Polishing method and polishing apparatus

Patent metadata

Field	Value
Publication number	US-2017190020-A1
Application number	US-201515304829-A
Country	US
Kind code	A1
Filing date	Apr 10, 2015
Priority date	Apr 22, 2014
Publication date	Jul 6, 2017
Grant date	—

Abstract

The present invention relates to a polishing method and a polishing apparatus for polishing a substrate such as a wafer while measuring a film thickness based on optical information included in reflected light from the substrate. The polishing method includes preparing a plurality of spectrum groups each containing a plurality of reference spectra corresponding to different film thicknesses; directing light to a substrate and receiving reflected light from the substrate; producing, from the reflected light, a sampling spectrum for selecting a spectrum group; selecting a spectrum group containing a reference spectrum which is closest in shape to the sampling spectrum; producing a measurement spectrum for obtaining a film thickness while polishing the substrate; selecting, from the selected spectrum group, a reference spectrum which is closest in shape to the measurement spectrum that has been produced when the substrate is being polished; and obtaining a film thickness corresponding to the selected reference spectrum.

First claim

1 . A polishing method comprising:
preparing a plurality of spectrum groups each containing a plurality of reference spectra corresponding to different film thicknesses; directing light to a substrate and receiving reflected light from the substrate; producing, from the reflected light, a sampling spectrum for selecting a spectrum group; selecting a spectrum group containing a reference spectrum which is closest in shape to the sampling spectrum; producing a measurement spectrum for obtaining a film thickness while polishing the substrate; selecting, from the selected spectrum group, a reference spectrum which is closest in shape to the measurement spectrum that has been produced when the substrate is being polished; and obtaining a film thickness corresponding to the selected reference spectrum.

2 . The polishing method according to claim 1 , wherein selecting the spectrum group comprises selecting a spectrum group containing a reference spectrum with a smallest deviation from the sampling spectrum.

3 . The polishing method according to claim 1 , wherein selecting the spectrum group is carried out when the substrate is being polished.

4 . The polishing method according to claim 3 , wherein selecting the spectrum group is carried out using the sampling spectrum which has been produced within a preset polishing time.

5 . The polishing method according to claim 1 , wherein selecting the spectrum group is carried out before the substrate is polished.

6 . The polishing method according to claim 5 , wherein selecting the spectrum group is carried out when the substrate is being water-polished in a presence of pure water existing between the substrate and a polishing pad.

7 . The polishing method according to claim 1 , further comprising:
reproducing a sampling spectrum while polishing the substrate; and reselecting a spectrum group containing a reference spectrum which is closest in shape to the reproduced sampling spectrum, wherein selecting the reference spectrum comprises selecting, from the reselected spectrum group, a reference spectrum which is closest in shape to the measurement spectrum that has been produced when the substrate is being polished.

8 . The polishing method according to claim 1 , wherein the plurality of spectrum groups are obtained by:
directing light to a plurality of areas defined on a reference substrate having a same film thickness as or a larger film thickness than a film thickness of the substrate, while polishing the reference substrate; producing a plurality of reference spectra from the light reflected from the plurality of areas; and classifying the plurality of reference spectra according to the plurality of areas.

9 . The polishing method according to claim 8 , further comprising:
preselecting spectrum groups obtained in areas near an area where the film thickness of the substrate is to be monitored.

10 . The polishing method according to claim 1 , wherein the plurality of spectrum groups are obtained by:
selecting one of a plurality of reference substrates each having a same film thickness as or a larger film thickness than a film thickness of the substrate; directing light to the selected reference substrate while polishing the selected reference substrate; obtaining one or more spectrum groups by producing a plurality of reference spectra from the light reflected from the reference substrate; and repeating the process of directing the light to the selected reference substrate and the process of obtaining one or more spectrum groups, while changing the reference substrate, to be selected, from one to another each time the repeating is performed.

11 . The polishing method according to claim 1 , wherein the plurality of reference spectra contained in each of the plurality of spectrum groups comprise spectra produced by a simulation of light reflection.

12 . The polishing method according to claim 1 , further comprising:
excluding in advance, from the plurality of spectrum groups, one of spectrum groups containing reference spectra which are close in shape to each other.

13 . The polishing method according to claim 1 , wherein the plurality of spectrum groups are stored in a common database shared by a plurality of polishing apparatuses.

14 . The polishing method according to claim 13 , the common database stores therein history information about the selection of the plurality of spectrum groups.

15 . A polishing method comprising:
obtaining at least one spectrum group containing a plurality of reference spectra by polishing a reference substrate; correcting the plurality of reference spectra such that a polishing rate of the reference substrate is regarded as constant, thereby obtaining a plurality of corrected reference spectra corresponding to different film thicknesses; directing light to a substrate and receiving reflected light from the substrate; producing a measurement spectrum for obtaining a film thickness while polishing the substrate; selecting, from the at least one spectrum group, a corrected reference spectrum which is closest in shape to the measurement spectrum that has been produced when the substrate is being polished; and obtaining a film thickness corresponding to the corrected reference spectrum selected.

16 . A polishing apparatus comprising:
a polishing table for supporting a polishing pad thereon; a polishing head configured to press a substrate against the polishing and polish the substrate; a storage device storing therein a plurality of spectrum groups each containing a plurality of reference spectra corresponding to different film thicknesses; and an optical film-thickness measuring device configured to obtain a film thickness of the substrate, the optical film-thickness measuring device being configured to:
direct light to the substrate and receive reflected light from the substrate;
produce, from the reflected light, a sampling spectrum for selecting a spectrum group;
select a spectrum group containing a reference spectrum which is closest in shape to the sampling spectrum;
produce a measurement spectrum for obtaining a film thickness while the substrate is being polished;
select, from the selected spectrum group, a reference spectrum which is closest in shape to the measurement spectrum that has been produced when the substrate is being polished; and
obtain a film thickness corresponding to the selected reference spectrum.

Assignees

• Ebara Corp

Inventors

• Kobayashi Yoichi
• Yagi Keita
• Kinoshita Masaki
• Shiokawa Yoichi

Classifications

• H10P74/238

  comprising acting in response to an ongoing measurement without interruption of processing, e.g. endpoint detection or in-situ thickness measurement · CPC title

• H10P74/203

  Structural properties, e.g. testing or measuring thicknesses, line widths, warpage, bond strengths or physical defects · CPC title

• H10P72/00

  Handling or holding of wafers, substrates or devices during manufacture or treatment thereof · CPC title

• B24B37/32

  Retaining rings · CPC title

• B24B49/12

  involving optical means · CPC title