Embedded coplanar waveguides for the characterization of thin-film materials and related methods

Abstract

System for the measurement and characterization of thin-film materials using an embedded coplanar waveguide device, comprising: a substrate layer, an upper conductor layer arranged on the top side of the substrate layer, the upper conductor layer comprising a first upper conductor layer and a second upper conductor layer separated from the first upper conductor layer by a gap, a signal conductor arranged on the top side of the substrate layer in the gap between the first upper conductor layer and the second upper conductor layer, and a superstrat layer arranged on the upper conductor layer and the signal conductor layer, the superstrat layer filling the gap between the first upper conductor layer and the second upper conductor layer to achieve accurate thin-film characterization in the millimeter wave bands.

Description

INTRODUCTION

[0001] The information in this section is intended to provide a general context for the disclosure. Work by the presently named inventors, to the extent described in this section, as well as aspects of the description that may not be prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.

[0002] The present disclosure relates generally to embedded coplanar waveguides for characterizing thin film materials and to related methods.

[0003] The electrical characterization of thin dielectric materials with a thickness of less than one-tenth of a wavelength can require complex and expensive measurement setups (e.g., terahertz spectroscopy (TS), coplanar waveguides (CPW), rectangular waveguides (RWG)). Furthermore, the characterization of paints and thin films with these complex measurement systems is unreliable because of their thin and flexible nature. The electromagnetic wave does not propagate through enough material to experience significant and measurable interaction within the sample, and air gaps between traces and ground conductors of the CPW device can lead to inaccurate material characterization due to measurement distortions.Accordingly, there is a desire to eliminate the formation of air gaps between the conductive traces and the ground conductors in order to reduce the measurement distortions associated with such configurations and to improve the accuracy of electromagnetic (EM) characterization of paints and thin films. SUMMARY

[0004] One aspect of the disclosure provides a system for characterizing embedded coplanar waveguides (E-CPW) configured to characterize thin layers, the characterization system comprising: a lower conductor layer, a substrate layer disposed on 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 separated from the first upper conductor layer by a gap, a signal conductor layer 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 the upper conductor layer and the signal conductor layer, the superstrate layer filling the gap between the first upper conductor layer and the second upper conductor layer,and a material to be tested arranged on the superstrate layer.

[0005] Implementations of the disclosure may include one or more of the following optional features. In some implementations, the system includes one or more connectors attached 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.

[0006] The superstrate layer may be substantially flat to accommodate the material to be tested.

[0007] The substrate layer and the superstrate layer can be made of the same material.

[0008] The superstrate layer can be designed to fill any air gaps in the system.

[0009] Another aspect of the disclosure provides a system for characterizing embedded coplanar waveguides (E-CPW) configured to characterize thin layers, the characterization system comprising: a lower conductor layer, a substrate layer disposed on 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 separated from the first upper conductor layer by a gap, a signal conductor layer 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 the upper conductor layer and the signal conductor layer, the superstrate layer filling the gap between the first upper conductor layer and the second upper conductor layer,and a material to be tested arranged on the superstrate layer.

[0010] Implementations of the 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.

[0011] The superstrate layer may be substantially flat to accommodate the material to be tested.

[0012] The substrate layer and the superstrate layer can be made of the same material.

[0013] The superstrate layer can be designed to fill any air gaps in the system.

[0014] Another aspect of the disclosure provides a system comprising: a substrate layer, a top conductor layer disposed on top of the substrate layer, the top conductor layer comprising a first top conductor layer and a second top conductor layer separated from the first top conductor layer by a gap, a signal conductor layer disposed on top of the substrate layer in the gap between the first top conductor layer and the second top conductor layer, and a superstrate layer disposed on top of the top conductor layer and the signal conductor layer, the superstrate layer filling the gap between the first top conductor layer and the second top conductor layer.

[0015] Implementations of the 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. 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.

[0016] The system may also include a lower conductor layer disposed beneath the substrate layer.

[0017] The system may also contain a material to be tested disposed on the superstrate layer.

[0018] Details of one or more implementations of the disclosure are set forth in the accompanying drawings and the description below. Other aspects, features, and advantages will become apparent from the description, drawings, and claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The drawings described herein are for illustrative purposes only and are not intended to limit the scope of the present disclosure. Fig. 1 is a schematic diagram of a vehicle with a radio frequency (RF) device, such as a millimeter wave radar; Fig. 2 is a perspective view of an embedded coplanar waveguide (E-CPW) characterization or measurement system of the present disclosure for use with the RF device of Fig. 1; Fig. 3A is a perspective view of an E-CPW assembly of the E-CPW characterization or measurement system of Fig. 2; Fig. Figure 3B is a cross-sectional view of the E-CPW assembly of Fig. 2 along line 3B-3B from Fig. 3A; Fig. Figure 3C is a cross-sectional view of the E-CPW assembly of Fig. 2 with a layer of varnish, along the line 3B-3B of Fig. 3A; Fig. Figure 4 is a schematic perspective view of the E-CPW assembly of Fig. 2; Fig. Figure 5A is a graphical representation of calibrated S-parameters from simulation / measurement; Fig. Figure 5B is a graphical representation of the calibrated S-parameters from the simulation / measurement after applying Nicholson-Ross-Weir (NRW)-based analytical formulas; and Fig. Figure 5C is a graphical representation of a multidimensional functional fitting curve applied to the NRW-adjusted S-parameters.

[0020] Corresponding reference numbers indicate corresponding parts in the drawings. DETAILED DESCRIPTION

[0021] Example configurations will now be described in more detail with reference to the accompanying drawings. Example configurations are provided so that this disclosure will be thorough and will convey the full scope of the disclosure to those skilled in the art. Specific details are set forth, such as examples of specific components, devices, and methods, in order to provide a thorough understanding of configurations of the present disclosure. Those skilled in the art will appreciate that specific details need not be used, that example configurations may be implemented in many different forms, and that the specific details and example configurations should not be construed to limit the scope of the disclosure.

[0022] The terminology used herein is for the purpose of describing specific example configurations only and is not intended to be limiting. As used herein, the singular articles "a," "an," and "the" can also include the plural forms unless the context clearly indicates otherwise. The terms "comprises," "comprising," "containing," and "having" are inclusive and therefore specify the presence of features, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, steps, operations, elements, components, and / or groups thereof. The method steps, processes, and operations described herein should not be construed as necessarily being performed in the order discussed or illustrated unless they are expressly identified as being in order of performance.Additional or alternative steps may be applied.

[0023] When an element or layer is described as being "on," "engaging," "connected," "attached to," or "coupled" to another element or layer, it may be directly on, engaging, connected, attached, or coupled to the other element or layer, or there may be intervening elements or layers. Conversely, when an element is described as being "directly on," "directly engaging," "directly connected to," "directly attached to," or "directly coupled to" another element or layer, there may be no intervening elements or layers. Other words used to describe the relationship between elements should be interpreted similarly (e.g., "between" versus "directly between," "adjacent" versus "directly next to," etc.).As used herein, the term “and / or” includes all combinations of one or more of the related listed items.

[0024] The terms "first," "second," "third," etc., may be used herein to describe various elements, components, regions, layers, and / or sections. These elements, components, regions, layers, and / or sections should not be limited by these terms. These terms may only be used to distinguish one element, component, region, layer, or section from another region, layer, or section, respectively. Terms such as "first," "second," and other numerical terms do not imply a sequence or order unless clearly indicated by the context. Thus, a first element, component, region, layer, or section discussed below could be referred to as a second element, component, region, layer, or section without departing from the teachings of the example configurations.

[0025] In this application, including the definitions below, the term "module" may be replaced by the term "circuit". The term "module" may refer to, be 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) executing code; memory (shared, dedicated, or group) storing code executed by a processor; other suitable hardware components providing the described functionality; or a combination of some or all of the above, e.g., in a system-on-chip.

[0026] The term "code" as used above can include software, firmware and / or microcode and can refer to programs, routines, functions, classes, and / or objects. The term "shared processor" includes a single processor that executes some or all of the code from multiple modules. The term "group processor" includes a processor that, in combination with other processors, executes some or all of the code from one or more modules. The term "shared memory" includes a single memory that stores some or all of the code from multiple modules. The term "group memory" includes memory that, in combination with other memory, stores some or all of the code from one or more modules. The term "memory" can be a subset of the term "computer-readable medium".The term "computer-readable medium" does not encompass transitory electrical and electromagnetic signals propagating through a medium and can therefore be considered tangible and non-transitory storage. Non-limiting examples of non-transitory storage include tangible, computer-readable medium, including non-volatile memory, magnetic storage, and optical storage.

[0027] The devices and methods described in this application may be implemented partially or entirely by one or more computer programs executed by one or more processors. The computer programs include processor-executable instructions stored on at least one non-transitory, tangible, computer-readable medium. The computer programs may also include and / or access stored data.

[0028] A software application (i.e., a software resource) may refer to computer software that causes a computing device to perform a task. In some examples, a software application may be referred to as an "application," "app," or "program." 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.

[0029] Non-transitory memory can be physical devices used to temporarily or permanently store programs (e.g., instruction sequences) 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 flash memory and read-only memory (ROM) / programmable read-only memory (PROM) / erasable programmable read-only memory (EPROM) / electronically erasable programmable read-only memory (EEPROM) (e.g., typically used for firmware such as boot programs). Examples of volatile memory include random-access memory (RAM), dynamic random-access memory (DRAM), static random-access memory (SRAM), phase-change memory (PCM), and floppy disks or tapes.

[0030] These computer programs (also referred to as programs, software, software applications, or code) contain machine instructions for a programmable processor and may be implemented in a procedural and / or object-oriented high-level language and / or assembly / machine language. 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., magnetic disks, optical disks, memory, programmable logic devices (PLDs)) designed to deliver 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 used to convey machine instructions and / or data to a programmable processor.

[0031] Various implementations of the systems and techniques described herein may be realized in digital electronic and / or optical circuits, integrated circuits, purpose-built ASICs (application-specific integrated circuits), computer hardware, firmware, software, and / or combinations thereof. These various implementations may include implementation in one or more computer programs executable and / or interpretable on a programmable system comprising at least one programmable processor, which may be used for special or general purposes and is coupled to receive data and instructions from and transmit data and instructions to a storage system, and at least one input device and at least one output device.

[0032] The processes and logic flows described in this specification may be performed by one or more programmable processors, also known as data processing hardware, which run one or more computer programs to perform functions by responding to input data and generating output. The processes and logic flows may also be performed by special-purpose logic circuits, such as an FPGA (Field Programmable Gate Array) or an ASIC (Application Specific Integrated Circuit). Processors suitable for executing a computer program include, for example, both general-purpose and special-purpose microprocessors, as well as one or more processors of any type of digital computer. Generally, a processor receives instructions and data from read-only memory or random-access memory, or both.The essential elements of a computer are a processor for executing instructions, and one or more storage devices for storing instructions and data. Generally, a computer will also include, or be operatively connected to, one or more mass storage devices for storing data, e.g., magnetic, magneto-optical, or optical disks, or to receive or transfer data to or from them. However, a computer is not required to have such devices. Computer-readable media suitable for storing computer program instructions and data includes all forms of non-volatile memory, media, and storage devices, including, for example, semiconductor memory devices such as EPROM, EEPROM, and flash memory devices; magnetic disks, e.g., internal hard disks or removable media; magneto-optical disks; and CD-ROM and DVD-ROM disks.The processor and memory can be supplemented by or integrated into special logic circuits.

[0033] To enable interaction with a user, one or more aspects of the disclosure may be implemented on a computer having a display device, e.g., a CRT (cathode ray tube), LCD (liquid crystal display) monitor, or a touchscreen for displaying information to the user, and optionally a keyboard and pointing device, e.g., a mouse or trackball, with which the user can provide input to the computer. Other types of devices may also be used to interact with the user; for example, the feedback to the user may be any form of sensory feedback, e.g., visual feedback, auditory feedback, or tactile feedback; and input from the user may be received in any form, including auditory, voice, or tactile input.In addition, a computer can interact with a user by sending and receiving documents to and from a device used by the user; for example, by sending web pages to a web browser on a user's client device in response to requests received from the web browser.

[0034] In Fig. 2, a system 10 for characterizing or measuring embedded coplanar waveguides (E-CPW) is shown. In certain configurations, a vehicle system 200 may include a bumper or fascia 202, as shown in Fig. 1. The E-CPW characterization or measurement system 10 can be used to characterize or measure paints and / or thin films embedded in the bumper or fascia 202, in which one or more radio frequency (RF) devices 204 are located. The one or more radio frequency devices 204 can include millimeter-wave radar sensors that emit 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 analyses to measure and characterize paint and thin film samples in a broad millimeter-wave frequency band (e.g., 60 to 140 GHz). The paint and thin film compatibility analyses can be performed at any suitable location, e.g.,in a vehicle manufacturing plant, a car dealership, a paint manufacturer, a thin-film polymer coatings manufacturer, a packaging material manufacturer (e.g., trim, grille, bumper, etc.), an RF equipment manufacturer, an RF equipment maintenance shop, an RF equipment installer, etc.

[0035] The E-CPW characterization system 10 may include an E-CPW assembly 100 having multiple components, as shown in the Fig. 2-4. The E-CPW assembly 100 may be mounted on a printed circuit board (PCB) 150, which may include two connectors 152 connected to a signal trace 104 of the E-CPW assembly 100. In some implementations, the connectors 152 may connect the E-CPW assembly 100 to a measurement system 300 (e.g., a vector network analyzer or equivalent RF transceiver system) via a 1 mm broadband coaxial cable 154 (e.g., DC - 100 GHz).

[0036] As in Fig. As shown in Figures 3A-4, the E-CPW assembly 100 includes a lower conductor layer 102a and a substrate layer 106 disposed on the lower conductor layer 102a. The E-CPW assembly 100 includes an upper conductor layer 102b disposed on the substrate layer 106. The conductor layers 102a, 102b may be made of any material suitable for electrical grounding, e.g., steel, copper, sheath steel, etc. The upper conductor layer 102b includes two sections spaced apart by air gaps 112 and a signal trace 104 disposed on top of the substrate layer 106.

[0037] The signal trace 104 is configured to carry radio frequency (RF) signals. The E-CPW assembly 100 can be used for operation in any frequency band, including microwave and millimeter waves.

[0038] The E-CPW assembly 100 includes a superstrate layer 108 disposed on 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 may be made of any suitable RF substrate material, including, but not limited to, Rogers, quartz, acrylic, etc. In some implementations, the substrate layer 106 and the superstrate layer 108 are made of the same material. In other implementations, the substrate layer 106 and the superstrate layer 108 are made of different materials.

[0039] The superstrate layer 108 has a flat or planar top surface, which enables repeatable and fixed-flat placement of resist and thin film samples.

[0040] The superstrate layer 108 can enable accurate characterization of the resist and thin film dielectric (e.g., permittivity and loss factor estimation) by preventing the formation of air gaps between the signal trace 104 and the upper conductor layer 102b and the upper surface of the substrate layer 106, particularly in the realization of a printed circuit board (PCB)-based fixture or device for less complex and less expensive broadband measurement technology (e.g., from 60 to 140 GHz).

[0041] As in Fig. As shown in Figure 3C, the E-CPW assembly 100 includes a paint layer 110 disposed on the substrate layer 108. The paint layer 110 may be configured to match the color of the bumper or fascia 202.

[0042] A material under test (MUT), e.g., the paint layer 110, can be analyzed to determine the actual dielectric constant of the MUT by applying analytical dielectric constant extraction formulas based on Nicholson-Ross Weir (NRW) using measured S-parameters of the paint- or thin-film-equipped E-CPW measuring device 10. The relevant formulas, based on conventional quasi-static field approximations, are as follows: εeff2=1+q1(εr1−1)+q2(εr2−1) q1,2=12K(m1,2)K(m'1,2)K(m'0)K(m0) m1,2=sinh(πS4h1,2)sinh(π(S+2W)4h1,2) m'1,2=1−m1,22 m0=SS+2W m'0=1−m02

[0043] The above formulas are approximations for thick copper conductors and for air gaps between the conductors, as mentioned above.

[0044] To eliminate the air gaps, the superstrate layer 108 is introduced to fill the gap 112 between the signal trace 104 and the top conductor layer 102b and the top surface of the substrate layer 106, thereby ensuring a flat placement of the resist layer 110 on the device without air gaps.

[0045] According to Fig. 4-5C, the method for extracting the dielectric constant is based on the calibrated measurement of the S-parameters of the ink- or thin-film-deposited device. Measured S-parameters are first used to determine the effective dielectric constant of the signal trace 104 without MUT from the wave propagation properties on the signal trace 104. The effective dielectric constant of the signal trace 104 without MUT can then be used, after calibration, to determine the material dielectric constant of the substrate layer 106 and the geometry of the embedded E-CPW assembly 100. This information is used in processing the measurement of the ink-coated embedded E-CPW assembly 100. Applying a thin ink layer 110 changes the effective dielectric constant and enables the extraction of the dielectric constant and loss tangent of the material sample on the E-CPW assembly 100.The change in dielectric constant can depend on the material properties and material thickness in a complex functional form, and a multidimensional polynomial / surface fitting curve using simulated paints with different thicknesses d (i.e., from 30 to 210 µm) and dielectric constants ∈. p (i.e., 3 to 15) is used to determine the sample's dielectric constant and loss factor using the effective dielectric constant of the empty and sample-loaded test fixtures, calculated using the NRW method. A multidimensional functional fitting curve can be: εeff(d,εp)=p00+p10d+p10εp+p20d2+p11d×εp+p02εp2+p30d3+p21d2×εp+p12d×εp2+p03εp3

[0046] In Fig. 5A shows the calibrated S-parameters (dB) as a function of frequency (GHz) from the simulation and / or measurement of an exemplary MUT. In Fig. 5B, the NRW method described above is applied to the calibrated S-parameters to calculate the effective dielectric constant of the MUT as a function of frequency (GHz). Fig. 5C, surface fitting operations are applied to the NRW-adjusted calibrated S-parameters to represent the dielectric constant relative to frequency (GHz).

[0047] A number of implementations have been described. However, it should be understood that various changes may be made without departing from the spirit and scope of the disclosure. Accordingly, other implementations are also within the scope of the following claims.

[0048] The foregoing description is for purposes of illustration and description. It is not intended to be exhaustive or limiting of the disclosure. Individual elements or features of a particular configuration are generally not limited to that particular configuration, but are optionally interchangeable and may be used in a selected configuration even if not specifically shown or described. The same may also be varied in many respects. Such variations are not to be considered as departing from the disclosure, and all such changes are intended to be included within the scope of the disclosure.

Claims

[1] Measuring device comprising: a lower conductor layer; a substrate layer disposed on 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 separated from the first upper conductor layer by a gap; a signal conductor track arranged 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 the upper conductor layer and the signal conductor, the superstrate layer filling the gap between the first upper conductor layer and the second upper conductor layer; and a material to be tested arranged on the superstrate layer. [2] The measuring device 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 measuring device of claim 1, wherein the superstrate layer is substantially flat to receive the material to be tested. [4] The measuring device according to claim 1, wherein the substrate layer and the superstrate layer are formed of the same material. [5] The measuring device of claim 1, wherein the superstrate layer is configured to fill all air gaps within the system. [6] Embedded coplanar waveguide (E-CPW) characterization system configured to characterize thin films, the E-CPW characterization system comprising: a lower conductor layer; a substrate layer disposed on 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 separated from the first upper conductor layer by a gap; a signal conductor track arranged 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 the upper conductor layer and the signal conductor, the superstrate layer filling the gap between the first upper conductor layer and the second upper conductor layer; and a material to be tested arranged on the superstrate layer. [7] The E-CPW characterization system of claim 6, further comprising one or more connectors connected to the signal trace, wherein the one or more connectors are configured to carry radio frequency (RF) signals, and wherein the signal trace is configured to carry RF signals. [8] The E-CPW characterization system of claim 6, wherein the superstrate layer is substantially flat to accommodate 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 all air gaps within the system.

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