Gradient Crystal Grain Sputtering Target for Uniform Film
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Solution Overview
Problem
Existing sputtering targets with large crystal-grain diameters lead to uneven film thickness, splashing, and reduced productivity due to local depletion and abnormal discharges during extended sputtering processes, necessitating a solution to control crystal-grain diameters and planes for uniform film formation and extended target life.
Innovation Solution
A sputtering-target aluminum plate with a purity of 99.999 mass % or higher, where the average crystal-grain diameters and crystal planes change continuously from the surface to the center in the plate-thickness direction, adhering to specific ratios and area ratios, inhibiting splashing and local depletion, and ensuring uniform film thickness even during prolonged sputtering.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of stationary object
If the crystal-grain diameter of the sputtering-target material is large, then the target material can be used for longer periods, but variations in film thickness become large and splashing occurs due to unevenness on the target surface
Solution Approach 1:
The patent applies local quality by creating a non-uniform crystal grain structure where the average crystal grain diameter increases from the surface toward the center of the target. Specifically, the surface region has smaller crystal grains (Ds ≤ 230 μm) to prevent splashing and maintain uniformity, while the center region has larger crystal grains (Dc ≤ 300 μm) to extend target life. This gradient structure optimizes both local surface performance and overall durability.
Solution Approach 2:
The patent implements dynamics by establishing a continuous gradient in crystal grain diameter through the plate thickness direction, rather than using uniform crystal grains throughout. The ratio Dq/Ds ≥ 1.2 and Dc/Ds ≥ 1.3 creates a dynamic transition zone that progressively changes the material properties from surface to center, allowing the target to maintain performance characteristics throughout extended operation.
2Stability of the object's composition
If the crystal-grain diameter is large, then the target structure is more stable, but unevenness due to differences in crystal planes occurs on the target surface leading to electric charge concentration and abnormal discharge
Solution Approach 1:
The patent applies local quality by controlling the crystal grain size distribution: smaller grains at the surface (Ds ≤ 230 μm) prevent abnormal discharge and splashing, while larger grains in the center provide structural stability. The surface region's fine grain structure ensures uniform crystal plane orientation and prevents charge concentration, while the center's coarse structure maintains overall target integrity during extended use.
Solution Approach 2:
The patent implements preliminary action by pre-establishing the gradient crystal grain structure during target manufacturing before the sputtering process begins. This pre-configured structure with controlled crystal plane orientations and grain size distribution prevents abnormal discharge and splashing from occurring in the first place, rather than attempting to correct these issues during operation.
3Productivity
If sputtering is performed for a long time to improve production efficiency, then productivity increases, but local depletion of the target material progresses due to unevenness from crystal plane differences
Solution Approach 1:
The patent applies local quality by creating a gradient crystal grain structure that distributes sputtering wear more evenly throughout the target volume. The surface region with smaller grains (Ds ≤ 230 μm) and specific crystal plane ratios resists rapid depletion, while the center region with larger grains (Dc ≤ 300 μm) provides a reservoir of material that depletes more uniformly, extending the target's usable life and maintaining consistent film deposition rates.
Solution Approach 2:
The patent implements dynamics through the continuous gradient in crystal grain diameter and crystal plane distribution from surface to center. This dynamic structure allows the target to adapt to sputtering conditions over time, with the gradient preventing localized hot spots of depletion and ensuring more uniform material consumption throughout the extended sputtering process.
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 effectively inhibits splashing and local depletion, maintaining film thickness uniformity and reducing production losses, while allowing for extended sputtering without significant increases in resistance, thus enhancing productivity and film quality.
Implementation Method 1
a so-called sputtering method, in which a plasma discharge is formed between the substrate and a target material, which constitutes a raw material when forming the thin film, and ionized argon ejects atoms, which are composed of the target material, using energy from the collision with the target material
Data Source
AI summary
A sputtering-target material (2) is composed of aluminum having a purity of 99.999 mass % or higher and unavoidable impurities. When an average crystal-grain diameter at the plate surface (21) is given as Ds [μm], an average crystal-grain diameter at a depth of ¼th of the plate thickness (22) is given as Dq [μm], and an average crystal-grain diameter at a depth of ½ of the plate thickness (23) is given as Dc [μm], the formulas below are satisfied, and the average crystal-grain diameter changes continuously in a plate-thickness direction.Ds≤230Dq≤280Dc≤3001.2≤Dq/Ds 1.3≤Dc/Ds