Optimization of Reactive Ion Etching Parameters Via Material Characterization
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OPTIMIZATION OF REACTIVE ION ETCHING PARAMETERS VIA MATERIAL CHARACTERIZATION M.W. COLE*,C.B. COOPER**, M. DUTTA*, C.S. WRENN*, L. FOTIADIS*, M-L. SAUNDERS*, AND W.H. CHANG* *US Army ETDL, Ft. Monmouth, N.J. 07703 **Varian Research Center, Palo Alto, Ca.,94303
S. SALIMAN**,
H.S.
LEE*,
ABSTRACT This study evaluates variations in SiClat reactive ion etching (RIE) process parameters in order to optimize the fabrication of lateral quantum well arrays (QWA) used in III-V semiconductor laser and detector designs. Since fabrication involves MBE regrowth on SiCI• etched surfaces, material quality of both the etched surface and GaAs regrowth are evaluated. The variation of RIE parameters involved power levels, DC bias and etch times (10 Watts, -30V, 8 min.; 25 Watts, -10OV, 5 min.; 95 Watts,-340V, 2 min.) while material removal was held constant (400nm). Evaluation of the etched surfaces revealed that the lattice damage depth exceeded lOOnm for all power levels. The extent of disorder beneath the etched surface was less for the low power long etch time. Etching at higher power levels for shorter time periods resulted in smoother surfaces and enhanced electrical characteristics, which in turn yielded a higher quality GaAs regrowth region. For the RIE parameters examined in this study, the variation in defect densities seemed to have a lesser effect on device performance as compared to the extreme differences in surface morphologies. Thus, for the parameters evaluated in this work, we suggest that QWA fabrication is optimized via SiCl& RIE at the high power level for a short time period. INTRODUCTION Reactive ion etching (RIE) is a preferred dry process step for fabrication of submicron microelectronic device structures. This kinetically assisted dry etch process combines controlled energetic ion bombardment with chemically reactive interactions to achieve highly selective anisotropic etching. Chemically reactive silicon tetrachlodide is a commonly used etch gas for GaAs [1,2]. Previous work has demonstrated SiCIL to be a very desirable etchant since silicon does not produce chlorinated polymer films which can contaminate the sample, the etching chamber and the pump fluids [2,3]. The directional nature of SiCI% combined with its etch rate control, selectivity, accuracy, uniformity, and reproducibility, make it desirable for use in the fabrication of semiconductor laser and detectors which incorporate lateral quantum well arrays (QWA) into their designs. Fabrication of QWA involves molecular beam epitaxial (MBE) regrowth on RIE semiconductors [4,5,6]. A major drawback of using SiC14 RIE in the QWA processing scheme is the potential lattice damage introduced into the etched material by energetic ion bombardment and contamination. This material damage may cause deterioration of device performance. In the present work we examine different SiCl9 RIE conditions in order to maximize device properties via optimization of SiCI4 etch parameters. Our methodology employs complimentary materials characterization techniques in order to
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