Patent Publication Number: US-2022216081-A1

Title: Method and device for detecting placement of wafers in wafer cassette

Description:
FIELD 
     The subject matter relates to detecting placement of wafers, and more particularly, to a method and a device for detecting placement of wafers in a wafer cassette. 
     BACKGROUND 
     After manufacturing, wafers are placed in different grooves of a wafer cassette by a robot arm. Then, top cover of the wafer cassette is closed, and a worker needs to check whether the quantity and the positions of the wafers in the wafer cassette are correct. Fragments dropped from the wafers, and errors such as more than two wafers being placed together in a single groove of the wafer cassette need to be manually detected. 
     However, the manual detection method may be low in efficiency and accuracy. When the wafer cassette and the cover have a poor transparency, light intensity of the ambient environment needs to be increased to clearly show the placement of the wafers in the wafer cassette. However, damages may cause to eyes of the workers when working under high intensity light. Furthermore, the wafers cannot be seen if the wafer cassette and the cover are opaque. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Implementations of the present technology will now be described, by way of example only, with reference to the attached figures. 
         FIG. 1  is a flowchart of an embodiment of a method for detecting placement of wafers in a wafer cassette according to the present disclosure. 
         FIG. 2  is a block diagram of an embodiment of a device for detecting placement of wafers in a wafer cassette according to the present disclosure. 
         FIG. 3  is a diagrammatic view of the device of  FIG. 2 . 
         FIG. 4  is a diagrammatic view of another embodiment of the device according to the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     It will be appreciated that for simplicity and clarity of illustration, where appropriate, reference numerals have been repeated among the different figures to indicate corresponding or analogous components. In addition, numerous specific details are set forth in order to provide a thorough understanding of the embodiments described herein. However, it will be understood by those of ordinary skill in the art that the embodiments described herein can be practiced without these specific details. In other instances, methods, procedures, and components have not been described in detail so as not to obscure the related relevant characteristic being described. Also, the description is not to be considered as limiting the scope of the embodiments described herein. The drawings are not necessarily to scale, and the proportions of certain parts may be exaggerated to better illustrate details and characteristics of the present disclosure. 
     The term “comprising,” when utilized, means “including, but not necessarily limited to”; it specifically indicates open-ended inclusion or membership in the so-described combination, group, series, and the like. 
       FIG. 1  illustrates an embodiment of a method for detecting a placement of wafers  2  in a wafer cassette  1 . The method is provided by way of embodiment, as there are a variety of ways to carry out the method. The method can begin at block  11 . 
     At block  11 , the wafer cassette  1  is provided. 
     Referring to  FIGS. 2 and 3 , the wafer cassette  1  includes a plurality of receiving grooves  11  arranged side by side. Each receiving grooves  11  is used to store one wafer  2 . The wafer cassette  1  further includes a housing  12 , a plurality of diaphragms  13  disposed in the housing  12 , and a cover  14  connected to the housing  12 . Adjacent diaphragms  13  are parallel with each other and cooperatively form a receiving groove  11 . One end of each receiving groove  11  close to the cover  14  defines an opening  15 . Each wafer  2  is placed in a receiving groove  11  through the corresponding opening  15 . 
     In an embodiment, one side of the cover  14  is rotatably connected to the housing  12 . The cover  14  and the housing  12  are locked together through a locking unit  16 , such as buckle. 
     In an embodiment, referring to  FIG. 4 , the wafer cassette  1  further includes a plurality of tenons  17  disposed on an inner side of the cover  14 . Each tenon  17  corresponds to one diaphragm  13 . A distance between adjacent tenons  17  is approximately equals to a thickness of the wafer  2 . The wafer  2  is clamped between adjacent tenons  17 . The adjacent tenons  17  fix the wafer  2  in the receiving groove  11  to avoid movement of the wafer  2 . 
     In an embodiment, the cover  14  is connected to a top end of the housing  12 . The opening  15  faces upwards, which is convenient for placing the wafer  2  in the corresponding receiving groove  11 . Furthermore, any separation of the wafer  2  from the receiving groove  11  is avoided when moving the wafer cassette  1 . 
     In an embodiment, each receiving groove  11  receives one wafer  2 , which can avoid damage to the wafer  2  caused by stacking the wafers  2  and facilitate a subsequent detection of the wafer  2 . The method of the present disclosure determines whether more than one wafers  2  is stacked in one receiving groove  11 . When the wafer  2  is placed in the receiving groove, the two diaphragms  13  of such receiving groove  11  and the wafer  2  cooperatively define a gap “b”. Light can pass through the gap “b”. 
     In an embodiment, the housing  12  may be transparent, translucent, or opaque. The cover  14  may be transparent, translucent, or opaque. When the housing  12  and the cover  14  are opaque, the light with a special wavelength (such as infrared light) can be used to irradiate the wafer cassette  1  and the cover  14 , so that the light passing through the gap “b” can be projected into an image of the placement of wafers  2  and the receiving grooves  11  in the wafer  2 . 
     The housing  12  may be made of, but is not limited to, plastic, or glass. The cover  14  may be made of, but is not limited to, plastic, or glass. In an embodiment, the housing  12  and the cover  14  are made of plastic. The tenon  17  may be made of, but is not limited to, plastic, or other elastic materials. The tenon  17  is deformable. 
     At block  12 , the light defined as “a” is transmitted to the wafer cassette  1 , so that the light “a” passes through the gaps “b” between each of the receiving grooves  11  and the corresponding wafer  2 . 
     In an embodiment, a light source  3  is used to transmit the light “a”. The light source  3  is disposed at a bottom of the wafer cassette  1 . The wafers  2  are disposed perpendicular to the light source  3 . The light “a” transmitted by the light source  3  is roughly parallel to a surface of the wafer  2 . The wafer cassette  1  is placed at a suitable position relative to the light source  3 . When the light source  3  transmits the light “a”, a portion of the light “a” reaches and is reflected by the wafers  2 . Other portion of the light “a” pass through the gaps “b”, so that the image of the wafers  2  and the receiving grooves  11  can be obtained. At the same time, definition and clarity of the image can be adjusted by adjusting the intensity and the color temperature of the light source  3 . 
     In an embodiment, the light source  3  may be, but is not limited to, LED light strips. A plurality of LED light strips is evenly disposed on the bottom of the wafer cassette  1 , which can illuminate a whole wafer cassette  1  and avoid dark areas. 
     Block  13 , an image of the light “a” passing through each of the gaps is captured. 
     In an embodiment, the light “a” passing through the gaps “b” is projected into an image by a camera unit  4 . The camera unit  4  is disposed on a side of the wafer cassette  1  away from the light source  3  to capture the image of the light “a”. 
     The camera unit  4  includes at least one camera. The camera is disposed along a transmission direction of the light “a” to capture the light “a” and project the light “a” into the image of the wafer cassette  1  with the wafers  2 . In an embodiment, in order to obtain images at different angles of the wafer cassette  1 , a plurality of cameras may be disposed on different positions above the wafer cassette  1 . The images of the receiving grooves  11  and of the wafers  2  in the wafer cassette  1  can be obtained at the same time. 
     The camera may be, but is not limited to, a general optical camera, or a CCD camera. 
     In an embodiment, the camera is a CCD camera. By setting a plurality of CCD cameras at different positions above the wafer cassette  1 , images of different angles of the wafer cassette  1  with the receiving grooves  11  and the wafers  2  can be captured. The clear images allow subsequent characteristic extraction, characteristic comparison, and determinations. 
     Block  14 , characteristic information is extracted from the image. 
     In an embodiment, the characteristic information is extracted through a controller  5 . The controller  5  is connected to the camera unit  4  to receive the image. 
     In an embodiment, the characteristic information of the image includes the quantity of the wafers  2  in each receiving groove  11 . The quantity of the wafers  2  in each receiving groove  11  can be determined from the image of the wafer cassette  1 , since the image includes the receiving grooves  11 , the tenons  17 , and the wafer(s)  2  in each receiving groove  11 . The quantity of the wafers  2  in each receiving groove  11  can be determined by calculating a total width of the wafer(s)  2  between adjacent tenons  17  of each receiving groove  11 . 
     Block  15 , the extracted characteristic information is compared with standard characteristic information of a preset image, and whether the placement of the wafers  2  in the wafer cassette  1  is acceptable and satisfactory is determined according to a compared result. 
     In an embodiment, the above determinative process is also executed through the controller  5 . 
     When the image does not include any wafer  2  in a receiving groove  11 , the controller  5  determines that there is no wafer  2  between two adjacent tenons  17  corresponding to one receiving groove  11 . At this time, the wafer  2  in the receiving groove  11  is missing or damaged. When the total width of the wafer(s)  2  in a corresponding receiving groove  11  of the image is larger than a standard width of the preset image, the controller  5  determines that more than one wafer  2  are stacked in a single receiving groove  11 . The placement of at least two wafers  2  in a single receiving groove  11  also presses against the tenons  17 , causing the tenons  17  to over-deform. When the tenons  17  are shown to be deformed in the image, it can be determined that at least two wafers  2  are in one single receiving groove  11 . When only one wafer  2  is disposed between two adjacent tenons  17  corresponding to each receiving groove  11 , the controller  5  determines that the placement of the wafers  2  in the wafer cassette  1  is qualified and satisfactory. 
     Therefore, through the determinative process of the above characteristic information, whether the placement of the wafer  2  in the wafer cassette  1  is qualified or not can be determined. 
     In an embodiment, the preset image is obtained by computer vision model training or artificial intelligence (AI) deep learning model training, including the following steps. 
     Firstly, a large number of standard images of the wafers  2  in the wafer cassette  1  are captured. Characteristic information is extracted from each standard image. Then, the wafer cassette  1  to be detected is detected under a constant environment. In an embodiment, the extracted characteristic information of the detection wafer cassette  1  is compared with the standard characteristic information of the preset image by the controller  5 . The placement of the wafers  2  in the wafer cassette  1  is determined to be acceptable when each characteristic information of the detection wafer cassette  1  conforms to the standard characteristic information of the preset image. The controller  5  will also automatically put a marking on the image of the detection wafer cassette  1 , if the characteristic information does not conform to the standard characteristic information of the preset image. Then, the placement of the wafers  2  in the wafer cassette  1  can be improved according to the marking. If the wafers  2  are stacked in a single receiving groove  11  or if the wafer  2  in the receiving groove  11  is damaged, the out-of-place wafer  2  can be removed. If a receiving groove  11  is unoccupied, a wafer  2  can be added in that receiving groove  11 . 
     The method of the present disclosure is high in efficiency and accuracy, which can also avoid damage to eyes of the workers. The method can detect the placement of the wafers  2  in an opaque wafer cassette  1  with an opaque cover  14 . Through the above method, positions whose characteristic information does not conform to the standard characteristic information of the preset image can be accurately achieved, which not only improves the detection efficiency, but also improves the product yield. 
       FIGS. 2 and 3  illustrate a device  100  for detecting the placement of the wafers  2  in the wafer cassette  1 . The wafer cassette  1  includes a light source  3 , a camera unit  4  disposed on a light emitting side of the light source  3 , and a controller  5  connected to the camera unit  4 . 
     In use, the wafer cassette  1  is disposed between the light source  3  and the camera unit  4 . The light source  3  transmits the light “a” to the wafer cassette  1 , so that the light “a” can pass through the gap “b” between the adjacent diaphragm  13  and the wafer  2 . 
     In an embodiment, the device  100  includes a plurality of light sources  3 . By setting the light sources  31  at positions corresponding to the receiving grooves  11 , the lights “a” transmitted by all the light sources  31  illuminates the receiving grooves  11 , so that all the receiving grooves  11  and the wafers  2  in the wafer cassette  1  can be examined and imaged. 
     The camera unit  4  is used to project the light “a” passing through the gaps “b” into the image. 
     The camera unit  4  includes at least one camera. The image of the wafer cassette  1  can be obtained by setting the camera along the transmission direction of the light “a”. 
     The camera unit  4  may also include at least two cameras. By setting the cameras at different positions of the wafer cassette  1 , images of the receiving groove  11  and the wafers  2  can be captured from different angle. 
     The controller  5  is used to extract characteristic information from the image, compare the extracted characteristic information with a standard characteristic information of a preset image, and determine whether a placement of all the wafers  2  in the wafer cassette  1  is in order and acceptable according to a compared result. 
     In an embodiment, the characteristic information includes the quantity of the wafers  2  in each receiving groove  11 . 
     The controller  5  is further used to display the images and the result of determination. 
     The device  100  in the present disclosure can be used to detect the placement of the wafers  2  in an opaque wafer cassette  1  with wafers  2 . Through the above device  100 , positions whose characteristic information does not conform to the standard characteristic information of the preset image can be accurately obtained, which not only improves the detection efficiency, but also improves the product yield. The device  100  also has a simple structure, which is portable, flexible, and convenient. 
     The embodiments shown and described above are only examples. Even though numerous characteristics and advantages of the present technology have been set forth in the foregoing description, together with details of the structure and function of the present disclosure, the disclosure is illustrative only, and changes may be made in the detail, including in matters of shape, size and arrangement of the parts within the principles of the present disclosure, up to and including, the full extent established by the broad general meaning of the terms used in the claims.