Abstract:
A photoresist vapor deposition system includes: a vacuum chamber having a heating element and cooled chuck for holding a substrate, the vacuum chamber having a heated inlet; and a vapor deposition system connected to the heated inlet for volatilizing a precursor into the vacuum chamber for condensing a photoresist over the substrate cooled by the cooled chuck. The deposition system creates a semiconductor wafer system that includes: a semiconductor wafer; and a vapor deposited photoresist over the semiconductor wafer. An extreme ultraviolet lithography system requiring the semiconductor wafer system includes: an extreme ultraviolet light source; a mirror for directing light from the extreme ultraviolet light source; a reticle stage for imaging the light from the extreme ultraviolet light source; and a wafer stage for placing a semiconductor wafer with a vapor deposited photoresist.

Description:
CROSS-REFERENCE TO RELATED APPLICATION(S) 
       [0001]    This application is a continuation of U.S. Non-Provisional application Ser. No. 14/139,457, filed Dec. 23, 2013, which claims the benefit of U.S. Provisional Patent Application Ser. No. 61/786,042 filed Mar. 14, 2013, to each of which priority is claimed and each of which are incorporated herein by reference in their entireties. 
         [0002]    The present application contains subject matter related to concurrently filed U.S. patent application Ser. No. 14/139,307. The related application is assigned to Applied Materials, Inc. and the subject matter thereof is incorporated herein by reference thereto. 
         [0003]    The present application contains subject matter related to concurrently filed U.S. patent application Ser. No. 14/139,371. The related application is assigned to Applied Materials, Inc. and the subject matter thereof is incorporated herein by reference thereto. 
         [0004]    The present application contains subject matter related to concurrently filed U.S. patent application Ser. No. 14/139,415. The related application is assigned to Applied Materials, Inc. and the subject matter thereof is incorporated herein by reference thereto. 
         [0005]    The present application contains subject matter related to concurrently filed U.S. patent application Ser. No. 14/139,507. The related application is assigned to Applied Materials, Inc. and the subject matter thereof is incorporated herein by reference thereto. 
     
    
     TECHNICAL FIELD 
       [0006]    The present invention relates generally to extreme ultraviolet lithography photoresists. 
       BACKGROUND 
       [0007]    Extreme ultraviolet lithography (EUV, also known as soft x-ray projection lithography) is a contender to replace deep ultraviolet lithography for the manufacture of 0.13 micron, and smaller, minimum feature size semiconductor devices. 
         [0008]    However, extreme ultraviolet light, which is generally in the 7 to 40 nanometer wavelength range, is strongly absorbed in virtually all materials. For that reason, extreme ultraviolet systems work by reflection rather than by transmission of light. Through the use of a series of mirrors, or lens elements, and a reflective element, or mask blank, coated with a non-reflective absorber mask pattern, the patterned actinic light is reflected onto a photoresist-coated semiconductor wafer. 
         [0009]    Advances in photolithography techniques utilized to transfer patterns to photoresist have enabled increasingly smaller patterns to be transferred. This means that smaller integrated circuit features can be formed in integrated circuits. As a result, more elements can be put in a given area on a semiconductor integrated circuit resulting in the ability to greatly reduce the cost of integrated circuits while increasing functionality in the electronic devices in which the integrated circuits are used. 
         [0010]    In the manufacture of semiconductor integrated circuits, a photoresist is deposited on a semiconductor wafer. On exposure to radiation and other processing, the exposed areas of the photoresist undergo changes that make those regions of the photoresist either harder or easier to remove. As a result, subsequent processing can selectively remove the easier to remove material, leaving behind the patterned, harder to remove material. This pattern can then be transferred to the semiconductor wafer via the photoresist, for example, by using the remaining photoresist as a mask for etching the desired features into the underlying layers of the semiconductor wafer. 
         [0011]    There are many demands that are being placed on EUV photoresists because of the need to make finer and finer masks. Currently, there is no known material that simultaneously meets resolution, line edge roughness, and sensitivity (RLS) requirements for a EUV photoresist. In addition to RLS issues, conventional spin-on techniques for EUV photoresists are deficient in a number of areas. 
         [0012]    First, spin-on photoresists are coated using a casting solvent, which can cause environmental problems. 
         [0013]    Second, spin-on deposition techniques do not provide good thickness control and have variations in thickness in the vertical Z direction, especially as film thicknesses decrease. 
         [0014]    Third, components of a spin-on photoresist solution may tend to segregate at the interfaces due to surface energy effects. 
         [0015]    Thus, as EUV lithography becomes more necessary, it is increasingly critical that answers be found to these problems. Additionally, the need to reduce costs, improve efficiencies and performance, and meet competitive pressures adds an even greater urgency to the critical necessity for finding answers to these problems. 
         [0016]    Solutions to these problems have been long sought but prior developments have not taught or suggested any solutions and, thus, solutions to these problems have long eluded those skilled in the art. 
       SUMMARY 
       [0017]    An embodiment of the present invention provides photoresist deposition system which includes: a vacuum chamber having a heating element and cooled chuck for holding a substrate, the vacuum chamber having a heated inlet; and a vapor deposition system connected to the heated inlet for volatilizing a precursor into the vacuum chamber for condensing a photoresist over the substrate cooled by the cooled chuck. 
         [0018]    An embodiment of the present invention provides an extreme ultraviolet lithography system that includes: an extreme ultraviolet light source; a mirror for directing light from the extreme ultraviolet light source; a reticle stage for placing an extreme ultraviolet mask blank; and a wafer stage for placing a wafer coated with a vapor deposited photoresist. 
         [0019]    An embodiment of the present invention provides an extreme ultraviolet lithography system that includes: an extreme ultraviolet light source; a mirror for directing light from the extreme ultraviolet light source; a reticle stage for placing an extreme ultraviolet mask that has been patterned using a vapor deposited photoresist; and a wafer stage for placing a wafer. 
         [0020]    An embodiment of the present invention provides a semiconductor wafer system that includes: a semiconductor wafer and a vapor deposition deposited photoresist over the semiconductor wafer. 
         [0021]    Certain embodiments of the invention have other steps or elements in addition to or in place of those mentioned above. The steps or element will become apparent to those skilled in the art from a reading of the following detailed description when taken with reference to the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0022]      FIG. 1  is a cross-section of the vapor deposition system in accordance with an embodiment of the present invention. 
           [0023]      FIG. 2  is a portion of a semiconductor wafer in accordance with an embodiment of the present invention. 
           [0024]      FIG. 3  is the vapor deposited photoresist of  FIG. 2  after patterning in accordance with an embodiment of the present invention. 
           [0025]      FIG. 4  is an optical train for a EUV lithography system in accordance with an embodiment of the present invention. 
           [0026]      FIG. 5  is shown a EUV lithography system in accordance with an embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0027]    The following embodiments are described in sufficient detail to enable those skilled in the art to make and use the invention. It is to be understood that other embodiments would be evident based on the present disclosure, and that system, process, or mechanical changes may be made without departing from the scope of the present invention. 
         [0028]    In the following description, numerous specific details are given to provide a thorough understanding of the invention. However, it will be apparent that the invention may be practiced without these specific details. In order to avoid obscuring the present invention, some well-known circuits, system configurations, and process steps are not disclosed in detail. 
         [0029]    The drawings showing embodiments of the system are semi-diagrammatic and not to scale and, particularly, some of the dimensions are for the clarity of presentation and are shown exaggerated in the drawing FIGs. Similarly, although the views in the drawings for ease of description generally show similar orientations, this depiction in the FIGs. is arbitrary for the most part. Generally, the invention can be operated in any orientation. 
         [0030]    The same numbers are used in all the drawing FIGs. to relate to the same elements. 
         [0031]    For expository purposes, the term “horizontal” as used herein is defined as a plane parallel to the plane or surface of the wafer, regardless of its orientation. The term “vertical” refers to a direction perpendicular to the horizontal as just defined. Terms, such as “above”, “below”, “bottom”, “top”, “side” (as in “sidewall”), “higher”, “lower”, “upper”, “over”, and “under”, are defined with respect to the horizontal plane, as shown in the figures. The term “on” indicates that there is direct contact between elements. 
         [0032]    The term “processing” as used herein includes deposition of material or photoresist, patterning, exposure, development, etching, cleaning, and/or removal of the material or photoresist as required in forming a described structure. 
         [0033]    Referring now to  FIG. 1 , therein is shown a cross-section of a vapor deposition system in accordance with an embodiment of the present invention. A vapor deposition system could be a standalone system or part of a deposition system  100 . A standalone system, designated as a vapor deposition system  100  includes a vacuum chamber  102  having a heated primary inlet  104  and one or more heated secondary inlets, such as an inlet  106 . The vapor deposition system  100  has an outlet  108 . 
         [0034]    The vacuum chamber  102  contains a heating element  110  and a cooled chuck  112  for holding a semiconductor wafer  115 , an extreme ultraviolet mask blank, or other mask blank. 
         [0035]    Precursors  116  are volatilized and introduced to the vacuum chamber  102 . When they reach the cooled chuck  112 , the precursors  116  condense on the surface of the semiconductor wafer  115 . Examples of the precursor  116  are metal alkoxides or other volatile metal oxide precursors such as hafnium t-butoxide, titanium n-butoxide, hafnium borohydride, and others. 
         [0036]    The precursor could optionally be reacted with water or another oxidizing agent like ozone or peroxide to convert the metal oxide precursor into a metal oxide film, or metal oxide particles. While any metal oxide is possible, hafnium, zirconium, tin, titanium, iron, and molybdenum oxides work well. The reaction oxidant could be introduced at the same time or sequentially with the metal oxide precursor. 
         [0037]    In some embodiments, precursors are introduced to the chamber to intentionally drive a gas phase reaction between them, resulting in the formation of larger molecules that are deposited on the semiconductor wafer  115 . A second precursor is also introduced (either at the same time, or in sequence as in an atomic layer deposition (ALD) reaction with the other precursors). 
         [0038]    This second precursor is a ligand that bonds with metal oxide particles or film, or initiates a ligand replacement reaction with existing ligands attached around a metal center. While any metal center is possible, hafnium, zirconium, tin, titanium, iron, and molybdenum metal centers work well. Examples include carboxylic acids like methacrylic acid, formic acid, acetic acid, and others, but may also include other functionalities such as sulfonic acids, dienes, or other chemistries which can form complexes with metal oxide particles or films. 
         [0039]    Referring now to  FIG. 2 , therein is shown a portion of the semiconductor wafer  115  in accordance with an embodiment of the present invention. The semiconductor wafer  115  has a substrate  200 , which may include such materials as crystalline silicon (e.g., Si&lt;100&gt; or Si&lt;111&gt;), silicon oxide, strained silicon, silicon germanium, doped or undoped polysilicon, doped or undoped silicon wafers, III-V materials such as GaAs, GaN, InP, etc., and be patterned or non-patterned wafers. Substrates may have various dimensions, such as 200 mm or 300 mm diameter wafers, as well as, rectangular or square panes. Substrates may be exposed to a pretreatment process to polish, etch, reduce, oxidize, hydroxylate, anneal and/or bake the substrate surface. 
         [0040]    The substrate  200  has a substrate surface  204 , which may be of any substrate or material surface formed on a substrate upon which film processing is performed during a fabrication process. For example, the substrate surface  204  on which processing can be performed include materials such as silicon, silicon oxide, strained silicon, silicon on insulator (SOI), carbon doped silicon oxides, silicon nitride, doped silicon, germanium, gallium arsenide, glass, sapphire, and any other materials such as metals, metal nitrides, metal alloys, and other conductive materials, depending on the application. Barrier layers, metals or metal nitrides on a substrate surface include titanium, titanium nitride, tungsten nitride, tantalum and tantalum nitride, aluminum, copper, or any other conductor or conductive or non-conductive barrier layer useful for device fabrication. 
         [0041]    A vapor deposited photoresist  206  having a top  209  and a bottom  207  is deposited on the substrate surface  204  by vapor deposition techniques using the vapor deposition system  100  of  FIG. 1 . The combination of the vapor deposited photoresist  206  and the substrate  200  form a semiconductor wafer system  210 . The vapor deposited photoresist  206  has been found to be of particular use in extreme ultraviolet or smaller lithography. The vapor deposition system  100  involves a heated chamber and heated chemical delivery lines combined with the cooled chuck. The vapor deposited photoresist  206  may be deposited by vapor deposition (evaporation, decomposition, etc.), chemical vapor deposition (precursor reaction), atomic layer deposition, or other processes than spin-on deposition. 
         [0042]    In addition, either simultaneously or in sequence, a photoactive compound may optionally be introduced into the chamber, also by vapor deposition techniques. This photoactive compound may be an acid generator, a radical generator, or a compound that can rearrange to generate an active chemical such as a ligand that can replace or catalyze the replacement, rearrangement, condensation, or change of ligands around the metal center such that a solubility change is induced in the film or particle. 
         [0043]    Referring now to  FIG. 3 , therein is shown the vapor deposited photoresist  206  of  FIG. 2  after patterning in accordance with an embodiment of the present invention. On exposure to radiation (UV, DUV, EUV, e-beam, visible, infrared, ion-beam, x-ray, and others), a chemical reaction is induced in the vapor deposited photoresist  206 , either at the metal oxide or in the photoactive compound. This reaction ultimately (either directly or after a post-exposure bake or other post exposure processing) results in a change in the solubility of the vapor deposited photoresist  206  in a solvent, or a change in the etch rate of the film in a plasma etch process. This change in solubility or etch rate can be used to ultimately pattern the vapor deposited photoresist  206  to provide a patterned vapor deposited photoresist  300 . 
         [0044]    In some embodiments, the process conditions are held constant throughout the deposition, giving rise to a photoresist  206  that is uniform in composition from top  209  to bottom  207 . In other embodiments, the deposition conditions or chemicals used are varied as the photoresist is being deposited, giving rise to different photoresist compositions from top  209  to bottom  207 . 
         [0045]    In some embodiments, the properties of the photoresist at the bottom of the stack may be tailored to achieve specific goals. For example, the material at the bottom of the stack may be more absorbing of EUV photons, which in turn can lead to the generation of excess secondary electrons, some of which would in turn be directed upwards into the photoresist to catalyze additional reactions and improve the performance of the EUV photoresist. This improvement could be manifested in terms of sensitivity, line edge roughness, reduction in scumming or footing, or other improvements. 
         [0046]    In other embodiments, the photoresist can be deposited on a substrate with desirable properties previously mentioned that instead was not deposited as part of the photoresist deposition, but instead was deposited by a separate, independent process. 
         [0047]    In yet other embodiments, the photoresist is deposited on a more conventional substrate such as semiconductors, metals, or dielectrics including silicon, silicon oxide, germanium, silicon nitride, metals, metal oxides, metal nitrides, bottom anti-reflective coatings, and other substrates. 
         [0048]    In some embodiments, the precursors are introduced into the vapor phase by thermal evaporation, but other techniques such as vacuum spraying may also be used for deposition. 
         [0049]    In some embodiments, the ratio of the number of ligands to the number of metal atoms or particle size is controlled to control photoresist properties such as photosensitivity 
         [0050]    In some embodiments, an additional precursor may be co-deposited in the photoresist to limit the reaction or diffusion of the photoactive compound. In the case of a photoacid generator, this additional precursor might be a base or photodecomposable base. In the case of a photoradical generator, this precursor might be a radical scavenger, and so on. 
         [0051]    In some embodiments, this process is performed on a system that uses a rotating chuck to improve the deposition thickness uniformity across the wafer. In other embodiments, a cold trap is used to capture unreacted precursor materials before they leave the chamber. 
         [0052]    Embodiments of the present invention have the potential to satisfy the requirements in these key areas better than existing technology. Furthermore, deposition of a photoresist by vacuum techniques has advantages over conventional spin-on techniques in several areas. First, it eliminates solvent from the system, which is an environmental benefit. Next, vacuum deposition techniques allow the user to tune the deposition from conformal to planarizing, whereas spin-on films tend to only be planarizing. Also, vacuum deposition techniques give the user more control over the film composition through thickness, and allow the user to create a uniform film in the Z direction, whereas during a spin on process, components of the photoresist solution may tend to segregate at the interfaces due to surface energy effects. Vacuum deposition techniques also would allow for the creation of a controlled composition change through thickness as the film is being deposited by varying the deposition conditions. This control is not possible with conventional techniques. 
         [0053]    Primary applications anticipated for embodiments of the present the invention are within the overall field of patterning for microelectronic and photonic devices using any type of patterned radiation technique (visible, deep UV, EUV, electron-beam or X-ray lithography). Because of the unique aspects of the deposition method described, applications would not be restricted only to flat, planar substrates. 
         [0054]    Referring now to  FIG. 4 , therein is shown an optical train  400  for a EUV lithography system in accordance with an embodiment of the present invention. The optical train  400  has an extreme ultraviolet light source  402 , such as a plasma source, for creating the EUV light and collecting it in a collector  404 . The collector  404  provides the light to a field facet mirror  408  which is part of an illuminator system  406  which further includes a pupil facet mirror  410 . The illuminator system  406  provides the EUV light to a reticle  412 , which reflects the EUV light through projection optics  414  and onto a patterned semiconductor wafer  416 . 
         [0055]    Referring now to  FIG. 5 , therein is shown a EUV lithography system  500  in accordance with an embodiment of the present invention. The EUV lithography system  500  includes a EUV light source area  502 , a reticle stage  504  and a wafer stage  506  as adjuncts to the optical train  400 . 
         [0056]    The resulting method, process, apparatus, device, product, and/or system is straightforward, cost-effective, uncomplicated, highly versatile, accurate, sensitive, and effective, and can be implemented by adapting known components for ready, efficient, and economical manufacturing, application, and utilization. The vapor deposited photoresist  206  of  FIG. 2  is a critical component of the EUV lithography system  500  and the EUV lithography system  500  cannot perform its function without a vapor deposited photoresist. 
         [0057]    Another important aspect of the present invention is that it valuably supports and services the historical trend of reducing costs, simplifying systems, and increasing performance. 
         [0058]    These and other valuable aspects of the present invention consequently further the state of the technology to at least the next level. 
         [0059]    While the invention has been described in conjunction with a specific best mode, it is to be understood that many alternatives, modifications, and variations will be apparent to those skilled in the art in light of the aforegoing description. Accordingly, it is intended to embrace all such alternatives, modifications, and variations that fall within the scope of the included claims. All matters hithertofore set forth herein or shown in the accompanying drawings are to be interpreted in an illustrative and non-limiting sense.