JP3204082B2 - Manufacturing method of metal bump - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a bare chip, a CS
P (Chip Scale Package), BGA (Ball Grid Array)
) Package and TCP (Tape Carrier Packag)
e) related to a method for manufacturing a metal bump.

With the recent demand for smaller and lighter electronic devices, electronic devices such as ICs and LSIs have been highly integrated, and the number of input / output terminals (electrode terminals) has reached hundreds. As a method of mounting such a multi-terminal electronic device on a circuit board at a high density, a metal bump is formed on a chip surface,
Transferring the metal bumps to pads of the electronic device and mounting the electronic device on a circuit board has been performed.

[0003]

2. Description of the Related Art As a method of forming metal bumps on bare chips, CSPs and BGAs, Japanese Patent Application Laid-Open No.
No. 1 (a method of manufacturing solder bumps and solder balls and a method of manufacturing a semiconductor device) are known. Japanese Unexamined Patent Application Publication No. 7-249631 discloses that "Si wafer is anisotropically etched to form a recess at a position corresponding to an electrode pad of an electronic component, and the recess is filled with a solder paste and heated. A metal ball is formed in the concave portion. Then, after positioning the metal ball and the electrode pad, the metal ball is transferred to the electrode pad by heating and reflowing to form a metal bump. " ing.

A conventional method for manufacturing a metal bump will be described below with reference to FIGS. The techniques disclosed in FIGS. 2 and 3 are similar to the technique disclosed in the above-mentioned Japanese Patent Application Laid-Open No. Hei 7-249631.

First, FIGS. 2 (a), (b), (c), (d) and
The technology disclosed in (e) will be described. In FIG. 2, (a) and (c) are schematic plan views of essential parts.
(b), (d), and (e) are schematic side sectional views of relevant parts.

[0006] The method disclosed in FIG.
A quadrangular pyramid-shaped recess 11 formed by anisotropically etching the (100) plane of a metal ball forming member 10A made of a wafer.
A: A step of filling the solder paste 1 into the solder paste A, and heating the filled solder paste 1 so that the metal balls 2
And a step of transferring the metal balls 2 to the electrode pads 51 of the electronic component 50 are sequentially executed to form the metal bumps 3 on the electrode pads 51 of the electronic component 50. " In the figure, 1 is a solder paste composed of solder particles and a viscous flux, 2 is a metal ball formed by melting the solder particles in the solder paste 1, and 3 is a metal ball 2 fused to the electrode pad 51. The resulting metal bumps, 10A, indicate metal ball forming members made of Si wafers having a predetermined number of concave portions 11A formed at predetermined positions, respectively.

In the metal ball 2 produced by the method disclosed in FIG. 2, the amount of protrusion of the metal ball forming member 10A from the (100) plane is about 10% (0.1%) of the diameter d of the metal ball 2.
d) and less. For this reason, there is a risk that the metal ball 2 manufactured using this method may have a defect (transfer leakage) when it is transferred to the electrode pad 51 of the electronic component 50.

Next, FIGS. 3 (a), (b), (c), (d), and (e)
The technology disclosed in (f), (g) and (h) will be described. In FIG. 3, (a), (d), and (e) are schematic plan views, and (b), (c), (f), (g), and (h) are schematic essential parts. It is a part side sectional view.

[0009] The method disclosed in FIG.
The included angle of the opening formed by anisotropically etching the (110) plane of the metal ball forming member 10B made of a wafer is 70.53.
And filling the solder paste 1 into the concave portion 11B having a rhombus shape, and forming the metal ball 2 in the concave portion 11B by heating the solder paste 1; The step of transferring to 51 (see FIG. 2E) is performed in sequence to form the metal bumps 3. "

As apparent from the above description, (11)
0) When the plane is anisotropically etched, if the opening is a rhombus of 70.53 °, a concave portion 11B having a depth of の the diagonal length can be obtained immediately below the short diagonal line [FIG. 3 (b)]. reference〕. Therefore, when the recess 11B is filled with the solder paste 1 and heated, the amount of protrusion of the metal ball 2 from the metal ball forming member 10B is 20% of the diameter d, which is twice that of the (100) plane. However, since the intersection of the two surfaces constituting the bottom surface is parallel to the (110) plane, that is, horizontal, the concave portion 11B formed by this method is
The movable range of the metal ball 2 is expanded to a range restricted by the wall surfaces on both sides of the short diagonal line. If the movement range of the metal ball 2 is expanded in this way, the formation position of the metal ball 2 will not be stable as disclosed in FIGS. 3 (d) and (e) or (f) and (h).

[0011]

In the future, in the case of ULSI (ultra class LSI), the interval between the metal bumps 3 is 150 μm.
It is expected that the number of bumps will be as large as several thousand as it goes back and forth. At this time, the size of the solder ball (metal ball 2) formed in the concave portion is 80 to 90 μm.

For this reason, in the concave portion 11A formed by the (100) plane, the average protrusion amount of the metal ball 2 from the metal ball forming member 10A is 10 μm or less (80 to 90 μm) for the above-described reason.
μm), and when the solder paste 1 is insufficiently filled in the concave portions, it is conceivable that the protrusion amount may be further reduced. Therefore, it is extremely difficult to transfer all the metal balls 2 in the recess 11A formed on the (100) plane to the electrode pad 51 of the electronic component 50 without any loss.

On the other hand, a recess 11B formed on the (110) plane
In this case, the amount of protrusion of the metal ball 2 from the metal ball forming member 10B is about 20% of the diameter of the metal ball 2 (about 18 μm when the diameter of the metal ball 2 is 90 μm). Therefore, it is relatively easy to transfer the metal ball 2 to the electrode pad 51 of the electronic component 50 without any loss. However, in the case of the concave portion 11B, the positions of the metal balls 2 may be irregular as described with reference to FIG.
Thousands of metal balls 2 formed in the recesses of the (110) plane are accurately transferred onto the electrode pads 51 of the electronic component 50 (see FIGS. 1 and 2) so as not to be displaced.
Is very difficult to form.

In particular, in order to form a metal bump on a ULSI electrode pad 51 having a pad interval of about 150 μm and several thousands without loss, the amount of protrusion of the metal ball 2 from the metal ball forming member is large. In addition, it is important that the positions of the metal balls 2 are aligned.

[0015]

In the method of manufacturing a metal bump according to the present invention, as shown in FIGS. 1 (a) to 1 (f), the plane orientation is inclined at a certain angle with respect to the (110) plane. ₁ Y ₁₀ )
The metal ball forming member 10 composed of a Si wafer represented by [X ₁ ≠ Y ₁ , X ₁ ≠ 0, Y ₁ ≠ 0] is anisotropically etched to form a recess 11, and the recess 11 is filled. The metal ball 2 generated by heating the solder paste 1 is used as an electronic component.
The above problem is solved by transferring the data to the 50 electrode pads 51. This technique is a technique based on a new idea different from the technique disclosed in the above-mentioned Japanese Patent Application Laid-Open No. Hei 7-249631.

FIGS. 1 (a), (b), (c), (d), (e) and
(f) is an embodiment diagram which also serves as an explanatory diagram of the principle of the present invention. In the figure, reference numeral 10 denotes a metal ball forming member made of a Si wafer having a (X ₁ Y ₁₀ ) plane inclined by θ from the (110) plane, and 11 denotes a concave portion formed by anisotropic etching.

The (110) plane has an included angle of the opening of 70.53 °.
When the concave portion 11 is formed by anisotropically etching into a rhombic shape of the above, the concave portion 11 has two side surfaces perpendicular to the (110) plane and an included angle of 54.74 ° with the XY plane of the Si crystal. It becomes a recess formed by the bottom surface. Each of these six planes is equivalent to the (111) plane in terms of atomic density.

Therefore, the plane orientation is θ from the (110) plane.
Metal ball forming member 10 (X
₁ Y ₁ 0) _{[X 1 ≠ Y 1, X 1} ≠ 0, Y 1 ≠ 0 ] when the surface was anisotropically etched, even two surfaces constituted the conventional bottom Si wafer (metal balls forming member 10) for θ
The deepest portion α is formed by a total of four surfaces that are inclined and are perpendicular to the two surfaces and the (110) surface.

According to the present invention, as disclosed in FIG. 1, the plane orientation (X ₁ Y) whose plane orientation is inclined by θ with respect to the (110) plane.
₁₀ ) By anisotropically etching the metal ball forming member 10 represented by [X ₁ ≠ Y ₁ , X ₁ ≠ 0, Y ₁ ≠ 0], the two surfaces constituting the bottom surface are changed to (X ₁ Y _The recess 11 having only one deepest portion α is formed by a total of four surfaces, two surfaces perpendicular to the (110) surface and two surfaces perpendicular to the (10) surface.

By using the metal ball forming member 10 in which only the deepest portion α is formed at one place,
The positions of the metal balls 2 formed in the metal ball 2 can be aligned, and the amount of protrusion of the metal ball 2 from the recess 11 important for transferring the metal ball 2 can be secured.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the drawings. 1 (a), (b), (c), (d), (e), and (f) are examples of the present invention which also serve as explanatory diagrams of the principle of the present invention. In the drawing, 1 indicates a solder paste, 2 indicates a metal ball, 10 indicates a metal ball forming member, and 11 indicates a concave portion.

The method for manufacturing a metal bump according to the present invention comprises:
“The plane orientation is inclined θ with respect to the (110) plane (X ₁ Y ₁
0) Anisotropically etching a metal ball forming member 10 made of a Si wafer represented by a [X ₁ ≠ Y ₁ , X ₁ ≠ 0, Y ₁ ≠ 0] plane to form a recess 11 The metal balls 2 generated by heating the filled solder paste 1 are transferred to the electrode pads 51 of the electronic component 50 to form the metal bumps 3. It is characterized by having done so.

In the embodiment disclosed in FIG. 1, the plane orientation (X ₁
= 10 Y ₁ = 12 Z ₁ = 0) Metal ball forming member 10 made of Si wafer [included angle θ with (110) plane = 11.31
°] is formed by anisotropic etching to form recesses 11 having one deepest portion α at a pitch of 150 μm (not shown), and heating the solder paste 1 filled in the recesses 11. Metal ball 2 to the electrode pad of electronic component 50
Transfer to 51 to form metal bumps 3. "

As is apparent from FIG. 1, the concave portion 11 formed by this method has the intersection of the two surfaces forming the bottom surface inclined at θ = 11.31 ° with respect to the (X ₁ Y ₁₀ ) plane. Therefore, the deepest portion α is formed only at one place. Therefore, when this method is applied, the reliability of forming the metal bumps 3 by transferring the metal balls 2 to the electrode pads 51 is remarkably improved.

Since it is difficult to make the metal ball forming member 10 by anisotropic etching, it is conceivable to make a duplicate of the metal ball forming member 10 by using an electroforming method or the like. However, since the duplicate of the metal ball forming member 10 must repel the solder, it is made of a material to which the solder does not adhere (for example, aluminum, chromium, synthetic resin, or the like).

As apparent from the above description, in the method for manufacturing a metal bump according to the present invention, (X ₁ Y ₁₀ ) [X ₁ ≠ Y ₁ , [X ₁ Y _10] whose plane orientation is inclined at an angle with respect to the (110) plane. X
An Si wafer having a { ₁ {0, Y ₁ {0}] plane is anisotropically etched to form a concave portion 11 having a deepest portion α only in one place, and a solder paste 1 is filled in the concave portion 11. The method of generating the metal balls 2 is adopted. For this reason, the positions of the generated metal balls 2 are well aligned, so that the positional deviation phenomenon of the metal bumps 3 does not occur. In addition, when the present method is applied, the amount of protrusion of the metal bumps 3 from the metal ball forming member 10 increases, so that the phenomenon of deficiency of the metal bumps 3 hardly occurs.

[0027]

As is apparent from the above description, according to the present invention, metal bumps can be stably formed on a bare chip, a CSP, a BGA package or the like without any loss.

[Brief description of the drawings]

FIG. 1 is an embodiment diagram also serving as an explanatory diagram of the principle of the present invention,

FIG. 2 is a view for explaining a conventional method (1) for manufacturing a metal bump;

FIG. 3 is a view for explaining a conventional method (2) for manufacturing a metal bump;

[Explanation of symbols]

 1 Solder paste, 2 Metal ball, 3 Metal bump, 10, 10A, 10B Metal ball forming member, 11, 11A, 11B recess, 50 Electronic component, 51 electrode pad, α deepest part,

Claims (1)

(57) [Claims] 1. A method of manufacturing a metal bump for transferring a metal ball formed in a recess of a silicon plate capable of forming a recess by anisotropic etching to an electrode pad of an electronic component, wherein the plane orientation is (110). Inclined at an angle to the plane (a
b 0) Anisotropically etching the crystal plate represented by [a ≠ b, a ≠ 0, b ≠ 0] to form a recess whose bottom surface is inclined in a certain direction, and solder particles filled in the recess. A method of manufacturing a metal bump, wherein a metal ball generated by heating a containing paste is transferred to an electrode pad of the electronic component to form a metal bump on the electrode pad.