Manufacturing of carbon nanotube thin film transistor backplanes and display integration thereof
Methods for producing and integrating single-walled carbon nanotubes (SWCNT) into existing TFT backplane manufacturing lines are provided. In contrast to LTPS and oxide TFT backplanes, SWCNT TFT backplanes exhibit either equivalent or better figures of merit such as high field emission mobility, low temperature fabrication, good stability, uniformity, scalability, flexibility, transparency, mechanical deformability, low voltage and low power, bendability and low cost. Methods and processes for integrating SWCNTs technologies into existing TFT backplane manufacturing lines, pilot test and mass production can start without additional capex needs are also provided.
1. A method for manufacturing a single-walled carbon nanotube thin film transistor backplane comprising:
providing a substrate having at least a size of Gen 4.5;
patterning a gate electrode and dielectric layer on the substrate to form a channel forming structure;
depositing a solution of a thin-film layer of single-walled carbon nanotubes on said dielectric layer to form a back-layer; and
patterning at least a n+ layer, and a drain and a source electrode on the back-layer using a photomask and photolithography process such that the portion of the back-layer overlapping the channel forming structure is exposed.
2. The method of claim 1 , wherein the back-layer is deposited by a spraying technique selected from the group consisting of aerosol spray, air spray and ultrasonic spray.
3. The method of claim 2 , wherein the single-walled carbon nanotube aerosol is formed from an aqueous solution of single-walled carbon nanotubes that are ultrasonicated in an ultrasonicating nozzle and emitted in a carrier gas flow.
4. The method of claim 1 , wherein the back-layer is printed atop the substrate using aerosol jet printing as a single-walled carbon nanotube aerosol.
5. The method of claim 4 , wherein the single-walled carbon nanotube aerosol is formed by a technique selected from ultrasonic atomization and pneumatic atomization.
6. The method of claim 1 , wherein the single-walled carbon nanotubes adhere onto the dielectric through hydrophobicity forces with a peel off force of at least 4.35 N/cm 2 .
7. The method of claim 1 , wherein the single-walled carbon nanotubes are high purity single chirality single-walled carbon nanotubes.
8. The method of claim 7 , wherein the single-walled carbon nanotubes have an index selected from (6,4), (9,1), (8,3), (6,5), (7,3), (7,5), (10,2), (8,4), (7,6), (9,2), and mixtures thereof.
9. The method of claim 1 , wherein the single-walled carbon nanotube thin film is formed of a plurality of discrete thin films.
10. The method of claim 1 , further comprising depositing and patterning an etch stop layer atop the back-layer such that the etch stop overlaps the channel forming structure.
11. The method of claim 1 , wherein further comprising treating the single-walled carbon nanotube thin film with an acidic etch.
12. The method of claim 11 , wherein the acidic etch is selected from a group consisting of 5% H 3 PO 4 , 15% HNO 3 , and 5% Acetic Acid.
13. The method of claim 1 , further comprising washing the treated single-walled carbon nanotube thin film.
14. The method of claim 1 , further comprising heating the single-walled carbon nanotube thin film during the depositing step at a temperature of from 60 to 200° C.
15. The method of claim 1 , wherein the thin films are formed with subthreshold leakage current comprising:
spin coating a photoresist on the single-walled carbon nanotube thin film;
defining a pattern atop the photoresist by photolithography to create regions of a defined photoresist and undefined photoresist;
solution developing the defined pattern to form a developed photoresist; and
plasma or wet etching the single-walled carbon nanotubes thin film using the developed photoresist to form a patterned single-walled carbon nanotube thin film.
16. The method of claim 1 , wherein the patterning comprises a chemical vapor deposition technique.
17. The method of claim 16 , wherein the patterning includes the use of a SiN x material.
18. The method of claim 16 , wherein the chemical vapor deposition technique comprises one of either a Unaxis 790 or STS device.
19. The method of claim 18 , wherein the chemical vapor deposition technique uses a Unaxis 790 device with a ratio of ammonium to silane of 10 to 5.3 sccm.
20. The method of claim 18 , wherein the chemical vapor deposition technique uses an STS device with a ratio of ammonium to silane of around 1 to 1 sccm.