LPCVD against PECVD for micromechanical applications

Abstract

After discussion of the basic aspects of CVD and its reaction kinetics LPCVD and PECVD will evolve as techniques commonly used at high temperature and lower temperature , respectively. Films deposited by these two techniques differ in several aspects, i.e., thickness, uniformity, purity, density, electrical properties, adhesion, step coverage, etc. Reactor designs are discussed in brief for optimization of the process parameters to yield optimized film properties. Then each of the major film materials such as polysilicon, SiN, , , SiC and some exotics such as diamond films are discussed with respect to their application in microstructures and their film properties in dependence on the deposition technique and follow-on processing, e.g., internal stresses due to imperfection in structure and composition or clamping, film density, pinhole density, and etchability. The discussion then moves to the application of LPCVD and PECVD in microstructures. A few typical examples will be presented for functional layers: films for membranes, cantilevers, etc in mono- and heterostructures, or ion sensitive films including passivation films as used in many sensors (e.g., microphones) and actuators (e.g., micromotors), especially such as fabricated by surface micromachining. Some room is also given to SiC, a new micromechanical material. A summary and weighting of the two CVD techniques is given.

Fundamentals of Chemical Vapor Deposited Graphene and Emerging Applications

“…The pressure for LPCVD system is typically ~10-1000 Pa, while the standard atmospheric pressure is 101,325 Pa. If the pressure in the CVD process is reduced from atmospheric pressure to about 100 Pa the diffusion will decrease by almost 1000 times [46]. Hence, the velocity of mass transport will reduce to the substrate surface inside growth chamber, allowing uniform and homogenous growth of graphene.…”

Ultrasonic Transducers

“…For cMUTs fabrication, deposited Si 3 N 4 film is frequently used as membrane material, because this material has high mechanical strength and chemical stability, and most important, it is possible to form tensile stress in it. Both theoretical and experiment analysis have showed that the residual stress σ in deposited Si 3 N 4 is proportion to d [25], i.e. T∝d 2 , hence for airborne ultrasound transducer, reduction of membrane thickness is particularly crucial for the improvement of the transducer's impedance match property.…”

Dust cloud evolution in sub-stellar atmospheres via plasma deposition and plasma sputtering

“…Plasma assisted deposition and sputtering is known to be much more effective than conventional gas-phase chemistry, since it is free of the thermodynamic restrictions of the latter, and able to harness electrostatic fields to produce higher-energy particle impacts, combined with electron-moderated chemistry (e.g. see Stoffel et al (1996); Alexandrov & Hitchman (2005); Jones & Hitchman (2009)). In contrast to previous studies, this paper considers how plasma collective effects self-consistently energise the plasma ions such that they can participate in plasma deposition and plasma sputtering.…”