JPH01175244A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To make a microscopic and high-integration semiconductor device by a method wherein a tungsten film deposited on a semiconductor substrate is heat-treated in an atmosphere of nitrogen at a high temperature in order to reduce an oxygen concentration value in said film and, when the tungsten film is to be etched by an RIE method using a fluorine-based reaction gas, in order to reduce the etching shift amount. CONSTITUTION:A gate SiO2 film 2 is formed, e.g., on an n-type or p-type semiconductor substrate 1; a tungsten film 3 is deposited. During this process, residual oxygen contained inside a sputtering apparatus is absorbed into the tungsten film 3. Then, in order to form an SiN film 6 for a blocking material, this assembly is heat-treated at a high temperature of 760 deg.C in a mixed gas of SiH4 and NH3. By this setup, oxygen in the tungsten film 3 is released; an oxygen concentration value in the film 3 is reduced. After that, in order to form a gate electrode, a resist film 4 is applied and patterned, and is etched in a reaction gas of SF6 by an RIE method; because the oxygen concentration value in the film 3 has been reduced, dissociation of a fluorine atom is suppressed, an etching rate is reduced; side etch is hardly caused; the etching shift amount can be reduced extremely.

Description

[Detailed Description of the Invention] [Summary] This invention relates to a method for forming a high melting point metal film for wiring or electrodes suitable for manufacturing highly integrated semiconductor devices, particularly a method for forming a tungsten film for wiring or electrodes with high precision. , A step of depositing a tungsten film on a semiconductor substrate for the purpose of miniaturizing and increasing the degree of integration of semiconductor devices; A step of heat-treating the semiconductor substrate on which the tungsten film is deposited at high temperature in a nitrogen atmosphere; The method includes a step of etching the tungsten film by the RIB method using a fluorine-based reactive gas.

[Industrial application field]

The present invention is a highly integrated semiconductor device! ! ! The present invention relates to a method for forming a high-melting point metal film for wiring or electrodes suitable for manufacturing, particularly a method for forming a tungsten film for wiring or electrodes with high precision.

2. Description of the Related Art In recent years, as semiconductor ICs have become highly integrated and miniaturized, low-resistance, high-melting-point metal films have been proposed for use in gate electrodes or wiring.

Among these, tungsten film is particularly popular because it is thermally stable.

(Prior Art) FIGS. 3(a) and 3(b) are schematic cross-sectional views showing a conventional method of forming a tungsten film for a gate electrode.

In the figure, 101 is a semiconductor substrate, 102 is a gate St.
o! 103 is a tungsten film with a thickness of about 4000, 104 is a resist film for etching mask, 105 is a SiO□ film as an oxygen blocking material for the tungsten film,
F represents a fluorine atom, 0 represents an oxygen atom, and SF4 represents a reactive gas molecule.

The figure (a) shows a method of etching the tungsten lff 103 by depositing and patterning a resist film 104 for an etching mask directly on the tungsten film 103, and the figure (b)
) is Si for oxygen blocking material on the tungsten film 103.
An NG film 105 is deposited, and a resist for etching mask [104 is deposited and patterned to form a tungsten film 103.
These methods are used depending on whether ion implantation or blocking of oxygen to tungsten V103 is required in the subsequent process.

[Problems to be Solved by the Invention] However, according to the above method, when the tungsten film 103 is etched by the RrE method using the reactive gas SFa as shown in FIG. When forming the tungsten film 103, the oxygen gas contained in the chamber or the oxygen gas coming out of the tungsten target will normally deposit 150 to 200 p of the formed tungsten film 103.
Since the oxygen is taken in at a concentration of about pm, this oxygen promotes the dissociation of fluorine atoms in the reaction gas, and the chemical etching effect becomes predominant. In other words, isotropic etching is more likely to occur, and etching shifts resulting in side etching occur even in areas masked by the etching mask resist film 104, hindering miniaturization and higher integration of semiconductor ICs.

This problem becomes more noticeable when 5toJtos for the oxygen blocking material is deposited on the tungsten film 103, as shown in FIG. 3(b).

Therefore, the present invention has developed a tungsten film for wiring or electrodes with R
The purpose of this invention is to reduce the amount of etching shift when etching is performed using the IE method, thereby achieving miniaturization and higher integration of semiconductor devices.

[Means for solving problems]

The above problems are solved by the steps of depositing a tungsten film on a semiconductor substrate, heat-treating the semiconductor substrate on which the tungsten film is deposited at high temperature in a nitrogen atmosphere, and RIBing the tungsten film using a fluorine-based reactive gas. The problem is solved by a method for manufacturing a semiconductor device characterized by including a step of etching using a method.

[For production]

That is, in the present invention, a tungsten film containing oxygen deposited by sputtering is heat-treated at high temperature in a nitrogen atmosphere to release the oxygen to the outside of the tungsten film and reduce the oxygen concentration in the tungsten film. This allows RrE
When etching a tungsten film using this method, the chemical etching action is suppressed by freezing the dissociation of fluorine from the reaction gas molecules, and the physical etching action is relatively predominant, thereby reducing the amount of etching shift.

This allows the mask dimensional margin to be minimized, thereby making it possible to miniaturize and increase the degree of integration of semiconductor devices.

〔Example〕

Hereinafter, the present invention will be specifically explained with reference to an illustrated embodiment.

Figures 1 (a), (b), and (c) show the process of heat treatment at high temperature in a nitrogen atmosphere.
2(a), (b), (c) are process cross-sectional views showing an embodiment of the present invention characterized in that it also serves as an iN film growth process.
FIG. 2 is a diagram illustrating the present invention in detail.

In FIG. 1, 1 is an n-type or p-type semiconductor substrate, 2 is a silicon film with a thickness of about 200 mm, and a film 9.3 is a film with a thickness of 40 mm.
Tungsten film for gate electrode, 4 is about 2000 thickness for oxygen and ion implantation block material Ost
Nffl, 5 is a patterned resist film for an etching mask, 0 is an oxygen atom, and N is a nitrogen atom.

Figure 2 (a) shows that the oxygen concentration in the tungsten film is N! at a heat treatment temperature of 760°C. The figure (b) shows how a resist film for an etching mask is deposited and patterned directly on a tungsten film with a thickness of 4,000 yen, and then patterned by the RrE method using a reactive gas SF. % over etching, that is, when etching for twice the time required for etching 4,000 people, one without medium heat treatment in N2, one treated at 760'C in N2 for 5 minutes, and one treated at 760'C in N2 for 20 minutes. This figure shows the results of investigating the relationship between the amount of etching shift, N, and oxygen concentration before medium heat treatment using three types of samples.
Figure c) shows the results of investigating the relationship between the etching rate and the oxygen concentration before heat treatment in N2 using the same conditions and samples as in figure (b).

As shown in FIG. 1, in the method for manufacturing a semiconductor device according to the present invention, for example, an n-type or p-type semiconductor substrate l is coated with a thickness of about 200 people (SLO□F!). 2 is formed, and a gengusten film 3 having a thickness of approximately 4,000 mm is deposited by sputtering using a magnetron sputtering device or the like. At this time, residual oxygen contained in the chamber of the spuck apparatus and oxygen released from the tungsten target are incorporated into the deposited tungsten II'23. This concentration is measured by X-ray absorption method, etc., and is usually 150 to 200 pplI and v&it (Figure 1 (
a)).

Next, in order to grow 5iNttff4 for block material, 5iNttff4 is grown.
By performing high temperature heat treatment at 760°C in a mixed gas of rHa and NH, oxygen in the tungsten film 3 is released to the outside, and the oxygen concentration in the tungsten film 3 is reduced (see Figure 1 (b). )). For example, as shown in FIG. 2(a), the oxygen concentration decreases with the time of the N2 heat treatment, and from about 200 ppm before the N2 heat treatment, it decreases to about 5 opp after the N□ heat treatment for 20 minutes.

Thereafter, in order to form a gate electrode as shown in FIG. 1(c), a resist film 5 is deposited and patterned on the semiconductor device shown in FIG. 1(b), and then in an SF4 reaction gas by RIE method. Etching.

At this time, since the oxygen concentration in s in the tungsten film 3 is decreasing, the dissociation of fluorine atoms from the reaction gas SF is suppressed, chemical etching is suppressed, and physical etching becomes dominant, so that the etching rate is reduced. decreases (second
At the same time, side etching becomes difficult to occur and the amount of etching shift is extremely reduced (see Figure 2 (C)).
b)).

CF4 and the like can also be used as the fluorine-based reactive gas.

It goes without saying that the process of performing high temperature heat treatment in a nitrogen atmosphere can also be used as the process of carbonizing the tungsten film.

The tungsten film is carbonized along the dale of the tungsten film in order to further improve the effect of preventing side etching.

〔Effect of the invention〕

As described above, according to the present invention, the amount of etching shift when forming a tungsten film for electrodes or wiring can be extremely reduced, so that mask dimensional margin can be minimized. Therefore, it is effective in achieving miniaturization and higher integration of semiconductor devices.

[Brief explanation of the drawing]

FIGS. 1(a), (b), and (c) are process sectional views showing one embodiment of the present invention. FIGS. 2(a), (b), and (c) are diagrams illustrating detailed explanations of the present invention. , FIGS. 3(a) and 3(b) are process cross-sectional views illustrating the problems of the conventional example. (Explanation of symbols) 1.101... Semiconductor substrate, 2, 102.105... SiO□ film 3.103...
- Tungsten film, 4.104... Resist film 6... SiN film, SF,... Reactive gas molecule, F... Fluorine atom, 0... Oxygen atom, N... Nitrogen atom. Process cross-sectional diagram showing one embodiment of the present invention 0 5 10 15 20 minutes N2 heat treatment time Detailed explanation diagram of the present invention Figure 2 (Part 1) Oxygen 1 degree <ppm) before N1 heat treatment Approximately oxygen 1 degree (ppm) Detailed explanation of the present invention Figure 2 (Part 2)

Claims (3)

[Claims] (1) Depositing a tungsten film on a semiconductor substrate; heat-treating the semiconductor substrate on which the tungsten film is deposited at high temperature in a nitrogen atmosphere; and subjecting the tungsten film to RIE using a fluorine-based reactive gas. 1. A method of manufacturing a semiconductor device, comprising the step of etching. (2) The method of manufacturing a semiconductor device according to claim 1, wherein the heat treatment step also serves as a step of growing a SiN film of the block material. (3) The method of manufacturing a semiconductor device according to claim 1, wherein the heat treatment step also serves as a step of carbonizing the tungsten film.