State-of-the-art plasma etch process and technologies for high aspect ratio pattern

With the 3D structure of semiconductor devices, the evolution of high aspect ratio (HAR) pattern etch technology is required. Reactive ion etch utilizes the synergy between activation by ion bombardment and reactant feed by radicals. Fluorocarbon (CF) contained gases plays important roles in HAR dielectric etch process. High temperature of the wafer transported CF polymer to form passivation layer on the sidewall and high ion energy transported ions to the bottom. Though, CF contained gases tends to grow carbon contained film at opening of the hole and it cause clogging. For precisely controlling of thickness of the film, pulsed RF power technology was applied. For sidewall passivation during etch, atomic-layer-deposition and etch combined process was developed. However, the transport of both ions and radicals are attenuated with increasing aspect ratio (AR). The lower etching rate due to the higher AR reduces the mask selectivity, which is a limiting factor in etching HAR features.

To address these issues, the novel gas chemistry in cryogenic temperature regime was developed. Novel gas with light-mass molecule enhanced the radical transport in HAR pattern. Then, cryogenic temperature regime not only suppress the spontaneous reaction at the sidewall but also enhanced adsorption of the radicals on the surface. Therefore, supply of etchant to the etch front was drastically increased. The novel process is capable of etching holes beyond 10 um depth with a diameter of approximately 100 nm.^[1] The novel technology promises to advance HAR dielectric etch.