A method of forming an interlayer dielectric (ILD) layer. A dielectric layer containing boron and phosphorous is formed overlying a substrate. A plasma treatment is subsequently performed on the dielectric layer using argon or nitrogen as a process gas. A capping layer is formed in-situ overlying the dielectric layer to serve as the ILD layer with the dielectric layer. A reflow process is subsequently performed on the ILD layer. A method for preventing formation of etching defects in a contact is also disclosed.