An ellipsometry initial incident angle calibration device and method

Abstract

The present invention discloses an ellipsometry initial incident angle calibration device and method. The calibration device includes a translation device, a first pitch adjustment device, a second pitch adjustment device, and an intermediate adjustment device. The translation device includes a translation platform, a CCD camera, and a telecentric lens. The telecentric lens is detachably mounted on the CCD camera, and the CCD camera translates on the translation platform. The first pitch adjustment device includes a first pitch and yaw adjustment platform and an autocollimator mounted on the first pitch and yaw adjustment platform. The second pitch adjustment device includes a second pitch and yaw adjustment platform and a frequency-stabilized laser mounted on the second pitch and yaw adjustment platform. The intermediate adjustment device includes a position adjustment platform and a pentaprism mounted on the position adjustment platform. Compared with the prior art, the present invention can achieve that the optical axis of the autocollimator is 90° with the movement axis of the CCD camera, and the optical axis of the frequency-stabilized laser is 180° with the movement axis of the CCD camera, so as to complete the calibration of the initial 90° incident angle of ellipsometry.

Description

Technical Field

[0001] The present invention relates to the technical field of ellipsometry, and particularly to an ellipsometry initial incident angle calibration device and method. Background Art

[0002] Currently, ellipsometry is widely used in the measurement of micro-nano thin films in the integrated circuit industry. Through ellipsometry, the optical constants (film thickness, refractive index, etc.) of the measured sample can be obtained, so it plays an important role in the field of integrated circuits. With the continuous reduction of semiconductor process nodes, the accuracy requirements for ellipsometry are also getting higher and higher. The incident angle of ellipsometry, as a constant in the mathematical model for film thickness calculation, directly affects the final measurement result.

[0003] Currently, the main methods for incident angle calibration in ellipsometry are the human eye observation method and the reverse fitting method. The human eye observation method uses a reflecting mirror to reflect the outgoing laser. When the optical axis of the reflected light coincides with the optical axis of the incident light, it is considered that the outgoing light forms an angle of 180° with the mirror surface. This method has high requirements for an individual's ability to adjust the optical path, and due to the certain diameter of the optical axis, there is a large error in the optical axis coincidence method; the reverse fitting method mainly measures a standard film thickness sample with known parameters, and then calculates the incident angle at this time in reverse. The calculated incident angle is used as the measurement azimuth angle. This calibration method is limited by the accuracy of the parameters of the measured standard sample and cannot quantify the ellipsometry incident angle. Summary of the Invention

[0004] The purpose of the present invention is to provide an ellipsometry initial incident angle calibration device and method, which can achieve that the optical axis of the autocollimator forms a 90° angle with the moving axis of the CCD camera, and the optical axis of the frequency-stabilized laser forms an 180° angle with the moving axis of the CCD camera, so as to complete the calibration of the initial 90° incident angle of ellipsometry.

[0005] To achieve the above purpose, the present invention provides the following solutions:

[0006] The present invention discloses an ellipsometry initial incident angle calibration device, including:

[0007] A translation device, which includes a translation platform, a CCD camera, and a telecentric lens. The telecentric lens is detachably installed on the CCD camera, and the CCD camera translates on the translation platform;

[0008] A first pitch adjustment device, which includes a first pitch and yaw adjustment platform and an autocollimator installed on the first pitch and yaw adjustment platform;

[0009] A second pitch adjustment device, which includes a second pitch and yaw adjustment platform and a frequency-stabilized laser installed on the second pitch and yaw adjustment platform;

[0010] An intermediate adjustment device, the intermediate adjustment device includes a position adjustment platform and a pentaprism mounted on the position adjustment platform, and the pentaprism can translate parallel to and perpendicular to the translation direction of the CCD camera;

[0011] The translation direction of the CCD camera is simultaneously parallel to the pitch rotation plane of the autocollimator axis and the pitch rotation plane of the frequency-stabilized laser axis.

[0012] Preferably, it further includes a base, and the translation platform, the first pitch-yaw adjustment platform, the second pitch-yaw adjustment platform and the position adjustment platform are all mounted on the base.

[0013] Preferably, the first pitch adjustment device further includes an autocollimator mount, the autocollimator is mounted on the autocollimator mount, and the autocollimator mount is mounted on the first pitch-yaw adjustment platform.

[0014] Preferably, the second pitch adjustment device further includes a frequency-stabilized laser mount, the frequency-stabilized laser is mounted on the frequency-stabilized laser mount, and the frequency-stabilized laser mount is mounted on the second pitch-yaw adjustment platform.

[0015] Preferably, the position adjustment platform is a two-dimensional motion platform, and the two motion directions of the position adjustment platform are respectively parallel to and perpendicular to the direction of the autocollimator axis.

[0016] The present invention also discloses a method for calibrating the initial incident angle of ellipsometry, using the above-mentioned device for calibrating the initial incident angle of ellipsometry, and includes the following steps:

[0017] S1. In the state of not installing the telecentric lens, make the translation platform drive the CCD camera to move repeatedly in one dimension;

[0018] S2. Adjust the pitch angle of the first pitch-yaw adjustment platform so that the position of the reflected light remains unchanged when the CCD camera moves repeatedly;

[0019] S3. Install the telecentric lens on the CCD camera, remove the pentaprism, the frequency-stabilized laser emits a beam of laser, and the laser spot is imaged on the photosensitive surface of the CCD camera through the telecentric lens, and make the translation platform drive the CCD camera to move repeatedly in one dimension;

[0020] S4. By adjusting the pitch angle of the second pitch-yaw adjustment platform, make the imaging position of the laser emitted by the frequency-stabilized laser on the photosensitive surface of the CCD camera unchanged.

[0021] The present invention has achieved the following technical effects compared with the prior art:

[0022] By adopting the calibration device and calibration method of the present invention, the problem of inaccurate adjustment of the initial optical axis angle in traditional ellipsometry can be overcome. During the adjustment process, the offset of the center pixel coordinates of the laser spot is calculated through the imaging of the CCD camera, and the angles of pitch and yaw can be quantified, thereby achieving high-precision angle calibration, which has important reference significance for the high-precision incident angle requirements of ellipsometry. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0024] Figure 1 It is a schematic structural diagram of the ellipsometry initial incident angle calibration device for this embodiment;

[0025] Description of reference numerals: 100 - ellipsometry initial incident angle calibration device; 1 - translation stage; 2 - CCD camera; 3 - telecentric lens; 4 - first pitch and yaw adjustment platform; 5 - frequency-stabilized laser mount; 6 - frequency-stabilized laser; 7 - autocollimator mount; 8 - autocollimator; 9 - position adjustment platform; 10 - pentaprism. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0026] The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the drawings in the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, rather than all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0027] The object of the present invention is to provide an ellipsometry initial incident angle calibration device and method to achieve that the optical axis of the autocollimator forms a 90° angle with the movement axis of the CCD camera, and the optical axis of the frequency-stabilized laser forms a 180° angle with the movement axis of the CCD camera, thereby completing the calibration of the initial 90° incident angle of ellipsometry.

[0028] To make the above objects, features, and advantages of the present invention more obvious and understandable, the present invention will be further described in detail below with reference to the drawings and specific embodiments.

[0029] As Figure 1 shown, this embodiment provides an ellipsometry initial incident angle calibration device 100, including a translation device, a first pitch adjustment device, a second pitch adjustment device, and an intermediate adjustment device.

[0030] Among them, the translation device includes a translation platform 1, a CCD camera 2, and a telecentric lens 3. The telecentric lens 3 is detachably mounted on the CCD camera 2, and the CCD camera 2 translates on the translation platform 1. The first pitch adjustment device includes a first pitch and yaw adjustment platform 4 and an autocollimator 8 mounted on the first pitch and yaw adjustment platform 4. The first pitch and yaw adjustment platform 4 can adjust the pitch angle of the axis of the autocollimator 8 (referring to the outgoing light of the autocollimator 8). The second pitch adjustment device includes a second pitch and yaw adjustment platform and a frequency-stabilized laser 6 mounted on the second pitch and yaw adjustment platform. The second pitch adjustment device can adjust the pitch angle of the axis of the frequency-stabilized laser 6 (referring to the outgoing light of the frequency-stabilized laser 6). The intermediate adjustment device includes a position adjustment platform 9 and a pentaprism 10 mounted on the position adjustment platform 9. The pentaprism 10 can translate parallel to and perpendicular to the translation direction of the CCD camera 2. The translation direction of the CCD camera 2 is simultaneously parallel to the pitch rotation plane of the axis of the autocollimator 8 and the pitch rotation plane of the axis of the frequency-stabilized laser 6.

[0031] Furthermore, this embodiment further includes a base. The translation platform 1, the first pitch and yaw adjustment platform 4, the second pitch and yaw adjustment platform, and the position adjustment platform 9 are all mounted on the base to ensure that their relative positions do not change during the calibration process.

[0032] For the convenience of installation, in this embodiment, the first pitch adjustment device further includes an autocollimator mounting seat 7. The autocollimator 8 is mounted on the autocollimator mounting seat 7, and the autocollimator mounting seat 7 is mounted on the first pitch and yaw adjustment platform 4; the second pitch adjustment device further includes a frequency-stabilized laser mounting seat 5. The frequency-stabilized laser 6 is mounted on the frequency-stabilized laser mounting seat 5, and the frequency-stabilized laser mounting seat 5 is mounted on the second pitch and yaw adjustment platform.

[0033] In this embodiment, the position adjustment platform 9 is a two-dimensional motion platform. The two motion directions of the position adjustment platform 9 are respectively parallel to and perpendicular to the direction of the axis of the autocollimator 8. According to different actual needs, those skilled in the art can also select other types of position adjustment platforms 9 such as a three-axis motion platform, as long as the position adjustment of the pentaprism 10 can be achieved.

[0034] This embodiment also provides a method for calibrating the initial incident angle of ellipsometry, using the above-mentioned ellipsometry initial incident angle calibration device 100, and including the following steps:

[0035] S1. In the state where the telecentric lens 3 is not installed, the translation platform 1 is used to drive the CCD camera 2 to move repeatedly in one dimension.

[0036] S2. Adjust the pitch angle of the first pitch and yaw adjustment platform 4 so that the position of the reflected light remains unchanged when the CCD camera 2 moves repeatedly. Thus, 90° calibration between the axis of the autocollimator 8 and the translation direction of the CCD camera 2 is achieved.

[0037] S3. Install the telecentric lens 3 on the CCD camera 2, remove the pentaprism 10, and let the frequency-stabilized laser 6 emit a beam of laser. The laser beam forms a laser spot on the photosensitive surface of the CCD camera 2 through the telecentric lens 3, and the translation stage 1 drives the CCD camera 2 to move repeatedly in one dimension.

[0038] S4. Adjust the pitch angle of the second pitch and yaw adjustment platform so that the imaging position of the laser beam emitted by the frequency-stabilized laser 6 on the photosensitive surface of the CCD camera 2 remains unchanged. Realize the 180° calibration of the axis of the frequency-stabilized laser 6 and the translation direction of the CCD camera 2.

[0039] It should be noted that in step S2, the propagation direction of the beam emitted by the autocollimator changes by 90° after passing through the pentaprism (the pentaprism can realize a 90° turn of the incident light), is reflected on the mirror surface of the CCD camera, and the reflected beam returns to the autocollimator after passing through the pentaprism. The beam that returns to the autocollimator is the reflected light referred to in step S2.

[0040] In this specification, specific examples are used to elaborate on the principle and implementation manner of the present invention. The description of the above embodiments is only used to help understand the method and its core idea of the present invention; at the same time, for those of ordinary skill in the art, according to the idea of the present invention, there will be changes in the specific implementation manner and application scope. In summary, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. An ellipsometry initial incident angle calibration method, using an ellipsometry initial incident angle calibration device, the ellipsometry initial incident angle calibration device comprising: A translation device, the translation device comprising a translation platform, a CCD camera, and a telecentric lens, the telecentric lens being detachably mounted on the CCD camera, and the CCD camera translating on the translation platform; A first pitch adjustment device, the first pitch adjustment device comprising a first pitch and yaw adjustment platform and an autocollimator mounted on the first pitch and yaw adjustment platform; A second pitch adjustment device, the second pitch adjustment device comprising a second pitch and yaw adjustment platform and a frequency-stabilized laser mounted on the second pitch and yaw adjustment platform; An intermediate adjustment device, the intermediate adjustment device comprising a position adjustment platform and a pentaprism mounted on the position adjustment platform, the pentaprism being capable of translating parallel to and perpendicular to the translation direction of the CCD camera; The translation direction of the CCD camera is simultaneously parallel to the pitch rotation plane of the axis of the autocollimator and the pitch rotation plane of the axis of the frequency-stabilized laser; The ellipsometry initial incident angle calibration method comprises the following steps: S1. In a state where the telecentric lens is not installed, the translation platform is made to drive the CCD camera to move repeatedly in one dimension; S2. The pitch angle of the first pitch and yaw adjustment platform is adjusted so that the position of the reflected light remains unchanged when the CCD camera moves repeatedly; S3. The telecentric lens is installed on the CCD camera, the pentaprism is removed, the frequency-stabilized laser emits a beam of laser, and the laser spot is imaged on the photosensitive surface of the CCD camera through the telecentric lens, and the translation platform is made to drive the CCD camera to move repeatedly in one dimension; S4. By adjusting the pitch angle of the second pitch and yaw adjustment platform, the imaging position of the laser emitted by the frequency-stabilized laser on the photosensitive surface of the CCD camera is made not to change.

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