A Novel TSV Etching using NLD and VHF CCP Plasma For 3-D Stacked Devices.

Abstract

In this study, the etch development of high etch rate and high aspect ratio for the fabrication of various diameters of thru silicon via is described. There are a lot of applications about TSV's methods. There TSV need to meet strict requirements with respect to high etch rate, sidewall roughness and undercut. For diameter of vias down to 10um a SiO2 hard mask based SF6/O2 etch approach is used by magnetic neutral loop discharge plasma (NLD plasma). This system can be used for oxide etching and Si etching. In the case of oxide etching, some magnetic coil currents are applied to generate magnetic neutral loop in the vacuum chamber in order to high density plasma in the low pressure below 1 Pa. On the other hand, in the case of Si etching, the pressure is raised up to 2∼10 Pa. As a result, an etched profile of TSV with diameter of 1.5 um and the etched depth of 11.5 um, aspect ratio is 7.6, was achieved. The etch rate is about 4.5 um/min. For diameter of vias up to 10um, a resist mask based and SF6/O2 etch approach is also used by very high frequency coactivity coupled plasma. VHF CCP etching system was used to high-pressure process, more than 50Pa, as a purpose to high etch rate of up to 10um pattern's TSV etching. As a result, a vertical profile of TSV with diameter of 50 um and the etched depth of 50 um, aspect ratio is 1.0, was achieved. The etch rate is about 45 um/min. NLD and VHF CCP processes are non-cycle etch methods, and to successfully smooth pattern TSV.