Gradient barrier layer for copper back-end-of-line technology

• Main Authors: Liou, Fu-Tai, Hung, Cheng-Yu, Yew, Tri-Rung
• Format: Patent
• Language: English
• Published: 02.10.2003

The present invention is directed to a structure of a gradient barrier layer. The gradient barrier with a composite structure of metal/metal salt of different composition/metal such as Ta/Ta x N 1−x /TaN/Ta x N 1−x /Ta (tantalum/tantalum x nitride 1−x /tantalum nitride/tantalum x nitride 1−x /tantalum) is proposed to replace the conventional barrier for copper metallization. The gradient barrier can be formed in a chemical vapor deposition (CVD) process or a multi-target physical vapor deposition (PVD) process. For CVD process, using the characteristics of well-controlled reaction gas injection, the ratio of tantalum (Ta) and nitrogen (N) can be modulated gradually to form the gradient barrier. For the multi-target PVD process, the gradient barrier is formed by depositing multi-layers of different composition Ta x N 1−x films. After subsequent thermal cycle processes such as metal alloy, the inter-layer diffusion occurs and a more smooth distribution of Ta and N is achieved for the gradient barrier. The advantages of forming the gradient barrier include a well-controlled process, a strong adhesion between via and landing metal, more uniform step coverage, and less brittle to reduce crack.