ZnSe/GaAs - Wet Etching

ZnSe/GaAs - Wet Etching

Material Name: ZnSe/GaAs
Recipe No.: 10359
Primary Chemical Element in Material: Zn, Ga
Sample Type: Thin film
Uses: Etching
Etchant Name: None
Etching Method: Wet etching
Etchant (Electrolyte) Composition: The composition and etching time are listed below:
1. A HF/HCl solution in a volume ratio of 1:l (Yeh and Holloway, 1990) for 20 seconds.
2. A hot 30% (wt) NaOH solution in D.I. water (Ohishi et al., 1988) for 5 seconds.
3. A H2S04/H202 (35%)1H,0 solution in a volume ratio of 5:l:l (Stutius, 1981) for 10 seconds.
4. A 0.5% Br2/CH3OH solution (Yodo et al., 1988, 1989) for 1-2 seconds then solution (1) for 20 seconds.
The entire etching process is as follows: 1) clean in a boiling Freon bath; 2) dip in etching solution; 3) rinse in D.I. water; and 4) drying.
Procedure (Condition): No data
Note: Cross-sectional transmission electron microscopy (TEM) sample preparation of ZnSeiGaAs epitaxial films is investigated. Conventional argon ion milling is shown to produce a high density of small (diameter -60-80 A) extended defects (stacking faults, microtwins, double positioning twins, etc.?. In addition, transmission electron diffraction results indicate a thin ZnO layer can also occasionally form upon ion milling or electron-beam irradiation although the exact conditions for ZnO formation are not well understood. Conventional TEM (amplitude contrast) and high-resolution TEM (phase contrast) imaging in combination with transmission electron diffraction studies were performed to determine the optimum method of removing the ion milling related damage and ZnO layers during sample preparation. HF/HCl, NaOH/H2O2 H2S04/H202/H20 and Br2/CH2OH etching mixtures as well as low voltage argon or iodine ion milling were studied. A low energy (2 keV) iodine or argon ion milling step was shown to remove the ZnO layer and reduced the density of the extended defects associated with Ar + ion milling, but was unsuccessful in removing all of the defects. Auger electron spectroscopy results indicate residual iodine was either left on the surface or implanted beneath the surface during iodine ion milling. Etching the XTEM samples in HFiHCl was shown to be effective in removing the ZnO layer but had little or no effect on the ion milling induced defects. Etching the samples in a 0.5% Br2/CH3OH solution resulted in complete elimination of the ion milling induced extended defects including the residual defects associated with iodine ion milling. In addition the Br,iCH,OH etch produced the best surface morphology. Thus a brief (1-2 seconds) Br2/CH3OH etch after conventional preparation (argon ion milling) of cross-sectional ZnSeiGaAs TEM samples appears to be an inexpensive and superior alternative to iodine ion milling.
Reference: J.E. YU, K.S. JONES, AND R.M. PARK, A Technique for the Preparation of Cross-Sectional TEM Samples of ZnSe/GaAs Heterostructures Which Eliminates Process-Induced Defects, JOURNAL OF ELECTRON MICROSCOPY TECHNIQUE 18:315-324 (1991).