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Self Aligned Metal Bipolar Process

IP.com Disclosure Number: IPCOM000048780D
Original Publication Date: 1982-Mar-01
Included in the Prior Art Database: 2005-Feb-09
Document File: 3 page(s) / 74K

Publishing Venue

IBM

Related People

Magdo, IE: AUTHOR [+2]

Abstract

The present process produces a very compact bipolar device. The emitters are abutted by using a silicon nitride sidewall recessed oxide isolation (ROI). The perimeter-to-area ratio is cut by about half due to the abutting of the emitters. This helps to speed up the device significantly. The use of separate dopings for the intrinsic and extrinsic bases optimizes the device characteristics by cutting down on sidewall injection.

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Self Aligned Metal Bipolar Process

The present process produces a very compact bipolar device. The emitters are abutted by using a silicon nitride sidewall recessed oxide isolation (ROI). The perimeter-to-area ratio is cut by about half due to the abutting of the emitters. This helps to speed up the device significantly. The use of separate dopings for the intrinsic and extrinsic bases optimizes the device characteristics by cutting down on sidewall injection.

The process begins with a P monocrystalline silicon substrate 10 having a N- epitaxial silicon layer 11 thereover with an appropriate pattern of N+ subcollector and P+ isolation diffusions within the silicon body. The process proceeds as follows: 1. Thermally oxidize the surface of the epitaxial layer 11

to form layer 12 of silicon dioxide (SiO(2))

(approximately 400 Angstroms). Deposit a layer

13 (2000 Angstroms) of silicon nitride, (Si(3)N(4)).

2. A photoresist mask (not shown) is used to define openings

where ROI is desired.

3. SiO(2) 12/Si(3)N(4) 13/Si 11 are reactively ion etched

using the photoresist mask. The Si is etched so that when

SiO(2) is subsequently grown, there will be substantial

planarity the remaining silicon major surface.

4. The exposed silicon surface is reoxidized to form a SiO(2)

layer 31 of about 1000 Angstroms.

5. Deposit a 2000 Angstrom layer 16 of Si(3)N(4).

6. The Si(3)N(4) layer 16 is removed by reactive ion etching.

It leaves behind nitride sidewalls 16.

7. Nitride sidewall ROI is formed by a thermal oxidation

process involving, e.g., 1000 degrees C for 320 minutes,

dry, wet, dry heat cycle to produce the Fig. 1 structure.

8. A photoresist mask is used to etch the Si(3)N(4) layer 13,

followed by a phosphorous ion-implantation pattern (not

shown,) for the base-collector separation is formed for

collector reach-through 33.

9. Another masking step used to define a window in the

Si(3)N(4) layer 13 and base 20 is formed by one of the

following:

Option I Ion implant boron through SiO(2) layer 12.

Option II Open SiO(2) layer 12, carry out BBr(3)

diffusion and reoxidize.

Option III Open SiO(2) layer 12, deposit 500 to 1000

Angstromspolysilicon layer 21, ion implant

boron, and reoxidize.

10. Deposit 500 to 1000 Angstrom polysilicon layer 21.

11. Option I Reoxidize to 200 to 400 Angstrom of SiO(2)

layer 19.

Op...