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Contactless Electrical Equivalent Oxide Thickness Measurement

IP.com Disclosure Number: IPCOM000038945D
Original Publication Date: 1987-Mar-01
Included in the Prior Art Database: 2005-Feb-01
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Curtis, HW: AUTHOR [+3]

Abstract

Proposed is a contactless electrical method of determining equivalent oxide thickness on semiconductor wafers. The method would replace the cumbersome and time-consuming optical approach, thereby improve productivity. In manufacturing semiconductor wafers the oxide thickness must be measured in order to measure the oxide charge of the wafers. In most instances optical equipment is used to estimate the equivalent electrical thickness of single and multilayer dielectrics. The proposal provides for a direct contactless electrical thickness measurement of dielectrics.

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Contactless Electrical Equivalent Oxide Thickness Measurement

Proposed is a contactless electrical method of determining equivalent oxide thickness on semiconductor wafers. The method would replace the cumbersome and time-consuming optical approach, thereby improve productivity. In manufacturing semiconductor wafers the oxide thickness must be measured in order to measure the oxide charge of the wafers. In most instances optical equipment is used to estimate the equivalent electrical thickness of single and multilayer dielectrics. The proposal provides for a direct contactless electrical thickness measurement of dielectrics. The concept is based on the parallel plate capacitor form of Gauss' law Q = CV where if the net charge density, Q, on an oxide surface can be controllably incremented by an amount dQ; and if the resultant change in oxide surface potential dV is measured, then the capacitance C of the oxide layer may be calculated from c = dQ/dV farads/cm2 (1) The oxide thickness Tox may be calculated from the expression for the capacitance of a simple plate capacitor Tox = (Eo) (Eox)/C cm (2) where: Eo = permittivity of free space (8.86E-14 farads/cm) Eox = relative dielectric constant of oxide In taking the measurement, a controlled corona discharge is used to increment the charge on an oxide surface by an amount dQ. A Kelvin probe is used to measure the resultant change in oxide surface potential dV. The oxidized wafer under test is placed on a grounded vac...