Pulsed Laser-Induced Single Event Effects ShiJie Wen Cisco Li Chen University of Saskatchewan June, 2012

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Single Event Laser Introduction An Example Laser Application

Content

SINGLE EVENT

WHAT?

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Single Event Upsets • Cause of Soft errors

– a. Ion creates electron hole pairs in the silicon – b. Charges drift and collect at nodes, producing a prompt current – c. Later charges diffuse toward the nodes, producing lower current

• If the current is large enough, storage nodes such as SRAMs can switch states

R. C. Baumann, IEEE Trans. Device Mater. Reliab., vol. 5(3), p. 305-316, Sept. 2005

Classification

SEU Single Event Upset

MBU Multi-bit Upset

SEL Single Event Latchup

SEB Single Event Burnout

SET Single Event Transient

Soft Error

Hard Error

n+ n+

P substrate

Gate Source Drain

- + - +

- + - +

- + - +

- + - + Energetic Particle

- +

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Single-Event

Laser Introduction

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Wavelength (λ)

Gamma X - ray UV Visible IR Micro Radio

Linear Absorption Coefficient

Photon Energy

Inverse proportion

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Laser Parameters

Pulse Width, Full Width at Half Maximum (FWHM)

Beam diameter, minimum value at one place along the beam axis

Pulse Duration

Pulse Energy

the sum of all the energies of photons in a pulse

Spot Size

Repetition Rate frequency of laser pulses

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Pulsed Laser Parameters

Photon Excitation

Photon Absorption

Photon Emission

Electron

Nucleus

Orbital

Excited Electron

Atom structure Photon & Electron Interaction

Absorption

Emission

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Photon Excitation

Excited State

Ground State

One Photon Absorption

Vibrational Energy (ie. heat)

Photon Emission

A quantum state that has higher energy than that of ground state. Life time is short

The lowest-energy state in a quantum mechanical system

Excitation is in the order

of picoseconds

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Single Photon Excitation

Excited State

Ground State

Virtual State

Photon Emission

Absorption E2

Absorption E1

First absorb E1 , then absorb E2 The interval is within 10-18 seconds Considered simultaneously

E1 and E2should be at least half the energy difference between the two states

E=E1+E2

Imaginary state Does not exist

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Two-Photon Excitation

A quantity that characterizes how easily a material or medium can be penetrated by laser or other energy or matter.

It is measured using units of reciprocal length.

Large Coef means quickly attenuated

Small Coef means relatively transparent

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Absorption Coefficient

TNS 2002 Dale McMorrow

Linear Absorption, one photon at a time

Photon Energy > Si Band Gap

Wavelength < 1.1 um

Feature

Conditions:

Each absorbed photon

A single e-h pair

Absorption Mechanism

(Beer’s Law)

Inject carrier density

Distance from

surface

generate

decrease

exponentially

I(z) = I0exp(-αz)

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Single Photon Absorption

Nonlinear Absorption, two photon simultaneously

Subbandgap

Wavelength > 1.15 um

Feature

Conditions:

Absorption Mechanism

High Intensity

Two absorbed photons

A single e-h pair

generate

2( ) ( ) ( )dI z I z I zdz

α β= − −

α, negligible

β, dominant

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Two-Photon Absorption

3D-mapping of the SEE sensitivity of a device

Backside illumination of circuits

Distinct charge track from that of SPA

charge injection at any depth Well controlled initial condition The ability to control the localization and density of photon generated carriers

Small absorption coefficient, negligible, relatively transparent The ability to penetrate the thick substrate

The generated carriers are highly concentrated in the high-irradiance region near the focus of the beam

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TPA Features

SPA TPA Exponential decrease in carrier density as a function of depth in the material.

The generated carriers are highly concentrated in the high-irradiance region.

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SPA vs. TPA

Electron-Hole Density

TNS 2002 Dale McMorrow

substrate

objective

active area

Application Older Process, Less Metal

Linear Circuits Testing

1. Maturity

1. Metallization issue

2. Limited Penetration Depth

3. Predefined Track Profile

Pros

Cons

2. Simplicity

Mechanism SPA based ,e.g. 800 nm, 920 nm

focused on surface

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Front Side Irradiation

substrate

objective

active area

Mechanism

1. Thinning, when λ < 1 um

Application

SPA based ,e.g. 1064 nm

TPA based, e.g. 1.26 um

Highly Scaled Memories

Flip – Chip Package

2. Polishing to minimize diffusion

1. Controlled Depth

2. Metallization issue free

3. Constant laser intensity

focused on any depth

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Back Side Irradiation

Pros

Cons

Verdi

Mira Pulse Picker

Optics

532 nm CW 10 W

700 nm – 1000 nm 76 MHz fs and ps level

DUT

(attenuator)

XY stage

Inverter

Detector for visible

(Photon Multiplier Tube)

Reflected mode

Transmission mode

Mirror

DUT should be capable of optical transmitted at laser wavelength.

10 kHz – 4.75 MHz

LSM410

Detector for visible

LSM 410 microscope

Mira Laser

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Front Side SPA Setup

University of Saskatchewan, Canada

Ti:Sipphire Clark-MXR CPA1000

Tunable Optical Parametric Amplifier Attenuator

Wavelength : 800 nm Repetition rate : 1 kHz Pulse width : 120 fs

Wavelength : 1.26 μm Energy per pulse: 70 μJ Pulse width : 120 fs Spot size : 1.6 μm

Waveplate Polarizer

precisely control

Microscope Objective

×100 DUT

XYZ stage

Pump

SET laser

Naval Research Lab, US 630 nm collinear

Schott RG850 long-pass filter

Imaging laser

TNS 2002 Dale McMorrow

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Back Side TPA Setup

Laser Particles

Carrier Generation

Photoionization Particle – material

Interaction

Energy Loss

Energy Absorption Coefficient

LET

Metal Layer

Opacity Transparentness

Penetration Depth

Absorption Coefficient Energy

LET

Pulse Duration

Laser source dependent ( both ps and fs)

Several picoseconds

Track Width

Larger (diffraction limit) Smaller

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Laser vs. Particles

1. No damage accumulated total dose displacement

2. Convenient better accessibility

3. Cost effective relative cheap

4. Precise location positioned at the desired spot

6. Temporal information synchronized with external frequency

5. Sensitive depth well controlled

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Laser Advantages

An Example :

DC/DC PWM

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DC/DC PWM

Circuit_A

Circuit_B

Circuit_C

Circuit_D

Circuit_E

Input Voltage

Voltage_3

Voltage_4

Voltage_5

Voltage_2

Voltage_1

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DC/DC PWM

Soft Start Circuitry

Pulse Width Modulation Circuitry

Band Gap Reference Circuitry

Supervisory Circuitry (PGOOD)

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Generic Schematic

System (reboot)

DC/DC chip

6-μs glitch

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Context

DC/DC (6-μs glitch)

Laser Parameters

Wavelength : 800 nm, 920 nm, 990 nm

Pulse Duration : 130 fs

Repetition Rate : 10 KHz to 4.75 MHz

Why Laser ?

Benefits

Cost effective

Controlled frequency & power

Precise location and depth

Goal Duplicate the 6 us glitch with laser

Locate the most sensitive transistors

Background A 6us glitch is observed on a commercial territorial DC-DC converter PWM chip output (PGOOD) at pre-qualification testing with α and neutron experiments, and causing system reboots

Correlate with simulation results

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SPA Front side testing

Laser System: Ti : Sapphire Laser Mira 900-D

Wavelength Range: 700nm – 1000nm

Pulse Duration Range: 130fs – 2ps

Repetition Rate Range: 10khz – 75Mhz

Laser Spot Size: 1um * 1um

DUT Platform Step Size: 0.1um * 0.1um

Laser Facility at University of Saskatchewan

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How to Process

Fast, whole chip auto scan

Spot scan

Slow, localized auto scan

Sensitive Blocks

Sensitive Transistors

Sensitive Nodes

1

2

3

Circuit simulation

Laser Experiment

Transient simulation

Sensitive node

pulsed current apply here

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Experiment Procedures

Power-on Reset (POR)

Band Gap (BG)

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Most Sensitive Areas

Resistor box

PGOOD is triggered and four types of waveforms can be observed when increasing the laser power:

6us glitch

Irregular glitches

Temporary Shutdown

Permanent shutdown

Laser power is increasing

stable Unstable vary glitch widths

recover when laser is off

Power-on reset is required

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Phenomena in Laser Experiment

Low repetition rates laser experiment results are in accordance with that of alpha and neutron SET experiments, should be adopted as it best approximates the practical operation environments

Different pulse repetition rates can trigger different SET failure phenomena The average laser power to cause an upset remains relatively low and constant

until the pulse repetition rate is in the MHz range The laser energy per pulse, shows similar behavior for BG circuit, but not for POR

circuit. For the POR circuit, the laser energy per pulse decreases gradually over the repetition rates

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Laser Energy vs. Repetition Rate

Whole Chip Individual (920 nm)

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Laser Cross-section

Results 6 us glitches are duplicated using schematic simulations

α particle, laser and circuit simulation results are consistent

Solutions System Level: a simple external RC filter tied to “PGOOD”

Chip Level: increase the currents of relevant paths, improve layout

POR

SET

Sensitive bipolar

Sub circuits

NAND

6us filtering

Band Gap Ref. Power-on Reset Soft Start

NAND PGOOD 1P35

BGOK

RMP_DN1

EN_SS1

SET Path

Circuit Simulation

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SET Propagation

Before hardening After hardening

Waveforms comparison

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Hardening

Location TSL, Uppsala

Energy broad beam, from 1 MeV to 164 MeV

Cross Section

1.5×10-8 cm2

FIT 200 FIT/chip

Facility ANITA neutron beam facility

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Neutron Testing

Current (nA)

Energy (Mev) SET Fluence

(#/cm2) Cross section

(cm2) 1 57.6 58 5.80E+09 9.99E-09 1 48.8 53 6.64E+09 7.98E-09 1 35.5 51 7.42E+09 6.87E-09 1 27.1 49 7.68E+09 6.38E-09 1 20.7 38 8.08E+09 4.70E-09 1 13.7 15 9.13E+09 1.64E-09 5 9.0 9 1.62E+10 5.57E-10 5 4.8 4 5.82E+09 6.87E-10 5 3.9 0 4.17E+10 N/A

Facility Proton cyclotron at TRIUMF, Vancouver, Canada

Energy from 4 to 60 MeV

Flux from 105 protons/cm2/s to 108 protons/cm2/s

Beam Diameter from 1 cm to 7.5 cm

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Proton Testing

Conclusions The saturated cross-section is in the same level with that of neutron testing. Proton cross-section can be derived from the Heavy-Ion data using a Rectangular Parallelepiped model.

Facility HI-13 tandem accelerator in Beijing, China

LET from 65 to 500 MeV

Fluence From 9×10-4 cm-2 to 9.9×10-5 cm-2

Beam Size 2 cm × 2 cm

LET (Mev/mg/cm2) SET Fluence

(#/cm2) Cross section

(cm2)

0.44 102 9.90E+05 1.03E-04

1.77 123 2.60E+05 4.73E-04

4.43 102 8.50E+04 1.20E-03

9.82 100 7.70E+04 1.30E-03

13.6 122 9.00E+04 1.36E-03

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Heavy-Ion Testing

LET Scale for Heavy-Ion

Pulse Energy Scale

for Laser

Cross-Section Curve

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Heavy-Ion vs. Laser

Conclusions 1. The cross-section for 920 nm fits well with that for 800 nm

2. The laser cross-section matches the heavy-ion one.

Laser Application

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Interrogation of the spatial and temporal aspects of SEU and SEL.

Investigation of the basic charge-collection mechanisms of individual transistors.

An important tool for unraveling the complex SEE response of bipolar linear circuits.

Identify and characterize sensitive circuits nodes.

Provide information vital to the development and optimization of radiation-hardened designs.

Powerful in determining relative upset thresholds for hardened and unhardened designs.

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General Applications

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Application - 1

SPA Front & back side testing : Linear Devices SEE

TNS 2002 F.Darracq, et al

DUT Operational Amplifier (LM124)

Laser 850nm, 905nm, 1064nm

Goal 1. Linear device sensitive depth detection 2. Compare different wavelengths

operational amplifier LM124

Results Sensitivity depths mapping

Laser threshold mapping

limitations Potential sensitivity due to metal opacity

Not for multiple sensitive depths

1064 nm gives most accurate results

Methodology Sensitive depth (Z) calculation with a variation of wavelength

2

1

2 ,

1 ,

2 1

ln( )laser

laser

EE

Z

λ

λ

ααα α

=−

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Application - 1

512 Mbit Elpida SDRAM

(flip - chip)

IR : 1.26 um

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Application - 2

TPA Backside testing : SDRAM SEE

TNS 2009 Ray L.Ladbury

DUT Elpida 512 Mbit EDS5108ABTA-75 SDRAM

Preparation Thinning to 50 μm and polishing

Goal 1. SDRAM errors detection 2. HI testing optimization comparison

Results Generally consistent results Different phenomena are explained

Drawbacks

Techniques

Free carrier scattering

Resolution limitation

Technique Reason

Thinning Attenuation mitigation

Daughter board Increase yield

Polishing Imperfection reduction

Repetitive testing Eth is the minimum Energy

Automatic scanning Rare error modes detection

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Application - 2

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Application - 3

SPA Backside testing : Multiple SEEs (SBU, MBU, SET, Latchup, SEFI)

Laser Facility EADS IW laser facility (France)

Pulse Duration --------------- 600 ps Wavelength ----------------- 1064 nm Beam diameter --------------- 4 μm

DUT 110nm 256Mbit SDRAM MT48LC16M16A2 (Micron Technology)

Tester Based on a FPGA controlling the DUT, an embedded memory and a USB link connected to a master PC

De-Latcher To monitor the DUT current and protect the device in case of a high current increase.

Mechanically opened from backside & thinned to 80 μm

Clock frequency is 70 MHz & Nominal bias voltage is 3.3 V

TNS 2010 A. Bougerol

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Application - 3

Testing Steps

— Perform functional test on the DUT.

— Write pattern, then start pulsed laser injections from backside with the

beam focused on the frontside where active transistors are located.

— Continuously read DUT and check errors.

— If an event is triggered, the recovering procedure is performed.

— Once the effect is classified for a given position, motorized stages move the

DUT to a neighboring position.

— This process is repeated until the whole SEE mapping is obtained.

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Application - 3

110nm 256Mbit Stacked DRAM laser mapping Motor step resolution : 5μm

TNS 2010 A. Bougerol

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Application - 3

Results Multiple SEEs are observed

Laser data are verified by HI testing

Sensitive locations are identified

SEE mapping is obtained

Advantages Spatial information allows performing precise mapping.

Accurate energy control enables to find sensitivity threshold.

Memory cell blocks

SBU & MBU

Logic circuit parts

Fuse-Latch Upset Soft SEFI Hard SEFI

TNS 2010 A. Bougerol

Curve

Word error number triggered by laser in an area (voltage buffer circuit) for different energies

Q & A

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