Titanium Sputtering Target Asymmetry Reduces Contamination
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Solution Overview
Problem
Conventional sputtering targets and process kit components in titanium sputtering chambers face issues such as titanium material accumulation on chamber surfaces leading to contamination, electrical shorts, and debonding due to thermal expansion stresses, while existing components do not effectively capture sputtered deposits, resulting in frequent downtime for cleaning.
Innovation Solution
A sputtering target with a central cylindrical mesa and peripheral inclined annular rim, along with a deposition ring and cover ring having specific surface roughness and geometries, and a shield assembly designed to reduce sidewall sputtering and prevent component sticking, allowing for increased accumulation of sputtered material on kit components without causing damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a conventional right-cylinder sputtering target is used, then the target structure is simple and easy to manufacture, but titanium material accumulates on chamber surfaces causing contamination and electrical shorts
Solution Approach 1:
The target is divided into two distinct geometric zones: a central cylindrical mesa and a peripheral inclined annular rim. This segmentation allows the sputtering surface to be split between vertical sidewalls (mesa) and inclined sidewalls (rim), directing titanium deposits to different locations and preventing accumulation on chamber surfaces that would cause contamination and electrical shorts
Solution Approach 2:
The target geometry transitions from a symmetric right-cylinder to an asymmetric structure with a central mesa and peripheral inclined rim. The asymmetric inclined rim (with slope angle α between 5-15 degrees) redirects sputtered titanium material away from chamber surfaces, solving the contamination problem while maintaining manufacturing feasibility
2Productivity
If conventional targets with vertical sidewalls are used, then material deposition is efficient, but sputtered material flakes off during thermal cycles and contaminates substrates
Solution Approach 1:
The inclined annular rim creates asymmetric sputtering geometry where titanium material deposits on the inclined surface at an angle, forming a stable configuration that adheres strongly during thermal expansion and contraction cycles, preventing flake formation and substrate contamination while maintaining deposition efficiency
3Ease of repair
If process kit components are made smooth, then cleaning is easier, but sputtered deposits do not adhere well and flake off contaminating substrates
Solution Approach 1:
The process kit components are given a localized rough surface treatment (surface roughness of 50-200 microinches) specifically on the surfaces that contact sputtered titanium deposits. This local quality change enhances deposit adhesion through mechanical interlocking while maintaining overall component cleanability, preventing flake formation during thermal cycles
4Object-affected harmful factors
If components are designed to capture maximum sputtered deposits, then contamination is reduced, but components stick together during removal causing damage
Solution Approach 1:
Components are designed with differentiated surface properties: surfaces facing the target (deposition surfaces) have rough textures to maximize titanium deposit capture and adhesion, while opposing surfaces and removal interfaces have smooth finishes to minimize sticking and facilitate easy separation during maintenance, solving both contamination and component damage issues
5Object-affected harmful factors
If a sputtering target with inclined rim is used, then sidewall sputtering is reduced, but the target geometry is more complex
Solution Approach 1:
The target employs an asymmetric geometry with a central cylindrical mesa and a peripheral inclined annular rim. This asymmetric design effectively reduces sidewall sputtering by directing material deposition away from chamber surfaces, while the geometry remains manufacturable using conventional techniques, balancing performance improvement with manufacturing complexity
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 solution significantly reduces contamination and downtime by minimizing titanium deposition on chamber surfaces, preventing electrical shorts, and enhancing the adhesion of sputtered material, thereby increasing the number of substrates that can be processed before chamber maintenance is required.
Implementation Method 1
In a magnetron PVD sputtering chambers, a target is sputtered in a magnetic field causing sputtered target material to deposit on a substrate facing the target.
Implementation Method 2
a process gas comprising an inert or reactive gas is supplied into the chamber, and the target is electrically biased while the substrate maintained at an electrical floating potential to generate charged plasma species in the chamber which sputter the target
Implementation Method 3
portions of the titanium layer in contact with the silicon are converted to titanium silicide layers by annealing
Implementation Method 4
the diffusion barrier layer below a metal conductor, includes a titanium oxide layer formed by sputter depositing titanium on the substrate and then transferring the substrate to an oxidizing chamber to oxidize the titanium by heating it in an oxygen environment to form titanium oxide
Data Source
AI summary
A process kit for a sputtering chamber comprises a deposition ring, cover ring, and a shield assembly, for placement about a substrate support in a sputtering chamber. The deposition ring comprising an annular band with an inner lip extending transversely, a raised ridge substantially parallel to the substrate support, an inner open channel, and a ledge radially outward of the raised ridge. A cover ring at least partially covers the deposition ring, the cover ring comprising an annular plate comprising a footing which rests on a surface about the substrate support, and downwardly extending first and second cylindrical walls.