A non-contact resistivity measurement method and system

Abstract

The present invention discloses a non-contact resistivity measurement method and system, belonging to the technical field of resistivity measurement. In this solution, the eddy current method is used to measure the resistivity of a standard sample for different time lengths. Curve fitting is performed based on the measurement duration and the resistivity measurement result data to obtain the relationship curve function P = C(T) between the measurement duration T and the resistivity measurement result P. The inverse function T = D(P) of P = C(T) is solved, and C(T) and D(P) are used to correct the resistivity measurement result of the specimen. By adopting the solution of the present invention, it is not easy to cause damage to the product surface, significantly reduces the influence of the heat generated by the eddy current effect on the resistivity, reduces the measurement error of the resistivity, improves the measurement accuracy of the resistivity, and reduces the misjudgment rate of the product quality caused by the temperature rise due to the eddy current effect.

Description

Technical Field

[0001] The present invention relates to the technical field of resistivity measurement, and particularly to a non-contact resistivity measurement method and system. Background Art

[0002] In the existing background of semiconductor resistivity measurement technology, it is mainly divided into two major technical paths: contact measurement and non-contact measurement. Contact measurement technology, especially the classical four-probe method, has been widely studied and applied. This method applies current to a semiconductor sample through four probes and measures the voltage drop to calculate the resistivity. However, this method faces several significant limitations: First, the testing process is time-consuming and is prone to causing physical damage to the fragile semiconductor sample during operation. Second, when dealing with samples with extremely small sizes or extremely low resistivities, the measurement accuracy will significantly decrease. In addition, the contact between the probe and the sample surface is easily affected by contamination, and the formation of an oxide layer will hinder good electrical contact, further increasing the measurement error and affecting the reliability of the test results.

[0003] Non-contact measurement technology, especially the eddy current method, provides an alternative solution to solve the above problems. The eddy current method estimates the resistivity according to the eddy current feedback amount by placing a detection coil carrying an alternating current near the conductor to be measured and using the principle of electromagnetic induction. This method is particularly suitable for non-destructive testing occasions and can avoid the damage risk caused by direct contact. However, since the eddy current effect generates heat, causing the sample temperature to rise, for those materials whose resistivity is sensitive to temperature, this temperature change will directly affect the measured value of the resistivity, thus introducing an additional error factor in the final measurement result and leading to misjudgment of the product quality. Summary of the Invention

[0004] The technical problem to be solved by the present invention is: aiming at the above-mentioned defects of the prior art, to provide a non-contact resistivity measurement method to improve the accuracy of resistivity measurement.

[0005] To achieve the above object, the present invention provides a non-contact resistivity measurement method, and the method includes the following steps:

[0006] Step S1, using the eddy current method to perform multiple resistivity measurements on a standard sample, where the measurement covers multiple measurement durations T of different lengths, and obtaining the standard sample resistivity measurement result P;

[0007] Step S2, performing curve fitting according to the measurement duration T and the standard sample resistivity measurement result P to obtain the relationship curve function P = C(T) between the measurement duration T and the standard sample resistivity measurement result P, and solving the inverse function T = D(P) of the curve function P = C(T);

[0008] Step S3: Measure the resistivity of the specimen using the eddy current method for a measurement duration of t to obtain the resistivity measurement result Q of the specimen;

[0009] Step S4: Correct the resistivity measurement result Q of the specimen according to the curve function P = C(T) and the inverse function T = D(P);

[0010] The standard sample and the specimen are of the same material and specification.

[0011] Preferably, in step S4, correct the resistivity measurement result Q of the specimen to Q ′ : Q ′ = q1 = P1 + C(Δt), where: Δt = t - T1, and T1 is a measurement duration less than t in step S1, and P1 is the resistivity measurement result of the standard sample corresponding to the measurement duration T1.

[0012] Preferably, in step S4, correct the resistivity measurement result Q of the specimen to Q ′ : Q ′ = q2 = Q + C(D(Δp) - Δt), where: Δt = t - T1, and Δp = Q - P1.

[0013] Preferably, in step S4, correct the resistivity measurement result Q of the specimen to Q ′ :

[0014] Preferably, in step S4, correct the resistivity measurement result Q of the specimen to Q ′ :

[0015] Preferably, in step S1, during the process of using the eddy current method to measure the resistivity of the standard sample multiple times, the excitation frequency of the resistivity measurement device is fixed.

[0016] Preferably, in step S1, during the process of using the eddy current method to measure the resistivity of the standard sample multiple times, the excitation frequency of the resistivity measurement device is not fixed.

[0017] Preferably, in step S2, the curve fitting methods include the kernel method, the spline method, the least squares method, and the maximum likelihood estimation method.

[0018] Preferably, in steps S1 and S3, the resistivity measurement further includes the process of converting the measured analog level value into a digital value.

[0019] The present invention also provides a non-contact resistivity measurement system, which includes a transmission and support device, a detection device, a conversion device, a storage and calculation device, and an output device, where:

[0020] The transmission and support device transports and places a standard sample or a test sample within the detection range of the detection device;

[0021] The detection device measures the resistivity of the standard sample or the test sample and transmits the detected analog level signal to the conversion device;

[0022] The conversion device is used to convert the analog level signal into a digital signal and then transmit it to the storage and calculation device;

[0023] The storage and calculation device is used to perform curve fitting, calculation and storage of the curve function C(T) and its inverse function D(P) based on the measurement data of the standard sample, and correct the resistivity of the test sample;

[0024] The output device is used to output the corrected resistivity of the test sample.

[0025] The present invention has the following beneficial effects: This solution uses the eddy current method to measure the resistivity of a standard sample for different time lengths, performs curve fitting based on the measurement duration and the resistivity measurement result data, obtains the relationship curve function P = C(T) between the measurement duration T and the resistivity measurement result P, solves the inverse function T = D(P) of P = C(T), and uses C(T) and D(P) to correct the resistivity measurement result of the test sample. By adopting the solution of the present invention, it is not easy to cause damage to the product surface, significantly reduces the influence of the heat generated by the eddy current effect on the resistivity, reduces the measurement error of the resistivity, improves the measurement accuracy of the resistivity, and reduces the misjudgment rate of the product quality caused by the temperature rise of the eddy current effect. Description of the Drawings

[0026] The drawings described herein are used to provide a further understanding of the present invention and constitute a part of the present invention. The schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation to the present invention. In the drawings:

[0027] Figure 1 It is a schematic diagram of the steps of non-contact resistivity measurement provided by an embodiment of the present invention.

[0028] Figure 2 It is a relationship curve between the resistivity and temperature of an impurity semiconductor.

[0029] Figure 3 It is a schematic diagram of the resistivity measurement scenario provided by an embodiment of the present invention. Detailed Embodiments

[0030] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0031] The standard sample referred to in the present invention means a standard sample produced in a laboratory environment with a resistivity highly close to the nominal specification. The specimen referred to in the present invention means a product mass-produced on an automated production line, whose resistivity is close to the nominal specification, but may still have a large gap due to processes and other reasons. To prevent the resistivity index of the specimens produced by the production line from being unqualified, it is necessary to accurately measure the resistivity of the specimens and determine whether the quality of the specimens is qualified according to the measurement results. For example, if the resistivity error of the specimen relative to the standard sample of the same specification exceeds 5%, it is considered that the quality of the specimen is unqualified. During the actual resistivity measurement process, there are many interference factors. External interferences include temperature, humidity, vibration, etc., and internal interferences include probe distance offset, electromagnetic interference, parasitic impedance, etc. It is not realistic to accurately measure the absolute value of the resistivity. The resistivity error of the actually measured specimen relative to the resistivity of the standard sample of the same specification easily exceeds 5%, resulting in a large proportion of specimens being misjudged as unqualified products. The objective of the present invention is to minimize the influence of the temperature rise caused by the eddy current effect during the eddy current method measurement on the resistivity measurement result and reduce the misjudgment rate.

[0032] The general idea of the present invention is as follows: Use the eddy current method to measure the resistivity of the standard sample for different time lengths, perform curve fitting based on the measurement duration and the resistivity measurement result data to obtain the relationship curve function P = C(T) between the measurement duration T and the resistivity measurement result P, solve the inverse function T = D(P) of C(T), and use C(T) and D(P) to correct the resistivity measurement result of the specimen.

[0033] The embodiments of the present invention will be further described in detail below with reference to the accompanying drawings of the specification. It should be understood that the embodiments described herein are only used to illustrate and explain the present invention and are not used to limit the present invention.

[0034] The present invention is applicable to the resistivity measurement of products such as metal materials, intrinsic semiconductors, doped semiconductors, and thin film materials, and can be applied to fields such as the semiconductor industry, solar cells, printed circuit boards, metal materials, ceramic materials, and biomedicine. There are simple mathematical conversion relationships between resistivity, conductivity, and sheet resistance. Therefore, the methods and systems of the present invention are also applicable to scenarios of measuring conductivity and sheet resistance.

[0035] As Figure 1As shown in the figure, an embodiment of the present invention provides a non-contact resistivity measurement method, and the method includes the following steps:

[0036] Step S1, using the eddy current method to perform multiple resistivity measurements on a standard sample, where the measurements cover measurement durations T of multiple different lengths, and obtaining a standard sample resistivity measurement result P;

[0037] In an embodiment of the present invention, the standard sample and the specimen have the same material and specifications, and the resistivities of the standard sample and the specimen are of the same order of magnitude.

[0038] The eddy current effect will generate heat, causing the temperature of the product under test to rise. In an embodiment of the present invention, when performing resistivity measurement on the standard sample, measurement durations of multiple different lengths are covered. At different measurement durations, the temperature increase of the product under test is different, and the temperature of the standard sample at the end of the measurement is different. Therefore, the obtained standard sample resistivity measurement result P is the resistivity measurement result under different temperature increases. Standard samples of different materials have different responses to the eddy current effect, and the temperature increases are different under the same measurement duration. The measurement duration T and the measurement result P during multiple measurements are stored correspondingly for subsequent analysis processes.

[0039] In an embodiment of the present invention, resistivity measurements can be performed on multiple standard samples of the same specification, and the measurement results are summarized. The resistivity measurements of the multiple standard samples can use the same measurement duration or different measurement durations.

[0040] In some embodiments of the present invention, in step S1, during the process of using the eddy current method to perform multiple resistivity measurements on the standard sample, the excitation frequency of the resistivity measurement device is fixed. In practical applications, an excitation frequency of 10 MHz is usually adopted.

[0041] Because the change in the excitation frequency of the resistivity measurement device only affects the voltage, and the resistivity of the product does not change with the value of the excitation frequency, in some embodiments of the present invention, in step S1, during the process of using the eddy current method to perform multiple resistivity measurements on the standard sample, the excitation frequency of the resistivity measurement device is not fixed, and a frequency conversion method is adopted to measure the resistivity of the standard sample at different measurement durations T.

[0042] In an embodiment of the present invention, the standard sample resistivity measurement further includes a process of converting the measured analog level value into a digital value.

[0043] In practical engineering applications, generally more than 10 groups of data need to be measured for subsequent curve fitting. To obtain a fitting curve, usually at least 3 groups of data need to be collected.

[0044] Step S2: Perform curve fitting based on the measurement duration T and the resistivity measurement result P of the standard sample to obtain the relationship curve function P = C(T) between the measurement duration T and the resistivity measurement result P of the standard sample, and solve the inverse function T = D(P) of the curve function P = C(T); the curve function P = C(T) is the resistivity theoretical value calculation function, and the inverse function T = D(P) is the resistivity temperature compensation function.

[0045] The resistivity of metal materials increases with the increase in temperature, and the resistivity of intrinsic semiconductors decreases monotonically with the increase in temperature. Therefore, for metal materials and intrinsic semiconductors, a monotonic and continuous curve can be fitted, and thus the inverse function of the curve function can be solved.

[0046] For impurity semiconductors, the relationship curve between their resistivity and temperature is as Figure 2 shown. In the AB section, the temperature is very low, and the resistivity decreases with the increase in temperature; in the BC section, the temperature continues to rise, and the resistivity increases with the increase in temperature; after point C: as the temperature continues to rise, the resistivity decreases with the increase in temperature. Point C is the maximum operating temperature of the device. Generally, the maximum operating temperature of germanium devices is 100 °C, that of silicon is 250 °C, and that of gallium arsenide can reach 450 °C. Point B is generally between -10 °C and 10 °C. During the process of measuring the resistivity of the standard sample of the impurity semiconductor, usually the temperature of the standard sample falls within the BC section, so a monotonic and continuous curve can also be fitted, and thus the inverse function of the curve function can be solved.

[0047] In some embodiments of the present invention, during the resistivity measurement, the temperature of the standard sample is detected by a temperature measuring device, so that the temperature of the standard sample does not exceed its maximum operating temperature, preventing the standard sample from being damaged.

[0048] In the embodiments of the present invention, the methods of curve fitting include the kernel method, the spline method, the least squares method, and the maximum likelihood estimation method.

[0049] In some embodiments of the present invention, the least squares method is used for curve fitting, and the curve is usually set as a quartic function or a quintic function. After obtaining the curve function P = C(T) through curve fitting, then solve the inverse function T = D(P) of the curve function. If the inverse function cannot be solved, try to reduce the constraints.

[0050] The processing procedure of steps S1 - S2 of the present invention will be described below through a simple example. Assume a standard sample with resistivity ρ is taken, and using an excitation frequency f, the standard sample is measured within a time T1 to obtain a measurement result p1; measured within a time T2 to obtain a measurement result p2; and measured within a time T3 to obtain a measurement result p3. Perform analog - to - digital conversion on p = {p1, p2, p3} to obtain P = {P1, P2, P3}. Using [T1, P1], [T2, P2], [T3, P3] as vertices, draw a curve C, and solve the function of curve C by the least - squares method.

[0051] Let T’=(T1 + T2 + T3) / 3 and P’=(P1 + P2 + P3) / 3, and calculate:

[0052]

[0053] b = P′ - kT′

[0054] Then C(T)=kT + b can be obtained.

[0055] Solve the inverse function of C(T) to obtain D(P)=(P - b) / k.

[0056] Step S3, use the eddy - current method to measure the resistivity of the specimen, with a measurement duration of t, to obtain the measurement result Q of the specimen resistivity;

[0057] In some embodiments of the present invention, during the measurement of the specimen resistivity, the temperature of the specimen is detected by a temperature - measuring device, so that the temperature of the specimen does not exceed its maximum operating temperature.

[0058] In an embodiment of the present invention, the resistivity measurement of the specimen further includes the process of converting the measured analog - level value into a digital value.

[0059] Step S4, correct the specimen resistivity measurement result Q according to the curve function P = C(T) and the inverse function T = D(P).

[0060] In some embodiments of the present invention, in step S4, the specimen resistivity measurement result Q is corrected to Q ′ : Q ′ =q1 = P1 + C(Δt), where: Δt = t - T1, T1 is a measurement duration less than t in step S1, and P1 is the resistivity measurement result of the standard sample corresponding to the measurement duration T1. q1 is actually the theoretical resistivity value calculated by the curve function C(T).

[0061] In some embodiments of the present invention, in step S4, the specimen resistivity measurement result Q is corrected to Q ′ : Q′ = q2 = Q + C(D(Δp) - Δt), where: Δt = t - T1, Δp = Q - P1. q2 is the resistivity value after the temperature compensation function takes effect.

[0062] In practical applications, a set of measurement duration and resistivity measurement result data can be selected from the measurement data in step S1 as the reference data for correcting the resistivity of the specimen, that is, the measurement duration in this set of data is used as T1, and the resistivity measurement result is used as P1 for calculating q1 and q2.

[0063] In addition to directly correcting the resistivity measurement result of the specimen using q1 and q2, the operation values of q1 and q2 can also be used to correct the resistivity measurement result of the specimen.

[0064] In some embodiments of the present invention, in step S4, the resistivity measurement result Q of the specimen is corrected to Q ′ :

[0065]

[0066] In some embodiments of the present invention, in step S4, the resistivity measurement result Q of the specimen is corrected to Q ′ :

[0067]

[0068] In practical applications, for products of different materials, the differences between q1 and q2 may be different, and it is necessary to correct the measurement results of the specimen in combination with specific situations. No matter which correction method is adopted, the specimen is adjusted in the same trend and amplitude according to the response of the standard sample to different measurement durations, so that the resistivity of the specimen approaches the resistivity of the standard sample, thereby minimizing the influence of the temperature rise caused by the eddy current effect on the resistivity measurement result.

[0069] After testing and verifying multiple products, the resistivity differences after the above several correction methods are not significant. After correction, the error between the resistivity of the specimen and the resistivity of the standard sample is reduced by about 3%. It can be seen that by adopting the solution of the present invention, the influence of the heat generated by the eddy current effect on the resistivity is significantly reduced, the measurement error of the resistivity is reduced, and the measurement accuracy of the resistivity is improved.

[0070] Corresponding to the above non-contact resistivity measurement method, an embodiment of the present invention further provides a non-contact resistivity measurement system, which includes a transmission and support device, a detection device, a conversion device, a storage and calculation device, and an output device.

[0071] The transmission and support device transports and places the standard sample or the specimen into the detection range of the detection device;

[0072] The detection device measures the resistivity of the standard sample or the test sample and transmits the detected analog level signal to the conversion device; the detection device includes a probe, a signal processing unit, and a main control unit.

[0073] The conversion device is used to convert the analog level signal into a digital signal and then transmit it to the storage and calculation device;

[0074] The storage and calculation device is used to perform curve fitting, calculate and store the curve function C(T) and its inverse function D(P) based on the measurement data of the standard sample, and correct the resistivity of the test sample; in practical applications, FPGA, ASIC, single-chip microcomputer, computer, edge processing unit, etc. can be selected as the storage and calculation device.

[0075] The output device is used to output the corrected resistivity of the test sample. The output device can be a display or other PLCs.

[0076] As Figure 3 shown is a schematic diagram of the resistivity measurement scenario provided by an embodiment of the present invention. The standard sample or the test sample is transmitted to the support device through devices such as a conveyor belt and a robotic arm. After entering the detection range of the probe of the detection device, the detection device starts to work, and the work content is as in steps S1 and S3. After the detection is completed, the detected analog level signal is transmitted to the conversion device. The conversion device converts the analog level signal into a digital signal and then transmits it to the storage and calculation device. The storage and calculation device performs curve fitting and calculates the curve function C(T) and its inverse function D(P) according to the method in step S2, and corrects the resistivity of the test sample according to the method in step S4.

[0077] In the actual process, first measure the resistivity of the standard sample, and store C(T) and D(P) as the resistivity theoretical value calculation function and the resistivity temperature compensation function respectively. Then, measure and correct the resistivity of the test samples produced in different batches, and output the corrected resistivity results of the test samples. Subsequently, at specific times such as a quarter, half a year, or one year, or according to actual needs, re-measure the resistivity of the standard sample and update the curve function C(T) and its inverse function D(P).

[0078] The present invention has the following beneficial effects: In this solution, the eddy current method is used to measure the resistivity of a standard sample for different lengths of time. Curve fitting is performed based on the measurement duration and the resistivity measurement result data to obtain the relationship curve function P = C(T) between the measurement duration T and the resistivity measurement result P. The inverse function T = D(P) of P = C(T) is solved, and C(T) and D(P) are used to correct the resistivity measurement result of the specimen. By adopting the solution of the present invention, it is not easy to cause damage to the product surface, significantly reduces the influence of the heat generated by the eddy current effect on the resistivity, reduces the measurement error of the resistivity, improves the measurement accuracy of the resistivity, and reduces the product quality misjudgment rate caused by the temperature rise due to the eddy current effect.

[0079] The above is only the specific implementation manner of the present invention, and the scope of the present invention cannot be limited thereby. Equivalent changes made by those of ordinary skill in the art according to this creation, as well as changes well-known to those skilled in the art, should still fall within the scope covered by the present invention.

Claims

1. A non-contact resistivity measurement method, characterized in that: The method comprises the following steps: Step S1, using an eddy current method to perform multiple resistivity measurements on a standard sample, wherein the measurements cover multiple measurement durations T of different lengths, and obtain a resistivity measurement result P of the standard sample; Step S2, performing curve fitting according to the measurement time T and the resistivity measurement result P of the standard sample, obtaining a relationship curve function P=C(T) between the measurement time T and the resistivity measurement result P of the standard sample, and solving an inverse function T=D(P) of the curve function P=C(T); Step S3, using the eddy current method to measure the resistivity of the sample, the measurement time is t, and the resistivity measurement result Q of the sample is obtained; Step S4, correcting the sample resistivity measurement result Q according to the curve function P=C(T) and the inverse function T=D(P); The material and specification of the standard sample and the test sample are the same.

2. The non-contact resistivity measurement method according to claim 1, characterized in that: In step S4, the sample resistivity measurement result Q is corrected to : ,in: , T1 is a measurement duration in step S1 that is less than t, and P1 is a resistivity measurement result of a standard sample corresponding to the measurement duration T1.

3. The non-contact resistivity measurement method according to claim 1, characterized in that: In step S4, the sample resistivity measurement result Q is corrected to : ,in: , , T1 is a measurement duration in step S1 that is less than t, and P1 is a resistivity measurement result of a standard sample corresponding to the measurement duration T1.

4. The non-contact resistivity measurement method according to claim 1, characterized in that: In step S4, the sample resistivity measurement result Q is corrected to : ,in: , , , , T1 is a measurement duration in step S1 that is less than t, and P1 is a resistivity measurement result of a standard sample corresponding to the measurement duration T1.

5. The non-contact resistivity measurement method according to claim 1, characterized in that: In step S4, the sample resistivity measurement result Q is corrected to : ,in: , , , , T1 is a measurement duration in step S1 that is less than t, and P1 is a resistivity measurement result of a standard sample corresponding to the measurement duration T1.

6. The non-contact resistivity measurement method according to claim 1, characterized in that: In the step S1, during the process of performing multiple resistivity measurements on the standard sample using the eddy current method, the excitation frequency of the resistivity measuring device is fixed.

7. The non-contact resistivity measurement method according to claim 1, characterized in that: In the step S1, during the process of performing multiple resistivity measurements on the standard sample using the eddy current method, the excitation frequency of the resistivity measuring device is not fixed.

8. The non-contact resistivity measurement method according to claim 1, characterized in that: In step S2, the curve fitting method includes kernel method, spline method, least square method, and maximum likelihood estimation method.

9. The non-contact resistivity measurement method according to claim 1, characterized in that: In the step S1 and the step S3, the resistivity measurement also includes a process of converting the measured analog level value into a digital value.

10. A non-contact resistivity measurement system, characterized in that: The system includes a transmission and support device, a detection device, a conversion device, a storage and calculation device, and an output device, wherein: The transmission and support device transmits and places the standard sample or the test specimen into the detection range of the detection device; The detection device measures the resistivity of the standard sample or the test specimen, and transmits the detected analog level signal to the conversion device; The conversion device is used to convert the analog level signal into a digital signal and then transmit it to the storage and computing device; The storage and calculation device is used to perform curve fitting according to the measurement data of the standard sample, calculate and store the curve function C (T) and its inverse function D (P), and use the curve function C (T) and its inverse function D (P) to correct the resistivity of the sample; The output device is used to output the corrected resistivity of the sample.

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