Apparatus and method for uniformly coating a substrate in an evacuable chamber

Donovan, R. P., Periasamy, R., Clayton, A., & Ensor, D. (1993). IPC No. U.S.Apparatus and method for uniformly coating a substrate in an evacuable chamber (Patent No. 5229171.)

An apparatus and method including a droplet coating generatorfor generating a stream of electrically charged coating dropletswithin an evacuable chamber towards a substrate positioned withinthe evacuable chamber. A piezoelectric vibrator and orifice platecoupled thereto generate the stream of coating droplets. Thecoating droplets are urged to move in a sweeping motion across thesubstrate by at least one pair of opposing spaced apart electrodespowered by an electrical power supply. A uniform coating is thusproduced while the evacuable chamber is maintained atsubatmospheric pressure as required during typical semiconductorprocessing. Multiple applications of a photoresist coating may beapplied by the coating apparatus without requiring that theevacuable chamber be repeatedly vented and pumped down tosubatmospheric pressure.