Title :
Elimination of notching and ARDE by simultaneous modulation of source and wafer RF
Author :
Hershkowitz, N. ; Harper, M.K.
Author_Institution :
Wisconsin Univ., Madison, WI, USA
Abstract :
Summary form only given. Notch formation and aspect ratio dependent etching (ARDE) are becoming serious problems in the over-etching of line and space structures in poly-Si on SiO/sub 2/. Experimental results for Cl/sub 2/ plasma etching of poly-Si and C/sub 2/H/sub 2/F/sub 4/ in SiO/sub 2/ in a helicon etch tool are presented which are modeled by differential charging and ion assisted etching. It is shown that modulation of the 13.56 MHz RF source can eliminate both of these effects in the absence of RF wafer bias but fails in the presence of CW wafer bias. It is also shown that simultaneous source and wafer modulation eliminates both notch formation and ARDE. On/off modulation with a 50% duty cycle and period ranging from 0 to 200 /spl mu/s are investigated and optimum notch and ARDE reduction are found at 40 to 200 /spl mu/s.
Keywords :
chlorine; elemental semiconductors; modulation; organic compounds; plasma materials processing; semiconductor technology; silicon; sputter etching; 0 to 200 mus; 13.56 MHz; 40 to 200 mus; ARDE; CW wafer bias; Cl/sub 2/; Cl/sub 2/ plasma etching; RF source; RF wafer bias; Si; SiO/sub 2/; aspect ratio dependent etching; charging; duty cycle; helicon etch tool; ion assisted etching; line structures; modulation; notch formation; notching; on/off modulation; optimum notch; over-etching; poly-Si; source RF; source modulation; space structures; tetrafluoroethane; wafer RF; wafer modulation; Etching; Optical interferometry; Physics; Plasma applications; Plasma chemistry; Plasma diagnostics; Plasma materials processing; Plasma measurements; Plasma sources; Radio frequency;
Conference_Titel :
Plasma Science, 1999. ICOPS '99. IEEE Conference Record - Abstracts. 1999 IEEE International Conference on
Conference_Location :
Monterey, CA, USA
Print_ISBN :
0-7803-5224-6
DOI :
10.1109/PLASMA.1999.829348
