Patent Publication Number: US-2022216065-A1

Title: Two-stage bake photoresist with releasable quencher

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This patent application is a divisional of U.S. patent application Ser. No. 16/075,555, filed Aug. 3, 2018, which is a U.S. National Phase Application under 35 U.S.C. § 371 of International Application No. PCT/US2016/026599, filed Apr. 8, 2016, entitled “TWO-STAGE BAKE PHOTORESIST WITH RELEASABLE QUENCHER,” which designates the United States of America, the entire disclosure of which are hereby incorporated by reference in their entirety and for all purposes. 
    
    
     TECHNICAL FIELD 
     Embodiments of the invention are in the field of semiconductor structures and processing and, in particular, two-stage bake photoresists with releasable quenchers for fabricating back end of line (BEOL) interconnects. 
     BACKGROUND 
     For the past several decades, the scaling of features in integrated circuits has been a driving force behind an ever-growing semiconductor industry. Scaling to smaller and smaller features enables increased densities of functional units on the limited real estate of semiconductor chips. For example, shrinking transistor size allows for the incorporation of an increased number of memory or logic devices on a chip, lending to the fabrication of products with increased capacity. The drive for ever-more capacity, however, is not without issue. The necessity to optimize the performance of each device becomes increasingly significant. 
     Integrated circuits commonly include electrically conductive microelectronic structures, which are known in the arts as vias, to electrically connect metal lines or other interconnects above the vias to metal lines or other interconnects below the vias. Vias are typically formed by a lithographic process. Representatively, a photoresist layer may be spin coated over a dielectric layer, the photoresist layer may be exposed to patterned actinic radiation through a patterned mask, and then the exposed layer may be developed in order to form an opening in the photoresist layer. Next, an opening for the via may be etched in the dielectric layer by using the opening in the photoresist layer as an etch mask. This opening is referred to as a via opening. Finally, the via opening may be filled with one or more metals or other conductive materials to form the via. 
     In the past, the sizes and the spacing of vias has progressively decreased, and it is expected that in the future the sizes and the spacing of the vias will continue to progressively decrease, for at least some types of integrated circuits (e.g., advanced microprocessors, chipset components, graphics chips, etc.). One measure of the size of the vias is the critical dimension of the via opening. One measure of the spacing of the vias is the via pitch. Via pitch represents the center-to-center distance between the closest adjacent vias. 
     When patterning extremely small vias with extremely small pitches by such lithographic processes, several challenges present themselves, especially when the pitches are around 70 nanometers (nm) or less and/or when the critical dimensions of the via openings are around 35 nm or less. One such challenge is that the overlay between the vias and the overlying interconnects, and the overlay between the vias and the underlying landing interconnects, generally need to be controlled to high tolerances on the order of a quarter of the via pitch. As via pitches scale ever smaller over time, the overlay tolerances tend to scale with them at an even greater rate than lithographic equipment is able to keep up. 
     Another such challenge is that the critical dimensions of the via openings generally tend to scale faster than the resolution capabilities of the lithographic scanners. Shrink technologies exist to shrink the critical dimensions of the via openings. However, the shrink amount tends to be limited by the minimum via pitch, as well as by the ability of the shrink process to be sufficiently optical proximity correction (OPC) neutral, and to not significantly compromise line width roughness (LWR) and/or critical dimension uniformity (CDU). 
     Yet another such challenge is that the LWR and/or CDU characteristics of photoresists generally need to improve as the critical dimensions of the via openings decrease in order to maintain the same overall fraction of the critical dimension budget. However, currently the LWR and/or CDU characteristics of most photoresists are not improving as rapidly as the critical dimensions of the via openings are decreasing. 
     A further such challenge is that the extremely small via pitches generally tend to be below the resolution capabilities of even extreme ultraviolet (EUV) lithographic scanners. As a result, commonly two, three, or more different lithographic masks may be used, which tend to increase the costs. At some point, if pitches continue to decrease, it may not be possible, even with multiple masks, to print via openings for these extremely small pitches using EUV scanners. 
     Thus, improvements are needed in the area of via manufacturing technologies. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIGS. 1A-1C  illustrates cross-sectional views and corresponding plan views of various operations in a method of patterning using photobuckets including a two-stage bake photoresist, in accordance with an embodiment of the present invention. 
         FIG. 2  illustrates a cross-sectional view of a conventional resist photobucket structure following photobucket development after a mis-aligned exposure. 
         FIGS. 3A-3E  illustrates schematic views of various operations in a method of patterning using photobuckets including a two-stage bake photoresist, in accordance with an embodiment of the present invention. 
         FIGS. 3A ′ illustrates a schematic view of an operation in another method of patterning using photobuckets, in accordance with an embodiment of the present invention. 
         FIGS. 3A ″ illustrates a schematic view of an operation in another method of patterning using photobuckets, in accordance with an embodiment of the present invention. 
         FIGS. 4A-4H  illustrate portions of integrated circuit layers representing various operations in a method of subtractive self-aligned via patterning using photobuckets including a two-stage bake photoresist, in accordance with an embodiment of the present invention, where: 
         FIG. 4A  illustrates a cross-sectional view of a starting structure following deposition, but prior to patterning, of a hardmask material layer formed on an interlayer dielectric (ILD) layer; 
         FIG. 4B  illustrates the structure of  FIG. 4A  following first time patterning of the first hardmask layer and subsequent first photobucket fill; 
         FIG. 4C  illustrates the structure of  FIG. 4B  following second time patterning of the first hardmask layer and subsequent second photobucket fill; 
         FIG. 4D  illustrates the structure of  FIG. 4C  following planarization to isolate the first and second photobuckets from one another; 
         FIG. 4E  illustrates the structure of  FIG. 4D  following exposure and development of select photobuckets to leave select via locations; 
         FIG. 4F  illustrates the structure of  FIG. 4E  following etching to form via locations; 
         FIG. 4G  illustrates the structure of  FIG. 4F  following preparation for metal fill; and 
         FIG. 4H  illustrates the structure of  FIG. 4G  following metal fill. 
         FIGS. 5A-5I  illustrate portions of integrated circuit layers representing various operations in a method of subtractive self-aligned via patterning using photobuckets, in accordance with another embodiment of the present invention, where: 
         FIG. 5A  illustrates a starting point structure for a subtractive via process following deep metal line fabrication; 
         FIG. 5B  illustrates the structure of  FIG. 5A  following recessing of the metal lines; 
         FIG. 5C  illustrates the structure of  FIG. 5B  following formation of an inter layer dielectric (ILD) layer; 
         FIG. 5D  illustrates the structure of  FIG. 5C  following deposition and patterning of a hardmask layer; 
         FIG. 5E  illustrates the structure of  FIG. 5D  following trench formation defined using the pattern of the hardmask of  FIG. 5D ; 
         FIG. 5F  illustrates the structure of  FIG. 5E  following photobucket formation by filling a two-stage bake photoresist with a releasable quencher in all possible via locations; 
         FIG. 5G  illustrates the structure of  FIG. 5F  following via location selection; 
         FIG. 5H  illustrates the structure of  FIG. 5G  following conversion of the remaining photobuckets to permanent ILD material; and 
         FIG. 5I  illustrates the structure of  FIG. 5H  following metal line and via formation. 
         FIG. 6  illustrates a computing device in accordance with one implementation of the invention. 
         FIG. 7  is an interposer implementing one or more embodiments of the invention. 
     
    
    
     DESCRIPTION OF THE EMBODIMENTS 
     Two-stage bake photoresists with releasable quenchers for fabricating back end of line (BEOL) interconnects are described. In the following description, numerous specific details are set forth, such as specific integration and material regimes, in order to provide a thorough understanding of embodiments of the present invention. It will be apparent to one skilled in the art that embodiments of the present invention may be practiced without these specific details. In other instances, well-known features, such as integrated circuit design layouts, are not described in detail in order to not unnecessarily obscure embodiments of the present invention. Furthermore, it is to be understood that the various embodiments shown in the Figures are illustrative representations and are not necessarily drawn to scale. 
     One or more embodiments described herein are directed to two-stage bake photoresists with releasable quenchers. Applications may be directed toward one or more of extreme ultra-violet (EUV) lithography, general lithography applications, solutions for overlay issues, and general photoresist technologies. In an embodiment, materials are described that are suitable for improving performance of so-called “PhotoBucket” based approaches. In such an approach, a resist material is confined to a pre-patterned hardmask. Select ones of the photobuckets are then removed using a high-resolution lithography tool, e.g., an EUV lithography tool. Specific embodiments may be implemented to improve uniformity of the resist material response across a given photobucket. 
     To provide context, one goal in a photobucket approach may be the ability to first diffuse any EUV-released acids across an exposed photobucket to improve the uniformity of the resist response across the selected bucket. In past approaches, this has been achieved by the use of special materials which enable the acid to diffuse across the photobucket at a low enough temperature to avoid a solubility-switch reaction instigated from these acids. However, the action of another resist component, namely the quencher, may prevent such an advantage from being fully realized. In particular, the quencher may neutralize the acids before they are able to diffuse or spread across a given photobucket. Addressing such issues, in accordance with one or more embodiments described herein, a standard quencher is replaced with a quencher that can be released by an ultra-violet (UV) exposure or the like, providing the ability to avoid premature acid neutralization. 
     More particularly, in accordance with one or more embodiments described herein, a photobucket resist material including a UV-released quencher is implemented to effectively provide a “2-stage PEB” where the effect of EUV exposure is effectively averaged across a given photobucket. Such embodiments may enable a “digital” bucket response, in which the entire photobucket either clears out or does not. In specific embodiments, such a response is more tolerant to edge-placement errors, in which an aerial image does not perfectly align to the photobucket grid. 
     To exemplify one or more of the concepts involved herein,  FIGS. 1A-1C  illustrates cross-sectional views and corresponding plan views of various operations in a method of patterning using photobuckets including a two-stage bake photoresist, in accordance with an embodiment of the present invention. 
     Referring to  FIG. 1A , a pre-patterned hardmask  104  is disposed above a substrate  102 . The pre-patterned hardmask  104  has openings filled with a two-stage bake photoresist  106 . The two-stage bake photoresist  106  is confined to the openings in the pre-patterned hardmask  104 , e.g., to provide a grid of potential via locations. 
     Referring to  FIG. 1B , select ones of the photobuckets are subjected to an exposure  107  from a lithography tool. The two-stage bake photoresist  106  is exposed with a lithography tool, e.g., an EUV lithography tool, to select which vias to open. In an embodiment, alignment between the lithography tool and the pre-patterned hardmask  104  grid is imperfect resulting in an asymmetry of exposure in the target bucket and/or partial exposure in the neighboring bucket. As seen in the plan view, the exposure  107  is a displaced aerial image  108 . 
     Referring to  FIG. 1C , although the exposure of  FIG. 1B  may have involved mis-alignment and partial exposure of non-selected photobuckets, only the selected photobuckets are cleared to form openings  120 , leaving unselected photobuckets as closed photobuckets  112 . In one embodiment, the process used to ensure only select photobuckets are ultimately opened, following exposure  107  of select regions of the two-stage bake photoresist  106 , all of the two-stage bake photoresist  106  is first baked for acid diffusion. An ultra-violet (UV) quench release is then performed for acid neutralization. A second bake is then performed for a solubility switch, as described in greater detail below. In a specific embodiment, the photoacids released from the first bake operation are diffused throughout the photobucket. The UV flood exposure releases quenchers and then the final solubility-switch bake is performed. The process is elaborated below in association with  FIGS. 3A-3E . 
     As a result, the select locations which receive a greater exposure are ultimately cleared to provide open photobucket locations  120  following development. The non-selected locations which receive no exposure, or only partial exposure but to a lesser extent in the case of mis-alignment, remain as closed photobucket locations  112  following development. 
     To exemplify a contrasting scenario where a conventional photoresist is used,  FIG. 2  illustrates a cross-sectional view of a conventional resist photobucket structure following photobucket development after a mis-aligned exposure. A photobucket region  204  is shown as only partially cleared  200  with some residual photoresist  202  remaining. In the case that the photobucket  204  is a selected photobucket, the misaligned exposure  107  only partially clears the photobucket, which may lead to subsequent poor quality fabrication of conductive structure in such locations. In the case that the photobucket  204  is a non-selected photobucket, some unwanted opening  200  occurs, potentially leading to subsequent formation of conductive structures in unwanted locations. 
     In a more detailed process description,  FIGS. 3A-3E  illustrates schematic views of various operations in a method of patterning using photobuckets including a two-stage bake photoresist, in accordance with an embodiment of the present invention. 
     Referring to  FIG. 3A , first  302  and second  304  photobuckets each include a photolyzable composition including an acid-deprotectable photoresist material, a photo-acid-generating (PAG) component  310 , and a photo-base-generating component  312 . A misaligned EUV or e-beam exposure  306  is performed on a selected photobucket  302  and a non-selected photobucket  304 , which heavily exposes the selected photobucket  302  and partially exposes the non-selected photobucket  304  but to a lesser extent. In a specific embodiment, the photo-base-generating component  312  is a UV-releasable quencher. 
     Referring to  FIG. 3B , a first bake is performed. In one embodiment, the first bake is performed at a temperature too low to cause a solubility switch. In one such embodiment, the bake is a diffusion only bake leading to diffused materials  320  and  322  of photobuckets  302  and  304 , respectively. 
     Referring to  FIG. 3C , quenchers  314  are released to form materials  324  and  326  for photobuckets  302  and  304 , respectively. In one embodiment, the quenchers  314  are UV-released quenchers. In a specific such embodiment, the UV-released quenchers are released by UV flood exposure, e.g., a 365 nm exposure. In an embodiment, the photobuckets  302  and  304  are both exposed to the flood exposure to the same extent. 
     Referring to  FIG. 3D , a second bake is performed to provide materials  328  and  330  of photobuckets  302  and  304 , respectively. In an embodiment, the second bake is generates a solubility switch, in which a sub-critical acid concentration quenched. In this manner, there are essentially no local acid concentrations. That is, deprotection of part of an unintended only partially exposed photobucket does not occur. 
     Referring to  FIG. 3E , the photobuckets  302  and  304  are subjected to a development process. The selected photobucket  302  is cleared upon development to provide a cleared photobucket  332 . The non-selected photobucket  304  is not cleared upon development and remains a blocked photobucket  334 . In this way, even in the event of a mis-aligned exposure, a digital photobucket response (open or closed only, without partial open) is achieved. 
     It is to be appreciated that not all embodiments require a single composition to achieve a two-stage bake photoresist. In a first alternative example,  FIGS. 3A ′ illustrates a schematic view of an operation in another method of patterning using photobuckets, in accordance with an embodiment of the present invention. Referring to  FIG. 3A ′, first  302 ′ and second  304 ′ photobuckets each include a grafted photo-base-generating component  350  along a bottom and sidewalls of the first  302 ′ and second  304 ′ photobuckets. A photolyzable composition is formed within the grafted photo-base-generating component  350 . The photolyzable composition includes an acid-deprotectable photoresist material and a photo-acid-generating (PAG) component  310 ′. An exposure  306 ′ and multi-stage development process may then performed similar to the above described approaches. 
     In a second alternative example,  FIGS. 3A ″ illustrates a schematic view of an operation in another method of patterning using photobuckets, in accordance with an embodiment of the present invention. Referring to  FIG. 3A ″, first  302 ″ and second  304 ″ photobuckets each include a photolyzable composition including an acid-deprotectable photoresist material and a photo-acid-generating (PAG) component  310 ″. Subsequent to performing a first bake, a layer  360  including a base-generating component is formed on the first  302 ″ and second  304 ″. The photobuckets  302 ″ and  304 ″ are then exposed to ultraviolet (UV) radiation. In this case, the base component does not need to be introduced via a photo-base generator, but may rather be deposited in a later process operation, e.g., by vapor deposition of a base layer or exposure to basic atmosphere NMP. 
     Applications of the above described photoresist compositions and approaches may be implemented for to create regular structures covering all possible via (or plug) locations, followed by selective patterning of only the desired features. To provide further material details, in an embodiment, referring again to  FIGS. 3A-3E , photobuckets  302  and  304  include photolyzable composition. The photolyzable composition includes an acid-deprotectable photoresist material having substantial transparency at a wavelength. The photolyzable composition also includes a photo-acid-generating (PAG) component having substantial transparency at the wavelength. The photolyzable composition includes a base-generating component having substantial absorptivity at the wavelength. In alternative embodiments, the acid-deprotectable photoresist material is not substantially transparent at the wavelength. 
     In an embodiment, the base-generating component is one selected from the group consisting of a photo-base-generating component, an electron-base-generating component, a chemical-base-generating component, and a UV-base-generating component. In one embodiment, the base-generating component is a sonication-base-generating component. In an embodiment, the base-generating component is UV-absorbing. In an embodiment, the base-generating component includes a low-energy UV chromophore. In a specific such embodiment, the low-energy UV chromophore is selected from the group consisting of anthracenylcarbamates, naphthalenylcarbamates, 2-nitrophenylcarbamates, arylcarbamates, coumarins, phenylglyoxylic acid, substituted acetophenones and benzophenones. In one embodiment, the low-energy UV chromophore is a photo-released amine. In an embodiment, the base-generating component includes a material selected from the group consisting of N,N-dicyclohexyl-2-nitrophenylcarbamate, N,N-disubstituted carbamates and mono-substituted carbamates. 
     In an embodiment, the PAG component includes a material selected from the group consisting of triethyl, trimethyl and other trialkylsulfonates, where the sulfonate group is selected from the group consisting of trifluoromethylsulfonate, nonanfluorobutanesulfonate, and p-tolylsulfonate, or other examples containing —SO3 sulfonate anion bound to organic group. In an embodiment, the acid-deprotectable photoresist material is an acid-deprotectable material selected from the group consisting of a polymer, a molecular glass, a carbosilane and a metal oxide. In one embodiment, a metal oxide is used and a release base is not needed. In an embodiment, the acid-deprotectable photoresist material includes a material selected from the group consisting of a polyhydroxystyrene, a polymethacrylate, small molecular weight molecular glass versions of a polyhydroxystyrene or a polymethacrylate which contain ester functionality sensitive to acid-catalyzed deprotection to carboxylic acid, a carbosilane, and a metal oxide possessing functionality sensitive to acid catalyzed deprotection or cross-linking. 
     In an embodiment, the wavelength is approximately 365nm. In an embodiment, the acid-deprotectable photoresist material is substantially absorbing at a wavelength of approximately 13.5 nanometers. In an embodiment, the acid-deprotectable photoresist material is substantially absorbing at an energy approximately in the range of 5-150 keV. In an embodiment, a molar ratio of the PAG component to the base-generating component is at least 50:1. 
     Referring again to  FIGS. 3A-3E, 3A ′ and  3 A″, in accordance with an embodiment of the present invention, a method of selecting a photobucket for semiconductor processing includes providing a structure having a first photobucket  302  neighboring a second photobucket  304 . The structure is exposed to extreme ultraviolet (EUV) or e-beam radiation  306 , where the first photobucket  302  is exposed to the EUV or e-beam radiation  306  to a greater extent than the second photobucket  304 . Subsequent to exposing the structure to EUV or e-beam radiation  306 , a first bake of the first and second photobuckets is performed as is described in association with  FIG. 3B . Subsequent to performing the first bake, the structure to ultraviolet (UV) radiation, where the first photobucket is exposed to the UV radiation to approximately the same extent as the second photobucket, as is described in association with  FIG. 3C . Subsequent to exposing the structure to UV radiation, a second bake of the first and second photobuckets is performed as is described in association with  FIG. 3D . Subsequent to performing the second bake, the structure is developed. The developing opens the first photobucket and leaves the second photobucket closed as is described in association with  FIG. 3E . 
     In an embodiment, exposing the structure to extreme ultraviolet (EUV) or e-beam radiation includes exposing the structure to energy having a wavelength approximately 13.5 nanometers. In another embodiment, exposing the structure to extreme ultraviolet (EUV) or e-beam radiation includes exposing the structure to energy in the range of 5-150 keV. In an embodiment, exposing the structure to UV radiation includes exposing the structure to energy having a wavelength approximately 365 nanometers. In an embodiment, the first bake is performed at a temperature approximately in the range of 50-120 degrees Celsius for a duration of approximately in the range of 0.5-5 minutes. In an embodiment, the second bake is performed at a temperature approximately in the range of 100-180 degrees Celsius for a duration of approximately in the range of 0.5-5 minutes. 
     In an embodiment, referring specifically to  FIG. 3A , the first and second photobuckets each include a photolyzable composition including an acid-deprotectable photoresist material, a photo-acid-generating (PAG) component, and a photo-base-generating component. In one such embodiment, exposing the structure to extreme ultraviolet (EUV) or e-beam radiation includes activating the PAG component. The first bake diffuses acid formed from activating the PAG component throughout the first and second photobuckets. Exposing the structure to UV radiation includes activating the photo-base-generating component. The second bake quenches a total amount of acid formed in the second photobucket with base generated from the photo-base-generating component but does not quench a total amount of acid formed in the first photobucket. 
     In another embodiment, referring specifically to  FIG. 3A ′, the first and second photobuckets each include a grafted photo-base-generating component along a bottom and sidewalls of the first and second photobuckets and a photolyzable composition formed within the grafted photo-base-generating component. The photolyzable composition includes an acid-deprotectable photoresist material and a photo-acid-generating (PAG) component. In one such embodiment, exposing the structure to extreme ultraviolet (EUV) or e-beam radiation includes activating the PAG component. The first bake diffuses acid formed from activating the PAG component throughout the first and second photobuckets. Exposing the structure to UV radiation includes activating the grafted photo-base-generating component. The second bake quenches a total amount of acid formed in the second photobucket with base generated from the photo-base-generating component but does not quench a total amount of acid formed in the first photobucket. 
     In another embodiment, referring specifically to  FIG. 3A ″, the first and second photobuckets each include a photolyzable composition including an acid-deprotectable photoresist material and a photo-acid-generating (PAG) component. The method further includes, subsequent to performing the first bake and prior to exposing the structure to ultraviolet (UV) radiation, forming a layer including a base-generating component on the first and second photobuckets. In one such embodiment, exposing the structure to extreme ultraviolet (EUV) or e-beam radiation includes activating the PAG component. The first bake diffuses acid formed from activating the PAG component throughout the first and second photobuckets. Exposing the structure to UV radiation includes activating the base-generating component. The second bake quenches a total amount of acid formed in the second photobucket with base generated from the base-generating component but does not quench a total amount of acid formed in the first photobucket. 
     In any of the above described cases, in an embodiment, developing the structure includes, in the case of positive tone development, immersion or coating with standard aqueous TMAH developer (e.g., in a concentration range from 0.1M-1M) or other aqueous or alcoholic developer based on tetraalkylammonium hydroxides for 30-120 seconds followed by rinse with DI water. In another embodiment, in the case of negative tone development, developing the structure includes immersion or coating with organic solvents such as cyclohexanone, 2-heptanone, propylene glycol methylethyl acetate or others followed by rinse with another organic solvent such as hexane, heptane, cyclohexane or the like. 
     In an exemplary embodiment, approaches described above build on approaches using so-called “photobuckets,” in which every possible feature, e.g. via, is pre-patterned into a substrate. Then, a photoresist is filled into patterned features and the lithography operation is merely used to choose select vias for via opening formation. In a particular embodiment described below, a lithography operation is used to define a relatively large hole above a plurality of photobuckets that include a two-stage bake photoresist, as described above. The two-stage bake photoresist photobucket approach allows for larger critical dimensions (CD)s and/or errors in overlay while retaining the ability to choose the via of interest. 
     To provide further context, current fabrication techniques for vias involves a “blind” process in which a via opening is patterned in a stack far above an ILD trench. The via opening pattern is then etched deep down into the trench. Overlay errors accumulate and can cause various problems, e.g., shorts to neighboring metal lines. In an example, patterning and aligning of features at less than approximately 50 nanometer pitch requires many reticles and critical alignment strategies that are otherwise extremely expensive for a semiconductor manufacturing process. In an embodiment, by contrast, approaches described herein enable fabrication of self-aligned plugs and/or vias, greatly simplifying the web of overlay errors, and leaving only one critical overlay step (Mx+1 grating). In an embodiment, then, offset due to conventional lithograph/dual damascene patterning that must otherwise be tolerated, is not a factor for the resulting structures described herein. 
     In general, one or more embodiments are directed to an approach that employs a subtractive technique to ultimately form conductive vias and, possibly, non-conductive spaces or interruptions between metals (referred to as “plugs”). Vias, by definition, are used to land on a previous layer metal pattern. In this vein, embodiments described herein enable a more robust interconnect fabrication scheme since alignment by lithography equipment is no longer relied on. Such an interconnect fabrication scheme can be used to save numerous alignment/exposures, can be used to improve electrical contact (e.g., by reducing via resistance), and can be used to reduce total process operations and processing time otherwise required for patterning such features using conventional approaches. 
     More specifically, one or more embodiment described herein involves the use of a subtractive method to pre-form every via or via opening using the trenches already etched. An additional operation is then used to select which of the vias and plugs to retain. Such operations can be illustrated using “photobuckets,” although the selection process may also be performed using a more conventional resist expose and ILD backfill approach. 
     In one aspect, a self-aligned via opening approach is used. As an example,  FIGS. 4A-4H  illustrate portions of integrated circuit layers representing various operations in a method of subtractive self-aligned via patterning using photobuckets including a two-stage bake photoresist, in accordance with an embodiment of the present invention. In each illustration at each described operation, cross-sectional views are shown. 
       FIG. 4A  illustrates a cross-sectional view of a starting structure  400  following deposition, but prior to patterning, of a first hardmask material layer  404  formed on an interlayer dielectric (ILD) layer  402 , in accordance with an embodiment of the present invention. Referring to  FIG. 4A , a patterned mask  406  has spacers  408  formed along sidewalls thereof, on or above the first hardmask material layer  404 . 
       FIG. 4B  illustrates the structure of  FIG. 4A  following first time patterning of the first hardmask layer and subsequent first photobucket fill, in accordance with an embodiment of the present invention. Referring to  FIG. 4B , the patterned mask  406  and corresponding spacers  408  are used together as a mask during an etch to form trenches  410  through the first hardmask material layer  404  and partially into the ILD layer  402 . The trenches  410  are then filled with first photobuckets  412  which include a two-stage bake photoresist. 
       FIG. 4C  illustrates the structure of  FIG. 4B  following second time patterning of the first hardmask layer and subsequent second photobucket fill, in accordance with an embodiment of the present invention. Referring to  FIG. 4C , the patterned mask  406  is removed and a second plurality of trenches  414  is etched through the first hardmask material layer  404  and partially into the ILD layer  402 , between spacers  408 . Subsequently, the trenches  414  are filled with second photobuckets  418  which include a two-stage bake photoresist. In one such embodiment, the second photobuckets  418  and the first photobuckets  412  are filled with a same two-stage bake photoresist material. 
     Referring again to  FIG. 4C , the negative pattern of the spacers  408  is thus transferred, e.g., by two etch processes forming trenches  410  and  414 , to the first hardmask material layer  404 . In one such embodiment, the spacers  408  and, hence, the trenches  410  and  414  are formed with a grating pattern, as is depicted in  FIG. 4C . In an embodiment, the grating pattern is a tight pitch grating pattern. In a specific such embodiment, the tight pitch is not achievable directly through conventional lithography. For example, a pattern based on conventional lithography may first be limited to mask  406 , but the pitch may be halved by the use of negative spacer mask patterning, as is depicted in  FIGS. 4A-4C . Even further, although not shown, the original pitch may be quartered by a second round of spacer mask patterning. Accordingly, the grating-like pattern of the photobuckets  412  and  418 , collectively, is spaced at a constant pitch and has a constant width. 
       FIG. 4D  illustrates the structure of  FIG. 4C  following planarization to isolate the first and second photobuckets from one another, in accordance with an embodiment of the present invention. Referring to  FIG. 4D , the second photobuckets  418  and the top portions of the spacers  408  are planarized, e.g., by chemical mechanical polishing (CMP), until the top surfaces of the first photobuckets  412  are exposed, forming discrete second photobuckets  418 . In one embodiment, the combination of first photobuckets  412  and second photobuckets  418  represent all possible via locations in a subsequently formed metallization structure. One of the first photobuckets  412  is labeled as  412 A to indicate that it is selected from removal for ultimate via fabrication. 
       FIG. 4E  illustrates the structure of  FIG. 4D  following exposure and development of two photobuckets to leave selected via locations, in accordance with an embodiment of the present invention. Referring to  FIG. 4E , a second hardmask  420  is formed and patterned on the structure of  FIG. 4D . The patterned second hardmask  420  reveals two of the first photobuckets  412 . The selected photobuckets are exposed to light irradiation, such as an EUV or e-beam exposure  421 . It is to be appreciated that description herein concerning forming and patterning a hardmask layer involves, in an embodiment, mask formation above a blanket hardmask layer. The mask formation may involve use of one or more layers suitable for lithographic processing. Upon patterning the one or more lithographic layers, the pattern is transferred to the hardmask layer by an etch process to provide a patterned hardmask layer. 
     In accordance with one embodiment, referring again to  FIG. 4E , neighboring one of the second photobuckets  418  are partially exposed, e.g., due to mis-alignment in the patterning of second hardmask  420 . In particular, two of the second photobuckets  418  are inadvertently exposed at regions  450 , even though they have not been selected as locations for via fabrication. Thus, the selected ones of the first photobuckets  412  are exposed to the EUV or e-beam radiation to a greater extent than the neighboring partially exposed ones of the second photobuckets  418 . Subsequent to exposing the structure to EUV or e-beam radiation  421 , a first bake of the photobuckets is performed. Subsequent to performing the first bake, the structure is exposed to ultraviolet (UV) radiation. In one embodiment, the mask  420  remains during the UV radiation and is then subsequently removed. However, in another embodiment, the mask  420  is first removed and the photobuckets are then all exposed to the UV radiation to approximately the same extent. In either case, subsequent to exposing the structure to UV radiation, a second bake of the photobuckets is performed. 
     Referring again to  FIG. 4E , the photobuckets are subjected to a develop process. During the develop process, the select one of the first photobuckets  412  targeted for via fabrication are emptied in that the photoresist is removable. However, locations not selected for via fabrication, including the ones of the second photobuckets  418  that were partially exposed at regions  450 , are not opened during the develop process, in that the resist material is not removable in the develop process. The developing provides selected via openings  413 A. 
       FIG. 4F  illustrates the structure of  FIG. 4E  following etching to form via locations, in accordance with an embodiment of the present invention. Referring to  FIG. 4F , the pattern of the via openings  413 A are subjected to a selective etch process, such as a selective plasma etch process, to extend the via openings deeper into the underlying ILD layer  402 , forming via patterned ILD layer  402 ′ with via locations  424 . The etching is selective to remaining photobuckets  412  and  418  and to the spacers  408 . 
       FIG. 4G  illustrates the structure of  FIG. 4F  in preparation for metal fill, in accordance with an embodiment of the present invention. Referring to  FIG. 4G , all remaining first and second photobuckets  412  and  418  are removed. The remaining first and second photobuckets  412  and  418  may be removed directly, or may first be exposed and developed to enable removal. The removal of the remaining first and second photobuckets  412  and  418  provides metal line trenches  426 , some of which are coupled to via locations  424  in patterned ILD layer  402 ′. 
     Referring to  FIG. 4H , subsequent processing can include removal of spacers  408  and hardmask layer  404 , and metal fill of metal line trenches  426  and via locations  424  to form conductive metal lines  440  and conductive vias  442 , respectively. In one such embodiment, metallization is formed by a metal fill and polish back process. The structure of  FIG. 4H  may subsequently be used as a foundation for forming subsequent metal line/via and ILD layers. Alternatively, the structure of  FIG. 4H  may represent the final metal interconnect layer in an integrated circuit. It is to be appreciated that the above process operations may be practiced in alternative sequences, not every operation need be performed and/or additional process operations may be performed. Referring again to  FIG. 4H , self-aligned fabrication by the subtractive approach may be complete at this stage. A next layer fabricated in a like manner likely requires initiation of the entire process once again. Alternatively, other approaches may be used at this stage to provide additional interconnect layers, such as conventional dual or single damascene approaches. 
     Additionally, it is to be appreciated that the approaches described in association with  FIGS. 4A-4H  are not necessarily performed as forming vias aligned to an underlying metallization layer. As such, in some contexts, these process schemes could be viewed as involving blind shooting in the top down direction with respect to any underlying metallization layers. In a second aspect, a subtractive approach provides alignment with an underlying metallization layer. As an example,  FIGS. 5A-5I  illustrate portions of integrated circuit layers representing various operations in a method of subtractive self-aligned via patterning using photobuckets including a two-stage bake photoresist with a releasable quencher, in accordance with another embodiment of the present invention. In each illustration at each described operation, an angled three-dimensional cross-section view is provided. 
       FIG. 5A  illustrates a starting point structure  500  for a subtractive via process following deep metal line fabrication, in accordance with an embodiment of the present invention. Referring to  FIG. 5A , structure  500  includes metal lines  502  with intervening interlayer dielectric (ILD) lines  504 . It is to be appreciated that some of the lines  502  may be associated with underlying vias for coupling to a previous interconnect layer. In an embodiment, the metal lines  502  are formed by patterning trenches into an ILD material (e.g., the ILD material of lines  504 ). The trenches are then filled by metal and, if needed, planarized to the top of the ILD lines  504 . In an embodiment, the metal trench and fill process involves high aspect ratio features. For example, in one embodiment, the aspect ratio of metal line height (h) to metal line width (w) is approximately in the range of 5-10. 
       FIG. 5B  illustrates the structure of  FIG. 5A  following recessing of the metal lines, in accordance with an embodiment of the present invention. Referring to  FIG. 5B , the metal lines  502  are recessed selectively to provide first level metal lines  506 . The recessing is performed selectively to the ILD lines  504 . The recessing may be performed by etching through dry etch, wet etch, or a combination thereof. The extent of recessing may be determined by the targeted thickness of the first level metal lines  506  for use as suitable conductive interconnect lines within a back end of line (BEOL) interconnect structure. 
       FIG. 5C  illustrates the structure of  FIG. 5B  following formation of an inter layer dielectric (ILD) layer, in accordance with an embodiment of the present invention. Referring to  FIG. 5C , an ILD material layer  508  is deposited and, if necessary, planarized, to a level above the recessed metal lines  506  and the ILD lines  504 . 
       FIG. 5D  illustrates the structure of  FIG. 5C  following deposition and patterning of a hardmask layer, in accordance with an embodiment of the present invention. Referring to  FIG. 5D  a hardmask layer  510  is formed on the ILD layer  508 . In one such embodiment, the hardmask layer  510  is formed with a grating pattern orthogonal to the grating pattern of the first level metal lines  506 /ILD lines  504 , as is depicted in  FIG. 5D . In an embodiment, the grating structure formed by the hardmask layer  510  is a tight pitch grating structure. In one such embodiment, the tight pitch is not achievable directly through conventional lithography. For example, a pattern based on conventional lithography may first be formed, but the pitch may be halved by the use of spacer mask patterning. Even further, the original pitch may be quartered by a second round of spacer mask patterning. Accordingly, the grating-like pattern of the second hardmask layer  510  of  FIG. 5D  may have hardmask lines spaced at a constant pitch and having a constant width. 
       FIG. 5E  illustrates the structure of  FIG. 5D  following trench formation defined using the pattern of the hardmask of  FIG. 5D , in accordance with an embodiment of the present invention. Referring to  FIG. 5E , the exposed regions (i.e., unprotected by  510 ) of the ILD layer  508  are etched to form trenches  512  and patterned ILD layer  514 . The etch stops on, and thus exposes, the top surfaces of the first level metal lines  506  and the ILD lines  504 . 
       FIG. 5F  illustrates the structure of  FIG. 5E  following photobucket formation in all possible via locations, in accordance with an embodiment of the present invention. Referring to  FIG. 5F , photobuckets  516  are formed in all possible via locations above exposed portions of the recessed metal lines  506 . In one embodiment, the photobuckets  516  are formed essentially co-planar with the top surfaces of the ILD lines  504 , as depicted in  FIG. 5F . Additionally, referring again to  FIG. 5F , the hardmask layer  510  may be removed from the patterned ILD layer  514 . 
     Referring again to  FIG. 5F , in an embodiment, the photobuckets  516  include a material based on a two-stage bake photoresist with a releasable quencher, example of which are described above. Three different possible via locations  516 A,  516 B and  516 C can be seen in the view provided in  FIG. 5F . 
       FIG. 5G  illustrates the structure of  FIG. 3F  following via location selection, in accordance with an embodiment of the present invention. Referring to  FIG. 5G , the photobuckets  516  from  FIG. 5F  in select via locations  518  are removed (i.e., photobuckets  516 A and  516 C are removed). In locations where vias are not selected to be formed, the photobuckets  316  are retained (i.e., photobucket  516 B remains after the development process). In one embodiment, photobucket  516 B is partially exposed during exposure of photobuckets  516 A and  516 C. However, as described above, since the photobucket  516 B is only partially exposed and is not a select via location, the two-stage bake photoresist with a releasable quencher approach enables retention of all of photobucket  516 B. 
       FIG. 5H  illustrates the structure of  FIG. 5G  following conversion of the remaining photobuckets to permanent ILD material, in accordance with an embodiment of the present invention. Referring to  FIG. 5H , the material of the photobuckets  516  is modified, e.g., by cross-linking upon a baking operation, in the locations to form a final ILD material  520 . In one such embodiment, the cross-linking provides for a solubility switch upon the baking. The final, cross-linked material has inter-dielectric properties and, thus, can be retained in a final metallization structure. However, in other embodiments, the photobucket material of photobucket  516 B is not converted to an ILD material and is instead ultimately removed and replaced with a permanent ILD material. 
     Referring again to  FIG. 5H , in an embodiment, the resulting structure includes up to three different dielectric material regions (ILD lines  504  +ILD lines  514 +cross-linked photobucket  520 , in one embodiment) in a single plane  550  of the metallization structure. In one such embodiment, two or all of ILD lines  504 , ILD lines  514 , and cross-linked photobucket  520  are composed of a same material. In another such embodiment, ILD lines  504 , ILD lines  514 , and cross-linked photobucket  520  are all composed of different ILD materials. In either case, in a specific embodiment, a distinction such as a vertical seam between the materials of ILD lines  504  and ILD lines  514  (e.g., seam  597 ) and/or between ILD lines  504  and cross-linked photobucket  520  (e.g., seam  598 ) and/or between ILD lines  514  and cross-linked photobucket  520  (e.g., seam  599 ) may be observed in the final structure. 
       FIG. 5I  illustrates the structure of  FIG. 5H  following metal line and via formation, in accordance with an embodiment of the present invention. Referring to  FIG. 5I , metal lines  522  and vias  524  are formed upon metal fill of the openings of  FIG. 5H . The metal lines  522  are coupled to the underlying metal lines  506  by the vias  524 . In an embodiment, the openings are filled in a damascene approach or a bottom-up fill approach to provide the structure shown in  FIG. 5I . Thus, the metal (e.g., copper and associated barrier and seed layers) deposition to form metal lines and vias in the above approach may be that typically used for standard back end of line (BEOL) processing. In an embodiment, in subsequent fabrication operations, the ILD lines  514  may be removed to provide air gaps between the resulting metal lines  524 . 
     The structure of  FIG. 5I  may subsequently be used as a foundation for forming subsequent metal line/via and ILD layers. Alternatively, the structure of  FIG. 5I  may represent the final metal interconnect layer in an integrated circuit. It is to be understood that the above process operations may be practiced in alternative sequences, not every operation need be performed and/or additional process operations may be performed. In any case, the resulting structures enable fabrication of vias that are directly centered on underlying metal lines. That is, the vias may be wider than, narrower than, or the same thickness as the underlying metal lines, e.g., due to non-perfect selective etch processing. Nonetheless, in an embodiment, the centers of the vias are directly aligned (match up) with the centers of the metal lines. Furthermore, the ILD used to select which plugs and vias will likely be very different from the primary ILD and will be perfectly self-aligned in both directions. As such, in an embodiment, offset due to conventional lithograph/dual damascene patterning that must otherwise be tolerated, is not a factor for the resulting structures described herein. Referring again to  FIG. 5I , then, self-aligned fabrication by the subtractive approach may be complete at this stage. A next layer fabricated in a like manner likely requires initiation of the entire process once again. Alternatively, other approaches may be used at this stage to provide additional interconnect layers, such as conventional dual or single damascene approaches. 
     Overall, in accordance with one or more embodiments of the present invention, approaches described herein involve use of photobucket interlayer dielectric (ILD) to select locations for plugs and vias. The details above regarding  FIGS. 4A-4H and 5A-5I  focus primarily on photobuckets including two-stage bake photoresist with a releasable quencher as used for via patterning. However, it is to be appreciated that photobuckets including a two-stage bake photoresist with a releasable quencher may also be used for plug patterning. 
     In an embodiment, the term “grating structure” for metal lines, ILD lines or hardmask lines is used to refer to a tight pitch grating structure. In one such embodiment, the tight pitch is not achievable directly through conventional lithography. For example, a pattern based on conventional lithography may first be formed, but the pitch may be halved by the use of spacer mask patterning, as is known in the art. Even further, the original pitch may be quartered by a second round of spacer mask patterning. Accordingly, the grating-like patterns described above may have metal lines, ILD lines or hardmask lines spaced at a constant pitch and having a constant width. The pattern may be fabricated by a pitch halving or pitch quartering approach. 
     In an embodiment, as used throughout the present description, interlayer dielectric (ILD) material is composed of or includes a layer of a dielectric or insulating material. Examples of suitable dielectric materials include, but are not limited to, oxides of silicon (e.g., silicon dioxide (SiO 2 )), doped oxides of silicon, fluorinated oxides of silicon, carbon doped oxides of silicon, various low-k dielectric materials known in the arts, and combinations thereof. The interlayer dielectric material may be formed by conventional techniques, such as, for example, chemical vapor deposition (CVD), physical vapor deposition (PVD), or by other deposition methods. 
     In an embodiment, as is also used throughout the present description, interconnect material (e.g., metal lines and/or vias) is composed of one or more metal or other conductive structures. A common example is the use of copper lines and structures that may or may not include barrier layers between the copper and surrounding ILD material. As used herein, the term metal includes alloys, stacks, and other combinations of multiple metals. For example, the metal interconnect lines may include barrier layers, stacks of different metals or alloys, etc. The interconnect lines are also sometimes referred to in the arts as traces, wires, lines, metal, or simply interconnect. 
     In an embodiment, as is also used throughout the present description, plug and/or cap and/or hardmask materials are composed of dielectric materials different from the interlayer dielectric material. In one embodiment, these materials are sacrificial, while interlayer dielectric materials are preserved at least somewhat in a final structure. In some embodiments, a plug and/or cap and/or hardmask material includes a layer of a nitride of silicon (e.g., silicon nitride) or a layer of an oxide of silicon, or both, or a combination thereof. Other suitable materials may include carbon-based materials. In another embodiment, a plug and/or cap and/or hardmask material includes a metal species. For example, a hardmask or other overlying material may include a layer of a nitride of titanium or another metal (e.g., titanium nitride). Potentially lesser amounts of other materials, such as oxygen, may be included in one or more of these layers. Alternatively, other plug and/or cap and/or hardmask material layers known in the arts may be used depending upon the particular implementation. The plug and/or cap and/or hardmask material layers maybe formed by CVD, PVD, or by other deposition methods. 
     It is to be appreciated that the layers and materials described above are typically formed on or above an underlying semiconductor substrate or structure, such as underlying device layer(s) of an integrated circuit. In an embodiment, an underlying semiconductor substrate represents a general workpiece object used to manufacture integrated circuits. The semiconductor substrate often includes a wafer or other piece of silicon or another semiconductor material. Suitable semiconductor substrates include, but are not limited to, single crystal silicon, polycrystalline silicon and silicon on insulator (SOI), as well as similar substrates formed of other semiconductor materials. The semiconductor substrate, depending on the stage of manufacture, often includes transistors, integrated circuitry, and the like. The substrate may also include semiconductor materials, metals, dielectrics, dopants, and other materials commonly found in semiconductor substrates. Furthermore, the structures depicted above may be fabricated on underlying lower level back end of line (BEOL) interconnect layers. 
     Embodiments disclosed herein may be used to manufacture a wide variety of different types of integrated circuits and/or microelectronic devices. Examples of such integrated circuits include, but are not limited to, processors, chipset components, graphics processors, digital signal processors, micro-controllers, and the like. In other embodiments, semiconductor memory may be manufactured. Moreover, the integrated circuits or other microelectronic devices may be used in a wide variety of electronic devices known in the arts. For example, in computer systems (e.g., desktop, laptop, server), cellular phones, personal electronics, etc. The integrated circuits may be coupled with a bus and other components in the systems. For example, a processor may be coupled by one or more buses to a memory, a chipset, etc. Each of the processor, the memory, and the chipset, may potentially be manufactured using the approaches disclosed herein. 
       FIG. 6  illustrates a computing device  600  in accordance with one implementation of the invention. The computing device  600  houses a board  602 . The board  602  may include a number of components, including but not limited to a processor  604  and at least one communication chip  606 . The processor  604  is physically and electrically coupled to the board  602 . In some implementations the at least one communication chip  606  is also physically and electrically coupled to the board  602 . In further implementations, the communication chip  606  is part of the processor  604 . 
     Depending on its applications, computing device  600  may include other components that may or may not be physically and electrically coupled to the board  602 . These other components include, but are not limited to, volatile memory (e.g., DRAM), non-volatile memory (e.g., ROM), flash memory, a graphics processor, a digital signal processor, a crypto processor, a chipset, an antenna, a display, a touchscreen display, a touchscreen controller, a battery, an audio codec, a video codec, a power amplifier, a global positioning system (GPS) device, a compass, an accelerometer, a gyroscope, a speaker, a camera, and a mass storage device (such as hard disk drive, compact disk (CD), digital versatile disk (DVD), and so forth). 
     The communication chip  606  enables wireless communications for the transfer of data to and from the computing device  600 . The term “wireless” and its derivatives may be used to describe circuits, devices, systems, methods, techniques, communications channels, etc., that may communicate data through the use of modulated electromagnetic radiation through a non-solid medium. The term does not imply that the associated devices do not contain any wires, although in some embodiments they might not. The communication chip  606  may implement any of a number of wireless standards or protocols, including but not limited to Wi-Fi (IEEE 802.11 family), WiMAX (IEEE 802.16 family), IEEE 802.20, long term evolution (LTE), Ev-DO, HSPA+, HSDPA+, HSUPA+, EDGE, GSM, GPRS, CDMA, TDMA, DECT, Bluetooth, derivatives thereof, as well as any other wireless protocols that are designated as 3G, 4G, 5G, and beyond. The computing device  600  may include a plurality of communication chips  606 . For instance, a first communication chip  606  may be dedicated to shorter range wireless communications such as Wi-Fi and Bluetooth and a second communication chip  606  may be dedicated to longer range wireless communications such as GPS, EDGE, GPRS, CDMA, WiMAX, LTE, Ev-DO, and others. 
     The processor  604  of the computing device  600  includes an integrated circuit die packaged within the processor  604 . In some implementations of the invention, the integrated circuit die of the processor includes one or more structures, such as self-aligned vias, built in accordance with implementations of the invention. The term “processor” may refer to any device or portion of a device that processes electronic data from registers and/or memory to transform that electronic data into other electronic data that may be stored in registers and/or memory. 
     The communication chip  606  also includes an integrated circuit die packaged within the communication chip  606 . In accordance with another implementation of the invention, the integrated circuit die of the communication chip includes one or more structures, such as conductive vias fabricated using a two-stage bake photoresist with a releasable quencher, in accordance with embodiments of the invention. 
     In further implementations, another component housed within the computing device  600  may contain an integrated circuit die that includes one or more structures, such as conductive vias fabricated using a two-stage bake photoresist with a releasable quencher, in accordance with embodiments of the invention. 
     In various implementations, the computing device  600  may be a laptop, a netbook, a notebook, an ultrabook, a smartphone, a tablet, a personal digital assistant (PDA), an ultra mobile PC, a mobile phone, a desktop computer, a server, a printer, a scanner, a monitor, a set-top box, an entertainment control unit, a digital camera, a portable music player, or a digital video recorder. In further implementations, the computing device  600  may be any other electronic device that processes data. 
       FIG. 7  illustrates an interposer  700  that includes one or more embodiments of the invention. The interposer  700  is an intervening substrate used to bridge a first substrate  702  to a second substrate  704 . The first substrate  702  may be, for instance, an integrated circuit die. The second substrate  704  may be, for instance, a memory module, a computer motherboard, or another integrated circuit die. Generally, the purpose of an interposer  700  is to spread a connection to a wider pitch or to reroute a connection to a different connection. For example, an interposer  700  may couple an integrated circuit die to a ball grid array (BGA)  706  that can subsequently be coupled to the second substrate  704 . In some embodiments, the first and second substrates  702 / 704  are attached to opposing sides of the interposer  700 . In other embodiments, the first and second substrates  702 / 704  are attached to the same side of the interposer  700 . And in further embodiments, three or more substrates are interconnected by way of the interposer  700 . 
     The interposer  700  may be formed of an epoxy resin, a fiberglass-reinforced epoxy resin, a ceramic material, or a polymer material such as polyimide. In further implementations, the interposer may be formed of alternate rigid or flexible materials that may include the same materials described above for use in a semiconductor substrate, such as silicon, germanium, and other group III-V and group IV materials. 
     The interposer may include metal interconnects  708  and vias  710 , including but not limited to through-silicon vias (TSVs)  712 . The interposer  700  may further include embedded devices  714 , including both passive and active devices. Such devices include, but are not limited to, capacitors, decoupling capacitors, resistors, inductors, fuses, diodes, transformers, sensors, and electrostatic discharge (ESD) devices. More complex devices such as radio-frequency (RF) devices, power amplifiers, power management devices, antennas, arrays, sensors, and MEMS devices may also be formed on the interposer  700 . In accordance with embodiments of the invention, apparatuses or processes disclosed herein may be used in the fabrication of interposer  700  or in one or more of the components of the interposer  700 . 
     Thus, embodiments of the present invention include two-stage bake photoresists with releasable quenchers for fabricating back end of line (BEOL) interconnects. 
     In an embodiment, a photolyzable composition includes an acid-deprotectable photoresist material having substantial transparency at a wavelength, a photo-acid-generating (PAG) component having substantial transparency at the wavelength, and a base-generating component having substantial absorptivity at the wavelength. 
     In one embodiment, the base-generating component is one selected from the group consisting of a photo-base-generating component, an electron-base-generating component, a chemical-base-generating component, and a UV-base-generating component. 
     In one embodiment, the base-generating component includes a low-energy UV chromophore selected from the group consisting of anthracenylcarbamates, naphthalenylcarbamates, 2-nitrophenylcarbamates, arylcarbamates, coumarins, phenylglyoxylic acid, substituted acetophenones and benzophenones. 
     In one embodiment, the base-generating component includes a material selected from the group consisting of N,N-dicyclohexyl-2-nitrophenylcarbamate, N,N-disubstituted carbamates and mono-substituted carbamates. 
     In one embodiment, the PAG component includes a material selected from the group consisting of triethyl, trimethyl and other trialkylsulfonates, where the sulfonate group is selected from the group consisting of trifluoromethylsulfonate, nonanfluorobutanesulfonate, and p-tolylsulfonate. 
     In one embodiment, the acid-deprotectable photoresist material is an acid-deprotectable material selected from the group consisting of a polymer, a molecular glass, a carbosilane and a metal oxide. 
     In one embodiment, the acid-deprotectable photoresist material includes a material selected from the group consisting of a polyhydroxystyrene, a polymethacrylate, small molecular weight molecular glass versions of a polyhydroxystyrene or a polymethacrylate which contain ester functionality sensitive to acid-catalyzed deprotection to carboxylic acid, a carbosilane, and a metal oxide possessing functionality sensitive to acid catalyzed deprotection or cross-linking. 
     In one embodiment, the wavelength is approximately 365 nm. 
     In one embodiment, the acid-deprotectable photoresist material is substantially absorbing at a wavelength of approximately 13.5 nanometers. 
     In one embodiment, the acid-deprotectable photoresist material is substantially absorbing at an energy approximately in the range of 5-150 keV. 
     In one embodiment, a molar ratio of the PAG component to the base-generating component is at least 50:1. 
     In an embodiment, a method of selecting a photobucket for semiconductor processing includes providing a structure having a first photobucket neighboring a second photobucket. The method further includes exposing the structure to extreme ultraviolet (EUV) or e-beam radiation, where the first photobucket is exposed to the EUV or e-beam radiation to a greater extent than the second photobucket. The method further includes, subsequent to exposing the structure to EUV or e-beam radiation, performing a first bake of the first and second photobuckets. The method further includes, subsequent to performing the first bake, exposing the structure to ultraviolet (UV) radiation, where the first photobucket is exposed to the UV radiation to approximately the same extent as the second photobucket. The method further includes, subsequent to exposing the structure to UV radiation, performing a second bake of the first and second photobuckets. The method further includes, subsequent to performing the second bake, developing the structure, where the developing opens the first photobucket and leaves the second photobucket closed. 
     In one embodiment, exposing the structure to extreme ultraviolet (EUV) or e-beam radiation includes exposing the structure to energy having a wavelength approximately 13.5 nanometers. 
     In one embodiment, exposing the structure to extreme ultraviolet (EUV) or e-beam radiation includes exposing the structure to energy in the range of 5-150 keV. 
     In one embodiment, exposing the structure to UV radiation incudes exposing the structure to energy having a wavelength approximately 365 nanometers. 
     In one embodiment, the first bake is performed at a temperature approximately in the range of 50-120 degrees Celsius for a duration of approximately in the range of 0.5-5 minutes. 
     In one embodiment, the second bake is performed at a temperature approximately in the range of 100-180 degrees Celsius for a duration of approximately in the range of 0.5-5 minutes. 
     In one embodiment, the first and second photobuckets each includes a photolyzable composition including an acid-deprotectable photoresist material, a photo-acid-generating (PAG) component, and a photo-base-generating component. 
     In one embodiment, exposing the structure to extreme ultraviolet (EUV) or e-beam radiation includes activating the PAG component, where the first bake diffuses acid formed from activating the PAG component throughout the first and second photobuckets, where exposing the structure to UV radiation includes activating the photo-base-generating component, and where the second bake quenches a total amount of acid formed in the second photobucket with base generated from the photo-base-generating component but does not quench a total amount of acid formed in the first photobucket. 
     In one embodiment, the first and second photobuckets each includes a grafted photo-base-generating component along a bottom and sidewalls of the first and second photobuckets and a photolyzable composition formed within the grafted photo-base-generating component, the photolyzable composition including an acid-deprotectable photoresist material and a photo-acid-generating (PAG) component. 
     In one embodiment, exposing the structure to extreme ultraviolet (EUV) or e-beam radiation includes activating the PAG component, where the first bake diffuses acid formed from activating the PAG component throughout the first and second photobuckets, where exposing the structure to UV radiation includes activating the grafted photo-base-generating component, and where the second bake quenches a total amount of acid formed in the second photobucket with base generated from the photo-base-generating component but does not quench a total amount of acid formed in the first photobucket. 
     In one embodiment, the first and second photobuckets each includes a photolyzable composition including an acid-deprotectable photoresist material and a photo-acid-generating (PAG) component, and the method further includes, subsequent to performing the first bake and prior to exposing the structure to ultraviolet (UV) radiation, forming a layer including a base-generating component on the first and second photobuckets. 
     In one embodiment, exposing the structure to extreme ultraviolet (EUV) or e-beam radiation includes activating the PAG component, where the first bake diffuses acid formed from activating the PAG component throughout the first and second photobuckets, where exposing the structure to UV radiation includes activating the base-generating component, and where the second bake quenches a total amount of acid formed in the second photobucket with base generated from the base-generating component but does not quench a total amount of acid formed in the first photobucket. 
     In an embodiment, a photolyzable composition includes an acid-deprotectable photoresist material having substantial transparency at 365 nm, a photo-acid-generating (PAG) component having substantial transparency at 365 nm, and a photo-base-generating component having substantial absorptivity at 365 nm. A molar ratio of the PAG component to the photo-base-generating component is at least 50:1. 
     In one embodiment, the acid-deprotectable photoresist material is substantially absorbing at a wavelength of approximately 13.5 nanometers or is substantially absorbing at an energy approximately in the range of 5-150 keV.