JP2009018996A - Production method of 1,1'-bicyclohexyl - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a purification method that assures stable optical properties of 1,1'-bicyclohexyl suitable as a liquid for immersion exposure exhibiting excellent transmittance at 193 nm by efficiently removing impurities contained therein by using an adsorbent. <P>SOLUTION: 1,1'-bicyclohexyl having an average transmittance of at least 99% at an optical path length of 1 mm of the liquid at a wavelength of 193 nm is produced by bringing the raw material 1,1'-bicyclohexyl into contact with an adsorbent composed of at least one oxide selected from silica alumina and zeolite. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method for producing 1,1′-bicyclohexyl, and more particularly to a production method capable of improving 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).
A compound having a carbon-carbon unsaturated bond or an aromatic ring, or a compound having a functional group such as a carbonyl group or a hydroxyl group has a large absorbance in the far-ultraviolet region by being mixed in a small amount in an alicyclic saturated hydrocarbon. Influence. In addition, these impurities are decomposed by the laser at the time of exposure, which causes a significant increase in absorbance, leading to a decrease in turnover number and an increase in burden on the on-site recycling unit. The In addition to the influence on the absorbance, there is a possibility that the lens is contaminated by impurities and its laser decomposition products adhering to the lens surface. Therefore, it is necessary to establish a purification method that further reduces impurities having absorption (absorption peak) in the far ultraviolet region.
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 of alicyclic saturated hydrocarbon compounds, particularly 1,1′-bicyclohexyl, at 193 nm is not sufficiently improved, and the number of steps is 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 including activated carbon 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. In addition, there is a problem that a liquid for immersion exposure with good reproducibility and stable optical properties cannot be obtained.
WO2005 / 114711 Japanese Patent Application No. 2006-329265 WO2005 / 119371 WO2006 / 115268

  The present invention has been made to cope with such problems, and is a purification method using an adsorbent, and is contained in 1,1′-bicyclohexyl suitable as an immersion exposure liquid having excellent transmittance at 193 nm. An object of the present invention is to provide a method for producing a liquid for immersion exposure that can efficiently remove impurities.

Various studies have been conducted regarding the efficient removal of impurities contained in 1,1′-bicyclohexyl by a purification method using an adsorbent with good reproducibility.
In the purification method using an adsorbent, an oxide is used as the adsorbent, and further, the transmittance per 1 mm of the optical path length of the liquid at a wavelength of 193 nm is 99% or more by sequentially contacting with two or more specific oxides. It has been found that 1,1′-bicyclohexyl can be produced.
The present invention has been made based on the above findings. That is, in the method for producing 1,1′-bicyclohexyl according to the present invention, the transmittance per 1 mm of the optical path length of the liquid at a wavelength of 193 nm is 99 by bringing 1,1′-bicyclohexyl as a raw material into contact with the adsorbent. % Of 1,1′-bicyclohexyl, wherein the adsorbent is at least two kinds of oxides having different compositions containing Si and Al, and the use amount of the at least two kinds of oxides Is characterized by being 5 to 60% by mass of the reference amount based on the case of using oxides having the same composition.
The purity of this raw material 1,1′-bicyclohexyl by gas chromatography is 99% by mass or more.
The oxides having different compositions are at least one oxide selected from silica alumina and zeolite.
In particular, the oxide is silica alumina and zeolite.

Since the production method of the present invention includes a step of bringing the raw material 1,1′-bicyclohexyl into contact with an adsorbent that is at least two kinds of oxides having different compositions, it causes a decrease in transmittance in a liquid at a wavelength of 193 nm. Can be efficiently removed.
By using 1,1′-bicyclohexyl 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 1,1′-bicyclohexyl 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.
When the transmittance value falls within the above range, heat generation due to light absorption can be suppressed, and optical image defocusing and distortion caused by refractive index fluctuations, resolution due to optical image defocusing, degradation of pattern shape, etc. Can be suppressed with good reproducibility.

The contact between 1,1'-bicyclohexyl, which is a raw material, and the adsorbent is performed by immersing the adsorbent in the raw material compound for an appropriate period of time, by adsorbing and filtering using the adsorbent as a filter medium, or by packing the adsorbent into a column. Column chromatography for allowing the starting compound to pass through.
The contact with the adsorbent is preferably performed multiple times with adsorbents having different composition ratios. Specific examples include a method in which an adsorbent is immersed or adsorbed and filtered in a raw material compound for an appropriate time, and then the adsorbent is immersed or adsorbed and filtered in place of a new adsorbent, and a method using a plurality of columns. The plurality of columns are preferably used by preparing two or more unused columns and connecting them in series. The column shape may be the same or different.

The column is a container filled with an adsorbent. A cylindrical container having openings at both ends is preferred, and 1,1′-bicyclohexyl 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.

Preferred adsorbents that can be used in the present invention are silica alumina, zeolites, or oxides obtained by combining these.
Silica alumina is called amorphous silica-alumina, and zeolite is called crystalline aluminosilicate.
When the adsorbent that can be used in the present invention is evaluated by the following method, the ratio between the absorbance after contact with the adsorbent and the absorbance of 1,1′-bicyclohexyl before contact with the adsorbent is as follows. 1.1 or less can be used.
<Evaluation method>
In a glass container, 30 ml of 1,1′-bicyclohexyl having a wavelength of 193 nm or less of 0.0437 or less per 1 cm of the optical path length of the liquid is put, and 1.5 g of an adsorbent is added to the 1,1′-bicyclohexyl to add 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. In the case of firing below 200 ° C. or unfired, the above evaluation value cannot be achieved.

In the production method of the present invention, 1,1′-bicyclohexyl as a raw material is brought into contact with a combination of at least two kinds of oxides having different compositions in the adsorbent.
Examples of the oxide containing Si and Al include silica alumina, zeolite, mullite, kaolin and the like, and silica alumina and zeolite are preferable in the production of 1,1′-bicyclohexyl.
Examples of the combination method include silica alumina having different compositions, zeolites having different compositions, and combinations of silica alumina and zeolite having different compositions. Particularly, combinations of silica alumina and zeolite having different compositions are more efficient per unit mass of oxide. It is preferable because 1,1′-bicyclohexyl having a transmittance of 99% / cm or more can be obtained.
In the combination of silica alumina and zeolite, the amount of all oxides used is 5 to 60% by mass, preferably 10 to 50% by mass, based on the case of using oxides having the same composition. If it is less than 5% by mass, 1,1′-bicyclohexyl having a transmittance of 99% / mm or more may not be obtained, and if it exceeds 60% by mass, the adsorbent may not be superior in cost. There is.
Further, as the order of bringing the raw material compounds into contact with the adsorbent, in the case of a combination of silica alumina and zeolite, it is efficient that the zeolite is first ordered in the order of silica alumina, and the transmittance per unit mass of oxide is 99% / It is preferable because 1,1′-bicyclohexyl having a diameter of at least mm can be obtained.

  In the purification method using the adsorbent, 1,1′-bicyclohexyl as a raw material preferably has a purity of 99% by mass or more by gas chromatography before contacting the adsorbent. Purity by gas chromatography can be measured with an Agilent 6890 gas chromatography system, column (TC1701), carrier gas (helium), and detector (TCD).

The raw material 1,1'-bicyclohexyl has little elution of resist components, especially volatile impurities, so it can be recovered and purified by a simple method to recover and reuse optical properties. Can do.
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 1,1′-bicyclohexyl disclosed in the present invention is effective in the above recovery and purification, and is generated by the decomposition of the acid-dissociable protecting group in the resin or the irradiation of the liquid with 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 immersion upper layer film is formed is irradiated with radiation through a mask having a predetermined pattern using 1,1′-bicyclohexyl 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. In addition, in a glove box with a nitrogen atmosphere controlled to have a light absorbance of 0.5 ppm or less, liquids were sampled in cells with optical path lengths of 1 cm and 2 cm with a lid made of polytetrafluoroethylene, 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 in the table shown in each example are values obtained by correcting the reflection of the cells by calculation.

The following adsorbents were used. Each adsorbent was used after baking at 500 ° C. for 3 hours.
Silica alumina-1: SiO ₂ / Al ₂ O ₃ ratio (6.4 mol / mol), N633L, manufactured by JGC Chemical Co., Ltd.
Zeolite-2: SiO ₂ / Al ₂ O ₃ ratio (2.0 mol / mol) manufactured by Tosoh Corporation, F-9

Example 1, Comparative Example 1 and Comparative Example 2
In the first purification, 40 mL of 1,1′-bicyclohexyl having a GC purity of 99.9% by mass was subjected to adsorption filtration using 5 g of each oxide 1 shown in Table 1, and the transmittance at 193 nm was measured. A new 1,1′-bicyclohexyl 40 mL was adsorbed and filtered on the oxide 1 after the adsorption filtration, and the transmittance at 193 nm was measured. The above operation is repeated until 1,1′-bicyclohexyl having an absorbance of 1.5 times or less of the absorbance of 1,1′-bicyclohexyl which has been first adsorbed and filtered is obtained. The capacity of 1,1′-bicyclohexyl relative to product 1 was defined as the purification life of oxide 1.

  In the second purification, 40 mL of 1,1′-bicyclohexyl after adsorption and filtration on oxide 1 was subjected to adsorption filtration using 5 g of each oxide 2 shown in Table 1, and the transmittance at 193 nm was measured. The same operation as in the first purification was repeated, and the point in time when the absorbance of 1.1 times or less with respect to the absorbance of 1,1′-bicyclohexyl first adsorbed and filtered was obtained as the purification lifetime of oxide 2. Table 1 shows the average transmittance, the purification life, and the required amount of oxide per unit volume of 1,1'-bicyclohexyl after the adsorption filtration of the obtained 1,1'-bicyclohexyl, respectively, in the first purification and the second purification. Shown in

  The total of the first and second purifications of the required amount of oxide per unit volume of 1,1′-bicyclohexyl was 0.0129, 0.08 and 0 in Example 1, Comparative Example 1 and Comparative Example 2, respectively. 0279 [g / mL]. In other words, from Example 1, Comparative Example 1 and Comparative Example 2, by treating with two types of oxides having different compositions containing Si and Al, 1,1′-bi with a transmittance of 99% / mm or more is efficiently obtained. Cyclohexyl can be obtained.

  In the method for producing 1,1′-bicyclohexyl of the present invention, the liquid at a wavelength of 193 nm is obtained by bringing 1,1′-bicyclohexyl as a raw material into contact with an adsorbent composed of at least two kinds of oxides having different compositions. Since this is a method for producing 1,1′-bicyclohexyl having a transmittance per 1 mm of optical path length of 99% or more, impurities contained in 1,1′-bicyclohexyl are efficiently removed, and optical properties are improved. 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)

In this method, 1,1′-bicyclohexyl as a raw material is brought into contact with an adsorbent to produce 1,1′-bicyclohexyl having a transmittance of 99% or more per 1 mm of the optical path length of the liquid at a wavelength of 193 nm. And
The adsorbent is at least two kinds of oxides having different compositions including Si and Al, and the amount of the at least two kinds of oxides used is based on the case where oxides having the same composition are used as a reference. The manufacturing method of 1,1'- bicyclohexyl characterized by being 5-60 mass%.   The method for producing 1,1'-bicyclohexyl according to claim 1, wherein the purity of 1,1'-bicyclohexyl as a raw material by gas chromatography is 99% by mass or more.   The method for producing 1,1'-bicyclohexyl according to claim 1 or 2, wherein the oxide is at least one oxide selected from silica alumina and zeolite.   The method for producing 1,1'-bicyclohexyl according to claim 1, 2 or 3, wherein the at least two kinds of oxides having different compositions are silica alumina and zeolite.