JPH01295445A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To improve the yield of devices, by forming a barrier metal layer between an In layer and a Cu layer when a bump electrode is formed on a substrate, and forming a mushroom shape for the shape of the Cu layer and the barrier metal layer after plating. CONSTITUTION:When a bump electrode is formed on a substrate 1, a barrier metal layer 12 is inserted between a Cu layer 11 and an In layer 13. The shape of the Cu layer 11 and the barrier metal layer 12 is formed in a mushroom shape when the layers 11 and 12 are plated. Therefore, alloy reaction between the In layer and the Cu layer 11 does not occur when the In layer 13 is fused. Therefore, the In layer 13 sufficiently remains. After a charge transfer device (CCD) and a photodiode array(PDA) undergo pressure welding, the PDA and the CCD are not separated when they are cooled. Since the In layer 13 is not lowered when the In layer 13 is fused, the pressure welding with the PDA is carried out positively, and electric short circuits are eliminated. In this way, the yield of the devices is improved.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Field of Application) The present invention provides a method for detecting infrared rays, which includes a large number of infrared sensing elements formed on a substrate,
The present invention relates to a method for forming a bump electrode at a connecting portion in an infrared imaging device in which a signal processing element formed on a substrate other than the substrate is bonded.

(Prior art) Several types of infrared imaging devices have been proposed, but
Here, infrared rays are received by a photodiode array (hereinafter referred to as PDA) as an infrared detection element, and an electric signal generated by the photoelectric conversion function is transferred to a charge transfer element (hereinafter referred to as CO).
An infrared charge transfer element (hereinafter referred to as IR-
(abbreviated as COD).

In IR-COD, the light-receiving section is a substrate made of semiconductor materials that are good for infrared sensors, such as InSb (indium antimony) or HgCdTe (mercury cadmium telluride), and photodiodes formed in a grid pattern. The electrons generated in each cell are transferred to a COD element to obtain an image. This method uses PDA,
This is the most commonly used method because it can optimize the characteristics of and COD.

Due to the large number of photodiodes and their arrangement, it is difficult to connect these PDAs and CODs by wire bonding. Therefore, the detection element and CCD
A method is adopted in which a metal protrusion (bump) electrode is provided on one or both of the two, and the detection element and CCD are faced to each other and connected using the bump electrode.

Since the IR-CCD is used after being cooled, distortion occurs because the expansion coefficients of the constituent material of the PDA and Si, which is the constituent material of the CCD, are different. In order to absorb the strain, soft In (indium) is used as one of the metals for the connection portion as the bump electrode metal. This allows In to absorb strain by plastically deforming.

Various methods have been proposed for connecting a PDA and a CCD using bump electrodes.
1-210656, shown in FIGS. 3 and 4. Figure 3 shows a CC with bump electrodes formed.
The D substrate 100, shown in FIG. 4, was proposed by the authors. This is an example of a process of making the height of bump electrodes uniform.

That is, in FIG. 3, 101 is S where COD is formed.
L substrate, 102 is an input part of CCD, 103 is an insulating film, 1
04 is the AQ electrode, 105 is the barrier metal Ti film, 10
6 is a Cu film used as an electrode during plating, 107 is a Cu layer formed by plating, and 108 is an In layer also formed by plating. As shown in FIG. 4, this 5L-CODloo and a flat substrate, for example, a Si substrate 109, are pressure-welded and heated to melt the In, and then the Si substrate 109 is separated. After making the height of the bump electrode surface uniform on the PDA
The connection was made by pressure contact. 108a in FIG.

108b shows the In layers separated after the above melting.

(Problems to be Solved by the Invention) There are two problems described below in manufacturing an IR-CCD using the conventional method described above.

(i) When In is melted, In and Cu react to form an intermetallic compound, and a considerable amount of In is consumed. As mentioned earlier, when In decreases, the strain that occurs when cooling is reduced by I
The plastic deformation of n alone cannot be absorbed and the In may be cut, resulting in separation of the PDA and COD.

(ii) As shown in FIG. 4, when In was melted, the In sometimes dripped onto the surface of the COD. The COD and PDA were not connected at that part, and sometimes electrical short-circuits occurred at that part.

The present invention was made to solve the problems in the conventional methods described above, and provides an improved method for manufacturing a semiconductor device having bump electrodes.

[Structure of the invention]

(Means for Solving the Problems) In order to achieve the above object, in the present invention, when forming a bump electrode on a substrate, in order to prevent an alloy reaction between the Cu layer and the In layer, the Cu layer and the InJll A barrier metal layer is inserted between them, and in order to prevent the In layer from dripping onto the surface of the CCD, the Cu layer and barrier metal layer are formed into a "mushroom" shape when formed by plating. That is, a step of forming a metal film on a semiconductor substrate, a step of forming a photoresist film on the metal film, and a step of forming an opening in the photoresist film in an area where an electrode is to be formed.
A Cu layer, a barrier metal layer, and an In layer are sequentially laminated on the metal film exposed in the opening by a selective plating method, and the upper part of the laminated metal layer formed of the Cu layer and the barrier metal layer is exposed to the photo film. This includes the step of forming a "mushroom"-shaped bump electrode that partially extends on the resist film.

(Function) The present invention is capable of applying pressure to a flat substrate on the surface of a plurality of bump electrodes, heating them and melting them, and then separating the flat substrate to make the heights of the surfaces of the plurality of bump electrodes uniform. To,
It is possible to prevent the In layer from being consumed by preventing the reaction between In and Cu, and also to prevent the In layer from dripping onto the surface of the CCD. That is, the bump electrode formed according to the present invention has a barrier metal layer inserted between the Cu layer and the In layer.

When the In layer is melted, no alloy reaction occurs between the In layer and the Cu layer. Therefore, a sufficient amount of In layer remains,
When the CCD and PDA are pressed together and then cooled down.

Peeling of the PDA and COD is almost eliminated, increasing reliability. Also, when the same <In layer is melted, I
Since the n-layer does not sag, pressure contact with the PDA is ensured, and there is no electrical short-circuit, which improves yield.

(Example) Hereinafter, one example of the present invention will be described with reference to the drawings.

FIG. 1(a) is a cross section of a main part of a 5i-CCD before bumps are formed. On the surface of a Si substrate 101, 64×64 signal input contact portions 102 are formed at a pitch of 80 μs, and on the surface, For example, an insulating layer 103 such as 5i02,
An AQ electrode 104 is formed. Next, on this surface
The i film 105 and the Cu film 106 are then formed by vapor deposition. The Ti film 105 is a barrier metal, and the Cu film 10
6 is an electrode film for plating. Next, a photoresist film 10 is formed on the entire surface, and then an opening 10a of 2 Ja++×20 μs is provided in the part where the bump electrode is to be formed (
Figure 1(b)).

Next, a Cu layer 11 is first formed in this opening 10a by selective plating. This Cu layer 11 is formed, for example, by immersing the substrate in a Cu plating solution in a copper sulfate bath, and plating at room temperature using the underlying metal film 106 as an electrode for ten minutes at a predetermined current. As a result, a “mushroom”-shaped C with a thickness of more than ten μm partially extending on the photoresist film is formed.
A u layer 11 is formed. Note that conventionally, an In layer was then formed by plating.

In the present invention, a barrier metal layer 12 is plated before that.

For example, Ni is recommended as the barrier metal. In addition, as another feature of the present invention, Cu and Nu
The shape after plating is made into a "mushroom" shape (see Figure 1 (
c)), Cu is made into a “mushroom” shape.

You can plate Ni there, or you can plate Ni on top of Cu that has been plated in a pillar shape to form a mushroom J shape. Either method will give you the same effect. Here, we will use the first method. The Ni layer 12 is formed by plating approximately enough at a predetermined temperature and a predetermined current in a Watts bath, for example.The thickness is several microns.N1
After plating Jl, an In layer 13 is subsequently plated. This In layer 13 is formed as thick as a ladle by immersing the substrate in a borofluoridation bath and plating at a predetermined current value for several minutes. Next, the photoresist film 10 is removed.

Subsequently, the Cu film 106 other than the bump electrode part and the Ti1i
105 is removed by etching to complete the bump electrode of the CCD substrate 1 according to the present invention (FIG. 1(d)).

According to the manufacturing method described above, the Ni layer is inserted as a barrier metal between the In layer and the Cu layer, so as shown in FIG. and Si facing on the CCD substrate.
After pressing the substrate 109 with a predetermined pressure and heating to melt the In layer 108, the CCD substrate and the Si substrate 109 are bonded together.
In and Cu do not react in the process of separating In and Cu. Therefore, the amount of In that contributes to bump bonding between the CCD and PDA increases, resulting in higher reliability.

In addition, since the shape after Ni plating is mushroom-shaped, when the In layer 108 is melted, it hardly drips onto the CCD surface, which improves the yield. Uniform bump electrode heights, which is a feature of this method, can be achieved at the same time without any problems.In this way, a sufficient amount of In remains, and a CCD substrate and PDA with uniform bump electrode heights can be used. By butting and integrating the corresponding terminal electrodes, the connection of multiple terminal electrodes is ensured, resulting in reliable IR-C.
CDs can be obtained with a high yield.

The present invention is not limited to the above-described embodiments, and can be modified in various ways without departing from the spirit of the invention.5For example, in the above explanation, a Ni layer is used as the barrier metal, For example, the same effect can be obtained by using a PT layer, a Zn layer, or the like.

〔Effect of the invention〕

As described above, according to the present invention, when forming bump electrodes on a substrate, a barrier metal layer is formed between an In layer and a Cu layer. Peeling between the PDA and CCD is almost eliminated, increasing reliability.

Furthermore, since the Cu layer and the barrier metal layer are plated into a "mushroom" shape, when the In layer is melted, it hardly hangs down on the CCD surface, improving the yield.

[Brief explanation of the drawing]

FIGS. 1(a) to (d) are cross-sectional views showing the method of manufacturing a semiconductor device according to the present invention in order of process, and FIG. FIG. 3 is a cross-sectional view for explaining a conventional method of manufacturing a semiconductor device, and FIG. 4 is a cross-sectional view for explaining a conventional step of making bump electrode heights uniform. 1 - CCD substrate 10... Photoresist film 10a... (Photoresist film) opening 11...
・Cu layer 12...Barrier metal layer 13・
...In layer 101...Si substrate 104.
・・AQ electrode (metal film) Agent: Patent attorney Norihiro Ogo Yumiya

Claims (1)

[Claims] a step of forming a metal film on a semiconductor substrate; a step of forming a photoresist film on the metal film; a step of forming an opening in the photoresist film in an area where an electrode is to be formed; and exposing in the opening. A Cu layer, a barrier metal layer, and an In layer are sequentially laminated on the metal film formed by selective plating, and the upper part of the laminated metal layer formed of the Cu layer and the barrier metal layer is placed on the photoresist film. A method for manufacturing a semiconductor device, including a step of forming a bump electrode in a "mushroom" shape by extending a portion of the bump electrode.