JP2008203226A - Photoresist resin evaluating method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of evaluating line edge roughness (LER) and line-width roughness (LWR) of a photoresist resin, using a simple operation. <P>SOLUTION: First, the photoresist resin evaluating method comprises evaluating the line edge roughness and line width roughness characteristics of the photoresist resin with the elastic modulus uniformity of a thin film of the photoresist. Secondly, the photoresist resin evaluating method comprises measuring the thin film of the photoresist in an atomic force microscope tapping method and evaluating the line edge roughness and line width roughness characteristics of the photoresist resin with the property cycle of an obtained phase image. Thirdly, the photoresist resin evaluating method comprises measuring the thin film of the photoresist in the atomic force microscope tapping method and evaluating the elastic modulus uniformity of the thin film of the photoresist with the property cycle of an obtained elastic modulus change of the thin film. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for evaluating a photoresist resin.

In the field of electronic device manufacturing represented by integrated circuit element manufacturing, improvement of the degree of device integration is still strongly demanded, and advanced lithography technology development for fine pattern formation continues.
The photoresist composition used in lithography for forming a fine pattern is mainly a photoresist resin, a substance that generates acid when irradiated with light (hereinafter referred to as a photoacid generator), and if necessary. And consists of additives and solvent. In a positive photoresist composition, the photoresist resin changes from alkali-insoluble to alkali-soluble by an acid generated from a photoacid generator, and forms a positive resist pattern when developed with an alkali developer. In a negative photoresist composition, the photoresist resin undergoes a crosslinking reaction with an acid generated from a photoacid generator, changes from alkali-soluble to alkali-insoluble, and forms a negative resist pattern when developed with an alkali developer. To do.

As described above, the photoresist resin is a component that plays the main role of the photoresist composition, and development of the photoresist resin is indispensable for improving the performance of the photoresist composition.
In recent years, in order to achieve advanced lithography, photoresist compositions include resist patterns called line edge roughness (LER) and line width roughness (LWR), along with improvements in basic performance such as sensitivity, resolution, and etching resistance. Is required to be reduced in surface roughness (hereinafter referred to as LER / LWR).

Many studies have been conducted on the occurrence of LER / LWR, and various factors have been pointed out. For example, variations in the dissolution rate occur when the resist is developed due to statistical variations in the pattern formation process, variations in molecular weight (molecular weight dispersion), variations in the composition ratio between polymer chains, etc., resulting in the surface of the pattern Roughness occurs. Among these, as a generation mechanism of LER / LWR caused by the resist resin, a mechanism in which LER / LWR is generated has been reported because a region having different solubility is formed in the resist resin (see Non-Patent Document 1). .) Photoresist resins have been developed so as to suppress the generation mechanism of LER / LWR caused by the resist resin.
Latest resist material handbook-Material characteristics, design, control, trouble and countermeasure-, published by Information Organization Co., Ltd., 2005, pp. 198-207.

  When developing a photoresist resin that is a component of a photoresist composition with an improved LER / LWR, the LER / LWR when a resist pattern of the photoresist resin is formed with a photoresist composition containing the photoresist resin as a component. As a method for evaluating the influence on the resin (hereinafter referred to as photoresist resin LER / LWR characteristics), a photoresist composition is conventionally prepared using a photoresist resin, and the photoresist composition is applied onto a substrate. A method of forming a resist film, exposing the resist film, developing the resist film to form a resist pattern, and observing the resist pattern with a microscope or the like has been performed. Since this method requires many operations, it is complicated as an evaluation method. In addition to the photoresist resin LER / LWR characteristics, other photoresist composition components such as a photoacid generator, an additive, and a solvent; Since the evaluation is performed including the exposure condition; the influence on the LER and LWR such as the development condition, there is a problem that the evaluation method of the photoresist resin LER / LWR characteristics is not necessarily appropriate.

  The present invention has been made in earnest to solve the above problems, and its object is to provide a method for evaluating the photoresist resin LER / LWR characteristics of a photoresist resin by a simple operation. is there.

  As a result of intensive studies on the relationship between the physical properties of the photoresist resin and the LER / LWR mechanism caused by the above-described photoresist resin, the present inventors have found that the elastic modulus uniformity of the resist resin thin film The inventors have found that the photoresist resin LER / LWR characteristics can be evaluated, and have completed the present invention.

That is, the present invention
1. A method for evaluating a photoresist resin, characterized by evaluating the line edge roughness and line width roughness characteristics of the photoresist resin based on a uniform modulus of elasticity of the thin film of the photoresist resin;
2. A photo resist resin thin film is measured by an atomic force microscope tapping method, and the line edge roughness and line width roughness characteristics of the photoresist resin are evaluated based on the characteristic period of the obtained phase image. Resist resin evaluation method;
3. A photo resist resin thin film is measured by an atomic force microscope tapping method, and the elastic modulus uniformity of the photo resist resin thin film is evaluated by the characteristic period of the elastic modulus variation of the thin film obtained. Evaluation method of resin.

  With the evaluation method of the present invention, the photoresist resin LER / LWR characteristics of the photoresist resin can be evaluated by a simple operation. Therefore, the method of the present invention can be suitably used for developing a photoresist resin that is a component of a photoresist composition for manufacturing a semiconductor device, which is expected to be further miniaturized in the future.

  The photoresist resin thin film used in the evaluation method of the present invention is dried at a temperature of 70 ° C. to 160 ° C. after a photoresist resin solution to be evaluated is applied to a substrate such as glass, quartz, or silicon. By doing so, it can be formed. The film thickness of the thin film can be controlled by the concentration of the resin, preferably 50 nm to 1000 nm, and more preferably 100 nm to 500 nm. The surface of the thin film is preferably smooth, and specifically, the unevenness is preferably 2 nm or less. Examples of a method for producing such a thin film include a method commonly used for producing a photoresist film, such as a spin coating method.

  The elastic modulus uniformity of the photoresist resin thin film is evaluated by measuring a two-dimensional distribution of the elastic modulus variation of the photoresist resin thin film and evaluating the distribution.

  The two-dimensional distribution of the elastic modulus variation of the photoresist resin thin film can be measured by the tapping method of an atomic force microscope.

  The atomic force microscope tapping method is a method of measuring the shape of the sample surface while exciting the cantilever with a piezo driver and vibrating it. At this time, due to the elastic properties of the sample surface, a phase delay occurs in the vibration signal of the cantilever with respect to the signal of the piezo drive that vibrates the cantilever. A phase image is obtained by mapping and imaging this phase difference. A portion with a large phase delay is observed dark, while a portion with a small phase delay is observed brightly.

  As the atomic force microscope, for example, an atomic force microscope Dimension 3100 manufactured by Digital Instruments can be used.

  The atomic force microscope tapping method can be observed with good reproducibility by making the tapping force, which is the force with which the probe presses the sample, constant. Also, the use of a contaminated probe is not preferable because the obtained image is disturbed.

  The phase image thus obtained represents the elastic modulus variation distribution of the photoresist resin thin film. That is, the portion observed brightly in the phase image is a hard portion having a small phase delay, and the portion observed dark is a soft portion having a large phase delay.

  As a method of evaluating the elastic modulus uniformity from the phase image representing the elastic modulus fluctuation distribution, the phase image representing the elastic modulus fluctuation distribution may be visually evaluated to evaluate the uniformity, but a method of more clearly quantifying The characteristic wavelength (Λ) of the phase of the phase image can be obtained and evaluated by the magnitude of Λ.

  Λ first binarizes the above phase image; performs two-dimensional fast Fourier transform (2D-FFT transform); obtains an intensity distribution by averaging the rings; obtains a distance (qm) from the center where the intensity is maximum; Obtained by substituting qm into the equation Λ = 2π / qm.

  The binarization of the phase image can be performed using image analysis software such as Photoshop 5.0LE manufactured by Adobe, for example. By binarizing the phase image, the period can be analyzed more clearly.

  The 2D-FFT conversion can be performed using image analysis software such as Image-Pro Plus manufactured by Media Cybernetics. A 2D-FFT image is obtained by performing 2D-FFT conversion on the phase image. The obtained 2D-FFT image represents the strength of correlation between a specific distance and direction.

  Next, the intensity distribution can be obtained by averaging the intensity of the 2D-FFT image in an annular shape (average of the intensity with respect to the distance (q) from the center of the 2D-FFT image). The ring average can be performed using image analysis software such as Image-Pro Plus manufactured by Media Cybernetics.

  The characteristic wavelength (Λ) is obtained by obtaining the distance (qm) from the center where the intensity is maximum from the intensity distribution obtained using the circular average, and substituting qm into the expression Λ = 2π / qm.

  The elastic modulus uniformity thus obtained is an index representing the LER / LWR characteristics of the photoresist resin. The reason is described below.

The solubility of the photoresist resin is presumed to be affected by the density of polymer chain ends in the resin (hereinafter referred to as end density). It is easy to dissolve when the end density is high, and dissolves when the end density is low. It is considered difficult to do.
The resin elastic modulus is also estimated to be affected by the terminal density, and is considered to be soft (low elastic modulus) when the terminal density is high and hard (high elastic modulus) when the terminal density is low.
From these, in the two-dimensional distribution of the elastic modulus variation used in the evaluation method of the present invention, the soft region represents a region having a high terminal density, and thus a region having high solubility; a hard region represents a region having a low terminal density. Therefore, it is considered that the solubility is low.
Furthermore, since LER / LWR is considered to be caused by non-uniform resin solubility, LER / LWR is unlikely to occur in a photoresist resin with high elastic modulus uniformity. In the case of a photoresist resin having a low value, LER / LWR is likely to occur.
From the above, it can be said that the elasticity modulus uniformity serves as an index representing the LER / LWR characteristics of the photoresist resin, and the LER / LWR characteristics of the photoresist resin can be evaluated by the elasticity modulus uniformity.

  The photoresist resin that can be evaluated by the evaluation method of the present invention is not particularly limited, and any photoresist resin of a negative photoresist resin and a positive photoresist resin can be evaluated.

  EXAMPLES Hereinafter, although an Example demonstrates this invention concretely, this invention is not limited at all by these Examples. The weight average molecular weight (Mw) and dispersity (Mw / Mn) of the polymer compound were determined by GPC analysis [column: TSK-gel SUPER HZM-H (trade name, 4.6 mm × 150 mm, manufactured by Tosoh Corporation) and TSK. -Gel SUPER HZ2000 (manufactured by Tosoh Corporation, 4.6 mm x 150 mm) was measured in series, eluent: tetrahydrofuran, calibration curve: polystyrene standard].

<Synthesis Example 1>
Synthesis of photoresist resin (1)

  In a 100 ml round bottom flask equipped with a nitrogen inlet, a stirrer, a reflux condenser and a thermometer, under a nitrogen atmosphere, 4.39 g (18.7 mmol) of 2-methacryloyloxy-2-methyladamantane, 1-hydroxy -3-methacryloyloxyadamantane 2.21 g (9.4 mmol), α-methacryloyloxy-γ-butyrolactone 3.18 g (18.7 mmol), methyl ethyl ketone 44 ml, and azoisobutyronitrile 0.66 g (4.0 mmol) And polymerized at 80 ° C. for 4 hours. The obtained reaction solution was added dropwise with stirring to 1000 ml of methanol at room temperature to obtain a white precipitate. The obtained precipitate was filtered off and dried under reduced pressure for 10 hours to obtain 6.06 g of photoresist resin (1). Mw = 8500, Mw / Mn = 1.93, l: m: n = 39: 20: 41.

<Synthesis Example 2>
Synthesis of photoresist resin (2) 5.0 g of the photoresist resin (1) obtained by the same method as in Synthesis Example 1 was dissolved once again in 44 mL of methyl ethyl ketone, and then added dropwise with stirring to 1000 mL of methanol at room temperature. A white precipitate was obtained. The obtained precipitate was filtered off and dried under reduced pressure for 10 hours to obtain 4.12 g of the desired photoresist resin (2). Mw = 11400, Mw / Mn = 1.51, l: m: n = 39: 20: 41.

<Synthesis Example 3>
The same method as in Synthesis Example 1 was performed except that 0.26 g of lauryl mercaptan was used as a synthetic chain transfer agent for the photoresist resin (3). 6.23 g of the desired photoresist resin (3) was obtained. Mw = 7000, Mw / Mn = 1.55, l: m: n = 36: 21: 43.

<Synthesis Example 4>
The same method as in Synthesis Example 1 was performed except that 0.15 g of 2-mercaptopropionic acid was used as a synthetic chain transfer agent for the photoresist resin (4). 5.95 g of the desired photoresist resin (4) was obtained. Mw = 8200, Mw / Mn = 1.57, l: m: n = 36: 21: 43.

<Synthesis Example 5>
Synthesis of photoresist resin (5)

  In a 100 ml round bottom flask equipped with a nitrogen inlet, a stirrer, a reflux condenser and a thermometer, under a nitrogen atmosphere, 4.39 g (18.7 mmol) of 2-methacryloyloxy-2-methyladamantane, 1-hydroxy -3-methacryloyloxyadamantane 2.21 g (9.4 mmol), methacryloyloxy-2-norbornanelactone 4.16 g (18.7 mmol), methyl ethyl ketone 44 ml, and azoisobutyronitrile 0.66 g (4.0 mmol) were added. And polymerized at 80 ° C. for 4 hours. The obtained reaction solution was added dropwise to 1000 ml of methanol with stirring at room temperature to obtain a white precipitate. The obtained precipitate was collected by filtration and dried under reduced pressure for 10 hours to obtain 7.15 g of the target polymer compound 4. Mw = 9700, Mw / Mn = 2.27, and l: m: n = 37: 21: 42.

<Atomic force microscope evaluation>
<Example 1>
The photoresist resin (1) obtained in Synthesis Example 1 was dissolved in dioxane to prepare a photoresist resin solution having a resin concentration of 12% by mass. After filtering this photoresist resin solution using a filter (made of tetrafluoroethylene resin (PTFE)) (0.2 μm), it was applied on a glass substrate by a spin coating method and dried by heating at 130 ° C. for 5 minutes. A thin film having a thickness of about 200 nm was formed. The surface of this thin film was measured by a tapping method using an atomic force microscope (Atomic Force Microscope Device Dimension 3100 manufactured by Digital Instruments) to obtain a phase image (FIG. 1) and an uneven image (FIG. 2). The measurement was performed for a range of 200 × 200 [nm] and recorded at 256 × 256 [pixel]. As shown in FIG. 2, the surface unevenness was very smooth, less than 2 nm, and no special structure was found. On the other hand, in the phase image, a periodic structure was seen as shown in FIG.

  Next, the periodic structure seen in the phase image was quantified using image analysis software. First, in order to analyze the period more clearly, the image was binarized using image analysis software (Photoshop 5.0LE manufactured by Adobe). Next, the binarized phase image was subjected to 2D-FFT conversion using image analysis software (Image-Pro Plus manufactured by Media Cybernetics) to obtain a 2D-FFT image shown in FIG.

  The size of the obtained 2D-FFT image is 256 × 256 [pixels]. In FIG. 3, the unit of the distance (q) from the center is = 0.00314 [1 / (nm · pixel)]. The 2D-FFT image was circularly averaged at a distance (q) from the center to obtain an intensity distribution (FIG. 4).

From FIG. 4, the distance (q _m ) from the center where the intensity is maximum was 0.26 [1 / nm]. The characteristic wavelength (Λ) was 24 [nm] from the equation Λ = 2π / q _m .

<Examples 2 to 5>
Surface irregularities and Λ were determined in the same manner as in Example 1 except that the photoresist resins (2) to (5) were used instead of the photoresist resin (1). The results are shown in the table.

  As shown in Table 1, the characteristic wavelength (Λ) for each photoresist resin was determined. It is presumed that the photoresist resin LER / LWR can be evaluated based on these sizes.

2 is a photograph of a phase image obtained by tapping method measurement using an atomic force microscope obtained in Example 1. FIG. The length of one side corresponds to 200 nm. 2 is a photograph of a concavo-convex image obtained by tapping method measurement with an atomic force microscope obtained in Example 1. FIG. The length of one side corresponds to 200 nm. The maximum unevenness scale is 2 nm. 2 is a photograph of a 2D-FFT image obtained in Example 1. FIG. 6 is a diagram illustrating a relationship between a distance (q) from the center of the 2D-FFT image obtained in Example 1 and intensity. FIG.

Claims (3)

  A method for evaluating a photoresist resin, comprising evaluating the line edge roughness characteristics and the line width roughness characteristics of the photoresist resin based on the elastic modulus uniformity of the thin film of the photoresist resin.   The thin film of the photoresist resin is measured by an atomic force microscope tapping method, and the line edge roughness characteristic and the line width roughness characteristic of the photoresist resin are evaluated by the characteristic period of the obtained phase image, Evaluation method for photoresist resin.   A photo resist resin thin film is measured by an atomic force microscope tapping method, and the elastic modulus uniformity of the photo resist resin thin film is evaluated by a characteristic period of the elastic modulus variation of the obtained thin film. Evaluation method of resist resin.