Robert Patrick Donovan

US Patent:

54395135, Aug 8, 1995

Filed:

May 31, 1994

Appl. No.:

8/251643

Inventors:

Ravindran Periasamy - Cary NC
David S. Ensor - Chapel Hill NC
Robert P. Donovan - Durham NC

Assignee:

Research Triangle Institute - Research Triangle Park NC

International Classification:

B03C 340

US Classification:

96 25

Abstract:

A device for controlling the motion of particles suspended in a gas stream is provided, including a pipe, through which at least a fraction of the gas stream flows, a source of AC voltage, a source of DC voltage, and a plurality of electrode sets positioned within the pipe in series, generating an inhomogeneous electric field to cause the particles suspended in the gas stream to concentrate into a narrow axial region in the center of the pipe. Each electrode set includes a first pair of opposed hyperboloidally shaped electrodes connected to the AC voltage source and a second pair of opposed hyperboloidally shaped electrodes connected to the DC voltage. The first and second pairs of opposed electrodes are positioned at spaced apart intervals around the circumference of the pipe to define an opening through which at least a fraction of the gas stream flows. The electrode sets are positioned within the pipe in series such that the gas stream flows through the openings defined by each successive electrode set. The spaced apart distance between the electrodes of each successive electrode set is decreased to reduce the size of the openings, causing the particles suspended in the gas stream to focus or concentrate along successively narrower axial regions in the center of the pipe.

US Patent:

52291715, Jul 20, 1993

Filed:

Dec 23, 1991

Appl. No.:

7/813121

Inventors:

Robert P. Donovan - Durham NC
Ravindran Periasamy - Cary NC
Anthony C. Clayton - Rougemont NC
David S. Ensor - Chapel Hill NC

Assignee:

Research Triangle Institute - Research Triangle Park NC

International Classification:

B05D 104

US Classification:

427483

Abstract:

An apparatus and method including a droplet coating generator for generating a stream of electrically charged coating droplets within an evacuable chamber towards a substrate positioned within the evacuable chamber. A piezoelectric vibrator and orifice plate coupled thereto generate the stream of coating droplets. The coating droplets are urged to move in a sweeping motion across the substrate by at least one pair of opposing spaced apart electrodes powered by an electrical power supply. A uniform coating is thus produced while the evacuable chamber is maintained at subatmospheric pressure as required during typical semiconductor processing. Multiple applications of a photoresist coating may be applied by the coating apparatus without requiring that the evacuable chamber be repeatedly vented and pumped down to subatmospheric pressure.