JPH03155138A - Manufacture of mosfet - Google Patents

Abstract

PURPOSE:To eliminate the need for resist and thus simplify the manufacture of a device by forming transition-metal oxide on a gate oxide over a silicon substrate, exposing the metal oxide to an ion beam to make a pattern, etching away the exposed areas, and reducing the remaining area. CONSTITUTION:Gate oxide 2 is formed, for example, on the surface of a lightly doped n-type substrate 1 by a heat treatment. Polysilicon film 3 and transition- metal oxide such as MoO3 film 7 are provided on the gate oxide. The MoO3 film 7 is exposed to a scanning ion beam 8 with a mask. The exposed areas are etched away by alkali solution, and the remaining area is an upper gate electrode 7a. The polysilicon 3 is masked the gate electrode 7a and etched to form a lower gate electrode 3a. B<+> ions 10 are implanted to form a source 11 and a drain 12 in the substrate 1. MoO3 in the gate electrode 9 is reduced in an H2 atmosphere and then heated so that it is converted to silicide.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for manufacturing a MOSFET, and more particularly to a method for manufacturing a MOSFET that simplifies the photolithography process.

[Conventional technology]

FIG. 2 is a diagram showing a conventional method for manufacturing a MOSFET, showing a photolithography process for forming a gate portion of the MOSFET. First, a silicon oxide film (SiOz) 2 that will become a gate oxide film is formed on the surface of a silicon substrate 1.
is formed by heat treatment, and a polysilicon film 3 and a molybdenum (Mo) film 4 are laminated thereon (FIG. 2(a)).
. Next, a photoresist (positive beam resist) 5 is coated on this molybdenum film 4, and an electron beam is irradiated and scanned from the top surface of the resist 5 to expose it to a mask pattern (FIG. 2(b)). .

Thereafter, the resist 5 is developed to remove the exposed portion (FIG. 2(C)), and the molybdenum film 4 and polysilicon film 3 are etched using the remaining resist 5a as a mask to form gate electrode parts 3a, 4a (FIG. 2(C)). Figure 2(d)). Thereafter, the resist 5a was removed to form the gate electrode portion 6 (FIG. 2(e)).

[Problem to be solved by the invention]

However, this conventional MOSFET gate forming process involves a photoresist coating process, a development process, and a removal process, and therefore requires a large number of processes and takes a long time.

Furthermore, the pattern accuracy was not very high due to side etching problems.

An object of the present invention is to provide a method for manufacturing a MOSFET that eliminates the use of resist and solves the above-mentioned problems.

[Means to solve the problem]

To this end, the present invention includes a step of forming a transition metal oxide film on a silicon substrate via a gate oxide film, a step of pattern-exposing the transition metal oxide film with an ion beam,
The method includes a step of etching away the exposed transition metal oxide film, and a step of reducing the transition metal oxide film left as a gate by the etching.

〔Example〕

Hereinafter, a method for manufacturing a MOSFET according to an embodiment of the present invention will be described. FIG. 1 is a diagram showing a process of forming a gate portion of a MOSFET according to the present invention. First, a silicon oxide film (SiO□) 2 with a thickness of 300 nm, which will become a gate oxide film, is formed on the surface of an n-type low concentration silicon substrate l by heat treatment, and a 1000 to 2000 nm thick silicon oxide film (SiO□) 2 is formed on the top surface to stabilize the interface. A polysilicon film 3 is deposited for oxidation.

In this embodiment, molybdenum oxide (MOO:l) 'fl'J 7 with a thickness of 2,000 to 3,000 people is deposited as a transition metal oxide on the upper surface of the polysilicon film 3 (see FIG. 1(a)). ). This transition metal oxide is Mo5
3, CrO2, W(h2, VzOs, Ti0z or mixtures thereof also containing Mo03, or Ta20
5 and others can be used. These metal oxides are deposited by vacuum deposition. In this case, electron beam evaporation,
Either resistance heating vapor deposition or flash light vapor deposition is effective, but in either case, temperature control (e.g. 150 to 200
℃) to make the transition metal oxide amorphous.

Next, the ion beam 8 is irradiated and scanned from above this MoO2 film 7 to expose the MoO3 film 7 in a predetermined mask pattern (FIG. 1(b)). This ion beam 8 has a beam diameter accelerated by several to several tens of KeV, and has extremely low scattering compared to an electron beam, so that resolution can be improved. Note that this ion beam is
For example, Ga'', Ar1, Ls'', etc. are used. By irradiating this ion beam 8, amorphous MoO
The s-film 7 is bombarded by ions having a large mass (approximately 1800 times as large as electrons), and its structure suddenly changes at a certain threshold dose.

Next, the entire structure is etched with an alkaline solution such as NaOH to remove the mob and film 7 portions irradiated by the ion beam 8 (FIG. 1(C)). However, transition metal oxides such as T'azOs and v20. In this case, HF is used.

Incidentally, regarding this MoO3, the etching treatment can also be performed by heat treatment (about 600° C.).

The Mob and film 7 left behind by this etching become the upper layer gate electrode portion 7a.

Next, using this gate electrode portion 7a as a mask, the polysilicon film 3 is removed by etching (FIG. 1(d)) L, to form a lower layer gate electrode portion 3a. The above gate electrode part 7a,
A gate electrode 9 is formed by 3a. Subsequently, a B ion beam 10 is implanted to form a source 11 and a drain 12 in the silicon substrate 1 (FIG. 1(e)). After that, the gate electrode 9 mob.

is reduced in an H3 atmosphere, and then heat-treated to alloy it with polysilicon and transform it into silicide (Fig. 1 (
f)).

In FIG. 1(f), 13 is PSG as an insulating film between the eyebrows, and 14 is A for the source electrode connected to the source 11.
Reference numeral 15 indicates an Al interconnect for a drain electrode connected to the drain 12, and reference numeral 16 indicates an SiO2 film in the field portion formed by the LOCO5 process. The LOGO5 process was omitted in the explanation of FIGS. 1(a) to (el) above.

The MOS FET manufacturing method described above does not use the photoresist that was conventionally required when forming the gate electrode, so there is no need for a process related to the resist.
Manufacturing time can be significantly shortened.

Furthermore, since a pattern is drawn directly on the transition metal oxide film that forms part of the gate electrode 9 without using a resist, problems such as side etching caused by the use of the resist are eliminated, and pattern accuracy is improved. This can be further improved by reducing the diameter of the ion beam to the submicron order.

Further, since the polysilicon forming the gate electrode 9 and the transition metal are alloyed and silicided, the gate electrode can be wired with low resistance.

〔Effect of the invention〕

As described above, according to the present invention, there is an advantage that the manufacturing process can be simplified and the manufacturing time can be shortened by eliminating the need for resist, and that a MOSFET with high precision can be realized.

[Brief explanation of the drawing]

FIG. 1 is a process diagram showing a method of manufacturing a MOSFET according to an embodiment of the present invention, and FIG. 2 is a process diagram showing a method of manufacturing a gate portion of a conventional MOSFET. Process...Silicon substrate, 2...Silicon oxide film (Si
3... Polysilicon film, 3a... Gate electrode part, 7... Molybdenum oxide (MOO3) film, 7a.
...Gate electrical grinding part, 8...Ion beam, 9...Gate electrode, 10...Boron ion beam, 11...
Source, 12...Drain, 13...PSG, 14
．． 15... Al wiring, 16... 5i of field part
Oz film.

Claims (1)

[Claims] (1) A step of forming a transition metal oxide film on a silicon substrate via a gate oxide film, a step of pattern-exposing the transition metal oxide film with an ion beam, and a step of exposing the exposed transition metal oxide film to an ion beam. A MOSFE comprising: a step of removing by etching; and a step of reducing the transition metal oxide film left as a gate by the etching.
Method for manufacturing T.