Hot spot detection- Optical Beam Induced Resistance Change (OBIRCH)
Laser resistance change detection (OBIRCH) is applied laser beam to scan the IC surface. The laser beam causes the material in the scanning area to be heated. If there is a defect part existed in the IC, the heat conduction in the nearby area is different from other complete areas. Then the temperature change caused by this area will be different, and the temperature change will cause the resistance value to be varied ΔR. If a constant voltage is applied to the sample while scanning, it can be detected that the current change relation is ΔI = (ΔR / R) I. Positioning can be made by recording the changes in resistance and current caused by laser heating in the scanning area that uses a computer in pixels.