Patent Number: 
Section: claims

1. A pattern measurement method for measuring a dimension of a predetermined pattern on a sample from a scanned image by a scanning electron microscope, comprising steps of:obtaining a standard pattern corresponding to the predetermined pattern and a measurement point specified in advance;setting a measurement area so that it includes two straight line segments on both sides of the measurement point out of outlines of the standard pattern; andmeasuring a dimension between two contours of a scanned image of the predetermined pattern in the measurement area by superposing the measurement area on the scanned image of the predetermined pattern,wherein the step of setting the measurement area sets the measurement area so that it does not include portions near corner portions connected to the two line segments. 2. The pattern measurement method according to claim 1,wherein the step of setting the measurement area includes steps of:selecting the two straight line segments on both sides of the measurement point and the closest to the measurement point among the outlines of the standard pattern;detecting end points of both ends of each of the two line segments and cutting a line segment of a predetermined length from the end points to shorten;selecting two end points the closest to the measurement point among the end points of both ends of each of the shortened two line segments; andsetting two sides of the measurement areas based on the selected two end points. 3. The pattern measurement method according to claim 2, wherein the steps of selecting the two line segments includes steps of calculating two points spaced away from the measurement point by a predetermined distance, and detecting the line segments including their respective two points or line segments the closest to their respective two points. 4. The pattern measurement method according to claim 1,wherein the step of setting the measurement area includes steps of:selecting straight two line segments on both sides of the measurement point and the closest to the measurement point among the outlines of the standard pattern;detecting two contours of the scanned image of the predetermined pattern corresponding to the selected two line segments;calculating a distance between the two line segments of the standard pattern and the two contours of the scanned image of the predetermined pattern corresponding to the two line segments;detecting an area the distance or a variation amount of the distance of which is larger than a predetermined threshold level;eliminating a line segment included in the detected area from the two line segments of the standard pattern to shorten;selecting two end points the closest to the measurement point among the end points of both ends of each of the shortened two line segments; andsetting two sides of the measurement areas based on the selected two end points. 5. The pattern measurement method according to claim 1, wherein the predetermined pattern on the sample is a pattern of a photomask used in semiconductor manufacturing, and the standard pattern is CAD data of the pattern of the photomask. 6. The pattern measurement method according to claim 5, wherein the CAD data of the pattern of the photomask is OPC processed CAD data. 7. The pattern measurement method according to claim 1, wherein the measurement area is provided on each of the two line segments. 8. The pattern measurement method according to claim 1, wherein only one measurement area is provided so as to include the two line segments. 9. A pattern measurement method for measuring a dimension of a pattern of a photomask from a scanned image by a scanning electron microscope, comprising steps of:obtaining both data of an OPC processed photomask pattern including a pattern of which width dimension changes in a step-like fashion, and a measurement point set in advance;setting a measurement area so as to include straight two line segments on both sides of the measurement point among outlines of the pattern of the photomask; andmeasuring a dimension between two line segments of the pattern of the photomask in the measurement area,wherein the step of setting the measurement areas includes steps of:selecting a group of the two line segments having different width dimensions on both sides of the measurement point among the outlines of the pattern of the photomask, and setting a measurement area for each of the group of the two line segments. 10. The pattern measurement method according to claim 9,wherein the step of setting the measurement area includes steps of:obtaining a standard pattern corresponding to the OPC processed photomask pattern; andsetting a standard dimension with respect to the standard pattern, andthe step of selecting the group of the two line segments selects the group of the two line segments in an area of the standard dimension. 11. The pattern measurement method according to claim 10, wherein the standard pattern is obtained by magnifying data of the pattern of the photomask without the OPC processing at a predetermined magnification. 12. The pattern measurement method according to claim 9, wherein data of the OPC processed photomask pattern is OPC processed CAD data. 13. A pattern measurement system for measuring a dimension of a predetermined pattern on a sample from a scanned image by a scanning electron microscope, comprising:a design data managing unit that stores both a standard pattern corresponding to the predetermined pattern and a measurement point specified in advance; anda control device that sets a measurement area so as to include two straight line segments on both sides of the measurement point among outlines of the standard pattern, superposes the measurement area on the scanned image of the predetermined pattern, and measures a dimension between two contours of the scanned image of the predetermined pattern in the measurement area,wherein the control device sets the measurement area so that it does not include portions near corner portions connected to the two line segments, and saves the measurement area in the design data managing unit. 14. The pattern measurement system according to claim 13, wherein a predetermined pattern on the sample is a pattern of the photomask used in semiconductor manufacturing, and the standard pattern is CAD data of the pattern of the photomask. 15. A pattern measurement system for measuring a dimension of a pattern of a photomask from a scanned image by a scanning electron microscope, comprising:a design data managing unit for storing data of an OPC processed pattern photomask including a pattern of which width dimension changes in a step-like fashion, and a measurement point set in advance; anda control device for setting a measurement area so that it includes two straight line segments on both sides of the measurement point among outlines of the pattern of the photomask to measure a dimension between two line segments of the pattern of the photomask in the measurement area,wherein the control device selects a group of two line segments having different width dimensions on both sides of the measurement point among the outlines of the pattern of the photomask to set a measurement area for each group of the two line segments. 16. The pattern measurement system according to claim 15,wherein the design data managing unit stores a standard pattern corresponding to the OPC processed photomask pattern, andthe control device sets a standard dimension with respect to the standard pattern to select the group of two line segments in an area of the standard dimension. 17. The pattern measurement method according to claim 16,wherein the standard pattern is obtained by magnifying data of the pattern of the photomask without the OPC processing at a predetermined magnification.