1、ESD Presentation OutlinePart 1:Introduction/Background Part 2:Electrostatic Problems Part 3:ResistancePart 4:IonizationPart 5:Charge Measurementhttp:/ S D P r e s e n t a t i o n O u t l i n e P a r t 1Charging MechanismsTriboelectric ChargingInduction Charginghttp:/ h a r g i n g Me c h a n i s m s
2、 T r i b o e l e c t rTriboelectrification+-+-MATERIAL CONTACThttp:/ r i b o e l e c t r i f i c a t i o n+-+-Triboelectrification+-+-MATERIAL SEPARATION-http:/ r i b o e l e c t r i f i c a t i o n+-+-Triboelectric ChargingThe amount of charge transferred depends onTypes of materials involved Area
3、of contactNumber of contacts Rate of separationSurrounding environmenthttp:/ r i b o e l e c t r i c C h a r g i n g T h e a m o uTriboelectric ChargingGlass Human Hair NylonWool Aluminum Paper Cotton Steel RubberNickel,Copper Brass,SilverPolyester Polyurethane Polyethylene Polypropylene PVCSilicon
4、Teflon_+Triboelectric Serieshttp:/ r i b o e l e c t r i c C h a r g i n g G l a s s H uTypical 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%RHhttp:/ y p i c a l C h a
5、 r g e L e v e l s T y p i c a l cTypical Charge LevelsTypical charge(voltage)measured on common objectsWafers5 kVWafer Carriers35 kV Quartz Ware15 kVPlastic Film40 kVSmocks10 kVhttp:/ y p i c a l C h a r g e L e v e l s T y p i c a l cInduction Charging-+-+http:/ n d u c t i o n C h a r g i n g-+-C
6、harge by Induction_ _ _ _+_+http:/ h a r g e b y I n d u c t i o n _ _ _ _ _ _ _ProblemsElectrostatic AttractionContamination“Static Cling”ESDDevice Damage Equipment Latch Up(ESC)http:/ r o b l e m s E l e c t r o s t a t i c A t t r a c t iProblemsElectrostatic AttractionContamination“Static Cling”
7、http:/ r o b l e m s E l e c t r o s t a t i c A t t r a c t iProblemsElectrostatic AttractionContamination“Static Cling”http:/ r o b l e m s E l e c t r o s t a t i c A t t r a c t iProblemsESDDevice DamageEquipment Latch Uphttp:/ r o b l e m s E S D h t t p:/w w w.d o c i n.c oProblemsESDDevice Da
8、mageEquipment Latch UpOften misdiagnosed as software bugs.Induced EM DisturbanceAn Extra Pulsehttp:/ r o b l e m s E S D I n d u c e d E M D i s t u r b aDischarge ModelsTribocharging or induction charging+metal contact=ESDHuman Body Model(HBM)Machine Model(MM)Charged Device Model(CDM)are used to si
9、mulate ESD events from various sourceshttp:/ i s c h a r g e Mo d e l s T r i b o c h a r g i n g 1500 ohmsHuman Body Model100k ohmsHVPower Supply100 pFDUThttp:/ 5 0 0 o h m s H u m a n B o d y Mo d e l 1 0 0 k Machine ModelZero ohms andlow L100k ohmsHVPower Supply200 pFDUThttp:/ c h i n e Mo d e l
10、Z e r o o h m s a n d 1 0 0 kCharged Device ModelHVPower SupplyCharge Platehttp:/ h a r g e d D e v i c e Mo d e l H V C h a r g e PCharged Device ModelHVPower SupplyCharge Platehttp:/ h a r g e d D e v i c e Mo d e l H V C h a r g e PGrounding(first line of defense)Grounding prevents charging.Groun
11、d everything-floors,mats,personnel,chairs,garments,machine parts.http:/ r o u n d i n g (f i r s t l i n e o f d e f e nSoft Grounds Use soft grounds to control discharges.Using dissipative materials limits discharge current to a level that does not cause damage.http:/ o f t G r o u n d s U s e s o
12、f t g r o u n d s tResistance MapInsulative1031041051061071081091013 1014 10151010 1011 1012Surface Resistance(Ohms)101102DissipativeConductiveShieldinghttp:/ e s i s t a n c e Ma p I n s u l a t i v e 1 0 31 0The Need for StandardsMany common items are rendered dissipative to control discharges.ESD
13、 control programs require qualification of these items.Thus a need for standardized test methods.Flooring Work Surfaces ChairsGloves Garments Packaginghttp:/ h e N e e d f o rS t a n d a r d s Ma n y c o mESD Association StandardsGarments WorksurfacesFlooring ChairsPlanar Materials10V100V10310410510
14、6107108109101310101011 1012Surface Resistance(ohms)http:/ S D A s s o c i a t i o n S t a n d a r d s G a r m eTEST VOLTAGEINPUTSHIELD/GROUNDVIPoint-To-Point MeasurementsFacility GroundRegulated Test Voltagehttp:/ E S T V O L T A G E I N P U T S H I E L D/G R O U N DINPUTITEST VOLTAGEVSHIELD/GROUNDR
15、TG MeasurementsFacility Groundhttp:/ N P U T R T G Me a s u r e m e n t s F a c i l i t y Measuring Small Objects5 lb probes are tool large to measure many objects of interest.ThermoformedTrays ClamshellsTape and Reel CarriersPick and Place Suction Cupshttp:/ a s u r i n g S m a l l O b j e c t s 5
16、l b p rIonizationInsulators cannot be grounded.Methods of Ion Generation Ionization by Radiation Electrical(Corona)Ionizationhttp:/ o n i z a t i o n I n s u l a t o r s c a n n o t b eIonization by RadiationRadioactive Decay Alpha particlesElectromagnetic Radiation Soft X-RayUltravioletInherently b
17、alancedhttp:/ o n i z a t i o n b y R a d i a t i o n R a d i o a cCorona Ionization+_HIGH VOLTAGE(+)http:/ o r o n a I o n i z a t i o n+H I G H V O L T A G ECorona IonizationHIGH VOLTAGE(+)+http:/ o r o n a I o n i z a t i o n H I G H V O L T A G E Corona IonizationTypes of Electrical IonizersAC D
18、CPulse DChttp:/ o r o n a I o n i z a t i o n T y p e s o f E l e cAC and Pulse DC Ionization+_HIGH VOLTAGE(AC)http:/ C a n d P u l s e D C I o n i z a t i o n+AC IonizationStep up line voltageLow costHigh airflow required to prevent recombination No control of balancehttp:/ C I o n i z a t i o n S
19、t e p u p l i n e v o l tPulsed DC IonizationFast transport of ions without air flowMinimum recombination Good for room ionizationhttp:/ u l s e d D C I o n i z a t i o n F a s t t r a n sDC IonizationAir ions will recombine and drift in the electric field.+_HIGH VOLTAGE(+)HIGH VOLTAGE(-)http:/ C I
20、o n i z a t i o n A i r i o n s w i l l r e cEfficiency and Balance_+HIGH VOLTAGE(+)HIGH VOLTAGE(-)http:/ f f i c i e n c y a n d B a l a n c e _ _ _ _+H ITesting IonizersSuitability for ApplicationIncoming Test Periodic Verificationhttp:/ e s t i n g I o n i z e r s S u i t a b i l i t y f oHow We
21、Test IonizersTest efficiency of ion generation.How quickly will the ionizer discharge a charged surface.Test the balance of positive and negative air ions.An imbalance will charge an uncharged surface.http:/ o w We T e s t I o n i z e r s T e s t e f f i cHow We Test IonizersThe instrument used to t
22、est ionizers is the Charged-Plate Monitor.http:/ o w We T e s t I o n i z e r s T h e i n s t r uDischarge(Decay)TestsEvaluate the quantity of ions produced by the ionizer.Charge a surface and measure the time to neutralize the charge.Perform for positive and negative charges.http:/ i s c h a r g e
23、(D e c a y)T e s t s E v a l u a tFloat(Balance)TestEvaluate the balance of positive and negative ions produced by the ionizer.http:/ l o a t (B a l a n c e)T e s t E v a l u a t e tCharged-Plate Monitors(CPMs)Conventional Constructionhttp:/ h a r g e d-P l a t e Mo n i t o r s (C P M s)Properties o
24、f Charged,Isolated Conductors_GROUNDQ=CVCharges are mobile.They are free to redistribute themselves on the surface of the objectCharge(Q)is fixed.Capacitance and voltage depend on the location of the charged(conductive)object.Chttp:/ r o p e r t i e s o f C h a r g e d,I s o l a t eProperties of Cha
25、rged Insulators_GROUNDQ X X=CVCharges are not mobile.They cannot redistribute themselves on the surface of the object.Charges on an insulator cannot be removed by connecting the surface of the insulator to ground.Charged insulators are more troublesome to characterize.Strictly speaking,the behavior
26、of charged insulators cannot be characterized by Q=CV.X XChttp:/ r o p e r t i e s o f C h a r g e d I n s u l a t oDirect Measurement of ChargeGROUNDDischarge isolated conductive objects into a coulombmeter.Destructive test.Cant test insulators this way.C_+_Q=CVhttp:/ i r e c t Me a s u r e m e n t
27、 o f C h a r g e G RDirect Measurement of ChargeOther objects(charged insulators)must be placed in a Faraday enclosure that is connected to a coulombmeter.+_http:/ i r e c t Me a s u r e m e n t o f C h a r g e O tDirect Measurement of ChargeIt is challenging to place object into a Faraday enclosure
28、 without adding or subtracting charge.Measuring charge using these direct methods may be impractical.(Objects may be too large to place into a Faraday enclosure or not removable.)+_http:/ i r e c t Me a s u r e m e n t o f C h a r g e I tMeasuring Voltages on Isolated Conductors0000GROUNDFamiliar te
29、st equipment,such as digital voltmeters and oscilloscopes,cannot be used to characterize electrostatic charges.Contacting charged conductive objects quickly discharges the object.Contacting insulators discharges the contact point and doesnt measure the un-contacted surface._http:/ a s u r i n g V o
30、l t a g e s o n I s o l a t e dContacting ElectrometersVery high input impedance.GROUNDMinor loading of the charged conductor.Okay for measuring isolated conductors.Doesnt work for insulatorsC_+_http:/ o n t a c t i n g E l e c t r o m e t e r s V e r y hGROUNDVoltage followerMinimal loading of the
31、charged conductorStill cant measure an insulatorC+_Contacting Electrometershttp:/ R O U N D V o l t a g e f o l l o w e r Mi n i m a l Properties of Charged ObjectsWe often evaluate a charged object indirectly by evaluating its electric field.Instruments that sense electric fields includeElectrostat
32、ic FieldmetersElectrostatic Voltmeters Non-contacting test method.+http:/ r o p e r t i e s o f C h a r g e d O b j e c t s WFieldmetersFieldmeters were originally used to measure large objects.Measuring in a uniform electric field is desired.Point-to-point or point-to-plane measurements yield diffe
33、rent measurement results.http:/ i e l d m e t e r s F i e l d m e t e r s w e r e o rFieldmetersElectrostatic 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 charg
34、e.Usually hand-heldBest suited for making general auditsCost-effective for measuring voltages above 3kV.http:/ i e l d m e t e r s E l e c t r o s t a t i c f i e l dFieldmetersFieldmeters do not resolve low voltages.Fieldmeter measurements vary significantly with distance from the charged object.Fi
35、eldmeters do not resolve small surface areas.Two common types of fieldmeters areInduction FieldmetersChopper-Stabilized Fieldmetershttp:/ i e l d m e t e r s F i e l d m e t e r s d o n o t Simplest type of fieldmeterNo system to improve drift and instabilityWont operate reliably in the presence of
36、ionizationFieldmeters are grounded instruments and modify the data.Induction Fieldmetershttp:/ i m p l e s t t y p e o f f i e l d m e t e r I n dChopper-Stabilized FieldmetersDo operate in the presence of ionizationFeedback systems to improve drift and instability performanceStill require a fixed s
37、pacinghttp:/ h o p p e r-S t a b i l i z e d F i e l d m e t e r sElectrostatic 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 inde
38、pendent of the 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.http:/ l e c t r o s t a t i c V o l t m e t e r s E l e c t rElectrostatic V
39、oltmetersThe sensor can be placed very close to the charged surface without 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
40、in ionization because they are chopper-stabilizedhttp:/ l e c t r o s t a t i c V o l t m e t e r s T h e s eAC-Feedback VoltmeterAC-feedback electrostatic voltmeters are part fieldmeter and part electrostatic voltmeter-a hybrid instrument with some characteristics of fieldmeters and some characteri
41、stics of electrostatic voltmeters.AC-feedback electrostatic voltmeters sense electric field and sense capacitance(distance)changes between the surface under test and the probe to indicate surface voltage even if the distance changes.Spacing independent accuracy of electrostatic voltmeters.Resolve sm
42、all surface areas.http:/ C-F e e d b a c k V o l t m e t e r A C-f e e d b aAC Feedback Electrostatic Voltmeterhttp:/ C F e e d b a c k E l e c t r o s t a t i c V o l tAC Feedback Electrostatic VoltmeterAlso known as a spacing compensated fieldmeter,spot meterHow it is like a voltmeterHow it is lik
43、e a fieldmeter Reports surface voltageLow costSpacing independent accuracyA grounded instrumentResolves small objectsArc over if used too close Good stability and drift performancehttp:/ C F e e d b a c k E l e c t r o s t a t i c V o l tComparisonsVoltmetersNot cost effective above 3kVExcellent spa
44、tial resolutionIntended 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 kV
45、Low spatial resolutionIntended for wide spacing,measure large objectsGroundedhttp:/ o m p a r i s o n s V o l t m e t e r s A C-F e e d b aUsing Voltmeters and Fieldmetersd4d-5dAs electrostatic voltmeters can be operated close to a charged surface without fear of arc-over,they can resolve smaller su
46、rface areas.Extraneous fields can negate the whole notion of spatial resolution.http:/ s i n g V o l t m e t e r s a n d F i e l d m e t eUsing Voltmeters and Fieldmeters_ _ _ _ _ _+Insulators do not have uniform charge distribution.As charge density is non-uniform,surface potentials are non-uniform
47、.What is measured is nebulous.Provides a figure of merit.http:/ s i n g V o l t m e t e r s a n d F i e l d m e t eAuditingHand-held meters are particularly useful for auditing.Grounding is important,especially for battery-operated instruments.Charge up objects of interest and see if they retain cha
48、rge.http:/ u d i t i n g H a n d-h e l d m e t e r s a r e pDiagnostics and Continous MonitoringHand-held instruments are cumbersome for monitoring inside of process equipment,but many do have electrical outputs.Both fieldmeters and electrostatic voltmeters can have remote probes.Probes can be fixtu
49、red 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.Most fieldmeters and electrostatic voltmeters can be inte
50、rfaced to facilities monitoring systems.http:/ i a g n o s t i c s a n d C o n t i n o u s Mo n iSummaryTriboelectric charging and induction charging are common causes of charges in electronic manufacturing.Electrostatic charge cause electrostatic attraction of contaminants and causes objects to sti
