Test system and substrate unit for testing

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

a plurality of test substrates that are arranged in overlapping layers, each test substrate having a plurality of test circuits formed thereon;

a plurality of connecting sections that transmit, to the plurality of chips under test, signals generated by the plurality of test circuits formed on one of the test substrates at a time; and

a control apparatus that controls each of the test circuits;

wherein each test substrate includes at least one via hole that enables the plurality of test circuits of a first one of the plurality of test substrates further from the wafer under test to bypass a second one of the plurality of test substrates closer to the wafer under test.

2. The test system according to claim 1 , wherein each test substrate has formed thereon a plurality of test circuits having a function that is predetermined for the substrate.

3. The test system according to claim 2 , further comprising a connecting unit disposed between the wafer under test and the test substrate closest to the wafer under test, wherein the plurality of connecting sections are disposed in the connecting unit to correspond respectively to the plurality of chips under test, and each connecting section connects the corresponding chip under test to a signal transmission path from one of the plurality of test circuits.

4. The test system according to claim 1 , wherein each connecting section is electrically connected to one of the plurality of test circuits at a time in each test substrate, through the at least one via hole.

5. The test system according to claim 4 , wherein each connecting section switches the test circuit electrically connected to the corresponding chip under test.

6. The test system according to claim 1 , wherein each connecting section includes a selecting wire that electrically connects, to one of the corresponding via holes, a connection pad that is electrically connected to the corresponding chip under test.

7. The test system according to claim 1 , wherein test circuits of test substrates that are closer to the wafer under test generate signals with higher frequencies.

8. The test system according to claim 1 , wherein the plurality of connecting sections are disposed on the test substrate that is closest to the wafer under test, from among the plurality of test substrates.

9. A test substrate unit that tests a plurality of chips under test formed on a wafer under test, the test substrate unit comprising:

a plurality of test substrates that are arranged in overlapping layers, each test substrate having a plurality of test circuits formed thereon; and

a plurality of connecting sections that transmit, to the plurality of chips under test, signals generated by the plurality of test circuits formed on one of the test substrates at a time;

wherein each test substrate includes at least one via hole that enables the plurality of test circuits of a first one of the plurality of test substrates further from the wafer under test to bypass a second one of the plurality of test substrates closer to the wafer under test.

10. A test system that tests at least one chip under test formed on a wafer under test, the test system comprising:

a first test substrate including a first test circuit formed thereon;

a second test substrate coupled to the first test substrate, the second test substrate including a second test circuit formed thereon; and

a control apparatus that controls the first and second test circuits;

wherein the first test substrate includes at least one via hole that enables the second test circuit of second test substrate to bypass the first test substrate.

11. A test substrate unit that tests a plurality of chips under test formed on a wafer under test, the test substrate unit comprising:

a plurality of test substrates that are arranged in overlapping layers, each test substrate having a plurality of test circuits formed thereon, wherein each test substrate has formed thereon a plurality of test circuits having a function predetermined for the substrate;

wherein each test substrate includes at least one via hole that enables the plurality of test circuits of a first one of the plurality of test substrates further from the wafer under test to bypass a second one of the plurality of test substrates closer to the wafer under test.