Radiation imagery chemistry: process – composition – or product th – Radiation modifying product or process of making – Radiation mask
Patent
1991-09-04
1994-01-25
McCamish, Marion E.
Radiation imagery chemistry: process, composition, or product th
Radiation modifying product or process of making
Radiation mask
430311, 430320, G03F 900
Patent
active
052815005
ABSTRACT:
A method of preventing null formation is performed on a phase shifted photomask including a clear quartz substrate, dark chrome feature features, and alternating clear phase shifters raised from the substrate. The phase shifter features are terminated in a transmissive, optically clear edge. To prevent null formation and consequent formation of stringers on the surface of the integrated circuit, the substantially vertical edge of the optically clear end of the phase shifter is tapered. The slope at any point along the tapered edge between the photomask substrate and the phase shifter is set to an angle, typically less than forty-five degrees, shallow enough that the point spread function does not produce an image. The point spread function of the imaging system spreads out the null, which is therefore not printed into the photoresist layer on the integrated circuit. The tapered edge of the phase shifter is created by either discrete or continuous etching methods. Both methods create the phase shifter and tapered edges simultaneously and are compatible with photomasks having either additive or subtractive type phase shifters.
REFERENCES:
patent: 4935334 (1990-06-01), Boettiger et al.
patent: 5045417 (1991-09-01), Okamoto
Exploration of Fabrication Techniques for Phase-Shifting Masks, A. K. Pfau et al., Dept. of Electrical Engineering and Computer Sciences, Electronics Research Lab., Univ. of California, Berkeley.
Phase-Shifting and Other Challenges in Optical Mask Technology, B. J. Lin, IBM Chemical Technology Division, Hopewell Junction, NY, Sep. 1990.
Subhalf-Micron Patterning of Negative Working Resist by Using New Phase-Shifting Maska, H. Jinbo et al., J. Vac. Sci. Technolo. B 8(6), Nov./Dec. 1990, pp. 1745-1748.
Modeling Phase Shifting Masks, A. R. Neureuther, Dept. of Electrical Engineering and Computer Sciences, Electronics Research Laboratory, Univ. of Cal., Berkeley.
Fabrication of 64M DRAM with i-Line Phase-Shifting Lithography, K. Nakagawa et al., 1990 IEEE.
Improved Resolution of an i-Line Stepper Using a Phase-Shifting Mask, T. Teraswa et al., J. Vac. Sci. Technolo. B 8(6), Nov./Dec. 1990, pp. 1300-1308.
Phase-Shifting Mask and FLEX Method for Advanced Photo-Lithography, H. Fukuda et al. SPIE vol. 1264 Optical/Laser Microlithography III, 1990.
New Phase-Shifting Mask With Highly Transparent SiO.sub.2 Phase Shifters, I. Hanyu et al., SPIE vol. 1264 Optical/Laser Microlithography III, 1990, pp. 167-177.
New Phase Shifting Mask With Self-Aligned Phase Shifters for a Quarter Micron Photolithography, A. Nitayama et al., 1989 IEEE, 3.3.1-3.3.4.
LSI Process Lithography, Recticle, Stepper, DRAM, Nikkei Microdevice, Jul. 1990, pp. 1-32.
The Phase-Shifting Mask II: Imaging Simulations and Submicrometer Resist Exposure, M.D. Levenson et al., IEEE Transactions on Electron Devices, vol. ED-31, No. 6, Jun. 1984, pp. 753-763.
0.3-Micron Optical Lithography Using a Phase-Shifting Mask, T. Terawawa et al., SPIE vol. 1088 Optical/Laser Microlithography II, 1989, pp. 25-33.
Use of a pi-Phase-Shifting X-Ray Mask to Increase the Intensity Slope at Feature Edges, Y.-C. Ku et al., J. Vac. Sci. Technolo., Spec. Issued of Proceedings 1987, Int'l Symposium on Electron Ion and Photon Beams.
Transparent Phase Shifting Mask, Watanabe et al. IEDM, 1990, pp. 821-828.
Cathey David A.
Rolfson Brett
Chapman Mark A.
Fox III Angus C.
McCamish Marion E.
Micro)n Technology, Inc.
LandOfFree
Method of preventing null formation in phase shifted photomasks does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method of preventing null formation in phase shifted photomasks, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method of preventing null formation in phase shifted photomasks will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-726972