TECHNIQUE CONTROLLING PROCESS OF GROWTH OF MONOCRYSTALS FROM MELT AND DEVICE FOR ITS REALIZATION Russian patent published in 2002 - IPC

FIELD: manufacture of semiconductors. SUBSTANCE: technique can be employed to produce monocrystalline ingots of germanium. Device for implementation of process ( Fig.1 ) presents microprocessor system based on microcomputer 7 which controls growth of monocrystalline ingot 13 having diameter d with elongation rate V₃ and crystal rotation velocity ω₃ in chamber 12 by the Czochralski process. Molten metal 14 placed in melting pot 15 ( with inner diameter D ) rotates with angular velocity ω₁ and simultaneously rises up with rate V_m.p ( as amount of melt in melting pot decreases ). Ingot 13 is extracted from additional intermediate melting pot 20 with diameter of replenishment hole d_dr which in addition to required purity of melt in intermediate melting pot and uniformity of doping of grown ingot makes it possible to position level gauge 3 in more overheated zone of melt and to utilize additional heater 19 fed from source 18 with setting of minimal heating current I_∂ by computer for automatic heating of lower part of gauge. This approach makes it feasible to guarantee temperature of lower part of gauge contacting melt above possible temperature of its crystallization and to secure absence of built-up of melt on gauge in process of operation. Given microprocessor control system determines refined difference control signal Y as function of deviation of present area from specified one on basis of immediate translations of crystal and melting pot measured by transducers in the course of evaluation cycle of control signal given that level of melt in melting pot is kept constant. In periods of open state of melt level gauge rate of upward rise of melting pot is set greater by advance value N than it is necessary for condition of constancy of level of melt with specified diameter d₃ of crystal, inner diameter D of melting pot and present elongation rate V₃ of crystal. In periods of closed state of melt level gauge rate of rise diminishes by factor of M as compared with rate of open state of gauge maintaining in this case conditions of stabilization of level of melt. Later more precise difference control signal Y is used in adjustment system to diminish misbalance of area of growing crystal and to send signals over four channels: T₃-temperature of side point of heater, V₃-elongation rate, ω₃-crystal rotation velocity, ω_т-rotation velocity of melting pot which secures stabilization of area or diameter, if form is round, of growing crystal in process of entire technological cycle of growth of crystal without use of any optical or other methods for stabilization of level of melt and determination of present diameter of ingot. Invention makes it possible to input systematic ( by chart ) changes into process of growth simultaneously with stabilization of area ( diameter ) of growing crystal under any present values of all four control channels (T₃,V₃,ω₃,ω_т), as well as to place whole crystal into closed cylindrical screen or closed heating equipment practically without any visual inspection of ingot. EFFECT: improved reliability of control over growth of monocrystals. 2 cl, 1 dwg