Embedded coplanar waveguides for thin film material characterization and related methods

Abstract

The invention discloses a thin film material measurement and characterization fixture system using an embedded coplanar waveguide fixture. The embedded coplanar waveguide fixture includes a substrate layer, an upper conductor layer disposed on top of the substrate layer, a signal trace disposed on top of the substrate layer in the gap between the first upper conductor layer and the second upper conductor layer, and a cladding plate layer disposed on top of the upper conductor layer and the signal trace, the upper conductor layer including a first upper conductor layer and a second upper conductor layer spaced apart from the first upper conductor layer by a gap, the cladding plate layer filling the gap between the first upper conductor layer and the second upper conductor layer, therefore, accurate thin film characterization in the millimeter wave band is realized.

Description

[0001] introduction

[0002] The information provided in this section is for the purpose of generally presenting the context of the present disclosure. The work of the presently named inventors, to the extent it is described in this section and in aspects of the description that may not qualify as prior art at the time of filing, is neither explicitly nor implicitly admitted to be prior art against the present disclosure. Technical Field

[0003] The present disclosure generally relates to embedded coplanar waveguides and related methods for film material characterization. Background Art

[0004] Electrical characterization of thin dielectric materials with thickness less than one-tenth of the wavelength may require complex and expensive measurement setups (e.g., terahertz spectroscopy (TS), coplanar waveguide (CPW), rectangular waveguide (RWG)). In addition, paint and film characterization using these complex measurement systems is unreliable because they are thin and flexible. Electromagnetic waves cannot propagate through enough material to experience significant and measurable interactions within the sample, and air gaps between the traces and ground conductors of the CPW fixture may lead to inaccurate material characterization due to measurement distortion. Therefore, it is desirable to eliminate the formation of air gaps between the traces and ground conductors to reduce measurement distortion associated with such configurations and improve the accuracy of electromagnetic (EM) characterization of paints and thin films. Summary of the invention

[0005] One aspect of the present disclosure provides an embedded coplanar waveguide (E-CPW) characterization system configured to characterize a thin film, the characterization system comprising a lower conductor layer, a substrate layer disposed on top of the lower conductor layer, an upper conductor layer disposed on top of the substrate layer, the upper conductor layer comprising a first upper conductor layer and a second upper conductor layer spaced apart from the first upper conductor layer by a gap, a signal trace disposed on top of the substrate layer in the gap between the first upper conductor layer and the second upper conductor layer, a superstrate layer disposed on top of the upper conductor layer and the signal trace, the superstrate layer filling the gap between the first upper conductor layer and the second upper conductor layer, and a material under test disposed on top of the superstrate layer.

[0006] Implementations of the present disclosure may include one or more of the following optional features. In some implementations, the system includes one or more connectors secured to the signal trace. The one or more connectors may be configured to conduct radio frequency (RF) signals. The signal trace may be configured to conduct radio frequency (RF) signals.

[0007] The superstrate layer may be substantially flat to receive the material being tested.

[0008] The substrate layer and the superstrate layer may be formed of the same material.

[0009] The superstrate layer may be configured to fill any air gaps within the system.

[0010] Another aspect of the present disclosure provides an embedded coplanar waveguide (E-CPW) characterization system configured to characterize a thin film, the characterization system comprising a lower conductor layer, a substrate layer disposed on top of the lower conductor layer, an upper conductor layer disposed on top of the substrate layer, the upper conductor layer comprising a first upper conductor layer and a second upper conductor layer spaced apart from the first upper conductor layer by a gap, a signal trace of a cladding layer, a cladding layer disposed on top of the upper conductor layer and the signal trace, the cladding layer filling the gap between the first upper conductor layer and the second upper conductor layer, and a material under test disposed on top of the cladding layer.

[0011] Implementations of the present disclosure may include one or more of the following optional features. In some implementations, the E-CPW system further includes one or more connectors connected to the signal trace. The one or more connectors may be configured to conduct radio frequency (RF) signals. The signal trace may be configured to conduct radio frequency (RF) signals.

[0012] The superstrate layer may be substantially flat to receive the material being tested.

[0013] The substrate layer and the superstrate layer may be formed of the same material.

[0014] The superstrate layer may be configured to fill any air gaps within the system.

[0015] Another aspect of the present disclosure provides a system, the system including a substrate layer, an upper conductor layer disposed on top of the substrate layer, a signal trace, and a cover layer, the upper conductor layer including a first upper conductor layer and a second upper conductor layer separated from the first upper conductor layer by a gap, the signal trace being disposed on top of the substrate layer in the gap between the first upper conductor layer and the second upper conductor layer, the cover layer being disposed on top of the upper conductor layer and the signal trace, the cover layer filling the gap between the first upper conductor layer and the second upper conductor layer.

[0016] Implementations of the present disclosure may include one or more of the following optional features. In some implementations, the system includes one or more connectors connected to the signal trace. One or more connectors may be configured to conduct radio frequency (RF) signals. The signal trace may be configured to conduct radio frequency (RF) signals.

[0017] The system may also include a lower conductor layer disposed below the substrate layer.

[0018] The system may also include a material under test disposed on top of the superstrate layer.

[0019] The details of one or more embodiments of the present disclosure are set forth in the accompanying drawings and the description below. Other aspects, features, and advantages will be apparent from the description, drawings, and claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The drawings described herein are for illustrative purposes only of selected configurations and are not intended to limit the scope of the present disclosure.

[0021] Figure 1 is a schematic diagram of a vehicle including a radio frequency (RF) device such as a millimeter wave radar;

[0022] Figure 2 is with Figure 1 A perspective view of an embedded coplanar waveguide (E-CPW) characterization or measurement system of the present disclosure for use with an RF device;

[0023] Figure 3A yes Figure 2 A perspective view of the E-CPW components of an E-CPW characterization or measurement system;

[0024] Figure 3B is along Figure 3A The line 3B-3B is intercepted Figure 2 A cross-sectional view of an E-CPW component;

[0025] Figure 3C is along Figure 3A The line 3B-3B intercepts the coating layer, Figure 2 A cross-sectional view of an E-CPW component;

[0026] Figure 4 yes Figure 2 A schematic perspective view of an E-CPW assembly;

[0027] Figure 5A is a graphical illustration showing calibrated S-parameters from simulation / measurement;

[0028] Figure 5B is a graphical representation showing calibrated S-parameters from simulation / measurement after applying an analytical formula based on Nicholson-Ross-Weir (NRW); and

[0029] Figure 5C is a graphical representation showing a multi-dimensional function fit of the S-parameters applied to NRW tuning.

[0030] Corresponding reference characters indicate corresponding parts throughout the several views of the drawings. DETAILED DESCRIPTION

[0031] Example configurations will now be described more fully with reference to the accompanying drawings. Example configurations are provided so that the present disclosure will be thorough and will fully convey the scope of the present disclosure to those of ordinary skill in the art. Specific details, such as examples of specific components, devices, and methods, are set forth to provide a thorough understanding of the configurations of the present disclosure. It will be apparent to those of ordinary skill in the art that specific details need not be employed, that example configurations may be embodied in many different forms, and that the specific details and example configurations should not be construed as limiting the scope of the present disclosure.

[0032] The terms used herein are only used to describe the purpose of specific exemplary configurations and are not intended to be limiting. As used herein, the singular article "a" may also be intended to include plural forms unless the context clearly states otherwise. The terms "include," "comprise," and "have" are inclusive and therefore specify the presence of features, steps, operations, elements, and / or parts, but do not exclude the presence or addition of one or more other features, steps, operations, elements, parts, and / or groups thereof. The method steps, processes, and operations described herein should not be interpreted as necessarily requiring them to be performed in the specific order discussed or shown, unless specifically identified as an execution order. Additional or alternative steps may be adopted.

[0033] When an element or layer is referred to as being "on another element or layer," "engaged to," "connected to," "attached to," or "coupled to" another element or layer, it may be directly on, directly engaged with, connected to, attached to, or coupled to another element or layer, or there may be intermediate elements or layers. Conversely, when an element is referred to as being "directly on another element or layer," "directly engaged to," "directly connected to," "directly attached to," or "directly coupled to" another element or layer, there may be no intermediate elements or layers. Other words used to describe the relationship between elements should be interpreted in a similar manner (e.g., "between" versus "directly between," "adjacent" versus "directly adjacent," etc.). As used herein, the term "and / or" includes any and all combinations of one or more associated listed items.

[0034] The terms "first", "second", "third", etc. may be used in this article to describe various elements, components, regions, layers and / or parts. These elements, components, regions, layers and / or parts should not be limited by these terms. These terms may only be used to distinguish an element, component, region, layer or part from another region, layer or part. Unless the context clearly indicates, terms such as "first", "second" and other numerical terms do not imply an order or sequence. Therefore, without departing from the teaching of the example configuration, the first element, component, region, layer or part discussed below may be referred to as a second element, component, region, layer or part.

[0035] In this application, including the definitions below, the term "module" may be replaced with the term "circuit". The term "module" may refer to, be a part of, or include an application specific integrated circuit (ASIC); a digital, analog, or mixed analog / digital discrete circuit; a digital, analog, or mixed analog / digital integrated circuit; a combinational logic circuit; a field programmable gate array (FPGA); a processor (shared, dedicated, or group) that executes code; a processor (shared, dedicated, or group) that stores code executed by a memory; other suitable hardware components that provide the described functionality; or a combination of some or all of the above, such as in a system on a chip.

[0036] The term "code" as used above may include software, firmware and / or microcode, and may refer to a program, a routine, a function, a class and / or an object. The term "shared processor" covers a single processor that executes some or all codes from multiple modules. The term "group processor" covers a processor that executes some or all codes from one or more modules in combination with an additional processor. The term "shared memory" covers a single memory that stores some or all codes from multiple modules. The term "group memory" includes a memory that stores some or all codes from one or more modules in combination with an additional memory. The term "memory" may be a subset of the term "computer-readable medium". The term "computer-readable medium" does not include transient electrical signals and electromagnetic signals propagated through the medium, and therefore can be considered to be tangible and non-transient memory. Non-limiting examples of non-temporary memory include tangible computer-readable media, which include non-volatile memory, magnetic memory, and optical memory.

[0037] The apparatus and methods described in this application may be implemented in part or in whole by one or more computer programs executed by one or more processors. The computer program includes processor executable instructions stored on at least one non-transitory tangible computer readable medium. The computer program may also include and / or rely on stored data.

[0038] Software applications (i.e., software resources) may refer to computer software that enables a computing device to perform tasks. Example applications include, but are not limited to, system diagnostic applications, system management applications, system maintenance applications, word processing applications, spreadsheet applications, messaging applications, media streaming applications, social networking applications, and gaming applications.

[0039] Non-transitory memory can be a physical device used to temporarily or permanently store programs (e.g., sequences of instructions) or data (e.g., program state information) for use by a computing device. Non-transitory memory can be volatile and / or non-volatile addressable semiconductor memory. Examples of non-volatile memory include, but are not limited to, flash memory and read-only memory (ROM) / programmable read-only memory (PROM) / erasable programmable read-only memory (EPROM) / electrically erasable programmable read-only memory (EEPROM) (e.g., commonly used for firmware, such as bootloaders). Examples of volatile memory include, but are not limited to, random access memory (RAM), dynamic random access memory (DRAM), static random access memory (SRAM), phase change memory (PCM), and disk or tape.

[0040] These computer programs (also referred to as programs, software, software applications, or code) include machine instructions for a programmable processor and may be implemented in high-level procedural and / or object-oriented programming languages ​​and / or assembly / machine languages. As used herein, the terms "machine-readable medium" and "computer-readable medium" refer to any computer program product, non-transitory computer-readable medium, apparatus, and / or device (e.g., disk, optical disk, memory, programmable logic device (PLD)) for providing machine instructions and / or data to a programmable processor, including a machine-readable medium that receives machine instructions as a machine-readable signal. The term "machine-readable signal" refers to any signal for providing machine instructions and / or data to a programmable processor.

[0041] Various implementations of the systems and techniques described herein can be realized in digital electronic and / or optical circuits, integrated circuits, specially designed ASICs (application specific integrated circuits), computer hardware, firmware, software, and / or combinations thereof. These various implementations may include implementations in one or more computer programs executable and / or interpretable on a programmable system that includes at least one programmable processor, which may be special purpose or general purpose, coupled to receive data and instructions from a storage system, at least one input device, and at least one output device, and to send data and instructions to the storage system, at least one input device, and at least one output device.

[0042] The processes and logic flows described in this specification can be performed by one or more programmable processors (also referred to as data processing hardware), which execute one or more computer programs to perform functions by operating on input data and generating outputs. The processes and logic flows can also be performed by special logic circuits (e.g., FPGA (field programmable gate array) or ASIC (application-specific integrated circuit)). As an example, processors suitable for executing computer programs include both general-purpose and special-purpose microprocessors, and any one or more processors of any type of digital computer. Typically, the processor will receive instructions and data from a read-only memory or a random access memory or both. The basic elements of a computer are a processor for executing instructions and one or more memory devices for storing instructions and data. Typically, a computer will also include one or more mass storage devices (e.g., magnetic disks, magneto-optical disks, or optical disks) for storing data, or be operably coupled to receive data from it or transmit data to it or both. However, a computer does not need to have such a device. Computer-readable media suitable for storing computer program instructions and data include all forms of nonvolatile memory, media, and memory devices, including, for example, semiconductor memory devices, such as EPROM, EEPROM, and flash memory devices; magnetic disks, such as internal hard disks or removable disks; magneto-optical disks; and CD ROM and DVD-ROM disks. The processor and memory may be supplemented by, or incorporated in, special purpose logic circuitry.

[0043] To provide interaction with a user, one or more aspects of the present disclosure may be implemented on a computer having a display device (e.g., a CRT (cathode ray tube), LCD (liquid crystal display) monitor, or touch screen) for displaying information to the user and optionally a keyboard and pointing device (e.g., a mouse or trackball) through which the user can provide input to the computer. Other kinds of devices may also be used to provide interaction with the user; for example, the feedback provided to the user may be any form of sensory feedback, such as visual feedback, auditory feedback, or tactile feedback; and input from the user may be received in any form, including sound, voice, or tactile input. In addition, the computer may interact with the user by sending documents to and receiving documents from a device used by the user; for example, by sending a web page to a web browser on a user's client device in response to a request received from the web browser.

[0044] refer to Figure 2 , generally showing an embedded coplanar waveguide (E-CPW) characterization or measurement system 10. In certain configurations, a vehicle system 200 may include a bumper or fascia 202, such as Figure 1As shown. The E-CPW characterization or measurement system 10 can be used to characterize or measure paint and / or films embedded in a bumper or fascia 202 that houses one or more radio frequency (RF) devices 204. The one or more radio frequency (RF) devices 204 may include a millimeter wave radar sensor that transmits radio frequency (RF) waves that propagate through the painted fascia or bumper 202, or through any other suitable layer, such as a windshield, window, etc. The E-CPW characterization system 10 can be used to perform compatibility analysis to measure and characterize paint and film samples within a wide millimeter wave frequency band (e.g., from 60 to 140 GHz). Paint and film compatibility analysis can be performed at any suitable location, such as a vehicle factory, a vehicle dealer shop, a paint manufacturing plant, a thin film polymer coating manufacturing plant, a packaging material (e.g., dashboard, grille, bumper, etc.) manufacturing plant, an RF equipment manufacturing plant, an RF equipment maintenance shop, an RF equipment installation plant, etc.

[0045] The E-CPW characterization system 10 may include an E-CPW assembly 100 including several components, such as Figure 2-4 The E-CPW assembly 100 can be incorporated on a printed circuit board (PCB) 150, which can include two connectors 152 connected to the signal traces 104 of the E-CPW assembly 100. In some embodiments, the connectors 152 can connect the E-CPW assembly 100 to an instrumentation system 300 (e.g., a vector network analyzer or an equivalent RF transmit-receive system) via a 1 mm broadband coaxial cable 154 (e.g., DC-100 GHz).

[0046] refer to Figure 3A-4 , the E-CPW component 100 includes a lower conductor layer 102a and a substrate layer 106 disposed on top of the lower conductor layer 102a. The E-CPW component 100 includes an upper conductor layer 102b disposed on top of the substrate layer 106. The conductor layers 102a, 102b may be formed of any suitable material for achieving electrical grounding, such as steel, copper, clad steel, etc. The upper conductor layer 102b includes two portions separated from each other by an air gap 112 and a signal trace 104 disposed on top of the substrate layer 106.

[0047] The signal trace 104 is configured to conduct radio frequency (RF) signals.The E-CPW component 100 may be implemented to operate in any frequency band including microwave and millimeter wave bands.

[0048] The E-CPW component 100 includes a superstrate layer 108 disposed on top of the upper conductor layer 102b and the signal trace 104. The superstrate layer 108 extends into the air gap 112 between the signal trace 104 and two portions of the upper conductor layer 102b and contacts the substrate layer 106. The superstrate layer 108 can be formed of any suitable RF substrate material, including but not limited to Rogers, quartz, acrylic, etc. In some embodiments, the substrate layer 106 and the superstrate layer 108 are formed of the same material. In other embodiments, the substrate layer 106 and the superstrate layer 108 are formed of different materials.

[0049] The superstrate layer 108 includes a flat top surface for repeatable and secure flat placement of coating and film samples. By eliminating the formation of air gaps between the signal traces 104 and the top surface of the upper conductor layer 102b and the substrate layer 106, the superstrate layer 108 can enable accurate coating and film dielectric characterization (e.g., dielectric constant and loss tangent estimation), especially when implementing a printed circuit board (PCB) based fixture for less complex and less expensive broadband measurement techniques (e.g., from 60 GHz to 140 GHz).

[0050] refer to Figure 3C , the E-CPW assembly 100 includes a paint layer 110 disposed on top of the substrate layer 108. The paint layer 110 may be configured to match the color of the bumper or fascia 202.

[0051] The material under test (MUT) (e.g., coating layer 110) can be analyzed to determine the actual dielectric constant of the MUT by applying a Nicholson-Ross Weir (NRW) based analytical dielectric constant extraction formula using the measured S parameters of the E-CPW measurement device 10 loaded with the coating or film. The relevant formula based on the conventional quasi-static field approximation is given by:

[0052]

[0053]

[0054]

[0055]

[0056]

[0057]

[0058] As mentioned above, the above formula is approximate for thick copper traces and air gaps between traces.

[0059] To eliminate the air gaps, the superstrate layer 108 is introduced to fill the gaps 112 between the signal traces 104 and the top surface of the upper conductor layer 102b and the substrate layer 106, thereby ensuring that the lacquer layer 110 lies flat on the fixture without air gaps.

[0060] refer to Figure 4-5C , the dielectric constant extraction process is based on calibrated measurements of S-parameters of a fixture loaded with paint or film. The measured S-parameters are first used to determine the effective dielectric constant of the signal trace 104 without the MUT based on the wave propagation characteristics on the signal trace 104. Then, after calibration, the effective dielectric constant of the signal trace 104 without the MUT can be used to determine the material dielectric constant of the substrate layer 106 and the geometry of the embedded E-CPW component 100. This information is used to process measurements of the embedded E-CPW component 100 loaded with paint. The addition of a thin layer of paint 110 changes the effective dielectric constant and enables the extraction of the coating dielectric constant and loss tangent of the material sample on top of the E-CPW component 100. The change in dielectric constant can depend on the material properties and its thickness in complex function form, and is analyzed using samples with different thicknesses d (i.e., 30 to 210 μm) and dielectric constant ∈ p A multi-dimensional polynomial / surface fit of simulated coatings (i.e., 3 to 15) is used to determine the sample dielectric constant and loss tangent using the effective dielectric constants of the empty test fixture and the test fixture loaded with the sample calculated by the NRW process. The multi-dimensional function fit can be:

[0061]

[0062] refer to Figure 5A , calibrated S-parameters (dB) are shown as a function of frequency (GHz) from simulations and / or measurements of an exemplary MUT. Figure 5B , the above NRW process is applied to the calibrated S-parameters to calculate the effective dielectric constant of the MUT with respect to frequency (GHz). Figure 5C , a surface fitting operation is applied to the NRW adjusted calibrated S-parameters to show the coating dielectric constant versus frequency (GHz).

[0063] Many embodiments have been described. However, it should be understood that various modifications can be made without departing from the spirit and scope of the present disclosure. Therefore, other embodiments are within the scope of the appended claims.

[0064] The foregoing description is provided for the purpose of illustration and description. It is not intended to be exhaustive or to limit the present disclosure. The individual elements or features of a particular configuration are generally not limited to that particular configuration, but are interchangeable where applicable and can be used in a selected configuration, even if not specifically shown or described. It can also be varied in many ways. Such variations should not be considered as departing from the present disclosure, and all such modifications are intended to be included within the scope of the present disclosure.

Claims

1. A measuring fixture, comprising: Lower conductor layer; a substrate layer disposed on top of the lower conductor layer; an upper conductor layer, the upper conductor layer being disposed on top of the substrate layer, the upper conductor layer comprising a first upper conductor layer and a second upper conductor layer spaced apart from the first upper conductor layer by a gap; a signal trace disposed on top of the substrate layer in the gap between the first upper conductor layer and the second upper conductor layer; a superstrate layer disposed on top of the signal trace and the upper conductor layer, the superstrate layer filling a gap between the first upper conductor layer and the second upper conductor layer; as well as A material to be tested is disposed on top of the cover layer. 2 . The measurement fixture of claim 1 , further comprising one or more connectors attached to the signal trace, wherein the one or more connectors are configured to conduct radio frequency (RF) signals and wherein the signal trace is configured to conduct RF signals.

3. The measurement fixture of claim 1, wherein the cover layer is substantially flat to receive the material being measured. The measurement fixture of claim 1 , wherein the substrate layer and the cover layer are formed of the same material. 5 . The measurement fixture of claim 1 , wherein the cladding layer is configured to fill any air gaps within the system.

6. An embedded coplanar waveguide (E-CPW) characterization system configured to characterize a thin film, the E-CPW characterization system comprising: Lower conductor layer; a substrate layer disposed on top of the lower conductor layer; an upper conductor layer, the upper conductor layer being disposed on top of the substrate layer, the upper conductor layer comprising a first upper conductor layer and a second upper conductor layer spaced apart from the first upper conductor layer by a gap; a signal trace disposed on top of the substrate layer in the gap between the first upper conductor layer and the second upper conductor layer; a superstrate layer disposed on top of the signal trace and the upper conductor layer, the superstrate layer filling a gap between the first upper conductor layer and the second upper conductor layer; as well as A material to be tested is disposed on top of the cover layer.

7. The E-CPW characterization system of claim 6, further comprising one or more connectors connected to the signal traces, wherein: The one or more connectors are configured to conduct radio frequency (RF) signals, and wherein the signal trace is configured to conduct RF signals.

8. The E-CPW characterization system of claim 6, wherein: The cover plate layer is substantially flat to receive the material to be tested.

9. The E-CPW characterization system of claim 6, wherein: The substrate layer and the superstrate layer are formed of the same material.

10. The E-CPW characterization system of claim 6, wherein: The superstrate layer is configured to fill any air gaps within the system.

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