JPH0435024A - Method of forming barrier metal - Google Patents

Abstract

PURPOSE:To improve heat resistance by increasing crystal grains of barrier metal and then depositing metal for wiring by depositing barrier metal of TiN in a contact hole and then emitting a pulse laser light having a short wavelength. CONSTITUTION:An SiO2 insulating film 12 is formed on a semiconductor substrate 11, a contact hole 13 is opened, and a TiN film 14 is deposited in the hole 13 by a sputtering method. The film 14 immediately after depositing has about 20nm of crystal grain size, and the film thickness at a bottom corner 13a is thin to the bottom center 13b, but when the film 14 is emitted with an excimer laser light 15 of an XeCl2, the crystal grain size of the film 14 is increased from 20nm to about 5mum. Accordingly, an Al film 16 is deposited as metal for wiring in the same apparatus, and patterned to form a wiring. Since not only the center 13b of the film 14 but also the bottom corner 13a are increased in the crystal grain size, Al penetration scarcely occurs.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method of forming a barrier metal for improving heat resistance when wiring to a contact hole.

[Summary of the invention]

In the present invention, when forming wiring to a contact hole, titanium nitride is deposited as a barrier metal, then short wavelength pulsed laser light such as an excimer laser is irradiated, and then wiring metal is deposited to form the wiring. This is a method for forming a barrier metal.

If the barrier metal is irradiated with short wavelength pulsed laser light,
As the crystal grains of the barrier metal become larger and the number of grain boundaries decreases, the frequency of penetration of the wiring metal decreases.

[Conventional technology]

A contact hole is opened in the active region of the semiconductor device,
It is common practice to use aluminum (hereinafter referred to as AI) or an alloy thereof as a wiring metal. Prior to this wiring formation, a barrier metal is deposited,
Efforts have been made to improve heat resistance by preventing the reaction between silicon, which is a semiconductor substrate, and AI. Nitrides and silicides of transition metals are known as barrier metals.
Among these, titanium nitride was known to have excellent heat resistance.

In recent years, with the increase in the density of integrated circuits, the active region diffusion region has become smaller and shallower.

For this purpose, the depth of the contact hole relative to the hole diameter,
In other words, the aspect ratio becomes larger and larger,
By simply depositing barrier metal, it has become difficult to prevent the upper wiring metal from penetrating through.

This punch-out phenomenon is caused by the fact that the frequency of punch-outs in the wiring metal increases in proportion to the number of crystal grain boundaries in the barrier metal, as shown in FIG. In other words, the penetration occurs because the wiring metal and the underlying silicon undergo a reaction due to grain boundary diffusion in the barrier metal.

In order to reduce the number of grain boundaries, there are examples of using titanium silicide or titanium nitride (hereinafter referred to as TiN) as a barrier metal, and then heat-treating with lamp annealing to increase the grain size and improve heat resistance. There was (1
1990 Latest Semiconductor Process Technology, published by Press Journal, November 1989, pp. 267-273).

In addition, the inventor of the present invention has developed a titanium salicide structure in which excimer laser irradiation was performed only on the AI contact area to increase the crystal grain size in order to improve the resistance to AI penetration. (No. 37, March 1990)
Proceedings of the Joint Conference on Applied Physics, Vol. 2, 59
bottom of page 2).

[Problem to be solved by the invention]

However, if the barrier metal is heated using visible light or infrared rays such as lamp annealing, the underlying semiconductor substrate will also be heated, causing the metal to invade the active region and become alloyed, resulting in an increase in leakage current, etc. , resulting in characteristic deterioration. In addition, since excimer laser irradiation on a titanium salicide structure only locally heats the surface, it does not affect the underlying layer and is effective in improving resistance to AI penetration, but it is effective in improving resistance to AI punching, but it is difficult to irradiate TiN into contact holes. The deposition is performed using a sputtering method to improve selectivity.

Therefore, as shown in FIG. 2, when a contact hole 3 is opened in the insulating film 2 on the semiconductor substrate 1 and a TiN film 4 is formed as a barrier metal, the shape of the TiN film at the bottom corner 3a is the same as that at the bottom center 3b. The film thickness is thinner than that of the conventional method, and penetration is undesirable in terms of quality.

[Means to solve the problem]

In order to solve the above problems, the present invention deposits a TiN barrier metal inside the contact hole, and then irradiates it with a short wavelength pulsed laser beam to directly heat only the barrier metal and enlarge the crystal grains. If a wiring metal is then deposited, heat resistance can be improved.

[Effect]

If the barrier metal is deposited and then irradiated with short wavelength pulsed laser light, the crystal grains of the barrier metal will uniformly increase in size, including the bottom corner of the contact hole, and if the wiring metal is then deposited, the crystal grains will be penetrated. can increase the effectiveness of prevention.

〔Example〕

An embodiment of the present invention will be explained using FIGS. 1a and 1b.

First, as shown in FIG. 1a, Si is placed on the semiconductor substrate 11.
An insulating film 12 like O□ is formed, and a contact hole 1 is formed.
Open 3. A TiN film 14 is deposited in this contact hole 13 using a sputtering method.

The TiN film 14 immediately after being deposited has a crystal grain size of 20r+n.
+, the film thickness at the bottom corner 1'3a is at the bottom center 13
Thin compared to b.

Next, XeC1z excimer laser light 15 (wavelength 3
08 nm) is irradiated onto the TiN film 14 through the irradiation window.

By this laser beam irradiation, the crystal grain size of the TiN film 14 is increased from 20 nm to about 5 μm. Then the first
As shown in the figure, A is used as wiring metal in the same device.
1 film 16 is deposited and patterned to form wiring. Since the crystal grain size is large not only at the bottom center 13b of the TiN film 14 but also at the bottom corners 13a, penetration of ^l is less likely to occur.

In the present invention, the underlying material of the semiconductor substrate is not limited to silicon, but may also be a compound semiconductor material that easily reacts with wiring metal. Also, Paris A
・It is also possible to use a material such as tungsten nitride, which uses a nitride or silicide of a transition metal with a high melting point as the metal to prevent grain boundary diffusion between the wiring metal and the underlying material. It is.

〔Effect of the invention〕

If a barrier metal is deposited using embodiments of the present invention,
Since the grain size of the barrier metal can be increased including the bottom corner of the contact hole, it is possible to prevent a reaction between the upper wiring metal and the underlying semiconductor substrate due to grain boundary diffusion. Therefore, penetration of the wiring metal does not occur, contributing to improved heat resistance. Furthermore, since the irradiation is performed using a short wavelength pulsed laser beam, there is little damage to the underlying semiconductor substrate, and leakage current is also small.

[Brief explanation of drawings]

1A and 1B are cross-sectional views of the process of forming the barrier metal of the present invention, FIG. 2 is a cross-sectional view of a conventional barrier metal, and FIG. 3 is a diagram showing the relationship between the number of grain boundaries and the degree of perforation. 1, L L------Semiconductor substrate 2, l 2'------Insulating film 3.13---Contact holes 3a, 13a
-Bottom corners 3b, 13b -Bottom center 4.1 t---------TjN film 15------- Eximer laser beam 16---
---I membrane urine

Claims (1)

[Claims] Formation of barrier metal consisting of a step of depositing titanium nitride in a contact hole on a semiconductor substrate, a step of irradiating the titanium nitride with short wavelength pulsed laser light, and a step of depositing wiring metal to form a wiring. .