WO2020081882A1 - Removable opaque coating for accurate optical topography measurements on top surfaces of transparent films - Google Patents

Removable opaque coating for accurate optical topography measurements on top surfaces of transparent films Download PDF

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Publication number
WO2020081882A1
WO2020081882A1 PCT/US2019/056839 US2019056839W WO2020081882A1 WO 2020081882 A1 WO2020081882 A1 WO 2020081882A1 US 2019056839 W US2019056839 W US 2019056839W WO 2020081882 A1 WO2020081882 A1 WO 2020081882A1
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WIPO (PCT)
Prior art keywords
highly reflective
reflective coating
wafer
topography
layer
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Ceased
Application number
PCT/US2019/056839
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French (fr)
Inventor
Dieter Mueller
Prasanna Dighe
Xiaomeng SHEN
Jason Saito
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KLA Corp
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KLA Corp
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Publication date
Application filed by KLA Corp filed Critical KLA Corp
Priority to KR1020217014973A priority Critical patent/KR102781743B1/en
Priority to CN201980065105.6A priority patent/CN112840442A/en
Priority to JP2021521026A priority patent/JP7423618B2/en
Publication of WO2020081882A1 publication Critical patent/WO2020081882A1/en
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

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    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10P—GENERIC PROCESSES OR APPARATUS FOR THE MANUFACTURE OR TREATMENT OF DEVICES COVERED BY CLASS H10
    • H10P74/00—Testing or measuring during manufacture or treatment of wafers, substrates or devices
    • H10P74/20—Testing or measuring during manufacture or treatment of wafers, substrates or devices characterised by the properties tested or measured, e.g. structural or electrical properties
    • H10P74/203—Structural properties, e.g. testing or measuring thicknesses, line widths, warpage, bond strengths or physical defects
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10P—GENERIC PROCESSES OR APPARATUS FOR THE MANUFACTURE OR TREATMENT OF DEVICES COVERED BY CLASS H10
    • H10P76/00—Manufacture or treatment of masks on semiconductor bodies, e.g. by lithography or photolithography
    • H10P76/20—Manufacture or treatment of masks on semiconductor bodies, e.g. by lithography or photolithography of masks comprising organic materials
    • H10P76/204—Manufacture or treatment of masks on semiconductor bodies, e.g. by lithography or photolithography of masks comprising organic materials of organic photoresist masks
    • H10P76/2041—Photolithographic processes
    • H10P76/2043—Photolithographic processes using an anti-reflective coating
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B82—NANOTECHNOLOGY
    • B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
    • B82Y20/00—Nanooptics, e.g. quantum optics or photonic crystals
    • 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
    • G01B11/24—Measuring arrangements characterised by the use of optical techniques for measuring contours or curvatures
    • G01B11/2441—Measuring arrangements characterised by the use of optical techniques for measuring contours or curvatures using interferometry
    • 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
    • G01B11/30—Measuring arrangements characterised by the use of optical techniques for measuring roughness or irregularity of surfaces
    • G01B11/306—Measuring arrangements characterised by the use of optical techniques for measuring roughness or irregularity of surfaces for measuring evenness
    • 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
    • G03F7/004—Photosensitive materials
    • G03F7/09—Photosensitive materials characterised by structural details, e.g. supports, auxiliary layers
    • G03F7/091—Photosensitive materials characterised by structural details, e.g. supports, auxiliary layers characterised by antireflection means or light filtering or absorbing means, e.g. anti-halation, contrast enhancement
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10P—GENERIC PROCESSES OR APPARATUS FOR THE MANUFACTURE OR TREATMENT OF DEVICES COVERED BY CLASS H10
    • H10P14/00—Formation of materials, e.g. in the shape of layers or pillars
    • H10P14/60—Formation of materials, e.g. in the shape of layers or pillars of insulating materials
    • H10P14/63—Formation of materials, e.g. in the shape of layers or pillars of insulating materials characterised by the formation processes
    • H10P14/6326—Deposition processes
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10P—GENERIC PROCESSES OR APPARATUS FOR THE MANUFACTURE OR TREATMENT OF DEVICES COVERED BY CLASS H10
    • H10P14/00—Formation of materials, e.g. in the shape of layers or pillars
    • H10P14/60—Formation of materials, e.g. in the shape of layers or pillars of insulating materials
    • H10P14/63—Formation of materials, e.g. in the shape of layers or pillars of insulating materials characterised by the formation processes
    • H10P14/6326—Deposition processes
    • H10P14/6342—Liquid deposition, e.g. spin-coating, sol-gel techniques or spray coating
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10P—GENERIC PROCESSES OR APPARATUS FOR THE MANUFACTURE OR TREATMENT OF DEVICES COVERED BY CLASS H10
    • H10P50/00—Etching of wafers, substrates or parts of devices
    • H10P50/20—Dry etching; Plasma etching; Reactive-ion etching
    • H10P50/28—Dry etching; Plasma etching; Reactive-ion etching of insulating materials
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10P—GENERIC PROCESSES OR APPARATUS FOR THE MANUFACTURE OR TREATMENT OF DEVICES COVERED BY CLASS H10
    • H10P74/00—Testing or measuring during manufacture or treatment of wafers, substrates or devices
    • H10P74/23—Testing or measuring during manufacture or treatment of wafers, substrates or devices characterised by multiple measurements, corrections, marking or sorting processes
    • H10P74/235—Testing or measuring during manufacture or treatment of wafers, substrates or devices characterised by multiple measurements, corrections, marking or sorting processes comprising optical enhancement of defects or not-directly-visible states
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10P—GENERIC PROCESSES OR APPARATUS FOR THE MANUFACTURE OR TREATMENT OF DEVICES COVERED BY CLASS H10
    • H10P74/00—Testing or measuring during manufacture or treatment of wafers, substrates or devices
    • H10P74/23—Testing or measuring during manufacture or treatment of wafers, substrates or devices characterised by multiple measurements, corrections, marking or sorting processes
    • H10P74/238—Testing or measuring during manufacture or treatment of wafers, substrates or devices characterised by multiple measurements, corrections, marking or sorting processes comprising acting in response to an ongoing measurement without interruption of processing, e.g. endpoint detection or in-situ thickness measurement
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10P—GENERIC PROCESSES OR APPARATUS FOR THE MANUFACTURE OR TREATMENT OF DEVICES COVERED BY CLASS H10
    • H10P95/00—Generic processes or apparatus for manufacture or treatments not covered by the other groups of this subclass
    • H10P95/11—Separation of active layers from substrates
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B82—NANOTECHNOLOGY
    • B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
    • B82Y30/00—Nanotechnology for materials or surface science, e.g. nanocomposites
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
    • G01B2210/00—Aspects not specifically covered by any group under G01B, e.g. of wheel alignment, caliper-like sensors
    • G01B2210/40—Caliper-like sensors
    • G01B2210/48—Caliper-like sensors for measurement of a wafer
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10P—GENERIC PROCESSES OR APPARATUS FOR THE MANUFACTURE OR TREATMENT OF DEVICES COVERED BY CLASS H10
    • H10P50/00—Etching of wafers, substrates or parts of devices
    • H10P50/20—Dry etching; Plasma etching; Reactive-ion etching
    • H10P50/28—Dry etching; Plasma etching; Reactive-ion etching of insulating materials
    • H10P50/286—Dry etching; Plasma etching; Reactive-ion etching of insulating materials of organic materials
    • H10P50/287—Dry etching; Plasma etching; Reactive-ion etching of insulating materials of organic materials by chemical means

Definitions

  • the described embodiments relate generally to optical topography measurement and more particularly to improved optical topography measurements on top surfaces of transparent films using removable opaque coating.
  • a method of using removable opaque coating for accurate optical topography measurements on top surfaces of transparent films includes: depositing a highly reflective coating onto a top surface of a wafer, measuring topography on the highly reflective coating, and removing the highly reflective coating from the wafer.
  • the highly reflective coating includes an organic material.
  • the highly reflective coating comprises a refractive index value between one and two.
  • the highly reflective coating comprises a complex wavelength greater than one at six-hundred and thirty-five nanometers.
  • the highly reflective coating reflects at least twenty percent of incident light.
  • the highly reflective coating when deposited maintains an underlayer pattern topography at a resolution of at least forty by forty micrometers.
  • the highly reflective coating does not cause shape changing stress to the wafer.
  • FIG. 1 is a diagram illustrating light reflections from multiple interfaces between transparent layers.
  • FIG. 2 is a diagram illustrating light reflection only from the top surface high reflectivity coating.
  • FIG. 3 is a diagram illustrating multiple steps of a wafer measuring process.
  • FIG.4 is a diagram illustrating a wafer high reflectivity coating process.
  • FIG. 5 is a flowchart 100 describing high reflectivity wafer coating process.
  • Wafer shape and topograpghy metrology is an important area and is gaining increasing importance in semiconductor industry. Many inline wafer processing steps comprise the use of one or more transparent layers. Wafers often are fabricated on top of a substrate that is also at least partially transparent. When using optical metrology to measure characteristics of an at least partially transparent layer, not all of the incident light reflects from the top surface. The light that does not reflect from the top surface of the at least partially transparent layer, travels through the at least partially transparent layer and then reflects from other subsequent surfaces. These reflections from subsequent surfaces cause inaccurate optical measurements of the top surface of the at least partially transparent layer.
  • the reason for the inaccuracy is that the light reflecting from the top surface cannot be differentiated from the light reflecting from the bottom surface of the at least partially transparent layer. Therefore, what is a contour on the bottom surface of the at least partially transparent layer may appear as a contour on the top surface of the at least partially transparent layer.
  • FIG. 1 illustrates the multiple reflections of incident light upon the top surface of an at least partially transparent layer.
  • the wafer illustrated in FIG. 1 comprises six layers.
  • Layer six (n6) is a substrate that is partially transparent.
  • Layers one through five are also at least partially transparent.
  • an incident light is directed to the top surface of layer one. In this example, measurement of the characteristics of the top surface of layer one is desired.
  • the indictment light is not totally reflected by layer one. Rather, a portion of the incident light travels through layer one and reflects from the surface interface between layer one and layer two. A portion of the incident light also travels through two and reflects from the surface interface between layer two and layer three.
  • FIG. 1 illustrates that multiple reflections of the incident light front the wafer are produced that are not reflections from the desired top surface of the top transparent layer. To improve measurement of characteristics of the top surface of the transparent layer a new method is needed.
  • FIG. 2 illustrates high reflectivity coating, also referred to as a "physical layer”, to improve optical measurements of the transparent layer top surface.
  • a highly reflective coating is deposited on the top surface of the transparent layer top surface.
  • the highly reflective coating is deposited such that the highly reflective coating has an even thickness across the top surface of the top transparent layer.
  • the even thickness of the deposited highly reflective coating ensures that the top surface of the deposited highly reflective coating matches the top surface of the first transparent layer.
  • the highly reflective coating material reflects at least twenty percent of the incident light.
  • the increased reflectivity of the high reflectivity coating increases the ability to differentiate, based on light intensity, the light reflected from the highly reflective coating from light reflected from the subsequent layers.
  • the highly reflective coating is an organic material, such as a type of photoresist.
  • the highly reflective coating has a refractive index value between one and two.
  • the highly reflective coating comprises a complex wavelength greater than one at six-hundred and thirty-five nanometers.
  • the highly reflective coating reflects at least twenty percent of incident light.
  • the highly reflective coating when deposited maintains an underlayer pattern topography at a resolution of forty by forty micrometers.
  • the highly reflective coating does not cause destructive stress to the top transparent layer top surface.
  • the highly reflective coating does not cause destructive stress to the top transparent layer.
  • the highly reflective coating does not cause destructive or shape or topography changing stress to the wafer.
  • the highly reflective coating does not comprise metal.
  • the highly reflective coating is opaque.
  • FIG. 3 illustrates the steps for measuring the top surface characteristics of a transparent layer using a highly reflective coating.
  • the top surface of the top transparent layer of a wafer is not coated.
  • the top surface of the top transparent layer of the wafer is coated in a highly reflective coating.
  • the coating is an organic, non-metallic, material.
  • the coating is a metallic layer. The coating prevents reflections from the bottom of transparent films or internal interfaces of the film stacks. Therefore, only the light reflected from the top surface is used to measure wafer top surface topology. It is noted herein, use of organic material for coating is advantageous in that deposition of organic films does not increase films stress to levels where stress induces wafer bending.
  • step three topography of the top surface of the wafer coated in highly reflective coating is measured. Measuring top surface topography after coating the wafer provides a more accurate optical topography measurement in the presence of transparent films since transparent films effects such as distortion of the reflected phase or loss of variation of reflected light intensity are avoided.
  • the highly reflective coating is removed.
  • the highly reflective coating can be removed using various methodologies.
  • the highly reflective coating is removed using a solvent.
  • Solvents include, but are not limited to, propylene glycol methyl ether, ethyl lactate, tetramethylammonium hydroxide.
  • FIG.4 illustrates a method for depositing the highly reflective coating to the top surface of the wafer. The wafer is in contact with a vacuum chuck. A dispenser of the highly reflective material is located above the wafer. The wafer is then rotated while the dispenser dispenses the highly reflective material onto the top surface of the wafer. While the wafer is rotated by the vacuum chuck, the dispenser is moved so to deposit the highly reflective material at the center of the wafer or at the outer edge of the wafer and all positions in between.
  • FIG. 5 is a flowchart describing the steps of removable opaque coating for accurate optical topography measurements on top surfaces of transparent films.
  • a highly reflective coating is disposed onto the top surface of the wafer.
  • top surface topography measurements are made of the highly reflective coating.
  • the surface topography measurement is performed using an optical interferometry based full wafer geometry metrology platform that can measure wafer shape, wafer flatness, dual-sided nanotopography and high-resolution edge roll-off.
  • step 103 once the stop surface topography measurements are completed, the highly reflective coating is removed front the wafer without damaging the wafer.
  • the reflective coating is removed using solvents, such as propylene glycol methyl ether, ethyl lactate, tetramethylammonium hydroxide.
  • step 104 the wafer is is further processed for final use.

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  • Engineering & Computer Science (AREA)
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  • Chemical & Material Sciences (AREA)
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  • Life Sciences & Earth Sciences (AREA)
  • Optics & Photonics (AREA)
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  • Crystallography & Structural Chemistry (AREA)
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  • Testing Or Measuring Of Semiconductors Or The Like (AREA)
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Abstract

A method of using removable opaque coating for accurate optical topography measurements on top surfaces of transparent films includes: depositing a highly reflective coating onto a top surface of a wafer, measuring topography on the highly reflective coating, and removing the highly reflective coating from the wafer. The highly reflective coating includes an organic material. The highly reflective coating comprises a refractive index value between one and two. The highly reflective coating comprises a complex wavelength greater than one at six-hundred and thirty-five nanometers. The highly reflective coating reflects at least twenty percent of incident light. The highly reflective coating when deposited maintains an underlayer pattern topography at a resolution of forty by forty micrometers. The highly reflective coating does not cause destructive stress to the wafer.

Description

REMOVABLE OPAQUE COATING FOR ACCURATE OPTICAL
TOPOGRAPHY MEASUREMENTS ON TOP SURFACES OF TRANSPARENT
FILMS
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application claims priority under 35 U.S.C. §1 19 from U.S. Provisional Application Number 62/748,300, entitled“REMOVABLE OPAQUE COATING FOR ACCURATE OPTICAL TOPOGRAPHY MEASUREMENTS ON TOP SURFACES OF TRANSPARENT FILMS," filed on October 19, 2018, the subject matter of which is incorporated herein by reference.
TECHNICAL FIELD
[0002] The described embodiments relate generally to optical topography measurement and more particularly to improved optical topography measurements on top surfaces of transparent films using removable opaque coating.
BACKGROUND INFORMATION
[0003] Optical topography measurements on transparent films on semiconductor wafers are impacted by transparent films effects affecting the accuracy of the measurement. Existing techniques used to compensate for transparent films effects are based on correction models which require additional information about the optical properties and thickness of the film(s). If this additional information about films properties is incorrect or incomplete, the correction will be inaccurate. While correction models may be useful in experimental or engineering analysis with well-known actual optical films properties, they are too complex and too time consuming for production metrology in high volume manufacturing environments with varying actual films properties. SUMMARY
[0004] In a first novel aspect, a method of using removable opaque coating for accurate optical topography measurements on top surfaces of transparent films includes: depositing a highly reflective coating onto a top surface of a wafer, measuring topography on the highly reflective coating, and removing the highly reflective coating from the wafer.
[0005] In a second novel aspect, the highly reflective coating includes an organic material.
[0006] In a third novel aspect, the highly reflective coating comprises a refractive index value between one and two.
[0007] In a fourth novel aspect, the highly reflective coating comprises a complex wavelength greater than one at six-hundred and thirty-five nanometers.
[0008] In a fifth novel aspect, the highly reflective coating reflects at least twenty percent of incident light.
[0009] In a sixth novel aspect, the highly reflective coating when deposited maintains an underlayer pattern topography at a resolution of at least forty by forty micrometers.
[0010] In a seventh novel aspect, the highly reflective coating does not cause shape changing stress to the wafer.
[0011] Further details and embodiments and techniques are described in the detailed description below. This summary does not purport to define the invention.
The invention is defined by the claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] The accompanying drawings, where like numerals indicate like components, illustrate embodiments of the invention.
[0013] FIG. 1 is a diagram illustrating light reflections from multiple interfaces between transparent layers.
[0014] FIG. 2 is a diagram illustrating light reflection only from the top surface high reflectivity coating.
[0015] FIG. 3 is a diagram illustrating multiple steps of a wafer measuring process. [0016] FIG.4 is a diagram illustrating a wafer high reflectivity coating process.
[ 0017 ] FIG. 5 is a flowchart 100 describing high reflectivity wafer coating process.
DETAILED DESCRIPTION
[0018] Reference will now be made in detail to background examples and some embodiments of the invention, examples of which are illustrated in the accompanying drawings. In the description and claims below, relational terms such as "top", "down", "upper", "tower", "top", "bottom", "left" and "right" may be used to describe relative orientations between different parts of a structure being described, and it is to be understood that the overall structure being described can actually be oriented in any way in three-dimensional space.
[0019] Wafer shape and topograpghy metrology is an important area and is gaining increasing importance in semiconductor industry. Many inline wafer processing steps comprise the use of one or more transparent layers. Wafers often are fabricated on top of a substrate that is also at least partially transparent. When using optical metrology to measure characteristics of an at least partially transparent layer, not all of the incident light reflects from the top surface. The light that does not reflect from the top surface of the at least partially transparent layer, travels through the at least partially transparent layer and then reflects from other subsequent surfaces. These reflections from subsequent surfaces cause inaccurate optical measurements of the top surface of the at least partially transparent layer. The reason for the inaccuracy is that the light reflecting from the top surface cannot be differentiated from the light reflecting from the bottom surface of the at least partially transparent layer. Therefore, what is a contour on the bottom surface of the at least partially transparent layer may appear as a contour on the top surface of the at least partially transparent layer.
[ 0020 ] FIG. 1 illustrates the multiple reflections of incident light upon the top surface of an at least partially transparent layer. The wafer illustrated in FIG. 1 comprises six layers. Layer six (n6) is a substrate that is partially transparent. Layers one through five are also at least partially transparent. During optical inspection an incident light is directed to the top surface of layer one. In this example, measurement of the characteristics of the top surface of layer one is desired. However, due to the at least partial transparency of the layer one the indictment light is not totally reflected by layer one. Rather, a portion of the incident light travels through layer one and reflects from the surface interface between layer one and layer two. A portion of the incident light also travels through two and reflects from the surface interface between layer two and layer three. A portion of the incident light also travels through layer three and reflects from the surface interface between layer three and layer four. A portion of die incident light also travels through layer four and reflects from the surface interface between layer four and layer five. A portion of the incident also travels through layer five and reflects from the surface interface between layer five and layer six. A portion of the incident light also travels through layer six and reflects from the bottom surface of layer six. Accordingly, FIG. 1 illustrates that multiple reflections of the incident light front the wafer are produced that are not reflections from the desired top surface of the top transparent layer. To improve measurement of characteristics of the top surface of the transparent layer a new method is needed.
[ 0021 ] A new method is illustrated in FIG. 2. FIG. 2 illustrates high reflectivity coating, also referred to as a "physical layer”, to improve optical measurements of the transparent layer top surface. A highly reflective coating is deposited on the top surface of the transparent layer top surface. The highly reflective coating is deposited such that the highly reflective coating has an even thickness across the top surface of the top transparent layer. The even thickness of the deposited highly reflective coating ensures that the top surface of the deposited highly reflective coating matches the top surface of the first transparent layer. In one example, the highly reflective coating material reflects at least twenty percent of the incident light. The increased reflectivity of the high reflectivity coating increases the ability to differentiate, based on light intensity, the light reflected from the highly reflective coating from light reflected from the subsequent layers.
[ 0022 ] In one example, the highly reflective coating is an organic material, such as a type of photoresist.
[0023] In another example, the highly reflective coating has a refractive index value between one and two.
[0024] In another example, the highly reflective coating comprises a complex wavelength greater than one at six-hundred and thirty-five nanometers. [ 0025 ] In another example, the highly reflective coating reflects at least twenty percent of incident light.
[0026] In another example, the highly reflective coating when deposited maintains an underlayer pattern topography at a resolution of forty by forty micrometers.
[0027] In another example, the highly reflective coating does not cause destructive stress to the top transparent layer top surface.
[0028] In another example, the highly reflective coating does not cause destructive stress to the top transparent layer.
[0029] In another example, the highly reflective coating does not cause destructive or shape or topography changing stress to the wafer.
[ 0030 ] In another example, the highly reflective coating does not comprise metal.
[0031] In another example, the highly reflective coating is opaque.
[ 0032 ] FIG. 3 illustrates the steps for measuring the top surface characteristics of a transparent layer using a highly reflective coating. In step one, the top surface of the top transparent layer of a wafer is not coated. In step two, the top surface of the top transparent layer of the wafer is coated in a highly reflective coating. In one example, the coating is an organic, non-metallic, material. In another example, the coating is a metallic layer. The coating prevents reflections from the bottom of transparent films or internal interfaces of the film stacks. Therefore, only the light reflected from the top surface is used to measure wafer top surface topology. It is noted herein, use of organic material for coating is advantageous in that deposition of organic films does not increase films stress to levels where stress induces wafer bending.
[0033] In step three, topography of the top surface of the wafer coated in highly reflective coating is measured. Measuring top surface topography after coating the wafer provides a more accurate optical topography measurement in the presence of transparent films since transparent films effects such as distortion of the reflected phase or loss of variation of reflected light intensity are avoided.
[0034 ] In step four, the highly reflective coating is removed. The highly reflective coating can be removed using various methodologies. In one example, the highly reflective coating is removed using a solvent. Solvents include, but are not limited to, propylene glycol methyl ether, ethyl lactate, tetramethylammonium hydroxide. [0035] FIG.4 illustrates a method for depositing the highly reflective coating to the top surface of the wafer. The wafer is in contact with a vacuum chuck. A dispenser of the highly reflective material is located above the wafer. The wafer is then rotated while the dispenser dispenses the highly reflective material onto the top surface of the wafer. While the wafer is rotated by the vacuum chuck, the dispenser is moved so to deposit the highly reflective material at the center of the wafer or at the outer edge of the wafer and all positions in between.
[0036] FIG. 5 is a flowchart describing the steps of removable opaque coating for accurate optical topography measurements on top surfaces of transparent films. In step
101 , a highly reflective coating is disposed onto the top surface of the wafer. In step
102, top surface topography measurements are made of the highly reflective coating. In one example, The surface topography measurement is performed using an optical interferometry based full wafer geometry metrology platform that can measure wafer shape, wafer flatness, dual-sided nanotopography and high-resolution edge roll-off.
[ 0037 ] In step 103, once the stop surface topography measurements are completed, the highly reflective coating is removed front the wafer without damaging the wafer. In one example, the reflective coating is removed using solvents, such as propylene glycol methyl ether, ethyl lactate, tetramethylammonium hydroxide. In step 104, the wafer is is further processed for final use.
[0038] This method of using removable opaque coating for accurate optical topography measurements on top surfaces of transparent films allows'.
[0039] - Accurate measurement of top surface topography
[0040] - Prevent physical damage to top surface of wafer when topography is measured by way of physical contact with the wafer.
[0041] - Faster measurement time by using optical measurements.
[0042] - Fast removal of the high reflectivity coating by solvent wash.
[0043] Although certain specific embodiments are described above for instructional purposes, the teachings of this patent document have general applicability and are not limited to the specific embodiments described above. Accordingly, various
modifications, adaptations, and combinations of various features of the described embodiments can be practiced without departing from the scope of the invention as set forth in the claims.

Claims

Listing of Claims What is claimed is:
1. A method, comprising:
depositing a highly reflective coating onto a wafer;
measuring topography on the highly reflective coating; and
removing the highly reflective coating from the wafer.
2. The method of Claim 1 , wherein the highly reflective coating comprises organic material.
3. The method of Claim 1 , wherein the highly reflective coating comprises a refractive index value between one and two.
4. The method of Claim 1 , wherein the highly reflective coating comprises a complex wavelength greater than one at six-hundred and thirty-five nanometers.
5. The method of Claim 1 , wherein the highly reflective coating reflects at least twenty percent of incident light.
6. The method of Claim 1 , wherein the highly reflective coating when deposited maintains an underlayer pattern topography at a resolution of forty by forty micrometers.
7. The method of Claim 1 , wherein the highly reflective coating does not cause destructive stress to the wafer.
8. The method of Claim 1 , wherein the highly reflective coating does not comprise metal material.
9. The method of Claim 1 , wherein the highly reflective coating is opaque.
10. The method of Claim 1 , wherein the wafer comprises a layer of transparent material.
1 1. The method of Claim 1 , wherein the depositing of the highly reflective coating is performed by a spin coater.
12. The method of Claim 1 , wherein the measuring topography is performed using an optical interferometry.
13. The method of Claim 1 , wherein the wafer shape is measured.
14. The method of Claim 1 , wherein wafer flatness is measured.
15. The method of Claim 1 , where dual-sided nanotopography is measured.
16. The method of Claim 1 , wherein high-resolution edge roll-off is measured.
17. The method of Claim 1 , wherein the removing of the highly reflective coating is performed using a solvent.
18. The method of Claim 17, wherein the solvent is propylene glycol methyl ether.
19. The method of Claim 17, wherein the solvent is ethyl lactate.
20. The method of Claim 17, wherein the solvent is tetramethylammonium hydroxide.
PCT/US2019/056839 2018-10-19 2019-10-18 Removable opaque coating for accurate optical topography measurements on top surfaces of transparent films Ceased WO2020081882A1 (en)

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KR1020217014973A KR102781743B1 (en) 2018-10-19 2019-10-18 Removable opaque coating for accurate optical topography measurements on the upper surface of transparent films
CN201980065105.6A CN112840442A (en) 2018-10-19 2019-10-18 Removable Opaque Coatings for Accurate Optical Topography Measurements on Top Surfaces of Transparent Films
JP2021521026A JP7423618B2 (en) 2018-10-19 2019-10-18 Removable opaque coating for precise optical topography measurements on top of transparent films

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CN112840442A (en) 2021-05-25
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