Title :
Independent control of ion density and ion bombardment energy in a dual RF excitation plasma
Author :
Goto, Haruhiro Harry ; Löwe, Hans-Dirk ; Ohmi, Tadahiro
Author_Institution :
Dept. of Electron. Eng., Tohoku Univ., Sendai, Japan
fDate :
2/1/1993 12:00:00 AM
Abstract :
A dual RF excited discharge is described. The dual RF excitation system provides a method to control the substrate self-bias without affecting the state of the discharge. The substrate can be RF-biased utilizing an appropriate excitation frequency and power significantly less than the plasma generating RF power. The substrate self-bias dependence on various system parameters, including substrate excitation frequency, pressure, plasma generating upper electrode RF power, substrate material, and process gas compositions, is described. For a simplified model, a linear relationship between self-bias and RF power is derived using the space-charge limited assumption. The effect of substrate bias on the thermal-oxide etch rate has been studied. The results show good correlation between the ion bombardment energy, i.e., the potential difference across the substrate dark space, and the SiO 2 etch rate. The SiO2 etch rate in a CF4 plasma increases linearly with the ion bombardment energy, having a threshold etch energy of ~19 V
Keywords :
silicon compounds; sputter etching; RF-biased; SiO2 etch rate; dual RF excitation plasma; dual RF excited discharge; ion bombardment energy; ion density control; ion energy control; model; plasma etching; plasma generating RF power; pressure; process gas compositions; selective etching; substrate excitation frequency; substrate material; substrate self-bias; tetrafluoromethane; thermal-oxide etch rate; threshold etch energy; Composite materials; Control systems; Electrodes; Etching; Plasma applications; Plasma density; Plasma materials processing; Power generation; Power system modeling; Radio frequency;
Journal_Title :
Semiconductor Manufacturing, IEEE Transactions on