As an important kind of micro optical component, microlens and its array have been widely used in various applications, for its abilities such as convergence, collimation and imaging. Correspondingly, methods for the fabrication of microlens also emerge one after another, becoming a research hotspot in the field of micro-optics. In this thesis, a novel method for the fabrication of microlens and its array has been developed, utilizing the spherical structures formed at the overplating stage of microvia electrodeposition, combined with soft replica molding. From both the perspective of numerical simulation and experimental verification, the shape evolution principle of the overplating structure has been studied thoroughly. Based on optimization of the process parameters, an integrated technique with favorable compatibility has been established. High-numerical-aperture microlenses with controllable sizes and micro lens arrays with various packing ratios which could reach 100% have been successfully obtained. What’s more, the geometric parameters and optical performance of the fabricated microlenses have been measured and evaluated. The research work is presented as following:Based on the basic electrochemical principles of electrodeposition process, the numerical computation model for the electrodeposition process in the microvia has been established. In this model, the flow field, the material transport of reactive ion and kinetics of electrochemical reaction are fully coupled. Combined with the moving mesh technology, this model realized the dynamic simulation of cathode deposition surface profile. On the basis of this, the effects of convective mixing on microvia electrodeposition process have been analyzed with a finite element method, and the simulation result was compared with the experiment, providing theoretical basis for further electroforming experiments.Mechanism of the shape evolution of overplating structures in electroforming process of microvia has been thoroughly investigated. Base on the numerical simulation model this thesis built, influence of the electrode size and the electrodeposition speed on the shape evolution of the overplating structures has been analyzed. With the electroforming experimental system built up on our own, experiments of overplating have been carried out, in which the influence of diameter and aspect ratio of the microvia, as well as the current density for deposition on overplating process has been explored. Both the results of the numerical calculations and the experiments show that overplating structure tend to form a spherical surface when microvia diameter and deposition current density decrease; and the overplating structure tend to form a crater like surface which is low in the middle and high on the around, when microvia diameter and deposition current density increase. What’s more, repeatability and stability of the overplating process has been verifiedThe entire fabrication process includes lithography, micro-electroforming and soft lithography. The process parameters have been optimized based on the influence mechanism of them, and a compatible integrated process has been established, realizing the fabrication of microlens and its arrays. Parameters of the lithography process have been optimized to obtain the photoresist mask with favorable structural stability for the subsequent electroforming process. Through the optimization of electric parameters in electroforming, roughness of the deposition surfaced has been improved, which guarantees the possibility for the optical application of the replicated microlenses. In the soft lithography process, parameters have been optimized to improve the filling property of the resin, which makes it possible to get high precision microlens and microlens arrays without defects.Geometric parameters and optical performance of the replicated lenses and lens arrays have been measured and evaluated. Combining the microscopy method together with image processing, geometric parameters of the lenses have been successfully measured through profile extraction and nonlinear fitting. Based on this measurement method, profile evolution of the lenses has been studied. According to the relationship between the geometric parameters of the microlenses and time of electrodeposition, the controllability of the fabrication process has been discussed. Results show that microlenses of various sizes with large numerical aperture can be made by adjusting the electroforming time. The focal lengths of the lenses have been measured using the home made optical measurement platform, and the optical properties of the lens arrays with different packing ratios have also characterized, which shows that the lens arrays obtained from this method possess good optical properties. |