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Conceptual design of a Pick and Place machine for 3D-IC. Jasper Winters, Mechatronic System Design. A TNO initiative. Contents. Introduction: Introduction to electronics Introduction: What is 3D-IC? Analysis: Pick and Place limits Design: Machine concepts

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conceptual design of a pick and place machine for 3d ic

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

Jasper Winters, Mechatronic System Design

A TNO initiative.

contents
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
introduction
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
introduction to electronics
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
what is 3d ic
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

what is 3d ic1
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
what is 3d ic2
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

pick and place limits
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
pick and place limits1
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
pick and place limits2
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
pick and place limits3
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
pick and place limits4
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]

pick and place limits5
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
conceptual design
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
concepts
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

concepts1
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

concepts2
Concepts

Colored arrows  high accuracy

Black arrows  low accuracy

Transport systems

Linear guide

Flexible carrier

Flexible carrier (x2)

concepts3
Concepts

Trade-off

  • Trade-off process
    • Criteria grouped in four items
      • Throughput
      • Accuracy
      • Yield
      • Miscellaneous
    • Weighting factors and scores determined by pair wise comparison
concepts4
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

concepts5
Concepts

Chosen concept – timing diagram

concepts6
Concepts

Chosen concept – picking and placing example

Picking

Placing

flexible carrier
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
flexible carrier1
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

flexible carrier2
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
flexible carrier3
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
electrostatic clamp
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
electrostatic clamp1
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

electrostatic clamp2
Electrostatic clamp

Experiment – setup

  • Force measurement
    • Pull off die
    • Measure maximum pulling force (maxhold)

Sample

Clamp

Scale

electrostatic clamp3
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)
electrostatic clamp4
Electrostatic clamp

Experiment – Die and wafer pickup

  • 5x5 mm die (t=750 μm)
  • 1 inch wafer (t=200μm)
summary and conclusions
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
recommendations and opportunities
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
pick and place limits6
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
motion profile
Motion profile

No constant velocity part

No constant acceleration part

Jerk is always not equal to zero: jerk limits cycle time

gantry motions
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
concepts7
Concepts

Chosen concept

  • Separation of high reaction forces and accuracy systems
  • Possibility of integrating
    • Probing
    • Cleaning
    • Inspection
pick and place cycle
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
pick and place cycle1
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.
concepts8
Concepts

Other concepts

Internal/External buffer

Single die Wafer2Wafer

higher accelerations means
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
concepts9
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
electric field
Electric field
  • Fundamental force
  • Capacitance
  • Self capacitance
electrode design
Electrode design

Three types of industrially available HV electrode designs

holding force
Holding force
  • Peeling
  • Residual charge
  • Dust
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