Low filling efficiency and large thermal stress are two important problems that limit the wide use of hot embossing especially in fabricating high aspect ratio patterns. Two types of flow barriers, the first being an accessorial slot on the mold (SFB), the other was a block on the hot embossing machine (BFB), were designed to enhance polymer filling and their performances were simulated with the finite element method. The numerical simulation results show that two kinds of flow barriers can also accelerate the polymer filling speed and improve filling efficiency. The BFB has a better promoting effect and can be easily used as a quasi close-die embossing process. The shrinkage of the polymer and mold is made uniform with a designed polymer grip holder to minimize the thermal stress. The polymer was clipped at a temperature in a cooling step and its deformation was fixed; thus, the shrinkage of the polymer can be equal to the mold at a special temperature. An improved hot embossing machine was designed and the hot embossing process was modified to satisfy these requirements. At last successful fabrication of the light guide plate verified the improvements. POLYM. ENG. SCI., 2013. (c) 2012 Society of Plastics Engineers