[Paper Review] Three-dimensional imaging of integrated-circuit activity using quantum defects in diamond

Marwa Garsi, Rainer Stöhr+9 more|arXiv (Cornell University)|Dec 22, 2021

Diamond and Carbon-based Materials Research73 references4 citations

TL;DR

This study demonstrates non-invasive, three-dimensional current density imaging in multi-layered integrated circuits using nitrogen-vacancy (NV) centers in diamond. By detecting Oersted fields generated by sub-micron current flows at room temperature, the method achieves sub-micron spatial resolution and sensitivity down to ~10 μA/μm², enabling reconstruction of 3D current components and localization of anomalous current flow across chip layers.

ABSTRACT

The continuous scaling of semiconductor-based technologies to micron and sub-micron regimes has resulted in higher device density and lower power dissipation. Many physical phenomena such as self-heating or current leakage become significant at such scales, and mapping current densities to reveal these features is decisive for the development of modern electronics. However, advanced non-invasive technologies either offer low sensitivity or poor spatial resolution and are limited to two-dimensional spatial mapping. Here we use near-surface nitrogen-vacancy centres in diamond to probe Oersted fields created by current flowing within a multi-layered integrated circuit in pre-development. We show the reconstruction of the three-dimensional components of the current density with a magnitude down to about $\approx 10 \, m μA / μm^2$ and sub-micron spatial resolution at room temperature. We also report the localisation of currents in different layers and observe anomalous current flow in an electronic chip. Our method provides, therefore a decisive step toward three-dimensional current mapping in technologically relevant nanoscale electronics chips.

Motivation & Objective

• To overcome the limitations of existing non-invasive current imaging techniques that are restricted to two-dimensional spatial mapping.
• To enable three-dimensional visualization of current density in multi-layered integrated circuits at nanoscale resolution.
• To develop a room-temperature, non-destructive method for probing current flow in pre-development semiconductor chips.
• To localize current distribution across different layers of a 3D IC and detect anomalous current behavior.
• To advance quantum sensing for failure analysis and optimization of next-generation nanoscale electronic devices.

Proposed method

• Utilization of shallow nitrogen-vacancy (NV) centers in diamond as nanoscale magnetometers to detect magnetic fields generated by current flow in integrated circuits.
• Employment of wide-field optical microscopy with laser excitation at 532 nm and microwave irradiation to drive optically detected magnetic resonance (ODMR) in NV centers.
• Implementation of a custom-built fluorescence microscope with a 50× objective (NA 0.95) and CCD camera to record photoluminescence from NV centers.
• Use of a bias magnetic field (~5.5 mT) to lift degeneracy in the NV center’s spin states, enabling detection of all three vector components of the magnetic field.
• Application of ODMR spectroscopy to measure shifts in resonance frequencies due to Zeeman interaction with Oersted fields from current-carrying conductors.
• Use of a UV-curable adhesive to mount a 1–2 μm thick diamond plate with a near-surface NV layer directly onto the IC, ensuring minimal standoff distance.

Experimental results

Research questions

• RQ1 Can NV centers in diamond enable non-invasive, three-dimensional mapping of current density in multi-layered integrated circuits?
• RQ2 What is the minimum detectable current density using NV-based magnetometry in a room-temperature, non-destructive setup?
• RQ3 Can the method resolve current flow across different layers of a 3D IC and identify anomalous current paths?
• RQ4 To what extent can spatial resolution and sensitivity be improved using decoupling sequences and material optimization?
• RQ5 Can this technique provide quantitative 3D current density reconstruction with sub-micron resolution in real technologically relevant chips?

Key findings

• The method achieved three-dimensional reconstruction of current density components with a sensitivity of approximately 10 μA/μm² at room temperature.
• Sub-micron spatial resolution (~192 nm effective pixel size) was demonstrated using a wide-field fluorescence microscope and ODMR detection.
• Current localization across multiple layers of a multi-layered IC was successfully achieved, revealing distinct current paths in different metal layers.
• Anomalous current flow was observed in a region of the chip, indicating potential device defects or non-uniform current distribution.
• The technique enabled detection of Oersted fields from current-carrying conductors through a protective overcoat, confirming non-invasive operation.
• Future improvements using dynamical decoupling sequences and optimized NV centers are expected to lower sensitivity to the nA range with sub-micron resolution.