Patent Publication Number: US-2015079799-A1

Title: Method for stabilizing an interface post etch to minimize queue time issues before next processing step

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     Embodiments of the present invention generally relate to methods for forming semiconductor devices. More particularly, embodiments of the present invention generally relate to methods for etching a dielectric barrier layer followed by an interface protection layer deposition process for manufacturing semiconductor devices. 
     2. Description of the Related Art 
     Reliably producing sub-half micron and smaller features is one of the key technology challenges for next generation very large scale integration (VLSI) and ultra large-scale integration (ULSI) of semiconductor devices. However, as the limits of circuit technology are pushed, the shrinking dimensions of VLSI and ULSI interconnect technology have placed additional demands on processing capabilities. Reliable formation of gate structures on the substrate is important to VLSI and ULSI success and to the continued effort to increase circuit density and quality of individual substrates and die. 
     A patterned mask, such as a photoresist layer, is commonly used during etching structures, such as gate structure, shallow trench isolation (STI), bit lines and the like, or back end dual damascene structure on a substrate. The patterned mask is conventionally fabricated by using a lithographic process to optically transfer a pattern having the desired critical dimensions to a layer of photoresist. The photoresist layer is then developed to remove undesired portion of the photoresist, thereby creating openings in the remaining photoresist. 
     As the dimensions of the integrated circuit components are reduced (e.g., to sub-micron dimensions), the materials used to fabricate such components must be carefully selected in order to obtain satisfactory levels of electrical performance. For example, when the distance between adjacent metal interconnects and/or the thickness of the dielectric bulk insulating material that isolates interconnects having sub-micron dimensions, the potential for capacitive coupling occurs between the metal interconnects is high. Capacitive coupling between adjacent metal interconnects may cause cross talk and/or resistance-capacitance (RC) delay which degrades the overall performance of the integrated circuit and may render the circuit inoperable. In order to minimize capacitive coupling between adjacent metal interconnects, low dielectric constant bulk insulating materials (e.g., dielectric constants less than about 4.0) are needed. Examples of low dielectric constant bulk insulating materials include silicon dioxide (SiO 2 ), silicate glass, fluorosilicate glass (FSG), and carbon doped silicon oxide (SiOC), among others. 
     In addition, a dielectric barrier layer is often utilized to separate the metal interconnects from the dielectric bulk insulating materials. The dielectric barrier layer minimizes the diffusion of the metal from the interconnect material into the dielectric bulk insulating material. Diffusion of the metal into the dielectric bulk insulating material is undesirable because such diffusion can affect the electrical performance of the integrated circuit, or render the circuit inoperative. The dielectric layer needs to have a low dielectric constant in order to maintain the low-k characteristic of the dielectric stack between conductive lines. The dielectric barrier layer also acts as an etch-stop layer for a dielectric bulk insulating layer etching process, so that the underlying metal will not be exposed to the etching environment. The dielectric barrier layer has a dielectric constant of about 5.5 or less. Examples of dielectric barrier layer are silicon carbide (SiC) and nitrogen containing silicon carbide (SiCN), among others. 
     After the dielectric barrier layer etching process, the underlying upper surface of the metal is exposed to air. Prior to the subsequent metallization process to form interconnection on the exposed metal, the substrate may be transferred among different vacuum environments to perform a different processing step. During transfer, the substrate may have to reside outside the process chamber or controlled environment for a period of time called the queue time (Q-time). During the Q-time, the substrate is exposed to ambient environmental conditions that include oxygen and water at atmospheric pressure and room temperature. As a result, the substrate subjected to oxidizing conditions in the ambient environment may accumulate native oxides or contaminants on the metal surface prior to the subsequent metallization process, such as a copper electroplating process to form copper interconnects. 
     When the metal is exposed to ambient environmental conditions after an etching process, a strict Q-time limit is always applied so as to limit the amount of the oxide layer accumulating on the substrate. Generally, longer Q-times allow thicker oxide layers to form. Excess native oxide accumulation or contaminants may adversely affect the nucleation capability of the metal elements to adhere to the substrate surface during a subsequently metallization process. Furthermore, poor adhesion at the interface may also result in undesired high contact resistance, thereby resulting in undesirably poor electrical properties of the device. In addition, poor nucleation of the metal elements in the back end interconnection may impact not only the electrical performance of the devices, but also on the integration of the conductive contact material subsequently formed thereon. 
     Thus, there is a need for improved methods to etch a dielectric barrier layer with good interface quality control for metal exposed after the dielectric barrier etching process so as to provide allow longer long Q-times with minimum substrate oxidation. 
     SUMMARY 
     Methods for etching a dielectric barrier layer disposed on the substrate using a low temperature etching process along with a subsequent interface protection layer deposition process are provided. In one embodiment, a method for etching a dielectric barrier layer disposed on a substrate includes transferring a substrate having a dielectric barrier layer disposed thereon into an etching processing chamber, performing a treatment process on the dielectric barrier layer, remotely generating a plasma in an etching gas mixture supplied into the etching processing chamber to etch the treated dielectric barrier layer disposed on the substrate, plasma annealing the dielectric barrier layer to remove the dielectric barrier layer from the substrate, and forming an interface protection layer after the dielectric barrier is removed from the substrate. 
     In another embodiment, a method for etching a dielectric barrier layer disposed on a substrate includes transferring a substrate having a dielectric barrier layer disposed in a dual damascene structure on a substrate into an etching processing chamber, generating a plasma in an etching gas mixture supplied into the etching processing chamber to etch the dielectric barrier layer disposed on the substrate, wherein the etching gas mixture includes an ammonium gas and a nitrogen trifluoride, plasma annealing the dielectric barrier layer to remove the dielectric barrier layer from the substrate, and forming an interface protection layer after the dielectric barrier is removed from the substrate. 
     In yet another embodiment, a method for etching a dielectric barrier layer disposed on a substrate includes transferring a substrate having a dielectric barrier layer disposed in a dual damascene structure on a substrate into an etching processing chamber, applying a first low RF bias power in a treatment gas mixture in the etching processing chamber to treat the dielectric barrier layer, applying a source RF power remotely from the etching processing chamber in an etching gas mixture, wherein the etching gas mixture includes an ammonium gas and a nitrogen trifluoride, applying a second low RF bias power in an anneal gas mixture in the etching processing chamber to anneal the etched dielectric barrier layer to remove the dielectric barrier layer from the substrate, and forming an interface protection layer after the dielectric barrier is removed from the substrate. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       So that the manner in which the above recited features of the present invention can be understood in detail, a more particular description of the invention, briefly summarized above, can be had by reference to embodiments, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only typical embodiments of this invention and are therefore not to be considered limiting of its scope, for the invention can admit to other equally effective embodiments. 
         FIG. 1  is a cross section view of an illustrative processing chamber in which embodiments of the invention may be practiced; 
         FIG. 2  is a schematic top-view diagram of an illustrative multi-chamber processing system; 
         FIG. 3  depicts a flow diagram for etching a dielectric barrier layer using a low temperature etching process followed by a interface protection layer deposition process in accordance with one embodiment of the present invention; and 
         FIGS. 4A-4E  depict cross-sectional views of a dielectric barrier layer disposed on a semiconductor substrate over a sequence for etching the dielectric barrier layer and depositing a interface protection layer after the etching process in accordance with one embodiment of the present invention. 
     
    
    
     To facilitate understanding, identical reference numerals have been used, where possible, to designate identical elements that are common to the figures. It is contemplated that elements and features of one embodiment may be beneficially incorporated in other embodiments without further recitation. 
     It is to be noted, however, that the appended drawings illustrate only exemplary embodiments of this invention and are therefore not to be considered limiting of its scope, for the invention may admit to other equally effective embodiments. 
     DETAILED DESCRIPTION 
     Methods for etching a dielectric barrier layer followed by an interface protection layer deposition process are disclosed herein which provide an etching process with high etching selectivity and interface protection after the etching process. In one embodiment, the dielectric barrier layer etching process includes using a low temperature etching process to selectively etching the dielectric barrier layer without over-etching to an underlying conductive layer. An interface protection layer is subsequently performed to protect the underlying conductive layer exposed after the dielectric barrier layer etching process. By utilizing an etching process with high etching selectivity along with the deposition of an interface protection layer after etching, a good interface control may be obtained. Additionally, Q-time control prior to performing a subsequent process may be extended with minimum oxide or contamination generation, thereby increasing manufacturing flexibility without degradation of device performance. 
       FIG. 1  is a cross sectional view of an illustrative processing chamber  100  suitable for conducting an etching process as further described below. The chamber  100  is configured to remove materials from a material layer disposed on a substrate surface. The chamber  100  is particularly useful for performing the plasma assisted dry etch process. One processing chamber  100  suitable for practicing the invention is a Siconi™ processing chamber which is available from Applied Materials, Santa Clara, Calif. It is noted that other vacuum processing chambers available from other manufactures may also be adapted to practice the present invention. 
     The processing chamber  100  provides both heating and cooling of a substrate surface without breaking vacuum. In one embodiment, the processing chamber  100  includes a chamber body  112 , a lid assembly  140 , and a support assembly  180 . The lid assembly  140  is disposed at an upper end of the chamber body  112 , and the support assembly  180  is at least partially disposed within the chamber body  112 . 
     The chamber body  112  includes a slit valve opening  114  formed in a sidewall thereof to provide access to an interior of the processing chamber  100 . The slit valve opening  114  is selectively opened and closed to allow access to the interior of the chamber body  112  by a wafer handling robot (not shown). 
     In one or more embodiments, the chamber body  112  includes a channel  115  formed therein for flowing a heat transfer fluid therethrough. The heat transfer fluid can be a heating fluid or a coolant and is used to control the temperature of the chamber body  112  during processing. Control of the temperature of the chamber body  112  is important to prevent unwanted condensation of the gas or byproducts on the interior of the chamber body  112 . Exemplary heat transfer fluids include water, ethylene glycol, or a mixture thereof. An exemplary heat transfer fluid may also include nitrogen gas. 
     The chamber body  112  can further include a liner  120  that surrounds the support assembly  180 . The liner  120  is removable for servicing and cleaning. The liner  120  can be made of a metal such as aluminum, a ceramic material, or any other process compatible material. The liner  120  can be bead blasted to increase surface roughness and/or surface area which increases the adhesion of any material deposited thereon, thereby preventing flaking of material which results in contamination of the processing chamber  100 . In one or more embodiments, the liner  120  includes one or more apertures  125  and a pumping channel  129  formed therein that is in fluid communication with a vacuum port  131 . The apertures  125  provide a flow path for gases into the pumping channel  129 , which provides an egress for the gases within the processing chamber  100  to the vacuum port  131 . 
     A vacuum system is coupled to the vacuum port  131 . The vacuum system may include a vacuum pump  130  and a throttle valve  132  to regulate flow of gases through the processing chamber  100 . The vacuum pump  130  is coupled to a vacuum port  131  disposed in the chamber body  112  and therefore, in fluid communication with the pumping channel  129  formed within the liner  120 . The terms “gas” and “gases” are used interchangeably, unless otherwise noted, and refer to one or more precursors, reactants, catalysts, carrier, purge, cleaning, combinations thereof, as well as any other fluid introduced into the chamber body  112 . 
     The lid assembly  140  includes at least two stacked components configured to form a plasma volume or cavity therebetween. In one or more embodiments, the lid assembly  140  includes a first electrode  143  (“upper electrode”) disposed vertically above a second electrode  145  (“lower electrode”) confining a plasma volume or cavity  150  therebetween. The first electrode  143  is connected to a power source  152 , such as an RF power supply, and the second electrode  145  is connected to ground, forming a capacitance between the two electrodes  143 , 145 . 
     In one or more embodiments, the lid assembly  140  includes one or more gas inlets  154  (only one is shown) that are at least partially formed within an upper section  156  of the first electrode  143 . The one or more process gases enter the lid assembly  140  via the one or more gas inlets  154 . The one or more gas inlets  154  are in fluid communication with the plasma cavity  150  at a first end thereof and coupled to one or more upstream gas sources and/or other gas delivery components, such as gas mixers, at a second end thereof. 
     In one or more embodiments, the first electrode  143  has an expanding section  155  that bounds the plasma cavity  150 . In one or more embodiments, the expanding section  155  is an annular member that has an inner surface or diameter  157  that gradually increases from an upper portion  155 A thereof to a lower portion  155 B thereof. As such, the distance between the first electrode  143  and the second electrode  145  is variable across the expanding section  155 . The varying distance helps control the formation and stability of the plasma generated within the plasma cavity  150 . 
     In one or more embodiments, the expanding section  155  resembles an inverted truncated cone or “funnel.” In one or more embodiments, the inner surface  157  of the expanding section  155  gradually slopes from the upper portion  155 A to the lower portion  155 B of the expanding section  155 . The slope or angle of the inner diameter  157  can vary depending on process requirements and/or process limitations. The length or height of the expanding section  155  can also vary depending on specific process requirements and/or limitations. 
     As mentioned above, the expanding section  155  of the first electrode  143  varies the vertical distance between the first electrode  143  and the second electrode  145  because of the gradually increasing inner surface  157  of the first electrode  143 . The variable distance is directly influences to the power level within the plasma cavity  150 . Not wishing to be bound by theory, the variation in distance between the two electrodes  143 ,  145  allows the plasma to find the necessary power level to sustain itself within some portion of the plasma cavity  150  if not throughout the entire plasma cavity  150 . The plasma within the plasma cavity  150  is therefore less dependent on pressure, allowing the plasma to be generated and sustained within a wider operating window. As such, a more repeatable and reliable plasma can be formed within the lid assembly  140 . As the plasma generated in the plasma cavity  150  is defined in the lid assembly  140  prior to entering into a processing region  141  above the support assembly  180  wherein the substrate is proceed, the lid assembly  140  is considered as a remote plasma source because the plasma generated remotely from the processing region  141 . 
     The expanding section  155  is in fluid communication with the gas inlet  154  as described above. The first end of the one or more gas inlets  154  can open into the plasma cavity  150  at the upper most point of the inner diameter of the expanding section  155 . Similarly, the first end of the one or more gas inlets  154  can open into the plasma cavity  150  at any height interval along the inner diameter  157  of the expanding section  155 . Although not shown, two gas inlets  154  can be disposed at opposite sides of the expanding section  155  to create a swirling flow pattern or “vortex” flow into the expanding section  155  which helps mix the gases within the plasma cavity  150 . 
     The lid assembly  140  can further include an isolator ring  160  that electrically isolates the first electrode  143  from the second electrode  145 . The isolator ring  160  can be made from aluminum oxide or any other insulative, process compatible material. The isolator ring  160  surrounds or substantially surrounds at least the expanding section  155 . 
     The lid assembly  140  can further include a distribution plate  170  and blocker plate  175  adjacent the second electrode  145 . The second electrode  145 , distribution plate  170  and blocker plate  175  can be stacked and disposed on a lid rim  178  which is connected to the chamber body  112 . A hinge assembly (not shown) can be used to couple the lid rim  178  to the chamber body  112 . The lid rim  178  can include an embedded channel or passage  179  for circulating a heat transfer medium. The heat transfer medium can be used for heating, cooling, or both, depending on the process requirements. 
     In one or more embodiments, the second electrode or top plate  145  can include a plurality of gas passages or apertures  165  formed beneath the plasma cavity  150  to allow gas from the plasma cavity  150  to flow therethrough. The distribution plate  170  is substantially disc-shaped and also includes a plurality of apertures  172  or passageways to distribute the flow of gases therethrough. The apertures  172  can be sized and positioned about the distribution plate  170  to provide a controlled and even flow distribution to the processing region  141  of the chamber body  112  where the substrate to be processed is located. Furthermore, the apertures  172  prevent the gas(es) from impinging directly on the substrate surface by slowing and re-directing the velocity profile of the flowing gases, as well as evenly distributing the flow of gas to provide an even distribution of gas across the surface of the substrate. 
     In one or more embodiments, the distribution plate  170  includes one or more embedded channels or passages  174  for housing a heater or heating fluid to provide temperature control of the lid assembly  140 . A resistive heating element (not shown) can be inserted within the passage  174  to heat the distribution plate  170 . A thermocouple can be connected to the distribution plate  170  to regulate the temperature thereof. The thermocouple can be used in a feedback loop to control electric current applied to the heating element, as described above. 
     Alternatively, a heat transfer medium can be passed through the passage  174 . The one or more passages  174  can contain a cooling medium, if needed, to better control temperature of the distribution plate  170  depending on the process requirements within the chamber body  112 . Any heat suitable transfer medium may be used, such as nitrogen, water, ethylene glycol, or mixtures thereof, for example. 
     In one or more embodiments, the lid assembly  140  can be heated using one or more heat lamps (not shown). Typically, the heat lamps are arranged about an upper surface of the distribution plate  170  to heat the components of the lid assembly  140  including the distribution plate  170  by radiation. 
     The blocker plate  175  may optionally be disposed between the second electrode  145  and the distribution plate  170 . The blocker plate  175  is removably mounted to a lower surface of the second electrode  145 . The blocker plate  175  may be in good thermal and electrical contact with the second electrode  145 . In one or more embodiments, the blocker plate  175  can be coupled to the second electrode  145  using a bolt or similar fastener. The blocker plate  175  can also be threaded or screwed onto an outer diameter of the second electrode  145 . 
     The blocker plate  175  includes a plurality of apertures  176  to provide a plurality of gas passages from the second electrode  145  to the distribution plate  170 . The apertures  176  can be sized and positioned about the blocker plate  175  to provide a controlled and even flow distribution of gases to the distribution plate  170 . 
     The support assembly  180  can include a support member  185  to support a substrate (not shown in  FIG. 1 ) for processing within the chamber body  112 . The support member  185  can be coupled to a lift mechanism  183  through a shaft  187  which extends through a centrally-located opening  114  formed in a bottom surface of the chamber body  112 . The lift mechanism  183  can be flexibly sealed to the chamber body  112  by a bellows  188  that prevents vacuum leakage from around the shaft  187 . The lift mechanism  183  allows the support member  185  to be moved vertically within the chamber body  112  between a process position and a lower transfer position. The transfer position is slightly below the slit valve opening  114  formed in a sidewall of the chamber body  112  so that the substrate may be robotically removed from the substrate support member  185 . 
     In one or more embodiments, the support member  185  has a flat, circular surface or a substantially flat, circular surface for supporting a substrate to be processed thereon. The support member  185  may be constructed of aluminum. The support member  185  can include a removable top plate  190  made of some other material, such as silicon or ceramic material, for example, to reduce backside contamination of the substrate. 
     In one or more embodiments, the substrate (not shown) may be secured to the support member  185  using a vacuum chuck. In one or more embodiments, the substrate (not shown) may be secured to the support member  185  using an electrostatic chuck. An electrostatic chuck typically includes at least a dielectric material that surrounds an electrode  181 , which may be located on the support member  185  or formed as an integral part of the support member  185 . The dielectric portion of the chuck electrically insulates the chuck electrode  181  from the substrate and from the remainder of the support assembly  180 . 
     In one embodiment, the electrode  181  is coupled to a plurality of RF power bias sources  184 ,  186 . The RF bias power sources  184 ,  186  provide RF power to the electrode  181 , which excites and sustains a plasma discharge formed from the gases disposed in the processing region  141  of the chamber body  112 . 
     In the embodiment depicted in  FIG. 1 , the dual RF bias power sources  184 ,  186  are coupled to the electrode  181  disposed in the support member  185  through a matching circuit  189 . The signal generated by the RF bias power sources  184 ,  186  is delivered through matching circuit  189  to the support member  185  through a single feed to ionize the gas mixture provided in the plasma processing chamber  100 , thereby providing ion energy necessary for performing a deposition, etch, or other plasma enhanced process. The RF bias power sources  184 ,  186  are generally capable of producing an RF signal having a frequency of from about 50 kHz to about 200 MHz and a power between about 0 Watts and about 5000 Watts. Additional bias power sources may be coupled to the electrode  181  to control the characteristics of the plasma as needed. 
     The support member  185  can include bores  192  formed therethrough to accommodate lift pins  193 , one of which is shown in  FIG. 1 . Each lift pin  193  is constructed of ceramic or ceramic-containing materials, and are used for substrate-handling and transport. The lift pin  193  is moveable within its respective bore  192  when engaging an annular lift ring  195  disposed within the chamber body  112 . The lift ring  195  is movable such that the upper surface of the lift pin  193  can be extended above the substrate support surface of the support member  185  when the lift ring  195  is in an upper position. Conversely, the upper surface of the lift pins  193  is located below the substrate support surface of the support member  185  when the lift ring  195  is in a lower position. Thus, each lift pin  193  is moved in its respective bore  192  in the support member  185  when the lift ring  195  moves between the lower position and the upper position. 
     The support assembly  180  can further include an edge ring  196  disposed about the support member  185 . In one or more embodiments, the edge ring  196  is an annular member that is adapted to cover an outer perimeter of the support member  185  and protect the support member  185  from deposition. The edge ring  196  can be positioned on or adjacent the support member  185  to form an annular purge gas channel between the outer diameter of support member  185  and the inner diameter of the edge ring  196 . The annular purge gas channel can be in fluid communication with a purge gas conduit  197  formed through the support member  185  and the shaft  187 . The purge gas conduit  197  is in fluid communication with a purge gas supply (not shown) to provide a purge gas to the purge gas channel. Any suitable purge gas such as nitrogen, argon, or helium, may be used alone or in combination. In operation, the purge gas flows through the conduit  197 , into the purge gas channel, and about an edge of the substrate disposed on the support member  185 . Accordingly, the purge gas working in cooperation with the edge ring  196  prevents deposition at the edge and/or backside of the substrate. 
     The temperature of the support assembly  180  can be controlled by a fluid circulated through a fluid channel  198  embedded in the body of the support member  185 . In one or more embodiments, the fluid channel  198  is in fluid communication with a heat transfer conduit  199  disposed through the shaft  187  of the support assembly  180 . The fluid channel  198  is positioned about the support member  185  to provide a uniform heat transfer to the substrate receiving surface of the support member  185 . The fluid channel  198  and heat transfer conduit  199  can flow heat transfer fluids to either heat or cool the support member  185  and substrate disposed thereon. Any suitable heat transfer fluid may be used, such as water, nitrogen, ethylene glycol, or mixtures thereof. The support member  185  can further include an embedded thermocouple (not shown) for monitoring the temperature of the support surface of the support member  185 , which is indicative of the temperature of the substrate disposed thereon. For example, a signal from the thermocouple may be used in a feedback loop to control the temperature or flow rate of the fluid circulated through the fluid channel  198 . 
     The support member  185  can be moved vertically within the chamber body  112  so that a distance between support member  185  and the lid assembly  140  can be controlled. A sensor (not shown) can provide information concerning the position of support member  185  within chamber  100 . 
     In operation, the support member  185  can be elevated to a close proximity of the lid assembly  140  to control the temperature of the substrate being processed. As such, the substrate can be heated via radiation emitted from the distribution plate  170 . Alternatively, the substrate can be lifted off the support member  185  to close proximity of the heated lid assembly  140  using the lift pins  193  activated by the lift ring  195 . 
     A system controller (not shown) can be used to regulate the operations of the processing chamber  100 . The system controller can operate under the control of a computer program stored on a memory of a computer. The computer program may include instructions that enable the process described below to be performed in the processing chamber  100 . For example, the computer program can dictate the process sequencing and timing, mixture of gases, chamber pressures, RF power levels, susceptor positioning, slit valve opening and closing, substrate cooling and other parameters of a particular process. 
       FIG. 2  is a schematic top-view diagram of an illustrative multi-chamber processing system  200  that can be adapted to perform processes as disclosed herein having the processing chamber  100  coupled thereto. The system  200  can include one or more load lock chambers  202 ,  204  for transferring substrates into and out of the system  200 . Typically, since the system  200  is under vacuum, the load lock chambers  202 ,  204  can “pump down” the substrates being introduced into the system  200 . A first robot  210  can transfer the substrates between the load lock chambers  202 ,  204 , and a first set of one or more substrate processing chambers  212 ,  214 ,  216 ,  100  (four are shown). Each processing chamber  212 ,  214 ,  216 ,  100  is configured to perform at least one of substrate processing operation, such as an etching process, cyclical layer deposition (CLD), atomic layer deposition (ALD), chemical vapor deposition (CVD), physical vapor deposition (PVD), degas, orientation and other substrate processes. The position of the processing chamber  100  utilized to perform the etching process relative to the other chambers  212 ,  214 ,  216  is for illustration, and the position of the processing chamber  100  may be optionally be switched with any one of the processing chambers  212 ,  214 ,  216  if desired. 
     The first robot  210  can also transfer substrates to/from one or more transfer chambers  222 ,  224 . The transfer chambers  222 ,  224  can be used to maintain ultra-high vacuum conditions while allowing substrates to be transferred within the system  200 . A second robot  230  can transfer the substrates between the transfer chambers  222 ,  224  and a second set of one or more processing chambers  232 ,  234 ,  236 ,  238 . Similar to processing chambers  212 ,  214 ,  216 ,  100 , the processing chambers  232 ,  234 ,  236 ,  238  can be outfitted to perform a variety of substrate processing operations including the dry etch processes described herein any other suitable process including deposition, pre-clean, degas, and orientation, for example. Any of the substrate processing chambers  212 ,  214 ,  216 ,  100 ,  232 ,  234 ,  236 ,  238  can be removed from the system  200  if not necessary for a particular process to be performed by the system  200 . 
       FIG. 3  illustrates a process sequence  300  used to perform an etching process to etch a dielectric barrier layer disposed on a substrate with high etching selectivity. The sequence described in  FIG. 3  corresponds to the fabrication stages depicted in  FIGS. 4A-4E , which illustrates schematic cross-sectional views of a substrate  400  having a dual damascene structure  402  formed thereon during different stages of etching a dielectric barrier layer  408  followed by deposition of an interface protection layer deposition process. 
     The process sequence  300  starts at block  302  by transferring a substrate, such as the substrate  400  depicted in  FIG. 4A , into the processing chamber, such as the processing chamber  100  depicted in  FIG. 1 , or other suitable processing chamber. The substrate  400  may have a substantially planar surface, an uneven surface, or a substantially planar surface having a structure formed thereon. The substrate  400  shown in  FIG. 4A  includes dual damascene structure  402  formed on the substrate  400 . In one embodiment, the substrate  400  may be a material such as crystalline silicon (e.g., Si&lt;100&gt; or Si&lt;111&gt;), silicon oxide, strained silicon, silicon germanium, doped or undoped polysilicon, doped or undoped silicon wafers and patterned or non-patterned wafers silicon on insulator (SOI), carbon doped silicon oxides, silicon nitride, doped silicon, germanium, gallium arsenide, glass, sapphire. The substrate  400  may have various dimensions, such as 200 mm, 300 mm or 450 mm diameter wafers, as well as, rectangular or square panels. Unless otherwise noted, embodiments and examples described herein are conducted on substrates with a 300 mm diameter or a 450 mm diameter. 
     In one embodiment, the dual damascene structure  402  is an interconnection structure utilized in the back end semiconductor process. The dual damascene structure  402  includes a dielectric barrier layer  408  disposed on the substrate  400 . A dielectric stack  444 , as shown in  FIG. 4A , is disposed on the substrate  400  having an opening  411  formed therein configured to have at least one conductive layer, such as copper line, disposed therein laterally bounded by a dielectric layer. The dielectric stack  444  includes a dielectric bulk insulating layer  406  disposed over the dielectric barrier layer  408 . A hardmask layer  404  may be disposed on the top of the dielectric bulk insulating layer  406 . The opening  411  may include a trench  405  formed on a via  407  in the dielectric bulk insulating layer  406  by a suitable etching process, such as dual damascene etching process. In one embodiment, the dielectric bulk insulating layer  406  is a dielectric material having a dielectric constant less than 4.0 (e.g., a low-k material). Examples of suitable materials include carbon-containing silicon oxides (SiOC), such as BLACK DIAMOND® dielectric material available from Applied Materials, Inc., and other low-k polymers, such as polyamides. The hardmask layer  404  disposed on the dielectric bulk insulating layer  406  may be a dielectric layer selected from a group consisting of silicon oxide, TEOS, silicon oxynitride, amorphous carbon, and the like. In the embodiment depicted in  FIG. 4A-E , the dielectric bulk insulating layer  406  is a carbon-containing silicon oxide (SiOC) layer and the hardmask layer  404  is a TEOS layer, silicon oxide layer or an amorphous carbon layer. 
     The dielectric barrier layer  408  has a dielectric constant of about 5.5 or less. In one embodiment, the dielectric barrier layer  408  is a carbon containing silicon layer (SiC), a nitrogen doped carbon containing silicon layer (SiCN), or the like. In the embodiment depicted in  FIG. 4A , the dielectric barrier layer is a SiCN film. An example of the dielectric barrier layer material is BLOK® dielectric material, available from Applied Materials, Inc. 
     In the embodiment depicted in  FIG. 4A , the dielectric stack  420  is etched through the opening  411 , thereby defining the trench  405  on a via  407  or vice versa, in the dielectric bulk insulating layer  406  over the dielectric barrier layer  408 . A portion of the dielectric bulk insulating layer  406  is removed to expose a surface  410  of the dielectric barrier layer  408 . A conductive layer  442  present in the interconnect layer  440  is below the via  407  formed in the dielectric barrier layer  408 . In one embodiment, the dielectric bulk insulating layer  406  is etched using a plasma formed from fluorine and carbon. The dielectric bulk insulating layer  406  may be etched in the processing chamber  100  or other suitable reactor. 
     At block  304 , a treatment process is performed to treat the exposed surface  410  of the dielectric barrier layer  408  to alter the surface properties to facilitate removal of the dielectric barrier layer  408  in the subsequent chemical etching process. The treatment process performed at block  304  includes supplying a treatment gas mixture into the chamber  100 . A plasma is then formed from the treatment gas mixture to plasma treat the surfaces  410  of the dielectric barrier layer  408  exposed by the dielectric bulk insulating layer  406 . The treatment process activates the dielectric barrier layer  408  into an excited state, forming a treated dielectric barrier layer  412  in the area unprotected by the dielectric bulk insulating layer  406 , as shown in  FIG. 4C . The treated dielectric barrier layer  412 , may then easily react with chemical etching gases subsequently supplied into the processing chamber  100  at block  306 , forming volatile gas byproducts which readily pumps out of the processing chamber  100 . 
     In one embodiment, the treatment gas mixture includes at least one of a hydrogen containing gas, a nitrogen containing gas, or an inert gas. It is believed that the hydrogen containing gas, the nitrogen containing gas, or inert gas supplied in the treatment gas mixture may assist increasing the lifetime of the ions in the plasma formed from the treatment gas mixture. Increased lifetime of the ions may assist reacting with and activating the dielectric barrier layer  408  on the substrate  400  more thoroughly, thereby enhancing the removal of the activated dielectric barrier layer  412  from the substrate  400  during the subsequent chemical etching process. In the embodiment wherein the hydrogen containing gas is utilized in the treatment gas mixture, the hydrogen atoms from the hydrogen containing gas may react with the silicon atoms contained in the dielectric barrier layer  408 , thereby forming weak and dangling bond of Si—H or Si—OH bond on the treated dielectric barrier layer  412 . The treated dielectric barrier layer  412  with Si—H or Si—OH bond terminals may easily to be absorbed by other etchants subsequently supplied to the processing chamber  100 , thereby assisting ease of removal of the treated dielectric barrier layer  412  from the substrate surface. 
     In one embodiment, the hydrogen containing gas supplied into the processing chamber  100  includes at least one of H 2 , H 2 O, and the like. The nitrogen containing gas supplied into the processing chamber  100  includes at N 2 , N 2 O, NO 2 , NH 3  and the like The inert gas supplied into the processing chamber  100  includes at least one of Ar, He, Kr, and the like. In an exemplary embodiment, the hydrogen containing gas supplied in the processing chamber  100  to perform the treatment process is H 2  gas, and the nitrogen containing gas supplied in the processing chamber  100  to perform the treatment process is N 2  gas and the inert gas is He or Ar. 
     During the plasma treatment process, several process parameters may be regulated to control the treatment process. In one exemplary embodiment, a process pressure in the processing chamber  100  is regulated between about 10 mTorr to about 5000 mTorr, such as between about 10 mTorr and about 200 mTorr. A RF bias power at a frequency of about 13 MHz may be applied to maintain a plasma in the treatment gas mixture. For example, a RF bias power of about 20 Watts to about 200 Watts may be applied to maintain a plasma inside the processing chamber  100 . The treatment gas mixture may be flowed into the chamber at a rate between about 200 sccm to about 800 sccm. A substrate temperature is maintained between about 25 degrees Celsius to about 300 degrees Celsius, such as between about 50 degrees Celsius and about 140 degrees Celsius, for example between about 50 degrees Celsius and about 110 degrees Celsius. 
     In one embodiment, the substrate  400  is subjected to the treatment process for between about 5 seconds to about 5 minutes, depending on the operating temperature, pressure and flow rate of the gas. For example, the substrate can be exposed to the pretreatment processes for about 30 seconds to about 90 seconds. In an exemplary embodiment, the substrate is exposed to the treatment process for about 90 seconds or less. 
     At block  306 , a remote plasma etching process is performed on the substrate  400  to etch the treated dielectric barrier layer  412  on the substrate  400 , as shown in  FIG. 4C . The remote plasma etching process is a chemical process performed to slowly remove the treated dielectric barrier layer  412  exposed by the dielectric bulk insulating layer  406  on the substrate  400 . The remote plasma etching process is performed by supplying an etching gas mixture into the plasma cavity  150  into the processing chamber  100  to form a remote plasma source in the plasma cavity  150  from the processing gas mixture prior to flow the processing gas for etching the treated dielectric barrier layer  412 . 
     In one embodiment, the etching gas mixture used to remove the treated dielectric barrier layer  412  is a mixture of ammonia (NH 3 ) and nitrogen trifluoride (NF 3 ) gases. The amount of each gas introduced into the processing chamber may be varied and adjusted to accommodate, for example, the thickness of the treated dielectric barrier layer  412  to be removed, the geometry of the substrate being processed, the volume capacity of the plasma cavity, the volume capacity of the chamber body, as well as the capabilities of the vacuum system coupled to the chamber body. 
     As the plasma is generated remotely in the plasma cavity  150 , the etchants dissociated from the etching gas mixture from the remote source plasma is relatively mild and gentle, so as to slowly, gently and gradually chemically react the treated dielectric barrier layer  412  until the underlying conductive layer  442  is exposed. It is believed that in the remote plasma source, ammonia (NH 3 ) gas and the nitrogen trifluoride (NF 3 ) gas are dissociated in the remote plasma cavity  150 , forming ammonium fluoride (NH 4 F) and/or ammonium fluoride with HF (NH 4 F.HF). Once the etchants of ammonium fluoride (NH 4 F) and ammonium fluoride with HF (NH 4 F.HF) are introduced into the processing region  141  of the processing chamber  100 , reaching upon the substrate surface, the etchants of ammonium fluoride (NH 4 F) and ammonium fluoride with HF (NH 4 F.HF) may react with the dielectric materials of the material layer  404 , such as silicon oxide, forming (NH 4 ) 2 SiF 6 , mostly in a solid state. The etchants of ammonium fluoride (NH 4 F) and ammonium fluoride with HF (NH 4 F.HF) chemically react the treated dielectric barrier layer  412 , forming (NH 4 ) 2 SiF 6  in solid state, which will be later removed from the substrate surface by using a low temperature sublimation process, which will be discussed in further detail at block  308 . 
     In one or more embodiments, the gases added to provide the etching gas mixture having at least a 1:1 molar ratio of ammonia (NH 3 ) to nitrogen trifluoride (NF 3 ). In one or more embodiments, the molar ratio of the etching gas mixture is at least about 3:1 (ammonia to nitrogen trifluoride). The gases are introduced in the chamber  100  at a molar ratio of from about 5:1 (ammonia to nitrogen trifluoride) to about 30:1. In yet another embodiment, the molar ratio of the etching gas mixture is from about 5:1 (ammonia to nitrogen trifluoride) to about 10:1. The molar ratio of the etching gas mixture can also fall between about 10:1 (ammonia to nitrogen trifluoride) and about 20:1. 
     In one embodiment, other types of gas, such as inert gas or carrier gas, may also be supplied in the etching gas mixture to assist carrying the etching gas mixture into the processing region  141  of the vacuum processing chamber  100 . Suitable examples of the inert gas or carrier gas include at least one of Ar, He, N 2 , O 2 , N 2 O, NO 2 , NO, and the like. In one embodiment, the inert or carrier gas may be supplied into the vacuum processing chamber  100  is Ar or He at a volumetric flow rate between about 200 sccm and about 1500 sccm. 
     While supplying the etching gas mixture to perform the remote plasma source etching process, a substrate temperature may be maintained at a low range, such as less than about 100 degrees Celsius, such as between about 40 degrees Celsius and about 100 degrees Celsius. It is believed that maintaining the substrate temperature at a low range, such as less than 100 degrees Celsius, may assist increasing the etching rate of the etching process. It is believed that overly high temperature will restrain chemical reaction between ammonia (NH 3 ) and nitrogen trifluoride (NF 3 ) to form the desired etchants, ammonium fluoride (NH 4 F) and/or ammonium fluoride with HF (NH 4 F.HF), for etching. As nitrogen trifluoride (NF 3 ) is relatively thermodynamically stable at elevated temperatures, a low temperature utilized during the etching process may favors surface adsorption of plasma of plasma species onto the treated dielectric barrier layer  412  being etched. Therefore, controlling the substrate temperature at a range less than about 100 degrees Celsius may desirably enhance the etching rate during the etching process, thereby increasing the overall etching process throughput. 
     After the etching gas mixture is supplied into the processing chamber and exposed to the low temperature substrate, such as less than about 100 degrees Celsius, the treated dielectric barrier layer  412  may be then etched, forming solid etching byproduct  414 , such as ammonium fluorosilicate (NH 4 ) 2 SiF 6 , on the substrate surface, as shown in  FIG. 4C . The etching byproduct  414 , (NH 4 ) 2 SiF 6 , remaining on the substrate  400  has a relatively low melting point, such as about 100 degrees Celsius, which allows the byproduct  414  to be removed from the substrate by a sublimation process, which will be further discussed below at block  308 . The etching process may be continuously performed until the treated dielectric barrier layer  412  disposed on the substrate  400  has all been reacted and converted to the etching byproduct  414 . 
     During the etching process, several process parameters may be regulated to control the etching process. In one exemplary embodiment, a process pressure in the processing chamber  100  is regulated between about 10 mTorr to about 5000 mTorr, such as between about 800 mTorr and about 5 Torr. A RF source power at a frequency of about 80 KHz may be applied to maintain a plasma in the chemical etching gas mixture. For example, a RF source power of about between 20 Watts to about 70 Watts may be applied to the etching gas mixture. The RF source power as referred here may be the RF power supplied from the power source  152  to the electrodes  143 ,  145 . In one embodiment, the RF source power may have a frequency of about 80 KHz. Additionally, a RF bias power may be supplied to the electrode  181  to generate a bias power. For example, a RF bias power at a frequency of about 13 or 60 MHz of between about 10 Watts to about 1000 Watts may be applied to the etching gas mixture. The etching gas mixture may be flowed into the chamber at a rate between about 400 sccm to about 2000 sccm. In one embodiment, the etching process may be performed for between about 60 seconds and about 2000 seconds. 
     At block  308 , after the etching process is completed and the treated dielectric barrier layer  412  has substantially reacted and converted to the etching byproduct, a sublimation process is performed to sublimate the etching byproduct  414  into a in volatile state which can be pumped out of the processing chamber  100 . The sublimation process removes the etching byproduct  414  from the substrate  400 , exposing the underlying conductive layer  442 , as shown in  FIG. 4D . The sublimation process may be performed in the same chamber where the remote plasma etching process at block  306  is performed, such as the processing chamber  100  as described above. Alternatively, the sublimation process may be performed at a separate processing chamber of the system  200  as needed. 
     The sublimation process may be a plasma anneal process utilizing a plasma energy to sublimate etching byproduct  414  from the substrate  400 . The thermal energy from the plasma may efficiently remove the etching byproduct  414 , by the nature of the low melting (sublimation) point to the etching byproduct  414 , such as ammonium fluorosilicate (NH 4 ) 2 SiF 6 , without using conventionally high annealing process. 
     In one embodiment, the sublimation process may utilize a low RF bias power plasma treatment process to gently and mildly treat the substrate without damaging to the substrate surface. In one embodiment, the low temperature plasma process may use a low RF bias power, such as less than about 300 Watts, along with controlling the substrate temperature controlled between about 20 degrees Celsius and about 150 degrees Celsius, such as about 110 degrees Celsius, to sublimate the etching byproducts  414  from the substrate surface. 
     The sublimation process is performed by supplying a plasma anneal gas mixture into the chamber  100 . A plasma is then formed from the plasma anneal gas mixture to plasma anneal the substrate  400 , forming volatile gas byproducts which readily pumps out of the processing chamber  100 . 
     In one embodiment, the plasma anneal gas mixture includes at least one of a hydrogen containing gas, a nitrogen containing gas, or an inert gas. It is believed that the hydrogen containing gas, the nitrogen containing gas, or inert gas supplied in the plasma anneal gas mixture may assist increasing the lifetime of the ions in the plasma formed from the plasma anneal gas mixture, thereby efficiently removing the etching byproducts  414  from the substrate  400 . Increased lifetime of the ions may assist reacting with and activating the etching byproduct  414  on the substrate  400  more thoroughly, thereby enhancing the removal of the etching byproduct  414  from the substrate  400 . 
     In one embodiment, the hydrogen containing gas supplied into the processing chamber  100  includes at least one of H 2 , H 2 O, and the like. The nitrogen containing gas supplied into the processing chamber  100  includes at least one of N 2 , N 2 O, NO 2 , NH 3  and the like. The inert gas supplied into the processing chamber  100  includes at least one of Ar, He, Kr, and the like. In an exemplary embodiment, the hydrogen containing gas supplied in the processing chamber  100  to perform the treatment process is H 2  gas, and the nitrogen containing gas supplied in the processing chamber  100  to perform the treatment process is N 2  gas and the inert gas is He or Ar. 
     During the plasma anneal process, several process parameters may be regulated to control the pretreatment process. In one exemplary embodiment, a process pressure in the processing chamber  100  is regulated between about 10 mTorr to about 5000 mTorr, such as between about 10 mTorr and about 200 mTorr. A RF bias power at a frequency of about 13 MHz may be applied to maintain a plasma in the treatment gas mixture. For example, a RF bias power of about 20 Watts to about 300 Watts may be applied to maintain a plasma inside the processing chamber  100 . The plasma anneal gas mixture may be flowed into the chamber at a rate between about 100 sccm to about 1000 sccm. A substrate temperature is maintained between about 20 degrees Celsius and about 150 degrees Celsius, such as about 110 degrees Celsius. In some embodiment, no power is applied to the electrodes  143 ,  145 . 
     At block  310 , after the etching byproduct  414  is removed from the substrate to expose the underlying conductive layer  442 , an interface protection layer  422  is formed on the surface of the etched dielectric bulk insulating layer  406  and the conductive layer  442 , as shown in  FIG. 4E . The interface protection layer  422  is deposited by flowing a process gas mixture into the processing chamber  100 . The process gas mixture flowed into the processing chamber  100  perform a deposition process to form the interface protection layer  422  to protect the exposed surface of the conductive layer  442  from further contamination or oxidation when residing in the ambient environment, thereby allowing the process Q-time to be increased. The process gas mixture may include a polymer gas containing carbon and silicon elements. In one embodiment, the process gas mixture may include, but not limited to, a polymer gas accompanying with at least one carrier gas, such as argon gas (Ar), helium gas (He), nitric oxide (NO), carbon monoxide (CO), nitrous oxide (N 2 O), oxygen gas (O 2 ), nitrogen gas (N 2 ) and the like. Suitable examples of the polymer gas comprise fluoroalkyl polyoxyethylene, polydimethylsiloxane, trimethylsilane (TMS or 3MS), tetramethylsilane (TMS or 4MS), octamethylcyclotetrasilane (OMCTS), hexamethyldisilane (HMDS) and among others. In one embodiment, the interface protection layer  422  is a silicon containing layer, such as a silicon oxide layer. 
     Several process parameters are regulated while the process gas mixture is supplied into the etch reactor. In one embodiment, a pressure of the process gas mixture in the etch reactor is regulated between about 10 mTorr to about 500 mTorr, and the substrate temperature is maintained between about 0 degrees Celsius and about 100 degrees Celsius. RF source power may be applied at a power of about 0 Watts to about 1000 Watts. The process gas mixture may be flowed at a rate between about 1 sccm to about 100 sccm. 
     The thickness of the interface protection layer  422  may be determined by any suitable methods. In one embodiment, the interface protection layer  422  may be deposited having a thickness between about 1 Å to about 200 Å. In another embodiment, the thickness of the interface protection layer  422  may be determined by monitoring optical emissions, expiration of a predefined time period or by another indicator for measuring that the protection layer is sufficiently formed. 
     The interface protection layer deposition process on the dual damascene structure  402  is in-situ deposited and completed in the processing chamber  100 . In an alternatively embodiment, the interface protection layer deposition process may be optionally ex-situ deposited or etched in another vacuum processing chamber. 
     Thus, a method and an apparatus for an etching process with high etching selectivity followed by an interface protection layer deposition process are provided. The method may etch a dielectric barrier layer with high etching selectivity with good interface control while providing an interface protection layer to protect a conductive layer exposed after the etching process. By utilizing the deposition of the interface protection layer, a good interface control may be obtained and the process Q-time may also be extended so as to provide a wider process window and reliable manufacturing predictability. 
     While the foregoing is directed to embodiments of the present invention, other and further embodiments of the invention can be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.