Compete hot plate temperature control system for hot treatment

A heat treatment control device to regulate a temperature to cure a photoresist material disposed upon a semiconductor substrate, comprising:

• a) a heating apparatus onto which said semiconductor substrate is positioned to heat said semiconductor substrate;
• b) a controlling device to selectively couple an electrical power source to the heating element, wherein the coupling of the electrical power source is determined by an error signal and said error signal will approach a null value when the temperature approaches the desired temperature;
• c) a first temperature sensing device coupled to the heating apparatus to provide and to condition a first electrical signal that represents the magnitude of the temperature;
• d) a second temperature sensing device coupled to the heating apparatus to provide and to condition a second electrical signal that represents the magnitude of the temperature;
• e) a comparing means to compare a temperature set signal that represents the desired temperature and the measured temperature signal to form the error signal;
• f) an over temperature alarm means coupled to the second temperature sensing device to monitor the second electrical signal, to provide an first audible signal and a first visual alarm if the temperature is at a level such as to cause damage to the photoresist material;
• and
• g) a power monitoring circuit to detect the presence and absence of the electrical power source, wherein said power monitoring circuit provides a second audible signal and a second visual alarm if the electrical power source is absent.

A method to control the heat treatment apparatus to heat a semiconductor substrate to cure a photoresist deposed upon said semiconductor substrate, comprising the steps of:

• a) coupling an electrical power source to a heating element to heat said semiconductor substrate;
• b) providing a first temperature measurement of the semiconductor substrate;
• c) comparing said first temperature measurement to a temperature set level to form an error signal;
• d) examining the error signal;
• e) for the error signal indicating a temperature greater than a desired temperature, diagnostic testing of the controlling device;
• f) for the controlling device functioning correctly, uncoupling said electrical power source to lower the temperature, and,
• g) for the controlling device not functioning correctly, uncoupling the electrical power source from the heating element and activating a first audible alarm and a first visual alarm;
• h) for the error signal indicating the temperature is less than the desired temperature, diagnostic testing of the controlling device;
• i) for the controlling device functioning correctly, sensing a current from said electrical power source to said heating element to verify said coupling;
• j) if said coupling is present, returning to providing the first temperature measurement while allowing the temperature to raise;
• k) if said coupling is not present and a fault timing period has elapsed, activating a second audible signal and a second visual alarm
• j) if said couplings become present before said fault timing period has elapsed, returning to providing the first temperature measurement while allowing the temperature to raise;
• m) for the controlling device not functioning correctly, uncoupling of the electrical power source and activating the second audible alarm and the second visual alarm;
• n) simultaneously to the foregoing steps, providing a second temperature measurement;
• o) comparing said second temperature measurement to an over temperature threshold;
• p) if said second temperature measurement is greater than the over temperature threshold, uncoupling of the electrical power source and activating a third audible alarm and a third visual alarm;
• and
• q) if said second temperature measurement is less than the over temperature threshold, repeatedly providing and comparing the second temperature measurement.