Wafer thin film measuring device and method

Abstract

The present invention provides a wafer thin film measurement device and method. The wafer thin film measurement method comprises the following steps: providing a wafer to be measured, selecting a measurement point on the wafer and measuring the film thickness to obtain a first film thickness value; after laser cleaning the measurement point, measuring the film thickness at the measurement point again to obtain a second film thickness value; obtaining the film thickness difference between the first film thickness value and the second film thickness value at the measurement point; and outputting a third film thickness value at the measurement point based on the film thickness difference. The wafer thin film measurement method provided by the present invention can use a set of initial cleaning window parameters for wafers of different thicknesses and structures, greatly simplifying the operation process. Secondly, through iterative cleaning, the contamination layer on the surface of the wafer can be accurately and effectively removed, thereby improving production efficiency.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor manufacturing technology, and in particular to a wafer thin film measuring device and method. Background Art

[0002] With the technological development of the semiconductor industry, the precise measurement and detection of various key parameters in the semiconductor manufacturing process has become a vital link. In the production and manufacturing process of wafers, accurate measurement of the thickness of the film on the wafer is the key to determining whether the process meets the requirements. The accuracy of the film thickness is related to the subsequent processes, but during the film measurement process, the film on the wafer will undergo an oxidation reaction with the air, thereby generating air contaminants (AMC). This phenomenon directly leads to deviations in the values ​​obtained from the film measurement. In order to achieve higher-precision film measurement, especially for extremely thin films, the industry generally uses energy beams to clean contaminants, that is, using a beam to heat the measurement area to remove contaminants. Under ideal conditions, after the contaminants are cleaned, the film measurement beam can directly act on the film to obtain accurate measurement results.

[0003] When it comes to laser cleaning technology, there are many challenges. The oxidation thickness of the air oxidation layer on the surface of the wafer is inconsistent, which makes it difficult to perfectly cope with wafers of all thicknesses with the same laser cleaning parameter setting, and even cannot ensure the effective cleaning of all measurement points on the same wafer. If the laser energy is set too low, the cleaning effect will be greatly reduced and cannot meet the actual cleaning needs; on the contrary, if the energy is too high, although it can remove contaminants, it will cause burns to the coating of the wafer itself, causing damage to it. At present, after most wafers are cleaned by AMC, there is a significant gap between the actual effect and the ideal state. Therefore, how to accurately control the energy beam to achieve efficient cleaning of AMC has always been a difficult problem to be overcome in the field of semiconductor manufacturing. The solution to this problem has far-reaching significance for improving the overall level of semiconductor manufacturing technology and product quality. Summary of the invention

[0004] In view of the problems existing in wafer cleaning in the prior art described above, the present application provides a wafer thin film measuring device and method.

[0005] On the one hand, the present application provides a wafer thin film measurement method, comprising the following steps:

[0006] Providing a wafer to be measured, selecting a measurement point on the wafer and measuring the film thickness to obtain a first film thickness value;

[0007] After laser cleaning the measuring point, the film thickness is measured again at the measuring point to obtain a second film thickness value;

[0008] Obtaining a film thickness difference between the first film thickness value and the second film thickness value at the measuring point;

[0009] Based on the film thickness difference, a third film thickness value T3 of the measuring point is output.

[0010] Optionally, based on the film thickness difference, a third film thickness value T3 of the measurement point is output, including: when the film thickness difference reaches a preset convergence condition, the third film thickness value T3 of the measurement point is output; or when the film thickness difference does not reach the preset convergence condition, the laser cleaning is performed on the measurement point again.

[0011] Optionally, the film thickness measurement step includes: light emitted by a light source is modulated to form polarized light;

[0012] The polarized light is focused to the measuring point to generate reflected light, and the reflected light is collected by an optical detector;

[0013] The thickness value of the film is obtained through the information of the reflected light.

[0014] Optionally, laser cleaning the measuring point includes:

[0015] Set the initial cleaning window parameters of the laser;

[0016] The laser focuses on the measurement point;

[0017] The laser emits cleaning light to perform laser cleaning at the measuring point.

[0018] Optionally, the area where the laser cleaning is performed on the measuring point is larger than the area where the film thickness is measured.

[0019] Optionally, after outputting the third film thickness value T3 of the measuring point, the next measuring point is selected to obtain the first film thickness value and the second film thickness value, and based on the film thickness difference, the corresponding third film thickness value T3 is output.

[0020] Optionally, when the film thickness difference does not reach a preset convergence condition, the laser cleaning is performed, and based on the difference in film thickness values ​​before and after the laser cleaning, the third film thickness value T3 corresponding to the measurement point is output.

[0021] Optionally, the initial cleaning window parameters of the laser include initial pulse power and pulse width of the laser.

[0022] Optionally, the center coordinates of the laser cleaning area are consistent with the center coordinates of the film thickness measurement area.

[0023] The present invention also provides a wafer thin film measuring device, which is used to implement the above-mentioned wafer thin film measuring method, and is characterized by comprising:

[0024] An optical measurement system that emits measurement light to the wafer to be measured and collects light reflected from the wafer surface;

[0025] A laser cleaning system, used for emitting cleaning light to the wafer to be tested;

[0026] The computer control system controls the wafer to be measured to move and focus in the working areas of the optical measurement system and the laser cleaning system, analyzes the obtained film thickness measurement results, and executes system tasks based on the system preset convergence conditions.

[0027] As described above, the wafer thin film measuring device and method provided by the present invention have at least the following beneficial technical effects:

[0028] Strong parameter versatility: The present invention proposes a set of initial cleaning window parameters for cleaning wafers of different thicknesses and structures, which greatly simplifies the operation process, reduces the cost and time of parameter adjustment when processing different types of wafers, and improves production efficiency.

[0029] High efficiency in removing contamination layers: Through iterative cleaning, the contamination layer on the wafer surface can be effectively and accurately removed.

[0030] Precise control of the cleaning process: The measuring points can be scientifically selected and the film thickness can be accurately measured. The difference in film thickness before and after cleaning at the measuring points can be compared with the preset parameters determined by rigorous experimental analysis to flexibly decide whether to perform cyclic cleaning. A time limit is set to avoid waste of resources and ensure overall efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 Shown is a flow chart of the wafer thin film measurement method provided in Example 1.

[0032] Figure 2a The standard film thickness is shown as Data results of wafer cleaning test.

[0033] Figure 2b The standard film thickness is shown as Data results of wafer cleaning test.

[0034] Figure 2c The standard film thickness is shown as Data results of wafer cleaning test.

[0035] Figure 3 Shown is a schematic diagram of the composition of a wafer thin film measuring device provided in the second embodiment.

[0036] Figure 4 Shown is a schematic diagram of the internal components of a wafer thin film measuring device provided in the second embodiment.

[0037] Figure 5 Shown is a schematic diagram of the composition of a wafer thin film measuring device provided in Example 4.

[0038] Reference numerals

[0039] 01. Measurement system; 02. Cleaning system; 03. Computer control system; 030. Signal processing module; 031. Signal comparison module; 032. Task planning module; 033. Verification and analysis module; 034. Control module; 04. Wafer; 040. Thin film; 041. Contaminants; 05. Wafer carrier; 10. Laser emission system; 101. Laser module; 1011. Pulse generation module; 1012. Pulse modulation module; 1013. Pulse incidence module; 102. Autofocus module; 20. Optical detector; 31. Measurement system; 310. Signal emission module; 311. Signal detection module; 32. Cleaning system; 320. Laser module; 321. Autofocus module; 33. Computer system; 330. Control module; 331. Task planning module. DETAILED DESCRIPTION

[0040] The following describes the embodiments of the present invention through specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention.

[0041] It should be noted that the illustrations provided in this embodiment only illustrate the basic concept of the present invention in a schematic manner. Although the illustrations only show components related to the present invention rather than being drawn according to the number, shape and size of components in actual implementation, the form, quantity, positional relationship and proportion of each component in actual implementation can be changed at will under the premise of realizing the technical solution of this party, and the component layout form may also be more complicated.

[0042] Embodiment 1

[0043] This embodiment also provides a wafer thin film measurement method, such as Figure 1 As shown, it is a flow chart of the wafer thin film measurement method provided by this embodiment; the wafer thin film measurement method provided by the present invention specifically includes the following steps:

[0044] Providing a wafer to be measured, selecting a measurement point on the wafer and measuring the film thickness to obtain a first film thickness value;

[0045] After laser cleaning the measuring point, the film thickness is measured again at the measuring point to obtain a second film thickness value;

[0046] Obtaining a film thickness difference between the first film thickness value and the second film thickness value at the measuring point;

[0047] Based on the film thickness difference, a third film thickness value T3 of the measuring point is output.

[0048] Specifically, the wafer to be tested is placed on the wafer carrier, and a measuring point on the wafer to be tested is selected; the computer system controls the wafer carrier, moves the wafer to be tested to the measuring area of ​​the measuring system, adjusts the height of the wafer to be tested from the measuring system, focuses, and then performs film thickness measurement.

[0049] Generally, the measurement system for measuring the film thickness includes: an optical measurement system, an electron beam measurement system, an X-ray measurement system, and other measurement systems. This embodiment takes the optical measurement system as an example.

[0050] The steps for measuring the film thickness include: the light emitted by the light source is modulated to form polarized light; the polarized light is focused to the measurement point to generate reflected light, and the reflected light is collected by an optical detector; and the thickness value of the film is obtained through the information of the reflected light.

[0051] Specifically, the wafer to be tested is placed on the wafer carrier, and measurement points are selected on the wafer. Generally, the selection of measurement points needs to consider many factors, such as the symmetry of the wafer, the distribution state of contaminants, the distribution law of film thickness, and the convenience of subsequent comparative analysis with other measurement points. Specifically, the measurement points are determined according to the task formula set by the system. Usually, the measurement points are evenly distributed on the film surface of the wafer to ensure that the film thickness measurement and cleaning effect evaluation of the measurement points can roughly reflect the situation of the entire wafer.

[0052] Specifically, the wafer carrier moves in the horizontal direction, moves the wafer to the measurement area of ​​the optical measurement system, and then the wafer carrier moves up and down to realize the focusing of the automatic focusing module of the optical measurement system and the wafer, ensuring that the laser energy can accurately act on the measurement point. After the focusing is completed, the laser emission system in the optical measurement system emits a measurement beam to the measurement point of the wafer. Specifically, the measurement beam emitted by the vector measurement point at least passes through the pulse generation module to generate a first predetermined light intensity, and passes through the polarizer to generate a modulated polarized light. Optionally, it also includes the first predetermined light intensity passing through the pulse modulation module to realize the denoising of the optical signal to obtain a modulated first laser pulse train. The polarized light formed by the polarizer, that is, the first measurement side signal, is focused to the measurement point, and the film thickness value of the measurement point is measured. The wafer reflects the first feedback signal, and the optical detector receives the first feedback signal from the wafer. Specifically, the first feedback signal at least passes through the analyzer to obtain a processed feedback signal. The first feedback signal is transmitted to the computer control system, and the computer control system obtains the first film thickness value T1 according to the first measurement signal and the first feedback signal.

[0053] Next, the measurement point is preliminarily laser cleaned, and the initial cleaning window parameters of the laser are set; the laser emits cleaning light based on the cleaning signal and performs cleaning after focusing on the measurement point. Generally, the area of ​​the measurement point where the laser cleaning is performed is larger than the area where the film thickness is measured. Specifically, the initial cleaning window parameters are obtained through multiple test analyses, and the initial cleaning window parameters are the maximum parameters that can remove the air pollutant layer without burning the film itself; specifically, the initial cleaning window parameters of the laser include the initial pulse power and pulse width of the laser.

[0054] In particular, the setting of the initial cleaning window parameters is a parameter obtained through a large number of experimental analyses in the early stage, which can effectively remove the contaminant layer (such as the air contaminant layer, AMC layer) and ensure that the film itself will not be burned. During the experiment, for multiple groups of wafer samples with the same specifications and similar films covered on the surface and contaminated with similar air pollutants, the key parameters in the laser cleaning process, such as the wavelength, pulse frequency, pulse energy and irradiation time of the laser, were gradually changed. After multiple groups of experiments with different parameter combinations and corresponding detection and analysis, the contaminant removal effect and film damage under different parameters were compared, and finally an optimal parameter range was determined. The boundary value of this range or a characteristic value within the range that can comprehensively reflect the best cleaning effect and film protection is set as the initial cleaning window parameter.

[0055] The initial cleaning window parameters are determined after a large number of experimental analyses and full consideration of various situations in actual production. They represent the optimal parameter range that can effectively remove pollutants on the wafer surface and is applicable to wafers of different thicknesses and structures, which is summarized based on many practical experiences. Therefore, in practical applications, as long as the laser cleaning operation is performed according to this parameter, the input of laser energy can be strictly controlled to avoid damage such as melting, cracking, and chemical property changes of the film due to excessive energy, thereby ensuring the safety of the wafer during the cleaning process and maintaining its original physical and chemical properties as well as subsequent processing performance.

[0056] Specifically, the wafer is moved to the cleaning area of ​​the wafer thin film measuring device, the center coordinates of the laser cleaning area are kept consistent with the center coordinates of the film thickness measurement area, and the wafer is moved up and down to achieve wafer focusing; then the laser emission system emits a cleaning beam to the measuring point of the wafer under the setting of the laser initial cleaning window parameters to perform laser cleaning. Generally, the laser cleaning area is larger than the film thickness measurement area.

[0057] Next, the film thickness is measured for the cleaned measuring point for the second time to obtain a second film thickness value T2; specifically, the steps for obtaining the second film thickness value T2 are the same as the steps for obtaining the first film thickness value T1, which will not be repeated here.

[0058] Obtaining a film thickness difference ΔT at the measuring point, ΔT=T1-T2, and ΔT≥0;

[0059] Specifically, the first film thickness value T1 and the second film thickness value T2 are input to a computer control system, and a signal processing module in the computer control system calculates a difference ΔT between the first film thickness value T1 and the second film thickness value T2. The difference ΔT is then transmitted to a signal comparison module, which compares the film thickness difference ΔT with a preset convergence condition, and when the film thickness difference reaches the preset convergence condition, outputs a third film thickness value T3 of the measurement point; or when the film thickness difference does not reach the preset convergence condition, performs the laser cleaning on the measurement point again.

[0060] Specifically, ΔT directly reflects the cleaning effect of the laser cleaning operation at the measurement point. If the value of ΔT is large, it means that more AMC layers or impurities are cleaned; conversely, if the value of ΔT is small, it means that less AMC layers or impurities are cleaned. In particular, the preset convergence condition is a preset parameter value T, referred to as preset parameter T for short. The preset parameter T is experimental analysis data. Specifically, the preset parameter T includes a film thickness parameter, which is set after statistical analysis of the film thickness and the thickness of the contamination layer cleaned.

[0061] The preset parameter T is the data obtained through a large amount of experimental analysis in the early stage. During the experiment, multiple cleaning operations and film thickness measurements are performed under various conditions such as different types of wafers, different surface contamination conditions, and different cleaning parameters. Then, the corresponding film thickness change data is collected, and then statistical function analysis (common statistical function analysis methods include but are not limited to mean analysis, variance analysis, regression analysis, and probability distribution analysis, etc.) is used to process these data, and finally a convergence value that can represent the ideal cleaning effect is determined as the preset parameter T. Therefore, the determination of the preset parameter T is a process that is closely centered on actual production needs, driven by rigorous experimental data, and continuously iterated and optimized using scientific statistical function analysis methods.

[0062] Specifically, when ΔT is less than or equal to T, that is, the film thickness difference ΔT reaches the preset convergence condition, it means that the cleaning effect at the measuring point has reached the expected or close to the expected state, and the third film thickness value T3 of the measuring point is output at this time. The next step can be executed according to the process, and the corresponding operations can be continued on other measuring points. Specifically, if only one laser cleaning is performed, the third film thickness value T3 is equal to the second film thickness value T2. If multiple cleanings are performed, the third film thickness value T3 is the film thickness value of the last measurement when the corresponding film thickness difference ΔT reaches the preset parameter T;

[0063] When ΔT is greater than the preset parameter T, that is, the film thickness difference ΔT does not reach the preset convergence condition, laser cleaning is performed again, and based on the difference in film thickness values ​​before and after laser cleaning, the third film thickness value corresponding to the measurement point is output. The fact that the film thickness difference ΔT does not reach the preset convergence condition indicates that the cleaning effect at the measurement point has not met expectations. At this time, it is necessary to re-measure the film thickness of the point and perform subsequent cleaning judgment operations, that is, to re-obtain the first film thickness value T1 and the second film thickness value T2 for the same measurement point. In order to avoid falling into an infinite loop or wasting resources for a long time on the processing of a measurement point, a preset time is set. Once the cumulative time of repeatedly executing related steps such as obtaining the first film thickness value T1 and the second film thickness value T2 for the measurement point exceeds this preset time, regardless of the current cleaning situation, the task will be determined to be completed to avoid affecting the efficiency of the entire production process and causing unnecessary waste of resources.

[0064] After the third film thickness value T3 of the measuring point is output, the next measuring point is selected to obtain the first film thickness value T1 and the second film thickness value T2, and based on the film thickness difference ΔT, the corresponding third film thickness value T3 is output.

[0065] Specifically, the selection of the next measurement point also has strict rules and basis. Generally, factors such as the wafer geometry, film thickness distribution uniformity, process requirements, and customer needs need to be considered. Specifically, the next key position on the wafer surface is selected as the next measurement point according to a certain angle interval or distance interval. This point may be located at another position in the radial direction of the wafer or a specific angle position in the circumferential direction.

[0066] After determining the next measurement point, repeat the above steps to measure the film thickness, laser clean, measure the film thickness again, calculate the difference, and make corresponding judgments. And according to the process, select the subsequent measurement points (the third measurement point, the fourth measurement point...), and repeat the subsequent related steps until the processing of all the measurement points pre-set by the system is completed. In this way, the cleaning effect of each key position on the entire wafer surface can be comprehensively evaluated and controlled to ensure that the cleaning quality of the entire wafer meets the process requirements.

[0067] After the task is completed, the wafer is moved out of the wafer thin film measuring device.

[0068] Specifically, the number of measurement points should be determined based on factors such as the size of the wafer, the characteristics of the film, and the distribution of pollutants, to ensure that all parts can be detected, so as to accurately grasp the cleaning conditions of pollutants such as dust in different areas. Specifically, the number of measurement points is between 1 and 50. Specifically, for a 4-inch wafer, 1 to 3 measurement points are selected; for an 8-inch wafer, 10 to 25 measurement points are selected.

[0069] Optionally, the measurement system for obtaining the first film thickness value T1 and the measurement system for obtaining the second film thickness value T2 are the same measurement system or the measurement systems are different measurement systems. Specifically, the same measurement system used in this embodiment is an optical measurement system.

[0070] If the same measurement system is used, its advantage is that it can ensure the consistency and continuity of the measurement, and the film thickness value has a higher reliability; when choosing different measurement systems, it is often based on some special needs. For example, different measurement systems may have their own unique measurement advantages. One measurement system may perform well in high-precision film thickness measurement and is suitable for obtaining accurate initial film thickness values ​​before cleaning; another measurement system may have a more sophisticated detection capability for the microscopic morphology of the film surface and the residual contaminants, which is convenient for a more comprehensive evaluation of the cleaning effect after cleaning. In short, there is a certain degree of flexibility in the selection of measurement systems.

[0071] As shown in Table 1, the wafer thin film measurement method described above is used to measure the standard film thickness of as well as The data results of laser cleaning test on the wafer; Pre represents the measurement value before cleaning; Fixed Power uses fixed cleaning window parameters (including fixed power and pulse value), and only cleans once; Adaptive1, 2, and 3 represent repeated cleaning using different initial cleaning window parameters (including power and pulse value). MIN: The smallest thickness measurement value among the measured values; MAX: The largest thickness measurement value among the measured values; MEAN: The mean of all measured values; RANGE: The upper and lower limits of all measured values; STD: refers to the standard deviation. STD is an important indicator for measuring the degree of data dispersion. The standard deviation is defined as the square root of the arithmetic mean of the square of the mean deviation, represented by σ. The larger the standard deviation, the higher the degree of data dispersion; conversely, the smaller the standard deviation, the lower the degree of data dispersion. The calculation formula is:

[0072]

[0073] Specifically, 25 measurement points were selected, and the cleaning times were independently iterated by the present invention until the iteration conditions were met and the adaptive cleaning process was completed. As can be seen from Table 1, the bold data represent the appropriate RANGE (range) and STD (standard deviation), that is, when the RANGE and STD values ​​are the smallest, the film cleaning of the wafer is the most uniform, close to the actual film thickness value of the film. If one of the RANGE and STD is lower and the other is higher, then according to the actual measurement requirements, select the indicators required by the customer and determine the cleaning parameters.

[0074] like Figure 2a , 2b , 2c, showing the standard film thickness is The data of the wafer cleaning test is the measurement data of all measurement points. The vertical axis is the film thickness, unit The horizontal axis is the measuring point; combined with the data in Table 1, it can be concluded that the standard film thickness is The wafers with the parameters of Adaptive 2 can be adaptively cleaned to obtain better results; the standard film thickness is The wafers with the parameters of Adaptive 2 can be adaptively cleaned to obtain better results; the standard film thickness is The wafers can be adaptively cleaned with the parameters of Adaptive 3 to obtain better results. During calibration, multiple parameters will be tested. After the best set is calibrated, this parameter will be used for subsequent batch cleaning of wafers.

[0075] Table 1 for standard film thickness as well as Data of laser cleaning test on wafers

[0076]

[0077] In summary, the wafer thin film measurement method provided in this embodiment is efficient and targeted: it can automatically focus during laser cleaning, and rely on the initial cleaning window parameters obtained through a large number of experiments, and use the same set of parameters to deal with wafers of different thicknesses and structures, simplifying the process, saving costs and time, and achieving comprehensive and efficient cleaning by reasonably determining the number of measurement points; the cleaning process is precisely controlled: the measurement points can be scientifically selected and the film thickness can be accurately measured. According to the comparison result of the film thickness difference before and after cleaning at the measurement point and the preset parameter T determined by rigorous experimental analysis, it can be flexibly decided whether to cycle cleaning, and a time limit is set to avoid waste of resources to ensure overall efficiency.

[0078] Embodiment 2

[0079] This embodiment provides a first wafer thin film measurement device, such as Figure 3 As shown, it is a schematic diagram of the composition of the wafer thin film measuring device provided in this embodiment; the wafer thin film measuring device provided in this embodiment includes: a measuring system 01, a cleaning system 02 and a computer control system 03. The measuring system 01 is used to emit a measuring beam to the wafer to be measured, and collect light reflected from the surface of the wafer 04 to obtain the thickness of the wafer thin film 040; the cleaning system 02 is used to emit a cleaning beam to the wafer to be measured 04 to clean the contaminants 041 on the surface of the wafer 04; the computer control system 03 controls the wafer to be measured to move and focus in the working area of ​​the measuring system and the cleaning system, and analyzes the obtained film thickness measurement results, and executes system tasks based on the preset convergence conditions of the system.

[0080] Generally, the measuring system 01 and the cleaning system 02 may be the same signal transmitting system or different signal transmitting systems. Specifically, in the present embodiment, the measuring system 01 and the cleaning system 02 are the same signal transmitting system. Only by changing the parameters of the signal transmitting system, the two functions of measurement and cleaning can be realized. It can also be understood that the measuring system 01 and the cleaning system 02 share a set of signal transmitting systems. Generally, the signal transmitting system includes an optical transmitting system, a non-optical transmitting system, and an integrated system of an optical transmitting system and a non-optical transmitting system. Specifically, the optical transmitting system includes a laser transmitting system, an infrared spectroscopy interference transmitting system, a white light interference transmitting system, an optical reflection transmitting system, etc.; the non-optical transmitting system includes an electron beam transmitting system, an X-ray transmitting system, etc. The signal transmitting system may be a single transmitting system or an integrated system of multiple transmitting systems. As long as the signal transmitting system can transmit the thickness of the thin film 040 of the wafer 04 to be measured, it can be included in the scope of this patent.

[0081] Specifically, Figure 4 As shown, it is a schematic diagram of the internal composition of the wafer thin film measurement device provided in this embodiment; in this embodiment, the signal transmission system is an optical transmission system, specifically including a laser transmission system 10 and an optical detector 20. The laser transmission system 10 is configured to transmit a measurement beam or a cleaning beam to the wafer, and the laser measurement and laser cleaning functions can be realized by changing the pulse power and pulse width of the laser transmission system. The optical detector 20 receives the reflected light beam from the wafer.

[0082] Specifically, the laser emission system 10 includes: a laser module 101 and an autofocus module 102. Generally, the laser emission system 10 may be a single laser module 101 or an integrated system integrating multiple laser modules 101. Specifically, in the present embodiment, the laser emission system 10 integrates multiple laser modules 101, that is, a multi-light source emission system. Specifically, each laser module 101 includes a pulse generating module 1011, a pulse modulation module 1012 and a pulse incident module 1013. The laser module 101 generates laser pulses of a predetermined wavelength. The pulse generating module 1011 includes a light intensity control module, which controls the pulses of different light intensities generated by the laser module 101 by controlling the light intensity control module to realize whether the wafer thin film measuring device is in a measurement mode or a cleaning mode. Generally, the light intensity control module is operated so that the pulse generation module 1011 outputs a first predetermined light intensity, and the wafer thin film measurement device is in a wafer measurement mode; the light intensity control module is controlled so that the pulse generation module 1011 outputs a second predetermined light intensity, and the wafer thin film measurement device is in a wafer cleaning mode; generally, the second predetermined light intensity is greater than the first predetermined light intensity. The pulse modulation module 1012 is used to combine with a phase-locked amplifier to achieve de-noising of the monitoring light signal reflected or diffracted by the sample. In the measurement mode: the pulse modulation module 1012 periodically modulates the first laser pulse train to obtain a modulated first laser pulse train; in the cleaning mode: the second laser pulse train is received, and the second laser pulse train is periodically modulated based on the second modulation signal to obtain a modulated second laser pulse train. The pulse injection module 1013 acts as an injection path, receiving the modulated first laser pulse train or the modulated second laser pulse train and injecting it into the two side points of the wafer. The automatic focusing module 102 is used to achieve focusing on the wafer.

[0083] The pulse injection module 1013 also includes a polarizer, which is configured to inject at least the first laser pulse train that has been polarized or the second laser pulse train that has been polarized into the sample. In addition to the polarizer, the pulse injection module 1013 may also include one or more of a first phase compensator and a first objective lens. In particular, the polarizer, the first phase compensator and the first objective lens may be arranged in sequence along the incident light path.

[0084] The optical detector 20 is used to receive the reflected light beam reflected from the wafer surface. The optical detector 20 includes a second objective lens, an analyzer, and a second phase compensator. The analyzer is used to limit the polarization direction of the light reflected from the wafer to a certain linear polarization direction, and at least analyze the light signal reflected or diffracted from the sample to obtain a processed light signal; the second objective lens, the second phase compensator, and the analyzer can be arranged in sequence along the reflected light path reflected from the sample. In the cleaning mode, only the laser emission system 10 is used, and the optical detector 20 is unnecessary.

[0085] The computer control system 03 includes a signal processing module 030 and a signal comparison module 031. The signal processing module 030 is configured to obtain a film thickness value according to a first measurement signal and a first feedback signal. The signal comparison module 031 is configured to compare the film thickness difference ΔT with a preset parameter T. Specifically, when performing the first measurement task for a measurement point, the optical detector 20 receives a first feedback signal from the wafer feedback, and transmits the signal to the signal processing module 030. The signal processing module 030 calculates a first film thickness value T1 based on the first measurement signal; similarly, when performing the second measurement task for the same measurement point, the optical detector 20 receives a second feedback signal from the wafer feedback, and transmits the signal to the signal processing module 030. The signal processing module 030 calculates a second film thickness value T2 based on the second measurement signal; the signal processing module 030 calculates a difference ΔT between the first film thickness value T1 and the second film thickness value T2, ΔT=T1-T2, and ΔT≥0. The difference ΔT is transmitted to the signal comparison module 031 , which compares the film thickness difference ΔT with the preset parameter T, and determines whether to end cleaning or continue cleaning based on the comparison result, and outputs a third film thickness value T3 , and outputs the comparison result to the control module 034 .

[0086] Specifically, the computer control system 03 also includes a task planning module 032, a verification and analysis module 033, and a control module 034. The task planning module 032 is responsible for receiving the user's cleaning requirements, including wafer type, contaminant type, cleaning accuracy, time requirements, etc.; then, according to the specific conditions of the wafer 04 and the cleaning requirements, it automatically generates a measurement task plan and a cleaning task plan to ensure the efficiency and pertinence of the cleaning process. The verification and analysis module 033 verifies the results of measurement and cleaning. The control module 034 is responsible for coordinating the measurement system 01 and the cleaning system 02. Specifically, the control module 034 controls the working parameters of all modules, as well as the trigger state.

[0087] For details, please continue to see Figure 3, the wafer thin film measuring device is also equipped with a wafer carrying device 05; the laser emitting system 10 includes an automatic focusing module 102. The wafer carrying device 05 is used to carry the wafer 04, and the wafer carrying device 05 is controlled by the control module 034 (not shown in the figure). Under the control of the control module 034, the wafer carrying device 05 moves the wafer with micron-level accuracy, so that the wafer 04 can move in the XYZ axis direction between the wafer thin film measuring devices to achieve wafer focusing. Specifically, the measurement system 01 and the cleaning system 02 of the wafer thin film measuring device provided in this embodiment share a laser emitting system 10, and the laser emitting system 10 includes multiple laser modules 101, that is, multiple light sources. During the wafer cleaning process, the wafer carrier 05 carries the wafer and moves it to the measuring and cleaning area of ​​the wafer thin film measuring device, and then the wafer carrier 05 moves in the height direction to adjust the height of the wafer 04 from the automatic focusing module 102 to achieve the focusing of the automatic focusing module 102 on the wafer. The wafer carrier 05 can realize the horizontal movement of the wafer 04 to achieve the focusing of the wafer 04 on different incident light sources, thereby ensuring the position accuracy during the cleaning and measurement process.

[0088] Generally, in order to cope with the vibration that may be generated during the high-speed cleaning process, the wafer carrier 05 is also equipped with a shock absorption and stabilization system to ensure the smooth operation of the wafer 04 during the cleaning process and reduce errors.

[0089] In summary, the wafer thin film measurement device provided in this embodiment realizes the integrated combination of measurement and cleaning functions. By adjusting the mode and parameters, it can not only measure the film thickness of wafer 04, but also clean the contaminants 041 on the surface of wafer 04. It has an efficient and adaptable cleaning function, which greatly improves the cleaning efficiency and accuracy, helps to improve the overall cleaning quality, and provides support for the wafer thin film measurement method provided in Example 1; in addition, the system also has an intelligent control module and a task planning module. The control module optimizes the cleaning path to ensure that the entire wafer cleaning process is carried out in an orderly and efficient manner, thereby avoiding waste of resources and time delays.

[0090] Embodiment 3

[0091] This embodiment provides another wafer thin film measuring device. The wafer thin film measuring device of this embodiment is based on the wafer thin film measuring device provided in the second embodiment, and the laser emission system 10 in the wafer thin film measuring device is set to include only one laser emission module 101, that is, only one light source. During the wafer measurement and cleaning process, it is only necessary to move the wafer 04 to the measurement area of ​​the wafer thin film measuring device to achieve the focusing of the wafer. After the first measurement is completed, there is no need to move the position of the wafer. Laser cleaning can be performed by changing the pulse signal of the laser emission system 10. Then, there is no need to move the position of the wafer. The second measurement can be performed by changing the pulse signal of the laser emission system 10. After completing the measurement and cleaning of one measurement point, the wafer is moved in the horizontal direction, and the next measurement point is selected for measurement and cleaning. This wafer thin film measuring device

[0092] The wafer thin film measuring device provided in this embodiment greatly simplifies the operation process. It only needs to fix the wafer in the measurement area, and then the dual tasks of measurement and cleaning can be completed by changing the pulse signal of the laser emission system. The production efficiency is improved, the number and time of wafer movement are reduced, and the measurement and cleaning process can be carried out continuously without interruption, which can further shorten the production cycle.

[0093] Embodiment 4

[0094] This embodiment provides another wafer thin film measurement device, such as Figure 5 As shown, it shows the composition schematic diagram of the wafer thin film measurement device provided by this embodiment; Figure 5 It can be seen that the wafer thin film measurement device provided in this embodiment includes a measurement system 31, a cleaning system 32 and a computer system 33. The measurement system 31 is configured to measure the film thickness value at the measurement point of the wafer; the measurement system 31 includes a signal transmission module 310 and a signal detection module 311, and the measurement system 31 is used to transmit a detection signal to the wafer 04 and receive a reflection signal from the wafer 04; the laser cleaning system 32 includes a laser module 320 and an automatic focusing module 321; the computer system 33 is connected to the measurement system 31 and the laser cleaning system 32 in communication; the computer system 33 includes a control module 330 and a task planning module 331, and the control module 330 controls the measurement system 31 and the laser cleaning system 32.

[0095] Optionally, the measurement system 31 is a single measurement system or an integrated system of multiple measurement systems. As long as the measurement system 31 can measure the thickness of the thin film 040 of the wafer 04 to be measured, it can be included in the scope of this patent. Generally, the measurement system 31 includes an optical measurement system, a non-optical measurement system, and an integrated system of an optical measurement system and a non-optical measurement system. Specifically, the optical measurement system includes an infrared spectroscopy interferometry measurement system, a white light interferometry measurement system, an optical reflection measurement system, etc.; the non-optical measurement system includes an electron beam measurement system, an X-ray measurement system, etc.

[0096] Specifically, the optical measurement system includes an optical illumination system, a detection system, an automatic focusing system, and a computer system. The automatic focusing system uses the principle of optical ellipsometry or optical reflection to focus on the wafer 04; the light illumination system includes a pulse generation module and a modulation module, which are used to provide a stable, uniform, and modulated light source to converge the light beam to the surface of the wafer 04; the detection system receives the reflected light from the wafer surface and converts it into an electrical signal for preliminary processing; the computer system receives the electrical signal for digital processing, obtains various parameters such as the film, and completes the measurement.

[0097] Specifically, the signal transmitting module 310 is responsible for generating and transmitting the detection signal to the surface of the wafer 04. Depending on the measurement requirements, the transmitted signal can be a light wave (such as infrared light, visible light), an electron beam or an X-ray, etc. The specific type and frequency of the signal are determined by the material properties of the film 040 to be measured and the measurement accuracy requirements. The signal detection module 311 is responsible for receiving the signal reflected back from the wafer 04. The reflected signal contains the thickness, uniformity, roughness and possible defect information of the film 040. The detection module converts these signals into electrical signals for subsequent processing.

[0098] Optionally, the laser module 320 includes a pulse laser, a continuous laser, a CO2 laser, a compound laser, or the like that can be used to clean pollutants on the surface of the wafer. Specifically, in the present embodiment, the pulse laser used can accurately control the energy density, pulse width, and frequency of the laser to meet the cleaning requirements of different materials and types of pollution. The laser beam is transmitted to the surface of the wafer through optical fiber or free space to achieve non-contact cleaning and avoid physical damage to the wafer. Automatic focusing module 021: can quickly adjust the laser focus position to ensure that the laser energy is concentrated on the measurement point of the wafer, thereby improving cleaning efficiency and accuracy.

[0099] Specifically, the control module 330 is responsible for coordinating the measurement system 31 and the laser cleaning system 32, and also optimizes the cleaning path and strategy through complex algorithms to ensure the cleaning quality within the specified time; the task planning module 331 is responsible for receiving the user's cleaning requirements, including wafer type, type of contaminant, cleaning accuracy, time requirements, etc.; then, based on the specific situation and cleaning requirements of wafer 04, it automatically generates measurement task planning and cleaning task planning to ensure the efficiency and pertinence of the cleaning process.

[0100] Optionally, the wafer thin film measuring device further includes a wafer carrier 05. The wafer carrier 05 can move the wafer with micron-level precision according to the instructions of the computer system 33, so that the wafer 04 can move between the wafer thin film measuring devices in the XYZ axis to ensure the position accuracy during the cleaning and measurement process. In order to cope with the vibration that may be generated during the high-speed cleaning process, the wafer carrier is also equipped with a shock absorption and stabilization system to ensure the smooth operation of the wafer during the cleaning process and reduce errors.

[0101] In summary, the wafer thin film measuring device provided in this embodiment has an efficient and adaptable cleaning function. The laser modules in the laser cleaning system are diversified, and the automatic focusing module ensures that the laser energy is accurately concentrated on the measurement point, which greatly improves the cleaning efficiency and accuracy, and helps to improve the overall cleaning quality; it has intelligent control and task planning, and the control module ensures that the entire wafer cleaning process is orderly and efficient by optimizing the cleaning path, avoiding waste of resources and time delays.

[0102] The above embodiments are merely illustrative of the principles and effects of the present invention, and are not intended to limit the present invention. Anyone familiar with the art may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by a person of ordinary skill in the art without departing from the spirit and technical concept disclosed by the present invention shall still be covered by the claims of the present invention.

Claims

1. A wafer thin film measurement method, characterized in that: The following steps are involved: Providing a wafer to be measured, selecting a measurement point on the wafer and measuring the film thickness to obtain a first film thickness value; After laser cleaning the measuring point, the film thickness is measured again at the measuring point to obtain a second film thickness value; Obtaining a film thickness difference between the first film thickness value and the second film thickness value at the measuring point; Based on the film thickness difference, a third film thickness value of the measurement point is output.

2. The wafer thin film measurement method according to claim 1, characterized in that: Based on the film thickness difference, outputting a third film thickness value of the measuring point includes: When the film thickness difference reaches a preset convergence condition, outputting the third film thickness value of the measuring point; or When the film thickness difference does not reach the preset convergence condition, the laser cleaning is performed again on the measuring point.

3. The wafer thin film measurement method according to claim 1, characterized in that: The steps of measuring the film thickness include: The light emitted by the light source is modulated to form polarized light; The polarized light is focused to the measuring point to generate reflected light, and the reflected light is collected by an optical detector; The thickness value of the wafer film is obtained through the information of the reflected light.

4. The wafer thin film measurement method according to claim 1, characterized in that: Laser cleaning of the measuring point includes: Set the initial cleaning window parameters of the laser; The laser focuses on the measurement point; The laser emits cleaning light to perform laser cleaning at the measuring point.

5. The wafer thin film measurement method according to claim 1, characterized in that: The area where the laser cleaning is performed on the measuring point is larger than the area where the film thickness is measured.

6. The wafer thin film measurement method according to claim 2, characterized in that: After the third film thickness value of the measuring point is output, the next measuring point is selected to obtain the first film thickness value and the second film thickness value, and based on the film thickness difference, the corresponding third film thickness value is output.

7. The wafer thin film measurement method according to claim 2, characterized in that: When the film thickness difference does not reach a preset convergence condition, the laser cleaning is performed, and based on the difference between the film thickness values ​​before and after the laser cleaning, the third film thickness value corresponding to the measurement point is output.

8. The wafer thin film measurement method according to claim 4, characterized in that: The initial cleaning window parameters of the laser include the initial pulse power and pulse width of the laser.

9. The wafer thin film measuring method according to claim 5, characterized in that: The center coordinates of the laser cleaning area are consistent with the center coordinates of the film thickness measurement area.

10. A wafer thin film measuring device, using the wafer thin film measuring method according to any one of claims 1 to 9, characterized in that: include: An optical measurement system that emits measurement light to the wafer to be measured and collects light reflected from the wafer surface; A laser cleaning system, used for emitting cleaning light to the wafer to be tested; The computer control system controls the wafer to be measured to move and focus in the working areas of the optical measurement system and the laser cleaning system, analyzes the obtained film thickness measurement results, and executes system tasks based on the system preset convergence conditions.

Images