Patent Publication Number: US-8114788-B2

Title: Method for manufacturing semiconductor device

Description:
This is a Continuation of Application Ser. No. 11/425,826 filed Jun. 22, 2006. The entire disclosure of Japanese Patent Application No. 2005-203487, filed Jul. 12, 2005 is expressly incorporated by reference herein. 
    
    
     BACKGROUND 
     1. Technical Field 
     The present invention relates to a method for manufacturing a semiconductor device. 
     2. Related Art 
     In order to improve electrical connection reliability, semiconductor devices using a resin core bump in which an electrical conducting layer is formed on a resin boss as an external terminal have been developed. According to such a semiconductor device, after the resin boss is formed on a semiconductor substrate, the electrical conducting layer is formed over from an electrode pad to the resin boss. In general, in a step of forming the electrical conducting layer, Ar contra-sputtering is performed to remove an oxide layer on the electrode pad. However, performing Ar contra-sputtering may lead to carbonization of the surface of the resin boss. In result, insulating resistance of the resin may be decreased, which might cause migration. In addition, in the case of the foregoing structure, the electrical conducting layer is formed to pass through over the three dimensional resin boss. Therefore, it is demanded to prevent the electrical conducting layer from being exfoliated or disconnected. 
     P-A-2-272737 is an example of related art. 
     SUMMARY 
     An advantage of some aspects of the invention is to improve contact characteristics of an electrical conducting layer and prevent migration. 
     A method for manufacturing a semiconductor device according to a first aspect of the invention includes: a. a step of forming an energy cured resin layer on a semiconductor substrate having an electrode pad and a passivation film; b. a step of fusing the resin layer without being cured and shrunk by a first energy supply processing; c. a step of forming a resin boss by curing and shrinking the resin layer after fusion by a second energy supply processing; and d. a step of forming an electrical conducting layer which is electrically connected to the electrode pad and passes through over the resin boss. 
     According to the first aspect of the invention, the resin layer is fused, the surface is formed into a smooth curved surface, and the resin layer is cured and shrunk from such a shape. Therefore, a resin boss with a moderate rising section can be finally formed. Thereby, the electrical conducting layer is prevented from being exfoliated and disconnected, and the contact characteristics thereof can be improved. 
     According to the first aspect of the invention, a state that B is provided on specific A includes the case that B is directly provided on A and the case that other element is sandwiched between A and B. The same is applied to the following aspect of the invention. 
     A method for manufacturing a semiconductor device according to a second aspect of the invention includes: a. a step of forming an energy cured resin layer on a semiconductor substrate having an electrode pad and a passivation film b. a step of fusing the resin layer so that fusion of a surface section is progressed more than of a central section by a first energy supply processing; c. a step of forming a resin boss by curing and shrinking the resin layer by a second energy supply processing; and d. a step of forming an electrical conducting layer which is electrically connected to the electrode pad and passes through over the resin boss. 
     According to the second aspect of the invention, the surface section of the resin layer is fused, the surface is formed into a smooth curved surface, and the resin layer is cured and shrunk from such a shape. Therefore, a resin boss with a moderate rising section can be finally formed. Thereby, the electrical conducting layer is prevented from being exfoliated and disconnected, and the contact characteristics thereof can be improved. 
     3. In the method for manufacturing a semiconductor device according to the second aspect of the invention, the resin layer other than the central section, that is, only the surface section may be fused in the step b. 
     4. In the method for manufacturing a semiconductor device according to the first aspect of the invention, both the first and the second energy supply processing may be heat processing, and the heating temperature in the step c may be higher than the heating temperature in the step b. 
     5. In the method for manufacturing a semiconductor device according to the first aspect of the invention, the resin layer may be formed in the shape of an approximate quadrangle on cross section by the step a, and the resin layer may be formed in the shape of an approximate semicircle on cross section by the step b. 
     6. In the method for manufacturing a semiconductor device according to the first aspect of the invention, in the step d, an oxide film may be removed from the surface of the electrode pad and carbonization of the surface of the resin boss may be progressed by Ar gas before forming the electrical conducting layer, and the resin boss may be partly removed by using the electrical conducting layer as a mask after forming the electrical conducting layer. 
     Thereby, even if carbonation of the resin boss is progressed by Ar gas and a carbonized layer (or plasma polymerization layer) is formed, the resin boss can be easily removed without leaving the carbonized layer or the like since the rising section of the resin boss is formed moderately. In particular, the carbonized layer or the like easily remains in the root section of the resin boss. However, according to the aspect of the invention, the carbonized layer or the like remaining in the root section of the resin boss can be easily removed. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will be described with reference to the accompanying drawings, wherein like numbers reference like elements. 
         FIG. 1  is a view explaining a method for manufacturing a semiconductor device according to this embodiment; 
         FIG. 2  is a view explaining the method for manufacturing a semiconductor device according to this embodiment; 
         FIG. 3  is a view explaining the method for manufacturing a semiconductor device according to this embodiment; 
         FIG. 4  is a view explaining the method for manufacturing a semiconductor device according to this embodiment; 
         FIG. 5  is a view explaining the method for manufacturing a semiconductor device according to this embodiment; 
         FIG. 6  is a view explaining the method for manufacturing a semiconductor device according to this embodiment; 
         FIG. 7  is a view explaining the method for manufacturing a semiconductor device according to this embodiment; 
         FIG. 8  is a view explaining the method for manufacturing a semiconductor device according to this embodiment; 
         FIG. 9  is a cross section taken along line IX-IX of  FIG. 8 ; 
         FIG. 10  is a cross section taken along line X-X of  FIG. 8 ; 
         FIG. 11  is a view explaining the method for manufacturing a semiconductor device according to this embodiment; 
         FIG. 12  is a view showing an electronic device according to this embodiment; 
         FIG. 13  is a view showing electronic equipment according to this embodiment; 
         FIG. 14  is a view showing electronic equipment according to this embodiment; 
         FIG. 15  is a view explaining a method for manufacturing a semiconductor device according to a modified example of this embodiment; and 
         FIG. 16  is a view explaining a method for manufacturing a semiconductor device according to a modified example of this embodiment. 
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
     An embodiment of the invention will be described with reference to the drawings. 
     Method for Manufacturing a Semiconductor Device 
       FIG. 1  to  FIG. 11  are drawings for explaining a method for manufacturing a semiconductor device according to the embodiment of the invention. 
     1. First, as shown in  FIG. 1  and  FIG. 2 , a semiconductor substrate  10  is prepared. The semiconductor substrate  10  is, for example, a semiconductor wafer (refer to  FIG. 1 ). In this case, the semiconductor substrate  10  has a plurality of chip regions  12  to become semiconductor chips. An integrated circuit  14  is formed inside each chip region  12 . That is, when the semiconductor substrate  10  is divided into the plurality of semiconductor chips, each semiconductor chip has each integrated circuit  14 . The integrated circuit  14  includes at least active devices such as a transistor. The chip region  12  is in the shape of an orthogon (for example, rectangle) in the plan view. In each chip region  12 , a plurality of electrode pads (for example, aluminum pad)  16  are formed. The plurality of electrode pads  16  may be arranged along opposed two sides of the chip region  12  (for example, two long sides) or four sides of the chip region  12 . In this case, one or a plurality of rows of the electrode pads  16  are arranged in each side. When the electrode pads  16  are arranged in the edge of the chip region  12 , the integrated circuit  14  may be formed in the central section surrounded by the plurality of electrode pads  16 . Otherwise, the electrode pad  16  may be formed in the region overlapped with the integrated circuit  14  in the plan view. The electrode pad  16  is electrically connected to the integrated circuit  14  through an internal wiring (not shown). 
     A passivation film (protective film)  18  is formed on the surface of the semiconductor substrate  10  (face on which the integrated circuit  14  is formed). The passivation film  18  may be formed either from an inorganic material or an organic material. For example, the passivation film  18  may be formed from at least one layer of a silicon oxide film and a silicon nitride film. An aperture  19  is formed in the passivation film  18  to provide the electrode pad  16  with opening. At least part of the electrode pad  16  (for example, only the central section) is exposed by the aperture  19 . In many cases, an oxide layer  17  is formed on the electrode pad  16 . The oxide layer  17  is formed by, for example, natural oxidation, and coats the surface of the electrode pad  16 . 
     2. Next, as shown in  FIG. 3  to  FIG. 5 , a resin layer  20  is formed. 
     The resin layer  20  can be formed on the semiconductor substrate  10  (more particularly on the passivation film  18 ) and in a region different from the electrode pad  16  in the plan view. The region where the resin layer  20  is formed is not limited, but for example, the resin layer  20  can be formed in the shape of a straight line having a given width. In this case, the resin layer  20  can be formed to extend along (for example, in parallel to) a boundary of the chip region  12  of the semiconductor substrate  10  (for example, in the long side direction). 
     Specifically, first, as shown in  FIG. 3 , the semiconductor substrate  10  is coated with a photosensitive resin layer  20   a  by, for example, spin coat method. After that, as shown in  FIG. 4 , a mask  22  having an aperture  24  is arranged over the semiconductor substrate  10 . Then, exposure is made by illuminating with light energy  26 . When a negative type resin layer  20   a  in which solubility of a developing solution is decreased in the section illuminated with the light energy  26  is used, the resin can remain only in the region exposed from the aperture  24  of the mask  22 . On the contrary, when a positive type resin layer  20   a  in which solubility of a developing solution is increased in the section illuminated with the light energy  26  is used, the resin can remain only in the region covered with the mask  22 . After that, by performing an image development step, as shown in  FIG. 5 , the resin layer  20  can be patterned in a given shape. The resin layer  20  can be formed in the shape of an approximate quadrangle (approximate orthogon) on cross section. 
     Here, as an example of a resin material of the resin layer  20 , an elastic resin material such as a polyimide resin, an acrylic resin, a phenol resin, an epoxy resin, a silicon resin, and a modified polyimide resin can be cited. Further, the resin layer  20  can be, for example, polyimide, polybenzoxazole, benzocyclobutene, epoxy or the like, which is an aromatic compound of an organic compound having a benzene ring or a condensed ring thereof. The resin layer  20  is an energy cured resin (for example, a heat cured resin and a light cured resin). 
     As a modified example of the foregoing patterning step of the resin layer  20 , for example, drop discharge method (for example, inkjet method) may be applied. According to the drop discharge method, a resin material can be directly discharged to an appropriate region. In particular, according to inkjet method, by applying a technology being in practical use for inkjet printers, the resin layer  20  can be provided speedy and economically without using needless ink (resin material). 
     3. After that, as shown in  FIG. 6  and  FIG. 7 , a resin boss  40  is formed. 
     First, as shown in  FIG. 6 , by a first energy supply processing (for example, heat processing and light illumination processing), a resin layer  30  is fused. In this case, the resin layer  30  is not cured and shrunk (crosslinking reaction). More particularly, the resin layer  30  is fused so that curing and shrinkage reaction of all or part of the resin layer  30  is not started. When a heat cured resin is used, heat processing is performed at temperatures and for time in which the resin is fused, the resin layer  30  is fused, and the surface is formed into a smooth curved surface. For example, when the cross section shape of the resin layer  20  after patterning is an approximate quadrangle, the cross section shape of the resin layer  30  after fusion can be formed in the shape of an approximate semicircle. The heating temperatures and heating time can be adjusted as appropriate according to the resin material. 
     After that, as shown in  FIG. 7 , by a second energy supply processing (for example, heat processing and light illumination processing), the resin layer  30  after fusion is cured and shrunk. When the cross section shape of the resin layer  30  after fusion is an approximate semicircle, by curing and shrinking the resin layer  30  (completing curing and shrinkage reaction) in this step, the resin boss  40  with a moderate rising section can be formed. When a heat cured resin is used, heat processing is performed at temperatures and for time in which the resin after fusion is cured and shrunk. In this case, the foregoing heating temperature in curing may be higher than the heating temperature in fusion. That is, the curing temperature of the resin material may be higher than the fusion temperature of the resin material. The curing temperature of the resin material may be adjusted as appropriate by changing an amount or constituents of additives (curing agent and crosslinking agent) added to the resin material. Further, the heating time in curing may be longer than the heating time in fusion. The first and the second energy supply processing may be performed in a series of steps. 
     As shown in  FIG. 7 , the surface of the resin boss  40  is a curved surface. The cross section of the resin boss  40  is in the shape of an approximate semicircle, for example. A rising angle of the resin boss  40  (angle made by a tangent line of an inclined plane in the vicinity of the rising section and the surface of the passivation film  18  (so-called contact angle)) θ is at least in the range of θ&lt;90 deg (optimally in the range of θ&gt;0 deg). Further, the rising section of the resin boss  40  is formed in a curve so that a concave shape is made in the outward direction (upward oblique direction). 
     4. Next, as shown in  FIG. 8  to  FIG. 10 , an electrical conducting layer  50  which is electrically connected to the electrode pad  16  and passes through over the resin boss  40  is formed.  FIG. 8  is a partial plan view of the state after a step of forming the electrical conducting layer.  FIG. 9  is a cross section taken along line IX-IX of  FIG. 8 .  FIG. 10  is a cross section taken along line X-X of  FIG. 8 . 
     First, before the electrical conducting layer  50  is formed, the oxide layer  17  on the electrode pad  16  is removed. The oxide layer  17  is, for example, a layer grown by natural oxidation or grown by the foregoing step of curing the resin. As a method of removing the oxide layer  17 , for example, contra-sputtering of Ar gas can be applied. When the contra-sputtering of Ar gas is performed on the whole face of the semiconductor substrate  10 , carbonization of the surface of the resin boss  40  is thereby progressed. That is, a carbonized layer or a precursory layer of the carbonized layer (for example, plasma polymerization layer) is formed on the surface of the resin boss  40 . This embodiment is particularly beneficial in the case that the carbonized layer or the like is formed as above. 
     The electrical conducting layer  50  can be formed by depositing an electrical conducting foil by sputtering method or vapor deposition method, and then patterning the electrical conducting foil. The electrical conducting layer  50  can be formed from a plurality of layers composed of a first layer (for example, TiW layer)  52  as a base and a second layer thereon (for example, Au layer)  54 , for example. In this case, it is possible that the electrical conducting foil is formed from the first and the second layers  52  and  54 , the second layer  54  is patterned by etching (for example, wet etching) by using a resist as a mask, and the first layer  52  is patterned by using the second layer  54  after patterning as a mask. The first layer  52  as a base can be utilized to prevent metal diffusion and improve contact characteristics, and can be utilized as a plated layer. As a modified example, it is possible that the first layer  52  as a base is formed by sputtering method or vapor deposition method, and the second layer  54  thereon is formed by electroless plating or electroplating. Thereby, the second layer  54  can be easily formed thicker. Otherwise, the electrical conducting layer  50  can be formed from a single layer (for example, Au layer). The material of the electrical conducting layer  50  is not limited to the foregoing, but, for example, Cu, Ni, Pd, Al, Cr or the like can be used as a material thereof. 
     The electrical conducting layer  50  is a wiring layer which electrically connects the electrode pad  16  to the resin boss  40 . The electrical conducting layer  50  is formed to pass through over at least the electrode pad  16 , the passivation film  18 , and the resin boss  40 . In this embodiment, since the rising section of the resin boss  40  is formed moderately, contact characteristics of the electrical conducting layer  50  can be improved. Therefore, the electrical conducting layer  50  can be prevented from being exfoliated and disconnected. In the example shown in  FIG. 9 , the electrical conducting layer  50  is formed to pass past the resin boss  40  to reach the passivation film  18  again. In other words, the electrical conducting layer  50  is formed to branch out in a plurality of directions (for example, opposite directions) from the resin boss  40  to reach the passivation film  18 . Thereby, contact characteristics to the base of the electrical conducting layer  50  can be further improved. The electrical conducting layer  50  has an electrical connection section  56  formed on the resin boss  40 . 
     As shown in  FIG. 10  and  FIG. 11 , it is possible that after the electrical conducting layer  50  is formed, the resin boss  40  is partly removed by using the electrical conducting layer  50  as a mask. Thereby, for example, emission characteristics of an adhesive in mounting can be improved. For example, when the resin boss  40  is formed in the shape of a straight line with a given width, and the plurality of electrical connection sections  56  are arranged at given intervals in the longitudinal direction of the resin boss  40 , a section exposed from between the adjacent electrical connection sections  56  is removed by etching with an anisotropic etchant (for example, O2 plasma)  58 . In this case, in order to prevent the passivation film  18  from being damaged, etching can be made so that a resin residual  44  is provided between the adjacent electrical connection sections  56 . According to this embodiment, the rising section of the resin boss  40  is moderate. Therefore, the anisotropic etchant easily enters the root section of the resin boss  40 . Thereby, the carbonized layer and the like formed in the root section of the resin boss  40  can be removed more easily than in the past. Consequently, migration resulting from the carbonized layer and the like can be prevented, and reliability can be improved. 
     In result, a semiconductor device  100  having a plurality of resin core bumps  60  can be manufactured. The resin core bump  60  is formed on one face of the semiconductor substrate  10  (face on which the integrated circuit  14  is formed). The resin core bump  60  includes a resin boss  42  and the electrical connection section  56  formed on the resin boss  42 . Thereby, since the resin boss  42  becomes a core and has elasticity itself, a stress relaxation function and electrical connection reliability in mounting can be improved. The semiconductor device according to this embodiment has a structure derivable from the foregoing contents of the method for manufacturing a semiconductor device. 
     Electronic Equipment 
       FIG. 12  is a view showing an electronic device according to the embodiment of the invention. An electrical device (for example, display device)  1000  includes the semiconductor device  100 . In the example shown in  FIG. 12 , the electronic device  1000  includes the semiconductor device  100 , a first substrate  200  made of a resin film or the like, and a second substrate  300  made of glass or the like. The semiconductor device  100  is mounted face-downward on the first substrate  200 , for example. More specifically, a wiring pattern formed on the first substrate  200  is electrically connected to the resin core bump  60  of the semiconductor device  100 . An unshown insulative adhesive (for example, NCF (Non Conductive Film) or NCP (Non Conductive Paste)) is provided between the semiconductor device  100  and the first substrate  200 . Otherwise, it is possible that the first substrate  200  is omitted, and the semiconductor device  100  is mounted face-downward on the second substrate  300 . As an example of the electron device  1000 , for example, a liquid crystal display, a plasma display, an EL (Electrical Luminescence) display and the like can be cited. As an example of the electronic equipment according to the embodiment of the invention, a notebook-sized personal computer is shown in  FIG. 13 , and a mobile phone is shown in  FIG. 14 . 
     Modified Example 
       FIG. 15  is a view explaining a method for manufacturing a semiconductor device according to a modified example of the embodiment of the invention. 
     In this modified example, by the first energy supply processing, a resin layer  130  is fused so that fusion of a surface section  132  is progressed more than of a central section  134 . For example, when a heat cured resin is used, heat processing is performed by hot air to fuse the surface section  132  of the resin layer  130 . The heat processing by hot air can be performed in a reduced pressure than the ambient pressure. Further, in the resin layer  130 , it is enough that fusion of the surface section  132  is progressed more than of the central section  134 . It is possible that the surface section  132  and the central section  134  are fused concurrently. Otherwise, the resin layer  130  other than the central section  134 , that is, only the surface section  132  may be fused. Further, it is enough that at least the surface section  132  of the resin layer  130  is progressed by the first energy supply processing. It is also possible that curing and shrinkage reaction of at least part of the surface section  132  is started concurrently with fusion. In this step, as shown in  FIG. 15 , the surface of the resin layer  130  can be formed into a smooth curved surface. 
     After that, by performing the second energy supply processing, the resin layer  130  after fusion is cured and shrunk. In this modified example, the surface of the resin layer  130  after fusion can be also formed into a smooth curved surface. Therefore, by curing and shrinking the resin layer  130  from such a shape, a resin boss with a moderate rising section can be formed. 
       FIG. 16  is a view explaining a method for manufacturing a semiconductor device according to other modified example of the embodiment of the invention. In this modified example, the mode of a resin boss  240  is different from the foregoing. 
     For details of patterning of a resin layer, the foregoing contents can be applied. However, in this modified example, before the step of forming the electrical conducting layer  50 , the plurality of resin bosses  240  are formed separately from each other so that one of the resin bosses  240  corresponds to one of the electrode pads  16 . Thereby, for example, after patterning the resin layer in the shape of a plurality of columns individually, the approximate semicircle resin boss  240  can be formed by performing the first and the second energy supply processing. The details thereof are as described above. 
     For example, the electrical conducting layer  50  electrically connects one electrode pad  16  to one resin boss  240 . In this case, the electrical conducting layer  50  may be formed to cover only part of one resin boss  240 , or can be formed to cover the whole thereof. In the former case, part of the resin boss  240  is exposed, and therefore external force is opened. In result, the electrical connection section  56  (electrical conducting layer  50 ) can be prevented from being cracked in mounting. 
     In this modified example, the resin boss  240  is formed separately from each other previously. Therefore, the step of partly removing the resin boss after forming the electrical conducting layer  50  as in the foregoing example can be omitted. 
     The invention is not limited to the foregoing embodiment, and various modifications may be made. For example, the invention includes structures which are substantially identical with the structure explained in the embodiment (for example, structures which are substantially identical with the structure explained in the embodiment in terms of the function, the method, and the result, or structures which are substantially identical with the structure explained in the embodiment in terms of the purpose and the result). Further, the invention includes structures, in which a part unessential for the structure explained in the embodiment is substituted. Further, the invention includes structures providing the operation and the effect which are identical with of the structure explained in the embodiment, or structures capable of attaining the purpose identical with of the structure explained in the embodiment. Further, the invention includes structures in which a well known art is added to the structure explained in the embodiment.