Exigent-Accommodation-Volume of Precipitation and Formation of Oxygen Precipitates in Silicon
- PDF / 712,368 Bytes
- 11 Pages / 420.48 x 639 pts Page_size
- 1 Downloads / 213 Views
EXIGENT-ACCOMMODATION-VOLUME OF PRECIPITATION AND FORMATION OF OXYGEN PRECIPITATES IN SILICON
T. Y. TAN IBM Thomas J. Watson Research Center, Yorktown Heights, NY 10598
ABSTRACT In this paper we first describe, in some detail, the nature of an exigentaccommodation-volume factor associated with oxygen (O) precipitation in Czochralski (CZ) Si. This factor is regarded as a causal or characteristicfactor which influences many aspects of the SiO 2 precipitate nucleation and growth phenomena. Employing this factor, we then describe the possible explanations of two outstanding features of Oi precipitation in CZ Si: the precipitation retardation/recovery phenomena and the nucleation incubation phenomena.
I. INTRODUCTON "The driving force for nucleation is the volume free energy change attending the transformation, AGe, minus the volume strain energy (if any) arising from the size and/or shape misfit between the cluster and the matrix, AGe. The barrier to nucleation is the interfacialfree energy of the cluster matrix interface, AGS." 1 From this statement, it is clear that materials scientists are aware of the importance of an exigent-volume factor of accommodation associated with precipitation, which constitutes as one reason leading to AGe. In metals, the effect due to AGe is usually small but need to be included quantitatively in the classicil theory of nucleation. Total dominance of this factor which leads to experimental results apparently defying the description of the classical nucleation theory (based on either a homogeneous or heterogeneous mechanism) on a qualitative basis, however, seems to be lacking. There exist at least two kinds of phenomena associated with oxygen precipitation in Czochralski (CZ) Si which seems to defy the description of the classical nucleation theory on a qualitative basis. The first is the precipitation retardation/recovery phenomena in lo-hi (or nucleation-growth) two-step anneal studies.2-4 The second is a nucleation incubation phenomena associated with a single step anneal using homogenized (high temperature annealed and rapidly 5 quenched) materials.
Mat. Res. Soc. Symp. Proc. Vol. 59. C1986 Materials Research Society
270
The purpose of this paper is to present a discussion of the exigent-volume factor and then use the insight to provide some possible explanations to the above mentioned phenomena.
II. EXIGENT-ACCOMMODATION-VOLUME OF PRECIPITATION In addition to the mass conservation law Si+20i O
SiO 2 ,
()
for precipitation deep inside silicon (which is a highly perfect single crystal with a very small self-diffusion coefficient), we must also consider a volume conservation law
vsi+2voi+6v = VSi 0 ,
(2)
where v denotes the volume of the appropriate atom or molecule. We call VSio2 the precipitation accommodation volume since this is the proper amount of volume needed for precipitate growth to proceed by the addition of one SiO 2 molecule without encountering a volume shortage, 8v the exigent-volume of precipitation since it is part of the accommodation volume urgently req
Data Loading...
