TRANSFORMATION OF DENSE CONTACT HOLES DURING SiO2 ETCHING

The profile transformation that occurs during SiO2 etching using an ArF positive resist is a serious problem. Authors investigate the characteristic transformation of the dense contact holes. Under the high-selectivity etch condition, the deformation of dense contact holes occurs only in the direction of the closest adjoining contact holes. Since the patterns have a small flat part at the top of the photoresist, deposition of a small amount of fluorocarbon can exist on the flat part. Therefore, the recession of the photoresist at the facet part progresses rapidly and erosion of the photoresist occurs. On the other hand, the deposition of fluorocarbon progresses at the spacious top of the photoresist. This fluorocarbon suppresses the recession of the photoresist at the facet part and overhangs the contact hole. Accordingly, the dense contact holes change from a circular shape to rectangular shape. 5 refs.