JPS6384154A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To improve the effects of diffusion and a reaction barrier even with a thin film, by nitriding the surface of a barrier metal when aluminum interconnection is performed. CONSTITUTION:A polycrystalline silicon gate 103, source and drain electrodes 104 and the like are connected to an aluminum wiring through a connecting hole 106 of an SiO2 insulating film 105. A high melting point metal film 107 made of tungsten and the like is formed as a barrier metal on the connecting surface of the gate 103 and the electrodes 104. The surface of the film 107 undergoes nitriding in a nitrogen atmosphere. Thus a tungsten nitride film 108 is provided. The effects of diffusion and a reaction barrier are enhanced remarkably even with the thin film by said nitriding. Thus, a semiconductor in which the interconnection having a high barrier effect is provided is formed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a method for manufacturing a semiconductor device, and particularly to a method for connecting wiring of a semiconductor device.

(Prior Art) Conventionally, for example, when forming a semiconductor device on a silicon substrate, or when connecting a silicon substrate or silicon wiring to an aluminum wiring, the following steps have been taken to prevent interaction between silicon and aluminum during a post-heating process. Various methods were used.

■Pre-contain supersaturated silicon at the post-heating process temperature in aluminum.

■A barrier metal, for example, a high melting point metal film several thousand angstroms thick, is interposed at the interface between silicon and aluminum to act as a diffusion/reaction barrier.

(Problems to be Solved by the Invention) The above method (1) has a problem in that silicon is precipitated in the wiring or in the connection hole because silicon is excessively contained in the wiring aluminum. Silicon precipitates generated in this way after the post-heating process can significantly shorten the lifespan of interconnects and contact characteristics, leading to problems such as lower production yields and design constraints for semiconductor devices. Ta.

On the other hand, method ■ basically uses aluminum and silicon.
This is a method to prevent mutual diffusion.

However, the film thickness of the barrier metal and its effectiveness are closely related, and if the film is not thick enough, a reaction between aluminum and silicon will occur.

Furthermore, the barrier metal may have defects such as pinholes, and the diffusion phenomenon through these defects degrades the performance of the barrier metal.

As described above, it is necessary to ensure a sufficient film thickness for conventional barrier metals, which is one of the causes of increased manufacturing costs and time for semiconductor devices.

[Structure of the Invention] (Means for Solving the Problems) The present invention has been made in view of the above-mentioned findings, and by forming a metal nitride film on the surface of the conventional barrier metal, diffusion and diffusion can be achieved even with a thinner film than in the past. The present invention provides a wiring connection method using a barrier metal having an extremely high reaction barrier effect.

(Function) The present invention dramatically improves the diffusion and reaction barrier effect of the film by nitriding the surface of a conventional barrier metal with ammonia gas or nitrogen gas to form a metal nitride film.

This method takes advantage of the fact that metal nitride films generally have higher diffusion and reaction barrier properties than non-nitrided metals.

(Example) Hereinafter, as an example of the present invention, an example using selective growth of tungsten and its nitride film will be described with reference to FIG.

For example, a polycrystalline silicon gate electrode (103) and arsenic-diffused source/drain electrodes (104) on a P-type silicon substrate (101) (diffusion depth is, for example, 1700 people)
A MOSFET having the following structure is formed, and 5,000 SiO2 films (105) are formed thereon as insulating films by vapor phase growth. Thereafter, each electrode connection hole (106) is formed using reactive ion etching as a photolithography method (Fig. 1(a)
)).

Next, a tungsten film (107) of approximately 300 layers is formed only on the open portion of the contact hole, that is, on the exposed silicon portion, by selective vapor deposition using tungsten hexafluoride gas.

Furthermore, a tungsten nitride film (108) of about 30 layers was formed on the tungsten film (107) by heat treatment for 60 minutes in an ammonia gas atmosphere (ammonia gas partial pressure is, for example, I Torr) at, for example, 550°C (Fig. 1). (
b)).

After this, for example, using a target with an aluminum purity of 99.9999%, 8,000 aluminum films are formed by sputtering, and this is processed as wiring (109) using photolithography and reactive ion etching (see Figure 1). C))
.

When the semiconductor device manufactured as described above was heat treated at 450° C. for 30 minutes to normalize the aluminum of the wiring, no interaction between silicon and aluminum was observed in the wiring connection hole.

On the other hand, when nitriding is not performed as in this example, the silicon-aluminum reaction is significant at a tungsten film thickness of 300 people, and even when a tungsten film is formed with a thickness of 3,000 people, which is 10 times that of this example, some parts of the silicon-aluminum reaction occur. Interaction of aluminum was observed, and contact characteristics were degraded at the connection area.

In this example, the tungsten film was formed using selective vapor deposition using tungsten hexafluoride gas, but the insulating film (105) and silicon A tungsten film may be formed on both exposed portions. Furthermore, it goes without saying that the nitriding conditions, device structure, etc. are not limited as long as they do not depart from the spirit of the present invention.

[Effects of the Invention] The present invention enables the easy formation of more complete aluminum wiring and silicon diffusion/reaction barriers than conventional methods, improving the performance of semiconductor devices and increasing the degree of freedom in design and manufacturing. An improvement in yield was achieved.

[Brief explanation of the drawing]

FIG. 1 is a process sectional view showing an embodiment of the present invention. 101... P-type silicon substrate 102... Gate insulating film 103... Polycrystalline silicon gate 104...
...Source fist drain electrode 105...SiO2
Membrane 106... Connection hole

Claims (4)

[Claims] (1) In a method of connecting a semiconductor substrate or a wiring layer formed on the substrate and its upper layer wiring through a connection hole formed in an insulating film, the upper layer of the wiring layer formed on the substrate or the substrate A semiconductor device comprising a first step of forming a high melting point metal film on a connection surface with wiring, and a second step of nitriding the surface of the high melting point metal film in an ammonia or nitrogen atmosphere. Production method. (2) The method of manufacturing a semiconductor device according to claim 1, wherein the high melting point metal film is formed by selective vapor deposition. (3) The method for manufacturing a semiconductor device according to claim 1 or 2, wherein the high melting point metal film is formed of tungsten. (4) The method for manufacturing a semiconductor device according to claim 1 or 2, wherein the high melting point metal film is formed of molybdenum.