Electron and chemical kinetics in methane rf glowdischarge deposition plasmasElectrical characterization of rf glow discharges using an operating impedance bridge Presented are the results of a systematic study of the effects of reactor pressure and rf power level on the electrical and chemical characteristics of a-C:H films prepared by glow discharge. Electrical resistivity has been found to increase rapidly with decreasing reactor pressure. This increase in electrical resistivity corresponded to an increase in the sp3 bonding content of the film. This composition change has been attributed to increased ion bombardment energy and greater time for adatom surface migration. Electrical resistivity decreased with rf power level. The sp2 bonding content of the film decreased while the sp3 bonding content increased with rf power level. The resistivity change and corresponding composition change could not be explained with the present model.

Infrared (IR) laser scanning microscopy (LSM) techniques have been characterized and developed to provide better root cause backside failure analysis (BFA) on products fabricated on multilayer CMOS technology. Spectral transmission studies, backside substrate thinning techniques, and examples of backside IR LSM fault isolation techniques applied on high performance microprocessors will be presented in this paper.As semiconductor device geometries continue to decrease in size, and the number of metal layers continue to increase, failures associated with front-end fabrication steps (polysilicon, sourceldrain diffusion, and gate oxide) can no longer be ea:sily identified or imaged from the topside of the die. Figure l a and lb, illustrates topside imaging limitations, when comparing the cache memory cells of a single layer metal (SLM) process to a four layer metal (FLM) using a 100 X objective lens. (Figure la) (Figure lb) Figure la, b: Cache memory cells on s SLM (Fig. la) and a FLM (Fig. lb) CMOS technology 0-7803-3985-1/$10.00 0 (997 IEEE 17IR LSM techniques have been developed and characterized to circumvent the limitations of conventional topside FA by isolating and imaging defects from the backside. It was also found that BFA techniques can extend the capabilities of topside fault isolation (FI) techniques like emission microscopy (EM) and optical beam induced current (OBIC) to further improve the success rate of failure analysis on high performance microprocessors.This paper will first present recent spectral transmission studies that show how doping density and substrate thickness significantly impact the transmission and detection of light through heavily doped silicon substrates. In addition, we will then present backside substrate thinning techniques that were developed to overcome transmission losses. These thinning techniques have a significant impact on the backside imaging quality and sensitivity of the backside fault isolation (BFI) techniques. Finally, examples of applying these BFA techniques to identify three common failure modes associated with defective or damaged pn junctions discovered in the Tape Carrier Package (TCP) reject units will be discussed. Spectral Transmission StudiesSpectral transmission studies were examined to better understand the transmission properties of highly doped silicon in the near IR. A matrix of samples with varying substrate thickness and doping densities were characterized for spectral transmission. The transmission plot in Figure 2, illustrates an exponential decrease in transmission with increasing substrate thickness. The plot roughly follows the formula: 2 ax T = (1-R) ewhere R is the reflectivity of silicon substrate, a is the absorption coefficient at a given wavelength, and x is the substrate thickness [' I.Proceedings of 6th IPFA '97, Singapore

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The electrical resistivity, optical band gap and activation energy for electrical conduction have been determined as a function of preparation conditions. The operating conditions for the glow discharge reactor have been interpreted in terms of ion energy and reactive species production. The change in the electrical properties could not be explained as a percentage of [SP3] versus [SP2] bonding ratio. Rather, these two species are embedded in an amorphous medium which determines the materials electrical properties.