Laser-Induced Modulated Reflectance in Semiconductor Materials Analysis

During the past few years, thermal wave physics has been successfully applied to studies of semiconductor materials and microelectronic devices. Previously, we described how these materials and devices might be examined with thermal wave imaging.1 This imaging is performed in a scanning electron microscope with a thermoelastic technique for thermal wave detection. Although this technique is a very sensitive detection method for thermal waves,2 it has limited applicability for integrated circuit process control and inspection because it requires contact to a transducer and thus is potentially contaminating. Furthermore the results are often strongly dependent on difficult to control acoustic variables such as sample geometry and sample/detector coupling. To overcome these problems we have developed a noncontact thermal wave technique that can be used at the high modulation frequencies required for micron-scale resolution.3–5