Critical Design Rules Research Articles

Understanding Antiferromagnetic Coupling in Lead-Free Halide Double Perovskite Semiconductors.

Solution-processable semiconductors with antiferromagnetic (AFM) order are attractive for future spintronics and information storage technology. Halide perovskites containing magnetic ions have emerged as multifunctional materials, demonstrating a cross-link between structural, optical, electrical, and magnetic properties. However, stable optoelectronic halide perovskites that are antiferromagnetic remain sparse, and the critical design rules to optimize magnetic coupling still must be developed. Here, we combine the complementary magnetometry and electron-spin-resonance experiments, together with first-principles calculations to study the antiferromagnetic coupling in stable Cs2(Ag:Na)FeCl6 bulk semiconductor alloys grown by the hydrothermal method. We show the importance of nonmagnetic monovalence ions at the BI site (Na/Ag) in facilitating the superexchange interaction via orbital hybridization, offering the tunability of the Curie-Weiss parameters between -27 and -210 K, with a potential to promote magnetic frustration via alloying the nonmagnetic BI site (Ag:Na ratio). Combining our experimental evidence with first-principles calculations, we draw a cohesive picture of the material design for B-site-ordered antiferromagnetic halide double perovskites.

2D Polymers with Lead Anchoring Groups Enable Perovskite Solar Cells with Over 24% Efficiency

The hygroscopic dopants used in Spiro‐OMeTAD hole‐transport materials (HTMs) in n–i–p perovskite solar cells (PSCs) inevitably cause device degradation. Herein, two polymer interface materials based on lead anchoring groups are developed. It is found that 2D polymers 2DP‐BT and 2DP‐Por can form dense films and exhibit excellent hydrophobicity. Importantly, 2DP‐Por can passivate the surface defects through noncovalent interactions, reducing nonradiative recombination loss. After introducing these polymer interface materials between the perovskite layer and the HTM layer, the optimized devices using 2DP‐Por and 2DP‐BT achieve champion power conversion efficiency of 24.12% and 23.29%, respectively, and the stability is significantly improved. These results indicate that developing polymer interface materials containing lead anchoring groups can improve PSC efficiency and stability and elucidate critical molecular design rules for interface materials.

(Invited) Hybrid Bonding for 3D Applications: Improvements and Limitations

Wafer direct bonding has attracted considerable concerns since it takes advantage of the ability to achieve strong adherence between flat, clean, and smooth surface without the use of intermediate materials. This technology experienced a consequent rise with the More than Moore's law. With this trend, added value to devices is provided by incorporating functionalities that do not necessarily scale according to "Moore's Law”. Indeed, this aims to realize three-dimensional (3D) integration systems by stacking devices and interconnecting them using Through-Silicon-Via (TSV) or Cu-Cu interconnections. Hybrid bonding is preferred to other chip stacking technologies because Cu-Cu hybrid bonding is easily capable of scaling down and present excellent reliability results.Hybrid bonding is key technology to address several applications especially images sensor. Even more specialized applications or better performances could be obtained through hybrid bonding pitch reduction [1]. High quality bonding for 3D technology has been demonstrated using an accurate wafer bonding tool with optimized metrology [2]. The total overlay values reached is below 110 nm with residuals values below 80 nm and scaling inferior to 0.5 ppm for interconnect pitches from 6.9 µm down to 0.6 µm. The electrical properties have been checked and confirmed the robustness of the fine pitch hybrid bonding module and the stability of the bonding interface [3]. The latest process and hardware developments have made it possible to greatly reduce scaling. However, distortion remains the most complicated parameter to optimize. It is strongly linked to the design of the chip (number of metal levels, stress...). Today, a minimum critical dimension design rule should be respected to avoid short between front side and backside layers and this is preventing pixel shrink. To reduce pixel size, distortion value needs to be decreased. For that purpose, in situ monitoring of the bonding wave is necessary as well as bonding chucks multiple vacuum zones in order to achieve homogenous bonding wave propagation.Even if hybrid bonding integration and performance have been considerably improved, we can notice that thermal budget is a main limitation for this technology. Indeed, to reach strong bonding energy which is mandatory for subsequent mechanical manufacturing; a bonding anneal of 800°C is required. By using plasma treatment prior bonding, anneal temperature can be decreased to 400°C. However, some devices cannot withstand such thermal budget because of thermosensitive materials integration (GST or quantum dots for example). To overcome this limitation, many studies have been performed on developing low temperature direct bonding process. Surface activated bonding (SAB) is a promising method to achieve high bonding energy at room temperature, but chemical surface treatments (as amino-alcohol organic molecule for example [4]) are easiest to implement for mass volume production and allows highly strong bonding at 200°C that can stand high stress process steps (grinding, CMP and dicing).Although specific plasma or surface preparation could decrease the required annealing temperature, the copper oxide will limit electrical performances with annealing below 250°C for standard hydrophilic bonding. That is why, new ECD Cu deposition like oriented nano-twin Cu is very promising to facilitate oxygen diffusion. [5][1] AYOUB, B., LHOSTIS, S., MOREAU, S., et al. Impact of Process Variations on the Capacitance and Electrical Resistance down to 1.44 µm Hybrid Bonding Interconnects. In : 2020 IEEE 22nd Electronics Packaging Technology Conference (EPTC). IEEE, 2020. p. 453-458.[2] DETTONI.Florent, DELOFFRE, Emilie, GRAUER, Yoav, et al. Advanced overlay metrology for CIS bonding applications. ECTC 2023 to be published[3] AYOUB, Bassel, LHOSTIS, Sandrine, MOREAU, Stéphane, et al. Sub 1µm Pitch Achievement for Cu/SiO 2 Hybrid Bonding. In : 2022 IEEE 24th Electronics Packaging Technology Conference (EPTC). IEEE, 2022. p. 418-424.[4] FOURNEL, Frank, CALVEZ, Aziliz, LARREY, Vincent, et al. Impact of an Amino-Alcohol Organic Molecule on SiO2 and Si Bonding Energy. ECS Transactions, 2020, vol. 98, no 4, p. 3.[5] CHEN, Chih, JUANG, Jing-Ye, CHANG, Shih Yang, et al. Low-temperature Cu-to-Cu direct bonding enabled by highly (111)-oriented and nanotwinned Cu. In : 2019 6th International Workshop on Low Temperature Bonding for 3D Integration (LTB-3D). IEEE, 2019. p. 38-38.

A comprehensively theoretical and experimental study of carrier generation and transport for achieving high performance ternary blend organic solar cells

Ternary blend organic solar cells (OSCs) composed of three components in the active layer shows the potential to achieve higher power conversion efficiency (PCE) as compared to the binary counterpart due to the wider absorption spectrum, higher generation rate, and better morphology. However, the physical understanding of carrier generation and transport processes in the ternary blend OSCs has been limited explored. In the work, together with experimental studies of the two donors, one acceptor ternary blend OSCs with PCE > 12%, we will theoretically and experimentally describe the roles of the carrier generation (including exciton transfer, delocalization and dissociation), and carrier transport (particularly the hole transport) on the performance of ternary blend OSCs. Through theoretical and experimental investigations, critical design rules for improving the device performance are concluded: (1) improving the exciton delocalization ratio via donor ratio optimization with physical understanding, (2) selecting the donors with well overlap of emission and absorption spectra to promote a beneficial exciton transfer, (3) engineering the energy level of donors to form the blocking barrier for reducing hole transfer into the donor with high recombination loss. The work unveils the device physics which is fundamentally important for designing and optimizing high-performance ternary blend OSCs.

Using business critical design rules to frame new architecture introduction in multi-architecture portfolios

When introducing new architectures to an industrial portfolio, counting multiple existing product and manufacturing solutions, time-to-market and investments in manufacturing equipment can be significantly reduced if new concepts are aligned with the existing portfolio. This can be done through component sharing, or sharing critical design principles. This alignment is not trivial, as extensive design knowledge is needed to overview a portfolio with many, often highly different products and manufacturing lines. In this paper, we suggest establishing a frame of reference for new-product introduction based on several ‘game rules’, or Business Critical Design Rules (BCDRs), which denote the most critical features of the product and manufacturing architectures, and should be considered an obligatory reference for design when introducing new architectures. BCDRs are derived from the portfolio, architecture and module levels, including modelling of the most critical links between the product and manufacturing domains. The suggested modelling principle has been tested as a frame for new-architecture introduction, capturing critical modularisation principles in a large and global OEM. Application of the suggested method revealed a potential for reducing time-to-market and potentially cutting 35% off investments in new manufacturing equipment when introducing new products in the portfolio.

Design of free‐standing microstructured conducting polymer films for enhanced particle removal from non‐uniform surfaces

ABSTRACTEfficient removal of particles from topologically‐complex surfaces is of significant import for a range of applications (e.g., explosive residue removal in security arenas). Here, we synthesize next‐generation polymeric particle removal swabs with tuned structural features to elucidate the influence of the polymer microstructure on the removal of trace particles from surfaces. Specifically, microstructured free‐standing films of the conducting polymer polypyrrole (PPy) were synthesized through template‐assisted electropolymerization techniques. The removal of polystyrene microspheres from representative aluminum surfaces of varying roughness was evaluated as a function of the PPy microstructure. PPy‐based microstructured swabs displayed increased particle trapping properties relative to non‐textured PPy‐based swabs and current commercial swabs. This increased effectiveness occurred from the more intimate particle‐swab contact, leading to increased van der Waals interactions for the microstructured swabs. Therefore, this effort provides critical design rules for the production of microstructured conducting polymer materials for their application toward advanced particle removal technologies. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016, 54, 1968–1974

Bio-inspired micropatterned hydrogel to direct and deconstruct hierarchical processing of geometry-force signals by human mesenchymal stem cells during smooth muscle cell differentiation

Micropatterned biomaterial-based hydrogel platforms allow the recapitulation of in vivo-like microstructural and biochemical features that are critical physiological regulators of stem cell development. Herein, we report the use of muscle mimicking geometries patterned on polyacrylamide hydrogels as an effective strategy to induce smooth muscle cell (SMC) differentiation of human mesenchymal stem cells (hMSCs). hMSCs were systemically coerced to elongate with varying aspect ratios (AR) (that is, 1:1, 5:1, 10:1 and 15:1) at a fixed projection area of ~7000 μm2. The results showed engineered cellular anisotropy with an intermediate AR 5:1 and AR 10:1, promoting the expression of alpha smooth muscle actin (α-SMA) and enhancement of contractile output. Further mechanistic studies indicated that a threshold cell traction force of ~3.5 μN was required for SMC differentiation. Beyond the critical cytoskeleton tension, hMSCs respond to higher intracellular architectural cues such as the stress fiber (SF) alignment, SF subtype expression and diphosphorylated myosin regulatory light-chain activity to promote the expression and incorporation of α-SMA to the SF scaffold. These findings underscore the importance of exploiting biomimetic geometrical cues as an effective strategy to guide hMSC differentiation and are expected to guide the rational design of advanced tissue-engineered vascular grafts. Muscle-mimicking geometries patterned on hydrogel facilitate the acquisition of a smooth-muscle-cell-like phenotype from human stem cells. Adult mesenchymal stem cells (MSCs) are a valuable source of cells for regenerative medicine. Now, researchers in Singapore and China have examined the complex interdependence of engineered cell shape and human transforming growth factor beta-1 treatment to direct smooth muscle cells differentiation of MSCs. They discovered that geometries resembling those of human smooth muscle cells provide the optimal shape for the expression and recruitment of the mechano-sensitive protein α-smooth muscle actin to the filamentous actin cytoskeleton. Based on these results, the researchers proposed an elegant model to describe the decision-making process that human MSCs take during differentiation into smooth muscle cells. The findings highlight the importance of using biomimetic cues for guiding differentiation of human MSCs. Inspired by the intrinsic morphology of smooth muscle cells (SMCs), a micropatterned hydrogel is developed to direct and define the boundary conditions for efficient SMC differentiation of human mesenchymal stem cells (hMSCs). The results show that in conjunction with TGF-β1 treatment, muscle-mimicking shapes with intermediate aspect ratios ranging from 5:1 to 10:1 exert the strongest pro-SMC differentiation effects in a structural–contractile force-dependent manner. These findings are expected to provide critical insights and design rules for vascular-related engineered tissue grafts.

Sensitivity Limits and Scaling of Bioelectronic Graphene Transducers

Semiconducting nanomaterials are being intensively studied as active elements in bioelectronic devices, with the aim of improving spatial resolution. Yet, the consequences of size-reduction on fundamental noise limits, or minimum resolvable signals, and their impact on device design considerations have not been defined. Here, we address these key issues by quantifying the size-dependent performance and limiting factors of graphene (Gra) transducers under physiological conditions. We show that suspended Gra devices represent the optimal configuration for cardiac extracellular electrophysiology in terms of both transducer sensitivity, systematically ~5× higher than substrate-supported devices, and forming tight bioelectronic interfaces. Significantly, noise measurements on free-standing Gra together with theoretical calculations yield a direct relationship between low-frequency 1/f noise and water dipole-induced disorders, which sets fundamental sensitivity limits for Gra devices in physiological media. As a consequence, a square-root-of-area scaling of Gra transducer sensitivity was experimentally revealed to provide a critical design rule for their implementation in bioelectronics.

Nanopatterned Substrates Increase Surface Sensitivity for Real-Time Biosensing

In this paper, we report critical design rules for improving the sensitivity of plasmonic biosensors. We use a scalable, parallel method to fabricate Au plasmonic crystal substrates patterned with an array of pits for real-time sensing. Capture ligands printed selectively in these pits resulted in a strong response to the binding of macromolecules. Angle-resolved sensorgrams showed quantitative differences between wavelength shifts produced by protein analyte bound within regions supporting localized and long-range electromagnetic fields. Contributions from the localized fields dominated the sensing response, especially at high angles. The angle-dependent far-field and near-field optical properties of selectively functionalized plasmonic crystals suggest that optimal performance is achieved at excitation parameters that produce an intense resonance with narrow spectral bandwidth and highly localized electromagnetic fields.

Silencing and enhancement of second-harmonic generation in optical gap antennas

Amplifying local electromagnetic fields by engineering optical interactions between individual constituents of an optical antenna is considered fundamental for efficient nonlinear wavelength conversion in nanometer-scale devices. In contrast to this general statement we show that high field enhancement does not necessarily lead to an optimized nonlinear activity. In particular, we demonstrate that second-harmonic responses generated at strongly interacting optical gap antennas can be significantly suppressed. Numerical simulations are confirming silencing of second-harmonic in these coupled systems despite the existence of local field amplification. We then propose a simple approach to restore and amplify the second-harmonic signal by changing the manner in which electrically-connected optical antennas are interacting in the charge-transfer plasmon regime. Our observations provide critical design rules for realizing optimal structures that are essential for a broad variety of nonlinear surface-enhanced characterizations and for realizing the next generation of electrically-driven optical antennas.

Standing Arrays of Gold Nanorods End‐Tethered with Polymer Ligands

Nanomaterials with vectoral electromagnetic properties have potential applications in solar cells, plasmonic cavity resonators, light polarizers, and biosensing. Here a new, simple, solution-based method for producing nanomaterials comprising vertically aligned standing arrays of gold nanorods (NRs) end-functionalized with polymer ligands is reported. The method utilizes the side-by-side assembly of the NRs into large 2D superlattices, followed by the precipitation of the lattices on a solid substrate. The critical design rules for the self-assembly of superlattices are demonstrated, and they show the generality of the method by forming standing arrays from the NRs end-tethered with poly(N-vinylcarbazole) or with polystyrene molecules.

High transmittance left-handed materials involving symmetric split-ring resonators

We present theoretical and experimental results for a new design of highly symmetric, multigap split-ring resonators (SRRs), as well as for left-handed materials of a broad and high transmittance left-handed band, achieved by combining those symmetric SRRs with continuous wires. Studying in detail, both theoretically and experimentally, our proposed symmetric SRRs, we proved that they avoid the electric field excitation of the magnetic SRR resonance; thus they are appropriate for the creation of two-dimensional and three-dimensional left-handed materials. Finally, we propose critical design rules for the development of low-loss and broad-band left-handed materials.

Extending aggressive low-k1 design rule requirements for 90 and 65 nm nodes via simultaneous optimization of numerical aperture, illumination and optical proximity correction

It has been a challenge for the lithography process to meet aggressive integrated circuit design rule requirements for 90 nm and upcoming 65 nm technology nodes under low-k1 patterning constraints. The geometric design rules are largely governed by numerical aperture (NA), illumination settings, and optical proximity correction (OPC) for any resolution enhancement technique-applied mask. A set of process feasible design rule criteria is explored based on state-of-the-art microprocessor chip that contains three different types of circuit design-standard library cell (SLC), random logic (RML), and static random access memory (SRAM). The critical design rule criteria to keep higher packing density for SRAM involve: achievable minimum pitch, sufficient area of contact-landing pad, minimum line-end shortening (LES) to ensure poly end-cap and preferably optimum pitch for placement of Scattering BarTM (SB). The goal is to achieve printing of ever-smaller critical dimension (CD) with greater CD uniformity control for RML. SLC should be designed with comparable criteria to both RML and SRAM devices. Hence, the design rule constraints for CD, space, line-end, minimum pitch and SB placement for SLC cell are critically confined. Unlike traditional method of assuming a linear scaling for the design rule set, achievable design rule criteria is explored for very low k1-imaging by simultaneously optimizing NA, illumination settings and OPC (for optimum placement of SB) for a calibrated process. This is done by analyzing CD uniformity control and maximum overlapped process window for critical lines, spaces and line-ends with the respective k1 factor for three types of circuits. A feasible set of design rules for 90 nm node with k1 as low as 0.36 can be obtained using 6% attenuated phase shift mask (attPSM) with 6% exposure latitude at 400 nm of overlapped depth of focus.

The Design, Analysis, and Development of Highly Manufacturable 6-T SRAM Bitcells for SoC Applications

We present here an extensive static random access memory (SRAM) bitcell development methodology that has led to the qualification and production of the smallest 6-T SRAM bitcell reported in 0.13-/spl mu/m CMOS technology. No additional processing steps were employed in accomplishing this result. Such a methodology is being extended also to subsequent technology generations. The development efforts included the electrical evaluation of several candidate 6-T SRAM bitcell architectures for both high-density and high-speed applications. Based on the electrical evaluations, the chosen cell architectures were incorporated in silicon and verified for their robustness with respect to critical design rules, yields and reliability. The methodology for optical proximity correction for bitcell development has been described here. Minor process enhancements to ensure compatibility of the overall process flow with the SRAM bitcells are described. The use of SRAM-specific electrical test structures serves an important role in validating the electrical performance and confirming the robustness of the bitcells in a manufacturing environment. The monitoring of V/sub ddmin/, the minimum voltage at which the memory is functional was used to drive overall process improvements and reliability. Lastly, measurements of soft error rates demonstrated excellent immunity of the bitcells to single event upsets.

Methodology for electromigration critical threshold design rule evaluation

We propose a methodology using nodal analysis techniques compatible with existing computer-aided design (CAD) tools for implementing critical threshold design rules for electromigration reliability. The concept underlying critical threshold design rules is the observation that a mechanical stress-induced backflow of metal atoms is created by electromigration in interconnect lines confined by a rigid dielectric. If the steady-state balance of these two atomic fluxes is achieved before critical electromigration damage is realized, then the line can be considered to be virtually immortal with negligible reliability risk. A design rule based on this critical threshold criterion has the potential to give designers added flexibility to use currents larger than present design rules typically allow in short interconnects.