Rapid repair of plasma ash damage in low-<i>k</i> dielectrics using supercritical CO2

Abstract

Plasma damage to methylsilsequioxane (MSQ) based low-k dielectrics degrades the material’s resistance to subsequent wet etch processes. In addition, the loss of methyl species during plasma exposure increases their susceptibility to water absorption leading to increased dielectric permittivities. In this article, we introduce a process in which silylating agents dissolved in supercritical CO2 are used to functionalize ash-damaged surfaces. This silylation process greatly decreases the time necessary to induce hydrophobicity (less than 1 min as determined by a change in contact angle from 18° to 90°). The process also reduces the concentration of reactive silylation agents needed for full hydrophobicity to less than 1 vol %. Further, this process is also shown to reduce material loss during subsequent wet etch processes. Film thickness measured by scanning electron microscopy before and after treatment illustrates a difference of approximately 0.1 μm after etching in a dilute HF solution for 30 s.