JP2998507B2 - Method for manufacturing semiconductor device - 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 manufacturing a semiconductor device, and more particularly to a mounting technique for achieving high density, thinness, and miniaturization of a semiconductor element and the like.

[0002]

2. Description of the Related Art In recent years, electronic devices using a large number of semiconductor elements have been rapidly increasing. For example, there are a memory card, a liquid crystal display, an EL display, and the like, all of which require a plurality of LSI chips to be mounted on a substrate having a fixed area at a high density and a low thickness. Thus, LSI
As an effective means for mounting chips at high density, there is a micro-bump bonding method (hereinafter referred to as MBB method).

In this method, a metal projection electrode formed on an AL electrode of an LSI chip and a wiring electrode of a wiring board are pressed against each other with a photocurable insulating resin. They are electrically connected to each other.

In this method, it is necessary to form a metal projection electrode on the AL electrode of the LSI chip. As a method of forming the metal projection, conventionally, a Cr-Cu, Ti-Pd or the like is formed on the AL electrode of the LSI chip. In this method, a multilayer metal film called a barrier metal is formed, and a metal projection called a bump is formed thereon by electrolytic plating.

However, in order to form the metal projection on the AL electrode of the LSI chip, a number of vapor deposition steps, photolithography steps, and etching steps are performed. Therefore, in the course of these steps, the LSI chip is damaged, which causes a reduction in the yield, and not only increases the mounting cost but also lowers the reliability as a whole. Further, the LS having the metal protrusion formed thereon
There is a drawback that it is difficult to obtain an I chip and the versatility is very low.

As a method of solving these problems, LS
There is a method in which a separately formed metal projection is transferred onto the AL electrode of the I-chip and directly joined. This step, together with the above-described step of the MBB method, will be described below in detail with reference to FIG.

FIG. 3 is a sectional view of the process in the above method, wherein 21 is a substrate for forming a metal projection, 22 is a metal projection made of Au, 23 is a semiconductor element, and 24 is an electrode of a semiconductor element made of Al. At this time, the metal projection forming substrate 21 is made of heat-resistant glass having a thermal expansion coefficient of about 4.0 × 10 ⁻⁶ / ° C.

In the process, first, as shown in FIG. 3A, the metal projection forming substrate 21 and the semiconductor element 23 are connected to the metal projection 22 on the metal projection forming substrate 21 and the Al electrode 24 of the semiconductor element 23. Align so that they face each other.

Then, as shown in FIG. 1B, the metal projection 22 and the Al electrode 24 are pressed and heated by a bonding tool 25. As the bonding tool 25, a tool having a flatness of the bottom surface of about 1 μm or less at room temperature is used.
By this pressurization and heating, the metal projection 22 on the metal projection forming substrate 21 is joined to the Al electrode 24 of the semiconductor element 23, and as shown in FIG. The semiconductor element 23 is formed by the hole 26.
When the semiconductor element 23 is peeled off from the metal projection forming substrate 21 by sucking the metal projections, the metal projections 22 are transferred and joined to the Al electrode 24.

Here, a metal projection 22 made of Au and Al
The electrode 24 is joined by forming a slight Au-Al alloy at the interface layer between them. Further, the shape and size of the metal projection 22 are not so different between the time of formation and the time of transfer. That is, only the temperature, pressure, and time necessary to form a small amount of Au-Al alloy at the interface layer between the two are required. Specifically, the temperature is about 380-460
C., pressure is 7 to 10 g per metal projection, and time is 1 second.

Next, as shown in FIG.
2 is transferred and bonded to the semiconductor element 23 and the metal projection 2
2 having wiring electrode 27 at a position corresponding to 2
And a photo-curable insulating resin 29 is applied to a region on the wiring substrate 28 where the semiconductor element 23 is located.

Thereafter, as shown in FIG. 1E, the metal projection 22 is pressed against the wiring electrode 27 by the press tool 30 at room temperature. At this time, the photocurable insulating resin 2 interposed
9 is pushed to the periphery, and the metal protrusion 22 and the wiring electrode 27 are pressed.
Is a state in which the connection is completely established electrically. Also,
At this time, the metal projection 22 needs to be largely deformed.
For example, a metal protrusion 22 having a thickness of about 10 μm
Is deformed to about 4 to 5 μm. The load required for this is 90-100 g per metal projection.

Thereafter, as shown in FIG. 1F, ultraviolet rays 31 are irradiated from the back surface or side surface of the wiring board 28 to cure the photocurable insulating resin 29. Thereafter, the pressurization is released and the connection is terminated ((g) in the figure).

As described above, in the prior art, the bonding between the wiring board 28 and the semiconductor element 23 is press-contacted without heating, and the two are fixed with the photo-curable insulating resin 29, which has been a problem which has been a problem in the past. It has improved and has the following features.

(A) Since the connection is made without heating, connection can be made without applying thermal stress. (B) Since the connection portion is merely pressed (contacted), no thermal stress is applied to the connection portion due to a difference in thermal expansion coefficient. (C) It has a feature that it can cope with a narrow pitch because the connection portion is not a junction having a metal bond.

[0016]

However, the above-mentioned conventional method has the following problems. This will be described with reference to FIG.

First, in the bonding step shown in FIG. 4A, the metal projection 22 formed on the metal projection forming substrate 21 is aligned with the Al electrode 24 of the semiconductor element 23 and heated from the back surface of the semiconductor element 23. Bonding tool 25
When pressure is applied, the heat supplied from the bonding tool 25 is transmitted to the metal projection forming substrate 21 via the semiconductor element 23 and the metal projection 22. At this time, the metal projection forming substrate 21 expands due to heat, and changes to an upwardly convex shape.

The flatness of the bonding surface of the bonding tool 25 is maintained at a normal temperature, but the flatness is not maintained at a high temperature of 380 to 460 ° C., which is the bonding temperature. Generally, a bonding surface that is flat at normal temperature is deformed in a convex shape at a high temperature due to a difference in thermal expansion coefficient of a material. In this state, the metal projection 22 is transfer-bonded onto the AL electrode 24 of the semiconductor element 23, so that the shape of the metal projection 22 after the transfer is at the corner of the semiconductor element 23 as shown in FIG. A phenomenon occurs in which the height becomes higher.

The height variation at this time is about 3 μm when the diameter of the metal projection 22 is 30 μm and the height is 10 μm, although it depends on the joining conditions. This is the MBB used in the next step
Direct bonding to the wiring board in a face-down manner, as in the system, has a large effect and causes a connection failure.

When connecting in a face-down manner,
In order to secure the electrical connection and eliminate this connection failure, an excessive load may be applied to the metal projection 22 to greatly deform it. This may cause a significant decrease in connection reliability.

An object of the present invention is to provide a method of manufacturing a semiconductor device which solves the above problems.

[0022]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention is ^{directed to} an insulating substrate having a coefficient of thermal expansion of 0.5 × 10 ⁻⁶ / ° C. or less only at a position corresponding to an Al electrode of a semiconductor element. A step of aligning the formed metal protrusions with the Al electrode of the semiconductor element, a step of pressing with a pressing jig having a flatness of 0.5 μm or less in flatness of a pressing surface heated from the back surface of the semiconductor element, and removing the pressing. Transferring the metal protrusions formed on the insulating substrate onto the Al electrode of the semiconductor element, completing the bonding, and connecting the metal protrusions to the wiring electrodes of the wiring board. It is characterized.

[0023]

According to the present invention, in the step of transferring and joining metal projections on an Al electrode, the substrate for forming metal projections has a coefficient of thermal expansion.
A substrate of low thermal expansion coefficient of 0.5 × 10 ^-6 / ℃ or less by using those flatness of 0.5μm or less at the bonding temperature for the bonding tool, arising metal protrusion formed by the heat during transfer The thermal expansion of the substrate for use and the bonding tool is suppressed, and the variation in height of the metal projections after transfer is 0.5 μm or less.

[0024]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to FIGS.

FIG. 1 is a sectional view for explaining steps of a method of manufacturing a semiconductor device according to one embodiment of the present invention. As a manufacturing method, first, as shown in FIG. 2A, the metal projection forming substrate 21 and the semiconductor element 23 are connected to the metal projection forming substrate 2.
Positioning is performed such that the metal protrusion 22 on the first and the Al electrode 24 of the semiconductor element 23 face each other.

FIG. 2 shows the detailed structure of the metal projection forming substrate 21 used here. The metal projection forming substrate 21 has a three-layer structure. A transparent conductive film 41 is formed on the entire surface of the insulating substrate 40. A quartz substrate is used as the insulating substrate 40, and its thermal expansion coefficient is 0.5 × 10 ⁻⁶ / ° C. As the transparent conductive film 41, an ITO (indium tin oxide) film was used.

An opening 43 is formed by forming a photosensitive insulating resin 42 on the transparent conductive film 41 and exposing and developing only a position corresponding to the Al electrode 24 of the semiconductor element 23. Thereafter, the transparent conductive film 41 is used as one electrode to form a metal projection 22 inside the opening 43 by Au electroplating. In addition, a positive photoresist, a polyimide resin, or the like was used for the photosensitive insulating resin 42. When transferring the formed metal protrusion 22 onto the semiconductor element 23, the insulating resin 42 used for the plating mask is removed before use.

Then, as shown in FIG. 2B, the metal projection 22 and the Al electrode 24 are pressed by a pressing tool 45. The pressing tool 45 is heated to about 380 ° C. to 480 ° C., and a tool whose pressing surface has a flatness of 0.5 μm or less at this heating temperature is used. Pressing tool 4
5 is supplied to the metal projection forming substrate 21 through the semiconductor element 23, the AL electrode 24, and the metal projection 22.
However, since a quartz substrate having a low coefficient of thermal expansion of 0.5 × 10 ⁻⁶ / ° C. is used for the metal projection forming substrate 21, expansion and deformation due to heat hardly occur in the above temperature range. There is no.

By these two actions, the metal projection 22 is transferred and joined onto the AL electrode 24 with high accuracy and without any variation in height. In this bonding step, the metal projection 22 on the metal projection forming substrate 21 and the Al electrode 24 of the semiconductor element 23 are formed.
Are sufficiently deformed and pressed against each other at the interface, and an Au-Al alloy is formed between the metal projection 22 and the Al electrode 24.

At this time, the load, heating and time are respectively 20 to 50 g / bump, 380 to 480 ° C., and 1 to 3 s.
ec. In particular, the load varies depending on the size of the metal projection, but it is necessary to set the load at which the metal projection is pushed down to about 1/3 to 2/3 of the thickness of the Al electrode.

Thereafter, as shown in FIG. 3C, after the pressing tool 45 is released, the semiconductor element 23 is pulled up by the transfer jig 44 having a vacuum suction hole , and the A of the metal projection 22 is removed.
The transfer and bonding to the 1 electrode 24 have been completed.

Next, as shown in FIG.
2 is transferred and bonded to the semiconductor element 23 and the metal projection 2
2 having wiring electrode 27 at a position corresponding to 2
And position. In this case, a silicon substrate or a glass substrate is used as the wiring substrate 28, and Cr-Au, Ti-Pd-Au, ITO, or the like is used as a material of the wiring electrode 27.

Thereafter, a photocurable insulating resin 29 is applied to the region of the wiring substrate 28 where the wiring electrodes 27 are formed.
Thereafter, as shown in FIG.
The semiconductor element 23 and the wiring board 28 pressed by 0, distribution
The photocurable insulating resin 29 is cured by irradiating ultraviolet rays 31 from the back surface or side surface of the wire substrate 28 (FIG. 4F). Thereafter, the pressurization is released and the connection is terminated ((g) in the figure).

[0034]

As described above, the present invention has the following effects. In a transfer method in which a protruding electrode can be easily and inexpensively formed on an AL electrode of a semiconductor element, the flatness at a bonding temperature of a bonding tool is 0.5 μm or less, and the coefficient of thermal expansion is 0.5 × 10 ^{− 6} / ℃
By using the following, it is possible to transfer and join a metal projection accurately formed on a substrate to an Al electrode of a semiconductor element with high accuracy without causing a height variation. In addition, it is possible to perform extremely good and stable Au-Al bonding even at the bonding at the interface between both the metal projection and the Al electrode, and it is possible to significantly improve the reliability. Further, when the present invention is applied to the flip-chip method or the MBB method by this method, the connection reliability of the entire semiconductor device can be greatly improved.

[Brief description of the drawings]

FIG. 1 is a process sectional view illustrating a method for manufacturing a semiconductor device according to an embodiment of the present invention.

FIG. 2 is a sectional view of the substrate for forming metal protrusions in the embodiment.

FIG. 3 is a process sectional view illustrating a method for manufacturing a semiconductor device in a conventional example.

FIG. 4 is an enlarged sectional view of a joint in the conventional example.

[Explanation of symbols]

Reference Signs List 21 Metal projection forming substrate 22 Metal projection 23 Semiconductor element 24 Al electrode 25 Bonding tool 26 Vacuum suction hole 27 Wiring electrode 28 Wiring board 29 Photocurable insulating resin 30 Press tool 31 Ultraviolet 40 Insulating substrate 41 Transparent conductive film 42 Insulation Resin 43 Opening 44 Transporting jig 45 Pressing tool

Claims (3)

(57) [Claims] A metal projection formed on an insulating substrate having a coefficient of thermal expansion of 0.5 × 10 ⁻⁶ / ° C. or less at a position corresponding to an Al electrode of a semiconductor element is aligned with the Al electrode of the semiconductor element. And after that, from the back surface of the semiconductor element, the flatness of the heated pressing surface is pressurized by a pressing jig of 0.5 μm or less, and the metal projection formed on the insulating substrate and the semiconductor element are pressed. A step of joining the contact surface with the Al electrode, and thereafter, a step of separating the semiconductor element and the insulating substrate, separating the metal projection from the insulating substrate, and transferring the metal projection to the semiconductor element side. Of manufacturing a semiconductor device having the same. 2. The method according to claim 1, wherein the metal projection formed on the insulating substrate having a coefficient of thermal expansion of 0.5 × 10 ⁻⁶ / ° C. or less at a position corresponding to the Al electrode of the semiconductor element is aligned with the Al electrode of the semiconductor element. And after that, from the back surface of the semiconductor element, the flatness of the heated pressing surface is pressurized by a pressing jig of 0.5 μm or less, so that the metal protrusions formed on the insulating substrate and the semiconductor element A step of joining the contact surface with the Al electrode, and thereafter, a step of separating the semiconductor element and the insulating substrate, separating the metal protrusion from the insulating substrate, and transferring the metal projection to the semiconductor element side. Connecting the metal protrusion to a wiring electrode of a wiring board, and thereafter, connecting the metal projection to a wiring electrode of the wiring board. 3. The method according to claim 2, wherein the wiring substrate and the semiconductor element are fixed with an insulating resin.