KR20070019662A - A method and apparatus for producing microchips - Google Patents

Abstract

The present invention relates to a method for manufacturing a microchip using immersion lithography, wherein the immersion fluid comprises an additive such that the refractive index of the immersion fluid is increased than that of the fluid containing no additive. In this way the exposure light improves the resolution, resulting in a microchip with increased integration density. The invention also relates to an apparatus for immersion lithography comprising an immersion fluid and an immersion fluid.

Description

Method and apparatus for manufacturing microchips {A METHOD AND APPARATUS FOR PRODUCING MICROCHIPS}

The present invention relates to a method and apparatus for manufacturing a microchip using immersion lithography.

Since the invention of integrated circuits in 1959, the computing power of microprocessors has doubled every 18 months, new generations of microchips have been introduced every three years, and the size of electronic devices has declined each time. This phenomenon is known as Moore's Law. The performance of a microchip is highly dependent on the size of the individual circuit elements in the microchip, such as copper and aluminum lines. In general, microchips include complex three-dimensional structures of intersecting stylized layers of conductors, dielectrics, and semiconductor films. In general, smaller circuit elements, faster microchips, and more operation can do more work per unit time. The increasing rate of these phenomena in the integration density of microchips continues with many advances in optical lithography, an alternative method of manufacturing microchips.

Higher degree of integration of circuits requires shorter wavelengths of exposed light used in methods of manufacturing microchips by optical lithography. Changing the exposure light to shorter wavelengths was in fact the method chosen to increase the resolution. However, the shift to shorter wavelengths is becoming less and less because new exposure tools and materials, such as photo-resist, must be designed. This is a difficult task and often leads to implementation issues and delays. Therefore, chip manufacturers generally tend to delay the introduction of new exposure wavelengths as long as possible and extend the life of existing technologies using alternative approaches. The era of immersion lithography is already being considered as an effective way to improve the resolution limitation of a given exposure wavelength. Here, the air between the bottom lens of the apparatus for manufacturing a microchip and the silicon wafer having a layer of photoresist on top is replaced by an immersion fluid, which essentially causes an effective reduction of the wavelength, see Example A below. do. See, US Pat. No. 4,480,910 (1984) to Takanashi et al. Preferably, a fluid having high transparency above the wavelength of the exposure light does not affect the chemistry of the photoresist on the top of the silicon wafer used for the manufacture of the microchip and does not deteriorate the surface of the lens.

For example, immersion lithography is possible for wavelengths of 248 nm, 193 nm and 157 nm. Because of its transparency, water at 193 nm is a major candidate for immersion fluids at these wavelengths (see J. H. Burnett, S. Kaplan, Proceedings of SPIE, Vol. 5040, P. 1742 (2003)). Because of the exceptional transparency of fluorinated siloxane-based compounds at 157 nm, such fluids are considered for 157 nm immersion lithography.

1 is a stirred pressure cell comprising a cell housing 1 stirrer 2 and an inlet for the immersion fluid to be used.

It is an object of the present invention to provide a method of manufacturing a microchip using immersion lithography which further enhances solubility.

Surprisingly, this object is achieved because the immersion fluid comprises an additive such that the refractive index of the immersion fluid is higher than that of the fluid which does not contain the additive.

Preferably, the refractive index of the immersion fluid is at least 1%, more preferably at least 2%, more preferably at least 5%, more preferably at least 10%, most preferably at least 20% than the fluid containing no additives. Is higher than Of course, the increase in refractive index is dependent on the type and concentration of the agent in the fluid.

Examples of immersion fluids are water and various types of alkanes, and fluorinated, siloxane-based fluids. Alkanes may have 6 to 10 carbon atoms. The pH of the immersion fluid is preferably less than 10, more preferably less than 8, more preferably 3 to 7.

Two types of additives may be added. To this end, additives which are soluble in pure fluid, and additives which are insoluble in pure fluid, must be dispersed as particles, preferably nanoparticles. As soluble additives, organic compounds and liquids, and inorganic compounds such as salts may be used. When water is used as the fluid, examples of organic compounds include various types of sugars, alcohols such as cinnamil alcohol and ethylene glycol, 2-picolin, phosphorus and sulfur-containing compounds such as salts of polyphosphoric acid, sodium poly Phosphate, sodium hexametaphosphate, cesium hexametaphosphate, cesium polyphosphate, ethoxy- (ethoxy-ethyl-phosphinothiosulfanyl) -ethyl acetate, 1-fluoro-1- (2-hydroxy- Phenoxy) -3-methyl-2,5-dihydro-1H-1λ5-phosphol-1-ol and water soluble functionalized silicon oil. Examples of inorganic compounds include mercury monosulfide, mercury bromide (I), maca sheet, calcit, sodium chlorate, lead monoxide, pyrite, lead sulfide (II), copper oxide (II), lithium fluoride, and tin sulfide (IV) , Lithium niobate and lead (II) nitrate.

Soluble additives may further comprise a compound of Formula 1:

RA _n

Wherein R is a hydrocarbon group of 1 to 100, more preferably 1 to 10 carbon atoms. The R group may be partially or completely fluorinated and may be branched structure, cyclic structure, or a combination thereof. A group is an acid group or the corresponding salt, for example phosphonic acid, phosphinic acid, sulfonic acid and carboxylic acid. n is preferably 1 to 10.

Preferably, the immersion fluid comprises 1 to 70%, more preferably 2 to 50%, more preferably 20 to 45% by weight of soluble additives.

Preferably, insoluble additives are used. Preferably nanoparticles, for example organic, inorganic or metal nanoparticles, are used in the immersion fluid as insoluble compounds. The average size of the particles is preferably 10 times, more preferably 20 times, more preferably 30 times, more preferably 40 times smaller than the corresponding exposure wavelength of the exposure light used in the process according to the invention. In this way, the average size of the nanoparticles may be less than 100 nm, preferably less than 50 nm, more preferably less than 30 nm, more preferably less than 20 nm and most preferably less than 10 nm. This results in high transparency of the immersion fluid, especially at the wavelength of the exposure light. The minimum size of the particles is 0.1 nm.

To measure the dimensions of nanoparticles, the particles are surfaced in thin layers so that a single nanoparticle can be observed in a photographic image of a layer of microscope (e.g., field emission scanning electron microscope (FE-SEM) or atomic force microscope (AFM)). Present in a highly diluted mixture applied to the phase. Random extraction from 100 nanoparticles is taken to measure dimensions and take an average value. For particles with an aspect ratio greater than 1, such as platelets, rods, or worm-shaped nanoparticles, take the distance value from the farthest end to the farthest end.

The volume percentage of the nanoparticles in the fluid is preferably at least 10%, more preferably at least 20%, more preferably at least 30%, even more preferably at least 40%. The most preferred volume percentage is at least 50%, resulting in a fluid having high refractive index, high transparency and low amount of dispersion of incident light. The volume percentage is preferably less than 80%, more preferably less than 70%. Examples of inorganic and metal nanoparticles include aluminum nitride, aluminum oxide, antimony pentoxide, tin antimony oxide, brass, calcium carbonate, calcium chloride, calcium oxide, carbon black, cerium, cerium oxide, cobalt, cobalt oxide, copper oxide, gold Hastelloy, Hermatite (alpha, beta, amorphous, epsilon, gamma), tin indium oxide, iron-cobalt alloy, iron-nickel alloy, iron oxide, iron sulfide, lanthanum, lead sulfide, lithium manganese oxide, titanic acid Lithium, Vanadium Lithium, Luminescent, Magnesia, Magnesium, Magnesium Oxide, Magnetite, Manganese Oxide, Molybdenum, Molybdenum Oxide, Montmorillonite Clay, Nickel, Niobia, Niobium, Niobium Oxide, Silicon Carbide, Silicon Dioxide , Preferably amorphous silicon dioxide, silicon nitride, yttrium oxide, silver, specialty, stainless steel, talc, tantalum, tin, tin oxide, titania, titanium, titanium diboride, titanium dioxide , Tungsten, tungsten carbide-cobalt has, tungsten oxide, vanadium oxide, yttria, here lithium oxide, zinc, zinc oxide, zirconium, zirconium silicate and zirconium oxide acid. Best results are obtained by using an indenter of a material that is very transparent to radiation, which is measured at the exposure wavelength, for example on the theoretical optical path of 1 mm of particles of material at a wavelength of 248, 193 or 157 nm. , A material having a transmittance of 50% or more.

In a preferred embodiment, nanoparticles comprising Al ³⁺ -compounds are used in the immersion fluid of the method according to the invention. This is because such immersion fluids not only have very high refractive indices but also high transparency. Good examples of such particles include Al ₂ O ₃ , preferably crystalline α-Al ₂ O ₃ (sapphire) and γ-Al ₂ O ₃ . Further suitable types of Al ₂ O ₃ are described in Z. Chemie. 25 Jahrgang, August 1985, Heft 8, p. 273-280. In this case, good results are obtained when the immersion fluid contains 25 to 65% by volume of nanoparticles comprising Al ^{3+ -compound} . Preferably, immersion fluids are used which comprise 25 to 45% by volume of particles, more preferably 30 to 40% by volume. In addition, good results are obtained by using nanoparticles comprising fused amorphous SiO ₂ , MgO, nanodiamonds or MgAl ₂ O ₄ , or mixtures of fused amorphous SiO ₂ and Al ₂ O ₃ . Such immersion fluids not only have desirable optical properties, for example high refractive index and high transparency, but can also be well processed in standard devices for manufacturing microchips. For example, the viscosity is low enough that the immersion fluid can be easily pumped.

Those skilled in the art are known how to prepare dispersions of nanoparticles that are stable in nanoparticles and immersion fluids.

For the production of nanoparticles, wet and solid state techniques may be used. Wetness methods include sol-gel techniques, hydrothermal processing, synthesis in supercritical fluids, precipitation techniques, and microemulsion techniques. Solid state techniques include gas phase methods such as flame / plasma techniques and machine-chemical processing. In particular, good results can be obtained using wet processes, such as sol-gel techniques. The sol-gel reaction can be carried out in an aqueous medium when the particles are stably charged. The counting ions are selected in a manner that ensures high optical transmission at the corresponding wavelengths. Preferably, phosphorus containing counting ions such as phosphoric acid are used. Alternatively, the sol-gel reaction may be carried out in a non-aqueous medium such as for example decane or cyclic alkanes such as decalin. In this case, the nanoparticles are stabilized by adding an appropriate dispersant. In this method, high concentrations, high refractive indices, and low viscosities are obtained. In order to ensure low absorption at deep ultraviolet wavelengths, fluorinated dispersants are preferably used. After sol-gel synthesis at ambient pressure, the fluid-containing nanoparticles may be heated under pressure to increase density and good optical properties such as high refractive index may be produced.

In addition, combinations of flame hydrolysis and wetting methods that may be used in particles made at high temperatures are deposited directly in a fluid such as water or alkanes such as decane or cyclic alkanes such as decalin. This method has the advantage that the accumulation and aggregation of very pure nanoparticles is prevented.

It is also possible to use immersion fluids according to the invention, which comprise a mixture of one or more soluble additives and one or more insoluble additives.

In a further preferred embodiment, a fluid comprising transparent particles having a refractive index higher than the refractive index of the pure fluid and the additive is used in an amount such that the refractive index of the fluid comprising the additive is equal to the refractive index of the transparent particles. Usually, because of their size, the particles scatter over some of the exposure light. In this manner, however, since the refractive index of the transparent particles is the same as the refractive index of the surrounding fluid, the particles do not scatter any exposed light.

For example, the average size of the transparent particles is greater than 0.4 micron, preferably 0.5 to 1000 microns. More preferably, the average particle size of the transparent particles is 1 to 100 microns. More preferably, the size of 90% by weight of the transparent particles is 1 to 10 microns, most preferably 4 to 10 microns.

Preferably, the particles have a broad weight distribution and spherical shape. In this way, high loading of fluid with transparent particles is possible, but the fluid can still be handled well in the method of making the chip, and the fluid still has high transparency.

The weight percent of the transparent particles in the immersion fluid containing the additive, in which the refractive index of the fluid comprising the additive is equal to the refractive index of the transparent particles, is preferably more than 20%, more preferably more than 40%, more preferably more than 60% to be.

The transparent particles may be composed of a material having a transmittance of 40% or more (measured on a theoretical light path of 1 mm). This transmittance is preferably at least 60%, more preferably at least 95%. Examples of suitable transparent particles are transparent crystals such as SiO ₂ , Al ₂ O ₃ , MgO and HfO ₂ . Preferably amorphous SiO ₂ particles, sapphire particles or MgO particles are used.

More preferably, fused amorphous SiO ₂ particles are used, which have a purity of at least 99% by weight, more preferably at least 99.5%, more preferably at least 99.9% by weight. In this way, a fluid with still improved transparency is obtained.

Examples of fused amorphous SiO ₂ particles suitable for use in immersion fluids include the Lithosil® series, preferably LitosylQ0 / 1-E193 and LitosylQ0 / 1-E248 (Short Litotech®). Schott Lithotec), and the fused SiO ₂ of Corning Code 7980 HPFS series from Corning is used in the manufacture of lenses for chip making devices. Such fused amorphous SiO ₂ is very pure and therefore has a transparency of more than 99%. The process for producing such particles is by flame hydrogenolysis and known to those skilled in the art.

In order to increase the refractive index of the fused amorphous SiO ₂ particles, it can be doped with a small amount of suitable doping element, such as germanium.

In fluids comprising transparent particles, one or more of these above-mentioned soluble or insoluble additives may be used as additives. Preferably, there is an additive which is soluble in the fluid, preferably cesium sulphate, cesium hexametaphosphate or sodium hexametaphosphate.

In a further preferred embodiment, fluids may be used which comprise transparent particles that are functionalized on their surface in such a way that the fluids can be dispersed in the immersion fluid. For example, it is possible by grafting particles with a surfactant, preferably a polymerizable surfactant. It is also possible for the purpose of dispersing the transparent particles by adding a surfactant to the immersion fluid comprising the transparent particles.

In a preferred embodiment, the method according to the invention comprises the following steps:

a) measuring the refractive index of the immersion fluid directly or indirectly; And

b) adjusting the refractive index of the immersion fluid at a predetermined value by adding extra pure fluid to the immersion fluid, or adding extra additive.

In this way, variations in the various refractive indices due to changes in temperature and concentration of additives are compensated for.

The refractive index may be measured directly by itself. It can also be used to measure one or more parameters and the refractive index. In this case, the immersion fluid comprises transparent particles and additives in an amount such that the refractive index of the fluid comprising the additive is equal to the refractive index of the transparent particles, to reduce the light dispersion and the measurement of light dispersion of the transparent particles. It is possible to add pure fluid or additives. The addition of excess pure fluid may be suitably performed by mixing the excess pure fluid with the immersion fluid. The addition of excess additives in pure fluid may be performed by mixing the concentrated resolution or dispersion of the additives with immersion fluid.

Still preferred embodiments according to the present invention include the following steps:

a) conveying the immersion fluid after use in the manufacture of the microchip to the cleaning unit;

b) cleaning the immersion fluid; And

c) recycling the washed immersion fluid to a process for making chips.

Due to the extraction of the component from the photoresist layer on top of the wafer, it can change chemically during the exposure step in the fluid component, which is why the immersion fluid tends to be contaminated. This means that after a certain period of using the fluid in the method of the invention, the fluid is refreshed. However, this increases fluid consumption and economically has a negative impact on the process. Surprisingly, this makes it possible to clean the fluid and to recycle the cleaned fluid to the process of the invention.

Cleaning the fluid is suitably carried out by cross flow filtration or dead end flow filtration using, for example, microfiltration, ultrafiltration, nanofiltration or reverse osmosis. Good results are obtained when agitated pressure cells are used. An example of agitated pressure cells is given in FIG. 1.

In FIG. 1, the stirred pressure cell comprises a cell housing 1 stirrer 2 and an inlet for the immersion fluid to be used. The membrane 3 is stacked between the cell housing 1 and the chamber 5. From gas cylinder 7, pressure is applied on top of the fluid in cell housing 1 via pressurized regulator 6. This pressure fluid containing contaminants is transported through the membrane in chamber 5 and further moved. Concentrated fluid compositions comprising particles in the cell housing 1 include nanoparticles and / or transparent particle residues, for example. The refractive index of the concentrated fluid is then adjusted back to its original value by adding the refractive index of the pure fluid and the appropriate soluble additive concentrated fluid.

Preferably, the immersion fluid is at least 10%, preferably at least 20%, more preferably at least 30%, more preferably through a path-length of 1 mm at at least one wavelength selected from the group consisting of 248, 193 and 157 nm. Preferably at least 40%, most preferably at least 50%.

The invention also relates to an apparatus for immersion lithography for the manufacture of microchips comprising immersion fluid.

Examples 1 to 10

A dispersion of nanoparticles of α-Al ₂ O ₃ , γ-Al ₂ O ₃ , MgO, MgAl ₂ O ₄ was prepared by the sol-gel method. Using this method the corresponding precursor was first dissolved in water or in decalin and the hydrolysis reaction started. Thereafter, hydro-heat treatment was performed, followed by peptisation. Finally, the immersion fluid was prepared by diluting the dispersion thus obtained with water, in particular decalin.

Nanoparticles of diamond were first prepared by the solid-state method and then dispersed in water and decalin to obtain an immersion fluid. The refractive index was measured at 193 nm to 248 nm using Ellipsometer VUV-VASE manufactured by J.A. Woollam Co., Inc., USA. The results for the different volume percentages of the nanoparticles are shown in Table 1 below:

In all cases, an increase in the refractive index was observed. In particular, the nanodiamond particles showed good results at a wavelength of 248 nm.

Examples 11-14

Solutions of different water soluble additives were prepared. The refractive index was measured at a wavelength of 193 nm to 248 nm using Ellipsomer VUV-VASE manufactured by J. Ulam Co., Ltd., USA. The data are shown in Table 2 below:

Immersion fluids are used in devices for making microchips based on immersion techniques at wavelengths of 193 nm.

Claims (17)

A method of manufacturing a microchip using immersion lithography, And wherein the immersion fluid comprises an additive such that the refractive index of the immersion fluid is higher than that of the fluid containing no additive. The method of claim 1, A method of manufacturing a microchip, wherein the refractive index of the immersion fluid is 1% or more. The method according to claim 1 or 2, And wherein the additive is soluble in the immersion fluid. The method of claim 3, wherein And wherein the immersion fluid comprises 1 to 70% by weight of soluble additive. The method according to claim 1 or 2, And the additive is insoluble in the immersion fluid. The method of claim 5, And wherein the immersion fluid comprises nanoparticles as an insoluble additive. The method of claim 6, The manufacturing method characterized in that the average size of the nanoparticles is 10 times smaller than the wavelength of the exposure light. The method of claim 6, The manufacturing method characterized in that the average size of the nanoparticles is less than 100nm. The method according to any one of claims 6 to 8, A method according to claim 1, wherein the fluid comprises at least 10% by volume of nanoparticles. The method according to any one of claims 6 to 9, And wherein the particles use a material having a transmittance of at least 50% measured on a theoretical optical path of 1 mm. The method of claim 10, A process for producing nanoparticles comprising Al ^{3+ -compounds} . The method of claim 10, A method for producing a nanoparticle comprising a fused amorphous SiO ₂ , MgO, nanodiamond or MgAl ₂ O ₄ , or a nanoparticle comprising a mixture of fused amorphous SiO ₂ and Al ₂ O ₃ . The method according to any one of claims 1 to 6, Wherein the fluid comprises transparent particles and additives having a refractive index higher than that of pure fluid in an amount such that the refractive index of the fluid comprising the additive is equal to the refractive index of the transparent particles. The method of claim 13, Method for producing a transparent particle characterized in that the average size of 1 to 1000 microns. The method according to claim 13 or 14, Wherein the transparent particles are transparent crystalline forms of SiO ₂ , Al ₂ O ₃ , MgO or HfO ₂ . The method according to any one of claims 1 to 15, a) conveying the immersion fluid after use in the manufacture of the microchip to the cleaning unit; b) cleaning the immersion fluid; And c) recycling the washed immersion fluid to a process for making chips Manufacturing method comprising a. An apparatus for manufacturing a microchip based on the technique of immersion lithography, comprising an immersion fluid used in the manufacturing method according to any one of claims 1 to 15.

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