Abstract:
The description relates to an adjustable nozzle capable of pivoting about an axis of the nozzle and translating along the axis of the nozzle. A high density plasma chemical vapor deposition (HDP CVD) chamber houses a plurality of adjustable nozzles. A feedback control system includes a control unit coupled to the adjustable nozzle and the HDP CVD chamber to form a more uniform thickness profile of films deposited on a wafer in the HDP CVD chamber.

Description:
BACKGROUND 
       [0001]    A high density plasma (HDP) chemical vapor deposition (CVD) chamber is an apparatus for forming a film on a wafer. The wafer is supported by a carrier and has a surface exposed to the interior of the HDP CVD chamber. Conventional HDP CVD chambers have nozzles which spray gas into an electrically induced plasma region in the chamber interior. The plasma then reacts to form a film on the wafer. The nozzles of a conventional HDP CVD chamber are spaced about the chamber above a top surface of the wafer. 
         [0002]    The film formed on the wafer using conventional techniques has significant variation in thickness across the surface of the wafer. Variations in thickness impacts the ability to form an intended semiconductor device using the wafer. For example, a relatively thicker portion of the film will take longer to etch, the result being either over-etching thinner portions of the film or under-etching thicker portions. Also relatively thinner portions of the film are removed faster during chemical and mechanical polishing (CMP), resulting in either damaging layers under the film if the thicker portions of the film are removed or a rougher surface if CMP stops once the thin portions of the film are removed. 
         [0003]    Thickness profiles for films deposited on wafers are evaluated using mean thickness, standard deviation of the thickness across the wafer surface and thickness range. These values are determined by taking thickness measurements at various locations across the surface of the wafer. The more uniform the thickness profile, the more likely the wafer will produce a usable device. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0004]    One or more embodiments are illustrated by way of example, and not by limitation, in the figures of the accompanying drawings, wherein elements having the same reference numeral designations represent like elements throughout. It is emphasized that, in accordance with standard practice in the industry various features may not be drawn to scale and are used for illustration purposes only. In fact, the dimensions of the various features in the drawings may be arbitrarily increased or reduced for clarity of discussion. 
           [0005]      FIG. 1  is a side view diagram of a high density plasma chemical vapor deposition (HDP CVD) chamber according to some embodiments; 
           [0006]      FIG. 2  is a diagram of a ring-shaped nozzle arrangement for an HDP CVD chamber according to some embodiments; 
           [0007]      FIG. 3  is a diagram of a side view of an adjustable nozzle according to some embodiments; 
           [0008]      FIG. 4  is a schematic diagram of a feedback control arrangement for determining a nozzle position according to some embodiments; 
           [0009]      FIGS. 5A and 5B  are a flow chart of a process of determining a nozzle position according to some embodiments; 
           [0010]      FIG. 6  is a side view diagram of a nozzle according to some embodiments; and 
           [0011]      FIG. 7  is a schematic diagram of a control unit for use in the feedback control arrangement of  FIG. 4 . 
       
    
    
     DESCRIPTION 
       [0012]    The following disclosure provides many different embodiments, or examples, for implementing different features of the invention. Specific examples of components and arrangements are described below to simplify the present disclosure. These are of course, merely examples and are not intended to be limiting. 
         [0013]      FIG. 1  is a side view diagram of an example HDP CVD chamber  100  having a wafer  108  supported on a carrier  110  disposed within the chamber interior  102 . An electrical field is induced in the chamber interior  102  using an inductive coil  114 . HDP CVD chamber  100  has nozzles  104  located around the periphery of chamber interior  102  for spraying gas into chamber interior  102 . HDP CVD chamber  100  has a hemispherical top portion  112  situated above wafer  108  to keep the gas sprayed by nozzles  104  in HDP CVD chamber interior  102 . Hemispherical top portion  112  has a baffle  106  to help redirect the plasma formed in chamber interior  102  toward wafer  108  to increase deposition speed and/or efficiency. In some embodiments, baffle  106  is equipped with a stationary nozzle or an adjustable nozzle. In some embodiments, nozzles  104  are situated above a top surface  116  of the wafer. 
         [0014]    In the embodiment of  FIG. 6 , a hollow cylindrical nozzle  104  has a base  602  and a tip  604 . Base  602  is connected on one end to a gas source  606  and to tip  604  on the other end. A hollow interior  610  conducts fluid in the form of a gas from the gas source to tip  604 . Tip  604  has an opening  612  to spray the gas into the HDP CVD chamber  100  ( FIG. 1 ). In some embodiments, opening  612  has a circular shape. In other embodiments, opening  612  has a slit shape oriented orthogonal to a longitudinal axis of base  602 . In still other embodiments, opening  612  is more than one opening formed in tip  604 . 
         [0015]      FIG. 2  is a diagram of an example nozzle arrangement in which nozzles  104  are distributed in a ring-shaped arrangement  200  around an inner surface  202  of HDP CVD chamber  100 . In other embodiments, nozzles  104  are arranged in different shapes. In the embodiment of  FIG. 2 , nozzles  104  are spaced periodically around inner surface  202 . In other embodiments, nozzles  104  are grouped together into a grouping of nozzles with larger spacing between groups. Each nozzle  104  is adjustable. In other embodiments, at least one nozzle  104  is stationary. In still other embodiments, only one nozzle  104  in the grouping of nozzles is adjustable. 
         [0016]    In the embodiment of  FIG. 3 , nozzle  104  is adjustable to be able to pivot about a longitudinal axis  306  extending through hollow interior  610  ( FIG. 6 ) of nozzle  104 . Nozzle  104  is able to pivot upward as shown by dash outline  304   a  or downward as shown by dash outline  304   b.  In some embodiments, nozzle  104  is pivoted using a piezoelectric motor coupled to the base  602 . In other embodiments, nozzle  104  is pivoted using a servo motor, stepper motor, pneumatic devices or other suitable movement inducing apparatus. The amount of pivot is represented by angle, θ n , which is the angle between the longitudinal axis of nozzle  104  extending perpendicular from an inner surface  202  ( FIG. 2 ) of a nozzle arrangement prior to pivoting and the longitudinal axis of the pivoted nozzle. For example,  FIG. 3  shows angle, θ n , between solid outline nozzle  104  and dashed outline nozzle  304   a.  In the embodiment of  FIG. 3 , the maximum pivot angle is about plus or minus 15-degrees. 
         [0017]    Nozzle  104  is also configured to translate (or extend) along the longitudinal axis as shown by dotted outline  302 . In some embodiments, nozzle  104  is configured to extend by using a piezoelectric motor coupled to the base  602 . In other embodiments, nozzle  104  is configured to extend by using a servo motor, stepper motor, pneumatic devices or other suitable movement inducing apparatus. The amount of translation is represented by distance, d, which is the distance between the opening of the nozzle tip prior to translation and the opening of the nozzle tip after translation. For example,  FIG. 3  shows distance, d, between solid nozzle outline  104  and dotted outline nozzle  302 . The ability to pivot and translate nozzle  104  allows the direction of gas sprayed by the nozzle to be adjusted to provide more uniform thickness of a film deposited on wafer  108  ( FIG. 1 ). In the embodiment of  FIG. 3 , the nozzle length is ranges from about 0.85 inches to about 1.76 inches. 
         [0018]    In an embodiment, pivot angle, θ n , and distance, d, are determined using a feedback control arrangement  400 . Feedback control system  400  includes HDP CVD chamber  402 , similar to HDP CVD chamber  100  ( FIG. 1 ), which also measures the thickness profile of wafer  108  following the film deposition process. The thickness profile of wafer  108  is measured using a metrology tool to determine the thickness of the deposited film at various locations across the surface of wafer  108 . The thickness profile data is then sent to a control unit  404 . In an embodiment, control unit  404  has the structure of  FIG. 7 . 
         [0019]      FIG. 7  is a schematic diagram of a control unit  404 . Control unit  404  includes a processor  712  configured to execute a set of instructions to cause the processor to perform calculations and comparisons between parameters. Processor  712  is connected to an input/output (I/O) device  714  by a bus  718  or similar mechanism. I/O device  714  is configured to receive signals from the HDP CVD chamber  402  and is configured to transmit control signals to an adjustable nozzle  406 . Processor  712  is also connected to a memory  716  by bus  718 . 
         [0020]    Memory  716  stores parameters used in the calculations and comparisons performed by processor  712 . Memory  716  includes a set of instructions comprising a nozzle adjustment system  720  configured to provide instruction for the calculations and comparisons performed by processor  712 . Memory  716  stores several parameters to control the positioning of the adjustable nozzle  406  ( FIG. 4 ). Memory  716  is configured to store a current thickness range  722  which is a measure of the uniformity of the thickness profile of a wafer most recently processed. Memory  716  is configured to store a reference thickness range  724  which is an updatable parameter which provides a basis for comparison for the current thickness range  722 . At the beginning of the control cycle, reference thickness range  724  is set to a predetermined value to erase any data stored for the parameter from an earlier control cycle. In at least some embodiments, the predetermined value is a maximum value. Memory  716  is configured to store an increment  726  which is an amount of movement of the adjustable nozzle  406  after each control cycle. Memory  716  is configured to store a current nozzle position  728  which is the orientation of the adjustable nozzle  406  including length and angle (as well as rotation or any other nozzle movement parameters). Memory  716  is configured to store a target nozzle length  730  which is a length of the current nozzle position at which the highest thickness uniformity is achieved. Memory  716  is configured to store a target nozzle angle  732  which is an angle of the current nozzle position at which the highest thickness uniformity is achieved. Memory  716  is configured to store a nozzle number  734  which is an identification number associated with each adjustable nozzle  406 . In at least some embodiments, each adjustable nozzle  406  is identified by a nozzle identifier. Memory  716  is configured to store a total nozzles  736  which is an overall number of adjustable nozzles controlled by control unit  404  for each HDP CVD chamber  402  ( FIG. 4 ). 
         [0021]    Memory  716  is configured to store a nozzle adjustment type  738  which is a value to inform control unit  404  ( FIG. 4 ) which type of movement is currently being controlled. In the embodiment of  FIGS. 5A-5B , the nozzle adjustment type is either length or angle. In other embodiments, the nozzle adjustment type includes other types of movement such as rotation. Rotation about the longitudinal axis  306  ( FIG. 3 ) is advantageous to the control cycle if the shape of opening  612  ( FIG. 6 ) is asymmetrical. In the embodiment of  FIGS. 5A-5B , a length nozzle adjustment type is controlled first. In other embodiments, an angle nozzle adjustment type is controlled first. In still other embodiments, the angle nozzle adjustment type and the length nozzle adjustment type are controlled simultaneously. In further embodiments, the nozzle adjustment type includes only one of length or movement. One of ordinary skill in the art would recognize parameters can be added or removed depending on the design of the adjustable nozzle  406  and the control unit  404 . 
         [0022]    In some embodiments, memory  716  includes a datastore  740  configured to store thickness data. Datastore  740  allows tracking of the control cycles and evaluation of the performance of HDP CVD chambers. In other embodiments, control unit  404  includes different or additional elements as recognizable by one of ordinary skill in the art. 
         [0023]    In the embodiment of  FIG. 4 , control unit  404  receives the thickness profile data, through I/O device  714  ( FIG. 7 ), and calculates mean thickness, thickness range and the standard deviation of thickness across the wafer surface, using processor  712  ( FIG. 7 ). In other embodiments, the mean thickness, thickness range and standard deviation of thickness across the wafer surface are calculated by a central processing unit included in HDP CVD chamber  402  and transmitted to control unit  404 , through I/O device  714 . Control unit  404  then determines whether the thickness profile of the current wafer is more uniform versus a previous wafer thickness profile, stored in memory  716  ( FIG. 7 ). Based on determinations in control unit  404 , control signals are sent to an individual adjustable nozzle  406 , using I/O device  714 , to change a position of the nozzle, e.g., angle and/or distance, or begin controlling a subsequent nozzle. In other embodiments, control signals are sent to groups of adjustable nozzles  406  to change the positions of the nozzles. Adjustable nozzle  406  is similar to the adjustable nozzle shown in  FIG. 3 . The deposition process in HDP CVD chamber  402  is repeated with the current position of adjustable nozzle  406 , stored in offset adjustment system  720  ( FIG. 7 ). In an embodiment, a control cycle is repeated until a constant thickness profile is obtained. In other embodiments, the control cycle terminates upon developing a thickness profile which satisfies production constraints determined by a process designer. In still other embodiments, the control cycle is continuously repeated to compensate for any dynamic changes within HDP CVD chamber  402 . 
         [0024]    In the embodiment of  FIG. 5A-5B , control unit  404  ( FIG. 4 ) determines, by execution of one or more sets of instructions, whether the thickness profile is improved using a predetermined thickness range parameter. In step  502 , control unit  404  ( FIG. 4 ) calculates the current thickness range based on data provided from HDP CVD chamber  402  ( FIG. 4 ). The thickness range is the difference between the maximum thickness and the minimum thickness measured on the wafer surface. In step  504 , current thickness range  722  is compared to reference thickness range  734 . In an initial control cycle, reference thickness range  734  is a predetermined maximum value. In subsequent control cycles, reference thickness range  734  is the thickness range of a previous wafer with a film formed in HDP CVD chamber  402  for a given set of nozzle parameters. If the current thickness range  732  is less than or equal to the reference thickness range  734 , then the current wafer has either the same or greater thickness uniformity than the predetermined maximum or the previous wafer. If the condition in step  504  is satisfied the process continues to step  506 , where memory  716  updates the value of reference thickness range  734  to equal current thickness range  732 . Step  506  establishes the basis for testing the thickness profile of a subsequent wafer. 
         [0025]    In step  508 , control unit  404  ( FIG. 4 ) determines whether a nozzle adjustment type  738  is set to length. Nozzle adjustment type  738  is the type of nozzle positioning currently being controlled. Nozzle adjustment type  738  set to length means distance, d ( FIG. 3 ), is the nozzle position currently being controlled. If control unit  404  determines the nozzle adjustment type  738  is set to length, control  404  increases distance, d ( FIG. 3 ), by one increment in step  510 . In an embodiment, one increment is about 0.9 inches. In other embodiments, one increment is greater or less than about 0.9 inches. Memory  716  is configured to store increment value  726 . An increment greater than about 0.9 inches will reach a target length after fewer repetitions by feedback control system  400 , thereby using fewer test wafers; however, the thickness profile obtained with the larger increment may not be as uniform as with an increment less than about 0.9 inches. After the current distance, d, is determined, a current nozzle position value is stored in step  512 . In step  514 , a control signal is sent to an adjustable nozzle  406  ( FIG. 4 ) to change the position of the nozzle to the position stored in step  512 . In some embodiments, increment value  726  is set at a large value during a control cycle and then reduced to a smaller value after several additional control cycles. 
         [0026]    If control unit  404  ( FIG. 4 ) determines the nozzle adjustment type  738  is not set to length, control  404  increases angle, θ n  ( FIG. 3 ), by one increment in step  516 . In an embodiment, one increment is about 3-degrees. In other embodiments, one increment is greater or less than about 3-degrees. Memory  716  is configured to store increment value  726 . An increment greater than about 3-degrees will reach a target length after fewer repetitions thereby using fewer test wafers; however, the thickness profile obtained with the larger increment may not be as uniform as with an increment less than about 3-degrees. After the current angle, θ n , is determined, the value is stored in step  512 . In step  514 , a control signal is sent to adjustable nozzle  406  ( FIG. 4 ) to change the position of the nozzle to the position stored in step  512 . In some embodiments, increment value  726  is set at a large value during a control cycle and then reduced to a smaller value after several additional control cycles. 
         [0027]    If control unit  404  ( FIG. 4 ) determines current thickness range  722  is not less than or equal to the reference thickness range  724  in step  504 , then the current wafer has lower thickness uniformity than the previous wafer. If the comparison of step  504  is not satisfied, the process continues to step  518 . In step  518 , control unit  404  determines if nozzle adjustment type  738  is set to length as in step  508 . If nozzle adjustment type  738  is set to length, then the nozzle length is decreased by one increment. In an embodiment, one increment is about 0.9 inches. In other embodiments, one increment is greater or less than about 0.9 inches. Distance, d ( FIG. 3 ), is decreased by one increment because the previous wafer had better thickness uniformity than the current wafer, so the nozzle position is restored to the target length. In step  522 , target nozzle length  730  is stored in memory  716 . 
         [0028]    After the length parameter is controlled for a nozzle, control unit  404  ( FIG. 4 ) then sets the nozzle adjustment type  738  to angle in step  524  and begins the process of controlling the angle parameter. In step  526 , the reference thickness range  724  is set to a predetermined maximum value to reset the basis for controlling the angle parameter. Control unit  404  then sends a control signal through I/O  714  in step  514  to adjustable nozzle  406  ( FIG. 4 ) to set the nozzle length to target nozzle length  730 . 
         [0029]    If control unit  404  ( FIG. 4 ) determines nozzle adjustment type  738  is not set to length in step  518 , the process continues to step  528 . In step  528 , the nozzle angle is pivoted back one increment. In an embodiment, one increment is about 3-degrees. In other embodiments, one increment is greater or less than about 3-degrees. Angle, θ n  ( FIG. 3 ), is decreased by one increment because the previous wafer had better thickness uniformity than the current wafer, so the nozzle position is restored to the target angle. In step  530 , target nozzle angle  732  is stored in memory  716 . Following step  530 , the process sets the nozzle adjustment type  738  to length in step  532 . In step  534 , reference thickness range  724  is set to a predetermined maximum value. Steps  532  and  534  are to prepare the feedback control system  400  ( FIG. 4 ) to control the next adjustable nozzle  406  ( FIG. 4 ). 
         [0030]    In step  536 , control unit  404  ( FIG. 4 ) compares current nozzle number  734  to a total number of nozzles  736 . The total number of nozzles is the number of adjustable nozzles to be controlled. In an embodiment, the number of adjustable nozzles to be controlled is every nozzle present in the HDP CVD chamber  100  ( FIG. 1 ). In other embodiments, not every adjustable nozzle is controlled. Controlling fewer nozzles results in fewer repetitions of the control cycle and uses fewer wafers, but may not obtain thickness profile uniformity as great as controlling every adjustable nozzle. If current nozzle number  734  is equal to total number of nozzles  736 , then the control cycle is complete. If current nozzle number  734  is not equal to total number of nozzles  736  then nozzle number  734  is increased by one in step  538 . In step  540 , a command to begin controlling the next nozzle is generated. Following step  540 , control unit  404  sends a control signal through I/O  714  in step  514  to adjustable nozzle  406  ( FIG. 4 ) to set the nozzle angle to the target angle  732 , θ n  ( FIG. 3 ) and to send the command to begin controlling the next adjustable nozzle. 
         [0031]    It was found that by using adjustable nozzles and controlling the position of the adjustable nozzles, the mean thickness of a film deposited on a wafer can be reduced to about 196.1 nm as compared with a mean thickness of about 258.4 nm using conventional techniques. The decrease in mean thickness means less material is being used to create the film and fill the features in the wafer surface, thereby reducing production costs. It was also found that the thickness range decreased from about 3.2% using conventional techniques to about 1.8% using controlled adjustable nozzles. Using controlled adjustable nozzles also reduced standard deviation along the surface from about 6.1% using conventional techniques to about 2.9%. The increased uniformity increases production efficiency because more wafers will pass quality control tests. 
         [0032]    One aspect of the description relates to an HDP CVD chamber including a plurality of adjustable nozzles, where an adjustable nozzle includes a base having a hollow center portion for conducting gas, the base configured for connection to a gas source, and a tip coupled to the base and having an opening formed therein for conducting gas from the base to the exterior of the nozzle, where the base is configured for pivoting about a longitudinal axis of the base and/or for translating along the longitudinal axis of the base in response to a control signal generated by a control unit. Another aspect of the description relates to a method of controlling a position of an adjustable nozzle including generating a control signal using a control unit, transmitting the control signal to the adjustable nozzle to alter the position of the adjustable nozzle, where the adjustable nozzle includes a base having a hollow center portion for conducting gas, the base configured for connection to a gas source, and a tip coupled to the base and having an opening formed therein for conducting gas from the base to the exterior of the nozzle, where the base is configured for pivoting about a longitudinal axis of the base and/or for translating along the longitudinal axis of the base in response to the control signal. Still another aspect of the description relates to a feedback control system for an HDP CVD chamber including a plurality of adjustable nozzles housed in the HDP CVD chamber and a control unit configured for generating a control signal, where an adjustable nozzle includes a base having a hollow center portion for conducting gas, the base configured for connection to a gas source, and a tip coupled to the base and having an opening formed therein for conducting gas from the base to the exterior of the nozzle, where the base is configured for pivoting about a longitudinal axis of the base and/or for translating along the longitudinal axis of the base in response to the control signal generated by the control unit. 
         [0033]    The above description discloses exemplary steps, but they are not necessarily required to be performed in the order described. Steps can be added, replaced, changed in order, and/or eliminated as appropriate, in accordance with the spirit and scope of embodiment of the disclosure. Embodiments that combine different claims and/or different embodiments are within the scope of the disclosure and will be apparent to those skilled in the art after reviewing this disclosure.