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Semiconductor device and method of fabricating same
| Details |
Inventors: Yamazaki, Shunpei;
Assignee: Semiconductor Energy Laboratory Co., Ltd. (Kanagawa-ken, JP)
Primary Examiner: Whitehead, Jr.; Carl
Assistant Examiner: Mitchell; James M.
Attorney, Agent or Firm: Robinson; Eric J. Robinson Intellectual Property Law Office, P.C.
There are disclosed TFTs that have excellent characteristics and can be fabricated with a high yield. The TFTs are fabricated, using an active layer crystallized by making use of nickel. Gate electrodes are comprising tantalum. Phosphorus is introduced into source/drain regions. Then, a heat treatment is performed to getter nickel element in the active layer and to drive it into the source/drain regions. At the same time, the source/drain regions can be annealed out. The gate electrodes of tantalum can withstand this heat treatment. |
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DETAILED DESCRIPTION It is an object of the present invention to provide a method of fabricating TFTs in which the foregoing problems have been mitigated.
One embodiment of the present invention lies in a device comprising: a gate electrode comprising a heat-resistant material; and an active layer comprising a semiconductor film comprising silicon to which a catalytic element is intentionally added to promote crystallization of silicon.
The source and drain regions of the active layer are more heavily doped with the metallic element than other regions.
Tantalum or a material mainly comprising tantalum can be used as the heat-resistant material described above.
Nickel can be the most favorable element as the catalytic element for promoting crystallization of silicon.
In the configuration described above, the concentration of the catalytic element in the source and drain regions is higher than in other regions by two or more orders of magnitude.
This can lower the catalytic element concentration in the channel region.
In consequence, the characteristics and reliability of the finished TFTs can be enhanced.
More particularly, the concentration of the catalytic element in the channel region is reduced less than 5.
times.
10.
sup.
16 atoms/cm.
sup.
3.
Consequently, the characteristics and the reliability of the TFTs can be improved.
One or more elements selected from the group consisting of Fe, Co, Ru, Rh, Pd, Os, Ir, Pt, Cu, and Au can be used as the aforementioned catalytic element, though the merits are less conspicuous than where nickel is used alone.
Furthermore, Ni may be added to one or more elements selected from this group, and the resulting compound may be used together with other catalytic element.
Another structure of the invention lies in a method of fabricating a semiconductor device having a gate electrode comprising a heat-resistant material and an active layer comprising a semiconductor film comprising silicon to which a catalytic element for promoting crystallization of silicon is added
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MEMS 
