Abstract:
The present invention discloses a semiconductor PN junction structure and a manufacturing method thereof. From top view, the PN junction includes a staggered comb-teeth structure. The PN junction forms a depletion region with enhanced breakdown voltage, hence broadening the applications of a semiconductor device having such PN junction.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of Invention 
         [0002]    The present invention relates to a semiconductor PN junction structure and a manufacturing method thereof, in particular to such structure and method that enhances the breakdown voltage of a semiconductor device. 
         [0003]    2. Description of Related Art 
         [0004]      FIGS. 1A and 1B  show, by top view and cross-section view respectively, a prior art semiconductor PN junction structure. As shown in the top view and cross-section view, a P-type region  11  and an N-type region  12  interface with each other to form a PN junction  13 . From top view, the interface of the PN junction  13  is approximately a straight line. When no bias voltage, or when a reverse bias voltage is exerted on the P-type region  11  and the N-type region  12  (that is, a positive voltage is exerted on the N-type region  12  and a negative voltage is exerted on the P-type region  11 ), as shown in  FIG. 1C , a depletion region  14  is formed around the PN junction  13 . The width and the electric field of the depletion region  14  are related to the bias voltage, and the species and concentration of P-type impurities and N-type impurities in the P-type region  11  and the N-type region  12 . When no bias voltage is exerted on the PN junction  13 , the strength and distribution of the electric field are shown as  FIG. 1D , while the width of the depletion region  14  is d 1  as shown in  FIG. 1C . In  FIG. 1D , the horizontal axis represents the position x; the vertical axis represents the electric field E; and the bold line  15  indicates the strength distribution of the electric field. 
         [0005]    The above-mentioned PN junction is widely applied in various semiconductor devices but it has a limit in its breakdown voltage. As the technology trend requires lower operation voltage of a semiconductor device and lower thermal budget in a semiconductor manufacturing process, the concentrations of the P-type and N-type well regions increase, while the breakdown voltage of the PN junction decreases. Hence, if it is desired to increase the breakdown voltage of the PN junction without changing the concentration of the impurities, a new PN junction structure is required such that a semiconductor device having such new PN junction structure may be applied to broader range of applications. 
         [0006]    In view of the above, the present invention proposes a semiconductor PN junction structure and a manufacturing method for enhancing the breakdown voltage of a semiconductor device, to overcome the drawback in the prior art and provide a broader range of applications. 
       SUMMARY OF THE INVENTION 
       [0007]    The objectives of the present invention are to provide a semiconductor PN junction structure and a manufacturing method. 
         [0008]    To achieve the foregoing objectives, the present invention provides a semiconductor PN junction structure comprising: a semiconductor substrate; and a PN junction including a P-type region and an N-type region interfacing with each other in the semiconductor substrate, wherein from top view, the PN junction includes a staggered comb-teeth interface between the P-type region and N-type region. 
         [0009]    The staggered comb-teeth interface may be any regularly or irregularly staggered shape, wherein from top view, the comb-teeth interface preferably includes one or more of the following shapes: rectangle-shape, wave-shape, jag-shape and arc-shape. Besides, an opposite conductive type island-shaped doped region may be provided in the P-type region or the N-type region. 
         [0010]    In one embodiment, the PN junction has multiple layers of comb-teeth interfaces under a surface of the semiconductor substrate. 
         [0011]    When a reverse bias voltage is exerted on the PN junction to form depletion regions around the multiple teeth, the depletion regions are preferably connected together to become one depletion region. 
         [0012]    In another perspective of the present invention, it provides a method for manufacturing a semiconductor PN junction structure comprising: providing a semiconductor substrate; and implanting impurities to form a PN junction including a P-type region and an N-type region interfacing with each other in the semiconductor substrate, wherein from top view, the PN junction includes a staggered comb-teeth interface between the P-type region and N-type region. 
         [0013]    The objectives, technical details, features, and effects of the present invention will be better understood with regard to the detailed description of the embodiments below, with reference to the drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]      FIG. 1A  illustrates, by top-view, a schematic diagram of a prior art semiconductor PN junction structure. 
           [0015]      FIG. 1B  illustrates, by cross-section view, a schematic diagram of the prior art semiconductor PN junction structure. 
           [0016]      FIG. 1C  illustrates a depletion region formed in the prior art semiconductor PN junction structure. 
           [0017]      FIG. 1D  shows the strength and distribution of the electric field of the prior art semiconductor PN junction structure. 
           [0018]      FIG. 2A  shows, by top-view, a first embodiment of the semiconductor PN junction according to the present invention. 
           [0019]      FIG. 2B  shows the electric field of the semiconductor PN junction of the first embodiment according to the present invention. 
           [0020]      FIG. 2C  illustrates a comparison between the present invention and the prior art with respect to the strength and width of the electric field of the depletion region. 
           [0021]      FIG. 3  shows, by top-view, another embodiment of the semiconductor PN junction according to the present invention. 
           [0022]      FIG. 4  shows, by top-view, yet another embodiment of the semiconductor PN junction according to the present invention. 
           [0023]      FIG. 5  shows, by top-view, a further other embodiment of the semiconductor PN junction according to the present invention. 
           [0024]      FIG. 6  shows, by top-view, a still other embodiment of the semiconductor PN junction according to the present invention. 
           [0025]      FIGS. 7A and 7B  show another embodiment of the present invention. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0026]    The drawings as referred to throughout the description of the present invention are for illustration only, to show the interrelations between the regions, but not drawn according to actual scale. 
         [0027]      FIGS. 2A-2C  show the first embodiment of the present invention, wherein  FIG. 2A  shows, by top view, a semiconductor PN junction formed by implanting impurities into a semiconductor substrate. As shown in  FIG. 2A , a semiconductor P-type region  21  and an N-type region  22  interface with each other to form a PN junction  23 , wherein from top view, the PN junction  23  includes a staggered comb-teeth interface between the P-type region  21  and N-type region  22 .  FIG. 2B  shows the electric field of the PN junction  23 , wherein because the PN junction  23  includes a staggered comb-teeth interface, depletion regions are formed along the interface, which turn left and right as the interface goes left and right, and if a spacing between the comb-teeth is not too large, the depletion regions around the comb-teeth are connected together to become one depletion region as the depletion region  24  shown in  FIG. 2B . When no bias voltage, or a reverse bias voltage is exerted on the PN junction  23 , the width of the depletion region  24  is d 2 . 
         [0028]      FIG. 2C  illustrates a comparison between the present invention and the prior art, wherein the bold line  25  indicates the strength and distribution of the electric field of the PN junction according to the present invention, while the dotted line  15  indicates the strength and distribution of the electric field of the PN junction according to the prior art. It can be seen from  FIG. 2C  that the present invention is superior to the prior art, because when the same reverse bias voltage is exerted on the PN junction  23 , the width of the voltage-withstanding region, that is, the depletion region  24 , is extended to d 2  which is wider than the width d 1  of the depletion region  14  in the prior art, and the electric field in the depletion region  24  is weaker than that in the depletion region  14  of the prior art. That is, when the same reverse bias voltage is exerted, the embodiment according to the present invention provides a weaker electric field and a wider depletion region, this means that the present invention can withstand a higher reverse bias voltage than that in the prior art, so that a semiconductor device having a PN junction of the present invention can be applied to a broader range of applications. 
         [0029]    Next,  FIGS. 3-6  show, by way of example, different shapes and distributions to embody the present invention. FIGS.  3 - 6  respectively show, by top view, four other PN junction of embodiments according to the present invention. Besides the rectangle-shaped comb-teeth interface shown in  FIG. 2A , the semiconductor PN junction may include, for example but not limited to, a wave-shaped, jag-shaped and arc-shaped interface shown in  FIGS. 3-5 , respectively. And as  FIG. 6  shows, an opposite conductive type doped region may be provided in the P-type region  21  and/or the N-type region  22  by implanting different conductive types of impurities. In fact, the “staggered comb-teeth interface” can be any regularly or irregularly staggered shape as long as the non-straight interface can broaden the depletion region and reduce the electric field. 
         [0030]      FIGS. 7A and 7B  show another embodiment of the present invention. As  FIG. 7A  shows, the staggered comb-teeth interface should not be limited to a single-layer structure, but also can include multiple layers of staggered comb-teeth interfaces under the surface of the semiconductor substrate. Furthermore, the different layers of comb-teeth interfaces need not be aligned with one another, but can be shifted from one other.  FIG. 7B  shows the cross-section of the PN junction according to this embodiment, wherein when the PN junctions of an upper layer and a lower layer are shifted from one the other, a vertical PN junction is formed. A depletion region is formed as the shaded region shown in the figure. According to one embodiment of the present invention, the depletion regions which are shifted from one another vertically is preferably connected together to become one depletion region so that the electric field is reduced and the breakdown voltage is increased. 
         [0031]    The present invention has been described in considerable detail with reference to certain preferred embodiments thereof. It should be understood that the description is for illustrative purpose, not for limiting the scope of the present invention. Those skilled in this art can readily conceive variations and modifications within the spirit of the present invention. For example, other manufacturing process steps or structures which do not affect the characteristics of the devices, such as a deep-well region, etc. As another example, the semiconductor substrate may be P-type or N-type, and in this case, it is not absolutely necessary for the PN junction to be formed by implanting two different conductive type impurities; in some cases, the PN junction may be formed just by implanting the impurities opposite to the conductive type of the semiconductor substrate. Thus, the present invention should cover all such and other modifications and variations, which should be interpreted to fall within the scope of the following claims and their equivalents.