Performing 3-D metrology and advanced repairs on leading-edge photomasks

摘要

As chipmakers continue to extend photolithographic processes to create subwavelength-sized features, photomasks have evolved from simple, binary, 2-D patterns of chrome on glass to complex 3-D structures. In addition to containing the circuit pattern, advanced photomasks include specialized structures that enhance the contrast and resolution of the image that will be transferred to the wafer. Resolution-enhancement techniques add or subtract small features from the pattern to improve the fidelity of the transferred image. Phase shifters manipulate light to improve image contrast and sharpen edges. While these advances have allowed manufacturers to extend the use of expensive equipment across device generations, they have also increased the need for advanced mask metrology and repair capability.