Patent Number: 
Section: claims

1. An image forming method for scanning a two-dimensional area on a sample with a charged particle beam and forming an image of the scanned area, the image forming method comprising the steps of:scanning a first scanning line;scanning a second scanning line;scanning a third scanning line between the first scanning line and the second scanning line;scanning an area having two sections, defined by the first, second, and third scanning lines, by sequentially scanning positions between the first and third scanning lines and scanning positions between the third and second scanning lines so as to reduce the area in stages; andrepeatedly scanning for a center by scanning lines between the first scanning line and the third scanning line, and scanning lines between the third scanning line and the second scanning line until scanning of the two-dimensional area is complete. 2. An image forming method according to claim 1, wherein said third scanning line is disposed at equidistance from said first and second scanning lines. 3. An image forming method according to claim 1, wherein scanning line disposed at the center of said plurality of scanning lines is a fourth scanning line which is scanned next to said third scanning line. 4. An image forming method according to claim 1, wherein said first and second scanning lines are disposed at the edge of said two-dimensional area or a part of area of said two-dimensional area. 5. A charged particle beam apparatus including a deflector for scanning charged particle beam on a sample and a control apparatus for controlling said deflector, wherein:said control apparatus controls said deflector to:scan a first scanning line and second scanning line on a two-dimensional area on said sample;scan a third scanning line between said first and second scanning lines;scanning an area having two sections, defined by the first second, and third scanning lines, by sequentially scanning positions between the first and third scanning lines and scanning positions between the third and second scanning lines so as to reduce the area in stages; andrepeatedly scanning for a center by scanning lines between the first scanning line and the third scanning line, and scanning lines between the third scanning line and the second scanning line until scanning of the two-dimensional area is complete. 6. A charged particle beam scanning apparatus according to claim 5, wherein:said control apparatus controls said deflector such that positioning said third scanning line at equidistance to said first and second scanning lines. 7. A charged particle beam apparatus according to claim 5, wherein:said control apparatus renders scanning line disposed at center of said plurality of scanning lines as a fourth scanning line which is scanned next to said third scanning line. 8. A charged particle beam apparatus according to claim 5, wherein:said control apparatus positions said first and second scanning lines at an edge of said two-dimensional are or part of area of said two-dimensional area. 9. A charged particle beam apparatus according to claim 5, wherein:said control apparatus controls said deflector such that structuring said two-dimensional are on said sample as a single or divided plural areas, and scanning said first, second and third scanning lines at each area. 10. A charged particle beam apparatus according to claim 9, wherein:said two-dimensional area is divided into any one of two parts, four parts, eight parts, sixteen parts, thirty-two parts and sixty-four parts. 11. An image forming method for scanning a two-dimensional area on a sample with a charged particle beam and forming an image of scanning area, the image forming method comprising the steps of:scanning a first scanning line at upper portion of said two-dimensional area on said sample, a second scanning line at lower part, and third scanning line between said first and second scanning lines and at the center of said two-dimensional area; andthen, further scans scanning lines between said first and third scanning lines and between said second and third scanning lines,wherein said further scanning of said scanning lines repeat scanning of new scanning lines at a center of scanning lines which already scanned, such that narrowing distance between said scanning lines already scanned and scanning lines newly scanned, andwherein scanning is repeatedly performed for a center by scanning between the first scanning line and the third scanning line, and scanning lines between the third scanning line and the second scanning line until scanning of the two-dimensional area is complete. 12. An image forming method according to claim 11, wherein:said scanning of said new scanning lines scans scanning line newly for narrowing distance of scanning lines which is already scanned, after scanning at the center between scanning lines haying a same scanning line distance is said two-dimensional area. 13. An image forming method according to claim 11, wherein:said second scanning line scans at far most position from said first scanning line in said two-dimensional area. 14. A charged particle beam apparatus including deflector for scanning charged particle beam on a specimen and a control apparatus for controlling said deflector, wherein:said control apparatus scans a first scanning line at an upper portion of two-dimensional area on said specimen scans, a second scanning line at a lower part of said two-dimensional area, scans a third scanning line at the center of said two-dimensional area, and scans scanning lines between said first and said third scanning lines, and between said second and said third scanning lines,wherein said further scanning of said scanning lines controls said deflector such that repeat scanning of new scanning lines at a center of scanning lines which already scanned, and narrowing distance between said scanning lines already scanned and scanning lines newly scanned, andwherein scanning is repeatedly performed for a center by scanning between the first scanning line and the third scanning line, and scanning lines between the third scanning line and the second scanning line until scanning of the two-dimensional area is complete. 15. A charged particle beam apparatus according to claim 14, wherein:said control apparatus controls said deflector such that scans said new scanning lines for narrowing distance of scanning lines already scanned, after scanning at the center of scanning lines having a same scanning line distance in said two-dimensional area. 16. A charged particle beam apparatus according to claim 14, wherein:said control apparatus controls said deflector such that said second scanning line is scanned at far most position from said first scanning line in said two-dimensional area. 17. A pattern dimension measurement method for scanning two-dimensional area on a specimen with a charged particle beam and for forming an image of scanning area, and measuring dimension of pattern formed on said specimen based on said image, said method comprising steps of:as said two-dimensional area of said specimen, scanning a first and second scanning lines and scanning a third scanning line between said first and second scanning lines, then, scanning a plurality of scanning lines between said first and third and scanning lines and between said second and third scanning lines so that forming image of said two-dimensional area, and measuring said pattern by setting measuring direction in a different direction of line direction of each scanning lines on said image;scanning an area having two sections, defined by the first, second, and third scanning lines, by sequentially scanning positions between the first and third scanning lines and scanning positions between the third and second scanning lines so as to reduce the area in stages; andrepeatedly scanning for a center by scanning lines between the first scanning line and the third scanning line, and scanning lines between the third scanning line and the second scanning line until scanning of the two-dimensional area is complete. 18. An image forming method for scanning a two-dimensional area on a sample with a charged particle beam and forming an image of scanning area, the image forming method comprising the steps of:as to area including two-dimensional area in said sample, scanning a first and second scanning lines, scanning a third scanning line between said first and second scanning lines, then, by scanning a plurality of scanning lines between said first and third scanning lines, between second and third scanning lines, rendering to charge area including two-dimensional area of said sample,forming an image of said scanning area by scanning said charged particle beam onto said charged two-dimensional area,scanning an area haying two sections, defined by the first, second, and third scanning lines, by sequentially scanning positions between the first and third scanning lines and scanning positions between the third and second scanning lines so as to reduce the area in stages; andrepeatedly scanning for a center by scanning lines between the first scanning line and the third scanning line, and scanning lines between the third scanning line and the second scanning line until scanning of the two-dimensional area is complete. 19. A charged particle beam apparatus for deflecting charged particle beam irradiated on a specimen in a spot like shape, a deflector, and control apparatus for controlling said deflector, wherein:said control apparatus controls said deflector such that deflects said charged particle beam so that said charged particle beam is irradiated at a first irradiating position positioned at four corners of said two-dimensional area on said specimen, then deflects said charged particle beam so that a second irradiating position is positioned at the center of said first irradiating positions, then scans an area having two sections, defined by a first scanning line, a second scanning line, and a third scanning line between the first and second scanning lines, by sequentially scanning positions between the first and third scanning lines and scanning positions between the third and second scanning lines so as to reduce the area in stages, and repeatedly scans for a center by scanning lines between the first scanning line and the third scanning line, and scanning lines between the third scanning line and the second scanning line until scanning of the two-dimensional area is complete.