Advanced plasma etching processes for dielectric materials in VLSI technology

Manufacturable plasma etching processes for dielectric materials have played an important role in the Integrated Circuits (IC) industry in recent decades. Dielectric materials such as SiO₂ and SiN are widely used to electrically isolate the active device regions (like the gate, source and drain from the first level of metallic interconnects) and to isolate different metallic interconnect levels from each other. However, development of new state-of-the-art etching processes is urgently needed for higher aspect ratio (oxide depth/hole diameter—6:1) in Very Large Scale Integrated (VLSI) circuits technology. The smaller features can provide greater packing density of devices on a single chip and greater number of chips on a single wafer.; This dissertation focuses on understanding and optimizing of several key aspects of etching processes for dielectric materials. The challenges are how to get higher selectivity of oxide/Si for contact and oxide/TiN for vias; tight Critical Dimension (CD) control; wide process margin (enough over-etch); uniformity and repeatability. By exploring all of the parameters for the plasma etch process, the key variables are found and studied extensively. The parameters investigated here are Power, Pressure, Gas ratio, and Temperature. In particular, the novel gases such as C₄F₈, C₅F₈, and C₄F₆ were studied in order to meet the requirements of the design rules. We also studied CF₄ that is used frequently for dielectric material etching in the industry. Advanced etch equipment was used for the above applications: the medium-density plasma tools (like Magnet-Enhanced Reactive Ion Etching (MERIE) tool) and the high-density plasma tools.; By applying the Design of Experiments (DOE) method, we found the key factors needed to predict the trend of the etch process (such as how to increase the etch rates, selectivity, etc.; and how to control the stability of the etch process). We used JMP software to analyze the DOE data.; The characterization of the etch processes included measurement of the etch rates, etch profiles, etch depth, top-down images, selectivity and etch margin. The cross-section images were taken on the Hitachi S-4500 Scanning Electron Microscope (SEM, Tokyo, Japan) tool.