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Porous Silicon Process for Power Transistors without Second Breakdown

IP.com Disclosure Number: IPCOM000086484D
Original Publication Date: 1976-Sep-01
Included in the Prior Art Database: 2005-Mar-03
Document File: 2 page(s) / 33K

Publishing Venue

IBM

Related People

Oleszek, GM: AUTHOR [+4]

Abstract

The introduction of an avalanche diode having a breakdown voltage less than the second breakdown voltage of the intrinsic transistor to eliminate exposure to transistor reverse bias second breakdown is described in "Second Breakdown Free Switch Transistor" published in the IBM Technical Disclosure Bulletin, Vol. 19, No. 4, September 1976, pages 1308-1309.

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Porous Silicon Process for Power Transistors without Second Breakdown

The introduction of an avalanche diode having a breakdown voltage less than the second breakdown voltage of the intrinsic transistor to eliminate exposure to transistor reverse bias second breakdown is described in "Second Breakdown Free Switch Transistor" published in the IBM Technical Disclosure Bulletin, Vol. 19, No. 4, September 1976, pages 1308-1309.

Fig. 1 shows the equivalent circuit. An integrated silicon semiconductor structure which incorporates the features of Fig. 1 is shown in Fig. 2.

The thickness t(1) is adjusted such that the P-N/-/ avalanche breakdown voltage below the base contact is less than the secondary breakdown voltage of the N/+/-P-N/-/ region.

A process for fabricating such an integrated power transistor structure using porous Si and conventional Si planar processing technology is as follows:
1. Grow initial SiO(2) layer (Fig. 3-1).
2. Remove frontside SiO(2) and diffuse boron base (Fig.3-2).
3. Form porous Si regions on wafer backside (Fig. 3-3).
4. Open frontside emitter diffusion windows in SiO(2).
5. Perform frontside and backside emitter (n-type) deposition

diffusion.
6. Strip backside PSG and deposit Si(3)N(4). (This prevents

porous Si regions from being completely oxidized during

subsequent emitter drive-in and re-oxidation step,)
7. Perform frontside (emitter) and backside (collector contact)

phosphorous drive-in (Fig. 3-4). Note that phosphorous

diffuses more...