JPS63175480A - Manufacture of recessed mesfet - Google Patents

Abstract

PURPOSE:To etch away the overhang of a space insulating film above a recess by a method wherein the upper part of a gate metal after lifting off is coated with a photoresist and after etching away the spacer insulating film, the photoresist is removed. CONSTITUTION:A photoresist is coated, exposed and developed on a spacer insulating film 2 to form a photoresist pattern 3 having an opening for recess. First, the spacer insulating film 2 is etched away until the overhang above the recess ends is removed by dry and wet etching processes. Second, excessive gate metal is removed by lifting off process and then the film 2 is newly coated with photoresist for exposure and development to cover the upper part of gate metal completely forming another photoresist pattern 5. Finally, the spacer insulating film 2 is etched away to remove the photoresist pattern 5. Through these procedures, the gate metal only having no overhang above the recess can be provided on a semiconductor substrate.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for manufacturing a recessed MES FET,
In particular, the present invention relates to a method of forming a gate electrode of a recessed MES FET.

[Conventional technology]

Conventionally, as shown in FIG. 2, in order to increase the film thickness of the gate metal, the method for forming the gate electrode of a recessed MES FET is to deposit an insulating film 2, which will serve as a spacer, on a semiconductor substrate (
After forming on a wafer (1), patterning was performed using a photoresist, the insulating film was opened, a recess was formed, a gate metal 4 was attached by vapor deposition, and lift-off was performed three times.

[Problem that the invention seeks to solve]

As mentioned above, in the conventional gate electrode formation method, after the excess metal is lifted off as shown in Figure 2, the eaves of the spacer insulating film remain, and the recess surface under the eaves cannot be sufficiently cleaned, and the gate When a passivation film is grown for surface protection after electrode formation, there are drawbacks such as insufficient coverage under the eaves, and the insulating film for the entire device becomes multilayered, resulting in increased stress.

The purpose of the present invention is to prevent the eaves of the spacer insulating film from remaining after depositing the gate metal and lifting off the excess metal.As a result, the recess surface can be sufficiently cleaned, and the formation of the surface protective film is reliably and easily made. Another object of the present invention is to provide a method for manufacturing a recessed MES FET that can reduce stress on an insulating film.

[Means for solving problems]

The method for manufacturing a recessed MES FET of the present invention includes the steps of forming a spacer insulating film for increasing the gate metal film thickness on a semiconductor substrate, and a photolithography process having a recess opening on the spacer insulating film. A process of forming a resist pattern, a process of etching the photoresist pattern as a mask to form a recess in the semiconductor substrate, a process of wet etching after forming the recess to remove the insulating film above the recess, and a process of depositing gate metal. a step of removing excess gate metal by lift-off, a step of applying a new photoresist, exposing and developing it to cover the gate metal on the semiconductor substrate, and removing the remaining insulating film. A recessed ME'S with a thick gate metal film and no eaves.
, it has the feature that a gate electrode of a FET can be attached.

〔Example〕

Next, embodiments of the present invention will be described with reference to the drawings. FIGS. 1(a) to 1(d) are cross-sectional views of a semiconductor device shown in the order of steps for explaining an embodiment of the present invention.

First, a spacer insulating film 2 is grown on a semiconductor substrate 1 as shown in FIG.
A photoresist is applied thereon, exposed and developed to form a photoresist pattern 3 having an opening for a recess. Next, the spacer insulating film 2 is wet-etched by dry etching, and the upper part of the recess end is removed by etching until the eaves disappear. A gate metal 4 is then deposited to obtain the structure shown.

Next, as shown in FIG. 1(b), the excess gate metal is removed by lift-off. Next, a new photoresist is applied, exposed and developed so as to completely cover the upper part of the gate metal, thereby forming a photoresist pattern 5 as shown in FIG. 1(c). Next, the spacer insulating film 2 is removed by etching.

Next, the photoresist pattern 5 is removed as shown in FIG. 1(d). In this case, a structure can be obtained in which only the gate metal without an eaves above the recess is attached on the semiconductor substrate.

〔Effect of the invention〕

As explained above, in order to increase the thickness of the gate metal film, the present invention removes the spacer insulating film from the upper part of the recess by wet etching, then evaporates the gate metal, lifts it off, and then coats the upper part of the gate metal. By forming a photoresist, etching away the spacer insulating film, and then removing the photoresist covering the upper part of the gate, no eaves of the spacer insulating film remain on the top surface of the recess, and as a result, the inside of the recess can be cleaned. Since the passivation film is completely covered, the passivation film coverage is improved, and the spacer insulating film is removed, the film stress in the entire device can be reduced.

[Brief explanation of the drawing]

FIGS. 1(a) to (d) are cross-sectional views of essential parts of a semiconductor device shown in order of process to explain an embodiment of the present invention, and FIG. 2 is a recessed MES FE not formed by a conventional method.
FIG. 3 is a cross-sectional view of the main part of the T element. DESCRIPTION OF SYMBOLS 1... Semiconductor substrate, 2... Spacer insulating film, 3.
...Photoresist pattern, 4...Gate metal, 5
...Photoresist pattern.

Claims (1)

[Claims] A step of forming a spacer insulating film for increasing the gate metal film thickness on a semiconductor substrate, a step of forming a photoresist pattern having a recess opening on the spacer insulating film, and the photoresist pattern. a step of etching using the recess as a mask to form a recess in the semiconductor substrate, a step of wet etching after the recess formation to remove the spacer insulating film above the recess, a step of depositing gate metal by vapor deposition, and a step of removing excess gate metal. a step of removing the spacer insulating film by lift-off, a step of newly applying photoresist, exposing and developing it to cover the gate metal on the semiconductor substrate, and a step of removing the remaining spacer insulating film. Method of manufacturing type MESFET.