Simulations of BCl3/Cl2 plasma in an inductively coupled gaseous reference cell

A gas mixture of BCl3/Cl2 is widely used in the microelectronics industry to etch the Al metal layers on semiconductor wafers. An understanding of the plasma chemistry is necessary and crucial to improve the uniformity and etch rate of the metal etch on the wafers. To study the plasma characteristics of metal etch reactors a two-dimensional numerical plasma reactor model is used to simulate the processing etching chemistry. The predictive capability of the model depends sensitively on the accuracy of the plasma chemistry mechanisms, the database, and the surface chemistry that are included in the model. First, the model is validated over a wide range of power, pressure, and gas compositions with the available experimental data. For low-pressure (few to tens of mTorr) etching reactors used in the semiconductor industry, the boundary conditions for the model are very important because of the relatively large gas mean-free paths. The gas phase chemistry is strongly influenced by the surface chemical processes. Unfortunately, the correct boundary conditions for the surface chemistry in the model are extremely difficult to set since the chamber wall condition is determined by the wall temperature, surface type (wall material and the covered chemical species), and the process history (wall coverage) of the reactor. The sensitivity of the surface condition is demonstrated with the aluminum etching chemistry in an inductively coupled plasma gaseous reference cell reactor geometry by performing numerical simulations with different wall recombination coefficients. copyright 1998 American Vacuum Society