JPS60200253A - Formation of pattern - Google Patents

Abstract

PURPOSE:To stabilize formation of the resist pattern of an lower layer by forming an upper layer of a UV resist, and the lower of a far UV resist, and developing the lower resist layer with a specified developing soln. in a pattern-forming process using the upper layer pattern as a mask for forming the lower layer pattern. CONSTITUTION:An upper layer resist 33 is made of a UV resist, and the lower layer resist 34 is made of a far UV resist, and the upper layer resist pattern is used as a mask for forming the lower layer resist pattern, and at that time, the lower layer resist 34 is developed with a developing soln. made of a mixture of 35-80% acetone (ACN) and isopropanol (IPA). ACN dissolves both resist layers 33, 34. IPA dissolves only the layer 33 but not the layer 34, thus permitting removal of an intermediate layer made of a mixture of both layers 33, 34, and development of the layer 34 to be executed at the same time, and the lower layer resist pattern to be stably formed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for forming a lower layer pattern in a two-layer resist method used for forming fine patterns.

[Prior art and its problems]

In recent years, fine patterns have been formed in conductor processes and the like by ion beam etching using a photoresist as a mask or by reactive etching. Therefore, the pattern shape and pattern accuracy after etching are strongly influenced by the resist pattern shape serving as a mask. Techniques for forming resist patterns with high accuracy on flat samples can be created using a general photoresist process. However, the actual element (
(conductor element, magnetic bubble element, etc.), the stepped portion (wiring pattern, etc.) 12 as shown in Figure 1 (α) is connected to the substrate 13.
There are many above. When the Mori photoresist 11 is spin-coated on such a stepped portion 12, non-uniformity occurs in the resist film thickness in the vicinity of the stepped portion 12. For this reason, in the exposed and developed resist pattern, a change in resist pattern width occurs at the stepped portion 12, as shown in FIG. 1(b). This is due to the non-uniformity of the resist film thickness at the stepped portion 12 and the uneven resist film thickness at the stepped portion 12.
This occurs due to changes in the reflectance of the substrate in step 2. As a method to solve this problem, a three-layer structure method as shown in Figures 2 (α) and (b) was developed (for example, J.
M Morantte Meydan's "High Resolution Step Profile Resist Pattern"
.

Journal Vacuum Science and Technology, 1
6, No. 6, pp. 1620 to 1624 (1979)), this method involves applying a polymer film (for example, photoresist) 23 to the surface of a sample with steps to a thickness that is not affected by the steps. Then, on top of this, intermediate mask material 22 (
For example, a photoresist 21 for forming a pattern is applied thereon. The photoresist pattern 21 is formed by exposure and development, and the intermediate mask material 22 is etched.Then, using the intermediate mask material 22 as a mask, the underlying polymer film is etched by reactive ion etching using oxygen gas. According to this method, It is possible to form a resist/mask pattern with high accuracy even in places with steps. However, this method removes the underlying polymer film by reactive ion etching, which causes defects on the surface of the substrate due to ion bombardment. There are some drawbacks, and the processing process is long.As a way to improve these drawbacks, the exposure wavelength of 21111, ultraviolet (UV)
) and deep ultraviolet (Damp UV) was developed (B. Liu and Lin, 1979, NISPP, Vol. 174, 114 of 114 of Developing Materials in Semiconductor Microlithography IV).
Pages ~ 121 truly published literature), Figure 3 (α) ~ (6)
is a schematic diagram of this method.

A lower resist (Da
mp-UV resist) 34 is applied, and an upper layer resist (LIV-resist) 33 is applied thereon. A mask material 32 is applied to this sample, and an upper resist pattern is formed using UV light 31 (Fig. 3 (6)).The UV resist has a certain degree of light blocking property against damp-UV light. It is. Using this upper layer resist 33 as a mask, the lower layer resist 34 is exposed to damp-UV light 37 and developed, thereby forming a resist pattern as shown in FIG. 3(6). With this method, there is no ion damage and the process steps are shortened. However, in this method, an intermediate layer is formed in which the upper resist layer and the lower resist layer are mixed, and this intermediate layer is not removed.
There was a drawback that the lower resist layer could not be patterned.

[Purpose of the invention]

It is an object of the present invention to provide a method for forming a lower resist pattern that does not have these conventional drawbacks.

[Principle of the invention]

In a two-layer resist structure, the present invention is capable of dissolving the upper resist and the lower resist by mixing a solvent that can dissolve the upper resist and the lower resist in an appropriate ratio and a solvent that dissolves the upper resist but not the lower resist. The pattern is formed using a lower resist developer that can simultaneously remove the intermediate layer mixed with the lower resist and develop the lower resist.

[Structure of the invention]

The present invention uses an acetone solution and Not from a mixture with purpyl alcohol solution,
The pattern forming method is characterized in that a developer containing an acetone solution in a proportion of 10% or more and less than 10% is used for developing the lower resist layer.

The present invention has solved the problems of the prior art by adopting the above-described configuration. An acetone solution is used as a solvent that can dissolve the upper resist and the lower resist, and isopropyl alcohol (IPA) is used as a solvent that dissolves the upper resist but not the lower resist, and the ratio of acetone to IPA is 35% or more and less than 8o. By using the mixed solution as a developing solution for the lower resist layer, it is possible to remove the upper and lower resist mixed intermediate layer and to obtain stable development characteristics of the lower resist layer. Therefore, a stable resist mask pattern can be obtained with a two-layer resist structure.

〔Example〕

Embodiments of the present invention will be described below in detail with reference to the drawings. Since the two-layer resist structure in the present invention is the same as the conventional one, the cross-sectional views shown in Fig. 3 6)) to (15) are shown below. I will explain using Regarding the resists used in the examples, photoresist l1ff Icrobosite 1300 (manufactured by Shipley Corporation) was used as the upper resist layer, and 0DUR- as the lower layer D$#jl-UV resist U.
1013 (manufactured by Tokyo Ohka) was used. The thickness of the upper resist layer is 0.5 μm, and the thickness of the lower resist layer is 1.01 bm. A photomask 32 was applied to the upper resist i, and the upper resist 33 was exposed to UV light 31 and developed with a specified developer (Microposit developer) to obtain the pattern shown in FIG. 3(b). . Damp-W to this
After irradiating with light, the lower resist layer 9 was developed with a mixed developer of acetone and IPA according to the present invention. At this time, by using a developer having an appropriate acetone concentration, the upper and lower mixed layers were removed and the lower resist layer was developed, thereby forming a resist pattern 34 (FIG. 3(C)). At this time, if the acetone concentration in the developer is too high, the development time will be extremely short and a stable resist pattern will not be formed.9 Conversely, if the acetone concentration is too low, the upper and lower resist layers will be damaged. Since the mixed intermediate layer cannot be removed and the resist pattern cannot be formed, there is an appropriate range for the acetone concentration in the developer. FIG. 4 shows the relationship between the acetone concentration in the developer and the development time when the lower resist film thickness was 1 and the Deep-Uq exposure time was 12 seconds. If the acetone concentration is less than 30q6, removal of the mixed intermediate layer will be incomplete. If t is 80% or more, the development time will be less than 5 seconds, making it difficult to obtain a stable resist pattern. Therefore, an acetone concentration in the lower resist developer of 35 qb to less than 80% is suitable as the lower resist developer. By using a developer within this range, the lower resist can be patterned.

〔Effect of the invention〕

As described in detail above, according to the present invention, in the two-layer resist structure method, acetone and I
Using a mixed solution of PA, the range of acetone concentration in the solution was set to 3.
By reducing the amount of 5 to 80 drops, removal of the mixed intermediate layer and development of the lower resist layer can be performed at the same time.
A stable lower layer regimen pattern can be formed. It goes without saying that even when the thickness of the lower resist film is changed, the same conditions as above can be used by changing the exposure time.

[Brief Description of the Drawings] Figure 1 (chrysanthemum is a cross-sectional view showing an example of a resist pattern of the prior art, (6) is a plan view of the same, Figure 2 (1) is a cross-sectional view showing an example of a three-layer structure) , (b) is the same plan view, Fig. 3 (α)
~(6) are cross-sectional views showing the forming process of a two-layer resist structure in order of process, and FIG. 4 is a diagram showing the relationship between the acetone concentration of the lower resist developer and the development time in the two-layer resist structure. 31... Ultraviolet light, 32...Mask material, 33...Upper layer resist, arm...Lower layer resist, 35...Substrate,
蕊...Step patent applicant NEC Corporation 71-1 Figure O 2 Figure 21 O 3 Figure

Claims (1)

[Claims] (1) In the forming process of a two-layer resist structure, in which the upper layer resist is molded with ultraviolet light resist and the lower layer resist is molded with deep ultraviolet light resist, and the upper layer resist pattern is used as a mask when forming the lower layer resist pattern, an acetone solution and an ingredient are used. A pattern forming method characterized in that a developer which is not a mixed solution with a building alcohol solution and in which the proportion of an acetone solution is at least 10% but less than 60% is used for developing the lower layer resist.