Tantalum Sputtering Target Processing for Stable Deposition Uniformity
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Solution Overview
Problem
Tantalum sputtering targets produced using conventional methods exhibit performance issues due to plate-to-plate variation, affecting the stability of deposited thin films in terms of deposition rate and film uniformity, which negatively impacts production yield.
Innovation Solution
A method involving electron beam melting, thermo-mechanical processing, and specific rolling techniques to produce tantalum sputtering targets with uniform texture and controlled crystallographic orientation, ensuring stable deposition rate and film uniformity throughout the target's life.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If conventional multi-step manufacturing processes are used to shape tantalum plates, then the desired round disc-shaped form is achieved, but plate-to-plate variation occurs affecting deposition rate and film uniformity
Solution Approach 1:
The patent applies parameter changes by controlling the crystallographic texture through specific rolling reduction ratios (total reduction of 60-80% in multiple passes) and heat treatment parameters (annealing temperature of 900-1100°C for 30-120 minutes). These parameter controls achieve a consistent {100}+{111} texture volume fraction of 70-85%, which directly improves deposition rate stability and film uniformity while maintaining the round disc shape.
Solution Approach 2:
The patent employs preliminary action by performing intermediate annealing treatments between rolling passes to establish a controlled recrystallized grain structure before final shaping. This preliminary microstructure control ensures that the final product has uniform crystallographic orientation, eliminating plate-to-plate variation in deposition performance while achieving the desired geometry.
2Shape
If violent deformation strains are applied to conform tantalum to the desired form, then the round disc shape is achieved, but microstructural non-uniformity occurs affecting film uniformity
Solution Approach 1:
The patent applies segmentation by dividing the single large deformation into multiple smaller rolling passes with intermediate annealing treatments. Instead of one violent deformation, the material undergoes sequential reductions (e.g., 10-15% per pass over 6-10 passes), allowing recrystallization between passes to maintain microstructural uniformity and achieve the desired shape without compromising film uniformity.
Solution Approach 2:
The patent employs periodic action through alternating rolling passes and intermediate annealing treatments. The periodic heat treatment cycles (rolling for 30-60 minutes, then annealing for 30-120 minutes) create a rhythm of deformation and recovery that prevents microstructural non-uniformity while progressively achieving the round disc shape, resulting in consistent film uniformity.
3Productivity
If conventional manufacturing processes are used, then production can proceed, but in-process parameter adjustments are frequently needed reducing yield
Solution Approach 1:
The patent applies self-service by designing a manufacturing process that is self-regulating through the controlled crystallographic texture development. The specific rolling reduction ratios and annealing parameters automatically produce the target {100}+{111} texture volume fraction of 70-85%, making the process self-correcting and eliminating the need for frequent in-process parameter adjustments, thereby improving both yield and ease of operation.
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 achieves stable deposition rate and film uniformity better than 2% throughout the target's life, reducing the need for in-process parameter adjustments and improving yield by ensuring predictable sputtering performance.
Implementation Method 1
a) electron beam melting tantalum material to form a tantalum ingot
Implementation Method 2
b) thermo-mechanically processing the tantalum ingot to break the coarse structure
Implementation Method 3
e) friction rolling the pressed billet to a defined strain and friction control process that distributes the strain uniformly from the surface to the bulk of the plate
Implementation Method 4
The invention produces tantalum sputtering targets with stable deposition rate from burn-in through the end-of-life
Data Source
AI summary
A method for making tantalum sputtering targets with stable through thickness {100}+{111} preferred crystallographic orientation volume fraction is disclosed. Starting from electron beam melted tantalum ingots, the method includes various forging, controlled rolling and recrystallization annealing. The resultant tantalum sputtering targets yield stable deposition rate and film uniformity from burn-in through the end-of-life during sputtering. Also disclosed is a tantalum sputtering target made in accordance with the disclosed method.