Abstract:
The invention relates to a single-chip gyro device, which includes a substrate, a plurality of metal layers and a plurality of dielectric layers, and a plurality of metal side walls. Each of the dielectric layers is located between two adjacent layers selected from a layer group consisting of the metal layers and the substrate. The metal side walls are located on edges of the plurality of dielectric layers so as to prevent the dielectric layers from being undercut and form a mechanical structure together with the metal layers and the dielectric layers to connect the circuit formed on the substrate.

Description:
FIELD OF THE INVENTION  
       [0001]     The invention relates to a gyro device, and more particularly to a gyro device implemented by the back-end semiconductor manufacturing process.  
       BACKGROUND OF THE INVENTION  
       [0002]     The conventional gyro device is operated in a way constantly pointing to a fixed direction by virtue of the concept of conservation of angular momentum. Usually, the gyro device is primarily designed to measure the Coriolis force and is applied to airplanes, airships, satellites, submarines, ships, missiles and so forth. Currently, most of the gyro devices are manufactured in a traditional mechanical means, and hence it is relatively bulky in terms of size and weight. Whereas, if the gyro device is manufactured in a semiconductor means, the mechanical structure and the circuits thereof are first fabricated separately and then connected with wires for the sake of maintaining the sensitivity. This would result in higher noise. For example, please refer to  FIG. 1 , which shows the schematic diagram of a conventional mechanical gyro device. The conventional mechanical gyro device includes a mechanical structure chip  1  and a circuit chip  2  connected with each other by means of wires  3 . This method results in larger parasite effect, bulky components and a higher cost.  
         [0003]     Please refer to  FIG. 2 , which shows a schematic diagram of a single-chip gyro device using the single-chip method to form a BiCMOS circuit  4  and a thick polycrystal layer  5 . The drawback of the prior art arises from a rectangular structure, the readout of the sensing signal being prone to be non-linear, the temperature drift and the impact on the stability of the manufacturing process.  
         [0004]     As far as the sensing theory of the gyro device is concerned, the formation of a symmetrically angular mechanical structure is the optimal design. However, a single chip integrating the mechanical structure and the circuit has its bottleneck to break through with the current technology. As a result, complicated circuit design is brought into play to overcome the nonlinear variation of the sensing signal, and the asymmetrical signal shift and the mismatching manufacturing process caused by temperature. Meanwhile, the conventional method roughly carries out the layout design without further making the most of the mature standard semiconductor manufacturing process.  
         [0005]     For overcoming the drawbacks of the prior art, the present invention provides a novel single-chip gyro device implemented by the back-end manufacturing process, which brings about an improved design of the gyro device.  
       SUMMARY OF THE INVENTION  
       [0006]     In accordance with a first aspect of the present invention, a gyro device is provided. The provided gyro device contains a substrate, a plurality of metal layers and a plurality of dielectric layers, wherein each of the plurality of dielectric layers is located between two adjacent layers selected from a layer group consisting of the plurality of metal layers and the substrate, and a plurality of metal side walls located on edges of the plurality of dielectric layers.  
         [0007]     Preferably, the gyro device is formed on a single chip.  
         [0008]     Preferably, the metal layers, the dielectric layers and the metal side walls form a mechanical structure.  
         [0009]     Preferably, the mechanical structure is fabricated by a back-end semiconductor manufacturing process.  
         [0010]     Preferably, the back-end semiconductor manufacturing process includes an etching process, a chemical vapor deposition process and a planarization process.  
         [0011]     Preferably, the gyro device further includes a circuit layer formed on the substrate.  
         [0012]     Preferably, the metal side walls and the metal layers provide an electrical connection between the circuit layer and the mechanical structure.  
         [0013]     Preferably, the mechanical structure is annular.  
         [0014]     Preferably, the mechanical structure is circular.  
         [0015]     Preferably, a lowest one of the dielectric layers is removed by an etching process based on a circuit layout design so as to make the mechanical structure movable.  
         [0016]     Preferably, the substrate is removed by an etching process based on a circuit layout design so as to make the mechanical structure movable.  
         [0017]     In accordance with a second aspect of the present invention, a mechanical structure for a gyro device is provided. The provided mechanical structure contains a plurality of metal layers, a plurality of dielectric layers respectively staggered between two of the metal layers, and a plurality of metal side walls respectively located on edges of the dielectric layers.  
         [0018]     Preferably, the mechanical structure is formed on a single-chip gyro device.  
         [0019]     Preferably, the mechanical structure is fabricated by a back-end semiconductor manufacturing process.  
         [0020]     Preferably, the back-end semiconductor manufacturing process includes an etching process, a chemical vapor deposition process and a planarization process.  
         [0021]     Preferably, the single-chip gyro device further includes a substrate and a circuit layer formed on the substrate.  
         [0022]     Preferably, the metal side walls and the metal layers provide an electrical connection between the circuit layer and the mechanical structure.  
         [0023]     Preferably, the mechanical structure is annular.  
         [0024]     Preferably, the mechanical structure is circular.  
         [0025]     Preferably, one of the dielectric layers is removed by an etching process based on a circuit layout design so as to make the mechanical structure movable.  
         [0026]     The foregoing and other features and advantages of the present invention will be more clearly understood through the following descriptions with reference to the drawing, wherein: 
     
    
     F BRIEF DESCRIPTION OF THE DRAWINGS  
       [0027]      FIG. 1  is a schematic diagram showing the conventional gyro device;  
         [0028]      FIG. 2  is a schematic diagram showing the conventional single-chip gyro device;  
         [0029]      FIG. 3  is a schematic diagram showing the single-chip gyro device prior to etching;  
         [0030]      FIG. 4  is a schematic diagram showing the single-chip gyro device after etching;  
         [0031]      FIG. 5  is a schematic diagram showing the single-chip gyro device of a preferred embodiment of the present invention prior to etching;  
         [0032]      FIG. 6  is a schematic diagram showing the single-chip gyro device of a preferred embodiment of the present invention after etching; and  
         [0033]      FIG. 7  is a schematic diagram showing the movable mechanical structure of a preferred embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0034]     The present invention will now be described more specifically with reference to the following embodiments. It is to be noted that the following descriptions of preferred embodiments of this invention are presented herein for purposes of illustration and description only; it is not intended to be exhaustive or to be limited to the precise form disclosed.  
         [0035]     Please refer to  FIG. 3 , which is a schematic diagram of the conventional single-chip gyro device prior to etching. Prior to etching, the conventional single-chip gyro device contains a substrate  10 , a circuit layer  11 , a dielectric layer  20 , a first metal layer  31 , a second metal layer  32 , a third metal layer  33  and a fourth metal layer  34 . Please refer to  FIG. 4 , which is a schematic diagram of the conventional single-chip gyro device after etching. After etching, the conventional single-chip gyro device contains the substrate  10 , the circuit layer  11 , the plurality of dielectric layers  20 , the first metal layer  31 , the second metal layer  32 , the third metal layer  33  and the fourth metal layer  34 . It is noted that the mechanical structure is actually cut out by means of an etching process and is composed of all metal layers and dielectric layers. As the wet etching or the dry etching hardly has a perfect selectivity for preparing the etching solution, the dielectric layers are all undercut to form an indentation thereon. Such undercut phenomenon results in the roughness and unevenness of the surface, which deteriorates the external appearance and the quality of the mechanical structure and further adds the difficulty to the designs of the elastic coefficient and the damping of the system. Besides, the existence of the dielectric layers leads to a smaller sensing area of the gyro device, making the sensitivity thereof even worse.  
         [0036]     In order to improve the above-mentioned condition and enhance the sensing capability of the gyro device, an improved single-chip gyro device is provided as shown in  FIG. 5 . Please refer to  FIG. 5 , which is a schematic diagram of the single-chip gyro device of a preferred embodiment of the present invention prior to etching. The single-chip gyro device contains a substrate  510 , a circuit layer  511 , a plurality of dielectric layers  520 , a first metal layer  531 , a second metal layer  532 , a third metal layer  533 , a fourth metal layer  534  and a plurality of vias  540 . Please refer to  FIG. 6 , which is a schematic diagram of the single-chip gyro device of a preferred embodiment of the present invention after etching. After etching, the single-chip gyro device contains the substrate  510 , the circuit layer  511 , the plurality of dielectric layers  520 , the first metal layer  531 , the second metal layer  532 , the third metal layer  533 , the fourth metal layer  534  and the plurality of vias  540 . The metal layers  531 ,  532 ,  533  and  534  are formed on the substrate  510 , and the lowest one of the dielectric layers  520  is formed between the substrate  510  and the metal layer  531 . Either of the dielectric layers  520  is formed between two of the metal layers  531 ,  532 ,  533  and  534 . The metal layers  531 ,  532 ,  533  and  534  and the dielectric layers  520  are formed as a mechanical structure  550 . The vias  540  that form a metal side wall connect the metal layers  531 ,  532 ,  533  and  534  and are exposed outside the dielectric layers  520  so as to prevent the dielectric layers  520  from being undercut. The existence of the vias  540  creates a wall to prevent the dielectric layers  520  sandwiched between the metal layers  31 ,  32 ,  33  and  34  from being undercut during the etching process. This not only allows a smooth metal surface and an excellent connection with equal potential using the vias  540  and the metal layers  531 ,  532 ,  533  and  534 , but also augments the sensing area or the capacitance of the gyro device, thereby enhancing the sensitivity of the gyro device.  
         [0037]     The mechanical structure  550  of the single-chip gyro device in  FIG. 6  is implemented by means of the back-end semiconductor manufacturing processes including etching, chemical vapor deposition (CVD) and planarization. The etching process is unnecessary to be implemented through ion etching. Usually, the etching process will undercut the dielectric layers  520 . As the existence of the vias  540  or the metal side wall prevent the dielectric layers  520  from being undercut, the wet etching is sufficient for the manufacturing process of the present invention to generate the mechanical structure  550 .  
         [0038]     The mechanical structure  550  in  FIG. 6  utilizes the metal layer  531  on the bottom to electrically connect with the circuit layer  511  on the substrate  510 . In consideration of better inertial sensing and simplification of the circuit design for the layout, the mechanical structure  550  is preferred to be annular or circular.  
         [0039]     Please refer to  FIG. 7 , which is a schematic diagram showing the movable mechanical structure of a preferred embodiment of the present invention. The movable mechanical structure includes a substrate  710 , a plurality of dielectric layers  720 , a first metal layer  731 , a second metal layer  732 , a third metal layer  733 , a fourth metal layer  734  and a plurality of vias  740 . On the substrate  710  where no circuit layer is formed, the lowest one of the dielectric layers  720  is removed so as to form a movable mechanical structure  751 . Contrary to the movable mechanical structure  751 , the stationary mechanical structure  752  on the right is fixed on the substrate  710 .  
         [0040]     In summary, the present invention provides a design using the back-end integrated circuit manufacturing process to implement the single-chip gyro device. In contrast to the prior art designed with the rough layout and failing to fully utilize the mature standard semiconductor manufacturing process, the present invention brings up a better layout design to attain better characteristics and quality. Consequently, the simplification of the circuit configuration, the compact size fulfilled by the single-chip design, high performance and low cost make the present invention innovative, progressive and practical.  
         [0041]     While the invention has been described in terms of what are presently considered to be the most practical and preferred embodiments, it is to be understood that the invention need not to be limited to the disclosed embodiment. On the contrary, it is intended to cover various modifications and similar arrangements included within the spirit and scope of the appended claims, which are to be accorded with the broadest interpretation so as to encompass all such modifications and similar structures.