Patterned structures fabricated by printing mask over lift-off pattern
View Patent ↗A patterned integrated circuit structure defining a gap or via is fabricated solely by digital printing and bulk processing. A sacrificial lift-off pattern is printed or otherwise formed over a substrate, and then covered by a blanket layer. A mask is then formed, e.g., by printing a wax pattern that covers a region of the blanket layer corresponding to the desired patterned structure, and overlaps the lift-off pattern. Exposed portions of the blanket layer are then removed, e.g., by wet etching. The printed mask and the lift-off pattern are then removed using a lift-off process that also removes any remaining portions of the blanket layer formed over the lift-off pattern. A thin-film transistor includes patterned source/drain structures that are self-aligned to an underlying gate structure by forming a photoresist lift-off pattern that is exposed and developed by a back-exposure process using the gate structure as a mask.
1. A method for fabricating a patterned layer structure on a substrate such that the patterned layer structure includes first and second layer portions separated by a void, the method comprising:
forming a lift-off pattern over the substrate by depositing a printing fluid onto a base layer such that the printing fluid attaches itself to the base layer through a wetting action, whereby the printing fluid solidifies to form said lift-off pattern such that the lift-off pattern has a rounded cross-sectional profile;
forming a blanket layer over the substrate such that first and second portions of the blanket layer are located on opposite sides of the lift-off pattern, a third portion located over the liftoff pattern, and attack point portions respectively extending between the third portion and the first and second portions, wherein the blanket layer is formed such that the attack point portions are thinner than the first, second and third portions;
depositing a source/drain metal layer over the liftoff pattern such that the source/drain metal layer includes first and second portions respectively located on opposing sides of the liftoff pattern;
patterning a mask over the first and second portions of the blanket layer such that the patterned mask extends over the lift-off pattern;
removing portions of the blanket layer exposed around the patterned mask, and the patterned mask and the lift-off pattern.
2. The method of claim 1 , wherein forming the patterned mask over the first and second portions of the blanket layer comprises jet printing.
3. The method of claim 1 , wherein forming the lift-off pattern comprises jet printing a phase change material.
4. The method of claim 1 , wherein patterning the mask comprises printing a phase change material using a printing system.
5. The method of claim 4 , wherein printing the mask further comprises printing the phase change material in multiple passes such that a plurality of printed elements are printed in a stacked arrangement.
6. The method of claim 1 , wherein removing the exposed blanket layer portions, the patterned mask, and the lift-off pattern comprises:
applying an etchant to the exposed blanket layer portions, and
applying a solvent to the patterned mask and the lift-off pattern.
7. The method of claim 1 , wherein removing the lift-off pattern further comprises at least one of applying sonication to the lift-off pattern and heating the lift-off pattern.
8. The method of claim 1 ,
wherein forming the lift-off pattern comprises forming a dot-like lift-off pattern,
wherein patterning the mask comprises forming said patterned mask such that an outer peripheral edge of the patterned mask surrounds the dot-like lift-off pattern, and
wherein removing the exposed blanket layer portions, the patterned mask, and the lift-off pattern comprises etching said exposed blanket layer portions to form an island-like patterned structure defining a via located between the first and second portions, wherein the via occupies a space created by removal of said dot-like lift-off pattern.
9. The method of claim 1 ,
wherein forming the lift-off pattern comprises forming an elongated lift-off pattern,
wherein patterning the mask comprises forming said patterned mask such that the elongated lift-off pattern extends between the first and second portions of the blanket layer, and
wherein removing the exposed blanket layer portions, the patterned, and the lift-off pattern comprises etching said exposed blanket layer portions such that a gap is defined between the first and second portions, wherein the gap occupies a space created by removal of said elongated lift-off pattern.
10. The method of claim 1 ,
wherein forming the lift-off pattern comprises forming said lift-off pattern such that the lift-off pattern is aligned with an underlying feature, and
wherein patterning the mask comprises forming said patterned mask such that the first and second portions of the blanket layer covered by said patterned mask are separated by the lift-off pattern, and
wherein removing the exposed blanket layer portions, the patterned mask, and the lift-off pattern comprises etching said exposed blanket layer portions such that a gap is defined between the first and second portions, wherein opposing edges of the gap are aligned with opposing edges of the underlying feature.
11. The method of claim 10 , wherein forming the lift-off pattern comprises printing a phase change material using a printing system.
12. A method for fabricating a thin-film transistor, the method comprising:
forming a gate structure over a substrate;
forming a liftoff pattern over the gate structure by depositing a printing fluid onto a base layer such that the printing fluid attaches itself to the base layer through a wetting action, whereby the printing fluid solidifies to form said lift-off pattern such that the lift-off pattern has a rounded cross-sectional profile;
depositing a source/drain metal layer over the liftoff pattern such that the source/drain metal layer includes first and second portions respectively located on opposing sides of the liftoff pattern, a third portion located over the liftoff pattern, and attack point portions respectively extending between the third portion and the first and second portions, wherein the source/drain metal layer is formed such that a thickness of each attack point portion is thinner than thicknesses of the first, second and third portions;
printing a source/drain mask over the first and second portions of the source/drain metal layer such that the printed mask extends over the lift-off pattern; and
removing portions of the source/drain metal layer exposed around the printed source/drain mask, the printed source/drain mask, and the liftoff pattern.
13. The method of claim 12 , wherein forming the liftoff pattern comprises jet printing a phase change material.
14. The method of claim 12 , wherein printing the mask comprises printing a phase change material using a printing system.
15. The method of claim 14 , wherein printing the mask further comprises printing the phase change material in multiple passes such that a plurality of printed elements are printed in a stacked arrangement.
16. The method of claim 12 , wherein removing the exposed source/drain metal layer portions, the print mask, and the liftoff pattern comprises:
applying an etchant to the exposed source/drain layer portions, and
applying a solvent to the print mask and the liftoff pattern.
17. The method of claim 12 , wherein removing the liftoff pattern further comprises at least one of applying sonication to the liftoff pattern and heating the liftoff pattern.