Abstract:
A method of forming interconnect structures in a semiconductor device, comprising the following steps. A semiconductor structure is provided. In the first embodiment, at least one metal line is formed over the semiconductor structure. A silicon-rich carbide barrier layer is formed over the metal line and semiconductor structure. Finally, a dielectric layer, that may be fluorinated, is formed over the silicon-rich carbide layer. In the second embodiment, at least one fluorinated dielectric layer, that may be fluorinated, is formed over the semiconductor structure. The dielectric layer is patterned to form an opening therein. A silicon-rich carbide barrier layer is formed within the opening. A metallization layer is deposited over the structure, filling the silicon-rich carbide barrier layer lined opening. Finally, the metallization layer may be planarized to form a planarized metal structure within the silicon-rich carbide barrier layer lined opening.

Description:
This is a division of patent application Ser. No. 09/594,415, filing date Jun. 16, 2000, now U.S. Pat. No. 6,429,129, Method Of Using Silicon Rich Carbide As A Barrier Material For Flourinated Materials, assigned to the same assignee as the present invention. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates generally to forming interconnect structures in semiconductor devices, and more specifically to methods of incorporating fluorinated amorphous carbon and fluorocarbon polymers in the formation of interconnect structures in semiconductor devices. 
     BACKGROUND OF THE INVENTION 
     The miniaturization of microelectronic devices and the need for higher speeds have created a demand for low dielectric constant (low-k) materials. Fluorinated amorphous carbon and fluorocarbon polymer films exhibit excellent low dielectric constant properties due to the incorporation of less polarizable fluorine atoms. 
     One of the primary concerns with these films is that they release fluorine upon heating. Materials, such as Ta, TaN, Ti, TiN, and Al, etc., in contact with these films may react with the fluorine and/or fluorine bearing species thereby compromising the interfacial adhesion between the films and materials. 
     Thus, a fluorine diffusion barrier is needed for the integration of fluorinated low-k materials. 
     U.S. Pat. No. 5,817,572 to Chiang et al. describes a method for forming interconnections for semiconductor fabrication and semiconductor devices. In one embodiment, a silicon carbide (SiC) etch barrier is used in a dual damascene process. 
     U.S. Pat. No. 5,744,817 to Shannon describes a hot carrier transistor and a method of making a hot carrier transistor wherein the emitter region films  20   a ,  20   b  may comprise silicon-rich amorphous silicon carbide. 
     U.S. Pat. No. 5,736,457 to Zhao describes a method of making a single or dual damascene process where an IMD layer  105  may be comprised of SiC. 
     U.S. Pat. No. 3,830,668 to Dearnaley et al. describes a method of forming electrically insulating layers in semi-conducting materials. A block of SiC is irradiated with protons to form a layer or radiation damage and releases a certain amount of carbon impurity atoms from their substitutional-sites. The structure is irradiated with low energy electrons and then annealed in which the released carbon atoms migrate and precipitate in the region of the radiation-damaged layer. 
     U.S. Pat. No. 5,891,803 to Gardner describes a dual damascene process with a dielectric layer  340  that may be comprised of SiC. 
     SUMMARY OF THE INVENTION 
     Accordingly, it is an object of the present invention to provide a method of forming a barrier layer for use with fluorinated dielectric layers and/or intermetal dielectric layers (IMDs). 
     Another object of the present invention to provide a method of forming a barrier layer for use with fluorinated dielectric layers and/or intermetal dielectric layers (IMDs) that blocks diffusion of fluorine through the barrier layer. 
     Other objects will appear hereinafter. 
     It has now been discovered that the above and other objects of the present invention may be accomplished in the following manner. Specifically, a semiconductor structure is provided. In the first embodiment, at least one metal line is formed over the semiconductor structure. A silicon-rich carbide barrier layer is formed over the metal line and semiconductor structure. Finally, a fluorinated dielectric layer is formed over the silicon-rich carbide layer. In the second embodiment, at least one fluorinated dielectric layer is formed over the semiconductor structure. The fluorinated dielectric layer is patterned to form an opening therein. A silicon-rich carbide barrier layer is formed within the opening. A metallization layer is deposited over the structure, filling the silicon-rich carbide barrier layer lined opening. Finally, the metallization layer may be planarized to form a planarized metal structure within the silicon-rich carbide barrier layer lined opening. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The features and advantages of the present invention will be more clearly understood from the following description taken in conjunction with the accompanying drawings in which like reference numerals designate similar or corresponding elements, regions and portions and in which: 
     FIGS. 1 to  3  schematically illustrate in cross-sectional representation a first embodiment of the present invention. 
     FIG. 4 is an enlarged portion of FIG. 3 within the dashed line box  4 — 4 . 
     FIGS. 5 and 6 schematically illustrate in cross-sectional representation a second embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     First Embodiment—Al/Low-k Scheme 
     Accordingly as shown in FIG. 1, starting semiconductor structure  10  is understood to possibly include a semiconductor wafer or substrate, active and passive devices and interconnects and contact plugs formed within the wafer, conductive layers and dielectric layers (e.g., inter-poly oxide (IPO), intermetal dielectric (IMD), etc.) formed over the wafer surface. The term, “semiconductor structure” is meant to include devices formed within a semiconductor wafer and the layers overlying the wafer. Unless otherwise specified, all structures, layers, etc. may be formed or accomplished by conventional methods known in the prior art. A “low-k” material is any material that has a dielectric constant that is less than silicon oxide. 
     The upper surface of semiconductor structure  10  can be comprised of a dielectric layer, e.g. ILD layer, an ILD layer with conductive plugs exposed, an intermetal layer (IMD), or an IMD layer with metal plugs or lines exposed (not shown). 
     Metal lines  12 , for example, are formed over semiconductor structure  10 . Metal lines  12  may be formed from one or more materials selected from the group comprising aluminum (Al), aluminum-copper alloy (Al—Cu), copper (Cu), and tungsten (W) with a titanium (Ti)/titanium nitride (TiN) and/or tantalum nitride (TaN) metal barrier layer and are preferably formed of a aluminum-copper alloy (Al—Cu) with a titanium (Ti)/titanium nitride (TiN) barrier layer. For purposes of illustration, metal lines  12  will be considered to be comprised of aluminum-copper alloy (Al—Cu) with a barrier layer. 
     Although a line structure is formed, the present invention is not so limited and other structures may be formed and used with the present invention. 
     As shown in FIG. 2, silicon-rich carbide (SRC) layer  14  is formed over Al—Cu lines  12  and semiconductor structure  10  to form a barrier layer. Barrier layer  14  is from about 30 to 2000 Å thick, and is more preferably from about 100 to 500 Å thick. 
     SRC layer  14  is formed within a plasma enhanced chemical-vapor deposition (PECVD) chamber (not shown) by varying the ratio of silane (SiH 4 ) and the source of carbon (such as C2H2, CH4, C2H6, etc.). The ratio of silane to the source of carbon may be from 0.05 to 10. Alkyl- and aryl-substituted silane precursors (e.g. (CCH 3 )SiH 3 ) may be used instead of silane. 
     Alternatively, SRC layer  14  may be formed by physical vapor deposition (PVD) on a magnetron sputtering equipment using a graphite target and silane gas. The main sputtering parameters are: power—between about 1 and 20 kW; magnetic field—between about 20 and 200 Gauss; temperature—between about 20 and 500° C.; and pressure—between about 0.1 and 1000 mTorr. 
     SRC layer  14  has a dielectric constant of from about 4.0 to 7.0. The parameters for forming SRC layer  14  are: temperature—from about 250 to 450° C., and more preferably about 400° C.; pressure—from about 0.01 to 10 Torr, and more preferably from about 0.5 to 2 Torr; time—from about 1 to 200 seconds, and more preferably from about 3 to 10 seconds; and microwave or RF power call be capacitively coupled to plasma at from about 200 to 5500W, and more preferably at about 1000W. 
     Alternatively, SRC layer  14  may be formed by physical vapor deposition (PVD) on a magnetron sputtering equipment using a graphite target and silane gas. The main sputtering parameters are: power—between about 1 and 20 kW; magnetic field—between about 20 and 200 Gauss; temperature—between about 20 and 500° C.; and pressure—between about 0.1 and 1000 mTorr. 
     Dielectric layer, or ILD,  16  is deposited over SRC barrier layer  14 . Dielectric layer  16  may be comprised of any low-k dielectric material, more preferably a fluorinated dielectric material such as fluorosilicate glass (FSG), and most preferably a fluorinated polyimide, amorphous fluorocarbon, polytetra-fluoroethylene (PTFE), Teflon® manufactured by DuPont, and parylene-F (PA-F). The fluorinated dielectric may be deposited through vapor deposition or spin-coating following by thermal treatment. For purposes of illustration, dielectric layer  16  will be considered to be comprised of a fluorinated dielectric. 
     SRC barrier layer  14  prevents diffusion of any fluorine released from fluorinated dielectric layer  16  into Al—Cu lines  12  as will be described below. 
     Fluorinated dielectric layer  16  has a dielectric constant from about 1.5 to 3.5. 
     Further, the adhesion between silicon-rich carbide barrier layer  14  and fluorinated dielectric layer  16 ,  16 ′ is good due to the high chemical compatibility between silicon carbide and carbon-containing species. 
     As shown in FIG. 3, fluorinated dielectric layer  16  may be planarized to form planarized fluorinated dielectric layer  16 ′. Although not shown, an undoped silicon dioxide (oxide) is typically deposited over fluorinated dielectric layer  16  prior to planarization by chemical mechanical polishing (CMP). This is done because not only is the CMP rate of the oxide layer is faster than a fluorinated dielectric material layer, but also CMP is not well established nor compatible with fluorinated organic low-k material. 
     Second Embodiment—Cu/Low-k Dual Damascene Scheme 
     As shown in FIG. 5, starting semiconductor structure  100  is understood to possibly include a semiconductor wafer or substrate, active and passive devices formed within the wafer, conductive layers and dielectric layers (e.g., inter-poly oxide (IPO), intermetal dielectric (IMD), etc.) formed over the wafer surface. The term “semiconductor structure” is meant to include devices formed within a semiconductor wafer and the layers overlying the wafer. Unless otherwise specified, all structures, layers, etc. may be formed or accomplished by conventional methods known in the prior art. A “low-k” material is any material that has a dielectric constant that is less than silicon oxide. 
     The upper surface of semiconductor structure  100  can be comprised of a dielectric layer, e.g. ILD layer, an ILD layer with conductive plugs exposed, an intermetal layer (IMD), or an IMD layer with metal plugs or lines exposed (not shown) or a conductor such as copper. 
     Dual damascene opening  102 , for example, is then formed within first and second planarized dielectric layers  104 ,  110 , respectively, separated by optional etch stop layer  106 , over semiconductor structure  100 . Optionally, a cap layer III may be formed over second planarized dielectric layer  110  and a passivation layer  113  may be formed over semiconductor structure  100 . 
     Cap layer  111 , etch stop layer  106 , and passivation layer  113  are typically comprised of silicon nitride. 
     First and second planarized dielectric layers  104 ,  110  may be any low-k dielectric material, more preferably a fluorinated dielectric material such as fluorosilicate glass (FSG), and most preferably a fluorinated dielectric material such as a fluorinated polyimide, amorphous fluorocarbon, polytetra-fluoroethylene (PTFE), Teflon® manufactured by DuPont, and parylene-F (PA-F). For purposes of illustration, first and second dielectric layers  104 ,  110  will be considered to be comprised of a fluorinated dielectric. 
     Although a dual damascene structure is formed, the present invention is not so limited and a single damascene structure, for example, or other structure may be formed. 
     First and second fluorinated dielectric layer  104 ,  110  each have a dielectric constant from about 1.5 to 3.0. 
     As shown in FIG. 6, silicon-rich carbide (SRC) barrier layer  112  is formed over the structure of FIG. 5, lining dual damascene opening  102 . SRC barrier layer  112  is from about 30 to 2000 Å thick, and more preferably from about 100 to 500 Å thick. 
     SRC barrier layer  112  is formed within a plasma enhanced chemicalvapor deposition (PECVD) chamber (not shown) by varying the ratio of Silane (SiH 4 ) and the source of carbon (such as C 2 H 2 , CH 4 , C 2 H 6 , etc.). The ratio of silane to the source of carbon may be from about 0.05 to 10. 
     SRC layer  112  may also be formed by physical vapor deposition (PVD) with a magnetron sputtering equipment using a graphite target and silane gas. The power is form about 1 and 20 kW; the magnetic field is between about 20 and 200 Gauss; the temperature is from about 20 and 500° C.; and the pressure is from about 0.1 and 1000 mTorr, 
     SRC layer  112  has a dielectric constant of from about 4 to 7. The parameters for forming SRC layer  112  are: temperature—from about 250 to 450° C., and more preferably about 400° C.; pressure—from about 0.01 to 10 Torr, and more preferably from about 0.5 to 2 Torr; time—from about 1 to 200 seconds, and more preferably from about 3 to 10 seconds; and microwave or RF power can be capacitively coupled to plasma at from about 200 to 5500W, and more preferably at about 1000W. 
     Metal barrier layer  114  is then formed over SRC layer  114  within dual damascene opening  102 . Metal barrier layer  114  may be comprised of Ta, TaN, Ti, TiN, W, WN, Mo, or MoN, etc. Metal barrier layer  114  may be from about 50 to 2000 Å thick. 
     A metallization layer is then deposited over the structure and planarized to form metal plug  116 . Metal plug may be comprised of Al, W, Ti, or Cu and is preferably Cu. For purposes of illustration, metal plug  116  will be considered to be comprised of copper (Cu). 
     Metal barrier layer  114  prevents diffusion of Cu into first and/or second fluorinated dielectric layers  104 ,  110 . 
     SRC barrier layer  112  prevents diffusion of any fluorine released from first and/or second fluorinated dielectric layers  104 ,  110  into metal barrier layer  114  as will be described below. 
     Further, the adhesion between silicon-rich carbide barrier layer  12  and first and second fluorinated dielectric layers  104 ,  110  is good due to the high chemical compatibility between silicon carbide and carbon-containing species. 
     Phases of SRC Barrier Layer  14 —Common to Both Embodiments 
     Common to both the first and second embodiment, and as shown in FIG. 4 (for example an enlarged portion of FIG. 3 within dashed line box  4 — 4 ) silicon-rich carbide (SRC) barrier layer, or film,  14  (and SRC barrier layer  112 ) includes two distinct phases: silicon islands  50 ; and PECVD silicon carbide  60 . 
     Due to a high reaction tendency between fluorine and silicon elements, silicon island regions  50  in SRC layer  14  act as a “sink” that attracts and traps any fluorine atoms released from fluorinated layers  16 ,  16 ′;  104 ,  110  and prevents them from migrating or diffusing to any adjacent metal layer  12 ,  114  and thus reacting and compromising the interfacial adhesion between the films. 
     SUMMARY 
     The present invention provides a fluorine diffusion barrier  14 ,  112  than can be used in both Al—Cu/low-k and Cu/low-k metallization technology. SRC barrier layer  14 ,  112  allows the use of fluorine-containing low-k materials, i.e. fluorinated dielectric layers  16 ,  16 ′;  104 ,  110 , as interlevel dielectrics (ILD) and intermetal dielectrics (IMD). Heretofore, such low-k fluorinated dielectric materials could not be used as ILDs and IMDs because of their fluorine reaction with metal layers, and their poor adhesion with metal layers. 
     While particular embodiments of the present invention have been illustrated and described, it is not intended to limit the invention, except as defined by the following claims.