Microloading effect in reactive ion etching

Abstract

The etch rate of silicon, during reactive ion etching (RIE), depends on the total exposed area. This is called the loading effect. However, local variations in the pattern density will, in a similar way, cause local variations in the etch rate. This effect is caused by a local depletion of reactive species and is called the microloading effect. Silicon wafers patterned with silicon dioxide have been etched in order to study the microloading effect. The pattern consists of a large exposed area and narrow lines at different distances from the edge of the large area. This arrangement makes it possible to study how the distance from the large area, which depletes the etchants, influences the etch rate. The influence of different processing parameters like, e.g., pressure, gas flow rate, and flow direction on the microloading effect have been investigated. It has been found that the microloading effect is small (<10%) compared to other pattern dependent nonuniformities. It is also shown that the nonuniformities caused by the microloading effect can be decreased by, e.g., decreasing the pressure or increasing the gas flow rate.

Electrokinetic trapping and surface enhanced Raman scattering detection of biomolecules using optofluidic device integrated with a microneedles array

“…It was reported that, for the larger patterned area, the distance from the center to the edge is larger, which may poses difficulty in removing the reaction byproduct from the center of array. 51 This leads to the higher etching rate at the edge of the array than that at the center. Figure 2(b) shows the timelapse images of microneedles array in the etching process.…”

Bottom-up engineering of InAs at the nanoscale: From V-shaped nanomembranes to nanowires

“…Unlike the TEM analysis reported above, in the AFM measurements the roughness of the silicon surface has been measured on large areas of the sample and not in the nanoscale holes: indeed, measuring roughness inside nanoscale holes is not within reach of the existing state-of-the-art AFM techniques. The AFM measurements proved inconclusive as we could not detect any difference in roughness on the large areas within the experimental error: this however does not disprove the TEM analysis conducted within the holes and is compatible with ARDE, the effect where the etch rate depends on the aspect ratio (depth/width) of the features to be etched [69].…”

“…In the case of dry etching the hole shows a deep dig in the crystalline silicon as the etching does not land selectively on the silicon substrate. The dig in silicon is reduced by decreasing the hole size due to the aspect ratio dependent etching (ARDE) phenomenon [69]. In Fig.…”

Top-down fabrication of very-high density vertically stacked silicon nanowire arrays with low temperature budget

“…A special case of the loading is the microloading effect. The microloading effect is the etching rate degradation due to the high density of a pattern, the main mechanism for microloading is, etchant depletion [17,18]. Etchant depletion happens inside an etching trench and it is due to the difficulty for the etchant species to be replenished, as the etching opening reducing.…”

“…More details are explained in the following paragraphs. The loading effect [17] is the decrease of the etching rate of the reactive ion etching due to the increased area exposed to the SF 6 plasma. In our test structures more than 90% of total wafer area is exposed.…”