Chemical and structural analysis on magnetic tunnel junctions using a decelerated scanning electron beam

Abstract

Current information technology relies on the advancement of nanofabrication techniques. For instance, the latest computer memories and hard disk drive read heads are designed with a 12 nm node and 20 nm wide architectures, respectively. With matured nanofabrication processes, a yield of such nanoelectronic devices is typically up to about 90%. To date the yield has been compensated with redundant hardware and software error corrections. In the latest memories, approximately 5% redundancy and parity bits for error corrections are used, which increase the total production cost of the devices. This means the yield directly affects the device costs. It is hence critical to increase the yield in nanofabrication. In this paper, we have applied our recently developed method to image buried interfaces in combination with chemical analysis to evaluate magnetic tunnel junctions and have revealed their different magnetoresistance ratios caused by the presence of materials formed at the junction edges. The formation of these materials can be avoided by optimising the junction patterning process to remove residual carbon introduced from resist. Our imaging method with chemical analysis have demonstrated a significant potential for the improvement of junction performance, resulting in higher yields. This can be used as a quality assurance tool in a nanoelectronic device production line.

Non-destructive imaging for quality assurance of magnetoresistive random-access memory junctions

“…Once the methodology for the non-destructive imaging technique had been streamlined, the technique was used to investigate batch productions of magnetic tunnel junction (MTJ) devices [16]. This was done with the intent on investigating the interfaces to explain the root cause of low tunneling magnetoresistance (TMR) devices and offer a solution to increase the yield of high TMR devices.…”

Non-Destructive Imaging on Synthesised Nanoparticles

“…Further, the combinations of spectroscopic and scattering/reflective chemical analysis allowed us to evaluate the origins of the defects, which is ideal as a quality assurance for nano-electronic industries. The defect details and the corresponding transport properties can be fed back to the processes of the device fabrication processes, improving the yields [ 4 ].…”

Revealing the importance of interfaces for pure spin current transport

“…Recently, however, a technique has been pioneered which provides direct non-destructive access to buried interface characterization via a scanning electron microscope (SEM). 9,10 This technique opens up possibilities for such a direct connection between the spin transport and interfaces in relation to the fabrication recipes.…”

“…A significant amount of the generated spin current in the sample based on recipe 2 is lost due to spin flip events at the interface and does not contribute to the (i)SHE signal.To directly probe the structural nature of the different relevant Py/Cu and Pt/Cu interfaces for devices made via the two recipes directly and thus to reveal the origin of the different results of the spin transport measurements, we additionally characterize the relevant interfaces via a special SEM technique. This technique allows for non-destructive buried interface imaging by employing a decelerated electron beam, as explained in detail in our previous work 9,10.…”