Using atomic force microscopy (AFM), we have developed an experimental method for evaluating interface strength of a small dot on a substrate. This technique is applied to tungsten (W) dots of micrometer size on a silicon (Si) substrate. The diamond tip is dragged horizontally along the Si surface and the load is applied to the side edge of the W dot at a constant displacement rate. Both the lateral and the vertical load and displacement are continuously monitored during the test. Results show that after the tip hits the W dot, the lateral load, F-1, increases almost in proportion to the lateral displacement, delta(1). The W dot is abruptly separated from the Substrate along the interface, and the apparent fracture energy of the interface, E-d, is successfully evaluated. (C) 2004 Elsevier Ltd. All rights reserved.