# US 5,350,941 A · Trench isolation structure having a trench formed in a LOCOS structure and a channel stop region on the sidewalls of the trench

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- Number: US 5,350,941 A
- Document ID: US5350941A
- Status: Granted
- Kind: A
- Application number: 07/949,656
- Filed: 1992-09-23
- Granted: 1994-09-27
- Earliest claimed: 1992-09-23
- Assignees: Texas Instruments Incorporated
- Inventors: Sudhir K. Madan
- Web page: https://patentgrep.com/patent/US5350941A

## CPC

- H10W 10/012: {using local oxidation of silicon [LOCOS]}
- H10P 50/695: {characterised by the process involved to create the mask, e.g. lift-off masks or sidewalls or to modify the mask}
- H10W 10/011: {of isolation regions comprising dielectric materials}
- H10W 10/014: {using trench refilling with dielectric materials, e.g. shallow trench isolations}
- H10W 10/0147: {the shapes being altered by a local oxidation of silicon process, e.g. trench corner rounding by LOCOS}
- H10W 10/041: {of isolation regions comprising polycrystalline semiconductor materials}
- H10W 10/10: Isolation regions comprising dielectric materials
- H10W 10/13: formed using local oxidation of silicon [LOCOS], e.g. sealed interface localised oxidation [SILO] or side-wall mask isolation [SWAMI]
- H10W 10/17: formed using trench refilling with dielectric materials, e.g. shallow trench isolations
- H10W 10/40: Isolation regions comprising polycrystalline semiconductor materials
- Y10S 148/05: Etch and refill
- H10W: GENERIC PACKAGES, INTERCONNECTIONS, CONNECTORS OR OTHER CONSTRUCTIONAL DETAILS OF DEVICES COVERED BY CLASS H10
- H10P: GENERIC PROCESSES OR APPARATUS FOR THE MANUFACTURE OR TREATMENT OF DEVICES COVERED BY CLASS H10
- Y10S: TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS

## Abstract

An isolation structure is disclosed which isolates an active region (24) from other proximate active regions. The isolation structure utilizes the combination of a LOCOS structure (26) comprising bird's beak structure (26a) and (26b). A trench (34) is formed through the LOCOS structure (26). A channel stop implant region (40) is formed along the sidewalls of the trench (34). A trench plug (46) is used to fill the trench. The isolation structure thereby uses the isolation capabilities of trench isolation structures, but prevents the leakage currents common along trench sidewalls by isolating the trench sidewalls from the active region using the LOCOS structures.

## Claims

### Claim 1

An isolation structure formed in a semiconductor layer between first and second active regions in order to electrically isolate the first and second active regions one from the other, the semiconductor layer comprising an outer surface, the isolation structure comprising:
a LOCOS structure formed on the outer surface, said LOCOS structure comprising a first bird's beak structure disposed laterally adjacent the first active region and a second bird's beak structure disposed laterally adjacent the second active region;
a trench plug disposed in a trench formed through said LOCOS structure between said first and second bird's beak structures and in said semiconductor layer, said trench comprising sidewalls defining an interface between said trench plug and the semiconductor layer; and a channel stop region located in said sidewalls of said trench.

### Claim 2 (depends on 1)

The isolation structure of claim 1 wherein the semiconductor layer comprises a predetermined conductivity type and wherein said channel stop region comprises impurities corresponding to said first predetermined conductivity type.

### Claim 3 (depends on 1)

The isolation structure of claim 1 wherein said channel stop region is formed by implanting impurities into the semiconductor layer.

### Claim 4 (depends on 1)

The isolation structure of claim 1 wherein said channel stop region is formed by diffusing impurities into the semiconductor layer using solid source materials.

### Claim 5 (depends on 1)

The isolation structure of claim 1 wherein the semiconductor layer comprises silicon and wherein said LOCOS structure comprises silicon dioxide.

### Claim 6 (depends on 1)

The isolation structure of claim 1 wherein said trench plug comprises oxide.

### Claim 7 (depends on 1)

The isolation structure of claim 1 wherein said trench plug comprises a region comprising oxide and a region comprising phosphosilicon glass.

### Claim 8 (depends on 1)

The isolation structure of claim 1 wherein said trench plug comprises a region comprising oxide and a region comprising borophosphosilicon glass.

### Claim 9 (depends on 1)

The isolation structure of claim 1 wherein said trench plug comprises a region of polycrystalline semiconductor material and a region comprising an oxide of said semiconductor material.

### Claim 10 (depends on 1)

The isolation structure of claim 1 wherein said trench plug comprises a first trench plug formed in a first trench and further comprising a second trench plug disposed in a second trench formed through said LOCOS structure proximate said first trench between said first and second bird's beak structures and in said semiconductor layer.

### Claim 11

An isolation structure formed in a semiconductor layer between first and second active regions in order to electrically isolate the first and second active regions one from the other, the semiconductor layer comprising an outer surface, the isolation structure comprising:
a LOCOS structure formed on the outer surface, said LOCOS structure comprising a first bird's beak structure disposed laterally adjacent the first active region and a second bird's beak structure disposed laterally adjacent the second active region;
a trench plug disposed in a trench formed through said LOCOS structure between said first and second bird's beak structures and in said semiconductor layer, said trench comprising sidewalls defining an interface between said trench plug and the semiconductor layer; and
a channel stop implantation region formed in the semiconductor layer adjacent said sidewalls of said trench, the semiconductor layer comprising silicon having a predetermined conductivity type and wherein said channel stop region comprises impurities corresponding to said first predetermined conductivity type, said LOCOS structure and said trench plug comprising silicon dioxide.

### Claim 12 (depends on 11)

The isolation structure of claim 11 wherein said trench plug comprises a region of polycrystalline semiconductor material and a region comprising an oxide of said semiconductor material.

### Claim 13 (depends on 11)

The isolation structure of claim 11 wherein said trench plug comprises a region comprising oxide and a region comprising phosphosilicon glass.

### Claim 14 (depends on 11)

The isolation structure of claim 11 wherein said trench plug comprises a region comprising oxide and a region comprising borophosphosilicon glass.

### Claim 15 (depends on 11)

The isolation structure of claim 11 wherein said trench plug comprises a first trench plug formed in a first trench and further comprising a second trench plug disposed in a second trench formed through said LOCOS structure proximate said first trench between said first and second bird's beak structures and in said semiconductor layer.