Abstract:
The invention includes semiconductor processing patterning methods and semiconductor constructions. A semiconductor processing patterning method includes forming a second composition resist layer over a different first composition resist layer. Overlapping portions of the first and second composition resist layers are exposed to actinic energy effective to change solubility of the exposed portions versus the unexposed portions of each of the first and second composition resist layers in a developer solution. The first and second composition resist layers are developed with the developer solution under conditions effective to remove the exposed portions of the first composition resist layer at a faster rate than removing the exposed portions of the second composition resist layer. Additional aspects and implementations are contemplated.

Description:
TECHNICAL FIELD  
         [0001]    The present invention relates to semiconductor processing patterning methods and constructions.  
         BACKGROUND OF THE INVENTION  
         [0002]    A continuing goal of semiconductor processing is increased miniaturization while maintaining high performance. Modern semiconductor processes are heavily reliant on photolithography when preparing semiconductors to achieve this goal.  
           [0003]    Photolithography typically involves the following steps. Initially, a layer of resist is formed over a substrate. A reticle/mask is subsequently placed above the resist and radiation is allowed to pass through openings of the reticle/mask and contact the resist in patterns defined by the reticle/mask. Depending on whether the resist is a negative resist or a positive resist, the radiation renders exposed portions of the resist more or less soluble in a solvent relative to unexposed portions. The solvent is subsequently utilized to remove the more soluble portions of the resist while leaving the less soluble portions as a patterned mask. The mask pattern can be transferred to the underlying substrate with a suitable etch. Exemplary methods of prior art photolithography and a problem therewith are illustrated in FIGS. 1-3.  
           [0004]    Referring first to FIG. 1, a semiconductor substrate  1  at one stage of semiconductor processing is shown that includes a bulk substrate  3 , multilayers  4  (e.g., conductive, semiconductive and/or insulative layers) and a resist  5 . To aid in interpretation of the claims that follow, the terms “semiconductive substrate” and “semiconductor substrate” are defined to mean any construction comprising semiconductive material, including, but not limited to, bulk semiconductive materials such as a semiconductive wafer (either alone or in assemblies comprising other materials thereon), and semiconductive material layers (either alone or in assemblies comprising other materials). The term “substrate” refers to any supporting structure, including, but not limited to, the semiconductive substrates described above.  
           [0005]    Referring to FIG. 2, photoresist layer  5  has been processed to form masking blocks  7 . It would be desirable that these masking blocks be of constant respective width in the illustrated cross-section from top to bottom. However in certain instances, the patterned photoresist tends to flare out at the bottoms/bases, as shown, forming what are commonly referred to as “footing”, depicted by feet  9 .  
           [0006]    Referring to FIG. 3, layers  4  have been etched using blocks  7  as an etch mask. As shown, feet  9  have functioned as part of that mask making the pattern of layers  4  substantially wider than the predominate width of blocks  7 . In many instances, this is undesirable and/or difficult to predict or control.  
         SUMMARY OF THE INVENTION  
         [0007]    The invention includes semiconductor processing patterning methods and semiconductor constructions. In one implementation, a semiconductor processing patterning method includes forming a second composition resist layer over a different first composition resist layer. Overlapping portions of the first and second composition resist layers are exposed to actinic energy effective to change solubility of the exposed portions versus the unexposed portions of each of the first and second composition resist layers in a developer solution. The first and second composition resist layers are developed with the developer solution under conditions effective to remove the exposed portions of the first composition resist layer at a faster rate than removing the exposed portions of the second composition resist layer.  
           [0008]    In one implementation, a semiconductor construction includes a semiconductor substrate having a patterned resist mask received thereon. The resist mask includes a first composition resist portion and a different second composition resist portion received over the first composition resist portion. The first composition resist portion has opposing sidewalls in at least one cross section and the second composition resist portion has opposing sidewalls in the one cross section. At least a portion of the opposing sidewalls of the first composition resist portion are recessed laterally inward of at least a portion of the opposing sidewalls of the second composition resist portion.  
           [0009]    Additional aspects and implementations are contemplated.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0010]    Preferred embodiments of the invention are described below with reference to the following accompanying drawings  
         [0011]    [0011]FIG. 1 is a diagrammatic cross-sectional view of a prior art semiconductor construction at one stage of processing.  
         [0012]    [0012]FIG. 2 is a view of the FIG. 1 construction shown at a processing step subsequent to that of FIG. 1.  
         [0013]    [0013]FIG. 3 is a view of the FIG. 2 construction shown at a processing step subsequent to that of FIG. 2.  
         [0014]    [0014]FIG. 4 is a diagrammatic cross-sectional view of a semiconductor construction in accordance with an aspect of the present invention at one stage of processing.  
         [0015]    [0015]FIG. 5 is a view of the FIG. 4 construction shown at a processing step subsequent to that of FIG. 4.  
         [0016]    [0016]FIG. 6 is a view of the FIG. 5 construction shown at a processing step subsequent to that of FIG. 5.  
         [0017]    [0017]FIG. 7 is an enlarged view of a portion of the FIG. 6 construction.  
         [0018]    [0018]FIG. 8 is a view of the FIG. 6 construction shown at a processing step subsequent to that of FIG. 6.  
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0019]    This disclosure of the invention is submitted in furtherance of the constitutional purposes of the U.S. Patent Laws “to promote the progress of science and useful arts” (Article 1, Section 8).  
         [0020]    An exemplary semiconductor processing patterning method, in accordance with some aspects of the invention, is described with reference to FIGS. 4-8. Referring to FIG. 4, a wafer fragment  12  includes a bulk semiconductor substrate material  14 , for example monocrystalline silicon. Of course other substrates, for example semiconductor-on-insulator substrates and other substrates whether existing or yet-to-be developed, could be utilized. One or more series of layers  16  are formed over material  14  for patterning. A first layer of resist  18  is formed over substrate  16 / 14 . Resist layer  18  might be photosensitive or otherwise impacted by actinic energy (for example UV radiation, e-beam or other actinic energy) to change solubility of exposed versus unexposed portions in a suitable developer solution. Further, resist layer  18  might be a positive resist or a negative resist. In one implementation, the first layer of resist layer  18  is photosensitive to electromagnetic radiation at no greater than about 325 nm. By way of example, an exemplary thickness for layer  18  is less than about 700 Å.  
         [0021]    A second layer of resist  20  is formed over first layer of resist  18 . As shown in one implementation, second layer of resist  20  is formed “on” (meaning in direct physical contact) with first layer of resist  18 . First layer of resist  18  and second layer of resist  20  can be of different compositions at least as initially formed. Further, second layer of resist  20  might be a positive resist or a negative resist.  
         [0022]    In one implementation, resist layers  18  and  20  are both positive resist with layer  18  being provided to have a greater solubility in a developer solution than does second positive resist layer  20  at least after exposure to actinic energy effective to increase the solubility of each of the first and second positive resist layers in the developer solution. An exemplary material for first layer of resist  18  includes 1-methoxy-2-propanol, while an exemplary material for second layer of resist  20  includes cyclohexanone and 2-heptanone. An exemplary developer solution for such materials inlcudes tetramethyl ammonium hydroxide (TMAH).  
         [0023]    Regardless of whether positive or negative resist are utilized, exemplary ways of modifying the erosion rate or the etch rate of a resist include adding to, subtracting from, or varying the composition of any of the components within the resist. For example, the use of, and/or type of resins, stabilizers, photoactive agents, polymers, molecular weight distribution, etc., can have an impact on the erosion or etch rate of a resist as is known and determined by people of skill in the art.  
         [0024]    By way of example only, a specific exemplary positive resist material for first layer of resist  18  is SEPR-402 available from Shin-Etsu Chemical Company of Chiyoda-ku, Tokyo. Such is understood to include 1-methoxy-2-propanol, ethyl lactate and one or more proprietary components. After suitable exposure to actinic energy and development in a 21° C., 2.26 N/2.25% by weight TMAH in H 2 O developer solution, SEPR-402 has an erosion or etch rate of about 500 Angstroms per minute.  
         [0025]    Another example for first layer of resist  18  is M230Y available from the JSR Corporation of Sunnyvale, Calif. Such is understood to include 1-methoxy-2-propanol, ethyl lactate and various proprietary components. In the same developer solution described above, such has an erosion rate of about 300 Angstroms per minute. With such exemplary different etch rates, the M230Y might be used as an exemplary material for second layer of resist  20 , with material SEPR-402 used as an exemplary material for first layer of resist  18 . However, in certain circumstances it may be beneficial to utilize a material having an even slower etch rate for second layer of resist  20 . By way of example only, such includes AR-360S manufactured by the JSR Corporation. Such is understood to include cyclohexanone, 2-heptanone and at least three proprietary components. Such material has an erosion or etch rate after exposure and development in the above developer solution of approximately 50 Angstroms per minute.  
         [0026]    Other layers of resist and/or with other non-resist layers might also be utilized. For example, multi-level resist which typically combines resist and non-resist layers might be utilized. Regardless, in one preferred implementation, first layer of resist  18  has a thickness which is less than a total thickness of all layers received above it. In one implementation, first layer of resist  18  has a thickness which is less than or equal to about 50% (more preferably 25%, even more preferably 10%, and still more preferably 5%) of the total thickness of first layer of resist  18  and all layers received over first layer of resist  18 . Further for example where the only other layer received above first layer of resist  18  is second layer of resist  20 , the above-referred relationships apply relative to the thickness of second layer of resist  20 .  
         [0027]    Referring to FIG. 5, overlapping portions of first resist layer  18  and second resist layer  20  have been exposed to actinic energy effective to change solubility of the exposed portions versus the unexposed portions of each of the first and second resist layers  18  and  20  in a developer solution. For example, such could be conducted using a photolithographic mask/reticle, or by any other existing or yet-to-be developed techniques. In the particular illustrated and described implementation, the first and second layers of resist are both positive resists, and the illustrated overlapping portions  22  and  24  are masked while the remaining portions of layers  18  and  20  would be exposed to effectively increase their solubility in a developer solution. Of course, negative resist could be utilized where the opposite relationship would occur.  
         [0028]    Referring to FIG. 6, first layer of resist  18  and second layer of resist  20  are developed with a suitable developer solution to form mask patterns  26  and  28  which comprise the first and second resist layers. In one implementation, the developing solution removes or etches the exposed portions, for example those exposed in FIG. 5, of first layer of resist  18  at a rate that is faster than the exposed portions of second layer of resist  20 . Regardless, first resist layer  18  of the respective mask patterns  26  and  28  has respective opposing sidewalls  30  and  32  in at least one cross-section, for example that illustrated by FIG. 6. Further in one implementation, second resist layer  20  of the respective mask patterns  26  and  28  has respective opposing sidewall  34  and  36  in the one cross-section. As shown, at least a portion of opposing sidewalls  30  and  32  of first resist layer  18  are received laterally inward of at least a portion of opposing sidewalls  34  and  36  of second resist layer  20  in the one cross-section. As shown, the entirety of the opposing sidewalls  30  and  32  of first resist layer  18  in the one-cross-section are recessed laterally inward of opposing sidewalls  34  and  36  of second resist layer  20  in the one cross-section (FIGS. 6 and 7).  
         [0029]    In one implementation, the opposing sidewalls of the first resist layer and the opposing sidewalls of the second resist layer are of different shapes in the one cross-section. For example and by way of example only, opposing sidewalls  34  and  36  of second resist layer  20  are generally straight along a substantial portion of their length, while opposing sidewalls  30  and  32  of first resist layer  18  are not. Further in one implementation, opposing sidewalls  30  and  32  of first resist layer  18  are at least partially curved in the one cross-section, with FIGS. 6 and 7 showing such sidewalls as being curved about their substantial entire lengths.  
         [0030]    In addressing the issue or problem identified in the Background section above, one goal or object might be to reduce or eliminate the described footing. Where reduced footing or footing elimination occurs, a possible non-limiting theory is that one or both of the sidewall recessing, or faster etching rate of the first layer of resist, provides for the attack of any forming foot from underneath the foot as well as to a greater degree from its sides. The prior art processes may essentially be limited to the attack of only the top of the foot by developer solutions.  
         [0031]    Referring to FIG. 8, material  16  of substrate  12  has been etched using mask patterns  26  and  28  as a mask. The artisan would, of course, select a suitable chemistry or chemistries in etching material  16 , and at least some of one or more of resist materials  20  and  18  might also be etched to some degree in the process.  
         [0032]    In one aspect, the invention also contemplates a semiconductor construction independent of the exemplary above-described methods. Such a construction comprises a semiconductor substrate having a patterned resist mask received thereon, for example as shown in FIG. 6. The resist mask comprises a first composition resist portion and a different second composition resist portion received over the first composition resist portion. The first composition resist portion has opposing sidewalls in at least one cross-section, and the second composition resist portion has opposing sidewalls in the one cross-section. At least a portion of the opposing sidewalls of the first composition resist portion are recessed laterally inward of at least a portion of the opposing sidewalls of the second composition resist portion. Exemplary and preferred attributes of the resist mask, first composition resist portion, second composition resist portion, and opposing sidewalls are as described above with respect to the methodical aspects.  
         [0033]    In compliance with the statute, the invention has been described in language more or less specific as to structural and methodical features. It is to be understood, however, that the invention is not limited to the specific features shown and described, since the means herein disclosed comprise preferred forms of putting the invention into effect. The invention is, therefore, claimed in any of its forms or modifications within the proper scope of the appended claims appropriately interpreted in accordance with the doctrine of equivalents.