200mm GaN-on-silicon technology and GaN power devices

Introduction

Gallium nitride (GaN) is anticipated to be the next-generation power semiconductor. With a higher breakdown strength, faster switching speed, higher thermal conductivity and lower on-resistance, power devices based on GaN significantly outperform Si-based power chips. The first-generation GaN-based power devices will play a key role in the power conversion within battery chargers, smartphones, computers, servers, automotive, lighting systems and photovoltaics. Today, GaN is grown on a variety of substrates, including sapphire, silicon carbide (SiC) and silicon (Si).

Imec takes today gallium nitride on silicon (GaN-on-Si) e-mode and diode technology to a higher level of maturity and explores the next generation GaN technology with higher level of integration (GaN-IC) and higher performances.

We have been pioneering GaN technology for more than 15 years, evolving 200mm/8-inch wafers to realize GaN-on-Si devices at lower costs while maintaining world-class performance. Our research covers GaN epitaxy as well as device engineering and processing technology. 

Imec’s engagement offering are:

• GaN Industrial Affiliation program: to be part of an ecosystem of IDMs and tool vendors where imec complements your research team by exploring and de-risking the next generation of GaN-based technologies (GaN-IC, novel substrates, higher voltages beyond 650V, (quasi) vertical device, evolution of GaN-on-Si, etc...)
• GaN technology transfer: transfer state of the art 200mm GaN-on-Si epitaxy, e-mode and diode technology to slash your time-to-market
• GaN private Lot: you can design your device into imec’sstate of the art 200mm GaN-on-Si technology platform for 200V and 650V (e-mode) power devices. Imec delivers prototype wafers to you, can tune the process for your needs and eventually sustain low-volume production.

We also provide a dedicated package for technology transfer to shorten your time-to-market, or help you to develop a solution tailored to your needs using our state-of-the-art Au-free CMOS compatible 200mm GaN-on-Si technology platform for 200V and 650V (e-mode) power devices. Our platform is also available for low-volume production.

Imec platform

Imec has built a 200mm/8-inch Au-free CMOS-compatible platform, with a major focus on E-mode and Schottky diodes for power-switching applications. With the same platform we can also enable GaN-based RF devices, thanks to a 200mm/8-inch GaN-on-Si substrate with low RF losses.

Epitaxy

200mm/8-inch GaN-on-Si epitaxy is challenging and requires a carefully-designed buffer for stress engineering to enable high-breakdown voltage and avoid formation of cracks and slip lines. Next to this, the buffer needs to be dispersion free. Imec has been exploring and optimizing several buffer architectures for 200mm/8-inch GaN-on-Si epitaxy.

Our latest 200mm/8-inch GaN-on-Si epitaxy shows excellent surface morphology and good reproducibility. Moreover, it is dispersion-free and has low vertical leakage current both at RT and at 150C.

Our 200mm/8-inch GaN-on-Si epi recipes are available on 3 different reactors from 2 vendors (Veeco K465i & Veeco Propel, Aixtron G5+ C). Imec’s proprietary recipes can be transferred to partners quickly, and are available for licensing.
 

Voltage Application	Voltage @ 1μA/mm2 - 25°C	Voltage @ 1μA/mm2 – 150°C	Max Breakdown at
200V	450	390	>700V
650V	780	750	>1200V

E-mode (Normally-off)

Imec has been pioneering GaN and on e-mode (i.e. normally off) device technology. 

Our latest GaN-on-Si e-mode device technology shows:

• large threshold voltage (VTH>2V)
• Very low specific on-resistance
• Dispersion free (<20% Dynamic RDS-ON)
• 200V and 650V voltage ranges

Imec’s 200mm CMOS compatible and Au free GaN technology can be transferred to your fab and also tuned to your specific needs. 

Moreover, imec can provide to you our PDK such that you can design your e-mode device within imec technology.

A lot of 12 200mm/8-inch GaN-on-Si wafers will then be processed with your private mask set, characterized and delivered to you. 

Imec can also help you in the device design and, if needed, tune the GaN processing according to your needs.

Parameter	Description	200V	650V
RDS_ON – 25°C	On-state resistance at 25°C	<10Ω mm	<20Ω mm
Dynamic RDS-ON	10µs ON, 90 µs OFF - substrate grounded - at maximum rated voltage and full temperature range	<20%	<20%
VTH_gm	Threshold voltage from maximum gm slope	2.9V	2.9V
VTH_current	Threshold voltage (ID=10µA/mm VDS=VGS)	2.15V	2.15V
ID_OFF	Off state drain leakage at rated voltage	<50nm/mm	<50nm/mm
IGS_ON	On-state gate-source leakage at VGS=6V	<10µA/mm	<10µA/mm
VGS_MAX	Absolute maximum gate voltage.	7V	7V
		More details	More details

Schottky diode

Imec has developed a 200mm GaN-on-Si diode technology with our proprietary Gate Edge Termination (GET) technology.

The main challenge that comes with developing power diodes is to obtain devices that simultaneously show low leakage current and low turn-on voltage – and exactly that can be realized with imec’s GET diode device architecture. Imec’s Schottky diodes meet forward and reverse specifications across the full temperature range (from 25˚C till 150˚C) with a tight distribution.

Imec’s technology can quickly be absorbed by our partners and can also be tuned to their specific needs.
 

    

Description	Test Conditions	200V	650V
VF_25C	Forward Voltage at 25˚C, IAC = 0.1 A/mm	1.3V	1.6V
VT_25C	Turn-on voltage at 25˚C, IAC = 0.001 A/mm	0.6V	0.7V
IR_25C	Reverse Leakage at 25˚C, VAC = rated voltage	10nA/mm	5nA/mm
RON	ON resistance 25˚C, Max slope ΔVAC/ΔIAC	3.5Ω·mm	5.7Ω·mm

Next-generation technologies

Next to improving GaN-on-Si e-mode and Schottky diode technology, imec is also investigating the next generations of GaN technologies that will provide:

• Higher level of integration (GaN-IC)
• Higher performance 
• Larger voltage rating toward 1200V and beyond

Our research stretches along 3 main paths tracks:

• Epitaxy on novel substrate technology: to enable GaN-IC (e.g. GaN-on-SOI) or thicker GaN epitaxy for higher voltage range and (quasi)vertical devices
• GaN-IC:to develop isolation and integration modules to enable and design GaN-based integrated circuits such as  high-side/low-side switches on chip. 
• Novel device: to explore (quasi) vertical device for high voltage/current applications and novel e-mode architecture for lower on-resistance

All these activities will be performed by using imec’sstate of the art 200mm/8-inch GaN-based CMOS compatible platform. 

As of today, imec has already demonstrated GaN-on-SOI epitaxy as well as a first high-side/low-side GaN-IC on chip with perfect isolation among the transistors.

Moreover, imec has shown 200mm GaN-on-QSTTMtransistors processed into imec’s200mm CMOS line. 

Next to this, a first prove of a concept of quasi-vertical device has been processed into the imec’s200mm CMOS line: the first version of imec’squasi vertical device shows a Vth beyond 4V.

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