Patent Publication Number: US-2015064921-A1

Title: Low temperature plasma anneal process for sublimative etch processes

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 material layer disposed on a substrate using a low temperature plasma annealing 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 in forming structures, such as gate structure, shallow trench isolation (STI), bit lines and the like, on a substrate by an etching process. 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. 
     In order to enable fabrication of next generation devices and structures, the geometry limits of the structures designed to be formed for the semiconductor devices has been pushed against technology limits, the need for accurate process control for the manufacture of small critical dimensional structures with high aspect ratio has become increasingly important. Poor process control during etching process will result in irregular structure profiles and line edge roughness, thereby resulting in poor line integrity of the formed structures. Additionally, irregular profiles and growth of the etching by-products formed during etching may gradually block the small openings used to fabricate the small critical dimension structures, thereby resulting in bowed, distorted, toppled, or twisted profiles of the etched structures. 
     Furthermore, the similarity between the materials selected for the hardmask layer and the adjacent layers disposed in the film stack, and even the underlying material on the substrate, may also result in similar etch properties therebetween, thereby resulting in poor selectivity during etching. Poor selectivity between the hardmask layer, adjacent layers and the materials on the substrate may result in non-uniform, tapered and deformed profile of the hardmask layer, thereby leading to poor pattern transfer and failure of accurate structure dimension control. The chemical etchant used in the etch process is required to have a greater etch selectivity for the material layers in the film stack. That is, the chemical etchant etches the one or more layers of the film stack at a rate much faster than the energy sensitive resist or the materials disposed on the substrate. The etch selectivity to the one or more material layers of the film stack over the resist prevents the energy sensitive resist from being consumed prior to completion of the pattern transfer. Thus, a highly selective etchant enhances accurate pattern transfer. However, conventional etchants are not selective enough to enable robust manufacturing of next generation devices. 
     In most cases, a slow etching process, such as etching rate less than 170 Å per minute, is also utilized to improve the etching selectivity so as to prevent over-etching to the underlying structures. However, the slow etching process may significantly impact the throughput of the etching process, thereby increasing manufacture cost and reducing process cycle time. 
     Thus, there is a need for improved methods for etching a material layer with high aspect ratio for manufacturing semiconductor devices with high etching selectivity, high throughput and accurate process and profile control. 
     SUMMARY 
     Methods for etching a material layer disposed on the substrate using a low temperature etching process along with a subsequent low temperature plasma annealing process are provided. In one embodiment, a method for etching a material layer disposed on a substrate includes transferring a substrate having a material layer disposed thereon into an etching processing chamber, supplying an etching gas mixture into the processing chamber, remotely generating a plasma in the etching gas mixture to etch the material layer disposed on the substrate, and plasma annealing the material layer at a substrate temperature less than 100 degrees Celsius. 
     In another embodiment, a method for etching a material layer disposed on a substrate includes performing an etching process in a processing chamber to etch a material layer exposed by a patterned mask layer disposed on a substrate, wherein a substrate temperature during the etching process is controlled less than about 100 degrees Celsius, and performing a plasma anneal process on the etched material layer in the processing chamber, wherein the substrate temperature during the plasma anneal process is controlled less than about 100 degrees Celsius. 
     In yet another embodiment, a method for etching a material layer on a substrate includes transferring a substrate having a material layer into a processing chamber, remotely generating a plasma from an etching gas mixture that includes an ammonium gas and a nitrogen trifluoride, controlling a substrate temperature less than about 100 degrees Celsius, etching the material layer from the substrate utilizing the etching gas mixture, subsequently supplying a plasma anneal gas mixture into the processing chamber, applying less than about 300 Watts of a RF bias power to the plasma anneal gas mixture, controlling the substrate temperature less than about 100 degrees Celsius, and sublimating an etching byproduct 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 material layer using a low temperature etching process followed by a low temperature plasma anneal process in accordance with one embodiment of the present invention; and 
         FIGS. 4A-4C  depict cross-sectional views of a material layer disposed on a semiconductor substrate over a sequence for etching the material layer 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 low temperature etching a material layer followed by a low temperature plasma anneal process are disclosed herein which provide an etching process with high etching selectivity and accurate profile control. In one embodiment, the etching process includes using a low temperature etching process along with a low temperature plasma anneal process to assist removing etching byproducts from the substrate. The combination of the low temperature etching process followed by the low temperature plasma anneal process can provide an etching process with high etching selectivity while maintaining process throughput comparable to conventional processes to minimize the manufacturing cost. 
       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  1558  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 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. 
     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 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  186  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  186  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  186  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 opening of the slit valve  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 of the chamber body. 
     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  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 from either the lower position to 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 assembly  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 material layer disposed on a substrate with high etching selectivity and good profile control. The sequence described in  FIG. 3  corresponds to the fabrication stages depicted in  FIGS. 4A-4C , which illustrates schematic cross-sectional views of a substrate  402  having a material layer  404  formed thereon during different stages of etching the material layer  404  illustrated by the processing sequence  300 . 
     The process sequence  300  starts at block  302  by transferring a substrate, such as the substrate  402  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  402  may have a substantially planar surface, an uneven surface, or a substantially planar surface having a structure formed thereon. The substrate  402  shown in  FIG. 4A  includes a material layer  404  formed on the substrate  402 . In one embodiment, the substrate  402  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  402  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 material layer  404  may be utilized to form a gate structure, shallow trench isolation (STI) structure, a contact structure or an interconnection structure in the front end or back end processes. In one embodiment, the method  300  may be performed on the material layer  404  to form a shallow trench isolation (STI) structure therein. The material layer  404  may be a dielectric layer selected from a group consisting of an oxide layer, a nitride layer, titanium nitride layer, a composite of oxide and nitride layer, at least one or more oxide layers sandwiching a nitride layer, and combinations thereof, among others. Other suitable materials for the material layer  404  also include undoped silicon glass (USG), such as silicon oxide or TEOS, boron-silicate glass (BSG), phosphorus-silicate glass (PSG), boron-phosphorus-silicate glass (BPSG) and combinations thereof. In an exemplary embodiment depicted herein, the material layer  404  is an undoped silicon glass (USG) layer. In one embodiment, the material layer  404  has a thickness between about 100 Å to about 15000 Å, such as between about 200 Å to about 5000 Å, for example about 2000 Å. 
     A patterned mask layer  406  is disposed on the material layer  404 . The patterned mask layer  406  has an open feature  408  that exposes portions  410  of the material layer  404  for etching. In one embodiment, the mask layer  406  may be a hardmask layer, a photoresist mask or a combination thereof. The open feature  408  in the mask layer  406  is used as an etch mask to form open features  416  in the material layer  404  with desired aspect ratios and profile. The open features  416  described herein may include trenches, vias, openings and the like. In one embodiment wherein the mask layer  406  is a hardmask layer, the mask layer  406  may be a material selected from a group consisting of silicon, silicon oxide, silicon nitride, silicon oxynitride, silicon carbide, amorphous carbon, and combinations thereof. In some embodiments, the mask layer  406  may be a patterned photoresist layer, such as a lithographically patterned mask. The photoresist layer may is a positive tone photoresist, a negative tone photoresist, a UV lithography photoresist, an i-line photoresist, an e-beam resist (for example, a chemically amplified resist (CAR)) or other suitable photoresist. 
     At block  304 , a remote plasma etching process is performed on the substrate  402  to etch the material layer  404  on the substrate  402 , as shown in  FIG. 4B . A remote plasma etching process is performed to slowly remove the material layer  404  exposed by the patterned mask layer  406  from the substrate  402 . 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 flowing the processing gas for etching the material layer  404 . 
     In one embodiment, the etching gas mixture used to remove the material layer  404  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 material layer  404  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 material layer  404  until the underlying substrate  402  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 of the processing chamber, 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, 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 material layer  404 , forming (NH 4 ) 2 SiF 6  in solid state, which will be later removed from the substrate surface by using a low temperature plasma anneal process, which will be discussed in further detail at block  310 . 
     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 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. 
     At block  306 , 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 material layer  404  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. 
     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. 
     At block  308 , after the etching gas mixture is supplied into the processing chamber with a low temperature substrate control, such as less than about 100 degrees Celsius, the material layer  404  may be then etched, forming solid etching byproduct  412 , ammonium fluorosilicate (NH 4 ) 2 SiF 6 , on the substrate surface, as shown in  FIG. 4B . The etching byproduct  412 , (NH 4 ) 2 SiF 6 , remaining on the substrate has a relatively low melting point, such as about 100 degrees Celsius, which may be removed from the substrate by a sublimation process, which will be further discussed below at block  310 . The etching process may be continuously performed until the material layer  404  disposed on the substrate  402  has all been reacted and converted to the ending byproduct  412 , such as ammonium fluorosilicate (NH 4 ) 2 SiF 6 . 
     In one embodiment, the etching process may be performed for between about 60 seconds and about 2000 seconds. 
     At block  310 , after the etching process is completed and the material layer  404  has substantially reacted and converted to the etching byproduct  412 , such as ammonium fluorosilicate (NH 4 ) 2 SiF 6 , a low temperature plasma anneal process is performed to sublimate the ending byproduct  412  in volatile state to be pumped out of the processing chamber. The low temperature plasma anneal process may be performed in the same chamber where the low temperature etching process at block  308  is performed, such as the processing chamber  100  as described above. Alternatively, the low temperature plasma anneal process may be performed at a separate processing chamber of the system  200  as needed. 
     During the low temperature plasma anneal process, the substrate temperature is maintained low, such as a low temperature range less than about 100 degrees Celsius. Conventional high temperature anneal processes may not only adversely increase the overall process time (e.g., an additional process step or waiting time to elevate substrate support member temperature from low temperature etching process to high temperature for annealing), but also affect the chemical reaction and the etching byproduct removal rate during the anneal process. Additionally, conventional high temperature annealing processes often causes damage to the substrate and increases condensation of the other etching byproducts adhering on the substrate surface. Therefore, by utilizing a low temperature plasma anneal process, not only can throughout be improved (e.g., by not requiring a temperature change from the etching process previously performed at block  308 ), but also the etching byproduct cleaning efficiency may be improved, by the nature of the low melting (sublimation) point to the etching byproduct  412 , such as ammonium fluorosilicate (NH 4 ) 2 SiF 6 . 
     In one embodiment, the low temperature plasma anneal 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 less than about 100 degrees Celsius, to sublimate the etching byproducts  412  from the substrate surface. 
     The low temperature plasma anneal 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  402 , 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  412  from the substrate  420 . Increased lifetime of the ions may assist reacting with and activating the etching byproduct  412  on the substrate  402  more thoroughly, thereby enhancing the removal of the etching byproduct  412  from the substrate  402 . 
     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 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 less than 100 degrees Celsius, for example between about room temperature to about 100 degrees Celsius, such as between about 40 degrees Celsius and about 100 degrees Celsius. In some embodiment, no power is applied to the electrodes  143 ,  145 . 
     Thus, a method and an apparatus for a low temperature etching process along with a low temperature plasma anneal process with high etching selectivity and good profile control are provided. The method may gradually etch a material layer with good interface control while providing an acceptable range of overall etching throughput. 
     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.