JP3550632B2 - Semiconductor device - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a semiconductor device having a capacitor in which a dielectric film and an upper electrode are sequentially stacked on a lower electrode through an opening formed in an insulating film, and a method for manufacturing the same.
[0002]
[Prior art]
2. Description of the Related Art In recent years, with the reduction in size, weight, and power consumption of electronic devices, high integration of VLSIs (very large scale integrated circuits) and extremely miniaturization of devices have been significantly advanced. In such a situation, in miniaturization of a bipolar LSI or BiCMOS LSI (bipolar LSI), it is important to miniaturize a capacitor (capacitor; for example, a MIS capacitor) which occupies a large proportion in the area of the LSI. . In order to obtain a capacitance value equal to or higher than the current value while miniaturizing this capacitor, it is necessary to develop a new high-dielectric material or to reduce the thickness of the dielectric film currently used.
[0003]
Conventionally, in forming a capacitor, an opening in an insulating film has been formed by wet etching or dry etching using an etching gas containing a halogen gas. In the case where the opening is formed by dry etching, the deposit and the damaged layer on the surface of the semiconductor substrate exposed by the opening are subjected to chemical dry etching after the dry etching, as in the case of forming the contact hole. To remove it. In a conventional semiconductor device in which an opening is formed in an insulating film as described above, a natural oxide film is generally formed on the surface of the semiconductor substrate exposed by the opening. This natural oxide film causes a reduction or variation in the capacitance value of the capacitor, and its influence cannot be ignored as the dielectric film becomes thinner.
[0004]
[Problems to be solved by the invention]
However, in the conventional semiconductor device and the method of manufacturing the same, the formation of the natural oxide film could not be controlled, so that it was difficult to miniaturize the capacitor with high accuracy, and there were problems in miniaturization and reliability of LSI. was there.
[0005]
Further, as the miniaturization of the capacitor progresses, the area of the opening formed in the insulating film becomes smaller, so that it becomes necessary to etch a very small area. Further, from the viewpoint of improving the reliability of the LSI, it has become necessary to improve the opening accuracy of the insulating film. Therefore, it has been necessary to form an opening in the insulating film by anisotropic dry etching that can be accurately performed.
[0006]
The present invention has been made in view of the above problems, and its object is by forming an acid-suppressing film between the lower electrode and the dielectric film, reducing the increase and variation in the capacitance value of the capacitor to provide a semiconductor equipment, which can.
[0007]
[Means for Solving the Problems]
A semiconductor device according to the present invention includes a capacitor in which a dielectric film and an upper electrode are sequentially stacked on a lower electrode through an opening formed in an insulating film, and the capacitor includes a lower electrode and a lower electrode. It is configured to include an oxidation suppressing film having at least a part of a Si—C bond between the dielectric film and the dielectric film.
[0009]
In the semiconductor device of the present invention, the capacitor is formed by sequentially laminating the dielectric film and the upper electrode on the lower electrode via the opening formed in the insulating film. Further, between the lower electrode and the dielectric film are acid-suppressing film is formed to have at least in part Si-C bond, between the lower electrode and the dielectric film in the manufacturing process of a semiconductor device The generation of an oxide film is suppressed.
[0011]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[0012]
FIG. 1 shows a configuration of a semiconductor device according to an embodiment of the present invention. In this semiconductor device, an impurity layer (for example, an N ⁺ impurity diffusion layer) 2 is formed as a lower electrode of a capacitor in a capacitor formation region of a semiconductor substrate (for example, a p-type silicon semiconductor substrate) 1. An insulating film (for example, a field insulating film) 3 made of silicon dioxide (SiO ₂ ) is formed on the impurity layer 2. An opening 3 a is formed in the insulating film 3, and a part of the surface of the impurity layer 2 is exposed from the insulating film 3.
[0013]
On the impurity layer 2 exposed by the opening 3a, an oxidation suppressing film 4 for suppressing generation of an oxide film (natural oxide film) on the surface of the impurity layer 2 is formed. The oxidation suppressing film 4 is formed together with the opening 3a by selectively etching the insulating film 3 using an etching gas containing a halogenated derivative of an organic compound, as will be described later. At least in part. FIG. 2 shows the result of analyzing the oxidation suppressing film 4 by X-ray photoelectron spectroscopy. Thus, it can be confirmed from FIG. 2 that the substance constituting the oxidation suppressing film 4 has Si—C bonds in at least a part thereof.
[0014]
A dielectric film 5 of a capacitor made of silicon nitride (Si ₃ N ₄ ) is formed on the oxidation suppressing film 4, and an appropriate material such as aluminum (Al) is formed on the dielectric film 5. An upper electrode 6 made of metal is formed.
[0015]
In this semiconductor device, a contact opening 3b for making contact with the impurity layer 2 as a lower electrode is formed in the insulating film 3, and another part of the surface of the impurity layer 2 is It comes to be exposed from. On the impurity layer 2 exposed by the contact opening 3b, an extraction electrode 7 for a lower electrode made of an appropriate metal such as aluminum is formed.
[0016]
A semiconductor device having such a configuration can be manufactured as follows. 3 and 4 are cross-sectional views of the semiconductor device shown in FIG. 1 in respective steps.
[0017]
First, as shown in FIG. 3A, a photoresist film 11 is formed on the semiconductor substrate 1 by coating, and the photoresist film 11 is selectively exposed and patterned. By implantation, phosphorus (P) is buried in the capacitor formation region of the semiconductor substrate 1 to form an n-type impurity layer 2.
[0018]
Next, after the photoresist film 11 is removed, as shown in FIG. 3B, for example, an alkoxysilane (Si (OC ₂ H ₅ ) ₄ ) gas is supplied onto the semiconductor substrate 1 as a reaction gas. An insulating film 3 made of silicon dioxide is formed by a CVD (Chemical Vapor Deposition) method. After that, a photoresist film 12 is formed on the insulating film 3 by application, and is patterned by selectively exposing the photoresist film 12 to form a pattern in which an opening region 12a corresponding to the opening 3a is opened.
[0019]
Subsequently, anisotropic dry etching is performed using the photoresist film 12 as a mask. At this time, a mixed gas of a trifluoromethane (CHF ₃ ) gas, a tetrafluoromethane (CF ₄ ) gas, and an argon (Ar) gas is used as an etching gas. Thereby, as shown in FIG. 3C, the insulating film 3 is selectively etched, and an opening 3a is formed. On the impurity layer 2 exposed by the opening 3a, an oxidation suppressing film 4 made of a substance having at least a part of a Si—C bond is formed, and on the oxidation suppressing film 4, A deposition layer 13 mainly composed of a carbon-based polymer is formed.
[0020]
After the opening 3a is formed in this way, plasma ashing with oxygen gas is performed to remove the photoresist film 12 as shown in FIG. After that, washing is performed with a mixed solution of sulfuric acid (H ₂ SO ₄ ) and aqueous hydrogen peroxide (H ₂ O ₂ ), and further, ammonium hydroxide (NH ₄ OH) and aqueous hydrogen peroxide (H ₂ O ₂₎ ) And water (H ₂ O). As a result, only the oxidation suppressing film 4 remains on the impurity layer 2 exposed by the opening 3a.
[0021]
After the cleaning, as shown in FIG. 4B, for example, dichlorosilane (SiH ₂ Cl ₂ ) gas and ammonia (NH ₃ ) gas are supplied as a reaction gas on the insulating film 3 and the oxidation suppressing film 4. While forming, the silicon nitride film 14 is formed by the CVD method.
[0022]
After forming the silicon nitride film 14, as shown in FIG. 4C, a pattern is formed on the silicon nitride film 14 with a photoresist film (not shown), and etching is performed using the photoresist film as a mask to perform etching. The film 14 is selectively removed to form the dielectric film 5. Thereafter, a pattern is formed on the dielectric film 5 and the insulating film 3 with a photoresist film (not shown), and etching is performed using the photoresist film as a mask to selectively remove the insulating film 3 to form the contact opening 3b. Form.
[0023]
After forming the contact opening 3b, a metal layer (not shown) made of, for example, aluminum is formed by vapor deposition, and the metal layer is selectively removed to form the upper electrode 6 and the lower electrode extraction electrode 7. This results in the semiconductor device shown in FIG.
[0024]
The characteristics of the semiconductor device manufactured as described above were examined. First, an opening 3a is formed in the insulating film 3 by the method of manufacturing a semiconductor device according to the present embodiment, and the photoresist film 12 is removed and washed (see FIG. 4A), and then exposed through the opening 3a. The thickness of the oxide film (natural oxide film) generated in the region of the impurity layer 2 was examined. FIG. 5 shows the result in comparison with a conventional semiconductor device. Note that Conventional Example 1 was manufactured in the same manner as in the present embodiment except that the opening 3a was formed by wet etching. Conventional example 2 is that the opening 3a is formed by dry etching using an etching gas containing a halogen gas, and then chemical dry etching is performed for about 10 °, and the deposited layer in the region of the impurity layer 2 exposed by the opening 3a is formed. Except for removing the and the damaged layer, the other parts were manufactured in the same manner as in the present embodiment. Thus, it can be seen that the semiconductor device of the present embodiment has a smaller oxide film thickness than the conventional semiconductor device, and suppresses the formation of the oxide film.
[0025]
Further, the fact that the formation of an oxide film was suppressed by the oxidation suppression film 4 formed in this semiconductor device was verified. Specifically, the silicon semiconductor substrate is anisotropically etched for 3 seconds using an etching gas containing a trifluoromethane gas and a tetrafluoromethane gas in the same manner as in forming the opening 3a in the method for manufacturing a semiconductor device according to the present embodiment. An oxidation suppression film was formed on the surface by dry etching. After that, the silicon semiconductor substrate on which the oxidation suppression film was formed was inserted into a horizontal diffusion furnace together with a silicon semiconductor substrate that had not been subjected to any treatment, and thermally oxidized at 950 ° C. in a dry oxygen atmosphere to form an oxide film. Was observed. FIG. 6 shows the result. As described above, the formation rate of the oxide film in the case where the oxidation suppression film 4 is formed in the present embodiment is lower than that in the case where the oxidation suppression film is not formed. That is, it can be seen that the oxidation suppressing film 4 in the present embodiment suppresses formation of an oxide film.
[0026]
Further, the uniformity of the capacitance value of the capacitor and the capacitance value in the same plane parallel to the surface of the semiconductor substrate in the semiconductor device according to the present embodiment were examined. The thickness of the dielectric film 5 was about 32 nm, and the diameter of the opening 3a was about 170 μm. The results are shown in FIG. 7 together with Conventional Example 1 and Conventional Example 2 described above. Thus, it can be seen that the semiconductor device according to the present embodiment has a higher capacitance value and a smaller variation in the capacitance value than the conventional semiconductor device.
[0027]
As described above, according to the semiconductor device of the present embodiment, since oxidation preventing film 4 is formed on impurity layer 2 exposed by opening 3a, the gap between impurity layer 2 and dielectric film 5 is formed. It is possible to suppress the formation of an oxide film at the same time. Therefore, the capacitance value of the capacitor can be increased, and the variation in the capacitance value can be reduced.
[0028]
Further, according to the method of manufacturing a semiconductor device according to the present embodiment, opening 3a is formed by anisotropically dry-etching insulating film 3 using a mixed gas of trifluoromethane gas, tetrafluoromethane gas, and argon gas as an etching gas. Therefore, the oxidation suppressing film 4 can be formed on the impurity layer 2 exposed by the opening 3a. Therefore, generation of an oxide film between the impurity layer 2 and the dielectric film 5 can be suppressed.
[0029]
Although the present invention has been described with reference to the embodiment, the present invention is not limited to the above embodiment, and various modifications are possible. For example, in the above embodiment, a mixed gas of a trifluoromethane gas, a tetrafluoromethane gas, and an argon gas is used as an etching gas when forming the opening 3a in the insulating film 3, but a trifluoromethane gas or a tetrafluoromethane gas is used. Anisotropic dry etching may be performed using an etching gas containing only one of the above.
[0030]
Further, the etching gas is not limited to the trifluoromethane gas and the tetrafluoromethane gas, and may be an etching gas containing at least one of other saturated fluoride gases such as a difluoromethane (CH ₂ F ₂ ) gas. An etching gas containing at least one kind of unsaturated fluoride gas such as a butene (C ₄ F ₈ ) gas and a hexafluoroethane (C ₂ F ₆ ) gas may be used. The etching gas is not limited to a saturated fluoride gas and an unsaturated fluoride gas, but may be an aliphatic fluoride gas or a fluorine derivative gas of an organic compound.
[0031]
Furthermore, not only fluorine derivatives of organic compounds but also halogen derivatives of organic compounds can be similarly used as an etching gas. Preferably, an aliphatic halide gas is used, and particularly preferably, a saturated halogenated gas or an unsaturated halogenated gas is used.
[0032]
In addition, in the above-described embodiment, a mixed gas of a halogen derivative of an organic compound and an argon gas is used as an etching gas when forming the opening 3a in the insulating film 3. An etching gas consisting of only a halogen derivative may be used. Further, an etching gas containing not only an argon gas but also another inert gas such as a helium (He) gas may be used, and an etching gas containing a carbon monoxide (CO) gas or an oxygen (O ₂ ) gas may be used. May be used.
[0033]
【The invention's effect】
As described above, according to the semiconductor device of the present invention, since the capacitor is provided with the oxidation suppressing film having at least a part of the Si—C bond between the lower electrode and the dielectric film, Can be increased, and the variation in the capacitance value can be reduced. Therefore, there is an effect that the capacitor can be miniaturized with high accuracy, the miniaturization of the semiconductor device can be achieved, and the reliability can be improved.
[Brief description of the drawings]
FIG. 1 is a configuration diagram illustrating a semiconductor device according to an embodiment of the present invention.
FIG. 2 is a characteristic diagram for explaining an oxidation suppressing film of the semiconductor device shown in FIG.
FIG. 3 is a process chart illustrating a method for manufacturing the semiconductor device illustrated in FIG.
FIG. 4 is a process drawing following FIG. 3;
FIG. 5 is a characteristic diagram relating to an oxide film generated between an impurity layer and a dielectric film of the semiconductor device shown in FIG. 1;
FIG. 6 is a characteristic diagram illustrating an oxidation suppressing effect of an oxidation suppressing film of the semiconductor device illustrated in FIG. 1;
FIG. 7 is a characteristic diagram relating to a capacitance value and its uniformity of the semiconductor device shown in FIG. 1;
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Semiconductor substrate, 2 ... Impurity layer (lower electrode), 3 ... Insulating film, 3a ... opening, 3b ... Contact opening, 4 ... Oxidation suppressing film, 5 ... Dielectric film, 6 ... Upper electrode, 7 ... Lower electrode Electrodes, 11 and 12: photoresist film, 13: deposited layer, 14 silicon nitride film

Claims (1)

A semiconductor device having a capacitor in which a dielectric film and an upper electrode are sequentially stacked on a lower electrode through an opening formed in an insulating film,
The semiconductor device according to claim 1, wherein the capacitor includes an oxidation suppression film having at least a part of a Si-C bond between the lower electrode and the dielectric film.

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