Field of the Invention
The present invention relates to an evaluation method for evaluating the gettering capability of a device wafer on which plural devices are formed on a surface.
Description of the Related Art
In small-size, light-weight electronic apparatus typified by mobile phones, a device chip having a device such as an IC is an essential configuration. The device chip is manufactured by partitioning a surface of a wafer composed of a material such as silicon by plural planned dividing lines called streets and forming a device in each region and then dividing the wafer along the streets, for example.
In recent years, there are increasing opportunities to process a wafer on which devices have been formed (hereinafter, device wafer) into a thin wafer for the purpose of size reduction, weight reduction, and so forth of the device chip. However, for example when the device wafer is polished to be thinned to 100 μm or thinner, the gettering effect to suppress the movement of metal elements harmful to the devices is lowered and operation failure of the device frequently occurs. To solve this problem, a processing method in which a gettering layer that captures metal elements is formed in a device wafer has been proposed (refer to e.g. Japanese Patent Laid-open No. 2009-94326). In this processing method, the device wafer is ground under predetermined conditions to form the gettering layer including predetermined grinding distortion while keeping the flexural strength of the device wafer.