The Super Chemical Plating Micro Erdaogou Filled Study

At present, ultra large-scale integration (ULSI) copper interconnects are fabricated by the "Damascene" process, in which a layer of diffusion barrier (TaN, TiN, WN etc.) and a copper seed layer were deposited on surface of submicrometer trenches the substrates by physical vapor deposition, and then, the submicrometer trenches were filled with electrodeposited copper, last, the planarization was fabricated by the process of chemical mechanical polishing (CMP). However, with the rapid development of the semiconductor technology and the rapid shrinkage in interconnection dimensions, it is difficult to fill the trenches and holes by bottom up electroplating copper, and so, people try to achieve bottom-up copper filling with the electroless copper plating solution.In this paper, the effects additives on the bottom-up filling in the electroless plating were investigated, and bottom-up copper filling was achieved using formaldehyde as a reducing agent. And the bottom-up electroless nickel filling was first achieved, using sodium hypophosphite as a reducing agent. The formation mechanism of bottom-up copper or nickel filling in the electroless copper or nickel plating bath included of various additions were investigated by electrochemistry method.The content of this thesis is as follows:First of all, the effects of the additives of2-MBT and PE-3650on bottom-up copper filling were studied by the cross-sectional SEM observation. The results indicated the electroless copper deposition was accelerated by an addition of2-MBT alone at a low concentration, and the electroless copper deposition could be inhibited by an addition of PE-3650. However, the inhibition of PE-3650for electroless copper deposition became very strongly with an addition of2-MBT. Because of large molecular weight and low diffusion coefficient of PE-3650, the concentration gradient of PE-3650between the bottom and the surface of the trenches could be formed. On the other hand,2-MBT has small molecular weight and high diffusion coefficient, which caused it to distribute evenly between the bottom and the surface of the trench. And so, the deposition rates of electroless copper on the surface and the opening of trenches were synergy inhibited by the high PE-3650concentration combined with the2-MBT. While the deposition rates of electroless copper in the bottom of trenches was accelerated by very low PE-3650concentration combined with the2-MBT. This thesis completed bottom-up filling used the synergy effect of2-MBT and PE-3650on electroless copper deposition. The effects of2-MBT and PE-3650on the polarization behaviors of the electroless copper plating bath were investigated by the linear sweep voltammetry method and mixed potential theory, and the formation mechanism of the bottom-up copper filling in the electroless copper plating were explained reasonably.This thesis also achieved bottom-up nickel filling by means of the principle and method of bottom-up copper filling in the electroless copper plating. The deposition rate of the electroless nickel and bottom-up filling behavior for different sub-micrometer trenches were also investigated by electroless deposition solution with an addition of PAA (Mw:3000-5000). The result indicated that PAA had a strong inhibition for the electroless nickel deposition, and when the PAA concentration was increased from0to2.0mg/L, the deposition rate of electroless nickel decreased from5.51to2.06μm/h. With a further increase of the PAA concentration, the deposition rate of electroless nickel decreased slowly. Therefore, when PAA concentration was2.0mg/L in electroless nickel bath, the bottom-up filling behaviors of electroless nickel bath with different trenches were investigated, and the cross-section SEM observation indicated the trenches with different widths ranging from80to280nm were all filled completely by electroless nickel. The inhibitions of PAA for both cathodic and the anodic reaction were demonstrated by linear sweep voltammetry (LSV) method.Finally, the effects of2-MBT on deposition rate, surface morphology and the micro structure of deposited copper film were studied in the electroless copper plating solution. The results indicated that electroless copper deposition rate was significantly increased with an addition of1.5mg/L2-MBT, and the deposition rates of electroless copper bath at70℃and40℃were increased from7.91and2.86to10.2and5.24μm/h, respectively, which indicated that2-MBT was used as a good accelerating agent for electroless copper. The acceleration mechanism of2-MBT for electroless copper was studied by a combination of linear sweep voltammetry and mixed potential theory. Meanwhile, the SEM observation indicated the size of depsited copper film became more small and uniform. The Energy Dispersive X-Ray Spectroscopy (EDX) measurement indicated that the purity of the depsited copper was improved with an addition of2-MBT. The surface contact angle measurement indicated that the smooth of the depsited copper film surface was increased with an addition of2-MBT. In addition, the crystallography of depsited copper film in the plating bath containing2-MBT was characterized by X-ray diffraction. The results showed that crystallinity of depsited copper film was increased with an addition of2-MBT.