MRAM Focus
Magnetoresistive Random-Access Memory (MRAM) can change the future of embedded memory for IoT and automotive chips.
MRAM Technology
There are big plans for MRAM. Beyond IoT and automotive chips, IC manufacturers are planning on integrating MRAM into other mobile applications. The high read/write speeds and non-volatility provide significant advantages. Logic circuits can access the memory quicker, resulting in an extended battery life.
MRAM Process
MRAM manufacturing requires the control of deposition, annealing, magnetization and etch of very thin ferromagnetic layers. These memory cells are embedded into the logic chip when the chip is getting close to completion. At this late stage, the value of the chip is high so the MRAM cell must be carefully controlled to maintain high yield.
MRAM Process Flow and Control
Magnetic Tunnel Junction (MTJ)
CIPT
Current In-Plane Tunneling (CIPT) is a 12-point probe electrical technique that measures resistance versus magnetic fields
CIPT provides important properties of the free layers after deposition, annealing and magnetization
This technique is considered the standard for inline MRAM monitoring
MOKE
Magneto-Optical Kerr Effect (MOKE) detects subtle changes in the free and pinned layers in the stack
The contactless measurement uses a strong magnetic field to determine polarization state changes
Optical technique with no special targets required allows measurement before and after etch
Film Thickness
Spectroscopic ellipsometry technology provides valuable film thickness information
High accuracy for individual metallic layer thickness measurements in the MTJ stack is required
Understanding the film thickness of thin layers is critical to control the MRAM device performance
Scatterometry
Optical scatterometry (SCD) measurement determines the shape of the individual cells after etch
On device measurement provides the most relevant structural information
The shape of the MRAM structure determines the final electrical properties of the MRAM cells