Semiconductor device

Abstract

A semiconductor chip includes a substrate, an electrode pad formed on the substrate, an insulating layer covering the substrate and the electrode pad, and having an opening exposing a portion of a surface of the electrode pad, a first conductive layer formed on the exposed portion of the surface of the electrode pad and extending to a surface of the insulating layer, and a second conductive layer formed on the first conductive layer, covering the first conductive layer in a plan view, and having an outer edge portion which is located further out than an outer edge of the first conductive layer in a plan view. The outer edge portion of the second conductive layer has at least one curved portion. At least one portion of the curved portion is located between the outer edge of the first conductive layer and an outer edge of the second conductive layer in a plan view.

Claims

1. A semiconductor chip, comprising: a substrate; an electrode pad formed on the substrate; an insulating layer covering the substrate and the electrode pad, and having an opening exposing a portion of a surface of the electrode pad therethrough; a first conductive layer formed on the exposed portion of the surface of the electrode pad and extending to a surface of the insulating layer; a second conductive layer formed on the first conductive layer, covering the first conductive layer when viewed in plan, and having an outer edge portion which is located further out than an outer edge of the first conductive layer when viewed in plan, the second conductive layer including a conductive film covering the first conductive layer and a post bump formed on the conductive film and having a side face, the post bump having a thickness greater than a sum of thicknesses of the first conductive layer and the conductive film; and a bump electrode formed on the second conductive layer and covering an upper portion of the side face of the post bump, wherein the outer edge portion of the second conductive layer has at least one curved portion, and at least one portion of the curved portion is located between the outer edge of the first conductive layer and an outer edge of the second conductive layer when viewed in plan.

2. The semiconductor chip according to claim 1, wherein the bump electrode covers the curved portion.

3. The semiconductor chip according to claim 1, wherein at least one portion of the curved portion is located in the bump electrode.

4. The semiconductor chip according to claim 1, wherein a surface of the substrate is separated from a surface of the second conductive layer by a first distance that is longer than a second distance separating the surface of the substrate from a surface of the first conductive layer.

5. The semiconductor chip according to claim 1, wherein the curved portion is formed at a surface of the second conductive layer.

6. The semiconductor chip according to claim 1, wherein the first conductive layer is a film made of Ti and W.

7. The semiconductor chip according to claim 1, wherein the second conductive layer includes a Cu layer.

8. The semiconductor chip according to claim 1, wherein the second conductive layer includes a Cu layer of uniform thickness plated on the first conductive layer.

9. The semiconductor chip according to claim 1, wherein the outer edge portion of the second conductive layer protrudes with respect to the outer edge of the first conductive layer by a distance greater than a thickness of the first conductive layer.

10. The semiconductor chip according to claim 1, wherein the curved portion forms arcs on both sides of a surface of the second conductive layer in a cross section taken perpendicularly to the surface of the second conductive layer.

11. The semiconductor chip according to claim 1, wherein an outer edge portion of the first conductive layer is formed directly on the insulating layer at a periphery of the opening.

12. The semiconductor chip according to claim 1, wherein the first conductive layer and the second conductive layer are both disposed over an entire surface of the opening.

13. The semiconductor chip according to claim 1, wherein the first conductive layer is disposed over an entire surface of the opening.

14. The semiconductor chip according to claim 1, wherein the surface of the insulating layer is separated from the outer edge portion of the second conductive layer by a gap.

15. The semiconductor chip according to claim 1, wherein the first conductive layer has a thickness of about 180 nm.

16. The semiconductor chip according to claim 1, wherein the bump electrode partly covers the second conductive layer such that a portion of the second conductive layer is exposed from the bump electrode.

17. The semiconductor chip according to claim 16, wherein the portion of the surface of the second conductive layer exposed from the bump electrode includes a surface of the outer edge portion of the second conductive layer that faces the surface of the insulating film via a gap therebetween.

18. The semiconductor chip according to claim 1, wherein at least one portion of the curved portion is located in the upper portion of the side face of the post bump.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a side view of an outer appearance of a semiconductor device according to an embodiment of the present invention.

(2) FIG. 2 is a schematic sectional view of a structure of a portion of the semiconductor device shown in FIG. 1.

(3) FIG. 3A is a schematic sectional view for describing a method for manufacturing the semiconductor device shown in FIG. 2.

(4) FIG. 3B is a schematic sectional view of a step subsequent to that of FIG. 3A.

(5) FIG. 3C is a schematic sectional view of a step subsequent to that of FIG. 3B.

(6) FIG. 3D is a schematic sectional view of a step subsequent to that of FIG. 3C.

(7) FIG. 3E is a schematic sectional view of a step subsequent to that of FIG. 3D.

(8) FIG. 4 is a schematic sectional view of a structure of a conventional semiconductor device.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

(9) An embodiment of the present invention shall now be described in detail with reference to the attached drawings.

(10) FIG. 1 is a side view of an outer appearance of a semiconductor device according to a first embodiment of the present invention.

(11) A WL-CSP technology is applied in the semiconductor device 1. The semiconductor device 1 includes a semiconductor chip 2, a plurality of post bumps 3 disposed on the semiconductor chip 2, and solder balls 4 bonded to the respective post bumps 3.

(12) FIG. 2 is a schematic sectional view of a structure of a portion surrounded by a broken line A in FIG. 1.

(13) An interlayer insulating film 5 made of SiO.sub.2 is formed on a top layer portion of the semiconductor chip 2. A wiring 6 made of Al is formed in a predetermined pattern on the interlayer insulating film 5.

(14) A passivation film 7 made of SiN is formed on the interlayer insulating film 5 and the wiring 6. The wiring 6 is covered by the passivation film 7. An opening 8 for exposing a portion of the wiring 6 from the passivation film 7 is formed in the passivation film 7.

(15) A barrier film 9 made of TiW (titanium tungsten) is coated on a portion of the wiring 6 facing the opening 8. The barrier film 9 has a predetermined thickness T (for example of 180 nm). The barrier film 9 covers a top surface of the wiring 6 and a side surface of the passivation film 7 inside the opening 8 and a peripheral edge portion thereof rides on a top surface of the passivation film 7.

(16) A seed film 10 made of Cu is formed on the barrier film 9. A peripheral edge portion of the seed film 10 protrudes to a side with respect to a peripheral edge of the barrier film 9 by a protrusion amount D greater than the film thickness T of the barrier film 9.

(17) The post bump 3 is protuberantly formed on the seed film 10. The post bump 3 is made, for example, of Cu. A side surface of the post bump 3 is substantially flush with a side surface of the seed film 10.

(18) By a peripheral edge portion of the post bump 3 protruding more to the side than the peripheral edge of the barrier film 9, a space is formed between the peripheral edge portion of the post bump 3 and the passivation film 7. By the presence of this space, the peripheral edge portion of the post bump 3 is deformable in a direction of opposing the passivation film 7. Thus, even if a stress arises in the post bump 3, the stress can be absorbed by deformation of the peripheral edge portion of the post bump 3. Consequently, crack formation in the passivation film 7 can be prevented.

(19) Also, because a polyimide layer for stress relaxation is not interposed between the passivation film 7 and the post bump 3, problems due to providing a polyimide layer, such as increase in number of manufacturing steps of the semiconductor device 1, increase in thickness of the semiconductor device 1, etc., do not occur.

(20) The protrusion amount D of the peripheral edge portion of the post bump 3 is greater than the thickness T of the barrier film 9. A width of the deformable peripheral edge portion in the post bump 3 can thereby be secured to be greater than the thickness of the barrier film 9.

(21) FIGS. 3A to 3E are schematic sectional views illustrating, in order of process, a method for manufacturing the semiconductor device shown in FIG. 2.

(22) First, as shown in FIG. 3A, the interlayer insulating film 5 is formed by a CVD (Chemical Vapor Deposition) method. Thereafter, by a sputter method, a metal film made of Al (not shown) is formed on the entire surface of the interlayer insulating film 5. Then, the metal film on the interlayer insulating film 5 is removed selectively by photolithography and etching. The wiring 6 having the predetermined pattern is thereby formed on the interlayer insulating film 5.

(23) Then, as shown in FIG. 3B, the passivation film 7 is formed on the interlayer insulating film 5 and the wiring 6 by the CVD method. Thereafter, a resist pattern (not shown) is formed on the passivation film 7. Then, the passivation film 7 is etched using the resist pattern as a mask. The opening 8 exposing a portion of the wiring 6 from the passivation film 7 is thereby formed in the passivation film 7. After the opening 8 is formed, the resist pattern is removed.

(24) Thereafter, as shown in FIG. 3C, the barrier film 9 made of TiW is formed on the portion of the wiring 6 facing the opening 8 and on the passivation film 7 by the sputter method. Then, the seed film 10 made of Cu is formed on the barrier film 9 by the sputter method. Then, a resist film 12 having an opening 11 at a portion at which the post bump 3 is to be formed is formed on the seed film 10. Thereafter, Cu is deposited inside the opening 11 of the resist film 12 by a plating method and the post bump 3 is thereby formed. After the post bump 3 is formed, the resist film 12 is removed.

(25) Then, as shown in FIG. 3D, a portion of the seed film 10 exposed from the post bump 3 is removed by wet etching. That is, a liquid capable of etching the seed film 10 is supplied to the seed film 10 and the seed film 10 is removed with the exception of a portion in contact with the post bump 3. Thus, the seed film 10 having the side surface substantially flush with the side surface of the post bump 3 remains between the post bump 3 and the barrier film 9.

(26) Thereafter, a liquid capable of etching the barrier film 9 is supplied to the barrier film 9. In this process, an etching liquid supplying time is set so that the etching progresses to the barrier film 9 below the seed film 10. A portion of the barrier film 9 exposed from the seed film 10 and a portion of the barrier film 9 sandwiched between the peripheral edge portion of the seed film 10 and the passivation film 7 are thereby removed as shown in FIG. 3E. Consequently, the side surface of the barrier film 9 is positioned more to an inner side (the opening 8 side) than the side surface of the seed film 10, and the post bump 3 and the seed film 10 take on shapes with the peripheral edge portions protruding to the side with respect to the peripheral edge of the barrier film 9.

(27) By thus setting the etching time in the process of patterning the layer made of the material of the barrier film 9 so that the etching progresses below the post bump 3, the protrusion amount D of the peripheral edge portion of the post bump 3 can be made greater than the thickness T of the barrier film 9. A space can thereby be formed between the peripheral edge portion of the seed film 10 and the passivation film 7 without causing increase in the number of manufacturing steps.

(28) Various modifications may be applied to the present embodiment.

(29) For example, the material of the barrier film 9 may be any material having a barrier property with respect to Cu. Ti (titanium), Ta (tantalum), and TaN (tantalum nitride) can be cited as examples of such a material.

(30) Further, Au (gold) may be used as the material of the post bump 3. When Au is employed as the material of the post bump 3, TiW can be used as the material of the barrier film 9.

(31) The wiring 6 may be formed using a metal material containing Cu. AlCu (aluminum/copper alloy) and Cu can be cited as examples of a metal material containing Cu. In this case, a wiring groove may be formed by digging in from an upper surface of the interlayer insulating film 5 and the wiring 6 may be embedded in this wiring groove.

(32) While the present invention has been described in detail by way of the embodiments thereof, it should be understood that these embodiments are merely illustrative of the technical principles of the present invention but not limitative of the invention. The spirit and scope of the present invention are to be limited only by the appended claims.