Magnetic Stack Annealing Tool With Single-Line Wafer Heating
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Solution Overview
Problem
Current magnetic annealing processes for magnetic film stacks in MRAM devices face challenges such as long annealing times and high temperatures, which lead to material diffusion, device performance degradation, and increased costs due to complex cooling systems and low wafer processing rates, along with difficulties in controlling thermal variations and gas flow dynamics.
Innovation Solution
A tool and method for annealing magnetic stacks using a housing with a heating chamber, a holding mechanism for single-line wafer processing, and a magnetic field generator, where the wafers are heated by a resistive heater and subjected to a magnetic field, allowing for simultaneous thermal and magnetic annealing with improved temperature control and reduced processing time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If large amounts of thermal energy are supplied for long time to achieve best film crystallographic qualities, then crystalline structure quality is improved, but material diffusion occurs and device performance deteriorates
Solution Approach 1:
The patent applies periodic action by using pulsed magnetic fields during the annealing process. The magnetic field is applied in pulses rather than continuously, which allows thermal energy to be supplied for crystallographic quality improvement while the periodic nature of the magnetic field prevents excessive material diffusion and maintains device performance.
Solution Approach 2:
The patent changes the parameter of magnetic field application from static to dynamic/pulsed. By varying the magnetic field parameters (applying it in pulses rather than continuously), the process achieves better crystallographic qualities without causing material diffusion that would deteriorate device performance.
2Manufacturing precision
If long annealing times and higher temperatures are used to achieve desired material properties, then material properties are improved, but prefabricated silicon integrated circuits performance is affected
Solution Approach 1:
The pulsed magnetic field application allows the annealing process to achieve desired material properties through periodic energy input rather than continuous high-temperature exposure, thereby improving material properties without degrading the heat-sensitive silicon integrated circuits.
Solution Approach 2:
The patent rushes through the annealing process by applying pulsed magnetic fields that deliver the necessary thermal and magnetic energy in concentrated bursts, achieving the desired material properties faster than conventional continuous annealing, thus preventing heat damage to the silicon circuits.
3Productivity
If conventional batch annealing of 25 or 50 wafers is performed, then throughput is maintained, but local thermal variations on wafers are difficult to control
Solution Approach 1:
The patent segments the batch annealing process into individual wafer treatment by using a wafer carrier with multiple susceptors, each independently controllable. This segmentation allows precise temperature control for each wafer while maintaining batch processing capability, thus achieving both high productivity and temperature uniformity.
Solution Approach 2:
The patent applies local quality by providing individual susceptors for each wafer position in the batch, allowing localized temperature control and compensation for thermal variations across different wafer locations, thereby maintaining temperature uniformity while processing multiple wafers simultaneously.
4Force
If huge electromagnets are used to generate magnetic field of 1 to 5 Teslas, then magnetic field strength is sufficient, but equipment complexity and manufacturing cost increase
Solution Approach 1:
The patent extracts the essential function of generating strong magnetic fields from complex huge electromagnets by using simpler permanent magnets or smaller electromagnets combined with the pulsed field application technique. This extraction maintains the required magnetic field strength while significantly reducing equipment complexity and manufacturing cost.
Solution Approach 2:
The patent replaces expensive, complex, and maintenance-intensive huge electromagnets with simpler, cheaper magnetic field generation methods (such as permanent magnets or smaller electromagnets used in pulsed mode), reducing equipment complexity and manufacturing cost while maintaining sufficient magnetic field strength for the annealing 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
This approach enables the achievement of perfect crystalline structures and optimal device performance characteristics, increases wafer processing throughput, reduces equipment complexity and cost, and enhances film and crystallographic uniformity by allowing for localized temperature control and efficient thermal energy delivery.
Implementation Method 1
the wafers are heated by a resistive heater
Implementation Method 2
a magnetic field generator to generate a magnetic field whose field lines pass through the single line of wafers during a magnetic annealing process
Data Source
AI summary
In one embodiment of the invention, there is provided a tool for annealing a magnetic stack. The tool includes a housing defining a heating chamber; a holding mechanism to hold at least one wafer in a single line within the heating chamber, a heating mechanism to heat the at least one wafer; and a magnetic field generator to generate a magnetic field whole field lines pass through the single line of wafers during a magnetic annealing process; wherein the holding mechanism comprises a wafer support of holding the single line of wafers between the heating mechanism and the magnetic field generator.