Chrome Etch for <0.13 μm Advanced Reticle Production

摘要

The continuous shrinking of design rules results in tighter specifications for advanced chrome dry etch. Specifically, the increasing number of OPC and phase shift layers in mask set for sub 0.13um technology drives research and development in this area. Chrome layers were traditionally dry etched using a Cl_2/O_2/He plasma. While this chemistry has proven to meet the chrome etch requirements in the past its limitations are becoming more and more obvious. In particular, critical dimension control in terms of uniformity and etch bias shows opposing trend lines with the standard chemistry which makes optimization difficult and minimizes the available process space. The Applied Materials Centura~R photomask etch chamber has been used along with new gas chemistries to provide improved critical dimension control in chrome for binary photomasks. Oxygen and chlorine are responsible for etching chrome. However, these gases alone do not provide the sidewall protection necessary for the excellent critical dimension control required for advanced mask making for 0.13 μm and below. In this systematic investigation, experiments show a factor of two improvement in etch bias over the standard chemistry (He/O_2Cl_2). Excellent CD uniformity is also demonstrated.