JPS62163333A - Plasma oxidation method and device thereof - Google Patents

Abstract

PURPOSE:To enable mask-less selective oxidation at a low temperature on the surface of a semiconductor through a plasma oxidation method combining electron beam irradiation. CONSTITUTION:A gas containing oxygen gas is introduced from a gas introducing port 2, and pressure in a vacuum tank is controlled at several Torr-10<-4> Torr. The introduced gas is excited by microwaves in a chamber 4, and oxygen plasma is generated. Since the periphery of a susceptor 7 is changed into the after-glow space of oxygen plasma, the periphery of the susceptor is filled with rich oxygen radicals. The surface of a work 8 consisting of a semiconductor is irradiated by electron beams from an electron-beam irradiation mechanism 5 under said conditions. The formation of an oxide progresses on the surface of the semiconductor in the presence of oxygen radicals and electrons.

Description

[Detailed Description of the Invention] [Summary] A method of thermal oxidation using a nitride film as a mask is exclusively used as a method of forming a selective oxide film on the surface of a semiconductor such as silicon. This causes problems such as integration and generation of defects.

The present invention describes a method of forming a selective oxide film at low temperature and without using a mask by applying an electron beam irradiation method and a plasma oxidation method.

[Industrial application field]

The present invention relates to a method and apparatus for performing selective oxidation using plasma at low temperatures without using a mask.

As a means for selectively forming an oxide film on the surface of silicon, a method is exclusively used in which a nitride film mask is stacked and oxidation is performed at high temperature in an atmosphere containing oxygen gas.

Anodic oxidation is a wet method for forming an oxide film other than thermal oxidation, and plasma oxidation is a dry method, but this method has the problem that a nitride film mask cannot be used.

In the case of GaAs as a semi-molar compound, like Si, there is a problem in which high temperature oxidation cannot be applied, and there is a demand for the development of a selective oxidation method at low temperatures.

(Prior Art) As a method for oxidizing semiconductor materials without exposing them to a high-temperature atmosphere, a method has been developed in which a semiconductor device is oxidized in oxygen plasma.

With this method, for example, it is possible to form an oxide film on the entire surface of the Si surface, but as in the case of thermal oxidation,
Even if selective oxidation is performed using the film as a mask, S i 3 N
4 membrane does not function as a mask. The problem is the development of mask materials.

As a selective oxidation method that does not use a mask, a method in which a substrate is irradiated with an electron beam in an oxygen atmosphere and only the irradiated area is selectively oxidized has been used, but this method has the disadvantage that the oxidation rate is low.

[Problem that the invention seeks to solve]

In the conventional methods described above, a selective oxidation method at low temperatures has not yet been established.

Alumina (A120.) film has been found to be effective as a mask material used in plasma oxidation.
This causes problems such as formation of a bubble in the Al2O3 film and removal of the Al2O3 film after oxidation.

The electron beam irradiation method can selectively oxidize a specific region by scanning the beam and does not require a mask, but the slow oxidation rate makes it difficult to put it into practical use.

[Means for solving problems]

The above-mentioned problems are solved by the oxidation method and apparatus of the present invention, which uses an electron beam to eliminate the need for a mask, while also using an oxygen plasma to increase the oxidation rate.

In the oxidation method, the workpiece is placed on a support stand installed in an afterglow space of plasma containing at least oxygen, and the workpiece is selectively irradiated with an electron beam. An oxide film can be formed in the irradiated area.

As the device, a vacuum chamber that accommodates a support on which the workpiece is placed has at least a gas introduction hole and a gas discharge hole;
A chamber for exciting plasma and a mechanism for irradiating the workpiece with an electron beam are provided.

In the above structure, the chamber is installed on the gas 4 inlet side of the vacuum chamber, and is spatially isolated from the vacuum chamber side where the workpiece is installed by a connecting plate that blocks electromagnetic waves and allows plasma to freely pass through. It has a built-in structure.

[Effect]

Electron beam irradiation to a semiconductor is performed not in an oxygen atmosphere but in an afterglow space of oxygen plasma, that is, an atmosphere rich in oxygen radicals.

It is not clear how electrons generated by an electron beam and oxygen radicals cause a physicochemical reaction on the surface of a semiconductor material. However, it has been found that the oxidation reaction is significantly accelerated as a result.

〔Example〕

An embodiment according to the present invention will be described in detail with reference to the drawings. The drawing schematically shows a cross section of a plasma oxidation apparatus used in the present invention. The main parts and functions of the structure will be explained below with reference to the drawings.

In the drawing, 1 is a vacuum chamber, 2 is a gas introduction hole, 3 is a gas discharge hole, 4 is a chamber for plasma generation, 5 is an electron beam irradiation mechanism, 6 is a microwave introduction tube, and 7 is a support stand. The main parts are configured.

A workpiece 8 made of a semiconductor material is mounted on a support base 7, and a voltage can be applied by a voltage #9 as needed.

The microwave introduction pipe 6 receives 2.
A high frequency of 45 GHz is supplied, and microwave power is irradiated into the chamber 4 through the dielectric window 10 .

Four gases containing oxygen gas are introduced through the gas introduction holes 2, and the pressure inside the vacuum chamber is controlled to fiTorr "10-'Torr".
Wholesale.

The introduced gas is excited by microwaves in the chamber 4 to generate oxygen plasma.

The chamber is isolated from the main part of the vacuum chamber by a shielding plate 11 made of a metal mesh or a metal plate with many holes, and microwaves are blocked, but plasma can freely pass through to the work area. spread to.

The area around the support base 7 is an after-glow space of oxygen plasma and is therefore filled with abundant oxygen radicals.

The surface of the semiconductor workpiece 8 is irradiated with an electron beam from the electron beam irradiation mechanism 5 under the above conditions. Due to the presence of oxygen radicals and electrons, oxide formation progresses on the surface of the semiconductor.

In this case, the reaction is promoted by applying a voltage of 20 to 100 V from the power source 9 to the workpiece.

By scanning the electron beam according to a predetermined pattern,
A selective mucooxide film can be formed in a specific region.

With the above method, it is possible to form a semiconductor oxide film without heating the workpiece or requiring a mask, and it is possible to form an oxide film not only on Si but also on compound semiconductors such as GaAs.

〔Effect of the invention〕

As explained above, the plasma oxidation method combined with electron beam irradiation of the present invention produces a low Maskless selective oxidation is now possible with L.

[Brief explanation of drawings]

The drawing schematically shows a structural cross-sectional view of a plasma oxidation apparatus according to the present invention. In the drawings, 1 is a vacuum chamber, 2 is a gas introduction hole, 3 is a gas discharge hole, 4 is a chamber, 5 is an electron beam irradiation mechanism, 6 is a microwave introduction tube, 7 is a support stand, 8 is a workpiece, 9 is a power source, 10 is a dielectric window, and 11 is a shielding plate. 2 gas 4 people J Otsu I Hisashi p small force・pi; 37° U2”
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Claims (2)

[Claims] (1) A workpiece (8) is placed on a support stand (7) installed in a plasma afterglow space containing at least oxygen, and an electron beam is irradiated toward the workpiece. A plasma oxidation method characterized by forming an oxide film on the electron beam irradiated area of the workpiece. (2) The vacuum chamber (1) that accommodates the support base (7) on which the workpiece (8) is placed has at least a gas introduction hole (2), a gas discharge hole (3), and a chamber that excites plasma. (
4) and a mechanism (5) for irradiating the workpiece with an electron beam. ) A plasma oxidation apparatus characterized by having a structure in which a workpiece is spatially isolated on the upstream side of a vacuum chamber in which a workpiece is installed.