Monitor method for process control in a semiconductor fabrication process

A monitor method for process control in a semiconductor fabrication process, comprising:

• forming a first alignment mark and a second alignment mark in a same layer in different die fields on a substrate before a fabrication process;
• measuring positions of the first alignment mark and the second alignment mark to determine a first vector between the first alignment mark and the second alignment mark and to generate a first measurement data;
• performing the fabrication process on the wafer after the step of generating a first measurement data;
• measuring positions of the first alignment mark and the second alignment mark to determine a second vector between the first alignment mark and the second alignment mark and generate a second measurement data after the step of performing the fabrication process;
• calculating offset values between the positions of the first alignment mark in the first measurement data and the position of the first alignment mark in the second measurement data and between the positions of the second alignment mark in the first measurement data and the position of the second alignment mark in the second measurement data;
• and
• comparing lengths of the first vector and the second vector and calculating an angle between the first vector and the second vector;
• and
• adjusting the fabrication process based on the offset values, the lengths of the first vector and the second vector and the angle between the first vector and the second vector when the offset values, the lengths and/or the angle are higher than predetermined values.