Silicon nitride, LPCVD thermal

The wafers were coated with silicon dioxide (400 nm thickness) and silicon nitride by low pressure chemical vapor deposition (LPCVD) alternately. The chips were fabricated by photolithography and etching. The catalyst (for the application Pt) was introduced as a wire (150 pm thickness), which was heated resistively for igniting the reaction. The ignition of the reaction occurred at 100 °C and complete conversion was achieved at a stochiometric ratio of the reacting species generating a thermal power of 72 W (Figure 2.28). 

After the quality of the plasma silicon nitride films and their dependence on the several system parameters has been evaluated, there still remains the question of whether or not a given process can be commercially viable. Here the issue is the deposition rate and the uniformity of deposition on a wafer and over all wafers in the reactor. The ideal solution is to deposit at a high rate uniformly over many wafers at one time. We cannot simply stack many wafers close together and run a low-pressure process, as in thermal LPCVD, because we have to be sure the plasma discharge is uniform as well. 

Despite the fact that the RF power is an additional parameter influencing the intrinsic stress of PECVD-silicon nitride, their stress range is less than that of LPCVD layers. By varying the deposition parameters for PECVD-silicon nitride, stress values between -300 MPa and +300 MPa can be obtained [17]. Similar to PECVD-oxides, subsequent thermal annealing pronouncedly shifts the stress towards more tensile values. 

---