Magnetron sputtering is a device that uses electron beams to heat the material to be vaporized under vacuum conditions, vaporizes and condenses it to form a film on the surface of the wafer.
The principle is that the electron beam generated by the electron gun obtains the function under the action of the electric field and hits the wafer. When the acceleration voltage is sufficiently high, the generated thermal energy causes the film to heat and vaporize. According to the trajectory of the electron beam, the electron gun can be divided into a direct type or a deflection type, and the deflection type electron gun can be divided into a ring type, an L type, and an E type. Currently, the E type electron gun is mainly used.
Generation of magnetron sputtering electron beam:
1. Thermomionic assion: When a high melting point metal is heated at a high temperature, the kinetic energy of the surface electrons is greater than the binding energy and escapes. When the emission current is large, its current density is controlled by the distance d between the positive and negative electrodes and the voltage v and follows the following equation: J = βV 3/2 / d2 where β is a constant equal to 2.335 * 10-6AMP / (unit area ).
2. Acceleration of the electron beam: Since the electrons have a charge, they can be accelerated by an electric field, so the function of the electron beam is 1 / 2mev2 = eV, me is the mass of the electron, generally V is 5kv to 15kv, assuming V is 10kv, then the electron The speed can reach 6 * 104km / sec (60,000 km / s). High-speed electrons hit the membrane material to convert it into thermal energy, and the temperature can reach several thousand degrees (the total energy is w = nev. N is the electron density). Evaporates into a gas.
Advantages of magnetron sputtering:
1. The deflection direction of the positive ions is opposite to that of the electrons, so the pollution of the aluminum layer by the positive ions in the direct gun can be avoided.
2. After the electron beam is accelerated, it can directly hit the film material to evaporate it. However, the evaporation of atoms and molecules will contaminate the electron source. Therefore, the electron source is usually placed under the gun holder of the film material and the electron beam is changed by a strong magnetic field. Into 2700
3. Because the electron beam is directly heated on the film material, and the bottom of the crucible of the crucible with film material is generally cooled by water, it has less pollution and higher film quality than the thermal resistance heating method.
4. Electron beam evaporation can obtain a large power density, and because the electron beam can be accelerated to a very high energy, some films with better film properties and higher melting points (gold, nickel, etc.) can be evaporated.