PRODUCTION ENGINEERING MEASURES (PEM) FOR A GERMANIUM MICROWAVE TRANSISTOR.
Abstract
The process flow used in fabricating the L-78 planar epitaxial germanium diffused-base transistor is described. The initial intrinsic f sub T of planar devices, approximately 1600 mc compared to 2050 mc for a mesa device of comparable design using similar fabrication techniques, was increased to equal that of the mesa by optimizing the composition of the emitter material. The L-78 planar devices fabricated exhibit minimum noise figure at 1.0 GgGc of 4.5 to 5.5 db at approximately 1.5 ma of emitter current while peak f sub T occurs at approximately 5.0 ma. A modification of the L-78 pattern, designated L-78A, via emitter area reduction from 0.76 mil squared to 0.27 mil squared manifested itself by a shift in peak f sub T toward lower values of emitter current. The purpose of this modification is to bring into registry the e peak gain of the device and minimum noise figure at one particular bias level. The materials used for the base stripes of the planar unit were optimized to provide good ohmic contact to germanium. Adherence of expanded contacts to the active region of the device, the emitter and base stripes, was improved by employing a chemical etch comprised of inorganic constituents. An excellent technique for uniformly depositing silicon dioxide onto germanium was obtained. A variation in the maximum to minimum thickness of the deposit across the slice was reduced from 10% to approximately 3%. A package suitable for the encapsulation of UHF transistors features minimum series inductance and high degree of mechanical rigidity.
Document Details
- Document Type
- Technical Report
- Publication Date
- Sep 30, 1964
- Accession Number
- AD0612617
Entities
Organizations
- Texas Instruments