Missing pattern wafers can sometimes be seen in the thumbnail images that are generated in the EAGLEview software causing the semiconductor wafers to appear as a different color. Unpolished (CMP) semiconductor wafers also appear as missing pattern wafers.
Some missing pattern wafers are very easy to detect as can be seen above on the thumbnail images from EAGLEview on the right. Other missing patterns on semiconductor wafers are more difficult to detect because the color differences are more subtle. These differences depend on the level (dark vs. bright), the cause of the missing pattern (lack of coat, expose or develop) and the throughout rate on the reticle.