Advantages And Disadvantages Of Chemical Vapor Deposition

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2. Basic theories and principles

2.1 Chemical vapor deposition
2.1.1 Definition of chemical vapor deposition
Chemical vapor deposition (CVD) is a versatile process which is widely applied to produce coatings, powders, fibers and monolithic components [1]. Applying the chemical vapor deposition, it is possible to produce alloy and compounds of metals and nonmetal materials.
Chemical vapor deposition can be defined as the deposition of a solid on a heated surface from a chemical reaction in the vapor phase [2]. Chemical vapor deposition belongs to the class of vapor-transfer processes. Differ from physical vapor deposition, CVD process includes chemical reactions. In the process, gaseous material change in to solid which means the process is
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2.1. Sequence of chemical vapor deposition.

2.1.2 Advantages and disadvantages of CVD process
Chemical vapor deposition process is preferred in many manufacturing process for following advantages:
 It is not restricted to a line-of-sight deposition which is ageneral characteristic of sputtering, evaporation and other PVD processes. As such, CVD has high throwing power. Difficult three-dimensional configurations like recesses and holes can be coated with relative ease.
 The deposition rate is high and thick coatings can be readily obtained and the process is generally competitive, and it is relatively easier to cause chemical reactions on the surface of substrate than physical change.
 The process is flexible for designing, and new technology can be developed on the base of existing producing unit.[6]
However the CVD process is not the universal coating panacea. It also has several disadvantages [7].
The first disadvantage is the high temperature supply. The particle material of process (also named as precursor) usually has a high evaporation temperature. Normally precursors evaporates at 600℃, at which temperature substrates are not stable. Only change the supply of the energy can eliminate this
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First problem is the temperature, most OMCVD processes which are operated thermally occur at 300~800℃ and this is still much higher than the room temperature[9]. Secondly, the organic exhaust gas is usually hazard and toxic to human healthy and can be serious environmental problem without proper treatment. Thirdly, as the goal of the OMCVD process, to produce zero-valent state of metal element with existing technology and producing units is only possible for the Ni(CO)4. The processes which apply other precursors usually produce the thin film of metal polluted by the carbon or

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