P‐7.11: Effect of etching conditions, MoNb thickness on gate profile and CD Bias of ADS Pro TFT.

The etched MoNb/Cu stack film is widely used as gate electrodes for ADS Pro TFTs. The CD Bias and profile angle(PA) are two important performance parameters for wet etching. The product‐specific bottom MoNb thickness and the fluctuation of wet etching conditions(time, temperature, and Cu ion concentration) make it difficult to precisely control the etching quality, thus it is of great significance to identify the influence of the above two factors on CD Bias and PAs. In this paper, the wet etching time, temperature and Cu ion concentration are taken as independent variables, and 11 different etching conditions are arranged based on the uniform experiments design to etch MoNb/Cu samples with two different MoNb thicknesses. The experiments reseluts shows that for the etched two MoNb/Cu stacks (15/300 nm, 30/300 nm) samples, the CD Bias and PAs are in the range of 0.22~0.73 µm and 40~51°, respectively. Both the CD Bias and PAs increase with the bottom MoNb thickness, etching temperature, etching time or Cu concentration, and the PAs increases with CD Bias. The etchant may form a reflux path during the etching process, along which the etching rate decreases. The difference between the etching rates at the top and bottom of the electrode contributes to the increase of PAs and CD Bias with etching severity. In the MoNb/Cu sidewall, MoNb acts as an anode due to the low corrosion potential, and the galvanic effect leads to the acceleration of MoNb etching, which ultimately results in the increase of PA and CD Bias under the thick MoNb. [ABSTRACT FROM AUTHOR]