Wafer process technology delivers WBG-like performance on standard substrate

Disruptive Bizen transistor technology, developed by Search For the Next (SFN) has been verified by physical wafer results and calibration to deliver the same voltage levels, switching speeds and power handling performance of wide bandgap devices, claims SFN.

The first devices to use Bizen are members of the QJT (Quantum Junction Transistor) family which will include three parts rated at 1200V/75A, 900V/75A and 650V/32A. They are available in the industry-standard TO247 or TO263 power MOSFET packages. Significantly, the devices can be made using standard silicon substrates on conventional, larger-geometry silicon processing lines.

Bizen applies quantum mechanics to a traditional bipolar wafer process. The result is a very rugged and reliable device with the heritage and pedigree of traditional bipolar silicon technology. Bizen also reduces lead times from 15 weeks – typical for integrating MOS to create large scale integration CMOS – to less than two, and halves the number of process layers. The QJTs use   eight layers and wafer process.

Wafer tests also show that the Bizen process exhibits an effective current gain of over one million. This will enable direct connection between the 1200V/75A Quantum Junction power transistor and a low voltage, low current CPU output port such as a PWM.

“To get this level of performance from traditional silicon-based MOSFETs, the device size must be much bigger. 1200V/75A in a TO247 housing can be achieved using wide bandgap materials like silicon carbide, but this approach has other well-known issues,” explained David Summerland, CEO and founder of SFN. For example, SiC, takes longer to process and has a significant manufacturing carbon footprint, he reported. It does not scale like silicon.

“The data we have obtained from physical wafer tests proves that by using Bizen on silicon substrates, our QJTs deliver the same performance as SiC or GaN,” said Summerland. “Yet the production equipment required to make a QJT is exactly the same as for a standard silicon MOSFET, and the Bizen process adds no extra manufacturing complexity,” he added.

Following the QJT, SFN will release the Processor Junction Transistor (PJT), an integrated Bizen device with its own processor which can also be produced on a manufacturing cycle time of eight days.

SFN has also released other comparative performance metrics for a 1200V/100A part – also in TO247. The losses at rated current will be 25 per cent (less than 300mV) of those exhibited by the SiC device, and its input capacitance will also be four to five times less (less than 1pF).

Bizen is patent-protected and is developed in the UK by Search For The Next (SFN). WaferTrain is the trading arm and a subsidiary of Search For The Next.


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