Thinning of IC chips

Transcription

1 1 Thinning of IC chips Annette Teng CORWIL TECHNOLOGY CORP McCarthy Blvd. Milpitas, CA CONTENT Industry Demand for thinness Method to achieve ultrathin dies Mechanical testing of ultrathin die Die strength variation source Methods to achieve strong ultrathin dies Assembly of Ultrathin dies Die Attach Films Interconnection

2 3 Reasons to go thin Decrease street width Stackable 3D packaging Smart cards Improved Heat dissipation Better electrical performance Higher speeds Ultra Paper thin Embedded packaging Wearable packaging -Appliques Skin patch Implantable Foldable 3D die -cylinders -cones -origami inemi Roadmap International Electronic Manufacturing Initiative 4

3 5 6

4 7 STATSchipPAC ECTC um flip chip Conventional Flow for Wafer Thinning (DAG) 8 Patterned Full thickness Wafer Apply front side tape Backgrind Wafer Wash wafer BACKGRIND Die Pick and place Singulate/dicing Laser or Blade Remove front side tape Mount dicing tape on backside of wafer SAW

5 9 DAG Results: LOW YIELD Warpage & curl Non conformal Transport challenge Storage challenge Lamination challenge Dice Before Grind DBG Flow Comparison 10 Conventional method DBG DAG

6 Dice Before Grind Method 11 Singulation Depth Rough grind 300 grit Removed thickness Trench depth Fine grind>2000 Final thickness Front side tape 12 Results No Wafer Warpage & curl No Wafer Breakage Conformal Transportable Storable Easy to Laminate Easier to bond/debond

7 32um after DBG with Polygrind wheel 13 Sidewall Flaws Punctures 14 15um silicon die attached to package by 25um DAF. 20um gold wire bond

8 Thin die Strength Characterization Techniques 15 width T=0.150 F radius L 2 Point Test width 3F*length Strength = *width*thickness 2 F r=0.025 L= 0.570mm T= Point Test width 3F*length Strength = width*thickness 2 l F r=0.025 T= Point Test Fracture strength Test Methods 16 Point Load test (PLT) Radius 0.1; 0.25; 0.3mm Plate on Elastic Foundation Test (PEFT) M.Y.Tsai, ASE et al Radius 0.1;0.25;0.3mm 1.4mm silicone Ball & Ring Test Radii (ball, ring) Radius 0.1;0.25;0.3mm 1.4mm silicone diameter

9 7 Thickness SCV Chapter, CPMT Society, IEEE January 28, Relative Strength Breaking-Strength F*length Strength = *width*thickness (µm), Ball-Ring-Method, only ground, backside untreated Die thickness(mils) Effect of flaw size on Die strength Silicon Dice after grind (DAG).125mmThick M P a s c a l T 0.1T 0.2T 0.3T Ratio of sidewall crack to die thickness

10 Effect of flaw size on strength Silicon DBG 0.150mm thick 1200 M 1000 P a 800 s c 600 a l T 0.1T 0.2T 0.3T 0.4T Dramatic strength variation 20 D i e s t r e n g t h ( M p a ) A B C D E F G H

11 21 Die Strength of various 0.150mm thick.670mm RFID dies Fracture 400 strength in N/mm Finish and dicing method 22 Distribution plot -sample size 50 Group H (CMP-blade saw) F r e q u e n c y Die strength in MPa

12 23 F r e q u e n c y Distribution plot -sample size 50 Group H (CMP-blade saw) Die strength in MPa 24 Distribution plot of 2000grit etched group 16 F r e q u e n c y to to to to to to to 409 Die strength of singulated random dies from 1 wafer

13 25 Examples of Surface defects Most common chipout is last side rip of the Smaller piece Snaps off Shifts away from blade Vibrates more.150mm Smaller Y channel Blade feed direction X channel blade step direction blade Bigger Large fracture strength variations within 1 wafer MPa Angle from Anvil

14 Laser generated roughness 27 Laser ablation SIDEWALL 0.250mm SIDEWALL 0.250mm 28 Laser scribe and break SIDEWALL 0.250mm Laser Stealth and expand

15 29 PERSONAL PREFERENCE - VISUAL REJECT ACCEPT Examples of Surface Flaws 30

16 Total thickness variation of a thinned wafer 31 TTV HAS MAJOR IMPACT ON ULTRATHIN DIE 32 Wafer Thinning Target Thickness 8 m TTV to thickness ratio mm 5.3% ( mm) mm 8% ( mm) mm 16% ( mm) TTV effect on 3 pt bend die strength 10.6% 16.0% 32.0%

17 33 Source:Disco 5 sided smoothening 34

18 DAF FLOW 35 Full thickness Wafer Apply front side tape Backgrind Wafer Wash wafer DAF Mount dicing tape on backside of wafer Die Pick and place Blade or Laser Saw Remove front side tape DBG 36 DAF Half Cut Dicer 2 lamination 1 detape 2 singulation Flow Comparison Of DBG For DAF DAF 2 lamination 1 detape 1 singulation DAG 3 lamination 2 detape 2 singulation DBG Conv.

19 DAF services are easily integrated into existing line -automated thin wafer grind -automated DAF mounting -automated dicing with DAF -automated die attach with DAF 37 CPMT-SCV Luncheon 37 Talk Film Over Wire (FOM) tape 38 Heat Stage Adhesive with viscosity so low that it will wrap around gold wire loops when heated to 150 o C CPMT-SCV Luncheon 38 Talk

20 39 Amkor CPMT-SCV Luncheon 39 Talk 40 Half Cut Dicer 2 lamination 1 detape 2 singulation

21 Full thickness Wafer Apply front side tape Backgrind Wafer DAF FLOW 41 Wash wafer DAF Mount dicing tape on backside of wafer Remove front side tape Die Pick and place Blade or Laser Saw Reasons to use DAF 1. NO VOIDS 2. NO PINHOLES 3. NO BUBBLES 4. NO DIE TILT 5. UNIFORM BONDLINE 6. NO FUMES 7. HIGH THROUGHPUT 1. Memory DRAM/SRAM 2. High adhesion to all surfaces 3. Pass MSL; Pass Reliability testing 4. Strength improvement for ultrathin die 5. Compact Medical prosthetics 6. For laminating ultrathin dies 7. Vertical Stacking 8. Die on flex/tape/film 9. Wafer bonding 42 paste DAF

22 Suppliers 1. Hitachi- 2. Lintec Adwill (UV) 3. Nitto Denko 4. Nippon Steel 5. Hysol/Ablestik DAF LIMITATIONS 1. Not quite DBG compatible 2. Not electrically conductive 3. Not thermally conductive 4. Not required for non stack pkg 43 Ultrathin die Interconnect 44 17um die IMEC, Belgium 140um package thickness

23 Ultrathin bumping is after thinning 45 Applied Physics Lab Johns Hopkins Univ. ECTC 2009 Summary of Ultrathin Technology Dice Before Grind Thickness as low as 10um available High flexibility High scatter of die strength After DAG laser or blade saw After DBG Independent of test methods Predictable by 5 side inspection Chemical Smoothening of 5 sides Decreases scatter dramatically Die attach using DAF 10um thickness available Interconnect Metal patterning Bump (Bump after thinning) 46

24 47 THANK YOU!! Finn Wilhelmsen Robert Corrao Dan Miranda Precision Wafer Thinning and Dicing Group CORWIL Technology. Ron Koepp IMPINJ