Slurry supplying apparatus and method of polishing semiconductor wafer utilizing same
A diluted slurry supplying apparatus utilized in a polishing apparatus for finishing a semiconductor wafer with a slurry containing colloidal silica and water-soluble polymer is provided. The polishing method comprises: a slurry supplier capable of supplying the slurry containing the colloidal silica and the water-soluble polymer; a diluent supplier capable of supplying a diluent containing an aggregation preventing agent to dilute the slurry; a mixer capable of receiving the slurry and the diluent having been supplied from the slurry supplier and the diluent supplier, respectively, the mixer forming a diluted slurry with a pH value of at least 9; and an ultrasonic vibrator capable of applying an ultrasonic vibration to the diluted slurry staying in the mixer or being fed out from the mixer. Here, the diluent supplying apparatus can change a dilution proportion of the diluted slurry.
1. A polishing method for finishing a semiconductor wafer with a slurry comprising colloidal silica and water-soluble polymer, the method comprising:
diluting the slurry at a predetermined proportion with ammonia water while an ultrasonic processing is applied to the diluted slurry; and
supplying the diluted slurry in an initial stage of polishing
wherein:
the diluted slurry comprises a pH value of at least 9;
diluting the slurry with ammonia water while the ultrasonic processing is stopped;
supplying the diluted slurry in an intermediate stage of polishing;
diluting the slurry with water while the ultrasonic processing is stopped; and
supplying the diluted slurry in a final stage of polishing.
2. The polishing method according to claim 1 wherein the aggregation preventing agent includes at least one salt constituted of a combination of a cation selected from a group consisting of Li + , Na + , K + , Me 2+ , Ca 2+ , and NH 4+ and an anion selected from a group consisting of CO 3 2− , Cl − , SO 4 2− , S 2− , F − , NO 3 − , PO 4 3− , CH 3 COO − , and OH − .
3. The polishing method according to claim 1 wherein the predetermined proportion of the diluent increases with elapse of time.
4. A polishing method for finishing a semiconductor wafer with a slurry comprising colloidal silica and water-soluble polymer, the method comprising:
diluting the slurry at a predetermined proportion with a diluent while an ultrasonic processing is applied to the diluted slurry;
supplying the diluted slurry in an initial stage of polishing;
wherein:
the diluent comprises KCl and has a colloidal density lower than that of the slurry,
the diluted slurry comprises a pH value of at least 9;
diluting the slurry with the diluent while the ultrasonic processing is stopped;
supplying the diluted slurry in an intermediate stage of polishing;
diluting the slurry with water while the ultrasonic processing is stopped; and
supplying the diluted slurry in a final stage of polishing.
5. The polishing method according to claim 4 wherein the diluted slurry comprises a pH value of 9 to 10.1.