Published online by Cambridge University Press: 28 February 2011
The etch behaviour of Al2O3 was studied in Ar, CHF3/Ar, CF4/O2 and Cl2 low pressure RIE plasmas.The influence of dc self-bias voltage, wafer temperature, gas flow and pressure on the Al2O3 etch behaviour was investigated.This was compared with the etch behaviour of SiO2, Mo, Au and Si under the same conditions.It was found that even though aluminum does not form volatile fluorides addition of CHF3 to an Ar plasma resulted in a ninefold increase in the A12O3 etch rate.This compares to a fivefold increase in the SiO2 etch rate and a 20% decrease in Au etch rate.
An A12O3 etch mechanism for fluorine based plasmas is proposed, comprising of the formation of AlFx and its subsequent removal under influence of high energy ion bombardment.The latter appears to be the rate limiting step.