US20190067203A1 - Semiconductor metrology target and manufacturing method thereof - Google Patents
Semiconductor metrology target and manufacturing method thereof Download PDFInfo
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- US20190067203A1 US20190067203A1 US15/692,151 US201715692151A US2019067203A1 US 20190067203 A1 US20190067203 A1 US 20190067203A1 US 201715692151 A US201715692151 A US 201715692151A US 2019067203 A1 US2019067203 A1 US 2019067203A1
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L23/00—Details of semiconductor or other solid state devices
- H01L23/544—Marks applied to semiconductor devices or parts, e.g. registration marks, alignment structures, wafer maps
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- G—PHYSICS
- G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
- G03F—PHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR
- G03F7/00—Photomechanical, e.g. photolithographic, production of textured or patterned surfaces, e.g. printing surfaces; Materials therefor, e.g. comprising photoresists; Apparatus specially adapted therefor
- G03F7/70—Microphotolithographic exposure; Apparatus therefor
- G03F7/70483—Information management; Active and passive control; Testing; Wafer monitoring, e.g. pattern monitoring
- G03F7/70605—Workpiece metrology
- G03F7/70616—Monitoring the printed patterns
- G03F7/70633—Overlay, i.e. relative alignment between patterns printed by separate exposures in different layers, or in the same layer in multiple exposures or stitching
-
- G—PHYSICS
- G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
- G03F—PHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR
- G03F7/00—Photomechanical, e.g. photolithographic, production of textured or patterned surfaces, e.g. printing surfaces; Materials therefor, e.g. comprising photoresists; Apparatus specially adapted therefor
- G03F7/70—Microphotolithographic exposure; Apparatus therefor
- G03F7/70483—Information management; Active and passive control; Testing; Wafer monitoring, e.g. pattern monitoring
- G03F7/70605—Workpiece metrology
- G03F7/70681—Metrology strategies
- G03F7/70683—Mark designs
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- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06T—IMAGE DATA PROCESSING OR GENERATION, IN GENERAL
- G06T7/00—Image analysis
- G06T7/0002—Inspection of images, e.g. flaw detection
- G06T7/0004—Industrial image inspection
- G06T7/001—Industrial image inspection using an image reference approach
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- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06T—IMAGE DATA PROCESSING OR GENERATION, IN GENERAL
- G06T7/00—Image analysis
- G06T7/60—Analysis of geometric attributes
- G06T7/68—Analysis of geometric attributes of symmetry
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L22/00—Testing or measuring during manufacture or treatment; Reliability measurements, i.e. testing of parts without further processing to modify the parts as such; Structural arrangements therefor
- H01L22/10—Measuring as part of the manufacturing process
- H01L22/12—Measuring as part of the manufacturing process for structural parameters, e.g. thickness, line width, refractive index, temperature, warp, bond strength, defects, optical inspection, electrical measurement of structural dimensions, metallurgic measurement of diffusions
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L22/00—Testing or measuring during manufacture or treatment; Reliability measurements, i.e. testing of parts without further processing to modify the parts as such; Structural arrangements therefor
- H01L22/30—Structural arrangements specially adapted for testing or measuring during manufacture or treatment, or specially adapted for reliability measurements
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- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06T—IMAGE DATA PROCESSING OR GENERATION, IN GENERAL
- G06T2207/00—Indexing scheme for image analysis or image enhancement
- G06T2207/30—Subject of image; Context of image processing
- G06T2207/30108—Industrial image inspection
- G06T2207/30148—Semiconductor; IC; Wafer
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L2223/00—Details relating to semiconductor or other solid state devices covered by the group H01L23/00
- H01L2223/544—Marks applied to semiconductor devices or parts
- H01L2223/54426—Marks applied to semiconductor devices or parts for alignment
Definitions
- a semiconductor integrated circuit is formed on multiple layers of a semiconductor substrate (or a semiconductor wafer).
- a semiconductor substrate or a semiconductor wafer.
- some layers of the substrate need to be aligned with each other.
- a metrology target or alignment mark formed in a semiconductor substrate is utilized to perform the overlay (or alignment) measurements.
- the metrology target may include a plurality of gratings, and an overlay shift between different layers of the semiconductor substrate can be measured based on the arrangement of the gratings.
- FIG. 1 shows a schematic diagram of an overlay-shift measurement system in accordance with some embodiments.
- FIGS. 2A-2C show a metrology target in accordance with some embodiments.
- FIGS. 3A-3D show a metrology target having a dishing effect in accordance with some embodiments.
- FIGS. 4A-4D show a metrology target including a dummy structure in accordance with some embodiments.
- FIG. 5 shows a metrology target including a dummy structure in accordance with some embodiments.
- FIGS. 6A-6B show metrology targets which respectively include a dummy structure in accordance with some embodiments.
- FIGS. 7A-7D show metrology targets which respectively include a dummy structure in accordance with some embodiments.
- FIGS. 8A-8D show metrology targets which respectively include a dummy structure in accordance with some embodiments.
- FIGS. 9A-9B illustrate a manufacturing method of a metrology target of a semiconductor device.
- first and second features are formed in direct contact
- additional features may be formed between the first and second features, such that the first and second features may not be in direct contact
- present disclosure may repeat reference numerals and/or letters in the various examples. This repetition is for the purpose of simplicity and clarity and does not in itself dictate a relationship between the various embodiments and/or configurations discussed.
- spatially relative terms such as “beneath,” “below,” “lower,” “above,” “upper” and the like, may be used herein for ease of description to describe one element or feature's relationship to another element(s) or feature(s) as illustrated in the figures.
- the spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures.
- the apparatus may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein may likewise be interpreted accordingly.
- FIG. 1 shows a schematic diagram of an overlay-shift measurement system 100 in accordance with some embodiments.
- the overlay-shift measurement system 100 includes a light source 101 , an optical device 102 , a semiconductor device 103 , a light detection circuit 105 , and a processor 106 .
- the semiconductor device 103 is a semiconductor substrate (or a wafer) and includes a metrology target 104 .
- the semiconductor device 103 includes multiple layers, and the metrology target 104 includes a plurality of gratings which are formed in different layers and overlap each other.
- the overlay-shift measurement system 100 may perform a diffraction-based overlay (DBO) measurement on the metrology target 104 .
- the light source 101 is configured to provide light to the optical device 102 , and then the optical device 102 provides the light LI to the metrology target 104 .
- the light LR is generated, and the light LR includes at least one diffraction light (e.g., +1 order or ⁇ 1 order) corresponding to the light LI.
- the light detection circuit 105 is configured to detect the light LR and then generates the data corresponding to the light LR (e.g., the image data generated by the light LR).
- the processor 106 is configured to receive the data from the light detector 105 . Subsequently, the processor 106 analyzes the data to determine the overlay shift between the gratings, which are formed in different layers, of the metrology target 104 .
- the processor 106 analyzes the light-intensity difference between the diffraction lights which are detected by the light detection circuit 105 to determine the overlay shift between gratings of the metrology target 104 .
- the aforementioned DBO measurement is performed after a lithography process.
- FIG. 2A shows a metrology target 104 in accordance with some embodiments.
- the metrology target 104 includes overlay targets OT 1 -OT 4 .
- the overlay targets OT 1 and OT 2 are fabricated as FIG. 2B
- the overlay targets OT 3 and OT 4 are fabricated as FIG. 2C .
- FIG. 2B shows the cross-sectional diagram of overlay targets OT 1 and OT 2 in accordance with some embodiments.
- the overlay target OT 1 includes gratings G 1 and G 3 .
- the grating G 1 is formed in layer m 1 of the semiconductor device 103
- the grating G 3 is formed in layer m 2 of the semiconductor device 103 .
- the gratings G 1 and G 3 are formed based on a spatial period P 1 .
- the components of grating G 1 are arranged to repeat with the spatial period P 1
- the components of grating G 3 are also arranged to repeat with the spatial period P 1 , as shown in FIG. 2B .
- the grating G 3 is placed to overlap the grating G 1 and placed to have a predetermined offset (along the direction X) compared with the grating G 1 .
- the process variation of the semiconductor device 103 may cause an unknown displacement between the gratings G 1 and G 3 , which makes the gratings G 1 and G 3 have a positional offset d 1 which is the combination of the predetermined offset and the unknown displacement.
- the positional offset d 1 is along the direction X, as shown in FIG. 2B .
- the overlay target OT 2 includes gratings G 2 and G 4 .
- the grating G 2 is formed in layer m 1 of the semiconductor device 103
- the grating G 4 is formed in layer m 2 of the semiconductor device 103 .
- the gratings G 2 and G 4 are formed based on the spatial period P 1 .
- the components of grating G 2 are arranged to repeat with the spatial period P 1
- the components of grating G 4 are also arranged to repeat with the spatial period P 1 , as shown in FIG. 2B .
- the grating G 4 is placed to overlap the grating G 2 and placed to have a predetermined offset (along the direction ⁇ X) compared with the grating G 2 .
- the process variation of the semiconductor device 103 may cause an unknown displacement between the gratings G 2 and G 4 , which makes the gratings G 2 and G 4 have a positional offset d 1 ′ which is the combination of the predetermined offset and the unknown displacement.
- the positional offset d 1 ′ is along the direction ⁇ X, and the direction of the positional offset d 1 ′ is opposite to the direction of the positional offset d 1 , as shown in FIG. 2B .
- the magnitude of the positional offset d 1 is the same as the magnitude of the positional offset d 1 ′ if the positional offsets d 1 and d 1 ′ are not affected by the unknown displacement.
- the unknown displacement is caused by the process variations which are generated during the manufacturing of the semiconductor device 103 (e.g., erosion, dishing, etc).
- the overlay-shift measurement system 100 performs the DBO measurement on the overlay targets OT 1 and OT 2 to determine the overlay shift, which occurs in directions X or ⁇ X, of the semiconductor device 103 based on the diffraction lights (e.g., +1 order, ⁇ 1 order, etc.) generated by the light LI and the overlay targets OT 1 and OT 2 .
- the diffraction lights e.g., +1 order, ⁇ 1 order, etc.
- the light LI in FIG. 1 illuminates the overlay targets OT 1 and OT 2 to generate the light LR.
- the light LR is detected by the light detection circuit 105 and converted to image data.
- the processor 106 determines an asymmetry signal (ASX 1 ) which represents the asymmetry in the intensity of different diffraction orders (e.g., +1 order and ⁇ 1 order, or other orders) generated by the light LI and the overlay target OT 1 and determines an asymmetry signal (ASX 2 ) which represents the asymmetry in the intensity of different diffraction orders generated by the light LI and the overlay target OT 2 .
- ASX 1 an asymmetry signal
- ASX 2 asymmetry signal
- the processor 106 determines the overlay shift (OVS 1 ), which occurs in directions X or ⁇ X, of the metrology target 104 based on equation (1) described below.
- OVS ⁇ ⁇ 1 c ⁇ ⁇ 1 ⁇ 1 + ( ASX ⁇ ⁇ 2 ⁇ / ⁇ ASX ⁇ ⁇ 1 ) 1 - ( ASX ⁇ ⁇ 2 ⁇ / ⁇ ASX ⁇ ⁇ 1 ) ( 1 )
- the constant (c1) is a predetermined offset
- the positional offsets d 1 and d 1 ′ are the combination of the predetermined offset (c1) and an unknown displacement (de1) caused by the process variations of the semiconductor device 103 .
- the positional offset d 1 is equal to “c1+de1”
- the positional offset d 1 ′ is equal to “ ⁇ c1+de1”.
- FIG. 2C shows the cross-sectional diagram of overlay targets OT 3 and OT 4 in accordance with some embodiments.
- the overlay target OT 3 includes gratings G 5 and G 7 .
- the grating G 5 is formed in layer m 1 of the semiconductor device 103
- the grating G 7 is formed in layer m 2 of the semiconductor device 103 .
- the gratings G 5 and G 7 are formed based on a spatial period P 2 .
- the components of grating G 5 are arranged to repeat with the spatial period P 2
- the components of grating G 7 are also arranged to repeat with the spatial period P 2 , as shown in FIG. 2C .
- the grating G 7 is placed to overlap the grating G 5 and placed to have a predetermined offset (along the direction Y) compared with the grating G 5 .
- the process variation of the semiconductor device 103 may cause an unknown displacement between the gratings G 5 and G 7 , which makes the gratings G 5 and G 7 have a positional offset d 2 which is the combination of the predetermined offset and the unknown displacement.
- the positional offset d 2 is along the direction Y, as shown in FIG. 2C .
- the spatial period P 1 can be equal to the spatial period P 2 . In some embodiments, the spatial period P 1 can be different from the spatial period P 2 .
- the overlay target OT 4 includes gratings G 6 and G 8 .
- the grating G 6 is formed in layer m 1 of the semiconductor device 103
- the grating G 8 is formed in layer m 2 of the semiconductor device 103 .
- the gratings G 6 and G 8 are formed based on the spatial period P 2 .
- the components of grating G 6 are arranged to repeat with the spatial period P 2
- the components of grating G 8 are also arranged to repeat with the spatial period P 2 , as shown in FIG. 2C .
- the grating G 8 is placed to overlap the grating G 6 and placed to have a predetermined offset (along the direction ⁇ Y) compared with the grating G 6 .
- the process variation of the semiconductor device 103 may cause an unknown displacement between the gratings G 6 and G 8 , which makes the gratings G 6 and G 8 have a positional offset d 2 ′ which is the combination of the predetermined offset and the unknown displacement.
- the positional offset d 2 ′ is along the direction ⁇ Y, and the direction of the positional offset d 2 ′ is opposite to the direction of the positional offset d 2 , as shown in FIG. 2C .
- the magnitude of the positional offset d 2 is the same as the magnitude of the positional offset d 2 ′ if the positional offsets d 2 and d 2 ′ are not affected by an unknown displacement.
- the unknown displacement is caused by the process variations which are generated during the manufacturing of the semiconductor device 103 (e.g., erosion, dishing, or the like).
- the overlay-shift measurement system 100 performs the DBO measurement on the overlay targets OT 3 and OT 4 to determine the overlay shift, which occurs in directions Y or ⁇ Y, of the semiconductor device 103 based on the diffraction lights (e.g., +1 order, ⁇ 1 order, etc.) generated by the light LI and the overlay targets OT 3 and OT 4 .
- the diffraction lights e.g., +1 order, ⁇ 1 order, etc.
- the light LI in FIG. 1 illuminates the overlay targets OT 3 and OT 4 to generate the light LR.
- the light LR is detected by the light detection circuit 105 and converted to image data.
- the processor 106 determines an asymmetry signal (ASY 1 ) which represents the asymmetry in the intensity of different diffraction orders (e.g., +1 order and ⁇ 1 order, or other orders) generated by the light LI and the overlay target OT 3 and determines an asymmetry signal (ASY 2 ) which represents the asymmetry in the intensity of different diffraction orders generated by the light LI and the overlay target OT 4 .
- ASY 1 an asymmetry signal
- ASY 2 asymmetry signal
- the processor 106 determines the overlay shift (OVS2), which occurs in directions Y or ⁇ Y, of the metrology target 104 based on equation (2) described below.
- OVS ⁇ ⁇ 2 c ⁇ ⁇ 2 ⁇ 1 + ( ASY ⁇ ⁇ 2 ⁇ / ⁇ ASY ⁇ ⁇ 1 ) 1 - ( ASY ⁇ ⁇ 2 ⁇ / ⁇ ASY ⁇ ⁇ 1 ) ( 2 )
- the constant (c2) is a predetermined offset
- the positional offsets d 2 and d 2 ′ are the combination of the predetermined offset (c2) and an unknown displacement (de2) caused by the process variations of the semiconductor device 103 .
- the positional offset d 2 is equal to “c2+de2”
- the positional offset d 2 ′ is equal to “ ⁇ c2+de2”.
- the placement of the metrology target 104 can be changed.
- the positions of overlay targets OT 1 and OT 2 can be exchanged, or the positions of overlay targets OT 3 and OT 4 can be exchanged.
- the component density of the metrology target 104 may be different from the component density around the metrology target 104 . In such cases, the dishing may occur at the metrology target 104 , or the erosion may occur at multiple metrology targets 104 .
- FIGS. 3A-3D show the metrology target 104 having a dishing effect in accordance with some embodiments.
- the component density of the metrology target 104 in layer m 1 is lower than the component density of patterns around the metrology target 104 in layer m 1 , and the dishing effect occurs at structures, which are formed over the layer m 1 , of the metrology target 104 .
- the dishing effect causes the metrology target 104 to have a substantially bowl shape (as shown in FIGS. 3B and 3C ), and the lowest position is located in the region R (as shown in FIGS. 3A-3D ).
- FIGS. 3B and 3C show the cross-sectional diagram of the metrology target 104 having the dishing effect in accordance with some embodiments.
- the component density of the metrology target 104 in the layer m 1 is different from the component density of patterns in the layer m 1 around the metrology target 104 (e.g., the component density of gratings G 1 , G 2 , G 5 , and G 6 is lower than the component density of patterns around the gratings G 1 , G 2 , G 5 , and G 6 ).
- dishing effect occurs at structures, which are formed over the layer m 1 (e.g., the layer m 2 ), of the metrology target 104 , and the gratings G 3 , G 4 , G 7 , and G 8 are sunk by the dishing effect, which causes the shift of the DBO measurement performed based on the metrology target 104 .
- the dishing effect makes the components in layer m 2 of the overlay targets OT 1 and OT 2 have different altitude and be tilted by different angles. Accordingly, the asymmetry signal (ASX 1 ) corresponding to the overlay target OT 1 and the asymmetry signal (ASX 2 ) corresponding to the overlay target OT 2 are affected by different altitude deviation and different angle changes, which makes the asymmetry signal (ASX 1 ) have deviation (A1) and makes the asymmetry signal (ASX 2 ) have deviation (A2) which is different from deviation (A1).
- the overlay shift OVS1 corresponds to the ratio of the asymmetry signals (ASX 2 ) and (ASX 1 ). Since the deviation (A1) of the asymmetry signal (ASX 1 ) is different from the deviation (A2) of the asymmetry signal (ASX 2 ), the ratio of the asymmetry signals (ASX 2 ) and (ASX 1 ) under the dishing effect has additional deviation and is not equal to the original ratio of the asymmetry signals (ASX 2 ) and (ASX 1 ), which can be represented as:
- the overlay shift (OVS1) in equation (1) is affected by the dishing effect, and the accuracy of the overlay shift (OVS1) is degraded.
- the ratio of the asymmetry signals (ASY 2 ) and (ASY 1 ) under the dishing effect has additional deviation and is not equal to the original ratio of the asymmetry signals (ASY 2 ) and (ASY 1 ), which can be represented as:
- the overlay shift (OVS2) in equation (2) is affected by the dishing effect, and the accuracy of the overlay shift (OVS2) is degraded.
- FIGS. 4A-4C show a metrology target 104 including a dummy structure DS in accordance with some embodiments.
- the dummy structure DS is formed between each grating in the layer m 1 of the metrology target 104 , and the material of the dummy structure DS is the same as the gratings G 1 , G 2 , G 5 , and G 6 .
- the layer m 1 can be metal.
- FIGS. 4B and 4C show the cross-sectional diagram of the metrology target 104 including the dummy structure DS in accordance with some embodiments.
- the component density of the metrology target 104 in layer m 1 is lower than the component density of patterns around the metrology target 104 in layer m 1
- the dummy structure DS is placed between each grating of the metrology target 104 in the layer m 1 .
- the dummy structure DS reduces the difference in component density between the metrology target 104 and the patterns formed around the metrology target 104 in layer m 1 .
- the dishing effect occurring at layer m 2 can be improved as shown in FIGS. 4B and 4C . In such cases, the accuracy of the DBO measurement performed based on the metrology target 104 is also improved.
- each grating in layer m 1 of the metrology target 104 is surrounded by dummy components. As shown in FIG. 4D , the gratings G 1 , G 2 , G 5 , and G 6 are respectively surrounded by the dummy components of the dummy structures DS and DSO to reduce the difference in component density between the metrology target 104 and the patterns formed around the metrology target 104 in layer m 1 .
- the metrology target 104 having dummy structure may still have the dishing effect in the area of each grating in the layer m 2 , as shown in FIG. 5 .
- the gratings of the metrology target 104 in the layer m 2 have similar shape distortion, as shown in FIG. 5 .
- the asymmetry signals (ASX 1 ), (ASX 2 ), (ASY 1 ), and (ASY 2 ) respectively corresponding to the overlay targets OT 1 , OT 2 , OT 3 , and OT 4 are affected by similar altitude deviation and similar angle changes.
- the deviation (A11) of the asymmetry signals (ASX 1 ) and the deviation (A22) of the (ASX 2 ) are similar to each other, which can be represented as:
- the deviation (B11) of the asymmetry signals (ASY 1 ) and the deviation (B22) of the (ASY 2 ) are similar to each other, which can be represented as:
- FIG. 6A shows the metrology target 104 including the dummy structure DS in accordance with some embodiments.
- the metrology target 104 includes overlay targets OT 1 and OT 2 as shown in FIG. 2B .
- FIG. 6A shows the components of the metrology target 104 in layer m 1 for the purpose of clarity.
- the gratings G 1 and G 2 are formed based on the spatial period P 1 .
- the components of grating G 1 are arranged to repeat with the spatial period P 1
- the components of grating G 2 are also arranged to repeat with the spatial period P 1 .
- the workable wavelength ( ⁇ x ) corresponding to the overlay targets OT 1 and OT 2 of the metrology target 104 can be represented by equation (3).
- the parameter (NA) is the numerical aperture of the optical device 102 .
- the parameter (NA) is a value from 0.7 to 1.35 (i.e., the parameter (NA min ) is 0.7 and the parameter (NA max ) is 1.35), which allows the light LR (as shown in FIG. 1 ) generated based on the overlay targets OT 1 and OT 2 to be detected correctly by the light detection circuit 105 .
- the dummy structure DS includes multiple dummy components DC which are periodically placed along the direction X.
- the dummy components DC are arranged to repeat with the spatial period P 11 which are the sum of the length L 11 (which is the side length of one dummy component DC) and length S 11 (which is the space between two adjacent dummy components DC).
- the spatial period P 11 is less than the spatial period P 1 to avoid the dummy components DC affecting the results of the DBO measurement performed based on the overlay targets OT 1 and OT 2 .
- the spatial period P 11 is less than the spatial period P 1 , the brightness of the image data corresponding to the dummy structure DS is different from (e.g., darker than) the brightness of the image data corresponding to the overlay targets OT 1 and OT 2 of the metrology target 104 (wherein the image data is generated by the light detection circuit 105 ).
- the processor 106 can analyze the image data corresponding to the overlay targets OT 1 and OT 2 of the metrology target 104 correctly.
- the spatial period P 11 is represented as
- the spatial period P 11 is less than the minimum workable wavelength ( ⁇ x,min ) corresponding to the overlay targets OT 1 and OT 2 of the metrology target 104 .
- the spatial period P 11 is greater than the spatial period P 1 to avoid the dummy components DC affecting the results of the DBO measurement performed based on the overlay targets OT 1 and OT 2 .
- the spatial period P 11 is represented as
- the spatial period P 11 is greater than the maximum workable wavelength ( ⁇ x,max ) corresponding to the overlay targets OT 1 and OT 2 of the metrology target 104 .
- the spatial period P 11 is greater than the spatial period P 1 .
- the brightness of the image data corresponding to the dummy structure DS is different from the brightness of the image data corresponding to the overlay targets OT 1 and OT 2 of the metrology target 104 (wherein the image data is generated by the light detection circuit 105 ), and the processor 106 is able to distinguish the image data corresponding to the dummy structure DS and the image data corresponding to the overlay targets OT 1 and OT 2 of the metrology target 104 and makes the processor 106 analyze the image data corresponding to the overlay targets OT 1 and OT 2 of the metrology target 104 correctly.
- FIG. 6B shows metrology target 104 including the dummy structure DS in accordance with some embodiments.
- the metrology target 104 includes overlay targets OT 1 and OT 2 as shown in FIG. 2B .
- FIG. 6B shows the components of the metrology target 104 in layer m 1 for the purpose of clarity.
- the dummy structure DS is extended along the directions Y and ⁇ Y to separate the gratings G 1 and G 2 .
- the dummy structure is not formed based on a spatial period and is formed by a single dummy component, which makes the brightness of the image data corresponding to the dummy structure DS different from the brightness of the image data corresponding to the overlay targets OT 1 and OT 2 of the metrology target 104 (wherein the image data is generated by the light detection circuit 105 ).
- the processor 106 can distinguish the image data corresponding to the dummy structure DS and the image data corresponding to the overlay targets OT 1 and OT 2 of the metrology target 104 and analyze the image data corresponding to the overlay targets OT 1 and OT 2 of the metrology target 104 correctly.
- FIG. 7A shows the metrology target 104 including the dummy structure DS in accordance with some embodiments.
- the metrology target 104 includes overlay targets OT 1 -OT 4 as shown in FIGS. 2A-2C .
- FIG. 7A shows the components of the metrology target 104 in layer m 1 for the purpose of clarity.
- the gratings G 1 and G 2 are formed based on the spatial period P 1 , and the workable wavelength ( ⁇ x ) corresponding to the overlay targets OT 1 and OT 2 of the metrology target 104 are represented by equation (3) according to the content described in FIG. 6A .
- the gratings G 5 and G 6 are formed based on the spatial P 2 . Specifically, the components of gratings G 5 and G 6 are arranged to repeat with the spatial period P 2 , respectively.
- the workable wavelength ( ⁇ y ) corresponding to the overlay targets OT 3 and OT 4 of the metrology target 104 can be represented by equation (6).
- the parameter (NA) is the numerical aperture of the optical device 102 .
- the parameter (NA) is a value from 0.7 to 1.35 (i.e., the parameter (NA min ) is 0.7 and the parameter (NA max ) is 1.35), which allows the light LR (as shown in FIG. 1 ) generated based on the overlay targets OT 3 and OT 4 to be detected correctly by the light detection circuit 105 .
- the dummy structure DS includes multiple dummy components DC which are periodically placed along the directions X and Y.
- the dummy components DC are arranged to repeat with the spatial period P 11 which are the sum of the length L 11 (which is the side length of one dummy component DC) and length S 11 (which is the space between two adjacent dummy components DC).
- the dummy components DC are arranged to repeat with the spatial period P 22 which are the sum of the length L 22 (which is the side length of one dummy component DC) and length S 22 (which is the space between two adjacent dummy components DC), as shown in FIG. 7A .
- the design condition (e.g., equations (3)-(5)) of the dummy components and the gratings G 1 and G 2 are similar (or equal) to the embodiments described in FIG. 6A , and they are not repeated again.
- the spatial period P 22 is less than the spatial period P 2 to avoid the dummy components DC affecting the results of the DBO measurement performed based on the overlay targets OT 3 and OT 4 .
- the spatial period P 22 is less than the spatial period P 2 to make the processor 106 be able to distinguish the image data corresponding to the dummy structure DS and the image data corresponding to the overlay targets OT 3 and OT 4 of the metrology target 104 (wherein the image data is generated by the light detection circuit 105 ), the processor 106 can analyze the image data corresponding to the overlay targets of the metrology target 104 correctly.
- the spatial period P 22 is represented as:
- the spatial period P 22 is less than the minimum workable wavelength ( ⁇ y,min ) corresponding to the overlay targets OT 3 and OT 4 of the metrology target 104 .
- the spatial period P 22 is greater than the spatial period P 2 to avoid the dummy components DC affecting the results of the DBO measurement performed based on the overlay targets OT 3 and OT 4 .
- the spatial period P 22 is represented as
- the spatial period P 22 is further represented by equation (8).
- the spatial period P 22 is greater than the maximum workable wavelength ( ⁇ y,max ) corresponding to the overlay targets OT 3 and OT 4 of the metrology target 104 .
- the spatial period P 22 is greater than the spatial period P 2 .
- the brightness of the image data corresponding to the dummy structure DS is different from the brightness of the image data corresponding to the overlay targets OT 3 and OT 4 of the metrology target 104 (wherein the image data is generated by the light detection circuit 105 ), and the processor 106 is able to distinguish the image data corresponding to the dummy structure DS and the image data corresponding to the overlay targets OT 3 and OT 4 of the metrology target 104 and makes the processor 106 analyze the image data corresponding to the overlay targets OT 3 and OT 4 of the metrology target 104 correctly.
- FIG. 7B shows metrology target 104 including the dummy structure DS in accordance with some embodiments.
- the metrology target 104 includes overlay targets OT 1 -OT 4 as shown in FIGS. 2A-2C .
- FIG. 7B shows the components of the metrology target 104 in layer m 1 for the purpose of clarity.
- the dummy structure DS is extended along the directions Y and ⁇ Y to separate the gratings G 1 and G 2 and extended along the directions X and ⁇ X to separate the gratings G 5 and G 6 .
- the dummy structure is not formed based on a spatial period and is formed by a single dummy component, which makes the brightness of the image data corresponding to the dummy structure DS different from the brightness of the image data corresponding to the overlay targets OT 1 -OT 4 of the metrology target 104 (wherein the image data is generated by the light detection circuit 105 ).
- the processor 106 can distinguish the image data corresponding to the dummy structure DS and the image data corresponding to the overlay targets OT 1 -OT 4 of the metrology target 104 and analyze the image data corresponding to the overlay targets OT 1 -OT 4 of the metrology target 104 correctly.
- FIG. 7C shows the metrology target 104 including the dummy structure DS in accordance with some embodiments.
- the difference between the metrology target 104 in FIG. 7A and the metrology target 104 in FIG. 7C is the dummy structure DS.
- the dummy structure DS includes multiple dummy components DC which are periodically placed along the direction X.
- the dummy components DC are arranged to repeat with the spatial period P 33 which are the sum of the length L 33 (which is the side length of one dummy component DC) and length S 33 (which is the space between two adjacent dummy components DC).
- the spatial period P 33 is less than the spatial period P 1 to avoid the dummy components DC affecting the results of the DBO measurement performed based on the overlay targets OT 1 and OT 2 .
- the spatial period P 33 is represented as
- the spatial period P 33 is further represented by equation (9).
- the spatial period P 33 is less than the minimum workable wavelength ( ⁇ x,min ) corresponding to the overlay targets OT 1 and OT 2 of the metrology target 104 .
- the spatial period P 33 is greater than the spatial period P 2 to avoid the dummy components DC affecting the results of the DBO measurement performed based on the overlay targets OT 1 and OT 2 .
- the spatial period P 33 is represented as
- the spatial period P 33 is further represented by equation (10).
- the spatial period P 33 is greater than the maximum workable wavelength ( ⁇ x,max ) corresponding to the overlay targets OT 1 and OT 2 of the metrology target 104 .
- the dummy components DC are extended along the directions Y and ⁇ Y and are not arranged to repeat with a spatial period, which makes the brightness of the image data corresponding to the dummy structure DS different from the brightness of the image data corresponding to the overlay targets OT 3 and OT 4 of the metrology target 104 (wherein the image data is generated by the light detection circuit 105 ). Accordingly, the processor 106 can distinguish the image data corresponding to the dummy structure DS and the image data corresponding to the overlay targets OT 3 and OT 4 of the metrology target 104 and analyze the image data corresponding to the overlay targets OT 3 and OT 4 of the metrology target 104 correctly.
- the dummy components DC in FIG. 7C can be modified to be periodically placed along the direction Y and extended along the directions X and ⁇ X, as shown in FIG. 7D .
- multiple dummy components DC of the dummy structure DS are periodically formed along the direction Y.
- the dummy components DC are arranged to repeat with the spatial period P 44 which are the sum of the length L 44 (which is the side length of one dummy component DC) and length S 44 (which is the space between two adjacent dummy components DC).
- the spatial period P 44 is less than the spatial period P 2 to avoid the dummy components DC affecting the results of the DBO measurement performed based on the overlay targets OT 3 and OT 4 .
- the spatial period P 44 is represented as
- the spatial period P 44 is further represented by equation (11).
- the spatial period P 44 is less than the minimum workable wavelength ( ⁇ y,min ) corresponding to the overlay targets OT 3 and OT 4 of the metrology target 104 .
- the spatial period P 44 is greater than the spatial period P 2 to avoid the dummy components DC affecting the results of the DBO measurement performed based on the overlay targets OT 3 and OT 4 .
- the spatial period P 44 is represented as
- the spatial period P 44 is further represented by equation (12).
- the spatial period P 44 is greater than the maximum workable wavelength ( ⁇ y,max ) corresponding to the overlay targets OT 3 and OT 4 of the metrology target 104 .
- the dummy components DC are extended along the directions X and ⁇ X and are not arranged to repeat with a spatial period, which makes the brightness of the image data corresponding to the dummy structure DS different from the brightness of the image data corresponding to the overlay targets OT 3 and OT 4 of the metrology target 104 (wherein the image data is generated by the light detection circuit 105 ). Accordingly, the processor 106 can distinguish the image data corresponding to the dummy structure DS and the image data corresponding to the overlay targets OT 3 and OT 4 of the metrology target 104 and analyze the image data corresponding to the overlay targets OT 3 and OT 4 of the metrology target 104 correctly.
- dummy structures can be formed in both layer m 1 and layer m 2 .
- the dummy structure DS 2 is formed between each grating in the layer m 2 of the metrology target 104 , and the material of the dummy structure DS 2 is the same as the gratings G 3 , G 4 , G 7 , and G 8 .
- the layer m 2 can be metal.
- FIGS. 8B and 8C show the cross-sectional diagram of the metrology target 104 including the dummy structures DS and DS 2 in accordance with some embodiments. Compared with the embodiments described in FIGS. 4B-4C , FIGS. 8B and 8C show that the metrology target 104 further has the dummy structure DS 2 in the layer m 2 . In such cases, the dishing effect on the structures formed over the metrology target 104 can be improved, and the metrology targets formed over the metrology target 104 can be fabricated properly.
- each grating in layer m 2 of the metrology target 104 is surrounded by dummy components. As shown in FIG. 8D , the gratings G 3 , G 4 , G 7 , and G 8 are respectively surrounded by the dummy components of the dummy structures DS 2 and DSO 2 to reduce the difference in component density between the metrology target 104 and the patterns formed around the metrology target 104 in layer m 2 .
- the dummy structure DS 2 can be formed based on the spatial period of the gratings G 3 , G 4 , G 7 , and G 8 .
- the dummy structure DS 2 in FIGS. 8B and 8C can be formed as one of the dummy structures DS described in FIGS. 6A, 6B, 7A, 7B, 7C, and 7D .
- the dummy structure DS and the dummy structure DS 2 are formed identically.
- the dummy structure DS and the dummy structure DS 2 are formed differently.
- FIG. 9A illustrates a manufacturing method 900 A of a metrology target (e.g., metrology target 104 ) of a semiconductor device (e.g., semiconductor device 103 ).
- a metrology target e.g., metrology target 104
- a semiconductor device e.g., semiconductor device 103
- a first grating (e.g., grating G 1 ) and a second grating (e.g., grating G 2 ) are formed in a first layer (e.g., layer m 1 ) of a substrate of the semiconductor device (e.g., semiconductor device 103 ), wherein the first grating and the second grating are formed based on a first spatial period (e.g., spatial period P 1 ).
- a first dummy structure (e.g., dummy structure DS) is formed in the first layer, wherein the first dummy structure is at least formed between the first grating and the second grating.
- a third grating e.g., grating G 3
- a fourth grating e.g., grating G 4
- a second layer e.g., layer m 2
- the third grating and the fourth grating are formed based on the first spatial period and placed to overlap the first grating and the second grating, respectively.
- the second layer is formed over the first layer.
- the first grating and the third grating are formed with a first positional offset (e.g., positional offset d 1 ) which is along a first direction (e.g., direction X).
- the second grating and the fourth grating are formed with a second positional offset (e.g., positional offset d 1 ′) which is along a second direction (e.g., direction ⁇ X).
- the first direction is opposite to the second direction.
- FIG. 9B shows simplified flowcharts illustrating a manufacturing method 900 B of a metrology target (e.g., metrology target 104 ) of a semiconductor device (e.g., semiconductor device 103 ).
- the manufacturing method 900 B includes operations 920 and 930 .
- the operation 920 includes operations 921 - 923
- the operation 930 includes operations 931 - 932 .
- a first grating (e.g., grating G 1 ) and a second grating (e.g., grating G 2 ) are formed in a first layer (e.g., layer m 1 ) of a substrate of the semiconductor device (e.g., semiconductor device 103 ), wherein the first grating and the second grating are formed based on a first spatial period (e.g., spatial period P 1 ).
- a fifth grating e.g., grating G 5
- a sixth grating e.g., grating G 6
- a second spatial period e.g., spatial period P 2
- a first dummy structure (e.g., dummy structure DS) is formed in the first layer, wherein the first dummy structure is at least formed between the first grating and the second grating and formed between the fifth grating and the sixth grating.
- a third grating e.g., grating G 3
- a fourth grating e.g., grating G 4
- a second layer e.g., layer m 2
- the third grating and the fourth grating are formed based on the first spatial period and placed to overlap the first grating and the second grating, respectively.
- a seventh grating e.g., grating G 7
- an eighth grating e.g., grating G 8
- the seventh grating and the eighth grating are formed based on the second spatial period and placed to overlap the fifth grating and the sixth grating, respectively.
- the second layer is formed over the first layer.
- the first grating and the third grating are formed with a first positional offset (e.g., positional offset d 1 ) which is along a first direction (e.g., direction X).
- the second grating and the fourth grating are formed with a second positional offset (e.g., positional offset d 1 ′) which is along a second direction (e.g., direction ⁇ X).
- the first direction is opposite to the second direction.
- the fifth grating and the seventh grating are formed with a third positional offset (e.g., positional offset d 2 ) which is along a third direction (e.g., direction Y).
- the sixth grating and the eighth grating are formed with a fourth positional offset (e.g., positional offset d 2 ′) which is along a fourth direction (e.g., direction ⁇ Y).
- the third direction is opposite to the fourth direction, and the third direction is perpendicular to the first direction.
- the metrology targets e.g. metrology target 104 having a dummy structure (e.g. the dummy structure DS) are provided.
- the metrology target having a dummy structure can reduce the dishing effect and improve the accuracy of the DBO measurement. Since the accuracy of the DBO measurement is improved, the yield in manufacturing the semiconductor device (e.g., semiconductor device 103 ) is also improved. Therefore, the efficiency of fabricating the semiconductor device is improved, and the cost of the semiconductor-manufacturing process can be reduced.
- a metrology target of a semiconductor device includes a substrate.
- the substrate includes a first layer and a second layer.
- the first layer includes a first grating, a second grating, and a first dummy structure.
- the first grating is formed based on a first spatial period.
- the second grating is formed based on the first spatial period.
- the first dummy structure is at least formed between the first grating and the second grating.
- the second layer is formed over the first layer and includes a third grating and a fourth grating.
- the third grating is formed based on the first spatial period and placed to overlap the first grating.
- the fourth grating is formed based on the first spatial period and placed to overlap the second grating.
- the first grating and the third grating are formed with a first positional offset which is along a first direction.
- the second grating and the fourth grating are formed with a second positional offset which is along a second direction.
- the first direction is opposite to the second direction.
- a metrology target of a semiconductor device includes a substrate which includes a first layer and a second layer.
- the first layer includes a first grating, a second grating, and a first dummy structure.
- the first grating is formed based on a first spatial period.
- the second grating is formed based on the first spatial period.
- the first dummy structure is at least formed between the first grating and the second grating.
- the second layer is formed over the first layer and includes a third grating, a fourth grating, and a second dummy structure.
- the third grating is formed based on the first spatial period and placed to overlap the first grating.
- the fourth grating is formed based on the first spatial period and placed to overlap the second grating.
- the second dummy structure is at least formed between the third grating and the fourth grating.
- the first grating and the third grating are formed with a first positional offset which is along a first direction.
- the second grating and the fourth grating are formed with a second positional offset which is along a second direction.
- the first direction is opposite to the second direction.
- a manufacturing method of a metrology target of a semiconductor device is provided.
- a first grating and a second grating in a first layer of a substrate of the semiconductor device are formed, wherein the first grating and the second grating are formed based on a first spatial period.
- a first dummy structure in the first layer is formed, wherein the first dummy structure is at least formed between the first grating and the second grating.
- a third grating and a fourth grating in a second layer of the substrate are formed, wherein the third grating and the fourth grating are formed based on the first spatial period and placed to overlap the first grating and the second grating, respectively.
- the second layer is formed over the first layer.
- the first grating and the third grating are formed with a first positional offset which is along a first direction.
- the second grating and the fourth grating are formed with a second positional offset which is along a second direction.
- the first direction is opposite to the second direction.
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Abstract
Description
- Generally, a semiconductor integrated circuit (IC) is formed on multiple layers of a semiconductor substrate (or a semiconductor wafer). In order to properly fabricate a semiconductor integrated circuit, some layers of the substrate need to be aligned with each other. In such cases, a metrology target (or alignment mark) formed in a semiconductor substrate is utilized to perform the overlay (or alignment) measurements.
- The metrology target may include a plurality of gratings, and an overlay shift between different layers of the semiconductor substrate can be measured based on the arrangement of the gratings.
- Although existing metrology targets have generally been adequate for their intended purposes, they have not been entirely satisfactory in all respects. Consequently, there is a need for a metrology target and manufacturing method thereof that provides a solution for the overlay-shift measurement.
- Aspects of the present disclosure are best understood from the following detailed description when read with the accompanying figures. It should be noted that, in accordance with the standard practice in the industry, various features are not drawn to scale. In fact, the dimensions of the various features may be arbitrarily increased or reduced for clarity of discussion.
-
FIG. 1 shows a schematic diagram of an overlay-shift measurement system in accordance with some embodiments. -
FIGS. 2A-2C show a metrology target in accordance with some embodiments. -
FIGS. 3A-3D show a metrology target having a dishing effect in accordance with some embodiments. -
FIGS. 4A-4D show a metrology target including a dummy structure in accordance with some embodiments. -
FIG. 5 shows a metrology target including a dummy structure in accordance with some embodiments. -
FIGS. 6A-6B show metrology targets which respectively include a dummy structure in accordance with some embodiments. -
FIGS. 7A-7D show metrology targets which respectively include a dummy structure in accordance with some embodiments. -
FIGS. 8A-8D show metrology targets which respectively include a dummy structure in accordance with some embodiments. -
FIGS. 9A-9B illustrate a manufacturing method of a metrology target of a semiconductor device. - The following disclosure provides many different embodiments, or examples, for implementing different features of the provided subject matter. Specific examples of components and arrangements are described below to simplify the present disclosure. These are, of course, merely examples and are not intended to be limiting. For example, the formation of a first feature over or on a second feature in the description that follows may include embodiments in which the first and second features are formed in direct contact, and may also include embodiments in which additional features may be formed between the first and second features, such that the first and second features may not be in direct contact. In addition, the present disclosure may repeat reference numerals and/or letters in the various examples. This repetition is for the purpose of simplicity and clarity and does not in itself dictate a relationship between the various embodiments and/or configurations discussed.
- Furthermore, spatially relative terms, such as “beneath,” “below,” “lower,” “above,” “upper” and the like, may be used herein for ease of description to describe one element or feature's relationship to another element(s) or feature(s) as illustrated in the figures. The spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. The apparatus may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein may likewise be interpreted accordingly.
- Some variations of the embodiments are described. Throughout the various views and illustrative embodiments, like reference numbers are used to designate like elements. It should be understood that additional operations can be provided before, during, and/or after a disclosed method, and some of the operations described can be replaced or eliminated for other embodiments of the method.
-
FIG. 1 shows a schematic diagram of an overlay-shift measurement system 100 in accordance with some embodiments. The overlay-shift measurement system 100 includes alight source 101, anoptical device 102, asemiconductor device 103, alight detection circuit 105, and aprocessor 106. In some embodiments, thesemiconductor device 103 is a semiconductor substrate (or a wafer) and includes ametrology target 104. In some embodiments, thesemiconductor device 103 includes multiple layers, and themetrology target 104 includes a plurality of gratings which are formed in different layers and overlap each other. - In some embodiments, the overlay-
shift measurement system 100 may perform a diffraction-based overlay (DBO) measurement on themetrology target 104. For example, thelight source 101 is configured to provide light to theoptical device 102, and then theoptical device 102 provides the light LI to themetrology target 104. In response to the light LI illuminating themetrology target 104, the light LR is generated, and the light LR includes at least one diffraction light (e.g., +1 order or −1 order) corresponding to the light LI. Thelight detection circuit 105 is configured to detect the light LR and then generates the data corresponding to the light LR (e.g., the image data generated by the light LR). Theprocessor 106 is configured to receive the data from thelight detector 105. Subsequently, theprocessor 106 analyzes the data to determine the overlay shift between the gratings, which are formed in different layers, of themetrology target 104. - In some embodiments, the
processor 106 analyzes the light-intensity difference between the diffraction lights which are detected by thelight detection circuit 105 to determine the overlay shift between gratings of themetrology target 104. In some embodiments, the aforementioned DBO measurement is performed after a lithography process. -
FIG. 2A shows ametrology target 104 in accordance with some embodiments. Themetrology target 104 includes overlay targets OT1-OT4. In some embodiments, the overlay targets OT1 and OT2 are fabricated asFIG. 2B , and the overlay targets OT3 and OT4 are fabricated asFIG. 2C . -
FIG. 2B shows the cross-sectional diagram of overlay targets OT1 and OT2 in accordance with some embodiments. The overlay target OT1 includes gratings G1 and G3. The grating G1 is formed in layer m1 of thesemiconductor device 103, and the grating G3 is formed in layer m2 of thesemiconductor device 103. In this embodiment, the gratings G1 and G3 are formed based on a spatial period P1. Specifically, the components of grating G1 are arranged to repeat with the spatial period P1, and the components of grating G3 are also arranged to repeat with the spatial period P1, as shown inFIG. 2B . Moreover, the grating G3 is placed to overlap the grating G1 and placed to have a predetermined offset (along the direction X) compared with the grating G1. In some embodiments, the process variation of thesemiconductor device 103 may cause an unknown displacement between the gratings G1 and G3, which makes the gratings G1 and G3 have a positional offset d1 which is the combination of the predetermined offset and the unknown displacement. In this embodiment, the positional offset d1 is along the direction X, as shown inFIG. 2B . - On the other hand, the overlay target OT2 includes gratings G2 and G4. The grating G2 is formed in layer m1 of the
semiconductor device 103, and the grating G4 is formed in layer m2 of thesemiconductor device 103. In this embodiment, the gratings G2 and G4 are formed based on the spatial period P1. Specifically, the components of grating G2 are arranged to repeat with the spatial period P1, and the components of grating G4 are also arranged to repeat with the spatial period P1, as shown inFIG. 2B . Moreover, the grating G4 is placed to overlap the grating G2 and placed to have a predetermined offset (along the direction −X) compared with the grating G2. In some embodiments, the process variation of thesemiconductor device 103 may cause an unknown displacement between the gratings G2 and G4, which makes the gratings G2 and G4 have a positional offset d1′ which is the combination of the predetermined offset and the unknown displacement. In this embodiment, the positional offset d1′ is along the direction −X, and the direction of the positional offset d1′ is opposite to the direction of the positional offset d1, as shown inFIG. 2B . - In some embodiments, the magnitude of the positional offset d1 is the same as the magnitude of the positional offset d1′ if the positional offsets d1 and d1′ are not affected by the unknown displacement. In some embodiments, the unknown displacement is caused by the process variations which are generated during the manufacturing of the semiconductor device 103 (e.g., erosion, dishing, etc).
- In some embodiments, the overlay-
shift measurement system 100 performs the DBO measurement on the overlay targets OT1 and OT2 to determine the overlay shift, which occurs in directions X or −X, of thesemiconductor device 103 based on the diffraction lights (e.g., +1 order, −1 order, etc.) generated by the light LI and the overlay targets OT1 and OT2. - For example, the light LI in
FIG. 1 illuminates the overlay targets OT1 and OT2 to generate the light LR. Next, the light LR is detected by thelight detection circuit 105 and converted to image data. Based on the image data, theprocessor 106 determines an asymmetry signal (ASX1) which represents the asymmetry in the intensity of different diffraction orders (e.g., +1 order and −1 order, or other orders) generated by the light LI and the overlay target OT1 and determines an asymmetry signal (ASX2) which represents the asymmetry in the intensity of different diffraction orders generated by the light LI and the overlay target OT2. - Furthermore, the
processor 106 determines the overlay shift (OVS1), which occurs in directions X or −X, of themetrology target 104 based on equation (1) described below. -
- The constant (c1) is a predetermined offset, and the positional offsets d1 and d1′ are the combination of the predetermined offset (c1) and an unknown displacement (de1) caused by the process variations of the
semiconductor device 103. For example, the positional offset d1 is equal to “c1+de1,” and the positional offset d1′ is equal to “−c1+de1”. - Similarly,
FIG. 2C shows the cross-sectional diagram of overlay targets OT3 and OT4 in accordance with some embodiments. The overlay target OT3 includes gratings G5 and G7. The grating G5 is formed in layer m1 of thesemiconductor device 103, and the grating G7 is formed in layer m2 of thesemiconductor device 103. In this embodiment, the gratings G5 and G7 are formed based on a spatial period P2. Specifically, the components of grating G5 are arranged to repeat with the spatial period P2, and the components of grating G7 are also arranged to repeat with the spatial period P2, as shown inFIG. 2C . Moreover, the grating G7 is placed to overlap the grating G5 and placed to have a predetermined offset (along the direction Y) compared with the grating G5. In some embodiments, the process variation of thesemiconductor device 103 may cause an unknown displacement between the gratings G5 and G7, which makes the gratings G5 and G7 have a positional offset d2 which is the combination of the predetermined offset and the unknown displacement. In this embodiment, the positional offset d2 is along the direction Y, as shown inFIG. 2C . In some embodiments, the spatial period P1 can be equal to the spatial period P2. In some embodiments, the spatial period P1 can be different from the spatial period P2. - Additionally, the overlay target OT4 includes gratings G6 and G8. The grating G6 is formed in layer m1 of the
semiconductor device 103, and the grating G8 is formed in layer m2 of thesemiconductor device 103. In this embodiment, the gratings G6 and G8 are formed based on the spatial period P2. Specifically, the components of grating G6 are arranged to repeat with the spatial period P2, and the components of grating G8 are also arranged to repeat with the spatial period P2, as shown inFIG. 2C . Furthermore, the grating G8 is placed to overlap the grating G6 and placed to have a predetermined offset (along the direction −Y) compared with the grating G6. In some embodiments, the process variation of thesemiconductor device 103 may cause an unknown displacement between the gratings G6 and G8, which makes the gratings G6 and G8 have a positional offset d2′ which is the combination of the predetermined offset and the unknown displacement. In this embodiment, the positional offset d2′ is along the direction −Y, and the direction of the positional offset d2′ is opposite to the direction of the positional offset d2, as shown inFIG. 2C . - In some embodiments, the magnitude of the positional offset d2 is the same as the magnitude of the positional offset d2′ if the positional offsets d2 and d2′ are not affected by an unknown displacement. In some embodiments, the unknown displacement is caused by the process variations which are generated during the manufacturing of the semiconductor device 103 (e.g., erosion, dishing, or the like).
- In some embodiments, the overlay-
shift measurement system 100 performs the DBO measurement on the overlay targets OT3 and OT4 to determine the overlay shift, which occurs in directions Y or −Y, of thesemiconductor device 103 based on the diffraction lights (e.g., +1 order, −1 order, etc.) generated by the light LI and the overlay targets OT3 and OT4. - For example, the light LI in
FIG. 1 illuminates the overlay targets OT3 and OT4 to generate the light LR. Next, the light LR is detected by thelight detection circuit 105 and converted to image data. Based on the image data, theprocessor 106 determines an asymmetry signal (ASY1) which represents the asymmetry in the intensity of different diffraction orders (e.g., +1 order and −1 order, or other orders) generated by the light LI and the overlay target OT3 and determines an asymmetry signal (ASY2) which represents the asymmetry in the intensity of different diffraction orders generated by the light LI and the overlay target OT4. - Furthermore, the
processor 106 determines the overlay shift (OVS2), which occurs in directions Y or −Y, of themetrology target 104 based on equation (2) described below. -
- The constant (c2) is a predetermined offset, and the positional offsets d2 and d2′ are the combination of the predetermined offset (c2) and an unknown displacement (de2) caused by the process variations of the
semiconductor device 103. For example, the positional offset d2 is equal to “c2+de2,” and the positional offset d2′ is equal to “−c2+de2”. - In some embodiments, the placement of the
metrology target 104 can be changed. For example, the positions of overlay targets OT1 and OT2 can be exchanged, or the positions of overlay targets OT3 and OT4 can be exchanged. In some embodiments, the component density of themetrology target 104 may be different from the component density around themetrology target 104. In such cases, the dishing may occur at themetrology target 104, or the erosion may occur at multiple metrology targets 104. -
FIGS. 3A-3D show themetrology target 104 having a dishing effect in accordance with some embodiments. In some embodiments, the component density of themetrology target 104 in layer m1 is lower than the component density of patterns around themetrology target 104 in layer m1, and the dishing effect occurs at structures, which are formed over the layer m1, of themetrology target 104. In such cases, the dishing effect causes themetrology target 104 to have a substantially bowl shape (as shown inFIGS. 3B and 3C ), and the lowest position is located in the region R (as shown inFIGS. 3A-3D ). -
FIGS. 3B and 3C show the cross-sectional diagram of themetrology target 104 having the dishing effect in accordance with some embodiments. The component density of themetrology target 104 in the layer m1 is different from the component density of patterns in the layer m1 around the metrology target 104 (e.g., the component density of gratings G1, G2, G5, and G6 is lower than the component density of patterns around the gratings G1, G2, G5, and G6). In such cases, dishing effect occurs at structures, which are formed over the layer m1 (e.g., the layer m2), of themetrology target 104, and the gratings G3, G4, G7, and G8 are sunk by the dishing effect, which causes the shift of the DBO measurement performed based on themetrology target 104. - As shown in
FIG. 3D , the dishing effect makes the components in layer m2 of the overlay targets OT1 and OT2 have different altitude and be tilted by different angles. Accordingly, the asymmetry signal (ASX1) corresponding to the overlay target OT1 and the asymmetry signal (ASX2) corresponding to the overlay target OT2 are affected by different altitude deviation and different angle changes, which makes the asymmetry signal (ASX1) have deviation (A1) and makes the asymmetry signal (ASX2) have deviation (A2) which is different from deviation (A1). - According to equation (1), the overlay shift OVS1 corresponds to the ratio of the asymmetry signals (ASX2) and (ASX1). Since the deviation (A1) of the asymmetry signal (ASX1) is different from the deviation (A2) of the asymmetry signal (ASX2), the ratio of the asymmetry signals (ASX2) and (ASX1) under the dishing effect has additional deviation and is not equal to the original ratio of the asymmetry signals (ASX2) and (ASX1), which can be represented as:
-
- In such cases, the overlay shift (OVS1) in equation (1) is affected by the dishing effect, and the accuracy of the overlay shift (OVS1) is degraded.
- Similarly, since the deviation (B1) of the asymmetry signal (ASY1) is different from the deviation (B2) of the asymmetry signal (ASY2), the ratio of the asymmetry signals (ASY2) and (ASY1) under the dishing effect has additional deviation and is not equal to the original ratio of the asymmetry signals (ASY2) and (ASY1), which can be represented as:
-
- In such cases, the overlay shift (OVS2) in equation (2) is affected by the dishing effect, and the accuracy of the overlay shift (OVS2) is degraded.
-
FIGS. 4A-4C show ametrology target 104 including a dummy structure DS in accordance with some embodiments. Referring toFIG. 4A , the dummy structure DS is formed between each grating in the layer m1 of themetrology target 104, and the material of the dummy structure DS is the same as the gratings G1, G2, G5, and G6. In some embodiments, the layer m1 can be metal. -
FIGS. 4B and 4C show the cross-sectional diagram of themetrology target 104 including the dummy structure DS in accordance with some embodiments. In some embodiments, the component density of themetrology target 104 in layer m1 is lower than the component density of patterns around themetrology target 104 in layer m1, and the dummy structure DS is placed between each grating of themetrology target 104 in the layer m1. The dummy structure DS reduces the difference in component density between themetrology target 104 and the patterns formed around themetrology target 104 in layer m1. Since the component density of themetrology target 104 in layer m1 is close to the component density of patterns formed around themetrology target 104 in the layer m1, the dishing effect occurring at layer m2 can be improved as shown inFIGS. 4B and 4C . In such cases, the accuracy of the DBO measurement performed based on themetrology target 104 is also improved. - In some embodiments, each grating in layer m1 of the
metrology target 104 is surrounded by dummy components. As shown inFIG. 4D , the gratings G1, G2, G5, and G6 are respectively surrounded by the dummy components of the dummy structures DS and DSO to reduce the difference in component density between themetrology target 104 and the patterns formed around themetrology target 104 in layer m1. - In some embodiments, the
metrology target 104 having dummy structure may still have the dishing effect in the area of each grating in the layer m2, as shown inFIG. 5 . In such cases, since each grating in the layer m2 (e.g., gratings G3, G4, G7, and G8) of themetrology target 104 is sunk based on its own central area, the gratings of themetrology target 104 in the layer m2 have similar shape distortion, as shown inFIG. 5 . Accordingly, the asymmetry signals (ASX1), (ASX2), (ASY1), and (ASY2) respectively corresponding to the overlay targets OT1, OT2, OT3, and OT4 are affected by similar altitude deviation and similar angle changes. - For example, the deviation (A11) of the asymmetry signals (ASX1) and the deviation (A22) of the (ASX2) are similar to each other, which can be represented as:
-
- In such cases, the accuracy of the overlay shift (OVS1) in equation (1) can be maintained.
- Similarly, the deviation (B11) of the asymmetry signals (ASY1) and the deviation (B22) of the (ASY2) are similar to each other, which can be represented as:
-
- In such cases, the accuracy of the overlay shift (OVS2) in equation (2) can be maintained.
-
FIG. 6A shows themetrology target 104 including the dummy structure DS in accordance with some embodiments. Themetrology target 104 includes overlay targets OT1 and OT2 as shown inFIG. 2B .FIG. 6A shows the components of themetrology target 104 in layer m1 for the purpose of clarity. - As shown in
FIG. 6A , the gratings G1 and G2 are formed based on the spatial period P1. Specifically, the components of grating G1 are arranged to repeat with the spatial period P1, and the components of grating G2 are also arranged to repeat with the spatial period P1. In such cases, the workable wavelength (λx) corresponding to the overlay targets OT1 and OT2 of themetrology target 104 can be represented by equation (3). -
P1×NAmin<λx <P1×NAmax (3) - The parameter (NA) is the numerical aperture of the
optical device 102. In some embodiments, the parameter (NA) is a value from 0.7 to 1.35 (i.e., the parameter (NAmin) is 0.7 and the parameter (NAmax) is 1.35), which allows the light LR (as shown inFIG. 1 ) generated based on the overlay targets OT1 and OT2 to be detected correctly by thelight detection circuit 105. - As shown in
FIG. 6A , the dummy structure DS includes multiple dummy components DC which are periodically placed along the direction X. In the direction X, the dummy components DC are arranged to repeat with the spatial period P11 which are the sum of the length L11 (which is the side length of one dummy component DC) and length S11 (which is the space between two adjacent dummy components DC). - In some embodiments, the spatial period P11 is less than the spatial period P1 to avoid the dummy components DC affecting the results of the DBO measurement performed based on the overlay targets OT1 and OT2. For example, when the spatial period P11 is less than the spatial period P1, the brightness of the image data corresponding to the dummy structure DS is different from (e.g., darker than) the brightness of the image data corresponding to the overlay targets OT1 and OT2 of the metrology target 104 (wherein the image data is generated by the light detection circuit 105). When the spatial period P11 is less than the spatial period P1 to make the
processor 106 be able to distinguish the image data corresponding to the dummy structure DS and the image data corresponding to the overlay targets of themetrology target 104, theprocessor 106 can analyze the image data corresponding to the overlay targets OT1 and OT2 of themetrology target 104 correctly. In some embodiments, the spatial period P11 is represented as -
- wherein the (λx,min) is the minimum workable wavelength corresponding to the overlay targets OT1 and OT2 of the
metrology target 104. Based on equation (3), the spatial period P11 is further represented by equation (4). -
- In some embodiments, the spatial period P11 is less than the minimum workable wavelength (λx,min) corresponding to the overlay targets OT1 and OT2 of the
metrology target 104. - In some embodiments, the spatial period P11 is greater than the spatial period P1 to avoid the dummy components DC affecting the results of the DBO measurement performed based on the overlay targets OT1 and OT2. In some embodiments, the spatial period P11 is represented as
-
- wherein the (λx,max) is the maximum workable wavelength corresponding to the overlay targets OT1 and OT2 of the
metrology target 104. Based on equation (3), the spatial period P11 is further represented by equation (5). -
- In some embodiments, the spatial period P11 is greater than the maximum workable wavelength (λx,max) corresponding to the overlay targets OT1 and OT2 of the
metrology target 104. - Based on equation (5), the spatial period P11 is greater than the spatial period P1. In such cases, the brightness of the image data corresponding to the dummy structure DS is different from the brightness of the image data corresponding to the overlay targets OT1 and OT2 of the metrology target 104 (wherein the image data is generated by the light detection circuit 105), and the
processor 106 is able to distinguish the image data corresponding to the dummy structure DS and the image data corresponding to the overlay targets OT1 and OT2 of themetrology target 104 and makes theprocessor 106 analyze the image data corresponding to the overlay targets OT1 and OT2 of themetrology target 104 correctly. -
FIG. 6B showsmetrology target 104 including the dummy structure DS in accordance with some embodiments. Themetrology target 104 includes overlay targets OT1 and OT2 as shown inFIG. 2B .FIG. 6B shows the components of themetrology target 104 in layer m1 for the purpose of clarity. - As shown in
FIG. 6B , the dummy structure DS is extended along the directions Y and −Y to separate the gratings G1 and G2. In this embodiment, the dummy structure is not formed based on a spatial period and is formed by a single dummy component, which makes the brightness of the image data corresponding to the dummy structure DS different from the brightness of the image data corresponding to the overlay targets OT1 and OT2 of the metrology target 104 (wherein the image data is generated by the light detection circuit 105). Accordingly, theprocessor 106 can distinguish the image data corresponding to the dummy structure DS and the image data corresponding to the overlay targets OT1 and OT2 of themetrology target 104 and analyze the image data corresponding to the overlay targets OT1 and OT2 of themetrology target 104 correctly. -
FIG. 7A shows themetrology target 104 including the dummy structure DS in accordance with some embodiments. Themetrology target 104 includes overlay targets OT1-OT4 as shown inFIGS. 2A-2C .FIG. 7A shows the components of themetrology target 104 in layer m1 for the purpose of clarity. - As shown in
FIG. 7A , the gratings G1 and G2 are formed based on the spatial period P1, and the workable wavelength (λx) corresponding to the overlay targets OT1 and OT2 of themetrology target 104 are represented by equation (3) according to the content described inFIG. 6A . The gratings G5 and G6 are formed based on the spatial P2. Specifically, the components of gratings G5 and G6 are arranged to repeat with the spatial period P2, respectively. In such cases, the workable wavelength (λy) corresponding to the overlay targets OT3 and OT4 of themetrology target 104 can be represented by equation (6). -
P2×NAmin<λy <P2×NAmax (6) - The parameter (NA) is the numerical aperture of the
optical device 102. In some embodiments, the parameter (NA) is a value from 0.7 to 1.35 (i.e., the parameter (NAmin) is 0.7 and the parameter (NAmax) is 1.35), which allows the light LR (as shown inFIG. 1 ) generated based on the overlay targets OT3 and OT4 to be detected correctly by thelight detection circuit 105. - As shown in
FIG. 7A , the dummy structure DS includes multiple dummy components DC which are periodically placed along the directions X and Y. In direction X, the dummy components DC are arranged to repeat with the spatial period P11 which are the sum of the length L11 (which is the side length of one dummy component DC) and length S11 (which is the space between two adjacent dummy components DC). In direction Y, the dummy components DC are arranged to repeat with the spatial period P22 which are the sum of the length L22 (which is the side length of one dummy component DC) and length S22 (which is the space between two adjacent dummy components DC), as shown inFIG. 7A . - The design condition (e.g., equations (3)-(5)) of the dummy components and the gratings G1 and G2 are similar (or equal) to the embodiments described in
FIG. 6A , and they are not repeated again. - In some embodiments, the spatial period P22 is less than the spatial period P2 to avoid the dummy components DC affecting the results of the DBO measurement performed based on the overlay targets OT3 and OT4. For example, when the spatial period P22 is less than the spatial period P2 to make the
processor 106 be able to distinguish the image data corresponding to the dummy structure DS and the image data corresponding to the overlay targets OT3 and OT4 of the metrology target 104 (wherein the image data is generated by the light detection circuit 105), theprocessor 106 can analyze the image data corresponding to the overlay targets of themetrology target 104 correctly. In some embodiments, the spatial period P22 is represented as: -
- wherein the (λy,min) is the minimum workable wavelength corresponding to the overlay targets OT3 and OT4 of the
metrology target 104. Based on equation (6), the spatial period P22 is further represented by equation (7). -
- In some embodiments, the spatial period P22 is less than the minimum workable wavelength (λy,min) corresponding to the overlay targets OT3 and OT4 of the
metrology target 104. - In some embodiments, the spatial period P22 is greater than the spatial period P2 to avoid the dummy components DC affecting the results of the DBO measurement performed based on the overlay targets OT3 and OT4. In some embodiments, the spatial period P22 is represented as
-
- Based on equation (6), the spatial period P22 is further represented by equation (8).
-
- In some embodiments, the spatial period P22 is greater than the maximum workable wavelength (λy,max) corresponding to the overlay targets OT3 and OT4 of the
metrology target 104. - Based on equation (8), the spatial period P22 is greater than the spatial period P2. In such cases, the brightness of the image data corresponding to the dummy structure DS is different from the brightness of the image data corresponding to the overlay targets OT3 and OT4 of the metrology target 104 (wherein the image data is generated by the light detection circuit 105), and the
processor 106 is able to distinguish the image data corresponding to the dummy structure DS and the image data corresponding to the overlay targets OT3 and OT4 of themetrology target 104 and makes theprocessor 106 analyze the image data corresponding to the overlay targets OT3 and OT4 of themetrology target 104 correctly. -
FIG. 7B showsmetrology target 104 including the dummy structure DS in accordance with some embodiments. Themetrology target 104 includes overlay targets OT1-OT4 as shown inFIGS. 2A-2C .FIG. 7B shows the components of themetrology target 104 in layer m1 for the purpose of clarity. - As shown in
FIG. 7B , the dummy structure DS is extended along the directions Y and −Y to separate the gratings G1 and G2 and extended along the directions X and −X to separate the gratings G5 and G6. In this embodiment, the dummy structure is not formed based on a spatial period and is formed by a single dummy component, which makes the brightness of the image data corresponding to the dummy structure DS different from the brightness of the image data corresponding to the overlay targets OT1-OT4 of the metrology target 104 (wherein the image data is generated by the light detection circuit 105). Accordingly, theprocessor 106 can distinguish the image data corresponding to the dummy structure DS and the image data corresponding to the overlay targets OT1-OT4 of themetrology target 104 and analyze the image data corresponding to the overlay targets OT1-OT4 of themetrology target 104 correctly. -
FIG. 7C shows themetrology target 104 including the dummy structure DS in accordance with some embodiments. The difference between themetrology target 104 inFIG. 7A and themetrology target 104 inFIG. 7C is the dummy structure DS. - As shown in
FIG. 7C , the dummy structure DS includes multiple dummy components DC which are periodically placed along the direction X. In the direction X, the dummy components DC are arranged to repeat with the spatial period P33 which are the sum of the length L33 (which is the side length of one dummy component DC) and length S33 (which is the space between two adjacent dummy components DC). - In some embodiments, the spatial period P33 is less than the spatial period P1 to avoid the dummy components DC affecting the results of the DBO measurement performed based on the overlay targets OT1 and OT2. In some embodiments, the spatial period P33 is represented as
-
- Based on equation (3), the spatial period P33 is further represented by equation (9).
-
- In some embodiments, the spatial period P33 is less than the minimum workable wavelength (λx,min) corresponding to the overlay targets OT1 and OT2 of the
metrology target 104. - In some embodiments, the spatial period P33 is greater than the spatial period P2 to avoid the dummy components DC affecting the results of the DBO measurement performed based on the overlay targets OT1 and OT2. In some embodiments, the spatial period P33 is represented as
-
- Based on equation (3), the spatial period P33 is further represented by equation (10).
-
- In some embodiments, the spatial period P33 is greater than the maximum workable wavelength (λx,max) corresponding to the overlay targets OT1 and OT2 of the
metrology target 104. - As shown in
FIG. 7C , in directions Y and −Y, the dummy components DC are extended along the directions Y and −Y and are not arranged to repeat with a spatial period, which makes the brightness of the image data corresponding to the dummy structure DS different from the brightness of the image data corresponding to the overlay targets OT3 and OT4 of the metrology target 104 (wherein the image data is generated by the light detection circuit 105). Accordingly, theprocessor 106 can distinguish the image data corresponding to the dummy structure DS and the image data corresponding to the overlay targets OT3 and OT4 of themetrology target 104 and analyze the image data corresponding to the overlay targets OT3 and OT4 of themetrology target 104 correctly. - In some embodiments, the dummy components DC in
FIG. 7C can be modified to be periodically placed along the direction Y and extended along the directions X and −X, as shown inFIG. 7D . - As shown in
FIG. 7D , multiple dummy components DC of the dummy structure DS are periodically formed along the direction Y. In the direction Y, the dummy components DC are arranged to repeat with the spatial period P44 which are the sum of the length L44 (which is the side length of one dummy component DC) and length S44 (which is the space between two adjacent dummy components DC). - In some embodiments, the spatial period P44 is less than the spatial period P2 to avoid the dummy components DC affecting the results of the DBO measurement performed based on the overlay targets OT3 and OT4. In some embodiments, the spatial period P44 is represented as
-
- Based on equation (6), the spatial period P44 is further represented by equation (11).
-
- In some embodiments, the spatial period P44 is less than the minimum workable wavelength (λy,min) corresponding to the overlay targets OT3 and OT4 of the
metrology target 104. - In some embodiments, the spatial period P44 is greater than the spatial period P2 to avoid the dummy components DC affecting the results of the DBO measurement performed based on the overlay targets OT3 and OT4. In some embodiments, the spatial period P44 is represented as
-
- Based on equation (6), the spatial period P44 is further represented by equation (12).
-
- In some embodiments, the spatial period P44 is greater than the maximum workable wavelength (λy,max) corresponding to the overlay targets OT3 and OT4 of the
metrology target 104. - As shown in
FIG. 7D , in directions X and −X, the dummy components DC are extended along the directions X and −X and are not arranged to repeat with a spatial period, which makes the brightness of the image data corresponding to the dummy structure DS different from the brightness of the image data corresponding to the overlay targets OT3 and OT4 of the metrology target 104 (wherein the image data is generated by the light detection circuit 105). Accordingly, theprocessor 106 can distinguish the image data corresponding to the dummy structure DS and the image data corresponding to the overlay targets OT3 and OT4 of themetrology target 104 and analyze the image data corresponding to the overlay targets OT3 and OT4 of themetrology target 104 correctly. - In some embodiments, dummy structures can be formed in both layer m1 and layer m2. Referring to
FIG. 8A , the dummy structure DS2 is formed between each grating in the layer m2 of themetrology target 104, and the material of the dummy structure DS2 is the same as the gratings G3, G4, G7, and G8. In some embodiments, the layer m2 can be metal. -
FIGS. 8B and 8C show the cross-sectional diagram of themetrology target 104 including the dummy structures DS and DS2 in accordance with some embodiments. Compared with the embodiments described inFIGS. 4B-4C ,FIGS. 8B and 8C show that themetrology target 104 further has the dummy structure DS2 in the layer m2. In such cases, the dishing effect on the structures formed over themetrology target 104 can be improved, and the metrology targets formed over themetrology target 104 can be fabricated properly. - In some embodiments, each grating in layer m2 of the
metrology target 104 is surrounded by dummy components. As shown inFIG. 8D , the gratings G3, G4, G7, and G8 are respectively surrounded by the dummy components of the dummy structures DS2 and DSO2 to reduce the difference in component density between themetrology target 104 and the patterns formed around themetrology target 104 in layer m2. - Refer to the aforementioned embodiments which respectively correspond to the equations (3)-(12): the dummy structure DS2 can be formed based on the spatial period of the gratings G3, G4, G7, and G8. In some embodiments, the dummy structure DS2 in
FIGS. 8B and 8C can be formed as one of the dummy structures DS described inFIGS. 6A, 6B, 7A, 7B, 7C, and 7D . In some embodiments, the dummy structure DS and the dummy structure DS2 are formed identically. In some embodiments, the dummy structure DS and the dummy structure DS2 are formed differently. -
FIG. 9A illustrates amanufacturing method 900A of a metrology target (e.g., metrology target 104) of a semiconductor device (e.g., semiconductor device 103). - In
operation 911, a first grating (e.g., grating G1) and a second grating (e.g., grating G2) are formed in a first layer (e.g., layer m1) of a substrate of the semiconductor device (e.g., semiconductor device 103), wherein the first grating and the second grating are formed based on a first spatial period (e.g., spatial period P1). - In
operation 912, a first dummy structure (e.g., dummy structure DS) is formed in the first layer, wherein the first dummy structure is at least formed between the first grating and the second grating. - In
operation 913, a third grating (e.g., grating G3) and a fourth grating (e.g., grating G4) are formed in a second layer (e.g., layer m2) of the substrate, wherein the third grating and the fourth grating are formed based on the first spatial period and placed to overlap the first grating and the second grating, respectively. - In some embodiments, the second layer is formed over the first layer. The first grating and the third grating are formed with a first positional offset (e.g., positional offset d1) which is along a first direction (e.g., direction X). The second grating and the fourth grating are formed with a second positional offset (e.g., positional offset d1′) which is along a second direction (e.g., direction −X). The first direction is opposite to the second direction.
-
FIG. 9B shows simplified flowcharts illustrating amanufacturing method 900B of a metrology target (e.g., metrology target 104) of a semiconductor device (e.g., semiconductor device 103). Themanufacturing method 900B includesoperations 920 and 930. The operation 920 includes operations 921-923, and theoperation 930 includes operations 931-932. - In
operation 921, a first grating (e.g., grating G1) and a second grating (e.g., grating G2) are formed in a first layer (e.g., layer m1) of a substrate of the semiconductor device (e.g., semiconductor device 103), wherein the first grating and the second grating are formed based on a first spatial period (e.g., spatial period P1). - In
operation 922, a fifth grating (e.g., grating G5) and a sixth grating (e.g., grating G6) are formed in the first layer, wherein the fifth grating and the sixth grating are formed based on a second spatial period (e.g., spatial period P2). - In
operation 923, a first dummy structure (e.g., dummy structure DS) is formed in the first layer, wherein the first dummy structure is at least formed between the first grating and the second grating and formed between the fifth grating and the sixth grating. - In
operation 931, a third grating (e.g., grating G3) and a fourth grating (e.g., grating G4) are formed in a second layer (e.g., layer m2) of the substrate, wherein the third grating and the fourth grating are formed based on the first spatial period and placed to overlap the first grating and the second grating, respectively. - In
operation 932, a seventh grating (e.g., grating G7) and an eighth grating (e.g., grating G8) are formed in the second layer, wherein the seventh grating and the eighth grating are formed based on the second spatial period and placed to overlap the fifth grating and the sixth grating, respectively. - In some embodiments, the second layer is formed over the first layer. The first grating and the third grating are formed with a first positional offset (e.g., positional offset d1) which is along a first direction (e.g., direction X). The second grating and the fourth grating are formed with a second positional offset (e.g., positional offset d1′) which is along a second direction (e.g., direction −X). The first direction is opposite to the second direction. The fifth grating and the seventh grating are formed with a third positional offset (e.g., positional offset d2) which is along a third direction (e.g., direction Y). The sixth grating and the eighth grating are formed with a fourth positional offset (e.g., positional offset d2′) which is along a fourth direction (e.g., direction −Y). The third direction is opposite to the fourth direction, and the third direction is perpendicular to the first direction.
- The metrology targets (e.g. metrology target 104) having a dummy structure (e.g. the dummy structure DS) are provided. The metrology target having a dummy structure can reduce the dishing effect and improve the accuracy of the DBO measurement. Since the accuracy of the DBO measurement is improved, the yield in manufacturing the semiconductor device (e.g., semiconductor device 103) is also improved. Therefore, the efficiency of fabricating the semiconductor device is improved, and the cost of the semiconductor-manufacturing process can be reduced.
- In some embodiments, a metrology target of a semiconductor device is provided. The metrology target includes a substrate. The substrate includes a first layer and a second layer. The first layer includes a first grating, a second grating, and a first dummy structure. The first grating is formed based on a first spatial period. The second grating is formed based on the first spatial period. The first dummy structure is at least formed between the first grating and the second grating. The second layer is formed over the first layer and includes a third grating and a fourth grating. The third grating is formed based on the first spatial period and placed to overlap the first grating. The fourth grating is formed based on the first spatial period and placed to overlap the second grating. The first grating and the third grating are formed with a first positional offset which is along a first direction. The second grating and the fourth grating are formed with a second positional offset which is along a second direction. The first direction is opposite to the second direction.
- In some embodiments, a metrology target of a semiconductor device is provided. The metrology target includes a substrate which includes a first layer and a second layer. The first layer includes a first grating, a second grating, and a first dummy structure. The first grating is formed based on a first spatial period. The second grating is formed based on the first spatial period. The first dummy structure is at least formed between the first grating and the second grating. The second layer is formed over the first layer and includes a third grating, a fourth grating, and a second dummy structure. The third grating is formed based on the first spatial period and placed to overlap the first grating. The fourth grating is formed based on the first spatial period and placed to overlap the second grating. The second dummy structure is at least formed between the third grating and the fourth grating. The first grating and the third grating are formed with a first positional offset which is along a first direction. The second grating and the fourth grating are formed with a second positional offset which is along a second direction. The first direction is opposite to the second direction.
- In some embodiments, a manufacturing method of a metrology target of a semiconductor device is provided. A first grating and a second grating in a first layer of a substrate of the semiconductor device are formed, wherein the first grating and the second grating are formed based on a first spatial period. A first dummy structure in the first layer is formed, wherein the first dummy structure is at least formed between the first grating and the second grating. A third grating and a fourth grating in a second layer of the substrate are formed, wherein the third grating and the fourth grating are formed based on the first spatial period and placed to overlap the first grating and the second grating, respectively. The second layer is formed over the first layer. The first grating and the third grating are formed with a first positional offset which is along a first direction. The second grating and the fourth grating are formed with a second positional offset which is along a second direction. The first direction is opposite to the second direction.
- The foregoing outlines features of several embodiments so that those skilled in the art may better understand the aspects of the present disclosure. Those skilled in the art should appreciate that they may readily use the present disclosure as a basis for designing or modifying other processes and structures for carrying out the same purposes and/or achieving the same advantages of the embodiments introduced herein. Those skilled in the art should also realize that such equivalent constructions do not depart from the spirit and scope of the present disclosure, and that they may make various changes, substitutions, and alterations herein without departing from the spirit and scope of the present disclosure.
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