I want to fabricate thin film transistors as part of my new research work. I would like to know how I can make good masks that I need to use during deposition of the different layers. Alternatively, which is the best approach to use to deposition each layer accurately using a solution based deposition method?
The simplest way to fabricate TFTs is to use silicon wafer (along with SiO2) as substrates. Then, with the help of three shadow masks (AL, S/D, PA) TFTs with channel length more than 100 um could be prepared.
Hello,
There are typically three ways to fabricate a TFT:
a) using shadow mask
b) using photolitho processes
c) combination of both
a) Shadow mask.- is a quick fabrication process to determine the overall characteristics of your TFT. Usually, you use a common bottom contact (highly doped silicon wafer or a metal layer), then deposit dielectric and semiconductor layers on top (without patterning) and finally S-D contacts through a shadow mask. Although this process is very simple (compared to photolitho defined process), it could lead to some parasitic effects such as: high leakage currents due to common semiconductor film (one defect on the dielectric will short gate and semiconductor), poor pattern definition and lack of isolation from device to device (very bad for circuits).
b) Photolitho processes.- this is a more sophisticated fabrication process where you reduce the parasitic effects related to shadow mask. However, this process requires facilities with mask aligners, acid/solvent hoods, software for layout design and tools to write masks. All these tools are normally found in a cleanroom.
c) Combination of both.- I have seen some papers where people se this technique, however if you already have the meanings to run photolitho processes, then use them for all the TFT structure.
Regarding your question for solution-based deposition process, there are several. I am attaching couple of papers for photolitho defined TFTs: organic and inorganic semiconductors.
https://www.researchgate.net/publication/220454113_Improved_upper_contacts_PMMA_on_P3HT_PTFTS_using_photolithographic_processes
https://www.researchgate.net/publication/258792735_Fabrication_and_Characterization_of_High-Mobility_Solution-Based_Chalcogenide_Thin-Film_Transistors
I hope this works.
Israel
Article Improved upper contacts PMMA on P3HT PTFTS using photolithog...
Article Fabrication and Characterization of High-Mobility Solution-B...
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