Methods of fault detection for multiplexed heater array

A method of fault detection in a substrate support assembly in a semiconductor processing apparatus, the method comprising:

• arranging a semiconductor substrate on the substrate support assembly;
• supplying power to a plurality of heater zones of a heating plate of the substrate support assembly via a plurality of power supply lines such that power is supplied to each of the heater zones independently of power supplied to others of the heater zones;
• obtaining a measured total heating power of the power provided by the plurality of heater zones by independently determining a respective heating power provided by each of the plurality of heater zones and calculating a sum of the respective heating powers;
• comparing the measured total heating power to a pre-established total heating power of the plurality of heater zones;
• and
• if the measured total heating power deviates from the pre-established total heating power by a pre-determined margin, triggering an alarm signal;
• wherein the measured total heating power is obtained by measuring a voltage V across each of the one or more heater zones, measuring a current I flowing through each of the one or more heater zones, multiplying V by I, and adding V·I of each of the one or more heater zones.