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The need for continued device scaling along with the increasing demand for high precision have lead to the development of atomic layer etch processes in semiconductor manufacturing. We have tested this new methodology with regard to patterning applications. While these new plasma-enhanced atomic layer etch (PE-ALE) processes show encouraging result...
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... use these processes to demonstrate a successful etch stop on SiN, as shown in Figure 1. While we are able to characterize the physical morphology of these etch processes, our chemical analysis and evaluation is hampered by the lack of in-situ characterization. The process of Chemistry A was further investigated by wafer uniformity measurements. Fig. 2 shows the measured selectivities and uniformities of the PE-ALE process and its corresponding CW processes. While we can see excellent selectivity of the PE-ALE process to OPL, only moderate selectivity to SiN was found. Additionally, we measure very good uniformity across wafer. When operating in CW mode, we noted a complete loss of ...
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... both cases studied, oxide as well as nitride etching, the most promising approach for multi-color patterning was enabled through optimization of the chemistry in addition to optimization of the other plasma parameters. For the patterning of oxide materials, further optimization of the discharge chemistry based on results reported in Figure 2 was explored. While excellent selectivity to OPL material was observed in both cases, a further selectivity increase to SiN materials was observed by discharge chemistry optimization. ...
Citations
... Use of the ALE process in patterning high-aspect-ratio features with narrow pitch sizes has been reported lately. 3,11,12 Because the ALE process is not perturbed by surface loading, patterns with different geometries are expected to be processed identically provided saturation of surface coverage is reached. Hence, designing a combination of micro-and nanostructured features on the same nanoimprint stamp is possible by employing the ALE process. ...
Atomic Layer Etching (ALE) is a cyclic etching process in which a well-defined atomically thick single layer is etched in one cycle [1-3]. This technique has recently attracted a lot of attention [4-6] and it is now recognized as a very promising process for atomic precision nanofabrication. This technique also holds a substantial promise for nanoimprint lithography (NIL), in particular for nanoimprint stamp fabrication. Nanoimprint demonstrated capability to replicate features of a few nanometers in size [7] and the main source for NIL resolution limitation is in the NIL stamp fabrication since the NIL resolution cannot be better than that of NIL stamp. Therefore, ALE can provide an improved control of NIL stamp fabrication precision. In addition, pattern transfer with ALE is expected to be equally good for different size features, e.g., with ALE it should be possible to combine micro-and nano-structures on the same stamp as in contrast to standard reactive ion etching (RIE) processes ALE is not sensitive to surface loading if it is optimized for saturation properties. In addition, one can expect better control over small features sizes and shapes and an improved NIL stamp surface. In spite of all these potential advantages, the ALE applicability to NIL has not been studied yet, to the best of our knowledge. In this work we have developed an ALE process in a conventional inductively coupled plasma reactive ion etching (ICP-RIE) system, Plasmalab-100, from Oxford Instruments. In this process we etch Si with Cl 2 surface activation and Ar plasma removal of the activated layer in a way previously reported for another type of system [2] where an Ar + beam was used for the activated layer removal instead of Ar plasma as in our case. We have characterized the ALE process, see Fig. 1, and demonstrate that the process is highly anisotropic and has good etch selectivity (> 10) for SiO 2 masks. Furthermore, we use the ALE process for NIL stamp fabrication in combination with electron beam lithography in HSQ (hydrogen silsesquioxane) resist and demonstrate that the stamps can be used for NIL of features with size down to 30 nm, Fig. 2. We also investigate different limitations of the ALE process for NIL stamp fabrication. More details will be presented during the conference. At this stage, ALE seems to be a very promising technique for further development of NIL and additional studies are needed for process development and optimization.
Pitch subdivision of tantalum nitride (TaN) lines is demonstrated across a 200 mm wafer using a cyclic quasi‐atomic layer etch process in an inductively coupled plasma reactor. Chlorine (Cl2) and hydrogen (H 2) chemistries are introduced sequentially to an argon plasma in discrete steps to etch the TaN film. The starting lithographic pattern with critical dimension (CD) of approximately 82 nm and pitch of 200 nm thus yields lines of approximately 40 nm CD and 100 nm pitch with minimal line edge roughness increase. We identify a synergistic effect between H 2‐exposed TaN and Cl 2 plasma as contributing to this result, as well as a potential link to surface oxidation. Optical emission spectroscopy analysis of the plasma discharge is used to characterize reactive species densities and explain the observed changes in profile. Pitch multiplication of tantalum nitride (TaN) line/space patterns is demonstrated using a plasma‐enhanced Cl 2‐based cyclic etch process. Modification of the surface through H 2 exposure and surface oxidation from mask materials are examined as facilitating factors. Cyclic quasi‐ALE (q‐ALE) processes show great potential for surpassing the limits of conventional plasma etching due to the tunability of discrete reactions.
Nanoimprint lithography (NIL) has the potential for low-cost and high-throughput nanoscale fabrication. However, NIL quality and resolution are usually limited by the shape and size of the nanoimprint stamp features. Atomic Layer Etching (ALE) can provide a damage-free pattern transfer with ultimate etch control for features of all length scales, down to atomic scale, and for all feature geometries, which is required for good quality and high-resolution nanoimprint stamp fabrication. Here, we present an ALE process for nanoscale pattern transfer and high-resolution nanoimprint stamp preparation. This ALE process is based on chemical adsorption of a monoatomic layer of Cl2 on the silicon surface, followed by the removal of a monolayer of Cl2-modified silicon by Ar bombardment. The nano-patterns of different geometries, loading and pitches were fabricated by electron beam lithography on a Si wafer and ALE was subsequently performed for the pattern transfer using resist as an etch mask. The post-ALE patterns allowed us to study different effects and limitations of the process, such as trenching and sidewall tapering. The ALE-processed Si wafers were used as hard nanoimprint stamps in a thermal nanoimprint process. Features as small as 30 nm were successfully transferred into a PMMA layer, which demonstrated a great potential of ALE in fabricating nanoimprint stamps with ultra-high resolution.
