Lithium Cobalt Oxide Target CIP Sintering
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Solution Overview
Problem
There is a lack of cost-effective methods for forming high-quality cylindrical sputtering targets, particularly for lithium-containing transition metal oxides like LiCoO2, which are essential for efficient thin film battery production, as existing techniques face challenges in achieving uniform density, resistivity, and grain size distribution, leading to issues such as nodule formation and material degradation during sputtering.
Innovation Solution
A method involving Cold Isostatic Pressing (CIP) and sintering of LiMO2 powders to form hollow cylindrical targets with specific density, resistivity, and grain size characteristics, followed by bonding to a backing support using metal solder or induction heating techniques to ensure durability and efficient deposition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional sintering methods are used to form cylindrical sputtering targets, then the target can be manufactured, but the density uniformity and grain size distribution deteriorate leading to nodule formation and material degradation
Solution Approach 1:
The patent applies preliminary action by performing Cold Isostatic Pressing (CIP) before sintering to pre-densify the compact. This pre-compression ensures uniform density distribution throughout the cylindrical target, preventing subsequent nodulation during sputtering. The CIP process creates a uniformly dense green compact that maintains dimensional stability throughout the sintering process, thereby resolving the contradiction between manufacturability and target stability.
Solution Approach 2:
The patent employs parameter changes by optimizing sintering temperature (900-1100°C), holding time (10-20 hours), and atmospheric conditions to achieve uniform grain growth and density. These controlled parameter changes ensure that the sintering process maintains the uniform density structure created by CIP, preventing nodule formation while achieving the desired ceramic properties for stable sputtering operation.
2Productivity
If cylindrical targets are formed using traditional methods, then the targets can be produced, but the deposition rate and material utilization deteriorate compared to planar targets
Solution Approach 1:
The patent applies preliminary action by forming a uniformly dense cylindrical compact through CIP before sintering. This pre-compression creates a target with optimized material distribution that enables higher deposition rates during sputtering, as the uniform density ensures consistent material ejection across the cylindrical surface, overcoming the traditional limitation of cylindrical targets having lower productivity.
Solution Approach 2:
The patent employs parameter changes by optimizing the CIP pressure (3000-4000 bar) and sintering conditions to achieve a dense, uniform microstructure in the cylindrical target. These parameter optimizations enable cylindrical targets to achieve deposition rates comparable to or exceeding planar targets, while maintaining the manufacturing feasibility through a standardized two-step process.
3Manufacturing precision
If high density is achieved through extended sintering, then the target quality improves, but the production time and energy consumption increase
Solution Approach 1:
The patent applies preliminary action by performing CIP to pre-densify the compact before sintering. This pre-compression significantly reduces the sintering time required to achieve high density targets, as the CIP process has already removed most porosity. The subsequent sintering step only needs to bond the pre-compressed particles, reducing production time from traditional 24+ hours to 10-20 hours while maintaining target quality.
Solution Approach 2:
The patent employs parameter changes by optimizing the sintering temperature range (900-1100°C) and holding time (10-20 hours) to achieve high density targets efficiently. The combination of moderate temperatures with extended but controlled holding times, following CIP, achieves superior target quality with reduced total process time and energy consumption compared to traditional high-temperature sintering alone.
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 sputtering targets with enhanced deposition rates, reduced nodule formation, and improved material utilization, ensuring high-quality thin film production while addressing the challenges of material degradation and assembly complexity.
Implementation Method 1
sintering, after said heating step, said molded body so to obtain the lithium-containing transition metal oxide cylindrical hollow target body
Implementation Method 2
bonding to a backing support using metal solder or induction heating techniques
Data Source
AI summary
A process for the formation of an LiM02 (e.g., LiCoO2) sputtering target with a bi-modal grain size distribution (as in a hollow cylinder target body) that includes a CIP-based process involving, for example, forming or sourcing an LiMO2 (e.g., Li—CoO2) powder; dispersion and milling (e.g., wet milling); binder introduction; drying (e.g., spray drying) to form a granulate; CIP processing of the granulate into a molded shape; and a heating cycle for debinding and sintering to form a densified sintered shape. The target body produced is suited for inclusion on a sputtering target assembly (as in a rotary sputtering target assembly with a plurality of cylindrical target bodies attached to a backing support). The invention is inclusive of the resultant target bodies formed under the CIP based process as well as an induction heater based process for attachment (e.g., metal solder bonding) of the low conductivity target body(ies) of LiMO2 (e.g., LiCoO2) to a common backing support through use of an added conductive wrap or layer provided to the target body and heated with the induction heater during the attachment process.