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Thickness Measurement Technology for Thin Films on Sapphire Substrate


TECHNOLOGY AREA(S): Electronics, Sensors

The technology within this topic is restricted under the International Traffic in Arms Regulation (ITAR), which controls the export and import of defense-related material and services. Offerors must disclose any proposed use of foreign nationals, their country of origin, and what tasks each would accomplish in the statement of work in accordance with section 5.4.c.(8) of the solicitation.

OBJECTIVE: Develop an innovative metrology system for measuring thickness of various thin films on a sapphire substrate.

DESCRIPTION: Currently there is no metrology tool to measure thickness of thin films on sapphire substrate wafer, which is also called silicon on sapphire (SOS) wafer, since sapphire is transparent to light. When fabricating integrated circuits with SOS wafer, a typical thickness of a thin film can’t be measured with the current tool set to verify the wafer process conditions. As a result, the SOS process is not well controlled, and it could lead to lower yield. Therefore, it is desirable to have an innovative and non-destructive system to perform thickness measurements on a processed SOS wafer. The measurements are for thin films and thin film stacks of epitaxial silicon (epi Si), silicon dioxide (oxide), silicon nitride (nitride), polycrystalline silicon (p-Si), and amorphous silicon (a-Si). The system should be capable of measuring thin film thickness with ± 10 percent accuracy.

PHASE I: Develop an optical method to measure thickness of the described thin films and a stack of the films on sapphire substrate wafer. The film stack should include oxide over epi Si, nitride over oxide and epi Si, p-Si or a-Si over oxide, and nitride over oxide and epi Si. The method also includes any possible hardware and software to be developed. The end result of Phase I is a feasibility study report.

PHASE II: From the result study of Phase I, develop a prototype system of film thickness measurement, which is integrated with DMEA (Defense Microelectronic Activity) foundry to provide and demonstrate the system capability. The system should be capable to measure thickness of the mentioned thin films and their stacks on a 150mm processed SOS wafer with the following metrics: 1) 0Å = epi Si <3000Å 2) 0Å= thin oxide/epi Si <500Å (measured oxide above epi Si) 3) 400Å= oxide <14000Å 4) 0Å= p-Si or a-Si/oxide <3000Å (measured p-Si or a-Si over oxide) 5) 0Å= nitride/thin oxide/epi Si <2000Å (measured nitride above oxide and epi Si) 6) 0Å= nitride/oxide <10000Å (measured nitride above oxide) Oxide and nitride can be made by either thermal oxidation or chemical vapor deposition (CVD) process.

PHASE III DUAL USE APPLICATIONS: Develop and expand the successful prototype system in Phase II into a production scale through government and commercialization. During this phase, the system should be refined and produce production quantities for both military and commercial applications.


  • Md Abull Hossion, Brij Mohan Arora, “Optical characterization of Intrinsic Poly Silicon Film for Photovoltaic Application on Sapphire and TiO2 Substrate by HWCVD,” International Conference on Electrical Engineering and Information & Communication Technology (ICEEICT) doi: 10.1109/ICEEICT.2014.69
  • Peregrine Semiconductor,, “UltraCMOS Process Technology – The Ultimate SOI”, July 2012
  • Dieter K. Schroder, “Semiconductor Material and Device Characterization” 3nd Edition, John Wiley & Son, 2006.

KEYWORDS: Thin Film/Sensors/Measurement/Sapphire


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