Active solid-state devices (e.g. – transistors – solid-state diode – Field effect device – Having insulated electrode
Reexamination Certificate
2001-05-18
2003-10-14
Ngô, Ngân V. (Department: 2814)
Active solid-state devices (e.g., transistors, solid-state diode
Field effect device
Having insulated electrode
C257S335000, C257S341000
Reexamination Certificate
active
06633064
ABSTRACT:
BACKGROUND OF THE INVENTION
Field of the Invention
The invention lies in the semiconductor technology field. More specifically, the present invention relates to a compensation component having a semiconductor body with a reverse-biasing pn junction, a first zone of a first conductivity type, which is connected to a first electrode and adjoins a zone of a second conductivity type, opposite to the first conductivity type, forming the reverse-biasing pn junction, and having a second zone of the first conductivity type, which is connected to a second electrode, that side of the zone of the second conductivity type which faces the second zone forming a first surface and, in the area between the first surface and a second surface, which lies between the first surface and the second zone, regions of the first and second conductivity type being interleaved with one another.
Such compensation components are, for example, n-channel or p-channel MOS field effect transistors, diodes, thyristors, GTOs or else other components. However, in the following text, the exemplary embodiment will be a field effect transistor (also referred to in brief as “transistor”).
In relation to compensation components, there have been various theoretical investigations scattered over a long time period (see, for example, U.S. Pat. Nos. 4,754,310 and 5,216,275), in which, however, the objective is specific improvements in the turn-on resistance RSDon and not the stability under current loading, such as, in particular, robustness with regard to avalanche and short circuit in the high-current case with a high source-drain voltage.
Compensation components are based on the mutual compensation of the charging of n-doped and p-doped regions in the drift region of the transistor. The regions are in this case arranged spatially in such a way that the line integral over the doping along a line running vertically to the pn junction in each case remains below the material-specific breakdown charge (for silicon: about 2·10
12
charge carriers cm
−2
). In this case, the breakdown charge is linked to the breakdown voltage via the second Maxwell equation.
For example, in a vertical transistor, as is common in power electronics, p-columns and n-columns or plates and so on are arranged in pairs. In the case of a lateral structure, p-conductive and n-conductive layers can be stacked alternately one above another laterally between a trench occupied by a p-conductive layer and a trench occupied by an n-conductive layer (see, U.S. Pat. No. 4,754,310).
As a result of the far-reaching compensation of the p-doping and n-doping, in compensation components the doping of the current-carrying area can be increased considerably, that is to say the n-conducting area for n-channel resistors and the p-conducting area for p-channel resistors, which, in spite of the loss in current-carrying area, results in a considerable gain in the turn-on resistance RDSon. The reverse-biasing ability of the transistor in this case depends substantially on the difference between the two dopings since, for reasons relating to the reduction in the turn-on resistance, a doping of the current-carrying area which is higher by at least one order of magnitude is desirable, managing the reverse voltage requires the controlled setting of the degree of compensation in the range≦+/−10%. In the case of a higher gain in turn-on resistance, the aforementioned range becomes still smaller. The degree of compensation can thereby be defined by (p-doping−n-doping)
-doping or by charge difference/charge of a doping region. However, other definitions are also possible in this context.
In order, then, to provide a robust compensation component of the type mentioned at the beginning which, firstly, is distinguished by a high avalanche resistance and high current-carrying ability before or during breakdown and, secondly, can be produced in a straightforward way with easily reproducible characteristics with regard to the technological range of fluctuation of manufacturing processes, the earlier, commonly assigned German patent DE 198 40 032 C1 provides for the regions of the first and of the second conductivity type in such a compensation component to be doped in such a way that, in areas close to the first surface, charge carriers of the second conductivity type predominate and, in regions close to the second surface, charge carriers of the first conductivity type predominate.
In the case of a compensation component, in the reverse-bias case, the voltage is sustained by p-conductive regions and n-conductive regions located close to one another depleting one another, that is to say the charge carriers of the one region, for example the n-conductive region, electrically “compensate” for the charges in the adjacent p-conductive region. As a result, a zone which is depleted of free charge carriers is formed, that is to say a space charge zone. At small voltages, this has the effect, in the individual planes, of a Predominately horizontally oriented electrical field E
h
, which runs at right angles to the connecting direction between the two electrodes. As the voltage increases, an increasing part of the volume of the component is depleted horizontally in this way. Once this horizontally oriented electric field E
h
has ultimately reached a maximum at a field strength E
h,Bub
, then during any further increase in the voltage across the electrodes, the depletion begins of the semiconductor body or substrate and of the zone forming the reverse-biasing pn junction. A vertical field E is therefore then built up.
An electrical breakdown occurs at a critical field strength Ec when the vertical field assumes a value E
Bv
, for which it is true that:
E
c
=
&LeftBracketingBar;
E
⇀
Bv
+
E
h
,
Bub
&RightBracketingBar;
⇒
E
Bv
=
E
c
2
-
E
h
,
Bub
2
With appropriate dimensions of individual cells in a compensation component, the horizontal field E
h,Bub
assumes only relatively low values, even with high doping levels of the regions of the first and second conductivity type, that is to say “high column doping levels”, which leads to a low turn-on resistance RDSon, so that the field E
Bv
is of the order of magnitude of E
c
. According to the relationship which results from this
U
B
(
E
Bv
;E
h,Bub
)=
U
BV
(
E
BV
)+
U
h,Bub
(
E
h,Bub
)
it is therefore possible for a compensation component designed in this way to bias high voltages in reverse in spite of a low turn-on resistance RSDon. In this case, U
B
designates the breakdown voltage, U
Bv
the vertical breakdown voltage and U
h,Bub
the horizontal breakdown voltage.
In the case of power components, a large number of individual components or “cells” are connected in parallel. The requirement on a robust power component in breakdown is a high current, caused by impact ionization, without the power component being destroyed. Destruction occurs when the breakdown current in the power component is distributed only poorly, that is to say the current densities are very high at only a few locations in the semiconductor body. This is the case when only individual cells break down, that is to say if an “avalanche event” is not homogeneously distributed over the semiconductor body.
Because of inhomogeneities in the cell field which are caused by their fabrication, are to some extent only marginally pronounced and cannot be avoided, a breakdown is initially always carried by only a few cells, at low breakdown currents, this being caused, for example, by fluctuations in the doping level. These few cells therefore break down earlier than all the other cells, which leads to an inhomogeneous current distribution. The breakdown will be distributed uniformly over the semiconductor body if, for a cell, the reverse-bias voltage rises with the breakdown current, that is to say there is a positive differential characteristic curve. This is because the more current the component is to supply in total in the case of an avalanche, the more cells break down.
In the case of compensation components, the charg
Auerbach Franz
Deboy Gerald
Weber Hans
Greenberg Laurence A.
Infineon Technologoes AG
Mayback Gregory L.
Ngo Ngan V.
Stemer Werner H.
LandOfFree
Compensation component with improved robustness does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Compensation component with improved robustness, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Compensation component with improved robustness will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3173139