Optics: measuring and testing – Inspection of flaws or impurities – Surface condition
Patent
1997-09-09
1999-08-10
Kim, Robert H.
Optics: measuring and testing
Inspection of flaws or impurities
Surface condition
3562373, 3562374, 3562375, G01N 2100
Patent
active
059367261
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention generally relates to the inspection of foreign particles attached on the surface of an object and measurement of defects within the object, and particularly to an inspection method of and apparatus for detecting foreign particles attached on the surface of a silicon crystal and on the surface of an amorphous silicon thin film, and for measuring crystal defects such as oxygen precipitates in a silicon wafer, and foreign particles within an amorphous silicon thin film, to standard samples for the correction of this apparatus, and to a semiconductor production method using this method or apparatus.
BACKGROUND ART
Recently, the integration density of LSIs (Large Scale Integrated Circuits) has been increased, and caused the serious problem that the yield of satisfactory MOS (Metal Oxide Semiconductor) transistors which form devices, and the reliability are decreased due to the defective transistors. The defectiveness of MOS transistors will be caused due to, typically, breakdown of insulating gate oxide films and excessive leak current in junctions. The latter gives rise to the loss of information called poor refreshment in DRAM (Dynamic Random Access Memory). These causes for unsatisfactory MOS transistors are ascribed to not only the foreign particles on the surface of the silicon substrate in which devices are built up, but also crystal defects present in the region near the surface. The region near the surface of the silicon substrate is specifically in the range from the substrate surface to about 0.5 .mu.m deep, and this region is a portion of the substrate that is converted into an oxide insulated layer (silicon oxide film) in the production process for devices such as LSIs or into a depletion layer when a metal thin film is deposited on the substrate surface. The crystal defects located within this portion form structural defects in the silicon oxide film, and causes insulation breakdown in the LSI operation. The defects in the depletion layer causes a large amount of leak current to occur. On the contrary, crystal defects located in the region deeper than the near-surface region, particularly, oxygen precipitates, have the effect (gettering effect) to catch metal ions mixed into the silicon substrate in various production processes, preventing the near-surface region of the substrate from being contaminated with metal.
Therefore, for the quality control of silicon substrates in which LSIs are formed, it is necessary to provide an inspection apparatus capable of not only detecting foreign particles on the substrate surface, but also selectively detecting crystal defects located in the near-surface region.
Moreover, when liquid crystal displays which are formed of thin film transistors (for example, amorphous silicon thin films) are produced under quality control, it is essential to detect the foreign particles on the surface of a transparent substrate on which thin films are formed, the foreign particles or defects present in the near-surface region, and the foreign particles which are mixed into the interior of the thin films in the thin film depositing process or which adhere to the substrate surface.
There is proposed an apparatus for detecting foreign particles or defects on or below the surface of a sample by irradiating S-polarized light and P-polarized light on the sample surface, as is disclosed in Japanese Patent Laid-open JP-A-63-12943 (or U.S. Pat. No. 4,893,932 associated therewith). This apparatus detects the foreign particles or defects located on the sample surface by utilizing the fact that the intensity distributions of the irradiation light scattered by the foreign particles and defects on the sample surface are different depending on the polarization direction. However, the specification disclosing the apparatus of the invention does not specifically describe any means for detecting the foreign particles or defects present on the lower side (namely, in the medium of which the refractive index is larger than that of air) of the sample surface.
REFERENCES:
patent: 4893932 (1990-01-01), Knollenberg
Hiraiwa Atsushi
Ishida Hidetsugu
Takeda Kazuo
Hitachi , Ltd.
Kim Robert H.
Merlino Amanda
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