Modelling deformation and fracture in confectionery wafers
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The aim of this research is to model the deformation and fracture behaviour of brittle wafers often used in chocolate confectionary products. Three point bending and compression experiments were performed on beam and circular disc samples respectively to determine the 'apparent' stress-strain curves in bending and compression. The deformation of the wafer for both these testing types was observed in-situ within an SEM. The wafer is modeled analytically and numerically as a composite material with a core which is more porous than the skins. X-ray tomography was used to generate a three dimensional volume of the wafer microstructure which was then meshed and used for quantitative analysis. A linear elastic material model, with a damage function and element deletion, was used and the XMT generated architecture was loaded in compression. The output from the FE simulations correlates closely to the load-deflection deformation observed experimentally.Keywords:
Brittleness
The wafer non-uniformity of WAT and yield within wafer (WIW) and wafer to wafer (WTW) is a major and everlasting problem, which is mainly caused by rapid thermal process and Spacer-2 Nitride deposition process. In this paper, we develop a simple method to remove nitride film on wafer backside with H 3 PO 4 treatment while protecting wafer front pattern completely by utilizing two different films. The excellent uniformity WIW and WTW can be acquired by utilizing this method, which is extremely promising for wafer thermal uniformity improvement and wafer edge yield enhancement.
Rapid thermal processing
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It may be more cost‐effective to produce larger diameter silicon CZ solar cells. However, greater thickness is anticipated to be necessary for larger diameter wafers to withstand wafering, cell processing, and handling. No means of quantifying this anticipated thickness increase is available to provide standards or guide for cell manufacturers. In this paper equations relating wafer thickness and diameter were derived by using fracture mechanics analysis. An analytical model was used as a guideline to estimate minimum silicon wafer thickness vs. diameter requirements for ID wafering in terms of fracture mechanics parameters. The model also indicated the minimum wafer side support required for various wafer thickness at any diameter.
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It was found that the dose uniformity of bare wafers in simultaneous arsenic ion implantation into thickly oxidized silicon wafers and bare silicon wafers varies according to the loading combination of wafers. The implantation was executed using a batch-process machine with a wafer loading disk in which a slit is cut to measure beam current during ion implantation. When an oxide wafer was loaded next to the slit with a beam irradiating the oxide wafer just after the slit, disk transverse motion was slowed, which subjected the middle band region of every bare wafer to a high dose. When an oxide wafer was loaded next to a bare wafer with the beam irradiating the oxide wafer just after the bare wafer, part of the bare wafer adjacent to the oxide wafer was subjected to a low dose. It was experimentally clarified that the bare wafer dose variation is caused by the beam blow-up due to the charging of the oxide wafer.< >
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In the heat treatment of silicon wafer, temperature control of the wafer surface is very important. This paper investigates the rapid radiative heating characteristics of the silicon wafers arranged in a row in the vertical heating furnace by the experiment and the numerical simulation. In present test, a wafer pitch was changed from 54 mm to 216 mm. The results showed that the maximum difference of surface temperature decreased with increase of a pitch of the silicon wafer. The maximum temperature difference was about 5℃, when a wafer pitch was 108mm and ramp-up ratio was 150℃/min. Simulation and experimental result agreed very well.
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Brittleness
Square (algebra)
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Silicon wafers are the most widely used substrates for fabricating Integrated Circuits (ICs). The quality of ICs depends directly on the quality of silicon wafers. Simultaneous Double Side Grinding (SDSG) is one of the processes used to flatten the sliced wafers. The literature contains several mathematical models for the wafer shape in Single Side Grinding (SSG). However, no systematical study on the wafer shape in SDSG has been reported. The first part of this paper gives an overview of current mathematical models for the wafer shape in SSG (or SDSG) of silicon wafers. Then a mathematical model for the wafer shape in SDSG of silicon wafers is developed. This developed model is then used to systematically study the effects of several SDSG parameters on the wafer shape.
Wafer backgrinding
Die preparation
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A new polishing machine has been constructed for the fabrication of bonded-wafer silicon-on-insulator (bonded-wafer SOI) through a numerically controlled polishing technique. The polishing machine is equipped with 32 small-area tools which produce the variation of polishing pressure over a wafer surface. The tools do not rotate. Instead, the wafers being polished perform an oscillatory motion. A tool removal profile which was adequate for selectively polishing one place on a wafer without affecting its neighboring areas was obtained. As a result of its test operation, the initial thickness deviation of σ=380 nm of the top Si layer of a bonded-wafer SOI sample has been improved to σ=48 nm.
Chemical Mechanical Planarization
Wafer backgrinding
Wafer Bonding
Die preparation
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This paper describes tests on cold-formed rectangular hollow sections (RHS) subject to combined bending and axial compression. The aim of the tests is to investigate the web element slenderness limits for RHS when classifying the section behaviour for local buckling. Compared to bending alone, when an RHS is under bending and net axial compression a greater proportion of the webs is in compression. This may affect the bending capacity of the member and may reduce the member's rotation capacity since local buckling may occur more easily. This paper describes a total number of 27 tests performed on 5 different sizes cold-formed RHS under combined bending and axial compression. Axial compression forces ranging from approximately 0% to approximately 50% of the section compression capacity of the sections were applied to the specimens in the tests. The results of these tests showed that the current limitation of classification in AS 4100 is unconservative for RHS and confirmed the simplified Wilkinson and Hancock (2001) proposal for limitation of compact section. It was also observed that the axial compression is likely to reduce the rotation capacity of sections and ultimately may lead to the change of a section's classification. However, there were some unexpected exceptions in which the rotation capacity increased as the axial compression increased.
Cold forming
Pure bending
Compression test
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In the silicon wafer polishing process, the mounting of wafer on the polishing head could be greatly influential in final quality of finished wafers. This paper focuses on the waxless wafer mounting technique which could replace the traditional wax wafer mounting. Mounting of wafers on the carrier block using a wetted porous template provides a simple way of securing wafer on polishing head for precision wafer polishing. Demounting of wafers from the porous pad is carried out by using the water jet impingement which takes only a couple of seconds for wafer demounting. A series of wafer polishing tests of 8 inch silicon wafers using the present wafer mounting system found that the developed waxless wafer mounting could be quite suitable for producing the wafers of the excellent surface qualities by meeting industry standard such as SBIR, LLS, and production yield.
Wafer backgrinding
Chemical Mechanical Planarization
Die preparation
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Today a remaining challenge is to determine the structural defect density (SDD) on a whole 156 x 156 mm2 multicrystalline (mc) silicon wafer over a timescale of a few minutes. In this contribution a new method is introduced to determine the SDD on large scale mc-Si wafers. The main advantage of the method presented is the possibility to obtain a complete map of the SDD of a 156 x 156 mm2 mc-Si wafer as well as a quantitative SDD analysis of the wafer in just a few minutes. Furthermore, the simple and quick sample preparation as well as the application of standard measurement equipment results in a convenient and cost-effective analysis tool. With these advantages, analysis of SDDs on large quantities of wafers, e.g. across the ingot height or width, can be easily realized in a few hours.
Ingot
Wafer-scale integration
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