Silicon substrate processing method for observing defects in semiconductor devices and defect-detecting method

A defect-detecting method comprising the steps of:

• (I) processing a silicon substrate using a method including the following steps (A) through (D) to achieve a thickness that enables appearance of light interference fringes in a defect-containing area, the thickness of the processed silicon substrate being greater than a depth of diffusion layers formed on a front side of the silicon substrate, and allowing a visible laser beam to reach the diffusion layers from a backside of the silicon substrate;
• (A) evenly reducing thickness of a backside of the silicon substrate to an extent where mechanical strength is maintained and the metal layer on the silicon substrate remains intact;
• (B) detecting a defect from the backside of the silicon substrate after the step (A);
• (C) further reducing the thickness of an area of the silicon substrate containing the defect by processing the backside of the silicon substrate;
• (D) measuring the thickness of the defect-containing area of the silicon substrate which is reduced in the step (C), and determining whether interference fringes are formed by irradiating the silicon substrate from the backside with a light, and if interferences are not formed, repeating steps (C) and (D), wherein the step (D) includes a step of measuring the thickness of the defect-containing area of the silicon substrate based on interference fringe formation and electron acceleration energy which is detected when a pattern on a front side of the defect-containing area is observed from the backside of the silicon substrate by using a SEM;
• (II) detecting a defect in the silicon substrate;
• and
• (III) placing on the backside of the silicon substrate a mark showing the defect location.