Electronic and Optoelectronic devices used in high-reliability applications such as defense, aerospace, medical, and telecom sectors, often require sealed packages to ensure optimal performance and long-term stability. These packages can be vacuum-sealed or filled with inert gases like argon or nitrogen, depending on the device’s type and operational mechanisms. However, outgassing and gas generation within these sealed environments can alter the internal atmosphere, leading to increased pressure in vacuum-sealed packages or contamination of the inert gas, ultimately causing performance degradation or device failure. Several sealed electronic devices need to work under vacuum and the requested pressure level may vary in the range from 1*10-7 mbar to 1 mbar. Typical devices that operate under vacuum conditions are X-Ray tubes, vacuum interrupters, cooled or uncooled bolometers, photomultipliers, MEMS (accelerometers, gyroscopes, microbolometers), microwave modules. Hydrogen, hydrocarbons, oxygen, carbon monoxide, carbon dioxide, nitrogen and moisture present as residual gases or outgassed from inner components tend to degrade the vacuum and are harmful contaminants in these systems. On the other side, in sealed electronic and optoelectronic devices containing a gas filling some impurities may be responsible of device malfunctioning and performance degradation. Main gas species that can be harmful are moisture, hydrogen and volatile organic compounds (VOCs). In some sealed optoelectronic modules, such as optical transceivers, hydrogen and moisture are the main contaminants to be removed: critical levels of these gases are 1000 ppmv for H2 and 5000 ppmv for H2O. There are several problems induced by the presence of these harmful gases. For instance, H2 is responsible of electrical performance degradation in RF modules and optoelectronic systems: it can diffuse through metal layers of active components, causing shifts in currents and trans-conductance, in addition it can reacts with surperficial oxides promoting the formation of moisture. Moisture can be responsible of electrical shorting or corrosion of solder joints. Photodetectors components may be degraded by water that can induce dark-current increase. In laser diode-based devices, water and Volatile Organic Compounds (VOCs) can cause gas condensation and the related signal attenuation issues. To mitigate these problems, some best practices are recommended: At first, it is essential to select materials, components, and package parts with low outgassing properties and suitable for device fabrication conditions. Then, it is requested to apply proper baking processes of the device well above 100°C, possibly under pumping, to reduce inner outgassing and gas load. Moreover, it is important to adopt suitable getters and active materials suitable to capture harmful gaseous impurities present or degassed in the devices. Advanced engineered getter solutions have been recently developed to effectively absorb contaminants. These include thin getter films and strips for vacuum-sealed packages and dispensable hybrid organic-inorganic materials for gas back-filled devices. Non Evaporable Getters (NEGs) are usually adopted to maintain proper vacuum and long-term stability in devices such as gyroscopes, IR sensors, pressure sensors, and resonators. NEGs can chemically sorb all active gases, including H2, H2O, CO, CO2, O2, and N2. New sputtered getter films, named PaGe®, deposited on metallic substrates have been developed to create getter solutions compatible with ceramic packages sealing and with wafer-to-wafer bonding techniques, widely adopted for wafer-level MEMs production. In addition special sorbing materials suitable for gas-filled devices have been developed during the last years. These getters, part of the so called ZeDry® family, are used in the form of thick films directly applied to device lids or to inner sub-components. The getter coating can withstand temperatures up to 325°C without degradation. Depending on the device type and application, the getter can be selected to interact with the main contaminants present in the package atmosphere. The present work will illustrate how the presence of detrimental gas contaminants can negatively affect the functionality and performance of high-reliability electronic and optoelectronic devices. The recently developed getter solutions, including thin sputtered getter films for vacuum-sealed packages and hybrid ZeDry getters for gas-filled modules will be described, showing their sorption capabilities suitable to ensure the removal of dangerous gases and to guarantee the proper operation of the devices throughout their lifetime.
Corazza et al. (Mon,) studied this question.