Presentation on theme: "Jie Sun EE 518 Instructor: Dr. Jerzy Ruzyllo Apr"— Presentation transcript:
1Jie Sun EE 518 Instructor: Dr. Jerzy Ruzyllo Apr. 4 2006 Advanced Photoresist TechnologyJie SunEE 518Instructor: Dr. Jerzy RuzylloApr
2Presentation outline Introduction of Photoresists Roadmap of Photoresist TechnologyPhotoresists Solution for SubmicronlithographySummary
3Introduction of Photoresists Photoresists Type:Positive: exposed regions dissolve (best resolution)Negative: Unexposed regions dissolve ( Swelling)Photoresists Structure:Resin: a binder that provides mechanical properties (adhesion, chemical resistance)Solvent: used to dissolve the resin, allowing the resin to be applied in a liquid statePhotoactive Compound (PAC): Act to inhibit or promote the dissolution of theresin in the developer. PAC inhibits dissolution in positive resists before lightexposure. After exposure the PAC promotes dissolution of the resin.* George Tech, “Photoresists and Non-optical Lithography”
4Photoresists Chemistry (1) Positive PhotoresistTwo-component DQN resists:DQN, corresponding to the photo-active compound, diazoquinone (DQ) and resin,novolac (N)Dominant for G-line (436nm) and I- line (365nm) exposure and not suitable for veryshort wavelength exposuresNovolac (N): a polymer whose monomer is an aromatic ring with two methyl groupsand an OH group.dissolves in an aqueous solution easilyDiazoquinone(DQ)20-50 % weightPhotosensitiveDQUVCarboxylic acid ( dissolution enhancer)*Stephen A. Campbell, “ The Science and Engineering of Microelectronic Fabrication”.
5Photoresists Chemistry (2) Positive PhotoresistDQ molecule will not dissolve in a base developer solution (pH >7).UV light breaks the nitrogen molecule off forming an unstable moleculeTo “stabilize” itself, one of the 6 carbon atoms in the ring pops out of the ring (leaving 5)Once exposed to water (a developer /water mixture), an OH group attaches to the carbon atom, forming an acid.The acid can then react and dissolve with the basic developer solution.Advantage:Unexposed areas unchanged by the presence of the developer, line width and shape of apattern precisely retained.Novolac fairly resistant chemical attack, a good mask for the subsequent plasma etching
6Performance of Photoresists Resolution (um) - linearity/ minimumSensitivity (mJ/cm2)Focus margin (um)Exposure margin (%)Dry etch resistance(X)Heat resistanceAdhesionStanding wave effect (and bulk effect)(um)BARC (bottom anti-reflective coating) compatibilityProcess margin/stabilityShelf-lifePhotoresists Profile* Han Ku Cho, Samsung Electronics Co., Ltd, “Lithography technology review of what it is and what to be”, March 2003
7Roadmap of Photoresists Technology * Han Ku Cho, Samsung Electronics Co., Ltd, “Lithography technology review of what it is and what to be”, March 2003
8Deep UV Photoresist Limitation of Novolac based Photoresist Strongly absorb below 250nm, KrF (248nm) marginally acceptable but not ArF (193nm)Photoresist Solution for Submicron FeaturesPMMAPAGs ( Photoacid generator) replace PACContrast enhancement layers (CELs)Inorganic resist (Ag-doped Ge-Se)Silicon-containing resists (dry developable)Multi-layer photoresist
9PMMA (Ploymethyl methacrylate) Short-wavelength lithography: deep UV, extreme UV, electron-beam lithographyResin itself is photosensitiveAdvantage: high resolutionDisadvantage:Plasma etch tolerance is very low and thick PMMA to protect the thin filmDissociation changes chemistry of the plasma etch and polymeric deposits on thesurface of the substrate.Low sensitivity: Add PAG (chemically reactive dissociating) or elevate exposuretemperature*Stephen A. Campbell, “ The Science and Engineering of Microelectronic Fabrication”.
10Contrast enhance layers (CELs) CEM photo-bleachableSpun onto the DQN PR after softbakeFormed in-situ “conformal contact mask”Enhanced contrastImportant for DUV resists with less optical intense and PR radiation absorbtion*
11Inorganic Resist Advantage: High contrast γ ≈ 7 Produce fine line Process: Ag-doped Ge-SeAg plated on sputtered Ge-SePhotodoping create Ag2Se after exposureDissolved in alkaline solutionDisadvantage:Require thick planarizing underlayer due tothin film naturePineholes and defects from Ge-Se*Stephen A. Campbell, “ The Science and Engineering of Microelectronic Fabrication”.
12Dry developable: Polysilynes Bi-layer processSilicon-containing resists on top of novolac based resistHighly resistant to plasma processBleaching under DUV exposure due to cross-linked siloxane networkEtch silicon selectively to silicon dioxide in HBr plasma* Roderick R. Kunz, et al, “193 nm Resists and Lithography”, Polymers for Advanced Technologies, Volume 5, p p.12-21
13Multi-layer Resists and Hard mask Tri-layer processThin layer PR + SiO2 +thicker planarizingOxide layer act as hard maskOxide layer: Dry etchingresistant layer*E.Ong and E.L.Hu, “Multilayer Resists for Fine Line Optical Lithography,” Solid State Technol.
14Process Comparison for SLR, BLR and MLR * Han Ku Cho, Samsung Electronics Co., Ltd, “Lithography technology review of what it is and what to be”, March 2003
15SummaryPhotoresists technology: Basic and key technology in lithographyPR chemistry structure changed with wavelength of light sourceSeveral PR solutions for DUV applicationMulti-layer PR replace the single layer for Sub-100nm features