Power device and manufacturing method thereof

Abstract

The invention discloses a power device and a manufacturing method thereof, and the power device comprises a first transistor and a second transistor, and comprises a substrate which serves as a first drain region; the first drift region is located on the substrate; the body region is located on the first drift region; the second drift region is located on the body region; a second drain region on the second drift region; the trench gate structure penetrates through the second drain electrode region, the second drift region and the body region and extends into the second drift region, the first transistor comprises a first drain electrode region, a first drift region, the body region and the trench gate structure, the second transistor comprises a second drain electrode region, a second drift region, a body region and the trench gate structure, the first drift region and the second drift region have a first doping type, and the body region has a second doping type. And the body region has a second doping type opposite to the first doping type. By integrating the two voltage-withstanding drift regions, the body region shared by the two transistors and the trench gate structure, bidirectional conduction and blocking are realized, and meanwhile, the cost, the area and the like of the device are reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of semiconductor devices, and in particular to a power device and a manufacturing method thereof. Background Art

[0002] Power devices are the foundation and core of power electronics technology, playing a vital role in power management and distribution. With the advancement of power electronics, bidirectional switching devices have emerged on the market, capable of conducting and blocking both DC and AC currents in the forward and reverse directions. Under AC current, bidirectional switches can achieve forward and reverse half-wave rectification at varying gate voltages. Compared to traditional single-gate devices, bidirectional switches significantly expand the AC rectification capabilities of GaN devices.

[0003] Due to the asymmetric structure of traditional power MOSFET, it is unable to achieve bidirectional blocking characteristics, which limits its application range. In situations where bidirectional voltage resistance is required, such as battery management systems (BMS), a single power MOSFET cannot meet the requirements. The traditional solution is to connect two power MOSFET devices in reverse series to form a bidirectional blocking and opening power device, such as Figure 1 As shown, two devices are connected in series at their source terminals. This allows the off state of one device to block the conduction of the body diode of the other, effectively blocking current when the circuit is off. However, using two devices to achieve current control doubles the cost, area, and weight of the bidirectionally conducting and blocking devices.

[0004] In addition, the flow and blocking of bidirectional current in the circuit process can be achieved by reverse parallel connection of two thyristor structures, such as Figure 2a and Figure 2b As shown, however, the cost, area, and weight of the bidirectional conductive device for realizing two different current paths by connecting two thyristor structures in parallel are still doubled, and the control circuit is also relatively complex. Summary of the Invention

[0005] In view of the above problems, the purpose of the present invention is to provide a power device and a manufacturing method thereof. By integrating two voltage-resistant drift regions in the vertical direction, the two transistors share the body region and the trench gate structure, which not only achieves bidirectional voltage-resistant blocking, but also reduces the cost, area, weight, etc. of the device.

[0006] According to one aspect of the present invention, a power device is provided, including a first transistor and a second transistor, the power device including: a substrate serving as a first drain region; a first drift region located on the substrate; a body region located on the first drift region; a second drift region located on the body region; a second drain region located on the second drift region; and a trench gate structure penetrating the second drain region, the second drift region and the body region, and extending into the second drift region, wherein the first transistor includes the first drain region, the first drift region, the body region and the trench gate structure, the second transistor includes the second drain region, the second drift region, the body region and the trench gate structure, the first drift and the second drift regions have a first doping type, and the body region has a second doping type opposite to the first doping type.

[0007] Optionally, the power device includes: a plurality of cells, each cell including a first transistor and a second transistor.

[0008] Optionally, the power device further includes: a contact region, wherein in the horizontal direction, the contact region is located between the second drift regions of two adjacent cells; in the vertical direction, the upper surface of the contact region is flush with the upper surface of the second drain region, and the lower surface of the contact region is flush with the lower surface of the body region.

[0009] Optionally, in the same cell, the second drift region separates the contact region and the second drain region, and the second drift region is adjacent to the contact region.

[0010] Optionally, the power device further includes: an isolation structure, the isolation structure being located between the contact region and the second drain region, the upper surface of the isolation structure being flush with the upper surface of the second drain region, and the lower surface of the isolation structure being adjacent to the upper surface of the body region.

[0011] Optionally, the power device also includes: a first electrode, located on the upper surface of the contact region and electrically connected to the contact region; a second electrode, located on the upper surface of the second drain region and electrically connected to the second drain region; a third electrode, located on the upper surface of the trench gate structure and electrically connected to the trench gate structure; and a fourth electrode, located on the lower surface of the substrate and electrically connected to the substrate.

[0012] Optionally, the substrate, the first drift region, the second drift region and the second drain region have a first doping type, and the body region and the contact region have a second doping type.

[0013] Optionally, the doping concentration of the substrate is greater than the doping concentrations of the first drift region and the second drift region, the doping concentration of the second drain region is greater than the doping concentrations of the second drift region and the first drift region, and the doping concentration of the contact region is greater than the doping concentration of the body region.

[0014] According to another aspect of the present invention, a method for manufacturing a power device is provided, comprising: forming a first drift region, a body region and a doped region in an epitaxial layer on a substrate, the substrate serving as a first drain region, the first drift region being located on the substrate, the body region being located on the first drift region, and the doped region being located on the body region; forming a trench gate structure, the trench gate structure penetrating the doped region and the body region to extend to the first drift region; forming a second drift region and a second drain region in the doped region, the second drain region being located on the second drift region; wherein the first transistor comprises the first drain region, the first drift region, the body region and the trench gate structure, the second transistor comprises the second drain region, the second drift region, the body region and the trench gate structure, the first drift and second drift regions have a first doping type, and the body region has a second doping type opposite to the first doping type.

[0015] Optionally, forming a first drift region, a body region and a doping region in the epitaxial layer includes: implanting first-type impurity ions and second-type impurity ions into the epitaxial layer, wherein the implantation region of the first-type impurity ions is located inside the implantation region of the second-type impurity ions; using a push-well process to diffuse the first-type impurity ions and the second-type impurity ions in the epitaxial layer to form a body region and a doping region, respectively, and a portion of the epitaxial layer located between the substrate and the body region forms a first drift region; wherein the diffusion depth and diffusion width of the first-type impurity ions in the body region are greater than the diffusion depth and diffusion width of the second-type impurity ions in the doping region.

[0016] Optionally, forming the trench gate structure includes: forming a trench penetrating the body region and the doped region, with the bottom of the trench located in the first drift region; and depositing a gate dielectric layer and a polysilicon layer in the trench, with the gate dielectric layer located between the polysilicon layer and the first drift region, the body region, and the doped region.

[0017] Optionally, the step of forming the trench gate structure further includes: forming a groove in a region of the doped region adjacent to the body region; and depositing a dielectric layer in the groove to form an isolation structure.

[0018] Optionally, an injection barrier layer is formed on the upper surface of the epitaxial layer, and in the step of forming the second drain region and the contact region through the injection barrier layer, the injection barrier layer exposes part of the upper surface of the body region and part of the upper surface of the doped region; the second type of ion doping is performed on the upper surface of the body region and the second type of ion doping is performed on the upper surface of the doped region; and a push-well process is used to diffuse the first type of impurity ions and the second type of impurity ions in the body region and the doped region to form a contact region and a second drain region.

[0019] Optionally, after the step of forming the second drain region and the contact region, it also includes: forming a first electrode on the upper surface of the contact region; forming a second electrode on the upper surface of the second drain region, forming a third electrode on the upper surface of the trench gate structure and forming a fourth electrode on the lower surface of the substrate.

[0020] The power device and manufacturing method provided by the present invention integrate two transistors in a vertical direction. The two transistors share a trench gate structure and body region, enabling the power device of the present application to be connected in series vertically. Furthermore, a second drift region and a first drift region are provided above and below the body region, respectively. This allows the shared trench gate structure to control bidirectional conduction of the power device, while also achieving voltage-resistant blocking through the PN junctions formed between the first and second drift regions and the body region. This achieves bidirectional conduction and blocking of the power device while saving some structural elements, and also reduces the occupied area and weight of the power device.

[0021] Furthermore, the two transistors connected in series in the power device respectively have a first drift region and a second drift region to withstand the bias voltage applied to both ends of the power device (ie, the back electrode and the drain contact electrode), thereby improving the reliability of the device.

[0022] Furthermore, the power device and its manufacturing method provided by the present invention integrate two voltage-resistant drift regions in the vertical direction, and at the same time achieve bidirectional voltage-resistant blocking through double diffusion and drift regions. Since the manufacturing process of the power device is the same as the traditional trench gate process, the manufacturing process can adopt the existing process, which has the advantages of simple process and low cost.

[0023] Furthermore, an isolation structure is included between the contact area and the second drain area of ​​the power device. The isolation structure can reduce the leakage problem between the contact area and the second drain area, while increasing the breakdown voltage between the contact area and the second drain area, thereby improving the reliability of the device. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The above and other objects, features and advantages of the present invention will become more apparent through the following description of the embodiments of the present invention with reference to the accompanying drawings, in which:

[0025] Figure 1 A circuit diagram showing horizontally series connected power devices according to the prior art is shown;

[0026] Figure 2a and Figure 2b shows a structural diagram of vertically parallel power devices according to the prior art;

[0027] Figure 3 shows a cross-sectional structural diagram of a power device according to some embodiments of the present invention;

[0028] Figure 4 shows a horizontal plane top view of a power device according to some embodiments of the present invention;

[0029] Figure 5A flow chart showing a method for manufacturing a power device according to some embodiments of the present invention is shown;

[0030] Figures 6a to 6e Schematic cross-sectional views of various stages of a method for manufacturing a power device according to some embodiments of the present invention are shown;

[0031] Figure 7 sectional views of power devices according to other embodiments of the present invention are shown. DETAILED DESCRIPTION

[0032] Various embodiments of the present invention will be described in more detail below with reference to the accompanying drawings. In each of the accompanying drawings, identical elements are represented by identical or similar reference numerals. For the sake of clarity, the various parts in the accompanying drawings are not drawn to scale.

[0033] For ease of description, spatially relative terms such as "below," "beneath," "lower," "above," and "upper" may be used herein to describe the relationship of one element or component to another (or additional) elements or components as illustrated in the figures. Spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. The device may be otherwise oriented (rotated 90 degrees or at other orientations), and the spatially relative descriptors used herein should be interpreted accordingly.

[0034] The specific implementation of the present invention is further described in detail below with reference to the accompanying drawings and examples.

[0035] Figure 3 shows a cross-sectional structural diagram of a power device according to a first embodiment of the present invention; Figure 4 FIG. 1 shows a horizontal top view of a power device according to a first embodiment of the present invention.

[0036] refer to Figure 3 The power device 100 of the present application includes a first transistor and a second transistor. The first transistor includes a first drain region 110 and a first drift region 121 located above the first drain region 110. The second transistor includes a second drift region 132 located above the first drift region 121 and a second drain region 133 located above the second drift region 132. The power device 100 also includes a body region 131 and a trench gate structure 150 shared by the first and second transistors. The body region 131 is located between the first drift region 120 and the second drift region 132. The trench gate structure 150 penetrates the second drain region 133, the second drift region 132, and the body region 131 and extends into the first drift region 120. In some embodiments, the first drain region 110, the first drift region 121, the second drift region 132, and the second drain region 133 are all of a first doping type, for example, while the body region 132 is of a second doping type, where the first doping type is opposite to the second doping type.

[0037] In the following embodiments, since the power device 100 can be formed from an initial structure including a substrate and an epitaxial layer 120, the first drain region 110 is formed by the substrate, and the first drain region 110 can also be referred to as the substrate 110. The first drift region 121, the body region 131, the second drift region 132 and the second drain region 133 are obtained by a series of processes on the epitaxial layer 120. It can also be considered that the first drift region 121, the body region 131, the second drift region 132 and the second drain region 133 are located in the epitaxial layer 120, and the upper surface of the epitaxial layer 120 can be coplanar with the upper surface of the trench gate structure 150 and the upper surface of the second drain region 133.

[0038] In some embodiments, the power device 100 may include one or more cells. Figure 3 The structure shown in the figure shows an embodiment including two cells, each cell including the first transistor and the second transistor described above, the first transistor and the second transistor being connected in series, and the number of cells can be equal to the number of trench gate structures 150. Between adjacent cells, the power device 100 further includes a contact region 134, which is shared by the two adjacent cells. The contact region 134 is laterally located between the second drift regions 132 of the two adjacent cells and is connected to one side of the body region 131. Figure 3 The other side of the body region 131 of the two cells (i.e. Figure 3 The body region 131 and the contact region 134 are shown as continuous with each other. In addition, multiple cells can be identical to each other. For ease of description, the following description takes one cell in the power device 100 as an example.

[0039] Combined with reference Figure 3 In some embodiments, the lateral dimension of the body region 131 in the epitaxial layer 120 is greater than the lateral dimension of the second drift region 132 in the epitaxial layer 120, and the lateral dimension of the second drift region 132 in the epitaxial layer 120 is greater than the lateral dimension of the second drain region 133 in the epitaxial layer 120. In further embodiments, the second drift region 132 may have an opening that opens upward, with the second drain region 133 disposed in the opening. In such an embodiment, the upper surface of the second drift region 132, the upper surface of the second drain region 133, and the upper surface of the epitaxial layer 120 are flush with each other.

[0040] In the cell of the power device 100, a first transistor and a second transistor connected in series share a trench gate structure 150 and a body region 131. The first transistor includes the trench gate structure 150, the body region 131, the first drift region 121, and the first drain region 110, while the second transistor includes the trench gate structure 150, the body region 131, the second drift region 132, and the second drain region 133. The first and second transistors share the trench gate structure 150 and the body region 131, and a channel region is formed near the contact interface between the body region 131 and the trench gate structure 150.

[0041] In the first transistor, the substrate 110 serves as the first drain region of the first transistor. In the vertical direction, the trench gate structure 150 extends downward from the upper surface of the second drain region 133 into the first drift region 121, but does not penetrate the first drift region 121. Therefore, the first drift regions 121 of the first transistors on both sides of the trench gate structure 150 in the same cell are continuous, and the substrate 110 is also continuous. Furthermore, in two adjacent cells, the first drift regions 121 in each cell are continuous with each other, and the first drain regions 110 in each cell are also continuous, so that the first transistors in all cells in the power device 100 can be electrically connected together. However, the present application is not limited to this. In other embodiments, in two adjacent cells, the first drift regions 121 in each cell are spaced apart from each other, and the first drain regions 110 in each cell are also spaced apart from each other, and are electrically connected together through the first drift regions 121 and the first drain regions 110 in each cell through additional metal wiring.

[0042] In the second transistor, the second drift region 132 vertically separates the second drain region 133 from the body region 131, and laterally separates the second drain region 133 from the contact region 134. In the vertical direction, the sidewalls of the body region 131, the second drift region 132, and the second drain region 133 are sequentially adjacent to the sidewalls of the trench gate structure 150. Furthermore, in the second transistor, the top surfaces of the contact region 134, the second drift region 132, and the second drain region 133 are coplanar with the top surface of the trench gate structure 150, i.e., at the same level as the top surface of the epitaxial layer 120.

[0043] In some embodiments, the power device 100 further includes a first electrode 141, a second electrode 142, and a third electrode 143 located on the upper surface of the epitaxial layer 120, and a fourth electrode 144 located on the lower surface of the substrate 110, wherein the first electrode 141 is electrically connected to the body region 131, the second electrode 142 is electrically connected to the second drain region 133, the third electrode 143 is electrically connected to the trench gate structure 150, and the fourth electrode 144 is electrically connected to the first drain region 110. In detail, in the power device 100, the first electrode 141 is located on the upper surface of the contact region 134 and is electrically connected to the body region 131 via the contact region 134; the second electrode 132 is located on the upper surface of the drain region 133 and is electrically connected to the drain region 133; the third electrode 143 is located on the upper surface of the trench gate structure 150 and is electrically connected to the trench gate structure 150; and the fourth electrode 144 is located on the lower surface of the substrate 110 and is electrically connected to the substrate 110. Although Figure 3 The first electrode 141 , the second electrode 142 , and the third electrode 143 are shown as being located in the same cross section, but it is understandable that the first electrode 141 , the second electrode 142 , and the third electrode 143 may be located in different cross sections to facilitate connection.

[0044] exist Figure 3 In the power device 100 shown, the second electrode 142 and the fourth electrode 144 are the inflow and outflow ends of the current, the third electrode 143 is the gate control end, and the first electrode 141 is the potential control end, which can control the turn-on voltage of the third electrode 143. The first electrode 141 to the fourth electrode 144 are not connected to each other and serve as independent ports of the device.

[0045] In this embodiment, the substrate 110, the first drift region 121, the second drift region 132, and the second drain region 133 all have, for example, a first doping type, the body region 132 and the contact region 134 have a second doping type, and the first doping type is opposite to the second doping type. The doping concentration of the second drain region 133 is greater than the doping concentrations of the second drift region 132 and the first drift region 121, the doping concentration of the substrate 110 is greater than the doping concentrations of the second drift region 132 and the first drift region 121, and the doping concentration of the body contact region 134 is greater than the doping concentration of the body region 131. Specifically, the first doping type is, for example, one of N-type and P-type, and the second doping type is the other of N-type and P-type. Therefore, in Figure 3 In the power device 100 shown, the second drift region 132 and the first drift region 121 respectively form a PN junction with the body region 132 .

[0046] Taking an N-channel power device as an example, the substrate 110, the first drift region 121, the second drift region 132, and the second drain region 133 are doped with N-type impurities, while the body region 132 and the contact region 134 are doped with P-type impurities. When the power device 100 is in use, a high voltage is applied to the third electrode 143 and the second electrode 142. Current flows from the second electrode 142 through the second drain region 133, the second drift region 132, the body region 131, the first drift region 121, and the substrate 110 to the fourth electrode 144.

[0047] If high voltage is applied to the third electrode 143 and the fourth electrode 144 of the power device, the current direction will be opposite to the current direction when high voltage is applied to the third electrode 143 and the second electrode 142. Specifically, the current flows from the fourth electrode 144 through the substrate 110, the first drift region 121, the body region 131, the second drift region 132 and the second drain region 133 to the second electrode 142.

[0048] If a low voltage is applied to the third electrode 143 of the power device, no current flows through the device, regardless of whether a high or low voltage is applied to the second electrode 142 and the fourth electrode 144. This is because the two PN junctions between the second drift region 132 and the body region 131, and between the first drift region 121 and the body region 131, cannot conduct when the trench gate structure 150 is at a low voltage.

[0049] Therefore, by controlling the specific electrodes among the second electrode 142 , the third electrode 143 and the fourth electrode 144 to which the voltage is applied and the level of the applied voltage, the forward conduction, reverse conduction and shutdown states of the power device 100 can be controlled.

[0050] In addition, whether the power device 100 is in the on state or the blocking state, the potential of the first electrode 141 should be kept at the lowest potential to ensure that the trench gate structure 150 can normally turn on and off the power device.

[0051] In the power device 100 of the present application, the bidirectional conduction of the power device 100 can be controlled by a shared trench gate structure 150, and voltage-resistant blocking is achieved by the PN junctions formed between the first drift region 121 and the second drift region 132 and the body region 131, thereby achieving bidirectional conduction and blocking of the power device 100. Compared with the conventional conduction and blocking power devices composed of devices such as VDMOS and SiC, the number of devices is reduced by half (for example, the source of the two transistors is omitted and the gate and body region are shared by the two transistors), thereby saving more space and cost.

[0052] Figure 4 FIG. 1 shows a horizontal top view of a power device according to some embodiments of the present invention, with reference to FIG. Figure 4 , for the convenience of description, the first direction can be defined as Figure 4The first direction, the second direction, and the third direction are perpendicular to each other.

[0053] On the upper surface of the power device 100, the upper surfaces of the contact region 134, the second drift region 132, and the second drain region 133 are all located within the area defined by the entire edge of the body region 131. In addition, the trench gate structure 150 extends along the second direction, and the length of the trench gate structure 150 along the second direction is greater than the length of the body region 131 along the second direction. A third electrode 143 is provided on an end portion of the trench gate structure 150 outside the body region 131, and along the third direction, a plurality of third electrodes 143 are electrically connected via a third wiring layer 163; a plurality of first electrodes 141 of the contact regions 134 are electrically connected via the first wiring layer 161; and a plurality of second electrodes 142 of the second drain regions 133 are electrically connected via the second wiring layer 162. The first wiring layer 161, the second wiring layer 162, and the third wiring layer 163 are, for example, located Figure 3 The electrodes are arranged on the upper surfaces of the first electrode 141 , the second electrode 142 , and the third electrode 143 , and are isolated from each other by an insulating layer.

[0054] In addition, although Figure 4 It is not shown in the figure, but it can be understood that the fourth electrode 144 located on the lower surface of the substrate 110 can be as follows Figure 3 As shown, a connected metal layer is used to shape the fourth electrodes 144 of the second transistors in multiple cells into a whole.

[0055] In other embodiments, the first drift region 121 and the substrate 110 of two adjacent cells can also be separated from each other through an isolation structure. In this case, the fourth electrode 144 electrically connected to the substrate 110 can be set accordingly according to the number of cells. The fourth electrodes 144 between adjacent cells are isolated, and the electrical connection between multiple fourth electrodes 144 is achieved through another wiring layer.

[0056] Figure 5 A flow chart showing a method for manufacturing a power device according to a first embodiment of the present invention is shown; Figures 6a to 6e Schematic cross-sectional views of various stages of a method for manufacturing a power device according to a first embodiment of the present invention are shown.

[0057] The following takes the case where the first doping type is N-type and the second doping type is P-type as an example, and combines Figure 5 、 Figures 6a to 6eThe manufacturing method of the power device of the present application is described in detail. It is understood that in other embodiments, the first doping type may also be P-type. Therefore, in other embodiments, those skilled in the art may also set the doping types of the body region 131, body contact region 134, first drift region 121, second drift region 132, etc. in the opposite direction according to the type of power device.

[0058] In this embodiment, the power device manufacturing method begins with a wafer comprising at least a substrate 110 and an epitaxial layer 120 located on the upper surface of the substrate 110. The thickness of the epitaxial layer 120 can be selected based on the breakdown voltage of the PN junction between the body region and the two drift regions in the cell of the power device. Both the substrate 110 and the epitaxial layer 120 are N-type doped, with the doping concentration of the substrate 110 being greater than that of the epitaxial layer 120.

[0059] Step S201 : forming a body region and a first drift region in the epitaxial layer 120 located on a substrate.

[0060] In this step, an ion implantation process is used to implant N-type impurity ions and P-type impurity ions into the epitaxial layer 120, wherein the implantation region of the N-type impurity ions is located inside the implantation region of the P-type impurity ions. Then, a push-in process is used to diffuse the N-type impurity ions and the P-type impurity ions in the epitaxial layer 120 to form a P-type body region 131 and a doped region 136, respectively. Figure 6a At this time, the portion of the epitaxial layer 120 located below the body region 131 forms the first drift region 121 , and the doped region 136 is subsequently used to form the N-type second drift region 132 .

[0061] During the push-in process, because P-type impurity ions diffuse faster than N-type impurity ions, the implantation region (implantation area) of P-type impurity ions is larger than that of N-type impurity ions, and the implantation depth of P-type impurity ions is greater than that of N-type impurity ions, the body region 131 formed by diffusion after the push-in process has a diffusion depth D1 and a diffusion width greater than the diffusion depth D2 and diffusion width of the doped region 136. That is, the body region 131 is located below and surrounds the doped region 136. The upper surfaces of the body region 131 and the doped region 136 are located on the same horizontal plane, namely, the upper surface of the epitaxial layer 120. That is, the body region 131 and the doped region 136 extend from the upper surface to the lower surface of the epitaxial layer 120.

[0062] In this embodiment, the implantation concentration and diffusion length of the P-type impurity ions and N-type impurity ions used to form the body region 131 and the doping region 136 can be selected according to the breakdown voltage of the PN junction between the body region and the drift region in the power device.

[0063] Step S202: forming a trench gate structure.

[0064] In this step, an etching process, such as dry etching, including ion milling etching, plasma etching, reactive ion etching, laser ablation, or wet etching or vapor etching, is used to etch the semiconductor structure to form a trench penetrating the doped region 136 and the body region 131. The trench extends from the upper surface to the lower surface of the epitaxial layer 120, and the bottom of the trench is located in the first drift region 121 below the body region 131. That is, the depth of the bottom of the trench extending downward from the upper surface of the epitaxial layer 120 is greater than the depth of the body region 131 extending downward from the upper surface of the epitaxial layer 120. Furthermore, a deposition process, such as chemical vapor deposition or physical vapor deposition, is used to sequentially deposit a gate dielectric layer and a polysilicon layer in the trench to form a trench gate structure 150, as shown in FIG. Figure 6b The gate dielectric layer is located between the polysilicon layer and the first drift region 121 , the body region 131 and the doped region 136 , and is used to isolate the polysilicon layer from the first drift region 121 , the body region 131 and the doped region 136 .

[0065] Step S203: forming an implantation blocking layer on the upper surface of the semiconductor structure, and forming a second drain region and a contact region through the implantation blocking layer.

[0066] In this step, a mask layer is formed on the upper surface of the semiconductor structure and patterned. The patterned mask layer serves as an implantation barrier layer 101 during ion implantation, exposing a portion of the upper surface of the body region 131 and the doped region 136. Figure 6c shown.

[0067] The upper surface of the doped region 136 exposed by the injection blocking layer 101 is divided into an N-type doped region P2 and a P-type doped region P1 according to different positions. Figure 6d The doping region P1 is located on the upper surface of the body region 131 , and the doping region P2 is located on the upper surface of the doping region 136 .

[0068] Furthermore, corresponding types of ion implantation are performed in corresponding regions through the implantation barrier layer 101, and a well-driving process is performed, so that a second drain region 133 is formed in the doped region 136, and a second drift region 132 is also formed accordingly, and a contact region 134 is formed at the junction of adjacent body regions, as shown in FIG. Figure 6e shown.

[0069] After forming the second drain region 133, it is readily understood that the extension depth of the second drift region 132 in the epitaxial layer 120 is greater than the extension depth of the second drain region 133 in the epitaxial layer 120; and the lateral dimension of the second drift region 132 in the epitaxial layer 120 is greater than the lateral dimension of the second drain region 133 in the epitaxial layer 120. The trench gate structure 150 extends through the body region 131, the second drift region 132, and the second drain region 133 into the first drift region 121 below the body region 131, such that the body region 131, the second drift region 132, and the second drain region 133 all surround the trench gate structure 150. Consequently, the extension depth of the body region 131 in the epitaxial layer 120 is less than the extension depth of the trench gate structure 150 in the epitaxial layer 120. The extension depth of the contact region 134 is equal to the extension depth of the body region 131. In the lateral direction, the upper side surfaces of the contact region 134 are adjacent to the side surfaces of the second drift region 132 in two adjacent cells respectively; the lower side surfaces of the contact region 134 are adjacent to the side surfaces of the body region 131 in two adjacent cells respectively. In other embodiments, the upper side surfaces of the contact region 134 may be spaced apart from the side surfaces of the second drift region 132 in two adjacent cells, such as Figure 4 shown.

[0070] Correspondingly, step S204: forming the first electrode to the fourth electrode.

[0071] In this step, a deposition process, such as chemical vapor deposition or physical vapor deposition and etching, is used to form the first electrode 141 to the third electrode 143 on the contact region 134, the second drain region 133 and the upper surface of the trench gate structure 150, and the fourth electrode 144 is formed on the lower surface of the substrate 110. Figure 3 shown.

[0072] Among them, the way of forming the fourth electrode 144 on the lower surface of the substrate 110 is similar to the electrode extraction method of the power device 100 of the embodiment of the present application and the conventional MOS device, so there is no need to change the existing packaging form and the packaging is simple.

[0073] In other embodiments, the fourth electrode 143 may be formed after the lower surface of the substrate 110 is processed.

[0074] Figure 7 FIG. 4 shows a cross-sectional structural diagram of a power device according to a second embodiment of the present invention.

[0075] Compared with the first embodiment, the power device 200 of the second embodiment is different in that it further includes an isolation structure 270. Other similarities are not described here in detail. Figures 3 to 6e Related description.

[0076] refer to Figure 7In the power device 200 of the second embodiment, in the horizontal direction, the contact region 134 and the second drain region 133 are separated by the isolation structure 270, and the second drift region 132 and the contact region 134 are also separated by the isolation structure 270, thereby reducing the leakage problem between the contact region 134 and the drain region 133 and increasing the breakdown voltage between the contact region 134 and the drain region 133.

[0077] In this embodiment, the isolation structure 270 is fabricated using, for example, a conventional shallow trench isolation (STI) process. In other embodiments, the isolation structure 270 may also be fabricated using other isolation processes.

[0078] When forming the isolation structure 270, the isolation structure 270 is formed simultaneously with the trench gate structure, for example. Specifically, in combination with the aforementioned method for manufacturing a power device, the step of forming the isolation structure includes: when forming a trench penetrating the doped region 136 and the body region 131, forming a groove in the doped region 136 adjacent to the body region 131, the groove is used to form the isolation structure 270, and the extension depth of the groove in the doped region 136 is less than the extension depth of the trench for the trench gate structure 150 in the doped region 136, and two grooves are included between adjacent trenches; further, when depositing the gate dielectric layer, the groove is also filled with an insulating material to form the isolation structure 270. The insulating material can be the same as or different from the material of the gate dielectric layer, but is preferably the same.

[0079] The power device and manufacturing method provided by the present invention integrate two transistors in a vertical direction. The two transistors share a trench gate structure and body region, enabling the power device of the present application to be connected in series vertically. Furthermore, a second drift region and a first drift region are provided above and below the body region, respectively. This allows bidirectional conduction of the power device to be controlled by the shared trench gate structure. Furthermore, bidirectional withstand voltage blocking is achieved through the PN junctions formed between the first drift region and the second drift region and the body region, thereby achieving bidirectional conduction and blocking of the power device while saving some structural elements. This also reduces the occupied area and weight of the power device.

[0080] Furthermore, the two transistors connected in series in the power device respectively have a first drift region and a second drift region to withstand the bias voltage applied to both ends of the power device (ie, the fourth electrode and the second electrode), thereby improving the reliability of the device.

[0081] Furthermore, the power device and its manufacturing method provided by the present invention integrate two voltage-resistant drift structures (i.e., two drift regions) in the vertical direction through a trench gate process, thereby achieving bidirectional voltage-resistant blocking. Since the manufacturing process of the power device is the same as the traditional trench gate process, the manufacturing process can adopt the existing process, which has the advantages of simple process and low cost.

[0082] Furthermore, an isolation structure is included between the contact region and the second drain region of the power device. The isolation structure can reduce leakage problems between the contact region and the drain region, while increasing the breakdown voltage between the contact region and the drain region, thereby improving the reliability of the device.

[0083] While embodiments of the present invention have been described above, these embodiments do not exhaustively describe all details and do not limit the invention to the specific embodiments described. Obviously, many modifications and variations are possible based on the above description. These embodiments are selected and described in detail in this specification in order to better explain the principles and practical applications of the present invention, thereby enabling those skilled in the art to better utilize the present invention and its modifications. The present invention is limited only by the claims and their full scope and equivalents.

Claims

1. A power device comprising a first transistor and a second transistor, the power device comprising: a substrate serving as a first drain region; a first drift region, located on the substrate; a body region, located on the first drift region; a second drift region located on the body region; a second drain region, located on the second drift region; as well as a trench gate structure, penetrating the second drain region, the second drift region, and the body region, and extending into the second drift region, The first transistor includes the first drain region, the first drift region, the body region and the trench gate structure, the second transistor includes the second drain region, the second drift region, the body region and the trench gate structure, the first drift and the second drift regions have a first doping type, and the body region has a second doping type opposite to the first doping type.

2. The power device according to claim 1, wherein: The power device includes: a plurality of cells, each cell including the first transistor and the second transistor.

3. The power device according to claim 2, further comprising: A contact region, wherein in the horizontal direction, the contact region is located between the second drift regions of two adjacent cells; In a vertical direction, an upper surface of the contact region is flush with an upper surface of the second drain region, and a lower surface of the contact region is flush with a lower surface of the body region.

4. The power device according to claim 3, wherein: In the same cell, the second drift region separates the contact region and the second drain region, and the second drift region is adjacent to the contact region.

5. The power device according to claim 3, further comprising: An isolation structure is located between the contact region and the second drain region, an upper surface of the isolation structure is flush with an upper surface of the second drain region, and a lower surface of the isolation structure is adjacent to an upper surface of the body region.

6. The power device according to claim 4 or 5, further comprising: a first electrode, located on an upper surface of the contact region and electrically connected to the contact region; a second electrode, located on an upper surface of the second drain region and electrically connected to the second drain region; a third electrode, located on an upper surface of the trench gate structure and electrically connected to the trench gate structure; The fourth electrode is located on the lower surface of the substrate and is electrically connected to the substrate.

7. The power device according to claim 3, wherein: The substrate, the first drift region, the second drift region, and the second drain region have a first doping type, and the body region and the contact region have a second doping type.

8. The power device according to claim 7, wherein: The doping concentration of the substrate is greater than the doping concentrations of the first drift region and the second drift region, the doping concentration of the second drain region is greater than the doping concentrations of the second drift region and the first drift region, and the doping concentration of the contact region is greater than the doping concentration of the body region.

9. A method for manufacturing a power device, comprising: forming a first drift region, a body region, and a doped region in an epitaxial layer on a substrate, wherein the substrate serves as a first drain region, the first drift region is located on the substrate, the body region is located on the first drift region, and the doped region is located on the body region; forming a trench gate structure, wherein the trench gate structure penetrates the doped region and the body region to extend to the first drift region; forming a second drift region and a second drain region in the doped region, wherein the second drain region is located on the second drift region; The first transistor includes the first drain region, the first drift region, the body region and the trench gate structure, the second transistor includes the second drain region, the second drift region, the body region and the trench gate structure, the first drift and the second drift regions have a first doping type, and the body region has a second doping type opposite to the first doping type.

10. The manufacturing method according to claim 9, wherein: Forming a first drift region, a body region, and the doped region in the epitaxial layer includes: Implanting first-type impurity ions and second-type impurity ions into the epitaxial layer, wherein an implantation region of the first-type impurity ions is located inside an implantation region of the second-type impurity ions; Using a push-in process, the first type impurity ions and the second type impurity ions are diffused in the epitaxial layer to form the body region and the doped region, respectively, and a portion of the epitaxial layer located between the substrate and the body region forms the first drift region; The diffusion depth and diffusion width of the first type impurity ions in the body region are greater than the diffusion depth and diffusion width of the second type impurity ions in the doping region.

11. The manufacturing method according to claim 10, wherein: Forming the trench gate structure includes: forming a trench penetrating the body region and the doped region, wherein a bottom of the trench is located in the first drift region; A gate dielectric layer and a polysilicon layer are deposited in the trench, wherein the gate dielectric layer is located between the polysilicon layer and the first drift region, the body region and the doped region.

12. The manufacturing method according to claim 11, wherein: The step of forming the trench gate structure further includes: forming a groove in the doped region in an area adjacent to the body region; A dielectric layer is deposited in the groove to form an isolation structure.

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