Resolution Enhancement Technologies

Attempts to improve the process window by optical means (sometimes called optical “tricks”) include:

• Optimization of the mask pattern shape (optical proximity correction, OPC)

• Optimization of the angles of light illuminating the mask (off-axis illumination, OAI)

• Adding phase information to the mask (phase-shift masks, PSM)

• Control of the polarization of the illumination

Collectively, these optical approaches are known as resolution enhancement technologies (RETs). While some techniques improve feature resolution at the expense of pitch resolution, many of the RET approaches can improve pitch resolution and increase the process window simultaneously. However, the most promising RETs (especially the best PSMs techniques) require a revolution in chip layout design that has yet to occur.