In Situ Seed Layer Etch for Damascene Sidewall Coverage
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Solution Overview
Problem
Conventional seed layer formation methods in damascene structures result in non-uniformity and asymmetry, leading to poor sidewall coverage and reliability issues in interconnect structures, which are exacerbated by the necking effect and overhangs, affecting the quality of electroplated metal lines.
Innovation Solution
A method involving a deposition-etch cycle is used to form a seed layer, where a first deposition step is followed by an in-situ etch step to reduce seed layer thickness, with additional cycles to achieve conformity, and electroplating to fill the openings, ensuring improved uniformity and conformity of the seed layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional PVD method is used to form seed layer, then deposition process is simple, but seed layer profile is non-uniform with poor sidewall coverage
Solution Approach 1:
The seed layer formation is divided into multiple deposition steps with different deposition rates. The first deposition step uses a higher deposition rate to quickly build up the seed layer, while the second deposition step uses a lower deposition rate to improve sidewall coverage and reduce overhangs. This segmentation of the deposition process allows optimization of different regions of the seed layer for different functions.
Solution Approach 2:
The patent employs periodic alternation between deposition and etch steps in a deposition-etch cycle. Multiple cycles of deposition followed by selective etching are performed to progressively improve the seed layer profile. This periodic action allows for controlled modification of the seed layer thickness distribution, removing excessive material from horizontal portions while preserving sidewall coverage.
2Manufacturing precision
If deposition rate is reduced to improve seed layer uniformity, then sidewall coverage improves, but throughput decreases
Solution Approach 1:
The deposition process is segmented into multiple steps with different deposition rates. The first deposition step uses a higher deposition rate to quickly build up the seed layer thickness, while the second deposition step uses a lower deposition rate to improve uniformity. This segmentation allows the process to achieve good uniformity without requiring the entire process to run at a low deposition rate, thus maintaining higher throughput.
Solution Approach 2:
Different regions of the seed layer are given different thicknesses and qualities through the multi-step deposition process. Horizontal portions of the seed layer are made thinner to reduce overhangs, while sidewall portions are maintained at appropriate thicknesses for good coverage. This local differentiation of seed layer quality allows optimization of both uniformity and throughput.
3Loss of time
If single deposition step is used, then process time is short, but necking effect and overhangs occur
Solution Approach 1:
The seed layer formation is segmented into multiple deposition steps followed by selective etching. The first deposition step quickly builds up the seed layer, and the first etch step removes excessive material from horizontal portions. Additional deposition-etch cycles can be performed to further refine the profile. This segmentation eliminates necking effects and overhangs that would occur in a single deposition step.
Solution Approach 2:
The patent performs preliminary deposition to build up the seed layer thickness before performing selective etching to remove excessive material. This preliminary action of depositing material that will later be partially removed allows for better control of the final seed layer profile, preventing necking and overhangs from forming in the first place.
4Shape
If blanket etch is used to remove excess seed layer, then overhangs are reduced, but sidewall coverage is compromised
Solution Approach 1:
The etching process is made selective to different regions of the seed layer. The first etch step selectively removes excessive material from horizontal portions of the seed layer while preserving the sidewall portions. This local differentiation in etching action reduces overhangs without compromising sidewall coverage, as each region of the seed layer is treated differently based on its location and function.
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 method significantly improves the conformity and uniformity of the seed layer, reducing overhangs and asymmetry, resulting in enhanced quality and reliability of metal lines without sacrificing throughput.
Implementation Method 1
copper seed layer 6 (including portions 61, 62, 63—1, and 63—2) is formed, either by physical vapor deposition (PVD), or by electroless plating
Implementation Method 2
performing a first etch step to remove a portion of the seed layer
Implementation Method 3
copper is electro plated into damascene openings
Data Source
AI summary
A method of forming a seed layer of an interconnect structure includes forming a dielectric layer; forming an opening in the dielectric layer; performing a first deposition step to form the seed layer; and in-situ performing a first etch step to remove a portion of the seed layer. The method may further includes additional deposition and etch steps for forming the seed layer.