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High Sheet RHO Resistors in ths Base-Etched Transistor Technology

IP.com Disclosure Number: IPCOM000045836D
Original Publication Date: 1983-Apr-01
Included in the Prior Art Database: 2005-Feb-07
Document File: 2 page(s) / 58K

Publishing Venue

IBM

Related People

Nijhuis, RH: AUTHOR [+3]

Abstract

A process is described which permits the fabrication of high sheet rho resistors with or without the simultaneous fabrication of bipolar devices. The ability to selectively vary the resistance provides a degree of freedom for the design of integrated circuits. The resistor may be processed along with other integrated circuit devices up to the point of emitter formation using conventional techniques. But, prior to emitter formation, a central portion of the base area 22, which is to be the resistor is dry etched using reactive ion etching. The existing silicon nitride and silicon dioxide layers 24 and 26, respectively, with the emitter opening therein, are used as the etching mask for this reactive ion etching procedure. Once the etching, as shown at 30 in Fig.

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High Sheet RHO Resistors in ths Base-Etched Transistor Technology

A process is described which permits the fabrication of high sheet rho resistors with or without the simultaneous fabrication of bipolar devices. The ability to selectively vary the resistance provides a degree of freedom for the design of integrated circuits. The resistor may be processed along with other integrated circuit devices up to the point of emitter formation using conventional techniques. But, prior to emitter formation, a central portion of the base area 22, which is to be the resistor is dry etched using reactive ion etching. The existing silicon nitride and silicon dioxide layers 24 and 26, respectively, with the emitter opening therein, are used as the etching mask for this reactive ion etching procedure. Once the etching, as shown at 30 in Fig. 1, is completed to the desired depth, the normal processing is resumed to form the emitter 34 and the rest of the metallization. Since the intrinsic base under the emitter is etched, and the normal emitter is formed afterwards, the etching reduces the resistor width by an amount approximately equal to the etched depth.

A typical layout using the base contacts Bl and B2 for the resistors is shown in Fig. 3. Fig. 2 is taken along line 2:2 of Fig. 3. The dashed line indicates the edge of the base diffusion. Appropriate biasing of the emitter 34 and the addition of the collector contact may be used as needed. The emitter window must be overlapped...