Neocera, Inc.

Alfred B Cawthorne

Thirumalai Venky Venkatesan

Lee A Knauss

Antonio Orozco

Elena Talanova

Solomon I Woods

Nesco M Lettsome

A scanning microscope for high resolution current imaging by direct magnetic field sensing of a sample maintained in an ambient environment. The scanning microscope uses a magnetic sensor such as a SQUID and a fiber probe magnetically coupled between the SQUID sensor and the sample under study. The fiber probe has a sharply defined tip for high resolution probing and for reaching minute cavities on the surface of the sample. The coupling between the tip of the fiber probe and the sample is controlled by a distance control mechanism, in the range of 1-100 nm. The material of the fiber probe with high permeability and low magnetic noise is chosen to optimize flux transmission to the magnetic sensor. Magnetic coupling to the sensor is maximized by keeping the distance between the end of the fiber probe and the sensor to approximately 0-100 &#x3bc;m. The fiber probe is integrated into the fiber holder for easy replacement of the fiber probe.

Hybrid squid microscope with magnetic flux-guide for high resolution magnetic and current imaging by direct magnetic field sensing

Circuit flaws in microelectronic circuitry present regions of high resistance in which a current distribution deviates from that of a defect-free circuit. The altered current distribution emits a correspondingly altered magnetic field in accordance with Ampere's Law. When compared with the magnetic field of a defect-free circuit, the anomaly in the magnetic field of the defective device is detected and the location of the circuit flaw may be determined therefrom. As the anomaly in the magnetic field is very small in magnitude, a sensitive magnetic microscope is utilized to obtain images of the magnetic fields of a defect-free reference device and a device-under-test. The distance between the magnetic sensor and the devices being scanned is precisely controlled to minimize influences of scanning distance on the difference in measured magnetic field strength. Comparative image analysis reveals the location of the circuit flaw. Maximal image registration through image interpolation, displacement and resampling optimizes the comparative image analysis.

Fault isolation of circuit defects using comparative magnetic field imaging

Growing community of inventors

Beltsville, MD, United States of America

Alfred B Cawthorne