Abstract: In a method of incorporating BIST (built-in self test) circuitry in an integrated circuit, at least one metal layer is arranged to relieve stress in the substrate under bond pads from wire attachment to these pads. By providing at least one stress relieving metal layer, which can be incorporated into electrical paths of the bond pads and related circuitry, BIST circuitry can be provided, at least partly, in the conventionally non-active semiconductive portion of the substrate under the bond pad. The method allows BIST circuitry to occupy conventionally non-active areas under the bond pads wherein leakage current from stress cracks in dielectric layers under the bond pads can be redirected to a metal layer.

Abstract: The present invention provides, in one embodiment, an integrated circuit having a substrate and active devices formed on the surface of the substrate. Other embodiments of the integrated circuit provide for having at least either three or four metal layers. In a particular embodiment of the present invention, the integrated circuit comprises a bond pad formed over a portion of the active devices. The bond pad has a footprint. As used therein the word footprint means the area covered by the device to which the word refers. The integrated circuit further incudes a patterned metal layer having a metal layer footprint that is located between the bond pad and the substrate and a built-in self-test (BIST) circuit that has a BIST footprint, which is located between the substrate and the bond pad. In this particular embodiment, the bond pad footprint overlays at least a portion of the metal layer footprint and the BIST footprint.

Abstract: A method for etching metal conductors and stacks of conductors is disclosed. A doped silicon dioxide layer is deposited upon a metal or stack of conductive layers to be etched. A silicon dioxide layer is doped with phosphorous. Next, the silicon dioxide layer is partially etched and the photoresist removed. Subsequent etching utilizes the raised feature created in the silicon dioxide layer as a mask to etch the underlying metal or stack of conductors.

Abstract: The transversal filter has a plurality of variable delay lines each having multiple voltage controlled delay stages in series, with one of the variable delay lines having a clock input, and the other variable delay lines having data signal inputs. A phase comparator is coupled to the output of two non-adjacent stages of the variable delay lines having the clock input. A feedback circuit is coupled to the comparator and provides voltage signals to the voltage controlled delay stages of all of the variable dealy lines, such that adjacent stages in a particular delay line are delayed in time equal fractions of a clock cycle from each other, and so that all delay lines are running on the same clock. A voltage weighting circuit is provided for shaping the voltage outputs of the data signal variable delay lines and the weighting circuit is coupled to the delay line stages by switches which are activated when a data signal is propagated through a delay line stage.

Abstract: A p-type tub in a CMOS integrated circuit is isolated from the adjacent n-type tub by means of a field oxide having a p-type channel stop region formed by a boron ion implant. The depth of the ion implant is selected so that the peak of the boron concentration is located immediately under the field oxide region that is subsequently grown. In addition, the implant is allowed to penetrate into the active device regions, producing a retrograde boron concentration in the n-channel region. This technique simultaneously improves device isolation and n-channel transistor punch-through characteristics, allowing the extension of CMOS technology to sub-micron device geometries.

Abstract: A method of forming a transistor is disclosed. Conventional fabrication techniques direct an ion implantation beam toward a substrate upon which a gate has already been formed. If the gate stack is too low relative to the incident beam energy, the dopant species may channel thorugh the gate stack, adversely affecting transistor performance. The present invention prevents channeling through this gate by covering the gate with a protective layer before ion implantation.

Abstract: A modular, expandable, non-blocking system for cross-connecting high speed digital signals is provided. The system is capable of connecting DSn, CEPTn, and STSn signals as desired, with lower rate signals being included as components of the high-rate signals or terminating on low speed lines, as desired. The system accomplishes its goals by converting all incoming signals into a substantially SONET format, and by processing all the signals in that format. The signals are typically cross-connected in the substantially SONET format, although an expandable non-blocking wide band cross-connect module is provided which cross-connects any like signals. If the outgoing signal is to be in other than SONET format, the substantially SONET formatted signal is reconverted into its outgoing format. To create a complete system, various modules are utilized, including: add/drop multiplexer means for add/drop applications of DS-0, DS-1, CEPTn signals, etc.

Abstract: A modular, expandable, non-blocking system for cross-connecting high speed digital signals is provided. The system is capable of connecting DSn, CEPTn, and STSn signals as desired, with lower rate signals being included as components of the high-rate signals or terminating on low speed lines, as desired. The system accomplishes its goals by converting all incoming signals into a substantially SONET format, and by processing all the signals in that format. The signals are typically cross-connected in the substantially SONET format, although an expandable non-blocking wide band cross-connect module is provided which cross-connects any like signals. If the outgoing signal is to be in other than SONET format, the substantially SONET formatted signal is reconverted into its outgoing format. To create a complete system, various modules are utilized, including: add/drop multiplexer means for add/drop applications of DS-0, DS-1, CEPTn signals, etc.

Abstract: A self-assigned, self-planarized metallization scheme for multilevel interconnections using self-aligned windows in integrated circuits is described. Trenches are etched into a dielectric and then, using an etch stop layer on top of the dielectric to prevent unwanted etching of the dielectric, self-aligned windows which expose portions of the substrate are etched in the dielectric. Self-aligned windows can also be formed without a mask.

Abstract: Circuit apparatus for supplying a loop current to a two conductor loop telephone line includes first and second differential amplifiers each having the same gain factor. The first amplifier is coupled to one side of the line via a series resistance, while the second amplifier is coupled to the other side of the line via a series resistance of the same magnitude. A feedback amplifier has one input terminal coupled to one side of the line and another input terminal coupled to the other side of the line. The inputs of the feedback amplifier are further coupled to the outputs of the above differential amplifers. The output of the feedback amplifier is coupled to the input of a variable gain amplifier which has its output coupled to an input terminal of the first differential amplifier. The first differential amplifier receives a voltage reference source at its other input which source controls the magnitude of the current supplied to the line circuit.

Abstract: The digital supervisory circuit comprises an amplitude comparator and EXCLUSIVE-OR gate to provide an output signal indicating the difference in time an input signal is above and below a predetermined reference potential. This output signal is integrated in an up-down binary counter and also is coupled to a first logic circuit under control of the counter which provides a ring present supervisory signal when a first threshold is exceeded and a second logic circuit under control of the counter which provides a switch hook detection supervisory signal when a second threshold is exceeded. A hit-timing circuit is provided coupled to the counter and the first and second logic circuits to prevent response of the counter and second logic circuit to line transients.