A New Implant-Through-Contact Method for Fabricating High-Voltage TFT's

A new process to fabricate offset-gate thin-film transistors (TFT's) for high-voltage (HV) (i.e., >60 V) large-area applications is demonstrated. In contrast to the conventional method where an additional masking step is applied to mask the channel and the offset regions, the n+ source-drain implant is performed in the new process only after contact is open, and is therefore self-aligned to the contact. The offset-gate transistors are achieved by proper transistor layout where the contact-to-gate distance equals the designed n+-to-gate offset. In addition to saving one masking count as compared with the conventional method, the new implant-through-contact (ITC) method also features a self-aligned field-plate structure and smaller transistor layout area.