JPS63316438A - Formation of photoresist pattern - Google Patents

Abstract

PURPOSE:To form an ultrafine pattern of high accuracy and high definition surely by a method wherein, for a two-layer method, a positive-type photoresist which is photosensitive to the ordinary light of a wavelength of 300-500nm is used as a first resist for a lower layer. CONSTITUTION:When a photoresist pattern is formed on a substrate 1 having a stepped part 2 on the surface, a photoresist layer 11 which is photosensitive to the light of a wavelength range of 300-500nm is formed in such a way that its surface 11a can be flat while the stepped part 2 is filled. A second photoresist 12 to which a paint material capable of absorbing the light of said wavelength range is added and which is photosensitive to the light of a wavelength shorter than this wavelength range is coated on the surface; a required pattern is exposed on the second photoresist layer 12; this layer is developed to form the pattern. The first photoresist 11 as the lower layer is exposed by the light of said wavelength range by making use of the patterned photoresist layer 12 as an exposure mask, and is then developed. By this setup, the pattern of high accuracy and with pattern sharpness can be formed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method of forming a photoresist pattern used as a mask for various microfabrication processes, such as dry etching, in the manufacturing process of various semiconductor devices, for example.

[Summary of the invention]

In the present invention, when a photoresist pattern is formed on a substrate having an uneven surface, that is, a stepped portion, a first photoresist sensitive to light in a wavelength range of 300 to 500 nm is applied to the surface of the substrate so as to bury the stepped portion. is formed so that it is flat, and on top of this a second photoresist is coated with a paint that absorbs light in the above-mentioned wavelength range and is sensitive to light of shorter wavelengths outside the above-mentioned wavelength range. Then, this second photoresist layer is exposed to a required pattern and developed to form a pattern, and the patterned second photoresist layer is used as an exposure mask to expose the first photoresist layer below. By exposing to light in the above-mentioned wavelength range and then developing, a highly sharp photoresist pattern having sharp pattern edges, that is, a pattern cross section having a rectangular shape is formed.

[Conventional technology]

For example, selective reactive ion etching RIE is used in the manufacturing process of various semiconductor devices such as high-density large-scale integrated circuit LSI.
Ultra-fine resist patterns are required for various purposes, such as dry etching resists, selective ion implantation resists, etc.

In forming this resist pattern, most of the resist patterns have unevenness, that is, a stepped portion, formed on the surface of the adhered substrate through various manufacturing steps. If there is a stepped portion on the surface to which the resist is adhered, a photoresist pattern can be formed by simply applying a single layer of photoresist with a uniform thickness, exposing it to light, and developing it, which is a commonly used method. However, it is difficult to obtain a highly accurate and sharp ultra-fine pattern due to uneven coating due to the presence of the stepped portion, light reflected from the uneven exposed portion, and the like.

On the other hand, for example, published by Kogyo Kenkyukai, Electronic Materials 4.198
A two-layer resist method is known, which is also described on page 6, page 47. This method is based on a structure in which two types of resist layers are laminated, and the step portion on the substrate surface is filled with the lower first resist layer to flatten the surface. A flat second photoresist layer is formed, and this is patterned by the required pattern exposure and development processing. Using this as a mask, the underlying first resist layer is etched in oxygen plasma (hereinafter referred to as 02).
In other words, the pattern is formed by anisotropic etching (referred to as RIE). In this case, the upper second resist layer is patterned by optical photographic technology using exposure and development as described above, but as described above, this upper second resist layer has a uniform thickness. High precision due to its flat layer.

It is possible to form fine patterns with high sharpness, and along with this, using this second resist layer as a mask, 02-RIH
It is said that the pattern of the first resist layer patterned by this method also provides a fine pattern with high accuracy and sharpness.

However, when using this method, in reality, during the operation of performing 02 RIE on the lower first resist layer using the above-mentioned second resist layer as a mask, the upper second resist layer is eroded and the ultra-fine pattern is formed. There is a problem with its applicability.

In addition, in the above-mentioned two-layer resist method, a photoresist sensitive to far ultraviolet rays (EEP UV) is used as the lower first resist layer, and D as the second resist layer.
After patterning the second resist layer by exposing and developing a required pattern using a normal positive photoresist that has a high absorption of eep UV, a second resist layer that has a high absorption of eep UV is used. Using the resist layer 2 as an optical mask, deep UV was applied over the entire surface.
There is a so-called PCM method in which an underlying first resist layer is exposed to light in a pattern that is an inversion of the pattern of the second resist layer, and then this first resist layer is developed to form a pattern.

However, this method has the problem that the upper second photoresist layer is a normal positive resist and the exposure wavelength for exposing it is relatively long, making it impossible to sufficiently increase the resolution. be. In addition, the thickness of the lower first resist layer is quite large in order to fill in the steps on the substrate surface, but its exposure sensitivity is not sufficiently high, and the exposure light source for it is not compatible with the Deep UV light source. Due to the current situation where the amount of light cannot be increased sufficiently, the exposure processing time for this first resist layer is long.Furthermore, the Deep UV resist as this first resist layer is
Because it has poor resistance to dry etching, the resist layer patterned in this way is masked (resist).
When processing a substrate, there is a problem in that the resist pattern becomes thinner, making it difficult to perform ultra-fine processing with high accuracy and sharpness.

[Problems to be Solved by the Invention] As described above, the present invention solves the above-mentioned problems when forming an ultra-fine resist pattern on a substrate having a stepped portion, and achieves high precision and sharpness. Provided is a method for forming a photoresist pattern that can reliably form an ultra-fine pattern.

[Means for solving problems]

As shown in FIG. 1A, the present invention applies light in the wavelength range from 300 to 500 nm, that is, from visible light to ultraviolet light (hereinafter simply referred to as wavelength range), on a base +ffl (1) having a stepped portion (2). A step of applying a first photoresist (11) made of, for example, a normal positive type photoresist and flattening its surface (lla), and absorbing light in the above-mentioned wavelength range on this first photoresist. A dye is added and light of a shorter wavelength outside this wavelength range, e.g. De
applying a second photoresist (12) sensitive to epUV, X-rays, electron beams, etc. and applying shorter wavelengths outside the above-mentioned wavelength range to which this second photoresist (12) is sensitive; After exposing it to light in a predetermined pattern and developing it, a window (12w
) is formed into a pattern, and this second resist (12
) is used as an optical mask, so to speak, and the first photoresist (11) is applied over the entire surface of the photoresist (30) to exhibit sensitivity.
The first photoresist (11) is exposed to light in a wavelength range of 0 to 500 nm. In this way, since the second photoresist (12) absorbs light in the above-mentioned wavelength range, only the first photoresist (11) exposed through the window (12w) is selectively exposed. Develop the first photoresist (11) to pattern the first photoresist (11) as shown in FIG.
A desired photoresist pattern in which a window (l1w) of a pattern corresponding to two jets is formed is obtained.

[Effect]

In the above-described present invention, a photoresist sensitive to a normal wavelength range of 300 to 500 nm is used as the lower first photoresist (11), and an exposure wavelength range for this first photoresist (11) is applied on top of this. De of a wavelength shorter than this wavelength range is added.
The second photoresist (1
2), the thickness of the first photoresist (11) is large enough to fill the stepped portion (2) of the substrate (1) and flatten its surface. However, since a normal mercury lamp that emits light at a wavelength of 300 to 500 nm can be used for exposure, a sufficiently large amount of exposure can be obtained, and the sensitivity is also high, so a pattern can be formed with short exposure. Coupled with the fact that the exposure mask for the first photoresist (11) is a pattern of the second photoresist (12) placed directly on top of it, highly accurate pattern exposure is possible. As a result, the pattern of the first photoresist (11) can be formed with high precision and high sharpness. Furthermore, this first photoresist (11
) can use a normal positive type photoresist and has excellent resistance to fine processing of the substrate (1), such as dry etching by RIH, and is therefore effective as a mask for ultra-m III processing evaporation.

〔Example〕

Furthermore, with reference to FIG. 1, a method for forming a photoresist pattern according to the present invention will be explained in detail.

In the figure, the substrate (1) is a variety of semiconductor substrates such as silicon (
A layer to be processed (IB) made of, for example, 5i02, on which plasma dry etching RIE processing is to be performed is formed on IA). A stepped portion (2) is formed on this substrate (11).A wavelength range of 300 to 500 nm obtained by a normal mercury lamp, for example, is placed on the substrate (1) so as to embed this stepped portion (2). The first type that is sensitive to light
A photoresist such as a naphthoquinone diazide resist, which is a normal positive type photoresist, is applied to make the surface (lla) flat.

Then, a dye that absorbs light in a wavelength range to which the first photoresist (11) is photosensitized is added onto this, and a dye that absorbs light in a wavelength range to which the first photoresist (11) is sensitive is added, so that deep ultraviolet rays with shorter wavelengths outside this wavelength range, such as De
A photoresist that is sensitive to epUV (200 to 260 nm) or to X-rays, electron beams, etc.
A second photoresist (12), for example polymethyl methacrylate (PMMA) or a copolymer of methyl methacrylate and methacrylic acid, is applied to a relatively small thickness (FIG. 1A).

Then, this second photoresist (12) is subjected to pattern exposure using short-wavelength UV, electron beam, or X-ray, etc., which exhibits photosensitivity, and is subjected to a development process to form windows (12*). That is, patterning is performed (FIG. 1B).

Next, using this second photoresist (12) as an exposure mask, the first photoresist (11) is exposed to visible light or ultraviolet light of a normal wavelength, for example, 300 to 500 na+, and then developed. A first photoresist (11) in which a window (l1w) corresponding to the window (12w) is formed is patterned (FIG. 1C).

In this way, the desired photoresist pattern according to the present invention is formed.

Next, for example, the layer to be processed (IB) of the substrate (1) is subjected to, for example, RIE dry etching to pattern the layer to be processed (IB) (FIG. 1D).

In addition, in the above-mentioned patterning process, for example, in the exposure process for the upper layer second resist, etc., the substrate (11
By heating the resist by placing it on a heating means equipped with a heater or the like, a curing effect of the resist can be obtained and the heat resistance and dry etching resistance can be further improved.

〔Effect of the invention〕

As described above, in the present invention, while taking advantage of the characteristics of the 2N resist method, the lower first resist (11) is a positive type photoresist, for example, which is sensitive to normal light with a wavelength of 300 to 500 nm. When dry etching is performed on the substrate (1), this lower layer resist (11) has excellent resistance, making it possible to perform fine microfabrication. ) Even when (11) is a thick film that embeds the stepped portion (2) on the substrate (1), a mercury lamp with a relatively large amount of light can be used as the exposure light source for this, and Since it is a positive type resist, its photosensitivity is high, so the exposure time can be shortened sufficiently, resulting in a decrease in accuracy due to light bleeding during long exposure, and a pattern sag or thinning, i.e. pattern cross section. The tendency for the shape to become trapezoidal can be avoided, and it is possible to form a pattern with high accuracy and sharpness.

Further, according to the present invention, the exposure mask for the first photoresist (11) becomes the second photoresist (12), and the exposure wavelength for patterning the second photoresist (12) is High precision due to short wavelength exposure using Deep UV, electron beams, X-rays, etc.
It has become possible to form ultra-fine patterns, and along with this, the first
Patterning of the photoresist (11) also makes it possible to form ultra-fine patterns with high accuracy and sharpness.

[Brief explanation of drawings]

FIG. 1 AND is an enlarged linear sectional view of each step of an example of the method for forming a photoresist pattern according to the present invention. (1) is a substrate, (2) is a stepped portion, (11) is a first photoresist, and (12) is a second photoresist.

Claims (1)

[Claims] A step of applying a first photoresist sensitive to light in a wavelength range of 300 to 500 nm on a substrate having a stepped portion to flatten the surface; applying a second photoresist to which a dye that absorbs light in the wavelength range is added and is sensitive to shorter wavelength light outside the wavelength range; exposing and developing the second photoresist to form a pattern; exposing the first photoresist to light having a wavelength within the wavelength range using the second photoresist as an exposure mask;
1. A method for forming a photoresist pattern, comprising the steps of developing and patterning.