Silicon Carbide Wafer and Its Annealing Activation Method

Abstract

The present application discloses a silicon carbide wafer and an annealing activation method thereof, belonging to the field of semiconductor device preparation. The annealing activation method of the silicon carbide wafer provided by the present application includes performing ion implantation on the first surface of the silicon carbide wafer; coating the first surface of the silicon carbide wafer to form a coating layer; attaching the coating layer of the silicon carbide wafer to one side surface of the first wafer to obtain a bonded wafer; annealing the bonded wafer; which can enable the wafers bonded to each other during high-temperature annealing to form protection for each other, reduce the influence of high-temperature annealing on the silicon carbide wafer, and the coating on the bonding surface melts at high temperature to increase the ion concentration on the surface of the silicon carbide wafer.

Description

Technical Field

[0001] The present application relates to the field of semiconductor device fabrication, and more particularly to a silicon carbide wafer and an annealing activation method thereof. Background Art

[0002] Silicon carbide (SiC) devices have good performance, which makes them widely used in the field of electronic devices. In the SiC device manufacturing process, due to the extremely low diffusion constant of impurities in SiC, SiC cannot be doped using the diffusion process like Si (silicon). Ion implantation technology is the key process for realizing SiC doping. In order to improve the activation rate of implanted impurities, activation annealing above 1600 °C is required after ion implantation. In the current process, even when heating during implantation (300 °C - 800 °C), the activation annealing temperature after implantation cannot be reduced below 1600 °C.

[0003] Ultra-high temperature annealing above 1600 °C will cause the precipitation and migration of atoms on the SiC surface, resulting in the precipitation of SiC in the form of Si, Si2C, SiC2, etc. on the SiC wafer surface, leading to severe surface roughening of the SiC wafer after annealing and affecting the performance of SiC devices. In order to prevent the sublimation of silicon on the silicon carbide wafer surface, in the traditional silicon carbide activation annealing process, a carbon film is covered on the SiC wafer surface before annealing and removed after annealing.

[0004] However, in the actual process flow, this process step is cumbersome, seriously affecting production efficiency and greatly increasing production costs. Moreover, an O plasma device is required to remove the carbon film after annealing, which is extremely likely to cause plasma damage and unnecessary oxidation on the SiC surface. Summary of the Invention

[0005] The present application proposes a silicon carbide wafer and an annealing activation method thereof to solve the problems of protecting the silicon carbide wafer in the silicon carbide annealing activation process, as well as low production efficiency and high costs.

[0006] To achieve the above object, the present application adopts the following solutions:

[0007] On the one hand, an embodiment of the present application provides an annealing activation method for a silicon carbide wafer, the method comprising:

[0008] Performing ion implantation on the first surface of the silicon carbide wafer;

[0009] Coating the first surface after ion implantation to form a coating layer;

[0010] Bonding the surface of the silicon carbide wafer with the coating layer to one side surface of the first wafer to obtain a bonded wafer;

[0011] Anneal the wafer after bonding.

[0012] Optionally, after coating the first surface after ion implantation and forming a coating layer, it includes:

[0013] Enhance the ion concentration on the first surface of the silicon carbide wafer by laser irradiation.

[0014] Optionally, the first wafer is a silicon carbide wafer, and one side surface of the first wafer is the side surface that has undergone ion implantation.

[0015] Optionally, when bonding the side surface of the silicon carbide wafer with the coating layer to one side surface of the first wafer, it further includes:

[0016] Insert at least one second wafer between the coating layer of the silicon carbide wafer and the side surface of the first wafer that has undergone ion implantation;

[0017] Wherein, if there are more than one second wafer, the inserted second wafers are bonded to each other on the surface.

[0018] The surface of the second wafer opposite to the coating layer of the silicon carbide wafer is bonded to the coating layer of the silicon carbide wafer;

[0019] The surface of the second wafer opposite to the side surface of the first wafer that has undergone ion implantation is bonded to the side surface of the first wafer that has undergone ion implantation.

[0020] Optionally, coating the first surface after ion implantation to form a coating layer includes:

[0021] Coat with a first material, and the first material contains the ion components implanted into the silicon carbide wafer.

[0022] Optionally, after annealing the bonded silicon carbide wafer and the first wafer, it includes:

[0023] Remove the coating layer of the silicon carbide wafer.

[0024] Optionally, removing the coating layer of the silicon carbide wafer includes:

[0025] Remove the coating layer of the silicon carbide wafer by wet process.

[0026] On the other hand, an embodiment of the present application provides a silicon carbide wafer, which is prepared by using the annealing activation method of the silicon carbide wafer provided in any one of the embodiments of the present application.

[0027] Optionally, a device structure is included on the silicon carbide wafer.

[0028] The beneficial effects brought by the technical solutions provided in the embodiments of the present application at least include:

[0029] The annealing activation method of the silicon carbide wafer provided in the present application includes ion implantation on the first surface of the silicon carbide wafer; coating the first surface of the silicon carbide wafer to form a coating layer; attaching the coating layer of the silicon carbide wafer to one side surface of the first wafer to obtain a bonded wafer; annealing the bonded wafer; which can enable the wafers bonded to each other during high-temperature annealing to form protection for each other, reduce the influence of high-temperature annealing on the silicon carbide wafer, and the coating on the bonding surface melts at high temperature to increase the ion concentration on the surface of the silicon carbide wafer. Description of the Drawings

[0030] Figure 1 It is a flowchart of an annealing activation method for a silicon carbide wafer provided in an embodiment of the present application;

[0031] Figure 2 It is a schematic diagram of coating silicon carbide provided in an embodiment of the present application;

[0032] Figure 3 It is a schematic diagram of a silicon carbide wafer bonded to a first wafer provided in an embodiment of the present application;

[0033] Figure 4 It is a schematic diagram of a bonded wafer provided in an embodiment of the present application;

[0034] Figure 5 It is a schematic diagram of a second wafer provided in an embodiment of the present application. Detailed Embodiments

[0035] To make the objectives, technical solutions, and advantages of the embodiments of the present application clearer, the technical solutions of the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present application. Obviously, the described embodiments are some, but not all, of the embodiments of the present application. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the present application without creative efforts shall fall within the protection scope of the present application.

[0036] The terms "first", "second", etc. in the description and claims of this application are used to distinguish similar objects, rather than to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged under appropriate circumstances, so that the embodiments of this application can be implemented in an order other than those illustrated or described herein, and the objects distinguished by "first", "second", etc. are generally of the same type, and the number of objects is not limited. For example, the first object can be one or more. In addition, "and / or" in the description and claims means at least one of the connected objects, and the character " / ", generally represents an "or" relationship between the associated objects before and after.

[0037] In addition, the technical features involved in different embodiments of this application described below can be combined with each other as long as they do not conflict with each other.

[0038] The following will combine the accompanying drawings and, through specific embodiments and their application scenarios, detail the silicon carbide wafer and its annealing activation method provided by the embodiments of this application.

[0039] Reference Figure 1 shows a flowchart of the annealing activation method of the silicon carbide wafer provided by the embodiment of this application, and the method includes:

[0040] Step 101, perform ion implantation on the first surface of the silicon carbide wafer.

[0041] Specifically, reference Figure 2 shows the silicon carbide wafer 200, the ion implantation layer, and the first surface 201, and the thickness of the ion implantation layer is greater than or equal to 500 nanometers.

[0042] Step 102, coat the first surface after ion implantation to form a coating layer.

[0043] Specifically, reference Figure 2 shows the coating layer 202, and the thickness of the coating layer is less than or equal to 1 micrometer.

[0044] Step 103, attach one side surface of the silicon carbide wafer with the coating layer to one side surface of the first wafer to obtain a bonded wafer.

[0045] Specifically, reference Figure 3 shows the bonded wafer. One side surface 301 of the first wafer 300 is bonded to the coating layer 202 of the silicon carbide wafer 200.

[0046] Step 104, perform annealing treatment on the bonded wafer.

[0047] Specifically, reference Figure 4Fix the bonded wafers using a high-temperature-resistant wafer clip and perform high-temperature annealing at a temperature above 1600 °C. Exemplarily, the high-temperature-resistant wafer clip can be made of high-temperature-resistant materials such as SiC and graphite.

[0048] Through the above steps 101-104, the silicon carbide wafer and the first wafer can be bonded to each other to form mutual protection during high-temperature annealing.

[0049] Optionally, after coating the first surface after ion implantation to form a coating layer, it includes:

[0050] Enhance the ion concentration on the surface of the silicon carbide wafer by laser irradiation.

[0051] Enhance the ion concentration on the surface of the silicon carbide wafer by laser irradiation before annealing activation to avoid the performance of the silicon carbide wafer being affected by the concentration decrease caused by annealing activation.

[0052] Optionally, the first wafer is a silicon carbide wafer, and one side surface of the first wafer is the side surface that has been ion implanted.

[0053] Specifically, the first wafer can be a silicon carbide wafer or other wafers.

[0054] Optionally, when bonding the side surface of the silicon carbide wafer with the coating layer to one side surface of the first wafer, it further includes:

[0055] Insert at least one second wafer between the coating layer of the silicon carbide wafer and the side surface of the first wafer that has been ion implanted;

[0056] Wherein, if there are more than one second wafer, the inserted second wafers are bonded to each other on the surface.

[0057] The surface of the second wafer opposite to the coating layer of the silicon carbide wafer is bonded to the coating layer of the silicon carbide wafer.

[0058] The surface of the second wafer opposite to the side surface of the first wafer that has been ion implanted is bonded to the side surface of the first wafer that has been ion implanted.

[0059] Specifically, referring to Figure 5 shows a schematic diagram of inserting the second wafer. In the figure, 501-50n are all second wafers. The material of the second wafer can be the same as that of the first wafer or the second wafer, or it can be a wafer of other materials. The second wafer may also have an ion implantation layer ( Figure 5 The ion implantation layer of the second wafer is not marked in the figure).

[0060] Exemplarily, referring to Figure 5, if n second wafers are inserted, these second wafers are attached to each other. After being attached to each other, the second wafers are respectively attached to the surface of the first wafer opposite to the ion implantation side surface, and the surface opposite to the second surface of the silicon carbide wafer of the second wafers attached to each other is attached to the second surface of the silicon carbide wafer, so that each surface between the silicon carbide wafer, the second wafer, and the first wafer is attached to each other to form mutual protection.

[0061] Optionally, coating the first surface after ion implantation to form a coating layer includes:

[0062] Coating with a first material, the first material containing the ion components implanted into the silicon carbide wafer.

[0063] Specifically, the first material containing the ion components implanted into the silicon carbide wafer can cause the coating to melt and precipitate the ion components implanted into the silicon carbide wafer during high-temperature annealing activation, which can further increase the ion doping concentration on the surface of the silicon carbide wafer.

[0064] Exemplarily, if aluminum ions are used to implant the silicon carbide wafer, the first material can be aluminum; if nitrogen ions are used to implant the silicon carbide wafer, the first material can be silicon nitride; if phosphorus ions are used to implant the silicon carbide wafer, the first material can be phosphosilicate glass.

[0065] Moreover, since the extraction of electrodes in device processes requires the combination of a heavily doped surface and a metal to form an ohmic contact, in the latter stage of ion implantation (first high energy and then low energy), low implantation energy (~25 eV) will be used to increase the surface doping concentration to above 1×1019 cm-3. However, due to the fact that the peak of the ion depth distribution in the implantation process cannot reach the SiC surface, there will be a certain concentration decrease on the implantation surface, which affects the effect of ohmic contact. Through the coating layer provided by the embodiments of the present application, the ion doping concentration on the surface of the silicon carbide wafer can be further enhanced during annealing activation.

[0066] Optionally, after annealing the attached silicon carbide wafer and the first wafer, it includes:

[0067] Removing the coating layer of the silicon carbide wafer.

[0068] Optionally, removing the coating layer of the silicon carbide wafer includes:

[0069] Removing the coating layer of the silicon carbide wafer by wet process.

[0070] Specifically, using a wet method to remove the coating layer of the silicon carbide wafer can ensure that the surface of the silicon carbide wafer is not damaged, remains flat and smooth, the ion concentration is not affected, and the silicon carbide wafer is not affected. Moreover, using a wet method to remove the coating does not require complex equipment, saves production costs, has a simple process, and improves production efficiency.

[0071] Exemplarily, if the coating is silicon nitride, hydrofluoric acid or other corresponding solutions are used for wet removal; if the coating is aluminum, phosphoric acid or other corresponding solutions are used for wet removal; if the coating is phosphosilicate glass, hydrofluoric acid or other corresponding solutions are used for wet removal.

[0072] On the other hand, an embodiment of the present application provides a silicon carbide wafer, which is prepared by using the annealing activation method of the silicon carbide wafer provided in any one of the embodiments of the present application.

[0073] Optionally, the silicon carbide wafer includes a device structure.

[0074] The silicon carbide device prepared by using the annealing activation method of the silicon carbide wafer provided in any one of the embodiments of the present application can increase the surface ion doping concentration, save production costs, has a simple process, and improves production efficiency.

[0075] It should be noted that in this article, the terms "include", "comprise" or any other variant thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements not only includes those elements, but also includes other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. Without further limitation, the element defined by the statement "including a..." does not exclude the existence of additional identical elements in the process, method, article or device including the element.

[0076] Obviously, the above embodiments are merely examples for clear illustration and not limitations on the implementation manners. For those of ordinary skill in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to enumerate all the implementation manners here. And the obvious changes or modifications derived therefrom are still within the protection scope of the present application.

Claims

1. An annealing activation method for a silicon carbide wafer, characterized in that, Including: Performing ion implantation on the first surface of a silicon carbide wafer; Coating the first surface after ion implantation to form a coating layer; Bonding the surface of the silicon carbide wafer having the coating layer to one surface of a first wafer to obtain a bonded wafer; Annealing the bonded wafer; The first wafer is a silicon carbide wafer, and one surface of the first wafer is the surface that has undergone ion implantation; The bonding of the surface of the silicon carbide wafer having the coating layer to one surface of the first wafer further includes: Inserting at least one second wafer between the coating layer of the silicon carbide wafer and the surface of the first wafer that has undergone ion implantation, and the second wafer has an ion implantation layer; Wherein, if there are more than one second wafer, the inserted second wafers are bonded to each other's surfaces; The surface of the second wafer opposite to the coating layer of the silicon carbide wafer is bonded to the coating layer of the silicon carbide wafer; The surface of the second wafer opposite to the surface of the first wafer that has undergone ion implantation is bonded to the surface of the first wafer that has undergone ion implantation; The coating the first surface after ion implantation to form a coating layer includes: Coating with a first material, and the first material contains the ion components implanted into the silicon carbide wafer.

2. The annealing activation method of the silicon carbide wafer according to claim 1, wherein After the coating the first surface after ion implantation to form a coating layer, it includes: Enhancing the ion concentration on the first surface of the silicon carbide wafer by laser irradiation.

3. The annealing activation method of the silicon carbide wafer according to claim 1, wherein After the annealing of the bonded wafer, it includes: Removing the coating layer of the silicon carbide wafer.

4. The annealing activation method of the silicon carbide wafer according to claim 3, characterized in that, The removing the coating layer of the silicon carbide wafer includes: Removing the coating layer of the silicon carbide wafer by wet process.

5. A silicon carbide wafer, characterized in that, Prepared by using the annealing activation method of the silicon carbide wafer according to any one of claims 1-4.

6. The silicon carbide wafer according to claim 5, characterized in that, The silicon carbide wafer has a device structure thereon.

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