# US 7,407,855 B2 · Method of producing semiconductor element and nonvolatile semiconductor memory produced by this method

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- Number: US 7,407,855 B2
- Document ID: US7407855B2
- Status: Granted
- Kind: B2
- Application number: 11/202,190
- Filed: 2005-08-12
- Published: 2007-01-04
- Granted: 2008-08-05
- Earliest claimed: 2002-01-31
- Assignees: Oki Electric Industry Co., Ltd.
- Inventors: Toshio Nagata
- Web page: https://patentgrep.com/patent/US7407855B2

## CPC

- H10P 14/69215: {the material being a silicon oxide, e.g. SiO2}
- H10D 30/6891: {characterised by the shapes, relative sizes or dispositions of the floating gate electrode}
- H10D 64/035: {comprising conductor-insulator-conductor-insulator-semiconductor structures}
- H10P 14/6308: {of Group IV semiconductors}
- H10P 14/6334: {using decomposition or reaction of gaseous or vapour phase compounds, i.e. chemical vapour deposition (deposition by physical ablation of a target H10P14/6329)}
- H10P 14/6529: {by exposure to a gas or vapour}
- H10P: GENERIC PROCESSES OR APPARATUS FOR THE MANUFACTURE OR TREATMENT OF DEVICES COVERED BY CLASS H10
- H10D: INORGANIC ELECTRIC SEMICONDUCTOR DEVICES

## Abstract

In a first embodiment, Tetraethyl Orthosilicate Si(OC2H5)4 is used at the process temperature of 650° C.±5° C. as film forming material, to decrease crystal defects occurring during deposition. In a second embodiment, annealing is carried out in sparse oxygen gas atmosphere after deposition, to mend crystal defects that occurred during deposition. In a third embodiment, initial temperature of the CVD device is kept at about 400° C., whereby the start of natural oxidation of the deposition surface is prevented and production circumstances of the semiconductor element is not deteriorated. Then, the CVD device is heated up to CVD temperature of about 750° C. or about 650° C., to deposit oxide.

## Claims

### Claim 1

A method of producing a semiconductor element comprising:
a process of forming a first oxide film on a semiconductor substrate,
a process of forming a semiconductor film and an oxidation stopping film on the first oxide film,
a process of forming an opening by patterning the oxidation stopping film,
a process of forming an insulating local oxide film by local oxidation of a surface of the semiconductor film exposed through the opening,
a process of removing the oxidation stopping film,
a process of forming a floating gate of the semiconductor film remaining under the insulating local oxide film, by selective etching of the semiconductor film masked with the insulating local oxide film,
a process of cleaning the semiconductor substrate, and
a process of transferring the silicon substrate with the floating gate to a chemical vapor deposition device where an initial temperature is kept in a range where oxidation of a surface of the floating gate is restrained,
a process of heating the chemical vapor deposition device from the initial temperature to a chemical vapor deposition temperature, and
a process of forming a second oxide film covering the floating gate by low pressure chemical vapor deposition,
wherein the initial temperature is in range of 400° C.±5° C. and the chemical vapor deposition temperature is in range of 750° C.±5° C.

### Claim 2

A method of producing a semiconductor element comprising:
a process of forming a first oxide film on a semiconductor substrate,
a process of forming a semiconductor film and an oxidation stopping film on the first oxide film,
a process of forming an opening by patterning the oxidation stopping film,
a process of forming an insulating local oxide film by local oxidation of a surface of the semiconductor film exposed through the opening,
a process of removing the oxidation stopping film,
a process of forming a floating gate of the semiconductor film remaining under the insulating local oxide film, by selective etching of the semiconductor film masked with the insulating local oxide film,
a process of cleaning the semiconductor substrate, and
a process of transferring the silicon substrate with the floating gate to a chemical vapor deposition device where an initial temperature is kept in a range where oxidation of a surface of the floating gate is restrained,
a process of heating the chemical vapor deposition device from the initial temperature to a chemical vapor deposition temperature,
a process of forming a second oxide film covering the floating gate by low pressure chemical vapor deposition, and
a process of annealing the second oxide film in a sparse oxygen atmosphere, after the process of forming the second oxide film,
wherein the initial temperature is in range of 400° C.±5° C. and the chemical vapor deposition temperature is in range of 750° C.±5° C.

### Claim 3

A method of producing a semiconductor element comprising:
a process of forming a first oxide film on a semiconductor substrate,
a process of forming a semiconductor film and an oxidation stopping film on the first oxide film,
a process of forming an opening by patterning the oxidation stopping film,
a process of forming an insulating local oxide film by local oxidation of a surface of the semiconductor film exposed through the opening,
a process of removing the oxidation stopping film,
a process of forming a floating gate of the semiconductor film remaining under the insulating local oxide film, by selective etching of the semiconductor film masked with the insulating local oxide film,
a process of cleaning the semiconductor substrate, and
a process of transferring the silicon substrate with the floating gate to a chemical vapor deposition device where an initial temperature is kept in a range where oxidation of a surface of the floating gate is restrained,
a process of heating the chemical vapor deposition device from the initial temperature to a chemical vapor deposition temperature,
a process of forming a second oxide film covering the floating gate by low pressure chemical vapor deposition,
wherein tetra-ethyl ortho-silicate is formed in the process of forming the second oxide film, and
wherein the initial temperature is in range of 400° C.±5° C. and the chemical vapor deposition temperature is in range of 750° C.±5° C.