Superconformal Copper Electrodeposition in Complexed Alkaline Electrolyte

Abstract

This paper examines superconformal filling of trenches during copper electrodeposition from alkaline cupric tartrate electrolyte. Localized bottom-up filling of submicrometer damascene trenches with minimal deposition on the sidewalls and the field around them is observed in electrolyte containing the deposition rate suppressing additive bis-(3-sulfopropyl) disulfide (SPS) for applied potential near that where suppression breakdown is observed. Deposits have rough surfaces and the deposited copper contains large voids. In contrast, conformal filling of trenches is observed in electrolyte containing polyethyleneimine (PEI), the deposits exhibiting macroscopically smoother surfaces with finer scale embedded porosity revealed by scanning electron microscopy. Electrolytes containing both additives yield bottom-up filling, in some cases with dense deposits at the bottoms of the features that transition to the porous structures observed for the PEI containing electrolyte. The feature filling and electrochemical measurements are discussed in the context of existing models for bottom-up deposition. Evolution of suppressor breakdown coupled with the electrical response of the electrochemical cell is of central importance.

3-Mercapto-1-Propanesulfonate for Cu Electrodeposition Studied by in Situ Shell-Isolated Nanoparticle-Enhanced Raman Spectroscopy, Density Functional Theory Calculations, and Cyclic Voltammetry

“…To produce microelectronics with high efficiency and performance, integrated circuits can be produced by Damascene processing to plate Cu into micron and submicron interconnect trenches. This plating of Cu into small trenches and vias requires uniform bottom-up, void-free filling. , To precisely control the rate of Cu deposition at certain locations in the chip structure, various organic agents can be added to the plating solution in combination with chloride or other additives. − For a typical acidic copper sulfate deposition bath, these include accelerators, suppressors, and levelers …”

Modeling of Dendrite Formation as a Consequence of Diffusion-Limited Electrodeposition

“…In the field of electrochemical copper deposition on microstructures Moffat et al developed impressive ways to suppress preferred growth on edges to fill trenches and vias. [13][14][15][16][17][18][19][20][21][22][23] Formation of dendrites is not limited to liquid electrolytes but was observed in solid electrolytes, too. 24 Due to the danger of short circuits through metal dendrites and subsequent detrimental steps possible, the prevention of dendrite formation in general is a crucial part in the development of, e.g., batteries.…”

The Ultrahigh-Rate Growth of Nanotwinned Copper Induced by Thiol Organic Additives

“…In addition to considering the complete via-filling, the microstructure of deposited Cu film/lines is also critically important, especially when the Cu patterns inside the ICs and PCBs become smaller with the view to pursue a higher interconnect density. However, in comparison with the extensive studies on via-filling, 3,[16][17][18][19] the strategy of using organic additives to ameliorate the Cu microstructure by electrodeposition is very few.…”