JPH07161711A - Pattern forming method - Google Patents

Abstract

PURPOSE:To enable a sure lift-off and realize an excellent pattern form without generating fence, by forming mask material on a substrate, the form of which mask material has a specific relation between the height of an undercut part and the undercut amount, and lifting off the mask material with solvent, after a thin film is formed. CONSTITUTION:A mask material 2 having a form wherein the relation between the height (y) of an undercut part and the undercut amount (x) is 3y-2x+1<=0 is formed on a substrate 1. After a thin film is formed, [he mask material is lifted off by using solvent. For example, the mask material 2 is composed of one layer resist or a multilayered resist. The thin film is formed by using a sputtering method or a bias sputter method. By decreasing the height of the undercut part of the mask material, the amount of a film entering the inside of the undercut is reduced. By increasing the undercut amount, the generation of fence is prevented. Thereby lift-off can be surely executed.

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 In Japanese Patent Laid-Open No. 167448/1985, the shape of a two-layer mask material is 1.5 times or more the thickness of a lower layer of a metal film, and the undercut is 0.1 μm or more, particularly 0.3. -0.7
A method is disclosed in which a metal film is formed in a range of μm by a bias sputtering method, and a metal wiring pattern is formed by lift-off.

[0003]

In order to form a pattern by the lift-off method, it is necessary to make a step break between the thin film on the substrate and the thin film on the mask material to allow the solvent to soak in. However, when a thin film is formed by the sputtering method, the particles fly to the substrate at a wide angle, so that the film adheres well and it is difficult to cut the film on the substrate and the mask material. Especially when the bias sputtering method is used, lift-off is difficult because the thin film on the substrate is reverse-sputtered and the throwing power of the thin film is further poor. In the method disclosed in Japanese Patent Laid-Open No. 60-167448, since the lower layer film thickness of the two-layer mask material is large, the formed film often enters the undercut, and the amount of the undercut is small. In addition, it is easy for the film to be formed to roll up, which is called a fence. When a fence is generated, the covering power of the film formed on the fence is deteriorated, and insulation failure is likely to occur.

An object of the present invention is to provide a shape of a lift-off mask material which can surely be lifted off and can realize a good pattern shape without generating a fence.

[0005]

According to the present invention, pattern formation is performed by forming a mask material having a shape in which the relationship between the height y of the undercut portion and the undercut amount x is 3y-2x + 1≤0 on the substrate. A step and a step of forming a thin film,
This is achieved by sequentially performing a step of lifting off the mask material with a solvent.

After the thin film is formed by the sputtering method and the bias sputtering method, in order to surely lift off and prevent the fence from being generated, it is necessary to reduce the penetration of the film into the undercut of the mask material. . For this purpose, the height of the undercut portion is made thin until the film on the substrate and the film on the mask material are surely cut off, that is, the height of the undercut portion and the film thickness of the film to be formed are made equal to each other. It is necessary to increase the cut amount. At this time, the mask material may have a multi-layered structure of a plurality of layers or a resist having one layer. The relationship between the height of the undercut portion that can be lifted off without generating a fence and the undercut amount is that when the film thickness of the formed film is equal to the height of the undercut portion, the height of the undercut portion of the mask material is y. , Where the undercut amount is x, the area is represented by 3y−2x + 1 ≦ 0 (FIG. 2). Even when the film thickness of the film to be formed is thinner than the height of the undercut portion, of course, when the relationship between the height of the undercut portion and the undercut amount is in the above region,
Even if the film is formed by the usual sputtering method and bias sputtering method, the fence is not generated and the lift-off can be surely performed.

[0007]

[Function] When performing pattern formation by the lift-off method,
When using the sputtering method for film formation, by lowering the height of the undercut portion of the lift-off mask material,
By reducing the amount of film that enters the undercut and increasing the amount of undercut, it is possible to prevent the occurrence of fences and reliably perform lift-off.

[0008]

EXAMPLE 1 Example 1 will be described below with reference to the drawings. FIG. 3 is an enlarged cross-sectional view (not to scale) of a structure formed by the process of the present invention. Figure 3
In (a), polyimide varnish (PIQ;
Hitachi Chemical Co., Ltd.) was applied by spin coating at 5000 rpm for 60 seconds and baked at 150 ° C. for 30 minutes on a hot plate to form a polyimide layer 3 having a thickness of 0.5 μm.
And a novolac-based photoresist (OFPR
8600-30cp) is spin-coated at 3000 rpm for 30 seconds, and then pre-baked at 90 ° C for 30 minutes to about 1μ.
The photo resist layer 4 having a thickness of m is obtained. In FIG. 3 (b), this substrate is placed through a photomask.
Photoresist layer 4 after irradiation with ² mJ / cm ² of ultraviolet rays
The polyimide layer 3 was developed with a 2.38% aqueous solution of tetramethylammonium hydroxide (NMD-3; manufactured by Tokyo Ohka Kogyo Co., Ltd.) for 2 minutes. Figure 3
In (c), only the photoresist layer is removed using acetone to form a dummy layer. next,
Photo resist (OFPR8600-30cp) 30
After spin coating at 00 rpm for 30 seconds, prebaking is performed at 90 ° C. for 30 minutes to form a photoresist layer 5 having a film thickness of about 1 μm. Here, alternatively, the photoresist may be applied on the photoresist layer 4 without removing it. In FIG. 3 (e), 72 mJ / cm ² of ultraviolet rays are radiated through a photomask, and NMD is applied.
-3 shows that development was carried out for 1 minute and 30 seconds. Then, while baking at 100 ° C. in a vacuum, far-ultraviolet rays are radiated at 3.6 J / cm ² to cure the upper photoresist layer and make it insoluble in the developing solution. In FIG. 3 (f), only the polyimide layer is selectively side-etched again using the developing solution. At this time, the undercut amount was 1 μm. 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. . In FIG. 3 (g), the Al ₂ O ₃ film 6 is formed to a thickness of 0.5 μm by the bias sputtering method. In FIG. 3 (h), a stripper containing N-methyl-2-pyrrolidone (NMP) as a main component (remover 116
5, manufactured by Shipley Co., Ltd.) and lifted off to form a pattern. A beautiful pattern could be formed without a fence.

The height of the undercut portion is controlled by the polyimide film thickness of (a), and the undercut amount is controlled by twice photolithography to prepare a mask material in which the height and the amount of the undercut are changed. Then, Al ₂ O ₃ having the same film thickness as the height of the undercut portion was formed by the bias sputtering method and lifted off to obtain the graph of FIG.

(Embodiment 2) This embodiment will be described below with reference to the drawings. FIG. 4 is an enlarged cross-sectional view (but not at uniform magnification) of the structure formed by the process of the present invention. Figure 4
In (a), after the substrate 1 was dehydrated and baked at 150 ° C. for 20 minutes, PMGI varnish [SAL110; (sales source: Shipley Co., Ltd.) was diluted with thinner to 2000 rp].
It is applied by spin coating at 30 m for 30 seconds, baked at 185 ° C. for 30 minutes on a hot plate to obtain a PMGI layer 7 having a thickness of 0.3 μm, and a novolac-based photoresist (OFPR8600-30cp) is applied at 3000 rp.
After spin coating at m 3 for 30 minutes, prebaking at 90 ° C. for 20 minutes was performed to obtain a photoresist layer 8 having a film thickness of about 1 μm. FIG. 4B shows a case where the substrate is irradiated with ultraviolet rays of 72 mJ / cm ² through a photomask. In FIG. 4C, the photoresist layer 8
Of tetramethylammonium hydroxide 2.
2 with 38% aqueous solution (NMD-3; manufactured by Tokyo Ohka Kogyo Co., Ltd.)
The figure shows the result of development for a minute. Thereafter, deep ultraviolet rays were radiated at 3.6 J / cm ^{2 in} a vacuum to cure the upper photoresist layer. FIG. 4D shows that 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 amount of undercut can be controlled by this development. Figure 4
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 Ti film 9 deposited to a thickness of 0.3 μm by sputtering. In FIG. 4 (f), N-methyl-2
-The figure shows a state where lift-off was performed using a stripping solution containing Pyrrolidone (NMP) as a main component (Remover 1165; manufactured by Shipley Co.). The pattern could be formed with high precision without forming a roll-up at the end of the Ti film 9.

The height of the undercut portion is changed by changing the film thickness of the PMGI shown in FIG.
In the developing step (d), a mask material having a different undercut amount was prepared by changing the developing time, and a Ti film having the same thickness as the height of the undercut portion was formed by a sputtering method and lifted off. I got a graph of.

[0012]

According to the present invention, a fence is not generated,
The pattern can be formed by performing reliable lift-off.

[Brief description of drawings]

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

FIG. 2 is an explanatory diagram showing the relationship between the height of an undercut portion that can be lifted off without a fence and the amount of undercut.

FIG. 3 is an enlarged cross-sectional view of the structure according to the present invention.

FIG. 4 is an enlarged sectional view of the structure according to the present invention.

[Explanation of symbols]

1 ... Substrate, 2 ... Mask material, 3 ... Polyimide layer, 4, 5,
8 ... Resist layer, 6 ... Al ₂ O ₃ film, 7 ... PMGI layer, 9
... Ti film.

Claims (5)

[Claims] 1. A step of forming a mask material having a shape in which a relationship between a height y of an undercut portion and an undercut amount x is 3y−2x + 1 ≦ 0 on a substrate, a step of forming a thin film, and the mask. Pattern forming method including a step of lifting off a material with a solvent. 2. The pattern forming method according to claim 1, wherein the mask material is a single layer resist. 3. The pattern forming method according to claim 1, wherein the mask material is formed of a multilayer resist having a plurality of layers. 4. The pattern forming method according to claim 1, wherein a sputtering method is used in the step of forming the thin film. 5. The pattern forming method according to claim 1, wherein the step of forming the thin film includes the step of using a bias sputtering method.