SILICIUM CARBIDE SEMICONDUCTOR DEVICE AND METHOD FOR ITS MANUFACTURING

Abstract

A semiconductor device that may include a silicon carbide substrate, a silicon layer placed on the silicon carbide substrate, and a gate oxide layer placed on the silicon layer. The silicon layer may be embedded within the silicon carbide substrate. The silicon layer may have a thickness of 100 angstroms to 5000 angstroms. The silicon layer may contain less than one percent carbon or may contain a certain percentage of carbon that decreases with increasing distance from the surface of the silicon carbide substrate.

Description

CROSS-REFERENCE TO RELATED REGISTRATION

[0001] This application claims priority over the preliminary US patent application No. 63 / 531,880, filed on August 10, 2023, and the non-preliminary US patent application No. 18 / 676,191, filed on May 28, 2024, the contents of which are incorporated herein by reference in their entirety. TECHNICAL AREA

[0002] The present disclosure relates generally to semiconductor substrates for electronic devices and in particular to silicon carbide substrates and a gate oxide layer with the silicon carbide substrate. SUMMARY

[0003] According to one aspect of one or more examples, a method for fabricating a semiconductor device is provided. The method may include forming a silicon layer on the surface of a silicon carbide substrate and forming a gate oxide layer over the silicon layer. The silicon layer may have a thickness of 100 angstroms to 5000 angstroms. The silicon layer may contain less than one percent carbon or may contain a certain percentage of carbon that decreases with increasing distance from the surface of the silicon carbide substrate. The step of forming the gate oxide layer may include oxidizing silicon from the silicon layer to form the gate oxide layer of silicon dioxide.

[0004] According to another aspect of one or more examples, a method for fabricating a semiconductor device is provided. The method may include implanting silicon into a silicon carbide substrate to form a first silicon-rich layer, forming a second silicon layer over the first silicon layer by epitaxial growth, and forming a gate oxide layer on the second silicon layer.

[0005] "Silicon-rich" means that the percentage of silicon is greater than the percentage of carbon; for example, the percentage of silicon could be 25 percent higher than the percentage of carbon. In some cases, a higher percentage of silicon may be preferable to a lower percentage; for instance, a higher percentage of silicon may reduce the number of defects. The first silicon layer and the second silicon layer together can have a thickness ranging from 100 angstroms to 5000 angstroms. The second silicon layer may contain less than one percent carbon or it may contain a certain percentage of carbon that decreases with increasing distance from the surface of the silicon carbide substrate. The gate oxide layer formation step may involve oxidizing silicon from the second silicon layer to form the silicon dioxide gate oxide layer.

[0006] According to another aspect of one or more examples, a method for fabricating a semiconductor device is provided. The method may include forming a first silicon layer on the surface of the silicon carbide substrate, polishing the first silicon layer, forming a second silicon layer over the first silicon layer, and forming a gate oxide layer over the second silicon layer. The first silicon layer and the second silicon layer together may have a thickness of 100 angstroms to 5000 angstroms. The second silicon layer may contain less than one percent carbon or may contain a certain percentage of carbon that decreases with increasing distance from the surface of the silicon carbide substrate. The step of forming the gate oxide layer may include oxidizing silicon from the second silicon layer to form the silicon dioxide gate oxide layer.

[0007] According to another aspect of one or more examples, a semiconductor device is provided that may include a silicon carbide substrate, a silicon layer placed on the silicon carbide substrate, and a gate oxide layer placed on the silicon layer. The silicon layer may be embedded in the silicon carbide substrate. The silicon layer may have a thickness of 100 angstroms to 5000 angstroms. The silicon layer may contain less than one percent carbon or may contain a certain percentage of carbon that decreases with increasing distance from the surface of the silicon carbide substrate. BRIEF DESCRIPTION OF THE DRAWINGS Fig. Figures 1A-1C show a silicon carbide substrate with a grown or deposited layer of silicon and an oxide layer, and a method for fabricating the semiconductor device according to one or more examples. Fig. Figure 2 shows a diagram illustrating the potential carbon concentration in the silicon layer of the semiconductor device according to one or more examples. Fig. Figures 3A-3C show a silicon carbide substrate with a first implanted silicon-rich layer, a second silicon layer grown or deposited thereon, and an oxide layer formed on the second silicon layer, as well as a method for fabricating the semiconductor device according to one or more examples. Fig. Figures 4A-4D show a silicon carbide substrate with a grown or deposited silicon layer which was then polished, with additional silicon grown or deposited on the polished silicon and an oxide layer formed thereon, and a method for fabricating the semiconductor device according to one or more examples. DETAILED DESCRIPTION OF VARIOUS EXAMPLES

[0008] The following various examples, illustrated in the accompanying drawings, will now be discussed in detail, with identical reference symbols consistently referring to the same elements. The following examples can take various forms and are not limited to those presented here.

[0009] Fig. Figures 1A-1C show a silicon carbide substrate and a method for fabricating the silicon carbide substrate according to one or more examples. Silicon carbide is widely used as a substrate for fabricating many semiconductor devices and, compared to other materials, can lead to lower switching losses, higher power density, improved heat dissipation, and increased bandwidth. Some semiconductor devices, such as metal-oxide-semiconductor field-effect transistors (MOSFETs), include a gate oxide layer, which is a dielectric layer that separates the silicon carbide substrate from a gate electrode, which may be made of metal or other conductive material.

[0010] When forming the gate oxide layer on a silicon carbide substrate, the interface between the silicon carbide substrate and the gate oxide layer (for example, a gate oxide layer made from silicon dioxide) can be very rough. This rough interface can impair charge carrier mobility in the silicon carbide substrate, potentially limiting the device's performance. To at least partially overcome this difficulty, and with reference to Fig. 1A, a layer of silicon (Si) 30 can be grown or deposited onto the surface of a silicon carbide substrate (SiC substrate) 20. According to one or more examples, the silicon layer 30 can be approximately 100 angstroms to 5000 angstroms thick, although other thicknesses may be used depending on the application. For example, the amount of silicon used to produce the silicon layer 30 may depend on the thickness of the gate oxide layer to be formed on the silicon layer 30. As in Fig. As shown in Figure 1B, a gate oxide layer 40 can be formed on the silicon layer 30. For example, the gate oxide layer 40 can be a layer of silicon dioxide that can be formed or grown by a thermal oxidation process of the silicon layer 30. According to a Fig. In the example shown in Figure 1C, a very thin layer of silicon 30 or no silicon may remain between the silicon carbide substrate 20 and the gate oxide layer 40 if the gate oxide layer 40 consists of silicon dioxide.

[0011] Fig. Figure 2 shows a diagram illustrating the potential carbon concentration of the silicon layer 30 according to one or more examples. As in the diagram in Fig. As shown in Figure 2, the vertical axis indicates the percentage of carbon contained in the silicon layer 30 and the silicon carbide substrate 20, and the horizontal axis indicates the depth from the top surface of the silicon layer 30. Thus, the silicon layer 30 exhibits a graded silicon carbide layer, as the percentage of carbon in the silicon layer 30 decreases with increasing distance from the surface of the silicon carbide substrate. At the point where the silicon layer comes into contact with the silicon carbide substrate, the percentage of carbon increases to indicate a fixed percentage of carbon in the silicon carbide substrate. According to a diagram of Fig. In the illustrated example 2, the percentage of carbon in the silicon layer at the top of silicon layer 30 can be approximately zero and can increase as the distance from the silicon carbide substrate decreases, i.e., as the distance from the top of silicon layer 30 increases. As in the example in Fig. As shown in Figure 2, the percentage of carbon in the silicon layer can increase approximately linearly until the silicon carbide substrate is reached; at this point, the percentage of carbon can become constant. Alternatively, the percentage of carbon in the silicon layer can increase non-linearly.

[0012] A method for producing a silicon layer on a silicon carbide substrate is described herein according to one or more examples. Fig. Figures 3A-3C show a silicon carbide substrate and a method for preparing the silicon carbide substrate according to one or more examples. Fig. 3A A first silicon-rich layer 70 can be implanted into an upper section of a silicon carbide substrate 20. “Silicon-rich” means that the percentage of silicon is greater than the percentage of carbon; for example, the percentage of silicon could be 25 percent higher than the percentage of carbon, without restriction. As an example, the implanted depth of the first silicon-rich layer 70 can be approximately 100 angstroms to 5000 angstroms thick, although other thicknesses can be used. The first silicon-rich layer 70 can be formed by implanting silicon into the silicon carbide substrate 20. As shown in Fig. As shown in Figure 3B, after implanting the first silicon-rich layer 70 into the upper section of the silicon carbide substrate 20, a second silicon layer 80 can be formed by epitaxial growth on the implanted first silicon-rich layer 70. By implanting the first silicon-rich layer 70, a sufficient amount of silicon is present on the silicon carbide substrate 20 to obtain a second silicon layer 80 of better quality; that is, the silicon layer 80 can have fewer defects than would be the case without the first silicon-rich layer 70. For example, the second silicon layer 80 can be a single-crystal layer. As shown in Figure 3B, the silicon layer 80 can be a single-crystal layer. Fig. As shown in Figure 3C, after the formation of the second silicon layer 80, a gate oxide layer 90 can be formed on the second silicon layer 80. For example, the gate oxide layer 90 can be a layer of silicon dioxide that can be formed or grown by a thermal oxidation process of the second silicon layer 80. Once the gate oxide layer 90 is formed, a portion of the second silicon layer 80 may remain between the implanted first silicon-rich layer 70 and the gate oxide layer 90, or no portion of the second silicon layer 80 may remain after the gate oxide layer 90 is formed. The second silicon layer 80 can enclose less than one percent carbon, or alternatively, the percentage of carbon in the second silicon layer 80 can be approximately zero at the top of the second silicon layer 80, and the percentage of carbon can increase with decreasing distance from the silicon carbide substrate 20.In other words, the percentage of carbon in the second silicon layer 80 can decrease with increasing distance from the silicon carbide substrate 20. This can be achieved during epitaxial growth, for example by gradually reducing the percentage of carbon incorporation.

[0013] A method for producing a silicon carbide substrate is provided herein according to one or more examples. Fig. Figures 4A-4D show a silicon carbide substrate and a method for preparing the silicon carbide substrate according to one or more examples. Fig. 4A A layer of silicon 30 can be grown or deposited onto the surface of a silicon carbide substrate 20. When the silicon layer 30 is grown, it can exhibit various types of defects. The silicon layer 30 can be polished to remove a section of the silicon layer, as shown in Fig. Figure 4B shows that this polishing process can remove sections of the silicon layer 30 that contain some of the defects. After the silicon layer 30 has been polished, additional silicon can be grown or deposited onto the existing silicon layer 30, as shown in Fig. 4C shown. The silicon layer 30 can then be repolished to remove any section of the silicon layer 30 that may contain defects. This process of growing or depositing silicon and polishing the silicon layer 30 can be repeated until a silicon layer 30 of sufficient quality is obtained. For example, the process can be repeated until a single crystalline silicon layer 30 is obtained. In one example, the additional silicon may contain less than one percent carbon. In another example, the percentage of carbon in the additional silicon decreases with increasing distance from the surface of the silicon carbide substrate. Once a sufficient silicon layer 30 is obtained, a gate oxide layer 40 can be formed on the silicon layer 30, as shown in Fig.4D shown. For example, the gate oxide layer 40 can be a layer of silicon dioxide that can be formed or grown by a thermal oxidation process of the silicon layer 30. According to one example, when the gate oxide layer 40 is formed, a silicon layer 30 may remain between the silicon carbide substrate 20 and the gate oxide layer 40. According to another example, a very thin silicon layer or no silicon at all may remain between the silicon carbide substrate 20 and the gate oxide layer 40.

[0014] Several examples have been disclosed herein in connection with the foregoing description and the drawings. It is understood that it would be unreasonable to describe and illustrate every combination and partial combination of these examples verbatim. Accordingly, all examples can be combined in any way and / or in any combination, and the present patent specification, including the drawings, is to be interpreted as constituting a complete written description of all combinations and partial combinations of the examples described herein and of the manner and process of their manufacture and use, and is also to be based on claims relating to any such combination or partial combination.

[0015] It will be understood by those skilled in the art that the examples described herein are not limited to what has been specifically shown and described above. Furthermore, unless otherwise stated above, it should be noted that all accompanying drawings are not to scale. In light of the foregoing teachings, a multitude of modifications and variations are possible. QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] US 63 / 531,880

[0001] US 18 / 676,191

[0001]

Claims

[1] Method for manufacturing a semiconductor device, the method comprising: Formation of a silicon layer on the surface of a silicon carbide substrate; and the formation of a gate oxide layer over the silicon layer. [2] Method according to claim 1, wherein the silicon layer comprises a thickness of 100 angstroms to 5000 angstroms. [3] Method according to claim 1, wherein the silicon layer contains less than one percent carbon. [4] Method according to claim 1, wherein a percentage of carbon in the silicon layer decreases as the distance from the surface of the silicon carbide substrate in the direction of the top of the silicon layer increases. [5] Method according to claim 1, wherein the step of forming the gate oxide layer includes oxidizing silicon from the silicon layer, such that the gate oxide layer consists of silicon dioxide. [6] Method for manufacturing a semiconductor device, the method comprising: Implanting silicon into a silicon carbide substrate to form a first silicon-rich layer; Formation of a second silicon layer above the first silicon-rich layer through epitaxial growth; and Formation of a gate oxide layer over the second silicon layer. [7] Method according to claim 6, wherein the second silicon layer contains less than one percent carbon. [8] Method according to claim 6, wherein the percentage of carbon in the second silicon layer decreases with increasing distance from the silicon carbide substrate. [9] Method according to claim 6, wherein the step of forming the gate oxide layer includes oxidizing silicon from the second silicon layer to form the gate oxide layer, such that the gate oxide layer consists of silicon dioxide. [10] Method for manufacturing a semiconductor device, the method comprising: Forming a silicon layer on a surface of Silicon carbide substrate; Polishing the silicon layer; Formation of additional silicon above the polished silicon layer; and Formation of a gate oxide layer over the additional silicon. [11] Method according to claim 10, wherein the polished silicon layer and the additional silicon comprise a combined thickness of 100 angstroms to 5000 angstroms. [12] The method of claim 10, wherein the additional silicon contains less than one percent carbon. [13] Method according to claim 10, wherein the percentage of carbon in the additional silicon decreases with increasing distance from the surface of the silicon carbide substrate. [14] Method according to claim 10, wherein the step of forming the gate oxide layer includes oxidizing silicon from the additional silicon to form the gate oxide layer, such that the gate oxide layer consists of silicon dioxide. [15] Semiconductor device comprising: a silicon carbide substrate; a silicon layer on a surface of the silicon carbide substrate; and a gate oxide layer above the silicon layer. [16] Semiconductor device according to claim 15, wherein the silicon layer comprises a thickness of 100 angstroms to 5000 angstroms. [17] Semiconductor device according to claim 15, wherein the silicon layer is implanted into the silicon carbide substrate. [18] Semiconductor device according to claim 15, wherein the silicon layer contains less than one percent carbon. [19] Semiconductor device according to claim 15, wherein the percentage of carbon in the silicon layer decreases with increasing distance from the silicon carbide substrate.

Images