SBIR-STTR Award

Immersion lithography using available 193 nm optics and laser sources provides an attractive near-term path to reducing the printable feature sizes of integrated circuits by using a high-index fluid to reduce the wavelength at the wafer, rather than using light with higher photon energy and shorter vacuum wavelength. An interferometric immersion lithography (IIL) tool has demonstrated rapid fabrication of grating structures with half-pitches of 35 nm over exposure areas of 0.5 mm. This Phase I project involves the design of a new fiber laser based 193 nm light source with very high spatial- and temporal-coherence to allow uniform high-contrast intensity fringes (35 nm HP) to illuminate a wafer surface over a substantially larger exposure area, on the order of one square cm per exposure site. In addition, the laser will have high power stability and be sufficiently robust to allow extended periods of operation with little maintenance or operator intervention.

Keywords:
Interference Immersion Lithography, Fiber Laser, 193 Nm, Long Coherence Length

Cost effective semiconductor processing tools that enable the high-resolution nano-fabrication of low-volume electronics are needed by the DOD. The printing of ultra-fine gratings on silicon wafers using interference immersion lithography is envisaged as a first maskless process step in the fabrication of advanced application specific integrated circuits. Next generation interference immersion lithography tools capable of rapidly printing grating structures with half-pitches down to 26 nm over large fields will require a new class of laser source that can provide both high spatial and temporal coherence as well as high power. Line narrowed ArF excimer lasers, while essential for high volume semiconductor production, are ill-suited to this interference lithography application due to their high costs and inherently poor spatial coherence. In this DARPA STTR we will develop a 1 MHz pulsed fiber laser and wavelength extension system that delivers greater than ¼ watt of average power in the far ultraviolet (near 193.4 nm) with a coherence length of 15 cm (2 GHz FWHM bandwidth).

Keywords:
Interference Immersion Lithography, Fiber Laser, Maskless Lithography, Far Ultraviolet Laser, Rapid