Correction method for high-precision CD measurements on electrostatically charged wafers

Yoichi Ose; Makoto Ezumi; Tatsuaki Ishijima; Hideo Todokoro; Kouichi Nagai

doi:10.1117/12.473508

Abstract

A correction method for automatic, high-precision CD-measurements on electrostatically charged wafers has been developed and installed in the Hitachi CD-SEM S-9260 to evaluate its performance. There are two types of charging: global and local. Global charging is stable and spreads all over a wafer while the local charging area is limited within the beam scanning area. A conventional CD-SEM has two weak points with respect to those charged wafers: one is failure at the positioning and autofocusing procedure which interferes with the fully automatic measurement sequence, and the other is disturbance of optical magnification which degrades the precision of CD-measurement values. By probing the global charging voltage with an electrostatic voltmeter prior to the CD-measurements, we subtract the voltage from a retarding voltage and then apply it to the wafer holder. The beam-focusing condition can stay within the fully automatically tunable range. And by generating numerical functions to represent the relationship between the global charging voltage, wafer height, excitation current of the objective lens and optical magnification, with the help of electron optical simulations, we can calculate the true optical magnification and the correct CD-measurement values. The local charging voltage is derived from the voltage shift of S-curves of secondary electron yield between conductive and insulated wafers measured with an energy filter. We correct the CD-measurement values using the simulated proportional relationship between magnifications of the electrostatic micro-lens and the local charging voltage. The coefficient is almost constant when the charging area is smaller than an equivalent circle of 100mm radius. We demonstrate that the CD-measurement values are successfully corrected within 0.1 percent in deviation for both charging types.

Citation Download Citation

Yoichi Ose, Yoichi Ose, Makoto Ezumi, Makoto Ezumi, Tatsuaki Ishijima, Tatsuaki Ishijima, Hideo Todokoro, Hideo Todokoro, Kouichi Nagai, Kouichi Nagai, } "Correction method for high-precision CD measurements on electrostatically charged wafers", Proc. SPIE 4689, Metrology, Inspection, and Process Control for Microlithography XVI, (16 July 2002); doi: 10.1117/12.473508; https://doi.org/10.1117/12.473508

ACCESS THE FULL ARTICLE

PERSONAL SIGN IN
Full access may be available with your subscription

Email or Username Forgot your username?

Password Forgot your password?

Show

Remember Email/Username on this computer

Remember Password

No SPIE account? Create an account
or Institutional Sign In via Shibboleth

PURCHASE THIS CONTENT

SUBSCRIBE TO DIGITAL LIBRARY

50 downloads per 1-year subscription

Members: $195

Non-members: $335 ADD TO CART

25 downloads per 1 - year subscription

Members: $145

Non-members: $250 ADD TO CART

PURCHASE SINGLE ARTICLE

Includes PDF, HTML & Video, when available

Members: $14.40

Non-members: $18.00 ADD TO CART

Show All Keywords

Keywords/Phrases

Search In:

Publication Years