JPH07142323A - Resist pattern formation method - Google Patents

Abstract

PURPOSE:To create a mask material whose shape can be controlled easily by forming a dummy layer pattern on a substrate. applying photoresist on the pattern, applying ultraviolet rays to a photoresist layer via a photomask for development. curing the photoresist, and then eliminating only a dummy layer. CONSTITUTION:Only a photoresist layer is eliminated using acetone and a dummy layer is formed. Then, after spincoating the photoresist, prebaking is performed and a photoresist layer 4 is formed. Then, ultraviolet rays are applied via a photomask and development is made. After this, far-ultraviolet rays are applied while heating in vacuum and the photoresist layer of an upper- layer part is cured and then is insolubilized in a development liquid. Then, only polyimide layer is selectively side-etched using the development liquid. Therefore, since the photoresist at the upper-layer part is not subjected to etching, the pattern dimension and accuracy of photoresist are maintained to be the same as the initial development.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a resist pattern used as a lift-off mask material.

[0002]

2. Description of the Related Art Japanese Unexamined Patent Publication (Kokai) No. 1-120832 discloses that after a resist layer is formed on the side wall of a dummy layer, light irradiation is performed to make a predetermined thickness of the resist layer a hardened layer, and then the dummy layer is uncured. A method of removing layers to form an eaves pattern is disclosed.

[0003]

[Patent Document 1] Japanese Patent Application Laid-Open No. 1-12083
In the invention described in Japanese Patent Publication No. 2), the resist layer on the side wall of the dummy layer is irradiated with light, and the lift-off mask is formed due to the difference in solubility in the solvent between the hardened layer and the non-hardened layer formed on the resist layer. Since it is formed, it is difficult to control the shape of the mask. Therefore, an object of the present invention is to provide a mask material manufacturing method in which the shape can be easily controlled using a resist.

[0004]

In the present invention, the resist pattern is formed by (1) a step of forming a dummy layer pattern on a substrate, (2) a step of applying a photoresist on the pattern, and (3) ) A step of irradiating the photoresist layer with ultraviolet rays through a photomask to develop, (4)
The step of curing the photoresist and the step of (5) removing only the dummy layer are sequentially performed, or (5) is followed by (4).
It is achieved by performing in the order of.

The resist pattern formation in the present invention is
The present invention relates to a pattern having a film thickness of several nm to several tens of μm and a size of submicron to several mm. Metal on the board,
If necessary, dehydration treatment or HMDS treatment is performed using a metal oxide and a semiconductor. A different type of pattern may be already formed on the substrate to have a step. It is necessary that the material forming the dummy layer does not form a mixed layer with the photoresist, and when a resin is used, as the resin that does not form the mixed layer with the photoresist, an ordinary polyimide resin or a photosensitive polyimide resin, polydimethylglutar is used. Imide (PMGI), Polymethylmethacrylate (PMMA)
And its derivatives, polymethyl isopropyl ketone (P
MIPK).

When a polyimide resin is used as the dummy layer, the polyimide resin is applied onto the substrate by a spinner and then baked to form the polyimide layer. After coating a photoresist on the polyimide layer, exposure and development are performed to form a pattern of the photoresist layer. The lower polyimide layer may be patterned by a known method such as a wet etching method or a dry etching method using the upper photoresist layer as a mask. Further, when the polyimide layer is baked under a temperature condition in which the polyimide resin is half cured, the polyimide can be dissolved and removed by the resist developing solution, so that the pattern formation of the polyimide layer can be performed simultaneously with the development of the photoresist layer. Next, the photoresist layer is peeled off or not peeled as it is, and a photoresist is further applied thereon. Here, exposure and development are performed again to form a pattern on the photoresist. Next, the polyimide layer is removed and a pattern of the mask material is produced. The resist layer may be cured before or after the removal of the polyimide layer. When the resist layer is cured before the removal, it is possible to reduce the deterioration of the pattern dimension and accuracy due to the reduction of the resist layer film when the polyimide layer is removed. Curing of the resist can be performed by heating, light irradiation or the like. The light irradiation can be achieved, for example, by irradiating deep ultraviolet rays while baking in a vacuum if necessary.

As a dummy layer, polydimethylglutarimide (PMGI), polymethylmethacrylate (PMM)
A), polymethyl isopropyl ketone (PMIPK),
When a photosensitive polyimide is used, a resist layer can be applied, and exposure and development can be performed to form a pattern in the same manner as in the case of using a polyimide resin. It is also possible to form a pattern by directly performing drawing exposure and development with ultraviolet rays, electron beams, or ultraviolet rays. Especially PMGI, PM
MA and PMIPK have a photosensitive band in the far-ultraviolet region, so if the resist is cured by irradiation with far-ultraviolet rays before removing the dummy layer, the dummy layer is exposed at the same time as the resist is cured, and the molecular weight is reduced. By doing so, the removal can be easily performed.

[0008]

In the present invention, the resist is formed into a pattern by ordinary photolithography, and then the resist is cured by irradiation with deep ultraviolet rays to obtain good pattern accuracy, high throughput, and a lift-off mask material is formed. it can. The undercut amount of the mask material is
Since it is controlled by ordinary photolithography, any undercut can be produced. By using a mask material having a large undercut, not only vapor deposition but also ordinary sputtering method and bias sputtering method can be used as a method for depositing a thin film. Further, when the photoresist of the entire mask material is hardened and a novolac resin-diazonaphthoquinone-based resist is used, the heat resistance is remarkably improved to about 300 ° C. Therefore, the substrate temperature in the step of depositing the thin film should be increased. It is possible to improve the thin film.

[0009]

EXAMPLES Example 1 Hereinafter, this example will be described with reference to the drawings. FIG. 1 is an enlarged cross-sectional view (not to scale) of a structure formed by the process of the present invention. In FIG. 1 (a), a substrate 1 having a polyimide varnish (PIQ; made by Hitachi Chemical Co., Ltd.) of 2P was applied by spin coating at 5000 rpm for 60 seconds, and baked at 150 ° C. for 30 minutes on a hot plate to obtain a surface roughness of 0.1. A polyimide layer 2 having a thickness of 5 μm is obtained, and a novolac photoresist (OFPR8600-30) is formed on the polyimide layer 2.
cp) is spin-coated at 3000 rpm for 30 seconds, then 90
Prebaking is performed at 30 ° C. for 30 minutes to obtain a photoresist layer 3 having a thickness of about 1 μm. In FIG. 1 (b), the substrate was irradiated with 72 mJ / cm ² of ultraviolet rays through a photomask, and then the photoresist layer 3 and the polyimide layer 2 were treated with a 2.38 wt% aqueous solution of tetramethylammonium hydroxide (NMD-3). A product developed by Tokyo Ohka Kogyo Co., Ltd.) for 2 minutes is shown. In FIG. 1C, only the photoresist layer is removed using acetone to form a dummy layer. Next, a photoresist (OFPR8600-30cp) was spin-coated at 3000 rpm for 30 seconds and prebaked at 90 ° C. for 30 minutes to form a photoresist layer 4 having a thickness of about 1 μm. Here, alternatively, the photoresist may be applied on the photoresist layer 3 without removing it. In FIG. 1 (e), ultraviolet rays of 72 mJ / cm ² are irradiated through a photomask, and development is performed for 1 minute 30 seconds by NMD-3. Then, while being heated to 100 ° C. in a vacuum, deep ultraviolet rays are radiated at 3.6 J / cm ² to cure the upper photoresist layer and insolubilize it in a developing solution. In FIG. 1 (f), the side surface of the polyimide layer is selectively etched again using the developing solution. In this step, since the photoresist in the upper layer is not subjected to etching, the pattern size and accuracy of the photoresist are kept as they were at the time of the first development, so that the pattern shape and size can be controlled with high accuracy. . Since the undercut amount is obtained by performing the photolithography twice, it is easy to control, and a large undercut of, for example, about 1 to 10 μm can be easily produced.

Embodiment 2 This embodiment will be described below with reference to the drawings. Since this embodiment also has the same shape as that of the first embodiment, FIG. 1 is used. FIG. 1 is an enlarged cross-sectional view (not to scale) of a structure formed by the process of the present invention. In FIG. 1A, the substrate 1
After dehydration baking at 150 ℃ for 20 minutes, PMG
I varnish [SAL110 (sold by Shipley Co., Ltd.) was diluted twice with thinner] was applied by spin coating at 2000 rpm for 30 seconds, baked at 185 ° C. for 30 minutes on a hot plate, and PMGI having a film thickness of 0.3 μm was applied. Layer 2 is obtained, on which a novolac-based photoresist (OFPR8
600-30 cp) was spin-coated at 3000 rpm for 30 seconds, and then prebaked at 90 ° C. for 30 minutes to about 1 μm.
The result shows that the photoresist layer 3 having the film thickness of is obtained. Figure 1
In (b), this substrate is placed through a photomask.
The photoresist layer 3 and the PMGI layer 2 were irradiated with ultraviolet rays of mJ / cm ² and developed with a 2.38% aqueous solution of tetramethylammonium hydroxide (NMD-3; manufactured by Tokyo Ohka Kogyo Co., Ltd.) for 2 minutes. Show. Figure 1 (c)
In FIG. 3, the photo resist layer is removed using acetone to form a dummy layer. In FIG. 1D, a photoresist (OFPR8600-30c
p) is spin coated at 3000 rpm for 30 seconds and then 90 ° C.
Pre-baking is performed for 30 minutes to form a photoresist layer having a thickness of about 1 μm. Alternatively, the photoresist may be applied on the photoresist layer 3 without removing it. In FIG. 1 (e), ultraviolet rays of 72 mJ / cm ² are irradiated through a photomask, NMD-3
Shows that the development was carried out for 1 minute. Then, while baking at 100 ° C. in a vacuum, far-ultraviolet rays are radiated at 3.6 J / cm ² to cure the photoresist layer in the upper layer to make it insoluble in a developing solution and at the same time pass through the photoresist layer to remove PMGI in the lower layer. It was exposed to light to reduce the molecular weight of PMGI. FIG. 1 (f) shows that the developing solution is used again to selectively side-etch only the PMGI layer. Since the photoresist is not etched in this step, the pattern dimensions and accuracy of the photoresist are
Since it is kept as it is at the time of the first development, it becomes easy to control the pattern shape and dimensions with high accuracy. Since the molecular weight of PMGI is reduced by far-ultraviolet rays, PMGI is quickly dissolved in the developing solution, so that an undercut can be easily formed.

[0011]

According to the present invention, a highly accurate and highly heat resistant lift-off mask material can be produced in which the amount of undercut, pattern shape and dimension can be easily controlled.

[Brief description of drawings]

FIG. 1 is an enlarged cross-sectional view of a structure according to an embodiment of the present invention (however, the magnification is not uniform).

[Explanation of symbols]

1 ... Substrate, 2 ... Polyimide layer, 3 ... Photoresist layer,
4 ... Photoresist layer.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Moriaki Fuyama 7-1-1 Omika-cho, Hitachi-shi, Ibaraki Hitachi Ltd. Hitachi Research Laboratory

Claims (7)

[Claims] 1. A method comprising: forming a pattern of a dummy layer on a substrate; forming a resist pattern on the pattern; and forming a resist pattern by removing only the dummy layer. And a resist pattern forming method. 2. The method for forming a resist pattern according to claim 1, further comprising the step of curing the resist pattern. 3. The method of forming a resist pattern according to claim 1, further comprising the step of using light irradiation to cure the resist pattern. 4. The method for forming a resist pattern according to claim 1, further comprising the step of using deep ultraviolet rays for the light irradiation. 5. The method of forming a resist pattern according to claim 1, wherein the dummy layer includes a step of using a substance that does not form a mixed layer with a photoresist. 6. The resin according to claim 1, wherein the dummy layer uses a resin that does not form a mixed layer with a photoresist.
A method for forming a resist pattern according to 2, 3, 4 or 5. 7. The dummy layer comprises a polyimide-imide resin,
7. The resist pattern according to claim 1, comprising at least one of polydimethylglutarimide (PMGI) and polymethylmethacrylate (PMMA) polymethylisopropylketone (PMIPK). Forming method.