Radiant energy – Inspection of solids or liquids by charged particles – Electron probe type
Patent
1988-07-25
1990-05-22
Anderson, Bruce C.
Radiant energy
Inspection of solids or liquids by charged particles
Electron probe type
250396ML, 250397, H01J 3726
Patent
active
049280104
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Art
The present invention relates to an apparatus adapted for observing an image composed of secondary electrons generated in a recessed portion when the charged particle beam is focused on a specimen having recessed portions, such as through holes formed in the processes carried out in an LSI production line, and a method for observing a surface by a charged particle beam.
2. Background of the Prior Art
Recently, there has arisen the problem of disconnection in wiring due to the residue of a photoresist on the bottom of a specimen having through holes, capacitive grooves, recesses and so on (all of which are referred to simply as "through holes" hereinafter in this specification) so that there has been a strong demand for an apparatus capable of observing the bottoms of through holes by a charged particle beam in the LSI production process.
FIG. 1 shows a column of an apparatus for observing a surface by utilizing a charged particle observation reported by Y. Furuya, T. Ohtaka, S. Yamada, H. Mori, M. Yamada, T. Watanabe and K. Ishikawa in "Model S-6000 Field Emission CD Measurement SEM", the 93rd study reference disclosed at the 132nd committee held on Japan Society for the Promotion of Science (November 8-9, 1985), p. 1.
Electrons 1 (to be referred to as "the primary electrons" hereinafter in this specification) emitted from a cathode 2 are accelerated by a first anode 3 and a second anode 4 and are focused on the upper surface of a specimen 8 through a condenser lens 5 and an objective lens 6. The focusing point on the surface of the specimen 8 at which the primary electrons 1 are focused is controlled by a deflection coil 7. Secondary electrons 9 produced in response to the impingement of the primary electrons 1 on the surface of the specimen 8 pass through the objective lens 6 and are detected by a secondary electron detector 10. The secondary electron image over the surface of the specimen 8 can be observed with the secondary electron detector 10 by detecting the secondary electrons 9 while the primary electrons 1 are caused to scan the surface of the specimen by using the deflection coil 7.
However, in order to observe the through holes with the above-mentioned conventional apparatus utilizing charged particle beam observation, almost all the secondary electrons emitted from the bottoms of through holes will not come out therefrom because the secondary electrons impinge the side walls of through holes. For instance, the trajectory of the secondary electrons emitted from a cylindrical through a hole 1 .mu.m in depth and 0.5 .mu.m in diameter is shown in FIG. 2. An insulating layer 12 is formed over the surface of a substrate 11 and the specimen 8 shown in FIG. 1 is composed of the substrate 11 and the insulating layer 12. The insulating layer 12 is formed with a through hole 0.5 .mu.m in diameter (D) and 1 .mu.m in depth (T). Corresponding to the following reference numerals: 13 represents the central axis of the through hole; 14 represents the trajectory of the secondary electron emitted at an angle of 5.degree. with respect to the central axis 13 from the center of the through hole; 15 represents the trajectory of the secondary electron emitted at an angle of 10.degree. with respect to the central axis 13 from the center of the through hole; and 16 represents the trajectory of the secondary electron emitted from the center of the through hole at an angle between 15.degree. and 85.degree. with respect to the central axis 13. The energy of the secondary electrons 14-16 is 5 eV. In the through hole, there exists magnetic flux of 1.times.10.sup.4 AT/m corresponding to the leakage flux of the objective lens 6 in parallel with the axis 13. It is seen that the secondary electrons emitted at angles in excess of about more than 15.degree. with respect to the axis 13 impinge on the side wall of the through hole and cannot come out therefrom. As described above, in the case of the conventional apparatus utilizing charged particle beam, almost all the secondary elec
REFERENCES:
patent: 4209701 (1980-06-01), Dietrich et al.
patent: 4658136 (1987-04-01), Ohtaka et al.
patent: 4740698 (1988-04-01), Tamara et al.
Patent Abstracts of Japan, vol. 11, No. 304 (E-545;) 2751, Oct. 3, 1987 & JP 62-097 246 (Mitsubishi Electric Corp.).
Electron Microscopy, 4th European Regional Conference, Sep. 1968, pp. 353-354, Fourth European Regional Conference on Electron Microscopy, etc.
Patent Abstracts of Japan, vol. 9, No. 288 (E358) 2011, Nov. 15, 1985, and JP 60 130 044 (Nippon Denshi K.K. Jul. 11, 1985 (Abstract).
"Modes S-6000 Field Emission CD Measurement SEM" the 93th study reference disclosed at the 132th committee held on Japan Society for the Promotion of Science (Nov. 8-9, 1985), no translation.
"Low-energy-electron ray tracing its application" the 97th study reference disclosed at the 132th committee held on Japan Society for the Promotion of Science (Nov. 14-15, 1986), no translation.
Electron ray tracing with high accuracy, Kenichi Saito et al., pp. 1913-1917.
Saito Ken-ichi
Wada Kou
Yoshizawa Masahiro
Anderson Bruce C.
Nippon Telegraph and Telephone Corp.
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