Micro-range uniformity control of the etching profile in the OLED display mass production referring to the PI-VM model

Abstract

The high-value process strategy in the organic light emitting diode display manufacturing requires strict etching profile control to obtain the normal performance of the display pixels because of the correlation between the etched structure of the processed pattern and the current–voltage characteristics of the pixels. The critical dimension, etch depth, and sidewall angle area are important management points of the etching profile. Because of two-dimensional continuous characteristics of the display as the numerous arrays of the thin film transistors, the etching profiles should be controlled in the analog way rather than only the fact of spec-in or -out. Therefore, the sheath properties which govern the ion flux-driven etching effect and the polymer passivation characteristics of the sidewall of the etching hole are needed to be tailored spatially even in the micro-range. The embossing structured electrode surface applied for the large area display manufacturing dry etching process causes micro-scale non-uniformity of the sheath and passivation properties, and introduces the process faults. To control this micro-range non-uniformity of the etching profiles, a PI-VM (Plasma Information based Virtual Metrology) model was developed by applying the PI parameters. PI parameters include the information on the sheath potential for electronegative plasmas and the heat transfer properties in the chamber. PI parameterization utilized a big data pool of the optical emission spectroscopy and equipment engineering system data accumulated during the mass production. The developed PI-VM model could predict the fault with 80% accuracy, and analysis of the highly contributing PI parameters to the events could give the way to control the manufacturing.