The organic-inorganic hybrid perovskite (OIHP) has high photoelectric efficiency and excellent photoluminescence properties. Based on these optical properties, it is widely used in applications including photo-light emitting diodes (LED), photodetectors, and solar cells. In the case of the solution manufacturing, many studies have been conducted on the manufacturing method because it can be synthesized simply and Reasonable in cost. However, in the long term, stability issues remain unresolved. When the perovskite is exposed to moisture and oxygen in the atmosphere the rate of degradation of the perovskite becomes faster. This phenomenon is closely related to the stability of the device when applied to the aforementioned applications. Defects such as vacancies and grain boundaries in metal halide-based perovskites (MHPs) can lead to the diffusion or desorption of cations/anions, which substantially degrade the crystallinity and lower the performance of the devices. Therefore, the stability enhancement of the perovskite crystal structure is an essential requirement for commercial device applications. Among the various approaches, surface passivation using ternary organic ammonium halide has been extensively studied. Ternary organic ammonium halide synthesizes 2D phase perovskite through substitution with cations at A site in the perovskite structure of ABX₃ or filling the grain boundaries or terminating the halide ion vacancies. it is desired to enhance the structural integrity of as-prepared perovskite crystals. However, most of the studies are using the solution based method. The solution manufacturing must be replaced in that the surface of the film is very rough due to the randomly deposited crystal domains and that other solvents that accelerate the degradation of the perovskite are necessarily used. Here, we present an optimized surface stabilization process of the MHP thin films prepared from the vapor deposition method. First, methylammonium lead iodide (MAPbI₃) thin films were grown via two steps of PbI₂ deposition and perovskite conversion process. The as-grown MAPbI₃ thin films were then treated with phenethylammonium iodide (PEAI) vapor, a surface passivating agent. The introduction period and time were controlled such that the PEAI was simultaneously evaporated with methylammonium iodide (MAI) or independently introduced onto the MAPbI₃ films. Combined analyses of SEM, XPS, XRD, and PL confirms that the post-introduction of PEAI for 2 min show the most enhanced structural stability and integrity. Our results offer an important insight into the process optimization for the stability enhancement of vapor-deposited perovskite thin films.