Comparison of one- and two-photon optical beam-induced current imaging

Abstract

Optical beam induced current (OBIC) imaging through the backside of integrated circuits was investigated in the wavelength λ region from 1.15 to 1.26 μm. With a subpicosecond excitation source and approximately 1 mW at the sample, the two-photon contribution to the generated photocurrent dominates at λ=1.25 μm but becomes negligible for λ<1.18 μm. One-photon- (1P-) and two-photon- (2P-) OBIC images are very different. In the 1P case a strong contribution by scattered light to the carrier generation leads to an edge enhancement effect that is entirely missing when 2P excitation dominates. 2P-OBIC images often show supply-voltage dependent intensity steps that are much sharper than the optical resolution permits. The advantages of 2P-OBIC lie in the spatial confinement of the free carrier generation, a more relevant contrast mechanism, and the promise of a substantial increase in spatial resolution because of the quadratic intensity dependence and the possibility of using silicon solid immersion lenses, which could eventually provide resolution sufficient for circuits made by deep UV lithography.

Scanning Photo-Induced Impedance Microscopy—Resolution studies and polymer characterization

“…1A). Two photon experiments have been used in the past to characterise electrical circuits using a technique called two-photon optical beam induced current imaging (TOBIC) [15,16]. In this case, light of energy smaller than the bandgap of silicon is used.…”

Solid immersion lens applications for nanophotonic devices

“…TOBIC imaging was first demonstrated by Xu [65,66] using a 1.3 µm femtosecond optical parametric oscillator, and addressed the contradictory requirements encountered using linear techniques of focusing through thick substrates while maintaining sufficient absorption at the beam focus of a laser beam to produce a strong OBIC signal. TOBIC imaging also has the attraction of producing an intrinsic increase in resolution for any given illuminating wavelength due to the nonlinear nature of the excitation.…”

Three-dimensional nanometric sub-surface imaging of a silicon flip-chip using the two-photon optical beam induced current method

“…TOBIC imaging was first demonstrated by Xu [12,13] using a 1.3 lm femtosecond optical parametric oscillator, and addressed the contradictory requirements of focusing through thick substrates while maintaining sufficient absorption at the beam focus of a laser beam to produce a strong OBIC signal.…”