Method for measuring wafer film layer

Abstract

The application provides a wafer film layer measurement method applied to an atomic force microscope, comprising the following steps: identifying an online wafer in a field of view, the online wafer being provided with a metal film layer on a surface thereof, and the metal film layer on a non-functional area of an edge of the online wafer being provided with a positioning mark point; identifying the positioning mark point and completing coordinate alignment of the online wafer; adopting a non-contact mode to perform segmented scanning on the metal film layer, so as to obtain topographic height data of a surface of the metal film layer in each scanning area; determining a height difference between a measurement end point and a measurement start point under each scanning path by using the topographic height data; and obtaining a topographic trend image of the metal film layer by using a plurality of height difference values, the topographic trend image being used for reflecting a detection result of the metal film layer. In this way, the metal film layer on the online wafer can be effectively measured and monitored in a non-contact mode.

Description

Technical Field

[0001] This application relates to the field of integrated circuit manufacturing technology, and in particular to a method for measuring wafer film layers. Background Technology

[0002] In semiconductor manufacturing processes, accurate measurement of parameters such as film thickness and critical dimension (CD) depends on accurate and stable measurement points.

[0003] For the measurement of metal thin films, sheet resistance (RS) instruments are typically used. However, the probes of RS instruments come into contact with the surface of the metal thin film, causing damage. Therefore, they cannot be used for inline wafer (IW) measurement and are only suitable for offline indirect monitoring, resulting in delayed control and large errors. Currently, there is an urgent need for a monitoring method for effectively measuring metal thin films on inline wafers (IW). Summary of the Invention

[0004] The purpose of this application is to provide a method for measuring wafer film layers, which can effectively perform non-contact measurement and monitoring of metal film layers on online wafers.

[0005] This application provides a method for measuring wafer film layers, applied to an atomic force microscope, including:

[0006] Identify online wafers within the field of view, wherein a metal film layer is formed on the surface of the online wafer, and positioning markers are formed on the metal film layer in the non-functional area at the edge of the online wafer;

[0007] Identify the positioning markers and complete the coordinate alignment of the online wafer;

[0008] The metal film layer is scanned in a segmented manner using a non-contact mode to obtain the morphological height data of the metal film layer surface in each segment scanning area;

[0009] The height difference between the measurement endpoint and the measurement start point under each scanning path is determined using the topographic height data.

[0010] The morphological trend image of the metal film is obtained by using multiple sets of height differences, and the morphological trend image is used to reflect the detection result of the metal film.

[0011] Furthermore, the positioning markers include a first marker group and a second marker group, wherein the extension directions of the first marker group and the second marker group are perpendicular to each other.

[0012] Furthermore, in the step of performing segmented scanning of the metal film layer in a non-contact mode, the segmented scanning is performed along two sets of orthogonal coordinate axes.

[0013] Furthermore, in the step of performing segmented scanning of the metal film layer using a non-contact mode, the scanning interval is controlled by the translation step size to perform multiple scans in different sections.

[0014] Furthermore, the step of identifying the positioning marker point includes:

[0015] For the first online wafer measured on the production line, an AFM measurement recipe for the online wafer is built and retained for reuse.

[0016] Furthermore, the AFM measurement formulation includes at least one scanning scheme associated with one of the set of positioning markers to constrain the scanning trajectory through the positioning markers.

[0017] Furthermore, the AFM measurement formula also includes setting the scanning mode to a non-contact mode, and performing morphology scanning on the online wafer according to the detection rules of the monitoring wafer.

[0018] Furthermore, the AFM measurement formulation includes two scanning schemes, one of which is associated with the first marker group and the other of which is associated with the second marker group.

[0019] Furthermore, the relationship between the fitted morphological trend image of the metal film layer using multiple sets of height differences includes:

[0020] , H represents the tilt of the topography of each scanned region, where H is the height difference and d is the path length of a single scan.

[0021] n is the x-axis data. For the ordinate data, The degree of tilt in the shape of the nth scanned region.

[0022] Furthermore, the RS machine is used to perform contact marking on the metal film layer of the non-functional area at the edge of the online wafer to form positioning marker points.

[0023] Furthermore, the positioning markers are all arranged on a non-functional area 5-10 mm away from the edge of the online wafer.

[0024] Furthermore, each group of positioning markers adopts a two-point layout, with the distance between two positioning markers in the same group set to 15μm~25μm, and the hole size of each positioning marker is less than 30μm.

[0025] In summary, the wafer film measurement method provided in this application combines an atomic force microscope (AFM) and an RS instrument. The RS instrument forms positioning markers on the edge non-functional area, and the AFM identifies the online wafer within its field of view. The online wafer has a metal film layer formed on its surface, and positioning markers are formed on the edge non-functional area of ​​the metal film layer. The positioning markers are then identified, and the coordinates of the online wafer are aligned. Next, a non-contact mode is used to perform segmented scanning of the metal film layer, obtaining the morphological height data of the metal film layer surface in each scanning area. The morphological height data is then used to determine the height difference between the measurement endpoint and the measurement start point under each scanning path. Finally, multiple sets of height differences are used to obtain a morphological trend image of the metal film layer. This morphological trend image reflects the detection results of the metal film layer. This design enables effective non-contact measurement and monitoring of the metal film layer on an online wafer. Attached Figure Description

[0026] One or more embodiments are illustrated by way of example with corresponding pictures in the accompanying drawings. These illustrations do not constitute a limitation on the embodiments. Unless otherwise stated, the pictures in the accompanying drawings do not constitute a limitation on scale. In order to more clearly illustrate the technical solutions in the embodiments of this application or in the conventional technology, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0027] Figure 1 This is a schematic flowchart of a wafer film layer measurement method according to an embodiment of this application;

[0028] Figure 2 This is a top view of an online wafer provided in an embodiment of this application;

[0029] Figure 3 This is a schematic diagram of an online wafer bidirectional dot measurement provided in an embodiment of this application;

[0030] Figure 4 This is a topographic diagram showing the height of a scanned area provided in an embodiment of this application;

[0031] Figure 5 This is a morphological trend image of the fitted metal film layer provided in the embodiments of this application;

[0032] Figure 6 This is a schematic flowchart of another wafer film measurement method according to an embodiment of this application. Detailed Implementation

[0033] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. The advantages and features of the present invention will become clearer from the following description. It should be noted that the drawings are in a very simplified form and use non-precise proportions, and are only used to facilitate and clarify the illustration of the embodiments of the present invention.

[0034] For ease of description, some embodiments of this application may use spatially relative terms such as “above,” “below,” “top,” and “under” to describe the relationship between one element or component and another (or more) elements or components as shown in the accompanying drawings. It should be understood that, in addition to the orientations described in the drawings, spatially relative terms are also intended to include different orientations of the device during use or operation. For example, if the device in the drawings is flipped, it is described as an element or component “below” or “under” other elements or components, and will subsequently be positioned “above” or “on” other elements or components. The terms “first,” “second,” etc., used below are used to distinguish between similar elements and are not necessarily used to describe a particular order or temporal sequence. It should be understood that these terms, as used, may be replaced where appropriate.

[0035] The purpose of this application is to provide a method for measuring wafer film layers, thereby solving the technical problem of the inability to effectively measure and monitor metal film layers on online wafers. A detailed description is provided below with reference to the accompanying drawings.

[0036] Figure 1 This is a schematic flowchart of a wafer film measurement method provided in an embodiment of this application. Figure 2 This is a top view of an online wafer provided in an embodiment of this application.

[0037] The wafer film measurement method provided in this embodiment is applied to atomic force microscopy (AFM). The wafer film measurement method includes the following steps:

[0038] Step S11: Identify the inline wafer (IW, short for Inline Wafer) 10 within the field of view. A metal film layer is formed on the surface of the inline wafer 10, and positioning markers are formed on the metal film layer in the non-functional area at the edge of the inline wafer.

[0039] In this context, "online wafer 10" refers to a mass-produced wafer that remains within the automated production line transport chain, is under real-time control by the production line's central control unit (MES), undergoes continuous process flow, performs only rapid measurement for the main production line, and is directly returned to production after testing. The non-functional area refers to the outermost edge of the wafer where no effective chip dies are fabricated or finished chips are produced; i.e., the edge invalid area. In this embodiment, the positioning markers do not disrupt the application of the metal film layer on the wafer. The metal film layer can be various essentially opaque metal interconnect films such as aluminum (Al), tungsten (W), and copper (Cu).

[0040] In specific implementation, before the step of identifying the online wafer 10 within the field of view, the following steps are included: forming a metal film layer on the surface of the wafer; and using an RS machine to perform contact marking on the non-functional area at the edge of the metal film layer of the wafer to form positioning mark points.

[0041] Furthermore, the in-line wafer 10 is placed within the field of view of an atomic force microscope (AFM) so that the AFM can identify the positioning markers on the non-functional regions at the edges of the metal film layer on the in-line wafer 10. An atomic force microscope is an important instrument for analyzing surface morphology and electromagnetic properties at atomic resolution, and it has wide applications in the scanning imaging and fabrication of nanostructures. In practice, the in-line wafer (IW) on the production line is fed into the cavity of the AFM via an automated transfer system to expose it within the AFM's field of view.

[0042] Furthermore, the step of identifying the online wafer within the field of view includes: identifying the edge notch mark A on the online wafer within the field of view. This embodiment completes the pre-alignment of the online wafer by identifying the edge notch mark A.

[0043] In one embodiment, the positioning markers include a first marker group B and a second marker group C, wherein the extension directions of the first marker group B and the second marker group C are perpendicular to each other. Exemplarily, the first marker group B is a horizontal marker, and the second marker group C is a vertical marker. The first marker group B and the second marker group C are used to construct the scanning coordinates of the online wafer and the coordinate alignment of the online wafer scanning scheme in an atomic force microscope.

[0044] As an example, both the first marker group B and the second marker group C are formed on a non-functional area 5 mm to 10 mm from the edge of the in-line wafer. Neither the first marker group B nor the second marker group C disrupts the functional chip area of ​​the in-line wafer. Furthermore, both sets of positioning markers are formed after the metal film deposition is completed.

[0045] As an example, each group of positioning markers adopts a two-point layout, with the distance between the two positioning markers in the same group set to 15μm~25μm, and the hole size of each positioning marker is less than 30μm. For example, the distance between the two positioning markers in the same group is 20μm. The hole size of the positioning markers formed by the probe of the RS instrument is less than 30μm. This embodiment uses two positioning markers with a differentiated layout to achieve directional distinction, avoiding identification errors and probe misalignment errors in atomic force microscopy.

[0046] Step S12: Identify the positioning markers and complete the coordinate alignment of the online wafer.

[0047] The atomic force microscope (AFM) in this embodiment is used to detect the morphology and uniformity of the metal film.

[0048] In specific implementation operations, such as Figure 2 As shown, the atomic force microscope identifies two sets of positioning markers on the online wafer. The two sets of positioning markers extend perpendicularly to each other. Based on this, the two sets of positioning markers are used for coordinate alignment, and then a scanning coordinate system (X,Y) is constructed. Next, a segmented scanning operation is performed based on the scanning coordinate system.

[0049] In step S12, the step of identifying the positioning marker points includes: for the first online wafer measured on the production line, building an AFM measurement recipe for the online wafer and storing it for reuse. Once the AFM measurement recipe is built, all subsequent mass-produced online wafers on the same platform, product line, and process can be directly reused without repeated debugging and configuration, adapting to routine mass production testing scenarios. Furthermore, for subsequent wafers measured on the production line, the pre-stored AFM measurement recipe is directly called.

[0050] As an example, an AFM metrology formulation includes at least one scanning scheme, each scan scheme being associated with a set of positioning markers to constrain the scan trajectory via the positioning markers. Preferably, the AFM metrology formulation includes two scanning schemes, one associated with a first set of markers and the other associated with a second set of markers, thus achieving full coverage of the surface of the in-line wafer.

[0051] As an example, the AFM measurement formulation also includes setting the scanning mode to a non-contact mode, performing a morphology scan on the online wafer according to the monitoring wafer inspection rules. This avoids contact with the surface of the online wafer.

[0052] In one implementation, the process of building an online wafer AFM metrology recipe may include: setting the scanning mode to non-contact mode and performing topographic measurement on the online wafer using non-graphical wafer monitoring detection logic. A metrology recipe file is constructed, and pre-stored blank reference data is loaded into the metrology recipe file. A positioning pattern is configured, with each positioning pattern having an equivalent crosshair mark. Two sets of orthogonally arranged positioning patterns are preset, with each set of positioning patterns having an equivalent crosshair mark. A scanning scheme is configured, scanning parameters are specified, and the scanning scheme is associated with one set of positioning patterns. A wafer scanning coordinate system is constructed based on the two sets of positioning patterns. When configuring the scanning scheme, the process also includes selecting height as the output format of the measurement results in the analysis options of the scanning scheme.

[0053] The process includes loading pre-stored blank reference data for morphology measurement data correction, automatic subtraction of instrument background noise, and correction of baseline uniformity. Each positioning pattern serves as a set of positioning markers, enabling joint calibration of wafer translational deviation and rotation angle. During the scanning process, global morphology height data acquisition is performed, outputting the actual measured values ​​(Raw Data) of the morphology measurement data. The actual measured values ​​of the online wafer are compared with the blank reference data to check surface uniformity, noise, and particle defects. Once the data is deemed acceptable, the measurement is completed, and the online wafer is returned to the production line.

[0054] Table 1 below shows a relationship table for a scanning scheme.

[0055]

[0056] Table 1

[0057] Furthermore, as shown in Table 2 below, the measurement parameters for the two different scanning schemes are presented.

[0058]

[0059] Table 2

[0060] like Figure 2 As shown, in the scanning scheme Method X, the scanning direction is from left to right along the X-axis, the matching and recognition pattern is the second marker group, the scanning range can be {X: 10mm, Y: 10μm}, the resolution can be {x=16, y=1}, the translation step size can be 10×2(n−1)mm, and the number of scan lines can be n=1~15, for a total of 15 lines. In the scanning scheme Method X, the frequency of segmented scanning can be... , n=1,2,3…15.

[0061] Continue to refer to Figure 2 In the scanning scheme Method Y, the scanning direction is from top to bottom along the Y-axis, the matching and recognition pattern is the first marker group, the scanning range can be {X: 10μm, Y: 10mm}, the resolution can be {x=1, y=16}, the translation step size can be 10×(2n−1)mm, and the number of scanning columns can be n=1~15, for a total of 15 columns. In the scanning scheme Method Y, the frequency of segmented scanning can be... , n=1,2,3…15.

[0062] For example, such as Figure 3 As shown, a 12-inch in-line wafer with a diameter of 300mm has measurement points from (0,0) to (20mm,0) in the X direction, with no measurement in the middle (10mm,20mm). The measurement point in the Y direction is selected as (0,10mm). In the in-line wafer, although the area between 10mm and 20mm is not measured in the X direction, it is measured in the Y direction, thus achieving full coverage of the surface of the in-line wafer.

[0063] Step S13: Perform segmented scanning on the online wafer using a non-contact mode to obtain the morphology and height data of the metal film surface in each scanning area.

[0064] In one implementation, the segmented scanning of the metal film layer using a non-contact mode is performed along two sets of orthogonal coordinate axes. Specifically, based on the fact that the extension directions of the two sets of positioning markers are perpendicular to each other, and each set of positioning markers is associated with a scanning scheme, the scanning operation is performed along the two sets of orthogonal coordinate axes when implementing the scanning scheme. In this way, after completing the segmented scanning in the two sets of orthogonal directions, a cross-shaped grid is formed to fully cover the online wafer, capturing the undulations of the metal film layer on the entire online wafer.

[0065] In one embodiment, in the step of segmented scanning of the metal film layer using a non-contact mode, the scanning interval is controlled by the translation step size to perform multiple scans in different sections. Specifically, in an atomic force microscope, a segmented scanning mode is used to acquire multiple independent morphological data for a large-sized wafer. The segmented scanning interval is controlled by the translation step size to achieve full-area coverage detection of the entire wafer without blind spots. For example, the translation step size in scanning method X can be 10 × 2(n−1) mm, and the translation step size in scanning method Y can be 10 × (2n-1) mm.

[0066] Step S14: Use topographic height data to determine the height difference between the measurement endpoint and the measurement start point under each scanning path.

[0067] In this specific implementation, height is used as the output form of the measurement results in the scanning scheme.

[0068] like Figure 4 The diagram shows a topographical representation of a scanned area. The height data includes the height of the measurement endpoint D1 and the height of the measurement start point D2. Each scan path is performed with the measurement start point as the reference point.

[0069] Step S15: Obtain the morphological trend image of the metal film layer using multiple sets of height differences. The morphological trend image is used to reflect the detection result of the metal film layer.

[0070] Figure 5 This is a fitted morphological trend image of a metal film. The steps of obtaining the morphological trend image of the metal film using multiple sets of height differences include: obtaining the morphological tilt degree of each scanned region based on each set of height differences; and fitting multiple sets of morphological tilt degrees to form a morphological trend image.

[0071] The relationship between the topographic tilt (raw data) of each scanned region and the height difference of each group is obtained by formulating the following: , The slope of each scanned area is represented by H, where H is the height difference and d is the path length for a single scan. The path length for a single scan is, for example, 10 mm.

[0072] Multiple sets of morphological tilt degrees are fitted to form a relational formula for the morphological trend image, including: n is the x-axis data. For the ordinate data, The degree of tilt in the shape of the nth scanned region.

[0073] Therefore, this embodiment performs segmented scanning of the metal film layer on the online wafer. A derivative function is introduced to address the tilt degree of the topography along each scanning path. However, due to the large order of magnitude difference between the scanning path and the height difference, an amplification factor is also introduced. This reflects the slope change along each scan path, thus reflecting the uniformity of the metal film. When the uniformity is poor, the degree of topographic tilt is reflected. When the value is large and the uniformity is good, the degree of morphological tilt is... The values ​​are relatively small. This enables the monitoring of metal films on in-line wafers (IW).

[0074] As an example, to implement the wafer film layer measurement method in this application embodiment, this application embodiment further includes: using an RS machine to perform contact marking on the metal film layer of the non-functional area at the edge of the online wafer to form positioning mark points.

[0075] Figure 6 This is a schematic diagram illustrating a process for forming positioning markers according to an embodiment of this application. Forming positioning markers includes the following steps:

[0076] S21. Identify an inline wafer (IW) within the field of view, wherein a metal film layer is formed on the inline wafer;

[0077] An RS (Sheet Resistance) instrument is used to measure the sheet resistance and resistivity of metal films. During the measurement process, the probes of the RS instrument make physical contact with the surface of the metal film, leaving marks on the surface. Based on this characteristic, this embodiment uses an RS instrument to create positioning markers by pricking the non-functional areas at the edges of the metal film on the in-line wafer. In this embodiment, the RS instrument only makes positioning marks over a very small area, resulting in minimal damage and no impact on device functionality.

[0078] S22. Identify the edge non-functional regions of the metal film layer. As an example, the edge non-functional regions include at least an invalid region 5-10 mm away from the edge of the online wafer.

[0079] S23. Make contact markings in the non-functional area at the edge to form positioning markers, which are used by the atomic force microscope to perform measurement steps.

[0080] As an example, both sets of positioning markers are arranged on a non-functional area 5-10 mm from the edge of the online wafer, and their positions do not overlap. As an example, each set of positioning markers adopts a two-point layout, with the distance between two positioning markers in the same set set to 15 μm-25 μm, and the hole size of each positioning marker is less than 0-30 μm.

[0081] In this embodiment, the two sets of positioning markers formed by the RS machine are used as visual positioning references for the atomic force microscope and are not included in the SPC manufacturing control.

[0082] In summary, the wafer film measurement method provided in this application identifies an online wafer within the field of view using an atomic force microscope. A metal film layer is formed on the surface of the online wafer, and positioning markers are formed on the metal film layer in the non-functional area at the edge of the online wafer. The positioning markers are identified, and the coordinate alignment of the online wafer is completed. A non-contact mode is used to perform segmented scanning of the metal film layer to obtain the morphological height data of the metal film layer surface in each scanning area. The morphological height data is used to determine the height difference between the measurement endpoint and the measurement start point under each scanning path. Multiple sets of height differences are used to obtain a morphological trend image of the metal film layer, which reflects the detection result of the metal film layer. This enables effective non-contact measurement and monitoring of the metal film layer on the online wafer.

[0083] It should be noted that the above embodiments can be combined with each other. The above description is only a description of preferred embodiments of this application and is not intended to limit the scope of this application in any way. Any changes or modifications made by those skilled in the art based on the above disclosure shall fall within the protection scope of this application.

Claims

1. A method for measuring wafer film layers, applied to an atomic force microscope, characterized in that, include: Identify online wafers within the field of view, wherein a metal film layer is formed on the surface of the online wafer, and positioning markers are formed on the metal film layer in the non-functional area at the edge of the online wafer; Identify the positioning markers and complete the coordinate alignment of the online wafer; The metal film layer is scanned in a segmented manner using a non-contact mode to obtain the morphological height data of the metal film layer surface in each segment scanning area; The height difference between the measurement endpoint and the measurement start point under each scanning path is determined using the topographic height data. The morphological trend image of the metal film is obtained by using multiple sets of height differences, and the morphological trend image is used to reflect the detection result of the metal film.

2. The method for measuring wafer film layers according to claim 1, characterized in that, The positioning markers include a first marker group and a second marker group, wherein the extension directions of the first marker group and the second marker group are perpendicular to each other.

3. The method for measuring wafer film layers according to claim 2, characterized in that, In the step of performing segmented scanning of the metal film layer in a non-contact mode, the segmented scanning is performed along two sets of orthogonal coordinate axes.

4. The method for measuring wafer film layers according to claim 1, characterized in that, In the step of performing segmented scanning of the metal film layer using a non-contact mode, the scanning interval is controlled by the translation step size to perform multiple scans in different sections.

5. The method for measuring wafer film layers according to claim 2, characterized in that, The steps for identifying the location markers include: For the first online wafer measured on the production line, an AFM measurement recipe for the online wafer is built and retained for reuse.

6. The method for measuring wafer film layers according to claim 5, characterized in that, The AFM measurement formulation includes at least one scanning scheme associated with one set of the positioning markers to constrain the scanning trajectory through the positioning markers.

7. The method for measuring wafer film layers according to claim 5, characterized in that, The AFM measurement formula also includes setting the scanning mode to a non-contact mode, and performing morphology scanning on the online wafer according to the detection rules of the monitoring wafer.

8. The method for measuring wafer film layers according to claim 6, characterized in that, The AFM measurement formulation includes two scanning schemes, one of which is associated with the first marker group and the other of which is associated with the second marker group.

9. The method for measuring wafer film layers according to claim 1, characterized in that, The relationship between the fitted morphological trend image of the metal film layer using multiple sets of height differences includes: , H represents the tilt of the topography of each scanned region, where H is the height difference and d is the path length of a single scan. n is the x-axis data. For the ordinate data, The degree of tilt in the shape of the nth scanned region.

10. The method for measuring wafer film layers according to any one of claims 1 to 9, characterized in that, The RS machine is used to perform contact marking on the metal film layer of the non-functional area at the edge of the online wafer to form positioning mark points.

11. The method for measuring wafer film layers according to claim 10, characterized in that, The positioning markers are all arranged on the non-functional area 5-10 mm away from the edge of the online wafer.

12. The method for measuring wafer film layers according to claim 11, characterized in that, Each group of positioning markers adopts a two-point layout, with the distance between the two positioning markers in the same group set to 15μm~25μm, and the hole size of each positioning marker is less than 30μm.

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