Selective Dry Etch Removal of Si and SiOxNy for Advanced Electron Beam Probing Applications

This paper presents a global die level sample preparation technique utilizing selective etch chemistry and laser interferometry to expose the entire die top-most metal layer surface for Ebeam electrical FI. A novel Ebeam based probing technique referred to as StaMPS is introduced alongside this prep technique to isolate logic structure failures observed through SEM image contrasts at different logic states. By landing SEM probe tips on exposed metal pads and controlling logic states via an applied bias, the varying states produce different contrast within SEM imaging highlighting structural failure locations. This global prep technique in combination with StaMPS Ebeam FI creates faster FI/FA turn-around time by delivering a globally delayered full die in under an hour and creating opportunity to locate several defect types within a single sample.

Clinical Outcome of Class II direct composite restorations using total-Cetch versus selective etch adhesives

Background: The composite restoration of anterior is always a challenging job. Aim: To compare the clinical outcome of class 2 direct composite restorations using total-etch and selective etch adhesives, according to USPHS criteria. Methods: One hundred patients were included in this randomized controlled clinical trial study at Operative Dentistry department of LMDC, Lahore. They were divided in two groups. Group 1 for total etch technique, group 2 for selective etch technique enamel was etched with 37% phosphoric acid for 20 second and then washed thoroughly with water for 5-10 seconds and was dried with air for 5 seconds till frosty white and bond with self etch. Results: The majority of patients were in the age range of 25-31 years, 25 (50%) patients used total etch technique and 22 (44%) patients used selected etch technique. When compare the overall rating for restorations, 38 patients (76%) have acceptable restoration in total etch technique and 46 patients (92%) in selected etch technique. Statistically the difference was significant (P<0.05). Conclusion: Selected etch technique presented a successful clinical performance over total etch technique for Class II restorations. Keywords: Class II direct composition restoration, Total etch technique, Selected etch technique.

Class I Composite Restorations Using Total-Etch Versus Selective Etch Adhesives

Background: Total etch versus selected etch adhesives can either be used. Aim: To compare the clinical outcome of class 1 composite restorations using total-etch and selective etch adhesives. Methods: 50 patients of class I restorations were included in this study. They were divided in two groups i.e. Group 1 for total etch technique, while Group 2 for selective etch technique. Results: The mean ages in total etch technique were 27.72±5.26 years and 27.52±5.56 years in selected etch technique. There were 20 males (40%) and 30 females (60%) in total etch technique with male while in selected etch technique, 22 males (44%) and 28 females (56%). Selected etch technique was found to be more successful in clinical performance for Class I filling restorations (P<0.05). Conclusion: Selected etch technique was found to be more successful in clinical performance for Class I filling restorations. Keywords: Class I direct composition restoration, Etching.

AlGaAs/InGaAs High-Electron Mobility Transistors Fabricated Using Silicon Nitride Passivation and Selective-Etching Process

AlGaAs/InGaAs high-electron mobility transistors (HEMTs) are grown by molecular beam epitaxy (MBE). The studied HEMTs use two AlAs layers as etch-stop layers in the selective-etch recessed-gate fabrication of the HEMTs. The influence of passivation using silicon nitride on HEMTs is examined. Passivation improves the dc, high-frequency, and power characteristics of AlGaAs/InGaAs HEMTs. The passivated HEMT has a maximum extrinsic transconductance of 207 mS/mm, a unity-current-gain frequency (fT) of 13 GHz, and a maximum oscillation frequency (fmax) of 26 GHz. Furthermore, the variation of dc characteristics of the passivated HEMT with temperature is reduced.

Comparative Evaluation of Cavosurface Marginal Integrity by Assessing Microleakage Scores of Three Different Composites using a Universal Adhesive in Self Etch and Selective Etch Modes- A Stereomicroscopic Study

Introduction: Composite resins are currently the most popular restorative materials due to their superior esthetics, strong mechanical properties and high resistance to dissolution. However, in spite of the improvements in resin composite formulations over the years, polymerisation shrinkage which necessitates incremental placement techniques still presents clinical challenges. Aim: To compare and evaluate cavosurface marginal integrity in Class I restorations by assessing microleakage scores using Tetric N-Flow Bulk fill, SureFil Bulk fill composites and Filtek Z350 XT and using selective etch and self etch modes of a universal adhesive. Materials and Methods: This in-vitro research study was carried out in the Department of Conservative Dentistry and Endodontics, Bapuji Dental College and Hospital, Davangere, Karnataka, India from April, 2018 to May, 2018. Sixty extracted non-carious, intact human mandibular molar teeth were selected for this study. Standardised Class I cavities of 4 mm depth were prepared by a single operator with a high-speed hand piece using carbide fissure # 245 (SS White Inc) bur under air-water coolant. Samples were randomly divided into two main groups in which Single Bond Universal was used: Group I: Selective Etch Mode (30), Group II: Self Etch Mode (30). These main groups were then divided into 3 subgroups each Subgroup TF: Tetric N- Flow Bulk fill (Ivoclar Vivadent), Subgroup SB: SureFil Bulk fill (Dentsply) and Subgroup FC: Filtek Z350 XT (3M ESPE). All the specimens were then sectioned longitudinally along the mesio-distal direction towards the center of the restoration. Each specimen was viewed under a stereomicroscope and grading was done according to dye penetration at the tooth-restoration interface. Kruskal-Wallis and Mann-Whitney U-test were used to analyse the results. Results: The results showed that there was statistically significant difference in the microleakage scores of Tetric N- Flow Bulk fill, Filtek Z350 XT and SureFil Bulk fill (p<0.001). Group I Subgroup TF yielded lower microleakage score 0.70±0.675 as compared to Group II Subgroup TF which had a higher score 1.60±1.578. This difference was not statistically significant. (p-value=0.266). Group I Subgroup SB yielded lower microleakage score 1.20±0.919 as compared to Group II Subgroup SB which had a higher score 2.10±0.568. This difference was statistically significant. (p-value=0.017). Group I Subgroup FC yielded lower microleakage score 2.50±1.354 as compared to Group II Subgroup FC which had a higher score 3.20±0.789. This difference was not statistically significant (p-value=0.260). Conclusion: Tetric N flow bulk fill flowable composite resin can be considered as a better choice when compared to SureFil bulk fill and Filtek Z350XT composite resins. Selective enamel etching with SureFil bulk fill should be considered as the better choice as compared to self-etch for providing adequate seal in mild universal adhesives in Class I cavities.

Growth and Selective Etch of Phosphorus-Doped Silicon/Silicon–Germanium Multilayers Structures for Vertical Transistors Application

Vertical gate-all-around field-effect transistors (vGAAFETs) are considered as the potential candidates to replace FinFETs for advanced integrated circuit manufacturing technology at/beyond 3-nm technology node. A multilayer (ML) of Si/SiGe/Si is commonly grown and processed to form vertical transistors. In this work, the P-incorporation in Si/SiGe/Si and vertical etching of these MLs followed by selective etching SiGe in lateral direction to form structures for vGAAFET have been studied. Several strategies were proposed for the epitaxy such as hydrogen purging to deplete the access of P atoms on Si surface, and/or inserting a Si or Si0.93Ge0.07 spacers on both sides of P-doped Si layers, and substituting SiH4 by SiH2Cl2 (DCS). Experimental results showed that the segregation and auto-doping could also be relieved by adding 7% Ge to P-doped Si. The structure had good lattice quality and almost had no strain relaxation. The selective etching between P-doped Si (or P-doped Si0.93Ge0.07) and SiGe was also discussed by using wet and dry etching. The performance and selectivity of different etching methods were also compared. This paper provides knowledge of how to deal with the challenges or difficulties of epitaxy and etching of n-type layers in vertical GAAFETs structure.

Influence of selective etching on the enamel and dentin leakage of three low shrinkage composites in class V restoration

This study determined if prior selective enamel etching affected leakage of enamel/dentin margins in Class V low-shrinkage resin-based composite restorations. Round cavities, centered on the cemento/enamel junction, 2 mm in diameter and 2 mm in depth were prepared on the buccal, palatal or lingual surfaces of premolar teeth to have a total of 60 cavities. One side of the tooth received selective enamel etching and both sides were restored using one of 3 restorative materials (n = 10): Aelite LS posterior/All-bond SE, Estelite Sigma Quick/Bond Force, or Filtek P90/P90 System Adhesive. The teeth were fatigued for 5000 thermal cycles, and the marginal sealing was challenged with 50% ammoniacal silver nitrate. The interface was analyzed and the leakage score was calculated. Two-way ANOVA revealed that Filtek P90 (25.5±17.4) had lower leakage than Estelite Sigma Quick (63.1±34.5) and Aelite LS Posterior (64.2±41.8) with self-etching. With selective etching, the three materials showed reduced leakage in enamel. A significant difference (P <0.05) was found between leakage in enamel and dentin for the Aelite LS Posterior selective etch group and for Estelite Sigma Quick. Selective etching reduced enamel leakage for all materials in one-step self-etch materials. Two-step self-etch adhesives bond better to enamel and dentin than one-step resin-based adhesives.

From Wafers to Bits and Back again: Using Deep Learning to Accelerate the Development and Characterization of SiC

A non-destructive, fast and accurate extended defect counting method on large diameter SiC wafers is presented. Photoluminescence (PL) signals from extended defects on 4H-SiC substrates were correlated to the specific etch features of Basal Plane Dislocations (BPDs), Threading Screw Dislocations (TSDs), and Threading Edge Dislocations (TED). For our non-destructive technique (NDT), automated defect detection was developed using modern deep convolutional neural networks (DCNN). To train a robust network, we used our large volume data set from our selective etch method of 4H-SiC substrates, already established based on definitive correlations to Synchrotron X-Ray Topography (SXRT) [1]. The defect locations, classifications and counts determined by our DCNN correlate with the subsequently etch-delineated features and counts. Once our network is sufficiently trained we will no longer need destructive methods to characterize extended defects in 4H-SiC substrates.