U.S. Pat. No. 5,669,303 discloses an apparatus for micro contact printing including a support structure, a flexible stamp having a stamping surface including a predetermined pattern disposed opposite the support structure, a pressure controlled chamber disposed above the support structure, and a mechanical attachment affixed to the flexible stamp. Furthermore, U.S. Pat. No. 5,669,303 discloses a method for micro contact printing. In the method, contact between a wetted stamping surface of a flexible stamp and the surface of an article is obtained by changing the pressure differential across the flexible stamp so that contact commences at the center of the flexible stamp and proceeds outwardly in a controlled way.
U.S. Pat. No. 5,669,303 relates to gradual establishment of contact between a flexible stamp and the substrate in order to avoid air inclusions between the stamp and the substrate. However, with the known methods and apparatuses the pattern gets distorted, since the stamp contacts the substrate in a deformed and stretched state.
U.S. Pat. No. 5,669,303 addresses the problem of a distortion of the pattern. In particular, it is noted that due to the elasticity and/or local strain of the flexible stamp, runout or a local deformation of the pattern may occur. A solution is found in compressing or stretching the flexible stamp at the appropriate locations, wherein mechanical attachments are provided with the appropriate detection and control elements to provide this correction when required. All in all, this solution requires a complicated correction system, and is far from practical.
The method and apparatus according to the invention constitute a major difference with respect to those of U.S. Pat. No. 5,669,303. While in the known method and apparatus the flexible sheet is pressed against the substrate, wherein stress is induced in the flexible sheet by the external pressing force, this is deliberately not done in the method and apparatus of the present invention.