RBB & FBB in FDSOIRBB & FBB in FDSOI

Philippe FLATRESSE, PhDFDSOI Expert, Business Development

Body Bias advantages

A key differentiator offering full flexibility in FD-SO I

Performance boost

Power optimization

2

Power optimization

Easy implementation

Process , T° and aging compensation

Extended Body Bias Range in UTBB FD -SOI

IGIDL(RBB)

IPN(FBB)

NMOS PMOS

3

BULK UTBB FD-SOI

noBB

FBBRBB

-300mV +300mV

noBB

FBBRBB-2V +2V

[Flatresse ISPLED 2014]

UTBB FD-SOI: Extended Body Voltage Range

• RVT: Conventional Well (CW) - RBB

p-Well n-Well

NMOS PMOSGndsn VddspnoBB

FBBRBB

+2V-2V

Vdd/2+ 300mV

4

-2V

• LVT: Flip Well (FW) - FBB

n-Well p-Well

NMOS PMOSGndsn Gndsp

Vdd/2+ 300mV

noBB

FBBRBB

+2V

-300mV[Flatresse et al. ISSCC 2013]

Body Bias Efficiency - Silicon Benchmark

FBB /LVT

5

RVT / RBB

[Pelloux-Prayer et al. S3S 2014]

Body Bias Usage – 6 different scenariosPerformance boosting

1.1V

Total Power

1.1VFBB

6

0.6V

Freq.FBB

Body Bias Usage – 6 different scenariosPerformance boosting

Power optimizationTotal Power

7

0.6V

0.9V

FBB

Freq.

0.8V0.9V

Body Bias Usage – 6 different scenariosPerformance boosting

Power optimization

Leakage saving

8

Body Bias Usage – 6 different scenariosPerformance boosting

Power optimization

Leakage saving

9

Area saving

Body Bias Usage – 6 different scenariosPerformance boosting

Power optimization

Leakage saving

10

Area saving

Yield recovery

Body Bias Usage – 6 different scenariosPerformance boosting

Power optimization

Leakage saving

11

Area saving

Yield recovery

P,T,A Compensation

Or any combination …

Body -Bias Product Use Case

12* Benchmarked with respect to noBB

ULV � Low power � Best mW/MHz � High performance

Courtesy STMicroelectronics

Body Bias - Key deployment steps

Body Bias IPs & Architecture

Product specification

13

Design implementation

Silicon engineering

Trade-off & Choices for Energy Efficiency

(Vdd, PB, BB ) choice becomes a

14

(Vdd, PB, BB ) choice becomes a power-delay trade-off exercise

Built-in Body Bias in your design flow is key !〉ARM Processor

〉Target frequency: 1GHz @ WC/0.85V

〉Two FD-SOI implementations comparison〉Standard WC methodology

〉SS corner compensated with 600mV FBB

15

Sign-off Standard Built-in BB

Area 1 0.95x

Total Power @ Vmax, 125C, RCmax

1 0.75x

Leakage @ Vmax, 125C

1 0.7x

Courtesy STMicroelectronics

FBB “Process Compensation” principle

FBB(to accelerate transitors speed)

NO FBB

CORNER BB

FF 0.0V

16

FFFFSS

TTTT

SS

Slow partFrequency, Power and area Gain

Fast parts unchanged

FF 0.0V

TT 0.3V

SS 0.6V

Body Bias - Key deployment steps

Body Bias IPs & Architecture

Product specification

17

Design implementation

Silicon engineering

Body-Bias Generator – a key IP

L

E

V

EchN

chP

nwell

VDD1V8

Neg.

Boot-

Strap

VDD1V8

GND

φ1

φ

φ2

φ

Cfly

pwellCharger

nwellChargerL

E

V

E

VDD1V0

VDD1V8

VDD1V0

VDD1V8

ON OFF

• Fully integrated generator for the NMOS/PMOS body voltage generation

• 50/100 mV FBB steps up to 1.8 V

gnds grid

PW

NM

OS

NWNW

18

E

L

S

H

I

F

T

dchN

dchP

pwell

GND

GND

Neg.

Boot-

Strap

GND

φ1 φ2

pwellDischarger

nwellDIscharger

E

L

S

H

I

F

T

ON OFF

ON OFF

ON OFF

ON OFF

• Charging and discharging well capacitances, challenge –Vss

• Switched capacitors generate negative bias and pump substrate

[Blagojevic et al. VLSI 2016]

PW

PW

NM

OS

PM

OS

D-N

WP

-SU

BNW

vdds grid

BB generators offer 19

〉Compact, Fully-Integrated

〉 Low-Power, High-Precision

〉Wide-Range, Positive and Negative

〉Towards a Body-Bias Compiler:

BB Brain

- DAC- Samplers- Comparators- Decision logic- Digital interface

BB DRIVER

- Positive & Negative charge pumps

High Level PMU

Version LVT HP LVT Comp RVT IoT

BB Well Area 1mm 2 1mm 2 1mm 2

Settling time 0.1us 100us 1000µs

Frequency 1GHz 500MHz 100MHz

Avg. Power 100uW 10uW 0.1µW

IP Area total 0.02mm² 0.01mm² 0.005mm²

[Flatresse LETI Days 2015]

IP requirement for Body-Bias

Open loop with On-chip BBG

IPs

BBgen

On Chip Sensors

BBG

control

bb-fing

driver #1

pwell

nwell

chP

chN

dchP

dchN

Power

Management

Unit (PMU)bb-fing

driver #1BBG

driver #1pwell-nwell

power grid

Debug & Trace

Registers (DTR)

I/O

20

Voltage sensor

Temperature sensor

OTP memory

FBBmin + NvsP search algo

Body Bias compensation Type vs VDD

21[Mhira et al. TCAS 2017]

Body-Bias Architecture SelectionOpen loop with

Off-chip BBGOpen loop with

On-chip BBGClosed loop with

On chip BBG

22

• For >0.9V

• FBB/Power

• For >0.9V

• FBB/Power/Process Comp.

• For full voltage range

• FBB/Power/PTA Comp

Body Bias - Key deployment steps

Body Bias IPs & Architecture

Product specification

23

Design implementation

Silicon engineering

Process compensation with Body Bias Implementation example

〉Multi-cores running @1GHz

〉Complexity ~50M gates

〉Body Bias Area: 80%

24

On Chip Monitors V/T SensorBBGen OTP

〉Body Bias Area: 80%

〉Power Supply 0.9V – Temp Inversion

Body Bias Island

Body-Bias for Process compensation - SpeedAfter

TrimmingBefore

Trimming

25

SSSS

FF

SS

FF

Freq (MHz) Freq (MHz)

+15% Speed increase wrt no BB

4X process spread reduction

15% Yield recovery

Courtesy STMicroelectronics

Frequency and leakage control with body bias

Leakage limit

IDD

Q

Trimmed

Untrimmed

26

〉Spread reduced for both frequency (4X) and leakage (2X)

IDD

Q

SS

FF

Courtesy STMicroelectronics

Full Vddmin control with FBBPre/Post TRIM

Before Trimming After PMB

Trimming

Vddmin reduction thanks to BB

27

Vm

inV

ddm

in

Vdd

min

FF SS

Courtesy STMicroelectronics

FF SS

Body Bias - Key deployment steps

Body Bias IPs & Architecture

Product specification

28

Design implementation

Silicon engineering

FBB “Process Compensation” calibration

Store BB in Store BB in

Search BB

Begin EWS

Production Test at ST(EWS)

Application (at

Optimal Body Bias level is defined Die by Die depending on Speed/Power characteristic

measured on “on chip monitors”

29

Normal operation

Read OTP BB

Set BB

Start-upEnd EWS

Store BB in OTP

Store BB in OTP Application (at

Boot)Optimal Body Bias level is stored in One Time

Programmable memoryTHEN

Read at Boot

An Embedded circuit (Body Bias Generator) set that Bias

level

VBB min Search

VDD and Temp condition for calibration Algorithm setting via frequency target and max allowable VBB

Algorithms to find common VBBN/VBBP, only used at EWS and start-up

VDD, tempVBBmax, Ftarget

Begin

VBBN=VBBP min search

NMOS vs PMOS

30

NMOS and PMOS separate measurement

Final VBBN and VBBP adjust by +/- 1 or 2 step;Guaranties minVBB with F >Ftarget

Stored in OTP for EWS calibration then in BBgen register for others

NMOS vs PMOSVBB offset calculation

+/- 1 or 2 VBB stepFinal adjust

Store VBBN, VBBP

end

BB compensation based on on -chip monitorsF

requ

ency

Frequency Target

31

BB codes distribution per wafer

SS

TT

Body-Bias code

Full distribution within target range. Thanks to FBB based Process compensation

TT

FF

Courtesy STMicroelectronics

The future is body bias adaptive ! 〉Adaptive voltage control will also be used to maximize performance and yields

32

Dynamic Body-Bias for P, T,A compensation

[Flatresse NEWCAS 2015]

Adaptive Body -Bias for Aging compensation〉Progressive degradation modes (BTI, HCI, TID) are captured by canary FF solutions

〉Compensation through ABB is possible under real-tim e conditions

33[Mhira et al. IRPS 2017]

PULPv3 SoC – RVT Conventional well

SOCDOMAIN T

CD

PROCESSMONITORINGBLOCKS

TEMPERATURE SENSORBODY BIAS GENERATORS

ROM

� PULP: Parallel Ultra-Low-Power Platform

� 4-cores near-threshold processor

� Frequency Range:

� 20 MHz @ 0.5V - 200 MHz @ 0.7V

� On-Chip Body Bias Generator

� Average power: 4,15 µW

� Body Bias Range: -1.5V to 0.4VCLUSTERDOMAIN

DM

L2

� Body Bias Range: -1.5V to 0.4V

RVT-based design with Body-Biasing Key flavor for IoT

PULP

35

Figure of merit @ 0.5V Vdd

FBB 0.5V � 160% Higher Freq RBB -1.8V � 10X Less Leakage

[Rossi , HCS 2015]

PULP: RBB/FBB frequency boosting

〉Body Bias varying from -1.0V to +0.5V

Frequency100Mhz

300Mhz

0.5V FBB

36

Body Bias

Leakage

-1.0V FBB

0.5V FBB

30µA

3000 µA

FDSOI & Body Biasing - Take away

〉True back gate solution for ultimate Vt control

〉Built-in Body Bias in the design is key, easy to implement !

〉Up to 200% performance boost and 10X leakage reduction at low voltage

〉Significant Vddmin reduction, leading to power saving and reliability relaxation

〉Variability spread reduction

〉FDSOI offers unique Body Bias control loop solutions for P,T,A compensation

〉Enabling/Disabling BB allows to create several product variants

Thank you !