High-resolution gas gauge proximity sensor
AssigneeASML Holding N.V.
InventorsBoguslaw F. Gajdeczko, Kenneth M. Bogursky, Daniel N. Galburt, Willy M. Sander, Kevin J. Violette
Life of this patent
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Abstract
An apparatus and method for precisely detecting very small distances between a measurement probe and a surface, and more particularly to a proximity sensor using a constant gas flow and sensing a mass flow rate within a pneumatic bridge to detect very small distances. Within the apparatus the use of a flow restrictor and/or snubber made of porous material and/or a mass flow rate controller enables detection of very small distances in the nanometer to sub-nanometer range. A further embodiment wherein a measurement channel of a proximity sensor is connected to multiple measurement branches.
Claims19
A gas gauge lithography proximity sensor for sensing a difference between a reference surface standoff and a measurement surface standoff, comprising:
- a junction that divides gas input into the gas gauge proximity sensor into a reference channel and a measurement channel;
- a first porous flow restrictor placed along the reference channel, wherein said first porous flow restrictor evenly restricts gas flow through the reference channel;
- a second porous flow restrictor placed along the measurement channel, wherein said second porous flow restrictor evenly restricts gas flow through the measurement channel;
- a reference probe at an end of the reference channel, wherein gas exits the reference channel through the reference probe and travels across a reference standoff to impinge upon a lithographic reference surface;
- a measurement probe at an end of the measurement channel, wherein gas exits the measurement channel through the measurement probe and travels across a measurement standoff to impinge upon a lithographic measurement surface;
- and
- a mass flow sensor coupled between the reference and measurement channels for sensing the mass of gas flow therebetween.
In lithography, a method for sensing a difference in a reference standoff and a measurement standoff, comprising the steps of:
- (a) distributing a flow of gas between a measurement channel and a reference channel;
- (b) forcing the flow of gas through porous restrictors substantially evenly across cross-sectional areas of both the measurement and reference channels;
- (c) outputting gas from the reference and measurement channels through nozzles to impinge upon a lithographic reference surface and a lithographic measurement surface, respectively;
- and
- (d) sensing a mass flow rate across a bridge channel that connects the reference and measurement channels, the mass flow rate being representative of the magnitude of a difference between a measurement standoff and a reference standoff.
A gas gauge proximity sensor for sensing a difference between a reference surface standoff and a measurement surface standoff, comprising:
- a junction that divides gas input into the gas gauge proximity sensor into a reference channel and a measurement channel;
- a first porous flow restrictor placed along the reference channel, wherein said first porous flow restrictor evenly restricts gas flow through the reference channel;
- a second porous flow restrictor placed along the measurement channel, wherein said second porous flow restrictor evenly restricts gas flow through the measurement channel;
- a reference probe at an end of the reference channel, wherein gas exits the reference channel through the reference probe and travels across a reference standoff to impinge upon a lithographic reference surface;
- a measurement probe at an end of the measurement channel, wherein gas exits the measurement channel through the measurement probe and travels across a measurement standoff to impinge upon a lithographic measurement surface;
- and
- a mass flow sensor coupled between the reference and measurement channels for sensing the mass of gas flow therebetween, wherein the first porous flow restrictor and the second porous flow restrictor are located between said junction and points on the reference channel and measurement channel wherein said mass flow sensor is coupled.
Dependencies are inferred from the claim text.