Double Exposure/Patterning Lithography

Hongki Kang

EE235 Mar 9 2009

Resolution

NA (Numerical Aperture) For higher resolution, R↓, λ↓, n↑, and α↑. ArF source (193 nm)

<Trend of k1 factor reduction since 2001,from Nanofabrication: Principles, Capabilities and Limits by Zheng Cui 2008>

Lithography Challenge ITRS 2007 Lithography

32 node

Single Exposure - No solution yetDouble Exposure - Solutions exist

What’s DE and DP?

<(a) single exposure, (b) double exposure, (c) double patterningfrom Nanofabrication: Principles, Capabilities and Limits by Zheng Cui 2008>

What’s DE and DP?Double Exposure Double 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

Double Patterning Usinga Protective Crosslinking Layer

< Process scheme of the examined double patterning method>

<A. Vanleenhove, D. Van Steenwinckel, "A litho-only approach to double patterning," Proc. of SPIE Vol. 6520, 65202F, 2007>

Double Patterning Usinga Protective Crosslinking Layer

<SEM pictures of lines throughout the different process steps. 90 nm mask features on a 240 nm pitch, which gives 60 nm half pitch in double patterning (right SEM picture), with the NA of 0.75 which was used.>

<A. Vanleenhove, D. Van Steenwinckel, "A litho-only approach to double patterning," Proc. of SPIE Vol. 6520, 65202F, 2007>

Double Patterning Usinga Protective Crosslinking Layer

<A. Vanleenhove, D. Van Steenwinckel, "A litho-only approach to double patterning," Proc. of SPIE Vol. 6520, 65202F, 2007>

~15 nm

~15 nm

Double Patterning Usinga Protective Crosslinking Layer

<A. Vanleenhove, D. Van Steenwinckel, "A litho-only approach to double patterning," Proc. of SPIE Vol. 6520, 65202F, 2007>

As the temperature decreases, the crosslinking layer thickness decreases.

Trade off with the ability to protect the first patterned layer

Double Patterning Usinga Protective Crosslinking Layer

<A. Vanleenhove, D. Van Steenwinckel, "A litho-only approach to double patterning," Proc. of SPIE Vol. 6520, 65202F, 2007>

As the acid concentration decreases, the crosslinking layer thickness decreases.

Double Exposure with Linear Resist

< Emil C. Piscani et al., "Continuing 193nm Optical Lithography for 32nm Imaging and Beyond," Proc. of SPIE Vol. 6924, 69242I, 2008 >

<Target Feature 70 nm>

<Target Feature 60 nm>

<Target Feature 55 nm>

<Target Feature 50 nm>

32 nm CMOS Platform Technology with Advanced Single Exposure Lithography

< S. Hasegawa et al., "A Cost-Conscious 32nm CMOS Platform Technology with Advanced Single Exposure Lithography and Gate-First Metal Gate/High-K Process," IEDM 2008 >

32 nm node SRAM was obtained by Toshiba with using ArF (193 nm) and “custom illuminate condition”

Conclusion

Current Lithography

Advanced Single

ExposureDouble

ExposureDouble

Patterning

32 nm Node and further

45 nmCurrent Node

Conclusion

Thanks,Questions?