JPH10200070A - Capacitor device and method of manufacturing the same - Google Patents

Abstract

(57) Abstract: A capacitor device and a method of manufacturing the same are realized by using a silicon nitride film having a high dielectric constant while maintaining a large capacitance and having high resistance to dielectric breakdown. It can be so. SOLUTION: In a capacitor dielectric film 3 made of a silicon nitride film, a portion in contact with a lower electrode 2 and an upper electrode 5, that is, a density in a high density silicon nitride film 3A and a high density silicon nitride film 3C is reduced. The density is higher than that of the portion not in contact with the electrode, that is, the low stress silicon nitride film 3B.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a capacitor device using a silicon nitride film as a dielectric film and an improvement in a method of manufacturing the same.

In general, a capacitor is an indispensable circuit element for forming a memory or a microwave device. In particular, a capacitor using a silicon nitride film as a dielectric film is widely used in semiconductor circuits. ing.

The requirements for this type of capacitor are that the dielectric constant of the dielectric is high in order to reduce the element area, that the dielectric breakdown voltage is high when a high voltage is applied, and that the reliability is high. And good uniformity and reproducibility of these characteristics.

[0004] In order to satisfy the above requirements, there is a problem in how to make a dielectric material and a structure of a dielectric film.
The present invention provides one means for responding to this need.

[0005]

2. Description of the Related Art In a conventional capacitor device, a silicon nitride film, which can be easily deposited and processed and belongs to a class having a high dielectric constant, is often used as a dielectric.

The mode of dielectric breakdown in a capacitor when a silicon nitride film is used is as follows.
In most cases, the dielectric breakdown between the upper and lower electrodes through holes is large, and when the stress in the silicon nitride film is large, the reliability decreases due to thermal cycling, that is, distortion due to repeated temperature rise and fall. Is known to occur.

By the way, the pin in the silicon nitride film
Increasing the density in order to reduce the holes increases the elemental bond and increases the film stress. Conversely, when the film stress is reduced, the number of pinholes increases, which involves a trade-off factor.

As a technique for solving this problem, an attempt has been made to use a composite film in which a silicon nitride film is sandwiched by a silicon oxide film as a dielectric film of a capacitor. The portion in contact with the electrode is made of a silicon oxide film with few pin holes.

However, since the silicon oxide film has a dielectric constant 1/2 that of the silicon nitride film, a reduction in capacity is inevitable. Further, in order to perform continuous processing, the deposition apparatus must be changed. No.

[0010]

As described above, when only a silicon nitride film is used as a dielectric film of a capacitor, problems caused by contradictory properties such as generation of pin holes and generation of film stress occur. Need to be resolved,
In addition, when a composite film of a silicon nitride film and a silicon oxide film is used, problems such as a decrease in capacitor capacity and a complicated manufacturing process must be solved.

The present invention makes it possible to realize a capacitor device which uses a silicon nitride film having a high dielectric constant to maintain a large capacitance and has a high resistance to dielectric breakdown.

[0012]

According to the present invention, a silicon nitride film is used as a dielectric film. The silicon nitride film having different properties is basically used as a multilayer film.

FIG. 1 is a cutaway side view showing a main part of a capacitor device for explaining the principle of the present invention.

In the figure, (A) is a cutaway side view of a main part showing the entire laminated structure of a capacitor, (B) is a cutaway side view of a main part showing an enlarged dielectric film, 1 is an interlayer insulating film, and 2 is a lower part. electrode,
Reference numeral 3 denotes a capacitor dielectric film, 3A denotes a high density silicon nitride film, 3B denotes a low stress silicon nitride film, 3C denotes a high density silicon nitride film, 4 denotes a protective insulating film, and 5 denotes an upper electrode.

As is apparent from the drawing, in this capacitor device, the capacitor dielectric film 3 is formed of a high-density silicon nitride film 3.
A, a low-stress silicon nitride film 3B, and a high-density silicon nitride film 3C.

The silicon nitride films 3A and 3C have a large stress but few pin holes, and the silicon nitride film 3B has a small stress but many pin holes.

From the above description, in the capacitor device and the method of manufacturing the same according to the present invention, (1) the upper and lower portions of the capacitor dielectric film (for example, the capacitor dielectric film 3) composed of a silicon nitride film. The portions (for example, the high-density silicon nitride films 3A and 3C) that are in contact with the electrodes (for example, the lower electrode 2 and the upper electrode 5) have a higher density than the portions (for example, the low-stress silicon nitride film 3B) that are not in contact. Or characterized by, or

(2) In the above (1), it should be noted that a portion of the capacitor dielectric film made of a silicon nitride film, which is not in contact with the upper and lower electrodes, has a lower stress than a portion in contact with the upper and lower electrodes. Features, or

(3) In the above (1), the capacitor dielectric film composed of a silicon nitride film is a multilayer laminate of a high density silicon nitride film and a low stress silicon nitride film, The part in contact with each electrode is characterized by being a high-density silicon nitride film, or

(4) In the above (1), the density and stress in the capacitor dielectric film composed of the silicon nitride film sandwiched between the upper and lower electrodes decrease from the upper and lower electrodes toward the center. (Eg, a gradual structure), or

(5) When a capacitor dielectric film composed of a silicon nitride film is formed by applying the plasma CVD method, a portion of the capacitor dielectric film that is in contact with an electrode is formed under conditions of low pressure and low deposition rate. And a step of forming a portion of the capacitor dielectric film that is not in contact with the electrode under conditions of high pressure and high deposition rate.

By adopting the above-mentioned means, in the capacitor, since the dielectric film in contact with the upper and lower electrodes where the dielectric breakdown due to the pinhole becomes a problem is used, a high-density silicon nitride film is used. Rarely lead to.

Since the silicon nitride film other than the silicon nitride film in contact with the upper and lower electrodes is a low-stress silicon nitride film, deterioration in reliability due to the film stress is unlikely to occur. Therefore, there is no problem in terms of capacity, and the silicon nitride films can be continuously deposited using a normal deposition apparatus.

As described above, the dielectric film used in the present invention is:
It can be considered as a composite film based on a silicon nitride film, and a highly reliable capacitor device can be realized without deteriorating the capacitance characteristics.

[0025]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 2 is a cutaway side view showing a main part of a capacitor device in a process step for explaining a first embodiment of the present invention, and will be described below with reference to the drawings. I do.

2A. (A) -1 By applying the sputtering method, a thickness of, for example, 0.1 [μm] is formed on the polyimide interlayer insulating film 11 which is a base.
Metal film 12 made of Au / Ti-based composite metal
Form A.

The base metal film 12A serves as a seed metal for plating and functions to improve the adhesion between the polyimide interlayer insulating film 11 and the plating film.

(A) -2 A resist film having an opening at a portion where a plating film is to be formed is formed by applying a resist process in lithography technology.

(A) -3 An Au plating film 12B having a thickness of about 1 [μm] is formed only in the opening by immersing the substrate in a plating solution and supplying a current to the wafer.

(A) -4 The base metal film 12A is removed using the Au plating film 12B as a mask by applying a milling method after immersing the resist film in a resist removing solution to remove and remove the resist film. A
The lower electrode 12 composed of the u-plated film 12B and the underlying metal film 12A is completed.

FIG. 2B (B) -1 Plasma CVD (plasma CVD)
The first silicon nitride film 13 </ b> A in contact with the lower electrode 12 is formed by applying an apour deposition method.

Since the silicon nitride film 13A must be a high-density film with few pin holes, a small input current of, for example, 0.5 A under a low pressure of 0.2 Torr, for example. The deposition was performed under each condition of the deposition rate.

(B) -2 Subsequently, the silicon nitride film 13B is formed by applying the plasma CVD method. In this case, the silicon nitride film 13B must be a low stress film even if there are many pin holes. Therefore, the growth conditions were changed, and deposition was performed under a high deposition rate under a high pressure of, for example, 0.6 [Torr] and an input current of, for example, 1.5 [A].

(B) -3 Subsequently, the uppermost silicon nitride film 13C is formed by applying the plasma CVD method. In this case, the conditions for deposition may be exactly the same as the conditions for growing the silicon nitride film 13A.

The above-described film deposition is performed in a continuous process in the chamber of the same deposition apparatus. The silicon nitride films 13A and 13C and the silicon nitride film 13B are the same silicon nitride film, but the density is 5 to 5. The relative difference is about 10%.

Below the relative difference, the difference in the properties of the film is small, and the effects aimed at by the present invention are hardly obtained.
If the relative difference is exceeded, it is difficult to obtain a high quality silicon nitride film due to the restrictions on the conditions of the deposition apparatus.

In order to suppress the deterioration of the reliability of the capacitor, the film stress in the silicon nitride film 13B not in contact with the electrode should be a compressive stress of less than 5 × 10 ⁸ [dynes / cm ² ]. Is desirable.

FIG. 2C (C) -1 By applying a spin coating method, a thermosetting method, a resist process in a lithography technique, or the like, a film thickness of, for example, 1.0 [μm] is obtained. And the silicon nitride film 13
A polyimide film 14 having an opening is formed on C.

(C) -2 By applying the same technique as the technique for forming the lower electrode 12, the upper electrode 15 composed of the base metal film 15A and the Au plating film 15B is formed.

In the present invention, many other modifications can be realized without being limited to the above embodiment.

For example, in the above-described embodiment, the silicon nitride film has a three-layer structure.
This may be made up of a high-density silicon nitride film in contact with the electrode and a low-stress silicon nitride film not in contact with the electrode.
It can have a gradual structure.

[0042]

In the capacitor device and the method of manufacturing the same according to the present invention, the capacitor dielectric film is formed of a silicon nitride film having a higher density than a portion in contact with each of the upper and lower electrodes as compared with a portion not in contact. Have been.

By adopting the above-described structure, in the capacitor, a high-density silicon nitride film is used as the dielectric film in contact with the upper and lower electrodes where the dielectric breakdown due to the pinhole becomes a problem. Rarely lead to.

Since the silicon nitride film other than the silicon nitride film in contact with the upper and lower electrodes is a low-stress silicon nitride film, deterioration in reliability due to the film stress is unlikely to occur. Therefore, there is no problem in terms of capacity, and the silicon nitride films can be continuously deposited using a normal deposition apparatus.

As described above, the dielectric film used in the present invention is:
It can be considered as a composite film based on a silicon nitride film, and a highly reliable capacitor device can be realized without deteriorating the capacitance characteristics.

[Brief description of the drawings]

FIG. 1 is a cutaway side view of a main part showing a capacitor device for explaining the principle of the present invention.

FIG. 2 is a fragmentary side elevational view showing a capacitor device at a key point in the process for describing Embodiment 1 of the present invention.

[Explanation of symbols]

 Reference Signs List 1 interlayer insulating film 2 lower electrode 3 capacitor dielectric film 3A high-density silicon nitride film 3B low-stress silicon nitride film 3C high-density silicon nitride film 4 protective insulating film 5 upper electrode 11 polyimide interlayer insulating film 12 lower electrode 12A base metal film 12B Au plating film 13 Silicon nitride film (capacitor dielectric film) 13A High density silicon nitride film 13B Low stress silicon nitride film 13C High density silicon nitride film 14 Polyimide film 15 Upper electrode 15A Underlying metal film 15B Au plating film

Claims (5)

[Claims] 1. A capacitor device, wherein a portion of a capacitor dielectric film made of a silicon nitride film that contacts upper and lower electrodes has a higher density than a portion that does not contact the upper and lower electrodes. 2. The capacitor according to claim 1, wherein a portion of the capacitor dielectric film made of a silicon nitride film, which is not in contact with the upper and lower electrodes, has a lower stress than a portion in contact with the upper and lower electrodes. apparatus. 3. A capacitor dielectric film composed of a silicon nitride film is composed of a multilayer laminate of a high-density silicon nitride film and a low-stress silicon nitride film, and at least a portion in contact with each of the upper and lower electrodes is made of a high-density silicon. 2. The capacitor device according to claim 1, wherein the capacitor device is a nitride film. 4. A capacitor dielectric film comprising a silicon nitride film sandwiched between upper and lower electrodes, wherein the density and the stress decrease from the upper and lower electrode sides toward the center. Capacitor device. 5. When forming a capacitor dielectric film composed of a silicon nitride film by applying a plasma CVD method, a portion in contact with an electrode in the capacitor dielectric film is subjected to low pressure and low deposition rate conditions. Forming a portion of the capacitor dielectric film that is not in contact with the electrode under high pressure and high deposition rate conditions.