TECHNICAL FIELD

This invention relates to configuring optical layers in imprint lithography processes, and more particularly to forming spacers on a substrate via a drop-on-demand dispensing technique.

BACKGROUND

Nanofabrication (e.g., nanoimprint lithography) can include the fabrication of very small structures that have features on the order of 100 nanometers or smaller. One application in which nanofabrication has had a significant impact is in the processing of integrated circuits. The semiconductor processing industry continues to strive for larger production yields, while increasing a number of circuits formed on a substrate per unit area of the substrate. To this end, nanofabrication has become increasingly important to achieving desired results in the semiconductor processing industry. Nanofabrication provides greater process control while allowing continued reduction of minimum feature dimensions of structures formed on substrates. Other areas of development in which nanofabrication has been employed include biotechnology, optical technology, mechanical systems, and the like. In some examples, nanofabrication includes fabricating structures on substrates that are assembled to form an optical device.

SUMMARY

The invention involves a realization that improvements in forming spacer layers on substrates can increase an accuracy and a precision and improve a mechanical integrity of such spacer layers while reducing a cost and a complexity associated with producing such spacer layers for stacking optically functional layers in order to clearly see world side objects without affecting an optical clarity of a device including the stacked layers. In this regard, various aspects of disclosed imprint lithography methods can result in spacer layers formed on substrates in a manner that more accurately positions spacers, more precisely sizes spacers with desirable platform areas, improves light visibility through the device including the stacked layers, and improves a mechanical integrity of spacers as compared to spacer layers produced via other techniques. For example, a polymerizable, highly transmissive substance (e.g., greater than 90% transmission of visible light in air) can be accurately dispensed as droplets according to a programmed drop-on-demand mapping scheme along a peripheral edge of a substrate on a same side as which a functional pattern is imprinted without contacting the functional pattern and therefore without interfering with an optical integrity of the functional pattern. In other examples, a polymerizable, highly transmissive substance (e.g., greater than 90% transmission of visible light in air) can be accurately dispensed as droplets across an entire side of a substrate that is opposite a side on which a functional pattern is imprinted to produce desired optical effects or to provide structural support. Such dispensed droplets are highly transmissive upon curing (i.e., polymerizing). Additionally, owing in part to their small size, the droplets are invisible to the naked eye when the device is looked through as intended (e.g., with the device located close to the near point (e.g., 25 mm) of the eye). Furthermore, properties of the polymerizable substance, as well as a precise dispense volume of the polymerizable substance, can yield precisely formed spacers that vary in height by as little as 5% across an area of a substrate. Additionally, an elasticity of such spacers in a cured state provides the spacers with a mechanical integrity that is sufficient for supporting adjoined and adjacent substrates in a manner that prevents bowing or warping along interior regions of the substrates.

One aspect of the invention features an imprint lithography method of configuring an optical layer. The imprint lithography method includes depositing a set of droplets atop a side of a substrate in a manner such that the set of droplets do not contact a functional pattern formed on the substrate. The imprint lithography method further includes curing the set of droplets to form a spacer layer associated with the side of the substrate and of a height selected such that the spacer layer can support a surface adjacent the substrate and spanning the set of droplets at a position spaced apart from the functional pattern.

In some embodiments, each droplet of the set of droplets has a volume of about 1 pL to about 100 pL.

In some embodiments, each droplet of the set of droplet is transparent.

In certain embodiments, the imprint lithography method further includes generating a drop-on demand programming scheme.

In some embodiments, the imprint lithography method further includes providing a printing screen.

In certain embodiments, the imprint lithography method further includes imprinting the functional pattern on the substrate.

In some embodiments, depositing the set of droplets atop the side of the substrate includes dispensing droplet volumes of a polymerizable substance atop the side of the substrate.

In certain embodiments, the set of droplets is a first set of droplets, and the imprint lithography method further includes depositing each drop of the first set of droplets directly on the side of the substrate and curing the first set of droplets directly on the side of the substrate.

In some embodiments, each droplet of the first set of droplets has a cured height of about 0.5 μm to about 20.0 μm.

In certain embodiments, the imprint lithography method further includes, after the first set of droplets is cured depositing a second set of droplets atop the side of the substrate such that each droplet of the second set of droplets is respectively dispensed directly atop a droplet of the first set of droplets and curing the second set of droplets directly atop the first set of droplets to increase a height of the spacer layer.

In some embodiments, a first number of droplets in the first set of droplets is equal to a second number of droplets in the second set of droplets such that the spacer layer has a uniform height.

In certain embodiments, a first number of droplets in the first set of droplets is not equal to a second number of droplets in the second set of droplets such that the spacer layer has a variable height.

In some embodiments, the spacer layer has a wedge shape.

In certain embodiments, the functional pattern is imprinted on the side of the substrate.

In some embodiments, the functional pattern is imprinted along an interior region of the side of the substrate, and the imprint lithography method further includes depositing the set of droplets along a peripheral edge of the side of the substrate.

In certain embodiments, the side of the substrate is a first side of the substrate, and the functional pattern is imprinted on a second side of the substrate that is opposite the first side of the substrate.

In some embodiments, the imprint lithography method further includes depositing the set of droplets across an entirety of the first side of the substrate.

In certain embodiments, the imprint lithography method further includes attaching the substrate to the surface adjacent the substrate at the set of droplets such that the spacer layer forms a gap between the substrate and the surface.

In some embodiments, the gap provides a low index region.

In certain embodiments, the low index region includes air with an index of refraction of 1.

In some embodiments, the method further includes filling the gap with a polymerizable material having an index of refraction in a range of 1.3-1.6.

In certain embodiments, the polymerizable material has an index of refraction that is equal to an index of refraction of the cured set of droplets that forms the spacer layer.

Another aspect of the invention features an optical layer that includes a substrate, a functional pattern formed on the substrate, and a cured set of droplets disposed on a side of the substrate and spaced apart from the functional pattern. The cured set of droplets form a spacer layer associated with the side of the substrate and of a height selected such that the spacer layer can support a surface adjacent the substrate and spanning the cured set of droplets at a position spaced apart from the functional pattern.

In some embodiments, a defined radius of curvature can be imparted to the stacked optical layers by forming spacer layers with drops of pre-defined, varying height. Such drops with varying heights can be formed by dispensing drops of the same material with different volumes, dispensing drops of different material such that the volumes and surface tensions of the individual drops define final end heights of the drops, and dispensing drops of the same material or of different materials atop one another to achieve a desired variation in height. Such drops with varying heights can also be formed using techniques including but not limited to conductive, convective, and/or radiative drop volume evaporation schemes to selectively alter volumes, surface tensions, and surface energies of the dispensed drops to affect heights of the drops upon curing.

The details of one or more embodiments of the invention are set forth in the accompanying drawings and the description below. Other features, aspects, and advantages of the invention will be apparent from the description, the drawings, and the claims.

