Photoluminescence Spectroscopy Sheds New Light on Silicon Microchip Functional Properties

Hanna Bandarenka, Andrey Kuzmin, Alexander Baev, Sonal Gupta, Paras N. Prasad

23 July 2024 | Institute for Lasers, Photonics and Biophotonics, State University of New York at Buffalo, Buffalo, New York | ACS Omega

Abstract

In this study, we demonstrate that photoluminescence spectroscopy probing local interaction and dynamics at the fundamental level is a versatile tool for testing and evaluation of semiconducting materials as well as microscale chips based on them. Monocrystalline silicon, which is still an undisputed leader among semiconductors in microelectronics, exhibits very low photoluminescence emission additionally shielded by the metallization and passivating layers at the integrated circuit level. To unleash the full potential of photoluminescence spectroscopy for advanced testing and evaluation of the functional properties of the silicon microchips, new essential conceptually built approaches are required that overcome this problem. Here, we report on the first fundamental research-based application of a potentiometric dye to sense the electric field of operational silicon chips. Furthermore, we demonstrate high sensitivity of crystalline silicon phonon-assisted photoluminescence to local temperature in the 27–64 °C range. Our results show that sensing and mapping of thermal and electric field distributions using photoluminescence can enable precision testing of the structure, function, operation, and security, not only at the component level but also at the level of the entire integrated circuit.

Keywords: Dyes and pigments, Electric fields, Microchips, Molecules, Silicon

Introduction

Since the advent of silicon-based integrated circuits (ICs) in ca. 1958, monocrystalline silicon has remained the main material for the microelectronics industry. The continuous evolution of this area, reflected in Moore’s law, led to an unavoidable complication associated with an urgent need for new nondestructive and minimally invasive metrology capabilities for the quantification and assessment of IC performance and security.

Addressing security and trusted electronics, potential design flaws, added features (Trojans), and other defects and vulnerabilities requires comparing latent energy (e.g., signatures, such as stray fields and heat flows) with those of known uncompromised devices. This can also reveal the effect of aging on IC function. At the same time, these latent energy flows represent a substantial security risk as the unshielded ICs become vulnerable to side-channel attacks, for example, power-analysis attack. 

Therefore, accurate mapping and interpretation of even extremely weak thermal and/or electric signals from the operating ICs are required to combat data leakage, prevent critical device failures, and isolate suspicious microchips of unrecognized structures.

Figure 2. Thermal sensing based on silicon PL: (a) schematic representation of the PL measurements with silicon wafer

…IR PL was investigated on the silicon wafer using a Nikon TE200 microscope with the attached DS-InGaAs-512 near-IR BW-16 Ham spectrometer (StellarNet Inc., FL, USA)…