METHOD FOR SEPARATING PART OF GROWN SILICON MONOCRYSTAL WITH DESIRED CARBON DOPE Russian patent published in 2002 - IPC

FIELD: growing silicon monocrystals with desired concentration of carbon dope. SUBSTANCE: method includes evaluation of carbon concentration on each end of ingot formed upon separation of lower conical part of ingot followed by separation of ingot lower part where carbon concentration is higher than desired value. This separation is effected at distance from lower end equal to (1), where C₁ is carbon concentration on lower end of ingot formed in the process; C₂ is desired concentration of carbon dope including confidence interval; M₁ is ingot mass from upper to lower end of ingot; M_charge is mass of charge for growing monocrystal ingot; k is effective coefficient of carbon dope distribution; D is mean diameter of ingot; ρ is silicon density. Confidence interval ±γσ is found from Chebyshev inequality P(C₂-γσ≤C≤C₂+γσ)≥1-1/γ² (2), where C₂ is desired concentration of carbon dope including confidence interval equal to desired concentration of carbon dope minus γσ product; C is carbon dope concentration at lower end of ingot after cutting off part of ingot; σ is square root of dispersion found from comparison of calculated and experimental data; γ is positive number calculated for desired probability P = α, from formula γ_а = 1/(1-α²)^1/2 (3). Proposed method provides for rather precise evaluation of silicon monocrystal ingot length to be cut off with desired probability. EFFECT: facilitated procedure due to reduced time and labor consumption; reduced probability of silicon loss. 2 cl, 1 ex