Patent Publication Number: US-7595885-B2

Title: Process monitoring system, process monitoring method, and method for manufacturing semiconductor device

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
   This is a division of U.S. patent application Ser. No. 11/882,275, filed Jul. 31, 2007, now U.S. Pat. No. 7,349,088 which is a continuation of U.S. patent application Ser. No. 10/969,860, filed on Oct. 22, 2004 now U.S. Pat. No. 7,327,455 which are incorporated herein by reference. 

   This application is based upon and claims the benefit of priority from prior Japanese Patent Application P2003-362134 filed on Oct. 22, 2003; the entire contents of which are incorporated by reference herein. 
   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to measurement techniques and in particular to a process monitoring system, a process monitoring method, and a method for manufacturing a semiconductor device. 
   2. Description of the Related Art 
   In semiconductor manufacturing process, a depth of an etched groove and a thickness of a deposited membrane are controlled by monitoring an etching time and a deposition time. However, such monitoring method cannot operate precisely when a process environment, such as temperature and pressure, is changed unexpectedly. The imprecise monitoring decreases the yield rate of the manufactured semiconductor devices. Therefore, process monitoring systems measuring the actual depth of the etched groove or the actual thickness of the deposited membrane has been recently introduced. 
   In Japanese Patent Laid-Open Publication No. 2002-93870, a process monitoring system is disclosed, in which an inspection light is irradiated on an object to be processed. The object is held in a process chamber. The light is irradiated through a monitor window provided in the process monitor. The disclosed system estimates the actual depth of the etched groove or the actual thickness of the deposited membrane on the object to be processed by detecting the reflected inspection light. 
   However, if the monitor window is composed of birefringent material and the inspection light is polarized, the monitor window interacts with the inspection light and modulates the phase of the light. Such phenomenon causes interference noises in a spectrum of the inspection light. Therefore, it is difficult to achieve a precise monitoring. 
   Also, an upper electrode is provided in the process chamber of plasma process. A plurality of nozzle holes is formed in the upper electrode in order to supply an interior of the process chamber with a reaction gas. However, if the monitor window is provided on the upper electrode, the monitor window disturbs a stable supply of the reaction-gas since the monitor window does not include the nozzle holes. Therefore, the reaction gas concentration beneath the monitor window becomes less than in other space. Consequently, the evenness of an etching rate or deposition rate in the process chamber is decreased. 
   SUMMARY OF THE INVENTION 
   An aspect of present invention inheres in a process monitoring system according to an embodiment of the present invention. The system includes a process chamber configured to hold an object to be processed, an illumination source configured to emit a light to the object, a polarizer configured to polarize the light, a monitor window having a birefringent material and provided on the process chamber to propagate the light, direction adjusting equipment configured to adjust a relationship between a polarization plane of the light and a direction of an optic axis of the monitor window, and a monitoring information processor configured to detect the light reflected from the object. 
   Another aspect of the present invention inheres in a process monitoring system according to the embodiment of the present invention. The system includes a process chamber configured to hold an object to be processed, an illumination source configured to emit a light to the object, a monitor window provided on the process chamber to propagate the light, the monitor window having a plurality of nozzle holes, the diameter of the nozzle holes being smaller than a beam diameter of the light in the monitor window, and a monitoring information processor configured to detect the light reflected from the object. 
   Yet another aspect of the present invention inheres in a process monitoring method according to the embodiment of the present invention. The method includes inserting an object to be processed into a process chamber, the process chamber having a monitor window containing a birefringent material, irradiating a light to the object through the monitor window, polarizing the light, adjusting a relationship between a polarization plane of the light and a direction of an optic axis of the monitor window, and detecting the light reflected from the object. 
   Yet another aspect of the present invention inheres in a process monitoring method according to the embodiment of the present invention. The method includes inserting an object to be processed into a process chamber, the process chamber having a monitor window, irradiating a light to the object through the monitor window, focusing the light so that a beam diameter of the light in the monitor window is larger than each diameter of a plurality of nozzles hole formed in the monitor window, and detecting the light reflected from the object. 
   Yet another aspect of the present invention inheres in a method for manufacturing a semiconductor device according to the embodiment of the present invention. The manufacturing method includes forming an insulating film above a semiconductor substrate, arranging an etching mask on the insulating film, inserting the semiconductor substrate into a process chamber, the process chamber having a monitor window containing a birefringent material, irradiating a polarized light to a surface of the semiconductor substrate through the monitor window, adjusting a relationship between a polarization plane of the light and a direction of an optic axis of the monitor window, etching the insulating film in the process chamber, monitoring an end point of the etching by detecting the light reflected from the semiconductor substrate having the insulating film thereabove, and stopping the etching. 
   Yet another aspect of the present invention inheres in a method for manufacturing a semiconductor device according to the embodiment of the present invention. The manufacturing method includes forming an insulating film above a semiconductor substrate, arranging an etching mask on the insulating film, inserting the semiconductor substrate into a process chamber, the process chamber having a monitor window, focusing a light so that a beam diameter of the light in the monitor window is larger than each diameter of a plurality of nozzle holes formed in the monitor window, supplying a reaction gas into the process chamber through the nozzle holes, etching the insulating film in the process chamber, monitoring an end point of the etching by detecting the light reflected from the semiconductor substrate having the insulating film thereabove, and stopping the etching. 

   
     BRIEF DESCRIPTION OF DRAWINGS 
       FIG. 1  is a diagram of a process monitoring system of plasma process in accordance with a first embodiment of the present invention; 
       FIG. 2  is a sectional view of a measuring object in accordance with the first embodiment of the present invention; 
       FIG. 3  is a plan view of the measuring object in accordance with the first embodiment of the present invention; 
       FIG. 4  is a first exploded perspective view of a polarizer and a monitor window in an optical system in accordance with the first embodiment of the present invention; 
       FIG. 5  is a second exploded perspective view of the polarizer and the monitor window in the optical system in accordance with the first embodiment of the present invention; 
       FIG. 6  is a third exploded perspective view of the polarizer and the monitor window in the optical system in accordance with the first embodiment of the present invention; 
       FIG. 7  is a sample graph of a spectrum of an inspection light in accordance with the first embodiment of the present invention; 
       FIG. 8  is a fourth exploded perspective view of the polarizer and the monitor window in the optical system in accordance with the first embodiment of the present invention; 
       FIG. 9  is a flowchart depicting a process monitoring method in accordance with the first embodiment of the present invention; 
       FIG. 10  is a flowchart depicting a method for manufacturing a semiconductor device in accordance with the first embodiment of the present invention; 
       FIG. 11  is a first sectional view of the semiconductor device depicting the manufacturing process in accordance with the first embodiment of the present invention; 
       FIG. 12  is a second sectional view of the semiconductor device depicting the manufacturing process in accordance with the first embodiment of the present invention; 
       FIG. 13  is a plan view of the semiconductor device depicting the manufacturing process in accordance with the first embodiment of the present invention; 
       FIG. 14  is a third sectional view of the semiconductor device depicting the manufacturing process in accordance with the first embodiment of the present invention; 
       FIG. 15  is a diagram of a dry process apparatus in accordance with a second embodiment of the present invention; 
       FIG. 16  is an exploded perspective view of a monitor window in accordance with the second embodiment of the present invention; 
       FIG. 17  is a flowchart depicting a process monitoring method in accordance with the second embodiment of the present invention; and 
       FIG. 18  is a flowchart depicting a method for manufacturing a semiconductor device in accordance with the second embodiment of the present invention. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   Various embodiments of the present invention will be described with reference to the accompanying drawings. It is to be noted that the same or similar reference numerals are applied to the same or similar parts and elements throughout the drawings, and the description of the same or similar parts and elements will be omitted or simplified. 
   First Embodiment 
   With reference to  FIG. 1 , a process monitoring system  10  of plasma process according to a first embodiment of the present invention has a process chamber  50  of plasma process configured to hold an object  16  to be processed, an illumination source  12  configured to emit an inspection light hγ i  to the object  16 , a polarizer  60  configured to polarize the inspection light hγ i , a monitor window  54  containing a birefringent material and provided on the process chamber  50  of the plasma process to propagate the inspection light hγ i , direction adjusting equipment  7  configured to adjust a relationship between a polarization plane “P” of the inspection light hγ i  and a direction of an optic axis “A” of the monitor window  54 , and a monitoring information processor  28  configured to detect reflected inspection light hγ i  reflected from the object  16 , which is to be processed. 
   The inspection light hγ i  emitted from the illumination source  12  is propagated through an optical fiber  20   a . Spatial noise of the inspection light hγ i  is eliminated by a spatial filter  62 . The inspection light hγ i  propagates through a beam splitter  18  and is condensed by a lens  14 . 
   The oscillation of the linearly polarized inspection light hγ i  is confined to a polarization direction “E” perpendicular to the propagation direction by the polarizer  60 . A rotator  5  is configured to rotate the polarizer  60  to define the polarization direction “E” of the oscillation. 
   The monitor window  54  is provided in an upper portion of the process chamber  50  of the plasma process. A direction adjuster  6  is attached to the monitor window  54 . The direction adjuster  6  is configured to adjust the optic axis “A” direction of the monitor window  54 . The details of the optic axis “A” will be described below. A z-axis goniometer and a rotation stage may be used for the direction adjuster  6 . The direction adjuster  6  and the rotator  5  implement a direction adjusting equipment  7 . 
   A substrate holder  15  is disposed in the process chamber  50  of the plasma process. The substrate holder  15  is configured to hold the object  16 . The inspection light hγ i  is focused on the surface of the object  16  through the monitor window  54 . A turntable that can rotate the object  16  is available as the substrate holder  15 . Therefore, it is possible to adjust the relationship between the polarization direction “E” of the oscillation of the inspection light hγ i  and an orientation of the disposed object  16  with the direction adjusting equipment  7  and the substrate holder  15 . 
   A reflected light hγ r  from the surface of the object  16  to be processed is transmitted to the monitoring information processor  28  through the monitor window  54 , the polarizer  60 , the lens  14 , the beam splitter  18 , and an optical fiber  20   b.    
   The monitoring information processor  28  analyzes a reflection light hγ r  of the inspection light hγ i . The monitoring information processor  28  has a spectroscope  22 , a detector  24 , and a calculator  26 . The spectroscope  22  observes a spectrum of the reflected light hγ r . The detector  24  detects the light intensity of the reflected light hγ r  at each wavelength. The calculator  26  calculates information on the thickness direction of the object  16  from the light intensity. Information about the thickness of a thin film and the depth of an etched groove is an example of the “information on the thickness direction of the object  16 ”. 
   An example of the object  16  is shown in  FIG. 2 . The object  16 , to be processed, has a semiconductor substrate  80 , a first insulating film  81  disposed on the semiconductor substrate  80 , a first circuit layer  82  disposed on the first insulating film  81 , second insulating film  83  disposed on the first circuit layer  82 , and a plurality of resist masks  85   a ,  85   b ,  85   c ,  85   d ,  85   e ,  85   f  disposed on the second insulating film  83 . The plurality of resist masks  85   a - 85   f  are arranged in parallel with a direction “D 1 ” as shown in  FIG. 3 . In the first circuit layer  82 , a plurality of wires  82   a ,  82   b ,  82   c ,  82   d ,  82   e  are arranged in parallel with a direction “D 2 ”. The direction “D 2 ” is perpendicular to the direction “D 1 ”. 
   With reference again to  FIG. 1 , the rotator  5  and the polarizer  60  confines the polarization direction “E” of the oscillation of the inspection light hγ i  to the direction “D 2 ” shown in  FIG. 3 . In this case, the inspection light hγ i  cannot penetrate the first circuit layer  82  and is reflected from the first circuit layer  82 . Therefore, it is possible to eliminate the influence on the inspection light hγ i  caused by layers beneath the first circuit layer  82 . 
   With reference next to  FIG. 4  and  FIG. 5 , the optical relationship between the polarizer  60  and the monitor window  54  is depicted. The monitor window  54  is composed of a birefringent crystal such as sapphire, quarts, and calcite. In the birefringent crystal, there is one direction such that any light, regardless of the state of polarization of the light, has the same speed in that direction. Such direction is called the “optic axis”. The direction adjuster  6  shown in  FIG. 1  adjusts relative relationship between a polarization plane “P” of the inspection light hγ i  and the direction of the optic axis “A”. In  FIG. 4 , the monitor window  54  is oriented so that the optic axis “A” is substantially parallel with the polarization plane “P”. In  FIG. 5 , a perpendicular plane “x” is substantially parallel to the propagation of the inspection light hγ i  and is perpendicular to the polarization plane “P”. Here, the monitor window  54  is oriented so that the optic axis “A” is substantially parallel with the perpendicular plane “X”. 
   With reference next to  FIG. 6 , the monitor window  54  is oriented so that the optic axis “A” is substantially parallel with a plane “B” crossing the polarization plane “P” at an angle of 45 degree. 
     FIG. 7  shows an example spectrum detected by the detector  24  shown in  FIG. 1 . As shown in  FIG. 7 , sawtooth pulses appear in the spectrum when the monitor window  54  is oriented so that the optic axis “A” is substantially parallel with the plane “B” crossing the polarization plane “P” at an angle of 45 degree as shown in  FIG. 6 . This is because the monitor window  54  composed of birefringent crystal interacts with the inspection light hγ i  and modulates the phase of the light. 
   On the other hand, the sawtooth pulses disappear when the monitor window  54  is oriented so that the optic axis “A” is substantially parallel with the polarization plane “P” (0 degree) as shown in  FIG. 4  or the optic axis “A” is substantially parallel with the polarization plane “P” (90 degree) as shown in  FIG. 5 . 
   It should be noted that it is permissible for the direction of the optic axis “A” shown in  FIG. 4  to be slightly different from the parallel direction of the polarization direction “E”. Also, it is permissible for the direction of the optic axis “A” shown in  FIG. 5  to be slightly different from the parallel direction of the perpendicular plane “X”. If the differences are less than ±1 degree, the sawtooth pulses are effectively eliminated. 
   It is also possible to eliminate the sawtooth pulses with the monitor window  54  having the optic axis “A” substantially parallel with the propagation of the inspection light hγ i  as shown in  FIG. 8 . The slight difference, such as ±1 degree, between the direction of the optic axis “A” and the propagation of the ins light hγ i  is permissible. In this case, the rotator  5  in the direction adjusting equipment  7  configured to adjust the orientation of the polarizer  60  may be solely controlled. 
   By adjusting the direction of the optic axis “A” in the monitor window  54  as shown in FIGS.  4 , 5  and  8 , the process monitoring system  10  makes it possible to eliminate the sawtooth pulses from the inspection light hγ i  spectrum. In an earlier process monitoring system, the optical relationship between the polarizer and the monitor window composed of birefringent crystal was not important. Therefore, the sawtooth pulses appeared in the spectrum affected precise measurement. However, the process monitoring system  10  makes it possible to obtain precise information on the thickness direction of the object  16 . Therefore, the process monitoring system  10  makes it possible to monitor the manufacturing process of fine and precise semiconductor devices. 
   With reference next to  FIG. 9 , a process monitoring method according to the first embodiment of the present invention is described. 
   In step S 10 , the object  16  such as the semiconductor substrate  80  covered with the second insulating film  83  and the resist masks  85   a - 85   f  shown in  FIGS. 2 and 3  is disposed on the substrate holder  15  in the process chamber  50  of the plasma process. 
   In step S 102 , the illumination source  12  emits the inspection light hγ i . The inspection light hγ i  is propagated through the spatial filter  62 , beam splitter  18 , lens  14 , polarizer  60 , and the monitor window  54 . Consequently, the object  16  is exposed to the inspection light hγ i . 
   In step S 103 , the polarizer  60  shown in  FIG. 1  is rotated by the rotator  5  so that the polarization direction “E” of the inspection light hγ i  and the direction “D 2 ” shown in  FIG. 3  are equivalent. Rotating the polarizer  60  by hand is an alternative. 
   In step S 104 , the direction adjuster  6  adjusts the orientation of the monitor window  54  in order to optimize the relationship between the polarization direction “E” of the linearly polarized inspection light hγ i  and the optic axis “A” of the monitor window  5  as shown in  FIGS. 4 and 5 . 
   In step S 105 , the monitoring information processor  28  detects the reflected light hγ r  propagated through the monitor window  54 , the polarizer  60 , the lens  14 , the beam splitter  18 , and the light fiber  20   b . Thereafter, the monitoring information processor  28  analyzes the reflected light hγ r  and calculates the thickness direction of the second insulating film  83  shown in  FIGS. 2  and  3 , based on the information received via the reflected light hγ r . 
   Process monitoring methods of earlier technology generate the noises as the sawtooth pulses in the light spectrum. Such noise caused by the birefringence prevent precise measuring of the information on the thickness direction. However, the process monitoring method according to the first embodiment makes it possible to calculate accurate information on the thickness direction since the relationship between the polarization direction “E” and the optic axis A is optimized in step S 104  in order to eliminate such noise. 
   With reference next to  FIG. 10 , a method for manufacturing the semiconductor device according to the first embodiment of the present invention is described. 
   With reference to  FIG. 11 , boron is implanted into a semiconductor substrate  1  such as an n-type Si wafer in step S 201 . The semiconductor substrate  1  is then heated to diffuse the implanted boron and a p-well  302  is formed. The semiconductor substrate  1  is selectively etched and trenches  303 ,  403  are delineated. Thereafter, an isolation insulator  304  is deposited into the trenches  303 ,  403  by chemical vapor deposition (CVD). The semiconductor substrate  1  is oxidized to form a gate oxide film  305 . A poly silicon gate  307  is deposited on the gate oxide film  305  by the CVD method and etching is performed. Then, self-aligned source/drain regions  310 ,  311  are formed by phosphorous ion implantation and annealing. Subsequently, an insulating film  400  is deposited by the CVD method. 
   In step S 202 , etch masks  900 ,  901 ,  902  shown in  FIGS. 12 and 13  are arranged on the insulating film  400  by lithography. In step S 203 , the semiconductor substrate  1  is inserted into the process chamber  50  of the plasma process shown in  FIG. 1 . 
   In step S 204 , the insulating film  400  is exposed to the polarized inspection light hγ i . In step S 205 , the orientation of the monitor window  54  is adjusted by the direction adjuster  6  in order to optimize the relationship between the polarization direction “E” of the linearly polarized inspection light hγ i  and the optic axis “A” of the monitor window  5  as shown in  FIGS. 4 and 5 . 
   In step S 206 , a reaction gas is introduced into the process chamber  50  of the plasma process after the pressure in the process chamber  50  of the plasma process is reduced. With AC power in the radio frequency (RF) range, a plasma glow discharge is generated to excite a reaction near the exposed surface of the insulating film  400 . Consequently, the exposed portions of the insulating film  400  are selectively etched so as to form damascene grooves  800 ,  801 . 
   In step S 207 , the reflected light hγ r  is propagated through the monitor window  54 , beam splitter  18 , and the light fiber  20   b . The reflected light hγ r  is detected by the monitoring information processor  28 . When the monitoring information processor  28  detects the end point of damascene grooves  800 ,  801  shown in  FIG. 14 , the dry etch process is stopped. 
   In step S 208 , the semiconductor substrate  1  is removed from the process chamber  50  of the plasma process. Thereafter, via holes are provided in the insulating film  400  at the bottom of the damascene grooves  800 ,  801  and on the source/drain regions  310 ,  311  by a dry etching process. Then, the damascene grooves  800 ,  801  and the via holes are filled with copper, for example, by electroplating. After a chemical mechanical planarization process so as to implement damascus interconnections in the damascene grooves  800 ,  801 , a circuit layer is formed. Thereafter, the insulating film formation and the circuit layer formation are repeated until the manufacturing of the semiconductor device is completed. 
   In earlier methods for manufacturing the semiconductor devices, noise appear in the spectrum of the inspection light. Such noise disturbs the accurate monitoring of the etch process and the deposition process. Therefore, problems such as short circuits may occur in the semiconductor devices. 
   However, in the method for manufacturing the semiconductor device according to the first embodiment, the relationship between the optic axis “A” and the polarization direction “E” is optimized as shown in  FIGS. 4 ,  5 , and  8 . Therefore, such noise is eliminated in the spectrum, which allows the etch process and the deposition process to be monitored accurately. Further, it becomes possible to increase a yield rate in the manufacturing process for the semiconductor devise. 
   Second Embodiment 
   With reference to  FIG. 15 , a dry process apparatus  30  has a process chamber  40  having a bottom portion  31 , a lateral portion  32  disposed on the edge of the bottom portion  31 , and a cap portion  33  disposed on the lateral portion  32 . 
   Further, an upper electrode  45  for plasma process is disposed below the cap portion  33 . The edge of the upper electrode  45  for the plasma process is attached to the lateral portion  32 . A space surrounded by the bottom portion  31 , the lateral portion  32 , and the upper electrode  45  for the plasma process serves as a reaction space  66  of plasma process. A vacuum pump  36  is attached to the lateral portion  32  of the process chamber  40 . A substrate holder  15  is disposed on the bottom portion  31 . The substrate holder  15  serves as a lower electrode. A temperature controller  35  is embedded in the substrate holder  15 . An object  16  to be processed is disposed on the substrate holder  15 . 
   The space surrounded by the cap portion  33 , the upper electrode  45  for the plasma process, and the lateral portion  32  comprises a gas head  65 . A ceiling window  55  is provided in the cap portion  33 . In a case where the ceiling window  55  is composed of the birefringent material, equipment similar to the direction adjuster  6  shown in  FIG. 1  may be attached to the ceiling window  55 . 
   Beneath the ceiling window  55 , a monitor window  56  is provided in the upper electrode  45  for the plasma process. A gas supplier  37  is attached to the gas head  65  through an inlet port  47 . The gas supplier  37  supplies the gas head  65  with a reaction gas. A plurality of gas holes  71   a ,  71   b ,  71   c ,  71   d  is formed in the upper electrode  45  for the plasma process. Further, a plurality of nozzle holes  70   a ,  70   b ,  70   c ,  70   d ,  70   e ,  70   f ,  70   g ,  70   h ,  70   i ,  70   j ,  70   k ,  70   l ,  70   m ,  70   n ,  70   o ,  70   p ,  70   q ,  70   r ,  70   s ,  70   t ,  70   u ,  70   v ,  70   w ,  70   x ,  70   y  is formed in the monitor window  56  as shown  FIGS. 15 and 16 . The reaction gas is supplied to the reaction space  66  of the plasma process shown in  FIG. 15  from the gas head  65  via the gas holes  71   a - 71   d  and the nozzle holes  70   a - 70   y.    
   The substrate holder  15  serving as the lower electrode is attached to an impedance matching device  42  for RF power. A variable capacitor may constitute the impedance matching device  42  of the RF power. The impedance matching device  42  is attached to a RF power supply  43 . The impedance matching device  42  is used for matching electrical impedances between the RF power supply  43  and the substrate holder  15 . On the other hand, the upper electrode  45  for the plasma process is grounded. 
   Disposed above the dry process apparatus  30  are the illumination source  12  and the lens  14 , shown in  FIG. 1 . The monitoring information processor  28  detects the reflected light of the inspection light hγ i  from the object  16 . 
   With reference again to  FIG. 15 , each diameter “a” of the nozzle holes  70   a - 70   y  formed in the monitor window  65  is smaller than a laser diameter. “d” of the inspection light hγ i  at the monitor window  65 . For example, the laser diameter “d” is 6-7 mm, and each diameter “a” of the nozzle holes  70   a - 70   y  is 1 mm. Since the inspection light hγ i  is not focused at each of the nozzle holes  70   a - 70   y , the inspection light hγ i  is not scattered by the nozzle holes  70   a - 70   y . Therefore, the nozzle holes  70   a - 70   y  do not affect spectrum obtained by the monitoring information processor  28  shown in  FIG. 1 . 
   Such nozzle holes are not formed in a monitor window of the process monitoring system in earlier technology. Therefore, the reaction gas concentration beneath the monitor window becomes lower than in other space. Consequently, the etching rate beneath the monitor window is decelerated and the uniformity of the surface of the substrate is decreased. On the other hand, since the nozzle holes  70   a - 70   y  are formed in the monitor window  56  as shown in  FIG. 16 , the reaction gas concentration beneath the monitor window  56  remains the same as other regions. Therefore, both etching rate beneath the monitor window  56  and of other area on the surface of the object  16  are equivalent, since the nozzle holes  70   a - 70   y  formed in the monitor window  56  is opposed to the object  16 . Consequently, the evenness of the etching rate on the object  16  is increased and the precision of the end point monitoring is also increased. 
   An amorphous material such as glass may be used for the monitor window  56  according to the second embodiment of the present invention. Also, birefringent crystals such as sapphire, quarts, and calcite are available for the monitor window  56 . 
   With reference next to  FIG. 17 , a process monitoring method according to the second embodiment of the present invention is described. 
   In step S 301 , the object  16  to be processed is disposed on the substrate holder  15  of the dry process apparatus  30  as shown in  FIG. 15 . In this case, the object  16  is opposed to the nozzle holes  70   a - 70   y  formed in the monitor window  56 . 
   In step S 302 , the inspection light hγ i  is emitted to the object  16  from the illumination source  12 . In step S 303 , the focus of the inspection light hγ i  is adjusted by the lens  14  so that the beam diameter “d” at the monitor window  56  becomes larger than the nozzle hole diameter “a” shown in  FIGS. 15 and 16 . 
   In step S 304 , the detector  24  of the monitoring information processor  28  detects the reflected light hγ r  spectrum from the object  16 . Based on the spectrum, the calculator  26  determines information on the thickness direction of the object  16   
   With reference next to  FIG. 18 , a method for manufacturing a semiconductor device according to the second embodiment of the present invention is described. 
   Steps S 401  and S 402  are similar to the steps S 201  and S 202  shown in  FIG. 10 . In step S 403 , the semiconductor substrate  1  shown in  FIG. 12  is disposed on the substrate holder  15  in the process chamber  40  shown in  FIG. 15 . In this case, the semiconductor substrate  1  is opposed to the nozzle holes  70   a - 70   y  formed in the monitor window  56 . 
   In step S 404 , the inspection light hγ i  propagates through the monitor window  56  and the insulating film  400  shown in  FIG. 12  is exposed to the polarized inspection light hγ i . Thereafter, the focus of the inspection light hγ i  is adjusted by the lens  14  so that the beam diameter “d” at the monitor window  56  becomes larger than the nozzle hole diameter “a” shown in  FIGS. 15 and 16 . 
   In step S 405 , the pressure of the process chamber  40  is reduced with the vacuum pump  36 . Thereafter, the reaction gas is supplied to the interior of the process chamber  40  through the nozzle holes  70   a - 70   y  of the monitor window  56  and the gas holes  71   a - 71   d  of the upper electrode  45  for the plasma process. 
   In step S 406 , the RF power is applied to the substrate holder  15 . Consequently, a plasma glow discharge is generated and the insulating film  400  exposed from the etchmasks  900 - 902  shown in  FIGS. 12 and 13  is selectively etched by the gas reaction. 
   In step S 407 , the reflected light hγ r  from the surface of the insulating film  400  is detected by the monitoring information processor  28  shown in  FIG. 1 . When the monitoring information processor  28  detects the end point of damascene grooves  800 ,  801  shown in  FIG. 14 , the dry etch process is stopped. 
   In step S 408 , the semiconductor substrate  1  is removed from the process chamber  50  of the plasma process. Thereafter, via holes are provided in the insulating film  400  at the bottom of the damascene grooves  800 ,  801  and on the source/drain regions  310 ,  311  by the dry etching process. Then, the damascene grooves  800 ,  801  and the via holes are filled with copper, for example, by electroplating. After a chemical mechanical planarization process so as to implement damascus interconnections in the damascene grooves  800 ,  801 , a circuit layer is formed. Thereafter, the insulating film formation and the circuit layer formation are repeated until the manufacturing of the semiconductor device is completed. 
   According to the process monitoring method shown in  FIG. 17  and the method for manufacturing the semiconductor device shown in  FIG. 18 , the inspection light hγ i  is not scattered by the nozzle holes  70   a - 70   e  shown in  FIG. 15  and it is possible to supply sufficient reaction gas even under the monitor window  56 . Therefore, it is possible to maintain the uniformity of the gas reaction on the substrate surface in the dry process apparatus  30 . 
   Other Embodiments 
   Although the invention has been described above by reference to the embodiment of the present invention, the present invention is not limited to the embodiment described above. Modifications and variations of the embodiment described above will occur to those skilled in the art, in the light of the above teachings. 
   For example, the method for manufacturing the semiconductor according to the embodiment is applied to manufacturing transistors as in above description. Furthermore, it is possible to apply the method according to the embodiment to manufacturing other active components such as diodes. 
   In  FIG. 15 , the substrate holder  15  serving as the lower electrode holds the object  16 . However, it is also possible to apply the process monitoring method according to the embodiment to downstream plasma etching systems. Further, it is possible to apply the process monitoring method according to the embodiment to chemical etching systems using barrel reactors. Also, it is possible to apply dry processes other than the plasma process such as a gas etching, a photo-excited etching, a high temperature CVD, and a photo-excited CVD. Furthermore, it is possible to apply the process monitoring method according to the embodiment to various apparatuses requiring information on a thickness direction of a film, such as chemical mechanical planarization systems. 
   As described above, the present invention includes many variations of embodiments. Therefore, the scope of the invention is defined with reference to the following claims.