Abstract:
In an inspection apparatus, inspection is carried out by linearly moving a wafer while rotating the wafer with respect to light. In a case where the wafer is rotated, the velocity of flow of air in outer regions of the wafer is increased, and there is a possibility that the flow of the air in the outer regions cause particles contained in an atmosphere in the vicinity of the wafer to be adhered to the wafer. In a case where such particles are adhered to the wafer, the particles are also detected as a defect, and therefore yields and cleanliness in a semiconductor production process cannot be correctly evaluated. Therefore, it is desirable that adhesion of the particles contained in the atmosphere in the vicinity of the wafer to the wafer be reduced as much as possible. Further, it is expected that, when, for example, rotation speed of the wafer is increased or a diameter of the wafer is increased, such particles are adhered further remarkably. This point has not been satisfactorily considered in the conventional arts. The invention has a feature that a conductor such as a draft to outer regions is supplied from above a substrate while the substrate is being rotated and the supplied conductor is exhausted on outside of the substrate.

Description:
TECHNICAL FIELD 
     The present invention relates to an inspection apparatus, a cleaning technique of a substrate, and a draft control technique. In particular, the invention relates to an inspection apparatus for inspecting a defect on a substrate such as a semiconductor wafer, a cleaning technique, and a draft control technique. 
     BACKGROUND ART 
     In a semiconductor production process, particles and defects such as scratches on a surface of a semiconductor substrate (wafer) cause failure such as insufficient insulation, short, and the like of wiring formed on the wafer and also cause insufficient insulation of a capacitor and breakage of a gate oxide film and the like. Therefore, in the semiconductor production process, it is important to detect a defect on a surface of a wafer and feedback the defect to the semiconductor production process. 
     A so-called inspection apparatus detects such a defect. As an example of the inspection apparatus, there is an optical inspection apparatus that detects a defect on a substrate by irradiating a substrate with light and detecting scattered light thereof. The optical inspection apparatus is broadly classified into two types, i.e., a surface inspection apparatus for inspecting a mirror wafer and a patterned wafer inspection apparatus for inspecting a wafer on which a circuit pattern is formed. 
     In particular, in a case of the mirror wafer inspection apparatus, it is known that inspection is carried out by linearly moving a wafer while rotating the wafer with respect to light. The following PTLs 1-8 are cited as conventional arts regarding an inspection apparatus and draft control. 
     CITATION LIST 
     Patent Literatures 
     
         
         PTL 1: JP-A-2005-327906 
         PTL 2: JP-T-2004-531879 
         PTL 3: JP-T-2004-527112 
         PTL 4: JP-T-2003-518735 
         PTL 5: JP-A-2009-142750 
         PTL 6: JP-A-2005-309999 
         PTL 7: JP-T-2004-528087 
         PTL 8: JP-A-2010-236948 
       
    
     SUMMARY OF INVENTION 
     Technical Problem 
     As described above, in a mirror wafer inspection apparatus, inspection is carried out by linearly moving a wafer while rotating the wafer with respect to light. In a case where the wafer is rotated, the velocity of flow of air in outer regions of the wafer is increased, and there is a possibility that the flow of the air in the outer regions cause particles contained in an atmosphere in the vicinity of the wafer to be adhered to the wafer. In a case where such particles are adhered to the wafer, the particles are also detected as a defect, and therefore yields and cleanliness in a semiconductor production process cannot be correctly evaluated. Therefore, it is desirable that adhesion of the particles contained in the atmosphere in the vicinity of the wafer to the wafer be reduced as much as possible. Further, it is expected that, when, for example, rotation speed of the wafer is increased or a diameter of the wafer is increased, such particles are adhered further remarkably. This point has not been satisfactorily considered in the conventional arts. 
     Solution to Problem 
     The invention has a feature that a conductor such as a draft to outer regions is supplied from above a substrate while the substrate is being rotated and the supplied conductor is exhausted on outside of the substrate. 
     Advantageous Effects of Invention 
     According to the invention, it is possible to reduce the number of particles adhered to a substrate in comparison with conventional arts. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  illustrates an inspection apparatus of Example 1. 
         FIG. 2  illustrates details of a chamber system  105 . 
         FIG. 3  illustrates a modification example of a chamber system. 
         FIG. 4  illustrates details of a chamber system  105  that does not have an aperture  211 . 
         FIG. 5  illustrates a flow of a draft. 
         FIG. 6  illustrates a cone-shaped chamber  201 . 
         FIGS. 7A and 7B  illustrate details of a draft supply unit  202  and a draft exhaust unit  210 . 
         FIG. 8  is a flow chart showing an inspection operation of Example 1. 
         FIGS. 9A-9C  illustrate Example 2. 
         FIG. 10  illustrates Example 2 (continuation). 
         FIG. 11  illustrates a chamber  201  having an aperture  801  in a side surface thereof. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Hereinafter, examples of the invention will be described with reference to drawings. 
     Example 1 
       FIG. 1  illustrates an inspection apparatus of this example. An illumination optical system  101  irradiates a substrate  103  with illumination light such as a laser beam to form an illuminated region  111  on the substrate  103 . Scattered light  108  generated from the illuminated region  111  is detected by detection optical systems  109  and  110 . Each of the detection optical systems  110  and  109  includes an objective lens, an imaging lens, an optoelectronic device (photomultiplier, one-dimensional CCD, two-dimensional CCD (including TDI), avalanche photodiode, and the like) (the detection optical system  110  similarly includes them). Electrical signals from the detection optical systems  109  and  110  are transmitted to an processing unit  113  via an A/D converter and the like. In the processing unit  113 , the electrical signals from the detection optical systems  109  and  110  are subjected to threshold processing with the use of a threshold. In a case where the electrical signals are equal to or less than the threshold, it is determined that the electrical signals indicate false. In a case where the electrical signals are larger than the threshold, it is determined that the electrical signals indicate defect. Note that, regarding the threshold processing, the electrical signals from the detection optical systems  109  and  110  are added and the added signals are subjected to the threshold processing in some cases or each of the electrical signals is subjected to the threshold processing in some cases. 
     The substrate  103  is mounted on a substrate mounting unit  104 . The substrate  103  is attached to the substrate mounting unit  104  with a back surface attachment method in which a whole back surface of the substrate  103  is attached to the substrate mounting unit  104  in some cases or with a so-called edge grip method in which only an end portion of the substrate  103  is held by the substrate mounting unit  104  instead of attaching the back surface thereof in some cases. The substrate mounting unit  104  is mounted on a spindle  106  for rotating the substrate mounting unit  104 . In a case where the spindle  106  is rotated, the substrate  103  is also rotated. The spindle  106  is mounted on a stage  107  capable of moving in X and Y directions or in an X direction and capable of moving upward and downward in a Z direction. That is, the substrate  103  is rotated by the spindle  106  and is moved by the stage  107  in a direction indicated by an arrow  115 . By this operation, the illuminated region  111  spirally scans relatively on the substrate  103 . By this scanning, a whole surface of the substrate  103  is inspected. Note that a moving distance of the stage and a rotation angle of the spindle are transmitted to the processing unit  113 . Therefore, the processing unit  113  can associate a result of the inspection with coordinates (polar coordinates) on the substrate, the coordinates being obtained on the basis of the moving distance and the rotation angle. The result of the inspection associated with the coordinates on the substrate is displayed on a monitor unit  114  as a map. 
     In this example, the inspection apparatus includes a chamber system  105  covering at least the substrate  103 . Details of the chamber system  105  will be described with reference to  FIG. 2 .  FIG. 2  illustrates the details of the chamber system  105 . The chamber system  105  includes a chamber part for covering at least the substrate  105 , a supply system for supplying a conductor such as gas, and an exhaust system for exhausting the supplied conductor. 
     In  FIG. 2 , the chamber part is indicated as a chamber  201 . The chamber  201  covers at least the substrate  103  and has a substantially circular cylinder shape. An aperture  211  is provided in an upper portion of the chamber  201 . Illumination light  102  from the illumination optical system  101  is supplied to the substrate  103  through the aperture  211 , and the scattered light  108  is detected by the detection optical systems  109  and  110  also through the aperture  211 . Note that, instead of the aperture  211 , an upper surface of the chamber  201  may be made from an optically transparent material. 
     Note that a size of the chamber system  105  is determined on the basis of required cleanliness and a size of the substrate  103  in some cases. Therefore, in a case where a required size of the chamber system  105  is large, as illustrated in  FIG. 3 , the chamber system  105  accommodates the illumination optical system  101  and the detection optical systems  109  and  110  in some cases. Further, the chamber system  105  does not have the aperture  211  in some cases. 
     Note that there is a case where guides are provided in an inner surface of the chamber  201  in order to reduce friction of drafts  205 ,  206 , and  207  (described below). There is also a case where protrusions or the like are provided, i.e., projections and pits are substantially provided in the inner surface of the chamber  201  in order to reduce the friction of the drafts  205 ,  206 , and  207  (described below). As a matter of course, the inner surface of the chamber  201  is substantially flat in some cases. 
     Supply systems will be described below. The supply systems are indicated as, for example, draft supply units  202 ,  203 , and  204  in  FIGS. 2 and 4 . In  FIG. 2 , the draft supply units  202 ,  203 , and  204  are located outside the aperture  211  on the upper surface of the chamber  201 . In  FIG. 4 , because there is no aperture portion on the upper surface, the draft supply units  202 ,  203 , and  204  are located at more preferable positions to perform draft control in comparison with a case of  FIG. 2 . 
     The draft supply units  202 ,  203 , and  204  supply a conductor such as gas into the chamber  201 . As the gas to be supplied, air may be employed, or inert gas such as nitrogen and argon may be employed. The gas supplied from the draft supply units  202 ,  203 , and  204  is indicated as the drafts  205 ,  206 , and  207  in  FIGS. 2 and 4 . 
     More specifically, as illustrated in  FIG. 5 , the drafts  205 ,  206 , and  207  are spirally fallen while forming independent and different laminar flows in an internal space along a side surface of the chamber  201  and are supplied to the outer regions from above the substrate  103 . The outer regions can be expressed in various ways, and, for example, can be expressed as positions closer to the end portion of the substrate  103  than to a center of the substrate  103 . Note that, in this case, paths of the respective drafts  205 ,  206 , and  207  are not overlapped with one another. That is, the drafts do not generate turbulence and are supplied to the substrate  103  while forming different laminar flows. Directions of the drafts  205 ,  206 , and  207  (more specifically, directions of loci at the time of projecting the drafts  205 ,  206 , and  207  onto the substrate  103 ) are the same as a direction in which the substrate  103  is rotated. The drafts  205 ,  206 , and  207  supplied to the outer regions of the substrate  103  are exhausted by draft exhaust units  208 ,  209 , and  210 , respectively, to outside of the chamber  201 . 
     Exhaust systems will be described below. The exhaust systems are indicated as, for example, the draft exhaust units  208 ,  209 , and  210  in  FIGS. 2 and 4 . The draft exhaust units  208 ,  209 , and  210  are located at different positions on a shield plate  212  provided between the substrate  103  and the substrate mounting unit  104 . The drafts  205 ,  206 , and  207  supplied to the outer regions of the substrate  103  are exhausted by the draft exhaust units  208 ,  209 , and  210 , respectively, to the outside of the chamber  201 . 
     Note that there is a case where protrusions or the like are provided, i.e., projections and pits are substantially provided in a surface of the shield plate  212  in order to reduce the friction of the drafts  205 ,  206 , and  207  to be exhausted. As a matter of course, the surface of the shield plate  212  is substantially flat in some cases. 
     Pressure distribution in the chamber  201  will be described below. A relationship between a height direction of the substrate  103  and a pressure in the chamber  201  is indicated as a linear function f 1  in  FIGS. 2 and 4 . That is, by supplying the drafts  205 ,  206 , and  207 , the distribution is such that the pressure in the chamber  201  becomes higher in an upward direction of the chamber  201  and becomes lower in a lower portion of the chamber  201 . Note that, in this case, a minimum value Pmin of the pressure is controlled to be higher than that on the outside of the chamber  201 . By setting the minimum value as described above, it is possible to prevent air from flowing from the outside. The pressure distribution may be a function f 2  whose degree is higher than the linear function, instead of the linear function f 1 . 
     Note that the chamber  201  may have other shapes. As illustrated in  FIG. 6 , an area of a lower surface  301  of the chamber  201  does not need to be the same as an area of the upper surface  302 . That is, the chamber  201  may have a substantially cone shape. In a case where the chamber  201  has the substantially cone shape, the side surface of the chamber is inclined with respect to a normal line  303  of the substrate  103 . In a case where the chamber  201  has the substantially cone shape, it is possible to improve the velocity of flows of the drafts  205 ,  206 , and  207  in a case where the drafts  205 ,  206 , and  207  are supplied to the outer regions of the substrate  103 . Note that the chamber  201  in  FIG. 6  also does not have the aperture  211  in some cases. 
     A relationship between the illumination light  102  and a height H (as another expression, a length between the substrate  103  and the upper portion of the chamber  201 ) of the chamber  201  will be described below. As illustrated in  FIG. 1 , the illumination light  102  is obliquely incident on the substrate  103  at a certain incident angle. At this time, it is desirable in some cases that the incident angle be substantially a Brewster&#39;s angle. Therefore, it is desirable in some cases that the chamber  201  have the height H at which the substrate  103  can be illuminated with the illumination light  102  at the Brewster&#39;s angle. Further, the Brewster&#39;s angle is a function of a reflective index on an incident side and a reflective index on a transmission side. In this example, as described above, as the gas to be supplied, not only air but also inert gas such as nitrogen and argon may be used. The substrate  103  to be inspected is in some cases a so-called mirror wafer or a substrate in which a certain film is formed on the mirror wafer. This means that at least one of the reflective index on the incident side and the reflective index on the transmission side is changed in a process of inspection, i.e., the Brewster&#39;s angle is changed. In view of this, this example may be structured to change the height H of the chamber  201  in accordance with a change of the Brewster&#39;s angle with the use of change means (e.g., combination of a rail and a block) for changing a relative distance between the substrate  103  and the chamber  201 . Further, at least one of a flow rate and the velocity of flow of gas to be supplied may be changed in accordance with a change of the height of the chamber  201 . 
     Details of the draft supply unit  202  and the draft exhaust unit  210  will be described below with reference to  FIG. 7 .  FIG. 7 ( a )  illustrates details of the draft supply unit  202  and the draft exhaust unit  210 , and  FIG. 7( b )  illustrates the draft supply unit  202  and the draft exhaust unit  210  from an A-A′ cross-section of the chamber  201 . When observed from above the substrate  103 , the draft supply units  202 ,  203 , and  204  are located to surround the substrate  103 . The same applies to the draft exhaust unit  210 . Outlet ports of the draft supply units  202 ,  203 , and  204  are directed in a circumference direction of the substrate. The same applies to an exhaust port of the draft exhaust unit  210 . 
     The draft supply unit  202  will be described in more detail. The draft supply unit  202  includes a gas supply unit  401  and a duct  402  that is a supply port. The gas supply portion  401  includes a gas source  4011  for supplying air, nitrogen, argon, or the like, a control portion  4012  for controlling at least one of a flow rate and the velocity of flow of gas, a dehumidification portion  4013  for controlling a dew point of the gas, and a filtering portion  4014  for removing particles from the gas. The gas controlled in terms of at least one of the flow rate and the velocity of the flow, humidity, and cleanliness is supplied, as the draft  205 , to the inner surface of the chamber  201  at a predetermined angle from the gas supply unit  401  through the duct  402 . Note that the duct  402  is inclined with respect to the upper surface of the chamber  201  so as to efficiently supply the gas to the chamber  201 , and a guide  4021  for rectifying the gas is provided in the duct  402 . 
     Note that protrusions  403  or the like or projections and pits are substantially provided in order to reduce the friction of the draft  205  in an inner surface and a side surface of the upper surface of the chamber  201 . 
     Details of the draft exhaust unit  210  will be described below. The draft exhaust unit  210  includes a duct  404  that is an exhaust port and an exhaust source  405  such as a pump. The duct  404  is inclined with respect to the lower surface of the chamber  201  so as to efficiently exhaust the draft  207 . A plurality of protrusions  4041  are provided in the duct  404  in order to reduce the friction of the draft  207 . That is, projections and pits substantially exist in the duct  404 . The draft  207  is exhausted by the exhaust source  405  at a predetermined angle through the duct  404 . Note that a control portion  4051  can arbitrarily change a flow rate and the velocity of flow of air exhausted by the draft exhaust unit  210 . In  FIG. 4 , the draft supply unit  202  and the draft exhaust unit  210  have been described, however, the draft supply units  203  and  204  and the draft exhaust units  208  and  209  have similar structures. In some cases, at least one of the flow rate and the velocity of the flow controlled by at least one of the draft supply unit  202  and the draft exhaust unit  210  is changed in accordance with at least one of the size (more specifically, diameter) of the substrate  103  and the number of rotations of the substrate. The draft supply unit  202  may be a fan filter unit. 
     A flowchart of this example will be described below with reference to  FIG. 8 . First, the stage  107  is moved downward by control of the processing unit  113 . Then, the substrate  103  that has been subjected to pre-alignment in a pre-alignment apparatus which is a former stage of the inspection apparatus is mounted on the substrate mounting unit  104 . After the substrate  103  is mounted on the substrate mounting unit  104 , the stage  107  is moved upward, and the substrate  103  is housed in the chamber  201  (step  501 ). Note that supply of the substrate  103  to the stage  107  in the chamber  201  may be carried out by an up-and-down operation (a Z position of the stage  107  is fixed) of a transportation mechanism. 
     Then, by control of the processing unit  113 , the chamber system  105  supplies a draft to the outer regions from above the substrate  103  at a predetermined flow rate and a predetermined velocity of flow of air under a predetermined condition (e.g., presence/absence of the substrate  103 , the size of the substrate  103 , the number of rotations of the substrate  103 ) (step  502 ). 
     After the processing unit  113  determines that the draft is supplied at the predetermined flow rate and the predetermined velocity of flow, the substrate  103  is rotated by the spindle  106  (step  503 ). 
     When the processing unit  113  determines that the number of rotations of the substrate  103  becomes a predetermined number of rotations (e.g., several thousand rpm or more) (step  504 ), inspection is carried out (step  505 ). Note that, in a case where the number of rotations of the substrate  103  is not the predetermined number of rotations, the draft is supplied and controlled in conjunction with the number of rotations of the substrate  103  (step  508 ). 
     After the inspection of the whole surface of the substrate  103  is completed, the spindle  106  gradually reduces the number of rotations of the substrate  103  and finally stops the rotation of the substrate (step  506 ). 
     Thereafter, supply of the draft is returned to the flow rate and the velocity of flow of the draft at the time of supply of the substrate (step  507 ). Control of the flow rate and the velocity of flow at the time of rotating and moving upward the spindle  106  and control thereof at the time of moving downward the spindle  106  are different in some cases. An operation in the step  501  to the step  507  is repeated for the next substrate. 
     According to this example, in a case where the substrate  103  is rotated at a high speed, for example, at several thousand rpm, an undesirable draft generated in the outer regions of the substrate  103  and adhesion of particles to the substrate  103  caused by the undesirable draft are effectively reduced by supplying the drafts  205 ,  206 , and  207  to the outer regions from above the substrate  103  and finally exhausting the drafts  205 ,  206 , and  207  to outside of the substrate  103 . 
     Example 2 
     Example 2 will be described below. In Example 1, the drafts  205 ,  206 , and  207  are supplied from above the chamber  201 . This example has a feature that the draft is supplied from the side surface of the chamber  201  and the draft supplied from the side surface of the chamber  201  is exhausted. 
     More specifically, this example will be described with reference to  FIG. 9 . Hereinafter, different parts from those of Example 1 will be mainly described.  FIG. 9( a )  illustrates the chamber  201  of this example.  FIG. 9( b )  illustrates arrangement of draft supply units  603 ,  604 , and  605  in a case of observing the chamber  201  of this example from above a Z axis.  FIG. 9 ( b )  illustrates arrangement of draft supply units  606 ,  607 , and  608  in a case of observing the chamber  201  of this example from above the Z axis. The chamber  201  of this example has a substantially tubular shape and has an aperture  602  in the upper surface thereof. Cleaned gas is supplied by a fan filter unit  601  through the aperture  602 . The draft supply units  603 ,  604 , and  605  are located on the side surface of the chamber  201 . The draft exhaust units  606 ,  607 , and  608  are located at positions lower (as another expression, positions closer to the substrate  103 ) than positions on which the draft supply units  603 ,  604 , and  605  are located. 
     As illustrated in  FIG. 10 , a duct  6031  of the draft supply unit  603  is inclined at an angle θ 1  with respect to a surface  609  that is in parallel to a cross-section of the chamber  201 , and the draft is supplied at the angle θ 1 . Further, a duct  6061  of the draft exhaust unit  606  is inclined at an angle θ 2  with respect to a surface  610  that is in parallel to a cross-section of the chamber  201 , and the draft supplied at the angle θ 2  is exhausted. The same applies to the draft supply units  604  and  605  and the draft exhaust units  607  and  608 . This example obtains an effect similar to that of Example 1. 
     Examples have been described as above, however, the invention is not limited to Examples. For example, as illustrated in  FIG. 11 , the substrate  103  may be illuminated with the illumination light  102  through an aperture  801  provided in a side wall of the chamber  201 . Further, the number of the draft supply units and the number of the draft exhaust units may be larger or smaller than those in Examples. Further, the chamber system  105  of this example may be applied to an apparatus for coating a liquid to a substrate, such as a spin coater. 
     REFERENCE SIGNS LIST 
     
         
           101  illumination optical system 
           102  illumination light 
           103  substrate 
           104  substrate mounting unit 
           105  chamber system 
           106  spindle 
           107  stage 
           108  scattered light 
           109 ,  110  detection optical system 
           111  illuminated region 
           113  processing unit 
           114  monitor unit 
           201  chamber 
           202 ,  203 , and  204  draft supply unit 
           205 ,  206 ,  207  draft 
           208 ,  209 , and  210  draft exhaust unit 
           211  aperture 
           301  lower surface 
           302  upper surface