Date: 29th May 2011
Power semiconductor devices on 200mm CMOS-compatible
GaN-on-Si, by imec
Imec has announuced, along with its partners in a program
called GaN industrial affiliation program (IIAP), it has
produced device-quality semiconductor wafers with GaN/AlGaN
layers on 200mm silicon wafers. The advantage of this development
is, the GaN MISHEMTs were processed using standard CMOS
tools and also the processes are compatible with the strict
contamination rules in a standard CMOS processing line (e.g.
no use of gold). The business gain in this process is mass
production of GaN devices can be made using high-productivity
The advantages and technology features of this process
is further explained below as stated by imec:
GaN is a promising material for next-generation power devices
with a performance beyond what is possible with silicon.
Imec has recently succeeded in producing 200mm GaN-on-Si
wafers with crack-free surfaces and a bow of less than 50µm.
The wafers were made using an advanced MOCVD system from
Applied Materials. The ability to use 200mm wafers is an
important milestone, because it brings processing in reach
of regular high-productivity 200mm fabs, allowing for an
important cost reduction compared to processing smaller
wafers on dedicated processing lines.
A second prerequisite for cost-effective processing, next
to the wafer size, is that power devices can be fabricated
with processes that are compatible with standard CMOS processes
and tools. Imec proved this by processing its GaN-on-Si
wafers using standard CMOS tools, yielding functional GaN
MISHEMTs (metal-insulator-semiconductor HEMT). All equipment
was verified for its capability to handle the wafers, and
required only minimal adjustments in software and hardware.
Conventionally, gold is used for ohmic contacts and gate
structures in power devices, but it makes GaN processing
incompatible with conventional CMOS processing. To overcome
this, imec based the ohmic contact formation on an Au-free
metallization system, and modified the Schottky gate to
a gate dielectric based gold-free metal-insulator-semiconductor
(MIS) structure. This introduction of the MISHEMT structure
had the added advantage of reducing the high leakage current
of conventional HEMTs.