Since 1999, LaTec ​​in Germany has sold the 1000th in-situ measuring device. At the International Nitride Symposium (IWN 2010) in Tampa, USA, Dr. Kolja Haberland of LayTec stated in his report entitled "In-situ Optical Measurement Systems for Thin Film Processes" that its latest in-situ tool Pyro 400 combines with EpiCurve TT The sensor was successfully used in the AIXTRON planetary reactor. Figure 1 shows the change in furnace pressure with temperature during LED growth.
Figure 1. Temperature changes during LED growth due to changes in furnace pressure (p).
Under standard GaN growth conditions and standard pressure (2), the pocket temperature and the center wafer temperature are well controlled. When changing the process conditions, such as lowering the furnace pressure and increasing the process temperature, the wafer temperature will drop by 20K. Pocket temperature, and these changes are not measurable by traditional metrology. The reason is that the heat transfer effect of the carrier gas from the pocket running to the wafer is deteriorated. Therefore, understanding and controlling this effect is critical to the temperature control of the device's growth process; in fact, only the Pyro 400 can be tested.
Figure 2. Pyro 400 line scan measurement: temperature distribution of the entire wafer for different growth steps (see Figure 1).
Figure 2 shows the temperature distribution of the entire wafer at different growth stages, depending on the specific growth conditions:
1. Before growth: Pyro 400 shows the plane temperature curve of the pocket on the sapphire die;
2, GaN buffer layer growth: the center of the wafer is hotter than the edge due to warping;
3. Superlattice growth: the reduction of the furnace pressure and the transfer of heat from the pocket to the wafer, causing the center temperature to drop;
4. Multiple quantum well growth: A flat wafer acquires a temperature profile that tends to be horizontal.
According to LayTec, the Pyro 400 with UV sensing directly measures the temperature of the GaN surface and exposes the temperature change of the growing surface to sunlight, which is not possible with conventional temperature measuring equipment.
36V Power Battery,Motorcycle Battery Pack,Custom Cruise Lithium Battery,Electric Motorcycle Lithium Battery
Sichuan Liwang New Energy Technology Co. , https://www.myliwang.com