Abstract:
An incremental offset measuring instrument is provided. The incremental offset measuring instrument includes a main base; a specimen seat mounted on the main base for resting a specimen; a measuring tool assembly for measuring the specimen; and a movable assembly mounted on the main base, wherein the movable assembly carries the measuring tool assembly, thereby achieving the goal of measuring the specimen.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an incremental offset measuring instrument for accurately determining dimensions of objects, thereby reducing product loss during manufacturing processes. 
     2. Description of the Prior Art 
     Please refer to FIG.  1 . FIG. 1 is a typical view of a prior art guide ring  10  and a wafer  15  to-be-polished. As shown in FIG. 1, the wafer  15  is subject to a typical polishing process in order to remove a layer of material from the wafer surface. During the polishing process, the wafer  15  is protected and restrained by the guide ring  10 . In an ideal case, the diameter of the wafer  15  is equal to the inner diameter of the guide ring  10  so that the water  15  can be fittingly placed in the guide ring  10 . It is known that large space between the wafer peripheral and the guide ring  10  can cause sever collision or even drop off of the wafer  15  during the polishing process. 
     However, a very small space between the wafer peripheral and the guide ring  10  and collision are usually inevitable during mass production. Frequent collision of wafers results in incremental offset of the inner diameter of the guide ring  10 . A step cross section of the guide ring  10  is observed due to incremental offset of the inner diameter of the guide ring  10 . Referring to FIG. 2, the cross section of the guide ring  10  without a step cross section is shown. Referring to FIG. 3, the cross section of the guide ring  10   a  with a step cross section is shown. When the step difference  12  exceeds a predetermined value, the wafer  15  is subject to sliding out of the guide ring  10  during the polishing process and may be broken. Consequently, it is an important task of measuring friction loss of the guide ring  10  and the step difference  12 . 
     Referring to FIG.  4  and FIG. 5, a typical way to the measurement of the step difference  12  of the guide ring  10  is according to experience of an operator. When measuring, the operator uses his nail of a finger as a measuring tool, thereby determining if the guide ring  10  can be used in the next polishing process or not. However, the prior art method is not accurate and cannot obtain quantified data that can be used as a basis for effective management of wafer polishing process. 
     SUMMARY OF THE INVENTION 
     It is therefore a primary object of the present invention to provide an incremental offset or step difference measuring instrument for accurately measuring the step difference of a guide ring. 
     Another object of the present invention is to provide an incremental offset or step difference measuring instrument for accurately measuring the step difference of a guide ring and obtaining quantified data that are used as a basis of a wafer polishing management standard. 
     Still another object of the present invention is to provide an incremental offset or step difference measuring instrument for accurately measuring the step difference of a guide ring thereby determining the lifetime of the guide ring and decreasing the cost of production. 
     Still another object of the present invention is to provide an incremental offset or step difference measuring instrument for accurately measuring the step difference of a guide ring thereby avoiding a dropped wafer from damaging pricey semiconductor equipment. 
     According to the claimed invention, an incremental offset measuring instrument is provided. The incremental offset measuring instrument includes a main base; a specimen seat mounted on the main base for resting a specimen; a measuring tool assembly for measuring the specimen; and a movable assembly mounted on the main base, wherein the movable assembly carries the measuring tool assembly, thereby achieving the goal of measuring the specimen. 
     It is to be understood that both the forgoing general description and the following detailed description are exemplary, and are intended to provide further explanation of the invention as claimed. Other advantages and features of the invention will be apparent from the following description, drawings and claims. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a typical view of prior art guide ring and wafer. 
     FIG. 2 is a cross sectional view of a guide ring without a step difference. 
     FIG. 3 is a cross sectional view of a guide ring with a step difference. 
     FIG.  4  and FIG. 5 are schematic diagrams showing the prior art method of manual measurement of step difference of the guide ring. 
     FIG. 6 is a typical view of the incremental offset measuring instrument of this invention. 
     FIG. 7 is a cross-sectional view of the incremental offset measuring instrument of this invention. 
     FIG. 8 is a schematic diagram showing the forward movement of the measuring tool assembly according to the present invention. 
     FIG. 9 is the same as FIG. 8, but showing the backward movement. 
     FIG. 9A is an enlarged view of FIG.  9 . 
     FIG. 10 is a cross sectional diagram showing the forward movement of the measuring tool assembly according to the present invention. 
     FIG. 10A is an enlarged view of FIG.  10 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Please refer to FIG.  6 . This invention provides an incremental offset measuring instrument for accurately measuring the step difference of a guide ring. The incremental offset measuring instrument of the present invention mainly includes a main base  20 , a specimen seat  30 , a movable assembly  40 , and a measuring tool assembly  50 . The specimen seat  30  and the movable assembly  40  are fixed on the main base  20 . Guide ring  10  is placed on the specimen seat  30 . The measuring tool assembly  50  is mounted on the movable assembly  40 . By using the movable assembly  40 , the measuring tool assembly  50  is capable of approaching the guide ring  10  and measuring the step difference of the guide ring  10 , as shown in FIG.  9 . 
     The main base  20  is a level basis platform having the specimen seat  30  and movable assembly  40  thereon. A positioning surface  32  is formed on the specimen seat  30 . Preferably, the positioning surface  32  has a V shaped cross section for adapting various sizes of guide rings  10 . A vertical wall  31  of the specimen seat  30  is provided to position the guide ring  10  in a vertical manner. When in use, a rear surface of the guide ring  10  leans against the vertical wall  31 . The opposite side (the side to be measured) of the guide ring  10  faces the measuring tool assembly  50 . As illustrated, the guide ring  10  is tightly fixed in the specimen seat  30  by using two stopping pieces  33 . 
     Referring to FIG. 7 with reference to FIG. 6, the movably assembly  40  is placed at a front side of the main base  20 . The movably assembly  40  carries the measuring tool assembly  50 . The movably assembly  40  includes a guide rail  42 , a fixed base  41 , a sliding base  43 , and a threaded rod  44 . The guide rail  42  and the fixed base  41  are secured to the main base  20 . The sliding base  43  has a sliding groove (not explicitly shown in FIG. 7) corresponding to the guide rail  42 . When assembly, the sliding base  43  fittingly engages with the guide rail  42  so that the sliding base  43  can move along the length of the guide rail  42 . The threaded rod  44  passes an aperture having a threaded interior surface of the fixed base  41  and is supported by the fixed base  41 . One end of the threaded rod  44  is pivotally mounted on the sliding base  43 . As illustrated, when the threaded rod  44  rotates, the sliding base  43  engaging with the guide rail  42  moves along Y-direction. A rotation button  45  may be disposed on the other end of the threaded rod  44  for facilitating the rotation of the threaded rod  44  with fingers. A connecting rod  46 , which is secured to the sliding base  43  by means of a screw  60 , is connected to the measuring tool assembly  50 . The connecting rod  46  is used to fasten the measuring tool assembly  50 . The measuring tool assembly  50  is used to measure the guide ring  10  placed on the specimen seat  30 . The measuring tool assembly  50  is preferably a commercial leverage-type micro-measurement instrument. The gauge is secured to the connecting rod  46  with X-direction and Z-direction adjusting screws  51 . The position of the measuring tool assembly  50  may be adjusted by adjusting the X-direction and Z-direction adjusting screws  51 . 
     The sliding base  43  of the movable assembly  40  includes an upper portion  431  and a lower portion  432 . The sliding groove (not shown) is formed on the lower portion  432  for engaging with the guide rail  42 . The upper portion  431  is secured to the lower portion  432  by screw  60 . A first hole  433  is provided at one side of the upper portion  431  for accommodating the front end of the threaded rod  44 . A groove  441  is provided at the front end of the threaded rod  44 . The screw  60  engages with the groove  441  of the threaded rod  44 . With such configuration, the threaded rod  44  is pivotally connected with the upper portion  431 . A recess  461  is provided on the connecting rod  46 . The connecting rod  46  is inserted into a second hole  434  of the upper portion  431  and the screw  60  engages with the recess  461  of the connecting rod  46 . 
     Referring to FIG.  8  through FIG. 10, the operation procedures of the present invention are now discussed. First, dust on the guide ring  10  is wiped off. Second, as shown in FIG. 8, button  45  is rotated in a counterclockwise direction to move the measuring tool assembly (leverage-type micro-measurement instrument)  50  away from the specimen seat  30 . As shown in FIG. 8, the guide ring  10  is placed on the positioning surface  32  of the specimen seat  30 . Then, as shown in FIG. 9, button  45  is rotated in a clockwise direction to move the probe  52  of the leverage-type micro-measurement instrument  50  toward the guide ring  10 . Next, as shown in FIG. 9, the probe  52  of the leverage-type micro-measurement instrument  50  is slightly uplifted with fingers and move the probe  52  forward to the basis surface  11  of the guide ring  10  (also see FIG.  9 A). Next, as shown in FIG. 9, the gauge  53  of the leverage-type micro-measurement instrument  50  is zeroed. Finally, as shown in FIG. 10, button  45  is rotated in a counterclockwise direction to move the probe  52  away from the guide ring  10  so as to measure the step difference of the step cross section of the guide ring  10  (also see FIG.  1 A). 
     It should be understood that the present invention can be used to measure other objects. The measurement is based on the measuring tool assembly  50  and the displacement of the measuring tool assembly  50 . 
     To sum up, the present invention provides an effective way to avoid manual errors from occurring. The friction loss of the guide ring and the degree of the step difference are quantified. Measured data according to the present invention can be used as a basis of determining lifetime of the guide ring and standard of recycling use of the guide ring. Further, the production cost is reduced. 
     Those skilled in the art will readily observe that numerous modification and alterations of the device may be made while retaining the teachings of the invention. Accordingly, the above disclosure should be construed as limited only by the metes and bounds of the appended claims.