SURFACE MODIFICATION AND ETCH PRODUCT DETECTION DURING REACTIVE ION ETCHING IN INP IN CH4-H-2 PLASMA

A detailed plasma-surface interaction study has been conducted using m ass spectrometry and optical emission spectroscopy for the plasma char acterization, and quasi in situ XPS analyses to central the surface ch emistry modifications. The experimental results clearly evidence the d ifferent etching behaviour of In and P in the CH4-H-2 plasma environme nt. A signature of the In and P etching mechanisms is available from t he diagnostic of the plasma phase through the detection of phosphine a s the major etching product of P and of excited In atoms related to th e In etching reaction. The observation of the In emission line at 451. 1 nm indicates a probable decomposition in the discharge of the organo indium compound which is regarded as the etch product of the group III element. XPS reveals the presence of P-H, C-In, In-In-C and In-In-P a s surface species, and allows us to quantify precisely the P surface d epletion. A time dependent etching mechanism is shown, first suggested by the etched thickness measurements and further confirmed by both et ch product signal intensity and surface stoichiometry evolution with t he plasma exposure time. Mass spectrometric PH3+ signal and In emissi on line intensities monitored as a function of time indicate that the in etching mechanism is responsible for this situation, It is conclude d that the reactive ion etching of InP is under the control of the rem oval mechanism of In. The combination of surface analysis and plasma d iagnostics is shown to be capable of providing an understanding of the plasma-surface interaction.