JP3514149B2 - Projection electrode formation method - Google Patents

Description

BACKGROUND OF THE INVENTION [0001] [Technical Field of the Invention The present invention provides a semiconductor device mounted face down on the mounting substrate, those about the protruding electrode forming how the semiconductor device. 2. Description of the Related Art Flip-chip mounting, in which a semiconductor device and a mounting substrate are directly connected face-down, greatly reduces the mounting area as compared with a conventional package in which a semiconductor chip is protected and molded with resin. It has the advantage of being able to do so, and is a technology that is expected in the future. Hereinafter, a conventional flip chip mounting will be described with reference to the drawings. Here, FIG. 9 is a diagram for explaining a bump forming process by a conventional plating method, and FIG.
Is a view for explaining a problem when the bump of FIG. 9 is formed,
FIG. 11 is a diagram for explaining the influence of FIG. As shown in FIG. 9A, a bump is formed by a plating method. First, as shown in FIG. 9A, a thin electrode pad 2 made of aluminum or the like and a surface protection film ( Hereinafter, a metal thin film (hereinafter, referred to as “barrier metal”) 4 and a resist 5 are sequentially formed on the semiconductor device 1 having the “passivation” 3, and then, as shown in FIG. The resist 5 at a position corresponding to the pad 2 is removed by etching to form an opening 5a. At this time, in order to improve the adhesion strength between the electrode pad 2 and the bump formed thereon, the width i of the opening 5 a is formed to be equal to or larger than the pad opening width a of the passivation 3, and
Overlap by about 5 μm. [0005] Next, as shown in FIG.
9a, a metal such as gold is formed by plating.
As shown in (d), the excess resist 5 is removed at once. Then, the barrier metal 4 is collectively removed (etched) using the metal plating formed in the previous step as an etching mask. By the above steps, FIG.
Are formed as shown in FIG. Here, as shown in FIG. 10, when the terminal pitch is narrowed and the space between the electrode pads 2 on the semiconductor chip 1 is narrowed, the space j between the bumps 16 is further narrowed. For example, if the opening size of the electrode pad 2 is 90 μm square at a pitch of 100 μm (this numerical value is a general value in the wire bonding specification), when the passivation 3 is overlapped by 4 to 5 μm, several μm is obtained.
There is a possibility that there is only a space of m or sometimes the adjacent bumps 16 are short-circuited. Also, if several μ
Even if there is a space of m, the problem of lowering of the insulation occurs, and in the ACF bonding in which the bonding is performed via the conductive particles 9, the conductive particles 9 are sandwiched between the adjacent bumps 16 as shown in FIG. There is a risk of short circuit. [0007] This problem is considered to be particularly noticeable in general-purpose semiconductor chips. The reason is that some general-purpose chips have the electrode pad 2a reduced in size in advance in consideration of bump formation by plating, but many are supposed to be packaged in QFP or the like. This is because the internal wiring in the packaging is designed to be bonded by wire bonding, and the pad size is widened. Here, if it is attempted to reduce the size of the opening 5a formed by the passivation 3 in order to avoid the above-mentioned problem, a new chip must be manufactured in a custom manner, leading to an increase in cost. As described above, in the bump formation by the conventional plating method, there is a possibility that short-circuiting occurs between the bumps due to the narrow pitch of the electrode pads. Further, even if there is no short circuit between the bumps, there is a possibility that a short circuit may occur depending on a mounting method such as ACF bonding. In order to avoid such a problem, it is necessary to newly produce a custom chip and change the size of the electrode pad, which leads to an increase in cost. [0010] The present invention has an object to provide an inexpensive projection electrode formed how insulation deterioration and short circuit no danger that occurs between the projecting electrodes even pitch narrows the electrode pad. In order to solve this problem, a method for forming a bump electrode according to the present invention comprises preparing a semiconductor device in which a predetermined circuit element is formed and an electrode pad is formed. A surface protection film and a metal thin film are sequentially formed to expose the electrode pads, a resist is applied on the metal thin film, the resist is selectively removed, and the first width is the opening width of the surface protection film along the first width. An opening portion smaller than a certain second width and having a third width orthogonal to the first width and larger than a fourth width which is an opening width of the surface protective film along the third width is provided at a position including the electrode pad. After forming, the opening is closed by plating to obtain a protruding electrode, the resist is entirely removed, and the metal thin film other than the plated portion is removed using the protruding electrode as a mask. As a result, an inexpensive semiconductor device can be obtained in which there is no risk of deterioration in insulation between the protruding electrodes or short-circuiting even if the pitch of the electrode pads becomes narrow. According to a first aspect of the present invention, there is provided a semiconductor device in which a predetermined circuit element is formed and an electrode pad is formed, and a surface protection for exposing the electrode pad is provided. A film and a metal thin film are sequentially formed, a resist is applied on the metal thin film, the resist is selectively removed, and the first width is larger than the second width which is the opening width of the surface protection film along the first thin film. An opening that is narrower and has a third width orthogonal to the first width and larger than a fourth width that is the opening width of the surface protective film along the third width is formed at a position including the electrode pad, and the opening is formed by plating. A method of forming a protruding electrode and a semiconductor device, in which a protruding electrode is obtained by removing the resist, and a metal thin film other than a plated portion is removed by using the protruding electrode as a mask. Deterioration of insulation between electrodes and This has the effect that an inexpensive semiconductor chip free from heat generation can be obtained. An embodiment of the present invention will be described below with reference to FIG.
This will be described with reference to FIG. In these drawings, the same members are denoted by the same reference numerals, and redundant description is omitted. (Embodiment 1) FIG. 1 is a view for explaining a bump forming step according to Embodiment 1 of the present invention, and FIG.
Sectional view showing adjacent bumps in the bump forming step of
FIG. 3 is a cross-sectional view in the direction of arrow A in FIG. 2, and FIG. 4 is a cross-sectional view in ACF bonding of adjacent bumps in the bump forming step in FIG. As shown in FIG. 1A, first, a predetermined circuit element is formed, and at the same time, a passivation 3 and a barrier metal for exposing the electrode pad 2 on the element forming surface of the semiconductor chip 1 on which the electrode pad 2 is formed. 4 are sequentially formed, and a resist 5 is applied on the barrier metal 4.
Here, aluminum is generally used as the material of the electrode pad 2 of the metal thin film, but another metal such as copper can be used, for example. Also, passivation 3
Include, for example, silicon oxide, silicon nitride,
Polyimide or the like is used. Further, as the barrier metal 4, for example, titanium, tungsten, nickel, copper, or the like is used. Next, as shown in FIG. 1B, the resist 5 is selectively removed by etching to form an opening 5a on the electrode pad 2. Here, the width b of the opening 5a
Are formed so as to be narrower than the opening width a of the passivation 3 along this. Then, as shown in FIG. 1C, the opening 5a is closed by plating to form a bump 6. Here, the material of the bump 6 is generally gold,
For example, other metals such as aluminum and copper can be used. After the formation of the bumps 6, the resist 5 is entirely removed as shown in FIG. Finally, FIG.
As shown in (e), the barrier metal 4 other than the plated portion is collectively removed using the bump 6 as a mask, and the protruding bump 6 is removed.
Get. As shown in FIG. 2, the two bumps 6 formed on the electrode pad 2 and the barrier metal 4 located below the bumps 6 have one of the first widths, as shown in FIG. The width of the passivation 3 is narrower than the second width, which is the width of the opening. Further, as shown in FIG. 3, the third width orthogonal to the first width of the bump 6 and the barrier metal 4 is wider than the fourth width which is the opening width of the passivation 3 along the bump 6, and the passivation. 3
(FIG. 3, part B). Then, the first width and the third width are deflected so that a wider space c is secured with respect to the adjacent electrode pad 2 located closer. Here, there is no overlap with the passivation 3 in the first width direction, but it overlaps with the passivation 3 in the third width direction, and the overlap dimension can be about twice as large as 4 to 5 μm. The adhesion strength of the barrier metal 4 to the electrode pad 2 is sufficiently ensured. Referring to FIG. 4, a case will be described in which the semiconductor chip 1 on which such bumps 6 and barrier metal 4 are formed is mounted on a mounting substrate 7 by ACF mounting. Here, the electrodes 8 that are electrically connected to the bumps 6 are formed on the mounting substrate 7. The mounting substrate 7 is made of a photosensitive epoxy resin, an epoxy resin impregnated with glass fiber, ceramic, or the like, and the electrode 8 is made of copper or the like. The conductive particles 9 contained in the ACF include:
Metallic plated resin balls or metal particles are used. As shown in the figure, according to the semiconductor chip 1 of the present embodiment, the first space is secured so that a wider space is secured for the adjacent electrode pad 2 located closer.
And the third width are turned, so that the bump 6
Even if the pitch between them is narrow and the size of the electrode pad 2 is large,
The problem of deterioration of insulation properties and short-circuiting due to the conductive particles 9 does not occur. Then, such bumps 6 are formed without newly raising a chip for plating bumps. As a result, an inexpensive semiconductor chip 1 is obtained in which the insulation between the bumps 6 does not deteriorate or a short circuit does not occur even when the pitch of the electrode pads 2 becomes narrow. (Embodiment 2) FIG. 5 is a diagram illustrating a bump forming process according to a second embodiment of the present invention, and FIG. 6 is a diagram illustrating a bump forming process according to a second embodiment of the present invention. 7 is a cross-sectional view in the orthogonal direction of FIG. 5 of adjacent bumps in the bump forming step of FIG. 5, and FIG. 8 is a cross-sectional view of ACF bonding of adjacent bumps in the bump forming step of FIG. Also in this embodiment, as shown in FIG. 5A, first, a predetermined circuit element is formed, and the electrode pad 2 is formed on the element forming surface of the semiconductor chip 1 on which the electrode pad 2 is formed. An exposed passivation 3 and a barrier metal 4 are sequentially formed, and a resist 5 is applied on the barrier metal 4. Next, as shown in FIG. 5B, the resist 5 is selectively removed by etching so that the resist 5 remains only on the electrode pad 2. Here, resist 5
Is the opening width d of the passivation 3 along it.
It is formed so as to be wider. Then, as shown in FIG. 5C, after the barrier metal 4 other than the portion covered with the resist 5 is removed by etching, the resist is removed. Then, a resist 5 is applied again and selectively removed so as to expose portions other than the outer periphery of the barrier metal 4, thereby forming openings 5a as shown in FIG. 6D.
Therefore, the width f of the opening 5a at this time is smaller than the opening width d of the passivation 3. And FIG.
As shown in FIG. 7E, the bumps 6 are formed by closing the openings 5a by plating. Finally, as shown in FIG. 6 (f), the bump 6 is used as a mask and the barrier metal 4 other than the plated portion is removed at a time to obtain a protruding bump 6. As shown in FIG. 6, the barrier metal 4 located below the two bumps 6 formed on the electrode pad 2 has a width, one of which is the fifth width, along which the passivation 3 extends. The opening width is wider than the sixth width. Further, as shown in FIG. 7, the seventh width orthogonal to the fifth width of the barrier metal 4 is also wider than the eighth width which is the opening width of the passivation 3 along the fifth width. Therefore, the barrier metal 4 overlaps the passivation 3 over the entire circumference. Also,
The bump 6 has a width smaller than the barrier metal 4 in both the fifth width direction and the seventh width direction. Here, since the barrier metal 4 overlaps the passivation 3 in the fifth width direction and the seventh width direction, the adhesion strength of the barrier metal 4 to the electrode pad 2 also in the present embodiment. Sufficiently secured. FIG. 8 illustrates a case where the semiconductor chip 1 on which such bumps 6 and barrier metal 4 are formed is mounted on a mounting substrate 7 by ACF mounting. As shown, according to the semiconductor chip 1 of the present embodiment,
Even if the pitch between the bumps 6 is narrow and the size of the electrode pad 2 is large, the problem of deterioration in insulation and short-circuiting due to the conductive particles 9 does not occur. And such a bump 6
It is formed without custom manufacturing a chip for plating bumps. As a result, also in the present embodiment, an inexpensive semiconductor device 1 that does not suffer from deterioration in insulation between the bumps 6 and short-circuiting even when the pitch of the electrode pads 2 becomes narrower is obtained. According to such a semiconductor device 1,
Since the barrier metal 4 overlaps the passivation 3 over the entire circumference, and the barrier metal 4 covers the entire electrode pad 2, the flip chip resin has a material (in particular, Even when a material containing halogen (such as bromine) must be used, the electrode pad 2 can be protected. As described above, according to the present invention, an inexpensive semiconductor device can be obtained which does not cause deterioration in insulation between the protruding electrodes and short-circuiting even when the pitch of the electrode pads becomes narrow. An effective effect of being obtained is obtained. According to the present invention, if the metal thin film overlaps the surface protective film over the entire circumference, the metal thin film covers the entire electrode pad. In the case where a material containing a substance having such an influence must be used, an effective effect that the electrode pad can be protected can be obtained.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a view for explaining a bump forming step according to a first embodiment of the present invention. FIG. 2 is a cross-sectional view showing adjacent bumps in the bump forming step in FIG. 2 is a cross-sectional view in the direction of arrow A of FIG. 4. FIG.
FIG. 5 is a cross-sectional view of an F junction. FIG. 5 is a diagram illustrating a bump forming process according to a second embodiment of the present invention. FIG. 6 is a diagram illustrating a bump forming process according to a second embodiment of the present invention. 5 is a cross-sectional view in the orthogonal direction of FIG. 5 of an adjacent bump in the bump forming step of FIG. 5; FIG.
FIG. 9 is a cross-sectional view of an F junction. FIG. 9 is a diagram illustrating a bump forming process by a conventional plating method. FIG. 10 is a diagram illustrating a problem when the bump of FIG. 8 is formed. FIG. Diagrams to be explained [Description of symbols] 1 Semiconductor chip 2 Electrode pad 3 Passivation (surface protective film) 4 Barrier metal (metal thin film) 5 Resist 5a Opening 6 Bump (protruding electrode)

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-64-77950 (JP, A) JP-A-9-94131 (JP, A) JP-A-4-199631 (JP, A) JP-A-6-96131 13382 (JP, A) JP-A-6-323824 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01L 21/60

Claims (1)

(57) [Claim 1] A semiconductor device in which a predetermined circuit element is formed and an electrode pad is formed is prepared, and a surface protective film and a metal thin film exposing the electrode pad are sequentially formed. A resist is applied on the metal thin film, and the resist is selectively removed, and a first width is smaller than a second width which is an opening width of the surface protective film along the first width. Forming an opening at a position including the electrode pad, the third width orthogonal to the width of the first electrode being larger than a fourth width along which the third width is the opening width of the surface protection film; A method for forming a protruding electrode, comprising: obtaining a protruding electrode, removing the resist entirely, and removing the metal thin film other than a plated portion using the protruding electrode as a mask.