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

Abstract

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

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of semiconductor manufacturing, and in particular to a parameter conversion method, a silicon carbide wafer orientation method and a silicon carbide wafer implantation method. BACKGROUND

[0002] In the prior art, before the cutting step, the crystal face orientation work is usually performed. Specifically, the specified crystal direction for channeling implantation is determined by taking the end face of the silicon carbide ingot as the reference plane. When cutting the ingot, the ingot is cut parallel to the end face of the ingot to obtain multiple wafers. In theory, the specified crystal direction of each wafer is the same.

[0003] However, there are many processing errors in the in-line cutting process, so that the surface of the cut wafer is not completely parallel to the end face of the ingot, and thus the relative direction of the surface of each wafer cut and the end face of the silicon carbide ingot is not completely consistent, that is, the specified crystal direction measured when the crystal face is oriented is not consistent, and there is a certain error. In addition, the silicon carbide ingot is very short, and a single crystal face orientation cannot ensure the output of a large number of consistent wafers. In view of the existing silicon carbide crystal face orientation accuracy, it cannot meet the production requirements of channeling implantation and other processes, so a simple and feasible specified crystal direction orientation method for a single wafer is needed.

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

[0005] In order to solve the above problems, the present application provides a parameter conversion method for calculating the crystal direction angle of the specified crystal direction required when implanting an ion beam into a wafer, comprising the following steps:

[0006] S1, determining two points on the surface of the wafer, taking the connecting line of the two points as the X axis, and taking the direction perpendicular to the X axis on the surface of the wafer as the Y axis, and determining the first coordinate system with the normal direction of the wafer as the Z axis;

[0007] S2, placing the wafer into the XRD machine, and making the X axis of the first coordinate system coincide with the X axis in the coordinate system of the XRD machine, and making the Y axis of the first coordinate system coincide with the Y axis in the coordinate system of the XRD machine;

[0008] S3, based on the crystal direction angle data measured by the XRD machine, converting the alpha angle and beta angle data of the specified crystal direction of the wafer in the first coordinate system, wherein the alpha angle is the included angle between the projection of the specified crystal direction on the XY plane of the first coordinate system and the X axis, and the beta angle is the included angle between the specified crystal direction and the Z axis of the first coordinate system;

[0009] S4, placing the wafer into the ion implanter, and aligning the X axis of the first coordinate system with the X axis in the coordinate system of the ion implanter, and aligning the Y axis of the first coordinate system with the Y axis in the coordinate system of the ion implanter;

[0010] S5, adjusting the wafer so that the specified crystal direction 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 perpendicular to the X axis through the center of the wafer is taken as the Y axis.

[0012] In the above method, in S3, the crystal direction angle of the specified crystal direction is measured by Laue method or Debye method, and the alpha angle and beta angle data are converted 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 step of adjusting the wafer comprises the following steps in sequence:

[0015] S51, rotating the wafer so 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, rotating the wafer so that the wafer rotates ±β degrees or 180±β degrees around the Y axis or the X axis of the coordinate system of the ion implanter.

[0017] The present application also proposes a method for orienting a silicon carbide wafer, comprising the following steps:

[0018] Cutting a silicon carbide ingot to obtain a plurality of wafers;

[0019] Using the above method, the angle expression of the specified crystal direction of each wafer in the first coordinate system is obtained respectively.

[0020] The present application also proposes a method for implanting a silicon carbide wafer, characterized by comprising the following steps:

[0021] Cutting a silicon carbide ingot to obtain a plurality of wafers;

[0022] putting a piece of the wafer into an ion implanter so that the normal Z axis of the wafer is parallel to the Z axis of the ion implanter;

[0023] adjusting the piece of wafer so that the specified crystal orientation of the piece of wafer coincides with the Z axis of the ion implanter coordinate system by using the method described above;

[0024] starting the ion implanter to implant an ion beam along the Z axis of the ion implanter coordinate system to the piece of wafer.

[0025] Compared with the prior art, the present application has the following advantages: 1) the crystal face orientation work is performed on each piece of wafer after cutting, which can improve the accuracy of orientation and avoid the possible error introduced when the ingot is cut after orientation in the prior art; 2) by establishing the first coordinate system on the wafer surface, the standard format data is established between two different coordinate systems (for example, the XRD machine and the ion implanter) to transfer the specified crystal orientation data, so as to make the ion implantation according to the specified crystal orientation and produce the channel effect. For the ion implantation process of the wafer, the standard format data can be easily converted into the process parameters of the ion implanter, which can significantly improve the efficiency of the implantation process. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1 the definition of the α angle and the β angle in the first coordinate system is shown;

[0027] Figure 2 a flow chart of the parameter conversion method according to some embodiments of the present application is shown;

[0028] Figure 3 a step-by-step schematic diagram of rotating the wafer in the ion implanter according to some embodiments of the present application is shown. DETAILED DESCRIPTION

[0029] The present application will be described by specific embodiments, and those skilled in the art can easily understand other advantages and effects of the present application from the disclosure. Although the description of the present application will be introduced in combination with the preferred embodiments, it does not mean that the features of the present application are limited to the embodiments. On the contrary, the purpose of introducing the present application in combination with the embodiments is to cover other options or modifications that can be extended based on the claims of the present application. In order to provide a deep understanding of the present application, many specific details will be included in the following description. The present application can also be implemented without using these details. In addition, in order to avoid confusion or obscure the focus of the present application, some specific details will be omitted in the description. It should be noted that the embodiments in the present application and the features in the embodiments can be combined with each other without conflict.

[0030] It should be noted that in the present specification, similar reference numbers and letters represent similar items in the following drawings, and therefore, once an item is defined in one drawing, it need not be further defined and explained in subsequent drawings, and the same definition applies.

[0031] In order to make the purpose, technical solutions and advantages of the present application clearer, the embodiments of the present application will be further described in detail below with reference to the drawings.

[0032] It is well known that when ion implantation is performed on a wafer, it is usually desirable to find a specified crystal orientation along which the implanted ions can penetrate to a deeper distance in the wafer, i.e. the channeling effect of ion implantation, so as to help manufacture a chip with better performance.

[0033] The specified crystal orientation described above can be measured by means of the diffraction principle of X-rays. For example, it can be measured by the Laue method or the Debye method or the diffractometer method. In industrial production, the diffractometer method is more commonly used, such as XRD machines (X-Ray Diffraction Analyzer) to measure. However, although the existing XRD machines can be used to measure the crystal orientation, on the one hand, they are mostly used to characterize the existence of the crystal orientation, and on the other hand, different models of XRD machines use their own defined coordinate systems to characterize the orientation of the specified crystal orientation in the coordinate system, and the coordinate system used by the ion implanter used in the subsequent steps is usually not consistent with the coordinate system of the XRD machine. Therefore, there is a conversion matrix between an XRD machine of one model and an ion implanter of one model, so the parameters output by the XRD machine cannot be directly applied as the process parameters of the ion implanter, i.e. the parameters output by the XRD machine cannot be directly applied to the production of the ion implanter.

[0034] In order to change the industry habit of only paying attention to the size of the angle of the specified crystal orientation output by the XRD machine, and not paying much attention to the direction of the vector (because the direction of the vector is determined by the respective defined coordinate system), the present application attempts to standardize the definition of the vector of the specified crystal orientation measured by different XRD machines. By defining a first coordinate system and making the X-axis of the first coordinate system parallel to a pre-defined reference straight line (such as the flat edge of the wafer) on the wafer surface, the vector is characterized, and by using the pre-defined reference straight line as the common reference straight line of the ion implanter and the XRD machine, the vector of the specified crystal orientation measured by the XRD machine is deflected by the α angle and the β angle defined by the present application in the ion implanter, so as to be parallel to the incident direction of the ion implanter, i.e. by means of the flat edge of the wafer, a conversion between the coordinate system on the wafer and the coordinate system on the ion implanter is established, so as to achieve the alignment of the specified crystal orientation of the wafer with the beam incident direction of the ion implanter, and to achieve the channeling effect of ion implantation.

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

[0036] As shown in Figure 1 , the present application first proposes the definitions of the α angle and the β angle in a first coordinate system. The first coordinate system is a coordinate system with the wafer plane as the XY plane (as shown in Figure 1 on the left side) and the normal of the wafer as the Z axis (as shown in Figure 1 on the right side). Among them, the X axis can be the connecting line of any two points on the wafer surface, and the Y axis is the direction perpendicular to the X axis on the wafer surface, and preferably the intersection of the X axis and the Y axis is the center of the wafer. Further, for some wafers that have a flat edge, the X axis is defined to be parallel to the flat edge, i.e. as shown in Figure 1 on the left side. Selecting the physically existing flat edge of the wafer as the reference of the X axis makes it more convenient to use the wafer as a common reference structure for positioning when the wafer is placed into the XRD machine and the ion implanter, respectively, facilitating positioning. Conversely, when the connecting line of any two points on the wafer surface is used as the X axis, the position of the X axis needs to be additionally marked or recorded.

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

[0038] The inventive idea of the present application is that no matter what method is used to measure the crystal orientation, it will be converted into the α angle and the β angle in the aforementioned first coordinate system, thereby unifying the data format, i.e. no matter whether the Laue method or the Debye method is used or whether the XRD machine is used, when the crystal orientation measurement is completed, the crystal orientation angle data will be converted into the α angle and the β angle of the first coordinate system, so that when the wafer enters the process step of ion implantation, the α angle and the β angle can be directly input into the ion implanter as process parameters, or can be input into the ion implanter as process parameters through simple arithmetic conversion.

[0039] For this purpose, the present application proposes a parameter conversion method for calculating the crystal orientation angle of the specified crystal orientation when implanting an ion beam into a wafer. That is, to simply and accurately transfer the crystal orientation angle data between the two process steps of crystal orientation measurement and ion implantation, thereby realizing the channeling effect of ion implantation.

[0040] Figure 2 The flowchart of the parameter conversion method proposed in the present application is specifically shown. As shown in the figure, the parameter conversion method comprises the following steps:​

[0041] S1, two points are determined on the wafer surface, the line connecting the two points is the X axis, and the direction perpendicular to the X axis on the wafer surface is the Y axis, and the normal direction of the wafer is the Z axis to determine the first coordinate system. Preferably, for some wafers with a flat edge, the flat edge is selected as the reference of the X axis, so that the X axis is parallel to the flat edge (such as Figure 1 The left side shows). Since the flat edge exists in most wafers, it is not necessary to additionally specify two points to connect into a straight line, and one operation can be omitted. Moreover, since the wafer flat edge physically exists, when the XRD machine or the ion implanter needs to be positioned, the reference (wafer flat edge) can be conveniently found.

[0042] S2, the wafer is placed into the XRD machine, and the X axis of the first coordinate system is coincided with the X axis in the coordinate system of the XRD machine, and the Y axis of the first coordinate system is coincided with the Y axis in the coordinate system of the XRD machine. Due to the diversity of the XRD machine coordinates, the three-dimensional coordinate system of the XRD machine and the first coordinate system can be different by 90°, 180° or 270°. When the first coordinate system (wafer) is placed into the coordinate system of the XRD machine, it needs to be adjusted according to the actual situation, and the angle difference needs to be recorded.

[0043] S3, the XRD machine is started to measure the crystal direction, and based on the crystal direction angle data measured by the XRD machine, the α angle and β angle data of the specified crystal direction of the wafer in the first coordinate system are converted, wherein the α angle is the included angle between the projection of the specified crystal direction on the XY plane (i.e. Figure 1 the equatorial plane of the middle sphere) of the first coordinate system and the X axis, and the β angle is the included angle between the specified crystal direction and the Z axis of the first coordinate system. In order to obtain a good channel effect, the specified crystal phase can be a crystal phase with a more obvious channel effect.

[0044] S4, the wafer is placed into the ion implanter, and the X axis of the first coordinate system is coincided with the X axis in the coordinate system of the ion implanter, and the Y axis of the first coordinate system is coincided with the Y axis in the coordinate system of the ion implanter. Similar to S2, when the first coordinate system (wafer) is placed into the coordinate system of the ion implanter, it needs to be adjusted according to the actual situation, and the data of the α angle is corrected according to the angle difference.

[0045] S5, the wafer is adjusted so that the specified crystal direction is consistent with the injection direction of the ion implanter. Generally, the injection direction of the ion implanter is the Z axis direction (including positive and negative directions) of the coordinate system of the ion implanter. That is, the specified crystal direction measured by the XRD machine is adjusted to a direction consistent with the Z axis of the coordinate system of the ion implanter. In another aspect, it can also be considered that the injection angle of the injection component of the ion implanter is adjusted, and the difference is that the rotation direction is opposite to the rotation direction when the wafer is adjusted.

[0046] Specifically, the adjustment of the wafer is divided into two steps. First, the projection of the specified crystal orientation on the XY plane is made to coincide with the X axis or the Y axis of the ion implanter. Then, the specified crystal orientation is made to coincide with the Z axis of the coordinate system of the ion implanter. Figure 3 More specifically, a step-by-step diagram of rotating the wafer in the ion implanter is shown. As shown, it specifically includes:

[0047] S51, rotating the wafer so that the wafer is rotated ±α degrees or 90±α degrees, 180±α degrees or 270±α degrees around the Z axis of the coordinate system of the ion implanter, as shown in the left side of FIG. 1. Figure 3

[0048] S52, rotating the wafer so that the wafer is rotated ±β degrees or 180±β degrees around the Y axis or the X axis of the coordinate system of the ion implanter, as shown in the right side of FIG. 1. Figure 3

[0049] Next, an example is taken to illustrate this method by taking the Axcelis type ion implanter as an example.

[0050] First, the NX0215-02-EV wafer is placed on the stage of the XRD machine, and it is ensured that the flat side of the wafer is parallel to the X axis of the XRD coordinate system. Further testing obtains the angles of the specific crystal orientation, and α=1.191° and β=4.035° are obtained.

[0051] Then, assuming that there is a fixed difference of 270° 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 the Tilt parameter (corresponding to the β angle) of the ion implanter corresponding to 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, the stage is adjusted according to α=271.191° and β=4°, and the normal Z axis of the wafer is made parallel to the Z axis of the ion implanter, and then the wafer is implanted.

[0052] The above embodiment successfully realizes the channel implantation of the crystal on the ion implanter after the crystal orientation of the crystal is positioned by the XRD, simplifies the process steps, and can be applied to the orientation of each wafer. Each wafer can realize channel implantation.

[0053] It should be noted that a large number of specific details are provided in the specification of the present application. However, it can be understood that the embodiments of the present application can be implemented without some or all of these specific details. In some examples, well-known methods, structures and techniques are not shown in detail in order not to obscure the understanding of the present specification.

[0054] ​​Similarly, to the extent that the terms "including", "includes", "having", "has", "with", or variants thereof are used in either the detailed description and / or the claims, such terms are used expansively and each means for purposes of the patent claims, without limitation and / or exclusion, that the stated feature is among the components, steps, and / or elements of the embodiments described and / or claimed. Similarly, the terms "comprises", "comprising", "includes", "including" and the like can be used herein and mean either "including but not limited to" or it can be used in the sense of "including for example" such that an listed element can be present or can not be present. In addition, it is to be appreciated that certain features which are, for clarity, described above and below as part of one embodiment, can also be implemented as part of one or more other embodiments. Thus, the disclosure is not to be strictly limited by the descriptions and depictions in the figures and accompanying text, but rather, is to be understood broadly as including all features that are within the scope of the present disclosure.

[0055] Those skilled in the art will appreciate that the modules in the apparatuses in the embodiments can be adapted and placed in one or more apparatuses other than the embodiments. The modules or units or components in the embodiments can be combined into one module or unit or component, and further can be divided into more sub-modules or sub-units or sub-components. Any combination of all the features disclosed in the specification (including the accompanying claims, abstract and drawings), and any method or apparatus so disclosed, can be used in any combination, except that at least some of such features and / or processes or units are mutually exclusive, unless explicitly stated otherwise. Each feature disclosed in the specification (including the accompanying claims, abstract and drawings) can be replaced by alternative features serving the same, equivalent or similar purpose, unless explicitly stated otherwise.

[0056] Furthermore, those skilled in the art will appreciate that the features of the different embodiments can be combined in any combination, which is within the scope of the present application and forms a different embodiment. For example, in the claims, any 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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