Dual Capping Layer for MRAM MTJ Protection
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Solution Overview
Problem
Current magnetoresistive random access memory (MRAM) devices face challenges in protecting the magnetic tunnel junction (MTJ) structure during manufacturing processes, as existing capping layers either damage the surface or fail to provide sufficient protection against thermal processes and chemical penetration.
Innovation Solution
A method of forming a magnetoresistive random access memory device involves creating a dual capping layer structure, where a first capping layer with a lower nitrogen concentration is formed using a pulsed radio-frequency power, and a second capping layer with a higher nitrogen concentration is formed using both high- and low-frequency radio-frequency powers, both layers being made of materials like silicon nitride or silicon oxynitride, to enhance protection and etch resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single capping layer is formed to protect the MTJ structure, then protection against thermal processes and chemical penetration is provided, but surface damage occurs and protection is insufficient
Solution Approach 1:
The capping layer is divided into two distinct layers: a first capping layer formed by pulsed RF PECVD and a second capping layer formed by dual-frequency RF PECVD. Each layer serves a specific protective function, with the first layer providing initial protection and the second layer enhancing protection against thermal processes and chemical penetration while reducing surface damage.
Solution Approach 2:
Different regions of the capping structure have different properties. The first capping layer has specific characteristics optimized for reducing surface damage during formation, while the second capping layer has different characteristics optimized for protection against thermal processes and chemical penetration. This local differentiation of properties allows each layer to excel at its specific protective function.
2Reliability
If plasma deposition is used to form the capping layer, then protection is provided, but surface damage occurs during formation
Solution Approach 1:
The plasma deposition process is segmented into two separate processes: first RF PECVD for the initial capping layer and then dual-frequency RF PECVD for the second capping layer. This segmentation allows optimization of each deposition process for its specific purpose, minimizing surface damage while providing comprehensive protection.
Solution Approach 2:
The pulsed RF power application in the first PECVD process creates periodic plasma conditions that reduce surface damage compared to continuous plasma exposure. This periodic action allows the MTJ structure to be protected while minimizing harmful plasma effects during formation.
3Ease of manufacture
If conventional single-layer capping is used, then manufacturing is simple, but etch resistance is insufficient
Solution Approach 1:
The capping structure uses a composite of two different capping layers formed by different PECVD processes. This composite structure provides enhanced etch resistance that neither layer could provide alone, while still maintaining manufacturability through sequential deposition in the same reaction chamber.
Solution Approach 2:
The capping formation is segmented into two sequential steps with different deposition parameters and materials characteristics. This segmentation enables each layer to contribute specific properties, including enhanced etch resistance, while the overall process remains manufacturable through automated sequential deposition.
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 dual capping layer structure effectively reduces surface damage during formation and provides enhanced protection against subsequent processes, improving the integrity and durability of the MTJ structure, while also offering improved etch resistance.
Implementation Method 1
forming a first capping layer to cover a surface of the memory structure by a deposition process using a plasma under first conditions; and forming a second capping layer on the first capping layer by a deposition process using a plasma under second conditions different from the first conditions
Implementation Method 2
forming a first capping layer to cover a surface of the memory structure by a deposition process using a plasma under first conditions
Data Source
AI summary
A method of manufacturing a magnetoresistive random access memory device, the method including forming a memory structure on a substrate, the memory structure including a lower electrode, a magnetic tunnel junction structure, and an upper electrode sequentially stacked; forming a first capping layer to cover a surface of the memory structure by a deposition process using a plasma under first conditions; and forming a second capping layer on the first capping layer by a deposition process using a plasma under second conditions different from the first conditions.