Conceptual design of a Pick and Place machine for 3D-IC

1. Conceptual design of a Pick and Place machine for 3D-IC Jasper Winters, Mechatronic System Design A TNO initiative.

2. Contents • Introduction: Introduction to electronics • Introduction: What is 3D-IC? • Analysis: Pick and Place limits • Design: Machine concepts • Design: Flexible carrier concept outline • Design: Carrier design • Experiment: Electrostatic clamp • Conclusions

3. Introduction: Introduction to electronics • Introduction: What is 3D-IC? • Analysis: Pick and Place limits • Design: Machine concepts • Design: Flexible carrier concept outline • Design: Carrier design • Experiment: Electrostatic clamp • Conclusions Introduction

4. A B C E D Introduction to electronics What is a die or chip? • Die (or chip) • Functional part of electronic device • Typical size 5x5 mm, thickness 50 – 750 micron • Usually packaged

5. What is 3D-IC? Stacking of dies Benefits of 3D-IC Form factor (smaller) Performance (lower latency) Memory capacity (more bits per area) Processor power consumption Interconnect with Through Silicon Vias (TSVs) Very short interconnect length TSV is elevator is silicon skyscraper Typical diameter 5 – 20 micron New packaging method

6. Carrier bonding Wafer thinning Bump creation TSV filling Dicing TSV creation Cleaning Inspection Singulation Picking Molding Placing Collective bonding What is 3D-IC? A TNO initiative. How to make 3D-IC? • About 20 different processes • TSV creation • Separation of dies • Pick and Place (stacking) • Packaging • … • Most commercial equipment does not suffice • Pick and Place too expensive with current equipment

7. What is 3D-IC? Die to wafer stacking Higher yield than w2w Heterogeneous stacks Different technologies Different die sizes Required specifications 5 dies per second 1 μm placement accuracy (related to TSV overlap) Pick and Place Die Wafer

8. Introduction: Introduction to electronics • Introduction: What is 3D-IC? • Analysis: Pick and Place limits • Design: Machine concepts • Design: Flexible carrier concept outline? • Design: Carrier design • Experiment: Electrostatic clamp • Conclusions Pick and place limits

9. Pick and Place limits Commercial equipment • Requirements for 3D-IC (die stacking) • 5 dies/s (cost effective solution) • 1 μm placement accuracy (for aligning TSVs) • Three main areas • Surface Mount Technology (SMT) • Die bonders • Micro Systems Technology (MST) • State of art machines: • 5 dies/s at 50 μm accuracy • 1 μm accuracy at 0.14 dies/s • But NOT combined: 5 dies/s at 1 μm accuracy

10. Pick and Place limits Cycle time limitations • 5 placements per second  cycle time of 200 ms • Typical values: • 60%-80% of this time, dies are moved • 40%-20% of this time, dies are measured or placed • Allowed movement: 80% of 200 ms = 160 ms • Pick and place of dies from 300 mm wafer to another 300 mm wafer

11. Pick and Place limits Cycle times overview • Compared to Datacon FC 8800 Quantum • speed is increased by factor 2.5 • acceleration is increased by factor 7 (!) • jerk is increased by factor 3

12. Pick and Place limits Accuracy limits Frame displacement in [m∙10-5] • Stages • Vision system (die measurement) • Vibrations • Floor • Supply systems • Reaction forces Time in [s]

13. Pick and Place limits Conclusions • Current architecture not suitable for new requirements • Accuracy limited • Error propagation (calibration and placement routines) • Reaction forces • Throughput limited by accelerations • Alternative ways on increasing throughput • Simultaneous actions on one die • Parallel end effectors in bondhead in one pick & place robot • Parallel pick & place robots in one machine • Parallel pick & place machines

14. Introduction: Introduction to electronics • Introduction: What is 3D-IC? • Analysis: Pick and Place limits • Design: Machine concepts • Design: Flexible carrier concept outline • Design: Carrier design • Experiment: Electrostatic clamp • Conclusions Conceptual design

15. Concepts Colored arrows  high accuracy Black arrows  low accuracy Nozzles on gantry Concept used in Datacon 8800 FCdie bonder Single nozzle Concept used in many SMT component mounters Multi nozzle Concept used in highest throughput SMT component mounters Turret on gantry

16. Concepts Colored arrows  high accuracy Black arrows  low accuracy Turret systems Turret radial Turret axial Turret supply Stationary turret, with XY substrate stage, used in chip shooters

17. Concepts Colored arrows  high accuracy Black arrows  low accuracy Transport systems Linear guide Flexible carrier Flexible carrier (x2)

18. Concepts Trade-off • Trade-off process • Criteria grouped in four items • Throughput • Accuracy • Yield • Miscellaneous • Weighting factors and scores determined by pair wise comparison

19. Concepts Chosen concept • Travel distance reduced to die pitch on tape • Separation high reaction forces and accuracy systems • Possibility of integrating • Probing • Cleaning • Inspection • Other parallel processes Flexible carrier Flexible carrier

20. Concepts Chosen concept – timing diagram

21. Concepts Chosen concept – picking and placing example Picking Placing

22. Flexible carrier Clamping mechanism • Several mechanisms were investigated for holding die on carrier • Most promising were • Chemical adhesive (glue) • Electrostatic • Vacuum • Electrostatic chosen for highest compatibility • No residue on die • Fast switching of force possible

23. Flexible carrier Electrostatics • Electrostatics adhesion • Electric field attracts charged particles (e.g. electrons) • Requirements • (Semi-) conductive electrodes • Charge can move or orient itself to field • Dielectric medium (e.g. air) • Medium should allow electric field F C=Capacitance [F] f=Pressure [Pa] F=Force [N] A=Electrode area [m2] ε(ε0 εr)=Permittivity [F/m] V=Electric potential [V] d=Airgap [m] ε0 ∙ εr F

24. Flexible carrier Electrostatics • Monopolar clamp • Electrical connection to die • Die is charged • Bipolar clamp • No electrical connection to die • Net charge is zero • Need two voltage sources

25. Flexible carrier Electrostatics – effect of insulator • Purpose of insulator • Avoid short circuit • Maintain electric field • Side effects • Shows up in pressure equation • Tune force dependence on air gap (stiffness) • Reduce maximum pressure • Optimizations • Maximize for maximal pressure • Increase insulator thickness for less dependence of pressure is on air gap • should be smaller than to be not too sensitive to air gap

26. Introduction: Introduction to electronics • Introduction: What is 3D-IC? • Analysis: Pick and Place limits • Design: Machine concepts • Design: Flexible carrier concept outline • Design: Carrier design • Experiment: Electrostatic clamp • Conclusions Electrostaticclamp

27. Electrostatic clamp Experiment – manufactured clamp • Bipolar clamp • 2 rectangular aluminum electrodes (total 16x16 mm) • Polyimide foil insulator (t=25 μm) • Glass base (40x40 mm) • Aluminum counter electrode (10x10 mm) (substitute for die) • Properties • Air gap 4.6 μm • Capacitance 18 pF Two 10x10 [mm] aluminum electrodes Clamp

28. Electrostatic clamp Experiment – setup • Force measurement • Pull off die • Measure maximum pulling force (maxhold) Sample Clamp Scale

29. Electrostatic clamp Experiment – results • Cleaned clamp best results • Polynomial fit inside expected range • Required minimal pressure (200 Pa) obtained at low voltage (80 V) • Uncertainties • Supply voltage • Sensor • Air gap (capacitance)

30. Electrostatic clamp Experiment – Die and wafer pickup • 5x5 mm die (t=750 μm) • 1 inch wafer (t=200μm)

31. Summary and Conclusions • Study, measurements  limitations current equipment • Limited Accuracy • Limited Throughput • Innovative Pick and Place concept created • Likely to reach both accuracy and throughput requirement for 3D-IC • Reduce effective transport distance • Decouple reaction forces from accuracy system • Parallel processes possible • Concept developed for flexible carrier • Low cost electrostatic clamp designed and tested • Sufficient clamping force obtained at low voltages • Fast clamping and declamping

32. Recommendations and opportunities • Further work is needed to design machine • Improve accuracy to 1 μm • Design flexible carrier and transport system • Flexible carrier related • Investigate risk of damage to die • Damage to circuits • Attracting dust to die • Use flexible carrier as mechanical support during die release

33. Questions?

35. 3D-IC Market

36. Pick and Place limits Commercial equipment • Requirements for 3D-IC (die stacking) • 5 dies/s (cost effective solution) • 1 μm placement accuracy (for aligning TSVs) • Three main areas in current PnP equipment • Surface Mount Technology (SMT) • Large diversity, High throughput, Low accuracy (up to 30 micron) • Die bonders • Only bare dies, Medium throughput, Medium accuracy (up to 3 micron) • Micro Systems Technology (MST) • Divers fragile devices, Low throughput, High accuracy (up to 0.2 micron) • State of art machines: (see next slide) • 5 dies/s at 50 μm accuracy • 1 μm accuracy at 0.14 dies/s • But NOT combined: 5 dies/s at 1 μm accuracy

39. Motion profile No constant velocity part No constant acceleration part Jerk is always not equal to zero: jerk limits cycle time

40. 1 2 3 4 5 6 7 8 Gantry motions p4 = 300 mm, v = 5.2 m/s, a = 175 m/s2, j = 6000 m/s3 • Move down die: 5 mm • Place die: 20 ms • Move op nozzle: 5 mm • Move nozzle to source wafer: 300 mm • Move nozzle down to source wafer: 5 mm • Pick die: 20 ms • Move up die: 5 mm • Move die to target wafer: 300 mm

41. Concepts Chosen concept • Separation of high reaction forces and accuracy systems • Possibility of integrating • Probing • Cleaning • Inspection

42. Pick and place cycle • Clearly current state-of-the-art is not sufficient • Example motor current: (60 kg mass) • j = 6000 m/s3 • a = 175 m/s2 10kN65 A x2 (two motors = configuration in 8800 FC) • v = 5,15 m/s • Compared to Datacon FC 8800 Quantum, • jerk is increased by factor 3 • acceleration is increased by factor 7 (!), • speed is increased by factor 2,5

43. Pick and place cycle • General conclusions: • Start-stop costs a lot of cycle time •  try to avoid stopping •  try to make one movement from source to target; don’t split up in e.g. XY and Z movements • For minimized setup time, jerk must be limiting (3rd order profiles) • For jerk limiting profiles, especially acceleration is increased a lot with respect to state-of-the-art solutions. • Increasing jerk over ~10000 m/s3 is (relatively) not very effective for reducing cycle times, when travelling ~300 mm. Parallelization will be much more effective in this case. • 5 dies/s with one robot is not realistic.

44. Concepts Other concepts Internal/External buffer Single die Wafer2Wafer

45. Higher accelerations means… • Higher reaction forces that disturb machine’s accuracy • More expensive hardware (actuators, amplifiers, measurement systems, guidance, materials, special machining) • Higher power consumption. Use of energy recuperation? • More thermal effects that affect accuracy

46. Concepts Chosen concept • Advantages • Possible to fully separate reaction force of source stage from the high accuracy system • Greatly reduced transport distance (die pitch)  shorter cycle time • Stationary placement location • Parallel processes possible • Simultaneous transport and alternate processes • Perform different processes on different dies at the same time (picking, placing and transport simultaneous) • Large buffer of flexible capacity • Picking and placing decoupled in timing and location • Single high accuracy nozzle (reduced cost) • Disadvantages • Longer start up time (buffer needs to be filled) • Separate unit required to change nozzles • Flexible carrier could wear out (consumables  higher cost) • Dies vulnerable to contamination on transport system • Dies on flexible carrier not trivial • Opportunities • Start stop of wafer stage can be replaced by short stroke moving gantry in same direction  die stationary relative to wafer during placement • Buffering allows multiple inspection and cleaning steps • Possibility for full continuous operation without any start stop by placing on flexible carrier instead of wafer

47. Timing diagram

48. Clamping mechanisms

49. Electrostatic clamp

50. Electric field • Fundamental force • Capacitance • Self capacitance