Linear inspection system
Embodiments of the disclosure generally relate to comprehensive, expandable substrate inspection systems. The inspection systems include multiple metrology units adapted to inspect, detect, or measure one or more characteristics of a substrate, including thickness, resistivity, saw marks, geometry, stains, chips, micro cracks, crystal fraction, and photoluminescence. The inspection systems may be utilized to identify defects on substrates and estimate solar cell efficiency of a solar cell produced with the substrate, prior to processing a substrate into a solar cell. Substrates may be transferred through the inspection system between metrology units on a track or conveyor, and then sorted based upon inspection data.
1. An inspection system, comprising: a front end comprising a robot to unload substrates from a cassette and load the substrates onto a first conveyor; a modular unit comprising three or more metrology units linearly disposed along the first conveyor to inspect substrates on the first conveyor, the three or more metrology units comprising: a micro-crack inspection unit; a thickness and resistance measurement unit to measure substrate thickness with a repeatability of 0.5 microns or less; a photoluminescence unit; a geometry inspection unit to measure substrate length with repeatability of less than about 10 microns; and a saw mark detection unit; a yield analysis server to receive and process inspection data from the metrology units; and a sorting unit to sort substrates based upon the inspection data.
2. The inspection system of claim 1 , wherein the metrology units are positioned in the sequential order of:
the micro-crack inspection unit; then
the thickness and resistance measurement unit; then
the photoluminescence unit; then
the geometry inspection unit; and then
the saw mark detection unit.
3. The inspection system of claim 1 , wherein the sorting unit comprises:
a second conveyor;
a plurality of bins disposed laterally outward of edges of the second conveyor; and
a plurality of sorting mechanisms for transferring substrates from the second conveyor to the plurality of bins.
4. The inspection system of claim 3 , wherein the second conveyor comprises two parallel belts disposed along the length of the sorting unit.
5. The inspection system of system of claim 1 , wherein the thickness and resistance measurement unit has resistivity repeatability of 1 percent or less.
6. The inspection system of claim 1 , wherein the yield analysis server is provided to generate a 3-dimensional virtual reconstruction of a brick or ingot from which the substrates were cut using inspection data received from the photoluminescence unit.
7. The inspection system of claim 1 , wherein the geometry inspection unit has width repeatability of less than about 40 microns.
8. The inspection system of claim 1 , wherein the geometry inspection unit has orthogonality repeatability of about 0.1 degrees or less.
9. The inspection system of claim 1 , wherein the geometry inspection unit has corner-to-corner distance repeatability of less than 40 microns.
10. The inspection system of claim 1 , wherein the geometry inspection unit has a false alarm rate of less than 0.5 percent when detecting stains having a size of about 150 microns.
11. The inspection system of claim 1 , wherein the geometry inspection unit has a false alarm rate of less than 0.5 percent when detecting chips having a size of about 60 microns.
12. The inspection system of claim 1 , wherein the geometry inspection unit includes a pair of U-shaped detectors.
13. The inspection system of claim 1 , wherein the saw mark detection unit is provided to analyze a profile of a top surface and a bottom surface of a substrate.
14. The inspection system of claim 1 , wherein the inspection system has a throughput of 3600 substrates per hour or more at a breakage rate of less than 0.1 percent.
15. An inspection system, comprising: a front end comprising a robot to unload substrates from a cassette and load the substrates onto a conveyor; a modular unit comprising three or more metrology units linearly disposed along the conveyor to inspect substrates on the conveyor, the three or more metrology units comprising: a micro-crack inspection unit; a thickness measurement unit to measure substrate thickness with a repeatability of 0.5 microns or less, and to measure substrate resistivity with a repeatability of 1 percent less; a photoluminescence unit; a geometry inspection unit to measure substrate length with repeatability of less than about 10 microns, the geometry inspection unit including a pair of U-shaped detectors; and a saw mark detection unit; a yield analysis server to receive and process inspection data from the metrology units and generate a 3-dimensional virtual reconstruction of a brick or ingot from which the substrates were cut using inspection data received from the photoluminescence unit; and a sorting unit to sort substrates based upon the inspection data.
16. The inspection system of claim 15 , wherein the inspection system has a throughput of 3600 substrates per hour or more at a breakage rate of less than 0.1 percent.
17. The inspection system of claim 16 , wherein the geometry inspection unit has a false alarm rate of less than 0.5 percent when detecting chips having a size of about 60 microns.
18. The inspection system of claim 16 , wherein the geometry inspection unit has orthogonality repeatability of about 0.1 degrees or less.
19. The inspection system of claim 16 , wherein the geometry inspection unit has width repeatability of less than about 40 microns.
20. An inspection system, comprising: a front end comprising a robot to unload substrates from a cassette and load the substrates onto a first conveyor; a modular unit comprising three or more metrology units linearly disposed along the first conveyor to inspect substrates on the first conveyor, the three or more metrology units comprising: a micro-crack inspection unit; a thickness measurement unit to measure substrate thickness with a repeatability of 0.5 microns or less, and to measure substrate resistivity with a repeatability of 1 percent less; a photoluminescence unit; a geometry inspection unit to measure substrate length with repeatability of less than about 10 microns, substrate width with repeatability of less than about 40 microns, and substrate orthogonality with repeatability of about 0.1 degrees or less, the geometry inspection unit including a pair of U-shaped detectors; and a saw mark detection unit; a yield analysis server to receive and process inspection data from the metrology units and generate a 3-dimensional virtual reconstruction of a brick or ingot from which the substrates were cut using inspection data received from the photoluminescence unit; and a sorting unit adapted to sort substrates based upon the inspection data, the sorting unit comprising: a second conveyor; a plurality of bins disposed laterally outward of edges of the second conveyor; and a plurality of sorting mechanisms for transferring substrates from the second conveyor to the plurality of bins.