Apparatus for repairing defects in emulsion masks by passing laser light through a variable shaped aperture

Defective portions, such as black dot defects, in an emulsion layer of an emulsion mask such as a photomask are repaired or removed by irradiating an ultraviolet laser beam from a laser oscillator, preferably an excimer laser. The laser beam is passed through an adjustable aperture for shaping and is then projected onto defective portions in dimensional alignment, whereby the defective portions are destroyed. In order to ensure that only the defective portions are destroyed, the image of the aperture projected on the emulsion layer is observed so as not to cover the emulsion mask where defective portions do not exist. Defective portions such as white defects can also be repaired by using additional procedure together with the irradiation of the laser beam.

BACKGROUND OF THE INVENTION 
The present invention relates to a method and an apparatus for repairing 
defects in emulsion masks and the like, and, in particular, to an 
apparatus and a method for removing defective portions existing in 
emulsion masks which are a type of photomasks used in the lithographic 
processes that is one of the processes for the manufacture of 
photoelectroformed products and photoetched products used for 
manufacturing semiconductors and the like, and for removing defective 
portions existing in patterns of organic layers (hereinafter also called 
emulsion masks) of color filters for LCD and CCD. 
In recent years, increasingly fine patterns are required in connection with 
higher levels of integration of IC and LSI, and the patterns of 
semiconductor elements have tended to have higher levels of accuracy and 
quality. Apart from semiconductor elements, high accuracy and high quality 
are also required in the case of, for example, photoetched products such 
as shadow masks for color televisions, print circuit boards, electrodes 
for various types of display tubes and the lines of optical measuring 
apparatus, and in the case of photoelectroformed products such as meshes 
for camera tubes, electron microscope meshes, and other meshes for 
filtering. The recent photofabrication technology has enabled the 
achievement of degrees of fineness and accuracy that were not possible 
with the conventional mechanical process method, and a high accuracy of 
pattern is required for the photomasks used in the photofabrication 
technology. 
In such photomasks that require a high pattern accuracy, it is necessary to 
repair small defects that occur in the mask manufacturing process. 
Currently, photomasks are classified by their materials, into two types of 
emulsion masks and hard masks. Emulsion masks have a high-resolution 
photographic emulsion coated to the surface of a glass substrate. 
Ordinary emulsion layer of the emulsion masks can be of either a silver 
emulsion or a non-silver emulsion, and the thickness of the layer is 
usually from 2 to 6 .mu.m. Hard masks have a light intercepting metal film 
such as that of chrome, ferric oxide or tantalum, for example, deposited 
onto the surface of a glass substrate using either the vapor deposition or 
spattering method to form a film with a thickness of approximately 0.1 
.mu.m. 
The defects that can occur in the photomask manufacturing method are black 
defects such as black dots and the like, and white defects such as 
pinholes and loss, etc. The method of correcting black dots and pinholes 
differ according to the type of photomask. 
In the case of hard masks, the specific method that is generally used to 
repair black dot defects such as a black spot or a protruding portion is 
to apply to the area other than the defects a photoresist or mask of a 
material that does not corrode the metal layer and to then remove the 
defects by etching. In the case where fine black dot defects of the order 
of 1 .mu.m have to be removed, then a positive resist such as the OFPR 
resist (product of Tokyo Oka Kabushiki Kaisha) is applied and then the 
light from a mercury lamp is focussed with a size of approximately 1 .mu.m 
onto the resist on the defect to expose the resist. The exposed resist is 
then removed by developing processing and then an etching liquid is used 
to remove the light intercept metal film. 
In the case of emulsion masks, the method of repairing defects is different 
because the emulsion layer is thick and there is no corrosive liquid such 
as used in the case of metals. For example, one of the methods for 
repairing black dot defects is to cut out the defect using the sharp end 
portion of a cutter knife or the like but the application of this method 
is limited to those instances where accuracy is not required or where 
those portions having defects are not connected to or adjacent to those 
portions that do not have defects. This method is not suitable for 
repairing the photomasks used for semiconductor manufacture or for fine 
processing. A repairing method using a YAG laser has been proposed in 
order to eliminate this deficiency. (Japanese Patent Laid Open Publication 
No. 60-207335) 
In the case of a hard mask, white defects such as a pinhole or missing 
portion are removed by a method that involves applying a photoresist to 
the entire surface of the mask, exposing the portion of the photoresist on 
the fault and then developing the photoresist so that only that portion of 
the resist that was on the defect is removed. Thereafter, in this status, 
by using either the vapor deposition or the spattering method, a light 
intercepting film of a metal such as chrome is formed. Then, separating 
the photoresist leaves the light intercepting film only on the defects so 
that white defects such as pinholes and the like are rendered 
light-intercepting. 
Hard masks have dimensions in the order of several inches square but the 
size of emulsion masks is large and is in the order of 20 to 40 inches. 
For this reason, in the case of the emulsion masks, the series of methods 
described above, which use vapor deposition and spattering, require 
large-scale coating apparatus and large-scale vacuum apparatus and the 
like. Since this is difficult as far as the facilities are concerned, it 
is more general to cover the defect by India ink applied manually using a 
brush having a fine hair tip. 
With the pattern repairing method described above for black dot defects, a 
YAG laser with a wavelength of 1060 nm and a second harmonic of 530 nm 
enables fine defect repair, but the portion around that portion for which 
removal processing was performed swells. In addition, the removal of the 
defect portion cannot be made linear and so there is the problem of 
ruggedness. 
When a YAG laser is used for defect removal, the swell of the peripheral 
portion of the defect amounts to 50% of the thickness of the layer and 
this becomes a cause of improper contact in uses where contact exposure is 
performed, thereby causing problems for its practical use. In addition, 
the non-linearity of the removed portion also presents a problem of 
quality now that finer patterns are being required. 
In addition, the previously described method for the repair of white defect 
has its application limited to those which do not require precision and 
for which the defects are not connected to or adjacent to portions that do 
not have defects, and it is not possible to use it for the repair in the 
case of photomasks used for semiconductor manufacturing or fine 
processing. 
SUMMARY OF THE INVENTION 
The object of the present invention is to provide a method for the repair 
of defects in emulsion masks and the like, by removing defective portions 
without providing an adverse influence to a portion that is peripheral to 
the defects, and with favorable finish processing for the defects. 
Another object of the present invention is to provide a novel and effective 
apparatus for repairing defects in emulsion masks and the like. 
According to an aspect of the present invention, there is provided a method 
for repairing a defect of an emulsion mask or the like, comprising the 
steps of: irradiating ultraviolet light to the defect in a shape 
corresponding to the defect; and destroying the defect as a result of the 
irradiation. The ultraviolet light is preferably a laser beam of an 
excimer laser. 
According to another aspect of the present invention, there is provided an 
apparatus for repairing a defect of an emulsion mask or the like, 
comprising an ultraviolet light source for generating ultraviolet light, 
aperture means for passing the ultraviolet light therethrough for shaping 
the same; and means for projecting the ultraviolet light onto the emulsion 
layer to form an image of the aperture on the defect so as to remove the 
defect. 
Preferred embodiments of the present invention will be described further in 
detail hereunder, with reference to the accompanying drawings.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
The following is a detailed description of preferred embodiments according 
to the present invention. 
FIG. 1 is a schematic view illustrating an apparatus that uses a lens to 
focus a laser beam from a laser light source and irradiate it onto an 
emulsion surface of an emulsion mask 7 in order to correct or repair a 
black dot defect portion D of the emulsion mask 7. 
The ultraviolet laser beam 2 from a laser oscillator 1 is magnified by a 
beam expander 3 and only the ultraviolet light of the beam is reflected by 
a selectively reflective mirror 4. A beam image is formed by an aperture 
5x in an aperture forming portion 5 so as to correspond to a shape of a 
defect. The beam is then reduced and projected by an image-forming lens 6 
so that it is irradiated to an area of the emulsion mask 7 corresponding 
to a black dot defect portion D of the emulsion surface. 
In addition, white light from a reference light lamp 8 is colored by a 
colored filter 9 and irradiated through the aperture 5x and the 
image-forming lens 6, projecting the shape of the aperture 5x onto the 
emulsion mask 7 as a colored image. A condenser lens (not shown) may be 
provided before the reference light lamp 8 to make the illumination 
uniform. The shape that is projected onto the emulsion mask 7 can be 
observed through an observation lens 11 by reflecting the shape by a half 
mirror 10. 
FIG. 2 is an enlarged perspective view indicating the relationship between 
an aperture forming portion 5, an image-forming lens 6 and an emulsion 
mask 7. The aperture forming portion 5 comprises four blades 5a, 5b, 5c 
and 5d and each of the blades can be advanced and retracted and can be 
rotated. This is to say that by controlling the position of the blades the 
shape of the beam can be made to correspond to the shape of the defect, as 
indicated in the examples shown in FIG. 3A through FIG. 3E. 
Rotating the blades 5a through 5d as indicated by the arrow a in FIG. 3B, 
rotating some of the blades as indicated by the arrow b in FIG. 3C, or 
rotating each blade individually can be performed to create apertures of 
various shapes. This is to say that trapezoidal shapes, triangular and 
other shapes can be created in addition to rectangular shapes and that 
such shapes can be rotated in an arbitrary direction with respect to the 
optical axis. 
The image-forming lens 6 reduces and projects the beam image that has been 
shaped by the aperture 5x. The defect portion can range from several mm to 
several tens of .mu.m and to about several .mu.m. It is advantageous to 
manufacture the aperture forming portion 5 with an enlarged dimension and 
then use reduction projection. The energy density of the laser beam 
irradiated to the aperture forming portion 5 is weakened to such a degree 
that there is no damage to the aperture forming portion 5 and the 
image-forming lens 6 performs reduction projection to raise the energy 
density to that required for the removal of the defect portion. 
Normally, as indicated in FIG. 4, the ultraviolet light laser beam 2 that 
is output from the laser oscillator 1 has a density distribution which is 
largest at the central portion of the beam 2 and is smaller towards the 
periphery. In this status, it is difficult to perform uniform processing 
since the processing speed due to the laser irradiation differs in the 
central portion from that of the peripheral portion. Because of this, an 
optical system using a beam expander 3 is used to enlarge the beam so that 
only the central portion for which the beam is uniform is selectively 
used. In addition, the beam expander 3 is also used to correspond to the 
enlarged aperture because the beam is irradiated to a relatively large 
area. 
If the sectional area of the ultraviolet light laser beam 2 that is 
obtained from the laser oscillator 1 is relatively large and the intensity 
distribution is not extremely poor, then an adequate result can be 
obtained without the use of the beam expander 3. 
An excimer laser is used as the laser oscillator 1 that oscillates to 
produce ultraviolet light. It is possible to have several types of 
ultraviolet light oscillations depending upon the type of halogen gas used 
in the excimer laser. The typical oscillation wavelengths are 308 nm 
(XeCl), 248 nm (KrF) and 198 nm (ArF), and the oscillation wavelength can 
be changed by exchanging the gas. The laser wavelength that is used for 
defect portion removal can be chosen from these three types but the 
permittivity ratio of the lens of the optical system deteriorates from 
about 200 nm and therefore either 248 nm or 308 nm is suitable. 
The laser energy necessary for defect portion removal is optimum at an 
energy density of 5 to 50 J/cm.sup.2 at the position of irradiation, and 
the pulse energy of the laser oscillator 1 is about 100 to 400 mJ/pulse. 
The actual procedure for removing defect portions is as described below. 
The observation lens 11 is used to observe the emulsion mask 7 and the 
position of the emulsion mask 7 is determined so that the defect portion D 
on the emulsion mask 7 is positioned at the center of the field of view. 
Then, the shape of the aperture 5x of the aperture forming portion 5 is 
projected onto the emulsion mask 7 by the colored light from the reference 
light lamp 8 and is made into dimensional alignment with the shape of the 
defect portion. This adjustment is made by advancing or retracting the 
blades 5a through 5d and adjusting their angles. In this status, the 
ultraviolet light laser beam 2 is output from the laser oscillator 1, 
magnified by the beam expander 3, and irradiated to the aperture forming 
portion 5. The beam corresponding to the shape of the aperture 5x produced 
by the blades 5a through 5d is reduced by the image-forming lens 6 and 
irradiated to the defect portion on the emulsion mask 7 to destroy and 
therefore remove the defect. 
The method described above can be used to remove a black dot defect portion 
D as indicated in FIG. 7, from an emulsion mask 7 requiring the repair of 
the black dot defect portion D that is connected to an image portion 12 as 
indicated in FIG. 6. In FIGS. 6 and 7, 14 represents a transparent 
emulsion layer and 15 represents a glass substrate. By the use of an 
ultraviolet light laser, it is also possible to remove protruding defects 
(where the film surface is high) that are transparent in visible light. 
FIG. 5 shows a view of another embodiment according to the present 
invention. A beam 2 from a laser oscillator is magnified by a beam 
expander 3, and a selectively reflective mirror 4 changes the direction of 
this beam to that of the emulsion mask 7. A focussing lens 16 focuses the 
central portion of the laser beam for which the energy intensity is 
relatively uniform. The aperture forming portion 5' is positioned to the 
position of the black dot defect portion D on the emulsion mask 7 and 
brought into contact with the surface of the mask, and the beam 2 is 
irradiated through the aperture forming portion 5'. When compared to the 
method in FIG. 1 where an aperture image is formed, this embodiment has 
the aperture forming portion 5' in direct contact with the emulsion mask 7 
so that it is not necessary to have lens focussing. This embodiment 
therefore has the advantage of being easier to use. In this embodiment, 
light from a reference light source 8' is irradiated to the aperture 
forming portion 5' from the rear side of the emulsion mask 7 and through a 
half mirror 10', and in the same manner, an observation lens 11' on the 
rear side of the emulsion mask 7 is used for monitoring while the position 
of the black dot defect portion D is determined. 
As has been described above, the application of the present invention is 
not limited to the silver emulsion of an emulsion mask that uses a silver 
emulsion photographic plate, and the present invention can also be used 
for the repair of emulsion masks using non-silver emulsion photographic 
plates such as glass substrates which have their surfaces applied with a 
diazo photo-sensitive liquid (a photo-sensitive liquid which is a mixture 
of diazo compound and a coloid substance such as gelatine and the like) 
and which has an image printed onto it and then colored to form an image 
portion made of an organic high polymer layer. The present invention is 
also applicable to the repair of organic layer patterns of color filters 
for use in LCD or CCD. 
As has been described above in detail, the method described can be used to 
precisely remove semi-transparent defect portions, transparent and 
protruding defect portions, or black dot defects of emulsion masks. The 
method has the advantage of being able to remove defect portions without 
damaging non-defect portions even if those defect portions are continuous 
with or adjacent to those non-defect portions. 
Moreover, other than the previously described oscillation wavelengths for 
the excimer laser, 351 nm (XeF), 222 nm (KrCl) or 157 nm (F.sub.2) may 
also be used as the laser source. In addition, it is possible to use 
wavelengths in the vicinity of 200 nm or less by using a reflective 
optical system instead of the glass lens. 
In the above embodiment, an excimer laser is used as the ultraviolet light 
laser source but it is also possible to use the fourth harmonic (266 nm) 
and the third harmonic (355 nm) of a YAG laser, and the use of any laser 
source in the vicinity of ultraviolet light is possible. 
A method for correcting white defects in an emulsion mask will be described 
below. 
FIG. 8 is a flow chart indicating the procedure of a method for repairing a 
white defect portion. FIG. 9A through FIG. 9D are schematic perspective 
views of an emulsion mask corresponding to the steps of FIG. 8. FIG. 10 is 
a schematic perspective view of an emulsion mask prior to repair. 
An emulsion layer 14 on a glass substrate 15 of the emulsion mask 7 has an 
image c printed onto it by an exposure. In FIG. 10, D' is a pinhole or a 
hole forming a white defect in this image c. The size of the white defect 
D' ranges from the order of 1 mm to several tens of .mu.m or several 
.mu.m. 
The following is a description of the procedure for the repair of this 
emulsion mask 7 having such a defect portion D'. 
In step 1, a weakly adhesive resin 17 is coated to the emulsion mask 7. 
Centering around the defect portion D' of the image c printed onto the 
emulsion layer 14, this resin is applied, as shown in FIG. 9A, as a layer 
17 that can be removed from around the defect portion D'. 
This weakly adhesive resin 17 can be a vinyl resin such as PVC, vinyl 
acetate or vinyl butyral or the like, a copolymer of vinyl acetate and 
vinyl hydrochloride, or a thermoplastic high-polymer material such as 
polyester, polyurethane or polyepoxy or the like which is dissolved in an 
organic solvent. The thus prepared liquid is coated by using a sponge 
brush or the like with the width of application of about 1 to 2 mm. 
In step 2, an ultraviolet light laser beam is irradiated to the weakly 
adhesive resin 17 coated to the emulsion mask 7 and in alignment with the 
defect portion D' for which repair is required. Thus, portions of the 
weakly adhesive resin 17 and the emulsion layer 14 are removed or recessed 
as indicated at 18 in FIG. 9B. This removed portion 18 is, for example, in 
the shape of a parallelepiped which includes the defect portion D'. There 
is no actual problem even if this removal process does not remove the 
emulsion layer 14. 
The apparatus for irradiating the ultraviolet light laser beam used for 
this removal is shown in FIG. 11, and is the same as the apparatus 
indicated in FIG. 1. 
The wavelength used is 248 nm in the case KrF is used as the gas source. 
The laser power is about 100 to 400 mJ per pulse. 
In step 3, a light intercepting pigment 19 is applied to the weakly 
adhesive resin 17 as shown in FIG. 9C so as to fill the removed portion 18 
from which the weakly adhesive resin 17 and the emulsion layer 14 have 
been removed. A black-colored pigment such as carbon black or the like, 
dissolved in water is used as the pigment 19. 
The pigment may contain an adhesive component, which facilitates adhesion 
of the pigment to the glass substrate 15 exposed by the removed portion 
18. An India ink that has been conventionally used may also be used as the 
light intercepting material. Furthermore, a black pigment material other 
than carbon black can also be used if it can block the component of the 
light wavelength that has to be blocked. The area of the application of 
the pigment is not limited to that area centering around the removed 
portion 18, and can be roughly applied without requiring skilled manual 
application using a fine brush or a precision positioning mechanism. 
In step 4, the removable weakly adhesive resin 17 that has been also 
applied around the defect portion D' is separated. Adhesive tape such as 
"Scotch tape" or the like is used for this separation. Separation of this 
adhesive tape causes the weakly adhesive resin 17 adhering to the adhesive 
tape to be pulled away from the emulsion layer 14. As mentioned before, 
the weakly adhesive synthetic resin 17 is used so that there is no damage 
caused to the surface of the emulsion layer 14 when the separation is 
made. 
The light intercepting pigment 19 applied to the surface of the weakly 
adhesive resin 17 is separated together with the resin 17, whereby the 
pigment 19 applied to the removed portion 18 remains as it is as indicated 
in FIG. 9D, and the removed portion 18 is filled with the pigment 19 so 
that the repair of the white defect portion D' is performed. 
The application of the weakly adhesive resin 17 in step 1, and the 
application of the light intercepting pigment 19 in step 3 can be 
performed using a microdispenser (an apparatus that discharges constant 
amounts of a liquid) 21 as indicated in FIG. 12. The microdispenser 21 has 
an application agent inside a tank 24 and this application agent is sent 
through a pipe 23 via a solenoid valve 22 controlled by a timer 20 and is 
discharged through a nozzle 25 by compressed air. 
In step 1, instead of applying and drying the liquid protective layer, it 
is possible to apply a film of PET or the like having a thickness of 
several .mu.m and having a weak adhesive applied to one surface thereof. 
The film can then be applied to the entire surface of the defect portion 
or the defect portion D' of the image c that is printed onto the emulsion 
layer 14. 
Furthermore, the weakly adhesive resin 17 that is coated to and formed on 
the surface of the emulsion layer 14 may be a liquid-expelling agent. The 
light intercepting agent that is applied to the removed portion 18 may be 
a hydrophilic substance such as water-soluble ink or pigment so that its 
adhesion to portions other than the removed portion 18 is prevented when 
applied, and so that the repair of the defect portion D' after the 
separation of the resin 17 can be performed stably. 
According to the method described above, it is possible to accurately 
repair a white defect such as a pinhole or missing portion in an emulsion 
mask or the like, and furthermore, this repair of defect portions is 
possible without damaging non-defect portions even if the defect portion 
is connected to or is adjacent to non-defect portions. In addition to 
pinholes and missing portions, it is also possible to regenerate patterns 
that have fallen off completely. 
FIG. 13 is a view indicating another embodiment of an apparatus that uses a 
laser beam to perform the repair of defects. In this Figure, those 
portions that are the same as corresponding portions in FIG. 1 are 
indicated using the same numerals, and the corresponding description of 
them is omitted. 
In this apparatus, an observation lens 30 and an image-forming lens 6 are 
located at opposite sides with respect to the emulsion mask 7, and a 
television camera 31 is used for observation via the observation lens 30. 
In addition, in the vicinity of the irradiation portion D of the emulsion 
mask 7 to which the laser light is irradiated through the image-forming 
lens 6, an air ejection nozzle 32 is provided at one side. As shown in 
FIG. 14, an air suction nozzle 33 may be disposed at a position opposite 
the air ejection nozzle 32 with respect to the irradiation portion D of 
the laser light. Furthermore, as indicated in FIG. 15, air may be ejected 
from the air nozzle 32 to the irradiation portion D on the emulsion mask 7 
and this air can be sucked out through an air suction nozzle 33. 
It is extremely difficult as far as the design of the optical system of the 
lens is concerned, to use a lens that resolves light ranging from visible 
light up to the ultraviolet light of the laser and without aberration. 
Lenses that can do this are very expensive and because of this, the lens 
that is used is one that has a favorable resolution for the laser 
ultraviolet light. 
Since a lens that is suitable for use in the ultraviolet light region is 
used as the image-forming lens 6, the colored filter 9 is a blue filter to 
produce reference light of a wavelength in the vicinity of the ultraviolet 
light of the reference light lamp 8. 
The observation lens 30 is disposed coaxially with the image-forming lens 6 
so that it is possible to observe the portion D of the emulsion layer 14 
which is irradiated by the laser, from the rear surface of the glass 
substrate 15, and has an independent illumination system 37, 38. 
The observation lens 30 is a lens that has a favorable resolution in the 
visible light region. An image of an aperture 5x formed by illumination by 
the reference light lamp 8 and the status of the laser irradiation portion 
D are observed through the illumination system 37, 38 and the reference 
light lamp 8 adjusted to observe the image through a television camera 31. 
The air ejection nozzle 32 is disposed so that the air is blown in the 
vicinity of the optical axis of the image-forming lens 6 on the emulsion 
mask 7 and normally, when the laser light is being irradiated, is blown so 
as to remove particles of the emulsion layer 14 that are removed and 
separated by the laser irradiation. 
The range of irradiation of the laser beam is small at from several tens of 
.mu.m to several .mu.m so that only a small air flow is required. 
Sufficient use can be achieved without a high pressure. 
The aperture forming portion 5 will be described below in more detail. When 
a rectangular pattern using only linear components is to be formed on an 
emulsion mask 7, this can be achieved using only the aperture blades 5a 
through 5d, but in cases where the pattern includes a curved component 
such as the defect portion D indicated in FIG. 16, where there is a 
protrusion from a circular pattern, it would be difficult to remove all of 
the defect portion D with one laser irradiation if an aperture comprising 
only linear blade portions was used. 
In such a case, the removal of a defect portion D having a portion with a 
curved shape is achieved by using aperture forming blades 5a' and 5b' that 
have a semicircular cutout 35 and a semicircular protrusion 36 of 
different radii of curvature as indicated in FIG. 17A, at the linear edges 
of linear blades 5a through 5d as shown in FIG. 2. By sliding and 
overlapping them as indicated in FIG. 17B, a crescent-shaped aperture is 
formed. 
In addition, blades 5a' and 5b' having semicircular cutouts and protrusions 
of different sizes and radii of curvature may be used in combination with 
linear blades 5a through 5d so that they can be exchanged and rotated for 
use with respect to defect portions in an arbitrary direction. 
FIG. 18 indicates a combination of blades 5a' and 5b' having semicircular 
cutout 35 and protrusion 36 of different radii of curvature in a direction 
perpendicular to blades 5a and 5b, while FIG. 19 indicates a combination 
of a blade 5b' having a semicircular protrusion 36 and a linear blade 5d 
that are in the perpendicular direction with respect to linear blades 5a 
and 5b. The aperture is therefore formed by two lines and two curves or by 
three lines and one curve. 
FIG. 20 indicates a single blade 5e having a linear protrusion portion 36d 
and semicircular protruding portions 36a, 36b and 36c of different radii 
of curvature, while FIG. 21 indicates a blade 5f that has a linear cutout 
portion 35d and semicircular cutout portions 35a, 35b and 35c of different 
radii of curvature. These blades are arranged as shown in FIG. 22, so that 
they can rotate independently with respect to spaced rotational axes 40 
and 41. By providing linear blades 5c and 5d extending in a direction 
perpendicular to the line joining the two axes 40 and 41 and by sliding 
and rotating the blades 5e, 5f, 5c and 5d, a variety of shapes of the 
aperture can be formed so as to correspond to various types of shapes of 
defect portions. 
The various types of blades described above can be formed by performing 
electrical discharge processing, etching processing, or mechanical 
processing or the like on a metal plate, but they can be formed by the 
vapor deposition or spattering of a metal film onto quartz glass, or by 
the adhesion of a metal foil. 
In the apparatus indicated in FIG. 13, the defect portion that is dispersed 
by the laser beam can be either blown away by the air from the air 
ejection nozzle 32, sucked in by the air suction nozzle 33 as indicated in 
FIG. 14, or either blown away by the air from the air ejection nozzle 32 
and sucked in by the air suction nozzle 33 as indicated in FIG. 15. 
FIG. 23 indicates yet another embodiment of the apparatus according to the 
present invention. 
In the apparatus of FIG. 13, the aperture image projects the light from the 
reference light lamp 8 onto the emulsion mask 7 by the image-forming lens 
6 and the apparatus is configured so that it is possible to observe this 
via the observation lens 30. However, in the apparatus indicated in FIG. 
23, there is provided a television camera 31, which operates to display on 
a monitor screen 42 the emulsion layer observed through an observation 
lens 30. On the other hand, the aperture image corresponding to the degree 
of opening of the aperture blades 5a through 5d is monitored on the 
monitor screen 42, and overlaps the image from the observation lens 30. 
More specifically, there are provided position detectors 43a through 43d 
that detect the position of the respective blades 5a through 5d, and a 
hairline image generator 44 that generates hairline images corresponding 
to the blade position detection signals from the position detectors 43a 
through 43d. A superimposer 45 operates to superimpose the image signals 
for the hairline images and the image signals from the television camera 
31. 
When the blades 5a through 5d are adjusted, the position detectors 43a 
through 43d read the positions of the respective blades, and these 
positions corresponding to the edges of the blades are generated as a 
hairline image by the hairline generator 44, and the shape of the aperture 
is displayed as a hairline image 42a on the monitor screen 42. 
In the embodiments indicated in FIG. 13 and FIG. 23, the surface of the 
emulsion layer 14 of the emulsion mask is faced upwards. However, the 
surface may face downward and the laser light may be irradiated from 
below, with observation performed from above so that the emulsion layer 14 
that is dispersed when the laser light is irradiated may fall by gravity 
and may not re-adhere to the layer. 
In the apparatus that has been described above, the image-forming lens 6 
that reduces and projects the aperture image is used also as a lens for 
observation and is used for a resolution for both visible light and 
ultraviolet light. As a matter of fact, it is not easy to manufacture a 
lens that is applicable to both visible light and ultraviolet light and 
that has no aberration, and the manufacture of a lens usable for the two 
purposes requires a large amount of money and time. In addition, in the 
previously described embodiments, the lens for observation is provided 
separately from the lens for reducing and projecting the aperture image, 
so that the aperture is illuminated with a blue reference light and the 
lens for observation is used to observe the image that is reduced and 
projected by the object lens for ultraviolet light. However, the lens for 
the ultraviolet light region cannot obtain a sufficient degree of 
resolution because of distortion of the projected image. 
These problems can be eliminated by the method indicated in FIG. 24. 
According to this method, in the apparatus indicated in FIG. 13 for 
example, the pulse energy of the laser light 2 from the laser oscillator 1 
has an output reduced to a low energy level such as from 10 to 50 mJ/pulse 
and this is passed through an aperture forming portion 5 and irradiated to 
the emulsion mask 7. The emulsion layer 14 of the emulsion mask 7 is not 
subjected to a change and the removal of the layer 14 is not effected 
because of a sufficiently low energy of the irradiation by the ultraviolet 
light laser beam 2. 
The ultraviolet light laser beam 2 irradiated to the aperture forming 
portion 5 is shaped in accordance with the aperture 5x of the aperture 
forming portion 5 and is reduced and projected onto the surface of the 
emulsion mask by the object lens. (FIG. 24; step 1) 
The ultraviolet light laser beam 2 irradiated to the emulsion mask 7 
excites the surface of the emulsion mask 7 but does not remove the 
emulsion layer 14, and fluorescence is induced so that the aperture image 
can be viewed by the television camera 31 as visible light. 
A pulse of the ultraviolet light laser beam 2 from the laser oscillator 1 
produces an instantaneous image that can be viewed by the human eye 
instantaneously, so that an image of the defect portion cannot be 
observed. For this reason, repeated oscillation of the ultraviolet light 
laser beam 2 is carried out to generate a continuous fluorescence so that 
it is possible for the aperture image to be observed as visible light 
(step 2). 
In the status where the aperture image is observed, the emulsion mask 7 is 
moved to position it at the center of the aperture image (step 3). 
While the aperture image is being observed in alignment with the shape of 
the defect portion in the center of the aperture image, the aperture 
blades are moved to perform adjustment (step 4). 
By the above work processes, while the aperture image is being observed, it 
is possible to align the aperture 5x of the aperture forming portion 5 to 
the shape of the defect, and then the normal irradiation of excimer laser 
beam light through the aperture 5x and irradiation to the defect portion 
can accurately remove only the defect portion. 
The method is not limited to the continuous oscillation of low energy laser 
light as has been described above, but another method can be used in which 
a low energy laser oscillation from a laser oscillator 1 is effected from 
one to several times, and an aperture image of the fluorescent light 
produced by the excitation due to the ultraviolet light laser beam 2 is 
stored in an image memory, and in which the image stored in the image 
memory is called and observed as the aperture image, and the above process 
is repeated for every time the aperture forming portion 5 is adjusted. 
FIG. 25 indicates an example of an aperture forming portion 5 where an 
aperture blade 51 and an aperture blade 52 are disposed on an aperture 
table 50, and where position adjustment mechanisms 53 and 54 are coupled 
to the aperture blade 51, and position adjustment mechanisms 55 and 56 are 
coupled to the aperture blade 52 so that it is possible to move the two 
blades 51 and 52 in mutually perpendicular directions. 
In addition, at the side of the aperture table 50 is provided a rotating 
mechanism 57 that can rotate the aperture blade 51 and 52 in their 
entirety. 
The position adjustment mechanisms 53 through 56 can be moved and adjusted 
by a servo mechanism, for example. In addition, the rotating mechanism 57 
can have a servo motor 57a that rotates the aperture image by rotating the 
entire table 50 by the engagement of a rack formed along the periphery of 
the table 50 and a pinion gear 59. 
FIG. 26 indicates the shape of the aperture blade 51 and FIG. 27 indicates 
the shape of the aperture blade 52. 
The aperture blade 51 is provided with a plural number of rectangular 
transparent portions 60 of different dimensions and a plural number of 
circular transparent portions 61 of different diameters. The aperture 
blade 52 is provided with one rectangular transparent portion 62, a plural 
number of rectangular light intercepting portions 63 of different 
dimensions and a plural number of light intercepting circular portions 64 
of different diameters. 
These two blades 51 and 52 can be moved by the position adjustment means 53 
through 57 described above so that an aperture corresponding to the shape 
of the defect can be formed and the laser beam light shaped. 
For example, in the case of a defect with a linear pattern, it is necessary 
to form an aperture with a variable size for the rectangle. Therefore, 
each of the blades 51 and 52 is moved such that the transparent portion 60 
of the aperture blade 51 and the transparent portion 62 of the aperture 
blade 52 are positioned along the optical axis of the laser beam, and the 
two rectangularly-shaped transparent portions 60 and 62 overlap along the 
optical axis of the laser beam and form the aperture. 
In order to match the size of the defect, the adjustment of the aperture of 
the aperture blade 51 is performed as indicated in FIG. 28 by moving the 
overlapping rectangularly-shaped transparent portions 60 and 62 relative 
to each other. The overlap of the two aperture blades 51 and 52 is limited 
to be smaller than one of the rectangularly-shaped transparent portions 60 
and 62. The irradiation of laser beam light to this causes the beam 
passing through the aperture 65 to be shaped in accordance with the shape 
of the aperture 65. In the case of a defect with a curved pattern, a 
circle with a suitable radius of curvature is selected from the 
circular-shaped transparent portions 61 in the aperture blade 51 and the 
position adjustment mechanisms 53 and 54 are adjusted so that the selected 
circle is positioned at the center of the beam axis. Then, a light 
intercepting circle having a diameter larger than the diameter of the 
transparent circle selected from the aperture blade 51 is selected, and 
this is positioned by the position adjustment mechanisms 55 and 56 so that 
it is finally positioned in such a way that it is not concentric with the 
circular-shaped transparent portion 61 along the laser beam axis, as shown 
in FIG. 29. This is to say that the circular window 61 is covered by the 
lid 64 formed by the circle with the slightly larger diameter to form an 
aperture 66 that has a crescent shape, and the laser beam light is then 
shaped to the shape of the defect having a circular pattern. 
In addition, combinations of a rectangularly-shaped transparent portion 60 
and a circular-shaped light intercepting portion 64 can be used to form 
apertures that are not crescent shaped. In this case, an aperture 67 that 
has an arc along one side as shown in FIG. 30 can be made to correspond 
with a defect. Furthermore, a combination of a circular-shaped transparent 
portions 61 and a rectangularly-shaped light intercepting portion 63 can 
be used to form a semicircular-shaped aperture as shown in FIG. 31 so as 
to correspond to a defect. 
Other than using the position adjustment means 53 through 56 for the 
aperture blades 51 and 52 to determine the position of the aperture 
forming portion 5, it is also possible to rotate the aperture forming 
portion 5 and therefore perform adjustment by the rotating mechanism 57 
(FIG. 25) that forms an image rotation mechanism. 
FIG. 32 indicates an example of an image rotation mechanism that rotates an 
aperture image by the use of an image rotator prism. Here, the aperture 
blades 51 and 52 do not rotate and are fixed and the rotation of the image 
prism 70 causes the projected aperture image to be rotated. In addition, 
as indicated in FIG. 33, it is also possible to use a tab-type of prism 71 
that has the same function as the image rotator prism. 
The aperture blade 51 and 52 can be formed by vacuum vapor deposition onto 
a glass substrate, of a plurality of layers of a dielectric material that 
reflects laser beam light. This is, the aperture blade 51 is formed by 
temporarily placing and fixing rectangularly-shaped and circular-shaped 
metal plates on a glass substrate and then performing the vapor deposition 
of a dielectric material thereon. The metal plates are thereafter removed 
from the glass substrate. Thus, an aperture blade 51 with rectangular and 
circular transparent portions 60 and 61 is produced. The aperture blade 52 
can be formed by temporarily placing and fixing rectangularly-shaped metal 
plates and metal plates having circular and rectangular windows on a glass 
substrate and by performing the vapor deposition of a dielectric material 
thereon. In this case, the vapor deposition is performed in areas 
corresponding to the windows so that reflective light intercepting 
portions 63 and 64 are produced, while vapor deposition is also performed 
in portions other than those that have the rectangular metal plate affixed 
thereto, and therefore the glass substrate under those portions that are 
covered by the metal plates remains transparent and forms a 
rectangularly-shaped transparent portion 62. 
Instead of a glass plate with shapes formed by vapor deposition, the 
aperture blade 51 may be a metal plate that has rectangularly-shaped and 
circular-shaped holes therethrough. Instead of a glass plate with shapes 
formed by vapor deposition, the aperture blade 52 may be glass plate that 
has a metal foil sheet or sheets affixed thereto to form transparent and 
light intercepting portions.