Study Of Key Techniques Impacting On Exposure Quality Of Laser Direct Writing In Cartesian Coordinate

Laser direct writing (LDW) is one of the important technologies used to fabricate diffractive micro-optical elements for its flexibility, simplicity and ability to make complex feature structure with smooth edge. With the development of science and technology, the urgent requirements for large aperture and refinement of micro-optical elements make the writing accuracy of LDW get more and more strict. Exposure is one of the most important working procedures, which plays a decisive role in the processing accuracy. However, there still exist three shortcomings relevant to exposure process such as low accurate exposure model, inadequate perfection of optical proximity correction method and poor positioning precision, which block the experimental research and processing quality improvement of LDW.The subject"Study of Key Techniques Impacting on Exposure Quality of Laser Direct Writing in Cartesian Coordinate"is to do research on the key techniques relevant to exposure quality, and focused on building the dynamic exposure model of actual condition, improving the optical proximity correction method, and discussing the method of reducing the positioning noise of coarse-fine driving table, which provides a powerful theoretical and technical basis for high precision LDW. The research of this subject also provides reliable models and techniques for making large aperture and complex structure diffractive micro-optical elements.In order to predict the laser direct writing quality in Cartesian coordinate, a new dynamic exposure model is established by taking into consideration the effect of the photoresist absorbing beam energy, the Gaussian attribute of the writing beam and the relative movement between writing beam and photoresist, to describe the influence of a change in writing velocity and writing power on the line width and sidewall angle in the photoresist, so that critical dimension process window can be obtained to provide a theoretical basis for LDW experiment.Correction method with low resolution acoustooptic modulator is proposed to efficiently correct the optical proximity effect in laser direct writing. Firstly, based on Iterative Error-Correction Method (IECM) proposed by Rajesh Menon, one virtual high resolution acoustooptic modulator is used to correct the direct writing pattern, then the exposure data of spots nearest to each error area barycenter are modulated, and the above steps help IECM correct the optical proximity with low resolution acoustooptic modulator and make a thorough optimization.In order to reasonably choose coupling damp to suppress the positioning noise of coarse-fine stage, model of dual stage with coupling damp is established based on parallel dual servo control and used to study the effect law of coupling damp, which reveals the effect of coupling damp on noise transmission and dynamic characteristic of each stage, and provides theoretical basement for the improvement of positioning stability and the accomplishment of nano-precision positioning with damp.In the last section of the paper, several key techniques in this subject have been studied through experiments. Firstly, the optical proximity correction method with low resolution acoustooptic modulator has been carried out through experimental study. Experimental results indicate that, taking"L"design pattern as example, compared with IECM unable to correct the direct writing pattern with low resolution acoustooptic modulator, the proposed method in this subject can correct the direct writing pattern, which decreases pattern error value by 70.88% relative to the initial error value. Then, the coarse-fine stage with damping oil damper has been developed, and the validity of coarse-fine system model and the action effect of coupling damp has been tested through experiments. Experimental results indicate that, based on the developed system and the same control parameters, the experimental coupling damp characteristics agree with the theoretical results, and the coupling damper with damping coefficient 293.78 N/(m/s) suppresses the positioning noise of coarse-fine driving control system from 80nm(pk-pk) to 60nm(pk-pk).