Automatic liquid dispensing apparatus for spinning surface of uniform thickness
AssigneeRCA Corporation
InventorsJohn P. Beltz, Kenneth W. Hang
Life of this patent
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Abstract
An automatic fluid dispensing apparatus for coating to a substantially uniform thickness a rotating surface, such as the surface of a semiconductor wafer, with a viscous liquid, such as a slurry of passivating glass. The wafer rotation rate is related to the radial movement of a dispensing arm to maintain a constant tangential velocity of the wafer at the radial location of the dispensing arm while a bead of the slurry is dispensed at a constant rate proportional to the tangential velocity to provide a spiral beaded coating of constant volume per square. By allowing the bead to heal during or following the dispense cycle, the viscous liquid spreads to a uniform thickness.
Claims13
In a system for automatically coating material on a rotating surface having means for dispensing viscous liquid containing the coating material on said surface through a dispenser nozzle supported by an arm, and means for moving said arm and said nozzle radially over said surface whereby the liquid is dispensed over said surface along a spiral path, characterized by
- means for varying the angular rotation velocity (.omega.) of said surface as a function of the radial position (R) of said dispensing nozzle such that the tangential velocity (V.sub.t) determined by R.times..omega. is substantially constant over said surface,
- means for varying the rate of radial movement of said nozzle to maintain a substantially constant pitch of the spiral path;
- and
- means for controlling the flow of said liquid through said nozzle at a substantially constant flow rate proportional to said tangential velocity whereby the liquid is dispensed so that the volume per square of material over said surface is constant.
A method for automatically coating a material on a rotating surface including the step of dispensing a viscous liquid containing the coating material through a nozzle moved radially over the surface whereby the liquid is dispensed over the surface along a spiral path, characterized by the steps of:
- varying the angular rotation velocity (.omega.) of said surface as a function of the radial position (R) of said dispensing nozzle such that the tangential velocity (V.sub.t)=R.times.(.omega.) is substantially constant over said surface,
- varying the rate of radial movement of said nozzle to maintain a substantially constant pitch of the spiral path;
- and
- controlling the flow of liquid through said nozzle to a substantially constant value,
- whereby the liquid is dispensed so that the volume per square of material over said surface is constant.
Dependencies are inferred from the claim text.