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Currently, many semiconductor devices employ mesa device structures, which are predominantly created through two types of etching: wet etching and dry etching. While the simple and rapid wet etching plays a significant role in semiconductor device fabrication, it has inherent drawbacks such as isotropic etching and poor uniformity, which result in limited control when transferring small-sized patterns. Dry etching, however, with its high anisotropy, good uniformity, and repeatability, has become prominent in semiconductor device fabrication processes. The term “dry etching” broadly refers to any non-wet etching technology used for removing surface materials and transferring micro and nano patterns, including laser etching, plasma etching, and chemical vapor etching. The dry etching discussed in this text specifically pertains to the narrow application of processes using plasma discharge—either physical or chemical—to modify material surfaces.

Gallium Nitride (GaN) epitaxial wafer growth is a complex process, often utilizing a two-step method. This method involves several critical stages, including high-temperature baking, buffer layer growth, recrystallization, and annealing. By meticulously controlling the temperature throughout these stages, the two-step growth method effectively prevents wafer warping caused by lattice mismatch or stress, making it the predominant fabrication method for GaN epitaxial wafers globally.

When producing large-sized GaN single crystal substrates, HVPE is currently the best choice for commercialization. However, the back carrier concentration of the grown GaN cannot be precisely controlled.

Oxidation processes play a critical role in preventing such problems by creating a protective layer on the wafer, known as the oxide layer, which acts as a barrier between different chemicals.

Homoepitaxy and heteroepitaxy play pivotal roles in material science. Homoepitaxy involves the growth of a crystalline layer on a substrate of the same material, ensuring minimal defects due to perfect lattice matching. In contrast, heteroepitaxy grows a crystalline layer on a different material substrate, which can lead to challenges like lattice mismatch. These processes are crucial in advancing semiconductor devices and thin films. For instance, heteroepitaxy significantly impacts microelectronics and quantum optics, contributing to innovations like Light Emitting Diodes.