Abstract:
A temperature control system for a semiconductor manufacturing process having at least one target includes: a heat exchange loop operatively associated with each target, and a mixing valve operatively associated with each heat exchange loop. This mixing valve has a body defining a mixing chamber. The mixing chamber has an inlet, an outlet, a hot inlet, a cold inlet, and a closure means associated with each inlet. Alternatively, the mixing valve may include: a body defining a mixing chamber, the mixing chamber having an inlet, an outlet, a hot inlet, and a cold inlet, a moveable gate operatively associated with each inlet for controlling the flow of fluid through said inlets, and a motor for moving the gates. A process for manufacturing semiconductors includes the step of providing a temperature control system having at least one target including a mixing valve, as described above.

Description:
FIELD OF THE INVENTION 
       [0001]    The instant invention is directed to a multi-loop temperature control system for a semiconductor manufacture process, a control valve used therein, and a process for manufacturing semiconductors. 
       BACKGROUND OF THE INVENTION 
       [0002]    The need for specialized thermal control systems for use in the manufacture of semiconductor devices is known. For example, see U.S. Pat. Nos. 6,026,896, 7,069,984, 7,225,864, 6,822,202, 7,180,036, 7,870,751, and 8,410,393, each of which is incorporated in its entirety herein. 
         [0003]    U.S. Pat. No. 6,026,896 teaches a heat exchanger, a manifold coupled to the heat exchanger, a plurality of fluid passages coupled to the manifold, a flow control valve in each fluid passage, and a process component associated with each fluid passage, FIG. 1. The controller may control the temperature of a device with multiple process components, FIG. 2. The controller may have two manifolds for distributing heat transfer fluid at differing temperatures, FIG. 3. The valve 74 is a 3-way valve for mixing the heat transfer fluids of the differing temperatures. 
         [0004]    U.S. Pat. No. 7,069,984 &amp; U.S. Pat. No. 7,225,864 teach a remote temperature control module (RTCM) for use in a temperature control system for a semiconductor process component. The RCTM includes a loop to the source of cooling fluid, a loop to the process component (tool), a heat exchanger thermally connecting the loops, and may include a heat source (362). The cooling loop includes a control valve coupled to a temperature controller. 
         [0005]    U.S. Pat. No. 6,822,202 &amp; U.S. Pat. No. 7,180,036 teach a temperature control system for use in a semiconductor process component. This system includes a loop to the process component, a loop to a first source of fluid, and a loop to a second source of fluid. The first and second fluid sources are at different temperatures. The first and second fluids are used, by mixing with the fluid of the process component loop, to control the temperature at the process component. 
         [0006]    U.S. Pat. No. 7,870,751 teaches a temperature control system for use in a semiconductor process component. This system includes a first loop to multiple processing components arranged in parallel (FIGS. 2 &amp; 5), a second loop coupled to a chiller, a heat exchanger thermally connecting the first and second loops, a control valve and heater on each line from the first loop to the process component. 
         [0007]    U.S. Pat. No. 8,410,393 teaches a temperature control system for use in a semiconductor process component. This system utilizes, for example see FIG. 5A, a set of recirculators, 510/520/530/540, each at a different temperature, and switching valves 561/562, to circulate fluid to the process component to control the temperature at the process component. 
         [0008]    While each of the foregoing devices has served well, there is a continuing need for the improvement for these specialized semiconductor manufacturing temperature control devices. Heretofore, semiconductor processes where conducted one step at a time. For example, one etch or material deposition step was performed on a wafer, and then the wafer was moved to the next step. Or, only one layer of the wafer was worked in a given step. Now, however, there is a need to increase throughput in these manufacturing processes. As progress is made to increase the size of the wafers, for example to 450 mm or more, there will be increased efforts to perform multi-step etchings and depositions, as well as, multi-layer etchings and depositions that are performed without movement of the wafer (which increasing the chance of, for example, particle contamination). These multi-step and multi-layer processes will require, among other things, more demanding temperature control because the etch/deposition rate, resolution (selectivity), and etch/deposition control for each step must be tailored to the process involved. Each of these considerations will require, for example, attention to fine temperature control to facilitate the process step, quick temperature set point movement from step-to-step, and varying power consumption (heating/cooling demand) for each step. Accordingly, there is a need for a new temperature control system for use in the semiconductor manufacturing process. 
       SUMMARY OF THE INVENTION 
       [0009]    A temperature control system for a semiconductor manufacturing process having at least one target includes: a heat exchange loop operatively associated with each target, and a mixing valve operatively associated with each heat exchange loop. This mixing valve has a body defining a mixing chamber. The mixing chamber has an inlet, an outlet, a hot inlet, a cold inlet. A closure means is associated with each inlet. Alternatively, the mixing valve may include: a body defining a mixing chamber, the mixing chamber having an inlet, an outlet, a hot inlet, and a cold inlet, a moveable gate operatively associated with each inlet for controlling the flow of fluid through said inlets, and a motor for moving the gates. A process for manufacturing semiconductors includes the step of providing a temperature control system having at least one target including a mixing valve operatively associated with each target, the mixing valve having a body defining a mixing chamber, the mixing chamber having an inlet, an outlet, a hot inlet, a cold inlet, and a closure means associated with each inlet. 
     
    
     
       DESCRIPTION OF THE DRAWINGS 
         [0010]    For the purpose of illustrating the invention, there is shown in the drawings a form that is presently preferred; it being understood, however, that this invention is not limited to the precise arrangements and instrumentalities shown. 
           [0011]      FIG. 1  is a schematic illustration of the inventive temperature control system (only two targets shown). 
           [0012]      FIG. 2  is a schematic illustration of the inventive mixing valve. 
           [0013]      FIG. 3  is a schematic illustration of the inventive mixing valve with the gates moved to a position. 
           [0014]      FIG. 4  is a schematic illustration of the inventive mixing valve with the gates moved to another position. 
           [0015]      FIG. 5  is a schematic illustration of the inventive mixing valve with the gates moved to yet another position. 
           [0016]      FIGS. 6   a - d  are schematic illustrations of a gate of the inventive mixing valve. 
           [0017]      FIG. 7  is an illustration of heat flow, mass flow, and temperatures for an embodiment of the invention. 
           [0018]      FIGS. 8   a - c  are illustrations of inventive temperature control system in operation with a representative sample of the programming logic of the controller. 
       
    
    
     DESCRIPTION OF THE INVENTION 
       [0019]    Referring to the figures, where like element have like numerals, there is shown in  FIG. 1  the temperature control system  10 . System  10 , all or parts thereof, may be contained within the clean room  12 . A source of cold fluid A and a source of hot fluid B may be located outside of the clean room  12 . 
         [0020]    For the purpose of illustration,  FIG. 1  shows system  10  controlling the temperature of two targets  14 ,  14 ′. It being understood, that the system  10  is not so limited; instead, the system  10  may control the temperature of a single target or multiple targets (i.e., &gt;2, e.g., 2, 3, 4, 5, 6 . . . ). The maximum number of targets being limited only by the size of the clean room  12  and the capacity of the cold fluid source A and the hot fluid source B. The systems  10  may be controlling the temperature of the their respective targets  14  to the same temperatures profiles as other targets or to different profiles. For example, each system  10  may be programmed for the same temperature profile or each system  10  may be programmed with different temperature profiles. 
         [0021]    Target, as used herein, refers to semiconductor processing equipment or semiconductor processing techniques/steps used to convert the virgin wafer into a semiconductor device(s) or semi-work semiconductor. These targets include any process by which the wafer is converted to a semiconductor(s) or semi-work semiconductor(s). Such process are well known and include, for example: deposition processes—chemical vapor deposition (CVD), plasma-enhanced chemical vapor deposition (PECVD), cupper deposition, sputter deposition; etching—dry etching, plasma etching, electron beam evaporation; resist strip, to name a few. The system described, hereinafter, may have particular relevance to etching processes, and/or those processes conducted in vacuum chambers. In operation, the wafer within the target and is thermal communication with the system  10 . As the various processes are used to convert the wafer in the semiconductor, the system  10  may be used to control the temperature (as well as the removal or input of heat into the wafer) as may be required to facilitate the completion of the process. 
         [0022]    In general, system  10  is coupled to a cold loop  18  and a hot loop  24 . The terms cold and hot are relative terms and are used to indicate differing temperatures. The exact temperature of cold and hot will be dictated by the requirements of the processes discussed above. It is desirable that the temperature difference between the hot and cold loops be as great as possible. These larger temperature differences facilitate quick change of the set point at the target. As an example, the system may have: a cold loop temperature (T a ) of −20° C. and a hot loop temperature (T h ) of 150° C.; or a T c  of 0° C. and a T h  of 120° C.; or a T c  of 10° C. and a T h  of 100° C. (or any combination or subcombination therebetween of the temperatures in those ranges). Coupling may be in any fashion, but typically refers to a parallel coupling, as opposed to a series coupling. Cold loop  18  includes a cold loop feed  20  and a cold loop return  22 . Additionally, the cold loop  18  may include a cold loop temperature sensor  19 , for example in feed  20 . Hot loop  24  includes a hot loop feed  26  and a hot loop return  28 . Additionally, the hot loop  24  may include a hot loop temperature sensor  25 , for example in feed  25 . There may be more than one temperature sensor in the respective loops. The temperature sensors are operatively connected to a controller  50 . 
         [0023]    System  10 , referring generally to the left hand side of  FIG. 1 , may include target  14 , a recirculating pump  32 , and a mixing valve  100 , discussed in greater detail below. Additionally, system  10  may also include a pump supply tank  38 , a flow sensor  34 , and a temperature sensor  36  (the sensors are operationally connected to the controller  50 ). The target may include a temperature sensor (not shown) that is operationally connected to the controller  50 . A heat exchange fluid may be any heat exchange fluid. Exemplary heat exchange fluids include FLUORINERT or GALDEN. The heat exchange fluid may be circulated between the mixing valve  100  and the target  14 . The supply tank  38  and the expansion tank  40  are intended to act as a reservoir for excess fluid that may arise by action of the mixing valve  100 . 
         [0024]    Mixing valve  100 , discussed in greater detail below, has a process inlet  102 , a process outlet  104 , a cold inlet  106 , and a hot inlet  108 . The cold loop  18  is in thermal communication with the cold inlet  106  of valve  100 . Heat exchange fluid is drawn from the cold loop feed  20  through a flow sensor  42 , operatively connected with controller  50 , to one side of a heat exchanger  44  and returned to cold loop return  22 . The cold inlet  106  is in fluid communication with another side of the heat exchanger  44 . The hot loop  24  is in thermal communication with the hot inlet  108  of valve  100 . Heat exchange fluid is drawn from the hot loop feed  26  through a flow sensor  46 , operatively connected with controller  50 , to one side of a heat exchanger  46  and returned to hot loop return  28 . The hot inlet  108  is in fluid communication with another side of the heat exchanger  46 . 
         [0025]    System  10 ′, referring generally to the right hand side of  FIG. 1 , is identical to system  10 . Moreover, systems  10  may be expanded, as discussed above. 
         [0026]    In operation, the heat exchange fluid is in thermal communication with the wafer held within the target  14 , for example, by a wafer chuck (not shown) of the target  14 , and is pumped to the mixing valve  100  by means of the pump  32 . In a steady state mode, the fluid is circulated through valve  100 , 100% in and 100% out via process inlet  102  and process outlet  104 . However, when the temperature set point needs to be changed (increased or decreased as may be demanded by the process being conducted at the target  14 ), the mixing valve comes into active operation. The mixing valve  100  selectively mixes, as will be discussed below, cold or hot fluid via cold inlet  106  or hot inlet  108 , while reducing flow at inlet  102 , and thereby changes the temperature of the fluid exiting outlet  104 . All of these being controlled by controller  50  which receives input from the noted flow and temperature and outputs instruction to the mixing valve  100 . 
         [0027]    The mixing valve  100  is shown in greater detail in  FIGS. 2-5 . 
         [0028]    In  FIG. 2 , mixing valve  100  is shown in greater detail. Valve  100  generally includes, for example, a body  110  and a motor  118 . The body  110  defines a mixing chamber  112 . The process inlet  102  empties into the chamber  112  and the process outlet  104  exits from the chamber  112 . Additionally, the cold inlet  106  and the hot inlet  108  empty into chamber  112 . Gates  114  and  116  are moveably mounted on the body  110  within the chamber  112 . As illustrated, compare  FIGS. 2-5 , the gates may be slidably mounted on the housing. The gates  114 / 116  are used to open and close the inlets  102 / 106 / 108 , as will be explained in greater detail below, and thereby allow heat exchange fluids of various temperatures to mix in chamber  112  prior to exit via outlet  106 . The gates  114 / 116  are operatively coupled to the motor  118  via an actuator  120 . 
         [0029]    In  FIGS. 6   a - d,  a front elevational view of one gate  114  is shown (gate  116  may be a mirror image of gate  114 ). Gate  114  has a gate portion  150  and a lug portion  160 . The lug portion  160  includes an actuator connection  162 . The gate portion  150  has a leading edge  152  and a trailing edge  154 . Leading edge  152  is the edge that engages the process inlet  102 . The trailing edge  154  engages the cold inlet  106  or hot inlet  108 , as the case may be. The leading edge  152  and the trailing edge  158  may include a profile  156  and  158 , respectfully. The profiles  156 / 158  may include any profile. The profiles  156  and  158  may be mirror images. In  FIG. 2 , the gate has a flat profile. In  FIG. 6   a , the profiles  156 / 158  include a triangular (or diamond) protrusion. In  FIG. 6   b , the profiles  156 / 158  are inclined flat protrusion. In  FIG. 6   c , the profiles  156 / 158  are arcuate protrusion. In  FIG. 6   d , the profiles  156 / 158  are trapezoidal protrusion. The profile may include multiple protrusions and multiple and varying protrusions. While not being bound by any theory, it is believed that the profiles  156 / 158  may contribute to the control of the temperature of the target and/or enhance the sensitivity of the temperature control. 
         [0030]    The body  110 , see  FIG. 2 , may be made of several pieces  110   a / 110   b / 110   c  to facilitate assembly. If manufactured in this way, seals  128 / 130 / 132 / 134 , for example O-rings, may be used to prevent leakage between these pieces. 
         [0031]    Motor  118 , see  FIG. 2 , may also be coupled to body  110  and seal  124  may be used to prevent leakage between the motor  118  and body  110 . Motor  118  may also include a bearing  126 . Bearing  126  may be a sealing bearing to prevent leakage. 
         [0032]    Motor  118  may be any motor capable of moving gates  114 / 116 . Motor  118 ′s operation is controlled via a connection to controller  50 . Motor  118  is operatively connected to gates  114 / 116  via an actuator  120 . Actuator  120  may be mounted in body  110  via a bearing  122 . As shown, motor  118  is a stepping motor that rotates actuator, e.g., a threaded rod. The gates  114 / 116  are mounted on actuator  120 , so that as actuator rotates, the gates  114 / 116  open and close inlets  102 / 106 / 108 . While motor  118  is shown as a stepper motor, it is not so limited and other mechanisms may be used to move gates  114 / 116 . Such mechanisms include, without limit, servomotors, linear motors, and hydraulic motors. 
         [0033]    Gates  114 / 116  are configured in such a way that by action of the actuator  120 , they open and close the inlets  102 / 106 / 108 . This is best illustrated by comparison of  FIGS. 2-5 . In  FIG. 2 , the gate position is such that fluid passes through the valve, 100% in, inlet  102 , and 100% out, outlet  104 . This position represents normal operation, i.e., steady state temperature at the target. However, if the set temperature must change, for whatever reason, the controller sends a signal to the motor  118 . That signal is translated in movement of the gates  114 / 116 . 
         [0034]    In  FIGS. 2-5 , several gates positions are illustrated, it being understood that many variations are possible. In  FIG. 3 , hot inlet  108  is partially opened, process inlet  102  is partially closed, and cold inlet  106  is completely closed. In this configuration, hot fluid is mixed with fluid in the process loop, so that the temperature of the process loop fluid is increased. In  FIG. 4 , cold inlet  106  is fully open, and hot inlet  108  and process inlet  102  are completely closed. In this configuration, cold fluid replaces with fluid in the process loop, so that the temperature of the process loop fluid is decreased. In FIG.  5 , cold inlet  106  and process inlet  102  are partially and hot inlet  108  is closed. In this configuration, cold fluid is mixed with fluid in the process loop, so that the temperature of the process loop fluid is decreased. 
         [0035]    As will be apparent to those of ordinary skill, the temperature and volume (or mass) of the cold/hot fluid will control the time it will take to decrease/increase the temperature of the fluid circulating in the process loop to the target  14 . It should be noted, that as gates  114 / 116  open/close cold/hot inlets  106 / 108 , the gates  114 / 116  close the inlet  102 , so that a material balance (inflow=outflow) is maintained around the mixing chamber. To more fully illustrate this point, the following non-limiting example is provided, it being understood that there may be other methods for determining the necessary parameters.  FIG. 7  illustrates an embodiment of the invention where hot inlet  108  is closed and cold inlet  106  and process inlet  102  are partially open. Energy Q 1  is inputted into target  14 . Heat exchange fluid pumped to target  14  enters at T 1  and exits at T 2  (those of ordinary skill will recognize that T 1  is &lt;T 2  when Q 1  is positive). To maintain the target  14  at a constant temperature, Q 1 =Q 2 . To determine T 1 , T 1 =(M c T c +M p T 2 )/(M l +M p ), where: T 1  is the temperature into the target, M c  is the mass flow cold, T c  is the temperature cold, M p  is the mass flow process, and T 2  is the temperature process. 
         [0036]    In  FIGS. 8   a - c,  a process for manufacturing a semiconductor using the foregoing temperature control system  10  is illustrated. 
         [0037]      FIG. 8   a  is a graph of the temperature profile at the target  14 . The x-axis is time (t x , x=0, 1, 2, 3 . . . n, &amp; t′ x , x=0, 1, 2, 3 . . . n). The y-axis is temperature (the temperatures are for illustration only and may be changed as dictated by the processes being carried out at the target). As illustrated, the first temperature set point is 40° and is held until t 1 , then the temperature is ramped to 80° over the time interval of t 1  to t′ 1  and then held there until t 2 , then the temperature is ramped down to 0° over the time interval of t 2  to t′ 2  and then held there until t 3 , and finally, the temperature is ramped to 40° over the interval of t 3  to t′ 3  and held there. The phantom lines above and below the solid temperature profile line represent the fine temperature control. 
         [0038]      FIG. 8   b  is a graph of gate position as a function of time. The x-axis is time (t x , x= 0 ,  1 ,  2 ,  3  . . . n, &amp; t′ x , x=0, 1, 2, 3 . . . n). The y-axis is gate position (the gate positions are for illustration only and may be changed as dictated by the processes being carried out at the target).  FIG. 8   b  illustrates how the gate positions may be changed to obtain the temperature profile shown in  FIG. 8   a . Focusing only the time intervals where temperature ramping occurs, one will note that the during ramping (change in set point temperature) the gates may be opened wider to over shoot the desired temperature thereby shortening the time to obtain the next set point temperature (note the slight over shoot in the temperature profile in  FIG. 8   a ). 
         [0039]      FIG. 8   c  is chart illustrating how the controller  50  may be programmed to implement the gate position of  FIG. 8   b  to obtain the temperature profile of  FIG. 8   a . As illustrated, two targets  14 / 14 ′ may be programmed into the controller  50 . Each target  14 / 14 ′ may be operated independently so that different operations may be conducted simultaneously. The program for  FIGS. 8   a - b  is illustrated in the top line of the chart. 
         [0040]    The present invention may be embodied in other forms without departing from the spirit and the essential attributes thereof, and, accordingly, reference should be made to the appended claims, rather than to the foregoing specification, as indicating the scope of the invention.