Ellipsometer-oriented light spot size measuring device and measuring method

Abstract

The present application relates to a kind of spot size measurement device and measurement method for ellipsometer, the device includes: camera module, grating reflection component, spot size detection sample and sample displacement platform.The method includes: obtaining the spot of ellipsometer on grating reflection component;Obtain the center position coordinate of spot;Using Gaussian model fitting spot gray value;Establish the three-dimensional morphology of spot;Obtain the barycenter position of spot;Establish detection coordinate system;Obtain the pattern center position of square pattern;Make pattern center and spot barycenter coincide;Measure spot size detection sample in the position in multiple detection coordinate systems;Establish detection thickness variation curve;Intercept qualified measurement part in detection thickness variation curve, obtain the size of qualified measurement part;Ellipsometer spot size is equal to the size of the square pattern minus the size of the qualified measurement part;Realize the detection of ellipsometer spot size and morphology.

Description

Technical Field

[0001] This invention relates to the field of optical measurement technology, specifically to a device and method for measuring the spot size of an ellipsometer. Background Technology

[0002] An ellipsometer is a precision instrument for measuring the optical constants and thickness of micro- and nano-thin films based on optical polarization. Its basic principle is to analyze the optical constants and film thickness of a sample by measuring the change in polarization state of elliptically polarized light before and after reflection from the sample surface. Compared to other optical thin film measurement methods, ellipsometers offer a self-referenced measurement method with high spectral sensitivity, making them the most effective means currently available for high-precision measurement of the optical constants and thickness of nanoscale thin films.

[0003] In recent years, in nanotechnology, especially in large-scale semiconductor chip manufacturing, chip manufacturing processes have been continuously advancing towards smaller nanoscales to improve chip performance, reduce power consumption, decrease chip area, and increase yield. To ensure accuracy in semiconductor chip manufacturing, semiconductor chip manufacturing equipment manufacturers need to keep pace with the times, improving measurement precision, expanding the measurement spectrum range, and compressing the measurement area size to meet the changes in manufacturing processes brought about by the advancement of chip manufacturing processes.

[0004] Ellipsometry is a key measurement device in semiconductor chip manufacturing. The size and shape of the light spot it illuminates on the sample determine the device's ability to measure minute areas. Generally, the size and shape of the ellipsometer's light spot are evaluated in two ways: first, the ideal light spot size and shape simulated by simulation software during the device's design; and second, the smallest area that the device can measure within a reasonable accuracy range during actual use, reflecting the actual size and shape of the ellipsometer's light spot.

[0005] However, due to the fact that the quality of the light beam and the assembly of the optical lens cannot be maintained ideally during the actual manufacturing process, the size and shape of the light spot reflected by the ellipsometer in actual use differ significantly from the ideal situation. Therefore, detecting the size and shape of the light spot is a necessary step in the production and use of the ellipsometer. Summary of the Invention

[0006] This invention provides a device and method for measuring the spot size of an ellipsometer, which solves the problem that the equipment cannot detect the spot size and shape in a timely manner during production and use, so as to meet the manufacturing process changes brought about by the advancement of chip manufacturing processes.

[0007] The technical solution of the present invention to solve the above-mentioned technical problems is as follows:

[0008] On one hand, the present invention provides a spot size measuring device for an ellipsometer, comprising:

[0009] A camera module used to capture the light spot pattern of an ellipsometer;

[0010] A grating reflector used to reflect the ellipsometer spot and allow light to enter the camera assembly;

[0011] A light spot size detection sample, wherein the light spot size detection sample is a SiO2 sample with a square pattern; and

[0012] A sample displacement stage used to place and adjust the size of the light spot to detect the position of the sample.

[0013] Furthermore, the camera module includes: a camera displacement stage and a camera assembly consisting of a camera lens and a CMOS sensor; the camera displacement stage is used to fix the camera assembly and has a three-dimensional linear displacement adjustment function.

[0014] Furthermore, the grating reflection component has a periodic grating structure, and the reflection angle of the light spot by the grating reflection component is smaller than the receiving angle of the camera component.

[0015] Furthermore, the difference between the thickness of the square pattern on the light spot size detection sample and the thickness of the blank area is not less than 100 nm.

[0016] On the other hand, the present invention also provides a method for measuring the spot size of an ellipsometer, which is implemented by the above-mentioned measuring device and includes:

[0017] Obtain the centroid position of the light spot;

[0018] Obtain the center of the square pattern;

[0019] A detection coordinate system is established with the aforementioned center of gravity position as the origin;

[0020] Obtain the detection thickness values ​​at multiple locations in the detection coordinate system;

[0021] Obtain the size of the qualified measurement section;

[0022] The size of the ellipsometer spot is equal to the size of the square pattern minus the size of the qualified measurement portion.

[0023] Furthermore, obtaining the centroid position of the light spot includes:

[0024] Control the camera displacement stage so that the camera assembly images the focal plane of the ellipsomer.

[0025] Control the sample displacement stage so that the surface of the grating reflection component is located at the focal plane of the ellipsometer;

[0026] Using the camera component, a light spot image is acquired on the grating reflection component, wherein the light spot image includes a light spot;

[0027] Obtain the coordinates of the center position of the light spot in the light spot image;

[0028] Establish an image coordinate system based on the center position coordinates;

[0029] In the image coordinate system, a Gaussian model is used to fit the gray values ​​of the light spots in the light spot image; the Gaussian model fitting includes denoising the light spot image.

[0030] Establish the three-dimensional morphology of the light spot on the light spot image;

[0031] Using a pre-established centroid model of the light spot, the centroid position of the light spot is obtained in the three-dimensional shape.

[0032] Furthermore, obtaining the detection thickness values ​​at multiple locations in the detection coordinate system includes:

[0033] The sample displacement stage is controlled to move to multiple positions preset in the detection coordinate system, and the ellipsometry is used to measure and obtain the detection thickness values ​​at multiple positions in the detection coordinate system; in the detection coordinate system, a detection thickness variation curve is established based on the detection thickness values.

[0034] Furthermore, obtaining the size of the qualified measurement portion includes:

[0035] In the thickness change curve, the qualified measurement portion is extracted based on a pre-set acceptable thickness error.

[0036] The beneficial effects of this invention are: this invention can detect the size and shape of the light spot in a timely manner during the production and use of the equipment, so as to meet the changes in manufacturing process brought about by the advancement of chip manufacturing process. Attached Figure Description

[0037] Figure 1 A schematic diagram of a measuring device for measuring the spot size and shape of an ellipsometer provided by the present invention; wherein 1-camera displacement stage, 2-CMOS sensor, 3-camera lens, 4-grating reflection assembly, 5-sample displacement stage;

[0038] Figure 2 This is a schematic diagram of a sample for spot size detection.

[0039] Figure 3 This is a schematic diagram showing the overlap between the light spot and the sample being tested for light spot size.

[0040] Figure 4 The measurement results in the X direction when measuring a 70um*70um square pattern. Detailed Implementation

[0041] The principles and features of the present invention are described below with reference to the accompanying drawings. The examples given are only for explaining the present invention and are not intended to limit the scope of the present invention.

[0042] This invention provides a method and apparatus for detecting the light spot measured by an ellipsometer, such as... Figure 1 and Figure 2 As shown, the device includes:

[0043] Camera assembly used to capture the light spot pattern of the ellipsometer;

[0044] The camera assembly includes a camera displacement stage 1, a camera lens 3, and a CMOS sensor 2.

[0045] The camera displacement stage 1 is used to fix the camera assembly;

[0046] The camera displacement stage 1 has a three-dimensional linear displacement adjustment function;

[0047] The camera lens 3 has a defined focal length and magnification.

[0048] The CMOS sensor 2 is used to acquire images;

[0049] The grating reflector 4 is used to reflect the light spot of the ellipsometer, allowing light to enter the camera module;

[0050] The grating reflective component 4 has a periodic grating structure;

[0051] The periodic grating structure is used to reflect the ellipsometer spot at the ellipsometer sample.

[0052] The reflection angle of the light spot by the grating reflection component 4 is smaller than the receiving angle of the camera module;

[0053] The light spot is the light focused onto the sample by the beam within the effective measurement spectrum range of the ellipsometer;

[0054] The sample for spot size detection is a SiO2 sample with a square pattern;

[0055] The sample used for spot size detection is used for ellipsometer measurement;

[0056] The square pattern is manufactured using a micro-nano manufacturing method.

[0057] The thickness of the square pattern differs greatly from that of the blank area;

[0058] The sample displacement stage has a three-dimensional linear displacement adjustment function;

[0059] This invention provides a method and apparatus for detecting the light spot measured by an ellipsometer, the method comprising:

[0060] Step 1: Obtain the coordinates of the center position of the light spot in the light spot image.

[0061] The grating reflector is placed on the sample displacement stage 5, and the camera displacement stage 5 is controlled so that the surface of the grating reflector is located at the focal plane of the ellipsometer. The camera displacement stage 1 is controlled so that the camera assembly images the focal plane of the ellipsometer. In actual operation, the focal plane of the ellipsometer (where the light spot image is smallest on the focal plane of the ellipsometer) can be determined by the light spot image on the grating reflector 4 acquired by the camera assembly. After acquiring the light spot image, the center coordinates of the light spot can be determined by the image edges.

[0062] Step 2: Obtain the centroid position of the light spot.

[0063] After obtaining the center coordinates of the light spot, a two-dimensional image coordinate system is established. Based on the coordinates and grayscale values ​​of each point on the light spot, a Gaussian model is used to fit the shape of the light spot. During the process of fitting the light spot shape using the Gaussian model, the image of the light spot is denoised to avoid the influence of environmental noise on the fitting. Using a pre-established centroid model of the light spot, the centroid position of the light spot is calculated by comprehensively considering the coordinates and grayscale values ​​of each point in the light spot. The centroid position of the light spot is the actual intensity center of the light spot after considering light intensity. Compared to the center position of the light spot, the centroid position better reflects the actual measurement and analysis center of the ellipsometer.

[0064] Step 3: Obtain the detection thickness values ​​at multiple locations in the detection coordinate system.

[0065] The sample for spot size detection is placed on the sample displacement stage. The sample displacement stage is controlled so that the surface of the sample is located at the focal plane of the ellipsometer, i.e., the surface with the smallest spot size. The camera assembly is used to photograph the sample, thereby obtaining the center of the square pattern on the sample, i.e., the center of the target object. The relative coordinates of the pattern center and the center of gravity are compared, and the sample displacement stage is controlled so that the center of gravity coincides with the pattern center in the horizontal direction. Figure 3As shown, both the grating reflection component and the spot size detection sample are located on the focal plane of the ellipsometer, therefore the center of gravity coincides with the center of the pattern in the vertical direction. A detection coordinate system is established with the center of gravity as the origin; the sample displacement stage is controlled to move to multiple positions preset in the detection coordinate system, and the ellipsometer is used to measure and obtain the detection thickness values ​​at these multiple positions. In actual operation, a symmetrical interval slightly larger than the side length of the square pattern can be selected for measurement in the detection coordinate system; for example, when measuring a 70um*70um square pattern, a symmetrical interval of -50um*50um in the X direction can be selected for measurement.

[0066] Step 4: Calculate the size of the broadband spot.

[0067] In the detection coordinate system, a detection thickness variation curve is established based on the detected thickness value; within the detection thickness variation curve, a qualified measurement portion is extracted based on a pre-set acceptable thickness error; for example, measuring a 70µm*70µm square pattern, the measurement result in the X direction is as follows. Figure 4 As shown, if the acceptable range for thickness error is set to ±0.1A, then... Figure 4 The measurement results shown indicate that the width of the qualified measurement portion is 20 μm. After obtaining the size of the qualified measurement portion, the ellipsometer spot size is equal to the size of the square pattern minus the size of the qualified measurement portion; taking the measurement of a 70 μm * 70 μm square pattern as an example, the measurement result in the X direction is as follows. Figure 4 As shown, the size of the light spot in the X direction can be calculated to be 50 μm wide.

[0068] Although preferred embodiments of the invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including both the preferred embodiments and all changes and modifications falling within the scope of the invention.

[0069] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A device for measuring the spot size of an ellipsometer, characterized in that, include: A camera module used to capture the light spot pattern of an ellipsometer; A grating reflector used to reflect the ellipsometer spot and allow light to enter the camera assembly; A light spot size detection sample, wherein the light spot size detection sample is a SiO2 sample with a square pattern; as well as A sample displacement stage used to place and adjust the size of the light spot to detect the position of the sample; The camera module includes: a camera displacement stage and a camera assembly consisting of a camera lens and a CMOS sensor; the camera displacement stage is used to fix the camera assembly and has a three-dimensional linear displacement adjustment function; Both the grating reflection component and the spot size detection sample are located on the focal plane of the ellipsometer, with their center of gravity coinciding with the center of the pattern in the vertical direction.

2. The measuring device according to claim 1, characterized in that, The grating reflector has a periodic grating structure, and the reflection angle of the light spot by the grating reflector is smaller than the receiving angle of the camera assembly.

3. The measuring device according to claim 1, characterized in that, The difference between the thickness of the square pattern on the sample and the thickness of the blank area is not less than 100 nm.

4. A method for measuring the spot size of an ellipsometer, the method being implemented based on the measuring device described in any one of claims 1 to 3, characterized in that, include: Obtain the centroid position of the light spot; The centroid of the light spot is the actual intensity center of the light spot after taking light intensity into account; Obtain the center of the square pattern; A detection coordinate system is established with the aforementioned center of gravity position as the origin; Obtain the detection thickness values ​​at multiple locations in the detection coordinate system; Obtain the size of the qualified measurement section; The size of the ellipsometer spot is equal to the size of the square pattern minus the size of the qualified measurement portion; Obtaining the centroid position of the light spot includes: Control the camera displacement stage so that the camera assembly images the focal plane of the ellipsomer. Control the sample displacement stage so that the surface of the grating reflection component is located at the focal plane of the ellipsometer; Using the camera component, a light spot image is acquired on the grating reflection component, wherein the light spot image includes a light spot; Obtain the coordinates of the center position of the light spot in the light spot image; Establish an image coordinate system based on the center position coordinates; In the image coordinate system, a Gaussian model is used to fit the gray values ​​of the light spots in the light spot image; the Gaussian model fitting includes denoising the light spot image. Establish the three-dimensional morphology of the light spot on the light spot image; Using a pre-established centroid model of the light spot, the centroid position of the light spot is obtained in the three-dimensional shape.

5. The measurement method according to claim 4, characterized in that, Obtaining the detection thickness values ​​at multiple locations in the detection coordinate system includes: The sample displacement stage is controlled to move to multiple positions preset in the detection coordinate system, and the ellipsometry is used to measure and obtain the detection thickness values ​​at multiple positions in the detection coordinate system; in the detection coordinate system, a detection thickness variation curve is established based on the detection thickness values.

6. The measurement method according to claim 5, characterized in that, Obtaining the size of the qualified measurement portion includes: In the thickness change curve, the qualified measurement portion is extracted based on a pre-set acceptable thickness error.

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