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•Crystalline ITO (2 2 2) after post-annealing at moderate temperature.•High optical transmittance (>90%) and low electrical resistivity (<10−4 Ω cm).•Surface roughness, RMS <1.0 nm ...and ITO grain size ∼13–18 nm.•Electrical resistivity is 6.68 × 10−4 Ω cm and mobility is 40.76 cm2/V s.
This paper reports on the enhancement of optical transmittance and electrical resistivity of indium tin oxide (ITO) transparent conductive oxides (TCO) deposited by radio frequency (RF) sputtering on Si substrate. Post-annealing was conducted on the samples at temperature ranges of 500–700 °C. From X-ray diffraction analysis (XRD), ITO (2 2 2) peak was observed after post-annealing indicating crystallization phase of the films. From UV–vis measurements, the ITO thin film shows highest transmittance of more than 90% at post-annealing temperature of 700 °C as compared to the as-deposited thin films. From atomic force microscope (AFM), the surface roughness becomes smoother after post-annealing as compared to the as-deposited. The lowest electrical resistivity for ITO sample is 6.68 × 10−4 Ω cm after post-annealed at 700 °C that are contributed by high carrier concentration and mobility. The improved structural and surface morphological characteristics helps in increasing the optical transmittance and reducing the electrical resistivity of the ITO thin films.
Over the last decade, lasers have been gradually employed for Si wafer dicing to replace blade dicing. Laser dicing has the potential to replace blade dicing as the future generation ultrathin wafer ...singulation method as it enables higher cutting speed, lower damage, and smaller kerf width but various technical challenges still remain to be resolved. In this article, laser ablation and dicing of Si wafers are reviewed in terms of the physics of laser-material interaction based on nanosecond, picosecond, and femtosecond pulse durations. The effects of various laser settings, dicing process parameters, and material factors on ablation rate, ablation precision and quality, and die fracture strength are discussed in detail. With the increasing usage of Cu stabilization layer on the backside of ultrathin Si wafers, we also review laser-material interaction in Cu and elaborate on recent findings on the effects of laser dicing through Si and Cu simultaneously on the microstructural and fracture strength properties of the die. Various approaches to improve the ablation rate, ablation quality, and die fracture strength are discussed.
•Laser dicing of thin Si wafers is gaining more importance in the semiconductor industry because of its cost-effectiveness compared to conventional blade dicing.•Understanding laser ablation mechanisms remains a huge challenge because of the complexity of the processes taking place, the variety of species involved, and the range of length and time scales covered.•Many challenges remain for laser dicing of Si wafers primarily in three critical areas, i.e., ablation rate, ablation precision and quality, and die fracture strength.•Optimization of the ablation rate, ablation quality, and die fracture strength will require thorough consideration of all the influencing laser and process parameters in order to meet the requirements of the end product applications.
Laser dicing of ultrathin dies is promising and is gaining importance because of its cost and quality advantages over mechanical and plasma dicing. However, the effects of laser dicing on the ...mechanical strength and microstructure of ultrathin Si dies need to be further understood, especially when dicing through Si wafers with backside Cu layer. A critical phenomenon effecting the Si die sidewall strength after nanosecond laser dicing of Si wafers with backside Cu is the formation and separation of a SiO
2
layer at the sidewall. The mechanisms behind the SiO
2
layer formation and separation were studied in this work. Si wafer samples without and with backside Cu layer were prepared by dicing with nanosecond laser using standard production parameters. The microstructure and phases formed were investigated by energy dispersive spectroscopy and nanobeam diffraction in a transmission electron microscope. In die samples without backside Cu, the sidewall consists of a thin surface layer of amorphous Si, followed by a polycrystalline Si layer, and finally an epitaxial Si layer. In die samples with backside Cu, the sidewall microstructure was observed to be vastly different. At the upper region of the sidewall, a surface layer of polycrystalline Cu was found, followed by a polycrystalline Cu
3
Si layer, a SiO
2
layer mixed with Cu
3
Si, and finally a thick SiO
2
layer. The Cu
3
Si catalyzes the growth of the SiO
2
through an oxidation step of the Cu
3
Si on the sidewall surface as well as at the SiO
2
/Si interface. In the lower region of the sidewall, the microstructure is similar to the upper region, but there is a separation of the SiO
2
layer from the crystalline Si. The SiO
2
undergoes a decomposition reaction at the SiO
2
/Si interface, releasing volatile SiO which causes microvoids to form and grow laterally at the interface. The growth and coalescence of the microvoids eventually lead to the separation of the SiO
2
layer from the crystalline Si, leaving behind a clean and rough crystalline Si surface with a peak-to-peak roughness of 100–200 nm. In the areas where the SiO
2
layer has separated from the Si die sidewall, the fracture strength of the sidewall is dependent on the material property and surface roughness of the crystalline Si, and not on the SiO
2
layer. In the sidewall region near the die frontside, the SiO
2
thickness is more than regions near the die backside, and no microvoiding and separation at the SiO
2
/Si interface were detected. This is hypothesized to be due to a higher O
2
pressure at the upper region of the narrow dicing trench which is open to the atmosphere compared to the lower regions where there could be O
2
deprivation and lower O
2
pressure.
Influence of annealing temperature on the properties of In
2
Ga
2
ZnO
7
(IGZO) thin film prepared using sol–gel method was extensively studied. Annealing treatment at four different temperatures ...(300, 500, 700 and 900 °C) has transformed the amorphous IGZO to polycrystalline IGZO. The increase in annealing temperature to 900 °C encouraged the formation of interfacial layer on the underlying Si substrate. As a result, a decrement in film current conductivity was perceived and the sample annealed at 900 °C was determined as the closest to having insulating properties. More characterization regarding the structural, morphological and optical characteristics of the annealed films was discussed in this study.
Ultrathin silicon wafer technology is reviewed in terms of the semiconductor applications, critical challenges, and wafer pre-assembly and assembly process technologies and their underlying ...mechanisms. Mechanical backgrinding has been the standard process for wafer thinning in the semiconductor industry owing to its low cost and productivity. As the thickness requirement of wafers is reduced to below 100 μm, many challenges are being faced due to wafer/die bow, mechanical strength, wafer handling, total thickness variation (TTV), dicing, and packaging assembly. Various ultrathin wafer processing and assembly technologies have been developed to address these challenges. These include wafer carrier systems to handle ultrathin wafers; backgrinding subsurface damage and surface roughness reduction, and post-grinding treatment to increase wafer/die strength; improved wafer carrier flatness and backgrinding auto-TTV control to improve TTV; wafer dicing technologies to reduce die sidewall damage to increase die strength; and assembly methods for die pick-up, die transfer, die attachment, and wire bonding. Where applicable, current process issues and limitations, and future work needed are highlighted.
Different post-deposition annealing temperatures were carried out in argon ambient to investigate the corresponding effects onto structural, morphological, optical, and electrical characteristics of ...RF magnetron sputtered gallium oxide (Ga2O3) films. Cubic phase of γ-Ga2O3 was transformed to mixed phases of cubic and monoclinic phases of β-Ga2O3 as the temperature was increased from 400 to 800 °C before became fully β-Ga2O3 phases at 1000 °C. Oxygen vacancies and oxygen interstitials were formed, generating deep energy levels in band gap of the Ga2O3 films. Findings revealed the acquisition of the highest current density in the Ga2O3 film annealed at 400 °C as a consequence of the highest density (J) of dislocation and oxygen vacancies in the film. Nonetheless, the formation of a thicker interfacial layer and location of oxygen vacancies in the film annealed at 1000 °C have caused minute increase in the J surpassing that of 800 °C at a gate voltage greater than 15 V.
The formation of nano-dendritic like structure and nano-spikes in AlInGaN films via ultraviolet-assisted photoelectrochemical (PEC) etching at different current densities (5, 20, and 40mA/cm2) could ...be potentially deployed as the hydrogen sensor. The ability of nano-dendritic like structure and nano-spikes to provide large surface area to volume ratio could improve hydrogen (H) adsorption in the AlInGaN films, and thereby offering a greater sensitivity as compared to the as-grown film. The film subjected to PEC etching at 40mA/cm2 has demonstrated the highest sensitivity (79.6%), followed by that subjected to PEC etching at 20 and 5mA/cm2. The acquisition of the highest sensitivity in the aforementioned film suggested that nano-spikes (40mA/cm2) surpassed nano-dendritic like structures (5 and 20mA/cm2) in term of providing larger surface area to volume ratio for H adsorption. Moreover, the largest total dislocation density present in the nano-spikes film could be the reason contributing to the increased gas sensitivity because the dislocation could serve as the trapping sites to mediate the diffusion of the adsorbed H, and thus facilitating the H detection. As a result, a fast response time (105s) and recovery time (46s) was obtained.
Structural, morphological, optical, and electrical characteristics of polycrystalline gallium oxide (Ga2O3) films subjected to different post-deposition annealing temperatures (400–1000 °C) in a ...stagnant oxygen stream ambient were systematically studied. The transformation from γ-Ga2O3 to β-Ga2O3 phase was perceived as the temperature was enhanced to/beyond 600 °C. An alleviation of oxygen related defects in Ga2O3 films was supported through a reduction in full-width half maximum (FWHM) for β-Ga2O3 peak oriented in (400) plane and dislocation density (δ), as well as an improvement in crystallinity when a higher temperature was employed. Nonetheless, the employment of the highest temperature has contributed to an excessive diffusion of oxygen anions to the interface contributing to the formation of a well-defined interfacial layer. Besides, the oxygen ions were also occupying the interstitial sites of Ga2O3 lattice at 1000 °C contributing to a sudden contraction of indirect band gap (Eg). These detrimental effects have suggested that 1000 °C was not a suitable annealing temperature for Ga2O3 films. Of these investigated films, Ga2O3 film annealed at 800 °C has demonstrated a better leakage current density characteristic than that of 400 and 600 °C due to acquisition of the lowest δ, the smallest FWHM, as well as the largest direct and indirect Eg.
Ultrathin silicon die is a key enabler for high performance semiconductor devices and ultrathin packaging. The quality of ultrathin wafers and dies has a significant influence on packaging assembly ...yield and device reliability. The key quality characteristics of ultrathin wafers and dies are bow/warpage, total thickness variation (TTV), subsurface damage (SSD), surface roughness, and mechanical strength. Wafer and die bow/warpage cause handling and processing problems in manufacturing processes, and induce defects during various packaging assembly processes that eventually lead to device reliability issues. The wafer TTV requirement is becoming more stringent for new generations of thin and 3-D packages. SSD, surface roughness, and dicing defects have adverse effects on die mechanical strength and reliability. Therefore, characterization methods are needed for these quality characteristics to control the manufacturing processes for ultrathin wafers and dies to ensure good device performance and reliability. The following ultrathin wafer and die characterization techniques are discussed in this paper: noncontact bow/warp/TTV measurement, materialographic analysis with optical and electron microscopy, high-resolution X-ray diffraction, micro-Raman spectroscopy, scanning infrared depolarization, optical profilometry, atomic force microscopy, and uniaxial/biaxial bending tests.
Effects of ultraviolet-assisted photo-electrochemical (PEC) etching current densities (J=20, 40, 80, and 160mA/cm2) towards structural, physical, and optical properties of aluminium indium gallium ...nitride (AlInGaN) semiconductors as well as corresponding schematized mechanism were studied and discussed. Formation of porous AlInGaN semiconductors at J lower than 80mA/cm2 has led to the acquisition of larger lattice parameters c and a, out-of-plane strain, in-plane strain, and hydrostatic strain as compared to the non-porous semiconductor, owing to the generation of more vacancy-type defects in the porous AlInGaN semiconductors. For the porous semiconductor formed at J greater than 80mA/cm2, the etching was affected by a limited mass transport of electrons and holes for anodic oxidation and cathodic reduction. According to the band gap (Eg) and Urbach energy (UE) determined from photoluminescence (PL) shift and UV–Vis absorption measurement, the vacancy-type defects were revealed as the radiative localized states that led to the enhancement in PL peak intensity. The acquisition of a lower density of dislocation-type defects in the porous semiconductors in contrast to the non-porous one on the other hand indicated that the dislocations were the non-radiative recombination centres, in which much of the density has been eliminated after PEC etching in the 1% potassium hydroxide electrolyte.
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