Contact type wafer thickness compensation method of probe station

Abstract

The invention discloses a contact type wafer thickness compensation method of a probe station. The method comprises three stages of setting a safe initial height, a pressure threshold value and other parameters after wafer alignment, large-step fast approximation, dichotomy interval compression and ultra-small-step fine positioning, and driving an electric chuck assembly to position an initial contact height; during testing, detecting an actual pin pressure value in real time, filtering the pin pressure value, fitting a pressure-height linear relation, comparing with the pin pressure of the first chip, and calculating a compensation amount to adjust the contact height of the next chip; the full-wafer dynamic compensation method has the advantages that the positioning precision reaches 0.1 mu m level, the compensation error is small, a special test key is not needed, the safety and the test efficiency are both considered, and the full-wafer dynamic compensation method is suitable for the field of semiconductor wafer test.

Description

Technical Field

[0001] This invention relates to the field of semiconductor testing equipment technology, and in particular to a contact-type wafer thickness compensation method for a probe station. Background Technology

[0002] In the semiconductor chip manufacturing process, wafer testing is a crucial step in ensuring product yield. As the core equipment in wafer testing, the probe station's accuracy directly affects the accuracy and reliability of the test results. During testing, the probes need to make precise and stable contact with the pads of the chip on the wafer. However, due to issues such as bending, warping, or uneven thickness of the wafer itself, the wafer surface is not an ideal plane. Without compensation, the same set probe height may lead to poor probe-chip contact (insufficient probe pressure or no contact) or excessive contact (excessive probe pressure, damaging the chip or probe) in different areas of the wafer.

[0003] To address the aforementioned issues, various thickness compensation schemes have been proposed in the prior art. For example, Chinese invention patent CN112014710B discloses a needle pressure adaptation method. This method discloses that, before testing, the contact resistance is calculated by measuring the resistance of two preset test keys of different sizes on the wafer at different pressing heights, and an optimal, fixed target detection height is determined based on the distribution of the contact resistance.

[0004] However, the technical solution in this prior art document has the following drawbacks: Dependence on Special Structure: This method heavily relies on the pre-fabrication of two different sized test bonds on the wafer, which limits its applicability. This method cannot be implemented on conventional wafers that do not have such test bonds.

[0005] Calibration is complex: It requires establishing and relying on a precise correlation between "resistance measurement value - test key size - contact resistance". This calibration process is complex and easily affected by wafer surface conditions (such as oxidation and contamination). If the calibration is inaccurate, the entire pin pressure fitting result will be deviated.

[0006] Static adaptation: This method is essentially a "pre-adaptation," performed only once before testing to determine a globally fixed target height. It cannot handle dynamic changes in wafer thickness or significant unevenness in local areas during testing, resulting in limited compensation accuracy.

[0007] Low efficiency: The test requires additional data collection and complex calculation processes, which increases test preparation time and reduces overall test efficiency.

[0008] Therefore, there is an urgent need for a compensation method that does not rely on special test structures, can dynamically respond to changes in wafer thickness during testing, and is more efficient. Summary of the Invention

[0009] To address the shortcomings of existing technologies, such as reliance on special test keys, complex calibration, static adaptation, and low efficiency, this invention proposes a contact-type wafer thickness compensation method for probe stations.

[0010] The core idea of ​​this invention is to detect the actual pin pressure when the probe contacts the current chip in real time during the wafer testing process, and based on this, actively adjust the pin height of the next chip to form a dynamic and iterative compensation closed loop.

[0011] The present invention proposes a contact-type wafer thickness compensation method for a probe station, comprising the following steps: S1. Initial Height Reference Setting: After the probe station aligns the wafer, the basic parameters and protection parameters are set first. These parameters include the safe starting height Z. start Theoretical height of wafer Z max Contact detection threshold P th Maximum safe pressure P of the probe max Pressure warning threshold P pre and step size parameters, pressure warning threshold P pre For P max 0.8 times, step size parameters include large step size. large Small step size small Ultra-small step size ultra The electric chuck assembly is then driven to rise in stages to determine the contact height. S11. Large step size rapid approximation: Control the electric chuck assembly from Z... start Begin with Step large Move upwards, and read the sensor pressure P after each movement; if P=0, continue moving until Z is reached. max If 80% of the time is reached, proceed to S12; if P>0 during the rapid approach with a large step size, it indicates abnormal contact and proceed to S13. S12. Bisection Interval Compression: Using the current position Z... n For the lower limit, Z max Construct an interval [Z] for the upper limit n Z max ] Calculate the intermediate point Z mid =(Z n +Z max ) / 2, control the electric chuck assembly to move to Z mid And read the pressure P mid If P mid >P pre or P mid ≤P pre And Pmid >P th Enter S13; if P mid ≤P th Update Z n =Z mid Repeat this step until the interval difference Z is reached. max -Z n ≤Step small Enter S13; S13. Ultra-small step size fine positioning: from the current Z... n Begin with Step ultra Move the electric chuck assembly upwards and read P in real time; if P th <P≤P pre Record the current height as the initial contact height; if P pre <P≤P max Record the initial contact height and trigger a high pressure warning; if P > P max Control the electric chuck assembly to move downwards by 2 × Step large Disengage and stop; if moved to Z max Still no P>P th Alarm and shutdown; S2. Dynamic Needle Pressure Detection: When performing electrical performance testing on a chip under test (DUT) on a wafer, the probe station uses mechanical feedback to detect the actual needle pressure value P when the probe contacts the DUT in real time. od ; S3. Iterative Height Compensation: After the test is completed, the industrial control computer performs P... od Process and compare with the first chip pin pressure value P first The comparison is performed, the height compensation is calculated, and a command is sent to the motion controller to adjust the contact height setting value of the next chip under test. S4. Repeat steps S2 and S3 to test all chips on the wafer, achieving dynamic compensation of the entire wafer thickness based on mechanical feedback.

[0012] Furthermore, prior to step S1, the thickness of different regions of the wafer is detected using a multi-point detection function to obtain overall wafer topography information, providing a reference for setting the initial contact height.

[0013] Furthermore, the multi-point detection function can select to detect 9, 16, or 25 points. These detection points are evenly distributed in a matrix on the wafer surface and are sequentially completed by probes on a probe holder with pressure sensing.

[0014] Furthermore, the mechanical feedback is implemented by a needle pressure detection and feedback component, which includes a probe holder with pressure sensing and a pressure gauge; the probe holder with pressure sensing uses a strain gauge as the sensing element to convert the deformation signal when the probe contacts the probe into a pressure signal; the contact determination threshold P... th The default value is 0.1g, and the Step parameter is... large For 100μm, Step small 1μm, Step ultra It is 0.1μm.

[0015] Furthermore, the pressure-sensing probe holder uses a lever design to calibrate the conversion relationship between analog voltage and needle depth. This conversion relationship is written into the control software of the industrial control computer to coordinate with the theoretical height Z of the wafer. max Maximum safe pressure P of the probe max The parameters are set to precisely adjust the height of the electric chuck assembly.

[0016] Furthermore, the pressure sensor is connected to the industrial control computer via a communication line. When the electric chuck assembly and the probe are in contact, the industrial control computer sends a query command to the pressure sensor to obtain the current pressure value. This pressure value is used for contact determination in step S1 and needle pressure comparison in step S3.

[0017] Furthermore, the step S3 described for P od The processing and calculation of height compensation includes the following operations: performing needle pressure value filtering, first performing amplitude limiting filtering, if the current P od Compared to the previous hour hand pressure value x n-1 The difference exceeds the limit, take x. n-1 As the effective needle pressure value; if the difference does not exceed the limit, take P. od As the effective needle pressure value; then perform smoothing filtering according to the formula. ; Calculate the smoothed needle pressure value, where N is the number of filtering windows; perform linear relationship fitting, taking n sample points within the effective range of needle pressure, and calculate the fitting coefficients k and b according to the formulas: ; ; In the formula, P is the pressure value and Z is the height value; the compensation amount is calculated and adjusted based on P. first The downward deviation value is ΔP min-od Upward deviation ΔP max-od and the iterative height adjustment amount ΔZ; if P od -P first <ΔP min-odIf the needle pressure is too low, the Z-axis adjustment amount ΔZ for the next chip is calculated as follows: ΔZ = (P od -P first If P*k+b; od -P first >ΔP max-od If the needle pressure is too high, the Z-axis adjustment amount ΔZ for the next chip is calculated as follows: ΔZ = (P od -P first )*k+b; if ΔP min-od <P od -P first <ΔP max-od If the pressure of the needle is within the allowable range, the Z-axis height of the next chip remains unchanged.

[0018] Furthermore, in step S2, when the electric chuck assembly and the probe are separated before each contact, the industrial control computer controls the pressure sensor to zero the sensor in the probe holder with pressure sensing to avoid test errors caused by sensor zero drift. The zeroed data is used for pressure reading in step S1 and filtering in step S3.

[0019] Furthermore, in step S2, if the actual needle pressure value received by the industrial control computer from the pressure sensor remains 0, and the full-stage positioning in step S1 has not yet detected P>P... th If the contact height is not found, the control software on the industrial control computer will issue an alarm and prompt the user to repeat step S1 to find the contact height again.

[0020] The contact-type wafer thickness compensation detection system for the probe station used to implement the above method includes: The wafer is the object to be tested. Electric chuck assembly, used to carry and drive wafers in three-dimensional and rotary motion; A probe holder with pressure sensing is used to mount test probes and has a built-in pressure sensor to detect needle pressure; A pressure sensor is used to receive signals from a probe holder with a pressure sensor and convert them into a specific pressure value. The industrial control computer, as the control core of the entire system, runs the control software; The motion controller is used to receive instructions from the industrial control computer and control the movement of the electric chuck assembly; The pressure sensor signal line connects the probe holder with pressure sensing and the pressure gauge to transmit the raw pressure signal. The pressure sensor communication cable connects the pressure sensor and the industrial control computer to enable the uploading of pressure data and the issuance of control commands. The motion controller communication cable connects the industrial control computer and the motion controller, and is used to transmit motion control commands. The motion control drive line connects the motion controller and the electric chuck assembly, converting electrical signals into driving force to achieve precise movement of the electric chuck assembly.

[0021] The advantages of this invention are: The first satellite was positioned accurately: through a three-order algorithm of large step size approximation, binary compression and ultra-small step size positioning, combined with multi-pressure threshold protection, the initial contact height positioning accuracy can reach the level of 0.1μm. High compensation accuracy: The needle pressure interference is processed by introducing a limiting and smoothing dual filter, and a quantitative relationship between pressure and height is established through linear fitting. The compensation error can be controlled within ±0.1μm. High security: Set P max P pre Dual pressure protection and abnormal shutdown mechanism, suitable for complex testing environments; Efficiency balance: Iterative compensation and testing process are seamlessly integrated without adding extra testing time, and it is suitable for wafer testing of different thicknesses. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the contact-type wafer thickness compensation detection system of the probe station.

[0023] In the diagram: 1. Wafer, 2. Electric chuck assembly, 3. Probe holder with pressure sensing, 4. Pressure gauge, 5. Industrial control computer, 6. Motion controller. Detailed Implementation

[0024] Example 1: The contact-type wafer thickness compensation method of the probe station according to the present invention includes the following steps: Preparation stage: Place the wafer to be tested on the electric chuck assembly and secure it; start the control software on the industrial control computer and input the basic parameters and protection parameters: Z start =5mm, Z max =8mm, P th =0.1g, P max =10g, P pre =8g, Step large =100μm, Step small =1μm, Step ultra =0.1μm; Set filter window N=3, ΔP min-od =-0.3g、ΔP max-od =+0.3g; The system self-checks components such as the pressure sensor and motion controller to ensure normal communication of all signal lines.

[0025] S1. Initial height reference setting: S11. Large Step Length Rapid Approach: The industrial control computer sends instructions to the motion controller, driving the electric chuck assembly to move upwards at 100μm / step, starting from 5mm; after each movement, the pressure sensor reads the pressure value and transmits it to the industrial control computer; after 24 steps, the height of the electric chuck assembly is 5mm + 24 × 0.1mm = 7.4mm, reaching Z. max =8mm 92.5%, at this time the pressure P=0, enter S12; S12. Bisection Interval Compression: Current Z n =7.4mm, Z max =8mm, interval [7.4mm, 8mm]; calculate Z mid =(7.4+8) / 2=7.7mm, read P after moving. mid =0.05g≤P th Update Z n =7.7mm; New interval [7.7mm, 8mm], calculate Z mid =7.85mm, P after movement mid =0.08g≤P th Update Z n =7.85mm; repeat the operation to the interval [7.92mm, 7.93mm], and calculate Z. mid =7.925mm, P after movement mid =0.12g>Pth and ≤Ppre, update the upper limit of the interval to 7.925mm; continue calculating Z. mid =7.9225mm, P after movement mid =0.11g, interval [7.92mm, 7.9225mm]; until Z is calculated. mid =7.9205mm, interval difference 0.5μm≤1μm, enter S13; S13. Ultra-small step size fine positioning: From Z... n Starting at 7.92mm, move upwards at 0.1μm / step; after 5 steps, the height is 7.92mm + 5 × 0.1μm = 7.9205mm, and read P = 0.105g, satisfying P. th <P≤P pre Record the initial contact height Z. c =7.9205mm; Testing the first chip, reading P first =5g.

[0026] S2. Dynamic needle pressure detection & S3. Iterative height compensation & S4. Loop execution: Test of the first chip under test: drive the wafer to the target position, control the electric chuck assembly to rise to Zc+20μm=7.9405mm, and read Pod=4.6g during the test; Compensation calculation: Perform amplitude limiting filtering, P od =4.6g and P first The difference of 0.4g from 5g exceeds the limit; take P. first =5g is taken as the effective needle pressure value; after smoothing filtering, the smoothed needle pressure value = (5+5+4.6) / 3≈4.87g; take n=5 sample points (P1=0.1g, Z1=7.9205mm; P2=2g, Z2=7.9245mm; P3=3g, Z3=7.9265mm; P4=4g, Z4=7.9285mm; P5=5g, Z5=7.9305mm). Calculate k: Numerator: 5×(0.1×7.9205+2×7.9245+3×7.9265+4×7.9285+5×7.9305)-(0.1+2+3+4+5)×(7.9205+7.9245+7.9265+7.9285+7.9305)≈5×79.272-14.1×39.6305≈396.36-558.79≈-162.43; Denominator: 5×(0.01+4+9+16+25)-(14.1)²≈5×54.01-198.81≈270.05-198.81≈71.24; k≈-162.43 / 71.24≈-2.28mm / g; b=(39.6305-(-2.28)×14.1) / 5≈(39.6305+32.148) / 5≈71.7785 / 5≈14.3557mm; P od -P first =4.6-5=-0.4g<ΔP min-od The Z-axis adjustment amount ΔZ for the next chip is (-0.4)×(-2.28)+14.3557≈0.912+14.3557≈15.2677mm (where ΔZ is the absolute height, which needs to be corrected in conjunction with the initial contact height; the actual adjustment amount is 15.2677-7.9405≈7.3272μm), and the new height is 7.9405+0.0073≈7.9478mm. Test on the second chip under test: Move to the target position, rise to 7.9478mm, and read P. od =4.9g, P od -P first =-0.1g at ΔP min-od ~ΔP max-od The Z-axis height remains constant between these points. Cyclic execution: Subsequent chips are dynamically adjusted according to the above logic until the entire wafer test is completed, with no pressure exceeding limits or contact abnormalities.

[0027] Example 2, as Figure 1 As shown, the contact-type wafer thickness compensation detection system for the probe station used to implement the method of the present invention consists of the following parts: Wafer 1: The semiconductor wafer to be tested, on which numerous chips are distributed.

[0028] Electric chuck assembly 2: As a wafer carrier platform, it can translate in the X, Y, and Z directions and rotate around the Z axis (θ) under the drive of motion controller 6 to accurately position any chip on the wafer.

[0029] The pressure-sensing probe holder 3 is mounted on the probe arm of the probe stage, with the test probe installed at its lower end. It integrates a pressure sensor centered on a strain gauge. When the probe contacts the surface of wafer 1, the resulting minute pressure causes the strain gauge to deform, converting the mechanical signal into a measurable electrical signal (such as voltage change). Its internal lever structure amplifies the minute deformation, improving detection sensitivity and calibrating the relationship between voltage and probe depth.

[0030] Pressure sensor 4: Connected to the probe holder 3 with pressure sensing via a pressure sensor signal line. It receives the raw analog electrical signal from the probe holder, amplifies, filters, and performs A / D conversion to calculate the precise pressure value (unit: grams or Newtons).

[0031] Industrial control computer 5: The "brain" of the entire system, running the control software that implements the method of this invention. It communicates with pressure sensor 4 via the pressure sensor communication line to query and receive real-time pressure data; at the same time, it sends motion commands and height setpoints to motion controller 6 via the motion controller communication line.

[0032] Motion controller 6: The "actuator" of industrial control computer 5. It receives instructions from industrial control computer 5, parses them into precise motor control signals, and sends them to each motor in electric chuck assembly 2 via motion control drive lines to control them to complete the corresponding movements.

[0033] Pressure sensor signal line: used to connect the probe holder 3 with pressure sensing and the pressure sensor 4 to transmit the raw analog pressure signal.

[0034] Pressure sensor communication line: used to connect the pressure sensor 4 and the industrial control computer 5. It is usually a serial communication line such as RS232 to realize bidirectional transmission of data and commands.

[0035] Motion controller communication cable: used to connect the industrial control computer 5 and the motion controller 6. It is usually an Ethernet or dedicated bus for high-speed and reliable transmission of complex motion control commands.

[0036] Motion control drive line: used to connect motion controller 6 and electric chuck assembly 2, transmit motor drive signals to the motors of each axis, and directly drive the mechanical structure to move.

[0037] All of the above components work together to achieve dynamic, real-time compensation for wafer thickness unevenness, ensuring that each chip can be tested with optimal needle pressure.

[0038] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A contact-type wafer thickness compensation method using a probe station, characterized in that, Includes the following steps: S1. Initial Height Reference Setting: After the probe station aligns the wafer, the basic parameters and protection parameters are set first. These parameters include the safe starting height Z. start Theoretical height of wafer Z max Contact detection threshold P th Maximum safe pressure P of the probe max Pressure warning threshold P pre and step size parameters, pressure warning threshold P pre For P max 0.8 times, step size parameters include large step size. large Small step size small Ultra-small step size ultra The electric chuck assembly is then driven to rise in stages to determine the contact height. S11. Large step size rapid approximation: Control the electric chuck assembly from Z... start Begin with Step large Move upwards, and read the sensor pressure P after each movement; If P=0, continue moving until Z is reached. max If 80% of the time is reached, proceed to S12; if P>0 during the rapid approach with a large step size, it indicates abnormal contact and proceed to S13. S12. Bisection Interval Compression: Using the current position Z... n For the lower limit, Z max Construct an interval [Z] for the upper limit n Z max ] Calculate the intermediate point Z mid =(Z n +Z max ) / 2, control the electric chuck assembly to move to Z mid And read the pressure P mid If P mid >P pre or P mid ≤P pre And P mid >P th Enter S13; if P mid ≤P th Update Z n =Z mid Repeat this step until the interval difference Z is reached. max -Z n ≤Step small Enter S13; S13. Ultra-small step size fine positioning: from the current Z... n Begin with Step ultra Move the electric chuck assembly upwards and read P in real time; if P th <P≤P pre Record the current height as the initial contact height; if P pre <P≤P max Record the initial contact height and trigger a high pressure warning; if P > P max Control the electric chuck assembly to move downwards by 2 × Step large Disengage and stop the machine; If moved to Z max Still no P>P th Alarm and shutdown; S2. Dynamic Needle Pressure Detection: When performing electrical performance testing on a chip under test (DUT) on a wafer, the probe station uses mechanical feedback to detect the actual needle pressure value P when the probe contacts the DUT in real time. od ; S3. Iterative Height Compensation: After the test is completed, the industrial control computer performs P... od Process and compare with the first chip pin pressure value P first The comparison is performed, the height compensation is calculated, and a command is sent to the motion controller to adjust the contact height setting value of the next chip under test. S4. Repeat steps S2 and S3 to test all chips on the wafer, achieving dynamic compensation of the entire wafer thickness based on mechanical feedback.

2. The contact-type wafer thickness compensation method for the probe station according to claim 1, characterized in that, Before step S1, the thickness of different regions of the wafer is detected by multi-point detection function to obtain the overall morphology information of the wafer and provide a reference for setting the initial contact height.

3. The contact-type wafer thickness compensation method for the probe station according to claim 2, characterized in that, The multi-point detection function can select to detect 9, 16, or 25 points. These detection points are evenly distributed in a matrix on the wafer surface and are completed sequentially by probes on a probe holder with pressure sensing.

4. The contact-type wafer thickness compensation method for the probe station according to claim 3, characterized in that, The mechanical feedback is achieved by a needle pressure detection and feedback component, which includes a probe holder with pressure sensing and a pressure gauge; the probe holder with pressure sensing uses a strain gauge as the sensing element to convert the deformation signal when the probe contacts the target into a pressure signal; the contact determination threshold P... th The default value is 0.1g, and the Step parameter is... large For 100μm, Step small 1μm, Step ultra It is 0.1μm.

5. The contact-type wafer thickness compensation method for the probe station according to claim 4, characterized in that, The pressure-sensing probe holder uses a lever design to calibrate the conversion relationship between analog voltage and puncture depth. This conversion relationship is written into the control software of the industrial control computer to coordinate with the theoretical height Z of the wafer. max Maximum safe pressure P of the probe max The parameters are set to precisely adjust the height of the electric chuck assembly.

6. The contact-type wafer thickness compensation method for the probe station according to claim 5, characterized in that, The pressure sensor is connected to the industrial control computer via a communication line. When the electric chuck assembly and the probe are in contact, the industrial control computer sends a query command to the pressure sensor to obtain the current pressure value. This pressure value is used for contact determination in step S1 and needle pressure comparison in step S3.

7. The contact-type wafer thickness compensation method for the probe station according to claim 6, characterized in that, The step S3 described for P od The processing and calculation of height compensation includes the following operations: performing needle pressure value filtering, first performing amplitude limiting filtering, if the current P od Compared to the previous hour hand pressure value x n-1 The difference exceeds the limit, take x. n-1 As the effective needle pressure value; if the difference does not exceed the limit, take P. od As the effective needle pressure value; then perform smoothing filtering according to the formula. ； Calculate the smoothed needle pressure value, where N is the number of filtering windows; perform linear relationship fitting, taking n sample points within the effective range of needle pressure, and calculate the fitting coefficients k and b according to the formulas: ； ； In the formula, P is the pressure value and Z is the height value; the compensation amount is calculated and adjusted based on P. first The downward deviation value is ΔP min-od Upward deviation ΔP max-od and the iterative height adjustment amount ΔZ; if P od -P first <ΔP min-od If the needle pressure is too low, the Z-axis adjustment amount ΔZ for the next chip is calculated as follows: ΔZ = (P od -P first If P*k+b; od -P first >ΔP max-od If the needle pressure is too high, the Z-axis adjustment amount ΔZ for the next chip is calculated as follows: ΔZ = (P od -P first If ΔP min-od <P od -P first <ΔP max-od If the pressure of the needle is within the allowable range, the Z-axis height of the next chip remains unchanged.

8. The contact-type wafer thickness compensation method of the probe station according to claim 7, characterized in that, In step S2, the industrial control computer controls the pressure sensor to zero the sensor in the probe holder with pressure sensing when the electric chuck assembly is separated from the probe each time it makes contact, so as to avoid the test error caused by the zero drift of the sensor. The zeroed data is used for pressure reading in step S1 and filtering in step S3.

9. The contact-type wafer thickness compensation method for the probe station according to claim 8, characterized in that, In step S2, if the actual needle pressure value received by the industrial control computer from the pressure sensor remains 0, and the full-stage positioning in step S1 has not yet detected P>P, th If the contact height is not found, the control software on the industrial control computer will issue an alarm and prompt the user to repeat step S1 to find the contact height again.

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