| AVS 62nd International Symposium & Exhibition | |
| Nanometer-scale Science and Technology | Tuesday Sessions |
| Session NS-TuP |
| Session: | Nanometer-scale Science and Technology Poster Session |
| Presenter: | Sungho Lee, Samsung Electronics, Republic of Korea |
| Authors: | S.H. Lee, Samsung Electronics, Republic of Korea C.W. Yang, Sungkyunkwan University, Republic of Korea |
| Correspondent: | Click to Email |
As the semiconductor device feature size continues to be scaled down, the aspect ratio of the capacitor becomes higher to satisfy the high capacitance requirement for cell operation. The higher the height of capacitor, the more storage node bent. Therefore, we adopt the Mechanically Enhanced Storage node for virtually unlimited Height (MESH) [1] process to prevent storage node’s bending nowadays. However, even with this process, there are failure problems and the yield is still less than 100%. To find methods to prevent these problems, the failures should be analyzed. Normally physical failure analysis (PFA) needs a site specific transmission electron microscopy (TEM) sample which is vertically cross-sectioned by using focused ion beam (FIB) [2], but sometimes a plan-view TEM (PVTEM) sample [3] is also required to clarify the exact cause of failure .
The nodes do not stand in a line after conventional FIB work for PVTEM sampling. The node may fall off a TEM thin foil sample in the worst case. In order to overcome this problem, we developed new FIB technique for PVTEM sampling of MESH capacitor. The new FIB technique comprises four major steps:
Step 1 : ‘1’ shape marking at the target height
Step 2 : milling a top part of capacitor
Step 3 : carbon deposition to fill the space between nodes
Step 4 : milling a bottom part of capacitor
Conventional FIB work consists of step1, 2, and 4. We add a carbon deposition step right after the 2nd step of the top part milling. We found that the nodes seem to move during the 3rd step milling (mill a bottom part) because of the void between nodes.
We adopted this modified milling method to the TEM sampling of a real failure case and obtained a PFA result of a 2 bit failure using plan-view TEM image. The new modified milling method turned out to be very effective and can be adopted in a mass production.
References
[1] D. Kim, J. Kim, M. Huh, Y. Hwang, J. Park, D. Han, D. Kim, M. Cho, B. Lee and H. Hwang, in Electron Devices Meeting, 2004. IEDM Technical Digest. IEEE International, p. 69 (2004).
[2] Moon-Yee Wang, S.X. Lee, S. Peri, “The Effect of FIB Technology on Design Methodology”, Circuits and Systems, 1993, 725-728 vol1.
[3] S. Lee, C.-W. Yang, T. J. Park, J. K. Kim, J. H. Ahn, J. Choi and G. Y. Song, in Meeting Abstracts, p. 1608 (2014).