Apparatus and method for inspecting metal thin film by using terahertz waves

Abstract

An apparatus for inspecting a metal thin film by using terahertz waves is provided. The apparatus for inspecting a metal thin film by using terahertz waves may comprise: an emitter which is disposed on one side of metal thin film formation equipment for performing a process of forming a metal thin film on a substrate, and which generates terahertz waves toward the metal thin film; a detector which is disposed on the other side of the metal thin film forming equipment, and which detects the terahertz waves generated by the emitter and reflected from the metal thin film; a monitoring unit for monitoring the thickness of the metal thin film in real time on the basis of the terahertz waves detected by the detector, while the process is performed by the metal thin film forming equipment; and a process control unit for controlling process conditions of the metal thin film forming equipment so that the thickness of the metal thin film satisfies a preset thickness criterion when the thickness of the metal thin film monitored by the monitoring unit deviates from the preset thickness criterion.

Description

Device and method for inspecting metal thin films using terahertz waves

[0001] The present invention relates to a device and method for inspecting a metal thin film using terahertz waves, and more specifically, to a device and method for inspecting a metal thin film using terahertz waves, which can rapidly inspect the formation thickness of the entire surface of a metal thin film in real time during a process of forming the metal thin film.

[0002] Current semiconductor manufacturing involves numerous stacking processes. When the number of I / Os on semiconductor chips, such as HBM (High Bandwidth Memory) and logic chips, is too high, it's impossible to create corresponding pads on the substrate. Therefore, an interposer is installed between the semiconductor chips and the substrate to accommodate these.

[0003] The above interposer is formed of various metal thin films such as RDL (Redistribution Layer), UBM (Under Bump Metallurgy), and metal wiring.

[0004] However, if the metal films forming these interposers are not thick enough, this can lead to poor electrical connections, warping, and delamination during subsequent processes. Therefore, thickness inspection of the metal films forming the interposer is necessary.

[0005] Here, when inspecting the thickness of a metal film using an ellipsometer, there is a problem that a considerable inspection time is required because the inspection device must be rotated per point.

[0006] In addition, when examining the thickness of a metal thin film using AFM equipment, there are limitations due to the contact inspection method, and there is the problem that the scanning time is long.

[0007] In this way, since the thickness of a metal thin film had to be inspected using a specimen in the past, the inspection time was long, and in particular, since it was impossible to inspect the thickness of the metal thin film in real time during the metal thin film formation process, there was a clear limit to controlling the uniformity of the thickness of the metal thin film during the process.

[0008] The technical problem to be solved by the present invention is to provide a metal thin film inspection device and method using terahertz waves, which can rapidly inspect the formation thickness of the entire surface of a metal thin film in real time during the process of forming the metal thin film.

[0009] The technical problems to be solved by the present invention are not limited to those described above.

[0010] To solve the above technical problem, the present invention provides a metal thin film inspection device using terahertz waves.

[0011] According to one embodiment, the metal thin film inspection device using terahertz waves may include: an emitter disposed on one side of a metal thin film forming equipment in which a process of forming a metal thin film on a substrate is performed, the emitter generating a terahertz wave toward the metal thin film; a detector disposed on the other side of the metal thin film forming equipment, the detector detecting a terahertz wave generated from the emitter and reflected from the metal thin film; a monitoring unit that monitors the thickness of the metal thin film in real time based on the terahertz wave detected by the detector while the process is in progress in the metal thin film forming equipment; and a process control unit that controls the process conditions of the metal thin film forming equipment so that the thickness of the metal thin film satisfies the preset thickness standard when the thickness of the metal thin film monitored by the monitoring unit deviates from a preset thickness standard.

[0012] According to one embodiment, depending on the transmittance of the metal thin film, the monitoring unit monitors the thickness of the metal thin film in real time through one of a first monitoring mode and a second monitoring mode, wherein the first monitoring mode and the second monitoring mode can monitor the thickness of the metal thin film in real time based on different parameters of the terahertz wave detected by the detector.

[0013] According to one embodiment, the monitoring unit selects one of the first monitoring mode and the second monitoring mode, wherein the first monitoring mode can be selected when the transmittance of the metal thin film exceeds 0%.

[0014] According to one embodiment, the first monitoring mode calculates the reflectance of the metal thin film through the peak amplitude of the terahertz wave reflected from the metal thin film, and monitors in real time whether the thickness of the metal thin film satisfies the preset thickness standard based on the calculated reflectance, wherein the reflectance of the metal thin film can be calculated through the following equation 1.

[0015]

[0016] [Formula 1]

[0017]

[0018]

[0019] Here, the above E reflector is the peak amplitude of the terahertz wave totally reflected from the reflector, and the E sample is the peak amplitude of the terahertz wave reflected from the above metal film.

[0020] According to one embodiment, as the thickness of the metal thin film increases, the reflectivity may increase.

[0021] According to one embodiment, the second monitoring mode calculates the thickness of the metal thin film through the time delay between peaks of terahertz waves reflected from the metal thin film, and monitors in real time whether the thickness of the metal thin film satisfies the preset thickness standard based on the calculated thickness of the metal thin film, wherein the thickness (d) of the metal thin film can be calculated through the following equation 2.

[0022]

[0023] [Formula 2]

[0024]

[0025]

[0026] Here, n is the refractive index of the metal thin film, c is the speed of light, Δt is the time delay, and θ is the angle of incidence.

[0027] According to one embodiment, as the thickness of the metal thin film increases, the time delay of the terahertz wave peak reflected from the metal thin film may decrease.

[0028] According to one embodiment, the monitoring unit simultaneously applies the first monitoring mode and the second monitoring mode to a point on the metal thin film, and then selects one of the first monitoring mode and the second monitoring mode based on a result value, and monitors the thickness of the metal thin film in real time through at least one of the first monitoring mode and the second monitoring mode for the entire metal thin film.

[0029] According to one embodiment, when a sputtering process is performed in the metal thin film forming equipment, if the monitoring unit monitors that the thickness uniformity of the metal thin film is less than a predetermined value, the process control unit can adjust at least one condition among a gas flow rate and a relative angle between the substrate and the target.

[0030] According to one embodiment, when an evaporation process is performed in the metal thin film forming equipment, if the monitoring unit monitors that the thickness uniformity of the metal thin film is below a predetermined value, the process control unit can adjust at least one condition among the distance between the substrate and the target material and the temperature of the heater.

[0031] According to one embodiment, when a CVD process is performed in the metal thin film forming equipment, if the monitoring unit monitors that the thickness uniformity of the metal thin film is below a predetermined value, the process control unit can adjust at least one condition among RF power, process temperature, gas flow rate, and substrate rotation speed.

[0032] According to one embodiment, when an electroplating process is performed in the metal thin film forming equipment, the process control unit can adjust at least one condition among the current density and the flow rate when the monitoring unit monitors that the thickness uniformity of the metal thin film is below a predetermined value.

[0033] Meanwhile, the present invention provides a method for inspecting a metal thin film using terahertz waves.

[0034] According to one embodiment, the method for inspecting a metal thin film using a terahertz wave may include: a step of generating a terahertz wave toward a metal thin film from one side of a metal thin film forming equipment in which a process of forming a metal thin film on a substrate is performed; a step of detecting a terahertz wave reflected from the metal thin film from the other side of the metal thin film forming equipment; a step of monitoring a thickness of the metal thin film in real time based on a terahertz wave detected in the step of detecting the terahertz wave while the process is in progress in the metal thin film forming equipment; and a step of controlling a process condition of the metal thin film forming equipment so that the thickness of the metal thin film satisfies the preset thickness standard when the monitored thickness of the metal thin film deviates from a preset thickness standard in the step of monitoring the thickness of the metal thin film in real time.

[0035] According to one embodiment, the step of monitoring the thickness of the metal thin film in real time selects one of a first monitoring process and a second monitoring process according to the transmittance of the metal thin film, wherein the first monitoring process is selected when the transmittance of the metal thin film exceeds 0%, and the first monitoring process and the second monitoring process can monitor the thickness of the metal thin film in real time based on different parameters of the terahertz wave detected in the step of detecting the terahertz wave.

[0036] According to an embodiment of the present invention, a metal thin film forming apparatus for forming a metal thin film on a substrate may include: an emitter disposed on one side of a metal thin film forming apparatus for generating terahertz waves toward the metal thin film; a detector disposed on the other side of the metal thin film forming apparatus for detecting terahertz waves generated from the emitter and reflected from the metal thin film; a monitoring unit for monitoring a thickness of the metal thin film in real time based on the terahertz waves detected by the detector while a process is in progress in the metal thin film forming apparatus; and a process control unit for controlling process conditions of the metal thin film forming apparatus so that the thickness of the metal thin film satisfies the preset thickness standard when the thickness of the metal thin film monitored by the monitoring unit deviates from a preset thickness standard.

[0037] Accordingly, a metal thin film inspection device and method using terahertz waves can be provided, which can rapidly inspect the formation thickness of the entire surface of the metal thin film in real time during the process of forming the metal thin film.

[0038] At this time, according to an embodiment of the present invention, when a thickness deviation occurs at each location of a metal thin film being formed, that is, when the thickness uniformity of the metal thin film being formed deviates from a preset standard, a metal thin film inspection device and method using terahertz waves can be provided that can immediately control the metal thin film formation process conditions, thereby enabling a high-quality metal thin film to be quickly formed on a substrate.

[0039] Accordingly, according to an embodiment of the present invention, problems such as poor electrical connection between a semiconductor chip and a substrate connected by an interposer formed of a metal thin film, such as an RDL (Redistribution Layer), an UBM (Under Bump Metallurgy), a metal wiring, and process defects such as warpage and delamination can be prevented in advance.

[0040] FIGS. 1 to 5 are schematic diagrams illustrating a metal thin film inspection device using terahertz waves according to one embodiment of the present invention.

[0041] FIG. 6 is a schematic diagram showing a metal thin film inspection device using terahertz waves according to an embodiment of the present invention.

[0042] FIGS. 7 to 9 are schematic diagrams illustrating an emitter and a detector of a metal thin film inspection device using terahertz waves according to an embodiment of the present invention.

[0043] FIG. 10 and FIG. 11 are drawings for explaining a monitoring unit of a metal thin film inspection device using terahertz waves according to one embodiment of the present invention.

[0044] Figures 12 to 16 are drawings showing the results of terahertz wave inspection on titanium (Ti) thin film specimens manufactured according to experimental examples.

[0045] Fig. 17 is a flowchart illustrating a method for inspecting a metal thin film using terahertz waves according to an embodiment of the present invention.

[0046] 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.

[0047] 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.

[0048] 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.

[0049] 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.

[0050] 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.

[0051] 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.

[0052]

[0053] FIGS. 1 to 5 are schematic diagrams for explaining a metal thin film inspection device using terahertz waves according to an embodiment of the present invention, FIG. 6 is a configuration diagram showing a metal thin film inspection device using terahertz waves according to an embodiment of the present invention, FIGS. 7 to 9 are schematic diagrams for explaining an emitter and a detector of a metal thin film inspection device using terahertz waves according to an embodiment of the present invention, and FIGS. 10 and 11 are drawings for explaining a monitoring unit of a metal thin film inspection device using terahertz waves according to an embodiment of the present invention.

[0054]

[0055] As illustrated in FIG. 1, a metal thin film inspection device (100) according to an embodiment of the present invention is a device that inspects the thickness of a metal thin film (M) in real time using terahertz waves while a process of forming a metal thin film (M) forming an interposer in a semiconductor stacking process, for example, an RDL (Redistribution Layer), an UBM (Under Bump Metallurgy), a metal wiring, etc., is being performed in a metal thin film forming device (10).

[0056] At this time, the metal thin film forming equipment (10) may be any one of a sputter equipment that forms a metal thin film (M) through a sputter process, an ion beam sputter equipment that forms a metal thin film (M) through an ion beam sputter process (see FIG. 2), an evaporation equipment that forms a metal thin film (M) through an evaporation process (see FIG. 3), a CVD equipment that forms a metal thin film (M) through a CVD process (see FIG. 4), and an electroplating equipment that forms a metal thin film (M) through an electroplating process (see FIG. 5).

[0057] Referring to FIG. 6, a metal thin film inspection device (100) according to one embodiment of the present invention may include an emitter (110), a detector (120), a monitoring unit (130), and a process control unit (140).

[0058]

[0059] The above emitter (110) is a device that generates terahertz waves toward a metal thin film (M). To this end, the emitter (110) may be placed on one side of a metal thin film forming equipment (10) in which a process of forming a metal thin film (M) on a substrate (21) is performed, for example, a sputtering equipment, an ion beam sputtering equipment, an evaporation equipment, a CVD equipment, and an electroplating equipment, so as to face the metal thin film (M).

[0060] At this time, according to one embodiment of the present invention, the emitter (110) may be placed on the outside of the metal thin film forming equipment (10).

[0061] Accordingly, a window (12) that transmits terahertz waves may be provided on one side of the metal thin film forming equipment (10) positioned on the optical path of the terahertz waves irradiated from the emitter (110).

[0062] Through this, terahertz waves generated from an emitter (110) placed on the outside of the metal thin film forming equipment (10) can be irradiated to the metal thin film (M) formed on the inside of the metal thin film forming equipment (10).

[0063] According to one embodiment of the present invention, the terahertz wave generated from the emitter (110) and irradiated toward the metal thin film (M) may be provided in a pulsed type or a continuous wave.

[0064] Here, pulsed terahertz waves have the advantage of being able to detect numerous frequencies at once.

[0065] 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).

[0066] At this time, according to one embodiment of the present invention, the frequency of the terahertz wave generated from the emitter (110) and irradiated onto the metal thin film (M) may be 0.1 ㎔ to 10 ㎔.

[0067] Meanwhile, 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 for the metal thin film (M).

[0068] To this end, the detector (120) may be arranged symmetrically with respect to the normal direction of the metal thin film (M) 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 metal thin film (M), the detector (120) may be arranged to be tilted -30 degrees from the normal direction of the metal thin film (M) so as to be symmetrical thereto.

[0069] At this time, according to one embodiment of the present invention, the detector (120) may be placed on the outside of the metal thin film forming equipment (10) like the emitter (110).

[0070] Accordingly, a window (12) that transmits terahertz waves can be provided on the other side of the metal thin film forming equipment (10) located on the optical path of terahertz waves generated from the emitter (110) and reflected from the metal thin film (M).

[0071] Through this, the terahertz wave reflected from the metal thin film (M) formed on the inside of the metal thin film forming equipment (10) can be detected by a detector (120) placed on the outside of the metal thin film forming equipment (10).

[0072] According to one embodiment of the present invention, terahertz waves generated from an emitter (110) and reflected from a metal thin film (M) formed inside a metal thin film forming device (10) and then detected by a detector (120) are used to inspect the thickness of the metal thin film (M), which will be described in more detail below.

[0073] Meanwhile, as illustrated in FIG. 7, optical devices (13) may be placed inside the metal thin film forming equipment (10). One optical device (13) may be placed on the optical path of terahertz waves generated from the emitter (110) and irradiated toward the metal thin film (M). In addition, another optical device (13) may be placed on the optical path of terahertz waves reflected from the metal thin film (M).

[0074] According to one embodiment of the present invention, the optical path of the terahertz wave irradiated toward the metal thin film (M) and the terahertz wave reflected from the metal thin film (M) can be adjusted by adjusting the angle of the optical device (13) placed on the optical path of the terahertz wave.

[0075] Accordingly, according to one embodiment of the present invention, terahertz waves can be irradiated to the entire surface of the metal thin film (M). Through this, thickness inspection of the entire surface of the metal thin film (M) can be performed.

[0076] As shown in FIG. 8, according to another embodiment, a stage on which a substrate (21) on which a metal thin film (M) is formed is mounted can be moved in the X-axis and Y-axis directions on a plane.

[0077] Accordingly, according to another embodiment, terahertz waves can be irradiated to the entire surface of the metal thin film (M). Through this, thickness inspection of the entire surface of the metal thin film (M) can be performed.

[0078] As shown in FIG. 9, according to another embodiment, the stage on which the substrate (21) on which the metal thin film (M) is formed is mounted can be rotated.

[0079] Accordingly, according to another embodiment, terahertz waves can be irradiated to the entire surface of the metal thin film (M). Through this, thickness inspection of the entire surface of the metal thin film (M) can be performed.

[0080] Meanwhile, the emitter (110) and detector (120) may be provided in one or two or more quantities. In this case, when two or more emitters (110) and detectors (120) are provided, the emitters (110) and detectors (120) may be provided in corresponding numbers to form a pair.

[0081]

[0082] Referring again to FIG. 6, the monitoring unit (130) can monitor the thickness of the metal thin film (M) in real time based on the terahertz wave detected by the detector (120) while the process of forming a metal thin film (M) on a substrate (21) is in progress in the metal thin film forming equipment (10), that is, the terahertz wave generated from the emitter (110) and reflected from the metal thin film (M) formed inside the metal thin film forming equipment (10) and then detected by the detector (120).

[0083] According to one embodiment of the present invention, the monitoring unit (130) can monitor the thickness of the metal thin film (M) in real time through one of the first monitoring mode and the second monitoring mode.

[0084] At this time, the monitoring unit (130) can select one of the first monitoring mode and the second monitoring mode depending on the transmittance of the metal thin film (M) formed inside the metal thin film forming equipment (10).

[0085] According to one embodiment of the present invention, the first monitoring mode may be selected when the transmittance of the metal thin film (M) exceeds 0%. On the other hand, the second monitoring mode may be selected when the transmittance of the metal thin film (M) is 0%.

[0086] That is, the second monitoring mode can be selected when the terahertz wave irradiated toward the metal thin film (M) is totally reflected by the metal thin film (M).

[0087] When the thickness of the metal thin film (M) is greater than a predetermined thickness, for example, when the metal thin film (M) has a thickness in micrometers (㎛), the terahertz wave irradiated toward the metal thin film (M) can be totally reflected by the metal thin film (M).

[0088] On the other hand, when the metal thin film (M) has a thickness in the nanometer (nm) unit, some of the terahertz waves irradiated toward the metal thin film (M) are reflected, and the rest can transmit through the metal thin film (M).

[0089] Accordingly, according to one embodiment of the present invention, the monitoring unit (130) can select the first monitoring mode when the thickness of the metal thin film (M) formed inside the metal thin film forming equipment (10) is thin enough to transmit even a little of the terahertz wave being irradiated.

[0090] In addition, the monitoring unit (130) can select the second monitoring mode when the thickness of the metal thin film (M) formed inside the metal thin film forming equipment (10) is thick enough to reflect all of the terahertz waves being irradiated.

[0091] For example, the monitoring unit (130) may select the first monitoring mode when the process currently being performed in the metal thin film forming equipment (10) is a process for forming a metal thin film (M) having a thickness in nanometers (nm), such as a sputter process, an evaporation process, and a CVD process.

[0092] On the other hand, the monitoring unit (130) may select the second monitoring mode when the process currently being performed in the metal thin film forming equipment (10) is a process for forming a metal thin film (M) having a thickness in micrometers (㎛), such as an electroplating process.

[0093] According to one embodiment of the present invention, the first monitoring mode and the second monitoring mode, which are selected according to the transmittance of the metal thin film (M) to terahertz waves, can monitor the thickness of the metal thin film (M) in real time based on different parameters of the terahertz waves detected by the detector (120).

[0094] Referring to Fig. 10, the terahertz wave that is irradiated to the metal thin film (M) formed on the substrate (21) inside the metal thin film forming equipment (10) and then reflected and detected by the detector (120) is the first peak (1) reflected from the metal thin film (M). st peak) and the second peak (2) reflected from the bottom of the substrate (21) nd can be divided into peaks.

[0095] According to one embodiment of the present invention, the first monitoring mode is a first peak (1) reflected from a metal thin film (M), which is two terahertz wave peaks detected by a detector (120). st peak) and the second peak (2) reflected from the bottom of the substrate (21) nd The first peak (1) reflected from the metal film (M) among the peaks st The reflectance of the metal film (M) can be calculated through the amplitude of the peak.

[0096] At this time, the reflectivity of the metal thin film (M) can be calculated using the following equation 1.

[0097]

[0098] [Formula 1]

[0099]

[0100]

[0101] Here, the above E reflector is the peak amplitude of the terahertz wave totally reflected from the reflector, and the E sample is the peak amplitude of the terahertz wave reflected from the metal film (M), i.e., the first peak (1 st is the amplitude of the peak.

[0102] In the first monitoring mode, the reason for calculating the reflectance of the metal thin film (M) is that the reflectance tends to increase as the thickness of the metal thin film (M) increases.

[0103] According to one embodiment of the present invention, the first monitoring mode can monitor in real time whether the thickness of the metal thin film (M) satisfies a preset thickness standard based on the reflectivity of the metal thin film (M) calculated by the above formula 1.

[0104] For example, the first monitoring mode can monitor in real time whether the thickness of the metal thin film (M) increases or decreases at each location through the change in reflectivity of the metal thin film (M) calculated by the above formula 1.

[0105] Referring to FIG. 11, the second monitoring mode is the first peak (1) of the terahertz wave reflected from the metal thin film (M). st The thickness of the metal film can be calculated through the time delay between the peaks.

[0106] Here, depending on the thickness of the metal thin film (M), a deviation may occur in the time at which the terahertz wave irradiated on the metal thin film (M) is reflected from the metal thin film (M) and detected by the detector (120).

[0107] For example, the time at which a terahertz wave is reflected from a substrate (21) on which a metal thin film (M) is not formed and is detected by a detector (120) may be later than the time at which a terahertz wave is reflected from a metal thin film (M) formed on the substrate (21) and is detected by a detector (120).

[0108] This is because, when a metal thin film (M) is formed on the substrate (21), the optical path is reduced accordingly.

[0109] Accordingly, the time it takes for a terahertz wave to be reflected from a thick metal film (M) and detected by a detector (120) may be faster than the time it takes for a terahertz wave to be reflected from a relatively thin metal film (M) and detected by a detector (120).

[0110] According to one embodiment of the present invention, the time delay may be defined as a time delayed from a preset point in time until the time at which the terahertz wave is reflected from the metal thin film (M) and detected by the detector (120).

[0111] Accordingly, the thicker the metal film (M), the more the time delay can be reduced.

[0112] According to one embodiment of the present invention, the second monitoring mode can calculate the thickness (d) of the metal thin film (M) through the following equation 2.

[0113]

[0114] [Formula 2]

[0115]

[0116]

[0117] Here, n is the refractive index of the metal thin film (M), c is the speed of light, and Δt is the time delay. θ is the incident angle of the terahertz wave irradiated onto the metal thin film (M), and cosθ° is defined as the ratio of the hypotenuse and the base of a right triangle formed by a hypotenuse set as an optical path of the terahertz wave reflected from the metal thin film (M) and detected by the detector (120), a base set as a line segment extending in the normal direction of the metal thin film (M) to the height of the detector (120) while forming an angle of θ with the hypotenuse, and a height set as a line segment connecting the hypotenuse and the upper end of the base.

[0118] As the thickness of the metal thin film (M) increases, the first peak (1) of the terahertz wave reflected from the metal thin film (M) increases. st The time delay of the peak) can be reduced. That is, as the thickness of the metal thin film (M) increases, the time at which the terahertz wave is reflected from the metal thin film (M) formed on the substrate (21) and detected by the detector (120) can be shortened.

[0119] According to one embodiment of the present invention, the second monitoring mode can monitor in real time whether the thickness of the metal thin film (M) satisfies a preset thickness standard based on the thickness of the metal thin film (M) calculated by the above formula 2.

[0120] For example, the second monitoring mode can monitor in real time whether the thickness of the metal thin film (M) increases or decreases at each location through the thickness of the metal thin film (M) calculated by the above formula 2.

[0121] Meanwhile, when the thickness of the metal thin film (M) formed on the substrate (21) is unknown, the monitoring unit (130) can simultaneously apply the first monitoring mode and the second monitoring mode to a point on the metal thin film (M), and then select one of the first monitoring mode and the second monitoring mode according to the result value.

[0122] In addition, for the entire surface of the metal thin film (M), the monitoring unit (130) can monitor the thickness of the metal thin film in real time through at least one monitoring mode among the first monitoring mode and the second monitoring mode.

[0123] In general, the edge portion of the metal film (M) may have a relatively thinner formation thickness than the center portion of the metal film (M).

[0124] Accordingly, the monitoring unit (130) can monitor the formation thickness in real time through the first monitoring mode for the edge portion of the metal thin film (M) that is expected to be formed relatively thinner than the center portion, and can monitor the formation thickness in real time through the second monitoring mode for the center portion of the metal thin film (M) that is expected to be formed relatively thicker than the edge portion.

[0125]

[0126] The above process control unit (140) can control the process conditions of the metal thin film forming equipment (10) so that the thickness of the metal thin film (M) monitored by the monitoring unit (130) exceeds the preset thickness standard, so that the thickness of the metal thin film (M) meets the preset thickness standard.

[0127] Referring again to FIG. 1, when the metal thin film forming equipment (10) is a general type of sputtering equipment, i.e., when a sputtering process is performed in the metal thin film forming equipment (10), the process control unit (140) can perform a feedback process for controlling the gas flow rate when the monitoring unit (130) monitors that the thickness uniformity of the metal thin film (M) is below a predetermined value.

[0128] At this time, referring to FIG. 2, if the metal thin film forming equipment (10) is an ion beam sputter equipment, the process control unit (140) can perform a feedback process to improve an uneven deposition surface by adjusting the relative angle between the substrate (21) and the target, and can increase the plasma density by increasing the gas flow rate and increase the deposition rate due to a decrease in the mean free path.

[0129] In addition, referring again to FIG. 3, when the metal thin film forming equipment (10) is an evaporation equipment, that is, when an evaporation process is performed in the metal thin film forming equipment (10), the process control unit (140) may perform a feedback process for adjusting at least one of the conditions of the distance between the substrate (21) and the target material and the temperature of the heater when the monitoring unit (130) monitors that the thickness uniformity of the metal thin film (M) is less than a predetermined value.

[0130] For example, the process control unit (140) can improve deposition uniformity by changing the distance between the substrate (21) and the target material.

[0131] Meanwhile, as demand for interposer technology rapidly increases, plastic or glass is being used as the substrate (21) material on which the metal thin film (M) is formed.

[0132] At this time, since the transition temperature of glass is around 600℃ to 700℃, the LPCVD (low pressure chemical vapor deposition) method, which decomposes and deposits raw material gas using heat energy at a high temperature of 1,000℃ or higher, cannot be used.

[0133] Accordingly, the PECVD (plasma-enhanced chemical vapor deposition) method is being used, but since the PECVD method has poor deposition uniformity compared to the LPCVD method, large-area real-time thickness uniformity inspection is required.

[0134] Referring again to FIG. 4, when the metal thin film forming equipment (10) is a CVD equipment, that is, when a PECVD process is performed in the metal thin film forming equipment (10), the process control unit (140) can perform a feedback process for adjusting at least one condition among RF power, process temperature, gas flow rate, and substrate rotation speed when the monitoring unit (130) monitors that the thickness uniformity of the metal thin film (M) is below a predetermined value.

[0135] For example, the process control unit (140) can improve the reaction rate and deposition rate by increasing the gas flow rate or increasing the RF power.

[0136] In addition, referring to FIG. 5, when the metal thin film forming equipment (10) is an electroplating equipment, that is, when an electroplating process is performed in the metal thin film forming equipment (10), the process control unit (140) may perform a feedback process for adjusting at least one condition among the current density (ASD) and the flow rate when the monitoring unit (130) monitors that the thickness uniformity of the metal thin film (M) is less than a predetermined value.

[0137] For example, the process control unit (140) can lower the current density and increase the flow rate to increase the deposition rate in areas with less plating.

[0138]

[0139] Experimental example

[0140] Titanium (Ti) thin film specimens of various thicknesses were fabricated by depositing titanium (Ti) on glass wafers at thicknesses of 10 nm, 50 nm, 75 nm, and 100 nm using sputtering equipment.

[0141] The fabricated titanium (Ti) thin film specimens were then examined in THz-TDS (Terahertz-Time Domain Spectroscopy) reflection mode. The terahertz wave incidence angle was set to 60 degrees. However, the terahertz wave incidence angle can be varied within the range of 0 degrees to 90 degrees.

[0142] Referring to Figure 12, the THz-TDS test results show that all titanium (Ti) thin film specimens manufactured by thickness have the first peak (1) of the terahertz wave reflected from the titanium (Ti) thin film. st peak) and the second peak (2) of terahertz waves reflected from the bottom of the glass wafer inside the specimen. nd It was detected by being separated into peaks.

[0143] Continuing with reference to FIG. 13, in the case of processes in which the deposition thickness of the titanium (Ti) thin film is set in nanometers (nm), such as sputtering, evaporation, and CVD, the deposition thickness of the titanium (Ti) thin film was monitored based on the reflectivity of the titanium (Ti) thin film.

[0144] The first peak of the terahertz wave totally reflected from the reflector (1 st The amplitude of the peak is E reflector Defined as , the first peak (1) of terahertz wave according to the deposition thickness of titanium (Ti) thin film st peak) amplitude E sample As a result of calculating the reflectance by defining it as , it was confirmed that the reflectance of the titanium (Ti) thin film increases as the thickness of the titanium (Ti) thin film increases.

[0145] Through this, it was confirmed that the thickness of a metal thin film (M) can be monitored in real time using terahertz waves.

[0146] At this time, referring to FIGS. 14 and 15, in order to confirm the possibility of metal thin film inspection in the actual semiconductor industry, a specimen was scanned with terahertz waves according to the thickness of a titanium (Ti) thin film, and the reflectivity was calculated and visualized. As a result, a difference in shade according to the thickness of the titanium (Ti) thin film was confirmed in the terahertz wave scanning image.

[0147] Through this, it was confirmed that real-time, full-surface, i.e., large-area, full-scale inspection of the thickness change of a metal thin film (M) during the deposition process during a semiconductor process is possible using terahertz wave inspection technology.

[0148] Meanwhile, referring to FIG. 16, in the case of a process in which the deposition thickness of a titanium (Ti) thin film is set in micrometers (㎛), such as electroplating, the first peak (1) of the terahertz wave according to the thickness of the titanium (Ti) thin film stThe deposition thickness of titanium (Ti) thin films was monitored based on the time delay between peaks.

[0149] As a result of monitoring, the first peak (1) of terahertz waves reflected on the reflector st Based on the peak) detection time, when the deposition thickness of the titanium (Ti) thin film is 100 ㎛, the first peak (1) of the terahertz wave st The detection time of the first peak (1) of the terahertz wave is when the deposition thickness of the titanium (Ti) thin film is 50 ㎛. st It was confirmed that the time delay was reduced compared to the peak detection time.

[0150] That is, when the deposition thickness of the titanium (Ti) thin film is 100 ㎛, the first peak (1) of the terahertz wave st The detection time of the first peak (1) of the terahertz wave is when the deposition thickness of the titanium (Ti) thin film is 50 ㎛. st It was confirmed that the peak detection time was faster than the peak detection time.

[0151] In this way, it was confirmed that monitoring of the thickness of a titanium (Ti) thin film is possible through different parameters depending on the deposition thickness of the titanium (Ti) thin film.

[0152] That is, when the deposition thickness of the titanium (Ti) thin film is in the nanometer (nm) unit, such as in sputter, evaporation, and CVD, the thickness of the titanium (Ti) thin film can be monitored in real time based on the reflectivity of the produced titanium (Ti).

[0153] Also, in cases where the deposition thickness of titanium (Ti) is in the micrometer (㎛) range, such as in electroplating, the first peak (1) of the terahertz wave st The thickness of a titanium (Ti) thin film can be monitored in real time based on the time delay between peaks.

[0154]

[0155] Hereinafter, a method for inspecting a metal thin film using terahertz waves according to an embodiment of the present invention will be described with reference to FIG. 17. Here, the drawing symbols of each component refer to FIGS. 1 to 11.

[0156]

[0157] Fig. 17 is a flowchart illustrating a method for inspecting a metal thin film using terahertz waves according to an embodiment of the present invention.

[0158]

[0159] Referring to FIG. 17, a method for inspecting a metal thin film using terahertz waves according to an embodiment of the present invention may include steps S110, S120, S130, and S140.

[0160]

[0161] S110 stage

[0162] The above step S110 is a step of generating terahertz waves toward the metal thin film (M) from one side of the metal thin film forming equipment (10) in which the process of forming the metal thin film (M) on the substrate (21) is performed.

[0163] At this time, in the above step S110, terahertz waves can be generated toward the metal thin film (M) through reflection mode.

[0164] To this end, in the step S110, the terahertz wave can be generated so that the terahertz wave is incident on the metal thin film (M) at an angle exceeding 0° and less than 90°.

[0165] At this time, the terahertz wave irradiated toward the metal thin film (M) can have its optical path controlled by an optical device (13) placed on the optical path of the terahertz wave inside the metal thin film forming equipment (10). Accordingly, the terahertz wave can be irradiated to the entire surface of the metal thin film (M).

[0166] In addition, the terahertz wave irradiated toward the metal thin film (M) can be irradiated to the entire surface of the metal thin film (M) by moving the stage on which the substrate (21) on which the metal thin film (M) is formed is mounted in the X-axis and Y-axis directions on a plane.

[0167] And the terahertz wave irradiated toward the metal thin film (M) can be irradiated to the entire surface of the metal thin film (M) by rotating the stage on which the substrate (21) on which the metal thin film (M) is formed is mounted.

[0168]

[0169] S120 stage

[0170] The above step S120 is a step of detecting terahertz waves reflected from the metal thin film (M) on the other side of the metal thin film forming equipment (10).

[0171] In the above step S120, while the process of forming a metal thin film (M) is in progress in the metal thin film forming equipment (10), terahertz waves reflected from the metal thin film (M) can be detected.

[0172] Here, the metal thin film forming equipment (10) may be any one of a sputter equipment (see FIG. 1) that forms a metal thin film (M) through a sputter process, an ion beam sputter equipment (see FIG. 2) that forms a metal thin film (M) through an ion beam sputter process, an evaporation equipment (see FIG. 3) that forms a metal thin film (M) through an evaporation process, a CVD equipment (see FIG. 4) that forms a metal thin film (M) through a CVD process, and an electroplating equipment (see FIG. 5) that forms a metal thin film (M) through an electroplating process.

[0173]

[0174] Step S130

[0175] The above step S130 is a step of monitoring the thickness of the metal thin film in real time based on the terahertz wave detected in the above step S120 while the process of forming a metal thin film (M) is in progress in the metal thin film forming equipment (10).

[0176] According to an embodiment of the present invention, the step S130 may select one of the first monitoring process and the second monitoring process depending on the transmittance of the metal thin film (M).

[0177] At this time, the first monitoring process can be selected when the transmittance of the metal thin film (M) exceeds 0%.

[0178] On the other hand, the second monitoring process can be selected when the transmittance of the metal thin film (M) is 0%. That is, the second monitoring process can be selected when the terahertz wave irradiated toward the metal thin film (M) is totally reflected by the metal thin film (M).

[0179] The above first monitoring process can be selected when the thickness of the metal thin film (M) formed inside the metal thin film forming equipment (10) is thin enough to transmit even a little of the terahertz wave being investigated.

[0180] For example, the first monitoring process may be selected when the process currently being performed in the metal thin film forming equipment (10) is a process for forming a metal thin film (M) having a thickness in nanometers (nm), such as a sputter process, an evaporation process, and a CVD process.

[0181] In addition, the second monitoring process may be selected when the thickness of the metal thin film (M) formed inside the metal thin film forming equipment (10) is thick enough to reflect all of the terahertz waves being irradiated.

[0182] For example, the second monitoring process may be selected when the process currently being performed in the metal thin film forming equipment (10) is a process for forming a metal thin film (M) having a thickness in micrometers (㎛), such as an electroplating process.

[0183] In this way, the first monitoring process and the second monitoring process, which are selected according to the transmittance of the metal thin film (M) to terahertz waves, can monitor the thickness of the metal thin film (M) in real time based on different parameters of the terahertz waves detected in the step S120.

[0184] That is, in the first monitoring process, the first peak (1) reflected from the metal thin film (M), which is one of the two terahertz wave peaks detected in the S120 step, st peak) and the second peak (2) reflected from the bottom of the substrate (21) nd The first peak (1) reflected from the metal film (M) among the peaks st The reflectance of the metal thin film (M) can be calculated through the amplitude of the peak. At this time, the reflectance of the metal thin film (M) can be calculated through the above equation 1.

[0185] In the above first monitoring process, it is possible to monitor in real time whether the thickness of the metal thin film (M) increases or decreases at each location through the reflectance of the metal thin film (M) calculated by the above formula 1.

[0186] On the other hand, in the second monitoring process, the first peak (1) of the terahertz wave reflected from the metal film (M) st The thickness of the metal thin film can be calculated through the time delay between the peaks. At this time, in the second monitoring process, the thickness (d) of the metal thin film (M) can be calculated through the above equation 2.

[0187] According to one embodiment of the present invention, in the second monitoring process, based on the thickness of the metal thin film (M) calculated by the above formula 2, it is possible to monitor in real time whether the thickness of the metal thin film (M) satisfies a preset thickness standard.

[0188] Meanwhile, in the step S130, if the thickness of the metal thin film (M) formed on the substrate (21) is not known, the first monitoring process and the second monitoring process may be performed simultaneously for a point on the metal thin film (M), and then, depending on the result value, one of the first monitoring process and the second monitoring fixation may be selected.

[0189] In addition, in the step S130, for example, the formation thickness of the edge portion of the metal thin film (M) that is expected to be formed relatively thinner than the center portion can be monitored in real time through a first monitoring process, and the formation thickness of the center portion of the metal thin film (M) can be monitored in real time through a second monitoring process.

[0190]

[0191] Step S140

[0192] The above step S140 is a step for controlling the process conditions of the metal thin film forming equipment (10) so that the thickness of the metal thin film (M) monitored in the above step S130 exceeds the preset thickness standard, so that the thickness of the metal thin film (M) meets the preset thickness standard.

[0193] For example, in the step S140, when the metal thin film forming equipment (10) is a general type of sputter equipment, if the thickness uniformity of the metal thin film (M) is monitored to be less than a predetermined value by the step S130, the gas flow rate can be adjusted.

[0194] At this time, in the step S140, if the metal thin film formation equipment (10) is an ion beam sputter equipment, a feedback process can be performed to improve an uneven deposition surface by adjusting the relative angle between the substrate (21) and the target, and by increasing the gas flow rate, the plasma density can be increased and the deposition rate can be increased due to a decrease in the mean free path.

[0195] In addition, in the step S140, when the metal thin film forming equipment (10) is an evaporation equipment, if the thickness uniformity of the metal thin film (M) is monitored to be less than a predetermined value by the step S130, a feedback process for adjusting at least one condition among the distance between the substrate (21) and the target material and the temperature of the heater can be performed.

[0196] For example, in the above step S140, the distance between the substrate (21) and the target material can be changed to improve deposition uniformity.

[0197] And in the step S140, when the metal thin film forming equipment (10) is a CVD equipment, if the thickness uniformity of the metal thin film (M) is monitored to be less than a predetermined value by the step S130, a feedback process for adjusting at least one condition among RF power, process temperature, gas flow rate, and substrate rotation speed can be performed.

[0198] For example, in the above step S140, the reaction rate and deposition rate can be improved by increasing the gas flow rate or increasing the RF power.

[0199] In addition, in the step S140, when the metal thin film forming equipment (10) is an electroplating equipment, if the thickness uniformity of the metal thin film (M) is monitored to be less than a predetermined value by the step S130, a feedback process for adjusting at least one condition among the current density (ASD) and the flow rate can be performed.

[0200] For example, in the above step S140, the current density can be lowered and the flow rate can be increased to increase the deposition rate in areas with less plating.

[0201]

[0202] 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 is placed on one side of a metal thin film forming device in which a process of forming a metal thin film on a substrate is performed and generates terahertz waves toward the metal thin film; A detector disposed on the other side of the metal thin film forming equipment and detecting terahertz waves generated from the emitter and reflected from the metal thin film; A monitoring unit that monitors the thickness of the metal thin film in real time based on the terahertz wave detected by the detector while the process is in progress in the metal thin film forming equipment; and A metal thin film inspection device using terahertz waves, comprising a process control unit that controls the process conditions of the metal thin film forming equipment so that the thickness of the metal thin film meets the preset thickness standard when the thickness of the metal thin film monitored by the monitoring unit deviates from the preset thickness standard.

2. In paragraph 1, Depending on the transmittance of the metal thin film, the monitoring unit monitors the thickness of the metal thin film in real time through one of the first monitoring mode and the second monitoring mode. A metal thin film inspection device using terahertz waves, wherein the first monitoring mode and the second monitoring mode monitor the thickness of the metal thin film in real time based on different parameters of the terahertz waves detected by the detector.

3. In paragraph 2, The above monitoring unit selects one of the first monitoring mode and the second monitoring mode, A metal thin film inspection device using terahertz waves, wherein the first monitoring mode is selected when the transmittance of the metal thin film exceeds 0%.

4. In paragraph 3, The first monitoring mode calculates the reflectivity of the metal thin film through the peak amplitude of the terahertz wave reflected from the metal thin film, and monitors in real time whether the thickness of the metal thin film satisfies the preset thickness standard based on the calculated reflectivity. A metal thin film inspection device using terahertz waves, wherein the reflectance of the metal thin film is calculated using the following equation 1. [Formula 1] Here, the above E reflector is the peak amplitude of the terahertz wave totally reflected from the reflector, and the E sample is the peak amplitude of the terahertz wave reflected from the above metal film.

5. In paragraph 4, A metal thin film inspection device using terahertz waves, wherein the reflectivity increases as the thickness of the metal thin film increases.

6. In paragraph 3, The second monitoring mode calculates the thickness of the metal thin film through the time delay between peaks of the terahertz wave reflected from the metal thin film, and monitors in real time whether the thickness of the metal thin film satisfies the preset thickness standard based on the calculated thickness of the metal thin film. A metal thin film inspection device using terahertz waves, wherein the thickness (d) of the metal thin film is calculated using the following equation 2. [Formula 2] Here, n is the refractive index of the metal thin film, c is the speed of light, Δt is the time delay, and θ is the angle of incidence.

7. In paragraph 6, A metal thin film inspection device using terahertz waves, wherein as the thickness of the metal thin film increases, the time delay of the terahertz wave peak reflected from the metal thin film decreases.

8. In paragraph 2, The monitoring unit simultaneously applies the first monitoring mode and the second monitoring mode to a point on the metal thin film, and then selects one of the first monitoring mode and the second monitoring mode based on the result value. A metal thin film inspection device using terahertz waves, which monitors the thickness of the metal thin film in real time through at least one of the first monitoring mode and the second monitoring mode for the entire metal thin film.

9. In paragraph 3, The above process control unit, A metal thin film inspection device using terahertz waves, which, when a sputtering process is performed in the metal thin film formation equipment, adjusts at least one condition among a gas flow rate and a relative angle between the substrate and the target when the monitoring unit determines that the thickness uniformity of the metal thin film is below a predetermined value.

10. In paragraph 3, The above process control unit, A metal thin film inspection device using terahertz waves, which controls at least one of the conditions of the distance between the substrate and the target material and the temperature of the heater when the thickness uniformity of the metal thin film is monitored by the monitoring unit to be less than a predetermined value when the evaporation process is performed in the metal thin film formation equipment.

11. In paragraph 3, The above process control unit, A metal thin film inspection device using terahertz waves, which, when a CVD process is performed in the metal thin film formation equipment, adjusts at least one condition among RF power, process temperature, gas flow rate, and substrate rotation speed when the monitoring unit determines that the thickness uniformity of the metal thin film is below a predetermined value.

12. In paragraph 3, The above process control unit, A metal thin film inspection device using terahertz waves, which controls at least one condition among current density and flow rate when the thickness uniformity of the metal thin film is monitored by the monitoring unit to be less than a predetermined value when an electroplating process is performed in the metal thin film forming equipment.

13. A step of generating terahertz waves toward a metal thin film from one side of a metal thin film forming equipment in which a process of forming a metal thin film on a substrate is performed; A step of detecting terahertz waves reflected from the metal thin film on the other side of the metal thin film forming equipment; A step of monitoring the thickness of the metal thin film in real time based on the terahertz wave detected in the step of detecting the terahertz wave while the process is in progress in the metal thin film forming equipment; and A method for inspecting a metal thin film using terahertz waves, comprising: a step of controlling the process conditions of the metal thin film forming equipment so that the thickness of the metal thin film satisfies the preset thickness standard when the monitored thickness of the metal thin film deviates from the preset thickness standard in the step of monitoring the thickness of the metal thin film in real time; 14. In paragraph 13, The step of monitoring the thickness of the metal thin film in real time selects one of the first monitoring process and the second monitoring process according to the transmittance of the metal thin film. The above first monitoring process is selected when the transmittance of the metal thin film exceeds 0%, A method for inspecting a metal thin film using terahertz waves, wherein the first monitoring process and the second monitoring process monitor the thickness of the metal thin film in real time based on different parameters of the terahertz waves detected in the step of detecting the terahertz waves.

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