An object is to provide a semiconductor device of which a manufacturing process is not complicated and by which cost can be suppressed, by forming a thin film transistor using an oxide semiconductor film typified by zinc oxide, and a manufacturing method thereof. For the semiconductor device, a gate electrode is formed over a substrate; a gate insulating film is formed covering the gate electrode; an oxide semiconductor film is formed over the gate insulating film; and a first conductive film and a second conductive film are formed over the oxide semiconductor film. The oxide semiconductor film has at least a crystallized region in a channel region.

Semiconductor device, and manufacturing method thereof

Process gas discharged from a bypass pipe to a gas exhaust system can be prevented from diffusing back to the inside of a process chamber without having to install a dedicated vacuum pump at the downstream side of the bypass pipe. The substrate processing apparatus includes a process chamber accommodating a substrate, a gas supply system supplying process gas from a process gas source to the process chamber for processing the substrate, a gas exhaust system configured to exhaust the process chamber, two or more vacuum pumps installed in series at the gas exhaust system, and a bypass pipe connected between the gas supply system and the gas exhaust system. The most upstream one of the vacuum pumps is a mechanical booster pump, and the bypass pipe is connected between the mechanical booster pump and the rest vacuum pumps located at a downstream side of the mechanical booster pump.

Substrate Processing Apparatus

The field of plasma etching is reviewed. Plasma etching, a revolutionary extension of the technique of physical sputtering, was introduced to integrated circuit manufacturing as early as the mid 1960s and more widely in the early 1970s, in an effort to reduce liquid waste disposal in manufacturing and achieve selectivities that were difficult to obtain with wet chemistry. Quickly, the ability to anisotropically etch silicon, aluminum, and silicon dioxide in plasmas became the breakthrough that allowed the features in integrated circuits to continue to shrink over the next 40 years. Some of this early history is reviewed, and a discussion of the evolution in plasma reactor design is included. Some basic principles related to plasma etching such as evaporation rates and Langmuir–Hinshelwood adsorption are introduced. Etching mechanisms of selected materials, silicon, silicon dioxide, and low dielectric-constant materials are discussed in detail. A detailed treatment is presented of applications in current silicon integrated circuit fabrication. Finally, some predictions are offered for future needs and advances in plasma etching for silicon and nonsilicon-based devices.

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Plasma etching: Yesterday, today, and tomorrow

Atomic layer etching (ALE) is a technique for removing thin layers of material using sequential reaction steps that are self-limiting. ALE has been studied in the laboratory for more than 25 years. Today, it is being driven by the semiconductor industry as an alternative to continuous etching and is viewed as an essential counterpart to atomic layer deposition. As we enter the era of atomic-scale dimensions, there is need to unify the ALE field through increased effectiveness of collaboration between academia and industry, and to help enable the transition from lab to fab. With this in mind, this article provides defining criteria for ALE, along with clarification of some of the terminology and assumptions of this field. To increase understanding of the process, the mechanistic understanding is described for the silicon ALE case study, including the advantages of plasma-assisted processing. A historical overview spanning more than 25 years is provided for silicon, as well as ALE studies on oxides, III–V compounds, and other materials. Together, these processes encompass a variety of implementations, all following the same ALE principles. While the focus is on directional etching, isotropic ALE is also included. As part of this review, the authors also address the role of power pulsing as a predecessor to ALE and examine the outlook of ALE in the manufacturing of advanced semiconductor devices.

https://avs.scitation.org/doi/pdf/10.1116/1.4913379

Overview of atomic layer etching in the semiconductor industry

Methods for accurate and conformal removal of atomic layers of materials make use of the self-limiting nature of adsorption of at least one reactant on the substrate surface. In certain embodiments, a first reactant is introduced to the substrate in step (a) and is adsorbed on the substrate surface until the surface is partially or fully saturated. A second reactant is then added in step (b), reacting with the adsorbed layer of the first reactant to form an etchant. The amount of an etchant, and, consequently, the amount of etched material is limited by the amount of adsorbed first reactant. By repeating steps (a) and (b), controlled atomic-scale etching of material is achieved. These methods may be used in interconnect pre-clean applications, gate dielectric processing, manufacturing of memory devices, or any other applications where removal of one or multiple atomic layers of material is desired.

Adsorption based material removal process

An experimental system and methodology were developed to realize dry etching of single crystal silicon with monolayer accuracy. Atomic layer etching of silicon is a cyclic process composed of four consecutive steps: reactant adsorption, excess reactant evacuation, ion irradiation, and product evacuation. When successful, completion of one cycle results in removal of one monolayer of silicon. The process was self‐limiting with respect to both reactant and ion dose. Control of the ion energy was the most important factor in realizing etching of one monolayer per cycle.

Realization of atomic layer etching of silicon

A molecular dynamics study of 50 eV Ar+ ion bombardment of a Si(100) crystal with a monolayer of adsorbed chlorine was conducted to simulate atomic layer etching (ALET) of Si. The total reaction yield (Si atoms removed per ion) was 0.172; 84% of silicon was removed as SiCl, 8% as elemental Si and 8% as SiCl2. Based on the total yield, an ion dose of 1.16×1016 ions/cm2 is necessary to remove one monolayer of silicon. Reaction occurs during the ps time scale of the ion–solid interaction. Long time‐scale chemistry (100s of ms) which is possible in ion‐assisted etching with simultaneous exposure to neutral and ion beams does not happen in ALET. It was further found that 93% of Si originated from the top silicon layer and 7% from the layer underneath. In addition, some structural ‘‘damage’’ was induced to the top three silicon layers. It appears that perfect ALET of silicon is not possible for an ion energy of 50 eV.

Molecular dynamics simulation of atomic layer etching of silicon

Nearly stoichiometric silicon, germanium, and tin nitride thin films were deposited from the corresponding homoleptic dimethylamido complexes M (NMe2)4 (M=Si, Ge, Sn; Me=CH3), and an ammonia plasma at low substrate temperatures (<400 °C). Tin nitride films were also deposited from Sn (NMe2)4 and ammonia without plasma activation. The films showed little (<few at. %) or no carbon or oxygen contamination. The barrier properties of the silicon and germanium nitride films were evaluated by using backscattering spectrometry. Homoleptic dimethylamido silicon and germanium compounds are attractive alternatives to silane and germane for use in the plasma‐enhanced chemical vapor deposition of nitride thin films.

Plasma‐enhanced chemical vapor deposition of silicon, germanium, and tin nitride thin films from metalorganic precursors

Nearly stoichiometric aluminum and gallium nitride thin films were prepared from hexakis(dimethylamido)dimetal complexes, M2[N(CH3)2]6 (M=Al,Ga), and ammonia at substrate temperatures as low as 200 °C by using low pressure thermal and plasma enhanced chemical vapor deposition (CVD). Both processes gave films that showed little or no carbon (<5 at. %) and no oxygen (<few at. %) contamination, but in all cases there was hydrogen incorporation. The films were highly transparent in the ultraviolet and visible regions. The barrier properties of the aluminum nitride films in a Si/AlN/Au metallization scheme were examined by using backscattering spectrometry. The growth rate of the aluminum nitride films was as high as 1300 A /min. Overall, the results suggest that M2[N(CH3)2]6 (M=Al,Ga) are promising precursors for low‐temperature/low‐pressure thermal and plasma‐enhanced CVD of group III nitride thin films.

Chemical vapor deposition of aluminum and gallium nitride thin films from metalorganic precursors

Silicon nitride films are grown by plasma enhanced chemical vapor deposition from tetrakis(dimethylamido)silicon, Si(NMe2)4, and ammonia precursors at substrate temperatures of 200-400 °C. Backscattering spectrometry shows that the films are close to stoichiometric. Depth profiling by Auger electron spectroscopy shows uniform composition and no oxygen or carbon contamination in the bulk. The films are featureless by scanning electron microscopy under 100,000X magnification.

https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0884291400076135

Satish D. Athavale

Papers

Realization of atomic layer etching of silicon

Molecular dynamics simulation of atomic layer etching of silicon

Plasma‐enhanced chemical vapor deposition of silicon, germanium, and tin nitride thin films from metalorganic precursors

Chemical vapor deposition of aluminum and gallium nitride thin films from metalorganic precursors

Plasma enhanced chemical vapor deposition of silicon nitride films from a metal-organic precursor