JPS5934652A - Manufacture of semiconductor integrated circuit device - Google Patents

Abstract

PURPOSE:To form extremely fine and extremely shallow irregular sections, and to increase the area of an electrode by etching a substrate fitted to the IC while using a thin-film formed in a large number of insular structure as a mask when the irregular surface sections are formed to the substrate. CONSTITUTION:The silicon substrate 1 is oxidized to form a thermal oxide film 2 in several hundred Angstrom , and polysilicon films 3 formed in a large number of insular structure because they are extremely thin are grown. When the film 2 is etched while using the films 3 as masks and the films 3 are removed, the fine and extremely shallow irregular sections, the width and depth of grooves thereof are several hundred - several thousand Angstrom , can be formed to the substrate 1. A thin uniform thickness thermal oxide film 4 is formed to the surface of the substrate 1, and a polysilicon film 5 is deposited, thus obtaining a capacitor, which uses the substrate 1 and the film 5 as electrodes and capacitance per unit projected area thereof increases.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for increasing capacitance per unit projected area and for forming irregularities on a substrate suitable for an IC.

Conventionally, a method of forming irregularities on electrodes in order to increase capacitance per unit projected area has been put to practical use in electrolytic capacitors and the like. For example, in the case of an aluminum electrolytic capacitor, this method corrodes the surface of the aluminum electrode with hydrochloric acid, etc., resulting in unevenness that looks spongy even when magnified to the level of an electron microscope. Forming a film, one electrode is of course
The above-mentioned aluminum electrode is used, and the other electrode is an electrolyte in the case of a liquid acid, and a solid type (for example, manganese oxide in the case of a solid type) to realize a small and large-capacity electrolytic capacitor.

When this kind of technology is applied to the manufacture of IC capacitors, the IC is often exposed to chemicals in the manufacturing process and then put into a high-temperature furnace. There is a drawback that the remaining chemicals contaminate the above-mentioned furnace.

In addition, chemicals remaining in the sponge-like holes reduce the reliability of the finished product, and even if you take the pains to create unevenness to increase the area, there is no choice in the counter electrode material, and only a small portion of that area There were drawbacks such as the fact that it could only be used in

Furthermore, although it is possible to create unevenness using the conventional photoetching method, the dimensions of the repeated unevenness are limited by photoetching.
O) The following two drawbacks occur because the size cannot be made smaller than the minimum size. In other words, if the area is increased by using unevenness, unless the depth is about the same or even larger than the width of the hole, it will not be possible to expect an increase in area commensurate with the adoption of a standard process.

Since the width of the hole is about 2 μm at the current practical level minimum width, the width of the hole is 2 μm or more. The first drawback is that it is only possible to form a pattern as fine as 2 μm on the electrode material in the subsequent process on such deep unevenness, and the other drawback is that #E of the capacitor in the IC The horizontal size was almost the same as the minimum dimension of the above-mentioned photo-X engraving, making it virtually impossible to apply.

The present invention was made in order to eliminate the drawbacks of the conventional methods as described above. Although the shape and dimensions are irregular, the object is to provide a method of forming extremely fine and extremely shallow irregularities to sufficiently increase the electrode area.

An embodiment of the present invention will be described below with reference to the drawings. 1st
4 to 4 are cross-sectional views showing the main steps of an embodiment of the present invention.

Figure 1 shows that a silicon substrate [11] was oxidized to form a thermal oxide film (2) of several hundred amperes, and then a polysilicon film (3), which was extremely thin and formed into many island-like structures, was grown. It is something. The particle size of the island-like structure of this polysilico/film (3) can be controlled by the film thickness, growth temperature, etc.
A range of 000 A is possible.

Figure 2 shows a thermal oxide film (2) using a polysilicon film (3) as a mask.
) is shown after being etched. At this time, actually
Appropriate undercutting is performed on the thermally liquefied film (2) under the polysilicon film (3) to maximize the subsequent increase in electrode area, and this thermally oxidized film (2) is removed. Needless to say, it is necessary to control the ratio.

FIG. 3 shows a state in which the silicon substrate f1) has been etched by several hundred to several thousand amps using the thermal oxide film (2) of FIG. 2 as a mask. At this time, it is advantageous to perform so-called anisotropic etching in order to increase the area.・If there is a cut, it is desirable to remove it by isotropic etching.

Figure 4 shows a state in which the thermal oxide film (3) in Figure 3 has been removed, and the width and depth of the grooves in the silicon substrate [1] ranges from several hundred to several tens.
This shows that it is possible to create fine and extremely shallow irregularities of 1,000 people.

Figure 5 shows that after forming a thin thermal oxide film (4) of uniform thickness on the surface of a silicon substrate i1) with extremely fine irregularities as shown in Figure 4, a polysilicon film (5) is formed. FIG. 3 is a diagram showing that a capacitor with increased capacitance per unit projected area is obtained by using a silicon substrate (1) and a polysilicon film (5) as electrodes.

In the above explanation, the process has been omitted for simplicity, but in an actual IC, the following ten steps are normally performed. That is,
For areas where there is no need to create unevenness, for example, in the state shown in Figure 1, a step of covering with a photoresist may be added to the surface of the silicon substrate fi+. A step of forming a diffusion layer, an epitaxial layer, etc. of the conductivity type or the opposite conductivity type in the state shown in FIG. 4 or before depositing the thermal oxide film (2) in FIG. Polysilicon film (5) in the figure
Needless to say, a step is included to diffuse impurities into the film to lower the sheet resistance.

The above describes the case where a thin island-shaped thin film made of the same material as the substrate is used as a mask, but the same effect can be obtained using a different material, such as metals such as gold and aluminum, other semiconductor materials, insulating materials, etc. It goes without saying that this can be achieved. Further, as a film for copying the shape of a thin film having an island-like structure, other than a thermal oxide film, there is a film that guarantees a uniform thickness even if it is as thin as several hundred amps, and has a masking effect on silicon.

For example, it may be a thermal nitride film.

In addition, if the above-mentioned thin film with an island-like structure is made of a material that acts as a mask for silicon, the thin film with an island-like structure can be directly attached to the silicon substrate and the silicon substrate can be etched as is. , the structure shown in FIG. 4 can be realized. However, in this case, it is not possible to control the ratio of uncut parts due to the undercutting described in the embodiment, so it is not possible to efficiently increase the area.

As described above, according to the present invention, since a thin film with an island-like structure is used in the mask, the average width interval of the recesses can be made short, although irregular, such as several 100 to several 100 OA. Since the depth of the recessed portion is also approximately several hundred to several thousand amps, there is an effect that the area can be sufficiently increased due to the unevenness.

[Brief explanation of the drawing]

1 to 4 are cross-sectional views showing the main steps of an embodiment of the present invention, and FIG. 5 is a cross-sectional view of a capacitor using the method of the present invention. In the figure, (1) is a silicon substrate, (2) is a thermal oxide film, (3) is a polysilicon film with an island-like structure, (4) is a thermal oxide film, and (5) is a polysilicon film. Note that the same reference numerals in the figures indicate the same or corresponding parts. Agent Shin Kuzuno - (1 other person)

Claims (1)

[Claims] fil A step of depositing a thin film thin enough to form a large number of fine island-like structures on a substrate, and etching the substrate using the thin film of the island-like structure as a mask to form a surface portion of the thin film. A method for manufacturing a semiconductor integrated circuit device, comprising a step of forming a large number of fine irregularities. (2) A step of forming a first thin film with a substantially uniform thickness on a substrate, and a second film thin enough to form a large number of fine island-like structures.
a step of depositing a thin film on the surface of the first thin film; a step of etching the first thin film using the second thin film having an island-like structure as a mask to form a large number of fine openings; A method for manufacturing a semiconductor integrated circuit device, comprising the step of etching the substrate using the first thin film in which the opening is formed as a master to form a large number of fine irregularities on the surface thereof. .