Paper PS-TuP14
Inductive Plasmas in Cl₂/Ar : Comparison of Hybrid Model Results with Experimental Measurements

Tuesday, October 19, 2010, 6:00 pm, Room Southwest Exhibit Hall

Inductively-coupled chlorine-based plasmas (often also containing HBr, O₂ and Ar) are widely used in the microelectronics industry for selective, anisotropic etching of silicon, and are currently being investigated for etching of III-V materials such as InP for the fabrication of photonic devices.

We have constructed a reactor, identical in geometry to an industrial 200mm etch tool, but adapted for advanced diagnostics and supplied with Cl₂/HBr/O₂ and Ar gases. It is excited by a flat spiral antenna though a dielectric window. In parallel we are developing a hybrid simulation code based on the HPEM (Hybrid Equipment Plasma Model) of Mark Kushner. Experimental measurements of internal plasma parameters (electron densities, temperatures, and also gas dissociation fraction and temperature) will be used to test and improve the simulation code. The aim is to reliably predict the plasma behaviour as a function of these parameters, and for arbitrary reactor geometries.

The electron density was measured using a microwave hairpin resonator, and with a Langmuir probe. Measurements were made as a function of pressure and power in pure Cl₂ and as a function of composition in Cl₂/Ar mixtures. The electron density decreased from 5x10¹⁰cm^-3 to 2x10¹⁰cm^-3 as the Cl₂ pressure was increased from 0.5 to 10 mTorr. The electron density also decreases monotonically as the Cl₂ fraction is increased in Ar/Cl₂ mixtures. The Langmuir probe measurements of n_e showed the same trend as the hairpin probe, but gave lower values, particularly at the highest pressures and lowest powers and for high Cl₂ fractions.