Growth Of Microdefects Research Articles

Кинетика образования и роста микродефектов в кристаллах

Кинетика образования и роста микродефектов в кристаллах

A Selective Review of the Quantification of Defect Dynamics in Growing Czochralski Silicon Crystals

A vast majority of modern microelectronic devices are built on the monocrystalline silicon substrates produced from the crystals grown by the Czochralski (CZ) process and the float-zone (FZ) process. Silicon crystals inherently contain various precipitates known as microdefects that often affect the yield and the performance of many devices. Hence, the quantitative understanding and the control of the microdefect formation and the microdefect distributions in silicon crystals play a central role in determining the quality of silicon substrates. This paper reviews significant developments in the field of the quantification of the defect dynamics in growing CZ and FZ crystals. The breakthrough discovery of the initial point defect incorporation in the vicinity of the melt/crystal interface made in the early 1980s allowed a simplified quantification of the CZ and the FZ defect dynamics. A deeper insight into the formation and the growth of microdefects was provided over the past decade by various treatments of the agglomeration of the intrinsic point defects of silicon. In particular, a rigorous quantification of the agglomeration of the point defects using the classical nucleation theory, a recently developed lumped model that captures the microdefect distribution by representing the actual population of microdefects by an equivalent population of identical microdefects, and another rigorous treatment involving the Fokker−Planck equations are discussed in detail.

Investigations to the effect of heating-rate on the mechanical properties of aluminum alloy LY12

Two classes of experiments were conducted with a Gleeble 1500 thermal–mechanical testing system to investigate the effect of heating-rate and its history on the mechanical behavior of aluminum alloy LY12. In the first class of experiment, specimens were heated at different heating-rates to prescribed temperatures and then stretched until fracture. It was found that the specimen heated with higher heating-rate possesses lower rupture strength. In the second class of experiment, the specimens were preloaded and then heated at different rates until fracture. It was found that the higher the heating-rate was, the lower the failure temperature would be. Metallographical analysis showed that there are more defects in the specimens undergoing higher heating-rate. It was conjectured that higher heating-rate may cause stronger local thermal inconsistency due to the heterogeneous nature of the material. It may then cause local residual microstress fields, which, together with external thermal–mechanical load, may result in the changes in the microstructure of the material, such as recovery, recrystallization, nucleation and growth of microdefects, accounting for the changes in the macroscopic mechanical properties including hardening/softening, damage and failure, etc. A numerical simulation was performed, in which the mechanisms of local thermal inconsistency and the effect of the influencing factors were investigated.

Formation of Micro-Precipitates at the Melt-Solid Interface in Semiconductors

AbstractA theory is developed for the formation of precipitates in very dilute hypereutectic two phase systems during solidification. It is based on a mechanism for the growth of microdefects at the melt -interface. The model presents a solution of the diffusion problem for the solute atoms in the melt and provides an analysis of the factors which determine the particle size and their mean distance. The possibility of microdefect nucleation in front of the melt -interface, which can lead to very large precipitates, is discussed. The model is suitable to describe the formation of microdefects in semiconductors where impurity concentrations are generally low but may exceed the solubility limit in the melt. The results of the theory are compared with experimental investigations of the silicon carbide formation in carbon rich silicon crystals grown from the melt.