Lithographic dry development using optical absorption
A novel approach to dry development of exposed photo resist is described in which a photo resist layer is exposed to a visible light source in order to remove the resist in the areas of exposure. The class of compounds used as the resist material, under the influence of the light source, undergoes a chemical/structural change such that the modified material becomes volatile and is thus removed from the resist surface. The exposure process is carried out for a time sufficient to ablate the exposed resist layer down to the layer below. A group of compounds found to be useful in this process includes aromatic calixarenes.
1. A process for lithographic development comprising:
(i) depositing a layer of a resist material on a substrate, wherein the resist material comprises an amount of conjugated groups and has a first absorption coefficient to a light source having a wavelength above 400 nm;
(ii) exposing a region of the resist material to a source of high-resolution radiation to increase the amount of conjugated groups resulting in a second absorption coefficient to the light source which is greater than the first absorption coefficient;
(iii) exposing the resist material to the light source, the difference between the second absorption coefficient of the region exposed to the high-resolution radiation and the first absorption coefficient of an unexposed region results in a high volatility contrast, wherein the region first exposed to the high-resolution radiation and then further exposed to the light source is volatilized.
2. The process of claim 1 wherein the light source is a laser light source.
3. The process of claim 2 wherein the laser light source is a 532 nm wavelength laser.
4. The process of claim 3 wherein the laser light source is operated at a power density of between 1 MW/cm2 and 14 MW/cm2.
5. The process of claim 1 wherein the source of high-resolution radiation is an electron beam.
6. The process of claim 1 wherein the source of high-resolution radiation is extreme ultra violet light.
7. The process of claim 1 wherein the conjugated resist material comprises aromatic groups.
8. The process of claim 1 wherein the resist material comprises a calixarene.
9. The process of claim 8 , wherein the calixarene comprises an aromatic OH.
10. The process of claim 8 , wherein the resist is substituted with a group selected from the group consisting of halo, cyano, and nitro.
11. The process of claim 1 wherein the resist material can be a mixture of materials.
12. The process of claim 1 wherein the exposure is a patterned exposure.
13. The process of claim 12 wherein the pattern is created using a mask interposed between the source of the high resolution radiation, and the layer of resist material.
14. The process of claim 1 wherein the substrate is in the form of a wafer.
15. The process of claim 1 wherein the wafer is a silicon wafer.
16. A dry lithography process in which:
i) a resist layer is first deposited on a substrate, wherein the resist material comprises an amount of conjugated groups and has a first absorption coefficient to a laser having a wavelength above 400 nm;
ii) the resist layer is exposed to an electron high resolution radiation beam to pattern the resist to increase the amount of conjugated groups resulting in a second absorption coefficient to the laser which is greater than the first absorption coefficient; and,
iii) the patterned resist is thereafter dry developed with the laser to volatilize the resist in the areas of exposure wherein the difference between the second absorption coefficient of the region exposed to the high-resolution radiation and the first absorption coefficient of an unexposed region results in a high volatility contrast.