Patent ID: 7473911
Filing Date: 2009-01-06
Classification: H01J,H01L

Abstract:
1. A method for process monitoring, comprising: operating a beam of charged particles directed towards a sample at energy in a negative charging domain of a second layer that is formed over an at least partially conductive first layer of the sample thereby to pre-charge the second layer of the sample, the second layer having contact openings therein and the pre-charging being in a vicinity of at least some of the contact openings; directing the beam of charged particles towards the sample along a beam axis that is oriented at a tilt angle from a normal to a surface of the sample, the tilt angle being greater than an arctangent of an aspect ratio of the contact openings, said aspect ratio being a ratio of a depth to a diameter of an individual one of the contact openings, so as to irradiate side walls of one or more of the contact openings, but not bottoms thereof, in each of a plurality of locations distributed over at least a region of the sample; creating, from measurements of (i) a specimen current flowing through the first layer in response to irradiation of the side walls of the one or more of the contact openings at each of the plurality of locations and (ii) a secondary electron current emitted from the sample responsive to the beam of charged particles, a map of at least the region of the sample indicating the specimen current measured in response to the irradiation at the plurality of the locations; and classifying, using the map of the specimen current, anomalies in a process used to create the contact openings.