Active solid-state devices (e.g. – transistors – solid-state diode – Field effect device – Having insulated electrode
Reexamination Certificate
2001-07-16
2003-02-25
Crane, Sara (Department: 2811)
Active solid-state devices (e.g., transistors, solid-state diode
Field effect device
Having insulated electrode
C257S458000, C257S342000, C257S461000, C257S147000
Reexamination Certificate
active
06525374
ABSTRACT:
The invention relates to a semiconductor component with a low-doped base region of the first conductivity type extending in the lateral direction (x) and two terminal areas which are separated at least by the base region in the lateral direction for connection to electrical contacts.
These semiconductor components are used especially in power electronics to accommodate blocking voltages in the high voltage range, i.e., the kV range. Here the low-doped base which is made especially as a n
−
-base is used to accommodate blocking voltages. The high voltage on the contacts is distributed accordingly over the entire semiconductor component, the variation of the high electrical field strength being adjusted in the base region. Since the voltage is an integral of the electrical field strength over the lateral direction and the allowable field strength in the semiconductor material, generally silicon, is limited by the pertinent breakdown field strength, these components are produced with a great lateral extension of the base region.
To achieve breakdown voltages as high as possible, a slope of the electrical field-strength distribution which is as small as possible and thus doping of the base region as low as possible are necessary. The allowable maximum base doping drops with increasing breakdown voltage. With respect to the required cosmic radiation resistance of the components they must be dimensioned such that the maximum attained electrical field strength is clearly below the breakdown field strength of the semiconductor material used, by which the essentially attainable blocking voltage is further reduced.
A further reduction of the blocking voltage which can be accomplished with a stipulated doping arises in so-called punch-through dimensioning for improving the on-state behavior, for which the base width of the components is chosen such that the electrical field at higher blocking voltages extends as far as the cathode emitter. An increase of the allowable blocking voltage is thus only possible by using semiconductor material with lower doping than the commercial starting material, but one such lower-doped semiconductor material cannot be economically produced.
Thus, when using commercial starting material, for example silicon with minimum doping of roughly 5×10
12
cm
−3
, components with breakdown voltages up to roughly 10 kV can be produced. Higher blocking voltages can only be accomplished by series connection of several components, for example stacked diodes. Since in the conducting state for each of the series connected components at least the diffusion voltage is necessary, these components have poor on-state behavior with a correspondingly high voltage drop.
DE 43 09 764 C2 shows a component with a base consisting of several thin successive layers which are alternately p-doped or n-doped. The dopant content in each individual layer is quantitatively the same and is so low that they are completely cleared at very low blocking voltages. For this purpose complex formation of successive layers of very low thickness with relatively high doping is accordingly necessary so that production is complex and expensive.
DE 196 04 043 A1 shows a semiconductor component which can be controlled by a field effect, with a drain zone of the first conductivity type, a gate electrode which is insulated relative to the drain zone, and a source region of the second conductivity type, made in the drain zone. In the drain zone, areas of the first and second conductivity type are formed, the concentration of the added n-regions corresponding roughly to the concentration of added p-regions. EP 0 818 825 A1 shows a thyristor in which the anode regions are separated from he cathode region among others by a doped substrate region. On the outer edge of the substrate area layers are formed which are of one conductivity type which is opposite the conductivity type of the substrate area.
The latter two publications are however not suited for high voltage applications as a result of their structure.
The object of the invention is to be able to produce a semiconductor component easily and economically and to enable use at high blocking voltages.
This object is achieved by the base material of the base region (
3
) being silicon (Si) and the dopant concentration of 10
12
to 5×10
14
cm
−3
and the dopant concentration (N
A
) determined by integration of the dopant concentration over the vertical thickness of the base region (
3
) along the lateral direction (x) being each less than 2×10
12
cm
−2
, by there being compensation layers (
6
,
6
a
,
6
b
,
6
c
,
7
,
7
a
,
7
b
,
7
c
,
8
) of the second conductivity type (p) opposite the first conductivity type which extend inside or outside the base region in the lateral direction (x), the lateral length (l
K
) of the compensation layers being greater than their vertical thickness (d
6
, d
7
) and the dopant surface concentration (N
A
) which is determined by integration of the dopant concentration over the vertical thickness of a compensation layer along the lateral direction (x) being less than 1×10
12
cm
−2.
The compensation layers can run on the outside of the base region or also within the base region. Here it is fundamentally also possible for the compensation layers to extend not only in the lateral direction, but also roughly in the vertical direction in their variation.
The invention is based on the idea of at least partially compensating for the space charge in the base region by layers of opposite doping which run essentially parallel thereto. Here individual sections can be made along the lateral direction, in which this compensation turns out to be of a different magnitude, and in part also complete compensation can be achieved, or overcompensation in which upon integration over the vertical thickness there is a higher dopant content of the compensation layers. Advantageously, in the compensation layers the dopant concentration is less than that breakdown dopant concentration which corresponds to the breakdown field strength of he corresponding semiconductor material. The semiconductor material can be especially the silicon which is conventional for power semiconductor components with doping of 10
12
-10
13
, especially 3×10
12-
10
13
. Thus, semiconductor components for applications preferably in the range 10-30 kV can be formed.
The terminal regions can consist especially of a highly doped semiconductor material.
The terminal regions can be especially an anode region of p
+
-conductive semiconductor material and a cathode region of n
+
-conductive semiconductor material.
REFERENCES:
patent: 6097063 (2000-08-01), Fujihira
patent: 6207994 (2001-03-01), Rumennik et al.
patent: 1614440 (1970-07-01), None
patent: 4309764 (1994-09-01), None
patent: 19604043 (1997-08-01), None
patent: 0818 825 (1998-01-01), None
patent: WO83/00582 (1983-02-01), None
Nagel Detlef
Sittig Roland
Crane Sara
Greenberg Laurence A.
Im Junghwa
Infineon - Technologies AG
Mayback Gregory L.
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