Impact of Subsurface Damage on SiC Wafer Shape

2019 ◽  
Vol 963 ◽  
pp. 530-533
Author(s):  
Kevin Moeggenborg ◽  
Ian Manning ◽  
Jon Searson ◽  
Gil Yong Chung
Keyword(s):  
Surface Stress ◽  
Surface Damage ◽  
Subsurface Damage ◽  
Wafer Surface ◽  
The Impact ◽  
Sic Wafer ◽  
Abrasive Size

The impact of surface stress due to polish and grind processes on wafer bow was studied as a function of abrasive size. Results indicate that sub-surface damage from these processes can introduce significant surface stress. For polishing processes, this stress is proportional to mean abrasive size. The study also investigates stress as a function of depth below the wafer surface and finds that most stress is concentrated near the wafer surface.

Correlation between Local Strain Distribution and Microstructure of Grinding-Induced Damage Layers in 4H-SiC(0001)

2017 ◽  
Vol 897 ◽  
pp. 177-180 ◽  
Author(s):  
Susumu Tsukimoto ◽  
Tatsuhiko Ise ◽  
Genta Maruyama ◽  
Satoshi Hashimoto ◽  
Tsuguo Sakurada ◽  
...  
Keyword(s):  
Strain Distribution ◽  
Elastic Strain ◽  
Electron Backscatter Diffraction ◽  
Local Strain ◽  
Surface Damage ◽  
Wafer Surface ◽  
Gradient Distribution ◽  
Damage Layer ◽  
Defective Region ◽  
Sic Wafer

Evaluation of surface damage layers formed by mechanical grinding processes is indispensable in epi-ready SiC wafer preparation. As well as microstructure, the analysis of local strain distribution in the damage layers gives a clue on control of the wafer quality. Advanced electron backscatter diffraction (EBSD) technique is applied to evaluate the strain distribution of the damage layers. It is revealed that the elastic strain distribution can be classified into a hierarchy of three regions with respect to depth from the surface. Combining EBSD analysis with TEM observation, large compressive elastic strain and misorientation are introduced in the highly-defective region underneath the ground wafer surface. In addition, the gradient distribution of the strain is observed clearly below the highly-defective region. The knowledge of correlating between strain distribution and microstructure is promising to control the damage layer for the wafer preparation.

Study of PSG Thickness Uniformity Influencing Factors in LPCVD

2015 ◽  
Vol 645-646 ◽  
pp. 3-8
Author(s):  
Wen Long Lü ◽  
Zhan Zhan ◽  
Xiao Hui Du ◽  
Ru Hai Zhou ◽  
Hao Er Zhang ◽  
...  
Keyword(s):  
Flow Field ◽  
Gas Flow ◽  
Flow Distribution ◽  
Temperature Sensors ◽  
Wafer Surface ◽  
Thickness Uniformity ◽  
Phosphosilicate Glass ◽  
The Impact ◽  
Sic Wafer ◽  
Deposition Conditions

In the fabrication of SiC high-temperature sensors, the phosphosilicate glass film (PSG) is deposited on the SiC wafer as the intermediate layer, achieving the bonding of two SiC wafers. The ease of bonding is affected by the PSG film thickness uniformity. In this paper, the flow field distribution in the LPCVD tube is simulated under different deposition conditions,obtaining the wafer surface uniformity of gas flow distribution, which was verified by the experiment, The aim of this work is to study the impact of several deposition conditions such as the location of SiC wafers, wafer inclination and wafer spacing on the thickness uniformity of PSG film. Experimental results show that SiC wafer position in the tube and its own inclination and wafer spacing affect gas flow field on the SiC wafer surface,leading to uneven distribution of gas flow, thus affect the thickness uniformity of PSG.

Effect of Surface Damage on SiC Wafer Shape

2015 ◽  
Vol 821-823 ◽  
pp. 545-548 ◽  
Author(s):  
Kevin Moeggenborg ◽  
Thomas Kegg ◽  
Christopher Parfeniuk ◽  
Thomas Stoney ◽  
Jeffrey Quast
Keyword(s):  
Thin Film ◽  
Silicon Carbide ◽  
Surface Damage ◽  
Wafer Surface ◽  
Processing Step ◽  
Shape Effects ◽  
Sic Wafer ◽  
Wafer Surfaces ◽  
Different Levels ◽  
Effect Of Surface

The flatness of a silicon carbide wafer in terms of bow and warp is the result of the combination of factors both material and process related. Sub-surface damage (SSD) from the wafering process steps can be considered as a thin film under compressive stress on the wafer surface. SSD is generally decreased with each subsequent processing step after the multiwire saw. Single-sided process steps can produce very different levels of SSD on opposing wafer surfaces, leading to high bow and warp values. The present study investigates the effects of SSD on wafer flatness at various process steps as well as methods to minimize shape effects due to SSD during and after processing.

scholarly journals The Surface Condition of Ni-Cr after SiC Abrasive Blasting for Applications in Ceramic Restorations

Materials ◽  
2020 ◽  
Vol 13 (24) ◽  
pp. 5824
Author(s):  
Weronika Czepułkowska-Pawlak ◽  
Emilia Wołowiec-Korecka ◽  
Leszek Klimek
Keyword(s):  
Surface Condition ◽  
Abrasive Particle ◽  
Surface Profile ◽  
Abrasive Particles ◽  
Dental Restorations ◽  
Large Width ◽  
Ceramic Restorations ◽  
The Impact ◽  
Abrasive Size ◽  
Abrasive Blasting

Abrasive blasting is a process widely used in dentistry. One of the uses is the development of metal surfaces for connections with ceramics in fixed prosthetic restorations. The purpose of this paper was to check how the rough surface profile (width, height, and depth on unevenness) impacts the surface’s condition, like its wettability and percentage of stuck abrasives. The Ni-Cr alloy surface was abrasive blasted by silicon carbide with the various pressure parameters (0.2, 0.4, and 0.6 MPa) and abrasive particle sizes (50, 110, and 250 µm). Cleaned surfaces were examined for roughness, wettability, and percentage of stuck abrasive particles on the surface. The surface after abrasive blasting using 110 µm of abrasive size and 0.4 MPa pressure has the best wettability results. The width of unevenness may cause it. When the unevenness has too small or too large width and depth, the fluids may not cover the entire cavities because of locking the air. The surface condition of dental alloys directly affects metal–ceramic connection strength. The knowledge about the impact of the abrasive blasting parameters on the bond strength will allow one to create durable dental restorations.

The impact of neutralizer-free ignition of a radio frequency ion thruster on the lifetime of the ion optics system

2021 ◽  
pp. 2140017
Author(s):  
Long-Fei Ma ◽  
Li Duan ◽  
Jian-Wu He ◽  
Qi Kang ◽  
Keyword(s):  
Radio Frequency ◽  
Pyrolytic Graphite ◽  
High Strength ◽  
Surface Damage ◽  
External Source ◽  
Ion Thruster ◽  
Neutral Gas ◽  
Discharge Ignition ◽  
Ion Optical System ◽  
The Impact

In the initial stage of a radio frequency ion thruster (RIT) ignition, an influx of electrons is required from an external source into the discharge chamber and ionization of the neutral gas propellant. A neutralizer-free method for Townsend breakdown discharge ignition based on Paschen’s law was developed in this study. The feasibility of the ignition method was confirmed by performing thousands of ignition experiments. Metallic Molybdenum (Mo), pyrolytic graphite (PG) and Zr[Formula: see text]Ti[Formula: see text]Cu[Formula: see text]Ni[Formula: see text]Be[Formula: see text]alloy acceleration grids were prepared, and ignition-induced damage on the grids was investigated. A field-emission scanning electron microscope was used to inspect surface damage on the grids after multiple ignitions and to analyze the influence of the ignition method on the lifetime of the ion optical system. Grid materials for space missions that require multiple RIT ignitions (10[Formula: see text] should be high-strength blocks that are resistant to sputtering corrosion and high temperature.

scholarly journals Breakdown Degradation Associated With Elementary Screw Dislocations In 4H-SiC P+N Junction Rectifiers

1997 ◽  
Vol 483 ◽  
Author(s):  
P. G. Neudeck ◽  
W. Huang ◽  
M. Dudley
Keyword(s):  
Video Camera ◽  
Initial Study ◽  
Hollow Core ◽  
Power Devices ◽  
Screw Dislocations ◽  
Burgers Vector ◽  
X Ray ◽  
Current Voltage ◽  
The Impact ◽  
Sic Wafer

AbstractIt is well-known that SiC wafer quality deficiencies are delaying the realization of outstandingly superior 4H-SiC power electronics. While efforts to date have centered on eradicating micropipes (i.e., hollow core super-screw dislocations with Burgers vector > 2c), 4H-SiC wafers and epilayers also contain elementary screw dislocations (i.e., Burgers vector = Ic with no hollow core) in densities on the order of thousands per cm2, nearly 100-fold micropipe densities. This paper describes an initial study into the impact of elementary screw dislocations on the reverse-bias current-voltage (I-V) characteristics of 4H-SiC p+n diodes. First, Synchrotron White Beam X-ray Topography (SWBXT) was employed to map the exact locations of elementary screw dislocations within small-area 4H-SiC p+n mesa diodes. Then the high-field reverse leakage and breakdown properties of these diodes were subsequently characterized on a probing station outfitted with a dark box and video camera. Most devices without screw dislocations exhibited excellent characteristics, with no detectable leakage current prior to breakdown, a sharp breakdown I-V knee, and no visible concentration of breakdown current. In contrast devices that contained at least one elementary screw dislocation exhibited a 5% to 35% reduction in breakdown voltage, a softer breakdown I-V knee, and visible microplasmas in which highly localized breakdown current was concentrated. The locations of observed breakdown microplasmas corresponded exactly to the locations of elementary screw dislocations identified by SWBXT mapping. While not as detrimental to SiC device performance as micropipes, the undesirable breakdown characteristics of elementary screw dislocations could nevertheless adversely affect the performance and reliability of 4H-SiC power devices.

scholarly journals Nondestructive Evaluation of Functionally Graded Subsurface Damage on Cylinders in Nuclear Installations Based on Circumferential SH Waves

2016 ◽  
Vol 2016 ◽  
pp. 1-7
Author(s):  
Zhen Qu ◽  
Xiaoqin Shen ◽  
Xiaoshan Cao
Keyword(s):  
Mechanical Properties ◽  
Phase Velocity ◽  
Nondestructive Evaluation ◽  
Surface Damage ◽  
Subsurface Damage ◽  
Functionally Graded ◽  
Horizontal Shear ◽  
Steel Cylinder ◽  
Sh Waves ◽  
Subsurface Layers

Subsurface damage could affect the service life of structures. In nuclear engineering, nondestructive evaluation and detection of the evaluation of the subsurface damage region are of great importance to ensure the safety of nuclear installations. In this paper, we propose the use of circumferential horizontal shear (SH) waves to detect mechanical properties of subsurface regions of damage on cylindrical structures. The regions of surface damage are considered to be functionally graded material (FGM) and the cylinder is considered to be a layered structure. The Bessel functions and the power series technique are employed to solve the governing equations. By analyzing the SH waves in the 12Cr-ODS ferritic steel cylinder, which is frequently applied in the nuclear installations, we discuss the relationship between the phase velocities of SH waves in the cylinder with subsurface layers of damage and the mechanical properties of the subsurface damaged regions. The results show that the subsurface damage could lead to decrease of the SH waves’ phase velocity. The gradient parameters, which represent the degree of subsurface damage, can be evaluated by the variation of the SH waves’ phase velocity. Research results of this study can provide theoretical guidance in nondestructive evaluation for use in the analysis of the reliability and durability of nuclear installations.

On the Relationship of CMP Wafer Nanotopography to Groove-Scale Slurry Transport

2005 ◽  
Vol 867 ◽  
Author(s):  
Gregory P. Muldowney
Keyword(s):  
Coherent Structures ◽  
Wafer Surface ◽  
Transverse Mixing ◽  
Mixing Dynamics ◽  
Slurry Transport ◽  
Relationship Of ◽  
The Impact ◽  
The Relationship ◽  
D Model ◽  
Groove Pattern

AbstractMaterial removal in CMP occurs during intervals of pad-wafer contact separated by intervals of non-contact. One predictable sequence of non-contact intervals for a fixed point on the wafer is the traverse of the pad grooves, during which the wafer surface is renewed with fresh chemistry and heat is conveyed away. It is well understood that good uniformity requires machine kinematics that expose all points on the wafer to the same total contact time, mean slurry concentration, and temperature. Less widely known is that coherent structures tens to hundreds of nanometers high and matching the pitch of the pad groove pattern may be formed on an otherwise planar wafer despite multiple rotary motions. This unexpected phenomena is of interest not only because it manifests the impact of grooves and transport at scales not easily studied, but also because shrinking device architectures will ultimately disqualify even nanoscale departures from planarity. Wafer polish experiments are conducted alternately using circular, Cartesian grid, and spiral groove patterns using specialized pad conditioning and CMP recipes to amplify groove-induced nanotopography. Polish results illustrate sharp patterns in finished wafers (visible to the naked eye) that should not survive dual-axis tool kinematics. Computational 3-D model results are then presented for transient slurry mixing in the pad-wafer gap of a 200-mm polisher using the same groove patterns. A direct correspondence is found between observed wafer nanotopography and predicted groove-scale slurry mixing dynamics. In particular, the surface structures are underpolished areas traceable to intervals of non-contact protracted by depleted polish chemistry that prevails in groove segments when oriented relative to the local pad and wafer motion in a way that suspends transverse mixing in the groove crosssection. The study conclusively defines the features required in a groove pattern and polish recipe to form coherent structures matching the groove pitch. As validation of the theory, a groove pattern expected to form no surface topography is defined, experimentally tested, and shown to perform as predicted. Findings are discussed in the context of next-generation pad grooving and texturing as required for progressively more demanding applications of CMP.

Damage-Free Planarization of 2-Inch 4H-SiC Wafer Using Pt Catalyst Plate and HF Solution

2008 ◽  
Vol 600-603 ◽  
pp. 835-838 ◽  
Author(s):  
Takeshi Okamoto ◽  
Yasuhisa Sano ◽  
Hideyuki Hara ◽  
Kenta Arima ◽  
Keita Yagi ◽  
...  
Keyword(s):  
Surface Roughness ◽  
Interference Microscopy ◽  
Pt Catalyst ◽  
Wafer Surface ◽  
Root Mean Square Roughness ◽  
Surface Irregularity ◽  
Maximum Height ◽  
Planarization Process ◽  
Plate Morphology ◽  
Sic Wafer

We report a damage-free and efficient planarization process for silicon carbide (SiC) using platinum as a catalyst in hydrofluoric acid (HF) solution. In previous studies, 4H-SiC (0001) on-axis wafers were planarized by this process and an extremely flat surface was obtained. However, electronic device substrates require off-axis wafers. In the present study, 4H-SiC (0001) 8° off-axis Si-face wafers were planarized using a Pt catalyst plate and HF solution. In the first trial using these wafers, the surface roughness worsened and a diagonal pattern was observed by phase-shift interference microscopy. The pattern seemed to have been formed when the Pt plate morphology was transcribed onto the wafer. The removal rate of the 8° off-axis Si-face wafer is much greater than that of the on-axis Si-face wafer. Thus, we concluded that the use of a smoother catalyst plate would be necessary to obtain a smooth 8° off-axis Si-face wafer surface. Improving the Pt plate morphology by hand lapping also improved the surface roughness of the processed wafer as compared with the preprocessed surface. The maximum height of the surface irregularity (peak-to-valley, P-V) and root-mean-square roughness were improved to 0.513 nm and 0.044 nm, respectively, as determined by atomic force microscopy (2×2 μm2).

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