COMPONENT ARRANGEMENT INCLUDING A MOS TRANSISTOR HAVING A FIELD ELECTRODE
A component arrangement including a MOS transistor having a field electrode is disclosed. One embodiment includes a gate electrode, a drift zone and a field electrode, arranged adjacent to the drift zone and dielectrically insulated from the drift zone by a dielectric layer a charging circuit, having a rectifier element connected between the gate electrode and the field electrode.
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This Utility Patent Application claims priority to German Patent Application No. DE 10 2007 004 323.8-33 filed on Jan. 29, 2007, which is incorporated herein by reference.
BACKGROUNDIn a component arrangement including a MOS transistor having a drift zone and a field electrode arranged adjacent to the drift zone the field electrode can be connected to a source zone of the MOS transistor. In this case, with the component in the off state, the field electrode provides a countercharge with respect to the charge which is present in the drift zone and which results from a doping of the drift zone. Charge carriers in the drift zone are compensated for by the countercharge, whereby a higher doping of the drift zone and thus a lower on resistance are possible for a given dielectric strength.
The field electrode can also be connected to a gate electrode of the MOS transistor. In this case, with the component in the on state, the field electrode brings about the formation of an accumulation channel in the drift zone. This reduces the on resistance for a given dielectric strength.
However, the connection of the field electrode to the gate electrode increases the gate-drain capacitance of the component and leads to an increase in the switching delay since with each switch-on operation, apart from the gate electrode the field electrode also has to be charged from the gate circuit or by using a gate driver circuit. For a given current yield of the gate driver circuit, when a field electrode is present, the time duration required to charge the gate electrode up to the threshold voltage and thereby to drive the component in the on state is lengthened in comparison with a component without a field electrode.
For these and other reasons, there is a need for the present invention.
SUMMARYOne embodiment provides a component arrangement including a MOS transistor having a gate electrode, a drift zone and a field electrode, which is arranged adjacent to the drift zone and is dielectrically insulated from the drift zone by a dielectric layer, and a charging circuit, which is connected between the gate electrode and the field electrode and which has a rectifier element.
The accompanying drawings are included to provide a further understanding of embodiments and are incorporated in and constitute a part of this specification. The drawings illustrate embodiments and together with the description serve to explain principles of embodiments. Other embodiments and many of the intended advantages of embodiments will be readily appreciated as they become better understood by reference to the following detailed description. The elements of the drawings are not necessarily to scale relative to each other. Like reference numerals designate corresponding similar parts.
In the following Detailed Description, reference is made to the accompanying drawings, which form a part hereof, and in which is shown by way of illustration specific embodiments in which the invention may be practiced. In this regard, directional terminology, such as “top,” “bottom,” “front,” “back,” “leading,” “trailing,” etc., is used with reference to the orientation of the Figure(s) being described. Because components of embodiments can be positioned in a number of different orientations, the directional terminology is used for purposes of illustration and is in no way limiting. It is to be understood that other embodiments may be utilized and structural or logical changes may be made without departing from the scope of the present invention. The following detailed description, therefore, is not to be taken in a limiting sense, and the scope of the present invention is defined by the appended claims.
It is to be understood that the features of the various exemplary embodiments described herein may be combined with each other, unless specifically noted otherwise.
One embodiment provides a component arrangement including a MOS transistor having a gate electrode, a drift zone and a field electrode, which is arranged adjacent to the drift zone and is dielectrically insulated from the drift zone by a dielectric layer, and a charging circuit, which is connected between the gate electrode and the field electrode and which has a rectifier element.
In one embodiment, the MOS transistor 10 is realized as a vertical transistor and has a drift zone 12 arranged in a vertical direction of the semiconductor body 100 between a drain zone 11 and a body zone 13. The body zone 13 is arranged between the drift zone 12 and a source zone 14 and is doped complementarily to the drift zone 12 and the source zone 14. A gate electrode 21 is arranged adjacent to the body zone 13, the gate electrode being dielectrically insulated from the body zone 13 by a first dielectric layer 22, which is referred to hereinafter as gate dielectric layer. The gate electrode 21 extends adjacent to the body zone 13 from the source zone 14 as far as the drift zone 12 and serves for controlling an inversion channel in the body zone 13 between the source zone 14 and the drift zone 12.
The source zone 14 is arranged in the region of a first side 101, which is referred to hereinafter as front side, of the semiconductor body 100 and contact is made with the source zone by a source electrode 51. The source electrode 51, in a manner known in principle, also makes contact with the body zone 13 in order thereby to short-circuit the body zone 13 and the source zone 14. In this case, a connection zone 15 of the same conduction type as the body zone 13 and doped more highly than the body zone 13 is optionally present, the connection zone being arranged between the connection electrode 51 and the body zone 13.
In one embodiment, the field electrode 31 is arranged in the drift zone 12 and is dielectrically insulated from the drift zone 12 by a second dielectric layer 32, which is referred to hereinafter as field electrode dielectric layer. The field electrode dielectric layer 32 can be composed of the same material as the gate dielectric layer 22, but the two dielectric layers 22, 32 can also be composed of different dielectric materials and can have in particular different thicknesses d1, d2.
The MOS transistor illustrated has a trench structure. In this case, the gate electrode 21 is arranged in a trench which extends, proceeding from the front side 101, in the vertical direction into the semiconductor body 100. In this case, the gate electrode 21 is arranged adjacent to the source zone 14 and the body zone 13 in a lateral direction of the semiconductor body 100. An inversion channel that forms when the MOS transistor is driven in the on state runs in the body zone 13 in the vertical direction of the semiconductor body 100 along the gate dielectric 22 between the source zone 14 and the drift zone 12.
In the case of the component illustrated in
The MOS transistor illustrated in
The component arrangement furthermore includes a charging circuit 40 with a rectifier element 41, for example a diode, which is connected between the gate electrode 21 and the field electrode 31. The charging circuit can optionally have a capacitive storage element 42 connected between the field electrode 31 and the source zone 14 or the source electrode 51.
The MOS transistor illustrated in
The drift zone 12, the source zone 14 and the drain zone 11 are n-doped in this case, the drift zone 12 being doped more lightly than the drain zone 11. The body zone 13 is p-doped in the case of the n-channel MOSFET. It should be pointed out that the invention is not restricted to the use of an n-channel MOSFET, however. The invention can also be applied to an IGBT, in particular. Such an IGBT differs from an n-channel MOSFET by virtue of the fact that its drain zone, which is also referred to as emitter zone in the case of an IGBT, is doped complementarily to the drift zone, which is represented between parentheses in
One embodiment of the functioning of the component arrangement is explained below with reference to
It shall be assumed for the further explanation that the gate electrode 21 and the field electrode 31 are initially fully discharged. In a first driving operation, by which the MOS transistor 10 is driven in the on state, the gate electrode 21 is charged to the driving potential by the driver circuit 200. In addition, the field electrode 31 is charged, by the charging circuit 40, to an electrical potential corresponding to the driving potential minus the forward voltage of the rectifier element 41. Assuming that the driving potential relative to the source potential is large in comparison with the forward voltage of the rectifier element 41, the field electrode 31 is charged approximately to the driving potential by the charging circuit 40. Depending on the capacitance of the field electrode 31 and depending on the duration for which the MOS transistor remains switched on after first being switched on, it can take one or more driving cycles of the MOS transistor for the field electrode 31 to be charged to driving potential.
A resistor (not illustrated) can optionally be connected in series with the diode 41, the resistor preventing a situation in which, during the first driving cycle or during the first driving cycles, the current portion flowing from the gate circuit into the field electrode 31 is so large that not enough charge flows onto the gate electrode and the component fails to be driven in the on state. Such a resistor only “brakes” the charging of the field electrode 31, such that fundamental switching on of the component is not prevented, although the full effect of the field electrode for reducing the on resistance commences only after a delay.
If the gate electrode 21 has been charged up to the driving potential, then an inversion channel forms between the source zone and the drift zone in the body zone 13 along the gate dielectric 22, and enables a current to flow between the drain connection D and the source connection S when supply voltage is present across the drain-source path of the MOS transistor. In this case, the field electrode 31 charged to the driving potential has the effect that an accumulation channel forms in the drift zone 12 along the field electrode dielectric 32. The electrical resistance in the accumulation channel is lower than in other regions of the drift zone 12, such that the on resistance of the MOS transistor 10 illustrated is lower than that of a comparable MOS transistor without a field electrode. In this case, the formation of the accumulation channel along the field electrode dielectric 32 is all the more pronounced, the better the capacitive coupling between the field electrode 31 and the drift zone 12. The capacitive coupling can be increased for example by using a high-dielectric (high-k) material for the field plate dielectric 32. Furthermore, the capacitive coupling improves as the thickness d2 of the field plate dielectric 32 becomes smaller. However, the thickness of the field plate dielectric 32 should be chosen to be large enough that the latter has a sufficient dielectric strength in relation to the voltage present when the component is driven in the off state, as is explained below. When the MOS transistor is driven in the off state, the gate electrode 21 is discharged by the driver circuit, for example to the value of the source potential, whereby an inversion channel previously present is interrupted and the component turns off. When voltage is present across the load path D-S, in this case a space charge zone propagates proceeding from the pn junction between the body zone 13 and the drift zone 12 essentially into the drift zone 12. In the case of an n-channel MOSFET and a positive drain-source voltage, the electrical potential rises in this case proceeding from the pn junction in the direction of the drain zone 11. The voltage loading of the field plate dielectric 32 increases in this case in the direction of the drain zone 11. The thickness of the field plate dielectric 32 should in this case be chosen to be thick enough to avoid a voltage breakdown.
Due to the rectifier element 41 of the charging circuit, the field electrode 31 retains the previously stored electrical charge when the MOS transistor is driven in the off state. During subsequent driving cycles, therefore, the driver circuit 200 only has to subsequently supply an amount of charge equal to that possibly lost as a result of leakage losses. With the component in the off state, if the electrical potential of the drift zone 12 rises, the electrical potential of the field electrode 32 also rises due to the capacitive coupling. The dielectric strength of the diode 41 should in this case be chosen such that no voltage breakdown occurs when the potential of the field electrode 31 rises.
If, with the component in the off state, the electrical potential of the drift zone 12 rises relative to the electrical potential of the source zone 14, then the electrical potential in the field electrode 31 also rises due to the capacitive coupling between the drift zone and the field electrode 31. In order to reduce this rise in potential, a storage capacitance 42 may be provided, the storage capacitance being connected between the field electrode 31 and the source zone. When the potential of the field electrode 31 rises, the storage capacitance buffer-stores part of the charge previously stored in the field electrode.
The circuit components 41, 42 of the charging circuit 40 can be realized as integrated components, that is to say as components integrated in the semiconductor body 100. There is furthermore the possibility of realizing the circuit components 41, 42 in any desired manner as external components, that is to say components arranged outside the semiconductor body 100.
Referring to
There is furthermore the possibility of realizing the gate electrode 21 with a plurality of elongated electrode sections, as is illustrated by dashed lines in
In the case of the component arrangement illustrated, the field electrode 31 and the second electrode 43 of the storage capacitance are arranged in buried fashion below the gate electrode 21. For making contact with the field electrode 31, a connection electrode can be provided in accordance with
A method for realizing a component structure in which a gate electrode, a field electrode and a storage capacitance are arranged within a trench of a semiconductor body is explained below with reference to
The auxiliary layer 36 is subsequently removed, which is illustrated as the result in
These method processes explained can be followed by known further implantation or diffusion methods for producing the body zone and the source zone and method processes for producing the connection electrodes.
Although specific embodiments have been illustrated and described herein, it will be appreciated by those of ordinary skill in the art that a variety of alternate and/or equivalent implementations may be substituted for the specific embodiments shown and described without departing from the scope of the present invention. This application is intended to cover any adaptations or variations of the specific embodiments discussed herein. Therefore, it is intended that this invention be limited only by the claims and the equivalents thereof.
Claims
1. A component arrangement comprising:
- a MOS transistor having a gate electrode;
- a drift zone;
- a field electrode, arranged adjacent to the drift zone and dielectrically insulated from the drift zone by a dielectric layer; and
- a charging circuit, having a rectifier element connected between the gate electrode and the field electrode.
2. The component arrangement of claim 1, comprising wherein the MOS transistor has a source zone, and the charging circuit has a capacitive storage element connected between the field electrode and the source zone.
3. The component arrangement of claim 2, comprising wherein the MOS transistor is integrated in a semiconductor body, and the capacitive storage element is integrated in the semiconductor body in which the MOS transistor is integrated.
4. The component arrangement of claim 1, comprising wherein the MOS transistor is integrated in a semiconductor body, and the gate electrode and the field electrode are arranged in a common trench in the semiconductor body.
5. The component arrangement of claim 4, comprising wherein the capacitive storage element is arranged in the trench.
6. The component arrangement of claim 5, comprising wherein the capacitive storage element has a first and a second electrode and a storage dielectric arranged between the first and second electrode.
7. The component arrangement of claim 6, comprising wherein the first electrode of the capacitive storage element is formed by the field electrode.
8. The component arrangement of claim 7, comprising wherein the second electrode of the capacitive storage element is arranged within the trench between the gate electrode and the field electrode.
9. The component arrangement of claim 1, comprising wherein the MOS transistor is a MOSFET.
10. The component arrangement of claim 1, comprising wherein the MOS transistor is realized as an IGBT.
11. The component arrangement of claim 1, in which the MOS transistor is realized as a vertical transistor, in which a current flow direction in the drift zone runs in a vertical direction of the semiconductor body.
12. The component arrangement of claim 1, comprising wherein the MOS transistor is a lateral transistor, a current flow direction in the drift zone runs in a lateral direction of the semiconductor body.
13. The component arrangement of claim 1, comprising wherein the rectifier element is polarized in such a way that the field electrode, when the component is driven in the on state, is charged with a charge suitable for forming an accumulation channel in the drift zone.
14. An integrated circuit comprising:
- a semiconductor body;
- a MOS transistor having a gate electrode;
- a drift zone;
- a field electrode, arranged adjacent to the drift zone and dielectrically insulated from the drift zone by a dielectric layer;
- a charging circuit, having a rectifier element connected between the gate electrode and the field electrode; and
- one or more additional electrical components.
15. The integrated circuit of claim 14, comprising wherein the MOS transistor has a source zone, and the charging circuit has a capacitive storage element connected between the field electrode and the source zone.
16. The integrated circuit of claim 15, comprising wherein the MOS transistor is integrated in the semiconductor body, and the capacitive storage element is integrated in the semiconductor body in which the MOS transistor is integrated.
17. The integrated circuit of claim 14, comprising wherein the MOS transistor is integrated in the semiconductor body, and the gate electrode and the field electrode are arranged in a common trench in the semiconductor body.
18. The integrated circuit of claim 17, comprising wherein the capacitive storage element is arranged in the trench.
19. The integrated circuit of claim 18, comprising wherein the capacitive storage element has a first and a second electrode and a storage dielectric arranged between the first and second electrode.
20. The integrated circuit of claim 19, comprising wherein the first electrode of the capacitive storage element is formed by the field electrode.
Type: Application
Filed: Jan 29, 2008
Publication Date: Jul 31, 2008
Applicant: INFINEON TECHNOLOGIES AUSTRIA AG (Villach)
Inventors: Armin Willmeroth (Augsburg), Franz Hirler (Isen)
Application Number: 12/021,709
International Classification: H01L 29/06 (20060101);