Post on 04-Feb-2021
transcript
AK Bipolar, Campeon Munich
November 14, 2012
IHP Im Technologiepark 25 15236 Frankfurt (Oder) Germany www.ihp-microelectronics.com © 2012
Substrate Coupling for 500GHz HBTs
Dr. Gerhard Fischer
Substrate Network @ AK Bipolar 2012 2 © 2012 - All rights reserved
Problem: Power Gain or fmax Above 100 GHz
Strong
function of
substrate
resistance!
Don’t care
for
substrate
resistance!
GU(f) as function of Rsub = 1Ω …1kΩ
Substrate Network @ AK Bipolar 2012 3 © 2012 - All rights reserved
Starting Point
• It is well-known that
𝑓𝑚𝑎𝑥 𝑓 = Mag(𝐺𝑈)0.5 ∙ 𝑓
is not constant in general.
• Assuming other parameters like base and collector resistances, collector-substrate
and collector-base capacitances, NQS parameters to be fixed.
• 𝑓𝑚𝑎𝑥 𝑓 for high frequencies as function of the “substrate network” has to be
worked out
for Gummel-Poon substrate resistor RSub in series to CCS,
for HICUM CSub parallel to RSub added (because of substrate permittivity).
Substrate Network @ AK Bipolar 2012 4 © 2012 - All rights reserved
Fmax (Frequency) as Function of Rsub
Minimum fmax for
RSub ≈ 100 Ω
0 200 400 600 800 1000
350
400
450
500
Extr
ap
ola
ted
fm
ax @
30
0 G
Hz
Substrate Resistance [ Ohm ]
Substrate Network @ AK Bipolar 2012 5 © 2012 - All rights reserved
Simulation of CCS(f)
Substrate Ring Variations
Substrate Network @ AK Bipolar 2012 6 © 2012 - All rights reserved
Determination of Substrate RC Network
• DUT: HBT (Emitter area: 4x0.13x10.16 µm²) with guard ring variations:
Variable distance active collector – guard ring
1 µm
3 µm
20 µm
Substrate Network @ AK Bipolar 2012 7 © 2012 - All rights reserved
CCS(V) as Function of Frequency I
• From S parameters: 𝐶𝐶𝑆 =Imag 𝑌22+𝑌12
2𝜋𝑓
Distance DUT – Guard Ring:
1 µm
3 µm
20 µm
Simulation with constant
RSub = 10 Ω
Substrate Network @ AK Bipolar 2012 8 © 2012 - All rights reserved
• From S parameters: 𝐶𝐶𝑆 =Imag 𝑌22+𝑌12
2𝜋𝑓
CCS(V) as Function of Frequency II
Distance DUT - GR
1 µm
3 µm
20 µm
Simulation with variable
RSub only
RSub
Substrate Network @ AK Bipolar 2012 9 © 2012 - All rights reserved
• From S parameters: 𝐶𝐶𝑆 =Imag 𝑌22+𝑌12
2𝜋𝑓
CCS(V) as Function of Frequency III
Simulation with
RSub + CSub
RSub
CSub
CCS
[fF]
RSub
[Ω]
CSub
[fF]
1u
5.50
500 120
3u 750 50
20u 2500 33
Substrate Network @ AK Bipolar 2012 10 © 2012 - All rights reserved
• From S parameters: 𝐶𝐶𝑆 =Imag 𝑌22+𝑌12
2𝜋𝑓
CCS(V) as Function of Frequency IV
Simulation with
RSub + Csub + Rsub_2
Rsub
Csub
CCS
[fF]
RSub
[Ω]
Csub
[fF]
Rsub_2
[Ω]
1u
5.50
560 95 100
3u 820 42 140
20u 2600 31 110
RSub_2
Substrate Network @ AK Bipolar 2012 11 © 2012 - All rights reserved
• IHP bipolar technology SG13G2 (AE = 0.12x0.95 µm²)
• HBT variants with emitter numbers 1 – 8
• Constant distance HBT active collector to guard ring (2 µm)
Substrate Network for SG13G2 I
4Nx = 1 Nx = 4 Nx = 8
2 µm
Substrate Network @ AK Bipolar 2012 12 © 2012 - All rights reserved
Substrate Network for SG13G2 II
Nx = 1 Nx = 4 Nx = 8
Low ohmic
version
Rsub = 50/Nx
Drastic reduction
above 100GHz
VBE = 0.92V
VCE = 1.2V
Substrate Network @ AK Bipolar 2012 13 © 2012 - All rights reserved
Substrate Network for SG13G2 III
Nx = 1 Nx = 4 Nx = 8
Fitted Substrate Network
Rsub = 500 + 6000/Nx
Csub = 2.7fF + 2.84fFNx
Less reduction
above 200GHz
VBE = 0.92V
VCE = 1.2V
Substrate Network @ AK Bipolar 2012 14 © 2012 - All rights reserved
0 1 2 3 4 5 6 7 8 90
1000
2000
3000
4000
5000
6000
RS
ub
[ ]
Nx
• Scaling of substrate resistance and capacitance
Substrate Network for SG13G2 IV
0 1 2 3 4 5 6 7 8 90
2
4
6
8
10
CC
S [ fF
]
Nx
0
5
10
15
20
25
30
CSub [ fF
]
Substrate Network @ AK Bipolar 2012 15 © 2012 - All rights reserved
• Variation of substrate resistance and capacitance
• The strong differences in power gain of the Nx=1 and Nx=8 devices are not
caused by the substrate network.
• RSub in actual HBT already very high RSubCSub optimization not necessary?
Substrate Network for SG13G2 V
Nx = 1
Nx = 8
CSub =
1fF…100fF
CSub =
1fF…100fF
Substrate Network @ AK Bipolar 2012 16 © 2012 - All rights reserved
Substrate Network for SG13G2 VI
Nx = 1 Nx = 4 Nx = 8
Introduction of RSub_2 = 100Ω
Better fit for f >10GHz
But worse fmax(f) !!!!!!!!!!!
Increased reduction above 200GHz VBE = 0.92V VCE = 1.2V
2 µm
Substrate Network @ AK Bipolar 2012 17 © 2012 - All rights reserved
SG13G2 - HICUM
Nx = 1 Nx = 4 Nx = 8
Parameters:
alit = 1
alqf = 0
Parameters:
rsu, csu