JPH0789553B2 - Method for manufacturing bump electrode type semiconductor device - Google Patents

Description

Description: TECHNICAL FIELD OF THE INVENTION The present invention relates to the manufacture of a semiconductor device in which a plurality of metal electrodes for ohmic connection are formed on a semiconductor substrate, and bump electrodes made of a low melting point metal are formed on the metal electrodes. Regarding the method.

[Technical background of the invention and its problems]

The CCD sensor is well known as an integrated sensor having a function of receiving an incident optical image by a plurality of two-dimensionally arrayed photodetecting elements and converting it into a time-series electric signal to take it out. Conventionally, a sensor for extracting a two-dimensional physical quantity has been limited to such an optical sensor. Recently, with the development of mechatronics technology, for example, there is an increasing demand for two-dimensionally detecting pressure to give a machine a function of pressure sense or tactile sense.
A semiconductor piezoresistive element is used as an example of such a pressure sensor. For example, if diffusion resistance elements are two-dimensionally arranged and formed on a Si substrate, when external stress is applied thereto, the resistance value at that time changes and a signal can be obtained. If such a pressure sensor is integrated with the CCD, an integrated sensor that detects the stress distribution and processes the electric signal can be obtained. In this case, to integrate the pressure sensor board and the CCD board, the corresponding electrodes are butted and connected.
A so-called bump electrode structure is used.

Fig. 2 shows the conventional bump electrode type CC used for such applications.
It is an example of a manufacturing process of D. As shown in (a), the CCD substrate 11
Has a plurality of signal input sections 12 (12a, 12b, ...) On its surface,
A contact hole electrode 13 (13a, 13b, ...) For forming a bump electrode is formed on each of them. Reference numeral 14 is an insulating film such as a SiO ₂ film. Although not shown in the drawing, a large number of transfer gate electrodes are arrayed and formed on the CCD substrate 11, and a polyimide film 15 which is usually adopted to flatten the surface unevenness is formed. The contact hole electrode 13 is, for example, an Al film. Then, as shown in (b), Ti
A laminated metal film 16 is formed by sequentially depositing a film 16 ₁ and a Cu film 16 ₂ . The Ti film 16 ₁ is a barrier metal and the Cu film 16 ₂ is a plating-like electrode. Next, as shown in (c), a photoresist 17 is patterned at a position where the bump electrode is to be formed, and a Cu layer 18 (18a, 18b, ...) Is formed by selective plating, followed by an In layer 19 (19).
a, b, ...) are formed. After this, as shown in (d), the photoresist 17 is removed, and then the In layer 19 is used as a mask for Cu.
The film 16 ₂ and the Ti film 16 ₁ are sequentially removed by etching to form an In bump electrode.

In such a conventional method, as shown in FIG. 2D, the Cu layer 18 and the In layer 19 formed by the selective plating method are higher in the peripheral portion than in the central portion of the substrate. Variation occurs. This is a result of the current density increasing in the peripheral portion as a phenomenon peculiar to electroplating even if the plating current is held at a constant value. Due to such variation in plating thickness, there is a drawback that the In electrode at the center of the substrate is not connected when the CCD substrate and the corresponding terminal electrode corresponding to the pressure sensor substrate are abutted and integrated, for example.

[Object of the Invention]

The present invention has been made in view of the above point, and a method for manufacturing a bump electrode type semiconductor device, which makes it possible to make the butt connection with the terminal electrodes of the corresponding substrate uniform by making the heights of the plurality of bump electrodes uniform. The purpose is to provide.

[Outline of Invention]

A method of manufacturing a bump electrode type semiconductor device according to the present invention comprises a step of forming a base metal film in ohmic contact with a plurality of regions for forming bump electrodes on a semiconductor substrate, and a low melting point metal on the base metal film by a selective plating method. A step of forming a plurality of bump electrodes, and a flat substrate is attached to the surface on which the bump electrodes are formed at a predetermined pressure and temperature to melt the bump electrode surface, and then the flat substrate is separated to make the surface tapered. And a step of forming bump electrodes.

〔The invention's effect〕

According to the present invention, the unevenness of the bump electrode height due to the variation of the plating thickness, which is unavoidable in the electroplating method, is eliminated. Therefore, for example, when a CCD substrate on which the bump electrodes are formed is integrated by associating and connecting another semiconductor element substrate with corresponding terminal electrodes, highly reliable connection can be performed.

Further, in the present invention, since the bump electrode having a tapered surface is formed, the following effects can be obtained.

That is, when connecting a semiconductor substrate having bump electrodes formed thereon (first semiconductor element substrate) and another semiconductor element substrate having terminal electrodes formed thereon (second semiconductor element substrate), the bump electrodes Since the surface of the element is tapered, the first semiconductor element substrate and the second semiconductor element substrate can be connected with a weak force.

Therefore, even if the first semiconductor element substrate and the second semiconductor element substrate have mechanically weak element structures and the like, the two semiconductor element substrates can be integrated without impairing reliability.

At this time, even if there are variations in the height of the bump electrode, if the range of this variation is within the height of the thin portion of the surface of the bump electrode, the above variation makes the first and second semiconductor element substrates weak. Since it disappears when connecting by force, a highly reliable connection can be performed.

Example of Invention

 An embodiment of the present invention will be described below.

The manufacturing process of the bump electrode type CCD of FIG. 1A is the same as that of FIGS. 2A to 2D described above. That is, a signal input portion 22 (22a, 22b, ...) Is formed on the surface of the CCD substrate 21, and an insulating film 23 having an opening in the signal input portion 22 and a polyimide film 24 are formed thereon, and each signal input portion 22 is formed. A contact electrode made of an Al film is formed on the. After this, Ti film is formed on the entire surface
A base metal film 26 is formed by sequentially depositing 26 ₁ and Cu film 26 ₂ . The Ti film 26 ₁ is a barrier metal and the Cu film 26 ₂ is a plating electrode film. Then, a Cu layer 27 (27a, 27b, ...) Is formed by a selective plating method that masks the photoresist pattern, and then
In layers 28 (28a, 28b, ...) Are formed. The Cu layer 27 is, for example,
Immersing the substrate in Cu plating solution of copper sulfate bath, a Cu film 26 ₂ of the base metal film as an electrode at room temperature, after cleaning by performing a few seconds the first reverse plating at a predetermined current value normal Cu plating It is formed after several tens of minutes. As a result, a Cu layer 27 having a thickness of several μm is formed. The In layer 28 is formed to have a thickness of several μm by immersing the substrate on which the Cu layer 27 is formed in, for example, an In plating solution in a borofluoride bath and performing electroplating at a predetermined current value for several tens of minutes. It The photoresist is then removed and the Cu layer 27
Using the bump electrode having the In layer 28 laminated thereon as a mask, the underlying metal film immediately below is left, and the other underlying metal films are sequentially removed by etching with a weak acid-based etchant.

After forming the In bump electrodes in this way, although not shown, the CCD substrate 21 is vacuum-chucked by using a pressure welding device having a high degree of parallelism, and a flat substrate such as a Si substrate is vacuumed facing the CCD substrate 21. Chuck. Then, as shown in FIG. 1 (a), the CCD substrate 21 and the Si substrate 29 are heated to, for example, 140 ° C. in a forming gas atmosphere, pressed at a predetermined pressure for several minutes, and then heated to, for example, about 160 ° C. Hold for a few minutes. After melting the surface of the In-pump electrode in this way, the CCD
The substrate 21 and the Si substrate 29 are separated. As a result, FIG. 1 (b)
As shown in, the In bump electrodes with uniform height are formed.

As described above, according to this embodiment, by heating and pressing the flat substrate on the electrode surface after forming the In bump electrode, the height of the bump electrode can be made uniform even if the plating thickness varies. it can. If a CCD substrate with such bump electrode heights that are uniform in height is integrated by, for example, abutting the corresponding terminal electrodes on the pressure sensor substrate, a large number of terminal electrodes can be reliably connected and even pressure signal processing can be performed. The sensor can be obtained with high yield.

The present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the invention. For example, any kind of flat substrate may be used for heating the bump electrode surface under pressure.

[Brief description of drawings]

1 (a) and 1 (b) are bump electrode types according to one embodiment of the present invention.
FIG. 2A to FIG. 2A for explaining the CCD manufacturing process
(D) is a figure for demonstrating the manufacturing process of the conventional bump electrode type CCD. 21 …… CCD board, 22 (22a, 22b, ...) …… Signal input section, 23
…… Insulating film, 24 …… Polyimide film, 25 (25a, 25b,…)…
… Contact hole electrode, 26 …… Base metal film, 26 ₁ …… T
i film, 26 ₂・ ・ ・ Cu film, 27 (27a, 27b,…) …… Cu layer, 28 (28
a, 28b,…) …… In layer (bump electrode), 29 …… Si substrate (flat substrate).

Claims (3)

[Claims] 1. A step of forming a base metal film in ohmic contact with a plurality of regions for forming bump electrodes on a semiconductor substrate,
A step of forming a plurality of bump electrodes made of a low melting point metal on the underlying metal film by a selective plating method, and a flat substrate is attached to the surface on which the bump electrodes are formed at a predetermined pressure and temperature to melt the bump electrode surface. After that, the flat substrate is separated, and a step of forming bump electrodes having a tapered surface is provided, and a method of manufacturing a bump electrode type semiconductor device. 2. The method for manufacturing a bump electrode type semiconductor device according to claim 1, wherein the semiconductor substrate is a CCD substrate. 3. The method of manufacturing a bump electrode type semiconductor device according to claim 1, wherein the flat substrate is a Si substrate.