Abstract:
The present invention provides a method of depositing a film on a surface of a coil that includes depositing a metal from a target onto a surface of a coil to form a first film on the surface and forming a second film over the first film at a low pressure and at a first power at the target that is substantially higher than a first power at the component&#39;s surface. The conditioned deposition tool is well suited for manufacturing integrated circuits.

Description:
TECHNICAL FIELD OF THE INVENTION  
         [0001]    The present invention is directed, in general, to a method of coil preparation for an ionized metal plasma process.  
         BACKGROUND OF THE INVENTION  
         [0002]    In the field of semiconductor device fabrication, the continuing trend toward smaller device feature sizes continues to challenge current process technologies. One such process that is currently employed to aid in achieving these small device dimensions is an ionized metal plasma (IMP) deposition process. Such IMP processes may be used to sputter deposit films of metal or metal-containing compounds and leads to better bottom and sidewall step coverage from the directionality afforded by the target/coil configuration in an IMP process for a variety of device structures. These advantages allow the use of relatively thinner films in forming the device features thereby saving on equipment and consumables and also significantly reducing the processing times for subsequent fabrication steps.  
           [0003]    Current IMP processes typically employ deposition chambers that have a coil that aids in the ionization of atoms as they are sputtered from the target. Commonly the coil is composed of the same material as the target. For example, for depositing a titanium or titanium-containing film on a wafer, the titanium is used as the coil material. When another film composition is desired, the coil is composed of the corresponding metal.  
           [0004]    During IMP deposition processes, the metal sputtered from the target builds up on the coil. It was discovered that this build-up of metal was a source of wafer contamination in that the built-up metal would often flake off of the coil and onto the wafer, thereby contaminating that particular level of the wafer. To reduce this contamination problem, the industry adopted a process of knurling the surface of the coil to increase adhesion of any metal deposited on the coil. Prior to use in conventional processing of semiconductor wafers, IMP coils are subjected to an extensive conditioning process, known as burn-in. During this conventional conditioning process, substantial quantities of material are deposited on the coil and on the walls of the deposition chamber. It had been thought that knurling of the coil surface provided sufficient adhesion between the deposited material and the coil surface.  
           [0005]    However, this knurling process has proven unsatisfactory in the manufacture of semiconductor devices because it has been found that these conventional methods do not prevent delamination or flaking of the deposited metal to a satisfactory degree, even where a coil having a knurled surface is used. This delamination or flaking is thought to be caused by non-uniformities, such as voids, that form at the interface of the coil and the deposited metal, which are illustrated in FIGS. 1A and 1B. FIG. 1A is a cut away view of a section of the coil after deposition of a metal thereon. As seen in FIG. 1B, which is an enlarged view of FIG. 1A, voids have formed at the interface of the coil and the deposited metal. It is believed that these voids cause deposited metal to adhere poorly to the coil, which in turn, causes the deposited metal to flake off prematurely and thus shorten the useful life of the coil. For example, while the useful life of a coil is rated at approximately 400 kWh by the manufacturer, delamination may be observed after the chamber has been operated only about 150 kWh. Even when operated for less than 150 kWh coils may show bubbles or blisters, indicating that the delamination process has begun. It is thought that these blisters result from poor adhesion between the coil surface and the layers deposited during the conditioning process. The poor adhesion eventually leads to blister formation and their subsequent delamination. In severe cases, the delamination may cause a particle concentration that uses shorts or arcing in the fabricated devices, thereby reducing the wafer yield. When the wafer yield is so affected, the chamber must be taken off-line, cleaned, and the coil replaced. Lowered wafer yield and unit down time ultimately reduce revenue and increase product cost.  
           [0006]    Accordingly, what is needed in the art is a process that improves adhesion and reduces delamination of the metal surface of the coil during operation.  
         SUMMARY OF THE INVENTION  
         [0007]    To address the above-discussed deficiencies of the prior art, the present invention provides a method of depositing a film on a surface of a component of a deposition tool. In an advantageous embodiment, the method includes depositing a metal from a target onto a component&#39;s surface of a deposition tool to form a first film on the component&#39;s surface and forming a second film over the first film at a low pressure and at a first power at the target that is substantially higher than a first power at the component&#39;s surface. In an exemplary embodiment the deposition tool may be a coil. It should, of course, be understood that the above process can be used for a processes for manufacturing integrated circuits.  
           [0008]    The foregoing has outlined, rather broadly, preferred and alternative features of the present invention so that those skilled in the art may better understand the detailed description of the invention that follows. Additional features of the invention will be described hereinafter that form the subject of the claims of the invention. Those skilled in the art should appreciate that they can readily use the disclosed conception and specific embodiment as a basis for designing or modifying other structures for carrying out the same purposes of the present invention. Those skilled in the art should also realize that such equivalent constructions do not depart from the spirit and scope of the invention in its broadest form.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0009]    For a more complete understanding of the present invention, reference is now made to the following descriptions taken in conjunction with the accompanying drawings, in which:  
         [0010]    [0010]FIG. 1A illustrates a coil-metal interface of an IMP coil prepared by conventional methods;  
         [0011]    [0011]FIG. 1B illustrates an enlarged view of FIG. 1A;  
         [0012]    [0012]FIG. 2 illustrates schematic representation of a deposition chamber for ionized metal processes;  
         [0013]    [0013]FIG. 3 illustrates a flowchart an embodiment of the present invention;  
         [0014]    [0014]FIG. 4 illustrates a schematic representation of a deposition tool formed by a embodiment of the present invention;  
         [0015]    [0015]FIG. 5A illustrates a cut away view of a deposition tool-metal interface of an IMP coil prepared by an embodiment of the present invention;  
         [0016]    [0016]FIG. 5B illustrates an enlarged view of FIG. 5A showing the uniform interface between the coil and the deposited metal; and  
         [0017]    [0017]FIG. 6 illustrates a schematic representation of an integrated circuit fabricated according to the principles of the present invention.  
     
    
     DETAILED DESCRIPTION  
       [0018]    Referring initially to FIG. 2, there is illustrated a deposition tool  200  which may be used to practice the present invention. The deposition tool  200  is suitable for ionized metal plasma deposition process. To that end, the deposition chamber  100  may includes various components, such as a vacuum chamber  210 , a shield  220 , a target  230 , or a coil  240 . While specific reference is made with respect to the coil  240 , it should be understood that the present invention may also be applicable to any of these components associated with the deposition tool  200 .  
         [0019]    In particular embodiments the target may comprise any material suitable for use as target  230  in a ionized metal plasma process. Particularly useful targets  230  may include a variety of materials such as aluminum, titanium, zirconium, vanadium, tantalum, molybdenum, or tungsten. However, the target material of the present invention is not limited to these materials since the method of the present invention may be applied to any material used as a target in ionized metal plasma deposition processes.  
         [0020]    One skilled in the art will also readily realize that the deposition tool  200  is capable of being operated at reduced pressures and various gas inputs and outputs for establishing, maintaining and monitoring the desired ambients present at different stages of the deposition process. The deposition tool  200  may also include a power supply  250  to apply a power to the target  230  and an RF power supply  260  to supply a power to the coil  240 .  
         [0021]    Now with Reference to FIG. 3 and continuing reference to FIG. 2, there is depicted a flow diagram of the method  300  that illustrates an embodiment of the present invention. Method  300  begins at Start Step  310  where the chamber of the deposition tool  200  is evacuated and readied for a conventional IMP process. Start Step  310  may be followed by First Deposition Step  320  wherein the a first film is deposited on the coil  240 . In an advantageous embodiment, First Deposition Step  320  may be followed by Erosion Step  330  where at least a substantial portion of the first film deposited in First Deposition Step  320  may be removed. In a more specific embodiment, the first film may be entirely removed, if so desired.  
         [0022]    Following the First Deposition Step  320  or Erosion step  330 , depending on the embodiment, a Second Deposition Step  340  is conducted in which a second film is deposited over either the first film or eroded surface, again depending on the embodiment. In other advantageous embodiments, Second Deposition Step  340  may be followed by a Third Deposition Step  350  wherein a third film is formed over the second film deposited in Second Deposition Step  340 . The film formed in Third Deposition Step  350  may comprise a single layer or a multilayer and may also comprise a metal, metal nitride, metal silicide, or metal silicide nitride. In an advantageous embodiment Third Deposition Step  350  produces an alternating metal/metal nitride multilayer. The process ends with Stop Step  360  after the final layer has been deposited. The specific requirements of each of these steps will be detailed below.  
         [0023]    Having discussed the general embodiments above, an example of a more specific advantageous embodiment will now be discussed. With continuing reference to FIGS. 2 and 3, FIG. 4 illustrates a schematic representation of the coil  400  formed according to the principles of the present invention. In a particular embodiment of the present invention, the First Deposition Step  320  may deposit a first film  430  on the surface  420  of a coil  240 . In an exemplary process for the preparation of a coil having a first metal of titanium, the deposition tool  200  may contain an argon ambient. Where a titanium nitride layer is also desired, the deposition tool  200  may contain an ambient including argon and nitrogen. One skilled in the art will recognize that other inert ambients may be employed and are not outside the scope of the present invention. In this exemplary process, the ambient may be maintained at a flow rate of about 25 sccm to about 30 scam and the pressure within the deposition tool  200  may be about 10 to about 15 mTorr when the metal is being deposited. To form at least a portion of the first film  430  on the coil  240 , an initially low power may be supplied from the power supply  250  to the target  230 . This low power setting may be about 500 watts and may be applied for about 300 seconds. After about 300 seconds the power to power supply  150  may be turned off to allow the target  230  and coil  240  to cool for about 60 seconds.  
         [0024]    In a subsequent burn step, the power supply  250  supplies a power of about 500 watts to the target while the RF power supply  260  applies a power from about 2000 to about 2500 watts to the coil. The power from RF power supply may be applied in a ramped manner. In a particular embodiment the RF power supply  260  is operated at a ramp of about 2000 watts/second to about 2500 watts/second. In this burn step the power to the power supply  250  and power supply  260  may be applied for about 180 seconds. Again, the power from the power supplies is turned off for about 60 seconds to allow the apparatus to cool. In certain embodiments, applying the power to the target  230  and coil  240  and subsequently cooling as discussed above may be repeated from 1-10 times. In an exemplary embodiment, the target and coil are both comprised of titanium. Thus, the first film may be a titanium film while the second film may be titanium, titanium nitride, or titanium silicide. It should be understood that the present invention is not limited to titanium inasmuch as other metals, such as aluminum, zirconium, vanadium, tantalum, molybdenum, tungsten and nitride and silicides, may also be used in a similar manner as just discussed for titanium.  
         [0025]    In a particularly useful embodiment this process may be repeated 7-10 times. After repeating this process as desired, the process of depositing the first film  430  may be continued by increasing the power applied to the target  230  to about 1000 watts and ramped at 2500 watts/second while that of the coil  240  is maintained as in the previous step. This burn step may be allowed to proceed for about 60 to about 120 seconds followed by a cooling period as described above. This alternating burning and cooling process step may also be repeated 7-10 times. In particular embodiments, the power applied to the target  230  during the repeated burn steps may be incrementally increased from 1000 watts to about 8000 watts to deposit material from the target  230  onto the coil  240 . One skilled in the art will understand that net deposition of portions of the first film  430  occurs where the power applied to the target  230  is greater than the power applied to the coil  240 . The First Deposition Step  320  may be terminated by cooling for 60 seconds and subsequently applying a vacuum to the deposition tool  200 . Thus, First Deposition Step  320  forms a first film  430  that includes a metal of which the target  230  is comprised on the surface  420  of the coil  240 . As discussed above, the first film  430  may comprise any material that may be suitable as a target  230  in an ionized metal plasma process. Particularly useful materials for this first film  430  include aluminum, titanium, zirconium, vanadium, tantalum, molybdenum, or tungsten. The particular steps of the First Deposition Step  320  of this exemplary embodiment of the present invention are detailed in Table 1.  
                                                   TABLE 1                           Exemplary Embodiment of First Deposition Step 320                    DC Power to Target   RF Power to Coil (W)/Ramp       Step   Time   (W)/Ramp (W/sec)   (W/sec)                    1   15   0/0   0/0       2   300   500/0    0/0       3   60   0/0   0/0       4   180   500/0    2000/2000       5   60   0/0   0/0       6   120   500/0    2500/2500       7   60   0/0   0/0       8       Repeat Steps 5-6           9   120   1000/0     2500/2500       10   60   0/0   0/0       11   120   2000/2000   2500/2500       12   60   0/0   0/0       13   120   3000/2000   2500/2500       14   60   0/0   0/0       15   60   4000/2000   2500/2500       16   60   0/0   0/0       17   60   5000/2000   2500/2500       18   60   0/0   0/0       19   60   6000/2000   2500/2500       20   60   0/0   0/0       21   60   8000/2000   2500/2500       22   60   0/0   0/0       23   3   0/0   0/0                  
 
         [0026]    One skilled in the art will appreciate that the first film  430  as formed above may be a considered a single layer although it is deposited in discrete portions or a multi-layer comprising multiple deposited layers of the target  230  material.  
         [0027]    In another aspect of the exemplary process discussed above, the First Deposition Step  320  above may be followed by an Erosion Step  330 . In other embodiments, Erosion Step  330  may be omitted. However, when employed, Erosion Step  330  erodes at least a portion of the first metal film  430 . In certain embodiments, the Erosion Step  330  erodes at least a substantial portion, if not all, of the first metal film  430 . For the purposes of this invention, at least a substantial portion means about 20%. Importantly, Erosion Step  330  should not substantially alter the surface structure, knurling, of the coil  240 . The Erosion Step  330  may be accomplished by a series of subsets as discussed below.  
         [0028]    Erosion Step  330  may begin by purging the deposition tool  200  for about 15 seconds with an inert ambient to establish a pressure of about 20 to 30 mTorr. Argon is a particularly useful ambient for this process and may be supplied at a rate of about 55 to about 60 sccm. Such flow rates permit faster erosion without increasing power to the coil. Thus, the power to the coil is applied from the RF power supply  260  at about 2750 watts. In preferred embodiments, the RF power supply  260  connected to the deposition tool operates in a non-ramped mode. Additionally, a relatively low power may then be applied to the target  230  from the power supply  250 . Advantageously, power supply  250  may be set at about 2250 watts in a non-ramping mode. These powers may be applied to the target  230  and coil  240  for about 180 seconds. Subsequently, the target  230  and coil  240  are allowed to cool for about 60 seconds. These erosion and cooling subsets may be repeated. In certain embodiments the erosion and cooling are repeated about 1 to about 20 times. In more particular embodiments the erosion and cooling may repeated about 10 to 15 times. After the final cooling step, the deposition tool may be subjected to a dynamic vacuum for about 3 seconds. Practiced in this manner, Erosion Step  330  may remove a substantial portion of the first metal film  430 . The particular steps of the Erosion Step  330  of an embodiment of the present invention are detailed in Table 2.  
                                                   TABLE 2                           Exemplary Embodiment of Erosion Step 330                Time   DC Power to Target   RF Power to Coil (W)/Ramp       Step   (sec)   (W)/Ramp (W/sec)   (W/sec)                    1   15   0/0   0/0       2   180   2250/0     2750/0         3   60   0/0   0/0       4       Repeat steps 2-3           5   3   0/0   0/0                  
 
         [0029]    Either the Erosion Step  330  just described or the First Deposition Step  320 , depending on the embodiment, may be followed by a Second Deposition Step  340  wherein the net effect is to form a second film  440  containing target  230  material over either the surface exposed by Erosion Step  330  or the first film. Again, the second film  430  may be formed by a series of substeps. In a particularly useful embodiment, after the deposition tool  200  is purged with argon and a pressure of about 5 to about 15 mTorr is maintained with a gas-flow rate of about 15 to about 20 sccm, the power supply  250  applies a power of 7000 watts to the target  230 . In an advantageous embodiment, the flow rate may be about 16 sccm and the pressure may be about 8 or about 9 mTorr. In this step the power supply  250  may be operated in a ramped mode at 7000 watts/sec. Substantially lower power without ramping may be applied to the coil  240 . In the exemplary embodiment the RF power supply  260  supplies no power to the coil  240 . This step continues for about 120 seconds and is followed by a cooling step that lasts for about 30 seconds. One skilled in the art will realize that the net effect of these steps just described will be to form a second film  440  over either the first film  430  or the exposed surface of the first film  430  where the Erosion Step  330  is conducted. In exemplary embodiments, the deposition and cooling as described above may be repeated 20-30 times. Again, the Second Deposition Step  340  is completed by exposing the deposition tool  200  to a dynamic vacuum for about 3 seconds. While the second metal film  440  may be formed in discrete portions, one skilled in the art will understand that it may be considered a single layer. Thus, due to the reduced coil power of this exemplary process step, thermal stressing of the coil and deposited layers is reduced. The reduction in thermal stressing reduces or substantially eliminates porosity of the deposited layers and concomitantly reduces premature delamination of the coil. A particular embodiment of this portion of the method of the present invention is detailed in Table 3.  
                                                   TABLE 3                           Exemplary Embodiment of Second Deposition Step 340                Time   DC Power to Target   RF Power to Coil (W)/       Step   (sec)   (W)/Ramp (W/sec)   Ramp (W/sec)                    1   15   0/0   0/0       2   120   7000/7000   0/0       3   30   0/0   0/0       4       Repeat steps 2-3           5   30   0/0   0/0                  
 
         [0030]    In a further aspect, various method embodiments the present invention may include a Third Deposition Step  350  for forming a third film  450  over the second film  440 . The third film  450  may be a single layer or a multilayer and may comprise a metal or a metal nitride layer. Particularly useful materials comprising the third film  450  are metals and metal nitrides. Desirable metals include, but are not limited to, aluminum, titanium, zirconium, vanadium, tantalum, molybdenum or tungsten. Useful metal nitrides include, but are not limited to, aluminum nitride, titanium nitride, zirconium nitride, vanadium nitride, tantalum nitride, molybdenum nitride or tungsten nitride. In other embodiments the third film  450  may be a metal silicide or a metal silicide nitride. Exemplary metal silicides and metal silicide nitrides include titanium silicide, zirconium silicide, vanadium silicide, tantalum silicide, molybdenum silicide or tungsten silicide, and the metal silicide nitride is titanium silicide nitride, zirconium silicide nitride, vanadium silicide nitride, tantalum silicide nitride, molybdenum silicide nitride or tungsten silicide nitride. However, one skilled in the art will realize that the process for forming the third film  450  is not limited to these materials.  
         [0031]    The third film  450  may be formed in an inert atmosphere at a by applying a power of 8000 watts ramped at 2000 watts/second to the target  230  and a substantially lower power to the coil  240  without ramping. In a particular embodiment no power is applied to the coil  240 . In advantageous embodiments, forming metal portions of the third film  450  may be performed for about 60 seconds. However, one skilled in the art will realize that the amount of material deposited is a function of the powers applied to the target  230  and coil  240  as well as the duration of the process and that these parameters may be optimized without undue experimentation.  
         [0032]    Where an exemplary titanium film is desired is the formation of third film  450 , argon may be used as the ambient and may be supplied at a rate of 55 sccm to about 60 sccm during the process. In an advantageous embodiment the argon flow rate may be about 58 sccm. Where an exemplary titanium nitride layer is desired in the formation of third film  450 , the ambient of the deposition tool  200  is adjusted to maintain an argon flow rate of about 20 scam to about 30 scam and a nitrogen flow rate of about 40 sccm to 50 sccm. An advantageous process may deposit titanium nitride at an argon flow rate of about 25 scam and a nitrogen flow rate of about 45 sccm. In an alternative embodiment the nitrogen flow rate may be reduced to about 25 sccm to about 30 sccm. However, one skilled in the art will realize that such a condition may increase the process time due to the lower concentration of nitrogen that is available for the formation of the nitride layer.  
         [0033]    Whether deposition of a titanium, a titanium nitride layer, or a multilayer containing alternating layers of titanium and titanium nitride is desired, power supply  250  may apply a power of about 4000 watts without ramping to the target while the RF Power supply  260  applies a power of about 1000 watts ramped at 2500 watts/second to the coil  240  for about 4 seconds. After about 4 seconds the power applied to the coil  240  is reduced for about 80 seconds while the power is maintained at the target  230 . In particular embodiments, no power is applied to the coil  240  during this time. Interleaving the metal deposition steps of Third Deposition Step  350  a gas stabilization procedure may be performed. In this procedure the appropriate ambient, as discussed above, may be established by exposing the deposition tool  200  to the desired ambient for about 15 seconds before continuing with the next deposition step. Third Deposition Step  350  ends by the application of a dynamic vacuum to the deposition tool  200 .  
         [0034]    In the exemplary embodiment, the Third Deposition Step  350  is carried out to form a multilayer comprising alternating layers of target metal and metal nitride. In a particular embodiment a multilayer having about 4 titanium layers and about 4 titanium nitride layers may be formed. Table 4 indicates an exemplary embodiment of this step of the present invention.  
                                                                                                               TABLE 4                           Exemplary Embodiment of Third Deposition Step 350                    DC Power to   RF Power to                   Time   Target (W)/Ramp   Coil (W)/Ramp   Ar Flow   N 2  Flow       Step   (sec)   (W/sec)   (W/sec)   (SCC)   (SCC)                    1   3   0/0   0/0   —   —       2   15   0/0   0/0   58    0       3   60   0/0   0/0   58    0       4   15   0/0   0/0   25   45       5   4   4000/1000   2500/2500   25   45       6   79   4000/0     2500/0     25   28            7       Repeat Steps 2-6                8   15   0/0   0/0   —   —                  
 
         [0035]    Turning briefly to FIG. 6, there is illustrated a cross-sectional view of a conventional integrated circuit  600 , that might be manufactured according to the principles of the present invention. The integrated circuit  600  may include devices, such as CMOS devices, BiCMOS devices, Bipolar devices, EEPROM devices, including Flash EPROMS, optical or optoelectronic devices, passive devices, such as resistors, inductors, or capacitors, or other type of similar devices. Also shown in FIG. 6 are components of the conventional integrated circuit  600 , including: transistors  610 , a first dielectric layer  615 , the metal feature  620  and the fluorinated dielectric layer  640 . The metal feature  620  along with interconnect structures  621  form part of an interconnect system that electrically connects the transistors  610  to form an integrated circuit  600 . Moreover, one having skill in the art knows how to electrically connect the metal feature  620  to complete the integrated circuit  600 . Also illustrated, are conventionally formed tubs,  623 ,  625 , source regions  633  and drain regions  635 , all located over a substrate  630 .  
         [0036]    The present invention as discussed in detail above substantially reduces delamination and thereby lengthens the useful life of the coil  400 , which is in contrast to conventional techniques. As depicted in FIG. 1, conventional processes produce coils where the interface between the original coil surface and the initial layers of deposited target material is very porous. Surprisingly, the present invention is capable of producing a coil having a substantially more uniform interface. FIG. 5 shows a microscopic view of the interface of the coil obtained according to the present invention. Compared to FIG. 1, the porosity of the interface is substantially reduced or eliminated. It is thought that the deposition of target material at a relatively lower chamber pressure and substantially reduced RF power supply setting produces this uniform interface between the surface of the tool and the deposited layers. In those embodiments that include the erosion step, it is believed that these results can be further enhanced. In turn, the uniform interface allows the subsequently deposited material to adhere well to the coil. Hence, the proper preparation of the surface by erosion and formation of the uniform interface may be highly important in substantially reducing or eliminating delamination of the coil. It will be apparent to those skilled in the art that the conditions recited in Tables 1-4 are included for illustrative purposes only and a range of conditions may be applied in the various steps where delamination of the coil may be substantially reduced.  
         [0037]    Although the present invention has been described in detail, those skilled in the art should understand that they can make various changes, substitutions and alterations herein without departing from the spirit and scope of the invention in its broadest form.