Preparation method of novel fast recovery diode and fast recovery diode

Abstract

The embodiment of the application provides a preparation method of a novel fast recovery diode and the fast recovery diode. The embodiment of the application adopts a kind of Schottky contact, and high-concentration second-doped-type well region and second-doped-type second injection region are made without increasing photolithography steps, and meanwhile, by filling the trench with second-doped-type polysilicon, a second-doped-type well region with a large aspect ratio is achieved through a diffusion process, so that, under the same active area, the proportion of Schottky contact can be increased, the high current density obtained can reduce the recovery time, and the fast recovery diode with a semi-super junction structure and high current density, low forward and super-fast recovery characteristics is realized.

Description

Technical Field

[0001] This application belongs to the field of semiconductor technology, specifically relating to a method for preparing a fast recovery diode and the fast recovery diode itself. Background Technology

[0002] The main performance parameter of fast recovery diodes is the reverse recovery time. Currently, the mainstream approach is to reduce minority carrier lifetime by controlling minority carrier lifetime and by forming recombination centers in the drift region of the device through platinum diffusion, electron irradiation, or hydrogen (helium) injection. Currently, not only is a short reverse recovery time required, but also a fast recovery characteristic. Existing fabrication processes reduce the effectiveness of minority carrier lifetime control in fast recovery diodes. Summary of the Invention

[0003] The purpose of this application is to solve or alleviate the technical problems existing in the prior art. The present invention provides a method for preparing a fast recovery diode and a fast recovery diode to solve the technical problem of reduced minority carrier lifetime control in fast recovery diodes prepared in the prior art.

[0004] This application provides a method for fabricating a fast recovery diode with low forward bias and ultrafast recovery characteristics, comprising:

[0005] A thick oxide layer is formed at intervals between the protective ring region and the active region on the front side of the substrate, wherein the substrate is of the first doping type;

[0006] Trenches are etched in the substrate corresponding to the region between the thick oxide layers of the active region.

[0007] A second type of doped polysilicon is deposited in the trench of the active region and on the substrate front side of the guard ring region, wherein the polysilicon in the guard ring region is spaced apart.

[0008] A second type of doped well region is formed on the sidewall of the trench;

[0009] A first implantation region having a first doping type is formed in the protection ring region;

[0010] A medium layer is deposited at intervals in the protective ring region;

[0011] A second implantation region with a second doping type is formed between the trenches and the guard ring region. The second implantation region is disposed in the substrate on the front side of the guard ring region substrate without polysilicon, the substrate corresponding to the dielectric layer and the thick oxide layer. The doping concentration of the second implantation region is less than the doping concentration of the well region.

[0012] A first metal layer is deposited on the front side of the substrate, and the first metal layer is photolithographically and etched to create a spaced first metal layer in the protective ring region;

[0013] A passivation layer is formed between and above the first metal layer in the protective ring region;

[0014] A second metal layer is deposited on the back side of the substrate.

[0015] In a preferred embodiment of this application, the thickness of the thick oxide layer is 10000 Å to 20000 Å.

[0016] In a preferred embodiment of this application, the trench depth is 3μm to 8μm.

[0017] As a preferred embodiment of this application, the step of forming a second-doped type well region on the trench sidewall includes:

[0018] The second type of doped well region is obtained by processing the second type of doped polycrystalline silicon, wherein the processing temperature of the second type of doped polycrystalline silicon is 1000℃~1200℃ and the time is 30min~180min.

[0019] In a preferred embodiment of this application, the junction depth of the well region is 4–10 μm.

[0020] In a preferred embodiment of this application, the element injected into the second injection region is boron, the injection energy is 120 keV to 500 keV, and the injection dose is 1E11 to 1E12.

[0021] In a preferred embodiment of this application, the junction depth of the first injection region is lower than the junction depth of the well region.

[0022] As a preferred embodiment of this application, after forming a second implantation region in the substrate corresponding to the dielectric layer and the thick oxide layer in the region between the trenches and the protection ring region where there is no polysilicon, the method further includes: performing metal sputtering and diffusion in the substrate.

[0023] In a preferred embodiment of this application, the first doping type is N-type and the second doping type is P-type.

[0024] Compared with the prior art, the embodiments of the present invention provide a method for fabricating a fast recovery diode and a fast recovery diode. The embodiments of this application employ a method with Schottky contacts to fabricate a high-concentration second-doped type well region and a second-doped type second implantation region without adding photolithography steps. At the same time, by filling the trench with second-doped type polysilicon and achieving a second-doped type well region with a large aspect ratio through diffusion process, the proportion of Schottky contacts can be increased under the same active region area, resulting in a high current density to reduce recovery time. This realizes a fast recovery diode with a semi-superjunction structure and high current density, low forward and ultra-fast recovery characteristics, solving the technical problem of reduced minority carrier lifetime control in fast recovery diodes fabricated in the prior art.

[0025] Secondly, embodiments of this application also provide a fast recovery diode with low forward bias and ultrafast recovery characteristics, which is prepared by the preparation method described in any one of the first aspects.

[0026] Compared with the prior art, the embodiments of this application also provide a fast recovery diode with low forward bias and ultra-fast recovery characteristics. The beneficial effects of this fast recovery diode are the same as those of the fast recovery diode preparation method described in the first aspect, and will not be repeated here. Attached Figure Description

[0027] Figure 1 A schematic flowchart illustrating a method for fabricating a fast recovery diode, as provided in an embodiment of this application;

[0028] Figures 2-10 The diagram shows the structural results obtained from each step of a fast recovery diode fabrication method provided in this application embodiment. Detailed Implementation

[0029] To enable those skilled in the art to better understand the technical solutions of this application, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of this application.

[0030] like Figure 1 and Figure 2 As shown in the figure, this application provides a method for fabricating a fast recovery diode with low forward bias and ultrafast recovery characteristics, including:

[0031] Step S01: A thick oxide layer 102 is formed between the protective ring region and the active region on the front side of the substrate 101, wherein the substrate 101 is of the first doping type;

[0032] It should be noted that the substrate 101 is N-type, that is, the substrate 101 is doped with impurities such as phosphorus, arsenic, and antimony. A thick oxide layer 102 of 8000A to 16000A is thermally oxidized on the front side of the substrate 101. Then, a photolithography and etching are performed. Finally, the photoresist is removed to obtain a thick oxide layer 102 that is formed between the protective ring region and the active region on the front side of the substrate 101.

[0033] like Figure 1 and Figure 3 As shown, in step S02, trenches 103 are etched in the substrate 101 corresponding to the region between the thick oxide layers 102 of the active region.

[0034] It should be noted that, due to the obstruction of the thick oxide layer 102 in step S01, when etching the trench 103 in the substrate 101, the trench 103 is etched only in the substrate 101 corresponding to the region between the thick oxide layers 102 in the active region, and the etching depth of the trench 103 is 3. μm ~8 μm Since the etching rate of silicon is much higher than that of silicon dioxide, with a ratio of approximately 15 to 20, the thick oxide layer 102 is retained in the protective ring region and the active region.

[0035] like Figure 1 and Figure 4 As shown, in step S03, a second type of doped polysilicon 104 is deposited in the trench 103 of the active region and on the front side of the substrate 101 of the guard ring region, wherein the polysilicon 104 in the guard ring region is spaced apart.

[0036] It should be noted that the second doping type is P-type, that is, indium, aluminum, boron, gallium and other impurities are doped in polysilicon 104. In the active region, polysilicon 104 is only disposed in trench 103, and in the guard ring region, polysilicon 104 is disposed on the front side of substrate 101. Specifically, polysilicon 104 needs to be deposited on the front side of substrate 101 first, followed by photolithography and etching of polysilicon 104, and finally photoresist removal.

[0037] like Figure 1 and Figure 5 As shown, in step S04, a second-doped type well region 105 is formed on the sidewall of the trench 103;

[0038] It should be noted that the formation process of the well region 105 is as follows: the well region 105 of the second doped type is obtained by processing the polysilicon 104 of the second doped type. The temperature for processing the polysilicon 104 of the second doped type is 1000℃~1200℃, the time is 30min~180min, and the junction depth of the well region 105 is 4~10μm. By setting the well region 105, due to the diffusion process of the polysilicon 104 in the trench 103 forming a well region 105 with a large aspect ratio, under the same active region area, this process can increase the Schottky contact ratio of the active region, and obtain a high current density to reduce the recovery time, thereby realizing a fast recovery diode with a semi-superjunction structure and high current density, low forward and ultra-fast recovery characteristics.

[0039] like Figure 1 and Figure 6 As shown, in step S05, a first implantation region 106 having a first doping type is formed in the protection ring region;

[0040] It should be noted that in order to form the cutoff ring, photolithography and etching are required to form a thick oxide layer 102 on the upper surface of the protection ring region. Then, the substrate 101 corresponding to the thick oxide layer 102 is removed by etching to form a first implantation region 106. Finally, the photoresist is removed to form a first implantation region 106 with a first doping type in the edge region of the protection ring region. In the embodiment of this application, the first implantation region 106 is N-type.

[0041] like Figure 1 and Figure 7 As shown, in step S06, a medium zone 107 is deposited in the protection ring zone;

[0042] It should be noted that the dielectric regions 107 deposited in the guard ring region specifically include: firstly, a dielectric region 107 is deposited on the front side of the substrate 101, then contact hole photolithography and dry etching are performed on the dielectric region 107, and then only the dielectric regions 107 are retained in the guard ring region, and there are no dielectric regions 107 on the front side of the substrate 101 where the active region is located.

[0043] like Figure 1 and Figure 8 As shown, in step S07, a second implantation region 108 with a second doping type is formed in the substrate 101 corresponding to the dielectric region 107 and the thick oxide layer 102 in the region between the trenches 103 and the protection ring region where there is no polysilicon 104. The doping concentration of the second implantation region 108 is less than that of the well region 105.

[0044] like Figure 1 and Figure 8 As shown, after forming a second implantation region 108 with a second doping type between the trenches 103 and the guard ring region, the method further includes sputtering and diffusing metal 109 in the substrate 101.

[0045] It should be noted that the second implantation region 108 is formed by low-concentration second-doped ion implantation. In this embodiment, boron element is implanted, the implantation energy range is 120 keV to 500 keV, and the implantation dose range is 1E11 to 1E12. The junction depth of the low-concentration second implantation region 108 is lower than that of the well region 105, so there is a certain concentration gradient between the second implantation region 108 and the well region 105.

[0046] like Figure 1 and Figure 9 As shown, in step S08, a first metal layer 110 is deposited on the surface of the substrate 101, and the first metal layer 110 is photolithographically and etched so that the first metal layers in the protective ring region are spaced apart.

[0047] It should be noted that the first metal layer 110 is copper. By setting the first metal layer 110 on the surface of the substrate 101, a Schottky contact is formed between the second implantation region 108 and the first metal layer 110, and an ohmic contact is formed between the well region 105 and the first metal layer 110.

[0048] like Figure 1 and Figure 10 As shown, in step S09, a passivation layer 111 is formed between and above the first metal layer 110 in the protection ring region;

[0049] In step S10, a second metal layer 112 is deposited on the back side of the substrate 101.

[0050] It should be noted that the second metal layer 112 is made of copper.

[0051] This invention provides a method for fabricating a fast recovery diode and the fast recovery diode itself. This embodiment employs a method with Schottky contacts to fabricate a high-concentration second-doped well region and a second-doped second-implant region without adding photolithography steps. Simultaneously, by filling trenches with second-doped polysilicon and performing a diffusion process to achieve a second-doped well region with a large aspect ratio, the proportion of Schottky contacts can be increased within the same active region area. This results in a high current density, reducing the recovery time and realizing a fast recovery diode with a semi-superjunction structure and high current density, exhibiting low forward and ultra-fast recovery characteristics. This solves the technical problem of reduced minority carrier lifetime control in fast recovery diodes fabricated in the prior art.

[0052] Secondly, embodiments of this application also provide a fast recovery diode, which is prepared by the preparation method described in any one of the first aspects.

[0053] Compared with the prior art, the embodiments of this application also provide a fast recovery diode with the same beneficial effects as the fast recovery diode preparation method described in the first aspect, which will not be repeated here.

[0054] Although this application has been described in detail herein with general description and specific embodiments, modifications or improvements can be made to it, which will be obvious to those skilled in the art. Therefore, all such modifications or improvements made without departing from the spirit of this application fall within the scope of protection claimed in this application.

Claims

1. A method for fabricating a fast recovery diode with low forward bias and ultrafast recovery characteristics, characterized in that, include: A thick oxide layer is formed between the protective ring region and the active region on the front side of the substrate, wherein the substrate is of the first doping type; Trenches are etched in the substrate corresponding to the region between the thick oxide layers of the active region. A second type of doped polysilicon is deposited in the trench of the active region and on the substrate front side of the guard ring region, wherein the polysilicon in the guard ring region is spaced apart. A second type of doped well region is formed on the sidewall of the trench; A first implantation region having a first doping type is formed in the protection ring region; A medium layer is deposited at intervals in the protective ring region; A second implantation region with a second doping type is formed between the trenches and the guard ring region. The second implantation region is disposed in the substrate on the front side of the guard ring region substrate without polysilicon, the substrate corresponding to the dielectric layer and the thick oxide layer. The doping concentration of the second implantation region is less than the doping concentration of the well region. A first metal layer is deposited on the front side of the substrate, and the first metal layer is photolithographically and etched to create a spaced first metal layer in the protective ring region; A passivation layer is formed between and above the first metal layer in the protective ring region; A second metal layer is deposited on the back side of the substrate.

2. The method for fabricating a fast recovery diode with low forward bias and ultrafast recovery characteristics as described in claim 1, characterized in that, The thickness of the thick oxide layer is 10000Å to 20000Å.

3. The method for fabricating a fast recovery diode with low forward bias and ultrafast recovery characteristics as described in claim 1, characterized in that, The depth of the trench is 3μm to 8μm.

4. The method for fabricating a fast recovery diode with low forward bias and ultrafast recovery characteristics as described in claim 1, characterized in that, The formation of a second-doped well region on the trench sidewall includes: The second type of doped well region is obtained by processing the second type of doped polycrystalline silicon, wherein the processing temperature of the second type of doped polycrystalline silicon is 1000℃~1200℃ and the time is 30min~180min.

5. The method for fabricating a fast recovery diode with low forward bias and ultrafast recovery characteristics as described in claim 1, characterized in that, The junction depth of the well region is 4–10 μm.

6. The method for fabricating a fast recovery diode with low forward bias and ultrafast recovery characteristics as described in claim 1, characterized in that, The element injected into the second injection region is boron, with an injection energy of 120 keV to 500 keV and an injection dose of 1E11 to 1E12.

7. The method for fabricating a fast recovery diode with low forward bias and ultrafast recovery characteristics as described in claim 1, characterized in that, The junction depth of the first injection region is lower than that of the well region.

8. The method for fabricating a fast recovery diode with low forward bias and ultrafast recovery characteristics as described in claim 1, characterized in that, After forming a second implantation region with a second doping type between the trenches and the guard ring region, the method further includes performing metal sputtering and diffusion on the substrate.

9. The method for fabricating a fast recovery diode with low forward bias and ultrafast recovery characteristics as described in claim 1, characterized in that, The first doping type is N-type, and the second doping type is P-type.

10. A fast recovery diode with low forward bias and ultrafast recovery characteristics, characterized in that, Prepared by the preparation method according to any one of claims 1 to 9.

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