JPH11186315A - Wire-bonding device and manufacture of semiconductor device using thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a wire-bonding technique, wherein the diameter of the ball to be formed at the tip part of a bonding wire for the capillary used in narrow pitch bonding, can be made small. SOLUTION: A capillary 9 is formed, in such a manner that a depth (h) of its wire lead-out hole 9b and a diameter H of a wire lead-out hole 9b are equal, or the diameter H of the wire lead out hole 9b is made larger than the depth (h) of the depth of the wire lead-out hole 9b. Also, the first inclined surface 9f, where a through-hole 9a is formed, and the second inclined surface 9g, ranging from the first inclined surface 9f to the wire lead out hole 9g are provided inside the capillary 9, and an angle θ2 of the second inclined surface 9g is formed larger than an angle θ1 of the first inclined surface 9f. In addition, the inclination angle of the inner surface of a chamfer part 9c is to be formed in two stages, and an angle θ3 of an inclined surface 9d of the wire lead-out hole is made smaller than an angle θ4 of a tip side inclined surface 9e.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wire bonding technique for assembling a semiconductor device, and more particularly to a wire bonding process which is effective when applied to a wire bonding process in the manufacture of a semiconductor device in which electrodes on a semiconductor chip are narrowed. It is about technology.

[0002]

2. Description of the Related Art External connection terminals (hereinafter referred to as "outside terminals").
In a semiconductor device having an external lead-out), as a means for electrically connecting an electrode pad on a semiconductor chip and the external lead-out, an electrical connection is made using a bonding wire made of gold, copper, aluminum or the like. In particular, when a gold wire is used, a nail head bonding method is often used.
The nail head bonding method generally involves (1) passing a bonding wire through a cylindrical bonding tool called a capillary, and melting the tip of the bonding wire with a discharge torch to form a ball. (2) attaching the ball to an electrode pad on a semiconductor chip ( (1) The capillary moves relatively to the semiconductor chip in the XY and Z-axis directions and is led out at the capillary tip portion while applying a pressing force and ultrasonic vibration to the capillary tip portion at the first bonding point). (4) The bonding wire is lifted while sandwiching the bonding wire with a clamper, and the bonding wire is separated from the bonding portion at the second bonding point.

[0003] Regarding the wire bonding technology,
For example, "VLSI Packaging Technology (2)" (Nikkei B
It is described on pages 22 to 30.

[0004]

Generally, the shape of the tip of the capillary is such that a chamfer angle and a chamfer diameter of a chamfer portion for pressing a ball to an electrode pad on a semiconductor chip, which is a first bonding point, and a bonding wire are inserted.
Alternatively, it is formed with a wire outlet that comes into contact with the ball neck, and a through-hole that allows a bonding wire to pass through the tip of the capillary.

However, it is necessary to reduce the diameter of the ball to be bonded to the electrode pad in response to the recent trend of narrowing the pitch of the electrode pad on the semiconductor chip. In order to make the ball diameter smaller, it is necessary to make the tip of the above-mentioned capillary thinner and to reduce the dimensions of the wire outlet and the like. However, it has been found that the following bonding failure occurs when wire bonding is performed using such a capillary.

(1) When the bonding wire is pressed to the second bonding point, that is, the bonding point on the lead-out lead side, and the bonding wire is cut off, the pressure bonding strength of the tail bonding portion at the second bonding point is small.
In addition, since the thickness of the bonding wire pressed at the tail bond portion is small, formation failure of a wire tip (hereinafter referred to as a tail wire) after separation at the time of raising the capillary occurs. As a result, a ball to be formed next by the discharge torch cannot be formed, and a so-called disconnection failure occurs in which the bonding wire comes off the capillary.

(2) After the ball is pressed and bonded to the first bonding point, that is, the electrode pad on the semiconductor chip, the bonding is performed when moving to the bonding point on the external lead-out side, which is the second bonding point. The wire is fed out of the capillary. At this time, the contact resistance between the bonding wire and the capillary through-hole is large, and the wire loop connecting the first and second bondings has a poor shape.

(3) When the bonding wire is pressed against the external lead-out side, which is the second bonding point, the tail wire has a large amount of bending and a variation in the amount of bending occurs. The ball is formed by applying a voltage between a discharge torch provided in the vicinity of the tail wire and a bonding wire conducting to the tail wire, and performing an electric discharge generated between the tail wire and the discharge torch. However, the above-described problem of tail wire bending causes defective formation such as variation in diameter and shape of a ball formed by electric discharge.

An object of the present invention is to provide a wire bonding technique which enables a ball formed at the tip of a bonding wire to be reduced in diameter in a capillary used for narrow pitch bonding.

Another object of the present invention is to reduce the contact resistance between the bonding wire and the capillary when the bonding wire passes through the capillary, and to improve the looping property of the wire loop connecting the first and second bondings. It provides a wire bonding technique that can be achieved.

Another object of the present invention is to provide a capillary used for narrow pitch bonding, a wire bonding technique for making it possible to reduce the diameter of a ball to be bonded to a first bonding point and to stabilize the formation of a tail wire and a ball. Is provided.

[0012]

The following is a brief description of an outline of typical inventions disclosed in the present application. That is, the semiconductor device has a through hole through which a bonding wire for electrically connecting an electrode pad provided on the semiconductor chip and an external lead is inserted, and a wire outlet having a diameter smaller than the diameter of the through hole at a tip end thereof. In a wire bonding technique using a capillary formed of a chamfer for joining the bonding wire to the electrode pad and the lead for external lead-out around the wire lead-out port, the depth of the wire lead-out port of the capillary is long. And the diameter of the wire outlet is equal to or greater than the depth of the wire outlet. Further, a first inclined surface forming the through hole inside the capillary and a second inclined surface extending from the first inclined surface to the wire outlet are provided, and an angle formed by the second inclined surface is It is formed to be larger than the angle formed by the first inclined surface. Further, the inclination angle of the inner surface of the chamfer portion is set to two stages, and the angle formed by the wire outlet side inclined surface of the chamfer portion is made smaller than the angle formed by the tip side inclined surface of the chamfer portion.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings. FIG. 1 schematically shows a wire bonding apparatus. The wire bonding apparatus 1 mainly includes a loader 2 for sending out a sample before processing, that is, a mounting substrate such as a lead frame, an unloader 3 for receiving a processed sample, a control unit 4 for controlling the apparatus, a monitor 5, a bonding wire for connection. And a bonding stage 7 for setting a bonding sample. The wire bonding process
The lead frame on which the semiconductor chip is mounted is set on the bonding stage 7, and the bonding stage 7
And the bonding head 6 are relatively moved in the X, Y, and Z directions.

FIG. 2 is a perspective view of the bonding head 6. A bonding wire 12 mainly made of gold or copper for electrically connecting an electrode pad of the semiconductor chip and an external lead is passed through the bonding head 6, and a pressing force and a pressing force are applied to the bonding wire 12 at the tip. By applying an external force such as ultrasonic vibration, the capillary 9 for bonding the bonding wire 12 to the electrode pad and the external lead, and the capillary 9 are fixed, and the pressing force and the ultrasonic vibration are applied to the bonding wire 12 through the capillary 9. It comprises a horn 8 for transmitting, a clamper 10 for clamping the bonding wire 12, and a discharge torch 11 for forming a ball by discharging to the tip of the bonding wire 12.

In the present invention, the inside and the tip of the capillary 9 are shaped so as to be able to perform the optimal crimping according to the bonding wire shape. FIG. 4 shows the shape characteristics. The capillary 9 has a through hole 9a at its center axis through which the bonding wire 12 is inserted, and a through hole 9a at its tip.
A wire outlet 9b having a diameter smaller than the diameter of the wire is formed. Around the wire outlet 9b, a chamfer portion 9c for bonding the bonding wire 12 to the electrode pad 14 or the external lead 15a by pressing the bonding wire 12 is formed. The depth h of the wire outlet 9b and the wire outlet 9b are formed. 9b diameter H
Are formed in a relationship of H ≧ h. With such a shape, the contact area between the bonding wire 12 and the capillary can be reduced, so that the contact resistance can be reduced and the looping of the bonding wire 12 can be stabilized. Also, a through hole 9a is provided inside the capillary.
And a second inclined surface 9g extending from the first inclined surface 9f and the first inclined surface 9d to the wire outlet 9b.
The angle θ2 formed by the second inclined surface 9g is equal to the first inclined surface 9f.
Is formed so as to be larger than the angle θ1 formed. In this case, the angle θ1 formed by the first inclined surface 9f is from 1 ° to 1 °.
0 °, the angle θ2 of the second inclined surface 9g is 10 ° to 20 °
The degree is preferred. By forming such a shape, the space inside the capillary 9 can be increased, and the bonding wire 12 inserted through the capillary 9 can be formed.
At the first bonding point, that is, the connection from the electrode pad 14 to the second bonding point, that is, the connection to the external connection lead 15 a (hereinafter referred to as looping), the bending of the bonding wire 12 in the capillary 9. A large radius can be secured.
Therefore, the contact resistance generated between the bonding wire 12 and the through hole 9a of the capillary 9 can be reduced. Also, by providing the angle θ2 of the second inclined surface 9g,
In the case where the capillary tip width TH is reduced, mechanical strength of the capillary tip can be ensured. In the present invention, the tip end portion of the capillary 9, that is, the inclination angle formed by the inner surface of the chamfer portion 9c is made into two stages, and the angle θ3 formed by the wire outlet side inclined surface 9d of the chamfer portion 9c is formed by the tip side inclined surface 9e It is smaller than θ4. In this case, the angle θ3 formed by the wire outlet side inclined surface 9d is 90 ° to 120 °.
°, the angle θ4 formed by the tip-side inclined surface 9e is 60 ° to 100 °.
° is preferred. With such a shape, the thickness of the bonding wire at the tail bond portion at the second bonding point is formed thick. Further, the ratio of the length L1 of the wire outlet opening side inclined surface 9d projected from the vertical direction to the pressure contact surface of the bonding wire to the length L2 of the distal end inclined surface 9e projected from the vertical direction to the pressure contact surface of the bonding wire is defined as the ratio. 1: 3
By setting the ratio to 3: 1, the size of the ball 12a connected to the electrode pad 14 of the semiconductor chip 13 can be controlled by arbitrarily changing the above ratio.

Hereinafter, the wire bonding method of the present invention will be described with reference to FIG. 3 and FIGS. First, the ball 1 is attached to the tip of the bonding wire 12 drawn out from the tip of the capillary 9 by the discharge torch 11.
2a is formed. In this case, the wire outlet side inclined surface 9d
The ratio of the length L1 projected from the perpendicular direction to the pressure contact surface of the bonding wire to the length L2 projected from the perpendicular direction to the pressure contact surface of the bonding wire 9e is 1:
Since the ratio is 3 to 3: 1, the size of the ball 12a connected to the electrode pad 14 of the semiconductor chip 13 can be controlled by arbitrarily changing the ratio between L1 and L2 within the above range.

Next, the capillary 9 is lowered, and as shown in FIG. 5, the ball 12a is pressed against the electrode pad 14 of the semiconductor chip 13 mounted on the semiconductor chip mounting substrate such as the lead frame 15 and the ultrasonic wave is applied. Vibration (for example, an ultrasonic frequency of about 60 KHz) is applied to the ball 12
a is bonded to the first bond point, that is, the electrode pad 14. At this time, the ball 12a is crushed to some extent by the pressing force of the capillary 9, but the energy is transmitted efficiently by increasing the applied ultrasonic frequency, so that the crushing width of the ball can be reduced. The ultrasonic frequency for reducing the crush width of the ball is, for example, 100 KHz.
The above is preferred.

Next, the capillary 9 is moved relative to the semiconductor chip mounting substrate 15 in the X, Y, and Z directions while the ball 12a remains bonded to the electrode pad 14, which is the first bonding point. , The second bonding point, that is, the bonding wire 1
2 are joined. At this time, since the depth h of the wire outlet 9b and the diameter H of the wire outlet 9b of the capillary 9 are formed in a relationship of H ≧ h, the contact area between the bonding wire 12 and the capillary is formed. Therefore, the contact resistance when the capillary 9 moves can be reduced, and the looping of the bonding wire 12 can be stabilized. Also, a through hole 9 is provided inside the capillary.
a of the first inclined surface 9f and the second inclined surface 9g extending from the first inclined surface 9f to the wire outlet 9b, and the angle θ2 formed by the second inclined surface 9g is equal to the first inclined surface 9g. Since the angle θ1 is larger than the angle θ1 and the space of the through hole 9a is large, a large bending radius r of the bonding wire 12 in the capillary 9 can be secured in the looping as shown in FIG. .
Therefore, the contact resistance generated between the bonding wire 12 and the through hole 9a of the capillary 9 can be reduced.

When bonding the bonding wire 12 to the external lead 15a, as shown in FIG. 7, the inner surface of the chamfer portion 9c has two inclination angles, and the inclined surface 9d of the chamfer portion 9c at the wire outlet opening side. Angle θ3
Is smaller than the angle θ4 formed by the front-end-side inclined surface 9e, so that the thickness t of the bonding wire at the tail bonding portion at the second bonding point can be increased. As a result, after the bonding wire 12 is separated from the external lead-out lead 15a, the ball can be reliably formed on the tail wire, and the ball cannot be formed and the wire comes off from the capillary, so-called tail wire disconnection defect. Is eliminated.

Finally, while the bonding wire 12 is clamped by the clamper 10, the capillary 9 and the bonding wire 12 are raised to separate the bonding wire 12 from the bonding portion, thereby forming the tail wire 12b before forming the ball 12a. . At this time, the through holes 9
Since the bending radius “r” of the bonding wire 12 in the capillary 9 is increased by increasing the space “a”, the bending amount of the tail wire can be reduced. Therefore, the shape and size of the ball formed by the discharge torch are stabilized. Thus, one cycle of the wire bonding operation is completed. These operations are repeated for the number of pins to be electrically connected, and the wire bonding process is completed. Thereafter, the semiconductor device is completed through processes such as sealing, cutting / molding, aging, marking, and sorting.

[0021]

The effects obtained by typical ones of the inventions disclosed in the present application will be briefly described as follows.

(1) Since the depth of the wire outlet of the capillary and the diameter of the wire outlet are formed in a relationship of H ≧ h, the contact area between the bonding wire and the capillary can be reduced. The contact resistance when the capillary moves can be reduced, and the looping of the bonding wire can be stabilized.

(2) A first inclined surface forming a through-hole inside the capillary and a second inclined surface extending from the first inclined surface to the wire outlet are provided, and the angle formed by the second inclined surface is first. Since the angle is larger than the angle formed by the inclined surface, the space for the through hole is increased, so that a large bending radius of the bonding wire in the capillary can be ensured in looping. Therefore, the contact resistance generated between the bonding wire and the through hole of the capillary can be reduced. Further, since the bending radius r of the bonding wire in the capillary 9 can be ensured to be large, the amount of bending of the tail wire can be reduced. Therefore, the shape and size of the ball formed by the discharge torch are stabilized.

(3) Since the inclination angle formed by the inner surface of the chamfer portion is made into two steps, and the angle formed by the inclined surface on the wire outlet opening side of the chamfer portion is made larger than the angle formed by the tip side inclined surface, the second bonding is performed. The thickness of the bonding wire at the tail bond portion at the point can be formed thick. As a result, the ball can be reliably formed on the tail wire after the bonding wire is cut off from the lead-out lead, and the so-called tail wire disconnection failure in which the ball cannot be formed and the wire comes off from the capillary is solved. Is done.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a wire bonding apparatus.

FIG. 2 is a perspective view of a bonding head in the wire bonding apparatus.

FIG. 3 is a diagram showing a wire bonding operation.

FIG. 4 is a cross-sectional view showing a shape characteristic of a tip portion of a capillary used in the present invention.

FIG. 5 is a diagram showing a state in which a ball is bonded to an electrode pad using the capillary of the present invention.

FIG. 6 is a diagram illustrating a state of a bonding wire when the capillary of the present invention performs looping.

FIG. 7 is a diagram showing a state in which a bonding wire is joined to an external connection lead using the capillary of the present invention.

[Explanation of symbols]

1 ... wire bonding device, 2 ... loader, 3 ...
Unloader, 4 Control unit, 5 Monitor, 6 Bonding head, 7 Bonding stage, 8
... Horn, 9 ... Capillary, 9a ... Through-hole, 9b ...
... wire outlet 9c ... chamfer part 9d ... wire outlet side inclined surface 9e ... tip side inclined surface 9f ... first inclined surface 9g ... second inclined surface 10 ... Clamper, 11 discharge torch, 12 bonding wire, 12a ball, 12b tail wire, 13
... Semiconductor chip, 14 ... Electrode pad, 15 ... Semiconductor chip mounting board, 15a ... External lead

Claims (7)

[Claims] 1. A through hole through which a bonding wire for electrically connecting an electrode pad provided on a semiconductor chip and an external lead is inserted, and a wire outlet having a diameter smaller than the diameter of the through hole at a tip end thereof. A wire bonding apparatus having a capillary formed around a chamfer for joining the bonding wire to the electrode pad and the lead for external lead-out around the wire lead-out opening, wherein a depth of the wire lead-out opening is The wire bonding apparatus is characterized in that the length of the wire outlet is equal to the length of the wire outlet or the diameter of the wire outlet is larger than the depth of the wire outlet. 2. A through hole through which a bonding wire for electrically connecting an electrode pad provided on a semiconductor chip and an external lead is inserted, and a wire outlet having a diameter smaller than the diameter of the through hole at a tip end thereof. A wire bonding apparatus having a capillary formed around a chamfer for connecting the bonding wire to the electrode pad or the external lead-out lead by pressing the bonding wire around the wire lead-out opening; A first inclined surface forming a through hole and a second inclined surface extending from the first inclined surface to the wire outlet are provided, and the angle formed by the second inclined surface is the first inclined surface. A wire bonding apparatus characterized in that the wire bonding apparatus is formed so as to be larger than the angle between the surfaces. 3. An angle formed by the first inclined surface is from 1 ° to 1 °.
0 °, the angle between the second inclined surface is 10 ° to 20 °
3. The wire bonding apparatus according to claim 2, wherein the wire bonding apparatus is formed with a wire. 4. A through hole through which a bonding wire for electrically connecting an electrode pad provided on a semiconductor chip and an external lead is inserted, and a wire outlet smaller in diameter than the through hole at a tip end thereof. A wire bonding apparatus having a capillary formed around a chamfer portion around the wire lead-out opening for connecting the bonding wire to the electrode pad or the external lead-out lead by pressing. A wire bonding apparatus characterized in that the inclination angle of the inner surface of the section is made into two stages, and the angle formed by the inclined surface on the wire outlet side of the chamfer section is made smaller than the angle formed by the inclined surface on the tip side of the chamfer section. 5. An angle formed by the inclined surface on the distal end side of the chamfer portion is from 60 ° to 100 °, and an angle formed by the inclined surface on the wire outlet opening side of the chamfer portion is from 90 ° to 120 °. Item 5. The wire bonding apparatus according to Item 4. 6. A length of the chamfer portion wire outlet opening side inclined surface projected from a direction perpendicular to the pressure contact surface of the bonding wire, and a tip side inclined surface of the chamfer portion is projected from a direction perpendicular to the pressure contact surface of the bonding wire. 6. The wire bonding apparatus according to claim 4, wherein a ratio of the length to the projected length is from 1: 3 to 3: 1. 7. A method for manufacturing a semiconductor device using any one of the wire bonding apparatuses according to claim 1.