Semiconductor device manufacturing: process – Coating with electrically or thermally conductive material – To form ohmic contact to semiconductive material
Reexamination Certificate
1998-01-21
2002-04-02
Everhart, Caridad (Department: 2825)
Semiconductor device manufacturing: process
Coating with electrically or thermally conductive material
To form ohmic contact to semiconductive material
C438S680000, C438S685000
Reexamination Certificate
active
06365517
ABSTRACT:
RELATED PATENTS/PATENT APPLICATIONS
The following co-assigned patents/patent applications are related to the present invention and are hereby incorporated herein by reference:
Patent or
Filing
Issue
Attorney
Serial No.
Date
Date
Docket
60/028 798
10-31-96
not issued
TI-22932
60/010 405
01-22-96
not issued
TI-22324
FIELD OF THE INVENTION
This invention relates generally to semiconductor device fabrication and more specifically to the formation of a TiN-based film.
BACKGROUND OF THE INVENTION
Films containing titanium nitride are commonly used as a diffusion barrier in contacts, vias, trenches, and interconnect stacks. They are also used as a “glue” layer for chemical vapor deposited (CVD) tungsten, as a nucleation layer for CVD tungsten and CVD aluminum, as a liner for contacts, vias and trenches, as a capacitor electrode, and as an anti-reflective coating. A good barrier layer should have: good step coverage to achieve void-free plug formation and adequate barrier thickness at the bottom of the contact/via/trench; good diffusion barrier properties to prevent diffusion of metals and other materials into underlying layers; inertness and low reactivity with adjacent materials during thermal cycles; and acceptable electrical properties such as low resistivity, low contact/via resistance and low junction leakage.
Currently, TiN-based barrier films are formed by physical vapor deposition (PVD) using reactive sputtering. This type of sputtering method is line-of-sight technique and produces films with poor step coverage. As minimum feature sizes continues to shrink and the aspect ratio of contacts/vias/trenches continues to increase, processes that produce conformal films are in great demand.
CVD processes offer the potential advantage of good step coverage and have attracted increasing attention in the past few years for fabricating TiN based films. Two types of CVD processes are being developed currently: one based on metal-organic (MO) precursors, such as tetras(dimethylamino)-titanium (TDMAT) and tetras(diethylamino)-titanium (TDEAT); and the other based on inorganic precursors, such as TiCl
4
/NH3. The MO based processes produce films with high carbon content and low stability. The TiCl
4
/NH
3
process requires high deposition temperature and have severe problems associated with NH
4
Cl salt formation.
Prior CVD process for TiSi
x
N
y
uses Ti[N(C
2
H
5
)
2
]
4
/NH
3
/SiH4 chemistry. The drawbacks of this approach includes: gas phase reaction between the Ti precursor and NH
3
, lower density, less stable films than those using TiCl
4
as a precursor, and lower vapor pressure of metalorganic precursor as compared to TiCl
4
.
A process for depositing a TiN film on tools was developed using CVD. See F. H. M. Sanders and G. Verspui,
Influence of Temperature on the Growth of TiN Films by Plasma
-
Assisted Chemical Vapor Deposition
, 161 THIN SOLD FILMS L87-L90 (1988). This method uses a combination of H
2
, N
2
, and TiCl
4
in conjunction with a plasma to form the TiN layer on the tool to prevent corrosion of the tool.
SUMMARY OF THE INVENTION
The instant invention relates to the deposition of titanium nitride based films for barrier layers, gate dielectrics, and for capacitor electrodes. Advantages of the instant inventions include: better step coverage than standard PVD formed TiN based films; use of TiCl
4
in the deposition of the film—TiCl
4
has higher vapor pressure and is less expensive than MO precursors; higher purity, density, and stability of the films formed by the instant invention than MOCVD formed films; greatly reduced formation of NH
4
Cl salts; lower deposition temperature than standard processes; and flexibility in control of Si/N and B/N atomic ratios.
An embodiment of the instant invention is a method of depositing a TiN-based film over a semiconductor wafer, the method comprising the steps of: substantially simultaneously subjecting the semiconductor wafer to TiCl
4
, H
2
, and N
2
; and subjecting the semiconductor wafer to a plasma, such that the combination of the TiCl
4
, H
2
, and N
2
and the plasma cause the deposition of a TiN based film to form over the semiconductor wafer. Another embodiment of the instant invention involves additionally subjecting the semiconductor wafer to SiH
4
so as to form a TiSi
x
N
y
film over the semiconductor wafer. Another embodiment of the instant invention involves additionally subjecting the semiconductor wafer to B
2
H
6
so as to form a TiN
x
B
y
layer over the semiconductor wafer.
REFERENCES:
patent: 5296404 (1994-03-01), Akahori et al.
patent: 5616518 (1997-04-01), Foo et al.
patent: 5770520 (1998-06-01), Zhao et al.
patent: 5789321 (1998-08-01), Oshita
patent: 5956616 (1999-09-01), Mizuno et al.
patent: 6090709 (2000-07-01), Kaloyeros et al.
Sanders, et al., “Influence of temperature on the growth on TiN films by plasma-assisted chemical vapour deposition,” Thin Solid Films, 161 (1988) L87-L90.
Hwang Ming-Jang
Lu Jiong-Ping
Everhart Caridad
Texas Instruments Incorporated
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