Bi2Te3 - Wet Etching

Bi2Te3 - Wet Etching

Material Name: Bi2Te3
Recipe No.: 10328
Primary Chemical Element in Material: Bi
Sample Type: Wafer
Uses: Etching
Etchant Name: None
Etching Method: Wet etching
Etchant (Electrolyte) Composition: To investigate semiconductor dissolution, ascertain the character of corresponding reactions and determine limiting stages of the process, we have used the method of rotating disk and appropriate device for its practical implementation – installation for CDP. The crystals of Bi2Te3 as well as n-(Bi2Te3)0.9(Sb2Te3)0.05(Sb2Se3)0.05 and p-(Bi2Te3)0.25(Sb2Te3)0.72(Sb2Se3)0.03 solid solutions were grown using vertical growth zone melting of the components. For the investigation, we cut from the ingots the wafers with dimensions (~5 x 7.1 x 5 cm), which were abraded by aqueous suspension of M10, M5 and M1 abrasive powder one after another. After each stage of wafer treatment – cutting, abrading, mechanical and chemical-mechanical polishing interoperable cleaning was performed to eliminate various contaminations from the surface. Physical or mechanical contaminations (mote, abrasive, metallic materials, fibers and semiconductor particles that are crumbled into small pieces) were eliminated with warm water with addition of surfactants. The final stage of treatment included washing in distilled water, degreasing by ethanol or acetone, then samples were dried up in air flow.
Mechanically polished surface of crystalline samples are stable in time, but it is not structurally perfect, and therefore, before researching, the layer with a thickness of 80-100 ìm was eliminated from it with etchant of the same composition, in which the process of chemical treatment was subsequently performed. Samples were stuck by their operation surface to glass substrates by using picein and placed on the disk of CDP installation. The dissolution rate of crystals was measured by the difference in the sample thickness before and after the etching process by using the watch indicator 1MIGP to within ±0.5 ìm. Etching time was chosen so that the process was shot by one of at least 10-15 µm of material.
To prepare etching compounds, we used 70% HNO3 and 36.6% HCl. Etching compositions were prepared directly before use, then they were hold up for 80-120 min. After completion of etching process, the samples were quickly bereaved from etching composition and immediately washed several times with deionized water and in ultrasonic bath for 5 min at 20 °C for surface cleaning from etchant residues, then dried up in air flow.
Procedure (Condition): No data
Note: The chemical etching of Bi2Te3 and n-(Bi2Te3)0.9(Sb2Te3)0.05(Sb2Se3)0.05 and p-(Bi2Te3)0.25(Sb2Te3)0.72(Sb2Se3)0.03 crystals of solid solutions with HNO3–HCl etchant compositions was investigated. The dependences of dissolution rate of these semiconductors on etchant composition, stirring, temperature and their shelf-time storage have been studied. It was shown that the process of dissolution of the investigated materials in the polishing solutions HNO3–HCl is limited by the diffusion stages.
Reference: I.I. Pavlovich, Z.F. Tomashik, I.B. Stratiychuk, V.M. Tomashik, O.A. Savchuk, A.S. Kravtsova, Chemical-dynamic polishing of semiconductor materials based on Bi and Sb chalcogenides by using HNO3–HCl solutions, Semiconductor Physics, Quantum Electronics & Optoelectronics, 2011. V. 14, N 2. P. 200-202.