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EP-4741928-A2 - METHOD AND SYSTEM FOR GENERATION OF LITHOGRAPHY PATTERNS

EP4741928A2EP 4741928 A2EP4741928 A2EP 4741928A2EP-4741928-A2

Abstract

A lithography pattern generation system (1) and method comprising - an incoming particle beam (21) with a most probable wavelength (λ) from a particle source (2) and - a mask (4) comprising through holes (3) arranged in the incoming particle beam (21). The lithography pattern generation system (1) generates a single nanometre feature size pattern (51) and wherein the through holes (3) are arranged non-periodically in the mask. A computer implemented method for generating a lithography mask (4) model is also disclosed.

Inventors

  • FIEDLER, JOHANNES
  • PALAU, Adrià Salvador
  • OSESTAD, Eivind Kristen
  • HOLST, Bodil

Assignees

  • Vestlandets Innovasjonsselskap AS

Dates

Publication Date
20260513
Application Date
20230308

Claims (15)

  1. A lithography pattern generation system (1) comprising - an incoming particle beam (21) with a wavelength (λ) from a particle source (2) and - a mask (4) comprising through holes (3) arranged in the incoming particle beam (21), wherein the lithography pattern generation system (1) is configured to generate a pattern (51) on a pattern target (5), wherein particles in the incoming particle beam (21) arrives at the mask (4) in an incoming particle wave, and wherein the mask (4) is configured to induce phase shifts across a wave front of the particle wave as it propagates through the mask, wherein the mask (4) has a mask extension (a) which is the maximum distance between two through holes in the mask (3) exposed by the incoming particle beam (21), wherein the system is configured to operate in a Fresnel diffraction regime wherein the Fresnel number F, defined as F = a 2 /(L2*λ), is greater than or equal to 1, where L2 is the target distance and λ is the wavelength of the incoming particle beam, and wherein a >= L2.
  2. The lithography pattern generation system (1) of claim 1, wherein the induced phase shift is at least π, 3/2π or 5/3π for a distance 0.016 times a minimum hole width (w) of the through holes (3) from the mask (4).
  3. The lithography pattern generation system (1) of any of claims 1 to 2, configured to reduce the background signal stronger than the diffraction orders compared to the diffraction of an optical wave propagating with the same wavelength through the same mask (4) in a direction axially through a through hole (3), to increase the fraction of the beam that is diffracted rather than passing straight through the contrast (c) of the pattern (51).
  4. The lithography pattern generation system (1) of any of claims 1 to 3, wherein the minimum hole width (w) is at least two times, three times or four times as large as a minimum feature-size of the pattern (51).
  5. The lithography pattern generation system (1) of any of claims 1 to 4, wherein the mask (4) is a binary holography mask.
  6. The lithography pattern generation system (1) of any of claims 1 to 5, wherein the through holes (3) are not arranged according to a predefined underlying periodic grid structure in non-periodic positions on the mask (4)
  7. The lithography pattern generation system (1) of any of claims 1 to 6, wherein the through holes (3) have non-uniform minimum hole widths (w).
  8. The lithography pattern generation system (1) of any of claims 1 to 7, wherein the through holes (3) have a minimum hole width (w) of 5nm, 4nm, 3nm, 2nm or 1nm, and/or the through holes (3) have a maximum hole width (w) of 100 nm.
  9. The lithography pattern generation system (1) of any of any of claims 1 to 8, wherein the through holes (3) have different shapes, and/or the centre-to-centre distance (c) between neighbouring through holes (3) is non-uniform.
  10. The lithography pattern generation system (1) of any of claims 1 to 9, wherein the mask thickness is below 500 nm, 100 nm, 50nm, 20 nm, 10 nm or 7 nm, and/or the mask thickness is less than the minimum hole width (w).
  11. The lithography pattern generation system (1) of any of claims 1 to 10, wherein the wavelength (λ) is smaller than any of the minimum feature-size (df), minimum pitch, minimum hole width (w) and mask thickness.
  12. A lithography pattern generation system (1) comprising - an incoming particle beam (21) with a wavelength (λ) from a particle source (2) and - a mask (4) comprising through holes (3) arranged in the incoming particle beam (21), wherein the lithography pattern generation system (1) is configured to generate a pattern (51) on a pattern target (5), wherein particles in the incoming particle beam (21) arrives at the mask (4) in an incoming particle wave, and wherein the mask (4) is configured to induce phase shifts across a wave front of the particle wave as it propagates through the mask, wherein the system is configured to operate in a Fresnel diffraction regime, and wherein the system is configured to generate a single representation of a desired pattern (51) on the pattern target (5) that is substantially free of a conjugate image pattern.
  13. The lithography pattern generation system (1) of claim 12, comprising any of the features of claims 2 to 11.
  14. A method for generating a pattern (51) by lithography comprising; - exposing a mask (4) comprising through holes (3) to an incoming particle beam (21) from a particle source (2), wherein particles in the incoming particle beam (21) arrives at the mask (4) in a particle wave, and wherein the mask (4) is configured to induce a phase shift of the particle wave as it propagates through the mask and generate a pattern (51) a target distance (L2) from the mask, wherein the mask (4) has a mask extension (a) which is the maximum distance between two through holes in the mask (3) exposed by the incoming particle beam (21), - operating in a Fresnel diffraction regime wherein the Fresnel number F, defined as F = a 2 /(L2*λ), is greater than or equal to 1, where L2 is the target distance and λ is the wavelength of the incoming particle beam, and wherein a >= L2.
  15. A method for generating a pattern (51) by lithography comprising; - exposing a mask (4) comprising through holes (3) to an incoming particle beam (21) from a particle source (2), wherein particles in the incoming particle beam (21) arrives at the mask (4) in a particle wave, and wherein the mask (4) is configured to induce a phase shift of the particle wave as it propagates through the mask, - operating in a Fresnel diffraction regime, where the method is configured to generate a single representation of a desired pattern (51) on the pattern target (5) that is substantially free of a conjugate image pattern.

Description

TECHNICAL FIELD The present invention relates to microlithography and the manufacture of integrated circuits and other devices, for example quantum devices which cannot be mass produced with existing technology. More specifically it is related to exposing a mask with a particle beam, generating a particle pattern based on the information coded into the mask and exposing a target, such as a resist on a silicon wafer with the particle pattern. BACKGROUND The fabrication of integrated circuits is currently based on pattern generation using mask-based photolithography: An enlarged version of the desired chip pattern or part of the desired chip pattern is printed on a substrate (photomask). The pattern on the mask may be distorted to account for aberration effects etc.. Light (photons) are transmitted through or reflected off the photomask using optical components (refractive or reflective lenses) to create a demagnified image of the pattern on a silicon wafer. The silicon wafer is coated with a photosensitive material (resist), which reacts with the photons thus creating a permanent imprint of the image in the resist. This is then used as a physical mask in the following fabrication steps. The two main light sources used in the semiconductor industry today are Deep Ultraviolet Light (DUV) which has a wavelength of 193 nm and Extreme Ultraviolet Light (EUV) which has a wavelength of 13.5 nm. The standing aim is to create patterns with smaller and smaller feature sizes at higher and higher information densities, commonly referred to as minimum pitch - the smallest distance between the centres of two features. For a standard optical system, the smallest pitch that can be obtained is half the wavelength of the projecting beam, when the process is performed in air or vacuum (refractive index 1, the Abbe criterion). The performance of DUV is further pushed by using wavefront engineering techniques such as phase shifting masks, off-axis illumination, or optical proximity correction, achieving a minimum pitch of ~30% of the wavelength. The ultimate pitch in DUV lithography is achieved using the Immersion Lithography technique, where a high-refractive index fluid is introduced between the final lens and the wafer. Combining these techniques allows DUV to operate at an effective wavelength of ~135 nm, leading to a minimum pitch of around 38 nm. Additional pitch reduction requires multiple exposures to create one chip pattern, thus decreasing throughput and increasing complexity. The state-of-the-art is extreme ultraviolet (EUV) photolithography, which, with photons (electromagnetic waves) of a wavelength of 13.5 nm, should be able to produce patterns with a minimum pitch or minimum feature size of around 6.75 nm according to the Abbe criterion with a refractive index of 1 (vacuum). However, due to the high energy of the photons in EUV lithography, the pattern generation process in the resist is mediated by photo-generated secondary electrons, which can travel for several nm before inducing a reaction. Current experiments and theory indicate that the secondary electron blur radius for EUV is around 3 nm, which would limit the feature size that can be achieved to around 6 nm. This means that quantum devices based on small quantum dots and individual atoms and molecules cannot be produced with EUV. Moving to wavelengths even shorter than 13.5 nm, would just exacerbate the secondary electron issue. In Berggren, K.K., Bard, A., Wilbur, J.L., Gillaspy, J.D., Helg, A.G., McClelland, J.J., Rolston, S.L., Phillips, W.D., Prentiss, M., Whitesides, G.M.: Microlithography by Using Neutral Metastable Atoms and Self-Assembled Monolayers. Science 269(5228), 1255-1257 (1995) https://arxiv.org/abs/https://www.science.org/doi/pdf/10.1126/science.7652572. https://doi.org/10.1126/science.7652572, lithography with metastable atoms is proposed as an alternative to photolithography. Pattern generation in a thiol-based resist is demonstrated in a proximity lithography setup using a beam of metastable argon atoms transmitted through a grating. In other experiments patterns have been generated with metastable atoms using light masks, in some case with the atoms being directly deposited onto a substrate. However, it has not been demonstrated that atomic beams can be used to generate any desired, complex pattern with a small minimum pitch. some experiments have been performed to focus atomic beams to a small point with solid state lenses or mirrors or fields. However, this can only be applied for serial writing and is thus unsuitable for mass production. In Fujita, J., Morinaga, M., Kishimoto, T., Yasuda, M., Matsui, S., Shimizu, F.: Manipulation of an atomic beam by a computer-generated hologram. Nature 380(6576), 691-694 (1996). https://doi.org/10.1038/380691a0 a desired pattern with metastable neon atoms is generated on a screen, by transmitting the atom beam through a solid mask consisting of a distribution of approximately circular through hol