Materials Research Society Fall meeting 2010, Boston, Massachusetts, USA
Three-dimensional dopant distributions in patterned MOSFETs
studied by laser-assisted atom probe tomography
2 Department of Materials Science and Engineering, Kyoto University, Kyoto 606-8501, Japan
3 Toshiba Nanoanalysis Corporation, Kawasaki, 212-8583, Japan
4 MIRAI-Selete, Tsukuba, Ibaraki, 305-8569, Japan
New Energy and Industrial Technology Development Organization ( NEDO )
Grants-in-Aid for Scientific Research of the Ministry of Education, Culture, Sport, Science and Technology, Japan ( No. 17002009, 20760212, and 21246142)
- As the sample has three dimensional structures, It is difficult to analyze the dopant distributions by SIMS. TEM-EDX is not suitable since the channel dopant concentration is lower than detection limit.
Laser-assisted atom probe tomography (APT) is possible to identify dopant positions in 3D with nearly atomic scale resolution .
- To obtain the three dimensional elemental maps of MOSFET which has gate patterned sample, and analyze the dopant distribution in gate and channel regions.
- To investigate the effect of fabricating the gate pattern and source/drain extension on channel dopant distribution.
Following three-type samples of n- and p- type MOSFETs are prepared in order to study the dopant distribution in gate patterned MOSFET structures.
- Gate patterned MOS structures with channel, source/drain extension and Halo implantation
- Gate patterned MOS structures with channel and source/drain extension implantation without halo (to study the effect of source/drain extension implantation on the channel dopant distribution)
- Only gate patterned structures with channel implantation
Table.1 A list of prepared samples
Needle specimens for APT are fabricated by FIB/SEM dual beam systems.
- Selection of the analysis region.
- Scraping out around the site.
- Lift out using manipulator.
- Mounting the sample on micro flattop tip.
- Sharpening the specimen using annular milling patterns.
- Needle specimen for APT measurement.
Result of APT
- Region ① and ②
Segregation of P atoms on grain boundaries was observed.
- Region ③
We observed extension of source/drain and halo structures clearly, and a high concentration of B atoms was observed at the edge of source/drain extension.
- Region ④ and ⑤
Distribution of B atoms seems to uniform in the gate.
- Region ⑥
We observed extension of source/drain and slightly observed P atoms implanted as halo.
-B density in the channel region underneath the gate was locally higher than that in neighboring channel region. This tendency is more remarkable in the samples without source/drain extension.
-There was no significant difference between the samples with and withoutsource/drain extension.