Simulation to confirm the existence of distinct low-temperature regions in a Si melt using an insulating plate under the crucible bottom for the noncontact crucible method

Abstract

The noncontact crucible (NOC) method has a large and deep low-temperature region in the upper central part of a Si melt to allow natural crystal growth inside it. Thanks to the low-temperature region, the NOC method can grow a uniform large Si single ingot without contact with the crucible wall. Using simulation of the temperature distribution in the Si melt, the establishment of the low-temperature region is clearly shown on basis of controlling the heat flow from the bottom heater into the Si melt using an insulating plate locally set under the crucible bottom. The heat from the bottom heater can be effectively weaken especially for the heat flow from the crucible center, resulting in the quite large low-temperature region in the melt. The effectiveness of such heat-flow control was proved by the growth of several Si single ingots using the NOC method. The effects of the heat power balance and the thickness of the insulating plate are also shown by the simulation. The temperature gradient in the NOC ingot is clearly smaller than that in an ingot grown by the Czochralski (CZ) growth mode.