Selective Accelerator Removal for Copper Electroplating Planarity
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Solution Overview
Problem
Current methods for copper electroplating in damascene processes face challenges with overburden deposition, leading to excessive metal usage, costly planarization techniques, and non-uniform topography, particularly in features with varying aspect ratios, resulting in defects and reduced throughput.
Innovation Solution
The implementation of selective accelerator removal (SAR) and selectively accelerated plating (SAP) techniques, which involve controlling the deposition of metal accelerators to minimize overburden and achieve uniform planarization without physical contact, using membrane-mediated elements and localized liquid treatment for isotropic wet etching, to reduce topography variations and enhance planarization efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional electroplating is used to fill high aspect ratio features, then complete void-free metal fill is achieved, but excessive metal overburden is deposited requiring costly planarization
Solution Approach 1:
The patent applies different properties to different regions of the substrate by using a dual-additive system where accelerators concentrate in high aspect ratio features to enhance plating rate locally, while suppressors remain on planar regions to limit metal deposition. This local differentiation enables precise control of metal fill in recessed features without excessive overburden on planar areas, resolving the contradiction between complete feature fill and minimal excess metal deposition
Solution Approach 2:
The patent changes the chemical parameters of the electroplating bath by incorporating specific accelerator and suppressor additives with controlled concentrations. The accelerators (e.g., mercapto compounds) and suppressors (e.g., polymeric inhibitors) create localized variations in plating rate through chemical concentration gradients, enabling selective acceleration in high aspect ratio features while maintaining parameter control to minimize overall metal consumption and overburden
2Productivity
If plating bath additives are used to promote rapid bottom-up filling, then high aspect ratio features are filled more rapidly without voids, but topography variations increase creating non-uniform surfaces
Solution Approach 1:
The patent creates local quality differences by having accelerators selectively concentrate in high aspect ratio features through geometric concentration effects, while suppressors remain distributed on planar regions. This spatial differentiation allows rapid filling in recessed areas without creating excessive topography variations on planar surfaces, as each region receives the appropriate chemical environment for its specific geometry
Solution Approach 2:
The patent implements a feedback mechanism where the plating bath additives dynamically respond to surface geometry during electroplating. As metal deposits and changes the geometry of features, the concentration of accelerators and suppressors automatically adjusts based on the evolving surface topology, maintaining optimal filling rates while controlling topography development throughout the plating process
3Manufacturing precision
If physical contact planarization methods are used to remove overburden, then surface planarity is improved, but device complexity and process costs increase
Solution Approach 1:
The patent replaces mechanical planarization systems (such as CMP equipment with abrasive pads) with a chemical system using electroplating bath additives. The chemical field action of accelerators and suppressors during electroplating inherently controls metal deposition to achieve planarity without requiring subsequent mechanical removal processes, thereby eliminating complex mechanical planarization equipment and processes while maintaining surface uniformity
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 reduces excess metal deposition, minimizes defects, and improves planarity, enabling efficient filling of features with reduced overburden and maintaining high throughput, while avoiding physical contact and associated costs and defects.
Implementation Method 1
electrochemical deposition techniques to deposit primary conductor films on semiconductor substrates
Implementation Method 2
the geometrical concentration of a strongly adsorbed plating bath 'accelerator' bound within and on the walls of the feature
Implementation Method 3
The rubbing element is pressed against the substrate face to rub thereon and remove deposited accelerator species from the substrate face
Data Source
AI summary
Plating accelerator is applied selectively to a substantially-unfilled wide (e.g., low-aspect-ratio feature cavity. Then, plating of metal is conducted to fill the wide feature cavity and to form an embossed structure in which the height of a wide-feature metal protrusion over the metal-filled wide-feature cavity is higher than the height of metal over field regions. Most of the overburden metal is removed using non-contact techniques, such as chemical wet etching. Metal above the wide feature cavity protects the metal-filled wide-feature interconnect against dishing, and improved planarization techniques avoid erosion of the metal interconnect and dielectric insulating layer. In some embodiments, plating of metal onto a substrate is conducted to fill narrow (e.g., high-aspect-ratio feature cavities) in the dielectric layer before selective application of plating accelerator and filling of the wide feature cavity.