JPH01125983A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To make the thickness of a resist layer for gate patterning smaller by a method wherein, after a recess trench is formed, glass coating with SiN, SiO or the like is applied over the whole surface of a wafer and the recess trench is filled with the glass coating and the glass on the source and drain is removed by etching. CONSTITUTION:A recess trench 6 is filled with glass coating 8 and the glass on source and drain electrodes 1 and 3 is removed to make the surface flat. The thickness of a photoresist layer 7 can be smaller and a pattern for forming a gate can be composed of a photoresist layer 7a which is substantially thinner compared to the thickness of a photoresist layer of the constitution wherein two photoresist layers overlap each other in the recess trench. Therefore, a fine pattern-like a mask can be obtained and a gate electrode with excellent ratio frequency characteristics can be obtained. After the gate is patterned, the glass coating 8 is etched through the aperture and a gate electrode 2 is formed by evaporation or the like and the photoresist is removed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for manufacturing a semiconductor device, and particularly to the formation of a gate electrode of an FET used in a microwave band.

[Conventional technology]

In general, GaAS field effect transistors used in ultra-high frequencies often have a shape called a recessed structure for the purpose of increasing the withstand voltage between the source and drain. FIG. 2 is a partially enlarged sectional view of a conventional field effect transistor having a recessed shape.

In the figure, +1) is the source electrode, (2) is the gate electrode, (31 is the drain electrode, (4) is the GaAs active layer, (
51 is a semi-insulating GaAS substrate. Conventionally, in order to form a GaA, S field effect transistor electrode having a recessed structure, a semi-insulating GaAs substrate (5
) is formed on the trapezoidal n-type GaAs active layer (41 is formed by mesa etching), and an ohmic source electrode (
After forming 1) and the drain electrode (3), a recess groove is created by chemical etching using a resist pattern for creating the recessed part (6) and the gate electrode (21), and then the gate electrode (2) is formed by vapor deposition. FIG. 3 (al to te+ are partially enlarged cross-sectional views showing a part of the process of manufacturing a field effect transistor having a conventional recessed shape. As is clear from the figure, the recess width can be adjusted to the desired width. In order to achieve this, the photoresist (7) for forming the recess is patterned with a resist pattern corresponding to the recess width, and then chemical etching is performed by selecting an etching solution that is fast in the depth direction, or dry etching is performed. A method of etching is used.If a recess is formed using this method, the desired recess width can be obtained, but in order to form a gate electrode, it is necessary to butter the gate again using a resist pattern. After forming the recess groove, resist coating and gate forming photoresist (7a) are performed.

Thereafter, a gate electrode is formed by vapor deposition of a gate electrode material.

[Problem that the invention seeks to solve]

In conventional resist coating after recess formation and subsequent gate patterning, the recess groove is filled with St-resist by uniformizing the resist using a spinner, and is further coated to cover the source and drain. The resist in the gate electrode forming area becomes thick, and gate patterning of the resist by optical exposure and development has the drawback that the resist pattern becomes thicker than the gate opening of the mask.

This invention was made in order to solve the above-mentioned problems, and it is an object of the present invention to enable gate patterning of a thin resistor equivalent to the gate opening of a mask even when patterning a resist gate after forming a recess groove. .

[Means for solving problems]

The method for manufacturing a semiconductor device according to the present invention is to perform gate patterning by coating the entire surface of the wafer with glass such as SiN, SiO, etc. to fill the recess grooves after forming the recess grooves, and etching away the glass on the source drache. This is to reduce the thickness of the resist during the process.

[Effect]

In this invention, the thickness of the resist for gate patterning can be reduced by filling the grooves in the glass coating with SiN, SiO, etc., and the spread of the pattern can be suppressed by gate patterning by optical exposure and development.
Thin resist gate patterning can be performed in the same manner as the gate opening of the mask.

[Embodiments of the invention]

Hereinafter, this invention will be explained with reference to the drawings. Figure 1 (al~(
hl is a partially enlarged view showing a part of the process of manufacturing a semiconductor device according to an embodiment of the present invention;
) is the state of resist patterning to obtain the recess groove after the source electrode (1) and drain electrode (31) are formed, (1)l is the state after recess groove etching, (0)
is the state coated with glass after removing the photoresist for forming the recess groove (Dl is the glass of the source/drain electrode part (
8; is removed and flattened; (e) is a state in which photoresist is coated for gate patterning and a gate pattern is formed; (f) is a state in which glass (81) is etched to open the gate forming part. (g)
is the gate electrode (2: formed by vapor deposition etc., +h
) shows the state in which the photoresist has been removed by lift-off. In this way, by filling the recess groove with glass coat and removing the glass on the top of the source and dray stain, flattening is achieved and the thickness of the photoresist can be reduced, which is much thinner than when the photoresist overlaps the recess groove. Since the resist can be patterned for gate formation, a photoresist gate pattern can have a thin pattern similar to a mask, and a gate electrode with good high frequency characteristics can be obtained. After buttering the gate, the glass can be etched from this opening, the gate electrode can be formed by vapor deposition, and the photoresist can be removed.

〔Effect of the invention〕

As described above, according to the present invention, after forming the recess, the recess groove can be filled with a glass coat to control the width of the recess groove, and the gate can be patterned with a thin photoresist film, so that a thin gate electrode can be formed. Ru. In other words, a gate electrode with good high frequency characteristics can be created while controlling the recess width.

Actually, by performing glass etching after gate patterning and then performing VcoaAs etching, a two-stage recess can be created. Furthermore, by performing glass etching and etching GaAs, multi-stage recess grooves can be formed. Since this multi-stage recess can be performed while controlling the width of the outermost recess, a gate electrode with good high frequency characteristics and high breakdown voltage can be formed.

[Brief explanation of the drawing]

1(a) to 1(h) are partially enlarged views showing a part of the process of manufacturing a semiconductor device according to an embodiment of the present invention, and FIG. 2 is a portion of a conventional field effect transistor having a recessed shape. The enlarged views and FIGS. 3A to 3E are partially enlarged sectional views showing a part of the process of manufacturing a conventional field effect transistor having a recessed shape. In the figure, (1) is a source electrode, and 2 is a Gate electrode, (
31 is a drain electrode, (4) is an n fJ GaAs active layer, (51 is a semi-insulating GaAs substrate, (61 is a recessed part, (7) is a photoresist (for recess formation), (7a)
) is photoresist (for gate formation), (81 is glass (81N, 810, etc.). In the figure, the same reference numerals indicate the same or equivalent parts◎

Claims (3)

[Claims] (1) A semiconductor device characterized by a step of forming a recess structure in the active layer, and forming a resist pattern for processing the inside of the recess structure after backfilling the inside of the recess structure with a semiconductor surface protective film. manufacturing method. (2) The method for manufacturing a semiconductor device according to claim 1, wherein the semiconductor surface protective film is of SiN or SiO type. (3) The electrode is formed after the steps of backfilling the inside of the recess structure with a semiconductor surface film, forming a resist pattern, and etching the GaAs surface on which the semiconductor surface film has been etched are repeated one or more times. A method for manufacturing a semiconductor device.