Active solid-state devices (e.g. – transistors – solid-state diode – Combined with electrical contact or lead – Of specified material other than unalloyed aluminum
Reexamination Certificate
2003-04-23
2004-12-07
Wilson, Allan R. (Department: 2815)
Active solid-state devices (e.g., transistors, solid-state diode
Combined with electrical contact or lead
Of specified material other than unalloyed aluminum
C257S754000, C257S763000
Reexamination Certificate
active
06828679
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a solid image pickup device and a method for producing the same, and in particular a solid image pickup device of mono-layered electrode structure and a producing method thereof.
2. Description of the Related Art
CCD solid image pickup devices used to such as area sensors have an electric charge transfer electrode for transferring signal charges from a photoelectric transferring section. A plurality of electric charge transfer electrodes is disposed on electric charge transferring paths located on a semi-conductor substrate, and each of the electric charges is arranged next to each other and driven in succession.
In the solid image pickup device, the number of imaging pixels is increasing. With increasing of the number of the imaging pixels, high-speed transfer of the signal charge, that is, drive by high-speed pulse of the charge transfer electrode is required. Therefore, the charge transfer electrode is demanded to have low resistance. As a method for producing the low resistance, it has been proposed to produce the charge transfer electrodes with two-layered structure of a silicon based conductive material such as a polycrystalline silicon and a metallic silicide.
On the other hand, an area of the photoelectric transferring section tends to become narrower with increasing the number of the imaging pixels. For concentrating much light at a narrow area, it is important to further lower height of surroundings of the photoelectric transferring section, such as charge transfer electrode producing section, with respect to the surface of the photoelectric transferring section. Therefore, the charge transfer electrode having a so-called mono-layered structure has been proposed, not overlapping the charge transfer electrodes one another. With the charge transfer electrode having the mono-layered structure, a light shielding property of a shielding film on the transfer electrode parts is improved more effectively.
However, in case the charge transfer electrode of the mono-layered structure is driven at high-speed pulse, a distance (gap) between the charge transfer electrodes arranged next to each other must be formed narrowly (0.1 &mgr;m or less). For providing pattern sizes as this degree (0.1 &mgr;m or less), a stepper of high cost is required as in a manner of using an EB direct drawing method. Moreover, even if the electrode pattern can be obtained, it is extremely difficult to fill the insulating film in a fine area between electrodes, probably causing pressure proof to be weakened, and practically insufficient.
Further, in case of that the charge transfer electrodes has the two-layered structure of the silicon based conductive material and the metallic silicide, it is difficult to oxidize metals of high melting points or metallic compounds of high melting points such as tungsten or tungsten suicide. Even if oxidation can be effected, electric pressure proof of an obtained insulating film is not sufficient. Therefore, it is impossible to form insulating films practically available caused by generating oxidation between the electrodes.
It is also proposed a two-layered structure charge transfer electrode, which has composed of the silicon based conductive material and the metallic silicide (see JP-A-2000-196060), instead of a mono-layered structure charge transfer electrode. But, only the surface of the silicon based conductive material is arranged with the metallic suicide, and the low resistance is not yet sufficient. Moreover, the distance between the electrodes of the charge transfer electrode is around 0.25 to 0.50 &mgr;m.
SUMMARY OF THE INVENTION
The invention has been built in view of the above mentioned-circumstances, and accordingly it is an object of the invention to offer such a solid image pickup device having high electric pressure proof between the charge transfer electrodes of mono-layered structure and enabling to drive at high speed with low consumption electric power, and a method of making such a solid image pickup device of simple structure and high reliability.
The present invention provides a solid image pickup device formed with a plurality of charge transfer electrodes located on an insulating film of a surface of a semi-conductor substrate. The solid image pickup device has inter-electrode insulating films formed on the insulating film between the charge transfer electrodes arranged next to one another. In the solid image pickup device, the charge transfer electrodes include adhesion is films so formed as to cover side walls of the inter-electrode insulating films and the insulating film, and conductive films containing metals formed in ranges surrounded with the adhesion films.
With such a structure, the inter-electrode insulating films of fine width size can be formed. And the inter-electrode insulating films are covered closely and desirably, leaving no spaces, with the adhesion film which is so formed as to cover the side walls of the inter-electrode insulating films. Moreover, the conductive film containing the metal of low resistance is formed in the upper layer of the conductive film. For the reasons stated above, it is possible to produce electrodes having lower resistance. Further, the surface of the conductive film can be made flat. Therefore, in case a wiring structure is formed thereon, the pattern can be efficiently formed.
The present invention provides a distance of 0.1 &mgr;m or less between the charge transfer electrodes formed with the inter-electrode insulating films of the solid image pickup device. If the distance between the charge transfer electrodes is 0.1 &mgr;m or less, it is extremely difficult to fill the insulating film between the electrodes. However, since the conductive film containing the adhesion film and metals is so formed as to cover the inter-electrode insulating films, it is possible to reduce the distance between the charge transfer electrodes to be 0.1 &mgr;m or less. Accordingly, it is possible to provide the solid image pickup device of low resistance and high reliability. Therefore, the charge transfer electrodes can be driven at high pulse.
The adhesion film of the solid image pickup device of the invention is a silicon based conductive film. The polycrystalline silicon film or the amorphous silicon film can be utilized as the adhesion film. The silicon based conductive film is easy to form a film excellent in shielding stepwise differences in level depending on, for example, a pressure reducing CVD. Moreover, the silicon based conductive film also has a good adhesion with metallic layers such as tungsten. If the polycrystalline silicon film is applied as an adhesion film, it is possible to provide a further low resistance by doping.
The conductive film of the solid image pickup device of the invention is a metallic silicide film. With this structure, it is possible to provide a still further low resistance.
The conductive film of the solid image pickup device of the invention includes tungsten. With this structure, the low resistance can be provided, and at the same time, a light shielding function can be provided owing to tungsten. Therefore, it is possible to omit a shielding film conventionally demanded and obtain the solid image pickup device at low cost and of high reliability.
The inter-electrode insulating film of the solid image pickup device of the invention is a film formed by thermal oxidation of a silicon based material. As the silicon based material, a non-doped silicon may be employed.
With this structure, the silicon based material such as the polycrystalline silicon or the amorphous silicon is subjected to the thermal oxidation, thereby enabling to provide the close insulating film. In addition, using the non-doped silicon, impurities as phosphorus are prevented from contribution to conductivity, so that insulation can be made secure between electrodes. Accordingly, since the inter-electrode insulating film of high quality is formed, pressure proof can be increased.
The present invention also provides a meth
Birch & Stewart Kolasch & Birch, LLP
Fuji Photo Film Co. , Ltd.
Wilson Allan R.
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