Silicon carbide power device and preparation method thereof
By first reducing the surface layer of the silicon carbide substrate in the silicon carbide power device to form a silicon film layer, and then thermal oxidation is carried out to form a silicon dioxide gate oxide layer, the problems of high interfacial state density and low electron mobility are solved, and higher density and lower on-resistance are achieved.
Patent Information
- Application Number
- CN202311462923.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2023-11-06
- Publication Date
- 2025-05-09
AI Technical Summary
When the SiO2 gate oxide is formed, the existing silicon carbide power devices have problems such as high interfacial density, low electron mobility and low gate oxide density.
Before forming the gate oxide layer, a part of the surface layer of the silicon carbide substrate is reduced to a silicon film layer, and then thermal oxidation is performed to form a dense silicon dioxide gate oxide layer.
By reducing the residue of carbon elements, the density of silicon dioxide is increased, the density of state between the silicon carbide substrate and the oxide interface is reduced, electron mobility is improved, and on-resistance is reduced.
Smart Images
Figure CN119967836A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the field of semiconductor technology, and in particular to a silicon carbide power device and a preparation method thereof. Background Art
[0002] As a representative material among the third-generation semiconductors, silicon carbide (SiC) has the physical properties of wide bandgap, high breakdown electric field, high thermal conductivity and high electron saturation rate, which makes it resistant to high temperature, high voltage, high frequency, high power and radiation. It can reduce the energy consumption of downstream products and reduce the terminal volume. It is mainly used in high-power electronic devices for power conversion and control circuits of power equipment, including power diodes, power triodes, thyristors, MOSFET, IGBT, etc.
[0003] At present, when SiC is used as a substrate to manufacture silicon carbide power devices, thermal oxidation, chemical deposition or physical deposition is often used to deposit insulating oxides as gate oxides of silicon carbide power devices. However, SiO2 and SiC formed by the above methods have problems of high interface state density and low electron mobility.
[0004] Regarding the origin of the SiC / SiO2 interface state, the current mainstream view is that during the chemical reaction between SiC and oxygen O2 at high temperatures, a part of the C atoms do not react with oxygen O2 to form gaseous compounds, but instead remain at the SiC / SiO2 interface in the form of C clusters, thus affecting the SiC / SiO2 interface quality.
[0005] In order to avoid the influence of C clusters formed by thermal oxidation process on the interface quality, insulating oxide can be deposited as gate oxide of silicon carbide power device by chemical deposition or physical deposition. However, the gate oxide obtained by deposition is often not dense enough. Summary of the invention
[0006] The object of the present invention is to provide a silicon carbide power device and a preparation method thereof. Before a gate oxide layer is formed, part of the surface layer of a silicon carbide substrate is first reduced to a silicon film layer, and then the silicon film layer is oxidized to silicon dioxide, thereby improving the density of silicon dioxide as a gate oxide layer, reducing the interface state density between silicon dioxide and the silicon carbide substrate, improving the electron mobility of the silicon carbide power device and reducing the on-resistance.
[0007] In a first aspect, in order to solve the above technical problems, the present invention provides a method for preparing a silicon carbide power device, comprising:
[0008] Providing a silicon carbide substrate;
[0009] Passing a mixed gas to bombard a portion of the surface layer of the silicon carbide substrate at high temperature, so as to break the chemical bonds between silicon atoms and carbon atoms in the portion of the surface layer of the silicon carbide substrate, and make the carbon atoms react with the mixed gas to volatilize, and at the same time make the portion of the surface layer of the silicon carbide substrate converted into a silicon film layer;
[0010] The silicon film layer is subjected to a thermal oxidation process to convert the silicon film layer into silicon dioxide, and the silicon dioxide serves as a gate oxide layer.
[0011] In some optional examples, the thickness ratio of the converted silicon film layer to the silicon dioxide ranges from 0.35 to 0.55.
[0012] In some optional examples, the mixed gas is a mixed gas of carbon monoxide and hydrogen.
[0013] In some optional examples, the ratio of carbon monoxide to hydrogen in the mixed gas is 1:0.5 to 1:0.25.
[0014] In some of the optional examples, before subjecting a portion of the surface layer of the silicon carbide substrate to mixed gas high-temperature bombardment, the preparation method further comprises: subjecting the silicon carbide substrate to ion implantation to form a silicon carbide P-type substrate or a silicon carbide N-type substrate.
[0015] In some optional examples, after forming the silicon carbide P-type substrate or the silicon carbide N-type substrate, the preparation method further includes:
[0016] A wet cleaning process is performed on the silicon carbide P-type substrate or the silicon carbide N-type substrate.
[0017] In some optional examples, after converting the silicon film layer into silicon dioxide, the preparation method further includes:
[0018] The silicon dioxide is subjected to an annealing treatment.
[0019] In some optional examples, the process conditions of the annealing treatment include: a temperature range of 1000°C to 1100°C, a process duration of 10 minutes to 30 minutes, and a reaction gas of at least one of hydrogen, nitrogen, nitric oxide, nitrogen dioxide or argon.
[0020] In some optional examples, after forming the silicon dioxide, the preparation method further comprises:
[0021] Using the silicon dioxide as a gate oxide layer and forming a polysilicon gate on a surface of the gate oxide layer; and
[0022] A source electrode and a drain electrode are formed in the silicon carbide substrate corresponding to two sides of the polysilicon gate.
[0023] In the second aspect, based on the same inventive concept as the method for preparing the silicon carbide power device, the present invention also provides a silicon carbide power device, which can be specifically prepared using the method for preparing the silicon carbide power device as described above, and the specific preparation process will not be repeated here.
[0024] Compared with the prior art, the technical solution provided by the present invention has at least one of the following beneficial effects:
[0025] In a method for preparing a silicon carbide power device provided by the present invention, after providing a silicon carbide substrate, a gate oxide layer is not directly formed on the surface of the silicon carbide substrate by thermal oxidation or chemical vapor deposition process as in the prior art. Instead, before forming the gate oxide layer, a mixed gas is introduced to bombard a part of the surface layer of the silicon carbide substrate at high temperature, so as to break the chemical bonds between silicon atoms and carbon atoms in the part of the surface layer of the silicon carbide substrate, and make the carbon atoms react with the mixed gas to volatilize, and at the same time make the part of the surface layer of the silicon carbide substrate to be converted (reduced) into a silicon film layer, and then the silicon film layer is oxidized into silicon dioxide, so as to obtain an unexpected effect: during the reduction process of the silicon carbide substrate, the carbon element contained therein is volatilized, while the silicon element is left, thereby reducing the carbon remaining due to the gate oxide formation reaction, thereby improving the density of the silicon dioxide as the gate oxide layer, reducing the interface state density between the silicon dioxide and the silicon carbide substrate, improving the electron mobility of the silicon carbide power device and reducing the on-resistance.
[0026] Furthermore, since the hydrogen in the mixed gas introduced by the present invention can repair defects in the silicon film layer obtained by reducing part of the surface layer of the silicon carbide substrate, it can indirectly reduce the interface state density between the gate oxide layer and the silicon carbide substrate, improve the electron mobility of the silicon carbide power device, and reduce the on-resistance. BRIEF DESCRIPTION OF THE DRAWINGS
[0027] Figure 1 A schematic flow chart of a method for preparing a silicon carbide power device provided in some embodiments of the present invention;
[0028] Figure 2 to Figure 5 The present invention is a schematic structural diagram of a method for preparing a silicon carbide power device during the preparation process provided in some embodiments of the present invention.
[0029] The reference numerals are as follows:
[0030] 100-silicon carbide substrate;
[0031] 110 - patterned photoresist layer;
[0032] 100.1-silicon film layer;
[0033] 120-silicon dioxide;
[0034] 130-polysilicon gate. DETAILED DESCRIPTION
[0035] In order to make the technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions of the present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. Although the exemplary implementation methods of the present invention are shown in the accompanying drawings, it should be understood that the present invention can be implemented in various forms and should not be limited by the implementation methods described here. On the contrary, these implementation methods are provided in order to enable a more thorough understanding of the present invention and to fully convey the scope of the present invention to those skilled in the art.
[0036] The present invention is described in more detail in the following paragraphs by way of example with reference to the accompanying drawings. The advantages and features of the present invention will become clearer according to the following description and claims. It should be noted that the accompanying drawings are all in very simplified form and use non-precise proportions, which are only used to conveniently and clearly assist in explaining the purpose of the embodiments of the present invention. It is understood that the meanings of "on", "above" and "above" in the present invention should be interpreted in the broadest way, so that "on" not only means that it is "on" something and there are no intervening features or layers (i.e. directly on something), but also includes the meaning of being "on" something and having intervening features or layers.
[0037] Additionally, for ease of description, spatially relative terms such as "on," "over," "above," "upper," and the like may be used herein to describe the relationship of one element or feature to another element or feature as illustrated in the figures. The spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. The device may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein may be interpreted accordingly.
[0038] In the embodiments of the present invention, the terms "first", "second", etc. are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be noted that the technical solutions recorded in the embodiments of the present invention can be combined arbitrarily without conflict.
[0039] The method for preparing the silicon carbide power device provided in the embodiment of the present invention will be explained below by combining a flow chart of the preparation method with a structural diagram of the preparation method during the preparation process.
[0040] See also Figure 1 , and combined with Figure 2 to Figure 5 , Figure 1 is a schematic flow chart of a method for preparing a silicon carbide power device provided in some embodiments of the present invention, Figure 2 to Figure 5 The present invention is a schematic structural diagram of a method for preparing a silicon carbide power device during the preparation process provided in some embodiments of the present invention.
[0041] like Figure 1 As shown, the method for preparing the silicon carbide power device comprises at least the following steps:
[0042] Step S101, providing a silicon carbide substrate;
[0043] Step S102, introducing a mixed gas to bombard a portion of the surface layer of the silicon carbide substrate at high temperature, so as to break the chemical bonds between the silicon atoms and the carbon atoms in the portion of the surface layer of the silicon carbide substrate, and make the carbon atoms react with the mixed gas to volatilize, and at the same time make the portion of the surface layer of the silicon carbide substrate converted into a silicon film layer;
[0044] Step S103 , performing thermal oxidation treatment on the silicon film layer to convert the silicon film layer into silicon dioxide.
[0045] See also Figure 2 In the above step S101, a silicon carbide substrate 100 may be provided first, and the silicon carbide substrate 100 is used to provide a platform for the subsequent formation of a silicon carbide power device.
[0046] In an optional example, the silicon carbide substrate 100 may then be doped with N-type or P-type ions using an ion implantation process to form a silicon carbide P-type substrate or a silicon carbide N-type substrate, wherein the N-type ions may specifically be at least one of phosphorus ions, arsenic ions, and antimony ions, and the P-type ions may specifically be at least one of boron ions, indium ions, and gallium ions.
[0047] Continue reading Figure 2 A patterned photoresist layer 110 having an opening may be formed on the surface of the silicon carbide substrate 100, wherein the area of the silicon carbide substrate 100 exposed at the bottom of the opening is the area where the silicon film layer is subsequently reduced and the gate oxide layer is formed.
[0048] In an optional example, after forming the patterned photoresist layer 110 , the silicon carbide substrate 100 may be further subjected to at least one wet cleaning process. Exemplarily, the solution of the wet cleaning process may be water.
[0049] See also Figure 3In the above step S102, a mixed gas may be further introduced to bombard a portion of the surface layer of the silicon carbide substrate 100 with high temperature, so as to break the chemical bonds between the silicon atoms and the carbon atoms in the portion of the surface layer of the silicon carbide substrate 100, and make the carbon atoms react with the mixed gas to volatilize, and at the same time make the portion of the surface layer of the silicon carbide substrate 100 be converted into a silicon film layer 100.1.
[0050] In this embodiment, a mixed gas of carbon monoxide and hydrogen in a certain proportion can be introduced into the silicon carbide substrate 100 having the patterned photoresist layer 110 formed on the surface, so that the carbon monoxide in the mixed gas reacts with the surface layer of the silicon carbide substrate 100 not covered by the patterned photoresist layer 110, thereby reacting the carbon atoms in the surface layer with the carbon monoxide, that is, consuming the carbon element in the surface layer of the silicon carbide substrate 100, that is, retaining only the silicon element in this area, that is, converting or reducing the silicon carbide material exposed by the patterned photoresist layer 110 into silicon material, and then, the hydrogen introduced this time can be used to repair defects in the silicon film layer obtained by reducing part of the surface layer of the silicon carbide substrate, thereby indirectly achieving the purpose of reducing the interface state density between the gate oxide layer and the silicon carbide substrate, improving the electron mobility of the silicon carbide power device, and reducing the on-resistance.
[0051] In an optional example, the ratio of carbon monoxide to hydrogen in the mixed gas may specifically be 1:0.5 to 1:0.25, and preferably is 1:0.5.
[0052] It should be noted that, in an embodiment of the present invention, there is a certain proportional relationship between the thickness of the silicon film layer 100.1 obtained by the conversion and the silicon dioxide 120 subsequently formed based on the silicon film layer 100.1, that is, the thickness of the silicon film layer 100.1 needs to be determined according to the thickness of the silicon dioxide 120 to be formed subsequently as a gate oxide layer.
[0053] Specifically, the thickness ratio range of the silicon film layer 100.1 and the subsequently formed silicon dioxide 120 in the direction perpendicular to the silicon carbide substrate 100 is: 0.35-0.55, that is, the ratio range can be 0.35 (the thickness of the silicon film layer 100.1 is 0.35 times the thickness of the subsequently formed silicon dioxide 120), 0.36, 0.38, 0.4, 0.41, 0.42, 0.43, 0.44, 0.45, 0.50, 0.55, etc., and preferably, the thickness of the silicon film layer 100.1 is 0.44 times the thickness of the subsequently formed silicon dioxide 120.
[0054] See also Figure 4In the above step S103, after a portion of the surface layer of the silicon carbide substrate 100 is converted into a silicon film layer 100.1, the silicon carbide substrate 100 can be subjected to an oxidation treatment, such as a thermal oxidation treatment, to oxidize the converted silicon film layer 100.1 into silicon dioxide 120, and the silicon dioxide 120 is used as a gate oxide layer (referred to as a gate oxide layer) of the silicon carbide power device.
[0055] According to the above steps S101 to S103, it can be known that compared with the prior art: the technical solution of directly using the surface oxide layer of silicon carbide substrate, silicon dioxide, as the gate oxide layer by thermal oxidation, or using chemical vapor deposition or physical vapor deposition process to form silicon dioxide as the gate oxide layer on the surface of silicon carbide substrate as the gate oxide layer, and the problems of high interface state density between the gate oxide layer (which can be referred to as gate oxide layer for short) and the silicon carbide substrate, low channel electron mobility of silicon carbide power devices and low density of the gate oxide layer.
[0056] The main inventive point of the present invention to solve the above problem is: silicon carbide material can be reduced to silicon material by using carbon monoxide under high temperature conditions, and on the basis of the high density property of silicon dioxide material obtained by thermal oxidation of silicon material, hydrogen is added while bombarding the silicon carbide material with carbon monoxide at high temperature, so that the hydrogen reduces the silicon carbide material to silicon material at the high temperature of carbon monoxide, and then repairs the silicon material, and then, in combination with other process technologies, a silicon carbide power device with high density, low electron mobility and low on-resistance can be obtained.
[0057] Optionally, after the above step S103, the preparation method provided in the embodiment of the present invention may further include: a step of annealing the silicon dioxide.
[0058] Among them, the process conditions of the annealing treatment of the gate oxide layer include: temperature range: 1000℃~1100℃, process duration: 10mins~30mins, and the reaction gas is at least one of hydrogen (H2), nitrogen (N2), nitric oxide (NO), nitrogen dioxide (NO2) or argon (Ar).
[0059] For example, after forming the silicon dioxide 120 , ie, the gate oxide layer, the silicon dioxide 120 may be subjected to NO annealing treatment to nitride the interface between the silicon carbide substrate 100 and the silicon dioxide 120 , so as to achieve the purpose of improving the channel mobility.
[0060] Furthermore, after the annealing treatment is performed on the silicon dioxide 120 , the preparation method further includes: a step of removing the patterned photoresist layer 110 , such as by wet cleaning, but not limited thereto.
[0061] See also Figure 5 After the above step S103, the preparation method provided in the embodiment of the present invention may further include: using a deposition process, such as a chemical vapor deposition process or a physical vapor deposition process, to form a polycrystalline silicon material burying the silicon dioxide 120 on the silicon carbide substrate 100 where the silicon dioxide 120 is located, and then using an etching process, such as a dry etching process, a wet etching process, or a mixed process of dry and wet etching, to etch away the polycrystalline silicon material outside the surface of the silicon dioxide 120, thereby forming Figure 5 The polysilicon gate 130 is shown; thereafter, an ion implantation process is used to perform N-type or P-type ion implantation on the silicon carbide substrate 100 on both sides of the polysilicon gate to form the source and drain of the silicon carbide power device.
[0062] As an optional solution, after forming the gate oxide layer (silicon dioxide 120), polysilicon gate 130, source and drain of the silicon carbide power device, it is further possible to perform other subsequent processes using the processes in the semiconductor manufacturing process. Since this is not the main invention point of the present application and is a prior art, it is not invented here and will not be described again.
[0063] In addition, based on the same inventive concept as the method for preparing the silicon carbide power device, the present invention also provides a silicon carbide power device, which can be specifically prepared using the method for preparing the silicon carbide power device as described above, and the specific preparation process will not be repeated here.
[0064] In summary, in a method for preparing a silicon carbide power device provided by the present invention, after providing a silicon carbide substrate, it does not directly form a gate oxide layer on the surface of the silicon carbide substrate by thermal oxidation or chemical vapor deposition process as in the prior art, but before forming the gate oxide layer, a mixed gas is first introduced to bombard a portion of the surface layer of the silicon carbide substrate at high temperature, so as to break the chemical bonds between silicon atoms and carbon atoms in the portion of the surface layer of the silicon carbide substrate, and make the carbon atoms react with the mixed gas to volatilize, and at the same time make a portion of the surface layer of the silicon carbide substrate converted (reduced) into a silicon film layer, and then the silicon film layer is oxidized into silicon dioxide, and an unexpected effect is obtained: during the reduction process of the silicon carbide substrate, the carbon element contained therein is volatilized, while the silicon element is left, thereby reducing the carbon remaining due to the gate oxide formation reaction, thereby improving the density of silicon dioxide as a gate oxide layer, reducing the interface state density between silicon dioxide and the silicon carbide substrate, improving the electron mobility of the silicon carbide power device and reducing the on-resistance.
[0065] Furthermore, since the hydrogen in the mixed gas introduced by the present invention can repair defects in the silicon film layer obtained by reducing part of the surface layer of the silicon carbide substrate, it can indirectly reduce the interface state density between the gate oxide layer and the silicon carbide substrate, improve the electron mobility of the silicon carbide power device, and reduce the on-resistance.
[0066] The above description is only a description of the preferred embodiments of the present invention, and is not intended to limit the scope of protection of the present invention. Any changes or modifications made by a person of ordinary skill in the art based on the above disclosure shall fall within the scope of protection of the present invention.
[0067] It should be noted that, although the present invention has been disclosed as a preferred embodiment, the above embodiment is not intended to limit the present invention. For any technician familiar with the art, without departing from the scope of the technical solution of the present invention, the technical content disclosed above can be used to make many possible changes and modifications to the technical solution of the present invention, or modified into equivalent embodiments of equivalent changes. Therefore, any simple modification, equivalent change and modification made to the above embodiment according to the technical essence of the present invention without departing from the content of the technical solution of the present invention still belongs to the scope of protection of the technical solution of the present invention.
[0068] In this article, relational terms such as first and second, etc. are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "comprise", "include" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the statement "comprise a ..." do not exclude the presence of other identical elements in the process, method, article or device including the elements.
[0069] The above description is only a preferred embodiment of the present invention and is not intended to limit the protection scope of the present invention. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention are included in the protection scope of the present invention.
Claims
1. A method for preparing a silicon carbide power device, characterized in that: include: Providing a silicon carbide substrate; Passing a mixed gas to bombard a portion of the surface layer of the silicon carbide substrate at high temperature, so as to break the chemical bonds between silicon atoms and carbon atoms in the portion of the surface layer of the silicon carbide substrate, and make the carbon atoms react with the mixed gas to volatilize, and at the same time make the portion of the surface layer of the silicon carbide substrate converted into a silicon film layer; The silicon film layer is subjected to a thermal oxidation process to convert the silicon film layer into silicon dioxide, and the silicon dioxide serves as a gate oxide layer.
2. The method for preparing a silicon carbide power device according to claim 1, characterized in that: The thickness ratio of the converted silicon film layer to the silicon dioxide is in the range of 0.35 to 0.
55.
3. The method for preparing a silicon carbide power device according to claim 1, characterized in that: The mixed gas is a mixed gas of carbon monoxide and hydrogen.
4. The method for preparing a silicon carbide power device according to claim 3, characterized in that: The ratio of carbon monoxide to hydrogen in the mixed gas is 1:0.5 to 1:0.
25.
5. The method for preparing a silicon carbide power device according to claim 1, characterized in that: Before subjecting a portion of the surface layer of the silicon carbide substrate to high-temperature bombardment with mixed gas, the preparation method further comprises: subjecting the silicon carbide substrate to ion implantation to form a silicon carbide P-type substrate or a silicon carbide N-type substrate.
6. The method for preparing a silicon carbide power device according to claim 5, characterized in that: After forming the silicon carbide P-type substrate or the silicon carbide N-type substrate, the preparation method further includes: A wet cleaning process is performed on the silicon carbide P-type substrate or the silicon carbide N-type substrate.
7. The method for preparing a silicon carbide power device according to claim 1, characterized in that: After converting the silicon film layer into silicon dioxide, the preparation method further comprises: The silicon dioxide is subjected to an annealing treatment.
8. The method for preparing a silicon carbide power device according to claim 7, characterized in that: The process conditions of the annealing treatment include: a temperature range of 1000° C. to 1100° C., a process duration of 10 minutes to 30 minutes, and a reaction gas of at least one of hydrogen, nitrogen, nitric oxide, nitrogen dioxide or argon.
9. The method for preparing a silicon carbide power device according to claim 8, characterized in that: After forming the silicon dioxide, the preparation method further comprises: forming a polysilicon gate on a surface of the gate oxide layer; and A source electrode and a drain electrode are formed in the silicon carbide substrate corresponding to two sides of the polysilicon gate.
10. A silicon carbide power device, characterized in that: The silicon carbide power device is prepared by the method for preparing the silicon carbide power device according to any one of claims 1 to 9.