Patent ID: 8378272

Claim:
A heat treatment apparatus to perform a heat treatment on a substrate for manufacturing a semiconductor disposed on a heat plate by a heater provided in the heat plate, comprising: three heat plates each configured to dispose the substrate and provided with the heater a temperature detecting part provided in each of the three heat plates configured to detect a temperature of the substrate disposed on each of the three heat plates; an adjusting unit configured to output a power control signal to each of the three heat plates based on a difference between a temperature setting value of the substrate and a temperature detection value of the temperature detecting part in each of the three heat plates; an AC power supply part configured to supply power to the heater provided in each of the three heat plates; a distribution part provided in the AC power supply part and configured to distribute each phase of three-phase AC of the AC power supply part to the heater of each of the three heat plates; a control unit configured to control a conduction rate of an AC voltage distributed from the distribution part of the AC power supply part and output to the heater of each of the three heat plates based on the power control signal in each of the three heat plates; a voltage detecting part configured to sequentially detect the AC voltage of each phase of three-phase AC; and a correction part configured to correct the power control signal output from the adjusting unit so that the conduction rate is decreased when a voltage detection value is increased or resistance of the heater is decreased, wherein the correction part corrects the power control signal output using a value obtained by multiplying a first correction value with a second correction value, the first correction value being generated according to a ratio of the voltage detection value of one of the phases of the three-phase AC detected by the voltage detecting part to a predetermined reference voltage, and the second correction value being generated according to a ratio of the resistance value of the heater of each of the three heat plates to which the AC voltage of a detected phase is distributed to a predetermined reference resistance value, and wherein the correction part corrects the power control signal output to each of the three heat plates, the reference voltage is the smallest value among a voltage variation of the AC voltage, the reference resistance is the largest value among a resistance variation of the heater, and the conduction rate becomes a maximum when the voltage detection value is the reference voltage and the resistance value is the reference resistance value.