Interference lithography

Interference lithography (or holographic lithography) is a technique for patterning regular arrays of fine features, without the use of complex optical systems or photomasks. The basic principle is the same as in interferometry or holography. An interference pattern between two or more coherent light waves is set up and recorded in a recording layer (photoresist). This interference pattern consists of a periodic series of fringes representing intensity minima and maxima. Upon post-exposure photolithographic processing, a photoresist pattern corresponding to the periodic intensity pattern emerges. For 2-beam interference, the fringe-to-fringe spacing or period is given by λ / 2 sin ⁡ ( θ 2 ) { extstyle {frac {lambda /2}{sin {igl (}{ frac { heta }{2}}{igr )}}}} , where λ is the wavelength and θ is the angle between the two interfering waves. The minimum period achievable is then half the wavelength.