Wavefront aberration measuring apparatus and wavefront aberration measuring method

Abstract

The application provides a wave aberration measuring device and a wave aberration measuring method. The device comprises a light source, a first substrate, a projection objective, a second substrate and an image detection unit arranged in sequence along the light path direction. The light source is used for emitting an illumination light beam. The first substrate is provided with a first grating extending along the X direction and a second grating extending along the Y direction. The width of the first grating along the Y direction is greater than the width of the field of view of the illumination light beam along the Y direction. The width of the second grating along the Y direction is greater than the width of the field of view of the illumination light beam along the Y direction. The second substrate is provided with a third grating extending along the X direction and a fourth grating extending along the Y direction. The projection objective projects the illumination light beam that passes through the first substrate onto the second substrate. The second substrate is moved along the Y direction. The image detection unit acquires a dynamic wave aberration image. The application improves the measurement accuracy and efficiency of the dynamic wave aberration.

Description

Technical Field

[0001] This invention relates to the field of semiconductor technology, and in particular to a wavefront aberration measurement device and a wavefront aberration measurement method. Background Technology

[0002] Wavefront aberration is a phenomenon where, due to aberrations in actual optical systems, the wavefront formed by a spherical wave after passing through the optical system is no longer spherical. The optical path difference between the actual wavefront and the ideal wavefront is called wavefront aberration. For general optical systems, geometric aberrations can be used to simply and intuitively evaluate the quality of the optical system. However, for optical systems with high image quality requirements, it is necessary to further study the deformation of the wavefront of the light wave after passing through the optical system. The smaller the wavefront aberration, the better the imaging quality of the system.

[0003] In existing technologies, measurements are typically performed only at a single field of view, i.e., static wave aberration measurement. For dynamic wave aberration measurement, dynamic wave aberration fitting is required, which means that wave aberration testing is performed on a large number of discrete field of view points, resulting in long detection times. Furthermore, since the illumination beam emitted by the light source has a Gaussian-like distribution along the Y-axis, the influence weight of wave aberration on exposure performance varies depending on the exposure dose at different positions along the Y-axis, making it impossible to directly determine the influence of light intensity distribution on dynamic wave aberration. Summary of the Invention

[0004] The purpose of this invention is to provide a wave aberration measurement device and a wave aberration measurement method to improve the measurement accuracy and efficiency of dynamic wave aberration.

[0005] To achieve the above objectives, the present invention provides a wavefront aberration measurement device, comprising a light source, a first substrate, a projection lens, a second substrate, and an image detection unit arranged sequentially along the optical path direction. The light source emits an illumination beam. The first substrate has a first grating extending along the X-direction and a second grating extending along the Y-direction. The width of the first grating along the Y-direction is greater than the width of the field of view of the illumination beam along the Y-direction, and the width of the second grating along the Y-direction is greater than the width of the field of view of the illumination beam along the Y-direction. The second substrate has a third grating extending along the X-direction and a fourth grating extending along the Y-direction. The projection lens projects the illumination beam transmitted through the first substrate onto the second substrate. The second substrate is moved along the Y-direction so that the image detection unit acquires a dynamic wavefront aberration image of the illumination beam transmitted through the second substrate.

[0006] Optionally, the magnification of the projection lens is N, and the period of the first grating and the second grating is N times the period of the third grating and the fourth grating.

[0007] Optionally, the width of the first grating along the Y direction is the same as the width of the second grating along the Y direction, and the centers of the first grating and the second grating are at the same position in the Y direction; the width of the third grating along the Y direction is the same as the width of the fourth grating along the Y direction, and the centers of the third grating and the fourth grating are at the same position in the Y direction.

[0008] Optionally, the first grating and the second grating are spaced apart in the X direction; the third grating and the fourth grating are spaced apart in the X direction.

[0009] Optionally, the duty cycle of the first grating, the second grating, the third grating, and the fourth grating is 1:1.

[0010] Optionally, the first grating, the second grating, the third grating, and the fourth grating are all one-dimensional gratings.

[0011] Optionally, an air gap is provided between the image detection unit and the second substrate.

[0012] Optionally, a motion stage is also included for driving the second substrate to move along the Y direction.

[0013] A wavefront aberration measurement method using the wavefront aberration measurement device described above includes:

[0014] The illumination beam emitted by the light source is incident on the first substrate;

[0015] The second substrate is moved along the Y direction so that the projection lens projects the illumination beam transmitted through the first substrate onto the second substrate; and,

[0016] The second substrate is moved along the Y direction, and the image detection unit acquires a dynamic wave aberration image of the illumination beam transmitted through the second substrate.

[0017] Optionally, when moving the second substrate along the Y direction, the second substrate is moved along the Y direction from the field of view that just enters the illumination beam to the field of view that completely exits the illumination beam.

[0018] Optionally, when the second substrate is moved along the Y direction, the first substrate remains stationary.

[0019] In the wavefront aberration measurement device and method provided by the present invention, a first substrate is provided with a first grating extending along the X direction and a second grating extending along the Y direction. The width of the first grating along the Y direction is greater than the width of the field of view of the illumination beam along the Y direction, and the width of the second grating along the Y direction is greater than the width of the field of view of the illumination beam along the Y direction, so that the illumination beam can pass entirely through the first grating and the second grating in the Y direction. A second substrate is provided with a third grating extending along the X direction and a fourth grating extending along the Y direction. Moving the second substrate along the Y direction allows the projection lens to pass through the first grating. The illumination beam from the light source is projected onto the second substrate. When the second substrate moves out of the field of view of the illumination beam along the Y direction, the image detection unit acquires a dynamic wave aberration image of the illumination beam transmitted through the second substrate. Since the illumination beam emitted by the light source has a Gaussian-like distribution along the Y direction, the dynamic wave aberration image obtained by moving the second substrate along the Y direction for dynamic measurement is more accurate when the exposure dose is different. The measurement accuracy of dynamic wave aberration is higher, and there is no need to perform multiple measurements and fittings on multiple discrete field points to obtain dynamic wave aberration, thereby improving the measurement accuracy and efficiency of dynamic wave aberration. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the wavelet aberration measuring device provided in an embodiment of the present invention;

[0021] Figure 2 This is a schematic diagram of the first grating and the second grating in a wavelet aberration measurement device provided in an embodiment of the present invention;

[0022] Figure 3 This is a schematic diagram of the third and fourth gratings in a wavelet aberration measurement device provided in an embodiment of the present invention;

[0023] Figure 4 This is a flowchart of a wavelet aberration measurement method provided in an embodiment of the present invention;

[0024] The attached figures are labeled as follows:

[0025] 10-First substrate; 11-Object plane grating mark; 111-First grating; 112-Second grating; 20-Projection lens; 30-Second substrate; 31-Image plane grating mark; 311-Third grating; 312-Fourth grating; 40-Image detection unit; 50-Air gap. Detailed Implementation

[0026] The specific embodiments of the present invention will now be described in more detail with reference to the accompanying drawings. The advantages and features of the present invention will become clearer from the following description. It should be noted that the drawings are all 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.

[0027] Figure 1This is a schematic diagram of the wavelet aberration measurement device provided in this embodiment. Figure 2 This is a schematic diagram of the first and second gratings in the wavelet aberration measurement device provided in this embodiment. Figure 3 This is a schematic diagram of the third and fourth gratings in the wavelet aberration measurement device provided in this embodiment. Please refer to... Figures 1-3 The wavelet aberration measuring device includes a light source (not shown in the figure), a first substrate 10, a projection lens 20, a second substrate 30 and an image detection unit 40 arranged sequentially along the optical path, wherein the light source is used to emit an illumination beam.

[0028] A surface grating mark 11 is provided on the first substrate 10. The first substrate 10 is made of a light-transmitting material, and the bottom of the first substrate 10 is coated with an opaque material, such as chromium. The surface grating mark 11 is formed by removing the opaque material. When an illumination beam shines on the first substrate 10, in order to ensure that the illumination beam in the Y direction can pass entirely through the surface grating mark 11, and to perform measurements in the X and Y directions, the surface grating mark 11 includes a first grating extending in the X direction and a second grating extending in the Y direction. The width of the first grating 111 in the Y direction is greater than the width of the field of view of the illumination beam in the Y direction, and the width of the second grating 112 in the Y direction is greater than the width of the field of view of the illumination beam in the Y direction. The X and Y directions are perpendicular. The illumination beam has a certain field of view in the X and Y directions. Since the illumination beam has a Gaussian-like distribution along the Y direction, the influence weight of the wavefront aberration at different positions along the Y direction on the exposure performance is different depending on the exposure dose. Therefore, it is necessary to measure the dynamic wavefront aberration of the entire exposure field of view along the Y direction and scan along the Y direction during subsequent exposure scanning.

[0029] In this embodiment, the width L of the first grating 111 along the Y direction is required to be greater than the width of the field of view of the illumination beam along the Y direction, and the width L of the second grating 112 along the Y direction is also required to be greater than the width of the field of view of the illumination beam along the Y direction. However, the widths of the first grating 111 and the second grating 112 along the X direction are not limited. To reduce the area of ​​the first substrate 10 and facilitate grating layout, it is preferable that the widths of the first grating 111 and the second grating 112 along the Y direction are the same, and the centers of the first grating 111 and the second grating 112 are at the same position in the Y direction. Furthermore, there is a spacing d1 between the first grating 111 and the second grating 112 along the X direction, the duty cycle of the first grating 111 and the second grating 112 are both 1:1, and both the first grating 111 and the second grating 112 are one-dimensional gratings.

[0030] The second substrate 30 is provided with an image grating mark 31. The second substrate 30 is also made of a light-transmitting material, and the bottom of the second substrate 30 is coated with an opaque material, such as chromium. The image grating mark 22 is formed by removing the opaque material. To allow the illumination beam passing through the first substrate 10 to be projected onto the second substrate 30 and acquired by the image detection unit 40, the image grating mark 31 includes a third grating 311 extending along the X direction and a fourth grating 312 extending along the Y direction. The positions of the third grating 311 and the fourth grating 312 need to correspond to the positions of the first grating 111 and the second grating 112, so that the illumination beam passing through the first grating 111 is projected onto the third grating 311 and acquired by the image detection unit 40; and the illumination beam passing through the second grating 112 is projected onto the fourth grating 312 and acquired by the image detection unit 40.

[0031] In this embodiment, the dimensions of the third grating 311 and the fourth grating 312 are not limited; that is, the widths of the third grating 311 and the fourth grating 312 along the X and Y directions are not required, but are determined according to the actual situation. To reduce the area of ​​the second substrate 30 and facilitate grating layout, it is preferable that the width of the third grating 311 along the Y direction is the same as the width of the fourth grating 312 along the Y direction, and the centers of the third grating 311 and the fourth grating 312 are at the same position in the Y direction. Furthermore, there is a spacing d2 between the third grating 311 and the fourth grating 312 along the X direction. The spacing d2 between the third grating 311 and the fourth grating 312 is different from the spacing d1 between the first grating 111 and the second grating 112. d1 and d2 are related to the magnification of the projection lens 20. The duty cycles of both the third grating 311 and the fourth grating 312 are 1:1, and both the third grating 311 and the fourth grating 312 are one-dimensional gratings.

[0032] In this embodiment, the magnification of the projection lens 20 is N, and the periods of the first grating 111 and the second grating 112 are both P. Then the periods of the third grating 311 and the fourth grating 312 are both P / N, that is, the periods of the first grating 111 and the second grating 112 are N times the periods of the third grating 311 and the fourth grating 312.

[0033] Furthermore, the image detection unit 40 is located directly below the second substrate 30 and is used to acquire dynamic wave aberration images. The image detection unit 40 is a high signal-to-noise ratio and high dynamic range area array image acquisition element. An air gap 50 is provided between the image detection unit 40 and the second substrate 30 to form far-field detection conditions.

[0034] Furthermore, it also includes a motion stage (not shown in the figure), on which the second substrate 30 and the image detection unit 40 are placed. The motion stage drives the second substrate 30 and the image detection unit 40 to move together along the Y direction. Figure 1 The direction of the middle arrow is the direction of movement along the Y-axis.

[0035] When the illumination beam shines on the first grating 111 and the second grating 112, diffraction occurs. At this time, the second substrate 30 is outside the field of view of the illumination beam, that is, outside the exposure field of view. In order to measure the dynamic wave aberration of the field of view of the illumination beam in the Y direction, the second substrate 30 is moved along the Y direction so that the illumination beam passing through the first substrate 10 is projected onto the second substrate 30 by the projection lens 20 and converges on the third grating 311 and the fourth grating 312 to generate shear interference, forming shear interference fringes. The interference image is recorded by the detection surface of the image detection unit 40. During the movement of the second substrate 30, the second substrate 30 is always within the exposure field of view. The detection surface of the image detection unit 40 records the interference image in real time. After the second substrate 30 is moved out of the field of view of the illumination beam along the Y direction, the interference image recorded by the detection surface of the image detection unit 40 is the integral of the interference images of all field points in the entire exposure field of view along the Y direction, that is, the dynamic wave aberration image of the entire exposure field of view along the Y direction.

[0036] In this embodiment, the first substrate is provided with a first grating extending along the X direction and a second grating extending along the Y direction. The width of the first grating along the Y direction is greater than the width of the field of view of the illumination beam along the Y direction, and the width of the second grating along the Y direction is also greater than the width of the field of view of the illumination beam along the Y direction, so that the illumination beam can pass through the first grating and the second grating in the Y direction. The second substrate is provided with a third grating extending along the X direction and a fourth grating extending along the Y direction. The second substrate is moved along the Y direction so that the projection lens projects the illumination beam passing through the first substrate onto the second substrate. When the second substrate moves out of the field of view of the illumination beam along the Y direction, the image detection unit acquires the dynamic wave aberration image of the illumination beam passing through the second substrate. Since the illumination beam emitted by the light source has a Gaussian-like distribution along the Y direction, when the exposure dose is different, the dynamic wave aberration image obtained by moving the second substrate along the Y direction for dynamic measurement is more accurate, the measurement accuracy of dynamic wave aberration is higher, and there is no need to perform multiple measurements and fitting on multiple discrete field points to obtain the dynamic wave aberration, thereby improving the measurement accuracy and efficiency of dynamic wave aberration.

[0037] Figure 4 This is a flowchart of the wavelet aberration measurement method provided in this embodiment. Please refer to it. Figure 4 The wavefront aberration measurement method using the aforementioned wavefront aberration measurement device includes:

[0038] Step S1: The illumination beam emitted by the light source is incident on the first substrate;

[0039] Step S2: Move the second substrate along the Y direction so that the projection lens projects the illumination beam transmitted through the first substrate onto the second substrate; and,

[0040] Step S3: Move the second substrate along the Y direction, and the image detection unit acquires a dynamic wave aberration image of the illumination beam transmitted through the second substrate.

[0041] The wavelet aberration measurement method provided in this embodiment will be described in detail below.

[0042] Step S1: The first substrate is placed on the mask stage and kept stationary, and the second substrate is placed on the motion stage. The extension directions of the second grating and the fourth grating are the same as the Y direction. The motion stage can provide the second substrate with movement along the Y direction. The illumination beam emitted by the light source is incident on the first substrate.

[0043] Step S2: When the illumination beam emitted by the light source is incident on the first substrate, the second substrate is outside the field of view of the illumination beam, which is the exposure field of view. The illumination beam that passes through the first substrate does not pass through the second substrate. The second substrate is moved along the Y-axis using a motion stage. The Y-axis is the Y direction of the field of view of the illumination beam. The illumination beam that passes through the first substrate is projected onto the second substrate by the projection lens, converging on the third and fourth gratings, causing shearing interference and forming shearing interference fringes. The interference image is recorded by the detection surface of the image detection unit. While the motion stage moves the second substrate along the Y-axis, the first substrate remains stationary.

[0044] Step S3: Since the illumination beam has a Gaussian-like distribution along the Y-direction, the influence weight of wavefront aberration at different positions along the Y-direction on exposure performance varies depending on the exposure dose. Therefore, it is necessary to measure the dynamic wavefront aberration of the entire exposure field of view along the Y-direction. The stage continues to drive the second substrate to move along the Y-direction. During the movement, the first substrate remains stationary. The illumination beam passing through the first substrate is projected onto the second substrate by the projection lens, converging on the third and fourth gratings to cause shearing interference, forming shearing interference fringes. The interference image is recorded by the detection surface of the image detection unit. During the movement of the second substrate, the second substrate remains within the exposure field of view. The detection surface of the image detection unit records the interference image in real time until the second substrate is completely moved out of the exposure field of view along the Y-direction. The interference image recorded by the detection surface of the image detection unit is the integral of the interference images of all field points in the illumination beam along the Y-direction, that is, the dynamic wavefront aberration image of the field of view of the illumination beam along the Y-direction. The dynamic wave aberration image obtained by moving the second substrate along the Y direction is more accurate, the measurement accuracy of dynamic wave aberration is higher, and there is no need to perform multiple measurements and fittings on multiple discrete field points to obtain dynamic wave aberration, thereby improving the measurement accuracy and efficiency of dynamic wave aberration.

[0045] In summary, in the wavefront aberration measurement device and method provided by this invention, a first grating extending along the X direction and a second grating extending along the Y direction are provided on a first substrate. The width of the first grating along the Y direction is greater than the width of the field of view of the illumination beam along the Y direction, and the width of the second grating along the Y direction is greater than the width of the field of view of the illumination beam along the Y direction, so that the illumination beam can pass entirely through the first and second gratings in the Y direction. A third grating extending along the X direction and a fourth grating extending along the Y direction are provided on the second substrate. Moving the second substrate along the Y direction allows the projection lens to pass through the first grating and the second grating. An illumination beam from a substrate is projected onto a second substrate. When the second substrate moves out of the field of view of the illumination beam along the Y direction, the image detection unit acquires a dynamic wave aberration image of the illumination beam transmitted through the second substrate. Since the illumination beam emitted by the light source has a Gaussian-like distribution along the Y direction, the dynamic wave aberration image obtained by moving the second substrate along the Y direction for dynamic measurement is more accurate when the exposure dose is different. The measurement accuracy of dynamic wave aberration is higher, and there is no need to perform multiple measurements and fittings on multiple discrete field points to obtain dynamic wave aberration, thereby improving the measurement accuracy and efficiency of dynamic wave aberration.

[0046] The above are merely preferred embodiments of the present invention and do not constitute any limitation on the present invention. Any equivalent substitutions or modifications made by those skilled in the art to the technical solutions and content disclosed in the present invention without departing from the scope of the present invention shall be deemed to have remained within the protection scope of the present invention.

Claims

1. A wavelet aberration measuring device, characterized in that, The system includes a light source, a first substrate, a projection lens, a second substrate, and an image detection unit arranged sequentially along the optical path. The light source is used to emit an illumination beam. The first substrate has a first grating extending along the X direction and a second grating extending along the Y direction. The width of the first grating along the Y direction is greater than the width of the field of view of the illumination beam along the Y direction, and the width of the second grating along the Y direction is greater than the width of the field of view of the illumination beam along the Y direction. The second substrate has a third grating extending along the X direction and a fourth grating extending along the Y direction. The projection lens projects the illumination beam passing through the first substrate onto the second substrate. The second substrate is moved along the Y direction so that the image detection unit can acquire a dynamic wavefront aberration image of the illumination beam passing through the second substrate.

2. The wavelet aberration measuring device as described in claim 1, characterized in that, The magnification of the projection lens is N, and the period of the first grating and the second grating is N times the period of the third grating and the fourth grating.

3. The wavelet aberration measuring device as described in claim 1, characterized in that, The width of the first grating along the Y direction is the same as the width of the second grating along the Y direction, and the centers of the first grating and the second grating are at the same position in the Y direction; the width of the third grating along the Y direction is the same as the width of the fourth grating along the Y direction, and the centers of the third grating and the fourth grating are at the same position in the Y direction.

4. The wavelet aberration measuring device as described in claim 3, characterized in that, The first grating and the second grating are spaced apart in the X direction; the third grating and the fourth grating are spaced apart in the X direction.

5. The wavelet aberration measuring device as described in claim 4, characterized in that, The duty cycles of the first grating, the second grating, the third grating, and the fourth grating are all 1:

1.

6. The wavelet aberration measuring device as described in claim 5, characterized in that, The first grating, the second grating, the third grating, and the fourth grating are all one-dimensional gratings.

7. The wavelet aberration measuring device as described in claim 1, characterized in that, An air gap exists between the image detection unit and the second substrate.

8. The wavelet aberration measuring device as described in claim 1, characterized in that, It also includes a motion stage for driving the second substrate to move along the Y direction.

9. A wavelet aberration measurement method using the wavelet aberration measuring device as described in any one of claims 1 to 8, characterized in that, include: The illumination beam emitted by the light source is incident on the first substrate; The second substrate is moved along the Y direction so that the projection lens projects the illumination beam transmitted through the first substrate onto the second substrate; as well as, The second substrate is moved along the Y direction, and the image detection unit acquires a dynamic wave aberration image of the illumination beam transmitted through the second substrate.

10. The wavelet aberration measurement method as described in claim 9, characterized in that, When the second substrate is moved along the Y direction, it is moved from the field of view that just enters the illumination beam to the field of view that is completely removed from the illumination beam.

11. The wavelet aberration measurement method as described in claim 9 or 10, characterized in that, When the second substrate moves along the Y direction, the first substrate remains stationary.

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