Surface Treatment Research On HgCdTe

Hg1-x Cdx Te is a solid solution consisted of Cd Te and Hg Te. The band gap can be adjusted by changing the component xcontinuously and the response wave of the Hg Cd Te covers the entire infrared band.Hg Cd Te infrared detectors have became one of the most important infrared semiconductor materials and play an important role in the field of missile guidance,the environment and resources of remote sensing, night vision, satellite and other civilian areas.The Hg Cd Te surface properties largely determine the optoelectronic properties of Hg Cd Te infrared detectors, in order to improve the performance of Hg Cd Te infrared detectors further,Hg Cd Te surface treatment processes are necessery for a deeper study. The main process of the Hg Cd Te surface treatment are the polishing process or cleaning process, which have a direct relationship with the roughness, flatness, damage and contaminationson the Hg Cd Te surface. Therefore, this article does some in-depthresearches about the Hg Cd Te polishing process and the cleaning process, which contain Chemical Mechanical Polishing, Bromine Polishing and Cleaning Technology.Firstly, the Hg Cd Te surface roughness in various CMP conditions was studied. We changed the weight of the loading jig, the polishing time and the speed of polishing platform in the CMP process, used a laser interferometerto measure the surface flatness which were analysed by the orthogonal analysis.At last,we obtained an optimum Hg Cd Te CMP process conditions about the surface flatness. In addition, the paper analysed the causes of the "convex" shape on the middle of Hg Cd Te wafers after CMP process and noted: Although the loading jig had been in rotation which led to different instantaneous speed of the center position or the edge position on the Hg Cd Te wafers, the average speed of Hg Cd Te wafers anywhere in aperiod T was the same.According to the mechanism of the CMP polishing, the polishing rate is proportional to the velocity V.Because the average speed was the same in a whole period T,the differentinstantaneous speed was not the cause of the "convex" shape of Hg Cd Te wafers and the phenomenon that the edge of the Hg Cd Te wafer contacted the fresh slurry earlier than the central region of the Hg Cd Te wafer maybe the real reason of the "convex" shape,for the chemical reaction in the edge of Hg Cd Te wafer was stronger than that in the center position.Besides CMP is used to thinning and optimize surface, the bromine polishing technology is also a common Hg Cd Te thinning and surface processing optimized technology. Compared to CMP technology, bromine polishing technology has not any great advantage in flatness, thickness control, polishing rate and adaptation degree, but bromine polishing technology has an important advantage that it causes a little surface damage. Several problems in the processing of bromine polishing that must be resolved is small pittings or oxides on the surface of Hg Cd Te after using bromine polishing.By adjusting the concentration of Br2-CH3 OH solution, the water in the polishing pad and the weight of loading jig, we found the cause and established a stable bromine polishing process.Now the stable bromine polishing process has been used in the production of Hg Cd Te devices from the engineering task.Secondly, the cleaning process is a main technology of removing organic substances, particles and ionic contaminationson the surface of Hg Cd Te, which have a huge impact on the performance of Hg Cd Te devices. This article drew on RCA cleaning technology using in the silicon processing and megasonic cleaning technology which applied to the conventional Hg Cd Te cleaning process,then designed a new Hg Cd Te cleaning technology.Finally, the article characterized and compared in the aspectof the X- ray photoelectron spectroscopy, charge density and device performance of Hg Cd Te materials that used different processing included the conventional Hg Cd Te cleaning technology and the new Hg Cd Te cleaning technology,and obtained four conclusions.The first one is thatthe conventional Hg Cd Te cleaning technology may introduce new organic pollution.The second one is that the Hg Cd Te surface using the new cleaning Hg Cd Te technology has fewer total ion contaminations and the Hg Cd Te surface density of slow states using the new cleaning techology is superior to that of the conventional cleaning techology. The third one is that the oxidation layer will introduce a large number of positive charge. The four one is that the 67% proportion of Hg Cd Te devicesusing the new Hg Cd Te cleaning technology is superior to that using the conventional Hg Cd Te cleaning technology.