Optics: measuring and testing – Inspection of flaws or impurities – Surface condition
Reexamination Certificate
1999-11-23
2001-11-06
Font, Frank G. (Department: 2877)
Optics: measuring and testing
Inspection of flaws or impurities
Surface condition
C356S237600, C356S394000, C250S225000
Reexamination Certificate
active
06313913
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a method and apparatus to inspect a surface for defects, flaws and foreign matter and a method and apparatus which can also automatically detect flaws and foreign matter, such as fine particulate matter, on the surface being inspected. The present invention also relates to a method for manufacturing liquid crystal displays.
BACKGROUND OF THE INVENTION
In photolithography, a circuit pattern is formed by a reticle or photomask (hereinafter referred to simply as a “mask”) on a substrate or wafer. The mask is typically a sheet of glass or similar material on which are formed patterns made from chromium or chrom-oxide. Stretched across the top of the mask is a pellicle which protects the mask from foreign matter such as dust and the like. The pattern of the mask is transferred onto the substrate during the photolithography process. However, if foreign matter such as large particles adhere to the pellicle, the image of the foreign matter will affect the pattern formed on the semiconductor wafer, resulting in a defective circuit pattern. Any defects in the circuit patterns in turn results in a reduction in manufacturing yield. Consequently, to assure defect free transfer of the pattern to the wafer prior to exposure of the pattern on the mask onto the wafer surface, the pellicle must be inspected to verify that foreign matter is not present.
FIG. 7
is a schematic perspective view from an oblique angle of the structure of a conventional foreign matter inspection apparatus as disclosed in U.S. Pat. No. 5,473,426. The apparatus shown in
FIG. 7
emits from semiconductor laser
11
a radial beam of laser light of approximately 780 nm wavelength. The beam of laser light is transformed into a parallel beam by collimator lens
12
. The beam is then expanded in the X direction in
FIG. 7
by anamorphic prism
13
to produce a laser light beam with an elliptical cross section perpendicular to the X direction. Stop
14
, which has a parallelogram-shaped aperture, then partially blocks the beam in the longitudinal or X direction. Mirror
15
then reflects the beam onto the surface to be inspected, pellicle
21
, at an angle of incidence &thgr; close to 90° as measured with respect to the surface normal of pellicle
21
.
The beam of light reflected onto pellicle
21
by mirror
15
forms a band-shaped illumination region
30
extending in the X direction across the pellicle
21
. Band-shaped irradiation region
30
constitutes the region on pellicle
21
to be inspected. Foreign matter present in this band-shaped illumination region
30
scatters the light incident the region. The scattered light from the foreign matter passes through light receiving lens
31
, and forms an image on linear image sensor
20
. The intensity of the scattered light detected by linear image sensor
20
helps determine the size of the foreign matter. The system inspects the entire surface of the pellicle
21
spread across mask
22
for foreign matter by moving the mask
22
and pellicle
21
in a direction perpendicular to the direction of the band-shaped illumination region
30
, the Y direction in
FIG. 7
, so that the band-shaped illumination region
30
moves across the entire surface of pellicle
21
. Thus, the conventional inspection system depicted in
FIG. 7
has one optical system which combines an incident light system with a receiving light system.
The trend in the semiconductor industry has been to use larger masks with much finer circuit detail. As a consequence, the reduction ratio of the projection lens in photolithography equipment is often increased from 4× to 8×. Thus, larger masks are needed to exposure the same area. This has increased the size of the area to be inspected while at the same time requiring inspection systems which are more sensitive. In the liquid crystal display industry, larger and preciser displays are required. To meet these needs conventional inspection systems, which must view a larger inspection region with the same or larger numerical aperture, have had to have the diameter of the light receiving lens and the size of other parts of the inspection system increased. The larger inspection systems (in particular the light receiving portion of the systems) also require a larger amount of space. The use of larger parts has increased the costs of these systems and has resulted in lower yields. The size of the incident light systems have also increased attendant with the increase in the size of the inspection region.
Additionally, use of one light receiving system in conventional inspection apparatus of increasingly larger size has also resulted in a significant difference in the sensitivity of detecting foreign matter between the center and the edges of the larger inspection regions. Thus, the system becomes much less sensitive to foreign matter towards the periphery of the inspection region viewed. This is in part due to the fact that the angle of the optical axis of the light receiving system with the region to be inspected varies greatly between the center and edges of the region being inspected.
SUMMARY OF THE INVENTION
The present invention addresses the problems in the prior art with the purpose of reducing the space required by the entire apparatus, i.e., making it compact, and providing a surface inspection method and apparatus with superior accuracy. The present invention also has the purpose of providing an accurate and effective method of manufacturing a liquid crystal display using the surface inspection method and apparatus.
A first aspect of the invention is a surface inspection system comprising a first light irradiation system that irradiates a surface to be inspected with a first beam of electromagnetic radiation (hereinafter, “light”) beam which forms a first band-shaped irradiation region along a predetermined first direction (X axis direction) on the surface to be inspected; a first light receiving system that receives scattered light from first band-shaped irradiation region; a second light irradiation system that irradiates the surface to be inspected with a second light beam which forms second band-shaped irradiation region along the first direction (X axis direction) on the surface to be inspected; a second light receiving system that receives scattered light from second band-shaped irradiation region; and a scanning mechanism that moves the first and second light irradiation systems and surface to be inspected with relative motion along a second direction (Y axis direction) substantially orthogonal to the first direction (X axis direction), in which the first band-shaped irradiation region and second band-shaped irradiation region are configured so that they are formed on surface to be inspected separated by just predetermined distance d along the second direction (Y axis direction). This assures the entire surface to be inspected is scanned during the inspection process.
In a second aspect of the present invention the first band-shaped irradiation region and the second band-shaped irradiation region are formed on the surface to be inspected separated from each other by a predetermined distance along the second direction (Y axis direction) to assure the irradiation regions do not overlap and create interference between the sets of inspection apparatuses.
A third aspect of the invention is a method for inspecting a surface which includes the steps of: forming a first illumination region on a surface to be inspected; detecting light scattered from said first illumination region; forming a second illumination region on a surface to be inspected; detecting light scattered from said second illumination region; and moving the surface to be inspected in a direction which allows said first and second illumination regions to move across an entire portion of the surface to be inspected.
A fourth aspect of the present invention is a liquid crystal display manufacturing method, including: inspecting a reticle for defects and foreign matter adhering to said reticle; forming with the reticle, after the
Komatsu Koichiro
Nakagawa Yumi
Font Frank G.
Nguyen Sang H.
Nikon Corporation
Oliff & Berrige PLC
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