Implementation of organic bottom anti-reflective coating in 0.35 μm polycide fabrication

Abstract

In the development of i-line 0.35 μm technology, the reflection from the poly-Si substrates become so severe that notching was observed in all the areas with larger than 2000 A ̊topological difference during the lithographical masking. As a result, microtrench.es and poor electrical characteristics were obtained after etching. By applying 1520 Å of organic bottom anti-reflective coating (organic BARC), the reflection from the substrates was greatly reduced from 50% to less than 5%. Consequently, the design rules developed for i-line 0.35 fim technology could be preserved without microtrench formation. The organic BARC also provided additional advantages of planarizing the different topological features on the substrates. And, its etching rate was about the same as the photoresists. The exposure energy and usable depth of focus latitudes were slightly improved with the application of organic BARC. There were basically no differences in masking linearity and iso-dense bias when comparing the critical dimensions of the photoresists with or without applying the organic BARC. The experimental data agreed with the computer simulation data very well. Furthermore, thickness uniformity and reflectivity uniformity across the wafer and from wafer to wafer were very good and were acceptable to the manufacturing environment. Defect density induced by the additional step of coating the organic BARC was very low. Therefore, the implementation of organic BARC was relatively simple and was essential to reduce the notching produced by substrate reflection in the critical layers of the 0.35 μm devices.