Target Centering in PVD Holder via Segmented Radial Indentations
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Solution Overview
Problem
Existing PVD processes face challenges in maintaining the target's concentric expansion on cooling plates, leading to potential electrical short circuits and mechanical stress due to limited thermal expansion, which restricts sputtering power and target longevity.
Innovation Solution
A disk-mount system with a panel and fixture having different thermal expansion coefficients, where the panel's circumference is larger than the fixture's at room temperature, and interlocking indentations guide the panel to remain centered during thermal expansion, allowing free expansion up to high temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the gap between the cooling plate and target is small to ensure proper positioning, then the target position is sufficiently determined, but the maximum permissible target temperature and sputtering power are severely limited
Solution Approach 1:
The holder is divided into multiple segments with radial indentations that can independently accommodate target expansion, allowing the target to expand freely while maintaining concentric positioning. This segmentation enables the holder to adapt to thermal expansion without requiring a large initial gap.
Solution Approach 2:
The holder design incorporates radial indentations with specific depth and spacing parameters that change the mechanical constraints on the target. These parameter changes allow the target to expand radially while maintaining concentricity, resolving the contradiction between small gap positioning and expansion freedom.
2Temperature
If the gap between the cooling plate and target is large to allow thermal expansion, then the target can expand freely, but the target becomes too eccentric on the cooling plate
Solution Approach 1:
The holder is segmented into sections with radial indentations that guide target expansion. These segments maintain the target's concentric position even when the gap is large enough to accommodate full thermal expansion, preventing eccentricity while allowing temperature increase.
Solution Approach 2:
The radial indentations act as intermediary guide elements between the target and holder wall. They provide contact points that constrain the target to expand concentrically while allowing sufficient gap width for thermal expansion, mediating between the conflicting requirements of large gap and concentricity.
3Temperature
If the target is eccentric on the cooling plate, then the target can expand with larger gap, but uneven mechanical stresses exceed permissible limits
Solution Approach 1:
The segmented holder design with radial indentations ensures uniform distribution of mechanical stresses during target expansion. By providing multiple contact points through the indentations, the stress is distributed evenly across the target holder interface, preventing stress concentration even with larger gaps.
Solution Approach 2:
The cooling medium pressure creates a uniform radial force distribution on the target back surface, working in conjunction with the segmented holder to ensure even stress distribution. The hydraulic pressure of the cooling medium helps maintain uniform contact and stress distribution during thermal expansion.
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
Ensures the target remains centered and expands freely, preventing short circuits and uneven stresses, thereby increasing the maximum permissible sputtering power and target temperature without mechanical failure.
Implementation Method 1
the material of the panel having a first coefficient of thermal expansion... the first coefficient of thermal expansion is greater than the second coefficient of thermal expansion... allowing the disk to expand freely in the fixture
Implementation Method 2
interlocking indentations guide the panel to remain centered during thermal expansion... the indentation-deformation pairs act as guide rails
Data Source
Figure 1~2
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AI summary
The invention relates to a system comprising a plate having a holder, wherein the plate is centered in the holder both at room temperatures and at higher temperatures, independently of the thermal expansion of the plate and the holder, and wherein the plate can freely expand in the holder at higher temperatures.