1. Field of the Invention
Exemplary embodiments of the present invention relate to a method of inspecting a substrate or, more particularly, to a method of inspecting a substrate capable of enhancing reliability of a process of inspecting a status of a target object formed on a substrate.
2. Discussion of the Background
In general, an inspection process is required to inspect reliability of a substrate with an electronic device mounted thereon before and after the electronic device is mounted on the substrate. For example, a pad area of a substrate is inspected in order to inspect a status of solder for mounting an electronic device onto the substrate, before the electronic device is mounted on the substrate, and the status of the electronic device is inspected if the electronic device is properly mounted after the electronic device is mounted on the substrate.
Recently, a method of inspecting a substrate has been used for inspecting three dimensional shape of a target object by using an apparatus of inspecting three dimensional shape, which includes a plurality of projecting parts, each of which includes a light source and a grating to project pattern light onto the target object, and a camera capturing an image of the target object.
In order to inspect the three dimensional shape of the target object, height data of the target object is required. The height data is obtained by multiplying a scale factor to the measured phase data. Further, when a plurality of projecting parts is used, all data measured by each of the projecting parts are merged to generate the height data.
However, each of the projecting parts irradiates different pattern light, so that phase data measured by using the projection part is different. Further, the height should be measured based on a reference corresponding to reliable ground, with regard to a plurality of projecting part in order to obtain reliable height without noise per projecting part. However, there is no way of excluding noise data. Additionally, when a target object is an electronic device with height, there exists a shadow induced by the electronic device, which makes effect data of the ground area insufficient, so that reliability of the height of the target object is lowered. Further, there may be tilt in measurement data in accordance with environment of the substrate to induce deviation between the projecting parts, so that reliability of the integrated height data is lowered.