Heating solutions for Chemical Vapor Deposition (CVD) in semiconductor applications

There are various vacuum deposition processes used to create thin film deposition (coatings) of metal, alloys and non-metals. This can be achieved through mechanical, electromechanical or thermodynamic means. Kamet’s mineral insulated heating elements have a broad range of application in deposition systems.

What is chemical vapor deposition (CVD)?

Chemical vapor deposition is a vacuum thin film deposition process using thermally induced chemical reactions on the substrate surface. The process varies slightly depending on the material used.

• When the coating is a metal or alloy, it is vaporized either through heating or pressure change. The vapours then settle on the cooler wafer semiconductor (substrate) creating an even coating.
• When the coating is a polymer, e.g. silicon nitride, two or more gas precursors (monomers) are decomposed using heat and they then react together in the vacuum chamber to form a new polymer compound which deposits as a thin film layer on the substrate.

Adjusting pressure, temperature and duration influences the thickness of the deposited layer. In fact there are a number of sub-categories of CVD processes depending on such variables. These include:

• Atmospheric pressure chemical vapor deposition (APCVD) is thermally driven at atmospheric pressure and has high deposition rates. Extremely high temperatures are required between 1000°C and 1300°C.
• Low pressure chemical vapor deposition (LPCVD) uses low pressure and heat to create a reaction with a precursor gas on the solid substrate. The reduced pressure reduces unwanted gas-phase reactions and improves film uniformity across the wafer semiconductor. The temperature range is usually between 570°C and 650°C.
• Ultra high vacuum chemical vapor deposition (UHCVD) takes place at very low pressure, typically below 10⁻⁶ Pa.
• Plasma enhanced chemical vapor deposition (PECVD) is a low temperature (and thus more economical) thin-film deposition process. It operates at between 100°C-400°C. Cold plasma is added with reactive gases to create the desired coating on the substrate.
• Photo-initiated chemical vapor deposition (PICVD) uses UV light to stimulate chemical reactions. It is similar to PECVD, given that plasmas are strong emitters of UV radiation. Under certain conditions, PICVD can be operated at or near atmospheric pressure.
• Atomic Layer Deposition (ALD) uses several alternating gases. Each gas reacts with and saturates the substrate surface. The chamber is then purged with an inert gas before allowing another reactive gas in to form the next deposition layer. This technique is also used in nanotechnologies.

What are the advantages and disadvantages of CVD?

CVD can be used for thin-film layers on a wide range of materials such as glass, ceramics, metals and metal alloys at a fairly high deposition rate. An advantage of CVD over Physical Vapour Deposition (PVD) is that it can be used to create uniform coats even on complex shapes. In fact this characteristic combined with the high purity of CVD deposition, make it very useful in sensitive nanotechnology processes. It is easy to remove impurities from gaseous precursors during chemical vapor deposition. This is another advantage for nanotechnology applications.

On the downside, CVD precursors can be highly toxic, explosive or corrosive and the residual products are a hazardous waste. Furthermore some of the precursors can be expensive.

Which heating solutions does Kamet offer for CVD processes?

There are multiple ways to heat up the processes in CVD coating applications, one of the most important and widely used is resistive heating. This is Kamet’s area of expertise, with a range of high quality mineral insulated heating elements well suited for CVD applications.

Due to the use of CVD for nanotechnologies, thermal performance is critical to control thin film deposition and ensure quality. At Kamet we have the know-how to design bespoke heating systems that meet the challenges of all the different CVD processes. Our high temperature precision heaters can be combined with leading-edge temperature sensors thus ensuring the thermal uniformity that is so crucial to these processes.

Advantages of mineral insulated heating elements for CVD

• Temperatures of up to 1000°C
• Mineral insulation ensures
  • the heating elements are suited to demanding atmospheres (vacuum, inert gases)
  • chemical resistance
  • excellent dielectric endurance
• Custom sheath materials are available to match any environment
• Seamless transitions between the hot and cold sections of heaters
• The hot and cold sections have equal diameters
• Termination is simple due to cold ends which prevents overheating
• Suited to high power density
• Uniformity of heat distribution to a source, wafer, target or substrate
• A large bending radius makes heating elements suited to intricate, curved applications
• Precise heating for critical processes
• Thinner, low mass designs are possible.
• Fast warming up times
• Sealed heating elements prevent contamination
• Thermocouples can be included in the design

More about our work for the semiconconductor industry you can read here. If you have any questions or like to talk to us about your application. You can contact us via this form.