Wafer inspection apparatus

1. A wafer inspection apparatus comprising:

a probe card having a plurality of contactors to be respectively brought into contact with a plurality of electrodes formed on a surface of a wafer as an inspection target;

a chuck top on which the wafer is mounted to face the probe card;

a vacuum mechanism configured to evacuate a sealable surrounding space surrounded by the chuck top and the probe card to a set pressure to allow or maintain a predetermined pressure-contact state between the probe card and the wafer,

wherein the vacuum mechanism includes:

a vacuum source;

an electropneumatic regulator having a proportional control valve having a first port connected to the vacuum source and a second port connected to the surrounding space, a pressure sensor configured to measure a pressure in a predetermined gas channel or a space which is sealed and connected to the second port, and a valve control unit configured to control the proportional control valve such that a pressure measured by the pressure sensor becomes close to or equal to the set pressure in response to an electrical signal instructing a desired set pressure; and

a gas channel network configured to be switched between a first mode in which the second port of the proportional control valve is connected to the surrounding space via the pressure sensor and a second mode in which the second port of the proportional control valve is connected to the surrounding space and the pressure sensor is connected to the surrounding space in parallel with the proportional control valve.

2. The wafer inspection apparatus of claim 1 , wherein the gas channel network includes:

a first switching valve having a third, a fourth and a fifth port;

a first gas channel configured to connect the second port of the proportional control valve with the third port of the first switching valve;

a second gas channel configured to connect the fourth port of the first switching valve with the surrounding space via the pressure sensor;

a third gas channel configured to connect the fifth port of the first switching valve and the surrounding space; and

a controller configured to control the first switching valve such that the third port is connected to the fourth port to select the first mode or the third port is connected to the fifth port to select the second mode.

3. The wafer inspection apparatus of claim 2 , wherein the controller receives a measured pressure signal indicating a pressure in the second gas channel from the pressure sensor or another pressure sensor in the first mode and switches the first mode to the second mode when a waveform of the measured pressure signal is shifted from a falling area to a saturated area.

4. The wafer inspection apparatus of claim 1 , wherein the vacuum mechanism further includes a compressed air source,

wherein the proportional control valve further has a six port connected to the second port in parallel with the first port and also connected to the compressed air source, and

wherein the electropneumatic regulator controls a pressure of the first port to a desired set value within a predetermined range by mixing a negative pressure and a positive pressure respectively inputted to the second port and the sixth port of the proportional control valve from the vacuum source and the compressed air source at a proper ratio.

5. The wafer inspection apparatus of claim 1 , further comprising a movable table configured to detachably support the chuck top.

6. The wafer inspection apparatus of claim 5 , wherein the movable table includes an elevation unit configured to vertically move the chuck top and the press-contact state is obtained between the probe card and the wafer by bringing the surface of the wafer on the chuck top into contact with the contactors of the probe card and pressing the chuck top by a desired overdrive amount.

7. The wafer inspection apparatus of claim 6 , wherein after the elevation unit presses the chuck top by the desired overdrive amount, the gas channel network is switched to the first mode and the valve control unit controls the proportional control valve such that the pressure measured by the pressure sensor becomes close to or equal to the set pressure under the first mode, and

wherein when the gas channel network is switched from the first mode to the second mode in a state where the measured pressure becomes stable in the saturated area, the valve control unit controls the proportional control valve such that the pressure measured by the pressure sensor becomes close to or equal to the set value under the second mode.

8. The wafer inspection apparatus of claim 1 , further comprising:

a cylindrical member provided around the probe card to be extensible and contractible in a direction perpendicular to a flat surface of the probe card; and

a connecting part provided around a wafer mounting surface of the chuck top on which the wafer is mounted, the connecting part being detachably and sealably attached to the cylindrical member by a vacuum attractive force.