Thermo-mechanical overlay signature tuning for Perkin-Elmer mask aligner

Claim 1

In an optical mask aligning apparatus used in the manufacturing of semiconductor devices by photolithography, said apparatus including: a first stage for receiving the semiconductor wafer; a second stage for receiving a mask; alignment means for aligning the mask and wafer relative to each other; an illuminator for illuminating the mask to form an image thereof; an image transferring means for transferring the mask image to the wafer; said image transferring means including a primary mirror suspended by a system of flexures; the improvement comprising: a reversible heat pump in thermal conductivity relationship to at least one of said flexures for adjusting the temperature of the flexure to establish stresses in the primary mirror suspension which are transferred to the primary mirror so as to compensate distortion in the image transfer means.

Claim 6

A method for compensating distortions arising in optical mask alignment apparatus, said apparatus including: a first stage for receiving a semiconductor substrate, a second stage for receiving a mask, means for aligning the substrate and the mask relative to each other, an illuminator for illuminating the mask and forming an image thereof, an image transferring means for transferring the mask image to the substrate, said image transferring means including a primary mirror suspended from a system of flexures, said method comprising the steps of: providing a reference substrate; providing a reference mask; illuminating the mask to form an image thereof; transferring the image of the mask to the substrate; adjusting the mask-wafer relative to positioning so that mask image aligns with the substrate; and heating or cooling the primary mirror flexure system to adjust their temperature so as to stress the flexures and associated primary mirror to reduce misalignment of the mask image caused by distortions in the image transfer means.

Claim 7

A method for compensating distortions arising in optical mask alignment apparatus, said apparatus including: a first stage for receiving a semiconductor substrate, a second stage for receiving a mask, means for aligning the substrate and the mask relative to each other, an illuminator for illuminating the mask and forming an image thereof, an image transferring means for transferring the mask image to the substrate, said image transferring means including a primary mirror suspended from a system of flexures, said method comprising the steps of: providing a reference substrate; providing a reference mask; illuminating the mask to form an image thereof; transferring the image of the mask to the substrate; adjusting the mask-wafer relative to positioning so that mask image aligns with the substrate; and heating or cooling the primary mirror flexure system to adjust their temperature so as to stress the flexures and associated primary mirror to reduce misalignment of the mask image caused by distortions in the image transfer means.