A new chemistry for a high-density plasma etcher that improves etch rate loading on the TiN ARC layer when geometries are below 0.5 micron

A series of process tests were conducted on a high density plasma etcher to improve the etch rate loading. Etch rate loading arises mainly from two different factors which are microloading and aspect ratio dependent etch (ARDE). Microloading can be defined as the etch rate non-uniformities due to pattern density variations. ARDE can be explained as etch nonuniformities between lines with different aspect ratios. Microloading is mainly a flow dependent phenomena while ARDE shows dependence on process chemistries as well. In this study, a new chemistry is introduced for etching the titanium nitride (TiN) ARC layer. With the introduction of this new chemistry, microloading for 0.5 micron geometry is improved by almost 50% compared to the values obtained from the baseline process. The new chemistry provides approximately 5:1 selectivity to the underlying oxide, and gives very high selectivity to the aluminum layer. When using this chemistry, the etch rate of the titanium nitride layer is more than a micron per minute. Details of the improvement obtained in etch rate loading and mechanisms that explain the observed trends are provided in the current paper. Different etch chemistries as well as the new chemistry were tried for the titanium nitride ARC layer etch, and a comparative evaluation of the process performance was done based on the different chemistries. Conventional BCl₃/Cl₂ chemistry was mainly used for etching the aluminum bulk layer underneath it