Abstract:
A method for forming a metal silicate as a high k dielectric in an electronic device, comprising the steps of: providing diethylsilane to a reaction zone; concurrently providing a source of oxygen to the reaction zone; concurrently providing a metal precursor to the reaction zone; reacting the diethylsilane, source of oxygen and metal precursor by chemical vapor deposition to form a metal silicate on a substrate comprising the electronic device. The metal is preferably hafnium, zirconium or mixtures thereof. The dielectric constant of the metal silicate film can be tuned based upon the relative atomic concentration of metal, silicon, and oxygen in the film.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional Patent Application Ser. No. 60/809,255 filed May 30, 2006. 
    
    
     BACKGROUND OF THE INVENTION 
     The electronics fabrication industry uses metal silicate films of zirconium or hafnium in the fabrication of electronic devices, such as used for high dielectric constant materials and gate dielectric films. 
     Metal silicates for electronic materials have been studied by those skilled in the art. For instance, Wilk, et. al., Hafnium and Zirconium silicates for advanced gate dielectrics, Journal of Applied Physics, Vol. 87, No. 1, 2000, pp. 484-492 describe the use of metal silicates as gate dielectric films with varying metal contents. Depositions were by sputtering and e-beam evaporation. Separate films were deposited at specific temperatures chosen over the range of 25° C. to 600° C. 
     U.S. Pat. No. 6,841,439 identifies metal silicates as desirable gate dielectric films and describes various synthesis routes. 
     US Pat. Appl. Pub. No. US 2005/0139937 A1 Pub. Date: Jun. 30, 2005, describes the growth of hafnium silicate films by atomic layer deposition, a process whereby the hafnium, silicon, and oxygen sources are alternately fed to and purged from the deposition chamber. The growth rates of the atomic layer deposition process are very low. 
     The present invention overcomes this deficiency by co-feeding the metal, silicon, and oxygen sources simultaneously to the deposition chamber in a chemical vapor deposition. 
     BRIEF SUMMARY OF THE INVENTION 
     One embodiment of the present invention is a method for forming a metal silicate as a high k dielectric in an electronic device, comprising the steps of: providing diethylsilane to a reaction zone; concurrently providing a source of oxygen to the reaction zone; concurrently providing a metal precursor to the reaction zone; reacting the diethylsilane, source of oxygen and metal precursor by chemical vapor deposition to form a metal silicate on a substrate. 
     Another embodiment of the present invention is a method for forming hafnium silicate as a high k dielectric in an electronic device, comprising the steps of:
         providing diethylsilane to a reaction zone;   concurrently providing a source of oxygen to the reaction zone;   concurrently providing tetrakis(diethylamino)hafnium to the reaction zone;   reacting the diethylsilane, source of oxygen and tetrakis(diethylamino)hafnium by chemical vapor deposition to form hafnium silicate on a substrate comprising the electronic device.       

     Another embodiment of the present invention is a method for forming zirconium silicate as a high k dielectric in an electronic device, comprising the steps of:
         providing diethylsilane to a reaction zone;   concurrently providing a source of oxygen to the reaction zone;   concurrently providing tetrakis(diethylamino)zirconium to the reaction zone;   reacting the diethylsilane, source of oxygen and tetrakis(diethylamino)zirconium by chemical vapor deposition to form zirconium silicate on a substrate comprising the electronic device.       

     The present invention also shows that the metal silicate film dielectric constant can be tuned based upon the relative atomic concentration of metal, silicon, and oxygen in the film. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
         FIG. 1  shows the absorbance as a function of Wavenumbers (cm −1 ) for films deposited from: a zirconium oxide film from Zr(N(CH 2 CH 3 ) 2 ) 4  alone—V1519; a silicon oxide film from Diethylsilane alone—V1522; and a zirconium silicate film from Zr(N(CH 2 CH 3 ) 2 ) 4  and Diethylsilane—V1525; in accordance with Table III. 
         FIG. 2  shows the index of refraction of Hf—Si—O films as a function of the flow rate (sccm) of SiH 2 (CH 2 CH 3 ) 2 ; in accordance with Table V. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The present invention is directed to the formation of metal silicates as high k dielectrical for an electronic device. The metal, silicon, and oxygen sources are simultaneously fed to the deposition chamber in a chemical vapor deposition. Among the silicon sources, diethylsilane has been selected in the deposition of metal silicate films in the present invention. The growth rate of the metal silicate is faster than that achieved by atomic layer deposition. Lower carbon contamination in metal silicate films are found as compared with our previously reported and demonstrated process, U.S. Pat. No. 6,537,613 (which is hereby specifically incorporated by reference in their entirety herein), that uses silicon amides as the silicon source. Lower carbon contamination results in higher dielectric constants. Another benefit is that silicon incorporation into these films can be achieved at lower process temperatures as compared with a process that uses silicon amides as the silicon source; the thermal process budget is reduced (and, thus, process cost is reduced). And most importantly, the present invention also shows that the dielectric constant of the metal silicate film can be tuned based upon the atomic concentration of metal, silicon, and oxygen in the film. 
     A Chemical Vapor Deposition (CVD) system is configured to simultaneously receive metal precursor feed by Direct Liquid Injection (DLI) (converted to vapor before the reaction zone), silicon precursor vapor feed by Vapor Draw, and oxygen reactant gas feed into the reaction zone above the heated substrate. The temperature and pressure of the reaction zone are established; and the precursor vapor and reactant gas flows are established prior to introduction into the reaction zone. A substrate is introduced into the reaction zone and allowed to equilibrate to the temperature and pressure of the reaction zone. The precursor vapor and reactant gas flows are introduced into the reaction zone and are allowed to flow for a time sufficient to grow a metal silicate film. 
     The operating conditions are: pressure ranging from 0.5 to 2 Torr; substrate temperature ranging from 250° C.-450° C.; DLI vaporizer temperature ranging from 85° C.-95° C.; metal precursor flow rate ranging from 0.05 to 0.1 ml/min; helium carrier gas flow ranging from 100 to 150 sccm (Standard Cubic Centimeters per Minute); silicon precursor flow rate ranging from 5 to 100 sccm; helium dilution gas flow rate ranging from 0 to 50 sccm, residence time ranging from 0.05 to 2 seconds. 
     WORKING EXAMPLES 
     The present invention is illustrated in the following examples. 
     Example 1  
     Zr—Si—O Thin Film  
     Reactants used in the Zr—Si—O thin film deposition were: 
     1) Tetrakis(DiEthylAmino)Zirconium(IV)—TDEAZ, Zr(N(CH 2 CH 3 ) 2 ) 4 ; 
     2) diethylsilane—DES (LTO-410), SiH 2 (CH 2 CH 3 ) 2 ; and 
     3) oxygen, O 2 . 
     Liquid Tetrakis(DiEthylAmino)Zirconium(IV) was delivered at 0.1 mL per minute to a direct liquid injection system with subsequent a vaporization at a temperature of 90° C. using a helium sweep gas flow of 100 sccm into a manifold that feeds a precursor delivery ring situated below the gas showerhead in a single wafer, cold wall LPCVD reactor. Diethylsilane vapor was simultaneously delivered at 6.3 sccm through a 100 sccm nitrogen Mass Flow Controller (MFC) (equivalent to 18 sccm full scale flow of diethylsilane) into the aforementioned manifold. Flows of oxygen varied between 100 sccm and 150 ccm, were delivered to the showerhead of this reactor. These three flows were simultaneously directed onto a silicon wafer that was maintained at temperatures between 250° C. and 450° C. on a resistively heated wafer pedestal. The reactor chamber pressure was varied between 1 Torr and 1.5 Torr. 
     Table I shows the process parameters required to deposit a ZrO 2  film from Zr(N(CH 2 CH 3 ) 2 ) 4  and O 2 ; “TDEAZ Only”. 
     Table II shows the process parameters required to deposit a SiO 2  film from SiH 2 (CH 2 CH 3 ) 2  and O 2 ; “DES Only”. 
     Table III shows the process parameters required to deposit a Zr—Si—O film by simultaneously delivering Zr(N(CH 2 CH 3 ) 2 ) 4 , SiH 2 (CH 2 CH 3 ) 2  and O 2  to the reaction chamber; “TDEAZ and DES”. 
     As shown in Table I, a high deposition rate and high index of refraction were obtained for ZrO 2  film. 
     As shown in Table II, a relatively lower index of refraction was obtained from SiO 2  film. The deposition rate varied. 
     Table III indicates a relatively lower deposition rate of the zirconium silicate film. The index of refraction of Zr—Si—O film is much higher than the index of refraction of SiO 2  film, and thus the high dielectric constant k of Zr—Si—O film. 
     
       
         
               
             
               
               
               
               
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
               
               
               
               
             
           
               
                 TABLE I 
               
             
             
               
                   
               
               
                 TDEAZ Only 
               
             
          
           
               
                   
                 Wafer 
                   
                   
                   
                   
                   
                 Run 
                 Index 
                   
                 Dep 
               
               
                   
                 Temp 
                 Press 
                 DLI 
                 He Swp 
                 DES 
                 O 2   
                 time 
                 of Ref. 
                 Thickness 
                 Rate 
               
               
                 Run 
                 (° C.) 
                 (mTorr) 
                 (ml/min) 
                 (sccm) 
                 (sccm) 
                 (sccm) 
                 (min) 
                 n 
                 (Å) 
                 (Å/min) 
               
               
                   
               
             
          
           
               
                 V1519 
                 296 
                 1000 
                 0.1 
                 100 
                 0 
                 100 
                 2.5 
                 2.146 
                 2618 
                 1047 
               
               
                 V1520 
                 316 
                 1000 
                 0.1 
                 100 
                 0 
                 100 
                 1.2 
                 2.143 
                 1857 
                 1592 
               
               
                 V1521 
                 277 
                 1000 
                 0.1 
                 100 
                 0 
                 100 
                 3.5 
                 2.092 
                 2412 
                 689 
               
               
                   
               
             
          
         
       
     
     
       
         
               
             
               
               
               
               
               
               
               
               
               
               
               
             
           
               
                 TABLE II 
               
             
             
               
                   
               
               
                 DES Only 
               
             
          
           
               
                   
                 Wafer 
                   
                   
                   
                   
                   
                 Run 
                 Index 
                   
                 Dep 
               
               
                   
                 Temp 
                 Press 
                 DLI 
                 He Swp 
                 DES 
                 O 2   
                 time 
                 of Ref. 
                 Thickness 
                 Rate 
               
               
                 Run 
                 (° C.) 
                 (mTorr) 
                 (ml/min) 
                 (sccm) 
                 (sccm) 
                 (sccm) 
                 (min) 
                 n 
                 (Å) 
                 (Å/min) 
               
               
                   
               
               
                 V1522 
                 400 
                 variable 
                 0 
                 0 
                 variable 
                 100 
                 na 
                 1.444 
                 variable 
                 variable 
               
               
                   
               
             
          
         
       
     
     
       
         
               
             
               
               
               
               
               
               
               
               
               
               
               
             
               
             
               
               
               
               
               
               
               
               
               
               
               
             
           
               
                 TABLE III 
               
             
             
               
                   
               
               
                 TDEAZ and DES 
               
             
          
           
               
                   
                   
                   
                   
                   
                   
                   
                   
                 Index 
                   
                   
               
               
                   
                 Wafer 
                   
                   
                   
                   
                   
                 Run 
                 of 
                   
                 Dep 
               
               
                   
                 Temp 
                 Press 
                 DLI 
                 He Swp 
                 DES 
                 O 2   
                 time 
                 Ref. 
                 Thickness 
                 Rate 
               
               
                 Run 
                 (° C.) 
                 (mTorr) 
                 (ml/min) 
                 (sccm) 
                 (sccm) 
                 (sccm) 
                 (min) 
                 n 
                 (Å) 
                 (Å/min) 
               
               
                   
               
             
          
           
               
                 DES injected through ring 
               
             
          
           
               
                 V1525 
                 405 
                 1500 
                 0.1 
                 100 
                 6.3 
                 100 
                 1.5 
                 1.942 
                 923 
                 615 
               
               
                 V1526 
                 405 
                 1500 
                 0.1 
                 150 
                 6.3 
                 100 
                 1.5 
                 1.882 
                 931 
                 621 
               
               
                 V1527 
                 405 
                 1500 
                 0.1 
                 100 
                 6.3 
                 150 
                 2 
                 1.711 
                 606 
                 303 
               
               
                   
               
             
          
         
       
     
       FIG. 1  shows the individual FTIR spectra of the ZrO 2 , SiO 2 , and the Zr—Si—O films superimposed on each other. Run V1519 is the spectrum of the ZrO 2  film. The absorbance at 1545 wavenumbers is the indication of a Zr—O—Zr stretch. Run V1522 is the spectrum of the SiO 2  film. The absorbance at 1074 wavenumbers is the characteristic of the Si—O—Si stretch. Run V1525 is the spectrum of the Zr—Si—O film; it exhibits the characteristic peaks of both the individual oxides, and thus indicates the characteristics of a Zr—Si—O film. 
     Example 2  
     Hf—Si—O Thin Film  
     Similar experiments as shown in Example 1 have been performed for Hf—Si—O thin film. Note that, chemical properties of Hafnium and Zirconium are very similar since they belong to the same group in the periodic table. 
     Reactants used in the Hf—Si—O thin film deposition were: 
     1) Tetrakis(DiEthylAmino)Hafnium(IV)—TDEAH, Hf(N(CH 2 CH 3 ) 2 ) 4 ; 
     2) diethylsilane—DES (LTO-410), SiH 2 (CH 2 CH 3 ) 2 ; and 
     3) oxygen, O 2 . 
     Liquid Tetrakis(DiEthylAmino)Hafnium(IV) was delivered at 0.1 mL per minute to a direct liquid injection system with subsequent a vaporization at a temperature of 90° C. using a helium sweep gas flow of 100 sccm into a manifold that feeds a precursor delivery ring situated below the gas showerhead in a single wafer, cold wall LPCVD reactor. Diethylsilane vapor was simultaneously delivered at 6.3 to 45 sccm through a 500 sccm nitrogen MFC (equivalent to 90 sccm full scale flow of diethylsilane) into the aforementioned manifold. Flows of oxygen varied between 75 sccm and 100 sccm, were delivered to the showerhead of this reactor. These three flows were simultaneously directed onto a silicon wafer that was maintained by heater set point, which was at 650° C. and 700° C., on a resistively heated wafer pedestal. The reactor chamber pressure was varied between 0.5 Torr and 1.5 Torr. 
     Table IV shows the process parameters required to deposit an HfO 2  film from Hf(N(CH 2 CH 3 ) 2 ) 4  and O 2 ; “TDEAH Only”. 
     
       
         
               
             
               
               
               
               
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
               
               
               
               
             
           
               
                 TABLE IV 
               
             
             
               
                   
               
               
                 TDEAH Only 
               
             
          
           
               
                   
                   
                   
                   
                   
                   
                   
                 Index 
                   
                   
                   
               
               
                   
                 Wafer 
                   
                   
                 He 
                   
                 Run 
                 of 
                   
                   
                 FTIR 
               
               
                   
                 Temp 
                 Press 
                 DLI 
                 Swp 
                 O 2   
                 time 
                 Ref. 
                 Thickness 
                 Dep Rate 
                 Peak 
               
               
                 Run 
                 (° C.) 
                 (mTorr) 
                 (ml/min) 
                 (sccm) 
                 (sccm) 
                 (min) 
                 n 
                 (Å) 
                 (Å/min) 
                 (cm −1 ) 
               
               
                   
               
             
          
           
               
                 V1541 
                 255 
                 1000 
                 0.1 
                 100 
                 100 
                 5 
                 1.954 
                 784 
                 156.8 
                 1582.6 
               
               
                   
                   
                   
                   
                   
                   
                   
                 1.957 
                 810 
                 162.0 
                 1583 
               
               
                   
                   
                   
                   
                   
                   
                   
                 2.177 
                 891 
                 178.2 
                 2210 
               
               
                 V1542 
                 253 
                 1000 
                 0.1 
                 100 
                 100 
                 5 
                 1.959 
                 737 
                 147.4 
                 1574 
               
               
                   
                   
                   
                   
                   
                   
                   
                 1.968 
                 850 
                 170.0 
                 2210 
               
               
                   
                   
                   
                   
                   
                   
                   
                 1.972 
                 918 
                 183.6 
               
               
                   
               
             
          
         
       
     
     Table V shows the process parameters required to deposit a Hf—Si—O film by simultaneously delivering Hf(N(CH 2 CH 3 ) 2 ) 4 , SiH 2 (CH 2 CH 3 ) 2  and O 2  to the reaction chamber; “TDEAH and DES”. 
     Again, as for the Zi—Si—O films, Table IV indicates that the index of refraction of Hf—Si—O film is much higher than the index of refraction of SiO 2  film, and thus the high dielectric constant k of Hf—Si—O film. 
     Most importantly, Table V also indicates that the index of refraction of Hf—Si—O films vary with the relative concentration (represented by the flow rates) of hafnium, silicon, and oxygen used in the CVD process. 
     As an example,  FIG. 2  shows the index of refraction of Hf—Si—O films as a function of the flow rate (sccm) of SiH 2 (CH 2 CH 3 ) 2 , in accordance with Table V. The silicon precursor flow rate varied from 6.3 sccm to 25 sccm; while the other conditions were kept unchanged. The pressure was at 1.5 Torr; the wafer temperature was at 492° C.; metal (Hafnium) precursor flow rate was at 0.1 ml/min; helium carrier gas flow was at 100 sccm; helium dilution gas flow rate was at 0 sccm; and oxygen flow rate was at 100 sccm. 
     
       
         
               
             
               
               
               
               
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
               
               
               
               
             
           
               
                 TABLE V 
               
             
             
               
                   
               
               
                 TDEAH and DES 
               
             
          
           
               
                   
                   
                   
                   
                   
                   
                   
                   
                   
                   
                 Index 
               
               
                   
                 Wafer 
                   
                   
                   
                   
                 He 
                 Dep 
                 Dep 
                 Thick- 
                 of 
               
               
                   
                 Temp 
                 Press 
                 DLI 
                 DES 
                 O 2   
                 dilute 
                 Time 
                 Rate 
                 ness 
                 Ref. 
               
               
                 Run 
                 (° C.) 
                 (Torr) 
                 (ml/min) 
                 (sccm) 
                 (sccm) 
                 (sccm) 
                 (min) 
                 (Å/min) 
                 (Å) 
                 n 
               
               
                   
               
             
          
           
               
                 1443-47-1 
                 492 
                 1.5 
                 0.1 
                 6.3 
                 100 
                 — 
                 1.5 
                 898 
                 1347 
                 1.9201 
               
               
                 1443-47-2 
                 492 
                 1.5 
                 0.1 
                 6.3 
                 100 
                 — 
                 1.5 
                 1068 
                 1602 
                 1.9246 
               
               
                 1443-48-1 
                 492 
                 1.5 
                 0.1 
                 10.3 
                 100 
                 — 
                 1.5 
                 1031 
                 1546 
                 1.8983 
               
               
                 1443-48-2 
                 492 
                 1.5 
                 0.1 
                 14.3 
                 100 
                 — 
                 1.5 
                 999 
                 1499 
                 1.8459 
               
               
                 1443-48-3 
                 492 
                 1.5 
                 0.1 
                 14.3 
                 100 
                 — 
                 1.6 
                 1093 
                 1748 
                 1.8451 
               
               
                 1443-48-4 
                 492 
                 1.5 
                 0.1 
                 25 
                 100 
                 — 
                 1.5 
                 1477 
                 2216 
                 1.7599 
               
               
                 1443-48-5 
                 492 
                 1.5 
                 0.1 
                 25 
                 100 
                 — 
                 1 
                 1417 
                 1417 
                 1.7870 
               
               
                 1443-49-1 
                 523 
                 1.5 
                 0.1 
                 25 
                 100 
                 30 
                 1 
                 879 
                 879 
                 1.7881 
               
               
                 1443-49-2 
                 523 
                 1.5 
                 0.1 
                 25 
                 100 
                 15 
                 1 
                 1366 
                 1366 
                 1.7558 
               
               
                 1443-49-3 
                 523 
                 1.5 
                 0.1 
                 25 
                 75 
                 15 
                 1 
                 831 
                 831 
                 1.7095 
               
               
                 1443-49-4 
                 523 
                 1.5 
                 0.1 
                 25 
                 75 
                 30 
                 2.5 
                 1408 
                 3519 
                 1.8332 
               
               
                 1443-50-1 
                 523 
                 1.5 
                 0.1 
                 25 
                 75 
                 30 
                 1 
                 570 
                 570 
                 1.6874 
               
               
                 1443-50-2 
                 523 
                 1.5 
                 0.1 
                 25 
                 75 
                 30 
                 2.5 
                 578 
                 1444 
                 1.7707 
               
               
                 1443-50-3 
                 523 
                 1.5 
                 0.1 
                 25 
                 75 
                 0 
                 1 
                 164 
                 164 
                 1.3200 
               
               
                 1443-50-4 
                 511 
                 1 
                 0.1 
                 25 
                 100 
                 0 
                 1 
                 1357 
                 1357 
                 1.8047 
               
               
                 1443-50-5 
                 493 
                 0.5 
                 0.1 
                 25 
                 100 
                 0 
                 1 
                 1061 
                 1061 
                 1.8920 
               
               
                 1443-50-6 
                 493 
                 0.5 
                 0.1 
                 25 
                 100 
                 5 
                 1 
                 1049 
                 1049 
                 1.9014 
               
               
                 1443-51-1 
                 493 
                 0.5 
                 0.05 
                 25 
                 100 
                 5 
                 1 
                 792 
                 792 
                 2.0525 
               
               
                 1443-51-2 
                 511 
                 1 
                 0.1 
                 45 
                 100 
                 15 
                 1 
                 1084 
                 1084 
                 1.7652 
               
               
                 1443-51-3 
                 511 
                 1 
                 0.1 
                 45 
                 100 
                 10 
                 1 
                 1321 
                 1321 
                 1.7887 
               
               
                   
               
             
          
         
       
     
     The salient feature shown in  FIG. 2  is the index of refraction of the Hf—Si—O films (thus the dielectric constant of the Hf—Si—O film) decreases approximately linearly as the flow rate of the silicon precursor (thus the relative atomic concentration of silicon) increases. Therefore,  FIG. 2  clearly indicates that the dielectric constant of hafnium silicate films can be tuned based upon the atomic concentration of hafnium, silicon, and oxygen in the film. 
     The embodiments of the present invention listed above, including the working examples, are exemplary of numerous embodiments that may be made of the present invention. It is contemplated that numerous other configurations of the process may be used, and the materials used in the process may be selected from numerous materials other than those specifically disclosed. In short, the present invention has been set forth with regard to particular embodiments, but the full scope of the present invention should be ascertained from the claims as follow.