A detection system and a control method thereof

Abstract

The application provides a detection system and a control method thereof, and relates to the technical field of semiconductor detection. The detection system comprises an illumination module and an imaging module arranged in sequence. A product to be detected is arranged between the illumination module and the imaging module. The illumination module and the imaging module respectively comprise a first time sequence diaphragm and a second time sequence diaphragm arranged in rotation. The first time sequence diaphragm is used for obliquely irradiating the product to be detected with illumination light generated by the illumination module. The second time sequence diaphragm is used for filtering or weakening low-frequency diffraction light from the product to be detected and retaining high-frequency diffraction light. The first time sequence diaphragm and the second time sequence diaphragm are synchronously arranged in time sequence, so that the illumination light incident on the product to be detected and the diffraction light from the product to be detected to the imaging module cross at an optical axis. The high-frequency diffraction light is prevented from being shielded while the 0th-order diffraction light is filtered. The final image is formed by fitting different images with reduced 0th-order diffraction light, the imaging effect is improved, the contrast of the system is improved, and high-pass filtering is realized.

Description

Technical Field

[0001] This application relates to the field of semiconductor detection technology, specifically to a detection system and its control method. Background Technology

[0002] In semiconductor testing equipment, because the microstructures on the mask surface are very small, with dimensions similar to the wavelength of the light source, the diffraction angle of the diffracted light generated by the incident light beam on the mask surface is generally large. When the imaging lens images the mask surface, the imaging principle is that the illumination light passes through the mask, and the diffracted light enters the imaging lens. Figure 1a As shown, diffracted light of different orders interferes and forms an image on the sensor surface after passing through the lens. The diffracted light of different orders is divided into low-frequency diffracted light and high-frequency diffracted light. Low-frequency diffracted light provides overall background illumination but does not provide contour information of the imaged object. High-frequency diffracted light has weaker energy but carries contour information of the imaged object.

[0003] To maximize the incidence of high-frequency diffracted light into the imaging lens, current technologies generally employ oblique illumination, allowing 0th-order (low-frequency) and ±1st-order (high-frequency) diffracted light to be incident, thus enabling imaging of the mask surface. Normal perpendicular incidence results in excessively large high-frequency diffraction angles that cannot reach the lens, leading to reduced image quality or even no imaging at all. Summary of the Invention

[0004] The purpose of this application is to provide a detection system that can improve imaging effects, enhance system contrast, and achieve high-pass filtering.

[0005] One aspect of this application provides a detection system, including: an illumination module and an imaging module arranged sequentially, with a product under test positioned between the illumination module and the imaging module. The illumination module and the imaging module each include a first timing aperture and a second timing aperture that are rotatably arranged. The first timing aperture is used to obliquely illuminate the product under test with the illumination light generated by the illumination module, and the second timing aperture is used to filter out or reduce low-frequency diffraction light from the product under test and retain high-frequency diffraction light. The timing of the first timing aperture and the second timing aperture is synchronized so that the illumination light incident on the product under test and the diffraction light incident from the product under test onto the imaging module intersect at the optical axis.

[0006] Optionally, the first timing aperture has a first aperture hole, the second timing aperture has a second aperture hole, and the first aperture hole and the second aperture hole are mirror images of each other along the optical axis.

[0007] Optionally, the first timing aperture has multiple first aperture holes, and the second timing aperture has multiple second aperture holes, with each of the multiple first aperture holes and the multiple second aperture holes corresponding one-to-one.

[0008] Optionally, the imaging module further includes a sensor, the exposure timing of which is set synchronously with the timing of the first timing stop and the timing of the second timing stop.

[0009] Optionally, it further includes a first driving module and a second driving module, wherein the first driving module is connected to the first timing aperture to drive the first timing aperture to rotate, and the second driving module is connected to the second timing aperture to drive the second timing aperture to rotate.

[0010] Optionally, the first timing aperture and the second timing aperture can be rotated arbitrarily within 360 degrees.

[0011] Optionally, when there are multiple first apertures of the first timing aperture, the multiple first apertures surround the first driving module; when there are multiple second apertures of the second timing aperture, the multiple second apertures surround the second driving module.

[0012] Optionally, the illumination module further includes an illumination lens group, which includes multiple illumination lenses, with the first timing stop located between the multiple illumination lenses; the imaging module further includes an imaging lens group, which includes multiple imaging lenses, with the first timing stop located between the multiple imaging lenses.

[0013] In another aspect of this application, a control method for a detection system is provided, for controlling the aforementioned detection system, comprising: The first timing aperture and the second timing aperture are driven to rotate synchronously so that the first aperture of the first timing aperture and the second aperture of the second timing aperture are always mirrored along the optical axis.

[0014] Optionally, the method further includes: The exposure timing of the sensor is controlled to be synchronized with the timing of the first timing stop and the timing of the second timing stop.

[0015] The detection system and control method provided in this application improve the imaging effect and enhance the system contrast by adding a second time-series aperture and a first time-series aperture to the imaging module and the illumination module. The second time-series aperture of the imaging module filters out or weakens the 0th order diffraction light and retains the high-frequency diffraction light. The first time-series aperture of the illumination module generates the illumination light required for tilted illumination. The timing of the first time-series aperture and the second time-series aperture needs to be synchronized to prevent the high-frequency diffraction light from being blocked while filtering out the 0th order diffraction light. By fitting different images with reduced 0th order diffraction light, the final image is formed, thereby improving the imaging effect, enhancing the system contrast, and achieving high-pass filtering. Attached Figure Description

[0016] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments of this application will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1a This is an optical path diagram of existing technology; Figure 1b This is the optical path diagram of conventional tilted illumination; Figure 1c yes Figure 1b The corresponding imaging pupil diffraction pattern; Figure 2a This is a schematic diagram of the optical path of the detection system provided in this embodiment; Figure 2b This is a comparison diagram of the positions of the first and second apertures of the detection system provided in this embodiment; Figure 3 This is a light spot diagram of the first time-series aperture of the detection system provided in this embodiment at different times; Figure 4a This is the light incident direction pattern of the product under test corresponding to the position of the first timing aperture A of the detection system provided in this embodiment; Figure 4b This is the light incident direction pattern of the product under test corresponding to the position of the first timing aperture B of the detection system provided in this embodiment; Figure 5 This is the second time-series aperture diffraction pattern of the detection system provided in this embodiment; Figure 6 This is a structural diagram of the second timing aperture of the detection system provided in this embodiment; Figure 7 This is a diagram showing the correspondence between the aperture position and the sensor timing of the detection system provided in this embodiment; Figure 8 This is a schematic diagram of each sub-position of the first timing aperture of the detection system provided in this embodiment.

[0018] Icons: 1-Illumination system; 2-Mask; 11-First timing aperture; 110-First aperture hole; 12-Illumination lens; 20-Product under test; 31-Second timing aperture; 310-Second aperture hole; 32-Imaging surface; 33-Imaging lens; a1-First angle; a2-Second angle. Detailed Implementation

[0019] The technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings.

[0020] In the description of this application, it should be noted that the terms "inner" and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product is in use. They are used only for the convenience of describing this application and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application. Furthermore, the terms "first," "second," etc., are used only to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0021] It should also be noted that, unless otherwise explicitly specified and limited, the terms "setup" and "connection" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0022] Since the diffraction energy of 0th-order diffraction light is generally higher than that of high-frequency diffraction light, and 0th-order diffraction light does not carry frequency domain information and cannot be imaged, it becomes necessary to increase high-frequency diffraction light and reduce low-frequency diffraction light. Current methods involve tilted illumination. Although 1st-order or -1st-order diffraction light can enter the imaging lens, its energy is relatively weaker than 0th-order light, reducing the overall imaging contrast and resulting in poor image extinction. Ordinary tilted illumination, such as... Figure 1b , Figure 1c As shown, the illumination light from illumination system 1 incident on the mask (mask 2) surface will generate diffracted light. The imaging pupil contains 0th-order diffracted light and ±1st-order diffracted light. The positions of the 0th-order diffracted light and ±1st-order diffracted light are basically overlapping, making it impossible to effectively filter the 0th-order diffracted light. Since the 0th-order diffracted light does not carry frequency domain information, it cannot be imaged independently. Therefore, high-frequency diffracted light forms an image through interference on the imaging surface. The 0th-order diffracted light usually has the strongest energy. Although it can interfere with high-frequency diffracted light for imaging, the intensity difference between the two is too large. Excessive 0th-order diffracted light will become the system's noise floor, thus reducing the imaging contrast and affecting the system's imaging. It is necessary to reduce the intensity of the 0th-order diffracted light to improve the imaging contrast and enhance the imaging effect.

[0023] In view of this, please refer to Figure 2aAs shown, this application embodiment provides a detection system, including: an illumination module and an imaging module arranged sequentially, with a test product 20 set between the illumination module and the imaging module. The illumination module and the imaging module each include a first timing aperture 11 and a second timing aperture 31 that are rotated. The first timing aperture 11 is used to tilt the illumination light generated by the illumination module to illuminate the test product 20. For example, the test product 20 is a mask. The second timing aperture 31 is used to filter out or reduce the low-frequency diffraction light from the test product 20 and retain the high-frequency diffraction light. The timing of the first timing aperture 11 and the second timing aperture 31 is set synchronously so that the illumination light incident on the test product 20 and the diffraction light incident from the test product 20 to the imaging module cross at the optical axis.

[0024] The function of the first timing aperture 11 of the illumination module is to tilt the illumination light onto the product under test 20. The function of the second timing aperture 31 of the imaging module is to filter out or reduce low-frequency diffraction light while retaining high-frequency diffraction light. The 0th order diffraction light is low-frequency diffraction light, while the other orders are high-frequency diffraction light. For example, the 1st order and -1st order diffraction light are both high-frequency diffraction light.

[0025] Because the timing of the first timing aperture 11 and the second timing aperture 31 are set synchronously, in Figure 2a After passing through the illumination module, the central illumination light can be obliquely incident on the product under test 20. At the same time, the diffracted light formed by the product under test 20 is directed towards the imaging module at the rear end at an angle symmetrical to the oblique illumination light along the product under test 20. The oblique illumination light and the diffracted light intersect at the intersection of the product under test 20 and the optical axis.

[0026] Furthermore, the first timing stop 11 has a first aperture 110, and the second timing stop 31 has a second aperture 310. When the timing of the first timing stop 11 and the second timing stop 31 is set synchronously, the first aperture 110 and the second aperture 310 are mirror images of each other along the optical axis, such as... Figure 2b As shown.

[0027] The mirror setting means that the tilted illumination light and the diffracted light intersect at the intersection of the product under test 20 and the optical axis. Specifically, assuming that the first aperture 110 is located at the 9 o'clock position of the first timing aperture 11, then the second aperture 310 is located at the 3 o'clock position of the second timing aperture 31. In this way, the illumination light passing through the first aperture 110 will tilt to illuminate the product under test 20 at a first angle a1, and then tilt to the imaging module at a second angle a2 as shown in Figure 2. The first angle a1 and the second angle a2 are symmetrical with respect to the product under test 20.

[0028] The imaging module also includes a sensor, which can be set at the imaging surface 32. The exposure timing of the sensor is set synchronously with the timing of the first timing stop 11 and the timing of the second timing stop 31.

[0029] Based on this, in order to improve the quality of the illumination light and the imaging light, the illumination module also includes a group of illumination lenses 12, which includes multiple illumination lenses 12, and a first timing aperture 11 is located between the multiple illumination lenses 12; the imaging module also includes a group of imaging lenses 33, which includes multiple imaging lenses 33, and a first timing aperture 11 is located between the multiple imaging lenses 33.

[0030] Figure 2a The first timing stop 11 is located between the two illumination lenses 12, and the second timing stop 31 is located between the two imaging lenses 33. The illumination lenses 12 and the imaging lenses 33 are used to collimate, converge, or diverge the light accordingly to meet the imaging quality requirements.

[0031] Therefore, the detection system provided in this application adds a second timing aperture 31 and a first timing aperture 11 to the imaging module and the illumination module. The second timing aperture 31 of the imaging module filters out or weakens the 0th order diffraction light and retains the high-frequency diffraction light. The first timing aperture 11 of the illumination module generates the illumination light required for tilted illumination. The timing of the first timing aperture 11 and the second timing aperture 31 needs to be synchronized to prevent the high-frequency diffraction light from being blocked while filtering out the 0th order diffraction light. The exposure timing of the sensor is synchronized with the positions of the two apertures. By fitting different images of reduced 0th order diffraction light, the final image is formed, improving the imaging effect, enhancing the system contrast, and achieving high-pass filtering.

[0032] Both the first timing stop 11 and the second timing stop 31 are rotated, meaning that the two stops need to rotate synchronously within the system. For example... Figure 3 As shown, taking the first timing aperture 11 as an example, at the first moment, the light spot emitted by the first timing aperture 11 is on the left, while at the second moment, the light spot emitted by the first timing aperture 11 is on the right, with the left light spot rotating exactly 180 degrees to the right light spot. Simultaneously, the second timing aperture 31 should also rotate exactly 180 degrees from the first moment to the second moment, and... Figure 3 Conversely, at the first moment, the light spot emitted by the second timing aperture 31 is on the right, while at the second moment, the light spot emitted by the second timing aperture 31 is on the left, mirroring the first timing aperture 11.

[0033] In other embodiments, the first timing aperture 11 and the second timing aperture 31 can rotate arbitrarily within 360 degrees, that is, both apertures can rotate at any angle from the first moment to the second moment, as long as they rotate synchronously by the same angle. The light spots at the first moment and the second moment are used alternately in a timing manner.

[0034] For example Figure 4a , Figure 4bAs shown, when the first aperture 110 of the first timing aperture 11 rotates to different positions, it corresponds to different incident angles of the incident light from the product under test 20, thereby generating tilted illumination at different angles. These tilted illuminations at different angles sequentially generate different 0 / 1 order diffraction spots and 0 / -1 order diffraction spots at the position of the second timing aperture 31, such as... Figure 5 As shown, the timing of the second timing aperture 31 is synchronized with that of the first timing aperture 11. At the same time, the second timing aperture 31 blocks the corresponding 0th order diffraction spot, reducing the intensity of the 0th order diffraction light.

[0035] Furthermore, referring to Figure 6 As shown, there can be multiple first aperture holes 110 of the first timing aperture 11 and multiple second aperture holes 310 of the second timing aperture 31, with multiple first aperture holes 110 and multiple second aperture holes 310 corresponding one-to-one.

[0036] One-to-one correspondence means that each first aperture 110 corresponds to a second aperture 310, and each pair of corresponding first apertures 110 and second apertures 310 must meet the above requirements, that is, the corresponding first apertures 110 and second apertures 310 are set in a mirror image along the optical axis.

[0037] like Figure 6 Taking the second timing aperture 31 as an example, it has multiple second aperture holes 310 distributed along the circumference. These second aperture holes 310 are not evenly distributed, but are basically distributed along the edge area of ​​the circumference. The central area of ​​the circumference is used to set the driving module to drive the second timing aperture 31 to rotate. Similarly, the first timing aperture 11 has multiple first aperture holes 110, which will not be described in detail here.

[0038] When the first timing aperture 11 and the second timing aperture 31 rotate, the first timing aperture 11 is driven by a first driving module connected to the first timing aperture 11 to drive the first timing aperture 11 to rotate; similarly, the second timing aperture 31 is driven by a second driving module connected to the second timing aperture 31 to drive the second timing aperture 31 to rotate.

[0039] The first drive module and the second drive module are located at the center of the first timing aperture 11 and the second timing aperture 31, respectively. Generally, both the first drive module and the second drive module can be motors.

[0040] pass Figure 6 As can be seen from the settings, when there are multiple first aperture holes 110 of the first timing aperture 11, the multiple first aperture holes 110 surround the first driving module. When there are multiple second aperture holes 310 of the second timing aperture 31, the multiple second aperture holes 310 surround the second driving module.

[0041] For example Figure 7 , Figure 8 As shown, the first timing stop 11 is time-synchronized with the second timing stop 31 at positions A (first moment) and B (second moment). The sensor's exposure timing is time-synchronized with the two timing stop positions. After exposure, the camera performs image fitting at positions A and B to form the final image.

[0042] Figure 8 The red area in the middle corresponds to the concave area of ​​the timing curve. Taking the first timing aperture 11 as an example, it shows that the illumination light in this period is blocked by the first timing aperture 11 and cannot pass through the first aperture hole 110.

[0043] Based on this, embodiments of this application also disclose a control method for a detection system, used to control the detection system as described above, the method comprising: Step 400: Drive the first timing aperture 11 and the second timing aperture 31 to rotate synchronously, so that the first aperture 110 of the first timing aperture 11 and the second aperture 310 of the second timing aperture 31 are always mirrored along the optical axis.

[0044] The timing of the first timing aperture 11 and the second timing aperture 31 needs to be synchronized. Therefore, they need to rotate synchronously to ensure that the first aperture 110 of the first timing aperture 11 and the second aperture 310 of the second timing aperture 311 are always mirror images along the optical axis in order to form a [synchronous structure]. Figure 2a The optical path shown.

[0045] Further, step 401: control the exposure timing of the sensor to synchronize it with the timing of the first timing stop 11 and the second timing stop 31, so as to ensure the synchronization of exposure and enable the images at different time positions to be fitted to form a formal image.

[0046] The control method of this detection system includes the same structure and beneficial effects as the detection system in the foregoing embodiments. The structure and beneficial effects of the detection system have been described in detail in the foregoing embodiments and will not be repeated here.

[0047] The above description is merely an embodiment of this application and is not intended to limit the scope of protection of this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of protection of this application.

Claims

1. A detection system, characterized in that, include: An illumination module and an imaging module are arranged sequentially, with a product under test positioned between them. The illumination module and the imaging module each include a first timing aperture and a second timing aperture that are rotated. The first timing aperture is used to tilt the illumination light generated by the illumination module onto the product under test, and the second timing aperture is used to filter out or reduce low-frequency diffraction light from the product under test while retaining high-frequency diffraction light. The timing of the first timing aperture and the second timing aperture is synchronized so that the illumination light incident on the product under test and the diffraction light incident from the product under test onto the imaging module intersect at the optical axis.

2. The detection system according to claim 1, characterized in that, The first timing aperture has a first aperture hole, and the second timing aperture has a second aperture hole. The first aperture hole and the second aperture hole are mirror images of each other along the optical axis.

3. The detection system according to claim 2, characterized in that, The first timing aperture has multiple first aperture holes, and the second timing aperture has multiple second aperture holes, with each of the multiple first aperture holes and the multiple second aperture holes corresponding one-to-one.

4. The detection system according to claim 1, characterized in that, The imaging module also includes a sensor, the exposure timing of which is set synchronously with the timing of the first timing stop and the timing of the second timing stop.

5. The detection system according to any one of claims 1 to 4, characterized in that, It also includes a first driving module and a second driving module. The first driving module is connected to the first timing aperture to drive the first timing aperture to rotate, and the second driving module is connected to the second timing aperture to drive the second timing aperture to rotate.

6. The detection system according to claim 5, characterized in that, The first timing aperture and the second timing aperture can rotate arbitrarily within 360 degrees.

7. The detection system according to claim 5, characterized in that, When there are multiple first apertures of the first timing aperture, the multiple first apertures surround the first driving module. When there are multiple second apertures of the second timing aperture, the multiple second apertures surround the second driving module.

8. The detection system according to any one of claims 1 to 4, characterized in that, The illumination module further includes an illumination lens group, which includes multiple illumination lenses, with the first timing stop located between the multiple illumination lenses; the imaging module further includes an imaging lens group, which includes multiple imaging lenses, with the first timing stop located between the multiple imaging lenses.

9. A control method for a detection system, used to control the detection system according to any one of claims 1 to 8, characterized in that, The method includes: The first timing aperture and the second timing aperture are driven to rotate synchronously so that the first aperture of the first timing aperture and the second aperture of the second timing aperture are always mirrored along the optical axis.

10. The control method for the detection system according to claim 9, characterized in that, The method further includes: The exposure timing of the sensor is controlled to be synchronized with the timing of the first timing stop and the timing of the second timing stop.

Images