FIB, Ellipsometry, Interferometry... Tools & Techniques FIB, Ellipsometry, Interferometry...

FIB, Ellipsometry, Interferometry... Tools & Techniques FIB, Ellipsometry, Interferometry...

Index Focussed Ion Beam (more of a preparatory tool) Thickness measurements Ellipsometry, Interferometry, pulse technology SIMS 1-Jan-19

FIB Similar to sputtering in some respects Generates beams with Liquid Metal Ion Source (LMIS) typically Gallium Steered using electric and magnetic fields Energy ~ 100 keV (flexible) Used for micro machining In Failure Analysis (FA) Use voltage contrast method in SEM to identify failing via in a chain Use FIB to ‘cut’ the failing via Tilt the sample and obtain SEM Implant dopant in select areas with out mask (mainly for modification) 1-Jan-19

Thickness Measurement Optics: Amplitude, Phase, Polarity Linearly polarized light, circularly and elliptically polarized Phase difference = 90 degree, circle Phase difference = 0 degree, linear Polarizer / Analyzer, Quarter Wave Plate Fast axis, slow axis Combination of Polarizer + QW Plate can change linear poliarized to elliptical polarized and vice versa Reflection in thin film: P and S components undergo different phase shifts polarization of reflected light depends on film thickness and refractive index and wavelength of light 1-Jan-19

Thickness Measurement Optics: Amplitude, Phase, Polarity Linearly polarized light, circularly and elliptically polarized Phase difference = 90 degree, circle Phase difference = 0 degree, linear Polarizer / Analyzer, Quarter Wave Plate Fast axis, slow axis Combination of Polarizer + QW Plate can change linear poliarized to elliptical polarized and vice versa Reflection in thin film: P and S components undergo different phase shifts polarization of reflected light depends on film thickness and refractive index and wavelength of light and angle of incidence 1-Jan-19

Ellipsometer Stokes’ Ellipsometer ©Gaertner Scientific 1-Jan-19

Ellipsometer Can measure thin metallic films (semi transparent) Non contact, non destructive technique Can also vary angle Angstrom level accuracy Newer techniques Stokes Ellipsometer Does not have moving parts (polarizer or analyzer) 1-Jan-19

Interferometry © Nanometric Light from 200 to 800 nm (Deuterium and W or Halogen lamps) Reflected light intensity vs wavelength detected Film stack quality must be known Not as accurate as ellipsometery Also cannot be used (accurately) to determine refractive index real and imaginary quantities Refractive index, exitinction coefficient Cheaper than ellipsometer (Another name; Spectral Reflectance ) © Nanometric 1-Jan-19

Interferometry Wavelengths used from about 200nm to IR (1700 nm) in some cases Plot of model vs experimental (to check for convergence) If film is very thin (less than one cycle of oscillation), difficult to measure many stacks are also difficult to measure May not give unique solution Remember n and k depend on wavelength Even for reasonably thick film, (single layer), approx thickness must be known 1-Jan-19

Pulse Technology Use a laser pulse to heat the surface Thermal expansion and contraction result in ultrasonic sound generation Various interfaces reflect the pulse Pioneered by Rudolph Tech 1-Jan-19