Thin Film Deposition Overview
Thin film deposition involves applying a thin layer of material onto a substrate or surface. This process allows for the modification of surface properties, the introduction of new functionalities, and the development of advanced materials and devices. The deposited films can be composed of metals, semiconductors, insulators, or organic compounds, depending on the desired application.
Techniques of Thin Film Deposition
There are several methods for depositing thin films, each with its unique advantages and suitable applications. The primary categories include Physical Vapor Deposition (PVD) and Chemical Vapor Deposition (CVD).
Physical Vapor Deposition (PVD)
PVD is a vacuum-based technique where material from a solid source is vaporized into a plasma or vapor phase and then condensed onto a substrate. Common PVD methods are:
- Thermal Evaporation: Material is heated until it vaporizes, and the vapor condenses on the cooler substrate surface.
- Electron Beam Evaporation: An electron beam precisely heats the target material, causing it to evaporate.
- Sputtering: Ions bombard a target material, ejecting atoms that then deposit onto the substrate.
Chemical Vapor Deposition (CVD)
CVD involves chemical reactions of gaseous precursors on or near the substrate surface, forming a solid material. Variations of CVD include:
- Low-Pressure CVD (LPCVD): Deposition occurs under reduced pressure for improved film uniformity and step coverage.
- Plasma-Enhanced CVD (PECVD): Plasma is used to enhance chemical reactions at lower temperatures, allowing for the deposition of films on temperature-sensitive substrates.
- Atomic Layer Deposition (ALD): A specialized form of CVD that deposits materials one atomic layer at a time, offering exceptional control over film thickness and composition.
Other Deposition Techniques
- Molecular Beam Epitaxy (MBE): An ultra-high vacuum technique for growing crystalline layers with precise control at the atomic level.
- Electrodeposition: An electrochemical process where a material is deposited from a solution onto a conductive substrate using an electric current.
- Spin Coating: A solution-based method where the substrate is spun at high speeds to spread a thin, uniform layer of material.
Applications of Thin Film Deposition
Thin films play a crucial role in numerous industries and technological advancements.
Electronics and Semiconductors
- Integrated Circuits (ICs): Thin films are used to create the multiple layers of conductors, semiconductors, and insulators in microchips.
- Thin-Film Transistors (TFTs): Essential components in displays, sensors, and other electronic devices.
- Data Storage: Magnetic thin films are critical in hard drives and other storage media.
Optics and Photonics
- Anti-Reflective Coatings: Reduce surface reflections on lenses, improving efficiency in optical systems.
- Optical Filters: Thin films allow selective transmission or reflection of specific wavelengths.
- Laser Mirrors and Components: High-quality thin films are used to produce mirrors with precise reflective properties.
Energy Generation and Storage
- Solar Cells: Thin-film photovoltaic materials offer flexible and lightweight alternatives to traditional solar panels.
- Batteries: Thin films enhance electrode performance in lithium-ion and other battery types.
- Fuel Cells: Thin-film electrolytes improve efficiency and reduce operating temperatures.
Surface Engineering
Protective Coatings: Thin films provide resistance against corrosion, wear, and high temperatures.
Decorative Finishes: Metallic and colored thin films are used in jewelry, watches, and consumer electronics for aesthetic appeal.
Functional Surfaces: Coatings with hydrophobic, oleophobic, or antibacterial properties for various applications.
Biomedical Applications
- Medical Implants: Thin films improve biocompatibility and functionality of implants like stents and prosthetics.
- Drug Delivery Systems: Controlled-release coatings allow for targeted and sustained medication delivery.
- Biosensors: Thin films enable the detection of biological molecules with high sensitivity.
Advanced Materials and Nanotechnology
- Nanostructured Materials: Creation of nanowires, quantum dots, and other nanoscale structures.
- Metamaterials: Engineered thin films with unique electromagnetic properties not found in natural materials.
- Superconductors: Thin-film superconducting materials for applications in quantum computing and medical imaging.
Advantages of Thin Film Deposition
- Precision: Allows for atomic-level control over film thickness and composition.
- Versatility: Capable of depositing a wide range of materials on various substrates.
- Customization: Films can be engineered to exhibit specific electrical, optical, or mechanical properties.
- Scalability: Suitable for both small-scale research and large-scale industrial production.
Future Trends in Thin Film Deposition
- Flexible Electronics: Development of bendable and wearable devices utilizing thin-film technology.
- Advanced Energy Solutions: Improved thin-film materials for more efficient solar cells and batteries.
- Nanoelectronics: Continued miniaturization of electronic components through precise thin-film deposition.
- Sustainable Materials: Focus on environmentally friendly deposition processes and recyclable materials.
We have a range of thin film deposition systems to address many of the common challenges. Browse our products to learn more.
Physical vapour deposition
Physical Vapour Deposition (PVD) is a vacuum deposition method used to produce thin films and coatings. The PVD process involves the transfer of material from a source to a substrate through the vapour phase. This technique is widely used in various industries, including electronics, optics, and material science, to enhance surface properties such as hardness, wear resistance, and corrosion resistance.
Key PVD Techniques:
Magnetron Sputtering
Magnetron sputtering is a form of PVD where ions generated in a plasma are accelerated towards a target material. The impact ejects atoms from the target, which then deposit onto the substrate forming a thin film. This technique is particularly effective for depositing high-melting-point materials and achieving excellent adhesion. Example Applications:
- Semiconductor Industry: Used for depositing metal and dielectric films in integrated circuits.
- Optical Coatings: Applied in manufacturing anti-reflective coatings and decorative films.
- Hard Coatings: Utilised in creating wear-resistant coatings on cutting tools and mechanical components.
Thermal Evaporation
Thermal evaporation is a PVD technique where the material to be deposited is heated to a high temperature until it evaporates. The vapourised atoms then condense on the substrate, forming a thin film. This method is straightforward and suitable for depositing metals and some compounds. Example Applications:
- Metallisation in Electronics: Used for depositing aluminium and other metals on semiconductor wafers.
- Solar Cells: Applied in creating thin metal films in photovoltaic cells.
- Decorative Coatings: Used in the jewellery industry for gold and silver coatings.
Electron-Beam (E-Beam) Evaporation In e-beam evaporation, a focused beam of electrons is directed at the target material, causing it to heat up and evaporate. This technique allows for precise control over the deposition rate and is suitable for materials with very high melting points. Example Applications:
- High-Precision Optics: Used in the deposition of optical coatings for lenses and mirrors.
- Aerospace Components: Applied in coating turbine blades and other high-performance components.
- Research & Development: Used in thin film deposition for new material exploration in laboratories.
PVD processes, including magnetron sputtering, thermal evaporation, and e-beam evaporation, offer versatile solutions for creating high-quality thin films and coatings. Each technique has its unique advantages and is suitable for a range of applications across different industries.
Magnetron sputtering
In magnetron sputtering, magnetic fields focus plasmas onto target material surfaces, ejecting material that moves through the plasma to coat substrates. Suitable for depositing most materials (with correct choice of sputtering power supply).
Physical Vapour Deposition (PVD) is a widely used technique for depositing thin films and coatings. A magnetron source is a critical component in this process, providing a means to efficiently sputter material from a target onto a substrate. The magnetron enhances the sputtering process by using a magnetic field to confine electrons close to the target surface, increasing the ionisation efficiency and sputter rate.
How The Magnetron Source Works
Magnetron sputtering involves bombarding a target material with high-energy ions (typically Argon ions). The collision dislodges atoms from the target, which then deposit onto the substrate. The magnetron source utilizes a magnetic field, created by magnets behind the target, to trap electrons near the target surface. Electrons, influenced by the magnetic field, follow helical paths, increasing their chance of ionizing the gas. The positively charged Argon ions are attracted to the negatively charged target, causing sputtering.
The sputtered atoms travel through the vacuum and deposit as a thin film on the substrate.
Choice of DC vs. RF Power Supply
DC Power Supply:
Used for sputtering conductive materials such as metals. A direct current (DC) power supply provides a constant voltage and current, creating a stable plasma.
- Advantages: Simplicity, cost-effectiveness, and efficiency for conducting targets.
- Limitations: Not suitable for insulating or dielectric materials, as the constant current can lead to charge buildup and arcing on the target surface.
RF Power Supply:
Used for sputtering both conductive and non-conductive materials. Radio frequency (RF) power supplies operate at high frequencies (typically 13.56 MHz), alternating the current rapidly to prevent charge buildup.
- Advantages: Versatility in sputtering a wide range of materials, including insulators and dielectrics. The alternating current prevents arcing and allows for uniform sputtering.
- Limitations: More complex and expensive than DC power supplies, with potentially lower sputter rates for conductive materials compared to DC.
Target Considerations
- Choice of Material: Depends on the desired coating. Common materials include metals (e.g., aluminium, titanium), alloys, and compounds.
- Target Thickness: Should be sufficient to avoid frequent replacements, but not too thick to cause issues with heat dissipation.
- Some thin or brittle targets may need a backing to provide support and prevent accidental cracking during use.
Substrate Preparation
- Cleanliness: Substrates must be clean and free from contaminants to ensure good adhesion and uniformity.
- Some PVD systems offer a substrate pre-clean using an in-chamber or load lock etch station.
- Temperature: Some processes require heating of the substrate to improve film quality and adhesion.
Thermal evaporation
Thermal evaporation is a straightforward means of thin film deposition with materials being heated to evaporation temperatures via a resistively heated support.
Thermal evaporation is a widely used technique for depositing thin films and coatings. This process involves heating a material to its evaporation point in a high vacuum chamber, allowing the vapourised atoms to travel and condense on a cooler substrate, forming a thin film.
How Thermal Evaporation Works
The material to be deposited (source material) is heated until it vapourises. This is typically achieved using resistive heating or electron beam heating.
The vapourised atoms travel through the vacuum chamber and condense onto the substrate, forming a thin, uniform film. In thermal evaporation it is important to use a high vacuum to reduce contamination and ensure a mean free path long enough for atoms to travel directly to the substrate. This typically means that evaporation chambers are taller than an equivalent magnetron sputtering system.
Depending on the material, resistive heating (using a heated filament or boat), electron beam heating, or induction heating is used to vapourise the source material.
Common thermally evaporated materials include metals (e.g., gold, aluminium), alloys, and compounds. Substrates must be clean and free from contaminants to ensure good adhesion and uniformity. Some processes require heating the substrate to improve film quality and adhesion.
Operation Considerations
- Temperature: Must be carefully controlled to ensure proper evaporation without decomposition of the source material.
- Deposition Rate: Controlled by adjusting the heating power, affecting film thickness and uniformity.
- Vacuum Level: High vacuum levels are essential to reduce contamination and ensure a direct path for vapour atoms.
Low temperature evaporation
In low temperature evaporation (LTE), resistive heating is used to evaporate materials held in a crucible.
LTE is suitable for materials with low evaporation temperatures of <600 °C, including organics (for OLED, OPV and OFET applications). Moorfield offers a range of solutions for LTE, including our MiniLab systems and our bench top nanoPVD-T15A system.
E-beam evaporation
In the realm of physical vapour deposition (PVD) research and development, e-beam evaporation stands out as a cutting-edge technique, offering unparalleled precision and versatility. This method is instrumental in the deposition of thin films, playing a crucial role in advancing various fields, from semiconductor manufacturing to optical coatings.
What is e-beam evaporation?
E-beam (electron beam) evaporation is a physical vapour deposition technique where an electron beam is focused on a source material to evaporate it. The material, typically in solid form, is heated to its boiling point, causing it to vapourise. The vapour then condenses on a substrate, forming a thin film.
Key advantages of e-beam evaporation:
- High Purity Films: E-beam evaporation can produce high-purity films since the source material is not contaminated by the crucible.
- Wide Range of Materials: This technique is compatible with a broad spectrum of materials, including metals, insulators, and semiconductors.
- Precision Control: E-beam evaporation offers precise control over the deposition rate and film thickness, making it ideal for applications requiring exact specifications.
- High Deposition Rates: Compared to other PVD techniques, e-beam evaporation can achieve higher deposition rates, improving efficiency.
- Applications in R&D
- Semiconductor Fabrication: In semiconductor R&D, e-beam evaporation is used to deposit thin films of metals and dielectrics, essential for creating microelectronic devices.
- Optical Coatings: E-beam evaporation is ideal for depositing multilayer coatings on optical components, enhancing reflectivity or transmission at specific wavelengths.
- Thin Film Sensors: Researchers use this technique to develop thin film sensors with precise control over film properties, crucial for sensitivity and specificity.
- Surface Engineering: In surface engineering, e-beam evaporation aids in creating wear-resistant and corrosion-resistant coatings, extending the lifespan of mechanical components.
E-beam evaporation process:
The e-beam evaporation process involves several key steps:
- Vacuum Chamber Preparation: The process begins by placing the substrate and source material in a high-vacuum chamber, minimizing contamination.
- Electron Beam Generation: An electron gun generates a focused beam of electrons directed at the source material.
- Material Evaporation: The intense electron beam heats the material to its evaporation point, converting it from a solid to a vapour.
- Film Deposition: The vapourised material travels through the vacuum and condenses on the substrate, forming a thin film.
- Monitoring and Control: Throughout the process, deposition rate and film thickness are monitored and controlled to ensure uniformity and adherence to specifications.
Challenges and considerations:
While e-beam evaporation offers many advantages, it also presents certain challenges:
- Thermal Damage: The high energy of the electron beam can cause thermal damage to the substrate or source material.
- Equipment Cost: E-beam evaporation systems can be more expensive compared to other PVD techniques due to the complexity of the equipment.
- Material Selection: Not all materials are suitable for e-beam evaporation, particularly those with low vapour pressures or those that decompose upon heating.
If you would like to know more about our range of electron beam evaporations systems please contact us.
Nanoparticle vacuum deposition
Nanoparticle vacuum deposition sources allow for the deposition, under high-vacuum conditions, of nanoparticles with sizes in the range of 1–20 nm. The sources can be fitted to MiniLab systems with process chambers customised for accepting the necessary hardware.
Nanoparticle vacuum deposition sources use sputtering to eject material from targets (up to 3 can be fitted to each source) positioned at one end of the source. Using a complex differential pumping system, controlled independently from that of the process chamber, the material is guided through the length of the source to emerge from an orifice at the far end as a stream of nanoparticles that are aimed at substrates. Substrates are supported on stages that can be equipped with the wide range of functionalities available as standard with the MiniLab range including heating, cooling, tilt, rotation and bias.
With fine control of process, substrates can be coated with nanoparticles of particular size ranges. Sources can also be equipped with quadrupole mass spectrometry (QMS) modules for characterising the nanoparticle sizes as they are being coated.
The sources can be combined with other techniques such as magnetron sputtering inside the same chamber, allowing for highly versatile vacuum deposition systems.
We have recently designed, built and installed our first MiniLab tool with a nanoparticle vacuum deposition source at the group laboratories of Professor Christian Mitterer at Montanuniversität Leoben in Austria.
Glovebox integrated systems
Glovebox-compatible MiniLab systems for physical vapour deposition (PVD), etching and annealing processes.
Glovebox Systems Overview:
For many applications, such as OLED, OPV and OTFT research, and graphene and 2D materials, samples are sensitive to oxygen and moisture and handling within inert environments is a must. In these cases, deposition tools must allow for transfer to and from glovebox enclosures with controlled inert atmospheres.
In addition to vacuum deposition, Moorfield can also equip glovebox-integrated tools with other hardware such as etching (including soft-etching) and annealing components.
Glovebox Setups:
Moorfield is flexible to customer requirements and can provide systems to be integrated with separately-procured gloveboxes or include gloveboxes to form a complete package obtained from one supplier.
Our MiniLab 026/090 tools can be fitted to gloveboxes from most manufacturers including Inert, Vigor and Jacomex. All gloveboxes are available with standard features such as water, oxygen and solvent purification units, oxygen and moisture sensors, transfer antechambers, shelving and lighting.
In all cases, Moorfield is experienced in working with glovebox design teams to provide hassle-free solutions.
Configurations:
Examples of combined MiniLab/glovebox setups include:
- A single glovebox section housing a MiniLab tool.
- A single glovebox section containing a MiniLab tool together with a spin-coater.
- A two-section glovebox system with a MiniLab tool in one section and a spin-coater in the other, allowing for independent solvent and deposition work.
Chemical vapour deposition
Moorfield’s nanoCVD range allow for rapid, cost-effective production of graphene using scalable Chemical Vapour Deposition (CVD) methods.
Developed together with academic partners and with proven performance including high-impact publications.
Graphene has been the focus of huge research efforts, given its unique electrical, mechanical and structural properties. Thanks to these properties, Graphene is expected to prove disruptive for a huge range of applications. In addition, exotic characteristics of these materials mean they will enable new types of devices and products.
nanoCVD systems from Moorfield are designed to produce conditions that allow for rapid, cost-effective production of graphene through the implementation of chemical vapour deposition (CVD) schemes. CVD methods are considered most promising for the industrial production of high-quality carbon nanomaterials.
System development has been carried out in collaboration with academic partners and has been awarded financial support for innovation. The tools are compact, easy-to-use and offer proven performance (including peer-reviewed publications in high profile journals).
Plasma etching
Plasma etching technology from Moorfield is used for Soft Etching of sensitive materials, reactive ion etching (RIE) and for substrate cleaning. The technology is available packaged into dedicated nanoETCH tools or in combination with other hardware inside larger MiniLab process chambers and load-locks.
Soft etching
Moorfield’s Soft Etching technology was developed in collaboration with the Nobel Prize-winning graphene group at Manchester University, UK. Headed by Prof. Andre Geim, the group received their first system from Moorfield when they started their 2D materials research over 10 years ago. Since then, the technology, implemented within our compact nanoETCH range, has become a critical part of all experimental work. They now have 3 tools, housed within the National Graphene Insitutute (NGI). There is also another tool at the Graphene Engineering Innovation Centre (GEIC) — also in Manchester.
Soft Etching technology is optimised for providing the fine control required for substrate and device preparation in graphene and 2D materials research:
Substrate preparation for mechanical exfoliation: When preparing 2D material ‘flakes’ via mechanical exfoliation (also known as the sticky-tape method), the nature of the substrate surface is crucial. Soft Etching tools are now being used to obtain the topological and chemical substrate surface properties necessary for producing large flake areas.
2D material patterning: Given their thinness, 2D materials are fragile and require finely-controlled etching conditions for device fabrication. Soft Etching technology provides this control and also allows for patterning without cross-linking common mask photoresists (e.g., PMMA).
Defect engineering: A key research theme for graphene science is defect engineering. Through controlled low plasma-powers, soft-etching technology is being used for creating point defects in lattices for implementing control over this aspect of the material. Fine control is necessary for reproducible results and to avoid uncontrolled material destruction.
As well as 2D materials, Soft Etching technology has found numerous other applications. For example, it has been used for precision removal of alternative resists such as PPA and for the tuning of hydrophobicity of glass slides prior to wet depositions.
Soft Etching is available within our nanoETCH and MiniLab platforms.
SF6 and CHF3 etching
While the etching of 2D materials can be done through the careful application Ar and/or O2 plasmas, other materials more commonly targeted by RIE require a more aggressive approach. For this, Moorfield etching technology has recently been enhanced to provide for the use of the fluorine-chemistry etchants SF6 and CHF3. To allow for this, both hardware and software have been upgraded in line with the demands these process gases introduce.
Some examples of applications are:
h-BN sidewalls: A pit was etched into a multi-layer stack of h-BN, using Moorfield etching technology contained within a MiniLab 026. With SF6 as the etchant gas and a Soft Etching approach, just 7–8 layers of material were removed during a 2 minute process. Residual roughness at the bottom of the pit was just 1 atomic layer.
h-BN bulk etching: By changing conditions, much higher etch rates were possible. Users were able to achieve an etch depth of 130 nm at a rate of 1.1 nm/s.
SiO2 etching: A thermally oxidised Si wafer was etched using a nanoETCH tool using CHF3 as etchant gas. An ultra-low etch rate of ~1.3 Å/s was obtained, allowing for excellent control.
Fluorine-chemistry etching is available within our nanoETCH and MiniLab platforms.
Pre-deposition cleaning
A requirement for many physical vapour deposition (PVD) processes is pre-cleaning of substrates. An effective method for this is to create reactive plasmas in close proximity to substrate surfaces, leading to the removal of unwanted contaminants. Moorfield, as a leading supplier of R&D deposition tools now routinely fit systems with etching stages that provide this functionality.
Etching stages can be fitted into a process chamber in combination with the deposition substrate stage itself (the stage is first active for etching, then for deposition). However, where possible, it is best to position the cleaning stage in a supporting load-lock as this confines removed material away from the process and also allows for equipping of the main deposition stage with hardware not compatible with plasma etching.
Pre-deposition etch cleaning is available in our MiniLab PVD tools.
Thermal processing
Complete thermal processing systems and bespoke components for high-temperature sample processing under controlled low-pressure, inert and reactive atmospheres.
Substrate heating is a common laboratory requirement, for numerous applications. Moorfield produce complete systems for precisely-controlled substrate heating up to 1000 °C under controlled atmospheres. A variety of different heating technologies are available—depending on the application. Stand-alone components including heating stages and power supplies can also be supplied.
