Process evaluation apparatus, process evaluation method, and process evaluation program

Abstract

To appropriately adjust a processing time and a processing condition in at least one of a deposition process, an anisotropic etching process and isotropic etching.SOLUTION: This device is equipped with light absorbing measuring parts 2A and 2B which irradiate gas containing a reactive product produced in a process with light and measure the reactive product on the basis of the absorbance of the light, and a state evaluating part 3 which evaluates the state of the process on the basis of measured values obtained by the light absorbing measuring parts 2A and 2B.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a process evaluation device, a process evaluation method, and a process evaluation program. [Background technology]

[0002] Deep RIE has traditionally been used to perform microfabrication on silicon substrates. Deep RIE is a type of reactive ion etching (RIE) with a high aspect ratio (narrow and deep).

[0003] 11, this deep RIE includes a process (so-called Bosch process) that repeats a deposition process of depositing a protective film on a substrate, an anisotropic etching process of anisotropically etching the bottom surface of the protective film, and an isotropic etching process of isotropically etching the substrate exposed after the protective film has been removed (for example, Patent Document 1). By this Bosch process, it is possible to form a deep trench or hole by etching the bottom surface of the trench or hole while protecting the side surface of the trench or hole with a protective film.

[0004] However, unless the processing time and processing conditions in at least one of the deposition step, the anisotropic etching step, and the isotropic etching step are appropriately adjusted, it is not possible to dig parallel trenches or holes, which may result in tapered or inversely tapered trenches or holes, or adjacent trenches or holes may be connected to each other. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 2019-102593 Summary of the Invention [Problem to be solved by the invention]

[0006] Therefore, the present invention has been made to solve the above-mentioned problems, and its main object is to make it possible to appropriately adjust the processing time and processing conditions in at least one of the deposition step, the anisotropic etching step, and the isotropic etching step in the process. [Means for solving the problem]

[0007] That is, the process evaluation device according to the present invention is a process evaluation device that evaluates a process that repeats a deposition step of depositing a protective film on a substrate, an anisotropic etching step of removing a portion of the protective film by anisotropic etching, and an isotropic etching step of removing the substrate, exposed by the removal of the protective film, by isotropic etching, and is characterized by comprising: an optical absorption measurement unit that irradiates light onto a gas containing reaction products generated in the process and measures the reaction products based on the absorption of the light; and a state evaluation unit that evaluates the state of the process based on the measurement value obtained by the optical absorption measurement unit.

[0008] This process evaluation device irradiates light onto gas containing reaction products generated in the process, measures the reaction products, and evaluates the state of the process based on the measured values ​​of the reaction products, making it possible to appropriately adjust the processing time and processing conditions in at least one of the deposition step, anisotropic etching step, and isotropic etching step in the so-called Bosch process.As a result, it is possible to form grooves, holes, or other processed shapes in a substrate in the Bosch process with desired shapes, thereby improving the performance of devices using the processed substrate.

[0009] The process is for etching silicon. In this case, it is considered that C4F8 is used as a process gas in the protective film deposition step, and SF6 is used as a process gas in the anisotropic etching and isotropic etching. In this case, it is preferable that the optical absorption measurement unit measures a first reaction product (e.g., SiF4) generated when silicon is etched, and the state evaluation unit evaluates the state of the process based on the measurement value of the first reaction product obtained by the optical absorption measurement unit.

[0010] By using an optical absorption measurement unit, the inventors of the present application have found that the first reaction product (e.g., SiF4) is generated not only in anisotropic etching and isotropic etching but also in the deposition process. This is thought to be because the exposed Si reacts with the plasma in the deposition process to generate the first reaction product (e.g., SiF4). Therefore, the state evaluation unit evaluates the state of the process based on the measured value of the first reaction product (for example, SiF4) during the deposition step.

[0011] As a specific embodiment of the state evaluation unit, it is desirable that the state evaluation unit detects the end point of the process based on the magnitude of the rise in the measurement value of the first reaction product (e.g., SiF4) during the deposition process.

[0012] In addition, as another specific embodiment of the state evaluation unit, it is desirable that the state evaluation unit determines that the deposition of the protective film is sufficient when the measured value of the first reaction product (e.g., SiF4) during the deposition process is below a threshold value.

[0013] Since the first reaction product (e.g., SiF4) is generated during the anisotropic etching process or the isotropic etching process, it is desirable that the state evaluation unit evaluates the state of the process based on the measurement value of the first reaction product (e.g., SiF4) during the anisotropic etching process or the isotropic etching process.

[0014] As a specific embodiment of the state evaluation unit, it is desirable that the state evaluation unit detects that the object being etched has switched from the protective film to silicon based on the measurement value of the first reaction product (e.g., SiF4) during the anisotropic etching process.

[0015] As a specific embodiment of the state evaluation unit, it is desirable that the state evaluation unit detects the end point of the process based on the measurement value of the first reaction product (e.g., SiF4) during the anisotropic etching process or the isotropic etching process.

[0016] Furthermore, it is desirable that the protective film is made of a compound containing carbon, the optical absorption measurement unit measures a second reaction product (e.g., any one of CO, CO2, and CF4) generated when the protective film is etched, and the state evaluation unit determines that the protective film is insufficient when the measurement value of the second reaction product obtained by the optical absorption measurement unit during the isotropic etching process is equal to or less than a threshold value.

[0017] The optical absorption measuring unit is preferably provided in an exhaust pipe connected to a chamber in which the process is performed. With this configuration, the reaction products flowing through the exhaust pipe are in a stable state compared to the reaction products inside the chamber, and measuring the reaction products in the exhaust pipe allows for more accurate evaluation of the process state. Although light emission detection has been considered as a process monitor, stable reaction products do not emit light and therefore cannot be measured.

[0018] It is desirable that the light absorption measuring unit irradiates the gas with laser light and measures the reaction product based on the absorption of the laser light. With this configuration, since laser light has the property of traveling in a straight line, it is easy to achieve high sensitivity even when a long optical path cell is used, and the process can be evaluated more appropriately.

[0019] Furthermore, the process evaluation apparatus according to the present invention is a process evaluation method for evaluating a process that repeats a deposition step of depositing a protective film on a substrate, an anisotropic etching step of removing a portion of the protective film by anisotropic etching, and an isotropic etching step of removing the substrate, exposed by the removal of the protective film, by isotropic etching, and is characterized in that the process evaluation method includes irradiating light onto a gas containing reaction products generated in the process, measuring the reaction products based on absorption of the light, and evaluating the state of the process based on the measured values ​​of the reaction products.

[0020] Furthermore, the process evaluation program according to the present invention is a process evaluation program for evaluating a process that repeats a deposition step of depositing a protective film on a substrate, an anisotropic etching step of removing a portion of the protective film by anisotropic etching, and an isotropic etching step of removing the substrate, exposed by the removal of the protective film, by isotropic etching, and is characterized in that the program has a computer equipped with a function as a state evaluation unit that evaluates the state of the process based on measurement values ​​obtained by an optical absorption measurement unit that irradiates light onto a gas containing reaction products generated in the process and measures the reaction products. [Effects of the Invention]

[0021] According to the present invention configured as described above, it becomes possible to appropriately adjust the processing time and processing conditions in at least one of the deposition step, the anisotropic etching step, and the isotropic etching step in the process. [Brief explanation of the drawings]

[0022] [Figure 1] 1 is a schematic diagram illustrating a process evaluation device according to an embodiment of the present invention. [Figure 2] 3 is a functional configuration diagram of a signal processing device and a calculation unit of the optical absorption measurement unit in the same embodiment. FIG. [Figure 3] 3A and 3B are schematic diagrams showing a method for modulating a laser oscillation wavelength in the embodiment. [Figure 4]10 is a time series graph showing an example of the oscillation wavelength, the light intensity I(t), the logarithmic intensity L(t), the feature signal Fi(t), and the correlation value Si in the embodiment. [Figure 5] FIG. 10 is a diagram showing a concept of concentration or partial pressure calculation using a single correlation value and a sample correlation value according to the embodiment. [Figure 6] 1A is a schematic diagram of the state before and after the deposition process in the same embodiment, and FIG. 1B is a graph of the measured values ​​of SiF4. [Figure 7] 10 is a graph showing (a) measured values ​​of SiF 4 when the protective film is insufficient, and (b) measured values ​​of SiF 4 when the protective film is sufficient in the same embodiment. [Figure 8] 1A is a schematic diagram showing the state before and after the anisotropic etching process in the same embodiment, and FIG. 1B is a graph showing the measured values ​​of SiF 4 . [Figure 9] 10 is a graph showing (a) measured values ​​of CO when the protective film is insufficient, and (b) measured values ​​of CO when the protective film is sufficient in the same embodiment. [Figure 10] In the same embodiment, (a) is a graph showing the measured values ​​of SiF4 and CO when the protective film is insufficient and the etching shape at that time, and (b) is a graph showing the measured values ​​of SiF4 and CO when the protective film is sufficient and the etching shape at that time. [Figure 11] FIG. 1 is a schematic diagram showing each step of the Bosch process. DETAILED DESCRIPTION OF THE INVENTION

[0023] Hereinafter, an embodiment of a process evaluation device according to the present invention will be described with reference to the drawings. In addition, in all of the drawings shown below, for the sake of clarity, some parts are omitted or exaggerated as appropriate, and the same components are denoted by the same reference numerals, and the description thereof will be omitted as appropriate.

[0024] <Device configuration> The process evaluation device of this embodiment evaluates a process by measuring reaction products produced in the process.

[0025] The process to be evaluated here is the so-called Bosch process, which is a process for forming a high aspect ratio (narrow and deep) trench or hole on a substrate by repeating the following steps: a deposition step for depositing a protective film on a substrate; an anisotropic etching step for anisotropically etching away a portion of the protective film; and an isotropic etching step for isotropically etching away the substrate exposed after the protective film has been removed, as shown in Fig. 11. The substrate in this embodiment has a SiO2 layer, a silicon (Si) layer formed on the top surface of the SiO2 layer, and a mask layer partially formed on the top surface of the Si layer.

[0026] The deposition process is a process of depositing a CF-based polymer film serving as a protective film on the upper surface of a substrate by supplying, for example, CF and O as process gases into a chamber where plasma is generated. Note that O may not be used as the process gas in the deposition process, or CF may be used instead of CF. On the other hand, the anisotropic etching process is a process of supplying, for example, SF and O as process gases into a chamber where plasma is generated, and applying a bias voltage to the substrate, thereby etching and removing a portion of the protective film (the protective film on the bottom of a trench or hole) using F ions. Note that O may not be used as the process gas in the anisotropic etching process. Furthermore, the isotropic etching process is a process of supplying, for example, SF and O as process gases into a chamber where plasma is generated, and etching and removing the Si layer on the exposed substrate (the bottom of a trench or hole) after the protective film has been removed using F radicals. Note that O may not be used as the process gas in the isotropic etching process.

[0027] In these anisotropic etching and isotropic etching processes, Si reacts with F ions and / or F radicals generated from the process gas SF6, producing SiF as a by-product. x(e.g., SiF, SiF2, SiF3, SiF4, etc.) are generated. Note that SiF, SiF2, and SiF3 cannot exist stably. Therefore, it is considered desirable to measure SiF4 when evaluating the state of the process. In addition, in the anisotropic etching process and isotropic etching process, F ions and / or F radicals generated from SF6, which is the process gas, react with the CF-based polymer film, which is the protective film, to generate C. x F y (e.g., CF, CF2, CF3, CF4, etc.) When O2 is used as the process gas, CO x F y (For example, CO, CO2, COF, COF2, etc.) etc. may be produced. Of these reaction products, if a substance exists as a gas and its absorption can be measured (in the above case, CF4, CO, CO2, or COF2), the state of the process can be evaluated.

[0028] Specifically, as shown in FIG. 1, the process evaluation device 100 includes two optical absorption measurement units 2A and 2B that measure reaction products generated in the Bosch process, and a state evaluation unit 3 that evaluates the state of the Bosch process based on the measurement values ​​obtained by the two optical absorption measurement units 2A and 2B.

[0029] Each of the optical absorption measurement units 2A and 2B irradiates a laser beam onto a gas containing reaction products generated in the Bosch process and measures the reaction products based on the absorption of the laser beam. The optical absorption measurement unit 2A (hereinafter also referred to as the first optical absorption measurement unit 2A) of this embodiment measures SiF4, which is a first reaction product generated when silicon is etched, and the laser absorption measurement unit 2B (hereinafter also referred to as the second optical absorption measurement unit 2B) measures CO, which is a second reaction product generated when the protective film is etched.

[0030] 1, these optical absorption measurement units 2A and 2B are incorporated into an exhaust pipe H of a chamber PC where the Bosch process is performed, and are configured to analyze reaction products contained in a gas (hereinafter referred to as a measurement target gas) flowing through the exhaust pipe H. In this embodiment, a turbomolecular pump TMP and a dry pump DP are provided in the exhaust pipe H, and the optical absorption measurement units 2A and 2B are provided between the turbomolecular pump TMP and the dry pump DP, but this is not limiting.

[0031] <Configuration of optical absorption measurement units 2A and 2B> The optical absorption measurement unit 2 continuously measures the concentration of reaction products (here, SiF4, CO) contained in the gas to be measured, and uses, for example, infrared laser absorption modulation (IRLAM (Infrared Laser Absorption Modulation)) (see Patent No. 6886507).

[0032] Specifically, as shown in FIGS. 1 and 2, the optical absorption measuring units 2A and 2B include a measurement cell 21 having a pair of multi-reflection mirrors M1 and M2 sandwiching the gas to be measured, a semiconductor laser 22 that irradiates the measurement cell 21 with laser light and causes the laser light to enter between the pair of multi-reflection mirrors M1 and M2, a photodetector 23 that detects the laser light that is emitted from between the pair of multi-reflection mirrors M1 and M2 and passes through the measurement cell 21, and a signal processing device 24 that calculates the concentration or partial pressure of the reaction product based on the detection signal of the photodetector 23.

[0033] The measurement cell 21 is a so-called Herriott cell that has a pair of multi-reflection mirrors M1 and M2 provided therein and thereby multiple-reflects the laser light. Note that, in addition to the Herriott cell, the measurement cell 21 may be a White cell having multiple multi-reflection mirrors provided on either side of the gas to be measured, or a ring cell having an annular multi-reflection mirror surrounding the gas to be measured.

[0034] The semiconductor laser 22 is a quantum cascade laser. A quantum cascade laser is a semiconductor laser that uses intersubband transitions due to a multi-stage quantum well structure, and oscillates laser light of a specific wavelength in the wavelength range of approximately 4 μm to approximately 20 μm. The semiconductor laser 22 is capable of modulating (changing) the oscillation wavelength by a given current (or voltage). The semiconductor laser 22 of the first laser absorption measurement unit 2A oscillates laser light in the absorption wavelength band of SiF4, and the semiconductor laser 22 of the second laser absorption measurement unit 2B oscillates laser light in the absorption wavelength band of CO.

[0035] Here, the photodetector 23 is a thermal type such as a relatively inexpensive thermopile, but other types, such as quantum photoelectric elements with good responsiveness such as HgCdTe, InGaAs, InAsSb, PbSe, etc., may also be used.

[0036] The signal processing device 24 comprises analog electrical circuits consisting of buffers, amplifiers, etc., digital electrical circuits consisting of a CPU, memory, etc., and AD converters, DA converters, etc. that mediate between these analog and digital electrical circuits.

[0037] 2, the signal processing device 24 functions as a light source control unit 241 that controls the output of the semiconductor laser 22, and a signal processing unit 242 that receives a detection signal from the photodetector 23 and processes the received signal to calculate the concentration, partial pressure, or a value related thereto of the component to be measured. Note that the value related to the concentration or partial pressure includes a value correlated with the concentration or partial pressure, such as absorption intensity.

[0038] Each unit will be described in detail below, taking as an example the case where the signal processing unit 242 calculates the concentration of the component to be measured.

[0039] The light source control unit 241 controls the current source (or voltage source) of the semiconductor laser 22 by outputting a current (or voltage) control signal. Specifically, the light source control unit 241 changes the drive current (or drive voltage) of the semiconductor laser 22 at a predetermined frequency, and modulates the oscillation wavelength of the laser light output from the semiconductor laser 22 at a predetermined frequency with respect to the center wavelength (see FIG. 3). This causes the semiconductor laser 22 to emit modulated light modulated at a predetermined modulation frequency.

[0040] In this embodiment, the light source control unit 241 changes the drive current to a triangular wave shape, and modulates the oscillation frequency to a triangular wave shape (see "Oscillation Wavelength" in FIG. 4). In practice, the drive current is modulated using a different function so that the oscillation frequency becomes a triangular wave shape. Also, as shown in FIG. 3, the oscillation wavelength of the laser light is modulated with the peak of the optical absorption spectrum of the component to be measured as the center wavelength. Alternatively, the light source control unit 241 may change the drive current to a sine wave shape, a sawtooth wave shape, or any other function shape, and modulate the oscillation frequency to a sine wave shape, a sawtooth wave shape, or any other function shape.

[0041] The signal processing unit 242 includes a logarithmic calculation unit 242a, a correlation value calculation unit 242b, a storage unit 242c, a concentration calculation unit 242d, and the like.

[0042] The logarithmic calculation unit 242a performs logarithmic calculation on the light intensity signal, which is the detection signal of the photodetector 23. The function I(t) showing the time-series change of the light intensity signal obtained by the photodetector 23 is shown as "light intensity I(t)" in Fig. 4, and by performing logarithmic calculation, it becomes shown as "logarithmic intensity L(t)" in Fig. 4.

[0043] The correlation value calculation unit 242b calculates correlation values ​​between an intensity-related signal related to the intensity of sample light obtained when measuring the measurement target gas and a plurality of predetermined feature signals. A feature signal is a signal for extracting waveform features of the intensity-related signal by correlating it with the intensity-related signal. The feature signal can be, for example, a sinusoidal signal or any other signal that matches the waveform feature to be extracted from the intensity-related signal. Here, the correlation value calculation unit 62 uses a logarithmically calculated light intensity signal (logarithmic intensity L(t)) as the intensity-related signal.

[0044] Furthermore, the correlation value calculation unit 242b calculates a number of characteristic signals F that is greater than the total number of types of measurement target components (reaction products in this embodiment) and the number of types of interference components. i (t) (i=1, 2, . . . , n), a plurality of sample correlation values ​​S, which are correlation values ​​between the intensity-related signal of the sample light and each of the plurality of feature signals, are calculated by the following equation (1): i where T in Equation 1 is the modulation period.

[0045]

number

[0046] When calculating the sample correlation value, the correlation value calculation unit 242b calculates the sample correlation value by using the intensity-related signal L(t) of the sample light and the plurality of feature signals F as shown in Equation 1. i (t) and the correlation value S i from the reference light intensity related signal L0(t) and multiple feature signals F i (t) is the correlation value with the reference correlation value R i The corrected sample correlation value S i It is desirable to calculate '. This removes the offset contained in the sample correlation value, resulting in a correlation value proportional to the concentrations of the measurement target component and the interfering component, thereby reducing measurement errors. Note that a configuration may be adopted in which the reference correlation value is not subtracted.

[0047] Here, the timing of acquiring the reference light may be simultaneous with the sample light, before or after measurement, or at any other timing. The intensity-related signal or reference correlation value of the reference light may be acquired in advance and stored in the storage unit 242c. In addition, one possible method of simultaneously acquiring the reference light is to provide two photodetectors 23, split the modulated light from the semiconductor laser 22 using a beam splitter or the like, and use one for measuring the sample light and the other for measuring the reference light.

[0048] In this embodiment, the correlation value calculation unit 242b calculates the correlation value based on a plurality of feature signals F i For (t), a function that more easily captures the waveform characteristics of the logarithmic intensity L(t) than a sine function is used. For sample gas containing the target component and one interfering component, two or more feature signals F1(t) and F2(t) may be used. For example, the two feature signals F1(t) and F2(t) may be a function based on a Lorentzian function that approximates the shape of the absorption spectrum, and a differential function of the Lorentzian function. Furthermore, instead of a function based on a Lorentzian function, a function based on a Voigt function or a Gaussian function may also be used as the feature signal. Using such a function as the feature signal can obtain a larger correlation value than when a sine function is used, thereby improving measurement accuracy.

[0049] Here, it is desirable to remove the DC component from the feature signal, i.e., to adjust the offset so that it becomes zero when integrated over the modulation period. This makes it possible to eliminate the effect of an offset on the intensity-related signal due to fluctuations in light intensity. Note that instead of removing the DC component from the feature signal, the DC component may be removed from the intensity-related signal, or the DC components may be removed from both the feature signal and the intensity-related signal. Alternatively, the feature signal may be a sample value of the absorption signal of the measurement target component and / or interference component, or a value simulating either of them.

[0050] By using two feature signals F1(t) and F2(t) as orthogonal function sequences or function sequences close to orthogonal function sequences, the features of the logarithmic intensity L(t) can be extracted more efficiently, and the concentration obtained by the simultaneous equations described later can be more accurately calculated.

[0051] The storage unit 242c stores the intensity-related signals and the plurality of characteristic signals F when the measurement target component and each interference component are present alone. i The individual correlation values, which are the correlation values ​​per unit concentration of the measurement target component and each interfering component, calculated from (t), are stored. i (t) is a plurality of feature signals F used in the correlation value calculation unit 242b. i It is the same as (t).

[0052] Here, when storing the single correlation value, the storage unit 242c desirably subtracts the reference correlation value from the correlation value when the measurement target component and each interference component are present alone, and then stores the corrected single correlation value converted to a value per unit concentration. This removes the offset contained in the single correlation value, resulting in a correlation value proportional to the concentrations of the measurement target component and interference components, thereby reducing measurement errors. Note that a configuration in which the reference correlation value is not subtracted is also possible.

[0053] The concentration calculation section 242d calculates the concentration of the measurement target component using the plurality of sample correlation values ​​obtained by the correlation value calculation section 242b.

[0054] Specifically, concentration calculation unit 242d calculates the concentration of the component to be measured based on the plurality of sample correlation values ​​obtained by correlation value calculation unit 242b and the plurality of single correlation values ​​stored in storage unit 242c. More specifically, concentration calculation unit 242d calculates the concentration of the component to be measured by solving simultaneous equations consisting of the plurality of sample correlation values ​​obtained by correlation value calculation unit 242b, the plurality of single correlation values ​​stored in storage unit 242c, and the concentrations of the component to be measured and each interfering component. Note that Fig. 5 shows a conceptual diagram of concentration or partial pressure calculation using the single correlation values ​​and sample correlation values ​​in concentration calculation unit 242d.

[0055] When the measurement target gas contains one measurement target component (here, SiF4) and one interference component, the concentration calculation unit 242d calculates the sample correlation values ​​S1' and S2' calculated by the correlation value calculation unit 242b and the single correlation value s 1t , s 2t , s 1i , s 2i and the concentration C of the target component and each interfering component tar , C int Solve the following simultaneous equations with two unknowns: 1t is the single correlation value of the measurement target component in the first feature signal, s 2t is the single correlation value of the measured component in the second feature signal, s 1i is the single correlation value of the interference component in the first feature signal, s 2i is the single correlation value of the interference component in the second feature signal.

[0056]

number

[0057] This allows the concentration C of the measurement target component (reaction product) with interference effects removed to be calculated by a simple and reliable calculation of solving the simultaneous equations in the above formula (Equation 2). tar can be determined.

[0058] Even when it is assumed that two or more interfering components are present, the concentration of the component to be measured, with the effects of interference removed, can be determined by adding a single correlation value equal to the number of interfering components and solving a system of equations with the same number of elements as the number of component types.

[0059] <Configuration of state evaluation unit 3> Next, we will explain the state evaluation unit 3 that evaluates the state of the Bosch process based on the measurement values ​​of the optical absorption measurement units 2A and 2B. Here, the measurement values ​​of the optical absorption measurement units 2A and 2B are the concentrations of the reaction products obtained by the signal processing unit 242 or values ​​related to the concentrations.

[0060] The state evaluation unit 3 includes analog electrical circuits such as buffers and amplifiers, digital electrical circuits such as a CPU and memory, and AD converters and DA converters that mediate between these analog and digital electrical circuits. The state evaluation unit 3 evaluates the state of the Bosch process by the CPU and its peripheral devices working together in accordance with a predetermined state evaluation program stored in a predetermined area of ​​the memory. The state evaluation unit 3 also receives information indicating whether the process being performed in the chamber PC is a deposition process, anisotropic etching, or isotropic etching. Here, information about the process being performed in the chamber PC is transmitted from a process control device (not shown) to the reception unit 4, and the received information is then transmitted to the state evaluation unit 3. Furthermore, the results of the state evaluation (determination) by the state evaluation unit 3 or the measured values ​​of the optical absorption measurement units 2A and 2B can be displayed on a display unit 5 such as a display.

[0061] (1) Evaluation of the condition during the deposition process The state evaluation unit 3 can evaluate the state of the Bosch process based on the measured value of SiF4 during the deposition process. Specifically, the state evaluation unit 3 can detect the end point of the Bosch process based on the magnitude of the rise in the measured value of SiF4 during the deposition process.

[0062] As shown in FIG. 6(a), before the end point of the Bosch process, F ions and / or F radicals generated from the process gas CF react with exposed Si to generate SiF. However, as the deposition of the protective film progresses, SiF ceases to be generated. On the other hand, after the end point of the Bosch process, SiO is exposed at the start of the deposition process, making it difficult for SiF to be generated. That is, as the end point of the Bosch process approaches, the rise (peak value) of SiF measured after the start of the deposition process gradually decreases (see FIG. 6(b)). Note that the rise of SiF may not only refer to the peak value of SiF, but also to a measurement value at a predetermined time after the start of the deposition process. Note that the predetermined time is the time from the beginning of the rise of the first peak of the SiF measurement value after the start of the deposition process until the value passes the peak value and stabilizes. Using this characteristic, the state evaluation unit 3 can detect the end point of the Bosch process when the magnitude of the rise (peak value) of the SiF measurement value during the deposition process becomes equal to or less than a first threshold.

[0063] As described above, silicon (Si) is exposed at the start of the deposition process, generating SiF4. However, as the deposition of the protective film progresses, SiF4 ceases to be generated. Using this characteristic, the state evaluation unit 3 can determine that the deposition of the protective film is sufficient when the measured SiF4 value during the deposition process is equal to or less than the second threshold. If the deposition of the protective film is insufficient (i.e., when the measured SiF4 value is greater than the second threshold (see Figure 7(a))), shape abnormalities such as undercuts (groove or hole bottoms bulging) or inverted tapers occur. In this case, the state evaluation unit 3 can propose a recipe that increases the deposition amount in the deposition process, such as by lengthening the deposition time. Figure 7(b) shows the measured SiF4 value when the deposition time in the deposition process is extended.

[0064] (2) Etching process status evaluation The state evaluation unit 3 can evaluate the state of the Bosch process based on the measurement value of SiF4 during the anisotropic etching process or the isotropic etching process. Specifically, the state evaluation unit 3 can detect that the target being etched has switched from the protective film to silicon based on the measurement value of SiF4 during the anisotropic etching process.

[0065] As shown in FIG. 8(a), the protective film is etched at the start of the anisotropic etching process, so no SiF4 is generated. Then, when etching of the protective film is completed, SiF4 is generated. Utilizing this characteristic, the state evaluation unit 3 can determine the etching end point of the protective film as the point at which the measured value of SiF4 during the anisotropic etching process reaches a maximum (see FIG. 8(b)). Alternatively, the state evaluation unit 3 may determine the etching end point of the protective film by determining that the measured value of SiF4 during the anisotropic etching process has reached a third threshold value (e.g., near 150% FS) and then determining that a predetermined time has elapsed.

[0066] The state evaluation unit 3 can also detect the end point of the Bosch process based on the measured value of SiF during the anisotropic etching process or the isotropic etching process. For example, the state evaluation unit 3 can detect the end point of the Bosch process when the measured value of SiF during the anisotropic etching process or the isotropic etching process becomes equal to or less than a fourth threshold. In this case, the state evaluation unit 3 can perform double end point detection in addition to detecting the end point of the Bosch process during the deposition process described above, and can stop the Bosch process at a more optimal end point.

[0067] Furthermore, the state evaluation unit 3 can determine that the protective film is insufficient when the measured value of CO during the isotropic etching process is equal to or less than the threshold value. Note that the CO during the isotropic etching process is derived from carbon (C) contained in the protective film.

[0068] For example, if the measured value of CO is equal to or less than the fifth threshold (see FIG. 9(a)), the state evaluation unit 3 can determine that the deposition of the protective film is insufficient. Note that if the deposition of the protective film is insufficient, the portions where the protective film is not present will be etched, resulting in shape abnormalities such as an inverted tapered shape. Also, if the measured value of CO gradually decreases (see FIG. 9(a)), the state evaluation unit 3 can determine that the area of ​​the protective film is decreasing. Note that if the area of ​​the protective film decreases, the silicon in the portions where the protective film has peeled off will be etched, resulting in shape abnormalities such as undercuts (groove or hole bottoms that bulge). In these cases, the state evaluation unit 3 can propose a recipe that increases the deposition amount in the deposition process, such as by lengthening the deposition time in the deposition process, and / or a recipe that reduces the etching amount of the protective film, such as by shortening the etching time of the protective film (the time of the isotropic etching process). Note that FIG. 9(b) shows the measured values ​​of CO when the deposition process is extended and the etching time of the isotropic etching process is shortened.

[0069] As shown in FIG. 10(a), when the state evaluation unit 3 determines that the deposition of the protective film is insufficient because the measured value of SiF4 during the deposition process is greater than the threshold value, and determines that the deposition of the protective film is insufficient because the measured value of CO during the isotropic etching process is less than the threshold value, the groove formed by etching has an inverse tapered shape. In response to this, the recipes for the deposition process and the isotropic etching process were optimized based on the above-mentioned judgment by the state evaluation unit 3, and the results are shown in Figure 10(b). Here, the deposition time in the deposition process was lengthened and the etching time in the isotropic etching process was shortened. By optimizing the recipes in this way, the grooves formed by etching were dug straight, and the reverse tapered shape was improved.

[0070] <Effects of this embodiment> The process evaluation apparatus 100 of this embodiment configured as described above irradiates a gas containing reaction products generated in the Bosch process with laser light, measures the reaction products, and evaluates the state of the Bosch process based on the measured values ​​of the reaction products, thereby making it possible to appropriately adjust the processing time, processing conditions, etc. in at least one of the deposition step, anisotropic etching step, and isotropic etching step in the Bosch process. As a result, it is possible to form grooves, holes, etc. in a substrate in the Bosch process with a desired shape, thereby improving the performance of devices using the processed substrate.

[0071] <Other embodiments> For example, in the above embodiment, the laser absorption measurement units 2A and 2B are configured to measure both SiF4 and CO as reaction products, but they may also measure either SiF4 or CO as the reaction product. Furthermore, if other reaction products are produced, they may also be measured.

[0072] Although the laser absorption measurement units 2A and 2B in the above embodiment measure the concentration of reaction products or a value related to the concentration, they may also measure the partial pressure of reaction products in the measurement target gas or a value related to the partial pressure. In this case, the output value of the laser absorption measurement units 2A and 2B is the partial pressure of reaction products or a value related to the partial pressure obtained by the signal processing unit 242.

[0073] Furthermore, the Bosch process may be controlled in real time based on the result of the state evaluation (determination) by the state evaluation unit 3. For example, when the state evaluation unit 3 determines that the deposition of the protective film is sufficient during the deposition step, the deposition step may be terminated and the process may proceed to the next anisotropic etching step.

[0074] Furthermore, in the above embodiment, the measurement unit 2 is configured to be incorporated into the exhaust pipe H of the process chamber PC, but it may also be configured to be provided in a bypass pipe branching off from the exhaust pipe H, or in a measurement pipe connected to the process chamber PC separately from the exhaust pipe H. Also, a pair of multi-reflection mirrors M1, M2 may be provided inside the process chamber PC, or may be connected to an enclosing wall such as a side wall or top wall of the process chamber PC.

[0075] Furthermore, the functions of the signal processing device 24 of the laser absorption measuring units 2A and 2B and the state evaluating unit 3 in the above embodiment may be provided in one computer (information processing device).

[0076] Although the light absorption measuring unit in the above embodiment irradiates laser light, it may also irradiate light other than laser light.

[0077] In addition, various modifications and combinations of the embodiments may be made as long as they do not go against the spirit of the present invention. [Explanation of symbols]

[0078] 100 Process evaluation equipment 2A, 2B...Laser absorption measurement section 3. Condition evaluation section PC Chamber H···Exhaust pipe

Claims

1. 1. A process evaluation apparatus for evaluating a process that repeats a deposition step of depositing a protective film on a substrate, an anisotropic etching step of removing a portion of the protective film by anisotropic etching, and an isotropic etching step of removing the substrate exposed by the removal of the protective film by isotropic etching, a light absorption measurement unit that irradiates light onto a gas containing reaction products generated in the process and measures the reaction products based on the absorption of the light; a state evaluation unit that evaluates a state of the process based on the measurement value obtained by the optical absorption measurement unit.

2. The process etches silicon; the optical absorption measurement unit measures a first reaction product produced when silicon is etched, 2. The process evaluation device according to claim 1, wherein the state evaluation unit evaluates the state of the process based on the measurement value of the first reaction product obtained by the light absorption measurement unit.

3. The process evaluation device according to claim 2 , wherein the state evaluation unit evaluates the state of the process based on a measurement value of the first reaction product during the deposition step.

4. 4. The process evaluation device according to claim 2, wherein the state evaluation unit detects an end point of the process based on the magnitude of a rise in the measured value of the first reaction product during the deposition step.

5. 5. The process evaluation device according to claim 2, wherein the state evaluation unit determines that the deposition of the protective film is sufficient when a measured value of the first reaction product during the deposition step is equal to or less than a threshold value.

6. 6. The process evaluation device according to claim 2, wherein the state evaluation unit evaluates the state of the process based on a measurement value of the first reaction product during the anisotropic etching step or the isotropic etching step.

7. 7. The process evaluation device according to claim 6, wherein the state evaluation unit detects that the target being etched has been switched from the protective film to silicon based on the measured value of the first reaction product during the anisotropic etching process.

8. 8. The process evaluation device according to claim 6, wherein the state evaluation unit detects an end point of the process based on a measurement value of the first reaction product during the anisotropic etching step or the isotropic etching step.

9. The optical absorption measurement unit detects SiF as the first reaction product produced by etching silicon. ４ The process evaluation device according to claim 2 , wherein the process evaluation device measures:

10. the light absorption measurement unit measures a second reaction product generated by etching the protective film, 9. The process evaluation device according to claim 1, wherein the state evaluation unit determines that the protective film is insufficient when a measurement value of the second reaction product obtained by the light absorption measurement unit during the isotropic etching step is equal to or less than a threshold value.

11. the protective film is made of a compound containing carbon, The optical absorption measurement unit measures CO, CO as second reaction products generated by etching the protective film. ２ or CF ４ The process evaluation device according to claim 10, wherein the device measures any one of the following:

12. 12. The process evaluation device according to claim 1, wherein the optical absorption measurement unit is provided in an exhaust pipe connected to a chamber in which the process is performed.

13. 13. The process evaluation device according to claim 1, wherein the light absorption measurement unit irradiates the gas with a laser beam and measures the reaction product based on absorption of the laser beam.

14. 1. A process evaluation method for evaluating a process that repeats a deposition step of depositing a protective film on a substrate, an anisotropic etching step of removing a portion of the protective film by anisotropic etching, and an isotropic etching step of removing the substrate exposed by the removal of the protective film by isotropic etching, the method comprising: irradiating a gas containing a reaction product produced in the process with light and measuring the reaction product based on the absorption of the light; and evaluating the state of the process based on the measurement values ​​of the reaction products.

15. 1. A process evaluation program for evaluating a process that repeats a deposition step of depositing a protective film on a substrate, an anisotropic etching step of removing a portion of the protective film by anisotropic etching, and an isotropic etching step of removing the substrate exposed by removing the protective film by isotropic etching, the program comprising: a process evaluation program that causes a computer to function as a state evaluation unit that evaluates the state of the process based on measurement values ​​obtained by an optical absorption measurement unit that irradiates light onto a gas containing reaction products generated in the process and measures the reaction products.

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