JP2006521580A - Digital micromirror device having window for transmitting ultraviolet light - Google Patents

Abstract

The UV transmissive window assembly for the DMD device includes a UV transmissive glass window provided on the frame. The window and frame are preferably glued together to seal between them. An optical coating specific to the intended wavelength for light transmission is applied to the inner and outer surfaces of the glass window to reduce reflection and enhance light transmission. A DMD comprising a window assembly, and the same, is adapted for excellent transmission of ultraviolet light, even in the far ultraviolet part of the spectrum. DMD window assemblies have utility in both medical surgery and device manufacturing, among other fields, in integrated circuit (IC) manufacturing, and in other optical lithographic applications.

Description

  The present invention relates generally to optical systems. More particularly, the present invention relates to a microelectromechanical system (MEMS) having optical reflective and transmissive elements, and more particularly to a system in which the optically transmissive elements are transmissive to ultraviolet light wavelengths. .

  The correction of a person's abnormal vision has made rapid progress over the past few years. Although glasses and contact lenses are still the primary approach for field correction, newer techniques that alter the shape of the cornea and internal human lens replacement or supplementation provide more accurate correction. A precision scalpel or laser is used to correct the field of view by changing the shape of the human cornea. Radial keratotomy (RK) using an orthopedic scalpel, which is still in use, has been replaced by laser refractive keratotomy (PRK) using laser and myopia surgery with laser beam (LASIK). It has been. The laser refractive surgery field has changed dramatically over the past few years with a number of new lasers and algorithms that correct the human field of view. The system currently uses laser wavelengths from far ultraviolet to infrared to change the shape of the cornea with a calculated pattern, which allows the eye to properly focus.

  Usually, artificial lenses (IOLs) that replace human lenses, due to cataract formation or lens damage, also provide very good visual field correction, but can provide "wide" spherical and astigmatic correction. Compared to contact lenses, artificial lenses have a limit in the accuracy of the correction force. Some artificial lenses are inserted into the chamber in the gap between the iris in front of the eye and the cornea, while supplementing refraction without touching the original lens. Light adjustable artificial lenses that can be changed outside or within the eye after implantation to make it more customer-friendly and allow more accurate correction forces are currently under investigation. Such an artificial crystalline lens is described in Patent Document 1 which is fully incorporated by reference. Mid-UV to deep-UV lasers are used to modify these artificial lenses to provide various refractive powers.

  More precise and more accurate methods of measuring human eye abnormalities have also improved over the past few years. Because of these improvements in measurement, the industry has been investigating ways to bring more customer correction to the eye or artificial lens. Digital micromirror devices (DMD) and microelectromechanical system (MEMS) semiconductor devices composed of hundreds or thousands of micromirrors are ideal devices for providing a laser beam pattern more accurately. With regard to laser eye surgery, the use of DMD is described in detail in co-pending US Pat. At present, DMD devices that can be used as commercial products are designed to give visible wavelengths (400 nm to 750 nm), but it is not possible to use UV energy in a large area by a protective window that protects micromirrors environmentally. . Ultraviolet energy can be classified by wavelength according to a physical definition. That is, extreme ultraviolet (EUV) (10nm to 100nm), vacuum ultraviolet (VUV) (10nm to 200nm, VUV and EUV are partially overlapped), deep ultraviolet (DUV) (200nm to 300nm) and near ultraviolet ( NUV) (300 nm to 400 nm). In addition, ultraviolet energy can be classified by wavelength according to the photobiological definition. UV-C (100 nm to 280 nm) partially overlapping with far ultraviolet rays, UV-B (280 nm to 315 nm), far ultraviolet rays partially overlapping with far ultraviolet rays and near ultraviolet rays, and also called mid-UV ultraviolet rays (mid-UV) And UV-A (315 nm to 400 nm), which partially overlaps with near ultraviolet light and is called near-ultraviolet (near-UV) for photobiological purposes.

Refractive surgery: Reforming the cornea with a laser Use of DMD The original system proposed by the US Food and Drug Administration (FAD) for cornea remodeling is based on a first-order approximation of refraction from a single spherical surface Means are provided for refractive correction by providing beam-like laser energy. These systems provide a means for a “broadbeam” approach, so that the laser beam is based on contours derived via the Mannerlyn derivation as discussed in [1]. It is formed by an electric iris (myopia and hyperopia) and an electric slit (astigmatism). Common systems that use this approach in the market are VISX and Summit. Over one million eyes have been treated in this way. However, this system has limitations when treating large areas of the cornea at one time. Anatomical drawings of the eye have been created, and more recently wavefront analysis has emerged, and the eye has a number of fine variations throughout the cornea. See Non-Patent Document 2. Referring to FIGS. 1 (a) and 1 (b), the wide beam laser approach cannot correct these minute variations.

  The latest systems on the market are small laser spots (typically 0.5mm to 1.0mm in diameter) or a combination of different spots across the cornea in a pattern set to achieve refractive correction Is called a “scannig spot system”. These scanning spot systems differ in that they are more flexible than the wide beam approach. With reference to FIG. 2, using the control of the small spot 10, the wide beam approach can form another region of the cornea 12 independent of the other regions. These techniques allow for a more general pattern to be applied to the cornea. A common system that uses the scanning spot approach is VISX®.

  However, there are several problems with the scanning spot approach when compared to the wide beam approach, but the supplied refractive index is clearly superior to these. Some of the issues include longer refractive surgery time (speed), safety, tracking and surface roughness, which are then discussed in more detail.

  For longer refractive surgery times, a scanning spot is a slower approach because a small spot (typically 1 mm in diameter) must travel over a large surface (up to 10 mm for hyperopia). The broad beam approach treats the entire cornea or the treatment strip for each laser pulse. Scanning spot systems must provide hundreds of spots per treatment strip, which can increase treatment time.

  In terms of safety, the wide beam laser is such that the cornea is treated symmetrically for each pulse (the iris is circular because all points on the cornea are treated identically for each laser pulse. It represents an annulus and a slit represents a rectangle.) From the viewpoint of interruption of treatment, it is intrinsically safe. If the procedure is interrupted, it is guaranteed to have some symmetrical spherical or cylindrical correction, which can be easily continued. A scanning spot using a small spot size cannot cover the entire corneal surface with a single laser pulse, since there is no guarantee of symmetric etching at that time if an interruption occurs.

  With respect to tracking, in a scanning spot system, the eye needs to be tracked in order to spot the correction point of the cornea as the eye moves. This is not a problem in a wide beam system where a larger area is treated with each pulse.

  With respect to surface roughness, laser spot overlap tends to produce roughness as a result of etching. For a given ablation zone, spot overlap is required for complete coverage, while the overlapped region is removed at twice the etch depth relative to the pulse. The smoothness of the removed mass depends on the overlap of the spots and the spread of the laser, ie the ratio between the spot diameter and the diameter of the area to be removed. This problem is not seen with the wide beam approach.

  More recently, eye outline anatomy has been used to provide a more accurate measure of refraction. Current FDA proposed refractive laser systems do not directly use an eye modeling system, such as a cornea mapper or wavefront sensor, to create an accurate treatment profile for the patient's eye. The anatomical chart is used directly by the surgeon to optimize the treatment plan (diopter correction and astigmatism optical axis). There are currently systems in place through FDA's attempt to use surface data of the corneal anatomy to directly guide the laser treatment algorithm. This is due to the use of certain types of scanning laser spots because current wide beam laser refractive surgery systems do not provide the details of the laser beam needed to use anatomical data. Each eye is individually analyzed for eye contours prior to performing the resection. The idea here is to consider the degree of curvature change and height change across the surface of the cornea, as opposed to assuming a spherical surface, as is currently done in wide-area beam systems. That is. If these curvatures, or abilities, are measured by an anatomical chart of the eye, for example using a system sold by Keratron, Orbtec, or Zuihan Hanfrey, they are made for each individual eye. To create an altered ablation pattern, one can consider within the scope of deriving from refractive correction (as described by Mannerin). These ablation must be performed by a scanning spot system, more specifically a DMD approach, because individual areas must be treated differently from other areas. References 2 and 4 previously incorporated discuss the DMD approach. Even this approach is limited in that only aberrations measured at the corneal surface are included in deriving from refractive correction.

  The best approach so far is the use of wavefront sensing analysis for eyes that have recently been introduced. Using this new technique, a set of very powerful tools are provided for correcting the corneal surface of the eye. Wavefront sensing provides a comprehensive refraction analysis result, taking into account the visual system of the entire eye, such as the cornea, lens, vitreous humor and retina. The result of the wavefront sensing analysis gives a waveform model that results in a nearly complete refraction measurement. This provides an excellent eye analysis result for current technical systems that analyze only the cornea. Wavefront data may be used to operate the scanning spot system, but it still encompasses the issues discussed previously. But it is directly compatible with the DMD approach due to the digital nature of wavefront sensor analysis. This wavefront sensor-DMD approach has been discussed in detail, incorporating Patent Document 3 first.

Refractive Surgery: Slightly Activated Intraocular Lens and DMD Applications Structures, materials, and materials for artificial lenses that will be a safe and practical method during surgery in recent decades to restore normal vision Rapid progress in transplant technology was made.

  More recently, the structure has provided a means of providing perspective adjustment by an artificial lens. Such attempts include refractive multifocal lenses, flexible (liquid-filled) lenses, multi-element structures and hinged optics. While these artificial lenses still only provide “wide” fixed ability (both spherical and astigmatism) correction, they provide certain necessary abilities.

  Even more recently, artificial lenses activated by light have been provided. These visual elements have a mixture that modulates refraction dispersed in a polymer matrix. Mixtures that modulate refraction can result in polymerization that induces stimulation, such as ultraviolet light stimulation (longer wavelength ultraviolet light: 325 nm to 340 nm range). In this way, visual measurements of the eye (eg geometrical properties, wavefronts, etc.) can be tracked by inducing polymerization of the mixture that regulates refraction, and the amount of polymerization is determined by visual measurement. Is done. Thus, over the entire corneal surface, the degree of curvature change and the change in height can be taken in as quantities to counter the assumption of a simple spherical surface. Currently, parallel light from a xenon-mercury arc lamp (340 nm through a 1 mm photomask) or parallel light from a helium-cadmium laser (325 nm, 1 mm beam diameter) activates a mixture that adjusts refraction and Used to stabilize (or “fix”). In order to polymerize the entire artificial lens, a 1 nm photomask or 1 mm laser beam must be moved or scanned across the artificial lens as described in US Pat. I must. Scanning a small mask or small diameter laser beam across the artificial lens results in similar problems as described above for the scanning spot approach that changes the shape of the corneal tissue. As a result, when connected to a precisely paralleled wide beam arc lamp, or wide beam laser, this technology is directly compatible with the DMD approach, either by geometrical characteristics or by digital characteristics of wavefront sensor analysis. And therefore can provide a larger and more specific laser beam pattern more accurately.

DMD Challenges for Ultraviolet Wavelengths From the above discussion, DMD is more sensitive to the finer resolution and special needs required by more advanced measurement techniques in both corneal shape changing applications and artificial lens activation applications. It becomes clear that it is ideally suited to provide the necessary laser radiation control to obtain the specified laser beam pattern. But to date, commercialized DMDs emitting at the excimer wavelength (193nm) used in laser refractive surgery or at the wavelength (325nm to 340nm) used in the light-activated artificial lens approach have been There wasn't. The shortest optimized wavelength can be given by fabrication, but still the experimental DMD is 365 nm, well above the 193 nm required to etch the cornea in the laser refractive surgery area.

  Referring to FIG. 3, it is noted that at the 325 nm wavelength used in artificial lens applications, only about 83% of the light is transmitted through the UV coated DMD window in a single pass. Furthermore, in a DMD device, the light hitting the mirror has to go through the path twice through the window, i.e. the light travels once through the window and reflects again off the mirror and again through the window to exit the device. Must be communicated. This means that only about 69% (0.83 x 0.83) of the original 325nm light returns from the DMD device, assuming 100% reflection from the DMD mirror or 31% loss due to the window alone. Yes. At 340 nm, only about 91% of the light is transmitted in a single pass. Thus, assuming about 100% reflection of the DMD mirror, or 17% loss due to the window alone, only about 83% (0.91 × 0.91) of the original 340 nm light returns from the DMD versus 340 nm. The result of this loss is that the laser source must be operated at a higher energy output level, which also increases the beam shape and damage to the emission optics. In addition, there are other losses (typically 45% to 60% loss) related to the optics required to form, homogenize and emit the laser beam. Additional losses result from optical coating damage as a result of use.

To further explain the window loss, a helium-cadmium laser beam with an energy density of 257 mJ / cm ² and a diameter of 1 mm and a diameter of 325 nm is required to induce polymerization of the mixture that adjusts the refractive index. Consider the example. If DMD is inevitably used to activate the refractive index adjusting mixture, this requires 81 mJ of energy in the artificial lens to cover the entire 6.35 mm artificial lens with the laser beam at once. is there. Combined with the above mentioned 325nm 31% window loss, for beam forming and emitting optics, combined with a 50% general loss, this is 500mJ from the laser during 2 to 10 minutes of operation. More energy is needed. Thus, it is advantageous to have a deep UV window that is as lossless as possible in order to keep the required amount of laser energy down.

As another example, consider the energy density required to etch corneal tissue. The energy density varies from system to system, but a typical value is 160 mJ / cm ² . Current commercially produced, but experimental, DMDs do not work for laser refractive surgery wavelengths between 190 nm and 250 nm (generally 193 nm). This is because, as can be seen from FIG. 3, the UV coating window covering the DMD mirror has an optical transmission of 0% for wavelengths below 250 nm. Thus, the only way to implement DMD for this application is to use windows that are for these far ultraviolet wavelengths. For a typical 6 mm spot used in laser refractive surgery, an energy density of 160 mJ / cm ² requires 45 mJ. For a 10mm spot used to correct hyperopia, 125mJ is required. Typical handling times for broadband lasers range from a few seconds to a minute. Thus, the deep ultraviolet window needs to be as lossless as possible in order to maintain the laser energy requirement below.

  Another significant challenge that exists with current DMD window structures is reflection from the window surface, specifically the reflection on the DMD mirror side of the window. If the window and its coating are not optimal for the wavelength used, the reflections bounce back and forth from the inside of the window to the mirror and the result of the incorrect pattern being radiated can cause interference problems. ".

  Current DMD window assemblies are constructed from a Kovar® (ASTM-F-15) alloy frame and a borosilicate glass window. This combination is a common glass-ceramic sealing system (eg EPROMS) for protecting semiconductors from local environments. Kovar® is a low thermal expansion alloy whose chemical composition is controlled within a narrow range of limits to ensure accurate and uniform low thermal expansion properties.

The most common borosilicate glass used in current DMD applications is Corning 7056. Corning 7056 glass works well for visible spectrum DMD applications. Because it transmits well visible light and has a coefficient of thermal expansion (CTE) very close to Kovar (Corning 7056: 5.15 × 10 ⁻⁶ / ° C. vs Kovar®: 5.2 × 10 ⁻⁶ / ° C). This allows glass and metal to be sealed when both are heated at approximately 1,000 ° C. The conventional definition of hermeticity is based on the helium precision leak test (mil-std803 or JEDIC-JESD22-A109-A), and the numerical value is 5 × 10 ⁻⁸ atm-cc / s helium or less. Sealing is formed by heating both glass and metal until the glass wets the metal and is followed by the development of chemical adhesives or some mechanical interlocking, thus maintaining the seal. ing. The basic transmission spectrum of Corning 7056 is shown in FIG. By applying an appropriate anti-reflective (AR) coating to the glass, the propagation spectrum of Figure 3 is achieved. It should be noted that optical transmission can be shifted lower to handle near ultraviolet wavelengths, but this degrades the quality of the visible spectrum portion. Finally, it should be noted again that this glass does not transmit as effectively as far ultraviolet to medium wave ultraviolet wavelengths. Instead, different materials are required, such as fused silica.

Fused silica is one of the most common materials used from deep UV to mid UV. Fused silica is a polycrystalline, isotropic material that has no crystal orientation. Its physical, thermal, dielectric and optical properties are uniform in all directions of measurement. There is a special quality fused silica called excimer grade fused silica that was specifically made for the above applications. Unfortunately, the coefficient of thermal expansion of fused silica (0.55 × 10 ^-6 / ° C) is never close to the coefficient of thermal expansion of Kovar (5.2 × 10 ^-6 / ° C) (almost orders of magnitude different) The seal between the two is not maintained during the manufacturing process and in the post-manufacturing environment when the temperature changes. This is to allow an external environment within the sealed DMD semiconductor space, which is detrimental to the micromirror behind the window, as the micromirror will not function properly. One of the most common problems is that the mirror stops and stops moving and does not respond to commands.

  There are three additional problems with current DMD mirror structures. First, current commercially operational DMD devices use bare aluminum mirrors to reflect incident light. Uncoated or bare aluminum has an absolute reflectivity of approximately 85% at wavelengths from 200 nm to 2000 nm. This reflectivity increases when the wavelength moves to the visible region within the main adaptive region of currently manufactured DMD devices (over 90% on average at over 750 nm over 400 nm) and below 200 nm (eg, Decrease to about 84-86% for 193nm and about 65-70% for 157nm). As a result, uncoated aluminum mirrors give less than 85% reflectivity or more than 15% loss for certain UV applications.

  Secondly, the UV energy hitting the mirrors also gradually erodes the mirrors, damaging and deforming them. This adversely affects the laser energy pattern applied to the target.

  Third, the energy of the incident ultraviolet light moves between the mirrors and affects the underlying semiconductor control structure behind the mirrors. This leads to degradation of the DVD device.

US Patent Application Publication No. 2002/0016629 US Pat. No. 5,624,437 US Pat. No. 6,394,999 US Pat. No. 6,413,251 US Pat. No. 6,242,136 C.R.Munnerlyn et al., “Photorefractive keratectomy: a technique for laser refractive surgery” J. Cataract Refract. Surg. 14, 1988, p. 46-52 J. Liang et al., `` Qbjective measurement of wave aberrations of the human eye with the use of a Hartmann-Shack wave-front sensor '' J. Opt. Soc. Am, Vol. 11, No. 7, 1994, p. 1949 -1957 Hornbeck, "Digital Light ProcessingTM for High Brightness, High resolution Applications", Electronic Imaging EI '97, Projection Displays III, San Jose, CA, February 10-12, 1997 `` Advanced Materials for Optoelectronic Packaging '' by Zweben, Carl, Electronic Packaging & Production Journal, September 1, 2002

  It is an object of the present invention to provide a window assembly for a DMD that is substantially transparent to ultraviolet light.

  It is another object of the present invention to provide a window assembly for a DMD that is substantially transparent to light wavelengths in the near, far and vacuum ultraviolet regions of the spectrum.

  It is a further object of the present invention to provide a window assembly for a DMD that has minimal reflectivity.

  It is also an object of the present invention to provide a window assembly for a DMD that includes a window sealed with a window frame.

  It is an additional object of the invention to provide a DMD having a window that is compatible with applications using ultraviolet wavelengths, particularly light in the near, far and vacuum ultraviolet wavelength regions of the spectrum.

  It is yet another object of the present invention to provide a DMD for use with ultraviolet wavelengths, where the DMD window seal does not face outgassing problems and does not adversely affect DMD mirrors or control electronics. is there.

  It is a still further object of the present invention to provide a DMD window structure that is adapted for use with ultraviolet light and is safely maintained by common optical care solutions such as acetone and methanol.

  It is a still further object of the present invention to increase the transmission and reflection of ultraviolet light throughout the DMD system.

  For these purposes discussed in detail below, near, far and vacuum ultraviolet wavelength window assemblies for DMD devices and DMD devices incorporating the same are provided. The window assembly includes fused silica glass provided in a high temperature metal alloy frame. In a preferred embodiment, the fused silica glass window is argon fluoride grade fused silica and the frame is made from a nickel-cobalt-iron alloy such as Kovar®. A lead / silver alloy joint member interface is provided at the joint of the frame window to provide a seal between the alloy and the glass. Optical coating specifications for wavelengths intended for light transmission are applied to the interior and exterior surfaces of glass windows that reduce reflection and increase light transmission.

  The resulting window assembly, and the DMD with the like, are applied for excellent transparency of ultraviolet light over the vacuum ultraviolet, far ultraviolet and near ultraviolet wavelengths. DMDs with windows applied for such ultraviolet light are both aspects of surgery and the manufacture of intraocular lenses, contact lenses or glasses, or medical devices that selectively alter the biological response of the surface. In medical technology, integrated circuit (IC) fabrication and other optical lithography applications (such as polymer arrays), industrial lens customization, micromachining (eg, micro-hole drilling, selective It also has applicability in other fields such as thin film stripping and milling) and precision surface treatment of materials.

  It will be apparent that the additional objects and advantages of the present invention are technically proficient in comparison with the detailed description made in connection with the provided drawings.

  Referring to FIGS. 5 (a) -5 (c), a UV transmissive DMD window assembly 20 for a DMD apparatus 50 is a fused silica glass window provided in a high temperature metal alloy frame 24 in accordance with a preferred embodiment of the present invention. 22 is included. The joining member 26 is supplied to the joining portion between the window 22 and the frame 24.

  In a desired embodiment, the fused silica glass window 22 is preferably an argon fluoride grade available from Corning (HPFS® ArF grade fused silica, Corning code 7980). The minimum surface quality is preferably specified to have a λ / 10 shape at 633 nm, a surface quality of 10/5 S / D (scratch / dig), and a parallel angle less than 3 arc-minutes The The external transmission spectrum of the base (uncoated or bare) of argon fluoride grade fused silica is shown in FIG. From FIG. 6, it is noted that argon fluoride grade fused silica has a transmission of at least 90% at ultraviolet wavelengths of 185 nm or higher. Alternatively, other types of excimer grade fused silica are readily available and can be substituted from CVI Laser, Coherent Auburn Group, and Acton Research / Roper Scientific.

  The high temperature alloy for frame 24 is preferably a nickel-cobalt-iron alloy such as Kovar® (ASTM F15), with 29% nickel, 17% cobalt, 0.30% magnesium, 0.02% carbon and the balance remaining Has an iron component.

  The desired bonding material 26 is a lead / silver alloy (approximately 97.5% lead and 2.5% silver). Although the desired rectangular shape of the window frame 24 (i.e., sharp corners) generates stress due to differential thermal expansion, a relatively ductile lead / silver alloy accommodates the differential thermal expansion, the lead / silver alloy is As desired, it helps to keep the glass physically fixed. Other lead-based alloys such as lead / copper, lead / nickel, lead / titanium and lead / tin are also used. In addition, tin / silver, tin / antimony, tin / silver / copper, tin / copper, tin / silver / copper / antimony, tin / copper / antimony / silver, tin / silver / bismal, and tin / tin containing tin Alloys are also used, but have generally higher melting points (melting points begin to amplify the differential thermal expansion of the materials involved), are less ductile than lead-based alloys, and have poor wettability for fused silica windows. Show. Indium-containing solder is superior to solder containing lead in terms of ductility, melting temperature and strength, and other physical properties, but is relatively expensive.

  The optical coatings discussed in detail below are applied to the interior and exterior surfaces 44 and 42 of the glass window 22, respectively. Such optical coatings are preferably optical coating specialists such as Acton Research / Roper Scientific, Acton, Massachusetts, Cleveland Crystals, Highland Heights, Ohio, or Alba, New Mexico, among others. Applied by Kirk CVI Laser, Inc.

  The window assembly 20 is assembled as follows. First, the high temperature metal alloy window frame 24 is assembled with a shape and size corresponding to the DMD. One reason that Kovar® is the desired material is that it can be easily adapted to the exact dimensions required and is a typical material for such applications. Such dimensions are available from DMD manufacturers such as Texas Instruments. In another approach, Kovar® frames are available directly from the manufacturer. In either case, the basic frame is changed by chamfering around the bottom mirror end (shown at 32).

  Argon fluoride grade fused silica window 22 is sized to fit frame 24 and, for example, the window member is chamfered along end 34 to provide intermediate lead / silver. Allocate groove gaps for alloy brazing material. A window 22 is installed in the opening 36 of the frame 24, and the chamfered ends 32, 34 of the frame 24 and the window 22 preferably define a symmetrical groove 38 to be assigned to the lead / silver alloy bonding material 26. In the desired embodiment, the fused silica material 22 is arranged in a rectangular shape (preferably with rounded corners for stress relaxation), but if the frame 24 is machined in shape, the resulting window If the aperture 36 allows light to pass through all of the DMD mirrors in the DMD 50 (FIG. 5 (e)) mirror arrangement, a square or circular arrangement (preferably with rounded corners) is possible. is there.

Next, the window 22 is joined to the frame 24. As a result, the chamfered end 34 of the window 22 is preferably rough and painted with a paint containing a titanium component. The lead / silver braze alloy 26 is then fed into the groove 38 and the window 22, frame 24 and braze alloy 26 are brought to the eutectic temperature of the braze alloy 26 (approximately 305 ° C. for the desired lead / silver alloy). Both are heated. During heating, a bond is formed between (1) paint and glass, (2) paint and lead / silver alloy, and (3) lead / silver alloy and frame, resulting in a hermetically sealed frame and window. Become. Heating may occur during or after alloy 26 is provided in groove 38. Preferably, a seal leak test is performed using a helium leak test that confirms a drop value of 2 × 10 ⁻¹⁰ atm-cc / sec at a predetermined differential pressure of the reference pressure and 0 ° C.

The transmission of light through the window 22 depends on the specific wavelength or required for coating application (depending on the application in which the DMD is used), discussed below, to the outer surface 42 and the inner surface 44 of the window 22. Optimized for wavelength flux. Prior to applying the coating, a physical mask is preferably placed in front of the sealed window assembly to ensure that the coating material does not diffuse outside the window of the frame or alloy joint. There are several existing methods for applying the coating. In the desired embodiment, one wavelength is selected and an anti-reflective coating is designed and applied to both surfaces of the window. For example, in a 193 nm application, an uncoated argon fluoride (ArF) grade fused silica window would only have about 4.7% reflection loss, or double, relative to the surface (at the front and back surfaces for each window). In route application (as in DMD application), it has a loss of about 17.5%. In order to increase the transmission of the window, an anti-reflective coating is applied via an attachment step after the joining step. For example, a single layer magnesium fluoride (MgF ₂ ) coating applied to the outer surface 42 and the inner surface 44 of the window is optimized for 193 nm and the correct angle of incidence, resulting in a surface reflection of about 1.7% at 193 nm. (Or 6.63% overall transmission loss for a two-pass application), yet nevertheless very resistant to common cleaning methods and chemicals.

The coating thickness is typically selected by starting with a thickness of a quarter wavelength (193 x 10 ^{-9 / 4} = 48.25 x 10 ^-9 m) for a beam that normally strikes the surface. Is done. For non-normal incident beam applications, effective differences in optical path length within the coating thickness range for non-normal incident beams must be considered. In the current application, the coating is in contrast to the entrance angle (20 ° for 16 micro DMD mirror (Figure 7 (a)) or 24 ° for 13.7 micro DMD mirror (Figure 7 (b)). Optimized for the exit angle (0 ° or perpendicular to the window). This minimizes the reflection of the beam at the exit of the DMD window, which can be harmful because it has a rebounding reflection between the mirror and the inner window surface. Ideally, however, the antireflective coating should be operable over an exit angle in the range of 0 ° to 10 ° (16 micromirrors) or 0 ° to 12 ° (13.7 micromirrors). While improving the antireflectance of the incident beam, the inner reflectivity should be sufficiently reduced.

  A “cold” deposition process, such as sputtering, is desirable for application of anti-reflective coatings. In sputtering techniques, positive energetic particles formed from a plasma impact the coating material of interest, transform the object as sputtered atoms through momentum, and are bonded to the substrate. Sputtering can produce a uniform coating over a large area and uses deposited materials more efficiently than vapor deposition techniques. Other deposition techniques can be used as long as the deposition process temperature does not reach the braze alloy eutectic temperature. That is, deposition techniques that use high temperatures, for example, techniques that may cause the seal to become defective at temperatures that exceed the melting point of the brazing alloy, hamper preference.

であり、n₀は、空気（約1.0）の屈折率である。所望される実施形態において、フッ化アルゴン（ArF）グレード溶融シリカは、193nmの適用に対して使用される。その屈折率n₃は、1.56である。耐久性保護層を備えるための第一フッ化マグネシウムを使用しているので、1.72の屈折率を持つ第二コーティング層がゼロ反射を達成するために要求される。しかし、このアプローチはコーティング材料の選択にいくらかの自由度を許容し、非常に低い反射率を与えることが出来るが、QQコーティングは、時にはデザイン、例えば、もしも、適切なコーティングが、当を得た屈折率を見つけることが出来ない、又は入ってくる光の入射角がガラスの表面に対して垂直でない場合において、制約がきつくなりすぎる。これらの場合について、代替の方法が使用できる。 In order to obtain even greater transmission, the desired embodiment uses a multi-layered coating optimized with an incident angle of 0 ° to 12 °, but with different degrees of incident angle, for example in FIG. 7 (a). The optimizations shown from 0 ° to 10 ° can be used. Such a laminate coating is available from Acton Research / Roper Scientific, Inc., Acton, Massachusetts, as shown in FIG. 8, at 193 nm, incident angle 0 °, better than 0.5% relative to the surface of the window. Provides reflectivity (99.5% or better transmission) (or 1.98% overall loss in dual path applications). These narrow-band anti-reflective coatings, often referred to as “V” coatings, give industrial properties to the coating manufacturer, such as materials used, number of layers, layer thickness design, coating material deposition techniques, computer optimization There are algorithms. In general, however, the V coating is a multilayer anti-reflective coating that reduces the reflectivity of the component to near zero for one particular wavelength. V coatings are extremely sensitive to both wavelength and incident angle. A basic multilayer anti-reflective coating optimized for a single wavelength is called a QQ (quarter / quarter) coating. In its simplest form, the QQ coating consists of two layers, both having a quarter-wave optical thickness at the critical wavelength. The outer layer is made from a low refractive index material and the inner layer is made from a material with a high refractive index (compared to a substrate, eg, argon fluoride grade fused silica). As shown in FIG. 9 (a), the wavefront B and the wavefront C (second and third reflections, respectively) are both exactly 180 ° out of phase with the wavefront A (first reflection). The performance of the coating is calculated for the relative magnitude and phase and summed to obtain the overall value of the net magnitude of the reflected beam. In the complete structure this result will be a zero reflectivity as shown by the “synthesized wave” in FIG. 9 (b). Typical examples of FIGS. 9 (a) and 9 (b) are a crown glass with a refractive index n ₃ of 1.52, a magnesium fluoride fluoride first layer with a refractive index n _{1 of} 1.38, and a refractive index n ₂ of 1.70. Describes a second layer (such as beryllium oxide or magnesium oxide). The exact zero reflectance equation for such a two-layer coating at normal incidence is

And n ₀ is the refractive index of air (approximately 1.0). In the desired embodiment, argon fluoride (ArF) grade fused silica is used for 193 nm applications. Its refractive index n ₃ is 1.56. Since the first magnesium fluoride is used to provide a durable protective layer, a second coating layer with a refractive index of 1.72 is required to achieve zero reflection. However, although this approach allows some freedom in the choice of coating material and can give very low reflectivity, QQ coatings sometimes get designs, for example if an appropriate coating is appropriate In cases where the refractive index cannot be found or the incident angle of incoming light is not perpendicular to the glass surface, the constraints are too tight. For these cases, alternative methods can be used.

  In an alternative method of producing a multilayer antireflective coating, the layers have different thicknesses. This allows the layer to be adjusted to match the refractive index of the materials that can be used, instead of having a constant layer thickness (as described above). For a given material combination, there are typically two sets of layer thicknesses that give nearly zero reflectivity at the design wavelength. These two combinations differ in overall thickness. This method also aids in the structure of the coating when the incident angle of incoming light is unusual with respect to the surface. However, two main results lead to complex incident angle dependence of reflectivity and transmissivity. First, the difference between the front and back surface reflection paths from any layer is a function of angle. When the angle of incidence increases normally from 0 ° with respect to the surface, the light path difference decreases. A change in path difference results in a change in phase difference between two interfering reflections. Secondly, since the reflectivity of any optical interface varies according to the angle of incidence, the phase difference between two directly related reflections, when combined, varies together with a relative magnitude. . Thus, the multilayer coating structure at an arbitrary incident angle is complicated. Appropriate computer modeling and optimization algorithms can be performed by optical coating companies such as Coherent Urban Group, Melles-Griot, and Acton Research / Roper Scientific, which provide appropriate physical property values, adhesion A coating material having properties, stress, durability and the like is provided. In addition, the coating can be optimized for both angles of incidence, for example (1) both 20 ° or 24 ° incident angle and (2) 0 ° exit angle.

  In another embodiment, the anti-reflective coating may be adapted to pass dual wavelengths using the same window substrate material. For example, a single-wavelength 193nm optimized magnesium fluoride coating on one side of an argon fluoride grade fused silica window can reduce the single-surface reflectivity to about 1.7% at 193nm and about 2.75% at 365nm. Yes, in the reflection of a plurality of wavelengths, it can be reduced in a similar manner between the wavelengths. Multilayer, dual wavelength VV coatings can be applied to achieve even lower reflectivity (more transmission) at the designed wavelengths. This generally requires an additional coating (lamination), which, for example, in a coating as described above, must be optimized by a computer expert using a computer algorithm.

  Finally, the optically coated and hermetically sealed window unit is installed on the DMD substrate in the normal manufacturing process of the DMD semiconductor package. For example, the DMD chip is separated from the wafer, plasma cleaned, re-lubricated, and sealed using the present invention. Preferably, this is done using a parallel resistance seam welding process, but other types of semiconductor welding processes may be used. See Non-Patent Document 3. The base 50 includes a port (not shown) to which a cable 54 for transmitting data from the processing device is connected to a mirror array 52 that implements the arrangement of mirrors arranged in a desired pattern.

  In accordance with another embodiment of the present invention, the window frame is assembled from a material that is significantly different from Kovar. The frame material can be either silica fiber or copper / long carbon fiber alloy and has a coefficient of thermal expansion that is relatively close to that of UV transmissive window materials and can be machined to the shape required for DMD packages. It is. The window material can be fused silica as described above, or another suitable UV transmissive material as described below. The wet bonded laminated window and frame assembly preferably uses a technique such as an active solder alloy process (eg, S-BOND® available from Material Resources International, Landsdale, Pa.). Or connected to the basic DMD body using low evaporation epoxy.

Referring to FIG. 10, according to yet another embodiment, a rectangular Kovar® seal ring 152 (on the DMD substrate and on the DMD substrate and Kovar® window directly on the DMD substrate 150) By using a window 122 of the appropriate size and shape, which is also joined to the frame as a gap and as a melting union, also to the shoulder used in the prior art, the window frame can be completely eliminated. . For example, low vapor pressure epoxy 154 can be used to provide a seal between the DMD window and the ceramic substrate. An example of a suitable epoxy 154 is Tullabond 2116 available from Tracon, Bedford, Massachusetts. Other suitable epoxies are available from Master Bond, Hackensack, NJ. Epoxy adhesion may not be considered as a true seal, as rarely exceeding 2 × 10 ^-8 atm-cc / sec in a helium leak test, while adhesion is 5 × 10 ^-8 atm-cc / sec. It is also a very good seal that meets the below mill standard 803 and is relatively easy to achieve. In order to achieve a seal, preferably the epoxy 154 is mixed and applied, the window 122 is placed, and the window 122 is uniformly pressed against the DMD substrate 150 or seal ring 152 until the epoxy is cured. is there.

  Referring to FIGS. 11 (a) and 11 (b), if a single epoxy is not adhered to both the window 222 and the DMD substrate 250 or seal ring 252 based on the selected material, An intermediate material 260, such as plastic, is provided between the window 222 and the base 250 or seal ring 252 to provide adhesion between the window 222 and the intermediate material 260 using the first epoxy 254, Two epoxies may provide adhesion between the intermediate material 260 and the base 250 or seal ring 252. Optionally, as discussed further below, an elastomeric O-ring 262 is provided between the window 222 and the base 250 or seal ring 252 to form a true seal (11 (b)). I can do it.

  Referring to FIGS. 12 (a) and 12 (b), in further accordance with a further embodiment, window 322 and DMD substrate 350 (and seal ring 352) are elastomeric seals, eg, vacuum gauge O-rings 362 that are hermetically sealed. Fixed around. Suitable elastomers include rubber, butyl, ethylene propylene, and fluorocarbon materials, such as Viton® available from DuPonder Welastomer. The O-ring 362 can be installed at various locations, for example, inside or outside the Kovar® seal ring 352. Oval ring 362 on O-ring 362 (discussed further below) and / or Koval® seal ring 352 above O-ring 362 is completely Because it may not be flat, O-ring seals may need to be improved to facilitate sealing.

  Referring to FIG. 12 (c), in response, an extremely flat intermediate material 364 is used on the current Kovar® seal ring 352 between the ceramic body 350 and the window 322. Alternatively, the intermediate material 364 may be adhered to the Kovar® seal ring 352 using a low evaporation epoxy 354. This approach provides a true seal. The clamping force for pressing the window and DMD base against the O-ring is accomplished in several ways, three of which will be discussed next.

  Initially, and with further reference to FIGS. 12 (a) and 12 (b), clamp 370 is on window 322 and includes a port 372 in the center of the clamp that allows light to pass into and out of window 322. . DMD board 350 is connected to heat sink 374. The clamp 370 preferably includes two arms 376, 378 that extend in a C-shape from the front of the clamp to the periphery of the rear of the DMD base and preferably to the heat sink 374. Alternatively, the arms 376, 378 can extend to the sole rear of the DMD base 350. Screw 380 is used to uniformly apply pressure across window 322 that is in contact with O-ring 362. There are several different ways to do this.

  Further, with reference to FIGS. 12 (a) and 12 (b), according to the first assembly, O-ring 362 is first applied and window 322 is properly positioned on the O-ring. A clamp 370 is then applied to hold the window 322 to the O-ring 362. Finally, screw 380 is screwed against clamp arms 376, 378 that uniformly draw window 322 to O-ring 362 to form a seal.

  Referring to FIGS. 13 (a) and 13 (b), according to the second assembly, the O-ring 462 is disposed on the ceramic DMD substrate 450 or on the seal ring 452. Next, a preferred low evaporation epoxy 454 is provided to at least one of the window 422 and either the DMD substrate 450 or the Kovar® seal ring 452. A window 422 is then appropriately placed over the O-ring 462. Finally, the window 422 is uniformly pressed against the O-ring 462 and the epoxy 454 and held until the epoxy hardens.

  Referring to FIG. 14, according to the third assembly, a metal rectangular base ring 582 is bonded to the DMD body 550 around a seal ring (not shown). The base ring 582 has a substantially flat and horizontal top surface with a surface area greater than the top surface area of the seal ring. The base ring 582 also has several tapped holes for receiving screws. The base ring 582 is bonded using epoxy 554 either directly to the seal ring, directly to the ceramic body 550, or both for further sealing performance. Because the O-ring 562 has a very good surface to adhere and seal, the metal base ring 582 ensures a flat and level surface. There are three approaches for attaching the window 522 to the base ring 582.

  In the first approach, the upper metal frame 584 can be used around the window 522. The frame 584 is preferably not glued but is simply contained in a notched opening (not shown). When a seal is made between the window 522 installed on the base ring 582 and the O-ring 562, this upper frame 584 around the window 522 need not be sealed. The upper metal frame 584 has a plurality of through-holes arranged in a straight line by being screwed to the base metal ring 582. The screw 580 extends through the hole in the upper metal frame 584 and engages the threaded hole in the base metal ring 582 to tighten to sufficiently apply a uniform pressure across the window 522. I can do it.

  Referring to FIG. 15, in the second approach, the window frame 584a is provided with a suitable alloy (other than Kovar®) or non-alloy material (eg, ceramic) having a coefficient of thermal expansion closer to that of the window material. Is done. Some materials developed for semiconductor applications are particularly suitable and include silica fibers and copper / long carbon fiber alloys. See Non-Patent Document 4. Window 522 is bonded to frame 584a. The frame 584a has a plurality of holes, and the screws 580 can be joined to the DMD base 550 or the rectangular base ring 582 bonded to the seal ring through the holes. In assembly, the window 522 is bonded to the frame 584a and the base ring 582 is bonded to the DMD body 550 or seal ring using a low evaporation epoxy 554. Once the epoxy 554 has solidified, the O-ring 562 is placed on the base ring 582 and the melting window / frame assembly is placed on the O-ring 562. Finally, screws 580 are inserted through the holes in frame 584a and tightened to apply uniform window pressure to O-ring 562.

  Referring to FIG. 16, according to a third approach, the window 522 is provided with a drill hole and the window itself is screwed into the base ring 582. The holes are drilled using a diamond drill bit or with a laser. During assembly, a hole is first opened through the window member. Second, a base ring 582 is provided in the notched hole and bonded to the seal ring using the DMD body 550 or the low evaporation epoxy 554. Third, once the epoxy 554 is solidified, the O-ring 562 is placed on the base ring 582. Fourth, window 522 is properly positioned on O-ring 562. Finally, a screw 580 is inserted through the hole in the window and tightened to apply uniform pressure to the O-ring 562.

  In any of the embodiments described as using epoxy bonding, an adhesive, preferably a polymer-based adhesive, can be used in place of the epoxy. The use of an adhesive can be removed relatively easily from the bonded components, if necessary.

  There are also additional methods and components that are similar to and better than elastomeric seals used to provide superior sealing. Referring to FIG. 17, one such method is a knife edge seal, generally using a copper or lead gasket 600, and generally a vacuum compatible grade. In this manner, both the top component (eg, frame 602 with through-hole 604) and the bottom component (eg, base ring 606 with threaded hole 608) can be (Not shown), including knife edges 610, 612 that project into the gasket when secured to the bottom component. Small defects in the knife edges 610, 612 are filled with the material when the gasket 600 is deformed to form a very good seal.

  Referring to FIG. 18, another method is commonly known as a C-seal, where a C-shaped member 650 includes two opposing components (eg, an upper frame 652 with a through-hole 654 and Used to seal between bottom base ring 656) with threaded holes. In a typical “C” seal, the opening 660 of “C” 650 is diverted from the sealing environment 662. When the joint is assembled, the seal is slightly compressed, for example when the top component is secured to the bottom component with screws (not shown). The elastic properties of the sealing member maintain pressure on the surface of the cavity to be sealed. The sealing material is more flexible than the cavity surface. A softer sealing material replenishes the cavity surface defects to make a hermetic bond. This method is further modified to provide a larger sealing cavity, such as an “energized” C-seal. Such seals, often referred to as Helioflex seals, are available from Garlock Helicoflex, Inc. of Columbia, South Carolina.

  Referring to yet another aspect of the present invention, the mirror on the DMD substrate is preferably coated with a high reflectivity coating applied to enhance the reflection of UV light with respect to an uncoated general aluminum mirror. The The high reflectivity coating is preferably adapted for incident angles (depending on the size of the mirror) of 10 ° to 30 ° or 12 ° to 36 °. In the “ON” position, the mirror is tilted towards the illumination that plugs in at 10 ° or 12 °. Thus, the illumination hits the mirror at either 10 ° or 12 °. Nearly the most highly reflective coating is made of a dielectric material and provides a narrow band of high reflectivity at a particular wavelength. High reflectivity dielectric layers operate on the same principle as dielectric anti-reflective coatings. Alternatively, quarter-wave thicknesses of high and low index materials are applied to aluminum mirror substrates to form dielectric multilayers. By selecting an appropriate index of refraction material, the various reflected wavefronts can be caused to interfere forward to produce a high efficiency reflector. The peak reflectivity value depends on the ratio of the refractive indices of the two materials, as well as the number of layers. Increasing either increases the reflectivity. Optimized coating reflection at 10 ° or 12 ° angle of incidence is 97% to 99% (or only 1 to 3% loss) at 193 nm and 90% to 95% (or only 5 to 10%) at 157 nm Loss). If the angle of incidence increases from 10 ° or 12 °, the reflectivity decreases. However, such losses are negligible for the full range of mirror motion. In addition, the single magnesium fluoride coating attached to the bare aluminum mirror provides 86% to 88% reflection over a wide band ranging from 157nm to 193nm, thus more general purpose Provides an approach, but the overall reflection is reduced. This may be met in some applications.

  The high reflectivity coating is applied during or after the DMD is made, but not before. In order to apply high reflectivity coating during DMD fabrication, a completed CMOS memory circuit (SRAM cell) of the DMD superstructure has been obtained, and the intermediate dielectric is the entire CMOS metal-bilayer. Provided. The dielectric is then planarized using chemical mechanical polishing (CMP), which provides a completely flat substrate for the DMD superstructure. Through the use of several photomask layers, aluminum and registered metal alloy layers for address electrodes (metal-3), hinges, yokes and mirror layers, and sacrificial layers (spacers-1 and The superstructure is formed using a cured photoresistor for spacer-2). The alloy of aluminum and metal is sputter deposited and plasma etched using plasma deposited silicon dioxide as an etching mask. After the mounting flow, the sacrificial layer is plasma etched to form a void. The high reflectivity coating is preferably deposited after the aluminum mirror layer is deposited and before the sacrificial layer is etched.

  In the second method, the HR coating is applied after the DMD has been fabricated, but before the UV window is applied. Referring to FIG. 19, during the coating process, the micromirror is preferably in a “flat” state, and the DMD unit is at an angle of the incident laser beam (eg, 20 ° for a 16-micromirror unit, and 13.7-rotated to engage with the micromirror unit (24 °). This allows the coating of the underlying structures behind the mirrors to protect these structures from UV energy. The HR coating is preferably applied using a cold deposition technique such as sputtering. In one of many possible embodiments, the UV window is attached to the DMD unit.

Other Applications There are other applications where the deep UV DMD window assembly of the present invention can be used. The DMD is an ideal device for supplying patterns to semiconductor materials, to other materials in the manufacture of integrated circuits (ICs), or to other optical lithography applications (eg, polymer arrays). Currently, expensive and unchangeable photomasks are used to provide deprotection patterns for the etching process. Photomasks that require sophisticated manufacturing techniques and complex mathematical algorithms for designing are at the forefront of ultra-miniaturization of semiconductor devices, and offer additional functionality for integration into smaller areas. Giving. A photomask is an indispensable element in a lithographic process of semiconductor manufacturing. A photomask consists of a high-purity quartz glass or glass photosensitive plate with an accurate pattern of an integrated circuit for optical transfer of a pattern image to a semiconductor wafer by chip manufacturers and other manufacturers. Used as the original version. Current advanced lithographic machines, such as deep ultraviolet steppers, project light through a photomask and a high aperture lens. The chief rays have wavelengths of 248 nm and 193 nm, but as discussed below, 157 nm wavelengths are beginning to appear. The intensity of the light casts a design image (ie, a photomask pattern) for the device onto a silicon wafer coated with a light sensitive material called a photoresist. If a negative photoresist is used, it can be etched to form grooves, or other materials can be deposited, so that this material is not exposed or masked Part is removed. If an anode photoresist is used, the process is reversed. Since integrated circuits are manufactured layer by layer, selective deposition / removal steps are repeated until the circuit is assembled. Current generation semiconductors often have 25 or more layers, each layer requiring a unique photomask.

  If the DMD has the requisite resolution, the use of the DMD eliminates the photomask because the desired pattern can be easily implemented on the DMD mirror array. With appropriate light, the DMD mirror can mold or direct an image onto a silicon wafer substrate or other material coated with a light sensitive photoresist. Since the host computer controls the DMD mirror, the pattern can be quickly changed by switching the appropriate mirror ON or OFF. There, the masked portion of this material is removed so that it can be etched to form a trench or other material can be deposited. Currently, DMD is generally not used in vacuum and deep UV applications due to the current commercially available UV limited DMD window structure. The inventive UV transmissive DMD window of this patent can enable the use of DMD in these applications.

  In addition, optical lithography using a 157 nm fluorine laser is rapidly emerging as a feasible technology in the post-193 nm era. In fact, it may be a technology choice for the 70nm node (ie small physical details) instead of 100nm. It is attractive for several reasons, and most importantly it is basically on the extension of the longer wavelength 248 and 193 nm optical lithographs. As a result, it has the potential that machine manufacturing and wafer processing infrastructure can be adapted relatively easily, and techniques that increase optical resolution can be adapted as well. However, this approach still uses photomasks for 248 and 193 nm wavelengths as described above. Thus, a DMD window that allows 157 nm transmission would be advantageous when semiconductor processing proceeds in this direction.

The main difference between the main window embodiment and the deep ultraviolet wavelength window (eg down to 157 nm and further down) is the window material and coating used for shorter wavelengths. Currently, in the application of vacuum ultraviolet (generally VUV defined between 100 nm and 200 nm), the desired optical material for the window is lens grade quality calcium fluoride (CaF ₂ ) (for wavelengths below 130 nm) The details of which are disclosed in US Pat. No. 5,057,097, which is hereby incorporated by reference in its entirety. Other candidate materials are beryl fluoride (BaF ₂ ) (having a transmittance of at least 50% for wavelengths below 150 nm), strontium fluoride (SrF ₂ ) (at least 50 for wavelengths below 140 nm) % Transmittance), lithium fluoride (LiF ₂ ) (having at least 70% transmittance for wavelengths below 120 nm), magnesium fluoride (MgF ₂ ) (for wavelengths below 120 nm) And sodium fluoride (NaF) (having a transmittance of at least 50% for wavelengths below 135 nm). The adhesion of the window to the frame is similar to that described in the above embodiment, but the adhesive alloy may have different properties.

  In order to optimize transmission for 157 nm wavelengths, most oxide compounds (eg silicon dioxide or hafnium oxide) absorb too much at 157 nm, so fluoride is the desired coating. For example, the low refractive index material may include magnesium fluoride and aluminum fluoride, while the high refractive index material may include lanthanum fluoride and gadolinium fluoride. The coating design and application techniques are very similar to those discussed above.

  Embodiments of (i) DMD, (ii) its UV transmissive window assembly, and (iii) a method for assembling the same have been described and described herein. While the detailed embodiments of the present invention are described, the present invention is intended to be read in the same way as the scope of the present invention is as broad as the technology is possible. It is not intended to be limited to the embodiments. Thus, it is understood that DMD windows for other ultraviolet wavelengths can be assembled in the manner described above by using the appropriate material for the particular wavelength. Further, with respect to DMD, the invention will be described in detail and it will be appreciated that the UV transmissive window assembly may have utility as an optical MEMS device, eg, a deformable and active mirror device. Those skilled in the art will appreciate that still other modifications can be made to the provided invention without departing from the spirit and scope of the claims.

Prior art FIG. 1 (a) illustrates fine changes in the corneal surface. Prior art FIG. 1 (b) illustrates the wide beam laser ablation of the corneal surface of FIG. 1 (a), showing the subtle changes in the surface being sustained after the wide beam laser ablation. Prior art FIG. 2 illustrates a scanning spot approach showing the flexibility to illuminate a number of small points. Prior Art FIG. 3 shows a graph of the transmission spectrum of a current commercial based DMD window. Prior art FIG. 4 shows the transmission spectrum of borosilicate glass used in current DMD applications. FIG. 5 (a) is a bottom perspective view of a window assembly according to the present invention. FIG. 5 (b) is an exploded view of the window and frame of the assembly of FIG. 5 (a). FIG. 5 (c) is a bottom perspective view of the top surface of the window and frame of the assembly of FIG. 5 (a). FIG. 5 (d) is a plan perspective view of the window and the bottom of the frame of the assembly of FIG. 5 (a). FIG. 5 (e) is a plan view of a DMD apparatus including the window assembly of FIG. 5 (a). FIG. 6 shows the external transmission properties of HPFS®, Corning 7980, argon fluoride-grade fused silica window material. FIG. 7 (a) exemplifies the projection angle of light entering and exiting a DMD apparatus having an ultraviolet transmission window according to the present invention, and relates to a 16 μm mirror arrangement. FIG. 7 (b) exemplifies the projection angle of light entering and exiting a DMD device having an ultraviolet transmission window according to the present invention, and relates to a 13.7 μm mirror arrangement. FIG. 8 is a reflectivity curve for a multilayer dielectric laminate V coating optimized for 0 ° or normal projection angle, showing a reflectivity of 0.5% or less for the window surface at a wavelength of 193 nm. FIG. 9 (a) shows a basic multilayer antireflection, ie V coating, optimized for a single wavelength. FIG. 9 (b) shows the harmful interference due to the layer of V coating of FIG. 9 (a). FIG. 10 is a schematic side view of a first alternative DMD assembly in accordance with the present invention. FIG. 11 (a) is a schematic side view of a second alternative DMD assembly in accordance with the present invention. FIG. 11 (b) is a schematic exploded view of the second alternative DMD assembly of FIG. 11 (a). FIG. 12 (a) is a schematic side view of a third alternative DMD assembly according to the present invention. FIG. 12 (b) is a schematic plan view of the third alternative DMD assembly of FIG. 12 (a). FIG. 12 (c) is a schematic side view of a variant of the DMD assembly of FIG. 12 (a). FIG. 13 (a) is a schematic side view of a fourth alternative DMD assembly in accordance with the present invention. FIG. 13 (b) is a schematic exploded view of the fourth alternative DMD assembly of FIG. 13 (a). FIG. 14 is a schematic side view of a fifth alternative DMD assembly in accordance with the present invention. FIG. 15 is a schematic side view of a sixth alternative DMD assembly in accordance with the present invention. FIG. 16 is a schematic side view of a seventh alternative DMD assembly in accordance with the present invention. FIG. 17 is a schematic side view of an eighth alternative DMD assembly in accordance with the present invention. FIG. 18 is a schematic side view of a ninth alternative DMD assembly in accordance with the present invention. FIG. 19 illustrates the structure underlying the high reflectivity (HR) coating of the DMD mirror.

Claims (123)

A window assembly for a digital micromirror device (DMD) having neatly arranged individually addressable mirrors,
a) a frame adapted to be connected to the DMD, the frame having an opening having a size suitable for at least a mirror arrangement, and having a first end chamfered around the opening; Frame,
b) an ultraviolet light transmissive window connected to the opening, including a perimeter with a chamfered second end, the chamfered first and second ends together having a groove; Said window defining;
c) a brazing material provided in the groove comprising a seal between the window and the frame;
A window assembly.   The window assembly of claim 1, wherein the seal is hermetic.   The window assembly of claim 1, wherein the window is selected to provide at least 50% transmission of light waves above 130 nm.   The window assembly of claim 1, wherein the window is selected to provide at least 65% transmission of light waves above 120 nm.   The window assembly of claim 1, wherein the window is selected to provide at least 80% transmission of light waves above 185 nm.   The window assembly of claim 1, wherein the window is a fused silica glass window.   The window assembly of claim 1, wherein the window is an argon fluoride (ArF) grade silica glass window.   The window assembly of claim 1, wherein the window complies with Corning Code 7980.   The window assembly of claim 1, wherein the window is made of a material selected from the group comprising calcium fluoride, barium fluoride, strontium fluoride, lithium fluoride, magnesium fluoride and sodium fluoride.   The window assembly of claim 1, further comprising a dielectric coating on the window.   The window assembly of claim 1, wherein the frame is made of a metal alloy.   The window assembly of claim 11, wherein the metal alloy is a nickel-cobalt-iron alloy.   The window assembly of claim 12, wherein the metal alloy is Kovar.   The window assembly of claim 12, wherein the metal alloy is comprised of about 29% nickel, 17% cobalt, 0.30% magnesium, 0.20% silicon, 0.02% carbon, and the remaining components being iron.   The window assembly of claim 1, wherein the brazing material is a lead / silver alloy brazing material.   The window assembly of claim 15, wherein the lead / silver alloy comprises about 97.5% lead and 2.5% silver.   The window assembly of claim 1, wherein the window includes an inner surface and an outer surface, wherein at least one of the inner surface and the outer surface comprises one or more optical coatings.   The window assembly of claim 17, wherein at least one of the optical coatings is a narrow band antireflective (AR) coating.   The window assembly of claim 17, wherein at least one of the optical coatings is a multi-layer laminate coating.   20. A window assembly according to claim 19, wherein the laminated coating is optimized for an angle of incidence between 0 ° and 12 °.   The window assembly of claim 17, wherein at least one of the optical coatings is optimized for a bi-directional angle of incidence. a) a base element with individually addressable mirrors in a two-dimensional array;
b) a frame connected to the base element, the frame having at least an opening sized to fit the mirror arrangement;
c) a window connected at the opening and bonded to the frame, the window being made of a material that allows high transmittance of light of ultraviolet wavelengths passing through the window;
A digital micromirror device (DMD).   The frame has a first end chamfered around the opening and the window has a perimeter with a chamfered second end, the chamfered first and first 23. The DMD of claim 22, wherein two ends define a groove and the window is adhered to the frame with a brazing material provided in the groove.   23. The DMD of claim 22, wherein the bond between the window and the frame forms a seal.   23. The DMD of claim 22, wherein the window is a fused silica glass window.   23. The DMD of claim 22, wherein the window is argon fluoride (ArF) grade silica glass.   23. The DMD of claim 22, wherein the window material is selected from the group comprising calcium fluoride, barium fluoride, strontium fluoride, lithium fluoride, magnesium fluoride and sodium fluoride.   28. The DMD of claim 27, further comprising a dielectric coating on the window.   23. The DMD according to claim 22, wherein the frame is made of a nickel-cobalt-iron alloy.   23. The DMD of claim 22, wherein the window includes an inner surface and an outer surface, and at least one of the inner surface and the outer surface comprises one or more optical coatings.   32. The DMD of claim 30, wherein at least one of the optical coatings is a narrow band antireflection (AR) coating.   32. The DMD of claim 30, wherein at least one of the optical coatings is a multilayer laminate coating.   36. The DMD of claim 32, wherein the laminated coating is optimized for incident angles between 0 ° and 12 °.   23. The DMD of claim 22, wherein the mirror comprises a coating to increase reflectivity.   35. The DMD of claim 34, wherein the coating is optimized for an angle of incidence between 10 ° and 36 °.   36. The DMD of claim 34, wherein the mirror is made from aluminum and the coating is a dielectric material. a) a base element with a two-dimensional array of individually addressable mirrors;
b) a frame connected to the base element, wherein the frame is made of a material having at least an opening sized to fit the mirror arrangement and having a first coefficient of thermal expansion;
c) a window connected to the opening of the frame, which is made of a material that allows high transmittance of light of an ultraviolet wavelength that passes through the window, compared to the first coefficient of thermal expansion; The window having a significantly different second coefficient of thermal expansion;
d) a seal between the window and the frame;
A digital micromirror device (DMD).   38. The DMD of claim 37, wherein the first and second coefficients of thermal expansion differ by approximately the order of magnitude.   38. The DMD of claim 37, wherein the seal is hermetic. a) a base element having a first side and a second side, wherein the first side comprises a two-dimensional array of individually addressable mirrors;
b) a Kovar alloy frame having at least an opening sized to fit the mirror arrangement;
c) an argon fluoride grade fused silica window between the frame and the base element;
d) sealing between the window and the base element;
A digital micromirror device (DMD). a) a base element having a first side and a second side, wherein the first side comprises a two-dimensional array of individually addressable mirrors;
b) a frame having an opening having a size that fits at least the mirror arrangement;
c) a window between the frame and the base element, wherein the window is made of a material that allows transmission of at least 90% of the ultraviolet wavelength above 185 nm, the window and the base The window in which an element is connected in a manner to establish a seal around the orderly mirrors;
A digital micromirror device (DMD). a) providing a frame having an opening;
b) providing a fused silica glass window;
c) bonding step of bonding the window to the opening of the frame to form a window unit;
d) optimizing the window for light transmission at one or more specific wavelengths;
A method of assembling a window unit for a digital micromirror device (DMD) comprising:   The window and the frame define a groove at a joint between them, and the bonding step provides a brazing alloy for the groove and a seal between the window and the frame; 43. The method of claim 42, comprising heating the window, the frame, and the braze alloy.   The window includes an inner surface and an outer surface, and wherein the optimizing step increases at least one coating adapted to increase the transmission of ultraviolet light through the window, the inner surface and the outer surface of the window. 43. The method of claim 42, comprising applying to at least one of the following.   45. The method of claim 44, wherein masking a portion of the window unit prior to applying the coating.   45. The method of claim 44, wherein the applying step utilizes a low temperature process.   45. The method of claim 44, wherein the applying step includes sputtering.   43. The method of claim 42, wherein the optimizing comprises optimizing the window for a particular angle of incidence.   43. The method of claim 42, wherein the optimizing comprises optimizing the window for a range of incident angles.   43. The method of claim 42, further comprising the step of mounting the window unit on a base element of the DMD, the DMD having a plurality of individually addressable mirrors.   51. The method of claim 50, further comprising coating the mirror with a relatively higher reflectivity coating. a) the foundation elements;
b) configurable means for optically reflecting light disposed on said base element;
c) a window arranged with respect to said means for optically reflecting light and having a transmittance of at least 80% of the ultraviolet wavelength above 185 nm;
An optical package comprising:   53. The optical package of claim 52, wherein the window has a transmittance of 130 nm or greater and at least 65% of the ultraviolet wavelength.   53. The optical package of claim 52, wherein the window has a transmittance of 120 nm or more and at least 50% of the ultraviolet wavelength.   54. The optical package of claim 53, wherein the window comprises fused silica.   56. The optical package of claim 55, wherein the fused silica is argon fluoride grade fused silica.   53. The optical package of claim 52, wherein the window is constructed from one of the lens qualities of calcium fluoride, barium fluoride, strontium fluoride, lithium fluoride, magnesium fluoride and sodium fluoride.   53. The optical package of claim 52, wherein the means for optically reflecting light comprises a two-dimensional array of individually addressable mirrors.   53. The optical package of claim 52, wherein the window surface includes an anti-reflective coating selected to reduce light reflection at at least one ultraviolet wavelength.   53. The optical package of claim 52, wherein the means for optically reflecting light comprises a reflective coating selected to increase light reflection at ultraviolet wavelengths.   53. The optical package of claim 52, further comprising a frame provided around the window.   62. The optical package of claim 61, wherein the frame element is assembled from a Kovar alloy.   64. The optical package of claim 61, wherein the frame element is assembled from a material other than Kovar alloy. The window and the base element are connected together so as not to allow greater than 5 × 10 ⁻⁸ atm-cc / sec helium in a manner comprising a seal with respect to the means for optical reflection. 52. The optical package according to 52.   65. The optical package of claim 64, wherein the seal is hermetically sealed. a) the foundation elements;
b) configurable means for optically reflecting light disposed on said base element;
c) a window arranged with respect to said means for optically reflecting light, wherein at least 85% of the ultraviolet wavelength in each of the vacuum-ultraviolet, far-ultraviolet and near-ultraviolet parts of the ultraviolet spectrum. The window having transmittance;
An optical package comprising:   68. The optical package of claim 66, wherein the window has a transmittance of at least 85% of the ultraviolet wavelength in each of the far-ultraviolet and near-ultraviolet portions of the ultraviolet spectrum.   67. The optical package of claim 66, wherein the window has a transmittance of at least 90% of the ultraviolet wavelength in each of the far-ultraviolet and near-ultraviolet portions of the ultraviolet spectrum.   68. The optical package of claim 66, wherein the means for optically reflecting light comprises a two-dimensional array of individually addressable mirrors.   68. The optical package of claim 66, wherein the window surface comprises an anti-reflective coating that is selected to reduce light reflection at at least one ultraviolet wavelength.   68. The optical package of claim 66, wherein the means for optically reflecting light comprises a reflective coating selected to increase light reflection at ultraviolet wavelengths. a) the foundation elements;
b) individually addressable mirrors of a two-dimensional array on the base element;
c) a window arranged with respect to said means for optically reflecting light, said window having a transmittance of at least 80% of ultraviolet radiation above 185 nm and comprising an optical coating of narrowband ultraviolet radiation;
An optical package comprising: a) the foundation elements;
b) individually addressable mirrors of a two-dimensional array on the base element;
c) a window arranged in relation to said means for optically reflecting light, said window having a transmittance of at least 80% of ultraviolet radiation above 185 nm and comprising a broadband ultraviolet optical coating;
An optical package comprising: a) the foundation elements;
b) individually addressable mirrors of a two-dimensional array on the base element;
c) a window arranged with respect to said means for optically reflecting light, said window having a transmittance of at least 80% of ultraviolet radiation above 185 nm and comprising an optical coating of double ultraviolet wavelengths; ,
An optical package comprising: a) the foundation elements;
b) a two-dimensional array of individually addressable mirrors on the base element, the mirror comprising a reflective coating thereon;
c) a window arranged with respect to said means for optically reflecting light;
An optical package comprising:   76. The optical package of claim 75, wherein the reflective coating is optimized for light wavelengths in the ultraviolet band. a) a base element having a first side and a second side, wherein the first side comprises a two-dimensional array of individually addressable mirrors;
b) a base ring connected to the base element around the regularly arranged mirrors;
c) a window made of a material adapted to allow transmission of at least 80% of the ultraviolet wavelength above 185 nm;
d) a frame element partially exceeding the window;
e) an elastomeric element between the window and the base element, wherein the window applies a force to the elastomeric element to at least partially define a seal around the ordered mirror. With an elastomeric element,
A digital micromirror device (DMD).   79. The DMD of claim 78, wherein the base element comprises a ceramic DMD base and a metal seal ring upstanding on the DMD base around the orderly mirrors. 79. The DMD of claim 78, wherein the seal does not allow greater than 2 x ^10-8 atm-cc / sec helium.   79. The DMD of claim 78, wherein the elastomeric element is an O-ring.   79. The DMD of claim 78, wherein the frame is screwed to the base ring. a) a base element having a first side and a second side, wherein the first side comprises a two-dimensional array of individually addressable mirrors;
b) a heat sink connected to the second side of the base element;
c) a frame having at least an opening sized to fit the mirror arrangement;
d) a window between the frame and the base element, the window being made of a material adapted to allow transmission of at least 90% of the ultraviolet wavelength above 185 nm;
e) a plurality of clamp arms extending around the frame and the heat sink such that the window is clamped between the frame and the base element by a clamping force;
f) an elastomer sealing element located between the window and the base element, wherein the clamping force and the sealing element seal between the window and the base element;
A digital micromirror device (DMD).   84. The DMD of claim 83, wherein the first side of the base element comprises an upstanding ring structure and the sealing element is provided in the ring structure.   85. The DMD of claim 84, wherein the ring structure is assembled from a Kovar alloy.   84. The DMD of claim 83, further comprising an epoxy that bonds the window to the base.   87. The DMD of claim 86, wherein the epoxy is a low evaporation epoxy.   84. The DMD of claim 83, wherein the first side of the base element comprises an upstanding ring structure, and the epoxy further comprises an epoxy that bonds the window to the ring structure.   84. The DMD of claim 83, wherein the clamping force is performed using screws that extend through the frame.   84. The DMD of claim 83, wherein the sealing element is an O-ring.   84. The DMD of claim 83, wherein the sealing element is made from vacuum grade rubber.   84. The DMD of claim 83, wherein there are exactly two arms.   84. The DMD of claim 83, wherein the frame is made from Kovar alloy.   84. A DMD according to claim 83, wherein the window comprises fused silica.   84. The DMD of claim 83, wherein the window comprises argon fluoride grade fused silica. a) a base element having a first side and a second side, wherein the first side comprises a two-dimensional array of individually addressable mirrors;
b) a frame having at least an opening sized to fit the mirror arrangement;
c) a window between the frame and the base element, wherein the window is made of a material adapted to allow transmission of at least 90% of the ultraviolet wavelength above 185 nm;
d) a plurality of clamp arms extending around the frame and the second side of the base element such that the window is clamped between the frame and the base element by a clamping force;
e) an elastomer element located between the window and the base element, wherein the clamping force and the elastomer element seal around the neatly arranged mirrors;
A digital micromirror device (DMD).   97. The DMD of claim 96, wherein the sealing element is assembled from rubber, butyl, ethylene polymer, and fluorinated hydrocarbon.   A ring structure that is positioned between the base element and the window and stands upright on the first side surface of the base element, further comprising a ring structure to which a substantially flat element is bonded to the ring structure; 97. The DMD of claim 96.   99. The DMD of claim 98, wherein the flat element is bonded to the ring structure using a low evaporation epoxy. A ring structure positioned between the base element and the window and upstanding on the first side of the base element, the upstanding ring having a top portion with a first surface region;
An external foundation ring having a substantially flat upper surface with a second surface area larger than the first surface area, the foundation ring comprising at least:
(I) the base ring bonded to one of the upstanding ring structure and (ii) the base element around the upright ring structure, the window being bonded to the second surface of the base ring When,
97. The DMD of claim 96, further comprising:   101. The DMD of claim 100, wherein the second surface is horizontal.   101. The DMD of claim 100, wherein the second surface is substantially flat.   97. The DMD of claim 96, wherein the frame is made from one of an alloy and a ceramic. a) a base element having a first side and a second side, wherein the first side comprises a two-dimensional array of individually addressable mirrors;
b) a window above the substrate element, the window being made of a material adapted to allow a transmittance of at least 80% of the ultraviolet wavelength above 185 nm;
c) an epoxy for bonding between the window and the base element;
A digital micromirror device (DMD).   105. The DMD of claim 104, further comprising an elastomer element positioned between the window and the first side of the base element.   106. The DMD of claim 105, wherein the window and the base element are connected together, and the connection and the elastomer element comprise a seal around the orderly mirrors.   106. The DMD of claim 105, wherein the window is connected to the base with a screw.   106. The DMD of claim 105, wherein the window is selected to provide at least 50% transmission of light waves above 130 nm.   106. The DMD of claim 105, wherein the window is selected to provide at least 50% transmission of light waves above 120 nm. a) The base has a first side and a second side, the first side comprising a two-dimensional array of individually addressable mirrors and a metal alloy seal ring around the neatly arranged mirrors The foundation,
b) a window above the seal ring, the window being made of a material adapted to allow transmission of at least 80% of the ultraviolet wavelength above 185 nm;
c) an epoxy that bonds between the window and at least one of the seal ring and the base;
A digital micromirror device (DMD).   111. The DMD of claim 110, further comprising an elastomer element positioned between the window and at least one of the seal ring and the base. a) the base having a first side and a second side, the first side comprising a two-dimensional array of individually addressable mirrors;
b) a window connected by screws to the substrate, the window being made of a material adapted to allow a transmittance of at least 80% of the ultraviolet wavelength above 185 nm;
A digital micromirror device (DMD).   113. The DMD of claim 112, further comprising an elastomer element positioned between the window and the first side of the base. a) the base having a first side and a second side, the first side comprising a two-dimensional array of individually addressable mirrors;
b) a window on the substrate, the window being made of a material adapted to allow transmission of at least 80% of the ultraviolet wavelength above 185 nm;
c) an intermediate element between the base and the window;
d) a first epoxy for bonding between the base and the intermediate element;
e) a second epoxy that bonds between the intermediate element and the window;
A digital micromirror device (DMD). a) a base element having a first side and a second side, wherein the first side comprises a two-dimensional array of individually addressable mirrors;
b) a window made of a material adapted to allow transmission of at least 80% of the ultraviolet wavelength above 185 nm;
c) a base ring connected to the base element around the orderly mirrors;
d) an elastomer element between the window and the base element;
e) a plurality of screws extending between the window and the base ring;
A digital micromirror device (DMD). 116. The DMD of claim 115, wherein the seal does not allow greater than 2 x ^10-8 atm-cc / sec helium.   116. The DMD of claim 115, wherein the foundation ring is bonded to the first side of a foundation element.   116. The DMD of claim 115, wherein the window is selected to provide at least 50% transmission of light waves above 130nm.   116. The DMD of claim 115, wherein the window is selected to provide at least 65% transmission of light waves above 120 nm. a) a base element having a first side and a second side, wherein the first side comprises a two-dimensional array of mirrors individually addressable;
b) a window made of a material adapted to allow transmission of at least 80% of the ultraviolet wavelength above 185 nm;
c) a frame bonded to both the window and the base element, wherein the frame is assembled of a material having a coefficient of thermal expansion closer to the window material than 5.2 × 10 ⁻⁶ / ° C .;
A digital micromirror device (DMD). a) a base element having a first side and a second side, wherein the first side comprises a two-dimensional array of mirrors individually addressable;
b) a base ring on the base element and around the orderly mirrors;
c) a window made of a material adapted to allow transmission of at least 80% of the ultraviolet wavelength above 185 nm;
d) a frame around the window;
e) a gasket between the base ring and the frame;
A digital micromirror device (DMD).   122. The DMD of claim 121, wherein the base ring, the frame, and the gasket together define a knife edge seal.   123. The DMD of claim 122, wherein the gasket is made from copper and lead.   124. The DMD of claim 123, wherein the gasket has a C-shaped cross section.

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