3 SiH2Cl2 + 4 NH3 → Si3N4 + 6 HCl + 6 H2
For this furnace, there are two kinds of recipes: stoichiometric and low-stress.
The stoiciometric film is targeted to be true Si3N4, which is charachterised by refractive index that shold be 2.023 at 632.8 nm. Unfortunately, this film will have a large tensile stress, making it useless for membranes
Low stress nitide is accomplished by decreasing the NH3/SiH2Cl2 gaseous ratio thereby depositing silicon-rich silicon nitride SiNx.
The SiH2Cl2 cylinder is placed in a cabinet at the back of the furnace, while the NH3, a house gas, is stored in the inner left corner of the leftmost container at the gable end of the clean room. Detailed instruction on how to change gas cylinder is to be found in the NH3 cas cabinet.
The SiH2Cl2 has an pneumatic interlock at the back of the furnece, while the NH3 has its interlock in the visitor's corridor at the gable end of the clean room. These have to be re-activated after any power failure.