Microscratch testing of thin films has mainly been done with a conical tip. In the wedge scratch technique introduced in this paper, thin film fine lines are scratched by a wedge-shaped diamond tip until a spallation occurs. A near plane strain situation arises, and finite element method (FEM) analysis is applied for more accurate evaluation of the work of adhesion. The material system used to demonstrate the micro-wedge scratch technique is rf-sputtered tungsten on thermally grown SiO2. When scratching a long line, delamination occurs by tow mechanism. At loads above 8-9mN/μm (normal load per unit line width), tensile stresses behind the indenter tip cause the tungsten to crack, and the thin film subsequently curls up. At loads above 11mN/μm, high shear stresses in front of the indenter cause delamination of the tungsten at the interface. This latter event is modeled by FEM using a biomaterial fracture mechanics approach to obtain a practical work of adhesion value.