High NA the Extension Path of EUV Lithography. Dr. Tilmann Heil, Carl Zeiss SMT GmbH

Transcription

1 High NA the Extension Path of EUV Lithography Dr. Tilmann Heil, Carl Zeiss SMT GmbH

2 Introduction This talk is about resolution. Resolution λ = k 1 NA High-NA NA k1=0.3 single exposure / nm What happens when increasing the NA of an EUV tool? What are the optical solutions?

3 Structure of presentation 1 Status EUV NXE:3300 optical system 2 Characteristics of High NA EUV optics projection optics and reticle 3 High NA EUV optics the solution space

4 EUV Roadmap has great extendibility. High NA optics enables single shot patterning of 10nm hp and beyond

5 The EUV NA0.33 optics for the HVM scanner NXE:3300 are in series production. NXE:3300 illuminator NXE:3300 projection optics NA = 0.33

6 Excellent and consistent wavefront performance of 3300 optical systems each bar is one system

7 enables single exposure imaging down to 13nm hp of the ASML NXE:3300 scanner.

8 Structure of presentation 1 The EUV NXE:3300 scanners are in series production. Higher NA optics extend the roadmap beyond 10nm. 2 Characteristics of High NA EUV optics projection optics and reticle 3 High NA EUV optics the solution space

9 EUV optical system grating reticle collector Intermediate focus source illuminator plasma Projection optics -2 nd -1 st 0 th 1 st diffraction orders +2 nd Projection optics catches and combines these diffraction orders on to the wafer wafer

10 EUV optical system the characteristics of a high NA projection optics. reticle Intermediate focus illuminator Projection optics collector source plasma wafer

11 Higher NA increases the light cone above the wafer, and Medium NA M6 High-NA M6 NA NA M5 M5

12 increases the angles on M5, and Medium NA M6 High-NA M6 M5 M5

13 increases the angular spread on M5. Medium NA M6 High-NA M6 M5 M5

14 Multi-layer coatings set limits for angles & angular spread on EUV mirrors. γ θ Substrate > 50 Bi Layers Si Mo d Standard EUV coatings are not able to reflect the combination of large angles and large angular spreads on M5 needed for High-NA. Angles must be reduced for high NA EUV optics.

15 There is a solution: We drill a hole into the mirror. M6 M6 Angles and angular spread on M5 decrease M5 M5

16 Central obscuration leads to an application dependent contrast loss this part lacks its corresponding 1 st order 0 th diffraction order unobscured pupil obscured pupil red colored parts of 0 th order can interfere with corresponding 1 st order ±1 st diffraction orders contrast loss obscuration blocks parts of 1 st diffraction orders

17 ...which can be tolerated if kept below ~20% radius. Generic Lines & Spaces through pitch simulation unobscured pupil obscured pupil

18 EUV optical system reticle impact on high NA EUV imaging. reticle Intermediate focus illuminator Projection optics collector source plasma wafer

19 Reflective mask requires non-telecentric illumination, reticle Geometrical rule: = / reduction 3300: NA=0.33 Reduction = 4x reticle CRAO = Chief Ray Object (6 for 3300)

20 so that increasing the NA leads to intersecting light cones. Increase NA

21 There are two potential solutions: Increase CRAO NA X reduction CRAO 9 high 0.45/4 =

22 There are two potential solutions: Increase CRAO or increase reduction NA X reduction CRAO 9 NA X reduction CRAO 7 high 0.45/4 = small 0.45/6 = 0.075

23 Increasing the CRAO is limited Absorber shadowing is angular dependent! Strong shadowing Weak shadowing reticle Absorber thickness 55nm.

24 Angular dependent absorber shadowing at high CRAO reticle NA 0.33 CRAO 6 15nm L&S Standard ML NA 0.45 CRAO 9 11nm L&S Standard ML

25 leads to telecentricity errors, efficiency losses, and reticle NA 0.33 CRAO 6 15nm L&S Standard ML NA 0.45 CRAO 9 11nm L&S Standard ML ML only 0 th order imbalance: telecentricity error

26 and loss of image contrast. reticle NA 0.33 CRAO 6 15nm L&S Standard ML NA 0.45 CRAO 9 11nm L&S Standard ML CRAO 9 ML only 0 th order imbalance: telecentricity error 0 th /1 st order imbalance: contrast loss ML & absorber

27 A 6x optics recovers imaging and efficiency by reducing CRAO to ~7 Simulation of 14nm dense 0.45 *) *) application dependent!

28 High NA imaging must avoid high NA at reticle / large CRAO by increased reduction. NA X reduction CRAO 9 NA X reduction CRAO 7 high 0.45/4 = small 0.45/6 = 0.075

29 Structure of presentation 1 The EUV NXE:3300 scanners are in series production. Higher NA optics extend the roadmap beyond 10nm. 2 A high NA EUV projection optics will have a slightly obscured pupil and an reduction ratio larger than 4x. 3 High NA EUV optics the solution space

30 Increased reduction ratio eases mask requirements, BUT NA X reduction CRAO 9 NA 0.5 8X reduction CRAO 6.5 dim@reticle = red dim@wafer 2X less sensitive to CD control, linearity, placement. focus@reticle = red² focus@wafer 4X less sensitive to blank topography.

31 gives smaller imaging or requires a larger mask for full field. High NA EUV imaging 104 x 132 mm² 104 x 132 mm² 156 x 198 mm² 6 reticle 4x 6 reticle 8x 9 reticle 6x 26 x 33 mm² FF Full 13x x16.5 QF QF QF QF 13x x16.5 Quarter 26 x 33 mm² FF Full

32 There is a wide solution space for High NA EUVL. Mask size 9 FF 6x HF 8x 6 mirrors 8 mirrors 7 HF 6x 6 FF 4x HF 5x QF 8x QF 8x NA

33 The triangle of High NA. Resolution 6x FF 9 8x QF Full Field 4x FF 6 Mask Angular limitations result in a triangle: Only 2 out of 3 requirements can be met resist triangle (resolution, LER, photo speed)

34 Structure of presentation 1 The EUV NXE:3300 scanners are in series production. Higher NA optics extend the roadmap beyond 10nm. 2 A high NA EUV projection optics will have a slightly obscured pupil and an reduction ratio larger than 4x. 3 High NA EUV optics show a large solution space, but trade off between resolution, field & mask size.

35 In conclusion High NA EUV lithography is natural extension of the semiconductor roadmap beyond 10nm hp. Technical solutions for such high NA EUV optical systems are available. The choice is up to the semiconductor community.