JPH01220856A - Semiconductor device - Google Patents

Abstract

PURPOSE:To enable the high density formation of capacitors of large capacitance, by alternately forming insulating films and conducting films in the form of multilayer, in trenches formed on a semiconductor substrate, and constituting a plurality of capacitors in the state of lamination. CONSTITUTION:On the surface of a P-type semiconductor substrate 1, an N-type epitaxial layer 2 is grown, a plurality of trenches 4 are formed thereon, an oxide film 5a is formed on the trenches 4 formed outside, an oxide film 5b is formed on the surface of the N-type epitaxial layer 2, and an N-type impurity diffusion region 6 is formed on the substrate 1 around the inside trenches 4 and the epitaxial layer 2. After that, a nitride film as a first insulating film 7 is formed on the inner surfaces of the trenches 4, a first conducting film 8 is formed of polysilicon inside the first insulating film 7, a nitride film 9 as a second insulating film 9 is formed inside the first conducting film 8, and further a second conducting film 10 is formed of polysilicon.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a semiconductor device, particularly a capacitor with a large capacitance value (
The present invention relates to a semiconductor device including a capacitor.

[Conventional technology]

Conventionally, various types of junction capacitors, such as base-collector junctions and emitter-base junctions of bipolar transistors, have been widely used in semiconductor devices that require capacitance in circuits. However, this type of capacity varies widely;
Due to the fact that the capacitance value is dependent on voltage and that the polarity of the voltage must be used without being reversed, recently MIs type reactors using oxide films and tin oxide films as insulating films have been developed. It has become a trend.

However, with this capacitance, even if a tinned film with a high dielectric constant is used as an insulating film, the capacitance per unit area is about 1.3 x 10-'PF/μ2, which means a capacitance of 0.01 μF. When I try to make it, 28fflII
The area required for one opening greatly exceeds the chip area, making it impractical. Recently, as a method to increase the capacitance per unit area, a silicon substrate is trench-etched to form a groove, a thin film of oxide or tin oxide is formed on the sides of the groove, and then the groove is filled with polysilicon. A capacitor with a trench structure in which an impurity such as phosphorus is diffused into silicon to serve as one electrode and a substrate as the other electrode has been proposed and has been adopted in DRAMs.

[Problem to be solved by the invention]

Although the conventional trench structure described above has a larger capacitance value than that of the planar structure, the capacitance values for phase compensation and filter characteristic determination used in bipolar analog ICs are extremely large. is required, so even if the capacitance is configured with a trench structure,
The area it occupies is large, making it difficult to incorporate it into an IC chip.

An object of the present invention is to increase the capacitance value per unit area (to provide a capacitor with a small area and a large capacitance value).

[Means to solve the problem]

In the semiconductor device of the present invention, a capacitor is formed by a conductive layer formed around a trench formed in a semiconductor substrate, an insulating film formed on the inner surface of this trench, and a conductive film formed inside this insulating film. , and inside this conductive film, insulating films and conductive films are alternately formed in multiple layers to form a plurality of capacitors in a stacked state.

[Operation] In the above-described configuration, since a plurality of capacitors are formed in multiple layers within the trench, a plurality of capacitance values can be constructed in the same area.

〔Example〕

Next, the present invention will be explained with reference to the drawings.

FIG. 1 is a sectional view of one embodiment of the present invention, and FIG.
) to (c) are cross-sectional views of the manufacturing process.

In FIG. 1, 1 is a P-type semiconductor substrate, with N on the surface.
A type epitaxial layer 2 is grown.

Then, a plurality of trenches (
Groove) 4 is formed. An oxide film 5a is formed in the trench 4 formed on the outside to separate the epitaxial layer 2, and a capacitance region is defined between the oxide films 5a and the trench 4 is electrically insulated from an element region such as a transistor. Further, an oxide film 5b is also formed on the surface of the N-type epitaxial layer N2.

A conductive layer as a capacitor electrode, here an N-type impurity diffusion region 6, is formed in the substrate 1 and epitaxial layer 2 around the inner trench 4. Further, a nitride film as a first insulating film 7 is formed on the inner surface of the trench 4. Furthermore, a first conductive film 8 is formed of polysilicon inside this, and the N-type impurity diffusion region 6. The first insulating film 7 and the first conductive film 8 constitute a first capacitor.

Further, a nitride film 9 as a second insulating film 9 is formed inside the first conductive film 8, and a second conductive film n'J10 is further formed inside this.
is formed of polysilicon, and the first conductive film 8. The second insulating film 9 and the second conductive film 10 constitute a second capacitor.

Then, the entire surface is insulated with an oxide film 11, and this oxide film 11
An aluminum electrode 12 is electrically connected through a contact hole formed in the aluminum electrode 12 .

A method of manufacturing the above-described structure will be explained using FIG. 2.

- First, as shown in FIG. 2(a), an oxide film 3 is grown to a thickness of 1 μm on an N-type epitaxial layer 2 on a P-type semiconductor substrate 1, partially etched with hydrofluoric acid, etc., and then trench-etched to a depth of 1 μm. A trench 4 reaching the substrate 1 with a thickness of 5 to 10 μm is formed.

Next, after growing a nitride film over the entire surface, the nitride film formed on the surface of the trench for insulation is selectively etched, and as shown in FIG. Oxide films 5a and 5b are simultaneously formed on the surface of the epitaxial layer N2.

Next, after removing the nitride film, using the oxide film 5b as a mask, an N-type impurity such as phosphorus is ion-implanted at an energy of 70 KeV and an implantation amount of IXIO"cm-".
Thermal diffusion is performed for 1 to 2 hours at 00°C to form an N-type impurity diffusion region 6 in the substrate 1 and epitaxial layer 2 around the inner trench 4. After that, a nitride film 7 as a first insulating film is formed on the inner surface of the inner trench 4 to a thickness of 300 to 500
Grown by vapor phase in humans.

Next, as shown in FIG. 2(C), 1 layer of polysilicon is
The first conductive film 8 is formed by growing a phase of 0.000 to 2000 and then implanting As ions at a high concentration.

Thereafter, as shown in FIG. 1, a nitride film 9 serving as the first insulating film 7 is grown in a vapor phase to a thickness of 300 to 500 nm. Thereafter, polysilicon is grown by 2,000 to 4,000 people, and the polysilicon is doped with arsenic or phosphorus at a high concentration to form the second conductive film 10.

Thereafter, the oxide film 11 is formed by 0.4
After growth with μ and opening a contact window, aluminum is vapor deposited and patterned by dry etching using a photoresist as a mask to form the electrode 12.

According to this configuration, by connecting the capacitors of the two-layer structure formed in the trench in parallel, it is possible to obtain approximately twice the capacitance value for the same area, and in addition to the large capacitance value of the trench structure. Even larger capacitance values can be obtained. Therefore, approximately twice the capacitance value can be obtained with the same area in a semiconductor device, and application to bipolar analog ICs and the like is possible.

Here, there is a method to form the nitride film and polysilicon by sputtering, but the current process technology has a problem with the uniformity of the film thickness within the trench, and as in this example, vapor phase growth (CVD) is used to form the nitride film and polysilicon.
) method is preferable.

In the above embodiment, the case where the capacitor has a two-layer structure has been described, but it goes without saying that the capacitor may have a structure of three or more layers. In addition, although a nitride film is used as the insulating film,
If a high dielectric material such as tantalum oxide TazO□ is used, the capacitance value can be further increased significantly.

〔Effect of the invention〕

As explained above, in the present invention, insulating films and conductive films are formed alternately and in multiple layers in a trench formed in a semiconductor substrate, and a plurality of capacitors are configured in a stacked state. This has the effect that a capacitance that is several times larger than that of the semiconductor substrate can be obtained, and that capacitors with large capacitance values can be formed at high density on a semiconductor substrate. Further, by configuring a capacitor with a large capacitance value within the semiconductor device, it is possible to cauterize the capacitor that was conventionally attached externally, and there is also an effect that the number of pins of the semiconductor device and the number of adjustment steps can be reduced.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of an embodiment of the present invention, and FIGS. 2(a) to 2(C) are sectional views showing the manufacturing method in order of steps. DESCRIPTION OF SYMBOLS 1... P-type semiconductor substrate, 2... N-type epitaxial layer, 3... Oxide film, 4... Trench, 5a, 5b.
... Oxide film, 6... N-type impurity diffusion region, 7... First insulating film, 8... First conductive film, 9... Second insulating film,
10... Second conductive film, 11... Oxide film, 12...
Aluminum electrode. Figure 2

Claims (1)

[Claims] 1. A capacitor is constituted by a conductive layer formed around a trench formed in a semiconductor substrate, an insulating film formed on the inner surface of this trench, and a conductive film formed inside this insulating film, and this conductive film 1. A semiconductor device characterized in that a plurality of capacitors are configured in a stacked state by alternately forming insulating films and conductive films in multiple layers inside the semiconductor device.