Jh. Kiely et al., THE DESIGN AND FABRICATION OF A MINIATURE THERMOELECTRIC GENERATOR USING MOS PROCESSING TECHNIQUES, Measurement science & technology, 5(2), 1994, pp. 182-189
The fabrication of thermoelectric generators using standard MOS thin f
ilm technology is described. Process sequences are presented for gener
ators based on both silicon on sapphire and polycrystalline silicon on
quartz substrates; the active elements being formed in both cases by
ion implantation of alternate n-type and p-type regions. Device perfor
mance is evaluated and presented for both types of converter in terms
of conversion efficiency and voltage and power outputs as a function o
f temperature difference. For thermoelements with a carrier concentrat
ion of 5 x 10(19) cm-3 the overall Seebeck coefficient for a single th
ermocouple is approximately 500 muV K-1 for both silicon on sapphire a
nd silicon on quartz. Extrapolation of results indicates that voltage
and current levels suitable for powering a microelectronic circuit (i.
e. greater than 1 muA at 1 V) can be obtained from a chip of dimension
s 0.5 cm x 1 cm x 0.045 cm. The use of polycrystalline silicon on quar
tz as opposed to silicon on sapphire has been shown to offer two major
advantages. Firstly, due to the high thermal resistivity of quartz, t
he conversion efficiency of the resulting silicon on quartz chip is gr
eater than for the silicon on sapphire case. For a substrate of dimens
ions 0.5 cm x 1 cm x 0.045 cm the improvement in device efficiency is
almost 50 fold. Secondly, material costs are reduced when polycrystall
ine silicon on quartz is adopted, whilst, since the actual processing
sequences are similar, manufacturing costs will remain approximately t
he same.