Abstract:
The present invention provides a multilayer wiring board in which resistive elements each of whose error from a desired value is smaller than in a conventional case are built, a method for manufacturing the same, and a probe apparatus utilizing the multilayer wiring board. The present invention is based on a basic concept of forming a flat surface on a surface of a multilayer wiring layer on which a resistive element material is to be deposited and depositing the resistive element material on the flat surface. The multilayer wiring board comprises a multilayer wiring layer on whose surface convexo-concave is formed, a dummy layer burying the convexo-concave within a desired area of the surface of the multilayer wiring layer and having an approximately flat surface, a resistance material layer made of an electrical resistance material deposited on the dummy layer and at an area going beyond the dummy layer, and a wire made of a conductive material deposited on the resistance material layer and ranging from the area going beyond the dummy layer to a part of the flat surface area of the dummy layer, wherein a resistive element is formed at an area of the resistance material layer that the wire does not reach.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    The present invention relates to a multilayer wiring board and a method for manufacturing the same and a probe apparatus using the multilayer wiring board. 
         [0002]    Semiconductor ICs such as semiconductor chips are collectively formed on a semiconductor wafer and undergo an electrical test before being separated into respective chips. For this electrical test, a probe apparatus connected to electrode pads of each semiconductor IC as a device under test is used in general. Respective probes of the probe apparatus contact the corresponding electrode pads of the device under test to cause the device under test to be connected to a tester for the electrical test (for example, refer to Patent Document 1). 
         [0003]    In such a probe apparatus, a multilayer wiring board is used as a probe board, and numerous probes are arranged on one surface of the probe board. Also, in wiring circuits built in this probe board or multilayer wiring board, electrical resistive elements are built for the purpose of electrical matching such as impedance matching. 
         [0004]    A method for building the resistive elements in the multilayer wiring board is proposed in Patent Document 2, for example. With the method described in Patent Document 2, in relation to a manufacturing process of a multilayer wiring board having an insulating substrate and a multilayer wiring layer provided on the insulating substrate, a titanium nitride film functioning as a foundation layer for wires and functioning as resistive elements is formed on the multilayer wiring layer, and wires are formed on the titanium nitride film by a conductor such as copper, thus to enable efficient building of the resistive elements in the multilayer wiring board. 
         [0005]    Meanwhile, in the multilayer wiring layer of the multilayer wiring board, a lower-layer conductive layer formed on the insulating substrate and an upper-layer conductive layer piled on the lower-layer conductive layer via an intermediate insulating layer are connected, for example. For this connection between the both conductive layers, a via hole penetrating the intermediate insulating layer in the thickness direction is formed, and the lower-layer conductive layer and the upper-layer conductive layer are electrically connected through a via deposited in the via hole. When a metal material for this via is deposited in the via hole, the metal material for the via partially rises at the rim portion of the via hole. Thus, when an upper-layer insulating film is formed to cover the upper-layer conductive layer connected to the lower-layer conductive layer through the via, convexo-concave corresponding to the rise of the via is formed on this upper-layer insulating film. 
         [0006]    When the aforementioned resistive elements are formed on this convexo-concave upper-layer insulating film by deposition of their material, these resistive elements are formed in a waved shape in the up-down direction along the convexo-concave surface of the aforementioned upper-layer insulating film. Accordingly, the substantial length of each resistive element increases, and the thickness dimension of the resistive element tends to change partially, as a result of which there is a disadvantage of increase in an error of a value of each resistive element built in the multilayer wiring board. 
         [0007]    (Patent Document 1) Japanese Patent Appln. Public Disclosure No. 2005-17121; (Patent Document 2) Japanese Patent Appln. Public Disclosure No. 2000-13016 
       BRIEF SUMMARY OF THE INVENTION 
       [0008]    It is an object of the present invention to provide a multilayer wiring board in which resistive elements each of whose error from a desired value is smaller than in a conventional case are built, a method for manufacturing the same, and a probe apparatus utilizing the multilayer wiring board. 
         [0009]    The present invention is characterized by forming a flat surface on a surface of a multilayer wiring layer on which a resistive element material is to be deposited and depositing the resistive element material on the flat surface. 
         [0010]    More specifically, a method for manufacturing a multilayer wiring board according to the present invention comprises the steps of forming a flat surface at a desired area on a surface of a multilayer wiring board having a multilayer wiring layer on whose surface convexo-concave is formed, and depositing an electrical resistance material on the flat surface to form a resistive element. 
         [0011]    The resistive element made of the electrical resistance material deposited on the flat surface will not wave in the up-down direction along the convexo-concave surface as in the conventional case, and it is possible to prevent increase or decrease of the substantial length of the resistor due to this meandering path in the up-down direction and variation in the thickness dimension due to deposition of the electrical resistance material on the convexo-concave surface. Thus, since the resistive element showing an accurate resistance value can be formed, it is possible to provide the multilayer wiring board in which variation in the resistance value is smaller than in the conventional case. 
         [0012]    The flat surface may be formed by a surface of a dummy layer. The dummy layer may be formed by depositing a material for the dummy layer so that the material may have a thickness dimension enough to bury the convexo-concave surface within the desired area and to form an approximately flat surface. 
         [0013]    The dummy layer may be made of a conductive material. For formation of the dummy layer made of the conductive material, a resist mask exposing an area for forming the flat surface is formed by a photoresist on the surface of the multilayer wiring layer, and the conductive material for the dummy layer may be deposited at the area exposed from the resist mask. 
         [0014]    An electroplating method may be used for deposition of the conductive material for the dummy layer. By this electroplating method, the dummy layer whose surface is flat can be formed by depositing the conductive material for the dummy layer so that the material may have a thickness dimension enough to bury the convexo-concave of the surface and thereafter polishing the material to be a flat surface. 
         [0015]    The conductive material for the dummy layer may be deposited at the same time as deposition of a conductive material for formation of a wire on the multilayer wiring layer. Consequently, it is possible to form the multilayer wiring board more efficiently. 
         [0016]    An insulating layer made of an electrical insulating material may be formed on the dummy layer, and the electrical resistance material may be deposited on the insulating layer. 
         [0017]    In the electroplating for formation of the dummy layer, pulse current may be used. By controlling this pulse current appropriately, the surface of the dummy layer can be flattened more than in normal electroplating using direct current. Thus, by selecting conditions of pulse current appropriately, the dummy layer having a flat surface can be formed without doing flat-surface polishing. 
         [0018]    A multilayer wiring board according to the present invention comprises a multilayer wiring layer on whose surface convexo-concave is formed, a dummy layer burying the convexo-concave within a desired area of the surface of the multilayer wiring layer and having an approximately flat surface, a resistance material layer made of an electrical resistance material deposited on the dummy layer and at an area going beyond the dummy layer, and a wire made of a conductive material deposited on the resistance material layer and ranging from the area going beyond the dummy layer to a part of the flat surface area of the dummy layer, wherein a resistive element is formed at an area of the resistance material layer that the wire does not reach. 
         [0019]    In the multilayer wiring board according to the present invention, since the resistive element is formed on the flat surface, increase or decrease of the substantial length of the resistor due to the meandering path in the up-down direction along the convexo-concave surface as in the conventional case is prevented. Thus, with the multilayer wiring board according to the present invention, since variation in the resistance value of the resistive element can be reduced more than in the conventional case, it is possible to improve accuracy of the resistance value of the resistive element built therein. 
         [0020]    The dummy layer may be made of a conductive material deposited in the same layer as that of a conductive material for forming a wire on the surface of the multilayer wiring board. 
         [0021]    An insulating layer covering the dummy layer may be formed on the dummy layer, and the resistive element may be formed on the dummy layer via the insulating layer. 
         [0022]    The dummy layer made of the conductive material may function as a wire electrically connected to another conductive layer under the dummy layer. 
         [0023]    A probe apparatus according to the present invention comprises a probe board comprising a multilayer wiring board having a multilayer wiring layer, a plurality of probes provided on a surface of the multilayer wiring layer of the probe board and connected to conductive paths of the multilayer wiring layer, and a resistive element connected to the conductive paths of the multilayer wiring layer, wherein on the surface of the multilayer wiring layer is formed convexo-concave, at a desired area of the surface of the multilayer wiring layer is formed a dummy layer having a flat surface that buries the convexo-concave surface within the area, and on the dummy layer is formed the resistive element. 
         [0024]    With the probe apparatus according to the present invention, since the resistive element formed on the probe board can be formed accurately so that its resistance value may become a desired value, electrical matching such as impedance matching can be done appropriately, and a highly accurate electrical test can be done by restricting troubles such as noise. 
         [0025]    The dummy layer may be made of a conductive material layer deposited on the multilayer wiring layer in the same layer as that of a pad portion of the multilayer wiring board to which the probe is fixed. On the dummy layer may be formed an insulating layer covering the dummy layer, and the resistive element may be formed on the dummy layer via the insulating layer. 
         [0026]    An electrical resistance material layer may be formed on the dummy layer and at an area going beyond the dummy layer, on the electrical resistance material layer may be formed a wire made of a conductive material deposited on the electrical resistance material layer and ranging from the area going beyond the dummy layer to a part of the flat surface area of the dummy layer, and the resistive element may be formed at an area of the resistance material layer that the wire does not reach. 
         [0027]    By forming the dummy layer by the conductive material, the dummy layer may function as a wire electrically connected to another conductive layer under the dummy layer. 
         [0028]    According to the present invention, since the resistive element is formed on the flat surface, and increase or decrease of the effective length due to meandering of the resistive element can be prevented, it is possible to provide the multilayer wiring board and the probe apparatus building therein the resistive element having an electrical resistance value with a smaller error than in the conventional case. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0029]      FIG. 1  is a schematic view showing a process for manufacturing a probe apparatus according to the present invention (No. 1). 
           [0030]      FIG. 2  is a schematic view showing the process for manufacturing the probe apparatus according to the present invention (No. 2). 
           [0031]      FIG. 3  is a schematic view showing the process for manufacturing the probe apparatus according to the present invention (No. 3). 
           [0032]      FIG. 4  is a schematic view showing the process for manufacturing the probe apparatus according to the present invention (No. 4). 
           [0033]      FIG. 5  is a schematic view showing the process for manufacturing the probe apparatus according to the present invention (No. 5). 
           [0034]      FIG. 6  is a schematic view showing the process for manufacturing the probe apparatus according to the present invention (No. 6). 
           [0035]      FIG. 7  is a cross-sectional view showing an embodiment of a probe apparatus according to the present invention. 
           [0036]      FIG. 8  is a view similar to  FIG. 7  showing another embodiment of a probe apparatus according to the present invention. 
           [0037]      FIG. 9  is a view similar to  FIG. 7  showing still another embodiment of a probe apparatus according to the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0038]      FIGS. 1 to 7  show a method for manufacturing a probe apparatus  10  (refer to  FIG. 7  ( r )) according to the present invention. In the probe apparatus  10  according to the present invention, a multilayer wiring board  12  is used as its probe board. 
         [0039]    As shown in  FIG. 1  ( a ), the multilayer wiring board  12  according to the present invention comprises an insulating substrate  14  such as a ceramic and a multilayer wiring layer  16  deposited on the insulating substrate. The multilayer wiring layer  16  has a plurality of insulating layers  18  ( 18   a ,  18   b ,  18   b  . . . ) and a plurality of conductive layers  20  ( 20   a ,  20   b ,  20   b  . . . ) each formed between the insulating layers  18 . 
         [0040]    The multilayered conductive layers  20  are electrically connected to each other by way of a via  24  formed through a via hole  22  in the insulating layer  18  located therebetween. For formation of this via  24 , at the rim portion surrounding the via  24  of each insulating layer  18  and conductive layer  20  is formed convexo-concave along with presence/absence of the conductive layer  20 , and convexo-concave on the surface of the uppermost insulating layer  18   a  is significant depending on the positional relationship between the upper and lower vias  24 . 
         [0041]    Under such circumstances, a later-described flat surface is formed on the surface of the multilayer wiring board  12  by applying the following process according to the present invention. For formation of connection pads for predetermined probes in relation to formation of this flat surface, a conductive metal layer  26  such as Ti or Pd is formed by e.g., a sputtering method so as to cover the entire surface of the insulating layer  18   a , which is a surface of the multilayer wiring board  12 . 
         [0042]    Next, as shown in  FIG. 1  ( b ), a photoresist  28  is applied by using e.g., a spin coat method so as to cover the entire surface of the conductive metal layer  26 , and predetermined parts of this photoresist  28  are removed. In a case where the photoresist  28  is in a positive type, the photoresist  28  is exposed through a glass mask  30  for exposing of parts to be removed. By a development process after this exposure, parts corresponding to transmissive areas excluding shielded areas  30   a  of the glass mask  30  are removed out of the photoresist  28  as shown in  FIG. 1  ( c ). These transmissive areas correspond to respective areas for a below-described electrode pad, a dummy layer and a probe connection pad, that is, an opening  28   a  for the electrode pad, an opening  28   b  for the dummy layer, and an opening  28   c  for the probe connection pad are respectively formed in the photoresist  28 , in the example shown in the figure. 
         [0043]    In these openings  28   a ,  28   b  and  28   c  of the photoresist  28  are deposited conductive metal materials  32  ( 32   a ,  32   b ,  32   c ) such as copper via the conductive metal layer  26  by e.g., an electroplating method referred to as an electroforming method, as shown in  FIG. 2  ( d ). Since the surfaces of the conductive metal materials  32  deposited by the plating are influenced by convexo-concave on the surface of the foundation layer, variation in the thickness dimension of the plated layer, and so on, the surfaces of the conductive metal materials  32  are not flat. 
         [0044]    Then, as shown in  FIG. 2  ( e ), after the photoresist  28  is removed, the surfaces of the conductive metal materials  32  ( 32   a ,  32   b ,  32   c ) undergo flat-surface polishing by e.g., chemical mechanical polishing (CMP). By this flat-surface polishing, the surface of the dummy layer  32   b  constituted by the conductive metal material  32  becomes a flat surface  34  similar to those of the electrode pad  32   a  and the probe connection pad  32   c.    
         [0045]    After the flat-surface polishing of the conductive metal materials  32 , parts of the conductive metal layer  26  without deposition of conductive metal material  32  are removed by e.g., etching processing using ion beam. By this etching processing are formed the electrode pad  32   a , the dummy layer  32   b , and the probe connection pad  32   c  mutually insulated and each having a flat surface ( 34 ), as shown in  FIG. 2  ( f ). 
         [0046]    After formation of the electrode pad  32   a , the dummy layer  32   b  and the probe connection pad  32   c , a photosensitive insulating layer  36  such as photosensitive polyimide is formed by e.g., the aforementioned spin coat method on the electrode pad  32   a , the dummy layer  32   b , the probe connection pad  32   c  and the insulating layer  18   a  exposed therefrom as shown in  FIG. 3  ( g ). This photosensitive insulating layer  36  is formed to have a uniform thickness dimension on the flat surfaces ( 34 ) on the electrode pad  32   a  and the probe connection pad  32   c  including the dummy layer  32   b.    
         [0047]    For removal of unnecessary parts out of the photosensitive insulating layer  36 , the photosensitive insulating layer  36  is partially exposed with use of a glass mask  38 , as shown in  FIG. 3  ( h ). In a case where the photosensitive insulating layer  36  is in a negative type, for the purpose of exposing an area of the photosensitive insulating layer  36  that should remain, shielded areas  38   a  corresponding to parts to be removed are formed on the glass mask  38 , and the transmissive area of the glass mask  38  corresponds to the dummy layer  32   b  and an area ranging from the position on the dummy layer to the adjacent edge portions on the upper surfaces of the electrode pad  32   a  and the probe connection pad  32   c  located at its both sides. 
         [0048]    Accordingly, by conducting development processing to the exposed photosensitive insulating layer  36 , an insulating layer  36   a  remains in a contiguous manner on the dummy layer  32   b  and the area ranging from the position on the dummy layer to the adjacent edge portions on the upper surfaces of the electrode pad  32   a  and the probe connection pad  32   c  located at its both sides, as shown in  FIG. 3  ( i ). 
         [0049]    After formation of the insulating layer  36   a , Cr and Pd are deposited by e.g., a sputtering method or a deposition method on the insulating layer  36   a , the surfaces of the electrode pad  32   a  and the probe connection pad  32   c  exposed from the insulating layer  36   a , and the exposed surface of the insulating layer  18   a , as shown in  FIG. 4  ( j ). By this deposition, a Cr/Pd alloy layer  40  having an approximately uniform predetermined thickness dimension is formed over the surface of the insulating substrate  14 . This Cr/Pd alloy layer is a thin-film resistive element layer  40  functioning as a thin-film resistive element and is utilized as a foundation electrode for later-described wire plating as well. 
         [0050]    The thin-film resistive element layer  40  functioning both as a thin-film resistor and as a foundation layer for wire plating for the thin-film resistor may be made of a metal showing a required appropriate sheet resistance value such as tantalum nitride, tantalum oxide, a Cr element, a Ti element, a Ti/Pd alloy, or the like, instead of the Cr/Pd alloy. Also, titanium nitride may be used for the thin-film resistive element layer  40 . However, the thin-film resistive element layer  40  made of the titanium nitride shows a relatively high sheet resistance value, and its variation is relatively high. On the contrary, the thin-film resistive element layer  40  made of the Cr/Pd alloy shows a lower and more appropriate sheet resistance value than that of the titanium nitride and is suitable for fine wires each having uniform thickness. 
         [0051]    The thin-film resistive element layer  40  formed on the flat surface of the insulating layer  36   a  by the sputtering method or the deposition method after formation of the insulating layer  36   a  on the flat surface  34  of the dummy layer  32   b  with an approximately uniform thickness dimension is deposited over the dummy layer  32   b  to have an approximately uniform thickness dimension along the flat surface  34 . Thus, since a part of the thin-film resistive element layer  40  over the dummy layer  32   b  is formed in a flat plate shape having approximately uniform thickness without waving in the up-down direction, change in the length due to the waving does not occur, and partial variation in the thickness dimension hardly occurs, and thus it shows more stable resistance value characteristics than a conventional resistive element formed on a convexo-concave surface does. 
         [0052]    A thin-film resistive element showing a predetermined resistance value on the dummy layer  32   b  and necessary parts are left out of the thin-film resistive element layer  40 , and unnecessary parts are removed from the thin-film resistive element layer  40 . To do so, a photosensitive insulating layer  42  similar to the aforementioned one is formed to cover the entire surface of the thin-film resistive element layer  40 , as shown in  FIG. 4  ( k ). This photosensitive insulating layer  42  is exposed through a glass mask  44  and thereafter undergoes development processing as shown in  FIG. 4  ( l ). On the glass mask  44 , a transmissive opening having a desired flat surface shape is formed by shielded areas  44   a . Also, this transmissive opening corresponds to the flat surface shape of a resistive element ( 40   a ) showing a predetermined resistance value on the dummy layer  32   b.    
         [0053]    Consequently, by the development processing of the photosensitive insulating layer  42 , an insulating layer  42   a  having a flat surface shape corresponding to the flat surface shape of the desired resistive element remains on the dummy layer  32   b , as shown in  FIG. 5  ( m ). 
         [0054]    Subsequently, a photoresist  46  similar to the aforementioned one is applied on the entire surface of the multilayer wiring board  12  including the insulating layer  42   a , as shown in  FIG. 5  ( n ). The photoresist  46  is exposed through a glass mask  48  having shielded areas  48   a  and thereafter undergoes development processing. As a result, on the photoresist  46  are respectively formed an opening  46   a  for a wiring path between the resistive element  40   a  formed on the dummy layer  32   b  and the electrode pad  32   a  and an opening  46   b  for a wiring path between the resistive element  40   a  and the probe connection pad  32   c , as shown in  FIG. 5  ( o ). 
         [0055]    Using the thin-film resistive element layer  40  exposed and remaining at the bottom portions of these openings  46   a ,  46   b  as a foundation electrode, a conductive metal material such as copper is deposited in the respective openings  46   a ,  46   b  by a plating method, and wires  50  ( 50   a ,  50   b ) are formed by this deposit. 
         [0056]    After formation of the wires  50  ( 50   a ,  50   b ), the photoresist  46  is removed, and the surface of the multilayer wiring board  12  is etched by ion beam, as shown in  FIG. 6  ( p ). By this etching processing using the ion beam, the thin-film resistive element layer  40  is removed at the entire areas excluding wire plating portions ( 50   a ,  50   b ) into which the conductive metal material has been plated on the thin-film resistive element layer  40  and a part covered with the insulating layer  42   a , as shown in  FIG. 6  ( q ). At this time, although the exposed wires  50   a ,  50   b  are also etched, the wires  50   a ,  50   b  have thickness dimensions enough to put up with this etching processing. Also, although the insulating layer  42   a  gets thin as well, it will not disappear. Thus, under the insulating layer  42   a  is formed a resistive element  40   a  connected to the electrode pad  32   a  and the probe connection pad  32   c  respectively by the wires  50   a ,  50   b  and sealed by the insulating layer  42   a.    
         [0057]    As shown in  FIG. 7  ( r ), on the probe connection pad  32   c  is fixed a probe  52  by e.g., welding with use of laser, with its probe tip  52   a  directing upward or in a direction distanced from the insulating substrate  14 . 
         [0058]    Accordingly, the thin-film resistive element  40   a  formed on the dummy layer  32   b  is connected to the electrode pad  32   a  via one wiring path  50   a  at its one edge and is connected to the probe  52  via the other wiring path  50   b  at its other edge. Thus, the probe  52  is connected to the conductive layer  20   a  or a conductive path constituting a part of the wiring paths inside the multilayer wiring board  12  via the thin-film resistive element  40   a . The conductive path  20   a  connected to the electrode pad  32   a  is connected to a not shown tester. 
         [0059]    Although one probe  52  has been shown representatively in  FIGS. 1 to 7 , numerous probes  52  are in fact provided on the multilayer wiring board  12  to correspond to electrode pads formed on a semiconductor IC as a device under test. Thus, by thrusting the probe tip  52   a  of each probe  52  on the multilayer wiring board  12  to the aforementioned corresponding electrode pad of the aforementioned device under test, it is possible to connect the aforementioned device under test to the aforementioned tester via the probe apparatus  10 . 
         [0060]    In the probe apparatus  10  according to the present invention, the resistive element  40   a  is inserted between the wires  50   a  and  50   b  connecting the electrode pad  32   a  to the probe connection pad  32   c . Since this resistive element  40   a  is formed by a part of the flat thin-film resistive element layer  40  deposited on the flat surface  34  of the dummy layer  32   b , it is formed in a flat plate shape having approximately uniform thickness without waving in the up-down direction. Therefore, the effective length of the resistive element  40   a  and the dimension in the length direction between both edges of the resistive element to which the wiring paths  50   a ,  50   b  are connected approximately correspond to each other. 
         [0061]    Thus, without causing increase in the effective length due to the waving deformation of the resistive element  40   a  in the up-down direction or variation in the resistance value due to increase or decrease of the thickness dimension as in the conventional case, variation of the effective value of the resistive element  40   a  from a desired value can be reduced more than in the conventional case. Consequently, a resistive element having an appropriate resistance value can be inserted in the wiring paths of the multilayer wiring board  12  accurately, which is extremely advantageous to highly accurate electrical measurement. 
         [0062]      FIGS. 8 and 9  respectively show other examples of probe apparatuses according to the present invention. In a probe apparatus  110  shown in  FIG. 8 , the probe connection pad part  32   c  and the dummy layer part  32   b  are formed in a contiguous manner. This contiguous layer ( 32   b ,  32   c ) of the probe connection pad part and the dummy layer part can be used as a part of the aforementioned wiring paths of the multilayer wiring board  12 . Also, in a probe apparatus  120  shown in  FIG. 9 , the electrode pad part  32   a  and the dummy layer part  32   b  are formed in a contiguous manner. This contiguous layer ( 32   a ,  32   b ) of the electrode pad part and the dummy layer part can be used as a part of the aforementioned wiring paths of the multilayer wiring board  12 . 
         [0063]    Also, in the aforementioned respective examples, one wiring path  50   a  out of the wiring paths  50   a ,  50   b  extending from the resistive element  40   a  of each of the probe apparatuses  10 ,  110 ,  120  is terminated on the wiring foundation area  40  without reaching the upper surface of the electrode pad  32   a . Also, the other wiring path  50   b  is terminated on the wiring foundation area  40  without reaching the probe connection pad  32   c . However, the aforementioned respective edge portions of these wiring paths  50   a ,  50   b  may be terminated on the corresponding pads  32   a ,  32   c  so as to contact the respective pads directly. 
         [0064]    In the foregoing description, an example of forming the resistive element  40   a  on the flat surface  34  of the dummy layer  32   b  has been explained. In a case where the upper surface of the insulating layer  18   a  or a layer deposited on the insulating layer can be polished to be a flat surface, the thin-film resistive element layer  40  may be formed on this flat polished surface, instead of forming the dummy layer  32   b.    
         [0065]    Also, an electrical insulating material may be used as the dummy layer  32   b . By forming the dummy layer  32   b  by the electrical insulating material, the insulating layer  36   a  on the dummy layer  32   b  can be eliminated. However, with respect to the fact that a process of forming the electrode pad  32   a  and the probe connection pad  32   c  is utilized to enable simultaneous formation of the dummy layer  32   b  and the fact that the dummy layer  32   b  can be utilized as a part of the wires, it is preferable that the dummy layer is made of a conductive material. 
         [0066]    Also, although a single resistive element  40   a  has been shown in the foregoing description, the resistive element may be separated, and these separated resistive elements may be mutually connected in series to form a resistive element  40   a.    
         [0067]    The present invention is not limited to the above embodiments but may be altered in various ways without departing from the spirit and scope of the present invention. The present invention may also be applied to various kinds of implemented circuit boards, not only to the probe board of the probe apparatus.