Kiyotaka Takano

Growth of silicon crystal with a diameter of 400 mm and weight of 400 kg

Since 1996, we have been investigating the crystal growth of 400-mm silicon crystals as the next generation of silicon wafer size after 300 mm. The first dislocation-free crystal was grown in 1998, and the heaviest dislocation free crystal ever, weighing 413 kg, was safely grown in 2000 using a crystal suspending system. In this paper, we describe an experimental study on large-diameter silicon crystal growth, its growth conditions, and the crystal properties of 400-mm silicon crystals.

Relationship between grown-in defects and thermal history during CZ Si crystal growth

Abstract An abrupt change of the crystal growth rate at temperatures in the range 1150–1080°C affects the annihilation or the agglomeration of grown-in defects such as flow pattern defects (FPD), crystal originated particles (COP), laser scattering defects (LSTD) and the defects measured by an optical precipitate profiler (OPPDs). Moreover, it is demonstrated that the densities of FPDs and LSTDs correlate with each other, and also with the cooling rate in such a temperature range. These relationships were investigated by growing several silicon single crystals in 10 kinds of hot-zone (HZ) configurations designed by using a numerical simulation. The cooling rate from 1412°C, the melting point of silicon, to 1150°C does not seem to be so important for the generation or the annihilation of these defects.

Cavities owing to hydrogen in Si single crystals grown by continuously charging CZ method

The quality of Si single crystals with a diameter of up to 150 mm in the length between 1 m to 1.5 m, grown by continuously charging Czochralski (CCZ) method, is studied and the possibility of CCZ method is discussed. The profile of interstitial oxygen concentration (O i ) is almost constant along the growth direction. The profile of precipitated O i exhibits a slight decrease along the first half of the crystal length, and a more remarkable decrease along the latter half. Many pits with a diameter up to 15 μm are observed on a chemically polished surface of Si CCZ wafer. We believe the origin of these pits is cavities formed during CCZ crystal growth owing to hydrogen contained in raw granular polycrystalline Si. Besides the cavity problem, we have to solve some serious cost problems to apply CCZ method for actual production.

Numerical simulation for silicon crystal growth of up to 400 mm diameter in Czochralski furnaces

In the SSi project, the growth technologies for 400 mm silicon single crystals have been investigated by several numerical simulation techniques, global heat transfer analysis in a Czochralski (CZ) furnace, structural analysis, analysis of fluid dynamics for melt convection and argon gas flow. In this paper, the bake out process, the initial meltdown process, the dip process and the body process are numerically simulated, respectively. According to these results, the numerical simulation is very useful and necessary for development of the CZ furnace, designing of hot zone structures and the prediction of experimental results.

Evaluation of the quality of HMCZ Si single crystals with a diameter of 200 mm

We studied the quality of Si single crystals with a diameter of 200 mm grown by the horizontal magnetic field applied Czochralski (HMCZ) method. The dopant impurity fluctuation of HMCZ crystals is less than that of CZ ones when a crystal is grown by setting the seed rotation rate at 15 rpm. The micro-distribution profiles of interstitial oxygen concentration ([O i ]) exhibit the same behavior as those of CZ crystals except for low [O i ]. Moreover, the oxygen precipitation and the grown-in crystal defects of HMCZ crystals exhibit the same behavior as those of CZ ones. We believe HMCZ Si wafers with low [O i ] can be used for ULSI fabrication without any change of the fabrication process.

Characterization of interstitial oxygen striations in silicon single crystals

Oxygen precipitation occurs along growth striations in Czochralski-grown (CZ) silicon single crystal. Interstitial oxygen (Oi) striations in various CZ and horizontal magnetic field Czochralski-grown (HMCZ) silicon single crystals were studied with a micro-Fourier transform infrared spectroscopy (micro-FTIR) mapping system. These striations were found in most crystals. The Oi profiles were irregular but their periods and heights were about 0.8 mm and 0.2 × 1017 atoms/cm3 except for several cases. Subsequently, oxygen microprecipitation was investigated for various conditions of thermal treatment. It was found that homogeneous nucleation was inferred to be operative in CZ and HMCZ crystals.