Wafer photoluminescence detection device and method based on spectral imaging

Abstract

The invention discloses a wafer photoluminescence detection device and method based on spectral imaging, and the device comprises a displacement platform which carries a to-be-detected sample; the light source system generates an excitation light beam; the alignment camera receives fluorescence generated by excitation and generates an alignment image; the spectral imaging system is used for receiving the fluorescence and carrying out spectral measurement; the first light splitting module is used for reflecting an excitation light beam emitted by the light source system to the microscope objective front group and irradiating the surface of a sample to be detected; the second light splitting module is used for splitting the fluorescence into first fluorescence and second fluorescence, the first fluorescence passes through the camera imaging objective lens and then enters the alignment camera, and the second fluorescence passes through the microscope objective lens rear group and then enters the spectral imaging system; and the first imaging surface of the alignment camera and the second imaging surface of the spectral imaging system are positioned on a conjugate surface of the imaging surface of the microscopic imaging system. By arranging the alignment camera, accurate alignment of spectral measurement is realized.

Description

Technical Field

[0001] The present invention mainly relates to semiconductor wafer detection, and in particular to a wafer photoluminescence detection device and method based on spectral imaging. Background Art

[0002] As Mini LED and Micro LED gradually become the mainstream development direction of new display devices, the size of LED light-emitting chips has shrunk from the millimeter level to the micron level. Their tiny electrodes are difficult to contact and the number to be tested is very large. Traditional contact-type luminescence characteristic detection methods will inevitably be replaced by non-contact photoluminescence measurement solutions.

[0003] When an LED is exposed to light, if the energy of the photon is greater than the band gap, electrons in a low-energy state absorb the photon's energy and transition to an excited state. These excited electrons are unstable and return to a low-energy state, emitting photons. This is the photoluminescence (PL) of the LED. By stimulating the LED wafer with a laser and detecting the emitted fluorescence with a camera or spectrometer, we can analyze the quality and defects of the LED wafer.

[0004] PL detection is a non-contact detection method. In the current solution, such as Figure 1 As shown, spectrometers can typically only measure PL spectral information at a single point on a wafer, limiting detection efficiency and lacking spatial resolution. Alternatively, area array image sensors can be used to obtain spatially resolved PL images. However, spectral signatures are crucial for PL detection, making high-precision image detection difficult. Summary of the Invention

[0005] In response to at least one defect or improvement need in the prior art, the present invention provides a wafer photoluminescence detection device and method based on spectral imaging, which achieves precise alignment of spectral measurement by setting an alignment camera.

[0006] To achieve the above objectives, according to a first aspect of the present invention, a wafer photoluminescence detection device based on spectral imaging is provided, the device comprising: The displacement platform is used to carry the sample to be tested; the light source system is used to generate an excitation light beam; the surface of the sample to be tested is excited to generate fluorescence after receiving the excitation light beam; an alignment camera, configured to receive the fluorescence and generate an alignment image; a spectral imaging system, configured to receive the fluorescence and perform spectral measurement; A microscopic imaging system, comprising a front microscope objective lens group, a first light splitting module, a second light splitting module, a camera imaging objective lens, and a rear microscope objective lens group; The first light splitting module is used to reflect the excitation light beam emitted by the light source system to the front group of the microscope objective lens, and irradiate the surface of the sample to be tested; The front group of the microscope objective lens is further used to receive the fluorescence, the first spectroscopic module is further used to transmit the fluorescence, and the second spectroscopic module is used to separate the fluorescence into a first fluorescence and a second fluorescence; wherein the first fluorescence enters the alignment camera after passing through the camera imaging objective lens; and the second fluorescence enters the spectral imaging system after passing through the rear group of the microscope objective lens; The first imaging plane of the alignment camera and the second imaging plane of the spectral imaging system are located at a conjugate plane of the imaging plane of the microscopic imaging system.

[0007] Furthermore, the above-mentioned wafer photoluminescence detection device based on spectral imaging further includes: The spectral imaging system includes an incident slit, a dispersion system, an imaging system and an image acquisition system arranged in sequence along the propagation direction of the second fluorescence; wherein the second imaging surface is the incident slit.

[0008] Furthermore, the above-mentioned wafer photoluminescence detection device based on spectral imaging further includes: The spectral imaging system further includes a collimation system, which is arranged between the incident slit and the dispersion system.

[0009] Furthermore, the above-mentioned wafer photoluminescence detection device based on spectral imaging further includes: The microscopic imaging system and the alignment camera have numerical apertures that match those of the spectral imaging system.

[0010] Furthermore, the above-mentioned wafer photoluminescence detection device based on spectral imaging further includes: The light source system includes a laser light source and a light source objective lens. The laser light source emits an excitation light beam, which enters the microscopic imaging system through the light source objective lens.

[0011] Furthermore, the above-mentioned wafer photoluminescence detection device based on spectral imaging further includes: The light source system further includes an LED light source and a light source beam splitter. The LED light source is used to provide an alignment light beam, which enters the microscopic imaging system through the light source beam splitter and is used to align the alignment camera.

[0012] Furthermore, the above-mentioned wafer photoluminescence detection device based on spectral imaging further includes: It also includes a control system for controlling the switch of the light source system, and for receiving the alignment image and the position information of the displacement platform, and adjusting the position of the displacement platform to make the alignment image clear.

[0013] Furthermore, the above-mentioned wafer photoluminescence detection device based on spectral imaging further includes: The control system includes a central computer and a displacement platform control system. The central computer is used to control the switch of the light source system and obtain the alignment image generated by the alignment camera when the light source system is turned on. The alignment state of the microscopic imaging system is determined based on the alignment image. The central computer is further configured to, when determining that the system is not aligned, send a first instruction to the displacement platform control system to control the position and posture of the displacement platform and continue to acquire alignment images until the central computer determines that the microscopic imaging system is in an aligned state; The central computer is also used to send a second instruction to the spectral imaging system after determining that the alignment is completed, so as to perform spectral measurement on the surface of the sample to be tested, and at the same time send a third instruction to the displacement platform control system to control the displacement platform to move along a specified path, so that the spectral imaging system can perform spectral measurement on different locations on the surface of the sample to be tested, thereby realizing comprehensive spectral measurement of the surface of the sample to be tested.

[0014] Furthermore, the above-mentioned wafer photoluminescence detection device based on spectral imaging further includes: It also includes an automatic focusing system for completing automatic focusing when the displacement platform moves along a specified path, and then performing spectral measurement on the surface of the sample to be measured through the spectral imaging system.

[0015] According to a second aspect of the present invention, a wafer photoluminescence detection method based on spectral imaging is also provided, which is applied to any of the above-mentioned wafer photoluminescence detection devices based on spectral imaging, comprising: Turning on the light source system to generate an excitation light beam, which is irradiated onto the surface of the sample to be tested via the microscopic imaging system, so that the surface of the sample to be tested generates fluorescence; An alignment camera receives the fluorescence and generates an alignment image; Adjusting the position of the displacement platform according to the alignment image until the alignment of the microscopic imaging system is completed; After alignment is completed, the spectral imaging system receives the fluorescence and performs spectral measurement.

[0016] In general, the above technical solutions conceived by the present invention can achieve the following beneficial effects compared with the prior art: (1) The present invention provides a wafer photoluminescence detection device based on spectral imaging. The sample to be tested is imaged by a microscopic imaging system. The imaging light path is split into two paths by a beam splitter. An alignment camera is set on the image plane of the first path, and an incident slit is set on the image plane of the second path. After the focusing process, when the alignment camera of the first path is clearly focused, a clear slit image is obtained on the second path at the same time. The slit image is passed through the spectral imaging system to obtain the spectrum of each point of the slit. (2) The present invention provides a wafer photoluminescence detection device based on spectral imaging, which obtains micron-level spatial resolution information of the sample through a microscopic imaging system with micron-level spatial resolution. The image-side output numerical aperture of the microscopic imaging system matches the input numerical aperture of the spectral imaging system, thereby avoiding the degradation of spatial resolution and realizing micron-level spatial resolution spectral measurement; (3) The present invention provides a wafer photoluminescence detection device based on spectral imaging, which can cover the spectral measurement of the entire surface of the sample to be tested by moving the displacement platform. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0018] Figure 1 Schematic diagram of a wafer photoluminescence detection device based on spectral imaging in the prior art; Figure 2 A schematic structural diagram of a wafer photoluminescence detection device based on spectral imaging provided by an embodiment of the present invention; Figure 3 A schematic diagram of the structure of a spectral imaging system of a wafer photoluminescence detection device based on spectral imaging provided by an embodiment of the present invention; Figure 4 A schematic diagram of the structure of a light source system of a wafer photoluminescence detection device based on spectral imaging provided by an embodiment of the present invention; Figure 5 A schematic diagram of the control system structure of a wafer photoluminescence detection device based on spectral imaging provided by an embodiment of the present invention.

[0019] In all the drawings, the same reference numerals are used to represent the same elements or structures, wherein: 1-displacement platform, 2-sample to be measured, 31-front group of microscope objective, 32-first spectroscopic module, 33-second spectroscopic module, 34-camera imaging objective, 35-rear group of microscope objective, 41-laser light source, 411-LED light source, 412-light source beam splitter, 42-light source objective, 5-alignment camera, 6-spectral imaging system, 7-control system; 61-incident slit, 62-collimation system, 63-dispersion system, 64-imaging system, 65-image acquisition system. DETAILED DESCRIPTION

[0020] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely for the purpose of explaining the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.

[0021] The terms "first," "second," "third," and so on, in the description and claims of the present invention and the accompanying drawings are used to distinguish between different items, not to describe a specific order. Furthermore, the terms "including," "having," and any variations thereof, are intended to cover non-exclusive inclusions. For example, a process, method, system, product, or apparatus comprising a series of steps or elements is not limited to the listed steps or elements but may optionally include steps or elements not listed, or may optionally include other steps or elements inherent to the process, method, product, or apparatus.

[0022] Photoluminescence (PL) is measured by illuminating the surface of a wafer under test with monochromatic light. The semiconductor material responds to this light by emitting excitation light. If a defect is present on the wafer surface, the spectrum of the excitation light at the defective location will differ from that at a normal location. By monitoring the spectrum of the excitation light, the wafer's performance can be assessed. For PL spectroscopy measurement methods, reference can also be made to the following prior art documents: Bel'kov, VV et al., "Microwave-induced patterns in n-GaAs and their photoluminescence imaging" (Physical Review B, Vol. 61, No. 20, The American Physical Society, May 15, 2000, pp. 13698-13702) and Masarotto et al., "Development of a UV scanning photoluminescence apparatus for SiC characterization" (Eur J AP 20, 141-144, 2002).

[0023] Based on the above principles, Figure 2 As shown, as a first embodiment of the present invention, a wafer photoluminescence detection device based on spectral imaging is provided. A light source system is formed by a laser light source 41 and a light source objective lens 42, which provides an excitation beam to the surface of the sample 2 to be tested, causing it to be stimulated to produce fluorescence. The main structure of the entire detection device is composed of a microscopic imaging system, which includes a front microscopic objective lens group 31, a first spectroscopic module 32, a second spectroscopic module 33, a camera imaging objective lens 34, and a rear microscopic objective lens group 35. The first spectroscopic module 32 is used to deflect the excitation beam toward the surface of the sample 2 to be tested. The front microscopic objective lens group 31 is the objective lens of the entire microscopic imaging system, which not only serves to converge the excitation beam, but also serves as an imaging objective lens for the stimulated fluorescence.

[0024] The fluorescence generated by the excitation on the surface of the sample 2 to be tested will enter the microscopic imaging system from the front group 31 of the microscope objective lens, pass through the first spectroscopic module 32, and then be divided into two beams by the second spectroscopic module 33: one beam passes through the camera imaging objective lens 34 and is imaged onto the alignment camera 5 for observation and alignment, and the other beam passes through the rear group 35 of the microscope objective lens and is imaged onto the spectral imaging system for spectral measurement.

[0025] The wafer photoluminescence detection device based on spectral imaging described in this embodiment requires alignment of the microscopic imaging system with the sample 2 to be measured using an alignment camera 5 before performing spectral measurement. A specific method for alignment using captured images can be as follows: the sample 2 to be measured is imaged by the microscopic imaging system, and the imaging light path is split into two paths by a beam splitter. An alignment camera 5 is set on the image plane of the first path, and an incident slit 61 is set on the image plane of the second path. By adjusting the degrees of freedom of the displacement platform 1, the microscopic imaging system can be presented as a clear image in the alignment camera 5. After focusing is completed, when the alignment camera of the first path is clearly focused, a clear slit image is simultaneously obtained on the second path. The slit image is passed through the spectral imaging system 6 to obtain the spectrum of each point of the slit.

[0026] To facilitate alignment of the test sample 2, the displacement platform 1 is configured with six degrees of freedom: displacement adjustment in the x, y, and z axes, as well as rotation adjustment around the x, y, and z axes. This allows the position and orientation of the test sample 2 to be adjusted in space, achieving optimal alignment.

[0027] In order for the alignment effect of the alignment camera 5 to be effective for the spectral measurement of the spectral imaging system 6, the alignment camera 5 and the spectral imaging system 6 need to be arranged at a conjugate plane of the image plane of the microscopic imaging system. Those skilled in the art will readily appreciate that the microscopic imaging system is provided with a second spectroscopic module 33, which causes the fluorescence to have an image plane in two directions, namely, the transmission direction and the reflection direction of the second spectroscopic module 33. Therefore, the alignment camera 5 and the spectral imaging system 6 need to be respectively arranged at the image plane in two directions, that is, the alignment camera 5 and the spectral imaging system 6 are located at a conjugate plane of the image plane. In this way, when the alignment camera 5 is aligned by collecting images, the spectral imaging system 6 is also aligned.

[0028] In this embodiment, the fluorescence received by the alignment camera 5 is the fluorescence transmitted through the second spectroscopic module 33, while the fluorescence received by the spectral imaging system 6 is the fluorescence reflected by the second spectroscopic module 33. Those skilled in the art can easily conceive of swapping the positions of the alignment camera 5 and the spectral imaging system 6 without affecting the implementation of this embodiment.

[0029] Furthermore, the alignment camera 5 is located on the image plane of the microscopic imaging system, which means that the imaging plane of the camera is located on the image plane of the microscopic imaging system; for the spectral imaging system 6, as shown in FIG. Figure 3As shown in FIG, its structure is sequentially arranged with an incident slit 61, a collimation system 62, a dispersion system 63, an imaging system 64, and an image acquisition system 65. Among them, the incident slit 61 serves as both the image plane of the microscopic imaging system and the object plane of the spectral imaging system 6. After passing through the collimation system 62, the dispersion system 63, and the imaging system 64, the light reaches the image acquisition system 65. The two-dimensional image obtained by the image acquisition system 65 is the spectral image corresponding to the slit object. The two dimensions of the two-dimensional image can be seen in FIG. Figure 3 , that is, the y-axis direction parallel to the length direction of the slit and the x-axis direction parallel to the width direction of the slit.

[0030] Furthermore, in order to maintain the spatial resolution of the system, the image-side output numerical aperture of the microscopic imaging system is matched with the input numerical aperture of the spectral imaging system 6 to avoid a decrease in spatial resolution and achieve micron-level spatially resolved spectral measurement.

[0031] In this embodiment, the light source module needs to include at least a laser light source 41 and a light source objective lens 42. The laser light source 41 provides monochromatic light for exciting the surface of the sample 2 to be tested, and the light source objective lens 42 plays a role in light source coupling. Figure 4 As shown, the light source module can also include an LED light source 411 and a light source beam splitter. On the one hand, the PL fluorescence excited by the laser light source 41 enters the alignment camera for alignment and is also used for PL spectrum measurement; on the other hand, the LED light source 411 can also provide illumination to achieve camera alignment.

[0032] This embodiment also includes a control system 7, which includes a central computer and a displacement platform control system. The central computer is used to receive the alignment image captured by the alignment camera 5, apply the alignment method mentioned above, calculate the displacement and angle required for the displacement platform 1, and generate a first instruction, which is sent to the displacement platform control system. The displacement platform control system adjusts the displacement and angle of the displacement platform 1 based on the received first instruction. The displacement platform 1 is configured to have six degrees of freedom, so its position can be adjusted arbitrarily in the xyz direction and rotated arbitrarily around the xyz axis through the displacement platform control system.

[0033] like Figure 1As shown, in the prior art, a fixed spectral imaging system is used, which can only perform spectral measurement on one point of the sample to be tested at a time. Therefore, in order to achieve all-round coverage of the entire surface of the sample to be tested, the central computer and the displacement platform control system cooperate to perform a comprehensive scanning spectral measurement on the sample to be tested. In this embodiment, the specific method is as follows: after determining that the alignment is completed, the central computer sends a second instruction to the spectral imaging system 6 to perform spectral measurement on all points on a line on the surface of the sample to be tested 2. When the measurement is completed, the displacement platform control system will move to the next line to be tested along the specified path according to the requirements of the third instruction issued by the central computer, and then control the spectral imaging system 6 to detect the points on this line. Repeating the above steps can achieve a comprehensive spectral measurement of all points on the surface of the sample to be tested 2.

[0034] Considering the possible unevenness of the surface of the sample 2 to be measured, a matching autofocus system can be provided. This allows for refocusing each time the displacement platform 1 moves, thereby ensuring the quality of the spectral measurement. The autofocus system can utilize an internal coaxial autofocus system based on spectral confocalization, or other autofocus systems, which will not be further described here.

[0035] As another embodiment of the present invention, a wafer photoluminescence detection method based on spectral imaging is provided, which is applied to any of the above-mentioned wafer photoluminescence detection devices based on spectral imaging, comprising: Turning on the light source system to generate an excitation light beam, which is irradiated onto the surface of the sample 2 to be tested via the microscopic imaging system, and the surface of the sample 2 to be tested generates fluorescence; The alignment camera 5 receives the fluorescence and generates an alignment image; Adjusting the position of the displacement platform 1 according to the alignment image until the alignment of the microscopic imaging system is completed; After the alignment is completed, the spectral imaging system 6 receives the fluorescence and performs spectral measurement.

[0036] The technical features of the above embodiments can be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0037] It will be easily understood by those skilled in the art that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A wafer photoluminescence detection device based on spectral imaging, characterized in that: include: The displacement platform (1) is used to carry the sample to be tested (2); the light source system is used to generate an excitation light beam; after the surface of the sample to be tested (2) receives the excitation light beam, it is excited to generate fluorescence; An alignment camera (5) for receiving the fluorescence and generating an alignment image; A spectral imaging system (6), used for receiving the fluorescence and performing spectral measurement; A microscopic imaging system, comprising a microscopic objective lens front group (31), a first light splitting module (32), a second light splitting module (33), a camera imaging objective lens (34), and a microscopic objective lens rear group (35); The first light splitting module (32) is used to reflect the excitation light beam emitted by the light source system to the front group of the microscope objective lens (31) to illuminate the surface of the sample to be tested (2); The front group of microscope objective lenses (31) is also used to receive the fluorescence, the first light splitting module (32) is also used to transmit the fluorescence, and the second light splitting module (33) is used to split the fluorescence into a first fluorescence and a second fluorescence; wherein the first fluorescence passes through the camera imaging objective lens (34) and enters the alignment camera (5); and the second fluorescence passes through the rear group of microscope objective lenses (35) and enters the spectral imaging system (6); Wherein, the first imaging plane of the alignment camera (5) and the second imaging plane of the spectral imaging system (6) are located at a conjugate plane of the imaging plane of the microscopic imaging system.

2. The wafer photoluminescence detection device based on spectral imaging according to claim 1, characterized in that: The spectral imaging system (6) comprises an incident slit (61), a collimation system (62), a dispersion system (63), an imaging system (64), and an image acquisition system (65) which are arranged in sequence along the propagation direction of the second fluorescence; wherein the second imaging surface is the incident slit (61).

3. The wafer photoluminescence detection device based on spectral imaging according to claim 2, characterized in that: Also includes: The spectral imaging system (6) further comprises a collimation system (62), wherein the collimation system (62) is arranged between the incident slit (61) and the dispersion system (63).

4. The wafer photoluminescence detection device based on spectral imaging according to claim 1, characterized in that: The image-side output numerical aperture of the microscopic imaging system matches the input numerical aperture of the spectral imaging system (6).

5. The wafer photoluminescence detection device based on spectral imaging according to claim 1, characterized in that: The light source system comprises a laser light source (41) and a light source objective lens (42); the laser light source (41) emits an excitation light beam which enters the microscopic imaging system through the light source objective lens (42).

6. The wafer photoluminescence detection device based on spectral imaging according to claim 5, characterized in that: The light source system further comprises an LED light source (411) and the light source beam splitter (412); the LED light source (411) is used to provide an alignment light beam, which, after entering the microscopic imaging system through the light source beam splitter (412), is used to align the alignment camera (5).

7. The wafer photoluminescence detection device based on spectral imaging according to claim 1, characterized in that: It also includes a control system (7) for controlling the switch of the light source system, and for receiving the alignment image and the position information of the displacement platform (1), and adjusting the position of the displacement platform (1) to make the alignment image clear.

8. The wafer photoluminescence detection device based on spectral imaging according to claim 7, characterized in that: The control system (7) comprises a central computer and a displacement platform control system, wherein the central computer is used to control the switch of the light source system and, when the light source system is turned on, obtain an alignment image generated by the alignment camera (5), and judge the alignment state of the microscopic imaging system based on the alignment image; The central computer is also used to send a first instruction to the displacement platform control system when it is determined that there is no alignment, to control the position and posture of the displacement platform (1), and to continue to acquire alignment images until the central computer determines that the microscopic imaging system is in an aligned state; The central computer is also used to send a second instruction to the spectral imaging system (6) after determining that the alignment is completed, so as to perform spectral measurement on the surface of the sample to be tested (2), and at the same time send a third instruction to the displacement platform control system to control the displacement platform (1) to move along a specified path, so that the spectral imaging system (6) can perform spectral measurement on different locations on the surface of the sample to be tested (2), thereby achieving comprehensive spectral measurement of the surface of the sample to be tested (2).

9. The wafer photoluminescence detection device based on spectral imaging according to claim 8, characterized in that: It also includes an automatic focusing system, which is used to first complete automatic focusing when the displacement platform (1) moves along a specified path, and then perform spectral measurement on the surface of the sample (2) to be measured through the spectral imaging system (6).

10. A wafer photoluminescence detection method based on spectral imaging, characterized in that: A wafer photoluminescence detection device based on spectral imaging applied to any one of claims 1 to 9, comprising: Turning on the light source system to generate an excitation light beam, which is irradiated onto the surface of the sample to be tested (2) via the microscopic imaging system, so that the surface of the sample to be tested (2) generates fluorescence; The alignment camera (5) receives the fluorescence and generates an alignment image; According to the alignment image, adjusting the position of the displacement platform (1) until the alignment of the microscopic imaging system is completed; After the alignment is completed, the spectral imaging system (6) receives the fluorescence and performs spectral measurement.

Images