RF Vacuum Microelectronics
Quarterly technical rept. 1 Oct-31 Dec 1992
HUGHES AIRCRAFT CO TORRANCE CA ELECTRON DYNAMICS DIV
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Findings from the first mask set that influenced the design of the second mask set were as follows 1 The original size of a chip was based on experience with semiconductor devices and was too small to dice adequately on the silver substrates 2 The one micron emitter tips were too small and had fully open gate apertures on only a few samples. As a result, the relative number of one micron pyramids should be much less than 1.5, 2.0 and 2.5 micrometer pyramids. The three larger sizes were, in general, properly formed on all samples 3 As a result of the large number of arrays on each chip, only a small fraction could be bonded to the header. Furthermore, the bonding pad arrangement made it difficult to run bond wires in certain directions without the wires crossing over an emitter array 4 Scribe streets were located too near the bond pads and may have resulted in some emitter to gate short circuits and 5 Dimensional stability of the silver substrates caused some misalignment of the gate metal to the emitter tips resulting in emitters on the edge of an array not being properly formed.
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