USJ Dopant Bleaching and Device Effects in Advanced Microelectronic Plasma Enhanced Resist Strip Processing
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1070-E01-12
USJ Dopant Bleaching and Device Effects in Advanced Microelectronic Plasma Enhanced Resist Strip Processing Frank Wirbeleit1, Volker Grimm1, Christian Krüger1, Christoph Streck1, Roger Sonnemans2, and Ivan Berry2 1 Technology Department, Advanced Micro Devices (AMD), Wilschdorfer Landstrasse 101, Dresden, 01109, Germany 2 Axcelis Technologies, Inc., Beverly, MA, 01915 Abstract The impact of low temperature plasma resist strip on doped silicon surfaces and microelectronic device performance is investigated using different chemical gas mixtures. In this investigation, different plasma treatments where applied on non-structured and structured silicon on insulator (SOI) wafers, post ultra shallow surface implants. The dopant bleaching and oxide loss effects in conjunction with plasma surface treatments were analyzed by time of flight secondary ion mass spectrometry (TOF-SIMS) and electrical measurements of microelectronic test devices. As the result, a long range plasma radiation induced dopant activation and diffusion is separated from the effects from surface oxide loss and re-oxidation processes. The data suggests the necessity for optimization of plasma resist strip processes for device improvements. Introduction When polymeric photoresist materials are subject to ion bombardment, volatile compounds and gases are released1,2. At doses greater than about 1x1015 ions/cm2, the surface of the resist has been transformed into a carbonaceous material to the depth of about twice the ion range3,4. Removal of this carbonaceous, or “crust” region is difficult and is typically requires a plasma process, because of its ability to efficiently remove the crust material, followed by an acid SPM/APM clean to remove residue and particulates4,5,6,7,8,9,10,11. Scaling devices down in the sub 100 nm range requires ultra shallow implants, which makes devices very sensitive to surface effects. It is well known that plasma processes can impact the junction in multiple ways: (1) plasma processes oxidize the surface or etch the surface oxide causing junction loss,12,13 (2) plasma reactants can bleach out near surface dopants, and (3) plasma can change the chemical bonding of the junction surface possibly leading to vacancy enhanced diffusion14. As junctions depths scale below 150nm, effects of the resist strip and wet clean on junction performance can be significant, especially for heavily amorphized junctions where the enhanced chemical reactivity accelerates the effects11,15,16,17. Multiple resist strips are applied in microelectronic technology during the integrated circuit manufacturing process, clean and surface treatment processes gain more and more attention therefore. The selected plasma resist processes for this work are commonly used in advanced microelectronic technology. All of these processes are proofed in production for complete resist removal at low defectivity level in combination with a post wet clean. The investigation of surface oxidation and dopant loss effects in advanced resist strip processing is the ana
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