Wafer unit for testing and test system

1. A test wafer unit that tests a plurality of circuits under test formed on a wafer under test, the test wafer unit comprising:

a test wafer that is formed of a semiconductor material and exchanges signals with each of the circuits under test; and

a plurality of loop-back sections that are provided in the test wafer to correspond to the plurality of circuits under test and that each loop a signal output by a transmission circuit of the corresponding circuit under test back to a reception circuit of the corresponding circuit under test.

2. The test wafer unit according to claim 1 , wherein

each loop-back section receives an output signal from the corresponding circuit under test via an actual operation output terminal, which is used when the circuit under test is mounted, and loops the received output signal back to the reception circuit of the corresponding circuit under test.

3. The test wafer unit according to claim 2 , wherein

each loop-back section loops the received output signal back to the reception circuit of the corresponding circuit under test via an actual operation input terminal, which is used when the circuit under test is mounted.

4. The test wafer unit according to claim 2 , wherein

each loop-back section loops the received output signal back to an internal node of the corresponding circuit under test via a measurement input terminal, which is not used when the circuit under test is mounted.

5. The test wafer unit according to claim 1 , wherein

each loop-back section receives an internal signal transmitted on an internal node of the corresponding circuit under test via a measurement output terminal, which is not used when the circuit under test is mounted, and loops the received internal signal back to the reception circuit of the corresponding circuit under test.

6. The test wafer unit according to claim 5 , wherein

each circuit under test includes:

a plurality of measurement lines that are provided to correspond to a plurality of measurement points in the circuit under test and that are each connected to a corresponding measurement point; and

a selecting section that selects which of the measurement lines is electrically connected to the measurement output terminal, and

each loop-back section includes a selection control section that controls which of the measurement lines the corresponding selecting section selects.

7. The test wafer unit according to claim 1 , wherein

each loop-back section includes an emulator circuit that passes the signal output by the transmission circuit of the corresponding circuit under test and simulates characteristics of a predetermined transmission path before the signal is looped back to the reception circuit of the corresponding circuit under test.

8. The test wafer unit according to claim 7 , wherein

each loop-back section further includes an impedance matching section that matches impedance between the corresponding circuit under test and a transmission path on which the signal output by the transmission circuit of the corresponding circuit under test is transmitted.

9. The test wafer unit according to claim 1 , wherein

each loop-back section includes a noise generating section that adds predetermined noise to the signal output by the transmission circuit of the corresponding circuit under test before the signal is looped back to the reception circuit of the corresponding circuit under test.

10. The test wafer unit according to claim 9 , wherein

each loop-back section further includes a measurement circuit that measures the signal output by the transmission circuit of the corresponding circuit under test.

11. The test wafer unit according to claim 10 , wherein

each measurement circuit measures timing characteristics of the signal output by the transmission circuit of the corresponding circuit under test.

12. The test wafer unit according to claim 10 , further comprising switches that switch whether the circuits under test are connected to the measurement circuits or the noise generating sections.

13. The test wafer unit according to claim 1 , wherein

each loop-back section includes a DC level adjusting section that adjusts a DC level of the signal output by the transmission circuit of the corresponding circuit under test before the signal is looped back to the reception circuit of the corresponding circuit under test.

14. The test wafer unit according to claim 1 , wherein

each loop-back section includes:

first wiring that supplies the signal output by the transmission circuit of the corresponding circuit under test to an operation circuit, which is formed in the wafer under test external to the transmission circuit and the reception circuit of the corresponding circuit under test, before the signal is looped back to the reception circuit of the corresponding circuit under test; and

second wiring that supplies, to the reception circuit of the corresponding circuit under test, a signal output by the operation circuit in response to the signal supplied from the first wiring such that the signal output by the transmission circuit of the corresponding circuit under test is looped back to the reception circuit of the corresponding circuit under test via the first wiring, the operation circuit, and the second wiring.

15. A test system that tests a plurality of circuits under test formed on a wafer under test, the test system comprising:

a test wafer unit that exchanges signals with the circuits under test; and

a control apparatus that controls the test wafer unit, wherein the test wafer unit includes:

a test wafer that is formed of a semiconductor material and exchanges signals with each of the circuits under test; and

a plurality of loop-back sections that are provided in the test wafer to correspond to the plurality of circuits under test and that each loop a signal output by a transmission circuit of the corresponding circuit under test back to a reception circuit of the corresponding circuit under test.

16. The test system according to claim 15 , wherein

each loop-back section includes a noise generating section that adds predetermined noise to the signal output by the transmission circuit of the corresponding circuit under test before the signal is looped back to the reception circuit of the corresponding circuit under test.

17. The test wafer unit according to claim 16 , wherein

each loop-back section further includes a measurement circuit that measures the signal output by the transmission circuit of the corresponding circuit under test.

18. The test system according to claim 15 , wherein

each loop-back section includes a DC level adjusting section that adjusts a DC level of the signal output by the transmission circuit of the corresponding circuit under test before the signal is looped back to the reception circuit of the corresponding circuit under test.

19. The test wafer unit according to claim 15 wherein

each loop-back section includes:

an emulator circuit that passes the signal output by the transmission circuit of the corresponding circuit under test and simulates characteristics of a predetermined transmission path before the signal is looped back to the reception circuit of the corresponding circuit under test; and

an impedance matching section that matches impedance between the corresponding circuit under test and a transmission path on which the signal output by the transmission circuit of the corresponding circuit under test is transmitted.

20. The test wafer unit according to claim 15 , wherein

beach loop-back section includes:

first wiring that supplies the signal output by the transmission circuit of the corresponding circuit under test to an operation circuit, which is formed in the wafer under test external to the transmission circuit and the reception circuit of the corresponding circuit under test, before the signal is looped back to the reception circuit of the corresponding circuit under test; and

second wiring that supplies, to the reception circuit of the corresponding circuit under test, a signal output by the operation circuit in response to the signal supplied from the first wiring such that the signal output by the transmission circuit of the corresponding circuit under test is looped back to the reception circuit of the corresponding circuit under test via the first wiring, the operation circuit, and the second wiring.