Structure of stacked barrier layer

Details Structure of stacked barrier layer Structure of stacked barrier layer

1998-10-28

2001-01-09

Lorin, Francis J. (Department: 1775)

Stock material or miscellaneous articles

Composite

Of inorganic material

Reexamination Certificate

active

06171717

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates in general to a structure of a stacked barrier layer in multilevel interconnects, and more particularly to a structure of a stacked titanium nitride barrier layer in multilevel interconnects.
2. Description of the Related Art
In the high density integrated circuit process titanium nitride is the most prevailing material for forming a barrier layer. The barrier layer is used for deterring the diffusion between alumnum and silicon to eliminate spiking and electromigration. In multilevel interconnect process, a barrier layer is preferrably composed of titanium nitride and titanium (TiN/Ti). A metal plug is composed of the barrier layer and alloys.
A conventional structure of a plug in multilevel interconnects is illustrated in FIG.
1
. First, a semiconductor substrate
100
is provided and a source/drain region
101
is formed in the semiconductor substrate
100
. A dielectric layer
102
is formed on the semiconductor substrate
100
to insulate metal layers. Photolithography process is performed to pattern the dielectric layer
102
and a contact opening
104
is formed in the dielectric layer
102
to expose the source/drain region
101
. A titanium layer
106
is formed on the contact opening
104
using physical vapor deposition (PVD), for example, DC magnetron sputtering. The titanium layer
106
is about 200-1500 Å thick. A titanium nitride layer
108
is formed on the titanium layer
106
using physical vapor deposition (PVD). The titanium layer
109
is about 800-1200 Å thick. A plug
110
is formed in the contact opening
104
. The method of forming the plug
110
is first depositing a metal layer, for example, alumnum to fill the contact opening
104
and etching back to form the plug
110
. Then the wafer is cleaned for subsequent metal interconnects process.
FIG. 2
showing a columnar structure of the titanium nitride layer. There are spacings between the columnar titanium nitride grains. Alumnum metal can diffuse along the spacings to react with silicon. Therefore, the method to deter the diffusion between alumnum and silicon is to elongate or to turn the diffusion path from alumnum to silicon. However, as shown in
FIG. 3
, the physical vapor deposition (PVD) is no longer a good method to form a titanium nitride layer and can not match the need that the size of devices decrease. It is difficult to fill the Ti/TiN layer
118
in the contact window
104
with high aspect ratio by PVD because of its poor step coverage. Therefore, the leakage current increases.
SUMMARY OF THE INVENTION
It is an object of the invention to provide a structure of a stacked barrier layer using plasma enhanced chemical vapor deposition (PECVD) to provide good step coverage and to match the need that the size of devices decrease.
It is an object of the invention to provide a structure of a stacked barrier layer to eliminate the diffusion between alumnum and silicon, and to reduce leakage current of contact regions.
It is another object of the invention to provide a structure of a stacked barrier layer to reduce the diffusion from alumnum to silicon and to eliminate spiking and electromigration.
A structure of a stacked barrier layer is provided. A first titanium layer is formed on a semiconductor substrate using plasma enhanced chemical vapor deposition (PECVD). At least a stacked barrier layer is formed on the first titanium layer. The stacked barrier layer includes a first titanium nitride layer and a plasma treated titanium nitride layer. The first titanium layer is formed using PECVD in which the source gas includes about 1-10 sccm TiCl
4
and about 1000-300 sccm H
2
, the RF power is about 100-500 W, the pressure is about 3-15 torr, and the temperature is about 570-650 ° C. The first titanium nitride layer is formed on the first titanium layer using low pressure chemical vapor deposition (LPCVD) in which the source gas includes about 35-42 sccm TiCl
4
, about 60-80 sccm ammonia gas and about 3000 sccm nitrogen gas, the pressure is about 10-30 torr and the temperature is about 570-650° C. The plasma treated titanium nitride layer is formed using first forming a second titanium layer on the first titanium nitride layer and treating the second titanium layer using a plasma gas to form the plasma treated titanium nitride layer. The second titanium layer is formed using plasma enhanced chemical vapor deposition (PECVD) in which the source gas includes about 1-10 sccm TiCl
4
and about 1000-3000 sccm H
2
gas, the RF power is about 100-500 W, the pressure is about 3-15 torr, and the temperature is about 570-650° C. When treating with plasma, the source gas includes about 1000-3000 sccm ammonia gas and about 1000-3000 sccm nitrogen gas, the plasma RF power is about 100-500 W and the temperature is about 570-650° C.


REFERENCES:
patent: 5236868 (1993-08-01), Nulman

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