JP2009227590A - Method for producing alicyclic saturated hydrocarbon compound - Google Patents

Abstract

[PROBLEMS] To improve the transmittance of an alicyclic saturated hydrocarbon compound suitable as an immersion exposure liquid having excellent transmittance at 193 nm, and to reduce the manufacturing cost and stably provide an immersion exposure liquid. Manufactured industrially.
A method for producing an alicyclic saturated hydrocarbon compound having an average transmittance of 99% or more per 1 mm optical path length of a liquid at a wavelength of 193 nm, the raw alicyclic saturated hydrocarbon compound being alumina. And a liquid contact step in which at least one adsorbent selected from silica alumina and zeolite is contacted for 2 to 20 hours, and the shape of the adsorbent used in the step is agglomerates such as pellets or beads.
[Selection figure] None

Description

  The present invention relates to a method for producing an alicyclic saturated hydrocarbon compound, and more particularly to a method for producing an alicyclic saturated hydrocarbon compound capable of improving the transmittance for use in an immersion exposure apparatus or an immersion exposure method.

Stepper-type or step-and-scan projection exposure that transfers a reticle pattern as a photomask to each shot area on a photoresist-coated wafer via a projection optical system when manufacturing semiconductor elements, etc. The device is in use.
The theoretical limit value of the resolution of the projection optical system provided in the projection exposure apparatus becomes higher as the exposure wavelength used is shorter and the numerical aperture of the projection optical system is larger. For this reason, with the miniaturization of integrated circuits, the exposure wavelength, which is the wavelength of radiation used in the projection exposure apparatus, has become shorter year by year, and the numerical aperture of the projection optical system has also increased.
As described above, in the field of manufacturing semiconductor devices and the like, conventionally, the exposure light source has been shortened in wavelength and the numerical aperture has been increased to meet the demand for miniaturization of an integrated circuit. At present, an ArF excimer laser (wavelength: 193 nm) is used as an exposure light source. ) Using 1L1S (1: 1 line and space) half pitch 90 nm node is under study. However, it is said that it is difficult to achieve the next generation half pitch 65 nm node or 45 nm node, which is further miniaturized, only by using an ArF excimer laser. Thus, for these next-generation technologies, the use of short-wavelength light sources such as F ₂ excimer laser (wavelength 157 nm), EUV (wavelength 13 nm), etc. is being studied. However, the use of these light sources is technically difficult and is still difficult to use.

In the above exposure technique, a photoresist film is formed on the exposed wafer surface, and a pattern is transferred to the photoresist film. In a conventional projection exposure apparatus, a space in which a wafer is placed is filled with air or nitrogen having a refractive index of 1.
Theoretically, the limit value of resolution and the depth of focus are increased to 1 / n and n times, respectively, by filling a liquid of refractive index n between the lens of the projection exposure apparatus and the wafer and setting an appropriate optical system. Is possible. For example, in the ArF process, when water is used as the liquid filled between the lens and the wafer, the refractive index n of water having a wavelength of 193 nm in water is n = 1.44. In comparison, it is theoretically possible to design an optical system with a resolution of 69.4% and a focal depth of 144%.
A projection exposure method capable of shortening the effective wavelength of radiation for exposure and transferring a finer pattern is referred to as immersion exposure, and for future miniaturization of lithography, particularly lithography of several tens of nanometers, It is considered an essential technology.

In the immersion exposure method, the applicant of the present invention has a refractive index larger than that of pure water conventionally used as a liquid for immersion exposure, and has excellent transparency, and a photoresist film or its upper layer film component (especially hydrophilic layer). Liquid) that can prevent elution and dissolution of the active ingredient), suppress the defects during resist pattern generation without eroding the lens, and can form patterns with better resolution and depth of focus when used as an immersion liquid. As a result of investigating various compounds for the purpose of providing immersion exposure liquids, we have filed applications for alicyclic saturated hydrocarbon compounds that have low absorption in the far ultraviolet region and have a high refractive index suitable as immersion exposure liquids. (Patent Document 1).
However, when an alicyclic saturated hydrocarbon compound synthesized by a known method or available on the market is used as a liquid for immersion exposure, it generally has a large absorption in the far ultraviolet region. There are cases where problems such as degradation of throughput due to decrease in throughput due to reduction, optical image defocus and distortion due to refractive index fluctuation due to heat generation of liquid due to light absorption of liquid, degradation of pattern shape, etc. due to defocus of optical image there were.

Absorption in the far-ultraviolet region is a compound having a carbon-carbon unsaturated bond or an aromatic ring, which has a large influence on the transmittance even in a very small amount, and a compound having a functional group such as a carbonyl group or a hydroxyl group as impurities. The alicyclic saturated hydrocarbon compound is considered to be slightly present, and therefore includes a plurality of sulfuric acid washing treatment steps having different treatment temperatures, and at least the final sulfuric acid washing treatment step has a treatment temperature higher than that of the washing treatment step. The present inventors have already proposed a method characterized by processing at a processing temperature lower than the processing temperature of the previous processing step (Patent Document 2). Moreover, the method of refine | purifying an alicyclic saturated hydrocarbon compound using an adsorbent is disclosed (patent documents 3 and 4).
However, even with the above purification method, there are problems that the transmittance at 193 nm of the alicyclic saturated hydrocarbon compound is not sufficiently improved, and the man-hours are complicated. For example, in the method of Patent Document 3, the transmittance at 193 nm cannot be increased to 99% or more per 1 mm of the optical path length. Further, the method of Patent Document 4 has a problem that two kinds of adsorbents must be used to increase the transmittance. Furthermore, the methods of Patent Document 3 and Patent Document 4 have a problem that when an attempt is made to industrially manufacture a liquid for immersion exposure, an alicyclic saturated hydrocarbon compound cannot be efficiently treated with an adsorbent.

  Techniques for industrial production of immersion exposure liquid by adsorbent treatment include fixed bed method, stirring tank adsorption method, moving bed method, fluidized bed method, etc. A stirred tank adsorption method is often used. However, when an attempt is made to remove impurities in the alicyclic saturated hydrocarbon compound so that the transmittance at 193 nm is 99% or more per 1 mm of the optical path length by the stirring tank adsorption method, it is necessary to carry out the batch stirring operation a plurality of times. is there. In some cases, the batch agitation operation is required three times or more, which increases the number of processes and the number of equipment, which may increase the product cost and make quality control difficult. On the other hand, the process of the fixed bed method is simple and has a small number of equipment. Moreover, since the amount of adsorbent required for the adsorption treatment is smaller than that of the stirring tank method, the product cost can be reduced. This is because the amount of impurities that can be removed per unit weight of the adsorbent increases in the fixed bed method.

The particle size of the adsorbent is greatly related to the rate of adsorbing impurities. For example, since the powdery adsorbent has a large surface area, the adsorption rate is higher than that of the pellet-like or bead-like adsorbent. That is, when a powdered adsorbent is used in a fixed bed type, the column length can be shortened, which is suitable for on-site adsorption processing that requires a small apparatus. Here, “pellet” refers to a cylindrical solid, and “bead” refers to a spherical solid.
However, when a powdery adsorbent is used, there is a problem that pressure loss increases. When the same liquid feed pump is used, it is necessary to reduce the flow rate, but this is not preferable because productivity decreases with a decrease in flow rate. In order to maintain the flow rate, it is necessary to increase the column diameter. However, as the column diameter increases, the flow in the column tends to be biased, and an alicyclic saturated hydrocarbon compound with insufficient impurity removal can be obtained. There is a possibility that.
Further, when the liquid for immersion exposure is a fixed layer type and an industrial production is attempted using a powdery adsorbent, there is a problem that handling is bad. A powder having a particle size of several to several hundreds of μm is likely to rise when put into a column or a stirring tank, and the workability is poor. In order for workers to work properly and not contaminate the surrounding environment, it is necessary to install dust removal equipment and collect the adsorbent. However, the collected adsorbent must be discarded due to the quality of the product called immersion exposure liquid.
WO2005 / 114711 Japanese Patent Application No. 2006-329265 WO2005 / 119371 WO2006 / 115268

  The present invention has been made in order to cope with such a problem. In a purification method using an adsorbent, the transmittance of an alicyclic saturated hydrocarbon compound suitable as an immersion exposure liquid excellent in transmittance at 193 nm is obtained. An object of the present invention is to provide a method for industrially producing a liquid for immersion exposure, which can be further improved, can be produced at a reduced cost.

Various studies have been conducted on efficiently removing impurities contained in alicyclic saturated hydrocarbon compounds by a purification method using an adsorbent.
The shape and particle size of the adsorbent are responsible for the pressure loss inside the column. When a powdery adsorbent with a small particle size is used, the flow rate is limited by the ability of the liquid feed pump, which may be less than the expected flow rate. This problem can be solved by using a pellet-like or bead-like adsorbent having a large particle size. There is a problem that the rate of adsorbing impurities decreases as the particle size of the agglomerates increases, but the increase in filling height and extension of the residence time leads to a fat with the same permeability as when a powdery adsorbent is used. A cyclic saturated hydrocarbon compound could be obtained.
The present invention has been made based on the above findings. That is, the method for producing an alicyclic saturated hydrocarbon compound of the present invention is a method for producing an alicyclic saturated hydrocarbon compound having an average transmittance of 99% or more per 1 mm of the optical path length of a liquid at a wavelength of 193 nm. And a liquid contact step of bringing the raw material alicyclic saturated hydrocarbon compound into contact with the adsorbent, wherein the shape of the adsorbent used in the step is agglomerate.
In particular, the agglomerates are pellets or beads.
Moreover, in the said liquid contact process, the contact time which makes a raw material and an adsorbent contact is 0.5 to 20 hours, It is characterized by the above-mentioned.
The adsorbent is at least one adsorbent selected from alumina, silica alumina, and zeolite.

Pressure loss could be reduced by using agglomerate adsorbents such as pellets instead of powder adsorbents. As a result, it is not necessary to extremely increase the capacity of the liquid feed pump or increase the column diameter, and the manufacturing cost can be reduced. Moreover, by adjusting the filling height of the adsorbent and the residence time of the alicyclic saturated hydrocarbon compound, an alicyclic saturated hydrocarbon having a transmittance of 99.5% / mm equivalent to that when using a powder adsorbent is used. A compound can be obtained.
By using an alicyclic saturated hydrocarbon compound purified by this production method, heat generation due to light absorption can be suppressed, and defocusing, distortion, or defocusing of the optical image due to refractive index variation. Problems such as resolution and pattern shape deterioration due to the above can be suppressed.

The alicyclic saturated hydrocarbon compound produced by the production method of the present invention has a light transmittance at a wavelength of 193 nm of 99% or more per 1 mm of the optical path length of the liquid.
Between the transmittance T per 1 mm of the optical path length and the absorbance A per 1 cm of the optical path length,

T (%) = 100 × 10 ^{−0.1 A}

Therefore, a transmittance of 99% or more per 1 mm of the optical path length corresponds to an absorbance of 0.0437 or less per 1 cm of the optical path length.
In the production method of the present invention, the transmittance is a value expressed as an average value of a plurality of measurement results. Further, the 3σ value is 0.1 or less. Here, the σ value is a standard deviation of the measurement sample calculated on the assumption that the measured value of transmittance has a normal distribution. Preferably, the number of measurements is a statistical value of 5 or more.
When the average value of transmittance and the 3σ value are within the above ranges, heat generation due to light absorption can be suppressed, and the resolution and pattern due to defocusing or distortion of the optical image due to refractive index fluctuations, or defocusing of the optical image. Problems such as shape deterioration can be suppressed with good reproducibility.

  The contact between the alicyclic saturated hydrocarbon compound as the raw material and the adsorbent is performed by immersing the adsorbent in the raw material compound for an appropriate time, stirring the adsorbent and the raw material compound for an appropriate time, and adsorbing the adsorbent to the column. A column chromatography method in which the raw material compound is allowed to pass through is packed.

The column is a container filled with an adsorbent. Preferably, it is a cylindrical container having openings at both ends, and is a container in which an alicyclic saturated hydrocarbon compound as a raw material is introduced from one opening and the purified product can be recovered from the other opening. The packing ratio (100ρ _b / ρ _p ) calculated from the particle density (ρ _p (g / cm ³ )) and bulk density (ρ _b (g / cm ³ )) of the adsorbent packed in the column is 15% or more. Is preferred. The particle density ρ _p can be measured using a pycnometer, and the bulk density ρ _b (g / cm ³ ) can be calculated as the mass of the adsorbent per unit volume when an adsorbent is placed in the column.

The adsorbent that can be used in the present invention is alumina, silica alumina, zeolite, or an oxide obtained by combining these.
Alumina is an oxide whose composition formula is represented by Al ₂ O ₃ . Silica alumina is called amorphous silica-alumina, and zeolite is called crystalline aluminosilicate.

The shape of the adsorbent is not powder, but is a lump having a particle size larger than that of the powder. The average particle size of the agglomerates is preferably 0.5 mm to 50 mm as measured by a sieving method.
If it is less than 0.5 mm, it becomes necessary to restrict the flow rate due to an increase in pressure loss, or it is difficult to handle industrially because it tends to scatter during work. The adsorption rate is remarkably lowered and productivity is lowered, which is not preferable.
Examples of the shape of the agglomerate include an agglomerate having an average particle diameter of about several millimeters to several centimeters, such as particulate, spherical, cylindrical, prismatic, cylindrical, and rectangular tube shapes.
Preferable agglomerates are pellets or beads.

The contact time for contacting the raw material alicyclic saturated hydrocarbon compound and the adsorbent is 0.5 to 20 hours, preferably 2 to 20 hours, more preferably 4 to 10 hours.
Here, the contact time is a residence time defined as [volume of adsorbent (ml) / flow rate of alicyclic saturated hydrocarbon compound (ml / h)] at a contact temperature of 25 ° C. under atmospheric pressure. A contact time of less than 0.5 hours is not preferable because an alicyclic saturated hydrocarbon compound such as 1,1′-bicyclohexyl having a low transmittance containing impurities may flow out. Further, if the contact time exceeds 20 hours, the processing efficiency is lowered, which causes a decrease in production volume and an increase in product price.

When the adsorbent that can be used in the present invention is evaluated by the following method, the ratio between the absorbance after contacting with the adsorbent and the absorbance of the alicyclic saturated hydrocarbon compound before contacting with the adsorbent is 1.1 or less can be used.
<Evaluation method>
30 ml of alicyclic saturated hydrocarbon compound of 0.0437 or less per 1 cm of optical path length of liquid at a wavelength of 193 nm is put in a glass container, and 1.5 g of adsorbent is added to this alicyclic saturated hydrocarbon compound to form nitrogen. Let stand at 25 ° C. for 72 hours under atmosphere. The absorbance (A) before contact with the adsorbent and the absorbance (B) after contact are measured with light having a wavelength of 193 nm, and the absorbance ratio (B / A) is calculated.

  For use in the present invention, the adsorbent is preferably calcined before use at a temperature of 200-500 ° C, preferably 250-500 ° C. If the firing is less than 200 ° C., the above evaluation value cannot be achieved, and if it exceeds 500 ° C., the shape of the agglomerates may not be maintained.

In the production method of the present invention, an alicyclic saturated hydrocarbon compound as a raw material is brought into contact with the adsorbent in an inert gas atmosphere.
The inert gas that can be used in the present invention refers to a gas that does not decrease the transmittance of the compound at 193 nm by contact with an alicyclic saturated hydrocarbon compound at 25 ° C. under atmospheric pressure.
Examples of the inert gas include noble gases such as helium and argon, nitrogen gas, and the like. Nitrogen gas is preferred because of its ease of industrial use.
Moreover, it is preferable that the said inert gas does not contain the component used as the factor which reduces the transmittance | permeability of an alicyclic saturated hydrocarbon compound. Examples of components that lower the transmittance include oxygen and hydrocarbons (particularly unsaturated hydrocarbons).
In the production method of the present invention, an inert gas having an oxygen concentration of 0.1 volume% or less and a hydrocarbon concentration of 1 volume ppm or less, particularly an oxygen concentration of 0.1 volume% or less, and a hydrocarbon concentration of 1 volume ppm or less. Nitrogen gas is preferred. By contacting the adsorbent with an alicyclic saturated hydrocarbon compound as a raw material in an atmosphere of nitrogen gas having an oxygen concentration of 0.1 vol% or less and a hydrocarbon concentration of 1 vol ppm or less, the average value of the transmittance Is 99% or more, and an alicyclic saturated hydrocarbon compound having a 3σ value of 0.1 or less is obtained.
The oxygen concentration can be measured by atmospheric pressure ionization mass spectrometry, and the hydrocarbon concentration can be measured by gas chromatography with a flame ionization detector.

In the purification method using the adsorbent of the above shape, the alicyclic saturated hydrocarbon compound used as a raw material is at least one selected from 1,1′-bicyclohexyl, exo-tetrahydrodicyclopentadiene, and trans-decahydronaphthalene. One alicyclic saturated hydrocarbon compound is preferable because the transmittance is easily set to 99% / mm or more by the production method of the present invention.
In particular, 1,1′-bicyclohexyl is preferable because the transmittance is easily set to 99% / mm or more.
Moreover, it is preferable that GC purity before making the alicyclic saturated hydrocarbon compound used as a raw material contact an adsorbent is 99 mass% or more. The GC purity can be measured with an Agilent 6890 gas chromatography system, a column (TC1701), a carrier gas (helium), and a detector (TCD).

The combination of the alicyclic saturated hydrocarbon compound and the adsorbent is such that when the alicyclic saturated hydrocarbon compound is 1,1′-bicyclohexyl or exo-tetrahydrodicyclopentadiene, the adsorbent is silica alumina, zeolite, or these This mixture is preferable because the impurities contained in the alicyclic hydrocarbon compound as a raw material can be efficiently removed.
Further, when the alicyclic saturated hydrocarbon compound is trans-decahydronaphthalene, the impurities contained in the alicyclic hydrocarbon compound from which alumina, silica alumina, zeolite, or a mixture thereof is used as a raw material can be efficiently removed. It is preferable because it can be removed.

Since the alicyclic saturated hydrocarbon compound produced by the method of the present invention has little elution of volatile impurities, particularly the resist components, the optical properties are recovered with good reproducibility by performing recovery and purification by a simple method. Can be reused.
As a purification method in the case of reusing, a method such as washing with water, acid washing (sulfuric acid washing), alkali washing, precision distillation, purification using an appropriate filter (packed column), filtration, etc., and the above-described method of the present invention Examples thereof include a purification method or a method using a combination of these purification methods. Among these, it is preferable to carry out purification by the purification treatment, water washing treatment, alkali washing, acid washing, precision distillation, oxide adsorption or a combination of these purification methods according to the method of the present invention.
The above alkali cleaning removes the acid generated by the exposure eluted in the immersion exposure liquid, the acid cleaning removes the basic components in the resist eluted in the immersion exposure liquid, and the water washing process elutes in the immersion exposure liquid. It is effective for removal of a photoacid generator, a basic additive, and an eluate such as an acid generated during exposure in the resist film.
The method for producing an alicyclic saturated hydrocarbon compound disclosed in the present invention is also effective in the above recovery and purification, and is caused by the decomposition of an acid-dissociable protecting group in a resin or irradiation of a liquid with radiation by this method. Since removal of impurities having carbon and carbon unsaturated bonds, which are photoreaction products, can be effectively performed, fluctuations in transmittance can be prevented.
In addition, precision distillation can be performed at the time of purification. Precision distillation is effective for removing low-volatile compounds among the above additives, and is effective for removing hydrophobic components generated by the decomposition of protecting groups in the resist during exposure.

The photoresist film or the photoresist film on which the upper layer film for immersion is formed is irradiated with radiation through a mask having a predetermined pattern using the alicyclic saturated hydrocarbon compound produced in the present invention as a medium, and then developed. Thus, a resist pattern can be formed.
The radiation used for immersion exposure depends on the photoresist film used and the combination of the photoresist film and the upper layer film for immersion, for example, visible rays; ultraviolet rays such as g rays and i rays; Various types of radiation such as ultraviolet rays; X-rays such as synchrotron radiation; and charged particle beams such as electron beams can be selectively used. In particular, an ArF excimer laser (wavelength 193 nm) or a KrF excimer laser (wavelength 248 nm) is preferable.

Examples are shown below. The absorbance was sampled in a 1 cm and 2 cm optical path length cell with a polytetrafluoroethylene lid in a nitrogen atmosphere glove box controlled to an oxygen concentration of 50 ppm or less, and JASCO-V7100 manufactured by JASCO Corporation was used. The absorbance was measured using the cell containing the liquid as a sample and air as a reference, and the difference between the two was defined as the absorbance per 1 cm. The measurement temperature is 23 ° C. Based on this value, the transmittance per mm was calculated according to Lambert Beer's law. If the transmitted light intensity of the sample is l ₀ and the transmitted light intensity of the reference is l, the absorbance is expressed as log ₁₀ (l ₀ / l). The values shown in each example are values obtained by correcting cell reflection by calculation.

The following adsorbents were used. Each adsorbent was used after baking at 500 ° C. for 3 hours.
Zeolite-1: manufactured by Tosoh Corporation, F-9 (powder: average particle size 6.2 μm)
Zeolite-2: manufactured by Tosoh Corporation, F-9 (columnar shape: diameter 1.5 mm, length 3 mm)

Example 1
Under a nitrogen atmosphere (oxygen concentration 50 ppm or less, nitrogen purity 99.999%), 1,1′− with a transmittance of 80.45% / mm at 193 nm was applied to a glass column having an inner diameter of 3 cm and roughly packed with 180 g of zeolite-2. 820 ml of bicyclohexyl was passed through. The liquid passage required 22 hours, and the residence time was 5.6 hours. The transmittance of this liquid at 193 nm was measured and found to be 99.51% / mm.

Example 2
In a nitrogen atmosphere (oxygen concentration of 50 ppm or less, nitrogen purity 99.999%), 1,1′- with a transmittance of 80.45% / mm at 193 nm was applied to a glass column having an inner diameter of 3 cm and roughly 68 g of zeolite-2. 820 ml of bicyclohexyl was passed through. The liquid passage required 8 hours, and the residence time was 0.85 hours. The transmittance of this liquid at 193 nm was measured and found to be 99.23% / mm.

Comparative Example 1
Under a nitrogen atmosphere (oxygen concentration 50 ppm or less, nitrogen purity 99.999%), 1,1′- with a transmittance of 80.45% / mm at 193 nm was applied to a glass column having an inner diameter of 7 cm and roughly packed with 20 g of zeolite-1. 550 ml of bicyclohexyl was passed through.
In order to obtain 1,1′-bicyclohexyl having a transmittance at 193 nm of 99.54% / mm, it took 88 hours to pass through and the residence time was 5.2 hours.

  From Example 1, Example 2, and Comparative Example 1, by using a pellet adsorbent instead of a powder adsorbent, the pressure loss is reduced and the transmittance 99 is the same as when a powder adsorbent is used. % / Mm or more of 1,1′-bicyclohexyl could be obtained.

  In the method for producing an alicyclic saturated hydrocarbon compound of the present invention, an alicyclic saturated hydrocarbon compound as a raw material is brought into contact with an adsorbent that is in the form of agglomerates, so that the liquid has an optical path length of 1 mm per wavelength of 193 nm. Since it is a method for producing an alicyclic saturated hydrocarbon compound having an average transmittance of 99% or more, impurities contained in the alicyclic saturated hydrocarbon compound are efficiently removed, with good reproducibility and optical properties. A stable immersion exposure liquid can be produced. Therefore, it can be used very suitably as a liquid used in immersion exposure, which is an essential technique for manufacturing semiconductor devices that are expected to be further miniaturized in the future.

Claims (4)

A method for producing an alicyclic saturated hydrocarbon compound having an average transmittance of 99% or more per 1 mm of the optical path length of a liquid at a wavelength of 193 nm,
A liquid contact step of bringing the raw material alicyclic saturated hydrocarbon compound into contact with an adsorbent,
The method for producing an alicyclic saturated hydrocarbon compound, wherein the adsorbent used in the contacting step is agglomerate.   The method for producing an alicyclic saturated hydrocarbon compound according to claim 1, wherein the agglomerates are pellets or beads.   3. The alicyclic saturated hydrocarbon compound according to claim 1, wherein in the liquid contact step, the contact time for contacting the raw material with the adsorbent is 0.5 hours to 20 hours. Production method.   4. The method for producing an alicyclic saturated hydrocarbon compound according to claim 1, wherein the adsorbent is at least one adsorbent selected from alumina, silica alumina, and zeolite. .