Backside Electroplating for Void-Free TSV Copper Filling
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Solution Overview
Problem
Conventional methods for depositing conductive materials into high aspect ratio features, such as those found in VLSI technology, often result in voids or seams, which are defects that hinder the reliable formation of void-free features necessary for advanced semiconductor applications.
Innovation Solution
A method involving the deposition of a conformal oxide layer, selective removal of the oxide layer from the bottom surface of the feature, and subsequent electroplating through the backside of the substrate to form a metal seed layer and barrier layer, allowing for conformal copper deposition without additives, thereby minimizing defects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional deposition methods are used to fill high aspect ratio features, then the deposition process can be performed with standard equipment and procedures, but voids or seams form within the contact plug
Solution Approach 1:
A conformal oxide layer is deposited on the sidewalls and bottom of the feature before the copper deposition process. This preliminary oxide layer serves as a foundation that promotes uniform copper nucleation and growth, preventing void and seam formation during subsequent electroplating operations.
Solution Approach 2:
The conformal oxide layer acts as an intermediary between the feature substrate and the copper deposit. It provides a controlled interface that facilitates uniform copper deposition by mediating the interaction between the deposition process and the feature geometry, ensuring reliable void-free filling.
2Reliability
If copper deposition is performed in high aspect ratio features, then conductive interconnect material can be deposited, but voids or seams form within the contact plug
Solution Approach 1:
The conformal oxide layer is deposited in advance to prepare the feature surface for copper deposition. This preliminary action creates a favorable surface condition that prevents harmful void and seam formation during the copper filling process, ensuring contact plug integrity.
Solution Approach 2:
The conformal oxide layer, which could be seen as an additional process step or complexity, actually converts the challenging high aspect ratio geometry into a benefit by providing a controlled surface that promotes uniform copper deposition and eliminates defects.
3Manufacturing precision
If electroplating is performed through the backside of the substrate, then conformal copper deposition can be achieved, but additional process steps are required
Solution Approach 1:
Instead of depositing copper from the front side of the substrate through the feature opening, the electroplating process is inverted by flowing current through the backside of the substrate. This inversion enables conformal deposition by reversing the traditional deposition direction, allowing the copper to grow uniformly from the bottom up.
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 enables defect-free, conformal copper deposition in high aspect ratio features, enhancing the reliability and quality of semiconductor interconnects by maximizing plating rates and maintaining simplicity in copper plating chemistry.
Implementation Method 1
depositing a conformal oxide layer over at least one sidewall and bottom surface of a feature
Implementation Method 2
depositing a conformal oxide layer over at least one sidewall and bottom surface of a feature
Implementation Method 3
depositing a metal seed layer on the exposed portion of the silicon substrate at the bottom of the feature
Implementation Method 4
exposing the silicon substrate to an electroplating process by flowing a current through the backside of the silicon substrate to form a metal layer on the metal seed layer
Data Source
AI summary
A method and apparatus for processing a silicon substrate are provided. In some implementations, the method comprises providing a silicon substrate having an aperture containing an exposed silicon contact surface at a bottom of the aperture, depositing a metal seed layer on the exposed silicon contact surface and exposing the silicon substrate to an electroplating process by flowing a current through a backside of the silicon substrate to form a metal layer on the metal seed layer.