A process for producing thin layers in electronic devices such as integrated circuit chips, is provided. The process includes the steps of injecting a precursor fluid into a thermal processing chamber containing a substrate, such as a semiconductor wafer. The precursor fluid is converted into a solid which forms a layer on the substrate. In accordance with the present invention, the precursor fluid is pulsed into the process chamber in a manner such that the fluid is completly exhausted or removed from the chamber in between each pulse. Light energy can be used in forming the solid layers.