Toshiro Ono

Electron Cyclotron Resonance Plasma Deposition Technique Using Raw Material Supply by Sputtering

A low temperature plasma deposition method using a raw material supply by sputtering has been developed. A microwave electron cyclotron resonance technique was used for highly ionized plasma generation and plasma stream extraction at low gas pressures of 10-3 to 10-1 Pa. Gas molecules, and particles sputtered by ions in the plasma stream are ionized and transported to the specimen substrate with an energy of 10 to 30 eV. Fully oxidized, dense and high quality films of tantalum oxide and aluminum oxide were obtained at room temperature.

Reactive ion stream etching utilizing electron cyclotron resonance plasma

Reactive ion stream etching has been developed for highly accurate etching with little bombardment induced damage by utilizing an electron cyclotron resonance (ECR) plasma. The ion energy during etching is controlled by utilizing the interaction between the ECR plasma and a divergent magnetic field, in a low energy range from 20 to 50 eV at low gas pressures of 10−2 Pa. Highly accurate submicron patterns of polysilicon and molybdenum were obtained with high selectivities to SiO2, larger than 30, by using Cl2 gas as the main etching gas.

An electron cyclotron resonance plasma deposition technique employing magnetron mode sputtering

Magnetron mode sputtering was applied to an electron cyclotron resonance (ECR) plasma deposition technique as a material supply at low gas pressures of 10−2 Pa. Fully reacted metallic‐compound films were deposited at low temperatures with much higher rates than those obtained in conventional reactive sputtering: 800 A/min for Al2O3 film and 1000 A/min for Ta2O5 film with uniformity of ±5% within an area of 10 cm in diameter. These results were used to develop an automated system. The superior deposition characteristics are due to the high‐rate sputtering of the metallic target surface in reactive gas, and to the features of the film formation reaction enhanced in the ECR plasma deposition technique.

Low-Temperature Formation of High-Quality

We have fabricated an Al2O3/GeO2 gate-dielectric stack on p-type Ge by electron-cyclotron-resonance plasma oxidation and sputtering without external substrate heating. We show that the midgap interface state density at the GeO2/Ge interface is 4.5 × 1010 cm-2 · eV-1. The hysteresis observed in capacitance-voltage measurements is reduced to 50 mV when the gate bias is swept from accumulation to inversion and back to accumulation or after a single dummy sweep from inversion to accumulation, indicating the possibility that the bulk oxide traps causing the hysteresis are deactivated by the injected holes. The band gap of GeO2 was determined by internal photoemission measurements to be 4.7 eV. The conduction- and valence-band offsets at the GeO2/Ge interface are moderately symmetric and large with values of 1.8 and 2.2 eV, respectively. These promising results suggest that low-temperature plasma-grown GeO2 is a suitable interlayer between high-dielectric-constant dielectrics and Ge.

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Ultrathin oxide films (SiO2, Al2O3,Ta2O5) with a minimum thickness of 2 nm have been deposited at low temperature by electron cyclotron resonance (ECR) sputter utilizing a plasma source coupled with a divided microwave beam. The uniformity of the film thickness was within ±2% over a 150 mm wafer. The surface roughness measured by atomic force microscopy was only 0.48 nm for a 100-nm-thick Al2O3 film. The fixed charge density of the Al/SiO2/Si metal oxide semiconductor capacitors decreased with increasing oxygen flow rate and substrate temperature during SiO2 deposition. A very low fixed charge density of about 5×1010 cm−2 was obtained without annealing the capacitor. The resistivities of SiO2, Al2O3, and Ta2O5 films with thicknesses from 2 to 40 nm were on the order of 1015 Ω cm. Under low electric fields the leakage current was a hopping current and under high electric fields it was a Poole–Frenkel current. The typical dielectric strength was 10 MV/cm for SiO2 and Al2O3 films. A high dielectric constant ...

Interlayer for High-

We have developed an electron cyclotron resonance (ECR) plasma source for conductive film deposition. In this source, 2.45 GHz microwaves are divided into two directions by an E‐plane divider and pass through a quartz window into the composer, where the microwave electric field is parallel to the external magnetic field. The quartz windows are set in the blind space from the ECR plasma and in a region of higher magnetic field than that of the ECR condition (875 G). The composed microwaves are transported from the higher magnetic field region to the ECR magnetic field region in the plasma source. Highly ionized plasma of over 10 mA/cm2 has been generated by preventing plasma generation in the composer. A good uniformity of ±5% over a 6 in. diameter has been obtained. TiN films and Al films have been deposited with high reliability over an extended operation time.

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An electron cyclotron resonance (ECR) plasma source for conductive film deposition has been developed and applied to chemical vapor deposition (CVD) and sputtering deposition. In the source, 2.45 GHz microwaves are divided into two directions and transported into the composer through quartz windows which maintain the vacuum. The windows are set blind to the ECR plasma to prevent film deposition on them and in a region of higher magnetic field than that of the ECR condition to produce high density plasma. High ion current densities over 10 mA/cm2 can be stably obtained with this source. In applying the source to CVD, SiC films can be deposited with high reliability using C2H4/SiH4 plasma. Moreover, Ti films can be deposited by using a sputtering material supply. Using a rotating inclined substrate holder the uniformity of the film is found to improve and a uniformity of ±5% should be obtained over a 6‐in. wafer.

Gate Dielectrics/Ge by Electron-Cyclotron-Resonance Plasma Techniques

In this paper, we present an equivalent circuit model of a germanium (Ge) MIS structure that is biased in the inversion region, which includes the effects of the high intrinsic carrier density and high diffusion-limited conductance of the Ge substrate at room temperature. The model can successfully express the gate bias and frequency dependences of the capacitance characteristics that are specific to the Ge MIS capacitor. Moreover, it will be shown that the interface trap density and its gate bias dependence in the inversion region can be spectroscopically determined from the gate bias and measurement frequency dependences of the equivalent parallel conductance of the Ge surface.

Ultrathin oxide films deposited using electron cyclotron resonance sputter

The gate-dielectric characteristics of an ultrathin Al2O3 film deposited by electron cyclotron resonance sputtering are investigated. The sputtering process is classified as operating in either of two deposition modes: a metal mode and an oxide mode. Characteristics of the deposited films, such as their surface morphology, uniformity of thickness, and degrees of interlayer-oxide formation, are presented for both modes. The electrical characteristics of metal-mode Al2O3 films after annealing in a high vacuum (around 10−4 Pa) are looked at in detail. The metal-mode condition and high-vacuum annealing prevents the formation of interlayer oxide and reduces the flat-band voltage (VFB) shift but also produces a rather large capacitance–voltage (C–V) hysteresis loop. A small equivalent oxide thickness of 1 nm, low values for leakage current of around 2×10−3 A/cm2, and a fixed negative-charge density of 7×1010 cm−2 are demonstrated for the metal-mode films. The large C–V hysteresis loop is reducible by oxidation.

Electron cyclotron resonance plasma source for conductive film deposition

The authors have fabricated germanium (Ge) metal-insulator-semiconductor (MIS) structures with a 7-nm-thick tantalum pentaoxide (Ta2O5)∕2-nm-thick germanium nitride (GeNx) gate insulator stack by electron-cyclotron-resonance plasma nitridation and sputtering deposition. They found that pure GeNx ultrathin layers can be formed by the direct plasma nitridation of the Ge surface without substrate heating. X-ray photoelectron spectroscopy revealed no oxidation of the GeNx layer after the Ta2O5 sputtering deposition. The fabricated MIS capacitor with a capacitance equivalent thickness of 4.3nm showed excellent leakage current characteristics. The interface trap density obtained by the modified conductance method was 4×1011cm−2eV−1 at the midgap.