Deposition of thin, uniform layers, or films, of material onto topographically complex surfaces is essential to produce several semiconductor devices for logic and memory. The uniformity of a film in, e.g., a recessed feature such as a via, is measured by the step coverage (SC) which is the ratio between the film thickness at the bottom of the feature and the film thickness at the top of the feature. A fully uniform film would render SC = 1, referred to as a conformal film. Atomic layer deposition (ALD) is generally regarded as the most competent technology for depositing conformal films, and forms part of the backbone in modern semiconductor chip manufacturing. The key to the high conformality in an ideal ALD process is the use of sequential self-limiting surface chemical reactions with precursor molecules, typically, supplied from the vapor phase. A sequential supply of, typically two, different precursors results in a process that alternates between adding one of two types of atoms to the surface in each reaction. However, if the film deposition requires filling of a recessed feature, such as a via or trench, a process that affords SC = 1 will not be sufficient. A perfectly conformal deposition will add a uniform layer of material in the feature to make it more and more narrow until the opening will be too narrow for molecules to diffuse down into the feature, and the film deposition pinch off the feature in the opening, leaving a hole in the middle of the feature. To properly fill a recessed feature, the deposition rate must instead be higher at the bottom of the feature, than at the top. This will lead to a SC > 1, referred to as a super-conformal deposition process. The most successful superconformal deposition processes have been chemical vapor deposition (CVD) processes. CVD relies, like ALD, on a supply of precursor molecules from the gas phase, but in CVD, the precursor supply is constant rather than sequential. This leads to a lower degree of control over the film deposition, as compared to ALD, and typically offers sub-conformal deposition, i.e., SC < 1. But CVD processes can be tuned to afford superconformal deposition. By carefully controlling the reaction rate and gas phase collisions for the precursors, by using lower deposition temperature and lower total pressure, super-conformal deposition zone diagrams has been developed. An alternative approach has been to add molecules which acts as surface inhibitors to the CVD gas mixture. These molecules have a very high sticking probability to the surface and will therefore preferentially inhibit film deposition at the first surface they encounter, which is the opening of the recessed features. 7