Silicon carbide device with an implantation tail compensation region

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.

BACKGROUND

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.

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).

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.

Thus, there is a need for an improved SiC device and methods of manufacturing thereof.

SUMMARY

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.

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.

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.

DETAILED DESCRIPTION

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.

FIG. 1illustrates a partial cross-sectional view of two adjacent transistor cells T1, T2of a semiconductor device100. The semiconductor device100may include tens, hundreds, thousands or even more of such transistor cells. The semiconductor device100includes a silicon carbide (SiC) substrate102. The SiC substrate102may include a SiC base104such as a SiC growth substrate or an epitaxial layer and one or more epitaxial layers106grown on the SiC base104. A drift region108of a first conductivity type is formed in the SiC substrate102and shared by the transistor cells T1, T2.

Each transistor cell T1, T2includes a body region110of a second conductivity type opposite the first conductivity type formed in the SiC substrate102above the drift region108. The body region110has a channel region112which adjoins a first surface114of the SiC substrate102. A source region116of the first conductivity type is formed in the body region110and adjoins a first end of the channel region112.

A drain region118of the first conductivity type is formed in the SiC substrate102below the drift region108. The drain region118adjoins a drain contact119at a second surface120of the SiC substrate102opposite the first surface114.

An extension region122of the first conductivity type is formed at the opposite side of the body region110as the source region116. The extension region122vertically extends to the drift region108. The extension region122provides a conducting path between the drift region108and a compensation region124of the first conductivity type formed in the SiC substrate102. The compensation region124laterally protrudes from the extension region122into the body region110along the first surface114of the SiC substrate102. According to the embodiment illustrated inFIG. 1, the compensation region124extends uninterrupted along the first surface114of the SiC substrate102between the body regions110of the adjacent transistor cells T1, T2.

The SiC device100also includes an insulated gate126formed on the first surface114of the SiC substrate102for controlling the conducting state of the channel region112of each transistor cell T1, T2. According to this embodiment, the SiC device100is a planar gate device and the insulated gate126includes a gate dielectric128and a gate electrode130. The gate dielectric128separates the gate electrode130from the first surface114of the SiC substrate102. The conducting state of the channel region112of each transistor cell T1, T2is controlled by applying a voltage between the gate electrode130and the corresponding source region116. The compensation region124may laterally extend further along the insulated gate126toward the source region116than the extension region122, for example, having the form of a peninsula or an elongated structure.

Each transistor cell T1, T2also includes a buried region132of the second conductivity type formed in the SiC substrate102below the body region110, and with the extension region122forms a pn-JFET (junction field-effect transistor). The buried region132shields the gate dielectric128against 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) region132of each transistor cell T1, T2has a sloped (angled) sidewall. The resulting buried region132therefore has an implantation tail134which extends toward the first surface114of the SiC substrate102, since the implantation mask does not have full blocking capability in this region. The tail134of the buried region132adjoins the extension region122of the first conductivity type formed at the opposite side of the body region110as the source region116. The tail134of each buried region132is represented by a respective set of dashed lines inFIG. 1.

The compensation region124terminates at a second end of the channel region112opposite the source region116, and is provided for overcompensating the tail134of the buried region132so that the tail134is separated from the second end of the channel region112. At least the upper part of the tail134closest to the first surface114of the SiC substrate102is overcompensated by the compensation region124, meaning that the initial conductivity type of at least the upper part of the tail134has been overcome by the opposite conductivity type due to the presence of the compensation region124. In other words, if not for the presence of the compensation region124, the second end of the channel region112opposite the source region116would adjoin a region of the second conductivity type instead of the first conductivity type.

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 tail134which was initially p-type is overcompensated by the compensation region124and therefore is now n-type. For a p-channel SiC device, at least the upper part of the tail134which was initially n-type is overcompensated by the compensation region124and therefore is now p-type.

In both (n- and p-channel) types of SiC devices, the compensation region124separates the tail134of the buried region132from the end of the channel region112opposite the source region116and forms a lateral connection between the channel region112and the extension region122. This way, the SiC device100is less susceptible to adverse effects associated with the edge/sidewall angle of the implantation mask used to form the buried region132of each transistor cell T1, T2.

For example, by including the compensation region124in the SiC device100, the tail134of the buried region132has little or no effect on the channel region112and thus threshold voltage. By providing the compensation region124, the buried region132is effectively extended to accommodate the lateral space for the resulting nose. Such an extended buried region132can shield the end of the channel region112opposite the source region116more effectively against the electric field induced by the drain potential. This may lead to lower DIBL. In addition, the compensation region124extends the length of the p-n JFET junction region formed between the buried region132and the extension region122, thereby reducing saturation current. Even without the implantation tail134, reduced saturation current results due to the extended JFET region enabled by the compensation region124.

The compensation region124may have a shallower average depth in the SiC substrate102than both the source region116and the body region110as measured from the first surface114of the SiC substrate102.

Separately or in combination, the compensation region124may have a larger doping concentration than the extension region122. In general, throughout this application, if the doping concentrations of two regions (e.g., the compensation region124and the extension region122) 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 region124may be in a range of about 3e16 cm−3to about 3e17 cm−3and the net doping concentration of the extension region122may be in a range of about 3e16 cm−3to about 1e17 cm−3in a non-overlapping part of the two regions122,124.

Separately or in combination, the compensation region124may have a slightly lower net doping concentration as the body region110at the first surface114of the SiC substrate102where the channel region112is formed. For example, the compensation region124and the channel region112may each have a net doping concentration in a range of about 3 e16 cm−3to about 3 e17 cm−3.

Separately or in combination, the compensation region124may have a net doping concentration which is about a factor of about 10 lower than the net doping concentration of the buried (shielding) region132. For example, the compensation region124may have a net doping concentration in a range of about 3e16 cm−3to about 3e17 cm−3and the buried region132may have a net doping concentration of about 3e18 cm−3.

Separately or in combination, the compensation region124may have a net doping concentration which is much lower than the net doping concentration of the source region116. For example, the compensation region124may have a net doping concentration in a range of about 3e16 cm−3to about 3e17 cm−3and the source region116may have a net doping concentration of about 2e19 cm−3. The doping concentration examples provided above may vary in a window around these values.

FIGS. 2A through 2Fillustrate respective simplified partial cross-sectional views of one transistor cell with the compensation region124during different stages of producing the semiconductor device100shown inFIG. 1.

FIG. 2Ashows the SiC substrate102during blanket implanting200of dopants of the first conductivity type into the first surface114of the SiC substrate102to define a doping profile202of the compensation region124. The dose of the blanket implant200is chosen so that the doping profile202yields an average doping concentration for the compensation region124which is greater than the average doping concentration of the tail134of the buried region132which is to be subsequently formed. If the average doping concentration of the compensation region124is too low, the resistance of the device in this region may be too large and worst case the compensation region124cannot overcompensate the tail134of the buried region132. If the average doping concentration of the compensation region124is too high, the electric field increases which may cause a reliability problem for the gate dielectric128. The minimum doping of the compensation region124depends on several factors, including the dose of the buried region implantation, the energy of the buried region implantation, and the angle (α) of the edge/sidewall216of the mask204used during the buried region implantation. If the angle α between the edge/sidewall216of the buried region implantation mask204and the implantation direction is large, the resulting tail134will be very pronounced and a higher implantation dose is used to form the compensation region124. Conversely, if the angle α between the edge/sidewall216of the buried region implantation mask204and the implantation direction is small (e.g. close to 0 degrees) and/or the edge/sidewall216of the buried region implantation mask204is nearly perpendicular to the first surface114of the SiC substrate102(e.g. close to 90 degrees), the resulting tail134is barely present and the dose for the compensation region124may be reduced accordingly.

After the blanket implanting200, a mask204is formed on the first surface114of the SiC substrate102as shown inFIG. 2B. The mask204has an opening206which defines a location for the source region116. In one embodiment, the mask204is an oxide hard mask and the opening206is etched through the oxide hard mask204using a polysilicon mask210. The source region116is formed by implanting208of dopants of the first conductivity type into the first surface114of the SiC substrate102through the opening206in the mask204.

After forming the source region116, the opening206in the mask204is widened to define a location for the body region110as shown inFIG. 2C. Alternatively, a new mask (not shown) with an opening that defines the location for the body region110may be formed on the first surface114of the SiC substrate102.

In either case, the body region110is then formed by implanting212of dopants of the second conductivity type into the first surface114of the SiC substrate102through the widened opening206′ in the mask204as shown inFIG. 2Dor through the opening in the new mask (not shown). The body region110has a slightly higher or roughly the same magnitude net doping concentration as the doping profile202for the compensation region124at the first surface114of the SiC substrate102where the channel region112is formed, to define the border/edge between the compensation region124and the channel region112.

After forming the body region110, the opening206′ in the mask204is widened again to define a location for the buried (shielding) region132as shown inFIG. 2E. Alternatively, a new mask with an opening that defines the location for the buried region132may be formed on the first surface114of the SiC substrate102.

In either case, implantation214of dopants of the second conductivity type into the first surface114of the SiC substrate102is performed through the widened opening206″ in the mask204as shown inFIG. 2For through the opening in the new mask (not shown), to define a doping profile of the buried region132. Due to the imperfect nature of lithographic and etching processes employed in the manufacture of semiconductor devices, the mask204used to implant the buried (shielding) region132has a sloped/angled sidewall216. The doping profile of the buried region132therefore includes an implantation tail134which extends toward the first surface114of the SiC substrate102, since the mask204does not have full blocking capability in this region. The dopants214of the second conductivity type which define the doping profile of the buried region132are implanted at a higher dose but also at a greater energy than the dopants200of the first conductivity type which define the doping profile202of the compensation region124, so that the dopants200of the first conductivity type which define the doping profile202of the compensation region124overcompensate the implantation tail134at the end of the channel region112opposite the source region116. The tail134of the buried region132is represented by a set of dashed lines inFIG. 2F, to indicate that at least the upper part of the tail134closest to the first surface114of the SiC substrate102has been overcompensated by the compensation region124.

FIGS. 3A through 3Fillustrate respective simplified partial cross-sectional views of one transistor cell with the compensation region124during different stages of producing the semiconductor device100shown inFIG. 1, according to another embodiment. The processing shown inFIGS. 3A through 3Ccorresponds to the processing shown inFIGS. 2A through 2C, respectively. Hence, no further description ofFIGS. 3A through 3Cis provided.

However, according to the embodiment illustrated inFIGS. 3A through 3F, the buried region132is formed before the body region110.

More particularly, after forming the source region116and before forming the body region110, the opening206in the mask204is widened to define a location for the buried region132as shown inFIG. 3D. Alternatively, a new mask (not shown) with an opening that defines the location for the buried region132may be formed on the first surface114of the SiC substrate102.

In either case, implantation300of dopants of the second conductivity type into the first surface114of the SiC substrate102is performed through the widened opening206′ in the mask204as shown inFIG. 3Dor the opening in the new mask (not shown) which defines the location for the buried region132, to define a doping profile of the buried region132. As explained above, the mask204used to implant the buried (shielding) region132has a sloped/angled sidewall216. Hence, the doping profile of the buried region132includes an implantation tail134which extends toward the first surface114of the SiC substrate102. The dopants300of the second conductivity type which define the doping profile of the buried region132are implanted at a higher dose but also at a greater energy than the dopants200of the first conductivity type which define the doping profile202of the compensation region124, so that the dopants200of the first conductivity type which define the doping profile202of the compensation region124overcompensate the implantation tail134at the end of the channel region112opposite the source region116, thereby defining a border/edge between the compensation region124and the channel region112.

After forming the buried region132, the widened opening206′ in the mask204is narrowed to define a location for the body region110. According to the embodiment illustrated inFIG. 3E, the widened opening206′ in the mask204is narrowed by forming a spacer302on the sloped/angled sidewall216of the widened opening206′ in the mask204. The spacer302may be formed, for example, by depositing a spacer material on the SiC substrate102and patterning the spacer material so as to leave the spacer302on the sloped/angled sidewall216of the widened opening206′ in the mask204. In another embodiment, a new mask with an opening that defines the location for the body region110may be formed on the first surface114of the SiC substrate102.

In each case, implanting304of dopants of the second conductivity type into the first surface114of the SiC substrate102is performed through the narrowed opening206′″ in the mask204as shown inFIG. 3For the opening in the new mask (not shown) which defines the location for the body region110, to define a doping profile of the body region110. The dopants304of the second conductivity type which define the doping profile of the body region110are implanted at a higher dose than the dopants200of the first conductivity type which define the doping profile202of the compensation region124, so that the dopants304of the second conductivity type which define the doping profile of the body region110overcompensate the dopants200of the first conductivity type in the channel region112.

FIG. 4illustrates a partial cross-sectional view of two adjacent transistor cells T1, T2of a semiconductor device400. The semiconductor device400illustrated inFIG. 4is similar to the semiconductor device100illustrated inFIG. 1. Different, however, the compensation region124does not extend uninterrupted along the first surface114of the SiC substrate102between the body regions110of the adjacent transistor cells T1, T2. Instead, each compensation region124is localized to the corresponding transistor cell T1, T2. According to this embodiment, a part of the extension region122which adjoins the first surface114of the SiC substrate102separates the compensation regions124of adjacent transistor cells T1, T2. The localized compensation regions124may be formed by a masked implantation, instead of the blanket implantation200shown inFIGS. 2A and 3A.

FIGS. 5A through 5Gillustrate respective simplified partial cross-sectional views of one transistor cell with the localized compensation region124during different stages of producing the semiconductor device400shown inFIG. 4.

InFIG. 5A, a mask500is formed on the first surface114of the SiC substrate102. The mask500has an opening502with a first width which defines a location for the source region116. In one embodiment, the mask500is an oxide hard mask and the opening502is etched through the oxide hard mask500using a polysilicon mask504. The source region116is formed by implanting506of dopants of the first conductivity type into the first surface114of the SiC substrate102through the opening502in the mask500.

After forming the source region116, the opening502in the mask500is widened508to a second width define a location for the body region110as shown inFIG. 5B. Alternatively, a new mask (not shown) with an opening that defines the location for the body region110may be formed on the first surface114of the SiC substrate102.

FIG. 5Cshows implanting510of dopants of the second conductivity type into the first surface114of the SiC substrate102through the widened opening502′ in the mask or the opening in a new mask (not shown) which defines the location for the body region110, to define a doping profile of the body region110.

After forming the body region110,FIG. 5Dshows widening512the opening502′ in the mask500to a third width greater than the second width to define a location for the buried region132. Alternatively, a new mask (not shown) with an opening that defines the location for the buried region132may be formed on the first surface114of the SiC substrate102.

In either case,FIG. 5Eshows implanting514dopants of the second conductivity type into the first surface114of the SiC substrate102through the widened opening502″ in the mask500or the opening in a new mask (not shown) which defines the location for the buried region132, to define a doping profile of the buried region132. As explained above, the mask500used to implant the buried (shielding) region132has a sloped/angled sidewall516. Hence, the doping profile of the buried region132includes an implantation tail134which extends toward the first surface114of the SiC substrate102since the mask500does not have full blocking capability in this region.

The dopants514of the second conductivity type which define the doping profile of the buried region132are implanted at a lower dose than the dopants506of the first conductivity type which define the doping profile of the source region116. The dopants514of the second conductivity type which define the doping profile of the buried region132are implanted at a greater energy than the dopants510of the second conductivity type which define the doping profile of the body region110, so that the buried region132is formed below the body region110in the SiC substrate102.

After forming the buried region132,FIG. 5Fshows widening516the opening502″ in the mask500to a fourth width greater than the third width to define a location for the compensation region124. Alternatively, a new mask (not shown) with an opening that defines the location for the compensation region124may be formed on the first surface114of the SiC substrate102.

In either case,FIG. 5Gshows implanting518dopants of the first conductivity type into the first surface114of the SiC substrate102through the widened opening502′″ in the mask500or through the opening in a new mask (not shown) that defines the location for the compensation region124, to define a doping profile of the compensation region124. According to this embodiment, a targeted implantation518of the first conductivity type is performed only where needed to compensate the implantation tail134of the buried region132.

The dopants518of the first conductivity type which define the doping profile of the compensation region124are implanted at a lower dose and at a lower energy than the dopants514of the second conductivity type which define the doping profile of the buried region132, so that the dopants518of the first conductivity type which define the doping profile of the compensation region124overcompensate the implantation tail134at the end of the channel region112opposite the source region116. The tail134of the buried region132is represented by a set of dashed lines inFIG. 5G, to indicate that at least the upper part of the tail134closest to the first surface114of the SiC substrate102has been overcompensated by the compensation region124.

FIGS. 6A through 6Fillustrate respective simplified partial cross-sectional views of one transistor cell with the compensation region124during different stages of producing the semiconductor device400shown inFIG. 4, according to another embodiment. The processing shown inFIGS. 6A and 6Bcorresponds to the processing shown inFIGS. 5A and 5B, respectively. Hence, no further description ofFIGS. 6A and 6Bis provided.

However, according to the embodiment illustrated inFIGS. 6A through 6F, the buried region132is formed before the body region110.

More particularly, after forming the source region116and widening508the opening502in the mask500or forming a new mask (not shown) with an opening that defines the location for the buried region132,FIG. 6Cshows implanting600dopants of the second conductivity type into the first surface114of the SiC substrate102through the widened opening502′ in the mask500or the opening in a new mask (not shown) which defines the location for the buried region132, to define a doping profile of the buried region132. As explained above, the mask500used to implant the buried (shielding) region132may have a sloped/angled sidewall512. In addition or as an alternative, dopants may be implanted at a high energy and/or a higher dose. Either a mask500with a sloped/angled sidewall512or a high implantation energy or a combination of both may result in a doping profile of the buried region132that includes an implantation tail134which extends toward the first surface114of the SiC substrate102.

After forming the buried region132, the widened opening502′ in the mask500is narrowed to a width between the width502′ used to form the buried region132and the width502used to form the source region116as shown inFIG. 6D, to define a location for the body region110. According to the embodiment illustrated inFIG. 6D, the widened opening502′ in the mask500used to form the buried region132is narrowed by forming a spacer602on the sloped/angled sidewall516of the widened opening502′ in the mask500. The spacer602may be formed, for example, by depositing a spacer material on the SiC substrate102and patterning the spacer material so as to leave the spacer602on the sloped/angled sidewall516of the widened opening502′ in the mask500. In another embodiment, a new mask with an opening that defines the location for the body region110may be formed on the first surface114of the SiC substrate102.

FIG. 6Dalso shows implanting604dopants of the second conductivity type into the first surface114of the SiC substrate102through the narrowed opening502″ in the mask500or the opening in a new mask (not shown) which defines the location for the body region110, to define a doping profile of the body region110. The dopants604of the second conductivity type which define the doping profile of the body region110are implanted at a lower dose than the dopants506of the first conductivity type which define the doping profile of the source region116. The dopants600of the second conductivity type which defined the doping profile of the buried region132were implanted at a greater energy than the dopants604of the second conductivity type which define the doping profile of the body region110, so that the buried region132is formed below the body region110in the SiC substrate102.

After forming the body region110,FIG. 6Eshows widening606the opening502″ in the mask500to a width greater than the width502′ used to form the buried region132. If a spacer602was previously used to narrow the opening502′ in the mask500to form the body region110, the spacer602is removed as part of the mask widening process. Alternatively, a new mask (not shown) with an opening that defines the location for the compensation region124may be formed on the first surface114of the SiC substrate102.

In either case,FIG. 6Fshows implanting608dopants of the first conductivity type into the first surface114of the SiC substrate102through the widened opening502′″ in the mask500or through the opening in a new mask (not shown) which defines the location for the compensation region124, to define a doping profile of the compensation region124. The dopants608of the first conductivity type which define the doping profile of the compensation region124are implanted at a lower dose and at a lower energy than the dopants600of the second conductivity type which define the doping profile of the buried region132, so that the dopants608of the first conductivity type which define the doping profile of the compensation region124overcompensate the implantation tail134at the end of the channel region112opposite the source region116.

The embodiments illustrated inFIGS. 5A-5G and 6A-6Favoid implanting the dopants used to form the compensation region124into the extension region122, thereby lower the electric field in the gate dielectric128compared to the blanket implantation process used to form the compensation region124inFIGS. 2A-2F and 3A-3F. The embodiments illustrated inFIGS. 2A-2F and 3A-3Fare simpler to implement, since a blanket implantation instead of a targeted implantation is used to form the compensation region124.

Each of the method embodiments described above and illustrated inFIGS. 2A-2F, 3A-3F, 5A-5G and 6A-6Fyield a SiC that includes: a drift region108of a first conductivity type; a body region110of a second conductivity type above the drift region108and having a channel region112; a source region116of the first conductivity type in the body region110and adjoining a first end of the channel region112; a buried region132of the second conductivity type below the body region110and having a tail134which extends upward toward the channel region112; and a compensation region124of the first conductivity type adjoining a second end of the channel region112opposite the first end, wherein the buried region132extends under the compensation region124, and wherein an average doping concentration of the compensation region124is greater than an average doping concentration of the tail134of the buried region132, so that the compensation region124overcompensates the tail134of the buried region132and separates the tail134from the second end of the channel region112.

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.

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.

Example 3. The semiconductor device of examples 1 or 2, wherein the compensation region is doped more heavily than the extension region.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.