Browse Prior Art Database

N+ Contact Resistance Monitor

IP.com Disclosure Number: IPCOM000060742D
Original Publication Date: 1986-May-01
Included in the Prior Art Database: 2005-Mar-09
Document File: 2 page(s) / 49K

Publishing Venue

IBM

Related People

Harper, B: AUTHOR [+3]

Abstract

This monitor structure avoids errors in measuring N+ contact resistance by (1) constraining the current to a completely vertical path and (2) avoiding "parasitic" resistance components by bringing out and contacting all essential nodes. The error from current spreading and lack of direct knowledge of voltage at a buried node are thus avoided. As can be seen in the cross-section, the N+ reach-throughs 10 are diffused into the P base diffusion 12 which compensate the P base to create ohmic regions. N++ emitter regions 14 are also added, as shown. The current is constrained to the N+ reach-throughs 10 and is completely vertical. The N+ contact resistance is measured by forcing a current IF between nodes 1 and 2 and sensing a potential VM between nodes 2 and 3.

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N+ Contact Resistance Monitor

This monitor structure avoids errors in measuring N+ contact resistance by (1) constraining the current to a completely vertical path and (2) avoiding "parasitic" resistance components by bringing out and contacting all essential nodes. The error from current spreading and lack of direct knowledge of voltage at a buried node are thus avoided. As can be seen in the cross-section, the N+ reach- throughs 10 are diffused into the P base diffusion 12 which compensate the P base to create ohmic regions. N++ emitter regions 14 are also added, as shown. The current is constrained to the N+ reach-throughs 10 and is completely vertical. The N+ contact resistance is measured by forcing a current IF between nodes 1 and 2 and sensing a potential VM between nodes 2 and 3. Since no current flows in the infinite impedance voltmeter, the Ncontact resistance can be calculated from: RN+CON = VM/IF . Definition of terms used in the "Schematic of Monitor": RN+CON = N+ contact resistance REMIT = Emitter resistance RRT = Reach-through resistance RSUBCOL = Subcollector resistance

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