Fin Formation Research Articles

Larval Development of the Blue Dolphin Cichlid (Cyrtocara moorii Boulenger, 1902): Morphological Changes

In this study, the larval development of Cyrtocara moorii was examined morphologically and compared with other Cichlidae species. The important morphological changes and critical developmental stages that C. moorii larvae undergo were determined during the process from hatching up to 20 days. It was observed that the larvae had a large yolk sac, transparent bodies, and undeveloped fins in the first days. Important developmental events such as eye development, mouth opening, onset of free swimming behavior, fin formation, and increased pigmentation were recorded. It was determined that the larvae started free swimming between 6-9 days, the yolk sac was completely depleted on the 10th day, and the larval development was completed, reaching the juvenile form on the 15-20th days. When the larval development of C. moorii was compared with other Cichlidae species, species-specific differences were observed as well as some similarities. It is thought that these differences may be related to the ecological adaptations, reproductive strategies, and evolutionary history of the species. It is suggested that future research should comparatively examine the larval development processes of more Cichlidae species and elucidate the mechanisms underlying this diversity.

Knockdown of vitamin D receptor affects early stages of pectoral fin development in zebrafish.

The vitamin D receptor (VDR) signalling has been implicated in vertebrate limb or fin formation. However, the involvement of VDR signalling in the early stages of limb/fin development remains to be elucidated. In this study, the role of VDR signalling in pectoral fin development was investigated in zebrafish embryos. Knockdown of vdr induced the severe impairment of pectoral fin development. The zebrafish larvae lacking vdr exhibited reduced pectoral fins with no skeletal elements. Insitu hybridization revealed depletion of vdr downregulated fibroblast growth factor 24 (fgf24), a marker of early pectoral fin bud mesenchyme, in the presumptive fin field even before fin buds were visible. Moreover, a perturbed expression pattern of bone morphogenetic protein 4 (bmp4), a marker of the pectoral fin fold, was observed in the developing fin buds of zebrafish embryos that lost the vdr function. These findings suggest that VDR signalling is crucial in the early stages of fin development, potentially influencing the process by regulating other signalling molecules such as Fgf24 and Bmp4.

Inhibition of the serine protease HtrA1 by SerpinE2 suggests an extracellular proteolytic pathway in the control of neural crest migration.

We previously showed that SerpinE2 and the serine protease HtrA1 modulate fibroblast growth factor (FGF) signaling in germ layer specification and head-to-tail development of Xenopus embryos. Here we present an extracellular proteolytic mechanism involving this serpin-protease system in the developing neural crest (NC). Knockdown of SerpinE2 by injected antisense morpholino oligonucleotides did not affect the specification of NC progenitors but instead inhibited the migration of NC cells, causing defects in dorsal fin, melanocyte and craniofacial cartilage formation. Similarly, overexpression of the HtrA1 protease impaired NC cell migration and the formation of NC-derived structures. The phenotype of SerpinE2 knockdown was overcome by concomitant downregulation of HtrA1, indicating that SerpinE2 stimulates NC migration by inhibiting endogenous HtrA1 activity. SerpinE2 binds to HtrA1, and the HtrA1 protease triggers degradation of the cell surface proteoglycan Syndecan-4 (Sdc4). Microinjection of Sdc4 mRNA partially rescued NC migration defects induced both by HtrA1 upregulation and SerpinE2 downregulation. These epistatic experiments suggest a proteolytic pathway by a double inhibition mechanism: SerpinE2 ┤HtrA1 protease ┤Syndecan-4 → NC cell migration

Inhibition of the serine protease HtrA1 by SerpinE2 suggests an extracellular proteolytic pathway in the control of neural crest migration

We previously showed that SerpinE2 and the serine protease HtrA1 modulate fibroblast growth factor (FGF) signaling in germ layer specification and head-to-tail development of Xenopus embryos. Here, we present an extracellular proteolytic mechanism involving this serpin-protease system in the developing neural crest (NC). Knockdown of SerpinE2 by injected antisense morpholino oligonucleotides did not affect the specification of NC progenitors but instead inhibited the migration of NC cells, causing defects in dorsal fin, melanocyte, and craniofacial cartilage formation. Similarly, overexpression of the HtrA1 protease impaired NC cell migration and the formation of NC-derived structures. The phenotype of SerpinE2 knockdown was overcome by concomitant downregulation of HtrA1, indicating that SerpinE2 stimulates NC migration by inhibiting endogenous HtrA1 activity. SerpinE2 binds to HtrA1, and the HtrA1 protease triggers degradation of the cell surface proteoglycan Syndecan-4 (Sdc4). Microinjection of Sdc4 mRNA partially rescued NC migration defects induced by both HtrA1 upregulation and SerpinE2 downregulation. These epistatic experiments suggest a proteolytic pathway by a double inhibition mechanism:SerpinE2 ┤HtrA1 protease ┤Syndecan-4 → NC cell migration.

Molecular control of cellulosic fin morphogenesis in ascidians

BackgroundThe tunicates form a group of filter-feeding marine animals closely related to vertebrates. They share with them a number of features such as a notochord and a dorsal neural tube in the tadpole larvae of ascidians, one of the three groups that make tunicates. However, a number of typical chordate characters have been lost in different branches of tunicates, a diverse and fast-evolving phylum. Consequently, the tunic, a sort of exoskeleton made of extracellular material including cellulose secreted by the epidermis, is the unifying character defining the tunicate phylum. In the larva of ascidians, the tunic differentiates in the tail into a median fin (with dorsal and ventral extended blades) and a caudal fin.ResultsHere we have performed experiments in the ascidian Phallusia mammillata to address the molecular control of tunic 3D morphogenesis. We have demonstrated that the tail epidermis medio-lateral patterning essential for peripheral nervous system specification also controls tunic elongation into fins. More specifically, when tail epidermis midline identity was abolished by BMP signaling inhibition, or CRISPR/Cas9 inactivation of the transcription factor coding genes Msx or Klf1/2/4/17, median fin did not form. We postulated that this genetic program should regulate effectors of tunic secretion. We thus analyzed the expression and regulation in different ascidian species of two genes acquired by horizontal gene transfer (HGT) from bacteria, CesA coding for a cellulose synthase and Gh6 coding for a cellulase. We have uncovered an unexpected dynamic history of these genes in tunicates and high levels of variability in gene expression and regulation among ascidians. Although, in Phallusia, Gh6 has a regionalized expression in the epidermis compatible with an involvement in fin elongation, our functional studies indicate a minor function during caudal fin formation only.ConclusionsOur study constitutes an important step in the study of the integration of HGT-acquired genes into developmental networks and a cellulose-based morphogenesis of extracellular material in animals.

Hox genes control homocercal caudal fin development and evolution.

Ancient bony fishes had heterocercal tails, like modern sharks and sturgeons, with asymmetric caudal fins and a vertebral column extending into an elongated upper lobe. Teleost fishes, in contrast, developed a homocercal tail characterized by two separate equal-sized fin lobes and the body axis not extending into the caudal fin. A similar heterocercal-to-homocercal transition occurs during teleost ontogeny, although the underlying genetic and developmental mechanisms for either transition remain unresolved. Here, we investigated the role of hox13 genes in caudal fin formation as these genes control posterior identity in animals. Analysis of expression profiles of zebrafish hox13 paralogs and phenotypes of CRISPR/Cas9-induced mutants showed that double hoxb13a and hoxc13a mutants fail to form a caudal fin. Furthermore, single mutants display heterocercal-like morphologies not seen since Mesozoic fossil teleosteomorphs. Relaxation of functional constraints after the teleost genome duplication may have allowed hox13 duplicates to neo- or subfunctionalize, ultimately contributing to the evolution of a homocercal tail in teleost fishes.

To the fin and back again: expanding our understanding of congenital limb malformation

Fins are not limbs. However, findings from comparative developmental and genetic analyses show that many of the processes essential in establishing a limb are similar for fin formation. Nevertheless, due to their structural differences, fins are not often used as models to understand the causes or potential treatment of limb disorders.Split hand/foot malformation (SHFM) presents with loss or mis-patterning of elements of hands or feet leading to a ‘clefting-like’ phenotype, often with joining of the digits. This rare disorder is genetically and phenotypically heterogeneous, and knowledge of its etiology remains largely incomplete. Recent work by Truong et al. provides new insight into SHFM by identifying new genetic variants within three different families, predicted to cause changes in function of the PRDM1/Blimp1 gene. PRDM1 is a transcription factor known to be essential for early appendage development in both zebrafish and mice. However, PRDM1 action is nuanced, in part due to its multifaceted roles in integrating signaling, transcription and chromatin state. This complicates the functional characterization of variants in this gene that have unknown significance in SHFM patients. Truong et al. demonstrate the utility of the zebrafish fin as an assay to directly address the function of domain-specific mutations in prdm1a by using the ability of the mutant alleles to rescue fin phenotypes caused by loss of Prdm1a function or, in the case of putative dominant variants, to suppress wildtype zebrafish fin development.A fin may not, or more likely will not, have the complete genetic networks underlying limb development and patterning. However, core mechanisms remain active and, at times, latent in fin development, allowing experimental dissection of mechanisms and gene function. Truong et al. harnessed the experimental malleability of zebrafish to isolate pectoral fin cells in early development and detail Prdm1a-dependent regulation of genes. These data establish aspects of the downstream regulatory network of fin development regulated by Prdm1a, providing insight into the broader array of changes involved in the etiology of this disorder.Core mechanisms and common evolutionary foundations allow for the establishment of defined genetic models of limb disorders in zebrafish and, importantly, accessible experimental models to formulate and test hypotheses on how these disease states are attained. Conversely, identification of disease-associating alleles provides insight into molecular action of genes in development and reveals details of the specificity of their regulation. Fin-in-hand, leading towards new discoveries for congenital limb malformations.

Postcranial skeletal development of the Atlantic herring (Clupeomorpha: Clupeidae: Clupeaharengus)

The Atlantic herring Clupea harengus is a small pelagic schooling fish belonging to the Clupeiformes. It constitutes a key species for fisheries and marine ecosystems of the Northern hemisphere. Due to its key importance for fishery several studies refer to the larval development of C. harengus and aim to further understand its reproductive biology. However, not much is known about the skeletal development of herring larvae. This study describes the axial skeleton development of Western Baltic herring. Cartilage and bone formation were traced by clearing and double staining herring larvae with a size spectrum of 6–35 mm. During the yolk-sac phase, the caudal fin starts to differentiate. Then, in the next phase the dorsal fin develops, followed by notochord flexion and anal fin formation. After a phase of pelvic fin development, the transition to the juvenile fish starts. The development of herring is compared to other clupeiforms, especially Alosa sapidissima, Engraulis japonicus and Sardinops melanostictus, for which information was available, and to previous research on herring larvae.

(Digital Presentation) Extending the Application of Capacitively Coupled Plasma Etching Tools to the Front-End-of-Line Fin-Cut Etching Process for FinFET Mass Production

As FinFET scales down to advanced technology nodes, Self-aligned Quadruple Patterning (SaQP) scheme is widely deployed for Fin formation, where two mandrels (MD1 and MD2) and corresponding mandrel spacers (MD1SP and MD2SP) are patterned for accurate CD transferring. The Fin-cut etching process of the MD2SP Cutting is very critical for the patterning of the Standard Cell and the SRAM patterns. This work studies the application of the Front End of Line (FEoL) MD2SP Cutting process in both inductively coupled plasma (ICP) and capacitively coupled plasma (CCP) etchers. The mismatch between the two tools is observed and discussed in detail. For CCP tools, a degradation of line width roughness (LWR) and increase of critical dimension (CD) loading between dense and isolated patterns are observed. Compared with the ICP etchers, the CCP etchers have lower plasma dissociation and stronger physical bombardment of ions. Furthermore, it is harder to control the plasma density and directionality separately. To increase CCP tool applications in FEoL processes, we introduce a Silicon coating process to modify the photoresist (PR) during the CCP etching to harden the surface of the PR and enhance the LWR performance. Furthermore, the application of atomic layer etching (ALE) technology ensures the CD loading between the dense and isolated patterns. With the application of our study, we can broaden the application of CCP tools in FEoL for FinFET mass production.

Phenotypic study for embryonic and larval development of common carp (Cyprinus carpio L., 1758)

The early development of common carp (Cyprinus carpio L., 1758) was studied from fertilizing until juvenile stage. The series developmental staging was done using morphological characteristics. Results identified eight main periods of embryogenesis: zygote, morula, blastula, gastrula, neurella, segmentation, pharyngula and hatching period. Results also identified and described nine larval development stages: hatching larva stage, rudimentary - pectoral fin and gill arch stage, melanoid-eye with gas bladder emergence stage, one chamber gas bladder with yolk absorption stage, two chamber gas bladder stage, pelvic fin bud with dorsal fin formation stage, anal-caudal and pelvic fin formation stage, squamation stage and juvenile stage. Hatching occurred at 38h after egg fertilization. The fertilized egg was spherical, yellowish, transparent and 2.5 mm in diameter. The transition from larva to juvenile occurred in 30 days.

New bending mode in SAQP Si fins and its mitigation

Self-Aligned Quadruple Patterning (SAQP) is used in advanced CMOS-FET technologies to enable the formation of arrays of fins at sub-40 nm pitches. As these technology nodes keep scaling down and the fins get taller for performance improvement, the patterns become denser and present very high aspect ratio (HAR). The scaling trends make the fin pattern more subject to mechanical instabilities during the processing steps. We describe in this paper a specific mechanical fin bending mode linked to the SAQP scheme targeting 24 nm pitch, the HAR and the formation and recess steps of the isolating oxide. We investigated the evolution of fin bending throughout the fin and isolation formation. We observed fins start bending at the FCVD deposition step exhibiting rotation angles up to 3 degrees. The bending was then worsened along the subsequent process steps causing mechanical failure after fin reveal where up to 7–8° of bending angles were observed. After having studied the influence of the key process steps, we can report a path to mitigate this phenomenon. Finally, we propose a simple mechanical analysis to validate quantitatively the root cause and extrapolate the mechanical robustness of this system for further scaling nodes where fin pitch is reduced.

Si0.5Ge0.5 channel introduction technique for the preparation of high mobility FinFET device

In this paper, the introduction technique of high mobility Si0.5Ge0.5 channel on bulk-Si substrate and its FinFET device preparation are explored in detail. First, a vertical Si0.5Ge0.5 fin formation on a slightly tapered SiGe strain relaxed buffer (SRB) can be attained by developing an optimized two-step etching process with HBr/O2/He plasma. Moreover, a SiN liner is introduced to further improve the thermal stability of the SiGe SRB/Si0.5Ge0.5 fin during a low temperature STI densification annealing. As a result, no obvious Si0.5Ge0.5 oxidation and Ge diffusion are observed. After the SiGe SRB/Si0.5Ge0.5fin structure is successfully prepared, a Si0.5Ge0.5 channel pMOS FinFET device is fabricated. Its drive current IDS of 123 μA/μm under |VDS| = |VGS| = 0.8 V, Ion/Ioff ratio of ∼3e4 and subthreshold slope of 120 mV/dec are demonstrated. The above results show that these newly developed processes can be a practical technique for the preparation of high mobility FinFET device.

Process Development of Dislocation-Free SiGe P-Channel in FinFET Technology

SiGe channel metal oxide semiconductor field effect transistor (MOSFET) became a choice of material as a performance booster in leading edge logic technologies. In this study, we demonstrate integration solutions for dual fin formation (Si for nFET, SiGe for pFET) using buried SiGe channel approach on 300 mm Si wafer. Plasma-induced damage (PID) layer, which thickness ranges from 0.5 nm to 2.5 nm, was observed after Si trench (p-trench) etch for SiGe EPI growth. This PID inorganic layer leads to SiGe dislocation defect. And careful sequencing and optimization of oxidation and wet removal steps were able to realize defect-free SiGe EPI channel along with a thin buffer SiGe layer. Besides, margin assessment of p-trench based buried SiGe approach was also presented in this study. Moreover, dual fin etch was demonstrated via inductively coupled plasma (ICP) using ALD-like function. The depth loading between SiGe and Si Fin was tunable via varying repeated cycles of advanced pulsing step, and less than 40 A of depth loading can be achieved. The progress reported represents a major leap for SiGe channel integration and paves the way for massive production.

Process Development of Dislocation-Free SiGe P-Channel in FinFET Technology

SiGe channel metal oxide semiconductor field effect transistor (MOSFET) became a choice of material as a performance booster in leading edge logic technologies. In this study, we demonstrate integration solutions for dual Fin formation (Si for nFET, SiGe for pFET) using buried SiGe channel approach on 300 mm Si wafer. Plasma-induced damage (PID) layer, which thickness ranges from 0.5 nm to 2.5 nm, was observed after Si trench (p-trench) etch for SiGe EPI growth. This PID inorganic layer leads to SiGe dislocation defect. And careful sequencing and optimization of oxidation and wet removal steps were able to realize defect-free SiGe EPI channel along with a thin buffer SiGe layer. Besides, margin assessment of p-trench based buried SiGe approach was also presented in this study. Moreover, dual Fin etch was demonstrated via inductively coupled plasma (ICP) using ALD-like function. The depth loading between SiGe and Si Fin was tunable via varying repeated cycles of advanced pulsing step, and less than 40 A of depth loading can be achieved. The progress reported represents a major leap for SiGe channel integration and paves the way for massive production.

Mechanical role of actinotrichia in shaping the caudal fin of zebrafish

Spear-like collagen complexes, known as actinotrichia, underlie the epidermal cell layer in the tip of teleost fins and are known to contribute toward fin formation; however, their specific role remains largely unclear. In this study, we investigated of actinotrichia in the role of caudal fin formation by generating collagen9a1c (col9a1c)-knockout zebrafish. Although actinotrichia were initially produced normally and aligned correctly in the knockout fish, the number of actinotrichia decreased as the fish grew and their alignment became disordered. Simultaneously, the fin tip gradually shortened in the dorsal-ventral direction and the entire fin became oval-shaped, while the fin-rays rarely bifurcated and instead underwent fusion, suggesting that actinotrichia are essential for spreading fins dorsoventrally. Furthermore, the epithelial cells that are usually thinly spread in normal fish became spherical in the knockout fish, reducing the area covered by each cell and thus the area of the fin tip. Together, these findings suggest that the tight alignment of actinotrichia provides physical support in the dorsal-ventral direction that allows caudal fins to expand in a triangular-shape.

Fabrication of High-Mobility Si0.7Ge0.3 Channel FinFET for Optimization of Device Electrical Performance

The fabrication process and electrical performance optimization of a high-mobility Si0.7Ge0.3 channel FinFET device were systematically explored. A high-quality of Si0.7Ge0.3 fin formation on Si substrates with shallow trench isolation-last (STI-last) scheme was first realized by a direct fin patterning and low-temperature STI annealing just after a blanket Si0.7Ge0.3 film growth on Si substrate. To solve the process compatibility issue of the Si0.7Ge0.3 fin, a new spacer etching process with CH3F/CF4-based plasma was developed because the existing spacer etching process is only appropriate for the Si fin and causes serious loss of the Si0.7Ge0.3 fin due to its low selectivity. Moreover, rapid thermal annealing at 850 °C for 30 s was chosen as the optimal source/drain (dopant activation process to maintain the thermal stability of the Si0.7Ge0.3 fin. In-situ O3 passivation, Al2O3/HfO2 bi-layer gate dielectric, and an extra ground-plane doping implantation were identified as key factors for improving the electrical performance of the Si0.7Ge0.3 channel FinFET device. Finally, a Si0.7Ge0.3 channel FinFET device with a subthrehold swing of 87 mV dec−1 and an Ion/Ioff ratio of 4e5 was fabricated successfully using the proposed processes.

Early development of the Neotropical fish known as long sardine Triportheus auritus (Valenciennes 1850) (Characiformes, Triportheidae)

Larvae and juveniles of long sardine, Triportheus auritus, from the lower Amazon river was described, evaluating ontogenetic changes in their external mor­phology, pigmentation, fin development, morphometry, and meristics. A total of 93 individuals, 83 larvae and 10 juveniles were analyzed, they were captured monthly between 2014 and 2019 in the Amazon river channel and in macrophytes aquatic stands in the alluvial plains located in the lower Amazon River. From each specimen, morphometric and meristic data were measured and then the growth pattern between morphometric variables was analyzed. The larvae have an elongated body in a fusiform shape, superior mouth, simple nostril, pigmented spherical eyes and long intestine, surpassing the median region of the body. Initial pigmentation is scarce, but intensifies through development forming a pattern composed of three longitudinal bands concentrated in the ventral, cephalo-dorsal and lateral line regions. There are also pigments in the mandible, surrounding the mouth, under the swim bladder, intestine and fins. The sequence of complete fin formation is: caudal, anal, dorsal, pectoral and pelvic. The total number of myomeres ranged from 45 to 48 (25–29 preanal and 17–22 postanal). Morphometric relationships indicated differential growth for measurable morphometric parameters, with abrupt growth of snout length, head length and body height in the transition from flexion to postflexion stages. The pre-dorsal distance showed a decrease in the growth rate at the threshold from the larval to the juvenile period. The pre-pectoral and pre-anal distances showed negative allometric growth. In conclusion, the combination of body shape pigmentation pattern and, the formation sequence of fins allow the identification of the genus and coupled with the number of myomeres, morphometric relationships, and ray numbers of the anal fin ensure the differentiation of T. auritus from the other congeneric species. The metamorphosis occurred mainly at the end of the larval period and it is related to changes in the physiological and ecomorphological characteristics of the species.

The Physical Role of Mesenchymal Cells Driven by the Actin Cytoskeleton Is Essential for the Orientation of Collagen Fibrils in Zebrafish Fins.

Fibrous collagen imparts physical strength and flexibility to tissues by forming huge complexes. The density and orientation of collagen fibers must be correctly specified for the optimal physical property of the collagen complex. However, little is known about its underlying cellular mechanisms. Actinotrichia are collagen fibers aligned at the fin-tip of bony fish and are easily visible under the microscope due to their thick, linear structure. We used the actinotrichia as a model system to investigate how cells manipulate collagen fibers. The 3D image obtained by focused ion beam scanning electron microscopy (FIB-SEM) showed that the pseudopodia of mesenchymal cells encircle the multiple actinotrichia. We then co-incubated the mesenchymal cells and actinotrichia in vitro, and time-lapse analysis revealed how cells use pseudopods to align collagen fiber orientation. This in vitro behavior is dependent on actin polymerization in mesenchymal cells. Inhibition of actin polymerization in mesenchymal cells results in mis-orientation of actinotrichia in the fin. These results reveal how mesenchymal cells are involved in fin formation and have important implications for the physical interaction between cells and collagen fibers.

Investigation on the formation technique of SiGe Fin for the high mobility channel FinFET device

In this work, SiGe Fin formation technique using shallow trench isolation (STI) first or STI last strategy for the high mobility channel FinFET device is systematically investigated. A 20 nm width and 35 nm height high crystalline quality of the Si0.7Ge0.3 Fin formation for STI first scheme is demonstrated by utilizing a new developed Si Fin etching, Si Fin recess and SiGe selective epitaxial growth process. For the STI last strategy, a novel chemical mechanical planarization (CMP) treated three-layer SiGe strain relaxed buffer (SRB) is successfully fabricated and a 50 nm high crystal quality and atomically smooth surface Si0.5Ge0.5 layer on this SRB is attained. Moreover, a spike annealing is employed to avoid the Si0.5Ge0.5 Fin oxidation during STI densification with an acceptable STI etching rate. However, both a spike annealing and a lower temperature of traditional furnace at 850 °C or 750 °C suffer micro-trench issue during the Fin reveal process. Therefore, a new developed process, named as STI recess first, is developed to resolve both thermal instability and micro-trench issue at the same time. A minor Si0.5Ge0.5 Fin loss with a sharp Si0.7Ge0.3 SRB/Si0.5Ge0.5 interfaces for STI last scheme is realized by utilizing this new developed STI recess first process.

Vertical InGaAs tunnel-field-effect transistors by an electro-plating fin formation technique

In this letter, we introduce for the first time a nano-fin patterning technique that combines Au electro-plating and high-temperature InGaAs dry etching processes. We applied this technique to fabricate vertical homojunction InGaAs tunnel-field-effect-transistors (TFETs). An InGaAs fin width (Wfin) of 60 nm was implemented with excellent line-edge-roughness (LER). The fabricated vertical homojunction InGaAs TFETs with a gate length (Lg) of 100 nm exhibited excellent device characteristics, such as a minimum subthreshold swing (Smin) of 80 mV/decade, an on–off-ratio (ION/IOFF) of 6.09 × 102 at VDS = 0.3 V, and a drain induced barrier lowering (DIBL) of 208 mV/V at room temperature.