Method for measuring hole depth by using phase extraction information of reflection spectrum, measuring system and computer readable medium

Abstract

The invention discloses a method for measuring hole depth by using phase extraction information of a reflection spectrum, a measuring system and a computer readable medium. The method comprises the following steps of: obtaining the reflection spectrum, obtaining the relevance between the intensity of reflected light and the wave number, extracting the phase and judging the hole depth. First distribution data between the intensity of the reflected light and the wave number is converted into second distribution data between the phase and the wave number, and information of the hole depth of the hole structure is obtained through operation of the slope value. Therefore, the measurement resolution can be increased, and the accuracy is also improved.

Description

Technical Field

[0001] The present invention relates to a measurement technique for a structure. More specifically, the present invention relates to a method, a measurement system, and a computer-readable medium for measuring the depth of a hole by extracting information on the phase of a reflection spectrum.

Background Art

[0002] In the technical field of semiconductor integrated circuits, in order to increase the space utilization rate and improve the problem of data transmission bottlenecks, semiconductor integrated circuits have entered a three-dimensional stacking (such as 2.5D, 3D) packaging process, and the problem described above is solved by stacking bare chips.

[0003] In these stacked structures, through the technology of Through Silicon Via (TSV), signals of different chips can be connected together, improving the space utilization rate and shortening the conduction distance, thereby achieving an increase in the transmission speed of signals and electricity.

[0004] In the process of fabricating Through Silicon Via (TSV), there are multiple steps due to slight differences in manufacturing techniques. Generally, these steps include, for example, Via Formation, Via Filling, Chemical-Mechanical Polishing (CMP), Wafer Thinning, Wafer Bonding, and various TSV integration techniques (such as Via First, Via Last), etc.

[0005] Among them, the hole is the basis of the entire Through Silicon Via structure. Therefore, the depth dimension of the hole plays an important role in the entire process of fabricating Through Silicon Via and must be accurately controlled. However, due to the high aspect ratio structural characteristics of the vias in the Through Silicon Via structure, it is difficult to measure the depth dimension of the holes, and the accuracy is even more severely tested.

Summary of the Invention

[0006] In some embodiments disclosed in the present invention, the measurement resolution of the depth dimension of the hole is increased, thereby improving the accuracy.

[0007] According to some embodiments, the present invention provides a method for measuring the depth of a hole by using phase extraction information of a reflection spectrum, including: obtaining a reflection spectrum from a target area having a hole structure with a high aspect ratio; based on the reflection spectrum, obtaining a first distribution data between the reflected light intensity and the wave number; converting the first distribution data into a second distribution data between the phase and the wave number through a phase extraction program; and determining the depth of the hole structure according to the slope value of at least one straight line presented by the second distribution data, and using the wavelength unit of the reflection spectrum as the measurement unit of the hole depth.

[0008] According to some embodiments, when the second distribution data presents a single straight line, half of the slope value of the straight line is the depth of the hole structure.

[0009] According to some embodiments, it discloses a phase extraction program, which includes: removing the DC term in the first distribution data; performing a Hilbert transform to obtain an analytic signal having a real part term in a cosine form and an imaginary part term in a sine form; and obtaining a distribution relationship between the phase and the wave number as the second distribution data based on the arctangent function of the real part term and the imaginary part term.

[0010] According to some embodiments, it discloses a phase extraction program, which includes: converting the first distribution data into an intermediate data having a real part term and an imaginary part term; performing a Fourier transform; performing steps of removing and filling points, only retaining one of the real part term or the imaginary part term, removing other data and filling in a complex number of data points with a fixed power density to maintain the data length; performing an inverse Fourier transform; and obtaining a distribution relationship between the phase and the wave number as the second distribution data.

[0011] According to some embodiments, when the surrounding surface of the hole structure has a light-transmitting oxide layer, the phase data in the first distribution data defines a hole depth phase and a thin film phase, and two straight lines can be presented in the second distribution data. Among them, the slope value of the straight line with a larger slope among the two straight lines is the first value, and the slope value of the straight line with a smaller slope among the two straight lines is the second value. Half of the second value can be the thickness of the oxide layer. Half of the sum of the first value and the second value can be the depth of the hole structure. The wavelength unit of the reflection spectrum can be the measurement unit of the thickness of the oxide layer.

[0012] According to some embodiments, the present invention also discloses a non-volatile computer-readable storage medium that can store a computer program. The computer program is used to be loaded into an arithmetic processing device and can be used to make the arithmetic processing device execute the method described above.

[0013] According to some embodiments, the present invention also discloses a measurement system for measuring the hole depth by using the phase extraction information of the reflection spectrum, including: an optical interference measurement device and an operation processing device. The optical interference measurement device can be used to obtain a reflection spectrum from a target area. The operation processing device is coupled to the optical interference measurement device, and the operation processing device can be used to execute the method described above.

[0014] In this way, based on the relationship between the reflected light intensity and the wave number, through conversion, the distribution relationship between the phase and the wave number is obtained. Subsequently, through the distribution relationship presented in a linear form, by calculating the slope value, the hole depth information of the hole structure is obtained, and further, the thickness information of the oxide layer can also be known. This achieves an increase in measurement resolution and also brings an improvement in accuracy.

Description of the Drawings

[0015] Figure 1 It is a schematic diagram of the hole structure; Figure 2 It is a schematic diagram of the measurement system according to some embodiments; Figure 3 It is a flowchart of the method for measuring the hole depth by using the phase extraction information of the reflection spectrum according to some embodiments; Figure 4 It is a relationship diagram between the reflected light intensity and the wave number according to some embodiments; Figure 5 For Figure 4 It is a relationship diagram between the phase and the wave number in the embodiment; Figure 6 It is a relationship diagram between the reflected light intensity after removing the DC term and the wave number according to some embodiments; Figure 7 It is a frequency spectrum diagram after Fourier transform of the first distribution data according to some embodiments; Figure 8 For Figure 7 It is a processed frequency spectrum diagram in the embodiment; Figure 9 It is a schematic diagram of the hole structure with an oxide layer; Figure 10 It is a relationship diagram between the reflected light intensity and the wave number of the hole structure with an oxide layer; Figure 11 For Figure 10 It is a relationship diagram between the phase and the wave number in the embodiment.

Detailed Embodiments

[0016] To fully understand the purpose, features, and effects of the present invention, the following specific embodiments are now used in conjunction with the accompanying drawings to make a detailed description of the present invention, as follows:

[0017] In this document, the terms "a" or "an" are used to describe elements or features. This is for convenience of description only and provides a general meaning to the scope of this document. Therefore, unless clearly indicated otherwise, such description should be understood to include one or at least one, and the singular also includes the plural.

[0018] In this document, the terms "comprising", "including", "having" or any other similar terms are not limited to only these elements or features listed in this document, but may include other parts that are not explicitly listed but are usually inherent to the described elements or features.

[0019] In this document, terms such as "first" or "second" and other similar ordinal terms are used to distinguish or refer to related elements or features that are the same or similar, and do not necessarily imply the procedural order of these elements or features. It should be understood that in certain situations or configurations, the ordinal terms can be used interchangeably without affecting the embodiments disclosed in this application or related embodiments.

[0020] Please refer to Figure 1 , which is a schematic diagram of a hole structure. After providing the probe light to the hole structure with a hole depth h, the incident light forms a first reflected light R1 on the surrounding surface of the hole structure 300, and the incident light forms a second reflected light R2 at the bottom of the hole of the hole structure 300. Since there is an optical path difference between the first reflected light R1 and the second reflected light R2, the hole depth h of the hole structure 300 can be obtained based on the information of this optical path difference.

[0021] Please refer to Figure 2 , which is a schematic diagram of a measurement system according to some embodiments. The measurement system includes: an optical interferometry device 100 and an arithmetic processing device 200. The optical interferometry device 100 is used to provide illumination light 101 to the object x to be measured having a hole structure 300 to scan the target area (providing illumination light one by one for each hole or each area). Among them, an interference signal corresponding to each provision of illumination light to a hole or an area is obtained. In some embodiments, each scanning measurement operation of the optical interferometry device 100 is only performed on a single hole (providing illumination light and obtaining a reflection spectrum). In this way, the relevant information of the hole structure can be determined more quickly and accurately.

[0022] Through the light source unit 120 and the beam splitting unit 130 in a coaxial illumination configuration, the reflected light from the hole structure 300 can be captured by the imaging unit 110 to form a spectral signal. Due to the aforementioned optical path difference, the imaging unit 110 can capture a spectral signal with an interference phenomenon on the object to be measured having the hole structure 300. The arithmetic processing device 200 is coupled to the light source unit 120 and the imaging unit 110 of the optical interferometry device 100 to control the scanning operation, receive the spectral signal, and perform subsequent processing steps such as phase extraction.

[0023] Figure 2 The configuration of the optical interferometric measurement device 100 is only an example. The optical interferometric measurement device can be, for example, a spectroscopic interferometer or other types of interferometers. That is to say, for the reflected light from the reference surface (such as the surface) of the object to be measured and the reflected light from the bottom of the hole structure, any measurement device that can acquire these two reflected lights and obtain the optical interference phenomenon between them can be applied to the embodiments of the present invention. The arithmetic processing device 200 can be a single computer, multiple computers, or a single arithmetic processing module or multiple arithmetic processing modules configured in the overall measurement system. The arithmetic processing device 200 is used to receive and process the spectral signals of the reflected light provided by the optical interferometric measurement device 100.

[0024] Next, please refer to Figure 3 , which is a flowchart of a method for measuring the hole depth by extracting information on the phase of the reflection spectrum according to some embodiments.

[0025] The arithmetic processing device 200 is configured to execute the following method for measuring the hole depth:

[0026] Step S110, a step of obtaining the reflection spectrum. In this step, the reflection spectrum from the target area is obtained. Among them, the target area has a hole structure with a high aspect ratio. Among them, the target area may have only a single hole structure or a plurality of hole structures.

[0027] Step S120, a step of obtaining the correlation between the reflected light intensity and the wave number. In this step, based on the reflection spectrum, it is converted into a distribution relationship that can present the correlation between the light intensity of the reflected light and the wave number, thereby obtaining the first distribution data that can represent the correlation between the light intensity and the wave number.

[0028] Step S130, a phase extraction step. In this step, the first distribution data is converted through a phase extraction program into a distribution relationship that can present the correlation between the phase and the wave number, thereby obtaining the second distribution data that can represent the correlation between the phase and the wave number.

[0029] Step S140, a hole depth determination step. In this step, based on the slope value of at least one straight line that can be presented by the second distribution data, the hole depth of the hole structure is determined. Among them, the wavelength unit of the reflection spectrum is used as the measurement unit of the hole depth.

[0030] Light has the characteristics of a sine wave. The different reflected lights from the surrounding surface (such as the hole top) of the hole structure and the bottom of the hole structure can cause a redistribution of the light intensity in space based on the optical path difference, forming an interference phenomenon. By extracting the phase information in the reflection spectrum, the distribution relationship between the phase and the wave number can be obtained, and this distribution relationship can be used to obtain the hole depth information of the hole structure. In addition, the resolution can be effectively improved.

[0031] In some embodiments, in step S120, corresponding light intensity values may be obtained based on wave numbers at the same interval. In this way, when the wavelengths in the reflected spectrum data are converted to wave numbers, common interpolation methods or other methods can be used to obtain the corresponding interpolated light intensity values.

[0032] Next, please refer to Figure 4 , which is a graph showing the relationship between the reflected light intensity and the wave number according to some embodiments. The wave number is the number of wavelengths within a length of 2π, or equivalently, the number of times the wave repeats within a length of 2π. Defining the wave number as k, then k = 2π / λ.

[0033] In the case where the reflected spectrum has an interference phenomenon based on the optical path difference, the optical path difference is twice the depth of the hole (an additional distance of h is traveled during incidence and reflection). Among them, the number of wavelengths λ within the distance of the optical path difference (hole depth h) can be expressed as (2h / λ), and multiplying by 2π gives the phase, as shown in Equation (1), where a(λ) and b(λ) represent the phenomenon that different substances exhibit different reflectivities for different spectral wavelengths, and a(λ) can represent the light intensity of the background.

[0034] After substituting the phase parameter in the sine wave term of Equation (1) with the wave number k, Equation (2) is obtained. Equation (2) represents a function that can present the first distribution data.

[0035] After Equation (2) undergoes a phase extraction process, the distribution relationship between the phase and the wave number as shown in Figure 5 can be obtained. Figure 5 The oblique straight line in

[0036] can be expressed by the following Equation (3), where P is the phase.

[0037] Regarding the phase extraction process, there are many ways to extract phase information from Equation (2) to convert the first distribution data into the second distribution data of the distribution relationship between the phase and the wave number.

[0038] In some embodiments, the Hilbert Transform may be used. Since Equation (2) is a cosine function, a sine function with a 90-degree phase shift can be obtained through the Hilbert Transform. Then, by taking the arctangent function of the real part term of the cosine function and the imaginary part term of the sine function, the second distribution data can be obtained.

[0039] Specifically, in the phase extraction procedure of this embodiment, to remove the background reflected light intensity that varies with the incident light wavelength (which has been converted to wave number in Equation (2)), Equation (2) can be rewritten to obtain the function of S(k) - Equation (4). The relationship diagram between the reflected light intensity and the wave number after removing the DC term is as Figure 6 shown. Among them, is After taking the Hilbert Transform of the function S(k), a function with a 90-degree phase shift is obtained - Equation (5).

[0040] Based on Equation (4) and Equation (5), the function of the analytical signal S a (k) is as shown in Equation (6). The analytical signal S a (k) represents the distribution function between the wave number and the signal value. The operations required for phase extraction of the analytical signal S a (k) are as shown in Equation (7). Divide the real part term and the imaginary part term of the analytical signal S a (k) respectively, and take the arctangent function to obtain the phase value corresponding to the corresponding wave number k. In this way, based on is the relationship formula of, the distribution relationship between each wave number k and the corresponding phase value as the second distribution data can be obtained (similar to Figure 5 ), which is an oblique straight line. Half of the slope of this oblique straight line (i.e., 2h) is the hole depth h of the hole structure.

[0041] In some other embodiments, the phase extraction procedure can also obtain the distribution relationship between the phase and the wave number through Fourier Transform. Specifically, in the phase extraction procedure of this embodiment, Equation (2) can be first transformed by Euler's formula to obtain the function of Equation (8).

[0042] Among them, And then, perform Fourier Transform on Equation (8) as the intermediate data to obtain as Figure 7The spectrum diagram shown can present the distribution relationship between the power density and the frequency f. After the Fourier transform of Equation (8), Equation (9) is presented, where c(f - 2h) is the non-conjugate term, c*(f + 2h) is the conjugate term, and A(f) is the power density value of the DC term (frequency is 0). FT(I(k)) = A(f) + C(f - 2h) + C * (f + 2h) Equation (9)

[0043] And, retain one of the non-conjugate term and the conjugate term, and remove the rest, as Figure 8 the processed spectrum diagram shown. That is, only retain the waveform represented by the non-conjugate term or the conjugate term (please refer to Figure 7 and Figure 8 ), and fill in the removed part with a complex number of data points with a fixed power density value (for example: 0) to maintain the overall data length for subsequent correct calculation of phase information. Taking the removal of the conjugate term as an example, Equation (9) is obtained after the inverse Fourier transform to obtain Equation (10).

[0044] Among them, Equation (10) can be used to obtain the phase corresponding to each wave number k, forming a distribution relationship as the second distribution data. After performing phase processing on Equation (10), a straight line similar to Figure 5 shown can be obtained (the relationship formula between phase and wave number, the function is which is an oblique straight line, and half of the slope of this oblique straight line (i.e., 2h) is the hole depth h of the hole structure. Among them, in the use of the expression (using the instruction imag), it can be as shown in the following Equation (11):

[0045] In some other embodiments, the phase extraction program can also directly obtain the corresponding function based on the first distribution data using curve fitting, and then obtain the second distribution data representing the distribution relationship between phase and wave number based on the known function and the corresponding parameters. Many algorithms can achieve the calculation of curve fitting. For example, but not limited to this, the Levenberg-Marquardt method (LM) algorithm is one of them.

[0046] Specifically, through the curve fitting of the first distribution data, the function can be directly obtained (the function that can plot the first distribution data, that is, Equation (2)). In addition to directly obtaining the hole depth h of the hole structure from the function, the distribution relationship between the wave number and the corresponding phase required in the phase extraction program can also be further obtained for comparison and verification.

[0047] In an embodiment of the present invention, the depth of the hole structure is obtained through the relationship between the phase and the wave number. Since the correlation information between the phase and the wave number is used, compared with the method of obtaining the hole depth with the frequency as the main parameter, the method of obtaining the hole depth based on the correlation information between the phase and the wave number provides higher resolution.

[0048] In the case of using a spectral interferometer, the probing light given to the probing target has the characteristic that the wavelength varies within an interval, and the formed synthetic wavelength can be expressed by Equation (20), where λ max is the longest wavelength within the interval, and λ min is the shortest wavelength within the interval.

[0049] In the method of estimating scale information (such as height, depth, etc.) based on the change characteristics caused by the optical path difference, the minimum observable change is δh (i.e., the resolution). In addition, in the method of estimating the scale information by determining the phase shift degree through the peak of the spectrogram after Fourier transform, the peak of the spectrogram can represent the number of periods of the optical interference fringes. The phase shift degree is related to the number of periods of the sine wave interference pattern. Among them, the length of each period is 2π, so the product of the number of periods and 2π is the total phase shift. In this way, the calculation formula of the resolution δh is as shown in Equation (21), where the total phase shift is approximately 2π in this operation.

[0050] On the other hand, as a comparison, also based on Fourier transform, but using the method of using phase and wave number information and related to the conjugate term (i.e., only retaining one of the real part term or the imaginary part term). In this method using phase information, the phase shift degree changes with the optical path difference, and the total phase shift is presented as shown in Equation (22), where N is the number of fringe periods (integer part) within the interference fringes, ε is the remaining part (fractional part) of the interference fringe pattern, and F is the number of imaging frames.

[0051] And, the calculation formula of the resolution δh is as shown in Equation (24),

[0052] In this way, taking the wavelength range of 450nm to 900nm, the number of imaging frames of 900, and the actual depth size of 202.3μm as an example.

[0053] For the method of obtaining the hole depth with the frequency as the main parameter, the algorithm of its resolution is as shown in Equation (24):

[0054] For the method using phase and wavenumber information and associated with conjugate terms, the resolution algorithm is as shown in Equation (25):

[0055] Based on the calculation results of Equation (24) and Equation (25), for the method of obtaining the hole depth information by using the correlation between phase and wavenumber in the embodiments of the present invention, compared with the method of determining the phase shift degree only based on the peak value of the spectrogram after Fourier transform, the resolution obtained in the embodiments of the present invention is increased by nearly 2.5 times. Obviously, the accuracy of the hole depth size can be effectively improved.

[0056] Next, please refer to Figure 9 , which is a schematic diagram of a hole structure with an oxide layer. When the surrounding surface of the hole structure 300 has a light-transmissive thin-film oxide layer 310, in addition to forming a first reflected light R1 on the surrounding surface of the hole structure 300 and a second reflected light R2 at the bottom of the hole structure 300, the incident light will also form a third reflected light R3 on the top surface of the oxide layer 310.

[0057] The information of the reflected light can be captured by the light interference measurement device 100 exemplified in Figure 2 . From the interference phenomenon between these reflected lights and the corresponding period presented, it can also be used as the basis for determining the information of the hole depth h and the oxide layer thickness d.

[0058] Please refer to Figure 10 , which is a relationship diagram between the reflected light intensity and the wavenumber of a hole structure with an oxide layer. In the figure, the waveform with low frequency and large amplitude presents the light intensity distribution of the interference light formed by the first reflected light R1 and the third reflected light R3, and this distribution relationship directly corresponds to the information of the oxide layer thickness d. On the other hand, the waveform with high frequency and small amplitude in the figure presents the light intensity distribution of the interference light formed by the second reflected light R2 and the third reflected light R3, and this distribution relationship does not directly correspond to the hole depth h. Among them, the waveform with high frequency and small amplitude presents a waveform form with the waveform with low frequency and large amplitude as the carrier wave.

[0059] In the embodiment where the surrounding surface of the hole structure 300 has a light-transmissive oxide layer 310, the relationship between the phase and the wavenumber of the interference light formed by the first reflected light R1 and the third reflected light R3 can be expressed by the following Equation (26) based on the Fresnel formula. Among them, is the phase of the interference light formed by the first reflected light R1 and the third reflected light R3. N 1 (k) is the refractive index of the oxide layer that varies with the wavenumber (that is, based on the different wavelengths of the incident light, the refractive index passed through is also different). is the non-linear term of such a thin-film oxide layer.

[0060] In addition, the relationship between the phase and the wave number of the interference light formed by the second reflected light R2 and the third reflected light R3 can be expressed by the following formula (27). Among them, is the phase of the interference light formed by the second reflected light R2 and the third reflected light R3. is the DC term.

[0061] From Figure 10 the relationship between the reflected light intensity and the wave number of the example (the first distribution data), the second distribution data between the phase and the wave number can be obtained through a phase extraction program (in this embodiment, the curve fitting method is adopted). Among them, the fitting function is as shown in formula (28), the fitting function is as shown in formula (29).

[0062] Please refer to Figure 11 , which is Figure 10 the relationship diagram between the phase and the wave number of the embodiment. Figure 11 Among the two straight lines of , the straight line L1 represents formula (28), and the straight line L2 represents formula (29), showing the relationship between the phase and the wave number. Among them, the oxide layer thickness d of the thin film type oxide layer 300 can be directly obtained based on the slope value of the straight line L2, and it can be known from formula (29) that half of the slope value of the straight line L2 is the thickness information of the oxide layer 300.

[0063] On the other hand, it can be known from formula (27) and formula (28) that the slope value obtained by formula (28) contains the relevant information of the hole depth h and the oxide layer thickness d, and the hole depth h is much larger than the oxide layer thickness d. Therefore, the slope value obtained from formula (28) is inherently larger than the slope value obtained from formula (29). That is to say, Figure 11 in the second distribution data of , two straight lines are presented. The slope value of the straight line with the larger slope among the two straight lines includes the information of the hole depth h and the oxide layer thickness d. The slope value of the straight line with the smaller slope among the two straight lines is the information of the oxide layer thickness d.

[0064] Furthermore, it can be known from formula (27) and formula (28) that the slope value obtained by formula (28) is not only simply the information of h, but also the information of N 1 (k)d is subtracted. In this way, to obtain the correct information of the hole depth h, the subtracted information needs to be added back, that is, the calculation method shown in formula (30) is presented.

[0065] Therefore, by adding the slope value obtained from Equation (28) to the slope value obtained from Equation (29) and then dividing the sum by 2, the hole depth h can be obtained. In this way, when the surrounding surface of the hole structure 300 has a light-transmitting oxide layer 310, the phase information in the first distribution data can present the phase information contributed by the hole depth and the phase information contributed by the thin film, and two straight lines can be presented in the second distribution data. Among them, the slope value with the larger slope among the two straight lines is the first value, and the slope value with the smaller slope among the two straight lines is the second value. Half of the second value is the oxide layer thickness d of the oxide layer 300, and half of the sum of the first value and the second value is the hole depth h of the hole structure 300. Among them, the wavelength unit of the reflection spectrum is the measurement unit of the hole depth h and the oxide layer thickness d.

[0066] In this way, as long as the second distribution data presented between the phase and the wave number is obtained, the determination of the hole depth h and the oxide layer thickness d can be performed. Therefore, any mathematical processing program that can obtain the distribution relationship between the phase and the wave number (the second distribution data) from the relationship between the reflected light intensity and the wave number (the first distribution data) can be applied. For example, since the relationship between the reflected light intensity and the wave number (the first distribution data) presents a corresponding distribution relationship related to the hole depth or the film thickness on different periods, by filtering out some signals first, the corresponding straight lines (the distribution relationship between the phase and the wave number) can be obtained one by one. Putting the two straight lines together can also present a distribution relationship diagram as shown in Figure 11 the example for performing the operations of the hole depth h and the oxide layer thickness d as described above.

[0067] The various functions and operations performed in the form of software as described above can be achieved by storing a computer program in a non-volatile computer-readable storage medium and then executing it. The computer program is stored in the medium. The computer program includes a plurality of instructions for causing an electronic device (such as the aforementioned arithmetic processing device 200, or various computer devices, network devices, or other electronic devices, etc.) or a processor to execute the method for measuring the hole depth by extracting information using the phase of the reflection spectrum according to each embodiment of the present invention.

[0068] In summary, based on the relationship between the reflected light intensity and the wave number, after conversion to obtain the relationship between the phase and the wave number, the information of the hole depth h of the hole structure 300 can be obtained by calculating the slope value from the distribution relationship presented in a straight line form, and further the information of the oxide layer thickness d can be obtained. It can not only increase the measurement resolution but also improve the accuracy.

[0069] The present invention has disclosed preferred embodiments above. However, those skilled in the art should understand that the embodiments herein are only used to describe the present invention and should not be construed as limiting the scope of the present invention. It should be noted that all equivalent changes and permutations to the embodiments should be understood to be covered within the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.

Reference Signs

[0070] 100 Optical interferometry device 101 Illumination light 110 Image acquisition unit 120 Light source unit 130 Beam splitting unit 200 Operation processing device 300 Hole structure d Oxide layer thickness h Hole depth L1 Straight line L2 Straight line R1 First reflected light R2 Second reflected light R3 Third reflected light S110 - S140 Steps x Object to be measured

Claims

1. A method for hole depth measurement using phase extraction information of a reflection spectrum, comprising: Obtaining a reflection spectrum from a target region having a hole structure with a high aspect ratio; Based on the reflection spectrum, obtaining a first distribution data between the intensity of the reflected light and the wave number; Converting the first distribution data into a second distribution data between phase and wave number through a phase extraction process; and The hole depth of the hole structure is determined according to the slope value of at least one straight line presented by the second distribution data, and the wavelength unit of the reflection spectrum is used as the measurement unit of the hole depth.

2. The method of claim 1, wherein: When the second distribution data presents a single straight line, half of the slope value of the straight line is the hole depth of the hole structure.

3. The method of claim 1, wherein: The phase extraction procedure includes: removing the DC term in the first distribution data; Performing a Hilbert transform to obtain an analytical signal having a real part term in a cosine form and an imaginary part term in a sine form; and Based on an inverse tangent function of the real part term and the imaginary part term, a distribution relationship between the phase and the wave number is obtained as the second distribution data.

4. The method of claim 1, wherein: The phase extraction procedure includes: Converting the first distributed data into a transfer data having a real part term and an imaginary part term; Perform a Fourier transform; Performing the steps of removing and filling points, retaining only one of the real part or the imaginary part, removing the other data and filling a plurality of data points with a fixed power density to maintain the data length; performing an inverse Fourier transform; and The distribution relationship between the phase and the wave number is obtained as the second distribution data.

5. The method according to any one of claims 1 to 4, wherein: When the surrounding surface of the hole structure has a light-transmitting oxide layer, the phase data in the first distribution data defines a hole depth phase and a thin film phase, and two straight lines are presented in the second distribution data, wherein the slope value of the straight line with a larger slope among the two straight lines is a first value, the slope value of the straight line with a smaller slope among the two straight lines is a second value, half of the second value is the thickness of the oxide layer, half of the sum of the first value and the second value is the hole depth of the hole structure, and the wavelength unit of the reflection spectrum is the measurement unit of the thickness of the oxide layer.

6. A non-volatile computer-readable storage medium storing a computer program for loading into a processing device and for causing the processing device to execute the method according to any one of claims 1 to 5.

7. A measurement system for hole depth measurement using phase extraction information of a reflection spectrum, comprising: an optical interferometry device for acquiring a reflection spectrum from a target area; and A processing device is coupled to the optical interferometry device, wherein the processing device is configured to execute the method as claimed in any one of claims 1 to 5.

8. The measuring system of claim 7, wherein: The optical interference measurement device is controlled so that a scanning measurement action is performed only on a single hole structure in the target area.

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