JP2699855B2 - Semiconductor device bonding method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of bonding a semiconductor device, and more particularly to a method of bonding to a bonding pad or a bump of a semiconductor device.

[0002]

2. Description of the Related Art A first example of a conventional bonding method between a lead and a bump is as shown in a sectional view of FIG.
A large number of bumps 2 formed on a main surface of a semiconductor substrate 1;
After positioning a large number of leads 3 formed on a film carrier (not shown) so as to face the bumps 2, the leads 3 are heated in advance, the pressing surface is flat, and the outer dimensions of the pressing surface are substantially the same as those of the above. The bumps 2 and the leads 3 are pressed by a bonding tool 4 having the same outer dimensions as the bumps 2, and the two are joined as shown in FIG. 5B. As shown in FIGS. 6A and 6B, the state of the lead 3 after bonding by this bonding method is such that the entire surface of the lead 3 on the main surface of the bump 2 is uniformly crushed. The crushing size at this time depends on the bonding conditions, the material of the leads 3 and the like, but is generally about 10% of the thickness TL of the leads 3.

A second conventional example is disclosed in
With reference to Japanese Patent Publication No. 110130, there is a technique in which a metal projection provided at the tip of a lead is pressed by a tool to an electrode on a main surface of a semiconductor substrate and adhered.

[0004]

In the first conventional method of bonding leads and bumps shown in FIGS. 5A and 5B, as shown in FIGS. Since the entire surface of the lead 3 on the main surface is uniformly crushed, the thickness of the lead 3 above the bump 2 is reduced, and a shear stress is generated in this portion during bonding. I have. For this reason, the strength of the lead 3 in this portion is reduced, which has caused a lead disconnection in a transport process after bonding.

In the second conventional example, the metal projections are plastically deformed in the form of being crushed by the pressing force of the tool, and this deformation is inevitably spread by 50% in the lateral direction. (Such a deformation is hereinafter simply referred to as a deformation). Due to such deformation, the main surface of the semiconductor element near the metal projection and the projection or the lead are likely to come into contact with each other and a short circuit accident is likely to occur, and when the gap between the electrodes is increased to prevent this,
There is a problem that high-density integration becomes difficult.

Referring particularly to FIG. 7 showing FIG. 6 of the publication, the metal projection 14 fixed on the main surface of the semiconductor substrate 1 is partially largely deformed. In addition, since the bonding area is smaller than the size of the metal protrusion 4, the bonding strength is small. The deformed portion has the above-mentioned problem.

The present invention solves the above problems and has the following objects (A) to (I). (A) The crimped portion between the lead and the bump or pad on the main surface of the semiconductor substrate is electrically bottom resistant and mechanically strong. (B) In the manufacturing process after crimping the lead to the bump or pad, the crimped portion does not separate or the lead does not break. (C) The crimped portion withstands external mechanical vibration. (D) To prevent the leads from directly contacting the semiconductor substrate. (E) Do not hinder high-density integration. (F) Do not deform the bump. (G) Do not reduce the effective crimping area. (H) To avoid adding a manufacturing process. (I) Improving the reliability of the bonding process.

[0008]

Bonding method of a semiconductor device of the present invention, in order to solve the problems], when the lead is thermally bonded to the pads or bumps provided on a main surface of a semiconductor substrate, said path
Press deformation of the lead on the pad or bump
Has a step smaller than the thickness of the lead.
The leading end portion of the lead is pressed and deformed to a greater extent than the portion following the leading end portion by being pressed by a cutting tool .

[0009]

FIG. 1A is a sectional view showing a manufacturing process before bonding according to a first embodiment of the present invention. In FIG. 1A, in this embodiment, a large number of bumps 2 (also referred to as projecting electrodes and metal projections) are already provided on the main surface of a semiconductor substrate 1. A film carrier (not shown) in which leads 3 having a thickness TL are arranged is provided on the bumps 2 so as to face each of the bumps 2. The film carrier is insulative and fixes the leads 3 together so that the leads 3 do not shift, but is removed in a later step. Above the semiconductor substrate 1, a bonding tool 4 is prepared. The lower surface of the tool 4 is provided so as to face the main surface of the rectangular semiconductor substrate 1, and a step portion having a thickness T and a width M is formed at an end of the lower surface serving as a pressing surface. I have. The width M is preferably about half the width of the bump 2. Bonding tool 4
The width of the lower surface (including the step) of the left and right bumps 2
Is approximately equal to the distance between the outer surfaces. The lead 3 is formed by plating a copper material with tin plating or gold plating. Bump 2
Gold plating is applied to the copper material.

Prior to thermocompression bonding of the leads 3 to the bumps 2, the bonding tool 4 itself is first preheated to about 500 ° C. by a heating means (not shown), and a table (not shown) on which the semiconductor substrate 1 is mounted. Is preheated to around 120 ° C. or higher.

First, the leads 3 and the semiconductor substrate 1 are positioned below the tool 4. Next, as shown in FIG. 1B, the tool 4 is lowered, and the lead 3 is held on the lower surface including the step portion.
When the bump 2 is pressed, the lead 3 is pressed against the bump 2, and at the same time, the upper surface of the lead 3 is plastically deformed by the pressing force. At this time, the plastic deformation of the bump 2 is so small that it can be ignored.

Referring to the top view of FIG. 2A and the cross-sectional view of FIG. 2B showing the state of the deformation, the crushing dimension t of the tip of the lead 3 is larger than the thickness T of the tool 4. It is necessary to make the tip of the lead 3 slightly wider, as shown in FIG. 2A, but to stay within the width of the bump 2. That is, in consideration of the width of the lead 3 and the amount of deformation, the width of the bump 2 is determined in advance. The step portion of the tool 4 causes the substantially inner half of the bump 2 to be crushed by the dimension t, and the subsequent substantially outer half of the bump 2 to be crushed by the dimension t. The dimension t is preferably 10% to 15% of the thickness TL of the lead 3. The dimension t '
Is preferably 1% to 5% of the thickness TL of the lead 3. As shown in FIG. 2A, the crushed portion having the dimension t 'is smaller but wider than the portion having the dimension t. Since the bonding area between the lead 3 and the bump 2 is the entire upper surface of the bump 2, it has a bottom resistance and is mechanically strong. There is a step in the deformation of the lead 3 and the crushed portion of the lead 3 on the outer surface of the bump 2 is small. Therefore, even if external vibration is applied to the lead 3 or stress is applied during the manufacturing process, the lead 3 is disconnected or cracked. Does not occur.

On the other hand, the bump 2 is not substantially deformed due to the above-mentioned material and the above-mentioned temperature setting conditions.
There is no fear that the lead 3 will come into contact with the main surface of the bump 2 and that the bump 2 will not come into contact with the main surface due to the deformation of the bump 2. The bonding tool 4 only needs to be provided with the above-mentioned stepped portion in advance, so that it is not necessary to particularly add a manufacturing process, and it is possible to secure mass productivity without reducing the manufacturing speed of the manufacturing process.

In this embodiment, not only the case where a large number of bumps 2 are arranged only on the left and right of the main surface of the semiconductor substrate 1 but also the case where bumps are arranged before and after (not shown). In this case, the step portion corresponding to the bump is provided.

FIGS. 3A and 3B are cross-sectional views showing steps before and after bonding according to a second embodiment of the present invention.
3A and 3B, in this embodiment, the target to which the lead 3 is crimped is a bonding pad formed on the main surface of the semiconductor substrate 1, which is a so-called bumpless case. It is an example. This embodiment is the same as the first embodiment except for the pad 6 and its bonding portion.
Only common reference numerals and the like are given to common parts, and description thereof is omitted. The right side of the lead 3 tilts upward due to the distortion at the time of the above-mentioned pressure deformation, or tilts due to an upward bending stress.

FIGS. 4A and 4B are cross-sectional views showing steps before and after bonding according to a third embodiment of the present invention.
In FIGS. 4A and 4B, this embodiment is common to the first embodiment except for the pressing surface of the bonding tool 4, and the description of the common parts is omitted.

The end of the tool 4 of this embodiment has a vertical dimension T and a horizontal dimension that is substantially half the width of the bump 2.
This results in a chamfered shape, and has a so-called taper. In accordance with the shape of the tool 4, as shown in FIG.
(> Dimension T), and the outer half portion is gradually tapered from this dimension t, and collapses by the dimension t ′ on the outer surface of the bump 2. These dimensions T,
t and t 'are the same as those in the first embodiment.

According to this embodiment, since the amount of compressive deformation of the lead 3 is gradually changed, the lead 3 is less likely to be disconnected or cracked, and the lead 3 is not affected by a slight displacement of the lead 3. There is no concern that the adhesive strength of the lead 3 will be significantly reduced, and it is hard to be affected by fluctuations in bonding conditions, variations in the material of the leads 3, and the like.

This embodiment can be applied to the bumpless structure of the second embodiment.

[0020]

As described above, according to the present invention, the above object is achieved, the electrical resistance of the bonding portion is small, the mechanical strength is strong, there is no fear of lead disconnection, the device is resistant to external vibration, and a contact / short circuit accident occurs. There is no fear of a decrease in reliability due to deformation of the bumps, and there is an effect that high-density integration can be performed without adding a manufacturing process. Further, according to the present invention, a decrease in lead strength at the time of bonding can be suppressed, so that a connection failure due to lead disconnection at the time of transportation in a later process is eliminated, and an assembly with a high yield can be performed,
In addition, there is an effect that a bonding pad or a bump having substantially the same size as the conventional one can be strongly bonded to a lead.

[Brief description of the drawings]

FIGS. 1A and 1B are cross-sectional views showing steps before and after bonding according to a first embodiment of the present invention.

FIGS. 2A and 2B are a top view and a sectional view showing a bonding portion of the first embodiment.

FIGS. 3A and 3B are cross-sectional views showing steps before and after bonding according to a second embodiment of the present invention.

FIGS. 4A and 4B are cross-sectional views showing steps before and after bonding according to a third embodiment of the present invention.

FIGS. 5A and 5B are cross-sectional views showing steps before and after the conventional bonding.

FIGS. 6A and 6B are a top view and a cross-sectional view showing a bonding portion of a first conventional bonding example.

FIG. 7 is a cross-sectional view showing a bonding portion of bonding according to a second conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Semiconductor substrate 2 Bump 3 Lead 4 Bonding tool 5 Joining part 6 Bonding pad 14 Metal projection 30 Tool 33 Resin film

Claims (2)

(57) [Claims] When a lead is thermocompression-bonded to a pad or bump provided on a main surface of a semiconductor substrate, the pad is
Or the pressing deformation portion of the lead on the bump ,
Bonding having a step smaller than the thickness of the lead
A method of bonding a semiconductor device , wherein a tip portion of the lead is pressed and deformed by a tool to a greater extent than a portion following the tip portion. 2. The bonding method for a semiconductor device according to claim 1, wherein the pressing deformation portion of the lead is pressed and deformed in a tapered shape.