JPH0629968B2 - Pattern formation method - Google Patents

Description

The present invention relates to a pattern forming method in a method of manufacturing various solid-state devices including a semiconductor integrated circuit. In particular, it relates to a pattern forming method using a so-called three-layer resist in which three layers of an organic polymer material layer, an intermediate layer and an organic polymer resist layer are laminated.

Conventionally proposed three-layer resists are constituted by using a thin film of silicon oxide, boron nitride, silicon nitride or various oxide glasses as an intermediate layer. Therefore, it has the following drawbacks. That is, in order to form these thin films uniformly and thinly on the substrate, in this case, the first organic polymer material layer, without forming defects such as pinholes, it is necessary to keep the substrate temperature at a certain temperature or higher. Yes, for example, when forming a thin film of silicon oxide (SiO ₂ ) by the so-called plasma CVD method, the substrate temperature is at least 200 ° C.
Need to This means that in order to avoid thermal deformation and decomposition of the first organic polymer material layer during formation of the intermediate layer, the first organic polymer material layer must be heat-treated at a temperature of 200 ° C. or higher before forming the intermediate layer. It means that it does not occur, and there is a problem that the frame for selecting the material of the first organic polymer material layer is limited and the peeling process of the first organic polymer material layer in the final step of pattern formation becomes difficult. It was

Optically, these conventional thin films of the intermediate layer material are almost transparent to the light of the wavelength of 436 nm or 405 nm which is the light emitted from the mercury lamp which is most frequently used in the photolithography process, for example. Therefore, the influence of reflected light from the surface of the substrate to be processed cannot be reduced, and one of the important advantages of the three-layer resist cannot be exhibited. Electrically, these intermediate layer materials are insulators, and accordingly, when they are applied to electron beam exposure, they cause electrification, which is a problem in performing good electron beam drawing.

In addition, the formation rate of thin films of these intermediate layer materials is generally relatively low, and there is a problem in the process throughput. Furthermore, the etching rate at the time of selectively etching the intermediate layer by the method of reactive ion etching using the patterned upper resist layer as an etching mask is relatively low, and the etching selection ratio with the upper resist layer is often insufficient, This means that the upper resist layer cannot be made sufficiently thin, but in the end, sufficient resolution cannot be obtained.

It is an object of the present invention to provide an intermediate layer material which completely eliminates these defects due to the intermediate layer material in the conventional three-layer resist construction, and thereby to improve the patterning method.

That is, when the present invention is outlined, the present invention provides three layers of an organic polymer material layer, an intermediate layer, and a resist layer on the main surface of a substrate to be processed.
Two layers are sequentially laminated, and then a desired pattern is formed on the resist layer by exposure and development with a desired pattern, and then the intermediate layer is selectively etched by using the patterned resist layer as an etching mask. Forming a desired pattern on the intermediate layer by removing the intermediate layer, and then using the patterned intermediate layer as an etching mask to selectively etch away the organic polymer material layer. It relates to a pattern forming method, wherein the layer is a chalcogenide glass material.

Hereinafter, the present invention will be specifically described with reference to the accompanying drawings.

The accompanying drawings (a) to (f) are schematic cross-sectional views showing the basic steps of the pattern forming method of the present invention in the order of steps. First, as shown in (a), an organic polymer material layer 2, a chalcogenide glass layer 3, and an organic polymer resist layer 4 are laminated in this order on the main surface of a substrate 1 to be processed into which a desired pattern is finally formed. Form. Next, as shown in (b), a desired pattern is formed on the organic polymer resist layer 4 by a known method. That is, a desired pattern is exposed using an exposure source such as near-ultraviolet light, ultraviolet light, far-ultraviolet light, electron beam, X-ray, and ion beam, and a resist pattern is formed by development processing. Therefore, the organic polymer resist material applied to the present invention may be appropriately selected according to the exposure source used. Next, as shown in (c), the patterned organic polymer resist layer is used as an etching mask to etch away the intermediate layer made of the chalcogenide glass material which is not covered by the organic polymer resist layer. As a result, a desired pattern is transferred to the chalcogenide glass layer as the intermediate layer. Next, as shown in (d), the patterned organic polymer resist layer and the chalcogenide glass layer are used as an etching mask to etch away the portion of the organic polymer material layer which is not covered thereby. The etching method at this time is suitable in that the so-called undercutting does not occur and there is no pattern conversion difference when the reactive ion etching method using discharge plasma of oxygen gas is applied. The organic polymer resist layer is also completely removed in this etching process, and the organic polymer material layer does not substantially function as an etching mask. Next, the substrate to be processed is etched by a known method using a laminated film of a chalcogenide layer and an organic polymer material layer patterned as shown in (e), and finally, as shown in (f), a pattern is formed. When the chalcogenide glass layer and the organic polymer material layer that have been formed are peeled off and removed, the substrate to be processed is etched into a desired pattern, and the pattern forming step of the present invention is completed. Note that the peeling treatment can be performed sequentially on the chalcogenide glass layer and the organic polymer material layer separately, or simultaneously. Further, for the purpose of preventing contamination due to the chalcogenide glass layer in the etching process of the substrate to be processed, only the chalcogenide glass layer can be removed before the etching process of the substrate to be processed.

Next, each of the above steps will be described in more detail. The chalcogenide glass layer as the intermediate layer, which is the main point of the present invention, is thin, uniform, and has no defects, and can be formed with good adhesiveness to the organic polymer material layer, and it is possible to etch with good quality, and oxygen Any material having a strong resistance to reactive ion etching using a gas can be used in the present invention. For example, chalcogenide glasses containing Se, S, Te, Ge and As as the main components all satisfy these requirements. In particular, the chalcogenide glass containing Se and Ge as the main components sufficiently satisfies the above requirements,
It is suitable for application to the present invention because it has good thermal stability and storage stability and is easy to handle. Examples are Se 95-70 atomic% and the balance Ge.

The formation of such a chalcogenide glass layer can be easily carried out by either the vacuum vapor deposition method or the sputtering method, but the sputtering method is suitable for application to the present invention particularly in terms of good adhesiveness. Etching of the chalcogenide glass intermediate layer can be easily performed by a wet etching method using an alkaline solution, but from the viewpoint of causing no pattern conversion difference, the reactive ion etching method is also preferable in this case. The thin film of chalcogenide glass containing Se and Ge as the main components according to the present invention can be etched at a high speed without undercut by a method of reactive ion etching using discharge plasma of fluorine-based gas, and thus the present invention Suitable to apply.

There are many advantages as described below derived from the characteristics of the chalcogenide glass material as the intermediate layer. The chalcogenide glass thin film enables high-speed film formation while keeping the substrate temperature low, thereby eliminating the above-mentioned drawbacks caused by the intermediate layer material in the conventional three-layer resist. Further, the chalcogenide glass thin film can have extremely large light absorption for near-ultraviolet light and ultraviolet light by appropriately selecting the composition. For example, Se ₈₀ Ge ₂₀ has an absorption coefficient of 10 ⁵ cm ⁻¹ or more for light with a wavelength of 436 nm. Therefore,
For example, even on a substrate having a large light reflectance such as Al, it is possible to completely eliminate the influence of reflected light from the substrate, and it is easy to form a highly accurate pattern. Further, the chalcogenide glass material generally has electric conductivity in the semiconductor region, and even when it is applied to electron beam exposure, the problem of charging does not occur at all. Another advantage of the present invention is that the reactive ion etching method using a fluorine-based gas makes it extremely easy to perform etching at high speed and with no pattern conversion difference.

Example Thickness 0. on a silicon wafer with a layer of thermal oxide on the surface.
A commercially available AZ-1370 resist was formed as an organic polymer layer on a substrate having an Al layer of 8 μm to a thickness of 2 μm by using a spinner, and the AZ-1370 resist was formed in a nitrogen atmosphere at 170 ° C. under the condition of 3
Heat treatment was performed for 0 minutes. Next, a thin film of Se ₈₀ Ge ₂₀ (atomic%) was formed to a thickness of 0.2 μm by the method of high frequency sputtering. The formation conditions are high-frequency power of 90 W and formation time of 3 minutes. Under these conditions, the temperature rise of the substrate surface was 100 ° C. at most, and no deformation or alteration of the organic polymer material layer was observed. Next, a commercially available OFPR-800 resist was formed to a thickness of 1 μm, and a line and space pattern of 1 μm was formed on the OFPR-800 resist by exposure using a reduction projection exposure apparatus and development by a known method. Next, CF ₄ gas 5Pa,
Se _{80 under} the conditions of 100 W, 1 minute, O ₂ gas 3 Pa, 100 W, 60 minutes and SiCl ₄ gas 8 Pa, 100 W, 10 minutes
The G ₂₀ organic polymer material layer and the Al layer were sequentially subjected to reactive ion etching, and finally the commercially available J-100 resist stripping solution was used to strip the remaining organic polymer material layer together with the Se ₈₀ Ge ₂₀ layer. Thus, a 1 μm line and space pattern of Al was formed.

As described in detail above, the present invention relates to a method for forming a three-layer resist pattern, which is characterized in that a chalcogenide glass layer is applied as an intermediate layer. The present invention eliminates all the drawbacks of the prior art and is excellent. Pattern formation can be performed.

[Brief description of drawings]

The accompanying drawings (a) to (f) are schematic cross-sectional views showing the basic steps of the pattern forming method according to the present invention in the order of steps. 1: substrate to be processed, 2: organic polymer material layer, 3: chalcogenide glass layer, 4: organic polymer resist layer

Claims (3)

[Claims] 1. A three-layer structure including an organic polymer material layer, an intermediate layer and a resist layer is sequentially laminated on a main surface of a substrate to be processed, and then a desired pattern is formed by exposing and developing the desired pattern. A desired pattern is formed on the intermediate layer by selectively etching the intermediate layer using the patterned resist layer as an etching mask, and then forming the desired pattern on the intermediate layer. A pattern forming method comprising a step of selectively etching and removing an organic polymer material layer using a layer as an etching mask, wherein the intermediate layer is a chalcogenide glass material. 2. The chalcogenide glass material layer is selenium (Se)
The pattern forming method according to claim 1, which is a glass material containing, as a main component, germanium (Ge). 3. The pattern forming method according to claim 1, wherein etching of the intermediate layer made of the chalcogenide glass material is performed by plasma generated by discharge in a gas atmosphere containing fluorine.