The loading effect study in Metal Hard-Mask All-In-One etch with double patterning scheme

In advanced CMOS technology node with Cu/low-K interconnection, double patterning scheme with Trench First Metal Hard-Mask (TFMHM) approach All-In-One (AIO) etch is used to define smaller scale via and trench. The loading effect between different patterns, such as via chain and via slot, will cause different final over-etch (OE) amount under etch stop layer. Chip performance will be affected if it suffers severe loading between various patterns. In this paper, we will study the effect of different film stack, etching gas, plasma condition and etch stop layer (ESL) in loading control between different patterns which will both contribute to final loading. Different methods' loading results and the basic theory for explaining the loading phenomenon will be compared and discussed in following part.

Introduction

Loading performance will affect final performance in following ways. For example severe loading will lead to tiger-tooth effect when landing metal top critical dimension (CD) is smaller than via bottom CD in region with large over-etch amount. Meanwhile, the longer exposure time of under layer Cu to plasma in via slot area during etch stop layer opening step will have bad influence on trench depth and residual defect. The smaller loading between different patterns are necessary to ensure beneficial VBD and TDDB performance.