BI-Layer Resist Approach of Photolithographic Patterning over PMMA based Polymer Dielectrics

Category-Electronics and Circuits

Industry Classification:

NIC (2008)- 26101– Manufacture of electronic capacitors, resistors, chokes, coils, transformers (electronic) and similar components
NAICS (2022)- 333242– Thin layer deposition equipment, semiconductor, manufacturing

Applications– Semiconductors- Organic Thin Film Transistors (OTFT) for flexible electronics.

Market Drivers-

Increasing demand for flexible displays and electronics- USD 14-15 Billion in 2023; expected CAGR of 33% for 2023-2031

Conventional photoresist processing causes severe degradation of the organic polymers resulting in poor device performance.
Polymer gate dielectrics/Semiconductors have poor organic solvent resistance while being difficult to process using photolithography.
Limited progress in the development of photolithography over pristine PMMA or PMMA based polymer dielectrics despite outstanding properties.
There is a need for developing a method of photolithographic patterning which facilitates the photolithography of PMMA based polymer dielectrics without using high-temperature processing and chemical modification which result in high fabrication cost.

UV/Deep-UV lithography over pristine Poly(methyl methacrylate) (PMMA) or PMMA based hybrid/blended and multilayered polymer dielectric systems using bilayer photoresist stack
Isopropyl alcohol) is used as photoresist stripper for easy stripping of the top resist layer during metal lift-off without dissolving or damaging the PMMA.
Electrical and dielectric properties of the pristine PMMA layer processed using the invented method was compared to a layer created using shadow mask process fabricated metal-insulator-metal (MIM) device
Formation of bi-layer resist with MicroChem’s PMGI as a bottom resist layer coated directly over pristine PMMA dielectric layer followed by the formation of the top resist layer (typical g-line, i-line, broadband, deep UV, and 193nm resist) by spin coating method. Exposed bi-layer resist stack developed using Shipley’s MF319.

The method does not involve any complicated process such as chemical modification or etching of PMMA thus avoiding surface damage.
The leakage current density in the fabricated device is reduced almost by two orders of magnitude compared to the device fabricated using a shadow mask.
Suitable for bottom gate bottom contact (BGBC), bottom gate top contact (BGTC) and top gate top contact (TGTC) device configuration. These configurations are difficult in case of traditional etching due to surface damage
PMMA dielectric processed by this method shows good electrical insulating properties. This is better than popular PVP based dielectrics that suffers from affinity to H2O and severe hysteresis
The method is more cost efficient because of the low-temperature processing steps and use of conventional photoresists/developers to perform photolithography

Prof. Soumya Dutta

Department of Electrical Engineering

TRL-4

Technology Validated in the Lab scale

Technology Transfer