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Obtaining High Resistance in Integrated Circuits

IP.com Disclosure Number: IPCOM000073559D
Original Publication Date: 1971-Jan-01
Included in the Prior Art Database: 2005-Feb-22
Document File: 2 page(s) / 33K

Publishing Venue

IBM

Related People

Samson, RS: AUTHOR

Abstract

Resistors in integrated structures are of two types. One has been the diffused resistor of either N or P type impurity. The P type is done during the base diffusion cycle, although a separate diffusion of either impurity type could be used. The upper limit of resistance is about 300-400 ohms per square with this method. A second method is the dumb-bell or pinch resistor formed by the base channel under the emitter diffusion. The resistance obtained is high, greater than 10 kilohms per square, but the channel is very narrow and is formed by the difference between the two diffusion depths. This structure results in a very high tolerance on the resistor value.

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Obtaining High Resistance in Integrated Circuits

Resistors in integrated structures are of two types. One has been the diffused resistor of either N or P type impurity. The P type is done during the base diffusion cycle, although a separate diffusion of either impurity type could be used. The upper limit of resistance is about 300-400 ohms per square with this method. A second method is the dumb-bell or pinch resistor formed by the base channel under the emitter diffusion. The resistance obtained is high, greater than 10 kilohms per square, but the channel is very narrow and is formed by the difference between the two diffusion depths. This structure results in a very high tolerance on the resistor value.

There is shown a buried channel resistor formed by, for example, a base diffusion into an N type epitaxial layer. Any well known process can be used to form a channel of 0.4 ohm-cm resistivity and a sheet resistance of 2-4 kilohms per square with a total tolerance of about +/- 20%. An N-type epitaxial layer is grown on a P type substrate. Resistor pockets are formed during the isolation diffusion. The channel is formed during the base diffusion cycle and N+ emitter diffusion used to form contacts.

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