JP2010223779A - Method of inspecting thin film and thin-film inspection apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of inspecting thin films capable of ideally inspecting a diffused state of a thin film in solution. <P>SOLUTION: The method of inspecting thin-film inspects thin films for inspecting diffused state of a thin-film material in solution. The thin-film inspection method includes the thin-film formation process for forming a thin film by a thin-film material, including a fluorescent particle on a substrate; a solution impregnation process for impregnating the substrate in the solution; an excitation light irradiation process for applying excitation light to the fluorescent particle vertical to the substrate in the solution; an image acquisition process for acquiring an image near the substrate while applying excitation light; a luminance distribution acquisition process for acquiring luminance distribution of a fluorescent particle from the image; and a calculation processing for calculating the degree of diffusion of a thin-film material dispersed to the solution from the luminance distribution. Since the fluorescent particles are mixed with the thin-film material, diffusion of the fluorescent particle following the diffusion of the thin-film material can be tracked and observed by the exciting light. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a thin film inspection method and a thin film inspection apparatus suitable for carrying out the thin film inspection method.

  In the lithography method, which is a fine processing technique, improvement in development resolution is required. In the lithography method, a resist is applied onto a substrate, the resist is irradiated with exposure light, and the resist is dissolved in a developer using a difference in polarity or molecular weight to form an arbitrary shape. At this time, in order to achieve high resolution of the resist shape, it is required to evaluate and optimize the relationship between the exposure amount of exposure light and resist characteristics such as development speed.

  Various thin film inspection apparatuses have been proposed as a method for evaluating characteristics of a thin film such as a resist.

For example, a thin film inspection apparatus using optical means has been proposed (see Patent Document 1).
As shown in FIG. 1, among the light 3 irradiated from the light source, the interference is caused by the optical path difference between the light 4 reflected by the surface of the resist thin film 1 and the light 5 transmitted and reflected by the substrate 2. Measure the thickness. Thus, the change in film thickness due to dissolution of the resist in the developer can be measured to evaluate the development characteristics.

  However, in a thin film inspection apparatus using optical means, in principle, the film thickness is limited to a range where laser light can interfere, and in the case of a film thickness outside the range where laser light can interfere, measurement can be performed with sufficient accuracy. Can not. In addition, the measurement site is limited to a narrow range where the laser beam hits. For this reason, it has been difficult to observe the spatial diffusion of the thin film formed on the substrate into the solution.

For example, a thin film inspection apparatus using a crystal resonator has been proposed (see Patent Document 2).
As shown in FIG. 2, in the method using a crystal resonator, a substance such as a resist is applied to the crystal resonator 6 attached to the electrode plate 7, a voltage is applied to the electrode 8, and the electricity due to the piezoelectric properties of the crystal is applied. It is possible to measure the change in film thickness by measuring the change in the resonant frequency.

  However, in a thin film inspection apparatus using a crystal resonator, since the piezoelectric property of the crystal is used, only the crystal can be used for the substrate. Therefore, the material of the film to be processed is limited to that which can be applied to the crystal, A thin film formed on a substrate other than quartz cannot be evaluated. Further, since the substrate itself swings slightly, it is difficult to accurately evaluate the diffusion of the thin film formed on the substrate into the solution.

JP 7-71924 A JP 2001-349816 A

  In the conventional thin film inspection apparatus as described above, it is difficult to observe the diffusion state of the thin film material in the solution.

  Then, an object of this invention is to provide the thin film inspection method which can test | inspect suitably the diffusion state of the thin film material in a solution.

  The present invention according to claim 1 is a thin film inspection method for inspecting a diffusion state of a thin film material in a solution, the thin film forming step of forming a thin film using a thin film material containing fluorescent particles on a substrate, A solution immersion step of immersing the substrate in the solution, an excitation light irradiation step of irradiating the fluorescent particles with excitation light perpendicular to the substrate in the solution, and an image for acquiring an image near the substrate while irradiating the excitation light A thin film comprising: an acquisition step; a luminance distribution acquisition step of acquiring a luminance distribution of fluorescent particles from the image; and a calculation step of calculating a diffusion degree of the thin film material diffused into the solution from the luminance distribution. Inspection method.

  According to a second aspect of the present invention, in the image acquisition step, a plurality of images are acquired by acquiring images every unit time, and in the calculation step, from a luminance distribution of the plurality of images, a predetermined region is acquired. The thin film inspection method according to claim 1, wherein brightness per unit area is acquired and a change in concentration per unit time of the thin film material diffused in the solution is calculated.

  According to the third aspect of the present invention, in the calculation step, the total amount of the thin film material diffused in the solution is calculated from the luminance integration in the luminance distribution of the image, and the film thickness of the thin film on the remaining substrate surface is calculated. The thin film inspection method according to claim 1, wherein:

  According to a fourth aspect of the present invention, in the image acquisition step, a plurality of images are acquired by acquiring images every unit time, and in the calculation step, the diffused thin film material is extracted from the luminance distribution of the images. The thin film inspection method according to claim 1, wherein a diffusion length with respect to a unit time is calculated.

  The present invention according to claim 5 is a substrate, a thin film formed using a thin film material containing fluorescent particles on the substrate, a solution bath in which the substrate is immersed, and excitation light into the solution bath. An illumination light source, an image acquisition mechanism for acquiring an image in the solution tank, and a calculation mechanism for calculating the diffusivity of the thin film material in the solution from the luminance distribution of the image acquired by the image acquisition mechanism. Is a thin film inspection apparatus.

  Since the thin film inspection method of the present invention mixes fluorescent particles with a thin film material, the diffusion of the fluorescent particles accompanying the diffusion of the thin film material can be tracked and observed using excitation light. At this time, since the luminance distribution of the fluorescent particles has a correlation with the concentration of the thin film material, the degree of diffusion of the thin film material in the solution at the time of observation can be evaluated from the luminance distribution of the fluorescent particles. Therefore, the diffusion state of the thin film material in the solution can be suitably inspected.

It is the schematic which shows the thin film inspection apparatus using the conventional optical means. It is the schematic which shows the thin film inspection apparatus using the conventional crystal oscillator. It is a flowchart figure which shows one Embodiment of the thin film test | inspection method of this invention. It is a perspective schematic diagram concerning the thin film inspection device of the present invention. It is the schematic which concerns on the thin film inspection apparatus of this invention. It is the schematic which concerns on the thin film inspection apparatus of this invention.

  Hereinafter, the thin film inspection method of the present invention will be described.

<Thin film formation process>
First, a thin film is formed on a substrate using a thin film material containing fluorescent particles.

  The substrate is not particularly limited as long as it has a mechanical strength that can support the thin film to be inspected. Specifically, for example, a silicon substrate, a quartz substrate, a glass substrate, a resin substrate, a metal substrate, or the like may be used.

  The fluorescent particles are particles that emit light by irradiation with excitation light described later. A material exhibiting fluorescence is supported on a carrier to form particles, and the particle size may be about 20 nm to 300 μm. At this time, a resin such as silica or polystyrene can be used as the carrier.

As the thin film forming method, a known thin film forming method may be used as appropriate according to the characteristics of the thin film material used for the thin film to be inspected. Specific examples include thin film forming methods such as dip coating, casting, spin coating, vacuum deposition, and electric field polymerization.
Further, before the thin film is formed, the substrate may be subjected to a surface treatment such as HMDS (Hexamethyldisilazane) treatment or UV treatment.

<Solution immersion process>
Next, the substrate on which the thin film is formed is immersed in the solution.

  The solution may be a solution corresponding to the thin film material used for the thin film to be inspected, and may be appropriately set according to the inspection environment. For example, when a resist material is inspected and evaluated, a developer for the resist material may be used.

The solution may be a stirred solution. In the thin film inspection method of the present invention, since the degree of diffusion of the thin film material is evaluated from the luminance distribution of the fluorescent particles, how the thin film material diffuses in the solution even when the solution is stirred. Can be observed.
Since the conventional thin film evaluation apparatus is an immersion type, it has been difficult to evaluate how the thin film material diffuses into such a stirred solution.
In a development process in a semiconductor, a substrate coated with a resist is often developed by a paddle method or the like, and the replacement efficiency of the developer on the resist thin film surface is high. For this reason, the thin film inspection method of the present invention can be suitably used particularly for evaluating the diffusion state of the developer of the resist material.

<Excitation light irradiation process>
Next, the excitation light for the fluorescent particles is irradiated into the solution to cause the fluorescent particles to emit light. By irradiating with excitation light, fluorescent particles can be emitted.

  The excitation light may be light having a wavelength corresponding to the fluorescent particles used.

<Image acquisition process>
Next, the light emission of the fluorescent particles in the solution is acquired as an image.

  As the image acquisition unit, a known image acquisition unit may be used as appropriate, and a still image may be acquired with an optical camera. Further, by acquiring images continuously every certain unit time, the degree of diffusion of the thin film material for each elapsed time can be evaluated. The image acquisition means may be a moving image.

<Calculation process>
Next, the luminance distribution of the fluorescent particles is acquired from the image acquired in the image acquisition step, and the diffusion degree of the thin film material is calculated from the luminance distribution.
Since the degree of diffusion of the fluorescent particles and the degree of diffusion of the thin film material can be regarded as almost equal, the luminance distribution of the fluorescent particles has a correlation with the concentration of the thin film material. For this reason, the diffusion degree of the thin film material in the solution at the time of observation can be evaluated from the luminance distribution of the fluorescent particles. Therefore, the diffusion state of the thin film material in the solution can be suitably inspected.
Since the present invention utilizes the correlation between the luminance distribution of the fluorescent particles and the concentration of the thin film material, the accumulated luminance of the entire dissolution zone is compared with the volume of the dissolved resist thin film, By creating the correlation reference data, the concentration of the thin film material can be calculated from the brightness of the unknown fluorescent particles.

For example, “In the image acquisition step, a plurality of images are acquired by acquiring images per unit time, and in the calculation step, the luminance per unit area of a predetermined part is acquired from the luminance distribution of the plurality of images. Then, the concentration change per unit time of the thin film material diffused into the solution may be calculated.
Since the change over time in the brightness of the fluorescent particles at the specified site in the acquired image correlates with the change over time in the concentration of the thin film material at the specified site, it is possible to calculate the concentration change per unit time of the thin film material that has diffused into the solution. I can do it.

For example, “in the calculation step, the total amount of thin film material diffused in the solution may be calculated from the luminance integration in the luminance distribution of the image, and the film thickness of the thin film on the remaining substrate surface may be calculated”.
The luminance distribution of the fluorescent particles has a correlation with the concentration distribution of the fluorescent particles. At this time, the number of fluorescent particles in the solution is the same in the thin film state before diffusion and in the state of diffusion in the solution, and therefore the luminance integration is always a constant value in the luminance distribution of the fluorescent particles. Therefore, by integrating the luminance distribution in the solution, the total amount of the thin film material eluted in the solution can be calculated. Further, by subtracting the integrated value of the luminance distribution of the fluorescent particles in the solution from the integrated value of the luminance distribution of the fluorescent particles in the state of the thin film before diffusion, the fluorescent particles remaining on the substrate are subtracted. The quantity can be calculated, whereby the quantity of thin film material remaining on the substrate (the film thickness of the thin film remaining on the substrate) can be obtained from the quantity of fluorescent particles remaining on the substrate. I can do it.

For example, “In the image acquisition step, a plurality of images are acquired by acquiring images per unit time, and in the calculation step, the diffusion length of the diffused thin film material per unit time is calculated from the luminance distribution of the image. "You may."
In the acquired image, the portion where the luminance has changed due to the emission of the fluorescent particles can be regarded as the portion where the diffused thin film material has reached. For this reason, in the image, the diffusion length per unit time of the diffused thin film material can be calculated from the change over time of the portion where the luminance change caused by the emission of the fluorescent particles.

As an example, FIG. 3 shows a flowchart of the thin film inspection method of the present invention in the case of inspecting a resist thin film.
First, a resist thin film containing fluorescent particles is formed on a substrate.
Next, the substrate is immersed in a developer.
Next, while being immersed, excitation light is irradiated perpendicularly to the substrate.
Next, an image of the diffusion state of the resist thin film is acquired with irradiation.
Next, the luminance distribution of the fluorescent particles is acquired from the image.
Next, the volume of the resist thin film dissolved in the developer is calculated from the acquired luminance distribution.

From the above, the thin film inspection method of the present invention can be carried out.
According to the thin film inspection method of the present invention, the film thickness in the thin film in the solution and the diffusion degree of the thin film material can be observed and evaluated from the luminance distribution of the fluorescent particles.

Hereinafter, the thin film inspection apparatus of the present invention will be described.
The thin film inspection apparatus of the present invention irradiates excitation light into a substrate, a thin film formed using a thin film material containing fluorescent particles on the substrate, a solution tank in which the substrate is immersed, and the solution tank. A light source; an image acquisition mechanism for acquiring an image in the solution tank; and a calculation mechanism for calculating a diffusivity of the thin film material in the solution from the luminance distribution of the image acquired by the image acquisition mechanism.

  According to the thin film inspection apparatus of the present invention, the fluorescent particles diffusing in the solution can emit light by irradiating with excitation light, and the emission of the fluorescent particles can be acquired as an image. At this time, the luminance distribution of the acquired image is correlated with the concentration distribution of the diffused fluorescent particles, and from the luminance distribution of the image, the diffusion degree of the thin film material in the solution at the time of observation can be evaluated from the luminance distribution of the fluorescent particles. I can do it. Therefore, the diffusion state of the thin film material in the solution can be suitably inspected.

  FIG. 4 shows a schematic view in which the substrate 2 is installed in the thin film inspection apparatus of the present invention. In FIG. 4, the substrate 2, the resist thin film 1 formed on the substrate 2, the exposed portion 16 of the resist thin film that is the pattern exposure portion of the resist thin film 1, the excitation light source 9 that irradiates the observation site with excitation light, and the light source 9. Excitation light 10 irradiated from the camera 11 and a camera 11 for imaging an observation site.

  FIG. 5 is a schematic view of the thin film inspection apparatus of the present invention viewed from the y-axis direction of FIG. In FIG. 5, the solution tank 12 filled with the developer 13 is disposed on the y-axis extension line with respect to the substrate 2, and the substrate 2 is immersed in the developer 13 when the substrate 2 is immersed.

  FIG. 6 is a schematic view of the thin film inspection apparatus of the present invention viewed from the x-axis direction of FIG.

  In FIG. 6, when the observation range is long in the z direction and short in the y direction, a spatial distribution of luminance that changes in the y direction and the z direction is obtained from the acquired image. Assuming that the resist thin film changes isotropically with time, the time change of the luminance distribution in the z direction corresponds to the time change of the diffusion distance of the resist thin film. Therefore, the diffusion length with respect to time of the resist thin film can be calculated.

  In FIG. 6, when the observation range is the observation range 15 short in the z direction and y direction near the resist thin film surface, the resist thin film dissolves in the developer, and the luminance per area of the selected region increases. For this reason, the density change of the resist thin film relative to the developer in the selected region can be calculated from the luminance distribution of the image and the correlation reference data.

  In FIG. 6, when the observation range is the entire area where the resist thin film is dissolved, the total volume of the dissolved resist thin film is calculated from the integration of luminance in the entire dissolution area of the image obtained by imaging the entire area and the reference data, The film thickness of the remaining resist thin film can be calculated. Further, at this time, by obtaining the change with time of the whole region of dissolution of the resist thin film, it is possible to calculate the time change of the film thickness of the resist thin film.

  Hereinafter, the thin film inspection method of the present invention will be specifically described.

First, fluorescent particles were mixed in the positive resist thin film 1.
The fluorescent particles are PSL (polystyrene) particles that emit red light when irradiated with single-wavelength light having a wavelength of 542 nm, and those having a particle diameter of 0.025 μm and a particle density of 1.05 g / cm ² were selected. The mixing ratio was 5% by volume with respect to the resist thin film.

Next, a positive resist thin film 1 mixed with fluorescent particles was applied to a glass substrate 2.
At this time, a resist coating method was used as a coating method. The conditions of the resist coating method were a temperature of 23 ° C., a humidity of 50%, a rotation speed of 1000 rpm, and a film thickness of about 0.7 μm.
Moreover, after apply | coating a resist, the heat processing for 10 minutes were performed at 120 degreeC.

Next, a pattern was drawn by electron beam exposure on the substrate 2 on which the resist thin film 1 was formed.
At this time, an electron beam was used as an exposure light source for the resist thin film 1. A 3 mm square pattern was drawn.
Moreover, after drawing, the heat processing for 10 minutes were performed at 110 degreeC.

Next, the substrate 2 on which the resist thin film 1 was applied and drawn was immersed in the developer 13.
At this time, TMAH (Tetra methyl ammonium hydroxide) was used as the developer 13.

  Next, the elution state of the resist thin film 1 in the developer 13 was acquired as an image by a camera.

  Next, image processing was performed on the obtained image to obtain a luminance distribution in the image.

  Next, the concentration of the resist material within the range imaged by the camera was calculated from the acquired luminance distribution, and the change in film thickness over time could be acquired as data.

  The thin film inspection method of the present invention can be used in a field where it is required to inspect the diffusion state of a thin film in a solution. Specifically, for example, it can be used to evaluate the diffusion state of a developer of a resist material in a lithography method that is a fine processing technique.

DESCRIPTION OF SYMBOLS 1 ... Resist thin film 2 ... Board | substrate 3 ... Exposure light 4 ... Reflected light of resist thin film surface 5 ... Reflected light which permeate | transmitted resist thin film 6 ... Crystal oscillator 7 ... Electrode plate 8 ... Electrode 9 ... ... light source 10 ... excitation light 11 ... camera 12 ... developer tank 13 ... developer 14 ... observation range 15 ... observation range 16 ... exposed portion of resist thin film

Claims (5)

A thin film inspection method for inspecting a diffusion state of a thin film material in a solution,
A thin film forming step of forming a thin film using a thin film material containing fluorescent particles on a substrate;
A solution immersion step of immersing the substrate in a solution;
An excitation light irradiation step of irradiating the fluorescent particles with excitation light perpendicular to the substrate in the solution;
An image acquisition step of acquiring an image near the substrate while irradiating the excitation light;
A luminance distribution acquisition step of acquiring a luminance distribution of fluorescent particles from the image;
A calculation step of calculating the degree of diffusion of the thin film material diffused into the solution from the luminance distribution;
A thin film inspection method comprising: In the image acquisition step, a plurality of images are acquired by acquiring images every unit time,
2. In the calculation step, the luminance per unit area of a predetermined part is acquired from the luminance distribution of the plurality of images, and the concentration change per unit time of the thin film material diffused in the solution is calculated. The thin film inspection method described in 1. 2. The calculation step according to claim 1, wherein the total amount of the thin film material diffused in the solution is calculated from the luminance integration in the luminance distribution of the image, and the film thickness of the thin film on the remaining substrate surface is calculated. The thin film inspection method described. In the image acquisition step, a plurality of images are acquired by acquiring images every unit time,
The thin film inspection method according to claim 1, wherein in the calculation step, a diffusion length per unit time of the diffused thin film material is calculated from the luminance distribution of the image. A substrate,
A thin film formed using a thin film material containing fluorescent particles on the substrate;
A solution bath for immersing the substrate;
A light source for irradiating excitation light into the solution tank;
An image acquisition mechanism for acquiring an image in the solution tank;
A calculation mechanism for calculating the diffusivity of the thin film material in the solution from the luminance distribution of the image acquired by the image acquisition mechanism;
A thin film inspection apparatus comprising:

Images