RC-IGBT device and preparation method thereof

Abstract

The embodiment of the invention provides an RC-IGBT device and a preparation method, the device comprises an N-drive region (1), a P + collector region (2) and an FS structure (3), and the FS structure (3) is connected below the N-drive region (1) and above the P + collector region (2); the lower structure and the upper structure are connected with the FS structure (3), the upper structure is connected to the N-drive region (1), the lower structure is connected to the P + Colletor region (2), and the phosphorus doping concentration of the lower structure is lower than that of the upper structure so as to increase the parasitic resistance above the P + Colletor region (2), that is, the short-circuit resistance of the P + Colletor region (2) at the collector side is increased, and the snapback phenomenon can be inhibited. And the width of the P + Collector region (2) is also reduced, so that the overall size of the primitive cell is reduced.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of RC-IGBT device preparation, and particularly relates to a RC-IGBT device and a preparation method. BACKGROUND

[0002] In the field of high voltage and high current, IGBT (Insulated Gate Bipolar Transistor) has become the mainstream device in the field of power electronics application due to its low saturation voltage drop. IGBT is different from MOS, without parasitic diode, and does not have reverse conduction capability. When the IGBT device is used as a switch under inductive load, a free-wheeling diode (FWD) is needed in anti-parallel. IGBT and FRD are interconnected together when packaged by two independent chips, which increases the size of the module and the complexity of production, and increases the parasitic inductance and capacitance of the module, affecting the stability of the IGBT module and the system. RC-IGBT (Reverse-Conducting IGBT) solves the above problems by integrating IGBT and FWD together.

[0003] Figure 8 For a traditional RC-IGBT device, it includes an N-drift layer 23, a P+ collector layer 24, an FS layer 13, an N+ collector layer 14, a collector collector 15, a Gate gate electrode 16, a P-body layer 17, an N+ layer 18, a P+ layer 19, an ILD layer 20, an Emitter emitter 21, a gate oxide layer 22, wherein the IGBT is a trench gate FS (Field Stop) IGBT, which is by introducing part of the N+ collector in the P+ collector on the back side of the collector, the P-body layer 17 and the N+ collector layer 14 form a diode, so that the IGBT works in reverse diode mode. Figure 8 Also known as trench gate FS RC-IGBT. The traditional IGBT will produce snapback phenomenon when the device is turned on in the forward direction due to the introduction of the back N+ collector. The snapback phenomenon is also known as voltage foldback phenomenon or negative resistance effect.

[0004] In the process of implementing the present application, the applicant found that there are at least the following problems in the prior art:

[0005] The traditional RC-IGBT mainly increases the collector side short-circuit resistance by increasing the width of the P+ collector, so as to suppress the snapback phenomenon, resulting in a large device cell size and a small N+ collector area, so that the collector-emitter saturation voltage V CEsatand diode forward voltage drop V F Relatively high. Summary of the Invention

[0006] This invention provides an RC-IGBT device and its fabrication method, which can solve the technical problems in the prior art.

[0007] To achieve the above objectives, in one aspect, embodiments of the present invention provide an RC-IGBT device, including an N-drift region, a P+collector region, and an FS structure, wherein the FS structure is connected below the N-drift region and above the P+collector region;

[0008] The FS structure connects the lower structure and the upper structure. The upper structure is connected to the N-drift region, and the lower structure is connected to the P+collector region. The phosphorus doping concentration of the lower structure is lower than that of the upper structure to increase the parasitic resistance above the P+collector region.

[0009] On the other hand, embodiments of the present invention provide a method for fabricating an RC-IGBT device, comprising:

[0010] After the front-side process of RC-IGBT is completed, the grooved FS IGBT is formed, exposing the N-drift area on the back side.

[0011] The RC-IGBT is flipped, and the N-drift region on the back side is thinned. Then, phosphorus ion implantation and annealing are performed to form an FS structure on the N-drift region. The FS structure has a connected lower structure and an upper structure, with the upper structure connected to the N-drift region. The phosphorus doping concentration of the lower structure is lower than that of the upper structure.

[0012] Adjacent P+collector regions and N+collector regions are formed on the FS structure to obtain an RC-IGBT device;

[0013] The lower phosphorus doping concentration of the lower structure compared to the upper structure increases the parasitic resistance above the P+collector region.

[0014] The above technical solution has the following beneficial effects: Because the phosphorus doping concentration of the lower structure is lower than that of the upper structure, the resistivity of the lower structure is higher than that of the upper structure, thereby increasing the parasitic resistance above the P+ collector region, i.e., increasing the short-circuit resistance of the P+ collector region on the collector side, which can suppress the snapback phenomenon. Furthermore, it can reduce the width of the P+ collector region, reduce the overall size of the unit cell, and better balance the collector-emitter saturation voltage and the diode forward voltage drop. Attached Figure Description

[0015] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0016] Figure 1 This is a structural diagram of an RC-IGBT device according to the present invention;

[0017] Figure 2 This is a flowchart of a method for fabricating an RC-IGBT device according to the present invention;

[0018] Figures 3-7 This is a schematic diagram of the process flow for fabricating the RC-IGBT device of the present invention;

[0019] Figure 8 It is an existing RC-IGBT device.

[0020] The reference numerals in the attached figures are as follows:

[0021] 1. N-drift region; 2. P+ collector region; 3. FS structure; 4. N+ collector region; 5. Collector electrode; 6. Gate region; 7. P-body region; 8. N+ region; 9. P+ region; 10. ILD region; 11. Emitter electrode; 12. Gate oxide layer;

[0022] 31. Combination area; 32. FS+ area; 311. FS- area; 312. N- area.

[0023] 23. N-drift layer; 24. P+ collector layer; 13. FS layer; 14. N+ collector layer; 15. collector electrode; 16. Gate electrode; 17. P-body layer; 18. N+ layer; 19. P+ layer; 20. ILD layer; 21. Emitter electrode; 22. Gate oxide layer. Detailed Implementation

[0024] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0025] like Figure 1 As shown, in conjunction with an embodiment of the present invention, an RC-IGBT device is provided, including an N-drift region 1, a P+collector region 2 and an FS structure 3, wherein the FS structure 3 is connected below the N-drift region 1 and above the P+collector region 2;

[0026] The FS structure 3 connects the lower structure and the upper structure. The upper structure is connected to the N-drift region 1, and the lower structure is connected to the P+collector region 2. The phosphorus doping concentration of the lower structure is lower than that of the upper structure to increase the parasitic resistance above the P+collector region 2.

[0027] Because the phosphorus doping concentration of the lower structure is lower than that of the upper structure, the resistivity of the lower structure is higher than that of the upper structure. This increases the parasitic resistance above the P+ collector region 2, i.e., increases the short-circuit resistance of the collector-side P+ collector region 2, which can suppress the snapback phenomenon. It can also reduce the width of the P+ collector region 2, reduce the overall size of the unit cell, and better balance the collector-emitter saturation voltage and the diode forward voltage drop.

[0028] Preferably, the lower structure is an N-region 312 and the upper structure is an FS region, with the N-regions 312 interspersed within the FS regions. The phosphorus doping concentration of the N-regions 312 is lower than that of the FS regions, resulting in a higher resistivity for the N-regions 312 compared to the FS regions. This increases the parasitic resistance above the P+ collector region 2, thereby increasing the short-circuit resistance on the collector side (P+ Collector region 2 and N+ Collector region 4) and suppressing the snapback phenomenon.

[0029] Preferably, the FS structure 3 includes an alternately connected combination area 31 and an FS+ area 32, wherein the combination area 31 includes an FS- area 311 and an N- area 312 arranged vertically;

[0030] Among them, all the FS-regions 311 and FS+regions 32 connected in sequence constitute the upper structure, and the N-region 312 constitutes the lower structure.

[0031] Preferably, the lower boundary of the N-region 312 is flush with the lower boundary of the FS+region 32.

[0032] Preferably, the upper boundary of the FS-region 311 is flush with the upper boundary of the FS+region 32.

[0033] Preferably, the electric field of the N-region 312 is zero.

[0034] like Figure 2 As shown, in conjunction with embodiments of the present invention, a method for fabricating an RC-IGBT device is provided, comprising:

[0035] S101: After the front-side process of RC-IGBT is completed, the groove FS IGBT is formed, exposing the N-drift region 1 on the back side;

[0036] S102: Flip the RC-IGBT, thin the back N-drift region 1, then perform phosphorus ion implantation and annealing to form an FS structure 3 on the N-drift region 1; the FS structure 3 has a connected lower structure and an upper structure, the upper structure is connected to the N-drift region 1; and the phosphorus doping concentration of the lower structure is lower than the phosphorus doping concentration of the upper structure.

[0037] S103: Form adjacent P+collector region 2 and N+collector region 4 on the FS structure 3 to obtain an RC-IGBT device;

[0038] The lower phosphorus doping concentration of the lower structure compared to the upper structure increases the parasitic resistance above the P+collector region 2.

[0039] Because the phosphorus doping concentration of the lower structure is lower than that of the upper structure, the resistivity of the lower structure is higher than that of the upper structure. This increases the parasitic resistance above the P+ collector region 2, i.e., increases the short-circuit resistance of the collector-side P+ collector region 2, which can suppress the snapback phenomenon. Furthermore, it can reduce the width of the P+ collector region 2, decrease the overall size of the unit cell, and better balance the collector-emitter saturation voltage and the diode forward voltage drop.

[0040] Preferably, phosphorus ion implantation and annealing are performed to form an FS structure 3 on the N-drift region 1, including:

[0041] Phosphorus ion implantation and annealing are performed in the N-drift region 1 at a set distance from the lower boundary of the N-drift region 1, so that the phosphorus doping concentration of the FS-region 311 is higher than that of the N-region 312, and the N-drift region 1 within the lower boundary of the N-drift region 1 forms the FS-region 311.

[0042] Interval photolithography is performed on the FS- region 311, and phosphorus ion implantation and annealing are performed at the photolithographic locations to form the FS+ region 32;

[0043] The N-drift region 1 below the FS-region 311 is the N-region 312;

[0044] Among them, all the FS-regions 311 and FS+regions 32 formed by phosphorus ion implantation are the upper structure FS regions, and the N-region 312 is the lower structure.

[0045] An array-type FS structure 3 is adopted, consisting of a combination region 31 and an array of FS+ regions 32. An N-region 312 is introduced into the combination region 31. The phosphorus doping concentration of the N-region 312 is the same as that of the N-drift region 1. The phosphorus doping concentration of the N-region 312 is lower than that of the FS-region 311. Therefore, the resistivity of the N-region 312 is higher than that of the FS-region 311, thereby increasing the parasitic resistance above the P+collector region 2, which increases the short-circuit resistance on the collector side (P+Collector region 2 and N+Collector region 4) and can suppress the snapback phenomenon.

[0046] Preferably, the method for fabricating the RC-IGBT device further includes:

[0047] The phosphorus doping concentration of the N-region 312 is the same as that of the N-drift region 1, and the phosphorus doping concentration of the N-region 312 is lower than that of the FS-region 311.

[0048] The lower boundary of the N-region 312 is flush with the lower boundary of the FS+region 32, and the upper boundary of the FS-region 311 is flush with the upper boundary of the FS+region 32.

[0049] An array-type FS structure 3 is adopted, consisting of a combination region 31 and an array of FS+ regions 32. An N-region 312 is introduced into the combination region 31. The phosphorus doping concentration of the N-region 312 is the same as that of the N-drift region 1. The phosphorus doping concentration of the N-region 312 is lower than that of the FS-region 311. Therefore, the resistivity of the N-region 312 is higher than that of the FS-region 311, thereby increasing the parasitic resistance above the P+collector region 2, which increases the short-circuit resistance on the collector side (P+Collector region 2 and N+Collector region 4) and can suppress the snapback phenomenon.

[0050] Preferably, adjacent P+collector regions 2 and N+collector regions 4 are formed on the FS structure 3, including:

[0051] Boron ion implantation and annealing are performed on the surfaces of the lower boundary of the N-region 312 and the lower boundary of the FS+region 32 to form the P+collector region 2.

[0052] N+ collector photolithography is performed on the lower structure on the side of the P+ collector region 2, followed by phosphorus ion implantation and annealing to form N+ collector region 4. The lower boundary of N+ collector region 4 is flush with the lower boundary of P+ collector region 2.

[0053] The method for fabricating the RC-IGBT device further includes:

[0054] The metal is evaporated to the lower boundary of the N+ collector region 4 and the lower boundary of the P+ collector region 2 through an evaporation process to form the collector electrode 5.

[0055] The technical solutions of the present invention will be described in detail below with reference to specific application examples. For technical details not described in the implementation process, please refer to the relevant descriptions above.

[0056] Compared to traditional RC-IGBTs that increase the width of the P+ collector region (P+ Collector region 2) to increase the short-circuit resistance of the collector, this invention provides an RC-IGBT device and its fabrication method that increases the short-circuit resistance of the collector side (P+ Collector and N+ Collector) by optimizing the FS region structure, thereby suppressing the snapback phenomenon. Furthermore, it can reduce the width of the P+ collector region, decrease the overall cell size, and better balance the collector-emitter saturation voltage and the diode forward voltage drop.

[0057] Figure 1This invention presents an RC-IGBT device according to an embodiment of the present invention, showing a cross-sectional view of the RC-IGBT device in the longitudinal direction. An array-type FS structure 3 is adopted, consisting of a combination region 31 and an array of FS+ regions 32. An N-region 312 is introduced into the combination region 31. The phosphorus doping concentration of the N-region 312 is the same as that of the N-drift region 1, but lower than that of the FS-region 311. The resistivity of the N-region 312 is higher than that of the FS-region 311, thereby increasing the parasitic resistance above the P+collector region 2, i.e., increasing the short-circuit resistance on the collector side (P+Collector region 2 and N+Collector region 4), which can suppress the snapback phenomenon. The snapback phenomenon refers to a negative resistance effect of "sudden voltage drop and sudden current increase" that appears in the characteristic curve when the device is subjected to high voltage or large current.

[0058] In the array-type FS structure 3, some FS structures (i.e., FS-region 311) are located above N-region 312, and the remaining FS structures are FS+region 32. The upper and lower structures of FS-region / N-region are arranged alternately and repeatedly with FS+region 32 to form the array-type FS structure 3.

[0059] The longitudinal distance of FS-region 311 plus the longitudinal distance of N-region 312 equals the longitudinal distance of FS+region 32. Similar to the FS region of a traditional FSRC-IGBT, the array-type FS structure 3 is located below N-drift region 1 and above P+collector region / N-collector region. In an FS IGBT, the FS region performs the field cutoff function; similarly, FS-region 311 and FS+region 32 in this embodiment can also perform the field cutoff function, ensuring that the electric field of N-region 312 is zero.

[0060] Compared with the traditional FS structure, the array-type FS structure 3 of this invention not only achieves the field cutoff function, but more importantly, introduces the N-region 312, thereby increasing the short-circuit resistance on the collector side to suppress the snapback phenomenon.

[0061] In this embodiment of the invention, the sequential steps of the fabrication process for the RC-IGBT device are as follows:

[0062] S1 and RC-IGBT are formed after the front-side process is completed. Figure 3 The structure shown has a trench gate region 6, a P-body region 7, an N+ region 8, a P+ region 9, an ILD region 10, an emitter electrode 11, and a gate oxide layer 12. This structure is a trench FS IGBT.

[0063] S2. Flip the RC-IGBT wafer and perform back-side thinning. The thinning thickness is determined by the required breakdown voltage of the IGBT. After back-side thinning, perform phosphorus ion implantation and annealing to form the FS-region 311, with the structure as shown. Figure 4 As shown, FS-region 311 is located in Figure 3 In N-drfit region 1, the lower boundary of FS-region 311 is higher than Figure 3 The lower boundary of N-drift zone 1, the lower boundary of FS-zone 311 and Figure 3 The lower boundary of the N-drift region 1 is the N-region 312. That is, after the formation of the FS-region 311, the remaining part at the bottom of the original N-drift region 1 is the N-region 312. The phosphorus doping concentration of the FS-region 311 is higher than that of the N-drift region 1 (i.e., higher than that of the N-region 312). When the collector is subjected to high voltage, the electric field needs to drop rapidly to zero in the FS-region 311.

[0064] S3, FS+ lithography: Phosphorus ion implantation and annealing are performed on the FS-region 311 between adjacent N-regions 312 to form FS+region 32, with the structure as follows. Figure 5 As shown, FS-region 311 and FS+region 32 are arranged alternately. The vertical distance of FS+region 32 is greater than that of FS-region 311. The vertical distance of FS-region 311 plus the vertical distance of N-region 312 equals the vertical distance of FS+region 32. The phosphorus doping concentration of FS+region 32 is higher than that of N-drift region 1. When the collector is subjected to high voltage, the electric field needs to drop rapidly to zero in FS+region 32.

[0065] S4. Boron ion implantation and annealing are performed on the surfaces of the lower boundary of N-region 312 and the lower boundary of FS+ region 32 to form P+ collector region 2, as shown. Figure 6 structure;

[0066] S5. Perform N+ photolithography on the side of P+ collector region 2, i.e., perform phosphorus ion implantation and annealing to form N+ collector region 4, with the structure as shown. Figure 7 As shown; the P+collector area 2 and N+collector area 4 are arranged in a repeating pattern.

[0067] S6. Evaporate the back metal: An evaporation process is used to evaporate the metal, which then falls onto the lower surfaces of the P+ collector region 2 and the N+ collector region 4, forming the collector electrode 5, as shown in the diagram. Figure 1 As shown.

[0068] It should be understood that the specific order or hierarchy of steps in the disclosed process is an example of an exemplary method. Based on design preferences, it should be understood that the specific order or hierarchy of steps in the process may be rearranged without departing from the scope of this disclosure. The appended method claims provide elements of various steps in an exemplary order and are not intended to limit the scope to the specific order or hierarchy described.

[0069] In the above detailed description, various features are combined together in a single embodiment to simplify this disclosure. This approach to disclosure should not be construed as reflecting an intention that embodiments of the claimed subject matter require more features than are explicitly stated in each claim. Rather, as reflected in the appended claims, the invention is presented with fewer features than all of the features of the single disclosed embodiment. Therefore, the appended claims are hereby explicitly incorporated into the detailed description, wherein each claim stands alone as a preferred embodiment of the invention.

[0070] The disclosed embodiments have been described above to enable any person skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be applied to other embodiments without departing from the spirit and scope of this disclosure. Therefore, this disclosure is not limited to the embodiments given herein, but is consistent with the broadest scope of the principles and novel features disclosed in this application.

[0071] The foregoing description includes examples of one or more embodiments. It is certainly impossible to describe all possible combinations of components or methods in order to describe the above embodiments, but those skilled in the art should recognize that further combinations and arrangements of the various embodiments are possible. Therefore, the embodiments described herein are intended to cover all such changes, modifications, and variations falling within the scope of the appended claims. Furthermore, the term "comprising" as used in the specification or claims is interpreted in a manner similar to the term "including," as interpreted when used as a conjunction in the claims. Additionally, the use of any term "or" in the specification of the claims is intended to mean "non-exclusive or." The specific embodiments described above further illustrate the purpose, technical solutions, and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. An RC-IGBT device, characterized in that, It includes an N-drift area (1), a P+collector area (2) and an FS structure (3), wherein the FS structure (3) is connected below the N-drift area (1) and above the P+collector area (2); The FS structure (3) connects the lower structure and the upper structure. The upper structure is connected to the N-drift region (1), and the lower structure is connected to the P+collector region (2). The phosphorus doping concentration of the lower structure is lower than that of the upper structure to increase the parasitic resistance above the P+collector region (2).

2. The RC-IGBT device according to claim 1, characterized in that, The lower structure is an N-region (312), the upper structure is an FS region, and the N-region (312) is embedded in the FS region at intervals.

3. The RC-IGBT device according to claim 2, characterized in that, The FS structure (3) includes a combination area (31) and an FS+ area (32) that are alternately connected. The combination area (31) includes an FS- area (311) and an N- area (312) that are arranged vertically. Among them, all the FS-regions (311) and FS+regions (32) connected in sequence constitute the upper structure, and the N-region (312) constitutes the lower structure.

4. The RC-IGBT device according to claim 3, characterized in that, The lower boundary of the N-region (312) is flush with the lower boundary of the FS+region (32).

5. The RC-IGBT device according to claim 3, characterized in that, The upper boundary of the FS- region (311) is flush with the upper boundary of the FS+ region (32).

6. The RC-IGBT device according to claim 3, characterized in that, The electric field of the N-region (312) is zero.

7. A method for fabricating an RC-IGBT device, characterized in that, include: After the front-side process of RC-IGBT is completed, a grooved FS IGBT is formed, exposing the N-drift region (1) on the back side. The RC-IGBT is flipped, and the back N-drift region (1) is thinned. Then, phosphorus ion implantation and annealing are performed to form an FS structure (3) on the N-drift region (1). The FS structure (3) has a connected lower structure and an upper structure. The upper structure is connected to the N-drift region (1). The phosphorus doping concentration of the lower structure is lower than that of the upper structure. Adjacent P+collector regions (2) and N+collector regions (4) are formed on the FS structure (3) to obtain an RC-IGBT device; The lower phosphorus doping concentration of the lower structure compared to the upper structure can increase the parasitic resistance above the P+collector region (2).

8. The method for fabricating the RC-IGBT device according to claim 7, characterized in that, The process of phosphorus ion implantation and annealing to form an FS structure (3) on the N-drift region (1) includes: Phosphorus ion implantation and annealing are performed in the N-drift region (1) at a distance set from the lower boundary of the N-drift region (1), so that the phosphorus doping concentration of the FS-region (311) is higher than that of the N-region (312), and the N-drift region (1) within the lower boundary of the N-drift region (1) forms the FS-region (311). Interval photolithography is performed on the FS- region (311), and phosphorus ion implantation and annealing are performed at the photolithographic locations to form the FS+ region (32); The N-drift region (1) below the FS-region (311) is the N-region (312); Among them, all the FS-regions (311) and FS+regions (32) formed by phosphorus ion implantation are the upper structure FS regions, and the N-region (312) is the lower structure.

9. The method for fabricating the RC-IGBT device according to claim 8, characterized in that, Also includes: The phosphorus doping concentration of the N-region (312) is the same as that of the N-drift region (1), and the phosphorus doping concentration of the N-region (312) is lower than that of the FS-region (311). The lower boundary of the N-region (312) is flush with the lower boundary of the FS+region (32), and the upper boundary of the FS-region (311) is flush with the upper boundary of the FS+region (32).

10. The method for fabricating the RC-IGBT device according to claim 8, characterized in that, Adjacent P+collector regions (2) and N+collector regions (4) are formed on the FS structure (3), including: Boron ion implantation and annealing are performed on the surfaces of the lower boundary of the N-region (312) and the lower boundary of the FS+ region (32) to form the P+collector region (2); N+ collector photolithography is performed on the lower structure on the side of the P+ collector region (2), and phosphorus ion implantation and annealing are performed to form the N+ collector region (4), the lower boundary of the N+ collector region (4) is flush with the lower boundary of the P+ collector region (2); The method for fabricating the RC-IGBT device further includes: The metal is evaporated to the lower boundary of the N+ collector region (4) and the lower boundary of the P+ collector region (2) by an evaporation process to form a collector electrode (5).

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