JP2007005556A - Charged-particle beam exposure device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To automatically detect the damaged site of a reticle in a charged-particle beam exposure device, regarding the device conducting an exposure by using charged-particle beams such as electron beams, ion beams or the like. <P>SOLUTION: In the charged-particle beam exposure device transferring the pattern of the reticle on a sensitive substrate, the damaged site of the reticle is detected by a position measuring means measuring the position of the reticle. An auto-focus device or a reticle microscope is used as the position measuring means. The damaged site of the reticle means a removing-treatment sub-field removing and treating the membrane of the reticle. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a charged particle beam exposure apparatus that performs exposure using a charged particle beam such as an electron beam or an ion beam.

  In recent years, an electron beam exposure apparatus having both high resolution and high throughput of exposure has been developed. Conventionally, a batch transfer system in which one die or a plurality of dies are exposed at a time has been studied for such a purpose. However, with this method, it is difficult to produce a reticle (mask) that serves as an original for transfer, and it is difficult to reduce the aberration to a required value or less within a wide optical field of one die or more. In view of this, recently, a division transfer method has been studied in which one die or a plurality of dies are not exposed at once, but are divided into small regions of about several hundred μm (hereinafter referred to as subfields) for transfer exposure.

On the other hand, a reticle used in such a divided transfer system is configured by dividing a membrane with a beam to form a large number of subfields, and forming a pattern on the membrane of each subfield. In such a reticle, not all of the subfields formed on the reticle are normal, and the membrane may be damaged. The subfield in which the membrane is broken is used in a state in which the membrane is completely removed in order to avoid the membrane from scattering in the lens barrel. When performing exposure using the reticle from which the membrane of some of the subfields has been removed as described above, the membrane is prevented from being transferred to the wafer by the large opening pattern of the subfield from which the membrane has been removed. Therefore, it is necessary to blank the sub-fields that have been removed so as not to be exposed.
JP 2005-50851 A

However, conventionally, since the detection of the subfield from which the membrane has been removed has been performed visually, there has been a problem that a great amount of man-hour is required to identify the subfield from which the membrane has been removed.
The present invention has been made to solve such a conventional problem, and an object thereof is to provide a charged particle beam exposure apparatus capable of automatically detecting a damaged portion of a reticle within the apparatus.

A charged particle beam exposure apparatus according to a first aspect of the present invention is a charged particle beam exposure apparatus that transfers a reticle pattern onto a sensitive substrate, and detects a damaged portion of the reticle by a position measuring unit that measures the position of the reticle. It is characterized by that.
A charged particle beam exposure apparatus according to a second invention is the charged particle beam exposure apparatus according to the first invention, wherein the position measuring means is an autofocus device or a reticle microscope.

A charged particle beam exposure apparatus according to a third aspect of the present invention is the charged particle beam exposure apparatus according to the first or second aspect, wherein the reticle damage site is a removal processing subfield in which the reticle membrane is removed. It is characterized by being.
A charged particle beam exposure apparatus according to a fourth invention is characterized in that, in the charged particle beam exposure apparatus according to the third invention, blanking of the removal processing subfield is performed when the pattern of the reticle is transferred onto a sensitive substrate. And

  The charged particle beam exposure apparatus according to a fifth aspect of the present invention is the charged particle beam exposure apparatus according to the third aspect, wherein the removal process subfield is a subfield for alignment of the reticle, and the removal process is performed during alignment of the reticle. The subfield alignment information is excluded.

  In the charged particle beam exposure apparatus of the present invention, the damaged part of the reticle is detected by the position measuring means for measuring the position of the reticle, so that the damaged part of the reticle can be automatically detected in the apparatus. .

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 schematically shows an optical system and a control system of a divided transfer type electron beam exposure apparatus which is an embodiment of the charged particle beam exposure apparatus of the present invention.
In FIG. 1, an electron gun 11 disposed at the uppermost stream of the optical system emits an electron beam downward in the drawing. Two-stage condenser lenses 13 and 15 are provided below the electron gun 11, and the electron beam is converged by these condenser lenses 13 and 15 and crossed over the blanking opening 17. O. Is imaged.

An illumination beam shaping opening 19 is provided below the two-stage condenser lenses 13 and 15. The illumination beam shaping opening 19 allows only an illumination beam that illuminates one subfield (pattern small area serving as one unit of exposure) of the reticle (mask) 21 to pass. The image of the illumination beam shaping opening 19 is formed on the reticle 21 by the lens 23.
A blanking deflector 25 is disposed below the illumination beam shaping opening 19. The blanking deflector 25 deflects the illumination beam when necessary and applies it to the non-opening portion of the blanking opening 17 so that the beam does not hit the reticle 21.

  An illumination beam deflector 27 is disposed below the blanking opening 17. The illumination beam deflector 27 scans the illumination beam mainly in the horizontal direction (X direction) in the drawing to illuminate each subfield of the reticle 21 in the field of view of the illumination optical system. An illumination lens 23 is disposed below the illumination beam deflector 27. The illumination lens 23 forms an image of the illumination beam shaping opening 19 on the reticle 21.

The reticle 21 actually extends in the plane perpendicular to the optical axis (XY plane) and has a number of subfields (details will be described later). A pattern (chip pattern) forming one semiconductor device chip as a whole is formed on the reticle 21. Of course, a pattern forming one semiconductor device chip may be divided and arranged on a plurality of reticles.
The reticle 21 is mounted on a movable reticle stage 29. By moving the reticle 21 in the direction perpendicular to the optical axis (XY direction), each sub-surface on the reticle 21 that extends over a wider range than the field of view of the illumination optical system. The field can be illuminated.

The reticle stage 29 is provided with a position detector 31 using a laser interferometer, so that the position of the reticle stage 29 can be accurately grasped in real time.
An alignment mark 33 is formed on the lower surface of the reticle 21 in the drawing (details will be described later). A reticle microscope 35 is disposed below the reticle 21. The reticle microscope 35 irradiates probe light (light or charged particle beam) to the alignment mark 33 and reflected light from the alignment mark 33. Image acquisition means (such as an optical system and a CCD) that detects and acquires an image of the alignment mark 33 is provided.

The image of the alignment mark 33 acquired by the reticle microscope 35 is sent to the mark image processing device 35a and processed. Then, exposure is performed based on the image of the alignment mark 33 processed by the mark image processing device 35a.
An autofocus device 37 is disposed below the reticle 21. The autofocus device 37 includes an illumination optical system 37b that irradiates the lower surface of the reticle 21 with probe light (light or charged particle beam), and an image acquisition unit that detects reflected light from the lower surface of the reticle 21 and acquires an image. 37c) (optical system and CCD). The autofocus device 37 projects a slit image on the lower surface of the reticle 21 from an oblique direction, and monitors the position of the reflected slit on the image acquisition means 37c side to detect the position of the reticle 21 in the vertical direction (Z direction). .

  Projection lenses 39 and 41 and a deflector 43 are provided below the reticle 21. The electron beam that has passed through one subfield of the reticle 21 is imaged at a desired position on the wafer 45 by the projection lenses 39 and 41 and the deflector 43. An appropriate resist is applied on the wafer 45. By applying an electron beam dose to the resist, the pattern on the reticle 21 is reduced and transferred onto the wafer 45.

A crossover C.D. O. The contrast opening 47 is provided at the crossover position. The contrast opening 47 blocks the electron beam scattered by the non-pattern part of the reticle 21 from reaching the wafer 45.
A backscattered electron detector 49 is disposed immediately above the wafer 45. The backscattered electron detector 49 detects the amount of electrons reflected by the exposed surface of the wafer 45 and the mark on the stage. For example, the relative positional relationship between the reticle 21 and the wafer 45 can be known by scanning the mark on the wafer 45 with a beam that has passed through the mark pattern on the reticle 21 and detecting reflected electrons from the mark at that time. .

  The wafer 45 is disposed on a wafer stage 51 that can move in the XY directions via an electrostatic chuck (not shown). By synchronously scanning the reticle stage 29 and the wafer stage 51 in opposite directions, each part in the chip pattern extending beyond the field of view of the projection optical system can be sequentially exposed. The wafer stage 51 is provided with a position detector 53 using a laser interferometer, so that the position of the wafer stage 51 can be accurately grasped in real time.

  The lenses 13, 15, 23, 39, and 41 and the deflectors 25, 27, and 43 are controlled by the controller 55 via the coil power supply controllers 13a, 15a, 23a, 39a, 41a, and 25a, 27a, 43a. Controlled. The reticle stage 29 and the wafer stage 51 are also controlled by the controller 55 via the respective stage control units 29a and 51a. The stage position detectors 31 and 53 send signals to the controller 55 via interfaces 31a and 53a including amplifiers and A / D converters. The backscattered electron detector 49 also sends a signal to the controller 55 via a similar interface 49a.

  The controller 55 grasps the control error of the stage position and the position error of the projection beam, and corrects the error by the image position adjusting deflector 43. Thereby, the reduced image of the subfield on the reticle 21 is accurately transferred to the target position on the wafer 45. Then, the images of the subfields are joined on the wafer 45, and the entire chip pattern on the reticle 21 is transferred onto the wafer 45.

FIG. 2 shows an example of a reticle 21 used in the above-described divided transfer type electron beam exposure apparatus. The reticle 21 is manufactured, for example, by performing electron beam drawing / etching on a silicon wafer.
In FIG. 2, a large number of squares are small membrane regions (thickness 0.1 μm to several μm) 57 including pattern regions corresponding to one subfield.

  As shown in FIG. 3B, the small membrane region 57 includes a central pattern region (subfield) 59 and a peripheral frame-shaped non-pattern region (skirt) 61. A subfield 59 is a portion where a pattern to be transferred is formed. The skirt 61 is a part where no pattern is formed, and the edge part of the illumination beam hits it. As a form of pattern formation, there are a stencil type in which a hole is formed in a membrane, and a scattering membrane type in which a pattern layer made of a high scattering body of electron beams is formed on a membrane.

  One subfield 59 has a size of about 1 mm square on the reticle 21, for example. The reduction ratio of the projection is ¼, and the size of the projection image obtained by reducing the subfield 59 onto the wafer 45 is 0.25 mm square. As shown in FIG. 3A, orthogonal grid-like portions (greage) 63 around the small membrane region 57 have a thickness of, for example, about 0.5 to 1 mm for maintaining the mechanical strength of the reticle 21. It is a beam. The width of the grage 63 is, for example, about 0.1 mm. Note that the width of the skirt 61 is, for example, about 0.05 mm.

In FIG. 3A, reference numeral 65 indicates a removal processing subfield 65 from which the subfield 59 is removed. The removal processing subfield 65 is a portion where the membrane of the reticle 21 is damaged due to a crack or the like, and the membrane of the subfield 59 at the damaged portion is completely removed in order to prevent the membrane from scattering in the lens barrel. .
As shown in FIG. 2, a large number of small membrane regions 57 are arranged in the horizontal direction (X direction) in the figure to form one group (electrical stripe 67), and such an electrical stripe 67 is formed in the vertical direction (Y One mechanical stripe 69 is formed side by side in the direction). The length of the electrical stripe 67 (the width of the mechanical stripe 69) is limited by the size of the deflectable field of view of the illumination optical system.

A plurality of mechanical stripes 69 exist in parallel in the X direction. A thick beam shown as a strut 71 between adjacent mechanical stripes 69 is for keeping the deflection of the entire reticle 21 small. The strut 71 is integrated with the grage 63.
An alignment mark 33 for aligning the reticle 21 is formed on the lower side of the mechanical stripe 69 in the drawing and on the back surface of the reticle 21. In this embodiment, each mechanical stripe 69 is formed with an alignment mark 73 for aligning the mechanical stripe 69 in the X direction and the Y direction. For example, the alignment mark 73 is formed by forming a hole in a cross shape in the upper and lower subfields 59 of the mechanical stripe 69.

  A hatched portion in FIG. 2 indicates the removal processing subfield 65 from which the subfield 59 is removed. In this embodiment, one of the subfields 59 for the alignment mark 73 located on the upper side of the mechanical stripe 69 in the drawing is the removal processing subfield 65A. The two subfields 59 at the center and the lower side are set as removal processing subfields 65B and 65C. These removal processing subfields 65A, 65B, and 65C are not absolutely necessary for the exposure of the wafer 45, and can be used as the reticle 21 in this state.

  According to the method considered to be dominant at present, the row of the subfields 59 in the X direction (electrical stripe 67) in one mechanical stripe 69 is sequentially exposed by electron beam deflection. On the other hand, the columns in the Y direction in the mechanical stripes 69 are sequentially exposed by continuous stage scanning. At the time of exposure, probe light is applied to the alignment marks 33 and 73 by the reticle microscope 35, and the alignment marks 33 and 73 are detected to perform alignment.

  In the electron beam exposure apparatus described above, detection processing subfield 65 (65A, 65B, 65C) of reticle 21 is detected using autofocus device 37 that detects the position of reticle 21 in the vertical direction (Z direction). . This detection is performed by moving the reticle stage 29 and scanning the entire surface of the reticle 21. That is, when the lower surface of the reticle 21 is irradiated with probe light from the illumination optical system 37b of the autofocus device 37, in the subfield 59 that has not been subjected to removal processing, the probe light is reflected by the subfield 59, and this image is image acquisition means 37c. To be acquired. On the other hand, in the removal processing subfield 65 (65A, 65B, 65C), the probe light is not reflected, and thus no image is acquired by the image acquisition unit 37c. Therefore, it is possible to automatically detect the address of the removal processing subfield 65 (65A, 65B, 65C) depending on the presence or absence of an image.

  The address information of the removal processing subfield 65 (65A, 65B, 65C) detected in this way is stored in the controller 55. When the wafer 45 is exposed, the address information is fed back to the setting of the exposure conditions, and the blanking deflector 25 deflects the illumination beam so that the beam is blanked so that it is not illuminated on the reticle 21. Accordingly, it is possible to reliably prevent the large opening pattern of the removal processing subfield 65 (65A, 65B, 65C) from being transferred onto the wafer 45.

Further, in this embodiment, one of the subfields 59 in which the alignment marks 73 for performing alignment of the mechanical stripes 69 are formed is a removal processing subfield 65A. Therefore, in this embodiment, the alignment information of the removal process subfield 65A is excluded by the controller 55, and the alignment of the mechanical stripes 69 is performed by the alignment marks 73 of the other normal subfields 59. Thereby, alignment can be performed exactly.
(Supplementary items of the embodiment)
As mentioned above, although this invention was demonstrated by embodiment mentioned above, the technical scope of this invention is not limited to embodiment mentioned above, For example, the following forms may be sufficient.

  (1) In the above-described embodiment, the example in which the removal processing subfield 65 of the reticle 21 is detected by the autofocus device 37 has been described. For example, the removal processing subfield 65 is detected by using the reticle microscope 35. Also good. In this case, the detection is performed by moving the reticle stage 29 and scanning the entire surface of the reticle 21 with the reticle microscope 35. That is, if the lower surface of the reticle 21 is irradiated with probe light from an illumination optical system (not shown) of the reticle microscope 35, the probe light is reflected by the subfield 59 in the non-removed subfield 59, but the removal processing subfield. At 65, the probe light is not reflected. Therefore, the image acquired by the image acquisition means (not shown) is subjected to image processing by the mark image processing device 35a, whereby the address of the removal processing subfield 65 can be automatically detected.

(2) In the above-described embodiment, an example in which the removal processing subfield 65 of the reticle 21 is detected has been described. However, the present invention can be widely applied to detection of a damaged portion such as a crack in the reticle 21.
(3) In the above-described embodiment, the example in which the present invention is applied to the electron beam exposure apparatus has been described. However, the present invention can be widely applied to charged particle beam exposure apparatuses such as an ion beam exposure apparatus.

It is explanatory drawing which shows one Embodiment of the charged particle beam exposure apparatus of this invention. It is explanatory drawing which shows the reticle of FIG. FIG. 3 is an explanatory diagram showing details of the reticle of FIG. 2.

Explanation of symbols

  21: reticle, 25: blanking deflector, 35: reticle microscope, 37: autofocus device, 45: wafer, 59: subfield, 65 (65A, 65B, 65C): removal processing subfield.

Claims (5)

In a charged particle beam exposure apparatus that transfers a reticle pattern onto a sensitive substrate,
A charged particle beam exposure apparatus, wherein a position measurement means for measuring the position of the reticle detects a damaged portion of the reticle. The charged particle beam exposure apparatus according to claim 1,
The charged particle beam exposure apparatus, wherein the position measuring means is an autofocus device or a reticle microscope. In the charged particle beam exposure apparatus according to claim 1 or 2,
The charged particle beam exposure apparatus according to claim 1, wherein the damaged portion of the reticle is a removal subfield in which the reticle membrane is removed. In the charged particle beam exposure apparatus according to claim 3,
A charged particle beam exposure apparatus, wherein blanking of the removal processing subfield is performed when the reticle pattern is transferred onto a sensitive substrate. In the charged particle beam exposure apparatus according to claim 3,
The charged particle beam exposure apparatus, wherein the removal processing subfield is a subfield for alignment of the reticle, and alignment information of the removal processing subfield is excluded during alignment of the reticle.

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