JPH04372130A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To manufacture a semiconductor device by forming a pattern consisting of submicron-order air gaps in an insulating film by a normal optical exposure method. CONSTITUTION:A semiconductor substrate is spread with an insulating film 23, and a photoresist layer 24 with a desired pattern is deposited over the insulating film 23; then, the photoresist layer 24 is used as a mask for etching the insulating film 23 so as to bite into the bottom of the photoresist layer 24 to form a bite-in 29. Another insulating film 25 is piled up, the insulating film 25 on the photoresist layer 24 and the photoresist layer 24 are lifted off.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a semiconductor device having a submicron pattern such as a gate electrode of an electronic device.

0002

2. Description of the Related Art MESFETs using GaAs have higher speeds than Si bipolar transistors, and have been put to practical use as individual microwave FETs. Furthermore, with the recent progress in thin film epitaxial growth techniques such as MBE and MOCVD, HEMTs using selectively doped heterojunctions have been developed as devices with higher speed performance. In order to operate these electronic devices at higher frequencies, it is necessary to shorten the gate length, increase mutual conductance, and reduce parasitic capacitance under the gate. Additionally, reducing the gate length can improve noise performance. Therefore, the gate length is usually 0.5
It is on the submicron order of ~1 μm. The short gates described above have been formed, for example, by the methods shown in FIGS. 2(a) to 2(c). That is, 1) First, a photoresist layer 11 is applied on the semiconductor substrate 10, and an opening 13 with a submicron width is formed (FIG. 2).
(a)). 2) Next, gate metal 12 is deposited on the entire surface (see FIG. 2(b)
)). 3) Next, the gate metal 12 and the photoresist layer 11 on the photoresist layer 11 are lifted off using acetone to form a gate electrode 14 with a submicron width (FIG. 2(c)).

0003

[Problems to be Solved by the Invention] However, the resolution of ordinary optical exposure methods is limited to about 1 μm, and in order to obtain submicron resist openings, reduction projection exposure methods or electron beam exposure systems are required. It is necessary to use very expensive equipment such as Furthermore, electron beam exposure apparatuses have low throughput and have problems with productivity.

0004

[Means for Solving the Problems] The present invention provides a method for manufacturing a semiconductor device that solves the above problems, and includes forming an insulating film on a semiconductor substrate, and then forming a desired pattern on the insulating film. forming a photoresist layer with
Using the photoresist layer as a mask, the insulating film is etched to cut into the underside of the photoresist layer to form a cut-in part, then an insulating film is laminated again, and then the insulating film on the photoresist layer is etched. and a step of lifting off the photoresist layer to form a desired void pattern made of the cut-in portions in the insulating film.

[0005]

[Operation] As mentioned above, when the insulating film is etched using the photoresist layer formed on the insulating film as a mask,
Since etching is performed isotropically, if the etching time is increased, the insulating film is etched to the bottom of the end of the photoresist layer in an undercut shape. Then, when the insulating film is laminated again, a gap portion corresponding to the undercut is created between this insulating film and the first insulating film. Next, when the photoresist layer is lifted off, the void portion of the insulating film can be used as an opening for a circuit pattern. Since the width of this gap portion is determined by the amount of undercut, a desired gap width on the order of submicrons can be obtained by controlling the etching time.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be explained in detail below based on embodiments shown in the drawings. FIGS. 1(a) to 1(g) are process explanatory diagrams of an embodiment of the method for manufacturing a semiconductor device according to the present invention,
A gate electrode of a GaAs MESFET was formed in the following manner. That is, 1) An n-type semiconductor layer 20 is formed on a semi-insulating GaAs substrate (not shown) by epitaxial growth or ion implantation, and a source electrode is formed thereon to make ohmic contact with a metal such as AuGe/Au. 21, a drain electrode 22 is formed (FIG. 1(a)). 2) Next, an insulating film 23 of SiO2 or SiNX is formed to a thickness of 2000 Å on the source electrode 21, drain electrode 22 and semiconductor layer 20 by thermal CVD method,
A photoresist layer 24 is formed thereon so that the end surface is between the source electrode 21 and the drain electrode 22 (see FIG.
(b)). 3) Next, using the photoresist layer 24 as a mask, the insulating film 23 is etched with buffered hydrofluoric acid for 40 seconds. Since the insulating film 23 is etched isotropically, by making the etching time longer, the insulating film 23 is etched so as to dig into the underside of the photoresist layer 24, thereby forming a digging part 29 (see FIG. 1). c)). 4) Next, an insulating film 25 is laminated over the entire surface. In this state, the insulating film 25 is not formed in the cut-in portion 29 (FIG. 1(d)). 5) Next, the insulating film 25 on the photoresist layer 24 is lifted off. Then, the width of only the cut-in part 29 is 0.
．． A gap 28 of 5 μm is created (FIG. 1(e)). 6) Next, a photoresist layer 26 is formed to define the shape of the gate electrode (FIG. 1(e)). 7) Next, a metal layer such as Au that forms a Schottky junction with the semiconductor layer 20 is deposited on the entire surface, unnecessary gate metal is lifted off, and a submicron-order gate electrode 2 is formed.
7 (Fig. 1(e)). Above, GaAs・MES
The explanation was given using FET as an example, but the semiconductor material is GaAs.
The material is not limited to, and other Group 3-5 compound semiconductors or Si may be used. Furthermore, in the above explanation, the etching of the insulating film 23 was performed using buffered hydrofluoric acid, but if the etching progresses isotropically, dry etching may be used. Good too.

[0007]

As explained above, according to the present invention, an insulating film is formed on a semiconductor substrate, a photoresist layer having a desired pattern is formed on the insulating film, and then the photoresist layer is Using the layer as a mask, the insulating film is etched to cut into the underside of the photoresist layer to form a cut-in part, and then the insulating film is laminated again, and then the insulating film and the photoresist on the photoresist layer are etched. In order to lift off the layer and form a desired void pattern consisting of the cut-in portions in the insulating film, the submicron order can be formed using conventional optical exposure methods without using expensive equipment such as reduction projection exposure equipment or electron beam exposure equipment. It has the excellent effect of being able to form a pattern. Therefore, a submicron gate electrode or a T-shaped gate electrode can be formed, and an electronic device with low gate resistance can be easily obtained.

[Brief explanation of the drawing]

FIGS. 1A to 1G are process explanatory diagrams of an embodiment of a method for manufacturing a semiconductor device according to the present invention.

FIGS. 2(a) to 2(c) are explanatory diagrams of steps for forming a conventional gate electrode.

[Explanation of symbols]

Claims (1)

[Claims] 1. An insulating film is formed on a semiconductor substrate, and then a photoresist layer having a desired pattern is formed on the insulating film, and then, using the photoresist layer as a mask, the insulating film is bonded to the photoresist. Etch to cut into the underside of the layer to form a cut-in portion, and then
A semiconductor device comprising the steps of laminating an insulating film again, then lifting off the insulating film on the photoresist layer and the photoresist layer, and forming a desired void pattern made of the cut-in portions in the insulating film. manufacturing method.