Chapter 3. Theory and Practicalities of Subwavelength Optical Lithography

  1. Ban P. Wong1,
  2. Anurag Mittal2,
  3. Yu Cao3 and
  4. Greg Starr4

Published Online: 27 JAN 2005

DOI: 10.1002/0471653829.ch3

Nano-CMOS Circuit and Physical Design

Nano-CMOS Circuit and Physical Design

How to Cite

Wong, B. P., Mittal, A., Cao, Y. and Starr, G. (2004) Theory and Practicalities of Subwavelength Optical Lithography, in Nano-CMOS Circuit and Physical Design, John Wiley & Sons, Inc., Hoboken, NJ, USA. doi: 10.1002/0471653829.ch3

Author Information

  1. 1


  2. 2

    Virage Logic, Inc., USA

  3. 3

    University of California-Berkeley, USA

  4. 4

    Xilinx, USA

Publication History

  1. Published Online: 27 JAN 2005
  2. Published Print: 12 NOV 2004

ISBN Information

Print ISBN: 9780471466109

Online ISBN: 9780471653820



  • numerical aperture;
  • optical proximity corrections;
  • phase shift reticles;
  • PSM;
  • sub-resolution assist features;
  • resolution enhancement;
  • annular;
  • quadrupole and dipole type illuminations;
  • antireflective layers;
  • depth of focus;
  • mask error enhancement factor;
  • aberrations;
  • low-κ imaging;
  • rules based OPC;
  • model based OPC;
  • COG;
  • aberrations;
  • CD variation;
  • exposure tolerance;
  • corner rounding radius;
  • layout/resolution-enhancement interrelationships;
  • radical design restrictions;
  • catadioptric system;
  • EUV lithography;
  • particle beam lithography;
  • direct write e-beam


Chapter 3 is a tutorial on optical lithography which encompasses the physics and theory of operation including issues associated with advanced processes, and corresponding solutions. It begins with a brief historical perspective, an introduction and simple imaging theory. Then it takes the reader through the challenges for the 100 nm nodes and beyond. This is followed by an overview of the significant process variations, the impact of low-κ imaging on process sensitivities. A detailed discussion of low-κ imaging follows, including its effect on depth of focus; exposure tolerance; mask error factor; sensitivity to aberrations; CD variation as a function of pitch; and corner rounding radius. The next topic covered is the state of the art resolution enhancement techniques which will extend the resolution of the current lithography down to a quarter of the wave-length of the illumination used. This is followed by a discussion of the Physical Design Style Impact on RET and OPC Complexity. The chapter concludes with a look ahead into the future Lithography Technologies—the evolutionary as well as the revolutionary road maps.