JPH0661265A - Formation of schottky junction gate - Google Patents

Abstract

PURPOSE:To make low gate resistance possible, to improve adhesion between a protecting film and a low resistance metal and to make selfmatching decision of gate configuration possible by plating a barrier metal inside a Schottky gate electrode region with a low resistance metal, by forming an adhesive metal thereon, and so forth. CONSTITUTION:An operational layer 2 and an insulating layer 3 are formed one by one on a gallium arsenic substrate 1 and a groove is formed in a Schottky gate electrode formation region by patterning the insulating film 3. A heat resistant metal 4 and a barrier metal 5 are formed one by on all over including the exposed operational layer 2, plating of a low resistance metal 6 is applied to the barrier metal 5 inside the Schottky gate electrode region and an adhesive metal 7A of good adhesion with a protecting film 9 is formed on the low resistance metal 6. After the heat resistant metal 4 and the barrier metal 5 outside the Schottky gate electrode region are removed by dry-etching an entire surface and a surface of the adhesive metal 7A inside the Schottky gate electrode region is scraped, the protecting film 9 is formed all over.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of forming a Schottky gate, and more particularly to a method of forming a gate of a field effect transistor.

[0002]

2. Description of the Related Art As a conventional method of forming a low resistance Schottky gate, an example of using gallium arsenide as a semiconductor is shown in FIG.
A description will be given using (a) to (c).

First, as shown in FIG. 3A, the operation layer 2
After depositing the insulating film 3 on the gallium arsenide substrate 1 having, the photoresist is patterned. Next, using the photoresist as a mask, the insulating film 3 is selectively etched and removed so as to obtain a desired opening, and the operating layer 2 is exposed.

Next, as shown in FIG. 3B, a refractory metal 4 such as tungsten silicide is deposited on the entire surface forming the Schottky junction with gallium arsenide by a sputtering method, and then a barrier metal 5 made of platinum or the like. Put on,
Subsequently, a low resistance metal 6 such as gold is deposited, and further a metal 7 such as Ti (titanium) or TiN (titanium nitride) is deposited. Then, the photoresist 8A is patterned so as to cover the opening, and using it as a mask, as shown in FIG. 3C, the metal 7, the low resistance metal 6, the barrier metal 5, and the like.
The heat resistant metal 4 and the insulating film 3 are removed by etching to form a Schottky gate (electrode), and then a protective film 9 is deposited on the surface thereof.

Ti or TiN is deposited on a low resistance metal 6 such as gold.
It is necessary to adhere the metal 7 such as the above in order to improve the adhesion between the protective film 9 and the low resistance metal 6.

[0006]

In the conventional method of forming the Schottky gate electrode described above, when a low resistance metal is thickly formed in order to reduce the resistance of the gate especially when the gate length is small, the coverage by the sputtering method is increased. Poorly, there was a problem that the resistance was not necessarily lowered because a nest (cavity) was formed in the gate.

[0007]

A method of forming a Schottky gate electrode according to the present invention comprises a step of sequentially forming an operating layer and an insulating film on a gallium arsenide substrate, and patterning the insulating film to form a Schottky gate electrode. A step of forming a groove in the region, a step of sequentially forming a refractory metal and a barrier metal on the entire surface including the exposed operation layer, and a step of plating a low resistance metal on the barrier metal in the Schottky gate electrode region. Depositing Ti on the low resistance metal,
Dry etching such as milling is performed on the entire surface to remove the refractory metal and the barrier metal outside the Schottky gate electrode region and the T inside the Schottky gate electrode region.
The step of scraping the surface of i and the step of forming a protective film on the front surface are included.

Further, in the above-mentioned forming method, after the step of depositing Ti on the low resistance metal, a step of implanting nitrogen ions into the surface to form TiN, and the entire surface is subjected to dry etching such as milling to obtain the shot. The process may include removing the refractory metal and the barrier metal outside the key gate electrode region, removing the surface of the TiN in the Schottky gate electrode region, and forming a protective film over the entire surface.

[0009]

The present invention will be described below with reference to the drawings.

FIGS. 1A to 1C are sectional views of a semiconductor chip showing a first embodiment of the present invention in the order of steps.

First, as shown in FIG. 1A, an insulating film 3 having a desired opening is formed on a gallium arsenide substrate 1 having an operating layer 2.

Next, as shown in FIG. 1B, 100 n of tungsten silicide or the like forming a Schottky junction is formed.
Heat-resistant metal 4 and film thickness 15 of about m (nanometer)
A barrier metal 5 of about 0 nm made of platinum or the like is deposited by the sputtering method. Then, a photoresist 8 having an opening width wider than the opening is formed. The photoresist 8 has a thickness of 2 μm or more, and the opening is inversely tapered by the image reverse method. Heat-resistant metal 4
Further, a metal as the low resistance metal 6 is formed to a thickness of about 400 nm by selective gold plating using the barrier metal 5 as a power supply layer, and then a Ti film 7A is vapor-deposited to a thickness of 500 to 600 nm. After that, the resist 8 and the Ti7A film on the resist 8 are removed by the lift-off method.

Next, as shown in FIG. 1C, dry etching such as milling is performed on the entire surface to remove the exposed portion of the power feeding layer made of the refractory metal 4 and the barrier metal 5. At that time, Ti7A on the gold plating is left to have a film thickness of at least 50 nm. Then, the protective film 9 is deposited.

FIGS. 2A and 2B are sectional views of a semiconductor chip showing a second embodiment of the present invention in the order of steps.

FIG. 2 (a) of the second embodiment shows that after the steps described in FIGS. 1 (a) and 1 (b) of the first embodiment, nitrogen ions are implanted into the surface to form TiN7B. Form.

Then, as shown in FIG. 2B, dry etching such as milling is performed on the entire surface to remove the exposed portions of the power feeding layers 4 and 5, and then the insulating film 3 is removed by wet etching. At this time, TiN is left to have a thickness that can withstand the wet etching of the insulating film 3, at least a film thickness of 50 nm. After that, the protective film 9 is deposited.

Since the insulating film 3 is removed in this embodiment, the gate capacitance is reduced and the characteristics of the field effect transistor are improved.

[0018]

As described above, according to the present invention, the low resistance metal 6 of the Schottky gate electrode is plated with gold to eliminate cavities (cavities), so that the gate resistance can be lowered and the gold plating can be performed. By leaving Ti (titanium) or TiN (titanium nitride) in the film, it is possible to improve the adhesion to the protective film and to determine the gate shape in a self-aligned manner.

[Brief description of drawings]

FIG. 1 is a sectional view of a semiconductor chip showing a first embodiment of the present invention in process order.

FIG. 2 is a sectional view of a semiconductor chip showing a second embodiment of the present invention in process order.

FIG. 3 is a cross-sectional view of a semiconductor chip showing a method of the related art in the order of steps.

[Explanation of symbols]

 1 gallium arsenide substrate 2 operating layer 3 insulating film 4 heat resistant metal 5 barrier metal 6 low resistance metal 7,7A metal 8,8A photoresist 9 protective film

Claims (3)

[Claims] 1. A step of sequentially forming an operating layer and an insulating film on a gallium arsenide substrate, and a step of patterning the insulating film to form a groove in a Schottky gate electrode formation region.
A step of sequentially forming a refractory metal and a barrier metal on the entire surface including the exposed operation layer, a step of plating a low resistance metal on the barrier metal in the Schottky gate electrode region, and a protective film on the low resistance metal. By the process of forming an adhesion metal having good adhesion with and the whole surface by dry etching,
A step of removing the refractory metal and the barrier metal outside the Schottky gate electrode area, a step of shaving the surface of the adhesion metal in the Schottky gate electrode area, and a step of forming a protective film on the entire surface. Method of forming Schottky gate. 2. The method of forming a Schottky gate according to claim 1, wherein the adhesion metal having good adhesion to the protective film is titanium, which is formed by vapor deposition. 3. The Schottky gate electrode is formed by using a step of implanting titanium ions on the surface to form titanium nitride after the step of depositing titanium on the low resistance metal, and a dry etching such as milling on the entire surface. 3. The method of forming a Schottky gate according to claim 2, including a step of removing the surface of the titanium nitride in the region and a step of forming a protective film on the entire surface.