IMEC, AIXTRON set important step towards low-cost GaN power devices

Jun 03, 2008
IMEC, AIXTRON set important step towards low-cost GaN power devices
Thickness uniformity map of a 1µm GaN layer deposited on 200mm Si(111) using an AlN/AlGaN buffer. The average thickness measured in-situ is 1008nm for the full wafer excluding a 5mm edge.

IMEC, Europe's leading independent research center in the field of nanoelectronics, and AIXTRON, the world leader in metal-organic chemical-vapor deposition (MOCVD) equipment, have demonstrated the growth of high-quality and uniform AlGaN/GaN heterostructures on 200mm silicon wafers. This demonstration is a milestone towards fabricating low-cost GaN power devices for high-efficiency/high-power systems beyond the silicon limits.

IMEC and AIXTRON deposited, for the first time ever, crack-free AlGaN/GaN structures onto 200mm Si(111) wafers. The layers show good crystalline quality as measured by high-resolution x-ray diffraction (HR-XRD). Excellent morphology and uniformity were obtained as well. The high-quality AlGaN and GaN layers were grown in AIXTRON’s application laboratory on the 300mm CRIUS metal-organic chemical-vapor-phase epitaxy (MOVPE) reactor.

"The demonstration of GaN growth on 200mm Si wafers is an important step towards processing GaN devices on large Si wafers", said Marianne Germain, Program Manager of IMEC’s Efficient Power program. "There is a strong demand for GaN-based solid-state switching devices in the field of power conversion. However, bringing GaN devices to a level acceptable for most applications requires a drastic reduction in the cost of this technology. And that is only possible by processing on large-diameter Si wafers. 150mm, and then 200mm are the minimum wafer sizes we need to fully leverage today’s silicon processing capabilities."

The bow of the resulting wafers is still quite large, in the range of 100µm; but IMEC believes that an optimized buffer can reduce this bow drastically, enabling further processing. Marianne Germain: "We aim to further develop the growth process and to qualify the wafers to be compatible with Si-CMOS process."

Gallium nitride (GaN) has outstanding capabilities for power, low-noise, high-frequency, high-temperature operations, even in harsh environment (radiation); it considerably extends the application field of solid-state devices. Due to the lack of commercially available GaN substrates, GaN heterostructures are nowadays grown mainly on sapphire and silicon carbide (SiC). Si is a very attractive alternative, being much cheaper than sapphire and SiC. Other benefits include the acceptable thermal conductivity of Si (half of that of SiC) and its availability in large quantities and large wafer sizes.

But until now, Si wafers with (111) surface orientation were only available with a diameter up to 150mm. The 200mm wafers were custom-made by MEMC Electronic Materials, Inc. using the Czochralski growth (CZ) method. CZ wafers are ideally suited for switching applications with large breakdown voltages. For such devices, the performance is independent of the resistivity of the Si substrate.

For the AlGaN/GaN heterostructures, a standard layer stack, that had already been successfully demonstrated on 100 and 150mm Si(111) substrates, was used. First an AlN layer was deposited onto the Si substrate, followed by an AlGaN buffer which provides compressive stress in the 1 micron thick GaN top layer. The stack was finished with a 20nm thin AlGaN (26% Al) layer and capped with a 2nm GaN layer. From in-situ measurements, researchers from IMEC were able to extract the thickness uniformity of the different layers which show a standard deviation well below 1% over the full 200mm wafers (5mm EE).

Source: IMEC

Explore further: New oscillator for low-power implantable transcievers

add to favorites email to friend print save as pdf

Related Stories

Recommended for you

Microsoft beefs up security protection in Windows 10

4 minutes ago

What Microsoft users in business care deeply about—-a system architecture that supports efforts to get their work done efficiently; a work-centric menu to quickly access projects rather than weather readings ...

US official: Auto safety agency under review

12 hours ago

Transportation officials are reviewing the "safety culture" of the U.S. agency that oversees auto recalls, a senior Obama administration official said Friday. The National Highway Traffic Safety Administration has been criticized ...

Out-of-patience investors sell off Amazon

13 hours ago

Amazon has long acted like an ideal customer on its own website: a freewheeling big spender with no worries about balancing a checkbook. Investors confident in founder and CEO Jeff Bezos' invest-and-expand ... domain sold for big payout

13 hours ago

The owners of the website have scored a big payday with the outbreak of the epidemic, selling the domain for more than $200,000 in cash and stock.

Hacker gets prison for cyberattack stealing $9.4M

17 hours ago

An Estonian man who pleaded guilty to orchestrating a 2008 cyberattack on a credit card processing company that enabled hackers to steal $9.4 million has been sentenced to 11 years in prison by a federal judge in Atlanta.

Magic Leap moves beyond older lines of VR

18 hours ago

Two messages from Magic Leap: Most of us know that a world with dragons and unicorns, elves and fairies is just a better world. The other message: Technology can be mindboggingly awesome. When the two ...

User comments : 0