The laser voltage probe (LVP) is a laser-based voltage and timing

waveform In electronics, acoustics, and related fields, the waveform of a signal is the shape of its graph as a function of time, independent of its time and magnitude scales and of any displacement in time.David Crecraft, David Gorham, ''Electronic ...

acquisition system which is used to perform

failure analysis Failure analysis is the process of collecting and analyzing data to determine the cause of a failure, often with the goal of determining corrective actions or liability. According to Bloch and Geitner, ”machinery failures reveal a reaction chain o ...

flip-chip Flip chip, also known as controlled collapse chip connection or its abbreviation, C4, is a method for interconnecting dies such as semiconductor devices, IC chips, integrated passive devices and microelectromechanical systems (MEMS), to exter ...

integrated circuits. The device to be analyzed is de-encapsulated in order to expose the silicon surface. The silicon substrate is thinned mechanically using a back side mechanical thinning tool. The thinned device is then mounted on a movable stage and connected to an electrical stimulus source. Signal measurements are performed through the back side of the device after substrate thinning has been performed. The device being probed must be electrically stimulated using a repeating test pattern, with a trigger pulse provided to the LVP as reference. The operation of the LVP is similar to that of a sampling oscilloscope.

Theory of operation

The LVP instrument measures voltage waveform signals in the device diffusion regions. Device imaging is accomplished through the use of a laser scanning microscope (LSM). The LVP uses dual

infrared Infrared (IR), sometimes called infrared light, is electromagnetic radiation (EMR) with wavelengths longer than those of visible light. It is therefore invisible to the human eye. IR is generally understood to encompass wavelengths from around ...

(IR)

laser A laser is a device that emits light through a process of optical amplification based on the stimulated emission of electromagnetic radiation. The word "laser" is an acronym for "light amplification by stimulated emission of radiation". The fir ...

s to perform both device imaging and waveform acquisition. One laser is used to acquire images or waveforms from the device, while the second laser provides a reference which may be used to subtract unwanted noise from the signal data being acquired. On an electrically active device, the instrument monitors the changes in the phase of the

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field surrounding a signal being applied to a junction. The instrument obtains voltage waveform and timing information by monitoring the interaction of

light with the changes in the electric field across a p-n junction. As the

reaches the silicon surface, a certain amount of that light is reflected back. The amount of reflected

light from the junction is sampled at various points in time. The changing

field at the

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affects the amount of laser light that is reflected back. By plotting the variations in reflected laser light versus time, it is possible to construct a timing waveform of the signal at the junction. As the test pattern continues to loop, additional measurements are acquired and averaged into the previous measurements. Over a period of time, this averaging of measurements produces a more refined waveform. The end result is a waveform that is representative of the electrical signal present at the

References

* {{cite conference, last=Kolachina, first=S., title=Introduction to Laser Voltage Probing (LVP) of Integrated Circuits , book-title=Microelectronics Failure Analysis , pages= 426–430 , year=2004 , publisher=ASM International , isbn= 0-87170-804-3 Reliability engineering Semiconductor analysis Diffraction