Abstract:
The present invention is a method of producing a semiconductor device in which at least one alignment mark to be used in an exposure process of a lithographic process is formed of a wiring material which is copper or includes copper as a main component, and the alignment mark is formed entirely in an area outside an area where dicing is to be executed.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 11-055703, filed Mar. 3, 1999, the entire contents of which are incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     The present invention relates to a semiconductor device and a producing method thereof, and particularly to the technique of dicing. 
     A plurality of semiconductor integrated circuits are generally produced on a single semiconductor wafer. Normally, elements and wiring are formed on a wafer, the wafer is cut along dicing lines, and the individual integrated circuit is divided into a plurality of chips. 
     Alignment marks for alignment of each layer are formed in a dicing line area. Therefore, the alignment marks may be damaged by the dicing and a material used for the alignment marks may adhere to the chips. Generally, the same material as that of the wiring is used for the alignment marks. In a conventional semiconductor integrated circuit, aluminum (Al) is used as the wiring material and a serious problem does not particularly occur even if Al adheres to the chips. 
     Recently, a request to use copper (Cu) for the wiring as the wiring material of a lower resistance has been increased. It is known that Cu gives a bad influence to the element characteristics such as the variation in the threshold voltage of the semiconductor element since Cu easily diffuses in SiO 2  and Si. In the producing process of the semiconductor element, the diffusion of Cu to peripheral elements can be prevented by covering the Cu wiring with a diffusion prevention film. 
     At the time of dicing, however, the alignment marks formed in the dicing line area are damaged, and flying Cu adheres to the side surface or the back surface of the chip. Cu adhering to the chip diffuses to the element area by a following thermal process and gives a bad influence to the element characteristics. 
     BRIEF SUMMARY OF THE INVENTION 
     The present invention is achieved to solve the above-described problem of the prior art, and its object is to provide a semiconductor device using the Cu wiring which can solve the problems caused by the dicing and also provide a producing method of the semiconductor device. 
     A first invention is a method of producing a semiconductor device in which at least one alignment mark to be used in an exposure process of a litho-graphic process is formed of a wiring material which is copper or includes copper as a main component, and the method comprises forming the alignment mark entirely in an area outside an area where dicing is to be executed. 
     In the first invention, it is preferable that the alignment mark is entirely formed in an area where wirings and elements are to be formed. 
     According to this invention, the alignment mark is entirely formed in an area outside an area (a first area) where the dicing is to be executed and, therefore, the alignment mark is not damaged in the dicing process. For this reason, as copper constituting the alignment mark does not adhere to the chips at the time of the dicing, it is possible to solve the problem that the copper adhering to the semiconductor chips diffuses to the element area by the thermal treatment and thereby give a bad influence to the element characteristics and the like as seen in the prior art. 
     In addition, by forming the alignment mark entirely in an area (i.e. a second area) where the wirings and elements are to be formed, an interval between the first area and the second area can be made small. (When the first area and the second area have same width, the interval therebetween becomes zero.) Therefore, an area other than the second area can be made smaller. 
     A second invention is a semiconductor device in which at least one alignment mark to be used in an exposure process of a lithographic process is formed of a wiring material which is copper or includes copper as a main component, and the alignment mark is entirely formed inside a semiconductor chip separated by a dicing process. 
     In this invention, as the alignment mark is entirely formed inside the semiconductor chip, the alignment mark is not damaged at the time of dicing. Therefore, copper constituting the alignment mark does not adhere to the semiconductor chip and it is thereby possible to solve the problem that the element characteristics and the like are worsened by diffusion of copper. 
     A third invention is a method of producing a semiconductor device in which at least one pattern region corresponding to at least one alignment mark to be used in an exposure process of a lithographic process is formed of a wiring material which is copper or includes copper as a main component. After forming the pattern region corresponding to the alignment mark, the wiring material of the pattern region is removed or inactivated. 
     According to this invention, as the wiring material of the pattern region corresponding to the alignment mark is removed or inactivated, copper that is the wiring material does not adhere to the semiconductor chips even if the alignment mark is damaged at the time of dicing. Therefore, it is possible to solve the problem that the copper adhering to the semiconductor chips diffuses to the element area by the thermal treatment and thereby give a bad influence to the element characteristics and the like as seen in the prior art. 
     After the process of removing or inactivating the wiring material has been executed, the pattern where the wiring material has been removed or inactivated functions as the alignment mark. 
     A fourth invention is a method of producing a semiconductor device in which at least one alignment mark to be used in an exposure process of a litho-graphic process is formed of a wiring material which is copper or includes copper as a main component. In this method, the wiring material which is separated from a region where the alignment mark is formed and which adheres to a semiconductor chip, in a dicing process, is removed or inactivated. 
     According to this invention, the wiring material adhering to the semiconductor chips in the dicing process is removed or inactivated after the dicing process. Therefore, it is possible to solve the problem that the copper adhering to the semiconductor chips diffuses to the element area by the thermal treatment and thereby give a bad influence to the element characteristics and the like as seen in the prior art. 
     A fifth invention is a method of producing a semiconductor device in which at least one alignment mark to be used in an exposure process of a litho-graphic process is formed of a wiring material which is copper or includes copper as a main component. This method comprises a step of covering a pad formed by using the wiring material, with a protection film, before a dicing process, a step of removing or inactivating the wiring material which is separated from a region where the alignment mark is formed and which adheres to a semiconductor chip, in the dicing process, and a step of removing a part of the protection film to expose a surface of the pad after removing or inactivating the wiring material. 
     According to this invention, the wiring material adhering to the semiconductor chips in the dicing process is removed or inactivated. Therefore, it is possible to solve the problem that the copper adhering to the semiconductor chips diffuses to the element area by the thermal treatment and thereby give a bad influence to the element characteristics and the like as seen in the prior art. 
     Further, as the pad area is covered at the time of removing or inactivating the wiring material adhering to the semiconductor chips, it is possible to prevent the wiring material in the pad area from being removed or inactivated. 
     A sixth invention is a method of producing a semiconductor device in which at least one alignment mark to be used in an exposure process of a litho-graphic process is formed of a wiring material which is copper or includes copper as a main component. Grooves for dividing a semiconductor wafer into semiconductor chips are formed on a surface of the semiconductor wafer opposite to an element formation surface thereof, in the dicing process. 
     According to this invention, as the formation of the grooves on the semiconductor wafer in the dicing process is executed on a surface opposite to the element formation surface of the semiconductor wafer, it is possible to prevent the alignment mark formed on the element formation surface side from being damaged. Therefore, it is possible to solve the problem that the copper adhering to the semiconductor chips diffuses to the element area by the thermal treatment and thereby give a bad influence to the element characteristics and the like as seen in the prior art. 
     Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter. 
    
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING 
     The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate presently preferred embodiments of the invention, and together with the general description given above and the detailed description of the preferred embodiments given below, serve to explain the principles of the invention. 
     FIGS. 1A and 1B are plan views showing a part of a semiconductor wafer according to a first embodiment of the present invention; 
     FIGS. 2A to  2 C are sectional views showing a part of a semiconductor wafer according to a second embodiment of the present invention; 
     FIGS. 3A and 3B are perspective views showing a third embodiment of the present invention; 
     FIGS. 4A and 4B are sectional views showing a part of a semiconductor wafer according to a fourth embodiment of the present invention; and 
     FIG. 5 is a sectional view showing a part of a semiconductor wafer according to a fifth embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The embodiments of the present invention will be explained below with reference to the drawings. 
     (Embodiment 1) 
     FIGS. 1A and 1B are plan views showing a part of a semiconductor wafer (a silicon wafer or the like) according to a first embodiment of the present invention. 
     Areas  11  are used to form integrated circuit patterns such as elements (semiconductor elements used for integrated circuit operations and the like) and wiring. The areas  11  are normally shaped in a quadrilateral and include outermost patterns of respective edges at the time of forming the patterns in all the layers. The areas  11  are sectioned from one another by an area  12 . 
     An area  13  is an area where the dicing is to be executed. However, an area  14  where the dicing is actually executed is varied. Therefore, the area  13  is defined by adding margin to the area  14  where the dicing is actually executed. 
     As shown in the figures, the area  13  wider than the area  14  where the dicing is actually executed exists in the area  12  between the adjacent areas  11 , and the width of the area  13  is equal to that of the area  12  at the maximum. 
     An alignment mark  15  is used in an exposure process of the lithography. The alignment mark  15  is formed by using a wiring material (Cu or a material formed by mixing Cu with a tiny amount of elements (Sn, Ag, Mg, C and the like)) of a wiring  16  formed in the area  11 , and in the same process as the formation of the wiring  16 . In the present embodiment, the entire alignment mark  15  is formed outside the area  13 . 
     FIG. 1A shows an example of arranging the alignment marks  15  to cross the boundary between the area  11  and the area  12 . The entire marks  15  may be arranged in an area sandwiched between the area  11  and the area  13 . 
     FIG. 1B shows an example of arranging the entire alignment marks  15  in the area  11 . When the entire alignment marks  15  are arranged in the area  11 , there is a merit that the width of the area  12  can be made smaller (i.e. the interval between the area  11  and the area  13  can be made smaller). 
     In the prior art, the alignment marks  15  are arranged in the vicinity of the center of the area  12 . Thus, the alignment marks may be damaged at the time of the dicing, and Cu constituting the alignment marks may fly and adhere to the side surface or the back surface of the chip. In the present embodiment, the entire alignment marks  15  are arranged outside the area  13  and, therefore, the alignment marks are not damaged at the time of the dicing. Therefore, the problem that Cu adhering to the chip may diffuse to the element area by the thermal process can be prevented. 
     The alignment mark  15  may be arranged outside a part where an element  17  is formed or may be arranged to overlap the part where the element  17  is formed. 
     (Embodiment 2) 
     FIGS. 2A to  2 C are sectional views showing a part of a semiconductor wafer (a silicon wafer or the like) according to a second embodiment of the present invention. 
     Areas  21  are areas where integrated circuit patterns of semiconductor elements, wirings and the like (which correspond to the areas  11  of the Embodiment 1). The areas  21  are sectioned from one another by an area  22  (which corresponds to the area  12  of the Embodiment 1) are formed. 
     FIG. 2A shows a condition that a wiring area  23  and a pattern area  24  corresponding to an alignment mark are formed on a main surface side of a semiconductor wafer (not shown). The process steps will be simply explained. First, interlayer insulation films  25  and  26  are formed on the main surface side of the semiconductor wafer where semiconductor elements and the like are formed. After that, a part of the interlayer insulation film  26  is removed to form a groove corresponding to a wiring pattern and a groove corresponding to the alignment mark. Subsequently, barrier metals  23   a  and  24   a  are formed in the grooves, and wiring materials (Cu or materials prepared by mixing Cu with a tiny amount of elements (Sn, Ag, Mg, C and the like))  23   b  and  24   b  are further formed on the barrier metals  23   a  and  24   a.    
     At a step of FIG. 2B, a resist pattern  27  is formed so as to cover the areas  21 . Subsequently, the wiring material  24   b  exposed to the area  22  is removed in a process using a liquid agent such as (hydrochloric acid and hydrogen peroxide), by using the resist pattern  27  as a mask. In this case, the groove pattern from which the wiring material  24   b  is removed or the pattern of the barrier metal  24   a  which is left in the groove functions as an alignment mark. 
     The wiring material Cu may be inactivated in place of removal of the wiring material  24   b  exposed in the area  22 . For example, an oxidizing treatment using hydrogen peroxide is executed or a thermal treatment is executed in an oxygen atmosphere. In such a treatment, Cu is oxidized and changed to a substance  24   c  of CuO, Cu 2 O or the like that is hardly diffused. The substance is not diffused to the element area even though it adheres to a side wall of the chip. 
     In the present embodiment, as described above, the wiring material formed in the region corresponding to the alignment mark is removed or inactivated. Therefore, even if the alignment mark is damaged at the time of dicing, the wiring material Cu does not adhere to the chip. For this reason, it is possible to solve the problem that Cu diffuses to the element area and gives a bad influence to the element characteristics and the like. 
     (Embodiment 3) 
     FIGS. 3A and 3B are perspective views showing a third embodiment of the present invention. 
     A semiconductor chip  31  is obtained by subjecting a semiconductor wafer in the dicing process. In the semiconductor chip  31 , an integrated circuit pattern  32  such as elements, wiring and the like, and alignment marks  33  formed of the same wiring material (Cu or a material prepared by mixing Cu with a tiny amount of elements (Sn, Ag, Mg, C and the like)) in the same process as the wiring, are formed. Cu adherents  34  adhere to the side surfaces of the semiconductor chip  31  by allowing Cu constituting the alignment marks to fly at the time of dicing. 
     In the present embodiment, after a semiconductor wafer is divided into the semiconductor chips  31 , a liquid agent  35  such as (hydrochloric acid and hydrogen peroxide) is sprayed onto the side walls of the chip as shown in FIG.  3 B. The Cu adherents  34  adhering to the side walls of the chip are removed by the liquid agent  35 . 
     The element formation surface of the semiconductor chip  31  may be coated with resin such as acrylic resin and dipped into the liquid agent, instead of spraying the liquid agent  35  onto the side walls of the chip. 
     In the process shown in FIG. 3B, the process of inactivating the Cu adherents  34  may be executed instead of removing them. For example, the oxidizing process using hydrogen peroxide is executed. Thus, the Cu adherents  34  are oxidized and changed to CuO or Cu 2 O, and thereby the diffusion of Cu can be prevented. 
     As described above, the Cu adherents adhering to the chip by the dicing are removed or inactivated and, therefore, it is possible to solve the problem caused by allowing Cu to diffuse to the element area and thereby give a bad influence to the element characteristics, in the present embodiment. 
     (Embodiment 4) 
     FIGS. 4A and 4B are sectional views showing a part of a semiconductor wafer (a silicon wafer or the like) according to a fourth embodiment of the present invention, and particularly showing a sectional structure in the vicinity of a pad. 
     A process of FIG. 4A will be explained here. First, an interlayer insulation film  42  is formed on an main surface side of the semiconductor wafer on which the semiconductor elements and wirings and the like are formed. After that, a part of the interlayer insulation film  42  is removed to form grooves for pads and also form grooves for wiring (not shown) and grooves for alignment marks (not shown). Next, a barrier metal  43   a  is formed in each of these grooves, and a wiring material  43   b  (Cu or a material prepared by mixing Cu with a tiny amount of elements (Sn, Ag, Mg, C and the like)) is further formed on the barrier metal  43   a.  Subsequently, interlayer insulation films  44  and  45  are formed. 
     After that, an opening is formed in the only upper interlayer insulation film  45 . No opening is formed in the interlayer insulation film  44  at this time. Thus, the dicing is executed while covering the wiring material  43   b  of a pad area  43  with the interlayer insulation film  44 . Cu adherents  46  adhere to the side walls of the chip by the dicing. 
     The Cu adherents  46  adhering to the side walls of the chip are removed by dipping the entire body of the chip into a liquid agent of (hydrochloric acid and hydrogen peroxide). At this time, the wiring material  43   b  of the pad area  43  is not processed in the liquid agent since it is covered with the interlayer insulation film  44 . After the liquid agent treatment, an opening is formed in the interlayer insulation film  44  to expose the surface of the wiring material  43   b  of the pad area  43  as shown in FIG.  4 B. 
     The process of inactivating the Cu adherents  46  may be executed instead of removing them. For example, the oxidizing process using hydrogen peroxide or the like is executed. In this oxidizing process, the Cu adherents  46  are oxidized and changed to a substance such as CuO or Cu 2 O, which is hardly diffused. In this case, too, the pad area  43  is covered with the interlayer insulation film  44  and, therefore, the wiring material of the pad area is not processed by the liquid agent. 
     As described above, the pad area is covered with the interlayer insulation film at the time of removing or inactivating the Cu adherents and, therefore, it is possible to prevent the wiring material of the pad area from being removed or inactivated, in the present embodiment. 
     (Embodiment 5) 
     FIG. 5 is a sectional views showing a part of a semiconductor wafer (a silicon wafer or the like) according to a fifth embodiment of the present invention. 
     An interlayer insulation film  52 , semiconductor elements (not shown), wirings  53  and alignment marks  54  are formed on a semiconductor wafer  51 . The wirings  53  and the alignment marks  54  are formed of the same material in the same process. Wiring materials  53   b  and  54   b  (i.e. Cu or a material prepared by mixing Cu with a tiny amount of elements (Sn, Ag, Mg, C and the like)) constituting the wirings  53  and the alignment marks  54  are formed on barrier metals  53   a  and  54   a.    
     As shown in FIG. 5, a scar which is not so deep as to reach the alignment mark  54 , is formed (i.e. a cutaway groove is formed) on the back surface side (i.e. a surface side opposite to the element formation surface) of the semiconductor wafer  51 , by a diamond scriber  55  or the like, at the time of the dicing. A cleavage is performed along this scar on the semiconductor wafer  51 , which is thereby divided into a plurality of semiconductor chips. 
     According to a conventional manner, a scar is formed on the front surface side of the semiconductor wafer by the diamond scriber or the like so that a cleavage is performed to the semiconductor wafer. For this reason, the alignment marks in the dicing line area are damaged and Cu adheres to the side surfaces of the chips. In the present embodiment, a scar is formed on the back surface of the semiconductor wafer by the diamond scriber or the like and, therefore, it is possible to prevent the alignment marks from being damaged. Thus, it is possible to solve the problem of allowing Cu adhering to the chips at the time of the dicing to diffuse to the element area by the thermal treatment as seen in the prior art. 
     Additional advantages and modifications will readily occur to those skilled in the art. Therefore, the invention in its broader aspects is not limited to the specific details and representative embodiments shown and described herein. Accordingly, various modifications may be made without departing from the spirit or scope of the general inventive concept as defined by the appended claims and their equivalents.