Gas Flow Engineering in Rapid Thermal Processing

Abstract

Gas flow engineering involves gas dynamics optimization for effective ambient change before heating and for homogeneous convective cooling of the wafers during the heating steps. Multiple gas buffle system, dynamical gas handling, low pressure operation, low temperature edge guard ring and independent top and bottom heater bank control are the proper tools for this optimization. Silicon surface or interface damage during inert gas anneal can be avoided by addition of a small amount of oxygen.

Rapid thermal processing of magnetic materials

“…For a pyrometer measurement system, the high background radiation originating from the lamps and walls affects the accuracy of the real temperature and the temperature measurement deviation for batch-to-batch samples. There are also some other indirect temperature measurements, such as the utilization of a 'hotliner' beneath the wafer as proposed by Nenyei et al [26] and the use of an acoustic thermometer developed by Degertekin et al [27]. The mechanism involved for the latter is the measurement of sound waves through the wafer whilst the temperature is believed to be insensitive to the emissivity variation, resolving the problem raised by optical pyrometry.…”

Improvement in ultrathin rapid thermal oxide uniformity by the control of gas flow

“…Methods proposed to improve this cooling effect are either limited by gas pressure or incomplete compensation to this effect. One method is to operate the RTP at a low pressure in the range of 1-100 millitorr, which is free from the cooling effect of the ambient gas and with a longer processing time [10], which violates the spirit of RTP. The other methods are concentrated on the increase of radiation by the design of lamp array [11] or the decrease of the radiation heat loss at the wafer edge by the usage of a guard ring which has the same thermal behavior as the wafer.…”

“…The other methods are concentrated on the increase of radiation by the design of lamp array [11] or the decrease of the radiation heat loss at the wafer edge by the usage of a guard ring which has the same thermal behavior as the wafer. But since the cooling effect is a strong function of the ambient gas and the gas pressure [10], radiation compensation can not completely solve the convection-induced nonuniformity. In addition to oxide thickness uniformity, heat convection should be considered to reduce the thermal stress on the wafer since as the heating process halts, the transferred heat is dominated by convection rather than the radiation loss from the wafer edge.…”

“… 10. shows the relation of the resulted oxide thickness and standard deviation versus the gap spaces.…”

Improvement in oxide thickness uniformity by repeated spike oxidation

“…The wafer absorbs heat from lamps mainly by radiation in RTP system so that much research was taken on the compensation of thermal radiation, such as system geometry [2], [3], number and location of lamps [4], [5], and patterned reflectors [6]. To suppress convection-induced nonuniform thermal distribution, some studies were performed on the gas flow phenomenon during the process [7], [8]. In addition, conduction compensation can be done by patterned susceptors [9].…”