U.S. patent application number 16/595375 was filed with the patent office on 2021-04-08 for silicon carbide device with an implantation tail compensation region.
The applicant listed for this patent is Infineon Technologies AG. Invention is credited to Rudolf Elpelt, Michael Hell, Caspar Leendertz, Dethard Peters.
Application Number | 20210104605 16/595375 |
Document ID | / |
Family ID | 1000005476211 |
Filed Date | 2021-04-08 |
United States Patent
Application |
20210104605 |
Kind Code |
A1 |
Hell; Michael ; et
al. |
April 8, 2021 |
Silicon Carbide Device with an Implantation Tail Compensation
Region
Abstract
A SiC substrate of a semiconductor device includes: a drift
region of a first conductivity type; a body region of a second
conductivity type having a channel region which adjoins a first
surface of the SiC substrate; a source region of the first
conductivity type adjoining a first end of the channel region; an
extension region of the first conductivity type at an opposite side
of the body region as the source region and vertically extending to
the drift region; a buried region of the second conductivity type
below the body region and having a tail which extends toward the
first surface and adjoins the extension region; and a compensation
region of the first conductivity type protruding from the extension
region into the body region along the first surface and terminating
at a second end of the channel region opposite the first end.
Inventors: |
Hell; Michael; (Erlangen,
DE) ; Elpelt; Rudolf; (Erlangen, DE) ;
Leendertz; Caspar; (Munich, DE) ; Peters;
Dethard; (Hoechstadt, DE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Infineon Technologies AG |
Neubiberg |
|
DE |
|
|
Family ID: |
1000005476211 |
Appl. No.: |
16/595375 |
Filed: |
October 7, 2019 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01L 29/66712 20130101;
H01L 29/167 20130101; H01L 29/7802 20130101; H01L 29/1608
20130101 |
International
Class: |
H01L 29/167 20060101
H01L029/167; H01L 29/16 20060101 H01L029/16; H01L 29/66 20060101
H01L029/66; H01L 29/78 20060101 H01L029/78 |
Claims
1. A semiconductor device, comprising: a silicon carbide (SiC)
substrate comprising: a drift region of a first conductivity type;
a body region of a second conductivity type above the drift region
and having a channel region which adjoins a first surface of the
SiC substrate; a source region of the first conductivity type in
the body region and adjoining a first end of the channel region; an
extension region of the first conductivity type at an opposite side
of the body region as the source region and vertically extending to
the drift region; a buried region of the second conductivity type
below the body region and having a tail which extends toward the
first surface and adjoins the extension region; and a compensation
region of the first conductivity type protruding from the extension
region into the body region along the first surface and terminating
at a second end of the channel region opposite the first end, the
compensation region overcompensating the tail of the buried region
so that the tail is separated from the second end of the channel
region.
2. The semiconductor device of claim 1, wherein the compensation
region has a shallower average depth in the SiC substrate than both
the source region and the body region as measured from the first
surface.
3. The semiconductor device of claim 1, wherein the compensation
region is doped more heavily than the extension region in a
non-overlapping part of the compensation and extension regions.
4. The semiconductor device of claim 1, further comprising an
insulated gate on the first surface and configured to control a
conducting state of the channel region, wherein the compensation
region laterally extends further along the insulated gate toward
the source region than the extension region.
5. The semiconductor device of claim 1, further comprising a drain
region of the first conductivity type below the drift region and
adjoining a second surface of the SiC substrate opposite the first
surface.
6. A method of producing a semiconductor device, the method
comprising: forming a drift region of a first conductivity type in
a silicon carbide (SiC) substrate; forming a body region of a
second conductivity type above the drift region and having a
channel region which adjoins a first surface of the SiC substrate;
forming a source region of the first conductivity type in the body
region and adjoining a first end of the channel region; forming an
extension region of the first conductivity type at an opposite side
of the body region as the source region and vertically extending to
the drift region; forming a buried region of the second
conductivity type below the body region, the buried region having a
tail which extends toward the first surface and adjoins the
extension region; and forming a compensation region of the first
conductivity type protruding from the extension region into the
body region along the first surface and terminating at a second end
of the channel region opposite the first end, the compensation
region overcompensating the tail of the buried region so that the
tail is separated from the second end of the channel region.
7. The method of claim 6, wherein forming the compensation region
comprises: blanket implanting dopants of the first conductivity
type into the first surface of the SiC substrate to define a doping
profile of the compensation region, the doping profile having an
average doping concentration greater than an average doping
concentration of the tail of the buried region.
8. The method of claim 7, wherein forming the buried region
comprises: after the blanket implanting, forming a mask on the
first surface of the SiC substrate, the mask having an opening
which defines a location for the source region; after forming the
source region, widening the opening in the mask or forming a new
mask with an opening to define a location for the body region; and
after forming the body region, further widening the opening in the
mask or forming a new mask with an opening to define a location for
the buried region and then implanting dopants of the second
conductivity type into the first surface of the SiC substrate
through the opening in the mask or new mask which defines the
location for the buried region, to define a doping profile of the
buried region, the doping profile of the buried region including an
implantation tail which corresponds to the tail of the buried
region, wherein the dopants of the second conductivity type which
define the doping profile of the buried region are implanted at a
higher dose and at a greater energy than the dopants of the first
conductivity type which define the doping profile of the
compensation region, so that the dopants of the first conductivity
type which define the doping profile of the compensation region
overcompensate the implantation tail at the second end of the
channel region.
9. The method of claim 7, wherein forming the buried region
comprises: after the blanket implanting, forming a mask on the
first surface of the SiC substrate, the mask having an opening
which defines a location for the source region; after forming the
source region, widening the opening in the mask or forming a new
mask with an opening to define a location for the buried region;
and implanting dopants of the second conductivity type into the
first surface of the SiC substrate through the opening in the mask
or new mask which defines the location for the buried region, to
define a doping profile of the buried region, the doping profile of
the buried region including an implantation tail which extends
toward the first surface, wherein the dopants of the second
conductivity type which define the doping profile of the buried
region are implanted at a higher dose and at a greater energy than
the dopants of the first conductivity type which define the doping
profile of the compensation region, so that the dopants of the
first conductivity type which define the doping profile of the
compensation region overcompensate the implantation tail at the
second end of the channel region.
10. The method of claim 9, wherein forming the body region
comprises: after forming the buried region, narrowing the widened
opening in the mask or forming a new mask with an opening to define
a location for the body region; and implanting dopants of the
second conductivity type into the first surface of the SiC
substrate through the opening in the mask or new mask which defines
the location for the body region, to define a doping profile of the
body region, wherein the dopants of the second conductivity type
which define the doping profile of the body region are implanted at
a higher dose than the dopants of the first conductivity type which
define the doping profile of the compensation region, so that the
dopants of the second conductivity type which define the doping
profile of the body region overcompensate the dopants of the first
conductivity type in the channel region.
11. The method of claim 10, wherein narrowing the widened opening
in the mask comprises: forming a spacer on a sidewall of the
widened opening in the mask.
12. The method of claim 6, wherein forming the source region
comprises: forming a mask on the first surface of the SiC
substrate, the mask having an opening with a first width which
defines a location for the source region; and implanting dopants of
the first conductivity type into the first surface of the SiC
substrate through the opening in the mask to define a doping
profile of the source region.
13. The method of claim 12, wherein forming the body region
comprises: after forming the source region, widening the opening in
the mask to a second width greater than the first width or forming
a new mask with an opening to define a location for the body
region; and implanting dopants of the second conductivity type into
the first surface of the SiC substrate through the opening in the
mask or new mask which defines the location for the body region, to
define a doping profile of the body region.
14. The method of claim 13, wherein forming the buried region
comprises: after forming the body region, widening the opening in
the mask to a third width greater than the second width or forming
a new mask with an opening to define a location for the buried
region; and implanting dopants of the second conductivity type into
the first surface of the SiC substrate through the opening in the
mask or new mask which defines the location for the buried region,
to define a doping profile of the buried region, the doping profile
of the buried region including an implantation tail which extends
toward the first surface, wherein the dopants of the second
conductivity type which define the doping profile of the buried
region are implanted at a lower dose than the dopants of the first
conductivity type which define the doping profile of the source
region, wherein the dopants of the second conductivity type which
define the doping profile of the buried region are implanted at a
greater energy than the dopants of the second conductivity type
which define the doping profile of the body region, so that the
buried region is formed below the body region.
15. The method of claim 14, wherein forming the compensation region
comprises: after forming the buried region, implanting dopants of
the first conductivity type into the first surface of the SiC
substrate through the opening in the mask having the third width or
a new mask having an opening that defines a location for the
compensation region, to define a doping profile of the compensation
region, wherein the dopants of the first conductivity type which
define the doping profile of the compensation region are implanted
at a lower dose and at a lower energy than the dopants of the
second conductivity type which define the doping profile of the
buried region, so that the dopants of the first conductivity type
which define the doping profile of the compensation region
overcompensate the implantation tail at the second end of the
channel region,
16. The method of claim 12, wherein forming the buried region
comprises: after forming the source region, widening the opening in
the mask to a second width greater than the first width or forming
a new mask with an opening to define a location for the buried
region; and implanting dopants of the second conductivity type into
the first surface of the SiC substrate through the opening in the
mask or new mask which defines the location for the buried region,
to define a doping profile of the buried region, the doping profile
of the buried region including an implantation tail which extends
toward the first surface.
17. The method of claim 16, wherein forming the body region
comprises: after forming the buried region, narrowing the opening
in the mask to a third width between the second width and the first
width or forming a new mask with an opening to define a location
for the body region; and implanting dopants of the second
conductivity type into the first surface of the SiC substrate
through the opening in the mask or new mask which defines the
location for the body region, to define a doping profile of the
body region, wherein the dopants of the second conductivity type
which define the doping profile of the body region are implanted at
a lower dose than the dopants of the first conductivity type which
define the doping profile of the source region, wherein the dopants
of the second conductivity type which define the doping profile of
the buried region are implanted at a greater energy than the
dopants of the second conductivity type which define the doping
profile of the body region, so that the buried region is formed
below the body region.
18. The method of claim 17, wherein narrowing the opening in the
mask to the third width comprises: forming a spacer on a sidewall
of the opening in the mask having the second width.
19. The method of claim 17, wherein forming the compensation region
comprises: after forming the body region, widening the opening in
the mask to a fourth width greater than the third width or forming
a new mask with an opening to define a location for the
compensation region; and implanting dopants of the first
conductivity type into the first surface of the SiC substrate
through the opening in the mask or new mask which defines the
location for the compensation region, to define a doping profile of
the compensation region, wherein the dopants of the first
conductivity type which define the doping profile of the
compensation region are implanted at a lower dose and at a lower
energy than the dopants of the second conductivity type which
define the doping profile of the buried region, so that the dopants
of the first conductivity type which define the doping profile of
the compensation region overcompensate the implantation tail at the
second end of the channel region.
20. A silicon carbide (SiC) device, comprising: a drift region of a
first conductivity type; a body region of a second conductivity
type above the drift region and having a channel region; a source
region of the first conductivity type in the body region and
adjoining a first end of the channel region; a buried region of the
second conductivity type below the body region and having a tail
which extends upward toward the channel region; and a compensation
region of the first conductivity type adjoining a second end of the
channel region opposite the first end, wherein the buried region
extends under the compensation region, wherein an average doping
concentration of the compensation region is greater than an average
doping concentration of the tail of the buried region, so that the
compensation region overcompensates the tail of the buried region
and separates the tail from the second end of the channel region.
Description
BACKGROUND
[0001] Doping of silicon (Si) devices can be easily realized by
both implantation and diffusion, Doping of silicon carbide (SiC)
devices can be easily realized only by implantation, except for
diffusion of boron. This poses challenges for achieving smooth
implantation profiles in SiC devices, and leads to peak-like
structures of doping profiles into the depth of SiC devices and
also mask edge effects. For example, at mask edges, deep
implantations lead to an implantation tail reaching up to the
surface of the SiC substrate. The implantation tail affects doping
profiles close to the surface.
[0002] For example, in a planar SiC MOSFET
(metal-oxide-semiconductor field-effect transistor) structure, mask
edge effects have an unwanted effect on channel doping. In power
MOSFETs particularly, the gate oxide is shielded against electric
fields for large source-drain voltages by a p-type buried region
formed below the channel/body region. Since the implants to form
both the p-type buried region and the channel/body region typically
use the same mask, the p-type buried region often has an
implantation tail which adjoins the end of the channel on the drain
side of the device. Since the edge angle of the implantation mask
changes due to process variation, the doping of the p-type
implantation tail changes. This affects the inversion condition for
the voltage-controlled channel and thus the threshold voltage for
turn-on. In this way, process variations of the mask angle lead to
strong variations of the threshold voltage and thus variations in
specific on-resistance (RonA).
[0003] Other adverse effects on device performance or lifetime,
such as large drain-induced barrier lowering (DIBL), may also be
worsened by such mask edge effects. In some cases, DIBL is a
limiting factor for the design of planar MOSFETs. Among other
effects, DIBL negatively impacts the short circuit time of the
device.
[0004] Thus, there is a need for an improved SiC device and methods
of manufacturing thereof.
SUMMARY
[0005] According to an embodiment of a semiconductor device, the
semiconductor device comprises a silicon carbide (SiC) substrate
which comprises: a drift region of a first conductivity type; a
body region of a second conductivity type above the drift region
and having a channel region which adjoins a first surface of the
SiC substrate; a source region of the first conductivity type in
the body region and adjoining a first end of the channel region; an
extension region of the first conductivity type at an opposite side
of the body region as the source region and vertically extending
from the first surface to the drift region; a buried region of the
second conductivity type below the body region and having a tail
which extends toward the first surface and adjoins the extension
region; and a compensation region of the first conductivity type
protruding from the extension region into the body region along the
first surface and terminating at a second end of the channel region
opposite the first end, the compensation region overcompensating
the tail of the buried region so that the tail is separated from
the second end of the channel region.
[0006] According to an embodiment of a method of producing a
semiconductor device, the method comprises: forming a drift region
of a first conductivity type in a silicon carbide (SiC) substrate;
forming a body region of a second conductivity type above the drift
region and having a channel region which adjoins a first surface of
the SiC substrate; forming a source region of the first
conductivity type in the body region and adjoining a first end of
the channel region; forming an extension region of the first
conductivity type at an opposite side of the body region as the
source region and vertically extending from the first surface to
the drift region; forming a buried region of the second
conductivity type below the body region, the buried region having a
tail which extends toward the first surface and adjoins the
extension region; and forming a compensation region of the first
conductivity type protruding from the extension region into the
body region along the first surface and terminating at a second end
of the channel region opposite the first end, the compensation
region overcompensating the tail of the buried region so that the
tail is separated from the second end of the channel region.
[0007] According to an embodiment of a silicon carbide (SiC)
device, the SiC device comprises: a drift region of a first
conductivity type; a body region of a second conductivity type
above the drift region and having a channel region; a source region
of the first conductivity type in the body region and adjoining a
first end of the channel region; a buried region of the second
conductivity type below the body region and having a tail which
extends upward toward the channel region; and a compensation region
of the first conductivity type adjoining a second end of the
channel region opposite the first end. The buried region extends
under the compensation region. An average doping concentration of
the compensation region is greater than an average doping
concentration of the tail of the buried region; so that the
compensation region overcompensates the tail of the buried region
and separates the tail from the second end of the channel
region.
[0008] Those skilled in the art will recognize additional features
and advantages upon reading the following detailed description, and
upon viewing the accompanying drawings.
BRIEF DESCRIPTION OF THE FIGURES
[0009] The elements of the drawings are not necessarily to scale
relative to each other. Like reference numerals designate
corresponding similar parts. The features of the various
illustrated embodiments can be combined unless they exclude each
other. Embodiments are depicted in the drawings and are detailed in
the description which follows.
[0010] FIG. 1 illustrates a partial cross-sectional view of an
embodiment of a SiC device having a buried region for shielding the
gate dielectric of the device against high electric fields and a
compensation region for overcompensating an implantation tail of
the buried region.
[0011] FIGS. 2A through 2F illustrate respective partial
cross-sectional views of one transistor cell with the compensation
region during different stages of producing the SiC device shown in
FIG. 1.
[0012] FIGS. 3A through 3F illustrate respective partial
cross-sectional views of one transistor cell with the compensation
region during different stages of producing the SiC device shown in
FIG. 1, according to another embodiment.
[0013] FIG. 4 illustrates a partial cross-sectional view of another
embodiment of a SiC device having a buried region for shielding the
gate dielectric of the device against high electric fields and a
compensation region for overcompensating an implantation tail of
the buried region.
[0014] FIGS. 5A through 5G illustrate respective partial
cross-sectional views of one transistor cell with the compensation
region during different stages of producing the SiC device shown in
FIG. 4.
[0015] FIGS. 6A through 6F illustrate respective partial
cross-sectional views of one transistor cell with the compensation
region during different stages of producing the SiC device shown in
FIG. 4, according to another embodiment.
DETAILED DESCRIPTION
[0016] The embodiments described herein provide a SiC device having
a buried region for shielding the gate dielectric of the device
against high electric fields and a compensation region for
overcompensating an implantation tail of the buried region (also
referred to as tail of the buried region in the following), and
methods of manufacturing such a SiC device. The compensation region
is of the opposite conductivity type as the buried (shielding)
region, and has a doping concentration sufficient for
overcompensating the tail of the buried region. As used herein, the
term "overcompensating" means outnumbering dopant impurities of one
conductivity type with dopant impurities of the opposite
conductivity type in the same region of the SiC device. For
example, an initially p-type semiconductor region becomes at least
weakly n-type when overcompensated. Likewise, an initially n-type
semiconductor region becomes at least weakly p-type when
overcompensated. By overcompensating the tail of the buried region
in the manner described herein, the tail is separated from the
channel region of the device by a region having the opposite
conductivity type as the buried region. This way, the SiC device
may be less susceptible to adverse effects associated with the edge
angle of the implantation mask used to form the buried region.
[0017] FIG. 1 illustrates a partial cross-sectional view of two
adjacent transistor cells T1, T2 of a semiconductor device 100. The
semiconductor device 100 may include tens, hundreds, thousands or
even more of such transistor cells. The semiconductor device 100
includes a silicon carbide (SiC) substrate 102. The SiC substrate
102 may include a SiC base 104 such as a SiC growth substrate or an
epitaxial layer and one or more epitaxial layers 106 grown on the
SiC base 104. A drift region 108 of a first conductivity type is
formed in the SiC substrate 102 and shared by the transistor cells
T1, T2.
[0018] Each transistor cell T1 T2 includes a body region 110 of a
second conductivity type opposite the first conductivity type
formed in the SiC substrate 102 above the drift region 108. The
body region 110 has a channel region 112 which adjoins a first
surface 114 of the SiC substrate 102. A source region 116 of the
first conductivity type is formed in the body region 110 and
adjoins a first end of the channel region 112.
[0019] A drain region 118 of the first conductivity type is formed
in the SiC substrate 102 below the drift region 108. The drain
region 118 adjoins a drain contact 119 at a second surface 120 of
the SiC substrate 102 opposite the first surface 114.
[0020] An extension region 122 of the first conductivity type is
formed at the opposite side of the body region 110 as the source
region 116. The extension region 122 vertically extends to the
drift region 108. The extension region 122 provides a conducting
path between the drift region 108 and a compensation region 124 of
the first conductivity type formed in the SiC substrate 102. The
compensation region 124 laterally protrudes from the extension
region 122 into the body region 110 along the first surface 114 of
the SiC substrate 102. According to the embodiment illustrated in
FIG. 1, the compensation region 124 extends uninterrupted along the
first surface 114 of the SiC substrate 102 between the body regions
110 of the adjacent transistor cells T1, T2.
[0021] The SiC device 100 also includes an insulated gate 126
formed on the first surface 114 of the SiC substrate 102 for
controlling the conducting state of the channel region 112 of each
transistor cell T1, T2. According to this embodiment, the SiC
device 100 is a planar gate device and the insulated gate 126
includes a gate dielectric 128 and a gate electrode 130. The gate
dielectric 128 separates the gate electrode 130 from the first
surface 114 of the SiC substrate 102. The conducting state of the
channel region 112 of each transistor cell T1, T2 is controlled by
applying a voltage between the gate electrode 130 and the
corresponding source region 116. The compensation region 124 may
laterally extend further along the insulated gate 126 toward the
source region 116 than the extension region 122, for example,
having the form of a peninsula or an elongated structure.
[0022] Each transistor cell T1, T2 also includes a buried region
132 of the second conductivity type formed in the SiC substrate 102
below the body region 110, and with the extension region 122 forms
a pn-JFET (junction field-effect transistor). The buried region 132
shields the gate dielectric 128 against high electric fields for
large source-drain voltages. Due to the imperfect nature of
lithographic and etching processes employed in the manufacture of
semiconductor devices, the mask (not shown) used to implant the
buried (shielding) region 132 of each transistor cell T1, T2 has a
sloped (angled) sidewall. The resulting buried region 132 therefore
has an implantation tail 134 which extends toward the first surface
114 of the SiC substrate 102, since the implantation mask does not
have full blocking capability in this region. The tail 134 of the
buried region 132 adjoins the extension region 122 of the first
conductivity type formed at the opposite side of the body region
110 as the source region 116. The tail 134 of each buried region
132 is represented by a respective set of dashed lines in FIG.
1.
[0023] The compensation region 124 terminates at a second end of
the channel region 112 opposite the source region 116, and is
provided for overcompensating the tail 134 of the buried region 132
so that the tail 134 is separated from the second end of the
channel region 112. At least the upper part of the tail 134 closest
to the first surface 114 of the SiC substrate 102 is
overcompensated by the compensation region 124, meaning that the
initial conductivity type of at least the upper part of the tail
134 has been overcome by the opposite conductivity type due to the
presence of the compensation region 124. In other words, if not for
the presence of the compensation region 124, the second end of the
channel region 112 opposite the source region 116 would adjoin a
region of the second conductivity type instead of the first
conductivity type.
[0024] In the case of an n-channel SiC device, the first
conductivity type is n-type and the second conductivity type is
p-type. Conversely, the first conductivity type is p-type and the
second conductivity type is n-type in the case of a p-channel SiC
device. For an n-channel SiC device, at least the upper part of the
tail 134 which was initially p-type is overcompensated by the
compensation region 124 and therefore is now n-type. For a
p-channel SIC device, at least the upper part of the tail 134 which
was initially n-type is overcompensated by the compensation region
124 and therefore is now p-type.
[0025] In both (n- and p-channel) types of SiC devices, the
compensation region 124 separates the tail 134 of the buried region
132 from the end of the channel region 112 opposite the source
region 116 and forms a lateral connection between the channel
region 112 and the extension region 122. This way, the SiC device
100 is less susceptible to adverse effects associated with the
edge/sidewall angle of the implantation mask used to form the
buried region 132 of each transistor cell T1, T2.
[0026] For example, by including the compensation region 124 in the
SiC device 100, the tail 134 of the buried region 132 has little or
no effect on the channel region 112 and thus threshold voltage. By
providing the compensation region 124, the buried region 132 is
effectively extended to accommodate the lateral space for the
resulting nose. Such an extended buried region 132 can shield the
end of the channel region 112 opposite the source region 116 more
effectively against the electric field induced by the drain
potential. This may lead to lower DIBL. In addition, the
compensation region 124 extends the length of the p-n JFET junction
region formed between the buried region 132 and the extension
region 122, thereby reducing saturation current. Even without the
implantation tail 134, reduced saturation current results due to
the extended JFET region enabled by the compensation region
124.
[0027] The compensation region 124 may have a shallower average
depth in the SiC substrate 102 than both the source region 116 and
the body region 110 as measured from the first surface 114 of the
SiC substrate 102.
[0028] Separately or in combination, the compensation region 124
may have a larger doping concentration than the extension region
122. In general, throughout this application, if the doping
concentrations of two regions (e.g., the compensation region 124
and the extension region 122) are compared, this comparison may
refer to only a non-overlapping part of the two regions if said two
regions partially overlap. For example, the net doping
concentration of the compensation region 124 may be in a range of
about 3e16 cm.sup.-3 to about 3e17 cm.sup.-3 and the net doping
concentration of the extension region 122 may be in a range of
about 3e16 cm.sup.-3 to about 1e17 cm.sup.-3 in a non-overlapping
part of the two regions 122, 124.
[0029] Separately or in combination, the compensation region 124
may have a slightly lower net doping concentration as the body
region 110 at the first surface 114 of the SiC substrate 102 where
the channel region 112 is formed. For example, the compensation
region 124 and the channel region 112 may each have a net doping
concentration in a range of about 3e16 cm.sup.-3 to about 3e17
cm.sup.-3.
[0030] Separately or in combination, the compensation region 124
may have a net doping concentration which is about a factor of
about 10 lower than the net doping concentration of the buried
(shielding) region 132. For example, the compensation region 124
may have a net doping concentration in a range of about 3e16
cm.sup.-3 to about 3e17 cm.sup.-3 and the buried region 132 may
have a net doping concentration of about 3e18 cm.sup.-3.
[0031] Separately or in combination, the compensation region 124
may have a net doping concentration which is much lower than the
net doping concentration of the source region 116. For example, the
compensation region 124 may have a net doping concentration in a
range of about 3e16 cm.sup.-3 to about 3e17 cm.sup.-3 and the
source region 116 may have a net doping concentration of about 2e19
cm.sup.-3. The doping concentration examples provided above may
vary in a window around these values.
[0032] FIGS. 2A through 2F illustrate respective simplified partial
cross-sectional views of one transistor cell with the compensation
region 124 during different stages of producing the semiconductor
device 100 shown in FIG. 1.
[0033] FIG. 2A shows the SiC substrate 102 during blanket
implanting 200 of dopants of the first conductivity type into the
first surface 114 of the SiC substrate 102 to define a doping
profile 202 of the compensation region 124. The dose of the blanket
implant 200 is chosen so that the doping profile 202 yields an
average doping concentration for the compensation region 124 which
is greater than the average doping concentration of the tail 134 of
the buried region 132 which is to be subsequently formed. If the
average doping concentration of the compensation region 124 is too
low, the resistance of the device in this region may be too large
and worst case the compensation region 124 cannot overcompensate
the tail 134 of the buried region 132. If the average doping
concentration of the compensation region 124 is too high, the
electric field increases which may cause a reliability problem for
the gate dielectric 128. The minimum doping of the compensation
region 124 depends on several factors, including the dose of the
buried region implantation, the energy of the buried region
implantation, and the angle (.alpha.) of the edge/sidewall 216 of
the mask 204 used during the buried region implantation. If the
angle .alpha. between the edge/sidewall 216 of the buried region
implantation mask 204 and the implantation direction is large, the
resulting tail 134 will be very pronounced and a higher
implantation dose is used to form the compensation region 124.
Conversely, if the angle a between the edge/sidewall 216 of the
buried region implantation mask 204 and the implantation direction
is small (e.g. close to 0 degrees) and/or the edge/sidewall 216 of
the buried region implantation mask 204 is nearly perpendicular to
the first surface 114 of the SiC substrate 102 (e.g. close to 90
degrees), the resulting tail 134 is barely present and the dose for
the compensation region 124 may be reduced accordingly.
[0034] After the blanket implanting 200, a mask 204 is formed on
the first surface 114 of the SiC substrate 102 as shown in FIG. 2B.
The mask 204 has an opening 206 which defines a location for the
source region 116. In one embodiment, the mask 204 is an oxide hard
mask and the opening 206 is etched through the oxide hard mask 204
using a polysilicon mask 210. The source region 116 is formed by
implanting 208 of dopants of the first conductivity type into the
first surface 114 of the SiC substrate 102 through the opening 206
in the mask 204.
[0035] After forming the source region 116, the opening 206 in the
mask 204 is widened to define a location for the body region 110 as
shown in FIG. 2C. Alternatively, a new mask (not shown) with an
opening that defines the location for the body region 110 may be
formed on the first surface 114 of the SiC substrate 102.
[0036] In either case, the body region 110 is then formed by
implanting 212 of dopants of the second conductivity type into the
first surface 114 of the SiC substrate 102 through the widened
opening 206' in the mask 204 as shown in FIG. 2D or through the
opening in the new mask (not shown). The body region 110 has a
slightly higher or roughly the same magnitude net doping
concentration as the doping profile 202 for the compensation region
124 at the first surface 114 of the SiC substrate 102 where the
channel region 112 is formed, to define the border/edge between the
compensation region 124 and the channel region 112.
[0037] After forming the body region 110, the opening 206' in the
mask 204 is widened again to define a location for the buried
(shielding) region 132 as shown in FIG. 2E. Alternatively, a new
mask with an opening that defines the location for the buried
region 132 may be formed on the first surface 114 of the SiC
substrate 102.
[0038] In either case, implantation 214 of dopants of the second
conductivity type into the first surface 114 of the SiC substrate
102 is performed through the widened opening 206'' in the mask 204
as shown in FIG. 2F or through the opening in the new mask (not
shown), to define a doping profile of the buried region 132. Due to
the imperfect nature of lithographic and etching processes employed
in the manufacture of semiconductor devices, the mask 204 used to
implant the buried (shielding) region 132 has a sloped/angled
sidewall 216. The doping profile of the buried region 132 therefore
includes an implantation tail 134 which extends toward the first
surface 114 of the SiC substrate 102, since the mask 204 does not
have full blocking capability in this region. The dopants 214 of
the second conductivity type which define the doping profile of the
buried region 132 are implanted at a higher dose but also at a
greater energy than the dopants 200 of the first conductivity type
which define the doping profile 202 of the compensation region 124,
so that the dopants 200 of the first conductivity type which define
the doping profile 202 of the compensation region 124
overcompensate the implantation tail 134 at the end of the channel
region 112 opposite the source region 116. The tail 134 of the
buried region 132 is represented by a set of dashed lines in FIG.
2F, to indicate that at least the upper part of the tail 134
closest to the first surface 114 of the SiC substrate 102 has been
overcompensated by the compensation region 124.
[0039] FIGS. 3A through 3F illustrate respective simplified partial
cross-sectional views of one transistor cell with the compensation
region 124 during different stages of producing the semiconductor
device 100 shown in FIG. 1, according to another embodiment. The
processing shown in FIGS. 3A through 3C corresponds to the
processing shown in FIGS. 2A through 2C, respectively. Hence, no
further description of FIGS. 3A through 3C is provided.
[0040] However, according to the embodiment illustrated in FIGS. 3A
through 3F, the buried region 132 is formed before the body region
110.
[0041] More particularly, after forming the source region 116 and
before forming the body region 110, the opening 206 in the mask 204
is widened to define a location for the buried region 132 as shown
in FIG. 3D. Alternatively, a new mask (not shown) with an opening
that defines the location for the buried region 132 may be formed
on the first surface 114 of the SiC substrate 102.
[0042] In either case, implantation 300 of dopants of the second
conductivity type into the first surface 114 of the SiC substrate
102 is performed through the widened opening 206' in the mask 204
as shown in FIG. 3D or the opening in the new mask (not shown)
which defines the location for the buried region 132, to define a
doping profile of the buried region 132. As explained above, the
mask 204 used to implant the buried (shielding) region 132 has a
sloped/angled sidewall 216. Hence, the doping profile of the buried
region 132 includes an implantation tail 134 which extends toward
the first surface 114 of the SiC substrate 102. The dopants 300 of
the second conductivity type which define the doping profile of the
buried region 132 are implanted at a higher dose but also at a
greater energy than the dopants 200 of the first conductivity type
which define the doping profile 202 of the compensation region 124,
so that the dopants 200 of the first conductivity type which define
the doping profile 202 of the compensation region 124
overcompensate the implantation tail 134 at the end of the channel
region 112 opposite the source region 116, thereby defining a
border/edge between the compensation region 124 and the channel
region 112.
[0043] After forming the buried region 132, the widened opening
206' in the mask 204 is narrowed to define a location for the body
region 110. According to the embodiment illustrated in FIG. 3E, the
widened opening 206' in the mask 204 is narrowed by forming a
spacer 302 on the sloped/angled sidewall 216 of the widened opening
206' in the mask 204. The spacer 302 may be formed, for example, by
depositing a spacer material on the SiC substrate 102 and
patterning the spacer material so as to leave the spacer 302 on the
sloped/angled sidewall 216 of the widened opening 206' in the mask
204. In another embodiment, a new mask with an opening that defines
the location for the body region 110 may be formed on the first
surface 114 of the SiC substrate 102.
[0044] In each case, implanting 304 of dopants of the second
conductivity type into the first surface 114 of the SiC substrate
102 is performed through the narrowed opening 206''' in the mask
204 as shown in FIG. 3F or the opening in the new mask (not shown)
which defines the location for the body region 110, to define a
doping profile of the body region 110. The dopants 304 of the
second conductivity type which define the doping profile of the
body region 110 are implanted at a higher dose than the dopants 200
of the first conductivity type which define the doping profile 202
of the compensation region 124, so that the dopants 304 of the
second conductivity type which define the doping profile of the
body region 110 overcompensate the dopants 200 of the first
conductivity type in the channel region 112.
[0045] FIG. 4 illustrates a partial cross-sectional view of two
adjacent transistor cells T1, T2 of a semiconductor device 400. The
semiconductor device 400 illustrated in FIG. 4 is similar to the
semiconductor device 100 illustrated in FIG. 1. Different, however,
the compensation region 124 does not extend uninterrupted along the
first surface 114 of the SiC substrate 102 between the body regions
110 of the adjacent transistor cells T1, T2. Instead, each
compensation region 124 is localized to the corresponding
transistor cell T1, T2. According to this embodiment, a part of the
extension region 122 which adjoins the first surface 114 of the SiC
substrate 102 separates the compensation regions 124 of adjacent
transistor cells T1, T2. The localized compensation regions 124 may
be formed by a masked implantation, instead of the blanket
implantation 200 shown in FIGS. 2A and 3A.
[0046] FIGS. 5A through 5G illustrate respective simplified partial
cross-sectional views of one transistor cell with the localized
compensation region 124 during different stages of producing the
semiconductor device 400 shown in FIG. 4.
[0047] In FIG. 5A, a mask 500 is formed on the first surface 114 of
the SiC substrate 102. The mask 500 has an opening 502 with a first
width which defines a location for the source region 116. In one
embodiment, the mask 500 is an oxide hard mask and the opening 502
is etched through the oxide hard mask 500 using a polysilicon mask
504. The source region 116 is formed by implanting 506 of dopants
of the first conductivity type into the first surface 114 of the
SiC substrate 102 through the opening 502 in the mask 500.
[0048] After forming the source region 116, the opening 502 in the
mask 500 is widened 508 to a second width define a location for the
body region 110 as shown in FIG. 5B. Alternatively, a new mask (not
shown) with an opening that defines the location for the body
region 110 may be formed on the first surface 114 of the SiC
substrate 102.
[0049] FIG. 5C shows implanting 510 of dopants of the second
conductivity type into the first surface 114 of the SiC substrate
102 through the widened opening 502' in the mask or the opening in
a new mask (not shown) which defines the location for the body
region 110, to define a doping profile of the body region 110.
[0050] After forming the body region 110, FIG. 5D shows widening
512 the opening 502' in the mask 500 to a third width greater than
the second width to define a location for the buried region 132.
Alternatively, a new mask (not shown) with an opening that defines
the location for the buried region 132 may be formed on the first
surface 114 of the SiC substrate 102.
[0051] In either case, FIG. 5E shows implanting 514 dopants of the
second conductivity type into the first surface 114 of the SiC
substrate 102 through the widened opening 502'' in the mask 500 or
the opening in a new mask (not shown) which defines the location
for the buried region 132, to define a doping profile of the buried
region 132. As explained above, the mask 500 used to implant the
buried (shielding) region 132 has a sloped/angled sidewall 516.
Hence, the doping profile of the buried region 132 includes an
implantation tail 134 which extends toward the first surface 114 of
the SiC substrate 102 since the mask 500 does not have full
blocking capability in this region.
[0052] The dopants 514 of the second conductivity type which define
the doping profile of the buried region 132 are implanted at a
lower dose than the dopants 506 of the first conductivity type
which define the doping profile of the source region 116. The
dopants 514 of the second conductivity type which define the doping
profile of the buried region 132 are implanted at a greater energy
than the dopants 510 of the second conductivity type which define
the doping profile of the body region 110, so that the buried
region 132 is formed below the body region 110 in the SiC substrate
102.
[0053] After forming the buried region 132, FIG. 5F shows widening
516 the opening 502'' in the mask 500 to a fourth width greater
than the third width to define a location for the compensation
region 124. Alternatively, a new mask (not shown) with an opening
that defines the location for the compensation region 124 may be
formed on the first surface 114 of the SiC substrate 102.
[0054] In either case, FIG. 5G shows implanting 518 dopants of the
first conductivity type into the first surface 114 of the SiC
substrate 102 through the widened opening 502''' in the mask 500 or
through the opening in a new mask (not shown) that defines the
location for the compensation region 124, to define a doping
profile of the compensation region 124. According to this
embodiment, a targeted implantation 518 of the first conductivity
type is performed only where needed to compensate the implantation
tail 134 of the buried region 132.
[0055] The dopants 518 of the first conductivity type which define
the doping profile of the compensation region 124 are implanted at
a lower dose and at a lower energy than the dopants 514 of the
second conductivity type which define the doping profile of the
buried region 132, so that the dopants 518 of the first
conductivity type which define the doping profile of the
compensation region 124 overcompensate the implantation tail 134 at
the end of the channel region 112 opposite the source region 116.
The tail 134 of the buried region 132 is represented by a set of
dashed lines in FIG. 5G, to indicate that at least the upper part
of the tail 134 closest to the first surface 114 of the SiC
substrate 102 has been overcompensated by the compensation region
124.
[0056] FIGS. 6A through 6F illustrate respective simplified partial
cross-sectional views of one transistor cell with the compensation
region 124 during different stages of producing the semiconductor
device 400 shown in FIG. 4, according to another embodiment. The
processing shown in FIGS. 6A and 6B corresponds to the processing
shown in FIGS. 5A and 5B, respectively. Hence, no further
description of FIGS. 6A and 6B is provided.
[0057] However, according to the embodiment illustrated in FIGS. 6A
through 6F, the buried region 132 is formed before the body region
110.
[0058] More particularly, after forming the source region 116 and
widening 508 the opening 502 in the mask 500 or forming a new mask
(not shown) with an opening that defines the location for the
buried region 132, FIG. 6C shows implanting 600 dopants of the
second conductivity type into the first surface 114 of the SiC
substrate 102 through the widened opening 502' in the mask 500 or
the opening in a new mask (not shown) which defines the location
for the buried region 132, to define a doping profile of the buried
region 132. As explained above, the mask 500 used to implant the
buried (shielding) region 132 may have a sloped/angled sidewall
512. In addition or as an alternative, dopants may be implanted at
a high energy and/or a higher dose. Either a mask 500 with a
sloped/angled sidewall 512 or a high implantation energy or a
combination of both may result in a doping profile of the buried
region 132 that includes an implantation tail 134 which extends
toward the first surface 114 of the SiC substrate 102.
[0059] After forming the buried region 132, the widened opening
502' in the mask 500 is narrowed to a width between the width 502'
used to form the buried region 132 and the width 502 used to form
the source region 116 as shown in FIG. 6D, to define a location for
the body region 110. According to the embodiment illustrated in
FIG. 6D, the widened opening 502' in the mask 500 used to form the
buried region 132 is narrowed by forming a spacer 602 on the
sloped/angled sidewall 516 of the widened opening 502' in the mask
500. The spacer 602 may be formed, for example, by depositing a
spacer material on the SiC substrate 102 and patterning the spacer
material so as to leave the spacer 602 on the sloped/angled
sidewall 516 of the widened opening 502' in the mask 500. In
another embodiment, a new mask with an opening that defines the
location for the body region 110 may be formed on the first surface
114 of the SiC substrate 102.
[0060] FIG. 6D also shows implanting 604 dopants of the second
conductivity type into the first surface 114 of the SiC substrate
102 through the narrowed opening 502'' in the mask 500 or the
opening in a new mask (not shown) which defines the location for
the body region 110, to define a doping profile of the body region
110. The dopants 604 of the second conductivity type which define
the doping profile of the body region 110 are implanted at a lower
dose than the dopants 506 of the first conductivity type which
define the doping profile of the source region 116. The dopants 600
of the second conductivity type which defined the doping profile of
the buried region 132 were implanted at a greater energy than the
dopants 604 of the second conductivity type which define the doping
profile of the body region 110, so that the buried region 132 is
formed below the body region 110 in the SiC substrate 102.
[0061] After forming the body region 110, FIG. 6E shows widening
606 the opening 502'' in the mask 500 to a width greater than the
width 502' used to form the buried region 132. If a spacer 602 was
previously used to narrow the opening 502' in the mask 500 to form
the body region 110, the spacer 602 is removed as part of the mask
widening process. Alternatively, a new mask (not shown) with an
opening that defines the location for the compensation region 124
may be formed on the first surface 114 of the SiC substrate
102.
[0062] In either case, FIG. 6F shows implanting 608 dopants of the
first conductivity type into the first surface 114 of the SiC
substrate 102 through the widened opening 502''' in the mask 500 or
through the opening in a new mask (not shown) which defines the
location for the compensation region 124, to define a doping
profile of the compensation region 124. The dopants 608 of the
first conductivity type which define the doping profile of the
compensation region 124 are implanted at a lower dose and at a
lower energy than the dopants 600 of the second conductivity type
which define the doping profile of the buried region 132, so that
the dopants 608 of the first conductivity type which define the
doping profile of the compensation region 124 overcompensate the
implantation tail 134 at the end of the channel region 112 opposite
the source region 116.
[0063] The embodiments illustrated in FIGS. 5A-5G and 6A-6F avoid
implanting the dopants used to form the compensation region 124
into the extension region 122, thereby lower the electric field in
the gate dielectric 128 compared to the blanket implantation
process used to form the compensation region 124 in FIGS. 2A-2F and
3A-3F. The embodiments illustrated in FIGS. 2A-2F and 3A-3F are
simpler to implement, since a blanket implantation instead of a
targeted implantation is used to form the compensation region
124.
[0064] Each of the method embodiments described above and
illustrated in FIGS. 2A-2F, 3A-3F, 5A-5G and 6A-6F yield a SiC that
includes: a drift region 108 of a first conductivity type; a body
region 110 of a second conductivity type above the drift region 108
and having a channel region 112; a source region 116 of the first
conductivity type in the body region 110 and adjoining a first end
of the channel region 112; a buried region 132 of the second
conductivity type below the body region 110 and having a tail 134
which extends upward toward the channel region 112; and a
compensation region 124 of the first conductivity type adjoining a
second end of the channel region 112 opposite the first end,
wherein the buried region 132 extends under the compensation region
124, and wherein an average doping concentration of the
compensation region 124 is greater than an average doping
concentration of the tail 134 of the buried region 132, so that the
compensation region 124 overcompensates the tail 134 of the buried
region 132 and separates the tail 134 from the second end of the
channel region 112.
[0065] Although the present disclosure is not so limited, the
following numbered examples demonstrate one or more aspects of the
disclosure
[0066] Example 1. A semiconductor device, comprising: a silicon
carbide (SiC) substrate which comprises: a drift region of a first
conductivity type; a body region of a second conductivity type
above the drift region and having a channel region which adjoins a
first surface of the SiC substrate; a source region of the first
conductivity type in the body region and adjoining a first end of
the channel region; an extension region of the first conductivity
type at an opposite side of the body region as the source region
and vertically extending to the drift region; a buried region of
the second conductivity type below the body region and having a
tail which extends toward the first surface and adjoins the
extension region; and a compensation region of the first
conductivity type protruding from the extension region into the
body region along the first surface and terminating at a second end
of the channel region opposite the first end, the compensation
region overcompensating the tail of the buried region so that the
tail is separated from the second end of the channel region.
[0067] Example 2. The semiconductor device of example 1, wherein
the compensation region has a shallower average depth in the SiC
substrate than both the source region and the body region as
measured from the first surface.
[0068] Example 3. The semiconductor device of examples 1 or 2,
wherein the compensation region is doped more heavily than the
extension region.
[0069] Example 4. The semiconductor device of any one of examples 1
through 3, wherein the semiconductor device further comprises an
insulated gate on the first surface and configured to control a
conducting state of the channel region, wherein the compensation
region laterally extends further along the insulated gate toward
the source region than the extension region.
[0070] Example 5. The semiconductor device of any one of examples 1
through 4, wherein the semiconductor device further comprises a
drain region of the first conductivity type below the drift region
and adjoining a second surface of the SiC substrate opposite the
first surface.
[0071] Example 6. A method of producing a semiconductor device, the
method comprising: forming a drift region of a first conductivity
type in a silicon carbide (SiC) substrate; forming a body region of
a second conductivity type above the drift region and having a
channel region which adjoins a first surface of the SiC substrate;
forming a source region of the first conductivity type in the body
region and adjoining a first end of the channel region; forming an
extension region of the first conductivity type at an opposite side
of the body region as the source region and vertically extending to
the drift region; forming a buried region of the second
conductivity type below the body region, the buried region having a
tail which extends toward the first surface and adjoins the
extension region; and forming a compensation region of the first
conductivity type protruding from the extension region into the
body region along the first surface and terminating at a second end
of the channel region opposite the first end, the compensation
region overcompensating the tail of the buried region so that the
tail is separated from the second end of the channel region.
[0072] Example 7. The method of example 6, wherein forming the
compensation region comprises blanket implanting dopants of the
first conductivity type into the first surface of the SiC substrate
to define a doping profile of the compensation region, the doping
profile having an average doping concentration greater than an
average doping concentration of the tail of the buried region.
[0073] Example 8. The method of example 7, wherein forming the
buried region comprises: after the blanket implanting, forming a
mask on the first surface of the SiC substrate, the mask having an
opening which defines a location for the source region; after
forming the source region, widening the opening in the mask or
forming a new mask with an opening to define a location for the
body region; and after forming the body region, further widening
the opening in the mask or forming a new mask with an opening to
define a location for the buried region and then implanting dopants
of the second conductivity type into the first surface of the SiC
substrate through the opening in the mask or new mask which defines
the location for the buried region, to define a doping profile of
the buried region, the doping profile of the buried region
including an implantation tail which corresponds to the tail of the
buried region, wherein the dopants of the second conductivity type
which define the doping profile of the buried region are implanted
at a higher dose and at a greater energy than the dopants of the
first conductivity type which define the doping profile of the
compensation region, so that the dopants of the first conductivity
type which define the doping profile of the compensation region
overcompensate the implantation tail at the second end of the
channel region.
[0074] Example 9. The method of example 7, wherein forming the
buried region comprises: after the blanket implanting, forming a
mask on the first surface of the SiC substrate, the mask having an
opening which defines a location for the source region; after
forming the source region, widening the opening in the mask or
forming a new mask with an opening to define a location for the
buried region; and implanting dopants of the second conductivity
type into the first surface of the SiC substrate through the
opening in the mask or new mask which defines the location for the
buried region, to define a doping profile of the buried region, the
doping profile of the buried region including an implantation tail
which extends toward the first surface, wherein the dopants of the
second conductivity type which define the doping profile of the
buried region are implanted at a higher dose and at a greater
energy than the dopants of the first conductivity type which define
the doping profile of the compensation region, so that the dopants
of the first conductivity type which define the doping profile of
the compensation region overcompensate the implantation tail at the
second end of the channel region.
[0075] Example 10. The method of example 9, wherein forming the
body region comprises: after forming the buried region, narrowing
the widened opening in the mask or forming a new mask with an
opening to define a location for the body region; and implanting
dopants of the second conductivity type into the first surface of
the SiC substrate through the opening in the mask or new mask which
defines the location for the body region, to define a doping
profile of the body region, wherein the dopants of the second
conductivity type which define the doping profile of the body
region are implanted at a higher dose than the dopants of the first
conductivity type which define the doping profile of the
compensation region, so that the dopants of the second conductivity
type which define the doping profile of the body region
overcompensate the dopants of the first conductivity type in the
channel region.
[0076] Example 11, The method of example 10, wherein narrowing the
widened opening in the mask comprises forming a spacer on a
sidewall of the widened opening in the mask.
[0077] Example 12. The method of example 6, wherein forming the
source region comprises: forming a mask on the first surface of the
SiC substrate, the mask having an opening with a first width which
defines a location for the source region; and implanting dopants of
the first conductivity type into the first surface of the SiC
substrate through the opening in the mask to define a doping
profile of the source region.
[0078] Example 13. The method of example 12, wherein forming the
body region comprises: after forming the source region, widening
the opening in the mask to a second width greater than the first
width or forming a new mask with an opening to define a location
for the body region; and implanting dopants of the second
conductivity type into the first surface of the SiC substrate
through the opening in the mask or new mask which defines the
location for the body region, to define a doping profile of the
body region.
[0079] Example 14. The method of example 13, wherein forming the
buried region comprises: after forming the body region, widening
the opening in the mask to a third width greater than the second
width or forming a new mask with an opening to define a location
for the buried region; and implanting dopants of the second
conductivity type into the first surface of the SiC substrate
through the opening in the mask or new mask which defines the
location for the buried region, to define a doping profile of the
buried region, the doping profile of the buried region including an
implantation tail which extends toward the first surface, wherein
the dopants of the second conductivity type which define the doping
profile of the buried region are implanted at a lower dose than the
dopants of the first conductivity type which define the doping
profile of the source region, wherein the dopants of the second
conductivity type which define the doping profile of the buried
region are implanted at a greater energy than the dopants of the
second conductivity type which define the doping profile of the
body region, so that the buried region is formed below the body
region.
[0080] Example 15. The method of example 14, wherein forming the
compensation region comprises: after forming the buried region,
implanting dopants of the first conductivity type into the first
surface of the SiC substrate through the opening in the mask having
the third width or a new mask having an opening that defines a
location for the compensation region, to define a doping profile of
the compensation region, wherein the dopants of the first
conductivity type which define the doping profile of the
compensation region are implanted at a lower dose and at a lower
energy than the dopants of the second conductivity type which
define the doping profile of the buried region, so that the dopants
of the first conductivity type which define the doping profile of
the compensation region overcompensate the implantation tail at the
second end of the channel region.
[0081] Example 16. The method of example 12, wherein forming the
buried region comprises: after forming the source region, widening
the opening in the mask to a second width greater than the first
width or forming a new mask with an opening to define a location
for the buried region; and implanting dopants of the second
conductivity type into the first surface of the SiC substrate
through the opening in the mask or new mask which defines the
location for the buried region, to define a doping profile of the
buried region, the doping profile of the buried region including an
implantation tail which extends toward the first surface.
[0082] Example 17. The method of example 16, wherein forming the
body region comprises: after forming the buried region, narrowing
the opening in the mask to a third width between the second width
and the first width or forming a new mask with an opening to define
a location for the body region; and implanting dopants of the
second conductivity type into the first surface of the SiC
substrate through the opening in the mask or new mask which defines
the location for the body region, to define a doping profile of the
body region, wherein the dopants of the second conductivity type
which define the doping profile of the body region are implanted at
a lower dose than the dopants of the first conductivity type which
define the doping profile of the source region, wherein the dopants
of the second conductivity type which define the doping profile of
the buried region are implanted at a greater energy than the
dopants of the second conductivity type which define the doping
profile of the body region, so that the buried region is formed
below the body region.
[0083] Example 18. The method of example 17, wherein narrowing the
opening in the mask to the third width comprises forming a spacer
on a sidewall of the opening in the mask having the second
width.
[0084] Example 19. The method of examples 17 or 18, wherein forming
the compensation region comprises: after forming the body region,
widening the opening in the mask to a fourth width greater than the
third width or forming a new mask with an opening to define a
location for the compensation region; and implanting dopants of the
first conductivity type into the first surface of the SiC substrate
through the opening in the mask or new mask which defines the
location for the compensation region, to define a doping profile of
the compensation region, wherein the dopants of the first
conductivity type which define the doping profile of the
compensation region are implanted at a lower dose and at a lower
energy than the dopants of the second conductivity type which
define the doping profile of the buried region, so that the dopants
of the first conductivity type which define the doping profile of
the compensation region overcompensate the implantation tail at the
second end of the channel region.
[0085] Example 20. A silicon carbide (SiC) device, comprising: a
drift region of a first conductivity type; a body region of a
second conductivity type above the drift region and having a
channel region; a source region of the first conductivity type in
the body region and adjoining a first end of the channel region; a
buried region of the second conductivity type below the body region
and having a tail which extends upward toward the channel region;
and a compensation region of the first conductivity type adjoining
a second end of the channel region opposite the first end, wherein
the buried region extends under the compensation region, wherein an
average doping concentration of the compensation region is greater
than an average doping concentration of the tail of the buried
region, so that the compensation region overcompensates the tail of
the buried region and separates the tail from the second end of the
channel region.
[0086] Example 21. A semiconductor device, comprising a silicon
carbide (SiC) substrate which comprises: a drift region of a first
conductivity type; a body region of a second conductivity type
above the drift region and having a channel region which adjoins a
first surface of the SiC substrate; a source region of the first
conductivity type in the body region and adjoining a first end of
the channel region; an extension region of the first conductivity
type at an opposite side of the body region as the source region
and vertically extending to the drift region; a buried region of
the second conductivity type below the body region; and a
compensation region of the first conductivity type protruding from
the extension region into the body region along the first surface
and terminating at a second end of the channel region opposite the
first end.
[0087] Example 22. A semiconductor device, comprising a silicon
carbide (SiC) substrate which comprises: a drift region of a first
conductivity type; a body region of a second conductivity type
above the drift region and having a channel region which adjoins a
first surface of the SiC substrate; a source region of the first
conductivity type in the body region and adjoining a first end of
the channel region; an extension region of the first conductivity
type at an opposite side of the body region as the source region
and vertically extending to the drift region; a buried region of
the second conductivity type below the body region; and a
compensation region of the first conductivity type at least
partially surrounded by the body region at a second end of the
channel region opposite the first end and at least partially
surrounded or overlapped by the extension region at a bottom of the
compensation region.
[0088] Terms such as "first", "second", and the like, are used to
describe various elements, regions, sections, etc. and are also not
intended to be limiting. Like terms refer to like elements
throughout the description.
[0089] As used herein, the terms "having", "containing",
"including", "comprising" and the like are open ended terms that
indicate the presence of stated elements or features, but do not
preclude additional elements or features. The articles "a", "an"
and "the" are intended to include the plural as well as the
singular, unless the context clearly indicates otherwise.
[0090] It is to be understood that the features of the various
embodiments described herein may be combined with each other,
unless specifically noted otherwise.
[0091] Although specific embodiments have been illustrated and
described herein, it will be appreciated by those of ordinary skill
in the art that a variety of alternate and/or equivalent
implementations may be substituted for the specific embodiments
shown and described without departing from the scope of the present
invention. This application is intended to cover any adaptations or
variations of the specific embodiments discussed herein. Therefore,
it is intended that this invention be limited only by the claims
and the equivalents thereof.
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