Cost effective mask design in CMOS transistor fabrication for undergraduates program

Abstract

This paper presents a new innovative way of teaching undergraduate program using low cost masks. In MOSFET fabrication, the cost to produce a complete mask set for pattern transfer process extremely high and not cost effective for undergraduates program. The purpose of these masks is to define certain functional region on a wafer. In this work, low cost masks have been fabricated with a simple technology. An economical solution of masks using transparency films with various channel lengths from 300 µm to 500 µm has been produced. Six layer photolithography masks of MOSFET were designed using AutoCAD drawing tools and then printed using high resolution laser printer on the transparency film. Contact printing method has been utilized to transfer the mask layouts onto a 4-inch silicon wafer using standard photolithography techniques to check the line uniformity. Optical observation using high power microscope shows that the mask layouts were successfully transferred onto photoresist with minimum variation. These masks are used to fabricate an n-well CMOS transistor and then tested using Keithley 2400 source meter with Lab-view measurement software. The cost effective mask design proposed was really practical for teaching microfabrication undergraduates program