High transmission mask technology for 45nm node imaging

Abstract

The lithography prognosticator of the early 1980's declared the end of optics for sub-0.5µm imaging. However, significant improvements in optics, photoresist and mask technology continued through the mercury lamp lines (436, 405 & 365nm) and into laser bands of 248nm and to 193nm. As each wavelength matured, innovative optical solutions and further improvements in photoresist technology have demonstrated that extending imaging resolution is possible thus further reducing k 1 . Several authors have recently discussed manufacturing imaging solutions for sub-0.3k 1 and the integration challenges.The requirements stated in the ITRS roadmap for current and future technology nodes are very aggressive. Therefore, it is likely that high NA in combination with enhancement techniques will continue further for aggressive imaging solutions. Lithography and more importantly "imaging solutions" are driven by economics. The technology might be extremely innovative and "fun", however, if it's too expensive it may never see the light of scanner.The authors have investigated and compared the capability of high transmission mask technology and image process integration for the 45nm node. However, the results will be graded in terms of design, mask manufacturability, imaging performance and overall integration within a given process flow. INTRODUCTIONLithographers are continuously trying to improve process windows for a manufacturing technology and developing new options for the next technology node. A way to achieve improvements in resolution is simply to migrate to a shorter wavelength. Unfortunately, a change in wavelength typically requires a large capital expense and significant process development effort. Alternatively, off-axis illumination techniques, such as annular and quadruple can be applied to enhance an existing process. All high-end exposure systems in use have the ability to utilize several different illumination schemes; so alternate illumination implementation is relatively straightforward to implement to the lithographer unless one begins looking at custom apertures. As the cost of tools continues to rise