Kokusai Electric is one of the leading semiconductor thin film process equipment manufacturers in the world. Recently, in the context of Japan Society of Applied Physics 69th Spring Meeting 2022, Kokusai presented their advanced thin film measurement and analysis concept used in their semiconductor process development.
The concept focuses on film thickness and localized film composition measurements from the special designed 3D patterned substrates, where the patterns are fine high aspect ratio structures.
The average film thickness is obtained indirectly by measuring the mass change in the special 3D patterned wafer before and after the film depositions. The thickness accuracy is further improved by taking into account the high aspect ratio and wafer level non-uniformity measured by PillarHall® Lateral High Aspect Ratio (LHAR) test chips positioned on the carrier wafer. The PillarHall® measurement, enables easy screening after peeling off the top roof membrane and by measuring the film thickness distribution and conformality by the ellipsometer line-scanning measurements.
PillarHall® LHAR test chip has also another important function in Kokusai’s analysis concept. Namely, it is used for film elemental composition characterization along the trench wall in high aspect ratio structure. The measurement is carried out as a line-scan by XPS or SEM-EDS. For example, the characterization showed that two kinds of SiN processes behaved differently and Si/N composition changes along the high aspect ratio (AR>1000) trench were observed.
Figure 1. PillarHall experiment summary
Figure 2. SiN film thickness data
Figure 3. SiN(2) XPS data
Figures 1-3 show the PillarHall experimental set-up, data from the film thickness penetration depth profiles and XPS composition data of two kind of Kokusai’s SiN processes, SiN (1) and SiN (2).
Kenji Kameda and Akane Kitamura from Metrology Team, Kokusai Electric emphasized that:” It is difficult to obtain the analysis of thin films on high aspect ratio patterns without cross-sectional TEM. PillarHall is a simple and effective tool, it has fine patterns, and it enables us to use XPS and ellipsometer instead of TEM. Therefore, PillarHall is useful as an efficient measurement tool to improve Kokusai’s film forming technology.”
PillarHall LHAR test chip is a product of Chipmetrics Ltd, Finland. Chipmetrics CEO Dr. Mikko Utriainen reminds that any PillarHall data can be published without confidentiality concerns and the results are also well comparable between reactor systems and processes. The openness and accuracy of the ALD conformality data was one of the reasons why pioneering ALD scientists in Finland started to develop the PillarHall concept already in 2014.
Kokusai’s example shows that PillarHall is an efficient measurement tool and help to improve film forming technology for advanced semiconductor processes.
PillarHall is a product of Chipmetrics Ltd. Contact: info@chipmetrics, www.chipmetrics.com