Photomask, method for manufacturing a semiconductor device and semiconductor device
Patent Information
- Authority / Receiving Office
- EP · EP
- Patent Type
- Applications
- Current Assignee / Owner
- Filing Date
- 2024-04-24
- Publication Date
- 2026-03-18
AI Technical Summary
Current photolithographic methods face challenges in accurately monitoring and ensuring alignment between adjacent step fields during the manufacturing of semiconductor devices, which is crucial for the production of large semiconductor devices with arrays of identical components.
A photomask with specific comb-patterned alignment marks is used in a photolithography stepper, featuring first and second alignment marks with distinct line orientations and spacings, allowing for precise monitoring of alignment accuracy by determining differences in edge distances between adjacent comb patterns.
This approach enables precise alignment monitoring and detection of misalignment between step fields, enhancing the accuracy and reliability of semiconductor device manufacturing by utilizing the photomask's comb patterns to assess alignment differences.
Smart Images
Figure EP2024061296_14112024_PF_FP_ABST
Abstract
Description
[0001] PHOTOMASK, METHOD OF MANUFACTURING A SEMICONDUCTOR DEVICE AND SEMICONDUCTOR DEVICE
[0002] The present disclosure relates to a photomask, a method for manufacturing a semiconductor device and a semiconductor device.
[0003] During the manufacture of semiconductor device, elements of the semiconductor device are patterned using photolithographic methods. According to concepts, a photomask including a specific pattern may be employed in a photolithography stepper. In such a photolithography stepper, the pattern of the photomask is replicated in adjacent step fields. Photolithographic steppers may be useful for manufacturing large size semiconductor device comprising an array of identical components.
[0004] Concepts are being developed, which allow monitoring the alignment between adjacent step fields.
[0005] It is an object of the present invention to provide an improved photomask, an improved method for manufacturing a semiconductor device and an improved semiconductor device.
[0006] According to embodiments, the above object is achieved by the claimed matter according to the independent claims. Further developments are defined in the dependent claims.
[0007] Embodiments relate to a photomask for use in a photolithography stepper. The photomask comprises a step field. The step field comprises a first alignment mark arranged in a first edge portion of the step field. The first alignment mark defines a comb pattern comprising a first line and a plurality of parallel second lines between the first line and a first boundary of the step field in a first direction, a distance between the first line and the first boundary being smaller in the first direction than in a second direction opposite to the first direction. The first line runs parallel to the first boundary, and the second lines run perpendicular to the first boundary, the second lines being connected to the first line. The first and second lines may be made of a transparent or an opaque material.
[0008] According to embodiments, the second lines of the first alignment mark may be arranged at a constant distance.
[0009] According to further embodiments, at least two second lines of the first alignment mark may be arranged at a distance that is different from a distance between other two second lines.
[0010] The step field may further comprise a second alignment mark in a second edge portion different from the first edge portion, the second alignment mark comprising a comb pattern comprising a first line and at least one second line between the first line and a second boundary of the step field in the second direction. The first line runs parallel to the second boundary, and the second line runs perpendicular to the second boundary. The second line is connected to the first line, wherein a distance between adjacent second lines of the first alignment mark is larger than a width of the second line of the second alignment mark.
[0011] For example, the first boundary may be parallel to the second boundary, and the second alignment mark may be arranged at a position, in a third direction perpendicular to the first direction, so that the first and the second alignment marks at least partially overlap along the third direction.
[0012] According to embodiments, the second alignment mark is arranged in the third direction so that at least one second line of the second alignment mark is arranged at a position along the third direction between two adjacent second lines of the first alignment mark.
[0013] For example, the second alignment mark is arranged in the third direction so that at least one second line of the second alignment mark is arranged at a same position along the third direction as a second line of the first alignment mark.
[0014] A method for manufacturing a semiconductor device comprises monitoring an alignment accuracy of a photolithography stepper process using the photomask as de- fined above. The method comprises determining a distance A between a first edge of the second line of a second comb pattern patterned using the second alignment mark and a second edge of the second line of an adjacent first comb pattern patterned using the first alignment mark. The method further comprises determining a distance B between a first edge of the second line of the first comb pattern and a second edge of the second line of the second comb pattern, and determining a difference between A and B. A monitoring result depends on the difference between A and B.
[0015] The method may further comprise determining a distance C between a third edge of the second line of the second comb pattern and a third edge of the second line of the first comb pattern, wherein the monitoring result further depends on the distance C.
[0016] According to embodiments, a semiconductor device comprises a first comb pattern comprising a first line and a plurality of parallel second lines between the first line and a first boundary of a first step field in a first direction. A distance between the first line and the first boundary is smaller in the first direction than in a second direction opposite to the first direction. The first line runs parallel to the first boundary, and the second lines run perpendicular to the first boundary. The second lines are connected to the first line, wherein a distance between adjacent second lines is larger than a width of the second lines. The semiconductor device further comprises a second comb pattern in a second step field adjacent to the first field, the second comb pattern being adjacent to the first comb pattern and to the first boundary. The second comb pattern at least partially overlaps with the first comb pattern, the second comb pattern comprising a first line and at least one second line between the first line and the first boundary in the second direction. The first line runs parallel to the first boundary, and the second line runs perpendicular to the first boundary. The second line is connected to the first line. A distance between adjacent second lines of the first comb pattern is larger than a width of the second line of the second comb pattern.
[0017] For example, the first and second lines may be made of a material selected from metal, single crystalline silicon, polysilicon and photoresist. According to further embodiments, a region surrounding the second lines is made of a material selected from metal, single crystalline silicon, polysilicon and photoresist. An electronic device comprises the semiconductor device as defined above. For example, the electronic device may be selected from a CMOS image sensor, a CMOS medical image sensor and a non-destructive testing sensor.
[0018] BRIEF DESCRIPTION OF THE DRAWINGS
[0019] The accompanying drawings are included to provide a further understanding of embodiments of the invention and are incorporated in and constitute a part of this specification. The drawings illustrate the embodiments of the present invention and together with the description serve to explain the principles. Other embodiments of the invention and many of the intended advantages will be readily appreciated, as they become better understood by reference to the following detailed description. The elements of the drawings are not necessarily to scale relative to each other. Like reference numbers designate corresponding similar parts.
[0020] Fig. 1 A shows a schematic view of a semiconductor device comprising a plurality of step fields.
[0021] Fig. 1 B is an enlarged view of a portion of the semiconductor device.
[0022] Fig. 1 C is a schematic top view of a wafer including a plurality of semiconductor devices.
[0023] Fig. 1 D is an enlarged view of a semiconductor device.
[0024] Fig. 1 E is an enlarged view of a portion of the semiconductor device.
[0025] Fig. 2A shows a photomask according to embodiments.
[0026] Fig. 2B shows a pattern of adjacent alignment marks.
[0027] Fig. 2C shows a portion of a semiconductor chip comprising comb patterns according to embodiments. Fig. 3A shows an example of adjacent alignment marks or comb patterns.
[0028] Fig. 3B shows a further example of two adjacent comb patterns or alignment marks.
[0029] Fig. 3C shows a further example of adjacent alignment marks or comb patterns.
[0030] Fig. 3D shows a further example of adjacent alignment marks or adjacent comb patterns.
[0031] Fig. 4A illustrates a method of monitoring an alignment.
[0032] Fig. 4B illustrates a further method of monitoring an alignment.
[0033] Fig. 5 summarizes a method according to embodiments.
[0034] Fig. 6 shows an electronic device according to embodiments.
[0035] DETAILED DESCRIPTION
[0036] In the following detailed description reference is made to the accompanying drawings, which form a part hereof and in which are illustrated by way of illustration specific embodiments in which the invention may be practiced. In this regard, directional terminology such as "top", "bottom", "front", "back", "over", "on", "above", "leading", "trailing" etc. is used with reference to the orientation of the Figures being described. Since components of embodiments of the invention can be positioned in a number of different orientations, the directional terminology is used for purposes of illustration and is in no way limiting. It is to be understood that other embodiments may be utilized and structural or logical changes may be made without departing from the scope defined by the claims.
[0037] The description of the embodiments is not limiting. In particular, elements of the embodiments described hereinafter may be combined with elements of different embodiments. Fig. 1 A shows a top view of an example of a semiconductor device 10 according to embodiments. As is illustrated in Fig. 1A, the semiconductor device 10 may comprise a repetitive pattern including an array of step fields 111. For example, the step fields 111 may be arranged in rows and columns. The single step fields 111 may be produced by photolithographically patterning e.g. a semiconductor wafer 15 using an identical photomask (not shown in Fig. 1A). For example, the size of the semiconductor device or chip 10 may be such that one single semiconductor device 10 may be generated from a single wafer 15.
[0038] Fig. 1 B is an enlarged view of a portion of the semiconductor device 10. As is illustrated, a plurality of step fields 111 , 113 are arranged in rows and columns. Boundaries 110 or stitching lines are arranged between the adjacent step fields 111 , 113. The boundaries 110 may e.g. extend in the x-direction and in the y-direction. As is readily to be appreciated, a precise alignment is necessary in order to ensure the performance of the semiconductor device. A step field may have a rectangular shape.
[0039] As is shown in Fig. 1 B, comb patterns 115, 117, 118, and 119 are arranged adjacent to the boundaries 110 of each of the step fields 111 , 113. As a result, it is possible to monitor an alignment of adjacent step fields using these comb patterns.
[0040] As is e.g. illustrated in Fig. 1 B, each of the step fields 111 comprises a first comb pattern 117 and may further comprise a second comb pattern 115. The first comb pattern 117 and the second comb pattern 115 may be arranged at opposing sides along a first direction, e.g. the x direction. When several step fields are arranged in one row, the alignment between the step fields of one row along a second direction, e.g. the y direction, may be monitored using the first and the second comb patterns of adjacent step fields 111 , 113. According to embodiments, each of the step fields may further comprise a third and a fourth comb patterns 118, 119. The third and the fourth comb patterns 118, 119 may be arranged at opposing sides along the second direction. Using the third and the fourth comb patterns 118, 119, an alignment along the first direction may be monitored. Each of the comb patterns may be arranged on one of the side faces of the step field 111. Each of the comb patterns may be arranged at a position so as to at least partially overlap with a comb pattern of an adjacent step field 113.
[0041] Within the present disclosure, term “overlap” is intended to mean that portions of e.g. the first comb pattern 117 are arranged at the same position along a first direction, e.g. the x-direction as portions of the second comb pattern 115. According to implementations, portions of the first comb pattern 117 may further have the same position along a second direction, e.g. the y-direction as portions of the second comb pattern 115. According to still further implementations, at least a portion of the first comb pattern 117 may be adjacent to a portion of the second comb pattern 115. In more detail, portions of the first comb pattern 117 may have a position along the second direction which is different from a position along the second direction of portions of the second comb pattern 115.
[0042] Fig. 1 C shows a further example of an arrangement of semiconductor devices 10. As is shown, a plurality of semiconductor devices 10 may be formed from one semiconductor wafer 15.
[0043] Fig. 1 D shows an enlarged view of a semiconductor device 10. As is illustrated, the semiconductor device 10 may comprise a plurality of step fields 111. The single step fields 111 may be arranged in rows and columns.
[0044] Fig. 1 E shows an enlarged view of two step fields 111 , 113 along the y direction and a boundary 110 or stitching line. As is shown, a first comb pattern 117 of the first step field 111 is arranged adjacent to a second comb pattern 115 of a second step field 113. The first comb pattern 117 and the second comb pattern 115 may at least partially overlap. The first comb pattern 117 comprises a first line 121 and a plurality of parallel second lines 122 between the first line 121 and a first boundary of the first step field 111 in a first direction. A distance between the first line 121 and the first boundary is smaller in the first direction than in a second direction opposite to the first direction. The first line 121 runs parallel to the first boundary 110, and the second lines 122 run perpendicular to the first boundary. The second lines 122 are connected to the first line 121 . A distance between adjacent second lines 122 is larger than a width of the second lines 122. The semiconductor device 10 further comprises a second comb pattern 115 in the second step field 113 adjacent to the first step field 111. The second comb pattern 115 is adjacent to the first comb pattern 117 and to the first boundary 110. The second comb pattern 115 at least partially overlaps with the first comb pattern 117. The second comb pattern 115 comprises a first line 121 and at least one second line 122 between the first line 121 and the first boundary 110 in the second direction. The first line 121 runs parallel to the first boundary 110. The second line 122 runs perpendicular to the first boundary 110. The second line 122 is connected to the first line 121. A distance between adjacent second lines 122 of the first comb pattern 117 is larger than a width of the second line 122 of the second comb pattern 115.
[0045] For example, the first and second lines 121 , 122 may be made of a material selected from metal, single crystalline silicon, polysilicon and photoresist.
[0046] For example, a region surrounding the second lines 122 may be made of a material selected from metal, single crystalline silicon, polysilicon and photoresist.
[0047] Fig. 2A shows an example of a photomask 20 according to embodiments. During a photolithography process, the pattern of the photomask 20 may be transferred to a step field of the semiconductor device. Fig. 2A especially shows alignment marks. As is to be clearly understood, the photomask 20 may further comprise patterns that may be used for patterning elements of the semiconductor device, e.g. conductive lines or doped portions. Usually, the alignment marks comprise patterns that are not used for patterning elements of the semiconductor device but that are used only for alignment purposes.
[0048] The photomask 20 comprises a step field 111 for circuit design. The step field 111 comprises a first alignment mark 107 which is arranged in a first edge portion 101 of the step field 111. The first alignment mark 107 defines a comb pattern comprising a first line 121 and a plurality of parallel second lines 122. The second lines are arranged between the first line 121 and a first boundary 110 of the step field 111 in a first direction 114. A distance between the first line 121 and the first boundary 110 is smaller in the first direction 114 (e.g. x direction) than in a second direction 116 (e.g. - x direction) opposite to the first direction 114. The first line 121 runs parallel to the first boundary 110. The second lines 122 run perpendicular to the first boundary 110.
[0049] The second lines 122 are connected to the first line 121 .
[0050] According to embodiments, the first and the second lines may be made of an opaque material, e.g. chrome. The term “opaque” is intended to mean that the material is opaque to electromagnetic radiation that is used for exposing the photoresist material line underneath the photomask. As a result, the portions lying under the first and second lines 121 , 122 will not be exposed to electromagnetic radiation. Rather the portions surrounding the first lines and the second lines, will be exposed to electromagnetic radiation. According to further embodiments, the first and the second lines may be made of a transparent material. This means, that during a photolithography process, underlying photoresist material is exposed to radiation transmitted by the first and second lines 121 , 122. For example, portions of the alignment mark surrounding the first and second lines may block the electromagnetic radiation. These portions may comprise an opaque material. For example, such a configuration may be useful in cases in which implantation processes are performed using a patterned photoresist mask.
[0051] For example, as is shown in Fig. 2A, a second alignment mark 105 is arranged in a second edge portion 112. The second edge portion 112 is different from the first edge portion 101. The second alignment mark 105 may also comprise a comb pattern comprising a first line 121 and at least one second line 122 that is arranged between the first line 121 and a second boundary 102 of the step field 111 in the second direction 116. The first line 121 runs parallel to the second boundary 102. The second line 122 runs perpendicular to the second boundary 102. The second line 122 is connected to the first line 121 . For example, the second boundary 102 may be parallel to the first boundary 110. The first line 121 of the first alignment mark 107 is parallel to the first line 121 of the second alignment mark 105. Further, the second line 122 of the first alignment mark 107 is parallel to the second line 122 of the second alignment mark 105. The second alignment mark 105 may be arranged at a position in a third direction (e.g. y direction) perpendicular to the first direction, so that the first and the second alignment marks at least partially overlap. In particular, portions of the first alignment mark 117 may be arranged at the same position in the third direction as portions of the second alignment mark 105. For example, the second alignment mark may be arranged so that at least one second line 122 of the second alignment mark 105 is arranged between two adjacent second lines of the first alignment mark 107. Further, the second alignment mark may be arranged so that at least one second line of the second alignment mark 105 is arranged at a same position in the third direction. This will be explained with reference to Fig. 3D in more detail.
[0052] The step field 111 may further comprise a third and a fourth alignment marks 108, 109 that may be arranged along the third direction, e.g. the y direction. The third alignment mark 108 may be arranged adjacent to a third boundary 103. The third alignment mark 108 may be arranged in a third edge portion 131. The fourth alignment mark 109 may be arranged adjacent to a fourth boundary 104. The fourth alignment mark 109 may be arranged in a fourth edge portion 132. The structure and arrangement of the third and fourth alignment marks 108, 109 may be identical to the first and second alignment marks 107, 105 rotated by 90°.
[0053] Fig. 2B shows alignment marks of adjacent step fields which are patterned using the photomask 20. For example, as is shown in the upper portion of Fig. 2B, a fourth alignment mark 109 may be arranged adjacent to a third alignment mark 108. Further, a first alignment mark 107 may be arranged adjacent to a second alignment mark 105. As is shown, a distance between adjacent second lines 122 may be identical or may be different among the different alignment marks. Further, a distance between adjacent second lines of any of the alignment marks may be larger than a width of the second line of an adjacent alignment mark. Due to this feature, it will be possible to monitor an alignment accuracy during the photolithography process more precisely. In more detail, by monitoring a distance between the second lines 122 of two adjacent alignment marks, it is possible to monitor an alignment accuracy.
[0054] Fig. 2C shows an example of comb patterns 118, 119 that are generated e.g. on the semiconductor wafer 15 illustrated in Fig. 1 C, for example. Depending on the processing, the comb patterns 118, 119 may be generated in a photoresist material or in a patterned layer, e.g. a conductive layer. Further, when patterning the layer, the material surrounding the first and second lines may be removed while maintaining the material corresponding to the first and second lines, or vice versa. As is shown, a portion of the third comb pattern 118 may extend to a position in the first and second directions, e.g. x and y direction which corresponds to a position in the first and second directions of a portion of the fourth comb pattern 119. To be more specific, portions of the third comb pattern 118 may overlap with portions of the fourth comb pattern 119 along the first and second directions. Likewise, portions of the first comb pattern 117 (not illustrated in Fig. 2C) may overlap with portions of the second comb pattern 115 along the first and second directions.
[0055] Fig. 3A shows an example of two adjacent alignment marks 107, 105 or comb patterns 117, 115. As is shown, the distance d between adjacent second lines 122 may be larger than a width w of a second line 122 of the second alignment mark 105 or the second comb pattern 115. The width w of the second lines of the first alignment mark 107 may be different from or identical to the width w of the second lines 122 of the second alignment mark 105. Likewise, the distance between adjacent second lines 122 may be identical or different for the first and the second alignment marks 107, 105. For example, the line width and distance may be designed according to a minimum design rule or minimum stitching design rule of the photolithographic pattern to be generated. For example, a length of the second lines may be more than 1 pm. The length of the second lines 122 may be less than 100 pm, e.g. less than 50 pm or less than 35 pm. A line width w of the second lines 122 may be e.g. less than 5 pm, e.g. 2 pm for a 0.35 pm design rule.
[0056] Depending on the space which is available for the alignment marks 107, 105, the alignment marks may be designed to have a larger number of second lines 122 or a reduced number of second lines 122. As is further illustrated in Fig. 3A, the first and the second alignment marks 107, 105 or comb patterns 117, 115 may be arranged so that a second line 122 of the second alignment mark 105 or comb pattern 115 is arranged between two adjacent second lines 122 of the first alignment mark 107 or comb pattern 117 and vice versa.
[0057] For example, as is illustrated in Fig. 3B, in order to place a second line 122 of the second alignment mark 105 or second comb pattern 115 between two adjacent second lines 122 of the first alignment mark 107 or fist comb pattern 117, it is sufficient that the second alignment mark 105 or the second comb pattern 115 comprised one single second line 122, whereas the first alignment mark 107 or the first comb pattern 117 comprises two second lines 122. In this way, the alignment marks 107, 105 may be employed with minimum space required.
[0058] According to further embodiments, as is illustrated in Fig. 3C, the first and second alignment marks may comprise a plurality of second lines 122. As a result, an accuracy of monitoring may be increased. In particular, in this case, the environmental influences may be reduced. Further noises such as isolation noise may be reduced.
[0059] According to further embodiments, the first and second alignment marks may be implemented as is illustrated in Fig. 3D. In more detail, the second lines 122 of the first and the second alignment marks 107, 105 may be designed, so as to fully overlap in some cases and so as to be arranged to form an interdigital structure. In more detail, as is illustrated in Fig. 3D, the two outermost second lines 122 of the first alignment mark 107 and the second alignment mark 105 are arranged so as to fully overlap along the first direction, e.g. the x-direction. The central second lines 122 are arranged so as to form an interdigital structure so that each of the second lines 122 of the first alignment mark 107 is arranged between adjacent second lines 122 of the second alignment mark 105. In this way, by monitoring the shape of the outermost second lines 122, a misalignment may be easily detected. Moreover, using the same measurement, a line width, e.g. the CD (“critical dimension”) of the outermost second lines 122 may be determined. As a consequence, it is possible to combine the misalignment measurement with a measurement of the line width or the critical dimension along the boundary or stitching line. Accordingly, the CD performance at the boundary may be easily determined. For example, the CD performance may be assessed from the comb patterns created without the need to measure the line width of patterned portions of the semiconductor device.
[0060] Fig. 4A illustrates concepts of a method for monitoring an alignment between adjacent step fields. Portions of a first comb pattern 117 and a second comb pattern 115 are e.g. patterned in a suitable metal, e.g. aluminum. The lower portion of Fig. 4A shows a measurement, e.g. a SEM (“scanning electron microscope”) measurement that may be made in order to detect the edges. As is to be clearly understood, the first and second comb patterns 117, 115 may be patterned in different materials and suitable detection methods (e.g. AFM, “atomic force measurement”) may be em- ployed. For example, a maximum signal may be obtained at the edges of each of the second lines.
[0061] By comparing a distance A between the first edge 127 of the second line of the second comb pattern and the second edge 126 of the second line of the first comb pattern with the distance B between the first edge 125 of the second line of the first comb pattern and the second edge 128 of the second line of the second comb pattern, a misalignment along a first direction, e.g. the x direction may be determined. Perfect alignment occurs when A = B. If A B, misalignment occurs.
[0062] As is illustrated in Fig. 4B, by determining a distance C between the third edge 123 of the second line of the second comb pattern and the third edge 124 of the second line of the first comb pattern, an alignment along the second direction, e.g. y direction, perpendicular to the boundary or stitching line may be determined. For example, a misalignment may be determined as (C-a) / 2, wherein a denotes the litho stitch overlapping setting value. For example, a may be less than 5 or 3 pm, e.g. 2 pm. The value a may be defined based on the lithography tool capability. When C is equal to or less than 0, this means that an “open” failure happened on the stitch line. In other words, the distance between the two comb pattern is too large.
[0063] Using the photomask described it is possible to monitor an alignment accuracy in a precise manner. As has been described, the photomask comprises alignment marks that are used for manufacturing comb patterns in one layer of the semiconductor device. Accordingly, misalignment of two step fields within the same layer may be detected.
[0064] Fig. 5 summarizes a method according to embodiments. A method for manufacturing a semiconductor device comprising monitoring an alignment accuracy of a photolithography stepper process between adjacent step fields 111 using the photomask as described above. The method comprises determining (S100) a distance A between a first edge of the second line of a second comb pattern patterned using the second alignment mark and a second edge of the second line of an adjacent first comb pattern patterned using the first alignment mark. The method further comprises determining (S110) a distance B between a first edge of the second line of the first comb pattern and a second edge of the second line of the second comb pattern, and determining (S120) a difference between A and B. A monitoring result depends on the difference. As is clearly to be understood, distance A may be determined before determining distance B or vice versa.
[0065] The method may further comprise determining (S130) a distance C between a third edge of the second line of the second comb pattern and a third edge of the second line of the first comb pattern. The monitoring result may further depend on the distance C. As is clearly to be understood, distances A, B, and C may be determined in arbitrary order.
[0066] Fig. 6 shows an example of an electronic device 30 comprising the semiconductor device 10 as described above. For example, the electronic device may comprise an image sensor, e.g. a large scale image sensor, a CMOS medical image sensor or a non-destructive testing sensor. Such image sensors may comprise an array of identical detector elements that may be defined by replicating a photomask pattern.
[0067] While embodiments of the invention have been described above, it is obvious that further embodiments may be implemented. For example, further embodiments may comprise any subcombination of features recited in the claims or any subcombination of elements described in the examples given above. Accordingly, this spirit and scope of the appended claims should not be limited to the description of the embodiments contained herein.
[0068] LIST OF REFERENCES
[0069] 10 semiconductor device
[0070] 15 semiconductor wafer
[0071] 20 photomask
[0072] 30 electronic device
[0073] 101 first edge portion
[0074] 102 second boundary
[0075] 103 third boundary
[0076] 104 fourth boundary
[0077] 105 second alignment mark
[0078] 107 first alignment mark
[0079] 108 third alignment mark
[0080] 109 fourth alignment mark
[0081] 110 first boundary
[0082] 111 first step field
[0083] 112 second edge portion
[0084] 113 second step field
[0085] 114 first direction
[0086] 115 second comb pattern
[0087] 116 second direction
[0088] 117 first comb pattern
[0089] 118 third comb pattern
[0090] 119 fourth comb pattern
[0091] 121 first line
[0092] 122 second line
[0093] 123 third edge of second line of second comb pattern
[0094] 124 third edge of second line of first comb pattern
[0095] 125 first edge of second line of first comb pattern
[0096] 126 second edge of second line of first comb pattern
[0097] 127 first edge of second line of second comb pattern
[0098] 128 second edge of second line of second comb pattern
[0099] 131 third edge portion
[0100] 132 fourth edge portion
Claims
CLAIMS1 . A photomask (20) for use in a photolithography stepper, the photomask (20) comprising a step field (111 ), the step field (111 ) comprising: a first alignment mark (107) in a first edge portion (101 ) of the step field (111 ), the first alignment mark (107) defining a comb pattern comprising a first line (121 ) and a plurality of parallel second lines (122) between the first line (121 ) and a first boundary (110) of the step field (111 ) in a first direction, a distance between the first line (121 ) and the first boundary (110) being smaller in the first direction than in a second direction opposite to the first direction, the first line (121 ) running parallel to the first boundary (110), and the second lines (122) running perpendicular to the first boundary (110), the second lines (122) being connected to the first line (121 ), and a second alignment mark (105) in a second edge portion (112) different from the first edge portion (101 ), the second alignment mark (105) defining a comb pattern comprising a first line (121 ) and at least one second line (122) between the first line (121) and a second boundary (102) of the step field (111 ) in the second direction, the first line (121) running parallel to the second boundary (102), and the second line (122) running perpendicular to the second boundary (102), the second line (122) being connected to the first line (121 ), wherein a distance between adjacent second lines (122) of the first alignment mark (107) is larger than a width of the second line (122) of the second alignment mark (105).
2. The photomask (20) according to claim 1 , wherein the first boundary (110) is parallel to the second boundary (102), and the second alignment mark (105) is arranged at a position, in a third direction perpendicular to the first direction, so that the first and the second alignment marks (107, 105) at least partially overlap along the third direction.
3. The photomask (20) according to claim 2, wherein the second alignment mark (105) is arranged in the third direction so that at least one second line (122) of the second alignment mark (105) is arranged at a position along the third direction between two adjacent second lines (122) of the first alignment mark (107).
4. The photomask (20) according to claim 2 or 3, wherein the second alignment mark (105) is arranged in the third direction so that at least one second line (122) of the second alignment mark (105) is arranged at a same position along the third direction as a second line (122) of the first alignment mark (107).
5. The photomask (20) according to any of the preceding claims, wherein the step field (111) further comprises: a third alignment mark (108) in a third edge portion (131 ) of the step field (111 ), the third alignment mark (108) defining a comb pattern comprising a first line (121 ) and a plurality of parallel second lines (122) between the first line (121 ) and a third boundary (103) of the step field (111 ) in a third direction, a distance between the first line (121) and the third boundary (103) being smaller in the third direction than in a fourth direction opposite to the third direction, the first line (121 ) running parallel to the third boundary (103), and the second lines (122) running perpendicular to the third boundary (103), the second lines (122) being connected to the first line (121 ), and a fourth alignment mark (109) in a fourth edge portion (132) different from the third edge portion (131 ), the fourth alignment mark (109) defining a comb pattern comprising a first line (121 ) and at least one second line (122) between the first line (121 ) and a fourth boundary (104) of the step field (111 ) in the fourth direction, the first line (121 ) running parallel to the fourth boundary (104), and the second line (122) running perpendicular to the fourth boundary (104), the second line (122) being connected to the first line (121), wherein a distance between adjacent second lines (122) of the third alignment mark (108) is larger than a width of the second line (122) of the fourth alignment mark (109).
6. The photomask (20) according to any of claims 1 to 5, wherein the first and second lines (121 , 122) are made of an opaque material.
7. The photomask (20) according to any of claims 1 to 5, wherein the first and second lines (121 , 122) are made of a transparent material.
8. The photomask (20) according to any of claims 1 to 7, wherein the second lines (122) of the first alignment mark (107) are arranged at a constant distance.
9. The photomask (20) according to any of claims 1 to 7, wherein at least two second lines (122) of the first alignment mark (107) are arranged at a distance that is different from a distance between other two second lines (122).
10. A method for manufacturing a semiconductor device (10) comprising monitoring an alignment accuracy of a photolithography stepper process between adjacent step fields (111 ) using the photomask (20) according to any of claims 1 to 4, the method comprising: determining (S100) a distance A between a first edge (127) of the second line of a second comb pattern patterned using the second alignment mark (105) and a second edge (126) of the second line of an adjacent first comb pattern patterned using the first alignment mark (107); determining (S110) a distance B between a first edge (125) of the second line of the first comb pattern and a second edge (128) of the second line of the second comb pattern; and determining (S120) a difference between A and B, wherein a monitoring result depends on the difference.11 . The method according to claim 10, further comprising determining (S130) a distance C between a third edge (123) of the second line of the second comb pattern and a third edge (124) of the second line of the first comb pattern, wherein the monitoring result further depends on the distance C.
12. A semiconductor device (10) comprising: a first comb pattern (117) comprising a first line (121 ) and a plurality of parallel second lines (122) between the first line (121 ) and a first boundary (110) of a first step field (111 ) in a first direction, a distance between the first line (121 ) and the first boundary (110) being smaller in the first direction than in a second direction opposite to the first direction, the first line (121 ) running parallel to the first boundary (110), and the second lines (122) running perpendicular to the first boundary (110), the second lines (122) being connected to the first line (121 ), wherein a distance between adjacent second lines (122) is larger than a width of the second lines (122); anda second comb pattern (115) in a second step field (113) adjacent to the first step field (111 ), the second comb pattern (115) being adjacent to the first comb pattern (117) and to the first boundary (110), the second comb pattern (115) at least partially overlapping with the first comb pattern (117), the second comb pattern (115) comprising a first line (121 ) and at least one second line (122) between the first line (121 ) and the first boundary (110) in the second direction, the first line (121 ) running parallel to the first boundary (110), and the second line (122) running perpendicular to the first boundary (110), the second line (122) being connected to the first line (121 ), wherein a distance between adjacent second lines (122) of the first comb pattern (117) is larger than a width of the second line (122) of the second comb pattern (115).
13. The semiconductor device (10) according to claim 12, wherein the first and second lines (121 , 122) are made of a material selected from metal, single crystalline silicon, polysilicon and photoresist.
14. The semiconductor device (10) according to claim 12, wherein a region surrounding the second lines (122) is made of a material selected from metal, single crystalline silicon, polysilicon and photoresist.
15. An electronic device (30) comprising the semiconductor device (10) according to any of claims 12 to 14.
16. The electronic device (30) according to claim 15, being selected from a CMOS image sensor, a CMOS medical image sensor and a non-destructive testing sensor.