sA room temperature copper etching process, which is based on a novel plasma-copper reaction, has been studied. The copper morphology, pattern variation, reaction product, and reaction mechanism have been examined and analyzed. Effects of process parameters, e.g., pressure, temperature, and plasma power, to the reaction were also studied. The result shows that copper can be etched into a vertical profile at a high rate at 25°C. This new process is potentially important to the multilevel copper process. Copper has been the ideal interconnection material for VLSI since the beginning of the industry. Compared with aluminum, copper has the advantages of lower resistance, less electro- migration, and negligible hillocks formation. For advanced circuit applications, copper has to be etched into fine lines with a vertical profile. A plasma etching method has to be used to reach these goals. However, copper cannot be etched with the conventional plasma process because copper compounds formed in the plasma process are non-volatile. In order to remove these compounds, excessive energy sources, such as UV, IR, laser, high temperature, high ion bombardment energy, or high-density plasma source, have to be added to the reactive ion etching tool (1-4). Although high copper etch rates can be obtained with these methods, the equipment design becomes complicated. Most of these methods are not applicable to large area substrates because of the poor etch uniformity. Currently, the chemical-mechanical polishing (CMP) method is most popular in etching copper fine patterns. However, CMP is a tedious process that requires new types of equipments. In addition, CMP has problems in the fabrication of sub-100 nm devices (5). Therefore, it is desirable to develop a copper dry etching process that has a high etch rate, supplies a vertical wall profile, and can be done at room temperature. Recently, the basic concept of a new copper etching method based on a novel plasma-copper reaction has been reported (6). The detailed information was not available. In this paper, results on process limits, material properties, and reaction mechanism of this new method will be reported.
展开▼
