Transcript 1 A Novel Model for An Integrated RF CMOS Schottky Diode

A Novel Model for An
Integrated RF CMOS
Schottky Diode
Xi-NingWang*, Bin Zhu, Jian-Kun Su, Ting-Huang Lee,
Li-Wu Yang
RF Group, Design Services Department, Semiconductor
Manufacturing International Corporation, Shanghai 201203,
P.R. China
*Email: [email protected],
[email protected], [email protected]
Adviser ：何彥仕 老師
Presented by 孫嘉偉
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Abstract
In this paper an interdigital n-type CoSi2-Si Schottky diode is
fabricated in SMIC 0.18 μ m RF CMOS process.
The novel model fits the measurement very well for different
voltage biases over the wide frequency range of 0.05GHz to
8.5GHz.
A type of four stages charge pump is designed using this new
Schottky diode model, the design charge pump can get
efficiency of 40%.
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Outline
Introduction
Designs and fabrication of Schottky diodes
Novel Model of RF CMOS Schottky Diode
Characterizations and discussion
Application
Summary
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Introduction
Schottky diodes due to their high operating frequency,
fast switching speed and low forward voltage drop have
been widely used in RF power detection circuits, mixers and
low-voltage reference circuits .
In order to design SBD (Schottky Barrier Diode) rectifier or
detector in a CMOS RF Transceiver chip, accurate and
reliable simulation of DC and RF characteristics of the
Schottky diode is required.
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Designs and fabrication of Schottky diodes
In our work an interdigital Schottky diode with a total area of
40μm2
is designed, the interdigital Schottky contacts have an area of
1μm×4μm.
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Novel Model of RF CMOS Schottky Diode
For a Schottky diode with series resistance, the net current of the
device can be expressed as
  q

V  IRs 
I  I 0 exp 

  nkT
(1)
The reverse saturation current I0 can be expressed as
I 0  A AT exp  qB / kT 
*
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(2)
Ideality factor n is contained in the slope of straight-line region of
the forward-bias logarithmic I-V characteristics through the
relation
q
d (V ) / d ln( I )
n
kT
(3)
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Novel Model of RF CMOS Schottky Diode
The values of ΦB and n are 0.43eV and 1.42 (at 300K) for this
Schottky diode, respectively.
The reverse saturation current I0 is about 222.3nA.
The mentioned n-type Silicon Schottky barrier height is about
0.42eV.
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Novel Model of RF CMOS Schottky Diode
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Characterizations and discussion
The Rs of the fabricated Schottky diode is about 21.6Ω.
The turn-on voltage is about 0.34V for this n-type Schottky diode.
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Characterizations and discussion
The leakage current density of this diode is about 0.26μA/μm2
at 1V reverse bias.
The breakdown voltage is about 4V.
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Characterizations and discussion
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Characterizations and discussion
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Characterizations and discussion
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Application
(4)
n is the number of diodes, VRF is the amplitude of the RF input
signal, and VD is the forward voltage of the Schottky diodes,
which is approximately 200mV at 45uA.
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Application
With a full match between the antenna and rectifier at pin=-10dBm,we
can get a VDD=2V at Rload=100Kohm,which the efficiency is about 40%.
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Summary
In this novel model a series resistance was used to
characterize the losses of dielectric and metal plates in high
frequency.
It was shown that there is an excellent agreement between
the measured and modeled performance of the Schottky
diode.
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