Abstract:
In order to rapidly inspect shape defects in the object of inspection that is the minute pattern on a magnetic recording medium formed from patterned media, in the disclosed patterned media defect inspection method detected spectral waveform data is compared with reference-standard spectral reflectance waveform data, which is stored in a database and the pattern-shape of which is known, and defects are detected. The type of the defects is determined on the basis of the disparity, for each detected wavelength, between the spectral waveform data of the detected defects, and the reference-standard spectral reflectance waveform data.

Description:
BACKGROUND 
       [0001]    The present invention relates to an inspection method and a device for the same for determining right or wrong of a pattern shape, and particularly to an inspection technique that discriminates a shape depending on a difference in the wavelength of the spectral waveform of reflected light from a pattern formed on a patterned medium and determines right or wrong of the pattern shape. 
         [0002]    The recording capacity of hard disks has been increased for years. As one of techniques for increasing the capacity, patterned media are expected to be introduced. The patterned media are classified into two types, namely, discrete track media and bit patterned media. In the technique of the discrete track media, concentric track patterns are formed on media disks. In the technique of the bit patterned media, countless bit patterns are formed. 
         [0003]    The patterned media are formed by physically forming the patterns on the surface of a disk to record magnetic information on the formed patterns. Since physical spaces are formed between the adjacent patterns, the recording density can be increased more than before. 
         [0004]    In order to form the patterns, a method using the nanoimprint technology is most likely to be employed. However, in the case where the sizes and shapes of the patterns vary, magnetic recording media do not correctly operate and malfunction as defects in some cases. Therefore, it is necessary to inspect whether the pattern shape is properly formed. 
         [0005]    As a conventional inspection method for detecting defects on the surface of a disk, there is a method described in Patent Literature 3. In this method, laser light is irradiated onto the surface of a disk to discriminate (concave-convex determination) defects on the basis of a signal obtained from a light-receiving element that detects scattering light and regular reflected light. 
         [0006]    Each of Patent Literature 1 and 2 describes an invention related to inspecting the surface of a patterned medium by spectral detection while allowing a spindle to rotate at relatively-low speeds. On the other hand, Patent Literature 3 describes an invention related to inspecting defects on the surface of a disk while allowing a spindle to rotate at high speeds to scan the surface of the disk in a spiral manner. 
       CITATION LIST 
     Patent Literature 
       [0000]    
       
         Patent Literature 1: Japanese Patent Application Laid-Open Publication No. 2009-257993 
         Patent Literature 2: Japanese Patent Application Laid-Open Publication No. 2009-150832 
         Patent Literature 3: Japanese Patent Application Laid-Open Publication No. 2008-268189 
       
     
       SUMMARY OF THE INVENTION 
       [0010]    In Patent Literature 1 and 2, a detailed inspection of a minute pattern formed on the surface of a disk such as a patterned medium can be realized. However, it takes time to process a detected signal, and it is difficult to apply to an actual production line in which a large amount of disks need to be processed in a short takt time. 
         [0011]    Further, the invention described in Patent Literature 3 relates to a technique to detect defects or foreign matters on the surface of a flat disk by detecting scattering light. In Patent Literature 3, an inspection of defects of a minute pattern shape is not considered. 
         [0012]    An object of the present invention is to provide a pattern shape inspection method and a device for the same in which defects of the minute pattern shape of a magnetic recording medium such as a patterned medium used as an inspection target can be inspected at high speeds. 
         [0013]    In order to achieve the above-described object, the present invention can determine the width and height of a pattern and the thickness of a base by comparing detected spectral waveform data with waveform data stored in advance in a defect inspection method for patterned media. 
         [0014]    Specifically, the present invention provides an inspection device including: a rotational axis unit that holds a sample on the surface of which a pattern is formed and rotates the held sample; a conveying unit that conveys the rotational axis unit holding the sample to an inspection position; a spectral detection optical system unit that irradiates a light spot containing plural wavelengths onto the sample conveyed to the inspection position by the conveying unit while being held by the rotational axis unit and carrying out spectral detection of reflected light from an area on the sample onto which the light spot is irradiated; and a signal processing unit that processes a signal obtained by spectral detection of the reflected light from the sample by the spectral detection optical system unit to determine defects of the pattern on the sample and the type of defects, the signal processing unit including: spectral reflectivity data obtaining means that processes the signal obtained by the spectral detection of the reflected light by the spectral detection optical system unit to obtain spectral reflectivity data; database means that stores spectral reflectivity data of reflected light from a normal pattern and spectral reflectivity data of reflected light from a pattern whose differences from the normal pattern are allowable; data processing means that compares the spectral reflectivity data obtained by the spectral reflectivity data obtaining means with the spectral reflectivity data stored in the database means to extract data in which the amount of differences from the spectral reflectivity data stored in the database means exceeds an allowable range; and defect determination means that determines defects of the pattern on the sample and the type of defects using information of the data which is extracted by the data processing means and in which the amount of differences from the spectral reflectivity data stored in the database means exceeds an allowable range. 
         [0015]    Further, the present invention provides an inspection method including the steps of: holding a sample on the surface of which a pattern is formed with a rotational axis unit; conveying the rotational axis unit holding the sample to an inspection position; irradiating a light spot containing plural wavelengths onto the sample conveyed to the inspection position while being held by the rotational axis unit and the spectral detection of reflected light from an area on the sample onto which the light spot is irradiated; and determining defects of the pattern on the sample and the type of defects by processing a signal obtained by the spectral detection of the reflected light from the sample, wherein the defects of the pattern on the sample and the type of defects are determined by comparing spectral reflectivity data obtained by the spectral detection of the reflected light with spectral reflectivity data stored in advance to extract data in which the amount of differences from the spectral reflectivity data stored in advance exceeds an allowable range and by using information of the data in which the amount of differences from the spectral reflectivity data extracted and stored in advance exceeds an allowable range. 
         [0016]    According to an aspect of the present invention, in the case where defects of a pattern shape on a patterned medium are detected to specify the type of defects, the amount of data to be handled can be reduced, a real-time process can be realized by shortening the data processing time, and a data processing unit can be reduced in size and weight. 
         [0017]    These features and advantages of the invention will be apparent from the following more particular description of preferred embodiments of the invention, as illustrated in the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0018]      FIG. 1  is a block diagram for showing an outline configuration of an inspection device. 
           [0019]      FIG. 2  is a flowchart for explaining an operational flow of the inspection device. 
           [0020]      FIG. 3  is a block diagram for showing an outline configuration of an optical system. 
           [0021]      FIG. 4  is a cross-sectional view of a disk on which a pattern is formed. 
           [0022]      FIG. 5  is a graph for showing an example of results of measuring spectral reflectivity distribution. 
           [0023]      FIG. 6  is a flowchart for explaining an inspection flow of the surface of a disk. 
           [0024]      FIG. 7  is a front view of a screen for showing an example of displaying an inspection result. 
       
    
    
     DESCRIPTION OF EMBODIMENTS 
       [0025]    A hard disk inspection device according to the present invention will be described using the drawings. 
         [0026]      FIG. 1  shows an outline configuration of a hard disk inspection device  100  according to the present embodiment. The inspection device includes: a spectral detection optical system  102  that irradiates detection light onto a hard disk (hard disk medium)  207  as an inspection target on the surface of which a resist pattern is formed and carries out a spectrum detection on a reflected light from the inspection target; a spindle unit  103  that holds the inspection target and rotates at high speeds; a turntable unit  104  that turns the spindle unit to position at the conveying side and at the optical system side; an optical stage unit  101  that allows an optical system to scan on the inspection target; an inversion unit  105  that inverts the inspection target; a control unit  120  that controls the operations of the spectral detection optical system  102 , the spindle unit  103 , the turntable unit  104 , the optical stage unit  101 , and the inversion unit  105 ; a data processing unit  110  that detects the shape or shape abnormality of the pattern formed on the surface of the inspection target on the basis of spectral detection data; and a spectral waveform processing unit  112  that processes an output signal from the spectral detection optical system  102 . The data processing unit  110  is provided with a display unit  111 . 
         [0027]    A procedure of inspecting the resist pattern formed on the surface of the hard disk medium  207  using the hard disk inspection device  100  shown in  FIG. 1  will be described using the flowchart of  FIG. 2 . 
         [0028]    First, the hard disk medium  207  as an inspection target is supplied and fixed to the spindle unit  103  using a handling unit (not shown) (S 201 ). Next, the turntable  104  rotates by 180 degrees and the spindle unit  103  moves to the side of the spectral detection optical system  102  for front-face inspection (S 202 ). The spindle unit  103  having moved to the side of the spectral detection optical system  102  for front-face inspection starts to rotate at high speeds (S 203 ), and the hard disk medium  207  as an inspection target fixed to the spindle unit  103  is rotated at high speeds. The optical stage  101  is allowed to move in synchronization with the high-speed rotation of the spindle unit  103  (S 204 ), so that the front face of the hard disk medium  207  is entirely scanned in a spiral manner (S 205 ). The inspection data obtained by the spectral detection optical system  102  for front-face inspection is processed by the data processing unit  110  to determine the pattern shape and the like, and the determination result is displayed on the display unit  111 . 
         [0029]    When the inspection of the front face of the hard disk medium  207  is completed, the turntable  104  rotates to turn the spindle unit  103  on which the hard disk medium  207  is held to the conveying side at which the hard disk medium  207  is supplied by the handling unit (not shown) (S 206 ). Next, the hard disk medium  207  is inverted by the inversion unit  105  and moved to the adjacent turntable  107  along a guide rail  108 , and is supplied and fixed to a spindle unit  106  (S 207 ). After the hard disk medium  207  is fixed to the spindle unit  106 , the turntable  107  rotates by 180 degrees to place the hard disk medium  207  at the side of a spectral detection optical system  109  for rear-face inspection (S 208 ). 
         [0030]    The spindle unit  106  having moved to the side of the spectral detection optical system  109  for rear-face inspection starts to rotate at high speed (S 209 ) to allow the hard disk medium  207  as an inspection target fixed to the spindle unit  106  to rotate at high speeds. The optical stage  101  moves in synchronization with the high-speed rotation of the spindle unit  106  (S 210 ), so that the rear face of the hard disk medium  207  is entirely scanned in a spiral manner (S 211 ). The inspection data obtained by the spectral detection optical system  109  for rear-face detection is processed by the data processing unit  110  to determine the pattern shape and the like, and the determination result is displayed on the display unit  111 . 
         [0031]    When the inspection of the rear face of the hard disk medium  207  is completed, the turntable  107  rotates to turn the spindle unit  107  to the conveying side at which the hard disk medium  207  is supplied by the handling unit (not shown) (S 212 ). Then, the hard disk medium  207  is taken out from the spindle  107  of the hard disk inspection device  100  by the handling unit (not shown) (S 213 ). 
         [0032]    Next, configurations of the spectral detection optical system  102  for front-face inspection and the spectral detection optical system  109  for rear-face inspection will be described using  FIG. 3 . 
         [0033]    The spectral detection optical system  102  ( 109 ) is fixed on the optical stage  101  as shown in  FIG. 3 , and includes: a light source  301  that emits broadband light containing deep ultraviolet (DUV) light; a collecting lens  302  that collects the light emitted from the light source  301 ; a field diaphragm  303  with an opening part  3031  that determines a detection field on the hard disk medium  207  as an inspection target held by the spindle  103  ( 107 ); a polarization control unit  304  that allows illumination light to polarize in a specific direction so as to be suitable for the inspection of the hard disk medium  207 ; a half mirror  305  that bends the optical path of the polarized illumination light towards the hard disk medium  207 ; an objective lens  306  that collects the illumination light on the surface of the hard disk medium  207 ; a diaphragm  307  with an opening part  3071  that allows the reflected light having been reflected from the surface of the hard disk medium  207  by the illumination of the illumination light, collected by the objective lens  306  again, and passed through the half mirror  305 , so that stray light from the surrounding areas is cut; and a spectroscope  310  having a diffraction grating  308  that carries out a spectral detection of light having passed through the opening part  3071  of the diaphragm  307  and a linear light detector  309  in which plural detection pixels that detect the spectral waveforms of light which is carried out the spectrum by the diffraction grating  308  are linearly arranged. 
         [0034]    A spectral waveform signal detected by the linear light detector  309  of the spectroscope  310  is transmitted to the spectral waveform processing unit  112  for A/D conversion, and then is transmitted to the data processing unit  110  to be processed, so that the pattern shape of the hard disk medium  207  is inspected. 
         [0035]    Next, a method of inspecting the pattern shape with the spectral detection optical system  102  ( 109 ) having the configuration shown in  FIG. 3  will be described. 
         [0036]    First, the optical stage  101  is set at the inspection start position under the control of the control unit  120 , and the spindle  103  ( 107 ) rotates at high speeds, so that the optical stage  101  moves in one direction at a constant speed in a state where the hard disk medium  207  held by the spindle  103  ( 107 ) is rotating at high speeds. The light source  301  controlled by the control unit  120  emits broadband (multi-wavelength) illumination light (for example, a wavelength of 200 to 800 nm) containing deep ultraviolet (DUV) light. As the light source  301 , an Xe lamp, a halogen lamp, a deuterium lamp, a mercury lamp, or the like can be used. 
         [0037]    The light emitted from the light source  301  is collected at the position of the opening part  3031  of the field diaphragm  303  by the collecting lens  302 . The image of the light collected at the opening part  3031  of the field diaphragm  303  is formed on the surface of the hard disk medium  207  by the objective lens  306 . Further, the illumination light having passed through the opening part  3031  of the field diaphragm  303  is adjusted to a polarization state preset by the polarization control unit  304  controlled by the control unit  120 . Then, a part of the illumination light is reflected in the direction of the objective lens  306  by the half mirror  305 , passes through the objective lens  306  and is irradiated onto the hard disk medium  207 . For the control of the polarization state by the polarization control unit  304 , the polarization direction of the illumination light is obtained beforehand the inspection and stored in the database unit  130  on the basis of the conditions under which high-sensitive measurement of the pattern shape formed on the hard disk medium  207  is performed, so that the optimum polarization conditions can be set in accordance with an inspection target 
         [0038]    The reflected light from the hard disk medium  207  on which the image of the opening part  3031  of the field diaphragm  303  is projected enters the objective lens  306  again, and a part thereof passes through the half mirror  305  to reach the diaphragm  307 . By adjusting the position of the field diaphragm, the image of the reflected light from the hard disk medium  207  and passes through the objective lens is formed at the position of the opening part  3071  of the diaphragm  307 . The size of the opening part  3071  of the diaphragm  307  is adjusted to that of the detection field (an area where the image of the opening part  3031  of the field diaphragm  303  is projected) on the hard disk medium  207 , so that stray light or light that is not imaged on the diaphragm  307  can be blocked. 
         [0039]    The reflected light (regular reflected light) from the detection field on the hard disk medium  207  having passed through the opening part  3071  of the diaphragm  307  reaches the diffraction grating  308  of the spectral optical system  310  to become spectral waveforms diffracted in accordance with the wavelengths by the diffraction grating  308 . Then, the spectral waveforms are detected on a wavelength basis by the linear light detector  309  in which plural detecting elements are arranged. The spectral waveform detection signal detected by the linear light detector  309  is input to the spectral waveform processing unit  112  for A/D conversion to obtain a digitalized spectral reflectivity waveform. The digitalized spectral reflectivity waveform is transmitted to the data processing unit  110  to be processed, and the pattern shape formed on the hard disk medium  207  is inspected. 
         [0040]    Next, an inspection method of the pattern shape executed by the data processing unit  110  will be described. First, spectral reflectivity waveform data of a standard sample which has a normal concave-convex pattern and whose pattern shape is already known is preliminarily obtained to be stored in the database unit  130 . In addition, a spectral reflectivity waveform in the case where a concave-convex pattern shape (the height and width of the resist pattern and the thickness of the base as shown in  FIG. 4 ) is changed is obtained by an electromagnetic wave analysis on the basis of the spectral reflectivity waveform data of the standard sample to be stored in the database unit  130 . At the same time, spectral reflectivity waveform data associated with the limit value of differences in the concave-convex pattern shape is determined to be registered in the database unit  130 . Specifically, as shown in  FIG. 5 , spectral reflectivity waveform data  502  of the normal concave-convex pattern and spectral reflectivity waveform data  503  and  504  associated with the limit of allowable differences in the concave-convex pattern shape are registered in the database unit  130 . It should be noted that the horizontal axis represents a channel (ch) number of the detector associated with a detected wavelength in  FIG. 5 , and the channel number is associated with a detected wavelength. As the number increases, the detected wavelength is long. 
         [0041]    The spectral reflectivity waveform is differently changed, for example, between a case in which the height of the concave-convex pattern shape is changed and a case in which the width thereof is changed. Specifically, the spectral reflectivity waveform differs in accordance with the cause of defects of the concave-convex pattern shape. With the use of the characteristics, a relation between the cause of defects of the concave-convex pattern shape and characteristics of the spectral reflectivity waveform is preliminarily registered in the database unit  130 . Then, the spectral reflectivity waveform data obtained by inspecting the inspection target sample is compared with that of the standard sample to obtain distribution characteristics of wavelength bands which are out of an allowable value. On the basis of information of the relation between the cause of defects of the concave-convex pattern shape and characteristics of the spectral reflectivity waveform registered in the database unit  130 , defects of the pattern shape of the inspection target sample can be detected and the type of defects can be specified. 
         [0042]    A processing flow (processes of S 205  and S 211  in  FIG. 2 ) in an actual inspection will be described using  FIG. 6 . A spectral reflectivity waveform is detected with the spectral detection optical system  102  ( 109 ) having the configuration shown in  FIG. 3  using the hard disk medium  207  as an inspection target (S 601 ) to obtain the spectral reflectivity data as shown by  501  of  FIG. 5  (S 602 ). Next, the measurement data  501 , the spectral reflectivity waveform data  502  of the normal concave-convex pattern and the spectral reflectivity waveform data  503  and  504  associated with the limit of allowable differences in the concave-convex pattern shape are compared with each other (S 603 ), and a part of the measurement data  501  out of range between the spectral reflectivity waveform data  503  and  504  associated with the limit of allowable differences in the concave-convex pattern shape is extracted (S 604 ). Next, on the basis of information of the extracted wavelength bands of the measurement data  501 , defects of the pattern shape of the inspection target sample are detected (S 605 ) and the type of defects is specified (S 606 ) from the information of the relation between the cause of defects of the concave-convex pattern shape and characteristics of the spectral reflectivity waveform registered in the database unit  130 . 
         [0043]    Since a part of the detected spectral reflectivity waveform data which is out of the range between the spectral reflectivity waveform data  503  and  504  associated with the limit of allowable differences in the concave-convex pattern shape is extracted and processed as described above, the amount of data to be handled can be decreased as compared with a case in which all the detected spectral reflectivity waveform data is processed to detect the defects of the pattern shape and the type of defects is specified. In addition, real-time processing can be realized by shortening the data processing time, and the data processing unit  110  can be reduced in size and weight. 
         [0044]    It should be noted that there has been described a case in which the resist pattern shape formed on the patterned media is inspected in the above-described embodiment. However, the embodiment can be applied to a case in which the pattern shape of a magnetic film formed by etching using a resist pattern as a mask is inspected. 
         [0045]    For example, as shown in  FIG. 5 , in the case where the measurement result  501  is below the lower slice level  504  at ch 1  and above the upper slice level  503  at ch 2 , ch 6 , and ch 7 , it can be determined that the pattern width is larger than a standard by referring to the relation between the cause of defects of the concave-convex pattern shape and characteristics of the spectral reflectivity waveform registered in the database unit  130 . 
         [0046]    An example of displaying the determination result on the display screen  111  of the data processing unit  110  is shown in  FIG. 7 . On the display screen  111 , displayed are a defect map  701  on the hard disk medium, the number of defects  704 , a determination result  703 , and disk information  702 . The defects are shown by dots in the example of  FIG. 7 . However, distribution based on the type of defects may be displayed by areas. 
         [0047]    As a result, for example, the abnormality of the pattern shape of the patterned medium can be detected at high speeds by the inspection device of the embodiment. 
         [0048]    The invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The present embodiment is therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims, rather than by the foregoing description, and all differences which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein. 
       INDUSTRIAL APPLICABILITY 
       [0049]    The present invention is applied to an inspection device that discriminates a shape depending on a difference in the wavelength of the spectral waveform of reflected light from a pattern formed on a patterned medium that is a kind of magnetic disks and determines right or wrong of the pattern shape.