Molybdenum Sputtering Target Segmentation via Hot Isostatic Pressing
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Solution Overview
Problem
Current methods for producing large molybdenum sputtering targets, such as cold isostatic pressing and sintering followed by hot rolling, result in undesirable microstructures and etching characteristics due to the rolling process, affecting sputter yield and thin film properties.
Innovation Solution
The method involves stacking sintered molybdenum powder metal bodies with powder metal joints and performing hot isostatic pressing to form diffusion bonds, creating a billet or bar with a microstructure of equiaxed grains and low oxygen content, which can be machined into a large sputtering target.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If cold isostatic pressing and sintering followed by hot rolling is used to produce large molybdenum sputtering targets, then large size targets can be manufactured, but the plate microstructure formed during rolling results in poor sputter yield and undesirable etching characteristics
Solution Approach 1:
The target is divided into multiple sintered powder metal bodies that are stacked and diffusion bonded together through hot isostatic pressing. This segmentation allows each body to maintain its beneficial sintered microstructure while achieving the required large overall size, avoiding the harmful effects of hot rolling on the microstructure.
Solution Approach 2:
The invention changes the manufacturing parameters by using hot isostatic pressing instead of hot rolling. This parameter change maintains the desired microstructure (equiaxed grains of small size) while achieving the required density (>99% theoretical density) and large target size, thereby improving sputter yield and etching characteristics.
2Volume of moving object
If hot rolling is used to reduce oxygen content and form the target plate, then large size targets can be produced, but the rolling process creates undesirable plate microstructure
Solution Approach 1:
Instead of forming a large plate through rolling, the invention segments the target into multiple smaller sintered bodies that are stacked and diffusion bonded. This preserves the equiaxed grain microstructure of each sintered body while achieving the required large overall dimensions.
Solution Approach 2:
The invention replaces the mechanical rolling process with hot isostatic pressing. This substitution eliminates the directional deformation and microstructure distortion caused by rolling, while still achieving density consolidation and large size through diffusion bonding of stacked bodies.
3Reliability
If diffusion bonding through hot isostatic pressing is used to join sintered bodies, then equiaxed grain microstructure and high density are achieved, but multiple processing steps are required
Solution Approach 1:
The invention merges multiple sintered bodies into a single integrated target structure through diffusion bonding in one hot isostatic pressing operation. This combining approach achieves the desired microstructure and density while creating the large size target, with the trade-off being the need for precise stacking and bonding process control.
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
This approach produces a billet or bar with a microstructure of small grain size and low oxygen content, achieving a density greater than 99% of theoretical density and enabling the creation of large sputtering targets with improved sputter yield and etching characteristics.
Implementation Method 1
The adjacent bodies are hot isostatically pressed to form a diffusion bond at each metal-to-powder metal layer-to-metal joint between adjacent bodies
Implementation Method 2
two or more sintered powder metal bodies (e.g. ingot bodies) comprising Mo are placed adjacent one another (e.g. stacked one on the other) with powder metal comprising Mo present at joints between adjacent bodies. The adjacent bodies are hot isostatically pressed to form a diffusion bond
Data Source
AI summary
A method of making a large Mo billet or bar for a sputtering target wherein two or more bodies comprising Mo are placed adjacent one another (e.g. stacked one on the other) with Mo powder metal present at gaps or joints between the adjacent bodies. The adjacent bodies are hot isostatically pressed to form a diffusion bond at each of the metal-to-Mo powder layer-to-metal joint between adjacent bodies to form a billet or bar that can be machined or otherwise formed to provide a large sputtering target. The number and dimensions of the Mo bodies placed adjacent one another are selected to yield a desired large size the billet or bar suitable for the sputtering target. The billet or bar for the sputtering target exhibits a microstructure comprising equiaxed grains of less than 30 microns grain size and exhibits a low oxygen content of less than about 100 ppm by weight.