Data processing: measuring – calibrating – or testing – Measurement system in a specific environment – Electrical signal parameter measurement system
Reexamination Certificate
2001-06-22
2003-09-23
Hoff, Marc S. (Department: 2857)
Data processing: measuring, calibrating, or testing
Measurement system in a specific environment
Electrical signal parameter measurement system
C324S750010
Reexamination Certificate
active
06625554
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention generally relates to the field of Electro-magnetic wave measurement and particularly to techniques for measuring a magnetic field of an integrated circuit (IC) inside the IC package, including the IC without the IC packaging. And more particularly to IC's with densities about or greater than the current Large Scale Integrated (LSI) circuits.
FIG. 1
shows an example of a magnetic field distribution
114
of a package
110
having an integrated circuit (IC), for example, a LSI or an Ultra Large Scale integrated (ULSI) circuit. In
FIG. 1
the package
110
is shown with cut-away section
112
illustrating the IC inside the package. Conventionally, the magnetic field distribution
114
outside of the package
110
is determined using a magnetic probe or sensor
116
from which induced voltage measurements are taken. In other words, typically measurements are taken of the IC outside of the IC packaging. The induced voltage is caused by currents in the integrated circuit and is used to determine the magnetic field at the position of the magnetic probe or sensor
116
.
One reason for determining the magnetic field distribution of the package
110
is to solve any Electro-Magnetic Interference (EMI) problems that may be caused by the currents in the IC. In order to reduce the EMI, the source of the interference needs to be pinpointed. An example is given in Japanese Patent Application “Apparatus And The Method For Detecting Electromagnetic Wave Source, And Method For Analyzing The Same,” by Uesaka Koichi, JP11-117028, filed Apr. 23, 1999. However, as circuit sizes shrink, for example, today LSI's are produced by a 0.1 &mgr;m process, it is necessary to perform measurements of the magnetic field very close to the circuit wirings, for example, cut-away section
112
inside the package
110
, in order to pinpoint the source of potential interference.
In addition, determining the magnetic field distribution inside the IC package
110
, may lead to production of low noise integrated circuits. Locations on the IC with a relatively high magnetic field indicate relatively high noise points. Of the several conventional techniques to reduce the magnetic field at these points, an example is changing the line pattern to reduce the noise.
Japanese Application No. JP11-006485, “Method And Apparatus For Measuring Electromagnetic Field Strength And Method And Apparatus For Measuring Current And Voltage Distribution,” by Satoshi Kazama, et. al., filed Jan. 13, 1999, discloses the use of a loop antenna as a probe to determine the magnetic field over, for example, a circuit board. Other examples given are a lead wire of several centimeters, a microstrip line (i.e., a planar transmission line), a unit of a component on a board, and a circuit substrate of an electrical equipment. The loop probe is used for measurements in the neighborhood of 2 mm from the submitted equipment. Thus the disclosed use was for improving magnetic field determinations above equipment, for example, a unit on a board, not for inside an IC package.
In the above Japanese Application No. JP11-006485, the electromagnetic field of the circuit board generates an electric field coupling current and a magnetic field coupling current in a loop antenna above the circuit board. In the probe the electric field coupling current and the magnetic field coupling current are outputted toward the same direction at a certain part of the loop probe, but toward opposite directions at another part of the loop probe. A first composite current, i.e., electric field coupling current and the magnetic field, measured at one end of the loop probe by a current measuring device, gives the electric field coupling current plus the magnetic field coupling current. A second composite current measured at the same end of the loop probe by the same current measuring device, after rotating the loop probe 180 degrees, gives the electric field coupling current minus the magnetic field coupling current. Therefore, the electric field coupling current and the magnetic field coupling current can be calculated using these two composite currents. And the electric field component and the magnetic field component of the electromagnetic field at the loop probe can be derived from these composite currents.
However, using Japanese Application No. JP11-006485 in determining the magnetic field distribution of an IC package has only a secondary improvement in the measurement of the magnetic near-field distribution. Thus the conventional technique provides sufficiently accurate magnetic field measurements, and there is no significant advantage in using the techniques disclosed in Japanese Application No. JP11-006485 over the conventional techniques in the case of packaged IC magnetic field measurements. In addition, Japanese Application No. JP11-006485 rotates the probe to take the composite current measurements, when using one current measuring device. This rotation is time-consuming and a more efficient method of taking measurements is needed.
In order to pinpoint the source of potential interference in IC's, measurements of the magnetic field on the order of tens of micrometers (&mgr;m), for example, 30 &mgr;m, above the IC wirings, i.e., inside the IC package, need to be made. Cut-away section
112
shows inside the IC package
110
. However, in measuring the magnetic field inside the IC package, a significant coupling capacitance due to the electric field develops and the accuracy of the magnetic field probe to measure only the magnetic field deteriorates. Therefore there is need for techniques which minimize the effect of the electric field on the magnetic field probe inside an IC package to improve the accuracy of measurements of the magnetic field distribution.
SUMMARY OF THE INVENTION
The present invention provides a magnetic field measuring method and device for accurately determining the magnetic field distribution of an integrated circuit inside the IC package, including the IC without the IC packaging. In one embodiment, induced voltages due only to the magnetic field are determined at measurement heights on the order of 30 &mgr;m, i.e., inside the IC package (or for example, the pre-packaged IC) by using a magnetic probe, having a loop of wire parallel to the current, for measuring the induced voltage of the horizontal component of the magnetic field. The induced voltage due to the electric field is removed by using a calculation including the difference of two measurements. The first measurement is taken with a voltage meter coupled to the first terminal of the loop of wire and ground coupled to the second terminal. And the second measurement has the couplings reversed due to a cross-bar switch, i.e., a voltage meter coupled to the second terminal of the loop of wire and ground coupled to the first terminal. Thus only the induced voltage due to the magnetic field remains, after the calculation. The magnetic field distribution for the integrated circuit may be determined by using the above procedure to scan a grid like pattern above the IC.
In another embodiment a method for determining a component of a magnetic field of an IC at a height above the IC on the same order of magnitude as a distance between the IC's lines is provided. The method includes measuring a first induced voltage, having a first electric field induced voltage, due to a current carrying line's electromagnetic field. A second induced voltage due to the current carrying line's electromagnetic field is measured, such that the second induced voltage includes a second electric field voltage that is substantially equal to the first electric field induced voltage; The component of the magnetic field is determined based on a difference between the first induced voltage and the second induced voltage.
An alternate embodiment of the present invention provides a method for determining a magnetic field for a current carrying line of a plurality of current carrying lines inside an IC package, for example a LSI or VLSI circuit packa
Hayashi Yoshihiko
Nakamura Satoshi
Suga Takashi
Uesaka Kouichi
Baran Mary Catherine
Hitachi , Ltd.
Hoff Marc S.
Townsend and Townsend / and Crew LLP
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