JP6127834B2 - Alignment method and patterning mask - Google Patents

Description

  The present invention relates to an alignment method and a patterning mask.

  It is known to form a pattern by a mask. Patent Document 1 discloses a manufacturing method for alignment in manufacturing a liquid crystal substrate. In such a manufacturing method, the glass substrate and the metal mask can be bonded with high positional accuracy.

  In this method, before the metal mask and the glass substrate are bonded together, the metal mask is arranged at a predetermined distance from the glass substrate. Next, the alignment mark is imaged with a camera to confirm the positional accuracy. Further, after adjusting the position of the glass substrate so that the predetermined position accuracy is obtained, the metal mask is bonded.

JP 2004-146560 A

  In the above method, when the contrast difference between the wafer and the mask is small during imaging, the alignment mark may not be recognized accurately. Furthermore, when two masks are used and stacked, it is difficult to distinguish the alignment marks of both masks, and the recognition accuracy may further decrease. An object of the present invention is to provide an alignment method for performing highly accurate patterning film formation in mask film formation.

  The alignment method of the present invention is an alignment method performed using a mask including a mask alignment mark having an inner surface of a hole, and the mask is placed on the wafer surface so that a tapered surface provided on the inner surface of the hole faces the opposite side to the wafer. Obtained by the superimposing step of superimposing, the imaging step of imaging the mask alignment mark and the surface of the wafer observed through the hole of the mask alignment mark in a state where the wafer and the mask are superimposed, and the imaging step. A confirmation step for confirming the alignment state of the wafer alignment mark and the mask alignment mark on the wafer surface based on the obtained image, and a result of the confirmation step, the position of the mask alignment mark with respect to the wafer alignment mark is not aligned. If the wafer and front Comprising an adjusting step of aligning the mask, a.

  In the imaging step, it is preferable that light is projected to the tapered surface side, and the camera images the mask alignment mark and the wafer surface from the tapered surface side.

  The present invention can provide an alignment method for performing highly accurate patterning film formation in mask film formation.

It is a schematic diagram which shows the element used for the alignment method of mask film-forming. It is a schematic diagram which shows the effect of the taper surface in embodiment. It is a top view of the piled up secondary and primary mask in an embodiment. It is sectional drawing of the primary mask and wafer which were overlap | superposed in embodiment. It is an expanded sectional view of the primary mask and wafer which were piled up in an embodiment. It is a top view of the piled up primary mask and wafer in an embodiment. 6 is a cross-sectional view of the superimposed secondary and primary masks in Example 2. FIG. 6 is an enlarged cross-sectional view of a superposed secondary and primary mask in Example 2. FIG. 6 is a cross-sectional view of a wafer and a film after film formation in Example 2. FIG. It is an expanded sectional view of the primary mask and wafer which were piled up in a comparative example. It is a top view of the overlapped primary mask and wafer in a comparative example. It is an expanded sectional view of the overlapped secondary and primary mask in a comparative example. It is a top view of the overlapped secondary and primary mask in a comparative example. It is sectional drawing of each mask and wafer bonded together in the comparative example. It is sectional drawing of the wafer and film | membrane after being formed into a film in a comparative example. FIG. 10 is a plan view of the superimposed secondary and primary masks in Example 3. FIG. 9 is a plan view of a superimposed secondary and primary mask in Example 4. FIG. 10 is a plan view of a superimposed secondary and primary mask in Example 5. 10 is a sectional view of a primary mask and a wafer superposed in Example 6. FIG. FIG. 10 is a cross-sectional view of a superimposed primary mask and wafer in Example 7.

1. About each element The alignment method of this embodiment is performed using each element shown in FIG. Wafer 30 is located at the bottom of FIG. The wafer can have any shape. For example, the wafer may be square or circular as shown in FIG.

  The wafer 30 includes a wafer alignment mark 40. As an example, the wafer alignment mark 40 is formed of a cylindrical protrusion as shown in FIG. The height of the cylindrical wafer alignment mark 40 may be equal to or less than its diameter or radius. When a normal semiconductor device manufacturing process is used, the wafer alignment mark 40 can have an arbitrary height.

  The wafer alignment mark 40 has another arbitrary shape. The shape of the wafer alignment mark 40 may be, for example, a tapered shape, a conical shape, a truncated cone shape, a hemispherical shape, or a shape obtained by rounding a sphere.

  The wafer alignment mark 40 may be a concave portion of the wafer 30 or a pattern drawn with a material different from that of the wafer 30. The wafer alignment mark 40 can have any shape that is possible in the design of the wafer 30.

  The primary mask 50 and the secondary mask 70 are masks for covering the wafer 30. The primary mask 50 and the secondary mask 70 are masks for forming a semiconductor pattern directly or indirectly on the wafer 30.

  The primary mask 50 and the secondary mask 70 can be designed according to the shape of the wafer. The primary mask 50 and the secondary mask 70 may be square or circular as shown in FIG. The primary mask 50 and the secondary mask 70 are preferably metal masks to enable mask vapor deposition film formation and mask sputtering film formation.

  The primary mask 50 includes a mask alignment mark 60. The primary mask 50 may include a plurality of mask alignment marks. The mask alignment mark 60 can have an arbitrary shape, and may be, for example, a circular opening.

  The opening area of the mask alignment mark 60 is preferably larger than that of the wafer alignment mark 40. It is preferable that the wafer alignment mark 40 is not behind the primary mask 50 when viewed from the side far from the wafer 30, that is, from the side opposite to the wafer 30. This is because an image is picked up by a camera 90 or the like to be described later and confirmed by an arbitrary image recognition means.

  The secondary mask 70 includes a mask alignment mark 80. The secondary mask 70 may include a plurality of mask alignment marks. The secondary mask 70 may further include a mask alignment mark 81. The mask alignment marks 80 and 81 can have an arbitrary shape, and may be, for example, a circular opening.

  The opening area of the mask alignment marks 80 and 81 is preferably larger than that of the mask alignment mark 60. When viewed from the side far from the wafer 30, that is, the side opposite to the wafer 30, it is preferable that the mask alignment mark 60 is not in the shadow of the secondary mask 70. This is because an image is picked up by a camera 90 or the like, which will be described later, and checked by an image recognition unit.

  A mask may be further bonded to the side of the secondary mask 70 that is further away from the wafer 30. When bonding a plurality of such masks, it is preferable that the mask to be pasted on the far side of the wafer 30 has a larger opening area of the alignment mark than the mask on the near side.

  In other words, when viewed from the far side with respect to the wafer 30, it is preferable that the mask alignment mark on the near side is not the shadow of the mask on the far side. This is because an image is picked up by a camera 90 or the like, which will be described later, and checked by an image recognition unit.

  The secondary mask 70 includes one or more mask openings 73. The mask opening 73 is a mask for forming a semiconductor pattern directly or indirectly on the wafer 30. The mask opening 73 defines a portion to be formed on the surface of the wafer 30 after performing the alignment method of the present embodiment.

  The plurality of mask openings 73 are located at arbitrary positions on the secondary mask 70 in accordance with the design of the semiconductor device created on the basis of the wafer. The plurality of mask openings 73 may be arranged in a straight line shape or a lattice shape.

  The mask opening 73 may be a square or a substantial square. The mask opening 73 may have an arbitrary shape according to the design of the semiconductor device created on the basis of the wafer. The mask alignment marks 80 and 81 or other mask alignment marks may be located between the mask opening 73 and the outer periphery of the secondary mask 70. The mask opening 73 may be located at the mask alignment marks 80 and 81.

  Similar to the secondary mask 70, the primary mask 50 also includes a mask opening and a mask alignment mark. The mask alignment marks 60 and 80 are preferably made of openings. The inner surfaces of the mask alignment marks 60 and 80 are formed as hole inner surfaces. Each mask alignment mark does not have to be an opening, and may have a shape cut out from the outer peripheral side of the mask, for example.

  The camera 90 images the mask alignment mark 60 or 80. The camera 90 can image the surface of the wafer 30 including the wafer alignment mark 40 simultaneously with the imaging of the mask alignment mark. The camera 91 images the mask alignment mark 81. The camera 91 can image other elements in the same manner as the camera 90.

  Cameras 90 and 91 are preferably located on the primary mask side with respect to the wafer. The cameras 90 and 91 are preferably located on the secondary mask side with respect to the primary mask. The camera 91 may also serve as the camera 90. In this case, it is preferable that the camera 90 or the wafer 30 can be moved by a planar moving means.

  In this embodiment, the cameras 90 and 91 recognize the alignment marks of the wafer and the mask, align the positions, and then bond the wafer and the mask or the masks together. If the design of the semiconductor device is possible, a mask may be further provided for the secondary mask.

2. Features of Alignment Method FIGS. 2 and 3 show the features of the alignment method of this embodiment. As shown in FIG. 2, the hole inner surfaces or cross sections of the mask alignment marks 60 and 80 of each mask are tapered. Therefore, as shown in FIG. 3, the inner and outer contours of each mask alignment mark can be clearly recognized.

  As shown in the lower part of FIG. 3, in the primary mask 50, the inner peripheral contour appears at the boundary between the image of the tapered surface 65 and the image of the wafer surface 31. Such an outer peripheral contour appears at the boundary between the image of the tapered surface 65 and the image of the surface 51 of the primary mask.

  In the secondary mask 70, the inner peripheral contour appears at the boundary between the image of the tapered surface 85 and the image of the surface 51 of the primary mask. Such an outer contour appears at the boundary between the image of the tapered surface 85 and the image of the surface 71.

  For example, when the image recognition means binarizes the surface of the primary or secondary mask and each tapered image to detect the boundary, the boundary becomes clear. For this reason, the alignment state can be detected with high accuracy.

  When the alignment mark is observed from the camera 90, the contrast difference between the wafer 30 and the primary mask 50 increases. In addition, the contrast difference between the primary mask 50 and the secondary mask 70 increases. For this reason, each mask alignment mark can be recognized accurately.

  In FIG. 2, when the secondary mask 70 is aligned, the primary mask 50 may already be laminated on the wafer (Example 2). It should be noted that, for those skilled in the art, this figure is a schematic diagram showing the characteristics of the alignment method of this embodiment.

3. Outline of Alignment Method An outline of each step in the alignment method will be described with reference to FIGS. The alignment method of this embodiment includes a multi-layer process, an imaging process, and a confirmation process shown in FIGS.

  In the alignment method of this embodiment, the mask may be a single layer or a plurality of layers. For example, as shown in FIG. 2, a primary mask 50 and a secondary mask 70 may be used. Further, only the primary mask 50 may be used. In this embodiment, the case where only one mask is used will be mainly described. For convenience, such a mask will be referred to as a primary mask 50.

  As shown in FIG. 4, the overlaying process is a process of overlaying a mask, that is, a primary mask 50 on the surface of the wafer 30. The imaging step is a step of imaging the mask alignment marks 60 and 61 and the wafer surface 31 using a camera 90 and a camera 91 as shown in FIG.

  In the confirmation step, the alignment state of the wafer alignment marks 40 and 41 and the mask alignment marks 60 and 61 on the wafer surface 31 is confirmed based on the image obtained in the imaging step.

  In FIG. 5, the wafer alignment mark 40 is not hidden behind the mask alignment mark 60 when viewed from the camera. Further, the centers of the wafer alignment mark 40 and the mask alignment mark 60 substantially coincide with each other.

  If the wafer alignment mark 41 and the mask alignment mark 61 are the same, it can be said that the wafer 30 and the primary mask 50 are aligned. In this case, a laminated body can be formed by bonding the primary mask 50 to the wafer surface 31 (see FIG. 7). The primary mask 50 can be peeled off again after bonding to adjust the position.

  Thereafter, a film is formed directly on the wafer surface 31 (see FIG. 9). The outline of the alignment method is the same in the overlaying process, imaging process, and confirmation process of the secondary mask 70 shown in FIGS. 7 and 8 unless otherwise specified (Example 2).

4). Details of Features of Alignment Method As shown in FIG. 2, after the primary mask 50 is superimposed on the wafer 30 in the multi-layer process, the irradiation light is applied to the wafer 30 and the primary mask 50 from the camera 90 side in the imaging process. 95 enters. In the present embodiment, the irradiation light 95 is preferably incident light that is irradiated from the upper camera 90 toward the lower wafer 30 or the primary mask 50.

  After the secondary mask 70 is superimposed on the wafer 30 and the primary mask 50 in the overlaying process, irradiation light 95 is incident on the primary mask 50 and the secondary mask 70 from the camera 90 side in the imaging process.

  The irradiation light 95 is preferably brighter if there is light in the environment that enters the wafer alignment mark 40 and the mask alignment mark 60 of the primary mask 50 from an unspecified direction. The irradiation light 95 is preferably brighter if there is light in the environment that enters the mask alignment mark 60 and the mask alignment mark 60 of the secondary mask 70 from an unspecified direction.

  Illumination (not shown) on the camera 90 side when viewed from the wafer 30 projects the irradiation light 95. For example, the illumination may be installed near the lens 93 in the camera 90 so as to face the wafer 30 side. In a preferred embodiment, the illumination of the camera 90 projects irradiation light substantially parallel to the optical axis of the lens 93, that is, irradiation light 95 in FIG.

  The irradiation light 95 is incident on the wafer surface 31, the surface 51 of the primary mask 50, and the surface 71 of the secondary mask 70. Surface 51 and surface 71 are on the far side of wafer 30 in each mask.

  A part of the irradiation light 95 is incident on the wafer surface 31 on the side where the wafer 30 is formed. A part of the irradiation light 95 enters the surface 45 of the wafer alignment mark 40. The surface 45 is in contact with the side surface 48 of the wafer alignment mark 40. The surface 45 corresponds to the top surface of the cylindrical wafer alignment mark 40 in FIG. 2 (see FIG. 3). The surface 45 is on the side far from the main body of the wafer 30.

  The wafer alignment mark 40 is positioned on the wafer surface 31 on the side where the wafer 30 is formed. The side surface 48 contacts the wafer surface 31. As shown in FIG. 3, the camera 90 images the wafer surface 31 and the surface 45 as bright surfaces. The camera 90 images the side surface 48 as a shadow.

  As shown in FIG. 2, a part of the irradiation light 95 enters the surface 51 of the primary mask 50 on the side far from the wafer 30. A part of the irradiation light 95 enters the tapered surface 65 of the mask alignment mark 60 of the primary mask 50.

  The tapered surface 65 corresponds to part or all of the hole inner surface of the mask alignment mark 60. The tapered surface 65 faces the side far from the wafer 30 or the opposite side to the wafer 30. In one example, the tapered surface 65 contacts the surface 51 and / or the surface 49. The surface 49 of the primary mask 50 is a surface closer to the wafer 30.

  Part or most of the reflected light 96 reflected from the irradiation light 95 incident on the tapered surface 65 does not become parallel to the optical axis of the lens 93. This is because the tapered surface 65 is not substantially perpendicular to the incident direction of the irradiation light 95. That is, the irradiation light 95 is reflected obliquely at the tapered surface 65. Therefore, the camera 90 does not receive part or most of the reflected light 96.

  As shown in FIG. 3, the taper surface 65 appears dark or black in the image captured by the camera 90. On the other hand, the wafer surface 31 and the surface 51 are bright and reflect the color of the material of the wafer 30 and the primary mask 50.

  The contour of the inner periphery of the taper surface 65, that is, the portion of the taper surface 65 closest to the wafer 30 forms a clear shadow. Further, when the tapered surface 65 is connected to the surface 51 or another surface that is substantially perpendicular to the irradiation light 95, it is desirable that the connecting portion has corners and is not substantially rounded. Thus, the tapered surface 65 is in marked contrast with the surface 51 in the image.

  The contour of the outer periphery of the taper surface 65, that is, the portion of the taper surface 65 farthest from the wafer 30 forms a clear shadow. Thus, the tapered surface 65 is in marked contrast with the wafer surface 31 in the image.

  Such an image of the tapered surface 65 can be easily distinguished from the wafer surface 31 or the surface 51 by means for automatically recognizing the image by a program. Therefore, the camera 90 or the image recognition means can recognize the mask alignment mark 60 with high accuracy.

  In the present embodiment, the tapered surface 65 is a truncated cone-shaped slope. The shape of the tapered surface 65 is not particularly limited. For example, the cross-sectional shape in the drawing may protrude toward the hole of the mask alignment mark 60, or conversely, may be recessed toward the inside of the primary mask 50.

  As shown in FIG. 2, a part of the irradiation light 95 is incident on the surface 71 of the secondary mask 70 on the side far from the wafer 30. A part of the irradiation light 95 enters the tapered surface 85 of the mask alignment mark 80 of the secondary mask 70.

  The tapered surface 85 corresponds to part or all of the hole inner surface of the mask alignment mark 80. The tapered surface 85 faces the side far from the wafer 30 or the opposite side to the wafer 30. The tapered surface 85 may contact the surface 71 and / or the surface 69. A surface 69 of the secondary mask 70 is a surface closer to the wafer 30.

  Part or most of the reflected reflected light 97 of the irradiation light 95 incident on the tapered surface 85 is not parallel to the optical axis of the lens 93. This is because the tapered surface 85 is not substantially perpendicular to the incident direction of the irradiation light 95. That is, the irradiation light 95 is reflected obliquely on the tapered surface 85. Therefore, the camera 90 does not receive a part or most of the reflected light 97.

  As shown in FIG. 3, the tapered surface 85 appears dark or black in the image captured by the camera 90. On the other hand, the surface 51 and the surface 71 of the primary mask 50 are bright and reflect the color of the material of the primary mask 50 and the secondary mask 70.

  The contour of the inner periphery of the tapered surface 85, that is, the portion of the tapered surface 85 closest to the wafer 30 forms a clear shadow. Further, when the tapered surface 85 is connected to the surface 71 or another surface that is substantially perpendicular to the irradiation light 95, it is desirable that the connection portion has corners and is not substantially rounded. In such a case, the tapered surface 85 is in marked contrast with the surface 71 in the image.

  The outline of the outer periphery of the tapered surface 85, that is, the portion of the tapered surface 85 farthest from the wafer 30 forms a clear shadow. Thus, the tapered surface 85 is in marked contrast with the surface 51 or surface 71 in the image.

  Such an image of the tapered surface 85 can be easily distinguished from the surface 51 or the surface 71 by means for automatically recognizing the image by a program. Therefore, the camera 90 or the image recognition means can recognize the mask alignment mark 80 with high accuracy.

  In the present embodiment, the tapered surface 85 is a truncated cone-shaped slope. The shape of the tapered surface 85 is not particularly limited. For example, the cross-sectional shape in the drawing may protrude toward the hole of the mask alignment mark 80, or conversely, may be recessed toward the inside of the secondary mask 70.

  In the confirmation step, it is confirmed that the overlay of the wafer and the mask in the overlaying step forms an appropriate alignment state from the images of the alignment marks obtained in the imaging step. Details of the confirmation process will be described in detail in Examples.

1. Multilayer Step As shown in FIG. 4, a primary mask 50 is superimposed on the wafer 30 in the multilayer step. The superposition is performed by bringing the primary mask 50 serving as the first mask closer to a predetermined distance above the wafer 30 in the drawing.

  When superimposing, the wafer surface 31 and the surface 49 do not need to contact each other. This is because the wafer 30 or the primary mask 50 may move in a plane substantially parallel to the wafer surface 31 in the adjustment process described later.

  The primary mask 50 includes mask alignment marks 60 and 61. The mask alignment marks 60 and 61 have a circular inner peripheral contour. Wafer alignment marks 40 and 41 also have a circular outline.

  There are a plurality of combinations of wafer alignment marks and mask alignment marks. Mask alignment mark 60 is combined with wafer alignment mark 40. The mask alignment mark 61 is combined with the wafer alignment mark 41.

  As shown in FIG. 4, the wafer 30 has one or a plurality of film formation scheduled positions 35. The primary mask 50 has one or more mask openings 53. The mask opening 53 is a mask for forming a semiconductor pattern directly or indirectly on the wafer 30. In the case of a normal design mode of a semiconductor device, a polygonal pattern such as a quadrangle often appears as the pattern of the deposition position 35 or the mask opening 53.

  In such a case, in the wafer 30 or the primary mask 50, there are few of the similar shapes in many patterns around the circular alignment mark. For this reason, it is easy for the camera to recognize a circular alignment mark as a unique shape.

  Further, since the mask alignment marks 60 and 61 have a circular opening, the camera can see the wafer surface 31 widely. For this reason, the possibility that the wafer alignment marks 40 and 41 cannot be observed from the cameras 90 and 91 by being hidden behind the primary mask 50 is small.

  The mask alignment marks 60 and 61 further have a hole inner surface. As shown in FIG. 4, when an appropriate alignment state of the wafer 30 and the primary mask 50 is realized, the mask opening 53 faces the front surface of the film formation scheduled position 35.

  FIG. 5 shows in detail the area delimited by the one-dot chain line in FIG. Thereafter, the same process as the mask alignment mark 60 proceeds in the mask alignment mark 61. The hole inner surface of the mask alignment mark 60 has a tapered surface 65. When the primary mask 50 is overlaid, the tapered surface 65 preferably faces away from the wafer 30 or opposite to the wafer 30.

2. Imaging Step As shown in FIG. 5, in the imaging step, the camera 90 images the mask alignment mark 60 with the wafer 30 and the mask overlapped. Further, the camera 90 images the wafer surface 31 observed through the hole of the mask alignment mark 60. The camera 90 preferably images both at the same time.

  In the imaging step, it is preferable that light is projected onto the tapered surface 65 side. The light is preferably the irradiation light 95 described above (see FIG. 2). From the tapered surface 65 side, the camera 90 images the mask alignment mark 60 and the wafer surface 31 as described above.

3. Confirmation Step In the confirmation step, the image recognition means confirms the alignment state of the wafer alignment mark 40 and the mask alignment mark 60 on the wafer surface 31 based on the image obtained in the imaging step.

  The image recognition means is preferably a computer. Such a computer operates in accordance with a program for realizing a predetermined image analysis algorithm. Moreover, you may confirm visually by an operator.

  As shown in FIG. 6, the alignment state may be that the mask alignment mark 60 is aligned with the wafer alignment mark 40 when the inner surface of the hole of the mask alignment mark 60 is outside the wafer alignment mark 40. Good.

  In a preferred embodiment, as shown in FIG. 6, the centers of the shadows of the side surface 48 and the tapered surface 65 are substantially coincident with each other. Further, whether or not the mask alignment mark 60 is aligned with the wafer alignment mark 40 can also be confirmed by the following method.

  A method for confirming on a computer using image software will be described below. First, a circle formed by the outer shape of the wafer alignment mark 40 is recognized by an image. The criterion for such recognition is whether or not the radius, roundness, contrast, etc. of the circle fall within a predetermined standard. The contrast is, for example, the contrast that the surface 45 forms with the wafer surface 31. After recognizing the circle, the center coordinates of the circle are calculated by fitting the circle. Similarly, the center coordinates of the mask alignment mark 60 are calculated. Next, the difference between the center coordinates of the circle of the wafer alignment mark 40 and the center coordinates of the mask alignment mark 60, that is, whether or not the amount of deviation between the center positions falls within a predetermined standard is calculated. If the amount of deviation is within a predetermined standard, it can be determined that the position of the mask alignment mark 60 is aligned with the wafer alignment mark 40.

4). Adjustment Step If the position of the mask alignment marks 60, 61 is not aligned with the wafer alignment marks 40, 41 as a result of the confirmation step, the wafer 30 and the primary mask 50 are aligned in the adjustment step. The alignment may be performed automatically based on the image obtained in the imaging process, or may be performed manually.

  That is, in this embodiment, two marks are provided on the wafer surface 31 or the surface 51. Therefore, it is preferable to introduce such a relative positional relationship into an algorithm for automatic alignment by the camera 90 and a robot (not shown). With this method, it is possible to perform accurate alignment with respect to the angle.

  For example, even if the wafer 30 or the primary mask 50 is moved so that the vector formed by the center of the wafer alignment mark 40 and the center of the wafer alignment mark 41 matches the vector formed by the center of the mask alignment mark 60 and the center of the mask alignment mark 61. Good.

  For example, the primary mask 50 may rotate on a plane parallel to the wafer surface 31 and linearly move on the same plane. The linear movement can be replaced with a two-stage linear movement in the biaxial direction on the same plane. The apparatus for holding the primary mask 50 and the wafer 30 preferably realizes such movement.

  In the alignment state, it is preferable to repeat the imaging process, the confirmation process, and the adjustment process until the mask alignment mark 60 is aligned with the wafer alignment mark 40. As shown in FIG. 4, when an appropriate alignment state of the wafer 30 and the primary mask 50 is realized, the mask opening 53 faces the front surface of the film formation scheduled position 35.

  The deviation between the mask opening 53 and the expected film formation position 35, that is, the deviation of the mask position is extremely small compared to the comparative example described later. That is, the alignment method of this embodiment improves the mask position accuracy between the wafer 30 and the primary mask 50.

5. Lamination process If the mask alignment mark 60 is aligned with the wafer alignment mark 40 as a result of the confirmation process, the process proceeds to the lamination process. In the stacking process, the primary mask 50 is bonded to the wafer 30 (see FIG. 7). In this embodiment, a magnet or a plate incorporating a magnet is provided on the opposite side of the wafer 30 from the primary mask 50. Such a magnet can attach the primary mask 50 to the wafer 30 by its magnetic force. For this reason, the wafer 30 and the primary mask 50 can maintain an accurate alignment state. Note that the external force of the alignment apparatus or gravity may be used as the force for attaching the primary mask 50 to the wafer 30.

1. Primary Mask Alignment Method An alignment method is performed in the same manner as in the first embodiment. As shown in FIG. 4, a primary mask 50 is superimposed on the wafer surface 31 in the primary layering step. As shown in FIG. 5, in the primary imaging step, the mask alignment mark 60 and the wafer surface 31 are imaged.

  As shown in FIG. 6, in the primary confirmation process, the primary alignment state of the wafer alignment mark 40 and the mask alignment mark 60 is confirmed. As shown in FIG. 7, a primary mask 50 is bonded to the wafer 30 in the primary lamination step. A stacked body 33 including the wafer 30 and the primary mask 50 is formed. When the alignment state is defective, the primary adjustment step may be performed in the same manner as the adjustment step.

2. Secondary Multilayer Process The secondary mask alignment method will be described below. As shown in FIG. 7, a secondary mask 70 is superimposed on the primary mask 50 in the secondary layering process. Specifically, as shown in FIG. 8, the surface 69 of the secondary mask 70 is superimposed on the surface 51 corresponding to the primary mask side surface of the stacked body 33. The superposition is performed by bringing the secondary mask 70 serving as the second mask close to a predetermined distance above the primary mask 50 in the drawing.

  When superimposing, the surface 51 and the surface 69 do not need to contact. This is because, in the secondary adjustment process described later, the stacked body 33 or the secondary mask 70 may move in a plane substantially parallel to the surface 51.

  The secondary mask 70 includes mask alignment marks 80 and 81. The mask alignment marks 80 and 81 have a circular inner peripheral contour. The primary and secondary overlay processes produce a plurality of wafer alignment marks and combinations of primary and secondary mask alignment marks.

  The mask alignment mark 80 is combined with the mask alignment mark 60 and the wafer alignment mark 40. The mask alignment mark 81 is combined with the mask alignment mark 61 and the wafer alignment mark 41.

  In the case of an ordinary semiconductor device design mode, the mask opening 53 or the mask opening 73 often has a polygonal pattern such as a quadrangle. Therefore, there are few patterns having a shape similar to a circular alignment mark in many patterns around. For this reason, it is easy for the camera to recognize a circular alignment mark as a unique shape.

  Further, since the mask alignment marks 80 and 81 have circular openings, the camera can see the surface 51 widely. For this reason, the mask alignment marks 60 and 61 are hidden behind the secondary mask 70, so that the possibility of being unable to observe from the cameras 90 and 91 is small.

  Mask alignment marks 80 and 81 have hole inner surfaces. As shown in FIG. 7, when an appropriate alignment state of the primary mask 50 and the secondary mask 70 is realized, the mask opening 73 faces the front of the mask opening 53.

  FIG. 8 shows in detail the region delimited by the one-dot chain line in FIG. Thereafter, the same process as the mask alignment mark 80 proceeds in the mask alignment mark 81. The hole inner surface of the mask alignment mark 80 has a tapered surface 85. When the secondary mask 70 is overlaid, the tapered surface 85 is preferably directed to the side far from the wafer 30 or the opposite side to the wafer 30.

3. Secondary Imaging Step As shown in FIG. 8, in the secondary imaging step, the camera 90 images the mask alignment mark 80 in a state where the primary mask 50 and the mask are overlapped. Furthermore, the camera 90 images the surface 51 observed through the hole of the mask alignment mark 80. The camera 90 preferably images both at the same time. The camera 90 may not be the same as the camera that performed the primary imaging process.

  In the secondary imaging process, it is preferable to project light onto the tapered surface 85 side. The light is preferably the irradiation light 95 described above (see FIG. 2). From the tapered surface 85 side, the camera 90 images the mask alignment mark 80 and the surface 51 as described above.

  The irradiation light 95 in the secondary imaging process may not be the light projected by the same illumination as the irradiation light 95 in the primary imaging process. Further, the irradiation light 95 in the secondary imaging step may have a different intensity and wavelength spectrum from the irradiation light 95 in the primary imaging step.

4). Secondary confirmation process In the secondary confirmation process, the image recognition means confirms the alignment state of the hole inner surface of the mask alignment mark 60 on the surface 51 and the mask alignment mark 80 based on the image obtained in the secondary imaging process. Such image recognition means may be different from the image recognition means in the primary confirmation step. An operator may confirm it visually.

  As shown in FIG. 8, in the primary mask 50, the surface 51 opposite to the surface 49 (see FIG. 5) that directly or indirectly covers the wafer 30 may not be smoothly connected to the tapered surface 65. preferable.

  In this case, when the image recognition unit binarizes the image of the surface 51 and the tapered surface 65 and detects the boundary, the boundary becomes clear. For this reason, the alignment state can be detected with high accuracy.

  This is because the boundary between the tapered surface 65 and the surface 51 becomes clear as shown in FIG. By clearly seeing such a boundary, it can be easily confirmed that the tapered surface 65 and the tapered surface 85 do not overlap.

  As shown in FIG. 8, in this embodiment, the inner peripheral contour of the hole inner surface of the mask alignment mark 80 of the secondary mask 70 is larger than the outer peripheral contour of the hole inner surface of the mask alignment mark 60 of the primary mask 50.

  As shown in FIG. 3, in the secondary alignment state, when the hole inner surface of the mask alignment mark 80 is outside the hole inner surface of the mask alignment mark 60, the mask alignment mark 80 is aligned with the mask alignment mark 60. It is good as it is.

  In the preferred embodiment, as shown in FIG. 3, the centers of the shadow of the tapered surface 65 and the shadow of the tapered surface 85 are substantially coincident with each other. Further, whether or not the mask alignment mark 80 is aligned with the mask alignment mark 60 can also be confirmed by the following method.

  A method for confirming on a computer using image software will be described below. First, a circle formed by the outer shape of the mask alignment mark 60 is recognized by an image. The criterion for such recognition is whether or not the radius, roundness, contrast, etc. of the circle fall within a predetermined standard. The contrast is, for example, the contrast that the tapered surface 65 forms with the surface 51. After recognizing the circle, the center coordinates of the circle are calculated by fitting the circle. Similarly, the center coordinates of the mask alignment mark 80 are calculated. Next, it is calculated whether or not the difference between the center coordinates of the mask alignment mark 60 and the center coordinates of the mask alignment mark 80, that is, the amount of deviation between the center positions falls within a predetermined standard. If the amount of deviation is within a predetermined standard, it can be determined that the position of the mask alignment mark 80 is aligned with the mask alignment mark 60.

5. Secondary adjustment process When the alignment of the mask alignment marks 80 and 81 with respect to the mask alignment marks 60 and 61 is not aligned as a result of the secondary confirmation process, the alignment of the stacked body 33 and the secondary mask 70 is performed in the secondary adjustment process. I do. The alignment may be performed automatically based on the image obtained in the secondary imaging process, or may be performed manually.

  That is, in this embodiment, two marks are provided on the surface 51 or the surface 71. Therefore, it is preferable to introduce such a relative positional relationship into an algorithm for automatic alignment by the camera 90 and a robot (not shown). With this method, it is possible to perform accurate alignment with respect to the angle.

  For example, the stacked body 33 or the secondary mask 70 so that the vector formed by the center of the hole inner surface of the mask alignment mark 60 and the center of the mask alignment mark 61 matches the vector formed by the center of the mask alignment mark 80 and the center of the mask alignment mark 81. May be moved.

  For example, the secondary mask 70 may rotate and move on a plane parallel to the surface 51 and linearly move in the same plane. The linear movement can be replaced with two-stage linear movement in the biaxial direction on the same plane. It is preferable that the apparatus for holding the secondary mask 70 and the primary mask 50 achieve such movement.

  In the alignment state, it is preferable to repeat the secondary imaging process, the secondary confirmation process, and the secondary adjustment process until the mask alignment mark 80 is aligned with the hole inner surface of the mask alignment mark 60. As shown in FIG. 7, when an appropriate alignment state of the primary mask 50 and the secondary mask 70 is realized, the mask opening 73 faces the front of the mask opening 53.

  The displacement between the mask opening 73 and the mask opening 53, that is, the displacement of the mask position is extremely small compared to the comparative example described later. That is, the alignment method of this embodiment improves the mask position accuracy between the primary mask 50 and the secondary mask 70. For this reason, the alignment method of the present embodiment improves the mask position accuracy between the wafer 30 and the secondary mask 70.

5. Secondary Laminating Step As a result of the secondary confirmation step, if the position of the mask alignment mark 80 with respect to the hole inner surface of the mask alignment mark 60 is aligned, the process proceeds to the secondary laminating step. In the secondary stacking process, the secondary mask 70 is bonded to the stacked body 33 or the primary mask 50. In this embodiment, a magnet or a plate incorporating a magnet is provided on the opposite side of the wafer 30 from the secondary mask 70. Such a magnet can attach the secondary mask 70 to the primary mask 50 by its magnetic force. For this reason, the wafer 30, the primary mask 50, and the secondary mask 70 can maintain an accurate alignment state. Note that as the force for attaching the secondary mask 70 to the primary mask 50, an external force of the alignment apparatus or gravity may be used.

  The stacked body 33 may be formed by bonding the primary mask 50 to the wafer 30 directly or indirectly. For example, the secondary mask 70 that is the second mask may be regarded as the primary mask 50 again, and the third mask may be bonded in the same manner as the secondary mask 70 described above. In such a case, the third mask can be aligned and bonded on the laminate including the laminate 33 and the secondary mask 70.

6). Film Formation After each mask is attached to the wafer 30 in accordance with the alignment method described above, film formation is performed. The film formation is performed by, for example, a mask vapor deposition film forming method or a mask sputtering film forming method. A film is formed directly on the wafer surface 31 through the mask opening 53 or through the mask opening 73 and the mask opening 53. After film formation, the secondary mask 70 and the primary mask 50 are peeled off sequentially or simultaneously.

  FIG. 9 shows the result of film formation. The film 100 is a film generated as a result of the above film formation. The film 100 is formed at the place where the mask opening 53 of the removed primary mask 50 was present. For this reason, the film 100 faces the deposition position 35.

  The mask opening 73 of the secondary mask 70 is preferably larger than the mask opening 53 of the primary mask 50. In such a case, the shape of the pattern of the film 100 formed by the primary mask 50 can be prevented from becoming different from a predetermined one by the mask opening 73.

  As shown in FIG. 9, the deviation between the deposition position 35 and the film 100, that is, the deviation of the deposition position is very small compared to the comparative example described later (see FIG. 15). This is because each mask can be placed on the wafer with high accuracy.

7). Creation of Semiconductor Device A semiconductor device can be formed using the alignment method or wafer of the above embodiment. The semiconductor device is, for example, an IGBT element. The defect rate of the semiconductor device is reduced by the alignment method of this embodiment.

9. Comparative Example The effect of the present example will be described using a comparative example shown in FIGS. The alignment method of this comparative example is the same as that of Example 2 except for the following differences. For this reason, a comparative example will be described focusing on the differences. Moreover, the same code | symbol is attached | subjected to an equivalent component and the description is abbreviate | omitted.

  As shown in FIG. 10, the primary mask 10 is overlaid on the wafer 30. The surface 29 of the primary mask 10 covers the wafer surface 31 to be deposited. The primary mask 10 includes a mask alignment mark 15.

  The mask alignment mark 15 has a hole inner surface 18. The hole inner surface 18 does not have a tapered surface corresponding to the above-described tapered surface 65 but has a non-tapered surface. The illumination provided in the camera 90 projects irradiation light onto the surface 11 of the primary mask 10 and the wafer surface 31.

  FIG. 11 shows the result of imaging the mask alignment mark 15 with the camera 90. The contrast difference between the surface 45 of the wafer alignment mark 40 and the surface 11 of the primary mask 50 is small. This tendency is particularly remarkable when the two colors are similar. Further, since the hole inner surface 18 is substantially parallel to the optical axis of the lens 93, the contour of the mask alignment mark 15 is not clear.

  For this reason, in this comparative example, the camera 90 cannot recognize the wafer alignment mark 40 and the mask alignment mark 15 with higher accuracy than in the first and second embodiments. For this reason, the positional accuracy of the wafer 30 and the primary mask 10 deteriorates.

  As shown in FIG. 12, the secondary mask 20 is overlaid on the laminate including the wafer 30 and the primary mask 10. The surface 19 of the secondary mask 20 covers the surface 11 on the side farther from the wafer 30 of the primary mask 10. The secondary mask 20 includes a mask alignment mark 25.

  The mask alignment mark 25 has a hole inner surface 28. The hole inner surface 28 does not have a tapered surface corresponding to the above-described tapered surface 85 but has a non-tapered surface. The illumination provided in the camera 90 projects irradiation light onto the surface 21 and the surface 11 of the secondary mask 20.

  FIG. 13 shows the result of imaging the mask alignment mark 25 with the camera 90. The difference in contrast between the surface 11 and the surface 21 is small. This tendency is particularly remarkable when the two colors are similar. Further, since the hole inner surface 28 is substantially parallel to the optical axis of the lens 93, the contour of the mask alignment mark 25 is not clear.

  For this reason, in this comparative example, the camera 90 cannot recognize the mask alignment mark 15 and the mask alignment mark 25 with high accuracy as compared with the second embodiment. For this reason, the positional accuracy of the primary mask 10 and the secondary mask 20 deteriorates.

  FIG. 14 shows a state in which each mask and the wafer 30 are bonded together. Since the mask alignment mark recognition accuracy is poor, the bonding position is shifted. The mask opening 13 and the planned deposition position 35 are shifted from each other. The mask opening 23 and the mask opening 13 are shifted from each other.

  FIG. 15 shows the result of film formation. The film 99 is a film generated as a result of film formation. The film 99 is formed at the place where the mask opening 13 of the removed primary mask 10 was present. For this reason, the film 99 formed by film formation after alignment according to this comparative example may be displaced from the film formation planned position 35. Such a semiconductor device may have a high defect rate.

  On the other hand, according to the alignment methods of the first and second embodiments, the wafer and the mask can be aligned with high positional accuracy. For this reason, highly accurate patterning film formation can be performed in mask film formation.

  Further, even when a plurality of masks are overlapped and aligned, each mask can be bonded onto the wafer with high positional accuracy. Therefore, each mask can be placed on the wafer with high accuracy.

  The alignment method of the following examples is the same as that of Example 1 or 2 except for the following differences. For this reason, the following examples will be described focusing on the differences. Moreover, the same code | symbol is attached | subjected to an equivalent component and the description is abbreviate | omitted.

  The upper part of FIG. 16 shows a cross section of a combination of alignment marks. The lower part of FIG. 16 shows an image of each alignment mark imaged from the camera 90 in a plan view. As shown in FIG. 16, the wafer 30 has a wafer alignment mark 39 instead of the wafer alignment mark 40.

  The outer periphery of the side surface 47 of the wafer alignment mark 39 and the surface 44 corresponding to the top surface of the wafer alignment mark 39 in the drawing forms the contour of the wafer alignment mark 39. Such a contour is non-circular. In this embodiment, the contour is a square.

  The primary mask 50 has a mask alignment mark 62 instead of the mask alignment mark 60. The hole inner surface of the mask alignment mark 62 has a tapered surface 66. The inner peripheral contour of the hole inner surface of the mask alignment mark 62 is non-circular. In the present embodiment, the inner peripheral contour is a square. The outer peripheral contour of the tapered surface 66 is non-circular. In this embodiment, the outer peripheral contour is a square.

  The secondary mask 70 has a mask alignment mark 82 instead of the mask alignment mark 80. The hole inner surface of the mask alignment mark 82 has a tapered surface 86. The inner peripheral contour of the hole inner surface of the mask alignment mark 82 is non-circular. In the present embodiment, the inner peripheral contour is a square.

  As in the first and second embodiments, even in the case of a combination of round marks that form concentric circles, even if the mask rotates and the orientation is shifted from the wafer, the combination cannot be detected. Here, the round mark refers to the wafer alignment mark 40, the mask alignment mark 60, and the mask alignment mark 80.

  When there is only one combination of wafer alignment mark and mask alignment mark, a non-circular mark is preferable. A non-circular mark is also preferred when there is only one mask alignment mark combination of the primary mask and the secondary mask.

  On the other hand, when circular marks are employed as in the first and second embodiments, the alignment accuracy in the angular direction may deteriorate with only one combination. Further, when the non-circular mark is a square, the two sides form a right angle, which is convenient for detecting a vertical / horizontal shift. In particular, it is easy to see when people are looking at each other.

  A single square alignment mark makes alignment possible. Therefore, the number of alignment marks on the wafer and mask can be reduced. This facilitates the processing of the wafer and the mask.

  The upper part of FIG. 17 shows a cross section of a combination of alignment marks. The lower part of FIG. 17 shows an image of each alignment mark imaged from the camera 90 in a plan view. As shown in FIG. 17, the wafer 30 has a wafer alignment mark 38 instead of the wafer alignment mark 40.

  The outer periphery of the side surface 46 of the wafer alignment mark 38 and the surface 43 corresponding to the top surface of the wafer alignment mark 39 in the drawing forms the contour of the wafer alignment mark 38. Such a contour is non-circular. In this embodiment, the contour has a cross shape.

  The primary mask 50 has a mask alignment mark 63 instead of the mask alignment mark 60. The hole inner surface of the mask alignment mark 63 has a tapered surface 67. The inner peripheral contour of the hole inner surface of the mask alignment mark 63 is non-circular. In this embodiment, the inner peripheral contour is a cross shape. The outer peripheral contour of the tapered surface 67 is non-circular. In this embodiment, the outer contour is a cross shape.

  The secondary mask 70 has a mask alignment mark 83 instead of the mask alignment mark 80. The hole inner surface of the mask alignment mark 83 has a tapered surface 87. The inner peripheral contour of the hole inner surface of the mask alignment mark 83 is non-circular. In this embodiment, the inner peripheral contour is a cross shape.

  The cross-shaped alignment mark, like the square alignment mark of the third embodiment, makes it possible to perform alignment with one. Therefore, the number of alignment marks on the wafer and mask can be reduced. This facilitates the processing of the wafer and the mask.

  As shown in FIG. 18, the primary mask 50 has a mask alignment mark 64 instead of the mask alignment mark 60. The hole inner surface of the mask alignment mark 64 has a tapered surface 68. The secondary mask 70 has a mask alignment mark 84 instead of the mask alignment mark 80. The hole inner surface of the mask alignment mark 84 has a tapered surface 88.

  The angle 59 formed by the taper surface 68 with the direction perpendicular to the wafer surface 31 is different from the angle 79 formed by the taper surface 88 with the direction perpendicular to the wafer surface 31. On the other hand, in the first and second embodiments, the angles formed by the tapered surfaces are the same. As shown in FIG. 18, the angle 59 is smaller than the angle 79. Angle 59 may be greater than angle 79.

  As shown in the lower part of FIG. 18, the angle between the tapered surfaces differs between the masks, so that the shadow of the tapered surface 68 and the shadow of the tapered surface 88 captured by the camera 90 have different thicknesses. In this embodiment, the shadow of the tapered surface 68 is thinner than the shadow of the tapered surface 88. For this reason, the image recognition means can distinguish a primary mask and a secondary mask easily. Although the primary mask 50 and the secondary mask 70 have the same thickness, they may have different thicknesses.

  As shown in FIG. 19, the primary mask 50 has a mask alignment mark 55 instead of the mask alignment mark 60. The inner surface of the mask alignment mark 55 or the inner surface of the hole has a non-tapered surface 57 in addition to the tapered surface 65. The non-tapered surface 57 is connected to the surface 49. Further, the non-tapered surface 57 may be connected to the tapered surface 65. As described above, the surface 49 is a surface that covers the wafer 30 in the primary mask 50.

  Such a tapered shape prevents the primary mask 50 from being strongly bonded to the wafer 30 after film formation. This is explained as follows. That is, when the film is formed by mask vapor deposition film formation or mask sputtering film formation, the film is formed after the primary mask 50 is attached to the wafer.

  The film is formed on the entire exposed surface including the wafer surface 31 and the surface 51 including the primary mask 50. Therefore, the film is formed not only on the wafer 30 but also in the mask alignment mark 60 on the primary mask 50. This is because the deposited particles fall from above in FIG. 19 without specifying the position.

  Further, since the direction in which the deposited particles fall may be oblique, the deposited film is also bonded to the inner surface of the hole. Therefore, the primary mask 50 and the wafer 30 may be bonded by the film generated in the alignment mark.

  For example, consider the case where the hole inner surface of the mask has a tapered shape like the mask alignment mark 60 of the first embodiment as shown in FIG. In this case, if the film is formed after the mask 60 is bonded to the wafer 30, the film may be bonded to the inner surface of the hole relatively firmly.

  This is because the end of the mask alignment mark 60 on the side closer to the wafer 30 of the mask alignment mark 60 contacts the wafer surface 31 after bonding. In such a case, it is difficult to remove the primary mask 50 from the wafer 30.

  On the other hand, if the inner surface of the hole has a non-tapered shape as in the present embodiment, the films are difficult to bond and are likely to break. For this reason, the coupling between the primary mask 50 and the wafer 30 can be prevented.

  As shown in FIG. 20, the primary mask 50 has a mask alignment mark 56 instead of the mask alignment mark 60. The inner surface of the mask alignment mark 56 or the inner surface of the hole has a reverse tapered surface 58 in addition to the tapered surface 65. The reverse tapered surface 58 is connected to the surface 49. Further, the reverse tapered surface 58 may be connected to the tapered surface 65.

  Such a tapered shape prevents the primary mask 50 from being strongly bonded to the wafer 30 after film formation. For this reason, the coupling between the primary mask 50 and the wafer 30 can be prevented. The reason is the same as in the sixth embodiment.

  The present invention is not limited to the above-described embodiments or examples, and can be appropriately changed without departing from the spirit of the present invention. For example, in the above, after the alignment method is performed, the primary mask is bonded to the wafer, and then the alignment method is performed again to bond the secondary mask to the primary mask.

  In another aspect, after performing the alignment method, the secondary mask may be bonded to the primary mask, and then the alignment method may be performed again to bond the primary mask to the wafer. In another aspect, the wafer, the primary mask, and the secondary mask may be bonded together after performing alignment of the primary mask and the secondary mask.

  In Example 6, in the combination of the mask alignment marks of the primary and secondary masks, the angles formed by the taper surfaces of the mask alignment marks and the direction perpendicular to the wafer surface were different.

  Similarly, in the first and second embodiments, the angles of the tapered surfaces of the hole inner surfaces of the mask alignment marks 60 and 61 shown in FIG. 4 may be different from each other. In the second embodiment, the angles of the tapered surfaces of the hole inner surfaces of the mask alignment marks 80 and 81 shown in FIG. 7 may be different from each other.

  In such a case, the angle formed by the tapered surface is different between the mask alignment marks in the same mask. Accordingly, the shadows of the tapered surfaces captured by the cameras 90 and 91 have different thicknesses. Therefore, the image recognition means can easily distinguish each mask alignment mark in the same mask.

  Although the primary mask 50 and the secondary mask 70 have the same thickness, they may have different thicknesses. In such a case, the shadows of the tapered surfaces captured by the cameras 90 and 91 have different thicknesses. Therefore, the image recognition means can easily distinguish each mask alignment mark in the same mask.

DESCRIPTION OF SYMBOLS 10 Primary mask 11 Surface 13 Mask opening 15 Mask alignment mark 18 Hole inner surface 19 Surface 20 Secondary mask 21 Surface 23 Mask opening 25 Mask alignment mark 28 Hole inner surface 29 Surface 30 Wafer 31 Wafer surface 33 Laminated body 35 Deposition position 38- 41 Wafer alignment mark 43-45 Surface 46-48 Side surface 49 Surface 50 Primary mask 51 Surface 53 Mask opening 55-56 Mask alignment mark 57 Non-tapered surface 58 Reverse taper surface 59 Angle 60-64 Mask alignment mark 65-68 Tapered surface 69 Surface 70 Secondary mask 71 Surface 73 Mask opening 79 Angle 80 to 84 Mask alignment mark 85 to 88 Tapered surface 90 to 91 Camera 93 Lens 95 Irradiation light 96 to 97 Reflected light 99 to 100 Film

Claims (3)

In an alignment method performed using a mask including a mask alignment mark having a hole inner surface including a tapered surface ,
Using a plurality of masks having different taper angles of the tapered surface,
For each mask,
So as to face opposite the tapered surface provided in the said hole inner surface to the wafer, a layer step of overlaying the mask on the wafer surface,
An imaging step of imaging the wafer alignment observed through the mask alignment mark and the hole of the mask alignment mark in a state where the wafer and the mask are overlaid,
A confirmation step for confirming the alignment state of the wafer alignment mark and the mask alignment mark on the wafer surface based on the image obtained in the imaging step;
As a result of the confirmation step, if the position of the mask alignment mark with respect to the wafer alignment mark is not aligned, an adjustment step for aligning the wafer and the mask;
Alignment method to carry out . In an alignment method performed using a mask including a mask alignment mark having a hole inner surface including a tapered surface and a non-tapered surface connected to a wafer side surface,
An overlaying step of superimposing the mask on the wafer surface such that the tapered surface of the hole inner surface faces the opposite side of the wafer;
An imaging step of imaging the wafer alignment observed through the mask alignment mark and the hole of the mask alignment mark in a state where the wafer and the mask are overlaid,
A confirmation step for confirming the alignment state of the wafer alignment mark and the mask alignment mark on the wafer surface based on the image obtained in the imaging step;
As a result of the confirmation step, if the position of the mask alignment mark with respect to the wafer alignment mark is not aligned, an adjustment step for aligning the wafer and the mask;
An alignment method comprising: In the imaging step, light is projected to the tapered surface side,
From the tapered surface side, the camera images the mask alignment mark and the wafer surface.
The alignment method according to claim 1 or 2 .

Images