Exploring Scanning Microwave Microscopy for Advanced Semiconductor Characterization

The continued scaling of semiconductor devices requires advanced characterization techniques capable of probing local electrical properties with nanoscale spatial resolution. Conventional electrical and optical characterization methods often provide either averaged information over relatively large areas or require specific device geometries, making it challenging to directly access local variations in electrical properties such as conductivity, carrier concentration and dielectric response. Scanning Microwave Impedance Microscopy (SMIM) is an emerging scanning probe technique that combines the high spatial resolution of Atomic Force Microscopy (AFM) with microwave measurements, providing access to local electrical and dielectric properties of materials and semiconductor structures.

This project aims to explore and establish SMIM as an advanced characterization capability for a plethora of semiconductor materials and devices, especially for FAB integration. A particular focus will be placed on developing a physical understanding of the measured microwave response, including the real and imaginary components of the signal, and on determining how these signals relate to local material properties. The intern will investigate how parameters such as carrier concentration, conductivity, dielectric properties, surface condition and measurement geometry influence the SMIM response. Calibration and measurements on well-defined reference samples will be used to establish the relationship between the measured microwave signals and the underlying physical properties. An important aspect of the research will be to investigate the information depth of SMIM measurements. Understanding how deeply the microwave field probes into a semiconductor is essential for interpreting measurements on thin films, multilayer structures and device architectures. The dependence of the measured response on material properties, frequency, tip-sample geometry and sample thickness will be investigated through a combination of experiments and physical modelling. This will help establish the sensitivity of SMIM to surface and subsurface electrical properties and identify the types of semiconductor structures for which the technique provides meaningful information. The project will further dive into the application of SMIM to doped semiconductor materials and device structures. Measurements on samples with different doping concentrations and/or well-defined semiconductor junctions will be used to investigate the sensitivity of SMIM to local carrier concentration and electrical properties. Where appropriate, SMIM measurements will be correlated with complementary characterization techniques such as scanning spreading resistance microscopy, scanning capacitance microscopy and Kelvin probe force microscopy. The ultimate objective is to develop a better understanding of how SMIM contrast can be interpreted in terms of semiconductor physics and to identify opportunities where SMIM can provide information that is difficult to obtain using conventional characterization techniques. Towards the end of the internship, SMIM will also be explored on imec pioneered reverse tip scanning approach that will enable multimodal SPM imaging and even 3D tomography. For this research, the student will be trained in advanced scanning probe microscopy, with a particular emphasis on SMIM and quantitative analysis of microwave signals. This will include sample preparation, measurement optimization, calibration, and data analysis.

With the guidance of the supervisors, data interpretation and analysis will be a major part of the thesis/internship. Depending on the student's interests and the progress of the project, the work can include numerical modelling of the tip-sample interaction and microwave response, analysis of doped semiconductor structures, and application of SMIM to increasingly complex device architectures. Complementary characterization and analysis can be performed through existing collaborations and available facilities. The project therefore provides an opportunity to combine experimental scanning probe microscopy with semiconductor physics, electrical characterization and quantitative data analysis.

A good command of English is necessary. Knowledge of semiconductor physics is a must. The project duration is 6 months, with the possibility of extension if further exploration is warranted.