A thin film coating apparatus is disclosed, including a sample holder rotatably configured in the apparatus. The sample holder is coupled to a motor configured to rotate the sample holder. The apparatus includes a heating chamber disposed around the sample holder. The heating chamber is configured to supply heat to a substrate loaded on the sample holder. The apparatus includes a top cover configured to selectively allow access to the substrate loaded on the sample holder. A controller is configured to: detect a speed of rotation of the sample holder; and operate the top cover to allow access to the substrate loaded on the sample holder when the detected speed of rotation of the sample holder is within a predefined range.