edfas.org ELECTRONIC DEVICE FAILURE ANALYSIS | VOLUME 27 NO. 3 4 EDFAAO (2025) 3:4-9 1537-0755/$19.00 ©ASM International® ELECTRICAL RESISTIVITY AND RESIDUAL STRESS IN SPUTTERED INDIUM TIN OXIDE THIN FILMS Jianhui Liang1, Jiali Zhang1, Kurt Johanns1, Oskar Amster1, Blaise Cuénod2, and Rémy Juttin2 1KLA Corp., Milpitas, California 2Center of MicroNanoTechnology, EPFL, Lausanne, Switzerland jianhui.liang@kla.com INTRODUCTION Transparent conductive thin films are crucial in various semiconductor devices, including solar cells, liquid crystal displays, light-emitting diodes, and sensors. Indium tin oxide (ITO) is a popular choice for these applications due to its excellent electrical conductivity, optical clarity, and unique nonlinear properties. Various methods can be used to create ITO thin films, such as magnetron sputtering, thermal evaporation, plasma ion-assisted deposition, and activated reactive evaporation. Among these, sputtering is particularly favored by industry for producing films with a dense structure and high transparency. The electrical resistivity in ITO determines its efficiency as a conductor, directly impacting the performance of devices in which it is integrated. A material with suboptimal resistivity may cause excessive heat dissipation and degrade the overall reliability of the device, leading to inefficiencies or failures in electronic and photonic applications. As such, understanding the factors that influence ITO’s resistivity, such as film thickness, grain size, composition, and deposition techniques, ensures that the material can be tailored for specific applications, providing the optimal balance between electrical conductivity and optical transparency. On the other hand, the residual stress that arises from the ITO film growth process can significantly impact performance of the ITO devices. One major issue is stress-induced warpage, which can disrupt the flatness of devices and complicate subsequent production steps. For example, tensile stress might lead to cracking or delamination, while compressive stress could cause buckling or warping. These mechanical failures can translate into electrical issues, such as open or short circuits, which are critical in precision applications like displays and sensors. Understanding and controlling residual stress is therefore essential to prevent mechanical failures and improve the longevity of devices, particularly in flexible electronics or applications subjected to thermal or mechanical stress. This article describes a study on the electrical resistivity and residual stress in sputtered indium tin oxide (ITO) films. The electrical resistivity of the ITO films was determined by measuring their thickness and sheet resistance, while the residual stress was quantified using a stylus profiler. It was observed that electric resistivity varies spatially and changes with film thickness. These variations are influenced by growth conditions, as well as electron scattering from surfaces and grain boundaries. Additionally noted was a transition from tensile to compressive stress as the film thickness increased, closely linked to the grain evolution process. Understanding these phenomena is crucial for enhancing the performance and reliability of electronic devices. By addressing the mechanical and electrical impacts of stress in ITO films, more robust and durable semiconductor devices can be developed, thereby reducing the risk of device failure. SAMPLE GROWTH ITO films are typically deposited on transparent insulating substrates that are in turn used for various electronic devices. In this study, ITO films were deposited on 100 mm diameter Borofloat 33 wafers, sourced from Siegert Wafer, using a standard radio frequency (RF) sputtering technique on a Pfeiffer Spider 600 system. The planar ITO target used for deposition measured 200 mm. The deposition process was carried out at room temperature with a target power of 500 W. The argon gas flow was maintained at 15 standard cubic centimeters per minute (cc/min), and the chamber discharge pressure was kept at approximately 0.5 Pa. Nine ITO films of varying thicknesses were prepared under
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