Control of resist flow process for sub-0.15-μm small contact hole by latent image

Abstract

Bake process of photo resist above glass transition temperature (Tg) increases its fluidity and shrinks contact holes patterned on the wafer. This process enables us to define sub-0.2 micrometers contact hole pattern with KrF, which is one of major issues of sub-0.15 micrometers device technology. However, the amount of PR flow depends on the contact hole size, pattern density and environment, which makes it difficult to control the fine critical dimension (CD) variation. In this paper, new approach to overcome the difficulties is studied with acetal type PR and attenuated phase shift mask (att. PSM). It is found that the change of chemical bonding in PR by light exposure decreases the resist flow sensitivity, which makes us solve the problems. The att. PSM enables us to control the aerial image intensity between contact holes, and the CD variation induced by bake process was drastically decreased when it is compared to Cr mask. The layout optimization by simulation for aerial image control in bulk region, and the resist flow process combined with att. PSM allows us to control the CD variation less than 20 nm for the sub-0.15 micrometers devices fabrication.