Etching aspect ratio dependent

Fig. 40. Aspect ratio dependent etching of silicon in a CCI2F2/O2 gas mixture. The etch rate is a function of the aspect ratio of the feature (depth/width). After [197).

Plasma Etching, Fig. 3 High aspect ratio silicon trenches with nearly vertical sidewall profile obtained by inductively coupled plasma (ICP) etching (a) SEM micrograph, (b) RIE lag, and (c) aspect ratio-dependent etching phenomena... 

The performance of anisotropy etching can be evaluated from the etching rate, selectivity, profile (directionality), loading effect, RIE lag, aspect ratio-dependent etching (ARDE), and uniformity. Besides the design of equipment... 

Aspect Ratio Dependent Etching Plasma Etching... 

In addition, aspect ratio considerations, dependent on mechanical stability and pattern collapse propensity of resist lines, limit the thickness of resists designed for these technology nodes to ultrathin resist thickness regimes ( 100 nm and lower). However, the aspect ratio considerations must be balanced against the etch stability requirements that ensure successful pattern transfer to underlying substrates in a device. Both the aspect ratio and etch stability requirements must be balanced against the intrinsic resolution, particularly pitch resolution, of the resist in question. Hence, there is a trade-off between aspect ratio requirements and etch stability requirements on the one hand, and pitch resolution on the other. Therein lies the motivation for these advanced resist-processing schemes. 

Anisotropic etching (i.e. etching of bulk material with etch rates depending on material/crystal orientation, used in single crystal material in order to determine clear features and geometry aspect ratios). 

Increase of Aspect Ratio for DT Si Etch up to 60 The maximum achievable DT depth is not limited by an Si Reactive Ion Etch (RIE) stop, but by hard mask erosion [277-279]. A boron doped silicon oxide (BSG) is used as the hard mask material (CVD deposition). The BSG is patterned by conventional photoresist technology. A photoresist to BSG RIE selectivity of above 4 1 is possible. In turn, the BSG hard mask to Si RIE selectivity was found to depend on the DT top dimension (lateral DT perimeter). The corresponding experimental relationship is shown in Figure 1.66 for a conventional Si RIE tool set. For each data point the required BSG... 

Change in deposition rate along via sidewalls leads to decrease of cleft depth in the via tops and void-free filling of the vias. The dependencies of cleft depth on via aspect ratio, applied current density, seed layer thickness and wafer center-edge nonuniformity were observed by FIB etching, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). 

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