Why Use Tungsten Heater Device that Cannot Deform under High-Temperature?

tungsten heater deviceIn hot wire CVD (Chemical Vapor Deposition) system, the energy of a chemical reaction is provided by the tungsten wire, the substrate is also heated to a certain growth temperature by thermal radiation of the tungsten wire, and uniformity of the temperature of the substrate surface would be different due to the shape of the tungsten wire. One of the most important factors of film nucleation and its uniformity growth is the uniformity of substrate surface temperature.

In typical laboratory CVD small and medium systems, the tungsten wire is wound into a solenoid-shaped tungsten heater. This winding method is relatively simple that the outer diameter of each turn is the same. But using a solenoid-shaped tungsten heater, temperature distribution on the surface of the substrate is uneven enough, using a vertical projection line of the substrate surface of solenoid axis as a reference line, if the substrate surface is far away from this line, the temperature would become lower. What’s more, the temperature of the middle of the solenoid itself is higher than the ends, which is one of the reasons for uneven temperature distribution of the substrate surface.

On the one hand, the solenoid-shaped tungsten heater will result in an uneven temperature of the substrate surface. On the other hand, in the CVD growth process, the tungsten wire usually deform under a high temperature, high temperature of the middle part would hang down and bend, led to the evenness of temperature distribution of substrate surface becomes lower, eventually makes it impossible to continue the CVD growth process, it must be replaced a new tungsten wire before continuing. As a result, it will have a certain impact on test results. Because the new tungsten wire can not exactly the same as original tungsten wire under various conditions, which will definitely affect the reliability of comparative test results.