The cause of the DC short-circuit of the large array interline transfer CCD is analyzed in this paper, and confirms that the etching residues of the second-layer Al are the main cause of the device failure. The scanning electron microscopy (SEM) is used to investigate the influence of etching process parameters on the etching residue of the second-layer Al in interline transfer CCD. The process conditions of pre etching, primary etching and over etching are optimized, and the etching residue of metal aluminum is eliminated in the three stages. With the optimized process parameters, the second-layer Al etching is carried ou, and the DC yield of the device is increased by 30%.