How Plasma Processing Enables The Best Silicon Carbide Devices

14 Feb 2019  |  Author: Dr Mark Dineen 

I was lucky enough to attend a conference in Birmingham last year on SiC, ECSCRM. If there is one thing that I will take as a lasting memory from the conference is that this is just the start for SiC devices, their future is very, very exciting. Whilst it is already established in some niche applications we will see it becoming more and more prevalent delivering performance improvements that mean great changes in many fields. Those of us involved in SiC are going to be very busy – SiC has a great future.

While SiC has excellent material properties: high bandgap, high thermal conductivity, high breakdown field etc compared to Si which makes its potential performance far superior to Si in the power switching/conversion application field. SiC has unfortunately always been difficult to make and process. Difficulty adds cost therefore until recently SiC has only been used in applications where its performance is essential…all that is changing! SiC wafers are still in short supply, the main gripe at last years conference was the lack of available wafers, they are being produced in higher volume and higher diameters both these are enabling more and more devices to be made.

Now that you have more high quality wafers you need to be able to process them efficiently and effectively, plasma processing is the answer.

Reason 1 Plasma etching of the wafers is great for improved SiC epitaxial growth

After wafers are made there can be a lot of damage on the surface, this would lead defects in the SiC epitaxial layers and to losses and heat generation in the devices. By removing a thin layer from the surface using Reactive Ion Etching (RIE) you can get rid of this damage to reveal the high quality SiC beneath, great for high quality material growth.

Reason 2 Plasma etching of the features makes for high performance device geometries

SiC devices such as UMOSFETs or Super Junction SBDs require features etched into the SiC. SiC is a very tough material but by using high density plasma etching ICP-RIE  it is possible to create the features you need at the COO that works. Oxford Instruments Plasma Technology (OIPT) has developed process solutions for smooth features with no footing.

Reason 3 Plasma deposition can provide the passivation and gate dielectrics to make high performance devices

From SiO₂ by Plasma Enhanced Chemical Vapour Deposition (PECVD) to Al₂O₃ by Atomic Layer Deposition (ALD) OIPT has solutions and understanding to modify surfaces and create interfaces that make SiC devices work.

As device processing becomes more mature, wafer size goes up (even 200mm wafers were on show at ECSCRM) and cost come down the markets for SiC becomes much wider. It already has a strong position in EV/HV power management and high power inverters for renewable energy applications, with the prices coming down it’s performance and overall system costs mean that it will become the device of choice for many more applications, saving money and energy. Plasma processing is key to this and OIPT has the high volume manufacturing solutions ready to go.

Find out more about SiC device processing by downloading our Whitepaper or listening to our Webinar.