Method for polishing silicon wafer

• US 10,460,947 B2
• Filed: 11/25/2015
• Issued: 10/29/2019
• Est. Priority Date: 12/15/2014
• Status: Active Grant

• Current Assignee: Shin-Etsu Handotai Co., Ltd. (Shin-Etsu Chemical Company Limited)
• Original Assignee: Shin-Etsu Handotai Co., Ltd. (Shin-Etsu Chemical Company Limited)
• Inventors: Sasaki, Masanao, Hashimoto, Hiromasa, Fujiyama, Kei
• Primary Examiner(s): Hail, Joseph J
• Assistant Examiner(s): Brady, Timothy Brian
• Application Number:
  US15/528,237
• Publication Number:
  US 20170345662A1
• Time in Patent Office: 1,434 Days
• Field of Search: 451 36, 451 37, 451 41, 451 60, 451 87, 451446, 451447
• CPC Class Codes: B24B 37/0056 taking regard of the pH-value of lapping agents
• CPC Class Codes: B24B 37/04 designed for working plane surfaces
• CPC Class Codes: B24B 55/12 Devices for exhausting mist of oil or coolant; Devices for collecting or recovering materials resulting from grinding or polishing, e.g. of precious metals, precious stones, diamonds or the like
• CPC Class Codes: B24B 57/02 for feeding of fluid, sprayed, pulverised, or liquefied grinding, polishing or lapping agents
• CPC Class Codes: H01L 21/304 Mechanical treatment, e.g. grinding, polishing, cutting H01L21/30625 takes precedence

Abstract

The present invention is method for polishing silicon wafer, the method including recovering used slurry containing polishing abrasive grains that have been supplied to the silicon wafer and used for polishing, and circulating and supplying the recovered used slurry to the silicon wafer to polish the silicon wafer, wherein mixed alkali solution containing chelating agent and either or both of a pH adjuster and a polishing rate accelerator is added to the recovered used slurry without adding unused polishing abrasive grains, and the recovered used slurry is circulated and supplied to the silicon wafer to polish the silicon wafer. As a result, there is provided a method for polishing a silicon wafer that can suppress the occurrence of metal impurity contamination and stabilize the composition (e.g., the concentration of the chelating agent) of the used slurry when the used slurry is circulated and supplied to the silicon wafer for polishing.

Claims

1. A method for polishing a silicon wafer, the method comprising:

recovering a used slurry containing polishing abrasive grains and obtained from a slurry that had been supplied to the silicon wafer and used for polishing; and

circulating and supplying the recovered used slurry to the silicon wafer to polish the silicon wafer, wherein

a mixed alkali solution containing

a chelating agent and

either or both of a pH adjuster and a polishing rate accelerator is added to the recovered used slurry without adding unused polishing abrasive grains, and the recovered used slurry is circulated and supplied to the silicon wafer to polish the silicon wafer,

and further comprising;

measuring a concentration of the chelating agent in the recovered used slurry by an absorbance measuring method when the used slurry is circulated and supplied;

quantifying the chelating agent in the used slurry based on a result of the measurement; and

setting a mixing condition of the chelating agent in the mixed alkali solution based on a result of the quantification such that the concentration of the chelating agent in the used slurry is kept constant.

2. The method for polishing a silicon wafer according to claim 1, wherein the pH adjuster is one or more of KOH, NaOH, TMAH, K₂CO₃, Na₂CO₃, KHCO₃, and NaHCO₃, and/or

the polishing rate accelerator is an amine, and

the chelating agent is a nitrogen-containing compound having a carboxylic acid or a phosphoric acid in its molecule.

3. The method for polishing a silicon wafer according to claim 2, wherein the silicon wafer to be polished has a diameter of 300 mm or more.

4. The method for polishing a silicon wafer according to claim 2, further comprising:

regularly monitoring a polishing rate during polishing of the silicon wafer; and

setting a mixing condition of either or both of the pH adjuster and the polishing rate accelerator in the mixed alkali solution such that the polishing rate is kept constant.

5. The method for polishing a silicon wafer according to claim 4, wherein the silicon wafer to be polished has a diameter of 300 mm or more.

6. The method for polishing a silicon wafer according to claim 1, further comprising:

regularly monitoring a polishing rate during polishing of the silicon wafer; and

setting a mixing condition of either or both of the pH adjuster and the polishing rate accelerator in the mixed alkali solution such that the polishing rate is kept constant.

7. The method for polishing a silicon wafer according to claim 6, wherein the silicon wafer to be polished has a diameter of 300 mm or more.

8. The method for polishing a silicon wafer according to claim 1, wherein the silicon wafer to be polished has a diameter of 300 mm or more.

9. The method for polishing a silicon wafer according to claim 1, wherein the silicon wafer is polished with a polishing stock removal of 0.1 μ

m or more.

10. The method for polishing a silicon wafer according to claim 1, wherein the polishing abrasive grains are silica abrasive grains.