Silicon Surface Characterization · L'H, Y., Mireles, L. K. X-ray photoelectron spectroscopy (XPS)...

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Allen Puente-Urbina and Lukas Schlemper

06.11.2018 1

Silicon Surface Characterization

Allen Puente-Urbina and Lukas Schlemper


(edit in slide master via “View” > “Slide Master”)06.11.2018Allen Puente-Urbina and Lukas Schlemper 2

Outline

Introductory remarks

▪ General aspects of:

▪ Integrated circuits (IC) and packaging

▪ 3D stacking using through silicon vias (vertical interconnect access) (TSV)

Characterization of silicon wafers

▪ Composition, physical and mechanical properties:

▪ Composition of different parts

▪ Topology

▪ Mechanical strain

Conclusions



Integrated circuits (IC)

Electronic circuit formed on a small piece of semiconducting material

Performs the same function as a larger circuit made from discrete

components

Trend:

▪ Increase integration to improve capabilities

▪ Increase performance (e.g. electrical and thermal)

▪ Decrease size

▪ Decrease costs

▪ …

Knickerbocker, J. U., Andry, P. S., Dang, B., Horton, R. R., Interrante, M. J., Patel, C. S., Polastre, R. J.,

Sakuma, K., Sirdeshmukh, R., Sprogis, E. J. Sri-Jayantha, S. M. IBM J. Res. Dev., 2008, 52, 553-569.



3D stacking using through silicon vias (TSV)

Vias: vertical interconnect access

TSV

TSV

Wolverton, M. Stressing out copper TSVs with temperature, Phys.org, 2014.



TSV fabrication

Zhang, Y., Ding, G., Wang, H., Cheng, P., Liu, R. J. Micromech. Microeng., 2015, 25, 045009.



Characterization of 3D devices

Composition

Surface

Anti-diffusion layer

TSV additives

Physical and mechanical

Surface topology

Wafer-to-wafer interconnects

Stress



Surface analysis

Inkson, B. J. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) for

materials characterization. In Materials characterization using nondestructive evaluation (NDE) methods,

Elsevier, 2016.

L'H, Y., Mireles, L. K. X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass

spectrometry (ToF SIMS). In Characterization of Polymeric Biomaterials, Elsevier, 2017.



Surface analysis

06.11.2018Allen Puente-Urbina and Lukas Schlemper 8



Elsevier, 2016.

Secondary electrons

▪ Topography

Back-scattered eletrons

▪ Contrast for different elements

X-rays

▪ Elemental analysis



Localized analyses


To reach specific locations:

▪ Chemical etching

▪ Gas etching

▪ Plasma etching

▪ Ion etching

Quirk, M., Serda, J. Semiconductor manufacturing technology (Vol. 1), Prentice Hall, 2001.

Rigort, A., Plitzko, J. M. Arch. Biochem. Biophys., 2015, 581, 122-130.



Localized analyses

06.11.2018Allen Puente-Urbina and Lukas Schlemper 10Okoro, C., Levine, L. E., Xu, R., Hummler, K., Obeng, Y. J. Appl. Phys., 2014, 115, 243509.

Anti-diffusion

layer



Elemental analysis




Elsevier, 2016.

Two types of detection:

▪ Energy dispersive X-ray spectroscopy

(EDS)

▪ Wave dispersive X-ray spectroscopy

(WDS)



Elemental analysis: EDS and WDS


Williams, D. B., Carter, C. B. Transmission electron microscopy: A textbook for materials science, Springer,

2009.

Henry, D., Goodge, J. Wavelength-dispersive X-ray spectroscopy (WDS). Science Education Resource

Center at Carleton College, serc.carleton.edu, 2018.



Elemental analysis: XPS

06.11.2018Allen Puente-Urbina and Lukas Schlemper 13Vickerman, J. C., Gilmore, I. S., Surface analysis – The principal techniques, 2nd Edition, Wiley, 2009.

EB = hν – Ekin – ϕ

▪ EB: binding energy

▪ hν : X-rays energy

▪ Ekin: kinetic energy

▪ ϕ: work function (depends on both

the spectrometer and the material)



Surface profile


Lee, D. H., Cho, N. G. Meas. Sci. Technol., 2012, 23, 105601.

Cross, S. E., Kreth, J., Wali, R. P., Sullivan, R., Shi, W., Gimzewski, J. K. Dent. Mater., 2009, 25, 1517-

1526.



▪ Real-time CTE analysis

▪ k: stress vs temperature slope

▪ α: CTE of the compounds

▪ Mf: biaxial modulus

▪ Elemental Analysis


Annealing process

Kiene, M., Morgen, M., Zhao, J.-H., Hu, C., Cho, T., Ho, P. S. Characterization of low-dielectric constant

materials. In Handbook of silicon semiconductor metrology, CRC Press, 2001.



Elemental Analysis

Stable Isotope Laboratory. Elemental analysis principles. Earth and Planetary Sciences, University of

California Santa Cruz, websites.pmc.ucsc.edu, 2018.

https://websites.pmc.ucsc.edu/~silab/ea.inst.php



▪ Two practical methods

▪ Raman-spectroscopy

▪ X-Ray diffraction


Strain measurements

Bianco, F., Fedus, K., Enrichi, F., Pierobon, R., Cazzanelli, M., Ghulinyan, M., Pucker, G. and Pavesi,

L. Semicond. Sci. Tech., 2012, 27, p.085009.



Raman measurement

▪ Basics:

▪ Si: 514-520 nm




Spolenak, R., Wyss, A., Wermelinger, T., Süess, M. Raman spectroscopy for stress analysis. Raman

Workshop 2018, ETH Zurich.



Raman measurement: Temperature

▪ Ratio Stokes : Anti-Stokes

▪ 𝐼𝐴𝑛𝑡𝑖 − 𝑆𝑡𝑜𝑘𝑒𝑠 = 𝐼𝑆𝑡𝑜𝑘𝑒𝑠 exp(−ħ𝜔

𝑘𝑇)

▪ Thermal expansion:

▪ Shift to lower wavenumbers

▪ Allows for temperature measurement







▪ Signal intensity:

▪ 𝑒𝑠 : electrical field of scattered light

▪ ∆𝜇: Raman tensor

▪ 𝑒𝑖 : electrical field of incident light


Raman measurement: Stress I







▪ Allows measurement of uniaxial stress along the z’-axis:

▪ Combination of the measurements:

▪ p, q, r: phonon deformation potentials (PDP)

▪ εij: strain tensor components


Raman measurement: Stress II





▪ Only 𝜔3 can be calculated:

▪ εij = sii σii

▪ Additional polarization can be used to measure the other axis


Raman measurement: Stress III





▪ Local stress measurement:

▪ Focal point of the exciting laser

▪ Depth information

▪ Resolution: ca. 0.5 μm

▪ Min. detectable stress: 25 MPa

▪ Penetration depth: ca. 770 nm

▪ Use repeatedly to map


Raman measurement: Stress IV







X-Ray diffraction

▪ Similar to Raman measurements:

▪ Change in lattice parameters

▪ Fit on new peaks

▪ Gaussian: stress

▪ Lorentzian: grain size

▪ Resolution is not sufficient

▪ Relaxation


Lippert, T. Characterisation of thin films. Functional Inorganics Course 2018, ETH Zurich.

Bowen, D. K., Tanner, B. K. X-ray metrology in semiconductor manufacturing, CRC Press, 2006.



Measuring the joints

▪ Small-angle X-ray Scattering

▪ SAXS

▪ Depth analysis

▪ Penetration depth

▪ Scattering is element dependant atomic scattering factor

▪ Problem:

▪ Separate the weak, scattered beam

▪ Use collimation:

▪ Point-collimation: 2D restriction

▪ Line-collimation: 1D restriction

▪ Not quite suitable

Roessle, M. Basics of X-ray scattering. EMBO Course 2012, Luebeck University of Applied Science.



Measuring the joints

▪ Second X-ray approach

▪ Sources: Ir-192, Co-60, Cs-137

▪ Shine through

▪ Scattering according to atoms

Hogan, H., Aviation Aftermarket Defense, 2015, 35.



Conclusions


▪ A comprehensive analysis of three-dimensional chips requires different

techniques with specific capabilities

▪ It is important to consider techniques with characteristics that allow the

determination of the parameters of interest

▪ The level of development and availability of an analytical technique influence its

application

Thank you!

Silicon Surface Characterization · L'H, Y., Mireles, L. K. X-ray photoelectron spectroscopy (XPS)...

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