Sanyo Electric Co., Ltd.

Yoshihiro Morimoto

Kiyoshi Yoneda

Toshifumi Yamaji

Kiichi Hirano

Shiro Nakanishi

Kazuhiro Imao

Tsutomu Yamada

Nobuhiko Oda

Takashi Kuwahara

Naoya Sotani

Ken Wakita

Hidenori Ogata

Koji Suzuki

Hisashi Abe

Hiroki Hamada

Yushi Jinno

Kyoko Hirai

Eiji Taguchi

Nobuhiro Gouda

Shoichiro Matsumoto

Masaru Takeuchi

Shoji Sudo

Takashi Hagino

Toshio Monzen

Kaoru Takeda

Kou Masahara

For obtaining p-Si by irradiating a laser beam to an a-Si layer to polycrystallize, an energy level in a region to be irradiated by the laser beam is set such that a level at the rear area of the region along a scan direction of the laser beam is lower than that at the front area or the center area of the region. The energy level at the front area or the center area of the region is set such that it is substantially equal to or more than the upper limit energy level which maximizes a grain size of the p-Si obtained. Since an energy profile is set as described above, when the laser beam is scanned on the a-Si layer, an irradiated energy of the laser on the region is gradually lowered from the upper limit as the laser beam passes through, which allows the semiconductor layer to be annealed within an optimal energy level during the latter half of the annealing process.

Laser anneal method of a semiconductor layer

In a bottom gate-type thin-film transistor manufacturing method, after ion doping, an ion stopper () is removed. The ion stopper () does not remain in the interlayer insulating film () lying immediately above the gate electrode. The thin-film transistor has such a structure that no ion stopper (), and the interlayer insulating layer is in direct contact with at least the channel region of the semiconductor layer (). The impurity concentration in the vicinity of the interface between the interlayer insulating film and the semiconductor layeris 10atoms/cc or less. This structure can prevent the back channel phenomenon and reduce variations in characteristic resulting from variations in manufacturing.

Bottom gate-type thin-film transistor and method for manufacturing the same

A method of fabricating a thin film transistor by setting the temperature of a heat treatment for crystallizing an active layer which is formed on a substrate at a level not deforming the substrate and activating an impurity layer in a heat treatment method different from that employed for the heat treatment, and a semiconductor device prepared by forming a heat absorption film, a semiconductor film, a gate insulating film, and a gate electrode on a substrate, the heat absorption film being provided within a region substantially corresponding to the semiconductor film.

Semiconductor device, display device and method of fabricating the same

In a fabrication process of a semiconductor device for use in a TFT liquid crystal display system, before the start of crystallizing amorphous silicon (a-Si), dehydrogenation annealing is carried out to not only decrease the density of hydrogen in the p-Si film () to 5&#xd7;10atoms/cmat most but also to prevent crystallization of the a-Si film () being obstructed due to possible excessive hydrogen remaining in the film. With the p-Si film () covered with an interlayer insulation film () in the form of a plasma nitride film, annealing is then carried out in nitrogen atmosphere at a temperature of 350&#xb0; C. to 400&#xb0; C. for one to three hours, more preferably 400&#xb0; C. for two hours. The result is that hydrogen atoms in the p-Si film () efficiently terminate dangling bonds of the film and hence do not become excessive, thus improving the electrical characteristics of the semiconductor device.

Semiconductor device and method of manufacturing the same comprising thin film containing low concentration of hydrogen

An a-Si film formed on an insulating substrate is irradiated with a laser to obtain a p-Si film, which is then exposed to an oxidation atmosphere to form a surface oxide film. The surface oxide film is then removed to reduce the height of a projection generated on the surface of the p-Si film, thereby planarizing the surface of the p-Si film.

Method for manufacturing a semiconductor film having a planarized surface

An a-Si film () formed on an insulating substrate () is irradiated with a laser so that the a-Si film () is fused and recrystallized to form a p-Si film (). Projections () generated on the p-Si film () at this stage are eliminated by irradiation of ion beams at the incident angle of 60&#xb0; to 90&#xb0; using an ion milling method to planarize the surface of the p-Si film (), thereby creating sufficient insulation between the p-Si film () and gate electrodes ().

Semiconductor device and method of producing the same

In a bottom gate-type thin-film transistor manufacturing method, after ion doping, an ion stopper is removed. The ion stopper does not remain in the interlayer insulating film lying immediately above the gate electrode. The thin-film transistor has such a structure that no ion stopper, and the interlayer insulating layer is in direct contact with at least the channel region of the semiconductor layer. The impurity concentration in the vicinity of the interface between the interlayer insulating film and the semiconductor layer is 10 atoms/cc or less. This structure can prevent the back channel phenomenon and reduce variations in characteristic resulting from variations in manufacturing.

A laser annealing apparatus is provided in which laser light is irradiated onto an amorphous semiconductor layer placed inside an annealing chamber through a chamber window, thereby poly-crystallizing the amorphous semiconductor film. Inside the annealing chamber a low degree vacuum (about 1.3&times;10 Pa to about 1.3 Pa) is maintained at a room temperature. An inert gas such as nitrogen, hydrogen, or argon is introduced into the atmosphere while maintaining the low degree vacuum. As a result, the surface smoothness of the polycrystalline semiconductor layer is comparable to that resulting from high degree vacuum annealing, while, unlike high degree vacuum annealing, there is less contamination of the chamber window and productivity is improved.

Method for manufacturing polycrystalline semiconductor layers and thin-film transistors and laser annealing apparatus

In a fabrication process of a semiconductor device for use in a TFT liquid crystal display system, before the start of crystallizing amorphous silicon (a-Si), dehydrogenation annealing is carried out to not only decrease the density of hydrogen in the p-Si film ( ) to 5&times;10 atoms/cm at most but also to prevent crystallization of the a-Si film ( ) being obstructed due to possible excessive hydrogen remaining in the film. With the p-Si film ( ) covered with an interlayer insulation film ( ) in the form of a plasma nitride film, annealing is then carried out in nitrogen atmosphere at a temperature of 350&deg; C. to 400&deg; C. for one to three hours, more preferably 400&deg; C. for two hours. The result is that hydrogen atoms in the p-Si film ( ) efficiently terminate dangling bonds of the film and hence do not become excessive, thus improving the electrical characteristics of the semiconductor device.

Semiconductor device having a semiconductor thin film containing low concentration of unbound hydrogen atoms and method of manufacturing the same

Reflectance of a p-Si film crystallized by laser annealing is measured, a wave length dependency of the reflectance is found, and a first order rate of change is calculated to determine a minimum value near a wave length of 500 nm. The value is to be an inherent optical value under the laser power and relates to a grain size measured by Secco etching or the like. A number of correspondence between the optical value and the grain size are recorded and linearly plotted. By calculating the optical value from the reflectance in the p-Si film at in-line, the grain size is correspondingly determined. Thus, the semiconductor film can be in-line monitored, thereby improving a yield and saving a cost in producing a semiconductor device.

Method and apparatus for evaluating semiconductor film, and method for producing the semiconductor film

A method of manufacturing a polycrystalline silicon film having a particular field effect mobility is disclosed. A first polycrystalline silicon film is formed on a transparent insulation substrate. The surface of the silicon film is oxidized, and an amorphous silicon film is formed on the first polycrystalline silicon film and oxide layer. The amorphous silicon film is subjected to a solid phase growth process to be converted to a second polycrystalline silicon film. The field effect mobility of the second polycrystalline silicon film can be adjusted to a desired value by controlling the relative thicknesses of the first and second polycrystalline silicon films.

Thin film transistors for display devices having two polysilicon active layers of different thicknesses

For obtaining p-Si by irradiating a laser beam to an a-Si layer to polycrystallize, an energy level in a region to be irradiated by the laser beam is set such that a level at the rear area of the region along a scan direction of the laser beam is lower than that at the front area or the center area of the region. The energy level at the front area or the center area of the region is set such that it is substantially equal to or more than the upper limit energy level which maximizes a grain size of the p-Si obtained. since an energy profile is set as described above, when the laser beam is scanned on the a-Si layer, an irradiated energy of the laser on the region is gradually lowered from the upper limit as the laser beam passes through, which allows the semiconductor layer to be annealed within an optimal energy level during the latter half of the annealing process.

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Inazawa, Japan

Yoshihiro Morimoto