DE10239310A1 - Production of an electrically conducting connection during the production of a source-down transistor comprises forming a recess extending from the front side up to a first layer - Google Patents

Abstract

Production of conducting connection between first trenched layer (2) of first conductivity arranged at distance from front side (101) of semiconductor body (100) and second layer (4) of second conductivity comprises forming recess from front side to first layer, and doping via recess into boundary region between first and second layer to produce strongly doped connecting zone (3). Production of an electrically conducting connection between a first trenched layer (2) of first conductivity arranged at a distance from a front side (101) of a semiconductor body (100) and a second layer (4) of a second conductivity comprises forming a recess (6) extending from the front side up to the first layer, and introducing doping atoms of first and second conductivity via the recess into a boundary region between the first layer and the second layer to produce a connecting zone (3) in the boundary region which is more strongly doped than the first layer forming a tunnel diode with the second layer.

Description

Process for producing an electrical conductive connection between a first and a second buried Semiconductor layer

The present invention relates to a method for producing an electrically conductive connection between a first and a second buried semiconductor layer in a semiconductor body.

Such an electrically conductive Connection is, for example, in a so-called source-down transistor required between the body zone and the source zone. With source-down transistors the source zone is located in the area of a rear side of a semiconductor body which join the body zone and the drift zone upwards, whereby the drain zone of the transistor in the drift zone in the area of the front of the semiconductor body is arranged. The process steps for making one Transistors are usually used on the Front of the semiconductor body or the wafer in which a multiplicity of semiconductor bodies or Chips are connected together before they are separated. On Change from front processing to rear processing such a wafer is very time consuming and therefore expensive.

An electrically conductive connection between that in the area of the back of the semiconductor body arranged source zone and the buried body zone is also at source-down MOSFET required to the in a well known manner Effect of a parasitic Eliminate bipolar transistor by the sequence of the source zone that complementary to the source zone doped body zone and complementary to that Body zone doped drift zone and drain zone is formed.

The aim of the present invention is it, therefore, a method of making an electrically conductive Connection between a first and a second buried semiconductor layer, in particular between a body zone and a source zone Source-down transistor.

This goal is achieved through a process according to the characteristics of claim 1 and by a method according to the features of claim 7 achieved. Advantageous refinements of the method according to the invention are the subject of the subclaims.

The manufacturing method according to the invention an electrically conductive connection between one spaced to a front side of a semiconductor body arranged first buried layer a first conduction type and a second one following the first layer A layer of a second conduction type comprises producing one Recess that extends from the front to the first Layer extends, and the introduction of dopant atoms first or second line type via the recess in a border area between the first layer and the second layer to a stronger than to produce the first layer doped connection zone in the border area, which forms a tunnel diode with the second layer. The electric conductive connection between the first layer and the second In the semiconductor component according to the invention, the layer takes place over this Tunnel diode, the connection layer and the second layer are suitably doped to form such a tunnel diode.

The dopant concentration in the The connection zone is preferably substantially larger than the dopant concentration of dopant atoms of the first conductivity type in the first layer.

The introduction of the dopant atoms in the border area between the first and the second layer takes place, for example, by means of an implantation process, at which dopant atoms or dopant ions over the bottom of the recess implanted in the border area between the first and second layers become. The implantation energy is chosen so that the dopant atoms from the bottom of the recess above the second layer lies in the border area between the first Layer and the second layer. At this implantation step includes preferably an activation step with which the introduced Dopant atoms built into the crystal lattice of the semiconductor body and thus be activated electrically. During this activation step the semiconductor body for example for very short time using an RTP process (RTP = Rapid Thermal Processing) heated up within a very short time and within cooled down again in a very short time.

Another possibility for introducing the dopant atoms in the border area between the first and second layers therein the bottom of the recess containing a dopant atom To occupy the layer and then the dopant atoms a temperature step in the semiconductor material to the limit between the first layer and the second layer. To produce a p-doped connection zone can be used as the material for the Covering the bottom of the recess, for example, borosilicate glass (BSG) or boron phosphor silicate glass (BPSG) can be selected.

Another method for producing an electrically conductive connection between a first buried layer of a first conduction type arranged at a distance from a front side of a semiconductor body and a second layer of a second conduction type adjoining the first layer comprises the production of a recess that extends from the front side the first layer extends into the second layer, and the production of an electrically conductive connection layer is exposed in the recess de areas in the area of the first layer and the second layer.

Preferably, before the Connection layer an area of the exposed in the recess first layer heavily doped with dopant atoms of the first conductivity type, around in the first layer in the area where the connection layer will later be is applied, a more heavily endowed Generate contact zone.

In one embodiment of this method it is intended to produce the recess in two stages, starting with a first recess section is generated, which extends into the first layer enough and that ends above the second layer, and starting from a second recess section is produced from a bottom of the first recess section that extends into the second layer and at least its side walls is partially covered by the electrically conductive connection layer.

Preferably the side walls of the first Recess section covered with a protective layer, after the manufacture of the second recess section dopant atoms of the first conductivity type be introduced into the first layer to make a more doped Get contact zone. The protective layer in the area of the first recess section also prevents that in this area of the first recess section Dopant atoms are introduced into the semiconductor body. The comprises protective layer applied in the first recess section for example an oxide layer and a nitride layer.

The electrically conductive connection layer exists when using silicon as the semiconductor material for the first and second layer of, for example, a silicide, e.g. tungsten silicide (WoSi) or tantalum silicide (TaSi).

The methods according to the invention are particularly suitable to establish an electrically conductive connection between the buried body zone and the source zone of a source-down transistor, in which the source zone is in the area of the back of the semiconductor body or wafer and where the body zone is up to the source zone followed. The establishment of the electrically conductive connection is in use of the method according to the invention Front of the semiconductor body or wafers possible, so that these process steps in the course of the remaining process steps Manufacture of the source-down transistor with machining from the front done here can be.

The present invention is hereinafter described in embodiments explained in more detail with reference to figures. In shows the figures

1 a semiconductor body with a buried doped semiconductor layer and a further semiconductor layer adjoining the buried layer in a side view in cross section during various method steps for producing an electrically conductive connection between the buried layer and the further layer,

2 a semiconductor body with a buried doped semiconductor layer while opposite 1 modified method steps for producing an electrically conductive connection between the buried layer and a further semiconductor layer,

3 4 shows a side view of a source-down transistor in cross section with an electrically conductive connection between the body zone and the source zone of the transistor,

4 a semiconductor body with a buried doped semiconductor layer and a further semiconductor layer adjoining the buried layer and with an electrically conductive connection zone between the buried layer and the further layer, which was produced by means of a further method according to the invention,

5 Semiconductor body in side view in cross section during various process steps for producing a connection zone according to 4 .

6 a source-down transistor in side view in cross section with an electrically conductive connection made by means of the further inventive method between the source zone and the buried body zone of the transistor.

Designate in the figures, if not specified otherwise, same reference numerals, same structural elements with the same meaning.

A first exemplary embodiment of a method according to the invention for producing an electrically conductive connection between a buried semiconductor layer 2 a first conduction type and one attached to the buried layer 2 subsequent semiconductor layer 4 of a second line type is subsequently based on the 1a to 1c explained.

1a shows a cross section through a semiconductor body 100 , the three semiconductor layers in the embodiment 2 . 4 . 5 comprises, namely a buried doped semiconductor layer 2 a first conduction type that is vertically spaced from a front 101 of the semiconductor body pers 100 is arranged. Starting from the front 101 follows this buried first semiconductor layer 2 down a second semiconductor layer 4 at that in the area of a back of the semiconductor body 100 can be exposed, but can also be formed as a buried layer, by further semiconductor layers attached to this second layer 4 connect what's in 1a is not explicitly shown. Between the buried first layer 2 and the front 101 there is another semiconductor layer 5 that with dopant atoms doped of the first conductivity type, doped with dopant atoms of the second conductivity type or can be undoped.

To establish an electrically conductive connection between the first layer 2 and the second layer 4 first becomes a recess 6 starting from the front 101 in the semiconductor body 100 introduced that into the first layer 2 enough, the recess 6 in the vertical direction of the semiconductor body 100 above the second layer 4 ends. The semiconductor body 100 with the trench 6 is in 1b shown.

Next, close using 1c explained method steps in which dopant atoms of the first or second conductivity type in a boundary region between the first layer 2 and the second layer 4 be brought in like this in 1c is shown. The introduction of these dopant atoms to create the connection zone 3 takes place, for example, by means of an implantation process, by the bottom of the recess 6 is irradiated with dopant atoms of the first or second conductivity type, these dopant atoms in the boundary region between the first layer 2 and the second layer 4 advance to the connection zone 3 to build. In order to produce a p-doped connection zone, acceptor atoms, for example boron, with a high radiation dose, for example in the range from 5 × 10 ¹⁵ cm ^{−2, are} in the boundary region between the first and second semiconductor layers 2 . 4 implanted. The implantation energy is chosen so that the dopant atoms start from the recess bottom 61 up to the border area where the connection zone 3 is formed.

An implantation of dopant atoms in the semiconductor layer 5 To avoid this, a protective layer is preferred before implantation 62 , for example an oxide layer, on the side walls of the recess 6 generated.

The implantation of the dopant atoms follows preferably a temperature step, in particular an RTP step at which the semiconductor body heated up in a very short time and within a very short time Time cooled down again to thereby electrically activate the dopant atoms. For one Activation only requires a low temperature budget, so for this one RTP step is sufficient.

The electrically conductive connection 3 produced by means of the method according to the invention is designed as a highly doped semiconductor zone which has a tunnel contact between the first buried semiconductor layer 2 and the buried layer 2 subsequent semiconductor layer 4 forms. The second semiconductor layer 4 has a sufficiently high doping to form this tunnel contact. This second semiconductor layer 4 is formed, for example, by a semiconductor substrate on which the first layer 4 is applied by epitaxy. Such semiconductor substrates are usually highly doped, so that one of the requirements for forming the tunnel contact is already met. The other requirement is through the connection zone 3 created higher than the first semiconductor layer 2 is endowed. The doping concentrations of the connection zone 3 and the second semiconductor layer 4 are preferably of the same height and are preferably more than 10 ¹⁹ cm ^-3 , preferably between 2 × 10 ²⁰ cm ^-3 and 8 × 10 ²⁰ cm ^-3 .

Such tunnel contacts or tunnel diodes are known to have a resistance characteristic within a voltage range around the zero point and are therefore suitable for the electrically conductive connection of the first semiconductor layer 2 and the second semiconductor layer 4 ,

A modification of the in 1a method described below is based on the 2a and 2 B explained.

2a shows the semiconductor body 100 after making the recess 6 that start from the front 101 down to the first shift 2 enough and that above the second layer 4 ends. On the ground 61 This recess becomes a layer containing dopant atoms 63 deposited like this in 2a is shown in the result. A material containing p-type dopant atoms is, for example, borosilicate glass (BSG) or borophosphosilicate glass (BPSG).

The arrangement according to 2a with the material containing dopant atoms 63 at the bottom of the recess 6 is then subjected to a temperature process to place the dopant atoms in the first layer 2 and the second layer 4 drive out and so a heavily doped connection zone 3 between the first layer 2 and the second layer 4 to create.

Relevant for that based on the 2a and 2 B The method explained is that the material containing the dopant atoms 63 is applied to the bottom of the recess. Since, in conventional deposition processes, materials suitable for this purpose, for example BSG or BPSG, are applied to the side walls of the recess 6 cannot be completely prevented, a protective layer is preferably used before the deposition step 64 applied to the side walls of the trench, which layer doping the semiconductor during the diffusion step 5 prevented. This protective layer is in 2a with the reference symbol 64 designated.

3 shows a side view in cross section of a source-down MOS transistor with a according to the 1 explained method produced connection zone between a buried body zone 2 and a source zone 4 , In the exemplary embodiment, the MOSFET is designed as an n-type trench MOSFET (trench MOSFET). The source zone 4 is in the area of the back of the semiconductor body 100 arranged and is for example by a heavily n-doped semi-lead ter substrate formed. To this source zone 4 is a p-doped body zone 2 applied, which was produced for example by means of an epitaxy process. To this body zone 2 a weakly n-doped drift zone closes at the top 5 which, for example, was also produced using an epitaxial process. In the area of the front 101 of the semiconductor body, heavily n-doped drain zones are present in this drift zone.

Starting from the front 101 trenches extend with gate electrodes formed therein 11 through the drift zone 5 and the body zone 2 down to the source zone 4 , The gate electrodes 11 are by means of insulation layers 12 , for example oxide layers, with respect to the semiconductor body 100 insulated and consist for example of polysilicon. The front 101 is with an insulation layer 10 covered, this insulation layer 10 Contact holes, not shown, for contacting the drain zones 9 having.

The recess 6 that are used to create the connection zone 3 starting from the front 101 was produced in accordance with the MOSFET 3 in the lateral direction between two control electrodes 11 and was used after the completion of the process steps to create the connection zone 3 with an insulation material 65 refilled.

The process steps for establishing the connection zone 3 can be carried out before the other process steps required to form the transistor structures, these process steps can also be carried out after the process steps for producing the transistor structure, or the process steps can be carried out together, for example by trenches for the gate electrodes 11 and the ditch 6 are generated during common process steps.

4 shows a cross section through a semiconductor body 100 with a buried doped semiconductor layer 2 of the first line type and one related to the front 101 down to the buried layer 2 subsequent second semiconductor layer 4 of a second line type and with one in a trench 7 arranged connection zone 8th for establishing an electrically conductive connection between the first and second layers 2 . 4 , The ditch 7 is used in this method to produce an electrically conductive connection between the semiconductor layers 2 . 4 starting from the front 101 of the semiconductor body 100 generated so that it passes through the first layer 2 down to the second shift 4 enough. Then the connection layer 8th , which consists for example of a silicide, on the side walls of the trench 7 adjacent to the first layer 2 and the second layer 4 deposited to form an electrically conductive connection between these layers 2 . 4 to ensure.

Preferably the first layer 2 in the area of the recess 7 more heavily doped with dopant atoms of the first conductivity type to more heavily doped contact zones 21 to generate the electrical resistance between the connection layer 8th and the first layer 2 reduce and so the electrically conductive connection between the semiconductor layers 2 . 4 improve.

A possible method for producing such a connection layer 8th is subsequently based on 5 explained.

5a shows the semiconductor body 100 after first process steps in which a first recess section 71 starting from the front 101 was generated, this recess section 71 down to the first shift 2 enough, but above the second layer 4 ends.

Then, as the result in 5b is shown, a protective layer on the semiconductor body 100 and especially in the recess section 71 on the semiconductor body 100 applied, this protective layer, for example, one on the semiconductor body 100 applied oxide layer 73 and one on the oxide layer 73 applied nitride layer comprises.

Then, as in 5c shown, starting from the bottom of the recess section 71 a second recess section 72 formed in the vertical direction up to the second layer 4 enough. This cutout section 72 is produced, for example, by means of an anisotropic etching process, with a paint mask shown in broken lines 200 the front 101 protects the semiconductor body during the etching process.

5d shows the arrangement according to 5c after further process steps in which the first layer 2 in the area of the second recess section 72 was doped more heavily with dopant atoms of the first conductivity type to more doped contact areas 21 of the first conduction type in the area of the second recess section 72 to create. Then on exposed semiconductor areas in the second recess section 72 the connection layer 8th generated. This connection layer 8th If silicon is used as the semiconductor material, it consists, for example, of a silicide such as, for example, tantalum silicide or tungsten silicide. To create this connection zone 8th becomes tantalum or tungsten on sidewalls in the second recess section 72 applied.

The production of the contact zones 21 is carried out, for example, by means of an implantation method in which dopant atoms are implanted obliquely, that is to say at an angle greater than zero degrees with respect to the vertical, or by a material containing dopant atoms in the second recess section 72 is deposited and then a diffusion process is carried out. The protective layers 73 . 74 protect the semiconductor layer 5 before doping with dopant atoms of the first conductivity type. Inevitably succeeded during this doping also dopant atoms of the first conductivity type into the second layer 4 , Especially when this second layer 4 forms the source zone of a source-down transistor, this second semiconductor layer is, however, so heavily doped with dopant atoms of the first conductivity type that the dopant atoms of the second conductivity type introduced during the doping process explained do not completely redoping the semiconductor layer 4 can effect. The area in which dopant atoms of the first conductivity type enter the second semiconductor layer 4 during the creation of the contact zone 21 is introduced in 5d shown in dashed lines.

Finally, the cutout sections 71 and 72 formed trench with an insulating material 75 , for example a semiconductor oxide.

6 shows a source-down transistor with a connection zone 8th between its source zone 4 and its body zone 2 based on the 5 explained method was produced. The other structures of the transistor correspond to those in 3 Structures shown and are provided with corresponding reference numerals, so that with respect to these transistor structures 3 is referred.

The trenches 6 and 7 that are used for the production of the electrically conductive connection between the semiconductor layers 2 and 4 are generated, after completion of the process steps explained for establishing the electrically conductive connection, each filled with an electrical insulation material, which can be, for example, a semiconductor oxide or also borophosphosilicate glass (BPSG).

2

buried Semiconductor layer of the first conductivity type

3

connecting zone

4

Semiconductor layer of the second line type

5

Semiconductor layer

6

recess

7

recess

8th

link layer

9

Drain region

10

insulation layer

11

Gate electrode

12

insulation layer

21

strongly doped zone

61

ground the recess

62

protective layer on side walls the recess

63

dopant atoms containing layer

64

protective layer on side walls the recess

65

insulation layer

71

first recess portion

72

second recess portion

73

protective layer

74

protective layer

75

insulation material

100

Semiconductor body

101

front of the semiconductor body

200

mask

Claims (14)

Method for producing an electrically conductive connection between a spaced from a front side ( 101 ) of a semiconductor body ( 100 ) arranged first buried layer ( 2 ) of a first conduction type and a second layer adjoining the first layer ( 4 ) of a second line type, which comprises the following method steps: - producing a recess ( 6 ) starting from the front ( 101 ) to the first shift ( 2 ) extends, - introduction of dopant atoms of the first or second power type over the recess ( 6 ) in a border area between the first layer ( 2 ) and the second layer ( 4 ) to be stronger than the first layer ( 2 ) doped connection zone ( 3 ) in the border area, which with the second layer ( 4 ) forms a tunnel diode. The method of claim 1, wherein the dopant atoms over a bottom ( 61 ) at a lower end of the recess in the border area between the first layer ( 2 ) and the second layer ( 4 ) are implanted. The method of claim 2, wherein a temperature step follows the implantation step closes. Method according to Claim 1, in which a layer (containing dopant atoms) for introducing the dopant atoms ( 62 ) is deposited in the trench, and the dopant atoms are driven into the boundary region between the first layer and the second layer by means of a temperature step. Method according to one of the preceding claims, in which the connecting zone ( 3 ) is of the first line type. Method according to one of the preceding claims, which the trench with after introducing the dopant atoms Insulation material filled up becomes. Method for producing an electrically conductive connection between a spaced from a front side ( 101 ) of a semiconductor body ( 100 ) arranged first buried layer ( 2 ) of a first conduction type and a second layer adjoining the first layer ( 4 ) of a second line type, which comprises the following method steps: - producing a recess ( 7 ) starting from the front ( 101 ) through the first layer ( 2 ) into the second shift ( 4 ) extends, - producing an electrically conductive connection layer ( 8th ) on surfaces exposed in the recess in the area of the first layer ( 2 ) and the second layer ( 4 ). The method of claim 7, wherein the recess ( 7 ) is generated in two stages, with a first recess section ( 71 ) that is generated up to the first layer ( 2 ) is sufficient, and, starting from a bottom of the first recess section, a second recess section ( 72 ) is generated, which extends into the second layer ( 3 ) and the side walls at least partially through the electrically conductive connection layer ( 8th ) is covered. Method according to Claim 7 or 8, in which, before the production of the second trench section ( 72 ) a protective layer is applied to exposed areas in the first trench section. The method of claim 9, wherein the protective layer is an oxide layer ( 73 ) and a nitride layer ( 74 ) includes. Method according to one of Claims 7 to 10, in which, before the connection layer ( 8th ) the first layer ( 2 ) adjacent to the second trench section ( 72 ) is doped with dopant atoms of the first conductivity type in order to form a more heavily doped contact zone ( 21 ) to create. Method according to one of Claims 7 to 12, in which the trench ( 7 ; 71 . 72 ) after establishing the connection layer ( 8th ) is filled with an insulation material. Use of the method according to one of the preceding claims during the manufacturing process of a source-down transistor, which has the following features: a semiconductor body ( 100 ) with a source zone ( 4 ) of a second line type, one above the source zone ( 4 ) arranged body zone ( 2 ) of a first line type and one above the body zone ( 2 ) below a front ( 101 ) of the semiconductor body ( 100 ) arranged drift zone ( 5 ) of the first line type, - at least one, starting from the front ( 101 ) in the vertical direction of the semiconductor body ( 100 ) through the drift zone ( 5 ), the body zone ( 2 ) to the source zone ( 4 ) extending trench ( 10 ), isolated from the semiconductor body ( 100 ) a gate electrode ( 12 ) is arranged for establishing an electrically conductive connection between the buried body zone ( 2 ) and the source zone ( 4 ). The method of claim 13, wherein the trench ( 6 ; 7 ; 71 . 72 ) for establishing the electrically conductive connection in the lateral direction spaced from the at least one trench ( 10 ) is generated with the control electrode.