Polishing method, manufacturing method of piezoelectric vibrating piece, piezoelectric vibrator, oscillator, electronic apparatus and radio-controlled timepiece

Abstract

Provided is a polishing method which can enhance thickness accuracy of a wafer at the time of polishing the wafer. In a polishing method of a crystal wafer (tuning fork substrate) which is held on a carrier between an upper platen and a lower platen, an AT cut wafer for thickness measurement is arranged on the carrier, the AT cut wafer is polished together with the crystal wafer (tuning fork substrate), resonance frequency of the AT cut wafer is detected, and a thickness of the crystal wafer (tuning fork substrate) is controlled based on a detection result.

1 . A method for polishing a wafer mounted on a polishing device that comprises a lower platen, an upper platen above the lower platen, a wafer carrier mounted on the lower platen, a probe mounted on the upper platen, the method comprising:
 mounting a first wafer and an AT cut wafer on the wafer carrier;   applying a polishing agent to upper and lower surfaces of the first wafer and the AT cut wafer;   rotating the upper platen and the lower platen while applying the polishing agent, thereby polishing the first wafer and the AT cut wafer by the rotating;   detecting a resonant frequency of the AT cut wafer, wherein the resonant frequency of the AT cut wafer corresponds to a thickness of the first wafer; and   continue rotating the upper and lower platens until a resonant frequency corresponding to a predetermined thickness of the first wafer is detected a predetermined number of times.   
     
     
         2 . The method of  claim 1 , wherein the upper and lower platens are rotated until the resonant frequency corresponding to a predetermined thickness of the first wafer is detected a predetermined number of times within the predetermined period of time. 
     
     
         3 . The method of  claim 2 , wherein the upper and lower platens are rotated until the resonant frequency corresponding to a predetermined thickness of the first wafer is detected at least three times within the predetermined period of time. 
     
     
         4 . The method of  claim 2 , wherein the predetermined period of time comprises the range of 0.5 seconds to 1.0 seconds. 
     
     
         5 . The method of  claim 1 , wherein the upper and lower platens are rotated until the resonant frequency corresponding to a predetermined thickness of the first wafer is detected at least once. 
     
     
         6 . The method of  claim 1 , wherein the AT cut wafer is mounted at a center of the carrier. 
     
     
         7 . The method of  claim 1 , further comprising mounting a second wafer on the carrier. 
     
     
         8 . The method of  claim 7 , wherein the AT cut wafer is mounted between the first and second wafers. 
     
     
         9 . The method of  claim 1 , wherein the AT cut wafer is mounted on the carrier at a position such that when the lower and upper platens rotate, the AT cut wafer periodically passes under the probe. 
     
     
         10 . The method of  claim 1 , wherein the upper and lower platens are rotated in opposite directions. 
     
     
         11 . A method for polishing a wafer mounted on a polishing device that comprises a lower platen, an upper platen above the lower platen, a wafer carrier mounted on the lower platen, a probe mounted on the upper platen, the method comprising:
 mounting a first wafer and an AT cut wafer on the wafer carrier;   rotating the upper platen and the lower platen, thereby polishing the first wafer and the AT cut wafer by the rotating;   detecting a resonant frequency of the AT cut wafer, wherein the resonant frequency of the AT cut wafer corresponds to a thickness of the first wafer; and   continue rotating the upper and lower platens until a resonant frequency corresponding to a predetermined thickness of the first wafer is detected a predetermined number of times within a predetermined period of time.   
     
     
         12 . The method of  claim 11 , further comprising applying a polishing agent to upper and lower surfaces of the first wafer and the AT cut wafer. 
     
     
         13 . The method of  claim 11 , wherein the upper and lower platens are rotated until the resonant frequency corresponding to a predetermined thickness of the first wafer is detected at least three times within the predetermined period of time. 
     
     
         14 . The method of  claim 11 , wherein the predetermined period of time comprises the range of 0.5 seconds to 1.0 seconds. 
     
     
         15 . The method of  claim 11 , wherein the upper and lower platens are rotated until the resonant frequency corresponding to a predetermined thickness of the first wafer is detected at least once. 
     
     
         16 . The method of  claim 11 , wherein the AT cut wafer is mounted at a center of the carrier. 
     
     
         17 . The method of  claim 11 , wherein the AT cut wafer is mounted on the carrier at a position such that when the lower and upper platens rotate, the AT cut wafer periodically passes under the probe. 
     
     
         18 . The method of  claim 11 , wherein the upper and lower platens are rotated in opposite directions. 
     
     
         19 . A method for polishing a wafer mounted on a polishing device that comprises a lower platen, an upper platen above the lower platen, multiple wafer carriers mounted on the lower platen, a probe mounted on the upper platen, the method comprising:
 mounting a first wafer and an AT cut wafer on each of the wafer carriers;   rotating the upper platen and the lower platen, thereby polishing the first wafer and the AT cut wafer mounted on each of the wafer carriers by the rotating;   detecting a resonant frequency of each of the AT cut wafers, wherein the resonant frequency of each AT cut wafer corresponds to a thickness of the corresponding first wafer; and   continue rotating the upper and lower platens until a resonant frequency corresponding to a predetermined thickness of one or more of the first wafers is detected a predetermined number of times within a predetermined period of time.   
     
     
         20 . The method of  claim 19 , wherein the AT cut wafers are each mounted on the corresponding wafer carrier at a position such that when the lower and upper platens rotate, each AT cut wafer periodically passes under the probe.