l i a b l eh k C o m p u t i n gL a b o r a t o r y

On Effective TSV Repair for 3D-Stacked ICs

Li Jiang†, Qiang Xu† and Bill Eklow§

†CUhk REliable Computing LaboratoryDepartment of Computer Science & Engineering

The Chinese University of Hong Kong

§ Cisco, CA,US

Outline Introduction

Motivation

TSV Redundancy Architecture

Routing Heuristic for Timing Consideration

Discussion & Conclusion

3D Product and To appear

3D stacked DRAM Package PCB

TSV DRAM

I/O BufferRD/WR

CMOS Image Sensor

Interposer based 2.5D FPGA Interposer

PackageTSV

PFGA Die

Memory on Processor More TSV

More Complicated

Requires manufacturing yield to be commercially viable

The Impact of 3D Stacking on Yield

Stack Yield Loss

Misalignment Impurity Open Short Leak & Delaminating

Void & Break

Assembly Yield Loss

Leveraged by KGD test and D2W stacking

Clustered TSV Defects

Assembly Yield is dramatically affected by TSV clustered faults

Source: IMECBond pad short Unsuccessful fill

TSV Repair Schemes: Neighboring Repair

1

2

1

N

1 Spare TSVN TSV Chain

2 Spare TSVs4 Signal TSVs

Redundancy Ratio

Signal-Switching Signal-Shifting

Source: Kang, SAMSUNG Source: H.H-S.Lee, GATech

M Spare TSV rows N x N TSV grid

Crossbar

Source: Loi, U. Bologna

M

N

Motivation

Signal-ShiftingSignal-Switching

Random

faults

Clustered TSV faults

Due toSurface

Roughness, Wafer bow, alignment

error

Redundancy Ratio: 1/2

CrossbarTo overcome: Repair faulty TSV from redundancy far apart

Motivation

Repair with TSV far-apart by topology

mapping

High repairing flexibility

Router based TSV grid

Reduce the cost of spare

TSVsReduce the

router complexity

Problem: TSV redundancy architecture and repair algorithms

Router Based TSV Redundancy

Successively Signal Rerouting• TSV Grid and Signal Routing Infrastructure

Redundant TSV

Signal TSV

SwitchSignal

Repair faulty TSV with nearest good TSV, and continue until a redundant TSV is used

M+N Spare TSVsM X N TSV Grid

M+NMxN

Switch DesignDirection of Rerouting

North to south, West to east (2 direction)Bypassing signal

Allow multi-hop signal reroutingMore Complex Design for more

routabilityTSV

Signal

East

North

South

West

Initial

TSV

Signal

East

North

South

West

Lend TSV to North

TSV

Signal

East

North

South

West

Lend TSV to North, bypass signal from west

Rerouting SchemeEdge Disjoint Paths Problem Maximum Flow

Method

W

TSV

Sig

E

N

S

Repair ChannelRepair Path

Problem Formulation

• Maximum Flow Method with 1 edge capability • Find Repair Path in Flow Graph (edge disjoint)

• Timing Constraint Length Constraint • Decision making in flow graph, affecting following

solution• Transfer the problem by finding Repair Channel

• Length Bonded Maximum Flow (NP-Hard)

a

b

min

c

b-min

a-min

c-min

0

Heuristic

Diagonal Direction GroupingBounded BFS Search (Length Bound & Maximal

Hops)

i=11

2

3

45

1 2 3 4 5

i=2

1

2

3

45

1 2 3 4 5i=2 C1,3

C1,4 C2,3

C1,5C2,4

C2,4C3,3

C2,2

C2,3 C3,2

C2,4 C3,3

C3,3 C4,2

i=3

1

2

3

45

1 2 3 4 5 i=3 C1,4

C1,5 C2,4

C2,5 C3,4

C2,3

C2,4 C3,3

C2,5 C3,4 C3,4 C4,3

C3,2

C3,3

C3,4 C4,3

C4,2

C4,3 C5,2

i=4 i=5

1

2

3

45

1 2 3 4 5

Maximal Hops = 2

Experiment Setup

Shifting: 2:1Switching: 4:2Crossbar: 8:2router: 4x4:8,8x8:16

Vary TSV Number: 1000 ~ 10000 ~ 100000

Fault Injection: • Poisson Distribution varying failure rate• Compound Poisson Distribution varying cluster

effect

Timing Constraint: • Assuming equal distances between

neighboring TSVs• Length constraint: 3 – 1 times of the distance

Comparison

Experimental ResultsCompound Poisson Distribution with Fixed TSV Failure Rate as 0.5%Alpha: Clustering Effect 0.4~3

1000 TSV

0.950000000000001

0.960000000000001

0.970000000000001

0.980000000000001

0.990000000000001

1shift2:1 cross8:2 switch4:2 router4x4 router8x8

10000 TSV

0.6

0.7

0.800000000000001

0.900000000000001

1shift2:1 cross8:2 switch4:2 router4x4 router8x8

Experimental ResultsCompound Poisson Distribution with Fixed TSV Failure Rate as 0.5%Alpha: Clustering Effect 0.4~3

100000 TSV

0

0.2

0.4

0.6

0.8

1shift2:1 cross8:2 switch4:2 router4x4 router8x8

100000 TSV

0.930.940.950.960.970.980.99

1

Experimental Results

1000 TSV

0.997

0.998

0.999

14x4(3T) 4x4(2T) 4x4(1T) 8x8(3T) 8x8(2T) 8x8(1T)

Conclusion

Cost Effective and scalable Solution to effectively repair clustered TSV faults.

From the cost perspective:• Limited extra Muxes and wires

• To achieve the same TSV yield, the required redundant TSVs with the proposed repair scheme is much less than existing solutions

l i a b l eh k C o m p u t i n gL a b o r a t o r y

Thank you for your attention !