Patent Document

The present application is a division of and claims priority to U.S. application Ser. No. 11/360,350, filed Feb. 23, 2006 now U.S. Pat. No. 7,732,322, which is hereby incorporated by reference herein in its entirety. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates generally to semiconductor device manufacturing, and more particularly to a dielectric material with a reduced effective dielectric constant and methods of manufacturing the same. 
     BACKGROUND 
     A porous low dielectric constant (k) or “low k” dielectric may be used to reduce a capacitance of an interconnect. However, conventional porous low k dielectric materials may fail mechanically due to back end of line (BEOL) processes such as chemical mechanical polishing (CMP). To prevent such mechanical failures, a mechanically-stronger dielectric material may be employed. However, mechanically-stronger dielectric materials typically have a higher k, which may result in an undesired increase in capacitance. Accordingly, dielectric material with a reduced dielectric constant and methods of manufacturing the same are desired. 
     SUMMARY OF THE INVENTION 
     In a first aspect of the invention, a first method of manufacturing a dielectric material with a reduced dielectric constant is provided. The first method includes the steps of (1) forming a dielectric material layer including a trench on a substrate; and (2) forming a cladding region in the dielectric material layer by forming a plurality of air gaps in the dielectric material layer along at least one of a sidewall and a bottom of the trench so as to reduce an effective dielectric constant of the dielectric material. 
     In a second aspect of the invention, a first apparatus is provided. The first apparatus is a semiconductor device component that includes (1) a dielectric material layer including a trench on a substrate; and (2) a cladding region in the dielectric material layer, the cladding region including a plurality of air gaps in the dielectric material layer along at least one of a sidewall and a bottom of the trench so as to reduce an effective dielectric constant of the dielectric material. 
     In a third aspect of the invention, a first system is provided. The first system is a substrate that includes an semiconductor device component having (1) a dielectric material layer including a trench on a substrate; and (2) a cladding region in the dielectric material layer, the cladding region includes a plurality of air gaps in the dielectric material layer along at least one of a sidewall and a bottom of the trench so as to reduce an effective dielectric constant of the dielectric material. Numerous other aspects are provided in accordance with these and other aspects of the invention. 
     Other features and aspects of the present invention will become more fully apparent from the following detailed description, the appended claims and the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         FIG. 1  illustrates a cross-sectional side view of a substrate following a first step of a method of manufacturing a dielectric material with a reduced dielectric constant (k) in accordance with an embodiment of the present invention. 
         FIG. 2  illustrates a cross-sectional side view of the substrate following a second step of the method of manufacturing a dielectric material with a reduced k in accordance with an embodiment of the present invention. 
         FIG. 3  illustrates a cross-sectional side view of the substrate following a third step of the method of manufacturing a dielectric material with a reduced k in accordance with an embodiment of the present invention. 
         FIG. 4  illustrates a cross-sectional side view of the substrate following a fourth step of the method of manufacturing a dielectric material with a reduced k in accordance with an embodiment of the present invention. 
         FIG. 5  illustrates a cross-sectional side view of the substrate following a fifth step of the method of manufacturing a dielectric material with a reduced k in accordance with an embodiment of the present invention. 
         FIG. 6  illustrates a cross-sectional side view of the substrate following a sixth step of the method of manufacturing a dielectric material with a reduced k in accordance with an embodiment of the present invention. 
         FIG. 7  illustrates a cross-sectional side view of the substrate following a seventh step of the method of manufacturing a dielectric material with a reduced k in accordance with an embodiment of the present invention. 
         FIG. 8  illustrates a cross-sectional side view of a simulation model of an interconnect structure that may be formed. 
         FIG. 9  illustrates a cross-sectional side view of a simulation model of an interconnect structure with a cladding region that may be formed in accordance with an embodiment of the present invention. 
         FIG. 10  illustrates a graph of results from a simulation of the simulation model of an interconnect structure that may be formed in accordance with an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     The present invention provides a dielectric material with a reduced dielectric constant (k) and methods of manufacturing the same. Such a dielectric material may be employed while forming semiconductor device components. For example, in some embodiments, the present invention provides and includes interconnect structures and methods of manufacturing the same. Specifically, the present invention provides an interconnect structure having a cladding region formed on one or more sides of an interconnect included therein. The cladding region may be included in the dielectric material region formed on one or more sides of the interconnect. The cladding region may include the dielectric material and gaps of air, process gases and/or the like. Consequently, an effective k of the cladding region may be lower than a k of the dielectric material in the remaining portions of the dielectric material region, thereby reducing an effective k of the dielectric material. Further, a mechanical strength of the cladding region may be greater than the mechanical strength of a dielectric material with a similar k. Consequently, CMP may be employed to form such interconnect. In this manner, the present invention provides and includes improved interconnect structures and methods of manufacturing the same. 
       FIG. 1  illustrates a cross-sectional side view of a substrate  100  following a first step of a method of manufacturing a dielectric material with a reduced dielectric constant (k) in accordance with an embodiment of the present invention. With reference to  FIG. 1 , a substrate  100  may be provided. Chemical vapor deposition (CVD), spin-on, or another suitable method may be employed to form a dielectric (e.g., silicon oxide doped with carbon and/or hydrogen elements (SiO(C,H)) and/or the like) material layer  102  on the substrate  100 . The dielectric material layer  102  may have a k of about 2.9 (although a layer of another suitable material with a different k may be employed). CVD, spin-on, or another suitable method may be employed to deposit a hard mask layer (e.g., silicon nitride (Si 3 N 4 ), silicon dioxide (SiO 2 ) and/or the like)  104  on a top surface of the dielectric material layer  102 . Reactive ion etching (RIE) or another suitable method may be employed to remove portions of the dielectric material layer  102  and hard mask layer  104  so as to form an interconnect trough  106 . The interconnect trough  106  may serve as a region in which conductive material (e.g., copper, aluminum, tungsten and/or the like) may be formed. In this manner, the dielectric material layer  102  may be patterned and etched to form a metal line pattern. The interconnect trough  106  may have dimensions with a width of about 500 to about 1500 angstroms (Å) and a depth of about 500 to about 5000 Å (although a larger or smaller and/or different width and/or depth may be employed). 
       FIG. 2  illustrates a cross-sectional side view of the substrate  100  following a second step of the method of manufacturing a dielectric material with a reduced k in accordance with an embodiment of the present invention. With reference to  FIG. 2 , CVD, spin-on, or another suitable method may be employed to form (e.g., conformably) a sacrificial layer of P+ doped silicon material (e.g., amorphous, polycrystalline and/or the like) on the patterned layers  102 ,  104  of the substrate  100 . The sacrificial layer of P+ doped silicon material may have a thickness of about 3 nm to about 100 nm (although a larger or smaller and/or different thickness range may be employed). Thereafter, anodization employing an anodization current or another suitable method may be employed to convert (e.g., chemically) the P+ doped silicon material layer into a porous silicon layer  200  having pores  201 . For example, the substrate  100  may be placed in an electrically-biased hydrofluoric (HF) or similar solution. The porosity of the porous silicon layer  200  may vary based on the density of the P+ dopant, the anodization current and/or the like. The porosity may range from about 10% to about 50% (although a larger or smaller and/or different porosity may be employed). As described below, the porous silicon layer  200  may be employed to form air gaps in portions of the dielectric material layer  102 . 
       FIG. 3  illustrates a cross-sectional side view of the substrate  100  following a third step of the method of manufacturing a dielectric material with a reduced k in accordance with an embodiment of the present invention. With reference to  FIG. 3 , oxidation or another suitable method may be employed to convert the porous silicon layer  200  into an oxide (e.g., SiO 2 ) layer  300 . Such reaction may be represented by the following formula: Si+O 2 →SiO 2 . For example, the substrate  100  may be exposed to a high-pressure unbiased oxygen (e.g., O 2  and/or the like) plasma treatment or another suitable process. During oxidation, oxygen may diffuse through pores ( 201  in  FIG. 2 ) in the porous silicon layer  200  so as to form protrusions  302  of an oxide (e.g., SiO 2 ) material in the dielectric material layer  102  behind the oxidizing porous layer. Such reaction may be represented by the formula: SiO(C,H)+O 2 →SiO 2 . The protrusions  302  may be about 5 Å in diameter and about 200 Å in length (although a larger or smaller diameter and/or length may be employed). The oxide layer  300  created by the high-pressure unbiased O2 plasma anisotropically penetrates normal to sidewalls of the dielectric material layer  102 . 
       FIG. 4  illustrates a cross-sectional side view of the substrate  100  following a fourth step of the method of manufacturing a dielectric material with a reduced k in accordance with an embodiment of the present invention. With reference to  FIG. 4 , a dilute HF wet etch (e.g., with a very high selectivity to SiO(C,H)) or another suitable method may be employed to remove all or substantially all of the oxide layer  300  and the protrusions  302  so as to form air gaps  400  in the dielectric material layer  102 . The dilute HF wet etch may be equivalent to removing an SiO(C,H) damage layer in a conventional BEOL process. The air gaps  400  may be 5 Å in diameter and about 200 Å in length (although a larger or smaller diameter and/or length may be employed). In this manner, a cladding region  402  that includes the air gaps  400  may be formed in the dielectric material layer  102 . The cladding region  402  will be adjacent or proximate an interconnect (e.g., metal wiring) subsequently formed in the interconnect trough  106 . The air gaps  400  may have a k of about 1.0 (although larger or smaller k may be employed). Consequently, the cladding region  402  may have an effective k that is less than the k of the dielectric material. For example, the cladding region  402  may have an effective k of less than about 2.0, and remaining portions of the dielectric material layer  102  may have a k of about 2.9 (although the cladding region  402  and/or the dielectric material may have a larger or smaller k). Further, the cladding region  402  and remaining portions of the dielectric material layer  102  may be mechanically-strong. For example, CMP or other such BEOL processes may be employed on the substrate  100  without damaging the cladding region  402  and remaining portions of the dielectric material layer  102 . 
       FIG. 5  illustrates a cross-sectional side view of the substrate  100  following a fifth step of the method of manufacturing a dielectric material with a reduced k in accordance with an embodiment of the present invention. With reference to  FIG. 5 , physical vapor deposition (PVD) or another suitable method may be employed to form a diffusion barrier (e.g., tantalum nitride (TaN), titanium nitride (TiN), ruthenium (Ru) and/or the like) layer  500  on the top surface of the dielectric material layer  102 . The thickness of the diffusion barrier layer  500  may be about 2 to about 80 nm (although a larger or smaller and/or different thickness may be employed). The diffusion barrier layer  500  may cover openings  502  of the air gaps  400  on at least one surface of the interconnect trough  106 . The diffusion barrier layer  500  may be employed to prevent material (e.g., copper (Cu) and/or the like) from diffusing into the dielectric material layer  102  and/or entering the voids  400  via the openings  502 , thereby sealing a surface of the dielectric material layer  102 . 
       FIG. 6  illustrates a cross-sectional side view of the substrate  100  following a sixth step of the method of manufacturing a dielectric material with a reduced k in accordance with an embodiment of the present invention. With reference to  FIG. 6 , as part of metal damascene processing CVD, electroplating or another suitable method may be employed to form a metal (Cu, aluminum (Al), Cu with Al impurities Cu(Al), tungsten (W) and/or the like) interconnect layer  600  on a top surface of the substrate  100 . In this manner, the metal interconnect layer  600  may fill the interconnect trough ( 106  in  FIG. 5 ). The thickness of the metal interconnect layer  600  on a top surface of the barrier layer  500  may be about 400 to about 1000 nm (although a larger or smaller and/or different thickness may be employed). 
       FIG. 7  illustrates a cross-sectional side view of the substrate  100  following a seventh step of the method of manufacturing a dielectric material with a reduced k in accordance with an embodiment of the present invention. With reference to  FIG. 7 , CMP or another suitable method may be employed to remove hard mask layer  104  and portions of the metal interconnect layer  600  and the barrier deposition layer  500  so as to form a metal interconnect  700 . A top surface of the metal interconnect  700  may be planar with a top surface of the dielectric material layer  102 . During CMP, a force may be applied to a top surface of the substrate  100  which may induce mechanical stresses in the dielectric material layer  102  and/or the cladding region  402 . The dielectric material layer  102  and the cladding region  402  may be mechanically-strong enough to withstand the mechanical stresses without failure. 
     The cladding region  402  adjacent the metal interconnect  700  may reduce the capacitance (e.g., parasitic capacitance) of the metal interconnect  700 . The capacitance of the metal interconnect  700  may be based on the effective k of the cladding region  402 . As discussed above, the cladding region  402  may have a k that is less than the k of remaining portions of the dielectric material layer  102 . Consequently, then effective capacitance of the entire dielectric material layer  102  may be reduced by the cladding region  402 . 
       FIG. 8  illustrates a cross-sectional side view of a simulation model of an interconnect structure that may be formed. With reference to  FIG. 8 , a simulation tool or environment (e.g., finite-element capacitance estimator (Foxi/Fierce) and the like) may be employed to simulate a model of an interconnect structure  800 . The simulation model of the interconnect structure  800  may be employed to accurately predict BEOL and front end of line (FEOL) capacitances of the simulated model of the interconnect structure  800  over a range of semiconductor technologies. 
     A first metal line  801  and a second metal line  802  (e.g., in an M3 wiring level) may be disposed in a dielectric (e.g., SiCOH and/or the like) layer  804 . The dielectric layer  804  may be disposed between a first metal layer  806  (e.g., an M4 wiring layer) and a second metal layer  808  (e.g., an M2 wiring layer). The dielectric layer  804  may have a k of about 3.2. 
     A distance between a top surface of the first metal line  801  and a bottom surface of the first metal layer  806  may be about 160 nm. A distance between a bottom surface of the first metal line  801  and a top surface of the second metal layer  808  may be about 160 nm. A distance between a right side surface of the first metal line  801  and a left side surface of the second metal line  802  may be about 100 nm. The respective widths of the first metal line  801  and the second metal line  802  may be about 100 nm. The respective heights of the first metal line  801  and the second metal line  802  may be about 175 nm. It should be noted that the first and second metal lines  801 - 802  are not adjacent a cladding region  402  of dielectric material that includes air gaps as described above. 
     The dielectric layer  804  may serve as an electrical insulator and/or the like during electrical simulations by the simulation tool or environment. More specifically, the dielectric layer  804  may serve as an electrical insulator between the first metal line  801 , the second metal line  802 , the first metal layer  806  and/or the second metal layer  808 . The first metal line  801 , the second metal line  802 , the first metal layer  806  and second metal layer  808  may serve as conductors and/or the like during a simulation by the simulation tool or environment. 
     Furthermore, the simulation tool or environment may calculate a line-to-line capacitance (C l-l ) of the first metal line  801 . Such C l-l  may be a capacitance of the first metal line  801  with respect to the second metal line  802  or another adjacent line in the same level. The calculated result of the line-to-line capacitance of the first metal line  801  may be 68.6 aF/μm. The simulation tool or environment may also calculate a total capacitance (C tot ) of the first metal line  801 . Such C tot  may be the capacitance of the first metal line  801  with respect to neighboring lines (e.g., the second metal line  802 , lines in the first metal layer  806  and the second metal layer  808 ). The calculated total capacitance of the metal line  801  may be 181.9 aF/μm. 
       FIG. 9  illustrates a cross-sectional side view of a simulation model of an interconnect structure  900  with a cladding region that may be formed in accordance with an embodiment of the present invention. With reference to  FIG. 9 , the interconnect structure  900  may be similar to the interconnect structure  800 . However, in contrast, the interconnect structure  900  may include a cladding region (e.g., voided SiCOH and/or the like)  902  disposed on at least one side of the first metal line  801  and/or the second metal line  802 . As depicted, the cladding region  902  may be disposed on a plurality (e.g., three) sides of the first metal line  801  and a plurality (e.g., three) sides of the second metal line  802 . The cladding region  902  may have an effective k of 1.5. This represents slightly more than 50% of the volume of the converted SiO(C,H) being occupied by voids. The dimensions of the cladding region  900  may be varied during simulation. 
       FIG. 10  illustrates a graph  1000  of results from a simulation of the simulation model of an interconnect structure  900  that may be formed in accordance with an embodiment of the present invention. With reference to  FIG. 10 , a plot of the C tot  and the C l-l  of the first metal line  801  with respect to the thickness of the cladding region  902  is depicted. A base case C l-l  dashed line  1001 , a base case C tot  dashed line  1002 , a C l-l  curved line  1004 , and a C tot  curved line  1006  are depicted. The base case C l-l  dashed line  1001 , and the base case C tot  dashed line  1002  may represent the capacitances, C l-l  and C tot , of the first metal line  801  in the interconnect structure  800 . The C l-l  curved line  1004  and the C tot  curved line  1006  may depict the capacitances, C l-l  and C tot , of the first metal line  801  with a cladding region  902  with respect to the thickness of the cladding region  902 . From the data depicted in the graph  1000 , an inverse relationship between the C l-l  curved line  1004  and the thickness of the cladding region  902  and between the C tot  curved line  1006  and the thickness of the cladding region  902  may be observed. Specifically, the graph  1000  illustrates as the thickness of the cladding region  902  increases, there may be a decrease in the capacitances, C l-l  and C tot , of the metal line  800 . For example, for a cladding layer thickness of 20 nm, the interconnect structure  900  provides a reduction of nearly 25% in total M3 wiring capacitance (e.g., C tot ) compared to the interconnect structure  800 . 
     In this manner, the present invention may preserve the mechanical strength of a dielectric material which includes a high-porosity structure (e.g., the cladding region  402 ) of the dielectric material in a volume adjacent a conductor (e.g., metal wire). Such structure may reduce a capacitance on the conductor. 
     The foregoing description discloses only exemplary embodiments of the invention. Modifications of the above disclosed apparatus and method which fall within the scope of the invention will be readily apparent to those of ordinary skill in the art. For instance, although in embodiments above the dielectric material layer  102  includes SiO(C,H), in other embodiments the dielectric material layer  102  may include additional and/or different materials. Although the dielectric material with a reduced dielectric constant (k) described above is employed for BEOL applications such as forming an interconnect structure, such a dielectric material may be employed to form a different semiconductor device component. 
     Accordingly, while the present invention has been disclosed in connection with exemplary embodiments thereof, it should be understood that other embodiments may fall within the spirit and scope of the invention, as defined by the following claims.

Technology Category: 5