Plasma Technology for Advanced Devices

SLM, or Spatial Light Modulator, is the basis of a new photomask pattern generation technology that is being developed by in partnership with the .

The SLM itself is an integrated circuit with a flat, mirror-like surface. Deep ultraviolet light is reflected off the surface of the SLM to expose photoresist on a photomask blank, forming the pattern of the mask.

The mirror-like surface of the SLM is actually composed of thousands of tiny moveable mirrors, each with their own storage cell within the integrated circuit. As the design of the photomask is feed to the SLM, individual mirrors are either flexed or remain flat. Light reflected off the flexed mirrors is scattered — it cannot pass through and expose the photoresist on the photomask blank. Light reflected off the flat mirrors does pass through to expose the resist, creating the pattern of the photomask. The closest analogy to stepper lithography is that of a chromeless phase shifting mask, which creates dark areas by scattering light away from the surface of the quartz mask substrate.

A version of the system that was presented at the 2002 SPIE CONFERENCE is able to produce any of 64 gray levels or “black” on each micro-mirror. The pixel size in the image plane is 100 nm. The effective pattern address grid is 1.56 nm. The SLM has over one million micromirrors. Because the illumination in the system is partially coherent, with a coherence length exceeding the mirror dimension, light from each mirror interferes with light from it’s near neighbors. Therefore the imaging system does not resolve individual mirrors, which moderates the effect in the printed pattern of poorly-behaved mirrors.

A more detailed description of the Spatial Light Modulator can be found here.

SLM was recently the focus of signifance attention. Earlier this year, Intel announced an inestment in Micronic Laser Systems AB. On July 18, 2003, Micronic Laser Systems AB (Micronic) and ASML Holding NV (ASML) announce that the two companies have signed a memorandum of understanding to form a joint venture company that will focus on the optical maskless lithography market for semiconductor manufacturing.

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