Atomic layer deposition analysis

In principle, ALD is a product obtained by chemical reaction, but it is different from traditional CVD in the principle of deposition reaction, the requirements of deposition reaction conditions, the quality of deposition and so on. In the traditional CVD process, the chemical vapor is continuously introduced into the vacuum chamber, so the deposition process is continuous, and the thickness of the deposited film is related to many factors such as temperature, pressure, gas flow, flow uniformity, time and so on. In ALD process, different reaction precursors are alternately sent into the reaction chamber in the form of gas pulses, so it is not a continuous process. Compared with the traditional deposition process, ALD has obvious advantages in film uniformity, step coverage and thickness control.

In some applications, it is necessary to coat the surface of the inner cavity with a large aspect ratio. In extreme cases, the aspect ratio will reach 15 or even 20, which cannot be achieved by traditional coating methods. Atomic layer deposition technology has a unique advantage in this respect, because it forms an adsorption layer on the surface of the substrate, and then generates a thin film through reaction, which can form a thin film with uniform thickness on the surface of the cavity with large aspect ratio.

Working principle diagram In recent years, there are more and more demands and researches on optical thin films in X-ray spectrum. Because the optical constants and properties of materials vary significantly with wavelength in the X-ray region, at the same time, in the preparation of X-ray multilayer films, the surface roughness of the substrate is very high and the film layer is very thin, which is difficult to control. These problems are still difficult in the research of optical thin films. Because ALD technology is based on the chemical adsorption of reaction precursors on the surface to form thin films, its main feature is that it is suitable for depositing thin films with good film quality, and it has absolute advantages in the preparation of X-ray optical thin film devices.

Photonic crystal is a new concept and new material put forward in the late 1980s. Because of its photonic band gap and photon localization, it has broad application prospects. Because photonic crystal is an artificial microstructure, there are only a few in nature, so the fabrication technology of photonic crystal has always been a research hotspot. Atomic layer deposition technology can accurately control the film layer, and the highly uniform surface has great influence on the photonic band gap characteristics, which provides a flexible and effective way to obtain high-performance photonic crystal structure.