Floating Lower Shield Biasing for Sputter Step Coverage
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Solution Overview
Problem
In sputtering processes for integrated circuits, collimators can adversely affect deposition uniformity and result in ion loss, leading to lower step coverage and electrical conductivity issues due to non-vertically traveling particles impacting the collimator and lower shields.
Innovation Solution
A process chamber design with a collimator and a lower shield that is electrically decoupled from the chamber body using a ceramic spacer, allowing the lower shield to be biased or kept electrically floating to control the electric field and reduce ion loss, thereby improving ion fraction and step coverage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a collimator is used to control particle trajectory and improve step coverage, then vertical particle trajectory is improved, but ion loss to the lower shield increases
Solution Approach 1:
A biasable shield is introduced as an intermediary component between the collimator and substrate. This shield, when biased with appropriate voltage, acts as a mediator to attract and capture ions that would otherwise be lost to the lower shield or chamber walls, thereby reducing ion loss while maintaining the collimator's step coverage improvement function.
Solution Approach 2:
The electrical parameter (voltage) of the lower shield is changed from a fixed grounded state to a biasable state. By applying different voltages to the lower shield, the system can dynamically control the electric field to reduce ion loss to the shield while maintaining effective step coverage through the collimator.
2Reliability
If the lower shield is grounded to the chamber body, then electrical stability is improved, but ion loss to the lower shield increases
Solution Approach 1:
The lower shield is electrically segmented from the chamber body through the use of ceramic spacers. This segmentation allows the lower shield to be independently biased or floated, enabling control over ion loss while maintaining overall electrical stability through proper grounding of the chamber body and controlled connection points.
Solution Approach 2:
Ceramic spacers are introduced as electrical insulators (intermediaries) between the lower shield and the chamber body. These spacers allow mechanical support while preventing direct electrical connection, enabling the lower shield to be biased independently to reduce ion loss while the chamber body remains grounded for electrical stability.
3Manufacturing precision
If collimators are biased to high voltages to control ion fraction, then ion fraction control is improved, but ion loss in the region between collimators and substrate increases
Solution Approach 1:
The biasable shield serves as an intermediary in the electric field between the collimator and substrate. When the collimator is biased to high voltage for ion fraction control, the biasable shield can be independently biased to create a controlled electric field that guides ions toward the substrate while preventing ion loss to surrounding surfaces in the region between collimator and substrate.
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 design enhances deposition uniformity and ion fraction on the substrate, reducing ion loss to the lower shield and improving the electrical conductivity of the deposited metal layer by controlling the electric field and maintaining a more vertical trajectory of particles.
Implementation Method 1
a lower shield disposed in the interior volume about the collimator and coupled to the chamber body at a location below an upper surface of the collimator via a ceramic spacer disposed between the lower shield and the chamber body configured to electrically decouple the lower shield from the chamber body
Implementation Method 2
allowing the lower shield to be biased or kept electrically floating to control the electric field and reduce ion loss, thereby improving ion fraction and step coverage
Implementation Method 3
The collimator provides relatively long, straight, and narrow passageways between the target and the substrate to filter out non-vertically travelling particles that impact and stick to the passageways of the collimator
Implementation Method 4
Sputtering, also known as physical vapor deposition (PVD), is a method of forming metallic features in integrated circuits. Sputtering deposits a material layer on a substrate. A source material, such as a target, is bombarded by ions strongly accelerated by an electric field. The bombardment ejects material from the target, and the material then deposits on the substrate
Data Source
AI summary
Embodiments of process chambers having a collimator are provided herein. In some embodiments, a process chamber includes: a chamber body having sidewalls and a top plate to define an interior volume therein, the top plate configured to support a target in the interior volume; a substrate support disposed in the interior volume opposite the top plate; a collimator disposed in the interior volume between the top plate and the substrate support; and a lower shield disposed in the interior volume about the collimator and coupled to the chamber body at a location below an upper surface of the collimator via a ceramic spacer disposed between the lower shield and the chamber body configured to electrically decouple the lower shield from the chamber body.