TOKYO Semiconductor start-up NEITAS has succeeded in creating semiconductor components in 20 hours -- just a fraction of the time normally required -- using a "minimal fab," a system that can produce even a single wafer with low capital spending. The breakthrough was confirmed jointly with Toyohashi University of Technology in Toyohashi, Aichi Prefecture. The company plans to set up a contract fabrication plant in Okinawa by the end of the year with the aim of achieving 10 billion yen ($88.4 million) in sales by 2020.
The minimal fab was born at the National Institute of Advanced Industrial Science and Technology (AIST) in Tsukuba, Ibaraki Prefecture. It can manufacture semiconductors using small wafers just 12.5mm, or 0.5 inch, in diameter.
Minimal fabs hold down costs. With existing fabrication systems, the circuit negatives known as masks that form circuits on wafers are expensive. But they are unnecessary in a minimal fab. Circuits are created by using some 1 million small mirrors. Clean rooms are also unnecessary.
NEITAS President Masataka Yoshida said, "Small-volume production from a single wafer is possible," something that cannot be done with existing systems that use standard large-diameter wafers measuring 300mm in diameter.
Delivery periods can also be shortened to several days from the usual several months. The technology comes in response to calls from research institutions and companies seeking high-mix, low-volume production with short delivery periods.
Existing fabrication systems are well suited for products produced in vast numbers, such as smartphone processors and memory chips. However, when chips are produced in small volumes, costs per unit soar. Consequently, in many cases companies have difficulty getting anyone to undertake production when they request small-volume output.
For small lots, even if they are accepted, prices start at 10 million yen or more, with a delivery time of three months. With a minimal fab, however, the cost is 50,000 yen to 100,000 yen per wafer, and chips can be delivered in around five days.
NEITAS' parent is the Nippon Electronic Device Industry Association, a group of electronic parts-related companies. The startup was founded in January. It inked a research contract with Toyohashi University of Technology in April, and starting in September has researched fabrication technology, such as exposure systems for minimal fabs at that university.
This time, it succeeded in producing in less than 20 hours ion sensors and n-type MOS transistors, which are one of the basic elements of semiconductors. For film-making processes for which the minimal fab's systems are not complete, existing fabrication systems for 4- to 8-inch (100mm to 200mm) wafers are used.
The company's plan is to set up a factory in Uruma, Okinawa Prefecture, by the end of the year. The facility is to have monthly production capacity of 1,000 wafers in 2017, climbing to 5,000 in 2018, 10,000 in 2019 and 20,000 in 2020. Realizing a monthly output of 10,000 wafers would require around 3 billion yen in capital spending -- an enormous reduction compared to conventional semiconductor fabrication facilities.
Research is being pursued with the university along with others, including the National Institute of Technology, Okinawa College, and the University of the Ryukyus, with plans to produce multiple devices. One of those would be a high-pass filter used in next-generation mobile phone base stations. High-frequency characteristics are improved by using diamond substrates. Diamond substrates are difficult to make larger in diameter and volumes needed for base stations would be small, making the device well suited to production at a minimal fab.
In addition, production of allergen detection sensors and agricultural sensors that measure moisture and acidity in the soil is also projected. With small-diameter wafers just 0.5 inch in diameter, it is easy to control surface processing variances. "This is beneficial in producing sensor devices with large unevenness," Yoshida said.
MASKLESS MANUFACTURING Minimal fabs are drawing attention as a semiconductor manufacturing system developed in Japan, but they still face the issue that reducing circuit linewidths is difficult.
One reason for this is that they are maskless. Typically, masks on which circuit designs have been drawn are exposed to ultraviolet light from above, transferring a miniature copy of the design to the chip under the mask. The new approach does not use masks, instead employing a method that creates circuits through a large number of mirrors but is subject to limitations on how fine linewidths can be.
NEITAS has installed an exposure system that uses the latest in maskless technology at Toyohashi University of Technology, but even then the smallest processing dimension possible is 0.8 micron. That is the same level achieved 30 years ago by existing semiconductor technology. Even if used for high-mix, low-volume production, widespread use would be difficult at that level.
To overcome this, NEITAS is working with system manufacturers to improve maskless exposure systems. At present, it is using the same exposure technology that is used for projectors and the like. "We aim to reduce circuit linewidths to 0.35 micron in 2018," Yoshida explained.
If that level of fineness can be achieved, fabrication of sensors and analog semiconductors will become possible, and there is a high likelihood that demand for minimal fabs will broaden all at once.