ESD介绍(英文资料.pptx

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1、ESDESD Presentation OutlinePart 1:Introduction/Background Part 2:Electrostatic Problems Part 3:ResistancePart 4:IonizationPart 5:Charge MeasurementCharging MechanismsTriboelectric ChargingInduction ChargingTriboelectrification+-+-MATERIAL CONTACTTriboelectrification+-+-MATERIAL SEPARATION-Triboelect

2、ric ChargingThe amount of charge transferred depends onTypes of materials involved Area of contactNumber of contacts Rate of separationSurrounding environmentTriboelectric ChargingGlass Human Hair NylonWool Aluminum Paper Cotton Steel RubberNickel,Copper Brass,SilverPolyester Polyurethane Polyethyle

3、ne Polypropylene PVCSilicon Teflon_+Triboelectric SeriesTypical Charge LevelsTypical charge(voltage)measured for different activitiesWalking on an untreated vinyl floor12 kV for 10%RH3 kV for 55%RHWorker standing up6 kV for 10%RH400 V for 55%RHTypical Charge LevelsTypical charge(voltage)measured on

4、common objectsWafers5 kVWafer Carriers35 kV Quartz Ware15 kVPlastic Film40 kVSmocks10 kVInduction Charging-+-+Charge by Induction_ _ _ _+_+ProblemsElectrostatic AttractionContamination“Static Cling”ESDDevice Damage Equipment Latch Up(ESC)ProblemsElectrostatic AttractionContamination“Static Cling”Pro

5、blemsElectrostatic AttractionContamination“Static Cling”ProblemsESDDevice DamageEquipment Latch UpProblemsESDDevice DamageEquipment Latch UpOften misdiagnosed as software bugs.Induced EM DisturbanceAn Extra PulseDischarge ModelsTribocharging or induction charging+metal contact=ESDHuman Body Model(HB

6、M)Machine Model(MM)Charged Device Model(CDM)are used to simulate ESD events from various sources1500 ohmsHuman Body Model100k ohmsHVPower Supply100 pFDUTMachine ModelZero ohms andlow L100k ohmsHVPower Supply200 pFDUTCharged Device ModelHVPower SupplyCharge PlateCharged Device ModelHVPower SupplyChar

7、ge PlateGrounding(first line of defense)Grounding prevents charging.Ground everything-floors,mats,personnel,chairs,garments,machine parts.Soft GroundsUse soft grounds to control discharges.Using dissipative materials limits discharge current to a level that does not causedamage.Resistance MapInsulat

8、ive1031041051061071081091013 1014 10151010 1011 1012Surface Resistance(Ohms)101102DissipativeConductiveShieldingThe Need for StandardsMany common items are rendered dissipative to control discharges.ESD control programs require qualification of these items.Thus a need for standardized test methods.F

9、looring Work Surfaces ChairsGloves Garments PackagingESD Association StandardsGarments WorksurfacesFlooring ChairsPlanar Materials10V100V103104105106107108109101310101011 1012Surface Resistance(ohms)TEST VOLTAGEINPUTSHIELD/GROUNDVIPoint-To-Point MeasurementsFacility GroundRegulated Test VoltageINPUT

10、ITEST VOLTAGEVSHIELD/GROUNDRTG MeasurementsFacility GroundMeasuring Small Objects5 lb probes are tool large to measure many objects of interest.ThermoformedTrays ClamshellsTape and Reel CarriersPick and Place Suction CupsIonizationInsulators cannot be grounded.Methods of Ion Generation Ionization by

11、 Radiation Electrical(Corona)IonizationIonization by RadiationRadioactive Decay Alpha particlesElectromagnetic Radiation Soft X-RayUltravioletInherently balancedCorona Ionization+_HIGH VOLTAGE(+)Corona IonizationHIGH VOLTAGE(+)+Corona IonizationTypes of Electrical IonizersAC DCPulse DCAC and Pulse D

12、C Ionization+_HIGH VOLTAGE(AC)AC IonizationStep up line voltageLow costHigh airflow required to prevent recombination No control of balancePulsed DC IonizationFast transport of ions without air flowMinimum recombination Good for room ionizationDC IonizationAir ions will recombine and drift in the el

13、ectric field.+_HIGH VOLTAGE(+)HIGH VOLTAGE(-)Efficiency and Balance_+HIGH VOLTAGE(+)HIGH VOLTAGE(-)Testing IonizersSuitability for ApplicationIncoming Test Periodic VerificationHow We Test IonizersTest efficiency of ion generation.How quickly will the ionizer discharge a charged surface.Test the bal

14、ance of positive and negative air ions.An imbalance will charge an uncharged surface.How We Test IonizersThe instrument used to test ionizers is the Charged-Plate Monitor.Discharge(Decay)TestsEvaluate the quantity of ions produced by the ionizer.Charge a surface and measure the time to neutralize th

15、e charge.Perform for positive and negative charges.Float(Balance)TestEvaluate the balance of positive and negative ions produced by the ionizer.Charged-Plate Monitors(CPMs)Conventional ConstructionProperties of Charged,Isolated Conductors_GROUNDQ=CVCharges are mobile.They are free to redistribute th

16、emselves on the surface of the objectCharge(Q)is fixed.Capacitance and voltage depend on the location of the charged(conductive)object.CProperties of Charged Insulators_GROUNDQ X=CVCharges are not mobile.They cannot redistribute themselves on the surface of the object.Charges on an insulator cannot

17、be removed by connecting the surface of the insulator to ground.Charged insulators are more troublesome to characterize.Strictly speaking,the behavior of charged insulators cannot be characterized by Q=CV.XCDirect Measurement of ChargeGROUNDDischarge isolated conductive objects into a coulombmeter.D

18、estructive test.Cant test insulators this way.C_+_Q=CVDirect Measurement of ChargeOther objects(charged insulators)must be placed in a Faraday enclosure that is connected to a coulombmeter.+_Direct Measurement of ChargeIt is challenging to place object into a Faraday enclosure without adding or subt

19、racting charge.Measuring charge using these direct methods may be impractical.(Objects may be too large to place into a Faraday enclosure or not removable.)+_Measuring Voltages on Isolated Conductors0000GROUNDFamiliar test equipment,such as digital voltmeters and oscilloscopes,cannot be used to char

20、acterize electrostatic charges.Contacting charged conductive objects quickly discharges the object.Contacting insulators discharges the contact point and doesnt measure the un-contacted surface._Contacting ElectrometersVery high input impedance.GROUNDMinor loading of the charged conductor.Okay for m

21、easuring isolated conductors.Doesnt work for insulatorsC_+_GROUNDVoltage followerMinimal loading of the charged conductorStill cant measure an insulatorC+_Contacting ElectrometersProperties of Charged ObjectsWe often evaluate a charged object indirectly by evaluating its electric field.Instruments t

22、hat sense electric fields includeElectrostatic FieldmetersElectrostatic Voltmeters Non-contacting test method.+FieldmetersFieldmeters were originally used to measure large objects.Measuring in a uniform electric field is desired.Point-to-point or point-to-plane measurements yield different measureme

23、nt results.FieldmetersElectrostatic fieldmeters measure the field strength associated with a charge.The unit of measure is the volt/meter(or some other convenient distance).Indicates the presence and approximate level of charge.Usually hand-heldBest suited for making general auditsCost-effective for

24、 measuring voltages above 3kV.FieldmetersFieldmeters do not resolve low voltages.Fieldmeter measurements vary significantly with distance from the charged object.Fieldmeters do not resolve small surface areas.Two common types of fieldmeters areInduction FieldmetersChopper-Stabilized FieldmetersSimpl

25、est type of fieldmeterNo system to improve drift and instabilityWont operate reliably in the presence of ionizationFieldmeters are grounded instruments and modify the data.Induction FieldmetersChopper-Stabilized FieldmetersDo operate in the presence of ionizationFeedback systems to improve drift and

26、 instability performanceStill require a fixed spacingElectrostatic VoltmetersElectrostatic voltmeters use voltage feedback to null the electric field between the surface under test and the voltmeter probe.Also known as voltage follower or electrometerHigh degree of accuracy that is independent of th

27、e distance from the charge.Electrostatic voltmeters generally provide a better approximation of the charge level as compared to fieldmeters,and are better suited for making accurate and repeatable measurements.Electrostatic VoltmetersThe sensor can be placed very close to the charged surface without

28、 arc-over.The sensor can resolve small surface areas.Very free of drift and environmental instability.Well suited for fixed installation in equipment.Not a grounded probePresence of high voltage on the reference surfaceWorks in ionization because they are chopper-stabilizedAC-Feedback VoltmeterAC-fe

29、edback electrostatic voltmeters are part fieldmeter and part electrostatic voltmeter-a hybrid instrument with some characteristics of fieldmeters and some characteristics of electrostatic voltmeters.AC-feedback electrostatic voltmeters sense electric field and sense capacitance(distance)changes betw

30、een the surface under test and the probe to indicate surface voltage even if the distance changes.Spacing independent accuracy of electrostatic voltmeters.Resolve small surface areas.AC Feedback Electrostatic VoltmeterAC Feedback Electrostatic VoltmeterAlso known as a spacing compensated fieldmeter,

31、spot meterHow it is like a voltmeterHow it is like a fieldmeter Reports surface voltageLow costSpacing independent accuracyA grounded instrumentResolves small objectsArc over if used too close Good stability and drift performanceComparisonsVoltmetersNot cost effective above 3kVExcellent spatial reso

32、lutionIntended for close spacing,measuring small objectsNot grounded Spacing independentaccuracyLow driftAC-FeedbackCost effective above 3 kVGood spatial resolutionGood at close spacings,measuring small objectsGroundedSpacing independent accuracyLow driftFieldmetersCost effective above 3 kVLow spati

33、al resolutionIntended for wide spacing,measure large objectsGroundedUsing Voltmeters and Fieldmetersd4d-5dAs electrostatic voltmeters can be operated close to a charged surface without fear of arc-over,they can resolve smaller surface areas.Extraneous fields can negate the whole notion of spatial re

34、solution.Using Voltmeters and Fieldmeters_ _ _ _ _ _+Insulators do not have uniform charge distribution.As charge density is non-uniform,surface potentials are non-uniform.What is measured is nebulous.Provides a figure of merit.AuditingHand-held meters are particularly useful for auditing.Grounding

35、is important,especially for battery-operated instruments.Charge up objects of interest and see if they retain charge.Diagnostics and Continous MonitoringHand-held instruments are cumbersome for monitoring inside of process equipment,but many do have electrical outputs.Both fieldmeters and electrosta

36、tic voltmeters can have remote probes.Probes can be fixtured to monitor a surface of interest.Probes must be fixtured in holders that isolate them from ground.Probes are available with various aperture locations and housing shapes.Most chopper-stabilized instruments are limited in temperature range.

37、Most fieldmeters and electrostatic voltmeters can be interfaced to facilities monitoring systems.SummaryTriboelectric charging and induction charging are common causes of charges in electronic manufacturing.Electrostatic charge cause electrostatic attraction of contaminants and causes objects to sti

38、ck together.Electrostatic discharges cause device damage and equipment lock up.These problems are reduced by using an ESD control program.Electrostatic measurements tell you how well you are doing,and allow informed choices about where to properly place ESD countermeasures and to determine the effec

39、tiveness of those countermeasures.SummaryDifferent instruments will excel in different situations.Understanding your instruments allows you to obtain the greatest benefit and best results from them.Measuring and monitoring for charge accumulation allows informed choices about where to properly place ESD countermeasures and to determine the effectiveness of those countermeasures.2002 Trek Incorporated