Abstract:
A solution for processing devices is provided, comprising an activator comprising at least one of pyridine, pyrole, pyrrolidine, pyrimidine, N,N-dimethylformamide, tetraethylamine chloride, 4 pyridinethiol, or other organic compounds with a single N with a lone pair electron activator and an etchant comprising at least one of thionly chloride, Cl 2 , Br 2 , I 2 , SOF 2 , SOF 4 , SO 2 Cl 2 , SOBr 2 , S 2 O 6 F 2 , HSO 3 F, or C 2 Cl 4 O 2 .

Description:
BACKGROUND OF THE INVENTION 
       [0001]    The present invention relates to methods and solutions for cleaning. More specifically, the present invention relates to methods and solutions for cleaning metal residues. 
         [0002]    During semiconductor wafer processing, the processing of metal containing layer may cause metal residue. It is desirable to remove such metal residue. 
       SUMMARY OF THE INVENTION 
       [0003]    To achieve the foregoing and in accordance with the purpose of the present invention, a solution for processing devices is provided, comprising an activator comprising at least one of pyridine, pyrrole, pyrrolidine, pyrimidine, N,N-dimethylformamide, tetraethylamine chloride, 4 pyridinethiol, or other organic compounds with a single N with a lone pair electron activator and an etchant comprising at least one of thionyl chloride (SOCl2), Cl 2 , Br 2 , I 2 , SOF 2 , SOF 4 , SO 2 Cl 2 , SOBr 2 , or C 2 Cl 4 O 2 . 
         [0004]    In another manifestation of the invention, a method for forming semiconductor devices on a substrate with at least one metal layer is provided. The at least one metal layer is exposed to a solution. The solution comprises an activator comprising at least one of pyridine, pyrole, pyrrolidine, pyrimidine, N,N-dimethylformamide, tetraethylamine chloride, 4 pyridinethiol, or other organic compounds with a single N lone pair electron activator and an etchant comprising at least one of thionyl chloride (SOCl2), Cl 2 , Br 2 , I 2 , SOF 2 , SOF 4 , SO 2 Cl 2 , SOBr 2 , or C 2 Cl 4 O 2 . 
         [0005]    In another manifestation of the invention, a solution for processing semiconductor devices is provided, comprising a nonaqueous solvent and an acid precursor. 
         [0006]    In another manifestation of the invention, a method for forming semiconductor devices on a substrate with at least one metal layer is provided. The at least one metal layer is exposed to a solution, comprising a nonaqueous solvent and an acid precursor. 
         [0007]    These and other features of the present invention will be described in more detail below in the detailed description of the invention and in conjunction with the following figures. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]    The present invention is illustrated by way of example, and not by way of limitation, in the figures of the accompanying drawings and in which like reference numerals refer to similar elements and in which: 
           [0009]      FIG. 1  is a high level flow chart of an embodiment of the invention. 
           [0010]      FIGS. 2A-B  are schematic views of a stack processed according to an embodiment of the invention. 
           [0011]      FIG. 3  is a high level flow chart of another embodiment of the invention. 
           [0012]      FIGS. 4A-B  are schematic views of a stack processed according to another embodiment of the invention. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0013]    The present invention will now be described in detail with reference to a few preferred embodiments thereof as illustrated in the accompanying drawings. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention. It will be apparent, however, to one skilled in the art, that the present invention may be practiced without some or all of these specific details. In other instances, well known process steps and/or structures have not been described in detail in order to not unnecessarily obscure the present invention. 
         [0014]    To facilitate understanding,  FIG. 1  is a high level flow chart of a process used in an embodiment. A metal containing stack is formed (step  104 ). The stack is cleaned with a solution (step  108 ). A wetting process is performed on the stack after exposure to the solution (step  112 ). 
         [0015]    In an embodiment, a metal containing stack is formed (step  104 ).  FIG. 2A  is a cross-sectional view of a stack  200  with a substrate  204  over which one or more intermediate layers  208  has been formed. The one or more intermediate layers  208  may have conductors  212 , such as contacts, trenches or vias. Stacks  216  with one or more layers are formed over the one or more intermediate layers  208 . A metal containing layer  220  forms at least one layer of the stacks  216 . In an example of this embodiment, the metal containing layer may be formed from one or more layers of titanium nitride (TiN), tantalum (Ta), and ruthenium, (Ru). In the formation of the stacks  216 , such as during a dry etching process, sidewalls of residue  224  are formed. Since one or more of the layers contains metal, the sidewalls of residue  224  contain metal, which may cause shorting between layers of the stacks  216 . In some embodiments the residue comprises a transition metal, an alkali metal and a noble metal. 
         [0016]    The stack  200  is cleaned using a solution (step  108 ). In this embodiment, the solution is a nonaqueous solution of pyridine and SOCl 2 . The ratio of pyridine and SOCL 2  is 1:1 at room temperature. The stacks  216  are exposed to the solution for 30 seconds. 
         [0017]      FIG. 2B  is a cross-sectional view of a stack  200  after the solution has been removed. The sidewalls of residues are removed with minimal etching of the layers of the stacks  216 . 
         [0018]    In this embodiment, a subsequent wet process is provided (step  112 ). The wet process is used to rinse off the cleaning solution and to stop the reaction. 
         [0019]    The combination of an activator and an etchant improves the etching ability of the solution. However, a diluent is also needed to provide selectivity. The ratio of the activator and etchant and the diluent may be used to tune selectivity and activity. It has found in embodiments that pyridine may act as both an activator and buffer. 
         [0020]      FIG. 3  is a high level flow chart of another embodiment of the invention. A metal layer is provided under a mask (step  304 ). The metal layer is exposed to a solution (step  308 ) to etch the metal layers. The metal layer is exposed to a wet process (step  312 ) to rinse of the chemical solution. The mask is stripped (step  316 ). 
         [0021]    In an example of this embodiment of the invention, the same metal stack is provided below a photoresist mask (step  304 ).  FIG. 4A  is a schematic cross-sectional view of a stack  400  comprising a substrate  404  under a metal layer  408 , which is under a patterned mask  412 . The metal layer  408  is exposed to the solution (step  308 ). In this embodiment, the solution is in vapor form. In this example, the solution is SOCl 2  with pyridine. The solution etches the metal layer  408 .  FIG. 4B  is a schematic cross-sectional view of the stack after the metal layer  408  is etched by the solution. The metal layer  408  is then subjected to a wet process (step  312 ). In this example the wet process is uses an inert nonaqueous solvent to remove residue and vapor, since the solvent in inert and nonaqueous, the solvent does not corrode or damage the stack. The patterned mask  412  is stripped (step  316 ). The stripping may be accomplished using an ashing step or a wet strip. 
         [0022]    In some embodiments, the nonaqueous solution comprises an activator comprising at least one of pyridine, pyrole, pyrrolidine, pyrimidine, N,N-dimethylformamide (DMF), tetraethylamine chloride, 4 pyridinethiol, or other organic compounds with a single N lone pair activator and an etchant comprising at least one of thionyl chloride, Cl 2 , Br 2 , I 2 , SOF 2 , SOF 4 , SO 2 Cl 2 , SOBr 2 , or C 2 Cl 4 O 2 . Some embodiments of the invention further comprise a diluent. In an embodiment of the invention, the diluents comprise at least one of acetonitrile, dimethyl sulphoxide (DMSO), sulfolane, halogenated hydrocarbon solvents, or alcohols. In some embodiments, the solution is in liquid phase. In other embodiments, the solution is in vapor phase. In embodiments of the invention, the activator comprises at least one of pyrrole, pyrrolidine, pyrimidine, N,N-dimethylformamide, tetraethylamine chloride, or 4 pyridinethiol. In embodiments of the invention, the etchant comprises at least one of Cl 2 , Br 2 , I 2 , SOF 2 , SOF 4 , SO 2 Cl 2 , SOBr 2 , or C 2 Cl 4 O 2 . Embodiments of the invention expose the stacks to the solution in a moisture free environment. 
         [0023]    In some embodiments, the concentration of activator to the concentration of the etchant is from 0.1:99.9 to 99.9:0.1. More preferably, the concentration of activator to the concentration of etchant is from 10:90 to 90:10. More preferably, the concentration of activator to the concentration of etchant is from 30:70 to 70:30. Most preferably, the concentration of the etchant to the concentration of the activator is 1:1. Preferably, the concentration of diluent to remaining solution is from 0:100 to 70:30. More preferably, the concentration of diluent to remaining solution is from 20:80 to 50:50. 
         [0024]    The combination of the active etchant with an activator provides a solution with improved etching abilities over the separate components. The ratio of the components provides control over the etching abilities. The addition of a diluent provides selectivity. Control of the diluent concentration provides a control over selectivity. 
         [0025]    In another embodiment of the invention the solution comprises a nonaqueous solvent and an acid precursor. Preferably the acid precursor comprises at least one of organic acids such as HCO 2 H, CH 3 COOH, oxalic acid, malonic acid or other acid precursors such as HNO 3 , HCl, H 3 PO 4 , SO 2 , SO 3 , Cl 2  or NO/NO 2 . Preferably the nonaqueous solvent comprises at least one of ethylene glycol, acetonitrile, IPA, choline chloride, choline, urea, DMSO, DMF, or CCl 4 . For example, the solution in one embodiment is acetic acid dissolved in ethylene glycol. By providing a nonaqueous solution metal residue may be removed or metal layers may be etched, while corrosion and other damage is reduced or minimized. It has been found that an aqueous solvent causes corrosion of the metal layers. In addition, an aqueous solvent may attack magnesium oxide dielectric barrier layers. 
         [0026]    While this invention has been described in terms of several preferred embodiments, there are alterations, permutations, modifications, and various substitute equivalents, which fall within the scope of this invention. It should also be noted that there are many alternative ways of implementing the methods and apparatuses of the present invention. It is therefore intended that the following appended claims be interpreted as including all such alterations, permutations, and various substitute equivalents as fall within the true spirit and scope of the present invention.