Transmission Grating Spectrometer for EUV Lithography Nathan Gray Advisors: Alexander Shevelko, Larry Knight, and Scott Bergeson Student Group Members:

Transmission Grating Spectrometer for EUV

Lithography

Nathan Gray

Advisors: Alexander Shevelko, Larry Knight, and Scott Bergeson

Student Group Members: Matthew Harrison, Jeff Kemp, Bryce Allred, Jershon Lopez

Extreme Ultraviolet (EUV)Extreme Ultraviolet (EUV)1-1000 1-1000 ÅÅ

Image modified from: NASAexplores Models of the Electromagnetic Spectrum student sheet. lot.astro.utoronto.ca/spectrum.html

http://lot.astro.utoronto.ca/spectrum.html



Absorbed by Everything:

•Air





•Air

•Glass





•Air

•Glass

•Plastic





•Air

•Glass

•Plastic

•Ponies


Extreme Ultraviolet (EUV)Extreme Ultraviolet (EUV)


•Air

•Glass

•Plastic

Must operate under vacuum (our chamber is at 30-100 mtorr)

Must use mirrors in place of conventional optics.

This makes spectroscopy in the EUV range complicated.

EUV range transmission gratings:


Recent transmission grating development allows for EUV range gratings

200 nm period

(5000 lines/mm)


Recent transmission grating development allows for EUV range gratings

200 nm period

(5000 lines/mm)

Transmission grating spectrometers are superior to reflection grating spectrometers

Possible ConfigurationsPossible Configurations

Entrance SlitEntrance Slit

Grating

Detector

Simple Transmission Grating Spectrometer

Possible ConfigurationsPossible Configurations Single Mirror GeometrySingle Mirror Geometry

Entrance SlitEntrance Slit

Grating

Detector

Spherical Mirror

•High spectral resolution and luminosity

•Mirror collects large solid angle

Our ConfigurationsOur Configurations Double Mirror GeometryDouble Mirror Geometry

Grating

Entrance SlitEntrance SlitFlat Mirror

Detector

Spherical Mirror

Designed by Dr. Alexander Shevelko

Knight/Shevelko Group Knight/Shevelko Group Spectrometer ConfigurationSpectrometer Configuration

0

1000

2000

3000

4000

5000

6000

7000

8000

0 50 100 150 200

Wavelength (Ǻ)

Inte

ns

ity

(c

ou

nts

)

B

#002

EL=405 mJ

40 shot sum

Grating 5000 ℓ/mmEntrance Slit 250 μm

BV

1s-

2p 4

8.6

Ǻ

BIV

1s2 -1

s3p

52.7

Ǻ, 1s2 -1

s4p

50.4

Ǻ

BIV

1s2 -1

s2p

60.3

Ǻ

OV

I 2s

-4p 1

15.8

3Ǻ, 2p

-5d

115.

83Ǻ

OV

I 2p

-4d 1

29.8

Ǻ

OV

I 2p

-3d 1

73Ǻ

OV

I 2s

-3p 1

50.1

Ǻ

0

5000

10000

15000

20000

0 50 100 150 200

Wavelength (Ǻ)

Inte

ns

ity

(c

ou

nts

)

Fe

#006

EL=300 mJ

40 shot sum


FeX-FeXI I IFeXVI 3d-5fFeXVI I 3s-4p

FeXVI 3s-4p

FeXV 3p-4dFeXVI 3p-4d

FeXIV 3p-4dFeXVI I 3d-4f

FeXV 3d-4f

FeXVI 3d-4f, FeXVI I 3d-4p

Electron Temperature StudyElectron Temperature StudyTungstenTungsten

0

500

1000

1500

2000

2500

3000

3500

4000

0 50 100 150 200 250 300

Wavelength (Ǻ)

Inte

ns

ity

(c

ou

nts

)

440mJ

300mJ

200mJ

150mJ

W

#024


0

500

1000

1500

2000

2500

3000

3500

4000

0 50 100 150 200 250 300

Wavelength (Ǻ)

Inte

ns

ity

(c

ou

nts

)

W

#015

EL=440 mJ

1 shot


WX

XII

-WX

XIX

4-5

tran

sition

s 25

-38

Ǻ

WXXVI I I -WXXX 4-4 transitions 48-65 Ǻ

Efficiency CalculationEfficiency Calculation

Major advantage of transmission grating over reflection grating

Must take transmission through wires into account (phase shift)

Materials:

Au 25 nm Au 25 nm

Si4N3 200 nm

Radiation

FormulaeFormulae

Efficiency CalculationEfficiency CalculationTotal Grating Efficiency

0

0.001

0.002

0.003

0.004

0.005

0.006

0 5 10 15 20 25 30 35 40 45

wavelength (nm)

Eff

icie

ncy

total efficiency

0

0.001

0.002

0.003

0.004

0.005

0.006

0 5 10 15 20 25 30 35 40 45

Fujikawa et al. MethodSchopper et al. Method

H. W. Schopper et al., Appl. Opt. 16, 1088 (1977).

C. Fujikawa et al., Rev. Sci. Instrum. 69, 2849 (1998).

Absolute CalibrationAbsolute Calibration

grating efficiency X spherical mirror reflectivity X flat mirror grating efficiency X spherical mirror reflectivity X flat mirror reflectivity reflectivity

= total spectrometer efficiency = total spectrometer efficiency




total spectrometer efficiency X detector calibration total spectrometer efficiency X detector calibration

= absolute calibration= absolute calibration






absolute calibration = Intensity scaled to units of actual photon absolute calibration = Intensity scaled to units of actual photon flux, instead of just relative intensity.flux, instead of just relative intensity.






absolute calibration = Intensity scaled to units of actual photon absolute calibration = Intensity scaled to units of actual photon flux, instead of just relative intensity.flux, instead of just relative intensity.

Detector calibration: completed at Lebedev Physical Institute by Oleg Yakushev

EUV LithographyEUV Lithography

International Technology Roadmap for Semiconductors printable patterns with 32 nm between features are required by the semiconductor industry by 2009


Main limitation is wavelength of light source

Higher Resolution requires a source with smaller wavelength

V. Bakshi, EUV Sources for Lithography, SPIE Press Book, 2006.V. Bakshi, EUV Sources for Lithography, SPIE Press Book, 2006.

Typical EUV wafer scannerTypical EUV wafer scanner


Typical EUV Lithography apparatus: 11 mirror multilayer Mo/Sn multilayer

mirrors with reflections around 66% each.

The overall transmission in the EUV scanner is less than 1%,

The mirrors reflect a bandwidth of 2% around a central wavelength of 135 °A.


0

50

100

150

200

250

300

350

75 85 95 105 115 125 135 145 155 165 175

Wavelength (Ǻ)

Inte

ns

ity

(c

ou

nts

)

Li

#001

EL=425 mJ

1 shot


Li I

II 1

s-4p

, 5p

Li I

II 1

s-3p

Li I I I 1s-2p

0

200

400

600

800

1000

1200

0 50 100 150 200 250 300

Wavelength (Ǻ)

Inte

ns

ity

(c

ou

nts

)

Sn

#025

EL=450 mJ

100 shot avg


Sn (4d-4f) UTA

Source candidates: Lithium and Tin plasmas


Mirror heatingMirror heating Unwanted radiationUnwanted radiation Target purityTarget purity Plasma parameters (electron Plasma parameters (electron

temperatures, absolute outputs, etc.)temperatures, absolute outputs, etc.)

Current WRS

Planned WRS with multiple gratings

AcknowledgementsAcknowledgements

Dr. ShevelkoDr. Shevelko Dr. KnightDr. Knight Matt Harrison and the other Matt Harrison and the other

members of my groupmembers of my group The chemists (especially Dr. Asplund)The chemists (especially Dr. Asplund)

Documents

Transmission Grating Spectrometer for EUV Lithography Nathan Gray Advisors: Alexander Shevelko, Larry Knight, and Scott Bergeson Student Group Members: