JPH0685085A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To prevent an increase in contact resistance by limiting the adhesion of a barrier metal to the side and bottom surfaces of a contact hole in a semiconductor device in which a deposited electrode interconnection layer consisting of Al-based metal and barrier metal is formed on a dielectric film including the contact hole. CONSTITUTION:After a dielectric film 12 has been formed on an Si semiconductor substrate 11, a contact hole 13 is formed in the dielectric film 12. A barrier metal 14 is deposited, in a mixed gas, on the dielectric film 12 containing the contact hole 13 by means of the reactive sputtering method in which a Ti metal plate is used as a target. The principal plane of the substrate 11 is polished, whereby the barrier metal other than that deposited on the side and bottom surfaces of the contact hole 13 is eliminated. Then, an Al alloy film 15a is formed on the entire surface of the substrate 11, and this is patterned, and an electrode interconnection 15 is formed under the presence of a photo-resist 16. This electrode interconnection 15 is formed in such a way that the contact hole is covered and the dielectric film 14 is covered by the lower edges of the side surfaces of the interconnection electrode 15.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a semiconductor device, and more particularly to a method for manufacturing a laminated electrode wiring made of Al-based metal and barrier metal on an insulating film including a contact hole on a semiconductor substrate. It is related to.

[0002]

2. Description of the Related Art An example of a conventional method for forming a laminated electrode wiring of Al type metal / barrier metal on an insulating film including a contact hole on a semiconductor substrate will be described with reference to FIG. The insulating film 2 is formed on the Si substrate 1, and then the contact hole 3 reaching the diffusion layer 1a is opened. Next, after depositing a barrier metal (for example, TiN) 4 on the entire surface, an Al-based metal (Al or Al alloy) 5 is further laminated thereon. Next, a resist pattern 6 is formed by photolithography, and using this as a mask, Al-based metal / barrier metal is dry-etched at one time to form a laminated electrode wiring 7, and then the resist 6 is peeled off.

In the above conventional wiring formation, the barrier metal 4 is formed between the base diffusion layer 1a in the contact portion and the Al-based metal 5.
Is intervening. As for the barrier metal, when Si and Al-based metal are directly contacted with each other, a spike phenomenon due to Al alloying in Si and Si at the contact portion between Al and Si are caused.
It is provided in order to prevent the element characteristics from being deteriorated and the contact resistance from being increased due to the precipitation of the.

The Al-based metal / barrier metal laminated film is etched by a reactive ion etching (RIE) apparatus to form laminated electrode wiring 7, and then the resist 6 used as a mask is peeled off. The resist stripping step (also referred to as ashing or ashing) is performed in the plasma of a mixed gas in which an F ₂ gas (for example, C ₂ F ₆ ) is added to O ₂ gas, and F ^* (fluorine radical, The barrier metal 4 is etched by the excited fluorine atoms), and as shown in FIG.
An increase in contact resistance due to a decrease in the contact area of the barrier metal 4a interposed in the contact portion, or
As shown in FIG. 5B, the laminated electrode wiring 7 and the Si substrate 1
There is a problem that the contact portion 3a comes off.

The addition of the F-based gas during ashing is
O ₂ alone cannot remove the resist that has been altered by etching or the reaction products attached during etching, and is necessary in order to leave no resist residue.

[0006]

As described above, on the insulating film including the contact hole, Al-based metal /
After the laminated electrode wiring of the barrier metal is formed, the used resist mask is ashed. At that time, it is necessary to use O ₂ gas to which an F-based gas is added as a reaction gas. Therefore, there is a problem that the barrier metal is etched by F ^* in the F-based gas, which causes an increase in contact resistance and peeling of electrode wiring.

On the other hand, with the high integration of devices, improvement of the step coverage (deposition state of the film in the step portion) of the electrode wiring filling the contact hole and reduction of the contact resistance are continuously desired. .

An object of the present invention is a resist stripping process after forming a laminated electrode wiring made of Al type metal / barrier metal,
Manufacture of a semiconductor device that prevents the barrier metal from being etched by F ^* in a reaction gas, solves the above-mentioned problems, and does not impair step coverage and contact resistance in the contact hole of the electrode wiring. Is to provide a method.

[0009]

According to the present invention, a step of forming a contact hole in an insulating film on a semiconductor substrate, a step of depositing a barrier metal on the insulating film including the contact hole, and a polishing process on the entire surface of the substrate. Removing the barrier metal on the insulating film and leaving the barrier metal on the side surface and the bottom surface of the contact hole; depositing an Al-based metal film on the insulating film including the contact hole; And a step of patterning the Al-based metal film on the insulating film to form an electrode wiring so that the barrier metal is not exposed to the surface, and then removing the resist. .

The Al-based metal film is an Al film or A
A whose main component is Al such as l-Si and Al-Si-Cu
l It is an alloy film.

The barrier metal is a barrier layer whose main purpose is to provide it between the Si substrate and the Al-based metal film to suppress the mutual reaction. This barrier metal is TiN, Ti
N (upper layer) / Ti (lower layer) laminated film and Ti W, Ti W
(Upper layer) / Ti (lower layer) Laminated film etc. is desirable

[0012]

According to the manufacturing method of the present invention, after the deposition (deposition) of the barrier metal is limited to the side surface and the bottom surface of the contact hole, the Al-based metal film is deposited on the insulating film including the contact hole to form the insulating film. Since the upper Al-based metal film is patterned to form the electrode wiring, the barrier metal is not exposed on the surface of the electrode wiring. Therefore, the barrier metal left on the side surface and the bottom surface of the contact hole is neither exposed to the reaction gas for ashing the resist nor etched by F ^* in the reaction gas.

Next, the barrier metal deposited on the bottom surface of the contact hole intervenes between the silicon substrate and the Al-based metal film and acts as a barrier layer for suppressing the mutual reaction between them. As a result, precipitation of Si and Al
The alloying of Si with Si is prevented, and the deterioration of element characteristics and the increase of resistance are eliminated.

The barrier metal deposited on the side surface of the contact hole serves to improve the step coverage (also called step coverage, which is the deposition state of the deposited film in the step portion) when depositing the Al-based metal film. do. That is, when an Al-based metal is deposited in the contact hole whose side surface is an insulating film, voids (Voi
(d, vacant space) often occurs, but when the manufacturing method of the present invention is applied, it is possible to maintain step coverage substantially equal to that of the conventional example shown in FIG.

The method of removing the barrier metal on the insulating film is performed by polishing, which is necessary at the same time to leave a barrier metal of sufficient thickness on the side surface and the bottom surface of the contact hole. Isotropic CDE (Chem
It is possible to remove the barrier metal on the insulating film and leave the barrier metal on the bottom surface and a part of the side surface of the contact hole also by the ical dry etching method. However, this method and the polishing method of the present invention Comparing the step coverages during Al-based metal deposition, there is a significant difference between the two with a high probability, and the polishing method provides better step coverage.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

First, an insulating film (SiO ₂ ) 12 having a thickness of about 1 μm is formed on a Si semiconductor substrate (wafer) 11.
Next, a contact hole 13 having a width of about 1 μm is formed in the insulating film 12 by anisotropic RIE (see FIG. 1A).

Next, a barrier metal (TiN) 14 having a thickness of about 0.1 μm is formed on the insulating film 12 including the contact holes 13 by a reactive sputtering method using a Ti metal plate as a target in a mixed gas of (Ar + N ₂ ). Accumulate (Fig. 1
(See (b)).

Next, the main surface of the wafer is polished by using a polishing apparatus to remove the barrier metal Ti N14 on the insulating film 12. Polishing uses, for example, a mixture of finer particles than lapping abrasive particles with a working liquid, attaches a polishing cloth on the surface plate, presses the wafer against this, and generates so-called chemical mechanical friction.・ By polishing. Since the side surface and the bottom surface of the contact hole are not directly polished, the barrier metal 14 having a sufficient thickness can be left (see FIG. 2C).

Next, on the entire surface of the substrate 11, an Al alloy (Al-
The thickness of Si-Cu is about 0.8 μm by sputtering.
It is deposited to form an Al alloy film 15a (see FIG. 2 (d)).

Next, the Al alloy film 15a on the insulating film 12 is patterned by photolithography to form the electrode wiring 15. A positive resist 16 is used as the photoresist, and a reactive gas containing BCl ₃ as a main component is used for etching. In this case, barrier metal 14
Is limited to the side surface and the bottom surface of the contact hole, the electrode wiring 15 covers the contact hole, and the lower end of the side surface of the electrode wiring 15 exists on the insulating film 14. Therefore, the barrier metal 14 is not exposed on the surface of the electrode wiring 15 (see FIG. 3E).

Next, the resist 16 is removed by ashing in a plasma gas in which an F type gas (for example, C ₂ F ₆ ) is added to O ₂ . Since the barrier metal 14 is not exposed on the surface of the electrode wiring 15, it is not etched by F ^{* in} the plasma. That is, the barrier metal 14 on the side surface and the bottom surface of the contact hole remains, and the increase in contact resistance and the peeling of the electrode wiring 15 which are problems in the conventional manufacturing method do not occur (see FIG. 3F).

Further, in the prior art, in the laminated electrode wiring of the barrier metal and the Al-based metal, corrosion due to the battery effect is likely to occur, but in the present invention, the step of patterning the Al-based metal film to form the electrode wiring (see FIG. 3 (e)), since the barrier metal is not exposed, BC which is an etching gas
Acceleration of corrosion can be prevented without being exposed to l ₃ .

In the above embodiment, the barrier metal is Ti N, but the barrier metal is not limited to this. A TiN / Ti laminated film, a Ti W, a Ti W / Ti laminated film and the like can also be used.
Although an Al-Si-Cu alloy is used as the Al-based metal, Al or an Al alloy such as Al-Si may be used.

[0025]

According to the manufacturing method of the present invention, after the barrier metal is deposited, the deposition of the barrier metal is limited to the side surface and the bottom surface of the contact hole by polishing. This prevents the barrier metal from being etched by F ^* in the reaction gas in the resist stripping step after forming the electrode wiring, and can prevent an increase in contact resistance and peeling of the electrode wiring.
Further, it is possible to provide a method for manufacturing a semiconductor device which does not impair the step coverage of the contact hole of the electrode wiring and the favorable state of the contact resistance.

[Brief description of drawings]

1A and 1B are cross-sectional views showing a manufacturing process of an embodiment of a method for manufacturing a semiconductor device of the present invention.

FIGS. 2C and 2D are cross-sectional views showing the manufacturing process following FIGS. 1A and 1B.

3E and 3F are cross-sectional views showing the manufacturing process following FIGS. 2C and 2D.

FIG. 4 is a cross-sectional view showing a manufacturing process for explaining a conventional manufacturing method.

5A and 5B are cross-sectional views for explaining the problems of the conventional manufacturing method after resist removal.

[Explanation of symbols]

 1, 11 Semiconductor substrate 2, 12 Insulating film 3, 13 Contact hole 4, 14 Barrier metal 5, 15a Al-based metal film 6, 16 Photoresist 7 Laminated electrode wiring 15 Electrode wiring

Claims (1)

[Claims] 1. A step of forming a contact hole in an insulating film on a semiconductor substrate, a step of depositing a barrier metal on the insulating film including the contact hole, and a polishing of the entire surface of the substrate to remove the barrier metal on the insulating film. A step of removing the barrier metal on the side surface and the bottom surface of the contact hole and a step of depositing an Al-based metal film on the insulating film including the contact hole, and a photolithography method to prevent the barrier metal from being exposed on the surface. And a step of patterning the Al-based metal film on the insulating film to form an electrode wiring, and then peeling off the resist.