JPH04279059A - Ccd image pickup element - Google Patents

Abstract

PURPOSE:To reduce the size of a CCD image pickup element by simplifying the wiring structure of the element while the occurrence of smears is reduced and the transferring speed is improved. CONSTITUTION:A light shielding film composed of 1-Al is also used for relaying the electrical connection between a transfer electrode composed of polysilicon and shunt wiring film composed of 2-Al. Since it becomes unnecessary to provide an opening through the light shielding film and to electrically connect the shunt wiring film with the transfer electrode through the opening, the wiring structure can be simplified and, at the same time, the thickness of an interlayer insulating film can be reduced by reducing the thickness of the light shielding film. Therefore, the smear can be lowered and, since the light shielding film is connected to the transfer electrode, the resistance of the transfer electrode can be reduced.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to a CCD image pickup device, particularly a CCD image sensor that can increase the transfer speed and increase the smear suppression rate.
This relates to a CD image sensor.

0002

2. Description of the Related Art The CCD image pickup device shown in FIGS. 4A to 4C is known. In the drawing, 1 is a semiconductor substrate, and 2 is an interlayer insulating film that insulates between the first layer aluminum film 1Al and the transfer electrode, and is made of, for example, PSG. 3 is a transfer electrode made of the first or second polycrystalline silicon layer, 4 is a buffer wiring film made of the third polycrystalline silicon layer, and the potential shift is caused by the first aluminum film 1Al. play a role in preventing 5 is a first layer aluminum film 1Al, and 6 is a second layer aluminum film 2Al.

The one shown in FIG. 4A is the most common CCD image sensor for NTSC currently on the market, in which the first layer aluminum film 5 is used only as a light-shielding film. In this CCD image sensor, the thickness of the first layer aluminum film 5 at the portion protruding from the transfer electrode 3 is made thinner, and the thickness of the interlayer insulating film 2 is also made thinner. Furthermore, since the interlayer insulating film 2 is made thinner, smear can be reduced. This is because the thinner the interlayer insulating film 2 is, the greater the number of reflections of light from the outside that is repeatedly reflected between the semiconductor substrate 1 and the first aluminum film 5 and enters the interlayer insulating film 2.
This is because the amount of attenuation of the incoming light increases. Note that this CCD image pickup device is compatible with NTSC, and there is no need to reduce the resistance of the transfer electrode to increase the transfer speed, so there is no shunt wiring film.

In the device shown in FIG. 4B, the first layer of aluminum film (1Al) 5 is used both as a shunt wiring film and a light shielding film, and high-speed transfer is possible. The first layer of aluminum film 5 is made thicker both at the portion protruding from the transfer electrode 5 and on the transfer electrode 5 from the viewpoint of lowering the resistance. Accordingly, the thickness of the interlayer insulating film 2 is also increased. Otherwise, the interlayer insulating film 2 will not be able to prevent the semiconductor substrate 1 from being damaged during etching for patterning the aluminum mask 5. In other words,
In order to prevent damage to the semiconductor substrate 1, it is necessary to increase the thickness of the interlayer insulating film 2 in proportion to the thickness of the aluminum film 5.

In the device shown in FIG. 4C, the first layer of aluminum film 5 is used as a light shielding film, and the second layer of aluminum film 6 is used as a shunt wiring film. Incidentally, a buffer wiring layer 4 made of polycrystalline silicon as a third layer is used for connection between the aluminum film 6, which is a shunt wiring film, and the transfer electrode 3. Such a CCD image pickup device has been introduced in Japanese Patent Laid-Open No. 2-87574 and the like. Such a CCD image sensor makes it possible to form a thin interlayer insulating film 2 by thinning the light shielding film made of the first layer of aluminum film 5, and by making the interlayer insulating film 2 thinner, smear can be reduced. be able to. By making the second layer of aluminum film 6 thicker, the resistance of the transfer control signal path can be lowered and high-speed transfer can be achieved. Specifically, it becomes compatible with HDTV (high definition) having 2 million pixels.

[0006]

[Problem to be solved by the invention] By the way, (A
) CCD image sensor does not have a shunt wiring film, so high-speed transfer is not possible, and even if it is compatible with NTSC, it is not compatible with HDT.
It is not possible to support V (high vision). (B) in Figure 4
The CCD image sensor shown in FIG.
It is necessary to form the film thickly in all parts, but this increases the height difference and is not suitable for miniaturization, making it difficult to contribute to the realization of high-definition compatibility with a 2/3-inch optical system CCD image sensor. Additionally, since the interlayer insulating film 5 becomes thick, there is a problem in that it is difficult to reduce smear. On the other hand, the CCD image sensor shown in FIG. 4C can perform high-speed transfer and reduce smear. It can be said that it is excellent in that respect. However, it has the disadvantage that the wiring structure is extremely complicated. I mean,
Since the first-layer aluminum film 5 is used only as a light-shielding film, electrical connection between the transfer electrode and the second-layer aluminum film 6 must be made through the opening 7 formed in the light-shielding aluminum film 5. This is because it will not happen. Furthermore, since the wiring structure is complicated, further miniaturization of cells becomes difficult. Since a considerable amount of cell miniaturization is required to make a CCD image sensor with a 2/3-inch optical system or even a 1/2-inch optical system compatible with HDTV, the complexity of the wiring structure is a problem that cannot be ignored.

The present invention has been made to solve these problems, and aims to increase the speed of transfer and reduce smearing without unnecessarily complicating the wiring structure.

[0008]

[Means for Solving the Problems] The CCD image pickup device of the present invention provides an electrical connection between the transfer electrode side made of a semiconductor layer and a shunt wiring film made of a second layer metal film. It is characterized in that it is carried out through a light-shielding film made of.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The CCD image pickup device of the present invention will be explained in detail below according to the illustrated embodiments. FIG. 1 is a sectional view showing one embodiment of the CCD image sensor of the present invention. In the drawing, 1 is a semiconductor substrate, and 2 is an interlayer insulating film between the transfer electrode 3 and the first layer aluminum film 5, which is formed thin. The reason why the interlayer insulating film 2 is made thin is to reduce smear. 3
is a transfer electrode made of a polycrystalline silicon layer.

The first layer aluminum film (1Al) 5 is a light-shielding film, and has a sufficient thickness to perform the light-shielding function.However, in the CCD image sensor shown in FIG. It is not formed as thick as the first layer aluminum film 5. Specifically, it is, for example, about 0.4 μm. The reason why the aluminum film 5 is not unnecessarily thick in this way is to allow the interlayer insulating film 2 to be thin. As mentioned above, the thinner the first layer aluminum film 5 is, the thinner the interlayer insulating film 2 becomes.
Further, as mentioned above, the reason why the interlayer insulating film 2 is made thinner is to make it more resistant to smear.

By the way, this first layer aluminum film (1Al) 5 is basically a light shielding film, but the transfer electrode 3
or to the second layer aluminum film (2Al) 6 which is a shunt wiring film,
It also serves as a relay wiring film between the shunt wiring film and the shunt wiring film. As a derivative of this, since the aluminum film 5 itself has a certain length and width, it also serves as a shunt wiring film, although it is thin. Reference numeral 8 denotes a contact portion that electrically connects between the aluminum film 5 and the transfer electrode 3, and a contact portion 10 formed in the interlayer insulating film 9 connects the aluminum film 5 and the second layer aluminum film. A shunt wiring film consisting of 6 is connected to the shunt wiring film.

The aluminum film (2Al) 6 is formed to have a sufficient thickness to serve as a shunt wiring film. As mentioned above, the first layer aluminum film 5, which was originally formed as a light-shielding film, is now used as a relay wiring film that serves as a relay for electrical connection between the shunt wiring film 6 and the transfer electrode 3. As a derivative of its role, it also functions as a shunt wiring film. Therefore, although it is not as strong as the thick aluminum film 6, it contributes to lowering the resistance and increasing the transfer speed.

By the way, the first layer of aluminum film 5 not only plays the role of a light shielding film, but also plays the role of a relay wiring film that relays between the shunt wiring film 6 and the transfer electrode 3. The greatest significance lies in the fact that the wiring structure can be easily created. That is, it is no longer necessary to provide an opening in the light-shielding film 5 and to make an electrical connection between the shunt wiring film and the transfer electrode through the opening. There is no need to complicate the structure. Therefore, further miniaturization can be achieved.

According to the present CCD image sensor, it is possible to achieve low smear similar to the CCD image sensor shown in FIG. 4(C), and even more than the CCD image sensor shown in FIG. It is possible to increase the transfer speed, and as shown in FIG.
The wiring structure can be made simpler than that of the CCD image sensor shown in (C).

FIG. 2 is a sectional view showing another embodiment of the CCD image sensor of the present invention. This CCD image sensor is a CCD image sensor of the type in which a buffer polycrystalline silicon film 4 is interposed between the first layer aluminum film 1Al and the transfer electrode to prevent a potential shift caused by the aluminum film.
This is applied to a CD image sensor (introduced in Japanese Patent Application Laid-Open No. 2-87574). Therefore, the first layer aluminum film 5 in this CCD image sensor is connected to the transfer electrode 3 via the buffer polycrystalline silicon film 4. On the other hand, it is directly connected to the shunt wiring film 6. Note that the buffer polycrystalline silicon film 4 is formed of a third or fourth layer of polycrystalline silicon film.

FIG. 3 is a sectional view of yet another embodiment of the CCD image pickup device of the present invention. In this embodiment, the light shielding film (and relay wiring and shunt wiring film) 5 made of the first layer aluminum film 1Al and the shunt wiring film 6 made of the second layer aluminum film 2Al are connected without passing through a contact hole. This allows for direct contact. Note that, in other respects, it is completely the same as the CCD image sensor shown in FIG. This is done in order to eliminate the need for a mask process for forming contact holes between the light shielding film 5 and the shunt wiring film 6, and to reduce the number of manufacturing steps.

That is, originally, in the CCD image sensor shown in FIGS. 1 and 2, the first layer of aluminum film 5 and the second layer of aluminum film 6, which is an upper layer, are at the same potential. It is possible to make both aluminum films have the same potential not only in the image area but also in peripheral circuits and the like. Therefore, the first and second layer aluminum films 5
- The interlayer insulating film 9 that insulates between the layers 6 and 6 is no longer required to have a withstand voltage, but is only required to have flatness. After the formation of the first layer of aluminum film, the highest point where a step occurs is the top surface of the first layer of aluminum film in both the image area and the storage area. This is the area to which the second layer of aluminum film is to be connected.

Therefore, after forming the interlayer insulating film 9, it is etched back for planarization until the upper surface of the first aluminum film 5 is exposed, and then the second layer is etched back until the upper surface of the first aluminum film 5 is exposed. Aluminum film (2Al
) 6 is formed. Then, a series of steps for forming a contact portion to the interlayer insulating film 9 can be omitted.

It should be noted that within the CCD image sensor, the first layer of aluminum film and the second layer are
Although there should be contact between the first layer and the aluminum film, there is no step like the image area or the aluminum film, so when the interlayer insulating film 9 is etched back, the top surface of the first layer of aluminum film is There is a possibility that there will be areas that cannot be exposed. Therefore, in that case, an appropriate dummy pattern made of polycrystalline silicon is formed,
It is preferable to forcibly create a step so that the upper surface of the first aluminum film is exposed when the interlayer insulating film is etched back. Since the dummy pattern can be formed simultaneously with the transfer electrode made of polycrystalline silicon and the buffer polycrystalline silicon film, the number of steps does not increase. Therefore, it is highly practical to omit the step of forming the contact portion by adopting the structure shown in FIG. 3, and can greatly contribute to cost reduction.

[0020]

Effects of the Invention In the CCD image sensor of the present invention, a light shielding film made of a first layer of metal film is formed above the transfer electrode made of a semiconductor layer, and a second layer of metal film is formed above the light shielding film. A shunt wiring film is formed, and the shunt wiring film and the transfer electrode side are electrically connected via the light shielding film. Therefore, according to the present CCD image sensor, since the light-shielding film made of the first layer of metal film relays between the transfer electrode side and the shaft wiring film, the first
There is no need to form an opening in the light-shielding film made of the metal film of the second layer and connect the transfer electrode side and the shunt wiring film made of the second metal film through the opening, and the wiring structure can be simplified. The light-shielding film made of the first metal film is connected to the shunt wiring film and contributes to lowering the resistance of the transfer control signal line, thereby increasing the transfer speed. Further, by making the light shielding film thinner, it is possible to make the underlying interlayer insulating film thinner, so that smear can be reduced.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing one embodiment of a CCD image sensor according to the present invention.

FIG. 2 is a sectional view showing another embodiment of the CCD image sensor of the present invention.

FIG. 3 is a sectional view showing still another embodiment of the CCD image sensor of the present invention.

FIGS. 4A to 4C are cross-sectional views showing different conventional examples of CCD image pickup devices.

[Explanation of symbols]

3 Transfer electrode 5 Light-shielding film 6 made of a first-layer metal film Shunt wiring film 8 made of a second-layer metal film Contact part 10 Contact part

Claims (1)

[Claims] 1. A light-shielding film made of a first-layer metal film is formed above the transfer electrode made of a semiconductor layer, and a shunt wiring film made of a second-layer metal film is formed above the light-shielding film. C, characterized in that the shunt wiring and the transfer electrode side are electrically connected via the light shielding film.
CD image sensor