Koji Egami

Influence of as‐deposited film structure on 〈100〉 texture in laser‐recrystallized silicon on fused quartz

A strong 〈100〉 texture has been achieved in cw neodymium:yttrium aluminum garnet laser recrystallization of the 700 °C low pressure chemical vapor deposited (LPCVD) polycrystalline silicon films which exhibit 〈100〉 preferred orientation. When 〈110〉 texture is dominant in as‐deposited films, the 〈100〉 texture is not so strong as in the 700 °C LPCVD films. The dependence of the 〈100〉 texture on as‐deposited film structure implies that the 〈100〉 grain growth occurs under such a melting condition as the initial film structure is partially maintained.

Epitaxial film transfer technique for producing single crystal Si film on an insulating substrate

Epitaxial film transfer, a new technique for producing a single crystal Si film with both large size and high quality on an insulating substrate, is demonstrated. The technique in which an epitaxial Si film is transferred to a secondary substrate by using three fundamental processes of epitaxial growth, bonding of two wafers, and substrate elimination, can produce a 2‐in. single crystal Si film as thin as 1.5 μm on a insulating substrate. Thickness variation can be controlled to ±0.06 μm across a 2‐in. wafer. An epitaxial Si film is transferred without significant degradation in quality although a fine film waving exists.

Crystalline correlation of epitaxial Si films with underlying spinel films in Si/(MgO Al2O3) spinel/Si structure

Using epitaxial magnesia spinel (MgO Al2O3) films on (100) Si, heteroepitaxial Si films (0.6–3 μm) on these substrates are obtained by a conventional chemical vapor deposition method. The crystallinity of both epitaxial Si and spinel films was investigated by x‐ray diffraction techniques. Silicon film quality becomes more perfect on thinner spinel films with smoother surfaces in the range of more than ∼0.1 μm, in spite of the spinel crystal perfection becoming inferior with decreasing film thickness. These results are discussed in terms of the spinel surface roughness effect on Si nuclei coalescence.

Laser recrystallization of silicon stripes in SiO2 grooves with a polycrystalline silicon sublayer

A new substrate structure has been proposed for obtaining laser‐recrystallized silicon on quartz glass. Single crystal Si stripes as large at 12×500 μm, dielectrically isolated with a width as small at 1.5 μm, have been obtained by use of the new structure, in which polysilicon stripes are placed in SiO2 grooves and a polycrystalline silicon sublayer is inserted between the SiO2 layer and quartz glass to improve the thermal profile in recrystallization. The proposed structure is useful for realizing both enlargement and positional control of Si grains.

Low‐temperature grain growth of initially 〈100〉 textured polycrystalline silicon films amorphized by silicon ion implantation with normal incident angle

〈100〉 textured polycrystalline silicon films deposited by low pressure chemical vapor deposition at 700 °C on SiO2/Si substrates have been amorphized by implantation with 100 keV 28Si+ ion at a dose of 2×1015/cm2 and thermally annealed at 550 °C for 168 h. In a 0.15‐μm‐thick film, the larger grain growth (1.5 μm) occurred, and the 〈100〉 oriented grains were found. This fact implies a possibility of the 〈100〉 oriented and large silicon grains formation by seed selection through ion channeling technique even if the 〈100〉 textured polycrystalline silicon film with relatively small channeling yields is utilized.

Crystallographic orientation control of silicon stripes in SiO2 grooves using a new double laser annealing technique

Crystallographic orientation control using a new double laser annealing of silicon stripes in SiO2 grooves is presented. In the laser recrystallization of silicon stripes in the structure consisting of SiO2 grooves/polysilicon sublayer/quartz glass substrates, first, a part of the Si stripe is intentionally recrystallized by a cw Nd:yttrium aluminum garnet laser to obtain 〈100〉 texture with a small grain size. Next, using these 〈100〉 oriented Si grains as seed crystals, 〈100〉 oriented large Si stripes are obtained by scanning a cw Ar ion laser along the stripe direction. This double laser annealing technique for orientation control can potentially be used to fabricate three‐dimensional devices.

Germanium film on SiO2 with a 〈100〉 texture deposited by the rf sputtering technique

Germanium (Ge) films on SiO2 with 〈100〉 texture deposited by a sputtering technique and the texture enhancement by a subsequent solid‐state thermal annealing are demonstrated for the first time. A 0.6‐μm‐thick Ge film on a surface oxidized Si wafer deposited by the rf sputtering technique at 600 °C produces a 〈100〉 texture, and the preferential orientation of the film is enhanced by a conventional grain growth process at 900 °C (approximately 0.95Tm, where Tm is the melting point in the Kelvin scale) for 1 h, while the crystallographic texture of the films has never changed at 650 °C (0.75Tm) annealing. The texture enhancement is interpreted by the existence of 〈100〉 oriented precursors and a simple coalescence and rearrangement model.

Hydrostatic float polishing for wafer preparation

A new float polishing technique for wafer preparation has been developed. The technique employs a floating gap controlled by static pressure, and is useful for both planarization and damage‐free surface preparation.

Strong 〈100〉 texture formation of polycrystalline silicon films on amorphous insulator by laser recrystallization

This letter demonstrates the optimization for the strong 〈100〉 texture formation of low pressure chemical vapor deposited (700 °C) polycrystalline silicon films on SiO2/backing substrates such as quartz glass, sapphire, and silicon by cw Ar ion laser recrystallization. We have examined the correlation of 〈100〉 texture formed with both the dwell time and the grain size. It has been found that the long dwell time (∼30 ms) and rather low laser power density are favorable for the formation of the strong 〈100〉 texture with lamellalike grains.

Minimization of Residual Stress in SOI Films by Using AlN Interlaid Insulator

It was found that residual stress in SOI film recrystallized by laser annealing depends on both substrates and interlaid insulator materials. For a stress free Si film, a thermal expansion coefficient of the underlaid material, comprising of a substrate and an interlaid insulator should be slightly larger than that of Si. AlN found to be a very effective interlaid insulator. In the structure of resolidified-Si/3 µm thick insulator/Si substrate, the residual stress in SOI film on AlN (5×109 dyn/cm2) was lower than that on SiO2 (7×109 dyn/cm2).