JPH04268731A - Formation of bump - Google Patents

Abstract

PURPOSE:To provide the title formation method of bump capable of restraining the dispersion in the level of the bump electrode as well as performing the formation step of the bump surface in specific shape using only one wire bonding tool while forming the one bump within a short time for increasing the productivity of the bump. CONSTITUTION:The front end of a wire fed in the almost oblique direction to the electrode pad is melted down to be formed into a ball shaped member. Next, after the formation of the bump by pressure-fixing the ball shaped member on the electrode pad, the wire is cut off from the bump.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a bump electrode, and more particularly to a method for forming a bump electrode on a pad electrode of a semiconductor device using a wire ball bonding tool.

0002

2. Description of the Related Art Conventionally, as a method for forming bump electrodes of this type, there are methods as described in, for example, Japanese Patent Laid-Open No. 63-173345 and Japanese Patent Laid-Open No. 63-188948. It is shown as follows. In addition, Figures 3 and 4
In the figure, 1 is a silicon substrate, 2 is an electrode pad that constitutes a bump electrode forming part made of aluminum or the like, and 3 is a silicon substrate.
is an insulating passivation film made of SiO2 etc., 4
is provided to be movable in the vertical direction with respect to the electrode surface of the electrode pad 2, and a supply passage 4a is provided in the center along the axial direction.
A wire ball bonding capillary tool 5 is formed with an Au wire as an electrode material inserted into a wire supply passage 4a, and this Au wire 5 is supplied from a spool (not shown) to the supply passage 4a. Further, 6 is a bump electrode, and 7 is a processing and forming tool.

First, the capillary tool 4 is attached to the electrode pad 2.
After placing the Au wire 5 facing the electrode pad 2, the Au wire 5 is supplied in a direction perpendicular to the electrode pad 2, and the Au wire 5 is placed outside the tip of the tool 4.
A part of the protrusion is made to protrude, and the tip of this protrusion is heated and melted using a hydrogen flame or the like. Therefore, as shown in Fig. 3(a), A
A ball portion 5a is formed at the tip of the U-wire 5. Then,
As shown in FIG. 3(b), the capillary tool 4 is lowered toward the electrode pad 2, and the ball portion 5a is pressed against the electrode pad 2 to be crimped thereto.

Next, as shown in FIGS. 3(c) and 4(a), the capillary tool 4 is moved upward to cut the Au wire 5 from the ball portion 5a to form a bump electrode 6. At this time, in the method described in Japanese Patent Application Laid-Open No. 63-173345, the capillary tool 4 is moved laterally without being moved upward, and then the capillary tool 4 is further lowered toward the silicon substrate 1. This is how it is cut.

Next, as shown in FIG. 4(a), a wire tail 6a is formed upwardly on the bump electrode 6, causing variations in the height of the bump electrode 6.
b) As shown in (c), press the bump electrode 6 with the processing and forming tool 7, remove the wire tail 6a, flatten the surface of the bump electrode 6, and make the height of the bump electrode 6 uniform. ing. That is, this wire tail 6
For example, when a tape carrier or the like is connected to the electrode pad 2 via the bump electrode 6, the tape carrier may be damaged, resulting in an extremely poor bonding property, and if variations in the height of the bump electrode 6 occur, the semiconductor Because variations occur in the characteristics of the device, the above-mentioned processing and forming tool 7
Therefore, it is necessary to eliminate variations in the height of the bump electrodes 6.

[0006]

However, in such a conventional bump electrode forming method, after the Au wire 5 is supplied in a direction perpendicular to the electrode surface of the pad electrode 2,
Since the height of the bump electrode 6 was made uniform by the processing and forming tool 7, a process using two tools 4 and 7 was required. For this reason, there is a problem in that it takes a lot of time to form one bump electrode 6, and the productivity of the bump electrode 6 deteriorates.

[0007] In recent years, bonding accuracy has increased from ±10 to
Since the precision is as high as about 15 μm, when forming the bump electrode 6 with such minute precision, the shape of the tip of the processing tool 7 must be made flat. It is said that it is not possible to form the surface shape of the bump electrode 6 into a desired shape while removing the bump electrode 6, that is, a spherical shape, etc., which will be joined to the object with deformation when it is bonded to the object to be bonded. There was a problem.

Therefore, the present invention is capable of suppressing variations in the height of bump electrodes and shaping the surface shape into a desired shape using one wire ball bonding tool, and can bond one bump electrode in a short time. It is an object of the present invention to provide a method for forming bump electrodes that can improve the productivity of bump electrodes.

[0009]

[Means for solving the problem] The invention according to claim 1 includes:
In order to achieve the above object, in a method of forming a bump electrode on an electrode pad using a wire ball bonding tool, the bump electrode is moved in a direction substantially perpendicular to the electrode surface of the electrode pad, and After preparing a wire ball bonding tool having a wire supply passage inclined at a predetermined angle and arranging the tip of the tool to face the electrode pad, the wire is supplied to the supply passage and the tip of the tool is removed. A process of protruding the tip of the wire in the opposite direction, and after melting the tip of the wire and forming it into a ball shape, the ball-shaped portion is crimped to the electrode pad at a predetermined location on the tip of the tool to form a bump electrode. and a step of separating the tool from the electrode pad and cutting the bump electrode and the wire.

In order to achieve the above object, the invention as set forth in claim 2 provides a wire ball bonding tool in which a recess is formed at a predetermined location of the tip, and the recess connects the ball-shaped portion to the electrode pad. The bump electrode is characterized in that the surface shape of the bump electrode becomes convex by crimping. In order to achieve the above object, the invention as set forth in claim 3 is characterized in that the entire tip of the wire protruding outward from the tip of the tool is melted and formed into a ball shape.

[0011]

According to the first aspect of the invention, after the wire is supplied to the electrode pad from a substantially oblique direction, the tip of the wire is melted to form a ball-shaped member. Next, the ball-shaped member is crimped onto the electrode pad to form a bump electrode, and then the wire is cut from the bump electrode. Therefore, after the bump electrode is cut from the wire, a wire tail is formed in the lateral direction of the bump electrode, and variations in the height of the bump electrode are suppressed. Further, this work is performed with one tool, and one bump electrode can be formed in a short time, improving the productivity of bump electrodes.

[0012] In the invention as claimed in claim 2, a wire ball bonding tool is prepared in which a recess is formed at a predetermined location on the tip, and the ball-shaped portion is pressed against the electrode pad by the recess, thereby improving the surface of the bump electrode. The shape becomes convex. Therefore, the surface of the bump electrode is formed into a convex shape at the same time as the bump electrode is crimped, and when the bump electrode is bonded to the part to be bonded, it is bonded to the object with deformation. As a result, highly precise bump electrodes with high bondability can be formed in a short time.

[0013] According to the third aspect of the present invention, the entire tip of the wire protruding outward from the tip of the wire ball bonding tool is melted and formed into a ball shape. Therefore, the heat applied to the tip of the wire when melting the tip is transmitted to the tool, and the expansion of the wire recrystallization region is suppressed. That is, the wire recrystallized region has larger crystal grains and lower tensile strength than the wire, so when the bump electrode is cut from the wire, it is cut in this wire recrystallized region. When the enlargement of the wire crystalline region is suppressed, the length of the wire tail generated on the bump electrode when the electrode is cut is shortened.

[0014]

EXAMPLES The present invention will be explained below based on examples. FIGS. 1 and 2 are diagrams showing an embodiment of a bump electrode forming apparatus for carrying out the bump electrode forming method according to the present invention. First, the configuration will be explained. In FIGS. 1 and 2, 11 is a silicon substrate, 12 is an electrode pad that constitutes a bump electrode forming portion made of aluminum or the like, and 13 is an insulating passivation film made of SiO2 or the like. Also, 14
is a wire ball bonding tool that is provided to be movable in the vertical direction with respect to the electrode surface of the electrode pad 12 and constitutes a bump electrode forming device. supply passage 1
4a (wire supply passage) is formed.

A recess 14b is formed at a predetermined location at the tip of the tool 14 in the downward direction, specifically, at a portion facing the electrode pad 12, and this recess 14b abuts against a ball-shaped portion as will be described later. It is now possible. In addition, the supply passage 14a includes an Au wire 15 (wire) as an electrode material.
is inserted, and this Au wire 15 is supplied to the supply passage 14a from a spool (not shown). Further, 16 is a bump electrode.

Next, a method of forming a bump electrode 16 having a width of approximately ±10 to 15 μm using such a wire ball bonding tool 14 will be described. first,
After placing the tool 14 facing the electrode pad 12, the Au wire 15 is
is supplied to cause the tip of the Au wire 15 to protrude outside the tip of the tool 14, and the entire tip is heated and melted with an electric torch or the like. Therefore, a ball portion 15a (ball-shaped portion) is formed at the tip of the Au wire 15, as shown in FIG. 1(a). Next, as shown in FIG. 1(b), the ball part 15a is made to protrude from the supply member 14a so as to be located below the recessed part 14b, and then the tool 14 is directed toward the electrode pad 12 as shown in FIG. 2(a). The ball portion 15a is pressed against the electrode pad 12 by the concave portion 14b, and the ball portion 15a is pressed onto the electrode pad 12 using an ultrasonic thermocompression bonder (not shown) or the like.

Next, as shown in FIG. 2(b), the tool 1
Move 4 upward. At this time, since the supply passage 14a is inclined with respect to the moving direction of the tool 14, the Au wire 15 engages with the tip of the supply passage 14a and the ball portion 15a
The Au wire 15 is cut from the Au wire 15, and a bump electrode 16 is formed on the electrode pad 12. Therefore, a wire tail 16a having a minute length is formed in the lateral direction of the bump electrode 16, and the surface of the electrode 16 is formed into a smooth convex shape. Next, all of the protruding portions of the Au wire 15 are heated and melted again to form a ball portion 15a again as shown in FIG. 1(a), and a bump electrode 16 is formed on a new electrode pad 12.

As described above, in this embodiment, after the Au wire 15 is supplied to the electrode pad 12 from a substantially oblique direction, the Au wire 15 is
The tip of the wire 15 is melted to form a ball portion 15a, and then the ball portion 15a is crimped onto the electrode pad 12 to form a bump electrode 16.
5, the wire tail 16a can be formed in the lateral direction of the bump electrode 16 after cutting the bump electrode 16 from the wire, and variations in the height of the bump electrode 16 can be suppressed. Further, this work can be performed with one tool 14, and one bump electrode 16 can be used.
can be formed in a short time, thereby improving the productivity of the bump electrodes 16.

Further, a tool 14 having a recess 14b formed at a predetermined location on the tip is prepared, and the ball portion 15a is pressed onto the electrode pad 12 using the recess 14b, thereby forming the surface shape of the bump electrode 16 into a convex shape. Therefore, the surface of the bump electrode 16 can be formed into a convex shape simultaneously with the crimping operation of the bump electrode 16. Therefore, the bump electrode 16
When the bump electrode 16 is bonded to the part to be bonded, it can be bonded with deformation, and a highly precise bump electrode 16 with high bondability can be formed in a short time.

Furthermore, the entire tip of the Au wire 15 protruding outward from the tip of the tool 14 is melted to form a ball portion 15a.
Therefore, when the tip of the Au wire 15 is melted, the heat applied to the tip can be transmitted to the tool 14, thereby suppressing the expansion of the wire recrystallization region. Therefore, the length of the wire tail 16a generated on the bump electrode 16 when the bump electrode 16 is cut can be shortened.

[0021]

According to the first aspect of the invention, after the wire is supplied to the electrode pad from a substantially oblique direction, the tip of the wire is melted to form a ball-shaped portion, and then,
Since the wire is cut from the bump electrode after the bump electrode is formed by crimping the ball-shaped part onto the electrode pad, a wire tail can be formed laterally on the bump electrode after cutting the bump electrode from the wire. , variations in the height of the bump electrodes can be suppressed. Further, this work can be performed with one tool, and one bump electrode can be formed in a short time, thereby improving the productivity of bump electrodes.

According to the second aspect of the invention, a tool having a recess formed at a predetermined location on the tip is prepared, and the ball-shaped portion is pressed onto the electrode pad using the recess, thereby making the surface shape of the bump electrode convex. Since the electrode is formed into a convex shape, the surface of the bump electrode can be formed into a convex shape at the same time as the bump electrode is crimped. Therefore, when the bump electrode is bonded to the portion to be bonded, it can be bonded with deformation, and a highly precise bump electrode with high bondability can be formed in a short time.

According to the third aspect of the invention, since the entire tip of the wire protruding outward from the tip of the tool is melted to form a ball-shaped portion, when the tip of the wire is melted, By transmitting the heat applied to the tip to the tool, it is possible to suppress the expansion of the wire recrystallization region. For this reason,
The length of the wire tail generated on the bump electrode when the electrode is cut can be shortened.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a bump electrode forming apparatus showing one step of the bump electrode forming method according to the present invention.

FIG. 2 is a sectional view of a bump electrode forming apparatus showing one step of the bump electrode forming method according to the present invention.

FIG. 3 is a sectional view of a bump electrode forming apparatus showing one step of a conventional bump electrode forming method.

FIG. 4 is a sectional view of a bump electrode forming apparatus showing one step of a conventional bump electrode forming method.

[Explanation of symbols]

12 Electrode pad 14 Wire ball bonding tool 14a
Supply passage (wire supply passage) 14b Recessed portion 15 Au wire (wire) 15a Ball portion (ball-shaped portion) 16
bump electrode

Claims (3)

[Claims] Claim 1: A method for forming a bump electrode on an electrode pad using a wire ball bonding tool, comprising:
A wire ball bonding tool having a wire supply path that moves in a direction substantially perpendicular to the electrode surface of the electrode pad and is inclined at a predetermined angle with respect to the moving direction is prepared, and the tip of the tool is attached to the electrode pad. After arranging the wires to face each other, a step of supplying a wire to the supply passage to make the tip of the wire protrude outward from the tip of the tool, and a step of melting the tip of the wire to form a ball shape; The process includes the steps of: forming a bump electrode by crimping a ball-shaped portion to an electrode pad at a predetermined location on the tip of the tool; and separating the tool from the electrode pad and cutting the bump electrode and the wire. A bump electrode forming method characterized by: 2. A wire ball bonding tool having a recess formed at a predetermined location on the tip is prepared, and the ball-shaped portion is pressed onto the electrode pad by the recess, thereby making the surface shape of the bump electrode convex. The bump electrode forming method according to claim 1, characterized in that: 3. The bump electrode forming method according to claim 1, wherein the entire tip of the wire protruding outward from the tip of the tool is melted and formed into a ball shape.