Abstract
The process of growing silicon single crystals by the Czochralski method has been improved, which involves the use of two argon streams. 1st, the main flow, 15—20 nl/min, is directed from top to bottom along the growing single crystal. It captures the reaction products of the melt with a quartz crucible (mainly SiO), removes them from the chamber through a nozzle in the lower part of the chamber and provide dislocation-free single crystals from large loads. Similar processes are known and widely used in world practice since the 1970s. 2nd, additional flow, 1.5—2 nl/min, is directed at an angle of 45° to the surface of the melt in the form of jets from nozzles arranged in a ring. This flow initiates the formation of a region of turbulent melt flow, which isolates the crystallization front from convective flows enriched with oxygen, and also enhances the evaporation of carbon from the melt. It is confirmed that the oxygen evaporated from the melt (in the form of SiO) is a «transport» for non-volatile carbon. Carrying out industrial processes showed that the carbon content in the grown single crystals can be significantly reduced, up to values smaller than in the feedstock. In single crystals grown using two argon streams, an increased macro- and micro-uniformity of the oxygen distribution, a significantly larger crystal length with a given, constant oxygen concentration, were also recorded. Achieving a carbon concentration of 5 to 10 times less than in the feedstock is possible with small amounts of argon for melting (15—20 nl/min compared to 50—80 nl/min used in conventional processes. The use of an additional argon flow, which has an outflow intensity 10 times lower than that of the main flow, does not distort the nature of the flow around the single crystal surface (“axial”), does not disrupt the growth of a dislocation-free single crystal, does not increase the density of microdefects, which indicates the absence of changes in temperature gradients and thermal shock leading to thermal stresses in a single crystal.
Highlights
The process of growing silicon single crystals by the Czochralski method has been improved, which involves the use of two argon streams. 1st, the main flow, 15—20 nl/min, is directed from top to bottom along the growing single crystal
П. Деформационное дефектообразование в процессе роста монокристаллов кремния по методу Чохральского // Металлургия
Summary
При проведении настоящих исследований нами было принято во внимание, что давление и динамика потока инертного газа в ростовой камере могут в значительной степени влиять на распределение и концентрацию кислорода в монокристалле [35, 36]. (Формулы (1) и (2) приведены для обозначения значимых факторов, влияющих на кинетику процесса испарения (диффузионно− конвективный коэффициент испарения, коэффициент диффузии углерода в расплаве, скорость конвективного потока при испарении в вакуум, размер поверхности расплава, с которой происходит испарение и др.), управляя которыми можно влиять на интенсивность испарения углерода). После полного расплавления кремния перед началом затравливания к поверхности расплава подводилось специальное устройство, включающее сопла из термостойкого материала для подачи дополнительного потока аргона в виде струй. 1. Схема процесса выращивания в потоке инертного газа: 1 — растущий монокристалл; 2 — теплозащитные экраны; 3 — нагреватель сопротивления; 4 — тигель с расплавом кремния; 5 — патрубок отвода газов из ростовой камеры; Ar−1 — поток аргона, омывающий растущий кристалл (15—20 нл/мин); Ar−2 — поток аргона в виде струй (1,5—2,0 нл/мин)
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More From: Izvestiya Vysshikh Uchebnykh Zavedenii. Materialy Elektronnoi Tekhniki = Materials of Electronics Engineering
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