Transformation of Dense Contact Holes during SiO₂Etching

Abstract

We have observed crystalline structures formed by laser cooled Ca + ions in a threedimensional confining potential. The potential has been realized using a linear Paul trap with different ratios of potential strength in the axial and radial directions. For radial confining potentials stronger than the axial potential, we find linear structures with a continuous transition from strings to helices with decreasing potential asymmetry. When a quasi-two-dimensional potential is formed we observe ring structures with a given maximum ion number per ring which we followed up to 19. The observations are essentially in agreement with molecular dynamics calculations in static two-dimensional potentials.

High aspect ratio SiO2/SiN (ON) stacked layer etching using C3HF5, C4H2F6, and C4H4F6

“…The MH RIE process must meet strict requirements for critical dimension control because the features at each control gate directly affect the characteristics of the memory cell. There are multiple challenges in this type of high aspect ratio etching such as achieving a high selectivity, suppressing bowing, 4,5) distortion, 6,7) twisting, 7) striation, 8) transformation, 9) and avoiding etch stop caused by sidewall necking or mask clogging. 5) In order to increase the etch rate at the bottom of high aspect ratio structures, sufficient transport and higher etching efficiency of reactive radical and ion species is essential.…”

Formation mechanism of sidewall striation in high-aspect-ratio hole etching

“…Therefore, the key technology of 3D flash memory is a high aspect ratio (HAR) hole etching process. However, the dry etching process of HAR holes has a variety of profile issues, including profile transformation, 2) bowing (increased hole diameter near the middle of a hole), 3,4) shape distortion, 5,6) twisting of the hole profile, 6) and striation.…”