Fabrication and characterization of III–V compound semiconductor Bragg-Fresnel lenses for hard x-ray microfocusing

• Published in: Microelectronic engineering 1997-02, Vol.35 (1-4), p.289-292
• Main Authors: Caine, E.J., Shi, S., Hu, E.L., Li, Y., Idziak, S.H.J., Subramanian, G., Safinya, C.R.
• Format: Article
• Language: English
• ISSN: 0167-9317; 1873-5568
• DOI: 10.1016/S0167-9317(96)00125-6

Hard x-ray phase Bragg-Fresnel lenses (BFLs) have been made in III–V semiconductors of (111) GaAs and InP, and in Si for comparison purposes. Diffractive linear and circular patterns were defined with conventional electron beam lithography. Pattern transfer was accomplished with reactive ion etching (RIE) using gases of BCl3/Cl2/SiCl4, CH4/H2/Ar, and BCl3Cl2, respectively. In addition, selective etching of heteroepitaxial GaAs devices for better process depth control was demonstrated by incorporating an epitaxial AlGaAs etch stop layer between the GaAs top layer and substrate and then etching with Cl2O2. Preliminary tests on focusing have been made at the Stanford Synchrotron Radiation Laboratory (SSRL) showing the ability to focus a 50 micron x-ray beam to ∼5 microns for Si structures. This is an essential requirement for x-ray microprobe technology development which has wide applications in x-ray imaging, deep field x-ray lithography, and in probing nanometer scale complex fluids such as boundary lubrication layers.