23 rd ASEMEP National Technical Symposium Manufacturing and R&D : Leveling Up the Philippines Capability ESD Failure Analysis, Detection, and Simulation

23rd ASEMEP National Technical Symposium

“Manufacturing and R&D : Leveling Up the Philippines’ Capability ”

ESD Failure Analysis, Detection, and Simulation

Ray Nicanor M. Tag-atiNARTE: ESD-00480-NE

HGST Phil. Corp, a Western Digital Company


2. Process Benchmarking

Systematic Approach in ESD Auditing

3. ESD Assessment

4. Perform Measurements

5. Modeling and Simulation

6. ESD Control Conceptualization

1. Failure Mode Identification

Course Outline




3. ESD Assessment





Course Outline


Product Failure Analysis and Characterization

The severity of the failure will somehow provide some clues as to the source/s of ESD or EOS.

This will confirm if indeed the failure is due to ESD or EOS, and not mechanical , contamination, or other defects.



Electrical Overstress (EOS) and ESD have almost the same failure mechanism but differs on the sources.

ESD Static or Transient

Sources:

The very fast (nano/picoseconds) ESD pulses. Low energy Often very small physical damage signatures



ESD or EOS?


ESD Damage

Direct ESD HBM, MM, and CDM

Semiconductors (CMOS Capacitor) Magnetic Heads

(GMR/TMR)

• Severity of damage depends on the source of ESD.

• Direct ESD happens when there’s a discharge path.

ESD or EOS?




ESD Damage

ESD from Within Field Induced Model (FIM)

• ESD happens within the device itself by mere exposure to the electrostatic field.

Good

Damaged Damaged

Magnetic Heads (TMR)

ESD or EOS?




A device is electrically stressed over it’s specified limits in terms of voltage, current, and/or power/energy.

EOS failure is the result of "long" duration stress events (millisecond duration or longer).

EOS Dynamic or Continuous

ESD or EOS?




EOS Damage

EOS damage is often the result of the high temperatures experienced during the EOS event.

External

• Visible bulge in mold compound• Physical hole in mold compound• Burnt/discolored mold compound• Cracked package

ESD or EOS?




EOS Damage

Internal

• Melted or burnt metal• Carbonized mold compound• Signs of heat damage to metal lines• Melted or vaporized bond wires

Melted TMR

ESD or EOS?




Indications of EOS

• Failure signature from excessive load dump.

Transistor failure of the emitter Transistor failure of the emitter region of the dieregion of the die

Fused wire bond.Fused wire bond. Metallization run on Op-Metallization run on Op-Amp ICAmp IC

*images courtesy of www.semlab.com

ESD or EOS?




• Failure signature from repetitive thermal cycling combined with high current.

Severely degradedSeverely degradedrecrystalized metal recrystalized metal (≥400(≥400ºC) ºC)

Indications of EOS

ESD or EOS?




Possible Causes of EOS

Uncontrolled voltage surge on the power supply or testers.

Voltage spikes due to internal PCB switching.

Voltage spikes due to an external connection –capacitive charge on an external cable, antenna pick-up of external switching noise, inductive loads.

Poor grounding resulting in excessive noise on the ground plane.

Overshoot or undershoot during IO switching.

EMI (electromagnetic interference) due to poor shielding in an electrically noisy environment.

ESD or EOS?




Distinguishing between ESD and EOS failures has always been of interest to failure analysts.

Since ESD and EOS failure attributes depends on the following:• nature of the electrical stress• circuit design• die lay-out, and • fab process used

It would be difficult (if not impossible) to come up with a catch-all manual to distinguish between EOS and ESD failures.

Summary

ESD or EOS?






3. ESD Assessment





Course Outline


Process Mapping/Traceability

This will help in narrowing down the area to be audited.

Highlighted are the ESD-potential processes or tools.



What to Look For in an Identified Process?

High-powered tools motors, transformers and HV power supplies, etc.High-powered tools motors, transformers and HV power supplies, etc.

Tools with pneumatics/mechanical movement or AC switching source of EMI.Tools with pneumatics/mechanical movement or AC switching source of EMI.

Tools with direct metal contact or probing to the ESDS.Tools with direct metal contact or probing to the ESDS.

Process Mapping/Traceability



Whole Line/Fab ESD Partition Assessment

Processes are being divided into different segments. ESD parametric testing is being done after each segment. Done to identify which process/es causes ESD failures.

Process Partition Experiment



New Tool/Process Split ESD Parametric Analysis

ESD parametric test is done initially for the samples. This will serve as the baseline data.

Samples are then split into equal parts. Experiment is then performed.

ESD parametric test is then conducted and compared to the baseline data.

Process Partition Experiment





3. ESD Assessment





Course Outline


Assess what are the ESD events that the identified process might contribute.

Note: This model is applicable to automated lines with less direct handling to ESD-sensitive devices.

High

Low

Probability of Occurrence

3. ESD Assessment


Recommended Measurements

ESD EventsMeasurements

Category Parameters Method

Machine Model (MM)

Static:- Non-powered Tools- Powered Tools But No Probing to ESDS

Voltage Static Charge Build-up Electrometer

Current

Transient Noise Tap Transient (CT-6)

Ground Noise Continuous Measurement (CT-6)

Dynamic: - Testers- Powered Tools With Direct Probing to ESDS

Voltage Signal Analysis Differential Voltage

Current

Ground Noise Measurement at the Probes (Static and Dynamic Mode)

Continuous Measurement (CT-6)

Tap Transient (Standby Mode)

Tap Transient (CT-6)

H-Fields EMI CheckEMI Sensor During Actual Testing/Probing

3. ESD Assessment


Recommended Measurements…cont’d.

ESD EventsMeasurements

Category Parameters Method

Charged Device Model (CDM)

Resistance

Material Resistance Check (High Charge Generation/Inhibition of Charge Dissipation)

MOM

Ground or Discharge Path DMM

E-FieldsStatic Field Charge Check (FIM) Fieldmeter/Charge Plate Analyzer

Point Charge Check Nanocoulomb Meter

Voltage

Tribocharge Check (Handling/Process/Operation)

Electrometer

Unbalanced Ionizer Electrometer/CPM

Current CDM Discharge Current Tap Transient (CT-6) to the device

3. ESD Assessment




3. ESD Assessment





Course Outline


Voltage

Static – From electrostatic charge.

Dynamic – Potential from constant voltage sources such as testers or power supplies.

- The difference in electric potential between two points.



Voltage Measuring Equipment and Probes

Electrometer Triax Probe

Single-Ended Voltage Active Probe

Voltage Active Differential ProbeDigital Oscilloscope

Keithley 6517A Electrometer

4. Perform Measurements Voltage


Active Differential Probe and Oscilloscope

Voltage Measurement - Dynamic Voltage

To Oscilloscope

Source (I) +/- Electronics

Device Under Test (DUT)

Voltage Active Differential Probe

Measures the differential voltage between the channel that injects signal to the DUT.

4. Perform Measurements Voltage


Current

Static – Transient current from electrostatic charge / discharge.

– Current leaks from tools, machines, or equipment. Can cause ground noise.

- Flow of electric charge.

Dynamic

– Noise or glitch from HF signal of testers.


- Energy sensitive devices are damaged by excessive current.


Current Probes

Tek CT-1 and CT-2 Probes

Tek CT-6 Probe

4. Perform Measurements Current


Tap Transient

Current Measurement - Static

Tester or metallic tool with electrical circuits/motors


Time (50 ns/div)

Vol

tage

(1

00 m

V/d

iv)

Simulated Device’s Resistance

CT-6 Probe

MM Transient Wave Form

To Oscilloscope

Simulated device’s resistance. Tap Transient Testing for static measurement, at single

shot mode.



Continuous Ground Noise Measurement

Current Measurement - Dynamic

Noise Propagation from the Ground to the Jigs/Fixtures.

Peak Current: 10.7 mAFreq: 9.137 MHz

Current Waveform

CT-6 ProbeTool/Machine

Jigs/Fixture

Continuous Transient Testing for at dynamic condition, using Norm mode.



Fields (E-Field and H-Field)

Voltage/Current Transients = E-field

Device Under Test (DUT)

Probe Pins (Dipole) acts like antenna




Field Probes

3M (Credence) EM Aware

Sanki EMI Locator

Novx 7000

Antenna Connected in Digital Oscilloscope

4. Perform Measurements Fields (E-Field and H-Field)




3. ESD Assessment





Course Outline


5. PSPICE Modeling and Simulation

SPICE

Simulation Program with Integrated Circuit Emphasis

General-purpose circuit program that simulates electronic circuits.

Used to perform various analyses:

- time-domain response- frequency response,- operating points or transistors, and so on.



PSPICE on ESD

Mostly, the Transient Analysis is being used in ESD Simulation.

Transient Analysis:

- Used for circuits with time-variant sources (AC or switched DC sources)

- Calculates all node voltages and branch currents over time interval.

Done to understand the sources and behavior of ESD, and determine how to control the sources.



Transient Analysis…cont’d.

Voltage Sources

Pulsed Voltage Source

PSPICE Model



Sinusoidal Voltage Source

Transient Analysis…cont’d. Voltage Sources…cont’d.

PSPICE Model



ESD Events Simulation – Transient Analysis

- Human Body Model (HBM)- Machine Model (MM)

- Charge Device Model (CDM)

HBM Simulated Circuit CDM Simulated Circuit MM Simulated Circuit

Run PSPICE




3. ESD Assessment

4. Actual Measurements




Course Outline


Key Considerations

Elimination of the HF voltage/current source

Current Suppression

Current Diversion


Run PSPICE


Thank You!Thank You!


Back-up


Discussion

Basic PSPICE Simulation

How to start the simulation?

- Simulation should be based on the actual condition.

- Prior ESD measurements should be made.

Transient Noise Measurements

RLC components identification.

Power source consideration.

L = 20 nH per inch of ground wire C for charge storage


Discussion

PSPICE Simulation Workshop

Actual PSPICE Simulation

- Understanding HF Noise from stepper motors, transformers, HV sources, etc.

- Charge Decay Simulation (Spot Decay Test Using CPM)

- Tools and series resistance

Documents

23 rd ASEMEP National Technical Symposium Manufacturing and R&D : Leveling Up the Philippines Capability ESD Failure Analysis, Detection, and Simulation