A non-contact height sensing system for wafer testing

Abstract

This invention discloses a non-contact height sensing system for wafer testing, comprising a computer, a signal converter, a sensor, a testing instrument, and a probe station. The computer includes control software and a server, and communicates with the signal converter, the testing instrument, and the probe station. The testing instrument is electrically connected to several test probes, and the probe station includes a stage for fixing the test chip. The signal converter receives analog signals from the sensor, converts them into digital signals, and sends them as feedback signals to the computer's control software. This invention integrates a sensor and a signal converter to form a non-contact height sensing system, and then uses a vacuum suction cup to vacuum-adhere and fix the test chip, solving the testing problems caused by wafer chip warpage and stage unevenness during testing. This significantly improves wafer testing efficiency and reduces integrated circuit manufacturing costs.

Description

Technical Field

[0001] This invention relates to the field of integrated circuit testing technology, and more specifically to a non-contact height sensing system for wafer testing. Background Technology

[0002] The integrated circuit manufacturing process can generally be divided into wafer fabrication, wafer testing, packaging, and final testing. Before chip packaging, electrical performance tests are usually performed on the integrated circuits on the wafer to determine their quality. In automated wafer testing, a fixed probe height is typically used, with a stage supporting the wafer and moving it up and down with a constant stroke to achieve contact and separation between the probes and the chip.

[0003] Wafers often exhibit varying degrees of warping. Furthermore, due to limitations in current machining technology, it's difficult to achieve a perfectly level stage surface, resulting in varying height differences. This makes it nearly impossible to achieve a perfectly level wafer surface during testing, and the resulting variations are unpredictable. Therefore, for wafers with significant height differences, the constant up-and-down reciprocating motion of the stage cannot guarantee accurate contact between the probes and the chip. This can lead to excessive probe contact that damages both the chip and the probes, or insufficient contact that prevents the test from being completed.

[0004] In China, there is currently no good solution to this problem, and the conventional approach is to conduct manual testing. Globally, while there are two solutions, both have certain limitations. One is to focus a microscope on the chip surface and compensate for the chip's rise height by changing the focal length; the other is to use a special probe to contact the chip, using it as a feedback signal to adjust the contact height between the chip and the test probe, thereby achieving accurate contact between the probe and the chip.

[0005] Each of the three methods described above has its own drawbacks: (1) Manual testing is too slow and is not suitable for wafers with a large number of chips. It will greatly increase the wafer testing cycle and reduce the efficiency of integrated circuit manufacturing.

[0006] (2) Focusing the microscope onto the chip surface is very slow in order to ensure accurate focusing. Therefore, the scheme of compensating for the chip's rising height by changing the focal length will greatly reduce the speed of automatic testing and increase the time cost of testing.

[0007] (3) For the method of contacting the chip with a dedicated probe, the contact between the probe and the chip will inevitably cause a certain degree of damage and contamination to the chip, which is often unacceptable in the strict chip manufacturing process. Secondly, the probe is a consumable and there is a certain limit to the number of times it can contact the chip. Therefore, this method will also greatly reduce the lifespan of the probe and increase the cost in terms of testing resources. Summary of the Invention

[0008] The technical problem solved by this invention is to provide a non-contact height sensing system for wafer testing that can improve wafer testing efficiency and reduce integrated circuit manufacturing costs.

[0009] The technical solution adopted by this invention to solve its technical problem is: A non-contact height sensing system for wafer testing includes a computer, a signal converter, a sensor, a testing instrument, and a probe station. The computer includes control software and a server. The computer communicates with the signal converter, the testing instrument, and the probe station. The testing instrument is electrically connected to a plurality of test probes. The probe station includes a stage for fixing a test chip. The signal converter receives analog signals from the sensor, converts the analog signals into digital signals, and sends them as feedback signals to the control software of the computer. The control software releases a control signal to the probe station through the computer to control the stage to move closer to the test probe with the test chip for testing. The sensor receives the distance between the test chip and the sensor. When the distance reaches a preset value, the control software releases another control signal to the stage of the probe station to stop moving. The control software then releases a control signal to control the testing instrument to release an excitation signal to the test chip and receive feedback signals from the test chip. The feedback signals are transmitted to the server for storage.

[0010] Furthermore, the sensor is fixed on the sensor module, which includes a magnetic base and an XYZθ four-axis positioner. The XYZθ four-axis positioner is fixed to the probe stage by magnetic adsorption through the magnetic base. The front end of the XYZθ four-axis positioner is a rotating shaft. A light arm is fixed to the rotating shaft through an adapter plate. A sensor support plate is provided at the front end of the light arm, and the sensor is fixed in the sensor support plate.

[0011] Furthermore, the XYZθ four-axis positioner includes an X-axis high-precision positioner, a Y-axis high-precision positioner, a Z-axis high-precision positioner, and an θ angle adjuster. The X-axis high-precision positioner and the Y-axis high-precision positioner are horizontally fixed by an adapter plate. The Z-axis high-precision positioner is vertically fixed to the Y-axis high-precision positioner by an L-shaped adapter plate. The θ angle adjuster is horizontally set at the front end of the Z-axis high-precision positioner by the adapter plate and controls the rotation angle of the adapter plate in the vertical plane.

[0012] Furthermore, a temperature-controlled vacuum suction cup is provided on the platform.

[0013] Furthermore, the temperature-controlled vacuum chuck integrates a vacuum wafer chuck, a water-cooling plate, and a heating plate. The vacuum wafer chuck has several vacuum adsorption holes and several sensors are installed inside it. The water-cooling plate and the heating plate are located below the vacuum wafer chuck to provide it with a simulated environment of high and low temperature or constant temperature.

[0014] Furthermore, the test probe is fixed on the test probe module, which includes a magnetic base and an XYZθ four-axis positioner. The XYZθ four-axis positioner is fixed to the probe stage by magnetic adsorption through the magnetic base, and the rotation axis at the front end of the XYZθ four-axis positioner is fixed to the test probe by an adapter plate.

[0015] Preferably, the sensor is a capacitive sensor.

[0016] By integrating sensors and signal converters to form a non-contact height sensing system, and then using a vacuum chuck to vacuum-adsorb and fix the test chip, the testing problems caused by warpage and unevenness of the stage during wafer chip testing can be solved, which can greatly improve the efficiency of wafer testing and reduce the manufacturing cost of integrated circuits.

[0017] The contactless sensing system also avoids damage and contamination to the chip, making it possible to perform highly efficient testing of extremely demanding chips.

[0018] The control software combines the testing system and sensor monitoring system without reducing testing speed, which can greatly improve testing efficiency and reduce losses. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the system principle of the present invention; Figure 2 This is a system structure diagram of one embodiment; Figure 3 for Figure 2 The structure diagram marked with 3 in the middle; The diagram is marked as follows: 1. Computer; 2. Signal converter; 3. Sensor module; 4. Probe station; 5. Vacuum suction cup; 6. Test instrument; 7. Test probe module; 301. Magnetic base; 302. XYZθ four-axis positioner; 303. Adapter board; 304. Fiber optic arm; 305. Sensor support plate; 306. Sensor; 307. Fiber optic cable. Detailed Implementation

[0020] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Many specific details are set forth in the following description to provide a thorough understanding of the present invention. However, the present invention can be practiced in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0021] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0022] A non-contact height sensing system for wafer testing, such as Figure 1 As shown, the system includes a computer, a signal converter, a sensor, a testing instrument, and a probe station. The computer includes control software and a server, and communicates with the signal converter, the testing instrument, and the probe station. The testing instrument is electrically connected to several test probes. The probe station includes a stage for fixing the test chip. The signal converter receives analog signals from the sensor, converts them into digital signals, and sends them as feedback signals to the computer's control software. The control software sends control signals to the probe station via the computer to control the stage to move the test chip closer to the test probe for testing. The sensor receives the distance between the test chip and the sensor. When the distance reaches a preset value, the control software sends another control signal to the probe station's stage to stop its movement. The control software then sends a control signal to the testing instrument to release an excitation signal to the test chip and receives the feedback signal from the test chip. The feedback signal is then transmitted to the server for storage.

[0023] By monitoring the height of the chip in real time with sensors, the non-contact sensing system avoids damage and contamination to the chip, enabling highly efficient testing of extremely demanding chips. It also does not reduce testing speed, significantly improving testing efficiency. Furthermore, once the stage stops moving, the chip height on the stage is the optimal contact height, and this consistent height reduces probe wear considerably.

[0024] like Figure 2 As shown, it is based on Figure 1 The schematic diagram presents a system structure diagram of one embodiment. The sensor is installed at the front end of the sensor module 3, and the test probe is installed at the front end of the test probe module 7. The middle of the probe stage is the test port, and the lower end of the test port is the stage. A vacuum suction cup 5 is provided on the stage, which is used to adsorb the test chip.

[0025] Among them, such as Figure 3 The diagram shows the structure of sensor module 3. Sensor module 3 includes a magnetic base 301 and an XYZθ four-axis positioner 302. The XYZθ four-axis positioner 302 is fixed to the probe stage by magnetic adsorption through the magnetic base 301. The front end of the XYZθ four-axis positioner 302 is a rotating shaft. The rotating shaft is fixed to a fiber optic arm 304 for fiber optic cable routing 307 via an adapter plate 303. A sensor support plate 305 is provided at the front end of the fiber optic arm 304, and the sensor is fixed in the sensor support plate 305. The XYZθ four-axis positioner 302 includes an X-axis high-precision positioner, a Y-axis high-precision positioner, a Z-axis high-precision positioner, and an θ angle adjuster. The X-axis high-precision positioner and the Y-axis high-precision positioner are horizontally fixed via an adapter plate. The Z-axis high-precision positioner is vertically fixed to the Y-axis high-precision positioner via an L-shaped adapter plate. The θ angle adjuster is horizontally set at the front end of the Z-axis high-precision positioner via the adapter plate and controls the rotation angle of the adapter plate 303 in the vertical direction. The front end of the tray 305 is inclined and has sensor mounting holes for mounting sensors.

[0026] Meanwhile, the test probe module 7 includes a magnetic base and an XYZθ four-axis positioner. The XYZθ four-axis positioner is fixed to the probe stage by magnetic adsorption through the magnetic base, and the rotation axis at the front end of the XYZθ four-axis positioner is fixed to the test probe by an adapter plate.

[0027] like Figure 2 As shown, a vacuum chuck 5 is installed at the lower end of the test port. This vacuum chuck is a temperature-controlled type, integrating a vacuum wafer chuck, a water-cooling plate, and a heating plate. The vacuum wafer chuck has several vacuum adsorption holes and also houses several sensors. The water-cooling plate and heating plate are positioned below the vacuum wafer chuck to provide a simulated high / low temperature or constant temperature environment. Through the vacuum adsorption holes on the vacuum chuck, the test chip can be flatly adsorbed and fixed, reducing chip warpage.

[0028] In this invention, the sensor is a capacitive sensor, which monitors the distance between the test chip and the plate by measuring the relationship between the capacitance of the plate capacitor and the spacing between the plates.

[0029] In practical applications, neither wafer warpage nor stage unevenness is abrupt; rather, it exhibits a gradual and continuous change with a certain trend. Therefore, within a very small area, the degree of change is extremely small. The sensor in this invention is located adjacent to the test probe during use, monitoring the wafer height at the contact point with the probe. The degree of warpage at this point can be approximated as being the same as at the contact point, thus ensuring that the monitoring always focuses on the contact position. The stage controls the repeated rising and falling of the test chip wafer to test the chip, and its continuous forward, backward, left, and right movements enable switching between different chips.

[0030] In this invention, the control software integrates the testing system and the sensor monitoring system, forming a one-to-one correspondence. First, the probe station is controlled to bring a specific test chip into contact with the probes. Then, the instrument releases and receives signals to complete the test, and the test result is the result for that chip. The process then repeats for the next chip, with each chip corresponding to a specific result. During the testing process, the sensor monitoring system continuously monitors the distance between the probe station and the chip, ensuring that the chip height on the stage is the appropriate contact height, and that the height is consistent with each contact. This solves the testing challenges caused by wafer warpage and stage unevenness, significantly improves testing efficiency, and avoids chip damage and contamination.

[0031] The above specific embodiments further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above are merely specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A non-contact height sensing system for wafer testing, characterized in that: The system includes a computer, a signal converter, a sensor, a testing instrument, and a probe station. The computer includes control software and a server. The computer communicates with the signal converter, the testing instrument, and the probe station. The testing instrument is electrically connected to several test probes. The probe station includes a stage for fixing a test chip. The signal converter receives analog signals from the sensor, converts them into digital signals, and sends them as feedback signals to the computer's control software. The control software releases a control signal to the probe station via the computer to control the stage, carrying the test chip, to move closer to the test probe for testing. The sensor receives the distance between the test chip and the sensor. When the distance reaches a preset value, the control software releases another control signal to the stage of the probe station to stop its movement. The control software then releases a control signal to control the testing instrument to release an excitation signal to the test chip and receive feedback signals from the test chip. These feedback signals are then transmitted to the server for storage.

2. The non-contact height sensing system for wafer testing as described in claim 1, characterized in that: The sensor is fixed on the sensor module (3). The sensor module (3) includes a magnetic base (301) and an XYZθ quad-axis positioner (302). The XYZθ quad-axis positioner (302) is fixed on the probe stage by adsorption through the magnetic base (301). The front end of the XYZθ quad-axis positioner (302) is a rotating shaft. The rotating shaft is fixed with a light arm (304) through an adapter plate (303). The front end of the light arm (304) is provided with a sensor support plate (305). The sensor is fixed in the sensor support plate (305).

3. The non-contact height sensing system for wafer testing as described in claim 2, characterized in that: The XYZθ four-axis positioner (302) includes an X-axis high-precision positioner, a Y-axis high-precision positioner, a Z-axis high-precision positioner, and an θ angle adjuster. The X-axis high-precision positioner and the Y-axis high-precision positioner are horizontally fixed by an adapter plate. The Z-axis high-precision positioner is vertically fixed to the Y-axis high-precision positioner by an L-shaped adapter plate. The θ angle adjuster is horizontally set at the front end of the Z-axis high-precision positioner by an adapter plate and controls the rotation angle of the adapter plate (303) in the vertical plane.

4. The non-contact height sensing system for wafer testing as described in claim 1, characterized in that: The stage is equipped with a temperature-controlled vacuum suction cup (5).

5. A non-contact height sensing system for wafer testing as described in claim 4, characterized in that: The temperature-controlled vacuum chuck (5) integrates a vacuum wafer chuck, a water-cooled plate, and a heating plate. The vacuum wafer chuck has several vacuum adsorption holes and several sensors inside. The water-cooled plate and the heating plate are located below the vacuum wafer chuck to provide it with a high-low temperature or constant temperature simulation environment.

6. The non-contact height sensing system for wafer testing as described in claim 1, characterized in that: The test probe is fixed on the test probe module (7), which includes a magnetic base (301) and an XYZθ quad-axis positioner (302). The XYZθ quad-axis positioner (302) is attracted and fixed on the probe stage by the magnetic base (301). The rotation axis at the front end of the XYZθ quad-axis positioner is fixed to the test probe by an adapter plate.

7. The non-contact height sensing system for wafer testing as described in claim 1, characterized in that: The sensor is a capacitive sensor.

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