During functional analysis of IC devices, several techniques such as infrared emission analysis (IREM) and time-resolved emission analysis (TRE) are employed that analyze light emissions. Other techniques use light energy to either measure wave-forms (laser voltage probing) or alternate the functional state (laser-assisted device alteration) of IC devices. Photon-based analysis is done through the backside of the silicon and applicable to flip chip technology-based products. Electron beam-based analysis is done through the frontside and used on wirebond products.
The infrared emission tool is used to analyze light emitted during functional and non-functional operation of a semiconductor. Various conditions, such as forward and reverse biased PN junctions, saturation of MOSFETs, latchup, and gate oxide defects, can be analyzed in the spectral range between 800 nm to 4000 nm. In a tester-docked configuration, the parts are exercised while emissions are observed through the backside of the device. Logic state imaging (LSI) determines logic states of signals by passive IREM emission collection.
The time resolved emission tool is used to analyze light emissions as a function of time. To resolve very small time increments, patterns are looped while photons are counted. After enough integration time, this leads to an oscilloscope-like result.
The laser voltage probing tool is used to measure voltage wave forms. It uses a specific optoelectronic interaction called electro-absorption (also known as Franz-Keldysh effect). The physical principle is that high electric fields, such as those present during reverse biased PN junctions, affect the absorption of light near the bandgap.
Both techniques are used to identify timing shifts and to measure rise and fall times.
The laser-assisted device alteration tool is used to analyze the functional sensitivity of a part upon interaction with a laser using a scanning optical microscope. The operation of a part on a tester that shows a functional/non-functional boundary during certain operating conditions is affected through localized electron-hole pair generation in the active areas using a 1064-nm laser or through resistance change at the metal layers due to heating using a 1340-nm laser.
For example, the affect of an additional current due to electron-hole pair creation on a PMOS transistor of an inverter is to slow down the falling edge of the switching inverter.
The LADA tool can also be used to do traditional (un-powered, two pin) photon probing such as light-induced voltage alteration (LIVA) using the 1064-nm laser and a constant current, or various techniques using the 1340-nm laser, such as thermally induced voltage alteration (TIVA), optical beam induced resistive change (OBIRCH), and Seebeck effect imaging (SEI).