Overlay measuring method using a voltage contrast image

An overlay measuring method comprising:

• placing lower patterns and upper patterns in a layout;
• shifting at least one of the upper patterns by a programmed misalignment to generate a plurality of shifted upper patterns, wherein the plurality of shifted upper patterns are classified into a plurality of shift pattern groups having different degrees of misalignment from each other;
• forming lower conductive patterns and upper conductive patterns on a key region of a substrate based on the layout, wherein the lower conductive patterns are formed to respectively correspond to the lower patterns, and the upper conductive patterns are formed to respectively correspond to the upper patterns;
• and
• obtaining an overlay value in the key region,
• wherein the lower conductive patterns and the upper conductive patterns form a plurality of conductive pattern groups that respectively correspond to the plurality of shift pattern groups, and
• wherein obtaining the overlay value in the key region comprises:
• measuring, for each of the plurality of conductive pattern groups, a defect count as a number of contacts between one or more upper conductive patterns included in the conductive pattern group and the lower patterns adjacent thereto;
• selecting, from among the plurality of conductive pattern groups, a first group having a minimum defect count;
• and
• calculating the overlay value based on a programmed misalignment value of a shift pattern group corresponding to the first group among the plurality of shift pattern groups.

An overlay measuring method comprising:

• placing a lower pattern and an upper pattern in a layout;
• shifting at least one of the lower pattern and the upper pattern, wherein the shifted at least one comprises a plurality of patterns shifted according to different programmed misalignments from each other;
• forming a lower conductive pattern and an upper conductive pattern on a key region of a substrate, based on the layout, wherein the lower conductive pattern and the upper conductive pattern comprise a plurality of conductive patterns respectively corresponding to the plurality of patterns;
• performing an e-beam inspection on the key region to obtain a voltage contrast (VC) image;
• determining a number of normal regions based on brightness information of the VC image;
• and
• obtaining an overlay value in the key region based on the number of normal regions.