Assessment of the Progress in Gas-Phase Processing of Silicon Surfaces

Abstract

The paper assesses progress of gas-phase silicon cleaning methods over the last 25 years. Early predictions regarding ability to clean silicon surface in gaseous ambient are confronted with the reality of today's advanced semiconductor technology where choices between liquid- and gas-phase cleans are based on the nature of species to be removed from the surface and composition and geometrical configuration of semiconductor material systems to be processed. Focusing on the former, extent to which control of particles, metallic and organic contaminants, as well native/chemical oxides and moisture on silicon surface can be accomplished using gas-phase processes is considered. It is concluded that gas-phase methods are effective in native/chemical oxide, organics and moisture control all of which fall into the broadly defined category of surface conditioning operations. In contrast, usefulness of gas-phase methods in particle and metallic contamination control, which fall into the category of surface cleaning steps, is limited. A conclusion from this elaboration is that, as practice shows, hybrid cleans appropriately combining, liquid- and gas-phase surface processing steps are a viable solution to the challenges of silicon surface processing.

NF3/NH3 Dry Cleaning Mechanism Inspired by Chemical and Physical Surface Modification of Si, SiO2, and Si3N4

“…Because HF concentration can be maximized in the reaction chamber when the ratio of NF 3 :NH 3 is 1:1 compared to the other ratios, the surface roughening intermediate reaction pathway would involve reaction [3] more than reaction [2].…”

“…As the Si-based semiconductor technology has entered the 10 nm gate length regime, every semiconductor process technology has been developed to meet the severe process specification. Wet chemical cleaning process is one of the processes that face technical and theoretical limits such as surface tension related issues of aqueous cleaning chemistries in the 10 nm technology node (1,2). Recently, chemical dry cleaning process technique using NF 3 and hydrogen-containing gas, such as H 2 and NH 3 , has been introduced into Si-based integrated-circuit (IC) fabrication industry to remove the surface native oxide selectively in the name of chemical oxide removal (COR) or native oxide removal (NOR) (3,4).…”