ABSTRACT
References ....................................................................................................................................578
The design requirements of successive generations of very large scale integrated (VLSI)
circuits have led to a reduction in lithographic critical dimensions. The aim of this chapter
is to discuss the progress of the resists for present and future lithography. It is worthwhile
describing the history and the trend of lithography and resists. It is evident from
Figure 10.1 that three turning points of resist materials have been reached [1]. The first
turning point was the replacement of a negative resist composed of cyclized rubber and a
bisazide by a positive photoresist composed of a diazonaphthoquinone (DNQ) and a
novolac resin. This was induced by the change of exposure system from a contact
printer to a g-line (436 nm) reduction projection step-and-repeat system-the so-called
stepper. The cyclized rubber system has poor resolution due to swelling during the
development and low sensitivity due to a lack of absorption at the g-line. The DNQ-
based positive photoresist shows sensitivity at the g-line and high resolution using
aqueous alkali development.
