Groove type power device

Abstract

The invention discloses a trench type power device, which comprises a trench gate and a second trench structure, at least one layer of interface charge is formed in the second trench structure, and the interface charge is formed by an interface of two material layers formed in the second trench; the interface charge is a first conductivity type charge. The second trench structure is at least located within a partial depth range of the channel region. By means of the attraction effect of interface charges on second conduction type charges in a channel region or the repulsive effect on first conduction type charges, the doping concentration of the second conduction type in the channel region is reduced or the doping concentration of the first conduction type in the channel region is increased under the condition that the threshold voltage of the groove type power device is kept to meet the requirement. Therefore, the number of carriers stored in the channel region during reverse conduction is reduced. According to the invention, the number of carriers stored in the channel region during reverse conduction can be reduced, and the reverse recovery performance of the device can be improved; the drift region resistance can be reduced; and the withstand voltage of the drift region can be increased.

Description

Technical Field

[0001] The present invention relates to a semiconductor device, in particular to a trench power device. Background Art

[0002] Compared with planar devices, trench devices effectively reduce the JFET effect, have lower specific on-resistance and higher current density, and are currently the most widely used power device structure. Figure 1 As shown, it is a schematic diagram of the structure of the existing trench power device. Figure 1 It is a typical trench MOSFET, including:

[0003] The N-type, highly doped semiconductor substrate 101 provides mechanical support. It is generally desirable for the thickness of the semiconductor substrate 101 to be as thin as possible. Currently, the thickness of the semiconductor substrate 101 is typically 100 μm, with some even ranging from 30 μm to 40 μm. The lower the doping concentration of the semiconductor substrate 101, the better. Currently, the semiconductor substrate 101 is typically doped with phosphorus, with a resistivity around 1 mΩ*cm, and some even below 0.7 mΩ*cm. Reducing the thickness of the semiconductor substrate 101 can reduce the device's thermal resistance, while increasing the doping concentration can also reduce the resistance of the semiconductor substrate 101. The thinned semiconductor substrate 101 serves as the drain region and is directly connected to the drain of the MOSFET.

[0004] A drift region 102 is formed on the semiconductor substrate 101 . The doping concentration and thickness of the drift region 102 depend on the breakdown voltage of the device. The higher the breakdown voltage required by the device, the lower the doping concentration of the drift region 102 and the thicker the drift region 102 .

[0005] The trench gate includes a gate dielectric layer 103 and a polysilicon gate 104 . The gate dielectric layer 103 is typically SiO 2 ; the polysilicon gate 104 is typically N-type heavily doped polysilicon.

[0006] A P-type doped channel region 105 is formed on the top of the drift region 102 , and an N-type heavily doped source region 106 is formed on the surface of the channel region 105 .

[0007] The channel region 105 and the source region 106 are connected to the source electrode composed of the front metal layer 108 through the through hole 107 on the top.

[0008] In order to reduce the contact resistance between the through hole 107 and the channel region 105, a P-type through hole injection can be performed after the through hole 107 is etched and before the through hole 107 is filled with metal. The injected impurity is usually BF2, the injection energy is usually between 15 and 25 keV, and the injection dose is usually 1e15 cm -2 ~5e15cm-2 between.

[0009] To reduce the channel resistance, the thickness of the gate dielectric layer 103 needs to be reduced. The device's threshold voltage decreases at high temperatures and, due to process fluctuations, fluctuates within a certain range. To prevent the device from turning on accidentally, it is necessary to ensure that the device has a certain threshold voltage, which is often selected to be around 3V. This requires increasing the doping concentration of the channel region 105. However, the higher the doping concentration of the channel region 105, the more likely the parasitic body diode will conduct during reverse conduction. This, in turn, injects a large number of holes into the drift region 102 from the channel region 105, increasing the number of minority carriers stored in the body and increasing Irrm and Trr during the body diode's reverse recovery process. Summary of the Invention

[0010] The technical problem to be solved by the present invention is to provide a trench power device that can reduce the doping concentration of the second conductive type impurities in the channel region of the first conductive type device or even directly adopt the first conductive type doping in the channel region, thereby reducing the number of carriers stored in the device body during reverse conduction and improving the reverse recovery performance of the device; it can also reduce the resistance of the drift region and increase the withstand voltage of the drift region.

[0011] In order to solve the above technical problems, the present invention provides a trench power device comprising: a trench gate and a second trench structure.

[0012] The trench gate passes through the channel region.

[0013] The channel region is formed on a top surface of the drift region doped with the first conductivity type.

[0014] A source region heavily doped with a first conductivity type is formed in a surface area of ​​the channel region.

[0015] At least one layer of interface charge is formed in the second trench structure, and the interface charge is formed by the interface between two material layers formed in the second trench; the interface charge is a first conductive type charge.

[0016] The second trench structure is located at least within a partial depth range of the channel region.

[0017] The channel region is doped with the second conductivity type or the first conductivity type, and the interface charge attracts the second conductivity type charges in the channel region or repels the first conductivity type charges. Under the condition of maintaining the threshold voltage of the trench power device to meet the requirements, the second conductivity type doping concentration in the channel region is reduced or the first conductivity type doping concentration in the channel region is increased, so as to reduce the number of carriers stored in the device body during reverse conduction.

[0018] A further improvement is that the number of layers of the interface charges in the second trench structure is one layer.

[0019] The interface corresponding to the interface charge is the interface between the first material layer and the second material layer.

[0020] The first material layer is formed on the inner surface of the second trench.

[0021] The second material layer is formed on a surface of the first material layer.

[0022] A further improvement is that the first material layer and the second material layer completely fill the second trench.

[0023] Alternatively, a third material layer is further formed on the surface of the second material layer, and the second trench is completely filled with the first material layer, the second material layer and the third material layer.

[0024] A further improvement is that the second trench and the first trench of the trench gate have the same process structure and are formed simultaneously, the first trench passes through the channel region, and the second trench also passes through the channel region.

[0025] A further improvement is that the process structures of the second trench and the first trench of the trench gate are independent;

[0026] The first trench passes through the channel region, the depth of the second trench is smaller than the depth of the first trench, and the bottom surface of the second trench is located above the bottom surface of the channel region;

[0027] Alternatively, the depth of the second trench is greater than the depth of the first trench, the second trench extends into the drift region, and the interface charges extending into the drift region form a lateral depletion structure for the first conductive type dopant impurities in the drift region.

[0028] A further improvement is that the trench power device is an N-type device, the first conductivity type is N-type, and the second conductivity type is P-type.

[0029] A further improvement is that the material of the first material layer includes silicon dioxide.

[0030] The material of the second material layer includes aluminum oxide.

[0031] A further improvement is that the thickness of the first material layer is 5 nm to 20 nm.

[0032] A further improvement is that the surface density of the interface charge is 2e12cm -2 ~8e12cm -2 .

[0033] A further improvement is that the deposition process of the second material layer is ALD, and the deposition temperature is 150°C to 350°C.

[0034] A further improvement is that the trench power device is a P-type device, the first conductivity type is P-type, and the second conductivity type is N-type.

[0035] A further improvement is that the third material layer is an insulating layer or a conductive material layer.

[0036] When the third material layer is a conductive material layer, the top of the conductive material layer is connected to the source electrode composed of the front metal layer through a through hole, or no through hole is formed on the top of the conductive material layer.

[0037] A further improvement is that the source region is connected to a source electrode composed of a front metal layer through a corresponding through hole on the top;

[0038] When the channel region is doped with the second conductivity type, the bottom of the through hole corresponding to the source region passes through the source region and a contact region heavily doped with the second conductivity type is formed at the bottom of the through hole;

[0039] When the channel region is doped with the first conductivity type, the channel region is connected to the source electrode through the source region and the through hole on the top of the source region.

[0040] A further improvement is that when the process structures of the second trench and the first trench of the trench gate are independent and the depth of the second trench is greater than the depth of the first trench, the depth of the first trench is 1.5 microns to 4 microns;

[0041] The second groove has a depth of 10 micrometers to 50 micrometers.

[0042] A further improvement is that the trench power device is a trench MOSFET, and a drain region heavily doped with the first conductivity type is formed on the back side of the drift region.

[0043] A further improvement is that the drain region is formed by a thinned semiconductor substrate or is formed by back ion implantation of a thinned semiconductor substrate heavily doped with the first conductivity type.

[0044] A further improvement is that the material of the semiconductor substrate includes silicon and silicon carbide.

[0045] A further improvement is that the threshold voltage of the trench power device is greater than or equal to 3V.

[0046] The present invention is provided with a second trench structure including interface charges of the first conductive type, and the second trench structure is located at least within a partial depth range of the channel region, so that the interface charges will act on the charges of the doped impurities in the channel region and change the threshold voltage of the device, or under the condition of keeping the threshold voltage of the device unchanged, the second conductive type doping concentration of the channel region can be reduced or even the first conductive type doping structure can be directly adopted; when the second conductive type doping concentration of the channel region is reduced, the body diode between the channel region and the drift region will be turned on when the device is reversed. Since the second conductive type doping concentration of the channel region is reduced, the number of minority carriers injected into the drift region from the channel region will become less, so the number of carriers stored in the device body when the device is reversed will be reduced, thereby improving the reverse recovery performance of the device; when the first conductive type is doped in the channel region, both the drift region and the channel region are doped with the first conductive type, so there is no body diode, which can further reduce the number of carriers stored in the device body when the device is reversed and improve the reverse recovery performance of the device.

[0047] The second trench structure of the present invention can be further extended into the drift region to form a lateral depletion structure for the drift region. Since the lateral depletion of the drift region is increased, the voltage resistance of the drift region is increased, or the doping concentration of the drift region can be increased while keeping the voltage resistance unchanged, thereby reducing the resistance of the drift region. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments:

[0049] Figure 1 It is a schematic diagram of the structure of an existing trench power device;

[0050] Figure 2 1 is a schematic structural diagram of a trench power device according to a first embodiment of the present invention;

[0051] Figure 3 1 is a schematic structural diagram of a trench power device according to a second embodiment of the present invention;

[0052] Figure 4 is a schematic structural diagram of a trench power device according to a third embodiment of the present invention;

[0053] Figure 5 is a schematic structural diagram of a trench power device according to a fourth embodiment of the present invention;

[0054] Figure 6 FIG. 1 is a schematic structural diagram of a trench power device according to a fifth embodiment of the present invention. DETAILED DESCRIPTION

[0055] A trench power device according to a first embodiment of the present invention:

[0056] like Figure 2 , which is a schematic structural diagram of a trench power device according to a first embodiment of the present invention; the trench power device according to the first embodiment of the present invention comprises: a trench gate and a second trench structure.

[0057] The trench gate passes through the channel region 5 .

[0058] The channel region 5 is formed on the top surface of the drift region 2 doped with the first conductivity type.

[0059] A source region 6 heavily doped with the first conductivity type is formed in the surface region of the channel region 5 .

[0060] At least one layer of interface charge is formed in the second trench structure. The interface charge is formed by the interface between two material layers formed in the second trench. The interface charge is a first conductive type charge.

[0061] The second trench structure is located at least within a partial depth range of the channel region 5 .

[0062] The channel region 5 is doped with the second conductivity type. By utilizing the attraction of the interface charges to the second conductivity type charges in the channel region 5, the second conductivity type doping concentration in the channel region 5 is reduced while maintaining the threshold voltage of the trench power device to meet the requirements, so as to reduce the number of carriers stored in the device body during reverse conduction.

[0063] In the first embodiment of the present invention, the threshold voltage of the trench power device is greater than or equal to 3V.

[0064] In the first embodiment of the present invention, the number of layers of interface charges in the second trench structure is one.

[0065] The interface corresponding to the interface charge is the interface between the first material layer 9 and the second material layer 10 .

[0066] The first material layer 9 is formed on the inner surface of the second trench.

[0067] The second material layer 10 is formed on the surface of the first material layer 9 .

[0068] The first material layer 9 and the second material layer 10 completely fill the second trench.

[0069] In the first embodiment of the present invention, the second trench and the first trench of the trench gate have the same process structure and are formed simultaneously. The first trench passes through the channel region 5, and the second trench also passes through the channel region 5. In other embodiments, the second trench and the first trench of the trench gate may have independent process structures, the depth of the second trench is less than the depth of the first trench, and the bottom surface of the second trench is located above the bottom surface of the channel region 15.

[0070] Figure 2In the embodiment, the trench gate includes a gate dielectric layer 3 and a gate conductive material layer 4 formed in a first trench. In some embodiments, the gate dielectric layer 3 includes a gate oxide layer, and the gate conductive material layer 4 includes a polysilicon gate.

[0071] When the second trench and the first trench have the same process structure and are formed simultaneously, the process cost can be reduced.

[0072] In a first embodiment of the present invention, the trench power device is an N-type device, the first conductivity type is N-type, and the second conductivity type is P-type. The charge of the first conductivity type is negative. In other embodiments, the trench power device may be a P-type device, the first conductivity type is P-type, and the second conductivity type is N-type; in this case, the charge of the first conductivity type is positive.

[0073] The material of the first material layer 9 includes silicon dioxide. The material of the second material layer 10 includes aluminum oxide.

[0074] In some embodiments, the thickness of the first material layer 9 is 5 nm to 20 nm. A further improvement is that the surface density of the interface charge is 2e12 cm -2 ~8e12cm -2 .

[0075] The deposition process of the second material layer 10 is ALD, and the deposition temperature is 150℃~350℃. The deposition temperature between 150℃~350℃ can generate negative charge, and by adjusting the deposition temperature, the surface density of the interface charge can be adjusted to 2e12cm -2 ~8e12cm -2 Changes between.

[0076] In the first embodiment of the present invention, the source region 6 is connected to the source electrode formed by the front metal layer 8 through the corresponding through hole 7 on the top.

[0077] The through hole 7 corresponding to the source region 6 also passes through the source region 6 and contacts the bottom channel region 5. In some preferred embodiments, a contact region heavily doped with the second conductivity type is further formed at the bottom of the through hole 7 corresponding to the source region 6 to achieve good contact between the channel region 5 and the through hole 7.

[0078] In the first embodiment of the present invention, the trench power device is a trench MOSFET, and a drain region 1 heavily doped with a first conductivity type is formed on the back surface of the drift region 2 .

[0079] The drain region 1 is composed of a thinned semiconductor substrate or is formed by back ion implantation of a heavily first conductive type doped semiconductor substrate.

[0080] In the first embodiment of the present invention, the semiconductor substrate is made of silicon. In other embodiments, the semiconductor substrate can also be made of other semiconductor materials such as silicon carbide.

[0081] In the first embodiment of the present invention, a plurality of trench-type power devices can be formed on the same semiconductor substrate, and the trench gates of the trench-type power devices are arranged together. Figure 2 Two trench gates are shown in FIG; a common second trench structure is formed between the two trench gates.

[0082] The first embodiment of the present invention is provided with a second trench structure including interface charges of the first conductivity type. The second trench structure passes through the channel region 5. In this way, the interface charges will affect the charges of the doping impurities in the channel region 5 and change the threshold voltage of the device. Alternatively, the second conductivity type doping concentration of the channel region 5 can be reduced while maintaining the threshold voltage of the device. When the second conductivity type doping concentration of the channel region 5 is reduced, the body diode between the channel region 5 and the drift region 2 will be turned on when the device is reverse-conducting. Due to the reduction in the second conductivity type doping concentration of the channel region 5, the number of minority carriers injected into the drift region 2 by the channel region 5 will decrease, thereby ultimately reducing the number of carriers stored in the device body when the device is reverse-conducting, thereby improving the reverse recovery performance of the device. In addition, the first trench and the second trench of the first embodiment of the present invention are formed simultaneously, and the second trench does not need to be separately defined and etched, thereby having the advantage of low process cost.

[0083] A second embodiment of a trench power device according to the present invention:

[0084] like Figure 3 , which is a schematic structural diagram of a trench power device according to a second embodiment of the present invention; the difference from the trench power device according to the first embodiment of the present invention is that in the trench power device according to the second embodiment of the present invention, the channel region 15 is doped with the first conductivity type, Figure 3 The channel region in the device is separately indicated by reference numeral 15. Here, the repulsive effect of the interface charge on the first conductivity type charge in the channel region 15 is utilized to increase the first conductivity type doping concentration of the channel region 15 while maintaining the threshold voltage of the trench power device to meet the requirements, so as to reduce the number of carriers stored in the device body during reverse conduction. Therefore, in the second embodiment of the present invention, due to the presence of interface charge, the doping type of the channel region 15 can be directly the first conductivity type instead of the second conductivity type. The conductivity type between the first conductivity type doped channel region 15 and the drift region 2 at the bottom is the same, so no parasitic body diode is formed. Therefore, when the device is reversely conducted, the number of carriers, i.e., minority carriers, stored in the body is smaller, and the reverse recovery characteristics are better.

[0085] In the second embodiment of the present invention, the channel region 15 is connected to the source electrode via the source region 6 and the via 7 at the top of the source region 6. Since the channel region 15 and the source region 6 have the same doping type, the source region 6 can be directly used as the contact region for the extraction of the channel region 15. There is no need to perform additional implantation at the bottom of the via 7 corresponding to the source region 6 to form a contact region. Therefore, in the second embodiment of the present invention, the step of extracting the contact region of the channel region 15 can be omitted.

[0086] A third embodiment of a trench power device according to the present invention:

[0087] like Figure 4 Figure 2 is a schematic diagram of the structure of a trench power device according to a third embodiment of the present invention. The difference from the trench power device according to the second embodiment of the present invention is that in the trench power device according to the third embodiment of the present invention, a third material layer 11 is further formed on the surface of the second material layer 10, and the first material layer 9, the second material layer 10, and the third material layer 11 completely fill the second trench. Since the second material layer 10 is usually formed by ALD deposition to adjust the interface charge, but the ALD deposition rate is very slow, when the second trench is relatively wide, the thickness of the second material layer 10 is relatively thin and cannot fill the second trench. Therefore, in the third embodiment of the present invention, by adding the third material layer 11, the second trench can be completely filled.

[0088] In the third embodiment of the present invention, the third material layer 11 is a conductive material layer. Preferably, the conductive material layer of the third material layer 11 is a polysilicon layer. In other embodiments, the third material layer 11 is an insulating layer or a conductive material layer.

[0089] A fourth embodiment of a trench power device according to the present invention:

[0090] like Figure 5 As shown, it is a schematic structural diagram of the trench power device of the fourth embodiment of the present invention; the difference from the trench power device of the third embodiment of the present invention is that in the trench power device of the fourth embodiment of the present invention, the top of the conductive material layer of the third material layer 11 is also connected to the source composed of the front metal layer 8 through the through hole 7.

[0091] A fifth embodiment of a trench power device according to the present invention:

[0092] like Figure 6 As shown in FIG, it is a structural schematic diagram of the trench power device of the fifth embodiment of the present invention; the difference from the trench power device of the second embodiment of the present invention is that in the trench power device of the fifth embodiment of the present invention, the process structures of the second trench and the first trench of the trench gate are independent, the depth of the second trench is greater than the depth of the first trench, the second trench extends into the drift region 2, and the interface charge extending into the drift region 2 forms a lateral depletion structure of the first conductive type doped impurities in the drift region 2.

[0093] In some embodiments, the depth of the first trench is 1.5 micrometers to 4 micrometers; the depth of the second trench is 10 micrometers to 50 micrometers.

[0094] The second trench structure of the fifth embodiment of the present invention can be further extended into the drift region 2 to form a lateral depletion structure of the drift region 2. Since the lateral depletion of the drift region 2 is increased, the voltage resistance of the drift region 2 is increased, or the doping concentration of the drift region 2 can be increased while keeping the voltage resistance unchanged, thereby reducing the resistance of the drift region 2.

[0095] In the present application, a second trench is added between the two first trenches. This second trench can be formed simultaneously with the first trench gate or separately. Preferably, after the trench gate is formed, the second trench is formed by etching using a photoresist. This second trench is filled with at least two layers of material. Both layers are insulating layers. The first layer of material functions to ensure good bonding with the semiconductor material, such as silicon, in the channel and drift regions, reducing the interface state density and the number of defects generated. SiO2 is generally preferred. The second layer of material functions because the atoms in the first and second layers are different, resulting in a large number of dangling bonds at the interface between the two materials. These dangling bonds can generate charge, known as interface charge, at the interface between the two materials. The polarity of the interface charge depends on the material. For NMOS, this interface charge is preferably negative, while for PMOS, it is preferably positive. The amount of interface charge (surface charge) generated depends on the material deposition conditions, particularly the deposition temperature. For NMOS, one embodiment is that the first material layer is SiO2; the thickness of SiO2 can be selected between 5nm and 20nm, and the second material layer is Al2O3, using the ALD deposition direction. By changing the deposition temperature of Al2O3, some typical conditions are that if the deposition temperature changes between 150 and 350℃, negative charge will be generated, and the corresponding surface charge number is 2e12cm -2 ~8e12cm -2 Changes between.

[0096] The negative charge generated at the interface of the two layers of material can significantly reduce the doping concentration of the second conductivity type in the channel region 5 at the same threshold voltage. When the channel doping concentration is reduced, the hole injection capability is weakened when the body diode is turned on, and the number of stored carriers is also reduced, thus optimizing the characteristics of the body diode. It is even possible to achieve the goal of eliminating the need for a channel, that is, the channel region 15 is entirely N-type, such as Figure 3As shown, the channel region 15 is no longer P-type, but N-type. The formation of the channel region 15 can be formed together with the drift region 2 during the long epitaxy (Epi), and no additional P-type injection is required to invert the N-type Epi to P-type, which can reduce the number of process steps. The doping concentration of the channel region 15 can be the same as that of the drift region 2, or it can be different. Preferably, it is different. The threshold voltage can be adjusted by: A. Selecting suitable materials in the second trench structure and changing the conditions for material deposition to change the amount of surface charge at the interface between the two layers of material; B. Changing the concentration of N-type impurities in the channel region 15. When the dose of the N-type impurity concentration is reduced, the threshold voltage will increase. Because the channel region 15 is also N-type, the number of carriers stored in the body will be greatly reduced when reverse conduction occurs.

[0097] In this application, because the ALD filling speed is very slow, when the width of the second trench is relatively wide, the thickness of the second material layer 10 is relatively thin and is not enough to completely fill the trench. Figure 4 The structure shown in FIG2 is further increased by adding a third material layer 11 to fill the second trench. The third material layer 11 can be an insulating layer, such as SiO2; or a conductive layer, such as heavily doped polysilicon. When the third material layer 11 is a conductive material, such as Figure 5 As shown, the third material layer 11 can be connected to the source through the through hole 7.

[0098] In this application, if Figure 6 As shown, when the second trench extends into the drift region 2, the present application can also increase the doping concentration of the drift region 2 and reduce the specific on-resistance of the device. Figure 6 As shown, the biggest feature of this structure is that the second trench between the trench gates is very deep, known as a "deep trench". A typical embodiment is that the depth of the trench gate is 1.5 to 4 μm, while the depth of the deep trench is 10 to 50 μm. The depth of the deep trench is related to the breakdown voltage required by the device. The higher the breakdown voltage of the device, the deeper the depth. For a 600V device, the typical deep trench depth is 40 μm. The negative charge between the two material layers 9 and 10 can not only reduce the doping concentration of the channel under the same threshold voltage, but also laterally deplete the N-type drift region 2, thereby significantly reducing the doping concentration of the drift region without reducing the breakdown voltage, thereby achieving a lower specific on-resistance.

[0099] This application is applicable to both N-type and P-type MOSFETs. It is not only suitable for silicon MOSFETs, but also for silicon carbide (SiC) MOSFETs. The trench MOSFETs of this application can be discrete devices or integrated, such as in combination with a BCD process.

[0100] The present invention has been described in detail above by means of specific embodiments, but these do not constitute limitations of the present invention. Without departing from the principles of the present invention, those skilled in the art may make many variations and improvements, which should also be considered as the scope of protection of the present invention.

Claims

1. A trench power device, characterized in that: include: A trench gate and a second trench structure; The trench gate passes through the channel region; The channel region is formed on the top surface of the drift region doped with the first conductivity type; A source region heavily doped with a first conductivity type is formed in a surface area of ​​the channel region; At least one layer of interface charge is formed in the second trench structure, and the interface charge is formed by the interface of two material layers formed in the second trench; The interface charge is a first conductive type charge; The second trench structure is located at least within a partial depth range of the channel region; The channel region is doped with the second conductivity type or the first conductivity type, and the interface charge attracts the second conductivity type charges in the channel region or repels the first conductivity type charges. Under the condition of maintaining the threshold voltage of the trench power device to meet the requirements, the second conductivity type doping concentration in the channel region is reduced or the first conductivity type doping concentration in the channel region is increased, so as to reduce the number of carriers stored in the device body during reverse conduction.

2. The trench power device according to claim 1, wherein: The number of layers of the interface charge in the second trench structure is one; The interface corresponding to the interface charge is the interface between the first material layer and the second material layer; The first material layer is formed on the inner surface of the second trench; The second material layer is formed on a surface of the first material layer.

3. The trench power device according to claim 2, wherein: The first material layer and the second material layer completely fill the second trench; Alternatively, a third material layer is further formed on the surface of the second material layer, and the second trench is completely filled with the first material layer, the second material layer and the third material layer.

4. The trench power device according to claim 2, wherein: The second trench has the same process structure as the first trench of the trench gate and is formed simultaneously. The first trench passes through the channel region, and the second trench also passes through the channel region.

5. The trench power device according to claim 2, wherein: The process structures of the second trench and the first trench of the trench gate are independent; The first trench passes through the channel region, the depth of the second trench is smaller than the depth of the first trench, and the bottom surface of the second trench is located above the bottom surface of the channel region; Alternatively, the depth of the second trench is greater than the depth of the first trench, the second trench extends into the drift region, and the interface charges extending into the drift region form a lateral depletion structure for the first conductive type dopant impurities in the drift region.

6. The trench power device according to claim 2, wherein: The trench power device is an N-type device, the first conductivity type is N-type, and the second conductivity type is P-type.

7. The trench power device according to claim 6, wherein: The material of the first material layer includes silicon dioxide; The material of the second material layer includes aluminum oxide.

8. The trench power device according to claim 7, wherein: The thickness of the first material layer is 5 nm to 20 nm.

9. The trench power device according to claim 7, wherein: The surface density of the interface charge is 2e12cm -2 ~8e12cm -2 .

10. The trench power device according to claim 9, wherein: The deposition process of the second material layer is ALD, and the deposition temperature is 150° C. to 350° C.

11. The trench power device according to claim 2, wherein: The trench power device is a P-type device, the first conductivity type is P-type, and the second conductivity type is N-type.

12. The trench power device according to claim 3, wherein: The third material layer is an insulating layer or a conductive material layer; When the third material layer is a conductive material layer, the top of the conductive material layer is connected to the source electrode composed of the front metal layer through a through hole, or no through hole is formed on the top of the conductive material layer.

13. The trench power device according to claim 1, wherein: The source region is connected to the source electrode composed of the front metal layer through the corresponding through hole on the top; When the channel region is doped with the second conductivity type, the bottom of the through hole corresponding to the source region passes through the source region and a contact region heavily doped with the second conductivity type is formed at the bottom of the through hole; When the channel region is doped with the first conductivity type, the channel region is connected to the source electrode through the source region and the through hole on the top of the source region.

14. The trench power device according to claim 5, wherein: When the process structures of the second trench and the first trench of the trench gate are independent and the depth of the second trench is greater than the depth of the first trench, the depth of the first trench is 1.5 microns to 4 microns; The second groove has a depth of 10 micrometers to 50 micrometers.

15. The trench power device according to any one of claims 1 to 14, characterized in that: The trench power device is a trench MOSFET, and a drain region heavily doped with the first conductivity type is formed on the back side of the drift region; The drain region is formed by a thinned semiconductor substrate or is formed by back ion implantation of a thinned semiconductor substrate heavily doped with the first conductivity type.

16. The trench power device according to claim 15, wherein: The material of the semiconductor substrate includes silicon and silicon carbide.

17. The trench power device according to claim 15, wherein: The threshold voltage of the trench power device is greater than or equal to 3V.

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