Thin (500 nm thick) and ultra thin (5 nm thick) Cu films were sputter deposited on as-received and sputter cleaned amorphous Si(3)N(4) substrates. Their stresses were determined by the X-ray diffraction sin(2)psi method. Due to the strong Cu {111} texture, stress measurement by diffraction was possible also for the ultra thin films. High tensile stresses (422 MPa) developed in these films upon island coalescence. The growth stress of the 500nm thick films indicates a correlation with the morphological changes from globular to columnar structures upon substrate sputter cleaning prior to film deposition.