JP2010210919A - Method and device for forming cvd thin film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To sufficiently uniform the transmittance of a defect correction part when it is applied to correction of a white defect part in a halftone area on a photomask. <P>SOLUTION: Laser beams emitted from a laser oscillator are made to pass through a still opening disposed in front of the optical axis, and are condensed with an objective lens. Thus, the beams are radiated to a surface of a sample placed in a reactive gas atmosphere, and the optical axis of the laser beams made to enter the opening is made to rock with respect to the opening. Thus, when irradiation light intensity on the sample surface is uniformed by time average action, the diameter of the laser beams made to enter the opening is set to be sufficiently smaller than the width of the opening, and the optical axis of the laser beams made to rock at an amplitude larger than the width of the opening. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method and apparatus for forming a CVD thin film suitable for an application that requires a high degree of film thickness uniformity, such as correction of white defects in a halftone region of a photomask. The present invention relates to a method and apparatus for forming a CVD thin film that uses a time averaging action by motion to improve unevenness of intensity of laser light in an irradiation spot.

  As a method and apparatus for forming a CVD thin film suitable for applications that require a high degree of uniform film thickness, such as the correction of white defects in the halftone area of a photomask, the time-averaging action by optical axis fluctuation is used. In order to improve the intensity unevenness of the laser beam in the irradiation spot, it has been conventionally known.

  An example of such a CVD thin film forming apparatus is shown in FIG. This CVD thin film forming apparatus covers a photomask 9 placed on an XY table 20 with a CVD gas supply / exhaust unit 6 having a known structure, thereby providing a white defect portion in a halftone region to be corrected. Is exposed to the CVD source gas atmosphere, and in that state, laser light is spot-irradiated on the white defect through the upper surface window of the CVD supply / exhaust unit 6, and the XY stage 20 is driven to make the photomask horizontal. By scanning the irradiation spot while reciprocating in a predetermined direction, a CVD thin film having an appropriate film thickness is deposited by the reaction of the CVD source gas to correct white defects in the halftone region. is there.

  In FIG. 6, a laser oscillator 1 generates and emits laser light having a wavelength suitable for a CVD source gas. The beam expander 2 enlarges the cross section of the laser light emitted from the laser oscillator 1 at a predetermined magnification. The optical attenuator 7 adjusts the intensity of the laser light that has passed through the beam expander 2 by changing the laser light transmittance. The beam scanning unit 3 irradiates the laser light whose intensity is adjusted by the optical attenuator 7 toward the rectangular opening 4 and swings the irradiation optical axis on the rectangular opening 4. At this time, the diameter of the laser light applied to the rectangular opening 4 is sufficiently larger than the opening width of the rectangular opening 4 due to the expanding action of the beam expander 2.

  The processing observation optical system 5A includes an objective lens 51 and a mirror 52. After passing through the rectangular opening 4, the processing observation optical system 5A reflects the laser light arriving through the optical system 5B downward by the mirror 52, which is then used as an objective. The light is condensed by the lens 51, and spot-irradiated onto the photomask 9 through the upper surface window of the CVD gas supply / exhaust unit 6. At this time, since the rectangular opening 4 and the photomask 9 are in an optically conjugate positional relationship, a minute rectangular irradiation spot by the laser beam appears on the surface of the photomask 9.

  The laser light reflected by the surface of the photomask 9 returns through the objective lens 51 and returns to the optical axis, and further passes through the mirror 52 and is guided to the observation optical system 12. Therefore, the irradiation spot on the photomask 9 can be observed through an observation optical system (for example, including a light receiving optical system and an image sensor).

  A part of the laser light that has passed through the rectangular opening 4 is reflected by the mirror 53 and then guided to the laser light intensity detector 10. Therefore, the intensity of the laser light passing through the rectangular opening 4 can be detected via the light intensity detector 10.

JP-A-8-8197

  According to the above-described conventional apparatus, the cross-sectional diameter of the laser light is enlarged sufficiently larger than the opening width of the rectangular opening 4 by the beam expander 2, and the difference in laser light intensity in the rectangular opening 4 is reduced (FIG. 7). (See (a)) Since the laser beam is further swung over the rectangular opening 4 (see FIG. 7B), the light intensity of each part in the rectangular opening 4 is theoretically uniform due to the time averaging action. It is a trap.

  However, in the first place, the intensity profile of the laser beam (particularly, the ripple component due to interference, etc.) itself is not necessarily symmetrical with respect to the optical axis, and the amplitude of the beam swing also depends on vignetting and aberration of the processing observation optical system 5A. Due to the deterioration of the intensity distribution, the light intensity is limited to a relatively small amplitude, and thus the temporal uniformity of the light intensity in the entire area of the rectangular opening 4 is not always sufficient (see FIG. 7C).

  On the other hand, even if the intensity of the laser beam in the entire area of the rectangular opening 4 can be made uniform over time, it occurs in an optical element (mirror, lens, window plate, etc.) existing between the rectangular opening 4 and the irradiation surface. The fluctuation of the laser beam has no effect on the non-uniformity of the intensity distribution caused by the optical system, such as the intensity unevenness or the diffraction phenomenon occurring in the rectangular aperture image (see FIG. 7D). Therefore, the time average value of the irradiation laser beam intensity on the irradiation surface is made uniform by using scanning of the irradiation spot (rectangular aperture image) using the XY stage 20 together (see FIG. 7E). ).

  However, in such combined use of irradiation spot scanning, although effective in making the time average value of the irradiation laser light intensity at the central portion of the irradiation portion uniform in the scanning direction (A in FIG. 7 (e)). A sufficient effect was not obtained for uneven distribution of irradiation intensity in the scanning direction and the vertical direction.

  For this reason, in the above-described conventional apparatus, when applied to the correction of the white defect portion of the halftone area on the photomask, the transmittance of the defect correction portion cannot be made sufficiently uniform. In addition, the laser beam intensity non-uniformity around the defect repairing part (refer to part B in FIG. 7 (e)) caused by scanning the irradiation spot overlaps with the normal partial transmission film. The defect could not be corrected.

  As for the measures to improve the film thickness reduction part that occurs at the end of scanning, the laser end is continuously irradiated with laser while the laser optical axis is shifted to increase the laser light intensity at the processing end. There has also been a proposal to increase the film thickness (see Patent Document 1).

  However, the above proposal is intended to correct a binary mask that is sufficient if the transmittance of the correction portion is less than about 1% (if the film thickness is more than a certain level), the present invention is In order to achieve the allowable transmittance range (target transmittance around ± 2%) required for correcting the halftone area in question, it is necessary to strictly control the intensity distribution of the irradiation spot at the end of scanning, It has been difficult to realize by only shifting the optical axis of the laser beam.

  The present invention has been made paying attention to such a conventional problem, and the object of the present invention is to provide a defect correction portion when applied to correction of a white defect portion of a halftone area on a photomask. It is an object of the present invention to provide a CVD thin film forming method and apparatus capable of sufficiently uniforming the transmittance.

  Other objects and operational effects of the present invention will be easily understood by those skilled in the art by referring to the following description of the specification.

  The problems to be solved by the above-described invention can be solved by a method for forming a CVD thin film having the following configuration.

  That is, in this CVD thin film forming method, laser light emitted from a laser oscillator passes through an opening provided stationary in front of the optical axis, and is then collected by an objective lens to be in a reactive gas atmosphere. And irradiating the surface of the sample placed on the surface, and by oscillating the optical axis of the laser light incident on the opening with respect to the opening, the intensity of the irradiated light on the surface of the sample is made uniform by time averaging In this method of forming a CVD thin film, the diameter of the laser beam incident on the opening is set sufficiently smaller than the width of the opening, and the optical axis of the laser beam is larger than the width of the opening. It is characterized by oscillating with amplitude.

  According to such a configuration, since the amplitude of the swing is larger than the light spot diameter on the opening, the time average of the irradiation laser light intensity is made uniform even if the intensity distribution of the laser light is not symmetric with respect to the optical axis. be able to. In addition, since the oscillation amplitude of the optical axis itself is not much different from the conventional one, there is no problem even if the oscillation amplitude is limited to a small amplitude due to deterioration of the intensity distribution due to vignetting and aberration of the processing observation optical system. .

  As a preferred embodiment of the above-described method, the intensity of the laser light incident on the opening may be changed according to the position of the optical axis during the oscillation of the laser light.

  According to such a configuration, in addition to the above-described effect due to the large amplitude fluctuation of the minute spot, the unevenness of the time average of the irradiation laser beam intensity on the irradiation surface due to the optical system can also be eliminated.

  At this time, when the optical axis position is in the vicinity of the edge of the opening, if the intensity of the laser beam is changed in a predetermined manner, the light intensity at the imaging edge due to diffraction and aberration of the processing observation optical system The correction of the distribution and the light spot entering the image across the edge of the light image of the rectangular aperture 4 can be compensated for inadequate seeding of the thin film growth.

  Similarly, at this time, when the optical axis position is in the inner region of the opening, if the intensity of the laser beam is changed according to a predetermined mode according to each position, each beam position is changed. In addition, the transmittance of the attenuator can be automatically changed, whereby the unevenness of the laser irradiation intensity caused by the optical system can be corrected.

  In each of the above methods, the diameter of the laser beam may be smaller than 1/3 of the width of the opening.

  In each of the above-described methods, the sample may be a photomask, and may be used for correcting a white defect portion in the halftone region.

  From another aspect, the problem to be solved by the above-described invention can be solved by a CVD thin film forming apparatus having the following configuration.

  That is, this CVD thin film forming apparatus can oscillate its optical axis while irradiating a laser oscillator and a laser beam emitted from the laser oscillator to an opening of a predetermined shape placed at a stationary position. An irradiation rocking means, and an objective lens for condensing the laser light after passing through the opening and irradiating the surface of the sample placed in the reaction gas atmosphere, The function of setting the diameter of the light spot on the opening sufficiently smaller than the opening width of the opening and setting the amplitude of the light spot fluctuation on the opening larger than the width of the opening is incorporated. It is characterized by that. Here, in one embodiment, the irradiation rocking means includes a beam expander 2 and a beam scanning unit 3.

  Even in such a configuration, since the amplitude of the swing is larger than the light spot diameter on the aperture, the time average of the intensity of the irradiated laser light is made uniform even if the intensity distribution of the laser light is not symmetric with respect to the optical axis. can do. In addition, since the oscillation amplitude of the optical axis itself is not much different from the conventional one, there is no problem even if the oscillation amplitude is limited to a small amplitude due to deterioration of the intensity distribution due to vignetting and aberration of the processing observation optical system. .

  As a preferred embodiment of the above-described apparatus, the laser beam to be incident on the irradiation rocking means is transmitted before the irradiation rocking means, and the light transmittance is controlled by an external control. Variable translucent means that can be changed, opening position detection means for generating and outputting an opening position signal indicating the position of the opening, and generating and outputting an optical axis position signal indicating the optical axis position of the laser beam at the opening position Determining the position of the optical axis with respect to the opening based on the optical axis position detecting means, the opening position signal output from the opening position detecting means, and the optical axis position signal output from the optical axis position detecting means. And a control means for controlling the light transmittance of the variable light-transmitting means based on the determination result.

  Even with such a configuration, in addition to the above-described effect due to the large amplitude fluctuation of the minute spot, it is possible to eliminate unevenness in the time average of the intensity of the irradiated laser beam on the irradiated surface due to the optical system. .

  At this time, if the control means determines that the optical axis is in the vicinity of the edge of the opening, and changes the light transmittance of the variable light transmission means in a predetermined manner, the processing observation optical system Correction of the light intensity distribution at the imaging edge due to diffraction and aberration of the light beam, and when the light spot enters the image across the edge of the optical image of the rectangular aperture 4 and the seed formation of the thin film growth is insufficient. Can be supplemented.

  At this time, when the control means determines that the optical axis is in the inner region of the opening, the control means changes the light transmittance of the variable light transmission means according to a predetermined mode according to each position. By doing so, it is possible to automatically change the transmittance of the attenuator for each beam position, thereby correcting the unevenness of the laser irradiation intensity caused by the optical system.

  In each of the above-described apparatuses, the diameter of the laser beam may be smaller than 1/3 of the width of the opening.

  In each of the above-described apparatuses, the sample may be a photomask that is used for correcting a white defect portion in the halftone region.

  According to the present invention, since the amplitude of the swing is larger than the light spot diameter on the aperture, the time average of the intensity of the irradiated laser light can be made uniform even if the intensity distribution of the laser light is not symmetric with respect to the optical axis. it can. In addition, since the oscillation amplitude of the optical axis itself is not much different from the conventional one, there is no problem even if the oscillation amplitude is limited to a small amplitude due to deterioration of the intensity distribution due to vignetting and aberration of the processing observation optical system. . Therefore, according to the present invention, when applied to the correction of the white defect portion of the halftone area on the photomask, the transmittance of the defect correction portion can be made sufficiently uniform.

It is a block diagram which shows one Embodiment of this invention apparatus. It is a block diagram which shows an example of a beam scanning unit. It is a graph which shows an example of the transmittance | permeability control content of the attenuator by a control part. It is a graph which shows the relationship between attenuator transmittance | permeability and laser beam intensity. It is a graph for demonstrating the effect | action of this invention. It is a block diagram which shows an example of a conventional apparatus. It is a graph for demonstrating the effect | action of a conventional apparatus.

  Hereinafter, a preferred embodiment of a CVD thin film forming method and apparatus according to the present invention will be described in detail with reference to the accompanying drawings.

  The block diagram which shows one Embodiment of this invention apparatus is shown by FIG. In this apparatus, a photomask placed on a table (not shown) is covered with a CVD gas supply / exhaust unit 6 having a known structure, so that a white defect portion in a halftone region to be corrected is exposed to a CVD source gas atmosphere. In this state, a white film is irradiated with laser light through the upper surface window of the CVD supply / exhaust unit 6 to deposit a CVD thin film having an appropriate film thickness by the reaction of the CVD source gas. , Trying to fix white defects.

  In FIG. 1, a laser oscillator 1 generates and emits laser light having a wavelength (for example, 266 nm) suitable for a CVD source gas. The beam expander 2 enlarges the cross section of the laser light emitted from the laser oscillator 1 at a predetermined magnification (for example, 7 times).

  The optical attenuator 7 adjusts the intensity of the laser light that has passed through the beam expander 2 by changing the laser light transmittance. As will be described in detail later, the value of the laser light transmittance of the optical attenuator is appropriately changed and controlled by a signal from the control unit 8.

  The beam scanning unit 3 irradiates the laser light whose intensity is adjusted by the optical attenuator 7 toward the rectangular opening 4 and swings the irradiation optical axis on the rectangular opening 4. As will be described in detail later, the beam scanning unit 3 forms a light spot having a width equal to or smaller than 1/3 of the opening width on the rectangular opening 4 and swings the light spot with an amplitude larger than the opening width. As is well known by those skilled in the art, the rectangular opening 4 is generally configured such that the shape or size of the opening can be changed by a combination of a plurality of knife edges or the like. An opening edge signal S2 indicating each of both end edge positions in the spot swinging direction is output.

  The processing observation optical system 5A includes an objective lens 51 and a mirror 52. After passing through the rectangular opening 4, the processing observation optical system 5A reflects the laser light arriving through the optical system 5B downward by the mirror 52, which is then used as an objective. The light is condensed by the lens 51, and spot-irradiated onto the photomask 9 through the upper surface window of the CVD gas supply / exhaust unit 6. At this time, since the rectangular opening 4 and the surface of the photomask 9 are in an optically conjugate positional relationship, a minute rectangular irradiation spot by the laser beam appears on the surface of the photomask 9.

  Since the defect correcting portion of the photomask 9 is placed in the CVD source gas atmosphere by the CVD gas supply / exhaust portion 9, the CVD source gas is decomposed at the irradiated portion of the light spot, and the reduced aperture image inside the rectangular opening 4 A thin film is formed.

  The laser light reflected by the surface of the photomask 9 returns through the objective lens 51 and returns to the optical axis, and further passes through the mirror 52 and is guided to the observation optical system 12. Therefore, the irradiation spot on the photomask 9 can be observed through an observation optical system (for example, including a light receiving optical system and an image sensor).

  Part of the laser light that has passed through the rectangular opening 4 is reflected by the mirror 53 and then guided to the laser light intensity detector 10. Therefore, the intensity of the laser beam that has passed through the rectangular opening 4 can be detected via the light intensity detector 10.

  The laser light transmitted through the photomask 9 is guided to a laser light detector 11 disposed under the photomask 9. Therefore, the intensity of the laser beam that passes through the photomask 9 can be detected via the laser intensity detector 11.

  FIG. 2 shows a configuration diagram illustrating an example of a beam scanning unit (in the case of one axis). As shown in the figure, the beam scanning unit 3 is positioned in front of the optical axis of the aperture 31 irradiated with the laser light whose intensity is adjusted by the attenuator 7 and transmitted through the aperture 31, and can be tilted to the galvanometer. The scanning mirror 30 that is mounted, and a lens that projects the laser light reflected by the scanning mirror 30 in a reduced manner so that a light spot having a width of 1/3 or less of the opening width is formed on the rectangular opening 4. Is done. The beam scan unit 3 outputs a beam position signal S1 that is generated based on the tilt angle of the scan mirror 30 and that indicates the current optical axis position of the laser beam with respect to the rectangular aperture 4.

  Along with the reciprocal tilt of the scan mirror 30, a light spot (for example, a circular light spot) of 1/3 or less of the opening width swings with a larger amplitude than the opening width of the rectangular opening 4 with respect to the rectangular opening 4. As a result, the time average intensity of the laser light in the rectangular opening 4 is made uniform. Here, the trajectory of the light spot swing is a one-dimensional swing mode in which the light spot swings in the horizontal direction or a two-dimensional swing in which horizontal swing and vertical swing are combined. It may be a moving mode.

  The distance between the scan mirror 30 and the lens 31 is adjusted so that the point P on the optical axis of the scanner mirror 30 forms an image on the entrance pupil 50 of the objective lens of the processing observation optical system 5. The focal length of the lens 31 is set so that the periphery of the light spot is not obstructed by the entrance pupil 50 of the objective lens, and when the light spot is at the edge position at the maximum size of the rectangular opening 4, the processing observation optical system 5 Is selected so as not to be affected by the aberration.

  On the other hand, the laser light transmittance of the optical attenuator 3 is set to a transmittance obtained by multiplying the set transmittance at the time of thin film formation by a predetermined change rate with respect to the swing angle of the laser light. Also, different rates of change can be set depending on the target transmittance of the thin film to be formed.

Here, the laser beam intensity detectors 10 and 11 are used for setting the laser beam intensity and coarsely adjusting the change rate of the optical attenuator 7. The coarse adjustment value Q of the change rate of the optical attenuator 7 is L1 for the output of the laser light intensity detector 10, L2 for the output of the laser light intensity detector 11, and a correction coefficient for correcting the loss of the processing observation optical system 5. If α is

Q = (L2 / L1) x α

And a fine adjustment is performed so as to actually form a partially transmissive film (halftone film) and reduce the transmittance unevenness.

  The control unit 8 recognizes the position of the current light spot with respect to the rectangular opening 4 based on the beam position signal S1 obtained from the beam scanning unit 3 and the opening edge signal S2 obtained from the rectangular opening 4, and corresponds to the position. By outputting a transmittance control signal S3 having a value, the laser light transmittance of the optical attenuator 7 is changed.

  Graphs showing examples of the transmittance control contents of the attenuator 7 by the control unit 8 are shown in FIGS. 3 and 4.

  In the example of FIG. 3, based on the value of the beam position signal S1, it is determined that the beam position has entered the opening (refer to part C in the figure) beyond the first edge of the rectangular opening 4. When the value of the transmittance control signal S3 (not shown) changes, the value of the attenuator 7 transmittance gradually decreases thereafter, and then stabilizes to a certain lower limit value. On the other hand, if it is determined that the beam position has escaped beyond the second edge of the rectangular opening 4 in the same manner, the value of the transmittance control signal S3 (not shown) changes, and the transmission through the attenuator 7 The value of the rate increases rapidly thereafter, and then stabilizes at a certain upper limit value.

  Thus, the purpose of changing the transmittance of the optical attenuator 7 near the edge position of the rectangular opening 4 is mainly to correct the light intensity distribution at the imaging edge portion due to diffraction and aberration of the processing observation optical system 5 and to adjust the light spot. This is to compensate for the insufficient seed formation of the thin film growth when entering the image across the edge of the optical image of the rectangular aperture 4.

  The example in FIG. 4 mainly explains the transmittance control of the attenuator 7 inside the rectangular opening 4. In this example, the beam position signal (S 1) and the transmittance are prepared in advance. Based on the relationship with the change rate data (Q), the transmittance of the attenuator is automatically changed for each beam position, thereby correcting the unevenness of the laser irradiation intensity caused by the optical system.

  Finally, a graph for explaining the operation of the present invention is shown in FIG. According to the present invention, since the swing amplitude is larger than the optical spot diameter (see (a) in the figure) on the rectangular opening 4 (see (b) in the figure), the intensity distribution of the laser beam is relative to the optical axis. Even if they are not symmetrical, the time average of the intensity of the irradiated laser beam can be made uniform (see (c) in the figure).

  On the other hand, the unevenness of the time average of the intensity of the irradiated laser beam on the irradiated surface due to the optical system (see FIG. 4D) indicates that the transmittance of the optical attenuator 7 is a light spot as shown in FIGS. Can be made almost uniform by changing the position according to the position of the optical axis and the size of the rectangular opening (see FIG. 5E). However, FIG. 5D does not show the transmittance adjustment of the edge portion by the rectangular opening size shown in FIG.

  In the above embodiment, both the technique of swinging a small-diameter beam with a large amplitude within the aperture and the technique of transmittance control corresponding to the beam position by the attenuator are combined. However, on the irradiation surface caused by the optical system. If the time average unevenness of the intensity of the irradiated laser beam is not so problematic, a technique for swinging a small-diameter beam with a large amplitude within the aperture is sufficient.

  The present invention can be widely applied not only to correcting white defects in a halftone region of a photomask but also to other uses that require a high degree of uniform film thickness.

  The present invention can be used for a CVD thin film forming apparatus suitable for applications requiring a high degree of uniform film thickness, such as correction of white defects in a halftone region of a photomask.

DESCRIPTION OF SYMBOLS 1 Laser oscillator 2 Beam expander 3 Beam scan unit 4 Rectangular opening 5A Processing observation optical system 5B Optical system 6 CVD gas supply exhaust part 7 Optical attenuator 8 Control part 9 Photomask 10 Laser light intensity detector 11 Laser light intensity detector 12 Observation optical system 30 Scan mirror 31 Aperture 32 Lens 50 Entrance pupil 51 Objective lens 52 Mirror 53 Mirror P Imaging point

Claims (12)

The laser light emitted from the laser oscillator passes through an opening provided stationary in front of the optical axis, and then is focused on the objective lens to irradiate the sample surface placed in the reaction gas atmosphere. This is a method for forming a CVD thin film in which the optical axis of laser light incident on the opening is oscillated with respect to the opening so that the irradiation light intensity on the surface of the sample is made uniform by a time-average action. And
The CVD is characterized in that the diameter of the laser light incident on the opening is set sufficiently smaller than the width of the opening, and the optical axis of the laser light is swung with an amplitude larger than the width of the opening. Method for forming a thin film.   2. The method of forming a CVD thin film according to claim 1, wherein the intensity of the laser beam incident on the opening is changed in accordance with the position of the optical axis during the oscillation of the laser beam.   The method of forming a CVD thin film according to claim 2, wherein when the optical axis position is in the vicinity of the edge of the opening, the intensity of the laser beam is changed in a predetermined manner.   3. The CVD thin film according to claim 2, wherein when the optical axis position is in an inner region of the opening, the intensity of the laser beam is changed according to a predetermined mode according to each position. Forming method.   The diameter of the said laser beam is smaller than 1/3 of the width | variety of the said opening, The formation method of the CVD thin film as described in any one of Claims 1-4 characterized by the above-mentioned.   The method for forming a CVD thin film according to claim 1, wherein the sample is a photomask and is used for correcting a white defect portion in a halftone region thereof. A laser oscillator;
Irradiation oscillating means capable of oscillating the optical axis while irradiating the laser beam emitted from the laser oscillator to an opening of a predetermined shape placed at a stationary position;
An objective lens that condenses the laser light after passing through the opening and irradiates the surface of the sample placed in the reaction gas atmosphere;
The irradiation rocking means is
The function of setting the diameter of the light spot on the opening sufficiently smaller than the opening width of the opening and setting the amplitude of the light spot fluctuation on the opening larger than the width of the opening is incorporated. An apparatus for forming a CVD thin film, wherein: Variable light transmission means that is in the preceding stage of the irradiation rocking means, transmits laser light to be incident on the irradiation rocking means, and whose light transmittance can be changed by external control,
Opening position detecting means for generating and outputting an opening position signal indicating the position of the opening;
Optical axis position detection means for generating and outputting an optical axis position signal indicating the optical axis position of the laser beam at the opening position;
Based on the opening position signal output from the opening position detection means and the optical axis position signal output from the optical axis position detection means, the position of the optical axis with respect to the opening is determined, and based on the determination result The CVD thin film forming apparatus according to claim 7, further comprising a control unit that controls a light transmittance of the variable light transmitting unit.   The said control means changes the light transmittance of the said variable light transmission means in a predetermined | prescribed aspect, when it determines with the said optical axis being near the edge of the said opening. CVD thin film forming equipment.   The control means, when it is determined that the optical axis is in the inner region of the opening, changes the light transmittance of the variable light transmission means according to a predetermined mode according to each position. The apparatus for forming a CVD thin film according to claim 8.   The diameter of the said laser beam is smaller than 1/3 of the width | variety of the said opening, The formation apparatus of the CVD thin film as described in any one of Claim 1 or 7-10 characterized by the above-mentioned.   12. The CVD thin film forming apparatus according to claim 7, wherein the sample is a photomask, and is used for correcting a white defect portion in a halftone region thereof.

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