Magnetic Shield Unit for MRAM Semiconductor Packages
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Solution Overview
Problem
Magnetoresistive random access memory (MRAM) devices are susceptible to external magnetic fields, which can interfere with their operation, and existing technologies have not effectively addressed this issue in semiconductor packaging.
Innovation Solution
A method of manufacturing a semiconductor package that involves forming cracks in a lattice structure on a wafer, grinding the back surface, bonding a tape, expanding it to divide the wafer into chips, forming shield layers on the chips, and bonding them to a substrate with additional shield patterns to create a magnetic shield unit that protects the MRAM devices from external magnetic fields.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If MRAM devices are used in semiconductor packages, then high-speed non-volatile memory functionality is achieved, but the devices become susceptible to external magnetic field interference
Solution Approach 1:
A magnetic shield layer made of permalloy is introduced as an intermediary between the external magnetic field and the MRAM device. This shield layer absorbs and redirects magnetic field lines, preventing them from reaching the sensitive MRAM structures. The shield layer is positioned between the MRAM device and the external environment, acting as a protective barrier that maintains operational stability while allowing the MRAM functionality to remain intact
2Object-affected harmful factors
If shield layers are added to protect MRAM devices, then magnetic field interference is reduced, but the device structure and manufacturing complexity increase
Solution Approach 1:
The magnetic shield layer is merged with the existing package structure by integrating it into the substrate or encapsulation layers. Rather than adding a separate, standalone shield component, the permalloy layer is deposited directly onto the substrate surface or within the encapsulation structure, combining the shielding function with the structural support and protection already provided by the package. This reduces the number of discrete components and simplifies the overall device architecture
Solution Approach 2:
The shield layer uses permalloy (an alloy of iron and nickel) which has specific magnetic properties including high permeability and low coercivity. By changing the material parameter to permalloy and controlling its thickness (typically tens to hundreds of nanometers), the shield provides effective magnetic field protection while maintaining a thin profile that does not significantly increase the overall device dimensions or complexity
3Object-affected harmful factors
If additional shield patterns are formed on chip surfaces, then magnetic shielding effectiveness is improved, but manufacturing process steps increase
Solution Approach 1:
The magnetic shield layer is formed on the substrate surface before the MRAM devices are mounted or before final packaging. By preparing the shield layer in advance on the substrate, the shielding structure is already in place to protect the devices once they are integrated. This preliminary formation of the shield layer simplifies subsequent assembly steps and ensures protection is built into the structure before devices are exposed to potential magnetic interference
4Productivity
If the wafer is divided into semiconductor chips after bonding tape, then chip separation is achieved, but crack formation and grinding precision are critical
Solution Approach 1:
The wafer is segmented into individual chips by forming cracks through the wafer thickness using laser irradiation or mechanical scribing. These cracks serve as initiation points for breaking the wafer into separate chips. The segmentation is controlled by positioning the cracks at predetermined locations between chip regions, allowing clean separation while maintaining the integrity of each chip. This segmentation approach enables efficient chip production while controlling the precision requirements through automated crack formation processes
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 effectively shields MRAM devices from external magnetic fields, ensuring stable operation by using permalloy shield patterns that absorb magnetic interference, thereby maintaining the integrity and functionality of the semiconductor package.
Implementation Method 1
forming a magnetic shield unit that shields the MRAM device from an external magnetic field
Implementation Method 2
The shield layer and the first and second shield patterns may include permalloy that is an alloy of Fe and Ni
Implementation Method 3
The forming of the cracks in the lattice structure on the wafer may include irradiating the active surface of the wafer with a laser beam in the lattice structure
Implementation Method 4
The semiconductor chips and the substrate are physically and electrically connected by a bonding wire
Data Source
AI summary
A method of manufacturing a semiconductor package having a magnetic shield function is provided. The method includes forming cracks in a lattice structure on an active surface in which electrode terminals are formed; grinding a back surface of a wafer facing the active surface, bonding a tape on the active surface of the wafer, expanding the tape such that the wafer on the tape is divided as semiconductor chips, forming a shield layer on surfaces of the semiconductor chips and the tape, cutting the shield layer between the semiconductor chips and individualizing as each of the semiconductor chips which has a first shield pattern formed on back surface and sides, bonding the semiconductor chips on a substrate, and forming a second shield pattern on each of the active surfaces of the semiconductor chips, wherein the semiconductor chips and the substrate are physically and electrically connected by a bonding wire.