Ion implantation method of silicon carbide device and silicon carbide device

Abstract

The invention provides an ion implantation method of a silicon carbide device and the silicon carbide device. The ion implantation method comprises the following steps: depositing a hard mask layer on the surface of a silicon carbide substrate; patterning the hard mask layer, wherein the pattern of the hard mask layer corresponds to a target ion implantation region; performing ion implantation on the silicon carbide substrate by taking the hard mask layer as an implantation mask, wherein an included angle between an implanted ion beam and the crystal axis direction of the silicon carbide substrate during ion implantation is 2-5 degrees; and removing the hard mask layer. According to the ion implantation method of the silicon carbide device, the included angle between the implanted ion beam and the crystal axis direction of the silicon carbide substrate is adjusted during ion implantation, so that the depth of ions implanted in the crystal axis direction of the silicon carbide substrate is prevented from being too large, and the uniformity of ion implantation in each region of the silicon carbide substrate is improved; therefore, the performance of each device on the silicon carbide substrate is ensured and the yield of the silicon carbide device is improved.

Description

Technical Field

[0001] The present invention relates to the technical field related to semiconductor devices, and in particular to an ion implantation method for a silicon carbide device and a silicon carbide device. Background Art

[0002] With the development of semiconductor technology, the characteristic size of semiconductor devices is getting smaller and smaller. Especially after the semiconductor process enters the deep submicron stage, different types of substrates are used in the device manufacturing process to achieve high integration and high performance devices. Compared with silicon, silicon carbide (SiC) has a wider bandgap, higher thermal conductivity, and extremely low intrinsic carriers under isothermal conditions, making it suitable for working under higher voltage, high current and high temperature conditions. Combining various excellent properties, silicon carbide substrates have great value and great potential in various fields.

[0003] Doping with impurities is a very important step in chip manufacturing. Almost all integrated circuits, LEDs, power devices, etc. require doping. For example, the electrical conductivity of silicon is very poor, and a small amount of impurities needs to be introduced into the intrinsic silicon to increase the number of mobile electrons or holes to improve its electrical properties so that silicon can meet the standards for semiconductor manufacturing. Diffusion and ion implantation are two common doping methods. However, compared with diffusion, ion implantation has many advantages and is the mainstream process in modern integrated circuit manufacturing. Since the diffusion coefficient of impurities in silicon carbide is very small, high-temperature implantation is usually used to increase the diffusion coefficient of impurity ions, which can reduce the damage to the lattice caused by ion bombardment and accurately control the implantation depth. However, there are still many problems in the high-temperature implantation process of silicon carbide materials. For example, the high-temperature implantation process will cause the warping of the silicon carbide wafer, resulting in uneven implantation of ions, which will affect the performance of the prepared silicon carbide device and reduce the yield of the silicon carbide device.

[0004] It should be noted that the information disclosed in the above background technology section is only used to enhance the understanding of the background of the present invention, and therefore may include information that does not constitute the prior art known to those skilled in the art. Summary of the invention

[0005] In view of the problems in the prior art, the purpose of the present invention is to provide an ion implantation method for a silicon carbide device and a silicon carbide device. The ion implantation method for the silicon carbide device adjusts the angle between the implanted ion beam and the crystal axis direction of the silicon carbide substrate during ion implantation, thereby avoiding excessive depth of implanted ions along the crystal axis direction of the silicon carbide substrate and improving the uniformity of ion implantation in various regions of the silicon carbide substrate.

[0006] Specifically, a first aspect of the present invention provides an ion implantation method for a silicon carbide device, characterized in that the ion implantation method comprises the following steps:

[0007] Providing a silicon carbide substrate, and depositing a hard mask layer on a surface of the silicon carbide substrate;

[0008] patterning the hard mask layer, wherein the pattern of the hard mask layer corresponds to the target ion implantation region;

[0009] Performing ion implantation on the silicon carbide substrate using the hard mask layer as an implantation mask, wherein the angle between the implantation ion beam and the crystal axis direction of the silicon carbide substrate during the ion implantation is 2° to 5°;

[0010] The hard mask layer is removed.

[0011] According to the first aspect of the present invention, the silicon carbide substrate has a surface crystal orientation of (0001).

[0012] According to the first aspect of the present invention, during ion implantation, the angle between the projection of the implanted ion beam on the silicon carbide substrate and the flat edge of the silicon carbide substrate is 30° to 50°.

[0013] According to the first aspect of the present invention, the implanted ions are aluminum ions, boron ions, nitrogen ions or phosphorus ions.

[0014] According to the first aspect of the present invention, the implantation temperature during ion implantation is 400°C to 600°C.

[0015] According to the first aspect of the present invention, the implanted ion energy during the ion implantation is 100 keV to 300 keV.

[0016] According to the first aspect of the present invention, the ion implantation dose is 1E 13 cm -3 -1E 15 cm -3 .

[0017] According to the first aspect of the present invention, the depth of ion implantation during ion implantation is 0.1 μm to 1.4 μm.

[0018] According to the first aspect of the present invention, the ion implantation method further comprises:

[0019] Treating the silicon carbide substrate with a heat treatment process to activate the implanted ions;

[0020] The heat treatment temperature is 1500° C. to 1900° C., and the time is 10 min to 30 min.

[0021] A second aspect of the present invention provides a silicon carbide device, the silicon carbide device comprising at least one ion implantation region, the ion implantation region being obtained by using the ion implantation method of the silicon carbide device.

[0022] The ion implantation method of the silicon carbide device of the present invention adjusts the angle between the implanted ion beam and the crystal axis direction of the silicon carbide substrate during ion implantation, thereby avoiding excessive depth of implanted ions along the crystal axis direction of the silicon carbide substrate, improving the uniformity of ion implantation in various regions of the silicon carbide substrate, thereby ensuring the performance of various devices on the silicon carbide substrate and improving the yield of the silicon carbide device. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The drawings herein are incorporated into the specification and constitute a part of the specification, showing embodiments consistent with the present application, and together with the specification, are used to explain the principles of the present application. By reading the detailed description of the non-limiting embodiments with reference to the following drawings, other features, purposes and advantages of the present invention will become more apparent. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can also be obtained based on these drawings without creative work. In addition, the drawings are only schematic illustrations of the present disclosure and are not necessarily drawn to scale. The same figure numbers in the figures represent the same or similar parts, and their repeated descriptions will be omitted. Some of the block diagrams shown in the drawings are functional entities and do not necessarily correspond to physically or logically independent entities.

[0024] Figure 1 A schematic flow chart of an ion implantation method for a silicon carbide device according to an embodiment of the present invention;

[0025] Figure 2 Schematic diagram of the process of step S300 of the ion implantation method for a silicon carbide device according to an embodiment of the present invention;

[0026] Figure 3 The implanted ion concentrations at different depths in the center and both side edges of the silicon carbide substrate obtained by the existing ion implantation method for silicon carbide devices; and

[0027] Figure 4 The implanted ion concentrations at different depths at the center and the edges of both sides are obtained by the ion implantation method of the silicon carbide device according to an embodiment of the present invention. DETAILED DESCRIPTION

[0028] Example embodiments will now be described more fully with reference to the accompanying drawings. However, example embodiments can be implemented in a variety of forms and should not be construed as limited to the examples set forth herein; rather, these embodiments are provided so that the disclosure will be more comprehensive and complete and to fully convey the concepts of the example embodiments to those skilled in the art. The described features, structures, or characteristics may be combined in any suitable manner in one or more embodiments.

[0029] In the description of this specification, the reference terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" and the like mean that the specific features, structures, materials or characteristics represented in conjunction with the embodiment or example are included in at least one embodiment or example of this specification. Moreover, the specific features, structures, materials or characteristics represented may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine different embodiments or examples and features of different embodiments or examples represented in this specification without contradiction.

[0030] Throughout the specification, when it is said that a device is "connected" to another device, this includes not only the case of "direct connection" but also the case of "indirect connection" by placing other elements therebetween. Terms indicating relative spaces such as "front", "rear", "upper", and "lower" may be used to more easily explain the relationship of a device illustrated in the accompanying drawings relative to another device. Such terms refer not only to the meanings indicated in the accompanying drawings, but also to other meanings or operations of the device in use. For example, if the device in the accompanying drawings is turned over, a device that was described as being "under" other devices is described as being "over" other devices. Therefore, the exemplary term "under" includes both upper and lower sides. The device can be rotated 90° or other angles, and the terms representing relative spaces are interpreted accordingly.

[0031] Although the terms first, second, etc. are used to represent various elements in some examples, these elements should not be limited by these terms. These terms are only used to distinguish one element from another element. For example, the first interface and the second interface, etc. are represented. Moreover, as used in this article, the singular forms "one", "one" and "the" are intended to also include plural forms, unless there is an opposite indication in the context. It should be further understood that the terms "comprising" and "including" indicate that there are the described features, steps, operations, elements, components, projects, kinds, and / or groups, but do not exclude the existence, occurrence or addition of one or more other features, steps, operations, elements, components, projects, kinds, and / or groups. The terms "or" and "and / or" used herein are interpreted as inclusive, or mean any one or any combination. Therefore, "A, B or C" or "A, B and / or C" means "any of the following: A; B; C; A and B; A and C; B and C; A, B and C". Only when the combination of elements, functions, steps or operations is inherently mutually exclusive in some way, will there be an exception to this definition.

[0032] Although not fully defined, all terms, including technical and scientific terms, used herein have the same meaning as those generally understood by those skilled in the art to which this specification belongs. Terms defined in commonly used dictionaries are additionally interpreted as having meanings consistent with the relevant technical literature and the current disclosure, and unless defined, shall not be overly interpreted as having an ideal or very formal meaning.

[0033] Ion implantation is a method of precisely introducing impurities into semiconductors. The desired impurities are first ionized and then accelerated in an electric field to form a concentrated ion beam. This beam of ions then hits the surface of a silicon wafer, where these high-energy particles enter the crystal lattice and collide with some silicon atoms, losing energy and eventually stopping at a certain depth, allowing the ions to penetrate and embed into the silicon wafer.

[0034] When ions are implanted into a solid, the ions collide with the atoms of the solid. If the solid is amorphous, the atoms that make up the solid are irregularly distributed in space. At this time, the collision between the ions and the atoms of the solid is random, and the size of the collision parameter P is a random parameter. If the solid is a crystal, the atoms are regularly arranged in space. When the ions are implanted along the main crystal axis of the crystal, they may have similar collisions with the lattice atoms (the collision parameter P is approximately equal). Each collision is related to each other. During each collision, the ion movement is deflected very little. When the ions pass near the same row of atoms in the lattice, they can penetrate deeper into the solid, which is the channeling phenomenon of ion implantation. This channeling effect is particularly obvious during ion implantation of silicon carbide substrates.

[0035] In order to overcome the above technical problems, the present invention provides an ion implantation method for a silicon carbide device and a silicon carbide device, the ion implantation method comprising the following steps: depositing a hard mask layer on the surface of the silicon carbide substrate; patterning the hard mask layer, wherein the pattern of the hard mask layer corresponds to a target ion implantation area; performing ion implantation on the silicon carbide substrate using the hard mask layer as an implantation mask, and the angle between the implanted ion beam and the crystal axis direction of the silicon carbide substrate during ion implantation is 2° to 5°; and removing the hard mask layer.

[0036] The ion implantation method of the silicon carbide device of the present invention adjusts the angle between the implanted ion beam and the crystal axis direction of the silicon carbide substrate during ion implantation, thereby avoiding excessive depth of implanted ions along the crystal axis direction of the silicon carbide substrate, improving the uniformity of ion implantation in various regions of the silicon carbide substrate, thereby ensuring the performance of various devices on the silicon carbide substrate and improving the yield of the silicon carbide device.

[0037] The ion implantation method of the silicon carbide device and the silicon carbide device of the present invention are further described below in conjunction with the accompanying drawings and specific embodiments. It can be understood that the various specific embodiments are not intended to limit the protection scope of the present invention. Figure 1 The present invention is a schematic flow chart of an ion implantation method for a silicon carbide device according to an embodiment of the present invention. Specifically, the ion implantation method comprises the following steps:

[0038] Step S100: Provide a silicon carbide substrate, and deposit a hard mask layer on the surface of the silicon carbide substrate; the silicon carbide substrate can be a single crystal silicon carbide substrate, or a silicon carbide substrate with an epitaxial layer. It should be pointed out that the present invention focuses on the relationship between the angle of ion (beam) implantation and the carbon surface crystal orientation of the silicon carbide substrate. The carbon surface crystal orientation of the silicon carbide substrate refers to the crystal orientation of the silicon carbide crystal on the surface of the wafer. The crystal orientation refers to the arrangement and directionality of atoms inside the crystal. On the carbon surface of the silicon carbide wafer, there are usually six main crystal orientations of silicon carbide crystals, namely (0001), (1-100), (11-20), (1-210), (2-110), and (10-13). These crystal orientations are different in the structure and physical properties of the lattice, and therefore have a very important influence on the preparation and application of silicon carbide wafers. The hard mask layer in step S100 may be a single layer or a multi-layer layer. For example, the hard mask layer may include a silicon dioxide layer and a silicon nitride layer, or include a silicon dioxide layer and a titanium nitride layer.

[0039] Step S200: patterning the hard mask layer. The most commonly used method for this step is to coat a photoresist layer on the surface of the hard mask layer and expose and develop the photoresist layer to obtain a patterned photoresist layer. The hard mask layer is etched using an etching process using the patterned photoresist layer as a mask. The etching process can be a dry etching process, such as reactive ion etching (RIE) process or plasma etching (PE) process, that is, the hard mask layer is patterned (Pattern Formation) to define the area where ion implantation is required, and the photoresist layer is removed to obtain a patterned hard mask layer, and the pattern of the hard mask layer corresponds to the target ion implantation area.

[0040] Step S300: Use the hard mask layer as an implantation mask to perform ion implantation on the silicon carbide substrate, and the angle between the implanted ion beam and the crystal axis direction of the silicon carbide substrate during ion implantation is 2° to 5°. As mentioned above, the crystal directions on the surface of the silicon carbide substrate include (0001), (1-100), (11-20), (1-210), (2-110), and (10-13). Accordingly, the crystal axis direction of the silicon carbide substrate here may be the above-mentioned crystal directions. Theoretically, since the implantation direction of the implanted ion beam is the normal direction of the wafer stage, the above-mentioned angle can be adjusted according to the relationship between the crystal direction of the silicon carbide substrate used and the normal of the wafer stage.

[0041] For example, taking a 4H-SiC substrate commonly used in SiC devices as an example, when the surface crystal orientation of the SiC substrate is <0001> When the angle between the implanted ion beam and the implanted ion beam is adjusted, the angle between the implanted ion beam and the implanted ion beam is more easily adjusted. Specifically, the ion implantation process of step S300 includes the following steps (see Figure 2 Flowchart of

[0042] Step S310: The electrons generated by the DC discharge of the ion source bombard the target molecules to generate positive ions and secondary electrons. The target can be determined according to the ions to be injected; when the injected ions are different, that is, the impurities introduced into the silicon carbide substrate by ion injection are different, the ion-implanted area forms different conductivity types. The injected ions can be aluminum ions or boron ions to form P-type doping, or nitrogen ions or phosphorus ions to form N-type doping.

[0043] Step S320: The positive ions are screened out as target injection ions by a mass analysis system;

[0044] Step S330: Accelerating the target injection ions through an accelerator to obtain an ion beam with target energy;

[0045] Step S340: the ion beam is focused by the quadruple lens and enters the ion implantation chamber;

[0046] Step S350: Load the silicon carbide substrate onto the wafer stage, rotate the wafer stage so that the angle between the ion beam and the crystal axis direction of the silicon carbide substrate is 2-5°; a silicon carbide substrate with a surface crystal orientation of (0001) is used as an example. At this time, the crystal axis direction of the silicon carbide substrate is the normal of the silicon carbide substrate, and the normal of the silicon carbide substrate coincides with the normal of the wafer stage. It is only necessary to control the angle between the focused ion beam and the vertical direction of the wafer stage to control the angle between the ion beam and the crystal axis direction of the silicon carbide substrate. The angle can be 2°, 3°, 4°, or 5°, etc. In one embodiment, it is also necessary to control the angle between the implanted ion beam and other crystal orientations of the silicon carbide substrate. Preferably, the angle between the projection of the implanted ion beam on the silicon carbide substrate and the flat edge of the silicon carbide substrate is 30°-50°, such as 30°, 40°, or 50°, etc. The flat edge of the silicon carbide substrate (wafer) is also called the positioning edge. The position and number of the flat edges of the wafer reflect the crystal orientation of the silicon carbide substrate. At the same time, the flat edge helps the equipment to accurately position and align the wafer during the manufacturing process, ensuring the accuracy and consistency of subsequent processing steps.

[0047] Step S360: The wafer stage moves to the implantation position to complete the ion implantation. The type of implanted ions, the concentration and depth of the implanted ions, etc. can be determined according to the type of silicon carbide device to be obtained and the performance to be achieved. At the same time, the acceleration voltage of the ion beam can be adjusted according to the concentration and depth of the implanted ions to be achieved. That is, the concentration and depth of the ion implantation can be accurately controlled by controlling the parameters of the ion implantation process. Preferably, the implanted ion energy during ion implantation is 100keV to 300keV, and the ion implantation dose during ion implantation is 1E 13 cm -3 -1E 15 cm -3 The depth of ion implantation is 0.1 μm to 1.4 μm. At the same time, since the diffusion coefficient of impurities in silicon carbide is very small, the diffusion rate of the implanted ions in the silicon carbide substrate can be increased by controlling the temperature during ion implantation. Preferably, the implantation temperature during ion implantation is 400° C. to 600° C.

[0048] Step S400: removing the hard mask layer.

[0049] In some other embodiments, the ion implantation method may further include:

[0050] Step S500: Treat the silicon carbide substrate with a heat treatment process to activate the implanted ions; in practice, it may also include removing a certain thickness of the silicon carbide substrate to remove the damaged portion of the surface of the silicon carbide substrate. Preferably, the temperature of the heat treatment is 1500°C to 1900°C, and the time is 10min to 30min. Treat the silicon carbide substrate with an ion implantation activation process. The high-temperature ion activation process temperature of the silicon carbide device can be 1500°C to 1900°C, and the process time can be 10min to 30min. The high-temperature process activates the implanted ions in each ion implantation area of ​​the silicon carbide substrate to improve the uniformity of ion dispersion. At the same time, the ion implantation process is to accelerate the impurity ions so that they can obtain a large kinetic energy and directly enter the silicon carbide substrate; but the above process may also generate some lattice defects in the silicon carbide substrate. Step S500 can eliminate some of the above lattice defects and reduce the warping of the silicon carbide substrate caused by the defects to a certain extent. In actual use, the specific parameters of the ion activation process can be further determined according to the different types of implanted ions, which will not be repeated here.

[0051] Existing data show that the depth of tunnel ion implantation along any of the [11-20] and

[0001] crystal directions of the silicon carbide substrate can reach 2 to 4 times the implantation depth of conventional random direction implantation or non-tunnel implantation. Figure 3 and Figure 4 The implanted ion concentrations at different depths in the center and both sides of the silicon carbide substrate obtained by the ion implantation method of the existing silicon carbide device (comparative example) and the ion implantation method of the silicon carbide device of one embodiment of the present invention are respectively, wherein the horizontal axis is the depth from the surface of the silicon carbide substrate, the vertical axis is the implanted ion concentration, and the watermark in the figure is the data export time, which has no effect on the technical effect to be displayed. Among them, the secondary ion mass spectrometry (SIMS) is used to test the comparative example and one embodiment of the present invention to obtain the ion implantation concentrations at different depths in the center and both sides of the edge of the silicon carbide substrate, and the depth at the maximum ion concentration is defined as the ion implantation depth. The results show that the ion implantation depths of the edge side, center and other side of the silicon carbide substrate obtained in the comparative example are different, and the difference in the ion implantation depth between the edges and the center on both sides is ~0.015μm, and the difference in the ion implantation depth between the edges on both sides is ~0.03μm. In an embodiment of the present invention, the ion implantation depth curves on one side of the edge, the center, and the other side of the edge of the silicon carbide substrate are basically overlapped, and the difference between the ion implantation depth on both sides of the edge and the ion implantation depth in the center is only ~0.002μm, that is, the ion implantation depth of the silicon carbide substrate obtained by the ion implantation method of the present invention is more uniform, and accordingly, the performance of the obtained silicon carbide device is more stable and the yield is higher.

[0052] The ion implantation method of the present invention selects a suitable ion implantation angle for ion implantation according to the crystal orientation of the silicon carbide substrate, obtains the required ion implantation concentration and depth, removes the high temperature resistant hard mask layer, and then removes a certain thickness of the silicon carbide substrate for subsequent ion activation process. Compared with the existing ion implantation process of silicon carbide substrates, the method of the present invention is used for large-scale mass production of ion implantation process of silicon carbide substrates, which can greatly reduce the surface damage of silicon carbide substrates, reduce the difficulty of annealing, improve the physical properties of the device, enhance the electrical properties of the device, and reduce the production cost.

[0053] The present invention also provides a silicon carbide device, the silicon carbide device includes at least one ion implantation region, and the ion implantation region is obtained by the ion implantation method of the silicon carbide device. For a silicon carbide device, such as a silicon carbide MOSFET device, there may be ion implantation regions with different conductivities, which can be achieved by repeating steps S100 to S400, except that the parameters of the ion implantation process and the implanted ion elements in step S300 are different due to the different conductivity types, ion implantation concentrations or depths of the ion implantation regions to be obtained.

[0054] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations of the present invention. A person skilled in the art may change, modify, replace and vary the above embodiments within the scope of the present invention.

[0055] The above contents are further detailed descriptions of the present invention in combination with specific preferred embodiments, and it cannot be determined that the specific implementation of the present invention is limited to these descriptions. For ordinary technicians in the technical field to which the present invention belongs, several simple deductions or substitutions can be made without departing from the concept of the present invention, which should be regarded as falling within the protection scope of the present invention.

Claims

1. A method for ion implantation of a silicon carbide device, characterized in that: The ion implantation method comprises the following steps: Providing a silicon carbide substrate, and depositing a hard mask layer on a surface of the silicon carbide substrate; patterning the hard mask layer, wherein the pattern of the hard mask layer corresponds to the target ion implantation region; Performing ion implantation on the silicon carbide substrate using the hard mask layer as an implantation mask, wherein the angle between the implantation ion beam and the crystal axis direction of the silicon carbide substrate during the ion implantation is 2° to 5°; The hard mask layer is removed.

2. The ion implantation method for a silicon carbide device according to claim 1, characterized in that: The silicon carbide substrate has a surface crystal orientation of (0001).

3. The ion implantation method for a silicon carbide device according to claim 1, characterized in that: During ion implantation, the included angle between the projection of the implanted ion beam on the silicon carbide substrate and the flat edge of the silicon carbide substrate is 30° to 50°.

4. The ion implantation method for a silicon carbide device according to claim 1, characterized in that: The implanted ions are aluminum ions, boron ions, nitrogen ions or phosphorus ions.

5. The ion implantation method for a silicon carbide device according to claim 1, characterized in that: The implantation temperature during ion implantation is 400°C to 600°C.

6. The ion implantation method for a silicon carbide device according to claim 1, characterized in that: The implantation ion energy during ion implantation is 100 keV to 300 keV.

7. The ion implantation method for a silicon carbide device according to claim 1, characterized in that: The ion implantation dose is 1E 13 cm -3 -1E 15 cm -3 .

8. The ion implantation method for a silicon carbide device according to claim 1, characterized in that: The depth of ion implantation during ion implantation is 0.1 μm to 1.4 μm.

9. The ion implantation method for a silicon carbide device according to claim 1, characterized in that: The ion implantation method further comprises: Treating the silicon carbide substrate with a heat treatment process to activate the implanted ions; The heat treatment temperature is 1500° C. to 1900° C., and the time is 10 min to 30 min.

10. A silicon carbide device, characterized in that: The silicon carbide device comprises at least one ion implantation region, and the ion implantation region is obtained by using the ion implantation method for a silicon carbide device according to any one of claims 1 to 9.

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