#do We Have Rf Performance Degradation Due To Substrate Noise
This document was uploaded by user and they confirmed that they have the permission to share it. If you are author or own the copyright of this book, please report to us by using this DMCA report form. Report DMCA
Overview
Download & View #do We Have Rf Performance Degradation Due To Substrate Noise as PDF for free.
More details
- Words: 1,559
- Pages: 30
Do We Have RF Performance Degradation Due To Substrate Noise?
Domine Leenaerts Philips Research Labs.
Domine Leenaerts, Workshop on Substrate Noise-coupling in Mixed-Signal ICs
Contents
Introduction to substrate noise-coupling. What can we do; guard rings. Is this enough? RF examples. Conclusions.
• • • •
Domine Leenaerts, Workshop on Substrate Noise-coupling in Mixed-Signal ICs
Introduction
• Substrate is connecting layer between all circuits on a single die. • If a circuit produces spiky signals (‘noise’) on the substrate, other circuits will ‘feel’ this. • Amount of generated noise on substrate is therefore an issue. You can minimise the influence of substrate coupling but not eliminate it. Domine Leenaerts, Workshop on Substrate Noise-coupling in Mixed-Signal ICs
Introduction; injection paths • PN-junction of MOS (mainly in digital circuits) – capacitive coupling to substrate – can be several hundreds pico Farad for digital
• N-Well
$
+
)*
"
&
# (
&
(
'
%
#
!"
– forms PN-junction with substrate – capacitive coupling between Vdd and substrate
Domine Leenaerts, Workshop on Substrate Noise-coupling in Mixed-Signal ICs
Introduction; injection paths
• Bond wires
/
6
45
-
1
. 3
1
3
2
0
.
,-
– MOS logic produces spikes on supply lines – Vss tightly connected to substrate – vdrop = Lbondwire ⋅ dI spike / dt – off-chip, digital ground connected to substrate Domine Leenaerts, Workshop on Substrate Noise-coupling in Mixed-Signal ICs
Introduction; reception paths • Bulk contacts – substrate is connected to ground via bulk contacts – resistive coupling
• PN-junction MOS / N-Well – capacitive coupling into supply lines – capacitive coupling into signal lines
• Backgate MOS :
A
?@
8
<
9 >
<
>
=
;
9
78
– injection into signal path Domine Leenaerts, Workshop on Substrate Noise-coupling in Mixed-Signal ICs
Introduction • Used technology is important
E
L
JK
C
G
D I
G
I
H
F
D
BC
– high resistive substrate – low resistive substrate on high resistive epi
Domine Leenaerts, Workshop on Substrate Noise-coupling in Mixed-Signal ICs
Introduction; problem?
P
W
UV
N
R
O T
R
T
S
Q
O
MN
• 2nd order low pass Sigma-Delta Mod • 0.25 µm CMOS, 10 mΩ.cm substrate on top of 11 Ω.cm epi of 3 µm • 1.8 V supply voltage • separate digital/analogue power lines • design rules to minimise substrate bounces applied Domine Leenaerts, Workshop on Substrate Noise-coupling in Mixed-Signal ICs
Introduction; problem? 8 bit 1 MHz
13.5 MHz
Filter
Quantizer
[
1 bit 216 MHz
b
`a
Y
]
Z _
]
_
^
\
Z
XY
DAC
Decimation
Domine Leenaerts, Workshop on Substrate Noise-coupling in Mixed-Signal ICs
Introduction; problem?
20dB
Clock off
Clock on
f
m
kl
d
h
e j
h
j
i
g
e
cd
Measured spectrum of signal at substrate Domine Leenaerts, Workshop on Substrate Noise-coupling in Mixed-Signal ICs
What can we do? Some people claim that you must use p-guard rings and n-guard rings around your circuits. We have tested this opinion for a 0.18 µm CMOS technology using high and low resistive substrate
q
x
vw
o
s
p u
s
u
t
r
p
no
(J. Pluymakers et.al. PS-LTG AMOS)
Domine Leenaerts, Workshop on Substrate Noise-coupling in Mixed-Signal ICs
Guard rings • 10 mΩ.cm substrate of 200 µm on top of 11 Ω.cm epi of 3 • 10 Ω.cm substrate of 200 µm
|
z
~
{
~
}
{
yz
Vdd
Domine Leenaerts, Workshop on Substrate Noise-coupling in Mixed-Signal ICs
Guard rings
Domine Leenaerts, Workshop on Substrate Noise-coupling in Mixed-Signal ICs
Guard rings
13 dB improvement of suppression relative to the situation without P-ring
Domine Leenaerts, Workshop on Substrate Noise-coupling in Mixed-Signal ICs
Guard rings
Only 4 dB improvement!
¤
¢£
¡
¡
N-Ring deteriorates the effect of the P-ring
Domine Leenaerts, Workshop on Substrate Noise-coupling in Mixed-Signal ICs
Guard rings; low ohmic substrate • N-ring around RF circuit does not help you • P-ring around RF circuit gives -13 dB improvement compared to no ring – Nail the substrate as good as possible to the ground
• Use N-ring only around your source of noise
¨
¯
®
¦
ª
§ ¬
ª
¬
«
©
§
¥¦
– collect ‘wandering’ electrons
Domine Leenaerts, Workshop on Substrate Noise-coupling in Mixed-Signal ICs
Guard rings; high ohmic substrate • N-ring around RF circuit does not help you • P-ring around RF circuit gives -40 dB improvement compared to no ring • Place source as far away as possible – 50 µm: -34 dB, 100 µm: -40 dB (reference: -24 dB)
³
º
¸¹
±
µ
² ·
µ
·
¶
´
²
°±
• Use N-ring only around your source of noise
Domine Leenaerts, Workshop on Substrate Noise-coupling in Mixed-Signal ICs
Is this enough? • Consider the low ohmic substrate • Can the substrate noise influence the RF performance of a certain circuit?
¾
Å
ÃÄ
¼
À
½ Â
À
Â
Á
¿
½
»¼
• Test circuit in 0.25 µm CMOS, 10 mΩ.cm substrate on top of 11 Ω.cm epi of 3 µm
Domine Leenaerts, Workshop on Substrate Noise-coupling in Mixed-Signal ICs
RF example: circuit 1
2
11
buffer
substrate
0.2
-15
0 -0.2 -0.4
-0.8
0
2
4
4
6 x 10
9
-0.8 s 22 (dB)
s 21 (dB) Ë
Ç ÎÏ
Ð
ÆÇ
É
È
È
Ê Ì
2
-0.6
-6
-1 -1.2
-8
Í
0
9
-4
-10
Ë
-25 -30
6 x 10
0
Í
-20
-0.6
-2
Domine Leenaerts, Workshop on Substrate Noise-coupling in Mixed-Signal ICs
clock out C
s 12 (dB)
11-stage ring oscillator center freq. 772 MHz Unmatched LNA: 2-5 GHz Wafer probe measurements: substrate noise due to pnjunction mechanism
s 11 (dB)
• • • •
Vtune
0
2 4 fre que nc y
6 x 10
9
-1.4
0
2 4 freque nc y
6 x 10
9
Ô
Û
ÙÚ
Ò
Ö
Ó Ø
Ö
Ø
×
Õ
Ó
ÑÒ
RF example: circuit
Domine Leenaerts, Workshop on Substrate Noise-coupling in Mixed-Signal ICs
RF example: circuit • Spectrum substrate • inside guard ring • LNA off
fundamental 2nd harmonic
ß
æ
äå
Ý
á
Þ ã
á
ã
â
à
Þ
ÜÝ
3rd harmonic
Domine Leenaerts, Workshop on Substrate Noise-coupling in Mixed-Signal ICs
RF example: circuit 2.3 GHz 772 MHz
ê
LNA and clock operational; spectrum at output LNA
ñ
ïð
è
ì
é î
ì
î
í
ë
é
çè
Only LNA is operational @ 2.3 GHz; spectrum at output LNA
2.3 GHz & 3rd harmonic of 772 MHz
Domine Leenaerts, Workshop on Substrate Noise-coupling in Mixed-Signal ICs
RF example: circuit; conclusion
õ
ü
úû
ó
÷
ô ù
÷
ù
ø
ö
ô
òó
• Not only amplified RF input signal at output LNA, but also (weakened) injected substrate noise at the drain. DISTORTION! • If LNA has gain, then substrate noise injected at RF input will be amplified. • S-parameters did not change, performance LNA is not changed due to substrate noise. Domine Leenaerts, Workshop on Substrate Noise-coupling in Mixed-Signal ICs
RF example: system • What if you have large digital circuitry and RF circuitry on the same substrate?
þ
ÿ
ÿ
ýþ
• Test circuit in 0.18 µm CMOS, 10 Ω.cm substrate
Domine Leenaerts, Workshop on Substrate Noise-coupling in Mixed-Signal ICs
RF example: system
• RF front-end @ 2.45 GHz • 500 kgates digital • 1.8 V
Domine Leenaerts, Workshop on Substrate Noise-coupling in Mixed-Signal ICs
RF example: system
• VCO runs at 2.45 GHz • Clock for digital is tuneable • Measure output spectrum VCO
Domine Leenaerts, Workshop on Substrate Noise-coupling in Mixed-Signal ICs
RF example: system
(
#
!
&'
%
#
%
$
"
Clock digital off Domine Leenaerts, Workshop on Substrate Noise-coupling in Mixed-Signal ICs
Clock digital: 13 MHz
RF example: system
,
3
12
*
.
+ 0
.
0
/
-
+
)*
Clock digital: 40 MHz Domine Leenaerts, Workshop on Substrate Noise-coupling in Mixed-Signal ICs
Clock digital: 64 MHz
RF example: system; conclusion
7
>
<=
5
9
6 ;
9
;
:
8
6
45
• FM modulation between digital clock switching and VCO • Can not be prevented by guard ring techniques. • Only smart system design can minimise the effects of substrate noise on system performance
Domine Leenaerts, Workshop on Substrate Noise-coupling in Mixed-Signal ICs
Concluding remarks
B
I
GH
@
D
A F
D
F
E
C
A
?@
• Yes, substrate noise coupling is an important issue in RF design • Yes, guard rings together with high ohmic substrate reduce the coupling • Yes, smart system and circuit design can reduce it too • No, you can not eliminate it Domine Leenaerts, Workshop on Substrate Noise-coupling in Mixed-Signal ICs
Domine Leenaerts Philips Research Labs.
Domine Leenaerts, Workshop on Substrate Noise-coupling in Mixed-Signal ICs
Contents
Introduction to substrate noise-coupling. What can we do; guard rings. Is this enough? RF examples. Conclusions.
• • • •
Domine Leenaerts, Workshop on Substrate Noise-coupling in Mixed-Signal ICs
Introduction
• Substrate is connecting layer between all circuits on a single die. • If a circuit produces spiky signals (‘noise’) on the substrate, other circuits will ‘feel’ this. • Amount of generated noise on substrate is therefore an issue. You can minimise the influence of substrate coupling but not eliminate it. Domine Leenaerts, Workshop on Substrate Noise-coupling in Mixed-Signal ICs
Introduction; injection paths • PN-junction of MOS (mainly in digital circuits) – capacitive coupling to substrate – can be several hundreds pico Farad for digital
• N-Well
$
+
)*
"
&
# (
&
(
'
%
#
!"
– forms PN-junction with substrate – capacitive coupling between Vdd and substrate
Domine Leenaerts, Workshop on Substrate Noise-coupling in Mixed-Signal ICs
Introduction; injection paths
• Bond wires
/
6
45
-
1
. 3
1
3
2
0
.
,-
– MOS logic produces spikes on supply lines – Vss tightly connected to substrate – vdrop = Lbondwire ⋅ dI spike / dt – off-chip, digital ground connected to substrate Domine Leenaerts, Workshop on Substrate Noise-coupling in Mixed-Signal ICs
Introduction; reception paths • Bulk contacts – substrate is connected to ground via bulk contacts – resistive coupling
• PN-junction MOS / N-Well – capacitive coupling into supply lines – capacitive coupling into signal lines
• Backgate MOS :
A
?@
8
<
9 >
<
>
=
;
9
78
– injection into signal path Domine Leenaerts, Workshop on Substrate Noise-coupling in Mixed-Signal ICs
Introduction • Used technology is important
E
L
JK
C
G
D I
G
I
H
F
D
BC
– high resistive substrate – low resistive substrate on high resistive epi
Domine Leenaerts, Workshop on Substrate Noise-coupling in Mixed-Signal ICs
Introduction; problem?
P
W
UV
N
R
O T
R
T
S
Q
O
MN
• 2nd order low pass Sigma-Delta Mod • 0.25 µm CMOS, 10 mΩ.cm substrate on top of 11 Ω.cm epi of 3 µm • 1.8 V supply voltage • separate digital/analogue power lines • design rules to minimise substrate bounces applied Domine Leenaerts, Workshop on Substrate Noise-coupling in Mixed-Signal ICs
Introduction; problem? 8 bit 1 MHz
13.5 MHz
Filter
Quantizer
[
1 bit 216 MHz
b
`a
Y
]
Z _
]
_
^
\
Z
XY
DAC
Decimation
Domine Leenaerts, Workshop on Substrate Noise-coupling in Mixed-Signal ICs
Introduction; problem?
20dB
Clock off
Clock on
f
m
kl
d
h
e j
h
j
i
g
e
cd
Measured spectrum of signal at substrate Domine Leenaerts, Workshop on Substrate Noise-coupling in Mixed-Signal ICs
What can we do? Some people claim that you must use p-guard rings and n-guard rings around your circuits. We have tested this opinion for a 0.18 µm CMOS technology using high and low resistive substrate
q
x
vw
o
s
p u
s
u
t
r
p
no
(J. Pluymakers et.al. PS-LTG AMOS)
Domine Leenaerts, Workshop on Substrate Noise-coupling in Mixed-Signal ICs
Guard rings • 10 mΩ.cm substrate of 200 µm on top of 11 Ω.cm epi of 3 • 10 Ω.cm substrate of 200 µm
|
z
~
{
~
}
{
yz
Vdd
Domine Leenaerts, Workshop on Substrate Noise-coupling in Mixed-Signal ICs
Guard rings
Domine Leenaerts, Workshop on Substrate Noise-coupling in Mixed-Signal ICs
Guard rings
13 dB improvement of suppression relative to the situation without P-ring
Domine Leenaerts, Workshop on Substrate Noise-coupling in Mixed-Signal ICs
Guard rings
Only 4 dB improvement!
¤
¢£
¡
¡
N-Ring deteriorates the effect of the P-ring
Domine Leenaerts, Workshop on Substrate Noise-coupling in Mixed-Signal ICs
Guard rings; low ohmic substrate • N-ring around RF circuit does not help you • P-ring around RF circuit gives -13 dB improvement compared to no ring – Nail the substrate as good as possible to the ground
• Use N-ring only around your source of noise
¨
¯
®
¦
ª
§ ¬
ª
¬
«
©
§
¥¦
– collect ‘wandering’ electrons
Domine Leenaerts, Workshop on Substrate Noise-coupling in Mixed-Signal ICs
Guard rings; high ohmic substrate • N-ring around RF circuit does not help you • P-ring around RF circuit gives -40 dB improvement compared to no ring • Place source as far away as possible – 50 µm: -34 dB, 100 µm: -40 dB (reference: -24 dB)
³
º
¸¹
±
µ
² ·
µ
·
¶
´
²
°±
• Use N-ring only around your source of noise
Domine Leenaerts, Workshop on Substrate Noise-coupling in Mixed-Signal ICs
Is this enough? • Consider the low ohmic substrate • Can the substrate noise influence the RF performance of a certain circuit?
¾
Å
ÃÄ
¼
À
½ Â
À
Â
Á
¿
½
»¼
• Test circuit in 0.25 µm CMOS, 10 mΩ.cm substrate on top of 11 Ω.cm epi of 3 µm
Domine Leenaerts, Workshop on Substrate Noise-coupling in Mixed-Signal ICs
RF example: circuit 1
2
11
buffer
substrate
0.2
-15
0 -0.2 -0.4
-0.8
0
2
4
4
6 x 10
9
-0.8 s 22 (dB)
s 21 (dB) Ë
Ç ÎÏ
Ð
ÆÇ
É
È
È
Ê Ì
2
-0.6
-6
-1 -1.2
-8
Í
0
9
-4
-10
Ë
-25 -30
6 x 10
0
Í
-20
-0.6
-2
Domine Leenaerts, Workshop on Substrate Noise-coupling in Mixed-Signal ICs
clock out C
s 12 (dB)
11-stage ring oscillator center freq. 772 MHz Unmatched LNA: 2-5 GHz Wafer probe measurements: substrate noise due to pnjunction mechanism
s 11 (dB)
• • • •
Vtune
0
2 4 fre que nc y
6 x 10
9
-1.4
0
2 4 freque nc y
6 x 10
9
Ô
Û
ÙÚ
Ò
Ö
Ó Ø
Ö
Ø
×
Õ
Ó
ÑÒ
RF example: circuit
Domine Leenaerts, Workshop on Substrate Noise-coupling in Mixed-Signal ICs
RF example: circuit • Spectrum substrate • inside guard ring • LNA off
fundamental 2nd harmonic
ß
æ
äå
Ý
á
Þ ã
á
ã
â
à
Þ
ÜÝ
3rd harmonic
Domine Leenaerts, Workshop on Substrate Noise-coupling in Mixed-Signal ICs
RF example: circuit 2.3 GHz 772 MHz
ê
LNA and clock operational; spectrum at output LNA
ñ
ïð
è
ì
é î
ì
î
í
ë
é
çè
Only LNA is operational @ 2.3 GHz; spectrum at output LNA
2.3 GHz & 3rd harmonic of 772 MHz
Domine Leenaerts, Workshop on Substrate Noise-coupling in Mixed-Signal ICs
RF example: circuit; conclusion
õ
ü
úû
ó
÷
ô ù
÷
ù
ø
ö
ô
òó
• Not only amplified RF input signal at output LNA, but also (weakened) injected substrate noise at the drain. DISTORTION! • If LNA has gain, then substrate noise injected at RF input will be amplified. • S-parameters did not change, performance LNA is not changed due to substrate noise. Domine Leenaerts, Workshop on Substrate Noise-coupling in Mixed-Signal ICs
RF example: system • What if you have large digital circuitry and RF circuitry on the same substrate?
þ
ÿ
ÿ
ýþ
• Test circuit in 0.18 µm CMOS, 10 Ω.cm substrate
Domine Leenaerts, Workshop on Substrate Noise-coupling in Mixed-Signal ICs
RF example: system
• RF front-end @ 2.45 GHz • 500 kgates digital • 1.8 V
Domine Leenaerts, Workshop on Substrate Noise-coupling in Mixed-Signal ICs
RF example: system
• VCO runs at 2.45 GHz • Clock for digital is tuneable • Measure output spectrum VCO
Domine Leenaerts, Workshop on Substrate Noise-coupling in Mixed-Signal ICs
RF example: system
(
#
!
&'
%
#
%
$
"
Clock digital off Domine Leenaerts, Workshop on Substrate Noise-coupling in Mixed-Signal ICs
Clock digital: 13 MHz
RF example: system
,
3
12
*
.
+ 0
.
0
/
-
+
)*
Clock digital: 40 MHz Domine Leenaerts, Workshop on Substrate Noise-coupling in Mixed-Signal ICs
Clock digital: 64 MHz
RF example: system; conclusion
7
>
<=
5
9
6 ;
9
;
:
8
6
45
• FM modulation between digital clock switching and VCO • Can not be prevented by guard ring techniques. • Only smart system design can minimise the effects of substrate noise on system performance
Domine Leenaerts, Workshop on Substrate Noise-coupling in Mixed-Signal ICs
Concluding remarks
B
I
GH
@
D
A F
D
F
E
C
A
?@
• Yes, substrate noise coupling is an important issue in RF design • Yes, guard rings together with high ohmic substrate reduce the coupling • Yes, smart system and circuit design can reduce it too • No, you can not eliminate it Domine Leenaerts, Workshop on Substrate Noise-coupling in Mixed-Signal ICs
Related Documents
Performance Degradation Due To Iq Imbalance In
November 2019 7
Do We Have. Eternal Security
October 2019 18
How Long Do We Have
June 2020 18
