Wafer Chips Research Articles

Spectroscopic ellipsometry-based aptasensor platform for bisphenol a detection

Endocrine-disrupting chemicals (EDC) are pollutants that alter the function of the endocrine system by interfering with hormone biosynthesis, metabolism, or action. In this study, a spectroscopic ellipsometry platform is proposed using aptamers for the sensitive and selective detection of an EDC, 2,2-Bis(4-hydroxyphenyl)propane (Bisphenol A, BPA). Two different BPA-specific aptamers (Anti-BPA1 and Anti-BPA2) were immobilized to silicon wafer chips by the layer-by-layer self-assembly, a detection limit of 215 pM and 36 pM was obtained using the ellipsometric method for Anti-BPA1 and Anti-BPA2, respectively. Sensor specificity was tested with 2,2-Bis(4-hydroxyphenyl)butane and a maximum RSD of 3.8% was obtained. It has been reported that both aptasensors based on spectroscopic ellipsometry exhibit adequate analytical performance.

Improved MSRN-Based Attention Block for Mask Alignment Mark Detection in Photolithography

Wafer chips are manufactured in the semiconductor industry through various process technologies. Photolithography is one of these processes, aligning the wafer and scanning the circuit pattern on the wafer on which the photoresist film is formed by irradiating light onto the circuit pattern drawn on the mask. As semiconductor technology is highly integrated, alignment is becoming increasingly difficult due to problems such as reduction of alignment margin, transmittance due to level stacking structure, and an increase in wafer diameter in the photolithography process. Various methods and research to reduce the misalignment problem that is directly related to the yield of production are constantly being conducted. In this paper, we use machine vision for exposure equipment to improve the image resolution quality of marks for accurate alignment. To improve image resolution quality, we propose an improved Multi-Scale Residual Network (MSRN) that combines Attention Mechanism using a Multi-Scale Residual Attention Block to improve image resolution quality. Our proposed method can extract enhanced features using two different bypass networks and attention blocks with different scale convolution filters. Experiments were used to verify this method, and the performance was improved compared with previous research.

Uncalibrated visual positioning using adaptive Kalman Filter with dual rate structure for wafer chip in LED packaging

In the LED packaging, the changes of calibration parameters will affect the positioning effect of wafer chip and eventually result in the quality degradation of packaging process. Moreover, the frequent visual calibration processes will reduce the production efficiency. Accordingly, an uncalibrated visual positioning method for wafer chips is presented and applied for LED packaging in this paper. Firstly, the calibration model of LED chip visual positioning system is established. After sensitivity test based on calibration model, two typical cases of calibration parameters variation in LED packaging are given and analyzed. Then, the Kalman Filter is used to online estimate the variable calibration parameters, where two kinds of state vectors are designed for the two cases respectively. To accelerate the convergence and heighten the robustness, an adaptive design is introduced to improve the iterative process of Kalman Filter. Considering the influence of real time problems in visual signal, a dual rate structure is proposed to compensate the visual delay and realize the time synchronization for the multi-rate sensing. Based on the presented adaptive Kalman Filter with dual rate structure, an uncalibrated visual positioning control system is designed and verified by simulation. Finally, the chip positioning experimental results demonstrate that the proposed method can effectively improve the positioning effect of wafer chips and the working efficiency in LED packaging, which can be applied in practical production.

DNA Origami Structures Interfaced to Inorganic Nanodevices.

We describe here one way to achieve hybrid DNA-inorganic nanostructures on rigid flat insulating substrates. We report methods to prepare rectangular DNA origami and incubate them onto arrays of anchoring gold nanodots either in a static solution or in a microfluidic system. We give details on the design and lithographic methods employed to pattern usable arrays of gold nanoanchors on naturally oxidized silicon wafer chips. Scanning electron and atomic force microscopy methodological details are also given for obtaining the relevant characterizations of the immobilized and ordered DNA origami.

Thermo-mechanical analysis of TSV and solder interconnects for different Cu pillar bump types

Graphical abstractDisplay Omitted Highlights? FE modelling of Cu pillar bumps of different types. ? Stress distribution in solder interface and TSV interface. ? Reliability of conical frustum type is excellent than other types. The through silicon via (TSV) is a technology for vertical interconnection between multiple chips that employ a hole bored through a Si wafer and stack chips, which is good for securing a number of I/O per unit area reducing the electric resistance. On the other hand, vertical multi-layers are structurally more unstable than a single-layer but are vulnerable to a thermo-mechanical effect. Therefore, in this study, finite element analysis (FEA) of a three-dimensional (3D) multi-layer semiconductor with TSV was carried out to examine the changes in thermo-mechanical stress at the bonding interface with different models of Cu pillar bumps and Sn-3.5Ag solder bumps. A numerical simulation was carried out with different models, such as a plate type, pin type, skirt type, zigzag type and conical frustum type. The height and diameter of each solder bump were 10µm and 30µm, respectively. The distribution of Von Mises stress occurred more at the solder joint interface and TSV joint interface. At the solder joint interface, the stress in the skirt type (100.6MPa) was approximately double that in the conical frustum type (53.1MPa). At the TSV joint interface, the stress in the plate type (17.2MPa) was higher than that in the other types. The stress values were similar in the other types except for plate type Cu pillar bump. Stress in the solder and TSV joint interface was caused partly by the difference in properties between the two materials. In particular, mismatch in the coefficient of thermal expansion (CTE) had the greatest effect on the stress distribution.

Field emission characteristics of thin-metal-coated nano-sheet carbon films

Nano-sheet carbon films (NSCFs) coated with very thin (≈5-nm-thick) metal layers were fabricated on Si wafer chips by means of quartz-tube-type microwave-plasma chemical-vapour-deposition method with hydrogen–methane gas mixture and an electron beam evaporation method. Field emission (FE) current densities obtained at a macroscopic average electric field, E, of ≈10V/μm changed from 13mA/cm2 for NSCF with no coated metal to 1.7, 0.7 and 30mA/cm2 for Ti-, Al- and Au-coated NSCFs, respectively, while the threshold E varied from 4.4V/μm for the former one to 5.3, 5.4 and 2.0V/μm for the corresponding latter ones, respectively. As the FE currents of Au-coated NSCFs tended to be saturated in a higher E region, compared to those of NSCFs with no coated metal, no simple Fowler–Nordheim (F–N) model is applicable. A modified F–N model considering statistic effects of the FE tip structures and a space-charge-limited-current effect is successfully applied to an explanation for the FE data observed in the low and high E regions.

Enhanced field emission characteristics of thin-Au-coated nano-sheet carbon films

This paper reports that the nano-sheet carbon films (NSCFs) were fabricated on Si wafer chips with hydrogenmethane gas mixture by means of quartz-tube-type microwave plasma chemical vapour deposition (MWPCVD). In order to further improve the field emission (FE) characteristics, a 5-nm Au film was prepared on the samples by using electron beam evaporation. The FE properties were obviously improved due to depositing Au thin film on NSCFs. The FE current density at a macroscopic electric field, E, of 9 V/μm was increased from 12.4 mA/cm2 to 27.2 mA/cm2 and the threshold field was decreased from 2.6 V/μm to 2.0 V/μm for Au-coated carbon films. A modified F-N model considering statistic effects of FE tip structures in the low E region and a space-charge-limited-current effect in the high E region were applied successfully to explain the FE data of the Au-coated NSCF.

Reduction of thermal conductivity in wafer-bonded silicon

Blocks of silicon up to 3mm thick have been formed by directly bonding stacks of thin wafer chips. These stacks showed significant reductions in the thermal conductivity in the bonding direction. In each sample, the wafer chips were obtained by polishing a commercial wafer to as thin as 36μm, followed by dicing. Stacks whose starting wafers were patterned with shallow dots showed greater reductions in thermal conductivity. Diluted-HF treatment of wafer chips prior to bonding led to the largest reduction of the effective thermal conductivity, by approximately a factor of 50. Theoretical modeling based on restricted conduction through the contacting dots and some conduction across the planar nanometer air gaps yielded good agreement for samples fabricated without the HF treatment.

Field emission properties of nano-structured carbon films with carbon needles deposited on Si using high-power-density microwave-plasma CVD method

Nano-structured carbon films (NCFs) were fabricated on Si wafer chips with hydrogen–methane gas mixture by creating high-power-density microwave (MW) plasma in a quartz tube with a low-output MW power source. Carbon sheets with many nano-protuberances were complicatedly twisted each other in the center region of the NCF while carbon needles were additionally formed in the fringe region of the NCF. These NCFs yielded field emission (FE) characteristics with the FE current density of 68 mA/cm 2 at a macroscopic electric field, E, of 10 V/μm. Since the FE currents tended to be saturated even in a medium E region, no simple Fowler–Nordheim (F–N) model was applicable. A model considering the F–N mechanism, statistic effects of FE tip structures and a space-charge-limited-current effect has been applied successfully to explain all the FE data observed for E < 10 V/μm. It turned out that E-dependent parameters such as the effective total emission area and the effective field enhancement factor should be employed to obtain sufficient quantitative agreements between the model and the experiments.

TEM Specimen Preparation Technique For Small Semiconductor Devices

Abstract One of the methods of preparing samples for analysis by Transmission Electron Microscopy (TEM) is the well-known procedure using a Tripod polisher and the wedge technique (1-3), developed in our laboratory. Though developed explicitly for preparing samples of integrated circuit structures built on silicon, the technique has been used in our lab for a wide variety of other materials, including metals and ceramics. In general when working with silicon samples, we have the luxury of starting with large wafer pieces or chips that are generally at least a couple of millimeters square or larger. Recently, however, we needed to work for an extended period on GaAs based lasers, where the devices requiring analysis were individual lasers extracted from individual packages. These small samples, measuring 100x100x50 microns, are too small for the manual handling involved in routine mechanical cross sectioning methods.

HVEM/AFM Observation of Hinge-Type Plastic Zones Associated with Cracks in Silicon Crystals

Dislocation structures developed in hinge-type plastic zones associated with cracks in silicon crystals have been studied using a high voltage electron microscope (HVEM). Fine slip bands due to those dislocations have been also examined by an atomic force microscope (AFM). {100} and {110} cracks were introduced into {110} silicon wafers at room temperature by Vickers indentation method. The temperature of the wafer chips indented was raised to higher than 823 K to activate dislocations around crack tips under a residual stress due to the indentation. In specimens with the heat-treatment, prominent dislocation arrays corresponding to the hinge-type plastic zone were observed not only near the crack tip but also in the crack wake. AFM observations showed that very fine slip bands with the step height of a few nano-meters were formed with the regular spacing of a few microns. Based on the analyses of those dislocations and slip bands, it has been revealed that those dislocations were shielding-type increasing the fracture toughness.

Optically Interconnected Kohonen Net for Pattern Recognition

The test chip of optically interconnected Kohonen net which realizes the parallel pattern recognition was designed and fabricated. The optical waveguides, micromirrors and photodiodes were integrated on a Si wafer and complementary metal oxide semiconductor (CMOS) chips were bonded on the same Si wafer. The optical input data are distributed to the CMOS circuits by the branched waveguide and the distances between the input and the reference data are calculated. This test circuit operated at a frequency of 6.7 MHz.

Formation and stability of {113} defects in oxygen implanted silicon-on-insulator material

High dose oxygen implantation into Si (SIMOX – Separation by Implantation of Oxygen) is a viable technique for producing silicon-on-insulator structures. The {113} defect was first observed in SIMOX by van Ommen. It has received considerable study in bulk Si. Bergholz et al. proposed that {113} defects are coesite, a high pressure monoclinic phase of silica, and are a possible precursor to amorphous silicon oxide. Recently Bourrel proposed a self-interstitial model for the formation of hexagonal silicon in the {113} planes in the diamond cubic lattice which was an extension of Tan's model and suggested that oxygen is generally not required for the creation of {113} defects. In this paper we have examined the formation and stability of {113} defects in as-implanted and annealed SIMOX.The first set of samples studied was implanted to 2.4×1018 cm-2 at 200 keV from 400°C to 600°C. The second set was implanted at 150 keV to 2.0×1018 cm-2 at 500°C. Five equivalent parts of the wafer were annealed from 650°C to 1050°C in steps of l00°C for two hours in Ar. Cross-section samples were made by gluing, grinding, dimpling and ion milling of the wafer chips.