Highly efficient shrinkage of inverted-pyramid silicon nanopores by plasma-enhanced chemical vapor deposition technology

Abstract

Solid-state nanopore-based analysis systems are currently one of the most attractive and promising platforms in sensing fields. This work presents a highly efficient method to shrink inverted-pyramid silicon nanopores using plasma-enhanced chemical vapor deposition (PECVD) technology by the deposition of SiN x onto the surface of the nanopore. The contraction of the inverted-pyramid silicon nanopores when subjected to the PECVD process has been modeled and carefully analyzed, and the modeling data are in good agreement with the experimental results within a specific PECVD shrinkage period (∼0-600 s). Silicon nanopores within a 50-400 nm size range contract to sub-10 nm dimensions. Additionally, the inner structure of the nanopores after the PECVD process has been analyzed by focused ion beam cutting process. The results show an inner structure morphology change from inverted-pyramid to hourglass, which may enhance the spatial resolution of sensing devices.

Controllable Shrinking Fabrication of Solid-State Nanopores

“…Based on the former use, Wang et al [39] soon switched to plasma-enhanced chemical vapor deposition (PECVD) depositing a Si 3 N 4 layer on silicon nanopores with higher efficiency in shrinking rate, where all the nanopores from 50 nm to 400 nm were reduced to less than 10nm within 600 s [39]. Even so, a higher shrinking rate was equivalent to relatively lower controlling time and lower size-control accuracy (approx.…”

“…Moreover, along with the accumulation of depositional time, uniformity of the Si 3 N 4 layer gradually declined. In another word, PECVD was more suitable for the pre-shrinkage of solid-state nanopores [39].…”

“…Recently, EBID was successfully realized in scanning electron microscope (SEM) to fine turned the Si 3 N 4 nanopore diameter from 90 nm to only 5.3 nm [37]. In addition, common deposition skills such as atomic layer deposition (ALD) [38] and chemical vapor deposition (CVD) [39] could also provide complete steps to fine-tune both the sizes and the surface properties of already-made nanopores. Hence, Nanopores in different materials have been successfully shrunk, not just silicon oxide [33] and silicon nitride [40] but crystalline materials such as magnesium and its alloys [41], particularly from the typical two-dimensional material graphene [42] to low-cost polymer [43].…”

Fabrication and Applications of Solid-State Nanopores

“…As discussed before, massively parallel fabrication technologies are not able to directly fabricate ordered <5 nm nanopore arrays. Thus, many advanced shrinking techniques have been proposed to contract the pores to desired sizes, such as FIB and FEB induced shrinkage [52,96,97,98,99,100,101,102], material deposition [103,104,105,106], and thermal oxidation [107,108]. Moreover, these shrinking technologies provide an opportunity to modify the surface properties because of the deposited material [103].…”

“…Depositing materials on the inner-surfaces of nanopores can contract numerous nanopores simultaneously. Techniques, such as ALD [103], evaporation [104], electroplating [105], and plasma-enhanced chemical vapor deposition (PECVD) [106], have been used to shrink nanopores. Atomic resolution and high conformity could be realized using the ALD technique.…”