Chemical treatment of CdTe and Cd0.9Zn0.1Te surfaces with iodine-containing solutions

The surface quality of semiconductors has a direct impact on the performance of devices made of them. One of the stages in the semiconductor materials technology is chemical treatment of the crystal surface. Etching solutions used for this purpose often contain halogens or compounds based on them. To reduce the dissolution rate of the semiconductor during its etching, a viscous component, such as glycerol, ethylene glycol, etc., is often added to the etching compositions. The paper studied the features of chemical interaction of CdTe and Cd0,96Zn0,04Te, oriented in different crystallographic directions of iodine-containing etchants based system I2 - CH3OH. The influence of ethylene glycol on the results of chemical-dynamic and chemical-mechanical polishing of these semiconductor materials has been clarified. The concentration dependence of the rate of chemical-dynamic and chemical-mechanical polishing of CdTe (111) B, CdTe (110), Cd0,96Zn0,04Te (211) A and Cd0,96Zn0,04Te (110) surfaces was studied. It is shown that the addition of ethylene glycol to solutions of the I2 - methanol system significantly slows down the dissolution rate of both CdTe and Cd0,96Zn0,04Te samples. The addition of only 16 vol.% ethylene glycol into basic solution slows down the interaction more than two times, although a further decrease in the etching rate with increasing ethylene glycol content is not so rapid. Only solutions with an ethylene glycol content not exceeding 40% (chemical-dynamic polishing) and 50% (chemical-mechanical polishing) have polishing properties. The use of solutions with higher ethylene glycol content causes the appearance of a light blue film on their surface, which does not disappear even after careful postoperative treatment. It is shown that the surface roughness of both CdTe and Cd0,96Zn0,04Te after its chemical-mechanical polishing does not exceed 10 nm. This is a characteristic of its high quality and makes it possible to recommend ethylene glycol-modified etchants of the I2 - CH3OH system for chemical-mechanical polishing of the surface of cadmium telluride and solid solutions based on it.