Selective area oxidation of with an ambient scanning tunneling microscope

Day, H. C.; Allee, David R.

doi:10.1088/0957-4484/7/2/002

Cited by 8 publications

(3 citation statements)

References 19 publications

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“…However, there are few reports in the literature to address this subject. In 1996, Day and Allee 19 reported the possibility of local oxidation on silicon nitride using the tungsten tip of a scanning tunneling microscope ͑STM͒. Very recently, we have successfully proved the conversion of Si 3 N 4 to SiO x with a conductiveprobe AFM.…”

Section: Introductionmentioning

confidence: 90%

Nano-oxidation of silicon nitride films with an atomic force microscope: Chemical mapping, kinetics, and applications

Chien

Chou

Chen

et al. 2001

Journal of Applied Physics

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We demonstrate that local oxidation of silicon nitride films deposited on conductive substrates with a conductive-probe atomic force microscope ͑AFM͒ is a very promising approach for nanofabrication. Scanning Auger microscopy and spectroscopy are employed to verify the chemical changes after AFM-induced oxidation. Furthermore, the growth kinetics are found to have a logarithmic relationship of oxide height versus pulse duration ͓hϰln(t/t 0)͔. In contrast to rather slow thermal oxidation process, AFM-induced oxidation on silicon nitride has an anomalously high initial oxidation rate ͑ϳ30 000 nm/s at 10 V͒ and a small onset time t 0 ͑ϳ10 s͒. As for the applications in ultrahigh-density recording, an oxide dot array ͑ϳ100 Gbit/in. 2 ͒ produced by this process is demonstrated. The nitride film patterned by AFM can be utilized as an etching mask to fabricate ''subtractive'' silicon nanostructures, due to the large etching selectivity of Si 3 N 4 :SiO 2 :Si in various etchants. With this method, which is entirely compatible with the existing microelectronic processes, synthesis of ultrahigh packing density and ordered nanostructures could become readily achievable.

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Section: Introductionmentioning

confidence: 90%

Nano-oxidation of silicon nitride films with an atomic force microscope: Chemical mapping, kinetics, and applications

Chien

Chou

Chen

et al. 2001

Journal of Applied Physics

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“…As is well known, the conventional silicon nitride removal mechanism involves two steps, 17,23 the first and the rate-determining step is the hydrolysis of the silicon nitride at the surface to an oxide 11,15,16 and the second step is the removal of this oxide during polishing. It appears then that Ce 3+ ions, when present in the dispersion, facilitate the conversion of a thin layer of the nitride surface to some form of silicon oxynitride via the following overall reaction, as shown schematically in Figure 13.…”

Section: Proposed Mechanism For Silicon Nitride and Silicon Dioxide R...mentioning

confidence: 99%

“…9,10 Interestingly, however, room temperature electrochemical oxidation of thin nitride films to SiOx has been reported. The early work of Day and Allee 11 showed that low pressure chemical-vapor-deposited (LPCVD) SiN can be oxidized to SiOx using the tungsten tip of an STM operated at a voltage of 10 V and a current of 1 nA. This was followed by a report by Chien et al 12 about the local oxidation of LPCVD silicon nitride films, deposited on conductive substrates, using an AFM at a bias voltage of 10 V with initial oxide formation rates of ∼ 30,000 nm/s but lasting for only ∼10 μs.…”

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confidence: 99%

Role of Ce³⁺Ions in Achieving High Silicon Nitride Polish Rates

Alety

Sagi

Babu

2017

ECS J. Solid State Sci. Technol.

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We show that Ce 3+ ions when used as an additive to ceria dispersions enhance plasma-enhanced chemical-vapor-deposited silicon nitride polish or removal rates (RRs). Ceria slurries (0.1 wt% and 140 nm avg. size) containing 2.3 mM Ce(NO 3 ) 3 and no other additive gave nitride RRs of ∼300 nm/min at 4 psi and ∼350 nm/min at 5 psi, both at pH4. The nitride RRs measured in the presence of Ce(NO 3 ) 3 , Ce(CH 3 COO) 3 and KNO 3 suggest that the rate enhancement is solely due to the presence of Ce 3+ ions. We discuss the underlying mechanism causing high silicon nitride RRs in the presence of Ce 3+ ions based on XPS analysis of pre-and post-polished silicon nitride and oxynitride film surfaces, streaming potential data and high oxynitride RRs obtained using the same ceria particle-based slurries as above. It is suggested that the Ce 3+ ions convert the upper layers of the nitride film into an oxynitride that is polished by the abrasives at a high rate. In this process, the conversion of the nitride film seems to be the rate controlling step with the oxidation and polishing occurring in a repetitive manner. © The Author Semiconductor device scaling led to the shrinking of device structures and also created new challenges in the front end of line integration schemes that required several additional new chemical mechanical planarization (CMP) steps. One such new integration scheme in the replacement metal gate (RMG) process is the self-aligned contact (SAC) module where a silicon nitride CMP step is required as shown in Figure 1 (Redrawn from Ref. 1). Since the composition of this silicon nitride film and those used in our experiments is nonstoichiometric, we will refer to them by the generic symbol SiN. In this SAC module, one of the challenges is the misalignment of the contact metal and source/drain, leading to device failure. In order to provide a wider process margin in contact alignment, a SiN cap is deposited on top of the metal gate.1 In the process of depositing this SiN cap, there will always be some SiN overburden, as shown in Fig. 1, which needs to be removed using a highly selective nitride slurry that has a very low oxide removal rate to minimize loss of the underneath oxide. This removal rate selectivity requirement in this SiN cap CMP process is the reverse of that needed in the more conventional shallow trench isolation (STI) CMP and is often referred to as reverse STI selectivity. 2-8Several authors 2-8 investigated reverse STI selectivity CMP processes using ceria and silica based dispersions with various additives. Recently Bae et al.2 achieved highly selective Si 3 N 4 to SiO 2 removal rate (RR) ratio of ∼ 95.0 at pH 1.5 using modified silica abrasives. They modified the surface charge of the silica abrasives toward more negative values (−50 mV) since creating higher negative charge on silica abrasives enables stronger attractive forces between them Si 3 N 4 films and a stronger repulsive force toward silica films in a low pH environment, which can lead to high nitride to oxide removal rate selectiv...

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