Active solid-state devices (e.g. – transistors – solid-state diode – Field effect device – Having insulated electrode
Reexamination Certificate
2000-01-06
2002-01-22
Meier, Stephen D. (Department: 2822)
Active solid-state devices (e.g., transistors, solid-state diode
Field effect device
Having insulated electrode
C257S410000
Reexamination Certificate
active
06340827
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to diffusion barriers, and more particularly, to improved diffusion barriers for use with high dielectric constant materials.
2. Description of the Related Art
High dielectric constant materials (∈
r
>>∈
SiO2
=3.9∈
0
) have been widely studied as a replacement for silicon dioxide (SiO
2
) and silicon nitride (Si
3
N
4
) in silicon-based electronic devices, such as capacitors in dynamic random access memories (DRAMs), radio frequency (RF) circuits, metal-oxide-metal (MOM) capacitors, and metal-oxide-silicon (MOS) transistors. (See, e.g., P. K. Roy and I. C. Kizilyalli, “Stacked High-∈ Gate Dielectric for Gigascale Integration of Metal-Oxide-Semiconductor Technologies,” Applied Physics Letters, Vol. 72, No. 22, pp. 2835-2837 (Jun. 1, 1988), and I. C. Kizilyalli, et al., “MOS Transistors with Stacked SiO
2
—Ta
2
O
5
—SiO
2
Gate Dielectrics for Giga-Scale Integration of CMOS Technologies,” IEEE Electron Device Letters, Vol. 19, No. 11, pp. 423-425 (November 1998), both of which are incorporated by reference herein).
In particular, tantalum pentoxide (Ta
2
O
5
) has been proposed as an alternative to SiO
2
with the advantage that it can be deposited by a low-temperature process (<500° C.). Generally, when manufacturing electronic devices incorporating Ta
2
O
5
, it may be advantageous to provide a titanium nitride (TiN) layer adjacent to the Ta
2
O
5
, for example, as a diffusion barrier or electrode, to form a Ta
2
O
5
/TiN structure. For example, a MOM capacitor could be formed from a layered stack of Al/TiN/Ta
2
O
5
/TiN/Ti. Likewise, a gate structure for an MOS transistor could be formed from a layered stack of Al/TiN/Ta
2
O
5
/SiO2/Si. It should be understood that many variations of the foregoing MOM capacitor and MOS transistor structures are well known in the art and the foregoing structures are meant to be illustrative and not limiting.
One problem associated with Ta
2
O
5
/TiN structures is that oxygen tends to migrate from the otherwise stable Ta
2
O
5
and diffuse into the TiN during heat treatments, especially in cases where the TiN is Ti-rich. In the case of Ta
2
O
5
/TiN/Ti structures, such as in a MOM capacitor, the oxygen diffuses into the Ti. This diffusion of oxygen tends to reduce the Ta
2
O
5
to elemental metal Ta. It has been found that this oxygen diffusion and reduction of Ta
2
O
5
can occur at temperatures as low as 400-600° C. This can be a serious problem when manufacturing electronic devices incorporating Ta
2
O
5
/TiN and Ta
2
O
5
/TiN/Ti structures as the resulting devices will have high leakage currents or will otherwise be inadequate or, in extreme cases, inoperable.
SUMMARY OF THE INVENTION
Accordingly, the present invention is directed to a diffusion barrier that substantially obviates one or more of the problems due to limitations and disadvantages of the related art.
Additional features and advantages of the invention will be set forth in the description that follows and, in part, will be apparent from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the diffusion barrier and method particularly pointed out in the written description and claims hereof as well as the appended drawings.
To achieve these and other advantages and in accordance with the purposes of the invention, as embodied and broadly described, the invention provides an electronic device comprising a titanium nitride layer, a high dielectric constant material, and a diffusion barrier disposed between the titanium nitride layer and the high dielectric constant material to prevent the diffusion of oxygen from the high dielectric constant material to the titanium nitride layer.
To further achieve these and other advantages and in accordance with the purposes of the invention, as embodied and broadly described, the invention also provides a metal-oxide-metal capacitor comprising a first interconnect layer, a first titanium nitride layer adjacent to the first interconnect layer, a first diffusion barrier adjacent to the first titanium nitride layer, a tantalum pentoxide layer adjacent to the first diffusion barrier, a second diffusion barrier adjacent to the tantalum pentoxide layer, a second titanium nitride layer adjacent to the second diffusion barrier, and a second interconnect layer adjacent to the second titanium nitride layer, wherein the first diffusion barrier prevents the diffusion of oxygen from the tantalum pentoxide layer into the first titanium nitride layer and the first titanium layer, and wherein the second diffusion barrier prevents the diffusion of oxygen from the tantalum pentoxide layer into the second titanium nitride layer.
To still further achieve these and other advantages and in accordance with the purposes of the invention, as embodied and broadly described, the invention also provides a metal-oxide-semiconductor transistor having a gate structure, the gate structure comprising an interconnect layer, a titanium nitride layer adjacent to the interconnect layer, a diffusion barrier adjacent to the titanium nitride layer, a tantalum pentoxide layer adjacent to the diffusion barrier, and a gate insulator adjacent to the tantalum pentoxide layer, wherein the diffusion barrier prevents the diffusion of oxygen from the tantalum pentoxide layer into the titanium nitride layer.
To still even further achieve these and other advantages and in accordance with the purposes of the invention, as embodied and broadly described, the invention also provides a diffusion barrier for preventing the diffusion of oxygen from a high dielectric constant material to a titanium nitride layer, the diffusion barrier comprising one or more layers, wherein each of the one or more layers comprises a material selected from the group consisting of metal carbide, metal nitride, metal boride, metal carbo-nitride, and silicon carbide.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed.
REFERENCES:
patent: 5912486 (1999-06-01), Summerfelt
patent: 5929475 (1999-07-01), Uemoto et al.
patent: 5942799 (1999-08-01), Danek et al.
patent: 6150706 (2000-11-01), Thakur et al.
I. C. Kizilyalli, etal. “MOS Transistors with StackedSiO2-Ta2O5-SiO2Gate Dielectrics for Giga-Scale Integration of CMOS Technologies” IEEE Electron Device Letters, 19, (11), Nov. 1998 pp. 423-425.
P. K. Roy et al., “Stacked high-e gate dielectric for gigascale integration of metal-oxide-semiconductor technologies” Applied Physics Letters 72 (22) pp. 2835-2837, Jun. 1, 1998.
J.H. Stathis et al., “Reliability Projection for Ultra Thin Oxides at Low Voltage”, 1998 IEDM Tech. Dig., pp. 167-170.
A. Chaterjee et al., “CMOS Metal Replacement Gate Transistors using Tantalum Pentoxide Gate Insulator” 1998 IEDM Tec. Dig., pp. 777-780.
Choi Seungmoo
Merchant Sailesh M.
Roy Pradip K.
Agere Systems Guardian Corp.
Meier Stephen D.
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