Patent ID: 8282766

Claim:
An etch apparatus, comprising: a process tank provided for an etch bath; a reservoir provided for a wet chemical etchant, the reservoir being connected to the process tank; a supply of a diluting liquid; a drip valve for controlling the amount of the diluting liquid in the supply; a drip directly connected to the process tank; a flow sensor arranged between the drip and the drip valve; a recirculation line connected with the process tank; a recirculation pump provided for the recirculation line, wherein the recirculation pump comprises a transducer sensor; a heater thermally connected with the recirculation line, the heater comprising at least two heater units, each heater unit having a current sensor, and the heater being operated at a power level that is required for maintenance of the etch bath; a temperature detector thermally connected with the process tank; and a control unit coupled to the temperature detector, the tranducer sensors, the current sensor, and the flow sensor, the control unit controlling the temperature of the process tank based on the acid concentration of the etch bath.