This article mainly introduces the principles, characteristics, applications of dielectric films and metal films, and compares the differences between them.

The dielectric film is non-conductive. Using the Fresnel formula, through a material with a certain refractive index and the condition of equidistant interference, the reflected wave is constructively constructed, so as to obtain a large reflectivity. The characteristics of the film in the long-wave region are weaker than those in the short-wave region. The films commonly used in semiconductor devices and integrated circuits include dielectric films (passivation films and optical films) and metal films (single-layer and multi-layer) ). Dielectric film is often used as passivation protection, interlayer SiO2, Al2O3, polysilicon, etc. for multi-layer wiring.

Different dielectric films can be combined into optical films according to a certain optical thickness, such as the combination of Ta2O5 and SiO2, etc., which can play the role of anti-reflection (anti-reflection) or high reflection for the outgoing light of a certain wavelength. In metal films such as Cr, Al, Ti, ZnAu, AuSn and other metals and alloys are mainly used for Schottky contacts, ohmic contacts, barrier layers, metal leads and bonding metals of N-type P-type semiconductor materials. Some are also commonly used in silicon devices. Silicides, such as TiSi, AlSiCu and other metal silicides.

The metal film is conductive, has good plasticity, toughness and strength, as well as adaptability to the environment and materials, does not have any periodic properties, its refractive index is very small, and the characteristics of the long-wave region are stronger than the short-wave region. Electromagnetic waves In the propagation, the property of electromagnetic wave propagation is determined by the dielectric constant. The real part of the dielectric constant corresponds to the ratio of the electric field amplitude when the light propagates, and the imaginary part corresponds to the energy loss of the light. The biggest difference between metals and media is that, The dielectric constant of metals can be described by the Drude model, which is generally a negative real part and a relatively large imaginary part; while the dielectric constant of a medium is generally a positive real part. Since metals have a relatively large imaginary part, It will cause loss, light will be absorbed when it is reflected by metal, and the reflectivity may only reach 98, 99; but the medium will not, so under certain conditions, the reflectivity can reach a true 100%. On the other hand , If the air (also a medium) is reflected by the incident medium, because it is an optically sparse medium (smaller dielectric constant) to an optically dense medium (larger dielectric constant), there is a half-wave loss, which will cause the phase loss of electromagnetic wave oscillations One; and when the air is incident on the metal, the reflection occurs in the ideal case, and a phase difference will inevitably occur.