BCC Metal Sputter Target Grain Refinement via Tri-Axial Forging
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Solution Overview
Problem
Current methods for producing sputter targets, particularly those made from Body Centered Cubic (BCC) metals like Ta and Nb, face challenges in achieving uniform grain size, purity, and texture, which are crucial for consistent thin film deposition in microelectronic devices.
Innovation Solution
A method involving tri-axial forging, vacuum annealing, and clock rolling of BCC metal ingots to refine the grain structure and texture, including e-beam melting and vacuum arc remelting, followed by multiple annealing steps to achieve a fine grain homogeneous structure with a {111} dominant texture gradient.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional metal working processes are used to fabricate sputter targets, then manufacturing cost is reduced, but uniformity in grain size, purity, and texture cannot be achieved
Solution Approach 1:
The patent applies parameter changes by controlling annealing temperature (950-1300°C), vacuum conditions, and deformation parameters during tri-axial forging and clock rolling to achieve uniform grain size of 50-100 microns and predominant {111} texture. These controlled parameter changes transform the material properties to achieve the desired uniformity in grain structure and texture.
Solution Approach 2:
The patent employs preliminary action through e-beam melting and vacuum arc remelting before forging and rolling operations. These preliminary purification and structuring actions prepare the ingot with optimal initial conditions, ensuring uniform grain size and purity are achieved in the final sputter target.
2Manufacturing precision
If multiple processing steps are applied to achieve fine grain homogeneous structure, then target quality is improved, but production time increases
Solution Approach 1:
The patent merges multiple processing objectives into integrated operation sequences. For example, tri-axial forging combines deformation and grain refinement in one operation, while clock rolling integrates shaping and texture control. The annealing steps are strategically positioned to achieve multiple goals (grain growth, texture development, stress relief) simultaneously, reducing total production time while maintaining quality.
Solution Approach 2:
The patent employs periodic action through alternating cycles of deformation (forging, rolling) and annealing. This periodic sequence of plastic deformation followed by thermal recovery allows grain refinement and texture development to occur efficiently, achieving fine grain homogeneous structure with predominant {111} texture while managing production time through optimized cycle timing.
3Stability of the object's composition
If tri-axial forging and clock rolling are used to refine grain structure, then texture uniformity is improved, but manufacturing complexity increases
Solution Approach 1:
The patent applies segmentation by dividing the grain refinement process into distinct stages: tri-axial forging for initial grain structure development, followed by clock rolling for texture uniformity, with intermediate annealing steps. Each segment focuses on a specific aspect of microstructure control, making the complex overall process more manageable and controllable.
Solution Approach 2:
The patent introduces another dimension by applying clock rolling with the ingot centerline maintained perpendicular to compressive forces, creating a specific three-dimensional grain orientation pattern. This dimensional control during processing achieves predominant {111} texture with gradient towards the midpoint of thickness, enhancing texture uniformity through controlled spatial orientation.
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 method produces sputter targets with a grain size of 50-100 microns and a predominant {111} texture, ensuring uniformity and consistency in thin film deposition, improving the quality of microelectronic device components.
Implementation Method 1
The process further comprises vacuum annealing of the ingot in a first annealing step and clock rolling the ingot while the centerline is maintained in the center of the ingot and perpendicular to the compressive forces used during the clock rolling. The ingot is further vacuum annealed in a second annealing step
Implementation Method 2
at least a portion of the tri-axial forging is provided under heated conditions of about 800° C.
Implementation Method 3
Physical vapor deposition (PVD) relates to a variety of vacuum deposition techniques in which thin films are deposited onto a desired substrate via condensation of a vaporized form of a source material
Implementation Method 4
Cathodic sputtering is one PVD form that is widely used for the deposition of thin layers of material onto substrates. Basically, a sputtering process requires gas ion bombardment of a target formed from a material that is to be deposited as a thin film or layer on a given substrate
Data Source
AI summary
A method of making sputter targets from a BCC metal or BCC metal alloy is provided. The ingot is e-beamed melted and subjected to vacuum arc reduction. The ingot is then tri-axially forged, keeping the centerline of the ingot in the center of the ingot during the tri-axial forging step. The ingot is then vacuum annealed and clock rolled. During the clock rolling, the center line of the ingot is maintained in the center of the ingot and perpendicular to the compressive forces used during the clock rolling. The clock rolled ingot is then vacuum annealed and provided in a near net shape for usage as a sputter target. Tantalum target materials are disclosed having a purity of at least 99.5% and an interstitial content (CONH) of less than about 25 ppm. Tantalum targets, in accordance with the invention, have a grain size of about 50 to 100 microns and a mixed {100}/{111} texture with a higher % {111} gradient towards the center.