Patent Number: 
Section: claims

1. A pattern observation method for observing a pattern formed on an insulating film and having a concave pattern and a convex pattern, the method comprising:irradiating both of the concave pattern and the convex pattern in the pattern with a first observing charged particle beam, to obtain a temporary image of the pattern having region information of a convex pattern region corresponding to the convex pattern and region information of a concave pattern region corresponding to the concave pattern;irradiating the convex pattern region in the pattern with a first electric field forming charged particle beam having a first incident voltage for forming an electric field in the convex pattern region and irradiating the concave pattern region in the pattern with a second electric field forming charged particle beam having a second incident voltage for forming an electric field in the concave pattern region, wherein the second incident voltage is different from the first incident voltage, based on the region information of the convex pattern region and the region information of the concave pattern region respectively, thereby forming an electric field between a top surface of the convex pattern and a bottom surface of the concave pattern so that charged particles emitted from the bottom surface of the concave pattern when the bottom surface is irradiated with the charged particle beam may be drawn out of the pattern; andirradiating both of the concave pattern and the convex pattern in the pattern with a second observing charged particle beam after the electric field is formed, to obtain an image of the pattern having the information of the bottom surface of the concave pattern. 2. The pattern observation method according to claim 1, comprising:when irradiating the convex pattern region with the electric field forming charged particle beam having the first incident voltage based on a dimension of the convex pattern which is contained in the region information of the convex pattern region, shifting a focus position of the electric field forming charged particle beam having the first incident voltage toward an inside of the pattern so that a first beam diameter on the top surface of the convex pattern may be equal to the dimension of the convex pattern; andwhen irradiating the concave pattern region with the electric field forming charged particle beam having the second incident voltage based on a dimension of the concave pattern which is contained in the region information of the concave pattern region, shifting a focus position of the electric field forming charged particle beam having the second incident voltage toward an inside of the pattern so that a second beam diameter on the bottom surface of the concave pattern may be equal to the dimension of the concave pattern. 3. The pattern observation method according to claim 2, wherein as the charged particle beam, an electron beam is used. 4. The pattern observation method according to claim 1, wherein as the charged particle beam, an electron beam is used. 5. The pattern observation method according to claim 4, whereinthe first incident voltage has a secondary electron emission coefficient larger than one, andthe second incident voltage has a secondary electron emission coefficient smaller than one. 6. The pattern observation method according to claim 4, wherein the first observing charged particle beam and/or the second observing charged particle beam have the incident voltage whose secondary electron emission coefficient is one. 7. The pattern observation method according to claim 4, whereinthe insulating film is a silicon oxide film,the first incident voltage is higher than 100 V and lower than 2000 V, andthe second incident voltage is lower than 100 V or higher than 2000 V. 8. The pattern observation method of claim 1, wherein the bottom surface of the concave pattern region is insulated. 9. A pattern observation method for observing a line and space pattern formed on an insulating film and having a line pattern and a space pattern, the method comprising:irradiating both of the line pattern and the space pattern in the line and space pattern with a first observing electron beam, to obtain a temporary image of the line and space pattern having region information of a line pattern region corresponding to the line pattern and region information of a space pattern region corresponding to the space pattern;irradiating the line pattern region with a first electric field forming electron beam having a first incident voltage for forming an electric field in the line pattern region and irradiating the space pattern region with a second electric field forming electron beam having a second incident voltage for forming an electric field in the space pattern region, wherein the second incident voltage results in a smaller secondary electron emission coefficient than that by the first incident voltage, based on the region information of the line pattern region and the region information of the space pattern region respectively, thereby forming an electric field between a top surface of the line pattern and a bottom surface of the space pattern so that secondary electrons emitted from the bottom surface of the space pattern when the bottom surface is irradiated with the electron beam may be drawn out of the line and space pattern; andirradiating both of the line pattern and the space pattern in the line and space pattern with a second observing electron beam after the electric field is formed, to obtain an image of the line and space pattern having the information of the bottom surface of the space pattern. 10. The pattern observation method according to claim 9, comprising:when irradiating the line pattern region with the electric field forming electron beam having the first incident voltage based on a line width of the line pattern which is contained in the region information of the line pattern region, shifting a focus position of the electric field forming electron beam having the first incident voltage toward an inside of the line and space pattern so that a first beam diameter on the top surface of the line pattern may be equal to the line width of the line pattern; andwhen irradiating the space pattern region with the electric field forming electron beam having the second incident voltage based on a line width of the space pattern which is contained in the region information of the space pattern region, shifting a focus position of the electric field forming electron beam having the second incident voltage toward an inside of the line and space pattern so that a second beam diameter on the bottom surface of the space pattern may be equal to the line width of the space pattern. 11. The pattern observation method according to claim 10, whereinthe first incident voltage has a secondary electron emission coefficient larger than one, andthe second incident voltage has a secondary electron emission coefficient smaller than one. 12. The pattern observation method according to claim 10, wherein the first observing electron beam and/or the second observing electron beam have the incident voltage whose secondary electron emission coefficient is one. 13. The pattern observation method according to claim 10 whereinthe insulating film is a silicon oxide film,the first incident voltage is higher than 100 V and lower than 2000 V, andthe second incident voltage is lower than 100 V or higher than 2000 V. 14. The pattern observation method according to claim 9, whereinthe first incident voltage has a secondary electron emission coefficient larger than one, andthe second incident voltage has a secondary electron emission coefficient smaller than one. 15. The pattern observation method according to claim 9, wherein the first observing electron beam and/or the second observing electron beam have the incident voltage whose secondary electron emission coefficient is one. 16. The pattern observation method according to claim 9, whereinthe insulating film is a silicon oxide film,the first incident voltage is higher than 100 V and lower than 2000 V, andthe second incident voltage is less than 100 V or higher than 2000 V. 17. The pattern observation method of claim 9, wherein the bottom surface of the space pattern region is insulated. 18. A pattern observation method for observing a two-step hole pattern formed on an insulating film and having a first hole pattern and a second hole pattern formed in a bottom surface of the first hole pattern, the method comprising:irradiating an entire observation region in the two-step hole pattern with a first observing electron beam, to obtain a temporary image of the two-step hole pattern having region information of a first region corresponding to a top surface of the two-step hole pattern, region information of a second region corresponding to a bottom surface of the first hole pattern, and region information of a third region corresponding to a bottom surface of the second hole pattern;irradiating the first region with a first electric field forming electron beam having a first incident voltage for forming an electric field in the first region, the second region with a second electric field forming electron beam having a second incident voltage for forming an electric field in the second region, wherein the second incident voltage results in a secondary electron emission coefficient smaller than that by the first incident voltage, and the third region with a third electric field forming electron beam having a third incident voltage for forming an electric field in the third region, wherein the third incident voltage results in which gives a secondary electron emission coefficient smaller than that by the second incident voltage, based on the region information of the first region, the region information of the second region, and the region information of the third region, to thereby form an electric field between the top surface of the two-step hole pattern and the bottom surface of the first hole pattern and an electric field between the bottom surface of the first hole pattern and the bottom surface of the second hole pattern so that secondary electrons emitted from the bottom surface of the first hole pattern and the bottom surface of the second hole pattern when they are irradiated with the electron beam may be drawn out to an outside of the two-step hole pattern; andirradiating the entire observation region in the two-step hole pattern with a second observing electron beam after the electric field is formed, to obtain an image of the two-step hole pattern having the information of the bottom surface of the first hole pattern and the bottom surface of the second hole pattern. 19. The pattern observation method according to claim 18, wherein the first observing electron beam and/or the second observing electron beam have the incident voltage whose secondary electron emission coefficient is one. 20. The pattern observation method of claim 18, wherein the bottom surface of the second hole pattern is insulated.