# US 7,071,073 B2 · Process for manufacturing low-cost and high-quality SOI substrates

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- Number: US 7,071,073 B2
- Document ID: US7071073B2
- Status: Granted
- Kind: B2
- Application number: 10/331,189
- Filed: 2002-12-26
- Published: 2003-08-07
- Granted: 2006-07-04
- Earliest claimed: 2001-12-28
- Assignees: STMicroelectronics S.r.l.
- Inventors: Flavio Villa; Gabriele Barlocchi; Pietro Corona
- Web page: https://patentgrep.com/patent/US7071073B2

## CPC

- H10P 90/191: {using full isolation by porous oxide silicon [FIPOS]}
- H10P 90/1912: {using selective deposition, e.g. epitaxial lateral overgrowth [ELO] or selective deposition of single crystal silicon}
- H10W 10/0123: {using auxiliary pillars in the regions}
- H10W 10/13: formed using local oxidation of silicon [LOCOS], e.g. sealed interface localised oxidation [SILO] or side-wall mask isolation [SWAMI]
- H10W 10/181: {Semiconductor-on-insulator [SOI] isolation regions, e.g. buried oxide regions of SOI wafers}
- H10P 14/6309: {of silicon in uncombined form, i.e. pure silicon}
- H10P: GENERIC PROCESSES OR APPARATUS FOR THE MANUFACTURE OR TREATMENT OF DEVICES COVERED BY CLASS H10
- H10W: GENERIC PACKAGES, INTERCONNECTIONS, CONNECTORS OR OTHER CONSTRUCTIONAL DETAILS OF DEVICES COVERED BY CLASS H10

## Abstract

For manufacturing an SOI substrate, the following steps are carried out: providing a wafer of semiconductor material; forming, inside the wafer, a plurality of passages forming a labyrinthine cavity and laterally delimiting a plurality of pillars of semiconductor material; and oxidizing the pillars of semiconductor material to form a buried insulating layer. For forming the labyrinthine cavity, a trench is first formed in a substrate; an epitaxial layer is grown, which closes the trench at the top; the wafer is annealed so as to deform the pillars and cause them to assume a minimum-energy handlebar-like shape, and a peripheral portion of the wafer is removed to reach the labyrinthine cavity, and side inlet openings are formed in the labyrinthine cavity. Oxidation is performed by feeding an oxidizing fluid through the side inlet openings.

## Claims

### Claim 1

A process for manufacturing a SOI substrate comprising the steps of:
separating two portions of a semiconductor material with at least one passage;
forming, after the separating step, at least one opening to the at least one passage through a side of the semiconductor material, the side formed by the two portions of the semiconductor material; and
converting a region of the semiconductor material into an insulating material via the at least one opening and the at least one passage.

### Claim 2 (depends on 1)

The process of claim 1, wherein the separating step includes the further step of forming a plurality of passages, the passageways being formed such that at least one passageway intersects with at least one other passageway and a plurality of pillars are formed separating the two planar regions.

### Claim 3 (depends on 2)

The process of claim 2, wherein at least one of the plurality of pillars assumes a shape narrower in the middle than at the ends.

### Claim 4 (depends on 1)

The process of claim 1, including the further step of annealing the semiconductor material.

### Claim 5 (depends on 1)

The process of claim 1, wherein the forming step further includes the step of removing a surface portion of the semiconductor material until at least one passage is reached.

### Claim 6 (depends on 5)

The process of claim 5, wherein the removing step further includes using a laser.

### Claim 7 (depends on 1)

The process according to claim 1, wherein the converting step further includes the step of sufficiently oxidizing at least one passage via the at least one opening to form an insulating layer that separates the semiconductor portions.

### Claim 8

A process for manufacturing a SOI substrate comprising the steps of:
separating two portions of a semiconductor material with at least one passage;
forming, after the separating step, at least one opening through the semiconductor material to the at feast one passage;
converting a region of the semiconductor material into an insulating material via the at least one opening and the at least one passage; and
wherein the separating step includes the further steps of,
selectively removing portions of a substrate of the semiconductor material to form at least one trench opening on a top surface of the semiconductor material, and
growing a layer of semiconductor material over the top surface to close the at least one trench and form the at least one passage.

### Claim 9 (depends on 8)

The process of claim 8, wherein the selectively removing step comprises etching the top surface of the substrate. least one passageway intersects with at least one other passageway and a plurality of pillars are formed separating the two planar regions.

### Claim 10

A process for manufacturing a SOI substrate comprising the steps of:
separating two portions of a semiconductor material with at least one passage;
forming, after the separating step, at least one opening through the semiconductor material to the at least one passage;
converting a region of the semiconductor material into an insulating material via the at least one opening and the at least one passage; and
wherein the separating step includes the further steps of,
forming a first plurality of passages generally having a first width and defining a first group of regions, and
forming a second plurality of passages having a second width smaller than said first width and defining a second group of regions.

### Claim 11 (depends on 10)

The process according to claim 10, wherein the separating step further includes the steps of:
growing a top layer; and
annealing the semiconductor material sufficiently to cause joining of the second plurality of passages to form at least one buried channel having a larger cross-sectional area than a passage of the first plurality of passages.

### Claim 12 (depends on 10)

The process according to claim 10, wherein the converting step further includes the step of sufficiently oxidizing at least one passage via the at least one opening to form an insulating layer.

### Claim 13

A process for manufacturing SOI substrates, comprising the steps of:
providing a wafer of semiconductor material;
forming, inside said wafer, a plurality of fully enclosed passages laterally delimiting a plurality of semiconductor material regions;
forming side inlet openings to the plurality of passages; and
oxidizing said semiconductor material regions to form a buried insulating layer;
wherein said oxidation step comprises feeding an oxidizing means through said side inlet openings.

### Claim 14 (depends on 13)

The process according to claim 13, wherein said wafer has a monocrystalline structure.

### Claim 15 (depends on 13)

The process according to claim 13, wherein said wafer has one larger surface, and said side inlet openings extend on a surface transverse to said larger surface.

### Claim 16 (depends on 13)

The process according to claim 13, wherein said step of forming side inlet openings comprises removing a surface portion of said wafer until said plurality of passages is reached.

### Claim 17 (depends on 16)

The process according to claim 16, wherein said step of removing a surface portion comprises removing a peripheral portion of said wafer.

### Claim 18 (depends on 16)

The process according to claim 16, wherein said step of removing a surface portion comprises coating said wafer with a masking layer, feeding a solvent to a preset portion of said masking layer, and etching said wafer wherever it is not coated by said masking layer.

### Claim 19 (depends on 16)

The process according to claim 16, wherein said step of removing a surface portion comprises coating said wafer with a masking layer; irradiating a preset portion of said masking layer with UV rays; removing said preset portion of said masking layer; and etching said wafer wherever it is not coated by said masking layer.

### Claim 20 (depends on 13)

The process according to claim 13, comprising, after feeding an oxidizing means, closing said side inlet openings with insulating material.

### Claim 21

A process for manufacturing SOI substrates, comprising the steps of:
providing a wafer of semiconductor material;
forming, inside said wafer, a plurality of passages laterally delimiting a plurality of semiconductor material regions;
forming side inlet openings to the plurality of passages; and
oxidizing said semiconductor material regions to form a buried insulating layer,
wherein said oxidation step comprises feeding an oxidizing means through said side inlet openings;
wherein said step of forming a plurality of passages comprises,
before forming said side inlet openings, selectively removing portions of a substrate of semiconductor material to form a plurality of trenches, and
growing a top layer of said semiconductor material on top of said substrate.

### Claim 22 (depends on 21)

The process according to claim 21, wherein said step of selectively removing comprises etching said substrate starting from a top surface thereof.

### Claim 23 (depends on 21)

The process according to claim 21, wherein said step of forming passages comprises, after growing a top layer, annealing of said wafer.

### Claim 24 (depends on 23)

The process according to claim 23, wherein said step of annealing is carried out in an atmosphere comprising nitrogen and oxygen.

### Claim 25 (depends on 23)

The process according to claim 23, wherein said step of annealing is carried out at a temperature of between 1100° C. and 1200° C.

### Claim 26 (depends on 23)

The process according to claim 23, wherein said passages form a reticular cavity.

### Claim 27 (depends on 26)

The process according to claim 26, wherein said semiconductor material regions form pillars having a hexagonal cross section and arranged in honeycomb fashion.

### Claim 28 (depends on 27)

The process according to claim 27, wherein, during said step of annealing, said pillars are deformed and assume a handlebar-like shape, with a minimum cross section in a cross-sectional plane approximately halfway up.

### Claim 29 (depends on 21)

process according to claim 21, comprising, before selectively removing portions of a substrate, selectively eliminating a peripheral portion of said substrate.

### Claim 30 (depends on 29)

The process according to claim 29, wherein said step of selectively eliminating a peripheral portion of said substrate comprises selectively growing a peripheral oxide region, and in that said peripheral oxide region is removed before said step of growing a top layer.

### Claim 31

A process for manufacturing SOI substrates, comprising the steps of:
providing a wafer of semiconductor material;
forming, inside said wafer, a plurality of fully enclosed passages laterally delimiting a plurality of semiconductor material regions;
forming side inlet openings to the plurality of passages; and
oxidizing said semiconductor material regions to form a buried insulating layer,
wherein said oxidation step comprises feeding an oxidizing means through said side inlet openings;
wherein said step of forming a plurality of passages comprises the steps of,
forming a first plurality of passages delimiting a first group of said semiconductor material regions having a first width, and
forming a second plurality of passages delimiting a second plurality of said semiconductor material regions having a second width smaller than said first width, said second plurality of passages extending along scribing lines of said wafer.

### Claim 32 (depends on 31)

The process according to claim 31, wherein said step of forming a plurality of passages comprises,
after growing a top layer, annealing said wafer, causing joining of said second plurality of passages during said annealing step; and
forming buried channels having a larger width than said plurality of passages.

### Claim 33 (depends on 32)

The process according to claim 32, wherein said step of selectively forming a peripheral oxide region comprises locally growing said peripheral oxide region by protected local oxidation.

### Claim 34

A process for manufacturing a SOI substrate comprising the steps of:
separating two portions of a semiconductor material with at least one cavity;
forming, after the separating step, at least one opening to the at least one cavity through the semiconductor material; and
converting a region of the semiconductor material into an insulating material via the at least one opening and the at least one cavity.

### Claim 35

A process for manufacturing a SOI substrate comprising the steps of:
separating two portions of a semiconductor material with at least one cavity;
forming, after the separating step, at least one opening to the at least one cavity through a side of the semiconductor material, the side formed by the two portions of the semiconductor material; and
converting a region of the semiconductor material into an insulating material via the at least one opening and the at least one cavity.