Abstract:
A method for depositing a film in a substrate processing system includes arranging a substrate on a pedestal in a processing chamber, heating the substrate to a temperature within a predetermined temperature range, and supplying a gas mixture to the processing chamber for a predetermined period to deposit the film on the substrate, wherein the gas mixture includes a first precursor gas, ammonia gas and diborane gas.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of U.S. Provisional Application No. 61/674,611, filed on Jul. 23, 2013. The entire disclosure of the application referenced above is incorporated herein by reference 
     
    
     FIELD 
       [0002]    The present disclosure relates to chemical vapor deposition, and more specifically to deposition of conformal films using chemical vapor deposition. 
       BACKGROUND 
       [0003]    The background description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure. 
         [0004]    Deposition of conformal films at lower temperatures is currently performed using plasma-enhanced chemical vapor deposition (PECVD) using costly, non-generic chemistry that is not widely used in the semiconductor industry. Some deposition techniques used to form conformal films, such as atomic layer deposition (ALD), have complicated sequencing with critical timing steps. As a result of these requirements, yields tend to be lower and cost tends to be higher. 
         [0005]    Typical silane (SiH 4 ) based CVD starts to occur in a reactor at ˜650° C. pedestal temperature, however the deposited film is typically non-uniform. Decomposition of the SiH 4  alone by pyroltic reaction forms amorphous silicon. Adding hydrogen to the reaction results in hydrogenated amorphous silicon, however the pedestal operating temperature still needs to be above ˜650° C. for deposition to occur. 
       SUMMARY 
       [0006]    This section provides a general summary of the disclosure, and is not a comprehensive disclosure of its full scope or all of its features. 
         [0007]    A substrate processing system for depositing a film includes a processing chamber, a heater, and a controller. The processing chamber includes a pedestal to support a substrate. The heater is configured to heat the substrate to a temperature within a predetermined temperature range. The controller is configured to supply a gas mixture to the processing chamber for a predetermined period, wherein the gas mixture includes a first precursor gas, ammonia gas and diborane gas, purge the processing chamber after the predetermined period, and repeat the supply and purging one or more times to deposit the film. 
         [0008]    A method for depositing a film in a substrate processing system includes arranging a substrate on a pedestal in a processing chamber, heating the substrate to a temperature within a predetermined temperature range, and supplying a gas mixture to the processing chamber for a predetermined period to deposit the film on the substrate, wherein the gas mixture includes a first precursor gas, ammonia gas and diborane gas. 
         [0009]    Further areas of applicability will become apparent from the description provided herein. The description and specific examples in this summary are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]    The present disclosure will become more fully understood from the detailed description and the accompanying drawings, wherein: 
           [0011]      FIGS. 1 and 2  are functional block diagrams of examples of substrate processing systems and methods according to the present disclosure; 
           [0012]      FIG. 3  is a flowchart illustrating an example of method for depositing a conformal film according to the present disclosure; 
           [0013]      FIG. 4  is a table illustrating various examples of flow ratios according to the present disclosure; and 
           [0014]      FIG. 5  is a graph illustrating examples of absorbance as a function of wavenumber according to the present disclosure. 
       
    
    
     DETAILED DESCRIPTION 
       [0015]    According to the present disclosure, substrate processing systems and methods are disclosed for forming a conformal film at relatively low temperatures. For example only, the substrate processing systems and methods may employ chemical vapor deposition (CVD) using basic nitride chemistry (for example, silane (SiH 4 ) and ammonia (NH 3 ) (in an inert carrier gas)) with the addition of diborane B 2 H 6 , which acts as a catalyzer. 
         [0016]    The substrate processing systems and methods described herein involve decomposition by a catalytic and pyroltic reaction, which enables a lower temperature boundary area that is less than 630° C. For example only, deposition of the conformal film may occur at pedestal temperatures at about 500° C. or greater. In other words, the addition of the catalyzer B 2 H 6  to the process reaction allows the deposition temperature to be significantly lowered to about ˜500° C. 
         [0017]    Referring now to  FIG. 1 , an example of a CVD reactor  100  includes a process chamber  124 , which encloses other components of the CVD reactor  100 . Within the CVD reactor  100 , a pedestal  118  supports a substrate  116 . A showerhead  120  delivers one or more precursors to the CVD reactor  100 . The pedestal  118  typically includes a chuck, a fork, or lift pins to hold and transfer the substrate during deposition or other treatment. The chuck may be an electrostatic chuck, a mechanical chuck or other type of chuck. 
         [0018]    The process gases are introduced via inlet  112 . Multiple source gas lines  110  are connected to a manifold  108 . The gases may be premixed or not. Appropriate valves and mass flow controllers generally identified at  113  are employed to ensure that the correct gases are delivered at predetermined flow rates and mixtures during the deposition and other treatment phases of the process. 
         [0019]    Process gases exit the process chamber  124  via an outlet  122 . A vacuum pump  126  (for example only, a one or two stage mechanical dry pump and/or a turbo-molecular pump) draws process gases out and maintains a suitable pressure within the reactor using a controlled flow restriction device  128 , such as a throttle valve or a pendulum valve. 
         [0020]    It is possible to index the wafers after every deposition and/or post-deposition treatment until all the required depositions and treatments are completed, or multiple depositions and treatments can be conducted at a single station before indexing the wafer. 
         [0021]    Referring now to  FIG. 2 , an example of a controller  200  for controlling the system of  FIG. 1  is shown. The controller  200  may include a processor, memory and one or more interfaces. The controller  200  may be employed to control devices in the system based in part on sensed values. In addition, the controller  200  may be used to control heating and cooling of the showerhead  120 . 
         [0022]    For example only, the controller  200  may control one or more of valves  202 , filter heaters  204 , pumps  206 , and other devices  208  based on the sensed values and other control parameters. The controller  200  receives the sensed values from, for example only, pressure manometers  210 , flow meters  212 , temperature sensors  214 , and/or other sensors  216 . The controller  200  may also be employed to control process conditions during precursor delivery and deposition of the film. The controller  200  will typically include one or more memory devices and one or more processors. 
         [0023]    The controller  200  may control the precursor delivery system and deposition apparatus. The controller  200  executes computer programs including sets of instructions for controlling process timing, delivery system temperature, pressure differentials across the filters, valve positions, mixture of gases, chamber pressure, chamber temperature, wafer temperature, pedestal RF power levels, wafer chuck or pedestal position, and other parameters of a particular process. The controller  200  may also monitor the pressure differential and automatically switch vapor precursor delivery from one or more paths to one or more other paths. Other computer programs stored on memory devices associated with the controller  200  may be employed in some embodiments. 
         [0024]    Typically there will be a user interface associated with the controller  200 . The user interface may include a display  218  (e.g. a display screen and/or graphical software displays of the apparatus and/or process conditions), and user input devices  220  such as pointing devices, keyboards, touch screens, microphones, etc. The controller parameters relate to process conditions such as, for example, filter pressure differentials, process gas composition and flow rates, temperature, pressure, and chamber wall temperature. 
         [0025]    The system software may be designed or configured in many different ways. For example, various chamber component subroutines or control objects may be written to control operation of the chamber components necessary to carry out the deposition processes. Examples of programs or sections of programs for this purpose include substrate positioning code, process gas control code, pressure control code, and heater control code. 
         [0026]    A substrate positioning program may include program code for controlling chamber components that are used to load the substrate onto a pedestal or chuck and to control the spacing between the substrate and other parts of the chamber such as a gas inlet and/or target. A process gas control program may include code for controlling gas composition and flow rates and optionally for flowing gas into the chamber prior to deposition in order to stabilize the pressure in the chamber. A filter monitoring program includes code comparing the measured differential(s) to predetermined value(s) and/or code for switching paths. A pressure control program may include code for controlling the pressure in the chamber by regulating, e.g., a throttle valve in the exhaust system of the chamber. A heater control program may include code for controlling the current to heating units for heating components in the precursor delivery system, the substrate and/or other portions of the system. Alternatively, the heater control program may control delivery of a heat transfer gas such as helium to the wafer chuck. 
         [0027]    Examples of sensors that may be monitored during deposition include, but are not limited to, mass flow controllers, pressure sensors such as the pressure manometers  210 , and the temperature sensors  214 . Appropriately programmed feedback and control algorithms may be used with data from these sensors to maintain desired process conditions. The foregoing describes implementation of embodiments in a single or multi-chamber semiconductor processing tool. 
         [0028]    The film growth is smooth and conformal. Using the same process space and temperature, ammonia gas (NH 3 ) can be introduced to the reaction (with or without hydrogen H 2 ) to form SiBN film conditions. The B—N and Si—N peaks (by Fourier transform infrared spectroscopy (FTIR)) can be modulated by a ratio of SiH 4  flow to B 2 H 6  flow. Alternatively, the stress and refractive index (RI) can be modulated by changing the ratio of SiH 4  to NH 3  flow. The amount of B 2 H 6  flow needed to act as the chemical catalyzer to start the deposition reaction can be very small. 
         [0029]    Referring now to  FIG. 3 , an example of a method  300  according to the present disclosure is shown. The method  300  includes setting process conditions for CVD deposition at  304 . For example, a process temperature and process pressure may be set to suitable values. At  308 , flows of a first precursor, NH 3  and B 2 H 6  are provided at predetermined flow rates for a predetermined period as determined at  312 . For example only, the first precursor may include SiH 4 , ethylene (C 2 H 4 ), N-Trimethylsilyl Acetamide (TMSA) or tetramethylsilane (4MS). Purge may be performed at  316 . The process may be repeated one or more times at  320  for the same predetermined period and/or for variable periods. 
         [0030]    For example, conformal films have been deposited with SiH 4  to B 2 H 6  ratios ranging from 1:0.01 to 1:0.025, although other ratios may be used. Using lower B 2 H 6  flow rates and/or toggling off the B 2 H 6  flow during the deposition of the film may decrease the amount of boron (as B—N) in the film and increase the Si—N bonding peak to form a full class of films from the boron nitride and true silicon nitride. The films are smooth and conformal. 
         [0031]    Multiple different films can be made like SiBN, SiB &amp; SiN with chemistry ratio changes with SiH 4 /NH 3 /B 2 H 6 . Replacing SiH 4  with carbon precursor like ethylene (C 2 H 4 ), N-Trimethylsilyl Acetamide (TMSA) or tetramethylsilane (4MS) allows deposition of conformal Boron Carbide films. 
         [0032]    The high pedestal temperatures of conventional deposition approaches (about 630° C.) constrain the hardware used since metals such as Al cannot be used at this temperature and chamber heating and outgassing may be problematic. Without adding a chemical to provide a catalytic component to the previously purely pyrolytic reaction, the thermal CVD deposition rate at 500° C. would be near zero. 
         [0033]    Referring now to  FIGS. 4 and 5 , various examples of the process are shown. In  FIG. 4 , FTIR analysis, refractive index (RI) and stress are shown for various flow rates of SiH 4 , NH 3  and B 2 H 6  in sccm. For example only, the process pressure may be approximately 5 Torr, although other process pressure values may be used. In  FIG. 5 , absorbance is shown as a function of wavenumber for the examples of  FIG. 5 . These examples employ a ratio of the silane precursor gas to the diborane gas that is between 1:0.22 and 1:0.5 
         [0034]    The foregoing description is merely illustrative in nature and is in no way intended to limit the disclosure, its application, or uses. The broad teachings of the disclosure can be implemented in a variety of forms. Therefore, while this disclosure includes particular examples, the true scope of the disclosure should not be so limited since other modifications will become apparent upon a study of the drawings, the specification, and the following claims. For purposes of clarity, the same reference numbers will be used in the drawings to identify similar elements. As used herein, the phrase at least one of A, B, and C should be construed to mean a logical (A or B or C), using a non-exclusive logical OR. It should be understood that one or more steps within a method may be executed in different order (or concurrently) without altering the principles of the present disclosure.