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We report on a study of the DC characteristics of MOCVD-grown AIGaAs/GaAs HBT structures with C-doped (3-5E19 ~m -~) base layers. Analysis of several series of AlGaAdGaAs HBTs suggest the DC gain is dependent upon base current only, and that the base current is largely limited by bulk recombination in the neutral base. As part of this study, we have obtained DC gains of -250 (@ lkA/cm2) at a base sheet resistance of 330 Ohmdsquare, which we believe is the highest DC gain ever observed for an AIGaAdGaAs HBT at this base sheet resistance. Proportionally high DC gains have also been realized in HBTs with base sheet resistance values as low as 115 Ohms/square.

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Presented here are laser processes for drilling debris-free and recast-free vias in silicon that are then integrated into downstream process. The process strategy consists of an integrated laser via drill system combined with an isotropic etch. By careful selection of both the laser and etch process parameters it is possible to control the via depth, diameter, sidewall slope/taper, and to eliminate the damaged Si material in the laser heat affected zone. Because the etch process is selective to Si, this is a mask-free and cost-effective process. Two different processes are demonstrated. For Part 1 we demonstrate an integrated process flow for TSVs with diameters in the range of 250 um for <500 um thick Si wafers and a dry etch process. For Part 2 we demonstrate with a wet etch process