A new fluorescent and Photoemission Microscope for submicron VLSI IC failure analysis

Photoemission Microscopy (PEM) has been widely used in modern VLSI IC failure analysis. As its camera normally detects the emissions from visible to near infrared light, it is more sensitive to non-heat-related failure such as junction related defect, gate oxide related defect, etc. As a complimentary technique, infrared photoemission microscope was developed by different companies or FA labs for heat-related defect fault isolation. However, its spatial resolution was limited due to the wavelength of the infrared light it used. This is especially a concern for submicron below VLSI technology. On the other hand, liquid crystal analysis (LCA) as an economical FA technique has been also used with great success for hot spot detection during IC failure analysis since 1980´s. Nevertheless, its thermal sensitivity is also limited by the reduction of device operating voltage in deep submicron technology IC. To overcome the disadvantages of both techniques, in this paper, we developed a system by using one slow-scan CCD camera to detect both heat related and non-heat-related defects. The principle of analyzing the non-heat-related failure is same as that of PEM. For the heat-related defect, we use a chemical film (mixture of EuTTA and PMMA) under UV light excitation to convert the heat generated by the defect to fluorescent light of a peak at about 612 nm, which is able to be detected by the CCD camera. This is actually a kind of fluorescent microthermal imaging (FMI). The system based on such a concept was setup in our lab for submicron and deep submicron VLSI IC failure analysis. In this paper, comparison between the liquid crystal analysis and FMI also discussed.