Apparatus, system, and method of depositing thin and ultra-thin parylene are described. In an example, a core deposition chamber is used. The core deposition chamber includes a base and a rigid, removable cover configured to mate and seal with the base to create the core deposition chamber and to define an inside and an outside of the core deposition chamber. The core deposition chamber also includes a conduit through a top of the cover. The conduit has a lumen connecting the inside to the outside of the core deposition chamber. The lumen has a length and a cross-section. The cross-section has a width between 50 μm and 6000 μm. The length is less than 140 times the cross-section width. The core deposition chamber can be placed in an outer deposition chamber and can achieve parylene deposition less than 1 μm thick inside the core deposition chamber.