Thermoreflectance microscopy and spectroscopy on integrated circuits

M. Bardoux, C. Boué, C. Filloy, D. Fournier, G. Tessier

UPR A005 CNRS, ESPCI, 10 Rue Vauquelin, 75005 Paris

1

Thermoreflectance under visible illumination

Microscope

White lamp

Pow.1: f

CCD

Circuit

4f < 40 Hz

Filter

CCD thermoreflectance imaging

T

R

R= T

Optical measurement of R(at virtually any wavelength)

measurement of T

oR

oRamb

t

oR

I1 I2 I3 I4

I1

I2

I3

I4

Microscope

White lamp

Pow.1: f

CCD

Circuit

4f < 40 Hz

Filter

2 2

1 3 2 40 4

I I I IR

Amplitude

CCD thermoreflectance imaging

R around 10-5

T around 0.1 KResolution 300 nm

Not leaky structures:

125 m

Transistor arrays (ST Microelectronics)

IDS = 0 - 60 mA, F=1 Hz

=518 nm

leaky structures:

13

m125 m

Vertical Cavity Surface Emission Lasers (VCSELs)

Vertical temperature distribution

M Bardoux, ESPCI, S. Bouchoule, A. Bousseksou, LPN

Laser emission(1.5 m)

VCSEL Cleavage

Top view (emission facet) T (°C)Side view (substrate, mirror, active layers)

Bragg mirror

Substrate

Active layers

T (°C)

90 m 250 m

Numerical circuit180 nm technology(TIMA Grenoble)

ThermoreflectanceResolution : 350 nm

80 m

T(K)

• Clock frequency 225 MHz• Lock-in at the repetition frequency of the test vectors (7.5 Hz)

Backside imaging ?

2

Near Infrared thermoreflectance

InGaAsCCD

Thermoreflectance with an InGaAs cameraSi Transparency region

Microscope

White lamp

Pow.1: f

4f < 40 Hz

Non coherent sourceseliminate interference in the substrate

position (microns)50 100 150 200 250

50

100

150

200

250

300

85 90 95 100 105 110 115 120-250

-200

-150

-100

-50

0

50

100

150

200

250

position (microns)

85 90 95 100 105 110 115 120

1400

1500

1600

1700

1800

1900

position (microns)

X50, 0.6N.A. objective Resolution 2 m (Diffraction limit : 1.7 m)

Dissipated power : 500 mW

Near Infrared back side imaging

position (microns)50 100 150 200 250

50

100

150

200

250

300

0.5

1

1.5

2

2.5

x 10-3

R/R

Position (microns)0 10 20 30 40 50 60

10

20

30

40

50

60

70

2

4

6

8

10

12

14

x 10-4

0 10 20 30 40 50 600

0.5

1

1.5x 10

-3

Re

lati

ve

am

pli

tud

e

0 10 20 30 40 50 60

-2

-1

0

1

2

x 10-4

position (microns)

de

riv

ati

ve

Resolution difficult to assess (noisy image)

Average of FWHM : 650 nmEffective N.A. : 1.55

Diffraction limit with a 0.42 N.A. objective: 2.4 m

10 20 30 40 50 60

10

20

30

40

50

60

70

R/R

3

Thermoreflectance and photoreflectance spectroscopy

Circuit

Microscope

Filter

P. Supply 1: F

WhiteLampP. Supply 2:

4F

CCDspectrometer

T

R

Thermo-/photo- reflectance spectroscopy

R and vary sharplydue to interference

Spatial selectivity : a few m Spectral resolution : 1 nm typ.Sensitivity : R/R~ 3.10-5 in 1 min

Compact fibered spectrometer+ focusing lens

Photoreflectance spectroscopy on passive materials

SiO2 (glass)

Heating=10.6 m

Measurement=615 nm

Amplitude R/R

F=0.5 Hz

F=1 Hz

F=3Hz

F=7.5 Hz

1850 m

Sample

Modulated CO2 laser

Microscope

Filter

P. Supply 1: F

WhiteLampP. Supply 2:

4F

CCDspectrometer

Si substrate

SiO2 + gold nanospheres (≈ 4 nm)

Heating=10.6 m

Gold nanospheres in silica (preliminary results)M. Rashidi, B. Palpant, INSP

450 500 550 600 650 700 750-20

-15

-10

-5

0

5x 10

-4

wavelength (nm)

450 500 550 600 650 700 750-20

-15

-10

-5

0

5x 10

-3

wavelength (nm)

Model T=50 KMajid Rashidi, INSP

R/R

R/R

t= 68 nm MeasurementT ≈ 3 K

x10-4

x10-3

Conclusions1 ) Visible thermoreflectance

resolution ≈ 300 nmprecision of calibrated measurement ≈ 5%

2 ) NIR imaging with Solid Immersion Lenses- Resolution : 650 nm at 1.65 nm, effective N.A.: 1.55 - Resolution improvement :

use narrow band illuminationbetter contact SIL / substrate

3) SpectroscopyFast and sensitive R/R~ 3.10-5 in 1 minGood spectral resolution (1 nm)Performance spectrometer dependentR/R~ 5.10-7 should be achievable in 1 min with a 1.5 108 e- well depth.