Developer endpoint detection in a track lithography system
A method of detecting developer endpoint. The method includes illuminating a device region of a substrate with a first optical beam prior to initiating a development stage of processing and detecting a baseline optical signal reflected from the device region of the substrate. The method also includes illuminating the device region of the substrate with a second optical beam during a development stage of processing and detecting an endpoint optical signal reflected from the device region of the substrate. The method further includes comparing the baseline optical signal to the endpoint optical signal and determining a developer endpoint based on the comparing step.
1. A method of detecting developer endpoint, the method comprising:
illuminating a device region of a substrate with a first optical beam prior to initiating a development stage of processing;
detecting a baseline optical signal reflected from the device region of the substrate prior to initiating a development stage of processing;
illuminating the device region of the substrate with a second optical beam during a development stage of processing;
detecting an endpoint optical signal reflected from the device region of the substrate during a development stage of processing;
comparing the baseline optical signal to the endpoint optical signal; and
determining a developer endpoint based on the comparing step.
2. The method of claim 1 wherein the step of illuminating the device region of the substrate with the first optical beam is performed while the substrate is coated with water prior to application of develop chemistry.
3. The method of claim 1 wherein the device region is a region comprising active elements.
4. The method of claim 1 wherein the baseline optical signal and the endpoint optical signal comprise reflected and diffracted portions.
5. The method of claim 1 wherein the first optical beam and the second optical beam are collinear and produced by the same laser source.
6. The method of claim 2 wherein the first optical beam is a laser beam having a first wavelength and the second optical beam is a laser beam having a second wavelength.
7. The method of claim 1 wherein detecting a baseline optical signal is performed prior to coating of the substrate with a photoresist layer.
8. The method of claim 1 wherein detecting a baseline optical signal is performed prior to exposing a photoresist layer.
9. The method of claim 1 wherein detecting a baseline optical signal is performed after baking of a photoresist layer.
10. The method of claim 9 wherein detecting a baseline optical signal is performed after coating of the substrate with a layer of deionized water prior to application of a developer solution.