Polysilicon Surface Research Articles

Multi-label oxide classification in float-zone silicon crystal growth using transfer learning and asymmetric loss

AbstractFloat-Zone (FZ) crystal growth process allows for producing higher purity silicon crystal with much lower concentrations of impurities, in particular low oxygen content. Nevertheless, the FZ process occasionally faces the problem of small contamination from oxidation. This can come in the form of a thin oxide layer that may form on un-melted polysilicon surface. The appearance of the oxide layer indicates degraded machine performance and the need for machine maintenance. Therefore, oxide investigation is important for improving both the FZ process and FZ machines, and the first step is oxide recognition. In this study, we characterized oxide into mainly three varieties, according to their surface texture characteristics, which are: (i) spot (ii) shadow and (iii) ghost curtain. We leveraged FZ images captured from the vision system integrated on the FZ machine to establish an oxide dataset. Targeted for data imbalance problem in our dataset, a method based on transfer learning and asymmetric loss for multi-label oxide classification is presented in this work. The results showed that the pre-trained model and the asymmetric loss used for training outperformed the baseline models and improved the classification performance. Furthermore, this study deeply investigated the effectiveness of the components of asymmetric loss. Finally, Gradient-weighted Class Activation Mapping (Grad-CAM) was employed to explain decision process of the models in order to adopt them in the industry.

The Effect of Poly Silicon Surface Roughness Reduction on LTPS Devices Applied to Flexible Displays

The Effect of Poly Silicon Surface Roughness Reduction on LTPS Devices Applied to Flexible Displays

A High-Speed Chip-Scale Rotary Polygon Optical Scanner Based on a Micromotor Integrated With a Micro-Polyhedron Mirror

Micro-opto-electro-mechanical systems (MOEMS) based mirrors with a suitable actuation range are often used for optical beam scanning applications. While several MOEMS scanners have been reported, they often have limitations with respect to their range of motion, field of view, mass, size and fabrication cost. In this work, we present a rotary micro-polygon scanner based on an electrostatic variable capacitance micromotor for laser beam steering applications. The miniaturized scanner consists of a hollow micro-polyhedron mirror with a base radius of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$200 {\mu }\text{m}$ </tex-math></inline-formula> and a height of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$400 {\mu }\text{m}$ </tex-math></inline-formula> . It is mounted on the rotor of a variable capacitance micromotor using an epoxy-based adhesive. The rotor has a diameter of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$600 {\mu }\text{m}$ </tex-math></inline-formula> and is <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$2.5 {\mu }\text{m}$ </tex-math></inline-formula> thick. The micromotor was fabricated using a commercial three-layer polysilicon surface micro-machining process (PolyMUMPs) and the micro-polyhedrons were fabricated using a commercial bulk micro-machining process (PiezeoMUMPs). After fabrication of the components, the micro-scanner was assembled and operated under atmospheric conditions using a three-phase square wave excitation ranging from 0 V to 200 V and achieved rotational speeds of up to 2100 rpm. An optical laser beam with a wavelength of 632 nm was reflected off the sidewall of the rotating micro-polyhedron, achieving an experimentally measured scanning angular range of 57.88°, an angular scan rate of 220 radians per second and a scan speed of 25,200 lines per minute or 420 lines per second with a 12 sided micro-mirror. The ratio of the output power over the input optical power is measured over a scanning range of 22°, which is limited by the size of the photo-detector, yielding a ratio spanning from 0.18 to 0.22. This rotary micro-scanner can provide high scanning speeds and a wide scanning field of view with a footprint of 1.25 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> and a thickness of 0.83 mm, which is suitable to implement chip-level high-performance micro-beam steering systems for various applications. [2022-0020]

Boron Impurity Deposition on a Si(100) Surface in a SiHCl3-BCl3-H2 System for Electronic-Grade Polysilicon Production

A study of boron impurities deposited on a Si(100) surface in a SiHCl3-BCl3-H2 system is reported in this paper, using periodic density functional theory with generalized gradient approximation (GGA). The results show that the discrete distances of BCl3 and SiHCl3 from the surface of the Si(100) unit cell are 1.873 Å and 2.340 Å, respectively, and the separation energies are −35.2549 kcal/mol and −10.64 kcal/mol, respectively. BCl3 and SiHCl3 are mainly adsorbed on the surface of the Si(100) unit cell in particular molecular orientations: the positive position and the hydrogen bottom-two-front position from the analysis of the bond length change and adsorption energy. The adsorption of SiHCl3 and BCl3 is accompanied by a charge transfer from the molecule to the surface of the unit cell of 0.24 and 0.29 eV, respectively. BCl3 reacts more readily than SiHCl3 with the Si(100) surface, resulting in the deposition of boron impurities on the polysilicon surface.

Investigation of abrasive-free slurry for polysilicon buffing chemical mechanical planarization

Abrasive-free slurries which control polysilicon removal and surface roughness are highly desirable for polysilicon buffing chemical mechanical planarization (CMP). Here, we show that the addition of poly(ethylene glycol) (PEG) to poly(diallyldimethylammonium chloride) (PDADMAC) solutions inhibits adsorption of PDADMAC on polysilicon films. The effects of PEG additive on polysilicon static etching and removal behavior during CMP were investigated as a function of PEG concentration. Polysilicon static etching and removal amounts were suppressed with an increase in PEG concentration, and surface roughness was improved by 19.2% and 55.3% compared to those obtained with 250 ppm PDADMAC and 1 wt% silica slurry, respectively, within a certain range of PEG concentrations. The adsorption mechanism of PEG on polysilicon films was investigated using attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy, contact angle measurements, X-ray photoelectron spectroscopy (XPS) and zeta potential measurements. Our results suggest that PEG adsorbs on the surface of polysilicon films and forms a passivation layer that interferes with the approach of PDADMAC. A possible mechanism for improvement in surface roughness was also proposed based on the inhibition effect of PEG during the CMP process.

π-Donor/π-Acceptor Interactions for the Encapsulation of Neurotransmitters on Functionalized Polysilicon-Based Microparticles.

Bipyridinium salts, commonly known as viologens, are π-acceptor molecules that strongly interact with π-donor compounds, such as porphyrins or amino acids, leading their self-assembling. These properties have promoted us to functionalize polysilicon microparticles with bipyridinium salts for the encapsulation and release of π-donor compounds such as catecholamines and indolamines. In this work, the synthesis and characterization of four gemini-type amphiphilic bipyridinium salts (1·4PF6–4·4PF6), and their immobilization either non-covalently or covalently on polysilicon surfaces and microparticles have been achieved. More importantly, they act as hosts for the subsequent incorporation of π-donor neurotransmitters such as dopamine, serotonin, adrenaline or noradrenaline. Ultraviolet-visible absorption and fluorescence spectroscopies and high-performance liquid chromatography were used to detect the formation of the complex in solution. The immobilization of bipyridinium salts and neurotransmitter incorporation on polysilicon surfaces was corroborated by contact angle measurements. The reduction in the bipyridinium moiety and the subsequent release of the neurotransmitter was achieved using ascorbic acid, or Vitamin C, as a triggering agent. Quantification of neurotransmitter encapsulated and released from the microparticles was performed using high-performance liquid chromatography. The cytotoxicity and genotoxicity studies of the bipyridinium salt 1·4PF6, which was selected for the non-covalent functionalization of the microparticles, demonstrated its low toxicity in the mouse fibroblast cell line (3T3/NIH), the human liver carcinoma cell line (HepG2) and the human epithelial colorectal adenocarcinoma cell line (Caco-2).

MEMS-based Micro-scale Wind Turbines as Energy Harvesters of the Convective Airflows in Microelectronic Circuits

As an alternative to conventional batteries and other energy scavenging techniques, this paper introduces the idea of using micro-turbines to extract energy from wind forces at the microscale level and to supply power to battery-less microsystems. Fundamental research efforts on the design, fabrication, and test of micro-turbines with blade lengths of just 160 µm are presented in this paper along with analytical models and preliminary experimental results. The proof-of-concept prototypes presented herein were fabricated using a standard polysilicon surface micro-machining silicon technology (PolyMUMPs) and could effectively transform the kinetic energy of the available wind into a torque that might drive an electric generator or directly power supply a micro-mechanical system. Since conventional batteries do not scale-down well to the microscale, wind micro-turbines have the potential for becoming a practical alternative power source for microsystems, as well as for extending the operating range of devices running on batteries.

Hand Gesture Control Robot

In this paper we have designed a basic robotic chassis which can be easily controlled with the help of accelerometer instead of using button control. Here the most significant device is accelerometer. The accelerometer is the 3 axis estimation gadget with +-3g range. This gadget is made by utilizing polysilicon surface sensor and signal controlling circuit to quantify acceleration. The outcome of the accelerometer is analog in nature and corresponding to the acceleration. This gadget measures the static acceleration of gravity when we tilt it. And gives an outcome in type of movement or vibration. The hand position is sensed and the coordinates generated is considered as the parameter and if neccessary conditions are met, the statement prescribed in the arduino code is executed and the direction of the robot chassis is changed accordingly. So that it can perform the task such as forward moving, backward moving, turning left, turning right and stop. In many cases, the robot devices are some tough and complex while we control it with the help of buttons and switches. The major fields that prefers hand gesture robots are Defence field, industrial robotics, vehicle part assemble in civil side, medical field for surgery. In these fields if we are using remote controls and the button, the task will become complex. Sometimes the operator may get confuse in the switch control and button control, so a new concept is used to manage the gadget with the motion of the hand and at the same time it will manage the motion of the device.

Investigation of wavelength effects on polycrystalline silicon damages using nanosecond pulse laser irradiation

Based on polyvinylidene fluoride(PVDF) piezoelectric sensing technology, this paper investigated the damage mechanism of polysilicon irradiated by three wavelengths (1064 nm, 532 nm, and 355 nm) of nanosecond pulsed laser. According to the damage characteristics of the polysilicon, the thermal shock damage mechanism of laser irradiation on polycrystalline silicon has been studied, and the propagation law of laser shock waves in the brittle materials has been explored. The results show that the melt spatter phenomenon of the polysilicon surface is caused by melting from the heat generated when the material absorbs high-energy laser photons, combined with the vapour pressure and plasma pressure. The main cause of the polysilicon material’s cleavage and destruction is the laser thermal stress. The corrugated field around the material’s radiation area is mainly the result of the coherent coupling of optics and thermodynamics. The peak value of the laser shock wave in polysilicon shows a linearly distributed attenuation.

MonoPoly™ cells: Large-area crystalline silicon solar cells with fire-through screen printed contact to doped polysilicon surfaces

Successful integration of carrier selective contacts (so-called passivated contacts) in p-type and n-type front-and-back contact (FAB) silicon solar cells could lift cell efficiencies to above 24% in mass production. In this work, we introduce one of SERIS’ monoPoly FAB cell structures, which features the monofacial (single-sided) application of a polysilicon (poly-Si) layer. Using industrial tools, doped poly-Si on an ultrathin interface oxide is shown to provide extremely low recombination current density of 4 fA/cm2 and implied open-circuit voltage of about 745 mV that are able to withstand the high-temperature firing process of screen-printed metal contacts. The interface oxide and the doping concentration of the poly-Si film are of great importance for the surface passivation quality and the transport of majority carriers, especially for fire-through screen-printed contacts as used in this work. Our initial pilot-line results show a very promising cell efficiency of 21.4% on large-area (244.3 cm2) n-type monocrystalline wafers with screen-printed and fire-through metal contacts on both sides. A roadmap for nFAB monoPoly cells towards 24% efficiency is presented on the basis of an optimisation of the device architecture and various processing steps.

Surface micromachined MEMS deformable mirror based on hexagonal parallel-plate electrostatic actuator

Deformable mirrors (DM) based on microelectromechanical system (MEMS) technology are being applied in adaptive optics (AO) system for astronomical telescopes and human eyes more and more. In this paper a MEMS DM with hexagonal actuator is proposed and designed. The relationship between structural design and performance parameters, mainly actuator coupling, is analyzed carefully and calculated. The optimum value of actuator coupling is obtained. A 7-element DM prototype is fabricated using a commercial available standard three-layer polysilicon surface multi-user-MEMS-processes (PolyMUMPs). Some key performances, including surface figure and voltage-displacement curve, are measured through a 3D white light profiler. The measured performances are very consistent with the theoretical values. The proposed DM will benefit the miniaturization of AO systems and lower their cost.

多晶硅表面皮秒激光阵列孔绒面制备

多晶硅表面皮秒激光阵列孔绒面制备

Enhancing Modulation of Thermal Conduction in Vanadium Dioxide Thin Film by Nanostructured Nanogaps

Efficient thermal management at the nanoscale is important for reducing energy consumption and dissipation in electronic devices, lab-on-a-chip platforms and energy harvest/conversion systems. For many of these applications, it is much desired to have a solid-state structure that reversibly switches thermal conduction with high ON/OFF ratios and at high speed. Here we describe design and implementation of a novel, all-solid-state thermal switching device by nanostructured phase transformation, i.e., modulation of contact pressure and area between two poly-silicon surfaces activated by microstructural change of a vanadium dioxide (VO2) thin film. Our solid-state devices demonstrate large and reversible alteration of cross-plane thermal conductance as a function of temperature, achieving a conductance ratio of at least 2.5. Our new approach using nanostructured phase transformation provides new opportunities for applications that require advanced temperature and heat regulations.

Fabrication of tunnelling gap of nanomechanicalaccelerometer by focused ion beam

The two-layer polysilicon surface micromachining process flow of nanomechanical accelerometerincluded a high aspect-ratio etch step was presented.In the experiments we defined modes, and developed the technology of tunnelling gap formation using focused ion beam. The nanomechanical accelerometer crystals were fabricated by surface micromachining and focused ion beams.

A Thermal Method to Reduce the Polysilicon Resistance for Deep Submicron Integration Process

In the ultra-large-scale integration (ULSI) technologies, polysilicon resistors are usually employed in the integrated circuits as a precise analog resistor element for a variety of applications, such as DAC (digital resistor give the solution of the linearity and Rs concerns to analog converter) in analogue circuits [1-3]. Conventionally the polysilicon resistance can be adjusted by ion implantation and post annealing process [4]. For the self-aligned implantation process, the dosage changes which are always utilized to adjust the resistance are feasible to induce the MOS characteristics changes, especially in the submicron process whose short-channel effects (SCE) are much more sensitive to the dosages [5]. In this work, we propose a new inner anneal process in N2ambient after polysilicon re-oxidation to reduce the polysilicon resistance by changing the polysilicon grain size. The test patterns are manufactured on 300mm-diameter wafer by 65-nm 1-poly 7-metal standard CMOS technology. After polysilicon re-oxidation to form oxide film on polysilicon surface, the wafers are annealed at 800oC, 900oC, 950oC and 1000oC in N2ambient, respectively. Fig. 1 shows the process flow and annealing process steps in the flow. After anneal, the polysilicon grain size is measured by X-ray powder diffraction (XRD). And the electric characteristics for NMOS, PMOS and polysilicon resistance are tested. Fig. 2 shows the poly resistance reduction proportion and poly grain size after anneal at 800oC, 900oC, and 1000oC for 5min, and 950oC for 20min in N2 ambient, respectively. Only after annealing at 950oC or above for 5min, the resistance can be obviously reduced, due to the poly grain size increasing. Fig. 3 shows threshold voltages (Vt) variation proportions of NMOS and PMOS owning gate length of 65nm and width 0.12µm after utilizing annealing process at different temperatures. PMOS is more sensitive to the anneal process than NMOS. But after anneal at 950oC or below, the threshold variation for both NMOS and PMOS is less than 5%, which is acceptable for the integration process manufacturing. A new anneal process at N2 ambient to adjust the polysilicon resistance has been proposed. It has been verified that utilizing anneal process at 950oC or below, the 65nm MOS performances can be maintained almost same as before. Consequently, it is considered that the anneal method can be to be applied to the deep submicron integration process.

Characterization and removal of polysilicon residue during wet etching

Process optimization of polysilicon removal by wet etching with alkaline chemicals in a gate-last device integration scheme was investigated. Initial surface condition of the polysilicon layer, spreading properties of wet etching chemicals, and generation of hydrogen bubbles during wet etching were revealed as key parameters affecting the degree of polysilicon residue after wet etching both in patterned structures and on non-patterned bare wafers. Wet etching starting from a hydrophilic polysilicon surface showed successful polysilicon removal (no residues) compared with a hydrophobic polysilicon surface, indicating that the spreading and wetting properties of the wet etching chemical on polysilicon surface is very important in the polysilicon wet etching process. Therefore, it is believed that chemicals showing lower contact angles on the polysilicon surface may be suitable to enhance process efficiency. Furthermore, hydrogen gas generated during silicon wet etching can hinder polysilicon removal, causing significant residues after processing. Ultrasonication or addition of IPA in the wet etching solution can be an alternative method for preventing the hydrogen bubble effect.

Surface-Micromachined MEMS Tunable Three-Leaf Trefoil-Type Corner Cube Retro-Reflector for Free-Space Optical Applications

This work has developed a three-leaf trefoil-type corner cube retro-reflector (CCR) fabricated with the MUMPs polysilicon surface micromachining process. Unlike other MEMS CCRs, this CCR's opening faces straight upward as its (1, 1, 1) direction, i.e., the direction along which the retro-reflection efficiency is maximum, is perpendicular to the substrate's surface. Simulation results show that the orthogonality of CCR plays an important role in the optical performance of the CCR. Two CCRs leaning against each other to form a CCR pair are also presented, showing the feasibility of achieving a linear CCR array. With the ability to independently set the on-off state of each CCR by employing an electrostatically actuated gap-closing mirror as one of the three reflecting “leaves,” a CCR array can be used to realize optical identification.

Design and test of reliable high strength ingressive polycrystalline silicon microgripper arrays

We present the design and validation of a micromachined gripper array that enables reliable transmission of forces of at least 14 mN. The gripper is constructed with polycrystalline silicon (polysilicon), a brittle material, and is compatible with polysilicon surface micromachining. Two ingressive snap-and-lock array designs are presented. After developing design guidelines, it is shown that the first gripper array is functional. However, a risk remains that the gripper array rather than the tensile bar that it grips in its intended application fails. Therefore, an improved geometry is designed and it is shown that it is robust with respect to failure. Scanning confocal Raman imaging directly confirms that the local peak tensile stresses in the robust gripper array are approximately 50% of the lower bound material strength, and also resolves a 25% stress variation across the array.

Optimized immobilization of lectins using self-assembled monolayers on polysilicon encoded materials for cell tagging

Self-assembled monolayers (SAMs) have been used for the preparation of functional microtools consisting of encoded polysilicon barcodes biofunctionalized with proteins of the lectin family. These hybrid microtools exploit the lectins ability for recognizing specific carbohydrates of the cell membrane to give an efficient system for cell tagging. This work describes how the control of the methodology for SAM formation on polysilicon surfaces followed by lectin immobilization has a crucial influence on the microtool biofunction. Several parameters (silanization time, silane molar concentration, type of solvent or deposition methodology) have been studied to establish optimal function. Furthermore, silanes incorporating different terminal groups, such as aldehyde, activated ester or epoxide groups were tested in order to analyze their chemical coupling with the biomolecules, as well as their influence on the biofunctionality of the immobilized protein. Two different lectins – wheat germ agglutinin (WGA) and phytohemagglutinin (PHA-L) – were immobilized, because they have different and specific cell recognition behaviour and exhibit different cell toxicity. In this way we can assess the effect of intrinsic bulk toxicity with that of the cell compatibility once immobilized as well as the importance of cell affinity. A variety of nanometrical techniques were used to characterize the active surfaces, and lectin immobilization was quantified using ultraviolet-visible absorption spectroscopy (UV–vis) and optical waveguide light mode spectroscopy (OWLS). Once the best protocol was found, WGA and PHA were immobilized on polysilicon coded barcodes, and these microtools showed excellent cell tagging on living mouse embryos when WGA was used.

A Bi-Directional Out-of-Plane Actuator by Electrostatic Force

Presented in this paper is a bi-directional out-of-plane actuator which combines the merits of the electrostatic repulsive principle and the electrostatic attractive principle. By taking advantage of the electrostatic repulsive mode, the common “pull-in” instability can be lessened to enlarge the displacement, and by applying the electrostatic attractive mode, the out-of-plane displacement is further enlarged. The implications of changing the actuator’s physical dimensions are discussed, along with the two-layer polysilicon surface microfabrication process used to fabricate such an actuator. The static characteristics of the out-of-plane displacement versus the voltage of both modes are tested, and displacements of 1.4 μm and 0.63 μm are obtained at 130 V and 15 V, respectively. Therefore, a total stroke of 2.03 μm is achieved, more than 3 fold that of the electrostatic attractive mode, making this actuator useful in optical Micro-Electro-Mechanical Systems (MEMS) and Radio Frequency (RF) MEMS applications.