Micro-nano gap measurement method

Abstract

The invention provides a micro-nano gap measurement method, and relates to the technical field of micro-nano machining, and the method comprises the steps: determining a gap range of a gap value between a mask and a substrate based on a spectrum of a gap between the mask and the substrate; under the condition that the gap value between the mask and the substrate is in a first gap range, determining the gap value between the mask and the substrate based on the white light interference spectrum between the mask and the substrate; under the condition that the gap value between the mask and the substrate is within a second gap range, determining the gap value between the mask and the substrate based on the monochromatic light interference spectrum between the mask and the substrate; the minimum gap value in the first gap range is greater than or equal to the maximum gap value in the second gap range.

Description

Technical Field

[0001] The present disclosure relates to the field of micro-nano processing technologies, and in particular, to a method for measuring micro-nano gaps. Background Art

[0002] Currently, the commonly used non-contact method for measuring the mask-substrate gap is the waveform matching method based on white light interference. This method requires pre-calculating a theoretical waveform library corresponding to different gap values according to the constituent materials of the mask, gap, and substrate. Then, after preprocessing the actually collected spectrum, it is matched with the theoretical waveform library one by one, and the most similar theoretical waveform is selected, and the corresponding gap value is the measured value.

[0003] Since the waveform matching method needs to match the collected spectrum with a huge theoretical waveform library, the time cost is very high. Moreover, the higher the measurement accuracy required, the larger the required waveform library and the longer the required waveform matching time. And in an externally applied immersion liquid or humid environment, the medium between the mask and the substrate will gradually change from air to liquid (such as water). Since the traditional waveform matching algorithm cannot determine the moment of the change of the gap medium, the gap value cannot be accurately calculated through the refractive index of the gap medium. In addition, in an externally applied immersion liquid or humid environment, the medium between the mask and the substrate will gradually change from air to liquid (such as water). When measuring a small gap with monochromatic light and the medium in the gap is air, the error of monochromatic light thickness measurement is too large to obtain a high-precision small gap measurement result. Due to the repeatability of the monochromatic light interference spectrum, when measuring the thickness at the micron level, due to the ambiguity of the interference order, there is a phenomenon of inaccurate measurement. Summary of the Invention

[0004] In view of this, embodiments of the present disclosure provide a method for measuring micro-nano gaps.

[0005] Embodiments of the present disclosure provide a method for measuring micro-nano gaps, including: determining a gap range in which the gap value between the mask and the substrate is located based on the spectrum of the gap between the mask and the substrate; when the gap value between the mask and the substrate is within a first gap range, determining the gap value between the mask and the substrate based on the white light interference spectrum between the mask and the substrate; when the gap value between the mask and the substrate is within a second gap range, determining the gap value between the mask and the substrate based on the monochromatic light interference spectrum between the mask and the substrate; the minimum gap value in the first gap range is greater than or equal to the maximum gap value in the second gap range.

[0006] According to an embodiment of the present disclosure, determining the gap value between a mask and a substrate based on the white light interference spectrum between the mask and the substrate includes: determining the number of periods in the wave number domain of the white light interference spectrum according to the extreme points and inflection points on the spectral curve corresponding to the white light interference spectrum, where the interval between adjacent inflection points and extreme points is one-quarter of a period; obtaining the starting value and ending value of the wave number of the white light interference spectrum and the refractive index of the gap medium between the mask and the substrate; determining the gap value between the mask and the substrate according to the number of periods in the wave number domain, the starting value and ending value of the wave number, and the refractive index of the gap medium.

[0007] According to an embodiment of the present disclosure, determining the gap value between a mask and a substrate based on the monochromatic light interference spectrum between the mask and the substrate includes: determining the monochromatic light intensity based on the monochromatic light interference spectrum between the mask and the substrate; determining the type of the gap medium between the mask and the substrate at different times based on the monochromatic light intensity; determining the gap value between the mask and the substrate based on the type of the gap medium.

[0008] According to an embodiment of the present disclosure, at the same monochromatic light wavelength, the maximum monochromatic light intensity when the gap medium is air is greater than the maximum monochromatic light intensity when the gap medium is liquid; when the monochromatic light intensity significantly decreases within a continuous time period, and the maximum value of the decreased monochromatic light intensity is not greater than the average value of the monochromatic light intensity before the decrease, it is determined that the gap medium at the detection point changes at the current moment.

[0009] According to an embodiment of the present disclosure, determining the gap value between a mask and a substrate based on the type of the gap medium includes: in the case where the gap medium is air, performing low-pass filtering on the monochromatic light interference spectrum, retaining the DC component and the fundamental frequency component in the monochromatic light interference spectrum, obtaining the filtered monochromatic light interference spectrum, and determining the gap value between the mask and the substrate based on the filtered monochromatic light interference spectrum; in the case where the gap medium is liquid, determining the gap value between the mask and the substrate based on the monochromatic light interference spectrum.

[0010] According to an embodiment of the present disclosure, determining the gap value between a mask and a substrate based on the filtered monochromatic light interference spectrum includes: obtaining the filtered maximum monochromatic light intensity, the filtered minimum monochromatic light intensity, the filtered monochromatic light intensity at the current moment, and the current interference order based on the filtered monochromatic light interference spectrum; calculating the gap value between the mask and the substrate according to the refractive index of the gap medium, the monochromatic light wavelength, the filtered maximum monochromatic light intensity, the filtered minimum monochromatic light intensity, the filtered monochromatic light intensity at the current moment, and the current interference order.

[0011] According to an embodiment of the present disclosure, determining the gap value between a mask and a substrate based on monochromatic light interference spectroscopy includes: obtaining the maximum monochromatic light intensity, the minimum monochromatic light intensity, the monochromatic light intensity at the current moment, and the current interference order based on the monochromatic light interference spectroscopy; calculating the gap value between the mask and the substrate according to the refractive index of the gap medium, the monochromatic light wavelength, the maximum monochromatic light intensity, the minimum monochromatic light intensity, the monochromatic light intensity at the current moment, and the current interference order.

[0012] According to an embodiment of the present disclosure, the first gap range is 1 μm to 80 μm, and the second gap range is 1 nm to 1 μm.

[0013] According to an embodiment of the present disclosure, it further includes: when the gap value between the mask and the substrate is within the third gap range, determining the gap value between the mask and the substrate based on the white light interference spectroscopy between the mask and the substrate, or determining the gap value between the mask and the substrate based on the monochromatic light interference spectroscopy between the mask and the substrate; the third gap range is 900 nm to 1 μm.

[0014] According to an embodiment of the present disclosure, the monochromatic light wavelength is 450 nm to 900 nm.

[0015] The micro-nano gap measurement method provided according to an embodiment of the present disclosure at least has the following technical effects:

[0016] This method first determines the gap range through the spectrum of the gap between the mask and the substrate, and then for different gap ranges, uses appropriate methods (white light interference method or monochromatic light interference method) to measure the gap value, improving the accuracy of the gap value. At the same time, by combining the white light interference method and the monochromatic light interference method, accurate measurement of the gap value in a large range of gaps can be achieved.

[0017] When using the white light interference method to measure the gap value, the thickness is measured by using the characteristic points (extreme points and inflection points) of the white light interference spectrum, with small time overhead and improved calculation efficiency on the premise of ensuring accuracy.

[0018] When using the monochromatic light interference method, the type of gap medium is accurately determined in advance according to the monochromatic light intensity method, and then whether to perform monochromatic light compensation is selected according to the type of gap medium, realizing accurate and rapid measurement of nano-scale gaps in multiple media such as air and pure water.

[0019] Using the characteristic point algorithm for white light interference thickness measurement in micron-scale gaps and using monochromatic light interference thickness measurement when the gap is in the nano-scale, high-precision detection results can be obtained regardless of the medium type and the size of the gap value. Description of the Drawings

[0020] Through the following description of the embodiments of the present disclosure with reference to the drawings, the above and other objects, features, and advantages of the present disclosure will become clearer. In the drawings:

[0021] Figure 1 Schematically shows a flowchart of a micro-nano gap measurement method according to an embodiment of the present disclosure.

[0022] Figure 2 Schematically shows a structural diagram of a gap measurement device according to an embodiment of the present disclosure.

[0023] Figure 3 Schematically shows a mask-substrate gap model diagram according to an embodiment of the present disclosure.

[0024] Figure 4 Schematically shows a simulated white light interference spectrum diagram at 1.1 μm according to an embodiment of the present disclosure.

[0025] Figure 5 Schematically shows a simulated spectrum diagram of monochromatic light with a monochromatic light wavelength of 600 nm and an air gap medium according to an embodiment of the present disclosure.

[0026] Figure 6 Schematically shows a simulated spectrum diagram of monochromatic light with a monochromatic light wavelength of 600 nm and a pure water gap medium according to an embodiment of the present disclosure.

[0027] Figure 7 Schematically shows an actual spectrum diagram between a mask and a substrate at a monochromatic light wavelength of 700 nm according to an embodiment of the present disclosure.

[0028] Figure 8 Schematically shows a comparison result diagram between an actual spectrum received when the gap medium is air and a simulated spectrum calculated by a monochromatic light thickness measurement algorithm according to an embodiment of the present disclosure.

[0029] Figure 9 Schematically shows a frequency domain diagram of an actual spectrum and a simulated spectrum calculated by a monochromatic light thickness measurement algorithm according to an embodiment of the present disclosure.

[0030] Figure 10 Schematically shows a comparison result diagram between an actual spectrum of a pure water medium at a wavelength of 700 nm and a simulated spectrum calculated by a monochromatic light thickness measurement algorithm according to an embodiment of the present disclosure.

[0031] Figure 11 Schematically shows a white light interference spectrum diagram with a gap of 950 nm and an air gap medium according to an embodiment of the present disclosure.

[0032] Figure 12 Schematically shows a monochromatic light interference spectrum diagram with a gap of 950 nm, a monochromatic light wavelength of 700 nm, and an air gap medium according to an embodiment of the present disclosure.

[0033] Figure 13Schematically shows the received actual white light interference spectrum according to an embodiment of the present disclosure and the spectrogram after transforming the actual white light interference spectrum from the wavelength domain to the wavenumber domain. Detailed implementation manners

[0034] To make the objectives, technical solutions, and advantages of the present disclosure clearer and more understandable, the present disclosure will be further described in detail below with reference to specific embodiments and the accompanying drawings. Obviously, the described embodiments are some, but not all, of the embodiments of the present disclosure. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the present disclosure without creative efforts shall fall within the scope of protection of the present disclosure.

[0035] The terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the present disclosure. The terms "including", "comprising", etc. as used herein indicate the presence of the described features, steps, operations, and / or components, but do not exclude the presence or addition of one or more other features, steps, operations, or components.

[0036] In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be construed as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Therefore, the features defined with "first" and "second" may explicitly or implicitly include one or more of such features. In the description of the present disclosure, "a plurality" means at least two, such as two, three, etc., unless otherwise specifically defined.

[0037] Figure 1 Schematically shows a flowchart of a micro-nano gap measurement method according to an embodiment of the present disclosure.

[0038] As Figure 1 shown, the micro-nano gap measurement method provided in this embodiment may include operation S110 to operation S130.

[0039] In operation S110, determine the gap range in which the gap value between the mask and the substrate is located based on the spectrum of the gap between the mask and the substrate.

[0040] In operation S120, when the gap value between the mask and the substrate is within the first gap range, determine the gap value between the mask and the substrate based on the white light interference spectrum between the mask and the substrate.

[0041] In operation S130, when the gap value between the mask and the substrate is within the second gap range, determine the gap value between the mask and the substrate based on the monochromatic light interference spectrum between the mask and the substrate.

[0042] According to an embodiment of the present disclosure, during the lithography process, the mask is controlled to approach the substrate, that is, the gap between the mask and the substrate changes from large to small. During this process, corresponding methods can be used to measure accurate gap values for different gap ranges.

[0043] According to an embodiment of the present disclosure, the minimum gap value in the first gap range is greater than or equal to the maximum gap value in the second gap range, that is, the first gap range is larger than the second gap value range. For example, the first gap range can be in the micrometer level, and the second gap range can be in the nanometer level.

[0044] In order to be able to select a suitable method for measuring the gap value, the gap range in which the gap value between the mask and the substrate is located can be determined in advance through the spectrum of the gap between the mask and the substrate, so that it can be determined whether to use the white light interference spectrum between the mask and the substrate to determine the gap value between the mask and the substrate, or to use the monochromatic light interference spectrum between the mask and the substrate to determine the gap value between the mask and the substrate.

[0045] Figure 2 The structural diagram of the gap measurement device according to an embodiment of the present disclosure is schematically shown. Figure 3 The mask-substrate gap model diagram according to an embodiment of the present disclosure is schematically shown.

[0046] As Figure 2 shown and Figure 3 shown, the gap measurement device may include a marble table 1, a support frame 2, a coarse travel displacement stage 3, a nano motion stage 4, a wafer chuck 5, a substrate 6, a mask 7, a main substrate 8, an immersion field droplet system 9, a control system 10, a CCD camera 11, a droplet ejection device 12, a mirror 13, and a gap light source and spectrometer 14.

[0047] The marble table 1 and the support frame 2 play a supporting role. The wafer chuck 5 is used to load the substrate 6 and drive the substrate 6 to move. The main substrate 8 is used to install the immersion field droplet system 9 and the mask 7. The immersion field droplet system 9 is located above the wafer chuck 5 and can eject droplets onto the substrate on the wafer chuck. The control system 10 is used to control the coarse travel displacement stage 3, the nano motion stage 4, the wafer chuck 5, and the immersion field droplet system 9. The CCD camera 11 monitors the morphology of the droplet falling in real time through the mirror 13. The gap is the area between the mask 7 and the substrate 6. The spectrometer of the device 14 shows the white light interference and monochromatic light interference spectra of the gap.

[0048] During the lithography process, the control system 10 controls the movement of the coarse travel displacement stage 3 and the nano motion stage 4, drives the movement of the wafer chuck 5, thereby driving the movement of the substrate 6, and further reducing the distance between the substrate 6 and the mask 7.

[0049] To ensure the lithography effect, the liquid film thickness of the immersion field needs to be set within a certain range. If it is too thin, the ability to improve the lithography resolution is limited; if it is too thick, the working distance between the mask 7 and the substrate 6 cannot meet the lithography requirements, and the excess liquid will overflow to the non-lithography area of the substrate 6. Therefore, the liquid film thickness is at the nanometer level.

[0050] During the movement of the substrate 6, the gap value between the mask 7 and the substrate 6 can be determined by the white light interference spectrum between the mask 7 and the substrate 6, or the gap value between the mask 7 and the substrate 6 can be determined by the monochromatic light interference spectrum between the mask 7 and the substrate 6.

[0051] Through the micro-nano gap measurement method of this embodiment, the gap range is determined in advance by the spectrum of the gap between the mask and the substrate, and then for different gap ranges, appropriate methods are used to measure the gap value, improving the accuracy of the gap value. At the same time, by combining the white light interference method and the monochromatic light interference method, accurate measurement of the gap value in a large range of gaps can be achieved.

[0052] Based on the above embodiment, determining the gap value between the mask and the substrate based on the white light interference spectrum between the mask and the substrate may include:

[0053] Determine the number of periods in the wave number domain of the white light interference spectrum according to the extreme points and inflection points on the spectral curve corresponding to the white light interference spectrum, where the interval between adjacent inflection points and extreme points is one-quarter of a period.

[0054] Obtain the starting value and ending value of the wave number of the white light interference spectrum and the refractive index of the gap medium between the mask and the substrate.

[0055] Determine the gap value between the mask and the substrate according to the number of periods in the wave number domain, the starting value and ending value of the wave number, and the refractive index of the gap medium.

[0056] According to the embodiment of the present disclosure, when the gap value is in the range of 900 nm to 80 μm, according to actual experiments, the gap medium is air, and the characteristic point algorithm calculates the gap value based on the number of spectral periods in the wave number domain (the reciprocal of the wavelength) of the white light interference spectrum. The white light interference spectrum is composed of multiple sine waves. Since one sine period contains one maximum point, one minimum point, and two inflection points, the number of periods of the sine spectrum can be determined by the inflection points and extreme points, and then the gap value can be calculated from the number of periods.

[0057] As a feasible implementation manner, an example of determining the gap value between the mask and the substrate according to the number of periods in the wave number domain, the starting value and ending value of the wave number, and the refractive index of the gap medium is formula (1):

[0058]

[0059] where GAP is the calculated gap thickness; is the number of periods; n is the refractive index of air; is the starting value of the wave number, is the ending value of the wave number.

[0060] It should be noted that the above formula is for clearly explaining the calculation method of the feature point algorithm and does not limit the present disclosure. Various deformations of the calculation method for determining the gap value between the mask and the substrate based on the number of periods in the wave number domain, the starting value and the ending value of the wave number, and the refractive index of the gap medium should fall within the protection scope of the present disclosure.

[0061] Figure 4 Schematically shows a simulated white light interference spectrum at 1.1 μm according to an embodiment of the present disclosure.

[0062] For example, taking Figure 2 the shown mask-substrate model as an example, the simulated white light interference spectrum with a gap of 1.1 μm has 4 extreme points and 5 inflection points in the wave number domain. The rectangular points can represent the inflection points, and the circular points can represent the extreme points. The interval between an inflection point and an extreme point is 1 / 4 period. Therefore, the number of periods in the middle section can be determined to be 2 according to the positions of the inflection points and the extreme points. The distances from the leftmost inflection point to the starting position and from the rightmost inflection point to the ending position can be calculated based on the difference in their abscissas.

[0063] Combined with Figure 4 it can be known that the actual white light interference spectrum has 4 extreme points and 5 inflection points in the wave number domain. The calculated value of the left-side distance is 0.0407, and the calculated value of the right-side distance is 0.0698. At this time, the number of periods 2 calculated using the number of feature points and the distances of the starting section and the ending section can be used to obtain the number of periods Period_Num as 2.1105.

[0064] Since the gap medium is air, the refractive index n is 1. Since the spectrum with a wavelength range from 450 nm to 900 nm is used, the wave number value , . According to the above values, GAP can be calculated to be 1085.4 nm, and the error from the simulated spectrum with a gap value of 1.1 μm is less than 2%.

[0065] Based on the above embodiments, determining the gap value between the mask and the substrate based on the monochromatic light interference spectrum between the mask and the substrate includes:

[0066] Determining the monochromatic light intensity based on the monochromatic light interference spectrum between the mask and the substrate.

[0067] Determining the type of the gap medium between the mask and the substrate based on the monochromatic light intensity.

[0068] Determine the gap value between the mask and the substrate based on the type of the gap medium.

[0069] According to an embodiment of the present disclosure, when the gap value between the mask and the substrate is below 1 μm, a monochromatic light thickness measurement method can be adopted to determine the gap value between the mask and the substrate based on the monochromatic light interference spectrum between the mask and the substrate.

[0070] According to a large number of experiments, when using immersion lithography, the liquid film thickness of the immersion field is usually below 200 nm. Therefore, during the process of gradually reducing the gap from 1 μm, the gap medium changes from air to liquid. When the gap medium is liquid, there is almost no difference between the actual spectrum collected by the spectrum and the simulated spectrum. Therefore, the monochromatic light thickness measurement method does not require compensation. However, when the gap medium is air, there is a difference between the actual spectrum collected by the spectrum and the simulated spectrum, and it is necessary to compensate the monochromatic light thickness measurement method. That is, when using the monochromatic light thickness measurement method, it is first necessary to judge the type of the gap medium.

[0071] The method for judging the type of the gap medium can be: at the same monochromatic light wavelength, the maximum monochromatic light intensity when the gap medium is air is greater than the maximum monochromatic light intensity when the gap medium is liquid; when the monochromatic light intensity decreases significantly within a continuous time period, and the maximum value of the monochromatic light intensity after the decrease is not greater than the average value of the monochromatic light intensity before the decrease, it is determined that the gap medium at the detection point at the current moment has changed.

[0072] When the mask-wafer gap device has exactly the same other conditions except for the gap medium and the incident light is also the same, the maximum monochromatic light intensity of a certain wavelength of monochromatic light when the gap medium is air is greater than the maximum monochromatic light intensity of the same wavelength of monochromatic light when the gap medium is only liquid (this wavelength range is 450 nm to 900 nm, belonging to the visible light range).

[0073] Figure 5 Schematically shows a monochromatic light simulation spectrum diagram with a monochromatic light wavelength of 600 nm and a gap medium of air according to an embodiment of the present disclosure. Figure 6 Schematically shows a monochromatic light simulation spectrum diagram with a monochromatic light wavelength of 600 nm and a gap medium of pure water according to an embodiment of the present disclosure.

[0074] As Figure 5 and Figure 6 shown, when the monochromatic light wavelength is 600 nm, the maximum light intensity when the medium is air is greater than the maximum light intensity when the medium is water. Therefore, the type of the gap medium at a certain moment can be determined by the monochromatic light intensity.

[0075] Taking the 700 nm monochromatic light as an example, the process of judging the medium type is introduced.

[0076] Adopt Figure 2The gap measurement device shown is used for gap detection. Initially, the gap between the mask and the substrate is large, the mask is in the air, and the gap medium is air. As the substrate moves, the gap between the substrate and the mask gradually decreases. Since there are droplets on the substrate, as the distance between the mask and the silicon wafer gradually decreases, the mask touches the droplets, and the area of the droplets will gradually increase due to the pressure of the mask, so that the gap medium at the detection point changes from air to liquid. Due to the different gap media, there is a large change in the light intensity.

[0077] Figure 7 Schematically shows the actual spectrogram between the mask and the substrate when the monochromatic light wavelength is 700 nm according to an embodiment of the present disclosure.

[0078] As Figure 7 shown, the ordinate in the figure is the light intensity, the abscissa is the number of spectral acquisitions, and the acquisition frequency is 25 Hz. Therefore, as the distance between the mask and the silicon wafer decreases, the increase in the number of spectral acquisitions will be accompanied by a change in the light intensity; finally, when the distance between the mask and the silicon wafer is basically constant, the number of spectral acquisitions increases, while the light intensity basically does not change. When the light intensity significantly decreases during a continuous period of time, and the maximum value of the light intensity after the decrease is not greater than the average value of the light intensity before the decrease, it can be considered that the gap medium at the detection point has changed.

[0079] From Figure 7 it can be seen that in the spectrum before point A (the first 250 spectral acquisitions), the light intensity is relatively large; the light intensity rapidly decreases between point A and point B (the number of acquisitions is between 250 and 500), and the maximum value of the light intensity in the spectrum after point B (the light intensity value at point C) is less than the average value of the light intensity before the light intensity decrease (point A). Therefore, it can be known that the medium between the mask and the silicon wafer has changed from air to liquid. And when the number of spectral acquisitions is more than 800, it can be observed that the light intensity is basically stable, and after the number of spectral acquisitions is 1700, the gap value is basically stable.

[0080] Figure 8 Schematically shows the comparison result diagram of the actual spectrum received when the gap medium is air and the simulated spectrum calculated by the monochromatic light thickness measurement algorithm according to an embodiment of the present disclosure.

[0081] As Figure 8 shown, the upper curve is the actual spectrum received by the spectrometer, and the lower curve is the monochromatic light simulated spectrum, and there are differences between the two spectra.

[0082] Figure 9 Schematically shows the frequency domain diagram of the actual spectrum and the simulated spectrum calculated by the monochromatic light thickness measurement algorithm according to an embodiment of the present disclosure.

[0083] As Figure 9 shown, the frequency domain of the monochromatic light simulated spectrum is as shown in the lower figure in Figure 9 below, and the frequency domain of the actual spectrum is asFigure 9 as shown in the upper figure above (both represented by decibel values, ), f dB is the vertical coordinate, which is the decibel value of the frequency of the sampling point (horizontal coordinate), and f is the frequency of the sampling point (horizontal coordinate).

[0084] Reasons for the difference between the actual spectrum and the simulated spectrum of monochromatic light: The simulated spectrum calculated by the monochromatic light thickness measurement algorithm only has the DC component and the fundamental frequency component of the received actual spectrum.

[0085] Figure 10 Schematically shows a comparison result graph of the actual spectrum of pure water medium at a wavelength of 700 nm and the simulated spectrum calculated by the monochromatic light thickness measurement algorithm according to an embodiment of the present disclosure.

[0086] As Figure 10 shown, the light intensity of the received actual spectrum is very close to the light intensity of the simulated spectrum inversely derived according to the monochromatic light thickness measurement algorithm. According to the numerical value, the maximum difference does not exceed 1 nm. And during the actual gap test, due to the influence of acquisition environmental noise, transmission noise, numerical truncation error, etc., the difference between the received light intensity of the spectrometer and the light intensity used in the monochromatic light thickness measurement algorithm is further reduced. Therefore, when applying the monochromatic light thickness measurement algorithm in pure water medium, numerical compensation is not required.

[0087] Based on this, in some embodiments, determining the gap value between the mask and the substrate based on the type of the gap medium may include:

[0088] When the gap medium is air, perform low-pass filtering on the monochromatic light interference spectrum, retain the DC component and the fundamental frequency component in the monochromatic light interference spectrum, obtain the filtered monochromatic light interference spectrum, and determine the gap value between the mask and the substrate based on the filtered monochromatic light interference spectrum.

[0089] When the gap medium is liquid, determine the gap value between the mask and the substrate based on the monochromatic light interference spectrum.

[0090] Further, when the gap medium is air medium, determining the gap value between the mask and the substrate based on the filtered monochromatic light interference spectrum may include:

[0091] Obtain the filtered maximum monochromatic light intensity, the filtered minimum monochromatic light intensity, the filtered monochromatic light intensity at the current moment, and the current interference order based on the filtered monochromatic light interference spectrum.

[0092] Calculate the gap value between the mask and the substrate according to the refractive index of the gap medium, the monochromatic light wavelength, the filtered maximum monochromatic light intensity, the filtered minimum monochromatic light intensity, the filtered monochromatic light intensity at the current moment, and the current interference order.

[0093] When the gap medium is pure water, determining the gap value between the mask and the substrate based on the monochromatic light interference spectrum includes:

[0094] Obtaining the maximum monochromatic light intensity, the minimum monochromatic light intensity, the monochromatic light intensity at the current moment, and the current interference order based on the monochromatic light interference spectrum;

[0095] Calculating the gap value between the mask and the substrate according to the refractive index of the gap medium, the monochromatic light wavelength, the maximum monochromatic light intensity, the minimum monochromatic light intensity, the monochromatic light intensity at the current moment, and the current interference order.

[0096] As a feasible implementation, an example of the monochromatic light thickness measurement algorithm based on monochromatic light interference and obtaining the gap thickness by analyzing the light intensity of the interference light is formula (2):

[0097]

[0098] where GAP is the calculated gap thickness; is the monochromatic light wavelength (monochromatic light within the range of 450 nm to 900 nm is acceptable); n is the refractive index of the medium; k is the current interference order; is the monochromatic light intensity at the current moment (the moment of gap measurement), is the maximum light intensity of the monochromatic light, is the minimum light intensity of the monochromatic light.

[0099] It should be noted that the above formula is to clearly illustrate the calculation method of obtaining the gap thickness by analyzing the light intensity of the interference light based on monochromatic light interference, and does not limit the present disclosure. All variations of the calculation method of obtaining the gap thickness by analyzing the light intensity of the interference light based on monochromatic light interference should fall within the protection scope of the present disclosure.

[0100] When the gap medium is air, I in the above formula λ 、I max and I min are all the light intensities after actual spectral low-pass filtering. When the gap medium is pure water, I in the above formula λ 、I max and I min are all the light intensities of the actual spectrum.

[0101] For example, continuing to refer to Figure 7 , when the gap medium is water, the minimum light intensity of the 700 nm wavelength monochromatic light is 1.1100, the maximum light intensity is 1.2661, and the light intensity value collected at the last time (i.e., the current moment) is 1.1367. After normalization, the value of the minimum light intensity of the monochromatic light can be 0, the value of the maximum light intensity of the monochromatic light can be 1, and the value of the light intensity collected at the last time is 0.1714.

[0102] Calculate the gap value corresponding to the last collected light intensity using formula (2), where the refractive index of pure water \(n = 1.333\); according to the amount of water droplets and the spread area of the water droplets, it can be known that the interference order \(k = 1\) of the monochromatic light spectrum diagram in formula (2).

[0103]

[0104] From the above formula, the gap value corresponding to the last collected spectrum is 35.67 nm.

[0105] Thus, the first gap range can be 1 μm to 80 μm, and the second gap range can be 1 nm to 1 μm.

[0106] Based on the above embodiments, when the gap value between the mask and the substrate is within the third gap range, determine the gap value between the mask and the substrate based on the white light interference spectrum between the mask and the substrate, or determine the gap value between the mask and the substrate based on the monochromatic light interference spectrum between the mask and the substrate. The third gap range can be 900 nm to 1 μm.

[0107] Next, the results of two methods with specific data between 900 nm and 1 μm will be described.

[0108] Figure 11 Schematically shows a white light interference spectrum diagram with a gap of 950 nm and an air gap as the gap medium according to an embodiment of the present disclosure.

[0109] As Figure 11 shown, according to Figure 11 the wavenumber domain spectrum diagram shown, based on the above feature point algorithm, Period_Num = 1.8659 can be obtained. Substitute the variable values into formula (1), and we can get:

[0110]

[0111] Figure 12 Schematically shows a monochromatic light interference spectrum diagram with a gap of 950 nm, a monochromatic light wavelength of 700 nm, and an air gap as the gap medium according to an embodiment of the present disclosure.

[0112] As Figure 12 shown, when the gap value is 950 nm, the received normalized monochromatic light intensity value is as shown by the ordinate at the position of the dot in Figure 12 . Calculate the GAP value using formula (2), taking the received light intensity of the 700 nm monochromatic light represented by the dot as an example. In formula (2), \(\lambda = 700\) nm, \(k = 6\), is the light intensity after low-pass filtering, is the normalized maximum light intensity value, which is 1; is the minimum light intensity value after normalization, which is 0; since the medium in the 950 nm time gap is air, so n = 1.

[0113] Substitute the variable values into Equation (2) and calculate to obtain:

[0114]

[0115] According to the above calculation results, when the air gap is 950 nm, both the feature point algorithm and the monochromatic light thickness measurement compensation algorithm can obtain relatively accurate gap values. However, it can be seen that the calculated gap value of the monochromatic light thickness measurement compensation algorithm is more accurate, that is, when the gap value is between 900 nm and 1 μm, either the feature point algorithm or the monochromatic light thickness measurement compensation algorithm can be used to measure the gap value. Therefore, according to the accuracy, the gap measurement cross-region of the feature point algorithm and the monochromatic light thickness measurement compensation algorithm can be expanded to 900 nm. If the gap value is less than 900 nm, only the monochromatic light thickness measurement compensation algorithm is used to calculate the gap value. At the same time, it also shows that the overlapping range of the gap value between 900 nm and 1 μm ensures that during the process of gap reduction, the feature point algorithm can accurately switch to the monochromatic light thickness measurement algorithm.

[0116] Figure 13 Schematically shows the received actual white light interference spectrum according to an embodiment of the present disclosure and the spectrum diagram after transforming the actual white light interference spectrum from the wavelength domain to the wave number domain.

[0117] As Figure 13 shown, Figure 13 In the left figure in [reference], it is the actual white light interference spectrum, and in the right figure, it is the spectrum diagram after transforming the actual white light interference spectrum from the wavelength domain to the wave number domain. When the gap is greater than 80 μm, the larger the gap, the more periods of the received spectrum, that is, the more extreme points, and it is impossible to accurately distinguish the sine period, so it is impossible to obtain the accurate number of periods. Therefore, the feature point algorithm is applicable to the case where the gap is less than 80 μm. When the gap is less than 1 μm, as the gap becomes smaller and smaller, the number of variable extreme points and the number of inflection points are smaller than the 4 and 5 at 1 μm. Since Period_Num in Equation (1) is determined by the number of extreme points and inflection points, when the number of extreme points and inflection points is too small, the calculation error of the Period_Num value increases and the accurate value decreases. And when the number of extreme points and inflection points is both 0, it is impossible to calculate the gap thickness GAP through Equation (1).

[0118] The specific embodiments described above further elaborate on the objective, technical solutions, and beneficial effects of the present disclosure. It should be understood that the above are only the preferred embodiments of the present disclosure and the technical principles applied. Those skilled in the art will understand that the present disclosure is not limited to the specific embodiments described herein. Various obvious changes, re-adjustments, and substitutions can be made by those skilled in the art without departing from the protection scope of the present disclosure. Therefore, although the present disclosure has been described in relatively detail through the above embodiments, the present disclosure is not limited to the above embodiments. Without departing from the concept of the present disclosure, more other equivalent embodiments can be included, all of which fall within the protection scope of the present disclosure.

Claims

1. A micro-nano gap measurement method, characterized in that: include: Determining a gap range in which the gap value between the mask and the substrate lies based on a spectrum of the gap between the mask and the substrate; When the gap value between the mask and the substrate is within a first gap range, determining the gap value between the mask and the substrate based on a white light interference spectrum between the mask and the substrate; When the gap value between the mask and the substrate is within a second gap range, determining the gap value between the mask and the substrate based on a monochromatic light interference spectrum between the mask and the substrate; The minimum gap value in the first gap range is greater than or equal to the maximum gap value in the second gap range.

2. The method according to claim 1, characterized in that The step of determining the gap value between the mask and the substrate based on a white light interference spectrum between the mask and the substrate comprises: Determining the number of periods in the wavenumber domain of the white light interference spectrum according to the extreme value points and inflection points on the spectrum curve corresponding to the white light interference spectrum, wherein the interval between adjacent inflection points and extreme value points is one quarter of a period; Obtaining the starting value and the ending value of the wave number of the white light interference spectrum and the refractive index of the gap medium between the mask and the substrate; The gap value between the mask and the substrate is determined according to the number of periods in the wave number domain, the starting value and the ending value of the wave number, and the refractive index of the gap medium.

3. The method according to claim 1, characterized in that: The step of determining the gap value between the mask and the substrate based on the monochromatic light interference spectrum between the mask and the substrate comprises: Determining the intensity of the monochromatic light based on the monochromatic light interference spectrum between the mask and the substrate; Determining the type of the gap medium between the mask and the substrate at different moments based on the intensity of the monochromatic light; A gap value between the mask and the substrate is determined based on the type of the gap medium.

4. The method according to claim 3, characterized in that Under the same monochromatic light wavelength, the maximum monochromatic light intensity when the gap medium is air is greater than the maximum monochromatic light intensity when the gap medium is liquid; When the intensity of the monochromatic light decreases significantly in a continuous period of time, and the maximum value of the intensity of the monochromatic light after the decrease is not greater than the average value of the intensity of the monochromatic light before the decrease, it is determined that the gap medium at the detection point at the current moment has changed.

5. The method according to claim 3 or 4, characterized in that: The step of determining a gap value between the mask and the substrate based on the type of the gap medium comprises: When the gap medium is air, low-pass filtering is performed on the monochromatic light interference spectrum to retain a DC component and a fundamental frequency component in the monochromatic light interference spectrum to obtain a filtered monochromatic light interference spectrum, and determining a gap value between the mask and the substrate based on the filtered monochromatic light interference spectrum; In the case where the gap medium is liquid, a gap value between the mask and the substrate is determined based on the monochromatic light interference spectrum.

6. The method according to claim 5, characterized in that The step of determining the gap value between the mask and the substrate based on the filtered monochromatic light interference spectrum comprises: Based on the filtered monochromatic light interference spectrum, obtain the maximum monochromatic light intensity after filtering, the minimum monochromatic light intensity after filtering, the monochromatic light intensity after filtering at the current moment, and the current interference order; The gap value between the mask and the substrate is calculated according to the refractive index of the gap medium, the wavelength of the monochromatic light, the maximum intensity of the monochromatic light after filtering, the minimum intensity of the monochromatic light after filtering, the intensity of the monochromatic light after filtering at the current moment, and the current interference order.

7. The method according to claim 5, characterized in that The step of determining the gap value between the mask and the substrate based on the monochromatic light interference spectrum comprises: Based on the monochromatic light interference spectrum, the maximum monochromatic light intensity, the minimum monochromatic light intensity, the monochromatic light intensity at the current moment, and the current interference order are obtained; The gap value between the mask and the substrate is calculated according to the refractive index of the gap medium, the wavelength of the monochromatic light, the maximum monochromatic light intensity, the minimum monochromatic light intensity, the monochromatic light intensity at the current moment, and the current interference order.

8. The method according to claim 1, characterized in that The first gap ranges from 1 μm to 80 μm, and the second gap ranges from 1 nm to 1 μm.

9. The method according to claim 8, characterized in that Also includes: When the gap value between the mask and the substrate is within a third gap range, determining the gap value between the mask and the substrate based on a white light interference spectrum between the mask and the substrate, or determining the gap value between the mask and the substrate based on a monochromatic light interference spectrum between the mask and the substrate; The third gap ranges from 900 nm to 1 μm.

10. The method according to claim 6, characterized in that The monochromatic light has a wavelength of 450 nm to 900 nm.

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