JPH05129583A - Charge transfer device and manufacture thereof - Google Patents

Abstract

PURPOSE:To provide a charge transfer device in which a high speed transfer can be conducted by reducing the resistance of the transfer electrode and which is easily realized in the process. CONSTITUTION:The charge transfer device comprises a polyside film in which a patterned polysilicon film 1 and a silicide film 2 are superposed on a semiconductor substrate 21, and a sidewall 3 made of polysilicon and formed on its sidewall. With the structure, elements can be easily miniaturized. A single layer gate electrode having a good planarity and a low resistance is formed, and the device can be operated at a high speed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a charge transfer device such as a high speed transfer CCD and a method for manufacturing the same.

[0002]

2. Description of the Related Art FIG. 2 is a sectional view of a conventional charge transfer device in the vicinity of an electrode portion. In FIG. 2, 21 is a semiconductor substrate, 2
Reference numeral 2 is an insulating film, 23 is a first-layer polysilicon electrode, 24 is a silicon oxide film, and 25 is a second-layer polysilicon electrode.

For the electrodes of a conventional CCD, an overlapping structure of two-layer polysilicon shown in the figure has been used in terms of easiness of production and stability. From the standpoint of forming the CCD electrodes, this is because the first-layer polysilicon electrode 23 is selectively formed and then the first-layer polysilicon electrode 23 is oxidized to form the first-layer polysilicon electrode 23. A silicon oxide film 24 which is an insulating film is formed around the. Next, the second-layer polysilicon electrode 25 is formed so as to fill the space between the first-layer polysilicon electrodes 23.

[0004]

The conventional structure can be stably formed in terms of process, but since polysilicon is used as the electrode material, it is difficult to reduce the resistance value of the electrode to 30Ω / □ or less. Yes, a clock delay during high-speed transfer is unavoidable.

The present invention solves the above problems, and an object of the present invention is to provide a charge transfer device which can sufficiently cope with high-speed transfer and is easy to realize in the process.

[0006]

In order to achieve the above object, the charge transfer device of the present invention comprises a single layer polycide electrode, and the side wall of the polycide electrode is made of polysilicon in order to shorten the distance between the electrodes. The side wall is formed.

[0007]

With the above structure, the sheet resistance of the transfer electrode is 4
It becomes less than Ω / □, and the clock delay is greatly improved.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to FIG. In FIG. 1, the same parts as those of the conventional example of FIG. That is, the feature of the present invention is that after forming the insulating film 22 on the semiconductor substrate 21, a single-layer gate electrode made of a polycide film in which the polysilicon film 1 and the silicide film 2 are superposed is patterned. As the distance between the polycide film and the polycide film, the minimum dimension of pattern formation in photolithography is used. For example, the dimension is 0.8 μm. Then, a polysilicon film is deposited on the entire surface at a thickness of 0.4 μm, which is about half of the above size, and then the entire surface is etched by the RIE (reactive ion etching) method so that only the side wall of the polycide film including the polysilicon film 1 and the silicide film 2 is formed. The sidewall 3 made of polysilicon is left. The size of the final finished polycide film between the gate electrodes is determined by the gap between the sidewalls 3. This interval is very important in determining the transfer efficiency of the CCD, and is about 0.2 μm in the conventional structure, and this dimension is sufficiently compatible with the above manufacturing method. Also,
In the structure according to the present invention, since the gate has a single layer structure, the flatness is better than that of the conventional structure, the post-process can be easily processed, and the device can be easily miniaturized.
Moreover, since the gate material itself blocks the transmission of light, the ability to suppress smear, which is a problem especially in area sensors, is increased.

In the above embodiments, the polycide film in which the polysilicon film 1 and the silicide film 2 are overlapped has been described as the gate electrode, but it is also possible to use only the polysilicon film without the silicide film.

[0010]

As described above, according to the present invention, a single-layer gate electrode made of a polycide film patterned on a semiconductor substrate and a sidewall formed on the side wall of the gate electrode are provided. As a result, the resistance value of the gate electrode can be greatly reduced, enabling high-speed operation,
Moreover, it is possible to provide a charge transfer device that is structurally simple, has good flatness, and can improve smear control capability.

[Brief description of drawings]

FIG. 1 is a cross-sectional view near a gate electrode of a charge transfer device according to an embodiment of the present invention.

FIG. 2 is a sectional view of the vicinity of a gate electrode of a conventional charge transfer device.

[Explanation of symbols]

 1 Polysilicon Film 2 Silicide Film 3 Sidewall 21 Semiconductor Substrate 22 Insulating Film

Claims (3)

[Claims] 1. A single-layer polycide gate electrode formed by stacking a patterned polysilicon film and a silicide film on a semiconductor substrate that has been subjected to a predetermined process, and polysilicon formed on a sidewall of the polycide gate electrode. And a sidewall including at least. 2. The charge transfer device according to claim 1, wherein a polysilicon gate electrode is used in place of the single-layer polycide gate electrode in which the polysilicon film and the silicide film are stacked. 3. A step of patterning a gate electrode made of a polysilicon film or a polycide film on a semiconductor substrate which has been subjected to a predetermined process, and a step of forming polysilicon on the semiconductor substrate including the gate electrode. And a step of selectively leaving the polysilicon only on the side wall of the gate electrode by etching back the polysilicon, the method for manufacturing a charge transfer device.