Christoph Nölscher

High Contrast Single Layer Resists And Antireflection Layers - An Alternative To Multilayer Resist Techniques

Optical lithography is reflection limited within the limits of the image contrast provided by the exposure tool. The introduction of antireflection layers (ARLs) enables the use of high contrast resists which reproduce the optical image within the theoretically maximum possible range. If such resists are available, the need for multilayer resist techniques is appreciably reduced. This work reviews the known lithographic tools that counteract the reflection problem especially in the case of Al-layers, and extends the application of ARLs to silicide, poly-Si and dielectric layers on Si. The results are based on simulations performed with SAMPLE and experimental work on submicron devices.

High Performance Resists Tailored for 248 nm Chemical Amplification of Resist Lines Technology

Different dry developable resist systems operating in positive bilayer (Si-CARL) and negative top surface imaging (Top-CARL) modes were investigated for application in 248 nm lithography. After exposure with the KrF excimer laser projection aligner (NA=0.37), development, aqueous silylation and oxygen reactive ion etching, 0.25 µm structures were obtained as the ultimate resolution of Si-CARL with a topresist containing diazoketone photoactive compounds. The process latitudes for 0.4 µm and 0.5 µm lines and spaces amount to 25% and 30% for exposure and to 3 µm and 3.2 µm for defocus, respectively. Comparable values were determined for an alternative Si-CARL system with a new acid catalysed topresist. The required doses for zero bias exposure are 65-70 mJ/cm2 (diazoketone) and 21 mJ/cm2 (acid catalysed). The Top-CARL resist also utilizes the acid catalysed deprotection chemistry for selective silylation of the exposed areas. The preliminary formulation presented well-shaped 0.35 µm structures at 10 mJ/cm2.

Evaluation Of Multilayer Resists For Submicron Technology

PCM-, trilevel-RIE- and singlelevel-RIE-resist systems are investigated for application in submicron technology. Simulation results of the PCM-technique are compared with experimental results using the K809/PMMA system. Gate and sub-micron contact hole etch results are presented for the Shipley PCM system using PMGI as the planarizing layer. For the trilevel technique using SOG or a-Si as intermediate layer, the loss of linewidth during bottom resist 02-RIE was of main interest. Finally, a dry developing technique, the DESIRE process using the PLASMASK resist, was studied and tested on device wafers.

Search for the optimum numerical aperture

Abstract Results on the dependences of focus and exposure dose latitudes on the numerical aperture of lithographic g-line, i-line, and KrF exposure systems are given for 0.6, 0.8 and 1.0 um lines and spaces. This is done for two different resist systems by both SAMPLE 1.7 simulations and g-line experiments. The data are analysed by the use of k-factors and show some unique behavior that is strongly resist dependent.