Wafer positioning method and semiconductor processing apparatus

Abstract

The application discloses a wafer positioning method and a semiconductor process equipment, and relates to the semiconductor field. The wafer positioning method is applied to an edge etching chamber, and the positioning method comprises the following steps: obtaining a current etching uniformity parameter value according to etching rates of a plurality of sampling points on a sampling circle of the wafer, and determining a desired correction direction; obtaining a desired correction amount of a wafer conveying mechanism according to an etching uniformity parameter target value, a change amount of the etching uniformity parameter value and a fitting function of the correction amount; and correcting the wafer conveying mechanism according to the desired correction amount and the desired correction direction. The application can solve the problem of large correction fluctuation.

Description

Technical Field

[0001] This application belongs to the field of semiconductor technology, specifically relating to a wafer positioning method and semiconductor process equipment. Background Technology

[0002] In the process of integrated circuit manufacturing, plasma etching is a very important step. As technology nodes extend to 65nm and more advanced process nodes according to Moore's Law, the impact on yield related to wafer edges and sides becomes particularly prominent. Edge etching removes unstable film deposits at the wafer edges caused by the interaction between thin film deposition, photolithography, etching and chemical mechanical polishing through plasma, reducing their impact on subsequent processes and thus improving yield.

[0003] Edge etching has high requirements for etching uniformity. Since several chips are integrated on a wafer, the plasma needs to make the etching state of the required etching position as consistent as possible to ensure the performance consistency and controllability of the final chip. We need to find a way to adjust the uniformity accurately and efficiently, which can improve the chip yield and reduce the number of debugging times, thereby reducing debugging costs.

[0004] In related technologies, some methods to improve uniformity rely solely on single-wafer data for correction, resulting in significant fluctuations in correction. Other methods employ adjustable and extended electrode structures to change electrode dimensions, thereby adjusting uniformity. However, this approach leads to complex hardware structures, high implementation difficulty, and high costs, and it cannot improve the misalignment between the wafer's geometric center and the processing center. Therefore, its effect on improving uniformity in wafers with edge etching is limited. Summary of the Invention

[0005] The purpose of this application is to provide a wafer positioning method and semiconductor process equipment that can solve at least one of the above-mentioned problems.

[0006] To solve the above-mentioned technical problems, this application is implemented as follows:

[0007] This application provides a wafer positioning method applied to an edge etching chamber, the positioning method comprising:

[0008] Based on the etching rate of multiple sampling points on the sampling circle of the wafer, the current etching uniformity parameter value is obtained and the direction to be corrected is determined;

[0009] Based on the target value of the etching uniformity parameter, and the fitting function of the change in the etching uniformity parameter value and the correction amount, the desired correction amount of the wafer transport mechanism is obtained.

[0010] The wafer transfer mechanism is corrected according to the desired correction amount and the desired correction direction.

[0011] This application also provides a semiconductor process apparatus, including an edge etching chamber, a wafer transfer mechanism, and a controller;

[0012] The wafer transport mechanism is used to transfer the wafer into or out of the edge etching chamber;

[0013] The controller includes a memory and a processor. When the memory is read by the processor, the wafer positioning method described above is executed.

[0014] The embodiments of this application can predict the distance that the wafer needs to move to reach the target of coinciding with the processing center during the edge etching process by using a wafer positioning method, and use the prediction results of this method to teach the wafer transport mechanism to correct the deviation, so as to achieve the uniformity of the etching results. Attached Figure Description

[0015] Figure 1 This is a flowchart of the positioning method disclosed in the embodiments of this application;

[0016] Figure 2 This is a schematic diagram illustrating the principle of wafer polarization correction disclosed in an embodiment of this application;

[0017] Figure 3 This is a schematic diagram of taking 8 sampling points on a sampling circle in the edge region of a wafer, as disclosed in an embodiment of this application.

[0018] Figure 4 This is a schematic diagram of the fitting function disclosed in the embodiments of this application;

[0019] Figure 5 This is a schematic diagram showing two sampling points selected at both ends of the first diameter and two sampling points selected at both ends of the second diameter on the same sampling circle disclosed in the embodiments of this application;

[0020] Figure 6 This is a schematic diagram showing the second diameter disclosed in the embodiments of this application forming an angle α with the X-axis;

[0021] Figure 7 This is a schematic diagram of the correction along the X-axis and Y-axis directions disclosed in the embodiments of this application. Detailed Implementation

[0022] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0023] The terms "first," "second," etc., used in the specification and claims of this application are used to distinguish similar objects and not to describe a specific order or sequence. It should be understood that such use of data can be interchanged where appropriate so that embodiments of this application can be implemented in orders other than those illustrated or described herein, and the objects distinguished by "first," "second," etc., are generally of the same class and the number of objects is not limited; for example, a first object can be one or more. Furthermore, in the specification and claims, "and / or" indicates at least one of the connected objects, and the character " / " generally indicates that the preceding and following objects are in an "or" relationship.

[0024] The embodiments of this application will be described in detail below with reference to the accompanying drawings and specific examples and application scenarios.

[0025] refer to Figures 1 to 7 This application discloses a wafer positioning method applied to an edge etching chamber. The disclosed positioning method includes:

[0026] Based on the etching rate of multiple sampling points on the sampling circle of the wafer, the current etching uniformity parameter value is obtained, and the direction to be corrected is determined.

[0027] Based on the target value of the etching uniformity parameter, and the fitting function of the change in the etching uniformity parameter value and the correction amount, the desired correction amount of the wafer transport mechanism is obtained.

[0028] The wafer transfer mechanism is corrected according to the desired correction amount and direction.

[0029] The embodiments of this application can predict the distance that the wafer needs to move to reach the target of coinciding with the processing center during the edge etching process by using a wafer positioning method, and use the prediction results of this method to teach the wafer transport mechanism to correct the deviation, so as to achieve the uniformity of the etching results.

[0030] In this embodiment of the application, at least one sampling circle can be selected in the edge region of the wafer. For example, for a wafer with a radius of 150 mm, a sampling circle in the range of 147.80 mm to 149.6 mm can be selected in the edge region. Multiple sampling points are selected on each sampling circle, and then the etching rate of each sampling point is calculated.

[0031] It should be noted that the diameter of the selected sampling circle can be chosen as either the inner or outer circle, or a specific radius of interest, depending on the requirements.

[0032] For example, the initial film thickness was measured using a silicon oxide wafer as the baseline, and the sampling points and coordinates are shown in Table 1.

[0033] Table 1. Sampling points and coordinates before etching

[0034]

[0035] Where R represents the distance from the center of the wafer, and X and Y represent the rectangular coordinate positions under that R.

[0036] Optionally, obtain the current etching uniformity parameter values, including:

[0037] From the etching rates of multiple sampling points, the maximum and minimum etching rates are selected, and the average etching rate of multiple sampling points is calculated.

[0038] The difference between the maximum and minimum etching rates is compared with twice the average etching rate to obtain the etching uniformity parameter value of the sampling circle.

[0039] For example, 8 sampling points are selected from each sampling circle, and the distribution of the 8 sampling points is as follows: Figure 3 As shown.

[0040] The wafer is placed in the edge etching chamber for etching. Then, post-etching values ​​are collected at the same coordinate positions, and the etching rate (ER) at each sampling point is calculated. The formula for calculating the etching rate is:

[0041]

[0042] During the adjustment process, uniformity (U-value) is used to characterize the etching uniformity parameter value, where the formula for calculating the etching uniformity parameter value is:

[0043]

[0044] The U-value collected before the wafer transport mechanism is corrected is denoted as U1, and the U-value collected after the wafer transport mechanism is corrected is denoted as U2. The change in the etching uniformity parameter value after correction is denoted as ΔU. The formula for calculating the change in the etching uniformity parameter value is as follows:

[0045] ΔU=U1-U2

[0046] Based on the above calculation formula, the etching rate at each of the eight sampling points on each sampling circle can be obtained, as shown in Table 2.

[0047] Table 2 shows the etching rate at the sampling points.

[0048] R ER1 ER2 ER3 ER4 ER5 ER6 ER7 ER8 Homogeneity (%) 149.60 10105 7487 10445 3928 6006 3323 4653 3816 57.2 149.55 7656 5750 7761 2761 4549 2443 3509 2849 57.1 149.50 5917 4114 6979 1988 3284 1809 2615 2122 59.9 149.45 4349 2911 4627 1516 2357 1402 1960 1642 62.1 149.40 3074 2126 3382 1208 1754 1122 1508 1294 58.5 149.35 2191 1583 2403 979 1347 914 1186 1043 51.1 149.30 1612 1239 1763 810 1068 762 963 860 44.1 149.20 955 807 1037 567 707 546 658 611 33.4 149.10 624 558 668 417 491 405 477 449 25.7 149.00 429 397 452 312 351 308 355 339 19.6 148.80 221 214 231 180 192 181 206 209 12.4 148.50 84 87 92 82 82 85 98 110 15.6 148.20 27 29 34 33 31 36 44 60 45.8 148.00 11 11 15 18 14 19 24 42 82.1 147.80 3 0 5 7 4 9 15 33 171.3

[0049] in addition, Figure 7 This is a MAP of etching rate, based on Figure 7The etching rate ER is too fast along the positive X-axis and the positive Y-axis, therefore the wafer transport mechanism should be moved in the negative X-axis and negative Y-axis directions. Thus, the desired correction direction is determined.

[0050] Optionally, the steps for obtaining the fitting function of the change in etching uniformity parameter value and the correction amount are as follows:

[0051] A historical database of component variations and correction amounts related to etching uniformity parameters;

[0052] The variation and correction amount of the etching uniformity parameter values ​​are fitted using a preset function to obtain the fitting function.

[0053] Specifically, process data from previous years under a preset fixed component configuration is collected, and the change in etching uniformity parameter value ΔU and the correction amount ΔR of the wafer transport mechanism are recorded respectively. Based on the previous process data, a historical database of the change in etching uniformity parameter value ΔU and the correction amount ΔR can be constructed.

[0054] Based on the aforementioned historical database, a model with a pre-defined function is used to fit the change ΔU and the correction amount ΔR to obtain a fitting function. The pre-defined function can be determined based on the specific degree of fit.

[0055] For example, the type of preset function can include: power function, polynomial function, exponential function, logarithmic function, etc. Of course, other types of function models are also possible, without specific limitations here. In practical applications, the function with better fit can be selected for fitting based on the mean square error of the fitted function. A mean square error greater than 0.5 is considered a good fit, and the closer to 1, the more accurate the fit.

[0056] Alternatively, a linear function can be used to fit the change in etching uniformity parameter value ΔU and the correction amount ΔR, resulting in a fitting function of the following form:

[0057] ΔU=kΔR+b

[0058] Where ΔU is the change in the etching uniformity parameter value, ΔR is the correction amount of the mechanical transmission mechanism, k is a coefficient, and b is a constant.

[0059] For example, a linear function is selected to fit the change ΔU and the correction amount ΔR at a radius of 149.4 mm to obtain the above-mentioned fitted function form. The derivative of the fitted function is then obtained to obtain (ΔU)'=k, which means that for every 1 μm change in ΔR, ΔU changes by k.

[0060] Furthermore, based on the difference between the current etching uniformity parameter value and the target etching uniformity parameter value, and the fitting function, the desired correction amount ΔR can be obtained.adjust The calculation formula is as follows:

[0061]

[0062] Wherein, ΔU adjust This represents the desired change in the etching uniformity parameter, ΔU. adjust The calculation formula is:

[0063] ΔU adjust =U now -U target

[0064] Among them, U now U represents the current etching uniformity parameter value. target This represents the target value for the etching uniformity parameter (i.e., the U value to be adjusted).

[0065] Figure 4 To fit the function curve, according to Figure 4 It can be seen that the mean square error (R²) of the fitted function 2 The value is 0.8, therefore, a linear function model can be used to predict the correction amount. Furthermore, according to this fitted function, under this hardware configuration, for a sampling circle with a radius of 149.4 mm, the etching uniformity parameter U changes by 10.8% for every 100 μm movement in a certain direction.

[0066] According to Table 2, at a radius of 149.4 mm, the etching uniformity parameter U is 58.5%. The desired adjustment of U is 10%, which results in a desired change ΔU. adjust =48.5%, that is, it should be moved 450μm in a certain direction.

[0067] Based on the above process, the desired correction amount ΔR can be obtained.

[0068] refer to Figure 2 Considering that during the adjustment of the wafer transfer mechanism, the distance in the X-axis direction and the distance in the Y-axis direction are adjusted, and the adjustment values ​​in the X-axis direction and the Y-axis direction can be vector-superimposed to obtain the distance the wafer moves along a certain radius direction, this distance is the aforementioned adjustment amount ΔR.

[0069] In the actual correction process, adjustments can be made in both the X-axis and Y-axis directions to achieve the desired correction amount ΔR. Therefore, it is necessary to calculate the distances to be moved in the X-axis and Y-axis directions respectively.

[0070] Based on the above settings, the embodiments of this application can obtain the desired correction amount in the X-axis direction and the desired correction amount in the Y-axis direction according to the desired correction amount, wherein the Y-axis or X-axis passes through the preset reference point of the edge etching chamber.

[0071] It should be noted here that the valve of the edge etching chamber is used as a reference, and the position of the edge of the wafer facing the valve when the wafer is transferred to the edge etching chamber is the preset reference point.

[0072] Furthermore, based on the desired correction amount, the desired correction amount in the X-axis direction and the desired correction amount in the Y-axis direction are obtained, including:

[0073] Obtain the etching rate of each of the two sampling points located at both ends of the first diameter on the sampling circle, and calculate the absolute value of the difference between the etching rates of the two sampling points, which is ΔER1;

[0074] Obtain the etching rates of two sampling points located at the two ends of the second diameter perpendicular to the first diameter on the sampling circle, and calculate the absolute value of the difference between the etching rates of the two sampling points, which is ΔER2; where,

[0075]

[0076] ΔR1 adjust Let ΔR2 be the distance moved along the first diameter direction. adjust This represents the distance traveled along the second diameter direction;

[0077] According to the Pythagorean theorem:

[0078]

[0079] Combining the two equations, the distance ΔR1 that can be moved along the first diameter direction can be calculated. adjust and the distance ΔR2 moved along the second diameter direction adjust .

[0080] refer to Figure 5 and Figure 6 The sampling points corresponding to ER4 and ER5 are located at the two ends of the first diameter, while the sampling points corresponding to ER1 and ER8 are located at the two ends of the second diameter.

[0081] The difference between ER4 and ER5 is:

[0082] △ER1=|ER4-ER5|

[0083] The difference between ER1 and ER8 is:

[0084] △ER2=|ER1-ER8|

[0085] For ease of understanding, the following three conditions are given:

[0086] 1. For a given sampling point on a wafer, the etching rate within a radius sufficiently close to that sampling point is linear;

[0087] 2. Under the same hardware configuration and for the same process formulation, different wafers are in the same plasma environment, including plasma density distribution, etc.

[0088] 3. Ideally, the plasma distribution is radially uniform, meaning that for sampling points with the same radius as the plasma processing center, the etching rate is the same.

[0089] Based on this, under the condition that "for sampling points with the same radius as the plasma processing center, the etching rate is the same", the moving distance ΔR1 along the first diameter direction adjust and the distance ΔR2 moved along the second diameter direction adjust The calculation formula is:

[0090]

[0091] By applying the Pythagorean theorem, the distance ΔR1 moved along the first diameter direction can be calculated. adjust and the distance ΔR2 moved along the second diameter direction adjust .

[0092] When the first diameter is parallel to the X-axis and the second diameter is parallel to the Y-axis, Figure 6 When α is 90°, the desired adjustment amount ΔX in the X-axis direction is... adjust With ΔR1 adjust Equal, the desired adjustment amount ΔY in the Y-axis direction adjust With ΔR2 adjust Equal. Of course, if the angle between the first diameter and the X-axis is less than or equal to the preset angle, it can be considered as within the unchangeable range, and the desired adjustment amount ΔX will not be changed without altering the X-axis direction. adjust Adjustable amount ΔY along the Y-axis adjust For example, the preset included angle can be 15°, but of course, it can also be other degrees, which are not specifically limited here.

[0093] For the embodiments of this application, the desired adjustment amount ΔX in the X-axis direction within the error range can be obtained through calculation. adjust =130μm, desired adjustment amount ΔY in the Y-axis direction adjust =430μm.

[0094] Thus, by adopting the positioning method in the embodiments of this application, the correction amount and correction direction of the wafer transfer mechanism are obtained, so that the wafer transfer mechanism can be corrected according to the correction amount and correction direction.

[0095] When the angle between the first diameter and the X-axis is outside the error range, appropriate adjustments need to be made to reduce error interference.

[0096] Specifically, when the angle between the first diameter and the X-axis is greater than a preset angle, the desired correction amount ΔX in the X-axis direction is... adjust The desired correction amount ΔY in the Y-axis direction adjust The calculation formulas are as follows:

[0097] ΔX adjust =ΔR1 adjust ×sinα+ΔR2 adjust ×cisα

[0098] ΔY adjust =ΔR1 adjust ×cosα+ΔR2 adjust ×sinα

[0099] Where α is the complementary angle between the first diameter and the X-axis.

[0100] Based on this, even outside the error range, the desired adjustment amount ΔX in the X-axis direction can still be obtained through calculation. adjust Adjustable amount ΔY along the Y-axis adjust .

[0101] To verify the effectiveness of the positioning method, the embodiments of this application collected the etching data after correction, as shown in Table 3.

[0102] Table 3 Etching data after correction

[0103] R ER1 ER2 ER3 ER4 ER5 ER6 ER7 ER8 Uniformity (%) 149.60 5878 6209 5689 4989 5306 4584 5618 4976 15.0 149.55 4127 4528 4118 3612 3828 3358 4253 3716 14.8 149.50 2835 3159 2866 2554 2678 2437 3143 2726 12.9 149.45 2048 2286 2053 1899 1957 1832 2311 2034 11.7 149.40 1560 1727 1550 1457 1492 1411 1737 1556 10.4 149.35 1214 1335 1202 1165 1174 1119 1341 1235 9.0 149.30 968 1077 963 953 947 927 1081 1002 7.8 149.20 662 733 652 664 644 652 733 702 6.5 149.10 475 527 462 479 457 477 522 514 7.2 149.00 350 389 335 358 334 357 389 385 7.6 148.80 198 220 191 210 190 213 230 229 9.5 148.50 92 103 85 100 88 102 116 121 17.5 148.20 41 46 38 48 40 48 59 67 30.4 148.00 22 26 20 30 22 28 40 48 47.5 147.80 13 16 13 18 13 16 29 35 56.6

[0104] The uniformity parameters of the two sets of data before and after correction were 58.5% and 10.4% respectively, with a radius of 149.4 mm. It can be seen that the positioning method in the embodiment of this application can correct the deviation between the wafer geometric center and the processing center, thereby improving the radial uniformity of the wafer.

[0105] Of course, after the current correction, the correction requirements may not be met. In this case, correction is needed to improve the correction effect. Based on this situation, in this embodiment of the application, if the etching uniformity parameter value does not meet the requirements after the wafer reaches the desired correction amount, the process data involved in the current correction process is stored in the historical database to update the historical database;

[0106] The changes and correction values ​​of the etching uniformity parameters in the updated historical database are refitted using a preset function to obtain an updated fitting function. For example, the preset function can be a linear function, etc.

[0107] Based on this, the updated correction amount can be obtained by taking the difference between the next etching uniformity parameter value and the target etching uniformity parameter value, as well as the updated fitting function.

[0108] Based on the updated desired correction value, the updated desired correction value in the X-axis direction and the updated desired correction value in the Y-axis direction are obtained respectively.

[0109] Therefore, the wafer transfer mechanism can perform correction based on the updated X-axis and Y-axis correction values ​​to ensure wafer position accuracy.

[0110] It should be noted that in this embodiment, the number of times the wafer is corrected is not limited, until the etching uniformity parameter value meets the requirements after the wafer reaches the desired correction amount.

[0111] Based on the above wafer positioning method, this application also discloses a semiconductor process apparatus, which includes an edge etching chamber, a wafer transfer mechanism, and a controller. The wafer transfer mechanism is used to transfer the wafer into or out of the edge etching chamber, and the controller includes a memory and a processor. When the memory is read by the processor, the above wafer positioning method is executed.

[0112] The embodiments of this application have been described above with reference to the accompanying drawings. However, this application is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many other forms under the guidance of this application without departing from the spirit and scope of the claims, and all of these forms are within the protection scope of this application.

Claims

1. A wafer positioning method applied to an edge etching chamber, characterized in that, The positioning method includes: Based on the etching rate of multiple sampling points on the sampling circle of the wafer, the current etching uniformity parameter value is obtained, and the direction to be corrected is determined. Based on the target value of the etching uniformity parameter and the fitting function of the change in the etching uniformity parameter value and the correction amount, the desired correction amount of the wafer transport mechanism is obtained. Specifically, process data under previous preset fixed component configurations are collected, and the change in the etching uniformity parameter value and the correction amount of the wafer transport mechanism are recorded respectively to construct a historical database of the change in the etching uniformity parameter value and the correction amount. Based on the historical database, a preset function is used to fit the change in the etching uniformity parameter value and the correction amount to obtain the fitting function. The wafer transfer mechanism is corrected according to the desired correction amount and the desired correction direction.

2. The positioning method according to claim 1, characterized in that, The step of fitting the change in the etching uniformity parameter value and the correction amount using a preset function to obtain the fitting function includes: The fitting function obtained by fitting the change in the etching uniformity parameter value and the correction amount using a linear function is as follows: ΔU=kΔR+b Where ΔU is the change in the etching uniformity parameter value, ΔR is the correction amount of the wafer transport mechanism, k is a coefficient, and b is a constant.

3. The positioning method according to claim 2, characterized in that, The desired correction amount is obtained based on the difference between the current etching uniformity parameter value and the target etching uniformity parameter value, and the fitting function.

4. The positioning method according to claim 1, characterized in that, The desired correction amount is obtained in the X-axis direction and the desired correction amount in the Y-axis direction, respectively, wherein the Y-axis or the X-axis passes through the preset reference point of the edge etching chamber.

5. The positioning method according to claim 4, characterized in that, The step of obtaining the desired correction amount in the X-axis direction and the desired correction amount in the Y-axis direction based on the desired correction amount includes: Obtain the etching rate of each of the two sampling points located at both ends of the first diameter on the sampling circle, and calculate the absolute value of the difference between the etching rates of the two sampling points, which is ΔER1; The etching rates of two sampling points located at the two ends of a second diameter perpendicular to the first diameter on the sampling circle are obtained, and the absolute value of the difference between the etching rates of the two sampling points is calculated and denoted as ΔER2; where, ΔR1 adjust ΔR2 is the distance traveled along the first diameter direction. adjust This represents the distance traveled along the direction of the second diameter. According to the Pythagorean theorem: Combining the two equations, the distance ΔR1 moved along the first diameter direction is calculated. adjust and the distance ΔR2 moved along the second diameter direction adjust .

6. The positioning method according to claim 5, characterized in that, When the angle between the first diameter and the X-axis is less than or equal to a preset angle, the desired correction amount ΔX in the X-axis direction is... adjust With ΔR1 adjust Equal, the amount of deviation to be corrected in the Y-axis direction ΔY adjust With ΔR2 adjust equal; When the angle between the first diameter and the X-axis is greater than a preset angle, the desired correction amount ΔX in the X-axis direction is... adjust The desired correction amount ΔY in the Y-axis direction adjust The calculation formulas are as follows: Wherein, α is the complementary angle between the first diameter and the X-axis.

7. The positioning method according to claim 1, characterized in that, The process of obtaining the current etching uniformity parameter value includes: From the etching rates of each of the multiple sampling points, the maximum etching rate and the minimum etching rate are selected, and the average etching rate of the multiple sampling points is calculated. The difference between the maximum etching rate and the minimum etching rate is compared with twice the average etching rate to obtain the etching uniformity parameter value of the sampling circle.

8. The positioning method according to claim 1, characterized in that, If the etching uniformity parameter value does not meet the requirements after the wafer reaches the desired correction amount, the process data involved in the current correction process is stored in the historical database to update the historical database. The preset function is used to refit the change in the etching uniformity parameter value and the correction amount in the updated historical database to obtain the updated fitting function.

9. A semiconductor process apparatus, characterized in that, include: Edge etching chamber, wafer transport mechanism, and controller; The wafer transport mechanism is used to transfer the wafer into or out of the edge etching chamber; The controller includes a memory and a processor, and when the memory is read by the processor, the wafer positioning method according to any one of claims 1 to 8 is executed.

Images