Charge collection microscopy of in-situ switchable PRAM line cells in a scanning electron microscope: technique development and unique observations

J L M Oosthoek; R W Schuitema; G H ten Brink; D J Gravesteijn; B J Kooi

doi:10.1063/1.4914104

Charge collection microscopy of in-situ switchable PRAM line cells in a scanning electron microscope: technique development and unique observations

Rev Sci Instrum. 2015 Mar;86(3):033702. doi: 10.1063/1.4914104.

Authors

J L M Oosthoek¹, R W Schuitema¹, G H ten Brink¹, D J Gravesteijn², B J Kooi¹

Affiliations

¹ Zernike Institute for Advanced Materials and Materials innovation institute M2i, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands.
² NXP Semiconductors, Kapeldreef 75, B 3001 Leuven, Belgium.

PMID: 25832233
DOI: 10.1063/1.4914104

Abstract

An imaging method has been developed based on charge collection in a scanning electron microscope (SEM) that allows discrimination between the amorphous and crystalline states of Phase-change Random Access Memory (PRAM) line cells. During imaging, the cells are electrically connected and can be switched between the states and the resistance can be measured. This allows for electrical characterization of the line cells in-situ in the SEM. Details on sample and measurement system requirements are provided which turned out to be crucial for the successful development of this method. Results show that the amorphous or crystalline state of the line cells can be readily discerned, but the spatial resolution is relatively poor. Nevertheless, it is still possible to estimate the length of the amorphous mark, and also for the first time, we could directly observe the shift of the amorphous mark from one side of the line cell to the other side when the polarity of the applied (50 ns) RESET pulse was reversed.