Method of estimating post-polishing waviness characteristics of a semiconductor wafer
AssigneeMEMC Electronic Materials, Inc.
InventorsMilind S. Bhagavat, Yun-Biao Xin, Gary L. Anderson, Brent F. Teasley
Life of this patent
Estimating the term…
Abstract
A method for estimating the likely waviness of a wafer after polishing based upon an accurate measurement of the waviness of the wafer in an as-cut condition, before polishing. The method measures the thickness profile of an upper and lower wafer surface to construct a median profile of the wafer in the direction of wiresaw cutting. The median surface is then passed through an appropriate Gaussian filter, such that the warp of the resulting profile estimates whether the wafer will exhibit unacceptable waviness in a post-polished stage.
Claims15
A method for estimating the post-polish waviness of an as-cut wafer comprising:
- measuring a thickness profile of an upper surface of a wafer along an angle of said wafer;
- measuring a thickness profile of a lower surface of said wafer along said angle;
- constructing a median surface profile of said wafer from said measurements;
- applying a band-pass filter to said median surface profile to form a filtered median surface profile;
- and
- comparing a warp measurement of said filtered median surface profile to a specification selected to estimate post-polish waviness.
A method of producing wafers cut from stock material which are capable of meeting a predetermined flatness specification after further processing of the wafers, the method comprising the steps of:
- a) cutting the stock material to form multiple wafers;
- b) measuring at least one of the wafers to establish a surface profile of the wafer;
- c) filtering the surface profile to produce a filtered surface profile which eliminates at least some of the features of the surface profile;
- d) determining the maximum deviation of the filtered surface profile;
- e) comparing the maximum deviation against a maximum deviation standard;
- and
- f) further processing only those wafers which have a maximum deviation less than the maximum deviation standard.
Dependencies are inferred from the claim text.