In-line monitoring of OLED layer thickness and dopant concentration

A metrology system comprising:

• a chamber to hold a workpiece under vacuum conditions, the chamber including a support to hold the workpiece;
• a first light source to generate a first light beam that impinges a surface of the workpiece at an oblique angle to induce photoluminescence in a layer on the workpiece in the chamber;
• a second light source to generate a second light beam that impinges the surface of the workpiece at a normal angle to be reflected from the layer on the workpiece;
• a detector assembly including
• optical components to collect on a common optical path both photoluminescent light emitted by the layer substantially normal to the surface and reflected light that is reflected from the workpiece substantially normal to the surface,
• a first detector to measure an intensity of the photoluminescent light,
• a second detector to measure an intensity of the reflected light, and
• a beam splitter on the common optical path to direct at least a portion of the photoluminescent light to the first detector and at least a portion of the reflected light to the second detector;
• and
• a control system configured to
• receive the measured intensity of the photoluminescent light,
• receive the measured intensity of the reflected light and generate a thickness measurement for the layer therefrom, and
• determine a doping concentration of the layer from the thickness measurement and the measured intensity of the photoluminescent light.