Electronic device test method and apparatus
AssigneeAmerican Telephone and Telegraph Company
InventorEric Y. Chan
Life of this patent
Estimating the term…
Abstract
Apparatus for automatically testing LEDs formed in a wafer (11) includes a computer (15), a test probe (21) for applying a bias to an individual LED and a sensor probe (32) for positioning the test probe with respect to a contact (57) on the LED. Light from the LED is transmitted by an optical fiber (22) to opto-electronic equipment (18) for analysis and characterization by the computer (15). LED bias is provided by a pulse generator (35) and faulty diodes are marked by a marker probe (31). Each LED contains a lens portion (60) for directing LED light to the optical fiber (22).
Claims15
A method for making electronic devices comprising the steps of forming the electronic devices in active regions of a semiconductor wafer, the remaining surface area of the wafer constituting inactive regions, each electronic device having an active contact region with a surface at a predetermined height with respect to the surface of an adjacent inactive region, contacting the active contact region with a conductive test probe, applying a current via the test probe through the electronic device, observing a response to the electronic device to the current, and thereafter cutting the wafer along inactive regions to separate the individual electronic devices, characterized by the steps of:
- locating the test probe a first distance d.sub.1 above a first active contact region;
- locating a sensor probe a second distance d.sub.2 above a first inactive region adjacent the first active region, the second distance d.sub.2 being smaller than the first distance d.sub.1 ;
- vertically moving, relative to the probes, the wafer to contact the first inactive region to the sensor probe and recording a function of the height Z.sub.2 of the wafer upon initial contact of the inactive region with the sensor probe;
- moving the wafer further with respect to the probes to make contact of the first active region with the test probe and recording a function of the hight Z.sub.4 of the wafer upon initial contact with the test probe;
- computing a distance d.sub.3 equal to the difference of the first and second distances, d.sub.1 -d.sub.2 ;
- and
- making repeated tests on other electronic devices of the wafer by, first, moving the wafer relative to the probes such that the test probe overlies an active contact region of an electronic device and the sensor probe overlies an adjacent inactive region, second, raising the wafer relative to the probes until the sensor probe is contacted, and, third, thereafter raising the wafer relative to the probes by a distance d.sub.3, whereby the test probe makes contact with the active contact region.
Apparatus for testing electronic devices in a wafer having inactive regions surrounding active regions in which the devices are formed, each electronic device having an active contact region with a surface at a predetermined height with respect to the surface of an adjacent inactive region;
- means comprising a conductive test probe for contacting the active contact region;
- means for applying a current via the test probe to the electronic device;
- means for recording a response of the electronic device to the current;
- characterized by
- means for locating the test probe at a first distance d.sub.1 above the first active contact region;
- means for locating a sensor probe at a second distance d.sub.2 above a first inactive region adjacent the first active region, the second distance d.sub.2 being smaller than the first distance d.sub.1 ;
- means for vertically moving, relative to the probe, the wafer to contact the first inactive region to the sensor probe;
- means comprising a computer for recording a function of the height Z.sub.2 of the wafer upon initial contact of the inactive region with the sensor probe;
- means for moving the wafer further with respect to the probes to make contact of the first active region with the test probe;
- means comprising the computer for recording a function of the height Z.sub.4 of the wafer upon initial contact with the test probe;
- means comprising the computer for computing a distance d.sub.3 equal to the difference of the first and second distances, d.sub.1 -d.sub.2 ;
- and
- means for making repeated tests on other electronic devices of the wafer by, first, moving the wafer relative to the probes such that the test probe overlies an active contact region of an electronic device and the sensor probe overlies an adjacent inactive region, second, raising the wafer relative to the probes until the sensor probe is contacted, and, third, thereafter raising the wafer relative to the probes by a distance d.sub.3, whereby the test probe makes contact with the active contact region.
A method for making LEDs comprising the steps of:
- forming a plurality of closely-spaced LEDs in a wafer, cutting the wafer to separate the individual LEDs, and testing the individual LEDs by monitoring light transmitted from such LED to a test circuit, characterized in that:
- the testing step occurs prior to the coating step;
- current is applied to individual successive LEDs under test to cause light emission therefrom, such current application unavoidably causing simultaneous emission of light from a plurality of adjoining LEDs;
- an optic fiber is used to transmit light from the LED to the test circuit;
- and
- an end of the optic fiber is successively brought into close proximity with successive individual LEDs under test so as to transmit light selectively from the LED under test without interference from other LEDs of the wafer.
Dependencies are inferred from the claim text.