JPH03286539A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To improve an adhesiveness of a resist to GaAs and a plasma-proof quality by using a photoresist for optics, which has a high adhesiveness to GaAs, as the photoresist on a GaAs substrate and by forming thereon a metal Ti, Cr or the like for shading which is used as the mask of the photoresist for optics and by applying a resist to the uppermost part. CONSTITUTION:An activated layer 2 is grown on a GaAs semi-insulating substrate 1, and a source electrode 3 and a drain electrode 4 are formed thereon, and further, a photoresist 5 for optics, having a high adhesiveness to the GaAs substrate 1, is applied to their surfaces. Then, a metal 6 for shading is formed wholly thereon. Then, a resist 7 is applied thereto and a gate pattern is formed by EB of a predetermined pattern. Then, etching is performed using the resist 7 as a mask. Thereafter, by using as a mask the metal 6 for shading of Ti or Cr, a total exposure and a development are performed, and a pattern is formed. Then, after forming a recess 8, a gate metal 9 is formed by a deposition, etc. Then, by a lift-off method, the photoresist for optics 5 in a first layer, the metal 6 for shading, the resist 7 and the unnecessary parts of the gate metal 19 are removed, and a gate electrode is formed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for manufacturing semiconductor devices such as GaAsFETs and HEMTs, and particularly provides a gate electrode type method.

[Conventional technology]

FIG. 2 is a cross-sectional view showing the manufacturing process of a conventional semiconductor device manufacturing method.

First, as shown in FIG. 2(a), an active layer (2) is grown on a GaAs semi-insulating substrate (1).
A source electrode (3) and a drain electrode (4), which are ohmic electrodes, are formed thereon by a lift-off method. Next, Figure 2 (
Photoresist for gate pattern formation like bl (
When performing EB direct writing, a PMM A photoresist (7)) is applied onto the GaAs substrate (1), photolithography is performed using EB direct writing, etc. to form a predetermined pattern, and then a recess (7) is formed by etching. 8). Then the second
As shown in Figure (C), after depositing the gate electrode metal (9) on the entire surface, the unnecessary parts of the photoresist (7) and gate metal (9) are removed by lift-off method as shown in Figure 2 (fd). Then perform gate formation.

[Problem to be solved by the invention]

Conventional semiconductor device manufacturing methods have been formed as described above, so when forming gates, GaAsFET, H
Cate length (L) to improve the performance of elements such as EMT
Since optical exposure is difficult to produce patterns with g ) of 0.25 μm or less, direct EB writing is required. but,
To perform EB direct writing, an EB photoresist such as PMMA is required in place of the conventional optical photoresist. Compared to conventional optical photoresists, this EB photoresist has poor adhesion to GaAs and poor plasma resistance, and when etching is performed, liquid may seep in, and photoresists exposed to plasma during RIE etc. There were problems such as the film being stained.

This invention was made to solve the above-mentioned problems, and aims to improve the adhesion between GaAs and photoresist and the plasma resistance.

[Means to solve the problem]

The method for manufacturing a semiconductor device according to the present invention uses an optical photoresist with high adhesion to GaAs as a photoresist on a GaAs substrate, and on top of that, a light shielding layer such as TiorCr used as a mask for the optical photoresist is applied. A metal is inserted and an EB photoresist is applied to the top.

That is, the uppermost EB photoresist is exposed to light by EB direct writing, and the first layer of optical photoresist is exposed to light using a light-shielding metal as a mask.

[For production]

The method for manufacturing a semiconductor device according to the present invention improves the adhesion of the photoresist by using an optical photoresist that has high adhesion to GaAs as the photoresist on the GaAs substrate, and also uses a fine pattern to mask the light-blocking metal. Mask alignment is no longer necessary.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings.

FIGS. 1(a) to 1(f+) are cross-sectional views showing the manufacturing process of the main part of gate formation in a method of manufacturing a semiconductor device according to an embodiment of the present invention.

First, as shown in Figure 1(a), a GaAs semi-insulating substrate (
1) Grow an active layer (2) on top, photolithography on top of it,
A source electrode (3) and a drain electrode (4) are formed using a lift-off method, and an optical photoresist (5) having high adhesion to the GaAs substrate (1) is applied thereon. Next, as shown in FIG. 1(b), a light-shielding metal (6) such as Ti or Cr is formed on the entire surface by vapor deposition, sputtering, or the like. Next, as shown in FIG. 1(C), an EB photoresist such as PMMA (
7) is applied, a predetermined pattern is directly drawn using EB, and development is performed to form a gate pattern. Next, Figure 1fd)
Using the EB photoresist (7) as a mask,
Etch Ti, Cr, etc. After that, using the light-shielding metals Ti and Cr (61) as a mask, the entire surface is exposed and developed to form a pattern. At this time, since the fine pattern is formed using the light-shielding metal as a mask, mask alignment is not required, and accuracy is Next, as shown in FIG. 1(e), after forming a recess (8), a gate metal (9) is formed by vapor deposition or the like.
As shown in Figure (f), unnecessary parts of the first layer of optical photoresist (5), light shielding metal (6), EB photoresist (7), and gate metal (9) are removed using the lift-off method. Then, a gate electrode is formed.

〔Effect of the invention〕

As described above, according to the present invention, between the GaAs substrate and the EB photoresist (PMMA), an optical photoresist with excellent adhesion to GaAs and a Tior for light shielding are used.
By adding a metal such as Cr, the adhesion of the EB photoresist is improved, and the exposure of the optical exposure photoresist on the GaAs substrate is performed through the opening of the light-shielding metal formed in the pattern of the EB photoresist. Since this is performed using a mask, there is no need for mask alignment, the entire surface can be exposed, and a fine pattern can be formed with high precision.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing the manufacturing process of a semiconductor device manufacturing method according to an embodiment of the present invention, and FIG. 2 is a sectional view showing the manufacturing process of a conventional semiconductor device manufacturing method. In the figure, (1) is a GaAs semi-insulating substrate, (2) is an active layer, (3) is a source electrode, (4) is a train electrode,
(5) is an optical photoresist, (6) is a light-shielding metal (
(Ti'orCr), (7) is a photoresist for EB, (
8) is a recess, and (9) is a gate metal. In addition, in the figures, the same reference numerals indicate the same or equivalent parts.

Claims (1)

[Claims] A method for manufacturing a semiconductor device, characterized in that an optical photoresist and a light-shielding metal such as TiorCr are used between the GaAs substrate and the EB photoresist.