Enhancement Of Mp 2400 Resist Contrast Using Immersion Development

Abstract

Novolac reists have been widely used in microlithography due to their high resolution, thermal stability and dry etch resistance. One such resist, Shipley MP 2400, is used for both e-beam and deep UV lithography. In this paper, using e-beam lithography, we explore the effect of resist development parameters upon MP 2400 contrast and resolution. In particular, it is observed that resist contrast is strongly dependent on both developer dilution and developer temperature. Our experiments were performed using an immersion development system with a laser endpoint detector. This system facilitates controlled experiments since resist dissolution can be monitored directly during development. Another consideration in these experiments was to determine how resist contrast affects exposure dose latitude. Increased contrast is shown to improve the resolution of patterned features, but electrical linewidth data demonstrates a degradation of process latitude with respect to exposure dose. That is, linewidth variation due to either the proximity effect or focus variation will increase with increasing resist contrast. Lastly, a simple relationship is derived which enables one to predict immersion development time as a function of resist contrast.