Fundamental characterization of shrink techniques on negative tone development based dense contact holes

Abstract

Enormous advances have been made in recent years to design sub 40nm dense contact hole pattern with local CD uniformity (CDU) that the process can tolerate. Negative tone development process (NTD) on 193nm photoresists has achieved this to a large extent without the requirement of additional processing steps on the patterned layer. With further shrinking of size of the subsequent nodes, the demand to produce smaller patterns with wider process window, low defectivity, and improved CDU is increasing, and reaching beyond what can be achieved through NTD alone. A number of techniques are in practice today to achieve this, most notably, implementation of a collar of Atomic Layer Deposited SiO2 (ALD) on photoresist or substrate. However, in recent years, various material suppliers have also proposed shrink chemistries to achieve this. In this paper, we have provided fundamental characterization of shrink via application of spin-on agents (organic as well as aqueous) on the post-imaged pattern. We have also compared them for their shrink capacity, defect tendency, dry etch capability and ease of implementation in the process flow. In addition, we have provided recommendations on which technique is suitable for a given set of process prerequisites.