CdZnTe is the most suitable epitaxial substrate material of HgCdTe infrared detectors, because its lattice constant is able to achieve full match with HgCdTe’s lattice constant. It is always needed to etch CdZnTe substrate during the process of device separation or when we want to fabricate micro optical device on CdZnTe substrate. This paper adopts the more advanced method, Inductive Coupled Plasma-Reactive Ion Etching(ICP-RIE). The etching conditions of ICP-RIE on CdZnTe substrate are explored and researched. First of all, a set of comparative experiments is designed. All of CdZnTe samples with the same component are polished by chemical mechanical polishing before etching. Then all samples are etched by different types of etching gases(CH4/H2/N2/Ar) and different ratios of gases as we designed. The etching time is all set to 30 minutes. After that, the surface roughness, etching rate, etching damage and the profile of etched mesas are tested and characterized by optical microscope, step profiler and confocal laser scanning microscope (CLSM), respectively. It is found that, Ar gas plays the role of physical etching, but the etching rate will decline when the concentration of Ar gas is too high. The results also show that, the introduction of N2 causes more etching damage. Finally, combination of CH4/H2/Ar is used to etch CdZnTe substrate. The ratio of these gases is 2sccm/2sccm/10sccm. The testing results of optimized etching show that, the maximum etching rate reaches up to 20μm/h and the etched CdZnTe surface is smooth with very low etching damage. At last, aimed at the shortcoming of photoresist’s degeneration after long-time etching, the ICP etching process of CdZnTe deep mesa is studied. Double-layer or triple-layer photoresist are spin-coated on CdZnTe substrate during the process of lithography. Then ICP etching is carried out with the optimized condition. It is seen that there is no more phenomena of degeneration.
Silicon nitride (SiNx) films on GaN were deposited, using the inductively coupled plasma chemical vapor deposition
(ICPCVD) method with different radio-frequency chuck power (RF power). After deposition, all the films were annealed
at 750℃ in N2, and some pins and bubbles were observed on the surface of some films, but this phenomenon was not
observed on the films which were deposited with RF power=0W, as well as films deposited by a two-step-deposition
method, which was consisted of setting RF power=0W at the beginning, and setting RF power=2W after that. To study
the mechanism of origin of these pins and bubbles, Atomic force microscopy(AFM) was performed to study surface
morphology and measure the height of the pins and bubbles, it was found that the height of bubbles was about 300nm,
and the depth of pins was about 300nm, which were almost the same as the film thickness. It was showed that the pins
and bubbles were originated from gas escaping from the inner films after high-temperature annealing. X-ray
photoelectron spectra(XPS) was used to characterize the chemical composition of the films before and after annealing,
independently. It was found that, on GaN-SiNx interface and SiNx film surface, the N element content decreased a lot
after annealing, but N content remained almost the same in those films with RF power=0W. which indicated that
reducing of N content was closely related with those pins and bubbles. RF power increased the plasma energy and caused
GaN surface damage. The ion bombardment broke some N-Si bonds and N-Ga bonds, as a result some N reactants didn’t
perform as Si-N bond, but performed in other bonds such as N-H bonds or N-N bonds, and a high-temperature annealing
process would cause NH3 or N2 escape from the film. The pins were voids which resulted from the film broken by the gas, and the bubbles came from bulge resulted from gas escape.
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