Electron-beam curing of resists

Okoroanyanwu, J. Shields, and C.Y. Yang, Process for preventing deformation of patterned photoresist features, U.S. Patent No. 6,589,709 (2003) C. Gabriel, H.J. Levinson, and U. Okoroanyanwu, Selective photoresist hardening to facilitate lateral trimming, U.S. Patent No. 6,716,571 (2004) W.R. Livesay, A.L. Rubiales, M. Ross, S. Woods, and S. Campbell, Electron beam hardening of photoresists, Proc. SPIE 1925, 426 436 (1993). 

BiUmeyer, Textbook of Polymer Science, p. 372, John Wiley Sons, Hoboken, NJ (1971). 

The cross-linking processes will persist with continued electron-heam irradiation and will stop only when the entire hulk of the film is cross-linked. 

The effect of the cross-linking of resist polymer films is to make the film stable to heat such that it cannot be made to flow or melt. A fully cross-linked resist polymer film is practically insoluble in most solvents, although it can be stripped with oxygen plasma etching. Its plasma etch resistance is superior to a similar film that is not cross-linked. 

Operationally, electron-beam processing is controlled by beam energy, dose, current, processing gas, and substrate temperature. The penetration depth of the electrons into the target material is determined by the energy of the electron 

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Figure 11.49 Effect of electron-beam curing of resists based on poly(methacrylate) platform and hybrid methacrylate/alicyclic polymer platform on polygate etch. Electron-beam curing improves etch resistance by up to 50% relative to the control (uncured) sample. Processing was done in a nitrogen environment of the ElectronCure Electron Beam Process Chamber utilizing these electron-beam parameters 3.75 keV, 6 mA, 2000 pC/cm. The wafer temperature of the standard (Std.) process was not controlled, that for the electron-beam standard cure (ESC) process was kept at a medium temperature, that for the low-temperature (LT) process was maintained at a iow temperature, whiie that for the control was at room temperature. [After R. Dammel, Practical resist processing, SPIE Short Course No. SC616 (2005).]...

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