In one of the embodiments, the metal conductive layer 400 is formed by an atomic layer deposition technology. It can be understood that the atomic layer deposition technology is a method of plating a substance in a form of a single atom membrane layer by layer on a surface of the base. Compared with an ordinary chemical deposition technology, the metal conductive layer 400 formed by the atomic layer deposition technology has a highly uniform membrane thickness and a consistency on its surface, and can directly form the second opening K2 located above the first opening K1. In some of other embodiments, the metal material layer 420 may be first formed by other chemical deposition processes, and then etched by back-etching to form the metal conductive layer 400 having the second opening K2. Additionally, the second opening K2 may not be formed. In this embodiment, in the case where the atomic layer deposition technology is used to form the metal conductive layer, since the metal barrier material layer 410 and the metal material layer 420 are also formed on a side wall of the first opening K1, the second opening K2 has a width slightly less than the first opening K1.