JPS6115349A - Wiring formation for semiconductor element - Google Patents

Abstract

PURPOSE:To enable the wiring material of aluminum series to be sputtered while being heated to high temperature by a method wherein a layer of high melting point metal is formed on an intermediate insulation film prior to the deposition of the wiring material of aluminum series on the intermediate insulation film. CONSTITUTION:After a field oxide film 12, a gate oxide film 13, a gate electrode 14, and a source-drain diffused layer 15 are formed on a semiconductor substrate 11, the intermediate insulation film 16 of phosphorus glass or the like is formed on the substrate 11, and a tungsten layer 17 is formed on the film 16 thinly as the layer of high melting point metal after glass flow. Next, contact holes 18 are formed on the electrode 14 and the layer 15; thereafter, an aluminum series metal is sputtered, while being heated to high temperature, as the wiring material of aluminum series on the layer 17 including the holes 18. Then, aluminum series wirings 19 are formed on the holes 18 and the layer 17 by patterning the aluminum series metal, and the layer 17 part exposed by patterning is removed.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a method for forming wiring for semiconductor elements in LSIs, etc., and more particularly, to a method for forming aluminum-based wiring on an intermediate insulating film such as phosphor glass. .

(Prior Art) A cross-sectional view of a conventional semiconductor element is shown in FIG. In this figure, l is a semiconductor substrate, 2 is a field oxide film, 3 is a gate oxide film, 4 is a gate electrode, 5 is a source/drain diffusion layer, 6 is an intermediate insulating film such as phosphor glass, 7 is a contact hole, and 8 is an aluminum-based wiring, and this aluminum-based wiring 8 is formed on the intermediate insulating film 6 including the front 8e contact hole portion by sputtering and patterning.

The aluminum-based wiring 8 thus obtained has two major problems. One is poor step coverage, and the other is the presence of hillocks that occur on the surface due to subsequent heat treatment. Wiring with poor step coverage causes disconnections. In addition, hillocks can sometimes be as flat as the film thickness, causing reliability problems such as breaking the overlying insulating film.

In order to solve these two problems at the same time, it is recommended to sputter the aluminum-based wiring material while heating it to as high a temperature as possible. This makes it easier for atoms on the surface to move, so that a film is formed evenly on the step portions. In addition, the compressive stress generated during the subsequent heat treatment is also alleviated, making it difficult for hillocks to form.

(Problems to be Solved by the Invention) However, when high-temperature heating sputtering is applied to the conventional method of directly depositing an aluminum wiring material on an intermediate insulating film such as phosphor glass, the wiring material and the intermediate insulating film (
The problem was that the reactants (aluminum and phosphorus glass) reacted, and the reactant strongly adhered to the intermediate insulating film and could not be removed, causing reliability problems.

(Means for Solving the Problems) Therefore, in the present invention, a high melting point metal layer is formed on the intermediate insulating film prior to depositing the aluminum wiring material on the intermediate insulating film.

(Function) In this way, high-temperature heating sputtering can be applied to the deposition of the aluminum-based wiring material in order to prevent the high-melting point metal layer from reacting with the aluminum-based wiring material and the intermediate insulating film.

(Example) FIG. 1 shows an example of the method for forming interconnections of a semiconductor element according to the present invention. This embodiment will be described below.

In FIG. 1(a), 11 is a semiconductor substrate on which a field oxide film 12, a gate oxide film 13, a gate electrode 14, and a source/drain diffusion layer 15 are formed. On such a semiconductor substrate ll, first, an intermediate insulating film 16 such as phosphor glass is completely formed, and after glass flow is performed, a tungsten layer 17 is thinly formed (500 ~ 1000λ thickness). This state is shown in FIG. 1(a).

Subsequently, the tungsten layer 17 and the intermediate insulating film 16 are etched by a photolithography process, so that the gate electrode 1 is formed on the tungsten layer 17 and the intermediate insulating film 16.
4 and the source/drain diffusion layer 15. A contact hole 18 is formed above the source/drain diffusion layer 15. This state is shown in FIG. 1(b). Here, dry etching is better than wet etching. In wet etching, the tungsten layer 17 and the intermediate insulating film 16 must be etched separately, and the tungsten layer 1
7 is left in the shape of an eaves, which has an adverse effect on step bag mounting made of aluminum-based wiring material.

On the other hand, with dry etching, the tungsten layer 17 and the intermediate insulating film 16 can be etched continuously without selectivity by using a gas such as CF. It will no longer be left behind.

Next, an aluminum-based metal is sputtered as an aluminum-based wiring material onto the tungsten layer 17 including the contact hole 18 portion while being heated to a high temperature.

Thereafter, the sputtered aluminum metal is patterned in a photolithography process to form an aluminum wiring 19f made of the patterned aluminum base on the contact hole 18 and the tungsten layer 17. Finally, the portion of the tungsten layer 17 exposed by the patterning of the aluminum metal is removed by etching. This state is shown in FIG. 1(c).

Specifically, the heating temperature during sputtering of the aluminum-based metal is 400° C. to 500° C., and it is desirable to set the temperature to the highest temperature in the subsequent steps or higher.

Further, the exposed portion of the tungsten layer 17 can be easily etched and removed using hydrogen peroxide solution or hydrofluoric acid/nitric acid◎ As described above, in one embodiment of the present invention, the intermediate insulating film 1
Prior to sputtering aluminum-based metal as an aluminum-based wiring material onto 6, a tungsten layer 17 is formed as an intermediate insulating material.
Since the aluminum metal is formed on the intermediate insulating film 16, it is possible to sputter the aluminum metal while heating it to a high temperature without being restricted by the reaction between the aluminum metal and the intermediate insulating film 16. It has a remarkable effect on improving and suppressing hirotsu. Further, in this embodiment, after forming the tungsten layer 17, the contact hole 18 is formed in the tungsten layer 17 and the intermediate insulating film 16, so that the tungsten layer 17 is present in the contact hole 18 portion. Therefore, the aluminum wiring 19 and, for example, the source/drain diffusion layer 1
Ohmic contact with 5 can also be easily formed.

In the above embodiment, tungsten is used as the high melting point metal, but molybdenum, titanium, and tantalum may be used in addition to tungsten to provide similar effects. In the case of these high melting point metals, the following chemicals may be used to remove the unnecessary parts. That is, for molybdenum, hydrofluoric acid, nitric acid, nitric acid, ammonia, for titanium, hydrofluoric acid, hydrofluoric acid, nitric acid, ammonia, and for tantalum, hydrofluoric acid, ammonia, etc. are used.

Further, in the above description, phosphorus glass is cited as a specific example of the intermediate insulating film, but the present invention can obtain similar effects even when the intermediate insulating film is 5i02.

(Effects of the Invention) As detailed above, in the method of the present invention, prior to depositing the aluminum-based wiring material on the intermediate insulating film,
Since the high-melting point metal layer is formed on the intermediate insulating film, it is possible to sputter the aluminum-based wiring material while heating it to a high temperature without being restricted by the reaction between the aluminum-based wiring material and the intermediate insulating film. This has a remarkable effect on improving the wiring material and thus the step coverage range of the wiring and suppressing hillocks.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view showing an embodiment of the method for forming interconnects in a semiconductor device according to the present invention, and FIG. 2 is a cross-sectional view of a conventional semiconductor device. 11... Semiconductor substrate, 16... Intermediate insulating film, 17.
...Tungsten layer, 19...Aluminum wiring.

Claims (1)

[Claims] Aluminum wiring is formed by forming a high melting point metal layer on the intermediate insulating film on the semiconductor substrate, depositing an aluminum wiring material on the high melting point metal layer formed by this process, and patterning it. 1. A method for forming wiring in a semiconductor element, comprising a step of forming a wiring, and a step of removing a high melting point metal layer exposed by patterning the aluminum-based wiring material after this step.