Justin L. Stay

Three-beam-interference lithography: contrast and crystallography

Specific configurations of three linearly polarized, monochromatic plane waves have previously been shown to be capable of producing interference patterns exhibiting symmetry inherent in 5 of the 17 plane groups. Starting with the general expression for N linearly polarized waves, three-beam interference is examined in detail. The totality of all possible sets of constraints for producing the five plane groups is presented. In addition, two uniform contrast conditions are identified and discussed. Further, it is shown that when either of the uniform contrast conditions is applied and the absolute contrast is maximized, unity absolute contrast is achievable.

Three-beam interference lithography methodology

Three-beam interference lithography represents a technology capable of producing two-dimensional periodic structures for applications such as micro- and nanoelectronics, photonic crystal devices, metamaterial devices, biomedical structures, and subwavelength optical elements. In the present work, a systematic methodology for implementing optimized three-beam interference lithography is presented. To demonstrate this methodology, specific design and alignment parameters, along with the range of experimentally feasible lattice constants, are quantified for both hexagonal and square periodic lattice patterns. Using this information, example photonic crystal rodlike structures and holelike structures are fabricated by appropriately controlling the recording wavevector configuration along with the individual beam amplitudes and polarizations, and by changing between positive- or negative-type photoresists.

Conditions for primitive-lattice-vector-direction equal contrasts in four-beam-interference lithography

Four distinct conditions for primitive-lattice-vector-direction equal contrasts in four-beam interference are introduced and described. By maximizing the absolute contrast subject to an equal contrast condition, lithographically useful interference patterns are found. Each condition is described in terms of the corresponding constraints on the plane wave wave vectors, polarizations, and intensities. The resulting locations of global intensity maxima, minima, and saddle points are presented. Subordinate conditions for unity absolute contrast are also developed. Three lattices are treated for each condition: simple cubic, face-centered cubic, and body-centered cubic.

Contrast in four-beam-interference lithography

Specific configurations of four linearly polarized, monochromatic plane waves have previously been shown to be capable of producing interference patterns exhibiting the symmetries inherent in all 14 Bravais lattices. We present (1) the range of possible absolute contrasts, (2) the conditions for unity absolute contrast, and (3) the types of interference patterns possible for configurations of four beams interference that satisfy the uniform contrast condition. Results are presented for three Bravais lattice structures: Base- and face-centered cubic and simple cubic.