MEPTEC Luncheon Presentation. Introduction of Ag Alloy Bonding Wire William (Bud) Crockett Jr.

Transcription

1 MEPTEC Luncheon Presentation Introduction of Ag Alloy Bonding Wire William (Bud) Crockett Jr. April 10, 2013

2 2012 Semiconductor Market Tracking Forbes 2012 Monthly rolling forecast Unit Growth Rates for Semiconductor Revenue, Unit and Wafer Demand Source: Semico Research Corp. Wafer Demand Model Sept

3 Semiconductor Market 2013 rebound? Source: IHS isuppli

4 Materials Market Snap-shots WW Au, Cu and PCC wire shipped Source: SEMI % 90% 80% 70% 60% 50% 40% 30% 20% 10% 0% Source: Tech Search 2011 PCC Bare Cu Gold

5 Bonding Wire Transition Gold => Copper

6 Copper Technical Challenges

7 Critical barriers in fine pitch applications associated with copper wire Challenges of Copper Wire Copper Wire is Hard Narrow process windows (Short tail, fish tail, lifted bonds) FAB (Forming Gas N2H2) Capillary life Reliability (PCT/HAST Failures, Oxidation) Al pad splash Die pad crack

8 Au/Cu/PCC Hardness & Compression Comparisons PCC PCC

9 Cu Wire Bonding Process Window Comparison High First Bond Second Bond Bonding Parameters Cu Au High Parameters Narrow Range Cu Wire Parameters Narrow Range Low Parameter Range Low Parameters Wide Range Std Parameters Wide Range 1) Copper wire is harder than Gold wire 2) Copper processes have work hardening issues

10 Existing Common problem in Cu bonding Short tail / No tail issue High High Parameters Bonding Parameters Cu Optimum Parameters Low Parameters Low Parameter Range

11 More Common problems in Cu bonding High High Parameters Aluminum splashing shorting to adjacent pad Bonding Parameters Low Cu Low Parameters Optimum Parameters Parameter Range Lifted Metal 1) Lifted metal occurs at lower side of optimum parameters

12 PCC Wire

13 PCC Wire Wire Attributes 4N Bare Cu wire Shape PCC Wire φ20um Thin Pd Coated layer Wire (tail) FAB φ40um Pd wt% 2.1wt% 2.1wt% Pd Thickness 0.1um 0.13um

14 FAB EPMA Mapping FAB make Wire: PCC 1, PCC 2 φ20um FAB: φ38um Bonder: UTC-3000 EFO: 80mA, 0.12ms Gas: N 2 +5%H 2, 0.5L/min Measurement count n=3 Molded by epoxy resin Polish and buff PCC EPMA-1600 SHIMADZU PCC 1 PCC 2 1) Pd remains more on the FAB surface of PCC 1 than that of PCC 2 wire type 2) Pd element diffused in FAB which makes it harder. Pad damage risk 3) Pd element on perimeter of ball more effective for retarding Halogen attack??

15 Reliability

16 Diffusion and IMC of Cu, Al, Pd Cu-Al diffusion is slower than Au-Al. Cu wire reliability is higher than Au wire on 4N grade. Boundary of Pd coated Cu wire and Al pad is also attacked by halogen on HTS test. Pd cannot protect copper base metal from halogen attack on 473K HTS test. HTS performance of PCC and bare copper wire are basically same using controlled Mold Halogen % and ph level Diffusion coefficient [-] 1E-12 1E-18 1E-24 Reference data from "Metal data book, Vol.4, Maruzen" Temperature [K] E-06 Au Al (773K-1223K) Cu Al (594K-928K) Pd Cu (1080K-1328K) Cu Pd: no data 1E-30

17 An estimate of the trouble mechanism in BGA PKG IMC of Cu/Al is corroded by moisture in HAST test and a tiny amount of Halogen is present in the water. One of cause is that water is easy to permeate, compared to QFP Pkgs because BGA resin is single side molding and transformed with reflow heat. When an initial bonding area is narrow, a bonding area gets smaller by increasing of the corrosion layer. And also, water comes in to attack bond easily. Bare Cu Pd/Cu It is estimated that resistance increase is not occurred because a Cu - Pd - Al interface area secure electrical contact by exist of Pd that is hard to corrode on FAB even if a Cu - Al interface is corroded H 2 O with halogen and so on. Pd-Cu Pd 2-2- Pd-Cu Pd Pd-Al Pd-Al

18 PCC Comparisons HTS 220deg C, QFP, Halogen resin Failure ratio (%) Failure=initial resistannce 20%up K&S MaxumPlus Bonder:K&S Maxum Plus Forming Gas :N2-5%H2, 0.5l/min Die-Pad :Al-0.5%Cu (t=0.8um) (Hitachi 6mm Al-Cu0.5%) Capillary :SPT SI E-ZS36 (H:25, T:130, CD:38, FA:8, OR:30) Wire Dia.:20um FAB Dia.:40um Squashed Ball Dia.:50um CLR-1A TD PCC CLR-1 PCC 1 Wire PCC E (ref) Time(h)

19 PCC Comparisons HTS 200deg C, QFP, Green resin 不良数 (Ω20%up) :PCC 1,N2-5%H2,90mA (1.60mil) :PCC 1,N2,90mA (1.69mil) :TD PCC,N2-5%H2,90mA (1.65mil) :TD PCC,N2,90mA (1.69mil) Time(h) 1135h (Next page) 1135h (Next page) X Y Bonder:K&S KnS ICONN Heat Stage Temperature=200 Die-Pad :Al-0.5%Cu-1%Si / SiO2 / Si (Renesas DG001 t=0.8um) Capillary :SPT SU F-ZU34TP (H25,CD38,T80) Wire Dia.:20um FAB Dia.:X=39.5um,Y=36 Squashed Ball Dia.: X=50.5um, Y=50.0, Z=10.0 1st B g Parameter Tip=7.0(mils),CV=0.3(mils/msec) Contact Threshold=70% Constant Current Contact Defect Mode=V Mode USG Current=85(mA) USG Profile=Square USG Bond Time=10(ms) USG Pre Bond=60(mA) Force=15(gf) Force Profiling=On Init l Force=45(gf) Init'l Force time=33(%) Force Ramp Time=10% X-Scrub=3(um), Y-Scrub=0(um) Scrub Cycles=2,Scrub Phase=90(deg) 1st Scrub mode=pre USG

20 HTS 200deg C, QFP, Green resin TD PCC N 2 90mA 1135h TD PCC N 2 H 2 90mA PCC 2 N 2 90mA PCC 1 N 2 H 2 90mA Observation is no corrosion in 1 st bond cross section

21 UHAST 130deg C 85%rh, QFP, Halogen resin :PCC 1,N2-5%H2,45mA (1.52mil) :PCC 1,N2,45mA (1.61mil) :TD PCC,N2-5%H2,45mA (1.55mil) :TD PCC,N2,45mA (1.67mil) 1085h 不良数 (Ω20%up) h Time(h) Bonder:K&S KnS ICONN Heat Stage Temperature=200 Die-Pad :Al-0.5%Cu-1%Si / SiO2 / Si (Renesas DG001 t=0.8um) Capillary :SPT SU F-ZU34TP (H25,CD38,T80) Wire Dia.:20um FAB Dia.:X=39.5um,Y=36 Squashed Ball Dia.: X=50.5um, Y=50.0, Z=10.0 1st B g Parameter Tip=7.0(mils),CV=0.3(mils/msec) Contact Threshold=70% Constant Current Contact Defect Mode=V Mode USG Current=85(mA) USG Profile=Square USG Bond Time=10(ms) USG Pre Bond=60(mA) Force=15(gf) Force Profiling=On Init l Force=45(gf) Init'l Force time=33(%) Force Ramp Time=10% X-Scrub=3(um), Y-Scrub=0(um) Scrub Cycles=2,Scrub Phase=90(deg) 1st Scrub mode=pre USG

22 UHAST 130deg C 85%rh, QFP, Halogen resin Corrosion? alloy layer? TD PCC N 2 45mA 1085h TD PCC N 2 H 2 45mA PCC 1 N 2 45mA PCC 1 N 2 H 2 45mA

23 Introduction: Ag alloy bonding wire

24 Benefit of Ag Alloy Wire For customers using 4N Au wire 1. Similar 2nd Bondability Wide 2nd bond process window Comparable stitch pull strengths 2. Good Reliability Longer HTS life 3. Cost Savings For customers using Pd coated Cu wire 1. Similar Cost More simplified production process 2. Better 1st Bondability Less Al splash

25 Wire Type Summary The advantage of switching from copper wire to silver wire is that silver wire meets ball bonding performance requirements, soft FAB and excellent loop formation while maintaining productivity on par with gold wire. Silver bonding wire has good elongation and breaking load properties and silver wire is ductile like gold wire with non existent work-hardening process issues like copper wire. Gold Silver Copper Material Cost Forming Gas - N 2 N 2 +H 2 Chip Damage Process window Reflectivity

26 Ag Wire FAB Formation [ Study of Gas Flow Rate ] Bonder : UTC-3000 with Gas-kit, Shield Gas : N2 0.2 l/min 0.4 l/min 0.6 l/min 0.8 l/min 1.0 l/min Good

27 FAB Compression Test Comparisons Ag Alloy Au>Ag>Cu>PCC

28 Al Splash Comparisons Ag alloy

29 Crystal Observation (Vertical Section) Ag alloy Heat Affected Zone 4N Au Heat Affected Zone Ultra low Loop & Reverse Bonding is possible for Ag alloy wire

30 Ag Alloy / 4N Au Ag alloy 4N Au

31 Ag alloy

32 PCT Comparisons Ag alloy

33 End Notes Silver wire shows good potential as it offers several advantages compared to bare copper and palladium coated copper wires; mainly, excellent bonding performance and reliability. Silver may not work for all applications but it can certainly help support many application areas where cost and performance define a product. Silver wire usage is expected to increase in the next few years in both the LED and semiconductor industry.

34 Thank you Tsutomu Yamashita Tanaka Denshi Kogyo K.K.