Patent Publication Number: US-2005127192-A1

Title: Endpoint detector for a substrate manufacturing process

Description:
BACKGROUND OF THE INVENTION  
      1. Field of the Invention  
      The present invention relates to a semiconductor manufacturing apparatus. More particularly, the present invention relates to an endpoint detector employed in the semiconductor manufacturing apparatus for detecting an endpoint of a semiconductor manufacturing process.  
      2. Description of the Related Art  
      Generally, manufacture of a semiconductor device, e.g., a random access memory (RAM), includes a fabricating step, an electrical die sorting step and a packaging step. In the fabricating step, an electric circuit is formed on a semiconductor substrate, e.g., a silicon wafer. In the electrical die sorting (EDS) step, the electrical characteristic of the electric circuit is inspected. In the packaging step, an epoxy resin encapsulates the electric circuit. If more than one semiconductor device is formed on the substrate, a die having the semiconductor device is separated from the substrate, e.g., by a sawing step.  
      In the fabricating step, a plurality of layers, e.g., a silicon dioxide layer, a polysilicon layer, an aluminum layer, and a copper layer, are formed on the silicon wafer. The layers may be formed by chemical vapor deposition (CVD), process, a physical vapor deposition (PVD) process, a thermal oxidation process, an ion implantation process and an ion diffusion process. The layers are selectively removed using etchant or plasma, thereby forming the electric circuit on the silicon wafer.  
      Most of the fabricating steps require in-situ monitoring of the electrical characteristics of various layers formed on the silicon wafer. Examples of in-situ monitoring include an optical emission spectroscopy (OES), an ellipsometry method, and an interferometry method.  
      An endpoint detector using the OES can monitor the thickness of the deposition film formed on the silicon wafer by the CVD process and the PVD process. Alternatively, the endpoint detector can monitor an overetching of the deposition film by the etchant or plasma.  
      An endpoint for the manufacturing process is determined based on the emission spectrum of the plasma, which is altered as the plasma reacts with the unprotected layers.  
      The endpoint detector for carrying out the OES includes a window for transmitting light emitted from plasma to an optical emission spectroscopy system. The window covers a view port formed on a sidewall of the process chamber. Typically, the window includes heat resistant quartz, which is also transparent to the wavelengths of interest in the emission spectrum.  
      The composition of the plasma is varied in accordance with the composition of the layers during etching of the layers formed on the silicon wafer. When the different layers formed on the silicon wafer are successively etched, the composition of plasma is varied. The emission spectrum of plasma varies in accordance with the composition of plasma. Thus, the endpoint of the etching is determined by the variation of the emission spectrum of plasma.  
      However, the plasma also creates a reaction product in the processing chamber. This reaction product is deposited on the surface of the window, resulting in a residue film. This residue film alters the intensity of the emission spectrum of plasma received by the OES, thereby interfering with the measurement of the emission spectrum of plasma.  
     SUMMARY OF THE INVENTION  
      The present invention is therefore directed to an endpoint detector, which substantially overcomes one or more of the problems due to the limitations and disadvantages of the related art.  
      It is a feature of the present invention to provide an endpoint detector for preventing the deposition of the residue product on the surface of the monitoring window disposed on the processing chamber.  
      At least one of the above and other features and advantages of the present invention may be realized by providing an endpoint detector in a substrate processing, including a window covering a passage formed through a sidewall of a processing chamber in which the substrate processing is performed, the window transmitting light generated from plasma during the substrate processing, an analyzing unit for analyzing the light to detect an endpoint of the substrate processing, a first temperature control unit, thermally coupled to the window, for maintaining the window at a first temperature, and a second temperature control unit, thermally coupled to an inner surface of the passage, for maintaining the inner surface of the passage at a second temperature, the second temperature being lower than the first temperature.  
      The window may have a first surface that contacts an outer surface of the sidewall of the processing chamber and a second surface that is spaced apart from the processing chamber. The first temperature control unit may include a ceramic heater that makes contact with the second surface of the window. The ceramic heater may be ring shaped, and have an outer diameter that is substantially identical to a diameter of the window.  
      The endpoint detector may include a thermal sensor and a control part. The thermal sensor may measure a temperature of the window and/or the temperature of the heater. The control part controls an operation of the heater in accordance with a temperature signal output from the thermal sensor to maintain the first temperature of the window.  
      The second temperature control unit may include a coolant cycling channel, a coolant cycling pipe and a coolant cycling unit, wherein the coolant cycling channel is disposed around the passage, the coolant cycling channel controlling a temperature of the inner surface of the passage, the coolant cycling pipe is connected to the coolant cycling channel, and the coolant cycling unit circulates the coolant through the coolant cycling unit and the coolant cycling pipe. The second temperature control unit may be installed on the coolant cycling pipe, and the second temperature control unit includes a heat exchanger for transmitting a heat from the coolant that flows in the coolant cycling pipe. The endpoint detector may include an adiabatic member formed between the coolant cycling channel and an inside surface of the processing chamber.  
      The passage may include just a view port formed in the sidewall of a processing chamber, or may include a view port extender coupling the view port, the view port extender having a hole connecting to the view port. The second temperature control unit may wind around the view port extender, and the second temperature control unit may have a coolant passageway for cycling a coolant. The second temperature control unit may include a plurality of pins formed on the outer surface of the view port extender. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      The above and other features and advantages of the present invention will become readily apparent to those of ordinary skill in the art by reference to the following detailed description when considered in conjunction with the accompanying drawings, in which:  
       FIG. 1  illustrates a schematic cross-sectional view of an end point detector according to a first embodiment of the present invention;  
       FIG. 2  illustrates an enlarged cross-sectional view of the end point detector shown in  FIG. 1 ;  
       FIG. 3  illustrates an enlarged cross-sectional view of an endpoint detector according to a second embodiment of the present invention;  
       FIG. 4  illustrates an enlarged cross-sectional view of an endpoint detector according to a third embodiment of the present invention; and  
       FIG. 5  illustrates an enlarged cross-sectional view of an endpoint detector according to a fourth embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
      Korean Patent Application No. 2003-91071, filed on Dec. 15, 2003, and entitled: “Endpoint Detector for a Substrate Manufacturing Process,” is incorporated by reference herein in its entirety.  
      The present invention now will be described more fully hereinafter with reference to the accompanying drawings, in which embodiments of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. In the drawings, the thickness of layers and regions are exaggerated for clarity. Like reference numerals refer to similar or identical elements throughout.  
       FIG. 1  illustrates a schematic cross-sectional view of an endpoint detector according to a first embodiment of the present invention.  FIG. 2  illustrates an enlarged cross-sectional view of the endpoint detector shown in  FIG. 1 .  
      Referring to FIGS. 1  and  2 , an endpoint detector  100  is employed in a film processing device  10  for processing a silicon wafer  30  using plasma  20 . The film processing device  10  may include, e.g., an etching device for patterning a variety of films formed on the silicon wafer  30  or an ashing device for removing a photo resist pattern or a photo resist film formed on the silicon wafer  30 .  
      The film processing device  10  may include a processing chamber  40 , a gas supply pipe  48 , a vacuum system  50 , a chuck  42 , an upper electrode  44 , a radio frequency power generator  54 , and a bios power generator  56 .  
      The processing chamber  40  provides a space for processing the silicon wafer  30 , and includes a first sidewall  46  and a second sidewall  52 . The chuck  42  is disposed in the processing chamber  40  for supporting the silicon wafer  30 . The upper electrode  44  converts a reaction gas into the plasma  20 . The gas supply pipe  48  is connected to the first sidewall  46  of the processing chamber  40 , and supplies the reaction gas in the space of the processing chamber  40 . The vacuum system  50  is connected to the bottom of the processing chamber  40  for creating a vacuum in the space of the processing chamber  40 . The radio frequency power generator  54  is electrically coupled to the upper electrode  44  for generating the plasma  20  in the processing chamber  40 , and the bios power generator  56  is electrically coupled to the chuck  42 .  
      The endpoint detector  100  is disposed on the second sidewall  52  of the processing chamber  40 . The endpoint detector  100  includes a window  110 , an analyzing unit  120 , a first temperature control unit  130 , and a second temperature control unit  140 .  
      The window  110  is disposed on an outer surface  62  of the second sidewall  52  of the processing chamber  40  to cover a view port  58  formed in the second sidewall  52 . The window  110  includes a first surface  112  and a second surface  114 . The first surface  112  is disposed on the outer surface  62  of the second sidewall  52  corresponding to the view port  58 , and the second surface  114  is opposite the first surface  112 . The window  110  may be made of transparent, heat resistant quartz and may have a disc shape.  
      The first temperature control unit  130  controls a temperature of the window  110 . The first temperature control unit  130  is disposed on the second surface  114  of the window  110 . The first temperature control unit  130  includes a heater, e.g., a ceramic heater  132 , for heating the window  110  to a first temperature. The first temperature of the window  110  may be maintained between about 10° C. and 20° C. by the ceramic heater  132 . The ceramic heater  132  may have a ring shape and a rectangular cross-section. The outer diameter of the ceramic heater  132  may be the same as the outer diameter of the window  110 .  
      The window  110  and the ceramic heater  132  may be mounted on the second sidewall  52  of the processing chamber  40  by an adapter  136  and a window holder  134 .  
      The window holder  134  may have the same shape as the ceramic heater  132 , here a ring shape with a rectangular cross-section. The inner diameter of the window holder  134  may be the same as that of an outer diameter of the window  110  and the ceramic heater  132 . The window holder  134  may be disposed on sides of the window  110  and the ceramic heater  132  to grip the window  110  and the ceramic heater  132 .  
      The adapter  136  may have a flange shape, and the adapter  136  fixes the window  110  and the ceramic heater  132  to the second sidewall  52  by a fixing member  138 . The fixing member  138  passes through the adapter  136  and the window holder  134 . In this exemplary embodiment, the fixing member  138  includes a plurality of bolts.  
      The adapter  136  may include a first part  136   a,  a second part  136   b  and a hole  136   c.  The first part  136   a  is disposed on the ceramic heater  132  and the window holder  134 . The first part may have a ring shape and a rectangular cross-section. The second part  136   b  is disposed on the first part  136   a,  and may have a cylindrical shape that extends in a perpendicular direction to the first part  136   a.  The hole  136   c  passes through the first part  136   a  and the second part  136   b,  and extends parallel to the second part  136   b.    
      The analyzing unit  120  includes an optical probe  122 , an optical cable  124  and an optical emission spectrometer  126 . The optical probe  122  may be disposed in the hole  136   c  of the adapter  136  so that the optical probe  122  contacts a central portion of the second surface  114  of the window  110 .  
      The optical cable  124  connects the optical probe  122  and the optical emission spectrometer  126 . The optical emission spectrometer  126  analyzes an emission spectrum of plasma input through the view port  58  of the process chamber  40 , the window  110 , the optical probe  122 , and the optical cable  124 , and calculates the endpoint from the spectrum of the plasma.  
      The second temperature control unit  140  includes a coolant cycling channel  142 , a coolant cycling pipe  144  and a cycling unit  146 .  
      The coolant cycling channel  142  controls a temperature of the inner surface  60  of the view port  58 , and is disposed around the view port  58  formed in the second sidewall  52  of the process chamber  40 . The coolant cycling channel  142  includes a coolant that flows through the coolant cycling channel  142 .  
      The coolant cycling pipe  144  connects an inlet port  142   a  and an outlet port  142   b.  The coolant cycling pipe  144  may include a heat exchanger  148  for transferring heat from the coolant that flows through the coolant cycling pipe  144 .  
      The cycling unit  146  for cycling the coolant through the coolant cycling channel  142  and the coolant cycling pipe  144  is installed in the coolant cycling pipe  144 . The cycling unit  146  includes a pump that controls flow of the coolant. Arrows adjacent to the inlet port  142   a  and the outlet port  142   b  in  FIG. 2 , indicate a cycling direction of the coolant. The coolant flowing through the coolant cycling pipe  144  may include a nitrogen N 2  gas, a helium (He), gas and cooling water.  
      The second temperature control unit  140  maintains the temperature of the inner surface  60  of the view port  58  of the process chamber  40  at a second temperature, which is lower than the first temperature. In this exemplary embodiment, a difference between the first and second temperatures may be more than about 10° C.  
      Light emitted from the plasma generated in the process chamber  40  transmits through the view port  58 , the window  110 , the optical probe  122 , and the optical cable  124  to the optical emission spectrometer  126 . The intensity of the light generated from the plasma is changed in accordance with the plasma etching in the process chamber  40 .  
      The optical emission spectrometer  126  measures the light in the emission spectrum of the plasma and calculates the endpoint of the etching process in accordance with the variation of the spectrum.  
      However, a reaction residue product is also generated in the process chamber  40  by the reaction between the layer formed on the silicon wafer  30  and the plasma in the processing chamber  40 . When the reaction residue product is deposited on the first surface  1   12  of the window  110 , a thin residue film is formed on the first surface  112  of the window  110 , interfering with the transmission of the emission spectrum. For example, a residue film including carbon fluoride (CFx) reaction residue product absorbs ultraviolet light having a wavelength less than 400 nm, which is of interest in determining the endpoint for that particular process.  
      Deposition of the reaction residue product on the first surface  112  of the window  110  will be described from a thermophoresis point of view. “Thermophoresis” means that the diffusion of the impurities onto different objects depends on a temperature deviation between the objects. Thermophoresis affects the movement of the impurities having a size between about 0.1 μm and about 1 μm.  
      Generally, when the temperature deviation occurs between a high temperature object and a low temperature object, the impurities included in a surrounding medium move from the high temperature region to the low temperature region, thereby forming a clean region around the high temperature object. The area of the clean region is determined in accordance with both temperature and pressure. For example, increasing the temperature and decreasing the pressure of the high temperature object will enlarge the area of the clean region. Meanwhile, the impurities attach to the low temperature object due to themophoresis.  
      In an exemplary embodiment, an inner temperature of the processing chamber  40  is higher than the temperature of the sidewalls  46 ,  52 , and the temperature of the window  110  is higher than or equal to the temperature of the sidewalls  46 ,  52 .  
      The first temperature control unit  130  maintains the window  110  at a higher temperature than that of the inner region  70  of the view port  58  and the inner surface  60  of the view port  58 . The second temperature control unit  140  maintains the inner surface  60  at a lower temperature than that of the inner region  70  of the view port  58 .  
      Thus, the clean region formed adjacent first surface  112  of the window  110  is enlarged by the temperature deviation formed between the process chamber  40  and the window  110 , so that the reaction residue products are deposited on the inner surface  60  of the view port  58 . Thus, the endpoint detector precisely monitors the spectrum of the plasma generated in the processing chamber  40 , improving the accuracy of endpoint detection.  
      The endpoint detector  100  further includes a temperature sensor  150  for measuring the temperature of the window  110 , and a control part  160  for controlling the ceramic heater  132  in accordance with the temperature signal output from the temperature sensor  150 , in order to maintain the first temperature of the window  110 . In this exemplary embodiment, the temperature sensor  150  may include a thermocouple and/or a thermister.  
      The control part  160  includes a control circuit (not shown) and a power supply module (not shown). The control circuit generates a control signal according to the temperature of the window  110  output by the temperature sensor  150 . The power supply module controls a level of the power supplied to the ceramic heater  132  in accordance with the control signal.  
      Alternatively, the temperature sensor  150  may measure a temperature of the ceramic heater  132 . Thus, the control part  160  may control the temperature of the window  110  via the temperature of the ceramic heater  132 .  
      The endpoint detector  100  may include a temperature sensor  172  for measuring the temperature of the coolant that flows in the coolant cycling pipe  144 . The control part  160  may control the cycling unit  146  in accordance with a coolant temperature output by the temperature sensor  172 .  
      Alternatively, the endpoint detector  100  the temperature sensor  172  may directly measure the temperature of the inner surface  60  of the view port  58 . The temperature sensor  172  would then be disposed near the inner surface  60  of the view port  58 . The control part  160  may control the cycling unit  146  in accordance with a temperature of the inner surface  60  output by the temperature sensor  172 .  
      Then, the control part  160  may compare the temperature of the window  110  that is measured by the temperature sensor  150  with the temperature of the inner surface  60  of the view port  58  that is measured by the temperature sensor  172 , so that the operation of the ceramic heater  132  and the cycling unit  146  can be precisely controlled in accordance with the comparison result data. Hence, the window  110  is maintained at a higher temperature than that of the inner surface  60  of the view port  58 .  
      The endpoint detector  100  may further include an adiabatic member  170  interposed between the coolant cycling channel  142  and an inner surface  64  of the second sidewall  52  of the processing chamber  40 . The adiabatic member  170  may have a ring shape, and encapsulates the view port  58  in order to thermally isolate the coolant cycling channel  142  and the inner surface  64  of the second sidewall  52 . Thus, the adiabatic member  170  prevents heat exchange between the processing chamber  40  and the coolant.  
       FIG. 3  illustrates an enlarged cross-sectional view of an endpoint detector according to a second embodiment of the present invention.  
      Referring to  FIG. 3 , the endpoint detector  200  is combined with the semiconductor manufacturing device. For example, the semiconductor manufacturing device may include a processing chamber for performing a plasma etching, a chuck for supporting a semiconductor substrate such as a silicon wafer, an upper electrode for generating plasma in the processing chamber, as set forth above in connection with  FIG. 1 . Again, the endpoint detector  200  is connected to the second sidewall  52  of the processing chamber.  
      The endpoint detector  200  includes a window  210 , an analyzing unit  220 , a first temperature control unit  230  and a second temperature control unit  240 .  
      In order to transmit the light emitted from the plasma in the processing chamber, the window  210  is disposed on the outer surface  62  of the second sidewall  52  of the processing chamber to cover the view port  58  formed in the second sidewall  52  of the processing chamber. The window  210  may have a disc shape, and the window  210  is disposed on the second sidewall  52  of the processing chamber. The window  210  includes a first surface  212  that contacts the outer surface  62  of the second sidewall  52 , and a second surface  214 , opposite the first surface  212 .  
      The analyzing unit  220  analyzes the light transmitted through the window  210 . The analyzing unit  220  includes an optical probe  222  connected to a central portion of the second surface  214  of the window  210 , an optical emission spectrometer  226  for analyzing the light generated in the process chamber, and an optical cable  224  for connecting the optical probe  222  and the optical emission spectrometer  226 .  
      The first temperature control unit  230  heats the window  210  to a first temperature. The first temperature control unit  230  may include a ceramic heater  232  disposed on the second surface  214  of the window  210  in order to heat the window  210 .  
      The second temperature control unit  240  is formed in the second sidewall  52  of the processing chamber, and surrounds the view port  58  of the processing chamber. The second temperature control unit  240  includes a cooling channel  242  connected to outside the processing chamber. The cooling channel  242  cools the inner surface  60  of the view port  58  using air external to the processing chamber, so that the temperature of the inner surface  60  of the view port  58  is maintained at a second temperature. In this exemplary embodiment, the second temperature is lower than the first temperature.  
      The cooling channel  242  may include a plurality of cooling pins  244  for radiating heat from the inner surface  60  of the view port  58 . The cooling pins  244  may be disposed adjacent to the inner surface  60  of the view port  58 .  
      The cooling channel  242  also includes a cooling portion  246 , an inlet port  248  and an exhaust port  250 . The cooling portion  246  is formed in the second sidewall  52  of the process chamber. The cooling portion  246  may have a ring shape and a rectangular cross-section. The cooling portion  246  is disposed around the view port  58 .  
      Cooling air is input through the inlet port  248  and is output through the exhaust port  250 . The cooling air cools the cooling pins  244 , which in turn cool the view port  58 .  
      The second temperature control unit  240  may include a cooling fan  252 . The cooling fan  252  is disposed at the inlet port  248 , and provides the cooling air to the cooling channel  242 . Alternatively, the cooling fan  252  may be disposed at the exhaust port  250 , and removes the cooling air from the cooling channel  242 . Alternatively, the second temperature control unit  240  may include a plurality of inlet openings to provide the cooling air to the cooling channel  242  and may include a plurality of outlet openings to exhaust the cooling air from the cooling channel  242 .  
      A window holder  234 , an adapter  236  and a plurality of the fixing members  238  secure the window  210  and the ceramic heater  232  to the second sidewall  52  of the processing chamber. A control part  260  controls the operation of the ceramic heater  232  in accordance with the temperature of the window  210  that measured by a temperature sensor  262 .  
      The endpoint detector  200  may further include an adiabatic member  270  that prevents heat exchange between the inner surface  64  of the processing chamber and the second temperature control unit  240 . The endpoint detector  200  may include a temperature sensor  272  for measuring the temperature of the inner surface  60  of the view port  58 . The control part  260  compares the temperature of the window  210  that is measured by the temperature sensor  262  with the temperature of the inner surface  60  of the view port  58  that is measured the temperature sensor  272 , to precisely control the operation of the ceramic heater  232 . Thus, the temperature of the inner surface  60  of the view port  58  may be maintained below that of the temperature of the window  210  by the second temperature control unit  240 . Therefore, the reaction residue products generated in the processing chamber are deposited on the inner surface  60  of the view port  58 , rather than the window  210 .  
      As it is described above, the light generated from the plasma is transmitted through the window  210  to the optical emission spectrometer  226  without decreasing the intensity of the light, increasing accurate endpoint detection.  
       FIG. 4  illustrates an enlarged cross-sectional view of an endpoint detector according to a third embodiment of the present invention.  
      Referring to  FIG. 4 , the endpoint detector  300  is combined with the semiconductor manufacturing device. For example, the semiconductor manufacturing device includes a processing chamber for performing a plasma etching, a chuck for supporting a semiconductor substrate such as a silicon wafer, an upper electrode for generating plasma in the processing chamber, as set forth above in connection with  FIG. 1 .  
      The endpoint detector  300  includes a view port extender  302  for extending a view port  58  in the second sidewall  52  of the process chamber, a window  310 , an analyzing unit  320 , a first temperature control unit  330 , and a second temperature control unit  340 .  
      The view port extender  302  for extending the view port  58  formed in the second sidewall  52  of the processing chamber may have a cylindrical shape, and connects the view port  58  formed in the sidewall of the process chamber to the window  310 . The view port extender  302  has a hole  304 , and an axis of the hole  304  is identical to an axis of the view port  58 .  
      The view port extender  302  includes a first lateral part  302   a,  a second lateral part  302   b,  a first flange  306  and a second flange  308 .  
      The first lateral part  302   a  is inserted into the view port  58 . The first flange  306  is disposed on the adjacent portion of the first lateral part  302   a  and contacts the outer surface  64  of the second sidewall  52  of the process chamber. The second lateral part  302   b  extends from the first flange  306  to the second flange  308 , which, in turn, contacts the window  310 .  
      The window  310  for transmitting the light generated from the plasma may have a disc shape and may be made of a transparent material such as quartz. The window  310  is disposed on the second flange  308  to cover the hole  304  of the view port extender  302 .  
      The window  310  has a first surface  312  and a second surface  314 , opposite the first surface  312 . The first surface  312  contacts the second flange  308  of the view port extender  302 .  
      The first temperature control unit  330  controls the temperature of the window  310  to reach a first temperature. The first temperature control unit  330  may have a ring shape and may include a ceramic heater  332  disposed on the second surface  314  of the window  310 . The ceramic heater  332  is electrically connected to a control part  360 , and the control part  360  is electrically connected to a temperature sensor  362  for measuring the temperature of the window  310 .  
      The control part  360  controls the operation of the ceramic heater  332  in accordance with a temperature signal output from the temperature sensor  362  to maintain the window  310  at the first temperature.  
      The analyzing unit  320  analyzes the light transmitted through the window  310  in order to detect the endpoint of the etching process processed in the processing chamber.  
      The analyzing unit  320  includes an optical probe  322 , an optical cable  324  and an optical emission spectrometer  326 . The optical probe  322  is connected to a central portion of the second surface  314  of the window  310 . The optical cable  324  extends from the optical probe  322  to the emission spectrometer  326 .  
      The emission spectrum of the plasma is successively transmitted from the processing chamber to the optical emission spectrometer  326  via the view port  58  of the processing chamber, the hole  304  of the view port extender  302 , the window  310 , the optical probe  322  and the optical cable  324 .  
      The optical emission spectrometer  326  analyzes the light generated from the processing chamber to determine the endpoint of the etching process.  
      A plurality of the first fixing members  338   a  secures the view port extender  302  to the second sidewall  52  of the processing chamber through the first flange  306 . A plurality of the second fixing member  338   b  secures the window  310  and the ceramic heater  332  to the view port extender  302  through the second flange  308 , the window holder  334  and an adapter  336 .  
      The temperature of an inner surface  304   a  of the hole  304  of the view port extender  302  is maintained at a second temperature by the second temperature control unit  340 . In this embodiment, the second temperature is lower than the first temperature.  
      The second temperature control unit  340  includes a cooling coil  342  wound around the view port extender  302 . A cooling coil  342  has a passageway that circulates a coolant. The cooling coil  342  is connected to a coolant cycling pipe  344 . A cycling unit  346  for cycling the coolant in the coolant cycling pipe  344  and a heat exchanger  348  for radiating the heat to the coolant cycled in the coolant cycling pipe  344  are connected to the coolant cycling pipe  344 . In this embodiment, the coolant may include a nitrogen gas, a helium gas or cooling water.  
      The endpoint detector  300  may include a second temperature sensor  372  for measuring the temperature of the coolant that flows in the coolant cycling pipe  344 . The output of the second temperature sensor  372  is provided to the control part  360 . The control part  360  controls the operation of the cycling unit  346  to control an amount of coolant in accordance with the temperature of the coolant measured by the second temperature sensor  372 .  
      Alternatively, the second temperature sensor  372  may be mounted adjacent to the inner surface  304   a  of the view port extender  302 , in order to directly measure the temperature of the inner surface  304   a  of the view port extender  302 .  
      The temperature of the inner surface  304   a  of the view port extender  302  is maintained at the second temperature, which is lower than the first temperature of the window  310 . Thus, the reaction residue products from the plasma are deposited on the inner surface  304   a  of the view port extender  302 , rather than the window  310  or elsewhere in the optical path between the processing chamber and the spectrometer.  
       FIG. 5  illustrates an enlarged cross-sectional view of an endpoint detector according to a fourth embodiment of the present invention.  
      Referring to  FIG. 5 , an endpoint detector  400  is combined with the semiconductor manufacturing device. For example, the semiconductor manufacturing device includes a processing chamber for performing a plasma etching, a chuck for supporting a semiconductor substrate such as a silicon wafer, an upper electrode for generating plasma in the processing chamber, as set forth above in connection with  FIG. 1 .  
      The endpoint detector  400  includes a view port extender  402  for extending the view port  58  in the second sidewall  52  of the process chamber, a window  410 , an analyzing unit  420 , a first temperature control unit  430 , and a second temperature control unit  440 .  
      The view port extender  402  for extending the view port  58  formed in the second sidewall of the processing chamber may have a cylindrical shape, and connects the view port  58  to the window  410 . The view port extender  402  has a hole  404 , and an axis of the hole is identical to an axis of the view port  58 .  
      The view port extender  402  includes a first lateral part  402   a,  a second lateral part  402   b,  a first flange  406  and a second flange  408 .  
      The first lateral part  402   a  is inserted into the view port  58 . The first flange  406  is disposed on the adjacent portion of the first lateral part  402   a  and contacts the outer surface  64  of the second sidewall  52  of the process chamber. The second lateral part  402   b  extends from the first flange  406  to the second flange  408 , which, in turn, contacts the window  410 .  
      The window  410  for transmitting the light generated from the plasma may have a disc shape and be made of a transparent material such as quartz. The window  410  is disposed on the second flange  408  to cover the hole  404  of the view port extender  402 .  
      The window  410  has a first surface  412  and a second surface  414 , opposite the first surface  412 . The first surface  412  contacts the second flange  408  of the view port extender  402 .  
      The temperature control unit  430  controls the temperature of the window  410  to reach a first temperature. The temperature control unit  430  may have a ring shape and the may include a ceramic heater  432  disposed on the second surface  414  of the window  410 . The ceramic heater  432  is electrically connected to a control part  460 , and the control part  460  is electrically connected to a first temperature sensor  462  for measuring the temperature of the window  410 .  
      A plurality of the first fixing members  438   a  secures the view port extender  402  to the second sidewall  52  of the processing chamber through the first flange  406 . A plurality of the second fixing members  438   b  secures the window  410  and the ceramic heater  432  to the view port extender  402  through the second flange  408 , the window holder  434  and an adapter  436 .  
      The temperature control part  440  includes a plurality of cooling pins  442  formed on the outer surface of the view port extender  402 . The cooling pins  442  are formed between the first flange  406  and the second flange  408 , and may have a ring shape. In this embodiment, each of the cooling pins may have a cylinder shape, a hemisphere shape, or a bar shape that extends perpendicular to the view port extender  402 .  
      The control part  460  controls the operation of the ceramic heater  432  in accordance with a temperature of the window  410  that is measured to the first temperature sensor  462 .  
      The endpoint detector  400  may include a second temperature sensor  472  for measuring the temperature of the inner surface  404   a  of the view port extender  402 .  
      The control part  460  compares the temperature of the window  410  with the temperature of the inner surface  404   a  of the view port extender  404  to maintain the window  410  at a higher temperature than the inner surface  404   a  of the view port extender  404 .  
      The endpoint detector may include a fan unit for supplying cooling air to the surfaces of the cooling pins  442 .  
      The analyzing unit  420  analyzes the light transmitted through the window  410  in order to detect the endpoint of the etching process processed in the processing chamber.  
      The analyzing unit  420  includes an optical probe  422 , an optical cable  424  and an optical emission spectrometer  426 . The optical probe  422  is connected to a central portion of the second surface  414  of the window  410 . The optical cable  424  extends from the optical probe  422  to the optical emission spectrometer  426 .  
      The light emitted from the plasma is successively transmitted from the processing chamber to the optical emission spectrometer  426  via the view port  58  of the processing chamber, the hole  404  of the view port extender  402 , the window  410 , the optical probe  422  and the optical cable  424 .  
      The optical emission spectrometer  426  analyzes the light generated from the processing chamber so that the endpoint of the etching process is detected.  
      Thus, in accordance with the present invention, by maintaining a window at a first temperature and an inner surface of a passage between a processing chamber and the window at a second temperature, any resultant reaction residue is deposited on the inner surface, rather than the window, thus being removed from the transmission path to the analyzing unit.  
      Exemplary embodiments of the present invention have been disclosed herein and, although specific terms are employed, they are used and are to be interpreted in a generic and descriptive sense only and not for purpose of limitation. Accordingly, it will be understood by those of ordinary skill in the art that various changes in form and details may be made without departing from the spirit and scope of the present invention as set forth in the following claims.