WO2016100740A1 - Line scan knife edge height sensor for semiconductor inspection and metrology - Google Patents
Line scan knife edge height sensor for semiconductor inspection and metrology Download PDFInfo
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- WO2016100740A1 WO2016100740A1 PCT/US2015/066505 US2015066505W WO2016100740A1 WO 2016100740 A1 WO2016100740 A1 WO 2016100740A1 US 2015066505 W US2015066505 W US 2015066505W WO 2016100740 A1 WO2016100740 A1 WO 2016100740A1
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- wafer
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- focused
- edge mirror
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
- G01N21/55—Specular reflectivity
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B11/00—Measuring arrangements characterised by the use of optical techniques
- G01B11/02—Measuring arrangements characterised by the use of optical techniques for measuring length, width or thickness
- G01B11/06—Measuring arrangements characterised by the use of optical techniques for measuring length, width or thickness for measuring thickness ; e.g. of sheet material
- G01B11/0608—Height gauges
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/84—Systems specially adapted for particular applications
- G01N21/88—Investigating the presence of flaws or contamination
- G01N21/8806—Specially adapted optical and illumination features
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/84—Systems specially adapted for particular applications
- G01N21/88—Investigating the presence of flaws or contamination
- G01N21/95—Investigating the presence of flaws or contamination characterised by the material or shape of the object to be examined
- G01N21/9501—Semiconductor wafers
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B21/00—Microscopes
- G02B21/0004—Microscopes specially adapted for specific applications
- G02B21/0016—Technical microscopes, e.g. for inspection or measuring in industrial production processes
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B21/00—Microscopes
- G02B21/24—Base structure
- G02B21/241—Devices for focusing
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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
- G03F7/70625—Dimensions, e.g. line width, critical dimension [CD], profile, sidewall angle or edge roughness
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2201/00—Features of devices classified in G01N21/00
- G01N2201/06—Illumination; Optics
- G01N2201/061—Sources
- G01N2201/06113—Coherent sources; lasers
- G01N2201/0612—Laser diodes
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S17/00—Systems using the reflection or reradiation of electromagnetic waves other than radio waves, e.g. lidar systems
- G01S17/02—Systems using the reflection of electromagnetic waves other than radio waves
- G01S17/06—Systems determining position data of a target
- G01S17/46—Indirect determination of position data
- G01S17/48—Active triangulation systems, i.e. using the transmission and reflection of electromagnetic waves other than radio waves
Definitions
- This disclosure relates to semiconductor wafer inspection and metrology. BACKGROUND OF THE DISCLOSURE
- 3D inspection and/or metrology process for silicon wafers. Such inspection can be used, for example, to test the through silicon via (“TSV”) and bump structure or the particle shape (e.g., size and height).
- Typical techniques for inspection or metrology include: (1 ) triangulation; (2) geometric shadow; (3) various confocal microscope techniques; and (4) white-light (or broadband light) interferometry. Triangulation and geometric shadow techniques are not precise enough for contemporary back-end of line (“BEOL”) applications. Confocal microscopy and interferometry techniques typically fail to meet throughput requirements.
- White-light interferometry is known to be a high-resolution method for 3D inspection and metrology and has been used in the semiconductor industry.
- SWI devices either the sample (e.g., the wafer under inspection) or the inspection optics scan along a direction perpendicular to the wafer surface, such as the z-direction, for a distance. Multiple frames are taken at specific z-values to determine the height measurement for a specific x-y location on the wafer surface.
- SWI devices are robust, but are generally slow.
- An auto-focus mechanism is used for an optical probe (OP) in semiconductor inspection and metrology processes.
- a chopper is used to test if the focal point is on, behind, or after the pre-set position. Light passes through the chopper to a bi- celi photodetector. The bi-celi photodetector and chopper are electronically connected with a iock-in amp.
- a system in a first embodiment, includes a light source configured to provide light; a stage configured to hold a wafer to receive the light from the light source; a knife-edge mirror; and a sensor configured to receive the light reflected from the wafer.
- the knife-edge mirror is configured to receive light reflected from the wafer.
- the knife-edge mirror includes a reflective film and an anti-reflection film that are both disposed on the knife-edge mirror thereby forming a boundary between the reflective film and the anti-reflection film.
- the knife-edge mirror is positioned at a focal z point of the light reflected from the wafer such that the reflective film is configured to block at least some of the light reflected from the wafer.
- the knife-edge mirror is configured such that a portion of the light blocked by the knife-edge mirror is different when the light reflected from the wafer is under-focused or over-focused.
- the sensor detects whether the light reflected from the wafer is under-focused or over-focused.
- the system can include an objective lens configured to illuminate the wafer with light from the light source and to combine light reflected from the wafer.
- the system can include a processor in electrical communication with the sensor.
- the processor may be configured to determine a height of an illuminated region on a surface of the wafer relative to a normal surface of the wafer.
- the sensor can include two photodiodes.
- the two photodiodes may receive different quantities of the light reflected from the wafer when the light reflected from the wafer is under-focused or over-focused.
- the sensor can include a bi-ceil photodiode and a prism configured to refract two halves of the light reflected from the wafer onto the bi ⁇ ceii photodiode.
- the system can include a diffractive optics configured to shape the light into a line that is projected onto the wafer.
- the sensor may include a photo-diode array.
- the knife-edge mirror can be positioned at a non-perpendicular angle relative to the light reflected from the wafer.
- the sensor can include two photodiodes.
- the system can further include a second sensor configured to receive the light reflected from the wafer that is reflected by the knife-edge mirror.
- the second sensor can include two photodiodes.
- the knife-edge mirror can be positioned at a non-perpendicular angle relative to the light reflected from the wafer.
- the sensor can include a bi-ceil photodiode.
- the system can further include a second sensor configured to receive the light reflected from the wafer thai is reflected by the knife-edge mirror.
- the second sensor can include a second bi-cell photodiode.
- the knife-edge mirror can be positioned at a non-perpendicular angle relative to the light reflected from the wafer.
- the sensor can include a bi-cell photodiode.
- the system can further include a diffractive optics configured to shape the light into a line that is projected onto the wafer; a prism configured to refract two halves of the light reflected from the wafer onto the bi ⁇ cell photodiode; a second sensor configured to receive the light reflected from the wafer that is reflected by the knife-edge mirror; and a second prism configured to refract two halves of the light reflected from the wafer that is reflected by the knife-edge mirror onto the second bi-cell photodiode.
- the second sensor can include a second bi-cell photodiode.
- the knife-edge mirror can be positioned at a non-perpendicular angle relative to the light reflected from the wafer.
- the second sensor can include two photo-diode arrays.
- the system can further include a diffractive optics configured to shape the light into a line that is projected onto the wafer and a second sensor configured to receive the light reflected from the wafer that is reflected by the knife-edge mirror.
- the second sensor can include two photo-diode arrays.
- the stage can be configured to scan the wafer relative to the light from the light source.
- a method is provided. The method includes reflecting light off a surface of a wafer; passing the light through a knife-edge mirror;
- the knife-edge mirror includes a reflective film and an anti-reflection film that are both disposed on the knife-edge mirror thereby forming a boundary between the reflective film and the anti-reflection film.
- the knife-edge mirror is positioned at a focal point of the light reflected from the wafer such that the reflective film is configured to block at least some of the light reflected from the wafer and such that a portion of the light blocked by the knife- edge mirror is different when the light reflected from the wafer is under-focused or over- focused;
- the method may further include determining a height of an illuminated region on a surface of the wafer relative to a normal surface of the wafer.
- the method may further include determining presence of defects on the wafer.
- the wafer can be scanned relative to the light.
- the method may further include splitting the light from the knife-edge mirror into two quantities and determining whether the quantities are equal.
- the light projected onto the wafer can be shaped into a line.
- Part of the light can be reflected from the knife-edge mirror to a second sensor. Whether the light is under-focused or over-focused can be determined using a reading from the second sensor.
- the method also may further include splitting the light that is reflected from the knife-edge mirror into two quantities and determining whether the quantities are equal.
- FIG. 1 is an embodiment in accordance with the present disclosure using two photodiodes
- FIGs. 2-4 represent readings for the photodiodes of FIG. 1 when the light is focused, under-focused, and over-focused, respectively;
- FIG. 5 is a schematic of light passing through a knife-edge mirror in accordance with an embodiment of the present disclosure
- FIG. 6 is an embodiment in accordance with the present disclosure using a bi-cell photodiode
- FlGs. 7-9 represent readings for the bi-cell photodiode of FIG. 6 when the light is focused, under-focused, and over-focused, respectively;
- FIG. 10 is an embodiment in accordance with the present disclosure using a photo-diode array
- FlGs. 1 1 -13 represent readings for the photo-diode array of FIG. 10 when the light is focused, under-focused, and over-focused, respectively;
- FIG. 14 is another schematic of light passing through a knife-edge mirror in accordance with an embodiment of the present disclosure.
- FIG. 15 is an embodiment in accordance with the present disclosure using four
- FlGs. 18-18 represent readings for the photodiodes of FIG. 15 when the light is focused, under-focused, and over-focused, respectively;
- FIG. 19 is an embodiment in accordance with the present disclosure using two bi-cell photodiodes
- FlGs. 20-22 represent readings for the bi-ceii photodiodes of FIG. 19 when the light is focused, under-focused, and over-focused, respectively;
- FIG. 23 is an embodiment in accordance with the present disclosure using four photo-diode arrays
- FlGs. 24-26 represent readings for the photo-diode arrays of FIG. 23 when the light is focused, under-focused, and over-focused, respectively;
- FIG. 27 is an embodiment in accordance with the present disclosure using two photo-diode arrays
- FlGs. 28-30 represent readings for the photo-diode arrays of FIG. 27 when the light is focused, under-focused, and over-focused, respectively;
- FIG. 31 is another embodiment in accordance with the present disclosure using two photodiode arrays
- FIG. 32 is a schematic representing reshaping the image in a photo-diode array
- FIGs. 33-35 represent readings for the photo-diode arrays of FIG. 31 when the light is focused, under-focused, and over-focused, respectively;
- FIG. 36 is a flowchart of a method in accordance with the present disclosure.
- a knife- edge mirror (KEM) is used to determine whether light is focused, under-focused, or over- focused. Though more signals can be used, only two to four signals per x-y point are needed to determine a height of the reflection point on a wafer. This design is more robust and lower cost than existing techniques and can be faster than white light interferometry. Especially for 3D inspection and metrology, embodiments of the system and method disclosed herein provide better throughput, cost, and accuracy compared to existing techniques. For example, throughput can be increased orders of magnitude compared to the chopper technique when using a line scan scheme.
- FIG. 1 is an embodiment using two photodiodes 1 15, 1 16.
- the system 100 has a light source 101 that is configured to provide light 102 having a spectrum of wavelength range.
- the light source 101 may be configured to provide white light (i.e., broadband light in the visible spectrum) or light that is partially or completely outside of the visible spectrum.
- the light 102 provided by the light source 101 includes wavelengths ( ⁇ ) from 400-800 nm.
- a laser light source can be used for the light source 101 , which can provide a higher brightness compared to spectroscopic methods, such as white light interferometry and chromatic confocal microscopy.
- Laser light sources, such as diode lasers improve lifetime, stability, and thermal control of the light source.
- the light source 101 may be, for example, a visible diode laser.
- the light 102 is projected toward a source pinhole 103 and a beam splitter
- the light 102 is then projected through an objective lens 105, which may be a high magnification objective lens. Some or all of the light 102 passes through the objective lens 105 onto at least a portion of a sample at an illumination point 107.
- the sample may be, for example, a wafer 106.
- the spot size of the light 102 at the illumination point 107 may be diffraction limited.
- the wafer 106 is disposed on a stage 1 17 configured to position the wafer
- the stage 1 17 can be fixed or can scan in the x-direction, y- direction, and/or z-direction.
- the wafer 106 may be clamped to the stage 1 17 in an instance, such as through mechanical and/or electrostatic clamping.
- the stage 1 17 can translate the wafer 106 in a plane perpendicular to the axis of the light 102 or the objective lens 105 (e.g., the x-y plane).
- the KEM 109 includes a reflective film 1 10 and an anti-reflection film 1 1 1 disposed on the KEM 109. There is a boundary between the reflective film 1 10 and the anti-reflection film 1 1 1 . For example, half the KEM 109 may be coated with the anti- reflection film 1 1 1 and half the KEM 109 may be coated with the reflective film 1 10.
- the boundary of the reflective film 1 10 and anti-reflection film 1 1 1 is a straight line and can behave like a knife edge in a Foucauit test.
- the boundary between the reflective film 1 10 and the anti-reflection film 1 1 1 of the KEM 109 is aligned at the focal point of the reflected light 108 at the middle of the focus spot when the surface of the wafer 106 is at its normal z-position.
- the KEM 109 provides a uniform transmitted light beam when the reflected light 108 passes through the KEM 109, This provides a balanced signal at both photodiodes 1 15, 1 16.
- the focal point 1 18 for the reflected light 108 relative to the KEM 109 can be better seen in the inset of FIG. 1 .
- the reflective film 1 10 shears the reflected light 108 in a manner that the transmitted beam has a uniform intensity distribution across the beam,
- Reflected light 108 that passes through the KEM 109 is split into two quantities by a prism 1 12 with a highly reflective coating on two sides and each constituent beam projects through one of the optional lenses 1 13, 1 14 to one of the photodiodes 1 15, 1 16.
- the prism 1 12 is placed at the pupil plane, via a relay lens when needed.
- the lenses 1 13, 1 14 are not necessary in this embodiment and the reflected light 108 can be projected from the prism 1 12 directly to the one of the photodiodes 1 15, 1 16,
- the photodiodes 1 15, 1 16 can provide the same performance in terms of the photo-electron efficiency, time response, and electronic amplification gains,
- F!Gs. 2-4 represent readings for the photodiodes 1 15, 1 16 of FIG. 1 when the light is focused, under-focused, and over-focused, respectively.
- the light 102 illuminates the wafer 106 at the illumination point 107. If the KEM 109 is at the focal point of the reflected light 108, the emerging beam from KEM 109 is uniform and then the two photodiodes 1 15, 1 16 will provide balanced signals, as seen in FIG. 2.
- the illumination point 107 on the wafer 106 may vary or otherwise be at different heights across a surface of the wafer 106. For example, there may be a bump, scratch, unfilled via, or defect on or in the wafer 106. This changes the focal point of the reflected light 108 relative to the KEM 109.
- the focal point of the reflected light 108 is beyond the KEM 109, which makes the reflected light 108 under-focused as seen in FIG. 3.
- the two photodiodes 1 15, 1 16 will provide unbalanced signals because the KEM 109 blocks more light emerging to photodiode 1 16 and less light to photodiode 1 15.
- the emerging beam from the KEM 109 is not uniform.
- the system 100 can distinguish whether the detected feature on the wafer
- the 106 is above or below the normal surface of the wafer 106 according to the signals of the two photodiodes 1 15, 1 16. Which of the photodiodes 1 15, 1 16 receives more or less light can be used to determine if the reflected light 108 is under-focused or over-focused. Thus, if the photodiodes 1 15, 1 16 do not receive equal quantities of the reflected light 108, then it can be determined that the detected feature on the wafer 106 is above or below the normal surface of the wafer 106.
- FIG. 5 is a schematic of light passing through a KEM 109 based on an illumination point.
- FIG. 6 is an embodiment using a bi-ceii photodiode 203.
- a bi-ceil is an embodiment using a bi-ceii photodiode 203.
- photodiode such as the bi-celi photodiode 203
- a prism 201 refracts two halves of the reflected light 108 onto a bi-celi photodiode 203. This may be through an optional lens 202.
- the bi-celi photodiode 203 will be balanced when the wafer 106 is in focus.
- FIGs. 7-9 represent readings for the bi-celi photodiode 203 of FIG. 6 when the light is focused, under-focused, and over-focused, respectively.
- Height differences on the surface of the wafer 106 changes the focal point of the reflected light 108. If the KEM 109 is at the focal point of the reflected light 108, then the bi-celi photodiode 203 will provide a balanced signal because the emerging beam from the KEM 109 is uniform as seen in FIG. 7. If the height of the surface of the wafer increases from the normal setting in the z-direction, then the focal point of the reflected light 108 is beyond the KEM 109, which makes the reflected light 108 under-focused as seen in FIG. 8.
- the focal point of the reflected light 108 is before the KEM 109, which makes the reflected light 108 over-focused as seen in FIG. 9.
- the system 200 can distinguish whether the detected feature on the wafer 106 is above or below the normal surface of the wafer 106 according to the signals of the bi-cell photodiode 203.
- FIG. 10 is an embodiment using a photo-diode array (PDA) 303.
- PDA photo-diode array
- a source slit 304 uses a source slit 304 to shape the light 102 into a line rather than a point.
- a source slit 304 may have a first dimension (e.g., the length" of the source slit 304, which may be the y-direction) that is substantially greater than a second dimension (e.g., the "width" of the source slit 304, which may be the z-direction).
- a first dimension e.g., the length" of the source slit 304, which may be the y-direction
- a second dimension e.g., the "width" of the source slit 304, which may be the z-direction.
- the source slit 304 may be 1 mm to 5 mm in length.
- the source slit 304 is 3 mm in length.
- the width of the source slit 304 is generally sufficiently small that the source slit 304 may be considered to be one-dimensional.
- the width of the source slit 304 may be similar to a diameter of a point beam in a traditional interferometer.
- the source slit 304 may be 5 ⁇ -30 ⁇ in size.
- Diffractive optics also may be included to shape the light 102 into a line rather than a point before the light 102 is incident on the beam splitter 104 or the source slit 304.
- An illumination line 305 is incident on the wafer 106.
- the KEM 109 is aligned so that its edge is parallel to the line of the reflected light 108.
- the boundary of the KEM 109 is aligned to block half of the imaged line of the illumination line 305, no matter if the wafer 106 is focused, under-focused, or over-focused.
- the spot size of the illumination line 305 may be diffraction limited.
- a prism 301 refracts two halves of the reflected light 108 onto a PDA 303 though lens 302.
- Lens 302 may be required to provide spatial resolution along the illumination line 305 on the wafer 106.
- a PDA such as the PDA 303, has an array of multiple areas that can detect a light beam. The PDA 303 will be balanced when the wafer 106 is in focus.
- the height can be extracted from signals from the PDA 303 based on the unbalanced intensities from the two or more photodiodes in the PDA 303, such as in a pixel-to-pixei manner.
- the PDA 303 can be, for example, two traditional PDAs aligned side-by-side, or another type of PDA that has 2-by-n pixels (e.g. , a PDA with 2 rows). The number of pixels in the PDA 303 can vary.
- FIGs. 1 1 -13 represent readings for the PDA 303 of FIG. 10 when the light is focused, under-focused, and over-focused, respectively. Height differences on the surface of the wafer 106 changes the focal point of the reflected light 108. If the focal point of the reflected light 108 is at the KEM 109, then the PDA 303 will provide a balanced signal, as seen in FIG. 1 1 . If the height of the surface of the wafer increases from the normal setting in the z-direction, then the focal point of the reflected light 108 is beyond the KEM 109, which makes the reflected light 108 under-focused as seen in FIG. 12.
- F!G. 14 is another schematic of light passing through a KEM 109 based on an illumination line, which can use the same mechanism as FIG.
- the focus spot has a finite size (an Airy disk) instead of an infinite small geometric point when the beam is focused.
- the boundary of the KEM 109 always reflects half of the beam and transmit half of the beam. When the focus changed, the only difference is the uniformity changes when the beams emerge from the KEM 109.
- FIG. 15 is an embodiment using four photodiodes 1 15, 1 16, 404, 405.
- the KEM 109 is tilted at an angle so that the beam section emerging from the R ⁇ l range (i.e., from the reflective film 1 10) is delivered to the photodiodes 404, 405 through a prism 401 and one of the optional lenses 402, 403.
- the KEM 109 can be tilted to be at a non-perpendicular angle relative to the reflected light 108 (e.g., an axis of the reflected light 108).
- the lenses 402, 403 are not necessary and the reflected light 108 can be projected directly from the prism 401 to the one of the photodiodes 404, 405.
- the signals of the photodiodes 404, 405 provide redundant and complimentary measurement that can be used to improve accuracy and precision.
- the photodiodes 1 15, 1 16, 404, 405 can provide multiple measurements, so that the final results can be the average of them.
- the systematical error can be split into symmetric and asymmetric parts, and the asymmetric part can be averaged out in the final calculation [0048]
- FIGs. 18-18 represent readings for the photodiodes 1 15, 1 16, 404, 405 of
- FIG. 15 when the light is focused, under-focused, and over-focused, respectively.
- Height differences on the surface of the wafer 106 changes the focal point of the reflected light 108. If the focal point of the reflected light 108 is at the KEM 109, then the photodiodes 1 15, 1 16, 404, 405 will provide a balanced signal, as seen in FIG, 16. If the height of the surface of the wafer increases from the normal setting in the z-direction, then the focal point of the reflected light 108 is beyond the KEM 109, which makes the reflected light 108 under-focused as seen in FIG. 17.
- the focal point of the reflected light 108 is before the KEM 109, which makes the reflected light 108 over-focused as seen in FIG. 18.
- the system 400 can distinguish whether the detected feature on the wafer 106 is above or below the normal surface of the wafer 106 according to the signals of the photodiodes 1 15, 1 16, 404, 405.
- FIG. 19 is an embodiment using two bi ⁇ cell photodiodes 203, 503.
- the bi-ceii photodiode 503 will be balanced when the wafer 108 is in focus.
- the signals of the bi-cell photodiodes 203, 503 provide redundant and complimentary measurement that can be used to improve accuracy and precision.
- FIGs. 20-22 represent readings for the bi-celi photodiodes 203, 503 of FIG.
- the focal point of the reflected light 108 is before the KEM 109, which makes the reflected light 108 over-focused as seen in FIG. 22.
- the system 500 can distinguish whether the detected feature on the wafer 108 is above or below the normal surface of the wafer 106 according to the signals of the bi-ceil
- FIG. 23 is an embodiment using four PDAs 604, 605, 609, 610.
- the system
- a source slit 304 uses a source slit 304 to shape the light 102 into a line rather than a point.
- Diffractive optics also may be included to shape the light 102 into a line rather than a point before the light 102 is incident on the beam splitter 104 or the source slit 304.
- An illumination line 305 is incident on the wafer 106.
- the KEM 109 is aligned so that its edge is parallel to the line of the reflected light 108.
- a prism 601 refracts two halves of the reflected light 108 onto two PDAs 604,
- Lenses 602, 603 are positioned between the prism 601 and the PDAs 604, 605 to provide spatial resolution along the illumination line 305.
- the PDAs 604, 605 will be balanced when the wafer 106 is in focus. If there is a point of wafer 106 on the illumination line 305 with a different height from the normal surface of the wafer 106, then the focal point corresponding to it will be shifted resulting in a different balance signal at the corresponding pixels on the PDAs 604, 605.
- the signal from the PDAs 604, 605 can be extracted based on the unbalanced intensity signal from the two photodiodes in each of the PDAs 604, 605, such as in a pixei-to-pixei manner.
- FIGs. 24-28 represent readings for the PDAs 604, 605, 609, 610 of FIG. 23 when the light is focused, under-focused, and over-focused, respectively.
- the system 600 can distinguish whether the detected feature on the wafer 106 is above or below the normal surface of the wafer 106 according to the signais of the PDAs 604, 605, 609, 610.
- FIG. 27 is an embodiment using two PDAs 303, 703.
- the PDA 703 will be balanced when the wafer 106 is in focus.
- the signals of the PDA 703 provides redundant measurement that can be used to improve accuracy and precision.
- FIGs. 28-30 represent readings for the PDAs 303, 703 of FIG. 27 when the light is focused, under-focused, and over-focused, respectively.
- Height differences on the surface of the wafer 106 changes the focal point of the reflected light 108. If the focal point of the reflected light 108 is at the KEM 109, then the PDAs 303, 703 will provide a balanced signal, as seen in FIG. 28. If the height of the surface of the wafer increases from the normal setting in the z-direction, then the focal point of the reflected light 108 is beyond the KEM 109, which makes the reflected light 108 under-focused as seen in FIG. 29.
- F!G. 31 is another embodiment using two PDAs 803, 806. Reflected light
- a prism 801 which refracts two halves of the beam section onto the PDA 803 through a lens 802 to provide spatial resolution along the illumination line 305.
- the PDA 803 will be balanced when the wafer 106 is in focus.
- the PDA 806 will be balanced when the wafer 106 is in focus.
- the signals of the PDA 806 provides redundant and complementary measurement that can be used to improve accuracy and precision.
- the PDAs 803, 806 may be configured like the PDA 807 in FIG. 32, Images of the line emerging from the KEM can be further reshaped by a beam-stitch technique so that the left and right halves of the line image are stitched as shown in FIG. 32. A difference between the left and right halves of the image line can be detected
- FIGs. 33-35 represent readings for the PDAs 803, 806 of FIG. 31 when the light is focused, under-focused, and over-focused, respectively.
- Height differences on the surface of the wafer 106 changes the focal point of the reflected light 108. If the focal point of the reflected light 108 is at the KEM 109, then the PDAs 803, 806 will provide a balanced signal, as seen in FIG. 33. If the height of the surface of the wafer increases from the normal setting in the z-direction, then the focal point of the reflected light 108 is beyond the KEM 109, which makes the reflected light 108 under-focused as seen in FIG. 34.
- the focal point of the reflected light 108 is before the KEM 109, which makes the reflected light 108 over-focused as seen in FIG. 35.
- the system 800 can distinguish whether the detected feature on the wafer 106 is above or below the normal surface of the wafer 106 according to the signals of the PDAs 803, 806.
- FIG. 36 is a flowchart of a method.
- light is reflected off a surface of a wafer, such as the wafer 106. !n 901 , the reflected light passes through a KEM.
- the reflected light from the KEM is received by at least one sensor.
- the controller can include a processor, an electronic storage device in electronic communication with the processor, and a communication port in electronic communication with the processor.
- the processor can receive readings from the sensors, such as through an electronic
- the processor can be configured to determine a height of an illuminated region of the wafer surface (e.g., point or line) or whether a defect is present on or in the wafer surface.
- the wafer may scan relative to the light in the x ⁇ direction and/or y ⁇ direction using the stage in the embodiments disclosed herein. This can provide surface topography information for an area of the surface of the wafer. This area may be, for example, a patch image, a full wafer inspection, or desired points as a bump-height inspection.
- embodiments disclosed herein may determine a surface height profile of a wafer without scanning in the z-direction, although the stage may be capable of movement in the z-direction for other purposes.
- Embodiments of the systems disclosed herein may need to be calibrated.
- Calibration can include determining the relationship of the relative signal difference (e.g., the ratio of the difference of pixels to the sum of them) to a known height difference.
- Power to the laser light source can be controlled, such as through modulating or pulsing, which can enable strobing.
- the optics can be kept steady or otherwise fixed and the wafer can move in a direction perpendicular to the illumination line in synchronization with a PDA readout timer.
- Strobe technology such as that caused by modulating the laser and synchronizing the laser with the PDA readout, can provide further spatial improvement because strobing can reduce blurring due to motion of a stage, such as the stage 1 17.
- Embodiments of the systems disclosed herein can be used for inspection or metrology of a wafer.
- a height of the wafer surface or whether defects are present on or in the wafer surface can be used as feedback during semiconductor manufacturing.
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JP2017532718A JP6580141B2 (en) | 2014-12-17 | 2015-12-17 | Line scan knife edge height sensor for semiconductor inspection and metrology |
EP15871121.8A EP3234990A4 (en) | 2014-12-17 | 2015-12-17 | Line scan knife edge height sensor for semiconductor inspection and metrology |
KR1020177019724A KR102280137B1 (en) | 2014-12-17 | 2015-12-17 | Line scan knife edge height sensor for semiconductor inspection and metrology |
CN201580065602.8A CN107003112A (en) | 2014-12-17 | 2015-12-17 | For semiconductor inspection and the line of metering scanning edge height sensor |
CN202210411750.2A CN114719765A (en) | 2014-12-17 | 2015-12-17 | Line scanning knife edge height sensor for semiconductor inspection and measurement |
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US14/967,432 US9885656B2 (en) | 2014-12-17 | 2015-12-14 | Line scan knife edge height sensor for semiconductor inspection and metrology |
US14/967,432 | 2015-12-14 |
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US10495446B2 (en) | 2015-06-29 | 2019-12-03 | Kla-Tencor Corporation | Methods and apparatus for measuring height on a semiconductor wafer |
US10088298B2 (en) | 2015-09-04 | 2018-10-02 | Kla-Tencor Corporation | Method of improving lateral resolution for height sensor using differential detection technology for semiconductor inspection and metrology |
US9958257B2 (en) | 2015-09-21 | 2018-05-01 | Kla-Tencor Corporation | Increasing dynamic range of a height sensor for inspection and metrology |
US11740356B2 (en) * | 2020-06-05 | 2023-08-29 | Honeywell International Inc. | Dual-optical displacement sensor alignment using knife edges |
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CN114719765A (en) | 2022-07-08 |
EP3234990A4 (en) | 2018-08-08 |
JP2018506843A (en) | 2018-03-08 |
US20160178514A1 (en) | 2016-06-23 |
JP6580141B2 (en) | 2019-09-25 |
CN107003112A (en) | 2017-08-01 |
KR20170096001A (en) | 2017-08-23 |
EP3234990A1 (en) | 2017-10-25 |
US9885656B2 (en) | 2018-02-06 |
KR102280137B1 (en) | 2021-07-20 |
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