Method for processing defects of silicon carbide epitaxial layer
By thinning the epitaxial layer with plasma etching technology after the thickness of the silicon carbide epitaxial layer is greater than the target thickness, the problems of pits, protrusions and particle defects in the thick epitaxial layer are solved, and a flatter surface and higher pressure resistance are achieved.
Patent Information
- Application Number
- CN202410935134.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-07-12
- Publication Date
- 2025-05-06
AI Technical Summary
As the thickness of the silicon carbide epitaxial layer increases, the size of the pits, protrusions and particle defects formed increases, and the number increases, which has a significant impact on device performance.
Defects on the surface of the epitaxial layer are improved by growing a silicon carbide epitaxial layer on the substrate so that its thickness is greater than the target thickness, and then etching is performed using fluorine-based gas in a plasma etching machine until the epitaxial layer reaches the target thickness.
It effectively reduces pits, protrusions and particle defects on the surface of the silicon carbide epitaxial layer, reduces surface roughness, makes the epitaxial layer smoother and smoother, and significantly improves the device's voltage resistance.
Smart Images
Figure CN119943647A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the field of semiconductor technology, and in particular to a method for processing defects in a silicon carbide epitaxial layer. Background Art
[0002] With the development of aerospace, ultra-high voltage transmission, high-speed rail and power conversion, higher voltage requirements are put forward for the devices used, which often require voltage resistance of tens of kilovolts or even hundreds of kilovolts. As the thickness of the SiC epitaxial layer used increases, the voltage resistance of silicon carbide devices increases accordingly. Silicon carbide thick epitaxial devices have certain market potential, but defects such as pits and bumps formed after SiC epitaxy are difficult to improve.
[0003] In thin epitaxy (e.g. 10μm), the number of pits and bumps is small, generally within 1000ea / pcs, and the size is also very small. Most defects are less than 1μm in length and width, and the area is less than 1μm. 2 The effect on the device is not significant; however, as the epitaxial thickness increases, the size of the defects also increases: when the epitaxial thickness reaches 30μm, the length and width of the defects increase greatly, generally exceeding three or four microns, and the area also increases to 10μm 2 As a result, the impact on device performance becomes greater, and the number becomes extremely large, reaching tens of thousands or even millions per chip.
[0004] It should be noted that the information disclosed in the background technology section of the invention is only intended to deepen the understanding of the general background technology of the invention, and should not be regarded as an admission or suggestion in any form that the information constitutes prior art already known to those skilled in the art. Summary of the invention
[0005] The object of the present invention is to provide a method for processing defects in a silicon carbide epitaxial layer, so as to solve the problem of defects formed in the silicon carbide epitaxial layer.
[0006] In order to solve the above technical problems, the present invention provides a method for processing defects in a silicon carbide epitaxial layer, comprising the following steps:
[0007] Growing a silicon carbide epitaxial layer on a substrate, wherein the thickness of the silicon carbide epitaxial layer is greater than a desired target thickness;
[0008] The substrate is placed on a plasma etching machine base, and etching gas is introduced to etch the silicon carbide epitaxial layer until it reaches the target thickness.
[0009] Preferably, the thickness of the silicon carbide epitaxial layer is greater than the required target thickness by 2-5 μm.
[0010] Preferably, after placing the substrate on the base of the plasma etching machine and before introducing the etching gas, a mechanical pump is started to draw the vacuum degree in the chamber to below 1 Torr.
[0011] Preferably, after starting the mechanical pump, the pipeline and chamber of the plasma etching machine are purged and cleaned.
[0012] Preferably, argon gas is introduced to purge and clean the pipes and chambers of the plasma etching machine.
[0013] Preferably, the flow rate of the argon gas is 1-3 slm, and the duration of the introduction is 5-15 min.
[0014] Preferably, the etching gas is a fluorine-based gas.
[0015] Preferably, when the fluorine-based gas is introduced to a desired flow rate, the plasma generator power is turned on, the power is set to 500-2000 W, and the etching is performed for 15-30 minutes.
[0016] Preferably, when the fluorine-based gas is introduced to 0.5-2 slm, the plasma generator is turned on to start etching.
[0017] Preferably, after etching the silicon carbide epitaxial layer, the power supply of the plasma generator is turned off, the introduction of the fluorine-based gas is stopped, and the substrate is taken out when the temperature is lowered to a desired temperature.
[0018] In the method for processing defects of silicon carbide epitaxial layer provided by the present invention, the problems caused by pits and protrusions are solved more thoroughly by etching the silicon carbide epitaxial layer. The surface of the silicon carbide epitaxial layer is also cleaned during the etching process, the particles existing on the surface of the silicon carbide epitaxial layer are reduced, and the particle problem on the thick epitaxial surface is solved. Furthermore, the roughness of the surface of the silicon carbide epitaxial layer can be reduced, and the scratches and cracks remaining on the surface can be eliminated by plasma etching, so that the surface of the silicon carbide after epitaxy is smoother. BRIEF DESCRIPTION OF THE DRAWINGS
[0019] Those skilled in the art will appreciate that the accompanying drawings are provided for a better understanding of the present invention and do not constitute any limitation on the scope of the present invention.
[0020] Figure 1 is a schematic structural diagram of a silicon carbide epitaxial layer according to an embodiment of the present invention;
[0021] Figure 2 It is a schematic structural diagram of a silicon carbide epitaxial layer treated by plasma etching according to an embodiment of the present invention;
[0022] Figure 3 It is a schematic diagram of the structure of the silicon carbide epitaxial layer after etching according to one embodiment of the present invention;
[0023] Figure 4 It is an execution flow chart of an embodiment of the present invention.
[0024] In the attached figure:
[0025] 100, silicon carbide epitaxial layer; 101, pits; 102, particles; 103, protrusions. DETAILED DESCRIPTION
[0026] In order to make the purpose, advantages and features of the present invention clearer, the present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be noted that the drawings are all in a very simplified form and are not drawn to scale, and are only used to conveniently and clearly assist in explaining the purpose of the embodiments of the present invention. In addition, the structure shown in the drawings is often a part of the actual structure. In particular, the emphasis of each drawing is different, and sometimes different scales are used.
[0027] As used in the present invention, the singular forms "a", "an" and "the" include plural objects, the term "or" is generally used in a sense including "and / or", the term "several" is generally used in a sense including "at least one", and the term "at least two" is generally used in a sense including "two or more". In addition, the terms "first", "second" and "third" are used for descriptive purposes only and cannot be understood as indicating or suggesting relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first", "second", and "third" may explicitly or implicitly include one or at least two of the features. The term "proximal end" is usually the end close to the operator, and the term "distal end" is usually the end close to the patient. "One end" and "the other end" as well as "proximal end" and "distal end" usually refer to two corresponding parts, which include not only the endpoints. The terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral body; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the internal connection of the two elements or the interaction relationship between the two elements. In addition, as used in the present invention, an element is arranged on another element, which usually only means that there is a connection, coupling, matching or transmission relationship between the two elements, and the connection, coupling, matching or transmission between the two elements can be direct or indirect through an intermediate element, and it cannot be understood as indicating or implying the spatial position relationship between the two elements, that is, one element can be in any position such as inside, outside, above, below or on one side of another element, unless the content clearly indicates otherwise. For those skilled in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.
[0028] The inventors have found that the high-voltage field places higher pressure-resistant requirements on various semiconductor devices. Among them, the thickness of the silicon carbide epitaxial layer is proportional to its pressure-resistant capability. When thicker silicon carbide epitaxial layers are produced, the size of defects such as pits, protrusions and particles also increases, and the number increases accordingly.
[0029] Based on this, the core idea of the present invention is to form a silicon carbide epitaxial layer thicker than the required target thickness, and then perform plasma etching to thin the silicon carbide epitaxial layer to the required target thickness while improving the defects on the surface of the silicon carbide epitaxial layer, thereby solving the problem of a large number of pits and protrusion defects in the thick epitaxial layer.
[0030] For details, please refer to Figure 1-Figure 4 , which is a schematic diagram of an embodiment of the present invention. Figure 1 As shown, the method for processing defects in a silicon carbide epitaxial layer comprises the following steps:
[0031] S1: growing a silicon carbide epitaxial layer 100 on a substrate, wherein the thickness of the silicon carbide epitaxial layer 100 is greater than a desired target thickness. In one embodiment, the thickness of the silicon carbide epitaxial layer 100 is greater than the desired target thickness by 2-5 μm.
[0032] For example, Figure 1 As shown, the target thickness of the silicon carbide epitaxial layer 100 is N μm, and then a silicon carbide epitaxial layer 100 with a thickness of N+3 μm is grown. It can be understood that the silicon carbide epitaxial layer 100 is slightly thicker than the required target thickness, and the production time consumed is shorter.
[0033] S2: The substrate is placed on the base of the plasma etching machine, and the mechanical pump is started to draw the vacuum degree in the chamber to below 1 Torr. After starting the mechanical pump, the pipes and chambers of the plasma etching machine are purged and cleaned. Argon gas is introduced to purge and clean the pipes and chambers of the plasma etching machine.
[0034] The flow rate of the argon gas is 1-3 slm, and the duration of the introduction is 5-15 min.
[0035] S3: introducing etching gas to etch the silicon carbide epitaxial layer 100 until it reaches the target thickness. The etching gas is a fluorine-based gas. When the fluorine-based gas is introduced to the required flow rate, the plasma generator power is turned on, the power is set to 500-2000W, and the etching is performed for 15-30 minutes. When the fluorine-based gas is introduced to 0.5-2slm, the plasma generator power is turned on to start etching.
[0036] When the fluorine-based gas is introduced to the required flow rate, the plasma generator power is turned on, the power is set to 500-2000W, and the etching is performed for 15-30 minutes. In particular, when the fluorine-based gas is introduced to 0.5-2slm, the plasma generator power is turned on. However, it is not limited to fluorine-based gas.
[0037] Fluorine-based gas molecules enter the plasma generator and are injected with enough energy to ionize a large amount of F - Fluorine ions are highly chemically active substances that react with the silicon carbide epitaxial layer. While etching the silicon carbide epitaxial layer 100, defects on the surface of the silicon carbide epitaxial layer 100 are eliminated, thereby reducing the impact of defects caused by growing a thicker silicon carbide epitaxial layer 100 on the performance of the device itself. Figure 3 As shown, the damage on the surface of the silicon carbide epitaxial layer 100 can be completely eliminated by plasma etching.
[0038] By etching the silicon carbide epitaxial layer 100, the problems caused by the pits 101 and the protrusions 103 are completely solved. Figure 1-Figure 3 As shown, the surface of the silicon carbide epitaxial layer 100 is also cleaned during the etching process, reducing the particles 102 on the surface of the silicon carbide epitaxial layer 100, and solving the problem of particles 102 on the thick epitaxial surface. Furthermore, the roughness of the surface of the silicon carbide epitaxial layer 100 can be reduced, and the scratches and cracks remaining on the surface can be eliminated through plasma etching, so that the surface of the silicon carbide after epitaxy is flatter and smoother.
[0039] As shown in Table 1 below, the number of pits 101 and protrusions 103 before and after plasma etching is compared, and it is found that the number of the two defects of the silicon carbide epitaxial layer treated by the technical solution of the present disclosure is greatly reduced, and both numbers are controlled within 100, especially for thick epitaxial (silicon carbide epitaxial layer with a thickness of more than 30 μm), the reduction rate of pits 101 and protrusions 103 defects exceeds 99%. This is because the plasma etching after the epitaxy etches away all the pits and protrusions on the surface, thereby completely solving the huge number of pits 101 and protrusions 103 defects in the thick epitaxy.
[0040] Table 1 Comparison of defects (pit and bump) before and after epitaxial plasma treatment of different thicknesses
[0041]
[0042] S4: Turn off the power of the plasma generator, stop introducing the fluorine-based gas, and take out the substrate when the temperature drops to a desired temperature, for example, when the substrate reaches room temperature.
[0043] The problems caused by the pits 101 and the protrusions 103 are solved more thoroughly by etching the silicon carbide epitaxial layer 100. The surface of the silicon carbide epitaxial layer 100 is also cleaned during the etching process, and the particles 102 on the surface of the silicon carbide epitaxial layer 100 are reduced, solving the problem of particles 102 on the thick epitaxial surface. Furthermore, the roughness of the surface of the silicon carbide epitaxial layer 100 can be reduced, and the scratches and cracks remaining on the surface can be eliminated by plasma etching, making the surface of the silicon carbide after epitaxy more flat and smooth.
[0044] The above description is only a description of the preferred embodiment of the present invention, and is not intended to limit the scope of the present invention. Any changes or modifications made by a person skilled in the art in the field of the present invention based on the above disclosure shall fall within the scope of protection of the technical solution of the present invention.
Claims
1. A method for treating defects in a silicon carbide epitaxial layer, characterized in that: The following steps are involved: Growing a silicon carbide epitaxial layer on a substrate, wherein the thickness of the silicon carbide epitaxial layer is greater than a desired target thickness; The substrate is placed on a plasma etching machine base, and etching gas is introduced to etch the silicon carbide epitaxial layer until it reaches the target thickness.
2. The method for treating defects in a silicon carbide epitaxial layer according to claim 1, characterized in that: The thickness of the silicon carbide epitaxial layer is 2-5 μm greater than the required target thickness.
3. The method for treating defects in a silicon carbide epitaxial layer according to claim 1, characterized in that: After the substrate is placed on the base of the plasma etching machine, before the etching gas is introduced, a mechanical pump is started to draw the vacuum degree in the chamber to below 1 Torr.
4. The method for treating defects in a silicon carbide epitaxial layer according to claim 3, characterized in that: After starting the mechanical pump, the pipes and chambers of the plasma etching machine are still being purged and cleaned.
5. The method for treating defects in a silicon carbide epitaxial layer according to claim 4, characterized in that: Argon gas is introduced to purge and clean the pipes and chambers of the plasma etching machine.
6. The method for treating defects in a silicon carbide epitaxial layer according to claim 1, characterized in that: The flow rate of argon gas is 1-3slm, and the duration of introduction is 5-15min.
7. The method for treating defects in a silicon carbide epitaxial layer according to claim 1, characterized in that: The etching gas is a fluorine-based gas.
8. The method for treating defects in a silicon carbide epitaxial layer according to claim 7, characterized in that: When the fluorine-based gas is introduced to the required flow rate, the plasma generator power is turned on, the power is set to 500-2000W, and the etching is performed for 15-30 minutes.
9. The method for treating defects in a silicon carbide epitaxial layer according to claim 8, characterized in that: When the fluorine-based gas is introduced to 0.5-2 slm, the plasma generator is turned on to start etching.
10. The method for treating defects in a silicon carbide epitaxial layer according to claim 1, characterized in that: After etching the silicon carbide epitaxial layer, turn off the power of the plasma generator, stop introducing the fluorine-based gas, and take out the substrate when the temperature drops to a required temperature.