Oxygen-inserted Si layers for reduced contact implant outdiffusion in vertical power devices

Abstract

A semiconductor device includes: a gate trench extending into a Si substrate; a body region in the Si substrate, the body region including a channel region extending along the sidewalls of the gate trench; a source region in the Si substrate above the body region; a contact trench extending into the Si substrate and separated from the gate trench by a portion of the source region and a portion of the body region, the contact trench being filled with a conductive material that contacts the source region at the sidewalls of the contact trench and a highly doped body contact region at the bottom of the contact trench; and a diffusion barrier structure formed along the sidewalls of the contact trench and disposed between the highly doped body contact region and the channel region, the diffusion barrier structure comprising alternating layers of Si and oxygen-doped Si.

Description

Background Art

[0001] As the size of trench-based transistors shrinks, the impact of highly doped source / body contacts on the net body doped near the channel region becomes more important. For a wider lateral distribution of source / body contact diffusion with a doping level 2-3 orders of magnitude higher than the body doping, the Vth (threshold voltage) and RonA (on-state resistance) of the device increase. Increasing the distance between the source / body contact and the channel region causes the body to be depleted at high drain voltages, which may lead to high DIBL (drain-induced barrier reduction). In addition, the process window variations of both trench width and contact width and contact misalignment must become smaller to avoid these adverse effects (higher Vth, higher RonA and higher DIBL).

[0002] Therefore, better control of the lateral outdiffusion of source / body contact doping is desirable. Summary of the invention

[0003] According to an embodiment of a semiconductor device, the semiconductor device includes: a gate trench extending into a Si substrate; a body region in the Si substrate, the body region including a channel region extending along the sidewalls of the gate trench; a source region in the Si substrate above the body region; a contact trench extending into the Si substrate and separated from the gate trench by a portion of the source region and a portion of the body region, the contact trench being filled with a conductive material that contacts the source region at the sidewalls of the contact trench and a highly doped body contact region at the bottom of the contact trench; and a diffusion barrier structure formed along the sidewalls of the contact trench and disposed between the highly doped body contact region and the channel region, the diffusion barrier structure including alternating layers of Si and oxygen-doped Si.

[0004] In an embodiment, the diffusion barrier structure may extend along the bottom of the contact trench.

[0005] Alone or in combination, the highly doped body contact region may only be laterally bounded by a diffusion barrier structure which is not at the bottom of the contact trench.

[0006] Alone or in combination, the conductive material filling the contact trench may extend onto the front main surface of the Si substrate beyond the diffusion barrier structure and in a direction towards the gate trench.

[0007] Either alone or in combination, the diffusion barrier structure may include a Si capping layer epitaxially grown on alternating layers of Si and oxygen-doped Si.

[0008] Either alone or in combination, the Si substrate may include one or more Si epitaxial layers grown on a base Si substrate.

[0009] According to an embodiment of a method for manufacturing a semiconductor device, the method includes: forming a gate trench extending into a Si substrate; forming a contact trench extending into the Si substrate and separated from the gate trench; forming a highly doped body contact region in the Si substrate at the bottom of the contact trench; forming a diffusion barrier structure along the sidewalls of the contact trench, the diffusion barrier structure including alternating layers of Si and oxygen-doped Si; forming a body region in the Si substrate, the body region including a channel region extending along the sidewalls of the gate trench; forming a source region in the Si substrate above the body region; and filling the contact trench with a conductive material, the conductive material contacting the source region at the sidewalls of the contact trench and the highly doped body contact region at the bottom of the contact trench.

[0010] In an embodiment, forming the diffusion barrier structure may include epitaxially growing alternating layers of Si and oxygen-doped Si on sidewalls and a bottom of the contact trench before filling the contact trench with a conductive material.

[0011] Either alone or in combination, the method may further comprise epitaxially growing a Si capping layer on the alternating layers of Si and oxygen-doped Si.

[0012] Either alone or in combination, forming the highly doped body contact region may include implanting dopant species into the alternating layers of Si and oxygen-doped Si at the bottom of the contact trench, and annealing the Si substrate to activate the implanted dopant species.

[0013] Alone or in combination, the method may further include removing the alternating layers of Si and oxygen-doped Si from at least a portion of the bottom of the contact trench.

[0014] Either alone or in combination, removing the alternating layers of Si and oxygen-doped Si from at least a portion of the bottom of the contact trench may include: epitaxially growing a Si capping layer on the alternating layers of Si and oxygen-doped Si; depositing a conformal spacer oxide on the Si capping layer; anisotropically etching the conformal spacer oxide to expose a diffusion barrier structure at the bottom of the contact trench; etching away the exposed diffusion barrier structure at the bottom of the contact trench; and removing the conformal spacer oxide after etching away the exposed diffusion barrier structure at the bottom of the contact trench.

[0015] Either alone or in combination, forming the diffusion barrier structure may include, before filling the contact trench with a conductive material, epitaxially growing alternating layers of Si and oxygen-doped Si only on the sidewalls of the contact trench, but not on the bottom.

[0016] Either alone or in combination, the method may further comprise epitaxially growing a Si capping layer on the alternating layers of Si and oxygen-doped Si.

[0017] Forming the highly doped body contact region may include, alone or in combination, implanting a dopant substance into a region at the bottom of the contact trench that is free of alternating layers of Si and oxygen-doped Si, and annealing the Si substrate to activate the implanted dopant substance.

[0018] Either alone or in combination, the method may further include, before filling the contact trench with a conductive material, etching back an insulating layer formed on the front main surface of the Si substrate so that the insulating layer has an opening that is aligned with the contact trench and is wider than a combined width of the contact trench and the diffusion barrier structure.

[0019] Alone or in combination, filling the contact trench with a conductive material may include depositing the conductive material in the contact trench and in an opening formed in the insulating layer so that the conductive material extends beyond the diffusion barrier structure on the front main surface of the Si substrate and in a direction toward the gate trench.

[0020] Either alone or in combination, forming the diffusion barrier structure may include epitaxially growing alternating layers of Si and oxygen-doped Si on the sidewalls and bottom of the contact trench prior to forming the body region and the source region.

[0021] Either alone or in combination, the method may further comprise, before forming the body region and the source region, epitaxially growing a Si capping layer on the alternating layers of Si and oxygen-doped Si.

[0022] Alone or in combination, the method may further include removing the alternating layers of Si and oxygen-doped Si from at least a portion of the bottom of the contact trench.

[0023] Either alone or in combination, removing the alternating layers of Si and oxygen-doped Si from at least a portion of the bottom of the contact trench may include: epitaxially growing a Si capping layer on the alternating layers of Si and oxygen-doped Si; depositing a conformal spacer oxide on the Si capping layer; anisotropically etching the conformal spacer oxide to expose a diffusion barrier structure at the bottom of the contact trench; etching away the exposed diffusion barrier structure at the bottom of the contact trench; and removing the conformal spacer oxide after etching away the exposed diffusion barrier structure at the bottom of the contact trench.

[0024] Either alone or in combination, forming a diffusion barrier structure may include: forming a sacrificial insulating layer at the bottom of the contact trench before forming the body region and the source region; after forming the sacrificial insulating layer, epitaxially growing alternating layers of Si and oxygen-doped Si on the sidewalls of the contact trench; and after epitaxially growing alternating layers of Si and oxygen-doped Si, removing the sacrificial insulating layer from the bottom of the contact trench.

[0025] Either alone or in combination, the method may further include: filling the contact trench with a sacrificial plug material after forming the diffusion barrier structure and before forming the source region and the body region; forming the source region and the body region in the Si substrate after filling the contact trench with the sacrificial plug material; removing the sacrificial plug material after forming the source region and the body region; implanting a dopant substance into the bottom of the contact trench after removing the sacrificial plug material and before filling the contact trench with a conductive material; and annealing the Si substrate to activate the implanted dopant substance, thereby forming a highly doped body contact region.

[0026] 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 DRAWINGS

[0027] The elements of the drawings are not necessarily to scale relative to each other. The same reference numerals designate corresponding similar parts. The features of the various illustrated embodiments may be combined unless they exclude each other. The embodiments are depicted in the drawings and are detailed in the following description.

[0028] Figure 1 A partial cross-sectional view of an embodiment of a trench based semiconductor device having a diffusion barrier structure is illustrated.

[0029] Figures 2A to 2F The diagram shows the different stages of the manufacturing process. Figure 1 ] A corresponding cross-sectional view of a trench-based semiconductor device is shown in FIG.

[0030] Figure 3 A partial cross-sectional view of another embodiment of a trench-based semiconductor device having a diffusion barrier structure is illustrated.

[0031] Figure 4 A partial cross-sectional view of another embodiment of a trench-based semiconductor device having a diffusion barrier structure is illustrated.

[0032] FIG. 5A to FIG. 5D Corresponding cross-sectional views of embodiments in which a diffusion barrier structure is omitted from at least a portion of a bottom portion of a contact trench are illustrated.

[0033] FIG. 6A to FIG. 6L Respective partial cross-sectional views of a trench-based semiconductor device during different stages of a fabrication process are illustrated, wherein a diffusion barrier structure is formed prior to body and source regions of the device. DETAILED DESCRIPTION

[0034] The embodiments described herein control the lateral outdiffusion of the source / body contact doping of the trench-based transistor, thereby allowing narrower Vth, RonA and DIBL distributions for a given geometric variation of the highly doped source / body contact and the gate trench, and / or allowing the lateral spacing between the source / body contact and the channel region of the device to be reduced for a given Vth, RonA and DIBL window. The lateral outdiffusion of the source / body contact doping is better controlled by inserting a diffusion barrier structure, which includes alternating layers of Si and oxygen-doped Si between the highly doped source / body contact and the channel region of the device. The oxygen-doped Si layer of the diffusion barrier structure limits the lateral outdiffusion of the source / body contact doping, thereby controlling the lateral outdiffusion of the source / body contact doping in the direction toward the channel region. The diffusion barrier structure enables a narrower Vth distribution of, for example, a narrow trench MOSFET, or enables a smaller distance between the contact trench and the gate trench for a predetermined Vth distribution width. Next, an embodiment of a semiconductor device having such a diffusion barrier structure and a corresponding manufacturing method are described in more detail.

[0035] Figure 1 A partial cross-sectional view of an embodiment of a trench-based semiconductor device 100 is illustrated. The semiconductor device 100 includes: one or more gate trenches 102 extending into a Si substrate 104. The Si substrate 104 may include one or more Si epitaxial layers grown on a base Si substrate. A gate electrode 106 disposed in each gate trench 102 is insulated from surrounding semiconductor material by a gate dielectric 108. A field electrode 110 may be disposed below the corresponding gate electrode 106, in each gate trench 102, and insulated from surrounding semiconductor material and the gate electrode 106 by a field dielectric 112. The gate dielectric 108 and the field dielectric 112 may include the same or different materials and may have the same or different thicknesses. Alternatively, the field electrode 110 may be formed in a different trench separate from the gate trench 102 or omitted entirely, depending on the type of semiconductor device. The trench-based semiconductor device 100 may be a power semiconductor device, such as a power MOSFET (metal oxide semiconductor field effect transistor), an IGBT (insulated gate bipolar transistor), or the like.

[0036] The trench-based semiconductor device 100 further includes a body region 114 formed in the Si substrate 104. The body region 114 includes a channel region 116 that extends vertically along the sidewalls 118 of the corresponding gate trench 102. The semiconductor device 100 also includes a source region 120 formed in the Si substrate 104 above the body region 114. The vertical current flowing through the channel region 116 is controlled by applying a gate potential to the gate electrode 106. A drain region or collector region (not shown) is formed below the drift region 122. Depending on the type of device, additional structures can be formed in the drift region 122 and / or between the drift region 122 and the drain / collector region. For example, in the case of an IGBT-type device, a charge compensation structure can be formed in the drift region 122 and / or a field stop layer can be formed between the drift region 122 and the drain / collector region. Once again, any type of semiconductor device with a trench gate can utilize the diffusion barrier teachings described herein.

[0037] The trench-based semiconductor device 100 further includes a contact trench 124 extending into the Si substrate 104. The contact trench 124 is separated from each adjacent gate trench 102 by a portion of the source region 120 and a portion of the body region 114. The contact trench 124 is filled with a conductive material 126 (such as doped polysilicon, metal, etc.) that contacts the source region 120 at the sidewalls of the contact trench 124 and a highly doped body contact region 128 at the bottom of the contact trench 124. The conductive material 126 filling the contact trench 124 may extend onto the front main surface 130 of the Si substrate 104 beyond the diffusion barrier structure 132 and in a direction toward the gate trench 102, so that the conductive material 126 contacts the source region 120 along the front main surface 130 of the Si substrate 104 between the gate trench 102 and the diffusion barrier structure 132.

[0038] The highly doped body contact region 128 at the bottom of the contact trench 124 has the same doping type as the body region 114, but at a higher concentration to provide a good ohmic contact with the conductive material 126 filling the contact trench 124. For example, in the case of an n-channel device, the source region 120 and the drift region 122 are n-type doped, and the body region 114, the channel region 116, and the highly doped body contact region 128 are p-type doped. Conversely, in the case of a p-channel device, the source region 120 and the drift region 122 are p-type doped, and the body region 114, the channel region 116, and the highly doped body contact region 128 are n-type doped.

[0039] In either case, a diffusion barrier structure 132 is formed at least along the sidewalls of the contact trench 124 and disposed between the highly doped body contact region 126 and the channel region 116. The diffusion barrier structure 132 may also extend along the bottom of the contact trench 124 (e.g., Figure 1 ), extending only along the side walls, or along only a portion of the side walls and the bottom, as described in more detail later in this document.

[0040] The diffusion barrier structure 132 includes alternating layers of Si 134 and oxygen-doped Si 136. The alternating layers of Si 134 and oxygen-doped Si 136 form oxygen-doped silicon regions grown by epitaxy. In an embodiment, the oxygen concentration of each oxygen-doped Si layer 136 is lower than 5e14 cm-3. Each oxygen-doped Si layer 136 may have a thickness in the atomic range (e.g., one or several atoms thick) or a thickness in the nanometer range to ensure sufficient crystal information for growing Si on the oxygen-doped Si layer 136. The alternating layers of Si 134 and oxygen-doped Si 136 may be achieved by epitaxially growing Si layers with oxygen layers adsorbed on the surfaces of the Si layers, respectively, for example, with a specific limited thickness for the oxygen-doped Si layer 136 to ensure sufficient Si growth.

[0041] Figure 1 An exploded view of a diffusion barrier structure 132 is provided, which may also include a Si buffer layer 138 between the Si substrate 104 and the alternating layers of Si 134 and oxygen-doped Si 136, and / or a capping layer 140 epitaxially grown on the alternating layers of Si 134 and oxygen-doped Si 136. The Si buffer layer 138 may be relatively thin, for example, in the range of 2-5 nm thick. The Si buffer layer 138 may be grown after an implantation or etching step. The capping layer 140 provides high carrier mobility in this region of the device 100. One or both of the buffer layer 138 and the capping layer 140 may be omitted. The oxygen-doped Si layer 136 of the diffusion barrier structure 132 limits the lateral outdiffusion of the source / body contact doping, thereby controlling the lateral outdiffusion of the source / body contact doping in the direction toward the channel region 116. The oxygen-doped Si layer 136 of the diffusion barrier structure 132 may also improve the carrier mobility within the vertical channel region 116 of the device 100.

[0042] The oxygen-doped Si layer 136 of the diffusion barrier structure 132 can be formed by introducing a partial monolayer of oxygen into the Si lattice. The oxygen atoms are placed intermittently to minimize damage to the Si lattice. The Si atomic layer 134 separates the adjacent oxygen partial monolayers 136. The alternating layers of Si 134 and oxygen-doped Si 136 can be formed by Si epitaxy with oxygen absorption at different steps. For example, the temperature and gas conditions can be controlled during the epitaxy process to form a partial oxygen monolayer 136. Oxygen can be introduced / incorporated between the epitaxial layers 134 of Si, for example, by controlling the introduction of an oxygen precursor into the epitaxial chamber. The resulting diffusion barrier structure 132 includes a monolayer 136 interlaced with a standard Si epitaxial layer 134 without oxygen, and the monolayer 136 mainly includes Si but has a certain doping level or concentration level of oxygen. The diffusion barrier structure 132 may also include a Si capping layer 140 epitaxially grown on the alternating layers of Si 134 and oxygen-doped Si 136, or the Si capping layer 140 may be omitted.

[0043] FIG. 2A to FIG. 2F The diagram shows the different stages of the manufacturing process. Figure 1 A corresponding cross-sectional view of a trench-based semiconductor device 100 is shown in FIG.

[0044] Figure 2A Device 100 is shown after forming gate trench 102, body region 114, and source region 120. Any common semiconductor fabrication processes for forming gate trenches, body regions, and source regions may be used, such as trench masking and etching, trench filling, dopant implantation and activation (annealing), and the like.

[0045] Figure 2B The device 100 is shown after etching a contact trench 124 into the Si substrate 104 in the semiconductor mesa between adjacent gate trenches 102. Any common trench etching process may be used. For example, a hard mask / insulating layer 200 such as silicon oxide may be formed on the front major surface 130 of the Si substrate 104 and patterned to form an opening 202. The exposed portion of the Si substrate 104 may then be isotropically etched to form a contact trench 124 having a width (W1) greater than the width (W2) of the opening 202 in the hard mask 200.

[0046] Figure 2CThe device 100 is shown after epitaxially growing a diffusion barrier structure 132 on the sidewalls and bottom of the contact trench 124. The diffusion barrier structure 132 includes alternating layers of Si 134 and oxygen-doped Si 136. A Si capping layer 140 may be epitaxially grown on the alternating layers of Si 134 and oxygen-doped Si 136. The Si capping layer 140 may be omitted. The diffusion barrier structure 132 may be doped in situ or thereafter with the same conductivity type as the source region 120 to provide good ohmic contact between the source region 120 and a conductive material 126 subsequently deposited in the contact trench 124.

[0047] Figure 2D The device 100 is shown during implantation of a diffusion barrier structure 132 into a lower portion of the contact trench 124 having a dopant 204 of the same conductivity type as the body region 114 to provide a good ohmic contact between the body region 114 and a conductive material 126 subsequently deposited in the contact trench 124. Activation of the implanted dopant 204 by annealing forms a highly doped body contact region 128 at the bottom of the contact trench 124 having the same doping type as the body region 114 but at a higher concentration to provide a good ohmic contact with the conductive material 126 subsequently deposited in the contact trench 124. The oxygen-doped Si layer 136 of the diffusion barrier structure 132 limits lateral outdiffusion of the source / body contact dopant, thereby controlling the lateral outdiffusion of the source / body contact dopant in a direction toward the channel region 116. In one embodiment, the diffusion barrier structure 132 is present at the bottom of the contact trench 124, as shown in FIG. Figure 2D According to this embodiment, the oxygen-doped Si layer 136 of the diffusion barrier structure 132 also limits the vertical outdiffusion of the source / body contact doping in the direction towards the drift region 122. In embodiments described in more detail later herein, the diffusion barrier structure 132 is partially or completely omitted from the bottom of the contact trench 124 and therefore does not limit the vertical outdiffusion of the source / body contact doping.

[0048] Figure 2E The device 100 is shown after etching back the hard mask 200 to widen (W2') the opening 202 in the mask 200. Any standard dielectric etch back process may be used. The widened opening 202 in the hard mask 200 is aligned with the contact trench 124 and is wider than the combined width (W3) of the contact trench 124 and the diffusion barrier structure 132.

[0049] Figure 2FThe device is shown after filling the contact trench 124 with a conductive material 126. The conductive material 126 contacts the source region 120 at the sidewalls of the contact trench 124 and the highly doped body contact region 128 at the bottom of the contact trench 124. The conductive material 126 may extend onto the front main surface 130 of the Si substrate 104 beyond the diffusion barrier structure 132 and in a direction towards the gate trench 102, for example, if the opening 202 in the hard mask 200 was previously widened, as in Figure 2E as shown in .

[0050] Figure 3 A partial cross-sectional view of another embodiment of a trench-based semiconductor device 300 is illustrated. Figure 3 The embodiment shown in is similar to Figure 1 However, the difference is that the body contact dopant implanted and activated in the capping layer 140 of the diffusion barrier structure 132 extends into the source region 120 of the device 300 .

[0051] Figure 4 A partial cross-sectional view of another embodiment of a trench-based semiconductor device 400 is illustrated. Figure 4 The embodiment shown in is similar to Figure 1 and Figure 3 . However, the difference is that the diffusion barrier structure 132 is omitted from the bottom of the contact trench 124, and thus the vertical outdiffusion of the source / body contact doping is not restricted. According to this embodiment, the dopants that diffuse outward from the highly doped body contact region 128 are vertically introduced deeper into the drift region / Si substrate 122 / 104. The diffusion barrier structure 132 can be omitted from the bottom of the contact trench 132 by epitaxially growing alternating layers of Si 134 and oxygen-doped Si 136 only on the sidewalls of the contact trench 124, but not on the bottom. For example, a dielectric spacer (not shown) can be formed at the bottom of the contact trench 124 to prevent the epitaxial growth of the diffusion barrier structure 132 at the bottom of the trench.

[0052] FIG. 5A to FIG. 5D A corresponding cross-sectional view of another embodiment in which the diffusion barrier structure 132 is omitted from at least a portion of the bottom of the contact trench 124 is illustrated.

[0053] Figure 5A The semiconductor device 500 is shown after forming a diffusion barrier structure 132 on the sidewalls and bottom of the contact trench 124, for example, as previously described in conjunction with Figure 2CThe conformal spacer oxide 502 is also deposited on the Si capping layer 140 of the diffusion barrier structure 132. If the capping layer 140 is omitted, the conformal spacer oxide 502 is deposited directly on the uppermost of the alternating layers of Si 134 and oxygen-doped Si 136 of the diffusion barrier structure 132. In either case, any standard conformal spacer oxide may be used, such as silicon oxide.

[0054] Figure 5B The semiconductor device 500 is shown during anisotropic etching of the conformal spacer oxide 502 from the top to expose the diffusion barrier structure 132 at the bottom of the contact trench 124. Figure 5B 1. If a Si capping layer 140 is provided, the capping layer 140 will be exposed at the bottom of the contact trench 124. Otherwise, the topmost layer of the alternating layers of Si 134 and oxygen-doped Si 136 will be exposed. The conformal spacer oxide 502 can be removed from the bottom of the contact trench 124 using any standard dielectric anisotropic etching process.

[0055] Figure 5C The semiconductor device 500 is shown during etching away the diffusion barrier structure 132 exposed at the bottom of the contact trench 124. Figure 5C Any standard Si etching process can be used.

[0056] Figure 5D The semiconductor device 500 is shown after etching away the exposed diffusion barrier structure 132 at the bottom of the contact trench 124 and after removing the conformal spacer oxide 502. After etching away the exposed diffusion barrier structure 132 at the bottom of the contact trench 124, the conformal oxide spacer 502 can be removed using any standard dielectric removal process (e.g., isotropic etching). The device 500 is then processed to form a highly doped body contact region at the bottom of the contact trench 124, fill the contact trench 124, etc., for example, as shown in FIG. FIG. 2D to FIG. 2F As shown.

[0057] FIG. 6A to FIG. 6L Respective partial cross-sectional views of a trench based semiconductor device 600 during different stages of a fabrication process are illustrated, wherein a diffusion barrier structure 132 is formed prior to the body region 114 and the source region 120 .

[0058] Fig. 6AThe semiconductor device 500 is shown after forming the gate trench 102 in the Si substrate 104 and after forming a hard mask / insulating layer 200 such as, for example, silicon oxide on the front major surface 130 of the Si substrate 104. Any common semiconductor manufacturing process for forming the gate trench and hard mask may be used, such as, for example, trench masking and etching, dielectric deposition and / or thermal oxidation, etc.

[0059] Figure 6B The semiconductor device 600 is shown after etching a contact trench 124 into the Si substrate 104 between adjacent gate trenches 102. Any common trench etching process may be used to form the contact trench 124. For example, an opening 202 may be formed in the hard mask 200 on the front major surface 130 of the Si substrate 104, and the exposed portion of the Si substrate 104 may be isotropically etched to form a contact trench 124 that is wider than the opening 202 in the hard mask 200.

[0060] Figure 6C The semiconductor device 600 is shown after epitaxially growing the diffusion barrier structure 132 on the sidewalls and bottom of the contact trench 124, for example, as previously described herein in conjunction with Figure 2C As described above, the Si capping layer 140 may be epitaxially grown on the alternating layers of Si 134 and oxygen-doped Si 136. Alternatively, the Si capping layer 140 may be omitted.

[0061] Fig.6D An alternative embodiment is shown in which the diffusion barrier structure 132 is omitted from the bottom of the contact trench 124. The diffusion barrier structure 132 may be partially or completely omitted from the bottom of the contact trench 124. For example, the diffusion barrier structure 132 may be omitted from the bottom of the contact trench 124 by epitaxially growing alternating layers of Si 134 and oxygen-doped Si 136 only on the sidewalls of the contact trench 124, but not on the bottom. A dielectric spacer may be formed at the bottom of the contact trench 124 to prevent the diffusion barrier structure 132 from epitaxially growing at the bottom of the trench.

[0062] In one embodiment, a sacrificial insulating layer 602 is formed at the bottom of the contact trench 124. After forming the sacrificial insulating layer 602, alternating layers of Si 134 and oxygen-doped Si 136 are epitaxially grown only on the sidewalls of the contact trench 132. After epitaxially growing the alternating layers of Si 134 and oxygen-doped Si 136, the sacrificial insulating layer 602 is removed from the bottom of the contact trench 124.

[0063] In another embodiment, alternating layers of Si 134 and oxygen-doped Si 136 may be grown on the sidewalls and bottom of contact trench 124 and then removed from part or all of the trench bottom, for example, as previously described herein in conjunction with FIG. 5A to FIG. 5DAs described.

[0064] FIG. 6E to FIG. 6L A portion of the diffusion barrier structure 132 disposed along the bottom of the contact trench 124 is illustrated, with dashed lines indicating that the diffusion barrier structure 132 may or may not be present at the bottom of the contact trench 124 .

[0065] Fig. 6E The semiconductor device 600 is shown after filling the contact trench 124 with a sacrificial plug material 604 (such as, for example, carbon or another material) that can be selectively etched to the material of the hard mask 200 formed on the front main surface 130 of the Si substrate 104 .

[0066] Fig. 6F The semiconductor device 600 is shown after etching back the hard mask 200 followed by forming a screen oxide 606 .

[0067] Figure 6G The semiconductor device 600 is shown after forming a body region 114 and a source region 120 in a Si substrate 104, for example, by dopant implantation and dopant activation by annealing. The body region 114 and the source region 120 are formed using dopants having opposite conductivity types. The dopants are implanted and then activated by annealing to form the body region 114 and the source region 120. The dopant implantation is performed by Figure 6G If the diffusion barrier structure 132 is omitted from the bottom of the contact trench 124 , the dopant species may be directly implanted into the Si substrate 104 at the bottom of the contact trench 124 without the alternating layers of Si 134 and oxygen-doped Si 136 .

[0068] Figure 6H The semiconductor device 600 is shown after depositing a mesa protection oxide 608 over the Si substrate 104 .

[0069] Fig.6I The semiconductor device 600 is shown after the mesa protection oxide 608 is planarized and the top surface 610 of the sacrificial plug material 604 in the contact trench 124 is exposed. Any standard planarization process may be used, such as CMP (chemical mechanical polishing), for example.

[0070] Figure 6J The semiconductor device 600 is shown after removing the sacrificial plug material 604 from the contact trench 124. The process used to remove the sacrificial plug material 604 from the contact trench 124 depends on the type of plug material. For example, the process may involve wet and / or dry chemical etching.

[0071] Figure 6KThe semiconductor device 600 is shown during the implantation of a dopant substance 612 into the bottom of the contact trench 124. The dopant type (p-type or n-type) is the same as that of the body region 114, but at a higher concentration to form an ohmic contact. The Si substrate 104 is annealed to activate the implanted dopant substance 612, thereby forming a highly doped body contact region 128 at the bottom of the contact trench 124. The oxygen-doped Si layer 136 of the diffusion barrier structure 132 at least limits the lateral outdiffusion of the source / body contact dopant in the direction toward the vertical channel region 116. If the diffusion barrier structure 132 is present at the bottom of the contact trench 124, the oxygen-doped Si layer 136 of the diffusion barrier structure 132 also limits the vertical outdiffusion of the source / body contact dopant in the direction toward the drift region 122.

[0072] Figure 6L The semiconductor device 600 is shown after filling the contact trench 124 with a conductive material 126. The conductive material 126 contacts the source region 120 at the sidewalls of the contact trench 124 and the highly doped body contact region 128 at the bottom of the contact trench 124. The conductive material 126 may extend onto the front main surface 130 of the Si substrate 104 beyond the diffusion barrier structure 132 and in a direction towards the gate trench 102 if the opening in the mesa protection oxide 608 is widened before depositing the conductive material 126, e.g. Figure 2E as shown in .

[0073] For ease of description, spatially relative terms such as "under", "below", "lower", "above", "upper", etc. are used to explain the positioning of one element relative to a second element. In addition to orientations that are different from the orientations depicted in the figures, these terms are intended to cover different orientations of the device. In addition, terms such as "first", "second", etc. are also used to describe various elements, regions, sections, etc., and are not intended to be limiting. The same terms refer to the same elements throughout the specification.

[0074] 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 exclude 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.

[0075] With the above range of variations and applications in mind, it should be understood that the present invention is not limited by the foregoing description, nor by the accompanying drawings. Instead, the present invention is limited only by the following claims and their legal equivalents.

Claims

1. A semiconductor device, comprising: A gate trench extending into the Si substrate; A body region in the Si substrate, the body region comprising a channel region extending along a sidewall of the gate trench; a source region in the Si substrate above the body region; A contact trench extending into the Si substrate and separated from the gate trench by a portion of the source region and a portion of the body region, the contact trench being filled with a conductive material that contacts the source region at a sidewall of the contact trench and a highly doped body contact region at a bottom of the contact trench; as well as A diffusion barrier structure is formed along a sidewall of the contact trench and disposed between the highly doped body contact region and the channel region, the diffusion barrier structure comprising alternating layers of Si and oxygen-doped Si. 2 . The semiconductor device according to claim 1 , wherein the diffusion barrier structure extends along a bottom of the contact trench. 3 . The semiconductor device according to claim 1 , wherein the highly doped body contact region is laterally confined only by the diffusion barrier structure, the diffusion barrier structure being not at the bottom of the contact trench. 4 . The semiconductor device according to claim 1 , wherein the conductive material filling the contact trench may extend onto the front main surface of the Si substrate beyond the diffusion barrier structure and in a direction toward the gate trench. 5 . The semiconductor device of claim 1 , wherein the diffusion barrier structure comprises a Si capping layer epitaxially grown on the alternating layers of Si and oxygen-doped Si.

6. A method for manufacturing a semiconductor device, the method comprising: forming a gate trench extending into the Si substrate; forming a contact trench extending into the Si substrate and separated from the gate trench; forming a highly doped body contact region in the Si substrate at the bottom of the contact trench; forming a diffusion barrier structure along the sidewalls of the contact trench, the diffusion barrier structure comprising alternating layers of Si and oxygen-doped Si; forming a body region in the Si substrate, wherein the body region includes a channel region extending along a sidewall of the gate trench; forming a source region in the Si substrate above the body region; as well as The contact trench is filled with a conductive material that contacts a source region at a sidewall of the contact trench and a highly doped body contact region at a bottom of the contact trench, wherein the diffusion barrier structure is disposed between the highly doped body contact region and the channel region.

7. The method according to claim 6, wherein forming the diffusion barrier structure comprises: Prior to filling the contact trench with the conductive material, the alternating layers of Si and oxygen-doped Si are epitaxially grown on the sidewalls and bottom of the contact trench.

8. The method according to claim 7, further comprising: A Si capping layer is epitaxially grown on the alternating layers of Si and oxygen-doped Si.

9. The method according to claim 7, wherein forming the highly doped body contact region comprises: implanting a dopant substance into the alternating layers of Si and oxygen-doped Si at the bottom of the contact trench; as well as The Si substrate is annealed to activate the implanted dopant species.

10. The method according to claim 7, further comprising: The alternating layers of Si and oxygen-doped Si are removed from at least a portion of a bottom portion of the contact trench.

11. The method of claim 10, wherein removing the alternating layers of Si and oxygen-doped Si from at least a portion of the bottom of the contact trench comprises: epitaxially growing a Si capping layer on the alternating layers of Si and oxygen-doped Si; depositing a conformal spacer oxide on the Si capping layer; anisotropically etching the conformal spacer oxide to expose a diffusion barrier structure at a bottom of the contact trench; etching away the exposed diffusion barrier structure at the bottom of the contact trench; as well as After etching away the exposed diffusion barrier structure at the bottom of the contact trench, the conformal spacer oxide is removed.

12. The method according to claim 6, wherein forming the diffusion barrier structure comprises: Before filling the contact trench with the conductive material, the alternating layers of Si and oxygen-doped Si are epitaxially grown only on the sidewalls of the contact trench but not on the bottom.

13. The method according to claim 12, further comprising: A Si capping layer is epitaxially grown on the alternating layers of Si and oxygen-doped Si.

14. The method of claim 12, wherein forming the highly doped body contact region comprises: implanting a dopant substance into a bottom portion of the contact trench, the bottom portion of the contact trench being free of the alternating layers of Si and oxygen-doped Si; as well as The Si substrate is annealed to activate the implanted dopant species.

15. The method according to claim 6, further comprising: Before filling the contact trench with the conductive material, an insulating layer formed on the front main surface of the Si substrate is etched back so that the insulating layer has an opening aligned with the contact trench and wider than a combined width of the contact trench and the diffusion barrier structure.

16. The method of claim 15, wherein filling the contact trench with the conductive material comprises: The conductive material is deposited in the contact trench and in the opening formed in the insulating layer such that the conductive material extends onto the front main surface of the Si substrate beyond the diffusion barrier structure and in a direction toward the gate trench.

17. The method of claim 6, wherein forming the diffusion barrier structure comprises: Before forming the body region and the source region, the alternating layers of Si and oxygen-doped Si are epitaxially grown on the sidewalls and the bottom of the contact trench.

18. The method according to claim 17, further comprising: Before forming the body region and the source region, a Si capping layer is epitaxially grown on the alternating layers of Si and oxygen-doped Si.

19. The method according to claim 17, further comprising: The alternating layers of Si and oxygen-doped Si are removed from at least a portion of a bottom portion of the contact trench.

20. The method of claim 19, wherein removing the alternating layers of Si and oxygen-doped Si from at least a portion of the bottom of the contact trench comprises: epitaxially growing a Si capping layer on the alternating layers of Si and oxygen-doped Si; depositing a conformal spacer oxide on the Si capping layer; anisotropically etching the conformal spacer oxide to expose a diffusion barrier structure at a bottom of the contact trench; etching away the exposed diffusion barrier structure at the bottom of the contact trench; as well as After etching away the exposed diffusion barrier structure at the bottom of the contact trench, the conformal spacer oxide is removed.

21. The method of claim 6, wherein forming the diffusion barrier structure comprises: Before forming the body region and the source region, forming a sacrificial insulating layer at the bottom of the contact trench; After forming the sacrificial insulating layer, epitaxially growing the alternating layers of Si and oxygen-doped Si on the sidewalls of the contact trench; After epitaxially growing the alternating layers of Si and oxygen-doped Si, the sacrificial insulating layer is removed from the bottom of the contact trench.

22. The method according to claim 6, further comprising: filling the contact trench with a sacrificial plug material after forming the diffusion barrier structure and before forming the source region and the body region; After filling the contact trench with the sacrificial plug material, forming the source region and the body region in the Si substrate; After forming the source region and the body region, removing the sacrificial plug material; implanting a dopant substance into a bottom of the contact trench after removing the sacrificial plug material and before filling the contact trench with the conductive material; as well as The Si substrate is annealed to activate the implanted dopant species, thereby forming the highly doped body contact region.

23. A semiconductor device comprising: A gate trench extending into the Si substrate; A body region in the Si substrate, the body region comprising a vertical channel region adjacent to a sidewall of the gate trench; a source region in the Si substrate above the body region; a contact trench extending into the Si substrate and separated from the gate trench by a portion of the source region and a portion of the body region; a conductive material in the contact trench; as well as A diffusion barrier structure is interposed between the sidewalls of the contact trench and the vertical channel region, the diffusion barrier structure comprising alternating layers of Si and oxygen-doped Si and configured to increase carrier mobility within the vertical channel region. 24 . The semiconductor device according to claim 23 , wherein the diffusion barrier structure extends along a bottom of the contact trench.

25. The semiconductor device according to claim 23, further comprising: A highly doped body contact region is formed at a bottom of the contact trench, wherein the diffusion barrier structure is interposed between the highly doped body contact region and the vertical channel region. 26 . The semiconductor device of claim 25 , wherein the highly doped body contact region is laterally confined only by the diffusion barrier structure, the diffusion barrier structure being absent from the bottom of the contact trench. 27 . The semiconductor device according to claim 23 , wherein the conductive material in the contact trench extends onto the front main surface of the Si substrate beyond the diffusion barrier structure and in a direction toward the gate trench.

28. The semiconductor device of claim 23, wherein the diffusion barrier structure comprises a Si capping layer epitaxially grown on alternating layers of Si and oxygen-doped Si.

29. A method for manufacturing a semiconductor device, the method comprising: forming a gate trench extending into the Si substrate; forming a contact trench extending into the Si substrate and separated from the gate trench; forming a body region and a source region above the body region in the Si substrate, wherein the body region includes a vertical channel region adjacent to a sidewall of the gate trench; forming a diffusion barrier structure interposed between the sidewalls of the contact trench and the vertical channel region, the diffusion barrier structure comprising alternating layers of Si and oxygen-doped Si and configured to increase carrier mobility within the vertical channel region; as well as The contact trench is filled with a conductive material.

30. The method of claim 29, wherein forming the diffusion barrier structure comprises: Prior to filling the contact trench with the conductive material, the alternating layers of Si and oxygen-doped Si are epitaxially grown on the sidewalls and bottom of the contact trench.

31. The method of claim 30, further comprising: A Si capping layer is epitaxially grown on the alternating layers of Si and oxygen-doped Si.

32. The method of claim 30, further comprising: forming a highly doped body contact region at the bottom of the contact trench, wherein the diffusion barrier structure is interposed between the highly doped body contact region and the vertical channel region.

33. The method of claim 32, wherein forming the highly doped body contact region comprises: implanting a dopant substance into the alternating layers of Si and oxygen-doped Si at the bottom of the contact trench; as well as The Si substrate is annealed to activate the implanted dopant species.

34. The method of claim 30, further comprising: The alternating layers of Si and oxygen-doped Si are removed from at least a portion of a bottom portion of the contact trench.

35. The method of claim 34, wherein removing the alternating layers of Si and oxygen-doped Si from at least a portion of the bottom of the contact trench comprises: epitaxially growing a Si capping layer on the alternating layers of Si and oxygen-doped Si; depositing a conformal spacer oxide on the Si capping layer; anisotropically etching the conformal spacer oxide to expose a diffusion barrier structure at a bottom of the contact trench; etching away the exposed diffusion barrier structure at the bottom of the contact trench; as well as After etching away the exposed diffusion barrier structure at the bottom of the contact trench, the conformal spacer oxide is removed.

36. The method of claim 29, wherein forming the diffusion barrier structure comprises: Before filling the contact trench with the conductive material, the alternating layers of Si and oxygen-doped Si are epitaxially grown only on the sidewalls of the contact trench but not on the bottom.

37. The method of claim 36, further comprising: A Si capping layer is epitaxially grown on the alternating layers of Si and oxygen-doped Si.

38. The method of claim 29, further comprising: Before filling the contact trench with the conductive material, an insulating layer formed on the front main surface of the Si substrate is etched back so that the insulating layer has an opening aligned with the contact trench and wider than a combined width of the contact trench and the diffusion barrier structure.

39. The method of claim 38, wherein filling the contact trench with the conductive material comprises: The conductive material is deposited in the contact trench and in the opening formed in the insulating layer such that the conductive material extends onto the front main surface of the Si substrate beyond the diffusion barrier structure and in a direction toward the gate trench.

40. The method of claim 29, wherein forming the diffusion barrier structure comprises: Before forming the body region and the source region, the alternating layers of Si and oxygen-doped Si are epitaxially grown on the sidewalls and the bottom of the contact trench.

41. The method of claim 40, further comprising: Before forming the body region and the source region, a Si capping layer is epitaxially grown on the alternating layers of Si and oxygen-doped Si.

42. The method of claim 40, further comprising: The alternating layers of Si and oxygen-doped Si are removed from at least a portion of a bottom portion of the contact trench.

43. The method of claim 42, wherein removing the alternating layers of Si and oxygen-doped Si from at least a portion of the bottom of the contact trench comprises: epitaxially growing a Si capping layer on the alternating layers of Si and oxygen-doped Si; depositing a conformal spacer oxide on the Si capping layer; anisotropically etching the conformal spacer oxide to expose a diffusion barrier structure at a bottom of the contact trench; etching away the exposed diffusion barrier structure at the bottom of the contact trench; as well as After etching away the exposed diffusion barrier structure at the bottom of the contact trench, the conformal spacer oxide is removed.

44. The method of claim 29, wherein forming the diffusion barrier structure comprises: Before forming the body region and the source region, forming a sacrificial insulating layer at the bottom of the contact trench; After forming the sacrificial insulating layer, epitaxially growing the alternating layers of Si and oxygen-doped Si on the sidewalls of the contact trench; After epitaxially growing the alternating layers of Si and oxygen-doped Si, the sacrificial insulating layer is removed from the bottom of the contact trench.

45. The method of claim 29, further comprising: filling the contact trench with a sacrificial plug material after forming the diffusion barrier structure and before forming the body region and the source region; After forming the body region and the source region, removing the sacrificial plug material; implanting a dopant substance into a bottom of the contact trench after removing the sacrificial plug material and before filling the contact trench with the conductive material; as well as The Si substrate is annealed to activate the implanted dopant species, thereby forming a highly doped body contact region at the bottom of the contact trench.

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