Optics: measuring and testing – Inspection of flaws or impurities – Surface condition
Reexamination Certificate
2000-01-18
2001-11-13
Pham, Hoa Q. (Department: 2877)
Optics: measuring and testing
Inspection of flaws or impurities
Surface condition
C356S600000, C356S237500
Reexamination Certificate
active
06317204
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a surface inspecting method and an apparatus for carrying out the inspecting method, for measuring the shape or the state of surfaces of measurement objective regions, more particularly, to a surface inspecting method and a surface inspecting apparatus, suitable for inspection of surface characteristics of specific measurement objective regions, which comprises a periodic irregular pattern formed thereon.
BACKGROUND OF THE INVENTION
Measurement of the shape or the state of a surface of an object is carried out for an instrumentation of the object's characters, a decision whether the quality of the object is good or not as a product, and the like. In particular, measurement of the shape or the state of the surface of the object is often used for measuring the irregularity of a surface of an object having an approximate plate-like shape.
FIG. 9
shows a typical example of a measuring apparatus for measuring the irregularity of the surface of the object having an approximate plate-like shape. As shown in
FIG. 9
, the measuring apparatus is provided with (a) a light source
910
for generating substantially parallel light beams, (b) a half mirror
920
for accepting the light beams output from the light source
910
and for outputting these light beams toward a specific measurement objective region on the object
990
to be measured, (c) an optical image formation system
930
for receiving the reflected light from the measurement objective region of the object
990
to be measured and for forming an optical image thereof, (d) an image pickup part
940
having a light receiving surface
941
at the image formation surface of the optical image formation system
930
, and (e) an image information processor
950
for collecting the luminance data output from the image pickup part
940
and for image processing the collected data.
By using the above-described measuring apparatus, measurement of the shape or the like of the measurement objective region is carried out as follows. A substantially parallel light beam outputs from the light source
910
are irradiated through the half mirror
920
onto measurement objective regions of the object
990
to be measured. Light beams reflected from the measurement objective region forms an image through the image formation system
930
, and the formed image is picked up by the image pickup part
940
. The picked up image results are output from the image pickup part
940
and are collected by the image information processor
950
. The processor
950
reconstructs the image of the measurement objective region by processing the collected luminance data. By inspection of the obtained image of the measured objective region, the presence or absence of irregularity or the position of the irregularity is measured through fading or blurry portions in the image.
Conventionally, since an object shape measurement has been carried out as described above, an approximate shape of the irregular portion could be recognized. However, when the irregularity is formed as a periodic pattern, for example, a circuit pattern is formed on a surface of a wafer, a precise measurement for the shape of the irregular pattern could not be performed.
Accordingly, in order to precisely measure the shape of the irregular pattern, use of a large scale, complicated and expensive apparatus such as a scanning confocal electron microscope has been required.
The present invention was developed in view of the above-described problems. An object of the present invention is to provide an improved surface inspecting method which enables measurement of the configuration of a pattern with irregularity in a wide surface region with a high accuracy and in a single operation by using an apparatus having relatively simple construction. Another object of the present invention is to provide an improved surface inspecting apparatus having a simple construction for suitably carrying out the surface inspecting method according to the invention.
SUMMARY OF THE INVENTION
The improved surface inspecting method of the invention according to the present invention is one for inspecting a surface condition a measurement objective region to be measured, which comprises a periodic irregular pattern with a period, by irradiating the measurement objective region with an illuminating light of an approximately parallel beam, comprising: a first step of irradiating a measurement objective region with an illuminating light in an oblique direction thereto; a second step of forming an image of reflected light from the measurement objective region by one system selected from the group consisting of an object-side telecentric optical system and an image-object-side telecentric optical system, which has an optical axis coinciding with an incident direction of the illuminating light to the measurement objective region, the formed image of reflected light having points with luminance corresponding to the incident angle of the illuminating light at respective points on the measurement objective region; a third step of picking up the formed image to collect luminance data of respective points in the measurement objective region; a fourth step of analyzing spatial frequencies of the luminance data with respect to positions in a desired direction to make a plurality of spatial frequency data; and a fifth step of extracting a desired frequency component from the plurality of spatial frequency data, to synthesize. In this specification, the term “parallel beam” or “parallel light flux” includes not only a perfect parallel beam or light flux but an approximately parallel beam or light flux which is formed by a pseudo-point light source.
The improved surface inspecting apparatus of the invention according to the present invention is one for inspecting a surface condition which comprises a periodic irregular pattern with a predetermined period of a measurement objective region to be measured by irradiating the measurement objective region with an illuminating light of a parallel beam, comprising: a light irradiation part for irradiating an measurement objective region with an illuminating light in an oblique direction of the measurement objective region; a system selected from the group consisting of an object-side telecentric optical system and an image-object-side telecentric optical system, for forming an image of reflected light from the measurement objective region, which has an optical axis coinciding with an incident direction of the illuminating light to the measurement objective region, the formed image of reflected light having points with luminance corresponding to the incident angle of the illuminating light at respective points on the measurement objective region; an image pickup part for picking up the formed image to collect luminance data of respective points in the measurement objective region; a first data changing part for analyzing spatial frequencies of the luminance data with respect to positions in a desired direction to make a plurality of spatial frequency data; and a second data changing part for extracting a desired frequency component from the plurality of spatial frequency data, to synthesize.
According to the present invention, the spatial frequency of periodic luminance data with respect to positions are analyzed in a predetermined direction to determine a plurality of spatial frequency data, and then a desired frequency component is extracted from the spatial frequency data, to synthesize, so that it is possible to detect a desired irregular state.
For example, it is possible to detect just an irregular state of a particular pattern of an integrated circuit formed on a semiconductor wafer with an eliminated irregular state of a base itself, or just the irregular state of the base itself with an eliminated irregular state of the particular pattern of the integrated circuit. It is extremely useful for the latter steps of the semiconductor device production (i.e., steps for producing the integrated circuit). The reason for this is that it is pos
Haga Kazumi
Ishiguro Yoshihiro
Sakai Motoshi
Crowell & Moring LLP
Newcreation Co., Ltd.
Nguyen Sang H.
Pham Hoa Q.
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