JPH0563002A - Pattern formation - Google Patents

Abstract

PURPOSE:To provide a method of forming a pattern to form a stabilized T-shaped gate by the lift-off. CONSTITUTION:First, a gate metal 4 of a trunk area of T-shaped gate 8 (lower part of T-shaped gate) is formed by lift off. Next, it is flattened with a material allowing lift off. Thereafter, the heading part of this gate metal 4 is aligned, a metal 7 which will become a protruded area (upper part) of the T-shaped gate 8 is vacuum-deposited on the gate metal 4 and the T-shaped gate 8 is formed by lift-off together with the material used for the flattening. Thereby, the trunk part of T-shaped gate and the protruded part can be coupled reliably and the T-shaped gate reliably coupling the T-shaped upper part and lower part by the lift off can be obtained.

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, and more particularly to a pattern for forming a T-type gate by lift-off.
Method for forming a film.

[0002]

2. Description of the Related Art A conventional T-type gate forming method using lift-off will be described with reference to FIG. 7A to 7C are cross-sectional views in the order of steps (A to C) showing the above-mentioned conventional method, in which a resist 22 is formed on a wafer 21 so that the cross section has a T-shape (step A). To the wafer 21 and the resist 2
In this method, a metal 23 such as aluminum is vapor-deposited on the entire surface of step 2 (step B), and then, as shown in step C, lift-off is performed to form the T-type gate 28.

A conventional method of forming a resist pattern cross section into a T-shape will be described with reference to FIG.
3A to 3C are cross-sectional views in the order of steps (A to C) showing the above-described conventional method.
A resist 32 is applied on top of the same, and baking is performed. Then, a resist 36 having a higher development speed than the resist 32, that is, a high sensitivity is applied as an upper layer resist to the same developing solution, and the same baking is performed. ..

Next, as shown in step B, the resist 32
And, a predetermined area of the same 36 is exposed and developed. By this step B, the upper layer resist 36 becomes the lower layer resist 3
Since the developing speed is faster than that of No. 2, as shown in step C, the opening of the upper resist layer 36 can be formed in a wide shape, that is, the resist pattern can have a T-shaped cross section (Japanese Patent Publication No.
53-24786 and JP-B-63-55208).

[0005]

However, in the conventional method of forming a T-type gate by the above-mentioned lift-off, there is a problem that it is difficult to form a T-type gate in which the upper and lower parts of the T-type are securely connected. is doing. That is, as shown in FIG.
When the metal 43 is vapor-deposited on 2, the T-shaped gate trunk portion 44 and the T-shaped gate projecting portion 47 are separated from each other, so that there is a drawback that the gate is unlikely to become the T-shaped portion at the time of lift-off. It was

Further, as shown in FIG. 10, when the groove 49 is provided, the distance between the T-type gate trunk portion 44 and the T-type gate protruding portion 47 is further increased as compared with FIG. 9 in which the groove is not provided. Therefore, it was more difficult to form the T-type gate.

Therefore, the present invention aims to provide a pattern forming method which solves the above problems and drawbacks, and more specifically, a T type in which an upper portion and a lower portion of the T type are securely joined by lift-off. It is an object of the present invention to provide a pattern forming method capable of forming a gate.

[0008]

In order to achieve the above object, the present invention first forms a gate metal under a T-type gate on a wafer, and then forms the gate metal. -A means for forming a metal to be an upper part of the T-type gate on the gate metal is adopted, whereby a T-type gate in which the upper part and the lower part of the T-type are securely coupled is obtained. is there.

That is, according to the present invention, (1) a step of forming a gate metal to be a lower portion of a T-type gate on a wafer by lift-off, (2) development in a solvent soluble in an organic solvent used for lift-off and development. A step of flattening with a material that is difficult to be etched by a liquid, and then etching the material used for this flattening, thereby performing the cueing of the gate metal, (3) the gated cueing A step of forming a T-type gate by evaporating a metal to be an upper part of the T-type gate on the metal and lifting off the metal together with the material used for the planarization. It is a forming method.

Further, according to the present invention, (1) a resist is applied on a wafer, exposed and developed, and the resist is patterned.
A step of forming a groove, (2) a step of etching the wafer using the resist pattern as a mask to form a groove (recess), and (3) a lower portion of the T-shaped gate in the groove (recess). Forming the gate metal by lift-off, (4)
The material used for the lift-off, which is soluble in the organic solvent and is not easily etched by the developing solution, is planarized, and then the material used for the planarization is etched.
(5) By depositing a metal to be the upper part of the T-shaped gate on the gate metal that has been cueed, and lifting off together with the material used for the planarization. , A step of forming a T-type gate, and a pattern forming method.

[0011]

EXAMPLE Next, FIG. 1 shows Example 1 and Example 2 of the present invention.
~ It demonstrates in detail based on FIG. 3 and FIG. 4 to FIG. (Embodiment 1) FIGS. 1 to 3 are sectional views showing a first embodiment of the present invention in the order of steps (A to J). First, as shown in step A of FIG. Is coated with a resist 2 having a film thickness of 0.5 to 1.5 .mu.m, the gate forming portion is exposed, and the exposed portion is developed as shown in step B of FIG. So that metal 3 on wafer-1
(For example, aluminum) is vapor-deposited with a thickness (for example, 0.4 μm) of 80% or less of the film thickness of the resist 2.

Then, as shown in step D of FIG. 2, the gate metal 4 is formed by lift-off. The gate metal 4 corresponds to the trunk of the T-type gate. Next, a solution prepared by dissolving 3% by weight of polymethyl methacrylate in a chlorobenzene solvent was spin-coated at 4000 rpm 3 to 5 times as shown in step E in FIG.
And baking at 150-200 ° C. for 10-60 minutes. As a result, the upper portion of the gate metal 4 is flattened by the polymethylmethacrylate layer 5.

Next, using a solution of methyl ethyl ketone and isopropyl alcohol in a volume ratio of 1: 3, Step F in FIG.
The gate metal 4 is cued as shown in FIG. This cueing will be explained. In the case where the above-mentioned 3% by weight polymethylmethacrylate solution was applied 3 times at 4000 rpm to the gate metal 4 having a thickness of 4000 angstrom and baked at 170 ° C. for 20 minutes ( 2), the thickness of the polymethylmethacrylate layer 5 on the gate metal 4 is about 1500 angstroms. The volume ratio of the methyl ethyl ketone-isopropyl alcohol mixture of 1: 3 has an etching rate of about 200 with respect to polymethyl methacrylate.
Since the thickness is angstrom / min, the gate metal 4 can be cued by immersing the wafer-1 in this mixed solution for 8 to 10 minutes.

Next, as shown in step G of FIG.
After applying a novolac resist 6 having a thickness of 8 to 1.6 μm, a portion directly above the gate is exposed with a width wider than that of the gate metal 4.
Then, development is performed with an alkaline developing solution (eg, sodium hydroxide aqueous solution). At this time, polymethylmethacrylate
Since the gate layer 5'is not etched with an alkaline developing solution, a resist pattern corresponding to the protruding portion of the T-type gate as shown in step H of FIG. 3 is formed.

Next, as shown in step I of FIG.
Is vapor-deposited and lifted off to form the T-type gate 8 shown in step J of FIG. Although polymethyl methacrylate was used as the planarizing material in Example 1, it could be lifted off, that is, it was soluble in an organic solvent such as methyl ethyl ketone, and the resist pattern of the T-shaped gate overhang portion. Any material can be used as long as it is a material that is hardly soluble in the developing solution used in the formation (in Example 1, the alkaline developing solution).

(Embodiment 2) FIGS. 4 to 6 show a second embodiment of the present invention.
FIG. 6 is a cross-sectional view showing the embodiment of FIG. 4 in the order of steps (A to H). In the second embodiment, first, as shown in the step A of FIG. Then, exposure and development are performed to form a pattern on the resist 12. Next, as shown in step B in the figure, the wafer 11 is etched using the resist pattern as a mask,
A groove 19 (recess) having a depth of 0.2 to 0.6 μm is formed.

After that, the metal 13 (for example, aluminum)
Is deposited to a height almost equal to the depth of the groove 19 (step C in FIG. 4) and lifted off to form the gate metal 14 in the groove 19 (step D in FIG. 5). Next, as in the case of Example 1, a 3 to 6 wt% polymethylmethacrylate solution was spin-coated and planarized (step E in FIG. 5), and then
As shown in Step F of FIG. 5 to Step H of FIG. 6, the T-type gate 18 is formed similarly to the first embodiment.

In the second embodiment, unlike the first embodiment, the gate metal 14 having a height substantially equal to the depth of the groove is provided in the groove 19.
Therefore, it is not necessary to apply the polymethyl methacrylate a plurality of times, and it is possible to flatten the surface by performing the application once. In addition, as in the second embodiment, T is lifted off in the deep groove.
In the case of forming the type gate, in the conventional method, as shown in FIG. 10, the distance between the T-type gate trunk portion and the T-type gate protruding portion is larger than that in the case without the groove. , T-type gate formation is very difficult, but T
The mold gate forming method is a very effective means.

[0019]

As described above, according to the present invention, the trunk of the T-type gate is first formed, and then the metal of the protruding portion of the T-type gate is formed on the trunk of the T-type gate. By vapor deposition, the trunk of the T-type gate and the overhanging portion can be surely connected to each other, and a T-type gate in which the upper and lower parts of the T-type are surely connected by lift-off is obtained. The effect that can be produced occurs.

[Brief description of drawings]

FIG. 1 is a sectional view showing a first embodiment of the present invention in the order of steps (A to C).

FIG. 2 is a cross-sectional view in the order of steps (D to G) subsequent to FIG.

3A to 3C are cross-sectional views in the order of steps (H to J) subsequent to FIG.

FIG. 4 is a sectional view showing a second embodiment of the present invention in the order of steps (A to C).

5A to 5C are cross-sectional views in order of steps (DF) subsequent to FIG.

FIG. 6 is a cross-sectional view in the order of steps (G to H) subsequent to FIG.

7A to 7C are cross-sectional views in order of steps (A to C) showing a conventional T-type gate forming method using lift-off.

FIG. 8 is a cross-sectional view in the order of steps (A to C) showing a conventional method of forming a resist pattern cross section into a T-shape.

FIG. 9 is a cross-sectional view showing a problem of the conventional technique.

FIG. 10 is a cross-sectional view showing a problem when a T-shaped gate is formed in a groove according to a conventional technique.

[Explanation of symbols]

 1 Wafer 2 Resist 3 Metal 4 Gate Metal 5 Polymethyl Methacrylate Layer 5 ′ Polymethyl Methacrylate Layer 6 Resist 7 Metal 8 T-type Gate 11 Wafer 12 Resist 13 Metal 14 Gate Metal 15 Polymethylmethacrylate layer 15 'Polymethylmethacrylate layer 16 Resist 17 Metal 18 T-type gate 19 Groove 21 Wafer 22 Resist 23 Metal 28 T-type gate 31 Wafer 32 Resist 36 Resist 41 Wafer 42 Resist 43 Metal 44 T-type Gate Trunk 47 T-type Gate Overhang 49 Groove

Claims (3)

[Claims] 1. A step of forming a gate metal as a lower portion of a T-type gate on a wafer by lift-off, and (2) being soluble in an organic solvent used for lift-off and being etched by a developing solution. Flattening with a difficult material, and then etching the material used for this flattening to thereby cue the gate metal, (3) T on the gated metal after cueing A method of forming a pattern, comprising the steps of forming a T-type gate by vapor-depositing a metal to be an upper portion of the type gate and lifting off with a material used for the planarization. 2. A step of (1) applying a resist on a wafer, exposing and developing the resist to form a pattern on the resist, (2) etching the wafer using the resist pattern as a mask A step of forming a groove (recess), (3) a gate which is a lower part of the T-type gate in the groove (recess).
Forming a metal layer by lift-off, (4) planarizing with a material that is soluble in the organic solvent used for lift-off and is not easily etched by the developing solution, and then etching the material used for this planarization, thereby (5) A metal serving as an upper part of the T-shaped gate is vapor-deposited on the gate metal which has been cueed, and lifted off together with the material used for the planarization. Accordingly, a step of forming a T-type gate is included. 3. The pattern forming method according to claim 1, wherein the material used for the flattening is polymethylmethacrylate.