Metalenses， with their unique optical field modulation characteristics and remarkable advantages of high integration and miniaturization， have broad applications in the integrated imaging system of lightweight and small-sized optoelectronic chips. In this paper， a metalens structure for pixel-level integrated infrared focal plane applications was designed. The preparation of the structure adopted a method combining stepper lithography technology and the Inductively Coupled Plasma （ICP） etching process. Through a systematic optimization of etching parameters， including gas flow rate， working pressure， and power， the loading effect was effectively suppressed and the standard deviation of the etching rate was decreased from 0.205% to 0.073%. Finally， a highly uniform metalens array was fabricated， with a pixel center distance of 30 μm， an array of 640×512， and a maximum aspect ratio of 3.42 of Si pillars. The focusing distance for 4.3 μm wavelength infrared light is 35 μm. The measured optical field convergence efficiencies， within radial ranges of 10 μm and 20 μm in the central area at the focal length， are 66.4% and 84.9%， respectively. The optical field energy is increased by 5.98 times and 1.91 times， respectively， compared with that without the integrated metalens within the same area range. This study will provide the structural design and processing foundation for the integration of pixel-level metalens arrays with infrared chips.