Abstract:
An integrated conductor arrangement comprises a substrate with a top side, at least one tubular conductor trench provided in the substrate below the top side of the substrate and a conductor. The conductor comprises at least one tubular conductor layer and is integrated in the conductor trench.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     The present invention relates to an integrated conductor arrangement, in particular a coaxial conductor arrangement, and a corresponding production method.  
         [0003]     2. Description of the Prior Art  
         [0004]     Without restricting the generality, the problem area on which the present invention is based is discussed with reference to coaxial conductors.  
         [0005]     Radio frequency cables are designed as waveguides for radio frequency signal transmission which are employed at frequencies of typically up to 2 GHz.  
         [0006]     A customary coaxial cable is a double line comprising two coaxial cylinders having a circular cross section. It comprises one or more coaxial pairs, in each coaxial pair the inner conductor, the dielectric, the outer conductor and the sheath being arranged coaxially. Advantages of coaxial cables are that no energy is radiated, and there is a relative insensitivity toward incident radiation.  
       SUMMARY OF THE INVENTION  
       [0007]     It is an object of the present invention to provide an integrated conductor arrangement, in particular a coaxial conductor arrangement, and a corresponding production method which make it possible to produce integrated, in particular coaxially arranged and shielded, conductors on the chip.  
         [0008]     The object is achieved in accordance with the invention by means of an integrated conductor arrangement, comprising:  
         [0009]     a substrate;  
         [0010]     at least one tubular conductor trench provided in the substrate below the top side of the substrate; and  
         [0011]     a conductor, in particular coaxial conductor, integrated in the conductor trench;  
         [0012]     the conductor having at least one tubular conductor layer.  
         [0013]     The object is also achieved in accordance with the invention by means of a method for producing an integrated arrangement, comprising the steps of:  
         [0014]     providing a substrate;  
         [0015]     providing a patterned mask layer on the top side of the substrate;  
         [0016]     etching a conductor trench and an adjoining contact trench, which has a larger diameter than the conductor trench, in the substrate using the patterned mask layer;  
         [0017]     undercutting the patterned mask layer in order to form an expanded conductor trench and an adjoining expanded contact trench;  
         [0018]     depositing an insulating outer insulator layer over the patterned mask layer, as result of which the walls of the expanded conductor trench and of the adjoining expanded contact trench are covered with the insulating outer insulator layer and the patterned mask layer is closed off in the region of the expanded conductor trench and remains open in the region of the expanded contact trench; and  
         [0019]     depositing an at least one conductor layer, in particular successively depositing a conductive outer conductor layer, an insulating middle insulator layer and a conductive inner conductor layer in order to form a conductor, in particular a coaxial conductor, integrated in the conductor trench.  
         [0020]     The idea on which the present invention is based consists in applying a deposition method, e.g. an ALD (Atomic Layer Deposition) deposition method, with the aid of which it is possible to uniformly coat long cavities of the substrate from the inside.  
         [0021]     Consequently, conductors, in particular coaxial conductors, can be produced by first forming long tubelike channels in the substrate, which are open only at their ends and in which at least one conductor, preferably an outer conductor, an insulation and an inner conductor are formed progressively by the deposition method.  
         [0022]     The arrangement of the tubelike channels in the substrate is arbitrary, that is to say a vertical (in particular through the chip), horizontal or arbitrarily angular course is conceivable. It is also possible, if necessary, for more than two conductors to be interleaved in one another.  
         [0023]     The conductive outer conductor layer, the insulating middle insulator layer and the conductive inner conductor layer may be in each case closed annularly.  
         [0024]     An insulating outer insulator layer may be provided between the conductive outer conductor layer and the substrate.  
         [0025]     A contact trench (or hole) having a larger diameter than the conductor trench may be provided at at least one end of the conductor trench, the coaxial conductor being led through the contact trench to the top side of the substrate.  
         [0026]     A contact trench having a larger diameter than the conductor trench may be provided at at least one end of the conductor trench, the conductive inner conductor layer being led through the contact trench to the top side of the substrate, and the conductive outer conductor layer being led from the conductor trench to the top side of the substrate. 
     
    
     DESCRIPTION OF THE DRAWINGS  
       [0027]      FIG. 1  is a schematic illustration of a trench structure for a first exemplary integrated conductor arrangement, in plan viewer.  
         [0028]     FIGS.  2 A-H are schematic sectional illustrations of successive method stages of a method for producing an integrated conductor arrangement, in particular coaxial conductor arrangement, in accordance with the first embodiment of the present invention, to be precise in each case along the line A-A′ and B-B′ in  FIG. 1 .  
         [0029]     FIGS.  3 A-F are schematic sectional illustrations of successive method stages of a method for producing an integrated conductor arrangement, in particular coaxial conductor arrangement, in accordance with a second embodiment of the present invention, to be precise in each case along the line A-A′ and B-B′ in  FIG. 1 . 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0030]     In the figures, identical reference symbols designate identical or functionally identical component parts.  
         [0031]      FIG. 1  shows a schematic illustration of a trench structure for an integrated conductor arrangement, in particular coaxial conductor arrangement, in accordance with a first embodiment of the present invention in plan view.  
         [0032]     In  FIG. 1 , reference symbol  1  designates a silicon semiconductor substrate, on the top side OF (cf.  FIG. 2 ) of which a patterned mask layer  5  made of silicon nitride, for example, is provided, which mask layer has openings for defining conductor trenches GB 1  to GB 4  and adjoining contact trenches KB 1  to KB 4 . The diameter of the conductor trenches GB 1  to GB 4  is illustrated by the reference symbol d G  in  FIG. 1  and is significantly smaller than the diameter d K  of the contact trenches KB 1  to KB 4 .  
         [0033]     As a scale for this, the upper region of  FIG. 1  illustrates a scale whose smallest unit F represents the minimum feature size that can be obtained by means of the technology.  
         [0034]     Consequently, the contact trenches KB 1  to KB 4  in  FIG. 1  have a diameter of 5 F, whereas the conductor trenches GB 1  to GB 4  have a diameter of 1 F.  
         [0035]     In  FIG. 1 , the contact trenches KB 1  to KB 4  are in each case depicted only at one end of the conductor trenches GB 1  to GB 4 . It goes without saying that further contact trenches may also be situated at the other end or at arbitrary locations laterally with respect to the conductor trenches GB 1  to GB 4  or be distributed or arranged arbitrarily over the length of the conductor trenches.  
         [0036]     FIGS.  2 A-H show schematic sectional illustrations of successive method stages of a method for producing an integrated conductor arrangement, in particular coaxial conductor arrangement, in accordance with the first embodiment of the present invention, to be precise in each case along the line A-A′ and B-B′ in  FIG. 1 .  
         [0037]      FIGS. 2A  to  2 H in each case illustrate on the left-hand side a section along the line A-A′ and on the right-hand side B-B′ as depicted in  FIG. 1 .  
         [0038]     The process state illustrated in  FIG. 2A  corresponds to the process state in accordance with  FIG. 1 . With the aid of the patterned mask layer  5  made of silicon nitride or some other material, the conductor trench GB 1  and the contact trench KB 1  have been etched into the substrate  1  by means of an anisotropic etching method.  
         [0039]     Referring further to  FIG. 2B , the substrate  1  is then etched isotropically under the patterned mask layer  5  in order to form an expanded conductor trench GB 1 ′ and an expanded contact trench KB 1 ′. The degree of expansion can be inferred from the broken line indicated in each case in  FIG. 2B , said line indicating the structure prior to the isotropic etching step.  
         [0040]     In a subsequent method step illustrated in  FIG. 2C , an insulating outer insulator layer  10  is then deposited over the structure, as a result of which the walls of the expanded conductor trench GB 1 ′ and of the adjoining expanded contact trench KB 1 ′ are covered with the insulating outer insulator layer  10  and as a result of which the patterned mask layer  5  is closed off in the region of the expanded conductor trench GB 1 ′ and remains open in the region of the expanded contact trench KB 1 ′. Consequently, long tubelike channels are formed in the substrate  1 , which are also closed off at the top and in which later the coaxial conductor runs.  
         [0041]     Afterward, in accordance with  FIG. 2D , a conductive outer conductor layer  15  is deposited conformally by means of an ALD method in such a way that it covers the walls of the extended conductor trench GB 1 ′ and of the extended contact trench KB 1 ′.  
         [0042]     Referring further to  FIG. 2E , an insulating middle insulator layer  20  is likewise deposited conformally by means of the ALD method, which layer is composed of silicon oxide, for example.  
         [0043]     Referring to  FIG. 2F , an ALD deposition of a conductive inner conductor layer  25  is then effected in order to complete the coaxial conductor which is integrated in the conductor trench GB 1 ′ and has the layers  10 ,  15 ,  20 , and  25 .  
         [0044]     In the process step illustrated in  FIG. 2G , the conductive inner conductor layer  25  is then removed as far as the top side of the insulating middle insulator layer  20  on the top side of the structure, for example by means of a chemical mechanical polishing step or an RIE (Reactive Ion Etching) etching-back step. A depression  50  is subsequently formed at the top side of the structure, through which a part of the conductive outer conductor layer  15  is removed, as a result of which the conductive outer conductor layer  15  is patterned.  
         [0045]     Referring further to  FIG. 2H , a further insulation layer  100  is deposited over the resulting structure, and the conductive inner conductor layer  25  and the conductive outer conductor layer  15  are subsequently contact-connected with a respective conductor track LI and LA.  
         [0046]     Although the conductor tracks LI, LA are depicted as non-shielded in the present example, it is possible, of course, also to shield these conductor tracks on the surface of the substrate.  
         [0047]     FIGS.  3 A-F show schematic sectional illustrations of successive method stages of a method for producing an integrated conductor arrangement, in particular coaxial conductor arrangement, in accordance with a second embodiment of the present invention, to be precise in each case along the line A-A′ and B-B′ in  FIG. 1 .  
         [0048]     In the second embodiment of the production method according to the invention, the starting point in accordance with  FIG. 3A  is the same state as the state in accordance with  FIG. 2D  (right-hand side).  
         [0049]     In this second exemplary embodiment, however, the conductive outer conductor layer  15  is removed in the region of the contact trench KB 1 ′ prior to deposition of the insulating middle insulator layer  20  and the conductive inner conductor layer  25 , as can be gathered from  FIG. 3B  (isotropic etching which, however, does not reach into the conductor trench). Consequently, as illustrated in  FIG. 3C  and  FIG. 3D , in the region of the contact trench KB 1 ′ only the conductive inner conductor layer  25  is led to the top side OF of the substrate  1 , where it is contact-connected by a conductor track LI′ in accordance with  FIG. 3E .  
         [0050]     The conductive outer conductor layer  15 , by contrast, is contact-connected by a conductor track LA′ in the region of the conductor trench GB 1 ′, to be precise after the outer insulator layer  10  has been removed in the through-plating region.  
         [0051]     Since the opening that remains in the contact trench KB 1 ′ at the top side is greater than in the case of the first exemplary embodiment, the deposition of the conductive inner conductor layer  25  is firstly carried out with high conformity, after which the conformity is lowered at the end in order to deposit the material with poorer edge coverage, so that it is possible to close the contact trench KB 1 ′ with the conductive inner conductor layer  25 .  
         [0052]     Although the present invention has been described above on the basis of a preferred exemplary embodiment, it is not restricted thereto, but rather can be modified in diverse ways.  
         [0053]     In particular, the invention can be applied in principle to arbitrary trench structures and material combinations.  
         [0054]     The geometry of the contact holes can be chosen as desired, in particular also round or oval. Moreover, relative sizes other than those illustrated are possible.  
         [0055]     Although modifications and changes may be suggested by those skilled in the art, it is the intention of the inventors to embody within the patent warranted heron all changes and modifications as reasonably and properly come within the scope of their contribution to the art.