Substrate Plating Method for Void-Free Copper Trench Filling
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Solution Overview
Problem
Current methods for electroplating copper into large trenches for three-dimensional semiconductor packaging face challenges such as saturation of plating accelerators leading to uneven plating rates and insufficient copper ion supply, resulting in prolonged processing times and void formation in deep trench regions.
Innovation Solution
A substrate plating method involving first plating with a plating accelerator, followed by reverse electrolytic processing to remove the accelerator from the surface, and subsequent plating at a constant electric potential using a solution without accelerators, with increased chloride ion concentration to promote uniform copper deposition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If plating accelerator is added to promote copper deposition in trenches, then plating rate in deep regions improves, but plating accelerator becomes saturated on surface leading to uneven plating rates
Solution Approach 1:
The plating process is divided into multiple sequential stages: initial plating with accelerator, accelerator removal, and final plating without accelerator. This segmentation allows different plating conditions to be applied at different times, preventing accelerator saturation and maintaining uniform plating rates throughout the process.
Solution Approach 2:
The plating accelerator is removed before the final plating stage to prevent saturation effects. By performing this removal action preliminarily, the system ensures that the accelerator does not accumulate on the surface and cause non-uniform plating in subsequent stages.
2Quantity of substance
If plating time is extended to fill deep trenches, then copper ion supply becomes insufficient, but shortening plating time results in incomplete trench filling
Solution Approach 1:
The plating accelerator is removed in advance before the final plating stage to prevent saturation. This preliminary removal action allows the final plating to proceed with optimal accelerator levels, maintaining high plating rates without requiring excessive time extensions that would deplete copper ion supply.
Solution Approach 2:
The plating conditions are dynamically changed by removing the accelerator at specific intervals. This parameter change prevents the system from entering a saturation state, allowing sustained high-speed plating throughout the process without extending total processing time.
3Productivity
If plating accelerator concentration is increased to maintain plating efficiency, then void formation increases in deep trench regions, but decreasing concentration reduces plating efficiency
Solution Approach 1:
The plating process is segmented into stages with different accelerator concentrations. The initial stage uses higher accelerator concentration for rapid deposition, while the final stage uses reduced or zero accelerator to prevent void formation, thus maintaining both efficiency and reliability.
Solution Approach 2:
The accelerator removal step is performed preliminarily before the final plating stage to prevent void formation. By removing the accelerator in advance, the system ensures that high accelerator concentration does not persist into stages where it would cause voids, while still benefiting from high efficiency in earlier stages.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This method ensures uniform copper plating into fine recesses without voids, maintaining plating efficiency throughout the process by controlling the balance of plating accelerator and inhibitor adsorption, even in deep trench regions.
Implementation Method 1
A plating accelerator, such as SPS, when added to the plating solution, is considered to be adsorbed onto the plating surface upon plating and weakens the plating inhibiting effect of PEG and Cl−
Implementation Method 2
The leveler that has been adsorbed onto the plating surface is considered to be consumed with the progress of plating either by being taken into the copper plated film or by decomposition
Implementation Method 3
Electroplating is mainly used for the filling of copper because preferential progress of plating from the bottoms of trenches becomes possible by carrying out electroplating using a plating solution which is an acidic copper sulfate solution
Implementation Method 4
the concentration of the leveler in the plating solution, which has intruded into the depth of a recess such as the trench 21, decreases by a diffusion-controlling mechanism
Data Source
AI summary
A substrate plating method makes it possible to plate a metal, such as copper or a copper alloy, uniformly into fine recesses in a substrate without forming voids in the metal-filled recesses. The substrate plating method for filling a metal into fine recesses in a surface to be plated of a substrate includes carrying out first plating on the surface to be plated in a plating solution containing a plating accelerator as an additive, carrying out plating accelerator removal processing by bringing a remover, having the property of removing or decreasing the plating accelerator adsorbed on the plating surface, into contact with the plating surface, and then carrying out second plating on the plating surface at a constant electric potential.