Study on the etching characteristics of amorphous carbon layer in oxygen plasma with carbonyl sulfide

Abstract

Carbonyl sulfide (COS) was added to oxygen as the additive etch gas for etching of amorphous carbon layers (ACL), and its effect on the etching characteristics of ACLs as the etch mask for high aspect ratio contact SiO2 etching was investigated. When a 50 nm amorphous carbon hole was etched in a gas mixture of O2 + 5% COS, not only did the etch profile of the ACL change more anisotropically but also the top/bottom opening ratio of the etch profile was improved by about 37% compared to those etched without COS. The improved ACL etch characteristics were related to the sidewall passivation of the amorphous carbon hole by the carbon sulfide related layer during the etching of the ACL. The distortion of the amorphous carbon hole was also reduced by about 6% due to the uniform deposition of the carbon sulfide related layer on the sidewall of the amorphous carbon hole. This uniform deposition improved the etch profile and opening ratio of the amorphous carbon hole, ultimately resulting in the enhanced contact oxide etching characteristics as evidenced by 5% improvement in the contact oxide opening and 20% improvement in the mask etch selectivity during the etching of an oxide having 20:1 high aspect ratio.

Reactive plasma cleaning and restoration of transition metal dichalcogenide monolayers

“…To avoid ambient exposure, it is interesting to perform resulfurization directly after H 2 exposure, without air break, ideally in situ. Multiple sources of sulfur could be considered, with a preference to halogen-free molecules so as to avoid etching the W layer; an interesting candidate is carbonyl sulfide (O = C = S), which is less toxic than H 2 S and adopted by the plasma etch community for its use as sidewall passivant 37 . The injection of OCS in a plasma would lead to dissociation of the molecule, and release oxidizing components that could be harmful to the exposed WS 2 .…”

In-Situ Photo-Dissociation and Polymerization of Carbon Disulfide with Vacuum Ultraviolet Microplasma Flat Lamp for Organic Thin Films

“…As a conductive polymer, CS 2 has been used as a sulfur dopant in organic chemistry and a solvent for various polymers [7,8]. In addition, CS 2 can be used as an etchant of the carbon layer when it is used with plasma [9]. It has been known that CS 2 can be readily dissociated to CS + S fragments through photons, catalytic reactions, and plasma processes in the vapor phases [10][11][12].…”

Step Coverage and Dry Etching Process Improvement of Amorphous Carbon Hard Mask

“…The amorphous carbon hard mask (ACHM) has been applied to the fabrication of semiconductors, replacing the conventional SiO 2 or Si 3 N 4 hard mask due to its excellent physical properties and chemical stability. ACHM can be deposited using a variety of deposition methods, among which the plasma-enhanced chemical vapor deposition (PECVD) method has been widely used because of its high productivity, low cost, and tenability in terms of its film properties [5][6][7]. However, experimental studies focusing on the simultaneous optimization of the film step coverage and dry etching characteristics, using different parameters, have rarely been conducted and reported.…”