JP2011017675A - Film measuring method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a film measuring method that facilitates performing high-throughput and highly-accurate film measurement at low cost.SOLUTION: Film quality information 3A acquired when measuring a film quality by irradiating with light, a sample film A formed on a first substrate is compared with film quality information 3B acquired when measuring the film quality by irradiating with light, a sample film B having the same kind of film material as the sample film A, and formed on a second substrate, and light having a wavelength wherein a difference of each film quality measurement result becomes smaller than a prescribed value is selected as light in a wavelength domain to be used for film thickness measurement. A measuring object film having the same kind of film material as the sample films A, B is irradiated with the light in the selected wavelength domain, thereby measuring the film thickness of the measuring object film.

Description

  The present invention relates to a film measuring method.

  As one of inspection processes when forming a semiconductor device on a substrate, there is a process of measuring the film quality, film thickness, etc. of the material deposited on the substrate by an optical technique. This optical method is roughly classified into two methods. One of the film measurements by an optical method is a method called spectral reflectance measurement. In this method, the film is measured by simply measuring only the reflection intensity from the sample. The other method of film measurement by an optical method is a method called spectroscopic ellipsometry. In this method, light is polarized and the film is measured by strictly capturing the change of light (for example, Non-Patent Document 1). reference).

  Spectroscopic ellipsometry is very excellent in terms of film measurement accuracy, and can be said to be an indispensable technique especially for analysis of film quality and the like. On the other hand, spectral reflectance measurement is simple and inexpensive, but the accuracy of film measurement is inferior to that of spectroscopic ellipsometry, so it is generally used only for simple film measurement. For this reason, spectroscopic ellipsometry is used when highly accurate film measurement is required.

  However, spectroscopic ellipsometry requires that the light be polarized, which complicates the device configuration, resulting in high device costs. In addition, since it is necessary to rotate the polarizer, the film measurement takes a longer time than the spectral reflectance measurement, and the throughput is lowered. Furthermore, since it is necessary to irradiate light irradiating the film obliquely, it is difficult to reduce the spot size of the light irradiating the film.

Nadine BLAYO, PhD Jobin Yvon SA, "Technical Information Magazine" Readout "", 'Refractometry by Spectroscopic Ellipsometry' (Full Automatic Spectroscopic Ellipsometer UT-300 Part 2 Basic Principles of Ellipsometry and PEM), Readout No.21 September 2000, HORIBA Technical Reports

  The present invention has been made in view of the above, and an object of the present invention is to provide a film measurement method capable of easily and inexpensively performing high-throughput and high-accuracy film measurement.

  According to one aspect of the present invention, the first film quality when the first sample film formed on the first substrate is irradiated with light and the film quality is measured, and the first film quality formed on the second substrate and the first film are measured. The second sample film, which is a film material of the same type as that of the first sample film, is irradiated with the light, and the second film quality when the film quality is measured. The wavelength selection step of selecting light as light in the wavelength region used for film thickness measurement, and the light in the wavelength region selected on the measurement target film that is the same type of film material as the first and second sample films A film thickness measuring step of measuring the film thickness of the film to be measured.

  According to the present invention, it is possible to easily perform film measurement with high throughput and high accuracy at low cost.

FIG. 1 is a diagram illustrating the configuration of the spectral reflectance measuring apparatus according to the first embodiment. FIG. 2 is a diagram showing the configuration of spectroscopic ellipsometry. FIG. 3 is a diagram for explaining a film measured by a spectral reflectance measuring device or a spectroscopic ellipsometer. FIG. 4 is a flowchart showing a processing procedure of the film thickness measuring method according to the first embodiment. FIG. 5 is a diagram illustrating a characteristic example of reflected light obtained from the sample film. FIG. 6 is a diagram showing the film quality calculated from the characteristics of the reflected light. FIG. 7 is a diagram for explaining sample film comparison processing. FIG. 8 is a diagram showing a film thickness measurement result when the film thickness of the sample film is measured by a conventional method. FIG. 9 is a diagram illustrating a film thickness measurement result when a sample film is measured by the film thickness measurement method according to the first embodiment. FIG. 10 is a flowchart showing a processing procedure of the film thickness measuring method according to the second embodiment. FIG. 11 is a diagram showing light intensity obtained by spectral reflectance measurement. FIG. 12 is a diagram showing the measurement results of the film thickness measured with the spectral reflectance measuring device. FIG. 13 is a diagram illustrating a calculation result of a refractive index calculated using a known film thickness. FIG. 14 is a diagram showing measurement results of film thickness and refractive index measured by a conventional spectral reflectance measurement method. FIG. 15 is a diagram showing measurement results of film quality measured using only spectroscopic ellipsometry. FIG. 16 is a diagram showing measurement results of film thickness and refractive index measured using only spectroscopic ellipsometry. FIG. 17 is a diagram illustrating a hardware configuration of the information processing apparatus included in the spectral reflectance measurement apparatus according to the first embodiment.

  Hereinafter, a film thickness measuring method according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings. Note that the present invention is not limited to these embodiments.

(First embodiment)
FIG. 1 is a diagram illustrating the configuration of the spectral reflectance measuring apparatus according to the first embodiment. In the present embodiment, the film quality of a film material (sample films A and B described later) to be measured is measured using a spectroscopic ellipsometry 2 described later. The spectral reflectance measuring apparatus 1 is used when measuring the film thickness of a measurement target film (measurement film C) formed on a substrate to be a product using the film quality measured by the spectroscopic ellipsometry 2. The wavelength of light (hereinafter referred to as a product measurement wavelength) is determined. And the spectral reflectance measuring device 1 measures the film thickness of the film C to be measured using the determined wavelength for product measurement. The film quality measured by the spectroscopic ellipsometry 2 is an optical constant, such as a refractive index or an extinction coefficient. The sample films A and B and the film C to be measured are the same type of film material (for example, silicon nitride film). Therefore, the spectral reflectance measuring apparatus 1 measures the film thickness of the same type of film material as the film material whose spectral ellipsometry 2 has measured the film quality.

  The spectral reflectance measuring device 1 includes an optical system 10 and an information processing device 20. The optical system 10 has a function of irradiating the film to be measured C with light and detecting reflected light from the film to be measured C. The film C to be measured is a film laminated (deposited) on a semiconductor substrate such as a wafer.

  The optical system 10 includes a light source 11, a spectroscope 15, and a detector 16. The light source 11 emits light such as white light. White light emitted from the light source 11 is sent to the film to be measured C as incident light 12 and reflected on the film to be measured C. The reflected light 14 reflected by the film to be measured C is sent to the spectrometer 15.

  The spectroscope 15 splits the reflected light 14 and sends it to the detector 16. The detector 16 is a device that detects the spectral light transmitted from the spectroscope 15. The detector 16 sends a detection signal corresponding to the detected spectral light to the information processing apparatus 20.

  The information processing apparatus 20 is an apparatus such as a computer that calculates the film thickness and film quality of the film C to be measured using the detection signal from the detector 16. The information processing apparatus 20 includes a control unit 21, a storage unit 22, a calculation unit 23, an input unit 24, and an output unit 25.

  The input unit 24 includes information on the film quality of the sample films A and B (sample film information) measured by the spectroscopic ellipsometry 2 and information on the type of film measured by the spectral reflectance measuring device 1 (the film material of the film C to be measured). The information to be designated) is input and sent to the calculation unit 23. The storage unit 22 is a memory that stores a detection signal from the detector 16 and a calculation result of the calculation unit 23 (film thickness of the film C to be measured).

  The control unit 21 controls the light source 11 and the calculation unit 23. The control unit 21 stores a film thickness measurement recipe used for film thickness measurement. The calculation unit 23 calculates the film thickness of the film C to be measured using the sample film information sent from the input unit 24, the detection signal stored in the storage unit 22, and the film thickness measurement recipe stored in the control unit 21. calculate. The output unit 25 outputs the film thickness of the film C to be measured calculated by the calculation unit 23 as a film thickness measurement result.

  Next, the configuration of the spectroscopic ellipsometry 2 for measuring the film quality of the sample films A and B will be described. FIG. 2 is a diagram showing the configuration of spectroscopic ellipsometry. The spectroscopic ellipsometry 2 includes an optical system 40 and an information processing device 50. The optical system 40 has a function of irradiating the sample films A and B with light and detecting reflected light from the sample films A and B. The sample films A and B are films formed on a semiconductor substrate such as a wafer.

  The optical system 40 includes a light source 41, a polarizer 42, an analyzer 45, and a detector 46. The light source 41 emits light such as white light. The polarizer 42 polarizes white light emitted from the light source 41 in, for example, two orthogonal directions, and aligns the amplitude and wavelength. Light exiting the polarizer 42 is sent as incident light 43 to the sample film A or sample film B at an incident angle θ, and is reflected on the sample films A and B. The reflected light 44 reflected by the sample films A and B is sent to the analyzer 45.

  The analyzer 45 extracts vibration components corresponding to the arrangement direction of the analyzer 45 from light polarized in two orthogonal directions and reflected by the sample films A and B, and sends the vibration component to the detector 46. The detector 46 is a device that detects a vibration component of light transmitted from the analyzer 45. The detector 46 sends a detection signal corresponding to the detected vibration component to the information processing apparatus 50.

  The information processing apparatus 50 is an apparatus such as a computer that calculates the film quality of the sample films A and B using the detection signal from the detector 46. The information processing apparatus 50 includes a control unit 51, a storage unit 52, a calculation unit 53, an input unit 54, and an output unit 55.

  The input unit 54 inputs information on the type of film measured by the spectroscopic ellipsometry 2 (information specifying the film material of the sample films A and B) and the like, and sends the information to the calculation unit 53. The storage unit 52 is a memory that stores a detection signal from the detector 46, a calculation result of the calculation unit 53 (film quality of the sample films A and B), and the like.

  The control unit 51 controls the light source 41 and the calculation unit 53. The control unit 51 stores a film quality measurement recipe used for film quality measurement. The calculation unit 53 uses the information specifying the film materials of the sample films A and B sent from the input unit 54, the detection signal stored in the storage unit 52, and the film quality measurement recipe stored in the control unit 51, The film quality of the sample films A and B is calculated. The output unit 55 outputs the film quality of the sample films A and B calculated by the calculation unit 53 as a film quality measurement result.

  Here, films (sample films A and B and film to be measured C) measured by the spectral reflectance measuring apparatus 1 and the spectral ellipsometry 2 will be described. FIG. 3 is a diagram for explaining a film measured by a spectral reflectance measuring device or a spectroscopic ellipsometer. In FIG. 3, the cross-sectional structure of the film | membrane measured by the spectral reflectance measuring device 1 or the spectroscopic ellipsometry 2 is shown. The films measured by the spectral reflectance measuring device 1 and the spectral ellipsometry 2 are sample films A and B and a film C to be measured, for example, a film formed on the silicon 31 (shown as a measurement film 32 in FIG. 3). is there. For example, the sample film A is formed on the first substrate, the sample film B is formed on the second substrate, and the measured film C is formed on the product substrate (third substrate). .

  The sample films A and B and the measured film C are formed of the same film material such as a silicon nitride film (SiN). The sample film A is, for example, a film manufactured with an allowable upper limit value of the process conditions, and the sample film B is, for example, a film manufactured with an allowable lower limit value of the process conditions. Thereby, the film thickness of the film C to be measured is measured using the film quality (sample film information) of the film formed from the allowable upper limit value to the allowable lower limit value of the process conditions. In this embodiment, the case where there are two types of sample films A and B used for measuring the film quality will be described. However, three or more types of sample films may be used. The sample films A and B are not limited to being formed under different process conditions, and may be formed with different apparatuses.

  Next, a processing procedure of the film thickness measurement method according to the first embodiment will be described. FIG. 4 is a flowchart showing a processing procedure of the film thickness measuring method according to the first embodiment. First, the film quality of the sample films A and B is measured by spectroscopic ellipsometry 2. Specifically, first, the sample films A and B are set in the spectroscopic ellipsometry 2, and the characteristics of the reflected light 44 from the sample films A and B are measured.

  FIG. 5 is a diagram illustrating a characteristic example of reflected light obtained from the sample film. When the sample films A and B are irradiated with the incident light 43, a detection signal corresponding to the reflected light 44 is sent to the information processing apparatus 50. This detection signal is converted into information indicating the characteristic of the reflected light 44 by the calculation unit 53. FIG. 5A shows the correspondence (characteristic information 101) between the wavelength of the incident light 43 and information (intensity ratio information) indicating the intensity ratio of the reflected light 44 orthogonal to each other. FIG. 5B shows a correspondence relationship (characteristic information 102) between the wavelength of the incident light 43 and the phase difference of the orthogonal light of the reflected light 44.

  In the characteristic information 101 shown in FIG. 5A, the horizontal axis is the wavelength of the incident light 43, and the vertical axis is intensity ratio information. In the characteristic information 102 shown in FIG. 5B, the horizontal axis represents the wavelength of the incident light 43, and the vertical axis represents the phase difference. The intensity ratio information of the characteristic information 101 and the phase difference of the characteristic information 102 standardize how the incident light 43 after being polarized changes before and after the sample films A and B are irradiated.

  The calculation unit 53 analyzes the waveform of the characteristic information 101 and the waveform of the characteristic information 102 shown in FIG. 5, and calculates the film quality of the sample films A and B. FIG. 6 is a diagram showing the film quality calculated from the characteristics of the reflected light. The calculation unit 53 uses, for example, a harmonic oscillator as a model for defining the film quality of the sample films A and B. The calculation unit 53 may use a model other than the harmonic oscillator as a model for defining the film quality of the sample films A and B. As described above, the calculation unit 53 analyzes the characteristics of the sample films A and B using the harmonic oscillator, and calculates (defines) the film quality of the sample films A and B.

  FIG. 6A shows a correspondence relationship (refractive index information 201) between the wavelength of the incident light 43 and the refractive index. FIG. 6B shows the correspondence (refractive index information 201) between the wavelength of the incident light 43 and the extinction coefficient. In this embodiment, the case where the film quality is the refractive index and the extinction coefficient will be described. However, the film quality may be defined only by the refractive index, or may be defined using elements other than the refractive index and the extinction coefficient. May be.

  In the refractive index information 201 shown in FIG. 6A, the horizontal axis is the wavelength of the incident light 43, and the vertical axis is the refractive index. In the extinction coefficient information 202 shown in FIG. 6B, the horizontal axis is the wavelength of the incident light 43, and the vertical axis is the extinction coefficient. The calculation unit 53 calculates the refractive index information 201 and the extinction coefficient information 202 by linking to the film quality measurement recipe in the control unit 51 using the waveform of the characteristic information 101 and the characteristic information 102. The calculation unit 53 calculates the refractive index information 201 and the extinction coefficient information 202 for each of the sample films A and B as the film quality of the sample films A and B (step S10).

  In this embodiment, by comparing the calculated film quality of the sample film A and the film quality of the sample film B, the wavelength for product measurement used when measuring the film thickness of the film C to be measured is calculated. The product measurement wavelength may be calculated by any one of the spectroscopic ellipsometry 2, the spectroscopic reflectance measuring device 1, and other devices. In the present embodiment, a case where the spectral reflectance measurement apparatus 1 calculates a product measurement wavelength will be described. The refractive index information 201 and extinction coefficient information 202 for each of the sample films A and B calculated by the calculation unit 53 are output from the output unit 55 and input to the input unit 24 of the spectral reflectance measurement apparatus 1.

  Refractive index information 201 and extinction coefficient information 202 for each of the sample films A and B are stored in the storage unit 22. The calculation unit 23 compares the film quality of the sample film A with the film quality of the sample film B. FIG. 7 is a diagram for explaining sample film comparison processing. In FIG. 7A, the film quality of the sample film A is indicated by film quality information 3A, and in FIG. 7B, the film quality of the sample film B is indicated by film quality information 3B. Further, in FIG. 7C, the comparison result (waveform superposition) of the sample films A and B is indicated by comparison information 3X.

  The film quality information 3A includes refractive index information 301A and extinction coefficient information 302A of the sample film A. The film quality information 3B includes refractive index information 301B and extinction coefficient information 302B of the sample film B. The comparison information 3X includes refractive index comparison information 301X indicating a comparison result between the refractive index information 301A and the refractive index information 301B, and an extinction coefficient comparison indicating a comparison result between the extinction coefficient information 302A and the extinction coefficient information 302B. Information 302X.

  Similar to the refractive index information 201, the refractive index information 301A and 301B is information indicating the correspondence between the wavelength of the incident light 43 and the refractive index, the horizontal axis is the wavelength of the incident light 43, and the vertical axis is the refractive index. . Similarly to the extinction coefficient information 202, the extinction coefficient information 302A and 302B is information indicating the correspondence between the wavelength of the incident light 43 and the extinction coefficient. The horizontal axis is the wavelength of the incident light 43 and the vertical axis is the extinction coefficient. Decay coefficient.

  The calculation unit 53 calculates the refractive index comparison information 301X using the refractive index information 301A and the refractive index information 301B as a comparison process of the refractive indexes of the sample film A and the sample film B (step S20). Further, the calculation unit 53 calculates the extinction coefficient comparison information 302X using the extinction coefficient information 302A and the extinction coefficient information 302B as a comparison process of the extinction coefficients of the sample film A and the sample film B (step S30). .

  As shown in the refractive index comparison information 301X, when the waveform of the refractive index information 301A and the waveform of the refractive index information 301B are overlapped, there is a portion (cross point P1 or the like) that shows the same refractive index at the same wavelength. Further, as shown in the extinction coefficient comparison information 302X, when the waveform of the extinction coefficient information 302A and the waveform of the extinction coefficient information 302B are overlapped, a portion that shows the same extinction coefficient at the same wavelength (cross point P2 or the like) )

  When the film quality of the sample films A and B is measured in a wavelength band showing substantially the same refractive index at substantially the same wavelength and showing substantially the same extinction coefficient at the substantially same wavelength, the sample film This means that there is no optical difference between the film quality of A and B. Therefore, if the film thickness of the film C to be measured is measured using the optical constant in this wavelength band, the film thickness of the film C to be measured can be accurately measured without being affected by the change in film quality.

  In the present embodiment, a product having a wavelength that exhibits substantially the same refractive index at approximately the same wavelength and that exhibits approximately the same extinction coefficient at approximately the same wavelength is a measurement wavelength of the film C to be measured. It is determined as a wavelength for measurement. In other words, the measurement wavelength in the refractive index comparison information 301X is a measurement wavelength in which the difference between the refractive index when the sample film A is measured and the refractive index when the sample film B is measured is smaller than a predetermined value. And the measurement wavelength in which the difference between the extinction coefficient when measuring the sample film A and the extinction coefficient when measuring the sample film B out of the measurement wavelengths in the extinction coefficient comparison information 302X becomes smaller than a predetermined value. Is the wavelength for product measurement.

  Thereby, the calculation part 53 determines the wavelength (wavelength area | region) close | similar to both the cross point P1 and the cross point P2 to a product measurement wavelength (step S40). For example, when the measurement target film C is a silicon nitride film, the calculation unit 53 determines the product measurement wavelength to be 500 nm to 600 nm. In addition, the calculation part 53 is good also considering the wavelength for product measurement as a wavelength range containing 500 nm-600 nm.

  Thereafter, the film quality of the sample films A and B and the film quality of the silicon 31 are input to the spectral reflectance measuring apparatus 1. The spectral reflectance measuring apparatus 1 measures the film thickness of the film C to be measured using the product measurement wavelength (wavelength region for film thickness measurement), the film quality of the sample films A and B, and the film quality of the silicon 31 (step S50). The film quality of the sample films A and B and the film quality of the silicon 31 may be values measured by the spectroscopic ellipsometry 2, or may be literature values.

  Next, the film thickness measurement results when the film thicknesses of the sample films A and B are measured using the light of the product measurement wavelength determined by the calculation unit 53, and the film thicknesses of the sample films A and B by the conventional method are obtained. The difference from the film thickness measurement result when measured is described. FIG. 8 is a diagram showing a film thickness measurement result when the film thickness of the sample film is measured by a conventional method, and FIG. 9 shows the sample film measured by the film thickness measurement method according to the first embodiment. It is a figure which shows the film thickness measurement result in a case. 8 and 9 show the film thickness measurement results when the sample films A and B are silicon nitride films.

  First, sample films A and B are formed on a wafer, and cross sections of the formed sample films A and B are observed with a scanning electron microscope (SEM) or the like. For example, the wafer cross sections of the sample films A and B are observed at four points in the plane, and the film thicknesses of the sample films A and B are measured. Further, as the film thickness measurement by the conventional method, the sample films A and B are measured at various wavelengths using the spectral reflectance measuring apparatus 1 at four locations on the wafer surface. Further, as a film thickness measuring method according to the first embodiment, sample films A and B are measured at four locations on the wafer surface at the product measurement wavelength (520 nm to 525 nm) using the spectral reflectance measuring apparatus 1. To do.

  As shown in FIG. 8, when the film thicknesses of the sample films A and B are measured by the conventional method, the film thickness obtained from the cross-sectional observation and the film thickness measured using the spectral reflectance measuring apparatus 1 There is a large difference in thickness difference (Δ) between sample film A and sample film B. Specifically, in the sample film B, Δ is about 10 A, and this value is about 3% of the film thickness. For example, as shown in FIG. 7C, such a variation in film thickness is caused by a change in the film quality measured by the wavelength for measuring the film thickness between the sample film A and the sample film B. is there. In other words, depending on the wavelength at which the film thickness is measured, different film qualities are measured for the sample film A and the sample film B. This difference in film quality is presumed to be due to the stability of the process.

  On the other hand, when the film thicknesses of the sample films A and B are measured by the film thickness measuring method according to the first embodiment, the film thickness obtained from the cross-sectional observation and the film thickness measured using the spectral reflectance measuring apparatus 1 The difference in film thickness (Δ) between the sample film A and the sample film B is only a small difference. Specifically, when the film thicknesses of the sample films A and B are measured by the film thickness measurement method according to the first embodiment, Δ is 1% or less of the film thickness at all measurement points of the sample films A and B. It has become. Thus, the difference between the film thickness obtained by measuring the sample films A and B by the film thickness measuring method according to the first embodiment and the actual film thickness obtained from the cross-sectional observation is small. It was confirmed that the measurement was performed correctly.

  In this way, in order to realize highly accurate film thickness measurement even with a simple spectral reflectance measurement method, the relationship between the film quality and the wavelength of light should be examined in advance, and the wavelength region for film thickness measurement should be selected appropriately. The film thickness is measured with high accuracy. That is, paying attention to the film quality of the film C to be measured, the film thickness measurement is performed by selecting a wavelength region with little optical change when the film quality is measured. Thereby, even if it is an inexpensive spectral reflectance measuring apparatus 1, it becomes possible to implement | achieve highly accurate film thickness measurement, without receiving to the influence of a film quality change.

  The film thickness value of the film C to be measured measured by the film thickness measuring method according to the first embodiment is compared with a film thickness allowable value set in advance. If the film thickness value of the film to be measured C is within the allowable film thickness range, the wafer on which the film to be measured C is formed is processed in the next step. Thus, a semiconductor device (semiconductor integrated circuit) such as a semiconductor device is manufactured using the film C to be measured. Specifically, the exposure apparatus performs wafer exposure processing, and then performs wafer development processing and etching processing. In other words, the mask material is processed with the resist pattern formed by transfer in the lithography process, and the film to be processed (measurement film C or the like) is patterned by etching using the patterned mask material. When manufacturing a semiconductor device, the film forming process of the film to be measured C, the film thickness measuring process of the film to be measured C, the exposure process, the developing process, the etching process, and the like are repeated for each layer.

  In this embodiment, the film quality of the sample films A and B is measured by the spectroscopic ellipsometry 2, but the film quality of the sample films A and B may be measured by an apparatus other than the spectroscopic ellipsometry 2. Further, the film thickness of the film C to be measured may be measured by an apparatus other than the spectral reflectance measuring apparatus 1. Further, the film to be measured by the product measurement wavelength is not limited to the film C to be measured, and any film may be measured as long as it is the same type of film material as the sample films A and B. Moreover, although the product measurement wavelength was calculated using the film quality of the sample films A and B measured by the spectroscopic ellipsometry 2, the product measurement wavelength was calculated using the literature values as the film quality of the sample films A and B. Good.

  As described above, according to the first embodiment, when film quality measurement is performed on the sample films A and B, the wavelength for product measurement that is unlikely to cause a difference in the film quality measurement results between the sample films A and B is selected. Since the film thickness of the film to be measured C is measured at this product measurement wavelength, the film thickness of the film to be measured C can be measured with high accuracy using the spectral reflectance measuring apparatus 1. Moreover, since the film thickness of the film C to be measured can be measured using the spectral reflectance measuring apparatus 1, high-throughput film thickness measurement can be easily performed at low cost.

  In addition, when the film C to be measured is a silicon nitride film, the film thickness of the film C to be measured is measured at a product measurement wavelength of 500 nm to 600 nm, so that the film thickness of the film C to be measured can be accurately measured. It becomes.

  Further, since the film qualities of the sample films A and B are measured using the spectroscopic ellipsometry 2, the film qualities of the sample films A and B can be accurately measured. Therefore, it is possible to accurately determine the product measurement wavelength capable of accurately measuring the film thickness of the film C to be measured.

(Second Embodiment)
Next, a second embodiment of the present invention will be described with reference to FIGS. In the second embodiment, the spectral reflectance measuring device 1 calculates the film quality of the film C to be measured using the film thickness calculated in the first embodiment.

  FIG. 10 is a flowchart showing a processing procedure of the film thickness measuring method according to the second embodiment. Also in the present embodiment, as in the first embodiment, the film quality (sample film information) of the sample films A and B made of the same material as the film to be measured C is input into the spectral reflectance measurement apparatus 1. Keep it. Note that the film quality of the sample films A and B input into the spectral reflectance measuring apparatus 1 is provisional, and eventually the film quality itself changes as a parameter. This is a significant difference from the case where only the film thickness is measured. In the present embodiment, high-accuracy film thickness measurement and high-accuracy film quality measurement are simultaneously performed using an inexpensive spectral reflectance measurement apparatus 1.

  First, the film thickness of the film C to be measured is measured by the same method as the film thickness measurement method of the first embodiment. Specifically, the spectroscopic ellipsometry 2 calculates the film quality of the sample films A and B, and determines the product measurement wavelength using the film quality. Then, the spectral reflectance measuring device 1 measures the film thickness of the film C to be measured at the product measurement wavelength (step S110). For example, in the present embodiment, the wavelength band of 545 nm to 555 nm is selected and the film thickness of the film C to be measured is measured. Specifically, the film C to be measured is irradiated with light having a wavelength of 545 nm to 555 nm, and information of reflected signals (light intensity ratio) shown in FIG. 11 is acquired.

  FIG. 11 is a diagram showing light intensity obtained by spectral reflectance measurement. In FIG. 11, the horizontal axis indicates the measurement wavelength, and the vertical axis indicates the light intensity ratio between the sample films A and B and the reference sample. The reference sample is, for example, bare silicon set in the spectral reflectance measuring device 1. When measuring the sample films A and B, the light intensity of the reference sample is measured, and the intensity ratio between the sample films A and B and the reference sample is measured based on the light intensity of the reference sample. As shown in FIG. 11, information obtained by spectral reflectance measurement is a correspondence relationship between the measurement wavelength and the light intensity ratio (hereinafter referred to as an intensity ratio waveform). The calculation unit 23 fits the intensity ratio waveform of the film C to be measured measured in the wavelength band of 545 nm to 555 nm with another intensity ratio waveform generated by simulation. Specifically, the intensity ratio waveform in the wavelength band of 545 nm to 555 nm is predicted by simulation using the film quality when measured in the wavelength band of 545 nm to 555 nm. Thereby, various intensity ratio waveforms are associated with film thicknesses. And the intensity ratio waveform which has a waveform substantially the same as the intensity ratio waveform measured using the to-be-measured film C is extracted from the intensity ratio waveforms predicted by simulation for various film thicknesses. The film thickness corresponding to the extracted intensity ratio waveform is the film thickness of the film C to be measured.

  Then, the spectral reflectance measurement apparatus 1 calculates the film quality of the film C to be measured using the measured film thickness (step S120). FIG. 12 is a diagram showing the measurement results of the film thickness measured with the spectral reflectance measuring device. FIG. 12 shows the measurement results when only the film thickness is measured at the selected product measurement wavelength. The horizontal axis of FIG. 12 is the film thickness measurement point in the wafer surface of the film C to be measured, and the vertical axis is the film thickness measurement result of the film C to be measured. This film thickness measurement result (waveform of film thickness T1) shows a stable value at each film thickness measurement point compared to a conventional film thickness measurement result (measurement result by a conventional spectral reflectance measurement method) described later. Yes.

  Next, the calculation unit 23 of the spectral reflectance measurement apparatus 1 sets the measured film thickness to a known value, and uses this film thickness value to determine the entire wavelength band of the film C to be measured (in the present embodiment). The film quality (optical constant such as refractive index) at 200 nm to 840 nm) is calculated (defined). FIG. 13 is a diagram illustrating a calculation result of a refractive index calculated using a known film thickness. FIG. 13 shows the refractive index when the film quality of the film C to be measured is measured (calculated) at a product measurement wavelength of 633 nm. The horizontal axis of FIG. 13 is a film quality measurement point in the wafer surface of the film C to be measured, and the vertical axis is a refractive index calculation result of the film C to be measured. This film quality measurement result (the waveform of the film quality N1) shows a stable value at each film quality measurement point as in the film quality measurement result using only the spectroscopic ellipsometry 2 described later.

  As described above, in the present embodiment, as in the first embodiment, the film thickness of the film C to be measured using the wavelength band in which the film quality measurement result does not change or changes little depending on the film quality of the sample films A and B. Measure the thickness. Then, using this film thickness, the film quality when the film quality is measured at various wavelengths is calculated. As described above, when measuring the film thickness and film quality of the film C to be measured, the measurement is performed in two stages of film thickness measurement and film quality measurement. Highly accurate film thickness and film quality can be measured.

  Here, the measurement result of the film thickness and the film quality by the conventional spectral reflectance measurement method and the film quality measurement result in the case where only the spectral ellipsometry 2 is used as in the prior art will be described. FIG. 14 is a diagram showing measurement results of film thickness and refractive index measured by a conventional spectral reflectance measurement method. In the conventional spectral reflectance measurement method, for example, the spectral reflectance measurement apparatus 1 measures the film thickness and film quality of the film C to be measured at the same time. The horizontal axis in FIG. 14 is the film thickness measurement point in the wafer surface of the film C to be measured. The vertical axis on the left is the film thickness measurement result of the film C to be measured, and the vertical axis on the right is the film quality measurement result of the film C to be measured. The film thickness measurement result (waveform of the film thickness T2) has a large variation compared to the film thickness measured by the film thickness measurement method of the present embodiment shown in FIG. Further, the film quality measurement result (the waveform of the film quality N2) has a large variation compared to the film quality calculated by the film quality measurement method of the present embodiment shown in FIG.

  As described above, when the film thickness and the film quality are measured by the conventional method, the measurement result varies. In the case of the spectral reflectance measurement, the intensity ratio of the light applied to the sample films A and B (obtained from the reference sample). This is because only the value (compared to the intensity) is detected.

  FIG. 15 is a diagram showing measurement results of film quality measured using only spectroscopic ellipsometry. In FIG. 15A, the horizontal axis represents the measurement wavelength, and the vertical axis represents the refractive index. In FIG. 15B, the horizontal axis indicates the measurement wavelength, and the vertical axis indicates the extinction coefficient. As shown in FIG. 15, the information obtained by the measurement using the spectroscopic ellipsometry 2 is two, that is, the correspondence relationship between the measurement wavelength and the refractive index, and the correspondence relationship between the measurement wavelength and the extinction coefficient. These two correspondences can be obtained by analyzing the characteristic information 101 and 102 of FIG. 5 measured by the spectroscopic ellipsometry 2. As described above, the information obtained by the spectral reflectance measurement is the one graph shown in FIG. 14, whereas the information obtained by the measurement using the spectral ellipsometry 2 is shown in FIG. 5 (FIG. 15). These are two graphs. Therefore, the information amount obtained by the spectral reflectance measurement and the information amount obtained by the measurement using the spectroscopic ellipsometry 2 have a double information amount difference, and this information amount difference appears as a difference in measurement accuracy.

  When measuring the film thickness and film quality of the film C to be measured using only the spectroscopic ellipsometry 2, the film quality shown in FIG. 15 is input to the storage unit 52, and the film thickness is measured in the control unit 51. The film thickness measurement and the film quality measurement are executed by linking with the film quality measurement recipe. At that time, in addition to the film thickness, a function defining the film quality is also added to the parameter (measurement target). Thus, if the film thickness and film quality of the to-be-measured film C are measured, the measurement result shown in FIG. 16 can be obtained.

  In the present embodiment, by using the film thickness of the film to be measured C measured at the product measurement wavelength, the film quality in the entire wavelength band of the film to be measured C is calculated, so that the spectroscopic ellipsometry 2 shown in FIG. Measurement results similar to the film quality measurement results can be obtained.

  FIG. 16 is a diagram showing measurement results of film thickness and refractive index measured using only spectroscopic ellipsometry. In FIG. 16, the value of the refractive index measured at a wavelength of 633 nm as the film quality is shown as a representative value of the film quality. In addition, the refractive index measured using another wavelength can also be calculated and displayed.

  In the measurement of film thickness and film quality using the spectroscopic ellipsometry 2, for example, the spectroscopic ellipsometry 2 simultaneously measures the film thickness and film quality of the film C to be measured. The horizontal axis in FIG. 16 is a film thickness measurement point within the wafer surface of the film C to be measured. The left vertical axis is the film thickness measurement result of the film C to be measured, and the right vertical axis is the film quality measurement result (refractive index) of the film C to be measured. The film thickness measurement result (waveform of the film thickness T3) shows a stable value at each film thickness measurement point in substantially the same manner as the film thickness measured by the film thickness measurement method of the present embodiment shown in FIG. Further, the refractive index (waveform of the film quality N3) shows a stable value at each film quality measurement point in substantially the same manner as the refractive index calculated by the film quality measurement method of the present embodiment shown in FIG.

  In other words, the film thickness measured by the film thickness measurement method of the present embodiment can be measured as a stable value at each film thickness measurement point, similarly to the film thickness measured using only the spectroscopic ellipsometry 2. . In addition, the film quality measured by the film quality measurement method of the present embodiment can be measured as a stable value at each film quality measurement point, similar to the film quality measured using only the spectroscopic ellipsometry 2. As described above, in the present embodiment, since the film thickness and film quality of the film C to be measured are measured using the spectral reflection measurement apparatus 1, simultaneous measurement of the film thickness and film quality can be accurately performed with a simple configuration apparatus. . Therefore, the apparatus cost can be greatly reduced.

  After obtaining the film thickness measurement results and film quality measurement results as shown in FIG. 12, FIG. 13 and FIG. 15, the film thickness measurement results and film quality measurement results are compared with the measurement results obtained so far. Film thickness determination and film quality determination are performed. For example, the film thickness determination and the film quality determination of the film C to be measured are performed based on the measurement results shown in FIGS. 12 and 13 and whether or not the variation in the measurement results is a value within an allowable range. Further, the waveform of the film C to be measured as shown in FIG. 15 is compared with the waveforms obtained so far, and it is determined whether or not the film quality of the film C to be measured has a desired film quality. If the film thickness or film quality of the film to be measured C is within an allowable range, the wafer on which the film to be measured C is formed is processed in the next step. Thereby, a semiconductor device such as a semiconductor device is manufactured using the film C to be measured.

  FIG. 17 is a diagram illustrating a hardware configuration of the information processing apparatus included in the spectral reflectance measurement apparatus according to the first embodiment. The information processing apparatus 20 calculates the product measurement wavelength used to measure the film thickness of the film C to be measured, and uses the film thickness of the film C to be measured measured using the product measurement wavelength. And a CPU (Central Processing Unit) 91, a ROM (Read Only Memory) 92, a RAM (Random Access Memory) 93, a display unit 94, and an input unit 95. In the information processing apparatus 20, the CPU 91, the ROM 92, the RAM 93, the display unit 94, and the input unit 95 are connected via a bus line.

  The CPU 91 calculates the product measurement wavelength used for the film thickness measurement of the film C to be measured using the measurement wavelength calculation program 97A which is a computer program for determining the product measurement wavelength. Further, the CPU 91 calculates the film quality of the film C to be measured using the film quality calculation program 97B, which is a computer program, and the film thickness measurement result of the film C to be measured.

  The display unit 94 is a display device such as a liquid crystal monitor. Based on an instruction from the CPU 91, the film quality measurement results of the sample films A and B, the comparison results of the sample films A and B, the product measurement wavelength (measurement wavelength Calculation result), the film thickness measurement result of the film C to be measured, the film quality measurement result of the film C to be measured, and the like are displayed. The input unit 95 includes a mouse and a keyboard, and receives instruction information (parameters necessary for calculating the product measurement wavelength, parameters necessary for calculating the film quality of the film C to be measured, etc.) externally input from the user. input. The instruction information input to the input unit 95 is sent to the CPU 91.

  The measurement wavelength calculation program 97A and the film quality calculation program 97B are stored in the ROM 92 and loaded into the RAM 93 via the bus line. The CPU 91 executes a measurement wavelength calculation program 97A and a film quality calculation program 97B loaded in the RAM 93. Specifically, in the information processing apparatus 20, the CPU 91 reads the measurement wavelength calculation program 97 </ b> A and the film quality calculation program 97 </ b> B from the ROM 92 and expands them in the program storage area in the RAM 93 in accordance with an instruction input from the input unit 95 by the user. Various processes. The CPU 91 temporarily stores various data generated during the various processes in a data storage area formed in the RAM 93.

  Thus, according to the second embodiment, the film thickness of the film to be measured C is measured at the product measurement wavelength, and the film quality of the film to be measured C is calculated using the film thickness that is the measurement result. It becomes possible to measure the film quality of the film C to be measured with high accuracy. In addition, since the film thickness of the film C to be measured can be measured using the spectral reflectance measuring apparatus 1, high-throughput film quality measurement can be easily performed at low cost.

  Further, when the film C to be measured is a silicon nitride film, the film thickness of the film to be measured C is measured at a product measurement wavelength of 500 nm to 600 nm, and the film quality is measured. Is possible.

  DESCRIPTION OF SYMBOLS 1 Spectral reflectance measuring device, 2 Spectral ellipsometry, 3A, 3B Film quality information, 3X comparison information, 20 Information processing apparatus, 23 Calculation part, 32 Measurement film, A, B Sample film, C Film to be measured

Claims (5)

A first film quality when the first sample film formed on the first substrate is irradiated with light to measure the film quality, and a film of the same type as the first sample film formed on the second substrate The wavelength used for the film thickness measurement is the light having a wavelength at which the difference between the film quality measurement results is smaller than a predetermined value when the film quality is measured by irradiating the light to the second sample film as a material. A wavelength selection step to select as the region light;
A film thickness measurement step of measuring the film thickness of the measurement target film by irradiating the measurement target film, which is the same type of film material as the first and second sample films, with light of the selected wavelength region; ,
A film measurement method comprising:   The film measurement method according to claim 1, wherein the film quality of the measurement target film in a wavelength region other than the selected wavelength region is calculated using the measured film thickness of the measurement target film.   The film material of the first sample film, the second sample film, and the measurement target film is a silicon nitride film, and the wavelength region to be selected is 500 nm to 600 nm. 2. The film measuring method according to 2.   The film thickness of the measurement target film is measured by a spectral reflectance measurement device, and the film quality of the measurement target film is calculated by a spectral reflectance measurement device. Membrane measurement method.   The first film quality of the first sample film and the second film quality of the second sample film are measured by a spectral reflectance measuring device, respectively. The film | membrane measuring method of description.

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