Patent Publication Number: US-11652007-B2

Title: Metrology method

Description:
PRIORITY CLAIM AND CROSS-REFERENCE 
     This application is a continuation of U.S. patent application Ser. No. 14/092,256, filed Nov. 27, 2013, now U.S. Pat. No. 10,460,999, issued Oct. 29, 2019, which is herein incorporated by reference in its entirety. 
    
    
     BACKGROUND 
     Technical Field 
     The present disclosure relates to a metrology device. 
     Description of Related Art 
     With the advancement of semiconductor technology, semiconductor devices become increasingly smaller and denser. The increasingly smaller and denser semiconductor devices are difficult to be manufactured and thus have inconsistent quality. Therefore, the semiconductor devices are examined before the semiconductor devices are released. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings are included to provide a further understanding of the disclosure, and are incorporated in and constitute a part of this specification. The drawings illustrate embodiments of the disclosure and, together with the description, serve to explain the principles of the disclosure. In the drawings, 
         FIG.  1    is a schematic diagram of a metrology device according to one or more embodiments of the present disclosure; 
         FIG.  2    is a flow chart of a metrology method according to one or more embodiments of the present disclosure; 
         FIG.  3    is a cross-sectional view of the wafer in  FIG.  1   ; 
         FIG.  4    is a 1D intensity graph of X-ray scattering spectrum measured from the wafer in  FIG.  3   ; and 
         FIG.  5    is a cross-sectional view of the wafer according to one or more embodiments of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     It is to be understood that the following disclosure provides many different embodiments, or examples, for implementing different features of the disclosure. Specific examples of components and arrangements are described below to simplify the present disclosure. These are, of course, merely examples and are not intended to be limiting. Moreover, the formation of a first feature over or on a second feature in the description that follows may include embodiments in which the first and second features are formed in direct contact, and may also include embodiments in which additional features may be formed interposing the first and second features, such that the first and second features may not be in direct contact. Various features may be arbitrarily drawn in different scales for the sake of simplicity and clarity. 
     The terms used in this specification generally have their ordinary meanings in the art and in the specific context where each term is used. The use of examples in this specification, including examples of any terms discussed herein, is illustrative only, and in no way limits the scope and meaning of the disclosure or of any exemplified term. Likewise, the present disclosure is not limited to various embodiments given in this specification. 
     As used herein, the terms “comprising,” “including,” “having,” “containing,” “involving,” and the like are to be understood to be open-ended, i.e., to mean including but not limited to. As used herein, “around”, “about”, “substantially” or “approximately” shall generally mean within 20 percent, in some embodiments within 10 percent, and in another embodiments within 5 percent of a given value or range. Numerical quantities given herein are approximate, meaning that the term “around”, “about”, “substantially” or “approximately” can be inferred if not expressly stated. The singular forms “a”, “an” and “the” used herein include plural referents unless the context clearly dictates otherwise. 
     Reference throughout the specification to “one embodiment” or “an embodiment” means that a particular feature, structure, implementation, or characteristic described in connection with the embodiment is included in at least one embodiment of the present disclosure. Thus, uses of the phrases “in one embodiment” or “in an embodiment” in various places throughout the specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures, implementation, or characteristics may be combined in any suitable manner in one or more embodiments. 
     Reference is made to  FIG.  1    which is a schematic diagram of a metrology device according to one or more embodiments of the present disclosure. The metrology device includes a light source  100  and an image sensor  200 . The light source  100  is configured for providing an X-ray  102  illuminating a wafer  900 . The image sensor  200  is configured for detecting a spatial domain pattern produced when the X-ray  102  illuminating the wafer  900 . 
     As such, the metrology device of this embodiment can be utilized to measure smaller scale structures of the wafer  900  since the X-ray  102  has shorter wavelength, and the reliability of the measurement result can be improved. 
     In one or more embodiments, the light source  100  may be an electromagnetic radiation source. More particular, the light source  100  can be an X-ray source. As a form of electromagnetic radiation, the X-ray  102  may have a wavelength in the range 0.01 to 10 nm corresponding to frequencies in the range 30 petahertz to 30 exahertz (3×10 16  Hz to 3×10 19  Hz). The wavelength of the X-ray  102  can be shorter than that of ultraviolet light. Since the optical resolution, which can be obtained from Rayleigh criterion, may be about half wavelength of the light beam illuminating to the wafer  900 , the optical resolution of the X-ray  102  may be about 0.005 to 5 nm. Taking the wafer  900  having linewidths which are about 20 nm as an example, the optical resolution of the X-ray  102  can be enough to distinguish the morphology of the wafer  900 . 
     In this embodiment, the wafer  900  can be disposed between the light source  100  and the image sensor  200 . In other words, the image sensor  200  can detect the X-ray  102  passing through the wafer  900 . Therefore, compared to the reflective portion of the X-ray  102 , the transmission portion of the X-ray  102  can form a smaller spot size illuminating on the wafer  900 , and a smaller scale structure of the wafer  900  can be measured. In addition, although the X-ray  102  passes through the wafer  900  during measurement, the X-ray  102  can not damage the wafer  900 . 
     Furthermore, the power of the X-ray  102  can be larger than 12 kW to pass through the wafer  900 . Taking the wafer  900  having a thickness 750 μm for example, the power of the X-ray  102  can be about 13 kW to 14 kW. However, in other embodiments, if the thickness of the wafer  900  has been reduced (such as being polished) before measurement, the power of the X-ray  102  can be smaller than 13 kW. Basically, the power of the X-ray  102  can be depend on the thickness of the wafer  900 . 
     In  FIG.  1   , the metrology device can further include a lens group  300  for focusing the X-ray  102  to the wafer  900 . To measure the smaller scale structure of the wafer  900 , the spot size of the X-ray  102  illuminating on the wafer  900  can be smaller. Therefore, the spot size of the X-ray  102  can be reduced by focusing the X-ray  102 . In one or more embodiments, the spot size of the X-ray  102  can be about 100 μm. It should be understood that the spot size of the X-ray  102  mentioned above is illustrative only and should not limit the scope of the claimed invention. A person having ordinary skill in the art may select a proper spot size of the X-ray  102  according to actual requirements. 
     In this embodiment, the lens group  300  can be disposed between the light source  100  and the image sensor  200 . More specifically, the lens group  300  can be disposed between the light source  100  and the wafer  900 . As such, the X-ray  102  provided by the light source  100  can pass through the lens group  300 , being focused by the lens group  300 , and then illuminating to the wafer  900 . After passing through the wafer  900 , the transmission portion of the X-ray  102  can form the spatial domain pattern and then be detected by the image sensor  200 . 
     In one or more embodiments, the metrology device can further include a processor  500  for obtaining the morphology of the wafer  900  according to the detected spatial domain pattern. The type of the processor  500  can depend on the type of the detected spatial domain pattern. 
     In one or more embodiments, the metrology device may further include a Fourier&#39;s transformer  400  for transforming the detected spatial domain pattern into a Fourier frequency domain data, and the processor  500  can obtain the morphology of the wafer  900  according to the Fourier frequency domain data. In greater detail, interference may occur in the transmission portion of the X-ray  102  and form the spatial domain pattern. In other words, the spatial domain pattern can be an interference pattern. The Fourier&#39;s transformer  400  can transform the interference pattern into the Fourier frequency domain data, such that the processor  500  can obtain the morphology of the wafer  900  according to the Fourier frequency domain data. 
     In this embodiment, the Fourier&#39;s transformer  400  can be connected to the image sensor  200 , and the processor  500  can be connected to the Fourier&#39;s transformer  400 . However, the claimed scope should be not limited to this respect. A person having ordinary skill in the art may design proper connections among the Fourier&#39;s transformer  400 , the processor  500 , and the image sensor  200  according to actual requirements. 
     In one or more embodiments, the X-ray  102  may illuminate the wafer  900  from the back side of the wafer  900 . It should be pointed out that the back side can be a side opposite to a structure of the wafer  900  which is desired to be measured. After passing through the wafer  900 , diffraction may occur within the X-ray  102  due to the interference effect caused from the measured structure of the wafer  900 . This portion of the X-ray  102  may undergo destructive or constructive interferences, such that the interference pattern detected by the image sensor  200  may be not so easy to be analyzed in the spatial domain. However, the Fourier&#39;s transformer  400  can transfer the interference pattern into the frequency domain, such that some frequency features of the wafer  900  may be shown. The data corresponded to the frequency features can be analyzed using the processor  500 , for example, the processor  500  can transfer the data from the frequency domain back to the spatial domain, and the features of the wafer  900  can be obtained. 
     In some examples, if the structure of the wafer  900  is periodic in the spatial domain, its frequency domain pattern may exist at least one main frequency which is corresponded to the period of the structure. That is, the main frequency is higher if the period of the structure is shorter, and the main frequency is lower if the period of the structure is longer. Therefore, according to the main frequency, the feature of the wafer  900  can be obtained. 
     In one or more embodiments, the metrology device may further include a rotation mechanism  600  for rotating the wafer  900 . The rotating mechanism  600  can be disposed between the lens group  300  and the image sensor  200 . However, the claimed scope is not limited to this respect. Through rotating the wafer  900  during measurement, more information of the wafer  900  can be obtained. In greater detail, the X-ray  102  may interact with the electrons and then scatter when it illuminates the wafer  900 . If the structure of the wafer  900  is uniform and disordered, the scattered X-ray  102  may be uniformly scattered in the spatial domain. However, if the electron distribution or the structure of the wafer  900  is ordered or regular, the feature of the scattered X-ray  102  may be changed according to the different incident angle of the X-ray  102 . Therefore, for rotating the wafer  900  during measurement, the directional features of the wafer  900  can be obtained. 
     It is understood that the embodiment of the metrology device mentioned above is provided merely as examples and are not intended to be limiting. The metrology device may have different configurations consistent with the spirit of the present disclosure in alternative embodiments depending on design requirements and manufacturing concerns. 
     Another aspect of the present disclosure provides a metrology method for measuring the morphology of a wafer. Reference is made to  FIG.  2    which is a flow chart of the metrology method according to one or more embodiments of the present disclosure. To illustrate clarity, the structure of the metrology device in  FIG.  1    is applied to the method shown in  FIG.  2    in this embodiment. However, the claimed scope is not limited to this respect. The metrology method for measuring the morphology of the wafer  900  includes the following acts: 
     As shown in act S 10 , the X-ray  102  is provided to illuminate the wafer  900 . Subsequently, as shown in act S 20 , the spatial domain pattern produced when the X-ray  102  illuminating the wafer  900  is detected. It should be noticed that the flow chart of  FIG.  2    shows exemplary acts, but they are not necessarily performed in the order shown. Acts may be added, replaced, changed order, and/or eliminated as appropriate, in accordance with the spirit and scope of disclosed embodiments. 
     In greater detail, the wavelength of the X-ray  102  can be about 0.01 to 10 nm, such that the optical resolution of the X-ray  102 , which may be about 0.005 to 5 nm, can be further improved. 
     In one or more embodiments, the metrology method may further include act: 
     focusing the X-ray  102  to the wafer  900 . 
     For example, the spot size illuminating on the wafer  900  may be 100 μm. Therefore, the spot size of the X-ray  102  can be reduced to measure the smaller scale structures of the wafer  900  if the wafer  900  has smaller devices. 
     The following paragraphs provide an example with respect to the data of measuring the wafer  900  using the metrology device of  FIG.  1   .  FIG.  3    is a cross-sectional view of the wafer  900  in  FIG.  1   , and  FIG.  4    is an 1D intensity graph of X-ray scattering spectrum measured from the wafer  900  in  FIG.  3   . Reference is made to  FIG.  3    and  FIG.  4   . In this example, a measured structure  902  of the wafer  900  was a metal layer structure. The thickness T of the wafer  900  was about 750 nm. The wavelength of the X-ray was about 0.1 nm. The power of the X-ray was about 14 kW. The X-ray was incident the back side of the wafer  900  normally, i.e., the incident angle of the X-ray was 0 degrees. 
     In  FIG.  4   , the detected spatial domain pattern was the 2D X-ray scattering spectrum (not shown), and the intensity of the 2D X-ray scattering spectrum along x direction was plotted as the “Experimental” curve in  FIG.  4   . Subsequently, the morphology was obtained. In this example, the “Experimental” curve was fitted to obtain a fitting curve, which was shown in the “Fitting” curve in  FIG.  4   . According to the “Fitting” curve, main peaks (repeat in scattering vector Qx˜0.0083 A −1 ) are obtained. According to the scattering vector, pitch P=75.79 nm was estimated. In addition, average width W=30.46 nm of the measured structure  902  was also estimated. In this example, the values of the pitch P and the average width W of the wafer  900  was smaller than the optical resolution of ultraviolet light, which has wavelength about 150 nm and optical resolution about 75 nm. As such, since the optical resolution of the metrology device in this example was much higher, the metrology device can achieve higher measurement reliability. 
     In other embodiments, the wafer  900  in  FIG.  3    can further be rotated during the measurement, such that more information of the morphology of the wafer  900  can be obtained. For example, top width TW of the measured structure  902 , middle width MW of the measured structure  902 , and the bottom width BW of the measured structure  902  can be obtained. It should be understood that the feature of the wafer  900  mentioned above is illustrative only and should not limit the scope of the claimed disclosure. A person having ordinary skill in the art may select a proper feature of the wafer  900  to be measured according to actual requirements. 
     It should be notices that in other embodiments, the measured structure  902  of the wafer  900  is not limited to the structure mentioned above. According to different manufacturing processes, the wafer  900  in  FIG.  3    may be a Fin field effect transistor (FinFET), and in other embodiments, the wafer  900  in  FIG.  3    may include conductive layers, dielectric layers, and/or semiconductor layers, such that the measured structure can be the morphology of the metal layer of the wafer  900 , the morphology of the dielectric layer of the wafer  900 , or the morphology of semiconductor layers of the wafer  900 . 
     In greater detail, the conductive layers may include metal layers (the material of which is such as Ag, Au, Cu, etc.), or transparent conductive oxide layers (the material of which is such as ITO, IZO, etc.). The dielectric layer may include oxide layers (such as SiO x ), or nitride layers (the material of which is such as SiN x ). The semiconductor layers may include silicon layers (the material of which is such as poly-Si, a-Si, etc.). However, the claimed scope should not be limited to the layers mentioned above. 
     Reference is made to  FIG.  5    which is a cross-sectional view of the wafer  900  according to one or more embodiments of the present disclosure. In this embodiment, the wafer  900  can further include raised source and drain structures  904 . The raised source and drain structures  904  can be grown on or above a substrate  910  of the wafer  900  using the epi-growth technique. The metrology device in this embodiment can measure the raised height H, pitches P, and/or widths W of the raised source and drain structures  904 . Furthermore, through rotating the wafer  900 , more information of the morphology of the wafer  900  can be obtained. 
     According to some embodiments, a method includes illuminating a wafer by an X-ray, detecting a spatial domain pattern produced when illuminating the wafer by the X-ray, identifying at least one peak from the detected spatial domain pattern, and analyzing the at least one peak to obtain a morphology of a transistor structure of the wafer. 
     According to some embodiments, a method includes illuminating a wafer by an X-ray, such that the X-ray is diffracted by the wafer, detecting the diffracted X-ray, conducting a Fourier&#39;s transform of the diffracted X-ray, and analyzing a main frequency of the Fourier&#39;s transform of the diffracted X-ray to obtain a morphology of a transistor structure of the wafer. 
     According to some embodiments, a method includes illuminating a wafer by an X-ray, detecting an X-ray scattering spectrum produced when illuminating the wafer by the X-ray, obtaining an experimental curve of intensity of the X-ray scattering spectrum as a function of scattering vector, and analyzing the experimental curve to obtain an average width of measured structures of the wafer. 
     The acts are not recited in the sequence in which the acts are performed. That is, unless the sequence of the acts is expressly indicated, the sequence of the acts is interchangeable, and all or part of the acts may be simultaneously, partially simultaneously, or sequentially performed. 
     Although the embodiments have been described in detail, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the embodiments as defined by the appended claims. For example, the wavelength of the X-ray  102  is not limited to the wavelength range mentioned above. 
     Moreover, the scope of the present application is not intended to be limited to the particular embodiments of the process, machine, manufacture, and composition of matter, means, methods, and steps described in the specification. A person having ordinary skill in the art can readily appreciate from the disclosure, processes, machines, manufacture, compositions of matter, means, methods, or steps, presently existing or later to be developed, that perform substantially the same function or achieve substantially the same result as the corresponding embodiments described herein may be utilized according to the disclosure. Accordingly, the appended claims are intended to include within their scope such processes, machines, manufacture, compositions of matter, means, methods, or steps. In addition, each claim constitutes a separate embodiment, and the combination of various claims and embodiments are within the scope of the disclosure. Accordingly, the scope of the present disclosure is defined by the appended claims rather than the foregoing description and the exemplary embodiments described therein.