LED light source probe card technology for testing CMOS image scan devices
Improved wafer-scale testing of optoelectronic devices, such as CMOS image scan devices, is provided. A probe card includes an LED light source corresponding to each device under test in the wafer. The LED light sources provide light from a phosphor illuminated by the LED. A pinhole and lens arrangement is used to collimate the light provided to the devices under test. Uniformity of illumination can be provided by closed loop control of the LED light sources using internal optical signals as feedback signals, in combination with calibration data relating the optical signal values to emitted optical intensity. Uniformity of illumination can be further improved by providing a neutral density filter for each LED light source to improve uniformity from one source to another and/or to improve uniformity of the radiation pattern from each LED light source.
1. Apparatus for testing an array of light-sensitive electronic devices, the apparatus comprising:
an array of LED (light emitting diode) light sources, wherein the array of LED light sources is configured to have an LED light source corresponding to each of the electronic devices;
wherein each LED light source includes a light emitting diode configured to provide LED light;
wherein each LED light source includes a phosphor disposed to receive the LED light and to provide phosphorescence light;
wherein each LED light source includes an aperture configured to provide point source illumination from the phosphorescence light;
wherein each LED light source includes a lens configured to provide collimated light from the point source illumination;
wherein each LED light source includes a uniformity filter disposed to receive the collimated light and to provide output light having improved uniformity of illumination.
2. The apparatus of claim 1 ,
wherein the apparatus is a probe card for testing optoelectronic imaging devices, and
wherein the probe card further comprises one or more electrical probes for making electrical contact to electrical terminals of optoelectronic imaging devices under test.
3. The apparatus of claim 1 , wherein the phosphor for each LED light source is configured as a thin film of uniform thickness disposed on the light emitting diode of the LED light source.
4. The apparatus of claim 1 , further comprising:
a feedback control system configured to measure optical signals from each LED light source and configured to control operation of the array of LED light sources using the measured optical signals to provide uniform illumination to the array of light-sensitive electronic devices.
5. The apparatus of claim 4 , wherein the feedback control system is configured to make use of a lookup table derived from calibration measurements of output light from the LED light sources.
6. The apparatus of claim 4 , wherein each LED light source further comprises:
a first photodetector;
wherein the optical signals are provided by the first photodetector.
7. The apparatus of claim 6 , further comprising a neutral density filter disposed on the first photodetector.
8. The apparatus of claim 6 , wherein the first photodetector is configured to receive light within the LED light source from both the LED and the phosphor of the LED light source.
9. The apparatus of claim 6 , wherein each LED light source further comprises:
a second photodetector;
and a neutral density filter disposed on the second photodetector;
wherein the optical signals are provided by both the first photodetector and the second photodetector.
10. The apparatus of claim 9 , wherein the first photodetector and the second photodetector are configured to receive light within the LED light source from both the LED and the phosphor of the LED light source.
11. The apparatus of claim 1 , wherein the uniformity filter for each LED light source is individually customized for its corresponding LED light source according to calibration measurements of output light uniformity of its corresponding LED light source prior to installation of the uniformity filter.
12. The apparatus of claim 1 , wherein the uniformity filter for each LED light source is individually customized for its corresponding LED light source according to calibration measurements of output light uniformity of the array of LED light sources prior to installation of the uniformity filter.