Systems and methods for detecting forcer misalignment in a wafer prober

{
  "publication_number": "US2022082589A1",
  "country": "US",
  "kind": "A1",
  "title": "Systems and methods for detecting forcer misalignment in a wafer prober",
  "abstract": "A system is provided for detecting a forcer misalignment, e.g., due to forcer loss of registration (FLR), in a wafer prober used for electrical testing of a semiconductor wafer. The system includes an optical sensor system including a transmitter and receiver affixed to the forcer or to a reference structure (e.g., the prober platen), and a reflector affixed to the other one of the forcer or reference structure. The transmitter emits radiation toward the reflector, which reflects the radiation toward the receiver. The receiver detects the reflected radiation, and generates an output signal indicating the quantity of received radiation. Alignment monitoring circuitry is configured to identify a misalignment of the forcer relative to the reference structure (e.g., platen) based on the output signal generated by the receiver, and in response, output an alert signal, e.g., to suspend operations of the prober and/or display an error notification to an operator.",
  "claims": [
    "1. A system for monitoring a wafer prober used for electrical testing of a semiconductor wafer, the system comprising: an optical sensor system configured to monitor an alignment of a forcer of the wafer prober, the optical sensor system comprising: a transmitter and a receiver both affixed to one of (a) the forcer or (b) a reference structure; and a reflector affixed to the other one of (a) the forcer or (b) the reference structure; wherein the transmitter is configured to transmit radiation toward the reflector; and wherein the receiver is configured to: receive reflected radiation from the reflector, the reflected radiation comprising at least a portion of the radiation transmitted by the transmitter and reflected by the reflector; and generate an output signal as a function of the reflected radiation received at the receiver; alignment monitoring circuitry configured to: identify a misalignment of the forcer relative to the reference structure based on the output signal generated by the receiver of the optical sensor system; and output an alert signal in response to identifying the misalignment of the wafer probe forcer. 2. The system of claim 1, wherein the alignment monitoring circuitry is further configured to control a display device to display an alert notification in response to the alert signal output by the alignment monitoring circuitry. 3. The system of claim 1, wherein the alignment monitoring circuitry is further configured to suspend an operation of the wafer prober in response to the alert signal output by the alignment monitoring circuitry. 4. The system of claim 1, wherein: the wafer prober comprises a chuck assembly configured to hold the semiconductor wafer; and the alignment monitoring circuitry is further configured to suspend a vertical movement of a chuck operation of the wafer prober in response to the alert signal output by the alignment monitoring circuitry. 5. The system of claim 1, wherein: the forcer is configured to move relative to the reference structure during a normal operation of the wafer prober; the reflector of the optical sensor system is affixed to the forcer; and the transmitter and receiver of the optical sensor system are affixed to the reference structure. 6. The system of claim 5, wherein the reference structure comprises a platen of the wafer prober. 7. The system of claim 1, wherein: the forcer is configured to move relative to the reference structure during a normal operation of the wafer prober; the reflector of the optical sensor system is affixed to the reference structure; and the transmitter and receiver of the optical sensor system are affixed to the forcer. 8. The system of claim 1, wherein: the forcer carries a chuck assembly that supports the semiconductor wafer; the forcer is configured to translate linearly along at least one axis relative to the reference structure during a normal operation of the wafer prober; and the alignment monitoring circuitry is configured to identify a misalignment of the wafer probe forcer resulting from a rotational movement of the forcer relative to the reference structure. 9. The system of claim 1, wherein: the forcer carries a chuck assembly that supports the semiconductor wafer; and the alignment monitoring circuitry comprises a relay configured to generate the alert signal as a function of (a) the output signal generated by the receiver of the optical sensor system and (b) control signals indicating a controlled movement of the forcer or chuck assembly. 10. The system of claim 1, wherein the transmitter of the optical sensor system is configured to transmit an infrared beam. 11. The system of claim 1, wherein the transmitter of the optical sensor system comprises a laser diode configured to emit laser radiation. 12. The system of claim 1, wherein each of the transmitter and the receiver of the optical sensor system is provided at an end of a respective optical fiber. 13. The system of claim 1, wherein: the output signal generated by the receiver indicates a measure of reflected radiation received at the receiver; and the alignment monitoring circuitry is configured to: compare the measure of reflected radiation received at the receiver to a threshold value; and identify a received radiation anomaly based on the comparison; and identify a misalignment of the wafer probe forcer relative to the reference structure in response to detecting (a) the received radiation anomaly and (b) a defined control movement of the forcer or a chuck supported by the forcer. 14. The system of claim 1, wherein: the output signal generated by the receiver indicates a measure of reflected radiation received at the receiver; and the alignment monitoring circuitry is configured to: compare the measure of reflected radiation received at the receiver to a threshold value; and identify a misalignment of the wafer probe forcer relative to the reference structure based on the comparison of the measure of reflected radiation received at the receiver to the threshold value. 15. The system of claim 1, wherein the reflector comprises a planar mirror or other planar reflector. 16. A method for monitoring a wafer prober used for electrical testing of a semiconductor wafer, the method comprising: operating the wafer prober for electrical testing of the semiconductor wafer, wherein operating the wafer prober includes moving a forcer, which supports the semiconductor wafer, relative to a reference structure to position the semiconductor wafer relative to a testing device for performing electrical tests on the semiconductor wafer; wherein a transmitter and a receiver of an optical sensor system are affixed to one of the forcer and the reference structure, and a reflector is affixed to the other of one the forcer and the reference structure; during operation of the wafer prober, emitting radiation from the transmitter toward the reflector; receiving reflected radiation at the receiver, the reflected radiation comprising at least a portion of the radiation transmitted by the transmitter and reflected by the reflector; generating an output signal, by the receiver of the optical sensor system, as a function of the reflected radiation received at the receiver; monitoring an alignment of the forcer relative to the reference structure based on the output signal generated by the receiver of the optical sensor system; identifying a misalignment of the forcer relative to the reference structure based on the output signal generated by the receiver of the optical sensor system; and outputting an alert signal in response to identifying the misalignment of the wafer probe forcer. 17. The method of claim 16, further comprising controlling a display device to display an alert notification in response to the alert signal output by the alignment monitoring circuitry. 18. The method of claim 16, further comprising automatically suspending an operation of the wafer prober in response to the alert signal output by the alignment monitoring circuitry. 19. The method of claim 16, wherein the forcer carries a chuck assembly that supports the semiconductor wafer. 20. The method of claim 19, wherein the method comprises automatically suspending a vertical movement of a chuck operation of the wafer prober in response to the alert signal output by the alignment monitoring circuitry. 21. The method of claim 16, wherein: the forcer is configured to translate linearly along at least one axis relative to the reference structure during a normal operation of the wafer prober; and the identified misalignment of the forcer relative to the reference structure results from a rotational movement of the forcer relative to the reference structure. 22. The method of claim 16, wherein the reference structure comprises a platen of the wafer prober."
  ],
  "cpc": [
    "G01R 1/06794",
    "G01D 5/30",
    "G01R 31/2831",
    "G01R 31/2891"
  ],
  "assignees": [
    "MICROCHIP TECH INC"
  ],
  "filing_date": "2021-01-13",
  "publication_date": "2022-03-17",
  "priority_date": "2020-09-17",
  "application_number": "US-202117147778-A",
  "family_id": "80626491",
  "citations": [
    "US2003085723A1",
    "US2007235133A1",
    "US7183759B1"
  ]
}