Polymer monitoring device and method using terahertz waves

Abstract

A polymer monitoring device using terahertz waves is provided. The polymer monitoring device using terahertz waves may comprise: an emitter which emits terahertz waves toward a polymer thin film coated on a target substrate; a detector which detects terahertz waves emitted from the emitter and reflected from a surface of the target substrate or terahertz waves penetrating the polymer thin film and the target substrate; and a monitoring unit which, during curing of the polymer thin film, acquires thickness and refractive index information of the polymer thin film in real time through the terahertz waves detected by the detector.

Description

Device and method for monitoring polymers using terahertz waves

[0001] The present invention relates to a polymer monitoring device and method using terahertz waves, and more specifically, to a polymer monitoring device and method using terahertz waves that can monitor in real time the curing state of a polymer thin film coated on a substrate.

[0002] Polymers are materials used in a variety of industrial fields. For example, polymers used in the semiconductor industry are applied to substrates through spin coating or other processes, and then cured to form functional layers.

[0003] However, in the past, it was not possible to measure or confirm the curing state of the polymer in real time during the polymer coating process.

[0004] In other words, conventionally, the condition of a polymer could only be confirmed after it was fully cured. Consequently, even if a problem arose in the material or equipment during the polymer layer formation process, immediate action could not be taken, leading to frequent product defects.

[0005] In addition, there was a problem that the process completion time was delayed because the curing state of the polymer was checked after the polymer was completely cured, and there was a concern that damage would occur to the formed polymer layer because the curing state of the polymer was checked through physical means.

[0006] In particular, as wafer area increases and line widths decrease, the yield of photoresist (PR) has a greater impact on product yield, and therefore, active measures are needed to improve the yield of photoresist (PR) during the curing process.

[0007] The technical problem to be solved by the present invention is to provide a polymer monitoring device and method using terahertz waves, which can monitor the curing state of a polymer thin film coated on a substrate in real time.

[0008] The technical problems to be solved by the present invention are not limited to those described above.

[0009] To solve the above technical problem, the present invention provides a polymer monitoring device using terahertz waves.

[0010] According to one embodiment, the polymer monitoring device using terahertz waves may include an emitter that generates terahertz waves toward a polymer thin film coated on a target substrate; a detector that detects terahertz waves generated from the emitter and reflected from a surface of the target substrate or terahertz waves transmitted through the polymer thin film and the target substrate; and a monitoring unit that obtains thickness and refractive index information of the polymer thin film in real time through terahertz waves detected by the detector while the polymer thin film is being cured.

[0011] According to one embodiment, the monitoring unit calculates the refractive index and thickness of the polymer thin film by considering a ratio of a frequency domain value of the terahertz wave in the target substrate and a frequency domain value of the terahertz wave in the reference substrate, wherein the reference substrate may be defined as a substrate on which the polymer thin film is not coated.

[0012] According to one embodiment, the refractive index of the polymer thin film ( ) is calculated through the following equation 1, and the thickness (d) of the polymer thin film p ) can be calculated using the following formula 2.

[0013]

[0014] [Formula 1]

[0015]

[0016]

[0017] [Formula 2]

[0018]

[0019]

[0020] Here, the above E t (t) is the terahertz wave reflected from the surface of the target substrate coated with the polymer thin film, and the E r (t) is a terahertz wave reflected from the surface of the reference substrate, ω is a frequency of the terahertz wave, φ is a phase difference between the terahertz wave reflected from the surface of the target substrate coated with the polymer thin film and the reference terahertz wave, c is the speed of light, θ1 is an angle of incidence of the terahertz wave, θ2 is an angle of refraction of the terahertz wave, and T ap ,T pa is the transmittance coefficient between air (a) and the polymer thin film, and the above D a is the absorption coefficient of air, the above D p is the absorption coefficient of the polymer thin film, R ps is the reflection coefficient between the target substrate and the polymer film, R as is the reflection coefficient between the reference substrate and the air, d a is the thickness of the air layer set corresponding to the polymer thin film, may be the refractive index of the above air layer.

[0021] According to one embodiment, the detector further detects terahertz waves reflected from inside the target substrate, and the monitoring unit can obtain thickness and refractive index information of the polymer thin film in real time through the terahertz waves reflected from inside the target substrate.

[0022] In one embodiment, the emitter and detector can scan the entire surface of the polymer thin film.

[0023] According to one embodiment, the method further comprises a database, wherein the database stores a reference range for a refractive index and a thickness for each stage in which the polymer thin film is cured, and the monitoring unit can monitor whether the thickness and refractive index information of the polymer thin film obtained in real time are included in the reference range.

[0024] According to one embodiment, the monitoring unit may provide the monitoring result as cause analysis data for an abnormality when the thickness and refractive index information of the polymer thin film are not included in the reference range.

[0025] According to one embodiment, the emitter and detector may be provided at least one, but may be provided in a corresponding number.

[0026] According to one embodiment, the emitter and detector may be operable in any one of a transmission mode, a normal mode, a reflection mode, and a multi-mode combining the transmission mode and the reflection mode, based on the optical path of the terahertz wave with respect to the polymer thin film.

[0027] According to one embodiment, the terahertz wave may be provided in a pulsed type or a continuous wave.

[0028] According to one embodiment, the frequency of the terahertz wave may be 0.1 ㎔ to 10 ㎔.

[0029] Meanwhile, the present invention provides a polymer monitoring method using terahertz waves.

[0030] According to one embodiment, the polymer monitoring method using terahertz waves may include the steps of: generating terahertz waves toward a polymer thin film coated on a target substrate; detecting terahertz waves reflected from a surface of the target substrate or terahertz waves transmitted through the polymer thin film and the target substrate; and, while the polymer thin film is being cured, obtaining in real time information on the thickness and refractive index of the polymer thin film through the terahertz waves detected in the step of detecting the terahertz waves.

[0031] According to one embodiment, in the step of generating the terahertz wave, the terahertz wave is further generated toward a reference substrate on which the polymer thin film is not coated, in the step of detecting the terahertz wave, the reference terahertz wave in the reference substrate is further detected, and in the step of obtaining in real time, the refractive index and thickness of the polymer thin film can be calculated by considering a ratio of a frequency domain value of the terahertz wave in the target substrate and a frequency domain value of the terahertz wave in the reference substrate.

[0032] According to one embodiment, in the step of generating the terahertz wave and the step of detecting the terahertz wave, the entire area of ​​the polymer thin film can be scanned.

[0033] According to an embodiment of the present invention, the device may include an emitter that generates terahertz waves toward a polymer thin film coated on a target substrate; a detector that detects terahertz waves generated from the emitter and reflected from a surface of the target substrate or terahertz waves transmitted through the polymer thin film and the target substrate; and a monitoring unit that obtains thickness and refractive index information of the polymer thin film in real time through the terahertz waves detected by the detector while the polymer thin film is being cured.

[0034] Accordingly, a polymer monitoring device and method using terahertz waves can be provided that can monitor the curing state of a polymer thin film coated on a target substrate in real time, thereby enabling immediate response when a problem occurs in the polymer curing process, such as an abnormality in the polymer thin film or an abnormality in the curing equipment.

[0035] That is, according to an embodiment of the present invention, active measures can be taken to improve yield during the process.

[0036] For example, the curing status of photoresist (PR) can be monitored in real time during the photolithography process, allowing for immediate response when a problem occurs.

[0037] In addition, by monitoring the curing status of photoresist (PR) in real time during the photolithography process, excellent curing quality can be obtained for stable etching according to large wafer area and fine line width.

[0038] FIG. 1 is a schematic diagram illustrating a polymer monitoring device according to one embodiment of the present invention.

[0039] Figure 2 is a schematic diagram showing a polymer monitoring device according to one embodiment of the present invention.

[0040] Figure 3 is a schematic diagram illustrating a polymer monitoring device according to one modified example of the present invention.

[0041] Figure 4 is a schematic diagram illustrating a polymer monitoring device according to another modified example of the present invention.

[0042] FIG. 5 is a schematic diagram illustrating a polymer monitoring device according to another modified example of the present invention.

[0043] Figures 6 to 9 are exemplary diagrams for explaining a monitoring unit of a polymer monitoring device according to one embodiment of the present invention.

[0044] FIG. 10 and FIG. 11 are results of monitoring the curing state of a photoresist coated on a silicon wafer while the photoresist is being cured through a polymer monitoring device according to one embodiment of the present invention.

[0045] FIG. 12 is a schematic diagram illustrating a photolithography process monitored in real time by a polymer monitoring device according to one embodiment of the present invention.

[0046] Figure 13 is a flowchart showing the process sequence of a polymer monitoring method using terahertz waves according to one embodiment of the present invention.

[0047] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the attached drawings. However, the technical concept of the present invention is not limited to the embodiments described herein and may be embodied in other forms. Rather, the embodiments introduced herein are provided to ensure that the disclosed content is thorough and complete and to sufficiently convey the spirit of the present invention to those skilled in the art.

[0048] In this specification, when a component is referred to as being on another component, it means that it can be formed directly on the other component, or a third component may be interposed between them. Furthermore, in the drawings, shapes and sizes are exaggerated for the purpose of effectively explaining the technical contents.

[0049] Additionally, although terms such as first, second, and third have been used to describe various components in various embodiments of this specification, these components should not be limited by these terms. These terms are only used to distinguish one component from another. Thus, what is referred to as a first component in one embodiment may be referred to as a second component in another embodiment. Each embodiment described and illustrated herein also includes its complementary embodiments. Additionally, the term "and / or" has been used herein to mean including at least one of the components listed before and after.

[0050] In the specification, singular expressions include plural expressions unless the context clearly dictates otherwise. In addition, terms such as "comprise" or "have" are intended to specify the presence of a feature, number, step, component, or combination thereof described in the specification, and should not be construed as excluding the presence or addition of one or more other features, numbers, steps, components, or combinations thereof. In addition, the term "connection" is used in the present specification to mean both indirectly connecting multiple components and directly connecting them.

[0051] Additionally, terms such as “part,” “unit,” and “module” described in the specification mean a unit that processes at least one function or operation, which may be implemented by hardware, software, or a combination of hardware and software.

[0052] In addition, when describing the present invention below, if it is determined that a detailed description of a related known function or configuration may unnecessarily obscure the gist of the present invention, the detailed description will be omitted.

[0053]

[0054] FIG. 1 is a schematic diagram illustrating a polymer monitoring device according to an embodiment of the present invention, FIG. 2 is a configuration diagram showing a polymer monitoring device according to an embodiment of the present invention, FIG. 3 is a schematic diagram illustrating a polymer monitoring device according to a modified example of the present invention, FIG. 4 is a schematic diagram illustrating a polymer monitoring device according to another modified example of the present invention, FIG. 5 is a schematic diagram illustrating a polymer monitoring device according to yet another modified example of the present invention, and FIGS. 6 to 9 are exemplary diagrams illustrating a monitoring unit of a polymer monitoring device according to an embodiment of the present invention.

[0055]

[0056] As illustrated in FIGS. 1 and 2, a polymer monitoring device (100) according to one embodiment of the present invention may include an emitter (110), a detector (120), and a monitoring unit (130).

[0057]

[0058] The above emitter (110) is a device that generates terahertz waves toward a polymer thin film (P) coated on a target substrate (W). To this end, the emitter (110) may be positioned so as to face the polymer thin film (P) coated on the target substrate (W).

[0059] At this time, the polymer thin film (P) may be coated on a target substrate (W) and being cured. For example, the polymer thin film (P) may be a photoresist (PR) coated on a target substrate (W) made of a silicon (Si) wafer for a photolithography process (see FIG. 11).

[0060] However, this is only an example, and the polymer thin film (P) in the present invention is not necessarily limited to photoresist (PR).

[0061] According to one embodiment of the present invention, the emitter (110) may be arranged to be inclined at a set angle from the normal direction of the polymer thin film (P). For example, the emitter (110) may be arranged to be inclined at 30 degrees from the normal direction of the polymer thin film (P). Accordingly, the terahertz wave generated from the emitter (110) may be incident on the polymer thin film (P) at an angle of 60 degrees with respect to the polymer thin film (P).

[0062] According to one embodiment of the present invention, the terahertz wave generated from the emitter (110) and irradiated toward the polymer thin film (P) may be provided in a pulsed type or a continuous wave.

[0063] Here, pulsed terahertz waves have the advantage of being able to detect numerous frequencies at once.

[0064] In order to generate such pulsed terahertz waves, a femtosecond laser that functions as a pump light for generating pulsed terahertz waves can be irradiated to the emitter (110).

[0065] Meanwhile, according to one embodiment of the present invention, the frequency of the terahertz wave generated from the emitter (110) and irradiated onto the polymer thin film (P) may be 0.1 ㎔ to 10 ㎔.

[0066]

[0067] According to one embodiment of the present invention, the emitter (110) and the detector (120) may be provided to be operable in a reflection mode based on the optical path of the terahertz wave with respect to the polymer thin film (P).

[0068] Accordingly, the detector (120) may be arranged to be symmetrical with respect to the normal direction of the polymer thin film (P) with respect to the emitter (110). For example, when the emitter (110) is arranged to be tilted 30 degrees from the normal direction of the polymer thin film (P), the detector (120) may be arranged to be tilted -30 degrees from the normal direction of the polymer thin film (P) to be symmetrical left and right with respect to the emitter (110).

[0069] In this way, when the emitter (110) and the detector (120) are equipped to operate in a reflection mode, the detector (120) can detect terahertz waves generated from the emitter (110) and reflected from the surface of the target substrate (W), which is the interface between the target substrate (W) and the polymer thin film (P).

[0070] For example, when the emitter (110) and the detector (120) are arranged in a reflection mode with a 30-degree inclination to the left and right with respect to the normal direction of the polymer thin film (P), the terahertz wave generated from the emitter (110) and incident on the polymer thin film (P) at an angle of 60 degrees is first refracted according to the difference in refractive index between the air and the polymer thin film (P), moves inside the polymer thin film (P), is reflected at the surface of the target substrate (W), and is secondarily refracted at an angle of -60 degrees at the interface between the air and the polymer thin film (P) to be received by the detector (120).

[0071] At this time, the inclination and direction of the emitter (110) and the detector (120) can be precisely controlled. For example, the emitter (110) and the detector (120) that are precisely controlled can have six degrees of freedom. The six degrees of freedom of the emitter (110) and the detector (120) can be three axes in the x, y, and z directions and rotational directions for each axis.

[0072] According to one embodiment of the present invention, the detector (120) can further detect terahertz waves reflected from the inside of the target substrate (W). To this end, a reflector (R) may be placed on the lower side of the target substrate (W).

[0073] In this way, the terahertz wave information generated from the emitter (110) and reflected from the surface of the target substrate (W) or the inside of the target substrate (W) and detected by the detector (120) can be used to calculate the thickness and refractive index of the polymer thin film (P) to monitor the curing state of the polymer thin film (P) coated on the target substrate (W) in real time.

[0074] Meanwhile, as illustrated in FIG. 3, according to one modified example of the present invention, the emitter (110) and the detector (120) may be configured to operate in a transmission mode based on the optical path of the terahertz wave to the polymer thin film (P).

[0075] To this end, the emitter (110) may be placed facing the normal direction on the polymer thin film (P), and the detector (120) may be placed on the lower side of the polymer thin film (P) in the normal direction of the polymer thin film (P), and may be placed on the same line as the emitter (110) with the polymer thin film (P) interposed therebetween, in a direction facing the emitter (110).

[0076] Accordingly, the terahertz wave generated from the emitter (110) can be detected by the detector (120) by passing through the polymer thin film (P).

[0077] In addition, as illustrated in FIG. 4, according to another modified example of the present invention, the first emitter (110) and the first detector (120) may be provided to operate in a normal mode based on the optical path of the terahertz wave with respect to the polymer thin film (P).

[0078] To this end, the emitter (110) may be positioned so as to face the polymer thin film (P) in a normal direction so that the angle of incidence of the terahertz wave with respect to the polymer thin film (P) is 0 degrees. At this time, a beam splitter may be provided on the optical path of the terahertz wave generated from the emitter (110) and directed toward the polymer thin film (P).

[0079] The above detector (120) may be provided on one side of the beam splitter so as to detect terahertz waves split by the beam splitter.

[0080] In the case of the existing reflection mode, there is a limitation that the spot shape of the terahertz wave is not a perfect circle because the terahertz wave is incident at an angle, but if the first emitter (110) and the first detector (120) are equipped to operate in normal mode, there is an advantage in that the precision of the measurement area is increased because the terahertz wave is incident perpendicularly to the polymer thin film (P).

[0081] And, as illustrated in FIG. 5, according to another modified example of the present invention, the first emitter (110) and the first detector (120) may be provided to be operable in a reflection mode based on the optical path of the terahertz wave with respect to the polymer thin film (P).

[0082] And according to another modified example of the present invention, the second emitter (110') and the second detector (120') may be provided to be operable in a transmission mode based on the optical path of the terahertz wave to the polymer thin film (P).

[0083] That is, according to another modified example of the present invention, the polymer monitoring device (100) can be operated in a multi-mode in which the reflection mode of the first emitter (110) and the first detector (120) and the transmission mode of the second emitter (110') and the second detector (120') are combined.

[0084] To this end, the first emitter (110) and the first detector (120) can be arranged symmetrically and tilted on both sides with respect to the normal direction of the polymer thin film (P).

[0085] For example, when the emitter (110) and the detector (120) are arranged in a reflection mode with a 30-degree inclination to the left and right with respect to the normal direction of the polymer thin film (P), the terahertz wave generated from the emitter (110) and incident on the polymer thin film (P) at an angle of 60 degrees is first refracted according to the difference in refractive index between the air and the polymer thin film (P), moves inside the polymer thin film (P), is reflected at the surface of the target substrate (W), and is secondarily refracted at an angle of -60 degrees at the interface between the air and the polymer thin film (P) to be received by the detector (120).

[0086] In addition, the second emitter (110') and the second detector (120') may be positioned facing each other in the normal direction of the polymer thin film (P) on the upper and lower sides of the polymer thin film (P) with the polymer thin film (P) interposed therebetween.

[0087] Accordingly, the terahertz wave generated from the second emitter (110') can be detected by the second detector (120') by passing through the polymer thin film (P).

[0088] Meanwhile, according to one embodiment of the present invention, the emitter (110) and the detector (120) may be provided in one or two or more quantities. In this case, when the emitter (110) and the detector (120) are provided in two or more quantities, the emitter (110) and the detector (120) may be provided in corresponding quantities to form a pair.

[0089] In addition, according to one embodiment of the present invention, the emitter (110) and the detector (120) can target the entire polymer thin film (P). In this way, when the emitter (110) and the detector (120) target the entire polymer thin film (P), the emitter (110) and the detector (120) can scan the entire area of ​​the polymer thin film (P).

[0090] For this purpose, the emitter (110) and detector (120) may be provided to be able to move forward, backward, left, and right.

[0091] In this way, when the entire surface of the polymer thin film (P) is scanned by the emitter (110) and detector (120), the curing state of the polymer thin film (P) can be monitored more accurately.

[0092] In addition, when the entire surface of the polymer thin film (P) is scanned by the emitter (110) and detector (120), it is possible to determine, for example, which step of the photolithography process is in progress.

[0093] For example, when photoresist (PR) is coated on a target substrate (W) through spin coating, the thickness of the center of the coated photoresist (PR) may temporarily become thinner than the thickness of the edge due to centrifugal force.

[0094] A polymer monitoring device (100) according to one embodiment of the present invention can monitor the thickness difference between the center and edge of a photoresist (PR) in real time through an emitter (110) and a detector (120) that scan the entire surface of a polymer thin film (P), and can analyze that the thickness difference is caused by spin coating rather than a process problem.

[0095] In addition, a polymer monitoring device (100) according to an embodiment of the present invention can obtain refractive index information by scanning a photoresist (PR) during an exposure process after spin coating through an emitter (110) and a detector (120), and monitor the curing degree distribution over the entire surface of a wafer (W) based on this refractive index information.

[0096] In this way, the reason for monitoring the distribution of the degree of curing over the entire surface of the wafer (W) is that patterning defects, etc. occur due to non-uniformity in the degree of curing of the wafer (W) during the actual process.

[0097] Meanwhile, the polymer monitoring device (100) according to one embodiment of the present invention can also monitor the curing state of the entire area of ​​the photoresist (PR) by predicting the thickness of a specific area of ​​the photoresist (PR), for example, the center and the edge, through the emitter (110) and the detector (120).

[0098]

[0099] Referring again to FIG. 2, the monitoring unit (130) can obtain information on the thickness and refractive index of the polymer thin film (P) in real time through the terahertz waves detected by the detector (120) while the polymer thin film (P) is being cured.

[0100] The above monitoring unit (130) can monitor the curing state of the polymer thin film (P) coated on the target substrate (W) in real time based on the thickness and refractive index information of the polymer thin film (P) obtained in real time in this way.

[0101] Through this, it becomes possible to respond immediately when a problem occurs in the polymer curing process, such as an abnormality in the polymer thin film (P) or an abnormality in the curing equipment.

[0102] That is, according to one embodiment of the present invention, as the curing state of the polymer thin film (P) coated on the target substrate (W) is monitored in real time, active measures can be taken to improve yield during the process.

[0103] For example, according to one embodiment of the present invention, by monitoring the curing state of photoresist (PR) in real time during a photolithography process, it is possible to respond immediately when a problem occurs.

[0104] In particular, according to one embodiment of the present invention, by monitoring the curing state of photoresist (PR) in real time during a photolithography process, it is possible to obtain excellent curing quality of photoresist (PR) for stable etching according to large wafer area and fine line width.

[0105] As shown in Fig. 6, the terahertz wave generated from the emitter (110) and irradiated toward the polymer thin film (P) coated on the target substrate (W) is reflected from the surface of the target substrate (W) according to the reflection position. st Peak) and terahertz waves reflected from inside the target substrate (W) (2 nd Peak, 3 rd Peak and 4 th Peak) can be distinguished.

[0106] Accordingly, the monitoring unit (130) detects terahertz waves (1) reflected from the surface of the target substrate (W) while the polymer thin film (P) is being cured. st Peak) and terahertz waves reflected from inside the target substrate (W) (2 nd Peak, 3 rd Peak and 4 th Through Peak), the thickness and refractive index information of the polymer thin film (P) can be obtained in real time.

[0107] At this time, among the terahertz waves detected by the detector (120), the terahertz waves (1) reflected from the surface of the target substrate (W) stPeak) can have the largest amplitude.

[0108] Accordingly, according to one embodiment of the present invention, the monitoring unit (130) detects terahertz waves (1) reflected from the surface of the target substrate (W). st Based on the peak, the thickness and refractive index information of the polymer thin film (P) can be obtained in real time while the polymer thin film (P) is being cured.

[0109] As shown in Fig. 7, the monitoring unit (130) detects terahertz waves (1) reflected from the surface of the target substrate (W). st After performing FFT (Fast Fourier Transformation) on the peak, the curing state of the polymer thin film (P) can be monitored.

[0110] According to one embodiment of the present invention, the monitoring unit (130) can calculate the refractive index and thickness of the polymer thin film (P) by considering the ratio of the frequency domain value of the terahertz wave in the target substrate (W) and the frequency domain value of the terahertz wave in the reference substrate.

[0111] Here, the reference substrate can be defined as a substrate not coated with a polymer thin film (P).

[0112] According to an example, the frequency domain value of the terahertz wave on the reference substrate means a frequency domain value of the terahertz wave that can be a reference, and may include, for example, at least one of a frequency domain value of the terahertz wave reflected from a reflector, a frequency domain value of the terahertz wave measured in a vacuum, a frequency domain value of the totally reflected terahertz wave, and a frequency domain value of the terahertz wave transmitted in a transmission mode.

[0113] As shown in FIGS. 8 and 9, for example, the monitoring unit (130) can numerically calculate the refractive index and thickness of the polymer thin film (P) by considering the ratio of the frequency domain value of the terahertz wave reflected from the surface of the target substrate (W) having the polymer thin film (P) coated on the upper surface and the frequency domain value of the terahertz wave reflected from the surface of the reference substrate (W) having the polymer thin film (P) not coated on the upper surface.

[0114] According to one embodiment of the present invention, the refractive index of such a polymer thin film (P) ) can be calculated using the following formula 1.

[0115]

[0116] [Formula 1]

[0117]

[0118]

[0119] In addition, according to one embodiment of the present invention, the thickness (d) of the polymer thin film (P) p ) can be calculated using the following formula 2.

[0120]

[0121] [Formula 2]

[0122]

[0123]

[0124] Here, the above E t (t) is the terahertz wave reflected from the surface of the target substrate coated with the polymer thin film, and the E r (t) is a terahertz wave reflected from the surface of the reference substrate, ω is a frequency of the terahertz wave, φ is a phase difference between the terahertz wave reflected from the surface of the target substrate coated with the polymer thin film and the terahertz wave reflected from the surface of the reference substrate, c is the speed of light, θ1 is an angle of incidence of the terahertz wave, θ2 is an angle of refraction of the terahertz wave, and T ap,T pa is the transmittance coefficient between air (a) and the polymer thin film, and the above D a is the absorption coefficient of air, the above D p is the absorption coefficient of the polymer thin film, R ps is the reflection coefficient between the target substrate and the polymer thin film, R as is the reflection coefficient between the reference substrate and the air, and d a is the thickness of the air layer set corresponding to the polymer film, is the refractive index of the above air layer.

[0125]

[0126] Equations 1 and 2, which reflect the optical path of terahertz waves, were developed by setting the terahertz waves reflected from the surface of a silicon wafer coated with photoresist (PR) as a sample wave (Fig. 7) and setting the terahertz waves reflected from the surface of a silicon wafer not coated with photoresist (PR) as a reference wave (Fig. 8).

[0127] According to one embodiment of the present invention, the monitoring unit (130) inputs sample wave information and reference wave information into Equations 1 and 2, and performs repeated numerical analysis to determine the refractive index ( ) and the thickness (d) of the polymer film (P) p ) can be calculated numerically.

[0128] Through this, the monitoring unit (130) can monitor the curing status of the polymer thin film (P) in real time while the polymer thin film (P) is being cured.

[0129] Accordingly, immediate response can be made when a problem occurs in the polymer curing process, such as an abnormality in the polymer thin film (P) or an abnormality in the curing equipment.

[0130] At this time, referring again to FIG. 4, if the first emitter (110) and the first detector (120) are equipped to operate in normal mode, the incident angle of the terahertz wave incident on the polymer thin film (P) is 0 degrees, so the values ​​of cos(θ1) and cos(θ2) in Equations 1 and 2 become 1, and accordingly, the calculation process is simplified, so that the measurement accuracy can be increased.

[0131] FIG. 10 and FIG. 11 are results of monitoring the curing state of a photoresist coated on a silicon wafer while the photoresist is being cured through a polymer monitoring device according to one embodiment of the present invention.

[0132] That is, FIGS. 10 and 11 are the results of numerically calculating the refractive index and thickness of the photoresist through terahertz waves reflected from the surface of a silicon wafer.

[0133] Referring to FIGS. 10 and 11, it was confirmed that the refractive index of the photoresist (PR) increases due to the coating of the photoresist (PR) and converges to a specific value as curing progresses.

[0134] At this time, it was confirmed that the thickness of the photoresist (PR) showed a similar trend to the refractive index as curing progressed.

[0135] In this way, it was confirmed that the refractive index and thickness of photoresist (PR) can be numerically calculated through terahertz waves reflected from the surface of a silicon wafer, and through this, the curing state of photoresist (PR) can be monitored in real time while the photoresist (PR) is being cured.

[0136] FIG. 12 is a schematic diagram illustrating a photolithography process monitored in real time by a polymer monitoring device according to one embodiment of the present invention.

[0137] As illustrated in FIG. 12, a polymer monitoring device according to an embodiment of the present invention can monitor in real time the curing state of a photoresist cured on a silicon wafer (Si wafer) in all steps of a photolithography process, for example, a cleaning step, a spin coating step, a soft bake step, an exposure step, a post-bake step, a development step, and a hard-bake step, through terahertz waves reflected from the surface of the silicon wafer (Si wafer), and thus, an additional inspection process after curing may be unnecessary.

[0138] Through this, the polymer monitoring device according to one embodiment of the present invention can shorten the process completion time and prevent damage to the photoresist by physical means for checking the curing state in advance.

[0139]

[0140] Referring again to FIG. 2, the polymer monitoring device (100) according to one embodiment of the present invention may further include a database (DB).

[0141] The above database (DB) can store reference ranges for refractive index and thickness for each stage of curing of a polymer thin film (P).

[0142] For example, the database (DB) can store reference ranges for the refractive index and thickness of a photoresist (PR) in each of the cleaning step, spin coating step, soft bake step, exposure step, post-bake step, develop step, and hard-bake step of a photolithography process.

[0143] Accordingly, the monitoring unit (130) can monitor whether the thickness and refractive index information of the photoresist (PR) acquired in real time is included in the above reference range.

[0144] That is, the monitoring unit (130) can check whether the refractive index and thickness of the photoresist (PR) calculated through the above formulas 1 and 2 are included in the reference range for the refractive index and thickness of the photoresist (PR) in the corresponding photolithography process step.

[0145] If the monitoring unit (130) above confirms that the refractive index and thickness of the photoresist (PR) calculated through the above equations 1 and 2 are within the standard range for the refractive index and thickness of the photoresist (PR) in the corresponding photolithography process step, it can be determined that the curing of the photoresist (PR) is being performed properly without any abnormalities.

[0146] On the other hand, if the monitoring unit (130) determines that the refractive index and thickness of the photoresist (PR) calculated through the above equations 1 and 2 are not within the standard range for the refractive index and thickness of the photoresist (PR) in the corresponding photolithography process step, it can determine that a problem has occurred in the corresponding photolithography process step, such as an abnormality in the photoresist (PR) or an abnormality in the curing equipment.

[0147] If the monitoring unit (130) determines that a problem has occurred in the photolithography process step, it can alert the process manager or worker of the monitoring result in which an abnormality has been detected.

[0148] Through this, the monitoring unit (140) can enable immediate response when a problem occurs in the polymer curing process.

[0149] That is, the monitoring unit (140) can enable active measures to be taken to improve yield during the polymer curing process.

[0150]

[0151] Hereinafter, a polymer monitoring method using terahertz waves according to an embodiment of the present invention will be described with reference to FIG. 13. In this case, the drawing symbols of each component will refer to FIG. 1.

[0152]

[0153] Figure 13 is a flowchart showing the process sequence of a polymer monitoring method using terahertz waves according to one embodiment of the present invention.

[0154]

[0155] Referring to FIG. 13, a polymer monitoring method using terahertz waves according to one embodiment of the present invention may include steps S110, S120, and S130.

[0156]

[0157] S110 stage

[0158] The above step S110 is a step of generating terahertz waves toward a polymer thin film (P) coated on a target substrate (W).

[0159] At this time, in the above step S110, terahertz waves can be generated toward the polymer thin film (P) through reflection mode.

[0160] To this end, in the step S110, terahertz waves can be generated so that the terahertz waves are incident on the polymer thin film (P) at an angle greater than 0° and less than 90°, for example.

[0161] Additionally, in the above step S110, terahertz waves can be generated toward the polymer thin film (P) through the transmission mode.

[0162] To this end, in the step S110, the terahertz wave can be generated so that the terahertz wave is incident on the polymer thin film (P) in the normal direction of the polymer thin film (P).

[0163] And in the above step S110, terahertz waves can be generated toward the polymer thin film (P) through a multi-mode in which the reflection mode and the transmission mode are combined.

[0164] To this end, in the step S110, the terahertz wave may be generated so that the terahertz wave is incident on the polymer thin film (P) at an angle greater than 0° and less than 90°, and the terahertz wave may be generated so that the terahertz wave is incident on the polymer thin film (P) in the normal direction of the polymer thin film (P).

[0165]

[0166] S120 stage

[0167] The above step S120 is a step of detecting terahertz waves reflected from the surface of the target substrate (W) or terahertz waves transmitted through the polymer thin film (P) and the target substrate (W).

[0168] When terahertz waves are generated toward the polymer thin film (P) through reflection mode in the above step S110, terahertz waves reflected from the surface of the target substrate (W) can be detected in the above step S120.

[0169] At this time, in the above step S120, terahertz waves reflected from the inside of the target substrate (W) can also be detected.

[0170] In addition, when terahertz waves are generated toward the polymer thin film (P) through the transmission mode in the step S110, the terahertz waves transmitted through the polymer thin film (P) and the target substrate (W) can be detected in the step S120.

[0171] If the above polymer thin film (P) is provided alone rather than in a form coated on a target substrate (W), the transmission mode may be more preferable.

[0172] And when terahertz waves are generated toward the polymer thin film (P) through a multi-mode in which a reflection mode and a transmission mode are combined in the above step S110, the terahertz waves transmitted through the polymer thin film (P) and the target substrate (W) can be detected in the above step S120, and terahertz waves reflected from the surface of the target substrate (W) or the inside of the target substrate (W) can be detected at the same time.

[0173] Meanwhile, in the step S110, terahertz waves can be further generated, for example, through reflection mode, toward a reference substrate not coated with the polymer thin film (P) for comparison with the target substrate (W) coated with the polymer thin film (P).

[0174] Accordingly, in the step S120, terahertz waves from the reference substrate, for example, terahertz waves reflected from the surface of the reference substrate, can be further detected.

[0175] In addition, according to one embodiment of the present invention, in steps S110 and S120, the entire surface area of ​​the polymer thin film (P) can be scanned. Accordingly, in step S130, the entire surface area of ​​the polymer thin film (P) can be monitored.

[0176] As another example, in the step S130, the curing state of the entire area of ​​the polymer thin film (P) can be predicted through terahertz waves reflected by each area of ​​the polymer thin film (P).

[0177]

[0178] Step S130

[0179] The above step S130 is a step of obtaining in real time information on the thickness and refractive index of the polymer thin film (P) through the terahertz waves detected by the above step S120 while the polymer thin film (P) is being cured.

[0180] In the above step S130, while the polymer thin film (P) is being cured, the terahertz wave (1) reflected from the surface of the target substrate (W) st Peak) and terahertz waves reflected from inside the target substrate (W) (2 nd Peak, 3 rd Peak and 4 th Through Peak), the thickness and refractive index information of the polymer thin film (P) can be obtained in real time.

[0181] At this time, among the terahertz waves detected through the above step S120, the terahertz waves (1) reflected from the surface of the target substrate (W) st Peak) can have the largest amplitude.

[0182] Accordingly, in the above step S130, the terahertz wave (1) reflected from the surface of the target substrate (W) st Based on the peak, the thickness and refractive index information of the polymer thin film (P) can be obtained in real time while the polymer thin film (P) is being cured.

[0183] According to one embodiment of the present invention, in the step S130, terahertz waves (1) reflected from the surface of the target substrate (W) st After performing FFT (Fast Fourier Transformation) on the peak, the curing state of the polymer thin film (P) can be monitored.

[0184] More specifically, in the step S130, the refractive index and thickness of the polymer thin film (P) can be calculated by considering the ratio of the frequency domain value of the terahertz wave in the target substrate (W) and the frequency domain value of the terahertz wave in the reference substrate.

[0185] Here, the reference substrate can be defined as a substrate (W) not coated with a polymer thin film (P).

[0186] For example, in the above step S130, the refractive index and thickness of the polymer thin film (P) can be numerically calculated by considering the ratio of the frequency domain value of the terahertz wave reflected from the surface of the target substrate (W) having the polymer thin film (P) coated on the upper surface and the frequency domain value of the terahertz wave reflected from the surface of the reference substrate (W) having the polymer thin film (P) not coated on the upper surface.

[0187] According to one embodiment of the present invention, the refractive index of such a polymer thin film (P) ) can be calculated using the following formula 1.

[0188]

[0189] [Formula 1]

[0190]

[0191]

[0192] In addition, according to one embodiment of the present invention, the thickness (d) of the polymer thin film (P) p ) can be calculated using the following formula 2.

[0193]

[0194] [Formula 2]

[0195]

[0196]

[0197] Here, the above E t (t) is the terahertz wave reflected from the surface of the target substrate coated with the polymer thin film, and the E r (t) is a terahertz wave reflected from the surface of the reference substrate, ω is a frequency of the terahertz wave, φ is a phase difference between the terahertz wave reflected from the surface of the target substrate coated with the polymer thin film and the terahertz wave reflected from the surface of the reference substrate, c is the speed of light, θ1 is an angle of incidence of the terahertz wave, θ2 is an angle of refraction of the terahertz wave, and T ap ,T pais the transmittance coefficient between air (a) and the polymer thin film, and the above D a is the absorption coefficient of air, the above D p is the absorption coefficient of the polymer thin film, R ps is the reflection coefficient between the target substrate and the polymer thin film, R as is the reflection coefficient between the reference substrate and the air, and d a is the thickness of the air layer set corresponding to the polymer thin film, is the refractive index of the above air layer.

[0198]

[0199] Equations 1 and 2, which reflect the optical path of terahertz waves, were developed by setting the terahertz waves reflected from the surface of a silicon wafer coated with photoresist (PR) as a sample wave (Fig. 7) and setting the terahertz waves reflected from the surface of a silicon wafer not coated with photoresist (PR) as a reference wave (Fig. 9).

[0200] According to one embodiment of the present invention, in the step S130, sample wave information and reference wave information are substituted into Equations 1 and 2, and the refractive index of the polymer thin film (P) is determined through repeated numerical analysis. ) and the thickness (d) of the polymer film (P) p ) can be numerically calculated, and through this, the curing state of the polymer thin film (P) can be monitored in real time while the polymer thin film (P) is being cured.

[0201] Accordingly, immediate response can be made when a problem occurs in the polymer curing process, such as an abnormality in the polymer thin film (P) or an abnormality in the curing equipment.

[0202] That is, according to one embodiment of the present invention, as the curing state of the polymer thin film (P) coated on the target substrate (W) is monitored in real time, active measures can be taken to improve yield during the process.

[0203] For example, according to one embodiment of the present invention, by monitoring the curing state of photoresist (PR) in real time during a photolithography process, it is possible to respond immediately when a problem occurs.

[0204] In particular, according to one embodiment of the present invention, by monitoring the curing state of photoresist (PR) in real time during a photolithography process, it is possible to obtain excellent curing quality of photoresist (PR) for stable etching according to large wafer area and fine line width.

[0205] In addition, according to one embodiment of the present invention, since an additional inspection process after completion of curing of the photoresist (PR) becomes unnecessary, the process completion time can be shortened, and damage to the photoresist (PR) by physical means for inspection of the curing state can be prevented in advance.

[0206]

[0207] While the present invention has been described in detail using preferred embodiments, the scope of the present invention is not limited to the specific embodiments described above, and should be interpreted in accordance with the appended claims. Furthermore, those skilled in the art will appreciate that numerous modifications and variations are possible without departing from the scope of the present invention.

Claims

1. An emitter that generates terahertz waves toward a polymer thin film coated on a target substrate; A detector that detects terahertz waves generated from the emitter and reflected from the surface of the target substrate or terahertz waves transmitted through the polymer thin film and the target substrate; and A polymer monitoring device using terahertz waves, comprising a monitoring unit that obtains thickness and refractive index information of the polymer thin film in real time through terahertz waves detected by the detector while the polymer thin film is being cured.

2. In paragraph 1, The above monitoring unit calculates the refractive index and thickness of the polymer thin film by considering the ratio of the frequency domain value of the terahertz wave in the target substrate and the frequency domain value of the terahertz wave in the reference substrate. A polymer monitoring device using terahertz waves, wherein the above reference substrate is defined as a substrate not coated with the above polymer thin film.

3. In paragraph 2, The refractive index of the above polymer thin film ( ) is calculated using the following formula 1, The thickness of the polymer film (d) p ) is a polymer monitoring device using terahertz waves, which is calculated through the following equation 2. [Formula 1] [Formula 2] Here, the above E t (t) is the terahertz wave reflected from the surface of the target substrate coated with the polymer thin film, and the E r (t) is a terahertz wave reflected from the surface of the reference substrate, ω is a frequency of the terahertz wave, φ is a phase difference between the terahertz wave reflected from the surface of the target substrate coated with the polymer thin film and the terahertz wave reflected from the surface of the reference substrate, c is the speed of light, θ1 is an angle of incidence of the terahertz wave, θ2 is an angle of refraction of the terahertz wave, and T ap ,T pa is the transmittance coefficient between air (a) and the polymer thin film, and the above D a is the absorption coefficient of air, the above D p is the absorption coefficient of the polymer thin film, R ps is the reflection coefficient between the target substrate and the polymer thin film, R as is the reflection coefficient between the reference substrate and the air, and d a is the thickness of the air layer set corresponding to the polymer thin film, is the refractive index of the above air layer.

4. In paragraph 1, The above detector further detects terahertz waves reflected from the inside of the target substrate, The above monitoring unit is a polymer monitoring device using terahertz waves, which can obtain information on the thickness and refractive index of the polymer thin film in real time through terahertz waves reflected from the inside of the target substrate.

5. In paragraph 1, A polymer monitoring device using terahertz waves, wherein the above emitter and detector scan the entire surface area of ​​the polymer thin film.

6. In paragraph 1, Including more databases, The above database stores reference ranges for refractive index and thickness for each stage in which the polymer thin film is cured, The above monitoring unit is a polymer monitoring device using terahertz waves that monitors whether the thickness and refractive index information of the polymer thin film obtained in real time are included in the reference range.

7. In paragraph 6, A polymer monitoring device using terahertz waves, wherein the monitoring unit provides the monitoring results as cause analysis data for an abnormality occurrence when the thickness and refractive index information of the polymer thin film are not included in the reference range.

8. In paragraph 1, A polymer monitoring device using terahertz waves, wherein the above emitter and detector are provided in at least one, but corresponding numbers.

9. In paragraph 1, A polymer monitoring device using terahertz waves, wherein the emitter and detector are operable in any one of a transmission mode, a normal mode, a reflection mode, and a multi-mode combining the transmission mode and the reflection mode, based on the optical path of the terahertz wave for the polymer thin film.

10. In paragraph 1, A polymer monitoring device using terahertz waves, wherein the above terahertz waves are provided in a pulsed type or continuous wave type.

11. In paragraph 1, A polymer monitoring device using terahertz waves, wherein the frequency of the terahertz waves is 0.1 ㎔ to 10 ㎔.

12. A step of generating terahertz waves toward a polymer thin film coated on a target substrate; A step of detecting terahertz waves reflected from the surface of the target substrate or terahertz waves transmitted through the polymer thin film and the target substrate; and A method for monitoring a polymer using terahertz waves, comprising: a step of obtaining information on the thickness and refractive index of the polymer thin film in real time through terahertz waves detected in the step of detecting terahertz waves while the polymer thin film is being cured; 13. In paragraph 12, In the step of generating the above terahertz wave, the terahertz wave is further generated toward a reference substrate on which the polymer thin film is not coated, In the step of detecting the above terahertz wave, a reference terahertz wave from the reference substrate is further detected, A polymer monitoring method using terahertz waves, wherein in the step of acquiring in real time, the refractive index and thickness of the polymer thin film are calculated by considering the ratio of the frequency domain value of the terahertz wave in the target substrate and the frequency domain value of the terahertz wave in the reference substrate.

14. In paragraph 12, A method for monitoring a polymer using terahertz waves, wherein the step of generating the terahertz waves and the step of detecting the terahertz waves scan the entire area of ​​the polymer thin film.

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