Papers by Keyword: Backside Cleaning

Abstract: Wet chemicals for ruthenium (Ru) etching are required for the formation of reliable Ru interconnects in advanced semiconductor technology nodes. In the present study, a novel alkali wet etchant, referred to as TK-1, has been developed in order to overcome issues with conventional Ru etchants, such as a low etch rate and the formation of toxic RuO₄ gas. Regardless of the Ru deposition process, TK-1 exhibits a high Ru etching selectivity of greater than 100 relative to dielectric and liner materials. It also suppresses the production of RuO₄ during the etching process. TK-1 has potential applications for Ru recess etching during fully self-aligned via fabrication.

Abstract: For EUV lithography, a reflective mask is essential because of use of the strong energy, wavelength of 13.5 nm. The EUV mask consists of multi-layered, multi-material structure and is susceptible to various contaminants. Since EUV lithography process should be used in a high vacuum environment, an electrostatic chuck (ESC) is used to fix or hold the EUV mask using electrostatic force. In general, in order to use ESC chuck, it needs a thin conductive layer (CrN layer) on the backside. However, the contact points of the electrostatic pin chuck can make exfoliation of conductive CrN layer producing CrN particles. If these particles are present on the backside of the mask, CD or DOF may be affected during EUV exposure. The 1 μm particle can leads to a gap radius of 42mm [4]. Moreover, these backside particles may travel to the front side. Therefore, backside cleaning should be performed to remove particles from the mask backside surface.

Abstract: of preventive backside cleaning steps. These cleaning steps can be introduced after processes that generated high backside defect counts or right before a lithographic wafer exposure. In this study that was performed at imec’s 300mm cleanroom facility, the study objective was to evaluate the focus spot reduction performance of a stand-alone scrubber in a case study featuring known focus spot generating equipment sets. . In the first part of the study, monitoring of various production tools in terms of backside cross-contamination was done. A set of equipment’s that generated high backside defect counts was selected for generating adequate backside contaminated test material for the cleaning evaluation. This backside contaminated test material was used in our cleaning experiments and evaluation of focus spot reduction by performing leveling tests on an immersion scanner that was able to measure out of plane deviations.

Abstract: In this study, we used an SEZ single-wafer spin-processor to develop a single backside cleaning solution able to remove any metallic or exotic contaminants by etching a few angstroms of the wafer backside, whatever its coating (no coating, Si3N4 or SiO2). An H2O:H2O2:H2SO4:HF mixture was selected because it allowed independent control of the etch rate on the 3 materials of interest, without roughening to much the silicon surface. Chemistry efficiency was then checked on wafers intentionally contaminated with various metals, and on “production wafers” contaminated during exotic materials deposition or classical copper processes.

Abstract: In this work the removal of different metallic and particulate contaminants relevant for high-k/metal gate processing is studied. Best cleaning efficiency of both silicon and nitride substrates is achieved using a HF/HNO3-based cleaning resulting in a particle removal efficiency higher than 90% and metal removal down to 1010 at/cm2.