In this study, Cu wire-Al bond pad (Cusingle bondAl) samples were produced by means of Thermosonic wire bonding technique. Both IMC and ball shear strength were assessed for samples produced with different bonding temperatures, HTS duration and forming gas supply. The experiments were carried out using Taguchi and conventional “one parameter at a time” approaches. For Taguchi method, experiment was managed with L9 orthogonal array for optimizing the wire bonding process. It was observed that the process was optimized with forming gas supply ON, bonding temperature of 400 °C and after 1000 h of HTS treatment. This was achieved by a continuous and uniform growth of the IMC across the bonding interface. As for experiment based on “one parameter at a time” approach, a linear proportionality between IMC thickness and ball shear strength was observed. This indicated no void formation at the bonding interface of the sample. In addition, with increased number of run in this experiment, the regression analysis involving interaction of factors was allowed. The measurements' data was found to fit better in the additive model including the interaction of factors. Besides, an additional model based on the fundamental IMC growth behaviour with regards to the bonding temperature and HTS duration was proposed. Regression analysis of this model showed an agreement with measurement data.

Ball shear strength of the thermosonic wire bond interconnection relates closely to the reliability of the microchip during performance of its function in any application. Concerns regarding the reliability of Cu wired electronic microchips are raised due to formation of void at the copper (Cu) wirealuminium (Al) bond pad bonding interface, predominantly after high temperature storage (HTS) annealing conditions. The interfacial void formation is suspected originated from a volumetric shrinkage during the growth of the Cu-Al intermetallic compound (IMC) layer in the Cu–Al bonding interface. In this report, the ball shear strength and interfacial microstructure of the thermosonic Cu wire-Al bond pad system bonded at difference temperature (150 °C, 280 °C and 400 °C); and annealed at different HTS durations (as-synthesized, 500 hours and 1000 hours) were studied. It was observed no significant difference in the mean of the ball shear strength of bonds bonded at different temperature before HTS treatment. On the other hand, the ball shear strength increase with the HTS duration. This is due to the fact that higher bonding temperature and longer HTS promoted better growth of the Cu-Al IMC layer. A transmission electron microscopy - energy dispersive X-ray analysis (TEM-EDX) has also been carried out to observe the formation of the Cu-Al IMC layer in the sample.

Bond strength evaluation of wire bonding in microchips is the key study in any wire bonding mechanism. The quality of the wire bond interconnection relates very closely to the reliability of the microchip during performance of its function in any application. In many reports, concerns regarding the reliability of the microchip are raised due to formation of void at the wire-bond pad bonding interface, predominantly after high temperature storage (HTS) annealing conditions. In this report, the quality of wire bonds prepared at different conditions, specifically annealed at different HTS durations are determined by measurements of the strength of the interface between the bond wire and the bond pad. The samples are tested in pull test and bond shear test. It was observed that the higher bonding temperature as well as the longer duration of HTS increased the bond strength. This is represented through the analysis of the measurements of ball shear strength. This is due to the fact that higher bonding temperature and longer HTS promoted better growth of the Cu-Al IMC layer. A transmission electron microscopy - energy dispersive X-ray analysis (TEM-EDX) has been carried out to observe the formation of the Cu-Al IMC layer in the sample.

Quality requirement in the semiconductor industry is getting more stringent due to the application of semiconductor components that are widely used in automotive. Furthermore different materials combination is being introduced to semiconductor packages to improve their package performance and reduce cost. The new materials combination can increase the packages functionality adversely mismatch of different materials properties induced higher interconnection and package stress. With such scenario, quality of interconnects in the semiconductor products need more robust in order to withstand more severe condition and longer life. In this study the interfacial stress of Copper (Cu) Aluminium (Al) intermetallic compound (IMC) structure during high thermal stress condition is focused. Cu wire has been widely accepted as a main-stream interconnects to replace Au wire. Whereas Al bond pad is always the mostly used material for silicon semiconductor bond pad. According to Arrhenius equation, intermetallic growth is proportional to temperature. The Cu-Al IMC is complex due to the nanoscale and multiple phases exist. The Cu-Al IMC layer formed are normally in nanometer thickness, whereas Au-Al IMC is more thicker in micrometer. Analysis performed on Cu-Al IMC required more sophisticated and advanced tools. This is a big challenge for Cu-Al IMC studies. Thus the formation homogenous of Cu-Al IMC is more difficult to form compare to gold (Au) and Al IMC. Therefore using finite elements analysis (FEA) simulations of 3D models of various Cu-Al IMC compounds with different thickness is conducted to understand the stress and strain distribution at IMC layer. The numerical simulation is linear in nature and is based on linear isotropic material properties. Hence the equivalent stress is linear against increment of temperature. The modeling is using thermal-mechanical structure as the loading system. The effect of different IMC compound material properties is examined. From the numerical analysis once the IMC formed between Cu-Al interconnect the interfacial stress increased 22%. The stress reduced ~3% when IMC growth thicker. The equivalent stress saturated when IMC growth more than 50% of the total Al bond pad thickness. Comparing different Cu-Al IMC compound Cu9Al4 showed the most dominant impact towards the interfacial stress.

Copper metallization process, using electroplating, in Integrated Circuit interconnect, poses big challenge in semiconductor fabrication. Besides the stringent Dual Damascene requirement, the copper material itself is prone to rapid interface diffusion as well as surface oxidation. Thus the copper metallization process has to be performed within specific time after copper seed deposition process. This study investigated the impact of bilayer TaN/Ta barrier on copper sheet resistance changes at different time intervals. The study was based on 200mm wafer. In addition to that, correlation between sheet resistance to other copper film properties such as reflectance and stress was also investigated. Based on results of this study, bilayer TaN/Ta barrier inclusion in copper seed greatly improved film sheet resistance stability.

Pure and calcium-doped zinc oxide thick films were deposited on Aluminium substrate by screen printing technique using nanocrystalline powder synthesized from co-precipitation method. Shear thinning phenomenon with increment of shear rate was observed during the rheological analysis for all pastes. X-ray diffraction results confirmed the formation of ZnO with preferred orientation along (101) plane. Peak shifting to lower angle was observed upon increment of doping concentration of calcium. Crystallite size of doped ZnO powder decreased in the range (from 35.4 to 42.4 nm) from 116.1 nm of pure ZnO. Surface morphology analysed by FESEM had revealed the reduction of voids with increasing doping concentration up to 7 wt% of doping, followed by a slightly increase in the number of voids at 9 wt% doping. AFM analysis showed that the surface roughness of films exhibited a decreasing trend with the increase of calcium dopant until 7 wt% but became rougher at 9 wt%. Peaks shifting of ZnO to lower wavenumber revealed by FTIR study indicated that doping had affected the lattice structure of ZnO in the films. Thermal characterization showed the introduction of calcium dopant had increased the thermal resistance of the thick films. This led to a better junction temperature (Tj) of LED of 46.4 °C when compared with Tj of pure ZnO film at 47.3 °C.

The impact of various applied temperatures, pressures, and driving currents on the screenprinted dielectric thick film is discussed in this paper. The screen-printed dielectric thick film is treated as thermal interface material (TIM) that draws heat out from the heat source. The experimental setup has been modified based on the conventional ASTM 5470 standard where the thermal transient response of the dielectric layer is investigated. Bare and screen-printed substrates are heated up by MOSFET (heat source) at two different driving currents (0.5A and 1A). The dependency of either temperature (25°C to 55°C) or pressure (1 bar to 4 bar) measurement towards the thermal resistance of the dielectric thick film is measured by Thermal Transient Tester (T3ster). The total thermal resistance of both bare and screen-printed substrates are found to decrease with the increasing of pressure at constant temperature for all driven currents. This signifies that the thermal resistance of the dielectric layer is more dependenton pressure. In addition, the pressure applied to the dielectric layer serves to facilitate the longitudinal heat flow to the substrate. Variations in temperature has a less significant effect on the performance of dielectric layer compared to the variation in pressure.

Effects of screen-printed AgxZn1−xO thick film deposited on Al substrate with composition 3 wt% ≤ x ≤ 9 wt% on the rheological, surface, vibrational and thermal properties were investigated in this paper. AgxZn1−xO powder with different doping concentration was synthesized through co-precipitation method and further mixed with solvent to form a thixotropic paste. The paste was screen-printed on Al substrate. Rheological behavior of pastes showed shear thinning phenomenon with increment of shear rate. Structural properties of pure and doped thick films were investigated by X-ray diffraction (XRD). It showed that (101) was a strong preferred orientation among other peaks. Field emission scanning electron microscopy (FESEM) results indicated the aggregated flake-like structure that become more prominent with increase of doping from 3 to 7 wt%. Surface roughness of the films exhibited a decreasing trend with the increase of silver content whereas the step analysis facilitated to identify the contact surface point of the film for thermal conduction in application purposes. By increasing the dopant’s concentration, peak position of ZnO had shifted within the range from 503 to 506 cm−1. FTIR spectra of the films showed no vibrational peaks related to AgO or Ag2O. Thermal characterization revealed a decreasing trend of film’s resistivity when the doping was increased to 7 wt%. The lowest achieved junction temperature with tested LED was measured at 47.32 °C at 7 wt% of silver doping.