JPH01147535A - Multilayer resist film - Google Patents

Abstract

PURPOSE:To remarkably reduce the interference of light by incorporating a water soluble org. compd. contg. 5-95wt.% of an UV absorber as a flattening resist film material in the title film. CONSTITUTION:Stage differences and ruggedness on a substrate 1 are flattened with a flattening resist 2, the film thickness of an upper layer resist 4 forming a pattern by exposure of light is made uniform with a improved reproducibility, and the reflected ray of the resist film is made small. Namely, the flattening resist 2 is thickly applied on the substrate 1 as a 1st layer to flat the substrate having the stage differences and the ruggedness. The upper resist 4 which has been applied on the uppermost part thereof is patterned by exposing and developing a thin and flat upper resist layer 4. And then, the pattern is transferred to a surface resist with good accuracy by etching an intermediate layer 3 and the flattening resist 2 in this order. This intermediate layer 3 is mainly composed of an inorg. material such as SiO2 and Si etc., which has the large etching grade ratio of the layer 3 to the resist. Thus, the clear pattern with good dimensional precision is formed with a thin upper resist, without being affected by the stage differences and ruggedness of the substrate.

Description

DETAILED DESCRIPTION OF THE INVENTION (Object of the Invention) Industrial Field of Use The present invention relates to a multilayer resist film used for transferring electronic devices or circuit patterns onto a λ4 plate or as a lithography.

The increase in the scale of integrated circuits, which has evolved from the conventional technology 1C to LSI and finally to VLSI, is inevitably accompanied by the problem of finer patterns.

Conventionally, the pattern forming method with the highest resolution among the exposure technologies used in mass production of LSI is a method using a positive resist and reduction projection exposure method.
A pattern of about 1.5 microns is formed.

In the reduction projection exposure method, light from a mercury lamp, which is a light source, is passed through a filter to have a single wavelength, and after passing through a condenser lens, it is irradiated onto the original image. The light that has passed through the bright areas of the original image passes through a reduction lens and is focused onto the wafer. The spectral lines of a mercury lamp include Q-line (wavelength 436nrT1), h-line (wavelength 405nm), or i-line (wavelength 365nm).
etc., and generally the q-line or i-line is often used.

When manufacturing VLSI, we need to further refine the pattern.
Conventional single-layer resist films have the following problems.

On actual devices, there are steps of various shapes and unevenness due to the small size of multiple films, and if a photosensitive resist is deposited without flattening such steps or unevenness, the depth of focus of exposure Exposure performance is degraded due to blur due to insufficient exposure and uneven exposure due to oblique exposure.

Furthermore, when a conventional single-layer resist film is exposed, the exposure light interferes within the resist film, resulting in multiple interference effects within the resist film and standing wave effects resulting from interference between incident light and reflected light. Decreases dimensional accuracy.

An inherent problem with optical lithography is reflection from the substrate and light scattering from the edges of various patterns on the substrate.

A new resist process that has been proposed and is being actively developed for practical use in order to solve the various problems described above is the multilayer resist method.

As shown in FIG. 1, this method uses a flattened resist 2 to flatten the steps and irregularities of the substrate 1, and makes the thickness of the upper resist 4, which is patterned by exposure, uniform and with good reproducibility. The purpose of this is to reduce the size of most half-poles of light.

The basic process of the multilayer resist method is to apply a thick layer of resist to the first layer on the substrate, flatten the underlying steps and unevenness,
The thin flat upper layer resist 4 coated on the top is exposed and exposed.
After development, patterning of the upper layer resist is first performed. After that, middle layer 3 and flat.

By sequentially etching the etched resist 2, the pattern is accurately transferred to the underlying resist. For the intermediate layer 3, inorganic materials such as silicon dioxide (Si02) and silicon (S r >), which have a large erating gray ratio of 1 to 1 with the resist, are mainly used.

With this method, a clear pattern with high dimensional accuracy can be formed using a thin resist as an upper layer without being affected by differences in base level or unevenness.

Problems to be solved: The last step of lithography, in which devices and circuit patterns are transferred onto the surface of a silicon wafer, is unnecessary after the base processing by etching is completed. After that, it is often baked at a temperature of 200-400°C.

For this reason, it is extremely difficult to remove resist that is no longer needed.

To remove the resist, a synergic liquid is used to remove the resist inside the shell. Large amounts of harmful organic solvents must be used.

Further, it is necessary to use a large amount of ultrapure water for cleaning such syneresis.

Furthermore, since all layers of the multilayer resist film must be dissolved and removed using a synergist, the resist removal process takes an extremely long time.

The present invention provides a multilayer resist film that can be removed extremely easily without using harmful bacterium syneresis such as atomizer, and a multilayer resist film that absorbs exposure light within the flattened resist and minimizes light interference. The purpose is to provide a resist film.

(Structure of the Invention) Means for Solving the Problems The present invention provides five methods for flattening resist in a multilayer resist method.
It uses a water-soluble organic compound containing ~95% by weight of ultraviolet absorber, so it is easy to remove the unnecessary part under the resist after the base processing is completed by dissolving the flattened resist with water. The multilayer resist film can be separated and removed from the substrate. Therefore, it is not necessary to dissolve and remove all layers of the multilayer resist film.

Furthermore, since the planarized resist contains a water-soluble ultraviolet absorber, the exposure light is absorbed within the planarized resist, making it possible to minimize light interference.

The water-soluble ultraviolet absorber is crocin (C441-164024>), which is a vitamin A compound that absorbs the q-line, h-line, or i-line, which are the spectrum lines of a mercury lamp.

Vitamin 82 (C17H2ON406) or vitamin B2 phosphate ester (C17)-121N40
9 P) Vitamin M (C19H19N706), oxyphylline (C9H12N403), which is a vitamin L class
”) Ah Louis is Jihui IJn (C10H14N404
), quinonetramnin (C3), which is a vitamin 1)
4+-142020) Quercetin (C15H1007
), or delphinidin (C15H1107Cl
), or vitamin 5 (C11H11No)
Vitamins or vitamin-like compounds such as or azo compounds such as diaminoazobenzene (CI2H12N4) can be used. Alternatively, a mixture of two or more of these compounds may be used.

Water-soluble flattening resist] contains the neutral glucan pullulan, mannitol, bitroxypropylcellulose (H
PC) or polyvinyl alcohol can be used.

However, these flattened resists do not necessarily have good adhesion to the substrate. One way to improve this is to use a surfactant, but many surfactants have a low melting point and therefore deteriorate the properties of the planarized resist.

A water-soluble ultraviolet absorber has a hydrophobic ultraviolet absorbing portion, and has a structure in which the molecule has a hydrophilic side chain in order to make this hydrophobic substance hydrophilic. This structure is similar to the chemical structure of a surfactant, and therefore, by incorporating such a water-soluble ultraviolet absorber into the planarized resist, the adhesion to the substrate can be significantly improved.

Example 1 Pullulan containing 20% by weight of vitamin B2 was coated on a quartz substrate to a thickness of 2 microns using a spinner, and an absorption spectrum with peaks at 370 nm and 445 nm was observed for this film. A portion of this film was covered with glass, the substrate humidity was maintained at 150° C., and plasma etching using oxygen was performed for 5 minutes. As a result, this film was completely etched and removed. Furthermore, when the remaining film covered with glass was immersed in water, it was easily dissolved and removed.

Fruit #A2 Hydroxypropyl cellulose containing 3 oam% diaminoazobenzene was applied onto a quartz substrate to a thickness of 2 microns using a spinner.

An absorption spectrum with a peak at 400 nm was observed for this film. Cover part of this film with glass and lower the substrate temperature to 15
The temperature was maintained at 0° C., and plasma etching using oxygen was performed for 5 minutes. As a result, this film was completely etched and removed. Furthermore, when the remaining film covered with glass was immersed in water, it was easily dissolved and removed.

The above examples show that the film produced in this way can be plasma etched with oxygen, retains water solubility even after the etching process, and absorbs the spectral lines of a mercury lamp, making it suitable for multilayer resist methods. It was found that it can be satisfactorily used as a water-soluble planarizing resist.

(Effects of the Invention) According to the present invention, since a water-soluble organic compound containing a water-soluble ultraviolet absorber is used as a flattening resist in a multilayer resist method, exposure light is absorbed in the flattening resist and the light is emitted. The interference of
It has the feature of significantly improving pattern dimensional accuracy and exposure performance.

Furthermore, the multilayer resist method has a feature that it is not necessary to dissolve and remove all layers of the resist film with a harmful peeling solution, and the multilayer resist can be easily removed by simply dissolving the flattened resist with water. Furthermore, since the resist removal process is also extremely simplified, there is an advantage that manufacturing costs can be reduced.

Further, there is an advantage that the amount of ultrapure water used in the cleaning process can be reduced.

Further, according to the present invention, the adhesion between the substrate and the planarized resist can be improved by incorporating a water-soluble ultraviolet absorber into the planarized resist.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a multilayer resist film. In the figure, 1 is a substrate, 2 is a flattened resist]-13 is an intermediate layer, and 4 is an upper layer resist.

Claims (1)

[Claims] A multilayer resist film characterized in that a water-soluble organic compound containing 5 to 95% by weight of a water-soluble ultraviolet absorber is used as a flattened resist film material.