Abstract:
An integrated circuit is produced to include interconnection levels each incorporating a metallization level covered with an insulating material. The integrated circuit includes at least one capacitor possessing at least one part lying within a single interconnection level. The capacitor is produced before the interconnection level is produced. The covering of part of the capacitor with an insulating protective layer occurs before the metallization level of the interconnection level is produced.

Description:
PRIORITY CLAIM 
   The present application claims priority from French Application for Patent No. 05 03893 filed Apr. 19, 2005, the disclosure of which is hereby incorporated by reference. 
   BACKGROUND OF THE INVENTION 
   1. Technical Field of the Invention 
   The present invention relates to integrated circuits and more particularly to integrated circuits comprising at least one capacitor. 
   2. Description of Related Art 
   It is known to produce planar or three-dimensional capacitors using an aluminum technology (by reactive ion etching or RIE) or a copper technology (damascene method). 
   Capacitors are conventionally obtained from an MIM (metal-insulator-metal) capacitive multilayer in which the lower layer is a conducting material, such as for example, TiN, the insulator is a dielectric, for example having a high permittivity (or high-k dielectric), and the upper electrode is a conducting material, such as TiN. These capacitors are generally produced separately and then assembled in a complex circuit. The production of capacitors within even one integrated circuit still remains today a challenge, given that this production must be compatible with the existence of active components within this complex circuit. 
   Within an integrated circuit, the capacitor is generally produced before the interconnection level is produced. The production of the interconnection level comprises a metallization level, a metal etching step in order to obtain the interconnection lines and the deposition of an insulator, such as an intermetallic dielectric. Generally, during the metal etching step, the electrodes of the capacitor are damaged. More particularly, the electrodes may be partly or completely eroded by the overetching of the metal. When the lower electrode is offset, the overetching of the metal may completely erode it to the point of eliminating its offset part. It may also happen that two electrodes are brought into contact with each other via residues of underetched metal. 
   SUMMARY OF THE INVENTION 
   Embodiments of the present invention provide a solution to these problems, especially by depositing an insulating protective layer over the entire capacitor. 
   According to one aspect of the invention, what is proposed is a process for producing an integrated circuit, comprising the production of interconnection levels each incorporating a metallization level covered with an insulating material and the production of at least one capacitor possessing at least one part lying within a single interconnection level, wherein the capacitor is produced before said interconnection level is produced and said part of said capacitor is covered with an insulating protective layer before the metallization level of said interconnection level is produced. 
   According to one method of implementation, the production of said part of the capacitor includes the formation of a metal-insulator-metal capacitive multilayer, the deposition of a metal layer on the capacitive multilayer, the photoetching of the upper metal layers so as to form the upper electrode of the capacitor, then the deposition of the insulating protective layer followed by simultaneous photoetching of the insulating protective layer, the dielectric and the lower metal layer offset with respect to the upper electrode and covered by the dielectric and said insulating protective layer. 
   Preferably, the insulating protective layer consists of silicon oxide or silicon nitride. 
   More particularly, the insulating protective layer is at least 1000 Å. 
   According to a preferred method of implementation, the capacitor is a planar capacitor lying entirely within said interconnection level. 
   According to a preferred method of implementation, the capacitor is a three-dimensional capacitor possessing said offset part covered with the insulating protective layer and at least one capacitive trench lying within at least one interconnection level below that in which said offset part lies. 
   More particularly, the three-dimensional capacitor has at least two capacitive trenches lying within a dielectric. The process comprises producing a metal layer embedded in said dielectric, etching the dielectric, stopping on said metal layer so as to form said trenches, and depositing a layer of conductive material forming the lower electrode of the capacitor, at least on the sidewalls of said trenches and in contact with said metal layer. 
   According to another aspect of the invention, what is proposed is an integrated circuit comprising one capacitor coated with an insulating protective layer, said layer lying on a single interconnection level of the integrated circuit. 
   According to one embodiment, the insulating protective layer covers the upper electrode and the dielectric deposited on an offset part of the lower electrode of the capacitor. 
   Preferably, the insulating protective layer consists of silicon oxide or silicon nitride. 
   More particularly, the insulating protective layer is at least 1000 Å. 
   According to another embodiment, the capacitor is a planar capacitor lying within a single interconnection level. 
   According to another embodiment, the capacitor is a three-dimensional capacitor possessing an upper part covered by said protective layer and at least one capacitive trench. 
   More particularly, the three-dimensional capacitor lying within a dielectric includes a metal layer embedded in the said dielectric, at least two capacitive trenches, the bottoms of which bear on said metal layer, and a layer of conducting material forming the lower electrode of the capacitor, said layer of conducting material being located at least on the side walls of said trenches and in contact with said metal layer. 
   In accordance with another embodiment, a process for producing an integrated circuit comprises producing at least one lower interconnection level of the integrated circuit and producing a capacitive multilayer structure possessing at least one portion which lies on a top surface of the at least one lower interconnection level. Following producing of the capacitive multilayer structure, the at least one portion thereof is covered with an insulating protective layer. Then, at least one upper interconnection level of the integrated circuit is produced within which the at least one portion and insulating protective layer lie. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     A more complete understanding of the method and apparatus of the present invention may be acquired by reference to the following Detailed Description when taken in conjunction with the accompanying Drawings wherein: 
       FIGS. 1 to 9  illustrate schematically the main steps of a method of implementing a process for fabricating a three-dimensional capacitor according to the invention and of a planar capacitor according to the invention in  FIGS. 5 to 9 . 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1  shows an integrated circuit CI comprising a silicon substrate A on which a dielectric layer B has been deposited. Several interconnection levels C, D and E rest on the dielectric layer B. Each interconnection level comprises a metallization level formed from metal tracks and a via level, the combination of the two being embedded in a dielectric. The production of each interconnection level is conventional and known per se to those skilled in the art. In the example described here, the metallization level M i  of the interconnection level C includes a metal layer  1   a . The layer  1   a  may be made of aluminum or copper. The metallization level M i+1  of the interconnection level D includes an interconnection line or track  1   b . The metallization level M i+2  of the interconnection level E includes an interconnection line or track  1   c . The interconnection lines  1   a ,  1   b ,  1   c  of the various interconnection levels C, D, E are connected together by the vias Va, Vb, Vc made in the dielectrics  2   a ,  2   b  and  2   c . The interconnection levels C, D and E may incorporate passive components. 
     FIG. 2  illustrates the production of two trenches within the integrated circuit IC. The two trenches  3   a  and  3   b  are produced in a conventional manner known per se to those skilled in the art within the intermetallic dielectrics  2   a ,  2   b  and  2   c  of the levels C, D and E by photolithography followed by etching. The etching of these trenches stops on the metal layer  1   a.    
     FIG. 3  illustrates the conventional formation, for example by deposition, of a capacitive feature formed from three successive layers, namely metal  4   a , insulator  4   b  and metal  4   c . The metal layers forming the electrodes may be made of TiN, TaN or W. The insulator layer may consist of SiO 2  or a dielectric such as Al 2 O 3  or SiN or a dielectric having a high permittivity or high-k dielectric, such as Ta 2 O 5  or HfO 2 . 
   This capacitive multilayer is in particular deposited on the sidewalls of the trenches and in the bottom of the trenches, in such a way that the lower metal layer  4   a  comes into contact with the metal layer  1   a . This metal layer  4   a  is intended to form the lower electrode of the capacitor. 
     FIG. 4  illustrates the filling of the trenches with a conducting material  5  such as W, TiN or Al, for example by deposition. 
     FIG. 5  illustrates a three-dimensional capacitor  6  and a planar capacitor  7  on the same interconnection level, the lower interconnection levels not being shown. This figure illustrates the capacitors after the upper metal layers  5  and  4   c  have been etched so as to form the upper electrode of said capacitors  6  and  7 . 
     FIG. 6  illustrates the three-dimensional capacitor  6  and the planar capacitor  7 , on which an insulating protective layer  8  has been deposited by PECVD (plasma-enhanced chemical vapor deposition), for example at a temperature of 400° C. and a pressure of a few torr (typically 3 to 7 torr) for a time ranging from a few seconds to 60 seconds. Preferably, the insulating protective layer consists of silicon oxide or silicon nitride. The thickness h 1  of the insulating protective layer is preferably at least 1000 Å. 
     FIG. 7  illustrates the three-dimensional capacitor  6  and the planar capacitor  7  after the protective layer  8 , the dielectric  4   b  and the lower electrode  4   a  have been simultaneously etched. This etching is carried out so as to slightly offset the dielectric  4   b  and the subjacent lower electrode  4   a  with respect to the metal layers  4   c  and  5  that form the upper electrode, constituting the offset part P. Thus, any lateral short-circuiting between the lower electrode and the upper electrode of the capacitor during etching is prevented. The distance d between the end of the upper electrodes  4   c  and  5  and the end of the dielectric  4   b /lower electrode  4   a  multilayer is preferably between 0.3 and 2 μm, typically 1 μm. This distance is controlled by the conventional photoetching process. 
   Next, the metallization level M i+3  ( FIG. 8 ) is conventionally produced, in particular to form the tracks  9  in contact with the vias Vc. While the metal is being etched, the protective layer is partially eroded, its thickness h 2  becoming less than the initial thickness h. 
     FIG. 9  illustrates the end of the process for producing the interconnection level F by deposition of a dielectric  2   d . A via Vd 1  lying along the extension of the vias Vc, Vb and Va and of the interconnection lines  1   a ,  1   b ,  1   c  and  9  is produced. A second via Vd 2  is produced so as to come into contact with the metal layer  5  of the upper electrode of the three-dimensional capacitor  6  by etching the dielectric  2   d  and the protective layer  8 . 
   Another via  1   d   1  lying along the extension of the via Vc and of the interconnection lines  1   c  and  9  is produced. A final via  1   d   2  is produced so as to come into contact with the metal layer  5  of the upper electrode of the planar capacitor  7  by etching the dielectric  2   d  and the protective layer  8 . Interconnection lines  10  are then produced in the metal level M i+4  on the vias Vd 1 , Vd 2 ,  1   d   1  and  1   d   2 . 
   In the case of the three-dimensional capacitor, the lower electrode  4   a  is contacted via the tracks  10 ,  9 ,  1   c  and  1   b , the vias Vd 1 , Vc, Vb and Va and the metal layer  1   a . The upper electrode  5  is contacted via the track  10  and the via Vd 2 . 
   The metal layer  1   a  contacting the bottom of the trenches serves both as a stop layer for etching the trenches  3   a  and  3   b  and serves to partly short-circuit the lower electrode  4   a  of the three-dimensional capacitor  6 . Thus, the height of the trenches is controlled from one batch to another, and the access resistance of the capacitor is reduced. 
   The embodiment of the three-dimensional capacitor illustrated in  FIG. 9  is in no way limiting. The contacting of the lower electrode  4   a  may take place directly on the latter and not by means of the metal layer  1   a . The three-dimensional capacitors implemented according to the invention may comprise one or more capacitive trenches, and are not limited to two trenches as illustrated. 
   The embodiment of the planar capacitor illustrated in  FIG. 9  is in no way limiting. The contacting of the lower electrode  4   a  may take place directly on the latter and not from below by means of the track  1   c.    
   The insulating protective layer  8  makes it possible to absorb the overetching of the interconnection lines. The good resistance of silicon oxide and silicon nitride to the metal etching process prevents the dielectric  4   b , the subjacent lower electrode  4   a  and the metal layer  5  from being etched. The thickness of the dielectric layer  4   b  and the thickness of the metal layer forming the subjacent lower electrode  4   a  and the thickness of the metal layer  5  are maintained. In addition, the electrodes can no longer be contacted by metal residues. Finally, the insulating protective layer makes it possible to eliminate any defective behavior at the edge of capacitors, such as leakage currents or premature breakdowns. 
   Although preferred embodiments of the method and apparatus of the present invention have been illustrated in the accompanying Drawings and described in the foregoing Detailed Description, it will be understood that the invention is not limited to the embodiments disclosed, but is capable of numerous rearrangements, modifications and substitutions without departing from the spirit of the invention as set forth and defined by the following claims.