JPS61212020A - Pattern forming method - Google Patents

Abstract

PURPOSE:To obtain a high resolution pattern which is not subjected to the influence of steps by a method wherein a pattern forming organic film, on which a bleaching or fading function for radioactive rays is given, is formed on radiation ray sensitive resin. CONSTITUTION:The steps on a substrate are flattened by coating a thick organic film 4, an inorganic film 5 to be used to isolate from the resist for formation of a pattern is coated on the organic film, a resist 2 is coated on the inorganic film, and a flat triple-layer structure resist is formed. After a bleaching function is given to the above-mentioned triple-layer structure resist using the radiation rays such as ultraviolet rays and it is completely bleached, a pattern forming organic film 3, having the transmittance of 80% or above and a water-soluble property for the developing solution such as alkaline aqueous solution used in the developing process performed on the pattern forming resist 2, is formed. The organic film 3 gives a contrast enhancement effect on the positive resist 2 when a resist pattern 2a is formed. A reactive ion etching (RIE) is performed on the inorganic film 5 using the positive resist 2a as a mask, and a pattern 4a which is not subjected to the influence of a stepping is obtained by performing RIE with oxygen on the organic film 4 using the inorganic film 5a.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application This invention adds a bleaching action to radiation, such as ultraviolet rays, and increases the transmittance after complete bleaching [horizontal axis: exposure energy (3), vertical axis: transmittance] The characteristic equation (7), Y=
When AX+B, A tends to be large and B tends to be small], using a patterned organic film that is water-soluble,
The present invention relates to fine pattern formation that improves the resolution achieved by conventional exposure methods.

BACKGROUND OF THE INVENTION The high degree of integration and density of integrated circuits has increased due to advances in conventional phosphorography technology. The minimum line width has become around 1 μm, and in order to achieve this processed line width, there are two methods: ultraviolet exposure using a reduction projection method with a high aperture lens (high NA), and electron beam direct writing on the substrate. Examples include exposure method and proximity exposure method using X-rays. However, in order to form a pattern without sacrificing throughput, the former method of ultraviolet exposure using a reduction projection method is best. However, the resolution R of ultraviolet exposure is expressed by the following Rayles law.

R=0.6Xλ/N, Ax (1+1/m) ・−・・
-(1) λ: Wavelength N, A: Lens aperture m; To improve magnification resolution, shorter wavelength, higher N, and A can be considered, but the performance of currently available optical systems is, for example, wavelength λ is 3
When 65 nm (i-ray y) and N and A are 0.4, the resolution R is 0.6 μm, which is said to be inferior to the resolution of electron beam exposure and X-ray exposure.

However, in 1983, GE's B, F, Grif
announced a method for improving resolution and pattern shape by laminating a contrast-enhanced layer that promotes the contrast of light intensity profiles on a resist for pattern formation (Contrast
Enhancecl Photolithograp
hy.

B.F.Griffing at al.I.E.
E E-ED, VOL.

EDL-4, 41, Jan, 1983). According to them, the normal reduction projection method (λ: 436 nm, N, A: 0.3
2) reports that resolution at 0.4 μmi is possible.

As a result of research by the inventors, it has been found that the characteristics of a patterned organic film to enhance contrast must be as follows.

Referring to FIG. 3, first, problems in light exposure, such as the reduction projection method in general, will be described.

The output light intensity profile in the reduction projection exposure method is
Processing is performed using the optical lens system. To explain, when exposure 4 is performed through the reticle 6 [FIG. 3A], the ideal input light intensity profile without diffraction can be said to be a perfect rectangular wave, and its contrast C is expressed by the following equation. At that time, contrast C becomes 100% [
Figure 3B]. The input waveform passes through an optical lens and is determined by the transfer function of the optical lens system [Figure 3C]
, after being Fourier transformed, the output waveform becomes a cosine wave shape and the contrast C also deteriorates. This deterioration of contrast greatly affects pattern shape, such as resolution and pattern shape. By the way, the contrast required for resist pattern resolution is 60-
As a result, the contrast C value becomes 60 inches or less, making it impossible to form a pattern.

Therefore, in the characteristic curve shown in Figure 4, in the region where the exposure time (N light energy) is small, the transmittance to ultraviolet rays is small (min increase is small), and in the region where the exposure energy is large, the transmittance to ultraviolet rays is large. (Engineering ma
By using a resist film that tends to have a large increase in w and passing the output waveform shown in the third diagram above through this film, a tendency for the contrast C value to increase is discovered. In order to explain this more quantitatively, we will discuss IBM's F, H, Di
The report of ll et al.
f P□5itivePhOtoresist, F
, H., Dill et al., IEEE-ED
, VOL, ED-22, 47, Ju17.1975)
The parameters given in the exposure absorption term A of the positive resist are used. In general, A becomes T)) A=zn[E ・・・・・・・・・(3)d
T(o) is shown, and it is desirable that the A value tends to be large for contrast enhancement. In order to make A have a similar tendency, it is necessary that d (film thickness) be thin and the ratio between T (0) (initial transmittance) and T (oo) (final transmittance) be large.

By the way, in the above-mentioned announcement by GE, the material of the contrast enhanced layer has not yet been disclosed. Second
A conventional pattern forming process using contrast enhanced lithography (abbreviated as CEL) by GE's Griffin et al. will be described with reference to the drawings. A resist 2 is spin-coated onto the substrate 1 (FIG. 2A). Next, apply a contrast ennouncing layer (CEL) on resist 2.
) 3t-Do transfer coating [Figure 2B]. Then, it is selectively exposed to ultraviolet light 4 using a reduction projection method (FIG. 2C). At this time, a part of the resist 2 is also selectively exposed. and C
Remove the entire EL3 [Figure 2D]. Finally, a normal development process is performed to form a pattern of resist 2 [FIG. 2 ED]. In the method described above, the conditions that CEL must have are that it has a contrast-enhancing property and that it is prevented from dissolving with the underlying pattern forming resist 2, and that the removal liquid used to remove CEL 3 is not as strong as the resist 2.
It is possible to avoid deteriorating the characteristics of These conditions that must be met place great restrictions on the material composition. Furthermore, from the process perspective of the CEL3 removal process,
There are complex and dangerous processes.

Furthermore, a step is inevitably created on the substrate of an actual semiconductor integrated circuit (hereinafter referred to as LSI), and even if a resist is applied on the step, the surface will not become flat. When the contrast-enhancing layer 3 is applied on the non-flat resist, a dramatic difference in film thickness occurs. The toes are not flat. Since the parameter A shown in equation (3) depends on d (film thickness), the A value changes due to film thickness variation, the contrast enhancement effect changes at the same time, the resist line width changes, and pattern accuracy deteriorates. This will be briefly explained using FIG.

A resist 2 is applied onto a substrate 1 having steps (FIG. 6A). In this state, the film thickness of the resist 2 cannot be made flat using the current spin coating method. Next, when the CEL film 3 is applied onto the resist 2, the thickness of the CEL film 3 changes as shown in B, and the above-mentioned parameter A changes. Therefore, resist 2 is developed to form pattern 2a.
When the CEL film 3 is formed and the CEL film 3 is removed, the width of the resist pattern 2a is no longer constant as shown in FIG. 6C, resulting in deterioration of the accuracy of the pattern width.

Problems to be Solved by the Invention The present invention takes into consideration matching with the underlying pattern-forming resist (photosensitive resin) and eliminates the influence of the removal liquid when dissolving and removing the contrast enhanced layer and the resist. The object of the present invention is to provide a pattern forming method with high turn accuracy, which eliminates a complicated removal process, prevents variations in the thickness of a contrast enhanced layer, and improves contrast.

In order to solve the above-mentioned problems, the present invention provides a layer structure resist for flattening the stepped substrate, for example, firstly, a thick organic film is applied on the stepped substrate to flatten it. A three-layer structure resist in which a high-temperature heat treatment is applied, an inorganic film is applied or deposited on the organic film to separate it from a pattern-forming resist, and a resist is applied on the inorganic film to achieve almost perfect flatness. To,
It has a bleaching or fading effect with radiation such as ultraviolet rays, has a transmittance of, for example, ao% or more after complete bleaching, and has a water-soluble property that is easily soluble in a developer such as an alkaline aqueous solution in the developing process of a pattern-forming resist. A layered structure is used in which a patterned organic film is formed.

Furthermore, as a second method, the above-mentioned pattern-forming organic film is laminated on a two-layer structure resist in which a thick first resist is applied and the second resist is overlaid and flattened.

In addition, as a third method, a first resist is applied thickly, the entire surface is irradiated with radiation, and a second resist similar to the first resist is applied.
The above-described pattern-forming organic film is laminated on a two-layer structure resist made by laminating and flattening resists, thereby suppressing variations in the thickness of the CEL film and improving pattern accuracy.

According to the present invention, the variation in the thickness of the pattern-forming organic film (contrast enhancement layer) caused by the variation in film thickness on the step of the conventional resist can be eliminated by flattening it, and the equation (3) can be solved. The film thickness d of the A value becomes constant, and a similar contrast enhancement effect can be expected in stepped portions and flat portions, and highly accurate pattern formation and high resolution patterns that are completely unaffected by stepped portions can be obtained.

Example (Part 1) An organic film 4 such as a positive resist is evenly applied to a thickness of 2 to 3 μm on a substrate having steps, such as a semiconductor substrate 1, and an inorganic film 6 is coated on the organic film 4 with a thickness of 0.1 to 0.0 μm. Coating or depositing to a thickness of 2 μm, such as liquid spin-on glass (abbreviation, 5OG
) was applied by rotation. At this time, the heat treatment of the organic film 4 was performed at 140°C.
The SOG film 5 was heat-treated at a temperature of about 200° C. (FIG. 1A). Next, on the inorganic film 6, a normal ultraviolet positive resist 2 is applied, for example, Shipley Company Standard MP1.
400-27 is applied to a thickness of 0.5 to 1.0 μm.

Then, a pattern-forming organic film 3 is formed on the resist 2. For example, water-soluble polymers as the base polymer of this membrane 3 include polysaccharides, proteins, and PVP.

Examples include PVA, but in this example, the polysaccharide pullulan (manufactured by Hayashibara Biochemical Research Institute) was mixed with 100% deionized water.
Using 109 dissolved in CC, further 360 to 45
A diazo compound having a bleaching effect in the wavelength range of 0 nm was dissolved in an amount of about 0.2f.

The aqueous solution at this time was of course water-soluble and stable to heat treatment and exposure processes. This pattern-forming organic film 3 is 0.5
It was coated to a thickness of about μm [Fig. 1B].

Next, the positive resist 2 is exposed through the pattern-forming organic film 3 using a reduction projection fogging method. Next, positive resist 2
A resist pattern 2a is formed by developing with a developer. At this time, the pattern-forming organic film 3 imparts a contrast enhancement effect to the positive resist 2, and since it is water-soluble, it instantly dissolves in water and disappears by itself. Moreover, due to the thinning of the positive resist 2 and the CEL effect, fine lines and spaces of 0.4 μm in particular were possible using the ordinary reduction projection exposure method [FIG. 1C].

Next, using the patterned positive resist 2a as a mask, the inorganic film 6 is subjected to reactive ion etching (abbreviated as RIE) L using an anisotropic fluorine-based etching gas, and then the patterned inorganic film 5a is etched. Using an oxygen-based RIEI as a mask, the organic film 4 was subjected to RIEI, and a pattern 4a having a high aspect ratio and having no effect on steps was obtained [FIG. 1D].

(Part 2) A deep ultraviolet resist 6, for example 30
C) PMMA having sensitivity around nm is formed to a thickness of 2 to 3 μm so as to be flat. Next, the sensitivity peak is 380
UV resist 2 near nm is changed to far UV resist 6
Layer it on top and apply around 0.6 to 10 μm [Figure 6 A
]. Next, the pattern-forming organic film 3 used in Example (Part 1) is coated on the ultraviolet resist 2 to a thickness of about 0.5 μm, and a reduction projection exposure method of ultraviolet 7, for example, 436 nm (g-line) is selectively applied. The ultraviolet resist 2 is exposed through the pattern-forming organic film 3 (FIG. 6B). Next, development is performed using a developer for the ultraviolet resist 2 to form a pattern, thereby forming a pattern 2a. At this time, the pattern-forming organic film 3 is self-removed. Using this patterned ultraviolet resist 2a as a mask, that is, as a wavelength filter, the entire surface is exposed 8 at a wavelength around 300 nm to expose the deep ultraviolet resist 6 (FIG. 6C).

Next, develop the far ultraviolet resist 6 to form a resist pattern 6.
form a. At this time, the ultraviolet resist (2a) patterned by the developer may remain or disappear [6th
Figure D]. According to this method, a 0.4 μm line-and-space pattern could be formed regardless of steps due to the flatness of the deep ultraviolet resist 6, the thinning of the ultraviolet resist 2, and the CEL effect of the pattern-forming organic film 3.

(Part 3) A UV resist 2 such as MP is placed on a substrate 1 having steps.
1400-27 (manufactured by Prey Co., Ltd.) with a thickness of 2 to 3 μm [
The surface is made flat and exposed to light at a wavelength of 9 around 43 e nm [FIG. 7A]. Next, a positive resist 2 similar to the ultraviolet resist 2 described above is applied in an overlapping manner, and the patterned organic film 3 described above is further applied in an overlapping manner to a thickness of about 0.5 μm. Next, selective ultraviolet light exposure 1o is applied to pattern-forming organic film 3. The upper and lower two layers of positive resist 2 are exposed to light (FIG. 7B). Finally, the entire surface of the pattern-forming organic film 3 and the upper and lower two layers 2 of the positive resist are developed at once to form a pattern 2a (FIG. 7C).

In carrying out the present invention, the resist 2 may be one that can be developed with an aqueous developer such as water or an alkali, and for example, a commonly used diazo positive type resist is a typical example.

Effects of the Invention As described above, this invention improves contrast and eliminates the deterioration of resolution and pattern shape that was limited by the optical system of the conventional reduction projection method, and uses a water-soluble organic film that requires fewer steps. By using , it is possible to make ultraviolet ray exposure finer, which is to say, to extend the lifespan, and it is possible to reduce the need to introduce expensive EB exposure machines and X-ray exposure machines.
It has great engineering value.

[Brief explanation of the drawing]

Fig. 1 is a sectional view of a pattern forming process according to an embodiment of the present invention, Fig. 2 is a sectional view of a conventional contrast enhancement process flow, Fig. 3 is an explanatory diagram of conversion of an optical profile in a reduction projection method, and Fig. 4 is a sectional view of a conventional contrast enhancement process flow. A transmission characteristic diagram of the pattern-forming organic film used in the invention, FIG. 5 is a process diagram of a pattern-forming method using a conventional pattern-forming organic film, and FIGS. 6 and 7 are process diagrams of a pattern-forming method according to other embodiments of the present invention. FIG. 1... River/substrate, 2... Positive resist, 4...
...Organic film, 3...Pattern forming organic film,
5...Inorganic film. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 3
Figure L,
J↓ Ward-ω Kyou Dai (N 4th Museum 9th Gate (Second) Figure 5 Figure 6 Figure 7 Procedure Amendment Document February 26, 1986 1 Case Indication 1985 Patent Application No. 53135 No. 2: Name pattern forming method of invention 3: Relationship with the person making the amendment Patent application
Colonel Tokoro 1006 Kadoma, Kadoma City, Osaka Prefecture
Name (582) Matsushita Electric Industrial Co., Ltd. Representative Akio Tanii 4 Agent 571 Address 1006 Oaza Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. 5 Subject of amendment 6, Contents of amendment (1) Specification "A process exists" on page 8, line 13.
Correct as follows. ``There is a process.
In the CEL process described in No.-104642, CΣL
The complex process of removing the film with trichlorethylene and then removing the exposed portions of the resist underneath is shown. (2) Add the following sentence between lines 17 and 18 on page 12 of the statement.

Claims (3)

[Claims] (1) A step of applying an organic film to a substrate, a step of applying or depositing an inorganic film on the organic film, a step of applying a radiation-sensitive resin on the inorganic film, a step of applying a radiation-sensitive resin on the radiation-sensitive resin. a step of forming a pattern-forming organic film with a bleaching or fading effect; a step of exposing the radiation-sensitive resin to radiation through the pattern-forming organic film; A step of developing and dissolving the exposed portion of the resin or a portion other than the exposed portion to form a pattern, a step of forming a pattern on the inorganic film by an anisotropic dry etching method via the patterned radiation-sensitive resin, and a step of forming the pattern on the inorganic film using an anisotropic dry etching method. A pattern forming method comprising the step of patterning the organic film through the formed inorganic film by an anisotropic dry etching method. (2) a step of applying a first radiation-sensitive resin to the substrate;
a step of irradiating the entire surface of the first radiation-sensitive resin with radiation; a step of applying a second radiation-sensitive resin on the first radiation-sensitive resin whose entire surface has been irradiated with the radiation; and a step of applying the second radiation-sensitive resin. a step of forming a pattern-forming organic film on the sensitive resin that has a bleaching or fading action against radiation; a step of exposing the first and second radiation-sensitive resins to radiation through the pattern-forming organic film; A pattern forming method comprising the step of developing and dissolving the exposed portions of the pattern forming organic film and the first and second radiation sensitive resins. (3) applying a first radiation-sensitive resin to the substrate;
a step of coating the second radiation-sensitive resin on the first radiation-sensitive resin, forming a pattern-forming organic film with a bleaching or fading effect on radiation on the second radiation-sensitive resin; a step of exposing the second radiation-sensitive resin to a first radiation via the patterned organic film;
A step of developing and dissolving the exposed portion of the radiation-sensitive resin to form a pattern, a step of exposing the second radiation-sensitive resin through the second pattern-formed radiation-sensitive resin, and a step of exposing the second exposed radiation-sensitive resin to the radiation-sensitive resin. A pattern forming method comprising a step of developing and dissolving.