Printed metal mask for UV, e-beam, ion-beam and X-ray patterning
View Patent ↗A method of forming vias and pillars using printed masks is described. The printed masks are typically made from droplets that include suspended metal nanoparticles. The use of the same metal nanoparticle solution in both the mask formation and the subsequent formation of conducting structures simplifies the fabrication process.
1. A method of forming a via opening comprising:
forming a dielectric layer;
using a printer to deposit at least one individual droplet including suspended metal nanoparticles over a first portion of the dielectric layer to form a mask pattern;
exposing the dielectric layer to radiation such that regions which are not masked by the mask pattern of metal nanoparticles become chemically altered;
removing areas of the dielectric layer that have not been exposed to radiation to create a via in the dielectric.
2. The method of claim 1 further comprising:
allowing a carrier liquid in the droplet to evaporate over time leaving the metal nanoparticles to form the mask pattern.
3. The method of claim 2 wherein the droplet shrinks in size as the carrier evaporates such that the area covered by the nanoparticles after evaporation is less than 75% of the area covered by the droplet diameter upon initial deposition on the dielectric layer.
4. The method of claim 1 wherein a surface of the dielectric layer is a nonplanar surface and the via is formed at the bottom of a well.
5. The method of claim 1 wherein the operation of removing areas of the dielectric layer is done through an etching process.
6. The method of claim 1 wherein the dielectric layer is a negative acting photopolymer.
7. The method of claim 1 wherein the viscosity of solution making up the first set of droplets is between 1 and 30 centipoise.
8. The method of claim 1 wherein the particle loading in the solution making up the first set of droplets is between 1% and 30%.
9. The method of claim 1 further comprising:
using the printer to deposit a second set of droplets of suspended metal nanoparticles in the via to form an electrical contact between a top circuit and a bottom circuit, the top circuit and the bottom circuit separated by the dielectric layer.
10. The method of claim 9 wherein the first set of droplets and the second set of droplets have approximately the same constituent components.
11. The method of claim 9 wherein metal nanoparticles used in the first set of droplets are made from a material selected from a group including silver, gold, nickel or copper.
12. The method of claim 9 wherein the dielectric layer is deposited over a conductor, the conductor connects to a source or a drain line of a transistor.
13. A method of forming a pillar structure comprising:
using a printer to deposit a first set of droplets including suspended metal nanoparticles over a first portion of a first layer to form a mask pattern;
exposing the pattern to radiation; and,
removing portions of the first layer that are not protected by the mask pattern.
14. The method of claim 13 wherein the first layer is a positive acting photopolymer, the method further comprising the operations of:
exposing the substrate to radiation such that regions which are not masked by the mask pattern of metal nanoparticles are altered; and,
etching the substrate to remove the altered areas of the substrate.
15. The method of claim 13 wherein the pillar structure is used to form a cantilever structure, the method further comprising:
using a printer to deposit a cantilever material over a top portion and one side of the pillar, and,
removing the remaining first layer material that was protected by the mask pattern such that a cantilever structure remains.
16. The method of claim 15 wherein the cantilever material is a printed metal including printed metal nanoparticles.
17. The method of claim 15 wherein the cantilever material is a printed polymer.
18. The method of claim 15 wherein the first layer is formed over a second layer, the second layer being a conductor that supports the cantilever structure.
19. The method of claim 15 wherein the viscosity of solution making up the first set of droplets is between 1 and 30 centipoise.
20. The method of claim 15 wherein the particle loading in the solution making up the first set of droplets is between 1 and 30%.
21. The method of claim 15 wherein the pillar width is less then 75% of the diameter of a droplet in the first set of droplets.
22. A method of making a thin film transistor comprising the operations of:
forming a gate electrode over a substrate;
forming a first dielectric layer over the gate electrode;
forming a drain electrode over a first region of the first dielectric layer and a source electrode over a second region of the first dielectric layer;
forming a second dielectric layer over the source electrode and the drain electrode;
printing droplets of metal nanoparticles to mask a gate area between the source electrode and the drain electrode;
exposing the substrate to radiation that chemically alters areas of the substrate exposed to the radiation; removing areas of the substrate that are not chemically altered to form a via in the interlayer dielectric layer at least in the region between the source and drain electrodes; and,
filling the via area with a semiconductor-forming solution.