JPS6043654A - Photo-lithographic method - Google Patents

Abstract

PURPOSE:To easily obtain a high-precision resist pattern suitable for IC manufacture through photo-lithography by immersing a resist film in o-dichlorobenzene or m-dichlorobenzene immediately before or after exposure. CONSTITUTION:A positive type resist is formed on a substrate 1 by spinner coating, and prebaked. It is immersed into o- or m-dichlorobenzene at 30 deg.C for >=5 min or at 40 deg.C<=1min immediately before or after exposure, and then, developed. The section of the resist film 2 thus developed is reversely tapered, and the protruding length A at the top is <=300nm, no visor occurs, and a pattern having no irregular ruggedness on the edges is obtained. A metal is vapor deposited by using this resist pattern as a mask, and then, the resist film 2 and the metal just on it are removed to obtain an IC circuit high in precision.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a photolithography method for positive resists that can be used in the integrated circuit (1, c,) industry. The photolithography method of the invention is compatible with a lift-off process.

(Conventional configuration and its problems) In recent years, 1. C. With the development of industry, as an essential technology,
Photolithography methods for resist films have been extensively researched, and the results are now being put into practical use.

Table 1 shows the outline and procedure of the usual photophosphorography method. In addition, FIG. 1(a) shows a cross section of the resist after development by a normal photolithography method, and the resist 2 formed on the substrate 1 has a considerable taper at the step as shown in the figure. have. When a lift-off process is used, the resist step must be steep, and the photolithography method described above satisfies this requirement.

Here, the lift-off process will be explained with reference to FIG. In FIG. 2, 1 is a substrate, 2 is a resist film after photolithography, and 3 and 4 are vapor-deposited metals. First, a resist film is processed by photophosphorography (a). Next, metal 3.4 is deposited on the entire surface (
b). Next, the resist film 2 and the metal film 3 thereon are removed by immersion in heated acetone or the like to dissolve the resist film, leaving only the metal film 4. With this, the process is completed.

A known photolithography method for use in the lift-off process involves immersing the resist film in monochlorobenzene at 20 to 30°C before or after exposure using a positive type photolithography process. There is a way to do that. When this method is adopted and photolithography is performed, the result is as shown in Figure 1(b).
become that way.

In other words, the positive type renost 2 formed on the substrate 1 has a bulge at the step. Such resist steps are suitable for the lift-off method. but,
There are some shortcomings. In Figure 1(b), A is approximately 5oo~
3oooX position and L is 2o.

The eave-like protrusion is therefore mechanically weak, and the tip of the curved protrusion has an irregular shape. This is disadvantageous for the lift-off method.

Furthermore, the monochlorobenzene used at this time has a high vapor pressure even at room temperature, which is a problem in terms of the working environment.

(Object of the Invention) An object of the present invention is to improve the drawbacks of the above-mentioned prior art and to provide a photolithography method that is more suitable for the lift-off method.

(Structure of the Invention) The photolithography method of the present invention includes resist application using a spinner, pre-bake, exposure, development, and post-I...bake in one photolithography process, which is performed immediately before exposure. Or immediately after, ortho.
The resist film is immersed in dichlorobenzene or meta-dichlorobenzene, thereby making it possible to obtain a resist film suitable for the lift-off method.

(Description of Examples) Examples of the present invention will be described below. Table 2 shows the results of the embodiments of the present invention and comparative examples with the prior art. The resist is positive type RENOST AZ] 350. J with a viscosity of 30 cp was used.

Further, as the substrate in this example, a silicon substrate manufactured by Nippon Silicon was used. The obtained silicon substrates were immersed in fuming nitric acid, washed with water, dried, and then disposed of.

Apply the resist using Mikasa (K, K) spinner, I
It was done using H'-D S. spinner rotation is 40
0 rpm for 1 second, then 5000 rpm for 20 seconds.

Thereafter, it was prebaked for 25 minutes at 901C in a nitrogen stream.

In conventional photolithography, this was followed by exposure with a Kasper 2001 Ba5ic aligner, followed by development with Siwaplay's MF-312.

Mono-chlorobenzene, ortho-dichlorobenzene, and meta-dichlorobenzene were obtained from Wako Junm (K, K).

When the cross section of the lenost formed according to the present invention was observed using a scanning electron microscope (SEM), the shape of the resist cross section was divided into three types as shown in FIG.

In the figure, 1 is a substrate and 2 is a renost.

In the column of "7 Nost cross-sectional shape after development" in Table 2, entries are made in correspondence with FIGS. 3(A), (B), and (C).

Also, the lengths A and L in Figure 3 (B) and (C), respectively.
are entered in Table 2. Regarding suitability to the riff-off method, the case shown in FIG. 3(C) is the most desirable, followed by the case shown in FIG. 3(B), and the case shown in FIG. 3(4) is unsuitable. What is a little dissatisfying with the case shown in Figure 3 (B) is that the tip of the rim of the lenost tends to wear out irregularly. In the column ``Compatibility with lift-off method'', the X mark corresponds to Figure 3 (A), and the one with strong irregularity at the tip corresponds to Figure 3 (B). Δ marks, those with relatively small irregularities are marked ○,
A mark ◎ was entered corresponding to Figure 3 (C).

Lot numbers 1 to 3 in Table 2 are comparative examples using the conventional method.

Lot number 1 was produced using conventional photolithography methods. Lot numbers 2 and 3 were immersed in monochlorobenzene before or after exposure. The length of L is small, that is, the thickness of the sleeve is small, and the tip of the sleeve tends to be irregular. In other words, the resist is cut irregularly. The length of A was measured using a SEM photograph and averaged.

Lot numbers 4 to 12 in Table 2 are examples in which the present invention was implemented. Lot number 4, 5, 7. Comparing St with the comparative example, the length of L is relatively thick, and therefore the irregularity of the tip of the sleeve is relatively small.

In other words, Lennost's sharpness is good. Furthermore, there was no significant difference between dipping in dichlorobenzene immediately before and after exposure.

Lot number 6 in Table 2 was immersed in dichlorobenzene for 10 minutes, but in this case, when the resist was examined with a metallurgical microscope after development, it was found that the resist was completely removed at the location where it should have been removed. There is a black residue left. Therefore,
Very unsuitable for lift-off method. Therefore, in the photolithography method according to the present invention, when the liquid temperature of chlorobenzene is about 30° C., it is estimated that the appropriate immersion time is 5 minutes or less.

In Table 2 9 to 12, the liquid temperature of dichlorobenzene is 4
This is the case when the temperature is 0°C. In this case, if the Lennost film is immersed for 1 minute, the cross section of the resist will become as shown in Figure 3 (C>, which is the most desirable. In addition, if the Lennost film is immersed for 15 minutes, the resist film will quickly turn black and lose its photosensitivity. Furthermore, fine cracks can be observed under a microscope, making it completely unusable.

From the above, it can be seen that the photolithography method according to the present invention is superior to conventional methods.

Also, using a MacLeod mercury vacuum gauge, 20℃ and 30℃
The equilibrium vapor pressure of each chlorobenzene was investigated. The results are shown in Table 3, and the vapor pressure of rimodi-chlor-benzene is lower than that of the conventionally used mono-chloro-benzene, and therefore, di-chlorobenzene is superior in terms of work hygiene. I know that there is.

Table 3 (Effects of the Invention) As is clear from the above description, the present invention provides photolithography in which resist coating using a spinner, yellow baking, exposure, and development are performed in sequence (in one step, The resist film is immersed in ortho-dichlorobenzene or meta-dichlorobenzene immediately before or after exposure, and as a result, a resist pattern having a reverse take-coup type cross section is obtained.
A resist cross section suitable for the lift-off method can be obtained. Furthermore, the benzene used has a lower vapor pressure than conventional benzene, leading to improvements in work hygiene.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a cross section of a resist after development by the conventional photolithography method, FIG. 2 is a process cross-sectional diagram for explaining the one-knot offgraphy method, and FIG. FIG. 3 is a diagram showing various resist cross sections. 1. Substrate, 2... Resist. ＼ Patent Applicant Matsushita Electric Industrial Co., Ltd. Representative Hisashi Hoshino Figure 1 (0) Figure 2 (a) (c) Figure Otsu Figure 3 (A)

Claims (1)

[Claims] In the photophosphorography process, which consists of applying resist with a spinner, baking, exposing, developing, and post-baking in sequence, the resist is coated with ortho-dichlorobenzene or meta-dichlorobenzene just before or after exposure. Positive-type rennost photophosphorography method characterized by seven immersion membranes.