Probe pressure measurement device and method for four-point probe tester

Abstract

The application belongs to the field of automatic testing, and discloses a probe pressure measuring device and method for a four-probe tester, which comprises a carrier table, a control module and a probe testing module, wherein the probe testing module comprises a probe, a chip resistor and a cantilever frame, the probe and the chip resistor are arranged side by side at the lower end of the cantilever frame and above a to-be-tested piece; the control module is used for controlling the probe to apply pressure to the to-be-tested piece; the carrier table is used for placing the to-be-tested piece, and a piezoelectric sensor is further arranged on the carrier table, and the piezoelectric sensor is used for measuring the pressure applied by the probe to the to-be-tested piece; in working, the probe presses the to-be-tested piece with different forces, and each pressing can drive the cantilever frame to warp and deform to different degrees, and make the chip resistor also deform to different degrees, and further make the resistance of the chip resistor change differently.

Description

Technical Field

[0001] This invention belongs to the field of automatic testing, and more specifically, relates to a probe pressure measuring device and method for a four-probe tester. Background Technology

[0002] Wafer testing involves applying probe pressure to each die on a wafer, testing its electrical characteristics by having probes contact the contacts within the die. During wafer testing, the wafer is placed on a stage in the wafer testing system opposite the wafer test probes and aligned with a very thin probe tester. The probes contact each contact on the wafer, and the tester, driven by a power supply, performs the tests and records the results.

[0003] Because of its simple principle, ability to eliminate the influence of contact resistance, and high testing accuracy, the four-probe technique has become one of the most widely used process monitoring methods in semiconductor manufacturing. It is widely used in testing the thin-film resistance of silicon substrates, epitaxial wafers, diffused wafers, ion-implanted wafers, getter wafers, metal films, and coatings. Resistance testing controls the quality of various processes in thin-film samples, including substrate, epitaxy, diffusion, ion implantation, gettering, and annealing. The conventional four-probe method involves pressing four probes arranged in a straight line perpendicularly onto the surface of the sample under test with a certain pressure, measuring the generated voltage, and calculating the resistivity and resistance of the sample using appropriate formulas depending on the measurement method and sample size. However, this measurement technique has a large measurement error, and the resistance values ​​obtained from multiple calculations are not accurate. Summary of the Invention

[0004] In view of the shortcomings of the prior art, the purpose of this invention is to provide a probe pressure measuring device and method for a four-probe tester.

[0005] To achieve the above objectives, the present invention provides a probe pressure measuring device for a four-probe tester. The device includes a stage, a control module, and a probe testing module. The probe testing module includes probes, a surface mount resistor, and a cantilever frame. The probes and the surface mount resistor are arranged side-by-side at the lower end of the cantilever frame and positioned above the workpiece under test. The control module controls the probes to apply pressure to the workpiece under test. The stage is used to place the workpiece under test and is also equipped with a piezoelectric sensor. The piezoelectric sensor measures the pressure applied by the probes to the workpiece under test. During operation, the probes press the workpiece under test with different forces. Each press causes the cantilever frame to warp and deform to varying degrees, resulting in different degrees of deformation of the surface mount resistor and consequently, different changes in the resistance value of the surface mount resistor.

[0006] Furthermore, the cantilever frame includes a vertically arranged support frame and a horizontally arranged probe clamp. One end of the probe clamp is connected to the support frame, and the other end is used to clamp the probe and position the probe above the test piece. The patch resistor is attached to the probe clamp, and its resistance value can change with the deformation of the probe clamp.

[0007] Furthermore, the distance between the patch resistor and the connection end of the probe holder and the support frame is equal to the distance between the patch resistor and the clamping end of the probe holder; preferably, the stage can rotate 360°; more preferably, the probe holder can move back and forth, up and down and left and right on the support frame.

[0008] Furthermore, the area of ​​the patch resistor is equal to the surface area of ​​the probe holder. arrive

[0009] According to another aspect of the present invention, a method for measuring probe pressure in a four-probe tester is also disclosed, characterized in that the method can be implemented on a probe pressure measuring device for a four-probe tester as described above, the method comprising:

[0010] S1. The control module controls the probe to press the test piece multiple times at a preset pressure, and records the probe pressure value measured by the piezoelectric sensor and the change in resistance value measured by the patch resistor at each press.

[0011] S2. The control module establishes a comparison relationship between the probe pressure value measured each time and the changing resistance value, and obtains a pressure resistance value comparison table based on the comparison relationship;

[0012] S3. The control module controls the probe to press the wafer to be tested according to the preset pressure and reads the resistance value of the chip resistor. Based on the pressure-resistance value lookup table, the actual pressure corresponding to the resistance value is obtained.

[0013] S4. Determine whether the actual pressure deviates from the preset pressure: if it deviates, adjust the preset pressure and repeat step S3; if it does not deviate, end the measurement.

[0014] Furthermore, the preset pressure is the pressure value corresponding to the measurement range of the piezoelectric sensor after dividing it equally according to the number of presses; preferably, the number of presses is 6-8 times; more preferably, if the probe pressure value measured after any press exceeds the maximum measurement value of the piezoelectric sensor, the measurement is stopped.

[0015] Furthermore, in step S1, the pressure is pressed in a sequentially increasing order according to the preset pressure, and the probe pressure value and the change in resistance value of the patch resistor are measured for each press.

[0016] Further, in step S1, the pressure is pressed in an increasing order according to the preset pressure, and the actual pressure value and the change in resistance of the chip resistor corresponding to each preset pressure are measured; then the pressure is pressed in a decreasing order according to the preset pressure, and the actual pressure value and the change in resistance of the chip resistor corresponding to each preset pressure are measured; then the average of the two measured pressure values ​​corresponding to each preset pressure is taken as the probe pressure value, and the average of the two change in resistance corresponding to each preset pressure is taken as the change in resistance value.

[0017] Furthermore, in step S2, a smooth curve is fitted to the probe pressure value and the changed resistance value, with the probe pressure value on the x-axis and the changed resistance value on the y-axis, thereby establishing a comparison relationship.

[0018] Furthermore, if the deviation between the actual pressure and the preset pressure value is within 2% of the preset pressure value, it is considered as not deviating.

[0019] Compared with the prior art, the above technical solutions conceived by this invention have the following main advantages:

[0020] 1. The probe pressure measuring device of the present invention includes a stage, a control module, and a probe testing module. The probe testing module includes a probe, a surface mount resistor, and a cantilever frame. The probe and the surface mount resistor are arranged side by side at the lower end of the cantilever frame and above the workpiece under test. The control module is used to control the probe to apply pressure to the workpiece under test. The stage is used to place the workpiece under test and is also equipped with a piezoelectric sensor. The piezoelectric sensor is used to measure the pressure applied by the probe to the workpiece under test. During measurement, the probe presses the workpiece under test with a preset pressure. Each press causes the cantilever frame to warp and deform to different degrees, and causes the surface mount resistor arranged side by side to deform to different degrees, thereby causing the resistance value of the surface mount resistor to change differently, and the change in resistance value can be recorded intuitively.

[0021] 2. The probe pressure measuring device of the present invention uses a patch resistor with an area not greater than 2 / 3 of the effective surface area of ​​the probe holder to ensure sufficient operating space when the patch resistor sensor is installed and pasted. Its area is not less than 1 / 2 of the effective area of ​​the probe holder to ensure the sensitivity of the patch sensor during operation and to ensure the accuracy of the measured resistance change value. Furthermore, the stage can rotate 360°, and the probe holder can move in the forward, backward, left, right, and up / down directions. After each measurement, the positions of the probe holder and the stage can be restored. Since the pasting position of the patch resistor remains unchanged, it helps to improve the measurement accuracy of the patch resistor, thereby improving the problems of large measurement errors and low accuracy in the prior art.

[0022] 3. The probe pressure measurement method of the present invention involves a control module controlling a probe to press the test piece multiple times at a preset pressure, and recording the probe pressure value measured by the piezoelectric sensor and the change in resistance measured by the chip resistor at each press. The control module establishes a correlation between the probe pressure value and the change in resistance at each press, and obtains a pressure-resistance value reference table based on the correlation to complete the calibration of the resistance value. During actual testing, the control module controls the probe to press the wafer under test at a preset pressure and reads the resistance value of the chip resistor. Based on the aforementioned calibrated pressure-resistance value reference table, the actual pressure value corresponding to the resistance value is obtained. Then, it is determined whether the actual pressure value deviates from the corresponding preset pressure value. If it deviates, the preset pressure is readjusted and the measurement is repeated; if it does not deviate, the measurement ends. Furthermore, in this invention, when the probe pressure value measured after any press exceeds the maximum measurement value of the piezoelectric sensor, the measurement is stopped, which improves measurement efficiency.

[0023] 4. The probe pressure measurement method of the present invention, when pressing the wafer, first presses in a preset pressure incrementing order, and measures the actual pressure and the change in resistance of the chip resistor corresponding to each preset pressure; then presses in a preset pressure decrementing order, and measures the actual pressure and the change in resistance of the chip resistor corresponding to each preset pressure; after the two rounds of measurement, the average of the two measured pressure values ​​corresponding to each preset pressure is taken as the probe pressure value, and the average of the two change in resistance corresponding to each preset pressure is taken as the change in resistance value. Then, a smooth curve is fitted to the probe pressure value and the change in resistance value, with the x-axis representing the probe pressure value and the y-axis representing the change in resistance, thereby establishing a more accurate numerical correlation. This minimizes measurement errors at each measurement node, and a deviation of less than 2% of the preset pressure value from the actual pressure value is considered acceptable. Since the difference between the actual pressure value and the preset pressure value corresponding to the resistance value measured by the aforementioned method is very small, as long as the error is within 2%, the measurement accuracy requirement is met. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the probe pressure measuring device structure disclosed in an embodiment of the present invention;

[0025] Figure 2 This is a schematic diagram of the pressure resistance calibration method disclosed in the embodiments of the present invention;

[0026] Figure 3 This is a schematic diagram of a probe pressure measurement method disclosed in an embodiment of the present invention.

[0027] In the figure: 1-support frame, 2-probe, 3-probe clamp, 4-surface resistor, 5-stage, 6-test device, 7-piezoelectric sensor, 8-guide rail. Detailed Implementation

[0028] 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.

[0029] Example 1

[0030] like Figure 1 As shown in this embodiment, a probe pressure measuring device for a four-probe tester is provided. The device includes a stage 5, an external control module, and a probe testing module. The probe testing module includes a probe 2, a patch resistor 4, and a cantilever frame. The probe 22 and the patch resistor 4 are arranged side by side at the lower end of the cantilever frame and are located above the workpiece 6 under test. The control module is used to control the probe 2 to apply pressure to the workpiece 6 under test. The stage 5 is used to place the workpiece 6 under test, and a piezoelectric sensor 7 is also provided on it. The piezoelectric sensor 7 is used to measure the pressure applied by the probe 2 to the workpiece 6 under test. During operation, the probe 2 presses the workpiece 6 under test with different forces. Each press causes the cantilever frame to warp and deform to different degrees, and the patch resistor 4 also deforms to different degrees, thereby causing the resistance value of the patch resistor 4 to change differently.

[0031] In a preferred embodiment, the cantilever includes a vertically arranged support frame 1 and a horizontally arranged probe clamp 3. One end of the probe clamp 3 is connected to the support frame 1, and the other end is used to clamp the probe 2 and position the probe 2 above the workpiece 6 to be tested. The patch resistor 4 is attached to the probe clamp 3, and its resistance value can change with the deformation of the probe clamp 3.

[0032] In a preferred embodiment, the distance between the connection end of the chip resistor 4 and the probe holder 3 and the support frame 1 is equal to the distance between the clamping end of the chip resistor 4 and the probe holder 3, which can ensure the working sensitivity of the chip resistor.

[0033] In a preferred embodiment, the stage 5 can rotate 360°. After pressing and measuring, its position can be adjusted by the control module to restore the relative position between the test piece 6 and the probe. The probe clamp 3 can move up and down and left and right on the guide rail 8 under the drive of the support frame 1. When a guide rail along the front and back direction is added to the guide rail 8, the probe clamp 3 can also move back and forth.

[0034] Furthermore, the area of ​​the surface mount resistor 4 is equal to the surface area of ​​the probe holder 3. arrive It can ensure that there is sufficient installation space for the patch sensor and that it can be completely glued, while also ensuring its sensitivity during operation and ensuring that the measured resistance change value is accurate.

[0035] The aforementioned patch resistor sensor is mounted on the probe holder using strong adhesive (epoxy resin) to measure the real-time pressure of the probe. A piezoelectric sensor provides a standard pressure measurement value, which is transmitted to the patch resistor sensor via a wire. A conditioning circuit is installed between the piezoelectric and patch resistor sensors to supply power and extract signals. The pressure generated by the probe pressure measuring device is transmitted to the probe holder, causing it to warp and deform. This deformation of the patch resistor alters its resistance value, which is then converted into a voltage value by the conditioning circuit. The piezoelectric sensor accurately measures the pressure applied by the probe, and the resistance change caused by the deformation of the patch resistor. This data is processed by the control module to achieve numerical mapping, thus completing the pressure-resistance calibration.

[0036] Example 2

[0037] like Figure 1 As shown, this embodiment provides a probe pressure measuring device for a four-probe tester. The device includes a stage 5, an external control module, probes 2, a patch resistor 4, and a cantilever frame. Probes 22 and patch resistor 4 are fixed side by side on the probe clamp 3 at the lower end of the cantilever frame and are located directly above the workpiece 6 to be tested. The patch resistor 4 is a patch resistor sensor with a sensitivity coefficient of 2. The control module is used to control probes 2 to apply pressure to the workpiece 6 to be tested according to a preset pressure. A piezoelectric sensor 7 is also provided on the stage 5 to measure the pressure applied by probes 2 to the workpiece 6 to be tested. During operation, probes 2 press the workpiece 6 to be tested with different forces. Each press causes the cantilever frame to warp and deform to different degrees, and causes the patch resistor 4 to deform to different degrees, thereby causing the resistance value of the patch resistor 4 to change differently.

[0038] In a preferred embodiment, the cantilever includes a vertically arranged support frame 1 and a horizontally arranged probe clamp 3. One end of the probe clamp 3 is connected to the support frame 1, and the other end is used to clamp the probe 2 and position the probe 2 above the workpiece 6 to be tested. The patch resistor 4 is attached to the probe clamp 3, and its resistance value can change with the deformation of the probe clamp 3.

[0039] In a preferred embodiment, the distance between the connection end of the chip resistor 4 and the probe holder 3 and the support frame 1 is equal to the distance between the clamping end of the chip resistor 4 and the probe holder 3, which can ensure the working sensitivity of the chip resistor.

[0040] In a preferred embodiment, the stage 5 can rotate 360°. After pressing and measuring, its position can be adjusted by the control module to restore the relative position between the test piece 6 and the probe 2. The probe clamp 3 can move up and down and left and right on the guide rail 8 under the drive of the support frame 1. When a guide rail along the front and back direction is added to the guide rail 8, the support frame 1 has three movement paths, which in turn drives the probe clamp 3 to move along the three paths.

[0041] In a preferred embodiment, the area of ​​the patch resistor 4 is equal to the surface area on which the probe holder 3 can be effectively attached. (That is, excluding the surface area occupied by probe fixture 2), it can ensure that the patch sensor is completely adhered, and can also ensure its sensitivity during operation, so as to ensure the accuracy of the measured change resistance value.

[0042] Example 3

[0043] According to another aspect of the invention, a method for measuring probe pressure in a four-probe tester is also disclosed, which can be implemented on a probe pressure measuring device for a four-probe tester as described above, such as... Figure 2-3 As shown, this measurement method includes:

[0044] S1. The control module is equipped with a probe pressure measurement program for a four-probe tester. When the program is started, it can control the probe 2 to press the test piece 6 multiple times at a preset pressure, and record the pressure value of the probe 2 measured by the piezoelectric sensor 7 and the change in resistance value measured by the patch resistor 4 at each press.

[0045] The preset pressure is the pressure value corresponding to the measurement range of the piezoelectric sensor after being evenly divided according to the number of presses, that is, multiple preset pressures form an arithmetic sequence; the number of probe presses is 6-8 times, and in this embodiment, it is preferred to press 6 times, so as to obtain enough data and save measurement time; during the measurement process, it is not necessary to press all the preset pressures to test. As long as the probe pressure value measured after any press exceeds the maximum measurement value of the piezoelectric sensor, the measurement is stopped.

[0046] S2. The control module establishes a comparison relationship between the probe pressure value measured each time and the changing resistance value, and obtains a pressure-resistance comparison table based on the comparison relationship;

[0047] A smooth curve is fitted to the probe pressure value and the changing resistance value, with the probe pressure value on the x-axis and the changing resistance value on the y-axis, to establish a comparison relationship. An approximate function can be obtained using fitting interpolation methods in conventional numerical analysis software such as MATLAB, and a smooth transition curve of the approximate function can be obtained. Based on this smooth transition curve, a pressure-resistance comparison table consisting of multiple sets of pressure-resistance comparison arrays is obtained.

[0048] Table 1. Pressure Resistance Value Comparison Table

[0049]

[0050]

[0051] S3. The control module controls probe 2 to press the wafer to be tested according to the preset pressure and reads the resistance value of chip resistor 4. Based on the pressure-resistance value reference array, the module obtains the actual pressure corresponding to the read resistance value.

[0052] S4. Determine whether the actual pressure deviates from the preset pressure. If the deviation between the actual pressure and the preset pressure is within 2% of the preset pressure, it is considered not to deviate. If it deviates, adjust the preset pressure and repeat step S3. If it does not deviate, end the measurement.

[0053] In this embodiment, a preset pressure of 5N is applied to the wafer under test, and the resistance change ΔR of the chip resistor is read as 31.5Ω. Table 1 shows that the corresponding ΔR change for 5N pressure is 32Ω, indicating a deviation of 0.5Ω. The calculated deviation ratio is 1.6%. Since the deviation ratio is less than 2%, the test can be stopped, and 5N is the true pressure of the probe. In other embodiments, if the measured deviation ratio is greater than 2%, the preset pressure for the next test needs to be readjusted until the difference between the true pressure and the preset pressure corresponding to the resistance change ΔR in Table 1 does not exceed 2% of the preset pressure. This is when the true pressure of the probe is obtained.

[0054] In a preferred embodiment, in step S1, the pressure is pressed in a preset order of increasing pressure, and the probe pressure value and the change in resistance of the patch resistor 4 are measured for each press.

[0055] In a preferred embodiment, in step S1, the pressure is pressed in an order of increasing preset pressure, and the actual pressure and the change in resistance of the patch resistor 4 corresponding to each preset pressure are measured; then the pressure is pressed in an order of decreasing preset pressure, and the actual pressure and the change in resistance of the patch resistor 4 corresponding to each preset pressure are measured; then the average of the two measured pressure values ​​corresponding to each preset pressure is taken as the probe pressure value, and the average of the two change in resistance corresponding to each preset pressure is taken as the change in resistance value. This makes the measured data more accurate.

[0056] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A probe pressure measuring device for a four-probe tester, characterized in that, The device includes a stage, a control module, and a probe testing module. The probe testing module includes a probe, a surface mount resistor, and a cantilever. The probe and the surface mount resistor are arranged side-by-side at the lower end of the cantilever and above the workpiece under test (DUT). The control module controls the pressure applied to the DUT by the probe. The stage holds the DUT and is equipped with a piezoelectric sensor to measure the pressure applied by the probe. During operation, the probe presses the DUT with varying forces, and each press causes different forces to be applied to the cantilever. The warping deformation causes varying degrees of deformation in the chip resistor, resulting in different changes in its resistance value. The control module controls the probe to press the test piece multiple times with different preset pressures, recording the probe pressure value measured by the piezoelectric sensor and the change in resistance value measured by the chip resistor each time, establishing a pressure-resistance comparison table. During actual testing, the actual pressure is obtained by looking up the table based on the resistance value of the chip resistor. When the deviation between the actual pressure and the preset pressure exceeds a preset threshold, the preset pressure is adjusted and the measurement is repeated to achieve closed-loop calibration.

2. The probe pressure measuring device for a four-probe tester as described in claim 1, characterized in that, The cantilever frame includes a vertically arranged support frame and a horizontally arranged probe clamp. One end of the probe clamp is connected to the support frame, and the other end is used to clamp the probe and position the probe above the test piece. The patch resistor is attached to the probe clamp, and its resistance value can change with the deformation of the probe clamp.

3. The probe pressure measuring device for a four-probe tester as described in claim 2, characterized in that, The distance between the patch resistor and the connection end of the probe holder and the support frame is equal to the distance between the patch resistor and the clamping end of the probe holder.

4. A probe pressure measuring device for a four-probe tester as described in claim 2 or 3, characterized in that, The area of ​​the patch resistor is equal to the surface area of ​​the probe holder. arrive .

5. A method for measuring probe pressure in a four-probe tester, characterized in that, This measurement method can be implemented on a probe pressure measuring device for a four-probe tester as described in any one of claims 1-4, the measurement method comprising: S1. The control module controls the probe to press the test piece multiple times at a preset pressure, and records the probe pressure value measured by the piezoelectric sensor and the change in resistance value measured by the patch resistor at each press. S2. The control module establishes a comparison relationship between the probe pressure value measured each time and the changing resistance value, and obtains a pressure resistance value comparison table based on the comparison relationship; S3. The control module controls the probe to press the wafer to be tested according to the preset pressure and reads the resistance value of the chip resistor. Based on the pressure-resistance value lookup table, the actual pressure corresponding to the resistance value is obtained. S4. Determine whether the actual pressure deviates from the preset pressure: if it deviates, adjust the preset pressure and repeat step S3; if it does not deviate, end the measurement.

6. The probe pressure measurement method for a four-probe tester as described in claim 5, characterized in that, The preset pressure is the pressure value corresponding to the measurement range of the piezoelectric sensor after dividing it equally according to the number of presses.

7. The probe pressure measurement method for a four-probe tester as described in claim 5, characterized in that, In step S1, the pressure is pressed in a sequentially increasing order according to the preset pressure, and the probe pressure value and the change resistance value are measured for each press.

8. The probe pressure measurement method for a four-probe tester as described in claim 5, characterized in that, In step S1, the pressure is pressed in an increasing order according to the preset pressure, and the actual pressure value and the change in resistance of the chip resistor corresponding to each preset pressure are measured; then the pressure is pressed in a decreasing order according to the preset pressure, and the actual pressure value and the change in resistance of the chip resistor corresponding to each preset pressure are measured; then the average of the two actual pressure values ​​corresponding to each preset pressure is taken as the probe pressure value, and the average of the two change in resistance corresponding to each preset pressure is taken as the change in resistance value.

9. A probe pressure measurement method for a four-probe tester as described in any one of claims 5-8, characterized in that, In step S2, a smooth curve is fitted to the probe pressure value and the changed resistance value, with the probe pressure value on the x-axis and the changed resistance value on the y-axis, thereby establishing a correlation between the probe pressure value and the changed resistance value.

10. A probe pressure measurement method for a four-probe tester as described in claim 5, characterized in that, The deviation between the actual pressure and the preset pressure is considered to be within 2% of the preset pressure when it is considered not to have deviated.

Images