1 Thin Resist film Processing issues Ioannis Raptis Patterning Group Institute of Microelectronics National Center for Scientific Reasearch ‘Demokritos’ Ag. Paraskevi Attikis, Greece Contents  Glass transition changes in thin resist films  Etching rate of thin resist films  Dissolution properties of thin resist films

SW-OPTI methodology / Results C.D.Diakoumakos, I.Raptis Polymer (2003) D.Niakoula, I.Raptis, D.Goustouridis, P.Argitis Jpn. J. Appl. Phys. 43 (5247)2004 Interference Equation Operation Principle Parameters affecting T g film  film thickness  film – substrate interactions  coating method  distribution of molecules At glass transition  Specific volume  Refractive index  Surface roughness change Exposure layout 50  m rectangular pads

T g film values of AZ-EM materials MMC13: terpolymer Mw: MMC14: terpolymer Mw: MMC15: terpolymer Mw: 45000

MW-OPTI interferometry method / Results Specifications: Real time calculation of polymeric film thickness Controlled heating and cooling rate Controlled atmosphere (humidity level) Results: Evaluation of T g film for films down to 50nm Thin exposed PMMA resist

Etch Rate is decreasing as the initial film thickness declines For initial thicknesses >150nm ER gets its bulk value ER bulk – ER thickn~50nm >20nm/min Relative decrease of about 20% depending on the polymer Increased etch resistance of thin polymeric films Possible explanations for this are based on the effect of: Sample heating (during process) Physical properties of polymer (Free volume, Density, Diffusivity) Etch Rate vs. initial thickness N.Vourdas, A.G.Boudouvis, E.Gogolides Microelec. Eng. 78, 474(2005)

Multi Wavelength Dissolution Rate Monitor Characteristics Low-Moderate sampling Rate (<50samples/sec) Need for fitting Applicable to very thin films (>40nm) Allows detailed study of swelling Spectrometer A.Kokkinis, E.S.Valamontes, I.Raptis J. Physics (2005) “Dissolution properties of ultrathin photoresist films for the fabrication of nanostructures ” Dissolution behaviour depends on film thickness Effect of Molecular Weight on dissolution

Conclusions / Future Plans Conclusions Non destructive Optical methodologies were developed for the in-situ monitoring of the thin film properties. T g film in case of thin films are different from the bulk ones. Exposed and unexposed areas present different properties Dissolution of thin films was studied. Results depend on the polymer/resist material. Thin film issues are important for the sub 45nm nodes Future Plans Comparison of the three available optical methodologies for the T g film calculation. Development processing conditions effect on the development rate of thin films Thermal processing (PAB, PEB) effects on polymer/resist properties in the case of thin films