Abstract:
A bipolar junction transistor (BJT) device including a base region, an emitter region and a collector region comprises a substrate, a deep well region in the substrate, a first well region in the deep well region to serve as the base region, a second well region in the deep well region to serve as the collector region, the second well region and the first well region forming a first junction therebetween, and a first doped region in the first well region to serve as the emitter region, the first doped region and the first well region forming a second junction therebetween, wherein the first doped region includes a first section extending in a first direction and a second section extending in a second direction different from the first direction, the first section and the second section being coupled with each other.

Description:
BACKGROUND OF THE INVENTION 
     The present invention generally relates to a semiconductor device and, more particularly, to a semiconductor bipolar junction transistor (BJT) device with an enhanced beta gain. 
     In a semiconductor BJT device, by controlling the voltages applied to its base and collector terminals, the device may operate in a forward-active mode. Taking an NPN-type BJT device as an example, i.e., a BJT device with a P-type base region and N-type collector and emitter regions, in operation, a positive voltage V BE  and a positive voltage V CE  higher than V BE  may be applied to the base terminals and the collector terminals, respectively. The emitter-base junction may be therefore forward-biased and the base-collector junction may be therefore reverse-biased, and a base current I B  and a collector current I C  which by definition is β F  times the base current I B  may be induced. The BJT device may therefore serve as a current amplifier with a current gain or beta gain β F . 
       FIG. 1A  is a schematic cross-sectional view of a BJT device  1 - 1  in prior art. Referring to  FIG. 1A , the BJT device  1 - 1  may include base terminals B, emitter terminals E and collector terminals C. When these terminals are appropriately biased, the junction between the base region and the emitter region, i.e., the emitter-base junction, may be forward-biased and the junction between the base region and the collector region, i.e., the base-collector junction, may be reverse-biased. The BJT device  1 - 1  may therefore operate in a forward-active mode, in which base currents I B  may be induced and flow in a base region from the base terminals B via an emitter region to the emitter terminals E. Meanwhile, collector currents I C  may be also induced and flow in a collector region from the collector terminals C via the base and emitter regions to the emitter terminals E, wherein the collector current I C  is β F  times the base current I B . The beta gain β F  may be a function of the area of the base region. For example, the current gain β F  may be increased as the base area of the BJT device  11 - 1  is decreased. However, the distance W 1  between a P +  region associated with the base terminals and an N +  region associated with the emitter terminals and the distance W 2  between the P +  region and the collector-base junction may be subject to a design rule limit. 
       FIG. 1B  is a layout of the BJT device  1 - 1  illustrated in  FIG. 1A . Referring to  FIG. 1B , the emitter region, i.e., the N +  region under the emitter terminals E, may be formed in a square pattern and the P +  region under the base terminals B may be formed in a ring pattern. The P +  region may substantially surround the emitter region and may be separated from the emitter region by W 1 . Furthermore, the P +  region may be separated from the collector-base junction by W 2 . Due to the limits of W 1  and W 2 , it may be difficult to directly downsize the area of the base region of the BJT device  1 - 1  in order to increase the beta gain without violating the design rules. 
     It may therefore be desirable to have a BJT device with a new layout that may achieve a downsized base area and in turn an enhanced beta gain while observing the design rules. 
     BRIEF SUMMARY OF THE INVENTION 
     The present invention is directed to a semiconductor bipolar junction transistor (BJT) device with an inventive arrangement of the base, emitter and collector regions thereof. 
     Examples of the present invention may provide a BJT device including a base region, an emitter region and a collector region. The BIT device may comprise a substrate, a deep well region in the substrate, a first well region in the deep well region to serve as the base region, a second well region in the deep well region to serve as the collector region, the second well region and the first well region forming a first junction therebetween, and a first doped region in the first well region to serve as the emitter region, the first doped region and the first well region forming a second junction therebetween, wherein the first doped region includes a first section extending in a first direction and a second section extending in a second direction different from the first direction, the first section and the second section being coupled with each other. 
     Some examples of the present invention may provide a BJT device including a base region, an emitter region and a collector region. The BJT device may comprise a substrate, a deep well region in the substrate, a first well region in the deep well region to serve as the base region, a second well region in the deep well region to serve as the collector region, a first doped region in the first well region to serve as the emitter region, at least one second doped region dispersed in the first well region over which at least one base electrode is disposed, and a third doped region in the second well region over which at least one collector electrode is disposed, wherein the at least one second doped region is dispersed between the first doped region and the third doped region. 
     Examples of the present invention may also provide a BJT device including a base region, an emitter region and a collector region. The BJT device may comprise a substrate, a deep well region in the substrate, a first well region in the deep well region to serve as the base region, a second well region in the deep well region to serve as the collector region, a first doped region in the first well region to serve as the emitter region, the first doped region including a first section extending in a first direction and a second section extending in a second direction different from the first direction, the first section and the second section being coupled with each other, and at least one second doped region dispersed in the first well region, wherein the at least one second doped region is separated by the first section and the second section of the first doped region. 
     Additional features and advantages of the present invention will be set forth in portion in the description which follows, and in portion will be obvious from the description, or may be learned by practice of the invention. The features and advantages of the invention will be realized and attained by means of the elements and combinations particularly pointed out in the appended claims. 
     It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention as claimed. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
       The foregoing summary, as well as the following detailed description of the invention, will be better understood when read in conjunction with the appended drawings. For the purpose of illustrating the invention, examples are shown in the drawings. It should be understood, however, that the invention is not limited to the precise arrangements and instrumentalities shown in the examples. 
       In the drawings: 
         FIG. 1A  is a schematic cross-sectional view of a bipolar junction transistor (BJT) device in prior art; 
         FIG. 1B  is a layout of the BJT device illustrated in  FIG. 1A ; 
         FIG. 2A  is a layout of a BJT device in accordance with an example of the present invention; 
         FIG. 2B  is a schematic cross-sectional view of the BJT device illustrated in  FIG. 2A  taken along a line corresponding to line AA′; 
         FIG. 3A  is a layout of a BJT device in accordance with another example of the present invention; 
         FIG. 3B  is a layout of a BJT device in accordance with still another example of the present invention; and 
         FIG. 3C  is a layout of a BJT device in accordance with yet another example of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Reference will now be made in detail to the present examples of the invention illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like portions. It should be noted that the drawings are in greatly simplified form and are not to precise scale. 
       FIG. 2A  is a layout of a bipolar junction transistor (BJT) device  2 - 1  in accordance with an example of the present invention. Referring to  FIG. 2A , the BJT device  2 - 1  may include a substrate  21 , a deep well region  22 , a first well region  23 , a second well region  24 , a first doped region  25 , second doped regions  26 - 1  to  26 - 4 , a third doped region  27  and a patterned conductive layer  28 . 
     The first doped region  25  may serve as an emitter region for the BJT device  2 - 1 . Unlike the emitter region of the BJT device  1 - 1  illustrated in  FIG. 1B  that takes the form of a square or rectangular pattern, the first doped region  25  may further include a first section  25 - 1  and a second section  25 - 2 , which may intersect each other in substantially a cross pattern. Specifically, the first section  25 - 1  may extend in a first direction and the second section  25 - 2  may extend in a second direction substantially orthogonal to the first direction. Moreover, the patterned conductive layer  28  may include contacts  28 - 1  over the first doped region  25 , which may serve as emitter electrodes for the first doped region  25 , i.e., the emitter region. 
     The first well region  23  may serve as a base region for the BJT device  2 - 1 . In the first well region  23 , the second doped regions  26 - 1  to  26 - 4  may be separated from one another by the first section  25 - 1  and the second section  25 - 2  of the first doped region  25 . Furthermore, each of the second doped regions  26 - 1  to  26 - 4  may be disposed in a quadrant defined by the first and the second sections  25 - 1  and  25 - 2  of the first doped region  25  and may be arranged to space apart from one of the first section  25 - 1  and second section  25 - 2  by a suitable distance in conformity with design rules. Moreover, the patterned conductive layer  28  may include contacts  28 - 2  over the second doped regions  26 - 1  to  26 - 4 , which may serve as base electrodes for the first well region  23 , i.e., the base region. 
     The first doped region  25  and the second doped regions  26 - 1  to  26 - 4  may be formed in the first well region  23  and substantially surrounded by the third doped region  27 . Furthermore, the first well region  23  and the second well region  24  may be formed in the deep well region  22 , and the first well region  23  may be substantially surrounded by the second well region  24 . Moreover, the second well region  24  may serve as a collector region for the BJT device  2 - 1 . The patterned conductive layer  28  may include contacts  28 - 3  over the third doped region  27 , which may serve as collector electrodes for the second well region  27 , i.e., the collector region. 
     Referring back to  FIG. 1B , the emitter doped region associated with the emitter electrodes “E” is surrounded by the base doped region (P +  region) associated with the base electrodes “B”, which in turn is surrounded by the collector doped region associated with the collector electrodes “C”. Unlike the arrangement illustrated in  FIG. 1B , in the present example according to the present invention, the second doped regions  26 - 1  to  26 - 4  (over which the base electrodes  28 - 2  may be disposed) are dispersed in the first well region  23  so that the first doped region  25  (over which the emitter electrodes  28 - 1  may be disposed) is not surrounded by the second doped regions  26 - 1  to  26 - 4 . Specifically, in the present example, the second doped regions  26 - 1  to  26 - 4  may be dispersed around the first doped region  25 . 
       FIG. 2B  is a cross-sectional view of the BJT device  2 - 1  illustrated in  FIG. 2A  taken along a line corresponding to line AA′. 
     Referring to  FIG. 2B , isolation structures  29  such as field oxide (FOX) may be disposed at desired locations to provide electrical isolation in the BJT device  2 - 1 . The substrate  21  of the BJT device  2 - 1  may include a first-type impurity, such as P-type impurity. The deep well region  22 , which may include a second-type impurity, such as N-type impurity, may be formed in a portion of the substrate  21 . Furthermore, the patterned second well region  24 , which may include the second-type impurity, may be formed in the deep well region  22 . The first well region  23 , which may include the first-type impurity, may also be formed in the deep well region  22 . Moreover, the second doped regions  26 - 1  to  26 - 4  may include the first-type impurity while the first doped region  25  and the third doped region  27  may include the second-type impurity, resulting in an npn-type BJT device  2 - 1 , where a first junction (base-emitter junction) may exist between the first well region  23  and the first doped region  25 , and a second junction (base-collector junction) may exist between the first well region  23  and the second well region  24 , 
     To comply with the design rules of the semiconductor process for manufacturing the BJT device  2 - 1 , the distance W 3  between the first doped region  25  and the second doped regions  26 - 1  to  26 - 4  in terms of mask may not be less than a lower limit. For example, W 3  may not be less than 0.9 um given a 0.5-um complementary metal-oxide-semiconductor (CMOS) process. Moreover, the distance W 4  between the second doped regions  26 - 1  to  26 - 4  and the junction associated with the first well region  23  and the second well region  24  may not be less than another lower limit so as to comply with the above-mentioned design rules. For example, W 4  may not be less than 0.3 um given the 0.5-um CMOS process. 
     Referring back to  FIG. 1B , a single base doped region (P +  region) may be disposed between the base-emitter junction and the base-collector junction. Unlike the arrangement illustrated in  FIG. 1B , in the present example, a number of second doped regions  26 - 1  to  26 - 4  may be disposed between the base-emitter junction and the base-collector junction. 
       FIG. 3A  is a layout of a BJT device  3 - 1  in accordance with another example of the present invention. Referring to  FIG. 3A , the BJT device  3 - 1  may be similar to a quarter of the BJT device  2 - 1  described and illustrated in  FIG. 2A . 
     Specifically, the BJT device  3 - 1  may include in the deep well region  22  a first well region  23   a  and a second well region  24   a . The first well region  23   a  and the second well region  24   a  may serve as a base region and a collector region for the BJT device  3 - 1 , respectively. A base-collector junction may exist between the first well region  23   a  and the second well region  24   a . Furthermore, the BJT device  3 - 1  may include a first doped region  25   a  in the first well region  23   a . The first doped region  25   a  may serve as an emitter region for the BJT device  3 - 1 . A base-emitter junction may exist between the first well region  23   a  and the first doped region  25   a.    
     The first doped region  25   a  may include a first section  25   a - 1  and a second section  25   a - 2  coupled to each other. In one example according to the present invention, the first section  25   a - 1  may extend in a first direction and the second section  25   a - 2  may extend in a second direction different from the first direction. In another example, the first section  25   a - 1  may extend in a first direction and the second section  25   a - 2  may extend in a second direction substantially orthogonal to the first direction. Furthermore, one or more second doped region  26   a  may be dispersed in the first well region  23   a  substantially between the first doped region  25   a  and a third doped region  27   a . The at least one second doped region  26   a  may be spaced apart from one of the first section  25   a - 1  and second section  25   a - 2  by a suitable distance in conformity with design rules. Moreover, the first doped region  25   a  is not surrounded by the at least one second doped region  26   a.    
       FIG. 3B  is a layout of a BJT device  3 - 2  in accordance with still another example of the present invention. Referring to  FIG. 3B , the BJT device  3 - 2  may be similar to the BJT device  3 - 1  illustrated in  FIG. 5A  except that, for example, the first doped region  25   b  of the BJT device  3 - 2  may have a substantially uniform width, which may allow more contacts  28 - 1  to be disposed thereon. 
       FIG. 3C  is a layout of a BJT device  3 - 3  in accordance with yet another example of the present invention. Referring to  FIG. 3C , the BJT device  3 - 3  may be similar to a half of the BJT device  2 - 1  illustrated in  FIG. 2A . Specifically, the BJT device  3 - 3  may include in the deep well region  22  a first well region  23   c  and a second well region  24   c . The first well region  23   c  and the second well region  24   c  may serve as a base region and a collector region for the BJT device  3 - 3 , respectively. A base-collector junction may exist between the first well region  23   c  and the second well region  24   c . Furthermore, the BJT device  3 - 3  may include a first doped region  25   c  in the first well region  23   c . The first doped region  25   c  may serve as an emitter region for the BJT device  3 - 3 . A base-emitter junction may exist between the first well region  23   c  and the first doped region  25   c.    
     The first doped region  25   c  may include a first section  25   c - 1 , a second section  25   c - 2  and a third section  25   c - 3  coupled to one another. In one example according to the present invention, the first section  25   c - 1 , the second section  25   c - 2  and the third section  25   c - 3  may extend in a first direction, a second direction and a third direction, respectively, which may be different from one another. In another example, the first section  25   c - 1  and the third section  25   c - 3  may extend in a first direction and the second section  25   c - 2  may extend in a second direction substantially orthogonal to the first direction. Furthermore, second doped regions  26   c - 1  and  26   c - 2  may be dispersed in the first well region  23   c , wherein one or more second doped region  26   c - 1  may be substantially disposed between the first and third sections  25   c - 1 ,  25   c - 3  and a third doped region  27   c , and one or more second doped region  26   c - 2  may be substantially disposed between the second and third sections  25   c - 2 ,  25   c - 3  and the third doped region  27   c . The second doped regions  26   c - 1  and  26   c - 2  may be spaced apart from one of the first section  25   c - 1 , second section  25   c - 2  and third section  25   c - 3  by a suitable distance in conformity with design rules. Moreover, the first doped region  25   c  is not surrounded by the second doped regions  26   c - 1  and  26   c - 2 . 
     It will be appreciated by those skilled in the art that changes could be made to the examples described above without departing from the broad inventive concept thereof. It is understood, therefore, that this invention is not limited to the particular examples disclosed, but it is intended to cover modifications within the spirit and scope of the present invention as defined by the appended claims.