Objective lens for producing a radiation focus in the inside of

Details Objective lens for producing a radiation focus in the inside of Objective lens for producing a radiation focus in the inside of

1992-02-20

1993-09-21

Sugarman, Scott J.

Optical: systems and elements

Lens

Microscope objective

359660, 359664, G02B 2102, G02B 300

Patent

active

052473929

ABSTRACT:
Objective lens for producing a radiation focus in the inside of a specimen. Many laser measuring methods for sensing charge carrier density or the distribution of a potential in the inside of an integrated circuit (IC) of microelectronics are based on what is referred to as "backside-probing" technique, whereby the laser radiation (LA) is focused into the plane of the voltage-carrying components (SK) from the backside of the component using a conventional microscope objective. Since the irradiation occurs through the substrate (SU), a pronounced spherical aberration arises that limits the spatial resolution to approximately 2 through 4 .mu.m. For producing a sub-.mu. probe in the substrate (SU), a lens is arranged on the polished backside (RS) of the integrated circuit (IC), this lens being composed of a silicon base plate (GP, refractive index of n.sub.1), a sphere (KU, refractive index of n.sub.2 <n.sub.1, radius of r.sub.2) lying in a recess of the base plate (GP), and a hemispherical silicon shell (KS, refractive index of n.sub.1, outside radius of r.sub.1, inside radius of r.sub.2). Given a suitable selection of the refractive indices and of the radii, the lens and the substrate (SU) form an optical unit acting as a 2-index Luneburg lens that focuses an incident, parallel ray beam (LA) at a point (LF) lying in the inside of the substrate (SU).

REFERENCES:
patent: 4577566 (1985-12-01), Kikuchi et al.
patent: 5004328 (1991-04-01), Suzuki et al.
"Picosecond Noninvasive Optical Detection of Internal Electrical Signals in Flip-Chip-Mounted Silicon Integrated Circuits", by H. K. Heinrich, IBM Journal of Research & Development, vol. 34, No. 2/3, Mar./May 1990, pp. 162-172.
"Spherical Lenses for Infrared and Microwaves", by G. Toraldo Di Francia, J. Appl. Phys. 32, May 19, 1961, p. 2051.
"Microwave Scanning Antennas", Edited by R. C. Hansen, Academic Press, New York, (1964), pp. 214-218.

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