JPH06267843A - Pattern forming method - Google Patents

Abstract

PURPOSE:To form a pattern by a lift-off method using a sputtering method, after a mask member having an undercut is formed on a two-layered film using photoresist on the upper layer part and polydimethyl glutaric imide on the lower layer part, by combining irradiation of ultraviolet rays and far ultraviolet rays with a plurality of times development. CONSTITUTION:After photoresist 3 of the upper layer part and polydimethyl glutaric imide 2 of the lower layer part are developed, the resist 3 of the upper layer is cured and the polydimetnyl glutaric imide 2 is exposed to light by the irradiation of far ultraviolet rays 6. By the second development, only the lower layer part is subjected to selective side etching, and a mask member having an undercut is formed. A thin film is deposited on the mask member by a sputtering method, and a pattern is formed by a lift-off method using organic solvent.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pattern forming method using a lift-off method.

[0002]

2. Description of the Related Art Japanese Unexamined Patent Publication (Kokai) No. 2-17643 discloses a metal lift-off method using low molecular weight polymethylglutarimide (hereinafter referred to as PMGI). JP 4-119629
In the publication, an electron beam resist is used for the upper layer and PM for the lower layer.
A lift-off method using GI is disclosed. JP 62
-36845 discloses a method in which a photoresist irradiated with deep ultraviolet rays is side-etched to be used as a lift-off mask. Further, Japanese Patent Laid-Open No. 1-120832 discloses a method of irradiating light to form a hardened layer having a predetermined thickness from the resist layer surface, and then removing the non-hardened layer to form a lift-off mask for the hardened layer. Have been described.

[0003]

[Patent Document 1] Japanese Unexamined Patent Publication No. 3-17643
In the invention of the publication, since the sputtering method is used, in order to obtain a large undercut, it is necessary to increase the exposure amount of radiation and prolong the developing time. However, in this case, the film thickness of the resist layer is large, and it is difficult to control the shape of the mask. Further, in the conventional invention of Japanese Patent Laid-Open No. 4-119629, only a method of using an electron beam resist as an upper layer is shown, and a method of using a resist having sensitivity to ordinary ultraviolet rays and a method of curing this resist are mentioned. Absent. Further, in the conventional inventions of JP-A-62-36845 and JP-A-1-120832, a single resist layer is irradiated with light to form a hardened layer and a non-hardened layer formed in the resist layer. Since the lift-off mask is formed due to the difference in solubility in the solvent, it is difficult to control the shape of the mask.

An object of the present invention is to provide a lift-off method using a mask whose shape is easy to control using a resist sensitive to ultraviolet rays, and to provide a method for forming a highly accurate pattern. is there.

[0005]

According to the present invention, a pattern is formed by forming a two-layer resist film on a substrate in a desired shape, depositing a thin film, and lifting off the resist film to form a pattern. After the upper layer resist portion of the two-layer resist is patterned, the upper layer resist portion is cured by light irradiation, or the upper layer resist is cured, and at the same time, the lower layer of the two-layer resist film is interposed via the upper layer resist. This is achieved by exposing the resist portion to light, side etching only the lower layer resist portion to form a pattern, depositing a thin film, and forming a pattern by lift-off.

The lower layer resist used in the present invention is required not to be mixed with the upper layer resist and to be capable of side etching after the upper layer resist is cured. As such a lower layer resist, polyimide resin, polymethylmethacrylate (PMMA), polymethylisopropylketone (PMI)
PK) and polydimethylglutarimide (PMGI).

PMGI is a resist which has sensitivity in the deep ultraviolet region and can be developed with an alkaline aqueous solution. When PMGI is used as the lower layer resist, pattern formation is
(1) applying a PMGI layer to the substrate; (2) applying a photoresist on the layer; and (3) irradiating the photoresist layer with ultraviolet light through a photomask. 4) a step of developing the photoresist layer as a single layer or both the photoresist layer and PMGI, and (5)
Single photoresist layer or photoresist layer and PM
Both layers of the GI layer are irradiated with deep ultraviolet rays to cure only the photoresist layer, or to cure the photoresist layer and at the same time expose the PMGI layer under the photoresist to light (6) Side the PMGI layer The steps of etching, (7) depositing a thin film by a sputtering method or vapor deposition, and (8) lifting off a PMGI layer and a photoresist layer with a solvent to form a pattern are sequentially performed. The pattern formation in the present invention relates to a pattern having a film thickness of several nm to several tens μm and a size of submicron to several mm. Substrates made of metal, metal oxides, semiconductors, etc. are used for dehydration treatment or HMD
S processing is performed if necessary. A different type of pattern may be already formed on the substrate to have a step. PM on the substrate
GI is applied with a spinner and then baked to form a PMGI layer. The resist applied on this has photocurability,
A resist having this property is, for example, a novolac resin-based photoresist. In the case of a novolac-diazonaphthoquinone type photoresist, it can be developed with an alkaline aqueous solution and can be cured by irradiation with deep ultraviolet rays. Ultraviolet rays to be used for pattern formation are those used in ordinary photolithography, and thus a much higher throughput is possible compared to those using electron beam resist. Next, use an alkaline developer to remove only the upper photoresist layer or the photoresist layer and PMG.
Develop both layers, layer I. Far ultraviolet irradiation, for example,
The baking is performed in a vacuum to cure the photoresist layer, or to cure the photoresist layer and at the same time expose the PMGI layer through the photoresist layer,
Side etch can also be facilitated by reducing the molecular weight. As an etching solution for side etching the PMGI layer, an alkaline aqueous solution such as a photoresist developing solution, an organic solvent, or the like can be used as long as it does not dissolve the photoresist cured by deep ultraviolet rays. The material to be deposited may be metal, semiconductor, carbon, organic material, oxide, nitride, halide or the like. As the deposition method, a normal resistance heating type or electron beam heating type vacuum vapor deposition method, DC and RF sputtering method, ion beam sputtering method, facing target type sputtering method is used as it is, or sputtered particles are incident. A device provided with a shielding plate or the like for aligning the directions can be used. After depositing the thin film, lift-off is performed using an organic solvent or an alkaline aqueous solution to form a pattern.

[0008]

In the present invention, the resist in the upper layer portion is formed into a pattern by ordinary photolithography, and then the resist is cured by irradiation with light to make it insoluble in the etching liquid for the lower layer portion. And a high throughput, and a lift-off mask material having a large undercut can be formed. By using the mask material with this big undercut,
As a method used for depositing a thin film, not only vapor deposition but also sputtering method can be used. Also, P used for the lower layer
MGI has a high glass transition point of 189 ° C., and the photoresist used for the upper layer is also cured by irradiation with deep ultraviolet rays, and when a novolac resin-diazonaphthoquinone type resist is used, the heat resistance is significantly improved to about 300 ° C. It is possible to raise the substrate temperature in the step of depositing, and improve the characteristics of the substance.

[0009]

[Examples] In the examples, the case where PMGI is used as the lower layer resist will be described. However, the same effect can be obtained when polyimide resin, polymethylmethacrylate (PMMA), or polymethylisopropylketone (PMIPK) is used instead of PMGI. Is obtained.

This embodiment will be described below 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), the substrate 1 was dehydrated and baked at 150 ° C. for 20 minutes, and then PMGI varnish [SAL110-PL1; (sales company Shipley Co., Ltd.) was diluted twice with thinner] was spun at 2000 rpm for 30 seconds. It is applied by coating and baked on a hot plate at 185 ° C for 30 minutes, and PM with a film thickness of 0.3 μm
A GI layer 2 is obtained, and a novolac photoresist (OFPR8600-30cp) is applied on the GI layer 2 at 3000 rpm for 30 minutes.
After the spin coating for 2 seconds, prebaking is performed at 90 ° C. for 30 minutes to obtain a photoresist layer 3 having a film thickness of about 1 μm. FIG. 1B shows a case where the substrate is irradiated with ultraviolet rays of 72 mJ / cm ² through the photomask 4. In FIG. 1C, the photoresist layer 3 and the PMGI layer 2 are developed with a 2.38% aqueous solution of tetramethylammonium hydroxide (NMD-3; manufactured by Tokyo Ohka Kogyo Co., Ltd.) for 2 minutes. After that, deep JV radiation of 3.6 J / cm ^{2 is} applied in a vacuum to cure the photoresist layer in the upper layer and insolubilize it in a developing solution, and at the same time expose the PMGI in the lower layer through the photoresist layer to expose the PMGI of PMGI. The molecular weight was reduced. In FIG. 1D, only the PMGI layer is selectively side-etched again using the developing solution. In this step, the photoresist in the upper layer is not subjected to etching, so that the pattern dimension and precision of the photoresist are maintained as they were at the time of the first development, so that the precision and the control of the pattern dimension are facilitated. The undercut amount can be controlled by this development, and the undercut can be quickly formed because the molecular weight of PMGI is reduced by far ultraviolet rays. Figure 1
In (e), a mask material having an undercut of 1 μm is produced by developing for 30 seconds with NMD-3,
The figure shows a state in which Ti is attached to 0.3 μm by sputtering. In FIG. 1 (f), the lift-off was performed while applying ultrasonic waves in a stripping solution (Remover 1165; manufactured by Shipley) containing N-methyl-2-pyrrolidone (NMP) as a main component, which was heated to about 80 ° C. Show. Ti
A pattern could be formed with high precision without forming a curl at the end of the film.

Since the shape is the same as that of the first embodiment, the second embodiment will be described below with reference to FIG. 1 which is the same as the first embodiment. In FIG. 1A, after the substrate 1 was dehydrated and baked at 150 ° C. for 20 minutes, the PMGI varnish [SAL11
0-PL1; (sold by Shipley Co., Ltd.)] by spin coating at 4000 rpm for 30 seconds, and at 30 ° C. at 185 ° C.
After baking on a hot plate for 7 minutes, a PMGI layer 2 with a thickness of 0.7 μm is obtained, and a novolak photoresist (OFPR8600-30cp) is spin-coated on the PMGI layer 2 at 3000 rpm for 30 seconds, and prebaked at 90 ° C. for 30 minutes. This shows that the photoresist layer 3 having a thickness of about 1 μm was obtained. FIG. 1B shows a case where the substrate is irradiated with ultraviolet rays of 72 mJ / cm ² through the photomask 4. In FIG. 1C, the photoresist layer 3 and the PMGI layer 2 are developed with a 2.38% aqueous solution of tetramethylammonium hydroxide (NMD-3; manufactured by Tokyo Ohka Kogyo Co., Ltd.) for 2 minutes. After that, deep JV radiation of 3.6 J / cm ^{2 is} applied in a vacuum to cure the upper photoresist layer and insolubilize it in a developing solution, and at the same time, through the photoresist layer, the lower PMGI
To reduce the molecular weight of PMGI. Figure 1
In (d), only the PMGI layer is selectively side-etched again using the developing solution. In this step, the photoresist in the upper layer is not subjected to etching, so that the pattern dimension and precision of the photoresist are maintained as they were at the time of the first development, so that the precision and the control of the pattern dimension are facilitated. The undercut amount can be controlled by this development, and the undercut can be quickly formed because the molecular weight of PMGI is reduced by far ultraviolet rays. In FIG. 1 (e), a mask material having an undercut of about 2 μm was prepared by developing with NMD-3 for 60 seconds, and alumina was 0.7 μm by bias sputtering in which a bias of −100 V was applied to the substrate.
m Shows where it is deposited. In FIG. 1 (f), N
-Methyl-2-pyrrolidone (NMP) as a main component, a stripping solution (Remover 1165; manufactured by Shipley) at about 80 ° C.
The figure shows a state where the substrate is lifted off while being heated to and applying ultrasonic waves. The pattern of the alumina film could be formed neatly without curling up at the edges.

[0012]

According to the present invention, not only vapor deposition but also pattern formation of a thin film by a lift-off method using a sputtering method can be performed.

[Brief description of drawings]

FIG. 1 is a sectional view of a structure according to an embodiment of the present invention.

[Explanation of symbols]

1 ... Substrate, 2 ... PMGI layer, 3 ... Photoresist layer, 4
... Photomask, 5 ... UV, 6 ... Deep UV, 7 ... Adhering substance.

Front Page Continuation (72) Inventor Moriaki Fuyama 7-1, Omika-cho, Hitachi City, Ibaraki Hitachi Ltd. Hitachi Research Laboratory (72) Inventor Makoto Morishiri 2880 Koufu, Odawara, Kanagawa Hitachi, Ltd. Factory Storage Systems Division

Claims (9)

[Claims] 1. A step of patterning a two-layer resist film in a desired shape on a substrate; a step of depositing a thin film;
A step of lifting off the layer resist film to form a pattern, after forming the pattern of the upper layer resist layer of the two-layer resist film, curing the upper layer resist portion by light irradiation, and side etching only the lower layer resist portion. After pattern formation, a thin film is deposited, and pattern formation is performed by lift-off. 2. The pattern forming method according to claim 1, wherein after the pattern of the upper layer resist layer is formed, the upper layer resist portion is cured by light irradiation and the lower layer resist portion is exposed. 3. The pattern forming method according to claim 1, wherein the upper layer resist is made of a photocurable resin. 4. The pattern forming method according to claim 1, wherein the upper layer resist is made of novolac resin. 5. The pattern forming method according to claim 1, 2, 3 or 4, wherein deep ultraviolet rays are used for the light irradiation. 6. The method according to claim 1, 2, 3, 4 or 5.
A pattern forming method in which the light irradiation is performed while baking. 7. The pattern forming method according to claim 1, 2, 3, 4, 5 or 6, wherein the light irradiation is performed in a vacuum. 8. The lower resist layer according to claim 1, 2, 3, 4, 5, 6 or 7, wherein the lower resist layer is made of at least one of polyimide resin, polymethylmethacrylate, polymethylisopropylketone and polydimethylglutarimide. Pattern forming method. 9. The pattern forming method according to claim 1, 2, 3, 4, 5, 6, 7 or 8, wherein the developing solution for the upper layer resist and the developing solution for the lower layer resist are the same solution.