Abstract:
Semiconductor processors, sensors, semiconductor processing systems, semiconductor workpiece processing methods, and turbidity monitoring methods are provided. According to one aspect, a semiconductor processor includes a process chamber configured to receive a semiconductor workpiece for processing; a supply connection in fluid communication with the process chamber and configured to a supply slurry to the process chamber; and a sensor configured to monitor the turbidity of the slurry. Another aspect provides a semiconductor workpiece processing method including providing a semiconductor process chamber; supplying slurry to the semiconductor process chamber; and monitoring the turbidity of the slurry using a sensor.

Description:
RELATED PATENT DATA 
   This patent resulted from a divisional application of and claims priority to U.S. patent application Ser. No. 09/324,737, filed on Jun. 3, 1999, entitled “Semiconductor Processors, Sensors, and Semiconductor Processing Systems”, naming Scott E. Moore, Scott G. Melkle and Magdel Crum as Inventors, now U.S. Pat. No. 6,290,576, which Issued on Sep. 18, 2001, the disclosure of which is incorporated herein by reference. 

   TECHNICAL FIELD 
   The present invention relates to semiconductor processors, sensors, semiconductor processing systems, semiconductor workpiece processing methods, and turbidity monitoring methods. 
   BACKGROUND OF THE INVENTION 
   Numerous semiconductor processing tools are typically utilized during the fabrication of semiconductor devices. One such common semiconductor processor is a chemical-mechanical polishing (CMP) processor. A chemical-mechanical polishing processor is typically used to polish or planarize the front face or device side of a semiconductor wafer. Numerous polishing steps utilizing the chemical-mechanical polishing system can be implemented during the fabrication or processing of a single wafer. 
   In an exemplary chemical-mechanical polishing apparatus, a semiconductor wafer is rotated against a rotating polishing pad while an abrasive and chemically reactive solution, also referred to as a slurry, is supplied to the rotating pad. Further details of chemical-mechanical polishing are described in U.S. Pat. No. 5,755,614, incorporated herein by reference. 
   A number of polishing parameters affect the processing of a semiconductor wafer. Exemplary polishing parameters of a semiconductor wafer include downward pressure upon a semiconductor wafer, rotational speed of a carrier, speed of a polishing pad, flow rate of slurry, and pH of the slurry. 
   Slurries used for chemical-mechanical polishing may be divided into three categories including silicon polish slurries, oxide polish slurries and metals polish slurries. A silicon polish slurry is designed to polish and planarize bare silicon wafers. The silicon polish slurry can include a proportion of particles in a slurry typically with a range from 1-15 percent by weight. 
   An oxide polish slurry may be utilized for polishing and planarization of a dielectric layer formed upon a semiconductor wafer. Oxide polish slurries typically have a proportion of particles in the slurry within a range of 1-15 percent by weight. Conductive layers upon a semiconductor wafer may be polished and planarized using chemical-mechanical polishing and a metals polish slurry. A proportion of particles in a metals polish slurry may be within a range of 1-5 percent by weight. 
   It has been observed that slurries can undergo chemical changes during polishing processes. Such changes can include composition and pH, for example. Furthermore, polishing can produce stray particles from the semiconductor wafer, pad material or elsewhere. Polishing may be adversely affected once these by-products reach a sufficient concentration. Thereafter, the slurry is typically removed from the chemical-mechanical polishing processing tool. 
   It is important to know the status of a slurry being utilized to process semiconductor wafers inasmuch as the performance of a semiconductor processor is greatly impacted by the slurry. Such information can indicate proper times for flushing or draining the currently used slurry. 
   SUMMARY OF THE INVENTION 
   The present invention provides semiconductor processors, sensors, semiconductor processing systems, semiconductor workpiece processing methods, and turbidity monitoring methods. 
   According to one aspect of the invention, a semiconductor processor is provided. The semiconductor processor includes a process chamber and a supply connection configured to provide slurry to the process chamber. A sensor is provided to monitor turbidity of the slurry. One embodiment of the sensor is configured to emit electromagnetic energy towards the supply connection providing the slurry. The supply connection is one of transparent and translucent in one embodiment. The sensor includes a receiver in the described embodiment configured to receive at least some of the emitted electromagnetic energy and to generate a signal indicative of turbidity responsive to the received electromagnetic energy. 
   In another arrangement, plural sensors are provided to monitor the turbidity of a subject material, such as slurry, at different corresponding positions. In addition, one or more sensors can be provided to monitor turbidity of a subject material within a horizontally oriented supply connection or container, a vertically oriented supply connection or container, or supply connections or containers in other orientations. 
   One sensor configuration of the invention provides a source configured to emit electromagnetic energy towards the supply connection. The sensor additionally includes plural receivers. One receiver is positioned to receive electromagnetic energy passing through the subject material and configured to output a feedback signal indicative of the received electromagnetic energy. The source is configured to adjust the intensity of emitted electromagnetic energy to provide a substantially constant amount of electromagnetic energy at the receiver. Another receiver is provided to monitor the emission of electromagnetic energy from the source and provide a signal indicative of turbidity. 
   The invention also includes other aspects including methodical aspects and other structural aspects as described below. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Preferred embodiments of the invention are described below with reference to the following accompanying drawings. 
       FIG. 1  is an illustrative representation of a slurry distributor and semiconductor processor. 
       FIG. 2  is an illustrative representation of an exemplary arrangement for monitoring a static slurry. 
       FIG. 3  is an illustrative representation of an exemplary arrangement for monitoring a dynamic slurry. 
       FIG. 4  is an isometric view of one configuration of a turbidity sensor. 
       FIG. 5  is a cross-sectional view of another sensor configuration. 
       FIG. 6  is an illustrative representation of an exemplary arrangement of a source and receiver of a sensor. 
       FIG. 7  is a functional block diagram illustrating components of an exemplary sensor and associated circuitry. 
       FIG. 8  is a schematic diagram of an exemplary sensor configuration. 
       FIG. 9  is a schematic diagram illustrating circuitry of the sensor configuration shown in FIG.  6 . 
       FIG. 10  is a schematic diagram of another exemplary sensor configuration. 
       FIG. 11  is an illustrative representation of a sensor implemented in a centrifuge application. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   This disclosure of the invention is submitted in furtherance of the constitutional purposes of the U.S. Patent Laws “to promote the progress of science and useful arts” (Article 1, Section 8). 
   Referring to  FIG. 1 , a semiconductor processing system  10  is illustrated. The depicted semiconductor processing system  10  includes a semiconductor processor  12  coupled with a distributor  14 . Semiconductor processor  12  includes a process chamber  16  configured to receive a semiconductor workpiece, such as a silicon wafer. In an exemplary configuration, semiconductor processor  12  is implemented as a chemical-mechanical polishing processing tool. 
   Distributor  14  is configured to supply a subject material for use in semiconductor workpiece processing operations. For example, distributor  14  can supply a subject material comprising a slurry to semiconductor processor  12  for chemical-mechanical polishing applications. 
   Exemplary conduits or piping of semiconductor processing system  10  are shown in FIG.  1 . In the depicted configuration, a static route  18  and a dynamic route  20  are provided. Further details of static route  18  and dynamic route  20  are described below with reference to  FIGS. 2 and 3 , respectively. In general, static route  18  is utilized to provide monitoring of the subject material of distributor  14  in a substantially static state. Such provides real-time information regarding the subject material being utilized within semiconductor processing system  10 . Dynamic route  20  comprises a recirculation and distribution line in one configuration. In addition, subject material can be supplied to semiconductor processor  12  via dynamic route  20 . 
   Distributor  14  can include an internal recirculation pump (not shown) to periodically recirculate subject material through dynamic route  20 . Subject material having particulate matter, such as a slurry, experiences gravity separation over time. Separation of such particulate matter of the slurry is undesirable. For example, the particulate matter may settle in areas of piping, valves or other-areas of a supply line which are difficult to reach and clean. Further, some particulate matter may be extremely difficult to resuspend once it has settled over a sufficient period of time. Accordingly, it is desirable to monitor turbidity (percent solids within a liquid) of the subject material to enable reduction or minimization of excessive settling. 
   Referring to  FIG. 2 , details of an exemplary static route  18  coupled with distributor  14  are illustrated. Static route  18  includes an elongated tube or pipe  19  for receiving subject material from distributor  14 . In a preferred embodiment, pipe  19  comprises a transparent or translucent material, such as a transparent or translucent plastic. Static route  18  is coupled with distributor  14  at an intake end  22  of pipe  19 . Piping hardware provided within the depicted static route  18  includes an intake valve  24 , sensors  26  and an exhaust valve  28 . Exhaust valve  28  is adjacent an exhaust end  30  of static route  18 ., 
   Valves  24 ,  28  can be selectively controlled to provide monitoring of the subject material of distributor  14  in a substantially static state. For example, with exhaust valve  28  in a closed state, intake valve  24  may be selectively opened to permit the entry of subject material within an intermediate container  32 . Container  32  can be defined as the portion of static route  18  intermediate intake valve  24  and exhaust valve  28  in the described configuration. In typical operations, intake valve  24  is sealed or closed following entry of subject material into container  32 . In the depicted arrangement, static route  18  is provided in a substantially vertical orientation. Static route  18  using valves  24 ,  28  and container  32  is configured to provide received subject material in a substantially static state (e.g., the subject material is not in a flowing state). 
   Plural sensors  26  are provided at predefined positions relative to container  32  as shown. Sensors  26  are configured to monitor the opaqueness or turbidity of subject material received within static route  18 . In one configuration, plural sensors  26  are provided at different vertical positions to provide monitoring of the turbidity of the subject material within container  32  at corresponding different desired vertical positions of container  32 . Such can be utilized to provide differential information between the sensors  26  to indicate small changes in slurry settling. 
   As described in further detail below, individual sensors include a source  40  and a receiver  42 . In one configuration, source  40  is configured to emit electromagnetic energy towards container  32 . Receiver  42  is configured and positioned to receive at least some of the electromagnetic energy. As described above, pipe  19  can comprise a transparent or translucent material permitting passage of electromagnetic energy. Sensors  26  can output signals indicative of the turbidity at the corresponding vertical positions of container  32  responsive to sensing operations. 
   It is desirable to provide plural sensors  26  in some configurations to monitor settling of particulate material (precipitation rates) over time within the subject material at plural vertical positions. Monitoring a substantially static subject material provides numerous benefits. Utilizing one or more sensors  26 , the rate of separation can be monitored providing information regarding the condition of the subject material or slurry (e.g., testing and quantifying characteristics of a CMP slurry) 
   Properties of the subject material can be derived from the monitoring including, for example, how well particulate matter is suspended, adequate mixing, amount of or effectiveness of surfactant additives, the approximate size of the particulate matter, agglomeration of particulate matter, slurry age or lifetime, and likelihood of slurry causing defects. Such monitoring of settling rates can indicate when to change or drain a slurry being applied to semiconductor processor  12  to avoid degradation in processing performance, such as polishing performance within a chemical-mechanical polishing processor. 
   Subject material within container  32  may be drained via exhaust valve  28  following monitoring of the subject material. Exhaust end  30  of static route  18  can be coupled with a recovery system for direction back to distributor  14 , or to a drain if the subject material will not be reused. 
   Referring to  FIG. 3 , details of dynamic route  20  are described. Dynamic route  20  comprises a recirculation pipe  50  coupled with a supply connection  52 . Recirculation pipe  50  and supply connection  52  preferably comprise transparent or translucent tubing or piping, such as transparent or translucent plastic pipe. 
   Recirculation pipe  50  includes an intake end  54  and a discharge end  56 . Subject material or slurry can be pumped into recirculation pipe  50  via intake end  54 . An intake valve  58  and an exhaust or discharge valve  60  are coupled with recirculation pipe  50  for controlling the flow of subject material. Plural sensors  26  are provided within sections of recirculation pipe  50  as shown. One of sensors  26  is vertically arranged with respect to a vertical pipe section  62 . Another of sensors  26  is horizontally oriented with respect to a horizontal pipe section  64 . Sensors  26  are configured to monitor the turbidity of subject material or slurry within vertical pipe section  62  and horizontal pipe section  64 . 
   Individual sensors  26  configured to monitor horizontal pipe sections (e.g., pipe section  64 ) may be arranged to monitor a lower portion of the horizontal pipe for gravity settling of particulate matter. As described below, an optical axis of sensor  26  can be aimed to intersect a lower portion of horizontally arranged tubing or piping to provide the preferred monitoring. Such can assist with detection of precipitation of particulate matter which can form into large undesirable particles leading to defects. Accordingly, once a turbidity limit has been reached, the tubing or piping may be flushed. 
   Supply connection  52  is in fluid communication with horizontal pipe section  64 . In addition, supply connection  52  is in fluid communication with process chamber  16  of semiconductor processor  12  shown in FIG.  1 . Supply connection  52  is configured to supply subject material such as slurry to process chamber  16 . A sensor  26  is provided adjacent supply connection  52 . Sensor  26  is configured to monitor the turbidity of subject material within supply connection  52 ., Additionally, a supply valve  66  controls the flow of subject material within supply connection  52 . 
   Although only one supply connection  52  is illustrated, it is understood that additional supply connections can be provided to couple associated semiconductor processors (not shown) with recirculation pipe  50  and distributor  14 . The depicted supply connection  52  is arranged in a vertical orientation. Supply connection  52  with associated sensor  26  may also be provided in a horizontal or other orientation in other configurations. 
   Referring to  FIG. 4 , an exemplary configuration of sensor  26  is shown. The illustrated configuration of sensor  26  includes a housing  70 , cover  72  and associated circuit board  74 . The illustrated housing  70  is configured to couple with a conduit, such as supply connection  52 . For example, housing  70  is arranged to receive supply connection  52  with a longitudinal orifice  76 . Cover  72  is provided to substantially enclose supply connection  52 . In a preferred arrangement, housing  70  and cover  72  are formed of a substantially opaque material. 
   Housing  70  is configured to provide source  40  and receiver  42  adjacent supply connection  52 . More specifically, housing  70  is configured to align source  40  and receiver  42  with respect to supply connection  52  and any subject material such as slurry therein. In the depicted configuration, housing  70  aligns source  40  and receiver  42  to define an optical axis  45  which passes through supply connection  52 . 
   The illustrated housing  70  is configured to allow attachment of sensor  26  to supply connection  52  or detachment of sensor  26  from supply connection  52  without disruption of the flow of subject material within supply connection  52 . Housing  70  can be clipped onto supply connection  52  as illustrated or removed therefrom without disrupting the flow of subject material within supply connection  52  in the described embodiment. 
   Source  40  and receiver  42  may be coupled with circuit board  74  via internal connections (not shown). Further details regarding circuitry implemented within circuit board  74  are described below. The depicted sensor configuration provides sensor  26  capable of monitoring the turbidity of subject material within supply connection  52  without contacting and possibly contaminating the subject material or without disrupting the flow of subject material within supply connection  52 . 
   More specifically, sensor  26  is substantially insulated from the subject material within supply connection  52  in the described arrangement. Accordingly, sensor  26  provides a non-intrusive device for monitoring the turbidity of subject material  80 . Such is preferred in applications wherein contamination of subject material  80  is a concern. Utilization of sensor  26  does not impede or otherwise affect flow of the subject material. 
   In one configuration, source  40  comprises a, light emitting diode (LED) configured to emit infrared electromagnetic energy. Source  40  is configured to emit electromagnetic energy of another wavelength in an alternative embodiment. Receiver  42  may be implemented as a photodiode in an exemplary embodiment. Receiver  42  is configured to receive electromagnetic energy emitted from source  40 . Receiver  42  of sensor  26  is configured to generate a signal indicative of the turbidity of the subject material and output the signal to associated circuitry for processing or data logging. 
   Referring to  FIG. 5 , source  40  and receiver  42  are coupled with electrical circuitry  78 . In the illustrated embodiment, source  40  and receiver  42  are aimed towards one another. Source  40  is operable to emit electromagnetic energy  79  towards subject material  80 . Particulate matter within subject material  80  operates to absorb some of the emitted electromagnetic energy  79 . Accordingly, only a portion, indicated by reference  82 , of the emitted electromagnetic energy  79  passes through subject material  80  and is received within receiver  42 . 
   Electrical circuitry  78  is configured to control the emission of electromagnetic energy  79  from source  40  in the described configuration. Receiver  42  is configured to output a signal indicative of the received electromagnetic energy  82  corresponding to the intensity of the received electromagnetic energy. Electrical circuitry  78  receives the outputted signal and, in one embodiment, conditions the signal for application to an associated computer  84 . In one embodiment, computer  84  is configured to compile a log of received information from receiver  42  of sensor  26 . 
   Referring to  FIG. 6 , an alternative sensor arrangement indicated by reference  26   a  is shown. In the depicted embodiment, an alternative housing  70   a  is implemented as a cross fitting  44  utilized to align the source and receiver of sensor  26   a  with supply connection  52 . Supply connection  52  is aligned along one axis of cross fitting  44 . 
   In the depicted configuration, light-carrying cable or light pipe, such as fiberoptic cable, is utilized to couple a remotely located source and receiver with supply connection  52 . A first fiberoptic cable  46  provides electromagnetic energy emitted from source  42  to supply connection  52 . A lens  47  is provided flush against supply connection  52  and is configured to emit the electromagnetic light energy from cable  46  towards supply connection  52  along optical axis  45  perpendicular to the axis of supply connection  52 . Electromagnetic energy which is not absorbed by subject material  80  is received within a lens  49  coupled with a second fiberoptic cable  48 . Fiberoptic cable  48  transfers the received light energy to receiver  42 . Sensor arrangement  26   a  can include appropriate seals, bushings, etc., although such is not shown in FIG.  6 . 
   As previously mentioned, supply connection  52  is preferably transparent to pass as much electromagnetic light energy as possible. Supply connection  52  is translucent in an alternative arrangement. Lenses  47 ,  49  are preferably associated with supply connection  52  to provide maximum transfer of electromagnetic energy. In other embodiments, lenses  47 ,  49  are omitted. Further alternatively, the source and receiver of sensor  26  may be positioned within housing  70   a  in place of lenses  47 ,  49 . Fiberoptic cables  46 ,  48  could be removed in such an embodiment. 
   Referring to  FIG. 7 , another implementation of sensor  26  is shown. Source  40  and receiver  42  are arranged at a substantially 90° angle in the depicted configuration. Source  40  operates to emit electromagnetic energy  79  into supply connection  52  and subject material  80  within supply connection  52 . As previously stated, subject material  80  can contain particulate matter which may operate to reflect light. Receiver  42  is positioned in the depicted arrangement to receive such reflected light  82   a . Associated electrical circuitry coupled with source  40  and receiver  42  can be calibrated to provide accurate turbidity information responsive to the reception of reflected light  82   a . Although source  40  and receiver  42  are illustrated at a 90° angle in the depicted arrangement, source  40  and receiver  42  may be arranged at any other angular relationship with respect to one another and supply connection  52  to provide emission of electromagnetic energy  79  and reception of reflected electromagnetic energy  82   a.    
   Referring to  FIG. 8 , one arrangement of sensor  26  for providing turbidity information of subject material  80  is shown. Source  40  is implemented as a light emitting diode (LED) configured to emit infrared electromagnetic energy  79  towards supply connection  52  having subject material  80  in the depicted arrangement. A positive voltage bias may be applied to a voltage regulator  86  configured to output a constant supply voltage. For example, the positive voltage bias can be a 12 Volt DC voltage bias and voltage regulator  86  can be configured to provide a 5 Volt DC reference voltage to light emitting diode source  40 . 
   Source  40  emits electromagnetic energy of a known intensity responsive to an applied current from dropping resistor  87 . Receiver  42  comprises a photodiode in an exemplary embodiment configured to receive light electromagnetic energy  82  not absorbed within subject material  80 . Photodiode receiver  42  is coupled with an amplifier  88  in the depicted configuration. Amplifier  88  is configured to provide an amplified output signal indicating the turbidity of subject material  80 . Other configurations of source  40  and receiver  42  are possible. 
   Referring to  FIG. 9 , additional details of the arrangement shown in  FIG. 8  are illustrated. Source  40  is implemented as a light emitting diode (LED). Receiver  42  comprises a photodiode. A potentiometer  90  is coupled with a pin  1  and a pin  8  of amplifier  88  and can be varied to provide adjustment of the gain of amplifier  88 . An exemplary variable base resistance of potentiometer  90  is 100 Ωk. 
   Another potentiometer  92  is coupled with a pin  5  of amplifier  88  and is configured to provide calibration of sensor  26 . Potentiometer  92  may be varied to provide an offset of the output reference of amplifier  88 . An exemplary variable base resistance of potentiometer  92  is 500 Ω. 
   A positive voltage reference bias is applied to a diode  94 . An exemplary positive voltage is approximately 12-24 Volts DC. Voltage regulator  86  receives the input voltage and provides a reference voltage of 5 Volts DC in the described embodiment. 
   Referring to  FIG. 10 , an alternative sensor configuration is illustrated as reference  26   b . The illustrated sensor configuration includes a driver  95  coupled with source  40 . Additionally, a beam splitter  96  is provided intermediate source  40  and supply connection  52 . Further, an additional receiver  43  and associated amplifier  97  are provided as illustrated. 
   A reference voltage is applied to driver  95  during operation. Source  40  is operable to emit electromagnetic energy  79  towards beam splitter  96 . Beam splitter  96  directs received electromagnetic energy into a beam  91  towards supply connection  52  and a beam  93  towards receiver  43 . Receiver  42  is positioned to receive non-absorbed electromagnetic energy  91  passing through supply connection  52  and subject material  80 . Receiver  42  is configured to generate and output a feedback signal to driver  95 . The feedback signal is indicative of the electromagnetic energy  91  received within receiver  42 . 
   The depicted sensor  26   b  is configured to provide a substantially constant amount of light electromagnetic energy to receiver  42 . Driver  95  is configured to control the amount or intensity of emitted electromagnetic energy from source  40 . More specifically, driver  95  is configured in the described embodiment to increase or decrease the amount of electromagnetic energy  79  emitted from source  40  responsive to the feedback signal from receiver  42 . 
   Receiver  43  is positioned to receive the emitted electromagnetic energy directed from beam splitter  96  along beam  93 . Receiver  43  receives electromagnetic energy not passing through subject material  80  in the depicted embodiment. The output of receiver  43  is applied to amplifier  97  which provides a signal indicative of the turbidity of subject material  80  within supply connection  52  responsive to the intensity of electromagnetic energy of beam  93 . 
   Referring to  FIG. 11 , an exemplary alternative configuration for analyzing slurry in a substantially static state is shown. The illustrated static route  18   a  comprises a centrifuge  100 . The depicted centrifuge  100  includes a container  102  configured to receive subject material  80 . Plural sensors  26  are provided at predefined positions along container  102  to monitor the turbidity of subject material  80  at different radial positions. Centrifuge  100  including container  102  is configured to rapidly rotate in the direction indicated by arrows  104  about axis  101  to assist with precipitation of particulate matter within subject material  80 . Such provides increased setting rates of the particulate matter. Sensors  26  can individually provide turbidity information of subject material  80  at the predefined positions of sensors  26  relative to container  102 . Such information can indicate the state or condition of the slurry as previously discussed. Centrifuge  100  can be configured to receive samples of slurry or other subject material during operation of semiconductor workpiece system  10 . Information from sensors  26  can be accessed via rotary couplings or wireless configurations during rotation of container  102  in exemplary embodiments. 
   From the foregoing, it is apparent the present invention provides a sensor which can be utilized to monitor turbidity of a nearly opaque fluid. Further, the disclosed sensor configurations have a wide dynamic range, are nonintrusive and have no wetted parts. In addition, the sensors of the present invention are cost effective when compared with other devices, such as densitometers. 
   In compliance with the statute, the invention has been described in language more or less specific as to structural and methodical features. It is to be understood, however, that the invention is not limited to the specific features shown and described, since the means herein disclosed comprise preferred forms of putting the invention into effect. The invention is, therefore, claimed in any of its forms or modifications within the proper scope of the appended claims appropriately interpreted in accordance with the doctrine of equivalents.