Non-Invasive Metrology Tool for Wafers, Semiconductor Devices and MEMS

Resolves Depth and Angles to Deliver Precise Measurements

This tool is a type of interferometer that non-invasively measures wafers, layers in semiconductor devices and microelectromechanical systems (MEMS). Used in a wide range of computer products, MEMS are small electric-powered machines 100 microns or less in length. Available interferometers, used heavily in manufacturing to assess the quality of these items, only measure a sample by optical thickness (a multiplication of geometric thickness and refractive index). For example, the refractive index of a typical silicon wafer varies among different areas of the wafer, so a conventional interferometer is unable to accurately determine the thickness or thickness variation of the wafer. The new interferometer, developed by UF researchers, overcomes this deficit. Precise and non-destructive, the invention is positioned to capitalize on a growing field: The worldwide semiconductor market is projected to reach $490 billion in 2019 and the MEMS market, $26.8 billion by 2023.

Application

Measurement tool that improves quality control of semiconductor devices and microelectromechanical systems by assessing these objects without destroying them

Advantages

• Measurement is nondestructive, eliminating waste
• Requires no access to the back side of a sample, allowing measurements of large and non-transparent objects
• Eliminates physical contact with sample, increasing ease of operation
• Removes need for combining multiple measurement techniques, making the tool highly reliable, and saving time and money
• Increased accuracy and power, improving quality control

Technology

In the manufacturing field, interferometers measure semiconductor devices and MEMS for quality control. A simplified interferometer layout can include a two-beam interference structure with a single wavelength (monochromatic) laser source. Conventional Low-Coherence Interferometers (LCI)s facilitate a 3D profile or tomography. Low-coherence interferometers can employ a white light interferometer (WLI) when using a broadband light source and may be referred to as a temporal low-coherence interferometer (T-LCI). T-LCI offers little angular information in a measurement, so it is difficult to accurately separate the components of thickness and refractive index from the result. University of Florida researchers have developed a new kind of scanning spatial low-coherence interferometer (S-LCI) that retains similar data acquisition and processing to scanning T-LCI. Unlike a T-LCI, however, this S-LCI can resolve depth and angles while delivering precise measurements.