Method and apparatus for critical dimension and tool resolution determination using edge width

Apparatus for monitoring a process in which a feature is formed on a substrate, comprising:

• means for receiving a plurality of measurements of the feature that are collected by a tool;
• means for calculating an edge width of the feature based on the plurality of dimensions;
• and
• means for determining whether the process is operating within a desired specification based on the edge width and having:
• (a) means for comparing the calculated edge width to a baseline edge width measurement to determine a difference therebetween,
• (b) means for determining that the process is operating within the specification if the difference is less than a threshold value,
• (c) diagnostic means for determining whether the difference is caused by a change in resolution of the tool, if the difference is greater than or equal to the threshold value, and
• (d) means for determining that the process is not operating within the specification, if the difference is greater than or equal to the threshold value, and the difference is not caused by a change in resolution of the tool.

A method for monitoring a process in which a feature is formed on a substrate, comprising the steps of:

• (a) measuring a plurality of dimensions of the feature using a tool;
• (b) calculating an edge width of the feature based on the plurality of dimensions;
• (c) determining whether the process is operating within a desired specification based on the edge width;
• (d) determining whether the resolution of the tool has changed from a baseline resolution, based on the edge width;
• and
• (e) automatically adjusting the resolution of the tool without operator intervention if resolution of the tool has changed from the baseline resolution.

A method for monitoring a process in which a feature is formed on a substrate, comprising the steps of

• (a) measuring the feature using a scanning electron microscope, and generating from the measurement a waveform having an amplitude;
• (b) identifying a respective top point on each side of the feature based on the amplitude of the waveform, each top point being the top of a respective edge;
• (c) identifying a first inner point, the first inner point being a point closest to a center of the feature, at which the waveform has a maximum negative slope among the points between the two top points, and
• (d) identifying a second inner point, the second inner point being a point closest to a center of the feature, at which the waveform has a maximum positive slope among the points between the two top points;
• (e) identifying a respective bottom point on each side of the feature based on the amplitude of the waveform, each bottom point being the bottom of a respective edge;
• (f) calculating a first distance between the bottoms of the edges and a second distance between the first and second inner points;
• and
• (g) determining whether the process is operating within a desired specification based on the first and second distances.

A method of monitoring a process in which a feature is formed on a substrate, comprising the steps of:

• (a) measuring a plurality of dimensions of the feature using a tool;
• (b) calculating a humpwidth of the feature based on the plurality of dimensions;
• and
• (c) determining whether the process is operating within a desired specification based on the humpwidth by:
• (c1) comparing the calculated edge width to a baseline edge width measurement to determine a difference therebetween,
• (c2) determining that the process is operating within the specification if the difference is less than a threshold value,
• (c3) determining whether the difference is caused by a change in resolution of the tool, if the difference is greater than or equal to the threshold value, and
• (c4) determining that the process is not operating within the specification, if the difference is greater than or equal to the threshold value, and the difference is not caused by a change in resolution of the tool.

A method for monitoring a process in which a feature is formed on a substrate, comprising the steps of

• (a) measuring the feature using a scanning electron microscope, and generating from the measurement a waveform having an amplitude;
• (b) identifying a respective point on each side of the feature as the top of a respective edge;
• (c) calculating the derivative of the amplitude at a plurality of points located between the points identified as the tops of the edges in step (b);
• (d) identifying a respective inner point on each side of the feature, such that the inner points are located between the points identified as the tops of the edges in step (b), and the absolute value of the derivative of the amplitude begins to decrease from a maximum value at each inner point;
• (e) identifying a respective point on each side of the feature as the bottom of a respective edge;
• (f) calculating a first distance between the bottoms of the edges and a second distance between the inner points;
• and
• (g) determining whether the process is operating within a desired specification based on the first and second distances.