Film thickness testing structure and method for monitoring position of light spot in real time in measurement process

Abstract

The invention provides a film thickness testing structure and a method for monitoring the position of a light spot in the measuring process in real time, the film thickness testing structure comprises a plurality of measuring blocks which are sequentially arranged at intervals in the X direction, each measuring block is correspondingly provided with a pair of numbered characters, the pair of numbered characters are provided with four symmetrical feature points located at the four vertexes of a rectangle, and the number of the numbered characters is larger than the number of the numbered characters. The intersection point of two diagonals of the rectangle is used as the central point of the measuring block. In the actual film thickness measuring process, the light spot is projected to the measuring block, the positions of the four symmetrical feature points of the pair of numbered characters corresponding to the measuring block are selected to be grabbed and positioned, the position coordinates of the four symmetrical feature points are recorded, and meanwhile the position coordinates of the light spot are recorded in real time. Calculating the position coordinates of the central point of the measuring block according to the recorded position coordinates of the four symmetrical feature points, and calculating the offset of the light spot position relative to the position of the central point of the measuring block; according to the invention, the actual measurement position of the light spot on the line can be monitored in real time, so that the position of the light spot can be adjusted in time, and an accurate measurement result is obtained.

Description

Technical Field

[0001] The invention belongs to the technical field of semiconductors and relates to a film thickness test structure and a method for real-time monitoring of a light spot position during a measurement process. Background Art

[0002] A chip is a 3D structure composed of a series of active and passive circuit elements stacked together. Insulating dielectric films such as SiO2 and silicon nitride and metal conductive films such as Al and Cu are alternately stacked on the surface of the wafer through physical / chemical methods. Mask pattern transfer (photolithography), etching and other processes can be performed on the film to ultimately form circuit structures of each layer.

[0003] During the wafer manufacturing process, the wafer group (lot) needs to be transferred to the film thickness measurement machine for testing after the thin film deposition is completed. When the light spot is deflected or the light spot measurement position shifts during the actual thickness (THK) measurement process, the measurement machine will output erroneous measurement results, resulting in an OCAP (Out of Control Action Plan) online. Currently, engineers mostly infer the light spot position offset by measuring abnormal results, which is time-delayed.

[0004] Therefore, how to improve the film thickness test structure and provide a method for real-time monitoring of the light spot position during the measurement process and timely adjust the actual light spot measurement position to ensure the measurement position accuracy and output measurement result accuracy has become an important technical problem that technical personnel in this field need to solve urgently.

[0005] It should be noted that the above introduction to the technical background is only for the convenience of providing a clear and complete description of the technical solutions of the present application and for the convenience of understanding by those skilled in the art. It cannot be considered that the above technical solutions are well known to those skilled in the art simply because they are described in the background technology section of the present application. Summary of the invention

[0006] In view of the above-mentioned shortcomings of the prior art, an object of the present invention is to provide a film thickness test structure and a method for real-time monitoring of the light spot position during the measurement process, so as to solve the problem of delay in determining the light spot position offset in the prior art.

[0007] To achieve the above-mentioned and other related purposes, the present invention provides a method for real-time monitoring of the position of a light spot during a measurement process, comprising the following steps:

[0008] A wafer is provided, the wafer comprising a film thickness measurement area, the film thickness measurement area is provided with a plurality of measurement blocks arranged sequentially and at intervals along an X direction, each of the measurement blocks is correspondingly configured with a pair of numbered characters;

[0009] Projecting a light spot onto the measuring block, selecting four symmetrical feature points of a pair of numbered characters corresponding to the measuring block as four vertices of a rectangle, grasping and locating the positions of the four symmetrical feature points, and recording the position coordinates of the four symmetrical feature points in a preset coordinate system, while recording the position coordinates of the light spot in the preset coordinate system in real time;

[0010] Taking the intersection of the two diagonals of the rectangle as the center point of the measurement block, and calculating the position coordinates of the center point of the measurement block according to the recorded position coordinates of the four symmetrical feature points;

[0011] The offset of the light spot position relative to the center point position of the measurement block is calculated according to the recorded light spot position coordinates and the calculated center point position coordinates of the measurement block.

[0012] Optionally, when the offset is less than a preset value, it is determined that the light spot position is located at the center of the measurement block;

[0013] When the offset is greater than a preset value, it is determined that the light spot position deviates from the center of the measuring block, and the offset is fed back to the machine end, and the relevant position parameters are adjusted until the offset is less than the preset value.

[0014] Optionally, after the offset is fed back to the machine end, the machine automatically adjusts the relevant position parameters until the offset is less than a preset value, or prompts the engineer to adjust the relevant position parameters through an alarm.

[0015] Optionally, the relevant position parameters include at least one of a spot size, an exposure field size and a mechanical platform parameter.

[0016] Optionally, two numbered characters in a pair of numbered characters are arranged on both sides of the corresponding measurement block along the X direction and are mirror-symmetric about the Y direction center axis of the corresponding measurement block, the Y direction is perpendicular to the X direction, the numbered characters corresponding to different measurement blocks have different shapes, and each of the numbered characters is symmetrical about its own X direction center line.

[0017] Optionally, the numbering character is selected from at least one of the letters I, C, D, E, B, H, K, O and X.

[0018] Optionally, a cross mark is provided at a preset position on the wafer, and the preset coordinate system uses the center of the cross mark as a coordinate origin.

[0019] Optionally, calculating the position coordinates of the center point of the measurement block according to the recorded position coordinates of the four symmetrical feature points includes:

[0020] A first straight line equation y1=k1x+b1 is obtained according to the position coordinates (x1, y1) and (x2, y2) of the two symmetrical feature points located on the first diagonal line of the rectangle, and a second straight line equation y2=k2x+b2 is obtained according to the position coordinates (x1, y2) and (x2, y1) of the two symmetrical feature points located on the second diagonal line of the rectangle;

[0021] According to the condition y1=y2, the center point position coordinates (x0, y0) of the corresponding measurement block are calculated.

[0022] Optionally, calculating the offset of the light spot position relative to the center point position of the measurement block includes:

[0023] The coordinates of the center point of the measuring block are marked as (x0, y0), and the coordinates of the light spot are marked as (x3, y3);

[0024] Use |x0-x3| as the x-direction offset and |y0-y3| as the y-direction offset.

[0025] Optionally, when the x-direction offset is smaller than a first preset value, and the y-direction offset is smaller than a second preset value, it is determined that the light spot position is located at the center of the measurement block.

[0026] Optionally, the measuring block is rectangular in shape.

[0027] The present invention also provides a film thickness test structure, which is arranged in a film thickness measurement area of ​​a wafer, wherein the film thickness test structure includes a plurality of measurement blocks, the plurality of measurement blocks are arranged sequentially and at intervals along the X direction, and each of the measurement blocks is correspondingly configured with a pair of numbered characters, wherein the pair of numbered characters corresponding to the measurement block has four symmetrical feature points located at the four vertices of a rectangle, and the intersection of the two diagonals of the rectangle serves as the center point of the measurement block.

[0028] Optionally, two numbered characters in a pair of numbered characters are arranged on both sides of the corresponding measurement block along the X direction and are mirror-symmetric about the Y direction center axis of the corresponding measurement block, the Y direction is perpendicular to the X direction, the numbered characters corresponding to different measurement blocks have different shapes, and each of the numbered characters is symmetrical about its own X direction center line.

[0029] Optionally, the numbering character is selected from at least one of the letters I, C, D, E, B, H, K, O and X.

[0030] Optionally, the measuring block is rectangular in shape.

[0031] As described above, the present invention provides a film thickness test structure and a method for real-time monitoring of the position of a light spot during a measurement process, wherein the film thickness test structure is arranged in a film thickness measurement area of ​​a wafer and includes a plurality of measurement blocks arranged sequentially and at intervals along the X direction, each measurement block is configured with a pair of numbered characters, a pair of numbered characters has four symmetrical feature points located at the four vertices of a rectangle, and the intersection of two diagonal lines of the rectangle is used as the center point of the measurement block. In the actual film thickness measurement process, the light spot is projected onto the measurement block, and the four symmetrical feature points of the pair of numbered characters corresponding to the measurement block are selected as the four vertices of the rectangle, the positions of the four symmetrical feature points are captured and located, and the position coordinates of the four symmetrical feature points in a preset coordinate system are recorded, and the position coordinates of the light spot in the preset coordinate system are recorded in real time; then the intersection of the two diagonal lines of the rectangle is used as the center point of the measurement block, and the position coordinates of the center point of the measurement block are calculated according to the recorded position coordinates of the four symmetrical feature points, and the offset of the light spot position relative to the center point position of the measurement block is calculated according to the recorded light spot position coordinates and the calculated center point position coordinates of the measurement block. The present invention can monitor the actual measurement position of the light spot on the line in real time, thereby facilitating timely adjustment of the light spot position and obtaining accurate measurement results. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 Shown is a flow chart of the method for real-time monitoring of the light spot position during the measurement process of the present invention.

[0033] Figure 2 Displayed as a graphic of the film thickness measurement area.

[0034] Figure 3 A diagram showing a film thickness test structure used in the method for real-time monitoring of the light spot position during the measurement process of the present invention.

[0035] Figure 4 It is a schematic diagram showing a method of real-time monitoring of the position of a light spot during a measurement process of the present invention, wherein specific symmetrical points are selected in a symmetrical character to form a rectangle, the end points of the rectangle are cross-connected, and the intersection of the cross-connected lines of the rectangle is used as the center point of the corresponding measurement block.

[0036] Figure 5 It is a schematic diagram showing the position coordinates of four symmetrical feature points and the position coordinates of the light spot in a plane rectangular coordinate system with the center O(0,0) of the cross mark as the coordinate origin in the method of real-time monitoring the light spot position during the measurement process of the present invention.

[0037] Description of Reference Numerals

[0038] Steps S1 to S4 101, 201 measuring block DETAILED DESCRIPTION

[0039] The following describes the embodiments of the present invention through specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention.

[0040] See also Figures 1 to 5 It should be noted that the illustrations provided in this embodiment are only used to illustrate the basic concept of the present invention in a schematic manner, and the drawings only show components related to the present invention rather than being drawn according to the number, shape and size of components in actual implementation. In actual implementation, the type, quantity and proportion of each component may be changed arbitrarily, and the component layout may also be more complicated.

[0041] The present invention provides a film thickness test structure and a method for real-time monitoring of the light spot position during the measurement process. Figure 1 , shown as a flow chart of the method, comprising the following steps:

[0042] S1: providing a wafer, the wafer comprising a film thickness measurement area, the film thickness measurement area being provided with a plurality of measurement blocks arranged sequentially and at intervals along an X direction, each of the measurement blocks being correspondingly configured with a pair of numbered characters;

[0043] S2: Projecting the light spot onto the measuring block, selecting four symmetrical feature points of a pair of numbered characters corresponding to the measuring block as four vertices of a rectangle, grasping and locating the positions of the four symmetrical feature points, and recording the position coordinates of the four symmetrical feature points in a preset coordinate system, while recording the position coordinates of the light spot in the preset coordinate system in real time;

[0044] S3: taking the intersection of the two diagonals of the rectangle as the center point of the measurement block, and calculating the position coordinates of the center point of the measurement block according to the recorded position coordinates of the four symmetrical feature points;

[0045] S4: Calculating the offset of the light spot position relative to the center point position of the measurement block according to the recorded light spot position coordinates and the calculated center point position coordinates of the measurement block.

[0046] Specifically, in step S1 of the present invention, a unique and symmetrical character pad number (Pad No.) is designed, and in the subsequent actual measurement process, these number characters can be used to accurately locate the center position of the measurement pad.

[0047] For comparison, see Figure 2, showing a graphic of a film thickness measurement area, wherein TK represents thickness, a plurality of measurement blocks 101 are arranged in sequence and at intervals along the X direction, a number character is correspondingly arranged on the left side of each measurement block, and the plurality of number characters are named in alphabetical order, such as A, B, C, D, E, F, G, and these number characters only serve to number the measurement blocks. In the present invention, each of the measurement blocks 201 is correspondingly configured with a pair of number characters with a positioning function, which, in addition to serving as the numbering function of the measurement block, can accurately locate the center position of the measurement block in actual measurement.

[0048] As an example, see Figure 3 , which shows a graphic of a film thickness test structure used in the present invention, wherein the film thickness test structure is arranged in a film thickness measurement area of ​​a wafer, wherein TK represents thickness.

[0049] Specifically, the film thickness test structure includes a plurality of measurement blocks 201, which are arranged in sequence and at intervals along the X direction, and each of the measurement blocks 201 is correspondingly configured with a pair of numbered characters, wherein the pair of numbered characters corresponding to the measurement block has four symmetrical feature points located at the four vertices of a rectangle, and the intersection of the two diagonals of the rectangle serves as the center point of the measurement block.

[0050] As an example, two numbered characters in a pair of numbered characters are arranged on both sides of the corresponding measurement block 201 along the X direction and are mirror-symmetrical. The numbered characters corresponding to different measurement blocks 201 have different shapes, and each numbered character is symmetrical about its own X-direction center line.

[0051] As an example, the shape of the measurement block 201 is rectangular, and the number character is selected from at least one of the letters I, C, D, E, B, H, K, O and X.

[0052] Specifically, the positioning function of the symmetrical numbered characters in the present invention is reflected in that: a rectangle can be formed by selecting specific symmetrical points in the symmetrical characters, and the end points of the rectangle are cross-connected, and the intersection of the cross-connected lines of the rectangle is the center point of the corresponding measurement block. For example, see Figure 4For a measurement block using a pair of numbered characters I, the top point of the numbered character I on the left side of the measurement block is selected as the first symmetric feature point, the bottom point of the numbered character I on the left side of the measurement block is selected as the second symmetric feature point, the top point of the numbered character I on the right side of the measurement block is selected as the third symmetric feature point, and the bottom point of the numbered character I on the right side of the measurement block is selected as the fourth symmetric feature point, wherein the first symmetric feature point is symmetric with the second symmetric feature point about the X-direction center line of the numbered character itself, the third symmetric feature point is symmetric with the fourth symmetric feature point about the X-direction center line of the numbered character itself, the first symmetric feature point is mirror-symmetric with the third symmetric feature point about the Y-direction center axis of the measurement block, and the second symmetric feature point is mirror-symmetric with the fourth symmetric feature point about the Y-direction center axis of the measurement block. For other symmetrical numbered characters, the selection of the four symmetric feature points satisfies the above principles.

[0053] Specifically, the measurement block 201 includes a film layer to be measured located at the top layer. For example, in one embodiment, the measurement block 201 includes a Si layer, a TEOS layer, and an Al layer stacked sequentially from bottom to top. The area around the measurement block 201 includes the Si layer and the TEOS layer stacked sequentially from bottom to top, but does not include the Al layer to be measured. In the step S2, an ellipsometer or other suitable film thickness measurement equipment can be used to project a light spot on the measurement block 201. Subsequently, by inverting the polarization state of the reflected light, the film thickness information of the film layer to be measured can be obtained, thereby realizing the measurement of the film thickness.

[0054] Specifically, during the film thickness measurement process, four symmetrical feature points of a pair of numbered characters corresponding to the measuring block 201 are selected as the four vertices of the rectangle, the positions of the four symmetrical feature points are captured and located, and the position coordinates of the four symmetrical feature points in the preset coordinate system are recorded, and the position coordinates of the light spot in the preset coordinate system are recorded in real time.

[0055] As an example, a cross mark is provided at a preset position on the wafer, and the preset coordinate system uses the center of the cross mark as the coordinate origin.

[0056] As an example, see Figure 5 , which is displayed as the position coordinates of the four symmetrical feature points and the position coordinates of the light spot in a plane rectangular coordinate system with the center O(0, 0) of the cross mark as the coordinate origin.

[0057] As an example, the step S3 of calculating the position coordinates of the center point of the measurement block 201 according to the recorded position coordinates of the four symmetrical feature points includes the following process:

[0058] (1) A first straight line equation y1=k1x+b1 is obtained based on the position coordinates (x1, y1) and (x2, y2) of the two symmetrical feature points located on the first diagonal line of the rectangle (the diagonal line extending diagonally upward from left to right), and a second straight line equation y2=k2x+b2 is obtained based on the position coordinates (x1, y2) and (x2, y1) of the two symmetrical feature points located on the second diagonal line of the rectangle (the diagonal line extending diagonally downward from left to right);

[0059] (2) According to the condition y1=y2 (i.e., the intersection of the two straight lines), the coordinates of the center point position (x0, y0) of the corresponding measurement block are calculated.

[0060] As an example, the step S4 of calculating the offset of the light spot position relative to the center point position of the measurement block includes the following process:

[0061] (1) Mark the coordinates of the center point of the measurement block as (x0, y0), and the coordinates of the light spot as (x3, y3);

[0062] (2) Use |x0-x3| as the offset in the x direction and |y0-y3| as the offset in the y direction.

[0063] As an example, after the offset of the light spot position relative to the center point position of the measurement block is calculated in step S4, the following judgment step is further performed:

[0064] When the offset is less than a preset value, it is determined that the light spot position is located at the center of the measurement block;

[0065] When the offset is greater than a preset value, it is determined that the light spot position deviates from the center of the measuring block, and the offset is fed back to the machine end, and the relevant position parameters are adjusted until the offset is less than the preset value.

[0066] As an example, when the x-direction offset is less than a first preset value and the y-direction offset is less than a second preset value, it is determined that the spot position is located at the center of the measurement block, wherein the first preset value and the second preset value can be set according to the actual process and are not specifically limited in the present invention.

[0067] As an example, when the x-direction offset is greater than a first preset value and / or the y-direction offset is greater than a second preset value, it can be determined that the spot position deviates from the center of the measurement block. At this time, the offset is fed back to the machine end, and the relevant position parameters are adjusted until the offset is less than the preset value.

[0068] In some embodiments, after the offset is fed back to the machine, the machine automatically adjusts the relevant position parameters until the offset is less than a preset value.

[0069] In other embodiments, after the offset is fed back to the machine end, the machine prompts the engineer to adjust the relevant position parameters through an alarm.

[0070] As an example, the relevant position parameters include but are not limited to at least one of a spot size, an exposure field size, and a mechanical platform parameter.

[0071] Specifically, adjusting the spot size is, for example, increasing or decreasing the diameter of the spot, for example, adjusting the spot size to 10 microns or other suitable sizes.

[0072] Specifically, the exposure field (wafer shot) is also called the light field. It refers to the size of the area covered by each exposure when the photolithography machine performs photolithography on the wafer during the semiconductor manufacturing process. The size of the exposure field directly affects the number and layout of integrated circuits that can be manufactured on the wafer. The exposure field size is usually expressed in area units, such as square millimeters (mm 2 ) or square micrometer (μm 2 ), this size can be set according to the requirements of the process technology. For example, in one embodiment, the exposure field size is adjusted to 10 microns×10 microns or other suitable sizes as needed.

[0073] Specifically, the mechanical platform in the present invention refers to a "stage wafer", which is used to place and move the wafer in a lithography machine or other semiconductor manufacturing equipment. This mechanical platform must have a high degree of accuracy and stability, because it is directly related to the positioning accuracy of transistors or other components on the wafer, thereby affecting the performance and yield of the entire chip. In the present invention, when it is determined that the spot position deviates from the center of the measurement block, the mechanical platform parameters can be adjusted as needed to improve the transmission position accuracy and help align the center of the spot with the center of the measurement block.

[0074] At this point, the present invention has designed a measurement-symmetrical measurement block number, which can accurately locate the center position of the measurement block during the actual measurement process. The position coordinates of the center point of the measurement block can be calculated through the position coordinates of the actual measurement number character feature points, and compared with the actual light spot position in real time. It can monitor in real time whether the light spot on the line is deviated, which helps to adjust the actual light spot measurement position in time, thereby ensuring the measurement position accuracy and the accuracy of the output measurement results.

[0075] In summary, the present invention provides a film thickness test structure and a method for real-time monitoring of the position of a light spot during a measurement process, wherein the film thickness test structure is arranged in a film thickness measurement area of ​​a wafer and includes a plurality of measurement blocks arranged sequentially and at intervals along the X direction, each measurement block is configured with a pair of numbered characters, a pair of numbered characters has four symmetrical feature points located at the four vertices of a rectangle, and the intersection of two diagonal lines of the rectangle is used as the center point of the measurement block. In the actual film thickness measurement process, the light spot is projected onto the measurement block, and the four symmetrical feature points of the pair of numbered characters corresponding to the measurement block are selected as the four vertices of the rectangle, the positions of the four symmetrical feature points are captured and located, and the position coordinates of the four symmetrical feature points in a preset coordinate system are recorded, and the position coordinates of the light spot in the preset coordinate system are recorded in real time; then the intersection of the two diagonal lines of the rectangle is used as the center point of the measurement block, and the position coordinates of the center point of the measurement block are calculated according to the recorded position coordinates of the four symmetrical feature points, and the offset of the light spot position relative to the center point position of the measurement block is calculated according to the recorded light spot position coordinates and the calculated center point position coordinates of the measurement block. The present invention can monitor the actual measurement position of the light spot on the line in real time, thereby facilitating timely adjustment of the light spot position and obtaining accurate measurement results. Therefore, the present invention effectively overcomes various shortcomings of the prior art and has high industrial utilization value.

[0076] The above embodiments are merely illustrative of the principles and effects of the present invention, and are not intended to limit the present invention. Anyone familiar with the art may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by a person of ordinary skill in the art without departing from the spirit and technical concept disclosed by the present invention shall still be covered by the claims of the present invention.

Claims

1. A method for real-time monitoring of the position of a light spot during a measurement process, characterized in that: The following steps are involved: A wafer is provided, the wafer comprising a film thickness measurement area, the film thickness measurement area is provided with a plurality of measurement blocks arranged sequentially and at intervals along an X direction, each of the measurement blocks is correspondingly configured with a pair of numbered characters; Projecting a light spot onto the measuring block, selecting four symmetrical feature points of a pair of numbered characters corresponding to the measuring block as four vertices of a rectangle, grasping and locating the positions of the four symmetrical feature points, and recording the position coordinates of the four symmetrical feature points in a preset coordinate system, while recording the position coordinates of the light spot in the preset coordinate system in real time; Taking the intersection of the two diagonals of the rectangle as the center point of the measurement block, and calculating the position coordinates of the center point of the measurement block according to the recorded position coordinates of the four symmetrical feature points; The offset of the light spot position relative to the center point position of the measurement block is calculated according to the recorded light spot position coordinates and the calculated center point position coordinates of the measurement block.

2. The method for real-time monitoring of the light spot position during the measurement process according to claim 1, characterized in that: When the offset is less than a preset value, it is determined that the light spot position is located at the center of the measurement block; When the offset is greater than a preset value, it is determined that the light spot position deviates from the center of the measuring block, and the offset is fed back to the machine end, and the relevant position parameters are adjusted until the offset is less than the preset value.

3. The method for real-time monitoring of the light spot position during the measurement process according to claim 2, characterized in that: When the offset is fed back to the machine, the machine automatically adjusts the relevant position parameters until the offset is less than the preset value, or prompts the engineer to adjust the relevant position parameters through an alarm.

4. The method for real-time monitoring of the light spot position during the measurement process according to claim 3, characterized in that: The relevant position parameters include at least one of a spot size, an exposure field size and a mechanical platform parameter.

5. The method for real-time monitoring of the light spot position during the measurement process according to claim 1, characterized in that: Two numbered characters in a pair of numbered characters are arranged on both sides of the corresponding measurement block along the X direction and are mirror-symmetrical about the Y direction center axis of the corresponding measurement block, the Y direction is perpendicular to the X direction, the numbered characters corresponding to different measurement blocks have different shapes, and each of the numbered characters is symmetrical about its own X direction center line.

6. The method for real-time monitoring of the light spot position during the measurement process according to claim 5, characterized in that: The number character is selected from at least one of the letters I, C, D, E, B, H, K, O and X.

7. The method for real-time monitoring of the light spot position during the measurement process according to claim 1, characterized in that: A cross mark is provided at a preset position on the wafer, and the preset coordinate system uses the center of the cross mark as the coordinate origin.

8. The method for real-time monitoring of the light spot position during the measurement process according to claim 1, characterized in that: Calculating the position coordinates of the center point of the measurement block according to the recorded position coordinates of the four symmetrical feature points includes: A first straight line equation y1=k1x+b1 is obtained according to the position coordinates (x1, y1) and (x2, y2) of the two symmetrical feature points located on the first diagonal line of the rectangle, and a second straight line equation y2=k2x+b2 is obtained according to the position coordinates (x1, y2) and (x2, y1) of the two symmetrical feature points located on the second diagonal line of the rectangle; According to the condition y1=y2, the center point position coordinates (x0, y0) of the corresponding measurement block are calculated.

9. The method for real-time monitoring of the light spot position during the measurement process according to claim 1, characterized in that: Calculating the offset of the spot position relative to the center point of the measurement block includes: The coordinates of the center point of the measuring block are marked as (x0, y0), and the coordinates of the light spot are marked as (x3, y3); Use |x0-x3| as the x-direction offset and |y0-y3| as the y-direction offset.

10. The method for real-time monitoring of the light spot position during the measurement process according to claim 9, characterized in that: When the x-direction offset is smaller than a first preset value, and the y-direction offset is smaller than a second preset value, it is determined that the light spot position is located at the center of the measurement block.

11. The method for real-time monitoring of the light spot position during the measurement process according to claim 1, characterized in that: The measuring block is in a rectangular shape.

12. A film thickness test structure, arranged in a film thickness measurement area of ​​a wafer, characterized in that: The film thickness test structure includes a plurality of measuring blocks, which are arranged in sequence and at intervals along the X direction, and each of the measuring blocks is correspondingly configured with a pair of numbered characters, wherein the pair of numbered characters corresponding to the measuring block has four symmetrical feature points located at the four vertices of a rectangle, and the intersection of the two diagonals of the rectangle is used as the center point of the measuring block.

13. The method for real-time monitoring of the position of a light spot during a measurement process according to claim 12, characterized in that: Two numbered characters in a pair of numbered characters are arranged on both sides of the corresponding measurement block along the X direction and are mirror-symmetrical about the Y direction center axis of the corresponding measurement block, the Y direction is perpendicular to the X direction, the numbered characters corresponding to different measurement blocks have different shapes, and each of the numbered characters is symmetrical about its own X direction center line.

14. The method for real-time monitoring of the light spot position during the measurement process according to claim 13, characterized in that: The number character is selected from at least one of the letters I, C, D, E, B, H, K, O and X.

15. The method for real-time monitoring of the light spot position during the measurement process according to claim 12, characterized in that: The measuring block is in a rectangular shape.

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