Error detection/correction and fault detection/recovery – Pulse or data error handling – Memory testing
Reexamination Certificate
1999-03-02
2002-06-04
Decady, Albert (Department: 2133)
Error detection/correction and fault detection/recovery
Pulse or data error handling
Memory testing
C714S727000, C324S754090, C324S763010
Reexamination Certificate
active
06401224
ABSTRACT:
BACKGROUND OF THE INVENTION
Field of the Invention
The invention relates to an integrated circuit and to a method for testing the integrated circuit via contact areas disposed on a main area of the circuit.
Integrated circuits are fabricated on wafers composed of semiconductor material. Each wafer has a number, the number being very large under certain circumstances, of mutually adjacent integrated circuits which are disposed in such a way that the area of the wafer is utilized to the best possible effect. The main areas of the integrated circuits are usually rectangular. Contact areas are situated on the surface of each integrated circuit, via which contact area signals can be transferred from and to the integrated circuit. The contact areas are also referred to as pads.
In order to test the integrated circuits situated on the wafer, the contact areas are usually contact-connected to test probes (that is to say test contacts in the form of needles) of a test apparatus. The signals are then transferred from the test apparatus to the integrated circuit, and vice versa, via the test probes and the contact areas which are contact-connected thereto.
Many integrated circuits have contact areas only along two opposite sides of the main area. If two of the integrated circuits are disposed next to one another on a wafer, all of their contact areas can be contact-connected simultaneously to test probes without difficulty. However, there are also integrated circuits that have contact areas on more than two sides of their main area. In order to be able to test such a circuit, it is necessary for test probes to be contact-connected to the corresponding contact areas from all four sides. If two circuits of this type are adjacent to one another on the wafer, the contact areas cannot readily be contact-connected simultaneously to test probes since it is then possible for the test probes to experience a crossover, above all at the mutually adjacent sides of the two circuits. Therefore, adjacent circuits with contact areas on four sides are, as a rule, contact-connected and tested one after the other. This prolongs the time required for testing a plurality of adjacent circuits in comparison with the case of simultaneously testing the circuits.
SUMMARY OF THE INVENTION
It is accordingly an object of the invention to provide an integrated circuit and method for testing it that overcome the above-mentioned disadvantages of the prior art devices and methods of this general type, in which testing via its contact areas using test contacts is facilitated.
With the foregoing and other objects in view there is provided, in accordance with the invention, an integrated circuit, including: a first sub-circuit; a first contact area transferring data to and from the first sub-circuit during a first operating mode; and a second sub-circuit; a second contact area transferring data to and from the second sub-circuit in the first operating mode, in a second operating mode the second contact area transferring data to and from the first sub-circuit.
The integrated circuit according to the invention has at least one first and one second contact area for data transfer from and/or to a first and/or a second sub-circuit in a first operating mode of the circuit. It being the case that in a second operating mode of the circuit, the second contact area serves for data transfer from and/or to the first sub-circuit.
In the second operating mode, then, the second contact areas serve to transfer signals that are to be transferred via the corresponding first contact areas in the first operating mode. Therefore, the function performed by the first contact area in the first operating mode is taken over by the second contact area in the second operating mode. The corresponding signals are therefore fed into and/or removed from the circuit in the second operating mode at a different location (namely that of the second contact area) from that in the first operating mode. As a result, these signals can be transferred without any problems in the second operating mode if the first contact area can be contact-connected only with difficulty to test contacts of a test apparatus and the second contact area, on the other hand, can readily be contact-connected.
The circuit according to the invention is suitable for a procedure in which only the second contact areas, but not the first contact areas, are contact-connected to test probes in the second operating mode, with the result that the functions performed by the first contact areas in the first operating mode can then be tested via the second contact areas. This facilitates, in particular, the simultaneous testing of circuits which are adjacent on a wafer and in which the first contact areas are disposed on mutually facing sides of the circuits, where they can be contact-connected simultaneously to test contacts only with difficulty.
In the second operating mode, the second contact area may serve, on the one hand, exclusively to transfer signals that are transferred via the first contact areas in the first operating mode. The signals that are to be transferred via the second contact area in the first operating mode are not transferred via the second contact area in that case. This is possible, for example, if the second operating mode is a test operating mode of the circuit in which a smaller number of contact areas are required than in the first operating mode, because only specific functions of the circuit are tested.
In the second operating mode, the second contact area may also serve, in addition to transferring the signals which are to be transmitted via the first contact area in the first operating mode, furthermore to transfer the signals which it also transfers in the first operating mode. This can be realized for example by the second contact area serving to transfer the various types of signals using time division multiplexing in the second operating mode.
According to a development of the invention, the first and the corresponding second contact areas are disposed in respectively different rows of contact areas, the rows being respectively disposed parallel on different sides of a main area of the circuit.
In this case, in the second operating mode, bottlenecks in the event of contact-connecting the circuit to test probes at the side with the first contact areas are circumvented by displacing their function to the second contact areas. If there are two directly adjacent circuits on a wafer, e.g. the mutually facing sides constitute bottlenecks of this type, since it is there that, without the invention, test probes must be contact-connected on both circuits in direct proximity to one another, with the result that the risk of the test contacts experiencing a crossover is particularly high in this region. The invention makes it possible to gain space at the most critical location for attaching the test contacts (the location being the one at which the two circuits face one another) by the use of fewer test contacts than there are contact areas, it being possible for contact to be made with the remaining contact areas more easily as a result.
If the first contact areas are disposed on at least one of two opposite sides of the main area and the second contact areas are disposed on at least one of two other, likewise opposite sides, contact-connection bottlenecks at the first-mentioned two sides are circumvented in the second operating mode. Therefore, the simultaneous contact-connection and testing of at least three adjacent circuits is advantageously facilitated, which circuits are disposed in such a way that the first contact areas are in each case disposed on the side facing the adjacent circuit. At these sides, fewer contact areas than are present have to be contact-connected in the second operating mode. On the other hand, those sides on which the second contact areas are situated can be contact-connected without difficulty and without the test probes experiencing a crossover, since no adjacent circuits which are to be contact-connected simultaneously are disposed on these
Dietrich Stefan
Hein Thomas
Schöniger Sabine
Schrögmeier Peter
De'cady Albert
Lerner Herbert L.
Torres Joseph D.
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