Study on Quantitative Adjustment of CD Bias and Profile Angle in the Wet Etching of Cu-Based Stacked Electrode

The electrodes of thin film transistors (TFTs) have evolved from conventional single Cu layers to multi-layered structures formed by Cu and other metals or alloys. Different etching rates of various metals and galvanic corrosion between distinct metals may cause etching defects such as rough or uneven cross-sectional surfaces of stacked electrodes. Therefore, the etching of stacked electrodes faces new challenges. CD Bias and profile angle (PA) are two main performance indicators for the wet etching of TFT electrodes. Adjusting CD Bias and PAs quantitatively and evaluating their stability accurately is crucial to ensure the performance and yield of TFTs. In this work, the bilayer MoNb/Cu-stacked electrodes with different MoNb thicknesses and the MoNb/Cu/MTD triple-layered electrodes were prepared, and the influence of MoNb thickness and stacked structure on the CD Bias and PAs was investigated. It is found that in the H₂O₂-based etchant, the order of corrosion potential is E_MTD < E_MoNb < E_Cu; both MoNb/Cu and Cu/MTD will form a primary cell with MoNb or MTD as the anodes. The CD Bias and PAs of the MoNb/Cu bilayer structure also increase with MoNb thickness, but those of the MoNb/Cu/MTD triple-layered structure decrease with the introduction of the top MTD film. Finally, regression equations between CD Bias or PA and etching parameters were established based on the results of uniform experiments, and the 95% confidence intervals for CD Bias and PA were proposed after the Monte Carlo simulation. These obtained results provide a basis for quantitative adjustment of CD Bias and PA and precise control of etching stability.