Conformal Copper Seeding on Ultrathin Liners for Void-Free Filling
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Solution Overview
Problem
Current copper deposition methods in semiconductor manufacturing face challenges with non-conformal deposition and high sheet resistance, leading to issues such as overhangs, voids, and increased line and via resistance in narrow features.
Innovation Solution
Conformal deposition of a thin or ultrathin copper layer on a liner layer, using electroless deposition, which can be catalytic or less noble than copper, allowing for a controlled etching process to achieve a continuous and thin copper seed layer, reducing liner thickness and enhancing copper fill volume.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional copper deposition methods are used, then copper can be deposited in trenches and holes, but non-conformal deposition occurs leading to overhangs and voids
Solution Approach 1:
The patent replaces conventional physical vapor deposition (PVD) or chemical vapor deposition (CVD) methods with electroless deposition. This chemical deposition method allows copper to deposit conformally on the liner layer surfaces through chemical reactions rather than physical processes, eliminating overhangs and voids by ensuring uniform deposition on all surfaces including vertical sidewalls and bottom surfaces of narrow features
Solution Approach 2:
The patent changes the deposition mechanism from physical/chemical vapor deposition to electroless chemical deposition. This parameter change in the deposition process enables conformal copper layer formation with uniform thickness on complex three-dimensional structures, directly addressing the non-conformal deposition issue
2Reliability
If conventional deposition methods are used, then copper can be deposited, but high sheet resistance occurs in narrow features
Solution Approach 1:
The patent replaces conventional deposition methods with electroless deposition, which provides superior conformality and coverage in narrow features. This ensures continuous copper layers with uniform thickness, reducing sheet resistance by eliminating gaps, voids, and non-uniform regions that would increase electrical resistance in narrow interconnect features
Solution Approach 2:
The patent uses a composite structure consisting of a barrier layer and a thin liner layer as the substrate for copper deposition. This composite material system provides both the necessary barrier properties and the catalytic surface needed for electroless copper deposition, enabling continuous copper layers with low sheet resistance in narrow features
3Volume of stationary object
If liner layer thickness is reduced to enhance copper fill volume, then more copper can be deposited, but maintaining continuous copper coverage becomes difficult
Solution Approach 1:
The patent replaces physical vapor deposition with electroless chemical deposition, which can achieve continuous copper coverage on ultrathin liner layers (5-12 Å). The chemical reaction mechanism ensures uniform deposition even on extremely thin substrates, maintaining copper layer continuity while maximizing copper fill volume by using the minimum necessary liner thickness
Solution Approach 2:
The patent changes the deposition method to electroless deposition, which allows for continuous copper layer formation on ultrathin liner layers. This parameter change in the deposition process enables the use of liner layers as thin as 5-12 Å while maintaining copper continuity, thereby maximizing copper fill volume without sacrificing layer continuity
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
Enables void-free copper filling in narrow features with reduced line and via resistance, improving the efficiency and effectiveness of copper interconnect formation in semiconductor devices.
Implementation Method 1
the liner layer includes a catalytic metal or catalytic metal alloy for initiating electroless deposition of copper
Implementation Method 2
conformally depositing a copper layer that is continuous over the liner layer... conformally depositing the copper layer by electroless deposition
Implementation Method 3
exposing the liner layer to a reducing atmosphere or reducing solution to treat the liner layer
Data Source
AI summary
Various embodiments described herein relate to conformal deposition of a copper seed layer on a thin or ultrathin liner layer to enable bulk copper filling of a recessed feature. The copper seed layer may be continuous and thin, where a thickness can be equal to or less than about 30 Å. The liner layer may be very thin, where a thickness can be equal to or less than about 12 Å after deposition of the copper seed layer. In some implementations, the copper seed layer may be deposited directly on an ultrathin liner layer without etching the liner layer. In some implementations, the copper seed layer may be deposited on the liner layer while etching the liner layer to an ultrathin thickness. In some implementations, the copper seed layer is deposited by electroless plating.