Silicon etching in a pulsed HBr/O2 plasma. II. Pattern transfer

Abstract

The strong impact of synchronized plasma pulsing on an HBr/O 2 silicon pattern etch process is studied with respect to the continuous process. This article focuses on blanket etch rates and a detailed analysis of the etched profiles, where several significant features of plasma pulsing are identified. First, the time compensated (TC) silicon etch rate is increased while the SiO 2 TC etch rate is decreased at a low duty cycle, whereby the selectivity between silicon and SiO 2 etching is strongly increased. Furthermore, the thickness of the sidewall passivation layer is reduced, thereby guiding the etched profile. Finally, the overall homogeneity is increased compared to the continuous wave etching process.

Dry-Etching Processes for High-Aspect-Ratio Features with Sub-10 nm Resolution High-χ Block Copolymers

“…As depicted in Figure , the PDMSB lamellae were transferred into the silicon substrate using a HBr/O 2 chemistry , to assess the etch resistance of the modified PDMSB as a mask to pattern amorphous silicon, which is common to many patterning stacks. Bromine-based species are the main etchant here, forming mainly SiH 2 Br 2 and SiBr 4 as volatile products .…”

“…Bromine-based species are the main etchant here, forming mainly SiH 2 Br 2 and SiBr 4 as volatile products. 29 The stickiness of most etch byproducts can be enhanced by adding some oxygen in the gas mixture so that these sticky byproducts passivate the sidewalls. The transfer plasma is synchronously pulsed at a pulsing frequency of 1 kHz (cycle times of 1 ms) and RF ON times of 200 μs (20% duty cycle) to reduce the dissociation of HBr.…”

The Study of Reactive Ion Etching of Heavily Doped Polysilicon Based on HBr/O2/He Plasmas for Thermopile Devices

“…Instead, bromine-containing plasmas are used for polysilicon etching because spontaneous etching by bromine atoms is very slow, as is ion-assisted etching of SiO 2 . Thus, there has been increasing interest in HBr-based plasma because of improved selectivity with respect to the photoresist mask and SiO 2 , as well as superior control of the etched sidewall profile [ 10 , 12 , 13 , 14 ]. Although successful results of polysilicon etching have been obtained based on HBr plasmas, most of them are undoped polysilicon.…”

Role of vibrationally excited HBr in a HBr/He inductively coupled plasma used for etching of silicon

“…Because of the lower reactivity of bromine towards silicon compared to fluorine, the etching of very thin layers can be more properly controlled with bromine-based plasmas. [1][2][3][4][5][6][7] A bromine-containing gas that is often used for silicon etching is HBr, which is commonly mixed with Cl 2 and/or CF 4 . [8][9][10][11][12][13] Furthermore, HBr can also be combined with a noble gas like helium, to tune the ratio between physical ion sputtering and chemical etching, or with O 2 , for controlling the anisotropy during etching.…”