Abstract: A wafer probe station adapted for low-current measurements provides electrically active upper and lower chuck assembly elements where air gaps are provided between a major portion of either a lower or nonlower surface on the upper chuck assembly element and a corresponding conductive surface on or connected to the lower chuck assembly element thereby minimizing leakage currents therebetween. The chuck assembly elements are preferably enclosed by an environment control enclosure having a sidewall portion relative to which the upper chuck assembly element can move laterally. During such movement, the upper chuck assembly remain in constant spacing with a conductive member that laterally surrounds it so as to stabilize electromagnetic conditions. Concurrently, the sidewall portion is kept motionless relative to the probe holder which keeps contaminants away from the region immediate to the upper chuck assembly element, including any moisture droplets that have condensed during low-temperature testing.

Abstract: A method of evaluating the signal conditions in a probe measurement network of the type having a plurality of separate measurement channels, where each channel communicates through a corresponding device-probing end. The method includes providing an assembly which includes a conductive planar probing area on the upper face of a base and a reference junction connected to the probing area by a high-frequency transmission structure. The method further includes placing the respective device-probing end of a first one of the measurement channels into contact with the planar probing area, transmitting a high-frequency signal through both the measurement channel and the reference junction and, thereafter, measuring the signal.

Abstract: A probe station suitable for low noise measurements includes a chuck for supporting a test device and a supporting surface for the test device. The probe station has means for controlling the temperature in the vicinity of the test device by sensing the temperature and, in response to the sensing, alternatively raising or lowering the temperature. At least two layers including a first electrically conductive layer adhered to an insulator layer are disposed between the supporting surface and the chuck. The electrically conductive layer is electrically connected to one of the chuck and supporting surface.

Abstract: A wafer probe station is equipped with an integrated environment control enclosure substantially surrounding a supporting surface for holding a test device, such enclosure limiting fluid communication between the interior and exterior of the enclosure and preferably also providing EMI shielding and a dark environment. The limited communication between the interior and exterior of the enclosure is kept substantially constant despite positioning movement of either the supporting surface or probe holders. The positioning mechanisms for the supporting surface and probe holders each have portions located at least partially outside of the enclosure for transferring movement mechanically to the surface or holders, respectively.

Abstract: A shielded microwave probe tip assembly includes an end of a coaxial cable coupled to probe fingers forming a coplanar controlled impedance microwave transmission line where the ground probe fingers are interconnected by a shield member that is spaced apart from the signal line probe finger but is positioned between the signal line probe finger and a device under test. The shield prevents the generation of extraneous signals or parasitic coupling from the device under test which would otherwise degrade measurement accuracy.

Abstract: An interconnect assembly for evaluating a probe measurement network includes a base, respective inner and outer probing areas in mutually coplanar relationship on the upper face of the base, a reference junction, and a high-frequency transmission structure connecting the probing areas and the reference junction so that high-frequency signals can be uniformly transferred therebetween despite, for example, variable positioning of the device-probing ends of the network on the probing areas. A preferred method for evaluating the signal channels of the network includes connecting a reference unit to the reference junction and successively positioning each device-probing end that corresponds to a signal channel of interest on the inner probing area.

Abstract: A wafer probe station is equipped with an integrated environment control enclosure substantially surrounding a supporting surface for holding a test device, such enclosure limiting fluid communication between the interior and exterior of the enclosure and preferably also providing EMI shielding and a dark environment. The limited communication between the interior and exterior of the enclosure is kept substantially constant despite positioning movement of either the supporting surface or probe holders. The positioning mechanisms for the supporting surface and probe holders each have portions located at least partially outside of the enclosure for transferring movement mechanically to the surface or holders, respectively.

Abstract: A probe suitable for low-loss microwave frequency operation has a tip assembly including a semi-rigid coaxial cable having a Teflon.TM. dielectric for temperature stability and a freely-suspended end. On this end a semicylindrical recess is formed defining a shelf along which an inner finger and outer pair of fingers are mounted, each made of resilient conductive material, so as to form a coplanar transmission line. Cantilevered portions of the fingers extend past the end of the cable to form an air-dielectric transmission path of uniform and stable characteristic despite exposure to numerous contact cycles and to provide suitable means for probing nonplanar device pads while also offering good visibility of device pads generally.

Abstract: A probe station includes a fully guarded chuck assembly and connector mechanism for increasing sensitivity to low-level currents while reducing settling times. The chuck assembly includes a wafer-supporting first chuck element surrounded by a second chuck element having a lower component, skirting component and upper component each with a surface portion extending opposite the first element for guarding thereof. The connector mechanism is so connected to the second chuck element as to enable, during low-level current measurements, the potential on each component to follow that on the first chuck element as measured relative to an outer shielding enclosure surrounding each element. Leakage current from the first chuck element is thus reduced to virtually zero, hence enabling increased current sensitivity, and the reduced capacitance thus provided by the second chuck element decreases charging periods, hence reducing settling times.

Abstract: A probe station is equipped with an integrated guarding system which facilitates the use of the station for low-current measurements, as well as integrated Kelvin connections to eliminate voltage losses caused by line resistances. The station has a chuck assembly which consists of at least three chuck assembly elements. A first element supports the test device, while an underlying second element acts as a guard to reduce leakage currents. These elements are electrically insulated from each other and from their underlying supporting structure, which is the third element. Ready-to-use, selectively detachable electrical connector assemblies provide for signal and guard connections to the first and second chuck assembly elements, respectively, as well as providing Kelvin connections thereto. The capacitance between the respective chuck assembly elements is extremely low due to the provision of air space as the primary electrical insulator.

Abstract: A probe station is equipped with an integrated guarding system which facilitates the use of the station for low-current measurements, as well as integrated Kelvin connections to eliminate voltage losses caused by line resistances. The station has a chuck assembly which consists of at least three chuck assembly elements. A first element supports the test device, while an underlying second element acts as a guard to reduce leakage currents. These elements are electrically insulated from each other and from their underlying supporting structure, which is the third element. Ready-to-use, selectively detachable electrical connector assemblies provide for signal and guard connections to the first and second chuck assembly elements, respectively, as well as providing Kelvin connections thereto. The capacitance between the respective chuck assembly elements is extremely low due to the provision of air space as the primary electrical insulator.

Abstract: A wafer probe station is equipped with a compact, integrated controlled-environment enclosure providing EMI shielding, substantially hermetic sealing for a dry purge gas for low-temperature testing, and a dark environment. The sealing isolation of the wafer chuck and test probe provided by the enclosure is maintained despite the fact that the probe and chuck positioning mechanisms extend partially outside the enclosure, with positioning members extending movably between the interior and exterior of the enclosure. Sealing is maintained by movable sealing members at the locations where the positioning members penetrate the enclosure.

Abstract: A return line for a probe station includes a sheet-like conductive strap having a first end connected electrically to a first probe and a self-coiling second end connected automatically detachably to a second probe, as by insertion of the second probe centrally within the coils of the second end. If the spacing between the probes exceeds a maximum distance, the strap harmlessly disconnects. The flat central portion of the strap automatically tracks any reductions in the spacing between the probes, which enables fast probe travel and minimizes noise pickup. Preferably a spindle rotatably engages the coiled probe and has a post member that carries the second end of the strap to a far side of the probe to improve tip visibility and electrical connection during close-in probing.

Abstract: A wafer probe station has a wafer-supporting vacuum chuck, together with one or more substrate-supporting auxiliary vacuum chucks having independent vacuum controls for mounting contact substrates and calibration substrates simultaneously with the wafer. A detachable interconnection of the various chucks enables independent replacement of each chuck to accommodate various different chuck types, and also permits the elevations of the respective chuck surfaces to be adjusted relative to each other to compensate for differences in thicknesses between the wafer substrate and the calibration or contact substrates. The invention is especially useful in wafer probe stations equipped with enclosures for controlled-environment testing where a large variety of different wafer chucks must be readily interchangeable for testing under different conditions.

Abstract: A method for on-wafer testing of microwave devices, such as photodiodes, including a biasing method applicable when the device has a lower end connected to the ground plane of the wafer. Elements having a diode-like characteristic, such as photodiodes, are arranged side-by-side with the device, each preferably being of like geometry with the device, and each having an end connected to the ground plane. A first voltage is applied between the ground conductors of the probe and the ground plane of the wafer to place each element in forward-biased condition thereby creating a return path for the lower end of the device to the ground conductors located on the upper side of the wafer.

Abstract: A fiber optic wafer probe, for use in measuring the parameters of photodetectors and other optoelectronic test devices at the wafer level, has a probe body along which an optical fiber extends to protrude from a tip of the probe body. The probe body loosely guides the optical fiber so that at least a significant portion of the length of the optical fiber is movable longitudinally with respect to the tip and probe body. This provides protection against excessive contact force between the fiber and the test device by enabling the optical fiber to buckle longitudinally in response to longitudinal overtravel of the fiber toward the test device. The probe body is of elongate shape with a probe tip at one end and a connector at the other end for detachably connecting the optical fiber to the probe body.

Abstract: A one port tuner having a source port for connection to a device under test so that, in combination with a noise meter, the noise performance of such device can be evaluated. Preferably the one port tuner includes a plurality of predetermined admittances, a switching device having an output port for selectively connecting one of the admittances to the output port, and a two port device having a selectable response and interconnected between the output port of the switching device and the source port of the one port tuner. Desirably, the two port device includes a multiple-state attenuator where the signal passing through the attenuator is selectable in degree. Alternatively, or in combination, the two port device includes a phase shifter where the phase of the signals passing through the phase shifter are selectively shiftable.

Abstract: A method for correcting inaccuracies in error factors of an error model used for vector-corrected, microwave-frequency measurements. Verifying de-embedded measurements are compared to known characteristics of at least one verification standard. At least one parameter of the calibration standards, or an error factor, or measuring network geometry, is changed and the error factors are recalculated to bring the verifying measurements into conformity with the known characteristics of the verification standard.

Abstract: A high-frequency probe comprising a semirigid coaxial line which terminates in an active circuit assembly. The coaxial line's outer conductor is connected to a box while its inner conductor is connected to an active circuit chip. A signal contact needle is attached to the active circuit chip and extends linearly with the coaxial line. The signal needle is held in place with a mass of epoxy filled with silica microballoons, providing a low-capacitance mount. A ground contact needle is connected to a wiper which contacts the box, thus providing a direct, and short, path between the coaxial line's outer conductor and the ground contact needle.

Abstract: An electrical probe tip is yieldably mounted on a probe mount so that, as the probe mount and a device under test are advanced toward each other, the contact force between the probe tip and the device under test first increases gradually and then decreases. This prevents excessive contact force if the probe mount and device under test are inadvertently advanced excessively toward each other, and thereby prevents damage to the probe tip.