Thin film coatings have long been a key part of our optical manufacturing capabilities. Now, we’re taking those coatings to an entirely new level with the installation of a plasma assisted e-beam vacuum deposition system from Tecport Optics.
Plasma assisted deposition represents an evolution of the ion assisted e-beam process that Inrad has successfully employed for years. Like ion assist, the new plasma-based deposition process relies on electron beams to evaporate coating materials prior to deposition on a substrate. And like ion assist, the plasma assist process uses ionized reactive gases to promote the adhesion and improve the structure of optical coatings. Unlike its predecessor, however, plasma assist combines the reactive ions and evaporated coating materials within a high-density DC plasma. Characterized by low voltages and high currents, this plasma achieves far greater efficiencies than the ion sources used by previous e-beam processes. The resulting thin films are of a measurably higher quality than previous processes.
Here’s a closer look at what our new thin film process can do:
Aside from producing superior coatings, the new machine dramatically increases the size of the optical components we can coat. Our existing ion assist e-beam systems, while still state-of-the-art and useful on a wide range of coating applications, have a 38-inch chamber and can accommodate parts up to 13 inches in diameter. The new plasma assist system has a 96-inch chamber and can handle parts up to 60 inches in diameter. This big jump in capacity opens up a variety of applications, including next-generation optics for semiconductor equipment, large telescope mirrors and astronomy optics.
High-volume jobs too. Parts that are well-suited for plasma assist don’t have to be big. The new coating machine’s high-volume chamber can efficiently coat batches of small parts at low cost. While we plan to use our plasma assist system primarily for our internal needs, the system has such a large throughput that we will soon offer contract thin film coating services on customer supplied optics.
Thin film quality enhanced. The high density plasma technology dramatically enhances the quality of thin films compared with earlier deposition methods. In particular, it improves a wide variety of mechanical and optical properties, including:
- Residual stresses
- Surface smoothness
- Scratch resistance
- Wavelength shift
New design possibilities. One interesting aspect of the larger new machine is that it incorporates a pair of expanded electron beam carousels. These expanded carousels allow the machine to manage a wider variety of coating materials than previous machines.
By pairing the greater selection of materials with the high-density plasma technology, we predict that plasma assist technology will enable innovative thin film coating designs that exhibit unparalleled optical and mechanical properties. To take one example, we’ve been investigating layered coatings that feature fine gradients of optical properties through the thickness of the coating.
In upcoming posts, we'll delve more deeply into the technical advantages, design possibilities and applications of plasma assisted deposition. So check back soon. Or sign up here to have email updates delivered to your inbox.