lfsr test pattern crosstalk in nanometer...

LFSR Test Pattern Crosstalk in Nanometer Technologies

DieterDieter TreytnarTreytnar, Michael , Michael RedekerRedeker, , Hartmut Hartmut Grabinski Grabinski and and FaFaïïez Ktataez Ktata

Laboratory for Information TechnologyUniversity of Hannover, Germany

LFSR Test Pattern Crosstalk in Nanometer Technologies - Dieter Treytnar

6th Workshop on Signal Propagation on Interconnects 20022

OutlineOutline

!! IntroductionIntroduction!! Line ParametersLine Parameters!! Linear Feedback Linear Feedback Shift Shift RegisterRegister!! Simulation Simulation ResultsResults!! SummarySummary



IntroductionIntroductionSIA predicts a very aggressive path of technologies

! Technology will decrease from 150 nm (today) down to 35 nm (year 2012)

! Number of gates will increase from 220 M up to 20,000 M

! Frequency will increase from 1.4 GHz up to 8 GHz

! Power Voltage will decrease from 1.2 Volts down to 0.45 Volts



How does scaling How does scaling ininnanometer technologies nanometer technologies

affect the quality affect the quality of of signals signals ??

How stable areHow stable are test test patterns against crosstalkpatterns against crosstalk ? ?



ContentsContents




Line ParametersLine Parameters

≥≥ 0.200.20≥≥ 0.260.26≥≥ 0.390.39≥≥ 0.550.55≥≥ 0.810.81spacing spacing [µm][µm]

3.3453.3453.873.874.7254.7255.7355.7356.546.54distdist. to . to substsubst. . [µm][µm]

0.290.290.360.360.550.550.770.770.920.92height height [µm][µm]

≥≥ 0.080.08≥≥ 0.100.10≥≥ 0.160.16≥≥ 0.220.22≥≥ 0.330.33width width [µm][µm]35nm35nm50nm50nm70nm70nm100nm100nm150nm150nmtechnologytechnology

Geometric Data for Copper Lines in Metal 5

Source: Int. Technology Roadmap for Semiconductors 1999



Self CapacitanceSelf Capacitance

0.25

0.15

0.10

0.07

0.05

0.03

5 54

32

105

1015202530

C'[pF/m]

technology

metal

Strong decrease in local wires

Nearly constant in global wires

FSub = 10.000 S/m

5 parallel copper lines



Mutual CapacitanceMutual Capacitance

0.25

0.15

0.10

0.07

0.05

0.03

5 54

32

10

20406080

100120140160

C'[pF/m]

technology

metal

�Saturation effect� in smaller technologies



Self InductanceSelf Inductance

0.25

0.15

0.10

0.07

0.05

0.03

5 54

32

10,000,200,400,600,801,001,201,401,60

L'[µH/m]

technology

metal

Increasing L� for smaller technologies



Mutual InductanceMutual Inductance

0.25

0.15

0.10

0.07

0.05

0.03

5 54

32

10,000,200,400,600,801,001,201,40

L'[µH/m]

technology

metal

Increasing L� for smaller technologies



ResistanceResistance

0.25

0.15

0.10

0.07

0.05

0.03

5 54

32 1

0500

10001500200025003000

R'[kOhm/m]

technology

metal

Very strong increasing R� for smaller technologies



Resistance Resistance per per unit length unit length plays plays a a very important very important

rolerole in in the future the future

Crosstalk Crosstalk effects have effects have to to be taken into accountbe taken into account



ContentsContents




Linear Feedback Linear Feedback Shift Shift Register IRegister IFuture integrated circuits will likely be tested by self test strategies only (M.Rodgers, Intel; ITC�99)

Most common built-in test pattern generator used in today�s chip design is the LFSR

An LFSR is very easy to implement and further on very powerful for self testing



Linear Feedback Linear Feedback Shift Shift Register IIRegister II

Shift register with XOR feedback loop

Dividing polynomial is primitive



Linear Feedback Linear Feedback Shift Shift Register IIIRegister III

Singular state:

111100001414110000001515

111100117711001100880011001199110011111010001111111111111111111212111111001313

16 = 116 = 1

665544332211

timesteptimestep

00000011

001111000000111111000011001100000000110000000011

Bit 3Bit 3Bit 2Bit 2Bit 1Bit 1Bit 0Bit 0

Bit 3Bit 3Bit 2Bit 2Bit 1Bit 1Bit 0Bit 0tsteptstep

00000000nn0000000011

It can adopt 2n-1 states(pseudo random patterns)



Linear Feedback Linear Feedback Shift Shift Register IVRegister IV

LFSR produces ones and zeros so that very strong crosstalk arise



ContentsContents




Simulation Simulation ResultsResults

Simulated line system with a 5 bit LFSR

TP1

TP5ZD CL

TP2

TP3

TP4

V(1)

V(5)

V(4)

V(3)

V(2)

V(10)

V(9)

V(8)

V(7)

V(6) V(12)

V(20)

V(18)

V(16)

V(14)

copper, l = 1 mm



70 nm technology70 nm technology

Line 1

Line 3

Line 2




Line 1

Line 3

Line 2



Crosstalk Crosstalk EffectsEffects! 70 nm technology

- few crosstalk effects- fault free in the digital world

! 50 nm technology- stronger crosstalk effects- propagation is dominated by delay effects

! 35 nm technology- strong crosstalk effects- strongly increasing resistance- LFSR test patterns will be transmitted with errors



What are the influences What are the influences of of coupling parameters coupling parameters

in detail ? in detail ?



Comparison Comparison 35 nm technology35 nm technology

With coupling (L�, C�)Purely resistive



ConclusionsConclusions! It is nearly impossible to transmit LFSR test

patterns through a line system longer than 1 mmbeyond the 50 nm technology

! Propagation through lines shorter than 0.5 mmcan be expected to be fault free for the 35 nm technology

! Delay due to higher resistances is an important problem in nanometer technologies

! Crosstalk will further play an important role for LFSRtesting in the future and has to be taken into account



Possible SolutionsPossible Solutions

! ...new test techniques (e.g. cellular automatas, chip partioning for testing)

! ...new line geometries (e.g. wave guides on chip)

! ...implementing long lossy lines in larger geometries(e.g. double the width and spacing)

Problems of testing �monster� chips can be reduced by...



Thank you very much Thank you very much for your attention for your attention

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