26th Australian Institute of Physics Congress and the Australian and New Zealand Conference on Optics and Photonics

Quantitative Second Harmonic Generation Metrology for Non-Contact, In-Situ Detection of Interfacial Charge

Not scheduled

1h 30m

Belinda Hutchinson Building (The University of Sydney )

Contributed Oral COMMAD - Optoelectronic and Microelectronic Materials and Devices Parallel sessions

Description

Trapped and mobile interfacial charge is a primary driver of device instability in microelectronics, shifting threshold voltages in MOSFETs, limiting long-term reliability in high-k gate stacks, and degrading surface passivation in photovoltaics [1,2]. Characterizing this charge is central to interface quality control, yet established techniques remain limited: capacitance-voltage (C-V) measurements require a full capacitor structure and electrical contacts, while corona oxide characterization of semiconductors (COCOS) is confined to ex-situ analysis and relies on surface charge persisting long enough to be read via contact potential difference [3]. Both consequently fail for interfaces incorporating conductive or semi-conductive layers, where charge is rapidly screened or dissipated, and neither can isolate individual contributions to the total measured charge.

We present electric-field-induced second harmonic generation (EFISHG) as a non-contact, in-situ metrology technique for measuring interfacial charge density [4]. SHG is a second-order nonlinear process that is dipole-forbidden in centrosymmetric media, making it an intrinsically sensitive probe of symmetry breaking at an interface, without requiring electrical contacts. This sensitivity allows EFISHG to access interfacial charge density even in conductive systems where other techniques are inapplicable.

We calibrate the technique by benchmarking SHG measurements against independent COCOS characterization across material systems subjected to varying thermal treatments, spanning a range of flat-band voltages and trapped-charge densities. The two techniques show strong quantitative agreement, and we develop an analytical model reproducing the SHG response as a function of interfacial charge, enabling extraction of charge density from optical data alone.

This establishes a calibrated framework for SHG as a standalone probe of interfacial charge, extensible to conductive and semi-conductive interfaces and buried device layers inaccessible to conventional metrology, opening a route to non-destructive interface characterization across the device lifecycle.

References (DOI):
[1] 10.1016/J.SOLMAT.2006.04.014;
[2] 10.1063/1.3021091/146161;
[3] 10.1063/1.1354401;
[4] 10.1103/PhysRevB.35.1129