Probe station infrared small light spot coaxial observation system and method suitable for optoelectronic chip testing

Abstract

This invention provides a coaxial infrared small-spot observation system and method for testing optoelectronic chips, belonging to the field of chip testing technology. The system includes an infrared light input module, a beam splitting module, an imaging lens group, a dual CCD detection module, and an image synthesis module, connected sequentially by optical paths. The infrared light input module is equipped with a replaceable fiber optic collimator to adapt to different wavelengths. The beam splitting module utilizes a dichroic mirror and a beam splitter to achieve coaxial separation of infrared and visible light. The objective lens of the imaging lens group is replaceable; a 20X APO objective lens can accommodate a spot size smaller than 10μm and a working distance of 20mm, while a reflective objective lens can achieve even smaller spot focusing. The dual CCDs separately acquire infrared spot and visible light images of the chip, which are then fused together by the image synthesis module. This invention achieves integrated precise positioning of the infrared small spot and visual observation of the chip morphology. The observation optical path is coaxial with the test laser optical path, providing high positioning accuracy. Its compact size makes it easy to integrate into a probe station, making it particularly suitable for high-precision testing of optoelectronic device chips such as APDs and SPADs.

Description

Technical Field

[0001] The present invention relates to the technical field of chip test optical observation, and particularly relates to a probe table infrared small spot coaxial observation system and method suitable for optoelectronic chip test. Background Art

[0002] In the manufacturing and testing of semiconductor and optoelectronic devices (such as APD, SPAD), the probe table is a key device for electrical and optical performance testing. During testing, it is often necessary to accurately irradiate a small infrared laser spot onto the micron-level test sites of the chip, and simultaneously observe the chip morphology to assist in probe positioning. The existing optical observation equipment supporting the probe table has many limitations: the observation optical path is single, it cannot simultaneously achieve infrared spot positioning and visible light morphology observation of the chip, the operation is cumbersome and the positioning error is large; the flexibility of adjusting the infrared spot is poor, the objective lens is fixed, resulting in the spot size being non-adjustable; the observation optical path and the laser test optical path are not coaxial, introducing positioning deviation; the working distance of the objective lens is short, and it is easy to interfere with the probe; the infrared band adaptability is poor; and the equipment has a large volume and low integration.

[0003] Although some patents have proposed simple infrared-to-visible light spectroscopic observation structures, they have not achieved coaxial design of the optical path and the laser optical path, and have not solved the balance problem between small spot formation and working distance. At the same time, they lack a replaceable objective lens structure and a multi-band adaptation structure, and cannot meet the actual needs of high-precision and refined testing of chips such as APD and SPAD. Therefore, there is an urgent need for an observation system and method that can achieve coaxial observation from infrared to visible light, can flexibly adjust the accuracy of the infrared spot, has a suitable working distance, is adaptable to multiple infrared bands, and is easy to integrate into the probe table. Summary of the Invention

[0004] The present invention aims to provide a probe table infrared small spot coaxial observation system and method suitable for optoelectronic chip test, so as to solve the problems of single observation optical path, inflexible adjustment of spot accuracy, non-coaxial optical path, limited working distance, poor band adaptability and low integration in the prior art.

[0005] To achieve the above object, the present invention adopts the following technical solutions: A probe station infrared small spot coaxial observation system suitable for testing optoelectronic chips includes an infrared light input module, a beam splitting module, an imaging lens group, and a dual CCD detection module connected in sequence by optical paths, and an image synthesis module connected to the beam splitting module by optical paths. The infrared light input module includes a replaceable fiber optic collimator for collimating infrared light into the incident light. The beam splitting module includes a dichroic mirror and a first beam splitter and a second beam splitter located on either side of it. The dichroic mirror is infrared-transmitting and visible-reflecting, used to separate infrared light from visible light in the mixed beam from the imaging lens group and guide them to the first and second beam splitters respectively. The imaging lens group includes replaceable objectives, including a 20X APO objective or a reflective objective. The 20X APO objective is adapted to the 780~1800nm ​​wavelength band and is used to focus infrared light into a spot with a diameter of less than 10μm and provide a working distance of 20mm. The dual CCD detection module includes an infrared CCD corresponding to the first beam splitter and a regular color CCD corresponding to the second beam splitter, used to acquire infrared spot images and chip visible light images respectively. The image synthesis module is used to fuse the infrared spot image and the chip visible light image to generate an integrated observation image. As a further improvement of the present invention, the infrared observation optical path of the system is coaxially set with the laser optical path of the chip test, and the deviation between the laser irradiation position and the infrared spot positioning position is less than 2μm.

[0006] As a further improvement of the present invention, the imaging lens group further includes a telecentric lens, which is located between the objective lens and the beam splitter module, for converging and transmitting the light beam, and matching the outgoing parallel light path of the selected objective lens.

[0007] As a further improvement of the present invention, the replaceable fiber optic collimator is a component adapted to different infrared bands within the 780~1800nm ​​band, and can be replaced to achieve system adaptation for multi-infrared band testing. As a further improvement of the present invention, the image synthesis module is an embedded hardware module or a software program module running on a computer, supporting real-time registration, fusion, display and storage of two images.

[0008] As a further improvement of the present invention, the system is a miniaturized integrated structure, the size of which is adapted to the installation space of the probe station and can be directly integrated into the probe station testing station.

[0009] On the other hand, the present invention also provides a probe station infrared small spot coaxial observation method suitable for testing optoelectronic chips, which is applied to the observation system described above. The method includes the following steps: S1, test adapter selection: according to the test requirements, select and install the appropriate objective lens and the appropriate fiber collimator for the test band. S2. Infrared light loading and spot formation: After being collimated by the fiber collimator, the infrared light passes through the beam splitting module and the imaging lens group in sequence, and is finally focused by the selected objective lens onto the chip test position to form a small infrared spot. S3. Dual-path signal acquisition: The objective lens receives a mixed light signal containing visible and infrared light from the chip test position, and returns it to the beam splitting module through the imaging lens group; the beam splitting module separates the mixed light, the infrared light is transmitted to the infrared CCD, and the visible light is transmitted to the ordinary color CCD, and the infrared spot image and the chip visible light image are acquired respectively. S4. Image Synthesis and Observation: The image synthesis module fuses the infrared spot image with the visible light image of the chip to generate and display an integrated observation image, which is used to determine and adjust the position of the infrared spot on the chip.

[0010] As a further improvement of the present invention, in step S4, when it is determined that there is a deviation in the position of the infrared spot based on the integrated observation image, the precise positioning of the infrared spot at the μm level is achieved by fine-tuning the probe stage displacement platform or the system optical path adjustment knob.

[0011] As a further improvement of the present invention, in step S4, the visible light band acquired by the ordinary color CCD is 400~700nm.

[0012] As a further improvement of the present invention, in step S1, if it is necessary to change the test infrared band, the fiber collimator is replaced; if it is necessary to adjust the spot accuracy, the objective lens is replaced; then steps S2 to S4 are repeated to adapt to the new test conditions.

[0013] The beneficial effects of this invention are: 1. It achieves coaxial integration of infrared spot positioning and visible light morphology observation of chips, and provides intuitive display through image fusion, greatly improving operational convenience and positioning accuracy. 2. It adopts a replaceable objective lens (20XAPO objective lens / reflective objective lens) design, accommodating different needs for long working distances and high-precision small spot sizes, offering high flexibility. 3. The coaxial design of the observation optical path and the test laser optical path fundamentally reduces system errors, resulting in high positioning accuracy (deviation <2μm). 4. It uses a replaceable fiber collimator, easily adapting to the wide infrared band of 780~1800nm, offering good versatility. 5. The system is miniaturized and highly integrated, easily integrated with existing probe stations without complex modifications. 6. It provides a dedicated solution for the refined testing of optoelectronic device chips such as APDs and SPADs, filling a gap in the industry. Attached Figure Description

[0014] Figure 1 This is a schematic diagram of the optical path structure of the observation system of the present invention. In the figure, 1 is an infrared CCD, 2 is a second beam splitter, 3 is a replaceable fiber optic collimator, 4 is a dichroic mirror, 5 is a telecentric lens, 6 is a replaceable objective lens, 7 is a first beam splitter, 8 is a regular color CCD, and 9 is a visible light illumination source. Detailed Implementation

[0015] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0016] like Figure 1 As shown, this embodiment provides an observation system with a miniaturized, integrated structure (approximately 150x80x100mm in size), which can be directly installed on the probe station.

[0017] Infrared light input module: includes a replaceable fiber optic collimator 3, which is adapted to the mid-infrared band in this embodiment.

[0018] The beam splitting module includes a first beam splitter cube 7 (compatible with visible light), a dichroic mirror 4 (transmits infrared light and reflects visible light), and a third beam splitter cube 2 (compatible with infrared light). The dichroic mirror 4 is coated with a high infrared transmittance and high visible light reflectance film.

[0019] Imaging lens group: In view of the ultra-high precision requirements of the SPAD chip for the light spot, this embodiment selects a reflective objective lens as objective lens 6 and configures a matching telecentric lens 5.

[0020] Dual CCD detection module: Infrared CCD 1 is a high-sensitivity model, and ordinary color CCD 8 is a high-definition model.

[0021] Image synthesis module: This is a software module that runs on an industrial computer and has built-in image registration and fusion algorithms.

[0022] Optical path transmission direction: Infrared laser optical path: 3→2→4→5→6 focused on the chip surface; Chip surface illumination optical path: 9→7→4→5→6 focused on the chip surface; Visible light band color image output: Chip surface→6→5→4→7→8; Infrared band fused image output: Chip surface→6→5→4→2→1; Finally, the visible light band color and infrared band fused images are synthesized by software.

[0023] The observation method is as follows: S101. Install the reflective objective lens 6 and the matching fiber optic collimator 3.

[0024] S102. Infrared light is collimated by collimator 3, passes through beam splitter 2, is transmitted through dichroic mirror 4, passes through telecentric lens 5, and is focused onto the SPAD chip surface by reflective objective lens 6 to form an ultra-small spot. The debugging system ensures that this optical path is coaxial with the test laser optical path (deviation <3μm).

[0025] S103. Reflected light (including visible and infrared light) from the chip surface travels backward through objective lens 6 and telecentric lens 5 to dichroic mirror 4. Infrared light is transmitted and received by infrared CCD 1 via beam splitter 2. Visible light is reflected and received by ordinary color CCD 8 via beam splitter 7.

[0026] S104. The two images are transmitted to the image synthesis module and displayed in real time after fusion. Observation revealed a 2μm deviation between the light spot and the test point, which was corrected by fine-tuning the probe stage displacement platform.

[0027] S105. After positioning, perform high-precision photoelectric testing on the SPAD chip. The process can be monitored in real time by fusion image to determine the position of the light spot.

[0028] The system structure of this embodiment is similar to that of Embodiment 1, with the main difference being: Imaging lens group: To balance working distance and basic spot accuracy, a 20X APO objective lens was selected as objective lens 6. Its working distance is 20mm, and it can form infrared small spots with a diameter of less than 10μm.

[0029] The observation method is similar to that in Example 1, including: S201. Install the APO objective lens and the compatible fiber optic collimator 3.

[0030] S202. Infrared light is collimated by collimator 3, passes through beam splitter 2, is transmitted through dichroic mirror 4, and then through telecentric lens 5. Finally, it is focused onto the surface of the APD chip by the APO objective lens, forming an ultra-small spot. The debugging system ensures that this optical path is coaxial with the test laser optical path.

[0031] S203. Reflected light (including visible and infrared light) from the chip surface travels backward through the APO objective lens and telecentric lens 5 to the dichroic mirror 4. Infrared light is transmitted and received by infrared CCD 1 via beam splitter 2. Visible light is reflected and received by ordinary color CCD 8 via beam splitter 7.

[0032] S204. The two images are transmitted to the image synthesis module and displayed in real time after fusion. Observation revealed a 4μm deviation between the light spot and the test point, which was corrected by fine-tuning the probe stage displacement platform.

[0033] S205. After positioning, perform high-precision photoelectric testing on the APD chip. The process can be monitored in real time by fusion image to determine the position of the light spot.

[0034] After completing the testing of one type of chip (such as a SPAD), if you need to test another type of chip (such as a general semiconductor chip), the procedure is as follows: S301. Turn off the light source and carefully remove the current reflective objective lens 6, replacing it with a 20X APO objective lens. Simultaneously, replace the fiber optic collimator 3 according to the new test band requirements.

[0035] S302. Repeat the aforementioned steps of optical path mounting, image acquisition and fusion.

[0036] S303. By positioning and observing through integrated observation images, the testing of the new chip can begin.

[0037] This process demonstrates the high flexibility of the invention in objective lens and wavelength adaptation, enabling multiple uses and improving equipment utilization.

[0038] The above description, in conjunction with specific preferred embodiments, provides a further detailed explanation of the present invention. It should not be construed that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art, various simple deductions or substitutions can be made without departing from the concept of the present invention, and all such modifications and substitutions should be considered within the scope of protection of the present invention.

Claims

1. A probe station infrared small spot coaxial observation system suitable for optoelectronic chip testing, characterized in that, The system includes an infrared light input module, a beam splitting module, an imaging lens group, and a dual CCD detection module connected in sequence by optical paths, and also includes an image synthesis module that is signal-connected to the dual CCD detection module. The infrared light input module includes a replaceable fiber optic collimator for collimating infrared light into the incident light. The beam splitting module includes a dichroic mirror and a first beam splitting cube and a second beam splitting cube located on its two sides. The dichroic mirror is of the infrared light transmission and visible light reflection type, used to separate the infrared light and visible light in the mixed beam from the imaging lens group and guide them to the first beam splitting cube and the second beam splitting cube respectively. The imaging lens group includes replaceable objectives, which include a 20X APO objective or a reflective objective. The 20X APO objective is adapted to the 780~1800nm ​​wavelength band and is used to focus infrared light to form a spot with a diameter of less than 10μm and provide a working distance of 20mm. The dual CCD detection module includes an infrared CCD corresponding to the first beam splitter and a regular color CCD corresponding to the second beam splitter, which are used to acquire infrared spot images and visible light images of the chip, respectively. The image synthesis module is used to fuse the infrared spot image with the visible light image of the chip to generate an integrated observation image.

2. The system of claim 1, wherein, The infrared observation optical path of the system is coaxially set with the laser optical path of the chip test, and the deviation between the laser irradiation position and the infrared spot positioning position is less than 2μm.

3. The system of claim 1, wherein, The imaging lens group also includes a telecentric lens, which is located between the objective lens and the beam splitter module. The telecentric lens is used to converge and transmit the light beam and matches the outgoing parallel light path of the selected objective lens.

4. The system of claim 1, wherein, The replaceable fiber optic collimator is a component adapted to different infrared bands within the 780~1800nm ​​band. By replacing it, the system can be adapted to multi-infrared band testing.

5. The system of claim 1, wherein, The image synthesis module is an embedded hardware module or a software program module running on a computer, which supports real-time registration, fusion, display and storage of two images.

6. The system of claim 1, wherein, The system is a miniaturized, integrated structure whose size is adapted to the installation space of the probe station and can be directly integrated into the probe station testing station.

7. A method for coaxial observation of infrared small spot probe station for testing optoelectronic chips, applied to the observation system according to any one of claims 1-6, characterized in that, The method includes the following steps: S1. Test adapter selection: Select and install the appropriate objective lens and fiber optic collimator for the test band according to the test requirements. S2. Infrared light loading and spot formation: After being collimated by the fiber collimator, the infrared light passes through the beam splitting module and the imaging lens group in sequence, and is finally focused by the selected objective lens onto the chip test position to form a small infrared spot. S3. Dual-path signal acquisition: The objective lens receives a mixed light signal containing visible and infrared light from the chip test position, and returns it to the beam splitting module through the imaging lens group; the beam splitting module separates the mixed light, the infrared light is transmitted to the infrared CCD, and the visible light is transmitted to the ordinary color CCD, and the infrared spot image and the chip visible light image are acquired respectively. S4. Image Synthesis and Observation: The image synthesis module fuses the infrared spot image with the visible light image of the chip to generate and display an integrated observation image, which is used to determine and adjust the position of the infrared spot on the chip.

8. The method of claim 7, wherein, In step S4, when it is determined that there is a deviation in the position of the infrared spot based on the integrated observation image, the precise positioning of the infrared spot at the μm level is achieved by fine-tuning the probe stage displacement platform or the system optical path adjustment knob.

9. The method of claim 7, wherein, In step S4, the visible light band acquired by the ordinary color CCD is 400~700nm.

10. The method of claim 7, wherein, In step S1, if the test infrared band needs to be changed, the fiber collimator is replaced; if the spot accuracy needs to be adjusted, the objective lens is replaced; then steps S2 to S4 are repeated to adapt to the new test conditions.

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