuit patterns are becoming finer. Currently, for these circuit patterns, a combination of a reduction projection exposure method which is excellent in mass productivity and resolution performance and a single layer resist process using spin coating and wet development is widely used.

In the single-layer resist process, a liquid resist is dropped on a substrate to be processed and rotated at a high speed to form a resist film (spin coating method). Next, the resist film is irradiated with patterned light to induce a photosensitive reaction in the exposed portion, and then wet development is performed to form a resist pattern. The resist pattern is used as a mask or the like when etching the underlying substrate to be processed. As the resist, a positive resist having a novolac resin as a base resin is widely used.

On the other hand, for the purpose of completely drying the resist process, a dry resist process has been proposed in which a resist film is formed by a chemical vapor deposition method using an organic silane compound as a raw material, and further development after exposure is performed by plasma. There is. The dry resist process is described in, for example, Applied Physics Letter, Vol. 62 (1993), pages 372 to 374 (Applied Physics Letter, Vo
l. 62 (1993) pp.372-374.

[0005]

Since the resolution limit of the reduction projection exposure method is proportional to the wavelength of light used for exposure, it is desired to shorten the wavelength for improving resolution. Therefore, the g-line (wavelength 436 nm) to i-line (365 n
m), and KrF or ArF excimer laser lasers (248 nm and 193 nm, respectively), which are far-ultraviolet light sources, are used. However, in many conventional resists typified by novolac positive resists, the light absorption by the resist material increases with the shortening of the wavelength, so that the photosensitive reaction mainly occurs on the upper part of the resist film. For this reason, the cross-sectional shape of the resist pattern after development becomes trapezoidal, or the development does not proceed to the bottom of the resist. Such a phenomenon similarly causes a problem when a soft X-ray having a wavelength of about 5 to 30 nm is used as a light source or when an exposure is performed using a low acceleration electron beam of 10 keV or less.

On the other hand, when the resist is exposed using an electron beam having an acceleration voltage of 10 keV or more, on the contrary, the photoreaction occurs more in the lower part of the resist film due to backscattering, so that the cross-sectional shape of the resist pattern after development is reversed. It may become trapezoidal. However, in order for the resist pattern to function as a mask for the underlying etching, it is desirable that the cross-sectional shape be as vertical as possible.

The circumstances described above are exactly the same in the dry resist process. Therefore, in the conventional dry resist process, a thin resist film is formed by the dry resist process on the thick organic film formed by the spin coating method, and this is used as the upper layer film of the two-layer resist method. However, in this case, it is necessary to add a new process such as dry development of the organic film after developing the upper layer film, which causes a problem of complicating the LSI manufacturing process. Further, since the underlying organic film is formed by spin coating, there is a problem that it is not compatible with the complete dry process.

On the other hand, when the light absorption of the resist is small, the so-called standing wave effect, halation, etc. become a problem due to reflection from the base substrate reflection. Further, as a result of the light incident on the resist causing multiple interference in the resist film, there is a problem in that the intensity of the light incident on the resist film changes depending on the film thickness and the line width changes. In order to solve these problems, an antireflection film (ARC) for suppressing light reflection at the interface between the resist and the base substrate, or a resist for suppressing light reflection at the interface between the resist and the air layer above it The application of an on-film antireflection film (top-ARC) is under study. However, in order to apply these, it is necessary to add a new step, which also causes a problem of complicating the LSI manufacturing process. Further, since the antireflection film is formed by spin coating, there is a problem that it is not compatible with the complete dry process.

The object of the present invention is to provide excellent etching resistance,
Another object of the present invention is to provide a pattern forming method using a complete dry resist process that can obtain a resist pattern with excellent resolution.

Another object of the present invention is to easily and without a new step, deteriorate the resist shape due to light absorption in the resist, and to obtain a standing wave effect or halation due to reflection from the underlying substrate reflection, or It is an object of the present invention to provide a pattern forming method using a complete dry resist process, which can reduce problems such as line width variation due to multiple interference in a resist film.

[0011]

The above object is to form an energy ray sensitive thin film on a substrate using a chemical vapor deposition method using an organic metal material such as an organic silane as a raw material, and to form a pattern-like energy on the thin film. When a thin film pattern is formed by irradiating with a line and then developing, it is achieved by changing the composition of the above-mentioned organometallic material raw material or the thin film growth conditions.

Further, the above object is to form a film while changing the composition of the raw material of the organometallic material or the growth condition of the thin film so that the sensitivity to the energy rays increases or decreases in the depth direction of the film. To be achieved.

Further, the above object is to form a film by changing the composition of the metal-organic material raw material or the growth condition of the thin film so that the light absorption in the film with respect to light increases in the depth direction of the film. To be achieved.

Further, the above-mentioned object is to change the composition of the organic metal material or the growth conditions of the thin film such that the refractive index of the film from the surface of the thin film to a depth of about half the wavelength of the light is deeper than that. This is achieved by forming the film while changing the value to be approximately the square root of.

[0015]

The operation of the present invention will be described with reference to FIGS.

In the conventional resist process, since light is absorbed by the resist, the light intensity is attenuated in the depth direction of the resist film (FIG. 2 (a)). On the other hand, the sensitivity of the resist is constant in the depth direction (FIG. 2 (b)). Therefore, the amount of photochemical reaction decreases in the depth direction (FIG. 2C), and the pattern shape deteriorates (FIG. 2D).

On the other hand, in the resist process according to the present invention, the point that the light intensity is attenuated in the depth direction of the resist film is the same as in the conventional case (FIG. 1A), but the sensitivity of the resist in the depth direction of the resist film is improved. Can be increased (Fig. 1
(B)). As a result, even if the light intensity is attenuated, a uniform photochemical reaction occurs in the depth direction (FIG. 1 (c)). Therefore, a resist pattern having a vertical cross section can be obtained (FIG. 1d).

However, in the case of the conventional resist coating method by the spin coating method, it was very difficult to form a sensitivity distribution in the depth direction of the resist film, for example. This is because the coating is performed by a liquid, so that the upper and lower layers are mixed with each other even if the components or properties of the resist are changed in the depth direction of the film.

In the present invention, the resist film is formed by a dry process such as CVD deposition, so that the resist film is formed from the lower part to the upper part over time, and the components are almost always mixed in the vertical direction. Absent. Therefore,
The properties of the resist can be changed in the depth direction of the resist film.

In the dry resist film forming method, there are various methods for changing the sensitivity of the resist, such as changing the material composition or growth conditions such as temperature, pressure and plasma power. By changing to, it is possible to create various sensitivity distributions in the depth direction. For example, when an organic silane film is formed from various organic silanes as a raw material, the number of Si-H bonds in the film is increased by lowering the substrate temperature or plasma power or raising the pressure, and the sensitivity is increased accordingly. Is generally known.

In the case of electron beam exposure in which a lower photosensitivity reaction occurs in the lower part of the resist film, contrary to the above description, if the sensitivity of the resist is decreased in the depth direction of the resist film, the depth of the resist film is reduced. A uniform photochemical reaction occurs in the direction to obtain a vertical resist pattern.

On the other hand, by using the above characteristics of the dry resist film forming method, various properties such as optical properties of the resist film can be changed in the depth direction in addition to the sensitivity. For example, optical conditions such as a light absorption rate and a refractive index of the resist film can be controlled by material composition, temperature, pressure, plasma power and the like. By changing these conditions during the resist film deposition, it is possible to create various light absorption distributions and refractive index distributions in the depth direction. Thereby, the antireflection film (ARC) and the antireflection film on the resist film (to be formed by a process different from the conventional resist coating) are formed.
The resist layer itself can have a function of p-ARC). That is, for example, when a film is deposited at a very early stage of resist film growth under conditions where light absorption is large, and then a resist film is formed under normal conditions, the initially deposited portion functions as an antireflection film. Also, if the refractive index of the film from the resist surface to a depth of about half the wavelength used for exposure is set to be smaller than the internal refractive index (preferably about the square root value), the upper part of the resist is also reflected. Acts as a preventive film.

[0023]

【Example】

Example 1 A resist film having a thickness of about 0.5 μm was formed on a Si substrate by plasma polymerization using monomethylsilane as a raw material. At this time, the pressure inside the reaction chamber was adjusted to 500 mTorr to 100 mTorr between the start and the end of film formation.
To a certain rate. Next, NA is applied to the resist film.
After a fine mask pattern was projected and exposed using a 0.5 ArF excimer laser reduction projection exposure apparatus, dry development was performed using chlorine gas. As a result, a resist pattern with a minimum line width of 0.2 μm having a substantially vertical cross-sectional shape was formed. For comparison, when a film is formed with the pressure inside the reaction chamber kept constant (300 mTorr), the cross-sectional shape of the resist pattern becomes trapezoidal, and a fine pattern of 0.3 μm or less is formed at a resist film thickness of 0.5 μm. could not.

(Example 2) 0.1 μm to 0.2 μm on the surface
A resist film having a thickness of about 0.1 μm was formed by plasma polymerization using monoethylsilane as a raw material on a Si substrate having a step of m, and then the raw material gas was changed to monophenylsilane in the same reaction chamber. A resist film having a thickness of about 0.2 μm was formed by plasma polymerization. Further on,
A resist film having a thickness of about 0.096 μm was formed by plasma polymerization in which the source gas was changed to tetramethylsilane in the same reaction chamber. Next, a fine mask pattern was projected and exposed on the resist film by using an ArF excimer laser reduction projection exposure apparatus of NA 0.5, and then dry development was performed using chlorine gas. As a result, a resist pattern having a minimum line width of 0.2 μm was formed. In this example, a pattern having a constant line width was obtained even when the resist film thickness was changed due to the substrate step.

In the above embodiments, only a very limited combination of materials, process conditions, exposure methods, etc. was described, but various other materials, process conditions, exposure methods are possible without departing from the spirit of the present invention. Needless to say, can be used.

[0026]

According to the present invention, a resist film is formed on a substrate by a chemical vapor deposition method using an organic metal material such as organic silane as a raw material, and the resist film is irradiated with a patterned energy beam. When a resist pattern is formed by post-development, film formation is performed while changing the composition of the organometallic material or the growth conditions of the thin film, so that various sensitivity distributions and light absorptivity distributions in the depth direction of the resist film can be obtained. A refractive index distribution can be created. As a result, the effects of light absorption of the resist and reflection from the underlying substrate can be reduced, and a resist pattern having an excellent shape can be stably formed.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing the principle of the present invention.

FIG. 2 is an explanatory view showing the problems of the conventional method.

Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display location H01L 21/205 21/312 A 7352-4M

Claims (6)

[Claims] 1. An energy ray-sensitive thin film is formed on a substrate by a chemical vapor deposition method using an organic metal material as a raw material, and the thin film is irradiated with a pattern of energy rays and then developed. In a pattern forming method for forming a thin film pattern by removing either an energy beam irradiation part or a non-irradiation part, the film formation is performed while changing the composition of the organometallic material raw material or the thin film growth condition. Pattern forming method. 2. The pattern forming method according to claim 1, wherein the organometallic material is organosilane. 3. The process according to claim 1, wherein the process of forming a film while changing the composition of the organometallic material or the growth conditions of the thin film is performed so that the sensitivity to the energy rays increases in the depth direction of the film. Pattern formation method. 4. The process according to claim 1, wherein the process of forming a film while changing the composition of the organic metal material or the growth conditions of the thin film is performed so that the sensitivity to the energy rays decreases in the depth direction of the film. Pattern formation method. 5. The process according to claim 1, wherein the energy ray is light, and the light absorption coefficient of the film with respect to the light is changed in the process of forming the film while changing the composition of the organic metal material or the growth conditions of the thin film. A pattern forming method performed so as to increase in the depth direction of the film. 6. The process according to claim 1, wherein the energy rays are light, and the process of forming the film while changing the composition of the metal-organic material raw material or the growth conditions of the thin film is about the wavelength of the light from the surface of the thin film. A pattern forming method in which the refractive index of a film up to a half depth is approximately the square root of the refractive index of a deeper part.