Constitutional Supercooling during the Crystal Growth of Germanium and Silicon

Abstract

Growth of heavily doped germanium and silicon crystals is investigated from the standpoint of constitutional supercooling. When the impurity concentration exceeds a certain value, corrugations appear on the crystal surface. The impurity concentration necessary for the appearance of the corrugation, the doping limit, is determined for various impurity elements. The analysis of the experimental results shows that definite magnitude of supercooling is required for the irregular growth of crystals which gives rise to corrugations on the crystal surface and results in the formation of polycrystals.

Phosphorus Concentration Limitation in Czochralski Silicon Crystals

“…When constitutional supercooling occurred, the characteristic corrugated structure appeared on the cross section of a crystal. 3,4 In this study, we did not observe the corrugated structure. Instead, we observed dislocations generated in the center of crystals some distance above the solid/melt interface where doping concentrations reach a critical value.…”

“…1 In the Czochralski (CZ) crystal growth process, the concentration of a dopant that can be incorporated in a crystal is usually limited by the solid solubility limit of the dopant in the silicon lattice and the constitutional supercooling phenomenon. [2][3][4] For the n-type dopants in silicon, the maximum solid solubility limit for phosphorus is 1.3 ϫ 10 21 atom/cm 3 which is slightly lower than the maximum solid solubility of arsenic (1.7 ϫ 10 21 atom/cm 3 ) and much higher than that of antimony (7 ϫ 10 19 atom/cm 3 ). 4,5 If a crystal can incorporate the maximum solid solubility of an individual dopant, the lowest resistivity for a Sb-doped wafer would be about 0.0011 ⍀-cm and for P-doped and As-doped wafers would be lower than 0.00015 ⍀-cm.…”

“…[2][3][4] For the n-type dopants in silicon, the maximum solid solubility limit for phosphorus is 1.3 ϫ 10 21 atom/cm 3 which is slightly lower than the maximum solid solubility of arsenic (1.7 ϫ 10 21 atom/cm 3 ) and much higher than that of antimony (7 ϫ 10 19 atom/cm 3 ). 4,5 If a crystal can incorporate the maximum solid solubility of an individual dopant, the lowest resistivity for a Sb-doped wafer would be about 0.0011 ⍀-cm and for P-doped and As-doped wafers would be lower than 0.00015 ⍀-cm. However, due to other constraints, the lowest resistivity (tang-end) wafer producible for 100 mm (111) Sb-doped wafers is about 0.004 ⍀-cm, for P-doped wafer is about 0.0007 ⍀-cm (1.1 ϫ 10 20 atom/cm 3 ) and for As-doped wafer is about 0.0012 ⍀-cm (6.04 ϫ 10 19 atom/cm 3 ).…”

“…4 This reported value was performed on very small diameter crystals in 1963. When constitutional supercooling occurred, the characteristic corrugated structure appeared on the cross section of a crystal.…”

Enhancement effect of nitrogen co-doping on oxygen precipitation in heavily phosphorus-doped Czochralski silicon during high-temperature annealing

“…Note that the heavily phosphorous (P)-doped CZ-Si could possess the lowest resistivity among n-type heavily doped CZ-Si [3,4], thus, it is a promising material for some certain power devices that require the substrates with resistivity as low as possible. However, it is generally believed that oxygen precipitation is suppressed in heavily doped n-type CZ-Si [1,5,6].…”