JP2008263106A - Recycling method of liquid for liquid immersion exposure - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a recycling method of liquid for liquid immersion exposure enabling recycling by efficiently removing impurities generated in liquid for liquid immersion exposure upon exposure and by stabilizing the optical properties of the liquid for liquid immersion exposure. <P>SOLUTION: In the method of recycling liquid for liquid immersion exposure, the liquid for liquid immersion exposure used for exposure is brought into contact with heat-treated adsorbent for purification, and then is recycled for exposure. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method for recycling a liquid in an immersion type exposure system that performs exposure through a liquid filled between an optical element of a projection optical means and a substrate.

  When manufacturing an electronic device such as a semiconductor element or an imaging element, a substrate (wafer, glass plate, etc.) on which an image of a pattern of an original (reticle or mask) is applied via a projection optical means An exposure apparatus (projection type) that transfers to each of the above shot areas is used. In such an exposure apparatus, it is required to improve the resolution of the projection optical means in order to cope with the miniaturization of circuits accompanying the miniaturization and high integration of electronic devices.

  As long as an electronic device is manufactured by a lithography technique, an exposure technique (exposure apparatus) is indispensable, and the exposure wavelength used in the exposure apparatus has been shortened year by year as the circuit becomes finer. Yes. As the electronic device design rule becomes finer from 90 nm to 65 nm, and further to 45 nm, the exposure technology uses an immersion method using ArF laser light using pure water, and a high refractive index instead of pure water. The use of liquids (materials) has evolved, and in the future, exposure technology is expected to advance from immersion methods to the use of extreme ultraviolet light (EUV).

  The present invention is related to the use of the high-refractive-index liquid that has been put to practical use in the immersion method in the course of the development of such exposure technology, and the demand for reuse has increased in consideration of the environment. It was made as.

For example, Patent Documents 1 to 5 can be cited as related prior art documents.
US Patent Application Publication No. 2005/0286031 International Publication No. 05/119371 Pamphlet WO 06/115268 pamphlet International Publication No. 05/114711 Pamphlet JP 2006-210542 A

  In the immersion method, the space between the lower surface of the projection optical means and the substrate surface is filled with a liquid, and the wavelength of the exposure light source in the liquid is 1 / n times that in air when the refractive index of the liquid is n. This is an exposure technique that improves the resolution and enlarges the depth of focus by about n times. When the exposure wavelength is shortened and the numerical aperture is increased in order to increase the resolution, the depth of focus becomes narrow. Therefore, the immersion method that can expand the depth of focus is a useful exposure technique.

  As the liquid, pure water has been mainly used, but with the miniaturization of the circuit, the use of a liquid having a refractive index larger than that of pure water (refractive index 1.44) is being shifted. For example, Patent Documents 4 and 5 propose an alicyclic hydrocarbon compound such as decalin as an immersion exposure liquid (also simply referred to as an exposure liquid) suitable for the next generation immersion exposure method. ing.

  The alicyclic hydrocarbon compound has a large refractive index in ArF laser light and has excellent properties as an immersion exposure liquid. However, when this exposure liquid with a high refractive index is used for exposure, side effects such as photolysis, oxidation, dehydrogenation and the like may occur due to light irradiation, and the purity of the exposure liquid may be lowered. Further, since the exposure liquid is in contact with the resist film, the purity of the exposure liquid may be lowered even if the components in the resist film are eluted.

  As purity decreases in this way, impurities caused by side reactions and elution absorb light, which reduces the amount of light that reaches the resist film and is necessary to resolve the pattern to the optimal dimensions. There is a risk that the amount of irradiation will decrease. Doing so causes a significant reduction in exposure throughput, and the amount of light varies from one substrate to another depending on the amount of impurities contained in the exposure liquid. As a result, the yield of electronic devices deteriorates and the production efficiency decreases. Invite For this reason, it is not preferable that impurities exist in the exposure liquid.

  However, when the exposure liquid containing impurities as described above is continuously used and made disposable, it is considered that various problems caused by impurities generated by light can be avoided. However, such a response reduces competitiveness due to an increase in running cost accompanying an increase in consumption and an increase in device production cost. Further, when the exposure liquid is the alicyclic hydrocarbon compound (organic compound), the environmental load is increased by discarding. Therefore, it cannot be said that it is a preferable response.

  On the other hand, Patent Documents 2 and 3 disclose a method of recycling an exposure liquid having a high refractive index using an adsorbent. However, the recycling methods disclosed in these documents have problems that the transmittance at 193 nm cannot be recovered to 99% or more per 1 mm of the optical path length, and that two types of adsorbents must be used for recovery. .

  The present invention has been made in view of such circumstances, and the object thereof is to efficiently remove impurities generated in the immersion exposure liquid by exposure, and to improve the optical properties of the immersion exposure liquid. An object of the present invention is to provide a method for recycling a liquid for immersion type exposure that can be reused with its properties stabilized. As a result of repeated research, it has been found that the above-mentioned problems can be solved by the following means, and the present invention has been completed.

That is, according to the present invention, an immersion type exposure liquid whose transmittance at a wavelength of 193 nm is less than 99% per 1 mm of an optical path length by being used for exposure is converted into an oxide containing one kind of Al ₂ O _3. By contacting, the transmittance at a wavelength of 193 nm is recovered to 99% or more per 1 mm of the optical path length, and a method for recycling an immersion type exposure liquid that is reused for exposure is provided.

In the recycling method for immersion type exposure liquid according to the present invention, the oxide containing Al ₂ O ₃ is preferably an oxide selected from an oxide group consisting of silica alumina and zeolite.

  In the method for recycling an immersion type exposure liquid according to the present invention, the silica alumina preferably has a silica / alumina ratio of 3 mol / mol to 10 mol / mol.

  In the method for recycling the immersion type exposure liquid according to the present invention, the zeolite preferably has a silica / alumina ratio of 7 mol / mol or less and a pore diameter of 0.8 nm or more.

  The liquid immersion type exposure liquid recycling method according to the present invention is suitably used when the liquid immersion type exposure liquid to be recycled is a saturated hydrocarbon compound.

  The liquid immersion type exposure liquid recycling method according to the present invention is suitably used when the liquid immersion type exposure liquid to be recycled is trans-decahydronaphthalene.

  The liquid immersion type exposure liquid recycling method according to the present invention is suitably used when the liquid immersion type exposure liquid to be recycled is exo-tetradicyclopentadiene.

  The liquid immersion type exposure liquid recycling method according to the present invention is preferably used when the liquid immersion type exposure liquid to be recycled is 1,1'-bicyclohexyl.

  The method for recycling the immersion type exposure liquid according to the present invention is a method for purifying impurities in an immersion type exposure liquid generated by side reaction by exposure or elution of resist film components by contact with a heat-treated adsorbent. For example, the transmittance at 193 nm (the wavelength of ArF laser light) is stabilized within a certain range, and can be used again for exposure. Since the immersion exposure liquid is not discarded, the environmental burden can be reduced and the running cost for manufacturing the electronic device can be suppressed.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, the present invention should not be construed as being limited to these embodiments, and the knowledge of those skilled in the art can be obtained without departing from the scope of the present invention. Various changes, modifications and improvements can be made based on this. For example, the drawings show preferred embodiments of the present invention, but the present invention is not limited by the modes shown in the drawings or the information shown in the drawings. In practicing or verifying the present invention, means similar to or equivalent to those described in the present specification can be applied, but preferred means are those described below.

Recycling method of immersion exposure liquid of the present invention, the immersion exposure liquid of transmittance at a wavelength of 193nm is less than 99% per 1mm by using at least once the exposure, one of Al ₂ O _{In this} method, the transmittance at a wavelength of 193 nm is recovered to 99% or more per mm, and then used again for exposure.

The exposure is exposure performed through a liquid filled between the optical element of the projection optical means and the substrate, and the immersion exposure liquid is the liquid used for the exposure. As long as the immersion type exposure liquid recycling method according to the present invention is immersion type exposure, the exposure performed on the immersion type exposure liquid to be purified and the purified immersion type exposure liquid are used. The specific method of exposure and the light (light source) for exposure are not limited. The exposure light (light source) may be ArF laser light (193 nm), KrF laser light (248 nm), F ₂ laser light (157 nm), etc., and an ultraviolet emission line (g line, h) emitted from a mercury lamp. Line, i-line).

  In the method for recycling the immersion type exposure liquid according to the present invention, the contact of the immersion type exposure liquid with the adsorbent can be performed by, for example, a batch method or a column chromatography method. The contact of the immersion exposure liquid with the adsorbent may be performed in a single stage or in a plurality of stages.

  The heat treatment of the adsorbent is preferably performed at a temperature of 200 ° C. or higher and 500 ° C. or lower. A more preferable heat treatment temperature is 250 ° C. or higher and 500 ° C. or lower. It is desirable to perform the heat treatment at such a high temperature and calcinate it to remove the organic substances and moisture adhering to the adsorbent, and then contact the liquid with an immersion type exposure liquid.

The adsorbent is preferably an oxide containing Al ₂ O ₃ , and specific examples include silica alumina and zeolite. And it is preferable that the silica / alumina ratio which comprises a silica alumina is 3 mol / mol or more and 10 mol / mol or less. Moreover, it is preferable that the silica / alumina ratio which comprises a zeolite is 7 mol / mol or less, and a pore diameter is 0.8 nm or more.

  As the immersion type exposure liquid to be recycled by the method for recycling the immersion type exposure liquid according to the present invention, a fat having a refractive index n at a wavelength of 193 nm of 1.64 (when the temperature of the liquid is 23 ° C.). Mention may be made of cyclic saturated hydrocarbon compounds. For example, trans-decahydronaphthalene. In addition, examples of recycling targets include exo-tetradicyclopentadiene and 1,1'-bicyclohexyl.

  EXAMPLES Hereinafter, although this invention is demonstrated further in detail based on an Example, this invention is not limited to these Examples.

  30 ml of trans-decahydronaphthalene (transmittance of 96.8% / mm for a wavelength of 193 nm) was adsorbed and filtered using 1.5 g of zeolite (manufactured by Tosoh, HSZ-341NHA), and the transmittance (before irradiation) Transmittance, transmittance before dissolution) were measured. The transmittance at a wavelength of 193 nm was 99.1% / mm. In this embodiment, the liquid is EK-1.

  50 ml of exo-tetradicyclopentadiene (transmittance 31.6% / mm at a wavelength of 193 nm) was subjected to adsorption filtration 5 times using 1.5 g of zeolite (manufactured by Tosoh, HSZ-341NHA). The transmittance (transmittance before irradiation) was measured. The transmittance at a wavelength of 193 nm was 99.9% / mm. In this example, the liquid is EK-2.

  After performing adsorption filtration five times using 1.5 g of silica alumina (manufactured by JGC Chemical Co., Ltd., N633L) for 50 ml of 1,1′-bicyclohexyl (transmittance of 50.1% / mm at a wavelength of 193 nm). The transmittance (transmittance before irradiation) was measured. The transmittance at a wavelength of 193 nm was 99.5% / mm. In this embodiment, the liquid is EK-3.

Against (Example 1) EK-1 (30ml) , it was irradiated with ArF laser beam at 150 J / cm ^2, measured transmittance at a wavelength of 193nm (the transmittance after irradiation). The post-irradiation transmittance at a wavelength of 193 nm was 96.8% / mm. Thereafter, 1.5 g of zeolite (manufactured by Tosoh, HSZ-341NHA) having a pore diameter of 0.8 nm and a silica / alumina ratio of 7 mol / mol was used as an oxide for the sample (30 ml). Then, after making contact with this and performing adsorption filtration, the transmittance (permeability after recycling) was measured to evaluate the oxide recycling ability. The post-recycling transmittance at a wavelength of 193 nm was 99.2% / mm.

  (Example 2) Except that 1.5 g of zeolite (F-9, manufactured by Tosoh Corporation) having a pore diameter of 0.9 nm and a silica / alumina ratio of 2.5 mol / mol was used as an oxide. In the same manner as in Example 1, the oxide recycling ability was evaluated. The post-recycling transmittance at a wavelength of 193 nm was 99.1% / mm.

  (Example 3) As oxide, except that 1.5 g of silica alumina (manufactured by JGC Chemical Co., Ltd., N633L) having a silica / alumina ratio of 6.4 mol / mol was used, The recycling ability of oxide was evaluated. The post-recycling transmittance at a wavelength of 193 nm was 99.1% / mm.

  (Comparative Example 1) Example 1 except that 1.5 g of silica gel (manufactured by Wako Pure Chemicals, C-200, silica / alumina ratio is infinite) having a pore diameter of 7 nm was used as the oxide. Similarly, oxide recycling ability was evaluated. The post-recycling transmittance at a wavelength of 193 nm was 98.5% / mm.

  (Comparative Example 2) As oxide, except that 1.5 g of zeolite (manufactured by Tosoh, HSZ-690HOA) having a pore diameter of 0.7 nm and a silica / alumina ratio of 240 mol / mol was used. In the same manner as in Example 1, the oxide recycling ability was evaluated. The post-recycling transmittance at a wavelength of 193 nm was 98.8% / mm.

  (Comparative Example 3) As the oxide, except that 1.5 g of zeolite (manufactured by Tosoh, A-3) having a pore diameter of 0.3 nm and a silica / alumina ratio of 2 mol / mol was used. In the same manner as in Example 1, the oxide recycling ability was evaluated. The post-recycling transmittance at a wavelength of 193 nm was 98.1% / mm.

  (Comparative Example 4) Implementation was performed except that 1.5 g of zeolite (manufactured by Tosoh, A-4) having a pore diameter of 0.4 nm and a silica / alumina ratio of 2 mol / mol was used as the oxide. In the same manner as in Example 1, the oxide recycling ability was evaluated. The post-recycling transmittance at a wavelength of 193 nm was 98.4% / mm.

  (Comparative Example 5) As an oxide, except that 1.5 g of silica alumina (manufactured by JGC Chemical Co., N633HN) having a silica / alumina ratio of 2.6 mol / mol was used, The recycling ability of oxide was evaluated. The post-recycling transmittance at a wavelength of 193 nm was 98.7% / mm.

  (Example 4) A PAG (Photo Acid Generator) added to an ArF resist was dissolved in EK-1 (30 ml) in a nitrogen atmosphere over one week, and then the transmittance (transmittance after dissolution) was determined. It was 95.2% / mm when measured. Then, when the transmittance (transmittance after recycling) was measured with respect to the sample (30 ml) after adsorption filtration using 1.5 g of zeolite (manufactured by Tosoh, HSZ-341NHA) as an adsorbent, the wavelength was 193 nm. The post-recycling transmittance was 99.1% / mm.

  (Example 5) The adsorbent was purified in the same manner as in Example 4 except that the amine added to the ArF resist was dissolved in EK-1 (30 ml) in a nitrogen atmosphere over 1 week. The ability was evaluated. The transmittance after dissolution was 31.6% / mm, and the transmittance after recycling was 99.1% / mm.

(Example 6) EK-2 (50 ml) was irradiated with ArF laser light at 600 J / cm ² and the transmittance at a wavelength of 193 nm (transmittance after irradiation) was measured. The post-irradiation transmittance at a wavelength of 193 nm was 91.6% / mm. Thereafter, 1.5 g of zeolite (manufactured by Tosoh Corporation, HSZ-341NHA) was used as an adsorbent for the sample (30 ml), and after performing adsorption filtration, the transmittance (permeability after recycling) was measured. The purification capacity was evaluated. The post-recycling transmittance at a wavelength of 193 nm was 99.9% / mm.

Against (Example 7) EK-3 (50ml) , it was irradiated with ArF laser beam at 800 J / cm ^2, measured transmittance at a wavelength of 193nm (the transmittance after irradiation). The post-irradiation transmittance at a wavelength of 193 nm was 96.4% / mm. Thereafter, 1.5 g of silica alumina (manufactured by JGC Chemical Co., N633L) was used as an adsorbent for the sample (30 ml), and after performing adsorption filtration, the transmittance (transmittance after recycling) was measured. The purification capacity was evaluated. The post-recycling transmittance at a wavelength of 193 nm was 99.5% / mm.

  In the above examples, each liquid was sampled in cells with optical path lengths of 1 cm and 2 cm with a lid made of polytetrafluoroethylene in a nitrogen atmosphere glove box controlled to 0.5 ppm or less, and manufactured by JASCO. Using V7100, absorbance was measured using the cell containing each of the liquids as a sample and air as a reference, and the difference between the two was defined as absorbance per 1 cm. Based on this value, the transmittance per mm was calculated according to Lambert Beer's law. The transmittance value shown in each example is a value obtained by correcting the reflection of the cell by calculation. Each adsorbent was used after firing at 500 ° C. for 3 hours.

(Discussion) From Examples 1 to 3, 6, 7 and Comparative Examples 1 to 5, after using an oxide containing Al ₂ O ₃ as an adsorbent (zeolite (aluminosilicate), silica alumina), after recycling The transmittance could be recovered to a value equal to or higher than 99% / mm equivalent to the transmittance before irradiation. In the case of recycling using zeolite, when the silica / alumina ratio was 7 mol / mol or less and the pore diameter was 0.8 nm or more, the transmittance after recycling could be recovered to 99% / mm or more. . Furthermore, in the case of recycling using silica alumina, when the silica / alumina ratio was 3 mol / mol or more, the transmittance after recycling could be recovered to 99% / mm or more. From these facts, it was found that impurities generated in the immersion type exposure liquid due to side reactions caused by irradiation (exposure) can be removed by contact with the adsorbent.

  From Examples 4 and 5, it was possible to recover the transmittance after recycling to a value equivalent to the transmittance before dissolution. From this, it was confirmed that when impurities such as PAG and amine that can be dissolved in the immersion exposure liquid are extracted by contacting the resist film, these impurities can be removed by contact with the adsorbent. .

  The liquid recycling method for immersion exposure according to the present invention is a method for reusing a liquid applied to an immersion exposure means for performing exposure through a liquid filled between an optical element of a projection optical means and a substrate. It can be used. In particular, it can be suitably used when the liquid is an alicyclic saturated hydrocarbon compound.

Claims (8)

By contacting the immersion type exposure liquid whose transmittance at a wavelength of 193 nm is less than 99% per 1 mm of the optical path length by being used for exposure with an oxide containing one kind of Al ₂ O ₃ , the wavelength at 193 nm A method for recycling a liquid for immersion type exposure, wherein the transmittance is recovered to 99% or more per 1 mm of the optical path length and reused for exposure. The method for recycling a liquid for immersion type exposure according to claim 1, wherein the oxide containing Al ₂ O ₃ is an oxide selected from an oxide group consisting of silica alumina and zeolite. _3. The immersion exposure according to claim 2, wherein when the oxide containing Al ₂ O ₃ is the silica alumina, the silica alumina has a silica / alumina ratio of 3 mol / mol to 10 mol / mol. Liquid recycling method. _3. The liquid according to claim 2, wherein when the oxide containing Al ₂ O ₃ is the zeolite, the zeolite has a silica / alumina ratio of 7 mol / mol or less and a pore diameter of 0.8 nm or more. Recycling method for immersion exposure liquid.   The method for recycling an immersion type exposure liquid according to any one of claims 1 to 4, wherein the immersion type exposure liquid to be recycled is a saturated hydrocarbon compound.   The method for recycling an immersion type exposure liquid according to any one of claims 1 to 5, wherein the immersion type exposure liquid to be recycled is trans-decahydronaphthalene.   The method for recycling an immersion type exposure liquid according to any one of claims 1 to 5, wherein the immersion type exposure liquid to be recycled is exo-tetradicyclopentadiene.   The method for recycling an immersion type exposure liquid according to claim 1, wherein the immersion type exposure liquid to be recycled is 1,1′-bicyclohexyl.