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E beam lithography
This document discusses electron beam lithography. It begins with an introduction and overview of electron beam lithography, explaining that it uses a beam of electrons to selectively expose and develop a resist film in order to create very small structures. It then provides a schematic of the electron beam lithography process and describes the lithography process steps. The document also covers the advantages of high resolution and no diffraction limit but disadvantages of low throughput and high costs. It includes details on electron beam sources and lenses used.
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E beam lithography
- 1. Group 2: TrầnPhúc Thành. Cao Văn Phước. Tống Văn Khoa.
- 2. Introduction. WhyE-beam lithography? Schematic of e-beam lithography. Lithography Process Advantages and disadvantages. Summary. References.
- 3. - Electron beamlithography (often abbreviated as e-beam lithography) is the practice of emitting a beam of electrons in a patterned fashion across a surface covered with a film (called the resist), ("exposing" the resist) and of selectively removing either exposed or non-exposed regions of the resist ("developing"). - The purpose, as with photolithography, is to create very small structures in the resist that can subsequently be transferred to the substrate material, often by etching. It was developed for manufacturing integrated circuits, and is also used for creating nanotechnology architectures.
- 6. Lower resolution systems can usethermionic sources, which are usually formed from LaB6. However, systems with higher resolution requirements need to use field electron emission sources, such as heated W/ZrO2 for lower energy spread and enhanced brightness.
- 7. A magnetic lensis a device for the focusing or deflection of moving charged particles, such as electrons or ions , by use of the magnetic Lorentz force. Its strength can often be varied by usage of electromagnets.
- 8. - Sometime weaslo use electrostatic lens however, electrostatic lenses have more aberrations and so are not used for fine focusing. -Systems of electrostatic lenses can be designed in the same way as optical lenses. -Electrostatic lenses in an electron diffraction experiment.
- 9. Clean sample ◦Remove oils, organics, etc (Acetone, IPA, ultraso nic) Spin coating of photoresist on surface of film (positive or negative resist) substrate Deposited film Photoresist
- 10. E-beam lithography anddevelop Etching (multi-step processes) Evaporate metal contacts substrate film substrate Deposited film substrate film substrate film
- 11. Direct writing withnarrow beam Electron projection lithography using a mask :EPL
- 12. oIssues: oThroughput of directwriting is very low : research tool or low pattern density manufacturing oProjection stepper (EPL) is in development stage only (primarily by Nikon). oMask making is the biggest challenge for the projection method oBack-scattering and second electron result in proximity effect –reduce resolution with dense patterns there is also the proximity effect oOperates in high vacuum (10-6 –10-10 torr) –slow and expensive
- 13. Raster Scan Thee-beam is swept across the entire surface, pixel by pixel Beam is turned on and off Beam is scanned across the entire surface
- 14. Vector Scan ◦The e-beam “jumps” from one patterned area to the next ◦ Adjustments to the beam can also be made relatively easily ◦ It takes longer for the beam to settle, making it more difficult to ◦ maintain accurate placing for the beam
- 15.
- 16. o Diffraction isnot a limitation on resolution ( < 1 Å for 10-50 keV electrons) o Resolution depends on electron scattering and beam optics the size of the beam, can reach ~ 5 nm
- 17. 17 In EBLthe resolution is not limited by diffraction In EBL backscattering causes the electron beam to broaden and expose a large volume of resist then expected. The proximity effect places a limit on the minimum spacing between pattern feature.
- 18. • Thepattern is written directly onto the electron-sensitive resist (no mask is used) • More precise than photolithography or X- Ray lithography • Used to make high-resolution masks for photolithography and X-Ray lithography • Beats the diffraction limit of light, minimum feature size around 5 nm
- 19. Very slow.Takes over 10 hours to scan across the entire surface of a wafer • Very costly. One e-beam system costs upwards of 5 to 10 MILLION dollars • Potential problems with electron scattering: –Electron energy: 100eV -> very slow, inefficient, damage the substrate –Electron energy: 10eV -> lower penetration depth and lower resolution
- 20. S.M. Sze,Semiconductor Devices, Physics and Technology, Willey, 2002. C.Y. Chang and S.M. Sze, Eds., ULSI Technology, McGraw-Hill, 1996. S.M. Sze, Ed., VLSI Technology, McGraw-Hill, 1988. Nguyễn Đức Chiến, Nguyễn Văn Hiếu, Công nghệ chế tạo mạch vi điện tử, NXB Bách khoa, 2007.