JPH0513325A - Pattern formation method - Google Patents

Abstract

PURPOSE:To get a method of accurately forming a pattern which is made on an upper layer resist and is transcribed on a lower layer resist in double layer resist structure. CONSTITUTION:An upper layer pattern is gotten by exposing and developing an upper layer resist 3, and then oxygen-resistant reactive ion etching property is given only to the surface of this pattern, and using the pattern, the lower layer resist 2 is processed by oxygen reactive ion etching.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of forming a photoresist pattern in manufacturing a semiconductor device, and more particularly to a method of forming a multilayer photoresist pattern.

[0002]

2. Description of the Related Art With the miniaturization of semiconductor devices, the problem of interference of exposure light in the reflection photoresist from the underlying substrate or underlying pattern in the reduced projection exposure method or electron beam drawing method is eliminated, and its high resolution is eliminated. The multi-layer resist method is used in order to make full use of the method described in J. Vac. Sci,
Technology. B, vol. 1, No. 4,
October-December 1983, pp1247-1250, "Two-layer photoresist process for patterning high-reflective substrates".
stprocess for patterning
high-reflectivity substrat
e) ”.

Based on this document, an outline of this two-layer pattern forming method will be described with reference to FIG. In FIG. 2A, for example, polymethyl methacrylate (PMMA) is formed on the substrate 1.
Thick positive type resist layer 2 made of a material such as
Is applied by spin coating, and a relatively thin negative resist layer 3 made of a material such as RD2000N is also formed thereon by spin coating. The upper layer resist 3 is exposed to light and developed by ordinary photolithography to form an upper layer pattern 3a as shown in FIG. 2 (b).
Then, as shown in FIG. 2C, the lower layer resist 2 is collectively exposed with light having a wavelength of about 220 nm in this case by using the pattern 3a as a mask, and reactive etching is performed to expose the upper layer pattern 3a. To obtain a lower layer pattern 2a.

[0004]

In this two-layer pattern forming method, since the upper layer resist 3 and the lower layer resist 2 are laminated, a mixed layer, that is, an intermediate layer 4 is formed between them as shown by the diagonal lines in FIG. 2 (a). Occurs. This intermediate layer 4 generally remains even after the development of the upper layer resist 3, and the upper layer pattern 3
The exposure of the lower layer resist 2 using a as a mask tends to absorb the light. Therefore, the exposure amount of the lower layer resist is changed, and the exposure accuracy is lowered. Further, in the exposure of the lower layer resist 2, light may be diffracted at the edge portion of the upper layer pattern 3a, and the portion of the lower layer resist 2 immediately below the edge portion of the upper layer pattern 3a may be exposed. When the amount of light is increased to compensate for the absorption of exposure light by the intermediate layer,
The exposed portion due to diffraction also increases, resulting in a problem that the edge portion of the lower layer pattern 2a is not vertical as shown in FIG.

The object of the present invention is to solve this problem.

[0006]

A relatively thin lower layer resist is formed into a two-layer resist structure consisting of a relatively thick upper layer resist, and the upper layer is exposed to light and developed to form an upper layer pattern. Next, according to the present invention, only the surface portion of the upper layer pattern is given a specific resistance to, for example, oxygen reactive ion etching, and then the lower layer is patterned by reactive ion etching.

[0007]

According to this reactive ion etching, the problems of absorption of light by the intermediate mixed layer in light exposure and diffraction by the upper layer pattern etching are essentially eliminated, and the pattern transfer to the lower layer can be performed accurately.

[0008]

Embodiments of the present invention will be described in detail below with reference to FIG. (Example 1) After forming a lower layer resist 2 of polymethylmethacrylate (PMMA) on a base substrate 1 to a thickness of 0.5 μm by a spin coating method, the thermal crosslinking temperature of PMMA is 200 to 250 ° C. After baking, an upper layer resist 3, which is a novolac-based positive photoresist containing naphthoquinonediazide as a photosensitizer, is formed on the lower layer resist 2 by a spin coating method to a thickness of 1 μm in the same manner as shown in FIG. A two-layer resist structure is obtained.

Next, the upper layer resist 3 is exposed to light and developed to obtain the upper layer pattern shown in FIG. 1 (b). Next, oxygen-reactive ion etching (O
₂ Performs a process for giving resistance to RIE). In this example, the entire structure shown in FIG. 1 (b) is heated in an atmosphere of hexamethyldisilane (HMDS), and silicon is selectively bonded only to the surface of the upper layer pattern to perform silylation treatment,
A resistant film 5 against oxygen reactive ion etching shown in FIG. 1C is obtained. The heating temperature is preferably 120 to 150 ° C. which is the decomposition temperature of, for example, the naphthoquinonediazide photosensitizer used as the upper layer resist 3. At a temperature in this range, the decomposition of the photosensitizer, the incorporation of HMDS and the thermal crosslinking can be simultaneously performed.

Then, the upper layer pattern having the silylated surface is transferred to the lower layer resist 2 by oxygen reactive ion etching to obtain the structure shown in FIG. 1 (d). The etching rate of the PMMA forming the lower layer resist 2 is about twice that of the upper layer photoresist 3 of the novolac system, and the film thickness reduction rate is 1 μm / min under conditions of an oxygen flow rate of 30 SCCM and an RF power of 200 W, for example. This is larger than that of the upper layer photoresist 3 under the same conditions by about 0.5 μm / min. However, the etching rate of the upper layer photoresist 3 is further reduced by this silylated film 5, and compared with the etching rate of the lower layer resist 2. As a result, the upper layer pattern can be satisfactorily held during the pattern transfer to the lower layer resist 2.

(Embodiment 2) As the upper layer resist 3, a negative type resist of oxygen generation type (SAL-601 manufactured by Shipley) was used in place of the novolac type positive type photoresist, and prebaked and post-exposure baked (PEB) was applied after pattern exposure.
Same as Example 1 except that the process is performed at a relatively low temperature of 0 ° C. for about 1 minute. Due to PEB at such a low temperature, the oxygen generating agent remains in the upper layer pattern considerably even after development.
Post-baking at about 140 ° C. after development. Oxygen is again generated by this post-baking to cause a crosslinking reaction in the upper layer pattern, and at the same time, the silylation of the surface can be efficiently performed.

(Embodiment 3) The same P as in Embodiment 1 is applied to the substrate 1.
An MMA lower layer resist 2 is formed to a thickness of 0.5 μm by a spin coating method, baked at about 200 to 250 ° C. to be crosslinked, and then an upper layer resist 3 similar to that of Example 1 is formed thereon.
Was formed to a thickness of 1 μm by a spin coating method.
The structure of (a) is obtained. Next, the upper layer resist 3 is exposed with a predetermined pattern and developed to obtain the upper layer pattern shown in FIG.

Next, the structure of FIG. 1 (b) is subjected to plasma treatment using CHF ₃ gas to selectively form a Teflon-like polymer film 5 only on the surface portion of the upper layer pattern as shown in FIG. 1 (c). Form. This process uses CHF ₃ gas at a flow rate of 30 SC
It is advisable to perform the process under the conditions of CM, output of 100 W, and substrate temperature of 120 to 150 ° C. for about 1 minute. The polymer film is resistant to oxygen reactive ion etching. Next, transfer is performed to the lower layer resist by oxygen reactive ion etching using the upper layer pattern having this polymerized film to obtain the structure of FIG. 1 (d).

(Embodiment 4) An oxygen generating resist is used as the upper layer resist 3 in Example 3, and the upper layer resist 3 is heated in the vicinity of the oxygen generating temperature while being plasma-treated with CHF ₃ gas. Others are the same as in the third embodiment.

[0015]

According to the present invention, after patterning the upper layer resist by exposure and development, the surface thereof is made resistant to oxygen reactive ion etching, and then the upper layer pattern is used to carry out oxygen reactive ion etching of the lower layer resist. By performing the transfer of the upper layer pattern to the lower layer resist, it is possible to obtain the lower layer pattern having a vertical edge without being affected by the intermediate mixed layer and the diffraction of light in the formation of the conventional two-layer photoresist pattern. You can

[Brief description of drawings]

FIG. 1 is a process drawing showing a method for forming a two-layer pattern according to the present invention.

FIG. 2 is a process drawing showing a conventional method for forming a two-layer pattern by light exposure.

[Explanation of symbols]

1 substrate 2 Lower layer resist 3 Upper layer resist 4 Middle (mixed) layer 5 Reactive ion etching film

Claims (4)

[Claims] 1. A step of: (a) forming a lower resist film on a substrate; (b) a step of forming a photoresist film on the lower resist film; (c) exposing and developing the photoresist film to form an upper layer pattern. And (d) forming an etching resistant film on the surface of the upper layer pattern, and (e) etching the lower resist film using the etching resistant upper layer pattern as a mask. A pattern forming method characterized by the above. 2. The pattern forming method according to claim 1, wherein an etching resistant film is formed by silylating the surface of the upper layer pattern in the vicinity of a thermal crosslinking temperature of the pattern, and oxygen reactive etching is performed as the etching. A method for forming a pattern, which comprises: 3. The pattern forming method according to claim 1, wherein an oxygen generating type is used as the upper layer resist, and an etching resistant film is formed by silylating the surface of the upper layer pattern near the oxygen generating temperature of the pattern. A method for forming a pattern, which comprises forming and performing oxygen reactive etching as the etching. 4. The pattern forming method according to claim 1, wherein an etching resistant film is formed by forming a plasma polymerized film on the surface of the upper layer pattern.