Electricity: measuring and testing – Fault detecting in electric circuits and of electric components – Of individual circuit component or element
Reexamination Certificate
2002-03-06
2004-05-11
Cuneo, Kamand (Department: 2829)
Electricity: measuring and testing
Fault detecting in electric circuits and of electric components
Of individual circuit component or element
C324S763010
Reexamination Certificate
active
06734695
ABSTRACT:
BACKGROUND OF THE INVENTION
Field of the Invention
The invention relates to a method and a semiconductor component, in particular an integrated circuit, in which, in addition to the operating voltage, there are one or more internal voltages.
One problem that frequently occurs in integrated (semiconductor) circuits which, owing to their complexity, are frequently accommodated in special housings with up to several hundred connecting pins, is that internal voltages which are generated by appropriate voltage sources cannot be measured at a connecting pin on the housing since, owing to the lack of line connections and the lack of free connecting pins, or as a result of standardization, they are not externally accessible.
On the other hand, during the production process, it is important to record the internal voltages when testing the components and for control of the production process, and then to assess the functions or the quality of that component. Problems such as these occur, for example, in computer chips or in memory components such as SRAM, DRAM, etc. By way of example, in the case of a DRAM module, the behavior of the module is governed by the magnitude of the boosted word line voltage. An excessively high or low voltage can result in it being impossible to either read or write the data and information. It is thus very important to check the voltage during the production process, to ensure that the component will carry out the desired functions during its subsequent use.
Until now, this problem has been circumvented by measuring the relevant internal voltages, using special measurement probes, just during the wafer-level test. However, appropriate measurement pads must be provided on the chip, for this measurement, to which the measurement probes can be applied. The method costs additional chip surface area, which is then no longer available for other functional modules.
It is also known for special housings (characterization housings) to be manufactured for measuring the internal voltages, which have appropriate connecting pins for the relevant internal voltages. The internal voltages are passed to the connecting pins, so that they can then be measured from the outside. This can, of course, only be carried out for a sample with a correspondingly small number of components, since the method is highly complex and costly. Furthermore, such components can no longer be sold, since they do not comply with the predetermined specifications.
SUMMARY OF THE INVENTION
It is accordingly an object of the invention to provide a method and a semiconductor component having a device for determining an internal voltage that overcomes the above-mentioned disadvantages of the prior art methods and devices of this general type.
With the foregoing and other objects in view there is provided, in accordance with the invention, a method for detecting an internal voltage in an integrated circuit. The integrated circuit receives an operating voltage and generates internal voltages, in which case the internal voltages cannot be measured directly via existing, isolated connecting pins of the integrated circuit. The method includes dividing the internal voltage using a voltage divider disposed within the integrated circuit resulting in a divided internal voltage. A controller disconnects a selected connecting pin for a predetermined time period by opening a switch from its previous connection to an internal circuit part resulting in a disconnected connecting pin. The divided internal voltage is applied to the disconnected connecting pin during the predetermined time period.
The invention is based on the object of temporarily changing the use of a connecting pin to allow the measurement of an internal voltage that is not directly accessible.
The method according to the invention has the advantage that internal voltages can be measured directly at one or more selected connecting pins on the housing. One particularly advantageous feature in this case is regarded as the fact that the voltages can be measured on all the components and that the components nevertheless still comply with their full electrical specification in accordance with the datasheet. It is also advantageous that the measurements can be repeated as often as desired, so that the internal voltages can, in particular, be checked during subsequent use, using suitable measurement methods. A further advantage is also the fact that the number of internal voltages to be measured is in practice unlimited, so that the method provides considerably better criteria for assessing the component quality. The additional technical complexity is, in contrast, negligibly small.
It is regarded as being particularly advantageous in this case that the voltage that is measured at the connecting pin, by a measuring device, can be multiplied by the division ratio of the associated voltage divider, thus producing the actual value of the internal voltage. There is then no need for any further conversion calculations.
It is also particularly advantageous for the division ratio of the voltage divider to be configured such that the measurement range that is produced does not cause any reaction with the rest of the circuit. This ensures that the component cannot be damaged by the measurement process.
If it is intended to measure a number of internal voltages, in particular, at different levels, and the voltage divider can be adapted as appropriate. This also advantageously results in that the measurement of the internal voltage cannot have any adverse effect on the component.
Particularly when a number of internal voltages are intended to be measured, the advantageous solution is to measure the voltages using a known multiplexing method. Therefore, the same connecting pin can always be used, for example, for the different measurements. This also considerably simplifies the interconnect routings within the semiconductor component.
Since individual chip surface areas are freely available for the formation of voltage dividers even in large scale integrated semiconductor components, it is possible to use chip surface areas such as these advantageously. In consequence, there is scarcely any influence on the existing layout.
For the semiconductor component, it may be important for the circuit part (module, receiver) that is disconnected during the measurement phase to retain its function at that time. Any change to the function could, for example, lead to a change in the internal voltage, and could thus cause an undesirable measurement error.
It is also advantageous for the semiconductor component that the voltage divider is used to divide the internal voltage to a safe level, which is applied to the connecting pin by appropriately configured switches. Any internal voltage can thus be applied to the connecting pin by switching the switches. Only a simple control action is required to do this, so that the switches can be controlled from the outside via control commands that are sent via an appropriate control bus.
With the foregoing and other objects in view there is provided, in accordance with the invention, an integrated circuit. The integrated circuit contains a housing, connecting pins disposed in the housing and isolated from one another, at least one circuit part having connections connected to the connecting pins, and at least one internal voltage source generating an internal voltage. At least one voltage divider is coupled to the internal voltage source and by which the internal voltage can be divided resulting in a divided internal voltage. Switches are provided for routing the divided internal voltage to a selected connecting pin of the connecting pins. The switches are connected between the voltage divider and at least one of the connecting pins.
Particularly in the case of a memory component such as DRAM or SRAM, this advantageously makes it possible to test internal voltages such as the word line voltage.
Transistor switches are fast switches that are relatively simple to produce, particularly when they are in the form of NMOS or PMOS switches (N-conductive
Schaffroth Thilo
Schneider Ralf
Cuneo Kamand
Greenberg Laurence A.
Mayback Gregory L.
Nguyen Tung X.
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