Super-junction IGBT (Insulated Gate Bipolar Translator) structure and preparation method thereof

Abstract

The invention provides a super-junction IGBT (Insulated Gate Bipolar Translator) structure and a preparation method thereof. The super-junction IGBT structure comprises a second conductive type epitaxial layer and a first conductive type cylindrical diffusion region in the second conductive type epitaxial layer, the device comprises a first conductive type well region, a first conductive type heavily doped region, a second conductive type heavily doped region, a grid electrode, a buffer layer and a collector electrode. According to the invention, the concentration of the super junction structure is gradually reduced from top to bottom, holes injected by a collector are prevented from being collected by a cylindrical diffusion region, the conductivity modulation effect of the structure during conduction is enhanced, the conduction voltage drop is reduced, and the compromise relationship between the conduction voltage drop and the turn-off loss is optimized; meanwhile, the doping concentration of the super-junction structure is linearly changed, so that the conductivity modulation effect is uniformly changed, and the performance reliability is improved; in addition, a cylindrical diffusion region doping concentration change mode is set to adapt to the process level and improve the change uniformity; and finally, the doping concentration of the epitaxial layer is gradually changed, so that the doping process adjusting step in the preparation process is reduced, and the preparation efficiency is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of semiconductor integrated circuit manufacturing, and in particular relates to a super junction IGBT structure and a preparation method thereof. Background Art

[0002] In the prior art, such as Figure 1 The superjunction insulated gate bipolar transistor (SJ-IGBT) shown benefits from the charge modulation mechanism of the superjunction. Compared with the traditional field-stop insulated gate bipolar transistor (FS-IGBT), it has a higher drift region doping concentration, which can significantly reduce the on-state voltage drop of the device. Moreover, due to the mutual depletion between the P-type column (the first conductive type columnar diffusion region) and the N-type column (the second conductive type epitaxial layer), the device can speed up the extraction of excess carriers and reduce the turn-off loss during the turn-off process, thereby greatly optimizing the compromise relationship between the on-state voltage drop and the turn-off loss of the device.

[0003] However, the SJ-IGBT in which the P-type column is connected to the P-type well (first conductive type well region) has a unipolar conduction mode when the device on-current density is small. Most of the holes injected from the collector are collected by the P-type column and flow out from the emitter through the P-type well, while the electrons diffuse in the drift region. The existence of the unipolar conduction mode will lead to a weaker conductivity modulation effect of the device and an increase in the on-voltage drop.

[0004] Therefore, there is an urgent need for a structure or method that can reduce the impact of the unipolar conduction mode on super junction IGBT devices.

[0005] It should be noted that the above introduction to the technical background is only for the convenience of providing a clear and complete description of the technical solutions of the present application and for the convenience of understanding by those skilled in the art. It cannot be considered that the above technical solutions are well known to those skilled in the art simply because these solutions are described in the background technology part of the present application. Summary of the invention

[0006] In view of the above shortcomings of the prior art, an object of the present invention is to provide a super junction IGBT structure and a preparation method thereof, so as to solve the problem in the prior art that the on-state voltage drop of the super junction IGBT increases when the on-state current density is small.

[0007] To achieve the above object, the present invention provides a super junction IGBT structure, the super junction IGBT structure comprising:

[0008] a first conductive type substrate;

[0009] A second conductive type epitaxial layer disposed on the first conductive type substrate;

[0010] A first conductivity type columnar diffusion region is arranged in the second conductivity type epitaxial layer, the second conductivity type epitaxial layer and the first conductivity type columnar diffusion region form a super junction structure; the direction from the second conductivity type epitaxial layer to the first conductivity type substrate is a first direction, and the doping concentration of the second conductivity type in the second conductivity type epitaxial layer and the doping concentration of the first conductivity type in the first conductivity type columnar diffusion region both decrease in a preset order from top to bottom along the first direction;

[0011] A first conductivity type well region disposed in the second conductivity type epitaxial layer, on the first conductivity type columnar diffusion region and connected to the first conductivity type columnar diffusion region;

[0012] A heavily doped region of the first conductivity type disposed in the well region of the first conductivity type;

[0013] A second conductivity type heavily doped region;

[0014] Gate;

[0015] A collector, the collector being located on a side of the first conductive type substrate away from the second conductive type epitaxial layer;

[0016] A metal interconnection layer is electrically connected to the gate and the first conductive type heavily doped region respectively to draw out electrical connection between the gate and the emitter.

[0017] Optionally, the doping concentration of the second conductivity type in the second conductivity type epitaxial layer and the doping concentration of the first conductivity type in the first conductivity type columnar diffusion region decrease in a non-step-like manner from top to bottom along the first direction.

[0018] Optionally, the doping concentration of the second conductivity type in the second conductivity type epitaxial layer and the doping concentration of the first conductivity type in the first conductivity type columnar diffusion region decrease linearly from top to bottom along the first direction.

[0019] Optionally, the doping concentration of the second conductivity type in the second conductivity type epitaxial layer and the doping concentration of the first conductivity type in the first conductivity type columnar diffusion region decrease in a step-like manner from top to bottom along the first direction.

[0020] Optionally, at the same height along the first direction, the doping concentration of the second conductivity type in the second conductivity type epitaxial layer is equal to the doping concentration of the first conductivity type in the first conductivity type columnar diffusion region.

[0021] Optionally, the first conductivity type is P type and the second conductivity type is N type.

[0022] Optionally, the first conductivity type is N-type and the second conductivity type is P-type.

[0023] The present invention also provides a method for preparing a super junction IGBT structure, the method being used to prepare any one of the above-mentioned super junction IGBT structures, the method comprising:

[0024] providing a first conductive type substrate;

[0025] A super junction structure including a second conductive type epitaxial layer and a first conductive type columnar diffusion region is provided on the first conductive type substrate; a direction from the super junction structure to the first conductive type substrate is a first direction, and a doping concentration of the second conductive type in the second conductive type epitaxial layer and a doping concentration of the first conductive type in the first conductive type columnar diffusion region in the super junction structure both decrease in a preset order from top to bottom along the first direction;

[0026] Disposing a second conductive type epitaxial surface layer on the super junction structure, and disposing a gate on a side of the second conductive type epitaxial surface layer away from the super junction structure;

[0027] A first conductivity type well region, a first conductivity type heavily doped region, and a second conductivity type heavily doped region are provided in a corresponding region of the second conductivity type epitaxial surface layer, wherein the first conductivity type well region is connected to the first conductivity type columnar diffusion region;

[0028] A high temperature drive-in process is performed to integrate the second conductive type epitaxial surface layer and the second conductive type epitaxial layer into the second conductive type epitaxial layer.

[0029] Optionally, the method for setting the super junction structure includes:

[0030] Step A1: providing a second conductivity type epitaxial single layer with a preset second conductivity type doping concentration on the first conductivity type substrate;

[0031] Step A2: performing first conductivity type doping on the second conductivity type epitaxial single layer at a position corresponding to the first conductivity type columnar diffusion region to form a first conductivity type columnar diffusion unit region with a preset first conductivity type doping concentration;

[0032] Step A3: determining whether the total thickness of the super junction structure reaches a predetermined thickness value; if the total thickness of the super junction structure is less than the predetermined thickness value, returning to step A1, and increasing the preset second conductivity type doping concentration and the preset first conductivity type doping concentration in a preset increasing manner; if the total thickness of the super junction structure reaches the predetermined thickness value, proceeding to step A4;

[0033] Step A4: Perform a high-temperature drive-in process to connect each of the second conductive type epitaxial single layers in the first direction to form the second conductive type epitaxial layer, and connect each of the first conductive type columnar diffusion unit regions in the first direction to form the first conductive type columnar diffusion region, thereby completing the setting of the super junction structure.

[0034] Optionally, the method for setting the super junction structure includes:

[0035] B1: forming an epitaxial layer of the second conductivity type on the substrate of the first conductivity type, wherein the second conductivity type doping concentration of the epitaxial layer of the second conductivity type decreases from top to bottom along the first direction in a preset decreasing manner;

[0036] B2: a mask layer is provided on a side of the second conductive type epitaxial layer away from the first conductive type substrate; the mask layer is patterned to expose a region on the second conductive type epitaxial layer corresponding to a position of the first conductive type columnar diffusion region; a deep groove is etched in the second conductive type epitaxial layer by grinding the patterned mask layer;

[0037] B3: a first conductivity type columnar epitaxial layer having a first conductivity type doping concentration that decreases in a preset decreasing manner from top to bottom along the first direction is provided in the deep trench.

[0038] As described above, the super junction IGBT structure and the preparation method thereof of the present invention have the following beneficial effects:

[0039] The present invention gradually reduces the concentration of the super junction structure of the super junction IGBT structure from top to bottom, inhibits the first type of carriers injected from the collector from being collected by the first conductive type columnar diffusion region, enhances the conductivity modulation effect when the structure is turned on, reduces the on-state voltage drop, and optimizes the compromise relationship between the on-state voltage drop and the turn-off loss;

[0040] The present invention realizes uniform change of conductivity modulation effect by setting linear change of doping concentration of super junction structure, avoids structural defects and improves structural performance reliability;

[0041] The present invention reasonably sets the doping concentration variation mode of the columnar diffusion zone to control the doping concentration variation of the columnar diffusion zone to achieve the optimal variation uniformity while adapting to the process level;

[0042] The present invention reduces the steps of adjusting the doping process in the preparation process by using an epitaxial layer with a gradually changing doping concentration, thereby improving the preparation efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 It shows a schematic diagram of a super junction IGBT structure in the prior art and its corresponding doping concentration variation along a first direction.

[0044] Figure 2 It shows a schematic diagram of the super junction IGBT structure in Embodiment 1 of the present invention and its corresponding linear decreasing doping concentration change along the first direction.

[0045] Figure 3 It shows a schematic diagram of the super junction IGBT structure in Embodiment 1 of the present invention and its corresponding step-like decreasing doping concentration change along the first direction.

[0046] Component number description

[0047] 10. First conductive type substrate; 11. Second conductive type heavily doped buffer layer; 20. Second conductive type epitaxial layer; 30. First conductive type columnar diffusion region; 31. First conductive type columnar diffusion unit region; 32. First conductive type well region; 33. First conductive type heavily doped region; 34. Second conductive type heavily doped region; 41. Gate; 42. Emitter; 43. Collector; 44. Metal interconnect layer; 50. First direction. DETAILED DESCRIPTION

[0048] The following describes the embodiments of the present invention through specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention.

[0049] For example, when describing the embodiments of the present invention in detail, for the sake of convenience, the schematic diagrams showing the device structure will not be partially enlarged according to the general scale, and the schematic diagrams are only examples, which should not limit the scope of protection of the present invention. In addition, in actual production, the three-dimensional dimensions of length, width and depth should be included.

[0050] For convenience of description, spatially relative terms such as "under", "below", "below", "below", "above", "on", etc. may be used herein to describe the relationship of one element or feature shown in the drawings to other elements or features. It will be understood that these spatially relative terms are intended to encompass other orientations of the device in use or operation in addition to the orientation depicted in the drawings.

[0051] In the context of the present application, a structure in which a first feature is described as being "above" a second feature may include embodiments in which the first and second features are in direct contact, and may also include embodiments in which additional features are formed between the first and second features, such that the first and second features may not be in direct contact.

[0052] It should be noted that the illustrations provided in this embodiment are only used to illustrate the basic concept of the present invention in a schematic manner, and therefore the illustrations only show components related to the present invention rather than being drawn according to the number, shape and size of components in actual implementation. In actual implementation, the type, quantity and proportion of each component may be changed arbitrarily, and the component layout may also be more complicated.

[0053] Embodiment 1:

[0054] This embodiment provides a super junction IGBT structure, the super junction IGBT structure comprising:

[0055] A first conductive type substrate 10;

[0056] A second conductivity type epitaxial layer 20 disposed on the first conductivity type substrate;

[0057] A first conductive type columnar diffusion region 30 is disposed in the second conductive type epitaxial layer 20, and the second conductive type epitaxial layer 20 and the first conductive type columnar diffusion region 30 form a super junction structure; a direction from the second conductive type epitaxial layer 20 to the first conductive type substrate 10 is a first direction 50, and a doping concentration of the second conductive type in the second conductive type epitaxial layer 20 and a doping concentration of the first conductive type in the first conductive type columnar diffusion region 30 both decrease in a preset order from top to bottom along the first direction 50;

[0058] A first conductivity type well region 32 disposed in the second conductivity type epitaxial layer 20 , on the first conductivity type columnar diffusion region 30 and connected to the first conductivity type columnar diffusion region 30 ;

[0059] A first conductivity type heavily doped region 33 disposed in the first conductivity type well region 32;

[0060] A second conductivity type heavily doped region 34;

[0061] Gate 41;

[0062] a collector electrode 43 , the collector electrode 43 being located on a side of the first conductive type substrate 10 away from the second conductive type epitaxial layer 20 ;

[0063] A metal interconnection layer 44 is electrically connected to the gate 41 and the first conductive type heavily doped region 33 respectively to draw out an electrical connection between the gate 41 and the emitter 42 .

[0064] In the prior art, such as Figure 1The superjunction insulated gate bipolar transistor (SJ-IGBT) structure shown in the left half benefits from the charge modulation mechanism of the superjunction. Compared with the traditional field-stop insulated gate bipolar transistor (FS-IGBT), it has a higher drift region doping concentration, which can significantly reduce the on-state voltage drop of the device; and due to the mutual depletion between the P-type column (the first conductive type columnar diffusion region 30) and the N-type column (the second conductive type epitaxial layer 20), the device can speed up the extraction of excess carriers and reduce the turn-off loss during the shutdown process, thereby greatly optimizing the compromise relationship between the on-state voltage drop and the turn-off loss of the device. However, the SJ-IGBT in which the P-type column (the first conductive type columnar diffusion region 30) is connected to the P-type well (the first conductive type well region 32) has a unipolar conduction mode when the device conduction current density is small, and most of the holes injected from the collector 43 are collected by the P-type column (the first conductive type columnar diffusion region 30) and flow out from the emitter 42 through the P-type well (the first conductive type well region 32), while the electrons diffuse in the drift region; the existence of the unipolar conduction mode will lead to a weaker conductivity modulation effect of the device and an increase in the on-state voltage drop; and, as Figure 1 As shown in the right half of , the horizontal axis is the doping concentration of the corresponding second conductive type epitaxial layer 20, and the vertical axis is the position along the first direction 50 corresponding to its left side. Since the doping concentration of a general super junction IGBT structure along the first direction 50 is almost the same, and since a higher drift region doping concentration is required to reduce the on-state voltage drop, it is inevitable that a more obvious unipolar conduction mode will exist when the on-state voltage drop is further reduced.

[0065] The present invention gradually reduces the doping concentration in the super junction structure (first conductive type columnar diffusion region 30 and second conductive type epitaxial layer 20) of the super junction IGBT structure along the first direction 50 from top to bottom; since it is found that the greater the doping concentration of the super junction structure, the more obvious the effect of unipolar conduction, so when the doping concentration of the super junction structure close to the collector 43 is set to be lower, the unipolar conduction mode in which the first conductive type carriers injected from the collector 43 are collected by the first conductive type columnar diffusion region 30 can be suppressed, thereby enhancing the conductivity modulation effect of the super junction IGBT structure when it is turned on, reducing the on-state voltage drop, and optimizing the compromise relationship between the on-state voltage drop and the turn-off loss.

[0066] Specifically, the doping concentration of the first conductive type heavily doped region 33 is greater than the doping concentration of the first conductive type well region 32; the second conductive type heavily doped region 34 is located at the surface boundary of the first conductive type heavily doped region 33, and the doping concentration of the second conductive type heavily doped region 34 is greater than the doping concentration of the second conductive type epitaxial layer 20.

[0067] Specifically, the metal interconnection layer 44 connected to the first conductive type heavily doped region 33 leads to an electrical connection of the emitter 42 .

[0068] In one embodiment, the collector 43 is a heavily doped collector 43 of the first conductivity type.

[0069] In one embodiment, a second conductive type heavily doped buffer layer 11 is further disposed between the collector electrode 43 and the first conductive type substrate 10 .

[0070] In this embodiment, the doping concentration of the second conductivity type in the second conductivity type epitaxial layer 20 and the doping concentration of the first conductivity type in the first conductivity type columnar diffusion region 30 decrease in a non-step-type manner from top to bottom along the first direction 50. Specifically, the non-step-type decrease may be any other decreasing method other than the step-type decrease described in Embodiment 2, all of which are within the protection scope of the present invention.

[0071] In one embodiment, Figure 2 As shown, the left half is a schematic diagram of the super junction IGBT structure, the horizontal axis of the right half is the doping concentration of the second conductive type epitaxial layer 20 corresponding to the present embodiment, and the vertical axis is the position along the first direction 50 corresponding to its left side. The doping concentration of the second conductive type in the second conductive type epitaxial layer 20 and the doping concentration of the first conductive type in the first conductive type columnar diffusion region 30 decrease linearly from top to bottom along the first direction 50.

[0072] The present invention realizes uniform change of conductivity modulation effect by setting linear change of doping concentration of super junction structure, avoids malfunction of super junction IGBT structure during operation due to uneven change of doping concentration, and improves performance reliability of super junction IGBT structure.

[0073] In one embodiment, at the same height along the first direction 50 , the doping concentration of the second conductivity type in the second conductivity type epitaxial layer 20 is equal to the doping concentration of the first conductivity type in the first conductivity type columnar diffusion region 30 .

[0074] The present invention sets the doping concentration of the second conductivity type in the second conductivity type epitaxial layer 20 and the doping concentration of the first conductivity type in the first conductivity type columnar diffusion region 30 at the same height to be equal, which is beneficial to further improve the mutual depletion between the first conductivity type columnar diffusion region 30 and the second conductivity type epitaxial layer 20, further accelerate the extraction speed of excess carriers and reduce the turn-off loss during the device shutdown process, and further optimize the compromise relationship between the device on-state voltage drop and the turn-off loss.

[0075] In this embodiment, the first conductivity type is P type and the second conductivity type is N type.

[0076] In one embodiment, a surface passivation layer is further provided on the surface of the metal interconnection layer 44 , and the surface passivation layer is used to protect the metal interconnection layer 44 from being affected by external oxidation and the like.

[0077] In one embodiment, the gate 41 is a polysilicon gate.

[0078] Embodiment 2:

[0079] This embodiment provides a super junction IGBT structure, and the other features of the super junction IGBT structure are basically the same as those of any one of the super junction IGBT structures described in Embodiment 1, except that:

[0080] In this embodiment, Figure 3 As shown, the left half is a schematic diagram of the super junction IGBT structure, the horizontal axis of the right half is the doping concentration of the second conductivity type epitaxial layer 20 corresponding to this embodiment, and the vertical axis is the position along the first direction 50 corresponding to the left side thereof, and the doping concentration of the second conductivity type in the second conductivity type epitaxial layer 20 and the doping concentration of the first conductivity type in the first conductivity type columnar diffusion region 30 decrease from top to bottom along the first direction 50 in a step-like manner. Specifically, as Figure 3 The step-type decrease shown in the figure only includes one step, but it can also be a step-type decrease of multiple steps, all of which are within the protection scope of the present invention.

[0081] The present invention arranges the doping concentration of the super junction structure to decrease in a step-like manner, which is conducive to the implementation of doping concentration control in actual processes, thereby facilitating implementation in actual applications and widespread industrial use.

[0082] Embodiment 3:

[0083] This embodiment provides a super junction IGBT structure, and the other features of the super junction IGBT structure are basically the same as those of any one of the super junction IGBT structures described in Embodiments 1-2, except that:

[0084] In this embodiment, the first conductivity type is N type and the second conductivity type is P type.

[0085] Embodiment 4:

[0086] This embodiment provides a method for preparing a super junction IGBT structure, the method for preparing the super junction IGBT structure described in any one of the above embodiments 1-3, the method comprising:

[0087] Step 1: providing a first conductive type substrate 10;

[0088] Step 2: a super junction structure including a second conductive type epitaxial layer 20 and a first conductive type columnar diffusion region 30 is provided on the first conductive type substrate 10; the direction from the super junction structure to the first conductive type substrate 10 is a first direction 50, and the doping concentration of the second conductive type in the second conductive type epitaxial layer 20 and the doping concentration of the first conductive type in the first conductive type columnar diffusion region 30 in the super junction structure both decrease from top to bottom in a preset order along the first direction 50;

[0089] Step 3: disposing a second conductive type epitaxial surface layer on the super junction structure, and disposing a gate 41 on a side of the second conductive type epitaxial surface layer away from the super junction structure;

[0090] Step 4: a first conductivity type well region 32, a first conductivity type heavily doped region 33 and a second conductivity type heavily doped region 34 are provided in a corresponding region of the second conductivity type epitaxial layer, wherein the first conductivity type well region 32 is connected to the first conductivity type columnar diffusion region 30;

[0091] Step 5: Perform a high temperature drive-in process to integrate the second conductivity type epitaxial surface layer and the second conductivity type epitaxial layer 20 into the second conductivity type epitaxial layer 20 .

[0092] The preparation method of the super junction IGBT structure of the present invention will be described in detail below with reference to the accompanying drawings. It should be noted that the above sequence does not strictly represent the sequence of the preparation method of the super junction IGBT structure protected by the present invention, and those skilled in the art may change it according to the actual preparation steps.

[0093] First, step 1 is performed to provide a first conductive type substrate 10 .

[0094] Then, step 2 is performed to set a super junction structure including a second conductive type epitaxial layer 20 and a first conductive type columnar diffusion region 30 on the first conductive type substrate 10; the direction from the super junction structure to the first conductive type substrate 10 is a first direction 50, and the doping concentration of the second conductive type in the second conductive type epitaxial layer 20 in the super junction structure and the doping concentration of the first conductive type in the first conductive type columnar diffusion region 30 both decrease from top to bottom along the first direction 50 in a preset order.

[0095] In this embodiment, the method for setting the super junction structure includes:

[0096] Step A1: providing a second conductivity type epitaxial single layer with a preset second conductivity type doping concentration on the first conductivity type substrate 10;

[0097] Step A2: performing first conductivity type doping on the second conductivity type epitaxial single layer at a position corresponding to the first conductivity type columnar diffusion region 30 to form a first conductivity type columnar diffusion unit region 31 with a preset first conductivity type doping concentration;

[0098] Step A3: determining whether the total thickness of the super junction structure reaches a predetermined thickness value; if the total thickness of the super junction structure is less than the predetermined thickness value, returning to step A1, and increasing the preset second conductivity type doping concentration and the preset first conductivity type doping concentration in a preset increasing manner; if the total thickness of the super junction structure reaches the predetermined thickness value, proceeding to step A4;

[0099] Step A4: Perform a high-temperature drive-in process to connect each of the second conductive type epitaxial single layers in the first direction 50 to form the second conductive type epitaxial layer 20, and connect each of the first conductive type columnar diffusion unit regions 31 in the first direction 50 to form the first conductive type columnar diffusion region 30, thereby completing the setting of the super junction structure.

[0100] The present invention can better control the variation of doping concentration at each height by setting the second conductive type epitaxial single layer and the first conductive type columnar diffusion unit area 31 with different doping concentrations layer by layer, which is beneficial to ensure that the actual decreasing variation of doping concentration meets expectations. However, the process of setting the second conductive type epitaxial single layer and the first conductive type columnar diffusion unit area 31 multiple times and performing multiple doping is not conducive to improving process efficiency.

[0101] In one embodiment, the method for forming the first conductive type columnar diffusion unit area 31 with a preset first conductive type doping concentration in step A2 is: photoresist is applied to the second conductive type epitaxial single layer, and patterned photoresist is obtained by exposing and developing the photoresist to reveal the position where the first conductive type columnar diffusion unit area 31 is set on the second conductive type epitaxial single layer; ion implantation is performed on the exposed second conductive type epitaxial single layer using the patterned photoresist as a mask to obtain the first conductive type columnar diffusion unit area 31; and the remaining photoresist and the surface oxide layer are removed to ensure the normal growth of the second conductive type epitaxial single layer and the first conductive type columnar diffusion unit area 31 of the next layer.

[0102] In one embodiment, in step A1, the preset second conductivity type doping concentration of each second conductivity type epitaxial single layer is controlled by an ion implantation dose.

[0103] Next, step 3 is performed to dispose a second conductivity type epitaxial surface layer on the super junction structure, and dispose a gate 41 on a side of the second conductivity type epitaxial surface layer away from the super junction structure.

[0104] Specifically, the doping concentration of the second conductivity type epitaxial surface layer may be greater than or equal to the doping concentration of the second conductivity type epitaxial surface layer close to the second conductivity type epitaxial surface layer of the unintegrated second conductivity type epitaxial layer 20 .

[0105] In one embodiment, the gate 41 is located directly above the second conductivity type epitaxial layer 20 between the first conductivity type columnar diffusion regions 30 .

[0106] In one embodiment, the gate 41 is a planar gate located above the surface of the epitaxial layer of the second conductivity type.

[0107] In one embodiment, the gate 41 is a buried gate located inside the epitaxial layer of the second conductivity type.

[0108] Specifically, the gate 41 may be formed by photolithography, deposition, doping, etc.

[0109] Then, step 4 is performed to set a first conductivity type well region 32 , a first conductivity type heavily doped region 33 and a second conductivity type heavily doped region 34 in the corresponding area of ​​the second conductivity type epitaxial layer, wherein the first conductivity type well region 32 is connected to the first conductivity type columnar diffusion region 30 .

[0110] In one embodiment, the first conductivity type well region 32 , the first conductivity type heavily doped region 33 , and the second conductivity type heavily doped region 34 are respectively formed by ion implantation with corresponding doping concentrations.

[0111] Finally, step 5 is performed to perform a high temperature drive-in process to integrate the second conductivity type epitaxial surface layer and the second conductivity type epitaxial layer 20 into the second conductivity type epitaxial layer 20 .

[0112] In one embodiment, after a high-temperature drive-in process, a metal interconnection layer 44 is disposed on a side of the integrated second conductive type epitaxial layer 20 away from the first conductive type substrate 10 , and the metal interconnection layer 44 is electrically connected to the gate 41 and the first conductive type heavily doped region 33 , respectively, to lead out an electrical connection between the gate 41 and the emitter 42 .

[0113] In one embodiment, after the metal interconnection layer 44 is provided, a surface passivation layer is provided on the outer surface of the metal interconnection layer 44 to protect the metal interconnection layer 44 .

[0114] In one embodiment, after the metal interconnection layer 44 is provided, a collector electrode 43 is provided on a surface of the first conductive type substrate 10 away from the second conductive type epitaxial layer 20 .

[0115] In one embodiment, before setting the collector electrode 43 , a second conductive type heavily doped buffer layer 11 is set on a side of the first conductive type substrate 10 away from the second conductive type epitaxial layer 20 ; and a collector electrode 43 is set on a side of the second conductive type heavily doped buffer layer 11 away from the first conductive type substrate 10 .

[0116] Embodiment 5:

[0117] This embodiment provides a method for preparing a super junction IGBT structure. The other features of the method are basically the same as those of the method for preparing a super junction IGBT structure described in Embodiment 4, except that:

[0118] In this embodiment, the method for setting the super junction structure includes:

[0119] B1: forming the second conductivity type epitaxial layer 20 on the first conductivity type substrate 10, wherein the second conductivity type doping concentration of the second conductivity type epitaxial layer 20 decreases from top to bottom along the first direction 50 in a preset decreasing manner;

[0120] B2: a mask layer is provided on a side of the second conductive type epitaxial layer 20 away from the first conductive type substrate 10; the mask layer is patterned to expose an area on the second conductive type epitaxial layer 20 corresponding to the position of the first conductive type columnar diffusion region 30; a deep groove is etched in the second conductive type epitaxial layer 20 by grinding the patterned mask layer;

[0121] B3: a first conductivity type columnar epitaxial layer is provided in the deep trench, wherein the doping concentration of the first conductivity type decreases from top to bottom along the first direction 50 in a preset decreasing manner.

[0122] The present invention can reduce the steps of doping in the process of preparing the super junction IGBT structure by directly using the second conductive type epitaxial layer 20 that has been manufactured with a decreasing doping concentration, thereby greatly improving the process efficiency; and because the second conductive type epitaxial layer 20 manufactured in batches can be batch-quality inspected before setting the deep trenches, the yield of the final super junction structure can be greatly improved, thereby improving the product yield of the overall super junction IGBT structure.

[0123] In one embodiment, the mask layer is silicon dioxide.

[0124] In one embodiment, the method for etching a deep groove includes: exposing an area on the second conductive type epitaxial layer 20 corresponding to the position of the first conductive type columnar diffusion region 30 through a photolithography mask layer; removing the photoresist used for photolithography; and etching a deep groove on the second conductive type epitaxial layer 20 for setting the first conductive type columnar diffusion region 30 using the mask layer as a mask.

[0125] In one embodiment, after the deep trench is formed, the etching residue and the oxide layer on the surface of the deep trench are removed to improve the bonding strength between the surface of the deep trench and the subsequent epitaxial deposition material.

[0126] In one embodiment, after the first conductivity type pillar-shaped epitaxial layer is provided in step B3, the remaining mask layer is removed.

[0127] In one embodiment, the method for forming the second conductive type epitaxial layer 20 includes: stacking multiple layers of second conductive type epitaxial single layers with preset second conductive type doping concentration on the temporary substrate, and the preset second conductive type doping concentration of each layer of the second conductive type epitaxial single layer increases from bottom to top in a preset increasing manner.

[0128] In one embodiment, the preset second conductivity type doping concentration of each second conductivity type epitaxial single layer is controlled by an ion implantation dose.

[0129] In one embodiment, the method for setting the first conductive type columnar epitaxial layer is: controlling the doping gas flow rate of the epitaxially grown first conductive type columnar epitaxial layer to control the first conductive type doping concentration of the first conductive type columnar epitaxial layers of different heights to decrease in a preset decreasing manner.

[0130] Specifically, the first conductivity type columnar epitaxial layer and the second conductivity type epitaxial layer 20 may also be prepared by other methods to achieve a gradual decrease in doping concentration from top to bottom.

[0131] In summary, the super junction IGBT structure and preparation method of the present invention can gradually reduce the concentration of the super junction structure of the super junction IGBT structure from top to bottom, inhibit the first type of carriers injected from the collector from being collected by the first conductive type columnar diffusion region, enhance the conductivity modulation effect when the structure is turned on, reduce the on-state voltage drop, and optimize the compromise relationship between the on-state voltage drop and the turn-off loss; at the same time, by setting the linear change of the doping concentration of the super junction structure, a uniform change of the conductivity modulation effect is achieved, the structure is avoided from being defective, and the reliability of the structural performance is improved; in addition, by reasonably setting the doping concentration change mode of the columnar diffusion region, the doping concentration change of the columnar diffusion region is controlled to achieve the optimal change uniformity while adapting to the process level; finally, by using an epitaxial layer with a gradually changing doping concentration, the steps of adjusting the doping process in the preparation process are reduced, thereby improving the preparation efficiency.

[0132] Therefore, the present invention effectively overcomes various shortcomings in the prior art and has high industrial utilization value.

[0133] The above embodiments are merely illustrative of the principles and effects of the present invention, and are not intended to limit the present invention. Anyone familiar with the art may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by a person of ordinary skill in the art without departing from the spirit and technical concept disclosed by the present invention shall still be covered by the claims of the present invention.

Claims

1. A super junction IGBT structure, characterized in that: The super junction IGBT structure comprises: a first conductive type substrate; A second conductivity type epitaxial layer disposed on the first conductivity type substrate; A first conductive type columnar diffusion region is disposed in the second conductive type epitaxial layer, the second conductive type epitaxial layer and the first conductive type columnar diffusion region constitute a super junction structure; from the second conductive type epitaxial layer to the The direction of the first conductive type substrate is the first direction, and the doping concentration of the second conductive type in the second conductive type epitaxial layer and the doping concentration of the first conductive type in the first conductive type columnar diffusion region both decrease in a preset order from top to bottom along the first direction; A first conductivity type well region disposed in the second conductivity type epitaxial layer, on the first conductivity type columnar diffusion region and connected to the first conductivity type columnar diffusion region; A heavily doped region of the first conductivity type disposed in the well region of the first conductivity type; A second conductivity type heavily doped region; Gate; A collector electrode, the collector electrode being located on a side of the first conductive type substrate away from the second conductive type epitaxial layer; A metal interconnection layer is electrically connected to the gate and the first conductive type heavily doped region respectively to draw out electrical connection between the gate and the emitter.

2. The super junction IGBT structure according to claim 1, characterized in that: The doping concentration of the second conductivity type in the second conductivity type epitaxial layer and the doping concentration of the first conductivity type in the first conductivity type columnar diffusion region decrease from top to bottom along the first direction in a non-step-like manner.

3. The super junction IGBT structure according to claim 2, characterized in that: The doping concentration of the second conductivity type in the second conductivity type epitaxial layer and the doping concentration of the first conductivity type in the first conductivity type columnar diffusion region decrease linearly from top to bottom along the first direction.

4. The super junction IGBT structure according to claim 1, characterized in that: The doping concentration of the second conductivity type in the second conductivity type epitaxial layer and the doping concentration of the first conductivity type in the first conductivity type columnar diffusion region decrease in a step-like manner from top to bottom along the first direction.

5. The super junction IGBT structure according to any one of claims 1 to 4, characterized in that: At the same height along the first direction, the doping concentration of the second conductivity type in the second conductivity type epitaxial layer is equal to the doping concentration of the first conductivity type in the first conductivity type columnar diffusion region.

6. The super junction IGBT structure according to claim 1, characterized in that: The first conductivity type is P type and the second conductivity type is N type.

7. The super junction IGBT structure according to claim 1, characterized in that: The first conductivity type is N type and the second conductivity type is P type.

8. A method for preparing a super junction IGBT structure, characterized in that: The preparation method is used to prepare the super junction IGBT structure according to any one of claims 1 to 7, and the preparation method comprises: providing a first conductive type substrate; A super junction structure including a second conductive type epitaxial layer and a first conductive type columnar diffusion region is provided on the first conductive type substrate; a direction from the super junction structure to the first conductive type substrate is a first direction, and a doping concentration of the second conductive type in the second conductive type epitaxial layer and a doping concentration of the first conductive type in the first conductive type columnar diffusion region in the super junction structure both decrease in a preset order from top to bottom along the first direction; Disposing a second conductive type epitaxial surface layer on the super junction structure, and disposing a gate on a side of the second conductive type epitaxial surface layer away from the super junction structure; A first conductivity type well region, a first conductivity type heavily doped region, and a second conductivity type heavily doped region are provided in a corresponding region of the second conductivity type epitaxial surface layer, wherein the first conductivity type well region is connected to the first conductivity type columnar diffusion region; A high temperature drive-in process is performed to integrate the second conductive type epitaxial surface layer and the second conductive type epitaxial layer into the second conductive type epitaxial layer.

9. The method for preparing a super junction IGBT structure according to claim 8, characterized in that: The method for setting the super junction structure comprises: Step A1: providing a second conductivity type epitaxial single layer with a preset second conductivity type doping concentration on the first conductivity type substrate; Step A2: performing first conductivity type doping on the second conductivity type epitaxial single layer at a position corresponding to the first conductivity type columnar diffusion region to form a first conductivity type columnar diffusion unit region with a preset first conductivity type doping concentration; Step A3: determining whether the total thickness of the super junction structure reaches a predetermined thickness value; if the total thickness of the super junction structure is less than the predetermined thickness value, returning to step A1, and increasing the preset second conductivity type doping concentration and the preset first conductivity type doping concentration in a preset increasing manner; if the total thickness of the super junction structure reaches the predetermined thickness value, proceeding to step A4; Step A4: Perform a high-temperature drive-in process to connect each of the second conductive type epitaxial single layers in the first direction to form the second conductive type epitaxial layer, and connect each of the first conductive type columnar diffusion unit regions in the first direction to form the first conductive type columnar diffusion region, thereby completing the setting of the super junction structure.

10. The method for preparing a super junction IGBT structure according to claim 8, characterized in that: The method for setting the super junction structure comprises: B1: forming an epitaxial layer of the second conductivity type on the substrate of the first conductivity type, wherein the second conductivity type doping concentration of the epitaxial layer of the second conductivity type decreases from top to bottom along the first direction in a preset decreasing manner; B2: a mask layer is provided on a side of the second conductive type epitaxial layer away from the first conductive type substrate; the mask layer is patterned to expose a region on the second conductive type epitaxial layer corresponding to a position of the first conductive type columnar diffusion region; a deep groove is etched in the second conductive type epitaxial layer by grinding the patterned mask layer; B3: a first conductivity type columnar epitaxial layer having a first conductivity type doping concentration that decreases in a preset decreasing manner from top to bottom along the first direction is provided in the deep trench.

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