Ion irradiation system and method

An ion irradiation method for an ion irradiation system which comprises:

• an ion microprobe;
• a deflector for deflecting an ion microbeam generated by said ion microprobe;
• a micro slit for extracting a single or predetermined number of ions from said microbeam deflected by said deflector;
• a sample holder mechanism for holding a sample to be irradiated with said single or predetermined number of ions extracted through said micro slit;
• a scanning electron microscope mechanism for observing the surface of said sample in real time;
• a secondary electron detecting system including a secondary electron multiplier, for detecting secondary electrons emitted from said sample surface;
• and an electric field control circuit for controlling an electric field which is applied to said deflector, said electric field control circuit being composed of a clock generator, a counter connected to said clock generator and a high-voltage amplifier connected at an input to said counter and at an output to said deflector, and wherein said counter counts output signal pulses from said secondary electron multiplier and supplies said field control circuit during counting of said single or predetermined number of ions and stops the supply of said clock signal to said high-voltage amplifier upon completion of counting of said single or predetermined number of ions, whereby said ion microbeam is chopped by said deflector one or more times to instantaneously reverse its direction of deflection with respect to said micro slit to thereby extract therethrough said single or predetermined number of ions;
• said method comprising;
• a first step of observing a secondary electron image over said sample surface through electron scanning by said scanning electron microscope mechanism to detect the positional relationship between a position of said sample surface which there is a desire to irradiate with said single or determined number of ions and a reference position on said sample or sample holder mechanism;
• a second step of observing a secondary electron image at said reference point through ion microbeam scanning by said scanning electron microscope mechanism to determine the position for ion irradiation of said sample;
• a third step of moving said sample holder mechanism by a distance based on said positional relationship detected in said first step to bring said position for ion irradiation of said sample into agreement with said position for ion irradiation of said sample;
• a fourth step of applying a bias voltage to said deflector from said electric field control circuit to chop said ion microbeam to permit the passage of said single or predetermined number of ions through said micro slit for only an extremely short period of time during which said ion microbeam is deflected across said micro slit widthwise thereof;
• and
• a fifth step of detecting secondary electrons emitted from said sample surface by irradiation with said single or predetermined number of ions to count the number of ions incident to said sample surface.