Understanding the Mechanisms of Vacuum Evaporation Coating

Vacuum evaporation coating is a common method used to deposit thin films onto a substrate. This technique is widely used in a variety of industries, such as electronics, optics, and aerospace, due to its ability to create precise and uniform coatings with a high level of purity. There are several mechanisms used to achieve vacuum evaporation coating, each with its own advantages and limitations.

RESISTANCE EVAPORATION

One common method is resistance evaporation, which uses a resistance evaporation source made of tungsten, molybdenum, or tantalum to evaporate low melting point materials such as gold, silver, zinc sulfide, magnesium fluoride, chromium oxide, and others. However, this method may not meet the needs of vapor deposition of certain metals and non-metals.

ELECTRON BEAM EVAPORATION

Electron beam evaporation is another technique used for vacuum evaporation coating. It involves heating the evaporating material with an electron beam, which can provide a much larger energy density than the resistance heat source. This allows for the heating of refractory metals and non-metallic materials such as tungsten, molybdenum, niobium, SiO2, AI2O3, and others. Additionally, the material to be vapor-deposited is placed in a water-cooled crucible, which helps to avoid evaporation of the container material and reaction between the container material and the membrane material, thus improving the purity of the membrane.

Various Types of Evaporation Pellets Materials

HIGH-FREQUENCY INDUCTION HEATING EVAPORATION

High-frequency induction heating evaporation is another method used for vacuum evaporation coating. The metal is heated to the evaporation temperature using the principle of induction heating. The crucible containing the evaporation material is placed in the center of the spiral coil, and a high-frequency current is passed through the coil to heat the metal evaporation material until evaporation. This method has a large evaporation rate, uniform and stable evaporation source temperature, easy temperature control, and requires less purity of the evaporation materials.

ARC HEATING EVAPORATION

Arc heating evaporation uses the arc discharge heating method, which is similar to the electron beam heating method. This method is particularly suitable for evaporation of refractory metals and graphite that have a high melting point and a certain conductivity. It also has the advantage of being relatively inexpensive compared to the electron beam heating apparatus.

CONCLUSION

In conclusion, vacuum evaporation coating is a versatile and widely used technique for depositing thin films onto a substrate. There are several methods used to achieve this, each with its own advantages and limitations. By understanding the different mechanisms of vacuum evaporation coating, researchers and industry professionals can choose the appropriate method to achieve the desired coating properties for their specific applications.

If you want to learn more about sputtering targets, such as metals, alloys, oxides, and ceramic materials, you can visit the website of Stanford Advanced Materials (SAM) Corporation at https://www.sputtertargets.net/. SAM is a global supplier of various sputtering targets and regularly updates their knowledge and interesting stories related to sputtering targets on their website.

Requirements of The Width of ITO Glass: Thinner Is Better?

In recent years, the requirements for processing technology in various industries have been continuously improved. Taking ITO materials as an example, the line width and interval of processing ITO conductive patterns have higher requirements. And often there is such a question, can the ITO laser etching machine be able to achieve a line width below 20 microns? Can the processing interval be 20 microns? The answer is yes. So what is the smallest line width of the ITO laser etching machine? Let SAM Sputter Target answer it for you.

Further Reading: An Introduction to ITO – Indium Tin Oxide

The thickness of the ITO line width is determined by the laser and the optics and relates to the spot size of the focus and the thermal influence of the source on the material. Shorter wavelength results in lower energy, narrower pulse width, higher magnification of the beam expander, smaller negative of the field lens, and smaller spot size, so it could produce a line with thinner width. Of course, several of the above-mentioned parameters have a relative limit value. For example, if the magnification of the beam expander is too high, the energy density will be poor, which is not suitable for processing. Therefore, we need to take a range of values in order to apply them to the processing needs.

Related: Indium Tin Oxide Sputtering Target

In addition, even with the same laser etch machine, the line widths made by different materials are different. For example, the etch line width of a nickel alloy material is thicker than that of an ITO material, depending on the absorption of the laser wavelength by the material itself. This article analyzes based on ITO conductive glass.

The general requirement for ITO glass in the touch screen industry is less than 20 microns, which uses a narrow pulse-width infrared nanosecond laser. Different industries have different requirements for ITO line width. In some industries, the resistance of ITO line width has relatively high requirements, while in some industries, it is required to ensure that it is cut and insulated.

In the current laser market, the minimum line width of ITO conductive glass is 5 micrometers, and different line widths can be selectively selected according to different light sources. For example, the minimum line width of an ultraviolet nanosecond laser can be 15 micrometers. Of course, there are also EUV lithography machines that can achieve nanometer levels by means of extreme ultraviolet lasers. The requirements for line width are mainly determined by different product requirements.

ITO Glass – Thinner Is Better?

In recent years, the requirements for processing technology in various industries have been continuously improved. ITO (indium tin oxide) materials, for instance, have stricter criteria for line width and processing interval for ITO conductive patterns. The subject of whether the ITO laser etching machine can produce lines smaller than 20 microns comes up frequently. Is a 20-micron processing interval possible? The answer is yes. So what is the smallest line width of the ITO laser etching machine? Let SAM Sputter Target answer it for you.

What Determines the Line Width?

The laser and the optics define the thickness of the ITO line width, which is related to the size of the focus spot and the thermal impact of the source on the material. A line with a thinner width might be produced by a shorter wavelength because it has lower energy, a narrower pulse width, a higher beam expander magnification, a smaller field lens negative, and a smaller spot size. Several of the aforementioned parameters, of course, have a relative limit value. For instance, if the beam expander’s magnification is too great, the energy density will be inadequate and unsuitable for processing. As a result, we must choose a variety of values and apply them to the processing requirements.

In addition, even with the same laser etch machine, the line widths made by different materials are different. For example, the etch line width of a nickel alloy material is thicker than that of an ITO material, depending on the absorption of the laser wavelength by the material itself. This article analyzes based on ITO conductive glass.

ITO glass

Thickness Requirements of Different Industries

The general requirement for ITO glass in the touch screen industry is less than 20 microns, which uses a narrow pulse-width infrared nanosecond laser. Different industries have different requirements for ITO line width. In some industries, the resistance of ITO line width has relatively high requirements, while in some industries, it is required to ensure that it is cut and insulated. In the current laser market, the minimum line width of ITO conductive glass is 5 micrometers, and different line widths can be selectively selected according to different light sources. For example, the minimum line width of an ultraviolet nanosecond laser can be 15 micrometers. Of course, there are also EUV lithography machines that can achieve nanometer levels by means of extreme ultraviolet lasers. The requirements for line width are mainly determined by different product requirements.

Thinner is Better?

From the above, you can see that different industries have different thickness requirements for ITO glass. What is certain is that the thinner is not always the better. It still needs to be designed and manufactured according to the specific application.

Differences Between CVD and PVD Processes and Technologies

The most popular surface treatment technologies, chemical vapor deposition (CVD) and physical vapor deposition (PVD), have been used extensively for nearly 50 years to harden the surfaces of tools and molds. The context that follows compares the technologies and processes of CVD and PVD using the illustration of cutting tools.

Rationale

In the process known as chemical vapor deposition (CVD), a vapor containing a gaseous reactant or a liquid reactant that makes up a thin film element as well as other gases necessary for the reaction are introduced into a reaction chamber in order to chemically react on the surface of the substrate to form a thin film.

Physical vapor deposition (PVD) uses low-voltage, high-current arc discharge technology under vacuum conditions to evaporate the target and ionize the vaporized material and the gas, and finally make the evaporated material and its reaction deposited on the workpiece.

Image Credit: Stanford Advanced Materials

Process and Equipment

1. Temperature

The fundamental distinction between CVD and PVD is temperature. The tools must undergo a vacuum heat treatment after coating since the process temperature of the CVD method is higher than the high-speed steel’s tempering temperature. This will restore the tools’ hardness.

2. Compared to PVD, the CVD method requires less cleaning of the tool entering the reactor.

3. The PVD coating (approximately 2.5 m) is thinner than the CVD coating (about 7.5 m) on the tool’s surface.

4. The CVD coating’s surface is marginally rougher than the substrate’s surface. On the other hand, the PVD coating has a good metallic sheen without grinding and effectively reflects the tool’s surface.

5. The crafting process

CVD has good coating performance and takes place in a gaseous atmosphere with low vacuum. Hence, every surface of the cutters encased in the reactor, including deep holes and inner walls, can be entirely coated, with the exception of the support points.

In contrast, all PVD technologies have poor coating performance both on the back and sides of the tool due to low air pressure. To prevent the production of shadows, the PVD reactor must minimize its loading density, and loading and fixing are challenging. In a PVD reactor, the tool typically revolves constantly, though occasionally it must also reciprocate.

6. Cost

Although the PVD production cycle is one-tenth that of CVD, the initial equipment expenditure is three to four times that of CVD. Whereas PVD is severely constrained, a wide range of workpieces can be treated within a CVD operating cycle. In other words, PVD can cost more than CVD in some cases.

7. Safety

As a form of “green engineering,” PVD creates less pollution when operating. Contrarily, the reactive gas and reaction tail gas of CVD may have some corrosiveness, flammability, and toxicity, and the reaction tail gas may contain powdered and fragmented chemicals, thus particular precautions for the equipment, environment, and operators must be taken.

Stanford Advanced Materials supplies high-quality and consistent products to meet our customers’ R&D and production needs. You can visit our website for more information.

The Role of Sputtering Targets in Vacuum Sputtering

Introduction to Vacuum Sputtering

Vacuum sputtering is a thin-film technology to deposit thin films and coatings by creating a sub-atmospheric pressure environment and an atomic or molecular condensable vapor source. The basic principle is to make argon (Ar) ions hit the surface of the sputtering target through glow discharge in a vacuum, so that the target atoms overflow and deposit on the substrate to form a thin film.

Most general metal materials use DC sputtering, while non-conductive ceramic materials use RF sputtering. The new sputtering coating equipment uses powerful magnets to accelerate the ionization of argon gas around the target material in a spiral shape, thereby increasing the probability of collision between the target material and argon ions, thereby increasing the sputtering rate.

Characteristics of Sputtering Coating Process

(1) It has a wide range of applications, and can make metal, alloy or insulator materials into thin films.

(2) Under proper setting conditions, multi-component targets can be made into thin films with the same composition.

(3) A mixture or compound of the target substance and gas molecules can be produced by adding oxygen or another reactive gas to the discharge atmosphere.

(4) The target input current and sputtering time are controllable, which is conducive to obtaining high-precision film thickness.

(5) Sputtering coating is more conducive to producing large-area uniform films than other processes.

(6) The sputtered particles are not affected by gravity, and the positions of the target and the substrate can be freely arranged.

(7) The bonding strength between the substrate and the film is more than 10 times that of the general evaporated film, and because the sputtering particles have high energy, the surface of the film is continuously diffused to obtain a hard and dense film. At the same time, high energy allows the substrate to obtain a crystalline film at a lower temperature.

(8) The nucleation density is high at the initial stage of film formation, and an extremely thin continuous film of 10 nm or less can be produced.

(9) The target has a long service life and can be continuously produced for a long time.

(10) The target can be made into various shapes, and with the special design of the machine, it can be controlled better and has the highest efficiency.

How Target Purity Affects Thin Film Quality

Many factors can affect the quality of a thin film, of which the purity of the sputtering target has the greatest impact. If the target material is not pure enough, the impurity particles in the target material will adhere to the surface of the substrate during the sputtering process, causing the film layer in some positions to be weak and peel off. Simply put, the higher the purity of the target material, the better the performance of the film.

For targets with poor thermal conductivity, such as silicon aluminum sputtering targets, the heat transfer is often hindered by impurities in the target. There is a difference between the cooling water temperature used in production and the actual water temperature of the coating line, which leads to cracking of the target during use. Generally speaking, slight cracks will not have a great impact on coating production. However, when the target has obvious cracks, the charge is easily concentrated on the edge of the crack, resulting in abnormal discharge on the surface of the target. Discharging will lead to slag falling, abnormal film formation, and increased product scrapping. Therefore, in the process of target preparation and purity control, it is also necessary to control the preparation process conditions.

Stanford Advanced Materials (SAM) is a global sputtering targets manufacturer which supplies high-quality and consistent products to meet our customers’ R&D and production needs. Please visit https://www.sputtertargets.net/ for more information.

 

Impact of Thin Film Technology on The Crystalline Silicon Industry

Judging from the current development of photovoltaic technology, thin films, especially CIGS thin films, will gradually become the mainstream of solar power generation.

Thin-Film Solar Cell

Thin-film photovoltaic cells, also known as solar cells, are devices that use the photovoltaic effect to convert light energy into electrical energy. They are considered novel photovoltaic devices that can alleviate the energy crisis.

Thin-film solar cells can be fabricated on substrates using materials such as ceramics, graphite, and metal sheets. These raw materials, while relatively cheap, work very well. They can make thin films with a thickness of only a few micrometers, and the current conversion efficiency can reach 13%.

In addition to planar, thin-film solar cells can also be made into non-planar structures because of their flexibility. Therefore, they have a wide range of applications and can be combined with or become part of buildings.

CIGS Film

The aforementioned CIGS is mainly composed of Cu (copper), In (indium), Ga (gallium), and Se (selenium), and the complete chemical formula is CuInxGa(1-x)Se2. This material has many advantages, including strong light absorption ability, good power generation stability, high conversion rate, long daytime power generation time, low production cost, short energy recovery cycle, etc.

Polycrystalline Silicon Solar Cells
Ogunshile, Emmanuel. (2017). An Investigation into the Use of Hybrid Solar Power and Cloud Service Solutions for 24/7 Computing. 743-754. 10.5220/0006380007430754.

CIGS VS. Silicon

Why thin film technology will beat traditional crystalline silicon products? Comparing the two, you will find the following results.

  • The absolute power generation of the thin film is higher, and the average power generation is about 8-10% higher than that of crystalline silicon (depending on the location and climate of the power station).
  • The decay rate of CIGS thin film power generation is controllable, which means that the occurrence of power generation decay can be controlled by adopting effective technical means. The practice has proved that during the operation of the CIGS thin-film station, the power generation does not decrease, but increases slightly.

For the comparison between CIGS thin film and Silicon materials, you can refer to this article Silicon Thin-Film VS. CIGS Thin-Film for Solar Panels.

Conclusion

Although the crystalline silicon industry has matured and the conversion efficiency of monocrystalline silicon has also been improved, technical shortcomings restrict the sustainable development of the crystalline silicon industry. What’s worse is that its industrial chain is long, the cost is difficult to control, and crystalline silicon products are not competitive. From this point of view, the development of thin film technology, especially CIGS thin film, will get better and better.

Stanford Advanced Materials (SAM) is a global sputtering target manufacturer which supplies high-quality and consistent products to meet our customers’ R&D and production needs. We provide high-purity CIGS materials and we insure you will be satisfied with our products. Please visit our website https://www.sputtertargets.net/ for more information.

 

6 Facts About Semiconductor Wafers

1. Semiconductor, as it literally seems to be, is a solid substance whose conductivity is between insulators and most metals, either due to the addition of an impurity or because of temperature effects. In other words, the conductivity of the semiconductor can be controlled by adding impurities as a specific amount of other materials to the semiconductor.

2. Most semiconductor wafers are made of silicon, which is the second-most abundant element in the Earth’s crust (about 28% by mass) after oxygen and the eighth-most common element in the entire universe by mass. In addition to silicon, semiconductors also use other materials, including germanium, gallium arsenide, germanium, indium phosphide, sapphire and quartz.

3. Semiconductor wafers are available in a spread of diameters. The first semiconductor wafer made in the US in 1960 was just 1 inch in diameter. Today, standard semiconductor wafers go up from 12 inches to 18 inches.

4. Water is the key component of manufacturing Silicon wafers. It is a compound that basically is a general solvent for all substances, silicon included. A large production facility uses up to 4.8 million gallons of water every day to supply Silicon wafers for manufacturing needs and supply.

5. The thickness of semiconductor wafers varies greatly. The thickness of the wafer is always determined by the mechanical strength of any material used to make it. Regardless of what the semiconductor is made of, the wafer must be thick enough to support its own weight so that it does not break during processing.

6. Contamination is inevitable during the manufacture and transportation of semiconductors. Appropriate storage conditions must be in place to prevent contamination and/or degradation after shipment. Semiconductor wafers that are not vacuum sealed must be placed in a Nitrogen (N2) cabinet at a flow rate of 2 to 6 SCFH (Standard Cubic Feet per Hour).

Stanford Advanced Materials (SAM) is a global sputtering targets manufacturer which supplies high-quality and consistent products to meet our customers’ R&D and production needs. Please visit https://www.sputtertargets.net/ for more information.

Application of Molybdenum Target in Mobile Phone LCD Screen

Nowadays, society is full of phubbers, and mobile phones have become the most indispensable thing for the masses. Mobile phone displays are also becoming more and more high-end, such as full-screen design, small bang design, and so on.

Do you know what the important step is in making a mobile phone LCD screen? — Coating, using magnetron sputtering to sputter metal molybdenum from the molybdenum target onto the liquid crystal glass.

As an advanced film material preparation technology, sputtering has two characteristics of “high speed” and “low temperature”. It concentrates ions into a high-speed ion stream in a vacuum to bombard a solid surface. The kinetic energy exchange between the ions and the atoms on the solid surface causes the atoms on the solid surface to leave the target and deposit on the surface of the substrate to form a nano (or micro) film. The bombarded solid is a material for depositing a thin film by sputtering, which is called a sputtering target.

In the electronics industry, molybdenum sputtering targets are mainly used for flat panel displays, electrodes and wiring materials for thin film solar cells, and barrier materials for semiconductors. These are based on its high melting point, high electrical conductivity, low specific impedance, good corrosion resistance, and good environmental performance.

Molybdenum used in components of LCDs can greatly improve the brightness, contrast, color, and life of the LCD. One of the major applications for molybdenum sputtering targets in the flat panel display industry is in the TFT-LCD field.

molybdenum target

In addition to the flat panel display industry, with the development of the new energy industry, the application of molybdenum sputtering targets on thin film solar photovoltaic cells is also increasing. The molybdenum sputtering target mainly forms a CIGS (Copper Indium Gallium Selenide) thin-film battery electrode layer by sputtering. Among them, molybdenum is at the bottom of the solar cell, and is a back contact of the solar cell. It plays an important role in the nucleation, growth, and morphology of the CIGS thin film crystal.

Stanford Advanced Materials(SAM) is a global sputtering targets manufacturer which supplies high-quality and consistent products to meet our customers’ R&D and production needs. Please visit https://www.sputtertargets.net/ for more information.

3 Minutes to Know PVD Gold Sputtering

Gold is a popular precious metal that has been used for centuries as currency, hedging and jewelry for its noble and beautiful gold color.

PVD Gold Sputtering

Gold sputtering coating is a thin film deposition process in which gold or gold alloy is bombarded with high-energy ions in a vacuum chamber, causing gold atoms or molecules to be “sputtered” into the vapor and condensed on the substrate to be coated. Sputtering is one method of the PVD (Physical Vapor Deposition) process, the other two of which are thermal evaporation deposition and electron beam vapor deposition, and gold is also applied in these two methods. In thermal evaporation deposition, gold evaporates in a low-pressure environment with resistive heating elements; and in electron beam vapor deposition, gold is heated by an electron beam, and then condensed on the substrate to be coated.

Gold Plating

Apart from PVD coating, there are other ways for gold coatings such as gold plating and gold filling. Gold plating is a method that deposits a thin layer of gold on the surface of another metal by chemical or electrochemical plating. The advantages of gold plating are inexpensive and easy. However, the coating it produces is relatively soft and less durable, and what’s worse, its chemical process would cause pollution that is far away from environmentally friendly.

Gold Filling

Gold filling is the mechanical bonding of gold to metal under high temperatures and pressure. It produces a thicker coating than PVD gold sputtering and gold plating, and thus it is usually more expensive.

Advantages of PVD gold sputtering

The constant contact of skin or clothing may abrade the coatings, especially in the watch and jewelry industry. Thus, PVD gold sputtering is preferred in these two industries because the coatings it produces are harder and more durable than that of electrolytic gold plating or gold filling.

Compared to other types of gold coatings, the main advantages of PVD gold sputtering coating are their durability, retention of gloss, corrosion resistance, and abrasion resistance in contact with the skin, thus extending the life of the jewelry. PVD gold sputtering not only provides the exact color and brightness which evokes the general feeling of love and attraction with jewelry, but also has the advantage of being more environmentally friendly and durable than gold plating or gold filling for producing a gold coating.

Stanford Advanced Materials(SAM) is a global sputtering targets manufacturer which supplies high-quality and consistent products to meet our customers’ R&D and production needs.

Pros & Cons of 4 Film Manufacturing Methods

The properties of the thin film are determined by the manufacturing method, and different methods have their own advantages and disadvantages. Commonly used preparation processes include magnetron sputtering, chemical vapor deposition, vacuum evaporation, pulsed laser deposition, etc. Among them, magnetron sputtering deposition technology has been widely researched and applied due to its high film formation rate and good uniformity.

thinfilm_main

Magnetron Sputtering

The basic principle of the method is that under the action of electric and magnetic fields, the accelerated high-energy particles (A, +) bombard the surface of the target, and after the energy is exchanged, the atoms on the surface of the target escape from the original lattice, and finally, the sputtering particles are deposited on the surface of the substrate and react with oxygen atoms to form an oxide film. The magnetron sputtering process is characterized by excellent optical and electrical properties of the film deposited at low temperatures. In addition, it has the advantages of a high deposition rate, low substrate temperature, good film adhesion, easy to control, and large-area film formation. Therefore, it has become the most researched and widely used film-forming technology in industrial production today as well as a research hotspot in ITO film preparation technology.

Chemical Vapor Deposition

The chemical vapor deposition method is a process in which a gaseous reactant (including a gaseous reactant that becomes a vaporized condensed matter after evaporation) is chemically reacted on the surface of the substrate to deposit a film. This chemical reaction occurring on the surface of the substrate is usually the thermal decomposition and in-situ oxidation of the source material. The reaction system selected by the CVD method must satisfy:

(1) At the deposition temperature, the reactant must have a sufficiently high vapor pressure;
(2) The chemical reaction product must be in a gaseous state except for the solid matter deposited on the substrate;
(3) The vapor pressure of the deposit should be low enough to ensure good adsorption on a substrate having a certain temperature.

Vacuum Evaporation

The vacuum evaporation method is a method in which a raw material of a to-be-formed film in an evaporation vessel is vaporized from a surface to form a vapor stream, and is incident on a surface of the substrate to react with a gas to form a film in a vacuum chamber. A high-quality ITO film can be prepared by the electron beam evaporation deposition method, in which the evaporation substance is In2O3 doped with SnO2, and the mass percentage of SnO2 is 10%. Under suitable process conditions, the deposited film has a minimum resistivity of 4×10-4 Ω•cm and an average transmittance in the visible range of more than 90%.

Pulsed Laser Deposition

The pulsed laser deposition (PLD) process is a very competitive new vacuum physical deposition process developed in recent years. Compared with other processes, it has the advantages of precise control of stoichiometry, synthesis, and deposition, and no requirement for the shape and surface quality of the target, so the surface of the solid material can be processed without affecting the material body.

Stanford Advanced Materials(SAM) is a global sputtering targets manufacturer which supplies high-quality and consistent products to meet our customers’ R&D and production needs. Please visit https://www.sputtertargets.net/ for more information.