JPH02271543A - Manufacture of charge transfer element - Google Patents

Abstract

PURPOSE:To make a film thickness of a first electrode layer and a film thickness of a second electrode layer film uniform by a method wherein a second insulating film is deposited, by a vapor method, on a semiconductor substrate including the surface of the first electrode layer and a second conductor is formed on a second insulating film. CONSTITUTION:A first insulating film 13 is formed on the main surface of a semiconductor substrate 11; a first conductor layer 15 is formed on the first insulating film 13; the first conductor layer 15 is etched selectively; a first electrode layer 15 is formed. Then, a second insulating film 16 is deposited, by a vapor method, on the semiconductor substrate including the surface of the first electrode layer 15; a second conductor layer 17 is formed on the second insulating film 16; the second conductor layer 17 is etched selectively; a second electrode layer 17 which is situated so as to be arranged alternately with the first electrode layer 15 is formed. That is to say, the second insulating film 16 which electrically insulates the first electrode layer 15 from the second electrode layer 17 is formed by the vapor method. Thereby, it is not required to thermally oxide the first electrode layer 15; a film thickness of the first electrode layer 15 and that of the second electrode layer 17 can be made easily uniform.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for manufacturing a charge transfer device, and particularly to a method for forming an insulating film that electrically insulates electrodes.

[Prior art] The process up to the middle of the conventional method for manufacturing a charge transfer device is performed as a second process.
This will be explained using the second engineering drawings from Drawing A.

As shown in FIG. 2A, a relief channel 2 is formed on the main surface of the silicon substrate 1 by first implanting phosphorus ions into a p-type silicon substrate 1 and then thermally diffusing it.

Signal charges move within the relief channel 2.

Next, as shown in FIG. 2B, a first silicon oxide film 3 is formed on the relief channel 2 by heat-treating the silicon substrate 1, and a silicon oxide film 3 is formed on the first silicon oxide film 3.
A first polysilicon film 4 is deposited using the VD method.

Then, as shown in FIG. 2C, the first polysilicon film 4
A resist 5 is applied thereon, and the resist 5 is processed into a predetermined pattern.

As shown in FIG. 2D, using the resist 5 as a mask, the first
selectively etching and removing the polysilicon film 4 of
A first electrode layer is formed.

Furthermore, as shown in FIG. 2E, the first silicon oxide film 3 is selectively etched and removed using the resist 5 as a mask to expose the main surface of the silicon substrate 1 located in the formation area of the second electrode layer. .

Next, as shown in Figure 2F, by applying heat treatment,
A second silicon oxide film 6 is formed on the exposed main surface of silicon substrate 1 and on the surface of first polysilicon 1114, which is the first electrode layer.

Then, as shown in FIG. 2G, a second silicon oxide film 6 is formed.
A second polysilicon film 7 is deposited thereon using the CVD method.

Next, as shown in FIG. 2H, a resist 8 is applied onto the second polysilicon film 7, and the resist 8 is formed into a predetermined pattern.

Then, as shown in FIG. 21, the second polysilicon film 7 is selectively etched and removed using the resist 8 as a mask to form a second electrode layer.

After that, move on to the post-process.

By the way, as shown in FIG. 2I, the first electrode layer
The electrical insulation between the polysilicon film 4 and the second polysilicon film 7 which is the second electrode layer is achieved by the second polysilicon film 7 formed between the first polysilicon film 4 and the second polysilicon film 7. This is done using a silicon oxide film 6. Conventionally, the second silicon oxide film 6 was formed by subjecting the first polysilicon film 4 to thermal oxidation. The thickness of the first polysilicon film 4, which is the first electrode layer, and the thickness of the second polysilicon film 7, which is the 211th pole layer, must be uniform due to the characteristics of the charge transfer element. For this reason, conventionally the first electrode layer
In order to prevent thinning of the polysilicon film 4 due to thermal oxidation,
The second polysilicon film 4 was deposited to be thicker than the second polysilicon film 7.

[Problems to be Solved by the Invention] However, since thermal oxidation is difficult to control, the thickness of the first polysilicon film 4, which is the first electrode layer, may become thicker than necessary or thinner than necessary. It happens. Therefore, the thickness of the first polysilicon film 4, which is the first electrode layer, and the second polysilicon film 7, which is the second electrode layer, are not uniform, which is one of the causes of performance deterioration of the charge transfer element. It became.

Therefore, the present invention has been made to solve such conventional problems, and its purpose is to provide a charge transfer device that can make the thickness of the first electrode layer and the thickness of the second electrode layer uniform. An object of the present invention is to provide a manufacturing method.

[Means for Solving the Problems] The present invention provides a charge transfer element having a structure in which a plurality of electrode layers are alternately formed on an insulating film formed on the main surface of a semiconductor substrate having a charge transfer region. The present invention relates to a manufacturing method.

The method of manufacturing a charge transfer device according to the present invention includes a step of forming a first insulating film on the main surface of a semiconductor substrate, a step of forming a first conductive layer on the first insulating film, and a step of forming a first conductive layer on the main surface of a semiconductor substrate. By selectively etching the layer, a first insulating film is formed on the first insulating film.
A step of forming an electrode layer, a step of depositing a second insulating film on the semiconductor substrate including the surface of the first electrode layer by a vapor phase method, and a step of forming a second conductor layer on the second insulating film. By selectively etching the second conductor layer, the first
forming second electrode layers that are arranged alternately with the electrode layers.

[Function] In the method for manufacturing a charge transfer device according to the present invention,
A second insulating film that electrically insulates the first electrode layer and the second electrode layer is formed by a vapor phase method.

Therefore, it is not necessary to thermally oxidize the first electrode layer,
The film thicknesses of the first electrode layer and the second electrode layer can be easily made uniform.

Here, the vapor phase method includes, for example, CVD, sputtering,
This refers to vacuum evaporation methods, etc.

[Example] An example of the method for manufacturing a charge transfer device according to the present invention will be described with reference to FIGS. 1A to 1J.

As shown in FIG. 1A, by first implanting phosphorus ions into a p-type silicon substrate 11 and thermally diffusing it,
A relief channel 12 is formed on the main surface of a silicon substrate 11.

Next, as shown in FIG. 1B, a silicon oxide film 13 is formed on the relief channel 12 by heat-treating the silicon substrate 11, and a CV
A silicon nitride film 14 and a first polysilicon film 15 are sequentially deposited using the D method.

Then, as shown in FIG. 1C, a first polysilicon film 1 is formed.
A resist 21 is applied on top of the photoresist 5, and the resist 21 is processed into a predetermined pattern.

Next, as shown in FIG. 1D, by selectively etching and removing the first polysilicon film 15 and silicon nitride film 14 using the resist 21 as a mask, a first electrode layer is formed and a second electrode layer is formed. The silicon oxide film 13 located in the layer formation area is exposed. Then, the resist 21 is removed.

Thereafter, as shown in FIG. 1E, an HTO film 16 (high thermal oxide film) is deposited on the exposed silicon oxide film 13 and the first polysilicon film 15 using the CVD method.

Next, as shown in FIG. 1F, a second polysilicon film 17 is deposited on the HTO film 16 using the CVD method.

Next, as shown in FIG. 1G, a second polysilicon film 17 is formed.
A resist 18 is applied onto the resist 18, and the resist 18 is formed into a predetermined pattern.

Then, as shown in FIG. 1H, the second polysilicon film 17 is selectively etched and removed using the resist 18 as a mask to form a second electrode layer.

Then, the resist 18 is removed.

Next, as shown in FIG.
A smooth coat film 19 is formed on the HTO film 16 and on the HTO film 16, and a resist is applied thereon.

A predetermined pattern is applied to this resist, and using this resist as a mask, a contact hole is formed on the boundary between the first polysilicon film 15 and the second polysilicon film 17. The contact hole has a step because an etching method was used in which only the smooth coat 19 was etched and the polysilicon was not etched.

Then, as shown in FIG. 1J, an aluminum wiring layer 20 is formed on the smooth coat film 19, and the aluminum filled in the contact hole connects the first polysilicon film 15, which is the first electrode layer, and the second electrode layer. An aluminum wiring layer 20 is formed on each second polysilicon film 17 as a layer.
Connect electrically.

Through the above steps, one embodiment of the method for manufacturing a charge transfer device according to the present invention is completed.

As shown in FIG. 1J, a charge transfer device manufactured using an embodiment of the present invention consists of one aluminum wiring layer 20
One first electrode layer and one second electrode layer are connected to each other. Therefore, one potential well is formed by one first electrode layer and one second electrode layer.

Two unique effects of this embodiment will be explained. The first one will be explained below. As shown in FIG. 1J, between the first polysilicon film 15, which is the first electrode layer, and the relief channel 12, there are a silicon oxide film 13 and a silicon nitride film 14. Between the second polysilicon film 17, which is the second electrode layer, and the relief channel 12, a silicon oxide film 13 and an HT
There is an O film 16. The silicon nitride film 14 and the HTO film 16 have approximately the same dielectric constant. Therefore, the insulation film between the first polysilicon film 15, which is the first electrode layer, and the relief channel 12, and the insulation film, which is between the second polysilicon film 17, which is the second electrode layer, and the relief channel 12. Since the dielectric constant and the film thickness are almost the same as that of the film, this is preferable from the viewpoint of the characteristics of the charge transfer element. Note that the same effect can be achieved by using TE01 (tetraethyl orthosilicate film) instead of the HTO film 16.

Another unique effect of this embodiment will be explained below. In the conventional example, as shown in FIG. 2F, the first electrode layer
A second silicon oxide film 6 was formed on the surface of the polysilicon film 4 by thermal oxidation. In this case, the second silicon oxide film 6 is
, the first silicon oxide film 3 under the formation part of the second polysilicon film 7, which is the second electrode layer, becomes the first silicon oxide film 3.
It becomes thicker than the first silicon oxide film 3 under the first polysilicon film 4, which is an electrode layer.

Therefore, conventionally, as shown in FIG. 2E, the first silicon oxide film 3 under the formation part of the second polysilicon film 7, which is the second Ts pole layer, is removed, and the first silicon oxide film 3, which is the first electrode layer, is removed. The second silicon oxide film 6 formed on the surface of the polysilicon film 4 is also formed under the formation part of the second polysilicon film 7, which is the second electrode layer, and The thickness of the first silicon oxide film 3 under the first polysilicon film 4 and the second silicon oxide film 6 under the second polysilicon film 7 which is the second electrode layer are made to be about the same. Ta.

However, because of this, the first silicon oxide film 3 under the first polysilicon film 4, which is the first electrode layer, and the second polysilicon film 7, which is the second electrode layer,
There is a second silicon oxide film 6 under the second silicon oxide film 6.
As shown in the figure, there was a difference in level. This caused a difference in the depth of the potential wells, which was unfavorable in terms of charge transfer.

On the other hand, according to this embodiment, since the insulating film formed on the surface of the first polysilicon film 15, which is the first electrode layer, is not formed by thermal oxidation, the first polysilicon film 15 as shown in FIG. The silicon oxide film 13 under the first polysilicon film 15, which is an electrode layer, and the silicon oxide film 13 under the formation part of the second polysilicon film 17, which is a second electrode layer, have a thickness that is different from each other. There is no difference in Therefore, there is no need to remove the silicon oxide film 13 under the formation of the second polysilicon film 17, which is the second electrode layer, so that there is no step difference as in the conventional case.

In this embodiment, the HTO film 16, which is the second insulating film, was deposited using the CVD method, but the present invention is not limited to this, and the material that will become the second insulating film may be deposited by sputtering or other methods. It may also be deposited using a vacuum evaporation method.

[Effect] In the method for manufacturing a charge transfer device according to the present invention,
A second insulating film that electrically insulates the first electrode layer and the second electrode layer is formed by a vapor phase method.

Therefore, it becomes unnecessary to thermally oxidize the first electrode layer, and it becomes possible to make the thickness of the first electrode layer and the second electrode layer uniform.

[Brief explanation of drawings]

FIGS. 1A to 1J are diagrams showing an embodiment of the present invention in the order of steps. FIGS. 2A to 21 are diagrams sequentially showing the steps up to the middle of a conventional method for manufacturing a charge transfer device. In the figure, 11 is a silicon substrate, 12 is a relief channel, 13 is a silicon oxide film, 14 is a silicon nitride film, 1
5 is a first polysilicon film, 16 is an HTO film, and 17 is a second polysilicon film.

Claims (1)

[Scope of Claims] A method for manufacturing a charge transfer element having a structure in which a plurality of electrode layers are alternately formed on an insulating film formed on a main surface of a semiconductor substrate having a charge transfer region, comprising the steps of: forming a first insulating film on the main surface of the first insulating film; forming a first conductive layer on the first insulating film; selectively etching the first conductive layer; forming a first electrode layer on one insulating film; and forming a second electrode layer on the semiconductor substrate including the surface of the first electrode layer.
The first electrode layer is formed by depositing an insulating film by a vapor phase method, forming a second conductive layer on the second insulating film, and selectively etching the second conductive layer. A method of manufacturing a charge transfer device, comprising: forming second electrode layers arranged alternately with the second electrode layers.