DMD maskless lithography stitching error correction based on motion compensation
Jiang Xu, Yang Xu, Liu Hong, Hu Jun, Wang Yingzhi     
Electronic Information Engineering, Changchun University of Science and Technology, Jilin, Changchun 130000, China

Overview: Digital lithography is the core technology of PCB board. As the wiring density increases and the etch line width decreases, high-precision PCB boards place higher demands on lithography systems. Digital micromirror device (DMD) is a key component in digital lithography. The DMD unit used in this paper has a pixel size of 13.68 μm×13.68 μm and has the advantages of high filling ratio, fast response and high contrast. Mask lithography can expose micron or even nanoscale patterns. In the large-area exposure process, since the size of the PCB board is much larger than the size of the DMD, in order to obtain a high-precision PCB board, it is necessary to improve the stitching precision of the exposed image. But for the DMD lithography equipment, due to the exposed images joint errors which caused by mechanical loading errors, problems such as misalignment and overlap of the exposed images may arise. After the pixel is exposed, the platform will re-exposure the moving distance. Ideally, the pixel should be moved from position 1 to position 3 for exposure due to tilt error. The effect, in the actual test, the DMD moves along the platform scanning direction, that is, the X-axis positive direction moves a certain distance, then the pixel is moved to the position 2, resulting in the problem of misalignment of the exposed image. In order to eliminate the exposure error of DMD during large-area exposure, the error correction method was studied. Firstly, the exposure error was got by measuring the exposed substrate with a microscope. Then, an error model was established based on the known exposure error. Finally, an error correction based on motion compensation for DMD lithography system was proposed based on the error model. After measuring the tilt error, the method calculates the XY-axis offset of the image by using the triangular relationship, and then realizes the error compensation through the platform motion. The experimental results show that during the micron image exposure process, the exposure error is reduced by more than 80%, and the DMD exposure center offset distance is reduced from 175 μm to 21 μm. The stitching accuracy of the exposed image is improved effectively, which meets the requirements for high quality and high precision of large-area exposure images.

Supported by Jilin Province Science and Technology Development Plan Project (20170204053GX)