JP2010066320A - Inspection method for membrane shape of stencil mask and inspection apparatus for membrane shape of stencil mask - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inspection method for the membrane shape of a stencil mask and an inspection apparatus for the membrane shape of a stencil mask, in which qualities and reliability of a stencil mask can be improved and the yield can be improved as inspection of the membrane shape of the stencil mask is systematically and automatically carried out. <P>SOLUTION: The inspection method for the membrane shape of a stencil mask to be used for manufacturing semiconductors is characterized in that a stencil mask is placed on an XY stage and a sheet beam by a laser is made to be obliquely incident to the surface of the stencil mask so as to obtain an optical cutting image by reflection from the stencil mask. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a stencil mask membrane shape inspection method and a stencil mask membrane shape inspection device, and more particularly to a stencil mask membrane shape inspection method and a stencil mask membrane shape inspection device.

  In recent years, high integration has progressed in semiconductor device manufacturing, and an exposure apparatus using a charged particle beam capable of forming a finer circuit pattern is used in an exposure process for forming circuit wiring. The stencil mask is mounted on such a charged particle beam exposure apparatus.

  The stencil mask has a thin film portion called a membrane, in which a large number of various fine patterns and holes of several μm or 1 μm or less are formed as through holes faithfully to the design data. In the exposure process of semiconductor manufacturing, the charged particle beam passes through the through hole, and the circuit pattern is reduced or transferred at the same magnification on the wafer.

  Many fine patterns and holes are formed as through-holes on the stencil mask membrane faithfully to the design data, but it is a thin film with a thickness of several tens of μm, and it remains flat due to the influence of internal stress due to the manufacturing process. May not be possible. In particular, in the case of compressive stress, the membrane sags and the formed circuit pattern moves. At this time, there is a problem that the circuit pattern is not transferred to an accurate position on the wafer, causing wiring defects. Further, when the stencil mask is used, it is mounted in an exposure machine and exposure is performed close to the wafer. However, if the membrane is greatly slackened at this time, there is a risk of contact.

  Therefore, it was necessary to accurately inspect the flatness by inspecting the membrane shape during the stencil mask manufacturing process and at the time of shipment.

  The membrane shape is inspected without contact, and a focusing method using a laser displacement meter or a microscope is used. As an inspection method, a method of measuring many points on a membrane and analyzing collected data has been used.

  However, in the method of analyzing the collected data as described above, it is necessary to measure and analyze a large number of points in order to manage the membrane shape of the stencil mask, and the measurement data becomes enormous and takes a very long time. It was. Furthermore, since the method for analyzing the collected data is a manual operation using a general-purpose measuring device, there is a risk of foreign matter adhering, so that it was difficult to actually adapt to the product.

Further, Patent Document 1 discloses a stencil mask inspection method and inspection apparatus that perform inspection of foreign matter on the stencil mask surface without visual inspection. However, in Patent Document 1, although the foreign substance on the surface of the stencil mask is inspected, the membrane shape of the stencil mask is not inspected.
JP 2008-153258 A

  Since the present invention automatically performs the inspection of the membrane shape of the stencil mask by systematizing, the method for inspecting the membrane shape of the stencil mask and the membrane shape of the stencil mask that can improve the quality and reliability of the stencil mask and improve the yield. It is to provide an inspection device.

  According to a first aspect of the present invention, in a method for inspecting a membrane shape of a stencil mask used in semiconductor manufacturing, the stencil mask is disposed on an XY stage, and a sheet beam by a laser is inclined with respect to the surface of the stencil mask. The method for inspecting the membrane shape of the stencil mask is characterized in that a light cut image is obtained by incidence and reflection from the stencil mask.

  The invention according to claim 2 of the present invention is the method for inspecting a membrane shape of a stencil mask according to claim 1, wherein image processing for recognizing the uneven shape of the membrane is performed.

  The invention according to claim 3 of the present invention is characterized in that the concavo-convex shape of the membrane is determined as a defect when the size of the concavo-convex shape from the reference position is larger than a specified value. This is a method for inspecting the membrane shape.

  The invention according to claim 4 of the present invention is characterized in that the light section image is subjected to a process of interpolating the light section image missing at the penetration pattern portion of the membrane as continuous. This is a method for inspecting the membrane shape of the described stencil mask.

  The invention according to claim 5 of the present invention forms a light cutting optical system in which a laser is formed into a sheet beam and incident obliquely on the mask surface, and a light cutting image obtained by reflection by a membrane of a stencil mask. A stencil comprising an optical system and a camera, an automatic stage mounted with a stencil mask to be inspected and movable in the XY directions, and an image processing unit for recognizing a membrane shape captured from the camera This is a mask membrane shape inspection apparatus.

  6. The stencil mask membrane shape inspection device according to claim 5, wherein the invention according to claim 6 is determined as a defect when the shape of the membrane is larger than a prescribed value from the reference position. It is what.

  The invention according to claim 7 of the present invention is characterized in that the light section image is subjected to a process of interpolating the light section image missing at the penetration pattern portion of the membrane as being continuous. This is a stencil mask membrane shape inspection apparatus.

  According to the present invention, since the inspection of the membrane shape of the stencil mask is systematically performed automatically, the quality and reliability of the stencil mask can be improved, and the yield of the stencil mask membrane shape can be improved, and the stencil mask membrane A shape inspection apparatus can be provided.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the embodiments, the same components are denoted by the same reference numerals, and redundant description among the embodiments is omitted.

  FIG. 1 is a conceptual diagram showing a stencil mask to be inspected according to the present embodiment. As shown in FIG. 1, a stencil mask 1 to be inspected according to the present embodiment is formed using a silicon wafer or the like, processed into a thin film, and formed with a fine pattern for transmitting charged particle beams. The membrane 2 is provided. In the present embodiment, the uneven shape such as sagging of the membrane 2 is detected by using a stencil mask membrane shape inspection method and a stencil mask membrane shape inspection device.

  Hereinafter, a method for inspecting the membrane shape of the stencil mask will be described. FIG. 2 is a conceptual diagram showing a method for inspecting a membrane shape of a stencil mask according to an embodiment of the present invention. As shown in FIG. 2, in the method for inspecting the membrane shape of the stencil mask according to the embodiment of the present invention, the laser beam 3 is formed into a sheet beam 4 on the incident side, and is incident on the stencil mask 1 obliquely from above. . At this time, the vertical direction and inclination of the XY stage 12 of the stencil mask membrane shape inspection apparatus are adjusted in advance so that the sheet beam 4 can always scan the surface of the membrane 2 at the focal position 7.

  Thereafter, the sheet beam 4 is reflected by the surface of the stencil mask 1, and the light section image 5 obtained at that time reaches the inspection camera 6. Adjustment is made so that the focal position of the optical system on the reflection side is the focal position 7 on the stencil mask 1 of the sheet beam 4.

  In order to form the laser 3 into a sheet beam 4 shape, a slit or a cylindrical lens and a condenser lens such as an objective lens are combined so as to focus on the surface of the stencil mask 1 obliquely from above. On the surface, the sheet beam 4 can be irradiated with a width of about several μm.

  FIG. 3 is a conceptual diagram showing a light section image when the membrane 2 of the stencil mask according to the embodiment of the present invention is flat. As shown in FIG. 3, the light section image 5 maintains linearity in the membrane 2 and forms a single bright line. If the XY stage 12 having the stencil mask 1 mounted on the optical system that irradiates the sheet beam 4 of the laser 3 is adjusted so that the focal length remains the same without mechanical distortion, the height h on the image is high. It is possible to obtain a single light section image 5 in which linearity is always maintained at a fixed position. By using this light section image 5, it can be acquired at high speed as image information that can faithfully reproduce the uneven shape of an arbitrary portion of the membrane 2.

  FIG. 4 shows an image obtained by capturing the light section image 5 obtained in FIG. 3 from the inspection camera 6 and developing it on the frame memory. The XY stage 12 on which the stencil mask 1 is mounted has no mechanical distortion and is adjusted so that the focal length on the incident side is kept constant on the stencil mask 1, so that the obtained light section image 5 is always At the height h of the frame memory, it becomes one bright line.

  FIG. 5 shows a case where the membrane portion 2 of the stencil mask 1 is non-flat and uneven. The light section image 5 at this time becomes a bright line of a curve 8 along the unevenness of the membrane portion 2.

  FIG. 6 shows an image of the frame memory obtained in FIG. At this time, the light section image 5 reproduces the uneven shape of the membrane portion 2 and becomes a bright line of the curve 8. The curve 8 has a displacement amount d with respect to the position of the bright line at the height h of the frame memory shown in FIG.

  In order to numerically recognize the displacement d, the image in the frame memory is subjected to image processing as shown in FIG. First, binarization processing is performed, noise is removed from the obtained light section image, and only necessary bright lines are extracted. Next, by performing the thinning process, the height h in the horizontal direction of the frame memory is uniquely determined.

  Further, an allowable range 10 is defined with reference to the height h in the frame memory indicating the surface position of the stencil mask 1 in FIG. 3, and when the height d exceeds this, the uneven shape of the membrane portion 2 is It is possible to detect that it is larger than the specified value.

  FIG. 8 shows a conceptual diagram of the light section image 5 when a pattern is present on the membrane 2 of the stencil mask 1. Since the pattern of the membrane 2 is a through hole, no reflected light is obtained, resulting in an intermittent light section image 5 and undergoes the same image processing as in FIG. Furthermore, the pattern formed on the membrane 2 of the stencil mask 1 has a structure of a through hole through which a charged particle beam passes. Therefore, even if the sheet beam 4 is irradiated, no reflected light is obtained from the pattern, and the pattern is discontinuous. It is obtained as a light section image 5. Even if the pattern of the through hole is formed in the membrane 2 and the light cut image 5 becomes discontinuous, the membrane 2 can maintain a continuous uneven shape, so that the subsequent processing can be continued. The result is shown in FIG.

  FIG. 10 is a conceptual diagram for interpolating the intermittent light section image 5 as shown in FIG. Here, all are interpolated by connecting the ends of adjacent intermittent bright lines with a straight line 11 to obtain a continuous line.

  Next, a membrane shape inspection apparatus for a stencil mask according to an embodiment of the present invention will be described. FIG. 11 is a conceptual diagram showing a membrane shape inspection apparatus for a stencil mask according to an embodiment of the present invention. As shown in FIG. 11, the stencil mask membrane shape inspection apparatus according to the embodiment of the present invention includes a stencil mask 1, an XY stage 12, a stage controller 13, a computer 14, an image processing unit 15, and a light cutting optical system 16. It has. The stencil mask 1 is mounted on the XY stage 12. At this time, it is assumed that the alignment operation of the stencil mask 1 is completed.

  The light cutting optical system 16 has a laser 3 on the incident side and a camera 6 on the reflection side, and the XY stage 12 moves so that the formed sheet beam 4 scans the entire surface of the stencil mask 1. Further, in the light cutting optical system 16, the sheet beam 4 irradiated obliquely from above the stencil mask 1 is condensed on the surface and reflected to the opposite side, but the light cutting image 5 which is reflected light is a magnification of the imaging optical system. Depending on the size of the image sensor, it can be guided to the frame memory at an arbitrary magnification.

  The image processing unit 15 recognizes the concavo-convex shape of the membrane unit 2 of the stencil mask 1 and performs image processing on the light section image 5 on the frame memory in order to convert it into numerical data. A specific level is set for the obtained light section image 5 in the frame memory to perform a binarization process to exclude information other than the necessary information on the membrane portion 2 and further perform a thinning process. Further, all the images obtained by scanning the sheet beam 4 are subjected to processing as shown in FIG. 7, and are digitized as height h data of the inspection surface including the membrane 2. The processing result is transferred to the computer 14 as numerical data.

  The computer 14 analyzes the transferred numerical data, and outputs a signal to the stage controller 13 when the displacement d of the unevenness of the membrane 2 exceeds the set allowable value 10, and the stage coordinates at that time are output. Record sequentially. Further, the computer 14 performs input and display of inspection data and analysis and determination of output data after image processing from the optical system while controlling the mechanical unit such as the XY stage 12 and the inspection camera 6. And centrally manage the entire inspection system.

  As described above, when the series of membrane inspection is completed, the computer 14 displays the inspection map of the stencil mask 1. At this time, coordinates recorded with the displacement d of the unevenness of the membrane 2 exceeding the allowable value 10 are shown on the map.

  The stencil mask 1 is set on a microscope or review station having an automatic stage, and re-observation is performed based on coordinate data recorded as an inspection result. At this time, if the deflection of the membrane 2 is confirmed, it is determined as an NG product.

  By inspecting the membrane shape of the stencil mask according to the embodiment of the present invention, the shape of the membrane 2 of the stencil mask 1 can be inspected at high speed, and when the uneven shape of the membrane 2 is poor, feedback to the stress adjustment work is performed. The flatness can be corrected quickly.

  In addition, since the maximum displacement of the membrane 2 is revealed by the inspection of the membrane 2 shape, the risk of the membrane 2 coming into contact with the wafer is avoided by determining whether or not the predetermined displacement is within the proximity exposure. be able to.

  Since the inspection of the membrane shape of the stencil mask is performed automatically by systematization, there is no possibility of foreign matter adhering to the stencil mask, which has been a problem using a manual measuring instrument. As described above, it can be applied to an actual inspection of a stencil mask, and the quality and reliability of the stencil mask can be improved, thereby contributing to an improvement in yield.

It is a conceptual diagram which shows the stencil mask used as the test object which concerns on embodiment of this invention. It is a conceptual diagram which shows the test | inspection method of the membrane shape which concerns on embodiment of this invention. It is a conceptual diagram which shows the light cut image in case the membrane part which concerns on embodiment of this invention is flat. It is a conceptual diagram which shows a frame memory image when the membrane part which concerns on embodiment of this invention is flat. It is a conceptual diagram which shows the light cut image in case the membrane part which concerns on embodiment of this invention is non-flat. It is a conceptual diagram which shows a frame memory image when the membrane part which concerns on embodiment of this invention is non-flat. It is a conceptual diagram which shows the image processing result of the frame memory image which concerns on embodiment of this invention. It is a conceptual diagram which shows the light cut image in case there exists a pattern in the membrane part which concerns on embodiment of this invention. It is a conceptual diagram which shows the image processing result in case there exists a pattern which concerns on embodiment of this invention. It is a conceptual diagram which shows the light cut image in case there exists a pattern in the membrane part which concerns on embodiment of this invention. It is a conceptual diagram which shows the membrane-shaped test | inspection apparatus which concerns on embodiment of this invention.

Explanation of symbols

1: Stencil mask, 2: Membrane part of stencil mask, 3: Laser, 4: Sheet beam, 5: Optical cut image, 6: Inspection camera, 7: Focal position, 8: Membrane part of optical cut image, 9: Optical cut image in the case where a pattern exists in the membrane part, 10: Prescribed irregular value of the membrane part, 11: Interpolation data, 12: XY stage, 13: Stage controller, 14: Computer, 15: Image processing part, 16 : Optical cutting optical system

Claims (7)

In the inspection method of the membrane shape of the stencil mask used in semiconductor manufacturing,
Place the stencil mask on the XY stage,
A sheet beam by laser is incident obliquely on the surface of the stencil mask,
A method for inspecting a membrane shape of a stencil mask, wherein a light section image is obtained by reflection from the stencil mask.   2. The method for inspecting a membrane shape of a stencil mask according to claim 1, wherein image processing for recognizing the uneven shape of the membrane is performed.   The method for inspecting a membrane shape of a stencil mask according to claim 2, wherein the uneven shape of the membrane is determined as a defect when the size of the unevenness from a reference position is larger than a specified value.   3. The stencil mask membrane shape according to claim 1, wherein the light cut image is subjected to a process of interpolating the light cut image missing at the penetration pattern portion of the membrane as being continuous. 4. Inspection method. A light-cutting optical system that forms a laser into a sheet beam and makes it incident obliquely on the mask surface;
An optical system and a camera for forming a light section image obtained by reflection on a stencil mask membrane;
An automatic stage mounted with the stencil mask to be inspected and movable in the XY directions;
An image processing unit for recognizing the membrane shape captured from the camera;
A membrane shape inspection apparatus for a stencil mask, comprising:   6. The apparatus for inspecting a membrane shape of a stencil mask according to claim 5, wherein when the shape of the membrane is larger than a prescribed value from a reference position, it is determined as a defect.   6. The apparatus for inspecting a membrane shape of a stencil mask according to claim 5, wherein the light cut image is subjected to a process of interpolating the light cut image missing at the penetration pattern portion of the membrane as being continuous. .