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Automated Czochralski Crystal Growth

IP.com Disclosure Number: IPCOM000078460D
Original Publication Date: 1973-Jan-01
Included in the Prior Art Database: 2005-Feb-26
Document File: 2 page(s) / 43K

Publishing Venue

IBM

Related People

Angilello, J: AUTHOR [+2]

Abstract

In any Czochralski crystal growth system there is often a need to increase, decrease, or maintain the diameter of the growing crystal constant for a predetermined length of crystal without the presence of an operator.

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Automated Czochralski Crystal Growth

In any Czochralski crystal growth system there is often a need to increase, decrease, or maintain the diameter of the growing crystal constant for a predetermined length of crystal without the presence of an operator.

Since a temperature sensor (optical pyrometer) can sense the temperature of a growing crystal over a small area as indicated schematically in Fig. 1 and, can be moved to any area at the melt or crystal surface; it is possible to obtain a temperature profile similar to that shown in Fig. 2. The temperatures shown in Fig. 2 at points T1-T7 correspond to points T1-T7 in Fig. 1, where the temperatures were obtained at various points on the crystal and liquid melt. It should be noted that there is an abrupt change in temperature as one goes further away from the interface on the surface of the liquid melt. Note particularly the sharp transition from point T4 to point T7 in Fig. 2.

These signals placed on a recording potentiometer in conjunction with a pair of microswitches, one set for a lower and another for an upper limit, permit the diameter of the crystal to be controlled while it is being pulled. Thus, if the crystal starts to get too small in diameter, the temperature sensor shows a higher temperature, which in turn activates the high-temperature microswitch H, shown in Fig. 3, and the "Read Me" timer lowers the power to the power supply by desired increments, until the crystal obtains the desired diameter. If t...