The coating prepared by pulsed CVD is thicker at the bottom corner than at the top, while the one prepared by continuous CVD exhibits the opposite result. To understand the surface chemical mechanisms leading to such a drastic improvement in coating conformality by pulsed CVD, the GPC and the SC in 1-mm deep trenches with widths ranging from 250 μm to 1000 μm were investigated for H2 purge durations of 1 s and 5 s. Figure (a) and 4(b) display the variations of GPC and SCs, respectively, for increasing trench width. It can be observed that a longer purge generally results in higher GPCs of both upper and lower sidewalls of the trench, whereas a shorter purge results in higher SCs.