Effect of doping level during rapid thermal processing of multilayer structures
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Effect of doping level during rapid thermal processing of multilayer structures A. R. Abramson Thermal Analysis of Materials Processing Laboratory, Tufts University, Medford, Massachusetts 02155
P. Nieva Department of Electrical and Computer Engineering, Northeastern University, Boston, Massachusetts 02155
H. Tada Thermal Analysis of Materials Processing Laboratory, Tufts University, Medford, Massachusetts 02155
P. Zavracky Department of Electrical and Computer Engineering, Northeastern University, Boston, Massachusetts 02155
I. N. Miaoulis and P. Y. Wonga) Thermal Analysis of Materials Processing Laboratory, Tufts University, Medford, Massachusetts 02155 (Received 24 July 1998; accepted 5 February 1999)
A numerical model has been developed to examine the temperature history of a multilayer wafer undergoing rapid thermal processing (RTP) for various doping densities. Partial transparency and thin film interference effects are considered. Doping levels from ,1015 to ,1018 cm23 are examined. Numerical temperature predictions of the lightly doped wafer are compared with experimental measurements. Heating rates for the lightly doped wafer fluctuate due to partial transparency effects and reach a maximum of ,50 ±Cys. The heavily doped wafer sees a maximum heating rate of ,100 ±Cys. Because the wafers are opaque above 700 ±C regardless of their level of doping, all wafers reach steady state at ,845 ±C.
I. INTRODUCTION
The doping level of a semiconductor defines its conductivity, and therefore its suitability for a particular application. During the fabrication of microelectronic devices from silicon wafers, the doping density influences the heating characteristics of the wafer, thereby affecting the temperature uniformity, transient temperature variations, and possibly the functionality of the device. Because the rate of increasing temperature can be important to the success of a process, and temperature nonuniformity can lead to slip generation1,2 and nonuniform film deposition,3 the ability to measure, predict, and control the temperature profile of a silicon wafer during the entire thermal process is a strict requirement. In a typical thermal processing application such as rapid thermal annealing or rapid thermal processing (RTP), the requirement for high processing temperatures and short processing times makes temperature control imperative. The doping level of the wafer and various other properties including the wafer thickness, wafer temperature, angle of incident radiation, spectral distribution and a)
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2402
http://journals.cambridge.org
J. Mater. Res., Vol. 14, No. 6, Jun 1999
Downloaded: 23 Aug 2015
temperature of the heat source, and the presence of thin film structures or patterns further influence thermal radiative property variations during RTP. Although previous studies have examined individual microscale radiation effects for different doping densities,4–6 there has been limited study
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