JP3603240B2 - Capacitor device and method of manufacturing the same - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an improvement in a capacitor device using a silicon nitride film as a dielectric film and a method of manufacturing the same.
[0002]
Generally, a capacitor is an indispensable circuit element for configuring a memory or a microwave device. In particular, a capacitor using a silicon nitride film as a dielectric film has been widely put to practical use in semiconductor circuits.
[0003]
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 and the reliability is high when a high voltage is applied. Good uniformity and reproducibility of the characteristics are mentioned.
[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, and the present invention provides one means for responding to this requirement.
[0005]
[Prior art]
In a conventional capacitor device, a silicon nitride film which is easy to deposit and process and belongs to a class having a high dielectric constant is often used as a dielectric.
[0006]
The mode of dielectric breakdown in a capacitor when a silicon nitride film is used is that dielectric breakdown between upper and lower electrodes via pin holes of the silicon nitride film is almost the same, and stress in the silicon nitride film is large. It has been found that a problem arises in that the reliability is degraded due to thermal cycling, that is, distortion due to repeated temperature rise and fall.
[0007]
By the way, when the density is increased in order to reduce the pin holes in the silicon nitride film, the elemental bond becomes stronger and the film stress increases, and conversely, when the film stress is reduced, the pin holes increase. That is, it contains a reciprocal element.
[0008]
As a technique to solve this, a composite film in which a silicon nitride film is sandwiched between silicon oxide films is used as a dielectric film of a capacitor. In this case, contact is made between upper and lower electrodes where dielectric breakdown due to pinholes becomes a problem. The portion is made of a silicon oxide film with few pin holes.
[0009]
However, since the silicon oxide film has a dielectric constant 1/2 that of the silicon nitride film, a reduction in capacity is inevitable, and the deposition apparatus must be changed for continuous processing.
[0010]
[Problems to be solved by the invention]
As described above, when only the silicon nitride film is used as the dielectric film of the capacitor, it is necessary to eliminate the problems caused by the generation of pinholes and film stress, which are mutually contradictory properties. When a composite film of a nitride film and a silicon oxide film is used, problems such as a decrease in the capacitance of the capacitor and a complicated manufacturing process must be solved.
[0011]
The present invention makes it possible to realize a capacitor device that uses a silicon nitride film having a high dielectric constant to maintain a large capacitance and has high resistance to dielectric breakdown.
[0012]
[Means for Solving the Problems]
In the present invention, a silicon nitride film is used as a dielectric film, and it is basically based on using a silicon nitride film having different properties as a multilayer film.
[0013]
FIG. 1 is a cutaway side view showing a main part of a capacitor device for explaining the principle of the present invention.
[0014]
In the figure, (A) is a cut-away side view of the main part showing the entire laminated structure of the capacitor, (B) is a cut-away side view of the main part showing an enlarged dielectric film, 1 is an interlayer insulating film, 2 is a lower electrode, 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.
[0015]
As is apparent from the figure, in this capacitor device, the capacitor dielectric film 3 has a three-layer structure of a high-density silicon nitride film 3A, a low-stress silicon nitride film 3B, and a high-density silicon nitride film 3C.
[0016]
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.
[0017]
From the foregoing, in the capacitor device and the method of manufacturing the same according to the present invention,
(1) A portion (for example, a high-density silicon nitride film 3A and a portion in contact with upper and lower electrodes (for example, lower electrode 2 and upper electrode 5) in a capacitor dielectric film (for example, capacitor dielectric film 3) composed of a silicon nitride film 3C) is characterized by having a higher density than a portion not contacting (for example, low stress silicon nitride film 3B), or
[0018]
(2) In the above (1), a portion of the capacitor dielectric film composed 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. Or
[0019]
(3) In the above (1), the 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 the upper and lower electrodes are The contacting part is characterized by being a high density silicon nitride film, or
[0020]
(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 (for example, (Gradient structure), or
[0021]
(5) When a capacitor dielectric film made of a silicon nitride film is formed by applying a 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.
[0022]
By adopting the above-mentioned means, in the capacitor, the dielectric breakdown in contact with the upper and lower electrodes in which the dielectric breakdown due to the pinhole becomes a problem, the dielectric breakdown is caused because the high density silicon nitride film is used. Is less.
[0023]
In addition, 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 hardly occurs, and the dielectric constant does not change even if the film properties are different. Therefore, there is no problem in terms of capacity, and furthermore, such silicon nitride films can be continuously deposited using a normal deposition apparatus.
[0024]
As described above, the dielectric film used in the present invention may be considered as a composite film based on the silicon nitride film, and a highly reliable capacitor device can be realized without deteriorating the capacitance characteristics.
[0025]
BEST MODE FOR CARRYING OUT THE INVENTION
FIG. 2 is a cutaway side view of a main part showing a capacitor device in a process step for explaining the first embodiment of the present invention, which will be described below with reference to the drawings.
[0026]
See FIG. 2 (A) (A) -1
By applying the sputtering method, a base metal film 12A made of an Au / Ti-based composite metal having a thickness of, for example, about 0.1 [μm] is formed on the polyimide interlayer insulating film 11 as a base.
[0027]
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 plated film.
[0028]
(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.
[0029]
(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.
[0030]
(A) -4
After being immersed in a resist stripping solution to strip and remove the resist film, the milling method is used to remove the base metal film 12A using the Au plating film 12B as a mask, and the Au plating film 12B and the base metal film are removed. The lower electrode 12 made of 12A is completed.
[0031]
See FIG. 2 (B) (B) -1
By applying a plasma CVD (plasma chemical vapor deposition) method, a first silicon nitride film 13A in contact with the lower electrode 12 is formed.
[0032]
Since the silicon nitride film 13A must be a high-density film having few pin holes, it has a low deposition rate of, for example, 0.5 [A] under a low pressure of 0.2 [Torr]. Deposited under each condition.
[0033]
(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. In this case, the deposition was performed under a high deposition rate of, for example, 1.5 [A] under a high pressure of, for example, 0.6 [Torr] and at a large deposition rate with an input current of, eg, 1.5 [A].
[0034]
(B) -3
Subsequently, the uppermost silicon nitride film 13C is formed by applying the plasma CVD method. In this case, the deposition conditions may be exactly the same as the conditions under which the silicon nitride film 13A was grown.
[0035]
The above film deposition is performed by continuous processing in the chamber of the same deposition apparatus. Although the silicon nitride films 13A and 13C and the silicon nitride film 13B are the same silicon nitride film, the density is 5 to 10%. ] Relative difference.
[0036]
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, the condition of the deposition apparatus is limited, It becomes difficult to obtain a good quality silicon nitride film.
[0037]
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 is desirably a compressive stress of less than 5 × 10 ⁸ [dynes / cm ² ].
[0038]
See FIG. 2 (C) (C) -1
A polyimide having a thickness of, for example, 1.0 [μm] and having an opening on the silicon nitride film 13C by applying a spin coating method, a thermosetting method, a resist process in a lithography technique, or the like. The film 14 is formed.
[0039]
(C) -2
By applying the same technique as that 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.
[0040]
In the present invention, many other modifications can be realized without being limited to the above embodiment.
[0041]
For example, in the above-described embodiment, the silicon nitride film has a three-layer structure, but this is composed 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. If necessary, a further multilayer structure or a gradual structure can be used as necessary.
[0042]
【The invention's effect】
In the capacitor device and the method of manufacturing the same according to the present invention, the portion of the capacitor dielectric film that contacts the upper and lower electrodes is formed of a silicon nitride film having a higher density than the non-contact portions.
[0043]
By adopting the above configuration, in the capacitor, the dielectric breakdown in contact with the upper and lower electrodes, in which the dielectric breakdown due to the pinhole becomes a problem, uses a high-density silicon nitride film. Is less.
[0044]
In addition, 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 hardly occurs, and the dielectric constant does not change even if the film properties are different. Therefore, there is no problem in terms of capacity, and furthermore, such silicon nitride films can be continuously deposited using a normal deposition apparatus.
[0045]
As described above, the dielectric film used in the present invention may be considered as a composite film based on the 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 view showing a capacitor device in a process key point for explaining the first embodiment 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 plated 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 Base metal film 15B Au plating film

Claims (5)

A capacitor device characterized in that a portion of a capacitor dielectric film made of a silicon nitride film that contacts the upper and lower electrodes has a higher density than a portion that does not contact the upper and lower electrodes. 2. The capacitor device according to claim 1, wherein a portion of the capacitor dielectric film formed 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. The 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 the upper and lower electrodes is a high-density silicon nitride film. The capacitor device according to claim 1, wherein 2. The capacitor device according to claim 1, wherein 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. In forming a capacitor dielectric film composed of a silicon nitride film by applying a plasma CVD method,
Forming a portion in contact with the electrode in the capacitor dielectric film under conditions of low pressure and low deposition rate;
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.

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