Handbook of Deposition Technologies for Films and Coatings

Science, Applications and Technology

Peter M. Martin

• Publisher: William Andrew
• Year: 2009
• ISBN:
  9780815520320
• Edition: 3
• Topic: Technik & Maschinenbau
• Subtopic: Mikroelektronik

This 3e, edited by Peter M. Martin, PNNL 2005 Inventor of the Year, is an extensive update of the many improvements in deposition technologies, mechanisms, and applications. This long-awaited revision includes updated and new chapters on atomic layer deposition, cathodic arc deposition, sculpted thin films, polymer thin films and emerging technologies. Extensive material was added throughout the book, especially in the areas concerned with plasma-assisted vapor deposition processes and metallurgical coating applications.

CHAPTER 1

Deposition Technologies: An Overview

1.1 The Market

1.2 Introduction

1.3 Aim and Scope

1.4 Definitions and Concepts

1.4.1 Surface Engineering

1.5 Physical Vapor Deposition Process Terminology

1.6 Classification of Coating Processes

1.7 New Deposition Technologies

1.8 Microstructure and Properties

1.9 Unique Features of Deposited Materials and Gaps in Understanding

1.10 Current Applications

1.10.1 Decorative/Functional Coating

1.10.2 Transparent Conductive Thin Films

1.10.3 Thin Film Solar Cells and Batteries

1.10.4 Friction and Wear: Nanolaminates and Superlattices

1.10.5 Cutting Tools

1.10.6 Gas and Water Permeation Barriers on Plastic

1.10.7 Biomedical

1.10.8 Thin Film Solid Oxide Fuel Cells

1.10.9 Flat Panel Displays and Molecular Electronics

1.11 ‘Frontier Areas’ for Applications of the Products of Deposition Technology

1.11.1 Selection Criteria

1.12 Summary

1.1 The Market

The second edition of this handbook lists market areas for surface engineered products, including thin film coatings as of the mid-1990s. Since then the market for several types of thin film products has exploded, including photovoltaics, energy conversion, energy efficiency, biomedical, pharmaceutical, and flat panel displays. The demand for advanced tribological and corrosion-resistant coatings has also increased. It is estimated that the global market for optical thin film coatings alone will exceed $7.5 billion by 2010. This includes optical components, telecommunications, window glazings, large area and decorative applications, laser mirrors, automotive coatings (electrochromic rear view mirrors, etc.), ophthalmic applications, and aircraft windows. The global market for solar cells will increase to $32 billion by 2012 and for thin film solar panels alone is estimated to be $8.3 billion by 2030. As of 2008, there are at least 50 companies marketing thin film photovoltaic devices and systems. And this will only grow with increased renewable energy demands, increased efficiency of organic and transparent solar cells, and low-cost solar concentrator systems. Additional energy applications include photocatalytic coatings, thin film fuel cells, thin film lithium batteries, hydrogen generation, electrochromic and thermochromic coatings, and solar control coatings. Molecular electronics, including organic light-emitting devices (OLEDs), has changed the entire manufacturing process for flat panel displays and will continue to do so for plastic windows. Advanced wear- and corrosion-resistant materials are being developed for medical implants, combustion and gas turbine engines, and aircraft engines and parts.

As stated in the second edition, surface engineering will remain a growth industry well into the next decade because surface engineered products increase and improve performance, add functionality, reduce costs, improve materials usage efficiency, and provide performance not possible with bulk materials. Thin films thus offer enormous potential due to the following:

• creation of entirely new and revolutionary products

• solution of previously unsolved engineering problems

• improved functionality of existing products; engineering, medical, and decorative

• production of nanostructured coatings and nanocomposites

• conservation of scarce materials

• ecological considerations – reduction of effluent output and power consumption.

Research and development (R&D) expenditures in surface engineering are very expensive. Industrial deposition systems can cost as much as $20 million. Even in the mid-1990s it was reported that Japan spent $100–150 million on R&D in diamond and diamond-like carbon (DLC) coatings, and this had certainly escalated by 2008 with the increased use of DLC. A number of companies in the USA and Europe are now marketing DLC coatings for a wide range of applications. Investments in photovoltaics worldwide have increased by a factor of 80 in the last decade. The United States Department of Energy spent approximately $24 billion on R&D in 2007. While government support for R&D in biomedical materials in the USA has plateaued, the market is steadily increasing, with European countries leading the way. The same is true for many energy efficiency markets (thermoelectric power generation, advanced glazings, etc.). R&D spending in China has reached $10 billion. The list continues to expand with the need for renewable energy sources, energy efficiency improvements, more sophisticated optical applications and telecommunication, advancing display technology, and advanced medical applications with an aging population.

1.2 Introduction

This is the third edition of this handbook. While many of the chapter headings are the same as those found in the second edition, thin film processes and technologies have advanced significantly in the past 14 years and descriptions in most cases are very different. New authors have been added who focus on different and advanced aspects of this technology. Some chapters found in the second edition present mature technologies with plateaued or diminishing applications, and have been eliminated. The reader is referred to the second edition of this handbook for a description of earlier technology.

Since the second edition was published in 1994, thin film deposition technology and the science have progressed rapidly in the direction of engineered thin film coatings and surface engineering. Plasmas are used more extensively. Accordingly, advanced thin film deposition processes have been developed and new technologies have been adapted to conventional deposition processes. The market and applications for thin film coatings have also increased astronomically, particularly in the biomedical, display, and energy fields. Thin film is the general term used for coatings that are used to modify and increase the functionality of a bulk surface or substrate. They are used to protect surfaces from wear, improve lubricity, improve corrosion and chemical resistance, and provide a barrier to gas penetration. In many cases thin films do not affect the bulk properties of the material. They can, however, totally change the optical, electrical transport, and thermal properties of a surface or substrate, in addition to providing an enhanced degree of surface protection.

Thin films have distinct advantages over bulk materials. Because most processes used to deposit thin films are non-equilibrium in nature, the composition of thin films is not constrained by metallurgical phase diagrams. Crystalline phase composition can also be varied to a certain extent by deposition conditions and plasma enhancement. Virtually every property of the thin film depends on and can be modified by the deposition process and not all processes produce materials with the same properties. Microstructure, surface morphology, tribological, electrical, and optical properties of the thin film are all controlled by the deposition process. A single material can be used in several different applications and technologies, and the optimum properties for each application may depend on the deposition process used. Since not all deposit technologies yield the same properties or microstructures, the deposition process must be chosen to fit the required properties and application (see Chapter 12). For example, DLC films are used to reduce the coefficient of friction (COF) of a surface and improve wear resistance, but they are also used in infrared optical and electronic devices. Titanium dioxide (TiO₂) is probably the most important and widely used thin film optical material and is also used in photocatalytic devices and self-cleaning windows, and may have important applications in hydrogen production. Zinc oxide (ZnO) has excellent piezoelectric properties but is also used as a transparent conductive coating and in spintronics applications. Silicon nitride (Si₃N₄) is a widely used hard optical material but also has excellent piezoelectric response. Aluminum oxide (Al₂O₃) is a widely used optical material and is also used in gas barriers and tribology applications. The list goes on.

Engineered materials are the future of thin film technology. Engineered structures such as superlattices, nanolaminates, nanotubes, nanocomposites, smart materials, photonic bandgap materials, molecularly doped polymers, and structured materials all have the capacity to expand and increase the functionality of thin films and coatings used in a variety of applications and provide new applications. New advanced deposition processes and hybrid processes are being used and developed to deposit advanced thin film materials and structures not possible with conventional techniques a decade ago. Properties can now be engineered into thin films that achieve performance not possible when the second edition of this handbook was published. For example, until recently it was important to deposit fully dense films for all applications, but now films with engineered porosity are finding a wide range of new applications [1]. Hybrid processes, combining unbalanced magnetron sputtering and filtered cathodic arc deposition for example, are achieving thin film materials with record hardness [2].

Organic materials are also playing a much more important role in many types of coating structures and applications, including organic electronics and OLEDs. These materials have several advantages over inorganic materials, including low cost, high deposition rates, large area coverage, and unique physical and optical properties. It is also possible to molecularly dope and form nanocomposites with organic materials [3]. Hybrid organic/inorganic deposition processes increase their versatility, and applications that combine organic and inorganic films are increasing [4].

In addition to traditional metallizing and glass coating, large area deposition, decorative coating and vacuum web coating have become important industrial processes. Vacuum web coating processes employ a number of deposition technologies and hybrid processes, most recently vacuum polymer deposition (VPD), and have new exciting applications in thin film photovoltaics, flexible displays, large area detectors, electrochromic windows, and energy efficiency.

Hybrid deposition processes are gaining new applications because a single deposition process may not be able to achieve the optimum coating performance for multilayer and nanocomposite thin films. Unbalanced magnetron sputtering and electron beam evaporation are combined with filtered cathodic arc deposition to deposit films with improved tribological properties. Plasma-enhanced chemical vapor deposition (PECVD) is combined with unbalanced magnetron sputtering, magnetron sputtering is combined with electron beam evaporation, and polymer flash evaporation is combined with physical vapor deposition (PVD) processes. In addition, thin films with new properties are deposited with new deposition processes such as atomic layer deposition (ALD) [5], high-power pulsed magnetron sputtering (HPPMS) [6], mid-frequency/dual magnetron sputtering (MF/DMS) [7] and glancing angle of incidence deposition (GLAD) [8].

Deposition process technology must meet the demands of advanced thin film coating structures, such as superl...