In-line monitoring of OLED layer thickness and dopant concentration
An organic light-emitting diode (OLED) deposition system includes two deposition chambers, a transfer chamber between the two deposition chambers, a metrology system having one or more sensors to perform measurements of the workpiece within the transfer chamber, and a control system to cause the system to form an organic light-emitting diode layer stack on the workpiece. Vacuum is maintained around the workpiece while the workpiece is transferred between the two deposition chambers and while retaining the workpiece within the transfer chamber. The control system is configured to cause the two deposition chambers to deposit two layers of organic material onto the workpiece, and to receive a first plurality of measurements of the workpiece in the transfer chamber from the metrology system.
1. 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.
2. The system of claim 1 , wherein the first detector comprises a spectrometer.
3. The system of claim 1 , wherein the second light source and second detector comprise an interferometer.
4. The system of claim 1 , wherein the second light source and second detector comprise a digital holographic microscope.
5. The system of claim 4 , wherein the second detector comprises a CCD camera.
6. The system of claim 1 , wherein the detector assembly includes a metrology head positioned within the chamber, and wherein the first detector and the second detector are positioned outside the chamber.
7. The system of claim 6 , wherein the metrology head includes an optical fiber to transmit light collected in the chamber to the first detector and the second detector.
8. The system of claim 7 , wherein the optical fiber transmits light from the second light source to the workpiece.
9. The system of claim 6 , wherein the metrology head is movable within the chamber.
10. The system of claim 9 , comprising a height sensor secured to the metrology head to measure a height of the metrology head above the workpiece.
11. The system of claim 9 , comprising a tilt sensor secured to the metrology head to measure a tilt of the metrology head relative to the surface of the workpiece.
12. The system of claim 6 , wherein the metrology head comprises an objective lens.
13. The system of claim 1 , wherein the support is configured to hold the workpiece stationary as the first detector measures the intensity of the photoluminescent light and as the second detector measures the intensity of the reflected light.
14. The system of claim 1 , comprising a workpiece transport system configured to transfer a workpiece into and out of the chamber under vacuum conditions.
15. The system of claim 14 , the chamber comprises a transfer chamber positioned on a path of the workpiece between deposition chambers as provided by the workpiece transport system.