Method for monitoring semiconductor process

A method for monitoring a semiconductor process, comprising:

• providing a wafer having thereon a material layer;
• performing a semiconductor process comprising forming a measurement mark in the material layer, wherein the measurement mark comprises four rectangular regions arranged in a 2×2 array about a center, wherein the four rectangular regions comprise a first region and a second region arranged diagonally, and a third region and a fourth region arranged diagonally, wherein a plurality sets of first inner pattern blocks, first middle pattern blocks, and first outer reference pattern blocks is disposed in the first region, wherein each of the first inner pattern blocks comprises a plurality of line patterns extending along a first direction and a block pattern having a plurality of space patterns arranged therein, wherein each of the first middle pattern blocks comprises a plurality of line patterns extending along the first direction and a block pattern having a plurality of space patterns arranged therein, wherein the first inner pattern blocks are is rotationally symmetrical to the first middle pattern blocks;
• measuring a first offset between the first inner pattern blocks and the first outer reference pattern blocks;
• and
• measuring a second offset between the first middle pattern blocks and the first outer reference pattern blocks.