Study of the model of liquid-phase recrystallization of a polysilicon layer on a sapphire substrate
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Study of the Model of LiquidPhase Recrystallization of a Polysilicon Layer on a Sapphire Substrate G. A. Lebedev, S. P. Malyukov, and D. I. Cherednichenko Taganrog Institute of Technology, South Federal University, Taganrog, Russia email: [email protected] Received February 18, 2008
Abstract—The dynamics of the transformation of a polysilicon layer on a sapphire substrate by liquidphase recrystallization with a scanning heat source is considered. PACS numbers: 81.10.Fq DOI: 10.1134/S1063774509040233
a concentrated heat source scanning along the struc ture surface.
INTRODUCTION The fraction of silicononinsulator (SOI) struc tures among the initial substrates used in the produc tion of discrete devices and integrated circuits (ICs) constantly increases [1]. SOIbased ICs are more reli able because the isolation of IC elements by an insula tor is better than the isolation by p–n junctions in the ICs based on singlecrystal semiconductors. SOI structures can be used as a base to fabricate more com plex structures (for example, SiGe/Si [2]) with opto electronic properties, which are absent in silicon. In addition, SOI structures also have good prospects because the variety of their possible designs satisfy overwhelming majority of the requirements of IC developers [3]. The technologies of silicononsapphire (SOS) structures with ultrathin device layers are based on the processes of epitaxial layer transformation. One of the transformation methods is liquidphase recrystalliza tion of the epitaxial layer by a concentrated heat source. To exclude the chemical interaction of the substrate with the transformed layer, the melting depth is chosen so as to space the molten layer bottom at some distance (20–100 nm) from the substrate surface [3]. Combining solidphase recrystallization of the transient region of the device layer and liquidphase recrystallization of its surface part allows one to obtain high quality SOS layers. Along with a decrease in the defect density, liquidphase recrystallization improves the layer surface morphology, because the initial sur face roughness decreases to 0.2–0.5 nm. Although liquidphase recrystallization has been used for a long time, the search for new methods to obtain singlecrystal layers and study the their forma tion kinetics continues. In this paper, we report the results of studying the model of liquidphase recrystal lization of a polysilicon layer on a sapphire substrate by
FORMULATION OF THE COMPUTATIONAL MODEL IN THE MELTING ZONE The problem related to describing the processes of solid melting and melt crystallization, as stated by Ste fan, belongs to the theory of thermal conductivity for situations with a moving liquid–solid interface. The law of interface motion is generally unknown; there fore, one of the main tasks in solving the Stefan prob lem is to determine the interface motion law. This problem is nonlinear; it cannot be solved analytically in certain cases and requires the development of a spe cial research method. A closed solu
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