DE102005041322A1 - Trench transistor structure, with a field electrode array in the trenches, has a potential fixed for the field electrodes through semiconductor zones - Google Patents

Abstract

The trench transistor structure has a field electrode array (13) in trenches (4). The field electrode array has a conductive link to an array (17) of semiconductor zones (18a-18c) in a semiconductor zone (16) adjacent to a drift zone (8) of the transistor field (1). On applying a gate voltage to the transistor structure, the field electrodes (14a-14c) are fixed on a potential from a semiconductor zone through a space charge zone (20a-20c) extending from the semiconductor zone.

Description

The The invention relates to a trench transistor structure having the features of the preamble of claim 1 and a method for its production.

The development of trench transistors such as MOSFETs (metal oxide semiconductor field effect transistors) is driven by the minimization of the surface specific resistance R _on · A essential.

at of a MOS trench transistor structure defined by mesa regions spaced trenches a cell array of trench transistors. at the trench transistors is common a source region into a body region of the opposite conductivity type embedded, with the body area above a drain area and Drift region of the trench transistor is formed. For controlling the conductivity in a channel area adjoining the trench in the body region one opposite semiconductor regions insulated in the trench formed gate electrode.

decisive for the Withstand voltage of a trench transistor, i. the maximum between source and drain applicable voltage before occurrence of voltage breakdown, are in particular a dopant concentration and a vertical extent of the drift area. The drift area decreases with such components in the blocking state, i. the reverse-biased transition between Body and drift area, the majority the voltage applied between the source and drain blocking voltage. A Lowering of the dopant concentration in the drift region on the one hand favors one hand the dielectric strength leads however, on the other hand, due to the resulting lower conductivity to an enlargement of the area specific ON resistance.

The Provide a isolated in the trench opposite the drift region arranged Field electrode lying at a defined potential calls for compensation of carriers in the drift area. Due to this compensation effect results the opportunity the drift region of the trench transistor compared to trench transistors without such a field electrode with the same dielectric strength increase in its dopant concentration, which in turn leads to a Reduction of the on-resistance results.

Known are field plate trench transistor structures used for reduction the thickness of a blocking voltage receiving field oxide in the trench several Field plates one above the other which are held at different potentials.

Sun strikes DE 103 39 455 a vertical semiconductor device having a field electrode having drift zone. The field electrode is connected to a floating p-region buried in silicon. When a blocking voltage is applied, the space charge zone propagates from the body region, and when the floating p region is reached, its potential and thus the potential of the field plate is frozen at the corresponding potential predetermined by the space charge zone. If further field plates are integrated into the depth of the body region, these are also frozen successively as the blocking voltage is increased to a corresponding potential. This structure brings the disadvantage of a very high production costs. For each of these p-regions, a plurality of individual processes is necessary, the realization of which is questionable in the current state of the art, since, for example, a crystal-defect-free epitaxial overgrowth of insulators or electrodes would be required for this purpose.

DE 103 39 488 describes a lateral field plate transistor with multiple field plates whose potentials are determined by floating p-type regions.

As well it has been proposed to exploit the potential of the field plates from a voltage divider, realized as a Zener diode chain with a series resistance, tap off. However, such a concept has the disadvantage itself that when raising a reverse voltage, a uniform voltage drop across the individual zener diodes is caused. However, since the space charge zone gradually spreads from the body area into the drift zone, would it be however desirable the field plates step by step to a corresponding one To lay potential.

Of the Invention is based on the object, a trench transistor structure specify with field plate arrangement, which potentials for the field plates to disposal provides and can be produced in a simple and cost-effective manner.

The The object is achieved by a trench transistor structure having the features of the independent Claim 1 solved. A process for their preparation is defined in claim 12. Preferred developments of the invention can be taken from the dependent claims are and will be explained in the further description.

According to the invention, a trench transistor structure is indicated in a semiconductor body a trench of a transistor array extending from a surface and spaced from each other by a mesa region, a drift zone of a first conductivity type formed in the mesa region for receiving a reverse voltage, a body region formed above the drift zone of a second conductivity type opposite the first conductivity type having source regions adjacent to the trenches of FIG a first conductivity type, a drain region of the first conductivity type formed below the drift zone, a gate electrode formed in the trenches and spaced from the mesa region by a gate insulation structure for controlling the conductivity of channel regions formed between the source regions and the drift zone and adjacent to the trenches, and one in the trenches arranged field electrode assembly having at least one spaced by an insulating structure of Mesagebiet and the gate electrode and electrically conductive Fel delektrode, wherein the field electrode assembly with a semiconductor zone array, which is formed from at least one surface-reaching semiconductor zone of the second conductivity type and outside of the transistor field in a region adjacent to the drift zone semiconductor region of the first conductivity type is electrically connected.

the the transistor field defined above is an edge termination of Trench transistor structure not assigned. The semiconductor body can for example, from a semiconductor wafer, in particular a silicon wafer, exist, and have about an applied epitaxial layer. In the case of a silicon wafer with applied epitaxial layer The trenches protrude from the surface into the epitaxial layer into it. The arrangement of trenches and Mesagebieten example be a strip, so that the transistor array is made up of strips. alternative However, these are other geometries of the arrangement of trenches and Mesagebieten possible. An electrical connection between the semiconductor zone arrangement, i.e. the at least one surface-reaching semiconductor zone, with the at least one field electrode of the field electrode arrangement can, for example, over a metallization, wherein the at least one field electrode for example, in a zone adjacent to the semiconductor zone arrangement Area over the surface be contacted and thus conductively connected to the metallization can be. The outside of the transistor field adjacent to the drift region semiconductor region is of the same conductivity type as the drift zone, in particular these can Areas may be formed by the same semiconductor layer. Consequently couples the potential in the adjacent semiconductor area to one voltage applied between the source regions and the drain region.

Of the first conductivity type can be n-type and the second conductivity type can be p-type. It is also conceivable, the first conductivity type as p-type and the second conductivity type to train as an n-type.

at an advantageous embodiment the field electrode assembly a plurality of vertically with each other arranged and spaced by the insulation structure from each other field electrodes The semiconductor zone arrangement comprises one of the plurality of field electrodes corresponding plurality of mutually adjacent and the transistor array differently spaced semiconductor zones of the second conductivity type on, wherein the semiconductor zones with increasing lateral distance from Transistor field each arranged with an increasingly deeper in the semiconductor body Field electrode are connected.

There the second conductivity type semiconductor regions in the adjacent semiconductor region are of the first conductivity type and connected to no external potential are, these are floating. Freezing the potential a semiconductor zone is achieved in that when increasing a reverse voltage between drain and source in the transistor field of the adjacent semiconductor region lateral to the drift zone on freely movable charge carriers such as Electrons and holes cleared and the resulting space charge zone upon impact the semiconductor zone their potential and thus the potential of having the semiconductor zone connected field electrode fixed. As a deeper lying field electrode, each with a further from the transistor field spaced semiconductor zone is conductively connected, introduces successive increase of reverse voltage between drain and source first for fixing the potential of an uppermost field electrode as soon as the space charge zone the next to the transistor field adjacent semiconductor zone reached. The space charge zone expands by further increasing the Blocking voltage continues and reaches those of the semiconductor zone outward next adjacent semiconductor zone, so is the below the uppermost field electrode fixed field electrode in its potential. So that's it Potential of the uppermost field electrode the potential of the source regions of the Trench transistor next and the potential of the lowest field electrode is the potential next to the drain of the transistor field. As a result of this Voltage drop between the field electrodes and the laterally adjacent one Reduced area of the drift zone, this allows a reduction the thickness of the insulation structure, for example a field oxide of reasonable thickness.

In an advantageous embodiment is between a semiconductor zone and either one adjacent to the transistor field Halblei terzone or the body region of the transistor field formed on the surface of the semiconductor body extending auxiliary zone of the second conductivity type and a dopant concentration of the auxiliary zone is smaller compared with the dopant concentration of the semiconductor zones. When a reverse voltage between drain and source is applied, these auxiliary zones are successively cleared outwards from the transistor field, ie depleted on freely movable charge carriers, so that they do not conduct conductively between the semiconductor zones or between the transistor zone next to the adjacent semiconductor zone and the body region provide. In contrast, these auxiliary zones lead when you turn on the Trenchtransistorstruk structure for discharging the field plates, since they are not depleted in free-floating charge carriers in this operating state of the trench transistor structure and thus connect the floating semiconductor zones conductively connected to the source regions.

at A further advantageous embodiment forms a closer to Transistor field disposed semiconductor zone of two adjacent Semiconductor zones one drain and the other of the two adjacent semiconductor zones a source of an auxiliary transistor having a channel conductivity of the second conductivity type, wherein a gate electrode of the auxiliary transistor is connected to the drain and a transistor adjacent the next adjacent Semiconductor zone is a source of an additional auxiliary transistor whose Drain is formed in the transistor field and its drain potential determined by the potential of the body region in the transistor field is. Thus, the transistor field next adjacent semiconductor zone on the one hand, the source of an auxiliary transistor whose drain is the Body region in the transistor field forms, on the other hand, this semiconductor zone Also, the drain of a transistor, whose source by the of Transistor field out to the outside next represents adjacent semiconductor zone. Likewise, this is outwardly next adjacent semiconductor zone in the presence of further outward semiconductor zones again the drain of an additional auxiliary transistor Thus, it is a series connection of auxiliary transistors, wherein the semiconductor zones both as a source of a further inward trained auxiliary transistor as well as drain one after Outside trained auxiliary transistor act. If a reverse voltage to the Trench transistor applied, so arises in the range of auxiliary transistors a space charge zone in the adjacent semiconductor region. Such a space charge zone leads to a substrate control effect and thus a substantial increase in the threshold voltage the auxiliary transistors. Once the potential difference between drain and source of one of these auxiliary transistors, i. between adjacent semiconductor zones, reaches the threshold voltage of the auxiliary transistor, a Umladestrom flows to connected to the source of the corresponding auxiliary transistor Field electrode. Thus, the transistor field outwards in a row arranged semiconductor zones on the successive summation the potentials resulting from the tensions. The potential the next to the transistor field adjacent semiconductor zone in blocking operation is thus a threshold voltage from the source potential removed in the cell field. One to the transistor field overcomes neighboring semiconductor zone is thus in blocking operation by two threshold voltages from the source potential removed in the transistor field.

Preferably the auxiliary transistors are designed as planar transistors or as trench transistors. In the formation of the auxiliary transistors as trench transistors For example, the channel region becomes in the adjacent semiconductor region in the area of the side walls the Trenches trained.

at an advantageous embodiment a lying between the source and the drain of the auxiliary transistor Channel region of the first conductivity type a higher one Dopant concentration than that adjacent to the drift zone Semiconductor region. Here, the dopant concentration in Channel area, for example by ion implantation to increase the Threshold increased.

at A further advantageous embodiment is the field electrode arrangement with a further semiconductor zone arrangement having at least one formed in the adjacent to the drift region semiconductor region another semiconductor zone of the second conductivity type conductively connected. Here it is possible in that the semiconductor zone arrangement and the further semiconductor zone arrangement be formed together and adjacent to the drift zone Semiconductor area flowing merge.

In an advantageous manner, the further semiconductor zone arrangement has a plurality of further semiconductor zones which are adjacent to each other and are differently spaced from the transistor array, the further semiconductor zones being conductively connected to an increasingly lower field electrode with increasing lateral distance from the transistor field. Thus, a field electrode is connected to both an auxiliary transistor forming semiconductor zone and to another semiconductor zone. The further semiconductor zone arrangement serves, in particular, for discharging the field plates when the trench transistor structure is switched on again. Each connected to a same field electrode semiconductor zone and further semiconductor zone may overlap each other, so that the corresponding semiconductor zone and the further semiconductor zone a Form common semiconductor zone, ie these can be formed, for example, immediately adjacent to each other.

at a further advantageous embodiment is between a the other semiconductor zones and either one towards the Transistor field adjacent another semiconductor zone or the body area of the transistor field a reaching to the surface of the semiconductor body formed further auxiliary zone of the second conductivity type and a dopant concentration of the second auxiliary zone is smaller compared with the dopant concentration of the further semiconductor zone. When applying a reverse voltage between drain and source these further auxiliary zones from the transistor field outwards gradually eliminated, i.e. depleted on freely movable charge carriers, so this in blocking mode no conductive connection between the others Semiconductor zones or between the next closest to the transistor array Provide semiconductor zone and the body area. In contrast to this to lead these auxiliary zones when the trench transistor structure is switched on again for unloading the field plates, since they are in this operating condition of Trench transistor structure is not depleted on freely movable charge carriers are and thus the floating semiconductor zones conductive with the source regions connect.

In Advantageously, one is closer to the transistor array arranged further semiconductor zone of two adjacent another semiconductor zones one source and the other of the two other Semiconductor zones, a drain of another auxiliary transistor with a channel conductance of the second conductivity type, wherein a gate electrode of the further auxiliary transistor is connected to the drain and a transistor adjacent the next adjacent another semiconductor zone, the drain of an additional additional auxiliary transistor forms, whose source is formed in the transistor array and whose Source potential through the potential of the body region in the transistor field is fixed. These additional auxiliary transistors show when switched on Trench transistor has a lower threshold voltage than that through the Semiconductor zones defined auxiliary transistors due to the attributable Substrate control effect. Thus, the other auxiliary transistors are suitable for discharging the field electrodes when the trench transistor structure is switched on again and prevent the field electrodes from turning on the trench transistor structure again led to negative potential become.

at an advantageous embodiment the semiconductor region adjacent to the drift zone forms one Edge termination of the transistor field. Thus, the space charge zone expands upon application of a reverse voltage between the drain region and the Source regions in the edge conclusion into.

at an advantageous embodiment are the semiconductor zones and / or the other semiconductor zones in arranged further Mesagebieten, the width of the other Mesa offers essentially the width of the mesa regions in the transistor field equivalent. This embodiment is particularly advantageous if a dopant concentration in the drift zone is equal to or less than the dopant concentration in the adjacent semiconductor area.

One inventive method for producing a field electrode arrangement of a trench transistor structure has the steps: providing the semiconductor substrate with the trenches formed therein and one adjacent to the trenches Isolation structure as well as the further steps filling up the Trenches with a conductive Material, applying an etching mask, from the transistor field in the adjacent to the drift zone Semiconductor region covered parts of the trenches and covered in the Transistor field lying parts of the trenches exposing, forming a field electrode by etching back a Part of the conductive Materials in the formed in the transistor field parts of the trenches and forming an isolation structure on the field electrode. Following these further steps may be optional formation one or more field plates by successively repeating the followed by further steps, after which a completion of the transistor field including Forming the semiconductor zone arrangement in the adjacent semiconductor region and connecting the semiconductor zones each with a field electrode he follows. Thus, the field electrodes are respectively to the surface of the Semiconductor body led in the adjacent semiconductor region, from where they, for example, via contact holes with a Metallisierungsebene and from here with the semiconductor zones as well as the other semiconductor zones can be connected. As well Is it possible, for example, the top field electrode, i. that of the gate electrode next adjacent field electrode to put on source potential. The finishing of the transistor field can, inter alia, form the gate electrode, of doped areas such as the source areas or the body area, optional channel implantations for setting the threshold voltage, Include intermediate oxides as well as metallization levels.

Advantageous is to form the insulation structure as a thermal oxide.

In a preferred embodiment, polysilicon is used as the conductive material. The conductivity of the polysilicon can be adjusted in a simple manner, for example, by adding dopants of the p or n conductivity type, for example boron or phosphorus. It should be noted, however, that In addition to polysilicon, a large number of other conductive materials, such as doped semiconductor layers or metallic layers can be suitable. The selection of a suitable conductive material is essentially determined by the process integration.

In Advantageously, the etching mask formed as a structured photoresist. This is for example first Photoresist over the entire surface applied and then lithographically structured, so that the Photoresist in the transistor field is removed and the field electrode in despite being etched back in the semiconductor region adjacent to the drift zone Transistor field continues to reach the surface.

The Invention will be described below in embodiments with reference to Figures closer explained.

1 shows in part a) a schematic cross-sectional view of a detail of a transistor cell array with field electrode assembly and in part b) a schematic cross-sectional view of a first embodiment of a semicon terzonenanordnung in a adjacent to a drift zone semiconductor region,

2 shows a schematic plan view of an embodiment of in 1a represented transistor field and the in 1b illustrated semiconductor zone arrangement,

3 shows a schematic cross-sectional view through a part of a trench in the adjacent semiconductor region with a guided to a surface of a semiconductor body field electrode assembly according to an embodiment,

4 shows in the sub-figures a) and b) views successive process stages during the formation of the field electrode assembly according to an embodiment,

5 shows an embodiment of a semiconductor zone arrangement with planar transistors in the adjacent semiconductor region,

6 shows a further embodiment of a further semiconductor zone arrangement in the adjacent semiconductor region for discharging the field plates when the trench transistor structure in the transistor field is switched on again,

7 shows a schematic cross-sectional view of another embodiment of the other semiconductor zone arrangement in the adjacent semiconductor region for discharging the field plates when the trench transistor structure in the transistor field.

In 1a is a schematic cross-sectional view of a section of a transistor array 1 shown. In a semiconductor body 2 , preferably of silicon, extend from a surface 3 from trenches 4 into it. The trenches 4 are through a mesa area 5 spaced apart. In the Mesagebiet 5 is a body area 6 formed, which to the surface 3 of the semiconductor body 2 enough. In the body area 6 embedded and also to the surface 3 trained as well as the trenches 4 adjacent are source areas 7 of the n ⁺ conductivity type.

In order to indicate a gradation in the conductivity of various semiconductor regions in the figures, n ^{+ is used} to designate a n-type semiconductor region of high conductivity, n denotes a n-type semiconductor region of moderate conductivity and n ^- denotes a semiconductor region used of the n-conductivity type with low conductivity. The attributes large, moderate and low conductivity are to be interpreted relative to each other.

Below the body area 6 is a drift zone 8th formed of n ^- conductivity type. The drift zone 8th is used in particular for receiving voltage when applying a blocking voltage to the trench transistor structure. Below the drift zone 8th is a drainage area 9 which is, for example, a n ⁺ -type metal-bonded semiconductor region. The drainage area 9 For example, it may have a silicon wafer with n ⁺ conductivity.

Inside the trenches 4 is in each case essentially at the level of the Budy area 6 a gate electrode 10 formed, which has a gate insulation structure 11 from the body area 6 spaced and electrically isolated. Thus, over a potential of the gate electrode 10 a conductivity in a channel area 12 between the source areas 7 and the drift zone 8th to be controlled. Below the gate electrode 10 is a field electrode arrangement 13 educated. The field electrode arrangement 13 has three electrically conductive field electrodes positioned one below the other 14a . 14b and 14c on which from each other and from the gate electrode 10 through an isolation structure 15 spaced and electrically isolated. The field electrodes 14a . 14b and 14c as well as the gate electrode 10 are preferably formed of doped, ie conductive, polysilicon.

In 1b is a schematic cross-sectional view of one of the drift zone 8th adjacent semiconductor region 16 shown. In the adjacent semiconductor region acting as edge termination 16 of the n ^- conductivity type is a semiconductor zone arrangement consisting of a first Semiconductor zone 18a , a second semiconductor zone 18b and a third semiconductor zone 18c formed of the p-type conductivity. The semiconductor zones 18a . 18b and 18c reach to the surface 3 of the semiconductor body 2 and are each with one of the field electrodes 14a . 14b and 14c in the transistor field 1 conductively connected. Here is the transistor field 1 next adjacent first semiconductor zone 18a with one immediately below the gate electrode 10 arranged first field electrode 14a conductively connected. Likewise, one below the first field electrode 14a positioned second field electrode 14b with the first semiconductor zone 18a outwards, ie from the transistor field 1 further away, positioned second. Semiconductor zone 18b conductively connected. A corresponding conductive connection also lies between a third field electrode 14c and the third semiconductor zone 18c in front.

Between the adjacent semiconductor zones as well as between the first semiconductor zone 18a and the body area 6 In each case, an auxiliary zone of the p ^- conductivity type is formed. When applying a blocking voltage between the source regions 7 and the drain 9 becomes the adjacent semiconductor region 16 laterally by forming one in the form of equipotential lines 20a . 20b and 20c marked space charge zone cleared of freely movable charge carriers. Here are also the auxiliary zones 19 cleared out and impoverished on freely movable charge carriers. The space charge zone initially spreads from the transistor field 1 to the first semiconductor zone 18a out. When they reach their potential and thus the potential on the first field electrode 14a fixed. As the blocking voltage is further increased, the second and the third field electrodes are successively fixed to correspondingly higher potentials.

If the trench transistor structure is switched on again from the blocking operation, the auxiliary zones set 19 a conductive connection between the semiconductor zones 18a . 18b . 18c as well as the body area 6 ready, causing the field plates 14a . 14b . 14c can discharge. This is due to the fact that the auxiliary zones 19 when the trench transistor structure is switched on again, the semiconductor zones 18a . 18b and 18c conducting with the body area 6 connect.

2 shows a schematic plan view of the transistor array 1 with adjacent semiconductor region 16 , In the extension of the Mesagebiets 5 in the adjacent semiconductor area 16 are the semiconductor zones 18a . 18b . 18c represented as well as the intermediate auxiliary zones 19 , In the 1a ) schematically illustrated cross-sectional view in the transistor field 1 is taken from a line marked AA '. In the 1b illustrated schematic cross-sectional view of the adjacent semiconductor region 16 is in 2 indicated as section line BB '.

In 3 is a schematic cross-sectional view in the adjacent semiconductor region 16 in the trench 4 shown. The cross-sectional view is in 2 characterized by a section line CC '. The upper part of 3 Perspectively shows the supervision of the Mesagebiet 5 , The first field electrode 14a is here in the area of the first semiconductor zone 18a to the surface 3 of the semiconductor body. An electrically conductive connection between the first field electrode 14a and the first semiconductor zone 18a is schematically indicated by a line-shaped connection. The second field electrode 14b is in the range of the second semiconductor zone 18b led to the surface and connected with this also electrically conductive. The same applies to the third field electrode 14c and the third semiconductor zone 18c , The field electrodes 14a . 14b . 14c are among each other and to the gate electrode 10 through the insulation structure 15 isolated. Likewise, the isolation structure isolates 15 the electrodes within the trench 4 to the neighboring mesa area 5 through which a section line BB 'is laid, which the in 2 illustrated section line BB 'corresponds. The simplified line illustrated electrically conductive connection between, for example, the first field electrode 14a and the first semiconductor zone 18a can be realized for example via contact openings and metallization levels.

In 4 In the partial illustrations a) and b) schematic cross-sectional views along the section lines AA '(left partial image) and CC' (right partial image) during successive process stages in the production of the field electrode arrangement are shown schematically. 4a shows a schematic cross-sectional view in the transistor field after filling the trenches 4 with a conductive material 21 for the lowest field electrode. The conductive material 21 the lowest field electrode is from the mesa area 5 through the insulation structure 15 spaced. In the right part of the figure is a schematic cross-sectional view along the section line CC 'from 2 shown. The conductive material 21 for the lowest field electrode is within the trenches 4 and trained beyond. An etching mask 22 covers an edge region of the adjacent semiconductor region and serves as an etch stop for the subsequent etching of the conductive material to form the lowermost field electrode. This etching mask makes it possible to bring the lowermost field electrode to the surface in the edge region of the adjacent semiconductor region 3 respectively.

In 4b is the schematic cross-sectional view in the transistor field along the section line AA 'in the left partial image 2 after re-etching of the conductive material 21 the lowest field electrode 21 ' shown. This etching leaves the lowest field electrode 21 ' deep in the trench 4 back. Above the lowest field electrode 21 ' is the isolation structure 15 re-educated. In the right part of the figure is a schematic cross-sectional view along the section line CC 'from 2 shown. The etching back of the conductive material 21 the lowest field electrode 21 ' is only lateral to the previously formed etch stop layer 22 performed, which is why the bottom field electrode 21 ' in this area to the surface 3 enough. Thus, the lowest field electrode 21 ' be electrically connected via the surface with a semiconductor zone arrangement. A successive repetition of the in the 4a and 4b shown method steps allows stacking a plurality of field electrodes.

In 5 is a schematic cross-sectional view of another embodiment of a semiconductor zone arrangement in the adjacent semiconductor region 16 shown. Next to the body area 6 in the transistor field 1 lies the first semiconductor zone 18a the semiconductor zone arrangement in the adjacent semiconductor region 16 , Outward, ie further from the transistor field 1 removed, lies the second semiconductor zone 18b followed by the third semiconductor zone 18c , The first semiconductor zone 18a serves in this embodiment, on the one hand as a source of an auxiliary transistor 23 whose drain is the body area 6 in the transistor field 1 represents in blocking operation of Tran sistorstruktur. At the same time serves the first semiconductor zone 18a as a drain of an additional auxiliary transistor 23 whose source is the second semiconductor zone 18b is. A gate electrode of the auxiliary transistor 24 is connected to the drain. Likewise, the second semiconductor zone serves as a drain of an auxiliary transistor 23 whose source is the third semiconductor zone 18c is. The gate electrode 24 also this auxiliary transistor 23 is connected to its drain. In this way, depending on the number of field electrodes or semiconductor zones now auxiliary transistors can be successively switched one behind the other. It should be noted at this point again that the first semiconductor zone 18a in particular with the example in 1a shown first field electrode 14a is electrically connected. Accordingly, the second semiconductor zone 18b with the second field electrode 14b and the third semiconductor zone 18c with the third field electrode 14c (please refer 1a ) connected conductively. The gate electrode 24 of the auxiliary transistor 23 that one through the body area 6 has trained drain, is at source potential.

When a blocking voltage is applied between the source regions and the drain region in the transistor field, the space charge zone expands laterally from the transistor field 1 in the adjacent semiconductor area 16 into it. In this case, the adjacent semiconductor region 16 , which has an n ^- -type conductivity, depleted of free charge carriers. Likewise, between the source and the drain of each auxiliary transistor 23 lying channel areas 25 having additionally introduced n-type dopants therein for adjusting the threshold voltage, initially depleted of floating charge carriers. Such a carrier depletion by forming the space charge region acts as a substrate control effect on the auxiliary transistors 23 , This leads to a further increase in their threshold voltage. Reaches between source and drain via an auxiliary transistor 23 abfal loin voltage whose threshold voltage, so is the channel area 25 conductive and the source of the auxiliary transistor 23 fixed to a threshold voltage of the auxiliary transistor above the potential of its drain. Thus, the field electrode connected to the source is also at this potential. By further increasing the blocking voltage in the transistor field, the mutually adjacent semiconductor zones are each a threshold voltage of the intermediate auxiliary transistor 23 kept apart. Thus, the field electrodes arranged below one another in the trench are also each at their potential around a threshold voltage of the auxiliary transistor 23 away from each other in potential.

In 6 is a schematic cross-sectional view of another semiconductor zone arrangement in the adjacent semiconductor region 16 shown. The further semiconductor zone arrangement has a first further semiconductor zone 26a , a second further semiconductor zone 26b and a third further semiconductor zone 26c on. These further semiconductor zones can, for example, the same distances to the body area 6 like the first semiconductor zone 18a , second semiconductor zone 18b and third semiconductor zone 18c (see. 5 ) and can be connected to these accordingly conductive. It is equally conceivable that the semiconductor zones 18a . 18b and 18c in the further semiconductor zone 26a . 26b and 26c to go over, ie they are immediately adjacent to each other. The other semiconductor zones 26a . 26b . 26c form like the semiconductor zones 18a . 18b . 18c further auxiliary transistors 27 which, however, differ from the auxiliary transistors 23 in 5 differ in that their gate electrodes 28 are connected in reverse. The first further semiconductor zone 26a When the trench transistor structure is switched on again, it forms a drain of a further auxiliary transistor 27 whose source is the body area 6 in the transistor field 1 given is. The gate electrode 28 this further auxiliary transistor 27 is thus connected to drain, but the source and the drain are compared to the Anord tion of the auxiliary transistors in 5 reversed. This is because the trench transistor structure in one case (see 5 ) in the blocking mode and in the other case (see 6 ) are operated in the switched-on state. The other auxiliary transistors 27 serve in particular for discharging the field electrodes 14a . 14b and 14c when the trench is switched on again transistor structure. These further auxiliary transistors 27 When the trench transistors in the transistor array are turned on, they have a low threshold voltage since the substrate control effect is eliminated. This can prevent the field electrodes 14a . 14b and 14c when turning on the trench transistor structure to negative potential. The semiconductor zone arrangement 17 as well as the further semiconductor zone arrangement can lie laterally adjacent to one another, for example, in the region of the edge termination. Thus, the semiconductor zone arrangement serves in particular for defining the potentials of the field electrodes in the case of blocking operation of the trench transistor, and the further semiconductor zone arrangement is used in particular for discharging the field electrode arrangement when the trench transistor structure is switched on again.

7 shows a schematic cross-sectional view of a compared to 6 alternative or supplementary embodiment of a further semiconductor zone arrangement for discharging the field electrodes 14a . 14b and 14c , As in 6 are also in the in 7 the embodiment shown, the first further semiconductor zone 26a , the second further semiconductor zone 26b and the third further semiconductor zone 26c corresponding to the first field electrode 14a , the second field electrode 14b and the third field electrode 14c electrically connected. However, the in. Serve 7 shown further semiconductor zones not as a source or drain of other auxiliary transistors, but a discharge of the field electrodes 14a . 14b and 14c When the trench transistor structure is switched on again, it is activated by means of further auxiliary zones 29 , which between the other semiconductor zones 26a . 26b and 26c as well as between the first further semiconductor zone 26a and the body area 6 lie, reached. When the trench transistor structure is switched on again, the further auxiliary zones which have been depleted in the blocking mode on free charge carriers become 29 again conductive and thus provide a conductive connection between the other semiconductor zones 26a . 26b and 26c and the body area 6 ago, so that the field electrodes 14a . 14b and 14c can discharge.

1

neckline from a transistor field

2

Semiconductor body

3

Surface of the Semiconductor body

4

Trench (es)

5

mesa region

6

Body area

7

source regions

8th

drift region

9

drain region

10

gate electrode

11

Gate insulating structure

12

channel region

13

Field electrode arrangement

14a, 14b, 14c

first Field electrode, second field electrode, third field electrode

15

isolation structure

16

adjoining Semiconductor region

17

Semiconductor zone arrangement

18a, 18b, 18c

first Semiconductor zone, second semiconductor zone, third semiconductor zone

19

auxiliary zones

20a, 20b, 20c

equipotential lines in the space charge zone with blocking voltage

21

conductive material the lowest field electrode

21 '

lowest field electrode

22

etching mask

23

auxiliary transistor

24

gate electrode of the auxiliary transistor

25

channel area of the auxiliary transistor

26a, 26b, 26c

first further semiconductor zone, second further semiconductor zone, third others Semiconductor zone

27

Another auxiliary transistor

28

gate electrode the further auxiliary transistor

29

Further auxiliary zones

Claims (16)

Trench transistor structure with - in a semiconductor body ( 2 ) from a surface ( 3 ) from reaching and from each other through a Mesagebiet ( 5 ) spaced trenches ( 4 ) of a transistor field ( 1 ); - one in the mesa area ( 5 ) formed for receiving a reverse voltage drift zone ( 8th ) of a first conductivity type; One above the drift zone ( 8th ) trained body area ( 6 ) of a second conductivity type opposite to the first conductivity type, to the trenches ( 4 ) adjacent source regions ( 7 ) of the first conductivity type; One below the drift zone ( 8th ) trained drainage area ( 9 ) of the first conductivity type; - one in the trenches ( 4 ) trained and from the Mesagebiet ( 5 ) by a gate insulation structure ( 11 ) spaced gate electrode ( 10 ) for controlling the conductivity of between the source regions ( 7 ) and the drift zone ( 8th ) trained and to the Trenches ( 4 ) adjacent canal areas ( 12 ); - one in the trenches ( 4 ) arranged field electrode arrangement ( 13 ) with at least one by an isolation structure ( 15 ) of the mesa area ( 5 ) and the gate electrode ( 10 ) spaced and electrically conductive field electrode ( 14a . 14b . 14c ), characterized in that - the field electrode arrangement ( 13 ) with a semiconductor zone arrangement ( 17 ), which consists of at least one surface ( 3 ) reaching semiconductor zone ( 18a . 18b . 18c ) is formed by the second conductivity type and outside the transistor field ( 1 ) in one to the drift zone ( 8th ) adjacent semiconductor region ( 16 ) of the first conductivity type is electrically connected. Trench transistor structure according to claim 1, characterized in that - the field electrode arrangement ( 13 ) a plurality of vertically arranged one below the other and through the isolation structure ( 15 ) spaced apart field electrodes ( 14a . 14b . 14c ) having; The semiconductor zone arrangement ( 17 ) one of the plurality of field electrodes ( 14a . 14b . 14c ) corresponding plurality of mutually adjacent and of the transistor field ( 1 ) differently spaced semiconductor zones ( 18a . 18b . 18c ) of the second conductivity type; wherein - the semiconductor zones ( 18a . 18b . 18c ) with increasing lateral distance from the transistor field ( 1 ) each with an increasingly deeper in the semiconductor body ( 2 ) arranged field electrode ( 14a . 14b . 14c ) are electrically connected. Trench transistor structure according to claim 1 or 2, characterized in that - between a semiconductor zone ( 18a . 18b . 18c ) and either one towards the transistor field ( 1 ) adjacent semiconductor zone ( 18a . 18b . 18c ) or the body area ( 6 ) of the transistor field ( 1 ) one to the surface ( 3 ) of the semiconductor body ( 2 ) reaching auxiliary zone ( 19 ) is formed of the second conductivity type; and a dopant concentration of the auxiliary zone ( 19 ) is smaller compared to the dopant concentration of the semiconductor zones ( 18a . 18b . 18c ). Trench transistor structure according to one of claims 1 to 3, characterized in that - one closer to the transistor field ( 1 ) ( 18a ) of two adjacent semiconductor zones ( 18a . 18b ) one drain and the other of the two adjacent semiconductor zones ( 18b ) a source of an auxiliary transistor ( 23 form) with a channel conductivity of the second conductivity type; A gate electrode ( 24 ) of the auxiliary transistor is connected to the drain of the auxiliary transistor; wherein - a transistor zone next adjacent semiconductor zone ( 18a ) a source of an additional auxiliary transistor ( 23 ) whose drain is in the transistor field ( 1 ) and its drain potential is determined by the potential of the body region ( 6 ) in the transistor field ( 1 ). Trench transistor structure according to claim 4, characterized in that - the auxiliary transistors ( 23 ) are designed as planar transistors or as trench transistors. Trench transistor structure according to one of claims 4 or 5, characterized in that a between the source and the drain of the auxiliary transistor ( 23 ) channel region ( 25 ) of the second conductivity type has a higher dopant concentration than that of the drift zone ( 8th ) adjacent semiconductor region ( 16 ). Trench transistor structure according to one of the preceding claims, characterized in that the field electrode arrangement ( 13 ) with a further semiconductor zone arrangement with at least one im to the drift zone ( 8th ) adjacent semiconductor region ( 16 ) formed further semiconductor zone ( 26a . 26b . 26c ) of the second conductivity type is conductively connected; Trench transistor structure according to claim 7, characterized in that - the further semiconductor zone arrangement has a plurality of field electrodes corresponding to the plurality of adjacent ones and of the transistor array ( 1 ) differently spaced further semiconductor zones ( 26a . 26b . 26c ) having; wherein - the other semiconductor zones ( 26a . 26b . 26c ) with increasing lateral distance from the transistor field ( 1 ) each with an increasingly lower field electrode ( 14a . 14b . 14c ) are electrically connected. Trench transistor structure according to claim 8, characterized in that - between one of the further semiconductor zones ( 26a . 26b . 26c ) and either one towards the transistor field ( 1 ) adjacent further semiconductor zone ( 26a . 26b ) or the body area ( 6 ) one to the surface ( 3 ) of the semiconductor body ( 2 ) reaching additional auxiliary zone ( 29 ) of the second conductivity type is formed; and - a dopant concentration of the further auxiliary zone ( 29 ) is smaller compared to the dopant concentration of the other semiconductor zones ( 26a . 26b . 26c ). Trench transistor structure according to claim 9, characterized in that - one closer to the transistor field ( 1 ) further semiconductor zone ( 26a ) of two adjacent further semiconductor zones ( 26a . 26b ) one source and the other of the two further semiconductor zones ( 26b ) a drain of another auxiliary transistor ( 27 ) is formed with a channel conductivity of the second conductivity type; A gate electrode ( 28 ) of the further auxiliary transistor ( 27 ) is connected to the drain; wherein - a transistor field ( 1 ) next adjacent further semiconductor zone ( 26a ) the drain of an additional additional auxiliary transistor ( 27 ) whose source is in the transistor field ( 1 ) and its source potential through the potential of Bodyge territory ( 6 ) in the transistor field ( 1 ). Trench transistor structure according to any one of Claims 1 to 10, characterized in that it is connected to the drift zone ( 8th ) adjacent semiconductor region ( 16 ) an edge termination of the transistor field ( 1 ). Trench transistor structure according to one of the preceding claims, characterized in that the semiconductor zones ( 18a . 18b . 18 ) and / or the further semiconductor zones ( 26a . 26b . 26c ) are arranged in further Mesagebieten, wherein the width of the further Mesagebiete substantially the width of Mesagebiete ( 5 ) in the transistor field ( 1 ) corresponds. Method for producing a field electrode arrangement of a trench transistor structure according to one of Claims 1 to 12, characterized by the step: - providing the semiconductor body ( 2 ) with the trenches formed therein ( 4 ) and one to the trenches ( 4 ) adjacent isolation structure ( 15 ); and the further steps: - filling the trenches ( 4 ) with a conductive material ( 21 ); - Applying an etching mask ( 22 ) from the transistor field ( 1 ) into the drift zone ( 8th ) adjacent semiconductor region ( 16 ) reaching parts of the trenches ( 4 ) and in the transistor field ( 1 ) lying parts of the trenches ( 4 ) uncovered; - Forming a field electrode ( 21 ' ) by re-etching a portion of the conductive material ( 21 ) in the in the transistor field ( 1 ) formed parts of the trenches ( 4 ); - forming an insulation structure ( 15 ) on the field electrode ( 21 ' ); and optionally forming one or more further field electrodes by successively repeating the further steps; and - completion of the transistor field ( 1 ) with forming the semiconductor zone arrangement ( 17 ). Method according to claim 13, characterized in that the isolation structure ( 15 ) is formed as a thermal oxide. A method according to claim 13 or 14, characterized in that as a conductive material ( 21 ) Polysilicon is used. Method according to claim 13 to 15, characterized in that the etching mask ( 22 ) is formed as a structured photoresist.