JP2017186254A - Deuteroxyl-doped silica glass, optical member and lithographic system comprising the same, and method of making the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a synthetic silica material having a low level of polarization-induced birefringence, and a high level of initial internal transmission, and to provide a method of making the same.SOLUTION: What is disclosed includes OD-doped synthetic silica glass capable of being used in optical elements for use in lithography with wavelengths below about 300 nm. OD-doped synthetic silica glass was found to have significantly lower polarization-induced birefringence value than non-OD-doped silica glass with comparable concentration of OH. Also disclosed are: the OD-doped synthetic silica glasses; an optical member comprising such glasses; and lithographic systems comprising such optical member. The glass is particularly suitable for immersion lithographic systems due to the exceptionally low polarization-induced birefringence values at about 193 nm.SELECTED DRAWING: Figure 6

Description

  The present invention relates to a synthetic quartz glass material, an optical element and an optical device having such a glass material, and a method for producing such a glass material. In particular, the present invention relates to a synthetic quartz glass material that can be used in an optical element of a lithographic apparatus operating at a wavelength shorter than about 300 nm, an optical element made of such a glass material, a lithography system comprising such an optical element, The present invention relates to a process for producing such a glass material and a soot preform produced by such a process. The invention is useful, for example, in the production of synthetic quartz glass for optical elements used in deep UV and vacuum UV lithographic apparatus, in particular lithographic apparatus involving immersion lithography in which linearly polarized UV light is used.

  As practiced in the industry, quartz glass optical components such as lenses, prisms, filters, photomasks, reflectors, etalon plates and windows are made from bulk quartz glass blocks made in a mass production furnace. Bulk quartz glass lumps produced in a mass production furnace are known in the art as preforms, boules or ingots. A blank is cut from a boule or ingot and completed from a glass blank using a manufacturing process, which can include, but is not limited to, cutting, polishing and / or coating of glass pieces from the blank. An optical member is produced. Many of these optical components are used in a variety of devices used in environments exposed to ultraviolet light having a wavelength of about 360 nm or shorter, such as an excimer laser beam or some other ultraviolet laser beam. Optical members are incorporated into a variety of devices, including laser exposure lithography equipment, laser generators, medical devices, fusion devices, or any other device that uses high power ultraviolet laser beams to create high density integrated circuits. It is.

  As the photon energy, pulse energy, and pulse rate of a laser increase, the energy level to which an optical member used with such a laser is exposed increases. Quartz glass has become widely used as the material of choice for optical members in such laser-based optical systems due to its excellent optical properties and light-induced damage strength.

  Laser technology has progressed into the short-wavelength high-energy ultraviolet spectral region, the effect of which is that the frequency of light produced by the laser increases (the wavelength decreases). Of particular note are short wavelength lasers operating in the UV and deep UV (DUV) and vacuum UV wavelength ranges, including but not limited to lasers operating at about 248 nm, 193 nm, 157 nm and even shorter wavelengths. Excimer laser systems are widespread in microlithography applications, and shortening the wavelength allows the highest resolution and therefore linear density in integrated circuit and microchip manufacturing to be increased, and thus circuits with reduced minimum dimensions Can be manufactured. The direct physical consequence of shorter wavelengths (higher frequencies) is higher photon energy. In such an optical system, the quartz glass optical system is exposed to a high illumination level for a long time, which can result in degradation of the optical properties of the optical member.

  Such light-induced degradation adversely affects the optical properties and performance of quartz glass optics by reducing the light transmission level, discoloring the glass, changing the refractive index, changing the density, and increasing the absorption level of the glass. give. Over the years, many methods have been proposed to improve the light damage resistance of quartz glass. It is generally known that high purity quartz glass made by methods such as flame hydrolysis, CVD soot remelting process, plasma CVD process, electromelting of quartz crystal powder and other methods are susceptible to laser damage to varying degrees. It has been.

  When quartz glass is exposed to an unpolarized or circularly polarized UV laser beam, additional birefringence (induced edge birefringence) is usually generated in the peripheral region of the exposure beam due to distortion caused by laser damage, but the light beam In the central region, induced birefringence is usually negligible. Recently, a new phenomenon of laser damage to quartz materials has been observed. When quartz glass is exposed to a linearly polarized deep UV laser beam, in addition to induced edge birefringence, birefringence (polarization induced birefringence or PIB) is further induced in the center of the exposed area of the glass. Induced birefringence, particularly polarization-induced birefringence, is particularly problematic for immersion lithography systems where the liquid fills the gap between the final lens element and the wafer in order to increase the numerical aperture of the lens system. In such an immersion lithography system, the polarization state of the UV light needs to be controlled, preferably to linear polarization. The induced birefringence of the glass changes the polarization state of the UV light and reduces phase contrast and system resolution. Thus, for deep UV and vacuum UV immersion lithography systems, the glass material used to make the lens elements can be linearly or elliptically polarized UV light in addition to low light induced wavefront distortion (LIWFD) and high transmittance. It is highly desirable to have low induced birefringence damage, particularly low polarization induced birefringence, when exposed.

  Accordingly, there is a need for synthetic quartz materials and methods of making the same that have, among other things, low levels of polarization-induced birefringence, low levels of light-induced wavefront distortion, and high levels of initial internal transmittance.

  It is an object of the present invention to provide a synthetic quartz material and a method of making the same having a low level of polarization-induced birefringence, a low level of light-induced wavefront distortion and a high level of initial internal transmittance.

  The above problems for synthetic quartz glass for use in lithography applications are determined by the present invention.

According to a first aspect of the present invention, an OD that can be used in the optical path of lithographic irradiation light of a lithographic apparatus that operates at a wavelength shorter than about 300 nm, and optionally contains OH and n (OD ) / (N (OD) + n (OH)) ratio is provided which is higher than 2 × 10 ⁻⁴ .

  In one embodiment of the first aspect of the present invention, the glass contains less than about 500 ppm by weight OH and 0.15-1400 ppm OD.

  In another embodiment of the first aspect of the invention, the glass contains less than about 150 ppm by weight OH and about 0.1-1400 ppm OD.

  In yet another embodiment of the first aspect of the invention, the glass contains less than about 20 ppm by weight OH and about 0.01-1400 ppm OD.

  In yet another embodiment of the first aspect of the invention, the glass contains less than about 20 ppm OH by weight and an OD in the range of about 0.01-300 ppm.

  In yet another embodiment of the first aspect of the invention, the glass contains less than about 20 ppm OH by weight and an OD in the range of about 0.01-150 ppm.

  In yet another embodiment of the first aspect of the invention, the glass contains less than about 1 ppm OH by weight and an OD in the range of about 0.01-150 ppm.

  A second aspect of the present invention can be used in the optical path of lithographic illumination light of a lithographic apparatus operating at a wavelength shorter than about 300 nm, as summarized above and described in detail below. It is an optical member made of OD-doped synthetic quartz glass. In some embodiments, the optical member is a refractive optical member in which illumination light passes through at least a portion of the body of the optical member. In some other embodiments, the optical member is a reflective optical member in which illumination light is reflected on at least a portion of the surface of the optical member.

  A third aspect of the present invention is a lithographic system comprising the optical member of the present invention as summarized above and described in detail below. In some embodiments, the lithography system is an immersion lithography system. The lithography system can operate at wavelengths of about 248 nm, 193 nm or even shorter.

A fourth aspect of the present invention is for creating an OD-doped synthetic quartz glass material that can be used in the optical path of lithographic irradiation light of a lithographic apparatus operating at a wavelength shorter than about 300 nm.
(I) providing a plurality of silica-containing particles;
(II) a step of depositing a plurality of particles on a high temperature support deposition surface so that the particles are consolidated in-situ into a transparent glass material;
Including
The resulting quartz glass contains OD and, optionally, OH, and the n (OD) / (n (OD) + n (OH)) ratio is higher than 2 × 10 ⁻⁴ , in some embodiments Preferably greater than about 0.1, in some other embodiments greater than about 0.3, in some other embodiments greater than about 0.5, in some other embodiments. And the particles provided in step (I) are D-containing particles such that is greater than about 0.8, and in some other embodiments greater than about 0.9, and / or In step (II), deposition and consolidation are performed in a D-containing atmosphere.
Is a process.

A fifth aspect of the invention of the present application is to create an OD-doped synthetic quartz glass material that can be used in the optical path of lithographic illumination light of a lithographic apparatus operating at a wavelength shorter than about 300 nm.
(A) providing a particle preform having a plurality of silica-containing particles;
(B) A step of purifying and / or drying the particle preform as required.
(C) A step of further doping the particle preform with a dopant, if necessary,
(D) a step of consolidating the particle preform at a high temperature to form a dense glass, and (E) if necessary, the consolidated glass obtained in step (D) is made of H ₂ , HD and / or D ₂ Process in the presence,
Including
In at least one of steps (A), (B), (C), (D) and (E), OD is introduced into or formed in the glass,
Is a process.

A sixth aspect of the present invention provides an OD-doped synthetic quartz glass,
(A) providing a plurality of OD-doped silica-containing particles, and (b) melting the particles at a high temperature to obtain transparent glass,
It is a process that includes

  A seventh aspect of the present invention is a particle preform formed during the process of the present invention, schematically described above and described in detail below.

An eighth aspect of the present invention provides an OD-doped synthetic quartz glass that can be used in the optical path of lithographic irradiation light of a lithographic apparatus that operates at wavelengths shorter than about 300 nm.
(A) providing a consolidated quartz glass containing OH;
(B) processing the consolidated glass in an atmosphere containing D ₂ , H ₂ and / or HD in order to perform H / D exchange in order to obtain the desired [OH] and [OD] in the glass;
It is a process that includes

  The OD-doped synthetic quartz glass of the present invention has the advantage of high optical performance at certain wavelengths shorter than about 300 nm, such as at 193 nm, compared to conventional quartz glass that is not substantially OD-doped.

  Additional features and advantages of the invention will be set forth in the following detailed description, and it will be apparent to those skilled in the art to practice the invention as described in the description and appended claims, and also in the accompanying drawings. Will be readily apparent or appreciated to some extent.

  The foregoing general description and the following detailed description are merely illustrative of the invention and are intended to provide an overview or framework for understanding the nature and features of the invention as claimed. Of course.

  The accompanying drawings are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification.

As used herein, the term “D-containing compound” refers to a deuterium atom (represented by D, ² ₁ H or ² ₁ D) and, optionally, a hydrogen atom (represented by H). , ¹ ₁ H), and the ratio of n (D) / (n (D) + n (H)) is higher than the natural isotope abundance ratio of D. Here, n (D) is the total number of D atoms in the D-containing compound molecule, and n (H) is the total number of H atoms in the D-containing compound molecule. Thus, examples of D-containing _{compound, D 2, DH, CD 4} , CDH 3, D 2 O, there is a DHO like, but are not limited to. As used herein, the term “D-containing” refers to a natural isotope abundance ratio where the n (D) / (n (D) + n (H)) ratio of an elemental substance, compound, material or atmosphere is D Means high.

As used herein, the term “hydroxyl” or OH means a component or component group each consisting of an oxygen atom and a hydrogen atom (H). The oxygen atoms can be ¹⁶ O, ¹⁷ O or ¹⁸ O or a mixture of any of these. As used herein, n (OH) means the total number of OH components in the material.

As used herein, the term “deuteroxyl” or OD means a component or component group each consisting of an oxygen atom and a deuterium atom (D). The oxygen atoms can be ¹⁶ O, ¹⁷ O or ¹⁸ O or a mixture of any of these. As used herein, n (OD) refers to the total number of OD components in the material.

In this application, the two terms “hydroxyl dope” and “OH dope” are used interchangeably. A hydroxyl-doped material or OH-doped material is a material containing an OH component and, if necessary, an OD component, and a natural n (OH) / (n (OD) + n (OH)) ratio of the material is H. It means a material with an isotope abundance ratio or higher. As far as this is concerned, materials originating from natural water consisting of H ₂ O and D ₂ O in which all OH components are substantially in the natural isotope ratio of H and D are considered OH doped.

  In this application, the two terms “deuteroxyl dope” or “OD dope” are used interchangeably. A deuteroxyl-doped material or OD-doped material is a material containing an OD component and, if necessary, an OH component, and the n (OD) / (n (OD) + n (OH)) ratio of the material is D. Means a material whose natural isotope abundance ratio is higher.

In the specification of the present application, OY means OH or OD, or means both unless otherwise specified. YY ′ means D ₂ or H ₂ , or HD or any mixture or combination of any two of these in any ratio, unless otherwise specified.

  As used herein, “F-doped” means that the glass contains at least 1 ppm fluorine by weight.

“It can be used in the optical path of lithographic irradiation light of a lithographic apparatus operating at a wavelength shorter than about 300 nm”,
(I) the lithographic apparatus is operating in normal usage for the intended function, ie, material is used in the optical path of the lithographic illumination light, for example, while performing a lithographic function in a semiconductor device fabrication process And (ii) materials can be used in the optical path for the purpose of redirecting or manipulating lithographic irradiation light,
Means that.

  For a person skilled in the lithography art, in order for a material to be able to be used in the optical path of lithographic irradiation light of a lithographic apparatus operating at a certain wavelength, the material must have the required composition and internal transmittance, laser-induced wavefront distortion, induced absorption. Of course, it should have the required properties, such as. Of course, it is generally desirable for those skilled in the lithography arts to be able to create materials at a reasonably low cost to manufacturers and to society as a whole (ie, with reduced negative environmental impact if possible). It is.

  In general, it is desirable that the internal transmittance of quartz glass at about 248 nm is at least 99.00% / cm so that it can be used in the optical path of lithographic irradiation light of a lithographic apparatus operating at a wavelength shorter than about 300 nm. In some applications, particularly lithographic applications for making semiconductor ICs operating at about 193 nm, it is highly desirable that the internal transmittance of quartz glass at about 193 nm is at least 99.00% / cm.

  In general, the sodium concentration of quartz glass is less than about 100 ppm by weight, and in some embodiments, less than about 50 ppm, so that it can be used in the optical path of lithographic illumination light of a lithographic apparatus that operates at wavelengths shorter than about 300 nm. Low, and in some other embodiments, less than about 10 ppm is desirable. In order to be able to be used in the optical path of lithographic irradiation light of a lithographic apparatus operating at a wavelength shorter than about 300 nm, such as about 248 nm or about 193 nm, the sodium concentration of quartz glass is lower than about 500 ppb by weight, In embodiments, it is desirable to be below about 100 ppb, in some embodiments below about 50 ppb, and in some embodiments below about 10 ppb.

  The fictive temperature is the temperature at which the frozen glass structure will be in equilibrium. The Si—O—Si bond angle is a function of fictive temperature. The infrared absorption wavelength, that is, the frequency of the Si—O—Si species varies depending on the bond angle. Therefore, the approximate virtual temperature can be determined using infrared absorption. The empirical relationship between the fictive temperature and the absorption frequency is given by Agarwal et al., “A Simple IR spectroscopic method for determining fictive temperature of silica glasses” , Journal of Non-crystalline Solids, 1995, 185, p.191. Raman scattering can also be used to determine the fictive temperature using the scattering frequency of silica defects associated with a distorted ring structure.

  As used herein, the term “polarization-induced birefringence” is used to refer to the initial birefringence of the glass prior to exposure, after a certain time or, if a pulsed laser beam is used, after a certain number of laser pulses. It means the peak value of the birefringence level measured at the central part of the uniform exposure area of the glass. Polarization-induced birefringence as claimed in this application is its magnitude (absolute value). In this application, a linearly polarized pulsed laser beam at approximately 193 nm with a given fluence and pulse length, approximately 3 mm in diameter, when exposing the glass for quantification of the polarization-induced birefringence level of quartz glass. Is directed to the fixed area of the glass sample. After a certain number of pulses, the birefringence in the central part of the exposure area is measured. The polarization induced birefringence value is calculated by subtracting the initial birefringence of the glass from the measured central birefringence.

  As used herein, the term “induced edge birefringence” refers to a certain time after a certain number of laser pulses, or after a certain time, if the pulsed laser beam is used, reducing the initial birefringence of the glass before exposure. , Which means the peak value of birefringence measured at the peripheral portion outside the exposed area of the glass but in contact with the exposed area (ie, the area where the light intensity changes from the nominal value to zero and just touching the aperture). In this application, the induced edge birefringence of quartz glass is approximately 3 mm in diameter with a given fluence and pulse length, a linearly polarized pulsed laser beam at approximately 193 nm for a given time or number of pulses. It is measured after being directed to the fixed area of the glass sample. The induced edge birefringence value is calculated by subtracting the initial birefringence of the glass from the birefringence peak value measured at the peripheral portion.

As used herein, the term “low polarization induced birefringence” refers to 5 × of a linearly polarized pulsed laser beam at about 193 nm with a fluence of about 40 μJ · cm ⁻² · pulse- ¹ and a pulse length of about 25 ns. Means polarization-induced birefringence of 0.1 nm / cm or less, measured at about 633 nm after 10 ⁹ pulses.

  As used herein, “normalized polarization-induced birefringence” is determined from the measured polarization-induced birefringence:

Is calculated according to Here, PIB (N) is normalized polarization-induced birefringence, and PIB (M) is the magnitude of the polarization-induced birefringence measurement in units of nm / cm measured at about 633 nm (ie, regardless of its sign). N ₁ is the number of pulses in units of ₁ billion (10 ⁹ ) pulses, and F is the unit of mJ · cm ⁻² · pulse ⁻¹ of a linearly polarized ArF laser on which the glass is exposed. Is a fluence. For example, for a glass sample having a measured PIB (M) size of 0.2 nm / cm as a result of exposure to an ArF laser with a fluence of 40 μJ · cm ⁻² · pulse- ¹ over 2 × 10 ¹⁰ pulses. , PIB (N) is the following formula:

It is calculated as follows.

When the same sample is measured at different N ₁ and F, the PIB (N) can also be different. If N ₁ and F are not specified, the PIB (N) value is an average value.

  The optically induced wavefront distortion (bulk LIWFD) of bulk glass is measured at 633 nm or 193 nm using methods and equipment available in the prior art. The normalized LIWFD (L633) measured at 633 nm and the normalized LIWFD (L193) measured at 193 nm of glass subjected to a pulsed ArF excimer laser (about 193 nm) are:

as well as

Is calculated according to Where LB633 is a bulk LIWFD measured at 633 nm in units of nm / cm (which could have a “+” or “−” sign depending on whether the glass shrinks or expands) LB 193 is a bulk LIWFD measured at 193 nm in units of nm / cm (which may have a “+” or “−” sign depending on whether the glass shrinks or expands) and N ′ is , LB 633 or LB 193 is the number of pulses in units of 1 million (10 ⁶ ) of a linearly polarized ArF excimer laser with which the sample is exposed, and F is in mJ · cm ⁻² · pulse ^−1. Is the fluence of the ArF excimer laser, where τ is the pulse length of the ArF excimer laser in units of ns. The L633 and L193 values allow a direct comparison of the LIWFD performance of quartz glass at different N ′, F and τ values.

  The induced absorption (IA) of the glass upon exposure to an excimer laser at about 193 nm is reported herein. The normalized induced absorption (IA (N)) of the glass is further calculated from the induced absorption. In this application, the calculation of induced absorption (IA) is:

Is done according to Here, T ₁ is the internal transmittance of the glass expressed in% / cm before laser exposure, and T ₂ is the internal transmittance of the glass expressed in% / cm after laser exposure. Then the following formula:

Calculates the normalized induced absorption IA (N). Where N ′ is the number of pulses in units of 1 million (10 ⁶ ), and F is the fluence of the ArF excimer laser to which the glass in units of mJ · cm ⁻² · pulse ⁻¹ is exposed, τ is the ArF laser pulse length in ns.

  As used herein, the term “refractive index change” or “refractive index change” or “Δn” is predetermined by using interferometry at about 633 nm (He—Ne laser). It means the maximum amount of change in refractive index (with tilt and translational displacement removed as shown below) measured in a plane perpendicular to the optical axis of the glass material or glass optical member along the direction. As is commonly done by those skilled in the art, tilt and translational displacement are subtracted when discussing refractive index changes along a direction. Thus, the amount of refractive index variation along a direction (such as the radial direction in a sample made using the OVD process) within the meaning of this application does not include tilt or translational displacement. Generally, the optical axis of a glass optical member, glass blank or glass material piece is perpendicular to the plane (cross section) where the measured refractive index non-uniformity is minimized to obtain a glass member having a large clear aperture area. Chosen.

A preferred method for determining interstitial H ₂ molecules in quartz glass, which is also the method used herein, is Raman scattering. Raman spectroscopy was obtained using a HORIBA Jobin Yvon Inc. T64000 spectrometer equipped with an EEV charge coupled device (CCD) detector. Hydrogen molecule concentration of the molecules / cm ³ as a unit, the ratio of the intensity in the laser Raman spectrum, which is detected from the hydrogen molecule scattering peak at 4135 cm ^-1 to silica scattering peak intensity _{(I 800)} at 800cm ^-1 _{(I 4135),} I ₄₁₃₅ / I ₈₀₀ (see SV Khotimchenko et al., Priklandnoi Spektroskopii, 1986, Vol. 46, No. 6, pp. 987-997). More specifically, the peak intensity was determined by integrating the area under the peak using a primary or secondary fitting to the background. The D ₂ and HD concentrations in the glass in this application were also measured using Raman spectroscopy (eg, B. Schrader, “Infrared and Raman spectroscopy: methods and applications”). Raman Spectroscopy, Methods and Applications ”, VCH, Weinheim, 1995, ISBN 3-527-26446-9; H. Komine, IEEE Journal of Quantum Electronics, April 1986, Volume QE-22. , No. 4). The D ₂ concentration was measured at 2973 cm ⁻¹ and the HD concentration was measured at 3606 cm ⁻¹ .

OH groups in the quartz ^glass, 2.72μm (3676cm -1), having a characteristic absorption band near 2.21μm (4525cm ^-1) and 1.38μm (7256cm ^-1). The concentration of OH was measured by FTIR using the peak height of 3676 cm ⁻¹ absorption band or 4525 cm ⁻¹ absorption band.

The OH concentration c in units of mole liter- ¹ is the Beer-Lambert Law:

Derived from. Here, absorbance A = log (T _reference / T _OH ), T _reference is the transmittance of the sample at the reference position of the non-absorption wavelength such as 4000 cm ⁻¹ , T _OH is the OH absorption peak (˜3676 cm ^{−1 for} silica) ) Is the molar absorptivity in units of liters · mol− ¹ · cm ⁻¹ , c is the concentration in units of mol·l− ¹ , and b is the path length in units of cm. (Sample thickness)

It is.

The concentration of OH in units of ppm in weight, the density of the quartz glass (approximately 2.2 g / cm ³⁾ and molecular weight of OH using (approximately 17 g / mol), a unit of mol-l ^-1 c Calculated from The constant ε for high purity quartz glass at a specific wavelength is available in the prior art.

  The OD concentration in the quartz glass was obtained in the same manner. That is, starting with FTIR measurements, Beer-Lambert law:

It was calculated by using. Here, the absorbance A ′ = log (T ′ _standard / T _OD ), the T ′ _standard is the transmittance of the sample at the standard position of the non-absorption wavelength such as 2780 cm ⁻¹ , and T _OD is the OD absorption peak (about ~ for silica) 2705cm ^-1 is the transmission of the sample at), epsilon 'is molar absorptivity (2705cm ^-1 in 57.4 l · mol ^-1 · ^cm -1 in units of liter mole ^-1 · ^{cm -1),} c ′ is a concentration in units of mol·liter− ¹ , b ′ is a path length (sample thickness) in units of cm,

It is.

The concentration of OD to the ppm on a weight units, the density of the quartz glass (approximately 2.2 g / cm ³⁾ and molecular weight of OD with (approximately 18 g / mol), a unit of mol-l ^-1 c 'Calculated from'. The constant ε ′ for high purity quartz glass at a specific wavelength is available in the prior art.

  As used herein, “particle preform” means an object having a shape and consisting of a plurality of solid particles. Accordingly, the particle preform in the present specification is, for example, a soot preform substantially composed of silica soot particles obtained from a flame hydrolysis process, a dough composed of many silica particles obtained from a sol-gel process, and the like. be able to.

  As used herein, the term “soot dispenser” is a device that dispenses preformed soot particles, for example, by spraying.

  In search of silica glass materials having desired optical characteristics, particularly with respect to initial internal transmittance, LIWFD, light-induced absorption, polarization-induced birefringence, etc. It has been found that the OH concentration is equivalent to an equivalent OD-free glass and shows performance that is superior in some important respects. The present invention is based on this finding.

Quartz glass containing D ₂ (deuterium molecules) has already been disclosed and studied in the prior art. For example, the specification of US Pat. No. 5,325,230 (A) to Yamagata et al states that, like H ₂ , D ₂ can be doped into quartz glass. However, this document does not give an example of a D ₂ doped quartz glass. Furthermore, this document does not mention OD doping into quartz glass. Moreover, this document does not mention the effects of possible of D ₂ doped into silica glass to optical properties of the glass. As another example, JE Shelby, “Molecular diffusion and solubility of hydrogen isotopes in vitreous silica,” Journal of Applied Physics, 1977. August, Vol. 48, No. 8 discloses the diffusion and solubility of D ₂ in quartz glass.

DL Fry et al., “Hydrogen-Deuterium Exchange in Fused Silica”, Journal of The Optical Society of America, December 1960, Vol. 50, No. 12 Pp. 1321-1322 discusses OD-doped quartz glass. In this paper, no mention is made of the optical properties of OD-doped quartz glass. Since this paper was published very early, it is obvious for those skilled in the art that the glass studied in this paper has the composition and optical properties necessary for use in current deep UV and vacuum UV lithography. I can think of it not. James E. Shelby, “Quantitative Determination of the Deuteroxyl Content of Vitreous Silica”, Communication of the American Ceramic Society, 1987 1 Moon, C-9-C-10 discloses OD-doped quartz glass and methods for characterization of such glass. Jay E. Shelby et al., “Radiation-induced isotope exchange in vitreous silica”, Journal of Applied Physics, August 1979, Vol. 50, No. 8, p. in .5533～5535, formation of OD in the quartz glass by the reaction of silica and _{D 2} when exposed to γ-rays has been studied.

None of the above references mentions a synthetic quartz glass material that can be used in the optical path of lithographic irradiation light of a lithographic apparatus operating at a wavelength shorter than about 300 nm. None of the above references disclose or suggest the desirability of OD or D ₂ doping in synthetic quartz glass for UV lithography applications. Since most of the above publications were published quite early, the person skilled in the art would know that the actual D ₂ or OD doped quartz glass samples studied in the above literature are deep UV or vacuum UV, such as at about 248 nm or 193 nm. For use in lithography applications, there are good reasons for not having the necessary composition and properties, particularly with respect to initial internal transmission, LIWFD, polarization-induced birefringence, induced absorption, and the like.

  The present invention is mostly described with respect to microlithography at about 193 nm. However, for other applications and for other applications, including but not limited to lithography at about 248 nm, lithography at about 157 nm, i-line lithography, g-line lithography, laser generators, lithography inspection apparatus, etc. Of course, the inventive materials may be used.

  The inventors of the present invention created an OD-doped synthetic quartz glass that can be used for UV lithography applications with wavelengths shorter than 300 nm. As described above, the inventors have unexpectedly discovered that OD-doped synthetic quartz glass for lithography, particularly OD-doped synthetic quartz glass having a high n (OD) / (n (OD) + n (OH)) ratio, is OH. And the total concentration of OD ([OH] + [OD]) has been found to tend to have optical properties superior to substantially the same level of non-OD doped quartz glass.

  In addition, the inventors have unexpectedly found that OD-doped high purity quartz glass exhibits improved light-induced absorption (IA) over the corresponding OH-doped high purity quartz glass. The data in FIG. 16 shows this improvement. Data was plotted as normalized induced absorption at 193 nm (expressed as normalized IA, IA (N)), calculated as described above.

  Synthetic SILICA HAVING LOW POLARIZATION-INDUCED BIREFRINGENCE, METHOD OF MAKING SAME AND LITHOGRAPHIC DEVICE COMPRISING SAME No. 11/241075 filed Sep. 30, 2005 (currently published as US Patent Application Publication No. 2006 / 0137399A1), which includes synthetic quartz. Polarization-induced birefringence phenomena in glass materials have been disclosed and studied. The contents of this specification are hereby incorporated by reference in their entirety. The quartz glass material studied in the examples of this patent application was substantially OH-doped quartz glass. In this specification, “among other things, the OH concentration in the glass is a major factor affecting the polarization-induced birefringence of the glass. In general, the higher the OH level, the higher the OH level if all other conditions remain equal. Polarization-induced birefringence is high, so we have found that in order to achieve low levels of polarization birefringence in quartz glass, the OH concentration in the glass is less than 500 ppm by weight, preferably less than 300 ppm, Preferably it is below 100 ppm, even more preferably below 50 ppm and most preferably below 20 ppm. "

  Without wishing to be bound by any particular theory, or without the need for it, the inventors have described the mechanism of polarization-induced birefringence in quartz glass containing OH and / or OD as n (OD) Presented below, along with a mechanism to explain the reduced polarization-induced birefringence in quartz glass with an increased / (n (OD) + n (OH)) ratio. The description is briefly shown in FIGS. In these three figures, Y represents H or D, and hydrogen bonds are indicated by broken lines.

Journal of Non-Crystalline Solids, 2000, Vol. 261, pp. 186-194, entitled “Hydroxyl Groups in High-Purity Silica Glass” in 1999 Various types of OH bonds within ₂ are described. The inventors expect the OD to bond within the SiO ₂ glass network in a substantially similar manner. FIG. 1 briefly illustrates the proposed mechanism for the purpose of elucidating at least in part the polarization-induced birefringence that occurs in quartz glass containing OH and / or OD. Chemical structural formulas (F1) and (F2) represent partial structures of quartz glass before and after UV light exposure, respectively. Initially, before UV light exposure, it is considered that Si—OY bonds are randomly arranged in the SiO ₂ network structure and some hydrogen bonds are formed. UV light exposure can provide sufficient activation energy to allow movement of -OY (or -Y) bonds (other wavelengths can be affected if there is sufficient absorption). If the light is linearly polarized light, the bonds aligned in the polarization direction of the light can be activated and move, resulting in the breaking of previously existing hydrogen bonds and / or the formation of new hydrogen bonds. Thus, polarization induced birefringence (PIB) damage occurs in the sample. The more SiOY in the sample, the greater the PIB damage. The inventors expect a nearly linear response to the amount of ppm OY in the silica.

  FIG. 2 briefly illustrates a slightly different mode of photochemical reaction than that of FIG. 1 that may possibly be involved in the polarization-induced birefringence phenomenon. As in FIG. 1, the mechanism includes breaking some hydrogen bonds that were already present in the partial glass network (F3) before exposure and forming new hydrogen bonds in the partial glass network (F4) after exposure. Is involved. The reaction rate k (Y) of the photoreaction is k (H) and k (D) when the atom Y in the figure is H and D, respectively. The inventors postulate that the reaction rate k (D) is much lower than k (H) due to the considerable mass difference between D and H (almost twice the difference). Therefore, if all other conditions, such as the total amount of OY in the glass, remain the same, the higher the ratio of n (OD) / (n (OD) + n (OH)), the higher the polarization-induced birefringence. It is thought to be lower.

Further, in FIG. 3, the inventors propose another mechanism in an attempt to explain both LIWFD and polarization-induced birefringence as a result of exposure to linearly or elliptically polarized UV irradiation light. This proposed mechanism is basically a two-step reaction involving both hydrogen bond and covalent bond breakage and formation. The first step, the photolysis reaction with a reaction rate of k ₁ (Y), involves the cleavage of the covalent bond b (Si—O bond) and possibly the hydrogen bond a in the partial structure (F5) before exposure. The reaction rate of the first stage reverse reaction is k ₁ ′ (Y). In the second stage, the reaction rate is k ₂ (Y), the cleavage of bond c (O—Y bond) in intermediate structure (F6), new bond d (Si—O bond) and e (Y—O) bond And possibly the formation of a new hydrogen bond f in the post-exposure substructure (F7). Since (F5) is a dense structure that is not as open as (F7), the density change in the exposed region occurs as a result of the reaction, and thus LIWFD occurs. It is assumed that k ₁ (D) <k ₁ (H) and / or k ₂ (D) <k ₂ (H). Therefore, it is considered that the quartz glass having a higher n (OD) / (n (OD) + n (OH)) ratio at a substantially same level of total OY concentration has a lower polarization-induced birefringence and a lower LIWFD. Based on this assumption, quartz glass doped with an OY component (OD and / or OH) having a high proportion of oxygen atoms ¹⁷ O and ¹⁸ O has a lower level of polarization-induced birefringence and a lower LIWFD level. It is considered to be. In some applications, it may be possible to form an OT-doped glass using tritium (T) atoms, another isotope of hydrogen, in making the glass.

FIG. 4 shows the induced absorption of silica containing OH / OD and various n (OD) / (n (OD) + n (OH)) ratios at approximately the same level of total [OD] + [OH] in the glass. The difference in the degree of induced absorption will be explained at least to some extent. As a result of the photolysis of Si—O bonds in the glass upon exposure to high energy photons, both E ′ centers (Si.) And Si—O., Which are believed to exhibit absorption in deep UV and / or vacuum UV. It is known that can be formed. The absorption at E ′ center has a central peak at about 215 nm and extends to about 193 nm. According to the simplified illustration of this figure, the E ′ center and Si—O.center generated by the photolysis reaction from the structure (F8) to the structure (F9) can be reversed to some extent. Thus, some absorption centers will be automatically repaired by the reverse reaction from structure (F9) to structure (F8). The intra-network reaction from structure (F9) to structure (F10) results in E ′ centers and Si—O., Which are larger in distance than E ′ centers and Si—O. It is hypothesized that the bonding reaction between them becomes more difficult, thus making the structure with E ′ and Si—O. Relatively stable and thus inducing absorption. The more structures (10) in the glass network, the more stable the absorption center and hence the higher the induced absorption. It is considered that k ₄ ″ (H)> k ₄ ″ (D). Therefore, at the same level of total [OD] + [OH], the higher the ratio of n (OD) / (n (OD) + n (OH)) in the quartz glass, the more stable due to structural relaxation, etc. The structure (10) is reduced. This is because quartz glass doped with a higher n (OD) / (n (OD) + n (OH)) ratio, the [OD] + [OH] level is substantially the same, the OD doping of the present invention. The reason why the level of induced absorption tends to be low as observed by the inventors from quartz glass will be described.

  FIG. 5 is a simplified illustration of the mechanism that explains the effect of hydrogen molecules (Y-Y ') doped on the glass on the induced absorption of the glass. Hydrogen molecules react with E 'and Si-O.color centers to form Si-Y' and Si-OY.

  The OD-doped quartz glass of the present invention can be used for lithography at wavelengths shorter than about 300 nm. It can also be used in lithographic apparatus operating at longer wavelengths, such as in i-line lithography at about 365 nm. In some preferred embodiments, the OD doped quartz glass of the present invention can be used as a refractive lens element in the path of UV illumination light utilized in dry lithographic apparatus operating at about 248 nm. In some preferred embodiments, the OD doped quartz glass of the present invention has the necessary composition and properties for use as a refractive lens element in the path of UV illumination light utilized in immersion lithography apparatus operating at about 248 nm. In some other preferred embodiments, the OD doped quartz glass of the present invention can be used as a refractive lens element in the path of UV illumination light utilized in dry lithographic apparatus operating at about 193 nm. In some preferred embodiments, the OD-doped quartz glass of the present invention has the necessary composition and properties for use as a refractive lens element in the path of UV illumination light utilized in an immersion lithographic apparatus operating at about 193 nm. Those skilled in the lithography arts will appreciate that for quartz glass to be used as a lens element in these applications, UV transmission, UV degradation with respect to induced absorption, light-induced wavefront distortion (LIWFD), refractive index uniformity, virtual temperature, It has been found that stringent requirements for optical performance such as birefringence, light induced birefringence must be met. A wealth of literature discusses the relationship between these required optical performances and glass compositions in terms of OH concentration and distribution, halogen concentration and distribution, alkali metal concentration and distribution, transition metal concentration and distribution, etc. It is in. As discussed above, in a totally unexpected manner, the inventors have found that OD-doped high purity quartz glass has excellent performance in polarization-induced birefringence, especially when exposed to linearly polarized light. I found. Accordingly, the glasses of the present invention, particularly those doped with a high OD ratio, can be advantageously used in immersion lithography techniques. Of course, OD-doped quartz glass can be used as a material for lens elements in reflective lithography operating in the vacuum UV and X-ray spectra. Such applications have special requirements for other physical properties of the glass.

The natural isotope abundance ratio of the deuterium atom (D) is about 1.15 × 10 ⁻⁴ in moles. The n (D) / (n (D) + n (H)) ratio of the OD-doped quartz glass of the present invention is higher than about 2 × 10 ⁻⁴ and thus higher than the natural isotope abundance ratio of D. The synthetic quartz glass material of the present invention can be substantially free of OH. However, within the scope of the present invention, it is possible for the glass to contain some level of OH. In any case, the n (OD) / (n (OD) + n (OH)) ratio of the glass is higher than about 0.05 in some preferred embodiments of the OD-doped synthetic quartz glass of the present invention, In some embodiments, preferably greater than about 0.1, in some embodiments, preferably greater than about 0.2, in some embodiments, preferably greater than about 0.3, In some embodiments, preferably greater than about 0.4, in some embodiments, preferably greater than about 0.5, and in some other embodiments, greater than about 0.8. Preferably in some other embodiments above about 0.90, in some other preferred embodiments above about 0.95, in some other embodiments Preferably higher than about 0.99. The inventors have demonstrated that high purity synthetic quartz glass with various [OD] levels can be obtained by using a soot-to-glass method. High isotopic purity D ₂ O, where n (D) / (n (D) + n (H)) is greater than 99.9%, is described below as one of the processes of the present invention. It can be used for the to-glass method and can be used to make synthetic quartz glass with n (OD) / (n (OD) + n (OH)) higher than 99%. If ordinary H ₂ O is used in various ratios, synthetic quartz glass having various levels of n (OD) / (n (OD) + n (OH)) can be produced.

In the OD-doped synthetic quartz glass of the present invention, the oxygen atoms in the OD component and, if necessary, the OH component can be ¹⁶ O, ¹⁷ O, and ¹⁸ O, each having a natural isotope abundance ratio. . The natural isotope abundance ratios of these three isotopes are 99.757%, 0.038% and 0.205%, respectively, in mol. As explained above, in some preferred embodiments, the quartz glass of the present invention contains a higher percentage of ¹⁷ O and ¹⁸ O, especially ¹⁸ O (stable isotope) than their respective natural isotope abundance. be able to.

  The OH concentration of the OD-doped quartz glass of the present invention is preferably by weight lower than about 600 ppm in some embodiments, lower than about 160 ppm in some preferred embodiments, and some other preferred implementations. In embodiments, it is preferably below about 50 ppm, in some other embodiments preferably below about 20 ppm, in some other embodiments preferably below about 1 ppm, in some other embodiments More preferably, is less than about 0.1 ppm.

  The OD concentration of the OD-doped synthetic quartz glass of the present invention is by weight, in some embodiments, less than about 1400 ppm, in some preferred embodiments, less than about 1000 ppm, and in some preferred embodiments about OD. Below 800 ppm, in some other preferred embodiments below about 500 ppm, in some other preferred embodiments below about 300 ppm, in some other preferred embodiments below about 150 ppm, In some other preferred embodiments below about 50 ppm, in some other preferred embodiments below about 20 ppm, in some other preferred embodiments below about 1 ppm, in some embodiments Is in the range of about 0.1 to 1400 ppm. In some other embodiments, in the range of about 0.1-1000 ppm, in some embodiments in the range of about 0.1-800 ppm, and in some other embodiments, in the range of about 0.1-1000 ppm. Between 0.1 and 500 ppm, in some other embodiments in the range of about 0.01 to 150 ppm, and in some other embodiments in the range of about 0.01 to 50 ppm; In some other embodiments, it is in the range of about 0.10-20 ppm.

  In some embodiments of the OD-doped synthetic quartz glass of the present invention, the glass contains less than about 500 ppm OH and 0.15-1400 ppm OD by weight. In some embodiments of the OD-doped synthetic quartz glass of the present invention, the glass contains less than about 150 ppm OH and 0.1-1400 ppm OD by weight. In some other embodiments of the OD-doped synthetic quartz glass of the present invention, the glass contains less than about 20 ppm OH and 0.01-1400 ppm OD by weight. In some other embodiments of the OD-doped synthetic quartz glass of the present invention, the glass contains less than about 20 ppm OH and 0.01-300 ppm OD by weight.

In some embodiments of the OD-doped synthetic quartz glass of the present invention, the ratio of OD concentration [OD] to OH concentration [OH] at various locations of the glass, ie, [OD] / [OH] is substantially It is constant. The “substantially constant ratio” is the difference between the measured maximum ratio (R _maximum ) and minimum ratio (R _minimum ): 2 (R _maximum− R _minimum ) / (R _maximum + R _minimum ) ≦ It means that 0.1 is satisfied. In some embodiments, 2 (R _max -R _min ) / (R _max + R _min ) ≦ 0.05.

  The OD-doped synthetic quartz glass of the present invention is less than about 10 ppm by weight in some embodiments, measured in a plane substantially perpendicular to the optical axis of the glass, and in some embodiments about 5 ppm. Less than about 2 ppm in some other embodiments, less than about 1 ppm in some other embodiments, less than about 0.1 ppm in some other embodiments, [OD] Have fluctuations. The OD-doped synthetic quartz glass of the present invention is less than about 10 ppm by weight in some embodiments, measured in a plane substantially perpendicular to the optical axis of the glass, and in some embodiments about [OH] variation less than 5 ppm, in some other embodiments less than about 2 ppm and in some other embodiments less than about 1 ppm, in addition to the [OD] variation described in this paragraph Or have no such [OD] variation.

  The OD-doped synthetic quartz glass of the present invention contains substantially no dopant other than OD and OH. However, the OD-doped synthetic quartz glass of the present invention may contain dopants such as Al, F, Cl and Ti. The OD-doped synthetic quartz glass of the present invention containing Ti requires high dimensional stability, particularly with respect to temperature changes, such as reflective optical elements used in reflective lithography technology operating in the vacuum UV and X-ray spectra. It is advantageous in that it can be used for a substrate for a reflective optical element. The OD-doped synthetic quartz glass of the present invention doped with F can contain, for example, less than 1000 ppm of fluorine by weight, with the fluorine content being less than about 500 ppm in some embodiments, Less than about 300 ppm in some other embodiments, less than about 100 ppm in some other embodiments, less than about 50 ppm in some embodiments, and less than about 10 ppm in some other embodiments. Few. In some embodiments of the OD-doped synthetic quartz glass of the present invention, the glass contains less than about 150 ppm by weight OH, about 0.1 to 1400 ppm OD by weight, and about 1 to 500 ppm F by weight. In some other embodiments of the OD doped synthetic quartz glass of the present invention, the glass contains less than about 20 ppm OH, about 0.01-1400 ppm OD, and about 1-500 ppm F by weight. In some other embodiments of the OD-doped synthetic quartz glass of the present invention, the glass contains less than about 20 ppm OH, about 0.01-300 ppm OD, and about 1-500 ppm F by weight.

The OD-doped synthetic quartz glass can be doped with H ₂ molecules, HD molecules and / or D ₂ molecules. The total amount of OD-doped synthetic quartz glass of the present invention is in the range of 1 × 10 ¹⁵ to 1 × 10 ¹⁹ molecules / cm ³ in some preferred embodiments, and about 5 × 10 5 in some embodiments. More than ¹⁵ molecules / cm ³ , in some embodiments more than about 1 × 10 ¹⁶ molecules / cm ³ , in some preferred embodiments less than about 5 × 10 ¹⁸ molecules / cm ³ , In another preferred embodiment less than about 5 × 10 ¹⁷ molecules / cm ³ , in some other preferred embodiments less than about 1 × 10 ¹⁷ molecules / cm ³ , in some other preferred embodiments Has a concentration of [H ₂ ], [HD] and [D ₂ ] in the range of about 1 × 10 ¹⁶ to 1 × 10 ¹⁷ molecules / cm ³ . The (2n (H ₂ ) + n (HD)) / 2 (n (H ₂ ) + n (HD) + n (D ₂ )) ratio of the OD-doped synthetic quartz glass of the present invention is 0 in some preferred embodiments. Higher than 0.1, in some preferred embodiments higher than about 0.3, in some other preferred embodiments higher than about 0.5, and in some other embodiments about 0.7. Higher, in some other preferred embodiments, higher than about 0.9. In some preferred embodiments, the glass has a (2n (H ₂ ) + n (HD)) / 2 (n (H ₂ ) + n (HD) + n (D ₂ )) ratio of substantially H It is a natural isotope abundance ratio. The (2n (D ₂ ) + n (HD)) / 2 (n (H ₂ ) + n (HD) + n (D ₂ )) ratio of the glass is higher than 0.1 in some other preferred embodiments, In some preferred embodiments greater than about 0.3, in some other preferred embodiments greater than about 0.5, in some other embodiments greater than about 0.7, In another preferred embodiment of the above, it is higher than about 0.9. In some preferred embodiments, the (2n (D ₂ ) + n (HD)) / 2 (n (H ₂ ) + n (HD) + n (D ₂ )) ratio of the glass is substantially equal to D It is a natural isotope abundance ratio.

In some embodiments of the OD-doped synthetic quartz glass of the present invention, the [D ₂ ] / [H ₂ ] ratio, R ′, at various locations of the glass is substantially constant. The “substantially constant ratio” is the difference between the measured maximum ratio (R ′ _maximum ) and minimum ratio (R ′ _minimum ): 2 (R ′ _maximum− R ′ _minimum ) / (R ′ _maximum ) + _R′minimum ) ≦ 0.1. In some embodiments, 2 (R ′ _max −R ′ _min ) / (R ′ _max + R ′ _min ) ≦ 0.05.

  The variation in OH and OD concentrations ([OH] + [OD]) measured in a plane perpendicular to at least one direction of the OD-doped synthetic quartz glass of the present invention is about 50 ppm in some embodiments. Preferably less than about 30 ppm in some embodiments, preferably less than about 20 ppm in some other embodiments, less than about 10 ppm in some other embodiments, In other embodiments, it is preferably less than about 1 ppm, and in some other embodiments it is preferably less than about 0.1 ppm.

  The Cl concentration of the OD-doped quartz glass of the present invention is below about 100 ppm in some embodiments, below about 50 ppm in some embodiments, and below about 10 ppm in some embodiments.

  It is known that alkali metals, alkaline earth metals and transition metals can be detrimental to the transmission properties of quartz glass. For example, PC Schultz, “Optical Absorption of the Transition Elements in Vitreous Silica”, Journal of The American Ceramic Society, July 1974, No. 57, No. 7, pp. 309-313; specification of US Pat. No. 6,174,509 B1 to Corning Incorporated with the name “Pure Fused Silica, Furnace and Method” U.S. Pat. No. 6,698,248 B2 to Corning, with the name “Methods and Furnaces for Fused Silica Production”. US Pat. No. 6,174,509 B1 describes an article made by collecting fused silica particles in a refractory furnace where at least a portion of the refractory is exposed to a halogen-containing gas that reacts with contaminating metal ions in the refractory. Disclosure. As disclosed in US Pat. No. 6,174,609, improvements in zircon refractories have reduced the impact of sodium ion contamination in quartz glassware. However, it was found that not only sodium but other contaminants were also present in the furnace refractory. Such contaminants include alkaline earth metals and transition metals such as iron, titanium and lead, aluminum, phosphorus and sulfur. U.S. Pat. No. 6,698,248 B2 discloses a method and apparatus for producing quartz glass members with high internal transmittance. The method and furnace as disclosed were able to produce quartz glass with an internal transmission at 193 nm of at least 99.65% / cm. In this document, “Next-generation quartz glass used in the fine lithography market is required to have an ArF (193 nm) internal transmittance of more than 99.65% / cm, preferably more than 99.75% / cm. The standard manufacturing process described above can consistently produce quartz glass lens blanks with an internal transmission of 99.5% / cm.The reduction of metal contaminants, which have a major impact on UV transmission, Played a major role in the production of higher quartz glass The effects of metals such as sodium, potassium and iron are evident at the tens of ppb level, with a transmittance of 99.65 without sacrificing glass homogeneity. The ability of a standard process to produce% / cm quartz glass has been demonstrated, but the amount required to produce lens blanks in large quantities has not yet been achieved. Therefore, consistent mass production of quartz glass with an internal transmission at 193 nm of 99.65% / cm or higher, preferably higher than 99.75% / cm, is inconsistent. It would be desirable to provide a possible method and apparatus. " However, it should be noted that the quartz glasses discussed in these documents are all OH-containing glasses and are OD-free glasses.

  Sufficient transmission properties (eg absorption, induced absorption, fluence-dependent transmittance, birefringence, light, etc.) at wavelengths of interest for UV, such as high purity synthetic quartz glass materials for use as refractive members in KrF and ArF lithographic apparatus It is also known that the levels of alkali metals, alkaline earth metals and transition metals must be very low in order to have induced birefringence, LIWFD, etc.). Some metals with multiple oxidation states can produce stronger absorption in one oxidation state than in other oxidation states. Thus, any alkali metal, any alkaline earth metal, and any transition metal that the OD-doped quartz glass of the present invention contains is less than 100 ppm in some embodiments by weight, in some embodiments. Is less than about 50 ppm, in some embodiments less than about 10 ppm, in some embodiments less than 1 ppm, in some embodiments less than 500 ppb, In embodiments, it is preferred to have less than about 300 ppb, in some embodiments less than about 100 ppb, in some embodiments less than 50 ppb, in some embodiments less than about 20 ppb, Smell It is preferred that less than about 10 ppb. Among all metals, sodium is one of the most difficult metals to reduce from glass composition because it is ubiquitous in nature and can be introduced into the glass during handling. Sodium also diffuses extraordinarily fast into consolidated glass and soot preforms at high temperatures, particularly above 800 ° C. Nevertheless, in order for a glass to have the ability to be used as a refractive optical element in a lithographic apparatus operating at wavelengths shorter than about 300 nm, such as about 248 nm or 193 nm, the sodium it contains is by weight Less than about 100 ppb is generally desirable, in some embodiments less than about 50 ppb, in some embodiments less than 30 ppb, some (such as for use in a lithographic apparatus operating at about 193 nm) In some embodiments, less than about 10 ppb and in some embodiments less than 5 ppb is desirable. The inventors created OD-doped high purity quartz glass with such a low sodium level. In some embodiments, the glass contains less than 2 ppb of any transition metal. In some embodiments, any transition metal that the glass contains is less than 1 ppb. In some embodiments, any transition metal that the glass contains is less than 0.5 ppb. In particular, in order for glass to be used as a refractive optical member in an ArF laser lithography apparatus, individual elements in the following oxidation states contained in glass, Ti (for example, +2, +4), V (for example, +5, +4) ), Cr (eg, +6, +3), Mn (eg, +6, +4, +2), Fe (eg, +3, +2), Co (eg, +3, +2), Ni (eg, +2), Cu (eg, +2, +1), Zn (eg +2), Ge (eg +4, +2), Zr (eg +4), Ag (eg +1), Cd (eg +1), Sn (eg +4, +2), Pb (eg , +4, +2), Bi (eg, +5, +3) and U (eg, +6, +3), preferably by weight, in some embodiments, less than 2 ppb. Preferably less than 1ppb in some embodiments, less than 0.5ppb in certain other embodiments, less than 0.1ppb in some embodiments. Of course, elemental metals (in the 0 state) are generally detrimental to the transmission properties of glass. Any and all metals in all oxidation states contained in the OD-doped synthetic quartz glass of the present invention are combined, by weight, in some embodiments less than 100 ppm, in some embodiments Less than about 50 ppm, in some embodiments less than about 10 ppm, in some embodiments less than 1 ppm, in some embodiments less than 500 ppb, in some embodiments Preferably less than about 300 ppb, in some embodiments less than about 100 ppb, in some embodiments less than about 50 ppb, and in some embodiments less than 30 ppb, in some other embodiments Less than 10 ppb Preferred. It is desirable that such elements be at a similar low level for OH-doped lithographic quartz glass and F-doped lithographic quartz glass.

The OD-doped synthetic quartz glass of the present invention when operated at approximately 193 nm, exposed to ¹⁰ billion (10 ¹⁰ ) pulses of a laser beam with a fluence of approximately 70 μJ / (cm ² · pulse) and a pulse length of approximately 25 ns The light induced wavefront distortion (LIWFD) shown is in the range of -0.1 to 0.1 nm / cm in some preferred embodiments, measured at 633 nm, and -0.5 in some preferred embodiments. In the range of ˜0.5 nm / cm, in some other preferred embodiments in the range of about 0-1 nm / cm, and in some other preferred embodiments in the range of about 0-0.5 nm / cm. It is in.

Measured at about 633 nm in addition to or regardless of the LIWFD characteristics described above when exposed to less than about 20 billion (2 × 10 ¹⁰ ) pulses of an excimer laser of about 193 nm The normalized wavefront distortion L633 exhibited by the OD-doped synthetic quartz glass of the present invention is −1.0 <L633 ≦ 1.0 in some embodiments and −0.5 ≦ in some embodiments. L633 ≦ 1.0, in some embodiments −0.1 ≦ L633 ≦ 1.0, and in some embodiments 0 ≦ L633 ≦ 1.0, some preferred implementations In embodiments 0 ≦ L633 ≦ 0.5, in some other preferred embodiments 0 ≦ L633 ≦ 0.4, and in some other embodiments 0 ≦ L633 ≦ 0.5. It is preferably 0.3.

In addition to, or regardless of, the LIWFD and L633 characteristics described above when exposed to about 20 billion (2 × 10 ¹⁰ ) or less pulses of an excimer laser of about 193 nm The normalized wavefront distortion L193 exhibited by the OD-doped synthetic quartz glass of the present invention, measured at 193 nm, is −1.0 <L193 ≦ 1.0 in some embodiments, and − in some embodiments— 0.5 ≦ L193 ≦ 1.0, in some embodiments −0.1 ≦ L193 ≦ 1.0, and in some embodiments 0 ≦ L193 ≦ 1.0, In some embodiments, 0 ≦ L193 ≦ 0.5 is preferable, and in some embodiments, 0 ≦ L193 ≦ 0.4 is preferable. In the embodiment, it is preferable that 0 ≦ L193 ≦ 0.3.

OD of the present invention measured at about 633 nm after exposure to 5 × 10 ⁹ pulses of a linearly polarized pulsed laser beam of about 193 nm with a fluence of about 40 μJ · cm ⁻² pulse- ¹ and a pulse length of about 25 ns The polarization induced birefringence (absolute value) exhibited by the doped synthetic quartz glass is preferably less than about 1 nm / cm in some embodiments and less than 0.1 nm / cm in some embodiments. OD of the present invention measured at about 633 nm after exposure to 1 × 10 ¹⁰ pulses of a linearly polarized pulsed laser beam of about 193 nm with a fluence of about 40 μJ · cm ⁻² pulse- ¹ and a pulse length of about 25 ns The polarization induced birefringence (absolute value) exhibited by the doped synthetic quartz glass is preferably less than about 1 nm / cm in some embodiments and less than 0.1 nm / cm in some embodiments. In some embodiments of the OD doped synthetic quartz glass of the present invention, the glass is 2 × of a linearly polarized pulsed laser beam of about 193 nm with a fluence of about 40 μJ · cm ⁻² · pulse- ¹ and a pulse length of about 25 ns. After exposure to 10 ¹⁰ pulses, it exhibits a polarization-induced birefringence (absolute value) of less than about 0.1 nm / cm, measured at about 633 nm. In some embodiments of the OD doped synthetic quartz glass of the present invention, the glass is 2 × of a linearly polarized pulsed laser beam of about 193 nm with a fluence of about 40 μJ · cm ⁻² · pulse- ¹ and a pulse length of about 25 ns. After exposure to 10 ¹⁰ pulses, it exhibits a polarization-induced birefringence (absolute value) of less than about 0.04 nm / cm, measured at about 633 nm. In some embodiments of the synthetic quartz glass of the present invention, the glass is 2 × 10 ^{10 of} a linearly polarized pulsed laser beam of about 193 nm with a fluence of about 40 μJ · cm ⁻² pulse- ¹ and a pulse length of about 25 ns. After exposure to the pulse, it exhibits a polarization-induced birefringence (absolute value) greater than about 0.001 nm / cm, measured at about 633 nm. In some embodiments of the OD doped synthetic quartz glass of the present invention, the glass is 2 × of a linearly polarized pulsed laser beam of about 193 nm with a fluence of about 40 μJ · cm ⁻² · pulse- ¹ and a pulse length of about 25 ns. After exposure to 10 ¹⁰ pulses, it shows a polarization-induced birefringence (absolute value) greater than about 0.01 nm / cm, measured at about 633 nm.

There are several normalized polarization-induced birefringences exhibited by the OD-doped synthetic quartz glass of the present invention when exposed to about 20 billion (2 × 10 ¹⁰ ) or less pulses of a linearly polarized excimer laser pulse of about 193 nm. Less than 10 in some embodiments and less than 5 in some embodiments.

The OD-doped quartz glass of the present invention is shown after being exposed to 2 × 10 ⁹ pulses of a linearly polarized pulsed laser beam of about 193 nm with a fluence of about 200 μJ · cm ⁻² pulse- ¹ and a pulse length of about 25 ns. Polarization-induced birefringence, measured at about 633 m, is less than about 0.04 nm / cm in some embodiments, less than about 0.02 nm / cm in some embodiments, and has a fluence of about 200 μJ ···. After exposure to 5 × 10 ⁹ pulses of an approximately 193 nm linearly polarized pulsed laser beam with a pulse length of approximately 25 ns at cm ⁻² pulse− ¹ , the polarization induced birefringence shown is In some embodiments, it is less than about 0.02 nm / cm.

The normalized polarization-induced birefringence exhibited by the OD-doped quartz glass of the present invention when exposed to about 2 billion (2 × 10 ⁹ ) or less pulses of about 193 nm linearly polarized excimer laser pulses is In embodiments, it is less than 2, in some embodiments, less than 1, and in some embodiments, less than 0.5. The normalized polarization-induced birefringence that the glass exhibits when exposed to about 5 billion (5 × 10 ⁹ ) or less pulses of about 193 nm excimer laser pulses in some embodiments is less than 2, In some embodiments less than 1 and in some embodiments less than 0.5. The normalized polarization-induced birefringence that the glass exhibits when exposed to no more than about 8 billion (8 × 10 ⁹ ) pulses of about 193 nm excimer laser pulses, in some embodiments, is less than 2, In some embodiments less than 1 and in some embodiments less than 0.5.

  The initial internal transmission exhibited by the OD-doped synthetic quartz glass of the present invention at about 193 nm is at least 99.00% / cm in some embodiments and at least 99.50% / cm in some embodiments. In some embodiments, it is desirable to be at least 99.65% / cm, and in some embodiments, it is preferably at least 99.75% / cm. In this embodiment, it is preferably at least 99.80% / cm.

  In some embodiments of the OD doped synthetic quartz glass of the present invention, the glass exhibits a fictive temperature below about 1150 ° C. In some other embodiments of the OD-doped synthetic quartz glass of the present invention, the glass exhibits a fictive temperature below about 1000 ° C. In some embodiments of the glass of the present invention, the glass exhibits a fictive temperature greater than about 800 ° C.

  The refractive index change measured in a plane perpendicular to at least one direction exhibited by the OD-doped synthetic quartz glass of the present invention is less than about 10 ppm in some embodiments and about 5 ppm in some embodiments. Preferably less than about 2 ppm, in some other embodiments, preferably less than about 1 ppm, and in some other embodiments, about Preferably it is less than 0.5 ppm.

  Another aspect of the present invention is an optical glass member composed of the OD-doped synthetic quartz glass material of the present invention, as described generally and in detail above. The optical glass member is advantageously used in the optical path of irradiation light having a wavelength shorter than about 300 nm, but the glass member of the present invention is used in the optical path of irradiation light having a longer wavelength, such as the visible spectrum or the infrared spectrum. Can be used. The OD doped glass of the present invention is particularly advantageous for use in some infrared applications where OH is undesirable and OD is acceptable. Non-limiting examples of such glass members of the present invention can include, but are not limited to, optical members, sputter targets, etc. for use as refractive lens elements. The refractive lens element can be used in, for example, a lithography scanner and a stepper device, a laser generator, a laser etalon, a lithography inspection apparatus, and the like. The OD-doped glass optical member of the present invention is particularly suitable for devices with high fluence irradiation light due to its improved laser damage resistance.

  Another aspect of the present invention is a lithography system including at least one optical member of the present invention. The lithographic system is advantageously an immersion system in which at least one lens element is brought into contact with the liquid. Immersion lithography systems typically use linearly polarized illumination light. Due to the high resistance to polarization-induced birefringence damage, the OD-doped synthetic quartz glass member of the present invention is particularly suitable for such lithography systems. Due to the superior performance of the OD-doped glass material of the present invention as described above, the OD-doped glass material of the present invention is a conventional dry lithographic apparatus that operates at wavelengths shorter than about 300 nm, such as at about 248 nm, 193 nm, and 157 nm. Can be used.

  The OD-doped synthetic quartz glass material of the present invention uses various methods such as direct-to-glass method, soot-to-glass method and sol-gel process, to name a few. Can be created. In general, the OD-doped quartz glass of the present invention comprises (i) the use of a D-exchange starting material or a D-enriched starting material to make silica, (ii) the production of quartz glass in a rich D environment, or (iii) quartz. It can be created by OD doping into the glass.

The first method considered by the inventors is the direct-to-glass method. Generally speaking, this process is
(I) providing a plurality of silica-containing particles;
(II) depositing a plurality of particles on the support deposition surface at a high temperature so that the particles consolidate in place into a transparent glass material;
Where, where
In step (II), the deposition and consolidation are carried out by the obtained quartz glass containing OD and optionally OH, and the ratio of n (OD) / (n (OD) + n (OH)) is about 2 ×. Preferably, it is performed in a D-containing atmosphere so that it is higher than 10 ⁻⁴ , and the n (OD) / (n (OD) + n (OH)) ratio is preferably higher than about 0.05 in some embodiments. Preferably higher than about 0.1 in some embodiments, higher than about 0.3 in some other embodiments, higher than about 0.5 in some other embodiments, In some other embodiments, greater than about 0.8, yet in other embodiments, greater than about 0.9, and in some other embodiments, greater than about 0.95.

In step (I), the plurality of silica-containing particles can be provided by flame hydrolysis of at least one precursor compound containing silicon, such as a silicon halide (such as SiCl ₄ ) or an organosilicon compound. . Non-limiting examples of organosilicon compounds include octamethylcyclotetrasiloxane (OMCTS). The precursor compound can contain D at a level higher than its natural isotope ratio (as in D-containing OMCTS), in which case the particles themselves are usually OD-doped at the time they are made. Alternatively, the precursor compound may contain D at a level that does not exceed its natural isotope abundance, but may contain D, such as added D ₂ O or CD ₄ , CDH ₃ , CD ₂ H ₂ , D ₂ , HD, etc. The precursor compound can be subjected to flame hydrolysis in an atmosphere containing D at a level higher than its natural isotope ratio, such as an atmosphere containing D ₂ O created by burning the compound as a fuel. The silicon-containing particles can be prepared in advance, or can be prepared in-situ in the same furnace in which the particles are deposited and consolidated in step (II). If the silicon-containing particles are pre-made, the particles can be provided by a soot dispenser in step (I) and sprayed onto the support deposition surface and consolidated. If the pre-made particles are D-containing particles, depending on the OD level of the pre-made particles and the desired OD level of the final consolidated glass, the process in an environment containing or not containing D ( II) can be performed. If the pre-made particles are not D-containing particles, step (II) is performed in order to introduce OD into the consolidated glass (as D ₂ O or D ₂ gas or a combination thereof is present). Should be done in a containing environment. This direct-to-glass method for making the OD doped quartz glass of the present invention can be a plasma assist process. Final OD doping in which OD is doped at a desired level by adjusting the n (D) / (n (D) + n (H)) ratio of the atmosphere in which the particles are made and the atmosphere in which step (II) is performed Glass can be created.

There is a wealth of literature on equipment and processes for making high purity quartz glass materials by using the direct-to-glass method that can be adapted to making the high purity OD doped quartz glass of the present invention. For example, it is highly desirable that the support deposition surface in step (II) is a substantially flat deposition surface of a horizontal turntable. In general, in order to obtain OD-doped quartz glass for use in deep UV and vacuum UV lithographic apparatus, the glass should be made using high purity raw materials and processing agents in a very clean environment, as desired. Care should be taken to avoid contamination with metals harmful to the properties. Equipment for making high purity starting materials and soot (and corresponding consolidated glass) and / or soot (and soot, for example, with Cl ₂ or Cl ₂ + CO to remove trace metals) Low metal impurities can be obtained by purifying the apparatus used for the above. However, as desired in the production of ordinary OD-free high purity quartz glass, if desired, various OD-doped synthetic quartz glass materials such as F, Al, Ti, etc. in a direct-to-glass furnace. It is also possible to dope with different dopants. If the particles are pre-made in step (I), the particles can have substantially the same composition, or can have different compositions (eg, some particles containing a dopant and substantially Particles containing no dopant can be mixed and provided in step (I)).

The consolidated glass produced in step (II)
(III) a step of treating the consolidated glass obtained in step (II) in an atmosphere containing H ₂ and / or HD and / or D ₂ ;
Can receive.

The purpose of step (III) is to adjust the level of molecular hydrogen (H ₂ , HD and / or D ₂ ) in the consolidated glass to a desired level. Hydrogen molecules doped into the glass at the desired level can improve the optical performance of the material. Such hydrogen treatment is desirably performed at a temperature lower than about 600 ° C. In some cases, it may be desirable for the hydrogen treatment to occur at a temperature above about 600 ° C. Generally, it is desirable that the hydrogen treatment be performed at a temperature lower than about 1000 ° C. In general, the processing time and temperature of step (III) is such that the total concentration of H ₂ , HD and D _{2 in} the processed glass is about 0.5 × 10 ¹⁵ to about 5 × 10 ¹⁹ molecules / cm ³ . In some embodiments, preferably in the range of about 0.5 × 10 ¹⁵ to about 5 × 10 ¹⁸ molecules / cm ³ , and in some other embodiments, preferably about 1 × 10 ^15. To about 1 × 10 ¹⁸ molecules / cm ³ , and in some embodiments preferably in the range of about 0.5 × 10 ¹⁶ to about 5 × 10 ¹⁸ molecules / cm ³ , In this embodiment, it is desirable to select it so as to be in the range of about 1 × 10 ¹⁶ to about 1 × 10 ¹⁸ molecules / cm ³ . In some embodiments, the atmosphere of step (III) is a D-containing atmosphere, ie the atmosphere is higher than the natural isotope abundance ratio of D (2n (D ₂ ) + n (HD)) / 2 (n (H ₂ ) + n (D ₂ ) + n (HD)) ratio. After step (III), the [D ₂ ] / [H ₂ ] ratio at various locations on the glass is substantially constant, ie the distribution profiles of D ₂ and H ₂ (concentrations may be different) It is also desirable that it be substantially the same). However, in order to reduce costs, in step (III), the atmosphere does not substantially contain D, that is, (2n (H ₂ ) + n (HD)) / 2 (n (H ₂ ) + n (D ₂ ) of the atmosphere. ) + N (HD)) ratio may be higher than or approximately equal to the natural isotope abundance ratio of H.

Another method of the present invention for making the OD-doped synthetic quartz glass of the present invention, referred to herein as “particle-to-glass”, is a porous particle preform. Including formation. This method
(A) providing a particle preform having a plurality of silica-containing particles;
(B) A step of purifying and / or drying the particle preform as required.
(C) A step of further doping the particle preform with a dopant, if necessary,
Step to consolidate the particles preform at a high temperature to densify the (D) glass, and (E) optionally, a consolidated glass obtained in step (D) of H _2, HD and D ₂ Processing in the presence of,
Including
In at least one of steps (A), (B), (C), (D) and (E), OD is introduced into or formed in the glass. In general, it is preferred that OD be introduced into the glass in one of steps (A), (B), (C) and (D).

In one embodiment of this process, step (A) comprises
(A1) providing a plurality of particles, and (A2) depositing particles on a support surface to form a particle preform,
including. In some embodiments, the support surface is preferably rotating.

In step (A1), the particles are (A1.1) flame hydrated of at least one silicon-containing precursor compound (such as a silicon halide (eg SiCl ₄ ) or an organosilicon compound), which can be a plasma assisted process. As an example of an organosilicon compound, octamethylcyclotetra can be provided by decomposition, or (A1.2) a soot dispenser, which can be a plasma assisted process, or (A1.3) other plasma assisted processes. Mention may be made of siloxane (OMCTS). In the present application, the particle-to-glass process with step (A1.1) is referred to as the “sout-to-glass” process. A soot-to-glass process for making conventional OD-free high purity quartz glass was filed, for example, on June 8, 2005 and is now published as US Patent Application Publication No. 2006/0137398. US Patent Application No. 11 /, a co-pending and co-assigned product with the name “HIGH REFRACTIVE INDEX HOMOGENEITY FUSED SILICA GLASS AND METHOD OF MAKING SAME” This is described in the specification of US Pat. The relevant portions of this specification are included herein by reference.

The particles provided by step (A1.1) can be OD-doped particles or non-OD-doped particles. When D-containing compounds are used in the flame hydrolysis process, the provided particles are usually OD-doped particles. If the atmosphere of the flame hydrolysis process of step (A1.1) contains D ₂ O, the particles so provided are usually OD-doped particles.

  Step (A2) can be performed by various methods such as (A2.1) external method, (A2.2) internal method, (A2.3) axial method, (A2.4) planar deposition method, etc. It can be carried out. There is a wealth of literature describing these methods for making conventional OD-free synthetic silica-containing glasses that can be adapted to make the OD-doped synthetic quartz glass of the present invention.

In step (A),
(A (i)) a step of forming a sol-gel containing silica, and (A (ii)) a step of forming a particle preform from the sol-gel,
A sol-gel process can be used to create a particle preform.

Step (A (i)) can be carried out in the presence of at least one D-containing compound or from at least one D-containing compound. In particular, step (A (i)) can be carried out in the presence of D ₂ O. For example, a sol-gel can be made by hydrolysis of a silicon-containing precursor compound (such as siloxane) in liquid D ₂ O. Accordingly, the particle preform created in step (A) has OD-doped silica particles. There is a wealth of literature describing methods for making silica-free OD-doped glasses made of silica by a sol-gel process that can be adapted to make the OD-doped synthetic quartz glass of the present invention. In general, the sol-gel process involves the hydrolysis of a silicon-containing precursor compound (such as a silane, siloxane or polysiloxane) in an aqueous medium to make a silica sol-gel. The sol-gel can then be cast into a dough, which is in the form of a particle preform in the sense of the present application. The dough is dried to some extent and then processed in the following steps (B) to (E).

Particle preforms made by flame hydrolysis and sol-gel processes can contain undesirably high amounts of OH and OD. Particle preforms made by the sol-gel process can even contain significant amounts of H ₂ O and / or D ₂ O. The above-mentioned flame hydrolysis with combustion of a fuel containing H and / or D (eg H ₂ , D ₂ , CH ₄ , CDH ₃ etc.) and / or a precursor compound containing H and / or D (eg OMCTS). Particle preforms (generally referred to as soot preforms) made by decomposition methods (IVD, OVD, VAD, PD) generally have OH groups and OD groups in the soot particles. For many applications, such amounts of OH and / or OD within the preform will result in a consolidated glass having an undesirably high level of OH and / or OD for the intended purpose. For example, for high purity quartz glass for use in optical components used in UV and deep UV lithographic apparatus, the total concentration is preferably less than 500 ppm, and in some embodiments less than 300 ppm, It is preferred that low OH / OD glasses, such as glasses containing OH and OD, are desirable, preferably in a form below about 150 ppm, and in some embodiments below about 50 ppm. Of course.

For such particle preforms that have undesirably high levels of H ₂ O, D ₂ O, OH, and / or OD, the glass is compacted prior to and doped with additional dopants as needed. It is desirable to dry at least in order to reduce the concentration of OH and / or OD to the desired level before it is made. In order to control the final OH and / or OD concentration in the consolidated glass, the total OH and / or OD concentration of the particle preform is less than about 50 ppm by weight, in some embodiments It is often dried so that it is preferably less than about 10 ppm, in some other embodiments preferably less than about 1 ppm, and in some other embodiments preferably less than about 0.01 ppm. desirable. A particle preform is considered substantially dry for purposes of this application if the total concentration of OH and / or OD it contains is less than about 1 ppm by weight.

In order to reduce H ₂ O, D ₂ O, OH and / or OD in the particle preform, a desiccant such as a dry inert gas, including but not limited to He, Ar, N _2, etc. It can be used at high temperatures above 500 ° C, and in some embodiments above about 800 ° C. Similarly, CO, CO _{2 and the} like can be used as a desiccant. CO can react with the silica particles to cause defects in the glass. Such defects can be repaired as described below. Preferred _{desiccants, F 2, Cl 2, Br} 2, halogen compounds, CO, a CO ₂ and their equivalent mixture. The halogen compound is preferably selected from HX, COX ₂ , SOX ₂ , CX ₄ and SX ₆ where X is selected from F, Cl, Br and combinations thereof. The most preferred desiccants are Cl ₂ and Br ₂ and mixtures thereof with or without CO.

  The particle preform as provided in step (A) may contain unacceptably large amounts of contaminants, particularly harmful metal ions. This is especially true when the sol-gel process is used to make a particle preform. Particle preforms made by the sol-gel process generally contain high levels of Fe, Na, etc. that are detrimental to the optical performance of the glass in the deep and vacuum UV spectra. If the glass is consolidated and contaminants are incorporated into the consolidated glass, removal of the contaminants becomes difficult. Therefore, if necessary, it is highly desirable to purify the particle preform prior to consolidation so that the concentration of contaminants is reduced to the desired level prior to consolidation of the preform.

Many of the desiccants for removing H ₂ O, D ₂ O, OD and / or OH from the particle preform also have a contaminant removal function. Such desiccants, when used in the drying process, can simultaneously serve to purify the particle preform. Thus, advantageously, drying and purification can be performed simultaneously. Alternatively, different agents can be used to achieve these two different functions, if desired. _Cl 2 Preferred purification _agents, F 2, Br _2, halogen-containing compounds, CO, CO _2, etc., and it is these air-fuel mixture and combination, but not limited to. The halogen-containing compound can be HX, COX ₂ , SOX ₂ , CX ₄ and SX _{6 and the} like, and X is selected from F, Cl, Br and combinations thereof. The most preferred desiccants are Cl ₂ and Br ₂ and their equivalent mixtures with or without CO.

The particle preform can be further doped in step (C) prior to solidification in step (D). Although it is difficult to dope the consolidated glass with dopants, it is also generally known that the doping of the particle preform can be performed in a controlled manner. Thus, a dopant such as OD, OH, F, Cl, etc. can be further doped into the particle preform with or without the drying / purification step (B). To facilitate the doping process, doping at high temperatures, such as above 500 ° C. and in some embodiments above 800 ° C., is desirable. By controlling the doping temperature, the concentration of the dopant in the doping atmosphere and the doping time, the final concentration of the desired dopant in the particle preform and thus the concentration of the desired dopant in the final consolidated glass can be controlled. In order to dope the particle preform with F, F-containing compounds such as HF, DF, COF ₂ , SOF ₂ , CF ₄ and SF ₆ can be used. Therefore, F can be doped during the drying and / or purification step (B). In order to dope the particle preform with Cl, Cl ₂ and Cl-containing compounds such as HCl, COCl ₂ , SOCl ₂ and CCl ₄ can be used. Therefore, Cl can be doped during the drying and / or purification step (B). That is, steps (B) and (C) can be performed at least to some extent simultaneously.

For the purposes of the present invention, as described above, it is highly desirable to control the concentration of OH and / or OD in the consolidated glass for many applications. This can desirably be done in steps (B) and / or (C). For example, in step (B), the particle preform can be dried and purified to a level substantially free of OH and / or OD. Subsequently, in step (C), the OH and / or OD is desired in a controllable manner in the dried particle preform such that the final consolidated OD-doped glass has the desired OD and / or OH concentration. Doped to level. It is desirable that the doping be performed at an elevated temperature, such as higher than 500 ° C. and in some embodiments higher than 800 ° C. By choosing the appropriate doping time, doping temperature, and concentration of dopant in the doping atmosphere, not only can the final concentration of OD and / or OH, and other dopants in the consolidated glass be controlled, but also their uniformity. A good distribution can be achieved. In order to dope the particle preform with OD and / or OH, the OD-containing compound and / or OH-containing compound can be used at various partial pressures in the dopin atmosphere. For example, to dope the OD particle preform doping atmosphere _may contain _{D 2, HD, D 2 O} , CH 3 OD, C 2 H 5 OD, CH 3 COOD and other OD-containing compound . When _{the D 2} and / or HD are present in the doping atmosphere, _{D 2} and / or HD may react with SiO ₂ glass, to produce a Si-OD and / or Si-OH in the glass. For doping the OH particle preform doping atmosphere _may contain _{H 2, HD, H 2 O} , CH 3 OH, C 2 H 5 OH, CH 3 COOH and other OH-containing compounds. Similarly, when H ₂ and / or HD is present in the doping atmosphere, D ₂ and / or HD may react with the SiO ₂ glass to produce Si—OH and / or Si—OD in the glass. it can. It is known that the reaction between hydrogen gas (D ₂ , DH and / or H ₂ ) and SiO ₂ can cause quartz glass to form oxygen deficient sites. Therefore, as described below, when hydrogen gas is used as a doping agent in the doping atmosphere, before or during the consolidation of the particle preform into a dense glass to repair the defects. It is desirable to treat the particle preform in an oxidizing atmosphere. When _{the D 2} O and / or _{H 2} O is used as a doping agent in the doping atmosphere, _{D 2} O and / or _{H 2} O as _{D 2} O and / or _{H 2} O upon entering doping environment Or can be formed in situ, for example by reaction between D ₂ / H ₂ and O ₂ supplied separately into the environment. In order to achieve the desired [OD] / [OH] ratio in the final consolidated glass, the doping atmosphere is adjusted in the doping step (C) so as to contain an OD-containing compound and an OH-containing compound having a desired partial pressure. be able to. The most preferred OD doping agent for the particle preform is D ₂ O. D ₂ O with an isotope purity of greater than 99.9% by mole is commercially available. The most preferred OH doping agent for the particle preform is H ₂ O. When doping a substantially dry pre-form, the doping atmosphere can be adjusted to have the desired D ₂ O and H ₂ O partial pressures to obtain the desired OD and OH concentrations in the final glass. . When doping a particle preform containing a certain level of OH with OD, a desired amount in the particle preform can be obtained in a doping atmosphere containing a D-containing compound, such as an OD-containing compound, eg, D ₂ O. It can be processed for a sufficient amount of time so that OH is exchanged at OD. By controlling the partial pressure ratio between the OD-containing compound and the OH-containing compound in the doping atmosphere, the doping temperature and the doping time, a glass having a desired level of [OD] and [OH] can be obtained also in this embodiment. The particle preform contains an amount of OD prior to step (C), and in step (C) it is doped with OH or OH only to achieve the desired OD and OH concentration in the final glass. Are also within the scope of the present invention. Higher than about 0.02, in some embodiments higher than about 0.05, in some other embodiments higher than about 0.1, and in some other embodiments about 0.3 Higher, in some other embodiments, greater than about 0.5, in some other embodiments, greater than about 0.9, and in some other embodiments, greater than about 0.95. , N (OD) / (n (OD) + n (OH)) ratio can be achieved.

The doping atmosphere can contain O ₂ and an inert gas in addition to the doping compound. Since doping of OH and OD is typically performed at high temperatures, such as higher than about 500 ° C., and in some embodiments, higher than about 800 ° C., H ₂ , D ₂ , HD, O ₂ , H ₂ O and D ₂ O is generally present in an amount determined by chemical equilibrium and kinetic factors. Steps (B) and / or (C) can be performed in the presence of a reducing gas other than H ₂ and D ₂ , such as hydrocarbons, D-containing hydrocarbons, and the like.

It is known that when a particle preform having silica is treated in a reducing atmosphere at a high temperature as in steps (B) and / or (C), oxygen deficiency defects can occur in the glass. Such defects are particularly detrimental to transmission properties in deep UV and vacuum UV, such as about 248 nm and 193 nm. Therefore, it is highly desirable to treat the particle preform in an oxidizing atmosphere in step (C (A)) after steps (B) and (C). The oxidizing agent in the oxidizing atmosphere can be, for example, O ₂ , O ₃ , D ₂ O, H ₂ O, or the like.

In step (D) of the process of the present invention, the particle preform is consolidated into a dense quartz glass. Steps (C) and (D) can be performed simultaneously at least to some extent in the sense that at least some doping is performed while the particle preform is consolidated into a dense glass. Step (C (A)) and step (D) described above are performed at least to some extent simultaneously in the sense that at least some of the oxygen deficiency defects in the glass are oxidized and repaired in at least part of step (D). be able to. In step (D), the particle preform is desirably higher than 1000 ° C., in some embodiments higher than 1200 ° C., in which the particles are sintered into a dense glass, in some embodiments about Heated to a high temperature above 1400 ° C. The heating rate during the consolidation step (D) can be controlled in such a manner that a uniform distribution of dopants such as OH, OD, F, etc. is achieved. Step (D) can be performed in a consolidated atmosphere containing an inert gas such as He, Ar, N ₂ or the like. The consolidation atmosphere may further contain O ₂ and / or D ₂ O and / or H ₂ O at a desired level. O ₂ , D ₂ O and / or H ₂ O can work to oxidize and repair oxygen deficient sites in the glass. If high [OD] glass is desired, the consolidation atmosphere can be an atmosphere that is substantially free of H ₂ O and HDO. The consolidation atmosphere can further contain H ₂ , D ₂ , HD, and the like. However, as mentioned above, the reaction of such reducing gases with quartz glass at high temperatures can result in the formation of defects in the glass. A glass with a high [OH] and / or [OD], when treated at a high temperature in a reducing atmosphere, such as an atmosphere containing H ₂ , HD and / or D ₂ , the [OH] and [OD] The inventors believe that they tend to have fewer defects than low glass.

Step (E) of this process of the present invention includes a hydrogen doping step on the consolidated glass with a hydrogen doping atmosphere containing H ₂ , HD and / or D ₂ molecules. The hydrogen doping atmosphere contains substantially D ₂ and HD, even for glasses doped with a high percentage of OD, especially when the hydrogenation temperature is relatively low, such as below about 500 ° C. The atmosphere can not be. In some embodiments, for glasses doped with a high percentage of OD, when the hydrogen doping temperature is greater than 500 ° C., the hydrogen doping atmosphere is an atmosphere that is substantially free of HD and H _2. It is desirable to be. In any case, when added to quartz glass at temperatures below about 500 ° C., it has been found that the addition of H ₂ or D ₂ does not appreciably change the [OH] and [OD] of the glass. Hydrogen doping can advantageously be performed at temperatures below about 600 ° C. (cold addition) or at temperatures above about 600 ° C. (thermal addition) to facilitate the process. However, hydrogen doping is usually performed at a temperature lower than 1000 ° C. Due to the law of diffusion, cold addition tends to take longer to reach the same added hydrogen level in the glass. In any case, quartz glass with relatively low water content (eg, [OD] + [OH] <100 ppm) for use in the production of certain types of quartz glass and refractive lens elements in deep UV and vacuum UV lithography equipment. Particularly, in the preparation of (2), cold addition is preferable because defects generated in the consolidated glass tend to be reduced.

As mentioned above, co-pending and co-assigned (filed on September 30, 2005 and now published as US Patent Application Publication No. 2006/0137399 A1, named “Low Polarization Induced Birefringence”). Synthetic Silica, a Method for Producing the Same, and a Lithographic Apparatus Comprising the Method (SYNTHETIC SILICA HAVING LOW POLARIZATION-INDUCED BIREFRIGENCE) The specification of US patent application Ser. No. 11 / 24,075 states that the polarization-induced birefringence of non-OD doped quartz glass tends to get worse as [OH] increases. This patent application also states that the magnitude of polarization-induced birefringence is approximately proportional to [OH] of OH-doped quartz glass. Thus, for OD-free synthetic quartz glass, it is generally preferred that it be lower than 500 ppm, in some embodiments lower than 160 ppm, in some other embodiments, to allow polarization-induced birefringence performance to be acceptable. Preferably has [OH] lower than 50 ppm. However, in a totally unexpected manner, the inventors have found that OD-doped quartz glass, in particular quartz glass substantially free of OH, has a significantly smaller polarization-induced birefringence than OD-free fused silica glass with equivalent [OH]. Found a tendency to have a value. After applying 8 billion (8 × 10 ⁹ ) pulses to a 193 nm linearly polarized excimer laser pulse of about 200 μJ · cm ⁻² · pulse- ¹ in some OD doped glass samples that are substantially free of OH Even so, the polarization-induced birefringence was found to be substantially zero. Accordingly, the inventors have found that the OD-doped high-purity synthetic quartz glass of the present invention, particularly the OD-doped high-purity synthetic quartz glass substantially lacking OH, has a high [OD] up to 1000 ppm or more than 1000 ppm. However, we believe that it will exhibit very little polarization-induced birefringence.

Another, co-pending, co-assigned (filed on October 26, 2005, named “Synthetic Silica with Low Fluence Dependent Transmittance and Method for Making It (SYNTHETIC SILICA WITH LOW FLUENCE-DEPENDENT-TRANSMISSION AND METHOD OF MAKING SAME), the relevant part of which is incorporated herein by reference), in the specification of US patent application Ser. No. 11 / 261,005, for OD-free high purity synthetic quartz glass, From the viewpoint of FDT) and LIWFD, it has been found that for non-OD doped quartz glass with [OH] ≦ 160 ppm, preferably H ₂ addition should be performed below about 600 ° C. It has been shown that heat addition can exacerbate FDT and LIWFD in non-OD doped quartz glass where [OH] ≦ 160 ppm. However, it has also been shown that for OH-doped quartz glass with [OH] ≧ 500 ppm, hot addition does not change FDT and LIWFD performance much more than cold addition.

  Accordingly, the inventors have found that the OD-doped synthetic quartz glass of the present invention, in particular, the OD-doped synthetic quartz glass containing substantially no [OH] even when [OD] is up to or exceeding 1000 ppm, It is believed that glass can be obtained with heat addition that has acceptable polarization-induced birefringence performance and does not degrade FDT and LIWFD characteristics. Therefore, a high [OD] quartz glass, at least a substantially OH-free quartz glass, may be usable in applications where an [OH] equivalent non-OD doped quartz glass cannot be used. Such high [OD] glass can be made with much higher efficiency and speed because it can be hot-added compared to OD-free, low [OH] glass, which generally requires cold addition. it can.

Another method of making the OD doped synthetic quartz glass of the present invention is:
(A) providing a plurality of OD-doped silica-containing particles, and (b) melting the particles at a high temperature to obtain transparent glass,
including.

Step (a) of this process is:
(A1) producing a plurality of silica-containing particles;
(A2) a step of purifying and / or drying the particles as necessary,
(A3) a step of doping the particles in an atmosphere containing at least one D-containing compound, if necessary, and (a4) an oxidizing atmosphere for repairing at least some of the oxygen-deficient sites in the particles, if necessary Processing the particles within,
Including
In at least one of steps (a1), (a2), (a3) and (a4), an OD component is introduced into the particles.

  In step (a1), the silica-containing particles are formed as described above in connection with the particle-to-glass process where the particle preform is finally consolidated instead of being melted to form glass. It can be produced by a flame hydrolysis process or a sol-gel process.

In step (a2), the purification and / or drying is as described above in connection with the particle-to-glass process where the particle preform is finally consolidated instead of being melted to form glass. You can make changes as needed. Used to consolidate soot (and soot, for example with Cl ₂ or Cl ₂ + CO, to make high purity starting materials and soot (and corresponding consolidated glass) and / or to remove trace metals A low metal impurity level can be obtained by means of a device for purifying the device.

  In step (a3), doping is necessary as described above in connection with the particle-to-glass process where the particle preform is finally consolidated instead of being melted to form glass. Changes can be made accordingly.

  In step (a4), processing is required as described above in connection with the particle-to-glass process where the particle preform is finally consolidated instead of being melted to form glass. Changes can be made accordingly.

  In step (b), the glass is heated to a temperature at which the glass melts, such as above 1500 ° C., in some embodiments above about 1800 ° C., and in some embodiments about 2000 ° C. The The molten glass can be further homogenized upon melting in order to obtain a highly uniform composition and properties in the final glass. When homogenization takes place, the glass particles to be melted can have substantially the same composition or have different compositions. For example, the particles can be a blend of particles having different [OH] and [OD]. If homogenized, the final glass obtained has a uniform [OH] and / or [OD].

  Similarly, the homogenized glass can be homogenized. That is, the consolidated OD-doped synthetic quartz glass of the present invention or a mixture thereof is higher than about 1500 ° C., regardless of the method of preparation, where the glass melts and homogenizes to form a glass having a uniform composition and properties. In some embodiments, it can be heated to an elevated temperature, such as above about 1800 ° C.

  Upon homogenization, the final, cooled, consolidated glass is related to a particle-to-glass process where the particle preform is consolidated instead of being finally melted to form the glass. As described above, hydrogen molecules can be further doped with modifications as needed.

In order to achieve a desired level of n (OD) / (n (OD) + n (OH)) ratio in a dense glass, consolidated, dense quartz glass containing OH and / or OD, for example 600 Higher in an atmosphere containing H ₂ , D ₂ and / or HD at higher temperatures, higher than 0 C, in some embodiments higher than about 800 0 C, and in some embodiments as high as 1000 0 C. By performing the / D exchange, it is possible to create the OD-doped quartz glass material of the present invention. The dense glass can be made by a direct-to-glass process or by the soot-to-glass process or sol-gel process described above. (For example, Corning HPFS® glass product code 7980 manufactured by Corning Incorporated, Corning, NY, containing approximately 1000 ppm OH by weight and substantially free of OD. A dense material substantially free of OD, such as OH-doped glass made with a conventional direct-to-glass process in a D-free environment starting from a D-free material (typically (trademark)) By adding D ₂ to glass over a sufficient time at a high temperature such as about 900 ° C., OD dope with various n (OD) / (n (OD) + n (OH)) ratios. Glass can be created. n (OD) / (n (OD) + n (OH)) ratio is greater than 0.5, in some embodiments greater than about 0.8, and in some embodiments greater than about 0.9. Such a glass with a very low [OH] can be successfully produced.

  The synthetic quartz glass material of the present invention is further processed into an optical member for use in the optical path of lithographic illumination light of a lithographic apparatus operating at a wavelength shorter than about 300 nm, such as about 248 nm, 193 nm or even shorter wavelengths. Can do. The optical member can take a variety of geometric shapes and dimensions. This optical member can be used for a low fluence irradiation optical path and a high fluence irradiation optical path. Thus, the process for making an optical member based on the quartz glass of the present invention can be a combination of the process of the present invention for making a glass material and an additional step of processing the glass material of the present invention. As described above, OD-doped synthetic quartz glass has already been studied and disclosed, but as far as the inventors know, it can be used as an optical member in the irradiation optical path of a lithographic apparatus operating at a wavelength shorter than about 300 nm. There is no document that discloses OD-doped synthetic silica glass, and there is no document that discloses OD-doped synthetic silica glass having unexpected optical performance at a wavelength such as about 193 nm. The example materials disclosed in the prior art documents discussed above are not believed to have the optical performance of the materials of the present invention, i.e., the optical performance required for lithographic applications at wavelengths shorter than about 300 nm.

  The invention is further illustrated by the following non-limiting examples.

Example 1a
In this example, the co-pending and co-assigned name is “High Refractive Index Homogeneity Fused SILICA GKASS AND METHOD OF MAKING SAME”, 2005. A soot-to-glass process as described in the specification of US patent application Ser. No. 11 / 148,764, filed Jun. 8, 2000 and now published as US Patent Application Publication No. 2006 / 0137398A1. By using it, an OD-doped quartz glass was prepared. The relevant portions of the above specification are included herein by reference. Specifically, a silica soot preform was formed by depositing a plurality of soot particles obtained by flame hydrolysis of octamethylcyclotetrasiloxane (OMCTS), which is a Si-containing precursor compound, on the rotating mandrel surface. The soot preform thus prepared was an OH-doped soot preform. Subsequently, in order to obtain an OD-doped soot, the preform is placed in a consolidation furnace set at approximately 1100 ° C., and helium containing 2.5% oxygen is bubbled through liquid D ₂ O and passed through the consolidation furnace for 6 hours. As a result, OD was doped by D / H exchange with D ₂ O having an isotope purity of 99.9 +%. Subsequently, the furnace temperature was raised to approximately 1400 ° C. to sinter the OD-doped preform in a D ₂ O-containing helium atmosphere to obtain a consolidated OD-doped quartz glass. Following consolidation, the quartz glass was placed in a nitrogen purge soaking oven at about 1100 ° C. for about 24 hours, cooled to 850 ° C. at a cooling rate of less than 25 ° C./hour, and then cooled to room temperature. Used for samples C, D and F in Table I). Deuteroxyl doping was successful and the consolidated glass contained about 130 ppm OD by weight and less than 1 ppm OH. [OD] and [OH] were measured along the radial direction of the glass and presented in FIG. These samples have sodium less than 10 ppb by weight, total alkali metals less than 10 ppb by weight, alkaline earth metals less than 10 ppb by weight, Fe, Cr and Ni may be less than 1 ppb by weight all right.

Example 1b
In this example, an OD-doped quartz glass was created by using a soot-to-glass process as described in Example 1a. The soot preform thus prepared was an OH-doped soot preform. Subsequently, in order to obtain an OD-doped soot, the preform is placed in a consolidation furnace set at approximately 1100 ° C., and helium containing 2.5% oxygen is bubbled through liquid D ₂ O and passed through the consolidation furnace for 6 hours. As a result, OD was doped by D / H exchange with D ₂ O having an isotope purity of 99.9 +%. Next, by raising the furnace temperature to approximately 1400 ° C., the OD-doped soot preform was sintered in a D ₂ O-containing helium atmosphere to obtain a consolidated OD-doped quartz glass. Following consolidation, the quartz glass was placed in a nitrogen purge soaking oven at 1100 ° C. for 24 hours, cooled to 850 ° C. at a cooling rate below 25 ° C./hour, and then cooled to room temperature (this quartz glass was cooled to Table I Used for sample H). Deuteroxyl doping was successful and the consolidated glass contained about 70 ppm OD by weight and less than 1 ppm OH. [OD] and [OH] were measured along the radial direction of the glass and presented in FIG. The fictive temperatures measured for samples H and G of these materials were 1126 ° C. and 1032 ° C., respectively. These samples have sodium less than 10 ppb by weight, alkali metals total less than 10 ppb by weight, total alkali metals total less than 10 ppb by weight, alkaline earth metals less than 10 ppb by weight, Fe , Cr and Ni were found to be less than 1 ppb by weight.

Example 1c
In this example, an OD-doped quartz glass was created by using a soot-to-glass process as described in Example 1a. The soot preform thus prepared was an OH-doped soot preform. This soot preform was placed in a consolidation furnace set at 1100 ° C., and treated with helium containing 1.6% by volume of Cl ₂ and 0.3% by volume of CO for 4 hours. This process was used to remove all OH and trace metals from the soot preform. Then, it exposed for 8 hours at 1100 ° C. the soot preform _{D 2} O and _{O 2} by flowing helium containing 2.5% _{O 2} by volume through a bubbler containing the _{D 2} O. This process removed all the chlorine and re-oxidized any silica that was reduced in the previous step. Thus, an OD dope soot preform was prepared. Next, the soot preform was sintered in a D ₂ O-containing helium atmosphere by raising the furnace temperature to approximately 1400 ° C. to obtain a consolidated OD-doped quartz glass. Following consolidation, the OD-doped silica was placed in a 1100 ° C. nitrogen purge soaking oven for 24 hours, cooled to 850 ° C. at a cooling rate of less than 25 ° C./hour, and then cooled to room temperature. Deuteroxyl doping was successful and the consolidated glass contained about 220 ppm OD and about 8 ppm OH by weight. [OD] and [OH] were measured along the radial direction of the glass and presented in FIG. To this OD-doped quartz glass sample, H ₂ was post-added to about 3 × 10 ¹⁶ molecules / cm ³ at about 425 ° C. The fictive temperature measured for this material was 1085 ° C. The internal transmittance of this sample at 193 nm was 99.66% / cm. This sample has less than 10 ppm Cl by weight, less than 10 ppb by weight sodium, less than 10 ppb total alkali metal, less than 10 ppb total alkaline earth elements, iron, chromium or nickel Was less than 1 ppb by weight.

Example 2
In this example, a soot-to-glass process as described in the co-pending and co-assigned US patent application Ser. No. 11 / 148,761 (U.S. Patent Application Publication No. 2006/0137398 A1) is used. By using it, an OD-doped quartz glass was prepared. Specifically, a silica soot preform was formed by depositing a plurality of soot particles obtained by flame hydrolysis of a Si-containing precursor compound on the rotating mandrel surface. The soot preform thus prepared was an OH-doped soot preform. Subsequently, in a manner similar to that described in Example 1a, helium was bubbled through liquid D ₂ O through the consolidation process and passed through a consolidation furnace during the consolidation process, thereby providing an isotope purity of 99.9 +% D ₂ O. Then, D / H was exchanged to some extent and OD was doped. Deuteroxyl doping was successful and the consolidated glass contained about 40-50 ppm OD and about 10 ppm OH by weight. [OD] and [OH] were measured along the radial direction of the glass and presented in FIG. It is noted that if the radial location changes, both [OD] and [OH] change, but the [OD] / [OH] ratio remains substantially constant. This indicates that the OH groups in the soot preform have been exchanged for OD groups at substantially the same ratio.

Example 3
All samples of OH-doped silica glass and OD-doped silica glass, annealed at manner similar to that described in Example 1b before the addition of H ₂ or D _2, was measured after the addition of H ₂ or D _2, The fictive temperature corresponding to each sample is shown in Table I. The sample OD-doped silica glass of Example 1a, 1b and 1c, were added after the _{H 2} or _{D 2} at 375 ° C. to about 4 × ^{10 16} molecules / cm ^3. OD made by using a soot-to-glass process as described in co-pending, co-assigned US patent application Ser. No. 11 / 148,761 (US Patent Publication No. 2006/0137398). H ₂ or D ₂ was added to the doped quartz glass at about 375 ° C. to about 4 × 10 ¹⁶ molecules / cm ³ to 6 × 10 ¹⁶ molecules / cm ³ . The FTIR results, the level of [OH] and [OD] in the glass showed that no change in the H ₂ or D ₂ addition process. The glass was exposed for several million pulses with a linearly polarized 193 nm ArF excimer laser having a repetition rate of 4 kHz, a fluence of 200 μJ · cm ⁻² · pulse- ¹ and a pulse length of 25 ns. Next, the characteristics of the exposed sample were measured by polarization-induced birefringence, normalized polarization-induced birefringence (PIB (N)), normalized LIWFD (L193) measured at 193 nm, normalized LIWFD (L633) measured at 633 nm, and normalized. Induced absorption (IA (N)) was determined. The data are presented in FIGS. 8, 9, 10, 11, 12, 13, 14, 15 and 16, respectively. Samples A, B, C, D, E, F, G, H, J, K, and L contain less than 10 ppb by weight, total alkali metals are less than 10 ppb by weight, and alkaline earth metals are The total was found to be less than 10 ppb by weight and Fe, Cr or Ni was less than 1 ppb by weight. Samples A, B, C, D, F, and H had an internal transmittance of about 99.78% / cm at 193 nm. Samples E, G, H, K, and L were found to have an internal transmittance of about 99.74% / cm. Moreover, it turned out that the internal transmittance in 193 nm of the sample J is about 99.70% / cm. Samples A, B, C, D, E, F, G, H, J, K and L have the compositions listed in Table I below.

8 and 13, the horizontal axis represents N (P) · F, where N (P) is the number of pulses in units of 1 million, and F is in units of mJ · cm ⁻² · pulse− ^1. The fluence of linearly polarized 193 nm excimer laser pulses. These figures are quite surprising and show that OD-doped samples (samples C, D, F, G and H) have fairly small bulk polarization-induced birefringence measurements (PIB (M)) at various N (P) · F. ) Is clearly shown. The normalized polarization-induced birefringence values given in FIGS. 9 and 14 further reinforce the conclusion that the magnitude of polarization-induced birefringence in OD-doped glass samples is much smaller than glass doped with OH at comparable levels. ing. The data in these figures clearly show that OD-doped quartz glass has better performance than OH-doped quartz glass with respect to polarization-induced birefringence. Even more surprising, the PIB (M) and PIB (N) data of Sample C measured over 8 billion (8 × 10 ⁹ ) pulses are approximately 2 billion (2 × 10 ⁹ ) and 5 billion (2−2 In contrast to the significant increase in polarization-induced birefringence of OH-doped samples A and B over 5 × 10 ⁹ ) pulses, the polarization-induced birefringence is not substantially changed.

Unexpectedly, the normalized LIWFD data for samples A, B, C, D and E in FIGS. 10, 11 and 15 show the OH when the LIWFD performance of OD-doped / OH-free quartz glass is equivalent in OD and OH concentrations. It shows that it is superior to doped glass. Furthermore, it was also found that the LIWFD is smaller in the quartz glass sample with the equivalent OD concentration but lower fictive temperature (T _f ) (ie, it has better performance with respect to LIWFD).

  As briefly mentioned above, the normalized induced absorption (IA (N)) data shown in FIG. 16 indicates that the OD-doped quartz glass of the present invention is the present invention when the exposure amount of linearly polarized light at 193 nm is the same. It clearly shows a much lower level of induced absorption than OH-doped glasses with [OH] comparable to that of OD-doped glasses. This was totally unexpected.

Example 4
In this example, OD-doped quartz glass was prepared by D / H exchange of OH-doped quartz glass. The OH-doped quartz glass used was Corning glass product code 7980 made by using a direct-to-glass process as described in US Pat. No. 6,698,248 B2. The tested glass contained approximately 1000 ppm OH, less than 10 ppb sodium, less than 10 ppb total alkali, less than 10 ppb total alkaline earth elements, and less than 1 ppb iron, chromium or nickel. D / H exchange, 10 mm × 25 mm × sample into a clean quartz muffle of 200 mm, the _{N 2} containing 5.4% of _{D 2} through by bubbling the sample to 99.9 +% of _{D 2} O To obtain an OD-doped quartz glass containing approximately 1000 ppm by weight of OD and less than 20 ppm by weight of OH and no further metal contamination.

  This example shows that the OD-doped quartz glass of the present invention can be produced by D / H exchange of OH-doped quartz glass.

  It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the scope or spirit of the invention. Therefore, it is intended that the present invention cover the modifications and variations of the present invention provided they come within the scope of the appended claims and their equivalents.

1 is a schematic representation of the proposed mechanism explaining at least in part polarization-induced birefringence in quartz glass containing OH and / or OD components. Explain at least to some extent the differences in polarization-induced birefringence and the level of polarization-induced birefringence between glasses with different n (OD) / (n (OD) + n (OH)) ratios in quartz glass containing OH and / or OD components. Is a schematic representation of the proposed mechanism Polarization-induced birefringence and light-induced wavefront distortion (LIWFD) and polarization-induced birefringence between glasses with different ratios of n (OD) / (n (OD) + n (OH)) in quartz glass containing OH and / or OD components And Schematic of the proposed mechanism, explaining at least in part the difference in the level of LIWFD Explain, at least in part, the difference in the level of induced absorption between glasses with different induced absorption (IA) and different n (OD) / (n (OD) + n (OH)) ratios in quartz glass containing OH and / or OD components. Is a schematic of the proposed mechanism FIG. 4 is a schematic representation of the proposed mechanism, explaining at least in part the effect of doped hydrogen molecules (H ₂ , D ₂ and / or HD) on induced absorption and reduced induced absorption in quartz glass containing OH and / or OD components. is there Figure 2 shows the OH concentration ([OH]) and OD concentration ([OD]) profiles of a consolidated quartz glass sample made according to one embodiment of the process of the present invention for making the OD doped quartz glass of the present invention. Is a graph 2 is a graph showing the [OH] profile and [OD] profile of a consolidated OD-doped quartz glass made according to one embodiment of the process of the invention for making the OD-doped quartz glass of the invention. A series of inventive OD-doped quartz glass samples and a series of OH-doped quartz glass samples with varying levels of H ₂ or D ₂ molecules as a function of N (P) · F, measured at 633 nm, FIG. 4 is a graph showing polarization-induced birefringence, where F is fluence, N (P) is the number of pulses of a pulsed laser beam having a wavelength of about 193 nm, and the glass sample has a fluence of about 200 μJ · cm ^−2.・ Pulse- ¹ with a pulse length of approximately 25 ns was exposed at a pulse repetition rate of about 4 kHz. 9 is a graph showing the normalized polarization-induced birefringence of the same sample as in FIG. 8 as a function of the number of pulses of a pulsed laser beam having a wavelength of about 193 nm, the glass sample having a fluence of about 200 μJ · cm ⁻² · pulse ⁻¹ . A pulse with a pulse length of about 25 ns was exposed at a pulse repetition rate of about 4 kHz. Measured at 633 nm of the same series of OD-doped quartz glass samples of the present invention and the same series of OH-doped quartz glass samples as shown in FIG. 8 above as a function of the number of pulses of a pulsed laser beam having a wavelength of about 193 nm The glass sample was exposed at a pulse repetition rate of about 4 kHz to a pulse length of about 25 ns with a fluence of about 200 μJ · cm ⁻² and pulse ⁻¹ . Measured at 193 nm of the same series of OD-doped quartz glass samples of the present invention and the same series of OH-doped quartz glass samples as shown in FIG. 8 above as a function of the number of pulses of a pulsed laser beam having a wavelength of about 193 nm. The glass sample was exposed at a pulse repetition rate of about 4 kHz to a pulse length of about 25 ns with a fluence of about 200 μJ · cm ⁻² and pulse ⁻¹ . 2 is an OH concentration ([OH]) profile and an OD concentration ([OD]) profile of a consolidated quartz glass sample made according to one embodiment of the process of the present invention for making the OD doped quartz glass of the present invention. A series of inventive OD-doped quartz glass samples and a series of OH-doped quartz glass samples with varying levels of H ₂ molecules as a function of the number of pulses of a pulsed laser beam with a wavelength of about 193 nm were measured at 633 nm. , A graph showing polarization-induced birefringence, in which glass samples G, H, J and K are exposed to a pulse having a fluence of 600 μJ · cm ⁻² · pulse ⁻¹ and a pulse length of approximately 21 ns at a pulse repetition rate of about 4 kHz. Glass samples F and L were exposed to a pulse repetition rate of about 4 kHz with a fluence of 200 μJ · cm ⁻² · pulse- ¹ and a pulse length of about 25 ns pulse. Wavelength as a function of the number of pulses of the pulse laser beam of about 193 nm, has of H ₂ molecules of various levels of OD-doped silica glass sample and a series of OH-doped silica glass sample set of the present invention, normalized polarization-induced It is a graph showing birefringence, and glass samples G, H, J and K are exposed to a pulse having a fluence of 600 μJ · cm ⁻² · pulse- ¹ and a pulse length of about 21 ns at a pulse repetition rate of about 4 kHz. Samples F and L were exposed to a fluence of 200 μJ · cm ⁻² · pulse- ¹ and a pulse length of approximately 25 ns to a pulse repetition rate of about 4 kHz. The same series of OD-doped quartz glass samples of the present invention and the same series of OH-doped quartz glass samples G, H, J as the sample presented in FIG. 14 above as a function of the number of pulses of a pulsed laser beam having a wavelength of about 193 nm. And K is a graph showing normalized LIWFD measured at 633 nm, where the glass sample is exposed to a pulse with a fluence of 600 μJ · cm ⁻² · pulse- ¹ and a pulse length of approximately 21 ns at a pulse repetition rate of about 4 kHz. The The same series of OD-doped quartz glass samples of the present invention and the same series of OH-doped quartz glass samples G, H, J as the sample presented in FIG. 14 above as a function of the number of pulses of a pulsed laser beam having a wavelength of about 193 nm. And K, a normalized induced absorption measured at 193 nm, ie, normalized IA, with a glass sample having a fluence of 600 μJ · cm ⁻² · pulse ⁻¹ and a pulse length of approximately 21 ns and a pulse length of about 4 kHz. Exposed with pulse repetition rate Figure 2 shows the OH concentration ([OH]) and OD concentration ([OD]) profiles of a consolidated quartz glass sample made according to one embodiment of the process of the present invention for making the OD doped quartz glass of the present invention. Is a graph

Claims (15)

In an OD-doped synthetic quartz glass material containing OD and optionally OH and less than 100 ppb sodium, which can be used in the optical path of lithographic irradiation light of a lithographic apparatus operating at a wavelength shorter than 300 nm,
The weight ratio of [OD] / ([OD] + [OH]) is 0.8 or more,
A synthetic quartz glass material having an internal transmittance of at least 99.00% / cm at a wavelength of 193 nm.   The synthetic quartz glass material according to claim 1, wherein a weight ratio of [OD] / ([OD] + [OH]) is 0.96 or more. The total of [H ₂ ], [HD] and [D ₂ ] containing H ₂ , HD, D ₂ and / or mixtures thereof is 0.5 × 10 ^{15 to} 5 × 10 ¹⁹ molecules / cm ³ The synthetic quartz glass material according to claim 1 or 2, wherein the material is in a range. Measured at 633 nm when subjected to ¹⁰ billion (1 × 10 ¹⁰ ) pulses of a laser beam operating at 193 nm and having a fluence of 70 μJ · cm ⁻² · pulse ⁻¹ and a pulse length of 25 ns, −1. The synthetic quartz glass material according to any one of claims 1 to 3, which exhibits a laser-induced wavefront distortion (LIWFD) between 0 nm / cm and 1.0 nm / cm. The normalized wavefront distortion L633 measured at 633 nm shown when receiving a pulse of 20 billion (2 × 10 ¹⁰ ) or less of the 193 nm excimer laser is −1.0 ≦ L633 ≦ 1.0. The synthetic quartz glass material according to claim 1 or 2. The normalized wavefront distortion L193 measured at 193 nm when receiving 193 nm excimer laser pulses of 20 billion (2 × 10 ¹⁰ ) or less is −1.0 ≦ L193 ≦ 1.0 The synthetic quartz glass material according to claim 1 or 2. The glass was subjected to 2 × 10 ¹⁰ pulses of a 193 nm linearly polarized pulsed laser beam having a fluence of 40 μJ · cm ⁻² · pulse- ¹ and a pulse length of 25 ns, and then measured at 633 nm to obtain 0.04 nm / cm The synthetic quartz glass material according to claim 1 or 2, which exhibits a smaller polarization-induced birefringence. In a process for making an OD-doped synthetic quartz glass material that can be used in the optical path of lithographic irradiation light of a lithographic apparatus operating at a wavelength shorter than 300 nm,
(A) providing a particle preform having a plurality of silica-containing particles;
(B) if necessary, a step of purifying and / or drying the particle preform;
(C) A step of further doping the particle preform with a dopant, if necessary,
Step (D) to said particulate preform consolidating to dense glass at a high temperature, and (E) optionally, the consolidated glass obtained in the step (D) H _2, HD and / or treating in the presence of D _2,
Including
In at least one of the steps (A), (B), (C), (D), and (E), the resulting quartz glass contains OD and, if necessary, OH, [OD ] / ([OD] + [OH]) is introduced into the glass or formed in the glass so that the weight ratio thereof is 0.8 or more, and the obtained quartz glass is 100 ppb. Less sodium and has an internal transmittance of at least 99.00% / cm at a wavelength of 193 nm,
Process characterized by that.   The process according to claim 8, wherein a weight ratio of [OD] / ([OD] + [OH]) is 0.96 or more.   The OD is introduced into or formed in the glass in at least one of the steps (A), (B), (C) and (D). Or the process according to 9. The step (A)
(A1) providing a plurality of particles, and (A2) depositing the particles on a rotating support surface to form the particle preform,
The process according to claim 8 or 9, characterized by comprising: The step (A)
(A (i)) a step of forming a sol-gel containing silica, and (A (ii)) a step of forming the particle preform from the sol-gel.
The process according to claim 8 or 9, characterized by comprising: Step (B) is performed, and such step comprises at least one purification / drying agent selected from F ₂ , Cl ₂ , Br ₂ , halogen-containing compounds, CO, CO ₂ and their equivalent mixtures. The process according to claim 8 or 9, wherein the process is performed in a containing atmosphere.   The process according to claim 8 or 9, wherein the step (C) is performed, and in the step (C), an exchange from OH to OD is performed. The dense glass obtained as a result of the step (D) contains OH,
Step (E) is performed,
In the step (E), since the glass performs H / D exchange in the glass to obtain desired [OH] and [OD] in the dense glass, D ₂ , HD and / or H ₂ Processed in an atmosphere containing
10. Process according to claim 8 or 9, characterized in that

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