Volatile products and endpoint detection in reactive ion etching of III–V compounds with a broad beam ECR source

A broad beam ECR plasma source has been applied to low pressure hydrocarbon reactive ion etching of III–V compounds. An additional RF bias is applied to the sample stage providing the means for independent control of current density and bombarding energy of ions on the sample surface. Chemical aspects of the etching process have been investigated with a differentially pumped energy selective Hiden quadrupole mass spectrometer. In particular, the dominant group III volatile species in InP and GaAs have been clearly identified for the first time as In(CH3)2+ and Ga(CH3)2+, respectively. Finally, we report the application of volatile product identification to endpoint detection and demonstrate resolution for multiple layers as thin as 50 Å. These results confirm that etch uniformity over the surface area of the sample is very good for these sources.