Specific Process Knowledge/Lithography/LiftOff: Difference between revisions
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If the resist layer used for lift-off is too thin compared to the deposited layer, solvent access to the resist may be limited, due to partial or full coverage of the sidewalls. This would result in a slow lift-off, possibly with line edge roughness of the deposited material. As a rule of thumb, the resist should be 5-10 times thicker than the deposited material. | If the resist layer used for lift-off is too thin compared to the deposited layer, solvent access to the resist may be limited, due to partial or full coverage of the sidewalls. This would result in a slow lift-off, possibly with line edge roughness of the deposited material. As a rule of thumb, the resist should be 5-10 times thicker than the deposited material. | ||
Small, tightly packed structures result in a very fast lift-off process. It is usually the big, uncovered areas between or around the device(s) that limit the lift-off speed. The less of the deposited material is to remain on the substrate after lift-off, the longer the sample has to spend in the lift-off solvent while resist under the deposited material is being dissolved and transported out. During the design of the pattern used for lift-off, it should be considered to fill any voids between devices with lift-off assisting dummy structures (e.g. hatching or squares/circles), in order to punctuate the open spaces, and allow for multiple, parallel | Small, tightly packed structures result in a very fast lift-off process. It is usually the big, uncovered areas between or around the device(s) that limit the lift-off speed. The less of the deposited material is to remain on the substrate after lift-off, the longer the sample has to spend in the lift-off solvent while resist under the deposited material is being dissolved and transported out. During the design of the pattern used for lift-off, it should be considered to fill any voids between devices with lift-off assisting dummy structures (e.g. hatching or squares/circles), in order to punctuate the open spaces, and allow for multiple, parallel starting points. Consider also if the edge of the substrate (exclusion zone) could be left covered with the deposited material. | ||