Laser-induced resistive change positioning device for tunable laser scanning

Abstract

This invention relates to the field of semiconductor wafer defect detection technology, specifically to a laser-induced resistance change positioning device with adjustable focus laser scanning. The device includes a laser scanning module for outputting an infrared laser beam and performing two-dimensional scanning of the wafer surface; a support module coaxially positioned below the laser scanning module, comprising an annular vacuum adsorption unit and a detachable concentric limiting unit; the annular vacuum adsorption unit only adsorbs the wafer edges, leaving the central detection area empty, allowing unobstructed laser scanning; the detachable concentric limiting unit coaxially engages with the adsorption unit to limit radial wafer displacement; and a photothermal isolation support module located at the bottom of the adsorption unit, made of highly insulating, low-reflection, and highly thermally conductive material, to suppress stray light from the bottom and stabilize the temperature field. This invention solves the problems of poor focus adaptability, detection area obstruction, large photothermal interference, difficulty in multi-wafer adaptation, and dust interference in the detection accuracy of existing wafer laser resistance testing equipment.

Description

Technical Field

[0001] This invention relates to the field of semiconductor wafer failure and defect detection equipment, specifically to a laser-induced resistance change positioning device with adjustable focus laser scanning. Background Technology

[0002] After the semiconductor wafer completes the front-end process, the internal and surface process structures of the wafer substrate are prone to hidden electrical defects such as micro-leakage and micro-short circuits. If the defect location cannot be accurately located, it will directly affect the yield of subsequent chip cutting, packaging and end products.

[0003] Currently, the industry generally adopts laser-induced resistance change detection to conduct full-area electrical failure screening and defect location on the entire wafer. This detection method mainly relies on an infrared laser beam to perform line-by-line two-dimensional scanning of the wafer surface. By using the laser thermal effect, corresponding resistance fluctuations are generated in the local area of ​​the wafer. Then, a special electrical detection structure is used to collect real-time resistance signals. Combined with the scanning coordinate data, the distribution location of various electrical defects on the wafer surface can be accurately determined.

[0004] Currently, conventional laser-induced resistance testing (LART) devices on the market are basically equipped with a laser scanning mechanism, a resistance signal acquisition mechanism, and a corresponding wafer carrier tray, which can meet the basic requirements of wafer electrical testing. However, the overall structural design of conventional equipment is relatively generalized, and it is mostly adapted to conventional fixed-process wafer testing operations. In practical applications, there is still room for optimization and improvement in terms of focusing adaptability for wafers of different thicknesses and process specifications, rapid changeover adaptability for multi-size wafers, and coordinated control of stray light and temperature field during the testing process. It is difficult to better adapt to the current needs of high-precision, multi-specification batch fine testing of wafers. Summary of the Invention

[0005] To address the problems in the prior art, the present invention provides a laser-induced resistance change positioning device for adjustable focus laser scanning.

[0006] The technical solution adopted by this invention to solve its technical problem is a laser-induced resistance change positioning device for adjustable-focus laser scanning, comprising:

[0007] The laser scanning module is used to output an infrared laser beam and perform two-dimensional scanning on the wafer surface;

[0008] The load-bearing module is coaxially positioned below the laser scanning module and includes an annular vacuum adsorption unit and a detachable concentric limiting unit.

[0009] The annular vacuum adsorption unit only adsorbs the edge of the wafer, leaving the central detection area empty and allowing unobstructed laser scanning.

[0010] The detachable concentric limiting unit is coaxially engaged with the adsorption unit to limit the radial displacement of the wafer.

[0011] The photothermal isolation support module, located at the bottom of the adsorption unit, is made of highly insulating, low-reflection, and highly thermally conductive materials to suppress stray light at the bottom and stabilize the temperature field.

[0012] The main control and image fusion module is connected to the laser scanning module, which collects laser-induced local resistance change data and synchronously collects scanning coordinates to generate a defect distribution image.

[0013] Specifically, the laser scanning module includes an electrically driven continuous zoom lens group and a high-speed galvanometer scanning unit; and / or the laser wavelength is selected as a near-infrared laser of 1300nm or 1064nm; and / or the spot diameter is continuously adjustable in the range of 1μm to 50μm.

[0014] Specifically, the detachable concentric limiting unit is equipped with multiple replacement parts of different specifications, corresponding to 6-inch, 8-inch and 12-inch standard semiconductor wafers respectively. The carrier module has limiting grooves adapted to the outer diameter of multiple wafer specifications. The limiting unit is exposed at the limiting groove position, and the replacement part only contacts the non-functional area of ​​the outer edge of the wafer.

[0015] Specifically, the annular vacuum adsorption unit is made of antistatic hard aluminum alloy with a matte insulating surface. The overall flatness error does not exceed 0.01mm, and the vacuum adsorption pressure is continuously adjustable.

[0016] Specifically, the surface of the annular vacuum adsorption unit is provided with uniformly distributed annular vacuum adsorption micropores to provide adsorption force only to the edge region of the wafer.

[0017] Specifically, the main control and image fusion module is equipped with several independent observation mirrors, which are circumferentially mounted on a flat plate. A gear plate is provided on the flat plate, and a motor is fixedly mounted on the main control and image fusion module. A gear that meshes with the gear plate is installed on the output shaft of the motor.

[0018] Specifically, a shaft is rotatably mounted at the central axis of the flat plate, and a dust removal pipe is fixedly mounted on the shaft. Inert gas is introduced into the dust removal pipe through a gas source treatment module.

[0019] Specifically, the dust collection pipe includes:

[0020] The inner cone is symmetrically and slidably installed on the inner side of the dust removal pipe.

[0021] The air intake duct has a hemispherical air chamber at the inner end of the inner cone. The air chamber is connected to the air source processing module by the air intake duct. A cone head is provided at the middle of the exposed end of the inner cone. The cone head is sunk into the cavity of the inner cone and has a micro-flow channel connected to the air chamber inside the cone head.

[0022] The air intake channel has annularly arranged air holes at the exposed end of the inner cone. Airflow overflowing from the cone head is drawn in through the air holes after diffusion. The air holes are connected to the air source processing module through the air intake channel.

[0023] Specifically, the main control and image fusion module is also used to identify the defect type based on the resistance change data, and the defect type includes leakage defects and micro short circuit defects.

[0024] Specifically, it also includes a light-shielding cabinet, which is equipped with a reference base and standardized installation interface for fixing the laser scanning module as a whole to the first platform of XYZ precision motion, and fixing the bearing module as a whole to the second platform of XYZ precision motion.

[0025] The beneficial effects of this invention are:

[0026] This invention optimizes and improves upon the shortcomings of existing wafer laser resistance testing equipment. Compared to traditional testing devices, it features a ring-shaped vacuum adsorption unit that adsorbs only the wafer edge area, leaving the central testing area completely unobstructed. This enables unobstructed full-area laser scanning and testing, while a photothermal isolation support module effectively suppresses stray light reflection. Utilizing a dynamically adjustable concentric limiting unit, it allows for rapid switching between testing of various standard wafer sizes. Combined with a blow-suction linked closed-loop dust removal structure, it promptly removes floating dust and impurities from the testing area, avoiding data distortion and adapting to the high-precision batch testing needs of wafers with different manufacturing processes. Attached Figure Description

[0027] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0028] Figure 1 This is a schematic diagram of the overall structure of a preferred embodiment of the present invention;

[0029] Figure 2 This is a partial sectional view of the server rack;

[0030] Figure 3 This is a schematic diagram showing the location of the first platform;

[0031] Figure 4 This is a schematic diagram showing the location of the second platform;

[0032] Figure 5 This is a schematic diagram showing the placement of the wafer;

[0033] Figure 6 This is a schematic diagram showing the location of the carrier module;

[0034] Figure 7 This is a schematic diagram showing the placement orientation between the wafer and the carrier module;

[0035] Figure 8This is a partial sectional view of the flat plate;

[0036] Figure 9 for Figure 8 Enlarged diagram of point A in the diagram;

[0037] Figure 10 This is a flowchart of the process of the present invention;

[0038] Figure 11 This is a schematic diagram of a hot spot indicating a resistance defect on a wafer during inspection.

[0039] In the diagram: Q, wafer; 1, laser scanning module; 2, carrier module; 21, adsorption unit; 22, limiting unit; 3, photothermal isolation support module; 4, main control and image fusion module; 23, limiting groove; 41, observation mirror; 42, flat plate; 43, gear plate; 44, motor; 45, gear; 46, shaft; 47, dust removal pipe; 471, inner cone; 472, conical protrusion; 473, conical groove; 474, spring; 475, air inlet; 476, micro-flow channel; 477, air intake channel; 478, vent; 11, first platform; 12, second platform; 5, air source processing module; 6, cabinet. Detailed Implementation

[0040] To make the technical means, creative features, objectives and effects of this invention easier to understand, the invention will be further described below in conjunction with specific embodiments.

[0041] Example 1:

[0042] like Figures 1 to 7 ,as well as Figure 10 and Figure 11As shown, the adjustable-focus laser scanning laser-induced resistance change positioning device includes a laser scanning module 1 for outputting an infrared laser beam and performing two-dimensional scanning on the surface of wafer Q. The laser scanning module 1 includes an electrically driven continuously zooming lens group and a high-speed galvanometer scanning unit. The laser wavelength is selected as a 1300nm or 1064nm near-infrared laser, which can effectively penetrate the silicon layer. The spot diameter is continuously adjustable within the range of 1μm to 50μm, and the focusing depth can be adapted in real time according to different process thicknesses and different process types of the wafer Q under test, ensuring laser scanning focusing accuracy and detection adaptability. It also includes a support module 2 coaxially disposed below the laser scanning module 1. The support module 2 contains an annular vacuum... The adsorption unit 21 and the detachable concentric limiting unit 22 are used. The annular vacuum adsorption unit 21 is made of anti-static hard aluminum alloy with a matte insulating surface. The overall flatness error does not exceed 0.01mm. The vacuum adsorption pressure can be continuously adjusted according to the different rigidity specifications of thin wafers and conventional wafers, effectively avoiding warping, deformation and stress damage after the wafer is adsorbed. The surface of the annular vacuum adsorption unit 21 is provided with uniformly distributed vacuum adsorption micropores to provide adsorption force only to the edge area of ​​the wafer Q, leaving the central detection area empty and allowing unobstructed laser scanning. The detachable concentric limiting unit 22 is coaxially matched with the adsorption unit 21 to limit the radial displacement of the wafer Q.

[0043] In this embodiment, the photothermal isolation support module 3 located at the bottom of the adsorption unit 21 is made of highly insulating, low-reflection, and highly thermally conductive materials, such as quartz glass or aluminum nitride ceramic plates. This effectively isolates stray light from the bottom of the device from reflecting upwards and interfering with the laser detection optical path. Simultaneously, it maintains a stable and balanced temperature field across the entire bottom of the wafer Q, preventing localized temperature fluctuations caused by external environmental temperature differences and device operation heat. This prevents temperature anomalies from inducing additional resistance value deviations, ensuring the stability and accuracy of subsequent weak resistance signal acquisition. Figure 11 As shown, Figure 11 The image shows a 20µm hotspot diagram and a superimposed image of the actual circuit, which clearly shows the circuit traces and component layout. The image marks hotspots with abnormal current concentration on the chip (dark / abnormal points within the red box in the image). After superimposition, the location of the abnormal hotspots can be accurately mapped to specific areas of the actual circuit, enabling precise determination of the failure location and improving the efficiency and accuracy of failure analysis.

[0044] like Figure 7 As shown, the detachable concentric limiting unit 22 is equipped with multiple replacement parts of various specifications, corresponding to 6-inch, 8-inch and 12-inch standard semiconductor wafers Q respectively, to adapt to the batch inspection requirements of wafers of different sizes. The carrier module 2 is provided with limiting grooves 23 that are adapted to the outer diameter of multiple sets of wafers Q. The limiting unit 22 is exposed at the limiting groove 23, so that the wafer Q is automatically centered and aligned when placed. The replacement parts only contact the non-functional area of ​​the outer edge of the wafer Q.

[0045] Example 2:

[0046] like Figure 5 , Figure 6 and Figure 8 As shown, the difference in this embodiment is that the laser-induced resistance change positioning device for adjustable-focus laser scanning also includes a main control and image fusion module 4 connected to the laser scanning module 1. During imaging, when the laser emitted by the laser scanning module 1 strikes the sample surface, it is reflected by the sample surface and enters the light intensity sensor of the main control and image fusion module 4. Different regions of the sample have different reflectivities, and the collected light intensity values ​​are also different, thereby reconstructing the morphology of the sample surface. By collecting the wafer local resistance change data induced by the laser thermal effect during the laser scanning process in real time, and simultaneously and accurately collecting the real-time coordinate position information of the laser scanning, the two sets of data are superimposed and fitted in real time to generate a visualized wafer global defect. The distribution image visually presents the location and range of wafer defects. The main control and image fusion module 4 is also used to identify the defect type based on the resistance change data. The defect types include leakage defects and micro-short circuit defects. The main control and image fusion module 4 is equipped with several independent observation mirrors 41, which are circumferentially mounted on a flat plate 42. A gear disk 43 is provided on the flat plate 42. A motor 44 is fixedly mounted on the main control and image fusion module 4. A gear 45 that meshes with the gear disk 43 is installed on the output shaft of the motor 44. The motor 44 drives the gear 45 to rotate, which in turn drives the gear disk 43 to rotate the flat plate 42 at a uniform speed. Different observation mirrors 41 can be switched to align the detection area as needed to meet the requirements of full-area observation adaptation.

[0047] like Figure 8 As shown, a shaft 46 is rotatably mounted at the central axis of the flat plate 42, and a dust removal tube 47 is fixedly mounted on the shaft 46. The dust removal tube 47 is coaxial with the observation mirror 41. An inert gas is introduced into the dust removal tube 47 through the gas source treatment module 5. The inert gas is nitrogen or argon. The purity of the gas meets the cleanliness standards for semiconductor wafer inspection. It is free of impurities, water vapor, and corrosiveness, and will not cause pollution or damage to the wafer surface and the mirror surface of the observation mirror.

[0048] In this embodiment, when abnormal fluctuations in the regional resistance value are detected, indicating that dust interference is causing data distortion, the cylinder drives the shaft 46 to rotate precisely. This rotates the dust removal tube 47 from its initial idle position to the corresponding dust removal station directly below the observation mirror 41. Simultaneously, the gas pressure and airflow rhythm are precisely controlled by the gas source processing module 5, introducing inert gas to prepare for dust removal. Dust removal and purification are simultaneously performed on the mirror surface of the observation mirror 41 and the detection area corresponding to wafer Q. The dust removal process is independent of the laser detection process. After the dust removal is completed, the shaft 46 drives the dust removal tube 47 back to its initial idle position, avoiding obstruction of the scanning optical path by the dust removal structure. The device then restarts the laser-induced resistance detection process to re-detect the abnormal area, effectively eliminating detection interference caused by dust and ensuring the accuracy and validity of the detection data.

[0049] Example 3:

[0050] like Figure 8 and Figure 9 As shown, the dust removal pipe 47 in this embodiment includes an inner cone 471, an air inlet 475, and an air intake 477.

[0051] Specifically, the inner cone 471 is symmetrically slidably installed on the inner side of the dust removal pipe 47. The inner cone 471 has a conical protrusion 472. The inner cavity of the dust removal pipe 47 has a conical groove 473 for limiting the axial sliding of the conical protrusion 472. A spring 474 is provided between the conical protrusion 472 and the inner cavity of the conical groove 473. The spring 474 enables the inner cone 471 to slide, buffer, and return to its original position. A hemispherical air chamber is opened at the inner end of the inner cone 471. The air chamber is connected to the air source processing module 5 by... The air intake duct 475 is connected, and a cone head is provided in the middle of the exposed end of the inner cone 471. The cone head is set in the cavity of the inner cone 471, and a micro-flow channel 476 connected to the air chamber is provided in the cone head. The exposed end of the inner cone 471 is provided with annularly arranged air holes 478. The airflow overflowing from the cone head position is drawn in through the air holes 478 after diffusion. The air holes 478 are connected to the air source treatment module 5 through the air intake duct 477, forming a closed-loop dust removal structure with blowing and suction linkage.

[0052] During the dust removal process, once the dust removal pipe 47 is precisely rotated and aligned to the working position below the observation mirror 41, the air source processing module 5 first performs pre-extraction on the suction duct 477 to create a negative pressure adsorption environment. At this time, suspended dust and fine particulate impurities on the surface of the observation mirror 41 and the wafer Q detection area are quickly drawn in by negative pressure through the air hole 478, completing the initial adsorption and cleaning of loose surface dust. Then, while maintaining the air extraction operation, the air source processing module 5 simultaneously and stably supplies inert gas to the air inlet duct 475. The high-pressure gas then enters the hemispherical air chamber for pressure stabilization and buffering, and is precisely blown out from the micro-flow channel 476 to the surface of the observation mirror 41 and the wafer Q, blowing away the adsorbed residue and firmly attached stubborn dust particles. At the same time, with the airflow pressure brought by the continuous air intake, the inner cone 471 is driven by the airflow thrust and slides smoothly axially along the inner cavity of the dust removal pipe 47, causing the compression of the spring 474 to gradually increase, and the spring 474 buffers and limits the sliding stroke. At the same time, the exposed end of the inner cone 471 gradually approaches the observation mirror 41 and the surface of the wafer Q, thereby adjusting the concentration of airflow and the range of dust removal in real time, enhancing the dust removal and cleaning effect. At the same time, the movement of the inner cone 471 is strictly controlled so that the inner cone 471 is close to the observation mirror 41 and the wafer surface but never in direct contact, preventing wafer damage and mirror scratches caused by mechanical contact. It can also effectively reduce the loss of the blowing airflow, so that all the blown and peeled floating dust is accurately sucked and collected at the air hole 478. The blowing and suction are synchronized throughout the process, thereby completely avoiding the formation of secondary pollution by dust dispersion and ensuring the quality of dust removal and purification.

[0053] Furthermore, such as Figure 3 and Figure 4 As shown, the adjustable-focus laser scanning laser-induced resistance change positioning device also includes a light-shielding cabinet 6. The core detection structure of the entire machine is integrated and assembled inside the light-shielding cabinet 6 to completely isolate stray light and direct ambient light interference from the outside environment, maintaining a standard detection environment that is sealed and light-free inside the cabinet at all times, and preventing external light from affecting the accuracy of laser scanning and resistance signal acquisition. The cabinet 6 is equipped with a reference base and standardized installation interface, which is used to fix the laser scanning module 1 as a whole on the first XYZ precision motion platform 11, and to fix the carrier module 2 as a whole on the second XYZ precision motion platform 12. Through the independent linkage and control of the two sets of XYZ precision motion platforms, the two-way precise adjustment of the laser scanning angle, scanning position and wafer carrier alignment position can be accurately realized, ensuring that the entire wafer is scanned without dead angles and the positioning is without deviation, adapting to the precise detection operation requirements of different detection positions and different focus depths. During the standby alignment phase of the device, a weak, non-thermal diffused auxiliary light source can be turned on, which is only used for wafer visual alignment calibration. During the formal resistance testing operation, the auxiliary light source is forcibly turned off, maintaining standard testing conditions without light or heat interference throughout the process.

[0054] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of protection claimed by the present invention. The scope of protection of the present invention is defined by the appended claims and their equivalents.

Claims

1. A laser-induced resistance change positioning device for adjustable-focus laser scanning, characterized in that, include: The laser scanning module (1) is used to output an infrared laser beam and perform two-dimensional scanning on the surface of the wafer (Q); The carrier module (2) is coaxially disposed below the laser scanning module (1) and includes an annular vacuum adsorption unit (21) and a detachable concentric limiting unit (22). The annular vacuum adsorption unit (21) only adsorbs the edge of the wafer (Q), leaving the central detection area empty and allowing unobstructed laser scanning; The detachable concentric limiting unit (22) is coaxially engaged with the adsorption unit (21) to limit the radial displacement of the wafer (Q); The photothermal isolation support module (3) is located at the bottom of the adsorption unit (21) and is made of a high-insulation, low-reflection, and high-thermal-conductivity material to suppress stray light at the bottom and stabilize the temperature field. The main control and image fusion module (4) is connected to the laser scanning module (1) to collect laser-induced local resistance change data and synchronously collect scanning coordinates to generate a defect distribution image.

2. The laser-induced resistance change positioning device for adjustable focus laser scanning according to claim 1, characterized in that, The laser scanning module (1) includes an electrically operated continuous zoom lens group and a high-speed galvanometer scanning unit; and / or The laser wavelength is selected as a near-infrared laser of 1300nm or 1064nm; and / or The spot diameter is continuously adjustable in the range of 1μm to 50μm.

3. The laser-induced resistance change positioning device for adjustable-focus laser scanning according to claim 1, characterized in that, The detachable concentric limiting unit (22) is equipped with multiple replacement parts of various specifications. The supporting module (2) has a limiting groove (23) adapted to the outer diameter of multiple wafers (Q). The limiting unit (22) is exposed at the limiting groove (23). The replacement parts only contact the non-functional area of ​​the outer edge of the wafer (Q); and / or Multiple replacement parts are available for 6-inch, 8-inch and 12-inch standard semiconductor wafers (Q).

4. The laser-induced resistance change positioning device for adjustable-focus laser scanning according to claim 1, characterized in that, The annular vacuum adsorption unit (21) is made of antistatic hard aluminum alloy.

5. The laser-induced resistance change positioning device for adjustable-focus laser scanning according to claim 1, characterized in that, The annular vacuum adsorption unit (21) has uniformly distributed annular vacuum adsorption micropores on its surface to provide adsorption force only to the edge region of the wafer (Q).

6. The laser-induced resistance change positioning device for adjustable-focus laser scanning according to claim 1, characterized in that, The main control and image fusion module (4) is provided with several independent observation mirrors (41). The observation mirrors (41) are circumferentially mounted on the flat plate (42). The flat plate (42) is provided with a gear plate (43). The main control and image fusion module (4) is fixedly mounted with a motor (44). The output shaft of the motor (44) is equipped with a gear (45) that meshes with the gear plate (43).

7. The laser-induced resistance change positioning device for adjustable-focus laser scanning according to claim 6, characterized in that, A shaft (46) is rotatably mounted at the central axis of the flat plate (42), and a dust removal pipe (47) is fixedly mounted on the shaft (46); and / or Inert gas is introduced into the dust removal pipe (47) through the gas source treatment module (5).

8. The laser-induced resistance change positioning device for adjustable-focus laser scanning according to claim 7, characterized in that, The dust removal pipe (47) includes: The inner cone (471) is symmetrically and slidably installed on the inner side of the dust removal pipe (47); The air intake (475) has a hemispherical air chamber at the inner end of the inner cone (471). The air chamber is connected to the air source processing module (5) by the air intake (475). A cone head is provided in the middle of the exposed end of the inner cone (471). The cone head is sunk into the cavity of the inner cone (471), and a micro-flow channel (476) connected to the air chamber is provided in the cone head. The air intake channel (477) has an annular arrangement of air holes (478) at the exposed end of the inner cone (471). The airflow overflowing from the cone head is drawn in through the air holes (478) after diffusion. The air holes (478) are connected to the air source processing module (5) through the air intake channel (477).

9. The laser-induced resistance change positioning device for adjustable-focus laser scanning according to claim 1, characterized in that, The main control and image fusion module (4) is also used to identify the defect type based on the resistance change data, and the defect type includes at least leakage defects and micro short circuit defects.

10. The laser-induced resistance change positioning device for adjustable-focus laser scanning according to claim 1, characterized in that, It also includes a light-shielding cabinet (6), which is equipped with a reference base and a standardized installation interface for fixing the laser scanning module (1) as a whole on the first platform (11) of XYZ precision motion, and fixing the bearing module (2) as a whole on the second platform (12) of XYZ precision motion.

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