Wafer polishing apparatus and wafer polishing method using same

1. A wafer polishing apparatus comprising:

a lower surface plate;

an upper surface plate disposed above the lower surface plate and configured to rotate;

a carrier disposed on the lower surface plate to receive a wafer;

a sensor unit secured to an upper surface of the upper surface plate for radiating light to the wafer received in the carrier, detecting light reflected by the wafer, and outputting detection data based on a detection result; and

a load-compensating unit secured to a region of the upper surface of the upper surface plate that is opposite a region of the upper surface of the upper surface plate to which the sensor unit is secured,

wherein the upper surface plate has a through-hole to allow light radiated from the sensor unit to pass therethrough,

wherein the load-compensating unit has a same weight as the sensor unit, and

wherein the sensor unit rotates together with the upper surface plate.

2. The wafer polishing apparatus according to claim 1 , further comprising:

a control unit for calculating a thickness of a polished wafer based on the detection data.

3. The wafer polishing apparatus according to claim 1 , wherein the sensor unit includes:

a thickness-measuring sensor configured to rotate together with the upper surface plate and to output the detection data;

a cable for transmitting the detection data to the control unit; and

a rotary connector connected to the cable.

4. The wafer polishing apparatus according to claim 1 , wherein the upper surface plate has a recess formed in the upper surface to allow one end of the sensor unit to be inserted in the recess, and the through-hole is formed through a bottom of the recess and the upper surface plate.

5. The wafer polishing apparatus according to claim 1 , further comprising:

a light-transmitting film disposed on an inner wall of the through-hole and configured to block a lower end of the through-hole.

6. The wafer polishing apparatus according to claim 2 , wherein the control unit acquires shape information and a GBIR (Global Backside reference Indicate Reading) of the polished wafer at each predetermined period, and determines whether to perform a polishing process with respect to the polished wafer based on the acquired GBIR, and

the GBIR is a difference between a maximum value and a minimum value of thicknesses of the wafer that are measured at the predetermined period.

7. The wafer polishing apparatus according to claim 6 , wherein, if a GBIR in a current period exceeds a GBIR in a previous period, the control unit stops the polishing process with respect to the polished wafer.

8. The wafer polishing apparatus according to claim 6 , wherein the control unit acquires information about a shape of the polished wafer based on coordinates of a movement path of a center of the carrier, coordinates of a movement path of a center of the wafer received in the carrier, and distances from the center of the wafer to points of the wafer at which the thicknesses are measured by the sensor unit.

9. The wafer polishing apparatus according to claim 3 , wherein the thickness-measuring sensor includes an optical unit for radiating light and a photodetector for detecting light reflected by the wafer, and

light radiated from the optical unit is aimed at a center of the through-hole so as to be aligned with the through-hole.

10. A wafer polishing method using a wafer polishing apparatus including a lower surface plate, an upper surface plate, and a sensor unit configured to rotate together with the upper surface plate, the method comprising:

starting a double-side polishing process with respect to a wafer loaded on at least one carrier disposed on the lower surface plate and measuring a thickness of the wafer that is being polished using the sensor unit;

determining whether the thickness of the wafer that is being polished has reached a predetermined reference thickness;

upon determining that the thickness of the wafer that is being polished has reached the reference thickness, acquiring a shape information about a thickness profile of the wafer in a radial direction of the wafer at a predetermined period;

calculating a GBIR (Global Backside reference Indicate Reading) of the wafer using the acquired shape information about the thickness profile of the wafer in a radial direction of the wafer; and

determining whether to stop a double-side polishing process with respect to the wafer based on the result of comparing a first GBIR of the wafer in a first period with a second GBIR of the wafer in a second period,

wherein the first period and the second period are periods that are defined after a time point at which a thickness of the wafer that is being polished has reached the reference thickness, and the first period is a predetermined period that follows the second period.

11. The wafer polishing method according to claim 10 , wherein the acquiring the shape information about the thickness profile of the wafer in the radial direction of the wafer includes:

measuring the thicknesses of the wafer that is being polished at a plurality of random thickness measurement points at the predetermined period; and

acquiring the thickness profile of the wafer in the radial direction of the wafer based on the measured thicknesses of the wafer that is being polished.

12. The wafer polishing method according to claim 10 , wherein the determining whether to stop the double-side polishing process with respect to the wafer includes:

when the first GBIR is equal to or exceeds the second GBIR, stopping the double-side polishing process with respect to the wafer.

13. The wafer polishing method according to claim 12 , wherein, when the first GBIR does not exceed the second GBIR, shape information about the thickness profile of the wafer in the radial direction of the wafer is acquired at a next predetermined period, a GBIR of the wafer is calculated using the acquired shape information at the next predetermined period, and it is determined whether to stop the double-side polishing process with respect to the wafer based on the calculated GBIR.

14. The wafer polishing method according to claim 10 , wherein each of the first and second periods is 30 seconds to 1 minute.

15. The wafer polishing method according to claim 10 , wherein the shape information about the thickness profile of the wafer in the radial direction of the wafer is acquired based on coordinates of a movement path of a center of the carrier, coordinates of a movement path of a center of the wafer received in the carrier, and distances from the center of the wafer to points of the wafer at which the thicknesses are measured by the sensor unit.

16. A wafer polishing apparatus comprising:

a lower surface plate;

an upper surface plate disposed above the lower surface plate and configured to rotate;

a carrier disposed on the lower surface plate to receive a wafer;

a slurry supply unit disposed on the upper surface plate to supply slurry to the upper surface plate and configured to rotate together with the upper surface plate;

a sensor unit secured to the slurry supply unit for radiating light to the wafer received in the carrier, detecting light reflected by the wafer, and outputting detection data based on a detection result; and

a load-compensating unit secured to a region of the slurry supply unit that is opposite a region of the slurry supply unit to which the sensor unit is secured,

wherein the load-compensating unit has a same weight as the sensor unit, and

wherein the sensor unit rotates together with the upper surface plate.