JP2667840B2 - Method for manufacturing compound semiconductor device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION The present invention relates to a method for manufacturing a compound semiconductor device, and more particularly to a method for manufacturing an integrated circuit using gallium arsenide. It provides a manufacturing method. [Prior Art] Conventionally, a method of manufacturing a field effect transistor used for a compound semiconductor integrated circuit is to coat an insulating heat-resistant film such as a silicon nitride film as described in, for example, JP-A-58-157172. It included the step of wearing and heat treating. [Problems to be Solved by the Invention] In the above prior art, as shown in FIG. 2 (a), a conductive layer 2 is formed on a GaAs substrate 1 by ion implantation, and then a heat-resistant coating 3 is applied and heat treatment is performed. , Activate impurities. Next, as shown in FIG. 2 (b), the heat-resistant coating was removed, and TiN,
A heat resistant metal 4 such as WSi is deposited, and then FIG. 2 (c).
As described above, the heat resistant metal was processed to form the gate electrode 5. In the above prior art, a structure in which the gate electrode 5 directly contacts the substrate 1 other than the conductive layer 2 is formed. For this reason, there is a problem that there is much unnecessary leak current (gate leak current) between the substrate and the gate electrode. In order to avoid this problem, as shown in FIG. 3 (a), heat treatment is performed in the same state as shown in FIG. 3 (a) as shown in FIG. Although the removal method is conceivable, even in this method, since the photoresist pattern has an alignment error, the positions of the holes in the conductive layer and the heat-resistant film do not coincide with each other, and as shown in FIG. The electrode 5 is the substrate 1
It is inevitable to contact with the gate leakage current. An object of the present invention is to provide a method for manufacturing a compound semiconductor device having a field-effect transistor with a small gate leakage current. [Means for Solving the Problems] The above object is achieved by using a plurality of heat-resistant coatings that can be selectively etched during heat treatment so that the gate electrode and the substrate do not come into contact with each other. To be done. [Operation] That is, prior to ion implantation, a silicon nitride film and a silicon oxide film, which are heat-resistant films, are laminated and applied, and a predetermined portion of the silicon oxide film is removed to expose the silicon nitride film. Thereafter, if ion implantation is performed, impurities are ion-implanted only through the portion where the silicon oxide film has been removed through the silicon nitride film. Thereafter, by performing a heat treatment and selectively removing only the silicon oxide film, the structure shown in FIG. 3C is formed without displacing the positions of the holes in the conductive layer 2 and the heat-resistant film 3. If the gate electrode 5 is formed thereafter, the gate electrode 5
And the substrate 1 do not come into contact with each other. [Examples] The present invention will be described below with reference to Examples. First, a reference example of the present invention will be described with reference to FIG. As shown in FIG. 1 (a), a silicon nitride film 6 was applied to a thickness of 2000 ° on a semi-insulating GaAs substrate 1, and a predetermined portion was etched and removed using CF ₄ gas using a photoresist as a mask. . Next, as shown in FIG. 1B, Si ions were implanted using the silicon nitride film as a mask to form a conductive layer 2.
Next, as shown in FIG. 1 (c), a silicon oxide film 7 was applied at 3000 ° C. and heat-treated at a temperature of 800 ° C. to activate the implanted Si ions. Next, as shown in FIG. 1D, only silicon oxide was selectively removed using hydrofluoric acid, a tungsten silicide film 8 was deposited, and a gate electrode 5 was formed as shown in FIG. 1E. . In such a method, the positions of the holes in the conductive layer 2 and the silicon nitride film 6 almost completely coincide with each other, so that the gate electrode 5 does not contact the substrate 1. [Embodiment 1] FIG. 4 is a diagram for explaining Embodiment 1 according to the present invention.
As shown in FIG. 4 (a), a silicon nitride film 6 and a silicon oxide film 7 were laminated on a semi-insulating GaAs substrate 1. Next, as shown in FIG. 4 (b), only the silicon oxide film 7 is partially removed using hydrofluoric acid with the photoresist as a mask.
Si ions are implanted through the exposed silicon nitride film 6,
The conductive layer 2 was formed. 4th after heat treatment at 800 ℃
As shown in FIG. 2C, the silicon nitride 6 was etched and removed using CF ₄ gas using the silicon oxide film 7 as a mask. Next, if only the silicon oxide film 7 is selectively removed with hydrofluoric acid and a tungsten silicide film 8 is applied, a structure similar to that shown in FIG. 1D is obtained. Then, if the tungsten silicide film 8 is processed,
As in FIG. 1E, a structure in which the gate electrode 5 does not contact the substrate 1 is obtained. In this method, the GaAs crystal is not exposed in the ion implantation step, and it becomes easy to prevent impurity contamination. [Effects of the Invention] As described above, according to the present invention, a structure in which the gate electrode is in contact with only the conductive layer and not in contact with the substrate can be formed, so that a field-effect transistor with small gate leak current can be obtained. According to the present embodiment, the silicon oxide film and the silicon nitride film are used as the heat-resistant film. However, a combination of a plurality of heat-resistant films that can be selectively etched, such as an aluminum oxide film and an aluminum nitride, can be used. is there. Although a GaAs crystal was used as a substrate, GaP, In which can form an integrated circuit using a Schottky gate electrode field effect transistor is used.
Of course, it can be applied to P, GaAlAs and the like.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 shows a reference example of the present invention, FIG. 4 shows a first embodiment of the present invention, and FIGS. 2 and 3 show conventional examples. 1 ... GaAs substrate, 2 ... conductive layer, 3 ... heat resistant coating, 4
... heat-resistant metal, 5 ... gate electrode, 6 ... silicon nitride film, 7 ... silicon oxide film, 8 ... tungsten silicide film.

Claims (1)

(57) [Claims] Stacking and depositing a silicon nitride film and a silicon oxide film in this order on a semi-insulating GaAs substrate; removing a portion of the silicon oxide film to expose the silicon nitride film; Implanting ions through the exposed portion of the silicon nitride film and the silicon oxide film, a step of activating the ion-implanted impurities by heat treatment in a state of being covered with the silicon oxide film, and after the activation step, Removing the exposed portion of the silicon nitride film to expose the ion-implanted portion; removing the exposed portion of the silicon nitride film after removing the exposed portion of the silicon oxide film; and removing the exposed portion by the removing step. A method for manufacturing a compound semiconductor device, comprising a step of forming a gate electrode of a field effect transistor on an ion implantation part and the silicon nitride film.