Trench Angle Research Articles

Uncertainty quantification of the superposition film cooling with trench using supervised machine learning

Film cooling technology is significant for aero-turbines development. However, uncertainty on operating and manufacturing conditions would put the high-pressure turbines at the risk of unexpected problems. To extend the service life of the gas turbines, it is necessary to conduct an uncertainty analysis of the effects of the geometry parameters at different blowing ratios on film cooling performance. A classical flat-plate film cooling model under the multiple-row superposition conditions with trench is investigated in this study. The uncertainty inputs included the hole location, depth, and width of the trench and compound angle, while the lateral-averaged film cooling effectiveness was seen as the output. To reduce the computational cost, a Multilayer Perceptron (MLP) model based on supervised learning is built to model the nonlinear regression between the film cooling parameters and the film cooling effectiveness. The computational Fluid Dynamics (CFD) method was utilized to provide the training dataset. After rigorous validation and comparison, the MLP model shows higher accuracy and performance than other classical methods. Then the statistical flow and thermal characteristics of the film cooling outputs and variance were analyzed by the Monte Carlo simulation method. Results of sensitivity analysis show that the uncertainty of compound angle has the greatest effect at both low and high blowing ratios, followed by the location of the first row, trench width, and depth. Besides that, the hole pitch upstream gains more influence than those downstream. Also, both at low and high blowing ratios, the uncertain interval due to compound angle is the biggest, and the uncertain interval due to the hole location of the last row is the smallest. In the design and manufacturing process, it is believed that the uncertainty of compound angle, the hole location of the first row, depth and width of the trench should be paid extra attention to.

Novel XPS Technique for Fluorocarbon Layer Evaluation on Nano-Scale Sicoh Sidewalls

Motivation: The Back End of Line (BEoL) in semiconductor industry uses carbon doped silicon oxides (SiCOH), also called ultra-low-k (ULK) or low-k dielectrics as insulating materials. During reactive ion etching (RIE) of those materials, fluorocarbon passivation layer is formed which controls the etch profile and the plasma induced damage of the material. The etch front of the dielectric is dynamically removed during etching. Due to anisotropic plasma the FC layer builds up differently on the trench sidewalls. Therefore the FC layer on trench sidewalls and the trench bottom should be quantified [i]. It is challenging to study the vertical sidewalls in a patterned film. This work aims to implement X-Ray Photoelectron Spectroscopy (XPS) technique to analyze the sidewalls of the etched film and quantify the buildup of passivating FC layer on the sidewalls in different etch recipes. Methodology: Dense SiCOH (k=2.75, open porosity=7%) with initial thickness of 160nm was deposited on 300mm Si wafers. The wafers were patterned using E-beam lithography. The pattern consists of parallel trench arrays of varying trench widths (50nm to 1500nm) and line widths (75nm to 125nm). Wafers were etched with C4F8/CF4/N2/Ar (Recipe_1) and CHF3/CF4 (Recipe_2) plasma in a Dual Frequency Capacitive Coupled Plasma (CCP) etch chamber. Post etch trench depth and critical dimension (CD) bias of the etched structures were measured using spectroscopic ellipsometry and critical dimension scanning electron microscopy (CDSEM) respectively. Each structures were then measured under XPS for the surface chemical composition.The XPS methodology is based on the mathematical separation of the photoelectron signal intensities of the three different surfaces of a trench, namely the Line Top, Trench Sidewalls and Trench Bottom[ii]. In a model-based approach, electron shadowing by the opposite trench sidewall is calculated using the measured geometry from ellipsometry and CDSEM. It assumes that every point surface on the sidewall emits electrons and only the electrons falling in the acceptance cone of XPS electron detector are counted which limits the conical opening to 60º inclined at 50º to sample surface normal (Fig.1a). Analysis depth of the sidewall varies with the trench width and the trench angle. A physical model is developed to calculate the sidewall analysis depth which is not shadowed by the opposite sidewall (Fig.1b).The layout contains various pitch size which constitute different area ratios of Line Top, Trench Sidewalls and Trench Bottom. In order to find the chemical composition of each surfaces independent of their visible areas, the system of linear equations is solved using Multiple Linear Regression method to find out the signal intensity per unit area from all three surfaces, assuming that each surface composition remains constant across every pitch size. Comparison of the signal intensity per unit area indicates amount of sidewall passivation w.r.t trench bottom. As an additional verification to the methodology and electron shadowing, parallel angle resolved XPS (pAR-XPS) have been carried out at the same structure to find out the variation in sidewall contributions with different angles. Observation: Recipe_1 is highly passivating (C4F8 presence) but directional (high Ar content), therefore shows less deposition of FC layer on the sidewalls compared to line top and trench bottom, shown by the least F1s F-C and C1s C-Fx (x=1:3) intensity but high FC layer deposition on flat surfaces with remaining photoresist adding more carbon and nitrogen to line top than trench bottom (Fig.1c).Recipe_2 shows lower passivation (CHF3 presence) and anisotropy (No Ar) than Recipe_1, therefore lower carbon is seen on line top and trench bottom compared to Recipe_1, but a thicker FC layer on sidewalls. In both the recipes sidewalls and trench bottom shows similar level of Si2p Si-O and O1s O-Si signal intensities but only differ in their FC layer buildup due to different plasma chemistry. Line top with higher carbon content has lesser intensity of Si2p Si-O and O1s O-Si than the other with thinner FC layer buildup. Conclusion: The results confirm that the physical model is capable of separating the signal intensities from the three surfaces through which the FC layer on each surfaces have been accurately predicted. Therefore the normal mode XPS technique can be utilized to gain insight into the chemical composition of sidewalls. Acknowledgement: This work was funded via subcontract from Globalfoundries Dresden within the framework Important Project of Common European Interest (IPCEI) by the Federal Ministry for Economics and Energy and by the State of Saxony.

Performance analysis of 4H-SiC super-junction devices: impact of trench angle and improvement with multi-epi structure

This paper studies the impact of the trench angle on SiC super-junction device performance through the numerical simulation. Devices with different structure parameter sets (mesa width, epi doping) targeting different voltage ratings have been considered. It is found that with the optimum epi doping, the highest Baliga’s figure of merit (BFOM) is always achieved at the trench angle of 90°. The advantage of 90° trench angle can be further increased by reducing the mesa width (MW). However, the 90° trench is hard to be achieved through the current fabrication technology. Once the trench angle is reduced slightly, the device BFOM will decrease evidently especially for high voltage devices. At this condition, the reduction of mesa width does not necessarily produce higher BFOM. For example, at the trench angle of 89° and trench depth of 25 μm, the BFOM of the device with MW = 3 μm is substantially higher than that of the device with MW = 1 μm. Such a phenomenon is contrary to conventional theory, which is crucial for device design. Finally, in order to improve the performance of devices with non-90° trenches, the multi-epi structure is proposed. With such a novel structure, significant improvements have been observed in the simulation. The BFOM increments for 2 kV, 3.5 kV and 5 kV voltage rating devices are 27.4%, 60.8% and 102.6% respectively, demonstrating the superiority of the proposed multi-epi structure for SiC super-junction devices.

Correlation Between Trench Angle and Wafer Warpage in Trench Field Plate Power MOSFETs and its Application to Quality Control

Field-Plate (FP) MOSFET structure has been studied to get higher performance characteristics. To get low drift layer resistance, reduction of the trench width is one typical method with FP-MOSFET because it enables us to design the fine cell pitch of the FP-MOSFET. The main method for reducing the trench width is to design large trench angle. However large trench angle for better characteristics causes some challenges. And process window always becomes narrow to get excellent characteristic. For quality control of trench angle, we found that the wafer warpage was related to the trench angle at two process steps. We confirmed these mechanisms by simulation and experiment. Furthermore, we examined which process step was appropriate for monitoring the trench angle by wafer warpage. Finally, we acquired four correlation data related to the wafer warpage after field plate oxidation. Subsequently, we derived the regression equation for quality control and confirmed the validity of the equation.

Shark-Skin-Inspired Micro-Riblets Forming Mechanism of TC17 Titanium Alloy With Belt Grinding

Belt grinding could improve the surface integrity of titanium alloys, but it is difficult to achieve breakthroughs in the grinding mechanism due to the lack of grinding mechanism of titanium alloy microriblets structure. The characteristics of micro-riblets structure are discussed, and the belt grinding method for the micro-riblets is proposed based on the structural features. On this basis, the corresponding relationship model between the belt grinding and the surface parameters of the micro-riblets structure is established. The standard experimental platform was built and the belt grinding experiment was completed. The typical structural characteristics based on the method were obtained. The influence of the belt grinding process parameters on the formation of micro-riblets structures was analyzed. The results show that the micro-riblets structure achieved by the belt grinding method is dominated by sawtooth riblets. The width of the trench (s) is between 2.5μm and 8μm, the average value is 4.91μm, the height of the trench (h) is between 3.5μm and 9μm, the average value is 5.91μm, and the angle of the trench (α) is between 28° and 68°, the average is 42.3°. At the same time, it can be seen that increasing the grinding positive pressure (Fn), the feed step (P), and reducing the grinding feed rate (v <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">p</sub> ) can increase the sawtooth riblets width (s), the groove height (h), and the trench angle (α) of the micro-riblets structure surface. It can also increase the surface of the micro-riblets structure surface sawtooth riblets b <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sub> , b <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> . Moreover, the groove ratio h/s and the groove bearing side length ratiob <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sub> /b <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> have a sinusoidal fluctuation tendency, and the ratio mainly jumps up and down at a fixed value.

Structure optimization of nozzle in quick-freezer based on Response Surface Methodology

The structural parameters of nozzle in quick freezer have great influence on the nozzle outlet velocity, and the nozzle outlet velocity directly affects the freezing efficiency of the quick freezer. A V type slot nozzle was simulated with CFD software. The effect of the V type slot nozzle structure parameters variation on nozzle outlet velocity was studied by using Response Surface Methodology. Finally, the optimal structural parameters of the nozzle were obtained: the nozzle outlet height was 3.97 mm, the nozzle outlet width was 8 mm, the V type diversion trench height was 71.63 mm and the V type diversion trench angle was 29.57°. The conclusion provided a theoretical basis for optimal design of nozzle structure of quick freezer.

Effects of trench profile and self-aligned ion implantation on electrical characteristics of 1.2 kV 4H-SiC trench MOSFETs using bottom protection p-well

The effects of a trench profile and self-aligned ion implantation on the electrical characteristics of 1.2 kV 4H-SiC trench MOSFETs employing a bottom protection p-well (BPW) were investigated to improve blocking capability by simulation studies. The trench profile and thickness of a SiO2 spacer during self-aligned ion implantation for BPW affect electrons flow through a trench gate as well as E-field concentration at the gate insulator on a trench bottom. At trench angle higher than 84° and a SiO2 spacer thicker than 0.2 µm showed that the Al concentration penetrated into the trench sidewall during ion implantation is less than 0.3% in comparison with the background doping concentration in a drift region. Under the optimum conditions with a trench angle of 90° and 0.2-µm-thick SiO2 spacer, a high breakdown voltage of 1.45 kV with a low E-field peak in the gate insulator was achieved.

Trench angle: a key design factor for a deep trench superjunction MOSFET

Why is the development of a deep trench superjunction (SJ) MOSFET above 600 V and under 8.0 mohm · cm2 difficult? A deep trench SJ MOSFET is expected to have a low turn-on resistance because the post thermal process after the epitaxial process, which is normally used in a multi-step epitaxy structure, is unnecessary. When designing a deep trench SJ MOSFET, the trench angle is the most important factor because this determines the breakdown voltage (BV) and BV variations. In this paper, we investigated how the trench angle affects the BV and BV window as a condition of the possible thermal process. By employing a physical concept, ΔCharge, we explained why the maximum BV is decreased and the BV window is increased as the trench angle decreases. Also, we systematically scrutinized the transition of the vertical electric field by varying the trench angle. Furthermore, in a real case, the principle of the trench angle which contributes to the deviation of the charge imbalance and specific resistance of SJ is described. Finally, we discuss the challenge of SJ MOSFET development in the industry.

Super Junction MOSFET의 트렌치 식각 각도에 따른 열 특성 분석에 관한 연구

본 논문에서는 Super Juction MOSFET의 우수한 열 특성을 검증하기 위해 도출된 공정 및 설계파라미터를 이용하여 열특성을 분석하였다. 열 특성 중 핵심공정인 Trench 식각 각도에 따른 온도차이, 열 저항, 그 때 흐르는 드레인 전류를 측정하여 전체 소비전력을 분석하였다. 분석한 결과 Trench 식각 각도가 <TEX>$89.3^{\circ}$</TEX> 일 때 온도차와 열 저항 값이 가장 작게 나왔으며, 식각 각도에 따라서 분포는 경향성을 보이지 않았다. 따라서 반복 시뮬레이션과 실험을 통해 최적의 값을 도출해야 되며, 본 측정 결과 최적의 식각 각도는 <TEX>$89.3^{\circ}$</TEX>와 <TEX>$89.6^{\circ}$</TEX>의 결과를 보였다. 다른 전기적인 특성을 고려하여 최종 식각 각도를 보여야 하며, 열 특성의 우수한 SJ MOSFET이 산업에의 이용을 위해 본 논문의 자료가 충분히 활용할 수 있을 것으로 판단된다. This paper analyzed thermal characteristics of super junction MOSFET using process and design parameters. Trench process is very important to super junction MOSFET process. We analyzed the difference of temperature, thermal resistance, total power consumption according to trench etch angle. As a result we obtained minimum value of temperature difference and thermal resistance at <TEX>$89.3^{\circ}$</TEX> of trench etch angle. The electrical characteristics distribution of super junction MOSFET is not showed tendency according to trench etch angle. We need iterative experiments and simulation for optimal value of electrical characteristics. The super junction power MOSFET that has superior thermal characteristics will use automobile and industry.

Trench 식각각도에 따른 Super Juction MOSFET의 래치 업 특성에 관한 연구

This paper was showed latch up characteristics of super junction power MOSFET by parasitic thyristor according to trench etch angle. As a result of research, if trench etch angle of super junction MOSFET is larger, we obtained large latch up voltage. When trench etch angle was <TEX>$90^{\circ}$</TEX>, latch up voltage was more 50 V. and we got 700 V breakdown voltage. But we analyzed on resistance. if trench etch angle of super junction MOSFET is larger, we obtained high on resistance. Therefore, we need optimal point by simulation and experiment for solution of trade off.

P-pillar 식각 각도에 따른 Super Junction MOSFET의 전기적 특성 분석에 관한 연구

In this paper, we analyze electrical characteristics of n/p-pillar layer according to trench angle which is the most important characteristics of SJ MOSFET and core process. Because research target is 600 V class SJ MOSFET, so conclusively trench angle deduced 89.5 degree to implement the breakdown voltage 750 V with 30% margin rate. we found that on resistance is <TEX>$22mohm{\cdot}cm^2$</TEX> and threshold voltage is 3.5 V. Moreover, depletion layer of electric field distribution also uniformly distributes.

Super Juction MOSFET의 공정 설계 최적화에 관한 연구

Department of Photovolatic Engineering, Far East University, Eumseong 369-851, Korea(Received July 17, 2014; Accepted July 24, 2014)Abstract: This paper was developed and described core-process to implement low on resistance which was the most important characteristics of SJ (super junction) MOSFET. Firstly, using process-simulation, SJ MOSFET optimal structure was set and developed its process flow chart by repeated simulation. Following process flow, gate level process was performed. And source and drain level process was similar to genral planar MOSFET, so the process was the same as the general planar MOSFET. And then to develop deep trench process which was main process of the whole process, after finishing photo mask process, we developed deep trench process. We expected that developed process was necessary to develop SJ MOSFET for automobile semiconductor.Keywords: Super juction, n-pillar, p-pillar, On-resistance, Breakdown voltage, Trench angle, Power devices, Power MOSFET, Epi-layer, Process design, Process parameter, Design parameter

Analysis of Lattice Temperature in Super Junction Trench Gate Power MOSFET as Changing Degree of Trench Etching

Super junction trench gate power MOSFETs have been receiving attention in terms of the trade-off between breakdown voltage and on-resistance [1]. The vertical structure of super junction trench gate power MOSFETs allows the on-resistance to be reduced compared with conventional Trench Gate Power MOSFETs. The heat release of devices is also decreased with the reduction of on-resistance. In this paper, Lattice Temperature of two devices, Trench Gate Power MOSFET and Super junction trench gate power MOSFET, are compared in several temperature circumstance with the same Breakdown Voltage and Cell-pitch. The devices were designed by 100V Breakdown voltage and measured from 250K Lattice Temperature. We have tried to investigate how much temperature rise in the same condition. According as temperature gap between top of devices and bottom of devices, Super junction trench gate power MOSFET has a tendency to generate lower heat release than Trench Gate Power MOSFET. This means that Super junction trench gate power MOSFET is superior for wide-temperature range operation. When trench etching process is applied for making P-pillar region, trench angle factor is also important component. Depending on trench angle, characteristics of Super junction device are changed. In this paper, we focus temperature characteristic as changing trench angle factor. Consequently, Trench angle factor don’t have a great effect on temperature change.

Enhancement of On-Resistance Characteristics Using Charge Balance Analysis Modulation in a Trench Filling Super Junction MOSFET

In Super Junction (SJ) MOSFETs, charge balance is the most important issue of the SJ fabrication process. In order to achieve the best electrical characteristics, such as breakdown voltage and on-resistance, the N-type and P-type drift regions must be fully depleted when the drain bias approaches the breakdown voltage, which is known as the charge balance condition. In conventional charge balance analysis, based on multi-epi process SJ MOSFETs, analytical model has only N, P pillar width and doping concentration parameter. But applying a conventional charge balance principle to trench filling process, easier than Multi-epi process, is impossible due to the missing of the trench angle parameter. To achieve much more superior characteristics of on-resistance in trench filling SJ MOFET, the appropriate trench angle is necessary. So in this paper, modulated charge balance analysis is proposed, in which a trench angle parameter is added. The proposed method is validated using the TCAD simulation tool.

Design and Fabrication of Super Junction MOSFET Based on Trench Filling and Bottom Implantation Process

In Super Junction MOSFET, Charge Balance is the most important issue of the trench filling Super Junction fabrication process. In order to achieve the best electrical characteristics, the N type and P type drift regions must be fully depleted when the drain bias approaches the breakdown voltage, called Charge Balance Condition. In this paper, two methods from the fabrication process were used at the Charge Balance condition: Trench angle decreasing process and Bottom implantation process. A lower on-resistance could be achieved using a lower trench angle. And a higher breakdown voltage could be achieved using the bottom implantation process. The electrical characteristics of manufactured discrete device chips are compared with those of the devices which are designed of TCAD simulation.

On the ‘trench effect’ theory: A biomechanical analysis of the relationship between traction and shoe orientation on third-generation artificial turf

Background: Based on mechanical device testing on third-generation artificial turf (3G turf) it has been theorised that when cleated shoes are rotated at an angle to the direction of sliding in the transverse plane, the number of separate cleats forced to carve unique paths through the infill increases, thus increasing translational traction (termed ‘trench effect’). The aim of the study was to investigate whether the magnitude of this angle (shoe trench angle) affected traction across cleat configurations and 3G turf systems during a standardised in vivo change of direction movement.Methods: Twenty-two male soccer players (mean ± SD: age, 23.1 ± 2.8 years; height, 1.81 ± 0.06 m; body mass, 77.5 ± 6.0 kg) performed five short sprints with a 90° cut over a turf covered force plate for each combination of three turf systems and three cleat configurations. The traction coefficient – shoe trench angle relationship across cleat configurations and turf systems was determined with an analysis of covariance (ANCOVA) and shoe displacement was assessed with a linear mixed model.Results: There was a significant positive slope of the traction coefficient – shoe trench angle relationship, with a predicted increase in traction coefficient of 0.0017 for every degree of medial shoe rotation. The relationship did not differ between cleat configurations or turf systems. Across all shoe-surface combinations, mean ± SD shoe displacement was 1.33 ± 0.60 cm.Conclusion: During a standardised in vivo change of direction movement, an increase in shoe trench angle was accompanied by an increase in traction coefficient. The order of occurrence of these variables in such a movement makes it reasonable to assume that the increase in shoe trench angle causes the increase in traction coefficient. However, the magnitude of shoe displacement makes it difficult to support the ‘trench effect’ theory for controlled human movement.

Stability of Slurry Trenches with Inclined Ground Surface

AbstractA method for assessing stability of slurry trenches within an inclined ground surface is presented using the Coulomb-type force equilibrium method. The influence of ground surface inclination on trench stability and angle of critical failure surface is investigated via parametric studies on an example trench. As expected, the factor of safety decreases considerably with an increase in the ground surface inclination. It is shown that it is unconservative to neglect ground surface inclination while analyzing trench stability. According to the example, no significant error in the minimum factor of safety is introduced by using the failure surface inclination angle of 45°+ϕ′/2 for trenches with an inclined ground surface. It is also found that differences between the angle of critical failure surface and 45°+ϕ′/2 may exist; therefore, the angle of the critical failure surface needs to be determined instead of using 45°+ϕ′/2 for the design of remedial measures.

Effects of Geometrical Properties of Rectangular Trenches Intended for Passive Isolation in Sandy Soils

Wave barriers are placed actively and passively in the ground to reduce the transmission of vibration produced by industry, traffic, train, etc. They include open trenches, in-filled trenches and sheet piles, etc. In most recent studies, the researchers have worked on parameters such as depth, width, length of trenches and also, the distance between the source of vibration and trench in cohesive soils. Most researches are evaluation on screening induced by shallow foundation. In this study the passive isolation has been investigated with the help of open trenches screening against the vibration produced by deep foundations in sandy soils, and the effect of trench angle and radius have been studied. Moreover, the reasons for amplitude increasing before open trenches have been evaluated. Three dimensional finite element analyses (FEM) with ANSYS software are used to achieve an exact parametric study on passive screening. The assumed strains are less than 10-3so the bilinear Elasto-Plastic behavior has been utilized.

트렌치 게이트 IGBT 에서의 공정 및 설계 파라미터에 따른 항복 전압 특성에 관한 연구

In this paper, effects of the trench angle() on the breakdown voltage according to the process parameters of p-base region and doping concentrations of n-drift region in a Trench Gate IGBT (TIGBT) device were analyzed by computer simulation. Processes parameters used by variables are diffusion temperature, implant dose of p-base region and doping concentration of n-drift region, and aspects of breakdown voltage change with change of each parameter were examined. As diffusion temperature of the p-base region increases, depth of the p-base region increases and effect of the diffusion temperature on the breakdown voltage is very low in the case of small trench angle() but that is increases 134.8 % in the case of high trench angle(). Moreover, as implant dose of the p-base region increases, doping concentration of the p-base region increases and effect of the implant dose on the breakdown voltage is very low in the case of small trench angle() but that is increases 232.1 % in the case of high trench angle(). These phenomenons is why electric field concentrated in the trench is distributed to the p-base region as the diffusion temperature and implant dose of the p-base increase. However, effect of the doping concentration variation in the n-drift region on the breakdown voltage varies just 9.3 % as trench angle increases from to . This is why magnitude of electric field concentrated in the trench changes, but direction of that doesn`t change. In this paper, respective reasons were analyzed through the electric field concentration analysis by computer simulation.