InP surface properties under ICP plasma etching using mixtures of chlorides and hydrides B.Liu 1 , J-P.Landesman 1 , J-L.Leclercq 2 , A.Rhallabi 1 ,M.Avella 3 , M.A. González 3 , J. Jiménez 3 , S. Guilet 2 , C.Cardinaud 1 and F.Pommereau 4 1 IMN, UMR CNRS 6502, 2 Rue de la Houssinière, 44322 Nantes Cedex 3, France 2 LEOM, Ecole centrale de Lyon, UMR CNRS 5512, 36 Avenue Guy de Collongue, France 3 Física Materia Condensada, ETSII, 47011 Valladolid, Spain 4 Alcatel -Thales III-V Lab., Route de Nozay, F-91460 Marcoussis, France Abstract InP wafers after etching in an ICP (Inductively-Coupled Plasma) reactor with different kinds of reactant gases have been carefully studied using surface sensitive techniques, in order to gain insight into the mechanisms that control the process. Two types of reactive gas systems have been investigated, namely Cl 2 /CH 4 /Ar mixtures on one side, and CH 4 /H 2 on the other. In both cases, the composition (flow rate) of the different components was varied. X-ray Photoelectron Spectroscopy (XPS), Atomic Force Microscopy (AFM) and micro-Raman were the techniques used. From the XPS data, information like the surface overall enrichment (in P or In depending on the nature of the etching gases), quantitative surface stoichiometry, and detailed chemical analysis could be derived. AFM images provided an estimate of the roughness increase, while micro- Raman results were used to get indications on the surface structural disordering associated with the etching process, as well as the changes induced in the electronic properties of the InP material (Surface Recombination velocity – SRV – and modifications of the free carrier densities). I. Introduction Plasma etching techniques nowadays play a major role in the fabrication process in the field of nano-technology, especially for example when features with very high surface/volume aspect ratio are necessary as is the case for photonic crystal (PC) structures in InP. PCs based on InP show an increasing number of applications as basic building blocks for devices of interest in the area of optical communications (waveguides with low optical losses, cavities with high quality factor, laser diodes, photo-detectors…) (1, 2). Amongst these etching techniques, Inductively-Coupled Plasma (ICP) etching is frequently used, in particular because of the possibility to control separately the various important process parameters in such a reactor (like the energy and density of the ions reaching the surface) (3, 4). However, the different aspects of the plasma/surface interaction mechanisms taking place in such tools, especially for the case of InP, have not been fully described yet. Several preliminary experimental studies adressing this problem were published in the past, but the results cannot be directly extended to processing techniques like ICP. For example, Feurprier et al. (5) have concluded that InP surfaces, during Reactive Ion Etching (RIE) with CH 4 /H 2 , display a strong P-depletion. In an experiment performed with Auger electron spectroscopy on InP surfaces etched by Chemically Assisted Ion Beam Etching (CAIBE), a technique somewhat different from standard dry etching techniques like RIE or ICP, Youstey et al. (6) observed an In depletion when Cl 2 was used as the chemically active species (in conjunction with etching by Ar ions). This approach to the problem of surface interactions taking place during processing (etching) requires specific experiments, where the whole area of the material is exposed to the plasma simultaneously, meaning that no geometrical structure (PC or other) defined by features transferred through a mask layer should be included. This is due to the limited spatial resolution of the characterisation techniques, in particular X-ray Photoelectron Spectroscopy (XPS). The drawback of this approach is of course that some phenomena (like for example the dependence of the etching mechanisms – etch rate, … - on the geometrical factors of the features to be etched) cannot be included. Nevetheless, the outputs of such an experimental approach are essential for the general understanding and control of etching techniques like ICP. In particular, many of the data necessary to develop modeling and simulation tools could in principle be derived (7,8). XPS, Atomic Force Microscopy (AFM) and Raman (or micro-Raman) provide complementary data on the InP surfaces. XPS allows to estimate the surface stoichiometry 278 WP3 1:30 pm – 3:30 pm 0-7803-9558-1/06/$20.00 ©2006 IEEE