Disruptive new wafer process technology to slash lead times & chip size and wind back Moore's Law
18 October 2019
A UK collaboration between start-up, Search For The Next & Semefab has unveiled Bizen: a transistor wafer process technology using quantum tunnel mechanics, promising to slash lead times, wafer area & process layers, while increasing speed, reducing power & increasing gate density over CMOS – enabling complex ICs to be made competitively in existing UK fabs.
A UK collaboration between Nottingham-based fabless semiconductor start-up, Search For The Next (SFN) and Glenrothes-based Semefab, a process development, set-up & volume foundry supporting silicon-based MEMS, CMOS, ASIC, bipolar-linear & discrete semiconductor device technologies, may be set to disrupt the semiconductor industry by implementing a fundamental change at transistor level, reaching back five decades to the early bipolar IC era, before CMOS became mainstream, using a new process called Bizen®.
Bizen applies the principles of quantum tunnel mechanics to any computing or power technology. When compared to CMOS, Bizen results in a five-fold lead time reduction – down from 15 weeks to just three weeks. Moreover, the new process achieves a three-fold increase in gate density that produces a matching three-fold reduction in die size. Lastly, Bizen halves the number of process layers required. All this is achieved while equalling or bettering the speed and low power capabilities offered by current CMOS devices.
David Summerland, SFN CEO explains: “The CMOS processing industry is hitting a brick wall as shrinking geometries bash up against the laws of physics. We went back to the very beginning and found a way to commercialise quantum tunnel mechanics in silicon or wide bandgap device manufacture. The result is ‘Bizen’ – Bipolar/Zener – which retains the advantages of traditional bipolar processing, yet removes the disadvantages by using Zener quantum tunnel mechanics. This results in lower dynamic power, higher speed and higher gate density, halving the number of process layers required, reducing material use by two thirds, and slashing manufacturing time. This enables any fab, such as Semefab (Si), Plessey (GaN) or Newport (Compound), to become a category killer.”
He continues: “Other ‘CMOS-alternatives’, such as metal air gap and MESO are, we understand, some way from being commercialised in standard fabs – and adding analogue and power would incur extra cost. Bizen reduces cost and also targets bottlenecks.”
Bipolar technology has traditionally been limited by its requirement for resistors, which have the disadvantage of becoming large in size with low power devices. In contrast, a Bizen transistor uses quantum tunnel technology, enabling designers to eliminate the resistor – as with MOS devices – and take advantage of the now-controllable current. This enables the realisation of a very low power circuit in which the transistor is Normally-On, but not saturated, and is controlled by an isolated tunnel connection, rather than a direct metal contact to the base well, as used in traditional bipolar transistors.
Therefore, Bizen technology lets designers create a simpler circuit with far fewer layers and increased logic density. For example, the number of layers needed for a Bizen device range from four to eight for devices supporting low to high voltage operation, compared with ten to seventeen for CMOS. The power consumption drops, the size drops and the integration and speed increases, allowing complex devices to be manufactured in the large geometry fabs that exist in the UK.
Since mid-2017, SFN has been in collaboration with Semefab, the well-known, indigenous, privately-owned semiconductor and MEMS fab based in Glenrothes, Scotland, for process development and qualification leading to device production. Semefab’s CEO, Allan James comments: “Semefab engaged with SFN, exploring ways to reduce smart power IC process complexity, while retaining an ability to program the chip. Early suggestions were rejected because they could not meet the low mask count target required to be disruptive in the industry. Eventually, SFN hit on the idea of using the quantum tunnel effect of miniature, reverse-biased Zener diode structures. It transpired that the integration of conventional lateral and vertical bipolar structures can, with careful modelling, be designed to incorporate Bizen without undue additional process complexity.
“I was initially quite sceptical, but having lived with the concept and seen early-stage results, it does indeed tick many of the boxes needed to disrupt the industry. It's not so much a question that CMOS is flawed – although CMOS is prone to latch up and ESD. CMOS is low power, has passed the test of time and is generally reliable. However, it is complex, and when integrated with power, even more so. Complexity means longer lead times and higher cost.”
Concludes James: “If Bizen had been discovered back in the late 60s, when the transition from Bipolar to MOS and CMOS took place in order to cost-effectively integrate logic functions, it is possible that the industry may have developed strongly in the direction we are now proposing. It is not too late however, and if it can be adopted by the industry, an important prize, given the reduction in die area at a given technology node comparing a Bizen and CMOS logic implementation, would be the ability to wind back the Moores’ Law clock by 10 years or more – and bring many wafer fabs back into mainstream manufacture. There is still a way to go before Bizen becomes a commercial reality and we are still learning. However, Semefab and SFN are working flat out to make it the huge success it may soon become.”