Fabrication of High Precision Silicon Spherical Microlens Arrays by Hot Embossing Process

Abstract

In this paper, a high-precision, low-cost, batch processing nanoimprint method is proposed to process a spherical microlens array (MLA). The nanoimprint mold with high surface precision and low surface roughness was fabricated by single-point diamond turning. The anti-sticking treatment of the mold was carried out by perfluorooctyl phosphoric acid (PFOPA) liquid deposition. Through the orthogonal experiment of hot embossing with the treated mold and subsequent inductively coupled plasma (ICP) etching, the microstructure of MLA was transferred to the silicon substrate, with a root mean square error of 17.7 nm and a roughness of 12.1 nm Sa. The average fitted radius of the microlens array units is 406.145 µm, which is 1.54% different from the design radius.

Fabrication of Large-Area Silicon Spherical Microlens Arrays by Thermal Reflow and ICP Etching

“…Notably, it requires ultra-precision machining of the opposite target microstructure on a mold first, and as mentioned above, the ultra-precision machining technology is still insufficient for machining large areas. Once, we [33] successfully machined a 6 × 6 microlens array on a silicon substrate using a hot embossing process; however cutting a 600 × 600 µm 2 highprecision mold already approached our machine tool limit and the surface roughness of the microlens unit was only 17.7 nm, which would affect the light throughput quality of the lens.…”

Inductively Coupled Plasma Dry Etching of Silicon Deep Trenches with Extremely Vertical Smooth Sidewalls Used in Micro-Optical Gyroscopes

“…ICP etching manufactures various semiconductor micro/nano structures on the substrates, such as Si, SiO 2 , SiC, and diamond, by sputtering the substrate with plasma generated from ionized appropriate gas (glow discharge), which is widely used in integrated circuits, MEMS, optics, etc. [26][27][28]. ICP etchers normally contain two radio frequency (RF) sources with a frequency of 13.56 MHz, serving as an ICP generator and a capacitively coupled plasma (CCP) generator, respectively.…”