René Raaijmakers
9 April

The Minimal Fab – a concept that has been in the works for more than a decade at a Japanese consortium – is now on sale. The technology brings small chip series within reach at affordable prices and a fast time to market.

A chip factory at roughly one-thousandth of the cost of a state of the art mega-fab. Shortly after the millennium change Japanese principle scientist Shiro Hara had this vision. He presented his first ideas for miniature wafer fabs in 2007 at the National Institute for Advanced Industrial Science and Technology (AIST). After more than a decade his idea has become reality: about forty mini-process modules are available for the manufacture of integrated circuits. A spacious office or workplace is sufficient to install an IC production line that doesn’t cost billions of dollars, but only tens of millions.

The distributor of the Minimal Fab, Tokyo Boeki Group, has its headquarters in Tokyo and a sales office in Moscow. Here, Domicro executives Marcel Grooten and Matthijs van Kooten got to know Shiro Hara. Both Grooten and Van Kooten previously worked at ODME and OTB and immediately recognized the power of the concept. Like the CD machines of ODME and the solar cell lines of OTB, the Minimal Fab process modules are operating in a one-piece flow in-line manufacturing principle without the need of a clean room. The entire manufacturing process sequence, from bare silicon to a functional wafer, is running in a closed and shielded environment.

‘An investment of several million euros is sufficient to produce your own ICs in a sizeable office’

The Domicro couple convinced AIST and Tokyo Boeki that the Netherlands would be a great launching area to introduce its mini-fab in Europe. To cut the story short: creator Shiro Hara will present his Minimal Fab concept at the Novio Tech Campus in Nijmegen, on 14 May.

Two euro cent

For decades, scientists and technologists have been confronted with an ever-recurring ironic contradiction: to reduce the parts on chips, more and more and bigger and bigger expensive machines are needed. Decades ago this started with photorepeaters and ovens of only thousands of dollars that fitted on a laboratory table. Now we are witnessing ASML’s effort to build a superlative: a villa-sized wafer scanner, priced at hundreds of millions of euros.

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The Icarus-like flight to ever smaller details on chips has great impact. For example, small series of advanced ICs have extremely high start-up costs and as a consequence can’t be manufactured at favorable costs in most cases. Hara’s mini-fab concept is heading for a breakthrough. The aim is to settle the cost of series volumes as small as hundreds to tens of thousands to tens of euros per chip.

This is to be achieved by small silicon wafers as small as a two euro cent coin (0.5 inches, 12.5 mm), being moved around in minimal shuttles. These closed cassettes are a miniature version of a FOUP, the standard transport container for wafers in conventional fabs. Mini-shuttles, however, only hold one wafer at the time and are transferred manually in between process modules.

In total, about forty different process modules are available and operational. There are modules for almost all processes that can be found in a megafab, like etching, oxidation and photoresist spinning. While conventional ion implanters, epitaxy oven equipment, and wafer steppers may differ in look, the Minimal Fab modules all have the same shape and size: a cabinet measuring 1.5 meter in height, 30 cm in width and 45 cm in depth.

The Minimal Fab wafers are as large as a two euro cent coin.

E-beam

Most interesting step is lithography by maskless direct laser writing in a photoresist at 0.5 microns. Theoretically, this technology can project several hundreds of thousands of transistors within a square millimeter. Not everybody requires 7-nanometer technology, as used for example by TSMC to manufacture the A12 Bionic processors for Apple’s Iphone. For the Minimal Fab, e-beam technology and exposure process modules at the 0.25-micron node are to be released this year and there is a roadmap that envisions shrinkage to 190 nm and smaller.

Now, most European chip designers don’t usually work at the advanced technology nodes that Apple, Intel, Nvidia or Xilinx need for their chips. However, their start-up investments can also be pretty high. Especially for the mask sets different companies on the continent are already making designs for 28 nanometers. A full set for that technology can easily cost as much as two million euros. For less advanced technology nodes like a quarter of a micron, it can be considerably less, but still, tens of thousands of euros are required.

Usually, multiple mask sets are needed in development cycles. Scale-up to mass production comes with ups and downs. In most cases, IC developers start with a part of a multi-project wafer with their design being a subset of the mask set containing many chips patterns. Only after having yielded functional dies – sometimes after several design revisions – the move to large series can be made.

The Minimal Fab lithographic module provides details of 0.5 micrometers.

One minute

While billion-dollar fabs need a large load to be economic and sometimes manufacture thousands of different chips inducing massive lead times, the Japanese Minimal Fab is able to deliver thousands of ICs in a short time frame. According to Shiro Hara, the cost can range from hundred euros per square centimeter at volumes of hundreds of chips, to tens of euros per square centimeter at volumes of tens of thousands.

For consumer electronics applications these kinds of numbers might not be sufficient, but for automotive this offers opportunities. ‘Toyota is one of the consortium members developing Minimal Fab,’ says Marcel Grooten. Also, small design companies having just one product can profitably manufacture their own silicon within a sizeable office. The typical process cycle time for each module is one minute. ‘Whereas with conventional wafer fabs you have to wait for months, I can now have chips delivered from a Minimal Fab within a week,’ Matthijs van Kooten adds.

While miniaturization means less output, it also offers many advantages. All kinds of process variables can be controlled much better on a small substrate. ‘Keeping temperature uniform over half an inch is way easier than over twelve inches,’ says Van Kooten. ‘This is also the case for wet processing and sputtering. Process control on small scale is so much easier to accomplish.’

At the end of the day, the manufacturing of chips is extremely complicated. Not only the factory itself but also every process tool or system is a complex integration and mix of chemistry, physics and control technology. Many decades of know-how, development, and experience materialize in an exposure tool, etcher, epitaxy oven, chemical-mechanical polisher or evaporator. As each module of the Minimal Fab concept is developed by specialized companies, the Japanese industry is taking a strong position. Yokogawa integrates the process modules and offers solutions for customers in cooperation with distributors. Other industrial market leaders like Disco, Koyo, Mitsubishi Electric, NEC, Omron, and Ricoh are also part of the Minimal Fab consortium of more than 150 companies.

On 14 May, Domicro organizes the Minimal Fab seminar at the Novio Tech Campus in Nijmegen, in collaboration with Business Cluster Semiconductors. You can register through Eventbrite.