Semiconductor device manufacturing method

Abstract

This semiconductor device manufacturing method comprises: a first step for acquiring the thickness distribution of a first layer formed on a front surface of a wafer; a second step for forming a second layer by performing prescribed processing on the first layer; a third step for irradiating the wafer with light in a planar manner after the second step, imaging the light from the wafer, and deriving the distribution of a measurement parameter in the plane of the wafer on the basis of a signal related to the imaging; and a fourth step for deriving the thickness distribution of the second layer on the basis of the thickness distribution of the first layer acquired in the first step and the distribution of the measurement parameter derived in the third step.

Description

Semiconductor device manufacturing method

[0001] One aspect of the present disclosure relates to a semiconductor device manufacturing method and a measurement apparatus.

[0002] Patent Document 1 discloses a technology in which a dichroic mirror whose transmittance and reflectance change depending on the wavelength is used to separate light from an object, and the wavelength centroid is determined by capturing an image of each of the separated light beams, and the film thickness of a semiconductor device is estimated based on the wavelength centroid.

[0003] International Publication No. 2021 / 161986

[0004] In recent years, with the increasing integration density of semiconductor devices, it has become increasingly important to ensure the uniformity of the thickness of each layer during the manufacturing process. Integration of layers without uniform thickness can lead to wiring defects, voids, and other failures. As semiconductor devices become increasingly miniaturized, the thickness of each layer has become extremely thin, e.g., 100 nm or less, necessitating highly accurate thickness measurement. A known method for measuring thickness involves detecting the reflected interference light from a semiconductor device using a spectroscope to obtain a spectrum and estimate the thickness of each layer. However, this measurement method involves point-by-point thickness measurement, and therefore requires extremely long measurement times when, for example, it is necessary to accurately derive the thickness distribution across the entire wafer.

[0005] The present disclosure has been made in view of the above circumstances, and has an object to provide a semiconductor device manufacturing method that can quickly and accurately derive the thickness distribution of a wafer.

[0006] (1) A semiconductor device manufacturing method according to one aspect of the present disclosure includes a first step of irradiating light onto the wafer in a planar manner, with a first layer formed on the front surface of the wafer, capturing an image of the light from the wafer, and acquiring a thickness distribution of the first layer within the plane of the wafer based on a signal related to the image; a second step of forming a second layer by performing a predetermined processing process on the first layer; a third step of irradiating light onto the wafer in a planar manner after the second step, capturing an image of the light from the wafer, and deriving a distribution of measurement parameters within the plane of the wafer based on the signal related to the image; and a fourth step of deriving a thickness distribution of the second layer based on the thickness distribution of the first layer acquired in the first step and the distribution of the measurement parameters derived in the third step.

[0007] In a semiconductor device manufacturing method according to one aspect of the present disclosure, after the formation of a second layer, the wafer is irradiated with light in a planar manner, and the light from the wafer is imaged to derive a distribution of measurement parameters within the wafer surface. The thickness distribution of the second layer is then derived based on the thickness distribution of the first layer acquired before the formation of the second layer and the distribution of measurement parameters within the wafer surface derived after the formation of the second layer. Because the thickness distribution of the first layer is acquired in advance before the formation of the second layer, the thickness distribution of the second layer, which is the layer on the front side of the wafer, can be appropriately (highly accurately) derived based on the distribution of measurement parameters within the wafer surface derived after the formation of the second layer and the thickness distribution of the first layer. Furthermore, the thickness distribution of the second layer is derived taking into account the image results of the light irradiated in a planar manner onto the wafer, so the thickness distribution of the second layer within the entire wafer surface can be derived all at once (in a short period of time). This significantly reduces the measurement time required to derive the thickness distribution within the entire wafer surface, compared to, for example, measuring the thickness of the second layer at specific points using a spectrometer or the like. As described above, according to the semiconductor device manufacturing method according to one aspect of the present disclosure, the thickness distribution of the wafer can be derived quickly and with high accuracy.

[0008] (2) The semiconductor device manufacturing method described in (1) above may further include a relationship information deriving step of deriving relationship information indicating the relationship between the measurement parameters and the thickness of the second layer for each predetermined region based on the thickness distribution of the first layer acquired in the first step, and in the fourth step, deriving the thickness distribution of the second layer based on the relationship information derived in the relationship information deriving step and the distribution of the measurement parameters derived in the third step. In this way, by deriving and using the relationship information indicating the relationship between the measurement parameters and the thickness distribution of the second layer for each predetermined spatial region under the conditions of the acquired thickness distribution of the first layer, it is possible to quickly and accurately derive the thickness distribution of the layer on the front side of the wafer from the distribution of the measurement parameters derived in the third step.

[0009] (3) In the semiconductor device manufacturing method described in (2) above, the related information deriving step may include deriving a theoretical reflectance for each predetermined region of the thickness distribution of the second layer based on the thickness distribution of the first layer acquired in the first step and previously acquired thin film information of the second layer, and deriving measurement parameters for each predetermined region of the thickness distribution of the second layer based on the theoretical reflectance for each thickness distribution of the second layer and previously acquired spectral characteristics, and deriving related information indicating the relationship between the measurement parameters and the thickness of the second layer for each predetermined region. In this way, by identifying the thickness distribution of the first layer and the thin film information of the second layer, it is possible to derive a theoretical reflectance for each predetermined region of the thickness distribution of the second layer with high accuracy. Then, by identifying the theoretical reflectance and spectral characteristics for each thickness distribution of the second layer, it is possible to derive measurement parameters for each predetermined region of the thickness distribution of the second layer, and derive the above-mentioned related information with high accuracy. With this configuration, the thickness distribution of the layer on the front side of the wafer can be derived with high accuracy from the distribution of measurement parameters derived in the third step using the related information.

[0010] (4) In the semiconductor device manufacturing method described in (2) or (3) above, the related information deriving step may be performed during the second step, thereby enabling the thickness distribution of the layer on the front side of the wafer to be quickly derived after the second step is performed.

[0011] (5) In the semiconductor device manufacturing method according to any one of (2) to (4), the relational information may be a relational expression or a table obtained by fitting for each predetermined region. By using such relational information, the thickness distribution of the layer on the front side of the wafer can be derived quickly and accurately.

[0012] (6) In the semiconductor device manufacturing method according to any one of (1) to (5), the measurement parameter may be a wavelength centroid. With this configuration, the wavelength centroid, which has a high correlation with film thickness, can be used as a measurement parameter to derive the thickness distribution of the layer on the front surface of the wafer with high accuracy.

[0013] (7) In the semiconductor device manufacturing method described in any one of (1) to (6) above, the processing may be any of a film formation process, a photoresist coating process, an etching process, a planarization process, an electrode formation process, a pattern formation process, an insulating film formation process, a contact hole formation process, a contact formation process, a trench formation process, and a wiring formation process. The thickness distribution of the layer on the front side of the wafer formed after these processes can be derived quickly and accurately using the above-described method. After the pattern formation process, it is difficult to derive the film thickness using conventional point measurements due to difficulties in alignment, etc. In this regard, the technique disclosed herein eliminates the need for alignment, etc. after the pattern formation process, and therefore the thickness distribution of the layer on the front side of the wafer can be easily derived.

[0014] According to the present disclosure, it is possible to provide a semiconductor device manufacturing method that can shorten the measurement time and perform thickness measurement with high accuracy.

[0015] FIG. 1 is a schematic diagram illustrating a film thickness measurement apparatus according to this embodiment. FIG. 2 is a diagram illustrating the relationship between the characteristics of a dichroic mirror and the wavelength of light emitted from a light source. FIG. 3 is a diagram illustrating the spectrum of light and the characteristics of an inclined dichroic mirror. FIG. 4 is a diagram illustrating wavelength shifts according to the amount of transmitted light and the amount of reflected light. FIG. 5 is a diagram illustrating the relationship between wavelength and film thickness. FIG. 6 is a schematic diagram illustrating an example of a configuration for estimating spectral characteristics. FIG. 7 is a diagram illustrating an example of a method for estimating spectral characteristics using the configuration shown in FIG. 6. FIG. 8 is a schematic diagram illustrating another example of a configuration for estimating spectral characteristics. FIG. 9 is a diagram illustrating the derivation of expected values ​​of measurement parameters. FIG. 10 is a diagram illustrating the derivation of relational expressions by curve fitting. FIG. 11 is a diagram illustrating the derivation of film thickness using relational expressions. FIGS. 12(a) to 12(c) are diagrams illustrating the derivation of relational expressions for measurement parameters other than the wavelength centroid. FIG. 13 is a schematic diagram illustrating a film thickness measurement apparatus according to a modified example. FIG. 14 is a cross-sectional view schematically illustrating a wafer having a multilayer film structure according to a modified example. FIG. 15(a) illustrates the distribution of wavelength centroids measured for the first layer, and FIG. 15(b) illustrates the film thickness distribution for the first layer derived based on the wavelength centroids shown in FIG. 15(a). FIG. 16 illustrates the distribution of wavelength centroids measured after the second layer is formed. FIG. 17 illustrates the derivation of the second layer film thickness based on the wavelength centroids measured after the second layer is formed and the first layer film thickness. FIG. 18 illustrates the relationship between the second layer film thickness and the wavelength centroid for each first layer film thickness. FIG. 19 illustrates a semiconductor device manufacturing process. FIG. 20 illustrates a semiconductor device manufacturing process. FIG. 21 illustrates a procedure for deriving the thickness distribution of the second layer. FIG. 22 illustrates the derivation of the theoretical reflectance for each film thickness candidate for the second layer. FIG. 23 illustrates the derivation of measurement parameters. FIG. 24 illustrates the derivation of relationship information between the measurement parameters and the thickness distribution of the second layer. Fig. 25 is a diagram for explaining derivation of the thickness distribution of the second layer, Fig. 26 is a diagram for explaining a problem of a semiconductor device according to a comparative example, and Fig. 27 is a diagram for explaining the action and effect of derivation of the thickness distribution according to this embodiment.

[0016] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. In each drawing, the same or corresponding parts are denoted by the same reference numerals, and duplicated explanations will be omitted.

[0017] FIG. 1 is a schematic diagram illustrating a film thickness measurement apparatus 1 according to the present embodiment. The film thickness measurement apparatus 1 is an apparatus that irradiates a wafer 100 with light in a planar manner and measures the thickness, specifically the film thickness distribution, of a film formed on the wafer 100 based on the light reflected from the wafer 100. The wafer 100 may be, for example, an integrated circuit (IC) having a PN junction such as a transistor, a large-scale integrated circuit (LSI) such as a logic device, memory device, or analog device, or a mixed-signal device combining these, or a power semiconductor device (power device) such as a high-current / high-voltage MOS transistor, bipolar transistor, or IGBT, or a light-emitting device such as an LED or semiconductor laser. The wafer 100 has a film 100b formed on the surface of a substrate 100a. Here, the wafer 100 will be described as having only one layer of film 100b formed on the surface of the substrate 100a. The film 100b may be, for example, an oxide film or a nitride film, but may also be other films.

[0018] As shown in FIG. 1, the film thickness measuring device 1 includes a light source 10 , a half mirror 11 , a field lens 12 , a camera system 20 , and a control device 30 .

[0019] The light source 10 irradiates the wafer 100 with light in a planar manner. The light source 10 irradiates, for example, substantially the entire surface of the wafer 100 with light in a planar manner. The light source 10 is, for example, a light source that can uniformly irradiate the surface of the wafer 100, and irradiates the wafer 100 with diffused light. The light source 10 may be a planar illumination unit using a white LED, an SC light source, a halogen lamp, a Xe lamp, or the like. Alternatively, the light source 10 may be a planar illumination unit using a monochromatic LD, a polychromatic LD, a monochromatic LED, or a polychromatic LED. The light emitted from the light source 10 passes through a half mirror 11 and a field lens 12, and is irradiated planarly onto the wafer 100.

[0020] The light source 10 irradiates the wafer 100 with light having a wavelength included in a predetermined wavelength range of an inclined dichroic mirror 22 (details of which will be described later) included in the camera system 20. As will be described in detail later, the inclined dichroic mirror 22 is an optical element that separates the light from the wafer 100 by transmitting and reflecting it according to the wavelength. The transmittance and reflectance of the inclined dichroic mirror 22 change according to the wavelength within the above-mentioned predetermined wavelength range.

[0021] FIG. 2 is a diagram illustrating the relationship between the characteristics of the tilted dichroic mirror 22 and the wavelength of light emitted from the light source 10. In FIG. 2, the horizontal axis represents wavelength, and the vertical axis represents the transmittance of the tilted dichroic mirror 22. As shown by the characteristic X4 of the tilted dichroic mirror 22 in FIG. 2, the light transmittance (and reflectance) of the tilted dichroic mirror 22 changes gradually (monotonically or linearly) with changes in wavelength in a predetermined wavelength range X10, while the light transmittance (and reflectance) remains constant regardless of changes in wavelength in wavelength ranges other than the specific wavelength range. As shown in FIG. 2, the light X20 output from the light source 10 includes light with wavelengths falling within the predetermined wavelength range X10. That is, the light source 10 outputs light with a broad spectrum that includes the predetermined wavelength range X10. The wavelength range (interference peak wavelength) involved in the measurement is determined by the material of the film formed on the wafer 100 and the range of film thickness to be measured.

[0022] 1, the half mirror 11 is a mirror that reflects the light emitted from the light source 10 toward the wafer 100 (more specifically, toward the field lens 12 that guides the light to the wafer 100) and transmits the light from the wafer 100 that has been irradiated with the light (more specifically, the light that has passed through the field lens 12 from the wafer 100). The field lens 12 is a lens that aligns the traveling direction of the light.

[0023] The camera system 20 includes a lens 21, an inclined dichroic mirror 22, an area sensor 23, and an area sensor 24. The camera system 20 may include a linear image sensor instead of the area sensor.

[0024] The lens 21 is a lens that collects light from the wafer 100 that has entered through the field lens 12 and the half mirror 11. The lens 21 may be disposed upstream of the inclined dichroic mirror 22, or in a region between the inclined dichroic mirror 22 and the area sensors 23 and 24. In this embodiment, the lens 21 is described as being disposed upstream of the inclined dichroic mirror 22. The lens 21 may be a finite focus lens or an infinity focus lens. When the lens 21 is a finite focus lens, the distance from the lens 21 to the area sensors 23 and 24 is set to a predetermined value. When the lens 21 is an infinity focus lens, the lens 21 is a collimator lens that converts light from the wafer 100 into parallel light, and aberrations are corrected to obtain parallel light. The light output from the lens 21 is incident on the inclined dichroic mirror 22.

[0025] The inclined dichroic mirror 22 is a mirror made of a special optical material, and is an optical element that separates light from the wafer 100 by transmitting and reflecting it according to the wavelength. The inclined dichroic mirror 22 is configured so that the transmittance and reflectance of light change according to the wavelength in a predetermined wavelength range.

[0026] FIG. 3 is a diagram illustrating the light spectrum and the characteristics of the inclined dichroic mirror 22. In FIG. 3, the horizontal axis represents wavelength, and the vertical axis represents spectral intensity (in the case of the light spectrum) and transmittance (in the case of the inclined dichroic mirror 22). As shown by characteristic X4 of the inclined dichroic mirror 22 in FIG. 3, in the inclined dichroic mirror 22, the light transmittance (and reflectance) changes gradually with changes in wavelength in a predetermined wavelength range (the wavelength range from λ1 to λ2). On the other hand, in wavelength ranges other than the predetermined wavelength range (i.e., wavelengths lower than λ1 and higher than λ2), the light transmittance (and reflectance) may be constant regardless of changes in wavelength. In other words, in a specific wavelength range (the wavelength range from λ1 to λ2), the light transmittance changes monotonically (reflectance changes monotonically) with changes in wavelength. Since transmittance and reflectance have a negative correlation, i.e., when one increases, the other decreases, the other decreases. Therefore, hereinafter, the terms "transmittance (and reflectance)" may be omitted and simply referred to as "transmittance." Note that "constant light transmittance regardless of wavelength" does not only refer to a completely constant light transmittance, but also includes, for example, a case where the change in transmittance is 0.1% or less per 1 nm change in wavelength. On the wavelength side lower than wavelength λ1, the light transmittance may be approximately 0% regardless of wavelength change, and on the wavelength side higher than wavelength λ2, the light transmittance may be approximately 100% regardless of wavelength change. Note that "light transmittance is approximately 0%" includes a transmittance of approximately 0% + 10%, and "light transmittance is approximately 100%" includes a transmittance of approximately 100% - 10%. In FIG. 3, waveform X1 indicates the waveform of light output from light source 10. 3, the light output from light source 10 includes light of wavelengths included in the predetermined wavelength range (the wavelength range of wavelengths λ1 to λ2) of inclined dichroic mirror 22. The predetermined wavelength range is, for example, the visible wavelength range, e.g., a wavelength range of 400 nm to 700 nm.

[0027] Returning to FIG. 1 , the area sensors 23 and 24 capture light from the wafer 100 (imaging step). The area sensors 23 and 24 capture light separated by the inclined dichroic mirror 22. The area sensor 23 captures light transmitted by the inclined dichroic mirror 22 and outputs a second signal. The area sensor 24 captures light reflected by the inclined dichroic mirror 22 and outputs a first signal. The wavelength range to which the area sensors 23 and 24 are sensitive corresponds to a predetermined wavelength range in which the light transmittance (and reflectance) of the inclined dichroic mirror 22 changes depending on the wavelength. The area sensors 23 and 24 are, for example, monochrome sensors or color sensors. The imaging results (images) by the area sensors 23 and 24 are output to the control device 30 by the first signal and second signal described above.

[0028] A band-pass filter (not shown) may be disposed in front (upstream) of the area sensors 23 and 24. Such a band-pass filter (not shown) may be, for example, a filter that removes light in a wavelength range other than the above-mentioned predetermined wavelength range (the wavelength range in which the transmittance and reflectance of light change depending on the wavelength in the inclined dichroic mirror 22).

[0029] The control device 30 is a computer, and is physically configured to include memories such as RAM and ROM, a processor (arithmetic circuit) such as a CPU, a communication interface, and a storage unit such as a hard disk. The control device 30 functions by executing a program stored in the memory with the CPU of the computer system. The control device 30 may be configured with a microcomputer or FPGA.

[0030] The control device 30 derives the film thickness of the wafer 100 (thickness distribution within the surface of the wafer 100) based on first and second signals, which are signals from the area sensors 23 and 24 that capture light. The control device 30 performs processes related to film thickness derivation, including a measurement parameter derivation process based on the signals from the area sensors 23 and 24 and a film thickness derivation process based on the measurement parameters, etc. Furthermore, the control device 30 stores relationship information indicating the relationship between film thickness and measurement parameters for each predetermined area, as a prerequisite for performing the film thickness derivation process. The control device 30 has a calculation unit 31, an analysis unit 32, and a memory unit 33 as functional components that realize the above-mentioned processes and storage. The calculation unit 31 has a function of performing the measurement parameter derivation process. The analysis unit 32 has a function of performing the film thickness derivation process. The memory unit 33 stores the above-mentioned relationship information. Each function will be described in detail below.

[0031] The calculation unit 31 derives measurement parameters for the wafer 100 for each predetermined region based on signals from the area sensors 23, 24 that capture the light. The signals from the area sensors 23, 24 indicate the transmitted light distribution and the reflected light distribution in the captured region. The measurement parameters may be any parameter that correlates with the film thickness, such as the wavelength centroid of the light from the wafer 100, the intensity of the light transmitted through the inclined dichroic mirror 22, the intensity of the light reflected from the inclined dichroic mirror 22, or the ratio of the intensity of the light transmitted through the inclined dichroic mirror 22 to the intensity of the light reflected from the inclined dichroic mirror 22 (IT / IR or IR / IT). In the following description, the measurement parameter is assumed to be the wavelength centroid of the light from the wafer 100.

[0032] The calculation unit 31 may derive the wavelength centroid of each light as a measurement parameter for each predetermined region based on the spatial distribution of the transmitted light amount (the intensity of light transmitted through the inclined dichroic mirror 22) determined based on the second signal from the area sensor 23 indicating the imaging result in the area sensor 23, and the spatial distribution of the reflected light amount (the intensity of light reflected from the inclined dichroic mirror 22) determined based on the first signal from the area sensor 24 indicating the imaging result in the area sensor 24. The predetermined region may be, for example, a region corresponding to a pixel of the area sensors 23, 24, or a region corresponding to a plurality of adjacent pixels. In the following description, a pixel is used as the predetermined region. Specifically, when deriving the centroid wavelength of the light, the calculation unit 31 derives the wavelength centroid of each pixel based on the following equation (1): In the following equation (1), x' indicates the wavelength centroid, IT' indicates the transmitted light amount, and IR' indicates the reflected light amount. x' = (IT' - IR') / 2 (IT' + IR') (1)

[0033] The calculation unit 31 may further derive the wavelength centroid of the light for each pixel by taking into consideration the central wavelength of the inclined dichroic mirror 22 (the central wavelength of a predetermined wavelength range) and the width of the inclined dichroic mirror 22. The width of the inclined dichroic mirror 22 is, for example, the wavelength width from the wavelength at which the transmittance of the inclined dichroic mirror 22 is 0% to the wavelength at which the transmittance is 100%. In this case, the calculation unit 31 may derive the wavelength centroid of each pixel based on the following formula (2). In the following formula (2), x' represents the wavelength centroid, IT' represents the amount of transmitted light, IR' represents the amount of reflected light, λ0 represents the central wavelength of the inclined dichroic mirror 22, and A represents the width of the inclined dichroic mirror 22. x'=λ0+A(IT'-IR') / 2(IT'+IR') (2)

[0034] FIG. 4 is a diagram illustrating wavelength shifts according to the amount of transmitted light and the amount of reflected light. When x' (wavelength center of gravity) is derived using the above-described formula (1) or (2), as shown in FIG. 4, for pixels where IT' (amount of transmitted light) = IR' (amount of reflected light), x' = λ0 (the center wavelength of the inclined dichroic mirror 22) is used. Furthermore, for pixels where IT' < IR', i.e., pixels where the amount of reflected light is greater than the amount of transmitted light, x' = λ1 (a wavelength shorter than λ0). Furthermore, for pixels where IT' > IR', i.e., pixels where the amount of transmitted light is greater than the amount of reflected light, x' = λ2 (a wavelength longer than λ0). In this way, the value of x' (wavelength center of gravity) shifts (wavelength shifts) based on the amount of transmitted light and the amount of reflected light.

[0035] Furthermore, since the wavelength centroid has a correlation with the film thickness, it can be used to derive the film thickness. FIG. 5 is a diagram showing the relationship between wavelength and film thickness. In FIG. 5, the horizontal axis represents wavelength and the vertical axis represents reflectance. In the example shown in FIG. 5, the relationship between wavelength and reflectance is shown for film thicknesses of 820 nm, 830 nm, and 840 nm. As shown in FIG. 5, the wavelength centroid differs depending on the film thickness. As such, since the wavelength centroid and the film thickness have a correlation, it is possible to estimate the film thickness by identifying the wavelength centroid.

[0036] Returning to FIG. 1 , the storage unit 33 stores relationship information between film thickness and measurement parameters (here, wavelength centroid). As described above, there is a correlation between film thickness and wavelength centroid. Therefore, by preparing the relationship information between film thickness and wavelength centroid in advance, it is possible to derive film thickness from the relationship information and the actually measured wavelength centroid. The storage unit 33 stores the relationship information for each type of film.

[0037] The relationship information may be derived based on the theoretical reflectance according to the type of film and the spectral characteristics (spectral sensitivity) of the entire film thickness measurement apparatus 1. The theoretical reflectance value for each wavelength is determined once the type of film (refractive index and extinction coefficient of the film) and film thickness are determined. The spectral characteristics of the entire film thickness measurement apparatus 1 may be specified (estimated) in advance using various methods. Below, examples of methods for estimating the spectral characteristics of the entire film thickness measurement apparatus 1 are described.

[0038] The spectral characteristics of the film thickness measurement apparatus 1 may be estimated, for example, as an accumulation of the spectral characteristics (spectral sensitivity) of each optical component constituting the film thickness measurement apparatus 1. Specifically, the spectral characteristics of the film thickness measurement apparatus 1 may be estimated by accumulating the luminance spectrum of the light source 10, the spectral transmittance (transmittance spectrum) of the half mirror 11, the spectral transmittance (transmittance spectrum) of the field lens 12, the spectral transmittance (transmittance spectrum) of the lens 21, the spectral transmittance of the inclined dichroic mirror 22, the quantum efficiency (QE) or spectral sensitivity of the area sensor 23, the quantum efficiency (QE) or spectral sensitivity of the area sensor 24, and the reflectance of a bare wafer placed in place of the wafer 100.

[0039] In this case, the spectral characteristic SCT_xm,yn(λ) on the transmission side that transmits through the inclined dichroic mirror 22 is given by the following equation (3): Furthermore, the spectral characteristic SCR_xm,yn(λ) on the reflection side that reflects off the inclined dichroic mirror 22 is given by the following equation (4): In equations (3) and (4), λ is the wavelength, xm and yn are coordinates on the surface of the wafer 100, SC1 is the luminance spectrum of the light source 10, SC2 is the spectral transmittance of the half mirror 11, SC3 is the spectral transmittance of the field lens 12, SC4 is the spectral transmittance of the lens 21, SC5 is the spectral transmittance of the inclined dichroic mirror 22, SC6 is the quantum efficiency or spectral sensitivity of the area sensor 23, SC7 is the quantum efficiency or spectral sensitivity of the area sensor 24, and R is the reflectance on the bare wafer. SCT_xm,yn(λ)=SC1(λ)xm,yn×SC2(λ)xm,yn×SC3(λ)xm,yn×SC4(λ)xm,yn×SC5(λ)xm,yn×SC6(λ)xm,yn×R(λ) (3) SCR_xm,yn(λ)=SC1(λ)xm,yn×SC2(λ)xm,yn×SC3(λ)xm,yn×SC4(λ)xm,yn×SC5(λ)xm,yn×SC7(λ)xm,yn×R(λ) (4)

[0040] In addition, for example, if the spectral characteristics are highly uniform spatially on the surface of the wafer 100 (there is little variation in the spectral characteristics for each coordinate), it is possible to use, for example, SC1(λ)xm,yn=SC1(λ) without taking into account the positional dependency for each coordinate (the same applies to SC2 to SC7).

[0041] The spectral characteristics of the film thickness measurement apparatus 1 may be estimated using, for example, multiple types of bandpass filters. FIG. 6 is a diagram schematically illustrating an example of a configuration for estimating the spectral characteristics of the film thickness measurement apparatus 1. In addition to the components included in the film thickness measurement apparatus 1 described above, FIG. 6 also illustrates multiple types of bandpass filters 51-54. For example, if the rate of change of the spectrum is a continuous, monotonic characteristic, the transmission-side spectral characteristics SCT_xm,yn(λ) and the reflection-side spectral characteristics SCR_xm,yn(λ) of the film thickness measurement apparatus 1 can be estimated simultaneously for each coordinate on the wafer 100 by sequentially switching between the multiple types of bandpass filters 51-54 using a filter wheel (not shown) or a filter slider (not shown). In this case, the spectral characteristics SCT_xm,yn(λ) on the transmission side are estimated from the amount of transmitted light measured by the area sensor 23, without individually considering the spectral characteristics of each optical component constituting the film thickness measurement apparatus 1, and the spectral characteristics SCR_xm,yn(λ) on the reflection side are estimated from the amount of reflected light measured by the area sensor 24. When estimating the spectral characteristics using this configuration, a bare wafer 500 is placed instead of the wafer 100.

[0042] In the configuration shown in Fig. 6, bandpass filters 51 to 54 are filters that remove light in wavelength ranges other than predetermined wavelength ranges. Bandpass filter 51 is a filter that removes light in wavelength ranges other than the first wavelength range, which has the lowest wavelength, for example. Bandpass filter 52 is a filter that removes light in wavelength ranges other than the second wavelength range, which is higher in wavelength than the first wavelength range described above. Bandpass filter 53 is a filter that removes light in wavelength ranges other than the third wavelength range, which is higher in wavelength than the second wavelength range described above. Bandpass filter 54 is a filter that removes light in wavelength ranges other than the fourth wavelength range, which is higher in wavelength than the third wavelength range described above.

[0043] Fig. 7 is a diagram illustrating an example of a method for estimating spectral characteristics performed by the configuration shown in Fig. 6. In Fig. 7, an image of one coordinate included in bare wafer 500 is shown on the left, the upper right shows the amount of transmitted light measured by area sensor 23 for the one coordinate while switching between band-pass filters 51 to 54, and the lower right shows the amount of reflected light measured by area sensor 24 for the one coordinate while switching between band-pass filters 51 to 54. In the upper right and lower right diagrams of Fig. 7, the horizontal axis represents wavelength and the vertical axis represents spectral intensity.

[0044] In the upper right diagram of FIG. 7 , the wavelength region corresponding to the first wavelength region of bandpass filter 51 is wavelength region 151, the wavelength region corresponding to the second wavelength region of bandpass filter 52 is wavelength region 152, the wavelength region corresponding to the third wavelength region of bandpass filter 53 is wavelength region 153, and the wavelength region corresponding to the fourth wavelength region of bandpass filter 54 is wavelength region 154. As shown in the upper right diagram of FIG. 7 , by determining the amount of transmitted light when using each bandpass filter 51 to 54, a curve 160 showing the relationship between wavelength and spectral intensity can be derived by performing, for example, curve fitting on the data on the amount of transmitted light. The relational expression (polynomial) showing such curve 160 is a relational expression showing the spectral characteristics SCT_xm,yn(λ) on the transmission side. Note that curve fitting methods include, for example, polynomial approximation and other curve fitting methods. In addition to curve fitting, a curve showing the relationship between wavelength and spectral intensity may also be derived using interpolation or other methods.

[0045] Similarly, in the lower right diagram of FIG. 7 , the wavelength region corresponding to the first wavelength region of bandpass filter 51 is wavelength region 251, the wavelength region corresponding to the second wavelength region of bandpass filter 52 is wavelength region 252, the wavelength region corresponding to the third wavelength region of bandpass filter 53 is wavelength region 253, and the wavelength region corresponding to the fourth wavelength region of bandpass filter 54 is wavelength region 254. As shown in the lower right diagram of FIG. 7 , by identifying the amount of transmitted light when using each bandpass filter 51 to 54, and performing curve fitting on the data on the amount of transmitted light, a curve 260 showing the relationship between wavelength and spectral intensity is derived. The relational expression (polynomial) showing such curve 260 is a relational expression showing the reflection-side spectral characteristic SCR_xm,yn(λ). Curve fitting methods include, for example, polynomial approximation and other curve fitting methods. In addition to curve fitting, a curve showing the relationship between wavelength and spectral intensity may also be derived using interpolation or other methods. As described above, the spectral characteristics of the film thickness measurement apparatus 1 can be estimated using the bandpass filters 51 to 54.

[0046] Furthermore, the spectral characteristics of the film thickness measurement apparatus 1 may be estimated using, for example, a spectroscope. Fig. 8 is a diagram schematically showing an example of another configuration for estimating the spectral characteristics of the film thickness measurement apparatus 1. Fig. 8 shows a configuration in which spectroscopes 60 and 70 are provided instead of the area sensors 23 and 24 of the film thickness measurement apparatus 1 described above.

[0047] The spectrometer 60 can derive a spectral characteristic SC8(λ)xm,yn, which is the cumulative sum of the spectral characteristics of each optical component, excluding SC6(λ)xm,yn, which is the quantum efficiency or spectral sensitivity of the area sensor 23, from the transmission-side spectral characteristic SCT_xm,yn(λ). The spectrometer 60 includes a measurement unit 61 and a probe head 62. The spectrometer 60 separates light input from the probe head 62 (light transmitted through the inclined dichroic mirror 22) into wavelengths, and derives the intensity of each wavelength in the measurement unit 61. In this manner, the above-described spectral characteristic SC8(λ)xm,yn is derived. The transmission-side spectral characteristic SCT_xm,yn(λ) is expressed as the product of SC6(λ)xm,yn, which is the quantum efficiency or spectral sensitivity of the area sensor 23, and the spectral characteristic SC8(λ)xm,yn, which is the cumulative sum of the spectral characteristics of each optical component, as shown in the following equation (5): SCT_xm,yn(λ)=SC6(λ)xm,yn×SC8(λ)xm,yn (5)

[0048] Similarly, the spectrometer 70 can derive a spectral characteristic SC9(λ)xm,yn, which is the cumulative sum of the spectral characteristics of each optical component of the reflection-side spectral characteristic SCR_xm,yn(λ), excluding SC7(λ)xm,yn, which is the quantum efficiency or spectral sensitivity of the area sensor 24. The spectrometer 70 has a measurement unit 71 and a probe head 72. The spectrometer 70 disperses light input from the probe head 72 (light reflected by the inclined dichroic mirror 22) into wavelengths, and derives the intensity of each wavelength in the measurement unit 71. In this manner, the above-mentioned spectral characteristic SC9(λ)xm,yn is derived. The reflection-side spectral characteristic SCR_xm,yn(λ) is expressed as the product of SC7(λ)xm,yn, which is the quantum efficiency or spectral sensitivity of the area sensor 24, and the spectral characteristic SC9(λ)xm,yn, which is the cumulative sum of the spectral characteristics of each optical component, as shown in the following equation (6): SCR_xm,yn(λ)=SC7(λ)xm,yn×SC9(λ)xm,yn (6)

[0049] Although the above describes several examples in which the spectral characteristics of the film thickness measurement apparatus 1 are estimated using the film thickness measurement apparatus 1, the estimation of the spectral characteristics of the film thickness measurement apparatus 1 does not necessarily have to be performed by the film thickness measurement apparatus 1. In other words, it is sufficient that the above-mentioned relationship information is stored in the storage unit 33, and the spectral characteristics of the film thickness measurement apparatus 1 used to derive the relationship information may be obtained in any manner.

[0050] As described above, the relationship information between film thickness and wavelength centroid is derived based on the theoretical reflectance corresponding to the type of film and the spectral characteristics of the film thickness measurement apparatus 1. In detail, the relationship information is derived by deriving the expected value of the wavelength centroid (measurement parameter) from the theoretical reflectance and the spectral characteristics of the film thickness measurement apparatus 1 (see FIG. 9 ), and then plotting the expected value of the wavelength centroid and deriving a relationship equation by curve fitting (see FIG. 10 ). An example of deriving the relationship information between film thickness and wavelength centroid for a certain type of film will be described below.

[0051] FIG. 9 is a diagram illustrating the derivation of the expected value of the wavelength centroid, which is a measurement parameter. Given a specific film type, the theoretical reflectance value for each wavelength is determined according to the film thickness. Assume that a specific film thickness is specified and the theoretical reflectance R' for each wavelength is determined. In this case, the expected value of the transmitted light amount IT' measured by the area sensor 23 can be estimated based on the theoretical reflectance R' for each wavelength and the spectral characteristics SCT_xm,yn(λ) of the transmission side of the film thickness measurement device 1 for each wavelength. Because the area sensor 23 does not have a spectroscopic function, the expected value of the transmitted light amount IT' measured by the area sensor 23 is the integrated value of the light intensity for each wavelength. Similarly, the expected value of the reflected light amount IR' measured by the area sensor 24 can be estimated based on the theoretical reflectance R' for each wavelength and the spectral characteristics SCR_xm,yn(λ) of the reflection side of the film thickness measurement device 1 for each wavelength. Then, using the above-described formula (1) or (2), the expected value of the wavelength centroid x' can be derived from the expected value of the transmitted light amount IT' and the expected value of the reflected light amount IR'. In this way, when the type of film is determined, the expected value of the wavelength centroid x' at a certain film thickness can be derived. Then, while changing the film thickness condition for the same film type, the expected value of the wavelength centroid x' at each film thickness is derived. This results in a state where the expected value of the wavelength centroid x' for each of a plurality of film thickness conditions is derived for a certain film type.

[0052] FIG. 10 is a diagram illustrating the derivation of a relational expression by curve fitting. For a certain film type, expected values ​​of the wavelength centroid x' under multiple film thickness conditions are derived. In the example shown in FIG. 10 , the expected values ​​of the wavelength centroid x' under three film thickness patterns (film thickness d = 90 nm, 100 nm, and 110 nm) are plotted on a graph with the horizontal axis representing the wavelength centroid x' and the vertical axis representing the film thickness d. In practice, more expected values ​​of the wavelength centroid x' under different film thickness conditions are plotted. Then, by performing curve fitting on each plotted data, a curve 360 ​​showing the relationship between the film thickness d and the wavelength centroid x' is derived. The relational expression showing such curve 360 ​​is the relational expression between the film thickness and the measurement parameters. The relational expression between the film thickness and the measurement parameters is expressed as a polynomial, for example, as shown in the following equation (7). By determining each parameter (a, b, c, ...) of the polynomial, the film thickness d can be derived by inputting the wavelength centroid x'. dxm,yn(x')=axm,yn+bxm,ynx'+cxm,ynx'2+... (7)

[0053] 1 , the storage unit 33 stores the relational expression between film thickness and wavelength centroid as shown in the above equation (7) as the above-mentioned relational information. In this case, the relational information is the relational expression between film thickness and wavelength centroid derived by plotting and fitting the expected values ​​of the wavelength centroid corresponding to each film thickness derived based on the theoretical reflectance and the spectral characteristics of the film thickness measuring apparatus 1. The storage unit 33 stores such a relational expression for each type of film.

[0054] The analysis unit 32 derives the film thickness of the wafer 100 based on the relational expression between the film thickness and the wavelength centroid stored in the storage unit 33 as relational information and the wavelength centroid, which is a measurement parameter for the wafer 100, determined by the calculation unit 31. The analysis unit 32 derives the film thickness of the wafer 100 based on the relational expression corresponding to the type of film on the wafer 100 and the wavelength centroid determined by the calculation unit 31 (analysis step). That is, the analysis unit 32 reads out the relational expression corresponding to the type of film on the wafer 100 from the storage unit 33 (reading step), and derives the film thickness d of the wafer 100 by inputting the wavelength centroid determined by the calculation unit 31 into the wavelength centroid x' of the relational expression as shown in equation (7).

[0055] 11 is a diagram illustrating the derivation of the film thickness using the relational expression. As shown in FIG. 11, when a curve 360 ​​showing the relationship between the film thickness d and the wavelength centroid x' is derived and the above-mentioned expression (7) is derived, the value of the film thickness d can be uniquely derived from the value of the wavelength centroid x' obtained by the calculation unit 31.

[0056] As described above, the measurement parameter may be any parameter other than the wavelength centroid x' that has a correlation with the film thickness. Figures 12(a) to 12(c) are diagrams for explaining the derivation of the relational expressions relating to the measurement parameters other than the wavelength centroid.

[0057] 12A is a diagram for explaining the derivation of a relational expression when the ratio between the amount of transmitted light IT' measured by the area sensor 23 and the amount of reflected light IR' measured by the area sensor 24 is used as the measurement parameter. The expected value x'' of the ratio is derived using the following equation (8): x''=IT' / IR' (8) By deriving multiple expected values ​​x'' of the ratio while changing the film thickness conditions for the same film type, plotting the expected values ​​x'' of each ratio, and performing curve fitting, a curve 460 showing the relationship between the film thickness d and the ratio x'' is derived, and the relational expression shown in the following equation (9) that shows the curve 460 is derived: dxm,yn(x'')=axm,yn+bxm,ynx''+cxm,ynx''2+... (9)

[0058] Similarly, when the amount of transmitted light IT' is used as the measurement parameter, multiple expected values ​​x''' of the amount of transmitted light IT' are derived while changing the film thickness condition for the same film type, and by plotting the expected values ​​x''' of each amount of transmitted light IT' and performing curve fitting, a curve 560 showing the relationship between the film thickness d and the amount of transmitted light x''' is derived (see FIG. 12(b)). The following relational equation (10) showing the curve 560 is derived: dxm,yn(x''')=axm,yn+bxm,ynx'''+cxm,ynx'''2+... (10)

[0059] Similarly, when the reflected light amount IR' is used as the measurement parameter, multiple expected values ​​x'''' of the reflected light amount IR' are derived while changing the film thickness condition for the same film type, and by plotting each expected value x'''' of the reflected light amount IR' and performing curve fitting, a curve 660 showing the relationship between the film thickness d and the reflected light amount x'''' is derived (see FIG. 12(c)). The following relational equation (11) showing the curve 660 is derived: dxm,yn(x'''')=axm,yn+bxm,ynx''''+cxm,ynx''''2+... (11)

[0060] In the above embodiment, the film thickness measurement device 1 is described as deriving measurement parameters and film thickness by capturing images of light transmitted through and reflected by the inclined dichroic mirror 22 using the area sensors 23 and 24. The present disclosure is not limited to this example, and for example, the film thickness of an object may be measured using a film thickness measurement device that does not include the inclined dichroic mirror 22.

[0061] FIG. 13 is a schematic diagram illustrating a film thickness measurement apparatus 1B according to a modified example. Note that the control device 30 (calculation unit, memory unit, and analysis unit) is not illustrated in FIG. 13 . As shown in FIG. 13 , the film thickness measurement apparatus 1B includes a camera system 20B instead of the camera system 20 in the film thickness measurement apparatus 1. The camera system 20B does not include an inclined dichroic mirror and includes only one area sensor. That is, the camera system 20B includes a lens 21 and one area sensor 23B. In this configuration, the area sensor 23B can measure the light quantity (the intensity of light from the wafer 100). Therefore, for example, by storing a relational equation showing the relationship between the light quantity and the film thickness as the above-mentioned relational information in advance, the film thickness can be derived based on the relational equation and the measured light quantity. Even in this case, the relational equation (relational information) is derived based on the theoretical reflectance corresponding to the film type and the spectral characteristics of the film thickness measurement apparatus 1B as a whole.

[0062] In addition, in the above embodiment, an example of measuring the film thickness of a wafer 100 in which only one layer of film 100b is formed on the surface of a substrate 100a has been described, but this is not limited to this, and the film thickness of a wafer with a multilayer film structure in which two or more layers of film are formed on the surface of a substrate may also be measured.

[0063] FIG. 14 is a cross-sectional view schematically illustrating a wafer having a multilayer film structure according to a modified example. As shown in FIG. 14, wafer 200 includes substrate 200a, film 200b, and film 200c. Film 200b is a first layer stacked on substrate 200a. Film 200c is a second layer stacked on film 200b. In other words, the second layer corresponds to a layer on the front surface side of the wafer. Here, as an example, film 200b is a silicon dioxide (SiO2) film and film 200c is a silicon nitride (SiN) film, but the types of films are not limited to this.

[0064] An example of a procedure for measuring the film thickness of a wafer 200 having a multilayer film structure as shown in Fig. 14 will be described below. Such film thickness measurement includes a first layer deriving step, a second layer forming step, a wavelength centroid deriving step after the second layer is formed, and a second layer deriving step. These steps are performed in order.

[0065] In the first layer derivation process, a wafer on which only the first layer, film 200b, is formed is prepared, and film thickness measurement (i.e., film thickness measurement related to film 200b) and evaluation are performed on the wafer. The film thickness derivation of only the first layer can be performed using the method described in the above embodiment. Figure 15(a) is a diagram showing the distribution of wavelength centroids measured for the first layer, and Figure 15(b) is a diagram showing the film thickness distribution for the first layer derived based on the wavelength centroids shown in Figure 15(a). In this way, once the distribution of wavelength centroids of the first layer is derived using the method described in the embodiment, the film thickness distribution of the first layer can be derived.

[0066] The second layer deposition process is performed following the first layer extraction process. In the second layer deposition process, a film 200c, which is a second layer, is deposited on the film 200b. This completes the wafer 200 shown in FIG. 14.

[0067] The wavelength centroid deriving step after the second layer deposition is performed following the second layer deposition step. In the wavelength centroid deriving step after the second layer deposition, similar to the wavelength centroid deriving step in the above embodiment, the wavelength centroid after the second layer deposition is derived based on the image capture results of the light from the wafer 200. Figure 16 is a diagram showing the distribution of wavelength centroids measured after the second layer deposition.

[0068] The second layer derivation process is performed following the wavelength centroid derivation process after the second layer is formed. Fig. 17 is a diagram illustrating the derivation of the second layer film thickness based on the wavelength centroid measured after the second layer is formed and the film thickness of the first layer. As shown in Fig. 17, in the second layer derivation process, the film thickness of the second layer is derived based on the wavelength centroid measured (derived) in the wavelength centroid derivation process after the second layer is formed and the film thickness of the first layer measured (derived) in the first layer derivation process.

[0069] As a prerequisite for performing the second layer derivation process, the memory unit 33 stores relationship information between the film thickness of the second layer and the wavelength centroid (measurement parameter) for each combination of the film type and film thickness of the first layer and the film type of the second layer. FIG. 18 is a diagram illustrating the relationship between the film thickness of the second layer and the wavelength centroid for each first layer film thickness. In FIG. 18, "SiO2 film thickness" indicates the film thickness of the first layer. As shown in FIG. 18, the relationship between the film thickness of the second layer and the wavelength centroid changes depending on the film thickness of the first layer. Therefore, by storing relationship information between the film thickness of the second layer and the wavelength centroid (see FIG. 18) in advance for each combination of the film type and film thickness of the first layer and the film type of the second layer, the film thickness of the first layer can be measured with high accuracy.

[0070] The analysis unit 32 derives the film thickness of the film 200c on the wafer 200 based on the relationship information corresponding to the combination of the film type and film thickness of the film 200b on the wafer 200 and the film type of the film 200c, and the wavelength centroid for the wafer 200 calculated by the calculation unit 31.

[0071] In this way, the relationship information between the film thickness of the second layer and the measurement parameters is specified for each combination of the type and film thickness of the first layer film and the type of film of the second layer, so that when the type and film thickness of the first layer film 200b, and the type and wavelength centroid of the second layer film 200c are known, the film thickness of film 200c can be measured with high accuracy and ease.

[0072] The following describes in detail how to derive the film thickness (thickness distribution) of the second layer in the wafer 200 having the above-described multilayer film structure.

[0073] First, the manufacturing process of the semiconductor device manufacturing method will be described, from when various processes are performed on the wafer 200 to when the semiconductor device (semiconductor chip) 600 is manufactured. Figures 19(a) to 19(i) and 20(a) to 20(j) are diagrams explaining the manufacturing process of the semiconductor device 600. Here, each state during the manufacturing of the semiconductor device 600 will be described as the wafer 200. Note that the manufacturing process described below is merely an example.

[0074] 19( a), first, for example, a single crystal ingot is sliced ​​and polished to produce a mirror-finished silicon substrate 210. Next, as shown in Fig. 19( b), an oxide film 211 and a nitride film 212 are formed on the silicon substrate 210. These films may function as insulating films in the semiconductor device 600, or may function as masks during an etching process.

[0075] Next, as shown in FIG. 19( c), a resist 213 (photoresist) is applied onto the nitride film 212 by spin coating or the like. The photoresist functions as an etching mask in the photolithography process. Next, as shown in FIG. 19( d), UV light is irradiated onto the wafer 200 through a mask 400 on which a circuit pattern is drawn. This changes the solubility of the resist 213, allowing partial removal of the resist 213 in the development process described below.

[0076] 19(e), unnecessary resist 213 is dissolved in a development step to form a mask for engraving a circuit pattern. That is, the resist 213 remaining in the development step serves as a mask for the etching step. Next, as shown in FIG. 19(f), unnecessary portions are removed by etching using the resist 213 as a mask to form a circuit.

[0077] Next, as shown in Fig. 19(g), unnecessary resist is peeled off and removed by a wet method, ashing method, or the like. Next, as shown in Fig. 19(h), an oxide film 214 is deposited in the grooves formed by etching. Such oxide film 214 serves as an insulating film for electrically insulating semiconductor elements from each other.

[0078] 19(i), unnecessary portions of the wafer 200 are polished by chemical mechanical polishing (CMP) or the like to achieve planarization. Next, as shown in FIG. 20(a), silicon is oxidized by thermal oxidation to form a gate oxide film 211A from the oxide film 211. Then, after the surface of the gate oxide film 211A is nitrided, a gate electrode layer 215 is formed by chemical vapor deposition (CVD).

[0079] Next, as shown in Fig. 20(b), a pattern is engraved in the gate electrode layer 215 by photography to form source / drain regions. Then, as shown in Fig. 20(c), dopants 216 are implanted into the source / drain regions by ion implantation. Ions are not implanted into the portions where the gate oxide film 211A remains. Thereafter, the dopants 216 are activated by a recovery heat treatment.

[0080] Next, as shown in Fig. 20(d), an oxide film 217 is deposited by chemical vapor deposition (CVD). The oxide film 217 functions as an insulating layer. Next, as shown in Fig. 20(e), contact holes 218 are formed by photolithography. The contact holes 218 are holes for forming and electrically connecting source and drain electrodes.

[0081] Next, as shown in Fig. 20(f), electrode metal 219 is deposited in the contact hole to form contact 220. At this point, unnecessary films are polished away by chemical mechanical polishing (CMP). Next, as shown in Fig. 20(g), trench 221 is formed by photolithography. The trench becomes a resist opening for electrical wiring.

[0082] 20( h), a metal film 222 is deposited to fill the trench 221. Unnecessary film is polished and removed by chemical mechanical polishing (CMP). Next, as shown in FIG. 20( i), the formation of trenches, the deposition of metal films, and planarization are repeated to form a three-dimensional wiring layer 223.

[0083] 20(j), the semiconductor device (semiconductor chip) 600 is cut by dicing with a diamond blade or stealth dicing, etc. The above is the manufacturing process of the semiconductor device manufacturing method.

[0084] FIG. 21 is a diagram illustrating a procedure for deriving the film thickness (thickness distribution) of the second layer of a wafer 200 having a multilayer film structure. The thickness distribution of the second layer is derived, for example, after various processing processes have been performed on the wafer 200. The processing processes are performed on the wafer 200, which has at least two or more layers stacked thereon. For example, the processing processes may be performed on the wafer 200 after a film formation process ( FIG. 19( b) ), a photoresist coating process ( FIG. 19( c) ), an etching process ( FIG. 19( f) ), a planarization process ( FIG. 19( i) ), an electrode formation process ( FIG. 20( a) ), a pattern formation process ( FIG. 20( b) ), an insulating film formation process ( FIG. 20( d) ), a contact hole formation process ( FIG. 20( e) ), a contact formation process ( FIG. 20( f) ), a trench formation process ( FIG. 20( g) ), or a wiring formation process (see FIG. 20( i) ). The following describes an example of deriving the film thickness of the second layer of the wafer 200 after a film formation process.

[0085] 21A, a wafer 200 is prepared on which only a first layer, film 200b, has been formed before the second layer is formed. With the first layer, film 200b, formed on the front surface of the wafer 200, the thickness distribution of film 200b is acquired (first step (corresponding to the first layer derivation step described above)).

[0086] Next, as shown in FIG. 21(b), a predetermined processing step (here, a film formation step) is performed on the film 200b to form a second layer, film 200c (second step (corresponding to the second layer film formation step described above)).

[0087] Then, as shown in Figure 21 (c), after the second step, light is irradiated in a planar manner onto the wafer 200 on which the film 200c is formed, the light from the wafer 200 is imaged, and measurement parameters (e.g., wavelength centroid) within the surface of the wafer 200 are derived based on the signal related to the image (third step (corresponding to the wavelength centroid derivation step described above)).

[0088] Finally, based on the thickness distribution of film 200b obtained in the first step and the measurement parameters (e.g., wavelength centroid) derived in the third step, the thickness distribution of film 200c is derived (fourth step (corresponding to the second layer derivation step described above)).

[0089] In addition to the above-described first to fourth steps, a related information derivation step may be performed, for example, during the second step. The related information derivation step is a step of deriving relationship information between the measurement parameters and the thickness distribution of the film 200c based on the thickness distribution of the film 200b acquired in the first step. If the related information is derived, the thickness distribution of the film 200c is derived in the fourth step based on the related information and the measurement parameters derived in the third step. The first to fourth steps and the related information derivation step will be described in detail below. In the following description, the configuration of FIG. 1 will be referenced as appropriate, but the wafer 100 in FIG. 1 will be replaced with a wafer 200 having a multilayer film structure.

[0090] In the first step, the thickness distribution of the first layer, film 200b, may be derived using the method described above. Specifically, in film thickness measurement apparatus 1, light source 10 irradiates wafer 200 with light in a planar manner, area sensors 23 and 24 capture images of light from wafer 200, calculation unit 31 of control device 30 derives measurement parameters (here, wavelength centroids) based on signals from area sensors 23 and 24, and analysis unit 32 derives the film thickness (thickness distribution) of film 200b based on relationship information stored in memory 33 and the measurement parameters calculated by calculation unit 31. In this case, the relationship information is derived based on the theoretical reflectance corresponding to the type of film and the spectral characteristics (system spectral sensitivity) of the entire film thickness measurement apparatus 1. The theoretical reflectance and spectral characteristics here are as described above.

[0091] In the second step, after the completion of the first step, a second layer, film 200c, is formed so as to be laminated on film 200b. A related information deriving step is simultaneously performed during the second step. While the related information deriving step is described here as being performed during the second step, the related information deriving step may be performed before the second step or after the second step is completed.

[0092] Specifically, in the relational information deriving step, a theoretical reflectance for each predetermined region (e.g., each pixel) for each thickness distribution of the film 200c is derived based on the thickness distribution of the film 200b acquired in the first step and the previously acquired thin film information of the film 200c. Thus, the theoretical reflectance described here is the "theoretical reflectance for each thickness distribution of the film 200c, which is the second layer." Each thickness distribution of the film 200c can be rephrased as each potential film thickness of the film 200c. As described above, the theoretical reflectance for each wavelength is determined once the film type (thin film information such as the film's refractive index and extinction coefficient) and film thickness are determined. For example, the memory unit 33 stores the thickness distribution of the film 200b acquired in the first step and the previously acquired thin film information of the film 200c. Then, the calculation unit 31 identifies thin film information of the film 200c by referring to the storage unit 33, and derives the theoretical reflectance for each film thickness candidate (thickness distribution) of the film 200c according to the thin film information.

[0093] 22 is a diagram illustrating the derivation of the theoretical reflectance for each second layer film thickness candidate. In the example shown in FIG. 22, under the condition that the type of film is constant, the theoretical reflectance for each wavelength when the second layer film thickness candidate is "d1," the theoretical reflectance for each wavelength when the second layer film thickness candidate is "d2," ... the theoretical reflectance for each wavelength when the second layer film thickness candidate is "dn" are derived. In this way, the theoretical reflectance is derived for each second layer film thickness candidate.

[0094] In the relational information deriving step, a measurement parameter (e.g., wavelength centroid) for each predetermined region (e.g., each pixel) for each thickness distribution of the second layer is further derived based on the theoretical reflectance for each thickness distribution (film thickness candidate) of the second layer and the previously acquired spectral characteristics. For example, the storage unit 33 stores the theoretical reflectance for each thickness distribution of the second layer and the previously acquired spectral characteristics of the film thickness measurement device 1. The calculation unit 31 then derives an expected value of the measurement parameter (e.g., wavelength centroid) for each thickness distribution of the second layer by referring to the storage unit 33.

[0095] FIG. 23 is a diagram illustrating the derivation of the wavelength centroid, which is a measurement parameter (more specifically, the derivation of the expected value of the wavelength centroid). Since the type of film is now determined, the theoretical reflectance value for each wavelength is determined according to the film thickness of the second layer. For example, assume that the theoretical reflectance R for each wavelength is determined for the second layer film thickness candidate "d1." In this case, the expected value of the transmitted light amount IT' measured by the area sensor 23 can be estimated based on the theoretical reflectance R for each wavelength and the spectral characteristics SCT_xm,yn(λ) of the transmission side of the film thickness measurement device 1 for each wavelength. Because the area sensor 23 does not have a spectroscopic function, the expected value of the transmitted light amount IT' measured by the area sensor 23 is the integrated value of the light intensity for each wavelength. Similarly, the expected value of the reflected light amount IR' measured by the area sensor 24 can be estimated based on the theoretical reflectance R for each wavelength and the spectral characteristics SCR_xm,yn(λ) of the reflection side of the film thickness measurement device 1 for each wavelength. Then, using the above-described formula (1) or (2), the expected value of the wavelength centroid can be derived from the expected value of the transmitted light amount IT' and the expected value of the reflected light amount IR'. Then, as shown in Figure 23, the expected value of the wavelength centroid for each film thickness candidate for the second layer is derived while changing the film thickness candidate from "d2" to "d3" ... "dn". Through the above processing, the expected value of the measurement parameter (here, the wavelength centroid) can be derived for each thickness distribution of the second layer.

[0096] The relational information deriving step further derives relational information indicating the relationship between the measurement parameters and the thickness distribution of the second layer for each predetermined region (for example, for each pixel) based on the expected values ​​of the measurement parameters (here, wavelength centroids) for each thickness distribution of the second layer. For example, the memory unit 33 stores the derived expected values ​​of the measurement parameters (here, wavelength centroids) for each thickness distribution of the second layer. The calculation unit 31 then refers to the memory unit 33 to identify the expected values ​​of the measurement parameters for each thickness distribution of the second layer and derives relational information between the measurement parameters and the thickness distribution of the second layer.

[0097] FIG. 24 is a diagram illustrating the derivation of relationship information between measurement parameters and the thickness distribution of the second layer. The expected value of the wavelength centroid is derived under multiple film thickness conditions for the second layer. For example, in the example shown in FIG. 24 , the expected value of the wavelength centroid is derived for each of the second layer film thickness candidates "d1," "d2," ... "dn," and is plotted on a graph with the horizontal axis representing the wavelength centroid and the vertical axis representing the second layer film thickness. While only three patterns are plotted in the example shown in FIG. 24 , in reality, many more expected values ​​of the wavelength centroid under different film thickness conditions are plotted. Then, by performing curve fitting on each plotted data, a curve 560 showing the relationship between film thickness and wavelength centroid is derived. The relational expression showing this curve 560 is the relational expression between the measurement parameters and the thickness distribution of the second layer. This relational expression is expressed as a polynomial, as shown in Equation (7) above. By determining each parameter (a, b, c, ...) of the polynomial, the film thickness d can be derived by inputting the wavelength centroid x'.

[0098] As described above, the relationship information may be a relational expression obtained by fitting or the like for each predetermined region (for each pixel, for example). The relationship information may also be a table instead of a relational expression. The relationship information is stored in the storage unit 33.

[0099] In the third step, in the film thickness measuring device 1, the light source 10 irradiates light in a planar manner onto the wafer 200 on which the film 200c is formed, the area sensors 23 and 24 capture images of the light from the wafer 200, and the calculation unit 31 of the control device 30 derives measurement parameters (here, the wavelength center of gravity) based on signals from the area sensors 23 and 24.

[0100] In the fourth step, the thickness distribution of the second layer is derived based on the relationship information (relationship information between the wavelength centroid and the thickness distribution of the second layer) derived in the relationship information derivation step based on the thickness distribution of the film 200b acquired in the first step, and the wavelength centroid derived in the third step. For example, the storage unit 33 stores the relationship information derived in the relationship information derivation step and the wavelength centroid derived in the third step. Then, the analysis unit 32 derives the thickness distribution of the second layer (film 200c) according to the wavelength centroid derived in the third step by referring to the storage unit 33.

[0101] 25 is a diagram illustrating the derivation of the thickness distribution of the second layer. As shown in Fig. 25, when a curve 560 showing the relationship between the film thickness (thickness distribution of the second layer) d and the wavelength centroid x', which is a measurement parameter, is derived and the relational expression shown in the above equation (7) is derived, the value of the film thickness (thickness distribution of the second layer) d can be uniquely derived from the value of the wavelength centroid x'.

[0102] Next, the effects of the semiconductor device manufacturing method according to this embodiment will be described.

[0103] In recent years, with the increasing integration density of semiconductor devices, ensuring uniformity in the thickness of each layer during the manufacturing process has become increasingly important. Figure 26 illustrates a problem with a semiconductor device 800 according to a comparative example. As shown in Figure 26, integration without uniform thickness of each layer can lead to failures such as wiring defects and voids. As semiconductor devices become increasingly miniaturized, the thickness of each layer has become extremely thin, e.g., 100 nm or less, necessitating highly accurate thickness measurement. A known method for measuring thickness involves detecting the reflected interference light from a semiconductor device using a spectrometer to obtain a spectrum and estimate the thickness of each layer. However, this measurement method involves point-by-point thickness measurement, which requires extremely long measurement times, especially when attempting to accurately derive the thickness distribution across the entire wafer. Therefore, measuring the thickness distribution across the entire wafer is not practical, and point-by-point thickness measurements at predetermined intervals along the wafer's scribe lines (lines divided by a dicer or the like) have been performed.

[0104] In this regard, the semiconductor device manufacturing method according to this embodiment includes a first step of acquiring the thickness distribution of the first layer when the first layer has been formed on the front surface side of the wafer 200; a second step of forming a second layer by performing a predetermined processing process on the first layer; a third step of irradiating light onto the wafer 200 in a planar manner after the second step, capturing an image of the light from the wafer 200, and deriving measurement parameters within the surface of the wafer 200 based on the image-related signal; and a fourth step of deriving the thickness distribution of the second layer based on the thickness distribution of the first layer acquired in the first step and the measurement parameters derived in the third step.

[0105] In the semiconductor device manufacturing method according to this embodiment, after the second layer is formed, the wafer 200 is irradiated with light in a planar manner, and the light from the wafer 200 is imaged, thereby deriving measurement parameters within the plane of the wafer 200. The thickness distribution of the second layer is then derived based on the thickness distribution of the first layer acquired before the second layer is formed and the measurement parameters within the plane of the wafer 200 derived after the second layer is formed. Because the thickness distribution of the first layer is thus acquired in advance before the second layer is formed, the thickness distribution of the second layer, which is the layer on the front side of the wafer, can be appropriately (highly accurately) derived based on the measurement parameters within the plane of the wafer 200 derived after the second layer is formed and the thickness distribution of the first layer. Furthermore, the thickness distribution of the second layer is derived taking into account the image results of the light irradiated in a planar manner onto the wafer 200, so the thickness distribution of the second layer within the plane of the entire wafer 200 can be derived all at once (in a short period of time). This allows for a significant reduction in the measurement time required to derive the in-plane thickness distribution of the entire wafer 200, compared to, for example, when the thickness of the second layer is measured at points using a spectrometer or the like. As described above, the semiconductor device manufacturing method according to this embodiment allows for the thickness distribution of the wafer 200 to be derived quickly and with high accuracy. Note that, in the case of point measurements such as those in the comparative example, it is necessary to store spectroscopic data at each measurement point for manufacturing records, which makes data management cumbersome. However, according to the measurement method according to this embodiment, it is only necessary to record reflected images and transmitted images, which simplifies data management.

[0106] 27A and 27B are diagrams illustrating the effect of thickness distribution derivation according to this embodiment. Fig. 27A shows the correct data for the thickness distribution of the second layer, Fig. 27B shows the derived result (film thickness analysis result) for the thickness distribution of the second layer, and Fig. 27C shows the error between the correct data for the thickness distribution of the second layer and the derived result. As shown in Fig. 27C, the error between the correct data for the thickness distribution of the second layer and the derived result can be kept within ±1 nm, enabling the thickness distribution of the layer on the front side of the wafer to be derived with high accuracy.

[0107] The semiconductor device manufacturing method may further include a relationship information deriving step of deriving relationship information between the measurement parameters and the thickness distribution of the second layer based on the thickness distribution of the first layer acquired in the first step, and in a fourth step, deriving the thickness distribution of the second layer based on the relationship information derived in the relationship information deriving step and the measurement parameters derived in the third step. In this way, by deriving and using the relationship information between the measurement parameters and the thickness distribution of the second layer under the conditions of the acquired thickness distribution of the first layer, it is possible to quickly and accurately derive the thickness distribution of the layer on the front side of the wafer from the measurement parameters derived in the third step.

[0108] In the semiconductor device manufacturing method, the relational information deriving step may include deriving a theoretical reflectance for each thickness distribution of the second layer based on the thickness distribution of the first layer acquired in the first step and previously acquired thin film information of the second layer, and deriving measurement parameters for each thickness distribution of the second layer based on the theoretical reflectance for each thickness distribution of the second layer and previously acquired spectral characteristics, and deriving relational information between the measurement parameters and the thickness distribution of the second layer. In this way, by identifying the thickness distribution of the first layer and the thin film information of the second layer, the theoretical reflectance for each thickness distribution of the second layer can be derived with high accuracy. Then, by identifying the theoretical reflectance and spectral characteristics for each thickness distribution of the second layer, the measurement parameters for each thickness distribution of the second layer can be derived, and the above-mentioned relational information can be derived with high accuracy. With this configuration, the thickness distribution of the layer on the front side of the wafer can be derived with high accuracy from the measurement parameters derived in the third step using the relational information.

[0109] In the semiconductor device manufacturing method, the related information deriving step may be performed during the second step, thereby enabling the thickness distribution of the layer on the front side of the wafer to be quickly derived after the second step is performed.

[0110] In the semiconductor device manufacturing method, the relational information may be a relational expression obtained by fitting or a table. By using such relational information, the thickness distribution of the layer on the front side of the wafer can be derived quickly and accurately.

[0111] In the semiconductor device manufacturing method, the measurement parameter may be a wavelength centroid. With this configuration, the wavelength centroid, which has a high correlation with film thickness, is used as a measurement parameter to derive the thickness distribution of a layer on the front side of the wafer with high accuracy.

[0112] In the semiconductor device manufacturing method, the processing may be any of a film formation process, a photoresist coating process, an etching process, a planarization process, an electrode formation process, a pattern formation process, an insulating film formation process, a contact hole formation process, a contact formation process, a trench formation process, and a wiring formation process on the wafer 200. The thickness distribution of the second layer formed after these processes can be derived quickly and accurately using the above-described method. After the pattern formation process, it is difficult to derive the film thickness using conventional point measurements due to difficulties in alignment, etc. In this regard, the method according to the present embodiment eliminates the need for alignment, etc., after the pattern formation process, and therefore the thickness distribution of the layer on the front side of the wafer can be easily derived.

[0113] Although the present embodiment has been described using an example of a two-layer film structure for convenience, the present disclosure may also be applied to the manufacture of semiconductor devices having a multilayer film of three or more layers. That is, the method of the present disclosure may be used to measure the film thickness (derive the thickness distribution) of the outermost layer of a multilayer film of three or more layers. In this case, the "first layer" in the present disclosure refers to each layer present below the outermost layer, and the "second layer" refers to the outermost layer.

[0114] 200...wafer, 200b...film (first layer), 200c...film (second layer), 600...semiconductor device.

Claims

1. A semiconductor device manufacturing method comprising: a first step of irradiating light onto the wafer in a planar manner, with a first layer formed on the front surface of the wafer, capturing an image of the light from the wafer, and obtaining a thickness distribution of the first layer within the plane of the wafer based on a signal related to the image; a second step of forming a second layer by performing a predetermined processing process on the first layer; a third step after the second step of irradiating light onto the wafer in a planar manner, capturing an image of the light from the wafer, and obtaining a distribution of measurement parameters within the plane of the wafer based on the signal related to the image; and a fourth step of deriving a thickness distribution of the second layer based on the thickness distribution of the first layer obtained in the first step and the distribution of the measurement parameters derived in the third step.

2. A semiconductor device manufacturing method as described in claim 1, further comprising a relationship information derivation step of deriving relationship information indicating the relationship between the measurement parameters and the thickness of the second layer for each specified region based on the thickness distribution of the first layer obtained in the first step, and in the fourth step, deriving the thickness distribution of the second layer based on the relationship information derived in the relationship information derivation step and the distribution of the measurement parameters derived in the third step.

3. A semiconductor device manufacturing method as described in claim 2, wherein the related information deriving step comprises: deriving a theoretical reflectance for each of the predetermined regions for each thickness distribution of the second layer based on the thickness distribution of the first layer acquired in the first step and thin film information of the second layer acquired in advance; and deriving the measurement parameters for each of the predetermined regions for each thickness distribution of the second layer based on the theoretical reflectance for each thickness distribution of the second layer and the spectroscopic characteristics acquired in advance, and deriving the related information indicating the relationship between the measurement parameters and the thickness of the second layer for each of the predetermined regions.

4. The semiconductor device manufacturing method according to claim 3, wherein the related information deriving step is performed during the second step.

5. A semiconductor device manufacturing method according to any one of claims 2 to 4, wherein the relationship information is a relational expression obtained by fitting for each of the predetermined regions, or a table.

6. A semiconductor device manufacturing method according to any one of claims 1 to 5, wherein the measurement parameter is wavelength centroid.

7. A semiconductor device manufacturing method according to any one of claims 1 to 6, wherein the processing is any one of film formation processing, photoresist coating processing, etching processing, planarization processing, electrode formation processing, pattern formation processing, insulating film formation processing, contact hole formation processing, contact formation processing, trench formation processing, and wiring formation processing on the wafer.

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