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Process Design & Integration of Salicide and Source/Drain process Modules for Improved Device Performance

Published online by Cambridge University Press:  10 February 2011

Pushkar P. Apte
Affiliation:
Texas Instruments, Dallas, TX
Shared Saxena
Affiliation:
Texas Instruments, Dallas, TX
Suraj Rao
Affiliation:
Texas Instruments, Dallas, TX
Karthik Vasanth
Affiliation:
Texas Instruments, Dallas, TX
Douglas A. Prinslow
Affiliation:
Texas Instruments, Dallas, TX
Jorge A. Kittl
Affiliation:
Texas Instruments, Dallas, TX
Terence Breedijk
Affiliation:
Texas Instruments, Dallas, TX
Gordon Pollack
Affiliation:
Texas Instruments, Dallas, TX
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Abstract

To enable swift integration of process modules into manufacturable process flows; three components – individual process modules, their interactions and their variability-must be understood well. At dimensions ≤ 0.25 μm, this understanding is especially critical, and also quite challenging. We present here an approach to address this challenge by joint process design, using two key modules-salicide and source/drain-as an example. Together, these modules impact the silicide-to-diffusion contact resistance, (Rc), and the gate sheet resistance (Rs); which, in turn, significantly affect transistor series resistance and circuit delays respectively. We have built a model to help provide insight into the underlying physical mechanisms, and to help provide a quantitative framework for optimizing performance and variability. Rc, depends critically on the doping concentration immediately adjacent to the silicide, and this concentration is determined by the combined effect of silicide processing and the two-dimensional source/drain dopant profile. Rs depends on the thickness and phase of the silicide film formed, which, in turn, depend on the salicide process variables as well as the source/drain doping concentration, because both affect the silicide growth kinetics. Process conditions favoring Rs. and Rc are opposite to each other: thicker silicide films and higher thermal budgets help in the phase-transformation to the low-resistivity C54 phase and improve Rs but they increase dopant redistribution and worsen Rc. Optimal process design can improve the transistor drive current (Id) by ≈5%, and circuit performance, as measured by the figure-of-merit (FOM) by ≈ 4%. This improvement is significant, and an added benefit of this approach is that other transistor characteristics such as effective channel length, off-current, substrate current, etc. remain unchanged. In summary, we have demonstrated that by joint process design and integration of the salicide and source/drain modules, insight can be gained into the underlying physical mechanisms, and device and circuit performance can be improved significantly.

Type
Research Article
Copyright
Copyright © Materials Research Society 1998

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