Application of an aerial image measurement system to mask fabrication and analysis

Application of an Aerial Image Measurement System (AIMSTM) to binary and phase- shift mask fabrication and evaluation is described. The AIMS tool, an optical system which measures the aerial image directly from a mask, provides rapid feedback on lithographic performance for a variety of stepper configurations through modifications of the wavelength, numerical aperture, and illuminator design. The AIMS tool has been applied during the implementation of an alternating phase-shift mask (PSM) fabrication process in order to understand the impact of the etched-quartz sidewall on lithographic performance. AIMS measurements were used to extract the effective phase and transmission as a function of phase- etch depth as well as post-etch treatment condition. A set of basic test structures are proposed which can be used in conjunction with the AIMS tool to automate the extraction of transmission, phase, and second-level overlay for phase-shifting processes such as alternating and attenuating PSM.

[1]  H. Moritz.  High-resolution lithography with projection printing , 1979, IEEE Transactions on Electron Devices.

[2]  T. A. Brunner,et al.  A Stepper Image Monitor For Precise Setup And Characterization , 1988, Advanced Lithography.

[3]  Alfred K. K. Wong,et al.  Phase-shifting mask topography effects on lithographic image quality , 1993, Advanced Lithography.

[4]  Andreas Grassmann,et al.  Contrast transfer function measurements of deep ultraviolet steppers , 1992 .

[5]  T.A. Brunner,et al.  In situ measurement of an image during lithographic exposure , 1985, IEEE Electron Device Letters.

[6]  William N. Partlo,et al.  Direct aerial image measurement as a method of testing high numerical aperture microlithographic lenses , 1993 .

[7]  B.J. Lin.  Partially coherent imaging in two dimensions and the theoretical limits of projection printing in microfabrication , 1980, IEEE Transactions on Electron Devices.

[8]  Takashi Sato,et al.  New phase shifting mask with self-aligned phase shifters for a quarter micron photolithography , 1989, International Technical Digest on Electron Devices Meeting.

[9]  Derek B. Dove,et al.  New tool for phase-shift mask evaluation: the stepper equipment aerial image measurement system--AIMS , 1994, Photomask Technology.

[10]  M. Levenson,et al.  Improving resolution in photolithography with a phase-shifting mask , 1982, IEEE Transactions on Electron Devices.

[11]  Christophe Pierrat,et al.  Exposure characteristics of alternate aperture phase‐shifting masks fabricated using a subtractive process , 1992 .