1. Double Exposure/Patterning Lithography Hongki Kang EE235 Mar 9 2009

2. Resolution NA (Numerical Aperture) For higher resolution, R ↓, λ ↓, n ↑, and α ↑. ArF source (193 nm) <Trend of k 1 factor reduction since 2001, from Nanofabrication: Principles, Capabilities and Limits by Zheng Cui 2008>

3. Lithography Challenge ITRS 2007 Lithography

4. What’s DE and DP? <(a) single exposure, (b) double exposure, (c) double patterning from Nanofabrication: Principles, Capabilities and Limits by Zheng Cui 2008>

5. What’s DE and DP? Double ExposureDouble Patterning Advantages - Can separate one dense feature into two less dense features (higher resolution possible with using current lithography system) - No considerable changes in infrastructure => more economical than other approaches (λ, NA…) - Keep the same depth of focus - Much simpler than Double Patterning- Current photoresist can be used Drawbacks - The discrepancy and delay between the second PR pattern and the first hardmask pattern, resulting in an additional source of variation - Well developed non-linear resist is needed (propagation of photon energy) - Additional steps causes longer process time and low throughput

6. Double Patterning Using a Protective Crosslinking Layer

7. Double Patterning Using a Protective Crosslinking Layer

8. Double Patterning Using a Protective Crosslinking Layer ~15 nm

9. Double Patterning Using a Protective Crosslinking Layer As the temperature decreases, the crosslinking layer thickness decreases. Trade off with the ability to protect the first patterned layer

10. Double Patterning Using a Protective Crosslinking Layer As the acid concentration decreases, the crosslinking layer thickness decreases.

11. Double Exposure with Linear Resist

12. 32 nm CMOS Platform Technology with Advanced Single Exposure Lithography 32 nm node SRAM was obtained by Toshiba with using ArF (193 nm) and “custom illuminate condition”

13. Conclusion Current Lithography Advanced Single Exposure Double Exposure Double Patterning

14. Conclusion Thanks, Questions?