Abstract:
In a method of cleaning a deposition process chamber, a remotely generated activated gas is supplied to the process chamber, in which, depending on the type of excitation means used, a specified chamber pressure in combination with a two-step clean process allows one to significantly reduce nitrogen fluoride (NF 3 ) consumption and increase throughput.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The present invention relates to process tools usable in the manufacture of integrated circuits, and, more particularly, to deposition tools, such as chemical vapor deposition (CVD) tools, for depositing silicon-containing dielectric layers on a substrate, wherein a cleaning process is periodically performed in order to remove deposition residuals from the walls of the process chamber and from other components located within the process chamber.  
           [0003]    2. Description of the Related Art  
           [0004]    The manufacture of integrated circuits requires the deposition and the subsequent patterning of material layers to form device features conforming to design requirements. Since individual features have to be electrically insulated from each other, dielectric layers are deposited at specific manufacturing stages to provide for the required insulation within a specified process level and/or with respect to overlying and underlying process levels. Most of the commercial integrated circuits are based on silicon-containing substrates and, for this reason, silicon-containing dielectric materials are successfully used as dielectric materials due to the superior characteristics of interfaces between silicon or polycrystalline silicon and the silicon-containing dielectric material, such as silicon dioxide or silicon nitride.  
           [0005]    Accordingly, a plurality of different techniques and correspondingly adapted process tools are available for depositing dielectric materials. Such techniques may include chemical vapor deposition (CVD) methods, such as plasma enhanced CVD techniques, physical vapor deposition (PVD) techniques, such as sputter deposition, and the like. In forming dielectric layers on a semiconductor substrate, plasma enhanced CVD has proven to be a valuable deposition technique. Through use of a precursor gas such as silane, tetraethylorthosilicate (TEOS), diborosilane and others, a plasma is created within a process chamber and the required dielectric compounds, such as silicon dioxide, are formed. The plasma prevailing in the process chamber also assists in improving directionality of the involved ions and molecules so that the required characteristics of the dielectric layer to be deposited may be correspondingly selected by adjusting process parameters determining the deposition process, such as the flow rate of precursor and additional gases, pressure within the process chamber, temperature of the substrate during the deposition, power supplied to radio frequency (RF) means and low frequency (LF) means or DC means provided for establishing the plasma and adjusting the directionality of ions and molecules, deposition time, temperature of the substrate, and the like.  
           [0006]    Although these process parameters may be optimized to obtain a high quality layer having the required characteristics, parts of the process chamber and components located within the process chamber may also receive a dielectric layer, since the heat that is mainly supplied to the substrate may also increase the temperature of the whole process chamber and reactive particles in the plasma may also hit the walls of the process chamber and any components located within the process chamber. Consequently, the thickness of the dielectric material accumulating on the walls of the process chamber and the components will increase during a process sequence so that process conditions may significantly vary over time when a large number of substrates are processed due to a variety of factors. For example, the reactive particles in the plasma may hit the chamber walls and the components having the dielectric material formed thereon and may re-sputter atoms of the dielectric material, thereby creating different process conditions depending on the amount of material accumulated on the chamber walls and the components.  
           [0007]    It has thus become standard practice to remove any residuals from the chamber walls and the internal components by cleaning the process chamber. Frequently, a so-called in situ cleaning process is contemplated, in which a chamber cleaning procedure is carried out immediately after the deposition process for a substrate is completed. In this way, substantially equal process conditions may be established for each substrate to be processed in the process chamber. Due to the desired in situ nature of the cleaning process that may be performed for each substrate or for a few substrates, the so-called wet cleaning processes are only used after several thousand of wafers have been processed. The wet cleaning process requires the disassembly of the process chamber and the components for the cleaning with an appropriate etching solution. Therefore, the so-called dry clean recipes have been developed, wherein specific precursor cleaning gases are fed into the process chamber under specified conditions to remove the dielectric material from the chamber walls and the components by establishing an appropriate plasma in the process chamber. Although these methods are effective in removing the dielectric residuals, plasma generating means are required and render these cleaning techniques impractical for heat-induced CVD reactors, in which no plasma generating means are provided. Moreover, the cleaning process is relatively aggressive in that the dielectric residuals are removed primarily by a sputter process rather than by a chemical reaction, so that as a consequence the chamber walls, covered by relatively thin dielectric material with respect to other regions in the process chamber, are also subjected to the sputter process, resulting in significant wear of the wall material which may lead to premature failure of the process tool. Furthermore, the chamber temperature increases during an in situ plasma clean process and causes thickness variations during the deposition process (this is especially true for TEOS).  
           [0008]    As a consequence, a so-called remote clean process has been developed, wherein an activated cleaning gas is generated at a remote reactor from appropriate precursor gases and the activated gas is supplied to the process chamber to be cleaned so that the dielectric residuals may be removed by chemical reaction substantially without any sputter events. Thus, this remote clean recipe may be applied to process chambers with and without plasma generating means.  
           [0009]    With reference to FIG. 1, a typical remote clean process will now be described. It should be noted that the process chamber and the remote clean gas source are depicted in an over-simplified manner to concentrate on the important features regarding this invention. In FIG. 1, a plasma enhanced CVD system  100  comprises a process chamber  110  and a remote reactor  150  coupled to the process chamber  110  by a supply line  101 , which may have a length and a diameter appropriate for feeding gas from the remote reactor  150  to the process chamber  110 . In the process chamber  110 , a first plate  102  is provided and adapted to receive and distribute gases supplied thereto. For the sake of clarity, any supply lines necessary for feeding gases during the deposition process are not depicted in FIG. 1. The first plate  102  may also be configured to serve as an electrode to establish an RF, LF or DC bias within the process chamber  110 . Spaced apart from the first plate  102 , and in an opposing relationship, a second plate  103  is provided that is coupled to a drive mechanism  104  that vertically moves the second plate  103  as indicated by the arrow  105 . The second plate  103  may be adapted to support a substrate during the deposition process and may also include heating means (not shown) with which the second plate  103 , and thus the substrate, may be maintained at a required temperature. The second plate  103  includes a plurality of lift pins  106  that are movably attached to the second plate  103  and may be moved from a first position, at which the lift pins  106  are, at least partially, exposed, to a second position in which the lift pins  106  are counter-sunk, i.e., are substantially flush with the upper surface of the second plate  103 . Moving the lift pins  106  from the first position into the second position and vice versa is indicated by the arrow  107 . For the sake of simplicity, an appropriate mechanism for moving the lift pins  106  is not shown in FIG. 1.  
           [0010]    The remote reactor  150  is connected to a source of precursor gas  151  via a supply line  152  including a valve means  153  for controlling a flow rate of the precursor gas. Moreover, the remote reactor  150  is coupled to appropriate excitation means, which are referred to in FIG. 1 as  155 , wherein the coupling is indicated by arrows  156  to indicate that an appropriate coupling is to be used depending on the type of excitation means used. As excitation means, RF, LF or DC generators may be employed to create a plasma within the remote reactor  150 , wherein the coupling  156  may be accomplished by inductive coupling or capacitive coupling when an RF generator provides for the excitation of the precursor gas. Moreover, a microwave power source, along with an appropriate wave guide, may be provided for the required activation of precursor gases. The process chamber  110  is also connected to a vacuum source  109  that is adapted to controllably establish a predefined pressure within the process chamber  110 .  
           [0011]    In operation, typically one or more substrates have been processed in the process chamber  110  by feeding, for example, TEOS into the process chamber and generating a plasma substantially between the first plate  102  and the second plate  103  to deposit a dielectric layer, such as a silicon dioxide layer, on the substrate that is supported on the second plate  103 . After completion of the deposition process, the substrate is removed from the process chamber by an appropriate transfer mechanism (not shown), a predefined pressure is established in the process chamber  110 , for example about 700 Torr, and the second plate  103  is maintained at a predefined temperature, for instance, approximately 400° C. A precursor gas from the source  151  is supplied to the remote reactor  150 , wherein the flow rate may be adjusted by the control means  153 . In a typical clean process, nitrogen fluoride (NF 3 ) diluted in argon (Ar) may be used as a precursor gas, which is transformed into an activated gas by supplying power from the excitation means  155 . Prior to supplying the activated gas to the process chamber  110 , the second plate  103  is lowered to a position in which the distance between the first plate  102  and the second plate  103  is outside of the range used during the deposition process and the lift pins  106  are in the first position, i.e., the lift pins  106  are exposed. Moreover, the pressure in the process chamber  110  is lowered to typically about 4.0 Torr and the activated cleaning gas, i.e., the activated nitrogen fluoride (NF 3 ) diluted by argon, is supplied to the process chamber  110 . The flow rate of the precursor gas, and thus of the activated gas, may be controlled to approximately 1400 sccm for nitrogen fluoride (NF 3 ) and to 2800 sccm for argon. Typically, the flow rate of nitrogen fluoride (NF 3 ) is increased in a step-wise manner to the final flow rate prior to the actual clean process in one or more so-called ramp-up steps to avoid a nitrogen fluoride burst at the beginning of the clean process. It should be noted that the pressure within the process chamber  110  and the flow rate of argon for diluting the nitrogen fluoride gas may preferably be selected in accordance with the type of excitation means  155  used to activate the precursor gas in the remote reactor  150 . The above-mentioned pressure and flow rate values refer to a plasma activation, whereas typically in microwave activation, dilution of the nitrogen fluoride gas is not necessary and a flow rate of approximately 1400 sccm of nitrogen fluoride at a pressure of about 2.0 Torr is used. In this case, typically a clean time of 90 and more seconds may be necessary for a typical interlayer dielectric deposition to obtain the required degree of cleanliness in the process chamber  110 .  
           [0012]    Although the processes described above allows an effective cleaning of the process chamber  110 , there is still room for improvement of this process in terms of throughput and environmental hazardous by-products of the clean process. That is, although a remote generation of the activated clean gas, i.e., the activated nitrogen fluoride (NF 3 ) or the diluted nitrogen fluoride (NF 3 ) gas, results in the creation of excited nitrogen and fluorine ions, a major part of which react with the dielectric material to be removed from the process chamber  110  without generating any ozone-destroying compounds, it is nevertheless highly desirable to further reduce the amount of these compounds, due to environmental aspects, while maintaining or even increasing the number of clean processes that are practical with a specified amount of nitrogen fluoride (NF 3 ) source gas in view of the limited availability of nitrogen fluoride.  
           [0013]    Accordingly, there is a need for an improved clean process, in which the expensive and restrictively available source gas nitrogen fluoride (NF 3 ) is utilized more efficiently.  
         SUMMARY OF THE INVENTION  
         [0014]    The present invention is directed to a method for cleaning a process chamber, preferably a process chamber for plasma enhanced CVD, wherein nitrogen fluoride (NF 3 ) is used as a source gas for the clean process in a highly efficient manner, in that specific process parameters, such as the chamber pressure, the distance of the first and the second plates in a process chamber as described in FIG. 1, the flow rate of the source gas or gases, as well as the position of lift pins, is taken into consideration and is optimized to minimize source gas consumption. According to the inventor&#39;s finding, the chamber pressure, in combination with the arrangement of the first and second plates, leads to a significant improvement in the cleaning efficiency, which, in turn, results in reduced nitrogen fluoride (NF 3 ) consumption and also a reduced clean time including a remarkably higher throughput.  
           [0015]    According to one illustrative embodiment of the present invention, a method of cleaning a deposition chamber after depositing a silicon-containing dielectric layer on a substrate is provided, wherein the deposition process chamber includes a first plate and a second plate, wherein the second plate is movable to adjust the distance between the first and the second plates. Moreover, a plurality of lift pins is movably coupled to the second plate, wherein the lift pins have a first position so as to be partially exposed and a second position in which the lift pins are substantially not exposed above a surface of the second plate. The method comprises generating, in a remote plasma source, an activated clean gas from a precursor gas including argon and nitrogen fluoride (NF 3 ). The activated clean gas is then supplied to the process chamber, in which a pressure is maintained in the range of approximately 3.0-3.5 Torr. The second plate is positioned for a first clean time period with a predetermined distance to the first plate, wherein the lift pins are located at the second position. Additionally, the lift pins are positioned in the first position for a second clean time period that is shorter than the first clean time period.  
           [0016]    According to a further embodiment of the present invention, a method for cleaning a deposition process chamber, after depositing a silicon-containing dielectric layer on a substrate, is provided. The deposition process chamber comprises a first plate and a second plate, wherein the second plate is movable to adjust the distance between the first plate and the second plate. Furthermore, a plurality of lift, pins is movably coupled to the second plate, wherein the lift pins are positionable at a first position so as to be partially exposed and at a second position so as to be counter-sunk with respect to the second plate. The method comprises generating an active clean gas using microwave excitation from a precursor gas including nitrogen fluoride (NF 3 ) and supplying the activated clean gas to the process chamber. A pressure in the process chamber is maintained in the range of approximately 2.5-3.0 Torr and the second plate is, for a first time clean period, positioned with a predetermined distance to the first plate with the lift pins in the second position. Subsequently, the lift pins are positioned to the first position for a second clean time period, wherein the second clean time period is shorter than the first clean time period.  
           [0017]    In a further illustrative embodiment, a method of cleaning a deposition process chamber after depositing a silicon-containing dielectric layer on a substrate is provided. The deposition process chamber includes a first plate and a second plate, wherein the second plate is movable to adjust the distance between the first plate and the second plate, wherein a plurality of lift pins are movably coupled to the second plate. The lift pins have a first position so as to be partially exposed and a second position wherein the pins are substantially not exposed above a surface of the second plate. The method comprises generating, in a remote plasma source, an activated clean gas from a precursor gas including argon and nitrogen fluoride (NF 3 ) and supplying the activated clean gas to the process chamber. A pressure in the chamber is maintained in the range of approximately 2.0-4.0 Torr. The method further includes positioning, for a first time period, the second plate at a distance from the first plate that is suitable for depositing the dielectric layer with the lift pins in the second position. The lift pins are then positioned in the first position for a second time period, wherein the second time period is shorter then the first time period.  
           [0018]    In yet another embodiment, a method of cleaning a deposition process chamber, after depositing a silicon-containing dielectric layer on a substrate, is provided. The deposition process chamber includes a first plate and a second plate with the second plate being movable to adjust a distance between the first plate and the second plate, wherein a plurality of lift pins are movably coupled to the second plate. The lift pins have a first position so as to be partially exposed and a second position so as to be counter-sunk with respect to the second plate. The method comprises generating an activated clean gas by microwave excitation from a precursor gas including nitrogen fluoride (NF 3 ) and supplying the activated clean gas to the process chamber. A pressure in the process chamber is maintained within a range of approximately 2.0-4.0 Torr and the second plate is positioned, for a first time period, at a distance from the first plate that is suitable to deposit the dielectric layer with the lift pins in the second position. The lift pins are then positioned in the first position for a second time period, wherein the second time period is shorter than the first time period. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0019]    The invention may be understood by reference to the following description taken in conjunction with the accompanying drawings, in which like reference numerals identify like elements, and in which:  
         [0020]    [0020]FIG. 1 shows a simplified schematic view of a CVD process tool with a reactor for carrying out a remote clean process;  
         [0021]    [0021]FIG. 2 is a schematic diagram depicting a graph of an end point signal characterizing the clean process in accordance with one illustrative embodiment with respect to a conventional example;  
         [0022]    [0022]FIG. 3 is a graph depicting end point signals of a further illustrative embodiment with respect to a corresponding conventional example; and  
         [0023]    [0023]FIG. 4 depicts a graph indicating the clean time of the embodiment of FIG. 3 with respect to the conventional example versus the thickness of the dielectric material that has been deposited prior to the clean process. 
     
    
       [0024]    While the invention is susceptible to various modifications and alternative forms, specific embodiments thereof have been shown by way of example in the drawings and are herein described in detail. It should be understood, however, that the description herein of specific embodiments is not intended to limit the invention to the particular forms disclosed, but on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the appended claims.  
       DETAILED DESCRIPTION OF THE INVENTION  
       [0025]    Illustrative embodiments of the invention are described below. In the interest of clarity, not all features of an actual implementation are described in this specification. It will of course be appreciated that in the development of any such actual embodiment, numerous implementation-specific decisions must be made to achieve the developers&#39; specific goals, such as compliance with system-related and business-related constraints, which will vary from one implementation to another. Moreover, it will be appreciated that such a development effort might be complex and time-consuming, but would nevertheless be a routine undertaking for those of ordinary skill in the art having the benefit of this disclosure.  
         [0026]    In the following, various specific embodiments of the present invention will be described, wherein it is referred to as a CVD tool having a process chamber and a remote activated gas reactor, as is schematically shown in FIG. 1. Unless otherwise specified in the description and the claims, the embodiments described herein below may be practiced in combination with a CVD tool having the features as pointed out with reference to FIG. 1.  
         [0027]    According to one illustrative embodiment of the present invention, a silicon wafer may be processed in the process chamber  110  to receive an interlayer dielectric substantially comprising silicon dioxide with a thickness in the range of approximately 600-1400 Å formed from TEOS. After removing the semiconductor wafer from the process chamber  110 , the pressure in the process chamber  110  may be adjusted to approximately 720 Torr. However, the pressure may also be within the range of 650-730 Torr. At the same time, the flow rate of argon from the precursor source  151  may be adjusted to approximately 3600 sccm by correspondingly controlling the flow control means  153 . The excitation means  155 , in this embodiment a plasma generating means, such as a plasma generating means including an RF means, is turned on to activate the argon arriving from the precursor source  151  and flowing to the process chamber  110  via the supply line  101 . In other embodiments, the flow rate of argon may be set in the range of approximately 3000-4000 sccm. After a predefined time period of, for example, approximately 5 seconds, the precursor source  151  may be actuated to additionally provide nitrogen fluoride (NF 3 ) at a flow rate of approximately 100 sccm, wherein in subsequent steps the nitrogen fluoride flow rate may be increased to 200 and 300 sccm, each lasting, for example, approximately one second.  
         [0028]    Next, the pressure in the process chamber  110  is reduced to approximately 3.0-3.5 Torr, and, in one particular embodiment, to approximately 3.3 Torr. After or shortly before or simultaneously to the establishment of this pressure, the nitrogen fluoride (NF 3 ) flow rate is increased to approximately 1400 sccm to provide for the required clean activity in the process chamber  110 . Prior to the time period with the reduced clean pressure in the range of 3.0-3.5 Torr, the second plate  103  is positioned so that a distance between the first plate  102  and the second plate  103  is within a range that may also be used during the deposition process, i.e., the second plate  103  is positioned in a typical process state rather than in a retracted position that may be appropriate for loading a substrate onto the second plate  103 . In one particular embodiment, the second plate  103  is positioned such that the distance is in the range of approximately 600 mil (15.24 mm) to 700 mil (17.78 mm), and preferably the distance is selected to be approximately 650 mil (16.51 mm).  
         [0029]    Moreover, the lift pins  106  are in the second position, i.e., the lift pins  106  are substantially flush with the surface of the second plate  103 ; that is, the lift pins  106  are substantially not exposed, so that in this stage of the clean process, the process chamber  110 , and in particular the corresponding process region, is cleaned in a condition similar to that of a deposition process. The second plate  103  and the lift pins  106  are maintained in this position for about 40-60 seconds, and preferably for about 45 seconds, when a deposition of silicon dioxide (SiO 2 ) with a thickness in the range of 1600-10000 Å has been carried out with the previously processed substrate. For other thicknesses, other process times may be required, as will be described later.  
         [0030]    Next, the lift pins  106  are moved into their first position so that they are partially exposed to the reactive ambient and thus any residual dielectric is removed from the lift pins  106 . To move the lift pins  106  into the first position, the second plate  103  may be moved into a lower position, or an appropriate mechanism may be provided that allows transferring of the lift pins  106  from the second to the first position irrespective of the actual position of the second plate  103 . Since usually the surface of the lift pins  106  is significantly less contaminated with dielectric residuals of the preceding deposition process, a clean time period for cleaning the lift pins  106  is relatively shorter and is selected to be approximately 3-7 seconds, and preferably about 5 seconds. Thereafter, the excitation means  155  is deactivated and the nitrogen fluoride (NF 3 ) flow and the argon flow are discontinued. Then, the condition within the process chamber  110  may be stabilized by introducing feed gases such as helium and oxygen, wherein the second plate  103  may be brought into a process position with a distance that is significantly smaller than the distance used during the clean process, that is the first and second plate  102  and  103  are closer together. During the entire process sequence, the temperature of the second plate  103  may be maintained in the range of approximately 350-450° C. and particularly at approximately 400° C.  
         [0031]    Consequently, an effective cleaning of the process chamber  110  may be obtained with a total clean time in the range of 50-65 seconds compared to approximately 75 seconds of a conventional sequence for the above specified layer thickness. Thus, the clean process, according to the above described embodiments, may be considered as a two-step clean, wherein in a first step the second plate  103  is arranged according to a typical process position with the lift pins  106  unexposed, whereas in a second, shorter step the lift pins  106  are cleaned.  
         [0032]    Compared to a typical conventional clean recipe, in which a higher chamber pressure of about 4.0 Torr is used and the second plate  103  is in a lowered position with the lift pins  106  exposed, essentially the same nitrogen fluoride (NF 3 ) flow rate is used, wherein, however, the argon flow rate, contrary to the embodiments described above, is reduced to about 2800 sccm. As a result, the embodiments described above yield a significant improvement in terms of nitrogen fluoride consumption and throughput. Due to a clean time reduction of up to 20%, the nitrogen fluoride consumption may be reduced to up to 20%, wherein at the same time the throughput of the deposition tool  100  increases to up to 10%.  
         [0033]    For a further comparison with the conventional process, it is now referred to FIG. 2. In FIG. 2, a schematic diagram depicts a graph of a typical conventional clean process and a typical clean process in accordance with one of the embodiments described above, wherein the output voltage of an end point detection system (not shown in FIG. 1) is plotted versus the process time. A conventional process is represented by curve A, whereas one embodiment of the present invention is represented by curve B. As is evident from the graph of FIG. 2, at an early stage of the cleaning process, i.e., the time period after which the chamber pressure is reduced to a value as required by the corresponding process recipe, a relatively steep rise occurs and is indicated by reference number  201  for curve B and by reference number  206  for curve A. A typical gradient is 200 millivolts per second for curve B, whereas the maximum gradient is approximately 80 millivolts per second for curve A. In an advanced period of the cleaning process, indicated by  202  and  205 , respectively, both curves flatten, wherein curve B exhibits a more step-like behavior than curve A. Accordingly, curve B shows a relatively horizontal progression at a time indicated by  203  that corresponds to about 50 seconds, whereas curve A reaches a substantially horizontal progression at a time  204  that is more than 60 seconds and typically is 75 seconds. It is thus evident that, in the embodiment of the present invention, the end of the cleaning process is achieved in significantly less time than according to the conventional example represented by curve A.  
         [0034]    In a further embodiment of the present invention, the remote reactor  150  is applied by microwave power, wherein nitrogen fluoride (NF 3 ) gas is supplied to the remote reactor  150  with a flow rate in the range of 1000-1600 sccm and preferably with a flow rate of about 1400 sccm. After a short transition step, with an increased chamber pressure of approximately 720 Torr, the chamber pressure is reduced to approximately 2.5-3.0 Torr, and in one particular embodiment to approximately 2.7 Torr. For positioning the second plate  103  and the lift pins  106 , the same criteria apply as pointed out in the embodiments described above. Thus, the microwave power is switched on with the second plate  103  positioned in a process position with the lift pins  106  unexposed and after a clean period of approximately 55-75 seconds (for the same layer thickness as in the preceding embodiments), and according to one particular embodiment of approximately 65 seconds, the lift pins  106  are exposed, possibly by lowering the second plate  103  or by raising the pins  106  independently of the second plate  103 , for approximately 3-7 seconds, and preferably for approximately 5 seconds. Next, the microwave power is switched off, nitrogen fluoride (NF 3 ) flow is discontinued and the process chamber  110  may then gradually be adapted to the process conditions required for the next deposition process. The temperature of the second plate  103  may be maintained at approximately 350-450° C. and preferably at approximately 400° C.  
         [0035]    In contrast thereto, a conventional process may use approximately the same nitrogen fluoride (NF 3 ) flow rate, whereas, contrary to the embodiment described above, the chamber pressure is lowered to approximately 2.0 Torr while the second plate  103  is maintained in an out of process range with the lift pins  106  exposed. To obtain a desired degree of cleanliness, a clean time of about 90 seconds is typically necessary. The remaining parameters regarding temperature and process steps after the cleaning is completed may be selected as in the embodiments of the present invention.  
         [0036]    [0036]FIG. 3 shows a schematic diagram of corresponding end point curves, wherein curves A and B represent the conventional process and the embodiments of the present invention, respectively. As is evident from FIG. 3, the output voltage of the end point detection system represented by curve B shows a relatively significant kink at  301 , whereas curve A exhibits a slope  302  indicating that the process of material removal is still in progress. Thus, at time  303 , curve B has already flattened which indicates the end of the cleaning process, whereas the end point of the clean process, indicated by  304 , is reached remarkably later in curve A, e.g., on the order of 15-20 seconds later.  
         [0037]    As a result, the overall clean time of the embodiments of the present invention based on the microwave excitation of nitrogen fluoride (NF 3 ) is significantly reduced, wherein in a first clean step, the main portion of the process chamber  110  is cleaned, and, in a second, significantly shorter step, the lift pins  106  are cleaned. In comparison to the conventional example, a nitrogen fluoride (NF 3 ) reduction of approximately 22% is achieved, whereas the throughput improvement yields approximately 8%.  
         [0038]    [0038]FIG. 4 shows a diagram depicting the relationship between the dielectric layer thickness deposited prior to the clean process with respect to the clean time for the conventional process recipe for microwave excitation and for one particular embodiment of the present invention using microwave excitation. In FIG. 4, curve A represents a fit curve presenting the conventional process, whereas reference sign B represents the fit curve according to one illustrative embodiment of the present invention. It is evident that for the entire range of 1,000-18,000 Å of layer thickness of the dielectric material deposited on the substrate prior to the clean process, a shorter clean time is required so that the results obtained for the embodiments described above (approximately 8,000 Å silicon dioxide thickness) are also obtained with other layer thicknesses. Consequently, the process recipes in accordance with the illustrative embodiments described so far are valid for a large number of dielectric layer thicknesses and thus these recipes may be used for any dielectric layer required in any manufacturing stage of an integrated circuit.  
         [0039]    It is to be noted that in accordance with the particular embodiments of the present invention described above, a plasma enhanced CVD tool from Applied Materials available under the name Producer™ system has been proven to be particularly advantageous in obtaining superior clean results.  
         [0040]    The particular embodiments disclosed above are illustrative only, as the invention may be modified and practiced in different but equivalent manners apparent to those skilled in the art having the benefit of the teachings herein. For example, the process steps set forth above may be performed in a different order. Furthermore, no limitations are intended to the details of construction or design herein shown, other than as described in the claims below. It is therefore evident that the particular embodiments disclosed above may be altered or modified and all such variations are considered within the scope and spirit of the invention. Accordingly, the protection sought herein is as set forth in the claims below.