US 5,473,185 AGranted

Static-random-access memory cell with channel stops having differing doping concentrations

AssigneeMotorola, Inc.

InventorsJames R. Pfiester, James D. Hayden

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Abstract

An SRAM cell is formed such that pass channel-stop regions, which are adjacent to the pass transistors, have a higher doping concentration compared to the latch channel-stop regions that are adjacent to the latch transistors. In one embodiment, the pass channel-stop regions are formed using two channel-stop doping steps, whereas the latch channel-stop regions are formed during only one channel-stop doping step. The doping steps may be performed before or after field isolation is formed. The higher doping concentration causes the dopant from the pass channel-stop regions to extend laterally further from the edge of the field isolation compared to the latch channel-stop regions. The process can be adapted for use in almost any type of field isolation process.

Claims12

Dependent claims

A static-random-access memory cell comprising:

a semiconductor substrate;
a field isolation region including a pass field isolation section having a pass field edge and a latch field isolation section having a latch field edge;
a pass transistor having a pass channel region that lies adjacent to the pass field isolation section;
a pass channel-stop region having a pass channel-stop doping concentration, wherein the pass channel-stop region:
lies within the semiconductor substrate;
lies adjacent to the pass field isolation section and the pass channel region;
and
extends laterally beyond the pass field edge away from the pass field isolation section by a first distance;
a latch transistor having a latch channel region that lies adjacent to the latch field isolation section;
and
a latch channel-stop region having a latch channel-stop doping concentration, wherein the latch channel-stop region:
lies within the semiconductor substrate;
lies adjacent to the latch field isolation section and the latch channel region;
and
extends laterally beyond the latch field edge away from the latch field isolation section by a second distance,
wherein the memory cell has a characteristic selected from a group consisting of:
the pass channel-stop doping concentration is higher than the latch channel-stop doping concentration;
and
the first distance is greater than the second distance.

16 more elements

A static-random-access memory array including a plurality of static-random-access memory cells, wherein each memory cell comprises:

a semiconductor substrate;
a first pass transistor having a first pass channel region that lies within the substrate and adjacent to a first pass field isolation section having a first pass field edge;
a first pass channel-stop region having a first pass channel-stop doping concentration, wherein the first pass channel-stop region:
lies within the semiconductor substrate;
lies adjacent to the first pass field isolation section and the first pass channel region;
and
extends laterally beyond the first pass field edge away from the pass field isolation section by a first distance;
a second pass transistor having a second pass channel region that lies within the substrate and adjacent to a second pass field isolation section having a second pass field edge;
a second pass channel-stop region having a second pass channel-stop doping concentration, wherein the second pass channel-stop region:
lies within the semiconductor substrate;
lies adjacent to the second pass field isolation section and the second pass channel region;
and
extends laterally beyond the second pass field edge away from the second pass field isolation section by a second distance;
a first latch transistor having a first latch channel region that lies within the substrate and adjacent to a first latch field isolation section having a first latch field edge;
a first latch channel-stop region having a first latch channel-stop doping concentration, wherein the first latch channel-stop region:
lies within the semiconductor substrate;
lies adjacent to the first latch field isolation section and the first latch channel region;
and
extends laterally beyond the first latch field edge away from the first latch field isolation section by a third distance;
a second latch transistor having a second latch channel region that lies within the substrate and adjacent to a second latch field isolation section having a second latch field edge;
a second latch channel-stop region having a second latch channel-stop doping concentration, wherein the second latch channel-stop region:
lies within the semiconductor substrate;
lies adjacent to the second latch field isolation section and the second latch channel region;
and
extends laterally beyond the second latch field edge away from the second latch field isolation section by a fourth distance;
and
first and second load components selected from a group consisting of resistors, transistors, and diodes,
wherein the memory cell has a characteristic selected from the group consisting of:
each of the first and second pass channel-stop doping concentrations is higher than each of the first and second latch channel-stop doping concentrations;
and
each of the first and second distances is longer than each of the third and fourth distances.

28 more elements

Dependencies are inferred from the claim text.

Facts

Application: 08/341,259Filed 17 Nov 1994 · division
Priority: 28 Feb 1994
Granted: 5 Dec 1995
Term ends: Not estimatedThe source records don’t support an estimate.

Classification4 codes

H10B 10/00
Static random access memory [sram] devices
Y10S 257/903
Active solid-state devices, e.g. transistors, solid-state diodes: fET configuration adapted for use as static memory cell
H10B
Electronic memory devices
Y10S
Technical subjects covered by former uspc cross-reference art collections [xracs] and digests