JPH0817802A - Semiconductor device and its manufacture - Google Patents

Abstract

PURPOSE:To prevent an electrode and a substrate from being short-circuited due to the undercut of the ground layer of the electrode. CONSTITUTION:A process for forming a ground oxide layer 8 on silicon substrate 7, a process for forming silicon nitride film 9 on an etching stop layer on the ground oxide layer 8, a process for forming a metal thin film 10 which becomes an electrode at a specific position on the silicon nitride film 9, and a process for forming silicon oxide film 12 with the same composition as that of the ground oxide layer 8 on the entire surface of a substrate by the plasma CVD after forming the metal thin film 10 are included, thus preventing the ground oxide layer 8 from being etched when etching the silicon oxide film 12 which becomes an electrode layer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a method of manufacturing a semiconductor device,
In particular, the present invention relates to a structure of a semiconductor device manufactured by a method of manufacturing a fixed piece of an electrostatic drive relay and a method of manufacturing the semiconductor device.

[0002]

2. Description of the Related Art An electrostatic force driven relay is a relay that opens and closes by applying a voltage between substrates, bending the movable piece by the electrostatic force acting between the substrates, and contacting the electrodes formed on each substrate. is there. FIG. 3 shows an example of a fixed piece of a conventional electrostatic drive relay. FIG. 3 is a sectional view of the fixing piece. In the figure, 1 is a substrate, 2 is an underlying oxide film formed on the substrate 1,
Reference numeral 3 denotes an electrode formed of gold, and reference numeral 4 denotes an electret layer formed at a position on the underlying oxide film 2 adjacent to the electrode 3.

As shown in FIG. 3, a fixed piece of an electrostatic drive relay has a base oxide film 2 formed as an insulating layer on the entire surface of a substrate 1, an electrode 3 formed on the base oxide film 2, and then an adjacent electrode 3. It was formed by forming the electret layer 4 at the position. The electret layer 4 is a layer that can semi-permanently retain charges on the surface. In the example of the fixing piece shown in FIG. 3, the electret layer 4 has a composition different from that of the base oxide film 2 which is an insulating layer, though the manufacturing method is different. Similarly, both are made of silicon oxide. The electret layer 4 is formed by poling the silicon oxide film formed by plasma CVD and then removing unnecessary portions by etching. When only the electret layer 4 is patterned, the selectivity of the electret layer 4 with the underlying oxide film 2 cannot be obtained. Therefore, the etching of the electret layer 4 is performed by time management with a monitor wafer. Therefore, there is a possibility that the underlying oxide film 2 may also be etched when overetched.

[0004]

The process of etching the electret layer will be described with reference to FIG. FIG. 4 is a sectional view of the substrate on which the fixing piece is formed. FIG. 4 shows the substrate 1
This shows a state in which a base oxide film 2 and an electrode 3 are formed on the substrate 1, and a silicon oxide film 5 is formed on the entire surface of the substrate 1 by plasma CVD. Here, the side surface portion (X portion) of the electrode 3
The silicon oxide film 5a formed on the substrate is thinner than the silicon oxide film 5b formed on the underlying oxide film 2 (Y portion). Therefore, when the silicon oxide film 5 to be the electret layer is etched, even if the silicon oxide film 5a formed on the side surface portion (X portion) of the electrode 3 is removed by etching, the underlying oxide film 2 (Y portion) is removed. The silicon oxide film 5b thus formed remains in a state where it remains. For this reason,
Silicon oxide film 5 formed on base oxide film 2 (Y portion)
When b is completely removed by etching, the silicon oxide film 5a formed on the side surface (X portion) of the electrode 3 has already been removed. Therefore, the etchant reaches the underlying oxide film 2 from the side surface of the electrode 3, There is a problem that the underlying oxide film 2 formed below the electrode 3 is also etched. The underlying oxide film 2 and the silicon oxide film to be the electret layer are both etched by the same etchant, but the etching rate of the electret layer is low, and the etching rate is only about half that of the plasma CVD film of the same thickness. It is considered that the undercut of the base of the electrode 3 (base oxide film 2) becomes large by reaching the base oxide film 2 from the side surface of the electrode 3 having a thin electret layer. Due to this large undercut, the electrode 3 bends downward by its own weight and comes into contact with the substrate 1 to cause a short circuit.

The present invention has been made in view of the above problems, and an object thereof is to etch an electret layer in a semiconductor device in which an electret layer having the same composition as that of the insulating layer is formed on the insulating layer. It is an object of the present invention to provide a method of manufacturing a semiconductor device capable of preventing the insulating layer from being etched, and a structure of the semiconductor device formed by the manufacturing method.

[0006]

In order to achieve the above object, a method of manufacturing a semiconductor device according to claim 1 includes a step of forming an insulating layer on a substrate, and at least one step on the insulating layer.
A step of forming an etching stop layer of the layer, a step of forming a metal thin film at a predetermined position on the etching stop layer, and an electret having the same composition as the insulating layer by plasma CVD on the entire surface of the substrate after forming the metal thin film. It is characterized by including a step of forming a layer and a step of etching the electret layer.

A method of manufacturing a semiconductor device according to claim 2 is
2. The method of manufacturing a semiconductor device according to claim 1, wherein the insulating layer is a film whose composition continuously changes from silicon oxide to silicon nitride as it goes upward, and the etching stop layer is composed of a silicon nitride film. It is characterized by being present.

According to another aspect of the semiconductor device of the present invention, a silicon oxide film is formed on a substrate, a metal thin film serving as an electrode is formed at a predetermined position on the silicon oxide film, and the metal thin film on the silicon oxide film is formed. An electret layer having the same composition as the silicon oxide film and formed by plasma CVD is formed at an adjacent position, and at least one etching stop layer is provided between the silicon oxide film and the metal thin film. It is a feature.

[0009]

According to the method of manufacturing a semiconductor device of claim 1, in the semiconductor device in which an electret layer having the same composition as that of the insulating layer and an electrode are formed on the insulating layer, between the insulating layer and the electret layer. Since at least one etching stop layer is formed, even if the electret layer formed on the side surface of the electrode is removed by etching, the silicon oxide film below the electrode is not etched.

According to the method for manufacturing a semiconductor device of the second aspect, in the semiconductor device in which the electret layer formed of silicon oxide and the electrode are formed on the silicon oxide film, the silicon oxide film and the electret layer are formed. Since the silicon nitride film is formed as the etching stop layer in between, even if the electret layer formed on the side surface of the electrode is removed by etching, the silicon oxide film formed below the electrode is not etched.

The etching stop layer of the present invention is made of a material which is not etched by the etching solution for the electret layer.

FIG. 2 shows an embodiment of a fixing piece having an etching stop layer formed thereon. By forming the silicon nitride film 6 as the etching stop layer on the base oxide film 2, the base oxide film 2 and the electret layer 4 are separated.
This allows only the electret layer 4 to be patterned, and the underlying oxide film 2 formed below the electrode 3 can be patterned.
It is possible to realize a structure in which the electrode 3 is not etched, and it is possible to prevent the electrode 3 and the substrate 1 from coming into contact with each other due to the undercut of the underlying oxide film 2. Conventionally, strict time management by an etching monitor is required, and the underlying oxide film 2 was etched even with a slight overetching. However, by forming the silicon nitride film 6 which is the etching stop layer, strict time management is required. No need for management.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the method for manufacturing a semiconductor device of the present invention will be described with reference to FIG. FIG. 1 is a sectional view showing a state in which a silicon oxide film to be an electret layer is formed on the entire surface of a substrate. First, a base oxide film 8 (insulating layer, silicon oxide film) is formed on a silicon substrate 7 which is a substrate by thermal oxidation to a thickness of 1.0 to 1.3 μm. Base oxide film 8
May be configured such that its composition continuously changes from silicon oxide to silicon nitride as it goes upward. Next, a silicon nitride film 9 is formed as an etching stop layer by the low pressure CVD method to a thickness of 1000 angstroms. When the silicon nitride film 9 is formed on the underlying oxide film 8, if the stress is not balanced, the silicon nitride film 9 may warp, so the thickness of the silicon nitride film 9 is important. The thickness of the silicon nitride film 9 is not limited to that in the embodiment as long as the stress acting between the underlying oxide film 8 and the silicon nitride film 9 is balanced. The film forming the etching stop layer is not limited to the silicon nitride film, and for example, the metal thin film 10 made of gold as an electrode is used.
Any material can be used as long as it can insulate the silicon substrate 7 from the silicon substrate and is not etched by the etchant of the silicon oxide film.

Next, a metal thin film 10 to be an electrode is formed.
Since the metal thin film 10 made of gold is easily peeled off, the metal thin film 10
A chromium layer 11 having a thickness of 1000 angstrom is formed between the silicon nitride film 9 and the silicon nitride film 9. This material is not limited to chromium, and other materials may be used as long as they have high adhesiveness. With the chrome layer 11 left unpatterned, a gold thin film is sputtered.
Deposit over μm.

Next, an ion milling apparatus for forming a resist mask for forming electrodes on the gold thin film and physically etching the silicon substrate 7 by applying argon ions vertically thereto,
Alternatively, the metal thin film 10 made of gold and the chrome layer 11 are simultaneously patterned by wet etching with aqua regia.

Next, a method for forming the electret layer will be described. Silicon oxide film 1 that becomes the electret layer
2 is formed on the entire surface of the silicon substrate 7 by plasma CVD. By performing a poling treatment on the formed silicon oxide film 12, electric charges are semipermanently retained on the surface of the silicon oxide film 12 to form an electret layer. Using a resist mask to form an electret layer at a position adjacent to the metal thin film 10, the buffered hydrofluoric acid (B
Etching with HF). In this case, as compared with the conventional example, since the silicon nitride film 9 is formed as the etching stop layer, the etching is stopped at the stage when the etching of the electret layer is completed, and the underlying oxide film 8 is formed.
Will not be etched. As a result, the underlying oxide film 8 that is the base of the metal thin film 10 that is an electrode is largely undercut, and the metal thin film 10 that is an electrode bends downward due to its own weight, causing contact with the silicon substrate 7 and causing a short circuit. Can be resolved.

[0017]

According to the method for manufacturing a semiconductor device of the first aspect, in the semiconductor device in which the electret layer having the same composition as the insulating layer and the electrode are formed on the insulating layer, the insulating layer and the electret layer are formed. Since at least one etching stop layer is formed between the electrodes, even if the electret layer formed on the side surface of the electrode is removed by etching, the silicon oxide film below the electrode is not etched, so that the electrode is formed on the substrate. There is no contact and short circuit.

According to the method for manufacturing a semiconductor device of the second aspect, in the semiconductor device in which the electret layer formed of silicon oxide and the electrode are formed on the silicon oxide film, the silicon oxide film and the electret layer are formed. Since a silicon nitride film is formed as an etching stop layer between the electrodes, even if the electret layer formed on the side surface of the electrode is removed by etching, the silicon oxide film formed below the electrode is not etched. Does not come into contact with the substrate to cause a short circuit.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an example of a method for manufacturing a semiconductor device of the present invention.

FIG. 2 is a sectional view showing an embodiment of a semiconductor device of the present invention.

FIG. 3 is a sectional view showing an example of a conventional semiconductor device.

FIG. 4 is a cross-sectional view showing an example of a conventional semiconductor device manufacturing method.

[Explanation of symbols]

1,7 Silicon substrate (substrate) 2,8 Silicon oxide film (insulating layer) 3,10 Metal thin film 4 Electret layer 6,9 Silicon nitride film (etching stop layer)

Claims (3)

[Claims] 1. A step of forming an insulating layer on a substrate, a step of forming at least one etching stop layer on the insulating layer, and a metal thin film serving as an electrode at a predetermined position on the etching stop layer. And a step of forming an electret layer having the same composition as the insulating layer by plasma CVD on the entire surface of the substrate after forming the metal thin film, and a step of etching the electret layer. Manufacturing method. 2. The insulating layer is a film whose composition continuously changes from silicon oxide to silicon nitride as it goes upward, and the etching stop layer is composed of a silicon nitride film. Item 2. A method of manufacturing a semiconductor device according to item 1. 3. A silicon oxide film is formed on a substrate, a metal thin film to be an electrode is formed at a predetermined position on the silicon oxide film, and the silicon oxide film is formed on the silicon oxide film at a position adjacent to the metal thin film. A semiconductor device having an electret layer formed by plasma CVD and having the same composition as the film, and at least one etching stop layer provided between the silicon oxide film and the metal thin film.