Abstract:
Methods and apparatuses for determining in-situ a temperature of a substrate with a thermal sensor in a vacuum chamber are described herein. In one embodiment a thermal sensor has a transmitter configured to transmit electromagnetic waves, a receiver configured to receive electromagnetic waves, and a controller configured to control the transmitter and receiver, wherein the controller determines a temperature from a difference between the transmitted electromagnetic wave and the received electromagnetic wave.

Description:
FIELD 
       [0001]    Embodiments of the invention relate to the manufacturing of semiconductor devices. More particularly, embodiments relate to measuring a temperature of semiconductor devices during manufacture. 
       BACKGROUND 
       [0002]    Rapid thermal processing (or RTP) refers to a semiconductor manufacturing process which quickly heats silicon wafers to high temperatures (up to 1,200° C. or greater) on a timescale of several seconds or less. During cooling, however, wafer temperatures must be brought down slowly to prevent dislocations and wafer breakage due to thermal shock. The rapid heating rates are often attained by high intensity lamps or lasers. RTP is used for a wide variety of applications in semiconductor manufacturing including dopant activation, thermal oxidation, metal reflow and chemical vapor deposition. 
         [0003]    Measuring the process temperature is critical for controlling the rapid heating and cooling rates in the RTP tool to prevent damage to the silicon wafers processed therein. Thus, the RPT tool requires a temperature measuring device which has a fast response, is accurate and able to measure temperatures accurately in the temperature range of about 250° C. to 1100° C. Often the ability for the RPT tool to measure the temperature of the substrate quickly and accurately at a relatively low-cost for one end of the temperature range compromises the ability to measure the temperature at the other end of the temperature range. 
         [0004]    Therefore, there is a need for an improved temperature measuring device. 
       SUMMARY 
       [0005]    Methods and apparatuses for determining in-situ a temperature of a substrate with a thermal sensor in a vacuum chamber are described herein. In one embodiment a thermal sensor has a transmitter configured to transmit electromagnetic waves, a receiver configured to receive electromagnetic waves, and a controller configured to control the transmitter and receiver, wherein the controller is operable to determine a temperature from a difference between the transmitted electromagnetic wave and the received electromagnetic wave. 
         [0006]    In another embodiment, a processing chamber is provided. The processing chamber includes a chamber body and a substrate support disposed in an internal volume of the chamber body. A transmitter is oriented to transmit electromagnetic waves through a substrate disposed on the substrate support. A receiver is oriented to receive electromagnetic waves emitted by the transmitter. A controller is configured to control the transmitter and receiver. The controller is operable to determine a temperature from a magnetic fielded variation of the transmitted electromagnetic wave and the received electromagnetic wave. 
         [0007]    In yet another embodiment, a method for non-contact measurement of a temperature of a substrate disposed in a processing chamber is provided. The method includes transferring a substrate into a processing chamber, directing an electromagnetic wave through the substrate disposed in the processing chamber, receiving the electromagnetic wave after having passed through the substrate, and determining a temperature of the substrate based on a metric indicative of a change between the directed electromagnetic wave and the received electromagnetic wave. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]    So that the manner in which the above-recited features of the present invention can be understood in detail, a more particular description of the invention may be had by reference to embodiments, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only typical embodiments of this invention and are therefore not to be considered limiting of its scope, for the invention may admit to other effective embodiments. 
           [0009]      FIG. 1  is a schematic sectional view of a processing chamber having a thermal sensor. 
           [0010]      FIG. 2  is a schematic sectional view of the thermal sensor shown in the processing chamber of  FIG. 1 . 
       
    
    
       [0011]    To facilitate understanding, identical reference numerals have been used, where possible, to designate identical elements that are common to the figures. It is contemplated that elements disclosed in one embodiment may be beneficially utilized on other embodiments without specific recitation. 
       DETAILED DESCRIPTION 
       [0012]    Embodiments of the present disclosure generally relate to an apparatus and methods for quickly measuring temperatures on a substrate undergoing processing in a chamber having rapid and extreme temperature changes. The temperature measuring device may assist in controlling the substrate temperature, so as to minimize damage due to overheating and instances of thermal shock which may damage the substrate during substrate processing. In one embodiment, the temperature control device may use radio waves diffraction to quickly and accurately measure a substrate temperature. In another embodiment, the temperature control device may use electromagnetic waves to quickly and accurately measure a substrate temperature. 
         [0013]      FIG. 1  is a schematic sectional view of a processing chamber  100  having a thermal sensor  190 , according to one embodiment. The processing chamber  100  may be used to process one or more substrates, including deposition of a material on an upper surface of a substrate, such as an upper surface  116  of a substrate  108  depicted in  FIG. 1 . The processing chamber  100  includes a chamber body  101  connected to, an upper dome  128  and a lower dome  114 . In one embodiment, the upper dome  128  may be fabricated from a material such as a stainless steel, aluminum, or ceramics including quartz, including bubble quartz (e.g., quartz with fluid inclusions), alumina, yttria, or sapphire. The upper dome  128  may also be formed from coated metals or ceramics. The lower dome  114  may be formed from an optically transparent or translucent material such as quartz. The lower dome  114  is coupled to, or is an integral part of, the chamber body  101 . The chamber body  101  may include a base plate  160  that supports the upper dome  128 . 
         [0014]    An array of radiant heating lamps  102  is disposed below the lower dome  114  for heating, among other components, a backside  104  of a substrate support  107  disposed within the processing chamber  100 . Alternately, the array of radiant heating lamps  102  is disposed above the upper dome  128  for heating, among other components, the upper surface  116  of the substrate  108  disposed within the processing chamber  100 . During deposition, the substrate  108  may be brought into the processing chamber  100  and positioned onto the substrate support  107  through a loading port  103 . The lamps  102  are adapted to the heat the substrate  108  to a predetermined temperature to facilitate thermal decomposition of process gases supplied into the processing chamber to deposit a material on onto the upper surface  116  of the substrate  108 . In one example, the material deposited onto the substrate  108  may be a group III, group IV, and/or group V material, or a material which includes a group III, group IV, and/or group V dopant. For example, the deposited material may be one or more of gallium arsenide, gallium nitride, or aluminum gallium nitride. The lamps  102  may be adapted to rapidly heat the substrate  108  to a temperature of about 300 degrees Celsius to about 1200 degrees Celsius, such as about 300 degrees Celsius to about 950 degrees Celsius. 
         [0015]    The lamps  102  may include bulbs  141  surrounded by an optional reflector  143  disposed adjacent to and beneath the lower dome  114  to heat the substrate  108  as the process gas passes thereover to facilitate the deposition of the material onto the upper surface  116  of the substrate  108 . The lamps  102  are arranged in annular groups of increasing radius around a shaft  132  of the substrate support  107 . The shaft  132  is formed from quartz and contains a hollow portion or cavity therein, which reduces lateral displacement of radiant energy near the center of the substrate  108 , thus facilitating uniform irradiation of the substrate  108 . 
         [0016]    In one embodiment, each lamp  102  is coupled to a power distribution board (not shown) through which power is supplied to each lamp  102 . The lamps  102  are positioned within a lamphead  145  which may be cooled during or after processing by, for example, a cooling fluid introduced into channels  149  located between the lamps  102 . The lamphead  145  conductively cools the lower dome  114  due in part to the close proximity of the lamphead  145  to the lower dome  114 . The lamphead  145  may also cool the lamp walls and walls of the reflectors  143 . If desired, the lampheads  145  may be in contact with the lower dome  114 . 
         [0017]    The substrate support  107  is shown in an elevated processing position, but may be moved vertically by an actuator (not shown) to a loading position below the processing position to allow lift pins  105  to contact the lower dome  114 . The lift pins  105  pass through holes  111  in the substrate support  107  and raise the substrate  108  from the substrate support  107 . A robot (not shown) may then enter the processing chamber  100  to engage and remove the substrate  108  therefrom through the loading port  103 . A new substrate is placed on the substrate support  107 , which then may be raised to the processing position to place the substrate  108 , with upper surface  116  wherein devices mostly formed thereon facing up, in contact with a front side  110  of the substrate support  107 . 
         [0018]    The substrate support  107  disposed in the processing chamber  100  divides the internal volume of the processing chamber  100  into a process gas region  156  (above the front side  110  of the substrate support  107 ) and a purge gas region  158  (below the substrate support  107 ). The substrate support  107  is rotated during processing by a central shaft  132  to minimize the effects of thermal and process gas flow spatial non-uniformities within the processing chamber  100 , and thus facilitate uniform processing of the substrate  108 . The substrate support  107  is supported by the central shaft  132 , which moves the substrate  108  in an up and down direction  134  during loading and unloading, and in some instances, during processing of the substrate  108 . The substrate support  107  may be formed from a material having low thermal mass or low heat capacity, so that energy absorbed and emitted by the substrate support  107  is minimized. The substrate support  107  may be formed from silicon carbide or graphite coated with silicon carbide to absorb radiant energy from the lamps  102  and rapidly conduct the radiant energy to the substrate  108 . In one embodiment, the substrate support  107  is shown in  FIG. 1  as a ring having a central opening to facilitate exposure of the center of the substrate to the thermal radiation generated by the lamps  102 . The substrate support  107  may support the substrate  108  from the edge of the substrate  108 . In another embodiment, the substrate support  107  may also be a disk member that has no central opening. In yet another embodiment, the substrate support  107  may also be a disk-like or platter-like substrate support, or a plurality of pins extending from a respective finger, for example, three pins or five pins. 
         [0019]    In one embodiment, the upper dome  128  and the lower dome  114  are formed from an optically transparent or translucent material such as quartz. The upper dome  128  and the lower dome  114  are thin to minimize thermal memory. In one embodiment, the upper dome  128  and the lower dome  114  may have a thickness between about 3 mm and about 10 mm, for example about 4 mm. The upper dome  128  may be thermally controlled by introducing a thermal control fluid, such as a cooling gas, through an inlet portal  126  into a thermal control space  136 , and withdrawing the thermal control fluid through an exit portal  130 . In some embodiments, a cooling fluid circulating through the thermal control space  136  may reduce deposition on an inner surface of the upper dome  128 . 
         [0020]    A liner assembly  162  may be disposed within the chamber body  101  and is surrounded by the inner circumference of the base plate  160 . The liner assembly  162  may be formed from a process-resistant material and generally shields the processing volume (i.e., the process gas region  156  and purge gas region  158 ) from metallic walls of the chamber body  101 . An opening  170 , such as a slit valve, may be disposed through the liner assembly  162  and aligned with the loading port  103  to allow for passage of the substrate  108 . 
         [0021]    Process gas supplied from a process gas supply source  173  is introduced into the process gas region  156  through a process gas inlet port  175  formed in the sidewall of the base plate  160 . Additional openings (not shown) may also be formed in the liner assembly  162  to allow gas to flow therethrough. The process gas inlet port  175  is configured to direct the process gas in a generally radially inward direction. During the film formation process, the substrate support  107  is located in the processing position, which is adjacent to and at about the same elevation as the process gas inlet port  175 , thereby allowing the process gas to flow along flow path  169  defined across the upper surface  116  of the substrate  108 . The process gas exits the process gas region  156  (along flow path  165 ) through a gas outlet port  178  located on the opposite side of the processing chamber  100  relative to the process gas inlet port  175 . Removal of the process gas through the gas outlet port  178  may be facilitated by a vacuum pump  180  coupled thereto. As the process gas inlet port  175  and the gas outlet port  178  are aligned to each other and disposed approximately at the same elevation, it is believed that such a parallel arrangement will enable a generally planar, uniform gas flow across the substrate  108 . Further radial uniformity may be provided by the rotation of the substrate  108  through the substrate support  107 . 
         [0022]    Purge gas supplied from a purge gas source  163  is introduced to the purge gas region  158  through a purge gas inlet port  164  formed in the sidewall of the base plate  160 . The purge gas inlet port  164  is disposed at an elevation below the process gas inlet port  175 . The purge gas inlet port  164  is configured to direct the purge gas in a generally radially inward direction. If desired, the purge gas inlet port  164  may be configured to direct the purge gas in an upward direction. During the film formation process, the substrate support  107  is located at a position such that the purge gas flows along flow path  161  across a back side  104  of the substrate support  107 . Without being bound by any particular theory, the flowing of the purge gas is believed to prevent or substantially avoid the flow of the process gas from entering into the purge gas region  158 , or to reduce diffusion of the process gas entering the purge gas region  158  (i.e., the region under the substrate support  107 ). The purge gas exits the purge gas region  158  (along flow path  166 ) and is exhausted out of the process chamber through the gas outlet port  178  located on the opposite side of the processing chamber  100  relative to the purge gas inlet port  164 . 
         [0023]    Similarly, during the purging process the substrate support  107  may be located in an elevated position to allow the purge gas to flow laterally across the back side  104  of the substrate support  107 . It should be appreciated by those of ordinary skill in the art that the process gas inlet port, the purge gas inlet port and the gas outlet port are shown for illustrative purposes, since the position, size, or number of gas inlets or outlet port etc., may be adjusted to further facilitate a uniform deposition of material on the substrate  108 . 
         [0024]    A reflector  122  may be optionally placed outside the upper dome  128  or the lower dome  114  to reflect infrared light that is radiating from the substrate  108  or transmitted by the substrate  108  back onto the substrate  108 . Due to the reflected infrared light, the efficiency of the heating will be improved by containing heat that could otherwise escape the processing chamber  100 . The reflector  122  can be made of a metal such as aluminum or stainless steel. The reflector  122  can have the inlet portal  126  and exit portal  130  to carry a flow of a fluid such as water for cooling the reflector  122 . If desired, the reflection efficiency can be improved by coating a reflector area with a highly reflective coating, such as a gold coating. 
         [0025]    One or more thermal sensors  190  may be disposed in the lamphead  145  and upper dome  128  for measuring thermal emissions of the substrate  108 . Each thermal sensor  190  includes a transmitter  191  and a receiver  192 , and is coupled to at least one sensor controller  194 . The thermal sensors  190  may be disposed at different locations in the lamphead  145  to facilitate viewing (i.e., sensing) different locations of the substrate  108  during processing. In one embodiment, the thermal sensors  190  are disposed on a portion of the chamber body  101  below the lamphead  145 . Sensing the temperature from different locations of the substrate  108  facilitates determining whether temperature anomalies or non-uniformities are present. Such temperature non-uniformities can result in non-uniformities in film formation, such as thickness and composition. Although one thermal sensor  190  (comprising the transmitter  191  and receiver  192 ) is illustrated in  FIG. 1 , one or more additional thermal sensors  190  may be utilized for obtaining an edge to edge temperature profile of the substrate  108 . It is contemplated that the thermal sensors  190  may be arranged to determine the temperature at a plurality of predefined locations of the substrate  108 . 
         [0026]    For example, each thermal sensor  190  may be positioned and/or oriented to view a zone of the substrate  108  and sense the thermal state of that zone. The zones of the substrate  108  may be oriented radially in some embodiments. For example, in embodiments where the substrate  108  is rotated, the thermal sensors  190  may view, or define, a central zone in a central portion of the substrate  108  having a center substantially the same as the center of the substrate  108 , with one or more zones surrounding the central zone and concentric therewith. However, it is not required that the zones be concentric or radially oriented. In some embodiments, zones may be arranged at different locations of the substrate  108  in non-radial fashion, for example in a Cartesian grid arrangement. 
         [0027]    The transmitter  191  of the thermal sensors  190  may be disposed between the lamps  102 , for example in the channels  149 , and are oriented substantially obliquely to the upper surface  116  of the substrate  108 . In some embodiments the transmitter  191  and the receiver  192  are oriented obliquely to the substrate  108  at a substantially similar angle. In other embodiments, the transmitter  191  and the receiver  192  may be oriented in slight departure from each other. For example, the transmitter  191  and the receiver  192  may have an orientation angle within about 5° of each other. 
         [0028]    During processing, a controller  182  receives a metric indicative of temperature from the thermal sensors  190  (or from the sensor controller  194 ) and separately adjusts the power delivered to each lamp  102 , or individual groups of lamps or lamp zones, based on the metric. The controller  182  may include a power supply  184  that independently powers the various lamps  102  or lamp zones. The controller  182  may also include the sensor controller  194 . The controller  182  can be configured to produce a desired temperature profile on the substrate  108 , and based on comparing the metric received from the thermal sensors  190  to a predefined temperature profile or target set point, the controller  182  may adjust the power to lamps and/or lamp zones to conform the observed (i.e., sensed) thermal information indicating of the lateral temperature profile of the substrate with to the desired temperature profile. The controller  182  may also adjust power to the lamps and/or lamp zones to conform the thermal treatment of one substrate to the thermal treatment of another substrate, to prevent chamber performance drift over time. 
         [0029]    The thermal sensor  190  may operate to detect the temperature on the substrate  108 . For example, the sensor controller  194  may instruct the transmitter  191  to send a transmitted signal  146 . The transmitted signal  146  may interact with the substrate  108 , or other bodies, which may modify, attenuate, or alter the transmitted signal  146 . A received signal  147  (the transmitted signal  146  which has been altered) is directed away from the substrate  108  to the receiver  192 . The receiver  192  then conveys the received signal  147  to the sensor controller  194 . The sensor controller  194  may compare the transmitted signal  146  to the received signal  147  to determine a temperature. The thermal sensor  190  is discussed in greater detail in  FIG. 2 . 
         [0030]      FIG. 2  is a schematic sectional view of the thermal sensor  190  shown in the processing chamber of  FIG. 1 . Although one or more transmitters  191  may direct one or more transmitted signals  146  at either the upper surface  116  of the substrate  108 , an underside  208  of the substrate  108 , or a combination thereof, the mechanics are similar and the discussion will be in reference a single transmitter. That is, the transmitter  191  directs the transmitted signal  146  at the underside  208  of the substrate  108  at a first angle  222  from a normal angle  210 ,  220  to the underside  208  of the substrate  108 . The transmitted signal  146  is altered by the substrate  108 , such as by changing the first angle  222  of the signal by diffraction to an intermediate angle  218 , as shown by an intermediary signal  240  propagating through the substrate  108 . The intermediate angle  218  may be dependent on the properties of the substrate  108  as well as the temperature of the substrate  108 . The properties of the substrate along with the intermediate angle  218  generate a displacement  216  of the signals  146 ,  147 . The intermediary signal  240  exits the upper surface  116  of the substrate  108 , where it may diffract again to a second angle  212 , as the received signal  147  which is then detected by the receiver  192 . In one embodiment, the first angle  222  and the second angle  212  are substantially similar. In a second embodiment, the first angle  222  and the second angle  212  are dissimilar. 
         [0031]    The thermal sensor  190  may work on one or more principles associated with the transmission of electromagnetic waves. The thermal sensor  190  may utilize the properties of the substrate  108  to effect a change in the transmitted signal  146 . The properties creates the displacement  216  from the transmitted signal  146  to the received signal  147  which is temperature dependent, and accordingly, may be used to determine the temperature of the substrate  108 . In one embodiment, a temperature of the substrate  108  can be detected as a function of the change in refraction and density of the substrate  108 . For example, silicon has a density of about 2.3290 g·cm 3  at 0° C. and about 2.57 g·cm 3  at 1414° C. The electromagnetic waves change in velocity and refract when the waves pass through a medium, such as the substrate  108 , and vary with the dynamic density of the substrate  108 . Thus, the change in the transmission signal may be indicative of the change in density of the substrate  108 , which can then be correlated to a temperature of the substrate  108 . Additionally, measuring the speed of the transmitted signal  146  affected by the density of the substrate  108  as it propagates through the substrate  108  may also be used to yield information about the temperature of the substrate  108 . In another embodiment, the electromagnetic waves may determine an electromagnetic field of the substrate  108 . Changes in the electromagnetic field of the substrate correlate to changes in the temperature of the substrate  108 . 
         [0032]    The thermal sensors  190  may be attuned to the same wavelength or spectrum, or to different wavelengths or spectra. For example, substrates used in the processing chamber  100  may be compositionally homogeneous, or they may have domains of different compositions, such as feature locations. Using thermal sensors  190 , attuned to different wavelengths, may allow monitoring of substrate domains having different composition and different emission responses to thermal energy. 
         [0033]    Although sound waves do not travel through a vacuum, radio waves are electromagnetic waves that are capable of traveling through a vacuum. Sound consists of pressure variations in matter, such as air or water and therefore will not travel through a vacuum. However, radio waves, like visible light, infrared, ultraviolet, X-rays and gamma rays, are electromagnetic waves that readily travel through a vacuum, making radio waves well suited for vacuum environments such as a plasma processing chamber and the like. 
         [0034]    In one embodiment, the thermal sensors  190  are attuned to infrared wavelengths, such as 700 nanometers to 1 mm, for example at about 3 μm. The thermal sensors  190  may generate a continuous wave, such as a sinusoidal wave. However, it should be understood that any suitable wave, such as a pulsing wave. Pulsing waves may beneficially have less noise, making pulsing waves desirable for use in the thermal sensor  190 . For example, a pulse wave may measure time variation from the transmitter to the receiver for the pulse wave and compare the time variations against various substrate temperatures. 
         [0035]    The actual speed of an electromagnetic wave through a material medium is dependent upon the density of that medium. Different materials cause a different amount of delay due to the absorption and reemission process of the electromagnetic wave. Different materials have atoms more closely packed and thus the amount of distance between atoms is also less. The variation of the density for the substrate  108  is dependent upon the nature of the material as well as certain properties, such as temperature, of the substrate  108 . Additionally, the speed of an electromagnetic wave is dependent upon the material and its density through which it is traveling. The speed of the electromagnetic wave changes gradually over a given distance. Thus, we can detect temperature as a function of change in refraction and density of the substrate  108  by analyzing the variation from input to output of an electromagnetic wave. The temperature can be validated at a particular point by comparing the change of frequency and speed along with refraction as a function of temperature. 
         [0036]    For example, the speed of a sound wave is about 343 m/s or about 767 mph in dry air maintained at 20° C. The speed of the wave depends on the temperature of the medium, i.e., air or substrate. The speed of sound in are may be expressed as: v=331 m/s+0.6 T; where v is the velocity of the wave, T is the temperature of the air in degrees Celsius, 331 m/s is the speed of sound in dry air at 0° C., and 0.6 is a constant. So as the temperature increases, so does the speed of sound at a rate of 0.6 m/s for each Celsius degree. The speed of sound also depends on the compressibility and inertia of the medium. The variation on speed due to compressibility of the medium can be represented as v2=(elastic property/inertial property). Where the elastic property is usually the bulk modulus or Young&#39;s modulus of the medium, and the inertial property is the density of the medium. These same principles can be applied to electromagnetic waves to measure the temperature of a substrate in a vacuum atmosphere. 
         [0037]    In another embodiment, a temperature of the substrate  108  can be determined using the sensor  190  configured to detect magnetic susceptibility. Using the Curie-Weiss Law, the magnetic fielded variation may be used to measure in the temperature of the substrate  108 . Magnetic susceptibility is inversely proportional to the temperature of the substrate through which the magnetic field is measured. Thus, measuring the magnetic field at the substrate  108  is indicative of a measured temperature. 
         [0038]    The transmitter  191 , in one embodiment, may be in the form of magnets placed beneath the substrate. The receivers  192 , one embodiment, may be in the form of a sensor for measuring the magnetic susceptibility of the substrate  108  using the field provided by the transmitter  191 . The magnets (i.e., the transmitters  191 ) may be placed in the reflector plate or below and controlled and isolated with respect to the magnetic field of the substrate. Changes in the substrate  108  magnetic field can be expressed as a function of temperature using Curie&#39;s Law, i.e., X=M/H=Mμ 0 /B=C/T. Where X is the magnetic susceptibility which is the influence of an applied magnetic field on the substrate  108 ; M is the magnetic moment per unit volume, H is the macroscopic magnetic field, μ 0  is the permeability of free space; B is the magnetic field; C is the material-specific Curie constant; and T is the temperature (of a substrate). 
         [0039]    The thermal sensors  190  may have different embodiments for different temperature ranges and operating conditions. In one embodiment, the thermal sensor  190  may be configured for general purposes and operable at temperatures of between about 250° C. (500° F.) and about 2500° C. (4500° F.). The general purpose thermal sensor may be comprised of narrow spectral band radiation thermometers operating at wavelengths of about 0.65 μm; or between about 0.7 μm and about 1.1 μm; or between about 0.9 μm and about 1.9 μm. The general purpose thermal sensors may have solid-state photoelectric detectors, such as Si or Ge among others, an optical resolution of about 0.9 mm diameter, and a distance-ratio (D-ratio) of about 250:1. 
         [0040]    In another embodiment, the thermal sensor  190  may be a high-precision thermal sensor having a two-color ratio pyrometer. The two colors represent two discrete wavelengths used for the thermal measurement. The high-precision thermal sensor may be used for temperatures between about 650° C. (1200° F.) and about 2500° C. (4500° F.). The high-precision thermal sensor may operate with spectral bands for the two colors of about 0.8 μm and about 0.9 μm. Advantageously, the high-precision thermal sensor is independent of emissivity, fluctuations and/or sight path disturbances, and automatically compensates for moving targets. 
         [0041]    In yet another embodiment, the thermal sensor  190  may be a programmable/high-performance thermal sensor. The programmable/high-performance thermal sensor may be used for temperatures between about 100° C. (212° F.) and about 2500° C. (4500° F.). The programmable/high-performance thermometer may have built-in signal conditioning and digital computing, spectral band choices in wide or narrow bands between about 2 μm and about 20 μm, a bidirectional interface, a plurality of programmable functions such as maximum/minimum/differential/hold, programmable ambient temperatures for a plurality of different material compositions, and a choice of through-lens-sighting, such as LED or laser. 
         [0042]    In yet another embodiment, the thermal sensor  190  may be a high temperature general purpose thermal sensor. The high temperature general purpose thermal sensor may be used for temperatures between about 250° C. (500° F.) and about 2500° C. (4500° F.). The high temperature general purpose thermal sensor may operate in a narrow spectral band such as about 0.65 μm; or about 0.7-1.1 μm; or about 0.9-1.9 μm. The high temperature general purpose thermal sensor may have solid-state photoelectric detectors, such as Si or Ge, an optical resolution 0.9 mm diameter, and a D-ratio of about 250:1. 
         [0043]    In yet another embodiment, the thermal sensor  190  may be a high-stability thermal sensor. The high-stability thermal sensor may be operable for complex applications at temperatures between about 300° C. (600° F.) and about 2500° C. (4500° F.). The high-stability thermal sensor may consist of one or more narrow spectral band radiation thermometers. For example, the high-stability thermal sensor may operate in a spectral band of about 3.9 μm for glass and/or through hot gas, in a spectral band of about 5.0 μm for glass surfaces, in a spectral band of between about 4.2 μm and about 5.3 μm for combustion gases; among other selected spectral bands. The high-stability thermal sensor may have a pyroelectric detector, is chopper stabilized, and have an optical resolution suitable for a 1 mm target as a 100:1 D-ratio. The high-stability thermal sensor has a response time of about 30 msec and may have an analog output of about 4 mA to about 20 mA. 
         [0044]    In yet another embodiment, the thermal sensor  190  may be a high-speed, two-color ratio thermal sensor. The high-speed, two-color ratio thermal sensor may be operable at temperatures between about 150° C. (300° F.) and about 2500° C. (4500° F.). The high-speed, two-color ratio thermometer may have narrow spectral bands such as between about 0.8 μm and about 2.1 for a first band and between about 0.9 μm and about 2.4 μm for a second band. The high-speed, two-color ratio thermal sensor may additionally have an internal calibration check. Advantageously, the high-speed, two-color ratio thermal sensor is greatly independent of emissivity, fluctuations and/or sight path disturbances, and automatically compensates for moving targets. 
         [0045]    While the foregoing is directed to embodiments of the invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof.