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Browse Prior Art Database

Subcollector for Pedestal Type Transistor

IP.com Disclosure Number: IPCOM000075674D
Original Publication Date: 1971-Oct-01
Included in the Prior Art Database: 2005-Feb-24
Document File: 2 page(s) / 69K

Publishing Venue

IBM

Related People

Maheux, LW: AUTHOR

Abstract

This subcollector has an upwardly protruding portion over which the emitter can be diffused. The resultant transistor has a lower base capacitance, because the surface area of the subcollector in close proximity to the base electrode junction is reduced.

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Subcollector for Pedestal Type Transistor

This subcollector has an upwardly protruding portion over which the emitter can be diffused. The resultant transistor has a lower base capacitance, because the surface area of the subcollector in close proximity to the base electrode junction is reduced.

As shown in A, the surface of a P- wafer 10 is oxidized forming an oxide layer
12. An opening 14 is made through layer 12 to define the subcollector region. A layer of silicon nitride 16 and an over lying layer of silicon dioxide 18 is then deposited over the top of wafer 10, as shown in B. Holes 20 are opened through layers 16 and 18, as shown in C. Layer 18 is used as a masking layer for opening the holes in layer 16. As shown in D, layer 18 is then removed and diffusions made through the holes 20 to form a portion of the buried layer. N+ regions 22 are preferably high-concentration arsenic doped regions. As shown in E, the resultant wafer is thereafter reoxidized and dip etched into hot phosphoric acid to remove portion of layer 16 overlying the region intermediate diffused regions 22, and a diffusion of high-concentration phosphorus made resulting in N+ type region 24.

The remaining oxide layer 12 is then removed and an epitaxial layer 26 deposited over the bare surface of wafer 10, as shown in F. During the diffusion, diffused region 24 will outdiffuse at a more rapid rate than region 22 due to the greater diffusivity of phosphorus in relation to arsenic. This produc...