JPS61121332A - Pattern forming method - Google Patents

Abstract

PURPOSE:To improve productivity reducing the process by suitable combination of an upper layer resist member, a lower layer resist member, developer and liquid rinse as the case may be. CONSTITUTION:A lower resist thick layer made by a resist member not contained an Si, which can be etched by means of plasma treatment and is insoluble to developer using for formation of an upper layer pattern, and an upper resist thin film made by a resist member contained an Si for sensitive ionizing radiation possessed anti-plasma etching are formed by turns on the surface of a member to be produced. For example, which is provided by resoluting polyvinylphenol to cychohexane is spin-coated on an Si substrate 1 and is baked, then a lower layer resist film 2 is provided. The resolution, which is provided by dissolving silylated polymethylsilsesquioxane in toluene, is spin-coated on the lower layer resist film 2 and is baked, then a upper layer resist film 3 is obtained. Subsequently, a latent image is formed to the upper layer resist thin film by projecting an image pattern of ionizing radiation, and latent image is developed, then plasma treatment is performed by means that the upper layer resist pattern is designated as a mask, then the upper layer resist pattern is duplexed to the lower layer resist thin film.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention relates to lithography technology, particularly to electron beam, Related to lithography technology using ionizing radiation such as ultraviolet rays and ion beams.

More specifically, the present invention first obtains an upper layer resist pattern by irradiating and developing an image pattern of ionizing radiation as described above onto a two-layer resist film, and then converts this resist pattern to a thickness of the lower layer resist below. The present invention relates to a method of forming a high aspect ratio resist pattern by transferring it onto a film. Here, ``high aspect ratio'' means that the ratio between the film thickness of each turn of the formed resist and the pattern width is large, in other words, microfabrication can be performed with higher dimensional accuracy.

[Conventional technology]

2. Description of the Related Art As semiconductor devices become more highly integrated, techniques for forming finer resist patterns are required. What has been proposed in response to this demand is the no-turn forming method using a two-layered resist film, which was mentioned earlier and which will be discussed here as well. double-layered structure)
Usually, the lower layer is made of a thick resin with high dryness resistance and oxidation properties such as cresol resin, and the upper layer is made of a thin layer of ionizing radiation resist such as polymethyl methacrylate. It is made with a structure. When such a resist film is subjected to electron beam writing and developed, a fine upper resist pattern can be obtained because the upper resist film is thin.Also, using this 14 turns of resist as a mask, the resin underneath is exposed to oxygen plasma. When etching is performed, the upper layer resist pattern is transferred to the lower layer resin, and as a result, a fine and thick resist pattern, that is, a high aspect ratio resist pattern can be obtained. According to this pattern forming method, it is not only possible to solve the problem of the step difference in the base of the resist film, but also to improve the resolution, drying resistance, and chipping properties that were problems with conventional single-layer resist films. .

[Problem that the invention seeks to solve]

By the way, when attempting to form a resist pattern with a high aspect ratio by selectively etching a two-layer resist film, there is a problem in that the resin material used for the lower resist film is limited.

In fact, the resins that can be used at present include the cresol-claw resin mentioned above, as well as the resin manufactured by Silagray Co., Ltd. in the United States.

Photoresists, phenolic resins, etc., commercially available as the AZ series from
It is essential to bake at a high temperature of around 0°C for 1 hour. In fact, such a baking step is an impediment to the practical application of the method, and it is desirable to omit or shorten the step.

[Means for solving problems]

In forming a resist film with a two-layer structure, the present inventors took into consideration the properties of the developing solution (and rinsing solution in some cases) used subsequently to form the upper resist pattern. It has been found that the above-mentioned problems can be solved by selecting the material of the layer, in other words, by appropriately combining the upper resist material, the lower layer/cyst material, the developer, and in some cases, the rinsing solution. .

According to the present invention, the lower layer is made of a silicon-free resist material that is insoluble in the developer used to form the upper resist and master turns but can be etched by plasma treatment. 5 to 2.0 μm), and an upper resist thin film (film thickness of approximately 0.1 to 0.0 μm) made of a silicon resist material containing ionizing radiation and having plasma etch resistance.
5 μm) on the surface of a workpiece such as a silicon substrate, a two-layer resist film can be formed.

After forming the resist film, the following steps are performed sequentially: irradiating an image pattern of ionizing radiation to form a latent image corresponding to the image pattern on the upper layer resist thin film, and developing the latent image with a developer to form the upper layer. A resist pattern is obtained, rinsed if necessary, and plasma processing is performed using the upper resist pattern as a mask to transfer the 14 turns of the upper resist to the lower resist thin film below.

The above-described series of steps can be performed using techniques commonly used in this technical field, and therefore detailed description thereof will be omitted here.

Some examples of combinations of the upper resist material, the lower resist material, the developer, and the rinsing solution that are useful in the present invention are as follows.

Combination I: Phenylsilo with sun-lacquer Combination ■: iv) Rinse liquid Water [Example] This example was carried out in the order shown in the cross sections in the attached Figures 1a to 1d.

A solution obtained by dissolving polyvinylphenol (M, = 27000) in 7 chlorohexane was spin-coded onto a silicon substrate 1. When baking was performed at 200° C. for 20 minutes to remove the coating solvent 7-chlorohexane, a lower resist film 2 with a thickness of 2.0 μm was obtained. Next, a solution obtained by dissolving in toluene polymethylsilsesquioxane (Mw = 300,000), in which the terminal hydrosilyl group was silylated with trimethylchlorosilane, was added to the previously formed lower resist film. 2. Spin coated on top. As above, the temperature was 80°C to remove the coating solvent.
When baked for 20 minutes at
An upper resist film 3 of m was obtained. FIG. 1a is a schematic cross-sectional view of a silicon substrate with a two-layer resist film obtained as described above.

Next, the resulting silicon substrate with the two-layer resist film was placed in an electron beam exposure device, and irradiated with an electron beam at an acceleration voltage of 20 kV and an exposure dose of 50 μC/α2 to draw a lean pattern (see Figure 1b). ; 3a is the exposed area, 3b is the unexposed area).

Next, the exposed silicon substrate was exposed by immersing it in a toluene bath for 30 seconds, and was further rinsed with n-hexane. As shown in Figure 46,
Only the upper resist film 3a in the exposed area remained on the lower resist film 2 as an upper resist pattern.

Next, the developed silicon substrate is placed in a parallel plate type dry etching device, and etched using a cardenter r using the remaining upper resist film 3a as a mask.

Using a high pressure oxygen plasma (15 mL,
rr.

Plasma etching was performed for 18 minutes at an applied voltage of 0.33 W, cm2). As a result of this etching,
As shown in FIG. 1d, upper resist pattern 3a
was directly transferred to the lower resist film 2&.

In this example, the sensitivity is 2 μC/cm and 0.4 μm.
Line & Space T! Turn resolved.

This example was carried out following a procedure similar to that described in Example 1 above. However, in this example, a silicon substrate with a two-layer resist a was manufactured as follows: A solution obtained by dissolving chloromethylated polystyrene (Mw = 50,000) in toluene was spin-coated onto the silicon substrate. It was then baked at 80° C. for 20 minutes to remove toluene. Film thickness 2. A lower resist film of Ottm was obtained. Next, a solution obtained by dissolving polymethylsilsesquioxane (CM, = 300,000) having a terminal hydrosilyl group in isopropyl alcohol is applied to the previously formed lower resist film by spinning, and the isopropyl alcohol is removed. The mixture was baked at 60° C. for 20 minutes. An upper resist film with a film thickness of 0.1 μm was obtained.

Further, in this example, Inglobil alcohol #1 and 'j'c were used in place of toluene as the developing solution in Example 1, and deionized water was used in place of n-hexane as the rinsing solution.

In this example, the sensitivity is 5μC/cIn2 and 0.5μC/cIn2.
m lines and spaces/4' turns were resolved.

〔Effect of the invention〕

According to the present invention, it is possible not only to obtain improved sensitivity, resolution, and dry etch resistance due to the use of a two-layer resist film, but also to avoid baking (thermal curing) of the lower resist film. Since it can be omitted or shortened, this pattern forming method can be made highly productive.

[Brief explanation of the drawing]

FIGS. 1a, 1b, 1c and 1d are schematic sectional views sequentially showing an example of the method of the present invention. In the figure, 1 is a silicon substrate, 2 is a lower resist film, and 3 is an upper resist film.

Claims (1)

[Claims] 1. A method for forming a resist pattern by selectively etching a resist film having a two-layer structure, wherein a developing solution used for forming an upper resist pattern is applied to the surface of a workpiece. A lower resist thick film made of a silicon-free resist material that is insoluble but can be etched by plasma processing, and an upper resist thin film made of a silicon-containing resist material that has plasma etch resistance and contains ionizing radiation are sequentially formed, and an ionizing radiation image is formed. irradiating the pattern to form a latent image corresponding to the image pattern on the upper resist thin film, developing the latent image with a developer to obtain an upper resist pattern, and performing plasma treatment using the upper resist pattern as a mask; A pattern forming method comprising transferring the upper resist pattern onto a lower resist thin film below the upper resist pattern. 2. The pattern forming method according to claim 1, wherein the upper resist pattern obtained by development is rinsed prior to the plasma treatment step.