Optical conductivity of Ni1 x Pt x Si monosilicides (0xLina S. Abdallah, Stefan Zollner, Christian Lavoie, Ahmet S. Ozcan, and Mark Raymond

Citation: Journal of Vacuum Science & Technology B 32, 051210 (2014); doi: 10.1116/1.4895111 View online: http://dx.doi.org/10.1116/1.4895111 View Table of Contents: http://scitation.aip.org/content/avs/journal/jvstb/32/5?ver=pdfcov Published by the AVS: Science & Technology of Materials, Interfaces, and Processing Articles you may be interested in Study on the occurrence of spontaneously established perpendicular exchange bias in Co49Pt51/IrMn bilayers J. Appl. Phys. 115, 17D726 (2014); 10.1063/1.4868915 Optical conductivity of Ni1 x Pt x alloys (0x AIP Advances 4, 017102 (2014); 10.1063/1.4861214 Tuning magnetic anisotropy in (001) oriented L10 (Fe1xCux)55Pt45 films Appl. Phys. Lett. 102, 132406 (2013); 10.1063/1.4799651 Silicide-phase evolution and platinum redistribution during silicidation of Ni0.95Pt0.05/Si(100) specimens J. Appl. Phys. 112, 064307 (2012); 10.1063/1.4751023 Optical detection of melting point depression for silver nanoparticles via in situ real time spectroscopicellipsometry Appl. Phys. Lett. 100, 051107 (2012); 10.1063/1.3681367

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Optical conductivity of Ni12xPtxSi monosilicides (0 < x < 0.3)from spectroscopic ellipsometry

Lina S. Abdallah and Stefan Zollnera)

Department of Physics, New Mexico State University, MSC 3D, P.O. Box 30001, Las Cruces,New Mexico 88003-8001

Christian LavoieIBM Research Division, T.J. Watson Research Center, P.O. Box 218, Yorktown Heights, New York 10598

Ahmet S. OzcanIBM, 850 rue Jean Monnet, 38926 Crolles, France

Mark RaymondGLOBALFOUNDRIES, 255 Fuller Rd., Albany, New York 12203

(Received 3 July 2014; accepted 26 August 2014; published 11 September 2014)

The optical constants of 22 nm thick Ni1�xPtxSi (0< x< 0.3) monosilicide films were measured

using spectroscopic ellipsometry, in the spectral range from 0.6 to 6.6 eV at room temperature.

Ni1�xPtx films sputtered on clean Si were annealed at 500 �C for 30 s to form nickel platinum

monosilicides. The correct silicide thickness was found by minimizing Si substrate artifacts in the

optical constants of Ni1�xPtxSi determined from ellipsometric data analysis. Two interband

transitions at 1.8 and 4.5 eV were observed (rather than three peaks in PtSi). The absorption peak at

4.5 eV broadens with increasing Pt content in the monosilicide. VC 2014 American Vacuum Society.

[http://dx.doi.org/10.1116/1.4895111]

I. INTRODUCTION

Due to their low resistivity (15 lXcm), nickel silicides

are used in microelectronic devices as ohmic metal–semi-

conductor contacts with superior chemical and physical and

good thermal stability. Nickel monosilicides have low for-

mation temperature and low Si consumption that result in

creating shallow NiSi contacts.1 However, NiSi is unstable

at high temperatures and subject to both agglomeration and

formation of NiSi2.2–6 Both need to be avoided, since they

lead to high silicide resistivity. Another reason to avoid the

formation of NiSi2 is the fact that it is lattice-matched to Si.

The disilicide NiSi2 tends to form inverted pyramid

defects into the Si (100) substrates used for complementary

metal–oxide–semiconductor (CMOS) transistors.7

Pt is known to be soluble in NiSi, but less soluble in

NiSi2, which prevents the formation of Ni1�xPtxSi2 due to

the decrease in the entropy of the system.3,8 Solutions with

complete solubility always result in higher entropy and this

is not the case in the Ni1�xPtxSi2 formation, which will tend

to phase-separate into NiSi2 and PtSi. Therefore, as we

increase the Pt content in the Ni1�xPtx alloys the Ni1�xPtxSi2nucleation barrier becomes higher. Thin silicide layers are

known to exhibit reduced thermal stability, easily forming

disilicide pyramids or rough (agglomerated) NiSi/Si interfa-

ces due to high interfacial energy.1 Adding Pt to the NiSi

increases the thermal stability of Ni1�xPtxSi by delaying the

formation of the disilicide as well as agglomeration.3,5,8,9

After we investigated the optical constants of Ni1�xPtxmetal alloys in our previous work,10,11 we are now able to

provide accurate optical constants for Ni1�xPtxSi monosili-

cides as a function of platinum content. In this work, our

goal is to develop an inline thickness metrology (using inline

ellipsometry tools) and enable thickness measurements of

Ni1�xPtxSi films used on CMOS product wafers. Our meth-

ods can be used for monosilicides formed on bulk Si as well

as on silicon-on-insulator wafers.12

We also explain our optical constants using the electronic

structure by studying the possible interband transitions in

Ni1�xPtxSi monosilicides in comparison with ab initio theory

and measurements on PtSi and NiSi.13

II. SAMPLES AND EXPERIMENTAL METHODS

Ni1�xPtx films were deposited on clean 300 mm Si sub-

strates. First, the native SiO2 oxide on Si was removed using

wet HF etching. The wafer was then transferred immediately

to a physical vapor deposition tool where Ni1�xPtx films

with 100 A thickness were deposited by cosputtering from

Ni0.9Pt0.1 and Ni0.7Pt0.3 targets. The samples were annealed

at 500 �C for 30 s. This temperature is sufficient to form a

monosilicide without causing agglomeration of the thin film

or disilicide formation. Figure 1 displays the steps involved

in the monosilicide formation showing the different phases

formed at each step.7,14 The monosilicide thickness is usu-

ally just above twice the thickness of the unreacted metal

(i.e., 220 A in our case). Composition and thickness of our

unreacted metal alloys were confirmed using sheet resist-

ance, x-ray fluorescence, and x-ray reflectivity measure-

ments.15 We also determined the unreacted metal thickness

by spectroscopic ellipsometry of similar films deposited on

SiO2.10,11

Spectroscopic ellipsometry measures two ellipsometric

angles w and D that represent the amplitude ratio and phase

difference between p- and s-polarization states, before and

after the light gets reflected off the sample. w and D area)Electronic mail: zollner@nmsu.edu. URL: http://ellipsometry.nmsu.edu

051210-1 J. Vac. Sci. Technol. B 32(5), Sep/Oct 2014 2166-2746/2014/32(5)/051210/6/$30.00 VC 2014 American Vacuum Society 051210-1

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related to the Fresnel reflection coefficients rp and rs for the

p- and s-polarization through16,17

q ¼ rp=rs ¼ ðtan wÞeiD ¼ ðErp=EipÞ=ðErs=EisÞ; (1)

where Erp (Eip) and Ers (Eis) are the electric field components

of the reflected (incident) light in the p- and s-direction,

respectively.

We acquired the ellipsometric angles w and D using a

variable angle of incidence rotating analyzer ellipsometer

with a computer-controlled Berek wave plate compensator.18

The angle of incidence was varied from 65� to 75�.Measurements were performed over a broad photon energy

range from 0.6 to 6.6 eV. The back sides of our samples

were roughened to avoid backside reflection, which would

result in depolarization of the reflected beam. In our experi-

ments, the depolarization is typically below 0.5% except at

the ends of our spectral range, where the noise increases.

III. DATA ANALYSIS AND RESULTS

Our experimental data for Ni0.9Pt0.1Si monosilicide, dis-

played as a pseudo-dielectric function, are shown in Fig. 2.

In this data representation, one assumes (incorrectly) that the

sample is a bulk substrate, which allows the conversion of

the ellipsometric angles into the pseudo-dielectric function

using Fresnel’s equations.16,17 For a layered sample, the

pseudo-dielectric function combines the electronic structure

of all materials and also considers interference effects.

Therefore, the Si substrate E1 critical point appears in the

pseudo-dielectric function at 3.4 eV as shown by the arrow.

In order to determine accurate optical constants of our

Ni1�xPtxSi monosilicides, we assume a layered sample struc-

ture as shown in the inset of Fig. 2, where the optical con-

stants for the silicon substrate and for SiO2 are well known.

Previous studies found that monosilicides are covered with a

thin SiO2 native oxide.15,19,20 We added a 10 A SiO2 layer in

our model to account for this, see Fig. 2.

If the silicide layer thickness is assumed to be known, we

can find the optical constants for the layer by solving the

Fresnel equations numerically.16,17 This is known as a point-by-

point fit. The critical points of the substrate appear as artifacts in

the optical constants of the layer if an incorrect thickness is

used for the monosilicide layer.21,22 Minimizing these artifacts

allows us to determine the correct silicide thickness.

Figure 3 shows an example of this procedure, which we

followed to choose the correct thickness for the Ni0.9Pt0.1Si

FIG. 1. (Color online) Steps involved in the formation of Ni1�xPtxSi monosilicides: (Ref. 7) (a) A 100 A thick Ni1�xPtx alloy is deposited on top of a clean Si

surface. (b) During deposition, some (but not all) Ni1�xPtx diffuses into the Si, creating a buried silicide layer covered by unreacted metal. (c) After some

annealing, when all the unreacted metal has been consumed, the resulting metal rich silicide has a thickness of 130 A. (d) Annealing the sample at 500 �C for

30 s leads to the formation of Ni1�xPtxSi monosilicide with a thickness of about 220 A.

FIG. 2. (Color online) Pseudo-dielectric function for a 220 A thick Ni0.9Pt0.1Si

monosilicide sample measured at three angles of incidence (65�, 70�, and

75�). The kink seen in the pseudo-dielectric function at 3.4 eV arises from the

Si E1 critical point. The graph shows both experimental data and results of a

point-by-point fit at all three angles. All data sets are in excellent agreement.

The inset shows the sample structure assumed for the point-by-point fit.

FIG. 3. (Color online) Imaginary part of the dielectric function for Ni0.9Pt0.1

Si monosilicide derived from the raw data assuming different monosilicide

thicknesses. The graph shows the Si critical point for the different thick-

nesses. The true monosilicide thickness (230 A) is the thickness leading to

the weakest Si structure.

051210-2 Abdallah et al.: Optical conductivity of Ni12xPtxSi monosilicides 051210-2

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monosilicide. The dip at 3.4 eV represents the E1 critical

point for Si.23 This dip can be minimized by choosing the

correct Ni1�xPtxSi thickness (230 A). However, this dip can-

not be eliminated completely since the interface between the

silicide layer and the Si substrate is not entirely flat and the

Pt distribution throughout the silicide is not uniform (based

on transmission electron micrographs with elemental map-

ping). Film inhomogeneities as well as surface roughness

can also cause incomplete removal of substrate artifacts. The

same procedure for choosing the correct silicide layer thick-

ness was followed for all the films, with results shown in

Table I. As expected,7 the ratio of the monosilicide to

unreacted metal thickness is about 2.2. (We stress that it is

not necessary to know the resistivity of the silicide to deter-

mine its thickness, as was argued in Ref. 12.)

After the Ni1�xPtxSi monosilicide thicknesses are deter-

mined, another fit is performed using a set of oscillators: A

Drude oscillator with two parameters EP and Cd (related to

the carrier density per unit volume and their scattering time)

describes the response of free carriers to the electromagnetic

wave. In addition, a sum of Lorentz oscillators describes the

interband transitions of bound electrons. Each Lorentz oscil-

lator j has three parameters: oscillator strength Aj, interband

transition energy Ej, and damping constant Cj.

The complex dielectric function �¼ �1þ i�2 versus photon

energy E for Ni1�xPtxSi alloys can thus be written in the fol-

lowing functional form known as the Drude–Lorentz

model:12,15,17,24–26

� Eð Þ ¼ 1� E2P

E Eþ iCdð Þ þX5

j¼1

AjE2j

E2j � E2 � iCjE

: (2)

The first term describes the permeability of vacuum, the sec-

ond term represents the Drude contribution and the third

term represents a sum of Lorentz oscillators.

The dielectric function of Ni1�xPtxSi monosilicides shows

two dominant peaks at 1.9 and 4.4 eV (which we label a and

c, see Fig. 3). The same peaks were seen in previous studies

for NiSi (Refs. 12, 15, and 27) and PtSi.13 In addition to

these two strong Lorentz oscillators, three weaker oscillators

are also necessary to achieve a good fit to the ellipsometric

angles. Therefore, a total of five Lorentz oscillators and one

Drude oscillator were used to expand the optical constants of

Ni1�xPtxSi monosilicides. Figure 4 shows that both methods,

point-by-point fit and Drude–Lorentz oscillator fit, yield the

same dielectric function of the silicide (for the same layer

thickness).

The real and imaginary parts of the dielectric function for

five Ni1�xPtxSi monosilicides (x¼ 0 to x¼ 0.3) are shown in

Fig. 5. The two strongest interband transitions are indicated

by the Greek letters a and c and will be discussed later.

Table I lists the Drude parameters obtained from the

Drude–Lorentz fit for all samples. Tables of the dielectric

functions of these silicides, obtained from a Drude–Lorentz

TABLE I. Drude parameters (plasma energy EP and scattering rate Cd) and

thickness t of different Ni1�xPtxSi monosilicide films obtained by minimiz-

ing substrate artifacts, see Fig. 3. r0 is the zero-energy optical conductivity

calculated from Eq. (4) and rexp is the DC electrical conductivity deter-

mined from sheet resistance measurements (in units of 1/X cm). For com-

parison, results for a pure Ni film on SiO2 from Ref. 11 are also given.

(The value of r0 for Ni on SiO2 is much lower than expected, as described

in Ref. 11.) As expected (Ref. 7), the ratio of the monosilicide to unreacted

metal thickness is about 2.2. Drude parameters for NiSi from a mid-infrared

reflectance experiment (Ref. 27) are also given.

x EP (eV) Cd (eV) r0 t (A) rexp

0 5.57 0.12 34 773 240 65 104

0.10 5.31 0.19 19 959 230 30 193

0.20 5.2 0.24 15 153 220 25 680

0.30 5.0 0.31 10 847 200 14 684

Ni metal 6.8 0.8 7799 101 143 000

NiSia 3.8 0.035 54 000 1900 83 000

aReference 27.

FIG. 4. (Color online) Real and imaginary parts of the dielectric function for

NiSi monosilicide using a point by point fit (squares) in comparison with a

Drude–Lorentz oscillator fit (circles). Both methods yield the same results

for the dielectric function. The solid line shows the contribution of interband

transitions (Lorentz oscillators) to the absorption, with free-carrier absorp-

tion (Drude term) subtracted. Since the Lorentz oscillator at 0.8 eV makes a

significant contribution to the dielectric function even at the lower end of

our spectral range, our Drude parameters are not robust due to parameter

correlations.

FIG. 5. (Color online) Real and imaginary parts of the dielectric functions

for different Ni1�xPtxSi monosilicides (x¼ 0 to x¼ 0.3) determined from a

point-by-point fit with thicknesses shown in Table I. Data obtained from a

fit with Eq. (2) are very similar. The two peaks labeled a and c are caused

by interband transition in the silicide.

051210-3 Abdallah et al.: Optical conductivity of Ni12xPtxSi monosilicides 051210-3

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fit in Eq. (2), are available as supplementary material28 and

on the authors’ web site. These dielectric functions are suita-

ble for inline metrology purposes. Slight variations due to

process conditions (annealing temperature, thickness, and

sputtering conditions) are possible.

Figure 4 shows that the contribution of the Drude term to

the dielectric function (intraband free-carrier absorption)

becomes small above 2 eV in comparison to the interband

absorption (Lorentz oscillators) shown by the solid line. On

the other hand, even at the lower end of our spectral range

(0.6 eV), there are still significant contributions of interband

transitions to the overall dielectric function. Because of our

limited spectral range, the two Drude parameters (plasma

frequency and broadening) are strongly correlated and there-

fore the parameters shown in Table I are only examples of

suitable parameters, not suggested values with known error

limits. There is also a strong correlation between the parame-

ters of the lowest Lorentz oscillator (at 0.8 eV) and the

Drude parameters.15 These correlations might be removed

with infrared ellipsometry measurements, which are planned.

Because of these parameter correlations, the observed trends

of our parameter sets with thickness or Pt content might be

misleading and need to be treated with caution.

IV. DISCUSSION

The band structure and the origin of the bonding in NiSi

and PtSi have been investigated by several authors.13,29–32 It

was shown that the overlap of Ni 3d (Pt 5d) with Si 3s and

3p bands is responsible for partially covalent bonding in

NiSi and PtSi.13,27 The valence band of Ni1�xPtxSi is com-

prised of Ni/Pt d-states and Si 3p-states, while the conduc-

tion band is dominated by Si 3p-states.31 We therefore

expect two types of interband transitions in Ni1�xPtxSi

monosilicides: (1) Transitions from Ni (3d) or Pt (5d) ground

states to Si (3p) excited states, and (2) transitions from Si

(3p) ground states to Si (3p) excited states. As we will show,

we identify peak a in Fig. 5 with type (2) and peak c with

type (1). Some mixing of the orbitals is possible, of course,

due to the covalent bonding between Ni-Pt and Si.13

Previous optical studies measured the real and the imagi-

nary parts of the dielectric function for NiSi using spectro-

scopic ellipsometry12,15,33 and reflectance followed by

Kramers–Kronig transform.27 These results showed two

peaks in the imaginary part at 1.9 and 4.4 eV.12 The same

two peaks were observed in the imaginary part of the dielec-

tric function for PtSi13 as well as another peak at 3 eV (not

observed in our results for Ni1�xPtxSi). Spectroscopic ellips-

ometry has also been used to study the formation of NiSi,33

NiGe,34 and PtSi (Ref. 35) by annealing of thin metal films

sputtered on Si.

Only the nickel monosilicide NiSi shows the two charac-

teristic peaks at 1.9 and 4.4 eV. Metal-rich silicides (such as

Ni3Si or Ni2Si) and the disilicide NiSi2 have peaks with dif-

ferent shapes and peak energies.27,33,36,37 In general, the am-

plitude of interband transitions increases with decreasing

metal–silicon ratio.33 Also, peak a shifts toward the UV as

the metal–silicon ratio is decreased.27 Therefore,

ellipsometry spectra are suitable to identify the silicide phase

that has formed on the wafer.

The dielectric function of conductors (metals, silicides,

doped semiconductors, etc) diverges at low photon energies

because of the Drude contribution in Eq. (2). In a perfect con-

ductor, the absorption is infinite and a static electric field can-

not exist. This divergence (see Fig. 5) dominates the dielectric

function. It is convenient to remove this divergence by multi-

plying the optical constants with the photon energy and defin-

ing the complex optical conductivity by the equation38

r Eð Þ ¼ �i�0

�h� Eð Þ � 1½ �E; (3)

where �0 is the permittivity of vacuum and �h is Planck’s con-

stant. For our monosilicide films, the optical conductivity as

a function of photon energy is shown in Fig. 6.

The imaginary part of � is related to absorption (energy

dissipated in the system), while its real part is related to the

speed of light (energy stored in the system). Similarly, r1 is

related to interband optical absorption and the attenuation of

an AC signal, while r2 is related to dispersion and the phase

shift of an AC signal in a system (circuit or material).

The DC conductivity is calculated at zero photon energy

(E¼ 0). Using the Drude parameters we obtained from our

fits (summarized in Table I), we calculate

FIG. 6. (Color online) Real and the imaginary parts of the optical conductiv-

ity for Ni1�xPtxSi monosilicides (x¼ 0, 0.1, 0.2, 0.3) (symbol) in compari-

son with 100 A pure Ni1.9Pt0.1 metal alloy (lines).

051210-4 Abdallah et al.: Optical conductivity of Ni12xPtxSi monosilicides 051210-4

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r0 ¼ r E ¼ 0ð Þ ¼ �0

�h

E2P

Cd

: (4)

Table I also shows the zero-frequency conductivity calcu-

lated from the oscillator fit. These values of optical conduc-

tivity are compared with the electrical conductivity r exp

calculated from the sheet resistance rs measured for our

films. This is the ratio rs ¼ q=t, where q ¼ r�1exp is the elec-

trical resistivity and t is the thickness of the silicide.39

For our monosilicide films, the plasma energy varies

between 5.6 eV for NiSi (x¼ 0) and 5.0 eV for Ni0.7Pt0.3Si,

see Table I. Therefore, the free carrier density, which is

related to the plasma frequency xP ¼ EP=�h, varies only

slightly with Pt content. In our earlier work10 on unreacted

Ni1�xPtx, we found plasma energies between 7 and 8 eV,

slightly higher than for monosilicides.

While the plasma energy does not show significant varia-

tions, the Drude broadening approximately triples as x is

increased from 0 to 0.3. Similarly, we find that the extrapo-

lated DC conductivity r0 also decreases by about a factor of

3. We speculate that the reduction in r0 with increasing Pt

content is due to increased scattering of carriers, not due to a

change in carrier concentration (or effective mass of the car-

riers). A threefold increase in Ni1�xPtxSi resistivity was also

observed in Ref. 40 as the Pt content was increased from 0 to

0.5. This was confirmed by our own sheet resistance meas-

urements shown in Fig. 7. It was argued40 that the reduction

in conductivity with increasing Pt content was due to

increased grain boundary scattering (reduced grain size for

larger Pt content). That statement is consistent with our

increase in the Drude broadening parameter.

As a word of caution, we need to stress that our Drude

parameters were obtained by fitting the dielectric function

from 0.7 to 1.0 eV and then extrapolating to E¼ 0. That is

not very reliable. As a matter of fact, our DC conductivities

determined from ellipsometry are consistently lower than the

conductivities determined from electrical sheet resistance

measurements (up to a factor of 2 for monosilicides, or a fac-

tor of 20 for pure unreacted Ni). In future work, we will

investigate if the agreement between optical and electrical

conductivity measurements can be improved with infrared

ellipsometry.

Figure 6 shows the complex optical conductivity as a

function of photon energy for the different monosilicides in

comparison with that of a Ni0.9Pt0.1 film deposited on SiO2.

The real part of the optical conductivity in the IR region

shows that the DC conductivity for the unreacted metal is

higher than for silicides. The conductivity in this part of the

spectrum is dominated by the Drude response of the free

electrons in the sample. The unreacted metal shows more

metallic behavior in the IR region than the monosilicide.27

For the visible and UV parts of the spectrum, the optical

conductivity for the monosilicide is higher than that of the

metal films due to the enhanced interband transitions driven

by the silicon in the monosilicide.27 The 4.5 eV absorption

peak clearly broadens with increasing platinum content in

the monosilicide. Similar broadening with increasing xwas found in our earlier work on unreacted Ni1�xPtxalloys.10 It was shown that the absorption peak broadens

with increasing Pt content in the alloy due to the enhanced

density of states that Pt causes when added to Ni. The larger

the Pt concentration in the alloy, the broader the peak. The

same argument can be applied in the monosilicide optical

conductivity. We claim that the peak at 4.5 eV is due to

interband transitions from the overlapped Ni(3d)-Pt(5d)

valence bands to the Si 3p conduction bands. The broadening

of the peak is therefore related to the broadening of the ini-

tial states in the valence band.

On the other hand, the peak at 1.8 eV does not seem to

depend on Pt content. This means that the transition at this

photon energy is caused mainly by Si electronic states. The

Pt content therefore does not affect the interband transition.

V. CONCLUSIONS

We performed ellipsometry measurements from 0.6 to

6.6 eV on Ni1�xPtxSi monosilicide films (0< x< 0.3) with

220 A thickness on Si substrates. Through careful analysis

of the data with two different methods (point-by-point

fit with variable thickness to reduce substrate artifacts

and Drude–Lorentz oscillator fitting), we were able to deter-

mine the optical constants of Ni1�xPtxSi monosilicides

(0< x< 0.3) with high accuracy. At low photon energies,

� diverges due to the Drude response of free carriers. The

Drude broadening increases with increasing Pt content. In

the visible and UV region of the spectra, we find peaks at 1.8

and 4.5 eV due to interband optical transitions. While the

peak at 1.8 eV does not change much with Pt content, there

is a significant broadening of the peak at 4.5 eV, presumably

due to mixing of the Ni 3d- and Pt 5d-related valence band

states in the silicide.

The optical constants of silicides can be determined using

spectroscopic ellipsometry not only on blanket wafers (as in

our work) but also on patterned wafers (using inline ellips-

ometry tools with a beam diameter of about 50 lm) similar

to the ones used in CMOS transistor applications. Since the

optical constants for silicides are expected to vary somewhat

with process conditions (such as annealing temperature,

thickness, and sputtering conditions), our method described

in this manuscript should be used to verify the silicide

FIG. 7. (Color online) Normalized sheet resistance of 220 A thick Ni1�xPtxSi

monosilicides determined using four-point-probe measurements as a func-

tion of Pt concentration (in atomic percent).

051210-5 Abdallah et al.: Optical conductivity of Ni12xPtxSi monosilicides 051210-5

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optical constants for each silicide process. Once the optical

constants for the silicide are known, on-wafer inline thick-

ness measurements are possible and process deviations can

easily be found.

ACKNOWLEDGMENTS

This work was supported by the National Science

Foundation (No. DMR-1104934). This work has been

partially supported by the independent Bulk CMOS and SOI

technology development projects at the IBM

Microelectronics Division Semiconductor Research &

Development Center, Hopewell Junction, NY 12533. L.S.A.

is grateful to the AVS Thin Film Division for being selected

as a finalist for the J.M.E. Harper Graduate Student Award at

the 2013 AVS International Symposium.

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