Wafer polishing apparatus and method
A wafer polishing apparatus capable of maintaining a drive ring in a flat state and a wafer polishing method are provided. In the wafer polishing apparatus and method according to an embodiment, when the head assembly moves to the initial descending position by the wafer elevation unit, the shape of the drive ring inside the head assembly may be measured by using the sensor, and thus the polishing process may be performed in the state where the descending position of the head assembly is automatically adjusted by using the head auxiliary elevation unit to maintain the drive ring in the flat state. Therefore, since the wafer polishing process is performed in the state the balance of the wafer mounting part is automatically adjusted by using the drive ring, the polishing quality of the wafer may be uniformly maintained, and also the polishing performance may be improved.
1. A wafer polishing apparatus, comprising:
a housing providing a predetermined pressure space thereunder;
a drive ring flatly connected to a lower portion of the housing, the drive ring having a central portion that is vertically variable in shape;
a head assembly disposed on a lower portion of the drive ring, the head assembly comprising a wafer mounting part having a bottom surface on which a wafer is mounted;
a head elevation unit disposed on an upper portion of the housing to vertically elevate the head assembly according to a control pressure;
a sensor disposed on a central portion of the drive ring to measure a distance of the central portion of the drive ring to the housing; and
a head auxiliary elevation unit disposed on the head elevation unit to adjust a height of the head assembly in response to a distance value measured by the sensor so that the central portion of the drive ring is flat during wafer polishing.
2. The wafer polishing apparatus according to claim 1 , wherein the head assembly further comprises a sleeve disposed above the central portion of the drive ring, and
the sensor is provided as an optical linear scale type that is disposed above the sleeve.
3. The wafer polishing apparatus according to claim 2 , wherein the sensor comprises:
a light emitting part disposed above the flange;
a light receiving part horizontally spaced a predetermined distance from the light emitting part; and
a linear scale movably disposed between the light emitting part and the light receiving part to measure a distance from the housing.
4. The wafer polishing apparatus according to claim 3 , wherein the sensor further comprises an amplifier detecting data transmitted to the light receiving part to amplify the detected data.
5. The wafer polishing apparatus according to claim 1 , wherein the head elevation unit comprises:
an elevation shaft connected to an upper portion of the housing;
a cylinder housing connected to an upper end of the elevation shaft to elevate the elevation shaft as a pressure is provided thereto;
at least one sealing part disposed on a circumference of the elevation shaft, the at least one sealing part being engaged with an inner wall of the cylinder housing.
6. The wafer polishing apparatus according to claim 5 , wherein the head auxiliary elevation unit comprises an upper nozzle providing a pressure into the cylinder housing from an upper side with respect to the sealing part.
7. The wafer polishing apparatus according to claim 5 , wherein the head auxiliary elevation unit comprises a lower nozzle providing a pressure into the cylinder housing from a lower side with respect to the sealing part.