Memc Electronic Materials, Inc.

Sunedison Semiconductor Limited

Marco Cornara

Massimiliano Olmo

Daniela Gambaro

Robert J Falster

Joseph C Holzer

Paolo Mutti

Bayard K Johnson

Steve A Markgraf

Seamus A McQuaid

Robert A Falster

Vladimir V Voronkov

Robert Falster

Processes for the treatment of silicon wafers to form a high density non-uniform distribution of oxygen precipitate nuclei therein such that, upon being subjected to the heat treatment cycles of essentially any arbitrary electronic device manufacturing process, the wafers form oxygen precipitates in the bulk and a precipitate-free zone near the surface are disclosed. The processes involve activation of inactive oxygen precipitate nuclei by performing heat treatments between about 400&#xb0; C. and about 600&#xb0; C. for at least about 1 hour.

Production of high precipitate density wafers by activation of inactive oxygen precipitate nuclei

The present invention is directed to a process for producing a silicon wafer which, during the heat treatment cycles of essentially any arbitrary electronic device manufacturing process, may form an ideal, non-uniform depth distribution of oxygen precipitates and may additionally contain an axially symmetric region which is substantially free of agglomerated intrinsic point defects. The process either comprises exposing the wafer's front and back surfaces to different atmospheres, or thermally annealing two wafers in a face-to-face arrangement.

Process for forming low defect density, ideal oxygen precipitating silicon

The present invention is directed to a silicon wafer which, during the heat treatment cycles of essentially any arbitrary electronic device manufacturing process, may form an ideal, non-uniform depth distribution of oxygen precipitates and may additionally contain an axially symmetric region which is substantially free of agglomerated intrinsic point defects.

Low defect density, ideal oxygen precipitating silicon

The present invention is directed to a process for producing a silicon wafer which, during the heat treatment cycles of essentially any arbitrary electronic device manufacturing process, may form an ideal, non-uniform depth distribution of oxygen precipitates and may additionally contain an axially symmetric region which is substantially free of agglomerated intrinsic point defects. The process including growing a single crystal silicon ingot from molten silicon, and as part of the growth process, controlling (i) a growth velocity, v, (ii) an average axial temperature gradient, G0, during the growth of a constant diameter portion of the crystal over a temperature range from solidification to a temperature of no less than about 1325&#xb0; C., and (iii) a cooling rate of the crystal from a solidification temperature to about 1,050&#xb0; C., in order to cause the formation of an axially symmetrical segment which is substantially free of agglomerated intrinsic point defects. A silicon wafer is then sliced from the ingot, subjected to a heat-treatment to form crystal lattice vacancies in the front surface and bulk layers of the wafer and cooled at a rate sufficient to cause a non-uniform vacancy concentration profile in the wafer such that a thermal treatment at a temperature in excess of 750&#xb0; C., is capable of forming in the wafer a denuded zone in the front surface layer and oxygen clusters or precipitates in the bulk zone with the concentration of the oxygen clusters or precipitates in the bulk layer being primarily dependant upon the concentration of vacancies.

Process for producing low defect density, ideal oxygen precipitating silicon

A process for heat-treating a single crystal silicon wafer to influence the precipitation behavior of oxygen in the wafer in a subsequent thermal processing step. The wafer has a front surface, a back surface, and a central plane between the front and back surfaces. In the process, the wafer is subjected to a heat-treatment to form crystal lattice vacancies, the vacancies being formed in the bulk of the silicon. The wafer is then cooled from the temperature of said heat treatment at a rate which allows some, but not all, of the crystal lattice vacancies to diffuse to the front surface to produce a wafer having a vacancy concentration profile in which the peak density is at or near the central plane with the concentration generally decreasing in the direction of the front surface of the wafer.

Ideal oxygen precipitating silicon wafers and oxygen out-diffusion-less process therefor

A process for heat-treating a single crystal silicon wafer to influence the precipitation behavior of oxygen in the wafer in a subsequent thermal processing step. The wafer has a front surface, a back surface, and a central plane between the front and back surfaces. In the process, the wafer is subjected to a heat-treatment to form crystal lattice vacancies in the wafer. During the heat-treatment, the front and back surfaces of the wafer are each exposed to either a nitriding or non-nitriding gas. The wafer is then cooled from the temperature of said heat treatment at a rate which allows some, but not all, of the crystal lattice vacancies to diffuse to the front surface to produce a wafer having a vacancy concentration profile determined in part by the gas that each surface is exposed to and in part by the cooling rate.

Ideal oxygen precipitating silicon wafer having an asymmetrical vacancy concentration profile and a process for the preparation thereof

The present invention is directed to a process for producing a silicon wafer which, during the heat treatment cycles of essentially any arbitrary electronic device manufacturing process, may form an ideal, non-uniform depth distribution of oxygen precipitates and may additionally contain an axially symmetric region which is substantially free of agglomerated intrinsic point defects. The process including growing a single crystal silicon ingot from molten silicon, and as part of the growth process, controlling (i) a growth velocity, v, (ii) an average axial temperature gradient, G , during the growth of a constant diameter portion of the crystal over a temperature range from solidification to a temperature of no less than about 1325&deg; C., and (iii) a cooling rate of the crystal from a solidification temperature to about 1,050&deg; C., in order to cause the formation of an axially symmetrical segment which is substantially free of agglomerated intrinsic point defects. A silicon wafer is then sliced from the ingot, subjected to a heat-treatment to form crystal lattice vacancies in the front surface and bulk layers of the wafer and cooled at a rate sufficient to cause a non-uniform vacancy concentration profile in the wafer such that a thermal treatment at a temperature in excess of 750&deg; C., is capable of forming in the wafer a denuded zone in the front surface layer and oxygen clusters or precipitates in the bulk zone with the concentration of the oxygen clusters or precipitates in the bulk layer being primarily dependant upon the concentration of vacancies.

A process for preparing a silicon epitaxial wafer. The wafer has a front surface having an epitaxial layer deposited thereon, a back surface, and a bulk region between the front and back surfaces, wherein the bulk region contains a concentration of oxygen precipitates. In the process, the wafer is first subjected to an ideal oxygen precipitating heat treatment to causes the formation of a non-uniform distribution of crystal lattice vacancies with the concentration of vacancies in the bulk region being greater than the distribution of vacancies in the front surface. The ideal precipitating wafer is then subjected to an oxygen precipitation heat treatment to cause the nucleation and growth of oxygen precipitates to a size sufficient to stabilize the oxygen precipitates, with the oxygen precipitates being formed primarily according to the vacancy profile. An epitaxial layer is then deposited on the surface of the oxygen precipitate stabilized wafer.

Ideal oxygen precipitating epitaxial silicon wafers and oxygen out-diffusion-less process therefor

A process for preparing an silicon epitaxial wafer. The wafer has a front surface having an epitaxial layer deposited thereon, a back surface, and a bulk region between the front and back surfaces, wherein the bulk region contains a concentration of oxygen precipitates. In the process, a wafer having interstitial oxygen atoms is first subjected to an oxygen precipitation heat treatment to cause the nucleation and growth of oxygen precipitates to a size sufficient to stabilize the oxygen precipitates. An epitaxial layer is then deposited on the surface of the oxygen precipitate stabilized wafer.

A process for heat-treating a single crystal silicon wafer to influence the precipitation behavior of oxygen in the wafer in a subsequent thermal processing step. The wafer has a front surface, a back surface, a central plane between the front and back surfaces, and a sink for crystal lattice vacancies at the front surface. In the process, the wafer is subjected to a heat-treatment to form crystal lattice vacancies, the vacancies being formed in the bulk of the silicon. The wafer is then cooled from the temperature of said heat treatment at a rate which allows some, but not all, of the crystal lattice vacancies to diffuse to the crystal lattice vacancy sink to produce a wafer having a vacancy concentration profile in which the peak density is at or near the central plane with the concentration generally decreasing in the direction of the front surface of the wafer.

A single crystal silicon wafer which, during the heat treatment cycles of essentially any electronic device manufacturing process, will form an ideal, non-uniform depth distribution of oxygen precipitates. The wafer is characterized in that is has a non-uniform distribution of crystal lattice vacancies, the concentration of vacancies in the bulk layer being greater than the concentration of vacancies in the surface layer and the vacancies having a concentration profile in which the peak density of the vacancies is at or near a central plane with the concentration generally decreasing from the position of peak density in the direction of a front surface of the wafer. In one embodiment, the wafer is further characterized in that it has a first axially symmetric region in which vacancies are the predominant intrinsic point defect and which is substantially free of agglomerated intrinsic point defects, wherein the first axially symmetric region comprises a central axis or has a width of at least about 15 mm. In another embodiment, the wafer is further characterized in that it has an axially symmetric region which is substantially free of agglomerated intrinsic point defects, the axially symmetric region extending radially inwardly from a circumferential edge of the wafer and having a width, as measured from the circumferential edge radially toward a center axis, which is at least about 40% the length of a radius of the wafer.

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Galliate, Italy

Marco Cornara