Abstract:
A reticle carrier for a polishing tool capable of accommodating a reticle includes a base plate with an obverse and reverse surfaces, a retaining ring secured to the obverse surface of the base plate forming a recess defined by the obverse surface of the rigid base plate and internal edges of the retaining ring. A reticle pad supports a reticle in the recess. The base plate and the reticle pad having an array of matching, aligned passageway holes therethrough for exhaustion of air from space between the base plate and a the reticle and for supply of air to that space so a vacuum can retain a the reticle in place on the reticle carrier under vacuum conditions and application of air under pressure can eject a reticle from the reticle carrier.

Description:
CROSS-REFERENCE TO RELATED APPLICATION(S) 
     This application is a divisional of U.S. application Ser. No. 13/278,571, filed on Oct. 21, 2011, which is a divisional of U.S. Pat. No. 8,110,321 filed on May 16, 2007, the disclosures of which are incorporated herein by reference. 
    
    
     BACKGROUND 
     The present application relates to methods of manufacture of photolithographic reticles, i.e. masks, and reticles produced thereby. More particularly the present application relates to methods for fabrication of reticles for exposure of microelectronic integrated circuits and other micro-scale devices and to the reticles produced thereby. 
     During the process of manufacturing of microelectronic integrated circuits on a substrate comprising a workpiece such as a semiconductor wafer or the like, layers of material on the workpiece are patterned photolithographically. A layer of a radiation sensitive resist (hereinafter resist) is deposited on the workpiece. The resist (e.g. photoresist) comprises a radiation sensitive material which can be exposed to a master image projected as patterns of radiation, e.g. light, ultraviolet light, x-ray, electron beam, or other forms of radiation. The resist is later exposed using an exposure tool and a reticle. The reticle comprises a photomask or the like which is patterned with opaque regions, transparent regions and possibly partially transparent regions. During the exposure process, radiation is directed onto the reticle to expose the resist selectively with patterns of radiation projected through the reticle. 
     The resist is developed, and then the remaining resist forms a mask on the workpiece which protects areas of the workpiece during subsequent fabrication processes, such as deposition, etching, or ion implantation. A mask or photomask is generally used for photoimaging with a positive or negative image when exposing a photosensitive material known as photoresist or analogous materials sensitive to electromagnetic or other forms of radiation. 
     Binary Reticle 
     A binary reticle includes a pattern corresponding to features to be formed on work pieces such as FET devices or other Integrated Circuit (IC) features. A binary reticle may be formed on a reticle mask plate comprising a transparent glass plate coated with a patterned, opaque (light blocking) material. This type of reticle is typically referred to as a binary mask since some of the light is completely blocked by the opaque material and the remainder of the light is fully transmitted through the transparent, glass portions. 
     Chrome on Glass (COG) Binary Reticle 
     A Chrome-On-Glass (COG) reticle (i.e. a mask, photomask, or photoreticle) typically comprises a quartz-chrome patterned mask. In more detail, a COG reticle comprises a single crystal quartz reticle mask plate that is substantially planar, which carries a mask pattern defined using a patterned chrome (Cr/CrO 2 ) layer, formed by sputtering. The chrome layer is laminated to the top surface of the reticle mask plate. A virgin or blank COG reticle mask plate or mask blank comprises a virgin reticle which has not been patterned. In other words, a virgin COG reticle comprises an unpatterned or blank planar layer of chrome deposited on a quartz reticle mask plate. 
     In the production of a COG patterned reticle, e.g. an Integrated Circuit Device (ICD), an image of one or more microelectronic devices is printed onto a virgin COG reticle via a lithographic process by exposure to radiation. A layer of resist is applied to the blank COG reticle mask plate covering the top surface of the chrome layer. After patterning by exposure of the resist to a master image, the resist is developed to reproduce the exposed pattern thereby producing openings down to the surface of the chrome of the COG mask. Exposed surfaces of the COG mask are removed by etching leaving the remaining portions of the chrome layer intact. Then the resist is removed with appropriate chemicals and washed away. 
     In the context of photolithography, the term reticle refers to a semiconductor photomask, which contains an image which is adapted to expose only a small part of a semiconductor wafer which is to be employed in a step-and-repeat exposure system, i.e. a wafer stepper or scanner. A semiconductor reticle typically contains the pattern of a several semiconductor devices. The reticle is employed in the wafer stepper to project an image to be exposed over and over onto a workpiece comprising a semiconductor wafer covered with unexposed photoresist by moving the workpiece relative to the reticle with the wafer stepper or scanner, which is employed to expose several areas of the unexposed photoresist repeatedly and sequentially. 
     In addition to visible light, the absorber may be capable of absorbing radiation such as infra-red, x-ray, E-beam, or light in ranges such as the UltraViolet (UV) range, Deep UltraViolet (DUV) range, Vacuum UltraViolet (VUV) range, and Extreme UltraViolet range (EUV). 
     The present application relates to processing of integrated circuit devices and particularly to the manufacturing of optical projection masks for deep submicron (&lt;0.25.μm) integrated circuit processes. 
     A common method of manufacturing of projection reticles for exposure of integrated circuit devices has relied on etching a pattern into an actinic radiation absorber comprising a layer of absorbent material which is deposited on a reticle mask plate (i.e. a transparent substrate or mask blank.) Currently in semiconductor fabrication the patterning of structures on a substrate is often performed with reticles defined by lithography performed on a blank COG reticle. 
     There is a serious problem with the process of etching through the chrome of a COG reticle mask plate down to the quartz therebelow which is that the etching process for the chrome also consumes the photoresist mask very quickly which forces certain restrictions in the mask making process (e.g. resist thickness.) 
     There are other serious problems with etched COG reticles. One such problem with etched COG reticles is that Electro-Static Discharge (ESD) can cause damage to the metal (chrome) pattern on a substrate composed of quartz as the insulating material. The problem is that unwanted Electro-Static Discharge (ESD), involving rapid dissipation of electric charge in a short amount of time, often causes delamination of the chrome pattern from the quartz substrate. In other words, at least a portion of the chrome pattern on the quartz substrate is lifted away from the top surface thereof, as the ESD energy is being dissipated in the laminated material. That renders the mask defective so that it is not useful for the fabrication of devices on semiconductor substrates. 
     Another serious problem with COG reticles is that they grow defects over the lifetime of the mask which limits the useful lifetime of such reticles and forces regular cleaning. 
     Phase Shift Mask (PSM) 
     Another type of reticle is the Phase Shift Mask (PSM), which can be produced by allowing some light to pass through a partially-transmissive chrome feature thereby changing the phase of the light that passes therethrough, i.e. creating phase shifted light. The phase shifted light from the partially-transmissive feature affects the interference pattern of the light transmitted from neighboring fully transparent areas, resulting in a higher contrast at the imaging plane. This allows imaging features with significantly smaller feature sizes than would be possible using the same mask pattern implemented as a standard COG reticle. These reticles are referred to as attenuated PSM (AttPSM) reticles. 
     Alternating PSM (AltPSM) Mask 
     A third type of reticle is known as an Alternating PSM (AltPSM) reticle (mask) wherein feature recesses are etched into the virgin reticle mask plate. The feature recesses result in a path length difference for the light passing therethrough, and the depth of the feature recess is tuned to result in a 180° phase shift of the incident electromagnetic radiation to be used in exposure of the image on the reticle. The AltPSM mask has limitations in that the termination of features can be difficult and a second mask called a block out has to be used in conjunction therewith to terminate the features that are desired on the substrate. The higher cost of these AltPSM reticle processes is negligible in view of expenses saved as compared to more advanced lithography tooling that would be required when only COG reticles would be used. However the cost of fabrication of a mask set has increased dramatically by introducing those extra processing steps required for AltPSM reticle processing. 
     Commonly assigned U.S. Pat. No. 5,932,377 of Ferguson et al. entitled “Exact Transmission Balanced Alternating Phase-Shifting Mask for Photolithography” describes forming an AltPSM mask with etched-quartz trenches. It states that a phase difference between two clear shapes for an AltPSM is achieved in standard industry practice by selectively etching into a quartz reticle mask plate so an optical path difference equivalent to the desired phase offset is obtained between two adjacent openings. After standard mask patterning, a second write step is used to selectively open a protective resist coating for a phase-shifted opening leaving a non-phase shifted opening covered. Typically, the quartz is then etched with an anisotropic Reactive-Ion Etching (RIE) process. 
     Commonly assigned U.S. Pat. No. 5,565,286 of Lin entitled “Combined Attenuated-Alternating Phase Shifting Mask Structure and Fabrication Methods Therefor” describes a structure and fabrication method for a phase-shifting lithographic mask. AltPSM and AltPSM are combined to provide a mask combination consisting of phase-shifted and unshifted attenuated backgrounds in which the phase-shifted attenuated background surrounds the unshifted components and the unshifted attenuated background surrounds the phase-shifted components. 
     U.S. Pat. No. 6,660,653 of Tzu et al. entitled “Dual Trench Alternating Phase Shift Mask Fabrication” describes fabricating a dual-trench AltPSM mask. A chromium layer formed over a quartz layer of the PSM is patterned with deep trenches by dry etching through a photoresist layer. The quartz layer is dry etched through another photoresist layer applied over the chromium layer and patterned according to the deep trenches and the shallow trenches of the AltPSM design using backside exposure to ultraviolet light. 
     Damascene Patterning 
     Traditionally, the term damask refers to rich tapestry patterns of damask silk, such as a figured fabric of silk, wool, linen, cotton, or synthetic fibers, with a pattern formed by weaving. An artistic damascene process of metal work involves inlaying metal into trenches in another metal is a process of inlaying different metals into one another, e.g. gold or silver into a darkly oxidized steel background, to produce intricate patterns. 
     In semiconductor technology, damascene or dual-damascene metal patterning processes have been employed in forming copper interconnects in a dielectric layer, e.g. silicon oxide, for external electrical connections and interconnections of semiconductor devices. The semiconductor damascene process starts by a subtractive process of etching open trenches reaching down into a dielectric layer wherein copper conductor patterns are to be formed. An additive patterning process is employed involving deposition of a conformal barrier layer followed by deposition of a blanket (thick) coating of copper that significantly overfills the trenches. Then, the excess copper is removed by planarization to the level of the top of the insulating layer by Chemical-Mechanical Polishing (CMP). The copper, which remains within the trenches of the insulating layer, comprises a patterned interconnect conductor. 
     U.S. Pat. No. 6,821,192 of Donohue entitled “Retaining Ring for Use in Chemical Mechanical Polishing” describes a retaining ring for use on a carrier head in a Semiconductor Wafer CMP (SWCMP) apparatus with a bottom surface, an inner surface and an outer surface, and a plurality of recesses on the bottom surface. Each recess includes an inner trailing surface and a slurry capture area. A channel connects the slurry capture area to the inner surface. The inner trailing surface can be configured for fastening thereon an insert tool having a contact edge for abrasively contacting a polishing pad. The Donohue patent states “Integrated circuits are typically formed on substrates, particularly silicon wafers, by the sequential deposition of conductive, semiconductive or insulative layers. After each layer is deposited, the layer is etched to create circuitry features. As a series of layers are sequentially deposited and etched, the outer or uppermost surface of the substrate, i.e., the exposed surface of the substrate, becomes successively less planar. This non-planar outer surface presents a problem for the integrated circuit manufacturer as a non-planar surface can prevent proper focusing of the photolithography apparatus. Therefore, there is a need to periodically planarize the substrate surface to provide a planar surface. Planarization, in effect, polishes away a non-planar, outer surface, whether a conductive, semiconductive, or insulative layer, to form a relatively flat, smooth surface.” 
     Transmissivity, τ and Opacity 
     Transmissivity in the context of this invention is defined as the fraction of incident radiation (at actinic wavelength) that passes through a mask, more specifically, a mask plate or combination of materials in or on the mask plate. In the context of this invention a material is considered to be transparent if it has a maximum value of transmissivity equal to that of the mask plate or substrate without any other materials than quartz. Opacity is defined as the fraction of incident radiation (at actinic wavelength) that is absorbed while passing through a mask, more specifically, a mask plate or combination of materials in or on the mask plate. In the context of this invention a material is considered to be opaque (having a value of opacity nearing a value of 1) if practically all the light is absorbed in the material, e.g. darkly pigmented glass. 
     SUMMARY 
     Embodiments of the present invention utilize techniques that will allow the formation of a reticle by creating structures in a virgin reticle mask plate, the formation of which structures presents an opportunity to create multiple features that are not presently available in mask processing today. 
     Embodiments of the invention leave the top surface of a reticle which is completely planar, improving the imaging performance by reducing the scattering of light between features. Such a fully planar surface also allows the sealing of the top surface of the reticle without adverse effects, eliminating growth of defects on the features of the reticle. 
     One embodiment of this invention allows the difficult process of absorber etching to be replaced by a silicon dioxide etch into the quartz of a COG plate to form an etched pattern, followed by the process of filling the etched pattern with an actinic absorber. 
     As employed herein the term reticle is intended to be interpreted to be synonym of the terms mask, photomask, and photoreticle. 
     In accordance with an embodiment of this invention, a damascene method for manufacturing optical projection masks comprises patterning a substrate for an optical projection mask having a first level of transmissivity with a feature recess; and filling the recess with a material having a different level of transmissivity. 
     In one example, the method involves forming a projection reticle in a transparent substrate having a top surface with a feature recess in the top surface of the transparent substrate; and forming a radiation transmissivity modifying material in the feature recess. The radiation transmissivity modifying material comprises a material selected from the group consisting of an opaque material and a partially transmissive material. 
     In one example, the method involves forming a projection reticle in a transparent substrate having a top surface with a feature recess in the top surface of the transparent substrate, and forming a radiation transmissivity modifying material in the feature recess. The radiation transmissivity modifying material comprises a material selected from the group consisting of an opaque material and a partially transmissive material. A plurality of films may be included in the feature recess with the deposited films having different degrees of transmissivity. Preferably, the radiation transmissivity modifying material is selected from the group comprising at least two deposited films including an opaque film and a transmissive film and an opaque film deposited with a partially transmissive material. 
     In one example, a liner is formed juxtaposed with the radiation transmissivity modifying material as a lens for focusing the exposure rays at the edge of the pattern to increase signal to noise levels so that scattering from the projected pattern is minimized. Preferably a sacrificial material is present in the recess. Next, a material for modifying radiation transmissivity is formed juxtaposed with the sacrificial material. Then the sacrificial material is removed from the recess. 
     In one example, the radiation transmissivity modifying material is deposited as a film upon the transparent substrate; and the radiation transmissivity modifying material is planarized with a polishing slurry consisting of fumed silica, a pH of from about 2.2 to about 2.6, and a 1:10 dilution in water on the order of one part of about 84% to about 88% parts phosphoric acid to 9 parts water, preferably deionized water. 
     In one example, a reticle carrier is provided for a polishing tool capable of accommodating a reticle comprising a rigid base plate; a retaining ring; a reticle pad adapted for supporting a reticle inserted onto the reticle carrier; and the base plate with the reticle pad having a plurality of aligned passageways therethrough for exhaustion of air from the space between the base plate and a reticle; whereby a vacuum is generated to retain a reticle in place under vacuum conditions and application of air under pressure can eject a reticle from the reticle carrier. 
     In one example, a metal base plate is provided having a plurality of passageways therethrough, preferably including a reticle pad installed on the metal base plate with matching aligned plurality of passageways therethrough. It is also preferred that a reticle holding ring is provided made of a low friction material that is attachable to the base plate. 
     In accordance with another embodiment of this invention, a projection reticle is formed in a transparent substrate having a top surface comprising a feature recess in the top surface of the transparent substrate; and a radiation transmissivity modifying material is formed in the feature recess. 
     In one example, the radiation transmissivity modifying material comprises a material selected from the group consisting of an opaque material, and a partially transmissive material. A plurality of deposited films may be included in the feature recess with the deposited films having different degrees of transmissivity. 
     In one example, the radiation transmissivity modifying material is selected from the group comprising at least two deposited films including an opaque film and a transmissive film, and an opaque film deposited with a partially transmissive material. 
     In one example, the radiation transmissivity modifying material comprises an opaque film juxtaposed with a phase error correction material selected from the group consisting of a solid or a gas. Preferably the recess has sidewalls and the radiation transmissivity modifying material is spaced away from the sidewalls by the phase error correction material. 
     In one example, a liner is juxtaposed with the radiation transmissivity modifying material as a lens for focusing the exposure rays at the edge of the pattern to increase signal to noise levels, whereby scattering from the projected pattern is minimized. 
     In accordance with another embodiment of the invention, a slurry for reticle polishing comprises fumed silica with a pH of from about 2.2 to about 2.6; and with on the order of a dilution of one part of 84-88% phosphoric acid in about 9 parts of water, preferably deionized water. 
     Embodiments of the invention avoid the difficult absorber etch employed in the subtractive process employed in patterning COG masks. 
     Embodiments of the invention provide a method for fabricating an optical projection mask using DUV resists. 
     Still other embodiments of the invention maximize the choices of absorbing materials for the optical projection mask manufacturer; to increase throughput on pattern generating tools in the mask making environment (higher sensitivity of DUV resists); minimize scattering from the projected pattern by adding a liner to function as a lens; focus the exposure rays at the edge of the pattern to increase signal to noise levels; and use of different absorbing materials, therefore allowing to tune linewidth per exposure. 
     Embodiments of the invention provide a reticle carrier to hold the reticle during polishing with the carrier consisting of a metal base plate that has a number of passages through it; and to provide a reticle holding ring that is made of a low friction material that attaches to the base plate. 
     Embodiments of the invention will be more readily apparent from the following detailed description and appended claims when taken with the drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIGS. 1A-1G  are schematic, elevational sections of a reticle mask plate during the process of manufacture of a damascene reticle in accordance with this invention. 
         FIG. 2A  shows a flow chart which describes the steps in accordance with the process flow illustrated by the drawings from  FIG. 1A  to  FIG. 1G ; and  FIG. 2B  shows a flow chart which describes alternative steps in accordance with the process flow illustrated by the drawings from  FIG. 1A  to  FIG. 1G . 
         FIGS. 3A-3F  are schematic, elevational sections of a reticle mask plate during the process of manufacture of another form of damascene reticle in accordance with the method of this invention in accordance with the method of this invention. 
         FIG. 4  is a flow chart which describes the steps in accordance with the process flow illustrated by the drawings from  FIG. 3A  to  FIG. 3F . 
         FIG. 5  is a perspective view depicting a reticle in accordance with this invention in which an annular, via type via feature is formed for a structure, e.g. a semiconductor via, in a transparent reticle mask plate. 
         FIG. 6  shows a perspective view depicting a reticle in accordance with this invention in which an rectangular type line patterning feature is shown in a transparent reticle mask plate with the light passing material and the light blocking material formed in a linear feature recess leaving a narrow feature recess inside the light blocking film. 
         FIGS. 7A-7F  illustrate an alternative process of manufacture which provides a patterned damascene reticle in accordance with the method of this invention. 
         FIG. 8  is a flow chart which describes the steps of the process flow illustrated by the drawings from  FIG. 7A  to  FIG. 7F . 
         FIGS. 9A-9I  illustrate the steps of a method of manufacture of a reticle mask plate which is patterned with feature recesses in accordance with this invention. 
       In combination,  FIG. 10A  and  FIG. 10B  show a flow chart of the steps of the process flow illustrated by the drawings from  FIG. 9A  to  FIG. 9I . 
         FIG. 11  is a perspective view depicting a reticle with an open peripheral space via feature in accordance with this invention in which an annular, via type via feature is formed for a structure, e.g. a semiconductor via, in a transparent reticle mask plate. 
         FIG. 12  is a perspective view of an open peripheral space line feature in accordance with this invention depicting a reticle showing a rectangular type line patterning feature in a transparent reticle mask plate with the planarized light blocking material formed in a linear feature recess leaving a narrow feature recess inside the light blocking film 
         FIGS. 13A and 13B  show sectional and bottom views respectively of a reticle polishing carrier in accordance with this invention which is adapted for use with a wafer polishing tool for the purpose of reticle polishing. 
         FIGS. 14A and 14B  show sectional and bottom views respectively of the reticle polishing carrier of  FIGS. 13A and 13B  with a reticle inserted therein for polishing. 
         FIG. 15  is a table showing representative slurry formulation. 
         FIG. 16  is a table showing the processing parameters and equipment employed for performing an exemplary Damascene Reticle CMP (DRCMP) process in accordance with this invention. 
         FIG. 17  is a table showing an implementation of the DRCMP process of this invention. 
         FIG. 18  is a table showing transparent materials and their refractive indicies. 
     
    
    
     DETAILED DESCRIPTION 
     A common feature of various embodiments is the use of the Damascene Reticle CMP (DRCMP) in the formation of a damascene reticle. Another feature common to different embodiments is the formation of recessed trenches in a transparent plate. 
     Damascene Quartz Binary Reticle 
     In this embodiment, a damascene reticle in accordance with the invention is formed employing photolithography. Structures are formed in and/or upon a reticle starting with a blank, planar, transparent reticle mask plate adapted for creating features for use in processes in the manufacture of microelectronic devices. 
     First Embodiment of a Damascene Mask Plate Formed in a Transparent Reticle Mask Plate 
     Heretofore, mask plate reticles have been formed by patterning opaque material on the top surface of a transparent substrate. In accordance with this invention a damascene mask plate is formed by first forming a pattern of recesses in a blank, transparent, reticle mask plate. Then the recesses are filled with opaque and/or partially transmissive materials depending upon which type of damascene mask plate is being formed in accordance with this invention. Several embodiments thereof are described below with reference to the appended drawings. The substrate can be selected to be transparent for an exposure radiation of an appropriate wavelength to be used with such mask plate reticles.  FIGS. 1A-1F  are schematic, elevational sections of a reticle  10  formed from a blank transparent reticle mask plate  11  (hereinafter mask plate  11 ). The process of manufacture provides a patterned damascene reticle  10  shown in  FIG. 1G  formed in accordance with the method of this invention.  FIG. 2  is a flow chart which describes the steps of the process flow illustrated by  FIGS. 1A to 1G .  FIG. 1G  shows a complete, patterned damascene reticle  10  in accordance with this invention after completion of the manufacture thereof. The damascene reticle  10  (mask) of  FIG. 1G  is adapted to be employed to expose patterns formed thereon. 
       FIG. 1A  shows the blank reticle  10  in the form of a blank, planar, transparent, reticle mask plate  11 , hereinafter mask plate  11 , (composed of quartz or silicon dioxide) in the initial stage of processing of step A in  FIGS. 2A and 2B  with a photoresist mask PR formed thereon. The mask plate  11  has a top surface upon which a blanket layer of photoresist PR is deposited and patterned into a mask PR. The mask PR is formed in accordance with photolithographic techniques, well understood by those skilled in the art. There is an open window W reaching down through the mask PR exposing the top surface of the reticle mask plate  11 , as will also be well understood by those skilled in the art. The mask plate  11  may comprise a virgin, planar quartz plate with no layer of chrome formed thereon. The top surface of the mask plate  11  is substantially flat or planar. Preferably, the photoresist mask PR may comprise a standard state-of-the-art DUV resist. 
       FIG. 1B  shows the previously blank reticle  10  of  FIG. 1A  after initial patterning by etching through the window W down into the blank mask plate  11  to form an initial feature recess  12  in the form of a trench formed in the mask plate  11  according to step B in FIGS.  2 A/ 2 B. The initial feature recess  12  extends down partially through the mask plate  11  from the top surface of reticle mask  10 . The initial feature recess  12  can be formed in a quartz or silicon dioxide mask plate  11  by using a conventional etching process, using either a wet etching or a dry etching process. For quartz or glass (silicon oxide) a wet etch can be performed with an acidic etchant, e.g. an aqueous hydrofluoric acid (HF) solution. A dry etch can be performed by Reactive Ion Etching (RIE) with a dry etchant such as CF 4 . TetraMethylAmmonium Hydroxide (TMAH) which is a base can etch the initial feature recess  12  into a silicon mask plate  11 . TMAH is a quaternary ammonium salt with the molecular formula (CH 3 ) 4 NOH used as an anisotropic etchant of silicon; and TMAH can be used as a basic solvent in the development of an acidic photoresist in photolithographic processing of a workpiece. 
       FIG. 1C  shows the reticle  10  of  FIG. 1B  after the photoresist mask PR is removed from the top of the patterned, mask plate  11  in accordance with step C in  FIG. 2 . 
       FIG. 1D  shows the reticle  10  of  FIG. 1C  after deposition of a radiation transmissivity modifying material on the top surface of the etched mask plate  11 . In this case the radiation transmissivity modifying material comprises a conformal, opaque-absorber film  15 C composed of an opaque material with a relatively uniform thickness. The absorber film  15 C is deposited on the top surface of the mask plate  11  and the sidewall and bottom surfaces of the initial feature recess  12  in accordance with step D in  FIG. 2 . The conformal, opaque-absorber film  15 C leaves a recess  15 R defining a shallower and narrower feature recess  12 ′ (representing a latent feature  15 F.) The absorber film  15 C preferably comprises an opaque material selected to have optical characteristics adapted to block the radiation (e.g. light) which can be employed for exposure (onto workpieces being manufactured) of patterns of damascene features to be formed in the mask plate  11 . One such damascene feature  15 F is shown after completion of processing thereof as shown by  FIG. 1G . 
       FIG. 1D  shows how a mask plate  11  is being prepared to be patterned with the feature  15 F of  FIG. 1E . After step D is completed the initial feature recess  12  is narrowed (forming a potential, damascene feature  15 R) by the thickness of the conformal, absorber film  15 C which lines the sidewall surfaces as well as the bottom surface of the initial feature recess  12  of  FIG. 1B . In other words a narrowed feature recess  12 ′ remains inside the initial feature recess  12 . It is preferred to employ Chemical Vapor Deposition (CVD) to deposit the absorber film  15 C when it comprises TaN, Ta, Ti, TiN, Ni, W, SiO 2 , SiN, or SiC or a combination thereof. Other deposition techniques can also be employed to deposit film  15 C, e.g. plating, atomic layer deposition, sputtering, evaporation, etc. that are all well known in the industry. 
       FIG. 1E  shows reticle  10  of  FIG. 1D  after planarization by a process such as DRCMP in step E of FIGS.  2 A/ 2 B to remove the uppermost (outer), exposed portions of the conformal layer of opaque material  15 C from the top surface of the mask plate  11 . The inner, remainder of the conformal layer of opaque material  15 P is formed into a patterned, opaque, damascene feature  15 F which remains on the sidewall surfaces and the bottom surface of the initial feature recess  12  of  FIG. 1E  leaving a shallower feature recess  12 ″. 
       FIG. 1F  shows the reticle  10  of  FIG. 1E  after a deposition in accordance with step F in  FIG. 2A  of a blanket transparent coating  16 B that will allow mask exposure, radiation, i.e. light, to pass through it and through the mask plate  11  as well, aside from the patterned, opaque, damascene feature  15 F. The transparent coating  16 B covers the top surface of the mask plate  11  and fills the shallower feature recess  12 ″ leaving the surface of the transparent coating  16 B with a depression  16 D therein above the shallower feature recess  12 ″ of  FIG. 1E . It is preferred to deposit the transparent coating  16 B by a CVD process. Alternatively, one can sputter and spin-on materials which are used as insulators (i.e. SiLK from Dow Chemical and flowable oxides) which can be deposited to form the transparent coating  16 B. These spin-on materials are applied in the same manner as photoresist. Additionally, if a spin-on component, is used, it can be planarized. The planarizing characteristics are dependant upon the viscosity of the material, as is well known by those skilled in the art. 
       FIG. 1G  shows the completed reticle  10  of  FIG. 1F  after a step of planarization, e.g. DRCMP planarization in accordance with step G in  FIG. 2A . The DRCMP planarization of step G has transformed the blanket layer of transparent material  16 B of  FIG. 1F  into a thin film  16 P of  FIG. 1G  comprising a planar remainder of the transparent coating  16 B with a substantially planar top surface. The planar transparent coating  16 P continues to fill the shallower feature recess  12 ″ and covers the top surface of the reticle mask plate  11 , providing protection for the remainder of the conformal layer of opaque material  15 P (which forms the patterned, opaque, damascene feature  15 F) and the reticle mask plate  11 . 
     Alternatively in  FIG. 2B , steps F and G have been replaced by step F′ in which spin coating a deposit of a blanket, planar, transparent layer  16 P (as shown in  FIG. 1G ) covers both the mask plate  11  and the patterned, opaque, damascene feature  15 F formed from the absorber film  15 C. 
     In the processing in accordance with  FIGS. 2A and 2B , it is preferable to deposit the layers by Chemical Vapor Deposition (CVD), where applicable. 
     Second Embodiment 
     Damascene PSM Reticle 
       FIGS. 3A-3F  are schematic elevational views of a damascene PSM reticle  30  during the process of manufacture of the reticle in accordance with another aspect of the method of this invention, as shown by the flow chart of  FIG. 4 .  FIGS. 3A-3F  illustrate process flow for patterning the reticle  30 . As shown in  FIG. 3F , the resulting reticle  30  has PSM features  36 F′ which are composed of deposited conformal film elements  33 P/ 35 P filling a feature recess  32  in a mask plate  31 . The reticle  30  is adapted to be used to expose patterns on a workpiece (not shown.)  FIG. 3F  shows a patterned reticle  30  which is to be employed as a PSM mask after the manufacture thereof in accordance with this invention for exposing patterns formed thereon. 
       FIG. 3A  shows the reticle  30  in an initial stage of processing in accordance with step A in  FIG. 4 . A transparent reticle mask plate  31  (hereinafter mask plate  31 ) is shown with a top surface on which a photoresist mask PR is formed. As with  FIG. 1A , an open window W through photoresist mask PR reaches down to the top surface of the mask plate  31 , which may comprise a virgin, planar quartz plate with no layer of chrome formed thereon. The top surface of the mask plate  31  is flat or planar. 
       FIG. 3B  shows the reticle  30  of  FIG. 3A  after an initial feature recess  32  was etched into the top surface of the mask plate  31  in accordance with step B in  FIG. 4 . In step B, the reticle mask plate  31  is etched with a conventional etching process, as described above with reference to step B in  FIG. 2 . 
       FIG. 3C  shows the reticle  30  of  FIG. 3B  after removal of photoresist mask PR from the top surface of the mask plate  31  according to step C in  FIG. 4 . 
       FIG. 3D  shows the reticle  30  of  FIG. 3B  after deposition of a radiation transmissivity modifying material, which in accordance with step G in  FIG. 4  comprises a conformal, partially-transmissive film  33 C (i.e. partially-transparent film). The partially-transmissive film  33 C is deposited on the top surface of the reticle  30  and the sidewalls and the bottom surface of the etched initial feature recess  32  leaving a narrower feature recess  32 ′ (forming a potential, damascene feature  33 R) representing a stage in the patterning of a feature  36 F′ shown in  FIG. 3F . The conformal, partially-transmissive film  33 C is selected to have optical characteristics adapted to provide partial blocking of the radiation (e.g. light) that can be employed for exposure (onto workpieces being manufactured) of patterns of features  36 F formed on the reticle  10 . In  FIG. 3F  the feature  36 F′ is shown after completion of processing of the device  30  by step I in  FIG. 4  of CMP planarization to polish down both the actinic absorber film  35 C and the partially-transmissive film  33 C (i.e. partially-transparent film) to expose the top surface of the mask plate  31  forming an opaque patterned damascene feature  36 F′ defined by the portions of both films remaining in the recess in the mask plate reticle  10 . 
     Summarizing, when step G in  FIG. 4  is completed the initial feature recess  32  is narrowed into narrower feature recess  32 ′ and reduced in depth by the thickness of the partially-transmissive film  33 C which lines the sidewall surfaces and the bottom surface of the etched initial feature recess  32  of  FIG. 3C  forming the potential, damascene feature  33 R. In other words a narrowed feature recess  32 ′ remains inside the etched initial feature recess  32  which is lined with the partially-transmissive film  33 C. 
       FIG. 3E  shows the patterned reticle  30  of  FIG. 3D  after a conformal, actinic/light blocking, opaque-absorber film  35 C is formed thereover in accordance with step H in  FIG. 4 . Thus, both laminated films  33 C/ 33 R including the partially-transmissive, conformal film  33 C and the conformal, opaque-absorber film  35 C cover the reticle  30 . The opaque-absorber film  35 C is deposited over the patterned reticle  30  with a relatively uniform thickness on the top surface of the partially-transmissive film  33 C including the sidewall and bottom surfaces of the feature recess  32 ′. As a result, the opaque-absorber film  35 C produces a potential feature  36 F in the even narrower feature recess  32 ″. The conformal, opaque-absorber film  35 C preferably comprises an opaque material selected to have optical characteristics adapted to block the radiation (e.g. light) which can be employed for exposure (onto workpieces being manufactured) of patterns of damascene features to be formed in the mask plate  11 . One such damascene feature  36 F′ is shown after completion of processing thereof as shown by  FIG. 3F . 
       FIG. 3F  shows the reticle  30  of  FIG. 3E  after the step I in  FIG. 4  of planarization of the two laminated films  35 C/ 33 C down to the top surface of the mask plate  31 . The initial feature recess  32  remains lined with the damascene PSM feature  36 F composed of the combination of a remainder element  33 P from partially-transmissive film  33 C and a remainder element  35 P from opaque-absorber film  35 C (nested in remainder element  33 P) which form the resulting damascene feature  36 F′. In step I of  FIG. 4  the conformal, opaque-absorber, actinic or light blocking film  35 C, and the conformal partially-transmissive film  33 C are polished away from the top of the reticle mask plate  31  by CMP planarization forming the damascene PSM Reticle  30 . Thus, the resulting feature  36 F′ comprises the laminated combination of the remaining conformal partially-transmissive remainder film  33 P which lines the sidewalls and bottom surface of the initial feature recess  32  and the remaining conformal, opaque-absorber film  35 P which lines the conformal partially-transmissive remainder film  33 P in the feature recess  32 , leaving a shallower, narrowed feature recess  32 ″ within the opaque-absorber remainder film  35 P. 
     The blanket films  33 C/ 35 C may be composed of a material selected from Silicon Oxide (SiO 2 ), Silicon Nitride (Si 3 N 4 ), and chromium (Cr) may be deposited on the reticle mask plate  31 . These are known materials and offer options of not just passing light, but also changing the light. Those changes in the light can be employed to provide attenuation or phase shifting. 
     Third Embodiment 
     Damascene PSM Reticle In-Situ Lens Formation on the Reticle 
     In a modification of the embodiment of  FIG. 3F , aside from the detail that the shape and index of refraction of the outer, partially-transmissive, remainder element  33 P is tuned so that parallel, focused light beams come out of the top side of the reticle  30  as illumination is to be projected from below for all images. Improvements can employ multiple different layers with varying refraction indexes to improve the focus effect. 
     Fourth Embodiment 
     Via Feature 
       FIG. 5  is a top perspective view depicting a reticle  50  in accordance with this invention in which an annular, via type via feature  56 F is formed for a structure, e.g. a semiconductor via, in a mask plate  51 . The reticle  50  is made in accordance with the method of this invention, as shown by the  FIG. 4  flow chart. In this case, as in  FIGS. 3B and 3C  and steps B and C in  FIG. 4 , a cylindrical initial feature recess  52  is formed in the reticle mask plate  51  by etching down into the mask plate  51 . Then the initial feature recess  52  is lined with a conformal light passing film  33 P (deposited as in  FIG. 3D , according to step G in  FIG. 4 ) which forms a narrower cylindrical recess  52 ′. Next the additional narrower cylindrical recess  52 ′ is lined with a conformal light blocking film  35 P (deposited as in  FIG. 3E , according to step H in  FIG. 4 ) covering the sidewalls and bottom thereof. Then a planarization step I in  FIG. 4  is performed producing a via patterning feature  56 F. A hollow well  52 W remains inside the conformal light blocking film  35 P. 
     Fifth Embodiment 
     Line Feature 
       FIG. 6  shows a top perspective view depicting a reticle  60  in accordance with this invention in which an rectangular type line patterning feature  66 F is shown in a transparent reticle mask plate  61  (hereinafter mask plate  61 ) with the light passing material  33 P and the light blocking  35 P material formed in a linear feature recess  62  leaving a narrow feature recess  62 W inside the light blocking film  35 P. The reticle  60  is made in accordance with the method of this invention, as shown by the flow chart of  FIG. 4 . In this case, as in  FIGS. 3B and 3C , the rectangular initial feature recess  62  is etched into the mask plate  61 . Then the rectangular initial feature recess  62  is lined with a conformal light passing film  33 P (deposited as in  FIG. 3D , according to step G in  FIG. 4 ) forming a narrower rectangular recess. Next the additional narrower rectangular recess is lined with a conformal light blocking film  35 P (deposited as in  FIG. 3E  according to step H in  FIG. 4 ) covering the sidewalls and bottom of the additional narrower rectangular recess. Then the planarization step I in  FIG. 4  produces line patterning feature  66 F. Thus the hollow well  62 W remains inside the conformal light blocking film  35 P. In summary, the line patterning feature  66 F was formed in the rectangular initial feature recess  62 . 
     Sixth Embodiment 
     Light Blocking Material Embedded in a Reticle 
       FIGS. 7A-7F  are schematic elevational views of the steps of forming a reticle  70  from a blank, transparent, reticle mask plate  71  (hereinafter mask plate  71 ) illustrating an alternative method of manufacture of a patterned damascene reticle  70  in accordance with the method of this invention.  FIG. 7F  shows a complete, patterned damascene reticle  70  in accordance with this invention after completion of the manufacture thereof. In  FIG. 7F  a fully opaque feature  75 F is embedded in a feature recess  72  in the mask plate  71  of the reticle  70 .  FIG. 8  is a flow chart which describes the steps of the process flow illustrated by the drawings from  FIG. 7A  to  FIG. 7F . The damascene reticle  70  (mask) of  FIG. 7F  is adapted to be employed to expose patterns formed thereon. 
     In  FIG. 7A , the process begins with a blank, planar, transparent reticle mask plate  71  in an initial stage of processing in accordance with step A in  FIG. 8  with a photoresist mask PR formed thereon. The mask plate  71  (composed of quartz or silicon dioxide) has a top surface upon which a blanket layer of photoresist PR is deposited and then patterned into a photoresist mask. The mask PR is formed in accordance with photolithographic techniques which are well understood by those skilled in the art. There is an open window W reaching down through the photoresist mask PR exposing the top surface of the mask plate  71 , as will also be well understood by those skilled in the art. The transparent reticle mask plate  71  may comprise a virgin, planar quartz plate with no layer of chrome formed thereon. The top surface of the mask plate  71  is substantially flat or planar. Preferably, the photoresist mask PR comprises a standard DUV resist. 
       FIG. 7B  shows the previously blank reticle  70  of  FIG. 7A  after initial patterning by etching through the window W down into the blank mask plate  71  to form a feature recess  72  in the form of a trench formed in the mask plate  71  extending down from the top surface of the mask plate  71  in accordance with step B in  FIG. 8 . In step B, the feature recess  72  can be formed in a quartz or silicon dioxide, mask plate  71  by etching the feature recess employing a conventional etching process; or by using either a wet etching or a dry etching process as described above. 
       FIG. 7C  shows the reticle  70  of  FIG. 7B  in accordance with step C in  FIG. 8 , after the photoresist mask PR is removed from the top surface of the mask plate  71  in accordance with step C in  FIG. 8 . 
       FIG. 7D  shows the reticle  70  of  FIG. 7C  after deposition of a blanket, opaque-absorber film  75 B composed of an opaque material with a relatively uniform thickness on the top surface of the mask plate  71 , which fills the feature recess  72  in accordance with step J in  FIG. 8 , leaving a depression  75 D over the feature recess  72 . The opaque material of the absorber film  75 B, which preferably has optical characteristics adapted to block the radiation (e.g. light), can be employed for exposure (onto workpieces being manufactured) of patterns of damascene features to be formed in the mask plate  71 . One such damascene feature  75 F is shown after completion of processing thereof as shown by  FIG. 7G . The layer  75 B is opaque to the actinic wavelength and completely fills up the feature recess  72 , which is a patterned trench. 
       FIG. 7E  shows the reticle  70  of  FIG. 7D  after a planarization step such as DRCMP to remove the outer, exposed portions of the blanket opaque absorber film  75 B from the top surface of the mask plate  71  in accordance with step K in  FIG. 8 . The inner, remainder  75 P of the blanket, opaque absorber film  75 B is formed into a patterned, opaque, damascene feature  75 F remaining in the feature recess  72  of  FIG. 7E . 
       FIG. 7F  shows the completed reticle  70  of  FIG. 7E  after deposition in accordance with step L in  FIG. 8  of a blanket, transparent coating film  77  covering the remainder  75 P of the film  75 B (i.e. the patterned, opaque, damascene feature  75 F) and the top surface of the mask plate  71 . The transparent coating film  77  allows mask exposure, radiation, i.e. light, to pass through it through the mask plate  71  as well, aside from the patterned, opaque, damascene feature  75 F. The transparent coating  77  provides protection from use or handling by encapsulating the remainder of the opaque absorber film  75 P (which forms the patterned, opaque, damascene feature  75 F) and the mask plate  71 . 
     Eighth Embodiment 
     Encapsulated Materials and Variable Index of Refraction 
       FIGS. 9A-9L  illustrate the steps of a method of manufacture of a reticle mask  100  patterned with feature recesses in accordance with this invention. FIGS.  10 A/ 10 B show a flow chart of the processing steps shown by  FIGS. 9A to 9L . 
     In the method of  FIGS. 9A-9L  and the flow chart of FIGS.  10 A/ 10 B, a reticle  100  is formed in a transparent reticle mask plate  101  (hereinafter mask plate  101 ) shown in  FIG. 9A . Pattern the mask plate  101  with feature recesses  102  with sidewall surfaces  102 S and bottom surfaces  102 B (FIGS.  9 B/ 9 C). Then deposit a conformal sacrificial film  103 C covering exposed surfaces on the top of the patterned mask plate  101  including the exposed surfaces  102 S/ 102 B forming narrowed feature recesses  102 ′ ( FIG. 9D .) Next etch back the conformal sacrificial film  103 C is using an anisotropic inside spacer process that leaves recessed sacrificial film sidewalls  103 S on the sidewalls  102 S, while exposing the bottom surfaces  102 B forming deepened narrowed feature recesses  102 ″ ( FIG. 9E .) 
     Then deposit a conformal opaque film  105 C ( FIG. 9F ), covering exposed surfaces including the bottom surfaces  102 B forming a pair of preliminary features  105 R with narrower and shallower feature recesses  102 ″. Then in a DRCMP step, remove the external portion of the conformal opaque film  105 C from the top surface of the reticle  100  ( FIG. 9G ) forming modified features  105 F with shallower recesses  102 F. Next, remove the recessed portions of the sacrificial film  103 S leaving gaps  107 O between the sidewalls  102 S and the features  105 F ( FIG. 9H ). The gaps  107 O can be filled, preferably with a gas or generation of a vacuum employing conventional equipment as will be well understood by those skilled in the art. If a gas is used it is preferable to fill the gap  107 O with an inert gas to prevent unwanted reactions with the solid materials. Finally deposit a protective capping layer  109  over the features  105 F. At this point a planarizing step can be performed (not shown) if needed. 
       FIG. 9A  shows the reticle  100  in an initial stage of processing according to step A in  FIG. 10A . A blank mask plate  101  is shown with a photoresist mask PR formed thereover. As with  FIG. 1A , there are two open windows W through photoresist mask PR down to the top surface of the mask plate  101 . The mask plate  101  may comprise a transparent, virgin, planar quartz plate with no layer of chrome formed thereon. The top surface of the mask plate  101  is flat or planar. 
       FIG. 9B  shows the reticle  100  of  FIG. 9A  after a pair of initial feature recesses  102  having sidewalls  102 S and bottom surfaces  102 B were etched into the top surface of the mask plate  101  in accordance with step B in  FIG. 10A . In step B, the reticle mask plate  101  is etched with a conventional etching process as described above in step B of  FIG. 2 , exposing the bottom surfaces  102 B of the recesses  102 . 
       FIG. 9C  shows reticle  100  of  FIG. 9B  after stripping the photoresist mask PR from the top surface of the mask plate  101  according to step C in  FIG. 10A . 
       FIG. 9D  shows reticle  100  of  FIG. 9C  after deposition according to step M in  FIG. 10A  of a conformal, sacrificial film  103 C on top of the reticle  100  and the sidewalls and the bottom surface of the etched initial feature recess  102  leaving a narrower feature recess  102 ′ representing a initial portion of a feature (feature  105 F in  FIGS. 9F-9I ). 
       FIG. 9E  shows the reticle  100  of  FIG. 9D  after performing an anisotropic inside spacer etching process in accordance with step N in  FIG. 10A  removing the horizontally extending regions of the sacrificial film  103 C exposing the top surface of the mask plate  101  and the bottom surfaces  102 B leaving a pair of narrowed and deeper features  102 ″ and leaving the sacrificial film sidewall spacers  103 S on the sidewalls  102 S. 
       FIG. 9F  shows the patterned reticle  100  of  FIG. 9E  after forming a conformal, actinic/light blocking, opaque-absorber film  105 C thereover in accordance with step P in  FIG. 10B . The conformal, opaque-absorber film  105 C covers the top surfaces of the reticle mask plate  101 , the bottom surfaces  102 B of both feature recesses  102 ″ and the exposed surfaces of the sacrificial film sidewall spacers  103 S. At this point, the opaque-absorber film  105 C and sidewall spacers  103 S have been deposited within the recesses  102 . The opaque-absorber film  105 C is deposited over the patterned reticle  100  with a relatively uniform thickness. As a result, the opaque-absorber film  105 C produces an even narrower feature recesses  102 ′″ defining preliminary features  105 R. The conformal, opaque-absorber film  105 C preferably comprises an opaque material selected to have optical characteristics adapted to block the radiation (e.g. light) which can be employed for exposure (onto workpieces being manufactured) of patterns of damascene features to be formed in the mask plate  101 . Two such damascene features  105 F are shown after completion of processing thereof as shown by  FIGS. 9H and 9I . 
       FIG. 9G  shows the reticle  100  of  FIG. 9F  after planarization of the opaque-absorber film  105 C in accordance with step Q in  FIG. 10B . The planarization step polishes away the conformal, opaque-absorber, actinic or light blocking film  105 C from the top surface of the mask plate  101  forming a pair of features  105 F from the planarized portion of the opaque-absorber film  105 C, inside the sacrificial sidewall spacers  103 S. The sacrificial sidewall spacers  103 S remain lining the initial feature recess  102  with light blocking features  105 F nested therein. However, at this point the now unwanted sacrificial sidewall spacers  103 S also remain in the feature recess  102 , and the narrower feature recesses  102 ′″ remain slightly shallower defining modified preliminary features  105 F. 
       FIG. 9H  shows the reticle  100  of  FIG. 9G  after stripping the sacrificial sidewall spacers  103 S from the recess sidewalls  102 S (in accordance with step R in  FIG. 10B ) leaving open spaces  107 O between the planarized conformal, opaque-absorber, actinic or light blocking features  105 F and the sidewalls  102 S. The narrower and shallower feature recesses  102 ″ remain with open spaces  107 O juxtaposed therewith. Sacrificial films, which are well known in the industry, can be carbonaceous materials that can be removed by oxygen based processes such as oxygen plasma stripping or other means. 
     Using this embodiment will allow filling of open spaces  107 O and then capping the reticle  100  as shown in  FIG. 9I  wherein the open spaces  107 O have been filled with a transparent, phase-error-correction filler  107 F (in accordance with step S in  FIG. 10R ) which can be solid or fluid (liquid or gas) to allow the exposure ambient to correct for any phase errors. This can be done for both via structures as well as line/space patterns. The index of refraction of the material in the open spaces  107 O/ 107 F will determine the exact phase change in conjunction with the depth of the trench  102 . This embodiment allows precise control of the phase change of the actinic wavelength in the path through the space area by virtue of keeping the n*length constant, independent of processing variables. 
       FIG. 9I  shows reticle  100  of  FIG. 9H  after formation of protective capping layer  109  (in accordance with step T in  FIG. 10B ) over the surface of device  100  leaving the open spaces  107 O juxtaposed with the planarized conformal, opaque-absorber, actinic or light blocking film  105 P. The capping layer  109  can be laminated, sputtered, or applied by any other method that does not interfere with the gap. Alternatively, the protective capping layer  109  can be deposited without filling the gap  107 O. This is done by utilizing the dimensions of the gap. It is well known in the industry that deposition non-conformally by means of vapor deposition results in what is referred to as “poor gap fill” in the industry. It is this very same “poor gap fill” that is employed at this stage in the process to create an embedded/protected unfilled gap in accordance with this invention. At this point planarization (not shown) can be performed. 
     Ninth Embodiment 
     Open Peripheral Space Via Feature 
       FIG. 11  is a top perspective view depicting a reticle  110  in accordance with this invention in which an annular, via type via feature  116 F is formed for a structure, e.g. a semiconductor via, in a mask plate  111  comprising a transparent reticle mask plate. The reticle  110  is made in accordance with the method of this invention, as shown by the flow chart in FIGS.  10 A/ 10 B. As in  FIGS. 9B and 9C  and steps B and C in FIGS.  10 A/ 10 B, first step is to etch the cylindrical initial feature recess  112  down into the mask plate  111 . Then line the cylindrical initial feature recess  112  with a sacrificial layer (not shown) as described above ( FIGS. 9E and 9F , steps M/N in  FIG. 10A ) and form a narrower cylindrical recess  112 ′. Next, line the narrower cylindrical recess  112 ′ with an actinic absorber film as in  FIGS. 9E and 9F  (according to steps P and Q in  FIG. 10B ) and planarize to form the actinic absorber film  115 P thereby producing a via patterning feature  116 F. Then remove the sacrificial layer as in  FIG. 9H  and step R in  FIG. 10B . A hollow well  112 W remains inside the conformal light blocking film  115 P and there is an open, i.e. hollow, annular space  117 O separating the planarized conformal, opaque-absorber, actinic or light blocking film  115 P from the sidewalls of the original recess  112 . 
     Tenth Embodiment 
     Open Peripheral Space Line Feature 
       FIG. 12  shows a top perspective view depicting a reticle  120  in accordance with this invention in which an rectangular type line patterning feature  126 F is shown in a mask plate  121  (comprising a transparent reticle mask plate) with the planarized light blocking  125 P material formed in a linear feature recess  122  leaving a narrow feature recess  122 W inside the light blocking film  125 P. The reticle  120  is made in accordance with the method of this invention, as shown by the flow chart of FIGS.  10 A/ 10 B. In this case the first step is to etch a rectangular initial feature recess  122  into the mask plate  121 . Then line the rectangular initial feature recess  122  with a sacrificial film (not shown) forming a narrower, rectangular recess  122 ′. Then planarize the sacrificial film to form a sacrificial sidewall spacer, as described above with respect to  FIGS. 9D-9E . Next line the additional narrower rectangular recess  122 ′ with a conformal light blocking film covering the sidewalls and bottom of the additional narrower rectangular recess. Then planarize to produce a line patterning feature  126 F. A hollow well  122 W remains inside the conformal light blocking film  125 P. Then remove the sacrificial material leaving a peripheral open space  127 O surrounding the light blocking film  125 P. In summary, the line patterning feature  126 F was formed in the rectangular initial feature recess  122 . 
     Damascene Reticle Chemical Mechanical Planarization 
     The processing required to achieve the above embodiments requires a method of Damascene Reticle Chemical Mechanical Planarization (DRCMP) of damascene reticles which is different from Semiconductor Wafer CMP (SWCMP) of semiconductor wafers. The DRCMP method is different from SWCMP because a reticle mask has a very different size and shape compared to a silicon wafer. Also, the necessary films on a reticle mask can be deposited in a different order from the order employed for performing SWCMP on surfaces of a silicon wafer. The following example is provided to facilitate explanation of the process involved, while it is intended to be clear that the materials can be changed and/or the order changed as will be well understood by those skilled in the art. 
     After a feature is etched into a reticle mask plate a conformal layer of optically transparent or light wave passing material is deposited. The material can be selected from a range of materials that include but are not limited to silicon dioxide (SiO 2 ), silicon nitride (Si 3 N 4 ), and TEOS. Experimentation was done with silicon nitride. A problem with the structure of this invention is that a silicon nitride layer formed on a silicon dioxide substrate is formed in the reverse order from that usually employed by SWCMP planarization. A silicon nitride layer is usually used as a polish stop especially when polishing silicon oxide, as is well known in the industry. A number of silica based slurries appropriate for such CMP processing are commercially available for the conventional SWCMP application. The relative polish rates, or selectivity, of these slurries typically range from about 3:1 to about 4:1, with silicon dioxide having the higher polish rate. 
     In contrast in the case of embodiments of the present invention, for reticle polishing, it is necessary to polish the silicon nitride and then to stop on the top surface of the reticle which is composed of quartz that is a material which is very similar to silicon dioxide used in the semiconductor industry. This requires provision of a slurry and a process with the reverse selectivity to the silica based slurries described above whereby the silicon nitride polish rate is substantially higher than the silicon dioxide polish rate. 
     Slurry Formulation 
     A slurry formulation in accordance with this invention (described below) provides the needed “reverse selectivity,” with a ratio of polish rates where the silicon nitride is polished at a rate 3 to 4 times faster than the silicon oxide. Thereafter Tantalum Nitride (TaN) and Tantalum (Ta) were deposited to allow this material to be the internally placed light blocking material. It was therefore necessary to employ semiconductor polishing chemistries and processing to provide adequate removal of the materials from the upper surface of the reticle mask plate without disrupting the internally placed materials (with reference to the plate) and avoiding damage to the upper surface that would result in unwanted imaging on the reticle mask plate the image is projected upon. 
     Two exemplary slurry chemistries, tool types, and process parameters are described next. There are many different process tools available and the process parameters will vary as the tool models vary as will be well understood by those skilled in the art. 
     1) Ta CMP Slurry and Process, Stopping on Silicon Nitride 
     A semiconductor slurry is employed to remove TaN/Ta (Tantalum Nitride/Tantalum) stopping on the silicon nitride. The slurry formulation suppresses a silicon oxide and silicon nitride polish rate while maintaining a Ta polishing rate. A representative slurry formulation is shown in  FIG. 15 . 
     Damascene Reticle CMP Process 
     In  FIG. 16 , a table is shown with the processing parameters and equipment employed for performing an exemplary DRCMP process in accordance with this invention. 
     2) CMP Slurry and Process for Removing Si 3 Na and Stopping on SiO 2 . 
     A slurry formulation is provided to remove silicon nitride and stop on silicon oxide. The selectivities are reversed as compared to a normal silica slurry. The slurry is prepared using a commercially available fumed silica suspension in water. This starting material, as obtained, is stabilized in alkaline media, with potassium hydroxide or ammonium hydroxide, to a pH of 9.5 to 12. The “reverse selectivity” slurry is prepared by adjusting the pH of the starting material to 2.4 (range 2.3 to 2.5) with dilute phosphoric acid. This acid solution is prepared by diluting 1 part of 86 percent phosphoric acid with 9 parts of water. The final pH of the slurry is critical to achieving the desired ratio of polish rates. The preparation of this slurry is shown in the table of  FIG. 16 . 
     CMP Process 
     In  FIG. 17  another table is shown with an implementation of the DRCMP process of this invention. 
     Reticle Polishing Carrier 
       FIGS. 13A and 13B  show sectional and bottom views respectively of a reticle polishing carrier  200  in accordance with this invention which is adapted for use with a wafer polishing tool for the purpose of reticle polishing.  FIGS. 14A and 14B  show sectional and bottom views respectively of the reticle polishing carrier  200  of  FIGS. 13A and 13B  with a reticle  210  inserted therein for polishing. 
     Referring to  FIGS. 13A and 13B  and  14 A and  14 B, a reticle polishing carrier  200  in accordance with this invention is shown which is adapted for use with a wafer polishing tool (not shown) for the purpose of DRCMP reticle polishing. This is significant because such polishing tools are made for SWCMP polishing of semiconductor wafers, which are round and have a relatively small thickness on the order of only 0.03 inches (0.0762 cm) as compared to a damascene reticle that is square or rectangular that has a relatively large thickness of about 0.25 inches (0.635 cm) which is approximately an order of magnitude larger. 
     Accordingly it was required to fabricate a reticle polishing carrier  200  for a wafer polishing tool capable of accommodating a thick reticle  210  shown in  FIG. 14A . The reticle polishing carrier  200  is made of component parts that include a rigid base plate  201 , a retaining ring  205 , and a reticle pad  207  to support the reticle  210  when it is positioned in place, i.e. mounted, on the reticle carrier  200 . The inner edges  206  match the external dimensions of the reticles to be process to retain such reticles  210  (shown in FIGS.  14 A/ 14 B in position during planarization. The retaining ring  205  is made of a chemically inert yet dimensionally stable polymeric material such as PolyTetraFluoroEthylene (PTFE), Delrin, PolyEtherEtherKetone (PEEK), and other similar commercially available materials. 
     The base plate  201  is preferably made of a rigid but corrosion resistant material such as titanium or stainless steel. The base plate  201  and the reticle pad have a series of matching aligned passageways  208  therethrough for exhaustion of air from the space between the base plate  201  and the reticle  210 . Additionally, a vacuum can be applied via passageways  208  to retain the reticle  210  in place while the reticle is being transported into position for polishing on the CMP pad and transported off the CMP pad after completion of polishing. During the actual polishing process air pressure can be applied to the back side of the reticle  210 . This has the advantage of distributing the downwardly applied force across the entire area of the reticle  210 , to improve the uniformity of material removal. 
     The thickness of a retaining ring  205  is selected to match the specified thickness of the reticle  210  so that the surface  210 S of the reticle  210  and the surface  205 S of the retaining ring  205  are nearly coplanar. This is essential to enable the uniform removal of material from the square reticle  210 , using a semiconductor manufacturing tool designed for SWCMP processing of round wafers. By making the surfaces of the reticle  210  and the retaining ring  205  nearly coplanar, the square shape of the reticle  210  will be properly embedded in the carrier  200 , and a problem will be avoided in that the straight edges of the reticle  210  will not be disproportionately eroded by the polishing pad (not shown.) The polishing process can be further optimized for uniformity across the diameter of the reticle  210  by careful adjustment of the level of the exposed reticle surface  210 S to be just above or just below (by plus or minus approx 0.010 inches) the surface  205 S of the retaining ring  205 . Raising the reticle  210  higher than the retaining ring  205  will increase polishing at the edge of the reticle  210 , while lowering the reticle surface  210 S will decrease polishing at the edge. 
     “Delrin is the brand name for an acetal resin engineering plastic invented and sold by DuPont. Often marketed and used as a metal substitute, Delrin is a lightweight, low-friction, and wear-resistant plastic capable of operating in temperatures in excess of 90° C.” Other names for this compound include: PolyOxyMethylene (POM), acetal resin, polytrioxane and polyformaldehyde.” 
     Materials Suitable for a Blank Transparent Mask Plate 
     A list of materials preferred for blank transparent mask plates includes crystalline aluminum oxide, lithium indium selenide, fused silica, ther materials which may be suitable for various optical ranges. It is necessary to match the material to the wavelength for either blocking or passing the energy. For example aluminum oxide (Al 2 O 3 ), and beryllium can be used for x-ray. Calcium fluoride (CaF 2 ), zinc selenide (ZnSe), sodium chloride (NaCl), barium fluoride (BaF 2 ) can be used for infrared. Al 2 O 3  which has several crystal forms which are called corundum, sapphire or ruby (depending on the color.) Sapphire comprises a single-crystal form of Al.sub.2O.sub.3 can be employed for infrared optical applications. Sapphire is unique when compared to optical materials useful within its transmission range because it is strong, and tough. Also, sapphire is resistant to both thermal shock and chemicals, and can be used at high temperatures. The thermal conductivity of sapphire is relatively high despite its extreme electrical non-conductivity. Sapphire has a moderate refractive index, transparency in the visible range of wavelengths, good transmission and relatively low emission at high temperatures plus unusual stability. CaF 2  can be used as a window material for both infrared and ultraviolet wavelengths At wavelengths as low as 157 nm, CaF 2  is useful for semiconductor manufacturing and as an ultraviolet optical material for integrated circuit lithography. CaF 2  is transparent in the range from about 0.15 μm to about 9 μm at which it exhibits extremely weak birefringence. BaF 2  is transparent from the ultraviolet to the infrared, from about 150-200 nm to about 11-11.5 μm, and can be used as a material to make optical components such as lenses. BaF 2  is used in windows for infrared spectroscopy and its transmittance at 200 nm is relatively low at 0.60, but at 500 nm it goes up to 0.96-0.97 and stays at that level until 9 μm, then falls off (e.g. 0.85 for 10 μm and 0.42 for 12 μm). Magnesium fluoride (MgF 2 ) is transparent over a wide range of wavelengths. Windows, lenses, and prisms made of MgF 2  can be used over the entire range of wavelengths from 0.140 μm (ultraviolet) to 8.0 μm (infrared).  FIG. 18  shows a list of certain transparent materials and their refractive indicies. 
     ADVANTAGES OF THE INVENTION 
     The method of this invention increases the yield of optical projection mask making in terms of resolution and the process window. The method of this invention improves yield in the fabrication of integrated circuits due to smaller line edge roughness. The method of this invention also improves the lifetime of optical projection masks due to the fact that the patterns in the mask have damascene patterns embedded in a reticle mask plate. 
     The foregoing description discloses only exemplary embodiments of the invention. Modifications of the above disclosed apparatus and methods which fall within the scope of the invention will be readily apparent to those of ordinary skill in the art. While this invention is described in terms of the above specific exemplary embodiment(s), those skilled in the art will recognize that the invention can be practiced with modifications within the spirit and scope of the appended claims, i.e. changes can be made in form and detail, without departing from the spirit and scope of the invention. Accordingly, while the present invention is disclosed in connection with exemplary embodiments thereof, it should be understood that changes can be made to provide other embodiments which may fall within the spirit and scope of the invention and all such changes come within the purview of the present invention and the invention encompasses the subject matter defined by the following claims.