Study of Oxide Hardmask Effect on High Dose Implant Process for ISFET Fabrication

The study of the effects of photoresist thickness and the use of PECVD deposited oxide hard mask layer during source/drain high dose ion implantation process in the fabrication of ion-sensitive field effect transistor (ISFET) is presented. Implementation of the new optimized process for the source/drain implant mask together with the improved process module have been successful in improving the threshold voltage (Vt) of the ISFET device from negative to more than 0.3 V. Consistent high ISFET yields of more than 90% were possible to achieve.