A growing number of commercial products such as displays, solar panels, light emitting diodes (LEDs and OLEDs),
automotive and architectural glass are driving demand for glass with high performance surfaces that offer anti-reflective,
self-cleaning, and other advanced functions. State-of-the-art coatings do not meet the desired performance characteristics
or cannot be applied over large areas in a cost-effective manner. “Rolling Mask Lithography” (RML™) enables highresolution
lithographic nano-patterning over large-areas at low-cost and high-throughput. RML is a photolithographic
process performed using ultraviolet (UV) illumination transmitted through a soft cylindrical mask as it rolls across a
substrate. Subsequent transfer of photoresist patterns into the substrate is achieved using an etching process, which
creates a nanostructured surface. The current generation exposure tool is capable of patterning one-meter long substrates
with a width of 300 mm. High-throughput and low-cost are achieved using continuous exposure of the resist by the
Here, we report on significant improvements in the application of RML™ to fabricate anti-reflective surfaces. Briefly,
an optical surface can be made antireflective by “texturing” it with a nano-scale pattern to reduce the discontinuity in the
index of refraction between the air and the bulk optical material. An array of cones, similar to the structure of a moth’s
eye, performs this way. Substrates are patterned using RML™ and etched to produce an array of cones with an aspect
ratio of 3:1, which decreases the reflectivity below 0.1%.
The demand for large area and low cost nanopatterning techniques for optical coatings and photonic devices has
increased at a tremendous rate. At present, it is clear that currently available nanopatterning technologies are unable to
meet the required performance, fabrication-speed, or cost criteria for many applications requiring large area and low cost
nanopatterning. Rolith Inc proposes to use a new nanolithography method - "Rolling mask" lithography - that combines
the best features of photolithography, soft lithography and roll-to-plate printing technologies. We will report on the first
results achieved on a recently built prototype tool and cylindrical mask, which was designed to pattern 300 mm wide
This paper presents the advantages of using a vapor deposited self-assembled monolayer (SAM) as a mold release layer for nano-imprint lithography. The release SAM was formed from a perfluorinated organo-silane precursor at room temperature in the gaseous state by a technique called Molecular Vapor Deposition (MVD<sup>TM</sup>). In contrast to a conventional coating from a liquid immersion sequence, the vapor deposition process forms a particulate free film resulting in a substantial reduction of surface defects. Another advantage of the vapor process is its excellent conformity onto the nanoscale topography of the mold. The self-assembling and self-limiting characteristics of the MVD process enables excellent CD control of the mold pattern. Pattern replication as small as 38nm features was achieved. Various other quantitative metrics of the MVD release layer are presented in this paper.
This paper reports on the results of an improved surface modification method called Molecular Vapor Deposition (MVD). MVD allows for the creation of molecular organic coatings which are denser and more durable than those obtained by current liquid or vapor-phase methods. This improvement has been achieved using a “sequential” or “layered” vapor deposition scheme of two different molecular films. The first molecular coating is a “seed” or adhesion promoter layer which is used to increase the binding sites for the subsequent functional molecular layer. The resulting surface coatings were observed to have improved stability to immersion applications, higher temperature stability and overall improved durability as a result of the increased surface coverage when compared to standard self-assembled monolayers (SAMs). These new film capabilities will have significant importance in improving the functionality and reliability of many micro- and nano-scale devices. The sequential approach with the seed layer has also been used to deposit molecular coatings on a variety of substrate materials (such as polymers, plastics and metals) which normally do not allow high quality surface coatings.
We have developed an improved vapor-phase deposition method and an apparatus for the wafer-scale coating of monolayer films typically used in anti-stiction applications. The method consists of a surface preparation step using an O<sub>2</sub> plasma followed by the tunable deposition of a monolayer film in the same reactor. This process has been successfully applied to MEMS test structures and has demonstrated superior anti-stiction performance. The deposition process allows tuning of the film properties by the precise metering of the precursor and a catalyst as part of the process control scheme. The anti-stiction monolayer film deposited from dimethyldichlorosilane (DDMS), tridecafluoro-1,1,2,2-tetrahydrooctyltrichlorosilane (FOTS), and heptadecafluoro-1,1,2,2-tetrahydrodecyltrichlorosilane (FDTS) were characterized using contact angle analysis, atomic force microscopy (AFM), and X-ray photoelectron spectroscopy (XPS). The coefficient of static friction was measured using a sidewall test device and the work of adhesion using a cantilever beam array. The results showed that excellent quality, uniformity, and reproducibility could be achieved across a whole wafer using this method and equipment.
The method of simultaneous positive and negative pattern formation on a single positive photoresist layer is described. A negative photoresist pattern was fabricated by using local laser exposure to crosslink a positive resist layer, consecutive UV flood exposure, and resist developing. The positive pattern is obtained on the same photoresist layer in the areas masked from the UV flood exposure. Effects of laser energy and resist processing parameters on height and width of negative type resist structures were investigated. Metal line grid structures with lines in the region of 3 to 30 micrometers in width were manufactured on a 5' X 5' glass substrate using this technique. The proposed method of positive/negative pattern formation significantly reduces the number of technological steps in the fabrication of diffractive elements for dual-wavelength applications.
A 3' diameter refractive-diffractive element is presented. The element is used as a corrector in the optical system of a head up display at 545 nm. Average grating density of the design was 6 cycles/mm peaking to 10 cycles/mm. A 4 mask 14 level design was utilized, having a theoretical efficiency of 98.3%. The diffractive pattern was etched by RIE on a plano-convex fused silica lens, and then AR coated. Mask design and manufacturing process considerations are given and discussed. Tolerances and fabrication errors are analyzed. Micron mask misalignment and duty cycle errors, etch depth error of +/- 5%, and +/- 6% uniformity were achieved over the entire area, yielding a total efficiency of the element of > 96%. Diffraction measurements were made and compared to the theoretical calculations. The design and fabrication results prove diffractive elements in the visible a viable solution to correct aberrations in high quality optical systems such as head up displays.
Multilevel diffractive optical elements for transforming Gaussian beams into rectangular distributions with uniform intensity profile are presented. The effects of different parameters, particularly the phase quantization, on the output field are discussed. It is shown that the interference between the different diffraction orders results in non-uniformity of the output intensity profile. The design is refined to minimize this non-uniformity. The performance of the final design is theoretically analyzed. Actual elements were fabricated and tested and the experimental results are presented. Fabrication considerations are also discussed along with suggestions for improvements.