Abstract:
A method for reducing contaminants in a processing chamber  10  having chamber plasma processing region components comprising the following steps. The chamber plasma processing region components are cleaned. The chamber is then seasoned as follows. A first USG layer is formed over the chamber plasma processing region components. An FSG layer is formed over the first USG layer. A second USG layer is formed over the FSG layer. Wherein the USG, FSG, and second USG layers comprise a UFU season film. A UFU season film coating the chamber plasma processing region components of a processing chamber comprises: an inner USG layer over the chamber plasma processing region components; an FSG layer over the inner USG layer; and an outer USG layer over the FSG layer.

Description:
FIELD OF THE INVENTION  
         [0001]    The present invention relates generally to fabrication of integrated circuit devices and specifically to methods of cleaning/seasoning reaction chambers used in the processes to fabricate integrated circuit devices.  
         BACKGROUND OF THE INVENTION  
         [0002]    In high temperature plasma processes, such as high-density plasma (HDP), and chemical vapor deposition (CVD) processes, the likelihood that undesirable mobile ion and metal contaminants will be driven out of the reaction chamber components increases. Therefore the chamber components and the exposed surface of the wafer chucks are seasoned, or coated, to minimize these undesirable mobile ion and metal contaminants and to also protect these parts/surfaces during the necessary cleaning processes.  
           [0003]    HDP-CVD Processing Chamber  
           [0004]    [0004]FIG. 1 illustrates a cross-sectional view of a typical HDP-CVD processing chamber  10 . Processing chamber  10  includes chamber body  12  supporting dielectric dome  14  on its upper edge: Chamber body  12  functions as an anode and may be composed of aluminum, for example. Inductive coil  16  insulated within insulative coil holder  18 , is positioned around dielectric dome  12  to provide an inductive plasma source. Conducting, or semi-conducting; chamber lid  20  is supported on the upper surface of dielectric dome  14  and functions as another anode. An electrostatic chuck  22  is positioned in the lower part of chamber  10  and supports substrate  24  during processing. Insulative dielectric material ring  26  surrounds the outer perimeter of chuck  22  to prevent arcing between chuck  22  and the grounded chamber walls. Insulative ring  26  may be comprised of a ceramic, for example.  
           [0005]    Gases enter chamber  10  through gas inlets (not shown) positioned around the perimeter of chamber body  12  and in chamber lid  20  above chuck  22 . Chamber  10  is exhausted through exhaust passage  28  outward of the outer edge of chuck  22  by an exhaust pump (not shown). A throttle and gate valve assembly control pressure within chamber  10  by controlling the exhaust of gases out of chamber  10 .  
           [0006]    An RF voltage is provided through inductive coil  16  (source RF) to generate a high density plasma (HDP). The RF voltage applied to coil  16  excite the gas introduced into chamber  10  into a plasma state. Additionally, an RF voltage may be coupled to chamber lid  20  to provide a bias RF signal into chamber  10 .  
           [0007]    Depending upon the application, precursor gases may be introduced into chamber  10  to deposit a material onto substrate  24 , or etch material from substrate  24 , to form integrated circuits (IC) on substrate  24 .  
           [0008]    Contaminant Material  
           [0009]    Chamber lid  20 , ceramic ring  26 , dielectric dome  14 , enclosure wall  12  and gas inlets form part of the plasma processing region and are sources of contaminant material which may be volatilized into the gas phase under operating conditions within chamber  10 , thereby contaminating the processing environment. For example mobile ions such as Na, Li and K, and metal particles such as Fe, Cr, Ar, Ni and Mg may be leached out of chamber components  20 ,  26 ,  14 ,  12  when a capacitive or an inductive plasma is struck in chamber  10 . Such mobile ions and/or metal particles, when incorporated into the deposited films, compromise the structural integrity and electrical performance of the devices formed on substrate  24 . Also, deposits on chamber components  20 ,  26 ,  14 ,  12  can buildup after a series of substrates  24  have been processed that can flake off and become another source of particles that can damage the circuits.  
           [0010]    Chamber Cleaning/Seasoning  
           [0011]    Such particle contamination within chamber  10  is controlled by periodically cleaning chamber  10  using cleaning gases, usually fluorinated compounds and inductively and capacitively coupled plasmas. Once the chamber has been sufficiently cleaned of the process gases and the cleaning by-products have been exhausted out of chamber  10 , a season step is performed to deposit a layer of material onto components  20 ,  26 ,  14 ,  12  of chamber  10  forming the processing region to seal the contaminants and reduce the contamination level during processing. The cleaning step is typically carried out by depositing a film to coat the interior surfaces forming the processing region.  
           [0012]    Silane gas may be used to deposit a layer of silicon dioxide onto components  20 ,  26 ,  14 ,  12 : 
           SiH 4 +O 2 →SiO 2 +2 H 2   
           [0013]    Silicon tetrafluoride may likewise be used to deposit a layer of silicon oxyfluoride: 
           SiF 4 +O 2 →SiO x F y   
           [0014]    Other season films may also be used.  
           [0015]    For example, U.S. Pat. No. 5,811,356 to Murugesh et al and U.S. Pat. No. 6,020,035 to Gupta et al. describe seasoning processes involving fluorinated silica glass (FSG) layers.  
           [0016]    U.S. Pat. No. 6,060,397 to Seamons et al. and U.S. Pat. No. 6,014,979 to Van Autryve et al. describe seasoning processes.  
           [0017]    U.S. Pat. No. 5,976,900 to Qiao et al. describes a method whereby a phosphorous and/or a boron coating film is used after cleaning.  
         SUMMARY OF THE INVENTION  
         [0018]    Accordingly, it is an object of the present invention to utilize a sandwich USG/FSG/USG (UFU) chamber season film regimen for high temperature chamber processing.  
           [0019]    Another object of the present invention is to improve the particle performance of the FSG season film.  
           [0020]    A further object of the present invention is to increase the available time of HDP FSG CVD machine (M/C) result from particle down.  
           [0021]    Yet another object of the present invention is to maintain a minimal statistical deviation of fluorine concentration ([F]) within the FSG layer of a UFU chamber season film.  
           [0022]    Other objects will appear hereinafter.  
           [0023]    It has now been discovered that the above and other objects of the present invention may be accomplished in the following manner. Specifically, the chamber plasma processing region components of a processing chamber are cleaned. The chamber is then seasoned as follows. A first USG layer is formed over the chamber plasma processing region components. An FSG layer is formed over the first USG layer. A second USG layer is formed over the FSG layer. Wherein the USG, FSG, and second USG layers comprise a UFU season film. A UFU season film coating the chamber plasma processing region components of a processing chamber comprises: an inner USG layer over the chamber plasma processing region components; an FSG layer over the inner USG layer; and an outer USG layer over the FSG layer.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0024]    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:  
         [0025]    [0025]FIG. 1 is a schematic view of an HDP-CVD process chamber.  
         [0026]    [0026]FIG. 2 is a flow diagram illustrating the method of the present invention.  
         [0027]    [0027]FIG. 3A is an enlarged view of the process chamber wall portion of FIG. 1 designated “FIG. 3A” illustrating the formation of the UFU seasoning film in accordance with the present invention.  
         [0028]    [0028]FIGS. 3B and 3C, with FIG. 3A, illustrate the preferred embodiment of the present invention.  
         [0029]    [0029]FIG. 4 is a table comparison of the particle count for the STD Clean Process (UF) known to the inventors and the present invention UFU Season Film for 2× Clean (UFU).  
         [0030]    [0030]FIG. 5 is a graph comparison of the particle count for the STD Clean Process known to the inventors and the present invention UFU Season Film for 2× Clean.  
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0031]    Unless otherwise specified, all structures, layers, steps, methods, etc. may be formed or accomplished by conventional steps or methods known in the prior art.  
         [0032]    Accordingly, FIG. 2 is a flow chart of the method of the present invention. That is: (1) two production runs are conducted within chamber  10  (i.e. two sets of wafers are processed within chamber  10 ); (2) the chamber plasma processing region components ( 20 ,  26 ,  14 ,  12  and the gas inlets (not shown)) are then cleaned; (3) a first undoped silica glass (USG) layer  30  is formed upon the cleaned chamber plasma processing region components; (4) a thin doped fluorine silica glass (FSG) layer  32  is formed upon the first USG layer; (5) a second USG layer  34  is then formed upon the FSG layer  32  to complete formation of UFU season film  50 .  
         [0033]    [0033]FIGS. 3A to  3 C illustrate cross-sectional schematic views of the preferred method in forming season film  50  in accordance with the present invention. It is noted that although only a portion of chamber body  12  wall is specifically illustrated in FIGS. 3A to  3 C, season film  50  is formed on all of chamber plasma processing region components  20 ,  26 ,  14 ,  12  and the gas inlets (not shown). FIG. 3A is an enlarged view of the portion of FIG. 1 denoted as “FIG. 3A.” 
         [0034]    The method of the present invention allows for two production runs wit hi chamber  10  before cleaning/seasoning steps are required. After two production runs, the chamber plasma processing region components ( 20 ,  26 ,  14 ,  12  and the gas inlets (not shown)) are cleaned by an appropriate process/method. The preferred chamber cleaning method used if UFU season film for two production runs.  
         [0035]    Formation of UFU Season Film  50   
         [0036]    As shown in FIG. 3A, a first undoped silica glass (USG) layer  30 , preferably having a thickness of from about 900 to 1100 Å, more preferably from about 950 to 1050 Å, and most preferably about 1000 Å, is formed upon the cleaned chamber plasma processing region components ( 20 ,  26 ,  14 ,  12  and the gas inlets (not shown)) under the following conditions:  
                                       Season - 1           about 20 seconds by time   Ar-side about 95 sccm       turbo about 50 mT   Ar-top about 15 sccm       about 3500 W RF, about 1W side-RF   O 2 -side about 270 sccm       0W OFF   O 2 -top about 20 sccm           SiH 4 -side about 180 sccm           SiF 4  0 sccm                  
 
         [0037]    Thin doped fluorine oxide (fluorine silica glass (FSG)) season layer  32 , preferably having a thickness from about 270 to 330 Å, more preferably from about 285 to 315 Å, and most preferably about 300 Å, is them formed upon first USG layer  30  under the following conditions:  
                                       F Intro           about 3 seconds by time   Ar-side about 95 sccm       turbo about 50 mT   Ar-top about 15 sccm       about 3500 W RF, about 1W side-RF   O 2 -side about 270 sccm       0W OFF   O 2 -top about 20 sccm           SiH 4 -side about 180 sccm           SiF 4  about 5 sccm       F Purge       about 3 seconds by time   Ar-side about 95 sccm       turbo about 50 mT   Ar-top about 15 sccm       about 3500 W RF, about 1W side-RF   O 2 -side about 270 sccm       0W OFF   O 2 -top about 20 sccm           SiH 4 -side about 180 sccm           SiF 4  about 5 sccm                  
 
         [0038]    FSG layer  32  has a fluorine concentration ([F})) less than about 4% but greater than the [F} of the wafer.  
         [0039]    FSG layer  32  avoids fluorine deviation for fluorine concentration from wafer to wafer because [F] is controlled by diffusion mechanism instead of surface concentration limit. Furthermore, because the layer  34  is fluorine free, the diffusion and not the surface concentration controls.  
         [0040]    Second USG layer  34 , having a thickness of preferably from about 1350 to 1650 Å, more preferably from about 1450 to 1550 Å, and most preferably about 1500 Å, is then formed upon FSG film  32  under the following conditions:  
                                       Season - 2           about 32 seconds by time   Ar-side about 95 sccm       turbo about 50 mT   Ar-top about 15 sccm       about 3500 W RF, about 1W side-RF   O 2 -side about 270 sccm       0W OFF   O 2 -top about 20 sccm           SiH 4 -side about 180 sccm           SiF 4  0 sccm                  
 
         [0041]    Second USG layer  34  seals the weakened surface of FSG layer  32 , avoiding particle source.  
         [0042]    First USG layer  30 /FSG layer  32 /second USG layer  34  sandwich structure comprise UFU season film  50 .  
         [0043]    Standard Clean Process—A Process Known to the Inventors  
         [0044]    The standard clean process (STD Clean Process) (not shown) known to the inventors (not to be considered prior art) is a 1× clean process, i.e. the plasma processing region components are cleaned/seasoned after only a single production run. Under the STD Clean Process a single USG layer is formed upon the cleaned chamber plasma processing region components under the following conditions:  
                                       Season           about 45 seconds by time   Ar-side about 95 sccm       turbo about 50 mT   Ar-top about 15 sccm       about 3500 W RF, about 1W side-RF   O 2 -side about 270 sccm       0W OFF   O 2 -top about 20 sccm           SiH 4 -side about 180 sccm           SiF 4  0 sccm                  
 
         [0045]    An FSG layer is then formed upon the single USG layer under the following conditions:  
                                       F Intro           about 3 seconds by time   Ar-side about 95 sccm       turbo about 50 mT   Ar-top about 15 sccm       about 3500 W RF, about 1W side RF   O 2 -side about 270 sccm       0W OFF   O 2 -top about 20 sccm           SiH 4 -side about 180 sccm           SiF 4  about 5 sccm       F Purge       about 3 seconds by time   Ar-side about 95 sccm       turbo about 50 mT   Ar-top about 15 sccm       about 3500 W RF, about 1W side-RF   O 2 -side about 270 sccm       0W OFF   O 2 -top about 20 sccm           SiH 4 -side about 180 sccm           SiF 4  about 5 sccm                  
 
         [0046]    However, the STD Clean Process still has an unacceptable particle count (see below)  
         [0047]    Particle Performance: Present Invention UFU 2× Season versus STD Clean Process  
         [0048]    Wafer cassettes having wafers designated “Bare-0.2,” “FSG 8-6.5K,” and “FSG 8-6.5K” were sequentially loaded processed. One cassette of wafers designated as “FSG 8-6.5K” were processed under STD Clean Process and one cassette of wafers designated as “FSG 8-6.5K” were processed under the present invention UFU Season Film for 2× Clean with the wafers designated as “Bare-0.2” not so processed:  
                                                                 STD Clean Process               Particle Count (EA)   UFU Season Film for 2X Clean           Total Count/Area Count   Total Count/Area Count                                    Bare-0.2   104/3    0/1       FSG 8-6.5K   15/0    0/0       FSG 8-6.5K   4/1   1/0                  
 
         [0049]    Comparison of Particle Counts for STD Clean Process and UFU Season Film for 2× Clean  
         [0050]    [0050]FIG. 4 is a chart comparison of the particle count for the STD Clean Process (“UF”) known to the inventors and the present invention UFU Season Film for 2× Clean (“UFU”) by KLA scan (in-line data). (KLA is a kind of instrument for particle detection production wafer.)  
         [0051]    As evidenced by the FIG. 4 chart, the particle count (EA) when utilizing the UFU method of the present invention is markedly decreased for particle sizes equal to or smaller than about 0.5 μm. That is: for particle size&lt;0.3 μm, the average EA for the UF split condition is 3 while the average EA for the UFU split condition is but 0.333; and for particle size from about 0.3 to 0.5 μm, the average EA for the UF split condition is 2 while the average EA for the UFU split condition is but 0.2. The particle count (EA) is not improved for particle sizes larger than about 0.5 μm when utilizing the UFU method of the present invention.  
         [0052]    [0052]FIG. 5 is a graph comparison (special precise control (SPC) off-line data) of the particle count for the STD Clean Process (STD CLN Process) known to the inventors and the present invention UFU Season Film for 2× Clean (UFU Season Structure). The SPC defines any control limits for production parameters, including particle.  
         [0053]    Particle count (EA) is plotted versus wafer count (pieces) with the raw data for two runs when the present invention is utilized is shown to the right of the graph. As is evident, the particle count when then the instant UFU invention is greatly, and consistently reduced, compared to the STD Clean Process as shown on the left side of the graph for pieces 1, 2, 5, and 6, and when two runs utilizing the present are graphed to the right of the STD Clean Prqcess comparison for pieces 1, 2, 3, 7, 14, 15, 16, 23, 24, and 25.  
         [0054]    A further study of particle trend and total particle count by using the UFU season film  50  in accordance with the present invention as compared to a UF season film presented the following results for three cases:  
                                                                 Average of UF   Average of UFU                                    1.   12.2   10.5       2.   17.9   10.5       3.   18.8   9.7                  
 
         [0055]    [F] Concentration Variation  
         [0056]    It has been found that the variation of fluorine concentration ([F]) when using the UFU Season Film method of the present invention is acceptable as compared to no introduction of F in the season film, with F introduction in the exposed season film, and using the UFU Season Film method (USG/FSG/USG) shown below:  
                                                                             No Fluorine   With Fluorine               introduction   introduction   UFU Season Film                                        1 st  w/f   3.99   4.17   4.42           2 nd  w/f   4.23   4.19   4.46           Δ   +0.24   +0.02   +0.04                      
 
         [0057]    The F deviation of +0.24 when no F is introduced is too great, while the F deviation when using the UFU season film  50  of the present invention is acceptable as the F concentration is controlled by diffusion mechanism instead of surface concentration limit. The F concentration refers to the layer with fluorine introduction, which is the UF layer.  
         [0058]    Advantages of the Present Invention  
         [0059]    The advantages of the present invention include:  
         [0060]    1. for particle count performance, the particle count (EA) could decrease 10 EA from 10 EA to 10EA for mean value of off-line SPC and in-line KLA data;  
         [0061]    2. deviation of [F] is largely decreased by using UFU season film  50 ; and  
         [0062]    3. the FSG machine (M/C) capacity is increased.  
         [0063]    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.