Electricity: measuring and testing – Fault detecting in electric circuits and of electric components – Of individual circuit component or element
Reexamination Certificate
1999-10-12
2001-08-07
Metjahic, Safet (Department: 2858)
Electricity: measuring and testing
Fault detecting in electric circuits and of electric components
Of individual circuit component or element
C324S754090, C438S015000, C438S016000, C257S760000
Reexamination Certificate
active
06271671
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention is a laser based solution for non-invasive high-speed testing of multi-chip modules (MCMs) and more particularly to using a chromophore-doped polyimide as an interlayer dielectric in a multi-level thin film metallized circuit structure. The dielectric is converted into an electro-optic material by poling the device in a strong electric field. The change in the electro-optic coefficients of the chromophore-doped polyimide in the presence of electrical signals in the circuit can be detected using a laser beam. The electro-optic interaction between the poled dielectric and the laser beam allows the strength of the internal fields within the MCM to be determined as a function of position.
2. Description of the Related Art
The ability to perform in situ testing and characterization of both integrated circuits and their interconnecting substrates in complex multi-chip packaging structures is becoming increasingly important as the packages become smaller.
Electro-optic probing relics on the change in the index of refraction of a material in the presence of an electric field (linear electro-optic effect). The linear electro-optic effect was first studied in crystalline solids belonging to crystal classes that lack a center of inversion symmetry. Gallium Arsenide (GaAs) and Indium Phosphide (InP) are examples of common semiconductor materials that exhibit this effect. Certain organic polymers when doped with non-linear moites and poled are also non-centrosymmetric and therefore exhibit the electro-optic effect. Doped organic polymers are poled by insertion into a strong electric field as the polymer is heated to near its glass transition temperature.
An electro-optic probing instrument makes point-to-point electric field measurements internal to microwave circuits instead of limiting the information to that gathered at the input or output ports of a circuit. The technique has been widely demonstrated with semiconductor substrates such as GaAs and InP. However, a substrate of silicon (Si) cannot be tested because it has a center of inversion symmetry. Although this technique is popular and polyimide is an increasingly popular organic polymer used in advanced packaging applications for high-speed circuits such as MCMs, no one has extended the application of electro-optic probing to circuit structures on polyimide and compared the results to more conventional substrates used for electro-optic probing such as GaAs and InP to demonstrate the potential to non-invasively probe circuit structures that are buried in central layers of an MCM as is proposed in the present invention.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a non-invasive electro-optic probing of standard circuit structures by converting integral layers into an electro-optic material.
It is another object of the present invention to selectively convert predefined regions of the circuit structure.
It is a further object of the present invention to use chromophore-doped polyimides as an interlayer dielectric in a multilevel circuit structure.
It is yet another object of the present invention to selectively change the amount of poling and the chromophore density of the layers in the circuit structure to develop unique signatures even in deeply buried circuit elements.
It is still a further object of the present invention to detect the change in a material's electro-optic coefficients in the presence of electrical signals using a laser beam, continuous wave (CW) or pulsed.
It is a further object of the present invention to develop suitable polymers for high-density packaging, such as multi-chip module-doped (MCM-Ds) packages, that are capable of being probed non-invasively by electro-optic probing techniques.
These objects arc achieved by providing a multi-chip module circuit structure including a substrate, a metal layer formed on the substrate, a plurality of chromophore doped polyimide interlayer dielectric layers formed on the metal layer, and patterned metal conductors formed on each of the plurality of chromophore doped polyimide interlayer dielectric layers. The substrate can be silicon and can include p-type, boron doped, (100) orientation having a resistivity between 25-30 ohm-cm and a thickness between 14.0-16.0 &mgr;m. The chromophore doped polyimide interlayer dielectric layers can include, for example, a polyimide of Ultradel 9020D doped with 4-(dicyanomethylene)-2-methyl-6-(p-dimethylaminostyryl)-4H-pyran (DCM).
The present invention also includes a method for improving testability of a multi-chip module circuit structure including the steps of forming a multi-chip module circuit structure including a plurality of chromophore doped polyimide dielectric layers formed on a metal layer and substrate, forming patterned metal conductors on or near each of the plurality of chromophore doped polyimide dielectric layers, poling the chromophore doped polyimide dielectric layers in a strong electric field, and focusing a laser probe on each of the patterned metal conductors for diagnosing module performance.
These objects, together with other objects and advantages which will be subsequently apparent, reside in the details of construction and operation as more fully described and claimed hereinafter, reference being had to the accompanying drawings forming a part hereof, wherein like reference numerals refer to like parts throughout.
REFERENCES:
patent: 5394098 (1995-02-01), Meyrueix et al.
patent: 5539080 (1996-07-01), Hogan et al.
patent: 5872360 (1999-02-01), Panniccia et al.
Charles, Jr. Harry K.
Francomacaro A. Shaun
Mechtel Deborah M.
Deb Anjan K
Krivak Carla Magda
Metjahic Safet
The Johns Hopkins University
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