Five-layer structure (2)
In order to verify the validity of the result of the five-layer structure I did last time, I deposited another wafer with NOSON stack, which has the identical thickness as that of the last time. The annealing condition is also same as the last time, which is 1 minute holding time at 1000C with a ramp up rate of 50C/s. The following TEM image is the annealed sample.
The porosity for this sample is 19.4% and the average pore diameter is 36.1nm, which is pretty close to the result from the first time with 20.5% porosity and 36.3nm average pore diameter. This result confirms the validity of my previous result.
To further discuss the result of this experiment, it seems that what we suspect that the nitride/silicon interface maybe the reason for the high porosity from NSN stack doesn’t work out. It is more likely that the outer capping layers would dominate the pore characteristics in the Si film. This five-layer structure experiment provides us another method to tune the pore characteristics in the pnc-Si membrane.