Active solid-state devices (e.g. – transistors – solid-state diode – Field effect device – Having insulated electrode
Reexamination Certificate
2003-01-29
2004-06-15
Nelms, David (Department: 2818)
Active solid-state devices (e.g., transistors, solid-state diode
Field effect device
Having insulated electrode
C257S331000, C257S330000
Reexamination Certificate
active
06750510
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a charge coupled device suitably employed in a solid-state imaging device for use in, for instance, a digital camera, and to the production thereof.
2. Related Background Art
A charge coupled device (hereinafter referred to as CCD) is a device having a structure in which a multiplicity of metal oxide semiconductor (MOS) structure electrodes are arranged on a surface of a semiconductor, and generally is used as a so-called solid-state imaging device in various types of electronic cameras, facsimiles, etc.
FIG. 2
illustrates a cross-sectional structure of a prior art CCD. A charge transfer region
22
is formed on a P-type silicon substrate
21
in which an impurity is doped, and a gate insulation film
23
is formed on the charge transfer region
22
. On the gate insulation film
23
, first gate electrodes
24
and second gate electrodes (transfer electrodes)
27
are formed alternately. When a voltage is applied to the gate electrodes, charge stored under each gate electrode is transferred from one electrode to another successively, and the charge is outputted as a voltage at an output section.
28
denotes a potential well.
The following will describe a method for producing the prior art CCD. First, as shown in
FIG. 3A
, the charge transfer region
22
is formed on the P-type silicon substrate
21
, and the gate insulation film
23
is formed on the charge transfer region
22
. Subsequently, the first gate electrodes
24
are formed on the gate insulation film
23
by patterning.
Next, as shown in
FIG. 3B
, the first gate electrodes
24
are oxidized so as to be covered with a silicon oxide film
25
. Subsequently, as shown in
FIG. 3C
, the second electrodes
27
are formed on the gate insulation film
23
so that each is arranged between adjacent first gate electrodes
24
. Thus, the first and second gate electrodes
24
and
27
are arranged alternately on the gate insulation film
23
, and the silicon oxide film
25
is formed between the gate electrodes, whereby the gate electrodes are insulated electrically from one another by the silicon oxide film
25
.
In the case where this method is used, the forming rate of the silicon oxide film
25
decreases with increasing proximity to the gate insulation film
23
since the supply of oxygen decreases. Therefore, as shown in the drawings, on side faces of the first gate electrode
24
, the thickness of the silicon oxide film
25
decreases (the silicon oxide film
25
is constricted) with increasing proximity to the gate insulation film
23
. The second gate electrode
27
is formed in a state of being in contact with the silicon oxide film
25
, and hence, it is formed to have acute-angle edges
32
in its base part on the gate insulation film
23
. When a voltage is applied to each gate electrode in the foregoing state, sometimes an electric field is concentrated at the edges
32
, thereby causing dielectric breakdown between the first gate electrode
24
and the second gate electrode
27
.
To cope with the foregoing problem, conventionally the varying of the conditions for the oxidization of the first gate electrode
24
has been attempted, or alternatively, the increase in the dielectric breakdown voltage between the gate electrodes was attempted by increasing a film thickness t
2
(
FIG. 3B
) of the silicon oxide film
25
on the first gate electrode
24
.
However, the foregoing problem has not been solved by any one of the foregoing methods, and particularly the increase in a film thickness t
2
″ (
FIG. 3B
) of the silicon oxide film
25
necessarily increases a distance g
2
(
FIG. 3C
) between the gate electrodes, thereby impairing the charge transfer efficiency of the CCD. Furthermore, at the same time, a difference t
2
′−t
2
″ between the film thickness t
2
′ of the silicon oxide film
25
on the side faces of the first gate electrode
24
and the film thickness t
2
″ thereof in contact with the gate insulation film
23
increases, thereby narrowing the angle of the edges
32
on the gate insulation film
23
. As a result, the dielectric breakdown tends to occur more easily.
SUMMARY OF THE INVENTION
Therefore, with the foregoing in mind, it is an object of the present invention to provide a charge coupled device that includes a charge transfer region layer and a gate insulation film that are formed in the stated order on a semiconductor substrate, first gate electrodes formed at predetermined spaces on the gate insulation film, and second gate electrodes arranged between the first gate electrodes with at least silicon oxide films being interposed therebetween. In the charge coupled device, each silicon oxide film has constricted portions where the silicon oxide film is in contact with the gate insulation film, and electric insulation films are formed on the constricted portions so as to form sidewalls.
Further, a charge coupled device producing method of the present invention includes (a) forming a gate insulation film on a charge transfer region layer formed on a semiconductor substrate, (b) forming a plurality of first gate electrodes on the gate insulation film so that the first gate electrodes are arranged at predetermined spaces, (c) covering the first gate electrodes with silicon oxide films, (d) forming at least an electric insulation film on the silicon oxide films and the gate insulation film, (e) removing the electric insulation film so that the electric insulation film remains on constricted portions of the silicon oxide films in contact with the gate insulation film, thereby forming sidewalls, and (f) forming second electrodes on the gate insulation film and the electric insulation films.
REFERENCES:
patent: 6515317 (2003-02-01), Bazan et al.
Henmi Ken
Tanaka Hiroshi
Merchant & Gould P.C.
Nelms David
Nguyen Thinh T
LandOfFree
Charge coupled device and production thereof does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Charge coupled device and production thereof, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Charge coupled device and production thereof will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3318308