Electropolishing TSV Copper Facets Without CMP
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Solution Overview
Problem
The existing semiconductor device packaging technologies face challenges in efficiently removing electroplated copper facets and reusing the barrier layer, leading to high costs and environmental waste due to the expense of chemical mechanical polishing (CMP) and its adverse effects on surface stress and corrosion resistance.
Innovation Solution
The method combines electropolishing technology with a wet etch process to remove overburden copper facets, allowing for the reuse of the barrier layer and achieving a smooth, level surface, thereby reducing integration process costs and environmental impact.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If chemical mechanical polishing (CMP) is used to remove electroplated copper facets, then the copper surface can be smoothed and deburred, but the barrier layer is removed and cannot be reused, increasing cost and environmental waste
Solution Approach 1:
The patent extracts the barrier layer removal step from the conventional CMP process by using selective electropolishing. The electropolishing process is configured to remove only the electroplated copper facets while leaving the barrier layer intact through selective dissolution, thus preserving the barrier layer for reuse in subsequent redistribution layers.
Solution Approach 2:
The patent replaces the mechanical CMP process with an electrochemical electropolishing process. Instead of using mechanical abrasion that removes both copper and barrier layer, electropolishing uses electrochemical dissolution to selectively remove copper facets while preserving the barrier layer, eliminating the need for mechanical polishing.
2Manufacturing precision
If chemical mechanical polishing (CMP) is used to remove copper facets, then the surface can be smoothed, but expensive CMP equipment and slurry consumption increase process cost
Solution Approach 1:
The patent replaces the expensive mechanical CMP system with an electrochemical electropolishing system. This substitution eliminates the need for costly CMP equipment and slurry consumption, significantly reducing process costs while achieving the same surface smoothing effect through electrochemical dissolution.
Solution Approach 2:
The patent changes the fundamental parameter of the surface treatment process from mechanical abrasion (CMP) to electrochemical dissolution (electropolishing). By controlling electrochemical parameters such as current density, electrolyte composition, and processing time, the method achieves cost-effective surface smoothing without requiring expensive CMP infrastructure.
3Manufacturing precision
If CMP is used to remove copper facets, then the surface can be flattened, but stress is introduced in the wafer surface structure, adversely affecting corrosion resistance
Solution Approach 1:
The patent replaces the stress-inducing mechanical CMP process with a stress-free electrochemical electropolishing process. Electropolishing dissolves copper facets through electrochemical reactions without applying mechanical stress to the wafer surface, thereby maintaining the intrinsic stress state and corrosion resistance of the underlying barrier layer and wafer structure.
4Productivity
If CMP process is used, then copper facets can be removed, but the barrier layer is removed and cannot be reused, producing waste harmful to the environment
Solution Approach 1:
The patent implements barrier layer recovery by using selective electropolishing to preserve the barrier layer during copper facet removal. The preserved barrier layer can be reused in subsequent redistribution layers, eliminating the need to discard and re-deposit barrier material, thereby reducing environmental waste and improving process efficiency.
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 approach effectively removes irregularities and stressed layers, enables the reuse of the barrier layer, decreases the cost of TSV integration processes, and lowers the industrialization threshold for TSV technology by using electropolishing to smooth and deburr the metal surfaces without the need for CMP.
Implementation Method 1
The purpose of the process of electrochemical polishing or electropolishing is to produce metal surfaces of high purity, and to smooth and deburr the metal surfaces
Implementation Method 2
Taking advantage of electropolishing technology combined with a wet etch process to remove the surface overburden copper produced in previous ECD process
Implementation Method 3
The electroplating deposition ('ECD') of copper is the main technology for through-silicon via ('TSV') filling in advanced packaging
Data Source
AI summary
A method for avoiding using CMP for eliminating electroplated copper facets and reusing barrier layer in the back end of line (“BEOL”) manufacturing processes. Electropolishing is employed to remove the deposited surface metal, stopping at the barrier layer to form a smooth surface that may be utilized in subsequent steps. The method is suitable for the electropolishing of metal surfaces after formation of filled vias for through-silicon via processes employing metals such as copper, tungsten, aluminum, or alloys thereof. The remaining barrier layer may be reused to fabricate the redistribution layer.