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Large Grained Polysilicon Resistor

IP.com Disclosure Number: IPCOM000056678D
Original Publication Date: 1988-Jan-01
Included in the Prior Art Database: 2005-Feb-14

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Cressler, JD [+details]


Polysilicon resistors for NPN bipolar applications can be fabricated with large grain size and less sensitivity to manufacturing processes by growing the large grains during the long thermal cycles required for producing recessed oxide. Referring to Fig. 1, following cleaning steps epitaxial silicon wafer 1 is coated with successive blanket layers of nitride 2, polysilicon 3, and nitride 4, and suitably doped with boron. By means of a mask, reactive ion etching removes layers 2, 3 and 4, but leaves them intact in the resistor area. Recessed oxide is grown by first forming thin stress relief oxide 5 and depositing nitride layer 6. The surface is etched by potassium hydroxide or reactive ion etching through a suitable mask to remove nitride layer 6 and oxide layer 5 at those locations 7 where recessed oxide is to be grown.