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Source: SEMICONDUCTOR MANUFACTURING HANDBOOK

CHAPTER 15

EPITAXY

Jamal Ramdani
MEMC Electronic Materials Inc.
St. Peter, Missouri

Giovanni Vaccari
MEMC Electronic Materials Inc.
Novara, Italy

15.1 INTRODUCTION

The last three decades have witnessed a remarkable growth in the electronic and optoelectronic
industry. The growth and preparation of semiconductor materials have played a major role in this
success.
The ability to prepare high-purity semiconductor materials, control interfaces and the doping pro-
file and type, and engineer new material combinations has opened the door to new and higher per-
formance electronic and photonic devices. Quantum-wells-based laser diodes and photodetectors,
high-mobility two-dimensional electron gas transistors, heterojunction bipolar transistors, high-
brightness GaN light emitting diodes, and strained silicon are a few examples of the devices that have
emerged from material growth processes.
Hand in hand with material engineering progress, equipment and chemical manufacturers have
shown similar aggressiveness in developing state-of-the-art deposition tools and high-purity source
materials to meet the ever-challenging demands for higher quality materials, lower costs, and safer
operations.
At the speed at which information technology is evolving, we look forward to meeting the mar-
ket demand and the challenge of next generation electronic and photonic devices.

15.1.1 Basics of Epitaxy
1
Royer first introduced the word epitaxy in 1928 from Greek meaning “ordered upon.” Epitaxy refers
to the growth of a crystal (epitaxial layer or epilayer) upon a host crystal (substrate) in an ordered
fashion. In other words, the symmetry between the contacting crystal planes must be respected. The
growth mode depends on lattice mismatch or the difference between the parallel lattice constant of
the epilayer and that of the substrate and their chemical compatibility. Thermodynamically, the equi-
librium morphology or the growth mode is governed by the relationship of the sum of epilayer sur-
face free energy (E ) and epilayer-substrate interface free energy (E ) with respect to substrate
ep i
surface free energy (E ), also known as wetting conditions. Three main growth regimes have been
s
identified and are illustrated in Fig. 15.1.

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