Multilayer Substrate Research Articles

Multilayer substrate integrated waveguide six-port junctions with embedded resistive films

Abstract This article deals with multilayer substrate integrated waveguide (SIW) six-port junctions with embedded carbon resistive films. SIW six-ports usually employ reactive power dividers, which degrade the amplitude and phase balance when the six-port is terminated with mismatched power detectors. The associated impairments are studied and two SIW six-port junctions with improved isolation and output matching are designed for K-/Ka-band applications to overcome these limitations. The proposed designs differ with respect to the configuration of the output ports making the underlying six-port topology applicable for different layout requirements. Measurements of the fabricated components validate the concept. The six-ports are compact, fully shielded and can be integrated in multilayer printed circuit boards.

Visualization of patterned alkanethiol monolayers on an antireflective substrate using a reflected-light microscope

Abstract Organic monolayers are extensively used in various applications to modify substrate surfaces. However, their characterization remains challenging owing to their small thickness. Optical visualization techniques using antireflective (AR) substrates are particularly effective for patterned monolayers. In this study, we demonstrate the visualization of patterned alkanethiol monolayers on an AR multilayer substrate produced through microcontact printing methods. The AR substrate was designed to achieve near-zero reflectance at ~540 nm. The formation of the octadecanethiol monolayer caused a shift of approximately 2 nm toward longer wavelengths in the reflection spectrum. This shift was detected as a color difference by the digital camera attached to a reflected-light microscope. The contrast of the imaged pattern was enhanced by over 15% using a narrow band-pass filter at 530 or 550 nm. Consequently, line patterns with a width of approximately 6 μm were easily photographed using a commercially available color camera in a standard setup.

Microcavity Array-Based Digital SERS Chip for Rapid and Accurate Label-free Quantitative Detection of Live Bacteria.

In this study, we developed a novel digital surface-enhanced Raman spectroscopy (SERS) chip that integrates an inverted pyramid microcavity array, a microchannel cover plate, and a multilayer gold nanoparticle (AuNP) SERS substrate. This innovative design exploits the synergistic effects of the microcavity array and the microchannel to enable rapid and large-scale digital discretization of bacterial suspensions. The concentration effect of the picoliter cavities, combined with the superior Raman enhancement effect of the multilayer AuNP SERS substrate, allows for the precise identification of live bacteria within the microcavities through in situ and label-free SERS testing after a short incubation period. By counting the resulting positive or negative signals, the concentration of the target analyte can be directly determined via Poisson statistics. Experimental results demonstrate that this method enables the accurate quantification of Escherichia coli (E. coli) BL21 within a 4-h incubation period. Compared with traditional analog SERS detection methods, our proposed digital SERS detection strategy reduces the impact of signal intensity fluctuations, thereby significantly improving detection efficiency and accuracy. We believe that this digital SERS chip has great application prospects in the fields of bacterial detection, antibiotic resistance analysis, and cellular dynamics monitoring.

Honeycomb-Shaped Phononic Crystals on 42°Y-X LiTaO3/SiO2/Poly-Si/Si Substrate for Improved Performance and Miniaturization

A SAW device with a multi-layered piezoelectric substrate has excellent performance due to its high Q value. A multi-layer piezoelectric substrate combined with phononic crystal structures capable of acoustic wave reflection with a very small array can achieve miniaturization and high performance. In this paper, a honeycomb-shaped phononic crystal structure based on 42°Y-X LT/SiO2/poly-Si/Si-layered substrate is proposed. The analysis of the bandgap distribution under various filling fractions was carried out using dispersion and transmission characteristics. In order to study the application of PnCs in SAW devices, one-port resonators with different reflectors were compared and analyzed. Based on the frequency response curves and Bode-Q value curves, it was found that when the HC-PnC structure is used as a reflector, it can not only improve the transmission loss of the resonator but also reduce the size of the device.

Novel design and implementation of 3d packaged wideband bandpass filters

This study presents an innovative method for designing a 3D packaged wideband bandpass filter (BPF) by vertically integrating a high-pass filter (HPF) and a low-pass filter (LPF) using an air cavity and vertical interconnect accesses (VIAs). This integration enhances performance while significantly reducing system size. The fabricated BPF, constructed on multilayer substrates, achieves a passband from 2.175 to 4.2 GHz with less than 2.5 dB insertion loss and a return loss exceeding 10 dB. The design utilizes a partial substrate integrated suspended line (SISL) structure, enabling precise control over the equivalent dielectric constant and characteristic impedance to optimize insertion loss. The height of the air cavity, determined through theoretical analysis and S-parameter inversion, is critical for achieving optimal filter performance. The methodology allows for independent circuit designs on each layer, resulting in a 3D assembly. This refined approach makes it easier to produce compact bandpass and multi-band filters, simplifying circuit development and enabling scalable fabrication. This design is versatile across different frequency ranges, demonstrating significant practical and theoretical benefits.

The study of temperature properties of I.H.P. structure and its application for filters on surface acoustic waves

The results of investigation of temperature properties of I.H.P.-structures on multilayer lithium tantalate/silicon dioxide film/silicon substrate used to improve the characteristics of surface acoustic wave devices are presented. Finite element modeling of the test structures was performed in COMSOL software and the temperature frequency coefficient was calculated. A comparison of the calculated transmission coefficient of a resonator filter on a conventional 36°YX-cut lithium tantalate monocrystal substrate and an I.H.P.-filter at different temperature values is presented. The possibility of minimizing the temperature coefficient of frequency by selecting the thickness of the substrate layers is shown. Comparison of the obtained results with the known data showed good agreement. The practical significance consists in the use of modeling results and calculated parameters in the development of various classes of devices on multilayer substrates, including those with I.H.P.-structures.

Characterization of plasma polymerized acetonitrile film for fluorescence enhancement and its application to aptamer-based sandwich assay.

Among biosensing systems for sensitive diagnoses fluorescence enhancement techniques have attracted considerable attention. This study constructed a simple multilayered structure comprising a plane metal mirror coated with a plasma-polymerized film (PPF) as an optical interference layer on a glass slide for fluorescence enhancement. Plasma polymerization enables the easy deposition of organic thin films containing functional groups, such as amino groups. This study prepared PPFs using acetonitrile as a monomer, and the influences of washing and the output powers of plasma polymerization on PPF thickness were examined by Fourier transform infrared spectroscopy. This is because controlling the PPF thickness is vital in fluorescence enhancement. Multilayered glass slides prepared using a silver layer with 84 nm-thick acetonitrile PPFs exhibited 11- and 281-fold fluorescence enhancements compared with those obtained from the substrates with a bare surface and only modified by the silver layer, respectively. Oligonucleotides labeled with a thiol group and cyanine5 were successfully immobilized on the multilayered substrates, and the fluorescence of the acetonitrile PPFs was superior to that of the allylamine and cyclopropylamine PPFs. Furthermore, an aptamer-based sandwich assay targeting thrombin was performed on the multilayered glass slides, resulting in an approximately 5.1-fold fluorescence enhancement compared with that obtained from the substrate with a bare surface. Calibration curves revealed the relationship between fluorescence intensity and thrombin concentration of 10-1000 nM. This study demonstrates that PPFs can function as materials for fluorescence enhancement, immobilization for biomaterials, and aptamer-based sandwich assays.

Er3+/ Yb3+ co-doped multi-functional silica phosphate glass films for integrated photonic applications

The multi-component silicate glasses co-doped with Er3+/Yb3+ were fabricated as thin films by the spin coating technique, which was analyzed for their optoelectronic response. Their monolith counterparts synthesized by the sol-gel route were used for the electrical studies. The films evidenced nanocristobalite phases at low levels of doping. The film micrographs explicated gas-trapped circular dimensions on the surface, due to the spreading of the sol on the substrate during the spin coating process. The glasses show a decrease in the number of polarizable non-bridging oxygen units with doping, reducing the polarizability and optical basicity. The films exhibit prominent green lasing in the downshifting process. The energy transfer from the Yb3+ ions endows the glasses with significant red lasing, suppressing the green emissions by the upconversion mechanism, which is also validated by the colorimetric chromaticity analysis. The gain cross-section of the glass doped with 1.5 mol% of Yb3+ is 23.3 × 10−20 cm2 in the S-band telecommunication domain. The glass film evidences its potential for NIR lasers, beyond a population inversion of 40 %, and a decreasing metastable lifetime of 6.6 μs. Beyond 1.5 mol% of the co-dopant Yb3+, energy transfer dominates, due to the dipole-quadrupole interactions, which has been corroborated by the Inokuti-Hirayama model. The conductivity in the glasses shows a decreasing trend with doping. The Randle's equivalent circuitry of the Nyquist impedance plots, predicts Warburg diffusion impedance that deters the space charge polarization. The consequential decrease in the dielectric constant and capacitance makes the glasses suggestive of multi-layer dielectric substrates in the integrated microelectronic technology for soldering of the printed circuit boards (PCB) that demand low signal losses.

Level set simulation of focused ion beam sputtering of a multilayer substrate.

The evolution of a multilayer sample surface during focused ion beam processing was simulated using the level set method and experimentally studied by milling a silicon dioxide layer covering a crystalline silicon substrate. The simulation took into account the redeposition of atoms simultaneously sputtered from both layers of the sample as well as the influence of backscattered ions on the milling process. Monte Carlo simulations were applied to produce tabulated data on the angular distributions of sputtered atoms and backscattered ions. Two sets of test structures including narrow trenches and rectangular boxes with different aspect ratios were experimentally prepared, and their cross sections were visualized in scanning transmission electron microscopy images. The superimposition of the calculated structure profiles onto the images showed a satisfactory agreement between simulation and experimental results. In the case of boxes that were prepared with an asymmetric cross section, the simulation can accurately predict the depth and shape of the structures, but there is some inaccuracy in reproducing the form of the left sidewall of the structure with a large amount of the redeposited material. To further validate the developed simulation approach and gain a better understanding of the sputtering process, the distribution of oxygen atoms in the redeposited layer derived from the numerical data was compared with the corresponding elemental map acquired by energy-dispersive X-ray microanalysis.

R2R‐Based Continuous Production of Patterned and Multilayered Elastic Substrates with Liquid Metal Wiring for Stretchable Electronics

AbstractThe roll‐to‐roll (R2R) process for fabricating elastic substrates is essential for the social implementation of next‐generation stretchable devices with soft interfaces. In recent years, there is a growing demand for soft heterostructures with multiple monolithically patterned organic materials. However, a continuous processing technique for substrates with heterostructures patterned using highly stretchable wiring has not yet been developed. Conventional manufacturing methods for stretchable electronics lack production capacity. This study introduces an R2R‐based method for the continuous production of multilayered substrates composed of various elastic materials, integrated with liquid metal (LM) wiring, suitable for stretchable electronics. Continuous fabrication of polymer films is achieved with pattern areas as small as 0.78 mm2, using three different polymers varying in hardness. The R2R coating process, paired with liquid metal wiring dispensing printing, allows for the creation of lines as fine as 140 microns. This process supports the batch production of 15 stretchable hybrid devices at a time and enables the creation of large‐area devices up to 400 cm2. The fabrication technique developed herein holds promise for the future manufacturing of not only stretchable electronics but also cutting‐edge soft electronics like smart packaging. This is expected to be a factor leading to the commercialization of stretchable electronics.

Nano-borosilicate glass-silica ceramic material jetting technology for additive manufacturing of multilayer LTCC substrates

Although one of the simplest methods, various must be resolved before industrializing material jetting technology to fabricate low-temperature co-fired ceramics (LTCC). This research examines related glass-ceramic ink configurations and multi-material jet-sintering. Firstly, we present a method for obtaining a nanoscale borosilicate glass powder via radio frequency plasma spheronization, and its surface is grafted with acrylate molecules to create a jettable nanosol. By fusing this configured glass nanosol with silica nanosol in the typical glass-ceramic LTCC combination (4:6) and adding suitable photosensitizing elements, it can be configured into light-curable LTCC inks. 3D printing of multilayer structures using a multi-material jetting device provides a three-layer structure of ceramic layer - conductive layer - ceramic layer, with the ceramic layer cured by ultraviolet light and the conductor pattern scanned and surface-dried by a laser to obtain high-precision delivery of the green part. The sintering effect between different materials is intact and synchronized shrinkage is achieved. Conductivity tests during the sintering stage yielded high conductivity values up to 1.43 × 107 S/m, which further provides the microscopic morphology of the two embedded wires, and the complete and continuous results demonstrate the effectiveness of multilayer wire fabrication. The nanopowder, sol-gel configuration and material jetting under multiple energy loading proposed in this paper significantly support the LTCC additive manufacturing route.

Maze-enclosed quad symmetric kite shaped SRR based metamaterial absorber for doppler navigation aids and earth exploration satellite remote sensing services

This paper represents a wide incident angle-polarization insensitive, stable in results, and compact-sized metamaterial absorber that can be used for Doppler navigation aids and remote sensing applications in Earth Exploration Satellite Services. The unit cell dimension was subwavelength-sized of 0.112λ X 0.112λ, with a good effective medium ratio (8.9), and achieved polarization insensitivity at a maximum incident angle up to 180°, making it more effective for proposed applications. The absorber resonated at 3.855 GHz, 5.13 GHz, 9.855 GHz, 13.335 GHz, and 16.02 GHz with single negative metamaterial properties due to negative permeability and absorptions of 99.7 %, 99.2 %, 98.6 %, 98.1 %, and 97.9 %, respectively. An RLC equivalent circuit on ADS was analyzed to validate the simulated results using the dipoles created by the surface currents. The absorber is cost-effective as no lumped elements or multilayer substrate materials were used, making fabricating less time-consuming and simple. The simulated results were validated by measuring data from a vector network analyzer after fabricating it. The proposed metamaterial absorber is suitable for use in Doppler navigation and Earth Exploration Satellite Services, and this research can further be extended to beamforming and sensing applications in the future.

Sewage sludge biochar as a sustainable and water-safe substrate additive for extensive green roofs

Article describes the application of nutrient-rich sewage sludge (SS) biochar as an innovative additive to extensive green roof substrate at application rates of 10 (SB10) and 20% (v/v) (SB20) and its long-term impact on discharge quality. In addition to a routine analysis of pH, EC, TSS, and COD in the discharge, concentrations of nutrients (total nitrogen and total phosphorus) and metals (Cd, Cu, Fe, Mn, Pb, and Zn) were used to monitor leaching from the experimental green plots. SS biochar improves the water-holding capacity and air-filled porosity of the developed substrates SB10 and SB20, where the chemical and physical parameters meet the minimum requirements for multi-layer extensive roof substrate. The addition of biochar didn't substantially increase the concentrations of nutrients in discharge compared to the conventional extensive substrate, even after 30 months. Results suggested that biochar tends to release nutrients gradually when leached out by rain and may therefore serve as a source of P and other micronutrients. Although an increase in the concentrations of metals (Cu, Pb, and Zn) in the SB10 and SB20 substrates was observed, no significant differences in metal leaching were found. Metal concentrations in the aboveground parts of Sedum plants indicated that the pyrolysis of SS transforms water-extractable forms of metals into stable forms, thereby significantly reducing their bioavailability to Sedum species and any direct ecotoxicological risk. Based on our results, we assert that SS biochar could be used as a sustainable, valuable and water-safe component of extensive substrates for green roofs.

Design and analysis of a complementary structure-based high selectivity tri-band frequency selective surface

This work presents a novel tri-band bandpass frequency selective surface (FSS) that achieves high-order filtering responses in different frequency bands by means of a complementary structure. The proposed FSS is composed of three metal periodic arrays, which are separated by multilayer dielectric substrates. The gridded-double convoluted loop (G-DCL) structure, which is the middle layer structure, is a hybrid resonator that generates different resonant frequencies. The top and bottom layer structures are designed as complementary structures to the middle layer. To accurately describe the frequency responses, an equivalent circuit model (ECM) has been constructed over the entire band from 0 to 16 GHz. The results of the simulation indicate that the developed FSS can generate three pass-bands operating at 3.79 GHz, 8.34 GHz, and 12.52 GHz, respectively, and − 3 dB fractional bandwidths are 52.8%, 13.7%, and 19.7%. The transmission responses at the edges of each passband show a quick roll-off from the passband to the stopband, and there is significant out-of-band suppression between adjacent passbands. Moreover, the FSS maintains excellent angular and polarization stability within a 50° range. For verification, the tri-band FSS has been fabricated and tested. The experimental results match the simulation results, validating the accuracy of the FSS design.

A Ka-Band Two-Channel Two-Beam Receiver Based on a Substrate-Integrated Suspended Line

To realize the miniaturization and high performance for the key transceiver components of a phased array antenna, we proposed a two-channel two-beam receiver based on a substrate-integrated suspended-line (SISL). Multi-layer composite substrate printing circuit is used in the SISL structure to replace the metal cavity and passive circuits. The active components are placed in the air cavity in the SISL structure. The substrates forming the cavity are soldered together to ensure the hermetic seal and high performance. The SISL circuits have the advantage of low loss, low cost, light weight, self-packaging, and high inter-channel isolation. The proposed Ka-band two-channel two-beam receiver shows a gain of >28 dB, a noise figure of <2.6 dB, with functions of 6-bit phase shifting and attenuation.

Design of a High-Gain and Tri-Band Terahertz Microstrip Antenna Using a Polyimide Rectangular Dielectric Column Photonic Band Gap Substrate

A high-gain and tri-band terahertz microstrip antenna with a photonic band gap (PBG) substrate is presented in this paper for terahertz communications. Polyimide dielectric columns are inserted into the silicon substrate to form the PBG substrate to improve the gain of the antenna. The PBG substrate and polyimide substrate constituted a multilayer substrate structure and enabled the multi-band operation of the antenna. The PBG substrate antenna achieves gains of 6.28 dB, 4.84 dB, and 7.66 dB at resonant frequencies of 0.360 THz, 0.580 THz, and 0.692 THz, respectively, outperforming the homogeneous substrate THz microstrip antenna (H antenna) by 1.18 dB, 1.74 dB, and 1.82 dB, respectively. The radiation efficiencies at three operating bands are over 93%, 92%, and 88%, respectively, which are slightly higher than that of the H antenna and greater than that of the standard multi-band antenna.

A Dual-Band Dual-Polarized 2x2 Antenna Array with Beamforming for 5G AiP and mmWave Applications

In this study, we present a dual-band (28/39GHz) 2 by 2 antenna array design on a 10(4+2+4) multi-layer organic substrate with broad bandwidth and higher isolation onto a compact AiP module. In addition, the H-type slot antenna structure can improve interference and isolation between 28 and 39GHz bands. The measured result shows the isolation can larger than 15dB between low and high band. For antenna measurement, the spherical of probing chamber is utilized to validate 28/39GHz antenna pattern and performance with a package level passive testing. Our AiP measured result shows the return loss is better than 10 dB in 23.5-30.5 GHz range, with ~7 GHz bandwidth and provides a high-gain per element (above ~6 dBi) radiation pattern for 28GHz applications. For 39GHz band, the antenna has 7 GHz bandwidth and provides a 5 dBi gain between 38-45 GHz. Comparison of S-parameter between simulated and measured results, there is a good correlation to obtain the quality of manufacturing. Furthermore, a 28GHz beamforming array is designed and demonstrated. The beamfoming array consists of a four-channel transceiver with 2 x 2 antenna array. The beamformer IC is implemented by TSMC 90-nm CMOS technology and the flip-chip bonded on BT substrate. For beamforming test, an integrated socket and load board are designed for support the mmWave module and then connection between DUT and test system. The load board substrate includes the IF, LO, and DC distribution network for respectively. There are 4-channel transmit beamforming array front-end module for testing. Finally, the 3D beam steering of 2 by 2 antenna array is measured with multi-states at 28 GHz, with a maximum realized gain of 11.8 dBi achieved in the main beam (θ=0°). It shows that beamforming can be generated at a specific beam direction by controlling the phase of the signal in each antenna element.

Multilayer Energy-Absorbing Substrate for Two-Layer Barriers with an External Ceramic Layer

Multilayer Energy-Absorbing Substrate for Two-Layer Barriers with an External Ceramic Layer

FT-Raman spectroscopic and electrical investigations of RE3+ doped multi-functional silicate glasses for cathode plating and integrated microelectronic technology

Lanthanide-doped silicate glasses were subjected to structural and temperature-dependent electrical investigations to validate their multi-functionality in the integrated microelectronic industries. Raman-active vibrations around 920 cm−1 and 1330 cm−1 confirmed the silicate and phosphate tetrahedra respectively. The Er3+ doped glass demonstrated the highest dielectric constant of 9.21 × 105, while Sm3+ infused glass exhibited the lowest dielectric constant of 4.37 × 104 at 0.1 Hz and 473 K. The Sm3+ doped glasses are prospective for plating on copper chips in printed circuit boards that necessitate low dielectric constants to minimize propagation delay. The equivalent circuitry fitted for the Nyquist impedance plot of Er3+ doped glass constituted parallel combinations of a resistor and Constant Phase Element (CPE), in series with Warburg diffusion impedance. The CPE approaching a capacitive nature in the Er3+ doped glass could be suggested for cathode plating in batteries, and fabrication of multi-layer dielectric substrates in radio frequency condensers.

Glass-Core Substrates for RF Heterogeneous Integrated Packages

Glass-core substrates with low-loss organic build-up layers are an attractive alternative to conventional multi-layer organic laminates and ceramic substrates for millimeter wave packages. Under the Department of Defense (DoD) State of the Art (SOTA) Heterogeneous Integrated Packaging (SHIP) RF program, Qorvo and our partners are exploring panel-sized glass-core substrates with fine-pitch multi-layer interconnects on low-loss buildup dielectrics and embedded in-core components for compact RF and mixed-signal microsystems. The suitability of this substrate technology is being evaluated through a series of test vehicles designed to characterize the process capability, RF behavior, and package reliability.