Active solid-state devices (e.g. – transistors – solid-state diode – Field effect device – Having insulated electrode
Reexamination Certificate
2002-04-01
2003-10-28
Flynn, Nathan J. (Department: 2826)
Active solid-state devices (e.g., transistors, solid-state diode
Field effect device
Having insulated electrode
C257S329000, C257S492000, C257S493000, C257S287000, C257S266000, C257S335000, C257S342000, C438S212000, C438S268000, C438S514000, C438S549000
Reexamination Certificate
active
06639272
ABSTRACT:
BACKGROUND OF THE INVENTION
Field of the Invention
The present invention relates to a compensation component having a semiconductor body of a first conduction type, in which a region extends between at least one first electrode and a second electrode arranged remote from the first electrode. The region adjoins the first electrode and has at least one zone of the second conduction type that is opposite to the first conduction type. The compensation component includes a drift zone that lies between the at least one zone of the second conduction type and the second electrode. The drift zone has compensation regions of the second conduction type, in which the charge balance is variable.
It is known that in compensation components, the electrical parameters, such as, in particular, the breakdown voltage, are greatly dependent on manufacturing fluctuations. This can be attributed to the fact that the breakdown voltage depends approximately parabolically on the p
charge balance in the bulk of the semiconductor body. However, this charge balance is subject to manufacturing fluctuations.
If the charge balance is not varied in the individual planes of a compensation component, which are preferably formed by epitaxy, to obtain a homogeneous doping depth profile in the compensation regions of the second conduction type (the so-called “p-type pillar”, if the second conduction type is the p conduction type), then this produces a very narrow compensation parabola with only a small opening width. In this case, then, the manufacturing window is relatively small.
However, if there is variation of the charge balance in the individual planes, i.e. if there is variation of the dose implanted per area in the planes, the parabola becomes wider, which provides a larger manufacturing tolerance.
FIG. 5
shows the typical profile of two such “manufacturing parabolas”. In this case, the breakdown voltage is plotted as a function of the degree of compensation, which may be p-loaded, n-loaded, or neutral. A significantly narrow manufacturing parabola is produced for a homogeneous pillar doping (cf. the broken line) and for a variable pillar doping (cf. the solid line).
The drift zone of a compensation component (the compensation regions being situated in the drift zone) is preferably implemented by repeatedly depositing a doped epitaxial layer that is respectively followed by a masked implantation with a dopant of the second conduction type. In other words, by way of example, an n-conducting epitaxial layer is applied to an n-conducting semiconductor substrate. A p-conducting compensation region is then produced using a masked implantation in the region of the drift zone. This operation is repeated a number of times.
If the drift zone is produced in this way, then the electric field exhibits great variation with the depth, that is to say in the direction perpendicular to the individual epitaxial layers. This variation of the electric field can be referred to as ripple.
The ripple is based on the distribution of the implanted dose that is inhomogeneous in the depth direction or the vertical direction, and also on a transverse electric field that is established between the compensation regions of the second conduction type and the semiconductor body surrounding the latter, that is to say, in the above example, with the p-type pillar, between the p-conducting regions of the pillar and the n-conducting semiconductor body.
FIG. 4
shows such a field profile in a conventional compensation component. In this case, the electric field strength E is plotted as a function of the component depth d in FIG.
4
.
This ripple of the electric field strength K means that the compensation component can take up significantly less voltage than in the case of a “flatter” field profile. In order nevertheless to be able to withstand relatively high voltages, the compensation component must be dimensioned to be relatively thick, which, however, leads to an increased on resistance RDSon between the drain and the source in the case of a compensation component formed as a transistor.
It should be attempted, then, to ensure that compensation components have a wide manufacturing parabola and a low degree of ripple.
The wide manufacturing parabola is achieved by providing a variable doping profile in the drift zone, in the p-type pillar in the above example. For this purpose, either the implantation dose can be set in a variable fashion or the doping in the individual epitaxial layers can be configured in a variable fashion. Such a variable configuration of the doping in epitaxial layers, that is to say the n-type doping in the above example, can only be realized with difficulty in practice, so that solely the variation of the doping dose in the compensation regions is preferred. This variation can be implemented by changing the implanted dose or by correspondingly dimensioning the masks used during the photo technology before the implantation.
The ripple of the electric field can be achieved by providing: longer drive-in times following the individual implantations, that is to say through a more homogeneous distribution of the implanted dopants that are achieved as a result; through the use of high-energy implantations; or through smaller layer thickness of the individual compensation regions, and thus through a larger number of epitaxial layers.
SUMMARY OF THE INVENTION
It is accordingly an object of the invention to provide a compensation component and a method for producing the compensation component which overcome the above-mentioned disadvantages of the prior art apparatus and methods of this general type.
In particular, it is an object of the invention to provide a compensation component that is distinguished by a wide manufacturing parabola and a low degree of ripple of the electric field.
With the foregoing and other objects in view there is provided, in accordance with the invention, a compensation component that includes: at least one first electrode; a second electrode configured remote from the at least one first electrode; a semiconductor body of a first conduction type; a region including at least one zone of a second conduction type that is opposite the first conduction type, the region configured in the semiconductor body and adjoining the first electrode; a drift zone lying between the at least one zone of the second conduction type and the second electrode; and compensation regions of the second conduction type. The compensation regions have different charge balances. The compensation regions are configured near the at least one zone of the second conduction type. At least some of the compensation regions have a dimension that is different from that of others of the compensation regions. The dimension is the layer thickness in the case of a vertically configured compensation component, and is the width in the case of a laterally configured compensation component.
In accordance with an added feature of the invention, the dimension is the layer thickness; and the layer thickness of each one of the compensation regions is different from that of others of the compensation regions.
In accordance with an additional feature of the invention, the dimension is the layer thickness; and the layer thickness of at least two of the compensation regions is different from that of others of the compensation regions.
In accordance with another feature of the invention, each one of the some of the compensation regions has a doping dose that is different from that of the others of the compensation regions.
In accordance with a further feature of the invention, the semiconductor body has a main surface; and the compensation regions are arranged vertically in the semiconductor body with respect to the main surface of the semiconductor body.
In accordance with a further added feature of the invention, the first conduction type is the n conduction type.
In accordance with a further additional feature of the invention, the compensation regions are doped with boron.
In accordance with yet an added feature of the invention, the dimension is
Ahlers Dirk
Weber Hans
Willmeroth Armin
Erdem Fazli
Flynn Nathan J.
Infineon - Technologies AG
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