Phase-change random access memory (PRAM) is a nonvolatile memory technology that has a number of advantages over flash memory technology. PRAM uses heat-induced changes of state (between crystalline and amorphous) in a chalcogenide glass to store information. The state changes are accompanied by changes in resistivity, which provide the electrical mechanism for data storage and retrieval. Chalcogenide glass is also found in optical storage media, though in these applications changes in refractive index are used to store information. Recent developments have demonstrated the ability to double PRAM storage density by incorporating two additional intermediate states (for a total of four) to store two bits of information per cell. The most commonly used chalcogenide glass, known as GST, is composed of germanium, antimony and tellurium (Ge2Sb2Te5).

The MetaPULSE's ultra-fast picoseconds acoustic technology provides a non-contact, non-destructive method for measuring the thickness of GST films being introduced with emerging PRAM devices. The MetaPULSE has the unique ability to measure the GST film thickness in via arrays on product wafers, avoiding the need to perform off-line, destructive cross-section analysis.

For additional information, request our Application Note "MetaPULSE-III for Measurement of GST Layers in PRAM Memory Devices".