Plasmas are widely used in the microelectronics industry for the fabrication of computer chips, i.e., in plasma etching and deposition of different materials. Nowadays there is increased interest for the use of very complex gas mixtures, such as based on CHxFy, sometimes even in combination with HBr, Cl2 and O2. In this project, we wish to obtain a better understanding of the plasma chemistry in several CHxFy plasmas, i.e., CHF3, CH2F2 , CH3F and CF4, by means of a computer model. For this purpose, we will make use of the hybrid plasma equipment model (HPEM). A reaction set will be created, based on a large number of plasma species, including various molecules, radicals, ions, excited species, as well as the electrons. These species react with each other in a large number of collisions, namely electron-neutral, electron-ion, ion-ion, ion-neutral and neutral-neutral reactions. A list of all possible reactions will be constructed, along with the corresponding cross sections and reaction rate coefficients. Subsequently, for every plasma species the various production and loss processes need to be specified, for solving the continuity equations. The transport of the species will be described based on diffusion, migration and advection. The electric field distribution inside the plasma will be calculated self-consistently from the charged species densities by solving Poisson's equation. Typical results of this model include the species densities, fluxes and energies, the electromagnetic field distribution, and information on the importance of various reactions in the plasma.