Sang Hak Lim

Silicon-based anti-reflective spin-on hardmask materials with improved storage stability for 193-nm lithography

As the feature sizes of integrated circuits shrink, thinner photoresist coating should be used in order to avoid high aspect ratio which can cause pattern collapse. Especially for 193 nm lithography, photoresist coating is too thin to subsequent etching step. One of the solutions to this problem is using hardmasks which have good etch selectivity to adjacent layers. In this paper, silicon-based anti-reflective spin-on hardmasks (Si-SOH) are described. One of the major problems of silicon based polymers in the hardmask compositions is poor storage stability because silanol group is reactive enough to condense each other, which can instigate molecular weight increase to yield gel-type particles. The storage stability of our hardmask materials have been improved by thermodynamically controlled synthesis and reactive mask strategy. Especially the reactive masked silanol groups can take part in crosslinking reaction under the process conditions without additional deprotection step. Although this strategy could encounter intermixing problems with other layers, we can produce silicon-based hardmasks without any deleterious effects. These hardmasks show antireflective properties and great etch selectivity to both photoresists and organic hardmasks (C-SOH).

Tunable resin reactivity of spin-on dielectric by controlling synthesis process

In the recent semiconductor industry, as the device shrinks, spin-on dielectric (SOD) has been adopted as a widely used material because of its excellent gap-fill, efficient throughput on mass production and highly competitive initial cost of ownership. Among various semiconductor applications, SOD is especially valued as the suitable gap-fill material for shallow trench isolation (STI), because the previously adopted technology, high density plasma chemical vapor deposition (HDP-CVD), has a significant problem with void-free gap-fill on patterns with high aspect ratios. As SOD is spin-coated on those narrow patterns, planarization is one of the important requirements. On the course of our efforts on developing novel modified SOD materials, we discovered that the reactivity of each SOD resins has meaningful correlation with the degree of planarization. In this paper, three experiments have been illustrated to prove this correlation, 1) step coverage test, 2) humid air bubble test, and 3) film thickness shrinkage upon prebake. The SOD resin with lower reactivity turned out to exhibit 1) larger size of circle around silica-beads, 2) slower molecular weight growth under humid bubble condition, and 3) higher shrinkage upon prebake.