Thermo-compression bonding for fine-pitch copper pillar flip chip interconnect

Intel : Amram Eitan, ASMP: SW Lau

Outline

• Drivers for Chip Attach Technology

• Thermo-Compression-Bonding (TCB) technology

– concept, unique features, as compared to Mass

Reflow

• TCB equipment characteristics to enable robust

chip attach processes

Chip Attach Assembly History

Multiple Chip Attach Technologies available: Technical and cost driven

• Drivers for Chip Attach Technology

• Thermo-Compression-Bonding (TCB) technology

– concept, unique features, as compared to Mass

Reflow

• TCB equipment characteristics to enable robust

chip attach processes

Drivers for Chip Attach Technology: Interconnect Scaling: FLI

FLI scaling Challenges: Placement accuracy and die alignment

5

Drivers for Chip Attach Technology: Package Geometry Aspects

Substrate and die thickness reduction to meet package Z height roadmap- challenges

die and substrate warpage (temperature dependent)

• Drivers for Chip Attach Technology

• Thermo-Compression-Bonding (TCB) technology

– concept, unique features, as compared to Mass

Reflow

• TCB equipment characteristics to enable robust

chip attach processes

Intel’s Mass reflow Chip Attach Technology

• Mass Reflow Chip Attach utilizes natural forces, to ensure die to

substrate position before and at reflow

• Limitations:

• When die and substrate are very thin, warpage overcomes

the natural forces, and non-contact opens occur

• Pitch scaling (FLI and towards 3D assembly) is driving

higher placement accuracy requirements

Non-Contact Open

TCB is becoming a high volume chip attach process in 2014 at Intel

Intel’s Next Generation Chip Attach Technology

Bond Force

Bond Head Temperature

Bond Head Z Position

Temperature ramp

up to melt solder Temperature ramp down to solidify solder Solder

chase

TCB bonding profiles

• TCB utilizes an actual process event to trigger the next step in the bond

operation

• TCB enables unit level process feedback, allowing automated process decisions

based on unit to unit output behavior

• TCB enables tight process control due to its ability to gauge the health of each

unit, as needed

Examples of TCB Bonding Results

Sensitivities that need Equipment features and performance:

• Thermal performance (heating/cooling, uniformity)

• Geometrical accommodation (flatness, warpage, thickness)

• Atmosphere

Process Time

• Process times of 4s and below have been

demonstrated

• Equipment features have been designed to enable short

process times

Key Messages:

• TCB technology is addressing Intel’s and

market’s roadmap towards finer pitch, thinner

and complex packages

• Process control in TCB allows “tailoring” of the

joint geometry, as well as real-time feedback for

quality assurance

• Process times are minimized by the unique

design of the TCB equipment

• Drivers for Chip Attach Technology

• Thermo-Compression-Bonding (TCB) technology

– concept, unique features, as compared to Mass

Reflow

• TCB equipment characteristics to enable robust

chip attach processes

Module Designs to Enable Robust Chip Attach Process

• Placement Accuracy (XY & angular)

• BHZ Position Accuracy

• Co-planarity Measurement & Adjustment

• Die & Substrate Vacuum

• BH Rapid Heating and Cooling

• Thermal Management

• Inert Environment

Placement Accuracy

• Best layout for placement accuracy

– Stationary bond head (BH) and moving

bond stage (BS) with split view optics on

optics table (OT)

• Air bearing for all moving axes with

high resolution encoders to reduce

motion errors

– BHZ, BH mini-Z, BS XY, OT XYZ

• High resolution camera to enhance

alignment accuracy

– With closed-loop temperature control

• The whole bonder structure is

supported by pneumatic isolators

– Best vibration isolation from environment

CoG XY Placement Results

• XY placement accuracy well within ±2µm

– CoG glass die size: 33mm x 22mm

– Each test: 2x 16 runs @ 3 BS positions on each BS

– BH & BS temperature: 150C

33mm

22mm

Worst Case Corner Performance

• Angular placement accuracy well

within ±0.01

• Worst case corner offset < 3µm

BH with Advanced Process Capabilities

• Completely in-line force production

• Both Large (500N) and Small (1N) force

produced from a single head

– Force sensors with dynamic ranges

• Air bearing guidance for zero wear and

ultra-low friction for long term reliability

• Ultra-high accuracy encoders for

ultimate Z position and bump height

control

• Advanced cooling method to prevent

thermal drift due to BH heater

• Advanced active tip tilt mechanism for

co-planarity adjustment

BHZ Position Accuracy

• Z position accuracy at 350C within ±1µm

– Ensure bump height control during local reflow process

BH mini-Z A-B B-C C-D D-E E-F F-G G-H All B&H C&G D&F

Mean 10.11 10.25 10.03 10.15 10.28 10.05 10.22 10.16 427.80 417.56 407.52

S.D. 0.05 0.05 0.05 0.05 0.06 0.06 0.05 0.10 0.07 0.08 0.07

Cpk@±1um 5.400 5.044 6.290 5.439 4.177 5.032 5.541 2.708 4.194 2.961 2.985

10um step

Bond Force Accuracy

• Force accuracy within ±0.1N when

set force is 1N

– BH temperature: 350C

– BH search speed: 1.0 mm/s

– Use insulator with ball contact

– Each test: 16 cycles

Set force (N) 5 2 1

Set force accuracy

Spec ±5% ±5% ±20%

Mean (N) 5.185 2.040 0.979

SD (N) 0.013 0.014 0.028

Cp 6.639 2.368 2.410

Cpk 1.729 1.421 2.161

Impact

Mean (N) 1.771 1.650 1.579

Max (N) 1.818 1.683 1.640

Min (N) 1.730 1.625 1.524

Range (N) 0.088 0.058 0.115

Co-planarity Measurement & Adjustment

Side View

Tip-tilt

actuators

US PATENTED over 30mm

Die & Substrate Vacuum • Die and substrate are hold flat firmly during bonding by product

specific vacuum trough design on die nozzle and substrate

pedestal

• Maximum 4 individual vacuum channels for substrate pedestal

• Real time monitoring of all vacuum channel analog vacuum

level during bonding

BH Rapid Heating and Cooling

• Performance designed for large die

– Die size up to 33mm x 22mm

• Heating rate

– Maximum without load: ≥ 125C/s in free air

– Controlled: within ±5% of set rate

• Cooling rate

– Maximum without load: ≤ -50C/s in free air

• Temperature uniformity

– ±5C @ Cpk 1.33

Advanced Thermal Management

• Split-view optics

– Symmetric layout

– Same length of optical path for up/down look optics

– Low CTE materials to reduce thermal drift

– Active temperature controlled chamber to ±0.5C

• Bond head heater

– Ceramic insulator in contact with heater

– Top cooling block with air flow

– Reduce temperature from 400C at heater surface

to 30C at top mounting surface

– Thermal mapping for BHZ position compensation

• Bond stage heater

– Ceramic insulator in contact with heater block

– Pillar support with air isolation

– Temperature rise < 3C at base plate when BS

heater surface at 200C

Innovative Inert Environment Solution

• Moving micro inert

– Pedestal on BS with shielding by air gap

• Macro inert chamber

– Enclose BH and OT modules

• Macro and micro chamber connected

by a bond window opening

High Volume Manufacturing (HVM) Configuration

Substrate

Die

Bonded units

Key Messages:

• Proven high quality HVM solution for high

precision, large die thermo-compression bonding

• Proven portable module solutions / core

technologies for current TCB challenges

• Future-proof platform that is forward compatible

with advancement in packaging roadmap

Summary

• Packaging roadmap towards thinner and more

complex assembled products is driving new

required chip attach capabilities

• Thermo-compression bonding was developed

and implemented at Intel towards High Volume

Manufacturing starting in 2014

• ASM’s TCB equipment provides unique

features to enable high quality, fast and robust

chip attach process

Thank You for Listening