Active solid-state devices (e.g. – transistors – solid-state diode – Regenerative type switching device – Bidirectional rectifier with control electrode
Reexamination Certificate
1997-08-19
2001-07-17
Chaudhuri, Olik (Department: 2814)
Active solid-state devices (e.g., transistors, solid-state diode
Regenerative type switching device
Bidirectional rectifier with control electrode
C257S109000, C257S544000
Reexamination Certificate
active
06262443
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to the implementation of a monolithic rectifying bridge protected against overvoltages.
2. Discussion of the Related Art
Power components currently available for sale are implemented based on technologies in which the rear surface of the component is uniformly coated with a metallization in contact with the apparent semiconducting layers of this rear surface. With these types of technologies, it has been considered, up to now, that it was not possible to implement in monolithic form a component providing the functions of a medium or high power rectifying bridge protected against overvoltages, and such components are not available for sale.
Besides, French patent application 94/16011 filed on Dec. 30, 1994, by the applicant, entitled “Integrated power circuit”, and incorporated herein by reference discloses a new concept of an integrated power circuit which enables monolithic assembly of many logic and power components in the same semi-conductor circuit. In order to achieve this result, this patent application notably teaches to appropriately use insulating layers formed on the rear surface of a component, the rear surface metallization being partly in contact with the rear surface semiconductor structures and being partly insulated by these insulating layers.
The use of the teachings of this patent application is extremely rich and enables implementation, in monolithic form, of many component assemblies which were previously implemented only as assemblies of discrete components.
Among the examples of application given in this patent application, there appear rectifying bridges protected against overvoltages.
FIG. 11A of this prior patent application, reproduced in
FIG. 1
, shows such a protected rectifying bridge including four rectifying diodes D
1
to D
4
and a double Shockley S. Diagrams equivalent to the diagram of FIG. 11A of this patent application are illustrated in FIGS. 11B and 11C, this last drawing being reproduced in FIG.
2
. It should be noted that from a functional point of view, the diagram of
FIG. 2
is strictly identical to that of FIG.
1
. In
FIGS. 1 and 2
, terminals T
1
, T
2
designate a.c. supply terminals and terminals T+ and T− designate d.c. voltage supply terminals.
Next, this prior patent application shows in its FIGS. 13A and 13B, reproduced in
FIGS. 3A and 3B
, a simplified example of implementation of the circuit illustrated in FIG. 11C (appended FIG.
2
). In
FIGS. 3A and 3B
, exactly the same reference numbers as in FIGS. 13A and 13B of the prior patent application are kept and, to describe these drawings, reference will be made to this prior patent application.
It will only be noted that:
N-type substrate
1
is lightly doped,
regions
30
and
31
correspond to P-type isolating walls,
diode D
2
and Shockley diode S
2
are formed vertically in a first well,
diode D
4
and Shockley diode S
4
are formed vertically in a second well,
diodes D
1
and D
3
are formed laterally in a third well.
Diode D
1
corresponds to PNN
+
regions
52
,
1
,
54
,
diode D
3
corresponds to PNN
+
regions
53
,
1
,
54
,
diode D
2
corresponds to PNN
+
regions
42
,
1
,
50
and diode D
4
to homologous regions,
Shockley diode S
2
includes from its anode to its cathode PNN+PN regions
40
,
1
,
46
,
42
and
44
and Shockley diode S
4
includes homologous regions.
The structure described and schematically shown in
FIGS. 3A and 3B
gives satisfactory results.
However, in the field of semiconductor component fabrication, manufacturers generally desire to derive as little as possible from conventional and tested dies. Thus, when it is possible to avoid using technologies requiring to use a rear surface insulated layer, this solution is preferred.
SUMMARY OF THE INVENTION
An object of the present invention thus is to provide a monolithic protected rectifying bridge structure wherein the rear surface metallization is, along its whole extent, in contact with a semiconducting structure.
Another object of the present invention is to provide such a structure wherein the properties of the various diodes are optimized by an appropriate selection of the doping steps used.
Another object of the present invention is to provide such a structure wherein the effects of possible parasitic transistors are made negligible.
To achieve these objects, as well as others, the present invention provides a semiconducting structure forming a protected rectifying bridge implemented in an N-type semiconductor substrate divided into first, second, and third wells by vertical P-type isolating walls, in which the rear surface of the substrate is coated with a first metallization and in which each of the first and second wells includes a vertical diode and a vertical Shockley diode, the first metallization corresponding to the anodes of the vertical diodes and to the cathodes of the Shockley diodes. The third well includes a P-type isolating layer on its rear surface side in contact with the first metallization and, on its front surface side, two lateral diodes, each of which is formed between a P-type region and the substrate.
According to an embodiment of the present invention, the anode layers of the rear surface side of the vertical diodes of the first and second wells are comprised of a deep diffused layer corresponding to an isolating wall diffusion.
According to an embodiment of the present invention, the anodes of each of the Shockley diodes are comprised of a central portion formed by a diffusion of the same type as that of the forming of an isolating wall and of a lateral portion formed by a P-type diffusion which is shallower and more doped in surface.
According to an embodiment of the present invention, each of the isolating walls is coated with an overdoped region of the same type of conductivity, the overdoped region being coated on most of its surface with a metallization.
According to an embodiment of the present invention, the anode layers of the lateral diodes and the P-type isolating layer are shallow and highly-doped layers.
These objects, characteristics and advantages as well as others, of the present invention, will be discussed in detail in the following non-limiting description of specific embodiments of the present invention, in relation with the accompanying drawings.
REFERENCES:
patent: 4228448 (1980-10-01), Lalumia et al.
patent: 4400711 (1983-08-01), Avery
patent: 5311042 (1994-05-01), Anceau
patent: 5471074 (1995-11-01), Pezzani
patent: 5473170 (1995-12-01), Bernier
patent: 5710442 (1998-01-01), Watanabe et al.
patent: 5808326 (1998-09-01), Bernier et al.
patent: 0 721 218 (1996-07-01), None
French Search Report from French Patent Application 96 10659, filed Aug. 27, 1996.
Ballon Christian
Bernier Eric
Chaudhuri Olik
Galanthay Theodore E.
Morris James H.
SGS-Thomson Microelectronics S.A.
Wille Douglas A.
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