Metal Seed Layer Sidewall Coverage via Simultaneous PVD and RF Plasma Etch
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Solution Overview
Problem
Conventional physical vapor deposition methods for forming metal seed layers in integrated circuits result in non-uniform, directional deposition, leading to excessive thickness at the bottom and inadequate coverage on sidewalls, causing overhangs and variations in interconnect performance across a wafer.
Innovation Solution
Simultaneous physical vapor deposition and radiofrequency plasma etching within an opening in a dielectric layer, with carefully controlled power settings and magnetic fields, to achieve an omni-directional deposition process that ensures uniformity and reduces overhangs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If conventional physical vapor deposition is used to deposit copper seed layer, then deposition speed is high, but sidewall coverage is inadequate and overhang is formed
Solution Approach 1:
The patent combines physical vapor deposition with radiofrequency plasma etching into a single integrated process. The plasma etching component removes excess copper material while the deposition component continuously supplies copper atoms, working synergistically to achieve uniform sidewall coverage without overhang formation, while maintaining high deposition speeds.
Solution Approach 2:
The patent modifies the deposition process parameters by introducing radiofrequency plasma energy and controlling magnetic field conditions. These parameter changes transform the conventional PVD process into a plasma-enhanced process that enables atomic-level control of copper deposition, achieving conformal sidewall coverage and eliminating overhang while preserving high deposition rates.
2Speed
If conventional physical vapor deposition is used, then deposition is rapid, but thickness control is difficult
Solution Approach 1:
The patent implements a feedback mechanism where the plasma etching process continuously removes excess deposited material. This self-regulating feedback loop automatically controls the final copper layer thickness by balancing deposition rate with etch rate, enabling precise thickness control even at high deposition speeds without requiring complex external monitoring systems.
Solution Approach 2:
The patent maintains continuous simultaneous deposition and etching throughout the process. The copper atoms are deposited and immediately processed by plasma to achieve the desired thickness and morphology. This continuous dual action eliminates the need for separate deposition and thickness adjustment steps, maintaining high speed while achieving precise thickness control.
3Ease of manufacture
If conventional physical vapor deposition is used, then deposition is directional, but uniform conformal coating is not achieved
Solution Approach 1:
The patent introduces radiofrequency plasma as an intermediary medium between the copper source and the substrate. The plasma acts as a mediator that transports copper atoms in a controlled manner, enabling them to reach and coat sidewall surfaces uniformly. This plasma intermediary transforms the inherently directional PVD process into an omnidirectional conformal deposition process while maintaining process simplicity.
4Reliability
If copper seed layer thickness is reduced to accommodate barrier layer, then diffusion barrier function is improved, but deposition control becomes more difficult
Solution Approach 1:
The patent applies preliminary anti-action by using plasma etching to preemptively remove potential defects, non-uniformities, and excess material during the deposition process itself. This prevents thickness variations and coating defects before they can compromise the ultrathin seed layer's diffusion barrier function, enabling reliable performance at reduced thicknesses that would be difficult to achieve with conventional methods.
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 method produces a conformal, uniformly thick metal seed layer with reduced overhangs, improving interconnect uniformity and throughput by eliminating the need for separate re-sputtering and additional deposition steps, and maintaining performance consistency across the wafer.
Implementation Method 1
physical vapor deposition of a metal within an opening located in a dielectric layer of a substrate
Implementation Method 2
a radiofrequency (RF) plasma etch of the metal deposited in the opening simultaneously with conducting the physical vapor deposition of the metal
Data Source
AI summary
The present invention provides a method of forming a metal seed layer 100. The method includes physical vapor deposition of seed metal 200 within an opening 140 located in a dielectric layer 135 of a substrate 110. The method also includes a RF plasma etch of the seed metal 200 deposited in the opening 140 simultaneously with conducting the physical vapor deposition of the seed metal 200.