The confluence of highly integrated computation chips, huge off-chip interconnectivity requirements, increasingly high channel speeds, and the large spatially extended systems being considered for future high end servers, together with the looming issues of thermal and power management offer an opportunity for optical interconnects to become the preferred solution for many interconnect domains. Optical interconnects are already the technology of choice for the longer length links required in computing systems (10's of meters). However, to achieve this status for link distances at the backplane and card level will require increasingly integrated optical interconnect solutions, which presents many challenges as well as opportunities. The primary inhibitor to adoption of optical interconnects in this ultra-short distance regime is poor cost competitiveness with electrical links. The cost reductions possible with evolutionary enhancement of today's parallel optical modules will not be enough. Potential technologies which could break this cost barrier include the use of waveguides on card to eliminate the optical "module," and chip integrated photonics plus electronics. This paper will discuss the issues and challenges for optics in this short distance regime and present some of the technical solutions that we are pursuing.
The ISICL sensor is a recently described measurement device for sensing and mapping the temporal and spatial distribution of isolated submicron particles in semiconductor processing plasma chambers, fluid tanks, and other inaccessible or hostile places. It requires no modifications to the chamber, and senses the volume directly over the wafer, while the process is running. Its detection sensitivity is extremely high: even in a very bright plasma, it requires only 50 scattered photons to detect a particle at a false alarm rate of 10<SUP>-5</SUP> Hz. Here we present theoretical and experimental results for the sensitivity and volumetric sampling rate of the sensor, as well as a method of using the measured pulse height histogram to obtain particle size information, and some practical tests of performance versus window quality and back wall material.
Inspection for contaminant particles on surfaces is of major interest in the semiconductor industry as well as many others. We have developed an optical inspection instrument which detects particles as small as 65 nm and give information about the refractive index as well. Such information can be used to identify contaminant particles leading to more rapid identification of the source. The instrument is based on a scanned laser Nomarski interferometer, and measures differential phase and amplitude over an inspected area. We have previously shown that the forward scattered light from a small particle (in this case in liquid) interferes with the incident beam to produce a phase shift and amplitude change (extinction) dependent on the particle size and refractive index. This method is also applicable to surfaces by using a reflection mode. Similar to ellipsometry, plotting phase shift against extinction can provide information on both size and refractive index. We have analyzed particles on a silicon surface for a range of compositions, and found that particles can be sorted into refractive index classes such as low index, moderate index and metals.