Plasma Enhanced Chemical Vapour Deposition: A Comprehensive Guide

Introduction to Plasma Enhanced Chemical Vapour Deposition

Discuss about the Plasma Enhanced Chemical Vapor Deposition for Growth.

The plasma enhanced chemical vapour deposition is a technology of chemical vapour deposition that uses a plasma to give some of the energy for the deposition reaction to be carried out. This gives a benefit of processing of lower temperature than the use of methods of purely thermal processing such as low-pressure chemical vapour deposition. The processing temperatures of plasma enhanced chemical vapour deposition range between 200^oC to 400^oC while the processing temperatures of the low-pressure chemical vapour deposition range between 425^oC to 900^oC. The plasma enhanced chemical vapour deposition system which is normally abbreviated as PECVD is a type of the chemical vapour deposition process which normally differs in the means by which the chemical reactions are initiated.

This research seeks to discuss on the addition of plasma into the system so as to make sure that the growth is vertically explicit since it is difficult to create the vertical nanotubes by the use of the system of chemical vapour deposition. This project is motivated towards coming up with enhanced and well-sized system of desktop plasma deposition. For this design to be effective, there is need for identification of the customer requirements and also quantitative engineering requirements and the analysis carried out using quality function deployment diagram (Chopra, 2012). The major requirements are:

• Operating contrition controller
• Sizable system size that can fit on the desktop easily
• A cap that is adjustable that changes the electric field condition(Franssila, 2010)

The dilution and reactant gases flow into process chamber by a shower head which is a huge metal plate that is perforated and situated above the sample. The shower heat assists in providing an extra uniform distribution of reactant gas flow over the surface of the sample. Electrons that are energetic in the plasma dissociate or ionize the reactant gases to produce extra radicals that are chemically reactive. The radicals react to produce the thin film of material deposition on the sample's top. The supplied energy by the plasma gives the major advantage of the minimized temperature of the process for plasma enhanced chemical vapour deposition compared to low-pressure chemical vapour deposition where every energy for reaction is thermally supplied (Konuma, 2011).

There are two methods which can be used when designing the plasma enhanced chemical vapour deposition, these methods include local techniques and remote techniques. In the remote plasma design, the substrate is developed on a substrate that is separate. Whereas for the local plasma design system, the plasma is generated directly on the substrate in the environment provided. In the local plasma. The electric field is developed on the substrate and the electric field can result in the destruction of the nanotubes. In the remote plasma, there is no development of the electric field over the substrate and there is weak electric field produced on the substrate (Mattox, 2016).

Remote and Local Techniques in Plasma Enhanced Chemical Vapour Deposition

From the features above of both the local plasma and the remote plasma, the most preferred technique is the remote design since there is weaker electric field produced on the substrate for this particular design. Some of the major components of the system that need to be developed when designing the plasma enhanced chemical vapor deposition system including the inductive plasma box, tube with remote inductive plasma and oven heating, tube with remote inductive plasma and DC substrate bias, steel or pyrex six-way cross with remote inductive plasma and DC substrate bias, pyrex cross with remote inductive plasma and DC substrate bias (Ostrikov, 2011).

The vapour deposition system can be categorized into three modules namely controllers, reaction chamber, and plasma coil. The methods that are normally used in generating plasma chemical vapour deposition system include inductively coupled, direct current, radiofrequency triode, and microwave (Pierson, 2012). These methodologies are shown in the figure below:

The plasma chemical vapor deposition system can be categorized into three different sections, these categories include the operating condition controllers which also supports the reaction chamber module, plasma coil and electronics which gives support to the reaction chamber module, and the reaction chamber which comprise of the central module which houses the internal chamber assembly (Rahtu, 2015).

The major component of the PCVD system is the reaction chamber which plays an important role during the development of the design module. The reaction chamber assists in the production of plasma and also providing a surface for the nanotubes development. The numerous sections of the reaction chamber are the inlet, outlet, chamber wall, an electrical feedthrough, reactant gas, and viewports. The production of the plasma is made possible by the supporting electronics, plasma coil, and operating conditioners. The remaining design submodules and modules depend on the reaction chamber's design. Therefore, it is in order, to begin with the reaction chamber design before continuing with the design of other modules (Richard, 2010).

The sub-modules which can be produced during the process of design include the adjustable electrode and the internal assembly chamber. The adjustable electrode assists in coming up with the preliminary design concept and is comprised of an automatic height adjustment concept that uses a DC motor so as to displace the wheel and also maintaining the difference in pressure in the chamber and outside atmosphere. In the manually adjustable electrode, a rod that is threaded joined to the rod that is rotating is applied which in turn moves downward and upward (Seshan, 2012).

Operating Conditions in Plasma Enhanced Chemical Vapour Deposition

The remote plasma source is the most appropriate method for designing of the plasma enhanced chemical vapour deposition since this method assist greatly in disconnecting the plasma and electric field and also enabling the system to be more adjustable. A box shape PECVD is important since it helps in promoting and easy access to the substrate.  The complete design of the plasma enhanced chemical vapour deposition is composed of three major sections namely quartz and the main reaction chamber. There is also internal chamber assembly which is made up of the various components of heating and holder to the substrate. There is also the base and the support which is made up of the base system, internal system, chamber support, and infrared sensor (Sherman, 2014).

The figure below shows the design of the plasma enhanced chemical vapour deposition:

Figure 6: Three subassemblies of the PECVD (Tavares, 2013)

Chamber: The chamber is made up of 2inch diameter and with a fitting on the left section of the chamber to allow gas entry. The tube is enclosed with copper material that is joined to the generator of radio frequency which is involved in the generation of the plasma.

Internal Subassembly: The internal subassembly is normally deigned to provide an efficient and safe environment for both the growing carbon nanotubes and internal components. The quartz rods provides support to the assembly and maintain the system tray and chamber electrically.

Support and base system: The base assist is provision of support to the entire system and is normally made of aluminium plate. There is need to provide support to the system for it to be in good and fixed position (Zhang, 2012).

Electronic components: There are many electrical connections throughput the entire system. The source acts as a generator while the plasma acts as the load. Therefore, there is a matching that is automatic which joins the generator and the load. The system is wrapped by the use of copper mesh so as to reduce the disturbances that may be as a result of the surrounding of the system (Pierson, 2012).

There is need of adopting possible failures in the system, the impacts of the failures to the system, and the actions required to avoid such failures from occurring through failure effect and mode analysis. The categories of failures in the system can be mechanical, fluid pressure, electrical, human factors, temperature, environment, biological and radiation. Electrical failure may be caused by live parts, lack or grounding, arcing, improper wiring, power supply interruption, and coil winding around quartz tube. Biological failure affects both the skin and the eye in case of leakage of methane leading to irritation (Ostrikov, 2011).

The quartz tube temperature could surpass the O-ring’s maximum service temperature which may lead to mechanical failure. The basic requirement when working around the CNT is to wear gloves, failure in which may lead to electric shock while handling electrical circuits. Hydrogen being one of the reactant gases may leak from the system leading to fire hazard since it is highly flammable. Other reactant gases which are flammable and pose a potential fire hazards include methane, hydrogen, and helium (Chopra, 2012).

The manufacturing of quartz and stainless steel impacts negatively on the climatic change, ozone layer, eco-toxicity, acidity, land use, and minerals. Majority of the environmental impacts are as a result of the stainless steel. These environmental impacts can be minimized by the use of different material which may pose a challenge because the stainless steel is readily available to be utilized in the chamber of the system. The stainless steel is also appropriate in non-reactive conditions and less expensive making it capable enduring plasma. The manufacture of quartz and stainless steel also has some effects on the health of humans (Richard, 2010). 

Chopra, K., 2012. Thin Film Device Applications. illustrated ed. Nawanshahr: Springer Science & Business Media.

Franssila, S., 2010. Introduction to Microfabrication. 2 ed. Helsinki: John Wiley & Sons.

Konuma, B., 2011. Film Deposition by Plasma Techniques. Prentice Hall: Spring-Verlag.

Mattox, D. M., 2016. Handbook of Physical Vapor Deposition (PVD) Processing. revised ed. Kentucky: William Andrew.

Ostrikov, K., 2011. PLASMA NANOSCIENCE. SYDNEY: JOHN WILEY AND SONS.

Pierson, H. O., 2012. Handbook of Chemical Vapor Deposition: Principles, Technology and Applications. Paris: Elsevier Science.

Rahtu, A., 2015. Atomic Layer Deposition of High Permittivity Oxides: Film Growth and In Situ Studies. Perth: University of Helsinki.

Richard, C., 2010. Introduction to Microelectronic Fabrication. New York: Upper Saddle River.

Seshan, K., 2012. Handbook of Thin Film Deposition: Techniques, Processes, and Technologies. illustrated, revised ed. Arizona: William Andrew.

Sherman, K., 2014. hemical Vapor Deposition for Microelectronics Principles, Technology, and Applications. Harrow: Noyes Publications.

Tavares, L., 2013. Plasma Synthesis of Coated Metal Nanoparticles with Surface Properties Tailored for Dispersion. Colorado: Plasma Processes and Polymers.

Zhang, Q., 2012. Advances in Nanodevices and Nanofabrication: Selected Publications from Symposium of Nanodevices and Nanofabrication in ICMAT. illustrated ed. london: CRC Press.