Low-Si Cobalt Sputtering Target for Thick Cu Cap Layers
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Solution Overview
Problem
Conventional cobalt sputtering targets fail to provide sufficient barrier properties and adhesiveness for thick film cap layers in Cu wiring structures due to high Si content, leading to silicide formation and reduced sputtering efficiency, especially when target thickness exceeds 3 mm.
Innovation Solution
A cobalt sputtering target with a purity of 99.99% to 99.999% and Si content of 1 wtppm or less, with a thickness of 4 mm to 15 mm, where the Pass-Through-Flux (PTF) value satisfies the relational expression (P−80)/T≥−2.5, is developed to suppress silicide conversion and enhance sputtering performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the target thickness is increased to 3 mm or more to form thick film cap layers, then the barrier properties and adhesiveness are improved, but the sputtering performance deteriorates due to magnetic properties
Solution Approach 1:
The patent changes the chemical composition parameters of the cobalt target by reducing Si content to 1 wtppm or less and controlling purity to 99.99% or higher. This parameter change resolves the contradiction by preventing silicide formation that would otherwise deteriorate sputtering performance in thick targets, enabling both thick film formation and maintained sputtering efficiency
2Strength
If the target thickness is increased to 3 mm or more to form thick film cap layers, then the barrier properties and adhesiveness are improved, but the target replacement frequency increases and costs increase
Solution Approach 1:
By changing the purity parameter to 99.99% or higher and controlling Si content to 1 wtppm or less, the patent enables thick targets (3 mm or more) to maintain stable sputtering performance without premature degradation, thereby reducing target replacement frequency and associated downtime
3Quantity of substance
If Si content in cobalt is high, then general impurity levels are acceptable, but silicide formation occurs which deteriorates barrier properties and adhesiveness
Solution Approach 1:
The patent applies parameter change by strictly limiting Si content to 1 wtppm or less in the cobalt target. This prevents Si from forming silicides with Cu or Ta, thereby maintaining reliable barrier properties and adhesiveness while still allowing the target to function effectively
Solution Approach 2:
The patent converts the potential harm of Si impurity into a benefit by reducing Si content to such low levels that Si no longer forms detrimental silicides, while the presence of trace Si does not significantly impact target performance, thus achieving high reliability without requiring absolute purity
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 improves barrier properties, adhesiveness, and sputtering efficiency by reducing Si content and optimizing the target structure, enabling stable high-speed deposition even with thick targets.
Implementation Method 1
deposition based on PVD (physical vapor deposition method), which enables stable deposition as well as ultrathin and uniform deposition by utilizing techniques such as reactive sputtering and reverse sputtering
Data Source
AI summary
A Co sputtering target having a purity of 99.99% to 99.999% and a Si content of 1 wtppm or less. Provided is a Co sputtering target capable of improving barrier properties and adhesiveness by suppressing conversion into highly reactive silicide by a reduction in the Si content in cobalt.