Method for determining the center of an electrostatic chuck on a wafer and wafer centering method

Abstract

The application provides a method for determining the center of an electrostatic chuck on a wafer, comprising: obtaining a distribution image of particles on the wafer; calculating an estimated center position of each boss according to the distribution image of the particles on the wafer; determining at least three reference straight lines according to the estimated center positions of a plurality of second-type bosses, wherein any two of the reference straight lines are substantially parallel to each other or intersect each other; determining at least two reference diameters on the wafer according to the at least three reference straight lines; correcting the reference diameters according to the estimated center positions of a plurality of first-type bosses to obtain at least two expected diameters on the wafer; and determining the center of the electrostatic chuck according to the connection points of the at least two expected diameters on the wafer. Correspondingly, a wafer centering method is also provided. The application can accurately calculate the center of the electrostatic chuck on the wafer and improve the accuracy of mechanical arm calibration.

Description

Technical Field

[0001] This invention relates to the field of semiconductor equipment technology, and in particular to a method for determining the center of an electrostatic chuck on a wafer, a wafer alignment method, an electronic device, and a computer-readable storage medium. Background Technology

[0002] The vacuum reaction chamber of the plasma processing apparatus includes a base with an electrostatic chuck mounted on it. The electrostatic chuck is used to hold the wafer for plasma processing (etching or deposition). Around the base and the electrostatic chuck are edge rings such as a focusing ring, a covering ring, and an isolation ring, used to adjust parameters such as temperature, electric field strength, and gas distribution within the vacuum reaction chamber of the plasma processing apparatus, thereby ensuring the uniformity of etching (or deposition) in the central and edge regions of the wafer to be processed.

[0003] In semiconductor manufacturing processes, a robotic arm places the wafer onto an electrostatic chuck during wafer transfer and removes it from the chuck after processing, transferring it out of the reaction chamber. To ensure etching uniformity, the robotic arm must be able to center the wafer on the electrostatic chuck. The alignment between the wafer and the chuck is determined by the placement accuracy of the robotic arm, thus requiring calibration of the arm's placement precision.

[0004] Typically, robotic arm calibration is based on the offset between the center of the wafer to be processed and the center of the electrostatic chuck. Therefore, a method is needed to determine the center of the electrostatic chuck on the wafer, calculate the electrostatic chuck center, and then calculate the offset between the center of the wafer to be processed and the electrostatic chuck center for robotic arm calibration to meet wafer transfer requirements. Summary of the Invention

[0005] The purpose of this invention is to provide a method for determining the center of an electrostatic chuck on a wafer, as well as a wafer alignment method, electronic device, and computer-readable storage medium, for accurately calculating the center of the electrostatic chuck on the wafer and improving the accuracy of robotic arm calibration.

[0006] To achieve the above objectives, the present invention is implemented through the following technical solution:

[0007] A method for determining the center of an electrostatic chuck on a wafer, wherein the electrostatic chuck has a plurality of protrusions, the protrusions including a first type of protrusion and a second type of protrusion, the lines connecting the first type of protrusions forming a plurality of straight lines passing through the center of the electrostatic chuck, the second type of protrusions being disposed in the edge region of the electrostatic chuck, the lines connecting the second type of protrusions forming a plurality of straight lines parallel to the lines connecting the first type of protrusions, the method comprising the following steps:

[0008] A distribution image of particles on a wafer is obtained; the distribution image of particles on a wafer is obtained by the following method: placing the wafer on the electrostatic chuck and applying a certain electrostatic attraction force, at least partially transferring the particles on the protrusions of the electrostatic chuck to the contact surface between the wafer and the protrusions; placing the wafer in an image acquisition device to obtain a distribution image of particles on the wafer;

[0009] The estimated center position of each boss is calculated based on the distribution image of particles on the wafer;

[0010] Based on the estimated center positions of several second-type protrusions, at least three reference lines are determined, with any two reference lines being substantially parallel or intersecting each other.

[0011] Based on at least three defined reference lines, determine at least two reference diameters on the wafer;

[0012] The reference diameter is corrected based on the estimated center positions of several first-type bosses to obtain at least two desired diameters on the wafer;

[0013] The center of the electrostatic chuck is determined based on at least two connection points of desired diameter on the wafer.

[0014] Furthermore, the step of calculating the estimated center position of each boss based on the particle distribution image on the wafer includes:

[0015] The location information of each particle in the distribution image is detected, and multiple particles that are clustered in a preset size area are regarded as particles originating from the same protrusion. The preset size area has the same cross-sectional area as the protrusion.

[0016] Based on the position information of each particle within a preset size area corresponding to each protrusion, the estimated center position of the protrusion is calculated.

[0017] Furthermore, the location information of particles in the size range of 0.16μm to 0.5μm was detected.

[0018] Furthermore, the step of calculating the estimated center position of the protrusion based on the position information of each particle within a preset size area corresponding to each protrusion includes:

[0019] For each protrusion, the estimated center position of the protrusion is calculated using the geometric mean or arithmetic mean method based on the position information of each particle within a preset size area.

[0020] Furthermore, determining at least two reference diameters on the wafer based on at least three defined reference straight lines includes:

[0021] For at least three reference lines, calculate the axes of symmetry of two substantially parallel reference lines and / or two intersecting reference lines to obtain at least two reference diameters on the wafer.

[0022] Furthermore, the lines connecting the first type of bosses form N straight lines that are at an angle of 360° / N to each other, where N≥2, and the lines connecting the second type of bosses form at least three straight lines located on the sides of a regular polygon whose diagonal is the straight line formed by the lines connecting the first type of bosses.

[0023] Furthermore, when N=3, the determination of at least three reference lines based on the estimated center positions of several second-type bosses includes:

[0024] Based on the estimated center positions of several second-type protrusions, four reference lines are determined;

[0025] Among them, the four reference lines are adjacent and intersect in sequence, and the first and last reference lines are roughly parallel; or,

[0026] Two of the four reference lines that are adjacent and intersect are substantially parallel to the other two adjacent and intersecting reference lines; or

[0027] One of the four reference lines is roughly parallel to the middle reference line among the three adjacent and intersecting reference lines.

[0028] Furthermore, the step of correcting the reference diameter based on the estimated center positions of several first-type bosses to obtain at least two desired diameters on the wafer includes:

[0029] For each of the aforementioned reference diameters, the correction shall be made as follows:

[0030] The estimated center position of the first type of boss, which is generally located on the reference diameter, is decomposed into a first vector along the direction of the reference diameter and a second vector perpendicular to the direction of the reference diameter.

[0031] The reference diameter is corrected by superimposing all the second vectors obtained from the decomposition.

[0032] Furthermore, the desired diameter is at least three;

[0033] Determining the center of the electrostatic chuck based on at least two connection points of desired diameter on the wafer includes:

[0034] Determine the connection point for each of the two desired diameters, resulting in at least three connection points;

[0035] The center of the electrostatic chuck is determined based on at least three connection points.

[0036] Furthermore, determining the center of the electrostatic chuck based on at least three connection points includes:

[0037] The center of the electrostatic chuck is calculated using the geometric mean or arithmetic mean method for at least three connection points.

[0038] A method for determining the center of an electrostatic chuck on a wafer, wherein the electrostatic chuck has multiple protrusions, including first-type protrusions and second-type protrusions. Lines connecting the first-type protrusions form several straight lines surrounding the center of the electrostatic chuck. The second-type protrusions are located in the edge region of the electrostatic chuck, and lines connecting the second-type protrusions form several straight lines parallel to the lines connecting the first-type protrusions. The method includes the following steps:

[0039] A distribution image of particles on a wafer is obtained; the distribution image of particles on a wafer is obtained by the following method: placing the wafer on the electrostatic chuck and applying a certain electrostatic attraction force, at least partially transferring the particles on the protrusions of the electrostatic chuck to the contact surface between the wafer and the protrusions; placing the wafer in an image acquisition device to obtain a distribution image of particles on the wafer;

[0040] The estimated center position of each boss is calculated based on the distribution image of particles on the wafer;

[0041] Based on the estimated center positions of several second-type protrusions, at least three reference lines are determined, with any two reference lines being substantially parallel or intersecting each other.

[0042] Based on at least three established reference straight lines, determine at least three reference center lines on the wafer;

[0043] The reference centerline is corrected based on the estimated center positions of several first-type bosses to obtain at least three desired centerlines on the wafer.

[0044] The center of the electrostatic chuck is calculated based on at least three desired center lines on the wafer.

[0045] Furthermore, the lines connecting the first type of bosses form a regular N-gon, where N ≥ 3.

[0046] A wafer alignment method includes the following steps:

[0047] S1, an inverted wafer is placed into the electrostatic chuck of the reaction chamber by a robotic arm;

[0048] S2, the wafer is adsorbed onto the electrostatic chuck, so that the particles on the boss of the electrostatic chuck are at least partially transferred to the contact surface between the wafer and the boss.

[0049] S3, Remove the wafer and obtain a distribution image of particles on the wafer;

[0050] S4, the electrostatic chuck center is obtained by using the method described above for determining the center of the electrostatic chuck on the wafer;

[0051] S5, calculate the offset of the wafer center relative to the center of the electrostatic chuck based on the center of the electrostatic chuck;

[0052] S6, determine whether the wafer is aligned with the electrostatic chuck based on the offset of the wafer center relative to the electrostatic chuck center; if not, adjust the settings of the robotic arm based on the offset of the wafer center relative to the electrostatic chuck center.

[0053] Furthermore, prior to step S1, the following steps are also included:

[0054] Several wafers are placed into the reaction chamber for processing to pre-treat the reaction chamber.

[0055] Furthermore, steps S1 to S5 are performed on multiple wafers respectively to obtain the offset of the center of each wafer relative to the center of the electrostatic chuck.

[0056] Before performing step S6, the method further includes: calculating the average offset of the wafer center relative to the center of the electrostatic chuck based on the offset of each wafer center relative to the center of the electrostatic chuck.

[0057] In step S6, it is determined whether the wafer is aligned with the electrostatic chuck based on the average offset of the wafer center relative to the electrostatic chuck center. If not, the settings of the robotic arm are adjusted based on the average offset of the wafer center relative to the electrostatic chuck center.

[0058] To achieve the above objectives, the present invention also provides an electronic device, including a processor, a communication interface, a memory, and a communication bus; wherein the processor, the communication interface, and the memory communicate with each other through the communication bus;

[0059] Memory, used to store computer programs;

[0060] The processor, when executing a program stored in memory, implements the steps of the method described above for determining the center of the electrostatic chuck on the wafer.

[0061] To achieve the above objectives, the present invention also provides a computer-readable storage medium storing a computer program that, when executed by a processor, implements the steps of the method for determining the center of an electrostatic chuck on a wafer as described above.

[0062] Compared with the prior art, the present invention has the following advantages:

[0063] The present invention provides a method for determining the center of an electrostatic chuck on a wafer. By setting a first type of boss and a second type of boss on the electrostatic chuck, after the wafer is placed on the electrostatic chuck and comes into contact with the boss, the particles on each boss are transferred to the wafer. The distribution of the particles on the wafer reflects the relative positional relationship between the wafer and the electrostatic chuck when the wafer is placed on the electrostatic chuck. After obtaining the distribution image of particles on the wafer, the estimated center position of each protrusion is first calculated. Then, based on the estimated center position of the second type of protrusion, at least three reference lines are determined, with any two reference lines being substantially parallel or intersecting each other. These at least three reference lines correspond to the lines formed by connecting the second type of protrusions on the electrostatic chuck. Then, at least two reference diameters on the wafer are determined from these at least three reference lines. These at least two reference diameters correspond to the lines formed by connecting the first type of protrusions on the electrostatic chuck, passing through the center of the electrostatic chuck (i.e., the diameter of the electrostatic chuck). However, the above calculation steps inevitably contain errors. Therefore, there is a large error between the currently determined at least two reference diameters and the diameter of the electrostatic chuck. Thus, the present invention further corrects each reference diameter based on the estimated center position of the first type of protrusion to obtain at least two expected diameters. These at least two expected diameters are closer to the diameter of the electrostatic chuck than the reference diameters. It can be seen that the correction can prevent further propagation of errors, and the center of the electrostatic chuck can be more accurately determined based on the connection point of these at least two expected diameters.

[0064] The wafer alignment method provided by this invention is used for robotic arm calibration. By using the above-mentioned method of determining the center of the electrostatic chuck on the wafer, the center of the electrostatic chuck can be calculated more accurately, thereby improving the accuracy of robotic arm calibration. Attached Figure Description

[0065] To more clearly illustrate the technical solution of the present invention, the accompanying drawings used in the description will be briefly introduced below. Obviously, the drawings described below are one embodiment of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort:

[0066] Figure 1 This is a distribution diagram of the bosses on the electrostatic chuck provided in the first embodiment of the present invention;

[0067] Figure 2 This is a flowchart of a method for determining the center of an electrostatic chuck on a wafer according to a first embodiment of the present invention;

[0068] Figure 3a An example image of the distribution of particles on a wafer provided in the first embodiment of the present invention;

[0069] Figure 3b This is another example image of the distribution of particles on a wafer provided in the first embodiment of the present invention;

[0070] Figure 3c This is a partial magnified view of the distribution image of particles on a wafer provided in the first embodiment of the present invention;

[0071] Figure 4 A schematic diagram illustrating the calculation of the reference diameter provided in the first embodiment of the present invention;

[0072] Figure 5 A flowchart of a method for determining the center of an electrostatic chuck on a wafer according to a second embodiment of the present invention;

[0073] Figure 6 This is a schematic diagram of the calculation of the center of the electrostatic clamp provided in the second embodiment of the present invention;

[0074] Figure 7 This is a flowchart of a wafer alignment method provided in an embodiment of the present invention;

[0075] Figure 8 This is a schematic diagram of the process parameters for the reaction chamber pretreatment provided in an embodiment of the present invention;

[0076] Figure 9 This is a structural diagram of an electronic device provided according to an embodiment of the present invention. Detailed Implementation

[0077] The following detailed description, in conjunction with the accompanying drawings and specific embodiments, further illustrates the solution proposed by the present invention. The advantages and features of the present invention will become clearer from the following description. It should be noted that the drawings are in a very simplified form and use non-precise proportions, used only to facilitate and clearly illustrate the embodiments of the present invention. Please refer to the drawings to make the objectives, features, and advantages of the present invention more apparent and understandable. It should be understood that the structures, proportions, sizes, etc., depicted in the accompanying drawings are only for illustrative purposes to aid those skilled in the art and are not intended to limit the implementation conditions of the present invention. Therefore, they have no substantial technical significance. Any modifications to the structure, changes in proportions, or adjustments to the size, without affecting the effects and objectives achieved by the present invention, should still fall within the scope of the technical content disclosed in the present invention.

[0078] To calibrate a robotic arm that transports wafers, this invention provides a method for determining the center of an electrostatic chuck on a wafer, a wafer alignment method, an electronic device, and a computer-readable storage medium.

[0079] First Embodiment

[0080] First, the electrostatic chuck used in implementing the embodiments of the present invention will be described. For example... Figure 1 As shown, the electrostatic chuck has multiple bosses, each with a cross-section that can be circular, triangular, square, or other shapes. Taking a circular boss as an example, the diameter of the boss can be, for example, 2 mm. The bosses include a first type of boss and a second type of boss. The lines connecting the first type of bosses form several straight lines passing through the center of the electrostatic chuck. Figure 1 The three dashed lines in the middle are the three straight lines formed by connecting the first type of bosses, passing through the center of the electrostatic chuck. The intersection of the three dashed lines is the center of the electrostatic chuck. The second type of bosses are disposed in the edge area of ​​the electrostatic chuck. The lines connecting the second type of bosses form several straight lines parallel to the lines connecting the first type of bosses. Figure 1 The six double-dotted lines (a1 to a6) are six straight lines formed by connecting the second type of bosses, which are parallel to the connecting lines of the first type of bosses.

[0081] like Figure 1 The electrostatic chuck shown is mounted on a base within the reaction chamber. A robotic arm transfers a wafer to be processed into the reaction chamber and places it on the electrostatic chuck. After applying a certain electrostatic attraction, the wafer is adsorbed onto the electrostatic chuck, and the wafer comes into contact with the protrusion. As a result, at least partially, particles on the protrusion of the electrostatic chuck are transferred to the contact surface between the wafer and the protrusion. The wafer is then removed from the reaction chamber and placed in an image acquisition device. The image acquisition device photographs or scans the wafer, thereby acquiring an image of the particle distribution on the wafer. This invention does not limit the type of image acquisition device. Figure 3a , Figure 3b , Figure 3c The images show two examples of particle distribution on a wafer, along with magnified views of the edge regions. In these distribution images, the thinner white circles at the outermost edge represent the wafer's edge, while the thicker white circles are formed by particles transferred from the wafer's edge upon contact with the electrostatic chuck. The white dotted areas within the thicker white circles are distributed similarly to the protrusions on the electrostatic chuck, also formed by particles transferred from the wafer upon contact with these protrusions. Optionally, the wafer can be a special type called a PA wafer, whose back side undergoes special treatment to achieve good particle adsorption.

[0082] Based on this, such as Figure 2 As shown, the method for determining the center of an electrostatic chuck on a wafer provided in this embodiment may include steps S101 to S106. This method can be applied to any type of electronic device, that is, the executing entity of the above method for determining the center of an electrostatic chuck on a wafer can be any type of electronic device, such as a laptop, a desktop computer, or a device integrating a processor and a display device, etc. The present invention does not limit this.

[0083] Step S101: Obtain an image of the distribution of particles on the wafer.

[0084] Specifically, after acquiring an image of the particle distribution on the wafer, the image acquisition device described above can transmit the image to the execution subject of this method, thereby enabling the execution subject of this method to obtain the image of the particle distribution on the wafer. The specific transmission method is not limited in the invention.

[0085] Step S102: Calculate the estimated center position of each boss based on the distribution image of particles on the wafer.

[0086] As mentioned earlier, the white dotted areas within the thicker white circles in the distribution image represent the aggregation areas of particles transferred from the protrusions to the wafer. Typically, when the electrostatic chuck and wafer are in close contact, the size of the white dotted areas is approximately the same as the cross-sectional area of ​​the protrusion. Therefore, by detecting the position of each white dotted area in the distribution image, the position of the particle aggregation area on the wafer can be obtained. The position of the particle aggregation area on the wafer can also be considered as the estimated position of each protrusion on the wafer. The position of the white dotted area is determined by the positions of the multiple particles aggregated in that area. Furthermore, by calculating the center position of each white dotted area, the estimated center position of each protrusion can be obtained.

[0087] Specifically, firstly, the position information of each particle in the distribution image is detected. Since the particles transferred from the same protrusion to the wafer are in an aggregated state, and the particles transferred from different protrusions to the wafer are far apart, multiple particles aggregated in a preset size area can be regarded as particles originating from the same protrusion. The preset size area is the same as the cross-sectional area of ​​the protrusion. Then, based on the position information of each particle in the preset size area corresponding to each protrusion, the estimated center position of the protrusion is calculated.

[0088] In one implementation, the positional information of each particle within a preset size area corresponding to each protrusion can be determined to determine the particle distribution area corresponding to the protrusion. The particle distribution area is the minimum contour of the area where each particle is located within the preset size area corresponding to the protrusion. The center of the particle distribution area is calculated as the estimated center position of the protrusion.

[0089] In another implementation, to reduce computational load, the estimated center position of each protrusion can be calculated using the geometric mean or arithmetic mean method based on the positional information of each particle within a preset size area corresponding to each protrusion. Specifically, a rectangular coordinate system is established in the distribution image, the coordinates of each particle within the preset size area corresponding to each protrusion are determined, and then the coordinates of the estimated center position of the protrusion are calculated using the geometric mean or arithmetic mean method. The specific calculation method is not elaborated here.

[0090] When the electrostatic chuck does not make sufficient contact with the wafer, the white dotted area will be significantly smaller than the cross-sectional area of ​​the boss. Figure 3c As can be seen, the shapes of the distribution areas of each particle are irregular. Therefore, the estimated center position of each protrusion calculated above inevitably contains errors. It can only roughly reflect the corresponding position of each protrusion on the wafer. Therefore, it is necessary to make corrections in subsequent steps to reduce the impact of this error on the calculation result of the electrostatic chuck center.

[0091] It is important to note that the size range of the detected particles has a significant impact on the calculation accuracy. Testing showed that particle counts saturate for particles smaller than 0.16 μm, and the particle detection tool (e.g., SP2 tool) will stop detecting when the particle count exceeds a certain threshold. Particles larger than 0.5 μm are less likely to adhere to the wafer, resulting in too few counts and low calculation accuracy. Therefore, this embodiment detects particles in the 0.16 μm to 0.5 μm size range and uses the positional information of these particles to calculate the estimated center position of the boss. This significantly improves the calculation accuracy of the boss position, thereby contributing to improved accuracy in determining the center of the electrostatic chuck on the wafer.

[0092] Step S103: Based on the estimated center positions of several second-type protrusions, determine at least three reference lines, with any two reference lines being substantially parallel or intersecting each other.

[0093] In step S102, the estimated center position of each boss has been calculated. Therefore, based on the estimated center position of the second type of boss, several reference lines can be drawn. Any two of these reference lines are generally parallel or intersecting.

[0094] Step S104: Determine at least two reference diameters on the wafer based on the determined at least three reference lines.

[0095] As mentioned above, on the electrostatic chuck, the lines connecting the second type of bosses form several straight lines parallel to the lines connecting the first type of bosses, while the lines connecting the first type of bosses form several straight lines passing through the center of the electrostatic chuck, that is, the lines connecting the first type of bosses are located on the diameter of the electrostatic chuck.

[0096] Therefore, for the at least three reference lines determined in step S103, at least two reference diameters on the wafer can be obtained by calculating the axes of symmetry of two generally parallel reference lines and / or two intersecting reference lines. These multiple reference diameters generally correspond to the diameter of the electrostatic chuck where the line connecting the first type of boss is located.

[0097] In a preferred embodiment, for ease of calculation, the electrostatic chuck can be designed such that: the lines connecting the first type of bosses form N straight lines that are at an angle of 360° / N to each other, where N≥2; that is, the lines connecting the first type of bosses divide the electrostatic chuck into 2N equal regions; and the lines connecting the second type of bosses form at least three straight lines located on the sides of a regular polygon whose diagonals are the lines connecting the first type of bosses. Figure 1 The electrostatic chuck shown has N=3. The lines connecting the first type of bosses form three straight lines that are at a 120° angle to each other. The lines connecting the second type of bosses form at least three straight lines located on the sides of a regular hexagon whose diagonal is the line formed by the lines connecting the first type of bosses.

[0098] In step S103, four reference lines can be determined based on the estimated center positions of several second-type bosses. The positional relationship between these four reference lines can be one of the following three cases:

[0099] a) Four reference lines are sequentially adjacent and intersect. The first and last reference lines are approximately parallel. For example, the distribution relationship of the four reference diameters is as follows: Figure 1 The distribution of the four double-dotted lines a1, a2, a3, and a4 is shown;

[0100] b, Two of the four reference lines that are adjacent and intersecting are substantially parallel to the other two adjacent and intersecting reference lines. For example, the distribution of the four reference diameters is as follows: Figure 1 The distribution of the four double-dotted lines a1, a2, a4, and a5 is shown;

[0101] c. One of the four reference lines is substantially parallel to the middle reference line among the three consecutive and intersecting reference lines. For example, the distribution of the four reference diameters is as follows: Figure 1 The distribution of the four double-dotted lines a1, a2, a3, and a5 is shown.

[0102] In step S400, for any of the three positional relationships described above, any two reference lines are generally parallel or intersecting. Therefore, by calculating the axes of symmetry of the two generally parallel reference lines and / or the axes of symmetry of the two intersecting reference lines, three reference diameters on the wafer can be obtained. The distribution relationship of these three reference diameters is as follows: Figure 1The distribution of the three dashed lines b1, b2, and b3 is shown. Figure 4 The three reference diameters calculated under the first positional relationship a are shown for easy distinction. Figure 4 Small triangles are used to represent the estimated center position of the second type of protrusion, and circles are used to represent the estimated center position of the first type of protrusion.

[0103] Depend on Figure 4 It can be seen that the three calculated reference diameters roughly correspond to the lines connecting the first type of bosses, but there is still a significant error between them. That is, there is an error between the three calculated reference diameters and the diameter of the electrostatic chuck on the wafer. Therefore, the present invention uses step S500 to correct this error.

[0104] Step S105: Correct the reference diameter based on the estimated center positions of several first-type bosses to obtain at least two desired diameters on the wafer.

[0105] As mentioned above, each reference diameter corresponds to the diameter of one electrostatic chuck formed by the line connecting the first type of bosses. In this step, the reference diameter is further corrected based on the estimated center positions of several first type of bosses, which can yield at least two more accurate expected diameters. Compared to the reference diameter, the expected diameter on the wafer is closer to the diameter of the electrostatic chuck, thus improving the accuracy of the electrostatic chuck center determined on the wafer.

[0106] For each of the aforementioned reference diameters, the correction shall be made as follows:

[0107] The estimated center position of the first type of boss, which is generally located on the reference diameter, is decomposed into a first vector along the direction of the reference diameter and a second vector perpendicular to the direction of the reference diameter.

[0108] The reference diameter is corrected by superimposing all the second vectors obtained from the decomposition.

[0109] Because the position of particulate matter adhering to the protrusion is random, it is necessary to perform mathematical averaging or other calculations along the second vector direction to reduce the error of the reference diameter in the second vector direction, ultimately obtaining a more accurate reference diameter after correction. Specifically, with Figure 4Taking a reference diameter A as an example, point a represents the estimated center position of a first-type boss roughly located on the reference diameter A. The coordinates of point a are decomposed into a first vector along the X direction and a second vector along the Y direction. Similarly, the coordinates of the estimated center positions of all other first-type bosses roughly located on the reference diameter A are also decomposed into a first vector along the X direction and a second vector along the Y direction. Finally, the second vectors are mathematically averaged or calculated using other methods to obtain a more accurate reference diameter after correction. The positional error in the direction of the first vector does not affect the positioning of the reference diameter, so it does not need to be corrected.

[0110] Therefore, it is possible to offset the error caused by the random distribution of particles on the protrusion in the direction perpendicular to the reference diameter, while the error along the reference diameter will not affect the calculation accuracy of the final center point position.

[0111] Step S106: Determine the center of the electrostatic chuck based on at least two connection points of desired diameter on the wafer.

[0112] If step S105 determines two desired diameters, then the connection point of these two desired diameters can be determined as the center of the electrostatic chuck.

[0113] If step S105 determines at least three desired diameters, then the connection points between every two desired diameters can be determined, resulting in at least three connection points. The center of the electrostatic chuck is then determined based on these at least three connection points. Specifically, the center of the electrostatic chuck can be calculated using either the geometric mean or the arithmetic mean method for these at least three connection points. That is, a rectangular coordinate system is established in the distribution image, the coordinates of each connection point are determined, and then the center of the electrostatic chuck is calculated using either the geometric mean or the arithmetic mean method. The specific calculation method is not elaborated here.

[0114] In summary, the method for determining the center of an electrostatic chuck on a wafer provided by the embodiments of the present invention involves setting a first type of boss and a second type of boss on the electrostatic chuck. After the wafer is placed on the electrostatic chuck and comes into contact with the boss, the particles on each boss are transferred to the wafer. The distribution of particles on the wafer reflects the relative positional relationship between the wafer and the electrostatic chuck when the wafer is placed on the electrostatic chuck. After obtaining the distribution image of particles on the wafer, the estimated center position of each protrusion is first calculated. Then, based on the estimated center position of the second type of protrusion, at least three reference lines are determined, with any two reference lines being substantially parallel or intersecting each other. These at least three reference lines correspond to the lines formed by connecting the second type of protrusions on the electrostatic chuck. Then, at least two reference diameters on the wafer are determined from these at least three reference lines. These at least two reference diameters correspond to the lines formed by connecting the first type of protrusions on the electrostatic chuck, passing through the center of the electrostatic chuck (i.e., the diameter of the electrostatic chuck). However, the above calculation steps inevitably contain errors. Therefore, there is a large error between the currently determined at least two reference diameters and the diameter of the electrostatic chuck. Thus, the present invention further corrects each reference diameter based on the estimated center position of the first type of protrusion to obtain at least two expected diameters. These at least two expected diameters are closer to the diameter of the electrostatic chuck than the reference diameters. It can be seen that the correction can prevent further propagation of errors, and the center of the electrostatic chuck can be more accurately determined based on the connection point of these at least two expected diameters.

[0115] Second Embodiment

[0116] The difference between this embodiment and the first embodiment is that, in this embodiment, the lines connecting the first type of bosses on the electrostatic chuck form several straight lines around the center of the electrostatic chuck (i.e., no corresponding boss is provided at the center of the electrostatic chuck, and the lines connecting the first type of bosses do not pass through the center of the electrostatic chuck). Optionally, the lines connecting the first type of bosses form a regular N-gon, where N ≥ 3. That is, the lines connecting the first type of bosses closest to and evenly distributed around the center of the electrostatic chuck form N straight lines, which enclose a regular N-gon, and the center of the electrostatic chuck is located at the center of this regular N-gon.

[0117] like Figure 5 As shown, the method for determining the center of an electrostatic chuck on a wafer provided in this embodiment may include the following steps:

[0118] Step S201: Obtain an image showing the distribution of particles on the wafer;

[0119] Step S202: Calculate the estimated center position of each boss based on the distribution image of particles on the wafer;

[0120] Step S203: Based on the estimated center positions of several second-type bosses, determine at least three reference lines, with any two reference lines being substantially parallel or intersecting each other.

[0121] Step S204: Based on the determined at least three reference straight lines, determine at least three reference center lines on the wafer;

[0122] Step S205: Correct the reference center line based on the estimated center positions of several first-type protrusions to obtain at least three desired center lines on the wafer;

[0123] Step S206: Calculate the center of the electrostatic chuck based on at least three desired center lines on the wafer.

[0124] The implementation methods of steps S201 to S203 can be referred to the relevant description of the first embodiment, and will not be repeated here.

[0125] Therefore, in step S204, there are at least three determined reference center lines, and each reference center line is closest to the center of the electrostatic chuck. The reference center lines are corresponding to straight lines passing through at least two bosses closest to the center point of the electrostatic chuck. Please refer to... Figure 6 It schematically shows three defined reference center lines, each corresponding to a straight line passing through the two bosses closest to the center point of the electrostatic chuck.

[0126] In step S205, each reference center line can be corrected based on the estimated center position of several first-type protrusions that are approximately located on the reference center line to obtain at least three desired center lines on the wafer, as can be found in the first embodiment.

[0127] In step S206, the connection points of every two of the at least three desired center lines can be determined, resulting in at least three connection points. The center of the electrostatic chuck is then determined based on these at least three connection points. Specifically, the center of the electrostatic chuck can be calculated using either the geometric mean or the arithmetic mean method for these at least three connection points.

[0128] In summary, the method for determining the center of the electrostatic chuck on the wafer provided in this embodiment can avoid error propagation, thereby determining the center of the electrostatic chuck more accurately.

[0129] Based on the same inventive concept, the present invention also provides a wafer alignment method, such as... Figure 7 As shown, it includes the following steps:

[0130] S1, an inverted wafer is placed into the electrostatic chuck of the reaction chamber by a robotic arm;

[0131] S2, the wafer is adsorbed onto the electrostatic chuck, so that the particles on the boss of the electrostatic chuck are at least partially transferred to the contact surface between the wafer and the boss.

[0132] S3, Remove the wafer and obtain a distribution image of particles on the wafer;

[0133] S4, the electrostatic chuck center is obtained by using the method described above for determining the center of the electrostatic chuck on the wafer;

[0134] S5, calculate the offset of the wafer center relative to the center of the electrostatic chuck based on the center of the electrostatic chuck;

[0135] S6, determine whether the wafer is aligned with the electrostatic chuck based on the offset of the wafer center relative to the electrostatic chuck center; if not, adjust the settings of the robotic arm based on the offset of the wafer center relative to the electrostatic chuck center.

[0136] In step S1, the back side of the wafer undergoes a special treatment to effectively adsorb particulate matter. Therefore, the wafer is placed upside down into the electrostatic chuck of the reaction chamber, and the particulate matter on the protrusions is at least partially transferred to the back side of the wafer. It should be noted that the robotic arm that places the wafer onto the electrostatic chuck in S1 is not required to be the same robotic arm that removes the wafer from the electrostatic chuck in S3, but the robotic arm that is adjusted in S6 must be the same as the robotic arm in S1.

[0137] In the image showing the distribution of particles on the wafer, such as Figure 1 As shown, the wafer center can be determined by the thinner white circle located on the outermost edge. The center of this thinner white circle is the wafer center. Simultaneously, a Cartesian coordinate system can be established with the wafer center as the origin and the line connecting the wafer center to the notch on the wafer as the x-axis. In this Cartesian coordinate system, the coordinates of the electrostatic chuck center can be determined. In step S5, the offset of the wafer center relative to the electrostatic chuck center can be calculated in this Cartesian coordinate system. It is understood that this offset is a vector, including both the offset value and the offset direction.

[0138] In step S6, a standard for wafer alignment can be preset. For example, the standard is that an offset value within ±200µm is considered to indicate that the wafer and the electrostatic chuck are aligned. If the actual calculated offset exceeds this standard, it indicates that the placement accuracy of the robotic arm does not meet the requirements, and the settings of the robotic arm need to be adjusted. The specific adjustment method will not be elaborated here.

[0139] After adjustment, the wafer alignment operation can be performed again following steps S1 to S6 to check whether the robotic arm is properly adjusted.

[0140] Furthermore, the wafer alignment method described above may also include step S0 before performing step S1, in which several wafers are placed into the reaction chamber for processing to pre-treat the reaction chamber.

[0141] For example, 10 wafers can be placed in the reaction chamber and operated in automatic mode to pre-season the reaction chamber, cleaning particles on the electrostatic chuck to prevent excessive particle residue on the bosses from transferring to the wafers and causing undetectable particle counts during particle detection of the distribution image. The process parameters used in the reaction chamber during pre-seasoning are as follows: Figure 8 As shown.

[0142] Furthermore, to improve the accuracy of wafer alignment, multiple wafers can be used to perform steps S1 to S5 respectively to obtain the offset of the center of each wafer relative to the center of the electrostatic chuck.

[0143] Before performing step S6, the method further includes: calculating the average offset of the wafer center relative to the center of the electrostatic chuck based on the offset of each wafer center relative to the center of the electrostatic chuck.

[0144] In step S6, it is determined whether the wafer is aligned with the electrostatic chuck based on the average offset of the wafer center relative to the electrostatic chuck center. If not, the settings of the robotic arm are adjusted based on the average offset of the wafer center relative to the electrostatic chuck center.

[0145] That is, for the same robotic arm, multiple wafers are used for wafer alignment operations, and the offset of the center of each wafer relative to the center of the electrostatic chuck is obtained. The average value is used to measure the placement accuracy of the robotic arm. This avoids the random errors caused by using a single wafer to measure the placement accuracy of the robotic arm, thereby improving the placement accuracy of the robotic arm.

[0146] In summary, the wafer alignment method provided by this invention is used for robotic arm calibration. By employing the above-described method of determining the center of the electrostatic chuck on the wafer, the center of the electrostatic chuck can be calculated more accurately, thereby improving the accuracy of robotic arm calibration.

[0147] Based on the same inventive concept, and according to the above-described method embodiment for determining the center of an electrostatic chuck on a wafer, the present invention also provides an electronic device, such as... Figure 9 As shown, it includes a processor 301, a communication interface 302, a memory 303, and a communication bus 304, wherein the processor 301, the communication interface 302, and the memory 303 communicate with each other through the communication bus 304.

[0148] Memory 303 is used to store computer programs;

[0149] The processor 301, when executing the program stored in the memory 303, implements the method described above for determining the center of the electrostatic chuck on the wafer.

[0150] The communication bus mentioned in the above electronic devices can be a Peripheral Component Interconnect (PCI) bus or an Extended Industry Standard Architecture (EISA) bus, etc. This communication bus can be divided into address bus, data bus, control bus, etc. For ease of illustration, only one thick line is used to represent it in the diagram, but this does not mean that there is only one bus or one type of bus.

[0151] The communication interface is used for communication between the aforementioned electronic devices and other devices.

[0152] The memory may include random access memory (RAM) or non-volatile memory (NVM), such as at least one disk storage device. Optionally, the memory may also be at least one storage device located remotely from the aforementioned processor.

[0153] The processors mentioned above can be general-purpose processors, including central processing units (CPUs), network processors (NPs), etc.; they can also be digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, or discrete hardware components.

[0154] In another embodiment of the present invention, a computer-readable storage medium is also provided, which stores a computer program that, when executed by a processor, implements the steps of the method for determining the center of an electrostatic chuck on a wafer as described above.

[0155] In another embodiment of the present invention, a computer program product containing instructions is also provided, which, when run on a computer, causes the computer to perform the steps of the method described above for determining the center of an electrostatic chuck on a wafer.

[0156] In the above embodiments, implementation can be achieved entirely or partially through software, hardware, firmware, or any combination thereof. When implemented using software, it can be implemented entirely or partially in the form of a computer program product. The computer program product includes one or more computer instructions. When the computer program instructions are loaded and executed on a computer, all or part of the processes or functions described in the embodiments of this application are generated. The computer can be a general-purpose computer, a special-purpose computer, a computer network, or other programmable device. The computer instructions can be stored in a computer-readable storage medium or transmitted from one computer-readable storage medium to another. For example, the computer instructions can be transmitted from one website, computer, server, or data center to another website, computer, server, or data center via wired (e.g., coaxial cable, fiber optic, digital subscriber line (DSL)) or wireless (e.g., infrared, wireless, microwave, etc.) means. The computer-readable storage medium can be any available medium that a computer can access or a data storage device such as a server or data center that integrates one or more available media. The available medium can be a magnetic medium (e.g., floppy disk, hard disk, magnetic tape), an optical medium (e.g., DVD), or a semiconductor medium (e.g., solid state disk (SSD)).

[0157] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0158] The various embodiments in this specification are described in a related manner. The same or similar parts between the various embodiments can be referred to each other. Each embodiment focuses on describing the differences from other embodiments.

[0159] Although the present invention has been described in detail through the preferred embodiments above, it should be understood that the above description should not be considered as a limitation of the present invention. Various modifications and substitutions to the present invention will be apparent to those skilled in the art after reading the above description. Therefore, the scope of protection of the present invention should be defined by the appended claims.

Claims

1. A method for determining the center of an electrostatic chuck on a wafer, wherein the electrostatic chuck has a plurality of protrusions, the protrusions including a first type of protrusion and a second type of protrusion, the lines connecting the first type of protrusions forming a plurality of straight lines passing through the center of the electrostatic chuck, the second type of protrusions being disposed in the edge region of the electrostatic chuck, the lines connecting the second type of protrusions forming a plurality of straight lines parallel to the lines connecting the first type of protrusions, characterized in that, Includes the following steps: A distribution image of particles on a wafer is obtained; the distribution image of particles on a wafer is obtained by the following method: placing the wafer on the electrostatic chuck and applying a certain electrostatic attraction force, at least partially transferring the particles on the protrusions of the electrostatic chuck to the contact surface between the wafer and the protrusions; placing the wafer in an image acquisition device to obtain a distribution image of particles on the wafer; The estimated center position of each boss is calculated based on the distribution image of particles on the wafer; Based on the estimated center positions of several second-type protrusions, at least three reference lines are determined, with any two reference lines being substantially parallel or intersecting each other. Based on at least three defined reference lines, determine at least two reference diameters on the wafer; The reference diameter is corrected based on the estimated center positions of several first-type bosses to obtain at least two desired diameters on the wafer; The center of the electrostatic chuck is determined based on at least two connection points of desired diameter on the wafer.

2. The method for determining the center of an electrostatic chuck on a wafer as described in claim 1, characterized in that, The step of calculating the estimated center position of each boss based on the particle distribution image on the wafer includes: The location information of each particle in the distribution image is detected, and multiple particles that are clustered in a preset size area are regarded as particles originating from the same protrusion. The preset size area has the same cross-sectional area as the protrusion. Based on the position information of each particle within a preset size area corresponding to each protrusion, the estimated center position of the protrusion is calculated.

3. The method for determining the center of an electrostatic chuck on a wafer as described in claim 2, characterized in that, Detects the location information of particles in the size range of 0.16μm to 0.5μm.

4. The method for determining the center of an electrostatic chuck on a wafer as described in claim 2, characterized in that, The step of calculating the estimated center position of each protrusion based on the position information of each particle within a preset size area corresponding to each protrusion includes: For each protrusion, the estimated center position of the protrusion is calculated using the geometric mean or arithmetic mean method based on the position information of each particle within a preset size area.

5. The method for determining the center of an electrostatic chuck on a wafer as described in claim 1, characterized in that, The determination of at least two reference diameters on the wafer based on at least three defined reference straight lines includes: For at least three reference lines, calculate the axes of symmetry of two substantially parallel reference lines and / or two intersecting reference lines to obtain at least two reference diameters on the wafer.

6. The method for determining the center of an electrostatic chuck on a wafer as described in claim 1, characterized in that, The lines connecting the first type of bosses form N straight lines that are at an angle of 360° / N to each other, where N≥2. The lines connecting the second type of bosses form at least three straight lines located on the sides of a regular polygon whose diagonal is the straight line formed by the lines connecting the first type of bosses.

7. The method for determining the center of an electrostatic chuck on a wafer as described in claim 6, characterized in that, When N=3, the determination of at least three reference lines based on the estimated center positions of several second-type bosses includes: Based on the estimated center positions of several second-type protrusions, four reference lines are determined; Among them, the four reference lines are adjacent and intersect in sequence, and the first and last reference lines are roughly parallel; or, Two of the four reference lines that are adjacent and intersect are substantially parallel to the other two adjacent and intersecting reference lines; or One of the four reference lines is roughly parallel to the middle reference line among the three adjacent and intersecting reference lines.

8. The method for determining the center of an electrostatic chuck on a wafer as described in claim 1, characterized in that, The step of correcting the reference diameter based on the estimated center positions of several first-type bosses to obtain at least two desired diameters on the wafer includes: For each of the aforementioned reference diameters, the correction shall be made as follows: The estimated center position of the first type of boss, which is generally located on the reference diameter, is decomposed into a first vector along the direction of the reference diameter and a second vector perpendicular to the direction of the reference diameter. The reference diameter is corrected by superimposing all the second vectors obtained from the decomposition.

9. The method for determining the center of an electrostatic chuck on a wafer as described in claim 1, characterized in that, The desired diameter is at least three; Determining the center of the electrostatic chuck based on at least two connection points of desired diameter on the wafer includes: Determine the connection point for each of the two desired diameters, resulting in at least three connection points; The center of the electrostatic chuck is determined based on at least three connection points.

10. The method for determining the center of an electrostatic chuck on a wafer as described in claim 9, characterized in that, Determining the center of the electrostatic chuck based on at least three connection points includes: The center of the electrostatic chuck is calculated using the geometric mean or arithmetic mean method for at least three connection points.

11. A method for determining the center of an electrostatic chuck on a wafer, wherein the electrostatic chuck has a plurality of protrusions, the protrusions including a first type of protrusion and a second type of protrusion, the lines connecting the first type of protrusions forming a plurality of straight lines surrounding the center of the electrostatic chuck, the second type of protrusions being disposed in the edge region of the electrostatic chuck, the lines connecting the second type of protrusions forming a plurality of straight lines parallel to the lines connecting the first type of protrusions, characterized in that, Includes the following steps: A distribution image of particles on a wafer is obtained; the distribution image of particles on a wafer is obtained by the following method: placing the wafer on the electrostatic chuck and applying a certain electrostatic attraction force, at least partially transferring the particles on the protrusions of the electrostatic chuck to the contact surface between the wafer and the protrusions; placing the wafer in an image acquisition device to obtain a distribution image of particles on the wafer; The estimated center position of each boss is calculated based on the distribution image of particles on the wafer; Based on the estimated center positions of several second-type protrusions, at least three reference lines are determined, with any two reference lines being substantially parallel or intersecting each other. Based on at least three established reference straight lines, determine at least three reference center lines on the wafer; The reference centerline is corrected based on the estimated center positions of several first-type bosses to obtain at least three desired centerlines on the wafer. The center of the electrostatic chuck is calculated based on at least three desired center lines on the wafer.

12. The method for determining the center of an electrostatic chuck on a wafer as described in claim 11, characterized in that, The lines connecting the first type of bosses form a regular N-gon, where N ≥ 3.

13. A wafer alignment method, characterized in that, Includes the following steps: S1, an inverted wafer is placed into the electrostatic chuck of the reaction chamber by a robotic arm; S2, the wafer is adsorbed onto the electrostatic chuck, so that the particles on the boss of the electrostatic chuck are at least partially transferred to the contact surface between the wafer and the boss. S3, Remove the wafer and obtain a distribution image of particles on the wafer; S4, the electrostatic chuck center is obtained by using the method for determining the center of the electrostatic chuck on the wafer as described in any one of claims 1-12; S5, calculate the offset of the wafer center relative to the center of the electrostatic chuck based on the center of the electrostatic chuck; S6, determine whether the wafer is aligned with the electrostatic chuck based on the offset of the wafer center relative to the electrostatic chuck center; if not, adjust the settings of the robotic arm based on the offset of the wafer center relative to the electrostatic chuck center.

14. The wafer alignment method as described in claim 13, characterized in that, Before step S1, the following is also included: Several wafers are placed into the reaction chamber for processing to pre-treat the reaction chamber.

15. The wafer alignment method as described in claim 13, characterized in that, Steps S1 to S5 are performed on multiple wafers respectively to obtain the offset of the center of each wafer relative to the center of the electrostatic chuck. Before performing step S6, the method further includes: calculating the average offset of the wafer center relative to the center of the electrostatic chuck based on the offset of each wafer center relative to the center of the electrostatic chuck. In step S6, it is determined whether the wafer is aligned with the electrostatic chuck based on the average offset of the wafer center relative to the electrostatic chuck center. If not, the settings of the robotic arm are adjusted based on the average offset of the wafer center relative to the electrostatic chuck center.

16. An electronic device, characterized in that, It includes a processor, a communication interface, a memory, and a communication bus, wherein the processor, the communication interface, and the memory communicate with each other through the communication bus; Memory, used to store computer programs; A processor, when executing a program stored in memory, implements the steps of the method described in any one of claims 1-12.

17. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores a computer program that, when executed by a processor, implements the steps of the method described in any one of claims 1-12.

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