• Welcome To Our Blog
  • Thermic Edge Company Story
  • Blog Entry Four - Cubic Silicon Carbide (SiC3)
  • Blog Entry Three - Coating Adhesion
  • Blog Entry Two - SiC 3 Coating
  • Blog Entry One - Laboratory Vacuum Furnace

Thermic Edge Blog

Hello and welcome to the Thermic Edge blog. Here you will find updates on our greatest achievements as a growing company in the South-East of England.

Thermic Edge Company Story

Read about how Thermic Edge grew to become the company it is today.

Ceramisis Ltd (now renamed to Thermic Edge) was started by me, Bob Burgess, in 2003 and was initially started as a trading company supplying high density graphite and technical ceramic products. This was drawing on my many years of experience as Technical Graphite salesman and subsequent involvement in the design and building of PVD vacuum deposition systems and hot stages, for thin film deposition.

Due to my knowledge of in vacuum sample heating, Ceramisis very quickly became involved in the design and manufacture of bespoke sample heaters and heater stages. Working closely with top European OEM thin film deposition system builders, such as Kurt J Lesker www.lesker.com , Moorfield www.moorfield.co.uk and Leybold GmbH www.leybold.com/en/products/vacuum-systems/univex-experimentation , we produced universal 800c and 1000c hot stages with sample heating, rotation, RF bias and sample transfer. The stages were suitable for use in high vacuum, inert atmospheres and a version produced for O2 Oxygen environments, using NiCr and SiC coated graphite heating elements.

Ceramisis very quickly gained a very good reputation for supplying bespoke in vacuum sample heating solutions, and working closely with our customers, our designs evolved to be very robust and reliable, with good performance. To produce our heaters, Ceramisis has always had very close links with our sister company Hivac Engineering http://www.hivac.co.uk . Paul Lennard the MD of Hivac is also a director of Ceramisis, and has been actively involved with our heater and furnace designs and production.

Hivac are specialists in the manufacture of vacuum chambers and vacuum components, with a sophisticated machine shop including chamber baking, cleaning, leak checking, mass spec analysis facilities, located in Hastings, England. For the first 10 years Ceramisis had its offices in the Hivac factory, with Hivac producing all the metalwork for our heaters and heater stages.

Ceramisis grew steadily over the next 10 years, increasing our product range to include heaters used in every application, 2000c laboratory furnaces, rotary feedthroughs and complex heater stages. We added more staff and an agent in Japan. By the end of 2013, Ceramisis had grown so much that it needed its own independent factory, and so in January 2014 we moved to our new factory in St Leonards on Sea.

We are now concentrating on standardising our vast range of heaters, heater stages, furnaces and vacuum components. For many years, we have just made bespoke products, but now we are putting all our efforts into producing standard heater ranges, to cover the majority of in vacuum heating applications. Our new Versatile Heater range will be launched very shortly, which offers a standard heater range from dia 2” to 6”, with a common design, but the versatility to be able to select from a range of body materials and element types, to cover virtually any heating application. These standard heaters can also be used on our range of rotation hot stages, for PVD deposition systems.

We will also maintain our support for bespoke heating solutions. We will always be happy to design special bespoke heaters, for in vacuum sample heating, to satisfy applications where our standard heaters are not suitable.

As we are now looking to push our range of standard heaters, furnaces and hot stages worldwide, we decided it was also time to rebrand Ceramisis. We had been receiving negative comments about the “ISIS” at the end of Ceramisis, and also Ceramisis had evolved from a ceramic and graphite company to an in-vacuum heating company. The name no longer reflected our products, and also wishing to lose the “isis” content, we decided to change our company name to Thermic Edge Ltd. This now represents our thermal cutting edge products that we produce, and our logo is of one of our heating elements.

One of our main areas of expertise is heating to high temperatures (up to 1200C+) in O2 environments. To achieve this, we use SiC coated graphite elements, which we previously bought from companies in the USA and Europe. Supply of these products has always been problematic, with us having to endure high prices and long lead times, from these foreign suppliers. In January this year, we opened our own SiC coating facility in Scotland, called Thermic Edge Coatings Ltd. We can now produce our own SiC coated graphite elements, and offer SiC coated graphite components, such as elements, susceptors and wafer holders.

Our aim is to be the number one heater supplier in the world, for in vacuum sample heating. The launch of our new versatile heater range, will enable us to take this position with a standard product range. This range will have the best performance, for the most cost effective price, with a short lead time and superb customer support. The Thermic Edge Journey continues…….

 

Bob Burgess

Managing Director

Thermic Edge Ltd

Thermic Edge Coatings Ltd

Blog Entry Four - Cubic Silicon Carbide (SiC3)

Blog 2, Cubic Silicon Carbide: SiC3

Thermic Edge Coatings (TEC) deposits a high purity silicon carbide coating on various materials. The cubic, SiC3, coating has excellent corrosion protective properties at low, medium and high temperature. Typically the coating finds application in semiconductor industry, LED and solar production and aerospace. Materials coated are graphite, carbon composites, various ceramics and refractory metals.

Silicon carbide consists of 50 % silicon and 50 % carbon and is the stable condensed state under normal conditions. Even though the composition is stoichiometric and simple the structure can vary considerable. Silicon and carbon form a strong covalent bond. The single basic unit of SiC consists of a tetrahedron of either a silicon atom which is bonded to four carbon atoms or either a carbon atom which is bonded to four silicon atoms.

Carbon and Silicon Centred Tetrahedrons

The stacking variation of a layer of single basic units causes the large variation in structure and is referred to as polytypism. It is estimated that over 200 polytypes are possible for SiC. The description of a polytype is based on the number of single basic units to describe the structure and the reference to the crystal symmetry. The description 3C means that 3 single basic units need to be stacked to get a repetition of the cubic structure.

Below is the structure shown in a plane through the centred carbon atoms. The other figure shows the stacking of a layer with centred carbon atoms (layer n) and on top of that a layer of centred silicon atoms (layer n + 1).

Layer of centred carbon atoms Layer of centred silicon atoms

Technically there are only a few polytypes of interest which are 3C, 2H, 4H, 6H and 15R where C stands for cubic, H stands for hexagonal and R refers to the rhombohedral crystal symmetry. Due to the variation in crystal structure there is also a variation in physical properties for the various SiC materials. One of the most obvious variation is the electrical bandgap which is also reflected in optical properties and others.

SiC has only one cubic polytype and as the lattice distance is the same in all directions the material is isotropic which means that all properties are the same in all directions. This is the preferred crystal structure of Thermic Edge Coatings and where the name SiC3 related to. The cubic structure is stable up to 2200 oC (at which temperature SiC3 transfers into one of the hexagonal structures) and more importantly small crystals do not grow at elevated temperatures (1500 oC).

SIC3 has a low thermal coefficient of expansion which fits very well to many materials and especially isostatic graphite used extensively in semiconductor industry for wafer support tools and alike. SiC3 has a high uniform thermal conductivity which gives it a very good thermal shock resistance. Both aspects of the coating avoid flaking and chipping of the coating from its base material.

Blog Entry Three - Coating Adhesion

Thermic Edge Coatings (TEC) deposits a high purity silicon carbide coating on various materials. The cubic, SiC3, coating has excellent corrosion protective properties at low, medium and high temperature. Typically the coating finds application in semiconductor industry, LED and solar production and aerospace. Materials coated are graphite, carbon composites, various ceramics and refractory metals.

The coating can only protect the underlying material effectively when the coating covers all areas visible to the environment, when it adheres well to the material and does not crack after the coating process.

A well adhering coating is therefore essential and the process carried out by TEC accomplishes this on various materials. The process is carried out at high temperature using ultrapure gases amongst which hydrogen which cleans the surface by removing oxides and other contaminants which might hinder good adhesion. During the initial stages of the process there is a trade-off between deposition and etching which further cleans the interface between underlying material and coating.

And of course in many applications graphite is used as the underlying material which has a high porosity. The TEC process penetrates the pores in the graphite very well and gives it a further enhancement for the adhesion. This is very well demonstrated in the figure below.

The adherence is measured regularly by making fracture surfaces from test plates. The method used is very destructive and would immediately show a lack of adhesion due to flaking of the coating from the area where the fracture occurs. Below are some images made by SEM which show the very good coverage of graphite and adherence to graphite.

Blog Entry Two - SiC 3 Coating

Thermic Edge Ltd Silicon carbide coating plant opens for business

Thermic Edge are pleased to announce that our Silicon Carbide coating plant is now open for business. Located in Carluke Scotland, our revolutionary new SiC coating facility started producing SiC coatings, denoted “SiC3”, on graphite components in February 2017.

Quartztec – Our Partners

We are pleased to welcome our partners Quartztec Europe, based in East Kilbride, Scotland, is the exclusive sales outlet for Thermic Edge’s non-heaters products and provides us with a wealth of experience in industries, including LED and Semiconductor.

Quartztec Europe is one of Europe’s leading quartz fabricators and have been manufacturing product for industries including Semiconductor, Solar, Optical and LED for over 25 years.

Thermic Edge Ltd are the sole manufacturers of SiC3, short for cubic silicon carbide. The process is unique as it combines a well-defined crystal size, isotropic structure and low surface roughness. The high growth rates achieved by SiC3 ensures that the product remains cost effective.

The coating can be used in semiconductor, aerospace and heating technologies. It will provide a high purity and impervious layer on graphite, porous ceramics and composites. The combination of graphite selection and graphite machining expertise, developed by Thermic Edge Coatings, will ensure that customers experience optimal support for various critical components within these industries. Layer thickness can be varied but typically a layer of 80 – 100μm is achieved.

SiC3 Major Advantage – coating down blind holes

One of the main problems with applying SiC coatings to graphite components, is getting the SiC coating into blind holes. Typically, with our competitor’s SiC coating, to achieve a coating down a blind hole, the diameter of the hole should be a minimum of twice or three times the size of the hole depth (a dia10mm hole can only be 5mm deep), and so the ratio of diameter to hole depth is 2:1.

With our cubic SiC3 silicon carbide coating we can coat a diameter 1mm hole to a depth of 5mm, giving a ratio of diameter to hole depth of 1:5. With this ratio we can still achieve a 30% layer thickness at the deepest point.

SiC3, short for cubic silicon carbide, is the isotropic, pure silicon carbide coating manufactured by Thermic Edge Coatings for a wide range of applications. High temperature resistant materials such as graphite, SiC based ceramics and some refractory metals such as tungsten and molybdenum can be coated in SiC3. The coating protects the underlying material against corrosion, oxidation, acts as a diffusion barrier and prevents absorption and desorption of impurities from the underlying material which can interfere with your processes. The coating also prevents particles from the underlying material interfering with the process or device to be made in the process. In combination with porous materials such as graphite, the upper layer of graphite is infiltrated with SiC3 coating, resulting in ultimate adhesion and corrosion protection. Applications can be found in the semi-conductor industry. LED manufacturing, solar, special heat treatment and aerospace.

Thermic Edge Coatings uses CVD technology to manufacture thin SiC3 layers between 10 and 200 μm. The coating produced has a preferential cubic, 3C structure which gives the best corrosion protection when compared to other SiC structures. Standard thickness is 80 – 100 μm and the technology allows to cover all areas with a dense coating.

The Process

Products are placed in the Thermic Edge Coatings in-house reactor on pure materials compatible to the process such as purified graphite and pre-coated SiC3 support materials. Combined with the use of semiconductor grade gases, it leads to a coating with minimum impurity levels and therefore improved corrosion resistance. The design of the reactor ensures only highly pure materials are present in the high temperature zone, along with high purity gases which results in extremely pure layers with a high electrical resistivity. High temperature processes at end customers, have proven the outstanding quality of the SiC3 coating, often outperforming OEM based solutions.

Wafers (silicon, sapphire, SiC, GaN) treated will benefit from the high purity and well defined SiC3 interface. Thermal conductivity is high and thermal transfer is not limited through the coating. Other material properties conform with theoretical values.

Thermic Edge Coatings is committed to further investments and scaling up of it’s process, and in the near-future will be able to coat larger sized parts. At the moment, the maximum sized part is restricted to diameter 360mm.

For more information on our SiC3 silicon carbide coating, please download our SiC3 technical document pdf, which you can find down below.

Blog Entry One - Laboratory Vacuum Furnace

The picture below shows the furnace successfully installed in a class 1000 clean room in Japan.

laboratory vacuum furnace installed

This furnace’s greatest assets are its very compact size measuring 1140mm high (lid closed) x 1120mm wide x 720mm deep, light weight (300kg), very safe and very easy to use, even for unskilled operators, with interlocked touch screen, but still boasting high power with 20kw of DC switch mode power, giving fast ramp rates of under 30 minutes to 2000°C. The furnace uses 3 phase mains supply, reducing the need for a very high current supply, the furnace above required 208v 3ph x 95 amp supply. The furnace vacuum chamber is constructed from 304 Stainless Steel, and is fully water cooled, having a double skinned body with water cooled top and bottom flanges, lid and power feedthroughs. This enables the furnace to operate indefinitely without overheating.

Although the furnace is small and light, it still boasts a large all graphite hot zone, with the usable area inside the crucible measuring Ø180mm x 140mm. Access to the top loading hot zone is enabled by an electric lid lift, operated from the touch screen, which effortlessly swings the heavy water cooled lid out of the way, allowing the operator to easily load and unload the furnace.

After the furnace is loaded and the lid closed, the operator starts the pumping sequence by pressing the “Pump” button on the touch screen control. The furnace uses a simple Edwards RV8 rotary pump to pump the chamber to vacuum. To ensure all of the Oxygen is removed from the chamber, the plc runs a pump / purge sequence, using the vent gas to shock, dilute and dislodge oxygen from the internal surfaces of the chamber and hot zone, and then pump it away. The pump / purge sequence is repeated several times to ensure all oxygen is removed from the chamber, protecting the graphite hot zone from oxidation and subsequent degradation.

laboratory vacuum furnace hot zone

At all times safety is the number one priority, both safety of the operator and safety of the laboratory vacuum furnace hot zone. Being made entirely from graphite, the hot zone can be easily destroyed if exposed to Oxygen, when it is above 500°C. The PLC ensures that the furnace is fully interlocked, monitoring water cooling flow to all areas, chamber external temperature, process and vent gas connections / pressure, hot zone temperature, vacuum integrity, lid closed position and internal atmospheric pressure. The PLC will not allow the operator to carry out any function that could harm the operator or the furnace.

After the furnace has been successfully pumped to vacuum, processing is then enabled. The furnace uses either an RKC900 or Eurotherm 3504 programmable pid temperature controllers, to control the thermal processing cycles. Recipes can be created and stored, for heating, soaking and cooling cycles. Both controllers come with free OEM software, that allows the operator to easily connect a laptop or PC, so that thermal processing and monitoring can be controlled from a laptop, rather than the small front screens of the controllers.

The Laboratory vacuum furnace above had a maximum operating temperature of 2000C, but this same furnace design can reach a maximum temperature of 3000C if needed.

Gas processing is also enabled, with the VCR gas lines ensuring high quality gas delivery to the hot zone. The furnace shown here was supplied with two gas inlet lines, with needle valves and flow meters to accurately control the gas flow rate into the chamber. The output from the furnace to the pump, is also controlled with an Edwards speedy valve, allowing the pumping speed to be controlled manually. The needle valves and throttle valves enable the operator to easily control the hot zone pressure and gas flow rate. The lid clamp enables processing at slightly over atmospheric pressure (<0.5 bar max), and an automatic pressure relief valve ensures the chamber cannot be over pressurised, for safety.

As our customers always seem to have their own special requirements for gas introduction and handling, our furnaces gas lines and control can be very easily customised to suit our customers’ exact requirements. The flexibility of the Mitsubishi touch screen and PLC, makes it very easy to customise the gas flow control, and the addition of extra gas lines.

The Mitsubishi plc and touch screen software are written by Thermic Edge, enabling the control functions to be easily modified during installation, to provide the exact control method required by our customers.

The simple touch screen control is arranged in three screens:-

The Home screen – contains the furnace control buttons for Pumping, Venting, Gas admission, Power supply enable and Chamber lid operation. This screen also displays the chamber state, Vacuum or Atmosphere, and a list of interlocks and their state.

Furance touch screen control home screen

Indicator lamps below the switches show the state of the process, for that particular switch, or if the switch is enabled for use. Certain switches are interlocked out for safety at certain times. The process lamp indicators show Red if the process has not started, flash red and green when the process is running and green when the process is complete.

This simple interlocked control means the furnace can be operated in total safety by low skilled staff.

The Interlocks Screen – This screen displays all the furnace interlocks and their current state, and gives more information about the application of each interlock.

Furnace touch screen control interlocks screen

The Mimic Screen – This screen displays the input and output valves for the gas lines and pumping lines, plus the state of the rotary pump. It shows when valves are open or closed and if the pump is on or off. It also displays a list of interlocks and their state, plus the state of the vacuum chamber.

furnace touch screen control mimic screen

The mimic screen enables the operator to easily see the state of the laboratory vacuum furnace at any time.

Furnace pressure is displayed on the built in colour screen of the MKS wide range gauge. The operator can easily select the preferred pressure units using the gauge touch screen and can select from Pascal, Torr or Millibar.

Laboratory furance vacuum gauge

The picture below shows the furnace successfully installed in a class 1000 clean room in Japan.

laboratory vacuum furnace installed

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