Backside observation of MOSFET chips using an infrared laser THz emission microscope

We developed an infrared laser terahertz emission microscope (IR-LTEM) using 1 μm wavelength fs laser pulses for inspecting electrical failures in large scale integration (LSI) chips from the backside. IR-LTEM detect the THz emission from the backside of the LSI chip and the THz emission image which reflects the photocurrent distribution in circuits can be obtained by scanning the chips with fs laser. We succeeded in obtaining the THz emission image of a MOSFET sample from the backside of the chip under zero bias condition. The backside observation of the LSI chip is indispensable for generating and detecting the THz emission because most LSI chips have a multilayered interconnection structure and their surface is mostly covered with metal interconnects, hindering the observation from the front surface.