Inspection method for semiconductor wafer and apparatus for reviewing defects
View Patent ↗An object of the present invention is to provide a suitable method of observing a wafer edge by using an electron microscope. The electron microscope includes a column which can take an image in being tilted, and thus allows a wafer edge to be observed from an oblique direction.
1. A semiconductor wafer inspection method, the method comprising steps of:
placing a semiconductor wafer on a sample stage of an electron beam apparatus having a first electron beam optical system for irradiating an electron beam from a direction normal to a surface of a sample, and a second electron beam optical system for irradiating an electron beam from a direction tilted from the direction normal to the surface;
obtaining defect position data on the semiconductor wafer from an inspection apparatus;
moving the stage to a position corresponding to a defect position obtained from the defect position data from the inspection apparatus, and capturing a scanning image of a defect by using the first electron beam optical system;
discriminating a mode of the defect on the basis of the captured defect image;
controlling a scanning direction of the electron beam of the second electron beam optical system, wherein the scanning direction of the electron beam of the second electron beam optical system is rotated through an angle the same as a rotation angle of the sample stage so that the viewing field of an image by the second electron beam optical system is rotated through an angle the same as the rotation angle of the stage; and
obtaining an image of an edge position of the semiconductor wafer by using the second electron beam optical system, wherein:
the image includes both the edge position of the semiconductor wafer and a background, and
altering the rotation angle of the electron beam creates more or less of the background in the image.
2. A defect review apparatus comprising:
a sample stage which moves with a semiconductor wafer held thereon;
a first electron beam optical system for irradiating an electron beam from a direction normal to a surface of the semiconductor wafer held on the sample stage;
a second electron beam optical system for irradiating an electron beam to an edge position of the semiconductor wafer from a direction tilted from the direction normal to the surface;
a display unit for displaying an image of the surface of the semiconductor wafer, the image generated by electron beam irradiation; and
a calculation unit configured to:
generate a wafer map showing positions of defects based on images obtained by the first electron beam optical system, and then cause the display unit to display the wafer map superimposing an image obtained by the second electron beam optical system; and
an electron optical system control unit configured to:
control a scanning direction of an electron beam from the second electron beam optical system, wherein the scanning direction of the electron beam is rotated through an angle the same as a rotation angle of the sample stage so that the viewing field of an image by the second electron beam optical system is rotated through an angle the same as the rotation angle of the sample stage, wherein:
the image includes both the edge position of the semiconductor wafer and a background, and
altering the rotation angle of the electron beam creates more or less of the background in the image.
3. The defect review apparatus according to claim 2 ,
wherein the viewing field of the image obtained by the second electron beam is displayed so as to be superimposed on a wafer map.