MRAM Magnetic Layer Protection During PECVD Film Formation
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Solution Overview
Problem
The existing methods for processing magnetic random access memory (MRAM) devices using plasma-enhanced chemical vapor deposition (PECVD) face challenges in maintaining the perpendicular magnetic anisotropy of magnetic layers due to exposure to hydrogen plasma and oxygen, leading to changes in composition, crystal orientation, and interfacial properties, which affect the magnetic properties of the MRAM.
Innovation Solution
A method involving a processing system with airtight chambers that perform etching and film forming processes, where the film forming process is conducted in a chamber with a hydrogen partial pressure of 15 mTorr or less and an internal pressure of 200 mTorr or more, ensuring minimal exposure to oxygen and hydrogen plasma, using a processing gas mixture of SiH4, N2, and H2 to form a SiN film, thereby reducing the impact on the magnetic layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If plasma-enhanced chemical vapor deposition (PECVD) is used to form an insulating film, then the film forming process can be performed at lower temperatures, but the magnetic layers are exposed to hydrogen plasma and oxygen which changes their composition and crystal orientation
Solution Approach 1:
The processing system is divided into separate first and second processing chambers. The first chamber performs etching processes while the second chamber performs film forming processes. This segmentation allows independent optimization of each process without compromising the other, enabling PECVD to be performed without exposing magnetic layers to harmful plasma conditions.
Solution Approach 2:
A connecting part with a shutter mechanism acts as an intermediary between the first and second processing chambers. The shutter can be opened or closed to control the transfer of workpieces between chambers, preventing direct exposure of magnetic layers to hydrogen plasma by ensuring film forming occurs in a separate, controlled environment.
2Reliability
If PECVD is performed with hydrogen plasma, then insulating films can be formed effectively, but the perpendicular magnetic anisotropy of magnetic layers is affected
Solution Approach 1:
The processing system separates etching and film forming operations into different chambers. This allows PECVD to be performed with full hydrogen plasma for reliable insulating film formation, while magnetic layers remain protected in the first chamber or are transferred only when necessary, preserving their perpendicular magnetic anisotropy.
Solution Approach 2:
The connecting part and chamber design create an inert environment that prevents oxygen and hydrogen plasma exposure to magnetic layers during film forming. The shutter mechanism ensures that the magnetic layers are either in a protected atmosphere or being transferred, eliminating harmful interactions while maintaining effective PECVD performance.
3Stability of the object's composition
If magnetic layers are exposed to oxygen during processing, then oxidation can occur which changes interfacial properties, but maintaining airtight chambers increases system complexity
Solution Approach 1:
The system divides the processing into separate airtight chambers, each optimized for specific processes. This segmentation allows standard PECVD equipment to be used without requiring complex modifications, as the airtight separation is achieved through modular chamber design with simple shutter mechanisms rather than complex integrated systems.
Solution Approach 2:
The connecting part with shutter acts as a simple intermediary that maintains airtight separation between chambers. This straightforward design prevents oxygen exposure to magnetic layers while avoiding the need for complex airtight systems, as the shutter provides effective isolation with minimal structural complexity.
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 effectively suppresses changes in the magnetic layers' composition and crystal orientation, maintaining the perpendicular magnetic anisotropy and coercive force of the MRAM devices, enhancing their magnetic properties and stability.
Implementation Method 1
an insulating film is formed on the first surface of the tunnel barrier layer and a second surface of the laminated portion by plasma of a processing gas that contains hydrogen
Implementation Method 2
two magnetic layers and the insulating layer are affected by heat of plasma
Data Source
AI summary
A method includes performing an etching process in a first process module, moving a workpiece formed by the etching process from the first process module to a second process module, and performing a film forming process on the workpiece in the second process module. In the performing the film forming process, an insulating film is formed on a first surface and a second surface of a laminated portion by plasma of a processing gas that contains hydrogen. In the performing the film forming process, an internal pressure of the second process module is 200 mTorr or more, and a hydrogen partial pressure of the second process module is 15 mTorr or less. The performing the etching process, the moving the workpiece, and the performing the film forming process are consistently performed in a state where oxygen is exhausted.