Investigations of the effects of blade type, dicing tape, blade preparation and process parameters on 55nm node low-k wafer

Abstract

This paper presents an investigation of the effects of blade type, dicing tape, blade preparation and the key process parameters optimization on improving topside ILD peeling (thicker scribe structures) and chipping for 55nm low-k wafer. An appropriate dicing blade selection, blade preparation / conditioning methodology and dicing tape selection plays an important role in developing a robust saw process. As such, experimental studies were conducted under varying Z1 spindle rotation, Z1 cut depth into Si as well as the blade type property variation as the input factors, in order to improve the ILD peeling and die chipping. The settings of machining parameters and blade types were determined by using the design of experiment (DOE) techniques and the critical process parameters and materials were analyzed statistically by using the analysis of variance (ANOVA). Dicing tape property variations (PO-base or PVC-base) as well as the blade preparation methodology posed some influences on the overall dicing quality, such as die backside chipping, die removal performance, ILD peeling and die topside chipping. SEM imaging and optical visual inspection were conducted to validate the impacts of the ILD peeling / chipping on post-processed low-k wafers. A thorough quantification and categorization of ILD peeling and chipping on heavy metallization at the saw scribe structures were described. As part of the recommendation for future works, a different approach in dicing technology, namely laser grooving was proposed to eliminate ILD peeling and chipping. In conclusion, the optimized dicing recipe for 55nm node low-k wafer suggested by the DOE model are: (1) a thinner PO-base dicing tape, (2) a dicing blade with higher diamond concentration and finer grit size, (3) blade preparation / conditioning done with SiC board and (4) processing at lower spindle rotation and deeper cut depth are much preferred. The overall dicing responses and cutting quality has improved and is better compared to current production recipe.