Parameter conversion method, silicon carbide wafer orientation method, and silicon carbide wafer implantation method

Abstract

The present application relates to the technical field of semiconductor manufacturing, and specifically discloses a parameter conversion method. The present application has the advantage that data measured by an XRD instrument can be converted into process parameters of an implanter by means of a standardized method, and can be directly used for production, thereby avoiding repeated calculation of translation matrixes for different brands and batches of wafers, and different brands and models of ion implanters.

Description

A parameter conversion method, a silicon carbide wafer orientation method, and a silicon carbide wafer implantation method. Technical Field

[0001] This application relates to the field of semiconductor manufacturing technology, and in particular to a parameter conversion method, a silicon carbide wafer orientation method, and a silicon carbide wafer implantation method. Background Technology

[0002] In current silicon carbide wafer fabrication processes, crystal orientation is typically performed before the dicing step. Specifically, this involves using the end face of the silicon carbide ingot as a reference plane to determine the designated crystal orientation for channeling implantation. During ingot dicing, the wafers are cut parallel to the end face to obtain multiple wafers. Theoretically, each wafer should have the same designated crystal orientation.

[0003] However, numerous processing errors exist in the wire dicing process, resulting in the diced wafer surface not being perfectly parallel to the ingot's end face. Consequently, the relative orientation of each diced wafer's surface to the silicon carbide ingot's end face is not entirely consistent, meaning the wafer surface does not match the specified crystal orientation measured during crystal plane orientation, introducing a certain degree of error. Furthermore, since silicon carbide ingots are very short, a single crystal plane orientation cannot guarantee the production of a large number of consistent wafers. The current precision of silicon carbide crystal plane orientation is insufficient to meet the production requirements of processes such as channel implantation. Therefore, a simple and feasible method for accurately orienting a single wafer to a specified crystal orientation is needed.

[0004] In addition, the crystal orientation angle data of a specified crystal orientation on a single wafer, after being measured, needs to be adopted by the ion implanter in a suitable manner / method so that the direction of the specified crystal orientation (or the normal direction of the specified crystal plane) is consistent with the direction of the ion implantation beam, so as to promote the occurrence of the channel implantation effect. Summary of the Invention

[0005] To address the aforementioned issues, this application proposes a parameter transformation method for calculating the crystal orientation angle required for a specified crystal orientation when implanting an ion beam into a wafer, comprising the following steps:

[0006] S1. Two points are determined on the surface of the wafer. The line connecting the two points is taken as the X-axis, the direction perpendicular to the X-axis on the surface of the wafer is taken as the Y-axis, and the normal of the wafer is taken as the Z-axis to determine the first coordinate system.

[0007] S2, the wafer is placed in the XRD machine, and the X-axis of the first coordinate system is made to coincide with the X-axis of the XRD machine's coordinate system, and the Y-axis of the first coordinate system is made to coincide with the Y-axis of the XRD machine's coordinate system.

[0008] S3. Based on the crystal orientation angle data measured by the XRD machine, calculate the α angle and β angle data of the specified crystal orientation of the wafer in the first coordinate system, wherein the α angle is the angle between the projection of the specified crystal orientation on the XY plane of the first coordinate system and the X axis, and the β angle is the angle between the specified crystal orientation and the Z axis of the first coordinate system.

[0009] S4, the wafer is placed in the ion implanter, and the X-axis of the first coordinate system is made to coincide with the X-axis of the coordinate system of the ion implanter, and the Y-axis of the first coordinate system is made to coincide with the Y-axis of the coordinate system of the ion implanter.

[0010] S5, Adjust the wafer so that the specified crystal orientation is consistent with the implantation direction of the ion implanter.

[0011] In the above method, in S1, the flat edge of the wafer is taken as the X-axis, and the direction that passes through the center of the wafer and is perpendicular to the X-axis is taken as the Y-axis.

[0012] In the above method, in S3, the crystal orientation angle of the specified crystal orientation is measured by the Laue method or the Debye method, and the α angle and β angle data are calculated in the first coordinate system.

[0013] In the above method, in S5, the implantation direction of the ion implanter is the Z-axis direction in the coordinate system of the ion implanter.

[0014] In the above method, the steps of adjusting the wafer include, in sequence:

[0015] S51, rotate the wafer such that the wafer rotates ±α degrees or 90±α degrees or 180±α degrees or 270±α degrees around the Z-axis in the coordinate system of the ion implanter.

[0016] S52, rotate the wafer such that the wafer rotates ±β degrees or 180±β degrees around the Y-axis or X-axis of the coordinate system of the ion implanter.

[0017] This application also proposes a method for oriented silicon carbide wafers, comprising the following steps:

[0018] Silicon carbide ingots are cut to obtain multiple wafers;

[0019] Using the aforementioned method, the angular expression of the specified crystal orientation of each wafer in the first coordinate system is obtained.

[0020] This application also proposes a silicon carbide wafer implantation method, characterized by comprising the following steps:

[0021] Silicon carbide ingots are cut to obtain multiple wafers;

[0022] One of the wafers is placed into an ion implanter such that the normal Z-axis of the wafer is parallel to the Z-axis of the ion implanter.

[0023] Using the aforementioned method, the wafer is adjusted so that the specified crystal orientation of the wafer coincides with the Z-axis of the ion implanter coordinate system;

[0024] The ion implanter is started, and an ion beam is implanted into a wafer along the Z-axis of the ion implanter coordinate system.

[0025] Compared with existing technologies, this application: 1) performs individual crystal plane orientation on each wafer after dicing, which improves the accuracy of orientation and avoids potential errors introduced during dicing after ingot orientation in existing technologies; 2) by establishing a first coordinate system on the wafer surface, a standard format of data is established between two different coordinate systems (e.g., XRD machine and ion implanter) to transmit data for a specified crystal orientation, thereby prompting ions to be implanted according to the specified crystal orientation and generating a channel effect. For wafer ion implantation processes, the application of this standard format of data can be easily converted into process parameters for the implanter, significantly improving the efficiency of the implantation process. Attached Figure Description

[0026] Figure 1 shows the definitions of angles α and β in the first coordinate system;

[0027] Figure 2 shows a flowchart of a parameter conversion method proposed according to some embodiments of the present invention;

[0028] Figure 3 shows a step-by-step schematic diagram of rotating a wafer in an implanter according to some embodiments of the present invention. Detailed Implementation

[0029] The following specific embodiments illustrate the implementation of this application. Those skilled in the art can easily understand other advantages and effects of this application from the content disclosed in this specification. Although the description of this application will be presented in conjunction with preferred embodiments, this does not mean that the features of this invention are limited to this embodiment. On the contrary, the purpose of describing the invention in conjunction with embodiments is to cover other options or modifications that may be derived based on the claims of this application. To provide a thorough understanding of this application, many specific details will be included in the following description. This application may also be implemented without using these details. Furthermore, to avoid confusion or obscuring the focus of this application, some specific details will be omitted in the description. It should be noted that, unless otherwise specified, the embodiments and features in the embodiments of this application can be combined with each other.

[0030] It should be noted that in this specification, similar reference numerals and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures, and is assumed to be the same definition.

[0031] To make the objectives, technical solutions, and advantages of this application clearer, the embodiments of this application will be described in further detail below with reference to the accompanying drawings.

[0032] As is well known, when performing ion implantation on a wafer, it is usually desirable to find a crystal orientation that can produce a channel effect. Ions implanted along this specified crystal orientation can penetrate to a deeper distance in the wafer, which is called the "channel effect of ion implantation", thus helping to manufacture chips with better performance.

[0033] The specified crystal orientation mentioned above can be determined using the principle of X-ray diffraction. For example, it can be measured using the Laue method, Debye method, or diffractometer method. In industrial production, diffractometer methods, such as XRD machines (X-ray Diffraction Analyzers), are more commonly used. However, while existing XRD machines can be used to measure crystal orientation, they are mostly used to characterize the existence of that orientation. Furthermore, different models of XRD machines use their own defined coordinate systems to characterize the orientation of the specified crystal orientation within those coordinate systems. The coordinate systems used by the ion implanter in subsequent steps are usually different from those of the XRD machine. Therefore, there is a transformation matrix between an XRD machine and an ion implanter, meaning that the parameters output by the XRD machine cannot be directly applied to the process parameters of the ion implanter.

[0034] To change the current industry practice of focusing only on the magnitude of a specified crystal orientation angle in XRD machine output, while paying less attention to the direction of its vector (because the direction of the vector is determined by each defined coordinate system), this application attempts to standardize the definition of the vector for a specified crystal orientation measured by different XRD machines. This vector is characterized by defining a first coordinate system and making its X-axis parallel to a predefined reference line (e.g., a flat edge of the wafer) on the wafer surface. This predefined reference line serves as a common reference line for both the ion implanter and the XRD machine, enabling the vector of the specified crystal orientation measured by the XRD machine to be deflected in the ion implanter by the α and β angles defined in this application, making it parallel to the incident direction of the ion implanter. In other words, by using the flat edge of the wafer, a transformation is established between the coordinate system on the wafer and the coordinate system on the ion implanter, thereby aligning the specified crystal orientation of the wafer with the beam injection direction of the implanter and achieving the channeling effect of ion implantation.

[0035] The parameter conversion method proposed in this application attempts to standardize the parameters output by different XRD machines, so that the azimuth data obtained from the XRD machine can be directly applied to the ion implanter as the process parameters of the ion implanter.

[0036] As shown in Figure 1, this application first proposes the definitions of angles α and β in a first coordinate system. The first coordinate system uses the wafer plane as the XY plane (as shown on the left side of Figure 1) and the wafer normal as the Z-axis (as shown on the right side of Figure 1). The X-axis can be the line connecting any two points on the wafer surface, and the Y-axis is the direction perpendicular to the X-axis on the wafer surface; preferably, the intersection of the Y-axis and X-axis is the center of the wafer. Furthermore, for wafers with a flat edge, their X-axis is defined as parallel to this flat edge, as shown on the left side of Figure 1. Using a physically existing wafer flat edge as the reference for the X-axis is more convenient as a common reference structure for positioning when placing the wafer into both the XRD machine and the ion implanter, facilitating positioning. Conversely, when using the line connecting any two points on the wafer surface as the X-axis, the position of the X-axis needs to be additionally marked or recorded.

[0037] Let's continue with Figure 1. The green sphere on the left is a schematic diagram of a sphere formed with the origin of the first coordinate system as its center and the wafer as its equatorial plane. Assuming that the line OA connecting point A on the sphere and the origin is the direction of the specified crystal orientation, the angle between its projection onto the equatorial plane (i.e., the wafer surface) and the X-axis can be defined as angle α (as shown by the angle between the dashed line and the negative half-axis of the X-axis in the left figure of Figure 1), and the angle between the line OA and the Z-axis can be defined as angle β.

[0038] The inventive concept of this application is that, regardless of the method used to measure the crystal orientation, it is converted into the α and β angles in the aforementioned first coordinate system, thereby unifying the data format. That is, whether the Laue method, the Debye method, or an XRD machine is used, after the crystal orientation measurement is completed, the crystal orientation angle data is converted into the α and β angles in the first coordinate system. Thus, when the wafer enters the ion implantation process, the α and β angles can be directly or through simple arithmetic conversion and input into the ion implanter as process parameters.

[0039] To this end, this application proposes a parameter conversion method for calculating the crystal orientation angle required for implanting an ion beam into a wafer. This method allows for the simple and accurate transfer of crystal orientation angle data between the two process steps of crystal orientation measurement and ion implantation, thereby achieving the channeling effect of ion implantation.

[0040] Figure 2 illustrates the flowchart of the parameter conversion method proposed in this application. As shown, the parameter conversion method includes the following steps:

[0041] S1. Determine two points on the wafer surface, using the line connecting these two points as the X-axis, the direction perpendicular to the X-axis on the wafer surface as the Y-axis, and the normal to the wafer as the Z-axis to establish a first coordinate system. Preferably, for wafers with a flat edge, this flat edge is selected as the reference for the X-axis, making the X-axis parallel to the flat edge (as shown on the left side of Figure 1). Since flat edges exist in most wafers, it is not necessary to specify two additional points to connect them into a straight line, thus omitting one operation. Furthermore, because the wafer flat edge physically exists, it is relatively easy to find this reference object (wafer flat edge) when both the XRD machine and the ion implanter need to locate it.

[0042] S2, place the wafer into the XRD machine, and align the X-axis of the first coordinate system with the X-axis of the XRD machine's coordinate system, and align the Y-axis of the first coordinate system with the Y-axis of the XRD machine's coordinate system. Due to the diversity of XRD machine coordinates, the three-dimensional coordinate system of the XRD machine may differ from the first coordinate system by 90°, 180°, or 270°. When placing the first coordinate system (wafer) into the XRD machine's coordinate system, adjustments need to be made according to the actual situation, and the difference in angle needs to be recorded.

[0043] S3. Start the XRD machine to perform crystal orientation measurement, and based on the crystal orientation angle data measured by the XRD machine, calculate the α angle and β angle data of the specified crystal orientation of the wafer in the first coordinate system. The α angle is the angle between the projection of the specified crystal orientation onto the XY plane of the first coordinate system (i.e., the equatorial plane of the sphere in Figure 1) and the X-axis, and the β angle is the angle between the specified crystal orientation and the Z-axis of the first coordinate system. To obtain a good channeling effect, the specified crystal phase can be a phase with a more pronounced channeling effect.

[0044] S4, place the wafer into the ion implanter, and align the X-axis of the first coordinate system with the X-axis of the ion implanter's coordinate system, and align the Y-axis of the first coordinate system with the Y-axis of the ion implanter's coordinate system. Similar to S2, when placing the first coordinate system (wafer) into the ion implanter's coordinate system, adjustments need to be made according to the actual situation, and the α angle data needs to be corrected based on the difference in angle value.

[0045] S5. Adjust the wafer to align the specified crystal orientation with the implantation direction of the ion implanter. Generally, the implantation direction of the ion implanter is the Z-axis direction (including positive and negative directions) of the ion implanter's coordinate system. In other words, the specified crystal orientation measured by the XRD machine must be adjusted to match the Z-axis of the ion implanter's coordinate system. Alternatively, this can be considered as adjusting the implantation angle of the ion implanter's implantation components; the difference is that its rotation direction is opposite to that used when adjusting the wafer.

[0046] Specifically, wafer adjustment involves two steps: first, aligning the projection of the specified crystal orientation onto the XY plane with the X or Y axis of the ion implanter; then, aligning the specified crystal orientation with the Z axis of the ion implanter's coordinate system. Figure 3 illustrates the step-by-step process of rotating the wafer in the ion implanter. As shown, the specific steps include:

[0047] S51, rotate the wafer such that the wafer rotates ±α degrees or 90±α degrees 180±α degrees or 270±α degrees around the Z-axis in the coordinate system of the ion implanter, as shown on the left side of Figure 3.

[0048] S52, rotate the wafer such that the wafer rotates ±β degrees or 180±β degrees around the Y-axis or X-axis of the coordinate system of the ion implanter, as shown on the right side of Figure 3.

[0049] The following example, using the Axcelis ion implanter, illustrates this method.

[0050] First, the NX0215-02-EV type wafer was placed on the stage of the XRD machine, ensuring that the flat edge of the wafer was parallel to the X-axis of the XRD coordinate system. Further testing was conducted to obtain the angle of a specific crystal orientation, resulting in α = 1.191° and β = 4.035°.

[0051] Then, assuming there is a fixed 270° difference between the coordinate system of the ion implanter and the XY plane of the first coordinate system, the Twist parameter (corresponding to the α angle) and Tilt parameter (corresponding to the β angle) of the ion implanter for the NX0215-02-EV wafer are Twist = (270 + 1.191) = 271.191° and Tilt = 4°, respectively. The adjusted Twist parameter and Tilt parameter are input into the ion implanter, and the stage is adjusted according to α = 271.191° and β = 4°, so that the normal Z-axis of the wafer is parallel to the Z-axis of the ion implanter, and then the wafer is implanted.

[0052] The above embodiments successfully realize the channel implantation of crystals directly on the ion implanter after crystal orientation is determined by XRD, which simplifies the process steps and can be applied to the individual orientation of each wafer, and channel implantation can be achieved on each wafer.

[0053] It should be noted that numerous specific details are provided in the specification provided in this application. However, it will be understood that embodiments of this application may be implemented without some or all of these specific details. In some instances, well-known methods, structures, and techniques have not been shown in detail so as not to obscure the understanding of this specification.

[0054] Similarly, for the sake of brevity and to aid in understanding one or more of the various inventive aspects, in the above description of exemplary embodiments of this application, various features of this application are sometimes grouped together in a single embodiment, figure, or description thereof. However, this method of disclosure should not be construed as reflecting an intention that the claimed application requires more features than expressly recited in each claim. Rather, as reflected in the claims, inventive aspects lie in fewer than all features of a single foregoing disclosed embodiment. Therefore, the claims following the detailed description are hereby expressly incorporated into that detailed description, wherein each claim itself is a separate embodiment of this application.

[0055] Those skilled in the art will understand that modules in the device of the embodiments can be adaptively changed and placed in one or more devices different from that embodiment. Modules, units, or components in the embodiments can be combined into a single module, unit, or component, and further, they can be divided into multiple sub-modules, sub-units, or sub-components. Except where at least some of such features and / or processes or units are mutually exclusive, any combination can be used to combine all features disclosed in this specification (including the accompanying claims, abstract, and drawings) and all processes or units of any method or device so disclosed. Unless expressly stated otherwise, each feature disclosed in this specification (including the accompanying claims, abstract, and drawings) may be replaced by an alternative feature serving the same, equivalent, or similar purpose.

[0056] Furthermore, those skilled in the art should understand that although some embodiments described herein include certain features but not others included in other embodiments, combinations of features from different embodiments are intended to be within the scope of this application and form different embodiments. For example, in the claims, any one of the claimed embodiments can be used in any combination.

Claims

1. A parameter conversion method, characterized in that, The crystal orientation angle required for implanting an ion beam into a wafer is calculated using the following steps: S1. Two points are determined on the surface of the wafer. The line connecting the two points is taken as the X-axis, the direction perpendicular to the X-axis on the surface of the wafer is taken as the Y-axis, and the normal of the wafer is taken as the Z-axis to determine the first coordinate system. S2, the wafer is placed in the XRD machine, and the X-axis of the first coordinate system is made to coincide with the X-axis of the XRD machine's coordinate system, and the Y-axis of the first coordinate system is made to coincide with the Y-axis of the XRD machine's coordinate system. S3. Based on the crystal orientation angle data measured by the XRD machine, calculate the α angle and β angle data of the specified crystal orientation of the wafer in the first coordinate system. The α angle is the angle between the projection of the specified crystal orientation on the XY plane of the first coordinate system and the X axis, and the β angle is the angle between the specified crystal orientation and the Z axis of the first coordinate system. S4, the wafer is placed in the ion implanter, and the X-axis of the first coordinate system is made to coincide with the X-axis of the coordinate system of the ion implanter, and the Y-axis of the first coordinate system is made to coincide with the Y-axis of the coordinate system of the ion implanter. S5, Adjust the wafer so that the specified crystal orientation is consistent with the implantation direction of the ion implanter.

2. The method as described in claim 1, characterized in that, In S1, the flat edge of the wafer is taken as the X-axis, and the direction that passes through the center of the wafer and is perpendicular to the X-axis is taken as the Y-axis.

3. The method as described in claim 1 or 2, characterized in that, In S3, the crystal orientation angle of the specified crystal orientation is measured using the Laue method or the Debye method, and the α and β angle data are calculated in the first coordinate system.

4. The method as described in claim 1 or 2, characterized in that, In S5, the implantation direction of the ion implanter is the Z-axis direction in the coordinate system of the ion implanter.

5. The method as described in claim 4, characterized in that, The steps for adjusting the wafer include, in sequence: S51, rotate the wafer such that the wafer rotates ±α degrees or 90±α degrees or 180±α degrees or 270±α degrees around the Z-axis in the coordinate system of the ion implanter. S52, rotate the wafer such that the wafer rotates ±β degrees or 180±β degrees around the Y-axis or X-axis of the coordinate system of the ion implanter.

6. A method for oriented silicon carbide wafers, characterized in that, Includes the following steps: Silicon carbide ingots are cut to obtain multiple wafers; Using the method described in any one of claims 1-5, the angular expression of a specified crystal orientation of each of the wafers in the first coordinate system is obtained.

7. A silicon carbide wafer implantation method, characterized in that, Includes the following steps: Silicon carbide ingots are cut to obtain multiple wafers; One of the wafers is placed into an ion implanter such that the normal Z-axis of the wafer is parallel to the Z-axis of the ion implanter; Using the method described in any one of claims 1-5, the wafer is adjusted so that the specified crystal orientation of the wafer coincides with the Z-axis of the ion implanter coordinate system; The ion implanter is started, and an ion beam is implanted into a wafer along the Z-axis of the ion implanter coordinate system.

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