Device Isolation in Hybrid Field-Effect Transistors by Semiconductor Micropatterning Using Picosecond Lasers

Abstract

A solid-state picosecond laser is used to ablate semiconductor thin films in spatially localized areas, providing an alternative to device isolation strategies based on chemical or ion etching techniques. Field-effect transistors (FET) of emerging organic and inorganic materials often utilize continuous semiconductor film and an array of top-contact electrodes. Electrically isolating individual FET components from other circuit elements is essential in order to reduce parasitic capacitances and unwanted current pathways, in order both to improve device performance and to enable the observation of new or enhanced physical phenomena. We pattern FET arrays with ultrafast pulse duration (1.5 ps) and low fluence (0.09 J cm-2) optical pulses using the fundamental wavelength (1030 nm) of an Yb-YAG laser. We investigate two representative semiconductor materials. First, zinc oxide (ZnO) is deposited onto Si/SiO 2 substrates by sol-gel methods and used to create n-channel FETs with aluminum top electrodes. Isolation of individual FETs enables the clear observation of photomodulation of the FET device parameters via photoinduced electron donation from an adsorbed chromophore. The second system comprises thin-film bilayers of tellurium and organic semiconductor molecules sequentially vapor-deposited onto Si/SiO 2 substrates, with gold electrodes deposited last. Charge carrier mobility is maintained for devices isolated by picosecond lasers, but leakage currents through the FET dielectric are drastically reduced.

High-throughput fabrication and semi-automated characterization of oxide thin film transistors

“…In a region with no devices, the SiO 2 was scratched away to expose the doped Si for contacting, which is a common method in the investigation of oxide TFTs. [20,21] The thin film channel layer was deposited as described above and patterned into 44 distinct areas by a shadow mask, where each area was identified with a unique point number from 1 to 44. They were separated from each other to avoid any cross influences and to isolate any local regions with a leaky dielectric layer.…”