Fig. 1. Schematic of proximity lithography ^[8]

Fig. 2. Schematic and physical photograph of mask aligner. (a) Schematic ^[7] ; (b) physical photograph ^[1]

Fig. 3. Schematic and setup of EUV proximity lithography experiment^[40]. (a) Schematic; (b) picture of experimental setup

Fig. 4. Schematic of TIR hologram recording

Fig. 5. Schematic of experimental setup of TIR hologram recording^[28]

Fig. 6. Schematic of TIR hologram reconstruction

Fig. 7. Schematic of hologram reconstruction^[43]

Fig. 8. Test pattern and reconstructed hologram^[56]. (a) Original binary mask; (b) reconstructed hologram

Fig. 9. Schematic of HMA150/400^[48]

Fig. 10. Schematic of HMA500^[49]

Fig. 11. SEM images of photoresist structures after exposure. (a) Grating structure with 0.5 µm period obtained by HMA150^[28]; (b) micro-hole array with 1 µm diameter obtained by HMA400^[48]; (c) line and space pattern with 0.4 µm linewidth obtained by HMA500 ^[58]

Fig. 12. Obtained intensity results using wave-optical method^[59]. (a) Desired binary pattern; (b) aerial intensity obtained by traditional proximity lithography; (c) aerial intensity obtained by holographic mask

Fig. 13. SEM image of non-periodic synthetic holographic mask ^[63]

Fig. 14. Mask pattern and spatial image intensity maps involved in Ref.[63].(a) Mask pattern; (b) simulated aerial image;(c) SEM image of resist profile

Fig. 15. Schematic of mask design under coherent illumination, where m(x',y') represents distribution of optical field on mask surface, and w(x,y) represents distribution of optical field on silicon wafer surface^[21]

Fig. 16. Target intensity,initial amplitude, and initial phase involved in Ref.[63]. (a) Target intensity; (b) initial phase distribution;

Fig. 17. Basic process of ASPW iterative algorithm^[63]

Fig. 18. Schematics of four-level phase layer recording ^[21]

Fig. 19. Schematics of amplitude modulation layer recording^[21]

Fig. 20. SEM images of 4-level holographic mask^[62]

Fig. 21. Schematic of discretization of phase^[26]. (a) Schematic of continuous phase; (b) multi-level surface-relief profile; (c) multiphase profile based on SWS

Fig. 22. Impact of local defect appearing on sub-wavelength holographic mask on imaging^[72]

Fig. 23. Comparison of imaging results under different placement errors^[72]

Fig. 24. Experimental demonstration of SWHL and software reliability ^[77]. (a) Test patterns used in experiment; (b) designed SWHL mask; (c) simulation of light intensity distributions; (d) observed light intensity distributions; (e) profile patterns in photoresist; (f) SEM image at location with minimum line width

Fig. 25. Profile distributions of photoresist on non-planar substrate ^[76].(a) Top surface of silicon wafer; (b) bottom surface of silicon wafer; (c) photoresist profile

Fig. 26. Relationship between sub-wavelength structure coefficient and phase delay^[26]. (a) Lateral size of sub-wavelength structure determines phase delay; (b) arbitrary phase direction; (c) SWHL mask

Fig. 27. Possible forms of holographic mask elements ^[79]

Fig. 28. Structure and SEM image of SWHL mask. (a) Structure of SWHL mask using rectangular pillars^[77]; (b) SEM image of SWHL mask^[26]

Fig. 29. Mask pattern used for testing ^[22]

Fig. 30. Simulated holographic masks for elbow structures with different linewidths and pitches, where upper left pattern has linewidth of 350 nm and half-pitch of 350 nm. Linewidth of test pattern increases by 50 nm one by one from left to right, and half-pitch of test pattern increases by 50 nm one by one from top to bottom^[22]

Fig. 31. Intensity distributions on focal plane^[79]

Fig. 32. SEM images and simulated results of photoresist profiles with different gaps under exposure wavelength of 13.5 nm^[82]

Fig. 33. Workflow of EUV holographic mask design algorithm^[82]

Fig. 34. Fabrication of EUV holographic masks^[22]

Fig. 35. Simulated image, AFM image, and SEM image of EUV holographic mask^[22]. (a) Simulated structure; (b) AFM image of actual manufacturing structure; (c) SEM image of actual manufacturing structure; (d) local simulation image in Fig.35(c), where areas covered by photoresist are black; (e) local magnification of Fig.35(c) ,where areas covered with photoresist are brighter

Fig. 36. Substrate with slope structure, where regions A, B, and C represent different imaging areas^[84]

Fig. 37. Binary holographic mask of line segment used for imaging on slanted substrate^[86]

Fig. 38. Simulated intensity and CCD camera detection image of line pattern ^[87]. (a) Cross section of simulated light intensity ; (b) light intensity distribution on substrate surface captured by CCD camera

Fig. 39. Photoresist profile after exposure^[87]. (a) Photoresist profiles after exposure of three regions on nonplanar substrate structure shown in Fig. 36; (b) contour of line end after development

Fig. 40. Binary phase/pseudo grayscale holographic mask and photoresist profiles after exposure ^[89]. (a) Section of binary phase/pseudo greyscale holographic mask; (b) contour of line end obtained using binary phase/pseudo-grayscale holographic mask; (c) contour of line end obtained using binary phase/slit grayscale holographic mask

Fig. 41. Three-dimensional micro/nano antennas obtained using nonplanar synthetic holography. (a) Spiral wire structure on conical substrate^[91]; (b) vertical track on sidewall^[93]; (c) wire structure on hemispherical substrate^[95]

Fig. 42. Photoresist profiles obtained under different numbers of interference beams and incident light angles^[101]. (a) Schematic of double beam interference and (b) corresponding one-dimensional periodic contour distribution; (c) schematic of spatial solid angle three-beam interference and (d) corresponding two-dimensional periodic contour distribution;(e) schematic of x‑z plane three-beam interference and (f) corresponding contour distribution

Fig. 43. Three directional diffraction gratings, interference intensity distribution, and photoresist profile involved in Ref. [105]. (a) Three directional diffraction gratings; (b) light intensity distribution; (c) three-dimensional contour distribution within photoresist

Fig. 44. Four-beam interference is used to achieve fabrication of three-dimensional micro/nano structures ^[106]. (a) Relative positions of four beams; (b) three-dimensional structure surface obtained through simulation; (c) SEM image of three-dimensional photonic crystal obtained by holographic lithography

Fig. 45. Periodic patterns obtained through four-beam interference using 515 nm laser exposure^[104]. (a) At incident angle of 1.74° with period of 12 μm; (b) at incident angle of 0.35° with period of 60 μm

Fig. 46. Photoresist structures obtained by four-beam interference under different exposure time^[104]. (a) 0.1 s; (b) 0.5 s; (c) 1.0 s

Fig. 47. Intensity distribution and photoresist profile ^[112]. (a) Intensity distribution under double equal-dose exposures; (b) SEM image of contour obtained under equal dose and double exposure