CVD titanium silicide for contact hole plugs

Details CVD titanium silicide for contact hole plugs CVD titanium silicide for contact hole plugs

1999-04-23

2001-07-10

Everhart, Caridad (Department: 2825)

Semiconductor device manufacturing: process

Coating with electrically or thermally conductive material

To form ohmic contact to semiconductive material

C438S649000, C438S629000

Reexamination Certificate

active

06258716

ABSTRACT:

BACKGROUND OF THE INVENTION
(1) Field of the Invention
This invention relates to methods of filling contact holes in dielectric layers with conducting metal plugs and more specifically to methods of using chemical vapor deposition of titanium suicide to form conducting metal plugs.
(2) Description of the Related Art
Contact holes in dielectric layers formed on integrated circuit wafers are typically filled by forming layers of titanium and titanium nitride using sequential sputtering forming layers of titanium and titanium nitride on the sidewalls and bottoms of the via holes. The wafer is then thermally processed to form titanium silicide at those points where the titanium is in contact with silicon. A blanket deposition of tungsten or other metal is then used to fill the contact holes.
U.S. Pat. No. 5,534,730 to Mori et al. describes contact holes with thin oxide at the bottom. Titanium silicide, TiSi
x
, is deposited in the contact hole using chemical vapor deposition. As the TiSi
x
film is formed the oxide is reduced and the titanium silicide forms a conductive contact to the silicon below the oxide.
U.S. Pat. No. 5,376,405 to Doan et al. describes a method of using chemical vapor deposition for depositing titanium silicide on a an integrated circuit wafer.
U.S. Pat. No. 5,066,612 to Ohba et al. describes the use of multilayer insulating layers for activating selective metal growth in filling contact holes with metal.
This invention describes methods of filling contact holes in dielectric layers formed on an integrated circuit wafer using chemical vapor deposition of titanium silicide.
SUMMARY OF THE INVENTION
In the manufacture of integrated circuit wafers a layer of dielectric is formed over the wafer after the devices have been formed in the wafer and some electrodes, usually polysilicon electrodes have been formed. It is necessary to form contact or via holes in this dielectric layer and to fill these contact or via holes with conductor metal so that electrical patterns formed on the dielectric layer have electrical connection to the appropriate points of the devices formed in the wafer and electrodes formed on the wafer.
FIG. 1A
shows a cross section view of a part of an integrated circuit wafer showing the semiconductor wafer
10
, a diffused region
14
formed in the wafer
10
, and a field oxide isolation region
12
. A polysilicon electrode
16
is shown formed on the field oxide region
12
. A dielectric layer
18
, usually silicon dioxide, is formed on the integrated circuit wafer and contact holes
20
are formed in the dielectric layer
18
.
A conventional method of filling the contact holes with conductor metal is shown in
FIGS. 1B and 1C
. As shown in
FIG. 1B
layers of titanium
22
and titanium nitride
24
are sequentially sputter deposited on the wafer forming layers of titanium
22
and titanium nitride
24
on the sidewalls and bottom of the via holes. The wafer is then thermally processed to form titanium silicide at those points
21
where the titanium is in contact with silicon. As shown in
FIG. 1B
the step coverage of the titanium nitride layer at the edge of the contact holes
23
is poor. As shown in
FIG. 1C
a blanket layer of tungsten
26
is deposited on the wafer to fill the contact holes. As shown in
FIG. 1C
the poor step coverage of the titanium nitride can cause voids
28
to form in the tungsten filling the via. The tungsten is then etched back to leave tungsten only in the contact holes, not shown.
The conventional method described above is a complex process and the poor step coverage of the titanium/titanium nitride layer causes reliability and other problems in the tungsten, or other metal, plug filling the contact hole. These problems become more severe as the diameters of the contact holes decrease, as happens with increasing circuit density.
It is a principle objective of this invention to provide simplified methods for filling contact holes with conducting metal plugs.
It is another r principle objective of this invention to provide methods for filling contact holes with conducting metal plugs which result in improved quality and reliability of the conducting metal plugs.
These objectives are achieved by using blanket deposition of titanium silicide to completely fill the contact holes, by selective deposition of titanium silicide to completely fill the contact holes, or by depositing a titanium silicide adhesion layer on the sidewalls and bottom of the contact holes and filling the contact holes with titanium silicide, tungsten, aluminum, or copper. The titanium silicide, tungsten en, aluminum, and copper are deposited using chemical vapor deposition.


REFERENCES:
patent: 5066612 (1991-11-01), Ohba et al.
patent: 5138432 (1992-08-01), Stanasolovich et al.
patent: 5376405 (1994-12-01), Doan et al.
patent: 5534730 (1996-07-01), Mori et al.
patent: 5846881 (1998-12-01), Sandhu et al.
patent: 5976976 (1999-11-01), Doan et al.
J. Hu, et al. “Electrical properties of Ti/TiN films prepared by CVD and their applications in submicron structures as contact and barrier materials”, Thin Solid Films, vol. 308-309, pp. 589-593, Oct. 1997.

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