This paper presents the first single element time resolved emission (TRE) data collected from microprocessors fabricated with 0.13 µm process silicon using tester loop lengths, and in many cases acquisition times, comparable to laser voltage probing. The data presented here demonstrate that TRE tools with highly sensitive single element detectors can be used for practical microprocessor circuit diagnostics with reasonable acquisition times.

The paper details a critical innovation for scaling optical probing to access the small feature sizes on advanced silicon process technologies. By using the liquid immersion principle to increase the numerical aperture of the microscope objective, a focused laser spot size of 0.50 µm is achieved for the first time. The liquid immersion objective is the first known application of the immersion principle to backside probing. This system improvement allows optical probing to be used in geometrically scaled processes that would not be accessible without it, and thus will extend the usefulness of laser probing for at least one more generation.

Single probe beam phase-sensitive detection has been applied to backside optical probing using an interferometer with a novel vibration cancellation scheme. Improved waveform quality and consistency, compared to amplitude-sensitive detection, has been successfully demonstrated on a number of CMOS microprocessors based on the 0.18 um logic process technology. The interferometric probing scheme will be described in detail and results will be presented.

Optical probing using the Schlumberger IDS-2000 and other infrared-based analysis techniques have proved to be critical in the debug and analysis of flip-chip-packaged microprocessors. During probing, processors are operating with test patterns that generate a large amount of power. This article demonstrates a method for dissipating the generated heat based on a diamond window-based transparent heat spreader. This method controls the microprocessor temperature to a high degree of stability, and reduces thermal gradients across the die. Waveform results are excellent, and the transparent heat spreader provides a path for optical probing to be applied to the entire range of integrated circuit applications. The discussion covers cooling system requirements, and standard configuration specifications, and shows how the transparent heat spreader technique is effective for probing high power microprocessors.

With the advent of C4 packaging technology, Intel has developed, in conjunction with a technology partner, an integrated, laser-based optical backside probing system. This article begins with a description of the basic system operation. This is followed by a discussion on the electro-optic effect in CMOS, which is used for the signal acquisition. The question of invasiveness of the photo-injected carriers is then discussed. Information on the entire probing environment is also provided. The article also discusses results and presents a comparison with other waveform acquisition techniques. It ends with a brief discussion on the developments needed to scale the technique to future processes.