MRAM, GMR and hard disk drive materials are all formed from the same types of layer structures, namely magnetic metal layers, with ultra-thin insulating spacers. These materials are ideally characterized by XRR and XRF.

{tab=MRAM}

MRAM is a low power, non-volatile alternative to DRAM memory cells, which require high power to refresh the charge every few milliseconds. Based on a one transistor one resistor design, information is stored via the magnetic alignment of a floating storage layer. Bits are programmed in the floating layer by passing a current through the word line. The electrical characteristics of the resistor are controlled via the precise deposition of a dielectric potential barrier made of Al2O3, as well as with the thickness and densities of metallic layers forming a stack of alternating magnetic domains.

In XRR mode, Jordan Valley meets the process integration challenges of MRAM thin metal and dielectric stacks by measuring thickness, phase density and roughness of individual layers, pending the choice of metal used.

In addition, the XRD mode enables characterization of the crystallographic phase of the materials following their deposition and anneal.

{tab=GMR}

GMR (Giant Magneto-Resistance) devices are utilized within the hard disk drive industry in the read-write heads. The layers utilized within the GMR devices are stacks of several ultra-thin magnetic and non-magnetic layers.

In XRR mode, Jordan Valley meets the process integration challenges of MRAM thin metal and dielectric stacks by measuring thickness, phase density and roughness of individual layers, pending the choice of metal used.

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General Thin Film XRD

X-ray diffraction has been utilised for nearly 100 years to characterize the structural properties of materials. The main focus of the Jordan Valley systems is in the characterization of the microstructure of thin films.

The D1 system is the ideal choice for all of these measurements. With the highest resolution goniometer commercially available on the market, wide Chi (tilt) and Phi (azimuthal rotation) ranges for residual stress and texture measurements, and the automated configuration of the system along with fully automated measurements, the D1 is perfect for all of your thin film XRD needs.

The fundamental principle is that of Bragg's law, where the position of the peak is related to the lattice spacing. However, using this simple principle gives the possibility to determine a number of key characteristics of the film, including

• Crystallinity
  • Peak intensities
• Phase
  • Peak positions/intensities
• Grain size/strain
  • Peak widths
• Texture
  • Peak intensities
• Residual stress
  • Peak positions

XRR: X-ray Reflectometry for Thin Films metrology

X-ray reflectometry (XRR) is gaining in popularity for the measurement of thickness, density and roughness of thin films. Unlike other techniques, multilayer structures can be determined, with no restriction on the crystalline nature of the films. The thicknesses can range from a few atomic layers to 1 micron of material. The measurement is fast (seconds) and can be applied for in-line product wafers metrology.

The measurement is performed at a glancing angle, with the specular reflection of the X-rays being detected by a detector. The intensity is recorded as a function of angle, and this information is modelled to determine the structure of the material in question.

The example above shows the fringe period which relates to the thickness of the layer (the thicker the layer, the shorter the period) and the critical angle, which is related to material density.

The simulation above shows a 2-layer structure, with the thickness, roughness and density determined for independent layers.