TSV Metallization via Nitridation to Reduce Voids
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Solution Overview
Problem
Conventional lithography and metallization processes face challenges in creating reliable high aspect ratio through silicon via (TSV) structures due to void formation, which affects the reliability of interconnections in 3D integrated circuits.
Innovation Solution
A method involving a nitridation process to convert a surface portion of the metallic barrier layer to a nitride surface layer, enhancing nucleation for subsequent depositions, and a multi-layer metal filling process with selective etching and barrier layers to reduce voids and improve copper metal fill quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional lithography and metallization processes are used to create through silicon via structures, then the manufacturing process is simple, but void formation occurs which reduces reliability
Solution Approach 1:
A copper seed layer is deposited on the sidewalls of the TSV structure before the main copper fill process. This preliminary copper layer provides a nucleation site that enables subsequent copper deposition to proceed uniformly, preventing void formation in the high aspect ratio via structure.
Solution Approach 2:
The patent applies different materials and processes to different regions of the TSV structure. The sidewalls receive a copper seed layer while the bottom receives a tungsten barrier layer. This localized differentiation ensures proper adhesion and prevents voids in critical regions without unnecessarily complicating the entire structure.
2Manufacturing precision
If high aspect ratio through substrate vias are created, then vertical interconnection density is improved, but void formation occurs during metallization
Solution Approach 1:
The copper seed layer is deposited on the sidewalls before the main copper electroplating process. This preliminary layer ensures that copper deposition begins uniformly from the sidewalls, preventing void formation even in high aspect ratio structures where voids are most likely to occur.
Solution Approach 2:
The copper seed layer acts as an intermediary between the dielectric wall and the main copper fill. It provides a transition zone that facilitates uniform copper deposition and prevents the formation of voids by ensuring continuous metal coverage throughout the high aspect ratio via.
3Strength
If the copper seed layer extends to the top surface, then adhesion is improved, but planarization difficulty increases
Solution Approach 1:
The copper seed layer is applied selectively only to the sidewalls of the TSV structure, not to the entire top surface. This localized application maintains strong adhesion where needed (at the dielectric-metal interface) while avoiding the planarization difficulties that would arise from having metal coverage across the entire surface.
Solution Approach 2:
The copper seed layer is segmented to cover only the vertical sidewall region rather than forming a continuous top surface layer. This segmentation allows the top surface to remain planar and suitable for subsequent processing while maintaining adhesion strength at the critical interface regions.
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
The nitridation treatment enhances TSV metallization, reducing voids by more than 50% and improving the reliability of interconnections between semiconductor chips, thereby enhancing the performance and yield of 3D integrated circuits.
Implementation Method 1
A nitridation process converts a surface portion of the metallic barrier layer to a nitride surface layer. The nitride surface layer enhances the nucleation of subsequent depositions.
Implementation Method 2
A first metallic barrier layer is deposited on the sidewalls of the through substrate via
Implementation Method 3
A first metal layer is deposited to fill the through substrate via
Data Source
AI summary
A method providing a high aspect ratio through substrate via in a substrate is described. The through substrate via has vertical sidewalls and a horizontal bottom. The substrate has a horizontal field area surrounding the through substrate via. A first metallic barrier layer is deposited on the sidewalls of the through substrate via. A nitridation process converts a surface portion of the metallic barrier layer to a nitride surface layer. The nitride surface layer enhances the nucleation of subsequent depositions. A first metal layer is deposited to fill the through substrate via. A selective etch creates a recess in the first metal layer in the through substrate via. A second barrier layer is deposited over the recess. A second metal layer is patterned over the second barrier layer filling the recess and creating a contact. Another aspect of the invention is a device produced by the method.