JPH0258338A - Manufacture of semiconductor element - Google Patents

Abstract

PURPOSE:To narrow between ohmic electrodes and to shorten the length of a gate by removing a mesa structure by etching a substrate layer from the face from which an insulating film is removed, forming a recess structure between ohmic metal films, and forming a gate electrode metal film by utilizing lift-off by the insulating film on the structure. CONSTITUTION:An insulating film 5 is formed on a surface by a plasma CVD or the like, coated with resist 6 in thickness for flattening the surface, removed to a thickness for presenting the film 5 on the surface on a reverse mesa structure 3 by ashing or the like, and the film 5 presented on the surface is removed by etching. Then, the structure 3 is removed by etching a substrate layer 1, and a recess structure 7 is formed between ohmic electrode metal films 4. Thereafter, a metal film 8 is deposited on the surface, lifted OFF by the film 5 on a recess structure 7, the film 5 is partly removed by etching, the resist 6 is dissolved, the film 8 on the resist 6 is removed, and the remaining film 5 is further removed by etching. Accordingly, a gate electrode 8 in which the length of a gate with the structure 7 is narrower than the width of a resist pattern is obtained.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention is applicable to gate length devices with a recess structure between ohmic electrodes, such as FETs and HEMTs used for signal amplification in the microwave band. The present invention relates to a method of manufacturing a semiconductor device having a short gate electrode.

[Conventional technology]

In FETs, HEJ/RRs, etc. used in the microwave band, it is necessary to reduce the gate electrode width, which is called the gate length. In addition, to increase the speed, it is necessary to increase the mutual conductance gm, and to achieve high gm, it is important to reduce the series resistance Rs between the source and gate. There is something.

Below, an example of the conventional manufacturing method for this type of semiconductor device will be explained in the third section.
This will be explained using figures.

As shown in the figure (, ), a semiconductor substrate (QAAs substrate) I
Form ohmic 1/4 by K lift-off method etc.
Next, as shown in Figure (b), the resist 15 is completely coated,
A gate gloss turn 16 is formed on the renost 15 in alignment with the all-ohmic electrode 11, as shown in FIG.
As shown in FIG. 3, a recess structure 7 is formed by etching.

Next, as shown in Figure (d), a metal film 8 is deposited on the surface, and using lift-off by the resist I5, the resist 15 is dissolved and removed using an organic solvent or the like. As shown in FIG. 8(e), the entire gate electrode 8 is formed in the recess structure 7 by a method of removing the entire gate electrode 8.

[Problem to be solved by the invention]

The conventional method described above requires alignment of the ohmic electrode and the r-t electrode, and usually takes into consideration the pitch deviation during alignment, and the gap between the ohmic electrodes (source and drain electrodes) cannot be completely narrowed, resulting in a resistance called Rs. Can't make it smaller. In addition, electrode gate patterning is done by phosphorography, but even if deep ultraviolet light is used, the gate length is limited to about 0.5 μm, and shortening the gate length is necessary to improve microwave characteristics. Setting the gate length to 0 even though it is necessary
．． There was a problem in that it was difficult to reduce the thickness to 5 μm or less.

The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a method that can narrow the distance between ohmic electrodes and shorten the cable length compared to conventional methods.

[Means to solve all problems]

The method of the present invention is to form an inverted mesa structure under a resist with a narrow width/turn by etching a semiconductor substrate by utilizing the plane orientation of the crystal of the substrate, and to prevent lift-off by the resist on this inverted mesa structure. An ohmic electrode metal film is formed on both sides of the inverted mesa structure, an insulating film is formed to cover the ohmic electrode metal film and the inverted mesa structure, and a resist is applied on this insulating film to a thickness that makes the surface flat. The insulating film on the upper inverted mesa structure is removed by ashing until it appears on the surface, and the insulating film that appears on the surface is removed by etching. The mesa structure is removed by etching the substrate layer from the removed surface, a recess structure is formed between the ohmic metal films, and a gate electrode metal film is formed in this recess structure by utilizing the lift-off caused by the insulating film on the recess structure. It is something.

[Effect]

According to the above method, the distance between the ohmic electrodes is approximately equal to the line width of the resist/mother turn for forming the entire inverted mesa structure, and the r-) length is narrower than the line width of the turn/or turn. Pitch deviation during alignment? There is no need to consider it.

〔Example〕

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

As shown in Figure (1), resist holes and turns 2 with narrow line widths are formed on the surface of the semiconductor substrate 1 by phosphorography,
By etching, as shown in (b), an inverted mesa structure 3 is formed under the resist pattern 2, and a gold pattern film 4 is formed on the surface.
The ohmic electrode metal film 4 is entirely formed on both sides of the inverted mesa structure 3 by vapor depositing the metal film 4, list-off the metal film 4 with the resist 2 on the inverted mesa structure 3, and dissolving and removing the resist 2.

An inverted mesa structure can be obtained by etching using the crystal orientation of the substrate. The second one shows an example using a GaAs substrate.

Next, as shown in Figure (c), an insulating film 5 is formed on the surface by Glazma CVD or the like, and as shown in Figure (d),
A resist 6 is applied on the insulating film 5 to a thickness that makes the surface flat, and the resist 6 is removed by ashing etc. so that the insulating film 5 on the inverted mesa structure 3 is on the surface, as shown in Figure (e). As shown in Figure (f), the insulating film 5 appearing on the surface is removed by etching, and then the inverted mesa structure 3 is removed by etching the substrate layer 1 to form an ohmic electrode metal film. 4, the recess structure 7 is completely formed.

Next, as shown in Figure (tr), a metal film 8 is deposited on the surface and lifted off by the insulation film 5 on the recessed structure 7, and as shown in Figure (h), the insulation film 5 is partially etched. As shown in Figure (i), the resist 6 is dissolved with an organic solvent or the like, and the deposited gold and metal film 8 on the resist 6 are removed together with the resist 6, and then as shown in Figure (j), The remaining insulating film 5 is removed by etching.

By the above method, the ohmic electrode 4 is placed over the entire distance approximately equal to the width of the resist pattern 2 using the sonography method.
The gate length with the recess structure 7 formed between the ohmic electrode 4 and the ohmic electrode 4 is the same as the above-mentioned length. An r-t electrode 8 narrower than the turn width is obtained.

〔Effect of the invention〕

As explained above, according to the present invention, with the recessed structure,
The space between the source and drain/electrode is narrower than the conventional one, and
The gate length can be shortened, contributing to the improvement of microwave characteristics called N, F, and Ga1n (noise figure gain), which are important as microwave amplification elements. 2 is an explanatory diagram showing an example of an inverted mesa structure in the method of the invention, and FIG. 3 is a sectional view showing a conventional manufacturing method.

1... Semiconductor substrate, 2... Resist 74' turn,
3... Inverted mesa structure, 4... Ohmic electrode metal film,
5... Insulating film, 6... Resist, 7... Recessed structure, 8... Gate electrode metal film.

Note that the same reference numerals in the figures indicate the same or corresponding parts.

Claims (1)

[Claims] In a method of manufacturing a semiconductor device having a short gate electrode with a recess structure between ohmic electrodes, a semiconductor substrate is etched to form a narrow pattern under a resist by using the plane orientation of the crystal of the substrate. a step of forming a mesa structure; a step of forming an ohmic electrode metal film on both sides of the inverted mesa structure using lift-off by a resist on the inverted mesa structure; and an insulating film covering the ohmic electrode metal film and the inverted mesa structure. A process of forming a resist on the insulating film to a thickness that makes the surface flat, and a process of applying the applied resist to a thickness such as ashing so that the insulating film on the inverted mesa structure appears on the surface. The insulating film appearing on the surface is removed by etching, and the inverted mesa structure is removed by etching the substrate layer from the surface where the insulating film is removed, forming a recess structure between the ohmic electrode metal films. and forming a gate electrode metal film on the recessed structure using lift-off caused by an insulating film on the recessed structure.