Skip to main content

Spectroscopic Ellipsometry Tool in the Integrated Measurements and Characterization Cluster Tool

This page provides details on the spectroscopic ellipsometry (SE) tool in the Integrated Measurements and Characterization cluster tool. This capability should be operational in 2009. Additional capabilities include attenuated total reflection (ATR), and, in the future, residual gas analysis (RGA). This tool supports the U.S. Department of Energy (DOE) Technology Roadmaps for crystalline and amorphous silicon, copper indium gallium diselenide, cadmium telluride, organic PV, and transparent conducting oxides. Access the Technology Roadmaps on the DOE Solar Energy Web site.

This spectroscopic ellipsometry tool can determine optical properties of photovoltaic (PV) materials under various temperature, ambient environment, and pressure conditions. Accurate knowledge of optical properties helps in designing PV devices and optimizing the device fabrication process. This tool plays a crucial role for the following reasons:

Photo of a large horizontal cylinder with multiple flanges, valves, and gauges.  A large flange on the right is part of the load lock.

Ellipsometer tool, which is part of the the Integrated Measurements and Characterization cluster tool.

  • The unique functionality of the chamber can simulate many different environmental conditions that PV materials undergo during device fabrication, and it can systematically monitor the materials/device degradation process.

  • SE is non-destructive and can determine refractive index (n) and extinction coefficient (k) over a wide range of photon energies. The SE used in this tool is an advanced dual-rotating compensator-type system with high accuracy and the capability of analyzing optically anisotropic materials.

  • By integrating this tool into the Integrated Measurements and Characterization cluster tool, samples can be transferred between the materials synthesis tools and other characterization tools under vacuum without exposing their surface to air. Possible changes in surface and/or bulk properties are minimized to obtain accurate optical properties.

Applications:

  • Monitoring or controlling the growth of PV devices by building the library of optical properties of materials under various conditions
  • By stopping device fabrication at any step and transporting the device to this tool, we can correlate the surface or bulk property to device performance.

Special features:

  • Temperatures for substrate heating range from room temperature to 800°C. Temperature uniformity is >±2% from the center to the edge of a 157-mm x 157-mm substrate
  • Pressure ranges from atmospheric to high vacuum (<10-8 torr)
  • Atmospheres include water vapor (wet and dry), oxygen, vacuum, and other ambient environments
  • Has control units for pressure and flow
  • Elliptical spot size is 3–4 mm
  • Scanning range is 245 to 1680 nm, with a typical spectral resolution of 1.6 nm
  • Angle of incidence is 70° for SE and 45° for ATR
  • Can rotate (but not move x-y) in-plane manually or by computer
  • Has its own load lock and additional ports for other in-situ measurements
  • Sample orientation is face-down

Contact Sukgeun Choi for more details on these capabilities.