U.S. patent application number 13/503439 was filed with the patent office on 2012-10-11 for schottky diode.
Invention is credited to Alfred Goerlach, Ning Qu.
Application Number | 20120256196 13/503439 |
Document ID | / |
Family ID | 43297169 |
Filed Date | 2012-10-11 |
United States Patent
Application |
20120256196 |
Kind Code |
A1 |
Qu; Ning ; et al. |
October 11, 2012 |
SCHOTTKY DIODE
Abstract
A semiconductor system of a Schottky diode is described having
an integrated PN diode as a clamping element, which is suitable in
particular as a Zener diode having a breakdown voltage of
approximately 20 V for use in motor vehicle generator systems. The
semiconductor system of the Schottky diode includes a combination
of a Schottky diode and a PN diode. The breakdown voltage of the PN
diode is much lower than the breakdown voltage of the Schottky
diode, the semiconductor system being able to be operated using
high currents during breakdown operation.
Inventors: |
Qu; Ning; (Reutlingen,
DE) ; Goerlach; Alfred; (Kusterdingen, DE) |
Family ID: |
43297169 |
Appl. No.: |
13/503439 |
Filed: |
September 23, 2010 |
PCT Filed: |
September 23, 2010 |
PCT NO: |
PCT/EP2010/064003 |
371 Date: |
June 29, 2012 |
Current U.S.
Class: |
257/77 ;
257/E21.002; 257/E29.338; 438/380 |
Current CPC
Class: |
H01L 29/66136 20130101;
H01L 29/47 20130101; H01L 29/66143 20130101; H01L 29/0615 20130101;
H01L 29/872 20130101; H01L 29/2003 20130101; H01L 29/1608 20130101;
H01L 29/475 20130101; H01L 29/8611 20130101 |
Class at
Publication: |
257/77 ; 438/380;
257/E29.338; 257/E21.002 |
International
Class: |
H01L 29/872 20060101
H01L029/872; H01L 21/02 20060101 H01L021/02 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 11, 2009 |
DE |
10 2009 046 596.0 |
Claims
1-20. (canceled)
21. A semiconductor system, comprising: a Schottky diode having an
integrated PN diode as a clamping element, which is suitable as a
Zener diode having a breakdown voltage of approximately 20 V for
use in a motor vehicle generator system, a breakdown voltage of the
PN diode being much lower than a breakdown voltage of the Schottky
diode.
22. The semiconductor system as recited in claim 21, wherein the
semiconductor system may be operated using high currents during
breakdown operation.
23. The semiconductor system as recited in claim 21, wherein the
Schottky diode includes an n-epitaxial layer applied to an
n.sup.+-substrate of a chip as a cathode zone of the Schottky
diode, n-wells diffused into the n-epitaxial layer are provided and
are used as a cathode zone of the PN diode, and corresponding
p.sup.+-wells diffused into the n-epitaxial layer and into the
n-wells are provided and are used as an anode zone of the PN
diode.
24. The semiconductor system as recited in claim 23, wherein a
metal layer is located on a rear side of the chip and is used as a
cathode electrode, and a metal layer is located on a front side of
the chip, having ohmic contact to the p.sup.+-wells and having
Schottky contact to the n-epitaxial layer, and is used as an anode
electrode.
25. The semiconductor system as recited in claim 24, wherein a
breakdown of the PN diode occurs at a junction between the
p.sup.+-wells and the n-wells.
26. The semiconductor system as recited in claim 23, wherein a
doping concentration of the n-epitaxial layer is much lower than a
doping concentration of the n-wells and the n-epitaxial layer has
sufficient thickness to implement a much higher breakdown voltage
of the Schottky diode in comparison to the breakdown voltage of the
integrated PN diode.
27. The semiconductor system as recited in claim 23, wherein the
n-wells are implemented in the form of one of diffused wells or
filled trenches.
28. The semiconductor system as recited in claim 27, wherein the
n-wells are implemented in the faun of filled trenches, the
trenches having one of a rectangular shape or a U-shape.
29. The semiconductor system as recited in claim 23, wherein the
n-wells extend up to the n.sup.+-substrate.
30. The semiconductor system as recited in claim 23, wherein
additional n-wells, having a higher doping concentration in
comparison to the n-wells, are located between the n-wells and the
n.sup.+-substrate.
31. The semiconductor system as recited in claim 23, wherein a
width of the n-wells is smaller than a width of the p.sup.+-wells
and the breakdown occurs at a largely one-dimensional PN
junction.
32. The semiconductor system as recited in claim 24, wherein
metallization of at least one of the metal layer on the rear side
of the chip and the metal layer on the front side of the chip is
made up of at least two layers lying upon each other.
33. The semiconductor system as recited in claim 23, wherein the
n-wells are situated in a strip arrangement.
34. The semiconductor system as recited in claim 23, wherein the
n-wells are situated as islands.
35. The semiconductor system as recited in claim 34, wherein the
islands are one of circular or hexagonal.
36. The semiconductor system as recited in claim 24, wherein the
Schottky contact is formed from one of nickel or nickel
silicide.
37. The semiconductor system as recited in claim 23, wherein the
semiconductor system includes a wideband gap semiconductor
material.
38. The semiconductor system as recited in claim 37, wherein the
wideband gap semiconductor material is one of SiC or a
semiconductor material based on nitrides.
39. The semiconductor system as recited in claim 23, wherein
additional structures for reducing edge field strength are in an
edge area of the chip.
40. The semiconductor system as recited in claim 39, wherein the
additional structures are at least one of weakly doped p-areas, and
magnetoresistors.
41. A method for manufacturing a semiconductor system, the
semiconductor system including a Schottky diode having an
integrated PN diode as a clamping element, which is suitable as a
Zener diode having a breakdown voltage of approximately 20 V for
use in a motor vehicle generator system, a breakdown voltage of the
PN diode being much lower than a breakdown voltage of the Schottky
diode, the method comprising: providing an n.sup.+-substrate as a
starting material for the semiconductor system; producing an
n-epitaxial layer using n-epitaxy; diffusing n-wells into the
n-epitaxial layer; producing p.sup.+-wells with the aid of
diffusion; and producing metal layers with the aid of metallization
on a front side and a rear side of a chip.
42. A method for manufacturing a semiconductor system, the
semiconductor system including a Schottky diode having an
integrated PN diode as a clamping element, which is suitable as a
Zener diode having a breakdown voltage of approximately 20 V for
use in a motor vehicle generator system, a breakdown voltage of the
PN diode being much lower than a breakdown voltage of the Schottky
diode, the method comprising: providing an n.sup.+-substrate as a
starting material for the semiconductor system; producing an
n-epitaxial layer using n-epitaxy; trench etching up to the
n.sup.+-substrate; filling up the trenches using one of n-doped
silicon or polysilicon; producing p.sup.+-wells with the aid of
diffusion; and producing metal layers with the aid of metallization
on a front side and a rear side of a chip.
43. A method for manufacturing a semiconductor system, the
semiconductor system including a Schottky diode having an
integrated PN diode as a clamping element, which is suitable as a
Zener diode having a breakdown voltage of approximately 20 V for
use in a motor vehicle generator system, a breakdown voltage of the
PN diode being much lower than a breakdown voltage of the Schottky
diode, the method comprising: providing an n.sup.+-substrate as a
starting material for the semiconductor system; producing an
n-epitaxial layer using n-epitaxy; implantating or diffusing
n-wells; producing the n-epitaxial layer with a second n-epitaxy;
trench etching up to the n-wells; filling up the trenches using one
of n-doped silicon or polysilicon; diffusing p.sup.+-wells;
producing metal layers with the aid of metallization on a front
side and a rear side of a chip.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to a semiconductor system of a
Schottky diode, which has a small leakage current and low forward
voltage, which may be manufactured with the aid of relatively
simple technology, and is suitable in particular as a Zener (Z)
power diode having a breakdown voltage of approximately 20 V for
use in motor vehicle generator systems.
BACKGROUND INFORMATION
[0002] More and more functions are being implemented using
electrical components in modern motor vehicles. An ever higher
demand for electrical power thus arises. In order to cover this
demand, the efficiency of the generator system in the motor vehicle
must be increased. Up to this point, PN diodes were typically used
as the Z diodes in the motor vehicle generator system. Advantages
of the PN diodes are, on the one hand, the low reverse current and,
on the other hand, the high robustness. The main disadvantage is
the high forward voltage UF. At room temperature, current does not
begin to flow until UF=0.7 V. Under normal operating conditions,
e.g., a current density of 500 A/cm.sup.2, UF rises to >1 V,
which means a non-negligible loss of efficiency.
[0003] Schottky diodes are theoretically available as an
alternative. Schottky diodes have a significantly lower forward
voltage than PN diodes, for example, 0.5 V to 0.6 V at a high
current density of 500 A/cm.sup.2. In addition, Schottky diodes
offer advantages during rapid switching operation as majority
carrier components. The use of Schottky diodes in motor vehicle
generator systems has heretofore not occurred, however. This is to
be attributed to several decisive disadvantages of Schottky diodes:
1) higher reverse current in comparison to PN diodes, 2) strong
dependence of the reverse current on the reverse voltage, and 3)
poor robustness, in particular at high temperature. Therefore,
there are ideas and concepts for improving Schottky diodes. Two
examples are described below.
[0004] So-called junction barrier Schottky diodes (JBS) are
described in H. Kozaka, etc., "Low leakage current Schottky barrier
diode," Proceedings of 1992 International Symposium on Power
Semiconductors & ICs, Tokyo, pp. 80-85. As may be inferred from
FIG. 1, a JBS includes an n.sup.+-substrate 1, an n-epitaxial layer
2, at least two p-wells 3 diffused into n-epitaxial layer 2, and
metal layers on front side 4 and rear side 5 of the chip.
Electrically considered, the JBS is a combination of a PN diode,
i.e., a PN junction between p-wells 3 as the anode and n-epitaxial
layer 2 as the cathode and a Schottky diode having the Schottky
barrier between metal layer 4 as the anode and n-epitaxial layer 2
as the cathode. The metal layer on rear side 5 of the chip is used
as the cathode electrode; the metal layer on front side 4 of the
chip is used as the anode electrode having ohmic contact to p-wells
3 and simultaneously as the Schottky contact to n-epitaxial layer
2.
[0005] Because of the small forward voltage of the Schottky diode
in comparison to the PN diode, currents only flow in the forward
direction through the area of the Schottky diode. As a result, the
effective area, i.e., the area per unit of area for the current
flow in the forward direction, is significantly lower in a JBS than
in a conventional planar Schottky diode.
[0006] In the reverse direction, the space charge regions expand
with increasing voltage and collide in the middle of the area
between adjacent p-wells 3 at a voltage which is lower than the
breakdown voltage of the JBS. The Schottky effect, or barrier
lowering effect, which is responsible for the high reverse
currents, is thus partially shielded and the reverse current is
reduced. This shielding effect is strongly dependent on structural
parameters Xjp (penetration depth of the p-diffusion), Wn (distance
between the p-wells), and Wp (width of the p-well) and of doping
concentrations of p-well 3 and n-epitaxial layer 2, see FIG. 1.
[0007] P-wells 3 of a JBS may be implemented via p-implantation and
subsequent p-diffusion. Through lateral diffusion in the
x-direction, whose depth is comparable to the vertical diffusion in
the y-direction, cylindrical p-wells result in the two-dimensional
illustration, i.e., infinite length in the z-direction
perpendicular to the x-y-plane, whose radius corresponds to
penetration depth Xjp. Because of the radial extension of the space
charge regions, this form of p-wells does not display very
effective shielding of the barrier lowering effect. It is not
possible to amplify the shielding effect solely through deeper
p-diffusion, since the lateral diffusion correspondingly becomes
wider at the same time. Decreasing distance Wn between the p-wells
is also not a good solution, since in this way the shielding effect
is amplified, but the effective area for the current flow in the
forward direction is reduced some more.
[0008] An alternative for improving the shielding effect of the
barrier lowering effect of a JBS is the so-called trench junction
barrier Schottky diode TJBS having filled trenches, which is
described in German Patent Application No. DE 10 2004 053 761 A.
FIG. 2 shows such a TJBS. It includes an n.sup.+-substrate 1, an
n-epitaxial layer 2, at least two trenches 6, which are etched into
n-epitaxial layer 2, and metal layers on front side 4 of the chip
as the anode electrode and on rear side 5 of the chip as the
cathode electrode. The trenches are filled up using p-doped silicon
or polysilicon 7. In particular, metal layer 4 may also be made up
of multiple different metal layers lying upon each other. For the
sake of clarity, this is not shown in FIG. 2.
[0009] Considered electrically, the TJBS is a combination of a PN
diode having a PN junction between p-doped trenches 7 as the anode
and n-epitaxial layer 2 as the cathode and a Schottky diode having
the Schottky barrier between metal layer 4 as the anode and
n-epitaxial layer 2 as the cathode. As in a conventional JBS,
currents only flow in the forward direction through the Schottky
diode. Because of a lack of lateral p-diffusion, however, the
effective area for current flow in the forward direction is
significantly greater in the TJBS than in a conventional JBS. In
the reverse direction, the space charge regions expand with
increasing voltage and collide in the middle of the area between
adjacent trenches 6 at a voltage which is lower than the breakdown
voltage of the TJBS. As in the JBS, the barrier lowering effect
which is responsible for high reverse currents is thus shielded and
the reverse currents are reduced. The shielding effect is strongly
dependent on structural parameters Dt (depth of the trench), Wm
(distance between the trenches), and Wt (width of the trench) and
of doping concentrations of p-well 7 and n-epitaxial layer 2, see
FIG. 2.
[0010] The p-diffusion is omitted for implementing the trenches in
the TJBS. Therefore, there is no negative effect of lateral
p-diffusion as in a conventional JBS. A quasi-one-dimensional
expansion of the space charge regions in the mesa area between
trenches 6 may be readily implemented, since depth Dt of the
trench, an important structural parameter for the shielding of the
Schottky effect, no longer correlates with the effective area for
current flow in the forward direction. The shielding effect of
Schottky effects is therefore significantly more effective than in
the JBS having diffused p-wells.
[0011] On the other hand, the TJBS offers a high robustness through
its clamping function. Breakdown voltage BV_pn of the PN diode is
designed in such a way that BV_pn is lower than breakdown voltage
BV_schottky of the Schottky diode and the breakdown occurs on the
base of the trenches. During breakdown operation, the reverse
current only flows through the PN junction. Forward direction and
reverse direction are therefore geometrically separated. The TJBS
therefore has a similar robustness as a PN diode. As a result
thereof, the TJBS is well suitable as a Z diode for use in motor
vehicle generator systems.
SUMMARY
[0012] An advantage of an example embodiment of the present
invention is that of providing a semiconductor system of a Schottky
diode having a small leakage current, low forward voltage, and high
robustness, which may be manufactured with the aid of relatively
simple technologies and is suitable as a Z power diode for use in
motor vehicle generator systems.
[0013] In a particularly advantageous way, the Schottky diode of
the present invention is a combination of a PN diode having a low
breakdown voltage and a Schottky diode having a much higher
breakdown voltage. This is implemented by different doping
profiles, which determine the different breakdown voltages of the
PN diode and the Schottky diode. The electrical field strength at
the Schottky contact is thus sufficiently strongly reduced that a
complex submicrometer trench technology for effective suppression
of the barrier lowering effect, as in a TJBS or a TMBS, is no
longer required.
[0014] In comparison to the JBS, a significantly lower leakage
current is advantageously obtained through significantly lower
electrical field strength at the Schottky contact. In comparison to
the TJBS, a comparable leakage current flows and comparable
robustness is obtainable with the special advantage of
significantly simpler manufacturing technology.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] FIG. 1 shows a junction barrier Schottky diode (JBS).
[0016] FIG. 2 shows a trench junction barrier Schottky diode (TJBS)
having a filled trench.
[0017] FIG. 3 shows a first exemplary embodiment of a semiconductor
system according to the present invention of a Schottky diode.
[0018] FIG. 3a shows an embodiment of the first exemplary
embodiment.
[0019] FIGS. 4-6 show another three exemplary embodiments of
Schottky diodes according to the present invention.
DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS
[0020] In a conventional JBS according to FIG. 1 or a TJBS
according to FIG. 2, the same n-epitaxial layer is typical, which
is used as the cathode zone of the Schottky diode and the cathode
zone of the integrated PN diode. Breakdown voltage BV_schottky of
the Schottky diode is, inter alia, not much higher than breakdown
voltage BV_pn of the integrated PN diode. Therefore, a high
electrical field strength also occurs at the Schottky contact in
the event of a breakdown of the PN diode and, as a result, the
barrier lowering effect also occurs, which results in the high
leakage current. To suppress the barrier lowering effect, or to
reduce the leakage current, in a JBS or a TJBS, a collision of the
space charge regions between the p-doped areas is utilized. This is
not particularly pronounced in a JBS because of the two-dimensional
effect of the diffused PN junctions. On the other hand, the TJBS
requires a high technological outlay to implement the fine trench
structures.
[0021] The barrier lowering effect increases with increasing
reverse voltage. The higher the electrical field strength at the
Schottky contact, the lower is the Schottky barrier. If the
electrical field strength at the Schottky contact may be kept
relatively low, e.g., approximately 1E5 V/cm, the effect of the
voltage dependency of the barrier lowering effect is negligible.
This may be implemented if a Schottky diode having an integrated PN
diode is designed in such a way that breakdown voltage BV_schottky
of the Schottky diode is selected to be much higher than breakdown
voltage BV_pn of the integrated PN diode. However, with an increase
of the breakdown voltage BV_schottky of a Schottky diode, the
voltage drop during operation in the forward direction also
increases, on the other hand. For this reason, high breakdown
voltages BV_schottky are avoided and the Schottky diode is designed
in such a way that BV_schottky is only slightly higher than BV_pn.
Using the measure proposed in the present invention, the Schottky
diodes for reverse current reduction may be designed for
substantially higher breakdown voltages, without the forward
voltage rising strongly.
[0022] The first exemplary embodiment of the present invention is
shown in FIGS. 3 and 3a. This semiconductor system of a Schottky
diode variant includes an n.sup.+-substrate 1, an n-epitaxial layer
2, n-wells 9, which are diffused into n-epitaxial layer 2, having a
width Wnw and a depth Xjn, p.sup.+-wells 8, which are diffused into
n-epitaxial layer 2 and into n-wells 9, having a width Wp and a
depth Xjp, and a distance Wn between adjacent p.sup.+-wells 8,
which form PN junctions together with n-wells 9, and metal layers
on front side 4 of the chip as the anode electrode and on rear side
5 of the chip as the cathode electrode. Depth Xjn of n-wells 9 is
greater than depth Xjp of p.sup.+-wells 8, and width Wnw of n-wells
9 is smaller than width Wp of p.sup.+-wells 8. As shown in FIG. 3a,
the depth of n-wells 9 may also extend, inter alia, up to
n.sup.+-substrate 1 or even beyond it.
[0023] This Schottky diode variant is a combination of a Schottky
diode having a Schottky barrier between metal layer 4 as the anode
and n-epitaxial layer 2 as the cathode and a PN diode having a PN
junction between p.sup.+-well 8 as the anode and n-well 9 as the
cathode.
[0024] In contrast to the JBS shown in FIG. 1, the integrated PN
diode of the Schottky diode of the present invention is no longer
implemented with the aid of p-wells diffused relatively deeper into
the n-epitaxial layer. The integrated PN diode now includes n-wells
9 diffused into n-epitaxial layer 2 and the relatively flatter
p.sup.+-wells 8. The Schottky diode is formed, as in the
conventional JBS, from the Schottky contact and the n-epitaxial
layer; the doping concentration of n-epitaxial layer 2 is much
lower, however, than the doping concentration of n-wells 9. The
doping profiles of n-wells 9 and p.sup.+-wells 8 are set in such a
way that breakdown voltage BV_pn of the PN diode is approximately
20 V. In addition, n-epitaxial layer 2 is designed to be
sufficiently thick so that breakdown voltage BV_schottky of the
Schottky diode is much higher than BV_pn, e.g., BV_pn=20 V and
BV_schottky>60 V.
[0025] The electrical field strength at the Schottky contact is
thus significantly lower upon the breakdown of the Schottky diode
of the present invention than the electrical field strength at the
PN junction, e.g., approximately 1E5 V/cm instead of 5E5 V/cm. The
Schottky diode described here is therefore also not in the range in
which the voltage-dependent barrier lowering effect plays a role in
the breakdown state. Suppressing the barrier lowering effect by
collision of the space charge regions and thus reducing the leakage
current is a completely different concept than in the conventional
JBS or the TJBS shown in FIG. 2. In comparison to the conventional
JBS, the reduction of the leakage current in the Schottky diode of
the present invention is much more effective, since the
voltage-dependent barrier lowering effect does not occur at all. In
comparison to the TJBS shown in FIG. 2, the technology outlay is
much less in the Schottky diode of the present invention, since
submicrometer trench technology for implementing fine trench
structures for effective suppression of the barrier lowering effect
is not necessary.
[0026] As in a conventional JBS or a TJBS, in the semiconductor
system of a Schottky diode of the present invention, currents flow
in the forward direction only through the Schottky diode if the
forward voltage of the Schottky diode is significantly lower than
the forward voltage of the PN diode. However, n-wells 9 are
additionally used for the purpose of reducing the forward voltage,
since the forward current will partially flow through more strongly
doped n-wells 9. The path resistance of the Schottky diode is
advantageously reduced by n-wells 9.
[0027] The Schottky diode of the present invention offers high
robustness due to the clamping function, like a TJBS shown in FIG.
2, since the breakdown also occurs at the PN junction, which is
located deep in the silicon, and reverse currents flow only through
the PN junction during breakdown operation. The Schottky diode of
the present invention therefore has similar robustness as a PN
diode. It is to be noted that the PN diode of the Schottky diode of
the present invention includes a largely one-dimensional PN
junction, since width Wnw of n-wells 9 is smaller than width Wp of
p.sup.+-wells 8, and this results in a homogeneous current
distribution during the breakdown and high robustness.
[0028] Numerous parameters may be optimized depending on the
application with respect to forward voltage, leakage current, and
robustness in the design of the Schottky diode of the present
invention. The doping concentration and the thickness of
n-epitaxial layer 2 play a decisive role in particular. If needed,
a graduated profile of n-epitaxial layer 2 may be advantageous.
[0029] FIG. 4 shows the second exemplary embodiment of the present
invention. The difference from the Schottky diode variant shown in
FIG. 3 is that n-wells 9 are implemented by trench technology. The
effect of the reduction of the forward voltage with the aid of
n-wells 9 is thus still more effective.
[0030] FIG. 5 shows the third exemplary embodiment of the present
invention. The difference from the Schottky diode variant shown in
FIG. 4 is that n-wells 9 now extend up to n.sup.+-substrate 1, or
even somewhat into substrate 1. Still another reduction of the
forward voltage or optimization with respect to forward voltage,
leakage current, and robustness is possible with this variant.
[0031] FIG. 6 shows the fourth exemplary embodiment of the present
invention. The difference from the Schottky diode variant shown in
FIG. 5 is that additional n-wells 10 are located at the base of
n-wells 9. These additional n-wells 10 have significantly higher
doping concentrations than n-wells 9 and may be implemented, e.g.,
with the aid of buried layer technology. This variant offers more
latitude for optimization with respect to forward voltage, leakage
current, and robustness through modification of the doping
concentration, width Wn1 and thickness Dn1 of additional n-wells
10.
[0032] Possible embodiments of the semiconductor system according
to the present invention are as follows:
[0033] The metallization of metal layer (4) and/or metal layer (5)
may be made up of two or more metal layers lying upon each
other.
[0034] N-wells (9) may be situated in a strip arrangement or as
islands and the islands may be circular or hexagonal or may have
any other predefinable shape.
[0035] The Schottky contact is formed, for example, from nickel or
nickel silicide. The semiconductor material is typically silicon;
however, it is also possible that another semiconductor material is
used instead of silicon, in particular a wideband gap semiconductor
material. For example, the wideband gap semiconductor material is
silicon carbide SiC or a semiconductor material based on
nitrides.
[0036] In the possible Schottky diode variants of the present
invention, additional structures may also still be provided in the
edge area of the chip to reduce the edge field strength. These may
be weakly doped p-areas, magnetoresistors, or similar structures
corresponding to the related art, for example.
[0037] Possible manufacturing methods of Schottky diode variants of
the present invention run as follows:
[0038] Variant 1 (for a Schottky diode according to FIG. 3)
[0039] Step 1: an n.sup.+-substrate is used as starting material 1
for the semiconductor system.
[0040] Step 2: n-epitaxial layer 2 is produced with the aid of
n-epitaxy.
[0041] Step 3: diffusion of n-wells 9 into n-epitaxial layer 2.
[0042] Step 4: p.sup.+-wells 8 are formed with the aid of
diffusion.
[0043] Step 5: production of metal layers 4, 5 with the aid of
metallization on the front side and rear side of the chip.
[0044] Variants 2 and 3 (for Schottky diodes according to FIG. 4 or
5)
[0045] Step 1: an n.sup.+-substrate is used as starting material 1
for the semiconductor system.
[0046] Step 2: n-epitaxial layer 2 is produced with the aid of
n-epitaxy.
[0047] Step 3: trench etching (up to n.sup.+-substrate in variant
3).
[0048] Step 4: filling up the trenches using n-doped silicon or
polysilicon 9.
[0049] Step 5: p.sup.+-wells 8 are formed with the aid of
diffusion.
[0050] Step 6: production of metal layers 4, 5 with the aid of
metallization on the front side and rear side of the chip.
[0051] Variant 4 (for a Schottky diode according to FIG. 6)
[0052] Step 1: an n.sup.+-substrate is used as starting material 1
for the semiconductor system.
[0053] Step 2: n-epitaxial layer 2 is produced with the aid of
n-epitaxy.
[0054] Step 3: implantation or diffusion of n-wells 10.
[0055] Step 4: second n-epitaxy to produce n-epitaxial layer 2.
[0056] Step 5: trench etching up to n-wells 10.
[0057] Step 6: filling up the trenches using n-doped silicon or
polysilicon 9.
[0058] Step 7: diffusion of p.sup.+-wells 8.
[0059] Step 8: production of metal layers 4, 5 with the aid of
metallization on the front side and rear side of the chip.
[0060] These steps may optionally still be supplemented by other
manufacturing steps.
* * * * *