Electricity: measuring and testing – Fault detecting in electric circuits and of electric components – Of individual circuit component or element
Reexamination Certificate
2001-09-05
2003-09-02
Cuneo, Kamand (Department: 2829)
Electricity: measuring and testing
Fault detecting in electric circuits and of electric components
Of individual circuit component or element
C324S1540PB, C324S765010
Reexamination Certificate
active
06614243
ABSTRACT:
BACKGROUND OF THE INVENTION
Field of the Invention
The invention relates to a measurement probe for detecting electrical signals in an integrated circuit on a semiconductor chip, to a measurement system having such a measurement probe, to a method for producing the measurement probe, and to a method of using the probe.
The enormous progress in the field of semiconductor technology in the last 20 years has led to increasingly more complex integrated circuits being produced in an increasingly smaller space on semiconductor chips. The increasing integration density of switching elements and their connections has, however, also considerably increased the requirements of the test facilities used for functionally analyzing the integrated circuits on the semiconductor chips. In order to allow effective functional analysis of integrated circuits on semiconductor chips to be carried out, for example, in the course of a final inspection of the chips, it is necessary to measure electrical signals at various points on the chip, for example, on different interconnects or transistor inputs. This requires a measurement apparatus which is distinguished by high-precision position resolution. Furthermore, in order to allow even very weak electrical signals to be detected in integrated circuits, it is necessary to use measurement probes with a very low capacitance. Such probes should also be able to follow voltage fluctuations with little noise.
Normally, integrated circuits on semiconductor chips are tested by means of measurement systems that have measurement probes with very fine measurement tips. The measurement tips are moved over the sample surface by means of a computer-aided movement system in order to then be placed on the desired measurement point in the integrated circuit. With the very fine measurement tips that are known, the radius at the tip is only approximately 0.2 &mgr;m, so that it is possible to measure interconnects down to less than such a width. In this case, the conventional measurement systems have a capacitance of approximately 20 to 40 fF, and this makes it possible to measure the electronic signals which are normally used in integrated circuits.
However, in the meantime, the progress in semiconductor technology, in particular in MOS technology, now allows the production of components in the sub-0.2 &mgr;m range. Furthermore, increasingly smaller electric currents are used for switching the components. This therefore necessitates measurement systems for functional analysis, which can record electrical signals in integrated circuits on semiconductor chips with virtually no capacitance and with extremely high position resolution.
Recently, scanning sensor microscopy has been used for nondestructive mapping and measurement of the topography or structure of semiconductor chips. The best known scanning sensor microscopes are in this case the scanning tunnel microscope and the scanning force microscope. Scanning tunnel microscopes (STM) can be used to scan the surfaces of electrically conductive solid bodies. This is done by moving an extremely fine metal tip over the sample surface at a distance of about 1 nm, by means of a computer-controlled piezoelectric movement system. In this case, a tunneling current occurs between the sample surface and the metal tip. This tunneling current which is carried by overlapping paths of the outermost tip electrons and of the surface electrons, changes by orders of magnitude when the distance between the metal tip and the surface is varied even only to a minimal extent. This system sensitivity to distance changes therefore allows the piezoelectric movement system to keep this distance constant with very high precision while the metal tip scans the surface. Surface topographies of electrically conductive samples can therefore be recorded with atomic resolution.
The scanning force microscope has been developed in order to allow the topography or structure of even sample surfaces that are not conductive to be mapped and measured with atomic position and depth resolution. In scanning force microscopes, the sample surface is likewise scanned with a very fine tip, which is attached to an extremely thin lever arm, by means of piezoelectric movement. The lever arm, with its tip, is in this case moved to a position sufficiently close to the sample surface that an atomic interaction occurs between the outer atoms of the probe tip and the sample surface. A computer then controls the piezoelectric movement system, such that the forces between the probe tip and the sample surface, which are typically between 10
−5
and 10
−11
N, remain constant. When scanning the sample, the probe tip records the topography of the sample surface in the process. The deflection of the lever arm can be registered by a photodiode, for example, by means of a light pointer. A three-dimensional map of the surface geometry can then be produced with atomic resolution, with computer assistance, from the defined movement of the sample tip. As explained, scanning sensor microscopes have admittedly already been used for measuring the topography of semiconductor chips. However, no scanning sensor microscope is known which is used for functional testing of integrated circuits on semiconductor chips for industrial manufacturing purposes.
SUMMARY OF THE INVENTION
It is accordingly an object of the invention to provide a measurement probe that can be used for functionally analyzing electrical circuits on a semiconductor chip which overcomes the above-mentioned disadvantageous of the prior art apparatus of this general type. It is also an object of the invention to provide a measurement system that includes the measurement probe and a method for producing such a measurement probe. In particular, it is an object of the invention to provide such a measurement system, by means of which, electrical signals in integrated circuits can be measured with extremely fine position resolution and in a virtually uninfluenced manner.
With the foregoing and other objects in view there is provided, in accordance with the invention, a measurement probe for detecting electrical signals in an integrated circuit on a semiconductor chip. The measurement probe includes a lever arm having a probe tip that is arranged on it. The lever arm and the probe tip are composed of a highly conductive material which is covered by an extremely thin insulator layer. The probe tip has a window in the insulator layer on its front radius, and contact is made with the lever arm through the insulator layer. Such a measurement probe can be operated first in a force mode, in order to detect the topology of the circuit by scanning the surface of the integrated circuit, in order to fix the probe tip above the desired measurement point, and then, in a tunneling mode, in order to determine the voltage at the measurement point in the integrated circuit by detecting a tunneling current between the measurement point and the probe tip.
The measurement probe for detecting electrical signals in an integrated circuit thus represents a combination of a scanning force microscope and a scanning tunnel microscope, with extremely fine position resolution down to the atomic range being feasible in the scanning force mode. The measurement probe can therefore be moved exactly to the desired measurement point on the integrated circuit, for example precisely on the center of an interconnect. In the tunneling mode, the electrical signals at the measurement point can then be measured very accurately, without these signals being influenced. The capacitance of the probe tip is in this case only about {fraction (1/10)} to {fraction (1/100)} of that of conventional measurement tips.
With the foregoing and other objects in view there is provided, in accordance with the invention, a method for producing the measurement probe. The measurement probe is produced from highly doped, monocrystalline silicon, which is thermally oxidized in order to produce an oxide layer with a thickness of at most 3 nm, preferably 2 nm. A window is opened in the oxide
Klehn Bernd
Lindolf Juergen
Cuneo Kamand
Greenberg Laurence A.
Infineon - Technologies AG
Locher Ralph E.
Nguyen Tung X.
LandOfFree
Measurement probe for detecting electrical signals in an... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Measurement probe for detecting electrical signals in an..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Measurement probe for detecting electrical signals in an... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3047864