Tantalum Sputtering Target Grain Size Control
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Solution Overview
Problem
The challenge in semiconductor device manufacturing is achieving uniform film thickness and reducing resistance variation in barrier films formed by sputtering tantalum targets, especially for fine wiring structures in high-integration semiconductor devices, where traditional methods of controlling crystal orientation alone are insufficient.
Innovation Solution
A tantalum sputtering target with controlled crystal grain size variation between 40% and 60% and an average grain size of 50 μm to 200 μm is produced through specific heat treatment, forging, and rolling processes to achieve uniform film thickness and reduced resistance variation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If traditional sputtering methods with conventional target structures are used, then the manufacturing process is simple, but the film thickness uniformity deteriorates and resistance value variation increases
Solution Approach 1:
The patent applies local quality by creating distinct regions within the target with different crystal grain characteristics. Specifically, it forms a first region with fine crystal grains (5-20 μm) at the sputtered surface for high uniformity, and a second region with coarse crystal grains (50-200 μm) in the interior for structural stability. This spatial differentiation of grain sizes optimizes both film quality and target performance.
Solution Approach 2:
The target structure is segmented into multiple functional regions: a surface layer with controlled fine grains, an interior bulk with coarse grains, and specific grain orientation zones. This segmentation allows each region to perform its specialized function - the fine-grained surface ensures uniform deposition while the coarse-grained interior provides mechanical strength.
2Manufacturing precision
If crystal orientation is controlled to improve film uniformity, then deposition characteristics improve, but resistance value variation cannot be sufficiently reduced
Solution Approach 1:
The patent employs parameter changes by precisely controlling crystal grain size (5-20 μm at surface, 50-200 μm in interior) and crystal orientation (<100> or <110>) through specific thermal processing parameters. The grain size distribution and orientation are controlled by managing austenite grain growth during heating to 700-1500°C and subsequent cooling rates, transforming material properties through thermal parameters.
Solution Approach 2:
The patent applies preliminary action by pre-forming the desired crystal grain structure and orientation through controlled thermal processing before the sputtering process. The austenite grain structure is established in advance by heating to specific temperatures and controlling cooling rates, ensuring the target has the optimal microstructure prior to deposition, which then guarantees consistent film properties.
3Productivity
If the target is used for extended periods, then productivity increases, but film thickness uniformity and resistance value stability deteriorate over time
Solution Approach 1:
The patent applies beforehand cushioning by incorporating a buffer layer with specific crystal grain characteristics between the fine-grained surface region and the coarse-grained interior region. This buffer layer, with intermediate grain size and specific orientation, cushions and distributes stress during sputtering, preventing crack propagation and maintaining target performance consistency over extended usage periods.
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 approach results in a tantalum sputtering target that significantly improves film thickness uniformity and reduces sheet resistance variation, enabling stable and high-quality thin film deposition for semiconductor devices.
Implementation Method 1
This kind of tantalum barrier film is generally formed by sputtering a tantalum target
Implementation Method 2
an ingot or a billet obtained by subjecting a tantalum raw material to electron beam melting and casting
Data Source
AI summary
Provided is a tantalum sputtering target, which is characterized that an average crystal grain size of the target is 50 μm or more and 200 μm or less, and variation of a crystal grain size in the target plane is 40% or higher and 60% or less. This invention aims to provide a tantalum sputtering target capable of improving the uniformity of the film thickness and reducing the variation of the resistance value (sheet resistance).