TWI328266B - Manufacturing method of flat-bump structure - Google Patents

Description

1328266 CN-9509003 22159twf.doc/n IX. Description of the Invention: [Technical Field] The present invention relates to a bump structure and a method of fabricating the same, and more particularly to a flat-bump Structure and its manufacturing method. [Prior Art] Flip chip interconnect technology is a packaging technique for connecting a die to a wiring board, which mainly forms a plurality of bumps on a plurality of pads of the wafer. The wafers are then flipped' and the bumps are used to connect the pads of the wafer to the terminals on the board such that the wafers can be electrically connected to the board via the bumps. Generally, there are several types of bumps, such as solder bumps, gold bumps, copper bumps, conductive polymer bumps, high molecular bumps, and the like. 1A is a cross-sectional view of a conventional gold bump, and FIG. 1B is a top view of a conventional gold bump. Referring to FIG. 1A and FIG. 1B, a conventional gold bump structure is suitable for being disposed on a wafer Π0, and a plurality of aluminum pads 120 have been formed on the wafer #11 (only one of FIG. 1A and FIG. Aluminum pads) with a protection, 130. Wherein, the protective layer 13 has a plurality of openings 13 〇 & In addition, the conventional gold bump structure includes a ball bottom metal layer 140 and a gold bump 15〇, wherein the ball bottom metal layer 14 is disposed in the opening 13〇a and covers a portion of the protective layer 130. The gold bumps 150 are disposed on the ball metal layer MG. Since the gold & block (10) covers the ball metal layer 14〇 above the partial protective layer 130, the gold bump 15 has 5 1J28266 CN-9509003 22159twf.doc/n - annular raised portion 150a' This is called the wall effect. However, this annular projection 150a affects the strength of the joint between the gold bumps 15A and other carriers (not shown). In addition, since the ball bottom metal layer 14 is disposed only under the gold bump 150, when the ball bottom metal layer 14 is bonded to the gold bump 150 or between the ball bottom metal layer 14 and the protective layer 13? In the case of cracks, such conventional gold bump structures are prone to undercut effects.

SUMMARY OF THE INVENTION The present invention provides a method of fabricating a flat-top bump structure to improve wall effects.

The present invention provides a flat top bump structure to improve the undercut effect. The present invention provides a method of fabricating a flat-top bump structure comprising the following steps. First, a substrate is provided, and the substrate has a plurality of pads and a protective layer' wherein the protective layer has a plurality of first openings, and each of the first openings exposes a portion of the corresponding pad. A layer of a spherical metal material is formed on the substrate to cover the pads exposed by the protective layer and the protective layer. Forming a plurality of flat-top bumps on the layer of the bottom metal material above the pads exposed by the protective layer, wherein the bottom area of each of the flat-top bumps is smaller than the bottom area of the corresponding first opening and the flat-top bumps The top surface is flat. The layer of ball metal material is patterned to form a plurality of ball-bottom metal layers, wherein a bottom surface area of each of the ball-bottom metal layers is greater than a bottom area of the corresponding first opening. In an embodiment of the invention, the step of forming a flat top bump includes forming a first patterned photoresist layer on the bottom metal material layer, and the first pattern 6 1328266 CN-9509003 22159twf.doc/n The resist layer has a plurality of second openings exposing the layer of the bottom metal material above the joint exposed by the protective layer. A flat top bump is formed in the second opening. The first patterned photoresist layer is removed. In an embodiment of the invention, the step of forming a ball-bottom metal layer includes forming a second patterned photoresist layer on the ball-bottom metal material layer, wherein the second patterned photoresist layer covers the flat-top bumps, and Exposing part of the bottom metal

Material layer. A layer of ball metal material is patterned to form a ball-bottom metal layer. The second patterned photoresist layer is removed. In an embodiment of the invention, in the step of forming the ball-bottom metal layer, the bottom surface area of each of the ball-bottom metal layers is larger than the bottom surface of the corresponding first opening.

The present invention provides a flat top bump structure that is adapted to be disposed on a substrate. The substrate has a pad and a protective layer, wherein the protective layer has an opening that exposes a portion of the pad. The flat top bump structure comprises a ball bottom metal layer and a flat top bump, wherein the ball bottom metal layer is disposed on the protective layer and covers the pads exposed by the protective layer. The flat top bumps are disposed on the bottom metal layer above the pads' wherein the top surface of the flat top bumps is planar. Further, the bottom surface of the flat top bump is smaller than the bottom area of the opening, and the bottom surface of the bottom metal layer is larger than the bottom area of the opening. In an embodiment of the invention, the material of the flat top bump may be gold. In an embodiment of the invention, the material of the pad may be aluminum. In one embodiment of the invention, the substrate can be a wafer or wafer. Based on the above, "the flat top bump is formed in the opening of the protective layer due to the present invention", such flat top bump has a flat top surface. In addition, since the bottom area of the bottom metal layer of the ball 7 1328266 CN-9509003 22159twf.doc/n is larger than the bottom area of the flat top bump, such a flat top bump structure is less likely to cause an undercut effect. The above described features and advantages of the invention will be apparent from the description of the appended claims. [Embodiment] FIG. 2A to FIG. 2D are schematic diagrams showing a method of manufacturing a flat-top bump structure according to an embodiment of the present invention. Referring first to Figure 2A, the method of fabricating the flat bump structure of the present embodiment includes the following steps. First, a substrate 210 ′ is provided, and the substrate 210 has a plurality of pads 220 and a protective layer 230 , wherein the protective layer 230 has a plurality of first openings 23 〇 a, and the first openings 23 〇 & respectively are exposed correspondingly One of the pads 220. It should be noted that, for the convenience of description, only one opening 230a and the pad 220 of the embodiment are shown. In addition, the substrate 210 may be a wafer or other carrier, and the material of the pad 220 may be aluminum, copper or other metal. Referring to FIG. 2A, a ball-bottom metal material layer 310' is formed over the substrate 210 to cover the pads 220 exposed by the protective layer 230 and the protective layer 230. Further, the method of forming the ball-bottom metal material layer 31 may be a sputtering process, a physical vapor deposition process, or a chemical vapor deposition process. Then, a first patterned photoresist layer 41 is formed on the ball-metal material layer 310, and the first patterned photoresist layer 410 has a plurality of second openings 4i〇a exposed to the protective layer 230, respectively. A layer of bottom metal material 310 over the pad 220 is formed. It is to be noted that the second opening 41〇a is smaller than the pad 22〇 and the first opening 230a. 8 1328266 CN-9509003 22159twf.doc/n Referring to Figures 2A and 2B', a flat top bump 320 is formed in the second opening 41A. In other words, a plurality of flat-top bumps 32 are formed on the ball-bottom metal material layer 310 above the pads 22 which are exposed by the protective layer 23A. Further, forming the flat top bumps 320 may be an electroplating process. Then, the first patterned photoresist layer 410 is removed. It should be noted that the bottom area of each flat top bump 32 is smaller than the bottom area of the corresponding first opening 230a, and the top surface 320a of the flat top bump 320 is a flat surface. Referring to FIG. 2C, a second patterned photoresist layer 420 is formed on the bottom metal material layer 31, wherein the second patterned photoresist layer 42 covers the flat top bumps 320 and exposes a portion of the bottom metal. The material layer 31〇. Referring to FIG. 2C and FIG. 2D, the second patterned photoresist layer 42 is used as a mask for the engraving process, and a portion of the ball-bottom metal material layer is removed to form the ball-bottom metal layer 312. At this time, the bottom area of the bottom metal layer 312 is larger than the bottom area of the corresponding first opening 230a. Then, the second patterned photoresist layer 420 is removed. So far, the manufacturing process of the flat top bump structure of this embodiment has been substantially completed. In addition, after the second patterned photoresist layer 42 is removed, a cutting process may be performed on the substrate 210 to form a plurality of wafer structures (not shown). The detailed structure of the flat-top bump structure will be described below. Figure 3 is a top plan view of a flat top bump structure in accordance with one embodiment of the present invention. Referring to FIG. 3 and FIG. 2D, the flat top bump structure is adapted to be disposed on a substrate 210. The substrate 210 has a pad 220 and a protective layer 230. The protective layer 230 has a first opening 230a that exposes a portion of the pad 220. Further, the substrate 210 may be a wafer or a wafer. The flat top protrusion 9 1328266 CN-9509003 22159twf.doc/n block structure includes a ball bottom metal layer 312 and a flat top bump mo, wherein the ball bottom metal layer 312 is disposed on the protective layer 230 and covers the protective layer 23 The exposed port 220 is exposed. The flat top bump 320 is disposed on the bottom metal layer 312 above the joint 220, wherein the top surface 32〇a of the flat top bump 32 is flat. Further, the bottom area of the flat top bump 302 is smaller than the bottom area ' of the first opening 23〇a' and the bottom area of the bottom metal layer 312 is larger than the bottom area of the first opening 23〇a (as shown in Fig. 3). In addition, the material of the flat top bump 32〇 can be gold. Since the flat top bump 320 is formed in the first opening 23〇a of the protective layer 230, and the bottom area of the flat top bump 302 is smaller than the bottom area of the first opening 23〇a, the flat top bump 320 has a flat shape. The top surface 32〇a is used to change the wall effect of the conventional technology. In addition, since the bottom area of the bottom metal layer 312 is larger than the bottom area of the flat top block 320, such a flat top bump structure is less likely to cause an undercut effect. The present invention has been disclosed in the above preferred embodiments, but it is not intended to limit the invention, and any person having ordinary skill in the art can make some changes without departing from the spirit of the invention. Retouching, therefore, the protection of the present invention is defined as the scope of the patent. [Simple diagram of the diagram] Figure

1Α is a cross-sectional view of a conventional gold bump. 1Β is a top view of a conventional gold bump. 2D to FIG. 2D is a schematic diagram of a manufacturing method of the structure of the flat top bump 1328266 CN-9509003 22159twf.doc/n. Figure 3 is a top plan view of a flat top bump structure in accordance with one embodiment of the present invention. [Main component symbol description] 110: Wafer 120: Aluminum pad

130: protective layer 130a: opening 140: ball bottom metal layer 150: gold bump 150a: annular boss 210: substrate 220: pad 230: protective layer 230a: first opening

310: ball bottom metal material layer 312: ball bottom metal layer 320: flat top bump 320a: top surface 410: first patterned photoresist layer 410a: second opening 420: second patterned photoresist layer 11

Claims (1)

1328266 Product/Year Female Month ^I Amendment 99-5-25 X. Patent Application Range: 1. A method for manufacturing a flat-top bump structure, comprising: providing a substrate having a plurality of pads and a protective layer The protective layer has a plurality of first openings, and each of the first openings exposes a corresponding portion of the pads; forming a layer of a spherical metal material on the substrate to cover the protective layer and the The pads exposed by the protective layer; θ forming a plurality of flat-top bumps on the layer of the bottom metal material above the pads exposed by the protective layer, wherein the bottoms of the flat-top bumps The area is smaller than the corresponding bottom area of the first opening, and the top surfaces of the flat top bumps are planar; and a first patterned photoresist layer is formed on the bottom metal material layer, wherein the first pattern The photoresist layer covers the flat top bumps and blasts the bottom metal material layer; the bottom metal material layer is patterned to form a plurality of ball bottom metal layers, and the bottom metal layer is The bottom area is greater than the corresponding bottom area of the first opening; Removing the first patterned photoresist layer. (4) The method for manufacturing a flat-top bump structure, wherein the step of forming the flat-top bumps comprises: forming a second patterned photoresist layer on the bottom metal material layer, the I resist layer Having a plurality of second openings respectively exposing the layer of the bottom metal material over the plurality of interfaces over which the layer is exposed; forming the flat top bumps in the second openings; and 12 266 266 The blast 99-5-25 removes the second patterned photoresist layer. The method for manufacturing a flat-top bump structure according to claim 1, wherein in the step of forming the ball-bottom metal layer, a bottom area of each of the bottom metal layers is greater than the corresponding third The bottom area of the opening. 4. The method of manufacturing a flat-top bump structure according to claim 1, wherein the material of the flat-top bump comprises gold. 5. The method of manufacturing a flat-top bump structure according to claim 1, wherein the material of the pad comprises aluminum. 6. The manufacture of a flat-top bump structure as described in claim 1 wherein the substrate comprises a wafer or wafer. 13