Patent Number: 063317125
Section: description

DETAILED DESCRIPTION OF THE INVENTION The device for carrying out the present invention will be shown in FIG. 3. A liquid metal ion source 1 has a needle 1a to generate an ion beam by an electric field caused by a leading electrode 1b. The ion beam thus taken out is focused by an ion beam optical system comprising an electrostatic lens 2 and the like, being formed into a focused ion beam 30. A beam blanking electrode 3 and a deflection electrode 5 are provided on an ion beam optical axis. The beam blanking electrode 3 turns on and off the irradiation of the focused ion beam 30 onto a sample 7. The deflection electrode 5 controls irradiation position of the focused ion beam 30. By inputting scanning signals to the deflection electrode 5, the focused ion beam 30 can be scanned over and irradiated to an arbitrary region on the sample 7. The sample 7 is placed on a sample stage 8 which is movable at least in three axes of X, Y, Z and can tilt and rotate the sample. In the vicinity of a focused ion beam 30 irradiation position of the sample 7, is provided a secondary charged particle detector 6 for detecting secondary charged particles occurring from the sample 7 due to irradiation of the focused ion beam. The state of a surface of the sample 7 is displayed on a display CRT 10 based on the intensity of secondary charged particles detected by the secondary charged particle detector 6. Next, a method of the present invention will be explained. The beam blanking electrode 3 is kept on. The sample has, as was shown in FIG. 1A and FIG. 1b, a substrate 50 as a first conducting layer and a gate interconnect 51 formed thereon as a second conducting layer through an insulating layer 57. The sample 7 is rested on the sample stage 8. Subsequently, a not-shown sample chamber (sub-chamber) in which the sample stage 8 is provided is evacuated by a not-shown vacuum pump. Then the sample stage 8 is moved to a main chamber by passing through a not-shown sub-gate. Further, movement is made such that a predetermined position of the sample 7 comes onto the optical axis and focus of the focused ion beam. The beam blanking electrode 3 is turned off to irradiate the focused ion beam 30 onto the sample 7. At this time, the focused ion beam 30 is scanned and irradiated by the deflection electrode 5 with using a work frame 60 as shown in FIG. 1A. Simultaneously, secondary charged particles occurring from the sample 7 are detected by the secondary charged particle detector 6 to detect and memorize an intensity of the secondary charged particles at a scan position. Based on distribution of the secondary charged particle intensity memorized, image data is created and displayed on the display CRT 10. At a time point that enough image data required for an architectural image is collected, the blanking electrode 3 is turned on to end the irradiation of the focused ion beam 30 to the sample 7. In the case that the image displayed on the display CRT 10 deviates from a position to form and observe a section, the sample stage 8 is actuated to bring the predetermined position of the sample 7 to an appropriate position for display. At this time, the sample 7 may be moved with the beam blanking electrode 3 turned off while performing image display. Also, the sample stage 8 may be moved based on a result of calculation of a moving distance due to a difference from a target position determined from the image display. After the sample 7 is moved to an appropriate position for section formation and observation, an image is re-taken and displayed on the display CRT 10. Next, from the image displayed on the display CRT 10 as in FIG. 4, a work frame 60 is set which is of a rectangular region having as one side a section observing position (broken line A-B) on the sample 7. A focused ion beam 30 is repeatedly scanned over and irradiated to this work frame 60 region. By sputtering due to irradiation of the focused ion beam 30, a work region 60 as a scanned region is etched and formed into a recess 61. The recess 61 has a bottom at which the substrate 50 is exposed. At this time, as was explained in the previous section, a gate interconnect 51 on the D side becomes a conducting layer electrically floating. Subsequently, a focused ion beam without scanning is irradiated for a constant time to a point (second work region 63) at other than the work frame 60 but extremely close to the gate interconnect 51 rendered in a floating state due to the former recess formation step. Then a hole 62 is formed reaching the substrate 50. The second work region 63 is a spot to which a focused ion beam is irradiated for a constant time without scanning. Also, the region may be formed by the above hole with a depth greater than a greatest diameter of the above hole due to scanning and irradiating a focused ion beam over a very narrow region for a constant time. A second work region 63 is preferably a spot selected from a view point of minimum working time. The second region 63 is on the gate interconnect 51 rendered in an electrically floating state. Usually, although the sample 7 is formed with a protection film, it is natural in this case that the hole 62 and the recess 61 are formed including the protection film. The hole 62 thus formed is deposited at its sidewall with re-deposited materials 72 as shown in FIGS. 2B and 2C, and electrical conduction is available between first and second conductive layers at the upper and lower portions. That is, the gate interconnect 51 is free from charge-up. Next, the sample 7 is inclined at an appropriate angle using a tilt function of the sample stage 8. The section to be observed is positioned upward with the section taken as a rotation axis. The section is scanned and irradiated by the focused ion beam in the afore-said method. Image data required for image formation is taken, and displayed on the display CRT 10 and memorized in an image data memory unit. At this time, a substrate 50 of the sample 7 is electrically connected to the sample stage 8 and the sample stage 8 is grounded. Due to this, the electric charge irradiated to the section is discharged without charging. Also, although one point irradiation of the focused ion beam 30 was performed after forming the section, it may be carried out before the section formation. Also, the irradiation is made without scanning, but irradiation with scanning may be applied provided that it is sufficiently narrow region for achieving the object. Furthermore, although the focused ion beam was used for section observation, a different scanning electronic microscope is applicable. Also, it is possible to use a scanning electronic microscope mounted on the focused ion beam in a complex form. According to a method of the present invention, it becomes possible to observe a floating conductive region of a sample such as a semiconductor integrated circuit without charge-up phenomenon.