Effect of Chloride on Microstructure in Cu Filled Microscale Through Silicon Vias

Area of Science:

• Materials Science
• Electrochemistry
• Semiconductor Manufacturing

Background:

• Through-silicon vias (TSVs) are critical for 3D integrated circuits.
• Controlling copper (Cu) deposition microstructure in TSVs is essential for device performance.
• Additive chemistry in CuSO4 + H2SO4 electrolytes influences Cu electrodeposition.

Purpose of the Study:

• To investigate the microstructure of copper deposited in TSVs.
• To understand the influence of poloxamine and chloride additives on Cu deposition.
• To correlate microstructure with applied potential and additive concentration.

Main Methods:

• Electron backscatter diffraction (EBSD) was used to analyze the microstructure.
• Copper was electrodeposited in TSVs using CuSO4 + H2SO4 electrolyte.
• Micromolar concentrations of poloxamine and chloride additives were employed.

Main Results:

• Distinct microstructural regions were observed: conformal deposition, seam formation at the bottom, and bottom-up filling.
• Microstructure evolution depended on applied potential and additive concentrations.
• Higher chloride concentrations promoted a (110) growth texture with horizontal growth fronts during bottom-up filling.

Conclusions:

• The microstructure of electrodeposited copper in TSVs is controllable via applied potential and additive levels.
• Additive chemistry, particularly chloride concentration, significantly impacts growth texture and morphology.
• Understanding these relationships enables optimization of TSV filling for advanced semiconductor applications.