Thin Glass Substrates Research Articles

Electrochemically growth and characterization of CuInTe2 chalcopyrite thin films

Copper indium tellurite (CIT) chalcopyrite compounds were electrochemically grown from an aqueous electrolyte including water-soluble Cu, In, and Te molecular sources onto indium thin oxide-coated glass substrates. CuSO4·5H2O, InCl3, and Na2TeO3 were used as copper, indium, and tellurium sources, respectively. Deposition mechanisms of the CIT thin films are explained by cyclic voltammetry (CV) studies. It is also noted that the effect of deposition potential on the electrical, optical, and structural facilities of the electrodeposited CIT thin films. Energy bandgap of the electrodeposited CIT films is in the range of 0.97–1.83 eV. Stoichiometry of the CIT films deposited at − 0.5, − 0.6, − 0.7, and − 0.8 V is near to CuInTe2. We report that the produced CIT films is polycrystalline nature, and CuInTe2 is a major chalcopyrite phase corresponding to (1 1 2), (2 0 4), and (1 1 6) directions at 2θ ~ 25°, 41°, and 49°, respectively. Hall-effect measurements show that the produced CIT thin films have p-type semiconducting conductivity with the acceptor concentration range of 2.8 × 1017 and 2.8 × 1018 cm−3. The variation of the mobility within 20.4–60.2 cm2/V s can be explained by the variation of Cu/In ratio within 2.19–0.59. The resistivity of the films is found to vary within 0.011–0.036 Ω cm, which is in good agreement with the literature data.

P‐156: Distinguished Poster: Curved Vertical‐alignment Liquid Crystal Display with Uniform brightness: from Pixel Design to Verification

Curved liquid crystal displays (LCD) suffers from an issue of uneven brightness among the vertical‐alignment (VA) LCD panels based on thin glass substrates. In this work, we investigared its origin through optical simulation and successfully realized uniform brilliance for 27‐inch curved LCD panels. The optical simulation revealed that the dark areas on the bending sides of the curved LCD panel originated from the reduced azimuth angle of the liquid crystals (LC) next to the ITO trunk. This issue could be resolved by decreasing the pretilt angle of the LC on the color filter (CF) side. Through developing pretilt angle tuning (PAT) technologies, we experimentally verified that the uniform brilliance could be achieved for 27‐inch curved LCD panels with 900‐mm curvature on thin glass substrates.

Ultrasonic Hydrogel Biochemical Sensor System.

In this work, we present a proof-of-concept hydrogel-based sensor system capable of wireless biochemical sensing through measuring backscattered ultrasound. The system consists of silica-nanoparticle embedded hydrogel deposited on a thin glass substrate, presenting two interfaces for backscattering (tissue/hydrogel and hydrogel/glass), which allows for system output to be invariant under the change in acoustic properties (e.g. attenuation, reflection) of the intervening biological tissue. We characterize the effect of silica nanoparticles (acoustic contrast agents) loading on the hydrogel's swelling ratio and its ultrasonic backscattering properties. We demonstrate a wireless pH measurement using dual modes of interrogations, reflection ratio and time delay. The ultrasonic hydrogel pH sensor is demonstrated with a sensing resolution of 0.2 pH level change with a wireless sensing distance around 10 cm.

Curved vertical‐alignment liquid crystal display with uniform brightness: From pixel design to verification

AbstractCurved liquid crystal display (LCD) suffers from an issue of uneven brightness among the vertical‐alignment LCD panels based on thin glass substrates. In this work, we investigated its origin through optical simulation and successfully realized uniform brilliance for 27‐inch curved LCD panels. The optical simulation revealed that the dark areas on the bending sides of the curved LCD panel originated from the reduced azimuth angle of the liquid crystals (LC) next to the ITO trunk. This issue could be resolved by decreasing the pretilt angle of the LC on the color filter side. Through developing pretilt angle tuning technologies, we experimentally verified that the uniform brilliance could be achieved for 27‐inch curved LCD panels with 900‐mm curvature on thin glass substrates.

Temperature sensor based on IR-laser reduced Graphene Oxide

A simple, cost-effective approach to realize a sensitive temperature sensor based on IR laser reduced graphene oxide (IRLrGO) is reported. The sensor has been obtained by irradiating a graphene oxide (GO) film, placed between two thin glass substrates, with a continuous wave diode laser operating at 970 nm along its entire length. A conductive strip, 13 mm long, 300 μm wide and 7 μm thick, has been generated by moving the GO film on an X-Y translator stage with a given velocity with respect to the fixed laser fiber tip position. The laser treatment has given rise to the GO reduction confirmed by the resistance R measurements as well as from SEM, EDX, ATR-FTIR and Raman analyses. The temperature dependence of the conductive strip resistance has been measured in air from 30̂C to 80̂C and in high vacuum from 80 K to 300 K. The sample acts as a sensitive and low mass Resistance Temperature Detector (RTD). Such a sensor is biocompatible and requires a very low bias (<1 V). While the performances of the IRLrGO temperature sensor are stable under high vacuum conditions at room temperature, its behavior remains to be studied when it operates under different environmental conditions.

Demonstration of Sputtering Atomic Layer Augmented Deposition: Aluminum Oxide-Copper Dielectric-Metal Nanocomposite Thin Films.

Designing a thin-film structure often begins with choosing a film deposition method that employs a specific process by which chemical species are formed and transported; in other words, a film deposition system in which two deposition methods are hybridized should lead to new ways of designing thin-film structures. This premise inspires us to combine atomic layer deposition (ALD) and magnetron sputtering (SPU) within a single chamber-supttering atomic layer augmented deposition (SALAD). SALAD takes full advantage of both ALD's precise and accurate precursor delivery and SPU's versatility in choosing chemical elements. A SALAD system is designed based on knowledge obtained from computational fluid dynamics with the goal of conceiving a film deposition system that satisfies deposition conditions distinctive for both ALD and SPU. As a demonstration, the SALAD system is utilized to deposit a unique nanocomposite made of aluminum oxide (Alox) thin films by ALD and copper (Cu) thin films by SPU-AlOx-Cu nanocomposite thin films. Spectroscopic reflectivity collected on AlOx-Cu nanocomposite thin films shows unique dispersion features to which conventional effective medium theories used for describing optical properties of composites made of a dielectric host that contains metallic inclusions do not seem to simply apply.

Flexible High-Efficiency CZTSSe Solar Cells on Diverse Flexible Substrates via an Adhesive-Bonding Transfer Method.

Cu2ZnSn(S,Se)4 (CZTSSe) thin-film solar cells are showing great promise due to using earth-abundant and nontoxic materials and tuning the band gap through the amount of S and Se. Flexible high-efficiency CZTSSe solar cells are one of the outstanding research challenges because they currently require the use of thick glass substrates due to the high-temperature heat treatment process, and for this reason, few flexible CZTSSe solar cells have been reported. Furthermore, most researchers have used thin glass and metal substrates with little flexibility; the power conversion efficiency (PCE or η) values of the solar cells made with them have been slightly lower. To overcome these hurdles, we transferred high-efficiency CZTSSe solar cells formed on a soda-lime glass substrate to flexible substrates via an adhesive-bonding transfer method. Through this method, we were able to achieve the PCE of 5.8-7.1% on completely flexible substrates such as cloth, paper, and poly(ethylene terephthalate) (PET). In particular, we were able to produce a CZTSSe solar cell on a PET substrate with a PCE of 7.1%, which is the highest among fully flexible CZTSSe solar cells currently known to us. In addition, we deeply analyzed the PCE degradation of the flexible CZTSSe solar cell fabricated by the transfer method through a panoramic focused ion-beam image and nanoindentation. From the results of our work, we provide an insight into the possibility of making flexible high-efficiency CZTSSe solar cells using our transfer method.

Estimation of deformation for a glass sheet on a noncontact air conveyor with film pressure feedback

Recently, air film conveyors equipped with porous pads have been developed to transport large, thin glass substrates in a contactless state. The deformation of the glass substrates should be monitored for the inspection process on the production line. Although laser sensors can be applied to detect the deformation along a given path, there are some problems such as poor efficiency and low real-time performance. For the purpose of estimating the deformation of the floating glass sheet indirectly, in this paper a film pressure feedback method is proposed and studied via theoretical analysis and experimental verifications. First, a theoretical model including the characteristics of the porous media and gap flow is established, and the model is solved by the finite volume method to obtain the film pressure distribution. Then, an experimental apparatus is built to measure the film pressure with different degrees of deformation of the glass sheet. Comparisons of the calculated film pressure with the measured data indicate that deviations gradually appear for the outer units as the deformation degree enlarges. Thus, we use four inner pressure points as the feedback and apply a proportional–integral algorithm to adjust the deformation shape in terms of a quadratic curve. Furthermore, we verify the method via a deformation measurement experiment. We find that the estimation method can afford an accuracy of 3% in cases where the glass sheet is symmetrically distributed, or asymmetrically distributed but with an asymmetry coefficient of less than 0.2. Finally, we find that the realistic boundary conditions, i.e. the film pressure in the groove and the edge deflection, greatly affect the estimation results, and an allowable measurement error to ensure adequate accuracy of the estimation is provided.

Combining super-resolution microscopy with neuronal network recording using magnesium fluoride thin films as cover layer for multi-electrode array technology

We present an approach for fabrication of reproducible, chemically and mechanically robust functionalized layers based on MgF2 thin films on thin glass substrates. These show great advantages for use in super-resolution microscopy as well as for multi-electrode-array fabrication and are especially suited for combination of these techniques. The transparency of the coated substrates with the low refractive index material is adjustable by the layer thickness and can be increased above 92%. Due to the hydrophobic and lipophilic properties of the thin crystalline MgF2 layers, the temporal stable adhesion needed for fixation of thin tissue, e.g. cryogenic brain slices is given. This has been tested using localization-based super-resolution microscopy with currently highest spatial resolution in light microscopy. We demonstrated that direct stochastic optical reconstruction microscopy revealed in reliable imaging of structures of central synapses by use of double immunostaining of post- (homer1 and GluA2) and presynaptic (bassoon) marker structure in a 10 µm brain slice without additional fixing of the slices. Due to the proven additional electrical insulating effect of MgF2 layers, surfaces of multi-electrode-arrays were coated with this material and tested by voltage-current-measurements. MgF2 coated multi-electrode-arrays can be used as a functionalized microscope cover slip for combination with live-cell super-resolution microscopy.

Thin Glass Substrates with Through-Glass Vias.

Abstract Glass substrates with fine-pitch through-glass via (TGV) technology is a promising approach to system in a package (SIP) integration. Millimeter wave applications, in particular, benefit from the superior RF properties, dimensional stability, and surface properties of glass. Glass can be made in very thin sheets (&amp;lt;200 um) which aids in integration and eliminates the need for back-grinding operations. The biggest challenge to adopting glass as a microelectronics packaging substrate is the existence of gaps in the supply chain, caused primarily by the difficulty in handling large, thin glass substrates using existing automation and processing equipment. This paper presents a temporary bonding technology that allows the substrates to be processed in a semiconductor fab environment without the need to modify existing equipment.

Laser Direct Writing of Heteroatom (N and S)-Doped Graphene from a Polybenzimidazole Ink Donor on Polyethylene Terephthalate Polymer and Glass Substrates.

In this paper, for the first time, a laser direct writing technique is reported to form S- and N-doped graphene patterns on thin (0.3 mm thickness) polyethylene terephthalate (PET) and glass substrates from a specially formulated organic polybenzimidazole (PBI) ink, without thermally affecting the substrates and without the need for a metallic precursor. Unlike standard graphene ink printing, postcuring at high temperatures is not needed here, thus avoiding potential substrate distortion and damages. A UV laser beam of 355 nm wavelength is used to generate photochemical reactions to break the CS bond (2.8 eV) from dimethyl sulfoxide (DMSO, a component of the PBI ink) and the CN bond (3.14 eV) of PBI and form N- and S-doped graphene on the substrates. The sheet resistance of the laser-induced graphene is as low as 12 Ω sq-1 on PET, matching that of indium-tin oxide (ITO). The laser-written doped graphene shows hydrophilic characteristics, unlike pristine graphene. The S- and N-doped graphene allows the tailoring of bandgaps and thus controlling electrical and chemical properties. The optical transparency of the written graphene is below 10% which could be improved in the future. Potential applications include printing of flexible circuits and sensors, and smart wearables.

Method for debonding of thin glass substrate and carrier for manufacturing thin flexible displays

Modern displays are becoming light, thin, and even curved and flexible. The thickness of glass substrates used in these displays has been reduced from its original value of 1.1 to 0.7 mm and eventually to 0.5 mm to create thinner displays. Glass substrates with a thickness of < 0.3 mm are extremely thin and fragile, can be easily deformed, and are therefore not suitable for direct incorporation into the display-manufacturing process. Glass-substrate suppliers bond thin glass substrates onto carrier glass substrates to form laminated glass substrates with increased overall thickness. The panel makers then manufacture the display on a laminated glass substrate. The carrier substrate is removed from the display to produce a thin panel. Glass-substrate makers debond the carrier from the thin glass substrate by applying mechanical force. However, the substrate may break during this debonding process. In this study, a novel method for bonding and debonding the carrier and glass substrates is proposed in which gas is injected between the carrier and thin glass substrate to separate them. This method effectively prevents the formation of edge defects in the thin glass substrate caused by breaks during the debonding process. We designed a debonding machine and established steps to debond the laminated glass substrate after a passive matrix organic light-emitting diode fabrication process. The results showed that this method can be used to efficiently debond the laminated glass substrate.

Effect of Substrate Temperature and Molarity on Optical and Electrical Properties of Mixed Structured Zn0.80Cd0.20O Thin Films

The present work focuses on the effect of substrate temperature and molar concentration on properties of polycrystalline Zn0.80Cd0.20O thin films deposited on glass substrates by chemical spray pyrolysis. X-ray diffraction (XRD) results have revealed the presence of mixed faces of cubic-hexagonal structure in the polycrystalline film and substrate temperature was optimized for 723 K to get good crystallinity of the deposited films. Crystallite size, dislocation density, micro strain and number of crystallites in the deposits were calculated by using XRD data. Scanning electron microscopy images showed the spherical grain surface morphology, which can be modified by the variation in the substrate temperature and molarity. It was noted that the optical transmittance and energy band gap increased as temperature increased and was found to decrease with molarity. The analysed optical measurements have been used to calculate the values of refractive index and extinction coefficients in the wavelength range of 400–600 nm. The n-type electrical conductivity was enhanced with increasing deposition temperature and molarity due to the increase in crystallinity and free carrier concentration respectively.

Temporary Bonding Technologies for Thin Wafer Handling

Thin glass substrates offer low dielectric constant and high temperature process capability for faster and thinner packages but handling is challenging due to lack of mechanical stiffness. Temporary bonding of thin wafers to stiffer carrier substrates offers a solution and has been an active area of research and development in recent years. Polymeric and tape wafer bonding solutions are available but usually for low temperature processes. In Corning, we have developed an array of surface treatment/coating technologies that offer high temperature capability (as high as 700°C). The common theme of all these technologies entails surface treatment or coating of a carrier substrate to achieve strong non-covalent bonding with the thin wafer. The desired attributes are: (a) high enough bond energy at room temperature to withstand vacuum, thermal, and wet processing steps, (b) low enough bond energy after the thermal processing steps rendering the pair mechanically separable, (c) spontaneous bonding via self-propagating bond wave, and (d) minimal outgassing or bubble formation between carrier and thin wafer due to degradation of bonding material. The technologies range from vacuum based sub-monolayer surface functionalization to vacuum based organometallic coating to high throughput solution processed ultra-thin molecular coatings. In this talk we will first describe the theoretical underpinnings of various surface and chemical forces that control the bond energy between the carrier and the thin wafer, models to predict the bond energy as function of surface chemistry and surface energy parameters, influence of surface chemistry on various process attributes such as bond wave propagation and outgassing during thermal treatment. We will also briefly review various processes developed and their relative strengths and applicability.

3D Integrated High-Precision Passives on Thin Glass Substrates for Miniaturized and High-Performance RF Components

Abstract Double-side or 3-D integration of high-precision and high-performance bandpass and lowpass filters that are interconnected with through-vias were designed and demonstrated on 100-micron thin glass substrates for ultra-miniaturized diplexer components. A novel process for achieving high precision with large-area fabrication was developed to achieve much improved tolerance in electrical performance. High-precision, high quality factor, and high component densities with thin-film layers on glass were used to realize innovative topologies on glass for high out-of-band rejection and low insertion loss. Low-loss 100-μm thick glass cores and multiple layers of 15-μm thin polymer films were used to build the filters on substrates. The demonstrated diplexers have dimensions of 2.3 ×2.8 ×.2 mm. Aided by the dimensional stability of glass and process control with semiadditive patterning, the performance of the fabricated filters showed excellent correlation with the simulation. The impact of process-sensitivity analysis on diplexer performance was also analyzed. Finally, a unique and innovative process solution was demonstrated to control the process deviation and achieve good diplexer tolerance. The performance deviation was controlled by ~3.5X with the new process.

Mechanism of bonding and debonding using surface activated bonding method with Si intermediate layer

Techniques of handling thin and fragile substrates in a high-temperature process are highly required for the fabrication of semiconductor devices including thin film transistors (TFTs). In our previous study, we proposed applying the surface activated bonding (SAB) method using Si intermediate layers to the bonding and debonding of glass substrates. The SAB method has successfully bonded glass substrates at room temperature, and the substrates have been debonded after heating at 450 °C, in which TFTs are fabricated on thin glass substrates for LC display devices. In this study, we conducted the bonding and debonding of Si and glass in order to understand the mechanism in the proposed process. Si substrates are also successfully bonded to glass substrates at room temperature and debonded after heating at 450 °C using the proposed bonding process. By the composition analysis of bonding interfaces, it is clarified that the absorbed water on the glass forms interfacial voids and cause the decrease in bond strength.

White light induced photo-thermal switching in a graphene-flake-mixed ZnO nanoparticle random laser

We experimentally demonstrate lasing mode switching within a graphene-flake-mixed ZnO nanoparticle film, in which the lasing suppression is observed when white light is illuminated on the film. The similar changes are also observed by changing the temperature of the same sample (about 30 °C increase form room temperature), while no lasing suppression is observed in a ZnO nanoparticle film without graphene flakes. In addition, we also observe that a thin glass substrate coated by a graphene-flake-mixed ZnO nanoparticle film shows a bend toward the film-coated side with increasing the white light intensity, due to the negative thermal expansion of graphene flakes. From these results, we consider that, beside the temperature dependent ZnO emission property, the photo-thermal response of graphene flakes is the dominant key for our observed lasing mode changes, in which the local structural change in a graphene-flake-mixed ZnO nanoparticle film would be induced by the white light absorption of graphene flakes. This study suggests the possibility to provide a method to remotely and non-invasively control and tune the lasing modes by external white light illumination.

Improved Performance of Zinc Oxide Thin Film Transistor Pressure Sensors and a Demonstration of a Commercial Chip Compatibility with the New Force Sensing Technology

AbstractA zinc oxide thin film transistor is developed and optimized that simultaneously functions as a transistor and a force sensor, thus allowing for scalable integration of sensors into arrays without the need for additional addressing elements. Through systematic material deposition, microscopy, and piezoelectric characterization, it is determined that an O2 rich deposition condition improves the transistor performance and pressure sensing characteristics. With these optimizations, a sensitivity of 4 nA kPa−1 and a latency of below 1 ms are achieved, exceeding the criteria for successful commercialization of arrayed pressure sensors. The functionality of 16 × 16 pressure sensor arrays on thin bendable glass substrates for integrated low weight and flexible touchscreen displays is fabricated and demonstrated and read‐out electronics to interface with the arrays and to record their response in real‐time are developed. Finally, the application of these sensors for mobile displays via their operation with an existing commercial touch integrated circuit controller is demonstrated.

Rapid formation of nanostructures in Au films using a CO2 laser

Abstract We systematically investigate the formation of nanostructures in magnetron-sputtered Au films using a CO 2 laser. By comparing the optical properties and surface morphologies of Au films on different kinds of substrates before and after laser irradiation with different laser powers and irradiation times, we find that the nanostructures are most rapidly formed in the Au film with 5 nm thickness on a thin glass substrate. With the laser power of 6 W and a beam diameter of ∼10 mm at the Au film, only a few tens of seconds of irradiation time is sufficient to induce nanostructures with the area size of ∼10 mm in the 5 nm Au film on a thin glass substrate.

Miniaturized Bandpass Filters as Ultrathin 3-D IPDs and Embedded Thinfilms in 3-D Glass Modules

This paper presents the modeling, design, fabrication, and characterization of an innovative and miniaturized thin-film bandpass filter with coupled spiral structures in ultrathin glass substrates (30– $100~\mu \text{m}$ ). This filter is demonstrated for two applications: 3-D integrated passive devices and embedded thinfilm filters in RF modules. A compact filter design was achieved through an integrated resonant structure that effectively utilizes the inductive and capacitive coupling between metal layers on either side of an ultrathin glass substrate or organic build-up layer. The designed filters (layout area $150~\mu \text{m}$ device thickness) were fabricated on a 30- $\mu \text{m}$ -thin glass substrate using a panel-based low-cost approach with double-side thin-film wiring processes. The effect of process variations on the performance of the proposed structures was also studied. Furthermore, an improved WLAN filter is designed and demonstrated by employing specific structural modifications. The measured frequency response of the filters shows good model-to-hardware correlation, with very low insertion loss (0.6 dB) in the passband, and high adjacent-band rejection (>25 dB).