Effects of bonding temperature on the properties and reliabilities of anisotropic conductive films (ACFs) for flip chip on organic substrate application

The effects of bonding temperatures on the composite properties and reliability performances of anisotropic conductive films (ACFs) for flip chip on organic substrates assemblies were studied. As the bonding temperature decreased, the composite properties of ACF, such as water absorption, glass transition temperature (T_g), elastic modulus (E′) and coefficient of thermal expansion (α), were improved. These results were due to the difference in network structures of cured ACFs which were fully cured at different temperatures. From small angle X-ray scattering (SAXS) test result, ACFs cured at lower temperature, had denser network structures. The reliability performances of flip chip on organic substrate assemblies using ACFs were also investigated as a function of bonding temperatures. The results in thermal cycling test (−55 °C/+150 °C, 1000 cycles) and PCT (121 °C, 100% RH, 96 h) showed that the lower bonding temperature resulted in better reliability of the flip chip interconnects using ACFs. Therefore, the composite properties of cured ACF and reliability of flip chip on organic substrate assemblies using ACFs were strongly affected by the bonding temperature.     

Deformation mechanism and its effect on electrical conductivity of ACF flip chip package under thermal cycling condition: An experimental study

In this study, experimental works are performed to investigate the deformation mechanism and electrical reliability of the anisotropic conductive adhesive film (ACF) joint subjected to temperature cycling for flip chip on organic board (FCOB) assemblies. This paper presents some dominant deformation parameters governing the electrical degradation in an ACF joint between a chip and a substrate when flip chip assembly is heated and cooled. The deformation mechanism of ACF flip chip assemblies during the temperature cycling are investigated using in situ high sensitivity moiré interferometry. A four-point probe method is conducted to measure the real-time contact resistance of ACF joint subjected to the cyclic temperature variation. As the temperature increases below T_g of ACF, the bending displacement of assembly decreases linearly. At the temperature higher than T_g of ACF, there is no further change in bending behavior and in-plane deformations of a chip and a substrate become approximately free thermal expansion. It is because that soft-rubbery ACF at the temperature above T_g cannot provide the mechanical coupling between a chip and a substrate. The effect of bump location on the temperature dependent contact resistance is evident. A characteristic hysteresis in bending curves is observed and discussed. The contact resistance of the corner bumps increases with increasing temperature at a higher rate when compared to that of the middle. Failure analysis is performed to examine the ACF interconnections before and after thermal cycling test. The results indicate that during the thermal loading, the shear deformation is more detrimental to the electrical degradation of ACF joints than normal strain.     

Material properties of anisotropic conductive films (ACFs) and their flip chip assembly reliability in NAND flash memory applications

In this paper, the material properties of anisotropic conductive films (ACFs) and ACF flip chip assembly reliability for a NAND flash memory application were investigated. Measurements were taken on the curing behaviors, the coefficient of thermal expansion (CTE), the modulus, the glass transition temperature (T_g), and the die adhesion strength of six types of ACF. Furthermore, the bonding processes of the ACFs were optimized. After the ACF flip chip assemblies were fabricated with optimized bonding processes, reliability tests were then carried out. In the pressure cooker test, the ACF with the highest adhesion strength showed the best reliability and the ACF flip chip assembly revealed no delamination at the chip-ACF interface, even after 96 h. In the high temperature storage test and the thermal cycling test, the reliability of the ACF flip chip assembly strongly depends on the T_g value of the ACF. In the thermal cycling test, in particular, which gives ACF flip chip assemblies repetitive shear stress, high value of CTE above T_g accelerates the failure rate of the ACF flip chip assembly. From the reliability test results, ACFs with a high T_g and a low CTE are preferable for enhancing the thermal and thermo-mechanical reliability. In addition, a new double-sided chip package with a thickness of 570 μm was demonstrated for NAND flash memory application. In conclusion, this study verifies the ACF feasibility, and recommends the optimum ACF material properties, for NAND flash memory application.     

Power cycling issues and challenges of SiC-MOSFET power modules in high temperature conditions

Silicon carbide (SiC) MOSFETs power modules are very attractive devices and are already available in the market. Nevertheless, despite technological progress, reliability remains an issue and reliability tests must be conducted to introduce more widely these devices into power systems. Because of trapping/de-trapping phenomena at the SiC/SiO₂ interface that lead to the shift of threshold voltage, test protocols based on silicon components cannot be used as is, especially in high temperature conditions. Using high temperature SiC MOSFET power modules, we highlight the main experimental difficulties to perform power cycling tests. These reversible physical mechanisms preclude the use of temperature sensitive parameters (TSEP) for junction temperature measurements, so we set up fiber optic temperature sensors for this purpose. Moreover, these degradation phenomena lead to difficulties in both controlling the test conditions and seeking for reliable aging indicator parameters. Finally, a power cycling test protocol at high temperature conditions is proposed for such devices.     

Reliability modeling of Sn–Ag transient liquid phase die-bonds for high-power SiC devices

In this work, a novel foil-based transient liquid phase bonding process has been used to mount the SiC Schottky diodes. The Sn–Ag TLP interlayer material was produced in the form of preforms of multilayer foils, using electrochemical deposition. The foils were designed to keep the overall composition of Ag and Sn about 80% and 20% respectively. The optimized TLP bonding process parameters were used during the assembly process. The die-attachment characterizations revealed that resulting intermetallic compounds (Ag₃Sn and ζ) have melting point beyond 480 °C. The die-attachment produced low bending stresses, while heated from 30 °C to 400 °C. The reliability of Sn–Ag TLP bonded samples was studied during passive temperature cycling and during active power cycling. During power cycling, the crack rates were determined by measuring the crack lengths of the TLP bonded joints after failure. The failure criteria were set to be an increase of diode's forward voltage by 10% since the start of the power cycling tests. The thermo-mechanical simulations were performed to determine the damage parameter i.e. strain range amplitude ∆ ε_p. Based on mechanical characterization of the TLP bonded layers, a plastic material model was used. The crack propagation rates were modeled using Paris' Law. Based on comparisons with state-of-the-art silver sintering technique, it can be stated that the TLP bonding is a promising die-attachment technique and its power cycling reliability is similar to silver sintering.     

Evaluation of SiGe:C HBT intrinsic reliability using conventional and step stress methodologies

The reliability of SiGe:C HBT devices fabricated using the Freescale’s 0.35-μm RF-BICMOS process was evaluated using both conventional and step stress methodologies. This device technology was assessed to determine its capability for various power amplifier applications (e.g., WLAN, Bluetooth, and cellular phone), which are more demanding than conventional circuit designs. The step stress method was developed to allow a rapid evaluation of product reliability, as well as, a quick method to monitor product reliability. For all tests the collector current I_C and collector voltage V_C were kept constant throughout the test, and the current gain β (I_C/I_B) was continuously monitored. The nominal bias condition was V_C = 3.5-V and J_C = 50-kA/cm² (or 0.5-mA/μm²). The “failure criterion” for all reliability evaluations was −10% degradation in β from the initial value at the start of each stress test or interval. The median time to failure (MTTF) at a junction temperature (T_JCN) of 150 °C for the conventional stress test was 1.86E6-h, and the thermal activation energy was 1.33-eV. In contrast for the temperature step stress tests the combined results gave an MTTF at T_JCN = 150 °C of 5.2E6-h and a thermal activation energy of 1.44-eV. Considering the differences in the two test methods, these results are quite close to one another. The intrinsic reliability of this device at the nominal bias condition and T_JCN = 150 °C is more than adequate for a 5-year system life.     

High-Tc Realization of Lead-Free Halide Hybrid Ferroelectrics via Steric Confinement Modulation

Hybrid organic–inorganic perovskite (HOIP) ferroelectrics with high Curie temperature (T_c), typified by the lead halide hybrid perovskite ferroelectrics, are developing rapidly owing to their maneuverable ferroelectricity at high temperatures. However, acquiring high-T_c lead-free HOIP ferroelectrics via rational strategy still needs development. In this study, a brand-new program by modulating the steric confinement in a cuplike cavity to design high-T_c bismuth-halide ferroelectrics [H₂mdap]BiX₅ (H₂mdap = N-Methyl-1,3-Propanediamine, X = Cl ( 1 ), Br ( 2 ), I( 3 )) is proposed. Emphatically, the T_c enhanced dramatically from 264 K of 3 to 318 K of 2 and 377 K of 1 , induced by the substitution of Br and Cl to I, accompanied with an interesting transition from second-order phase transition (for 3 ) to the first-order one (for 1 and 2 ). The extent of T_c increase is up to 113 K, which far outweighs that of reported Pb-halide hybrid ferroelectrics. Structural and computational analyses elucidate that this unprecedented improvement of T_c is due to the higher phase transition energy barriers induced by modulating the steric confinement of cuplike cavity via halogen substitution. These results will provide new inspiration for designing high-T_c lead-free HOIP ferroelectrics.     

Structural and magnetic properties of silver doped melt-textured YBCO prepared in a solar furnace

Magnetic measurements and structural investigation have been performed on melt-textured YBCO and AgYBCO HTS. The “sun” technique produces very dense YBCO (ρ=5.86 g cm⁻³) and AgYBCO [ρ=6.36 g cm⁻³; 10% b/w (by weight) silver. This technique renders samples with a large volume fraction of the Y₂BaCuO₅ (211) phase. The material is characterized by very high J_c values, as compared with bulk polycrystalline YBCO prepared by other methods. This feature is attributed to the enhanced amount of 211 particles which serve as pinning centers. Additional significant densification of the structure due to silver incorporation is obtained, and a reduction of the size of 211 inclusions is also observed. Silver doped samples show “butterfly”-like hysteresis loops at relatively high temperatures (T≥60K). This feature is probably associated with oxygen deficiency which arises from the slower oxygen diffusion into silver doped samples. J_c values enhancement was obtained in silver doped “sun” samples at high temperatures (T≥60K) and fields of 20–30 kOe. The temperature dependence of effective activation energy of pinning, U_eff, was measured for YBCO and AgYBCO materials. U_eff is higher in silver doped samples in the high temperature region T≥60K.     

Fast power cycling protocols implemented in an automated test bench dedicated to IGBT module ageing

This paper presents fast test protocols for ageing IGBT modules in power cycling conditions, and a monitoring device that tracks the on-state voltage V_CE and junction temperature T_J of IGBTs during ageing test operations. This device is implemented in an ageing test bench described in previous papers, but which has since been modified to perform fast power cycling tests.The fast test protocols described here use the thermal variations imposed on IGBT modules by a test bench operating under Pulse Width Modulation conditions. This test bench reaches the maximal values of power cycling frequencies attainable with a given module packaging in order to optimize test duration.The measurement device monitors V_CE throughout the ageing test that is needed to detect possible degradations of wire bonds and/or emitter metallization. This requires identifying small V_CE variations (a few dozen mV). In addition, the thermal swing amplitude of power cycling must be adjusted to achieve a given ageing protocol. This requires measuring junction temperature evolution on a power cycle, which is carried out by means of V_CE measurement at a low current level (100 mA).Experimental results demonstrate the flexibility of this test bench with respect to various power cycling conditions, as well as the feasibility of the proposed on-line monitoring methods.     

Thermoelectric Properties of Tix(HfyZr1?y)1?xNiSn0.998Sb0.002 Half-Heusler Ribbons

Ribbons of Ti _x (Hf _y Zr_1−y )_1−x NiSn_1−z Sb _z (x = 0.1 to 1, y = 0.1 to 0.9, z = 0, 0.002, 0.004) were prepared by spin casting and annealed for 1 h at T _a = 1000 K, 1050 K, 1073 K, and 1100 K. The crystal phase of the ribbons was investigated by x-ray diffraction analysis and transmission electron microscopy. All the ribbons consisted of a phase with a half-Heusler structure. The Seebeck coefficient, electrical conductivity, thermal conductivity, power factor, and figure of merit ZT at room temperature were clarified experimentally as a function of x, y, z, and T _a. Despite the large thermal conductivity, the power factor and figure of merit were remarkably large at x = 0.5, y = 0.5, z = 0.002, and T _a = 1073 K, because the Seebeck coefficient and electrical conductivity were large.     

Evaluation of the impact of the physical dimensions and material of the semiconductor chip on the reliability of Sn3.5Ag solder interconnect in power electronic module: A finite element analysis perspective

This paper primarily focuses on an evaluation study for the temperature cycling capability of tin silver solder interconnect in power electronic applications by the impact of die dimensions and die material properties. The study was investigated on finite element analysis perspective on chip/solder/substrate structure. A commercially available chip was chosen in the finite element analysis (FEA) as the nominal base die. Two thermal cycle profiles were utilised. The effect of die area, die thickness and material properties (Si and SiC) on the thermal cycling capability of the solder layer was investigated from FEA perspective. From the FEA, it was concluded that decrease in die thickness resulting in increment of thermal cycling capability of solder layer for both material (Si and SiC). Increase in die area increases the thermal cycling capability of solder. For higher ΔT thermal cycle, solder under SiC die perform better than solder under Si die in terms of thermal cycling capability. When the die thickness become smaller than a threshold value of the thermal cycle regime, solder under Si die have better thermal cycling capability than solder under SiC die. Additionally a parametric study was undertaken for a SiC chip/substrate structure under high ∆ T temperature cycling profile for solder layer geometric parameter (wetting angle, titling angle and thickness). From the parametric study which utilised design of experiments (DoE), a wavelet radial basis surrogate model was generated. A sensitivity analysis was performed on surrogate model in order to identify the most influencing parameter. From the sensitivity analysis, it was concluded that wetting angle and solder layer thickness of solder layer have significant impact on the thermal cycling capability of the solder layer.     

Influence of molar mass ratio,annealing temperature and cathode buffer layer on power conversion efficiency of P3HT:PC71BM based organic bulk heterojunction solar cell

In bulk heterojunction (BHJ) solar cells, the molar mass ratio of donor-acceptor polymers, the annealing temperature (T_an) and the cathode buffer layer plays very consequential role in improving the power conversion efficiency (PCE) by tuning the film morphology and enhancing the charge carrier dynamics. A comprehensive understanding of each of these factors is essential in order to optimize the performance of organic solar cells (OSCs). Albeit there are several fundamental reports regarding these factors, an altogether meticulous correlation of these physical processes with experimental evidence of the photo active layer are required. In this work, we systematically analyzed the influence of different molar mass ratio, the annealing temperature (T_an) and the cathode buffer layer of rrP3HT:PC₇₁BM based BHJ solar cells and their corresponding photovoltaic performances were correlated carefully with their thin film growth structure and energy level diagram. The device having 1:0.8 molar mass ratio of rrP3HT:PC₇₁BM and T_an = 150 °C annealing temperature with Bathocuproine (BCP) as the cathode buffer layer having ITO/PEDOT:PSS/rrP3HT:PC₇₁BM (molar mass ratio = 1:0.8; (T_an = 150 °C)/BCP/Al) configuration showed the best device performance with PCE, ɳ = 4.79%, Jsc = 14.21 mA/cm², V_oc = 0.58 V and FF = 57.8%. This drastic variation in PCE of the device having BCP/Al as the cathode contact compared to the other device configurations is due to the coalesced effects of better hole-blocking capacity of BCP along with Al and better phase separation of the active blend layer at 150 °C annealing temperature. These results explicate the cumulate role of all these physical parameters and their combined contribution to the PCE amendment and overall device performance with rrP3HT:PC₇₁BM based organic BHJ solar cell.     

Distribution of hydrogen in silicon and silicon carbide following high-temperature proton irradiation

The distribution of hydrogen in Si and SiC following high-temperature proton irradiation (T _irr=20–700 °C) is studied by secondary-ion mass spectrometry. It is shown that the hydrogen concentration profile in SiC depends weakly on irradiation temperature. In Si appreciable alteration of the concentration profile is observed already at T _irr⋍300 °C, and the profile completely loses its concentration gradient at T _irr⋍700 °C. Fiz. Tekh. Poluprovodn. 33, 1409–1410 (December 1999)     

Thermoelectric Properties of <Emphasis Type="Italic">In Situ</Emphasis> Formed Bi<Subscript>0.85</Subscript>Sb<Subscript>0.15</Subscript>/Bi-Rich Particles Composite

A Bi-15 at.%Sb alloy, homogenized by equal channel angular extrusion (ECAE) at T = 523 K, has been treated just above its solidus temperature, causing segregation of a secondary Bi-rich phase at the grain boundaries. This process results in an in situ composite. The thermoelectric properties of the composite have been measured in the range of 5 K < T < 300 K. The results are compared with those of the homogeneous alloy. The presence of a Bi-rich phase improves the Seebeck coefficient at T < 50 K, and enhances the electrical conductivity by a factor of 1.4 at T = 300 K up to a factor of 3.4 at T = 50 K; unfortunately, the thermal conductivity also increases by about 50% in the same temperature range. As a result, the figure of merit, Z, is slightly suppressed above T = 110 K, but increases at lower temperatures, reaching a peak value of 4.2 × 10⁻³ K⁻¹ at T = 90 K. The power factor considerably increases over the whole temperature range, rendering this material suitable as the n-type leg of a cryogenic thermoelectric generator for cold energy recovery in a liquefied natural gas plant.     

Lifetime and manufacturability of integrated power electronics

In case of battery electric cars, market data show a traditional exponential gradient of sales figures, known from other technology transitions. The worldwide installed wind and photovoltaic capacity show also an exponential gradient. Even the power density of power electronics is growing exponentially.Power electronics is a prerequisite to enable the exponential growth of power density.Requirements on power electronic packaging technologies are electric performance, thermal performance and robust design. Due to the lack of bond wires, SMD capacitors can be mounted close to semiconductors, resulting in a minimization of parasitic inductance. Thermally, the packaging technology benefits from heat spreading inside the copper leadframe and thin dielectric layers. It obtains a thermal resistance of 0.5 K/W, and there is potential to further reduce the thermal resistance by alternative dielectric material. The thermal resistance can be further reduced to at least 0.42 K/W by the construction of a double side chip cooling.A robust design can be offered by the combination of a chip copper metallization connecting to copper microvias connecting to the top copper layer, which means no difference in coefficients of thermal expansion. On the bottom side, a silver sinter layer offers a reliable connection between chip and leadframe.This paper describes production process optimizations, thermal optimization possibilities, power cycling lifetime measurements and first conductive anodic filament lifetime measurements at 1000 V DC. The outlook onto an integrated 120 A 700 V SiC MOSFET demonstrator is given.     

Thermoelectric Behavior of Sb- and Al-Doped <Emphasis Type="Italic">n</Emphasis>-Type Mg<Subscript>2</Subscript>Si Device Under Large Temperature Differences

The thermoelectric (TE) characteristics of Sb- and Al-doped n-type Mg₂Si elemental devices fabricated using material produced from molten commercial doped polycrystalline Mg₂Si were examined. The TE devices were prepared using a plasma-activated sintering (PAS) technique. To complete the devices, Ni electrodes were fabricated on each end of them during the sintering process. To realize durable devices for large temperature differences, thermodynamically stable Sb-doped Mg₂Si (Sb-Mg₂Si) was exposed to the higher temperature and Al-doped Mg₂Si (Al-Mg₂Si) was exposed to the cooler temperature. The devices consisted of segments of Sb-Mg₂Si and Al-Mg₂Si with sizes in the following ratios: Sb-Mg₂Si:Al-Mg₂Si = 4:1, 1:1, and 1:4. A device specimen composed solely of Sb-Mg₂Si showed no notable deterioration even after aging for 1000 h, while some segmented specimens, such as those with Sb-Mg₂Si:Al-Mg₂Si = 1:1 and 1:4, suffered from a considerable drop in output current over the large ΔT range. The observed power generated by specimens with Sb-Mg₂Si:Al-Mg₂Si = 1:1 and 1:4 and sizes of 2 mm × 2 mm × 10 mm were 50.7 mW and 49.5 mW, respectively, with higher and lower temperatures of 873 K and 373 K, respectively. For the sample composed solely of Sb-Mg₂Si, a power of 55 mW was demonstrated. An aging test for up to 1000 h for the same ΔT range indicated drops in output power of between ∼3% and 20%.     

Synthesis and Characterization of New Ceramic Thermoelectrics Implemented in a Thermoelectric Oxide Module

Novel thermoelectric oxides were developed, produced, and characterized to demonstrate their promising thermoelectric conversion potential in a thermoelectric converter. Four-leg thermoelectric oxide modules were fabricated by combining p- and n-type oxide thermoelements made of pressed polycrystalline GdCo_0.95Ni_0.05O₃ and CaMn_0.98Nb_0.02O₃, respectively. In these modules, the p- and n-type thermoelements were connected electrically in series and thermally in parallel. The materials were joined by electrical contacts consisting of a Ag/CuO composite material. Fairly good thermal contacts were ensured by pressing the thermoelements between alumina substrates. Cross-sections of the alumina/Ag–CuO mixture/thermoelement interface were investigated by scanning electron microscopy. The temperature distribution across the module was monitored using K-type thermocouples and a micro-infrared (IR) camera. The open-circuit voltage and the load voltages of the module were measured up to a temperature difference of ΔT = 500 K while keeping the temperature of the cold side at 300 K. The output power and internal resistance were calculated. The characteristics of the module evaluated from electrical measurements were compared with respective values of the p- and n-type leg materials. An output power of 0.04 W at ΔT = 500 K led to a power density of ~0.125 W/cm³, where the volume of thermoelectric material was determined by a cross-section of 4 mm × 4 mm and a leg length of 5 mm.     

High-Operating-Temperature HgCdTe Avalanche Photodiodes

In this communication we report the first results of electro-optical characterization of planar heterostructure HgCdTe avalanche photodiodes (APDs), which enables the operation of APDs at high gain, at low bias, and with low dark current and/or at high operating temperature (HOT). The APD is based on a heterostructure in which the photons are detected in a wide-band-gap layer, and the photoelectrons are amplified in a vertical junction in a confined narrow-gap layer. The dark diffusion current and thermal background sensitivity of the device are limited by using a thin narrow-band-gap amplification layer. In addition, the defect-limited dark current is also expected to be reduced due to the reduced volume of the narrow-band-gap depletion layer. The electro-optical performance was characterized at T = 80 K and T = 200 K for two devices with a nominal thickness of the amplification layer of w = 100 nm and 500 nm, realized in x _Cd = 0.3 Hg-vacancy-doped layers grown by molecular-beam epitaxy (MBE). The measurements show an average gain of 〈M〈 = 10 at a reverse bias of 5 V, which is slightly reduced compared with a conventional APD with x _Cd = 0.3. The thermal diffusion current measured at low reverse bias, V _b = 0.1 V, and at T = 200 K is about 0.1 mA/cm² to 0.3 mA/cm², which is a factor of 50 lower than standard x _Cd = 0.3 n-on-p APDs. The quantum efficiency due to absorption in the gain layer is high (QE_peak > 30%), although no antireflecting coating was used, indicating that the device can also be used for high-operating-temperature thermal detection.     

Thermoelectric Properties of Ag-doped Mg<Subscript>2</Subscript>Ge Thin Films Prepared by Magnetron Sputtering

Silver doped p-type Mg₂Ge thin films were grown in situ at 773 K using magnetron co-sputtering from individual high-purity Mg and Ge targets. A sacrificial base layer of silver of various thicknesses from 4 nm to 20 nm was initially deposited onto the substrate to supply Ag atoms, which entered the growing Mg₂Ge films by thermal diffusion. The addition of silver during film growth led to increased grain size and surface microroughness. The carrier concentration increased from 1.9 × 10¹⁸ cm⁻³ for undoped films to 8.8 × 10¹⁸ cm⁻³ for the most heavily doped films, but it did not reach saturation. Measurements in the temperature range of T = 200–650 K showed a positive Seebeck coefficient for all the films, with maximum values at temperatures between 400 K and 500 K. The highest Seebeck coefficient of the undoped film was 400 μV K⁻¹, while it was 280 μV K⁻¹ for the most heavily doped film at ∼400 K. The electrical conductivity increased with silver doping by a factor of approximately 10. The temperature effects on power factors for the undoped and lightly doped films were very limited, while the effects for the heavily doped films were substantial. The power factor of the heavily doped films reached a non-optimum value of ∼10⁻⁵ W cm⁻¹ K⁻² at 700 K.     

Surface Texturing of Ga-Doped ZnO Thin Films by Pulsed Direct-Current Magnetron Sputtering for Photovoltaic Applications

In this study, Ga-doped ZnO (GZO) transparent conducting thin films were prepared by pulsed direct-current magnetron sputtering, providing good transparency and relatively low resistivity. The films were further etched in different aqueous solutions, 0.5% HCl, 5% oxalic acid, and 33% KOH, to modify their light-scattering properties. The results showed that film textured by 0.5% HCl_aq. for 30 s had total optical transparency of T _total = 77.4% and haze value of H _T = 0.16, with electrical resistivity of ρ = 4.9 × 10⁻⁴ Ω-cm. For film textured in 5% oxalic acid solution for 75 s, the lowest electrical resistivity of 4.3 × 10⁻⁴ Ω-cm was achieved with relatively high total optical transparency of T _total = 75.1%, as well as a more ideal haze value of H _T = 0.3. Film textured in 33% KOH solution for 135 s (500 nm thickness) had optimal electrical conductivity of 5.1 × 10⁻⁴ Ω-cm with T _total = 75.6%, and a relatively low haze value of H _T = 0.12. GZO film textured with an agitated etch of 5% oxalic acid at 300 K would be the most suitable candidate for photovoltaic applications due to its high transparency and good electrical conducting properties.