墨尔本代写ASSIGNMENT ：Development History
Evaporation belongs to a process of metalization, which includes evaporation and sputtering. Due to the urgency to insure the transition going from semiconductor to metal to process smoothly, it is essential to develop and innovate technique constantly to protect and preserve metal, thus a need to deposit metal properly lead to in depth research for various means to deposit not only metal, but also other materials(Chrisey and Hubler, 2003).
There are several approaches that are currently trending in terms of depositing the metal layers. Physical Vapor Deposition techniques (代写ASSIGNMENT), for instance, is one of them. There are four major components in Physical Vapor Deposition techniques, to name it, Evaporation, sputtering, Chemical Vapor Deposition, and electrochemical techniques. Each one of them has its advantages and disadvantages. For example, evaporation has the benefits of greatest purity which has been proved to be at advantage for Schottky contacts, and because it has the edge of low pressures (Chrisey and Hubler, 2003). Moreover, evaporation is a much simpler process comparing to other means , and the price in executing the process is relatively inexpensive. However, the disadvantages are also obvious, for instance, evaporation is considered to have poor step coverage, and it has been proved difficult for it to form alloys; in addition, because of low vacuum, it has lower throughput. Like other scientific theories, evaporation is based on other concept as well; the concept here is that the existence of finite pressure called ‘vapor pressure’ that is above any material, which could go one of the following direction: it could induce solid to vapor change, or it could have a liquid to vapor transition (Chrisey and Hubler, 2003).
Like the process of Evaporation, Sputtering has its advantages and disadvantages. For example, it has benefits of improved step coverage; it causes less radiation effects than the damage induced by E-beam evaporation, also sputtering is much more easier to use in practive when depositing alloys. However, sputtering has been proved to be more beneficial for ohmics instead of Schottky diodes(Sorab, 1994), and the damage it can cause for certain plasma such as implanted argon is a downside as well. As a result, high pressure of a plasm has the tendency to pound on the metal atoms and know them out of a target range. Since atoms are considered to be energetic and they are usually located near their target, they deposit above a material called wafer. In addition, ions produce excessive energy, which help the material increase it mobility, as a result, atoms could move more smoothly on the surface instead of moving a slow pave and stuck with each other sometimes (Mattox, 2010).
The term physical vapor deposition was first introduced in 1966 in a book called ‘Vapor deposition’, however, the process of 代写ASSIGNMENT was invented and developed much earlier than 1966. It is the development of the vacuum techniques that push the development of physical vapor deposition, because of the breakthrough of gaseous chemistry, further study and development was generated to understand electricity and magnetism.
(Chamber for a simple parallel plate sputtering system)
(Methods of evaporation multicomponent films, including single - source evaporation, multisource simultaneous evaporation, and multisource sequential evaporation)
In 1640, people were studying how to pump water that are deep in the mines, and a type of vacuum called the piston were invented to use air to pump water out of the deep underground. Then in 1838, plasma was developed as a breakthrough, thanks to the invention vacuum tube, progress was made to the vacuum pump that researchers were able to use brass materials such as electrodes to achieve their purpose. In 1852, the term ‘sputtering’ was introduced after the in depth study of the glow discharges. A wire was used as a medium of coating material and researchers covered the wire surface with silver coverage, anode and cathode was made for the wire to construct electrical circuit. In 1858, a new form of deposition was developed by creating mirrors. Later at the end of the 1930s, a term called ‘electron trap’ was invented to describe how electrons could be gathered and restricted on a certain area of a surface, magnetic material was introduced, because of the need to develop a combination of magnetic and electric area to attract and confine electrons, it was essential to enhance the degree of ionization so that the plasma related process could go through smoothly. Using the inside of a cylinder to develop sputter, the process was valued a one of the very important breakthrough in the history of evaporation and sputtering for it was considered to serve as a infeudation of magnetron process (Chrisey and Hubler, 2003). In 1970s, scientist found out the relationship among pressure, voltage and deposition rates, they discovered that at a combination of decreased pressures, decreased voltages, and increased deposition rates, it was an ideal environment and condition for electric and magnetic fields for the sputtering to have a better performance. In 1968, cermet resistor films was developed by using metals such as Al, Cu, and Ni. In 1974, various type of magnetron development was made. Sue to the invention of putting a magnetic tunnel inside that of the surface of a cylindrical container, putter gun was identified as a very useful source. A range of configurations(Miller,1997), for example, the planar magnetron, was deemed as breakthrough in the sputtering development. Magnetron sputtering is considered to have a diverse range of benefits as a source of vaporization, for instance, the source offer a much longer life spectrum; it can also be operated at a higher rate while covering a higher range of area on space; in addition, it can maintain a lower temperature. Because of the above characteristics, the vaporization process can be executed in a lower gas pressure environment, not only did the pressure tolerance standard was innovated, the process also generated better sputtering rates compared to other sputtering resources that are not magnetic. Based on the superiority of the magnetron sputtering technique, it was widely accepted in the physical vapor deposition process. During 1970s, thanks to the innovation of the scanning electron microscope, researchers was able to closely examine the growth of the deposited film, and the technology of physical vapor deposition had a mature shape for the modern techniques in application that the industry is applying at high frequency today.
One of the key development of physical vapor deposition is the innovation of thin film technique, the huge break through had brough benefits to other important technique development. For example, the optical coating was invented and reformed thanks to the advancement of physical vapor deposition technique, the solar cells and semiconductors were one of the many areas of development due to the breakthrough of physical vapor deposition. What contributed most to the physical vapor deposition technique are the highly developed technology such as vacuum technology(Miller,1997). In order to develop a all around system that has the capability of generating suitable pressure that could adapt to films which were in growing uniform pattern, not only that, it was essential to research for the most appropriate rates of deposition (Mahan, 2000).
墨尔本代写ASSIGNMENT ：Development History
The vacuum technology has arisen to be one of the most aspect of study and research in physics, it has been widely recognized in the world today due the fact that it has a wide and diverse range when it come to applications. Vacuum technology is considered to be ideal when it forms a space where all kinds of particles are completely wiped out. Like a lot of systems that are not capable of achieving absolute equality, vacuum systems can’t be made equal as well; in the physics world, the ideal systems can be created to reach equality under a number of assumptions and coordination on paper, yet in reality, the real process of creation lacks the precise execution of the ideal situation on paper, and the actual creation process of system can lack factors that were presumed to be existed when designing the system, the vacuum system could not be made to be exactly ideal wither. The most important factor that plays a significant role in creating the ideal vacuum system is the designing and application process of maintaining the best bast pressure for a system. There are usually three levels of the pressure level settings, respectively defined as high, medium and low, some even has ultra high. There are various factors that could set up the difference levels of vacuum, of which the most important and obvious ones are how the equipment is chosen and used and the ones that defines how the system is constructed and configured.
(Vacuum quality and pressure range)
What’s worth mentioning about the vacuum technology is the development of the first vacuum pump, the pump enables researchers to examine some of the most basic and important characteristics of the vacuums(Middleman and Hochberg, 1993). At first researchers and scientists misunderstood the technicism of how the air was actually pumped out of a container, they believed that it was the pump that physically pushed the air out of the container, however, they were mistaken about the mechanism of the pressure. As result, it is the differences created by the pressure in the container rather than the pump its self drive the air out of a container. To be exact, the pump cause the inside space of the container to generate a difference in pressure of the air, as a result, the inside of the space then was divided to two air areas, respectively the high pressure area and the low pressure area, because of the difference in pressure, it creates a flow of the air, the high pressure drives the air to the low pressure area, therefore causing the gas to flow quickly, eventually, as the gas was flowing out of the inside of the chamber, the high pressure area takes on more and more space in the chamber and ultimately occupies the whole space inside the chamber, thus the low pressure area with gas was eaten up by the high pressure space as the gas was rushing out of the chamber at a faster and faster rate. However, as the gas was exiting the chamber, there was also gas outside of the chamber trying to flow in. The most important technicism of this activity is that the pressure difference lead to the air flowing outs of the chamber to move more quickly than the gas that was flowing in, therefore; the higher speed eventually took the lead of the flow competition until there was no gas left inside of chamber(Krebs, 2009).
There are also many other contributors to what is today the advanced physical vapor deposition. In the area of physics and electrical engineering, the technology of vacuum is also considered to be the development pioneer. There were a wide range of practices in the industry in history and today that are highly related to the innovation of the vacuum technology. For example, the packaging technique that people are using today is a derivative of the vacuum technology, because of the space saving technology, people now can compress items in a small bag without any air in it, this is deemed to be a great contribution to the advancement of consuming business and the logistic business. In addition, the vacuum technology contributes to the packaging business by expand the expiration date of products, therefore prolong the preservation period of people’s daily items. Moreover, welding and electron microscopes were among the greatest inventions due the advancement of the vacuum technology. Not only did the vacuum technology was applied in the world of physics, it also was devoted to elevate the quality of other research subjects, such as chemistry, biology and engineering(Middleman and Hochberg, 1993).
The development of Thin Films
Physical vapor deposition has played a key role in developing the thin films, it covers a broad range of techniques, techniques including plasma arc deposition approach, the sputtering approach, and the thermal approach. Although there were many choices in developing the Physical vapor deposition technique, the thermal one is still considered to be the most firmamental method in practice to make thin films(Jaeger, 1993). Nowadays, many other approaches were invented to produce films, and the most common and popular method is the one that produce alloy films. In addition, in order to research and produce more innovated films, the process was refined as well, for example, lots of fundings has been devoted to research and development in companies nowadays so that more adaptive means can be found for mass production of the films, since there is increasing demands on the market to purchase better quality films by consumers(Krebs, 2009).
In the market of today, in terms of consumer need, most of the producers are putting less focus on the vacuum coatings for their products, instead, they consider the film technology to be their edge to develop a competitive advantages against their competitors. For example, in the industries such as the semiconductor business, computer chip products are their most popular products, and in order to produce the most stable and fastest computer chip on the market, they invested heavily on the development of thin films, since the competition is fierce in the computer chip industry, whoever has the edge of the thin film technology can dominate the market(Helmersson et al, 2006). In addition, the optical business is another major application area for the thin films, companies apply physical vapor deposition technique in producing polarizers and splitters. In conclusion, modern practices reflects that it is impossible to separate the usage of vacuum system and the quality of the film, for they are connected together closely when it comes massive production and precision design when technology is needed(Wang and Dai, 2002). There are two main characters for the judgment of film quality, one is the uniformity of the configuration process, and the other is the purity of the film. Between the two determining factors, the more important factor is the film uniformity, since it is the essential factor to smooth out the whole system and help it to function properly, and one the precondition of this kind of function is to ensure film uniformity(Helmersson et al, 2006). On the other hand, purity is another essential factor when proceeding to the deposition process, where the system development reach to a critical stage that the composition of the air and the pressure were adjusted to the best condition to develop the film. As researchers and technicians, they are aware that the theses two characteristics are not easy to adjust.
Material selection for 代写ASSIGNMENT and PLD
It is common that technicians encounter complications when practice the vacuum theory, thus it is essential to figure out the fundamentals of theory before put any of the assumptions into practice. Data collection is considered to be an critical part when designing the theory configuration, to elaborate, poor data collection could lead to mistaken and wrongful data pattern therefore compromise the data with precision and accuracy. In addition, vacuum system was proved to have leaking problem and other gas situation during past experiments conducted by technicians. Therefore, conducting the identification research of the leaks had become one of most important priorities(Jaeger, 1993). As a result, experimentalists conducted a serious of experiments to identify various type of leaking sources, the results help them recognize multiple kinds of gas that entered the chamber due to the leaking situation. Moreover, they found out the causes for the chamber leaks. For instance, more often than not, the pressure problem that induces leaks in the vacuum cause imbalance of gas which ultimately caused a surplus inside of the chamber. The research of leaks help them realize that it was top priority to found out the leaks before any other experiment(Helmersson et al, 2006).
Humidity, another important factor that influences the pressure of the chamber, where water vapor and other kinds of air and gases can be absorbed at appropriate humidity. If in any case the humidity loses balance, it could become a force of disorders, since it could completely disrupt the gas balance and ultimately change the pressure situation. Therefore, it could not be strengthened enough that the material used to prepare the chamber could compromise the precision of the data collection process.
Plasma laser deposition was proved to have great sensibility to versatility set up, and it is essential for construct an appropriate range for the experimental parameters during the configuration process. Because the parameters can have great impact on film properties, there are a great range of factors to weigh out. Laser parameter is the first characteristic to be examined; for example, how the laser can influence the surface area and to what extent are usually studied carefully by the technicians, they later would research the history of different wavelength for various materials to match the compatible parameters, in addition, pulse duration is another important factor to be considered(Eason, 2007).
Plasma laser deposition technique went through its break through in the 1990s, and different types of materials were tested to search for the most appropriate methodology for the application of the technique, researchers and technicians tested different variables and possibilities for the reactive atmosphere and conditions, and eventually found out the more suitable and attractive characteristics for PLD. During the process, they tested the energy status when operating at different levels of parameters, by experimenting with the gas pressure, they realized that the energy could be reduced and altered in order to achieve designated purpose. By targeting specified purpose, they identified the possibility to construct and adjust the laser feature to the best condition to apply the Plasma laser deposition technique. In conclusion, the deposition conditions, distance and temperature were identified to affect the materials that are subjected to deposition.
Chrisey, DB and Hubler, GK 2003, “ Pulsed Laser Deposition of Thin Films”, Harvard University.