JPH0258827A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To make regions to be etched of a wiring electrode film undoped for allowing the use of a conventional etching technique of treating a single metal for etching these regions independently from a type or concentration of a dopant, by incorporating a dopant selectively in wiring regions of the wiring electrode film and etching off the non-doped regions of the wiring electrode film. CONSTITUTION:Photoresist is applied on a wiring electrode film 1 to provide a mask for dopant introduction 2 and then a dopant 3 is introduced only into wiring electrode regions 4 in the wiring electrode film 1, by ion implantation for example. The dopant 3 is not introduced into the regions of the wiring electrode film 1 other than the wiring electrode regions 4. The wiring electrode film 1 is in contact with a semiconductor substrate 7 via an aperture 6 provided partially as required in an electrically insulating film 5. After the mask 2 is removed, an etching mask 8 is formed of photoresist for example on the wiring electrode film. Since the regions to be etched are undoped, they can be etched anisotropically by a conventional technique. A wiring electrode 9 thus formed by anisotropic etching is then alloyed so that the dopant is diffused in the whole of the wiring electrode.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method of forming a wiring electrode for a semiconductor device, and particularly to a wiring electrode having a long wiring life.

[Conventional technology]

The higher the temperature and current density of the wiring electrode metal, the shorter the wiring life due to so-called electromigration. A structure in which impurities are added to the wiring electrode metal is used to improve electromigration resistance and extend the life of the wiring. A famous example is
As shown in FIG. 4, there is an example in which aluminum containing copper as an impurity is used for the wiring electrode coating 13.

[Problem to be solved by the invention]

Conventional methods for producing wiring electrodes containing impurities include a method of depositing a wiring electrode metal uniformly containing impurities on a wiring electrode material, or a method of manufacturing wiring electrodes that do not contain impurities or uniformly contain impurities. This method involved adding impurities to the entire surface after depositing the metal. For this reason, when forming a pattern by applying a photoresist to a wiring electrode film doped with impurities by the conventional method, etching becomes extremely difficult with anisotropic etching using plasma depending on the proportion of impurities. It is known that when copper is added to aluminum, the electromigration resistance is significantly improved as the amount of copper added increases. It was necessary to find new etching gas, pressure, and other conditions for each material with a different proportion of copper. In addition, in isotropic etching using a liquid, the etching conditions do not depend much on the amount of impurities, but since lateral etching also progresses, the wiring width must be widened in advance, making it unsuitable for microfabrication. Ta.

[Means to solve the problem]

In the present invention, the wiring electrode film is provided with an impurity-doped region and an impurity-free region, and the non-doped region is removed by etching.

〔Example〕

Next, the present invention will be explained with reference to the drawings.

FIG. 1 is a sectional view of a first embodiment of the present invention.

FIG. 1(a) is a diagram in which an impurity introduction mask 2 is formed by applying photoresist on the wiring electrode coating 1, and then impurities 3 are added only to the wiring electrode region 4 of the wiring electrode coating 1 by, for example, ion implantation. be. The impurity 2 is not added to the wiring electrode coating 1 except in the wiring electrode region 6. The wiring electrode coating 1 contacts the semiconductor substrate 7 via an opening 6 partially provided in the electrically insulating coating 5 as required.

FIG. 1(b) shows an etching mask 8 made of, for example, photoresist, formed on the wiring electrode coating after removing the impurity introduction mask 2 of FIG. 1(a). Since the region to be etched does not contain impurities, it can be anisotropically etched using conventional techniques.

FIG. 1(c) is a diagram in which the wiring electrode 9 is formed by anisotropic etching and then impurities are diffused throughout the wiring electrode by alloying. When copper is added to aluminum, an alloy of 450-500°C may be used.

FIG. 2 is a cross-sectional view of a second embodiment of the invention. In this figure, the impurity 3 is sandwiched between the first wiring electrode coating 10 and the second wiring electrode coating 11, which prevents the impurity from reacting with the atmosphere of the alloy.Furthermore, since the diffusion distance is halved, the alloying time is can be shortened. This method is particularly effective when impurities are formed by vapor deposition or sputtering.

FIG. 3 is a sectional view of a third embodiment of the invention. In this figure, a conductive impurity diffusion barrier 12 is provided below the wiring electrode 9. This impurity diffusion barrier is used to prevent heavy metals such as copper from diffusing into the semiconductor substrate and creating defects and generating leakage current when heavy metals such as copper are added to the wiring electrode coating. An example of such an impurity diffusion barrier is titanium nitride. Titanium nitride suppresses interdiffusion of copper, aluminum, and silicon to temperatures above 500°C.

〔Effect of the invention〕

As explained above, in the present invention, by selectively adding impurities to the wiring region of the wiring electrode coating, it is possible to create a structure in which impurities are not contained in the region to be etched.
This has the advantage that processing technology for a single wiring electrode metal can be used regardless of the type or concentration of impurities.

[Brief explanation of the drawing]

1(a) to (c) are cross-sectional views of a first embodiment of the present invention, FIG. 2 is a cross-sectional view of a second embodiment of the present invention, and FIG. 3 is a cross-sectional view of a third embodiment of the present invention. A cross-sectional view of an example, FIG. 4 is a cross-sectional view of a conventional case where the entire surface contains impurities. 1... Wiring electrode film, 2... Impurity introduction mask, 3... Impurity, 4... Wiring electrode region, 5... Electricity Insulating coating, 6...
...Opening, 7...Semiconductor substrate, 8...
Etching mask, 9... Wiring electrode, 10...
...First wiring electrode film, 11... Second wiring electrode film, 12... Impurity diffusion barrier, 13
・・・・・・Wiring electrode coating. (12nd (b) Mo!

Claims (3)

[Claims] (1) In a wiring electrode coating deposited on one main surface of a semiconductor substrate having a predetermined pn junction and optionally an electrical insulating film on the surface, selectively 1. A method of manufacturing a semiconductor device, comprising adding an impurity to the wiring electrode film, and etching away a region of the wiring electrode film to which the impurity is not added. (2) The method for manufacturing a semiconductor device according to claim (1), wherein the method for adding the impurity is ion implantation, vapor deposition, or sputtering. (3) The method for manufacturing a semiconductor device according to claim (1), wherein the wiring electrode film is aluminum or aluminum containing silicon, and the impurity is copper.