JPS6242392B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a capacitor for a semiconductor device.

Conventionally, capacitors for semiconductor devices have a structure in which an insulating layer is deposited on a metal or semiconductor, and an electrode made of metal or the like is further deposited.
Capacitors used in semiconductor devices must have large capacity, be small and inexpensive, and as an insulating layer,
Silicon dioxide (SiO ₂ ) and alumina that are easy to make
Films such as Al ₂ O ₃ and silicon nitride Si ₃ N ₄ have been used. Of these, SiO ₂ can be easily made into thin, high-quality materials without pinholes by heat-treating a silicon substrate in an oxidizing atmosphere, but it has a low dielectric constant, is susceptible to radiation, and is susceptible to impurity contamination. There are drawbacks such as weakness. Al ₂ O ₃ is generally produced by chemical vapor deposition or aluminum anodic oxidation, and has a high dielectric constant, but if it is thin, it will have a large leakage current and a large loss. Si ₃ N ₄ can also be produced by thermal nitridation of silicon, but this limits the film thickness and poses a problem with breakdown voltage. The insulating film also contains SiO, Ta ₂ O ₅ ,
TiO ₂ and the like are also used, but thin, high-quality films have not been obtained.

The present invention provides a new method for manufacturing a small capacitor for a semiconductor device with a large capacity, and is particularly characterized by excellent stability, uniformity, and mass productivity. The basic principle of the capacitor of the present invention is that a SiO ₂ film attached to an arbitrary substrate that can serve as one electrode of the capacitor is reacted with an atmosphere containing nitrogen atoms as constituent atoms.
The point is that an insulating film in which at least a part of the SiO ₂ film is converted into a silicon oxynitride layer is used.
The present invention will be described below with reference to Examples.

In a preferred embodiment of the present invention, SiO ₂ is produced by heat-treating a silicon substrate in an oxidizing atmosphere.
A film is used as a dielectric. For example, if a silicon wafer is heat treated in dry oxygen at 1000° C. for 1 hour, a SiO ₂ film with a thickness of about 700 Å can be obtained.
This SiO ₂ film is denser and more uniform than those deposited on the substrate by other methods, and is of good quality with no defects such as pinholes. followed by ammonia (NH ₃ )
When heat treated for 1 hour at 1200°C in an atmosphere containing gas, the surface layer of the SiO ₂ film of about 30 Å has an N/O ratio of about 1.
(O of SiO ₂ is converted into a silicon oxynitride layer in equal amounts as is and substituted with N). In addition to _NH3 , the nitriding atmosphere
N ₂ H ₄ or plasma N ₂ , more preferably plasma N ₂ and H ₂ mixed gas, etc. can also be used. It has been found that the insulating film produced by the above method is resistant to impurity contamination, that is, there are no pinholes, etc., and has a higher dielectric constant than a simple SiO ₂ film. Moreover, since the film thickness can be made extremely thin, a capacitor with a large capacity can be manufactured. Next, an example of the manufacturing process of the capacitor of the present invention will be explained with reference to FIG.

First, as shown in Figure 1, the specific resistance n of 0.1Ωcm
A type silicon semiconductor substrate 1 is heated in dry oxygen at 1000°C for 5 minutes to form a thermally oxidized SiO ₂ film 2 of about 100 Å on the surface of the substrate as shown in FIG.
By heating in 100% NH ₃ gas at 1200°C for 1 hour, the surface of the SiO ₂ film 2 with a thickness of approximately 30 Å is converted into a layer containing silicon nitride (silicon oxynitride layer), as shown in Figure 3. do. Silicon oxynitride (SiOxNy) is described in detail in Japanese Patent Application No. 72654/1983 filed by the present applicant. As shown in FIG. 4, aluminum with a thickness of 1 μm is deposited on the insulating films 2 and 3 (this may also be deposited on the back surface of the substrate 1), and patterned to form the electrodes 4.
make. Since the purpose here is miniaturization, the area of the electrode 4 is as small as 1 mm ² . Next, a heat treatment is performed for 10 minutes in a N ₂ atmosphere at 400° C. to form a capacitor, but in the case of forming individual elements, the substrate is cut along the periphery of the electrode 4. Although this device is small, it has a capacitance of 3500 pF and an excellent tan δ of 10 ^-3 .
Moreover, the yield is over 90% within the wafer surface, and it is characterized by being extremely inexpensive. This element is
As a hybrid integrated circuit element, especially microwave IC
It is useful as an element.

Another example is the one-transistor type MOS dynamic memory device shown in FIG. In 1 of FIG. 2, 10 is a p-type silicon substrate with a specific resistance of 5 Ωcm. 11 is a selectively formed field SiO ₂ film with a thickness of 8000 Å,
A SiO ₂ film 1 with a thickness of 200 Å is placed in the area where this film 11 is not present.
2 is formed by a thermal oxidation method. In FIG. 2, such a substrate is treated in NH ₃ gas at 1100° C. for 1 hour to form a silicon oxynitride layer 13 with a thickness of about 30 Å. In FIG. 3, polycrystalline silicon is deposited to a thickness of 3000 Å and a charge storage electrode 14 is formed by photo-etching. Figure 4
, the insulating layers 12 and 13 on the substrate 10 are
After etching the electrode 14 as a mask,
After processing for 30 minutes at 1100℃ in dry oxygen, the thickness of about 700Å
A SiO ₂ film 15 is deposited. In FIG. 5, similarly to the electrode 14, polycrystalline silicon is deposited to a thickness of 3000 Å, and then patterned to form the transfer transistor gate 1.
form 6. Furthermore, p ⁺ was increased by 2 using ion implantation method.
×10 ¹⁵ cm ⁻² and 150 KeV to form the n ⁺ layer 17. Furthermore, if necessary, an insulating film can be attached to the entire surface to perform multilayer wiring. This memory cell is characterized by having a high performance capacitor element according to the present invention. i.e. conventional _SiO2
Compared to the film, it has a silicon nitride layer.
Using the SiO ₂ film increases the capacitance by approximately 30%, so even with the same applied voltage, 30% more charge can be stored, reducing memory read errors. In Figure 2, an insulating film of 200 Å is used, but with the present invention, a film with a thickness of 100 Å or less can be made uniformly, so it is possible to store several times more charge. This means that the memory cell area can be reduced to a fraction of that of conventional ones.

Figure 3 shows the results of measuring the capacitance by applying a 1MHz high frequency voltage to the capacitor having the structure shown in Figure 1. The SiO ₂ film thickness was 100 Å. The relative permittivity of the structure equivalent to the conventional structure, which requires zero heat treatment time in an atmosphere containing nitrogen, was 3.85, but that of the structure at 1200°C.
The dielectric constant gradually increased by heat treatment in 100% NH ₃ and reached 5.30 after 5 hours, representing an increase of 38%. Since the leakage current does not particularly increase, tanδ
This is a 38% increase, which is a great practical advantage. According to this method, it is possible to make a practical capacitive element with a film thickness of 100 Å or less, and it also has the advantage of being easy to mass produce and being inexpensive.

As explained in detail above, the present invention relates to a capacitor having an insulating film formed by converting the surface of an SiO ₂ film to silicon oxynitride, which has a large capacity,
It has advantages such as high stability, easy miniaturization, suitable for memory, etc., and easy mass production.

[Brief explanation of the drawing]

Fig. 1 is a cross-sectional view explaining the manufacturing process of a capacitor according to the present invention, Fig. 2 is a process diagram showing an embodiment of the present invention applied to a one-transistor cell, and Fig. 3 shows the relationship between heat treatment time and dielectric constant. FIG. In the drawings, 1 is a semiconductor layer, 2 is a silicon dioxide film, 3 is a layer containing silicon nitride, and 4 is a metal electrode.

Claims (1)

[Claims] 1. A silicon dioxide film on a semiconductor layer or a metal layer deposited on the semiconductor layer is heat-treated in an atmosphere containing nitrogen as a constituent atom to transform the surface portion of the silicon dioxide film into a layer containing silicon nitride. A capacitor for a semiconductor device, characterized in that a semiconductor or metal electrode is coated on the insulating film to form a capacitor together with the semiconductor layer or the metal layer. 2. A capacitor for a semiconductor device according to claim 1, wherein the semiconductor layer is a silicon semiconductor substrate, and the silicon dioxide film is an oxide film obtained by thermally oxidizing the surface of the substrate.