Introduction and vacuum coating materials for evaporation source requirements

Introduction and vacuum coating materials for evaporation source requirements

A vacuum coating technique to produce a thin film material. In atomic vacuum chamber material is isolated from the heating source to hit the surface of the object to be plated. The technology used in the production of aluminum coated CD (compact disc) and by a mask on a printed circuit board metallized film.
Evaporation source in vacuum coating material requirements?
Evaporation source should typically be considered material and shape of the evaporation source, the evaporation source material for general requirements are:
(1) a high melting point. Because the evaporation temperature of the evaporation material (equilibrium vapor pressure for the temperature 1.3Pa) Most between 1000 ~ 2000 ℃, therefore, the melting point of the evaporation source material should be higher than this temperature.
(2) equilibrium vapor pressure. This is mainly to prevent or reduce the evaporation source material at a high temperature with an evaporation material is evaporated into the impurity into the deposited film layer. Only in equilibrium pressure of the evaporation source material is sufficiently low, in order to ensure self-evaporation has the smallest amount of evaporation, so as not to affect the vacuum system and contamination layer, the evaporation source materials in order to make a very small quantity of evaporated, and evaporated in selection temperature, while the evaporation source material, should be lower than the evaporation temperature of the material in the evaporation source material for the preparation of equilibrium pressure of 1.3 × 10-6Pa when high quality film can be used with the corresponding temperature are 1.3 × 10-3Pa.
(3) Stable chemical properties and should not chemically react with the evaporation material at high temperatures. At high temperatures may produce between some evaporation source material, and evaporation of the reaction and diffusion material to form compounds and alloys. In particular, the formation of a eutectic alloy evaporation source easily blown. For example, when a high temperature tantalum and gold may form an alloy, aluminum, iron, nickel, cobalt and also tungsten, molybdenum, tantalum alloy evaporation source material. Tungsten can also react with water or oxygen to form volatile oxides such as WO, WO2 or WO3; molybdenum can react with water or oxygen to form volatile MoO3 and the like. Therefore, the material should be selected with the coating material does not react or form an alloy made of the material of the evaporation source material