JPS62126631A - Formation of contact electrode - Google Patents

Abstract

PURPOSE:To form contact electrodes having no disconnection even in a small contact by a method wherein, after the contact electrodes are each formed in advance in the shape of a high-melting point metal pillar, an insulating film is formed on the peripheries of the electrodes. CONSTITUTION:A nitriding film 20 is formed on a tungsten layer 6 which is used as a high-melting point metal layer by an LPCVD method and photo resist films 21 are formed only on the contact electrode forming parts. Then, nitriding films 20a are left on the contact electrode forming parts by performing an etching on the nitriding film 20 using the resist films 21 as masks and after the resist films 21 are removed, a heat treatment is performed in an atmosphere of oxygen. Whereupon, the parts not being covered with the nitriding films 20a are turned into tungsten oxide films and parts of the tungsten oxide films are turned into tungsten silicide layers 7. Thereafter, the nitriding films 20a are removed, an oxide film 22 is formed as a second insulating film by an LPCVD method, a second resist film 23 is formed thereon by coating and thereafter, the contact electrode forming parts are etched until tungsten layers 6a on the contact electrode forming parts are exposed in such conditions that etching rates of the resist film 23 and the oxide film 22 become equal.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method of forming fine contact electrodes for semiconductor devices.

[Conventional technology]

FIGS. 2A-2F are cross-sectional views showing the main stages of a conventional field effect transistor and its contact electrode manufacturing method. First, as shown in FIG. 2A, a p-type silicon substrate (1) is coated with a gate insulating film (2) and a gate electrode (
3) is formed, and using this gate electrode (3) as a mask, low concentration n-type impurity ions are implanted to form low concentration n shadow regions (4) of the source and drain. Next, as shown in FIG. 2B, the reduced pressure is 0VD (LOW Pressure
Ohmica:L Vapor Depoeitio
An oxide film (5) is deposited by a method (hereinafter referred to as LPOVD). Furthermore, as shown in FIG. 2C, RI E (Rea
An oxide film (5a) is left only on the gate sidewalls by active IonEtQing (anisotropic etching), and then a high melting point metal such as tungsten (6) is sputtered over the entire surface, as shown in the second diagram. The tungsten (6) on the source/drain electrode (3) and the gate electrode (3) is silicided by heat treatment to form a silicide electrode (3).
8) and remove the tungsten (6) on the gate sidewall. Next, as shown in FIG. 2E, after depositing the oxide film (9), the resist film Q
Cover with O).

Then, this resist film ([1] is used as a mask to form an oxide film (
9) Etch and remove the resist edge, All wiring (b)
The device is completed.

[Problem that the invention seeks to solve]

Conventional methods for forming contact electrodes have had the problem that when the size of the contact hole becomes small, the contact hole is not covered sufficiently with electrode metal such as AI, leading to wire breakage and the like.

The present invention was made to solve the above problems, and an object of the present invention is to provide a method for forming a contact electrode without disconnection even in the case of a small contact.

[Failure to solve the problem]

In the method for forming a contact electrode according to the present invention, a high-melting point metal layer is formed on a base conductor on which a contact electrode is to be formed, and an insulating film is formed only on the contact electrode formation area thereon, followed by heat treatment in an oxygen atmosphere. The exposed high melting point metal is sublimated to leave a high melting point metal pillar as a contact electrode.

[Effect]

In the present invention, since the contact electrode is formed in advance in the form of a high-melting point metal column and then the insulating film is formed around it, no problem occurs even when the size of the contact is small.

〔Example〕

FIGS. 1A to 1E are cross-sectional views showing the main stages of an embodiment of the present invention, and the same reference numerals as in the conventional example of FIG. 2 indicate equivalent parts.

The steps up to FIG. 1A are the same as the conventional example up to FIG.
A photoresist film Qυ is formed using the OVD method, and only on the contact electrode formation portion (abbreviated as “contact portion”) using photolithography (FIG. 1B). And this resist film @1) '& nitride film as a mask -
A nitride film (20a) is etched on the contact area.
), and after removing the resist film Qη, heat treatment is performed in an oxygen atmosphere, and the portion not covered with the nitride film (20a) becomes tungsten oxide, and since this substance is volatile, it is partially removed. A portion becomes a tungsten silicide layer (7). The part covered with the nitride film (20a) is a tungsten layer (6a) (Fig. 10). After that, the nitride film (20a) is removed and an oxide film (a) is formed as a second insulating film. LPOV]) method, and a second resist film (e) is coated on top of it (Fig. 1D). After that, the etching rate of the resist film (e) and the oxide film (a) are made equal. Etching is performed under the following conditions until the tungsten layer (6a) of the contact part is exposed (this process is called an etching rate), and then the Al wiring layer (6a) is etched.
is formed to complete the device. (Figure 1E).

Although the case where the present invention is applied to an FET has been described above, the present invention can be applied to semiconductor devices in general.

〔Effect of the invention〕

As described above, according to the present invention, by forming contact pillars (high melting point metal) instead of forming contact holes, it is possible to prevent disconnection of the A/wiring, etc.

[Brief Description of the Drawings] Fig. 1 is a sectional view showing the main process steps of an embodiment of the present invention, and Fig. 2 shows the main steps of a conventional field effect transistor and its contact electrode manufacturing method. In Figure 0, which is a cross-sectional view, (1) is a semiconductor substrate, (6), (6a) are high melting point metal layers, (a),
(20a) is the first insulating film, b) is the first resist film,
(A) is the second insulating film, and (C) is the second resist film. Note that the same reference numerals in the figures indicate the same or corresponding parts.

Claims (1)

[Claims] (1) forming a high melting point metal layer on the semiconductor substrate; forming a first insulating film on the high melting point metal layer;
forming a first resist film at a desired location on the insulating film where a contact electrode is to be formed; etching the first insulating film using the first resist film as a mask; and etching the first resist film only at the desired location; A step of leaving the first insulating film, after removing the first resist film, heat treatment is performed in an oxygen atmosphere to oxidize and sublimate the high melting point metal layer in the portion not covered with the remaining first insulating film. After removing the remaining first insulating film, a second insulating film is formed on the semiconductor substrate including on the high melting point metal layer remaining in the desired region, and further a second insulating film is formed on the semiconductor substrate. a step of applying and forming a resist film, and a step of etching the second resist film and the second insulating film under conditions such that the etching rate is the same until the high melting point metal layer is exposed. A method for forming a contact electrode, comprising: obtaining a contact electrode made of the high melting point metal layer.