WIRELESS
FEATURE AT
Tackling the challenges of 5G with hybrid III-V/Si technology
Nadine Collaert fromimec explores how 5G is impacting the overall network infrastructure
T
tremendous opportunities. This fifth he advent of 5G networks will bring
broadband with data rates up to 10Gbps, expected to enable extrememobile generation of mobile networks is
machine communication in support of the and promises to enablemachine-to-
Internet-of-Things platform. These
reliability, and low latencies – below 1ms. applications require extremely high
experience, innovations are needed in the To allow for this almost unlimited
base stations and small cells) as well as in overall network infrastructure (including
In the first phase of 5G deployment, the technologies for mobile devices.
operate in the sub-6GHz radio frequency wireless communication radios will
upcoming spectrumscarcity within these (RF) bands. But to cope with the
bands, bandwidth is being sought at mm-wave bands. The introduction of thesemm-wave frequencies will have a significant impact on the overall 5G network infrastructure.
HIGH-SPEED FRONT- T-END DEVICES FOR 5G MOBILE HANDSETS
increasing complexity of the RF front-end smartphones, this translates into an For mobile handsets such as
Sub-6GHz bands andmm-wave bands power amplifiers and local oscillators. transmitter/receiver, bandpass filters, modules – containing e.g. the
common architecture, and devices will will now need to be enabled in one
need to access several bands
devices than currently used in 4G-LTE are Therefore, higher speed front-end simultaneously.
needed. Also, themm-wave functionality will have to be implemented in battery poweredmobile devices, which will put
consumption of themm-wave circuits. To severe restrictions on the power
meet all these challenges, we need high-
output power and a high power efficiency. speed devices that have both a high
STA TAT ATE-OF-T DEVICES
Today, several device technologies are being used for RF applications, including for example RF SOI and SiGe
technologies. Of particular interest is the use of III-V devices, such as III-V HEMTs (GaAs- or InP-based) and III-V heteroj
-THE-ART HIGH-SPEED
ojunction bipolar transistors (HBTs); and although originally designed for high-power applications, also III-N devices (such as GaN-based HEMT devices) have demonstrated high- frequency performance, exceeding 400GHz.
So far, Si and III-V (or III-N) circuits have been fabricated and packaged separately, and then later assembled on the same carrier substrate. This approach sets however restrictions on a further performance optimisation, and on the r, cost, formfactor and
factor will howeve circuit complexity. reduction of powe
r be essential, as space Reducing the form
within themobile handset is limited. Other challenges relate to the
compatibility of these circuits with cost- effective high-volume Si manufacturing.
HIGH-SPEED ANALOGUE/RF
To enable RF front-endmodules for future 5Gmobile handsets, imec is running its Industrial Affiliation Program ‘High-speed analogue/RF’. Within this program, imec and its partners jointly explore hybrid Si/III-V to enable high- performant RF devices with high output power and high power efficiency. They explore several device architectures, including III-V (GaAs- and InP-based) and III-N HEMT devices, III-V HBT, as well as III-V and III-N MOSFET devices. In a first phase, the programfocuses on integrating III-V and III-N standalone devices on a 200mmand 300mmSi platform. Specific process steps and modules are being developed that have been identified as critical for the integration.
/ ELECTRONICS
Figure 1: Imec houses several key
roof and is therefore well technologies under one
placed to develop hybrid Si/III-V RF front-end technologies for 5G applications
In a second phase, the programwill target the co-integration of the specialised high-speed III-V/ III-N
devices (used for the RF front-end) with standard Si CMOS (u transceiver and digit
This way, a higher degree of integration will be achieved – resulting in a reduced formfactor, and in an improved energy efficiency of the overall circuit. Several approaches for the c being explored, such
integration (with the Si devices and III- V/III-N devices in the same plane) or 3D integration (via either 3D stacking, or sequential 3D through the sequential processing of different device layers).
LEVERAGING EXISTING SOLUTIONS The analogue/RF programleverages imec’s expertise in III-N technology, such as its GaN-on-200mmSi technology platform. Originally developed for power electronics applications, the team investigates how these GaN-on-Si devices can be tuned towards RF
applications. imec uses its expertise on sub-6GHz andmm-wave wireless communication technologies.
Bringing together expertise in III-V and III-N technology, CMOS technology, wireless communication technologies, and inmodelling and circuit design technologies will be crucial to take RF beyond the speed and power limits of CMOS technologies.
imec
www.imec-int.com T: +32 16 28 12 11
e:
info@imec.be ELECTRONICS | MARCH 2019 25
al signal processing). sed for the
as monolithic or 2D o-integration are
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