Performance improvements of OFETs through use of field oxide to control ink flow
View Patent ↗An OFET includes a thick dielectric layer with openings in the active region of a transistor. After the field dielectric layer is formed, semiconductor ink is dropped in the active region cavities in the field dielectric layer, forming the semiconductor layer. The ink is bounded by the field dielectric layer walls. After the semiconductor layer is annealed, dielectric ink is dropped into the same cavities. As with the semiconductor ink, the field dielectric wall confines the flow of the dielectric ink. The confined flow causes the dielectric ink to pool into the cavity, forming a uniform layer within the cavity, and thereby decreasing the probability of pinhole shorting. After the dielectric is annealed, a gate layer covers the active region thereby completing a high performance OFET structure.
1. A method of forming an OFET comprising: providing an insulating substrate; providing a patterned first conductive layer to establish source, drain, and contact region; providing a patterned field dielectric layer to form an opening above a transistor active area between the source and the drain region, and above the contact region; depositing a solution-based semiconductor in the transistor active area cavity defined by the field dielectric layer; depositing a solution-based gate dielectric layer in the transistor active area cavity defined by the field dielectric layer; and depositing a second conductive layer in the transistor active area and contact cavities defined by the field dielectric layer.
2. The method of claim 1 wherein providing the patterned first conductive layer and/or the patterned field dielectric layer is achieved in a single step.
3. The method of claim 1 wherein providing the patterned first conductive layer and/or the patterned field dielectric layer is achieved in a deposition step followed by a patterning step.
4. The method of claim 1 wherein the insulating substrate comprises PET, PEN, or Kapton.
5. The method of claim 1 wherein the field dielectric layer comprises a low dielectric constant material including organic materials such as polyvinyl phenol PVP and derivatives PNP-CPC and PVP-CL, poly (3,4-ethylenedioythiophene), PVA, CYPEL, ferroelectric polymers, or silicon nitride or inorganic materials in the form of a precursor solution or suspended nanoparticles such as silicon dioxide, titanium dioxide, or aluminum oxide.
6. The method of claim 1 wherein depositing the solution-based semiconductor comprises inkjet printing, pico-dropping or spinning.
7. The method of claim 1 wherein the solution-based semiconductor comprises an organic semiconductor such as polythiophene or solution-based pentacene, or a solution based inorganic semiconductor in the form of a precursor solution or suspended nanoparticles such as silicon or gallium arsenide.
8. The method of claim 1 further comprising treating deposition surfaces prior to depositing the solution-based semiconductor to create improved order in the final semiconductor layer.
9. The method of claim 1 further comprising annealing the solution-based semiconductor subsequent to deposition to optimize order in the semiconductor layer.
10. The method of claim 1 wherein depositing the solution-based dielectric comprises inkjet printing, pico-dropping or spinning.
11. The method of claim 1 wherein the solution-based dielectric material comprises organic materials such as polyvinyl phenol PVP and derivatives PVP-CP and PVP-CL,
poly (3,4-ethylenedioythiophene), PVA, CYPEL, ferroelectric polymers, silicon nitride or
inorganic materials in the form of a precursor solution such as or suspended nanoparticles
such as silicon dioxide, titanium dioxide, and aluminum dioxide.
12. The method of claim 1 further comprising planarizing the second conductive layer.