Monocrystalline Silicon Growth in Microgravity Using Automated Technological Process Control System

Abstract

Solar batteries work based on special modules - photocells that capture solar energy and convert it into electric current using semiconductor devices. Photocells are solar panels made from homogeneous monocrystal silicon, which has not only high quality but also high performance. Under terrestrial conditions, the monocrystal silicon growth is carried out by the Czochralski method, in which, when the seed from the crystal comes into contact with the surface of the silicon melt, the atoms of which, in contact with the seed, lose energy and freeze, which leads to the growth of a silicon monocrystal. However, under terrestrial conditions, gravity creates a strong thermal gravitational convection, leading to instability of the monocrystal silicon growth parameters, which limits the possibility of obtaining monocrystal silicon with a high degree of uniformity.
Microgravity, where, due to the absence of the Archimedes force, thermo gravitational convection is not formed during the melting of silicon, opens up all the possibilities for obtaining monocrystal silicon with a high degree of uniformity
However, although the first results of monocrystal silicon growth in microgravity conditions showed the results of obtaining a more perfect, compared to terrestrial, monocrystal silicon, at the same time it was found that under microgravity conditions in silicon melts, new non-gravitational convective processes arise - Marangoni convection, as well as (in the presence of residual gravity) small thermo gravitational processes due to reduced gravity, leading to problems in the process of homogeneous monocrystals of silicon growth.
The task arises of developing such a technology that could eliminate these non-gravitational convection processes occurring in silicon melt under microgravity conditions in the process of monocrystal silicon growth under the control of a specially developed automated control system of this technological process.
The paper presents the developed automated control system of the technological process of monocrystals silicon of high homogeneity growth by the Czochralski method under microgravity conditions, in which the elimination of non-gravitational convective processes that occur under microgravity conditions is carried out using controlled vertical vibration in vibroturbulization mode for mixing of the internal components of the silicon melt, automatically.