Optics: measuring and testing – By polarized light examination – With light attenuation
Reexamination Certificate
2000-05-10
2001-08-14
Pham, Hoa Q. (Department: 2877)
Optics: measuring and testing
By polarized light examination
With light attenuation
C356S030000
Reexamination Certificate
active
06275293
ABSTRACT:
FIELD OF THE INVENTION
The instant invention relates to methods of evaluating silicon wafers and more particularly to a method of evaluating the OSF density on the surface of a silicon wafer.
BACKGROUND
Oxygen induced stacking faults (OSF) occur in the manufacture of silicon wafers. Measuring the OSF density is necessary for quality control in the manufacture of silicon wafers. Silicon wafers are used throughout industry, including by manufacturers of memory devices and microprocessors.
Known methods of measuring OSF density are limited to visual inspection by manufacturing operators. Visual inspection includes irradiating the surface of an oxidized and etched silicon wafer with a halogen lamp, spotting areas of haziness on the wafer, and measuring density with an optical microscope, either by photographing the location or directly through the optical microscope eyepiece, by counting the visible faults and multiplying by a factor based on magnification and area of image to determine density. Disadvantages of existing methods of measuring OSF density include the susceptibility to human error in visual inspection, the slowness of visual inspection by operators, and the lack of uniformity of visual inspection between operators. Other disadvantages include the need for a separate step in the manufacturing process for the visual inspection.
Heretofore, application of methods and articles for measuring OSF density by correlation to surface roughness measurement has never been performed. A method of measuring OSF density using methods and articles for measuring surface roughness of silicon wafers has never been performed. An automated method for measuring OSF density has never been performed. An automated method of measuring OSF density that does not rely on visual inspection by operators has never been performed. A method of measuring OSF density that uses existing inspection methods heretofore applied in other areas of inspection has never been performed.
EP 0702204 B1 (Aihara, et al) discloses a method of evaluating the crystal quality near the surface of a silicon wafer through microroughness analysis. The patent describes a relationship between microroughness and crystal quality and teaches that detection of the high sensitivity changes in the surface configuration of a silicon wafer provides a method of evaluating the crystal quality of silicon wafers. The invention defines crystal quality as “the surface configuration between each silicon crystal.” The patent discloses that a method for evaluating crystal quality through microroughness analysis will replace the evaluation method of measuring dielectric breakdown voltage of an oxide layer. The patent neither identifies OSF density, nor relates crystal quality to OSF density. As such, the patent teaches away from the use of surface roughness measurement as a means to measure OSF density. The patent does not disclose replacement of the OSF density inspection quality control process.
Therefore, it is highly desirable to create an automated method of measuring OSF density. It is further highly desirable for creating a method of measuring OSF density that does not rely on visual inspection. It is also highly desirable to create a method of measuring OSF density that utilizes existing inspection methods heretofore applied in other areas of inspection. Potential customers for methods that meet these objects include silicon wafer manufacturers, memory and microprocessor manufacturers—any manufacturer that uses silicon wafers and has a need to measure OSF density on a wafer.
SUMMARY
Accordingly, it is an object to provide novel methods for solving the above-mentioned problems. In particular, it is an object to provide novel automated methods for measuring OSF density in silicon wafers. It is an object to provide novel methods for measuring OSF density that do not rely on visual inspection. It is an object to provide novel methods of measuring OSF density that utilize existing inspection methods heretofore applied in other areas of inspection.
These and other objects and advantages are achieved by methods for automating the OSF density measurement process and by eliminating or reducing the need for visual inspection of OSF density.
The novel methods provide a number of advantages, including automation of methods for measuring OSF density, elimination or reduction of visual inspection and its inherent operator variation as a method of measuring OSF density, faster OSF density measurement, and reduction of cost of measuring OSF density. The novel methods also provide for more reliable and uniform OSF density measurement.
The methods are compatible with techniques for surface roughness measurement of silicon wafers. Commercially available equipment may be used.
The novel methods of the invention are well suited for use in connection with manufacturing silicon wafers. The methods allow automated measurement of OSF density without the aid of visual inspection by using methods of measuring surface roughness. In such uses the surface measurements are performed on the silicon wafers with surface measurement machines and the resulting data is multiplied by a predetermined correlation factor to determine the OSF density of the silicon wafer.
The embodiments of the invention utilize automated methods for measuring surface roughness on a silicon wafer to determine OSF density on wafers. In the preferred embodiment, the described invention utilizes a texture measurement machine to measure surface roughness on a polished silicon wafer surface to determine OSF density on wafers previously oxidized and etched. This described invention is not limited to use on a wafer from any specific phase of silicon wafer manufacturing, but wafers must be oxidized and etched before OSF density is measured using surface roughness.
Further benefits and advantages of the embodiments of the invention will become apparent from consideration of the following detailed description given with reference to the accompanying drawings, which specify and show preferred embodiments of the present invention.
REFERENCES:
patent: 4981549 (1991-01-01), Yamashita et al.
patent: 5298963 (1994-03-01), Moriya et al.
patent: 5373804 (1994-12-01), Tachimori et al.
patent: 5508800 (1996-04-01), Miyashita et al.
patent: 5677208 (1997-10-01), Itou et al.
patent: 5730800 (1998-03-01), Sato et al.
patent: 5903342 (1999-05-01), Yatsugake et al.
patent: 5933229 (1999-08-01), Yeh et al.
patent: 6190452 (2001-02-01), Sakurada et al.
patent: 0702204 (1999-11-01), None
Pham Hoa Q.
Rylander Kurt M.
SEH America Inc.
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