The process of metallization involves depositing a metal thin film coating over a dielectric film on a wafer or other substrate. It’s critical in the development of microchips, and is often required in various high-volume applications in consumer electronics, including RF filters and power amplifiers in cable TV and cell phones. Other optoelectronic devices, such as lasers and photodetectors, also require metallization. With the onset of 5G on the horizon, demand for even more lasers, filters and power amplifiers will be driving dramatically higher production levels.
A common metallization requirement in these applications is for gate stacks, where an adhesion layer (such as titanium) and conduction layers (such as platinum or gold) are deposited onto the device to supply current or provide an electronic signal. While this process is key to performance, the most important factor in the production of consumer devices is managing device cost. To keep costs down at the price point that consumers are willing to pay, manufacturers need to optimize cost for metallization by utilizing a high-volume, wafer-based production approach.
Without good adhesion between the metal thin film coating and the wafer, yield will be low and device performance will be poor. This directly affects the cost of production while also impacting user experience and satisfaction. To help improve adhesion, manufacturers need to prevent oxidation between the adhesion and conduction layers. In-situ pre-clean processing is also needed, which can be achieved through an ion source or other energetic physical or chemical method, to remove water and hydrocarbons from the surface of the substrate. For high-volume manufacturing, metallization also requires highly uniform and repeatable films from wafer to wafer.
Manufacturers should choose a thin film system that can meet high throughput needs in a compact footprint, particularly for cleanroom placement where space is at a premium. Ideally, your deposition system for metallization should pair uniformity, repeatability and throughput requirements with suitable pre-clean capability to ensure sufficient adhesion, while providing high uptime and low cost of ownership.
Depending on form factor and production volume, both sputtering and evaporation can be used for metallization. The most ideal thin film deposition configuration for high-volume metallization is a multi-chamber sputter module with cluster architecture. With multiple sputter chambers, or modules, manufacturers can coat substrates with different adhesion and conduction layers without breaking vacuum, which is critical for preventing oxidation and improving adhesion. A separate pre-clean module can provide excellent adhesion and prevent contamination of the sputter module. High-volume automation software powering the robotics behind the cluster tool on the front end is also critical.
E-beam or thermal evaporation are also good solutions for metallization, and a system offering high yield and a high deposition rate is ideal. Evaporation works well for form factors outside of standard wafer-based products, and it’s a good, cost-effective option for applications without such high throughput demands.
When designing your thin film system, it’s important to work with a provider who understands your specific needs for metallization. Your configuration should be tailored to your requirements for throughput, system uptime, reliability and film performance specs.