U.S. patent application number 14/692516 was filed with the patent office on 2015-08-13 for method for producing a semiconductor body having a recombination zone, semiconductor component having a recombination zone, and method for producing such a semiconductor component.
The applicant listed for this patent is INFINEON TECHNOLOGIES AUSTRIA AG. Invention is credited to Frank PFIRSCH, Hans-Joachim SCHULZE.
Application Number | 20150228716 14/692516 |
Document ID | / |
Family ID | 40298794 |
Filed Date | 2015-08-13 |
United States Patent
Application |
20150228716 |
Kind Code |
A1 |
PFIRSCH; Frank ; et
al. |
August 13, 2015 |
METHOD FOR PRODUCING A SEMICONDUCTOR BODY HAVING A RECOMBINATION
ZONE, SEMICONDUCTOR COMPONENT HAVING A RECOMBINATION ZONE, AND
METHOD FOR PRODUCING SUCH A SEMICONDUCTOR COMPONENT
Abstract
A semiconductor body may include impurities. The impurities may
act as recombination centers in the semiconductor body and form a
recombination zone are introduced into the semiconductor body
during the process of producing the semiconductor body.
Inventors: |
PFIRSCH; Frank; (Muenchen,
DE) ; SCHULZE; Hans-Joachim; (Ottobrunn, DE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
INFINEON TECHNOLOGIES AUSTRIA AG |
VILLACH |
|
AT |
|
|
Family ID: |
40298794 |
Appl. No.: |
14/692516 |
Filed: |
April 21, 2015 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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12170470 |
Jul 10, 2008 |
9012311 |
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14692516 |
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Current U.S.
Class: |
257/617 |
Current CPC
Class: |
H01L 21/221 20130101;
H01L 29/0623 20130101; H01L 29/66348 20130101; H01L 29/36 20130101;
H01L 29/8611 20130101; H01L 29/167 20130101; H01L 29/7802 20130101;
H01L 29/7397 20130101; H01L 29/0834 20130101; H01L 29/0634
20130101; H01L 29/1095 20130101; H01L 29/7395 20130101; H01L 29/861
20130101; H01L 29/7811 20130101; H01L 21/26506 20130101 |
International
Class: |
H01L 29/06 20060101
H01L029/06; H01L 29/861 20060101 H01L029/861; H01L 29/739 20060101
H01L029/739; H01L 29/78 20060101 H01L029/78; H01L 29/36 20060101
H01L029/36; H01L 29/10 20060101 H01L029/10 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 2, 2007 |
DE |
10 2007 036 147 |
Claims
1. A semiconductor component comprising: a semiconductor body
having a front surface and an opposite rear surface; a
recombination zone formed by impurities between the front and rear
surfaces, wherein the impurities act as recombination centers, and
wherein a surface state density at the front and rear surfaces of
the semiconductor body is just as high as the surface state density
at a front and rear surface of an identical semiconductor body
without a recombination zone.
2. The semiconductor component according to claim 1, wherein the
surface state density is less than 2*10.sup.11 cm.sup.2.
3. The semiconductor component according to claim 2, further
comprising a non-semiconductor layer is applied at the front or
rear surface of the semiconductor body and the recombination zone
is at a distance from the front or rear surface with the
non-semiconductor layer.
4. The semiconductor component according to claim 3, wherein the
non-semiconductor layer is a gate oxide arranged between the
semiconductor body and a gate electrode.
5. The semiconductor component according to claim 1, wherein the
impurities are introduced into the semiconductor body in a locally
delimited manner.
6. The semiconductor component according to claim 1, wherein the
impurities are introduced into the semiconductor body at a distance
from the front and rear surfaces of the semiconductor body.
7. The semiconductor component according to claim 1, wherein the
impurities include at least a heavy metal.
8. The semiconductor component according to claim 8, wherein the
heavy metal comprises tungsten or tantalum.
9. The semiconductor component according to claim 1, futher
comprising a semiconductor body portion on the semiconductor body,
the semiconductor body portion eppitaxially produced.
10. The semiconductor component according to claim 9, wherein the
semiconductor body portion is provided on the semiconductor body
subsequent to providing the recombination zone.
11. The semiconductor component according to claim 9, wherein the
semiconductor body portion includes impurities diffused from the
recombination zone.
12. A semiconductor component, comprising: a semiconductor body
having a first surface and a second surface; a recombination zone
formed by impurities between the first and second surfaces, a
surface state density at or near the first and second surfaces of
the semiconductor body is approximately the same as the surface
state density at or near a surface of an identical semiconductor
body without a recombination zone.
13. The semiconductor component according to claim 12, wherein the
surface state density is less than 2*10.sup.11 cm.sup.-2.
14. The semiconductor component according to claim 12, further
comprising a non-semiconductor layer is applied at the first or
second surface of the semiconductor body and the recombination zone
is at a distance from the first or second surface with the
non-semiconductor layer.
15. The semiconductor component according to claim 14, wherein the
non-semiconductor layer is a gate oxide arranged between the
semiconductor body and a gate electrode.
16. The semiconductor component according to claim 12, wherein the
impurities are introduced into the semiconductor body in a locally
delimited manner.
17. The semiconductor component according to claim 12, wherein the
impurities include at least a heavy metal.
18. The semiconductor component according to claim 17, wherein the
heavy metal comprises tungsten or tantalum.
19. The semiconductor component according to claim 12, futher
comprising a semiconductor body portion on the semiconductor body,
the semiconductor body portion eppitaxially produced.
20. The semiconductor component according to claim 19, wherein the
semiconductor body portion is provided on the semiconductor body
subsequent to providing the recombination zone.
21. The semiconductor component according to claim 19, wherein the
semiconductor body portion includes impurities diffused from the
recombination zone.
Description
REFERENCE TO RELATED APPLICATIONS
[0001] This application is a divisional application of U.S. patent
application Ser. No. 12/170,470 which was filed on Jul. 10, 2008
and claims the benefit of the priority date of the above US
application. U.S. patent application Ser. No. 12/170,470 claimed
foreign priortiy benefit of German Application No. 10 2007 036 147
filed Aug. 10, 2007.
[0002] The entire contents of the above identified prior filed
applications are hereby entirely incorporated herein by
reference.
BACKGROUND
[0003] Exemplary embodiments of the invention relate to a method
for producing a semiconductor body having a recombination zone, to
a semiconductor component having a recombination zone, and to a
method for producing such a semiconductor component.
[0004] Recombination is understood to mean the coming together
again of electron-hole pairs. In silicon, recombinations generally
proceed by way of recombination centers. These involve
contaminations of the semiconductor material which represent a
defect. From an energetic standpoint, these defects lie in the
forbidden band.
[0005] For some rapidly switching applications it is desirable to
realize a significantly reduced carrier lifetime in the
semiconductor body, in particular in the drift zone in the case of
power semiconductor components, such as, for example, an IGBT or a
fast freewheeling diode. This makes it possible for example to
reduce the reverse current and the turn-off losses.
[0006] Previously known possibilities for reducing the carrier
lifetime in such semiconductor components consist in exposing the
semiconductor components to an irradiation with high-energy
particles, such as electrons, for example, which bring about damage
to the crystal lattice and thus the production of recombination
centers. Another possibility is the indiffusion of heavy metals,
such as platinum or gold, for example, from the front side of the
wafer.
[0007] In both variants, however, the front side, in particular a
gate oxide situated thereon, is adversely influenced by the
front-side irradiation or by the diffusion from the front side.
Thus, by way of example, an undesirable shift in the threshold
voltage or else an instability of the electrical properties can
occur.
SUMMARY
[0008] One aspect relates to a method for producing a semiconductor
body, wherein impurities which act as recombination centers in the
semiconductor body and form a recombination zone are introduced
into a semiconductor body during the process of producing the
semiconductor body.
[0009] Furthermore, another aspect relates to a semiconductor
component, comprising a semiconductor body having a front surface
and an opposite rear surface, and also a recombination zone formed
by impurities between the front and rear surfaces, wherein the
impurities act as recombination centers, and wherein the surface
state density at the front and rear surfaces of the semiconductor
body is just as high as the surface state density at a front and
rear surface of an identical semiconductor body without a
recombination zone.
[0010] Another aspect relates to a method for producing a
semiconductor component, wherein a semiconductor body is produced
according to the abovementioned method, a multiplicity of
semiconductor component structures are formed in the semiconductor
body and the semiconductor body is severed in such a way that
individual semiconductor components arise.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS
[0011] Exemplary embodiments are explained in more detail below,
referring to the accompanying figures. However, the invention is
not restricted to the specifically described embodiments, but
rather can be modified and altered in a suitable manner. It lies
within the scope of the invention to combine individual features
and feature combinations of one embodiment with features and
feature combinations of another embodiment in a suitable manner in
order to attain further embodiments according to the invention.
[0012] Before the exemplary embodiments of the present invention
are explained in more detail below with reference to the figures,
it is pointed out that identical elements in the figures are
provided with the same or similar reference symbols and that a
repeated description of these elements is omitted. In the
figures:
[0013] FIG. 1 shows a schematic cross-sectional view of a
semiconductor body with a recombination zone.
[0014] FIG. 2 shows a schematic cross-sectional view of a
semiconductor body produced in two stages with a recombination
zone.
[0015] FIG. 3 shows a schematic cross-sectional view of a
semiconductor body with two recombination zones.
[0016] FIG. 4 shows a schematic cross-sectional view of an
[0017] IGBT with a recombination zone.
[0018] FIG. 5 shows a schematic cross-sectional view of an IGBT
with a field stop layer and a recombination zone.
[0019] FIG. 6 shows a schematic cross-sectional view of a power
diode with a recombination zone.
[0020] FIG. 7 shows a schematic cross-sectional view of an IGBT
with a reverse conducting diode and a recombination zone.
[0021] FIG. 8 shows a schematic cross-sectional view of a
superjunction MOSFET with two recombination zones.
[0022] FIG. 9 shows a schematic cross-sectional view of a
semiconductor device with two semiconductor components and a
recombination zone.
[0023] FIG. 10 shows a schematic cross-sectional view of a step of
producing recombination zones that are spaced apart laterally in a
semiconductor body.
[0024] FIG. 11 shows a schematic cross-sectional view of a
semiconductor body with two recombination zones having different
carrier lifetimes.
DETAILED DESCRIPTION
[0025] Exemplary embodiments below are concerned with a
recombination zone in a semiconductor body which has no adverse
surface influences.
[0026] FIG. 1 illustrates in a general form a semiconductor body 1,
in which impurities 2 which act as recombination centers in the
semiconductor body 1 and form a recombination zone 3 have been
introduced. The impurities are introduced during the process of
producing the semiconductor bodyl.
[0027] The impurities 2 are introduced in the semiconductor body 1
in a locally delimited manner. Moreover, the impurities 2 are
introduced into the semiconductor body 1 in such a way that an
outdiffusion of the impurities from the semiconductor body in
subsequent process steps does not occur. This avoids a disturbing
contamination of manufacturing equipment with the impurities2. This
can be achieved for example by virtue of the fact that the
impurities 2 are introduced into the semiconductor body 1 at a
distance from the surfaces 4 of the semiconductor body 1.
[0028] By way of example, heavy metals, in particular tungsten or
tantalum, are used as the impurities 2. In the method according to
the invention, the diffusion constant of these impurities is chosen
in particular such that the diffusion in the vertical wafer
direction is slower than the rate of growth of the epitaxial layer,
or that the diffusion of said impurities is so slow that the
diffusion of said impurities as far as the semiconductor surface is
avoided. The impurities 2 used have for example a diffusion
constant <10.sup.-13 cm.sup.2/s, in particular a diffusion
constant <10.sup.-14 cm.sup.2/s, at a temperature of
1000.degree. C. in the semiconductor body.
[0029] FIG. 2 illustrates a specific method for producing the
semiconductor body 1 in a two-stage process. In this case, the
production process comprises, as illustrated in FIG. 2a, providing
a first part 1' of the semiconductor body 1. The impurities 2 are
introduced in this first part 1'. This is done for example by
masked implantation of the impurities 2, in particular by such a
deep implantation that a liberation of the impurities 2 by
outdiffusion from the semiconductor body 1 during the subsequent
step of producing a second part 1'' of the semiconductor body does
not occur. The masking of the implantation can be effected e.g. by
means of a patterned resist layer.
[0030] FIG. 2b shows the second part 1'' produced on the first part
1', wherein the first part 1' and the second part 1'' together form
the semiconductor body 1.
[0031] The second part 1'' is produced for example epitaxially on
the first part 1' of the semiconductor body 1. In this case, in one
embodiment, the impurities 2 can also be introduced into the part
1'' by diffusion from the part 1' during the production of the
second part 1'' of the semiconductor body 1.
[0032] The impurities 2 diffuse on account of high temperatures in
subsequent process steps in the semiconductor body 1 and form a
recombination zone 3.
[0033] As shown in FIG. 2b, the recombination zone is enlarged by
comparison with the original introduction zone of the impurities 2.
By a suitable choice of the impurities, in particular with regard
to the diffusion constant, however, the recombination zone always
remains at a distance from the surfaces4of the semiconductor bodyl,
whereby an outdiffusion from the semiconductor body 1 and
influencing of the surfaces4of the semiconductor bodyldo not occur.
In particular, impurities with a lower rate of diffusion during the
epitaxy process than the rate of growth of the epitaxial layer
should be chosen.
[0034] FIG. 3 illustrates a development of the production process
described with regard to FIG. 1 and FIG. 2. In this case, the
method steps of producing the semiconductor body are repeated at
least once. The first part 1' is thus formed by a process sequence
that has already been run through once, as described with regard to
FIG. 2. The semiconductor body 1 with the recombination zone 3 as
described with regard to FIG. 2 is thus the first part 1' of the
semiconductor body when the method steps are repeated. The second
part 1'' of the semiconductor body together with a further
recombination zone 3 is then produced onto the surface 5 of this
new first part 1' of the semiconductor body. This can be repeated
as often as until the desired thickness of the semiconductor body 1
and the desired number of recombination zones 3 have been achieved.
It is then made possible to establish a local distribution of the
recombination zones 3 and thus also of the carrier lifetime in the
vertical direction of the semiconductor body 1.
[0035] Semiconductor components are normally produced in large
numbers in a semiconductor wafer in order thus to be able to
produce many semiconductor components as effectively as possible in
a process sequence.
[0036] Semiconductor components having a recombination zone can be
produced using the method described above in which a wafer is used
as the semiconductor body 1.
[0037] The wafer is therefore produced with a recombination zone 3
by means of the method steps of the method explained in more detail
with reference to FIGS. 1 to 3. In addition, a multiplicity of
semiconductor component structures are formed in and on the wafer
and, finally, the wafer is severed in such a way that individual
semiconductor components arise. Furthermore, it is possible to mask
the implantation of the impurities 2 in the edge region of the
semiconductor wafer in such a way that the lateral distance between
the implanted layer and the edge of the semiconductor wafer is
dimensioned such that the implanted impurities 2 cannot diffuse as
far as towards the wafer edge during the high-temperature steps
that succeed the implantation.
[0038] Semiconductor components which were produced according to
this method are described by way of example below.
[0039] What is common to all the semiconductor components in this
case is that a semiconductor body 10 has a front surface 40 and an
opposite rear surface 41. Moreover, the semiconductor body 10 has a
recombination zone 3 formed by impurities 2 between the front and
rear surfaces 40, 41, wherein the impurities 2 act as recombination
centers and wherein the surface state density at the front and rear
surfaces 40, 41 of the semiconductor body 10 is just as high as the
surface density at a front and rear surface of an identical
semiconductor body without a recombination zone3.
[0040] This means that the recombination zone 3 has no influence on
the surface of the semiconductor body.
[0041] FIG. 4 schematically illustrates an IGBT (Insulated Gate
Bipolar Transistor) as an example of a semiconductor component.
[0042] The IGBT 30 has a semiconductor body 10 composed of a first
part 10' and a second part 10''.
[0043] The first part 10' of the semiconductor body 10 is formed by
a highly doped p.sup.+-type substrate 15, and the second part 10''
is an epitaxial layer 16 produced on the p.sup.--type substrate
15.
[0044] A recombination zone 3 extends across a surface 5 of the
first part 10' into the second part 10'' of the semiconductor body
10, wherein a smaller part of the recombination zone 3 is situated
in the first part 10' and a larger part of the recombination zone 3
is situated in the second part 10'' of the semiconductor body 10.
This distribution can be produced e.g. by means of the multistage
epitaxy and impurity introduction as described in FIG. 3, wherein
the recombination zones 3 are converted by diffusion processes into
a recombination zone that is more extended in the vertical
direction. In the case of a two-stage process in accordance with
FIG. 2, the vertical extent of the recombination zone 3 is greater
in the first part 10', in accordance with the implantation depth,
by approximately double the implantation depth than in the zone
10''.
[0045] The epitaxial layer 16 has, at a front surface 40 of the
semiconductor body 10, first dopant regions 20 as source and second
dopant regions 21 as body of a field-effect transistor. Adjoining
the p-doped body region 21 and insulated from the epitaxial layer
16 by a gate oxide 23, there is a gate electrode 22 situated in a
trench extending into the semiconductor body 10 from a surface 40
of the semiconductor body l0.
[0046] The gate electrode 22 permits the formation of a conducting
channel in the body region 21 between the n.sup.+-doped source
region 20 and a lightly n-doped drift path 6 of the epitaxial layer
16.
[0047] An insulation layer 24 is situated at the front surface 40
of the semiconductor body 10, said insulation layer having cutouts
for a first electrode 7 for making contact with the source and body
regions 20, 21. In this case, contact is made with the body regions
21 via a highly doped body connection zone 21' in the body region
21.
[0048] A second electrode for electrical connection of the
p.sup.+-type substratel5is applied at a rear surface 41 of the
semiconductor body 10.
[0049] The recombination zone 3 of the IGBT 30 is at a distance
from the front surface 40 and in particular also from the surface
of the semiconductor body 10 with respect to the gate oxide 23,
such that an adverse influence with regard to the threshold voltage
of the field-effect transistor is avoided.
[0050] FIG. 5 shows an IGBT 31 slightly modified with respect to
FIG. 4, this IGBT additionally having a field stop zone 9. In this
exemplary embodiment, the first part 10' of the semiconductor body
10 is formed by the p.sup.+-type substrate 15 and the field stop
zone 9. In this case, the field stop zone 9 is an n-doped layer
produced epitaxially on the p.sup.+-type substrate 15. The
recombination zone 3 extends across the surface 5 of the first part
10' of the semiconductor body 10 into the second part 10'' of the
semiconductor body 10. The construction of the IGBT 31 otherwise
corresponds to the exemplary embodiment of the IGBT 30 from FIG.
4.
[0051] In the exemplary embodiment with regard to FIG. 5, the
recombination zone 3 is produced by implantation of impurities 2
into the field stop zone 9 with subsequent diffusion. In this case,
the diffusion takes place at least partly during the further
epitaxial deposition of the second part 10'' of the semiconductor
body 10 in the direction of the p.sup.+-type substrate 15 and into
the second part 10'' of the semiconductor body 10.
[0052] The field stop zone 9 has a higher doping than the lightly
n-doped drift path 6. The dopant concentration of the field stop
zone 9 lies in the range of 1.times.10.sup.15 cm.sup.-3 to
1.times.10.sup.18 cm.sup.-3. The field stop zone 9 has a thickness
in the range of 1 .mu.m to 30 .mu.m.
[0053] FIG. 6 illustrates a diode 32 as a further example of a
semiconductor component with a recombination zone. The diode 32 has
a semiconductor body 10 composed of a highly doped n.sup.+-type
layer 25, an n-doped field stop zone 9 applied thereon and a weakly
n-doped epitaxial layer 16 applied thereon with a further epitaxial
layer 16' applied thereon. At a front surface 40 of the diode, a
p-type well 26 is introduced in the further weakly n-doped
epitaxial layer 16' and together with the n-doped further epitaxial
layer 16' forms a pn junction 27 and thus represents a diode.
[0054] The p-type well 26 is connected by the first electrode 7
(anode). The first electrode 7 is applied on an insulation layer 24
on the front surface 40 of the semiconductor body 10, wherein the
insulation layer 24 has a cutout above the p-type well 26, and the
first electrode 7 (anode) can therefore make contact with the
p-type well 26.
[0055] A second electrode 8 (cathode) for the electrical connection
of the n.sup.+-type layer 25 is applied on a rear surface 41 of the
semiconductor body 10.
[0056] The recombination zone 3 is situated closer to the front
surface 40 than to the rear surface 41, but is at a distance from
the front surface 40.
[0057] The pn junction 27 is situated at least partly within the
recombination zone 3, and the recombination zone 3 is arranged at
the junction between the epitaxial layer 16 and the further
epitaxial layer 16'.
[0058] FIG. 7 shows a reverse conducting IGBT 34, that is to say an
IGBT in which a diode that conducts in the opposite current
direction of the IGBT is integrated, with a recombination zone 3 as
a further example of a semiconductor component.
[0059] The reverse conducting IGBT 34 is constructed similarly to
the IGBT 32 described with regard to FIG. 5. In contrast to the
IGBT 32 in FIG. 5, however, the reverse conducting IGBT 34 has a
semiconductor body 10 which has, at the rear surface 41, at least
one n.sup.+-type region 25 in the p.sup.--type substrate 15 which
is doped oppositely to the p.sup.--type substrate 15. A field stop
zone 9, a drift path 6, and also MOS field-effect transistor
structures 20, 21, 22, 23 are applied in a customary manner above
these alternately arranged p.sup.--type and n.sup.+-type regions at
the rear surface 41 of the semiconductor body 10. The diode that
conducts in the opposite current direction of the IGBT is formed by
the pn junction 28 of the body region 21 with the n-doped drift
path 6. The recombination zone 3 of the reverse conducting IGBT 34
is arranged at the pn junction 28, wherein the recombination zone 3
is arranged at a distance from the gate oxide.
[0060] FIG. 8 illustrates a power semiconductor component with
compensation structures as a further exemplary embodiment of a
semiconductor component with a recombination zone 3. Such a
component is also referred to as a superjunction MOSFET. The
superjunction MOSFET 36 in FIG. 8 has a semiconductor body 10
composed of a substrate 45 highly doped with n-type dopant, an
n-doped field stop zone 9 applied thereon, and an n-doped epitaxial
layer 16 applied on the field stop zone 9. The superjunction MOSFET
36 is divided into a cell array 50 and into an adjoining edge
region 5l. MOSFET structures such as source regions 20 and body
regions 21, for example, are situated in the cell array 50.
[0061] The n-doped epitaxial layer l6 is pervaded by p-doped
pillars 29. In the edge region 5l, said pillars 29 extend from the
front surface 40 of the semiconductor body 10 as far as the field
stop zone 9, while in the cell array 50 the pillars extend from the
body region 2l to the field stop zone 9 through the epitaxial
layer.
[0062] On the front surface 40 of the semiconductor body 10, gate
electrodes 56 suitable for forming a channel region in the body
regions 21 between the source regions 20 and the epitaxial layer 16
are arranged in insulation regions 55 in the cell array 50.
[0063] In the edge region 51, an insulation structure 57 with field
plates 58 arranged therein is applied on the front surface 40 of
the semiconductor body 10.
[0064] The body regions 21 and source regions 22 in the cell array
are electrically connected by a metallic first electrode 7.
[0065] A second metallic electrode 8 is applied on the rear surface
41 of the semiconductor body 10.
[0066] Two recombination zones 3 are arranged within the
superjunction MOSFET, wherein one recombination zone 3 is situated
closer to the front surface 40 of the semiconductor body 10 below
the body regions 21 in the epitaxial layer 16, while the other
recombination zone 3 is situated closer to the rear surface 41 of
the semiconductor body 10 and is arranged at the junction between
field stop zone 9 and epitaxial layer 16. In this case, the
recombination zones 3 are suitable for reducing the storage charge
of the inverse diode of the superjunction MOSFET 36.
[0067] In a further exemplary embodiment, FIG. 9 shows a
recombination zone 3 in a semiconductor component using smart power
technology, that is to say that the semiconductor component
combines at least two different component types, for example a
power transistor 60 and a logic component 70. In this case, the
power transistor 60 can be a DMOS, for example, and the logic
component 70 can contain transistors formed using CMOS
technology.
[0068] Both component types are formed on a common p-type substrate
62 composed of a highly doped first part 65 and a weakly doped part
66 produced thereon.
[0069] The recombination zone 3 is arranged within the p-type
substrate 62 at the junction between the first part 65 and the
second part 66 and reduces the effects of charge carriers--injected
into the p-type substrate 62--of one component on the other
component.
[0070] A further exemplary embodiment of the invention is for the
recombination zone 3 to be laterally subdivided into a plurality of
partial regions, such that the recombination zone 3 is present with
a short carrier lifetime only in parts of a semiconductor
component. Such arrangements are illustrated in FIG. 6 and FIG. 8,
for example, in which the recombination zones 3 were produced in
such a way that they have a laterally delimited extent. Thus, it
may also be desirable, for example, for a greater reduction of the
charge carrier lifetime to be provided in the region of the edge
termination of a blocking pn junction of a semiconductor component
than in the cell array, in order thus to reduce excessive increases
in the electric field strength that are produced during dynamic
operation.
[0071] One possibility for producing such a laterally locally
delimited recombination zone 3 is illustrated with reference to
FIG. 10. In a first part 110' of a semiconductor body 100,
laterally demarcated recombination zones 3 are produced by a
locally delimited implantation of the impurities 2. In this case,
the locally delimited implantation is effected by means of a mask
110 having a width that is greater than double the later lateral
diffusion of the impurities 2. The impurities 2 are thus introduced
into a plurality of partial sections of the semiconductor body,
such that regions without impurities remain between the partial
sections. Afterwards, the mask 110 is removed, the semiconductor
body 100 is completed by applying a second part in the manner
already described, and the recombination zone 3 is formed.
[0072] By using a mask 110 having widths that are smaller than
double the later lateral diffusion of the impurities, it is
possible to produce contiguous regions having a carrier lifetime
reduction to a lesser degree than in homogeneously implanted
regions. In particular, in this way a plurality of regions having
carrier lifetimes of different magnitudes can be produced in one
step, as is indicated by the reference symbols 3' and 3'' in FIG.
11. The regions, which are still separate after implantation,
subsequently diffuse together in this case. The area portion of the
regions masked by the mask 110 determines the dilution of the
concentration of the impurities and thus the carrier lifetime
reduction.
[0073] In all the exemplary embodiments, as a result of introducing
the impurities during the process of producing the semiconductor
body, an adverse influencing of the surfaces can be avoided because
the impurities do not come into contact with the surfaces of the
semiconductor body. A suitable measure of an uninfluenced surface
is the surface state density, which, with a recombination zone
present in a semiconductor component, should not be higher than in
the case of a semiconductor component in which no recombination
zone is present.
[0074] In general, many semiconductor components are produced with
a semiconductor wafer. If the recombination zone is formed over a
large area in such a wafer, a large number of semiconductor
components having recombination zones can be manufactured by
singulations of said semiconductor wafer in an effective form,
without the recombination zones having an adverse influence on the
critical surfaces of the semiconductor components.
[0075] The construction of the semiconductor body and of the dopant
regions formed therein as described in the respective exemplary
embodiments is intended to serve only by way of example for
understanding the invention and does not restrict the invention. In
particular, the dopant types chosen in the individual dopant
regions are interchangeable. Moreover, the semiconductor components
can be formed in a lateral as well as in a vertical embodiment
without restricting the invention.
* * * * *