2. Non-contact measurement devices for electrical conductivity

Non-contact measurement devices for electrical conductivity

  • School of Engineering/Graduate School of Engineering
  • Micro-Nano Mechanical Science and Engineering

Yang Ju [Prof.]


Outline of Seeds

Conductivity measurements are a critical part of both quality control and performance evaluations for the semiconductor wafers used in electronic devices. Until now, the four-point probe method was used to measure the conductivity of silicon wafers--but this method has problems in terms of damaging the wafer surface, since it requires that the probe tips contact the when measurements are taken. Qualitative evaluations also require calibrating wafer thickness. To resolve these issues, our team is developing a precision, non-contact method of measuring the conductivity of semiconductor materials using microwaves.

Our non-contact measurement method involves irradiating semiconductor wafers with microwaves and then measuring their response in order to evaluate conductivity.
- Low-cost and takes up less space
- Enables real-time measurements
- Also makes it possible to measure carrier concentration and mobility

Novelty and originality of this research

Taking advantage of the fact that microwaves greatly attenuate within wafers, our research team is the first to develop a surface reflection method for measuring thickness, making it possible to measure the conductivity of semiconductor wafers without contact. Weve also developed reflection-type microwave focusing sensor that has allowed us to obtain precise measurements while maintaining a significant distance between the sensor and the wafer.

Application and research area for Industry collaboration

Ripple effects in the local economy:
We expect our technology to have applications in measuring and evaluating electrical properties in on-line inspections (during production of semiconductor wafers), materials development, device manufacturing, and other processes.


Semiconductor wafers, conductivity, noncontact, quantitative evaluation, microwaves, manufacturing field, components, shared core technologies (measurement, evaluation, inspection)


  • Noncontact Measurement System for Electrical Conductivity

Monographs, Papers and Articles

  • Y. Ju, K. Inoue, M. Saka and H. Abé, Applied Physics Letters, 81 (2002), 3585-3587.