CN110112055B - Method for removing protective carbon film on surface of wafer - Google Patents
Method for removing protective carbon film on surface of wafer Download PDFInfo
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- CN110112055B CN110112055B CN201910333715.1A CN201910333715A CN110112055B CN 110112055 B CN110112055 B CN 110112055B CN 201910333715 A CN201910333715 A CN 201910333715A CN 110112055 B CN110112055 B CN 110112055B
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- H01—ELECTRIC ELEMENTS
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- H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
- H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
- H01L21/02002—Preparing wafers
- H01L21/02005—Preparing bulk and homogeneous wafers
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Abstract
The invention discloses a method for removing a wafer surface protection carbon film, which comprises the following steps: s0, providing a wafer, wherein the surface of the wafer is provided with a carbon film; and S1, carrying out chemical mechanical polishing on the surface of the wafer of S0. The method is used for removing the protective carbon film on the surface of the wafer subjected to high-temperature activation annealing, has the advantages of short film removing time and strong operability, can fundamentally solve the problems of surface silicon precipitation and roughness increase caused by high-temperature annealing, and is clean in carbon film removal and pollution-free; by taking silicon carbide as an example, the carbon film is removed, and the shallow layer on the surface of the SiC material is removed, so that the problem that ohmic contact of a device is not optimized due to the fact that the surface of the SiC material is not at the highest concentration of Al ions after Al ions are injected is solved, the on-resistance of the ohmic contact is effectively reduced, and the product performance is optimized.
Description
Technical Field
The invention belongs to the technical field of semiconductor materials, and particularly relates to a method for removing a protective carbon film on the surface of a wafer.
Background
The silicon carbide-based device has the advantages of high breakdown voltage, low on-resistance, high switching speed, high temperature resistance, radiation resistance and the like, and has wide application and prospect in the fields of power electronics, high frequency and high speed. At present, devices such as silicon carbide SBD, JBS, MOSFET and the like can be produced and applied in batches. Wherein the activation efficiency of the implanted ions is a critical factor in determining the device performance when the ions are implanted to form the silicon carbide ohmic contact region and the P region of the JBS. In order to activate implantation doping and eliminate lattice damage defects caused by ion implantation, activation annealing needs to be performed on the SiC wafer at a high temperature, which generally reaches as high as 1600 ℃ to 1800 ℃. However, at such a high activation annealing temperature, Si on the surface of silicon carbide is easily sublimated from the surface of SiC, and Si are easily sublimated2C、SiC2The silicon carbide is re-deposited on the surface of the wafer in an isocorm mode to form step clusters, so that the surface roughness of the SiC wafer is increased, and the interface state density is increasedAnd seriously affect device performance. At present, a carbon film protection method is commonly used in high-temperature annealing, and the manufacturing method generally comprises sputtering a carbon film protection layer or forming the carbon film protection layer through baking and curing of photoresist. After the high-temperature annealing is completed, the carbon film for protecting the silicon carbide surface needs to be removed, and if the carbon film is not completely removed, ohmic contact can be affected, and the performances of the device, such as switching characteristic, conductive characteristic, voltage withstanding characteristic and the like, are seriously affected. In severe cases, local peeling of surface points or surfaces due to poor metal adhesion occurs, which affects the performance and reliability of the device. It is important to remove the carbon film effectively.
Since the carbon film has high hardness, low friction coefficient and low chemical affinity, the carbon film is generally removed by the following four methods. One is to remove the diamond-like carbon film by dry and wet sand blasting. However, the diamond-like carbon film is removed by the sand blasting method, meanwhile, destructive damage is easily generated on the surface of the SiC piece, the damage is large and difficult to repair, in addition, the method cannot be accurately controlled, the repeatability is poor, and the method is not suitable for large-scale production. And secondly, the carbon film is removed by soaking in chemical solution, and most of the chemical solution is hydrochloric acid with certain concentration and a certain amount of nitric acid as a catalyst. The chemical soaking method is used for removing the carbon film, so that the surface damage and the silicon precipitation layer caused by high temperature are difficult to remove on one hand, and on the other hand, whether the carbon film is completely removed can not be rapidly confirmed, the production efficiency is affected by too long soaking time, and the cost is high. The thermal oxidation method removes the carbon film, and the method also has difficulty in removing surface damage and a silicon precipitation layer due to high temperature. The fourth use comprises O2、N2And plasma cleaning with CO to remove the carbon film. The surface roughness obtained by using the plasma etching method cannot be ensured, and other methods are needed for optimization assistance.
In the high temperature annealing, although the carbon film protects the epitaxial layer surface, a certain amount of silicon is precipitated to affect the surface roughness of the silicon carbide wafer. Therefore, the conventional method cannot fundamentally solve the problem of increase of surface silicon deposition layer, carbon layer and surface roughness caused by high-temperature annealing. In addition, the existing method can not solve the problem that ohmic contact is not optimized due to the fact that the surface of the silicon carbide material is not implanted with the layer with the highest ion concentration during Al ion implantation, and other methods are needed to realize the ohmic contact so as to effectively reduce the on-resistance of the ohmic contact.
Disclosure of Invention
In order to solve the technical problems, the invention provides a method for removing a carbon protection film on the surface of a wafer, and aims to effectively remove the carbon protection film on the surface of a silicon carbide wafer after high-temperature annealing. And meanwhile, the surface damage and the silicon precipitation layer and the shallow surface layer of the silicon carbide material, which is not the layer with the highest implanted ion concentration, are removed, and the ohmic contact on-resistance is reduced.
In order to achieve the purpose, the invention adopts the technical scheme that: a method for removing a carbon film for protecting the surface of a wafer comprises the following steps:
s0, providing a wafer, wherein the surface of the wafer is provided with a carbon film;
and S1, carrying out chemical mechanical polishing on the surface of the wafer of S0.
Further, the substrate is subjected to high-temperature ion implantation before high-temperature activation annealing, and the ion concentration of the surface layer of the wafer is not a peak value.
Further, the chemical mechanical polishing removes carbon films and a shallow surface layer of the wafer surface with a thickness of not more than 100 nm.
Further, after the step S0, before the step S1, the method includes a step S01 of mechanically grinding the silicon carbide wafer.
Further, in the step S1, the wafer material is GaN, SiC, GaAs, InP, or diamond.
Further, the wafer can be prepared into a Pin diode, a Schottky diode, a junction barrier Schottky diode, a gate turn-off thyristor, an insulated gate bipolar transistor or a metal oxide field effect transistor.
The method for removing the carbon film on the surface of the wafer has the following beneficial effects:
1. the process is simple, the film removing time is short, the carbon film is removed cleanly, the operability is high, and the cost is low;
2. the problems of surface silicon precipitation and roughness increase caused by high-temperature annealing are fundamentally and completely solved;
3. the removal of the shallow surface layer of the wafer material is beneficial to solving the problem that the ohmic contact is not optimized because the interface brought by injection is not the highest position of the impurity ion concentration, so that the on-resistance of the ohmic contact can be effectively reduced, and the performance of the device is optimized.
Drawings
The description includes the following figures, the contents shown are respectively:
FIG. 1 is a schematic process flow diagram of the method for removing a carbon film on a wafer surface according to the present invention;
FIG. 2 is a schematic diagram of a silicon carbide JBS carbon film protected high temperature anneal;
FIG. 3 is a schematic diagram of the removal of a silicon carbide JBS high temperature protective carbon film;
labeled as: 1. high temperature annealing the protected carbon film; 2. a silicon carbide epitaxial portion; 3. a P area formed by ion implantation of the epitaxial layer; 4. a substrate material; 5. implanting ions into the epitaxial shallow surface layer with lower impurity concentration; 6. all portions to be removed.
Detailed Description
The following detailed description of the embodiments of the present invention will be given with reference to the accompanying drawings for a purpose of helping those skilled in the art to more fully, accurately and deeply understand the concept and technical solution of the present invention and to facilitate its implementation.
The invention provides a method for removing a wafer surface protection carbon film, which comprises the following steps:
s0, providing a wafer, wherein the surface of the wafer is provided with a carbon film;
and S1, carrying out chemical mechanical polishing on the surface of the wafer of S0.
Specifically, in the present embodiment, the wafer is a silicon carbide wafer. As shown in fig. 2 and 3, activation annealing of the silicon carbide device at high temperatures is required in order to activate the implanted dopant impurities and to remove damage defects caused by the implantation process.
Before the silicon carbide wafer is subjected to high-temperature activation annealing, high-temperature ion implantation is carried out, and the ion concentration of the surface layer of the silicon carbide wafer is not a peak value (after the ion implantation, the impurity concentration is in Gaussian distribution along the depth direction, and the highest concentration position is not on the surface), namely the surface layer of the silicon carbide wafer is not a layer with the highest implanted ion concentration. And after the silicon carbide device is annealed, removing the carbon film for protecting the silicon carbide surface.
In the above step S1, the chemical mechanical polishing removes the carbon film and the surface layer of the silicon carbide wafer having a surface thickness of not more than 100nm, the material of the surface layer being SiC. When the carbon film is removed, the carbon film covers the surface layer. After the carbon film is removed, the surface layer is exposed, and then the surface layer with a certain thickness is removed, and the removal process of the surface layer is the same as that of the carbon film. Namely, after the carbon film on the surface of the silicon carbide device is effectively removed, the silicon carbide device extends to a certain depth (the depth is within 100 nm) towards the material layer, and the shallow surface layer is removed. The method can remove the carbon film and part of the shallow material layer quickly, effectively and completely without introducing foreign impurities.
As shown in fig. 1, in the above step S1, a Chemical Mechanical Polishing (CMP) process is used to remove the carbon film on the surface of the silicon carbide device.
As a modified embodiment, in step S1, the silicon carbide device is mechanically ground and then chemically and mechanically polished to remove the carbon film and the silicon carbide surface layer on the surface of the silicon carbide device. In step S1, a grinding wheel with a high mesh number is used for mechanical grinding or chemical mechanical polishing, and may be used in combination.
The silicon carbide device is a PiN diode, a schottky diode, a junction barrier schottky diode, a gate turn-off thyristor, an insulated gate bipolar transistor or a metal oxide field effect transistor and the like.
The invention is described above with reference to the accompanying drawings. It is to be understood that the specific implementations of the invention are not limited in this respect. Various insubstantial improvements are made by adopting the method conception and the technical scheme of the invention; the present invention is not limited to the above embodiments, and can be modified in various ways.
Claims (2)
1. A method for removing a carbon film used for protecting the surface of a wafer is characterized by comprising the following steps:
s0, providing a wafer, wherein the surface of the wafer is provided with a carbon film;
s1, carrying out chemical mechanical polishing on the surface of the wafer of S0;
before high-temperature activation annealing, the substrate is subjected to high-temperature ion implantation, the ion concentration of the surface layer of the wafer is not a peak value, and the surface layer of the wafer is not a highest ion implantation concentration layer;
in the step S1, a chemical mechanical polishing process is used to remove the carbon film and the shallow surface layer with a wafer surface thickness of no more than 100nm, where the shallow surface layer is made of SiC; when the carbon film is removed, the shallow surface layer is covered by the carbon film, and the removing process of the shallow surface layer is the same as that of the carbon film;
after the step S0, before the step S1, the method includes a step S01 of mechanically polishing the wafer;
in step S1, the wafer material is Sic.
2. The method as claimed in claim 1, wherein the wafer is fabricated into a PiN diode, a schottky diode, a gate turn-off thyristor, an insulated gate bipolar transistor or a metal oxide field effect transistor.
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| CN113594263A (en) * | 2021-07-15 | 2021-11-02 | 淄博绿能芯创电子科技有限公司 | Silicon carbide diode and method of manufacture |
| CN115739859A (en) * | 2022-10-25 | 2023-03-07 | 广东鼎泰高科技术股份有限公司 | Carbon film removing device and method |
| CN117059483B (en) * | 2023-10-12 | 2024-01-30 | 深圳基本半导体有限公司 | Method for removing and detecting carbon protective film on surface of silicon carbide device |
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| US5674107A (en) * | 1995-04-25 | 1997-10-07 | Lucent Technologies Inc. | Diamond polishing method and apparatus employing oxygen-emitting medium |
| CN1331636C (en) * | 2003-10-15 | 2007-08-15 | 广东工业大学 | Polishing method of diamond material |
| CN103909464B (en) * | 2013-01-09 | 2017-10-31 | 华邦电子股份有限公司 | Chemical and mechanical grinding method and self-aligned method |
| JP2015065318A (en) * | 2013-09-25 | 2015-04-09 | 住友電気工業株式会社 | Method for manufacturing silicon carbide semiconductor device |
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