MEMS probe performance test method and system

Abstract

The invention provides an MEMS probe performance test method and system. The method comprises the following steps: testing a stroke-pressure relation, calibrating an initial contact zero point, controlling a pressure sensor probe to press a probe tip at a fixed step length, collecting probe pressure data under different strokes, generating a curve, and judging the mechanical property of the probe according to the slope of the curve in a specific interval; and carrying current-pressure change test: after recording the initial probe pressure under a fixed stroke, circularly carrying out power-on-power-off test on the probe with stepped increasing current, and collecting the probe pressure data when the probe is powered on until the probe pressure change rate exceeds a threshold value, thereby determining the carrying current performance parameter of the probe. The system comprises a control and processing module, a three-dimensional motion platform, a pressure sensing module, a current source module, a visual positioning module and a data recording and displaying module. According to the invention, integrated quantitative evaluation of mechanical and electrical properties of the MEMS probe is realized.

Description

Technical Field

[0001] This invention relates to the field of semiconductor testing technology, and more specifically to a method for testing the combined mechanical and electrical performance of a microelectromechanical system (MEMS) probe and a testing system for implementing the method. Background Technology

[0002] As a critical interface component in wafer testing (CP testing), the stability of MEMS probes is paramount. Ideally, at a pressure of 60-80 μm, the probe should provide stable and consistent contact pressure (needle pressure) within its defined overdrive (OD) range, while maintaining stable pressure under specific test currents to ensure good electrical contact and minimize damage to the device under test. Currently, industry evaluations of MEMS probes often focus on single performance aspects, such as simple continuity tests or static pressure measurements, lacking a method that can systematically simulate actual testing conditions and quantitatively analyze the comprehensive performance of probes under dynamic pressure and power-on heating states. This leads to probe selection often relying on experience, easily introducing risks such as poor test repeatability, yield fluctuations, and even chip damage due to inconsistent probe force or insufficient current carrying capacity. Therefore, developing a method and system capable of comprehensively and accurately evaluating the travel-pressure characteristics and current-pressure variation characteristics of MEMS probes is urgently needed and of great significance for improving the reliability, consistency, and efficiency of semiconductor testing. Summary of the Invention

[0003] To address the shortcomings of existing technologies in evaluating the performance of MEMS probes—namely, the lack of comprehensiveness and systematic approach, and the inability to quantify their overall performance under simulated real-world operating conditions—this invention provides a method and system for testing the performance of MEMS probes. This method aims to accurately measure the change in probe pressure with the downward stroke and evaluate its pressure stability under a stepped increasing current load. This provides objective and quantitative data for the scientific selection, adaptation verification, quality control, and performance degradation analysis of probes.

[0004] To achieve the above objectives, the present invention adopts the following technical solution: In a first aspect, the present invention provides a method for testing the performance of a MEMS probe, which integrates stroke-pressure relationship testing and current-pressure change testing, specifically including the following steps: S1: Stroke-Pressure Relationship Test S11: Preparation and Positioning. Mount the MEMS probe under test onto the dedicated test fixture, and fix the fixture onto the motion platform of the test system. Identify the probe tip position using the vision system, and control the motion platform to move the tip directly below the pressure sensor probe.

[0005] S12: Zero-point calibration. Slowly lower the pressure sensor probe (negative Z-axis direction). When the pressure reading first shows a stable value greater than zero, record the current position as the contact point. Continue fine-tuning until the pressure value is exactly zero and the probe remains electrically connected to the conductive pads on the test fixture. Precisely define this position as the mechanical zero point (0OD point).

[0006] S13: Stepped Compression and Data Acquisition. Starting from the 0OD point, control the pressure sensor probe to press down towards the probe tip in fixed steps (e.g., 10μm). After each step and stabilization, record the current cumulative compression stroke (OD value) and the corresponding real-time needle pressure value. Repeat this process to acquire pressure data at a series of predetermined stroke points (e.g., from 10μm to 100μm).

[0007] S14: Curve Generation. The collected (pressure stroke, needle pressure) data are processed to automatically generate the stroke-pressure relationship curve for the probe.

[0008] S15: Performance Assessment. Based on the generated stroke-pressure relationship curve, calculate the slope of the curve within a preset critical stroke range (e.g., 60μm to 80μm). If the slope value is less than the set acceptable threshold (e.g., 0.02), the mechanical properties of the probe are deemed acceptable, indicating that the pressure change is gradual and consistent within the working range.

[0009] S2: Current-Pressure Variation Test S21: Initial state setting. Control the pressure sensor probe to press down to a preset fixed stroke (e.g., OD=100μm). Record the stable needle pressure value without current flow in this state as the initial needle pressure P0.

[0010] S22: Stepped current carrying test cycle.

[0011] a. Power the probe with a set initial current I1 (e.g., 400mA) for a first predetermined duration T1 (e.g., 120 seconds).

[0012] b. During the power-on period, collect and record needle pressure data at fixed time intervals (e.g., every 30 seconds) while the device is powered on.

[0013] c. After reaching T1, stop the power supply and control the pressure sensor probe to lift up, so that the probe rests for a second predetermined time T2 (e.g., 30 seconds) in a state of no pressure and no current.

[0014] d. Control the probe to press down again to the same fixed stroke (OD=100μm).

[0015] e. Increase the current value by a fixed increment ΔI (e.g., 100mA) to I2, and repeat the power-on, data acquisition, and rest process from steps a to c.

[0016] S23: Loop and Termination. Step S22 is executed repeatedly, with the current increasing by ΔI in each loop. During the energizing period of each current level, the rate of change of the collected needle pressure data (e.g., average value) relative to the initial needle pressure P0 is calculated. The test automatically terminates when this rate of change first exceeds a preset threshold (e.g., 20%).

[0017] S24: Results Analysis. Compile all current levels and corresponding needle pressure data recorded throughout the testing process, generating a current-pressure change graph. Record the maximum current value that can be applied without exceeding the needle pressure change rate threshold, as a key parameter for evaluating the probe's current-carrying capacity.

[0018] Preferably, in step S15, the preset critical stroke range is 60μm to 80μm, and the condition for passing the test is that the slope of the pressure change is less than 0.02.

[0019] Preferably, in step S13, the fixed step size is 10 μm, and the collected downward stroke points are ten points within the range of 10 μm to 100 μm.

[0020] Preferably, in step S23, the preset threshold is 20%, and the formula for calculating the rate of change is: |initial needle pressure - energized needle pressure| / initial needle pressure. Here, the energized needle pressure can be the needle pressure value collected at a single time point during the energization period (e.g., the instantaneous value at the end of energization), or it can be the statistical processing result of needle pressure values ​​at multiple time points, such as the arithmetic mean, median, or the last stable value.

[0021] Preferably, in step S22, the current value ΔI increases by 100mA each time, the first predetermined duration T1 is 120 seconds, the fixed time interval is 30 seconds, and the second predetermined duration T2 is 30 seconds.

[0022] Secondly, the present invention provides a MEMS probe performance testing system for implementing the above method, comprising: The control and processing module, as the core of the system, is used to execute the logical control of the test process, issue action commands to various components, and collect, process, and analyze data in real time.

[0023] A three-dimensional motion platform is electrically connected to the control and processing module and receives its motion commands. The platform includes at least an XY-plane motion module for loading the test fixture and a Z-axis motion module for driving the pressure sensing module, enabling planar positioning of the probe and precise downward pressure in the vertical direction.

[0024] The pressure sensing module is fixedly mounted on the Z-axis motion module of the three-dimensional motion platform. Its front end is a pressure probe, which is used to apply vertical pressure to the tip of the MEMS probe under test during the test, and to measure this pressure value (needle pressure) in real time with high precision and feed it back to the control and processing module.

[0025] The current source module, connected to the control and processing module, can output a precise and controllable stepped current according to the test program. This module is connected to the terminals on the test fixture via wires, thereby applying current to the MEMS probe under test.

[0026] The visual positioning module, typically including a high-resolution camera and a light source, is mounted at a location convenient for capturing images of the probe tip. The captured images are transmitted to the control and processing module, which identifies the tip position through image processing and guides the 3D motion platform for initial positioning.

[0027] The data recording and display module, integrated into or connected to the control and processing module, is used to store all raw test data, intermediate and final results, and to display the test results on the monitor in an intuitive form such as charts and curves.

[0028] Preferably, the system further includes a dedicated test fixture, which is securely mounted on the XY plane motion module of the three-dimensional motion platform. This fixture is used to clamp and fix the MEMS probe card under test. The fixture includes a test PCB board with gold-plated pads that reliably contact the probe tip. These gold-plated pads are connected to terminals on the fixture via wiring. The terminals are connected to the current source module via wires, thus forming a complete current loop from the current source through the probe, the probe itself, the gold-plated area of ​​the PCB, and back to the current source when the pressure sensor probe contacts the probe tip.

[0029] Preferably, the control and processing module has pre-installed dedicated data analysis software or templates. This software / template can automatically receive real-time data streams from the pressure sensing module, and automatically plot the stroke-pressure relationship curve and the current-pressure change curve according to a preset algorithm, calculate key parameters (such as slope and rate of change), and assist in the qualification judgment.

[0030] The beneficial effects of this invention are as follows: 1. Comprehensive evaluation system: This invention is the first to organically combine stroke-pressure testing and current-pressure testing on the same platform, fully simulating the real working conditions of mechanical compression and electrothermal load coupling experienced by MEMS probes in actual wafer testing, and realizing an integrated and systematic evaluation of its dynamic comprehensive performance.

[0031] 2. Precise Quantification of Results: By quantifying the slope of the stroke-pressure relationship curve in the 60-80μm range (e.g., less than 0.02 is considered acceptable), and by quantifying the current value when the needle pressure change rate exceeds 20% in the current-carrying test, the mechanical stability and electrothermal carrying capacity of the probe are accurately evaluated numerically, overcoming the subjectivity and inaccuracy of previous reliance on experience-based judgment.

[0032] 3. High degree of automation: The testing process runs semi-automatically or automatically under software control, with data automatically recorded, processed, and visualized. This not only significantly improves testing efficiency and reduces the technical requirements and workload of operators, but also greatly reduces human error, ensuring the consistency and repeatability of test results.

[0033] 4. Effective Risk Prevention: The probe can accurately identify its mechanical instability range and current carrying capacity limit before use, providing early warning of potential risks. This avoids test failures, decreased product yield, and even damage to expensive chips due to probe performance mismatch, reducing the overall risk and cost of production testing. Attached Figure Description

[0034] Figure 1 This is a schematic diagram of the structure of the MEMS probe performance testing system provided in an embodiment of the present invention; Figure 2 The overall flowchart of the MEMS probe performance testing method provided in the embodiments of the present invention is shown below; Figure 3 A detailed schematic diagram of the sub-process of the stroke-pressure relationship test; Figure 4 A detailed schematic diagram of the current-pressure change test sub-process; Figure 5 Here is an example stroke-pressure relationship curve generated based on test data; Figure 6 This is an example current-pressure variation curve generated based on test data.

[0035] Illustration: 1. Industrial computer; 2. 3D motion platform; 3. Pressure sensor; 4. Programmable DC power supply; 5. CCD camera; 6. Special test fixture; 7. MEMS probe card under test. Detailed Implementation

[0036] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be 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 illustrative and not intended to limit the invention.

[0037] In the description of this invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0038] Furthermore, in the description of this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal connection of two components; they can refer to a wireless connection or a wired connection. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0039] Furthermore, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0040] like Figure 1 As shown, the hardware configuration of the test system in a preferred embodiment of the present invention mainly includes: an industrial control computer 1 as the core control unit; a high-precision three-dimensional motion platform 2 that provides precise motion capabilities; a high-sensitivity pressure sensor 3 integrated on the Z-axis of the platform; a programmable DC power supply 4 that provides controllable current for testing; a high-resolution CCD camera 5 for visual positioning; and a special test fixture 6 for fixing the test piece, on which a MEMS probe card 7 to be tested is mounted.

[0041] The industrial computer 1 runs dedicated control software, integrating the functions of control and processing modules as well as data recording and display modules. The three-dimensional motion platform 2 typically includes three linear motion modules: X, Y, and Z. A dedicated test fixture 6 is mounted on the XY plane motion module of the platform and can be programmed to move within the plane, achieving coarse positioning of the probe card. A high-sensitivity pressure sensor 3 serves as a pressure sensing module; its probe is mounted vertically downwards and fixed to the Z-axis motion module via a mounting plate. The Z-axis motion module drives the pressure sensor 3 to perform vertical lifting and lowering movements, thereby achieving the pressing and lifting action of the probe on the probe tip. The pressure sensor 3 measures the pressure in real time and transmits it to the industrial computer 1. A programmable DC power supply 4 serves as a current source module; its output is connected to the probe of the pressure sensor 3 via a wire (the probe is conductive), while another circuit is connected to the wiring terminals of the dedicated test fixture 6. When the probe of the pressure sensor 3 contacts the probe tip, the current circuit is activated. A high-resolution CCD camera 5 serves as a visual positioning module, mounted at a suitable position on the frame; its field of view covers the probe tip area for precise positioning.

[0042] The design of the dedicated test fixture 6 is crucial. At its core is a specially designed test PCB board. The upper surface of this PCB board has gold-plated contact pads that correspond precisely to and are positioned for all the probe tails of the MEMS probe card 7 under test. These gold-plated pads are all electrically connected together through internal traces on the PCB, ultimately converging to the terminals on the side of the fixture. This design ensures that regardless of which probe the pressure sensor probe contacts, a complete electrical circuit can be formed through the probe, the PCB gold-plated pads, the terminals, and the programmable DC power supply 4.

[0043] When the system is working, the software (control and processing module) is the "brain" of the entire process. It not only controls the coordinated movement of the three-dimensional motion platform 2 and the programmable DC power supply 4, but also collects data from the pressure sensor 3 in real time, and calls the built-in data analysis template to automatically complete tasks such as data plotting, slope calculation, and rate of change analysis, with the results displayed on the screen in real time.

[0044] like Figure 2 As shown, the testing method of this invention is mainly divided into two test sequences: stroke-pressure relationship test (Sequence A) and current-pressure change test (Sequence B). These two tests can be performed independently or continuously on the same probe to obtain a complete performance profile.

[0045] Example 1: Stroke-Pressure Relationship Test Combination Figure 3 Taking the testing of a single MEMS probe as an example, the specific steps are as follows: (1) Installation and positioning: Insert the MEMS probe card 7 to be tested into the special test fixture 6 and lock it. Start the system, the CCD camera 5 takes a picture, and the software finds the tip of the target probe through image recognition. The industrial computer 1 controls the X and Y axes of the three-dimensional motion platform 2 to move the tip to directly below the probe of the pressure sensor 3.

[0046] (2) Zero-point calibration (finding the 0OD point): Control the Z-axis to slowly lower the pressure sensor 3 probe. When the pressure value displayed on the software interface changes from 0 to a stable small positive value (e.g., 0.1g), record the Z-axis coordinate at this moment as the "initial contact point". Then, control the probe to continue to descend or rise very slowly (micrometer-level steps), while observing the pressure reading and the continuity between the probe and the PCB gold-plated pad (judged by measuring the loop resistance). When the pressure reading is exactly 0.0g and the continuity indicator light just illuminates (indicating that the probe tip is in contact with the pad), precisely define this Z-axis position as the "0OD point". This is the absolute reference for all stroke measurements.

[0047] (3) Data acquisition: Starting from the 0OD point, the software controls the Z-axis to move downward (in the probe direction) in 10μm increments. After each step, the system pauses briefly to wait for the pressure reading to stabilize, and then automatically records the current cumulative downward stroke (10μm for the first step, 20μm for the second step, ..., 100μm for the tenth step) and the corresponding stable needle pressure value (in g).

[0048] The tests were conducted on five MEMS probe cards 7, and the data acquisition records are shown in Table 1:

[0049] (4) Processing and Judgment: After the data collection is completed, the software automatically fills the ten sets of data (stroke, needle pressure) into the preset template and draws the graph as shown below. Figure 5 The stroke-pressure relationship curve is shown. The software then automatically calculates the slope of the curve in the critical stroke range of 60μm to 80μm (the formula is (pressure 80μm - pressure 60μm) / (80μm - 60μm)). If the calculated slope value is less than 0.02, the software determines that the probe passes this test, indicating that its force value changes smoothly within its commonly used operating range, making it suitable for CP testing requiring high consistency. Table 1 shows examples of test data for multiple probes. Probe No. 5 exhibits a significant force jump in the 60-80μm range, exceeding the slope limit, and is therefore deemed unqualified.

[0050] Example 2: Current-Pressure Variation Test Combination Figure 4 The specific steps are as follows: (1) Initialization: After completing visual positioning, control the pressure sensor 3 probe to press down, so that the probe's pressing stroke is fixed at OD=100μm. Wait for the pressure reading to stabilize, and record the pressure value in this unpowered state as the initial needle pressure P0 (e.g., 12.5g).

[0051] (2) Stepped current-carrying cycle test: - First cycle: The industrial control computer 1 sets the programmable DC power supply 4 to output a current of I1=400mA and starts a 120-second timer. The current flows through the probe, probe board, and PCB board to form a loop, and the probe heats up due to power-on. The software automatically records the current needle pressure value at four time points: 30 seconds, 60 seconds, 90 seconds, and 120 seconds after power-on.

[0052] - Rest: After 120 seconds, the programmable DC power supply 4 shuts off its output (current is 0), and at the same time controls the Z-axis to lift the probe, allowing the probe to freely recover (rest) for 30 seconds in a pressure-free and current-free state.

[0053] - Second cycle: Press the probe down again to OD=100μm. Record the needle pressure at this moment. Then increase the current setting by 100mA to I2=500mA, and repeat the above process of 120 seconds of power-on (4 records) and 30 seconds of rest.

[0054] - Subsequent cycles: The current is increased to 600mA, 700mA, etc., and the test is repeated until the termination condition is met.

[0055] (3) Termination Condition: In each current level test, the software processes the needle pressure data recorded in that stage. As a preferred implementation, this embodiment calculates the arithmetic mean of four needle pressure values ​​as a representative value. Then, the rate of change of this representative value relative to the initial needle pressure P0 is calculated, with the formula: |P0 - average value| / P0. As shown in the example data in Table 2, when the current increases to 1100mA, the average needle pressure drops to 10.275g, and the rate of change is approximately (12.5 - 10.275) / 12.5 ≈ 17.8%, which the software determines is close to the threshold. If the rate of change in the next cycle exceeds 20%, the test will automatically terminate. When the instantaneous value is used as the representative value, the needle pressure at the contact point when the current is 1100mA and energized for 120S has dropped to 9.7g, with the rate of change formula being |P0 - instantaneous value| / P0. At this time, the rate of change is approximately (12.5 - 9.7) / 12.5 = 22.4%, which exceeds 20%, and the test will automatically terminate.

[0056] The data collection records are shown in Table 2:

[0057] (4) Result Output: All test data is automatically recorded and organized. The software generates the following output: Figure 6The current-pressure change curve shown can intuitively display the trend of needle pressure change under different currents and different energizing times. The purpose of this test is not to simply determine "pass / fail", but to quantitatively evaluate the current-carrying capacity of the probe. Generally, the maximum current value with a needle pressure change rate not exceeding 20% ​​(such as 1000mA or 1100mA in Table 2, depending on the precise calculation results) is recorded as the "recommended maximum safe operating current" of the probe, providing a selection basis for test items with different current requirements.

[0058] The above embodiments are merely preferred embodiments of the present invention and should not be construed as limiting the scope of protection of the present invention. Any non-substantial changes and substitutions made by those skilled in the art based on the present invention shall fall within the scope of protection claimed by the present invention.

Claims

1. A method for testing the performance of a MEMS probe, characterized in that, Includes the following steps: Stroke-pressure relationship test steps: calibrate the initial contact zero point between the tip of the MEMS probe under test and the pressure sensor probe; starting from the initial contact zero point, control the pressure sensor probe to press down towards the tip in fixed steps, and collect needle pressure data corresponding to different pressing stroke points; based on the needle pressure data and pressing stroke data, generate a stroke-pressure relationship curve, and determine the mechanical properties of the probe according to the pressure change slope of the curve within a preset stroke range; Current-pressure change test steps: Press the pressure sensor probe down to a preset fixed stroke at the probe tip and collect the initial needle pressure data when no power is applied; energize the probe with a set initial current value for a first predetermined duration, and collect multiple energized needle pressure data at fixed time intervals during the energization period; stop energizing and lift the pressure sensor probe to allow the probe to rest for a second predetermined duration; press the probe down to the fixed stroke again, increase the current value, and repeat the energization, data collection, and rest process; repeat the above steps until the calculated rate of change of the energized needle pressure data relative to the initial needle pressure exceeds a preset threshold, at which point the test stops; determine the current-carrying performance parameters of the probe based on the recorded current value and the corresponding needle pressure data.

2. The method according to claim 1, characterized in that, The determination of probe mechanical performance based on the slope of pressure change within a set stroke range specifically includes: calculating the slope of the stroke-pressure relationship curve within a stroke range of 60μm to 80μm; if the slope is less than 0.02, the probe mechanical performance is deemed qualified.

3. The method according to claim 1, characterized in that, The control of the pressure sensor probe to press down towards the needle tip in fixed steps is as follows: starting from the initial contact zero point, the probe is controlled to press down in 10 steps with a step size of 10μm until the total stroke is 100μm, and the corresponding needle pressure value is recorded after each step of pressing is stable.

4. The method according to claim 1, characterized in that, The preset threshold is 20%; the formula for calculating the rate of change is: |initial needle pressure - energized needle pressure| / initial needle pressure.

5. The method according to claim 1, characterized in that, The increase in current value specifically refers to an increase of 100mA per cycle; the first predetermined duration is 120 seconds, the fixed time interval is 30 seconds, and the second predetermined duration is 30 seconds.

6. A MEMS probe performance testing system, characterized in that, include: The control and processing module is used to execute test process control, issue data acquisition commands, and perform data processing and analysis. A three-dimensional motion platform is connected to the control and processing module. The three-dimensional motion platform includes an XY plane motion module for loading the MEMS probe under test and a Z-axis motion module for driving the pressure sensing module. The pressure sensing module is installed on the Z-axis motion module of the three-dimensional motion platform. Its probe is used to apply downward pressure to the tip of the MEMS probe under test and measure the needle pressure in real time. A current source module, connected to the control and processing module, is used to provide a programmable stepped current to the MEMS probe under test according to test commands. The visual positioning module is used to acquire an image of the tip of the MEMS probe under test and guide the three-dimensional motion platform to complete the positioning. The data recording and display module is used to store test data and display test curves and results.

7. The system according to claim 6, characterized in that, It also includes a test fixture, which is mounted on the XY plane motion module of the three-dimensional motion platform for fixing and loading the MEMS probe under test; the test fixture includes a test PCB board, which has a gold-plated area that is electrically in contact with the probe tail and a terminal block that is electrically connected to the gold-plated area. The terminal block is connected to the current source module to form a current loop.

8. The system according to claim 6, characterized in that, The control and processing module has a pre-set data analysis template, which is used to automatically generate stroke-pressure relationship curves and current-pressure change curves based on the data collected by the pressure sensing module.

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