MRAM Magnetic Shielding for Data Retention
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Solution Overview
Problem
Magnetic Random Access Memory (MRAM) devices are susceptible to external magnetic fields, which can cause fluctuations in the magnetization direction of the recording layer, leading to data retention issues and the need for effective magnetic shielding to maintain data integrity.
Innovation Solution
A semiconductor device configuration with a first magnetic shield material disposed between the die pad and the rear surface of the semiconductor chip and a second magnetic shield material covering the region where the magnetic memory elements are formed, with the second shield material having a thicker thickness and smaller area than the first, to effectively absorb external magnetic fields and improve data retention.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a magnetic shield structure is formed to protect MRAM from external magnetic fields, then data retention and reliability are improved, but device complexity and manufacturing difficulty increase
Solution Approach 1:
The magnetic shield structure is divided into multiple discrete components: a first magnetic shield layer formed on the lower surface of the semiconductor chip, a second magnetic shield layer formed on the upper surface, and additional shield structures around peripheral regions. This segmentation allows each layer to be optimized independently for specific shielding directions and reduces manufacturing complexity compared to a monolithic shield structure.
Solution Approach 2:
The patent employs composite magnetic shield structures combining different materials with complementary properties. The first and second magnetic shield layers use soft magnetic materials with high permeability for shielding low-frequency magnetic fields, while peripheral shield structures use materials with high saturation magnetization for high-frequency field shielding. This composite approach achieves comprehensive magnetic field protection while managing device complexity.
2Object-affected harmful factors
If magnetic shield layers are formed using soft magnetic metal, then shielding effectiveness against low-frequency magnetic fields is improved, but manufacturing process complexity increases
Solution Approach 1:
The patent replaces mechanical or manual magnetic shield installation with direct integration of magnetic shield layers into the semiconductor manufacturing process. Soft magnetic metal layers are deposited using sputtering or other thin-film deposition techniques performed in-situ during chip fabrication, eliminating separate mechanical assembly steps and reducing manufacturing process complexity while maintaining shielding effectiveness.
3Productivity
If the same sputtering apparatus is used for forming both MRAM element layers and magnetic shield layers, then manufacturing efficiency is improved, but manufacturing precision may be compromised
Solution Approach 1:
The patent employs a universal sputtering apparatus capable of performing multiple functions: forming both the functional MRAM element layers (tunnel barriers, ferromagnetic layers, non-magnetic layers) and the protective magnetic shield layers. The apparatus is equipped with multiple targets and process control systems that allow it to switch between different deposition modes, achieving both high productivity through single-apparatus operation and high precision through specialized process parameters for each layer type.
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 proposed configuration enhances the resistance of MRAM devices to external magnetic fields, improving data retention characteristics and reducing the overall thickness of the semiconductor package while maintaining reliability.
Implementation Method 1
a first magnetic shield material disposed between the die pad and the rear surface of the semiconductor chip and a second magnetic shield material disposed over the principal surface of the semiconductor chip so as to cover a region where magnetic memory elements are formed
Data Source
AI summary
To provide a technique that can improve the data retention characteristic of an MRAM device by improving the resistance against an external magnetic field in a semiconductor device including the MRAM device. A first magnetic shield material is disposed over a die pad via a first die attach film. Then, a semiconductor chip is mounted over the first magnetic shield material via a second die attach film. Furthermore, a second magnetic shield material is disposed over the semiconductor chip via a third die attach film. That is, the semiconductor chip is disposed so as to be sandwiched by the first magnetic shield material and the second magnetic shield material. At this time, while the planar area of the second magnetic shield material is smaller than that of the first magnetic shield material, the thickness of the second magnetic shield material is thicker than that of the first magnetic shield material.