11/8/2000 1 sensitivity of spectroscopic scatterometry: sub-100nm technology sfr workshop november...

11/8/2000

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Sensitivity of Spectroscopic Scatterometry: Sub-100nm Technology

SFR WorkshopNovember 8, 2000

Ralph Foong, Costas SpanosBerkeley, CA

2001 GOAL: To fully characterize the capabilities of scatterometry in fulfilling the metrology needs of the 100nm

technology node.

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Motivation• Capabilities of scatterometry and required equipment specifications

need to be formalized for 100nm metrology.– Commercial ellipsometers have been identified as being able to perform

spectroscopic scatterometry. Hence, the focus of this study is on these equipment.

– Precision of current generation commercial ellipsometers in measuring profiles consistent with 100nm technology node has to be confirmed.

• Scalability of scatterometry towards 70nm and 50nm metrology has to be explored.– Minimum commercial ellipsometer specifications necessary to successfully

implement 70nm and 50nm metrology need to be determined.

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Overall Framework of Sensitivity Analysis

Commercial Equipment Analysis

Profile Parameters

Simulations for variation in parameter X

[X(-),X(Nominal), X(+)]Cos

Lambda

Tan

Lambda

Determine Noise Contributions

Tan , Cos Noise Spectrum

Are Variations Detectable?

NoYes

EM Response Variations

Which part of the spectrum contains the

most information?

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Methodology• Electromagnetic simulations

are conducted for small changes in profile parameters to measure variations in EM response.

• Noise analysis of commercial ellipsometers is carried out to determine detectability of EM response variations.

d(Beam Divergence)

d(ISource)

d(Polarizer)

d(Analyzer)

d(IDetector)

Sample

PR

ARC

Poly-Si

RoundingSlopeAngle

Height CDFooting

Si

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Signal-to-Noise Ratio for SOPRA EllipsometerSignal-to-Noise Ratio vs Lambda

1

10

100

1000

10000

100000

1000000

10000000

100000000

0.19

0.23

0.27

0.31

0.35

0.39

0.43

0.47

0.51

0.55

0.59

0.63

0.67

0.71

0.75

lambda (nm)

Cts

/s (

Sig

nal

, N

ois

e),

SN

R

Intensity (cts/s)

Noise (cts/s)

S.N.R

• Signal averaged over 30 measurements

• Noise represents 1 standard deviation for each wavelength

• Empirical formula for signal-to-noise ratio:

Noise = 0.412(Intensity)0.632

(R2 Value = 0.937)

• Intensity fluctuation is the main contributor of measurement noise in ellipsometers.

• Monte-Carlo simulations incorporating intensity fluctuations are used to determine the final distributions of Tan and Cos

• The ‘Minimum Detectable Variation’ lines represent the sum of the 3 errors of each of the 2 profiles measured to obtain the variation.

• The graphs demonstrate a trend toward significant information contained in a narrow band in the lower wavelength spectrum.

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100nm Technology Simulations

Variation of Tan Psi for CD Variation vs Lambda

0.0001

0.001

0.01

0.1

1

10

100

Lambda(nm)

Tan

Psi

Var

iati

on Variation(-)

Variation(+)

Minimum DetectableVariation

Undetectable (Below yellow

line)

Detectable (Above yellow

line)

Variation of Cos Del for CD Variation vs Lambda

0.00001

0.0001

0.001

0.01

0.1

1

Lambda(nm)

Co

s D

el V

aria

tio

n Variation(-)

Variation(+)



0.001

0.01

0.1

1

10

Lambda(nm)

Tan

Psi

Var

iati

on Variation(-)

Variation(+)



0.0001

0.001

0.01

0.1

1

Lambda(nm)

Co

s D

el V

aria

tio

n Variation(-)

Variation(+)



line)


line)

100nm Dense Lines (ASIC) 65nm Isolated Lines (MPU)

spectrum of information

content

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70nm Technology Simulations70nm Dense Lines (ASIC) 45nm Isolated Lines (MPU)


0.0001

0.001

0.01

0.1

1

10

Lambda(nm)

Tan

Psi

Var

iati

on Variation(-)

Variation(+)



0.00001

0.0001

0.001

0.01

0.1

1

Lambda(nm)

Co

s D

el V

aria

tio

n Variation(-)

Variation(+)



0.0001

0.001

0.01

0.1

1

Lambda(nm)

Tan

Psi

Var

iati

on Variation(-)

Variation(+)



0.00001

0.0001

0.001

0.01

0.1

1

Lambda(nm)

Co

s D

el V

aria

tio

n Variation(-)

Variation(+)



line)


line)

11/8/2000

8


0.00001

0.0001

0.001

0.01

0.1

1

Lambda(nm)

Tan

Psi

Var

iati

on Variation(-)

Variation(+)


50nm Technology Simulations50nm Dense Lines (ASIC) 30nm Isolated Lines (MPU)


line)


line)


0.001

0.01

0.1

1

10

Lambda(nm)

Tan

Psi

Var

iati

on Variation(-)

Variation(+)



0.000001

0.00001

0.0001

0.001

0.01

0.1

1

Lambda(nm)

Co

s D

el V

aria

tio

n Variation(-)

Variation(+)



0.000001

0.00001

0.0001

0.001

0.01

0.1

1

Lambda(nm)

Co

s D

el V

aria

tio

n Variation(-)

Variation(+)


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2002 & 2003 Goals• Study the feasibility of building 100nm capable profile

extraction using small footprint, in-line spectroscopic ellipsometry, by 9/30/2002

• Implement lithography controller that merges full profile in-line information with available metrology, by 9/30/2003

Profile Diagnostics

DUV Photolithograph

yPR Deposition,

Focus, Exposure, Bake Time,

Development Time, etc

Process Flow

In-Line Scatterometr

y

Process Flow

Wafers

Feedback Control Loop

11/8/2000 1 sensitivity of spectroscopic scatterometry: sub-100nm technology sfr workshop november...

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