Copper–aluminum (Cu-Al) wire-bonded devices are widely used in microelectronic packaging; however, corrosion at exposed Cu-Al bimetallic interfaces can lead to Al pad degradation, undercutting, and eventual ball-bond lift-off or open-circuit failure under humid, halide-contaminated conditions. This work presents a scalable post-wire-bond wet-chemical passivation process using octadecylphosphonic acid (ODPA) to simultaneously modify exposed Cu/Pd-coated Cu (PCC) and Al surfaces. The passivation process includes a hydroxylation pretreatment to generate reactive oxide/hydroxide surface sites, followed by ODPA treatment and solvent rinsing to remove weakly adsorbed species. Surface modification was evaluated using contact-angle measurements, reflection–absorption infrared spectroscopy (RAIRS), atomic force microscopy (AFM), and X-ray photoelectron spectroscopy (XPS). ODPA treatment increased the water contact angle on Cu and Al, confirming a substantial increase in surface hydrophobicity following coating formation. RAIRS identified ODPA-associated aliphatic C-H bands, AFM showed treatment-induced nanoscale surface changes, and XPS supported metal–oxygen–phosphorus interfacial bonding. Under aggressive 100 ppm chloride-ion immersion, ODPA passivation strongly suppressed corrosion-induced ball-bond lift-off across both device platforms. Lift-off decreased from 99.0% to 0.73% for Cu-Al devices and from 23.3% to 0.42% for PCC-Al devices. Collectively, these findings establish an effective, process-compatible post-wire-bond strategy for substantially protecting corrosion-susceptible interfaces and thereby improving the reliability of wire-bonded interconnects in halide-containing environments.

The continuous scaling of semiconductor devices, driven by Moore’s Law, demands advancements in interconnect technologies. Cu-to-Cu direct bonding has emerged as a critical solution for enabling ultra-fine pitch, high-density interconnections with superior electrical and thermal performance compared to traditional Cu-to-solder joints. This bonding method is pivotal for applications such as 3D integration, FOWLP, and 2.5D/3D packaging, supporting miniaturization, high-speed data transfer, and improved thermal management. However, Cu oxidation during processing presents a significant barrier, degrading bond integrity, increasing interfacial resistance, and complicating backend-of-line (BEOL) packaging integration. To address these challenges, we developed an ultra-thin (2–5 nm) Cu-selective oxide-suppression coating using standard industry-compatible techniques, including chemical vapor deposition (CVD) and liquid-phase deposition (LPD). The coating effectively prevents Cu oxidation during high-temperature thermal compression bonding (TCB) without requiring high-vacuum equipment or costly metal coatings, enabling scalability for heterogeneous packaging. RAIRS-QCM metrology validated the coating’s chemical stability and persistent oxidation resistance even after two months of ambient storage. Oxidation suppression efficiency of ~53% was confirmed by RAIRS characterization following an annealing at ~300°C in ambient air for 1 hour. Bonding evaluations were performed on 5 nm passivated Cu substrates under optimized bonding conditions. Shear testing revealed an average force of 40.7 ± 4.2 kgf/cm 2 , exceeding MIL-STD-883 requirements. Cross-sectional STEM confirmed a defect-free Cu-Cu bonded interface, while STEM-EDX analysis verified that the coating effectively suppressed oxidation without impeding Cu-to-Cu bonding. This work establishes the developed coating as a scalable, high-throughput solution to enhance Cu-to-Cu bonding reliability, enabling next-generation semiconductor packaging with improved electrical, mechanical, and thermal performance.

Despite advances in 2.5D and 3D packaging, ultrasonic wedge (stitch) bonding remains the industry standard due to its cost-effectiveness. However, the transition to copper (Cu) and palladium-coated copper (PCC) wire introduces reliability challenges, traditionally mitigated by expensive and environmentally concerning silver (Ag) plating on leadframes (LF). To address this, we developed a low-cost, ultrathin Cu-selective passivation coating that suppresses oxidation, enabling direct Cu-Cu bonding without Ag. This process-compatible coating was evaluated on Cu-LFs using 25 µm Al-1 wt% Si and PCC wires under varying thermal conditions (125 °C-200 °C). Optimization of bonding force, time, and ultrasonic power yielded substantial improvements in pull strength. Notably, while bare-Cu bonds failed at the oxidized interface, passivated samples failed at the wire neck, confirming superior bond integrity. This work highlights a promising, environmentally sustainable alternative to Ag plating, enabling reliable Cu-Cu stitch bonding for next-generation, low-cost IC packaging solutions.

Two-dimensional molybdenum ditelluride (2D MoTe2) is an interesting material for artificial synapses due to its unique electronic properties and phase tunability in different polymorphs 2H/1T'. However, the growth of stable and large-scale 2D MoTe2 on a CMOS-compatible Si/SiO2 substrate remains challenging because of the high growth temperature and impurity-involved transfer process. We developed a large-scale MoTe2 film on a Si/SiO2 wafer by simple sputtering followed by lithium-ion intercalation and applied it to artificial synaptic devices. The Al2O3 passivation layer allows us to develop a stable 1T'-MoTe2 phase by preventing Te segregation caused by the weak bonding between Mo and Te atoms during lithiation. The lithiated MoTe2 film exhibits excellent synaptic behavior such as long-term potentiation/depression, a high Ion/Ioff ratio (≈103) at lower sweep voltage, and long-term retention. The in situ Raman analysis along with a systematic microstructural analysis reveals that the intercalated Li ion can provide an efficient pathway for conducting filament formation.

Despite advances in 2.5D and 3D packaging, wire bonding remains the industry’s most widely used interconnect method due to its cost-effectiveness. Ultrasonic wedge bonding, also known as stitch bonding, is a critical interconnection technique that links IC dies to external circuits for power and signal transmission, where precise control of bonding parameters is essential to ensure reliable connectivity. However, as the industry transitions from traditional gold (Au) wire to cost-effective copper (Cu) and palladium-coated copper (PCC) wire, new challenges have emerged in ensuring second bond (stitch) reliability, particularly on modern leadframe substrates with silver (Ag) coatings. While Ag plating helps suppress Cu oxidation, it adds to material cost and raises environmental concerns due to its bioaccumulation potential. To address this, we developed a low-cost, ultrathin Cu-selective passivation coating that effectively suppresses Cu oxidation and enables direct Cu-Cu stitch bonding without the need for Ag. This passivation layer is fully compatible with standard IC packaging processes and does not interfere with surrounding dielectrics or interconnects. This paper discusses the application of this ultrathin coating on copper-based leadframe (LF) and is subjected to stitch bonding with 25 μm (1 mil) aluminum (Al-1wt%Si) and palladium-coated copper wire (PCC) under different heating conditions (170°C-200°C). The bonding power, time, and force are kept constant throughout the work. Coated Cu leadframes demonstrated a substantial improvement in pull strength and reliability. Notably, bonds on bare-Cu LF failed at the interface due to oxidation, while passivated-Cu LF exhibited failure at the wire neck, indicating stronger bond integrity. Preliminary data with PCC wire at 125°C further support these findings. This work highlights a promising, environmentally sustainable alternative to Ag plating, enabling reliable Cu-Cu stitch bonding for next-generation, low-cost IC packaging solutions.

The exponential growth in computational demands driven by AI, Machine Learning, and data-heavy applications has accelerated the transition toward 3D integration in microelectronics, now considered a successor to Moore’s Law. Achieving high-performance communication, particularly between GPUs and HBM, demands robust, ultra-dense interconnects. Cu-solder microbumps and Cu-to-Cu direct bonding offer compact form factors, high-speed signaling, and thermal efficiency. However, Cu’s high chemical reactivity presents a major challenge. Oxidation in both ambient and high-temperature environments forms CuO and Cu2O, which impede solder wetting and interatomic diffusion, thereby degrading interconnect performance. In this study, we introduced a 2-5 nm Cu-selective passivation coating, deposited via industry-compatible methods, which suppresses oxidation by up to ~57% at 300°C while maintaining stability for over a month in air. The resulting fluxless Cu-solder bonding produced uniform, void-free Cu-Sn IMCs with a shear strength of 5.16 MPa and minimal resistance change after 1000 hrs of high-temperature storage. Cu-to-Cu direct bonding performed at 300°C achieved shear strengths of 40.7 ± 4.2 kgf, exceeding MIL-STD requirements, with SEM/EDS confirming robust, oxide-free interfaces. This scalable, fluxless approach offers robust and reliable fine-pitch Cu bonding, enabling next-generation AI and high-performance 3D integration platforms.

To ensure the highest safety standards in modern automobiles, the industry is constantly adopting zero-defect frameworks, such as AEC-Q100, which aims for defective-parts-per-billion (DPPB) or grade-0 level reliability standards in automotive integrated-circuit (IC) packages. Most contemporary wire-bonded packages use either pure copper (Cu) or palladium (Pd)-coated copper (PCC) wires bonded to aluminum (Al) bond pads as interconnections. This choice is made due to their lower cost and superior electrical and mechanical performance, compared to traditional gold wire-based devices. However, these Cu–Al wire-bonded interconnections are prone to ion-induced lift-off/open-circuit corrosion failures when exposed to even trace amounts (<20 ppm) of extrinsic and/or intrinsic halide (Cl− and Br−) contaminants, decreasing device longevity. This study investigates corrosion failure mechanisms in Cu and PCC wire-based devices by subjecting non-encapsulated devices to a highly accelerated aqueous-immersion screening test containing 100 ppm chloride (Cl−), 100 ppm bromide (Br−), and a mixed-ion solution (MX: Cl− + Br−). The screening results indicate that even control PCC-Al devices with a Pd overlayer can be susceptible to Cl− and Br− induced corrosion, with 21 ± 1.6% lift-off failures in MX-solution. In contrast, applying a novel Cu-selective passivation reduced lift-off to 3.3 ± 0.6% and introducing phosphonic-acid-based inhibitor into the MX solution eliminated lift-off failures, demonstrating markedly improved reliability.

The continuous scaling of semiconductor devices, driven by Moore’s Law, demands advancements in interconnect technologies. Cu-to-Cu direct bonding has emerged as a critical solution for enabling ultra-fine pitch, high-density interconnections with superior electrical and thermal performance compared to traditional Cu-to-solder joints. This bonding method is pivotal for applications such as 3D integration, FOWLP, and 2.5D/3D packaging, supporting miniaturization, high-speed data transfer, and improved thermal management. However, Cu oxidation during processing presents a major barrier, degrading bond integrity, increasing interfacial resistance, and complicating backend-of-line (BEOL) packaging integration. To address these challenges, we developed an ultra-thin (2–5 nm) Cu-selective oxide suppression coating using standard industry-compatible techniques such as chemical vapor deposition (CVD) and liquid-phase deposition (LPD). The coating effectively prevents Cu oxidation during high-temperature thermal compression bonding (TCB) without requiring high-vacuum equipment or costly metal coatings, enabling scalability for heterogeneous packaging. RAIRS-QCM metrology validated the coating’s chemical stability and persistent oxidation resistance even after two months of ambient storage. RAIRS analysis confirmed ~52% oxidation suppression after 1-hour annealing at 300°C in air. Bonding tests on 5 nm passivated Cu at 300°C, 40 MPa for 1 hour showed strong Cu–Cu bonds with a shear strength of 40.7 ± 4.2 KgF, exceeding MIL-standard. STEM-EDX confirmed a defect-free interface and effective oxidation suppression without hindering bonding. This work establishes the developed coating has strong potential as a scalable, high-throughput solution to enhance Cu-to-Cu bonding reliability, enabling next-generation semiconductor packaging with improved electrical, mechanical, and thermal performance.

Copper (Cu) wire bonding, with its advantages of higher electrical conductivity and better mechanical strength, has replaced gold wire bonding as a proven, cost-effective electrical interconnection solution for integrated circuit packaging for the past 15 y. Early Cu wire-bonding development required overcoming several technical challenges, including bond pad damage caused by copper’s hardness and brittleness relative to gold. A more chemistry-related challenge of using Cu as a bonding wire is its well-known reactivity with oxygen. An inert atmospheric envelope of forming gas surrounding bonding capillary was developed to prevent the oxidation of Cu wire during electronic flame off to enable a strong bonding. Another more elusive materialschemistry- related reliability challenge, with a typical low ppm occurrence, has been the chloride-induced corrosion defects between the Cu wire and Al bond pad. The opportunistic lowlevel chloride contaminations can originate from various points of the packaging manufacturing process flow, often rendering it untrackable. In this paper, we present recent efforts to systematically control interfacial materials chemistry across Cu-bonding wire, Cu-Al bimetallic contacts, and CuxAly intermetallic compounds to eliminate corrosion defects and improve the overall bonding reliability. The prevailing manufacturing solution is to utilize Pd-coated Cu-bonding wire that can only partially mitigate the CuxAly intermetallic corrosion vulnerability. We utilized a real-time corrosion screening metrology to explore the underlying interfacial materials chemistry that drives vigorous corrosion between Cu wire and Al bond pad when exposed to a trace level of chloride contaminant. Combined with scanning electron microscope, sensitive IR spectroscopy, and electrochemical characterization, our data show that strategic surface modification on both Cu-bonding wire and exposed CuxAly intermetallic can have a significant impact on reducing corrosion defect rates. The obtained mechanistic insights provide several new strategies enabled by a novel Cu-selective passivation coating technology to effectively mitigate Cu wire-bonding corrosion defects. Implications for improving overall Cu wire-bonding reliability will be presented based on these new approaches with low-cost and packagingfriendly advantages.

Copper (Cu) is widely considered as the material of choice for most interconnects in IC packaging due to its cost-effectiveness and superior electrical and thermal properties, making it integral to high-performance and energy-efficient electronic devices. However, Cu's susceptibility to corrosion and oxidation significantly challenges its reliability in various applications. This study focuses on utilizing an innovative Cu-selective passivation coating designed to enhance the reliability of Cu-Al wire bonding and promote flux-less Cu-to-solder wafer-level bonding applications. Our results showed the passivation coating effectively inhibits halide-induced corrosion by passivating exposed Cu regions on palladium-coated Cu (PCC) wires, and the ultra-thin(<10nm) passivation coating significantly reduced Cu oxidation and showed successful thermocompression bonding (TCB) without flux in ambient conditions. This critical advancement in addressing the reliability challenges in Cu interconnects offers a cost-effective solution, paving the way for more robust and reliable ICs in microelectronics packaging.

In response to the critical demand for enhanced reliability in semiconductor device packaging, under the rigorous safety standards of the automotive industry, the need to investigate the corrosion mechanisms of various ions present in epoxy molding compounds (EMCs) becomes essential. This paper highlights the challenges posed by halide-rich environments, particularly under chloride, bromide, fluoride, and, in addition, sulfate and sulfide ions, which may lead to corrosion and wirebond liftoff in copper-aluminum (Cu-Al) bonded devices. Using the immersion corrosion screening and SEM-EDX analysis, the effect of each ion is investigated individually, and the investigation unravels distinct corrosion insights with the chloride, bromide, and fluoride ions. Furthermore, our study reveals that applying passivation coatings significantly reduces the corrosion rate and wire-bond liftoff. The study also shows that sulfide ions can create a protective copper sulfide film, slowing down chloride-induced corrosion. Additionally, this paper explores direct copper-to- copper (Cu-Cu) bonding as an effective alternative to counteract ion-induced corrosion; this exhibits superior reliability by resisting corrosion and liftoff even in severe mixed ion environments. These results highlight the critical role of passivation strategies in improving the reliability of wire-bonded devices in harsh conditions.

Semiconductor device packaging reliability specifications are tightening toward a low ppb to zero defect rate standard due to the increasingly stringent automotive safety requirements. When exposed to chloride ions contamination, the typical copper (Cu) to aluminum (Al) wire-bonding connection could be a potential source of corrosion-related reliability concerns in wire-bonded devices. This article studies the effect of replacing the Al bond pad with Cu on the corrosion-induced lift-off of wire bonds when exposed to low ppm levels of chloride contamination. Real-time immersion corrosion screening was carried out on a wire-bonded device for accelerated time-dependent observation of corrosion progression in 100-ppm chloride solution. The newly developed Cu–Cu wire-bonded devices, enabled by selective passivation to prevent Cu oxidation, dramatically outperformed Cu–Al wire-bonded devices in complete immersion in chloride solution. A chemically discerning reflection–absorption infrared spectroscopy (RAIRS) metrology was used to measure the oxidation suppression provided by a mere few nanometers of passivation coating.

Copper (Cu) is the metal of choice for the redistribution layer (RDL) to facilitate fast I/O communication in an integrated circuit (IC). Cu can electrochemically migrate (ECM) between the array of electrodes under bias, electrolyte, and moisture. IC packages fail miserably when exposed to various ion impurities and moisture. Copper at the anode dissolves to form Cu+1, +2 ions. As the anodic dissolution continues, the concentration of copper ion increases. These anions deposit on cathode leading to Cu dendrite formation. To achieve the near zero ppb defectivity goal, elimination of (ECM) defects in packaged devices is critical. This work discusses development of a novel Cu-selective passivation and a method to accelerate reliability testing. A hydrophobic passivation with minimum stress to the IC package is proposed in this work. The new passivation coating is thermally stable, strongly adheres to Cu, corrosion resistant, low cost and shows good potential to prevent ECM defects. The coated packaged devices were tested by an accelerated PEG drop test (PDT) to explore its ECM prevention capabilities.

Abstract In most current wire-bonding applications, electrical interconnection is accomplished by fine Cu wires bonded to Al bonding pads microfabricated on an IC chip and external contact pins of the PCB board. Corrosion-related failure defects between the Cu wire and Al bond pad have been an ongoing un-trackable reliability issue plaguing the IC packaging industry for the past ten years, despite approaching ppb levels. Most prior studies hypothesized that intermetallic compounds (IMCs) like Cu9Al4, and CuAl2 were responsible for the observed acute wire-bond lift-off corrosion defects. Further studies sought to quantify the rates of corrosion of these IMCs and explore the effects of mitigation efforts of adding Pd, relevant to Pd-coated Cu wire-bonding. However, utilizing a novel real-time corrosion screening approach, we previously established that peripheral bimetallic contact between Cu ball-bonds and Al bond pads also plays a substantial role in the aggressive Al pad corrosion, induced by chloride ion penetration, which often leads to device failure. In this work, we further explored the role of IMCs corrosion in wire-bond lift-off failure utilizing fundamental electrochemical studies to quantify rates of galvanic-induced corrosion of IMCs within the broader context of an interconnected stack of Al bond pad, Cu-Al IMCs and Cu bonding wire. We also explored the use of a corrosion inhibitor to suppress the galvanic corrosion currents of Al bond pad, and Al-rich IMCs when electrically connected to Cu wire or Cu-rich IMCs.

The introduction of copper as wire bonding material brings about a new challenge of aluminum bond pad bimetallic corrosion at the copper/aluminum galvanic interface. Aluminum is well known to undergo pitting corrosion under halide-contaminated environments, even in slightly acidic conditions. This paper aims to study the corrosion morphology and progression of aluminum influenced by different halide contaminations in the presence and absence of galvanic contact with copper. We used a new corrosion characterization platform of the micropattern corrosion screening to simulate the copper wire bonding on the aluminum bond pad. The corrosion screening data and subsequent SEM–EDX analyses showed a striking difference in morphology and progression between chloride-induced and fluoride-induced aluminum corrosion. The corrosion products formed play a vital role in the resulting morphology and in sustaining further aluminum corrosion.

Accelerated reliability testing of integrated circuit (IC) packages, such as wire-bonded devices, is a useful tool for predicting the lifetime corrosion behavior of real-world devices. Standard tests, such as highly accelerated stress test, involves subjecting an encapsulated device to high levels of humidity and high temperature (commonly 85-121 ⁰C and 85-100% relative humidity). A major drawback of current reliability tests is that mechanistic information of what occurs between t = 0 and device failure is not captured. A novel method of in-situ investigation of the device corrosion process was developed to capture the real time mechanistic information not obtained in standard reliability testing [1]. The simple, yet effective methodology involves:•Immersing a micropattern or device directly into contaminant-spiked aqueous solution, and observing its morphological changes under optical microscope paired with a camera.•Short (2-48 h) time required for testing (compared to 24-300 h of standard tests).•No need for humidity chambers.

Microelectronic reliability requirements are tightening to a standard of near zero ppb defects due to the evolution of self-driving cars and wearable electronics. The successful transition from gold (Au) to copper (Cu) in wire-bonding introduces corrosion related reliability concerns to wire-bonded devices in integrated circuit (IC) packaging. This report studies the effect of bimetallic contact, Cu wire vs. aluminum (Al) bond pad, on the corrosion failure of Al bond pads when exposed to low ppm levels of chloride (Cl-) contamination. Real time corrosion screening was carried out on simulating Cu/Al micro patterns for time-dependent observation of corrosion progression in 5-20 ppm Cl- solutions at pH 5. Al in Cu/Al bimetallic couple corroded at accelerated rate compared to Al without bimetallic contact. Cathodic hydrogen evolution was found to be the key factor driving this aggressive Al bond pad corrosion under the influence of the peripheral Cu/Al bimetallic contact in acidic chloride solution. Chemically modifying the surface of Cu wires to prevent this H-2 evolution reaction resulted in the inhibition of Al bond pad corrosion.

Microelectronics are used in virtually all electronic equipment’s nowadays ranging from medical instruments, automobiles, computers, cell phones and home appliances. Wirebonding process which connects the chip to the lead frame in IC packaging plays a very important role in the commercial production of IC’s. Chip usually consists of Al bond pads with Cu/Au wires. Thin film Al bond pads are easily vulnerable to corrosion in presence of contaminants and moisture. Bond pad corrosion is one of the common modes of corrosion failure in wire-bonded devices IC packaging. Improper rinsing, packaging and passivation defects allows moisture and contaminants into bondpads resulting in severe corrosion. Most common source of this corrosion comes from the presence of halide ions contamination as (Cl-, F-, Br- etc.) However, the corrosion morphology and the severity varies from different ions contamination as the chemistry governing the corrosion differs from one ion to another. Our research is focused on key findings on corrosion of Aluminum bond pad due to chloride (Cl-) and fluoride (F-) contamination. Our central motivation is to identify this F- corrosion mechanism, so that it will help to develop a strategy to prevent it and study the comparison between Cl- and F- Corrosion using Micro-pattern corrosion screening technique, Wire-bonded device (WBD) and other characterization technique such as GC-MS, SEM and tafel. GC-MS reveals that H2 gas evolution is observed during Cl- corrosion of the WBD, whereas little or no H2 evolution is observed during F- corrosion. SEM and EDX reveals no presence of Cl- in the corroded areas of its corrosion, whereas strong F- signal is observed in F- corrosion of the bondpads revealing, that the corrosion products formed on the surface has very poor solubility showing that Cl- and F- has a complete different corrosion morphology. Striking contrasts in corrosion morphology observed during the Cl- and F- corrosion were explained in the present work and will lead to better understanding of factors influencing the bond pad corrosion leading to the wire bond failure in IC packaging devices. [Fig. 1] Figure 1

The explosion of microelectronics use in automobiles has made the microelectronic corrosion control more critical over the past decade. Wire bonded devices form an integral part of the microelectronic systems used in automobiles. With the reliability requirements of automobile microelectronics pushing towards ppb levels of failure, halide induced corrosion issues have to be controlled to achieve such high reliability goals. The corrosion of Aluminum bond pads in slightly acidic chloride solutions (ppm level) has been one of the main modes of wire-bonding failure in wire bonded devices. Earlier researches pointed out the possibility of intermetallic compound formation as the main reason for this corrosion. However, our investigation of the electrochemical nature of the corrosion led to the discovery that bimetallic contact of the aluminum bond pads with copper wires is the main reason for this type of corrosion. Copper and Aluminum being apart in the galvanic series can act as a galvanic corrosion cell under suitable conditions. Furthermore, the presence of halides causes de-passivation of Aluminum oxide layer making the Aluminum bond pad more susceptible to corrosion. In this report we introduce corrosion screening as a mimicking platform for studying wire-bond device corrosion. For the first time we reported that Hydrogen evolution is the cathodic reaction and is responsible for the explosive nature of this bond pad corrosion. By selective surface treatment of the Cu wires (cathodic part), we were able to prevent the corrosion by blocking the cathodic reaction and thereby stopping the electron flow required for the corrosion cycle to continue. The prevention treatment was then applied to commercial wire-bonded device and excellent corrosion prevention was observed. The corrosion inhibition coating exhibited high thermal stability up to 260 O C. We also report a novel testing method for corrosion testing of molded wire-bonded device with internal chloride ion contamination. Electrical continuity and delamination analysis showed that the chosen method of inhibition treatment was able to prevent corrosion even in cases of high chloride contamination and severe delamination. The results of the Pressure Cooker Test showed that the inhibitor coating is suitable for prevention of corrosion in even 100% Relative Humidity environments. Work is now in progress to apply these treatments to Palladium coated Copper wire bonded devices to check corrosion prevention ability of the reported corrosion prevention treatment.

Due to the constant miniaturization of microelectronics, the aim of the semiconductor industry has been to increase the packaging density of devices. Wire bonds form the primary interconnects between the integrated circuit chip and the metal lead frame in semiconductor packaging. Gold (Au) wire has been used for wire bonding in the electronics industry because of its mechanical and electrical properties, high reliability, and ease of assembly. However, due to the increasingly high cost of Au, alternative wire bonding materials have been considered. Copper (Cu) is gradually replacing Au because it exhibits not only a high resistance to electromigration, but also has excellent electrical conductivity and a low resistivity. The benefit of copper’s conductivity is that it reduces heat generated by joule heating, thus reducing RC delay. However, copper also has its drawbacks; tiny amounts of contaminant can corrode Cu interconnects, leading to the failure of entire microelectronic devices. On-chip corrosion within Cu interconnect microstructures can result in increased defectiveness, which causes serious reliability issues and decreases production yield. Copper is susceptible to corrode in acidic and strong alkaline solutions in the presence of oxygen and other oxidants. Effective corrosion monitoring is critical as an early alert before the onset of corrosion-related failure. In this study, we report a new method for monitoring the corrosion of copper relevant to the microelectronics industry through the combination of electrical resistance measurement changes of Cu wire and microscopic time-lapse imaging. Industry-grade 99.99% Cu bonding wire (diameter = 25μm) was exposed to the harsh, oxidizing conditions of ammonium persulfate, and its change in resistance was monitored. As the corrosion of Cu bonding wire took place, the cross-sectional area of the wire decreased, causing an increase in its resistance (via R= ρ•l/A). During the resistance monitoring, the simultaneous microscope time-lapse imaging enabled Cu corrosion to be observed in real time. Due to the combined quantitative and qualitative nature of this metrology, it provides detail on the corrosion process that might not be obtained by traditional corrosion tests. While ammonium persulfate will almost never be encountered by an IC device during normal use, it provides a rapid screening environment that can quickly distinguish between corrosion inhibition and no protection at all. This metrology was used to test both bare Cu bonding wire and corrosion-inhibitor coated bonding wire, and showed a drastic difference in their corrosion rate and behavior. This work ultimately aids with inhibitor selection and inhibitor coating design that will help ensure long term reliability of electronics used in industrial applications. Figure 1