Wafer warpage measuring method and wafer warpage measuring device

Abstract

The invention provides a wafer warpage measuring method and a wafer warpage measuring device. According to the wafer warpage measurement method, after the wafer is fixed, coordinates are established for the wafer, measurement points are marked, a light source is emitted to the measurement points through an automatic focusing light source, three-dimensional coordinates of all the measurement points on the wafer can be obtained after light signals emitted by the measurement points are received, and the wafer warpage condition can be obtained by analyzing z-axis values of all the measurement points; according to the wafer warpage measuring device, the wafer is fixed through the wafer fixing device, coordinates are established for the wafer through the coordinate control device, the measuring points are marked, the automatic focusing light source is controlled, and the automatic focusing light source emits light signals to all the measuring points; and receiving the optical signal reflected by each measurement point through a detection device and obtaining the three-dimensional coordinate of each measurement point. Finally, high-precision warpage measurement can be carried out on the wafer under the condition that the wafer is not contacted.

Description

Technical Field

[0001] The invention relates to the field of semiconductor detection, and is a wafer warpage measurement method and a wafer warpage measurement device. Background Art

[0002] In semiconductor wafer manufacturing, the flatness of the wafer is usually a very important parameter. Affected by the material properties of the wafer itself and the thermal stress in the process, the wafer will have a certain degree of warping during the process, and the warping of the wafer will have a direct impact on the manufactured semiconductor devices. Therefore, it is necessary to measure the warping of the wafer in semiconductor wafer manufacturing. In the prior art, a thickness gauge is generally used to measure the warping of the wafer, but this method has low accuracy, and because the thickness gauge is in direct contact with the wafer, it is likely to scratch the wafer, causing the wafer to be unusable.

[0003] Therefore, how to perform high-precision measurement of wafer warpage without contacting the wafer has become one of the urgent problems to be solved by technical personnel in this field.

[0004] 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 invention 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 these solutions are described in the background technology section of the present invention. Summary of the invention

[0005] In view of the above-mentioned shortcomings of the prior art, an object of the present invention is to provide a wafer warpage measurement method and a wafer warpage measurement device, so as to solve the problem in the prior art that it is difficult to perform high-precision measurement on the wafer without contacting the wafer.

[0006] To achieve the above-mentioned purpose and other related purposes, the present invention provides a wafer warpage measurement method, the steps of which include at least: S1: fixing the wafer; establishing coordinates for the wafer and marking a number of measurement points on the wafer, controlling an autofocus light source to aim at each measurement point, emitting a light signal to each measurement point, receiving a light signal reflected by each measurement point to obtain a three-dimensional coordinate of each measurement point; S2: counting the z-axis value of the three-dimensional coordinate of each measurement point, judging whether the warpage of the wafer is within a preset range, so as to determine whether the flatness of the wafer is qualified.

[0007] Optionally, in step S1, the wafer center and m concentric circles of the wafer are used as distribution trajectories of measurement points, and the measurement points on each concentric circle are evenly distributed, wherein m is a natural number greater than or equal to 1.

[0008] More optionally, in step S1, after all measurement points on a concentric circle are measured, the measurement is moved to the measurement point on the next concentric circle for measurement.

[0009] Optionally, in step S1, n diameters of the wafer are used as distribution trajectories of measurement points, and the measurement points on each diameter are evenly distributed, wherein n is a natural number greater than or equal to 1.

[0010] More optionally, in step S1, after all the measuring points on a diameter are measured each time, the measurement is moved to the measuring point on the next diameter for measurement.

[0011] Optionally, in step S2, the maximum value and the minimum value of the z-axis values ​​of all the measuring points are compared, and when the difference between the maximum value and the minimum value is within a first preset value, it is considered that the warpage of the wafer is within a preset range.

[0012] Optionally, in step S2, the median and the mean of the z-axis values ​​of all the measuring points are obtained, and when the difference between the median and the mean is within a second preset value, it is considered that the warpage of the wafer is within a preset range.

[0013] Optionally, the wafer warpage measurement method further includes: drawing a 3D simulation graph of the wafer using the three-dimensional coordinate value of each measurement point, and using the 3D simulation graph of the wafer to determine whether the overall flatness of the wafer is qualified.

[0014] To achieve the above-mentioned purpose and other related purposes, the present invention also provides a wafer warpage measurement device, which at least includes: a wafer fixing device, a coordinate control device, an autofocus light source and a detection device; the wafer fixing device is composed of n fixing components located at the outer edge of the wafer, wherein n is a natural number greater than or equal to 2; the coordinate control device is used to build coordinates for the wafer and mark a number of measurement points on the wafer, and is used to control the autofocus light source to align with each measurement point; the autofocus light source is used to emit a light signal to each measurement point on the wafer; the detection device is used to receive the light signal reflected by each measurement point and convert it into an electrical signal, and obtain the coordinate value of each measurement point.

[0015] As described above, the wafer warpage measurement method and wafer warpage measurement device of the present invention have the following beneficial effects:

[0016] The wafer warpage measurement method and the wafer warpage measurement device of the present invention reduce the warpage measurement error caused by wafer movement by fixing the wafer, reduce the measurement deviation caused by defocusing by using an autofocus light source, and accurately and conveniently obtain the warpage condition of the wafer by establishing coordinates for the wafer; the present invention also reduces the random error caused by process differences of the wafer by regularly distributed measurement points; finally, the present invention achieves the purpose of performing high-precision warpage measurement on the wafer without contacting the wafer, and the present invention has the advantages of good safety, high degree of automation, and efficient data processing. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a schematic flow chart of the wafer warpage measurement method of the present invention.

[0018] Figure 2 It is a schematic diagram showing a first distribution trajectory of wafer measurement points of the present invention.

[0019] Figure 3 It is a schematic diagram showing a second distribution trajectory of wafer measurement points according to the present invention.

[0020] Figure 4 Shown is a schematic diagram of a 3D simulation pattern of a wafer according to the present invention.

[0021] Figure 5 It is a schematic structural diagram of the wafer warpage measurement device of the present invention.

[0022] Figure 6 Shown is a structural schematic diagram of the wafer fixing device of the present invention.

[0023] Component number description

[0024] 21 Wafer Center

[0025] 22 Inner concentric circles

[0026] 23 Outer concentric circles

[0027] 31 First diameter

[0028] 32 Second diameter

[0029] 33 Third diameter

[0030] 34 Fourth diameter

[0031] 511 Wafer Fixing Device

[0032] 512 Coordinate Control Device

[0033] 513 Autofocus Light Source

[0034] 514 Detection Device

[0035] 52 Wafer

[0036] 611 First lifting pin

[0037] 612 Second lifting pin

[0038] 613 Third lifting pin 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 Figure 1-Figure 6 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 illustrations 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] Using a laser device to perform non-contact measurement on the upper and lower surfaces of the wafer can obtain a high-precision measurement result, but this method requires the introduction of the intermediate quantity of the distance between the upper and lower light sources. The distance between the upper and lower light sources minus the measured distance of the upper and lower light sources to the wafer surface can be used to obtain the warpage of the wafer surface. Therefore, this method not only has redundant links, but also is prone to misjudgment when judging the wafer warpage by the thickness value. The present invention determines the x-axis and y-axis values ​​for each measurement point of the wafer before measurement, and obtains the z-axis value of each measurement point through autofocus optics. The present invention does not need to repeatedly convert the intermediate quantity to obtain the wafer warpage, and the present invention can accurately judge the wafer condition by directly obtaining the three-dimensional coordinates of each measurement point. In addition, the present invention also maintains the regularity of the distribution of wafer measurement points during the measurement process, reduces the random errors caused by differences in wafer performance, focusing errors, and measurement conditions, and the specific scheme of the present invention is as follows:

[0042] Embodiment 1

[0043] like Figure 1 As shown, this embodiment provides a wafer warpage measurement method, and the steps of the wafer warpage measurement method at least include:

[0044] S1: Fix the wafer; establish coordinates for the wafer and mark several measurement points on the wafer, control the autofocus light source to align with each measurement point along the distribution trajectory of each measurement point, emit a light signal to each measurement point, receive the light signal reflected by each measurement point to obtain the three-dimensional coordinates of each measurement point.

[0045] Specifically, in this embodiment, the purpose of fixing the wafer is to prevent the wafer from vibrating and other phenomena from affecting the wafer warpage measurement.

[0046] Specifically, in this embodiment, the purpose of establishing coordinates for the wafer is to obtain the three-dimensional coordinates of each measurement point on the wafer. As an example, the center of the wafer can be used as the coordinate origin, that is, the point where the x-axis, y-axis and z-axis are all zero. When the z-axis is equal to 0, the plane formed by the x-axis and the y-axis coincides with the surface of the wafer to be detected under ideal flatness. In practical applications, the positions of the x-axis, y-axis and z-axis can be set as needed, not limited to this embodiment. Specifically, in this embodiment, the x-axis coordinates and y-axis coordinates of each measurement point are set before the autofocus light source starts measuring, and the z-axis coordinates of each measurement point are obtained by receiving the light signal reflected from each measurement point.

[0047] Specifically, in this embodiment, several measurement points are marked on the wafer. Theoretically, the more measurements marked on the wafer, the more accurate the measurement results. As an example, the number of marking points is 9 to 81, including but not limited to 13, 25, 36, 49, and 64. In actual applications, the number of marking points is set according to actual needs and is not limited to this embodiment.

[0048] Specifically, in this embodiment, an auto-focus coaxial laser is used as the auto-focus light source. In practical applications, the type of the auto-focus light source can be selected as needed, and is not limited to this embodiment.

[0049] Specifically, as an implementation method of the present invention, in step S1, the center of the wafer and the m concentric circles of the wafer are used as the distribution trajectory of the measurement points, and the measurement points on each concentric circle are evenly distributed, wherein m is a natural number greater than or equal to 1; the measurement points are evenly distributed on the concentric circles in order to reduce the errors caused by random factors and improve the stability of the measurement results on the circumference of the wafer. It should be noted that when m is greater than or equal to 3, the radii of the m concentric circles can show a uniform multiple increase, that is, the distance between each group of adjacent concentric circles is the same. Furthermore, in this embodiment, in step S1, each time all the measurement points on a concentric circle are measured, move to the measurement point on the next concentric circle for measurement. As an example, if Figure 2As shown, m is 2, and the two concentric circles are respectively recorded as the inner concentric circle 22 and the outer concentric circle 23. There are 8 and 12 measurement points on the two concentric circles, respectively. In practical applications, the positions and numbers of the concentric circles and the measurement points can be set as needed, which is not limited to this embodiment. As an example, after controlling the auto-focus light source to emit a light signal toward the wafer center 21, the auto-focus light source is controlled to move to the inner concentric circle 22. After all the measurement points are measured along the inner concentric circle 22, the auto-focus light source is moved to the measurement point of the outer concentric circle 23 for measurement. In practical applications, the movement order of the auto-focus light source between the concentric circles can be set as needed, which is not limited to this embodiment.

[0050] Specifically, as another implementation method of the present invention, in step S1, the n diameters of the wafer are used as the distribution trajectory of the measurement points, and the measurement points on each diameter are evenly distributed, wherein n is a natural number greater than or equal to 1; the measurement points are evenly distributed on the wafer diameter in order to reduce the errors caused by random factors and improve the stability of the measurement results on the wafer diameter. It should be noted that when n is greater than or equal to 2, the n diameters can divide the wafer into equal parts, that is, the wafer can be divided into 2n equal parts through the n diameters. Furthermore, in this embodiment, in step S1, each time all the measurement points on a diameter are measured, move to the measurement points on the next diameter for measurement. As an example, if Figure 3 As shown, n is 4, and the 4 diameters are respectively recorded as the first diameter 31, the second diameter 32, the third diameter 33 and the fourth diameter 34. There are 3 measuring points on each diameter. In practical applications, the positions and numbers of the diameters and measuring points can be set as needed, which is not limited to this embodiment. As an example, the auto-focus light source is controlled to align with each measuring point along the trajectory of each diameter. After all measuring points on the first diameter 31 are measured, it is moved to the measuring point on the adjacent second diameter 32 for measurement until all measuring points on the third diameter 33 and the fourth diameter 34 are measured in turn. In practical applications, the moving order of the auto-focus light source between the diameters can be set as needed, which is not limited to this embodiment.

[0051] S2: Count the z-axis value of the three-dimensional coordinates of each measurement point to determine whether the warpage of the wafer is within a preset range, so as to determine whether the flatness of the wafer is qualified.

[0052] Specifically, as an implementation of the present invention, in step S2, the maximum and minimum values ​​of the z-axis values ​​of all measurement points are compared. When the difference between the maximum and minimum values ​​is within a first preset value, it is considered that the warpage of the wafer is within a preset range. As an example, the first preset value is set to [0mm, 3000mm], including but not limited to 500mm, 1000mm, 1500mm, 2000mm, 2500mm. In actual applications, the first preset value can be set as needed, not limited to this embodiment.

[0053] Specifically, as another implementation of the present invention, in step S2, the median and the average of the z-axis values ​​of all the measurement points are obtained. When the difference between the median and the average is within the second preset value, it is considered that the warpage of the wafer is within the preset range. As an example, the second preset value is set to [0mm, 100mm], including but not limited to 20mm, 40mm, 60mm, 80mm. In actual applications, the second preset value can be set as needed, not limited to this embodiment.

[0054] Specifically, in this embodiment, a 3D simulation graph of the wafer is drawn by the three-dimensional coordinate value of each measurement point, and the 3D simulation graph of the wafer is used to determine whether the overall flatness of the wafer is qualified. Figure 4 As shown, a 3D simulation graphic of the wafer is established by a wafer warpage measurement device, and the coordinate ruler represents the height of the wafer on the z-axis. The 3D simulation graphic of the wafer intuitively displays the height value of each point on the wafer. The difference between the maximum and minimum values ​​of the wafer height can be used to represent the warpage value of the wafer. In practical applications, the definition of the wafer warpage value is formulated as needed, which is not limited to this embodiment. By establishing a 3D simulation graphic of the wafer to obtain the warpage condition of any point on the wafer, it is possible to more accurately judge whether the warpage of the wafer meets the flatness requirements.

[0055] Embodiment 2

[0056] like Figure 5 As shown, this embodiment provides a wafer warpage measurement device, which includes: a wafer fixing device 511 , a coordinate control device 512 , an auto-focus light source 513 and a detection device 514 .

[0057] like Figure 6 As shown, the wafer fixing device 511 is composed of n fixing components located at the outer edge of the wafer, where n is a natural number greater than or equal to 2.

[0058] Specifically, as an example, Figure 6 As shown, the wafer fixing device 511 uses three lifting pins to fix the wafer 52. The first lifting pin 611, the second lifting pin 612 and the third lifting pin 613 are evenly distributed around the center of the wafer. In actual applications, the structure of the wafer fixing device 511 can be set as needed and is not limited to this embodiment.

[0059] like Figure 5 As shown, the coordinate control device 512 is used to build coordinates for the wafer 52 and mark a number of measurement points on the wafer 52, and is used to control the auto-focus light source 513 to align with each measurement point.

[0060] Specifically, the coordinate control device 512 first determines the origin and direction of the x-axis and the y-axis on the wafer, marks the measurement points on the wafer 52, and controls the autofocus light source 513 to align with each measurement point; as an example, the coordinate control device 512 distributes the measurement points on the wafer 52 as follows: Figure 2 As shown, after the coordinate control device 512 controls the auto-focus light source 513 to measure the measurement points along the inner concentric circle 22, the coordinate control device 512 moves the auto-focus light source 513 to the outer concentric circle 23 for measurement. In actual applications, the distribution positions of the measurement points and the movement order of the auto-focus light source 513 between the concentric circles are set as needed, which is not limited to this embodiment. As another example, the coordinate control device 512 distributes the measurement points on the wafer 52 as shown in FIG. Figure 3 As shown, after the coordinate control device 512 controls the auto-focus light source 513 to measure the measurement points along the first diameter 31, the coordinate control device 512 moves the auto-focus light source 513 to the adjacent second diameter 32 for measurement until all the measurement points on the diameters are measured. In actual applications, the distribution positions of the measurement points and the movement order of the auto-focus light source between the diameters are set as needed, which is not limited to this embodiment.

[0061] like Figure 5 As shown, the detection device 514 is used to receive the light signal reflected by each measuring point and convert it into an electrical signal, and obtain the coordinate value of each measuring point.

[0062] Specifically, the detection device 514 can know the x-axis and y-axis of each measuring point in advance through the coordinate control device 512, and the detection device 514 obtains the z-axis of each measuring point through the light signal reflected by each measuring point; as an example, the detection device 514 uses a photodetector. In actual applications, the type of detection device 514 can be selected as needed, and is not limited to this embodiment.

[0063] It should be noted that this embodiment is used to implement the wafer warpage measurement method of Embodiment 1. In actual use, any hardware structure that can implement this method is applicable, and is not limited to the wafer warpage measurement device of the present invention.

[0064] In summary, the wafer warpage measurement method of the present invention establishes coordinates for the wafer and marks the measurement points after fixing the wafer, obtains the three-dimensional coordinates of each measurement point through the autofocus light source, and the warpage of the wafer can be obtained through the three-dimensional coordinates of each measurement point; the wafer warpage measurement device of the present invention fixes the wafer through a wafer fixing device, establishes coordinates for the wafer through a coordinate control device, distributes measurement points and controls the autofocus light source to align with each measurement point, and receives the light signal reflected by the wafer through a detection device to obtain the three-dimensional coordinates of each measurement point. The wafer warpage measurement method and wafer warpage measurement device of the present invention avoid the warpage error caused by the rotation of the wafer by fixing the wafer, avoids direct contact with the wafer and reduces the measurement error caused by defocusing by using an autofocus light source, and more accurately and directly obtains the warpage of the wafer by establishing coordinates for the wafer, and reduces the error caused by the measurement conditions and wafer process differences by regularly distributing the measurement points. Finally, the present invention can achieve high-precision warpage measurement without contacting the wafer, and the present invention has the advantages of good safety, high degree of automation, and efficient data processing. Therefore, the present invention effectively overcomes various shortcomings in the prior art and has high industrial utilization value.

[0065] 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 wafer warpage measurement method, characterized in that: The steps of the wafer warpage measurement method at least include: S1: Fixing the wafer; establishing coordinates for the wafer and marking a number of measuring points on the wafer, controlling the autofocus light source to aim at each measuring point, emitting a light signal to each measuring point, and receiving a light signal reflected from each measuring point to obtain the three-dimensional coordinates of each measuring point; S2: Counting the z-axis value of the three-dimensional coordinates of each measuring point to determine whether the warpage of the wafer is within a preset range, so as to determine whether the flatness of the wafer is qualified.

2. The wafer warpage measurement method according to claim 1, characterized in that: In step S1, the wafer center and m concentric circles of the wafer are used as distribution trajectories of measurement points, and the measurement points on each concentric circle are evenly distributed, wherein m is a natural number greater than or equal to 1.

3. The wafer warpage measurement method according to claim 2, wherein: In step S1, after all the measuring points on a concentric circle are measured, the measurement is moved to the measuring point on the next concentric circle for measurement.

4. The wafer warpage measurement method according to claim 1, wherein: In step S1 , n diameters of the wafer are used as distribution trajectories of measurement points, and the measurement points on each diameter are evenly distributed, wherein n is a natural number greater than or equal to 1.

5. The wafer warpage measurement method according to claim 4, characterized in that: In step S1, after all the measuring points on a diameter are measured, the measurement is moved to the measuring point on the next diameter for measurement.

6. The wafer warpage measurement method according to any one of claims 1 to 5, characterized in that: In step S2, the maximum value and the minimum value of the z-axis values ​​of all the measuring points are compared, and when the difference between the maximum value and the minimum value is within a first preset value, it is considered that the warpage of the wafer is within a preset range.

7. The wafer warpage measurement method according to any one of claims 1 to 5, characterized in that: In step S2, the median and the average of the z-axis values ​​of all the measuring points are obtained. When the difference between the median and the average is within a second preset value, it is considered that the warpage of the wafer is within a preset range.

8. The wafer warpage measurement method according to claim 1, characterized in that: The wafer warpage measurement method further includes: drawing a 3D simulation graph of the wafer using the three-dimensional coordinate value of each measurement point, and using the 3D simulation graph of the wafer to determine whether the overall flatness of the wafer is qualified.

9. A wafer warpage measurement device, used to implement the wafer warpage measurement method according to any one of claims 1 to 8, characterized in that: The wafer warpage measurement device at least includes: a wafer fixing device, a coordinate control device, an auto-focus light source and a detection device; The wafer fixing device is composed of n fixing components located at the outer edge of the wafer, where n is a natural number greater than or equal to 2; The coordinate control device is used to build coordinates for the wafer and mark a number of measurement points on the wafer, and to control the autofocus light source to align with each measurement point; The autofocus light source is used to emit light signals to each measuring point on the wafer; The detection device is used to receive the light signal reflected by each measuring point and convert it into an electrical signal, and obtain the coordinate value of each measuring point.

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