JP2697165B2 - Method for manufacturing semiconductor device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Summary] A method of manufacturing a semiconductor device, in particular, Schottky bonding to a compound semiconductor substrate by filling a groove provided in an insulating film on the substrate,
Also, the present invention relates to a method for forming a gate electrode having a laminated structure in order to enhance heat resistance, in which even if a crack occurs in a gate metal film bonded to a substrate at a ridgeline at the bottom of the groove, heat resistance is sufficiently ensured. Depositing a first metal film to be bonded to a substrate on a compound semiconductor substrate having an insulating film provided with a groove exposed on the surface of the substrate, and a first metal in the groove. Embedding a concave portion formed by the film with an insulating object; and forming a second metal film having lower resistance than the first metal film on the first metal film including on the insulating object, The structure is such that an electrode having a laminated structure is formed by filling the groove and joining to the substrate and using the first and second metal films.

[Industrial applications]

The present invention relates to a method for manufacturing a semiconductor device, and more particularly to a method for forming a gate electrode having a stacked structure in order to fill a groove provided in an insulating film on a compound semiconductor substrate and to form a Schottky junction with the substrate, and to improve heat resistance. About the method.

For the field effect transistor (FET) formed on a compound semiconductor substrate such as GaAs, the gate electrode that fills the groove provided in the insulating film on the substrate and is Schottky-bonded to the substrate is used to improve the heat resistance. A first metal film (for example, a tungsten silicide film or the like) of a refractory metal silicide or a high-melting metal formed by Schottky bonding and a second metal film (for example, a gold film) having lower resistance than the first metal film are stacked. Some are structured. When forming the gate electrode, it is important to ensure sufficient heat resistance.

[Conventional technology]

2 (a) to 2 (c) are cross-sectional views in the order of steps of a conventional example of a method of forming the gate electrode.

Referring to FIG. 1, first, referring to (a), a tungsten silicide (W) that is Schottky-bonded to a substrate 1 is formed on a GaAs substrate 1 having an insulating film 2 provided with a groove 3 exposed on the substrate.
A first metal film 4 of Si) is deposited by evaporation or sputtering. The thickness of the insulating film 2 and the width of the groove 3 are, for example, 30 respectively.
00 ° and 5000 °, and the thickness of the first metal film 4 is 1500 °. Note that 1a in the figure is an FET active region, and its formation is omitted because it is not directly related to the present invention.

Next, referring to (b), a titanium (Ti) film 5 having a thickness of 1000 ° and a gold (A) having a thickness of 1000
u) The second metal film 6 is deposited, and Au plating is added to
The thickness of the metal film 6 is set to 7000 to 8000 mm. Here Ti film 5
Are interposed to ensure the bonding of the second metal film 6 to the first metal film 4.

Next, referring to (c), the second metal film 6, the Ti film 5, and the first metal film 4 are patterned into the same
The formation of the stacked gate electrode 7 using the metal film 4 and the second metal film 6 is completed.

[Problems to be solved by the invention]

However, in the gate electrode 7 thus formed, as shown in the cross-sectional view of FIG. 3, the first metal film 4 is formed at the ridge at the bottom of the groove 3 due to the step formed by the groove 3.
When a crack 4a is generated in the second metal film 6 and heated to about 300 ° C., the metal (Au)
Have penetrated into the substrate 1 through the cracks 4a, causing deterioration of the gate breakdown voltage and short-circuiting. This disappoints the expectation of increasing the heat resistance in a laminated structure.

Therefore, the present invention relates to a method of manufacturing a semiconductor device, and more particularly, to a method of forming a gate electrode having a stacked structure for filling a groove provided in an insulating film on a compound semiconductor substrate and performing Schottky junction with the substrate, and improving heat resistance. It is an object of the present invention to ensure sufficient heat resistance even if a crack occurs in a gate metal film bonded to a substrate at a ridge portion at the bottom of the groove.

[Means for solving the problem]

The above object is to apply a first metal film of a high melting point metal silicide or a high melting point metal which is to be Schottky-bonded to a compound semiconductor substrate having an insulating film provided with a groove exposed on the substrate on the surface thereof, Filling a recess formed by the first metal film in the groove with an insulating object; forming a second metal film having lower resistance than the first metal film on the first metal film including on the insulating object; And forming a gate electrode having a stacked structure by using the first and second metal films to fill the groove and form a Schottky junction with the substrate.

(Operation)

As described above, the heat resistance of the conventional example could not be ensured because the second metal film was formed on the first ridge line at the bottom of the groove.
This is because the metal film is brought close to the metal film, which facilitates the penetration of the metal of the second metal film into the cracks generated in the first metal film.

On the other hand, in the present invention, since the insulating object is interposed between the first metal film and the second metal film at the ridge line at the bottom of the groove, even if the crack occurs, The penetration of the metal of the two-metal film is prevented, and the heat resistance is secured.

〔Example〕

Hereinafter, an embodiment of the present invention will be described with reference to the cross-sectional views in the order of steps shown in FIGS. The same reference numerals indicate the same objects throughout the drawings.

In this embodiment, the present invention is applied to the prior art.

That is, referring to FIG. 1, first, referring to FIG. 1A, a WSi for Schottky junction with a substrate 1 is formed on a GaAs substrate 1 having an insulating film 2 provided with a groove 3 which is exposed on the surface, as in the conventional example.
Is deposited by vapor deposition or sputtering. The thickness of the insulating film 2 and the width of the groove 3 are 3000
5000 °, and the thickness of the first metal film 4 is 1500 °. The formation of the FET active region 1a is omitted because it is not directly related to the present invention.

Next, referring to (b), SiO ₂ film 8 is formed on first metal film 4 by CVD method until Si 3 SiO ₂ is deposited so as to fill groove 3 and flatten the surface. . The deposition thickness is about 3000 ° except at the three grooves.

Next, referring to (c), the first metal film 4 on the insulating film 2 is formed.
The SiO ₂ film 8 is etched back until the surface is exposed to form an insulating object 9 of SiO ₂ filling the recess formed by the first metal film 4 in the groove 3. This insulating object 9 may be directly formed without etching back using bias sputtering or the like.

Next, referring to (d), similarly to the step of FIG. 2 (b) of the conventional example, a Ti film having a thickness of 100
A film 5 and a second metal film 6 of Au having a thickness of 1000 mm are deposited, and Au plating is added to make the thickness of the second metal film 6 7000 to 8000 mm.

Next, referring to (e), the second metal film 6, the Ti film 5, and the first metal film 4 are patterned into the same pattern as in the step of FIG. The formation of the stacked gate electrode 7 using the film 4 and the second metal film 6 is completed.

The gate electrode 7 formed in this manner has a crack 4a described in FIG.
Even if cracks occur, since the insulating object 9 is interposed between the first metal film 4 and the second metal film 6, penetration of the metal of the second metal film 6 into the crack 4a is prevented and heat resistance is improved. Is secured.

According to the confirmation of the present inventors, there was nothing that caused deterioration of the gate breakdown voltage or short-circuit even when heated to 500 ° C.

As can be easily understood from the above description, the present invention is not limited to the examples, and fills a groove provided in an insulating film on a compound semiconductor substrate, performs a Schottky junction with the substrate, and In order to increase the gate electrode thickness, a high melting point metal silicide or a high melting point metal may be used for the gate metal film to be bonded to the substrate, and the gate electrode may be applied to a case where a gate electrode having a laminated structure is formed. Material 9 is Si
Other than O ₂ , for example, Si nitride (Si ₃ N ₄ ) may be used.

〔The invention's effect〕

As described above, according to the configuration of the present invention, a method of manufacturing a semiconductor device, in particular, a method of filling a groove provided in an insulating film on a compound semiconductor substrate, performing a Schottky junction with the substrate, and stacking to improve heat resistance. Regarding a method for forming a gate electrode having a structure, even if a crack occurs in a gate metal film bonded to a substrate at a ridge portion at the bottom of the groove, heat resistance can be sufficiently ensured, and This has the effect of improving the quality of the semiconductor device.

[Brief description of the drawings]

1 (a) to 1 (e) are sectional views in the order of steps of the embodiment, FIGS. 2 (a) to 2 (c) are sectional views in the order of steps of the conventional example, and FIG. FIG. In the figure, 1 is a GaAs substrate (compound semiconductor substrate), 1a is an FET active region, 2 is an insulating film, 3 is a groove, 4 is a WSi first metal film, 4a is a crack, 5 is a Ti film, and 6 is an Au second. 7 is a gate electrode, 8 is a SiO ₂ film, 9 is a SiO ₂ insulating object.

Claims (1)

(57) [Claims] A step of depositing a first metal film to be bonded to a substrate on a compound semiconductor substrate having an insulating film provided with a groove exposed on the substrate on the surface thereof; Embedding a recess in the recess to be formed with an insulating object; and forming a second metal film having a lower resistance than the first metal film on the first metal film including the insulating object. A method for manufacturing a semiconductor device, comprising forming an electrode which is buried and bonded to the substrate and has a stacked structure using the first and second metal films.