This article was originally featured in the edition: Volume 24 Issue 3

Depositing Optical Coatings With A Metal-lift-off Evaporator


The capabilities of the Ferrotec UEFC-6100, which has a capacity of twenty-five 200 mm substrates, are not limited to efficient, uniform growth of metal layers – this tool can also deposit highly uniform oxide coatings by Shihu Deng and Philip Greene from Ferrotec - Temescal Division

The history of semiconductor manufacturing attests to the many advantages that come from moving to larger wafers. These benefits provide both a motivation and a driving force for the development of tools that are capable and efficient at undertaking processes on larger wafers. By succeeding in this endeavour, equipment providers can make their customers happy, by giving them an edge over their peers.

For different technologies, different diameters are adopted by the leading manufacturers. For silicon ICs, 300 mm represents the state-of-the-art. Meanwhile, for many other technologies – including GaN-on-silicon devices, such as microLEDs; SiC; filters, in the form of FBAR and BAW; MEMS on silicon; and thin-film batteries – the goal is to move to efficient processing on 200 mm wafers.

At Ferrotec of Livermore, CA, we are serving the needs of device makers with our latest generation of Ferrotec electron-beam evaporation tools. Our entire UEFC tool series is designed to deliver excellent uniformity and throughput on wafers up to 200 mm in diameter. For 200 mm wafers the UEFC-4900 can process 15 wafers/batch at a 0.9 m source-to-substrate distance, while the UEFC-5700 can process 18 wafers/batch at a distance of 1.07 m. The latest version, the UEFC-6100 further increases the batch size to 25 wafers, and can process at 1.07 m or 1.17 m for tighter design rules. This process equipment can efficiently and consistently deposit metal and oxide films.

This equipment portfolio may be better known for the creation of tools that provide efficient deposition of metals on 200 mm wafers of metals, prior to liftoff processing. However, the process equipment can also be used for the growth of optical oxide coatings.

Figure 1. The path that different regions within the wafer take through the chamber leads to a high degree of thickness and incident ion impingement uniformity.

The recently released UEFC-6100 sports these credentials, delivering excellent performance and flexibility by balancing a range of constraints, including thickness uniformity, material utilization, batch size (wafer count), and the basic metric of throughput per squarefoot of cleanroom floor space. Key features of the tool are: the conic product chamber; its capability to use two, three or four high-vacuum pumps; a dual-axis high uniformity lift-off apparatus (HULA) wafer motion, driven by non-contact magnetic gearing; a throw distance that is compatible with design rules for photo-resist structures (the incident angle must be less than 5°); and a ‘load-lock’ separation between the substrates and the electron-beam source.