Abstract:
The semiconductor device according to the present invention having an LSI circuit and an inductor element formed on the same substrate has an interlayer insulating film formed on the substrate, a first laminated wiring layer formed on the interlayer insulating film and serves as an internal wiring of the LSI circuit, and a second laminated wiring layer formed on the interlayer insulating film and constitutes the inductor element, wherein the first and second laminated wiring layers are mutually different, and no Ti layer which makes contact with an Al alloy layer exists on the second laminated wiring layer.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The present invention relates to a semiconductor device, and more particularly to a semiconductor device equipped with an inductor element suitable for high frequency operation.  
           [0003]    2. Description of the Prior Art  
           [0004]    The reduction of the resistance has been one of the important factors for an inductor element indispensable for high frequency operation.  
           [0005]    Normally, the wiring used inside the circuit of a large scale integrated circuit (LSI) makes use of a lower wiring layer while the wiring for the power supply makes use of a wiring layer which is the uppermost wiring layer or one in its vicinity, of the wiring layers of a multilayer wiring structure. In the multilayer wiring structure, the uppermost wiring layer or one in its vicinity has a thickness larger than that of the lower wiring layers. For this reason, in order to reduce the resistance of the inductor element, a method has normally been employed in which the uppermost wiring layer or one in its vicinity for the power supply wiring that has a larger thickness than the wiring layer for the LSI circuit is used for the formation of the inductor element.  
           [0006]    [0006]FIG. 9 is a sectional view showing an example of the conventional wiring structure for the semiconductor device. It has a Ti layer  401 , a TiN layer  402 , an AlCu layer  403 , a Ti layer  404  and a TiN layer  405  formed on an interlayer insulating film  100 . The wiring layer having the lamination structure of TiN/Ti/AlCu/TiN/Ti (representing the constituent metal species of each layer enumerated sequentially from the top layer, and the same manner of representation will be adopted hereinafter) is the one normally used for the LSI wiring. However, the wiring layer having the lamination structure of TiN/Ti/AlCu/TiN/Ti or the like normally used as the LSI wiring may form a high resistance TiAl alloy  406  between the AlCu layer  403  and the TiN layer  405  in the manufacturing process of the LSI, as shown in FIG. 9. Because of this, even if an inductor element is formed using the uppermost wiring layer or one in its vicinity, the resistance of the inductor element is increased when the high resistance TiAl alloy  406  is formed, defeating the purpose of reducing the resistance of the inductor element. In other words, the mere adoption of the method of formation of an inductor element by the use of the uppermost wiring layer or a wiring layer in its vicinity is difficult to realize an inductor element that is attaining a low resistance.  
           [0007]    Under these circumstances, as to the wiring layer that forms the inductor element, use of a wiring layer with the TiN/AlCu/TiN/Ti structure of a Ti layer  401 , a TiN layer  402 , an AlCu layer  403  and a TiN layer  405  formed on an interlayer insulating film  100  as shown in FIG. 10 is sometimes adopted. Alternatively, a wiring layer with the AlCu/TiN/Ti structure of a Ti layer  401 , a TiN layer  402  and an AlCu layer  403  formed on an interlayer insulating film  100  as shown in FIG. 11 may be used. These are lamination structures for the wiring devised so as not to form the TiAl alloy  406   
           [0008]    When the thickness of the TiN layer, the Ti layer, the AlCu layer, the TiN layer, and the Ti layer if the wiring layer with the TiN/Ti/AlCu/TiN/Ti structure shown in FIG. 9 are, for example, 500, 250, 8000, 500 and 250 Å, respectively, its wiring layer resistance is about 43 mΩ/mm 2 . In contrast, when the film thickness of the TiN layer, the AlCu layer, the TiN layer and the Ti layer of the wiring layer with the TiN/AlCu/TiN/Ti structure shown in FIG. 10 are 500, 8000, 500, and 250 Å, respectively, its wiring layer resistance is reduced to about 37 mΩ/mm 2 .  
           [0009]    Since this technology is aimed at preventing the formation of the TiAl alloy  406  in the LSI wiring, it is achieving an acceptable effect to the extent that an inductor element of a low resistance is realized without an increase in the wiring resistance.  
           [0010]    However, there exists the following problem in the conventional technology described in the above. Namely, when a laminated wiring structure, such as the AlCu/TiN/Ti structure (FIG. 11) or the TiN/AlCu/TiN/Ti structure (FIG. 10) in which no TiAl alloy  406  is formed, is adopted, there is introduced a problem that wiring reliability such as the resistance to electromigration is deteriorated. In other words, one needs to recognize the fact that the formation of the TiAl alloy  406  is playing the role of contributing to the resistance to electromigration of the wiring, although it has a high resistance. Therefore, without the formation of the TiAl alloy  406 , the resistance to electromigration of the wiring is deteriorated. As a result, another problem of deterioration in the reliability of the LSI as a whole is generated. For example, when the resistance to electromigration of the TiN/Ti/AlCu/TiN/Ti (with the corresponding thicknesses of 500/250/8000/500/250 Å) wiring structure shown in FIG. 9 is taken 1, it is considered that the resistance to electromigration of the TiN/AlCu/TiN/Ti (with the corresponding thicknesses of 500/8000/500/250 Å) wiring structure shown in FIG. 10 deteriorates to about 0.7, and the resistance to electromigration of the AlCu/TiN/Ti (with the corresponding thicknesses of 8000/500/250 Å) wiring structure shown in FIG. 11 deteriorates to about 0.4.  
           [0011]    Now, it is possible to avoid the deterioration in the resistance to electromigration through increase in the wiring width for the purpose of relaxing the current density, but it causes a problem of lowering the degree of integration. Since the degree of integration is often mild in the formation region of the inductor element, there are cases in which an increase in the wiring width is relatively tolerable, but in the formation region of the LSI internal circuit, an increase in the wiring width is intolerable from the design viewpoint.  
           [0012]    Moreover, as shown in FIG. 12, there is a case in which, for a first wiring  400  with a structure of AlCu layer  403 /TiN layer  402 /Ti layer  401 , a second interlayer insulating film  110  is formed newly on top of it, a connection hole  120  is provided in the interlayer insulating film  110 , and a second wiring  700  with a wiring structure of TiN layer  705 /Ti layer  704 /AlCu layer  703 /TiN layer  702 /Ti layer  701  to be connected to the first wiring  400 , is formed. Then, a contact hole connecting the first wiring  400  and the second wiring  700  is formed by depositing a TiN layer  121  on the bottom face and the side face of the connection hole  120 , and embedding a W region  122  inside the space surrounded by the layer  121 .  
           [0013]    In this case, an aluminum nitride alloy  130 , which is a high resistance material, is also formed in the interface between the TiN layer  121  of the connection hole  120  and the AlCu layer  403  in the lower layer, during the process of manufacture. When the high resistance aluminum nitride alloy  130  is generated in this way on the bottom face of the connection hole  120 , there may arise a situation in which the electrical connection between the first wiring  400  and the second wiring  700  is insufficient.  
           [0014]    Moreover, as shown in FIG. 13, even when the first wiring  400  has a structure of TiN layer  405 /AlCu layer  403 /TiN layer  402 /Ti layer  401 , an aluminum nitride alloy  131  already exists in the interface of the TiN layer  405  and the AlCu layer  403 , so that there is a case in which the electrical connection between the first wiring  400  and the second wiring  700  is difficult These facts may lead to the obstruction of applicability of the macro function which is one of the important design techniques of the system LSIs.  
           [0015]    In this way, the method of forming an LSI internal wiring and an inductor element by the use of wiring structures having the same lamination structure, as in the conventional method, may be said to have a limitation in regard to the point of meeting the requirements for the performance and the quality at the same time.  
         BRIEF SUMMARY OF THE INVENTION  
       SUMMARY OF THE INVENTION  
         [0016]    The semiconductor device according to the present invention in which an LSI circuit and an inductor element are formed on the same substrate, has an interlayer insulating film formed on the substrate, a first laminated wiring layer formed on the interlayer insulating film and serves as an internal wiring of the LSI circuit, and a second laminated wiring layer formed on the interlayer insulating film and constitutes an inductor element, wherein the first and second laminated wiring layers are mutually different, and no Ti layer which makes contact with an Al alloy layer exists on the second laminated wiring layer. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0017]    The above-mentioned and other objects, features and advantages of this invention will become more apparent by reference to the following detailed description of the invention taken in conjunction with the accompanying drawings, wherein:  
         [0018]    [0018]FIG. 1 is a sectional view of a step of the manufacturing method according to a first embodiment of this invention;  
         [0019]    [0019]FIG. 2 is a sectional view showing the step next to that in FIG. 1, which is a sectional view obtained along line A-A in FIG. 3;  
         [0020]    [0020]FIG. 3 is a plan view showing the step next to that in FIG. 1;  
         [0021]    [0021]FIG. 4 is a sectional view showing the step next to that shown in FIG. 2 and FIG. 3, which is a sectional view obtained along line B-B in FIG. 5;  
         [0022]    [0022]FIG. 5 is a plan view of the step next to that shown in FIG. 2 and FIG. 3;  
         [0023]    [0023]FIG. 6 is a sectional view showing a second embodiment of the invention;  
         [0024]    [0024]FIG. 7 is a sectional view showing a third embodiment of the invention;  
         [0025]    [0025]FIG. 8 is a sectional view showing a fourth embodiment of the invention;  
         [0026]    [0026]FIG. 9 is a sectional view showing a conventional manufacturing method of the semiconductor device;  
         [0027]    [0027]FIG. 10 is a sectional view showing a conventional manufacturing method of the semiconductor device;  
         [0028]    [0028]FIG. 11 is a sectional view showing a conventional manufacturing method of the semiconductor device;  
         [0029]    [0029]FIG. 12 is a sectional view showing a problem in the conventional technology; and  
         [0030]    [0030]FIG. 13 is a sectional view showing a problem in the conventional technology. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0031]    Referring to the accompanying drawings, the embodiments of the present invention will be described in detail next. FIG. 1 to FIG. 5 are drawings, given in the order of the steps, showing the manufacturing method of the semiconductor device according to a first embodiment of the invention (FIGS. 1, 2 and  4  are sectional views, and FIGS. 2 and 5 are plan views). First, as shown in FIG. 1, a wiring metal film of laminated structure consisting of, for example, a Ti layer  401  with thickness of 250 Å, a TiN layer  402  with thickness of 500 Å, an AlCu layer  403  with thickness of 8000 Å, a Ti layer  404  with thickness of 250 Å and a TiN layer with thickness of 500 Å is formed starting from the bottom, with respect to a first interlayer insulating film  100  on which an inductor element is to be formed. In FIG. 1, a normal LSI internal circuit region  200  and an inductor element region  300  are assigned adjacent with each other.  
         [0032]    Next, as shown in FIG. 2 and FIG. 3, a photoresist  500  is formed selectively on the LSI internal circuit region  200  in a manner similar to a normal wiring process, and the TiN layer  405  and the Ti layer  404  on the AlCu layer  403  in the inductor element region  300  are removed by photolithography using the photoresist  500  and wiring working technology. As a result, the AlCu layer  403  is exposed to the inductor element region  300 . After that, the photoresist  500  is removed.  
         [0033]    Finally, as shown in FIG. 4 and FIG. 5, a wiring pattern used in the normal LSI circuit and an inductor element pattern are formed simultaneously by using normal wiring formation processes such as photolithography and etching. In this case, since the TiN layer  405  and the Ti layer  404  are removed from the wiring layer constituting the inductor element in the process shown in FIG. 2, high resistance TiAl alloy  406  will not be formed, making it possible to form an inductor element with low resistance wirings.  
         [0034]    Next, referring to FIG. 6, a second embodiment of the invention will be described. In this embodiment, after removal of the TiN layer  405  and the Ti layer  404  from the inductor element region  300  as shown in FIG. 2, a TiN film  407  with thickness of 500 Å, for example, is formed on the entire surface as shown in FIG. 6. After that, by the processes similar to those shown in FIG. 3 and FIG. 5, a wiring pattern used in the normal LSI circuit and an inductor element pattern are formed simultaneously in the LSI internal circuit region  200  and in the inductor element region  300  by using the normal wiring formation processes such as photolithography and etching.  
         [0035]    In this embodiment configured as in the above, since inductor element region  300  is given the wiring structure TiN/AlCu/TiN/Ti, it is possible to prevent the formation of the high resistance TiAl alloy similar to the first embodiment, and moreover, it is possible to prevent the deterioration in the resistance to electromigration of the inductor element by the presence of the TiN film  407 . Accordingly, the wiring width of the inductor element can be reduced, and an inductor element with low resistance having a high resistance to electromigration can be formed.  
         [0036]    [0036]FIG. 7 is a sectional view showing the manufacturing method of the semiconductor device according to a third embodiment of the invention. As shown in FIG. 7, a five-layer laminated wiring structure of a Ti layer  401 , a TiN layer  402 , an AlCu layer  403 , a Ti layer  404  and a TiN layer  405  is formed in the LSI internal circuit region  200 . However, in the inductor element region  300 , the Ti layer  404  and the TiN layer  405  below the AlCu layer  403  may be omitted, and the inductor element in the inductor element region  300  may be formed exclusively of the AlCu layer  403 .  
         [0037]    [0037]FIG. 8 is a sectional view showing the manufacturing method of the semiconductor device according to a fourth embodiment of the invention. As shown in FIG. 8, in this embodiment, a TiN layer  407  is formed on the entire surface as in the third embodiment in FIG. 7, and the inductor element region  300  is composed of the AlCu layer  403  and its upper layer, TiN film  407 .  
         [0038]    In the embodiments shown in FIG. 7 and FIG. 8, patterning in the form of the LSI internal circuit and the inductor element is performed in the following stages similar to FIG. 4 and FIG. 5.  
         [0039]    Moreover, in this invention, it may be arranged to form a second (another) interlayer insulating film, on the laminated wiring layer (first laminated wiring layer) for the LSI internal circuit region  200  and the laminated wiring layer (second laminated wiring layer) for the inductor element region  300 , as in FIG. 12 and FIG. 13, form another wiring layer (second wiring  700 ; see FIG. 12 and FIG. 13) on top of it, and form a multilayer wiring structure by connecting the first laminated wiring layer and the second laminated wiring layer by a contact hole (connection hole  120 ). In this case, since the TiN layer  405  is formed as the topmost layer of the first laminated wiring layer according to the present embodiment, aluminum nitride alloy  130  will not be formed between the TiN layer  121  on the bottom face of the contact hole as shown in FIG. 12. Moreover, since the first laminated wiring layer has the Ti layer  404  formed between the topmost TiN layer  405  and the AlCu layer  403  in this embodiment, the aluminum nitride film  131  will not be formed as indicated in FIG. 13. Here, another wiring layer mentioned above maybe made as a single wiring layer rather than a laminated wiring layer, as is the case, in the second wiring  700  (see FIGS. 12 and 13).  
         [0040]    Furthermore, in the above embodiments, the first laminated wiring layer and the second laminated wiring layer of the invention are formed on the interlayer insulating film  100  on the substrate. However, the first and second laminated wiring layers may be formed as wiring layers in upper layers in a multilayer wiring structure.  
         [0041]    As described in detail in the above, according to the present invention, in a semiconductor device having a normal LSI circuit and an inductor element indispensable for a high frequency device are formed on the same substrate, a second laminated wiring layer to be used for the inductor element is given a different configuration from a first laminated wiring structure to be used for the LSI internal circuit so as not to form TiAl alloy in the second laminated wiring layer. Accordingly, the resistance of the inductor element can be reduced, and at the same time its resistance to electromigration can be made sufficiently high. As a result, a semiconductor device that is capable of coping with high frequency operation and is suitable for a system LSI can be obtained.  
         [0042]    Although the invention has been described with reference to specific embodiments, this description is not meant to be construed in a limiting sense. Various modifications of the disclosed embodiments will become apparent to persons skilled in the art upon reference to the description of the invention. It is therefore contemplated that the appended claims will cover any modifications or embodiments as fall within the true scope of the invention.