Glass Frit Research Articles

(Invited) High Accuracy Aligned Wafer Bonding for Wafer-Level Integration

Direct wafer bonding for SOI substrates manufacturing was probably the first volume production application based on bonding. As this application involves bonding of two non-patterned substrates the requirements for wafer-to-wafer alignment accuracy were very loose: mechanical (edge-to-edge) alignment with accuracies in the range of 50-100 µm was absolutely sufficient. For applications using other wafer bonding processes (the first sensors that were manufactured using glass frit bonding and anodic bonding) such rough alignment methods were still usable but in parallel optical alignment was adopted: in this case the alignment accuracy needs were going down to 5 – 20 µm. The increased device complexity of the applications which could benefit from wafer bonding advantages required for features from the bonding partners to be aligned to each other (either functional parts of the devices or structures necessary for the successful bonding process, such as bonding lines on both wafers): in such cases optical alignment became necessary and the technology progress was reflected also in more demanding requirements for the wafer-to-wafer optical alignment. For the early generations of these applications the required accuracy was still low, so it was possible to use adapted photolithography mask aligners. Later on, with higher accuracy requirements dedicated bond alignment systems were introduced in order to meet the tighter alignment specifications. With the adoption of direct (fusion) wafer bonding for backside illuminated (BSI) CMOS image sensors initially for consumer electronics this process found its way into the integration flow. For this application the device performance can be significantly improved by increasing the level of integration with the electronic components. For the first generations of devices the alignment accuracy was still not critical as one of the two substrates to be bonded did not have any electrically functional structures and optical alignment was required in order to guarantee a high yield for the patterning steps following the direct bonding and thinning of the CMOS image sensors wafer. This new application introduced a new requirement for direct bonding which was not considered before: besides the required alignment precision the need to simultaneously control the local wafer stress and deformation during the bonding process became crucial, as it leads to remaining distortion of the image sensor wafers. Patterns distortion causes problems with color filter manufacturing by subsequent stepper photolithography and ends up in cross talk between different colors. Especially for mobile devices the image sensors keep shrinking and combined with increasing the resolution at the same time the pixel sizes have reached levels where distortion levels below 50 nm are necessary. With further development of these image sensors also the second bonding partner wafer moved from the carrier wafer functionality to electrically active structures which required electrical connection to the image sensor wafer. Different integration schemes were developed, such as via last connection after the bonding where one wafer is thinned, vias are formed, which are subsequently filled with metal in order to achieve electrical connections. This paper aims to present an overview of the existing wafer-to-wafer alignment technology. The development of optical alignment methods will be reviewed with respect to applications requirements evolution over time. An overview of the different factors contributing to the overall misalignment budget and how they are controlled now or will be in the future in order to meet the stringent requirements will be presented with examples.

Glass Frit Wafer Bonding for Encapsulating Monolithic Integrated CMOS-MEMS Devices

CMOS-MEMS integration is getting a more and more important topic with growing expectations and requirements on the function and performance of micro sensors [1]. The integration of ASICs and memories to MEMS sensor structures allows by calibration the compensation of side effects (temperature influences, stress influences,…) and manufacturing tolerances. Thus, very accurate sensors, at acceptable cost structures for high volume applications become feasible. These high volume applications are often for mobile devices or other use cases where the form factor is important as well – here the wafer level integration and the wafer level packaging (wafer bonding) also offer many opportunities.

Ion Intercalation into Vanadium Sulfides for Battery Applications

Global battery manufacturing capacity will more than double by 2021 to about 280,000 megawatt-hours.1 Rechargeable batteries make up a significant fraction of battery manufacturing. A rechargeable battery cell is made up of two electrodes, the anode and the cathode, separated by an electrolyte. For solid electrodes, an electrolyte-permeable separator separates them. Chemical reactions at the anode and the cathode produces two components; ionic and electronic. The electrolyte conducts the movement of ions inside the cell while forcing electrons to pass through outside of the cell. Current collectors at the anode and the cathode deliver electric current to and from the external circuit. During discharge, electrons and ions flow from the anode to the cathode. On charge, an applied electric field forces the electrons and ion to flow back from the cathode to the anode.2 Lithium-ion technology has dominated the rechargeable battery industry because of their high energy density, and portability. High cost, safety issues, and charge storage capacity limit lithium-ion technology. These problems have sparked new interest in rechargeable batteries with multivalent ions like magnesium ion (Mg-ion). Magnesium is divalent, cheaper than lithium, easy to handle, and environmentally friendly. It has 1.85 times the theoretical volumetric capacity of lithium.3 Passivation and choice of cathode materials have hindered Mg-ion technology. Passivation produces a surface thin film on the metal anode that prevents reversibility of magnesium ions. Electrolytes from magnesium organo-halo-aluminate complexes in ether solvents have significantly reduced passivation problems.4 The choice of cathode material remains elusive. Theoretical predictions have shown high magnesium ion mobility in six-coordination, spinel close-packed frameworks.5 Mg-ion has been reported to favor octahedral environment in oxides and sulfides.6 This project focuses on investigating vanadium sulfides compounds, AxV5S8, AxV6S8, and V5S8 as candidate cathode materials for Mg-ion battery. A is an alkali metal, or monovalent cation and x = 0 – 0.8. AxV6S8 has a hexagonal unit cell formed from a distorted VS6 octahedral sharing faces and edges, with large hexagonal channels capable of intercalating ions.7 AxV5S8 has a monoclinic structure. It has a three-dimensional framework made from slightly distorted VS6 octahedral sharing edges and faces, with rectangular tunnels prime for ion insertion.8 Both AxV5S8 and AxV6S8 have short V-V zigzag chains that make both metallically conductive.5,6 V5S8 has a monoclinic structure with every three-quarter of metal atom position vacant in every layer of the NiAs structure.9 Stoichiometry mixtures of vanadium sulfide compounds are synthesized in evacuated sealed quartz tubes. The products are handled and analyzed under argon. Samples of AxV6S8, AxV5S8, and V5S8 are characterized using powder XRD. Electrochemical properties of the vanadium sulfide compounds are studied using cyclic voltammetry and chronopotentiometry. Cell assembly consists of lithium metal anode, 80 % vanadium sulfide compound cathode, 1 M LiClO4 in 1:1 EC:DEC electrolyte, glass frit, Kynar, and graphite. XRD pattern for as prepared KxV5S8 matched with a known KxV5S8 pattern in the International Center for Diffraction Data database (ICDD). KxV6S8 XRD pattern showed KxV5S8 phase peaks when matched with the ICDD database, indicating phase impurity. Potassium is not a big enough metal to make the AxV6S8 framework. The XRD patterns of RbxV5S8, RbxV6S8, and V5S8 matched with ICDD database patterns for each compound without showing any phase impurities. Cyclic voltammetry and chronopotentiometry data with a lithium anode and the lithium-ion electrolyte indicate that KxV5S8 and RbxV5S8 are not electrochemically active. V5S8 is electrochemically active. It shows significant oxidation and reduction peaks during cyclic voltammetry with a lithium anode. In the future, RbxV6S8 will be investigated for electrochemical activity. Intercalation reactions of magnesium ion will be investigated in the electrochemically active compounds of vanadium sulfide compounds for battery applications. Figure 1

Correction to: Optimization of Controllable Factors in the Aluminum Silicon Eutectic Paste and Rear Silicon Nitride Mono-Passivation Layer of PERC Solar Cells

Passivated emitter and rear contact (PERC) is a promising technology owing to high efficiency can be achieved with p-type wafer and their easily applicable to existing lines. In case of using p-type mono wafer, 0.5–1% efficiency increase is expected with PERC technologies compared to existing Al BSF solar cells, while for multi-wafer solar cells it is 0.5–0.8%. We addressed the optimization of PERC solar cells using the Al paste. The paste was prepared from the aluminum–silicon alloy with eutectic composition to avoid the formation of voids that degrade the open-circuit voltage. The glass frit of the paste was changed to improve adhesion. Scanning electron microscopy revealed voids and local back surface field between the aluminum electrode and silicon base. We confirmed the conditions on the SiNx passivation layer for achieving higher efficiency and better adhesion for long-term stability. The cell characteristics were compared across cells containing different pastes. PERC solar cells with the Al/Si eutectic paste exhibited the efficiency of 19.6%.

Effect of Ag-Te doped Glass Frits on Interface Reaction and the Electrical Properties of Silicon Solar Cells

Effect of Ag-Te doped Glass Frits on Interface Reaction and the Electrical Properties of Silicon Solar Cells

Effect of basicity of glass frits on electrical properties of Si solar cells

The purpose of this study is to understand the effects of the basicity parameter of glass frits added to the front contact of three-busbar Si solar cells on the removal of the anti-reflective coating (ARC) and the electrical characteristics of the cell. We investigated PbO-TeO2-SiO2 glass systems by adding oxides to improve the etching of the interface between the Ag electrode and the Si wafer. The thermal properties and viscous flows of the frits were characterized using differential thermal analysis and a hot-stage microscope. The microstructure of the glass layer at the interface of the Ag electrode and Si wafer was observed using scanning electron microscopy and transmission electron microscopy. The results showed that the electrical properties were dependent on the morphology of the interfacial structure. The addition of oxides to the glass system produced more recrystallites on the n+ emitter with a greater penetration depth in the Si wafer, thereby increasing the efficiency of the solar cell. The reactivity of the glass affected the removal of the ARC and the electrical properties of the Si solar cells were influenced by the charge transport facilitated by the Ag crystallites.

Interaction between lead‐free multicomponent alkali borosilicate glass frits and hematite in red overglaze enamels

AbstractJapanese traditional red overglaze enamel decorations on porcelain known as akae are produced using lead‐containing frits, leading to a problem of lead release. Although many lead‐free frits have been developed, a well‐colored akae has not yet been realized, mainly because of no information on the reaction between lead‐free frits and hematite during the heating process in akae production. To reveal the effect of such interaction between the frits and hematite in akae on the color tone, various akae test pieces were prepared and investigated. On using low‐melting‐point lead‐free alkali borosilicate glass system, which contain zinc oxide, the formation of zinc ferrite proceeds simultaneously with the dissolution and particle growth of hematite in the frit melt. The particle growth rate due to dissolution and precipitation in the frit melt is faster than that due to sintering of particles caused by heat treatment of hematite powder in dry process. The dissolving capacity and promoting effect of particle growth depended on frit compositions. We also showed that the composition of akae glass layer varies because of ions diffusing from the glaze layer. Compositional changes in the akae glass could strongly affect the reactivity between the frits and hematite, resulting in variation in the color tone, the crystal phases formed, and their segregated states.

Effect of the Flux on the Fire-Resistance Properties of Cerami-Fiable Epdm Rubber Composites

In this paper, two kinds of glass frit and zinc borate as fluxes were used to prepare ceramifiable EPDM rubber composites, and the mechanical test, SEM, XRD and TG-DSC were used to study the effects of fluxes on the thermal stability and pyrolysis performance of composite materials. The results showed that the addition of the three kind of fluxes helped the filler to form a large amount of liquid phase structure at high temperature, and then a good ceramic structure formed to improve the thermal stability of the composite material and the bending strength of the pyrolysis product. The XRD analysis showed that the main phases after pyrolysis of composite materials adding glass frit A were forsterite and quartz, and the main phases after pyrolysis of composite materials adding glass frit B or zinc borate were spinel and quartz.

Application of a glass fertilizer in sustainable tomato plant crops.

Glass frits with a P2 O5 /K2 O ratio equal to 0.65 and different concentrations of SiO2 (6.5-56.0 wt%), CaO (0-5.1 wt%) and Al2 O3 (0-14.6 wt%) have been prepared and analysed as potential glass fertilizers (GF). P2 O5 and K2 O were leached primarily within the first 5 days but the total amount was dependent on the SiO2 /Al2 O3 ratio of the glass frit. Sustained P2 O5 and K2 O leaching for more than 40 days could be obtained if the glass frit contained more than 7% Al2 O3 . A final glass frit composition (29% SiO2 , 5% CaO, 7% Al2 O3 , 30% P2 O5 , 25% K2 O) was selected and used in an experimental tomato crop of 1 ha area, where one half was fertilized with an NPK conventional fertilizer and the other half with the GF fertilizer. After harvesting the tomato crops, the GF fertilizer was found to result in a higher yield than the NPK conventional fertilizer: 59980 kg and 74 360 kg for NKP and GF, respectively. The general characteristics of the harvested tomato fruits and leaves were similar in the two cases and the differences fell within statistical error. No differences in any of the soil characteristics were detected as a result of the use of GF. © 2018 Society of Chemical Industry.

Fluxing Agents on Ceramification of Composites of MgO-Al2O3-SiO2/Boron Phenolic Resin

Fluxing agents of zinc borate, antimony oxide, galss frit A and glass frit B, with different melting or softening point temperatures, were added into MgO-Al2O3-SiO2/boron phenol formaldehyde resin (MAS/BPF) composites to lower the formation temperature of eutectic liquid phase and promote the ceramification of ceramifiable composites. The effects of fluxing agents on the thermogravimetric properties, phase evolution, and microstructure evolution of MAS / BPF composites were characterized by TG-DSC, XRD and SEM analyses. The results reveal that the addition of a fluxing agent highly reduces the decomposition rate of MAS / BPF composites. Fluxing agents lower the formation temperatures of liquid phases of ceramifiable MAS / BPF composites obviously, and then promote the ceramification and densification process. The final residues of composites are ceramic surrounded by large amount of glass phases.

Glass bonding with a reactive bonding layer fabricated by aerosol deposition

The bonding temperature was lowered by placing intermediate layers that are reactive with a glass bonding frit. A dense reactive intermediate layer, ~ 6 µm in thickness, was anchored on STS304 by aerosol deposition (AD). The intermediate layer with PbO reacted chemically with glass frit, lowering the glass temperature. Microstructure analysis showed that the intermediate layer disappeared during the bonding process due to a reaction with the glass frit. When a TiO2/PbO mixture was deposited as an intermediate layer, TiO2 did not react with the glass frit and remained under the same heating conditions. Unreactive TiO2 contributed physically to the improvement of the bonding strength by supplying a large bonding interface area and active PbO provided a large bonding interface through a chemical reaction with the glass frit.

Electrochemical promotion of carbon supported Pt, Rh and Pd catalysts for H2 oxidation in aqueous alkaline media

AbstractBACKGROUNDThe effect of electrochemical promotion of catalysis (EPOC) for the case of H2 oxidation reaction over commercial M (M=Pt, Rh, Pd)/Vulcan XC72 (ETEK) electrodes immersed in alkaline media was explored in this study. Various reactant mixtures (H2 and O2) fed simultaneously through a glass frit to the anodic electrode which was immersed in the electrolyte. Both positive and negative currents were applied between anode and cathode while all the reactants were followed by mass spectrometry.RESULTSIn the case of Pt electrode, it was found that application of small positive currents resulted in a reversible enhancement of both oxygen and hydrogen consumption rate, higher than the expected Faradaic one (I/2F). Pd and Rh electrodes exhibited lower catalytic activity at ambient temperature while positive current applications induced an acceleration of the catalytic reaction. Interestingly, modification of the catalytic activity of Pd and Rh electrodes was found to be irreversible even under negative current applications.CONCLUSIONCommercially available, carbon supported metal (Pt, Rh, Pd) catalysts, can be electrochemically promoted during hydrogen oxidation reaction in alkaline media. The rate enhancement could be explained by modification of the work function of the catalytic surface (thus the strength of the reactant's adsorption bond) during potential or current application as well as modification of the catalyst surface composition. © 2018 Society of Chemical Industry

Ceramifiable EVA/APP/SGF composites for improved ceramifiable properties

Ceramifiable ethylene-vinyl acetate (EVA) copolymer composites were prepared through incorporating silicate glass frits (SGF) and ammonium polyphosphate (APP) into the EVA. The ceramic residues were obtained by firing all samples at different temperatures. The effect of APP on the self-supporting property and shape stability of the composites were studied, and the effect of APP on the flexural strength and water absorption of the ceramic residues were investigated. The results show that the addition of APP improved the self-supporting property and the flexural strength of the composites due to the increased crystal phase. The shape stability and the porous structure of the residues increased due to water and NH3 released from the thermal decomposition of APP. XRD and SEM analysis demonstrated that APP promotes the precipitation of sodium phosphate and cristobalite. Furthermore, the growth process of the crystal was investigated by crystallization kinetic.

Plasma resistance of quartz with a glass coating layer by aerosol deposition

ABSTRACTTo improve the plasma resistance behaviour, glass frits of SiO2–Al2O3–Y2O3 with various powder sizes were coated onto quartz substrates by the aerosol deposition (AD) method. The thickness and microstructure of the coating layers were observed using a surface profiler and scanning electron microscopy. Plasma resistance was measured via the quartz substrate, after exposure to an inductively coupled plasma etcher. The coating layers were densely formed on the quartz substrates without additional heat treatment, and the layer thickness changed for the glass frit size distribution and AD process conditions. The SiO2–Al2O3–Y2O3 glass coating layer showed a higher plasma resistance than quartz. Furthermore, the AD coating layer was evenly etched after plasma exposure. This study improves the lifetime of plasma chamber components in the semiconductor industry.

Factors influencing the preparation of silver-coated glass frit with polyvinyl-pyrrolidone

In this work, a new electroless silver plating method for the synthesis of silver-coated glass frit composite powders with good morphology has been proposed and the polyvinyl-pyrrolidone (PVP) was used the activating agent. It was found that the weight ratio of PVP to glass frit affected the distribution and number of silver nanoparticles. Moreover, the loading capacity of the glass frit, the pH value and reaction temperature could influence the size of the silver nanoparticles and morphology of silver on the surface of glass frit. The as-prepared silver-coated glass frit was used to prepare a silver paste using an optimized process to form silver nanoparticles with uniform size and high density. The silver paste with silver-coated glass frit increased the photovoltaic conversion efficiency of silicon solar cells by 0.271% compared with the silver paste prepared with pure glass frit. The silver nanoparticles can promoted the precipitation of Ag crystallites on the silicon wafer. Therefore, the silver-coated glass frit can further optimize and enhance the electrical performance of solar cells.

Effects of particle size of aluminum powder in silver/aluminum paste on n-type solar cells

Silver paste, which mainly consists of silver metal, glass frit, and organics, has been used for contacting n + emitter of conventional p-type solar cells, whereas aluminum-added silver paste (silver/aluminum paste) has been used for p + emitter of n-type solar cells. It has been reported that the addition of aluminum powder to the silver paste decreases contact resistance between the paste electrodes and the p + emitter with increasing content of the aluminum powder in the paste, and in addition, that the silver/aluminum paste creates large and deep metallic spikes underneath the paste, which has been considered to decrease the contact resistance. However, how particle size of the aluminum powder affects the contact resistance and the electrical characteristics of the n-type solar cells has not been clear yet. In this study, the effects of the particle size of aluminum powder in the silver/aluminum paste on the contact resistance and the electrical characteristics are investigated. Our study demonstrates that the particle size of the aluminum powder strongly affects the contact resistance and the electrical characteristics. The contact resistance decreases not only with increasing the content of the aluminum powder in the silver/aluminum paste, but also with increasing the particle size of the powder. In addition, the optimization of the particle size of the aluminum powder can effectively increase FF of the n-type solar cells, resulting in increasing efficiency of the cells.

An Evaluation of Constituents in Paste for Silicon Solar Cells with Floating Contact Method: A Case Study of Tellurium Oxide Effects

Metallization contacts on emitter of silicon solar cells cause shunting of p-n junction and induce carrier recombination, resulting in a loss in open-circuit voltage Voc of the cells, which must severely limit cell efficiency. But, the mechanism of the shunting and the recombination has not been understood enough yet, especially on the contacts with conductive paste, because the shunting and the recombination caused by the paste come of multiple effects of each constituent in the paste such as silver metal, glass frit, and some additives. Thus, the effects of the each constituent in the paste should be clarified to elucidate the mechanism and to achieve an advanced paste for high-efficiency silicon solar cells. In our previous study, effects of aluminum in silver/aluminum paste and effects of glass frit itself on the shunting and the recombination in n-type solar cells were clearly shown by using “floating contact method”, and its effectiveness on the paste evaluation were demonstrated in the solar cells. In this study, the floating contact method was applied to conventional p-type solar cells with silver paste to clarify effects of tellurium oxide on the silver paste, because the detailed effects of the tellurium oxide on the shunting and the recombination have not been clear yet even though the oxide is widely used for commercial paste. Our study clearly shows that the tellurium oxide reduces the shunting and the recombination caused by the silver paste in the solar cells, and also demonstrates the effectiveness of the floating contact method on the paste evaluation.

Optical properties of phosphor-in-glass through modification of pore properties for LED packaging

The volume and size of the voids present between the frit and the phosphor particles used before sintering determine the pore properties of the resulting phosphor-in-glass (PIG). The pores formed from the voids influence the path of the incident light, thus changing the optical properties of the PIG. Therefore, the trends observed for the shrinkage and the green and sintered densities of the PIG were investigated using SiO2-B2O3-ZnO-K2O glass frit of four sizes to understand the tendency for the pore size, porosity, and optical properties of PIG. It has been demonstrated that variation in the pore properties according to the particle size influences parameters defining the light scattering phenomenon, such as the scattering angle of the light and the scattering coefficient, as well as the color rendering index, correlated color temperature, and package efficacy. The results obtained for the variation in the optical properties with the frit size can be used as a reference to select the appropriate glass frit size to achieve the required optical properties for a light-emitting diode (LED) package.

An experimental study on Sodalite and SAP matrices for immobilization of spent chloride salt waste

In the frame of Generation IV reactors a renewed interest in pyro-processing of spent nuclear fuel is underway. Molten chloride salt waste arising from the recovering of uranium and plutonium through pyro-processing is one of the problematic wastes for direct application of vitrification or ceramization. In this work, Sodalite and SAP have been evaluated and compared as potential matrices for confinement of spent chloride salt waste coming from pyro-processing. To this aim Sodalite and SAP were synthesized both in pure form and mixed with different glass matrices, i.e. commercially available glass frit and borosilicate glass. The confining matrices were loaded with mixed chloride salts to study their retention capacities with respect to the elements of interest. The matrices were characterized and leached for contact times up to 150 days at room temperature and at 90 °C. SEM analyses were also performed in order to compare the matrix surface before and after leaching. Leaching results are discussed and compared in terms of normalized releases with similar results reported in literature. According to this comparative study the SAP matrix with glass frit binder resulted in the best matrix among the ones studied, with respect to retention capacities for both matrix and spent fuel elements.

Electromagnetic interference shielding effectiveness of $$\hbox {MgO}{-}\hbox {Al}_{2}\hbox {O}_{3}{-}\hbox {SiO}_{2}$$ MgO - Al 2 O 3 - SiO 2 glass–ceramic system

\(\hbox {MgO}{-}\hbox {Al}_{2}\hbox {O}_{3}{-}\hbox {SiO}_{2}\) (MAS)-based glass–ceramic system was prepared using very-low-cost raw materials, i.e., talc, calcined alumina and calcined china clay with titanium dioxide as a nucleating agent. Glass–ceramics were prepared by a two-step process. In the first step, raw materials were mixed in the required proportion and melted at \(1450^{\circ }\hbox {C}\) followed by water quench into a glassy frit. In the second step, powdered glass frit was uniaxially dry pressed into pellets followed by sintering at \(1200^{\circ }\hbox {C}\) for 3 h. X-ray diffraction pattern of the sintered compact shows well-defined peaks of cordierite along with some anorthite and magnesium titanium oxide. The microstructure study of sample shows the presence of crystalline and glassy phases. Permittivity and permeability measurements were performed in the microwave frequency range 12.4–17 GHz. The permittivity value of 5.7–6.0 and the permeability value of \({\sim }1\) were obtained. The reflection and transmission measurements show that the material possesses a shielding effectiveness in the range 2–10 dB over the frequency range 12.4–17 GHz.