Method for imprint lithography using an electric field
View Patent ↗A lithography process for creating patterns in an activating light curable liquid using electric fields followed by curing of the activating light curable liquid is described. The process involves the use of a template that is formed of non-conductive and electrically conductive portions. The template is brought into close proximity to the activating light curable liquid on the substrate. An external electric field is applied to the template-substrate interface while maintaining a uniform, carefully controlled gap between the template and substrate. This causes the activating light curable liquid to be attracted to the raised portions of the template. Activating light is applied to the curable liquid while an electric field is applied to the template to create a patterned layer on the substrate.
1. A method of preparing patterned structures on a substrate, the method comprising:
applying an activating light curable liquid to a surface of the substrate;
positioning a template proximate to the activating light curable liquid, wherein the template comprises:
a non-conductive layer; and
an electrically conductive layer adjacent the non-conductive layer and substantially between the non-conductive layer and the substrate, wherein the electrically conductive layer forms a contiguous pattern of structures complementary to the patterned structures to be produced on the substrate; and
applying an electric field between the template and the substrate by passing a current through the electrically conductive layer, wherein the applied electric field creates an electric static force that attracts a portion of the activating light curable liquid toward the electrically conductive layer of the template.
2. The method of claim 1 , further comprising forming a transfer layer on the substrate prior to applying the activating light curable liquid.
3. The method of claim 1 , wherein the activating light curable liquid has a viscosity of less than about 30 centipoise measured at 25° C.
4. The method of claim 1 , wherein a viscosity of the activating light curable liquid is such that a pattern forms in the activating light curable liquid in less than about 1 second when the electric field is applied.
5. The method of claim 1 , further comprising curing the activating light curable liquid, wherein the electric field is applied between the template and the substrate while curing the activating light curable liquid.
6. The method of claim 1 , wherein the template further comprises a low-surface energy coating, with the low-surface energy coating providing the template with a free energy of the template, measured at 25° C., to less than about 40 dynes/cm.
7. The method of claim 1 , wherein the template further comprises a low-surface energy coating, with the low-surface energy coating providing the template with a free energy of the template, measured at 25° C., to less than about 40 dynes/cm, and wherein the low-surface energy coating is a fluorine containing coating.
8. The method of claim 1 , wherein the activating light curable liquid comprises a photoinitiator.
9. The method of claim 1 , wherein the electrically conductive material comprises indium tin oxide.
10. The method of claim 1 , wherein applying the electric field between the template and the substrate causes a portion of the activating light curable liquid to contact a portion of the template.
11. The method of claim 1 , wherein the activating light curable liquid is attracted to the electrically conductive layer but does not contact the electrically conductive layer when the electric field is applied between the template and the substrate.
12. The method of claim 1 , further comprising curing the activating light curable liquid, defining a cured liquid, and etching the cured liquid to expose portion of the underlying substrate.
13. The method of claim 1 , wherein the non-conductive layer is silicon dioxide.
14. The method of claim 1 , wherein the substrate comprises a silicon wafer.
15. The method of claim 1 , wherein the substrate comprises a GaAs wafer.
16. The method of claim 1 , wherein the substrate comprises a SiGeC wafer.
17. The method of claim 1 , wherein the substrate comprises a InP wafer.
18. The method of claim 1 , further comprising curing the activating light curable liquid by applying an activating light to the activating light curable liquid.
19. The method of claim 18 , wherein the template is substantially transparent to the activating light.
20. The method of claim 18 , wherein the substrate is substantially transparent to the activating light.