Patented Precision Patterning of Multiple Dichroic Coatings | Ocean Thin Films

Precision Patterning Process
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Patented Precision Patterning of Multiple Dichroic Coatings, Balzers, EIS Optics, Oerlikon Optics, Unaxis Home > Products > Optiical Components > Precision Patterning Process

	Advantages of the Precision Patterning Process
	Because the Ocean Thin Films process relies on precision microlithography instead of cut metal masks to pattern the deposited coatings, features (coated areas) as small as 2 µm can be produced, with spatial registration to within 1 µm. There are other advantages as well: Undesired "shadowing" or thickness drop-off of the coating at pattern edges -- unavoidable with cut masks -- is eliminated due to the pattern edge break produced in the lift-off process. Intricate coating patterns of any shape or size can be manufactured without the machining limits inherent to metal masks. The cost of microlithographic tooling does not increase significantly with pattern complexity. Cut metal masks are less durable than microlithographic tooling. Metal masks must be cleaned often to remove coating deposits, and can be easily damaged in handling. Patterned dichroic filter coatings have optical and physical properties comparable to traditional non-patterned coatings, and have very high resistance to humidity and temperature. And because the coatings are applied directly to substrates and devices, their mechanical resistance to shock and vibration is an improvement over commonly used bonded discrete filter windows.
	Optical Coatings with Micro-lithographic Precision
	Ocean Thin Films has pioneered an optical coatings production methodology that combines modern optical thin film deposition techniques with micro-lithographic procedures. This patented process enables micron-scale precision patterning of optical thin film dichroic coatings on a single substrate. (A dichroic filter selectively transmits light according to its wavelength.) Until recently, entire optical surfaces could be easily be coated with a bandpass filter, but precise deposition of patterned optical filter coatings required metal masking. Metal masking withstands the in-vacuum process heat needed to produce durable dielectric multi-layers, but is expensive to manufacture, difficult to align with the substrate and unable to produce a deposited pattern that can be cleanly aligned to existing patterns -- i.e., edge-to-edge, without gaps or overlapping. Other coatings technologies employed to transmit and reflect wavelengths of light are similarly limited. For example, the dicing and bonding of individual filters to form an assembly is tedious, with miniaturization limited by materials handling and dicing constraints. Also, materials such as gels and colored glass are not very robust and may not provide adequate transmission or blocking efficiency for some applications. With its patented process, Ocean Thin Films can create multi-patterned arrays of different optical filters for use in dense wavelength division multiplexers, micromechanical devices (commonly referred to as MEMS) and optical waveguide-based devices. The process can be applied to multi-part bonded filter applications common to the manufacture of digital data projectors and CCD camera detectors. In fact, a wide variety of optical coatings can be patterned, including dielectric multi-layer reflectors, bandpass filters, dichroic edge filters and broadband anti-reflection coatings. In addition, the Ocean Thin Films technique can be used to deposit enhanced metal reflectors, low-reflectivity opaque metals and electrically conductive transparent patterns.
	The Ocean Thin Films Process
	The production of a patterned optical multi-layer coated element begins with application of photoresist to the surface. To generate a pattern, we align the mask and then expose and develop the photoresist. This creates a resist pattern on the coating surface. Next, the prepared substrates are placed into a vacuum chamber for controlled deposition of the multi-layer coating. After deposition of the filter, the patterned coating is rinsed in solvent, which removes any unwanted layers and leaves the desired patterned filter coating. This sequence can be repeated as needed, allowing multiple filters to be deposited.