Electricity: measuring and testing – Measuring – testing – or sensing electricity – per se – With rotor
Reexamination Certificate
1999-04-21
2001-10-09
Brown, Glenn W. (Department: 2858)
Electricity: measuring and testing
Measuring, testing, or sensing electricity, per se
With rotor
C324S765010, C702S118000, C702S121000
Reexamination Certificate
active
06300757
ABSTRACT:
The invention relates to a procedure for the calibration of a measuring device for the measurement of RF parameters of integrated circuits on semiconductor wafers on which there are a large number of such integrated circuits.
When manufacturing integrated circuits it is normal procedure to test the viability of the individual circuits whilst they are still on a semiconductor wafer on which there may be hundreds or even thousands of such circuits. For the purpose of testing, the wafer is inserted into a testing device, and connections to the points on the integrated circuits to be tested are made by means of pointed test probes. These test probes enable any desired current or voltage to be applied to the circuit, and output currents and voltages to be measured.
As long as the testing procedures involve direct currents and voltages, it is not difficult to obtain precise measuring results, since the measuring device itself has but a negligible effect on the measured values. However, when the integrated circuits are RF circuits whose RF behaviour is to be tested, considerable difficulties present themselves when it comes to the gathering of the four-pole parameters, responsible for the RF behaviour, with any precision, since the measuring device itself and in particular the connecting leads between the actual measuring devices and the measuring points on the integrated circuit will be the cause of considerable variations of the values measured, due to the well-known transformation processes involved. The difficulty, therefore, consists in gathering the four-pole parameters to be measured on the plane of the measuring points on the integrated circuit. This leads to the requirement that the measuring device should be calibrated in such a way as to register the actual four-pole parameters as present on the plane of the measuring probes on the integrated circuit, instead of the values present at the output ends of the leads connecting to the measuring devices. Such a new calibration process must be carried out each time a test configuration is changed, as, for example, when changing the measuring point contact positions on the integrated circuit.
Calibration substrates with precisely known four-pole parameters, suitable for the calibration of such a measuring device, are certainly available, but these substrates are ceramic substrates with evaporation-deposited circuits and circuit elements which are inserted into the testing device and which are then used to carry out a calibration process. In the case of such a calibration process it is, however, not possible to reproduce exactly the actual geometrical conditions prevailing on a semiconductor wafer in the course of testing an integrated circuit. It follows, therefore, that a precise calibration of the measuring device at the plane of the measuring points contacted is not possible when using such ceramic substrates with standard circuit elements. Furthermore, these ceramic substrates are extremely expensive, and up to now it was almost impossible to use such calibration substrates for all possible application requirements.
The invention, therefore, is to satisfy the requirement for the provision of a calibration process of the type previously described which is not costly and yet allows the precise calibration of the measuring device at the plane of the measuring probes on the integrated circuit, even allowing for different measuring configurations.
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Dean A. Frickey, Member IEEE, Conversations Between S, Z, Y, h, ABCD, and T Parameters Which are Valid for Complex Source and Load Impedances, IEEE, vol. 42, No. 2, Feb. 1994, pp. 205-211.
Rual Yu, et al., Full Two-Port On-Wafer Vector Network Analysis to 120 GHz Using Active Probes IEEE, pp. 1339-1342, 1993.
Brown Glenn W.
Kempler William B.
Nguyen Jimmy
Telecky , Jr. Frederick J.
Texas Instruments Deutschland GmbH
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