Abstract:
A method for fabricating a semiconductor-based planar micro-tube discharger structure is provided, including the steps of forming on a substrate two patterned electrodes separated by a gap and at least one separating block arranged in the gap, forming an insulating layer over the patterned electrodes and the separating block, and filling the insulating layer into the gap. At least two discharge paths are formed. The method can fabricate a plurality of discharge paths in a semiconductor structure, the structure having very high reliability and reusability.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a Divisional of co-pending application Ser. No. 13/464,506, filed on May 4, 2012, for which priority is claimed under 35 U.S.C. §120; and this application claims priority of Application No. 101106427 filed in Taiwan. R.O.C. on Feb. 24, 2012 under 35 U.S.C. §119; the entire contents of all of which are hereby incorporated by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a semiconductor technology, particularly to a semiconductor-based planar micro-tube discharger structure and a method for fabricating the same. 
     2. Description of the Related Art 
     When connected with a long signal line, power cable or antenna, an electronic device is exposed to a transient phenomenon caused by inductance. The inductance is generated by lightning or electromagnetic pulses. An electric surge arrester protects an electronic device against the transient phenomenon via absorbing electric energy or grounding the electronic device. An electric surge arrester should be able to protect an electronic device against the transient phenomenon automatically and repeatedly and able to recover autonomously. 
     A gas tube is normally used to protect electronic devices but is also used as a switch device of a power switching circuit of such as a reel assembly or a vehicular gas discharge headlight. Refer to  FIG. 1  for an early-stage gas tube. The conventional gas tube comprises two solid-state electrodes  10  arranged at two ends of a tube  12  and separated by a gaseous gap  14  or a mica layer. The gas tube only has a single gas discharge path. The electrodes  10  will be gradually shortened during long-term use. Thus, the distance between two electrodes  10  will increase gradually. Finally, the electric field between the two electrodes  10  becomes insufficient to induce electric discharge. Further, the distance between the two electrodes  10  is hard to precisely control in fabrication. Such a problem results in that the actual breakdown voltage of the gas tube is often deviated from the nominal breakdown voltage by several folds. Therefore, the conventional gas tube is hard to protect ordinary electronic products working at low voltage but only suitable to protect against great electric surges in a high voltage environment. Therefore, the conventional gas tube lacks sufficient reliability and reusability but has a very high dropout rate. 
     Accordingly, the present invention proposes a semiconductor-based planar micro-tube discharger structure and a method for fabricating the same to overcome the abovementioned problems. 
     SUMMARY OF THE INVENTION 
     The primary objective of the present invention is to provide a planar micro-tube discharger structure and a method for fabricating the same, wherein a separating block is arranged between two electrodes to establish at least two discharge paths, whereby the micro-tube discharger has high reliability and high reusability. 
     To realize the abovementioned objective, the present invention proposes a planar micro-tube discharger structure, which comprises a substrate; two patterned electrodes arranged on the substrate and separated by a gap; at least one separating block arranged in the gap and made of a metallic or insulating material; and an insulating layer formed over the patterned electrodes and the separating block and filled into the gap to create at least two discharge paths. The patterned electrodes discharge via the discharge paths. When made of a metallic material, the separating block can stabilize the current direction under a fixed electric field. 
     The present invention also proposes a method for fabricating a planar micro-tube discharger structure, which comprises steps: forming two patterned electrodes separated by a gap and at least one separating block arranged in the gap and made of a metallic or insulating material; forming an insulating layer over the patterned electrodes and the separating block and filling the insulating layer into the gap to create at least two discharge paths interconnecting the patterned electrodes. When made of a metallic material, the separating block can stabilize the current direction under a fixed electric field. 
     Below, embodiments are described in detail in cooperation with drawings to make easily understood the technical contents, characteristics and accomplishments of the present invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  schematically shows a conventional gas tube; 
         FIG. 2  is a sectional view schematically showing that an insulating layer is deposited on a thinner metallic layer having a wider gap according to the present invention; 
         FIG. 3  is a sectional view schematically showing that an insulating layer is deposited on a thicker Metallic layer having a narrower gap according to the present invention; 
         FIG. 4  is a sectional view schematically showing a planar micro-tube discharger structure according to a first embodiment of the present invention; 
         FIG. 5  is a diagram schematically showing patterned electrodes and a separating block of the planar micro-tube discharger structure according to the first embodiment of the present invention; 
         FIGS. 6(   a )- 6 ( c ) are sectional views schematically showing the steps of fabricating the planar micro-tube discharger structure according to the first embodiment of the present invention; 
         FIG. 7  is a sectional view schematically showing a planar micro-tube discharger structure according to a second embodiment of the present invention; 
         FIG. 8  is a diagram schematically showing patterned electrodes, separating blocks and a first sub-insulating layer of the planar micro-tube discharger structure according to the second embodiment of the present invention; 
         FIGS. 9(   a )- 9 ( e ) are sectional views schematically showing the steps of fabricating the planar micro-tube discharger structure according to the second embodiment of the present invention; 
         FIG. 10  is a sectional view schematically showing a planar micro-tube discharger structure according to a third embodiment of the present invention; 
         FIG. 11  is a diagram schematically showing patterned electrodes and a separating block of the planar micro-tube discharger structure according to the third embodiment of the present invention; 
         FIG. 12(   a ) and  FIG. 12(   b ) are sectional views schematically showing the steps of fabricating the planar micro-tube discharger structure according to the third embodiment of the present invention; 
         FIG. 13  is a sectional view schematically showing a planar micro-tube discharger structure according to a fourth embodiment of the present invention; 
         FIG. 14  is a diagram schematically showing patterned electrodes and a separating block of the planar micro-tube discharger structure according to the fourth embodiment of the present invention; 
         FIG. 15(   a ) and  FIG. 15(   b ) are sectional views schematically showing the steps of fabricating the planar micro-tube discharger structure according to the fourth embodiment of the present invention; 
         FIG. 16  is a sectional view schematically showing a planar micro-tube discharger structure according to a fifth embodiment of the present invention; 
         FIG. 17  is a diagram schematically showing patterned electrodes, separating blocks and a first sub-insulating layer of the planar micro-tube discharger structure according to the fifth embodiment of the present invention; 
         FIGS. 18(   a )- 18 ( d ) are sectional views schematically showing the steps of fabricating the planar micro-tube discharger structure according to the fifth embodiment of the present invention; 
         FIG. 19  is a sectional view schematically showing a planar micro-tube discharger structure according to a sixth embodiment of the present invention; 
         FIG. 20  is a diagram schematically showing patterned electrodes, separating blocks and cover blocks of the planar micro-tube discharger structure according to the sixth embodiment of the present invention; 
         FIGS. 21(   a )- 21 ( d ) are sectional views schematically showing the steps of fabricating the planar micro-tube discharger structure according to the sixth embodiment of the present invention; and 
         FIG. 22  is a diagram schematically showing patterned electrodes and separating blocks of a planar micro-tube discharger structure according to the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Firstly is introduced the principle of the present invention. Refer to  FIG. 2  and  FIG. 3 . In  FIG. 2 , a metallic layer  17  is formed on a substrate  16 . The metallic layer  17  has a gap  18 . An insulating layer  19  is deposited on the metallic layer  17  with a chemical vapor deposition method. As the gap  18  is not wide and has a high step ratio, the insulating layer  19  has a cavity in the gap  18 . In  FIG. 3 , a metallic layer  21  is formed on a substrate  20 . The metallic layer  21  has a gap  22 . An insulating layer  23  is deposited on the metallic layer  21  with a chemical vapor deposition method. The metallic layer  21  is thicker than the metallic layer  17 , and the gap  22  is narrower than the gap  18 . Therefore, the step ratio in  FIG. 3  is higher than the step ratio in  FIG. 2 . Thus, a cavity is more likely to form in the gap  22 . In other words, the higher the step ratio of a gap is, the more likely a cavity is formed in the gap, which is exactly the principle that the present invention is based on. 
     Below is introduced a first embodiment. Refer to  FIG. 4  and  FIG. 5 . In the first embodiment, the planar micro-tube discharger structure comprises a substrate  24  made of silicon; two patterned electrodes  26  made of a metallic material, formed on the substrate  24  and separated by a gap  28 ; at least one separating block  30  in form of a metallic block  32 , arranged in the gap  28 , and not connected with any electric potential; a first insulating layer  34  comprises silicon dioxide or silicon nitride. The first insulating layer  34  is formed over the patterned electrodes  26  and the separating block  30 , and filled into the gap  28  originally containing air or inert gas. The air or inert gas in the gap  28  facilitates formation of at least two discharge paths. The patterned electrodes  26  discharge via the discharge paths. In the first embodiment, the planar micro-tube discharger structure has one separating block  30  and two discharge paths. When the potential of the two patterned electrodes  26  reaches the breakdown electric field intensity, tip discharge occurs. As the breakdown electric field intensity of vacuum or air is 100 times smaller than that of silicon dioxide or silicon nitride, the discharge current proceeds from one tip to another tip along the discharge paths generated by the step ratio of the gap. As not all tips discharge, it is unnecessary to demand absolute structural uniformity of the discharge paths. Electric discharge inevitably produces by-products blocking the discharge paths. However, the present invention can form many discharge paths in the plane. Therefore, the present invention outperforms the conventional gas tube in reliability and reusability. 
     In the first embodiment, the gap  28  does not contain any material except air. Alternatively, the gap  28  may be filled with a low-permittivity layer, and the first insulating layer  34  is formed over the low-permittivity layer, whereby discharge paths are created along the low-permittivity layer. The permittivity of the low-permittivity layer should be lower than that of the first insulating layer  34  and higher than that of the patterned electrodes  26 . 
     Below is introduced the process of fabricating the planar micro-tube discharger structure of the first embodiment. Refer to  FIGS. 6(   a )- 6 ( c ). Firstly, form a metallic layer  36  on a substrate  24 , as shown in  FIG. 6(   a ). Next, remove a portion of the metallic layer  36  to form patterned electrodes  26  and a metallic block  32  on the substrate  24 , wherein the patterned electrodes  26  are separated by a gap  28 , and wherein the metallic block  32  is arranged in the gap  28 , as shown in  FIG. 6(   b ). Next, use a CVD (Chemical Vapor Deposition) method to form a first insulating layer  34  over the patterned electrodes  26  and the metallic block  32  and fill the insulating layer  34  into the gap  28 , whereby air or inert gas is trapped in the gap  28  to function as the discharge paths interconnecting the patterned electrodes  26 , as shown in  FIG. 6(   c ). 
     The discharge paths may be alternatively realized with a low-permittivity layer. After the step of  FIG. 6(   b ), a low-permittivity layer is formed in the gap  28 , neighboring the patterned electrodes  26  and the metallic block  32 . Next, the first insulating layer  34  is formed over the patterned electrodes  26 , the metallic block  32  and the low-permittivity layer. Thus, the low-permittivity layer functions as the discharge paths. 
     Below is introduced a second embodiment. Refer to  FIG. 7  and  FIG. 8 . In the second embodiment, the planar micro-tube discharger structure comprises a substrate  38  made of silicon; a second insulating layer  40  comprising silicon dioxide or silicon nitride and formed on the substrate  38 ; two patterned electrodes  42  made of a metallic material arid separated by a gap  44 ; at least one separating block  46  in form of a metallic block  48  arranged in the gap  44  and connected with an electrical potential or disconnected from any electric potential; a first sub-insulating layer  50  formed over the patterned electrodes  42  and the separating block  46 , filled into the gap  44 , and having a groove  52  located in the gap  44  and interconnecting the patterned electrodes  42 ; and a second sub-insulating layer  54  formed over the first sub-insulating layer  50  and filled into the groove  52 . The first sub-insulating layer  50  and the second sub-insulating layer  54  comprise silicon dioxide or silicon nitride. The groove  52  has air or inert gas. Air or inert gas is trapped in the groove  52  by the second sub-insulating layer  54  to form at least two discharge paths. Thereby, the patterned electrodes  42  can discharge via the discharge paths. In the second embodiment, the planar micro-tube discharger structure has two separating block  30  and four discharge paths. The operation of the second embodiment is similar to that of the first embodiment. When the potential of the two patterned electrodes  26  reaches the breakdown electric field intensity of the gap  44 , tips discharge with the discharge current proceeding from one tip to another tip along the discharge paths. As the separating block  46  is a metallic block  48 , the separating block  46  can establish an electric filed between electrodes to stabilize the current direction under a fixed electric field. 
     In the second embodiment, the gap  44  does not contain any material except air. Alternatively, a low-permittivity layer may be filled into the gap  44 , and the second sub-insulating layer  54  is formed over the low-permittivity layer, whereby discharge paths are created along the low-permittivity layer. The permittivity of the low-permittivity layer should be lower than that of the first sub-insulating layer  50  and the second sub-insulating layer  54  and higher than that of the patterned electrodes  42 . 
     Below is introduced the process of fabricating the planar micro-tube discharger structure of the second embodiment. Refer to  FIGS. 9(   a )- 9 ( e ). Firstly, sequentially form a second insulating layer  40  and a metallic layer  56  on a substrate  38 , as shown in  FIG. 9(   a ). Next, remove a portion of the metallic layer  56  to form patterned electrodes  42  and metallic blocks  48  on the substrate  38 , wherein the patterned electrodes  42  are separated by a gap  44 , and wherein the metallic blocks  48  are arranged in the gap  44 , as shown in  FIG. 9(   b ). Next, form an inner insulating layer  58  over the patterned electrodes  42  and the metallic blocks  48  and fill the inner insulating layer  58  into the gap  44 , as shown in  FIG. 9(   c ). Next, remove a portion of the inner insulating layer  58  in the region of the gap  44  to form over the patterned electrodes  42  and the metallic block  48  a first sub-insulating layer  50  having a groove  52  interconnecting the patterned electrodes  42 , as shown in  FIG. 9(   d ). Next, use a CVD method to form a second sub-insulating layer  54  over the first sub-insulating layer  50  and fill the second sub-insulating layer  54  into the groove  52 , whereby air or inert gas is trapped in the groove  52  to form discharge paths interconnecting the patterned electrodes  42 , as shown in  FIG. 9(   e ). 
     The discharge paths may be alternatively realized with a low-permittivity layer. After the step of  FIG. 9(   d ), a low-permittivity layer is formed in the gap  44 , neighboring the patterned electrodes  42  and the metallic blocks  48 . Next, the second sub-insulating layer  54  is formed over the patterned electrodes  42 , the metallic blocks  48  and the low-permittivity layer. Thus, the low-permittivity layer functions as the discharge paths. 
     Below is introduced a third embodiment. Refer to  FIG. 10  and  FIG. 11 . The third embodiment is basically similar to the first embodiment but different from the first embodiment in that the separating block  30  is an insulating block  60  comprising silicon dioxide or silicon nitride. The operation of the third embodiment is similar to that of the first embodiment. 
     In the third embodiment, the gap  28  does not contain any material except air. Alternatively, the gap  28  may be filled with a low-permittivity layer, and the first insulating layer  34  is formed over the low-permittivity layer, whereby discharge paths are created along the low-permittivity layer. The permittivity of the low-permittivity layer should be lower than that of the first insulating layer  34  and higher than that of the patterned electrodes  26 . 
     Below is introduced the process of fabricating the planar micro-tube discharger structure of the third embodiment. Refer to  FIG. 12(   a ) and  FIG. 12(   b ). Firstly, form patterned electrodes  26  and an insulating block  60  on a substrate  24 , wherein the patterned electrodes  26  are separated by a gap  28 , and wherein the insulating block  60  is arranged in the gap  28 , as shown in  FIG. 12(   a ). Next, use a CVD method to form a first insulating layer  34  over the patterned electrodes  26  and the insulating block  60  and till the insulating layer  34  into the gap  28 , whereby air or inert gas is trapped in the gap  28  to function as the discharge paths interconnecting the patterned electrodes  26 , as shown in  FIG. 12(   b ). 
     The discharge paths may be alternatively realized with a low-permittivity layer. After the step of  FIG. 12(   a ), a low-permittivity layer is formed in the gap  28 , neighboring the patterned electrodes  26  and the insulating block  60 . Next, the first insulating layer  34  is formed over the patterned electrodes  26 , the insulating block  60  and the low-permittivity layer. Thus, the low-permittivity layer functions as the discharge paths. 
     Below is introduced a fourth embodiment. Refer to  FIG. 13  and  FIG. 14 . The fourth embodiment is basically similar to the third embodiment but different from the third embodiment in the material of the first insulating layer  34 . In the fourth embodiment, the separating block  30  is an insulating block  61  made of the same material as the insulating layer  34 . Therefore, the insulating block  61  and the insulating layer  34  have the same hatching lines. Besides, the operation of the fourth embodiment is similar to that of the third embodiment. 
     In the fourth embodiment, the gap  28  does not contain any material except air. Alternatively, the gap  28  may be filled with a low-permittivity layer, and the first insulating layer  34  is formed over the low-permittivity layer, whereby discharge paths are created along the low-permittivity layer. The permittivity of the low-permittivity layer should be lower than that of the first insulating layer  34  and higher than that of the patterned electrodes  26 . 
     Below is introduced the process of fabricating the planar micro-tube discharger structure of the fourth embodiment. Refer to  FIG. 15(   a ) and  FIG. 15(   b ). Firstly, form patterned electrodes  26  and an insulating block  61  on a substrate  24 , wherein the patterned electrodes  26  are separated by a gap  28 , and wherein the insulating block  61  is arranged in the gap  28 , as shown in  FIG. 15(   a ). Next, use a CVD method to form a first insulating layer  34  over the patterned electrodes  26  and the insulating block  61  and fill the insulating layer  34  into the gap  28 , whereby air or inert gas is trapped in the gap  28  to function as the discharge paths interconnecting the patterned electrodes  26 , as shown in  FIG. 15(   b ). 
     The discharge paths may be alternatively realized with a low-permittivity layer. After the step of  FIG. 15(   a ), a low-permittivity layer is formed in the gap  28 , neighboring the patterned electrodes  26  and the insulating block  61 . Next, the first insulating layer  34  is formed over the patterned electrodes  26 , the insulating block  61  and the low-permittivity layer. Thus, the low-permittivity layer functions as the discharge paths. 
     Below is introduced a fifth embodiment. Refer to  FIG. 16  and  FIG. 17 . The fifth embodiment is basically similar to the second embodiment but different from the second embodiment in the material of the separating blocks  46 . In the fifth embodiment, the separating blocks  46  are insulating blocks  62  comprising silicon dioxide or silicon nitride. When the potential of the two patterned electrodes  42  reaches the breakdown electric field intensity of the gap  44 , tips discharge with the discharge current proceeding from one tip to another tip along the discharge paths. 
     In the fifth embodiment, the gap  44  does not contain any material except air. Alternatively, the gap  44  may be filled with a low-permittivity layer, and the second sub-insulating layer  54  is formed over the low-permittivity layer, whereby discharge paths are created along the low-permittivity layer. The permittivity of the low-permittivity layer should be lower than that of the first sub-insulating layer  50  and the second sub-insulating layer  54  and higher than that of the patterned electrodes  42 . 
     Below is introduced the process of fabricating the planar micro-tube discharger structure of the fifth embodiment. Refer to  FIGS. 18(   a )- 18 ( d ). Firstly, form a second insulating layer  40 , patterned electrodes  42 , and insulating blocks  62  on a substrate  38 , wherein the patterned electrodes  42  are separated by a gap  44 , and wherein the insulating blocks  62  are arranged in the gap  44 , as shown in  FIG. 18(   a ). Next, form an inner insulating layer  58  over the patterned electrodes  42  and the insulating blocks  62  and fill the inner insulating layer  58  into the gap  44 , as shown in  FIG. 18(   b ). Next, remove a portion of the inner insulating layer  58  in the region of the gap  44  to form over the patterned electrodes  42  and the insulating blocks  62  a first sub-insulating layer  50  having a groove  52  interconnecting the patterned electrodes  42 , as shown in  FIG. 18(   c ). Next, use a CVD method to form a second sub-insulating layer  54  over the first sub-insulating layer  50  and fill the second sub-insulating layer  54  into the groove  52 , whereby air or inert gas is trapped in the groove  52  to form discharge paths interconnecting the patterned electrodes  42 , as shown in  FIG. 18(   d ). 
     The discharge paths may be alternatively realized with a low-permittivity layer. After the step of  FIG. 18(   c ), a low-permittivity layer is formed in the gap  44 , neighboring the patterned electrodes  42  and the insulating blocks  62 . Next, the second sub-insulating layer  54  is formed over the patterned electrodes  42 , the insulating blocks  62  and the low-permittivity layer. Thus, the low-permittivity layer functions as the discharge paths. 
     Below is introduced a sixth embodiment. Refer to  FIG. 19  and  FIG. 20 . In the sixth embodiment, the planar micro-tube discharger structure comprises a substrate  64  made of silicon; a second insulating layer  66  comprising silicon dioxide or silicon nitride and formed on the substrate  64 ; two patterned electrodes  68  formed on second insulating layer  66  and separated by a gap  70 ; at least one separating block  72  arranged in the gap  70 ; two cover blocks  74  respectively arranged on the patterned electrodes  68  and each separated from the neighboring separating block  72  by a sub-gap  76  that interconnects the gap  70  and the patterned electrode  68 ; and a first insulating layer  78  comprising silicon dioxide or silicon nitride, formed over the cover blocks  74  and the separating blocks  72 , and filled into the gap  70  and the sub-gaps  76 . The gap  70  and the sub-gaps  76  contain air or inert gas. The air or inert gas is trapped in the gap  70  and the sub-gaps  76  by the first insulating layer  78  to function as discharge paths. The patterned electrodes  68  discharge via the discharge paths. In the sixth embodiment, the planar micro-tube discharger structure has two separating block  72  and four discharge paths. The operation of the sixth embodiment is similar to that of the fifth embodiment. 
     In the sixth embodiment, the gap  70  does not contain any material except air. Alternatively, the gap  70  may be filled with a low-permittivity layer, and the first insulating layer  78  is formed over the low-permittivity layer, whereby discharge paths are created along the low-permittivity layer. The permittivity of the low-permittivity layer should be lower than that of the first insulating layer  78  and higher than that of the patterned electrodes  68 . 
     Below is introduced the process of fabricating the planar micro-tube discharger structure of the sixth embodiment. Refer to  FIGS. 1(   a )- 21 ( d ). Firstly, sequentially form a second insulating layer  66  and patterned electrodes  68  on a substrate  64 , wherein the patterned electrodes  68  are separated by a gap  70 , as shown in  FIG. 21(   a ). Next, form an inner insulating layer  80  over the patterned electrodes  68  and the substrate  64  and fill the inner insulating layer  80  into the gap  70 , as shown in  FIG. 21(   b ). Next, remove a portion of the inner insulating layer  80  in the region of the gap  70  to form separating blocks  72  and cover blocks  74  respectively covering the patterned electrodes  68 , wherein each cover block  74  is separated from the neighboring separating block  72  by a sub-gap  76  that interconnects the gap  70  and the patterned electrode  68 , as shown in  FIG. 21(   c ). Next, use a CVD method to form a first insulating layer  78  over the cover blocks  74  and the separating blocks  72  and fill the first insulating layer  78  into the gap  70  and the sub-gaps  76 , whereby air or inert gas is trapped in the gap  70  and the sub-gaps  76  to form discharge paths interconnecting the patterned electrodes  68 , as shown in  FIG. 21(   d ). 
     The discharge paths may be alternatively realized with a low-permittivity layer. After the step of  FIG. 21(   c ), a low-permittivity layer is formed in the gap  70 , neighboring the patterned electrodes  68  and the separating blocks  72 . Next, the first insulating layer  78  is formed over the cover blocks  74 , the separating blocks  72  and the low-permittivity layer. Thus, the low-permittivity layer functions as the discharge paths. 
     Summarized from the abovementioned embodiments, the primary structure of the present invention is shown in  FIG. 22 . The primary structure of the present invention comprises two patterned electrodes  82  separated by a gap  84 , and a plurality of separating blocks  86 , whereby is formed a plurality of discharge paths. Further, at least one cavity  88  is formed in each patterned electrode  82  when the patterned electrodes are formed on the substrate, whereby the tip electric field of each patterned electrode  82  is distributed more uniformly. 
     In conclusion, the micro-tube discharger structure of the present invention has a plurality of discharge paths to release electrostatic charge. In comparison with the conventional gas tube, the present invention has a much lower dropout rate. 
     The embodiments described above are only to exemplify the present invention but not to limit the scope of the present invention. Any equivalent modification or variation according to the shapes, structures, characteristics or spirit of the present invention is to be also included within the scope of the present invention.