Photolithographic masks define which materials are laid down where in a microelectronics device, and their functioning at finer size scales is vital to the ability to continue miniaturizing technology. It may come as a surprise that electrostatics poses a problem to these photomasks even though they are purely mechanical and not electrical in function.

Recent studies by Julian Montoya of Intel and Arnold Steinman of Ion Systems in Berkeley, Calif., show that shapes on masks can become charged and subsequently discharge to adjacent shapes, causing damage to the masks (see micrograph above). When the spacing between two lines is wide, it takes a higher voltage to jump the gap. Such large discharges release enough energy to cause highly visible damage. When lines are closer together, however, discharges occur at lower voltages, producing less visible damage, which can be overlooked by inspections of the photomasks but is still destructive enough to spoil the devices made with the mask.

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