AL ETCHING CHARACTERISTICS EMPLOYING HELICON WAVE PLASMA

Characteristics of helicon wave plasma employing Cl2 gas and its application to Al etching have been studied. Production of Cl ions dominates that of Cl atoms at 1200 W RF power at 2 mTorr. Liberated oxygen from a quartz tube sputtered with Cl ions oxidizes Al and the probe surface. This is overcome by adding 10% BCl3 to Cl2. Electron density, temperature and ion current in Cl2 Plasma at 2 mTorr are 5 X 10(10) cm-3, 5.5 eV and 15 mA/cm2, respectively. Formation of negative chlorine is dominant at higher pressure. Although the Al etch rate is 5000 angstrom/min, selectivity to resist and SiO2 is poor due to high substrate bias voltage. Initiation time depends strongly on bias voltage, while net etching time is not changed. This implies that Al etching follows a chemical reaction even at 2 mTorr. Considerably uniform etch rate was achieved in zero magnetic field in a reactor. Slight variation which may result in the helicon wave plasma was observed.